pon design

Understanding PON Design – FTTx Overview/Glossary

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Understanding PON Design

FTTx Overview/Glossary/Acronyms


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FTTx Overview

Fiber-to-the-x (FTTx) can be described using a number of optical fiber architectures. This section will briefly describe the following architectures:

Fiber-to-the-Premise (FTTP)

Fiber-to-the-Home (FTTH)

Fiber-to-the-Business (FTTB)

Fiber-to-the-Curb (FTTC)

Fiber-to-the-Node (FTTN)

FTTx is also discussed in the context of deployment scenarios such as Greenfield, Overbuild, Rehabilitation and Hybrid architectures.

General descriptions are offered for products and accessories for which actual design considerations may be built.

The next generation of broadband access networks must be able to provide the needed bandwidth for current demands as well as that for any future applications.

Optical fiber provides but one solution for existing and future requirements. With optical fiber technologies, bandwidth demands are satisfied, bringing the communications infrastructure more powerful tools that can interface directly with homes, businesses, offices, community centers, and government agencies. Optical fiber technology provides a higher capacity data transfer at very high speeds. This enables the community or service provider to supply a wide range services and applications, such as High Definition TV (HDTV), Video on Demand (VoD) and high-speed data all while providing the basic fundamentals of voice connectivity.

Broadband Access equipment providers are able to offer technology advances through the converged services of triple-play features using network aggregation and subtending in combination with the passive optical network (PON) technology.

The following is a partial list of advantages in using optical fiber systems: - Higher Bandwidth Capacity - Resistance to Outside Interference - Longer Reach - Lower Maintenance Costs - Longer Life - Better Reliability “Communities and service providers are able to offer a wide range of value-added services, above and beyond existing services over a fiber optic infrastructure.”

Fiber Access Overview Communities and service providers have responded to the growing demand for broadband services by either moving towards a wireless solution or upgrading their existing copper infrastructure with xDSL technologies. Both of these technologies are readily available today, and represent a natural evolution to more applications and better utilization of their copper plants. But this is considered as an intermediate solution, due to rate limitations of wireless, and the transmission limitations of copper lines. Both technologies impose a technical trade off between rate and reach. This affects the number and types of services that can be offered by the service providers and communities. It is becoming more economical - and even more important - strategically imperative, for communities and service providers to start bringing fiber as close to residential and small business premises sooner, rather than later.


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Exhibit 1: Schematic Diagram – PON Network

Fiber-To-The-Premises (FTTP) though an emerging technology is not new. Fiber-to-the-Home (FTTH) has been commercially available for about ten years, and FTTP is viewed as the next logical step in the evolution of the access network. In an FTTP architecture, an optical fiber is deployed all the way to the customer’s premise or location; either to the residence (FTTH - Fiber To The Home) or to a business (FTTB - Fiber To The Business). Exhibit 1 above is an expanded view of the components that comprise the Passive Optical Network (PON) between the Optical Line Termination (OLT) at the central office (CO) and the Optical Network Termination (ONT) at the home. Most of the active equipment providers have similar components that provide similar services. Basically, the Optical Line Termination (OLT) takes an electrical signal from a particular content, converts the signal into an optical signal, and then transports that signal down through the network. There are two downstream optical wavelengths, 1550 nm for a video overlay, and 1490 nm for traditional voice and data services. There may or may not be a 1550 nm Video OLT (V-OLT) in the network: This is dependent upon whether you are providing video content through a video overlay (which is analog CATV Services) or switched digital video (SDV) (which is IP Video, not streaming video). If you are providing video through SDV, there will not be a V-OLT within the network. However, there will always be a Packet or Digital OLT (P/D-OLT) in the network as this is where your voice and data are transmitted and received. When using the video overlay techniques where the Video OLT is a separate set of electronics within the Central Office (CO) or Head-End (HE), there are “new” combining or mixing techniques that are needed to provide the upstream video on demand (VOD) services from the Central Office (CO) or Head-End (HE). Video on Demand (VOD) Techniques are discussed in the Video Training Module later in this course. The additional wavelength is the 1590 nm wavelength that provides the RF Return when the video overlay is used. This combining or mixing is accomplished with the use of the coarse wave division multiplexer (CWDM). So, What is CWDM (Coarse Wavelength Division Multiplexing)? CWDM is the technology for combining up to 18 International Telecommunications Union (ITU) wavelengths and transmitting them simultaneously onto a single fiber to be separated at the far end. The ITU standard for CWDM defines the 18 channels, 20 nanometers spaced, between 1271nm and 1611nm wavelengths. If there is a V-OLT, the 1550 nm and 1490 nm signals are combined through a Wave Division Multiplexer (WDM) module or CWDM and sent to the OSP fiber through the Main Distribution Fiber Frame to the Optical Distribution Network (ODN). The ODN serves as the access portion of the network. The fiber is spliced to the primary feeder fiber (F1) within the OSP which is connected or spliced to a centralized splitter

1490 nm DS Digital

1310 nm US Digital1550 nm DS Overlay

1590 nm US RF Return


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housed within a Fiber Distribution Terminal or Hub (FDT or FDH). The cabinet containing the centralized splitter is also referred to as a Primary Flexibility Point (PFP), Local Convergence Point (LCP) or Fiber Service Area Interface (FSAI). The distribution fiber (F2) architecture may be centralized where all the F2 fiber extends from the FDH to the home, or distributed, where the splitting configuration extends at the FDH as well as the network access point (NAP) where the access terminals are located closer to the customer premise. The signals on the output of the splitter are distributed to homes or premises through the secondary or distribution fiber to a Fiber Access Terminal (FAT) that connects the Distribution Fiber to the Drop Cable terminating at the ONT. The fiber access terminal is also referred to as Network Access Point (NAP), and the ONT may be called a Network Interface Device (NID). The ONT must communicate upstream with the OLT. This is accomplished by an upstream 1310 nm laser within the ONT. The ONT converts the traditional voice and data electrical signals to an optical signal, and sends the optical signal through the same ODN through the WDM, which is finally received by the OLT. The OLT then converts the optical signal back into the corresponding electrical signals which is then processed. A Network Interface Device (NID) is located at the customer premise in the form of an Optical Network Termination (ONT), or Optical Network Unit (ONU). The ONT/ONU terminates the optical access network providing direct connectivity to the feature-rich services of voice, data, and video at the customer premise. The customer interfaces at the ONT comprise the transition from fiber to the customer premise wiring. These interfaces are as follows: RJ-45 10/100 Mbps Ethernet port for data (includes Voice over IP [VOIP] and Video over IP [SDV]), RJ-11 for voice, and F-Connector for video. In the early years, the high cost of building an “all optical” network limited deployments to “new” build or “Greenfield” areas. Just as infrastructure costs have decreased, and bandwidth needs have increased, communities and service providers are now recognizing the alternative solution to “over build” their networks with optical fiber. The initial investment required for optical fiber deployments is still fairly high and may require a proven return on a particular business case. A phase by phased approach is an alternative where the optical fiber access starts with a Fiber-to-the-Node (FTTN) or Fiber-to-the-Curb (FTTC) type of deployment either ADSL2+ or VDSL. In the FTTN/FTTC configurations, an optical link is deployed to a remote Digital Subscriber Line Access Mux (DSLAM) in a Service Area Interface (SAI) cabinet located near a residential community, subdivision or business setting. The DSLAM will convert the optical signal into an electrical signal where the services are easily transferred to existing copper facilities, and will interface directly with an ONU at the home. Due to the shorter reach of the copper infrastructure, service providers are able to offer higher bandwidth services without having to place the optical fiber directly to the premise. Future FTTP configuration upgrades can be economically justified, as a natural second phase, and/or service requirements grow. FTTN/FTTC are considered intermediate steps in providing broadband infrastructures. Greenfield

The ultimate FTTP deployment is the Greenfield scenario in newly built areas, where there is no existing broadband infrastructure and no constrictions exist. In new neighborhoods and planned communities, the application of FTTP is easy to justify as initial overheads are quickly repaid; the difference in infrastructure costs for fiber and copper is negligible, and construction costs are equivalent. Fiber greatly reduces future maintenance costs for the physical plant, thus it makes sense to deploy fiber to residences and businesses in Greenfield applications. Greenfield customers include:

Single-Dwelling Units (SDU) Multi-Dwelling Units (MDU). Small Business Units (SBU) Small/Medium Business Multi-Tenant Units (MTU).

Because of the nature of these new developments, a relatively high take-rate for second phone lines, data, and video services can be assumed, creating higher revenues and lowering the cost of deployment. Furthermore, due to the dense populations of FTTP customers in Greenfield applications, fiber can be cost-effectively run all the way from the CO to the Local Convergence Point (LCP), where the first passive split can be made.


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Overbuild

The Full Overbuild scenario is an FTTP application. Where market demand for advanced data and video services exists in serviced neighborhoods, it may be desirable to deploy fiber along with the existing copper network. The following factors can contribute to a decision to overbuild an existing plant:

Aging infrastructure. Projected high take-rates. Competitive pressures. Requirement for higher bandwidths than that available with the current copper technologies.

The objective of the Full Overbuild with fiber is to gradually transition all customers to the FTTP system, while in concurrent, retiring the aging copper plant and the active infrastructure such as Digital Loop Carrier (DLC).

Rehabilitation

The Rehabilitation scenario aims to save expenditure when there is insufficient justification for such. The aim is identical to that of the Greenfield scenario, and all services are provided to all customer premises. The difference is that Rehabilitation involves existing customers, served with existing services, and over an existing copper plant. Voice and data services are provided on the copper network, and video on an existing coaxial network, if such exists. FTTP and FTTN can be installed in close proximity to customer premises. Should there be a need for a high-speed data, it can be provided from the FTTN network to requesting customers prior to a direct fiber build to the customer. Auditing Your FTTP Network Deployment Successful FTTP deployment begins with building a solid network foundation. Here, we examine the objectives of your FTTP deployment, your network infrastructure considerations, and the operational requirements you may face by asking informed questions: After you’ve completed this audit and carefully examined the important aspects of FTTP deployment, call 1-866-210-1122 and let ADC answer your tough questions. 1. Do you have plans to deploy FTTP, or are you considering deploying FTTP?

_ Deploying now _ In the next 6 months _ In the next year _ Considering

1. Have you chosen a “Design Engineering” consultant?

_ Yes (Name: ) _ No _ Need assistance

3. Is your FTTP deployment...

_ Greenfield _ Overbuild _ Own overbuild _ Competitor _ Refurbish _ Unknown

4. Have you chosen an active component supplier?

_ Yes (name supplier) . _ No APON ( ) _ Need assistance _ GEPON ( ) _ BPON ( ) _ GPON ( ) _ P2P Ethernet ( ) _ Active Ethernet ( )


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5. Have you chosen a passive, outside plant (OSP) component supplier?

_ Yes (Name: ) _ No _ Need assistance

6. What business challenges lead you to consider FTTP? _ Increasing revenue/sales _ Retaining subscribers _ Supporting community quality of life _ Minimizing long-term maintenance costs by retiring copper plant _ Other ______________________

7. Have you built a business plan for FTTP? If so, what metrics do you target? (list metrics)

_ Revenue/subscriber (________________________) _ Cost/homes passed (________________________) _ MTTR- Mean-Time-To-Repair (____________ ___) _ Cost/truck roll (____________________________) _ Provisioning (______________________________) _ Other_______________________

8. Are you actively deploying other access technologies? Please check all that apply.

_ DSL _ Video _ Data services _ Voice services _ TI/T3 _ Wireless _ Satellite _ Other ___________

9. At what stage are your FTTP projects?

_ Activating service _ First office application and/or field trials _ Vendor selection _ Collecting information from vendors _ Securing funding/budgets _ Other ___________

10. What process will you use to select vendors?

_ RFI _ RFP/RFQ _ Sole source

11. What services will you offer over your FTTP network?

_ Voice _ TR008/GR303 _ Multiple lines _ T1/T3 (fractional T1) _ VoIP _ Video _ Video overlay with On-Demand/Pay-Per-View _ Video overlay without On-Demand/ Pay-Per-View _ QAM 256 _ Switched digital video _ HDTV _ IPTV


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_ Data (tiered service levels) _ Security _ Meter reading (municipalities and utilities) _ Interactive gaming _ Other ___________

12. Which architecture type are you deploying?

_ Passive Optical Network (PON) _ Point-to-Multipoint _ Point-to-Point Ethernet _ Point-to-Point ATM _ SONET Ring _ Other ___________

13. Which overall approach do you favor for your OSP network?

_ Aerial _ Direct burial _ Above ground cabinet _ Above ground access terminal (pedestal) _ Unknown

14. Which additional considerations do you favor for your OSP network?

_ Splicing _ Connectorization _ Combination of both _ Unknown _ Other _____________

15. Have you chosen a splitter architecture?

_ Distributed/Cascaded _ Centralized _ Unknown

16. How many “homes passed” does your FTTP network serve when fully deployed?

_ 100 or less _ 101 to 500 _ 501 to 1000 _ 1001 to 5000 _ 5001+

17. What initial “take-rate” is expected?

_ 0% _ 1% to 25% _ 26% to 50% _ 51% to 75% _ 76+

18. How many total subscribers do you expect your FTTP network to serve when fully deployed?

_ 100 or less _ 101 to 500 _ 501 to 1000 _ 1001 to 5000 _ 5001+


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19. If “currently deploying,” what percent of your potential subscribers are currently “turned up?” _ 0% _ 1% to 25% _ 26% to 50% _ 51% to 75% _ 76+

20. How would you rate the current state of fiber expertise among your technicians?

_ Excellent: They are thoroughly trained in FTTP and understand the nuances of fiber optic cable management and slack storage.

_ Fair: While some are experienced in FTTP, many technicians lack familiarity with the technology. _ Poor: We need to thoroughly train most of our staff in FTTP.

21. If you could offer FTTP now, what take-rates would you anticipate?

_ Less than 10% “homes passed” _ 10% to 24% “homes passed” _ 25% to 49% “homes passed” _ 50% or greater “homes passed”

22. What environmental extremes will your network face?

_ Temperature extremes _ Flooding _ Earthquakes/seismic activity _ Snow/ice _ Unknown

What would you say are the most critical FTTP challenges for you to overcome?

1.

2.

3. 23. What right-of-way constraints or community covenants impact your infrastructure options? (i.e. moratorium on “above ground” facilities, ROW federally mandated)

1.

2.

3.


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FTTH Council - Definition of Terms

Revision Date: August 2008 INTRODUCTION The mission of all the FTTH Councils in North America, Europe and Asia-Pac includes the communication to stakeholders in our respective regions of the extent of usage of FTTH throughout the world and forecasting the growth of FTTH. This task has been made difficult by the proliferation of terms and acronyms that, while no doubt useful to individual organizations for their specific purposes, lack precise definitions. This is of particular concern when different research organizations choose their own definitions when conducting research. As a consequence it becomes impossible to compare the research on FTTH between different regions, or between different studies of the same region. This document defines the terms used by all the FTTH Council’s (North-America, Europe, Asia-Pacific). To promote consistency when commissioning or commenting on research the Councils’ members will confine themselves to those terms defined in this document. This document specifically aims to reduce the terms used to a subset that are well defined, adequate and useful. THE TERMS Fiber-to-the-Home (FTTH)

“Fiber to the Home” is defined as a telecommunications architecture in which a communications path is provided over optical fiber cables extending from the telecommunications operator’s switching equipment to (at least) the boundary of the home living space or business office space. This communications path is provided for the purpose of carrying telecommunications traffic to one or more subscribers and for one or more services (for example Internet Access, Telephony and/or Video-Television). This definition excludes architectures where the optical fiber terminates in private space before reaching the home living space or business office space and where the access path continues to the subscriber over a physical medium other than optical fiber (for example copper loops). This definition excludes architectures where the optical fiber cable terminates in public space (for example an operator’s street-side cabinet) and where the access path continues to the subscriber over a physical medium other than optical fiber (for example copper loops). It is acknowledged that other parties such as the US FCC make specific concessions for such architectures. However, for the formal communications of the Councils, architectures that are excluded by this definition are NOT Fiber-to-the-Home.

Fiber-to-the-Building (FTTB)

“Fiber to the Building” is defined as a telecommunications architecture in which a communications path is provided over optical fiber cables extending from the telecommunications operator’s switching equipment to (at least) the boundary of the private property enclosing the home or business of the subscriber or set of subscribers, but where the optical fiber terminates before reaching the home living space or business office space and where the access path continues to the subscriber over a physical medium other than optical fiber (for example copper loops).


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FTTB construction is a transitional form commonly used as a means to deliver services to existing buildings in conjunction with associated FTTH construction (for example for new buildings). By introducing fiber cables from the fiber termination point to the home living space or business office space FTTB can be converted to full FTTH. Such a conversion is desirable as FTTH provides better capacity and longevity than FTTB. This communications path is provided for the purpose of carrying telecommunications traffic to one or more subscribers and for one or more services (for example Internet Access, Telephony and/or Video-Television). This definition excludes architectures where the optical fiber cable terminates in public space (for example an operator’s street-side cabinet) and where the access path continues to the subscriber over a physical medium other than optical fiber (for example copper loops). However, for the formal communications of the Councils, architectures that are excluded by this definition are NOT Fiber-to-the-Building.

Cable Plant Topology

The cable plant which connects the operators’ premises and subscribers’ premises can be deployed in the following different topologies: “Point-to-Point” (P2P) cable plant provides optical paths from the telecommunications operator’s switching equipment to a single contiguous location such that the optical paths are dedicated to traffic to and from this single location. In generic terms this is a star topology. “Point-to-Multipoint” (P2MP) cable plant provides branching optical paths from the telecommunications operators switching equipment to more than one contiguous location such that portions of the optical paths are shared by traffic to and from multiple locations. In generic terms this is a tree topology. “Ring” cable plant provides a sequence of optical paths in a closed loop that begins and ends at the telecommunications operators switching equipment and connects a series of more than one contiguous location such that portions of the optical paths are shared by traffic to and from several locations. A location is identified as being within the boundaries of the private property enclosing the home, business or premise of the subscriber or set of subscribers. Note that from these definitions it is not possible to identify the access protocol used over the cable plant. It is possible for a network to be built so that a common cable plant can include a mix of different topologies, or be re-configured over time to support different topologies, to allow for mixed user categories, to allow access diversity for reliability, and for future flexibility and network longevity.

Access Protocol

Access Protocols are the methods of communication used by the equipment located at the ends of the optical paths to ensure reliable and effective transmission and reception of information over the optical paths. These protocols are defined in detail by the standards organizations that have created them, and are recognized and implemented by manufacturers around the world. These definition of terms are to be used primarily within a Passive Optical Network (PON) where there are no or limited active components in the field. Networks may be passive where remote huts or cabinets are placed within a protected ring architecture and fiber may extend from these locations directly to the subscriber premises.


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The Access Protocols in use today for FTTH Networks and the optical portion of FTTB Networks are: “EFM” defined as Ethernet in the First Mile or Ethernet over P2P 100baseFX, 100baseLX, 100baseBX, 1000baseLX and 1000baseBX in IEEE 802.3ah “GEPON” defined as Gigabit Ethernet PON 1000basePX in IEEE802.3ah “BPON” defined as Broadband PON in ITU-T G.983 “GPON” defined as Gigabit PON in ITU-T G.984 “WDM PON” defined as a wavelength PON, not fully ratified under ITU-T at this time. Standards are being reviewed. “OTHER” access protocols such as proprietary or pre-standard access protocols may be noted for the purpose of completeness in research.

Network Usage

FTTH/FTTB Networks may be dedicated to the services of a single retail service provider, or made available to many retail service providers, who may connect to the network at the packet, wavelength or physical layer. “Exclusive Access” refers to the situation where a single retail service provider has exclusive use of the FTTH network. “Open Access (Packet)” refers to the situation where multiple retail service providers may use the FTTH Network by connecting at a packet layer interface and compete to offer their services to end users. “Open Access (Wavelength)” refers to the situation where multiple retail or wholesale service providers may use the FTTH Network by connecting at a wavelength layer interface and compete to offer their services. “Open Access (Fiber)” refers to the situation where multiple retail or wholesale service providers may use the FTTH Network by connecting at a physical layer (“dark” fiber) interface and compete to offer their services. “Open Access (Duct)” refers to the situation where multiple retail or wholesale service providers may share the use of a duct network covering a substantial region by drawing or blowing their fiber cables through the shared ducts, and compete to offer their services.

User Categories

FTTH/FTTB Networks may deliver services to the following categories of users: “Residential” refers to private users in their homes. Residential users may live in “MDU” (multi-dwelling units such as apartments/condominiums) or “SFU” (single family dwelling units such as stand-alone houses/villas/landed property). “Business” refers to large (corporate), medium, and small (Small Business, Small Office Home Office) business users. Businesses may occupy “MTU” (multi-tenanted units such as office blocks/towers) or “STU” (single-tenanted units such as a stand-alone office building or warehouse).


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NETWORK SIZE

The size of FTTH/FTTB Networks is described in the following terms: The number of “Homes/Premises Passed” is the number of residential and business premises to which an operator can currently deliver FTTH access within the operator’s standard service activation period (for example 30 days) should the owners/occupiers sign a contract for an access service. Typically new service activation will require the installation and/or connection of a drop cable from the street or basement to the home or office, and the installation of subscriber premises equipment. The network that is determined to be “drop ready” is considered to be a Homes/Premises Passed.” This definition excludes premises that cannot be connected without further installation of substantial cable plant such as feeder and distribution cables to reach the area in which a potential new subscriber is located. The number of “Homes/Premises Connected” is the number of residential and business premises to which an operator is supplying FTTH access under a commercial contract. The “Take-up Rate” or “Take Rate” for a network is calculated by the simple division of “Home/Premises Connected” by “Home/Premises Passed”, and is expressed as a percentage.

SERVICES

FTTH/FTTP Networks are used to deliver the following services: “Internet” refers to use of the Public Internet for exchanging email, web-browsing, etc. “Voice” refers to the exchange of human conversations by use of “IP” or “Other” encoding and transport protocols. (This category does not include Voice carried over the Public Internet.) “Video” refers to the exchange of visual material by use of “IP”, “RF” (carried via a separate optical wavelength) or “Other” encoding and transport protocols. (This category does not include Video carried over the Public Internet.) “Internet Video” Internet video is defined as any video being delivered using IP protocols over the internet. The video can range from download to streaming content. The video can also come in many forms ranging from standard MPEG2 and MPEG4 to WMV, AVI and MOV. It could also include raw digital video. The video can be supplied by any server on the internet. Most of these systems are open and available to anyone on the internet. Some may require membership or user login. “IPTV (IP-based TV)” The transmission of TV programs from private Internet providers such as cable and telephone companies or from a Web site using IP protocols over an IP network. Also called "TV over IP" or “Video over IP,” IPTV uses streaming video techniques to deliver scheduled TV programs. Unlike transmitting over the air or via standard cable to a TV set, IPTV uses the IP protocol as the delivery transport and requires a user’s device (Set Top Box or Mobile Video Device) to decode the images in real-time. In the IPTV environment, the user only receives the “channel’ that is being viewed. “IPTV Broadcast Video (IBV)” A set of network devices that encode broadcast channels, such as ESPN, CNN, History Channel, network broadcasts (ABC, NBC, CBS, Fox, PBS, etc.), Discover Channel, Disney, etc., using MPEG2 or MPEG4 encoding and distributed using IP multicast protocols over an IP network. These IP streams are transported over a broadband connection to the user and decoded at the user’s device (Set Top Box or Mobile Video Device). The multicast


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streams for a specific broadcast maybe different for the STB and the Mobile Video device. This would allow the BVS to provide encoding for a specific type of device. “IPTV Distribution System” The system used to distribute IPTV ‘channels’ from the Broadcast Video Server to the end users. The system consists of the headend (video acquisition system, encoders & video on demand servers), content management & Digital Rights Management (DRM), and IP fiber backbone & edge routers. The distribution system also includes a set of protocols used for content delivery to the end user. These protocols can be open, standard, proprietary, or a combination. This system is closed and available only to subscribers. “Personal Video Recorder” This is a device that allows trick plays on live content by recording all content to a hard drive. May be local (in the Set top) or in the network. Initial offering by TiVO. Video on Demand (VoD): Video on Demand systems allow users to select and watch stored video content over an IP network as part of an interactive television system. VOD systems are either "streaming", in which the video is streamed over the IP network to the user, or "download", in which the program is downloaded in its entirety to the user’s device (Set Top Box or Mobile Video Device) before viewing starts. VoD uses unicast IP protocols to deliver the Video to the end user. Video on Demand systems allow the user to pause, fast forward, fast rewind, slow forward, slow rewind, jump to previous/future frame etc (trick play) Applications other than those listed above are categorized as “Other”.

CONCLUSION The intention of this document is to make it possible for Council Members and the FTTH industry to speak a common language when discussing FTTH statistics and network characteristics. No doubt Council members and other stakeholders will feel the need to use a wide range of terms for technical solutions, concepts, and models. This document does not discourage this activity, as it is inherent in the free flow of communication on which our industry thrives. However to be successful, the terms defined in this document must be used frequently and consistently. Thus all Council Members and other stakeholders such as operators, analysts, journalists, and government and regulatory staff are encouraged to use these terms as the well-defined vocabulary that underpins the more general expressions. With regards to Market Research however, in order for research by different organizations conducted in the same or different regions to be meaningfully compared, it is essential that these terms are used and no others.

Design Questions


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Typically with any change in infrastructure, there are a number of assumptions or design questions that will arise. Below are only a few:

1. How many homes do you plan to serve out of each local convergence PON cabinet? • Is the Serving Area Greenfield or Overbuild Area? • If this is an Overbuild Area, are you overbuilding yourself or your competitor? • Is the Serving Area a single family or multi dwelling development or mix? • For Greenfield applications, is the Serving Area being developed in phases? • What is the total Serving Area Size? • Are the Serving Area Size and Distribution Area (DA) Size the same? (If different,

explain.)

2. Are you planning on “sparing” any fibers for the Feeder (F1) Fiber and/or the Distribution (F2) Fiber? • For Feeder Fiber sparing, there is no “rule-of-thumb” for count and size. Typically, the

sparing in the feeder fiber is accomplished by capitalizing on the buffer tube count. (i.e. The PON Cabinet that serves 216 subscribers. For this style of Cabinet, you would need 6.75 feeder fibers [216/32=6.75]. You will probably use some sparing of the Distribution (F2) fiber so in providing services for say, 192 subscribers, you will need only six (2) Feeder (F2) Fibers. However, connectorized and/or splice input feeder trays accept twelve (12) fibers (one buffer tube), and the buffer tube fiber count is generally twelve (12) fibers. Here, you would use this count, six (6) fibers for the distribution serving area (SA), and six (6) fibers as spare.)

• Service Providers today use sparing within the distribution (F2) on the order of 1.125 to 1.5 fibers per subscriber. Cabinets can be sized at 1.2 fibers per home (In some cases, up to 1.5 fibers per home.) (i. e. Example 1: The Cabinets that have two (2) 72-port pre-terminated panels for 144 distribution fibers. The centralized splitter configuration calls for four (4) 1x32 splitter couplers which will account for 128 subscribers. Here, we have 1.125 fibers per subscriber. Example 2: Another Cabinet has three (3) 72-port pre-terminated panels for 216 distribution fibers. The centralized splitter configuration calls for six (6) 1x32 splitter couplers which will account for 192 subscribers. Here again, we have 1.125 fibers per subscriber.) In both Example 1 and Example 2, the service provider is sparing within the cabinets. Some sparing may actually be in the distribution (F2) fiber itself. In Example 2, the cabinet supports 216 subscribers (only 192 subscribers used), where the distribution (F2) fiber count may be a 288-count fiber. Here, this will show 288/192=1.5 fibers per subscriber.


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Additional Assumptions and/or Questions for FTTx Projects With any project in the Outside Plant, additional assumptions may need to be understood. Below are just a few assumptions that may arise during the initial design stages.

- Is this a green field location with few placement obstacles? - What are the RW restrictions? - Very few placement restrictions – all Rights of Way (RW) are open for front and rear cable

placements. - Is cable placement along the interstate highway considered as a useable path? - Will above ground pedestals or below ground terminals be used for distribution cabling and drop

cables? - Will the drop cables will be connectorized or spliced at the pedestals? - Will 8”, 10” or 12” pedestals be used at the drop locations? - Will 12” pedestals will be used at drop/splice locations? - Will multi-fiber service terminals will be used at the drop locations? - For single family homes and town homes, how many spare fibers per residence? - Will each townhouse unit will be served individually or with MDU electronics? - Will the drops to the residential homes be placed from pedestals directly to each home? - For the business and industrial locations – Assume that at least two fibers are available for each lot

and approximately 1 spare per terminal. - Are copper facilities planned or needed in the development? - What is the distance of the feeder (F1) cable from the central office to the fiber distribution terminal

(local convergence point)? - Is the serving area (SA) fed by the feeder (F1) cable only, where no additional cables are placed

for large scale additions in the area – Is this area the end of the central office boundary? - Assume that common sized cables are used for better pricing (12, 24, 48, 96, 144, 218, 288, 384) - Assume that the cable count shown as an example of 24 F cable (i.e. 1-12 , 12DD) cable has 12

fibers active and 12 dead - For the video service solution, will the video be IP video or video overlay (RF Video)? - Is this a field trial? (equipment available? when needed in 2006/2007?) - All initial cost shown on the spread sheet are list prices. - Total pricing is based on total IP solution or mix. - Assume that the take rate for services are between 25%-30%. - What is the take rate for services? - The developer and/or service provider are committed to provide all home owners services, 100%

whether they use them or not. - What is the type of infrastructure placements? Buried, aerial, using above ground pedestals or all

out of sight below ground? - Is joint trenching with power company or others available? - 1 foot minimum separation from buried power cables. - 40-inch separation from the neutral for aerial cable placement. - Is locating drop cables a needed capability? - Are pass through capabilities needed? For business or special offerings. - Is your PON design for EFM, GEPON, BPON, GPON or WDM PON Design solution? - Are you designing the network for Active Ethernet? - Who is the active component provider (OLT/ONT)?


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Telcordia Reference Model The governing body of BellCore (Telcordia) has determined through GR-909 that specific definitions and practices for FTTH should be followed. Below are the most current definitions provided by Telcordia.

Telcordia Reference Model for FTTH

Exhibit 2. Reference Architecture from Telcordia GR-909 Release 2005

Telcordia Reference Definitions

• Application Environment: Residential and Small Business (large multi-dwelling unit and multi-tenant unit applications may be added in future.) From an earlier slide detailing end customers, for the residential community, the Segments, Services and Interfaces will include the Single Family and MDU Markets, while the business community will include the Retail and MTU Markets.

• ONT Definition: An ONT is an ONU which is the customer network interface device (NID)

located on customer premises that serves a single LEC customer. • ONT Ownership: ONTs are network equipment owned by the LEC, but in the future, may

become part of the customer-owned equipment. • ONT Powering: Primary and backup powering of ONTs is provided by the customer.


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• Digital Video Support with an Analog Video Overlay: If an analog video overlay is supported, digital video services will by provided via sub-carrier multiplexing on the AM-VSB system and not using baseband digital video transport on the FITL system. The RF Return can be provided as an IP return for VOD services.

• FTTB Definition – Fiber-to-the-Building, here the ONU is either attached to or located within a

building and serves multiple LEC customers. Applications include residential multi-dwelling unit (MDU) and business multi-tenet unit (MTU) buildings.

CABLE AND DROP WIRE SELECTION PROCESS Cable Design Considerations In order to select the correct fiber optic cable design for one’s planned application, the following should be asked and determined: “Is the planned infrastructure to be aerial, buried, or underground plant, or a combination of two, or all three?” “Is there a preference to use a dielectric cable or a metallic cable?” Then ask and determine: “Are there specific cable designs for each type of plant infrastructure?” The answer is no! The present day cable construction, both dielectric and metallic, can be used in aerial, buried, or underground plant. “The choice between Dielectric and metallic.” The dielectric cable requires no protection from foreign voltages, lightning strikes, etc., plus the sheath preparation time is much less than metallic. The metallic cable design requires the application of bonding and grounding hardware to provide a field of safety for those who work on these cable sheaths, as well as protection of the electronic equipment that the cable connects to on each end. The selection process for feeder, backbone/trunk, distribution cables, and the connecting drop wire.

FEEDER CABLE In making the first step toward selecting the proper feeder cable design, what are the key considerations?

A. When high-count fiber cables are required (such as 144 fibers to 864 fibers) the DriTube ribbon cable design will provide high productivity when applied with the mass fusion splicing method. It will also utilize minimal splice closure space.

B. Fiber requirements below the 144f count can be packaged in a DriCore loose-tube design. The

benefits of mass fusion splicing can still be attained in using this cable, by applying the ribbonizing method to the individual fibers contained within the buffer tubes.

C. The central office or head-end patch-panel terminations are best served by being equipped with DriTube ribbon cables, in both an FT-4 cable design (OFNR) (Sumitomo) and an Indoor/Outdoor cable design. The use of this cable design will enhance productivity of labor through the mass fusion splicing method.


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BACKBONE/ TRUNK CABLE As one gets deeper into the network, the use of backbone / trunk cables (96 fibers to 288 fibers) is utilized to distribute the feeder fibers. This cable can serve as a combination backbone / trunk cable and a distribution cable. When selecting the correct cable design for this application, the following should be considered.

A. When deploying any type of cross-connect housing, splitter housing, etc., most stubs from these types of apparatus are equipped as ribbon cable. Here again the benefits of mass fusion splicing are achieved when the backbone / trunk cables meet the stubs of these units.

B. The design of the distribution terminals that are being deployed in concert with the stubbed

products, will also have an impact on selecting the cable design to use in the backbone / trunk application. Those terminals with ribbon fanouts will mate well with ribbon cables, while those terminals equipped with single fusion pigtails (when less than four pigtails) will mate well with loose-tube cables.

DISTRIBUTION CABLE Within the deepest area of the network lies the distribution area, where fiber counts of 12 to 72 fibers are typical. In determining which cable design to apply, ribbon DriTube, Loose-Tube DriCore, or filled central tube Bundle cable, the design of the terminal and its splicing method should be considered. The following information should be relevant in selecting a cable product:

A. Aerial Taut Sheath Splicing. In selecting a loose-tube cable for this application, the spacing of and the identification method for the ROL (reverse oscillation lay) of the buffer tubes, is important. The unraveling of the buffer tubes at the ROL will provide the maximum in fiber slack during the splicing operation.

B. In using the ribbon product in this scenario, there is no need to locate a rol-type location. When

compared to the buffer tube accessing operation, the ribbon design yields less fiber slack. The access time to reach fibers in the loose-tube and ribbon cable is about the same.

C. When selecting the filled central tube bundled cable, here again there is no need to locate a rol-

type location. There is also no need to spend time accessing packaging such as a buffer tube or ribbon, to get at the individual fibers. The fiber slack yield is comparable to that of loose tube cables.

Slack Available in Aerial, Buried, and Underground Splicing Operations. Where cable slack is provided during the placing operation, the choice of loose-tube , ribbon, or bundled cables is influenced by the following:

A. Splice closure or terminal design. Fanout or pigtail, plus storage capacity.

B. Single fusion or mass fusion (4,8,&12 fibers)

C. The need for fiber access tools. FIBER DROP WIRE, 1 TO 12 FIBERS The final step in building an FTTP / FTTH connection is to select the proper drop wire for use in this application which brings the customer to the service structure. The choices are as follows:

• Aerial self-supporting drop wire - Aerial dielectric drop wire • Buried dielectric drop wire - Locatable buried drop wire


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The termination methods of pre connectorized; raw-end splice to fiber; raw-end splice to pigtail; are all common with the four designs listed above. For aerial drop wire applications, the following information must be known.

• What storm loading area applies? Heavy, medium, or light. • What span lengths are there to be met? • What flammability standard is required? • What is the attachment hardware preference? • What sheath access tools are required? • What are the bonding and grounding requirements of the area?

For aerial spans, the following applies.

• Heavy storm loading area, self-supporting span maximum is 300 feet, and the dielectric maximum is 75 feet.

• Medium storm loading area, self-supporting maximum is 500 feet, and the dielectric maximum is 150 feet.

• Light storm loading area, self-supporting span maximum is 750 feet, and the dielectric maximum is 250 feet.

• Self-supporting drop wire design requires a wire-vise type attachment hardware along with insulation hardware.

• Dielectric drop wire requires a clamping-type device for attachments. For the buried drop wire application, which can be plowed, trenched, or pulled into conduit, the following is information that should be known when selecting between the two designs.

• Is the drop wire required to be locatable? • If the drop wire is not required to be locatable, the standard dielectric drop should be selected.

Enabling Technologies for PON Due to the topology of PON, the transmission modes for downstream (i.e., from OLT to ONT) and upstream (i.e., from ONT to OLT) are different. For the downstream transmission, the OLT broadcasts optical signal to all the ONTs in continuous mode (CM), i.e., the downstream channel always has optical data signal. However, in the upstream channel, ONTs can not transmit optical data signal in CM. It is because that all the signals transmitted from the ONTs converge (with attenuation) into one fiber by the power splitter (serving as power coupler), and overlap among themselves if CM is used. To solve this problem, burst mode (BM) transmission is adopted for upstream channel. The given ONT only transmits optical packet when it is allocated a time slot and it needs to transmit, and all the ONTs share the upstream channel in the time division multiplexing (TDM) mode. The phases of the BM optical packets received by the OLT are different from packet to packet, since the ONTs are not synchronized to transmit optical packet in the same phase, and the distance between OLT and given ONT are random. Besides the characteristics of random phases in the burst mode packets, the other issue is about the amplitudes of the received packets. Since the distance between the OLT and ONTs are not fixed, the optical packets received by the OLT have different amplitudes, supposing the transmitted optical powers of the packets at ONT sides are similar. In order to compensate the phase variation and amplitude variation in a short time (e.g., within 40 ns for GPON), burst mode clock and data recovery (BM-CDR) and burst mode amplifier (e.g., burst mode TIA) need to be employed, respectively. Furthermore, the BM transmission mode requires the transmitter works in burst mode, and such burst mode transmitter shall be able to turn on and off in short time. The below three kinds of circuitries in PON are quite different from their counterparts in the point-to-point continuous mode optical communication link.


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PON Glossary Below is a glossary of terms that are frequently used within the PON environment. It contains many of the terms also associated with various parts of the Access Network of which PON is one type. Access Network The method, time, circuit, or facility used to enter the network. The service provided by local exchange carriers or alternate access providers, which connect an interexchange carrier with its customers. The Access Network today is predominantly passive twisted pair copper wiring. ADM Add/Drop Multiplexer capable of extracting or inserting lower-bit-rate signal from a higher-bit-rate multiplexed signal without completely demultiplexing the signal. ADSL Asymmetric Digital Subscriber Line transmits data asymmetrically meaning the bandwidth usage is much higher in one direction than the other. Typical ADSL applications transmit 8 Mbps downstream and 768Kbps upstream, depending on the length of the local twisted pair loop. This is particularly beneficial for residential Internet access, remote access and video on demand because downstream usage far exceeds upstream usage. ADSL2+ Asymmetric Digital Subscriber Line Two Plus (ADSL2+) extends the capability of basic ADSL by doubling the number of downstream bits. The data rates can be as high as 24 Mbit/s downstream and 1 Mbit/s upstream depending on the distance from the DSLAM to the customer's home.

ADSL2+ is capable of doubling the frequency band of typical ADSL connections from 1.1 MHz to 2.2 MHz. This doubles the downstream data rates of the previous ADSL2 standard of up to 12 Mbit/s, but like the previous standards will degrade from its peak bitrate after a certain distance.

Also ADSL2+ allows port bonding. This is where multiple ports are physically provisioned to the end user and the total bandwidth is equal to the sum of all provisioned ports. So if 2 lines capable of 24 Mbit/s were bonded the end result would be a connection capable of 48 Mbit/s. Not all DSLAM Vendors have implemented this functionality. ADSL2+ port bonding is also known as g.998.x or g.Bond

APON An Asynchronous Transfer Mode (ATM) based Passive Optical Network (PON). ATM Asynchronous Transfer Mode is a connection-oriented service that segments data into a succession of small units called cells. Data transmitted from multiple sources is segmented into cells by the ATM network device, and the cells are then interleaved onto a single transmission media. It is asynchronous in the sense that the recurrence of cells depends upon the required or instantaneous bit rate. See also TDM and packet switching. Backbone The part of a network used as the primary path for transporting traffic between network segments. A high-speed line - or series of connections - that forms a major pathway within a network. Bandwidth The throughput, or ability to move information through or from a device, system or subsystem tem, usually measured in quantities of data per second. A measure of the information-carrying capacity of a communications channel; range of usable frequencies that can be carried by a system, corresponding to the difference between the lowest and highest frequency signal that can be carried by the channel. BLEC Building Local Exchange Carrier B-PON Broadband Passive Optical Network (PON) Broadcast One-to-all transmission where the source sends one copy of the message to all nodes, whether they wish to receive it or not.


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CATV CATV (originally "community antenna television," now often "community access television") is more commonly known as "cable TV." In addition to bringing television programs to those millions of people throughout the world who are connected to a community antenna, cable TV is an increasingly popular way to interact with the World Wide Web and other new forms of multimedia information and entertainment services. Cell A unit of transmission in ATM. A fixed-size frame consisting of a 5-octet header and a 48-octet payload. Cell Delay Variation (CDV) CDV is a component of cell transfer delay, induced by buffering and cell scheduling. Peak-to-peak CDV is a QoS delay parameter associated with CBR and VBR services. The peak-to-peak CDV is the ((1-a) quintile of the CTD) minus the fixed CTD that could be experienced by any delivered cell on a connection during the entire connection holding time. The parameter “a” is the probability of a cell arriving late. CLEC (Competitive Local Exchange Carrier) In the United States, a CLEC (competitive local exchange carrier) is a company that competes with the already established local telephone business by providing its own network and switching. CO The Central Office is where communications common carriers terminate customer lines and locate switching equipment that interconnects those lines. Also, considered a location where Switching, Transmission and Power equipment that provide telephone service is centralized. Coaxial Cable A type of cable with a center conductor, an insulator, a solid or braided shield around this insulator with a tough jacket on the outside. The inner insulation provides a constant distance between the center conductor and the shielding, providing a superior quality signal over longer distances, which gives higher bandwidth and better immunity to external interference than simple twisted pair cable provides. Connection Admission Control (CAC) The set of actions taken by the network during the call setup phase (or during call renegotiation phase) in order to determine whether a connection request can be accepted or should be rejected (or whether a request for re-allocation can be accomplished). Constant Bit Rate (CBR) An ATM service category, which supports a constant or guaranteed rate to transport services such as video or voice as well as circuit emulation that requires rigorous timing control and performance parameters. QoS Parameter typically used for voice traffic. Core Network See backbone Coupler Fused fiber device that optically splits and multiplexes signals. The couplers used in the PON outside plant network are basically power splitter wherein the power from the OLT is sent into different branches of the network to feed the ONTs based upon their distance from the OLT. Another type of coupler/splitter is used to separate the incoming and outgoing signals into their respective wavelengths at the OLT and ONT. This is a WDM coupler/splitter and is sometimes referred to as an optical multiplexer/deplexer. CSMA/CA In computer networking, CSMA/CA belongs to a class of protocols called multiple access methods. CSMA/CA stands for: Carrier Sense Multiple Access With Collision Avoidance. In CSMA, a station wishing to transmit has to first listen to the channel for a predetermined amount of time so as to check for any activity on the channel. If the channel is sensed "idle" then the station is permitted to transmit. If the channel is sensed as "busy" the station has to defer its transmission. This is the essence of both CSMA/CA and CSMA/CD. In CSMA/CA (LocalTalk), once the channel is clear, a station sends a signal telling all other stations not to transmit, and then sends its packet. In Ethernet 802.11, the station continues to wait for a time, and checks to see if the channel is still free. If it is free, the station transmits, and waits for an acknowledgment signal that the packet was received.

CSMA/CA is a modification of pure Carrier Sense Multiple Access (CSMA). Collision avoidance is used to improve the performance of CSMA by attempting to be less "greedy" on the channel. If the channel is sensed busy before transmission then the transmission is deferred for a "random" interval. This reduces the probability of collisions on the channel.


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CSMA/CA is used where CSMA/CD cannot be implemented due to the nature of the channel. CSMA/CA is used in 802.11 based wireless LANs. One of the problems of wireless LANs is that it is not possible to listen while sending, therefore collision detection is not possible. Another reason is the hidden terminal problem, whereby a node A, in range of the receiver R, is not in range of the sender S, and therefore cannot know that S is transmitting to R.

CSMA/CA can optionally be supplemented by the exchange of a Request to Send (RTS) packet sent by the sender S, and a Clear to Send (CTS) packet sent by the intended receiver R, alerting all nodes within range of the sender, the receiver, or both, to keep quiet for the duration of the main packet. This is known as the IEEE 802.11 RTS/CTS exchange.

CSMA/CD In computer networking, Carrier Sense Multiple Access With Collision Detection (CSMA/CD) is a network control protocol in which

• a carrier sensing scheme is used. • a transmitting data station that detects another signal while transmitting a frame, stops transmitting that frame,

transmits a jam signal, and then waits for a random time interval (known as "backoff delay" and determined using the truncated binary exponential backoff algorithm) before trying to send that frame again.

CSMA/CD is a modification of pure Carrier Sense Multiple Access (CSMA).

Collision detection is used to improve CSMA performance by terminating transmission as soon as a collision is detected, and reducing the probability of a second collision on retry.

Methods for collision detection are media dependent, but on an electrical bus such as Ethernet, collisions can be detected by comparing transmitted data with received data. If they differ, another transmitter is overlaying the first transmitter's signal (a collision), and transmission terminates immediately. A jam signal is sent which will cause all transmitters to back off by random intervals, reducing the probability of a collision when the first retry is attempted. CSMA/CD is a layer 2 protocol in the OSI model.

Ethernet is the classic CSMA/CD protocol. See also the similar Carrier sense multiple access with collision avoidance (CSMA/CA) protocol.

CWDM Coarse wavelength division multiplexing (CWDM) is a method of combining multiple signals on laser beams at various wavelengths for transmission along fiber optic cables, such that the number of channels is fewer than in dense wavelength division multiplexing (DWDM) but more than in standard wavelength division multiplexing (WDM).

CWDM systems have channels at wavelengths spaced 20 nanometers (nm) apart, compared with 0.4 nm spacing for DWDM. This allows the use of low-cost, uncooled lasers for CWDM. In a typical CWDM system, laser emissions occur on eight channels at eight defined wavelengths: 1610 nm, 1590 nm, 1570 nm, 1550 nm, 1530 nm, 1510 nm, 1490 nm, and 1470 nm. But up to 18 different channels are allowed, with wavelengths ranging down to 1270 nm.

The energy from the lasers in a CWDM system is spread out over a larger range of wavelengths than is the energy from the lasers in a DWDM system. The tolerance (extent of wavelength imprecision or variability) in a CWDM laser is up to ± 3 nm, whereas in a DWDM laser the tolerance is much tighter. Because of the use of lasers with lower precision, a CWDM system is less expensive and consumes less power than a DWDM system. However, the maximum realizable distance between nodes is smaller with CWDM

Cyclic Redundancy Check (CRC) A mathematical algorithm commonly implemented as a cyclic shift register that computes a check field for a block of data. The sender transmits this check field along with the data so that the receiver can either detect errors, and in some cases even correct errors. Dark Fiber Dark fiber refers to unused fiber-optic cable. Often times companies lay more lines than what's needed in order to curb costs of having to do it again and again. The dark strands can be leased to individuals or other companies who want to establish optical connections among their own locations. In this case, the fiber is neither controlled by nor connected to the phone company. Instead, the company or individual provides the necessary components to make it functional.


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dBm Decibels in Milliwatts (dBm) Again, for the design engineer who is designing for the Passive Optical Network, the power out for most of the electronics is typically stated as decibels in Milliwatts, or dBm. Here, you see a table that is expressed in milliwatts of power, and the conversion to dBm. For most of us, when we talk about the optical power as in a system output power of 1 milliwatt, what we are saying is that the output power is 0 dBm. When we start calculating the link loss budget of a network in combination with the receiver specifications dictated by the active component providers we may think that if we increase the output power so the attenuation or loss is negated, then we can go unlimited distances with unlimited bandwidths. Because of some dispersion and scattering concepts, this is not so. Also in our link loss calculations, we will see when using the video overlay on the 1550 nanometer wavelength, the output power of the electronics will be stated as approximately 20 dBm or 100 milliwatts. 20 dBm of power is in the classification of lasers that can cause injury.

Table 1 Decibel Table Conversion: dBm = dB milliwatt = 10 x Log10 (Power in mW / 1 mW)

DLC Digital Loop Carrier DS0 Digital Signal level Zero: One 64 Kb channel DS1 Digital Signal level 1: 24 data channels (64 Kb) and 8 Kb for signaling; total data rate of 1.544 Mbps DS3 Digital Signal level 3: 28 DS1s encapsulated; 44.736 Mbps data rate. DSL Digital Subscriber Line is a method of providing high-speed data services over the twisted pair copper wires traditionally used to provide POTS. Types of DSL include ADSL (asymmetric digital subscriber line), HDSL (high data rate digital subscriber line), SDSL (single line digital subscriber line), and VDSL (very high data rate digital subscriber line). DSLAM Digital Subscriber Line Access Multiplexer Provides high-speed Internet or Intranet access over traditional twisted-pair telephone wiring through the use of ADSL technology. Provides simultaneous high-speed digital data access and POTS analog service over the same twisted-pair telephone line. Can be installed in the CO or at and ISP adjacent to the CO DWDM Dense Wave Division Multiplexing is an optical multiplexing technique used to increase the carrying capacity of a fiber network beyond what can currently be accomplished by time division multiplexing (TDM) techniques. Different wavelengths of light are used to transmit multiple streams of information along a single fiber with minimal interference.

Power Ratio dBm = 10 x Log10 (Power in mW / 1 mW) dBm 1 mW 1 mW/1mW=1 0 dBm = 10 x Log10 (1) 0dBm

2 mW 2 mW/1mW=2 3 dBm = 10 x Log10 (2) 3dBm



100mW 100 mW/1mW=100 20 dBm = 10 x Log10 (100) 20dBm

1 W 1000 mW/1mW=1000 30 dBm = 10 x Log10 (1000) 30dBm

10 W 10000mW/1mW=10000 40 dBm = 10 x Log10 (10000) 40dBm


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Dense wavelength division multiplexing (DWDM) is a technology that puts data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength. Using DWDM, up to 80 (and theoretically more) separate wavelengths or channels of data can be multiplexed into a lightstream transmitted on a single optical fiber. Each channel carries a time division multiplexed (TDM) signal. In a system with each channel carrying 2.5 Gbps (billion bits per second), up to 200 billion bits can be delivered a second by the optical fiber. DWDM is also sometimes called wave division multiplexing (WDM).

Since each channel is demultiplexed at the end of the transmission back into the original source, different data formats being transmitted at different data rates can be transmitted together. Specifically, Internet (IP) data, Synchronous Optical Network data (SONET), and asynchronous transfer mode (ATM) data can all be travelling at the same time within the optical fiber.

DWDM promises to solve the "fiber exhaust" problem and is expected to be the central technology in the all-optical networks of the future.

DWS DWS (Dynamic Wave Slicing™) extends WDM (Wave Division Multiplexing) by "slicing" each wavelength so that it can serve multiple end points (customers). This provides a division of available bandwidth over a PON by enabling a single fiber segment to allocate bandwidth to multiple customers according to their particular needs (from 1.7 to 100 Mbps in 1.7 Mbps increments). This provides effective utilization of the total capacity of the fiber optic media. Easement An easement is the right to use another person's land for a stated purpose. It can involve a general or specific portion of the property. EPON Ethernet based Passive Optical Network (PON). (IEEE 802.3ah) Ratified in 2004, EPON is the standard of the Institute of Electrical and Electronics Engineers Inc. (IEEE). Running at 1.25 Gbps symmetric, it is highly suitable for data services. EPON uses IP rather than ATM data encapsulation. Erbium-Doped Fiber Amplifier (EDFA) A key enabling technology of DWDM, EDFAs allow the simultaneous amplification of multiple signals in the 15xx nanometer region, e.g. multiple 2.5 Gbps channels, in the optical domain. EDFAs drastically increase the spacing required between regenerators, which are costly network elements because they (1) require optical/electrical/optical conversion of a signal and (2) operate on a single digital signal, e.g. a single SONET or SDH optical signal. DWDM systems using EDFAs can increase regenerator spacing of transmissions to 500-800 km at 2.5 Gbps. EDFAs are far less expensive than regenerators and can typically be spaced 80-120 km apart at 2.5 Gbps , depending on the quality of the fiber plant and the design goals of the DWDM system. Ethernet A LAN used to connect devices within a single building or campus at speeds up to 10 Mbps. Within the OSI model, Ethernet is defined at layer one (physical) and layer two (data link). Based on Carrier Sense Multiple Access/Collision Detection (CSMA/CD), Ethernet works by simply checking the wire before sending data. Sometimes two stations send at precisely the same time in which case a collision is detected and retransmission is attempted. EFM (Ethernet in the First Mile or Ethernet over P2P) In the context of an optical access network, this term describes and architecture in which all optical links are from one point to another, without optical branching. However branching can be (and usually is) done at an intermediate point by way of an active device. The intermediate active device can be located anywhere in the network including the central office or a curb side enclosure. Fiber Access Terminal (FAT) A fiber optic access point sometimes referred to as a network access point (NAP). This may be in the form of an above ground pedestal, and aerial or buried splice closure. Fiber Distribution Hub/Terminal (FDH/FDT) A fiber optic distribution point sometimes referred to as a fiber service area interface (FSAI), service area interface (SAI), or local convergence point (LCP). This is an area where the primary optical feeder fibers and secondary optical distribution feeders are facilitated or combined.


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Fiber Optic Cable A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves. Fiber optics has several advantages over traditional metal communications lines: Fiber optic cables have a much greater bandwidth than metal cables. This means that they can carry more data. Fiber optic cables are less susceptible than metal cables to interference. Fiber optic cables are much thinner and lighter than metal wires. Data can be transmitted digitally (the natural form for computer data) rather than analogically. Fibre Channel Fibre Channel is an industry standard technology for transmitting data between computer devices at up to 1.0625 Gbps and over 10 km in distance. Fibre Channel is optimized for connecting servers to shared storage devices and for interconnecting storage controllers and drives. Fibre Channel utilizes either an optical fiber or copper connection. FTTB Fiber to the Business/Basement FTTC Fiber to the Curb/Cabinet Fiber to the curb (FTTC) is a telecommunications system based on fiber-optic cables run to a platform that serves several customers. Each of these customers has a connection to this platform via coaxial cable or twisted pair.

Fiber to the curb allows delivery of broadband services such as high speed internet. High speed communications protocols such as broadband cable access (typically DOCSIS) or some form of DSL are used between the cabinet and the customers. The data rates vary according to the exact protocol used and according to how close the customer is to the cabinet.

FTTC is subtly distinct from FTTN or FTTP (all are versions of Fiber in the Loop). The chief difference is the placement of the cabinet. FTTC will be placed near the "curb" which differs from FTTN which is placed far from the customer and FTTP which is placed right at the serving location.

Unlike the competing fiber to the premises (FTTP) technology, fiber to the curb can use the existing coaxial or twisted pair infrastructure to provide last mile service. For this reason, fiber to the curb costs less to deploy. However, it also has lower bandwidth potential than fiber to the premises.

In the United States of America, the largest deployment of FTTC was carried out by BellSouth Telecommunications. With the acquisition of BellSouth by AT&T, deployment of FTTC will end. Future deployments will be based on either FTTN or FTTP. Existing FTTC plant may be removed and replaced with FTTP.[5]

FTTN Fiber to the Node (FTTN), also called fiber to the neighborhood or fiber to the cabinet (FTTCab),[3] is a telecommunication architecture based on fiber-optic cables run to a cabinet serving a neighborhood. Customers connect to this cabinet using traditional coaxial cable or twisted pair wiring. The area served by the cabinet is usually less than 1,500 m in radius and can contain several hundred customers. (If the cabinet serves an area of less than 300 m in radius then the architecture is typically called fiber to the curb.)[4]

Fiber to the node allows delivery of broadband services such as high speed internet. High speed communications protocols such as broadband cable access (typically DOCSIS) or some form of DSL are used between the cabinet and the customers. The data rates vary according to the exact protocol used and according to how close the customer is to the cabinet.

Unlike the competing fiber to the premises (FTTP) technology, fiber to the node can use the existing coaxial or twisted pair infrastructure to provide last mile service. For this reason, fiber to the node costs less to deploy. However, it also has lower bandwidth potential than fiber to the premises. FTTX Fiber to the "x" c/b/h/k FSAN Full Service Access Network. is a forum for the worlds leading telecommunications services providers and equipment suppliers to work towards a common goal of truly broadband access networks. For more information visit http://www.fsanet.net


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Gigabit Ethernet Another variation of the Ethernet protocol, is capable of transmitting data at one billion bits per second. This standard may eventually challenge ATM and Frame Relay as the high-speed LAN topology of choice, but, at present, ATM and Frame Relay still offer Quality of Service (QoS) guarantees that Gigabit Ethernet cannot match. Gigabit Ethernet can use high-quality copper wire at distances of less than 25 meters and optical fiber cabling for greater distances. GEPON Giga-Bit Ethernet Passive Optical Network (See EPON) Headend MSO (CATV) telecommunications office Header Error Control (HEC) A 1-octet field in the ATM cell header containing a CRC checksum on the cell header fields, HEC is capable of detecting multiple bit errors or correcting single bit errors. HDSL Unlike ADSL, High Bit Rate Digital Subscriber Line (HDSL) is a symmetric method of transmitting data at rates up to 1.5 Mbps in both directions. Because of the symmetric properties, the highest transmission rates can only be supported at lengths of 15,000-foot distances of two or more twisted pair lines. HPNA Home Phone Networking Alliance seeks to establish standards for home networking over regular coax and phone lines within the home - for compatibility between telecom, computer and network products. HomePNA is a relatively new technology, which allows you to network your home computers much like a LAN using your existing telephone wiring. Internet access can be shared among several computers with or without a router. Computers can access each other’s peripherals like printers and storage devices as well as the ability to play multiplayer games. HomePNA uses frequencies different from voice or fax calls while conducting data across the phone line.

Coaxial cables are included in the HomePNA 3.1 standard to increase the networking capabilities and overcome some limitations of phone jack location. It's not clear if this part of HomePNA 3.1 specification will be included in ITU G.9954 (01/07) or in any specification another standard body or will remain available only to HomePNA members.

ICP Integrated Communications Provider (e.g. ATG) Internet Protocol (IP) A set of rules for how data gets transmitted from one place to another on the Internet. IP is a connectionless protocol, in which data gets broken down into a number of small bundles known as packets, and each packet gets transmitted to the destination separately, possibly along a different route than other packets from the same message. IOT Intelligent Optical Terminal ISP Internet Service Provider ITU International Telecommunications Union IAD Integrated Access Device Lambda (l) Greek symbol used to signify wavelength. Last Mile The last mile is the local access network that extends from the Central Office (CO) to the end-user subscriber. Also called the local loop network, it is traditionally copper-based and suffers from the bandwidth limitations of that media. Leased Line A physical line that a single subscriber leases from a carrier, giving the subscriber exclusive rights to the line's capacity.


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Line (SONET) A transmission medium, together with the associated Line Terminating Equipment (LTE), required to provide the means of transporting information between two consecutive line terminating network elements, one of which originates the line signal and the other terminates the line signal. Multimedia over Coax Alliance The Multimedia over Coax Alliance (MoCA™) is an open, industry driven initiative promoting distribution of digital video and entertainment through existing coaxial cable in the home. MoCA technology provides the backbone for whole home entertainment networks of multiple wired and wireless products. The goal of the Multimedia over Coax Alliance is to facilitate home networking on existing coaxial cable in the 1 GHz microwave band. This cable can be used for data connections to televisions, set top boxes, and other entertainment devices without the need for new connections. The technology underlying MoCA provides the elements necessary to use this cable to distribute high-quality multimedia content and high-speed data with throughput exceeding 100 Mbit/s. MoCA is a non-profit mutual benefit corporation to develop and promote specifications for the transport of digital entertainment and information content over coaxial cable. MoCA members have agreed as part of membership to license under reasonable and non discriminatory (RAND) terms any intellectual property required for member companies to implement the MoCA Specification. Metro Network A network spanning a geographical area greater than a LAN but less than a WAN (Wide Area Network). IEEE 802.6 specifies the protocols and cabling for a MAN. MTU/MDU Multiple Tenant Unit/Multiple Dwelling Unit - a building with more than one residence or business. MSO Multiple Systems Operator (i.e., CATV company) Multi-mode Fiber Optical fiber supporting propagation of multiple modes of light. Multimode fibers have a larger core diameter than single mode fibers. Multi-Cast The ability of one network node to send identical data to a number of end-points. (Usually associated with multicast video techniques where the source will send a single stream and multiple end-points will accept the stream.) Transmission of information to a group of recipients via a single transmission by the source, in contrast to unicast or broadcast. In IP multicast, there is a one-to-many transmission, where a host may join or leave a group at any time. Multiplex A general concept that refers to combining independent sources of information into a form that can be transmitted over a single communication channel. Multiplexing can occur both in hardware (i.e., electrical signals can be multiplexed) and in software (i.e., protocol software can accept messages sent by multiple application programs and send them over a single network to different destinations). NGDLC Next Generation Digital Loop Carrier OAN Optical Access Networking OAS Optical Access Switch OC-# Short for Optical Carrier, used to specify the speed of fiber optic networks conforming to the SONET standard. The table shows the speeds for common OC levels.

OC-1 = 51.85 Mbps OC-3 = 155.52 Mbps OC-12 = 622.08 Mbps OC-24 = 1.244 Gbps OC-48 = 2.488 Gbps OC-192 = 9.952 Gbps OC-768 = 39.808 Gbps


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ODN The Optical Distribution Network is the optical fiber access network usually used to describe the PON Network, the outside plant (OSP). The ODN consists of but is not limited to the optical fiber, optical distribution cabinets, splitters, and optical access points. ODSI Optical Domain Service Interconnect is an open, informal initiative comprised of service providers and networking vendors. ODSI represents a coalition of networking professionals with a common interest in selecting, applying and promoting the open interfaces and protocols that will allow higher-layer service networks to effectively interoperate with the intelligent optical network core. http://www.odsi-coalition.com. Open Systems Interconnection (OSI) A logical structure for network operations standardized by the International Standards Organization (ISO). The OSI model organizes the communications process into seven different categories and places the categories in a layered sequence based on their relationship to other users. Layers, seven through four, deal with end-to-end communications between the message source and the message destination, while layers three through one deal with network access. OLT The optical line termination is the PON controller card or unit located at the CO. The terminal at the subscriber’s end of the network is the ONT or optical network terminal. Several OLTs may be located in a single chassis. The laser at the OLT is frequently a DFB (distributed-feedback laser) transmitting at 1490nm and is always on. Signals from the OLT tell the ONTs when to send upstream traffic to it. ONT The optical network termination resides at the subscriber’s end of the PON. It provides the interface between the network and the subscriber’s equipment. Frequently the laser used at the ONT is a Fabry Perot type and operates at 1310nm and only transmits when given permission by the OLT. Operations Administration and Maintenance (OAM) A group of network management functions that provide network fault indications, performance information and data and diagnosis functions. OSP Outside Plant (See ODN) Path (SONET) A path at a given bit rate is a logical connection between the point at which a standard frame format for the signal is assembled, and the point at which the standard frame format for the signal is disassembled. Payload The data in an ATM cell or IP packets that subscribers want to access (the message, conversation, file, etc.). The term payload is used to distinguish the subscriber's data from the "overhead," which is data in an ATM cell or IP packet that network equipment tacks on to the payload to help guide its transmission across the network. PBX Private Branch Exchange PON A Passive Optical Network (PON) is made up of fiber optic cabling and passive splitters and couplers that distribute an optical signal through a branched "tree" topology to connectors that terminate each fiber segment. Compared to other access technologies, PON eliminates much of the installation, maintenance, and management expenses needed to connect to customer premises. Per the FSAN specifications PON is a point to multipoint system with one OLT at the central office servicing up to 32 ONTs. The system is single fiber with downstream traffic sent in the 1550 nm wavelength window and upstream traffic being sent in the 1310 wavelength window. This is an example of Bi-directional transmission on a single fiber. Sometimes the PON is called B-PON, which indicates it is a Broadband PON. Also it can be an APON, which is an ATM based PON or an EPON, which is an Ethernet based PON. Point of Presence (POP) A facility used by a network access provider to house physical equipment that enables subscribers to access the network. The term is used to describe the location where a long distance carrier connects to a local service carrier, and also the location where an Internet service provider houses equipment that enables dialup subscribers to access the Internet.


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Public Switched Telephone Network (PSTN) The traditional voice network infrastructure, including both local service and long distance service that has been in use in various parts of the world for up to a century or so. Quality of service (QoS) The concept of applying and ensuring specific, quantifiable performance levels on a shared network. Performance can be assessed based on physical measurements of the network, the methods by which network traffic is prioritized, and on how the network is managed. Regional Bell Operating Company (RBOC) One of six telephone companies created after AT&T divestiture. Also, the acronym for the local telephone companies created in 1984 as part of the break-up of AT&T. (The six RBOCs are Ameritech, Bell Atlantic, Bell South, NYNEX, Southwestern Bell and U.S.West. Some of the six have and/or are merging.)

Right-of-Way - A right-of-way is a type of easement that gives someone the right to travel across property owned by another person.

Router A computer that directs bundles of data being transmitted between nodes on different networks. RT Remote Terminal Scalable The ability to add power and capability to an existing system without significant expense or overhead. Simple Network Management Protocol (SNMP) A set of protocols for managing complex networks. SNMP works by sending messages, called protocol data units (PDUs), to different parts of a network. SNMP compliant devices called agents, store data about themselves in Management Information Bases (MIBs) and return this data to the SNMP requesters. Single Mode Fiber Used to describe optical fiber that allows only one mode of light signal transmission SONET Synchronous Optical Network Standards for transmitting digital information over optical networks. It defines a physical interface, optical line rates known as Optical Carrier (OC) signals, frame formats and a OAM&P (Operations, Administration, Maintenance and Provisioning) protocol. The base rate is known as OC-1 and runs at 51.84 Mbps. Higher rates are a multiple of this such that OC-12 is equal to 622 Mbps (12 times 51.84 Mbps) STS-1 Synchronous Transport Signal 1 - Electrical SONET signal at 51.84 Mbps. T1 Refers to a networking standard capable of transmitting data at a rate of 1.54-Mbps. This protocol is commonly employed by very large enterprises such as telecommunications companies, the Internet backbone and connections from Internet service providers to the Internet backbone T3 A faster implementation of T1. Using coaxial cable, T3 allows for data transmission rates of 45 Mbps and is used for WAN backbones , the Internet backbone and connections from Internet service providers to the Internet backbone. TDM Time Division Multiplex - A method for transmitting multiple calls over a single line; each call is assigned a recurring timeslot on the line, and a small portion of that call gets transmitted over the line each time its assigned timeslot is available. TDMA Time Division Multiple Access


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Twisted pair cable A form of wiring in which a pair of wires are wrapped around one another again and again. Twisting two wires reduces their susceptibility to electrical interference. UBR Unspecified Bit Rate - a QoS parameter used typically used for data transmission. Unicast The transmit operation of a single PDU (protocol data unit) from one source to a single destination. In Unicast video, this is one channel delivered to a single interface device. Point-to-point transmission requiring the source to send an individual copy of a message to each requester. (See multicast.) Variable Bit Rate (VBR) An ATM Forum defined service category which supports variable bit rate data traffic with average and peak traffic parameters. A generic term for sources that transmit data intermittently. The ATM Forum divides VBR into real-time and non-real-time service categories in terms of support for constrained Cell Delay Variation (CDV) and Cell Transfer Delay (CTD). Vault Outside plant enclosure used to house telecommunications equipment. VDSL or VHDSL (Very High Bitrate DSL)[1] is a DSL technology providing faster data transmission over a single twisted pair of copper wires. VDSL is a scheme to boost transmission speeds to as much as 52 Mbps for very short distances (up to 1000 ft.) on copper wire, or longer distances in fiber-optic networks.

These fast speeds mean that VDSL is capable of supporting high bandwidth applications such as HDTV, as well as telephone services (Voice over IP) and general Internet access, over a single connection. VDSL is deployed over existing wiring used for POTS (Plain Old Telephone System) and lower-speed DSL connections.

Second-generation VDSL2 systems (ITU-T G.993.2) utilize bandwidth of up to 30 MHz to provide data rates exceeding 100 Mbit/s simultaneously in both the upstream and downstream directions. The maximum available bit rate is achieved at a range of about 300 meters; performance degrades as the loop attenuation increases.

Currently, the standard VDSL uses up to 7 different frequency bands, which enables customization of data rate between upstream and downstream depending on the service offering and spectrum regulations. First generation VDSL standard specified both QAM (Quadrature amplitude modulation) and DMT (Discrete Multi-Tone modulation.) In 2006, ITU-T standardized VDSL in recommendation G.993.2 which specified only DMT modulation for VDSL2. Virtual Private Network (VPN) A network service that employs encryption and tunneling to provide a subscriber with a secure private network that runs over public network infrastructure. Voice Gateway In the Central Office (CO), the Voice Gateway is a device that interfaces directly with the Class 5 Local Tandem Telephone switch and passes the requests from the Voice Gateway Controller to the Class 5 Switch. At the customer premises, the voice gateway is a device that takes a Voice over Internet Protocol transmission and converts the IP Packets to plain old telephone service. Voice Gateway Controller A Broadband Voice Gateway Controller is a device that allows you to make telephone calls over a high-speed Internet connection rather than through a regular telephone outlet without having to go through your computer. The device or gateway, which is about the size of a video cartridge, is plugged into your broadband DSL or cable modem. You then attach an ordinary cord or cordless telephone to the gateway and make calls just as you would with the plain old telephone system (POTS). On the Internet, your call is carried in packets using Voice over Internet Protocol (VoIP).

Because the gateway bypasses your computer, you can surf the Web at the same time that you or someone else uses your Internet connection for a phone call. No software is required. The gateway can be set up with or without a network router. You can add additional phone lines from the gateway with an RJ-11 splitter.

The major benefit of broadband voice service is saving money on long-distance charges, while enjoying better sound quality than afforded by a regular dial-up connection. However, there are other considerations that make it impractical


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as the sole telephone service in a household: unlike regular telephone service, if your Internet service is down, your phone will be down along with it, and a power outage means your phone is out as well.

The voice gateway controller is typically called the Voice over IP (VOIP) Soft Switch.

VOIP Voice over Internet Protocol

Wavelength A measure of the color of the light for which the performance of the fiber has been optimized. It is a length stated in nanometers (nm) or in micrometers (um). Wavelength Division Multiplexing (WDM) A type of multiplexing developed for use on optical fiber. WDM modulates each of several data streams onto a different part of the light spectrum. Sources: Telcordia, ADC Telecom, Alcatel, Alloptic Inc, Corning, Paceon, Quantum Bridge, Terawave Communications, Lightreading, and ITU.


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FTTP Glossary/Acronyms (Source FTTH Council) 10 Gigabit Ethernet (10 GigE)

Although the standard for this version of Ethernet is not yet released, it is nearly complete as of early 2002. It is already possible to buy 10 Gigabit devices based on the emerging standard, but these aren’t officially Ethernet devices until the standard issues.

100Base-T 100Mbps LAN that maintains backward compatibility with 10Base-T networks running at 100Mbps

10Base-T 10Mbps Ethernet LAN which runs over twisted pair wiring. This network interface was originally designed to run over ordinary twisted pair (phone wiring) but is predominantly used with Category 3 or 5 cabling

2B1Q (2B1Q) Modulation format used by ISDN (Stands for 2 Binary 1 Quaternary)

Access Line The physical telecommunications circuit connecting and end user location with the serving central office in a local network environment. Also called the local loop or "last mile"

Access Network A set of communications links which primarily serves to deliver data and/or communication services directly to and from end-users. Although an Access Network operator may own facilities for providing the services themselves, the Access Network is distinct from these facilities. Thus, the Access Network can be thought of as providing bi-directional access for end-users to services and/or geographically broader networks. See Distribution Network.

Access Nodes Points on the edge of the access network that concentrate individual access lines into a smaller number of feeder lines. Access nodes may also perform various forms of protocol conversion. Typical access nodes are DLC systems concentrating individual voice lines to T-1 lines, cellular antenna sites, PBXs and ONUs.

Access Rate The transmission speeds of the physical access circuit between the end user location and the local network. This is generally measured in bits per second (bps), also called Access Speed.

Actives Components that require electrical power and actively alter the signal and/or message properties. Examples are RF and optical amplifiers, and lasers.

ADSL Transmission Unit - Central Office

The ADSL (Stands for asymmetric digital subscriber line) modem or line card that physically terminates an ADSL connection at the telephone service provider's serving central office

ADSL Transmission Unit - Remote

The ADSL modem or PC card that physically terminates an ADSL connection at the end user's location

Analog Electrical signal of wave form in which the amplitude and/or frequency vary continuously

Analog Television The system of television transmission that has been practiced since the medium was invented. Video and Audio information are represented by a continuously varying voltage level.

Application Service Provider (ASP)

A company that provides software or applications for end-users. The ASP owns the actual applications and allows the end-user to use them, rather than selling them outright.

Aspect ratio The ratio of width to height of a picture. Standard definition television uses a 4:3 aspect ratio, and most HDTV systems use a 16:9 aspect ratio.

Asymmetrical Digital Subscriber Line (ADSL)

BellCore term for delivery of digital information over ordinary copper phone lines. ADSL uses a system of frequency division whereby lower frequency POTS signals are delivered to the home unaltered while digital signals traverse the phone line at higher frequencies for delivery to end stations such as a video CODEC or PC.

Asynchronous Transfer Mode (ATM)

A set of standards for digital transmission. ATM allows multiple data streams to be combined onto a single communication link by allowing a portion of each to be transmitted intermittently in turns. All information is broken into small, fixed-size pieces called cells. This transfer mode is called Asynchronous because it is not necessary for a portion of a particular data stream to be sent on a periodically recurring basis.


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ATM Cell An ATM cell is 53 bytes long containing a 5-byte header and 48-byte payload. The header of an ATM cell contains Virtual Circuit Identifier to allow it to be switched through the network. The payload portion of an ATM cell can contain any type of information, be it voice, video or data.

ATM Passive Optical Network

See APON

ATM PON (APON) A PON (see definition) which is built around ATM technologies.

Attenuation Power loss. It is generally measured in dB (decibels) for discrete components, and in dB per unit length (dB/km or dB/kft) for cables.

Backbone Point-to-point or ring connections between Headends, Central Offices or other types of major hubs.

Bandwidth Representative of the information-carrying capacity of a given transmission channel.

Baud Transmission rate of a multilevel-coded system when symbols replace multiple bits. Baud rate is always less than bit rate in such systems.

Bit A single binary data element having a value of either 1 or 0, usually represented by two different voltage levels.

Bit Error Rate (BER) A measure of the frequency with which transmission errors occur. By necessity, typical BERs are quite low, and so are expressed in Scientific Notation. For example, a BER of 1012 means that there is an average of one erroneous bit for every 1012

(written in long form as a 1 with 12 zeroes after it) or 1 trillion bits transmitted. Bit Rate The number of bits of data transmitted per second.

Broadband A loosely used term describing a system that has a lot of bandwidth or information carrying capacity. There is disagreement about exactly how much bandwidth constitutes a true Broadband system. However, the capability to transmit at least one channel of broadcast quality video is generally agreed to be an absolute minimum.

Broadband Integrated Services Digital Network (B-ISDN)

A standard for the integration of networks operating at speeds above 1.54 Mbps. This standard was developed to advance the existing Telephony standards beyond their capabilities at the time.

Broadband PON (BPON) A Broadband PON, BPON, is an APON (ATM PON—see Definition) that is modified to allow additional services, such as broadcast video or additional data. These enhancements are made possible by one or more additional WDM channels, as outlined in the ITU G983.wdm Recommendations.

Byte A sequence of eight bits.

Cable Binder In the telephone network, multiple insulated copper pairs are bundled together into a cable called cable binder.

Cable Modem Modem designed to operate over cable TV lines; used to access the Internet.

Cable Modem Termination System (CMTS)

Cable Television The transmission of television programming over a closed medium (such as coaxial cable or optical fiber) rather than by over-the-air transmission.

CableLabs Cable Television Laboratories. The research consortium of the cable television operating companies.

Caching The distributed storage of data to improve access speed to the data by the user. A common example of this is the caching of popular web sites. The original data is duplicated and stored in numerous local servers. An end-user can download the cached sites more quickly than if they were retrieved from the original source.

Carrier (1) A telecommunications network operator. (2) A signal on which another, lower frequency signal is modulated in order to transport the lower frequency signal to another location.

Category 3 Cabling Rating for twisted pair copper cabling that is tested to handle 16 MegaHertz of communications. Handles 10Mbps of LAN traffic and is commonly used as telephone wiring.

Category 5 Cabling Rating for twisted pair copper cable that is tested to handle 100 MegaHertz of communications. CAT-5 cable is generally required for higher-speed data communications, such as Ethernet LANs and possibly low-speed ATM.


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CATV Community Antenna Television. Today, this term is often used as an abbreviation for cable television. Historically, it described companies that were created to address poor television reception in rural, often mountainous, communities. A large, sensitive antenna would be erected in an advantageous location to pick up over-the-air television signals. These signals were then carried over a cable television system to subscribers who were otherwise unable to get adequate reception.

Cell In data transmission, this term refers to a small block or unit of data. Cells are most commonly associated with ATM, in which their length is fixed at 53 bytes (48 bytes of data and 5 bytes of address). Longer pieces of data are broken up into cells at the transmitter, and reassembled at the receiver. See also the definition for Packets.

Central Office (CO) A facility in a conventional telephone network where local switching gear is housed. The CO is the primary interconnection point between a caller and the rest of the network, and is often referred to as the local Exchange.

Channel A range of frequencies assigned to a service and/or network operator.

Channel Service Unit/Data Service Unit

Digital interface device that connects end user data communications equipment to the digital local access lines.

Chromatic Dispersion Optical signal dispersion that arises from variations in transmission delay amongst the range of wavelengths present in a single source. Because it is proportional to the spectral width of the source, using a source with a tighter spectral output (see DFB Laser) can reduce it. Chromatic Dispersion increases as a factor of length in all fibers, but is typically only of concern in Single Mode fibers.

Circuit Switched Network Network that establishes a physical circuit temporarily on demand (typically when a telephone or other connected device goes off hook) and keeps that circuit reserved for the user until it receives a disconnect signal.

Circuit Switching Switching system that establishes a dedicated physical communications connection between endpoints, through the network, for the duration of the communications session; this is most often contrasted with packet switching in data communications transmissions. See also Packet Switching.

CLEC See Competitive Local Exchange Carrier

Client/Server Architecture (CSA)

Distributed computing model that involves distributing information resources in servers that are accessed by so-called clients, the end users. This is generally opposed to centralized mainframe computing architecture.

CO See Central Office.

Coarse Wave Division Multiplexing (CDWM)

A WDM system in which the wavelengths of the individual signals or channels are widely spaced. An increasing number of CWDM components are becoming available with channel spacing of 20nm.

Coder/Decoder (CODEC) Hardware device or software program that converts analog information streams into digital signals, and vice versa; generally used in audio and video communications where compression and other functions may be necessary and provided by the CODEC as well.

Community Antenna Television (CATV)

Community Antenna Television. Today, this term is often used as an abbreviation for cable television. Historically, it described companies that were created to address poor television reception in rural, often mountainous, communities. A large, sensitive antenna would be erected in an advantageous location to pick up over-the-air television signals. These signals were then carried over a cable television system to subscribers who were otherwise unable to get adequate reception.

Competitive Local Exchange Carrier (CLEC)

A company that competes with an ILEC (see definition) to provide local phone service. These services can be over the CLEC’s own network or over the ILEC’s network, in accordance with terms outlined in the Telecommunications Act of 1996.

Conditional Access A generic term used to indicate that access to a program or channel is limited to authorized subscribers. Authorization typically involves payment of additional charges.

Constant Bit Rate (CBR) Specifies a fixed bit rate so that data is sent in a steady stream. (See Also ABR, UBR and VBR )

Crosstalk Interference on an analog line of an adjacent signal with the intended receive signal. Crosstalk makes it hard to hear just the intended signal, as there are multiple conversations on the line at once.


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Customer Premises Equipment (CPE)

The equipment portion of a Distribution or Access Network that is located in the Customer’s premises. This term can describe a wide array of equipment and capabilities.

CWDM See Coarse Wave Division Multiplexing

Cyclic Redundancy Check (CRC)

Test used to confirm that data has been delivered without error. In a data packet, the CRC character is calculated by assigning binary values to blocks of data. If the block of data does not match its assigned CRC value upon delivery, the data is erred

D Channel The "data" signaling channel in the ISDN scheme. This is the channel that carries signaling and limited packet communications. In basic rate ISDN, this is a full-duplex 16 Kbps channel. In primary rate ISDN, this is a full-duplex 64 Kbps channel.

Data Circuit Terminating Equipment

Any device that is connected to the subscriber end of a transmission circuit and provides the appropriate termination functions for that connection.

Data Service Unit (DSU) Digital interface device that connects end user data communications equipment to the digital access lines and provides framing of sub-64 Kbps customer access channels onto higher-rate data circuits.

Data-Over-Cable Service Interface Specification (DOCSIS)

DOCSIS is the formal name of the cable modem standard produced by a consortium led by CableLabs.

dB Shorthand notation for Decibel, a logarithmic unit used to represent the relative strength of two signals. Decibel loss is defined as ten times the logarithm (to the base 10) of the ratio of the two power levels. When calculating loss, the attenuated signal is compared to the original input power. Although this definition is often confusing to the layman, it is easier to calculate cumulative system losses in Decibel than in any other format.

dBm Decibel measure of a power level with respect to one milliwatt. A signal strength of 0dBm corresponds to one milliwatt of power.

Decibel (dB) A logarithmic unit used to represent the relative strength of two signals. Decibel loss is defined as ten times the logarithm (to the base 10) of the ratio of the two power levels. When calculating loss, the attenuated signal is compared to the original input power. Although this definition is often confusing to the layman, it is easier to calculate cumulative system losses in Decibel than in any other format.

Dedicated Line Transmission circuit that is reserved by the provider for the full-time use of the subscriber.

Demodulation Conversion of a carrier signal or wave form (analog) into an electrical signal (digital).

Dense Wave Division Multiplexing

High-speed versions of WDM, which is a means of increasing the capacity of SONET fiber optic transmission systems through the multiplexing of multiple wavelengths of light.

DFB Laser See Distributed Feedback Laser.

Dial Up The process of initiating a switched connection through the network.

Digital Access and Cross-Connect System

Digital cross-connect device for routing lines among multiple ports.

Digital Hierarchy The progression of digital transmission standards typically starting with DS-0 (64 Kbps) and going up through at least DS-3.

Digital Loop Carrier (DLC) A telephony system used to connect multiple analog subscribers to a switch through a single digital connection. The original purpose of this technology was to reduce the number of copper lines that had to be run out to groups of remote subscribers. The customers are still individually connected by an analog line to a remote terminal, but are multiplexed onto the DLC from the remote terminal back to the Central Office.

Digital Signal 0 (DS-0) Basic North American 64 Kbps digitized voice channel. In the digital hierarchy, this signaling standard defines a transmission speed of 64 Kbps.

Digital Signal 1 (DS-1) In the digital hierarchy, this signaling standard defines a transmission speed of 1.544 Mbps; a DS-1 is composed of 24 DS-0signals; this term is often used interchangeably with T-1.


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Digital Signal 3 (DS-3) In the digital hierarchy, this signaling standard defines a transmission speed of 44.736 Mbps; a DS-3 is composed of 28 DS-1 signals; this term is often used interchangeably with T-3.

Digital Subscriber Line (DSL)

A technology for increasing the bandwidth of twisted copper pair conductors. This is an important technology because it has allowed existing copper infrastructure to carry much more information than it was originally designed to handle. Several standards for upstream and downstream bandwidth have been created (ADSL, VDSL, HDSL). These variants seek to trade off bandwidth against range and physical plant requirements to address a wide range of applications. However, the Bandwidth of even the highest speed DSL connection is a small fraction of what can be carried by Optical Fiber. In addition, DSL connections are inherently vulnerable to electrical noise, including the noise produced by other DSL lines.

Digital Video (DV) Video signals in a digital format. Video information is represented by discrete, numerical values, rather than by continuously varying signal levels as in Analog Video. Because of this, it is simpler to maintain the fidelity of the Video information as it travels through a transmission medium.

Distributed Feedback Laser (DFB Laser)

A type of laser in which the desired transmission wavelength is more tightly controlled by means of a grating within the laser cavity. DFB lasers typically have narrower spectral outputs than Fabry-Perot Lasers. This helps to control Chromatic Dispersion in an optical transmission link. However, DFB lasers tend to be more expensive than Fabry-Perot lasers.

Distribution Network A set of communications links which delivers services to end-users. This term is often used in the context of a Cable Television network to describe the facilities that send programming from the headend out to the end-users or viewers. In this context, the Distribution Network may or may not be bi-directional. See Access Network.

DLC See Digital Loop Carrier.

Downstream The communications from the network towards the customer's premise.

DSL See Digital Subscriber Line

E-1 The European equivalent of a T-1 circuit. It is a term for a digital facility used for transmitting data over a telephone network at 2.048 Mbps.

E-3 The European equivalent of a T-3 circuit. It is a term for a digital facility used for transmitting data over a telephone network at 34 Mbps.

Egress A measure of the degree to which signals from a nominally closed coaxial cable system are transmitted through the air. Also known as Signal Leakage. The FCC requires that egress be monitored and controlled by CATV system operators.

EIA Electronic Industries Association. A trade organization in Washington representing manufacturers of electronic equipment in the United States.

Electrical to Optical (E/O) Shorthand notation for a location or device in which an electrical signal is converted to an optical signal. See also O/E and O/E/O.

Electromagnetic Interference (EMI)

A term used to describe disturbances to electrical signals that can arise from a wide range of sources. EMI can affect all types of copper communications cables and can disable an access or distribution network, particularly as a network ages. Optical fiber is completely immune to EMI.

Electronic Industries Association (EIA)

A trade organization in Washington representing manufacturers of electronic equipment in the United States.

Encapsulation The process of putting data inside a larger “package” that includes a header and possibly an end-of-packet identifier. The encapsulation may be thought of as putting a letter in an envelope for transport to another location.

Encryption The process of rendering a digital signal unintelligible to any receiver that doesn’t have some unique piece of information needed to recover that signal.

EPON See Ethernet PON

Error Correction In data transmission, the technique of adding extra bits to a transmitted signal, with the extra bits being used to detect and correct errors in the transmission.

Ethernet An IEEE data communications protocol originally developed for premises and local access networks (IEEE 802.3). It was originally developed for peer-to-peer communications using shared media over relatively short distances. Ethernet has been substantially improved over the years and now operates in a wide variety of


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settings. Ethernet features variable length packets, which allows data to be sent with less overhead. Although the early forms of Ethernet provided little control over QoS (see definition), newer versions have improved upon this considerably. Ethernet is currently the most widely deployed LAN protocol in the world. Efforts are currently underway in the IEEE to extend Ethernet to access networks. See also Fast Ethernet and Gigabit Ethernet.

Ethernet PON (EPON) A PON (see definition) that is built around Ethernet technologies.

Fabry-Perot Laser (FP Laser)

A semiconductor laser with a basic cavity structure. FP lasers typically have wider spectral outputs than DFB Lasers. This results in more Chromatic Dispersion in an optical transmission link. However, FP lasers tend to be less expensive than DFB lasers, and are adequate for shorter distances.

Far End CrossTalk Leakage of one or more foreign sources into the receiver of a system at the distant end of a transmission system.

Fast Ethernet Ethernet at 100 Megabits per second. When it was first standardized, this version of Ethernet was ten times faster than any previously available version. It has since been surpassed by Gigabit Ethernet. See also Ethernet.

FEC See Forward Error Correction

Federal Communications Commission (FCC)

The US federal regulatory agency responsible for regulating interstate and international communications.

Feeder The portion of a CATV coaxial sub-network which starts at an amplifier fed by a trunk or an express feeder, and supplies signals directly to subscriber taps.

Fiber in the Loop (FITL) Used by the telephone industry to describe the deployment of fiber on the subscriber side of class 5 telephone switches.

Fiber Optic Cable Transmission medium composed of glass or plastic fibers; pulses of light are emitted from a laser-type source. Fiber optic cabling is the present cabling of choice for all interexchange networks, and increasingly for the local exchange loops as well; it is high security, high bandwidth, and takes little conduit space.

Fiber To The Cabinet Network architecture where an optical fiber connects the telephone switch to a cabinet where the signal is converted to feed the subscriber over a twisted copper pair.

Fiber to the Curb (FTTC) An access network in which fiber is used for part, but not all of the link from the OLT to the end-user. An optical to electrical (O/E) conversion takes place somewhere close to the end-user. The terminal network segment of a FTTC network is usually twisted copper pairs or coaxial cable. The final optical receiver in a FTTC network typically serves several customers. See also Fiber to the Node.

Fiber to the Feeder (FTF) A term typically used to describe CATV Fiber to the Node networks. Coaxial cables are normally used for the terminal network segment (from the node to the end-user).

Fiber to the Home (FTTH) An OAN in which the ONU is on or within the customer’s premises. Although the first-installed capacity of an FTTH network varies, the upgrade capacity of a FTTHnetwork exceeds all other transmission media.

Fiber to the Node (FTTN) An access network in which fiber is used for part, but not all of the link from the OLT to the end-user. An optical to electrical (O/E) conversion takes place at an active device called a Node. This Node typically serves a neighborhood or geographically similar area, which is larger than the typical service area in an FTTC deployment. The terminal network segment is usually twisted copper pairs or coaxial cable. Most current CATV and Telephony networks have FTTN architectures.

Fiber-in-the-Loop (FITL) Used by the telephone industry to describe the deployment of fiber on the subscriber side of class 5 telephone switches (see Loop).

Forward Error Correction (FEC)

In data transmission, a process by which additional data is added that is derived from the payload by an assigned algorithm. It allows the receiver to determine if certain classes of errors have occurred in transmission and in some cases, allow other classes of errors to be corrected.

Franchise An agreement with a local governing body that permits a cable operator to construct and/or operate a cable system, and which spells out the conditions that must be met by that system. In many cases, franchises are exclusive, but multiple franchises have become more common.


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Frequency Division Multiplexing (FDM)

Multiplexing technique that uses different frequencies to combine multiple streams of data for transmission over a communications medium.

FTTC See Fiber to the Curb

FTTH See Fiber to the Home

FTTN See Fiber to the Node

Full Service Access Network (FSAN)

An industry consortium of telecom operators that drafted access network recommendations. These recommendations were submitted to the recognized standards bodies for approval and publication (e.g. ITU-T G.983). FSAN networks are expected to work with the ATM switches commonly used by ILECs. Thus, many features of an FSAN network are directly related to the capabilities of ATM equipment.

Gigabit Ethernet (Gig-E) Ethernet at 1000 Megabits per second. As of early 2002, this is the fastest standardized version of Ethernet available. However, the standard for 10 Gigabit Ethernet devices is expected soon. See also Ethernet.

Greenfield A term used to describe network deployment in an area that was previously undeveloped. Since everything is being built for the first time, network construction can be done with few obstructions and little or no risk to other utilities. By definition, there can be no incumbent network operators.

HDSL Transmission Unit - Central Office

The HDSL modem or line card that physically terminates an HDSL connection at the telephone service provider's serving central office.

HDSL Transmission Unit - Remote

The HDSL modem or PC card that physically terminates an HDSL connection at the end user's location.

Headend The point at which all cable television programming is collected and formatted for placement on the cable system.

Header The first part of a data cell or packet, containing such information as source and destination addresses, and instructions on how the telecommunications network is to handle the data. The Header is part of the Overhead in a data transmission protocol.

Hertz The basic unit of frequency measurement; one cycle per second.

High Bit Rate Digital Subscriber Line (HDSL)

Modulation method that enables T-1 and E-1 signals to be delivered over two and three pairs of copper wire respectively.

High Definition Television (HDTV)

Television with significantly more picture information (resolution) than that provided by a good NTSC or PAL television signal. The specific resolution (or definition) of HDTV can vary according to specifications. However, it is typically about twice the resolution of standard television signals in both the horizontal and vertical direction. It also has a wider aspect ratio.

Host Digital Terminal (HDT) Cable television digital headend equipment used to interface with a distribution plant.

Hybrid Fiber Coax (HFC) A distribution network commonly used for Cable Television. The cable segments closer to the Headend are optical fiber, while those closer to the customer are coaxial cable. The transition point from fiber to coax varies, and in many places, fiber is extended further into the network in successive upgrades. The signal is normally modulated onto an RF carrier throughout the system. Thus, HFC networks allow the physical medium to be upgraded without changing the signal format or capabilities.

IEEE 802.3 A subset of the IEEE responsible for Ethernet Standards.

IEEE 802.3 EFM See IEEE 802.3ah.

IEEE 802.3ah A subset of the IEEE responsible for Ethernet in the First Mile. Roughly speaking, this group is concerned with access networks.

Incumbent Local Exchange Carrier (ILEC)

The telephone network operator that has been in operation longest in a particular area. An ILEC can be a small, independent telephone company or an RBOC (see definition). It should be noted that an RBOC is not the ILEC by default, but may be a CLEC (see definition) in some areas of its operation.

Ingress Over-the-air signals that are inadvertently coupled into a nominally closed coaxial cable distribution system. Ingress can originate from broadcast signals, electrical noise, or equipment that the end-user has connected to the network. Ingress noise often originates within an end-user’s premises and is, therefore, difficult to locate or correct.


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Institute of Electrical and Electronics Engineers (IEEE)

A professional organization of technologists interested in all aspects of electrical engineering.

Insulation Displacement Connection (IDC)

Type of wire connection device in which a wire is punched down into a metal holder that strips away the insulation to achieve electrical connection.

Integrated Services Digital Network (ISDN)

A network standard for the combination of digital telephony and other services on the same network. ISDN is also used to describe a particular type of telephony-based data connection—the ISDN line.

Inter-Exchange Carrier (IXC) A long distance telephone carrier. The name arises from the fact that these carriers provide connections only between Central Offices (COs), which are sometimes called Exchanges. Strictly speaking, an IXC does not provide connections from the end-user to the CO or Exchange.

Interface Point of connection between two systems, networks, or devices.

InterLATA Telecommunications services that originate in one and terminate in another LATA.

International Electrotechnical Commission (IEC)

A standards body that produces a wide range of recommendations and standards for telecommunications.

International Standards Organization (ISO)

International organization for standardization which is based in Geneva. Publishes national and international standards for data communications.

Internet Access Node The Internet access provider's facility for receiving communications from subscribers and organizing it for transmission into the Internet.

Internet Protocol (IP) In addition to governing the operation of The Internet, IP is a set of rules for the interconnection of geographically dispersed users who may not be using a common data communication protocol. One important feature of IP is that it does not rely on the establishment of dedicated connections between users. This allows “idle” time between two users to be filled with other data, thereby increasing the utilization of the available bandwidth.

Internet Service Provider (ISP)

An organization whose business it is to connect users to the Internet. By serving as the interface between end-users and the Internet, the ISP’s equipment is analogous to a Cable Television Headend or Telephony Central Office. See also Point-of-Presence.

Interoperability The ability of equipment from multiple vendors to communicate using standardized protocols.

IntraLATA Telecommunications services that originate and terminate in the same LATA.

IP See Internet Protocol

IP Multicast A technique in which IP packets are simultaneously sent to multiple recipients. It is often used to send an audio and/or video program to multiple users on a network more efficiently. The efficiency is realized by sending only one data stream from the file server, rather than one stream for each recipient. The digital data stream is duplicated as necessary in the downstream path by routers and/or switches in order to account for different signal paths to the end-users.

ISP See Internet Service Provider

IXC See Inter-Exchange Carrier

Jitter Interference on an analog line caused by a variation of a signal from its reference timing slots. Jitter can cause problems in the receipt of data.

Kilobits per second Measure of bandwidth capacity or transmission speed. It stands for a thousand bits per second.

KiloHertz (kHz) One thousand hertz.

Lambda A term often used as a synonym for Wavelength (see Definition).

LAN See Local Area Network.

Last Mile Refers to the local loop and is the difference between a local telephone company office and the service user.

Latency Measure of the temporal delay. Latency refers to the delay in time between the sending of a unit of data at one end of a connection until the receipt of that unit at the


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destination. Layer OSI reference model; each layer performs certain tasks to move the information from

the sender to the receiver. Protocols within the layers define the tasks for the networks but not how the tasks are accomplished.

Layer Two Tunneling Protocol (L2TP)

Extension to the PPP protocol that enables ISPs to operate VPNs.

LEC Local Exchange Carrier. A local telephone company.

Loaded Pair Twisted pair phone line with inductors, or loading coils, inserted periodically to flatten the frequency response in the 4 KHz voice band.

Loading Coil Device used to extend the range of a local loop for voice grade communications. They are inductors added in series with the phone line which compensate for the parallel capacitance of the line.

Local Area Network (LAN) A network of individual PCs and servers which are in close geographic proximity and are using a common communication protocol.

Local Area Network (LAN) Network of individual PCs and servers which are in close geographic proximity and are using a common communication protocol.

Long Distance (LD) Representing the communications of information over a distance other than the local calling area.

Long Haul Term for Long Distance

Loop Local Office Outside Plant. That portion of a telephone network extending from the local (class 5) switch to the network termination points at individual subscribers.

Loopback Tests Test in which a test signal is injected at one end of a circuit, is looped back at the other end, and monitored at the originating end.

Low Water Peak Fiber A single mode fiber in which attenuation throughout the water peak range (between 1360nm and 1460nm) is less than or equal to the attenuation at 1310nm. Lower attenuation over this range allows these wavelengths to be utilized more easily than in conventional single mode fiber. The so-called “water peak” is caused by the natural tendency of moisture (specifically OH- ions) to filter light very strongly over the water peak range. Eliminating moisture in the fiber core and cladding creates Low Water Peak Fiber.

Main Distribution Frame (MDF)

Central point where all local loops terminate in the CO.

Mean Time Between Failure (MTBF)

A measure of the average time interval between circuit restoration from a previous failure and the onset of the next failure in a network.

Mean Time To Restore (MTTR)

A measure of the average time required to restore proper network/circuit operation after a failure.

Media Access Control (MAC)

The means by which access to a common medium is controlled for multiple transmitters. The objective is to minimize or avoid interference so as to make the most efficient use of the shared medium. Many different control schemes are available to provide different balances between features and implementation cost.

Megabits per second (Mbps)

Measure of bandwidth capacity or transmission speed. It stands for a million bits per second.

Mesh An architecture in which terminal points are connected to several other terminal points directly, rather than just to a central point (a star) or the adjacent terminals in a ring.

Messenger The support member in an aerial, electronic or fiber cable.

Metro Area Network (MAN) A general term used to describe any telecommunications network of intermediate size.

Metropolitan Area Network Data communication network typically covering the geographic area of a city; a communications network that is usually larger than a LAN but smaller than a WAN.

Metropolitan Serving Area Regional area served by a provider who is classified based on the metropolitan coverage area.

Modal Dispersion Optical signal dispersion that arises from variations in transmission delay amongst the propagation modes in an optical fiber. Modal Dispersion increases as a factor of length in Multi Mode fibers and can limit their transmission range. Single Mode fiber


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does not exhibit Modal Dispersion, since it has only one mo de of propagation. Modem Converter of analog waveforms into digital data and vice versa.

Modulation The process of imposing information on carrier signal by varying some parameter of the carrier. The parameters that can be varied are the amplitude, frequency or phase.

Motion Picture Experts Group (MPEG)

A group which developed standards for digital compression of television pictures. The second generation of this standard is MPEG-2, which is the current standard for digital television encoding and transmission throughout the world.

MPEG1 Compression scheme for full motion video. Compression algorithm introduced by MPEG in 1991, the common goal of MPEG is to compress 7.7 Meg down to about 150 Kbytes. MPEG1 is designed to provide a resolution of 352 by 240 pixels at 30 frames per second.

MPEG2 Video compression standard selected by MPEG. Designed to provide a resolution of 720 by 480 pixels at 30 frames per second. Likely to be the leading compression algorithm for a range of video applications including video on demand.

Multi-Dwelling Unit (MDU) An apartment, high-rise or any other building in which more than one residence is located.

Multi-Tenant Unit (MTU) A building that houses multiple tenants. This term can be generally applied to apartments (see MDU) but more often refers to business locations.

Multichannel Multipoint Distributed Service (MMDS)

MMDS is a pay television delivery system that delivers up to 33 channels of video programming via microwave transmission.

Multimode Fiber (MMF) An optical fiber that supports more than one mode of optical propagation. Multimode fiber exhibits modal dispersion, which typically is the limiting factor for its transmission range.

Multipath A condition where an over-the-air signal may reach a receiver via more than one path from a transmitter, leading to degraded reception. Applies to all transmission systems and frequencies

Multiple Dwelling Unit (MDU)

Apartment, high-rise or any other building in which more than one residence is located.

Multiple System Operator (MSO)

Historically, this term arose to describe companies that owned and operated more than one cable television system. These companies were often built through acquisitions, and many have since consolidated their holdings into a single operating unit. Thus, the term is often used today to indicate any large cable television company

Multiplexer Device that allows the transmission of multiple data streams over a common medium. Several communications paths or channels may be either permanently or dynamically established over the medium to accomplish this.

Multiplexing The transmission of more than one independent signal over a single transmission media. The transmitted signals need not operate continuously or simultaneously in order for Multiplexing to have occurred. See TDM and WDM.

Narrowband Term used to describe services with up to and including T-1 or 1.544 Mbps.

National Cable Television Association (NCTA)

A trade organization that represents companies in the cable television industry.

National Television System Committee (NTSC)

The entity that developed the analog TV specifications used in North America and some other portions of the world. There were actually two NTSCs: the first developed the monochrome transmission system and the second added color.

Near Video On Demand (NVoD)

A PPV service that approaches on-demand availability by offering frequent start times for popular events (movies). Half to quarter hour incremented start times are common.

Network Access Point Public network exchange facility where ISPs can connect with one another in peering arrangements.

Network Interface Card (NIC)

The circuit board or other form of computer hardware which serves as the interface between a computer, or other form of communicating DTE, and the communications network.

Network Interface Device One of many names for a box on the side of the house that contains any required interfaces between the inside wiring and the Distribution or Access Network.


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(NID) Network Managament System (NMS)

System that allows a provider to manage a telecommunications network.

Network Service Provider (NSP)

The term for an organization offering and providing network services on a telecommunications network.

Network Termination Unit (NSP)

Equipment at the customer premise that terminates a network access interface.

Node As a generic term, a node is a piece of outside plant equipment that connects multiple users to a common link, which extends back to a Headend, Central Office or similar location.

Operations Administration Management (OAM)

A generic term for software suites that allow centralized administration of a communication system.

Operations, Administration, Maintenance and Provisioning (OAM&P)

A generic term for software suites that allow centralized administration of a communication system. It is a superset of what the cable industry refers to as status monitoring.

Optical Access Network (OAN)

An Access Network made up of optical transmission links. This is in contrast with older technologies, which typically use copper links composed of twisted-pair or coaxial cables.

Optical Line Termination (OLT)

An OLT provides the network-side interface of the OAN, and is connected to one or more ONUs.

Optical Network Termination (ONT)

See ONU.

Optical Network Unit (ONU) An ONU provides (directly or remotely) the user-side interface of the OAN. Additional devices may be attached to the ONU at the user premises. However, this is the terminal element of what is commonly regarded as the access network. More than one ONU may be connected to the same OLT by means of passive or active intermediate elements.

Optical Splitter A passive optical component with at least three ports, which can split or combine optical signal power. When used in a PON, a splitter bi-directionally couples one OLT to multiple ONUs. Signal power from the OLT is split among the ONUs according to the design parameters of the splitter. The OLT signal strength at each ONU is reduced accordingly. Signals from the ONUs are aggregated by the splitter and must be appropriately multiplexed to avoid interference.

Optical to Electrical (O/E) Shorthand notation for a point or device in which an optical signal is converted to an electrical signal. See also E/O and O/E/O.

Optical to Electrical to Optical (O/E/O)

Shorthand notation for a point or device in which an optical signal is converted to an electrical signal and back to an optical signal. This is often done to facilitate processing which can only be done electrically, but which is at an intermediate point within an optical network. Common examples are routers and equipment for cleaning up a degenerated optical signal. See also E/O and O/E.

Overbuild A term used to describe new network deployment in an area that is served by an incumbent network operator. Although the services offered by the new provider may differ from those offered by the incumbent provider(s), some degree of competition is usually implicit.

Overhead In data transmission, the portion of the data that is included to manage transmission. Examples include address information and error correction data. See Payload.

Overlay (1) Sometimes used as a synonym for Overbuild (see above). (2) A term used to describe the insertion of additional information or services into an optical link. See also Wavelength Overlay.

P2MP See Point-to-Multi-Point.

P2P See Point-to-Point.

Packet A unit of data in certain communications protocols such as Ethernet and IP. Typically the term “packet” is used for data units which can be of variable length. This is in contrast to cells (see definition), which are of fixed length. Packets allow some flexibility when packaging data for transmission by allowing more data to be sent


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without breaking it up into pieces and then reassembling it at the receiver. This, in turn, reduces the overhead.

Packet Switched Network Network that does not establish a dedicated path through the network for the duration of a session, opting instead to transmit data in units called packets in a connectionless manner. Datastreams are broken into packets at the front end of a transmission, sent over the best available network connection, and then reassembled in their original order at the destination endpoint.

Packet Switching Switching system that uses a physical communications connection only long enough to transit a data message; data messages are disassembled into packets and reassembled at the receiving end of the communication link. Packets may travel over many diverse communications links to get to the common endpoint.

Passive A component that requires no electrical power to operate. Examples include Optical Splitters, tap couplers, and fixed optical attenuators.

Passive Optical Network (PON)

An OAN in which each OLT is connected with more than one ONU by means of passive intermediate elements. Optical Splitters serve as the intermediate elements in typical PONs. See also Point-to-Multi-Point.

Pay Per View (PPV) The selling of programs to subscribers on a per-program basis as opposed to a subscription basis.

Payload The portion of transmitted data that is actually intended for the recipient. Any other information added for the sake of transmission or processing is considered Overhead.

Permanent Virtual Circuit (PVC)

Term found in frame relay and ATM network which a virtual connection between two fixed endpoints is established through the network.

Personal Video Recorder (PVR)

A video device that includes a large hard drive and video compression/decompression capability. It is used to record and play back programs just like a Video Cassette Recorder (VCR), but has more advanced capabilities for recording and viewing.

Plain Old Telephone Service (POTS)

A term used to describe basic Telephony.

Point-of-Presence (POP) A local interface point where a number of end-users are actually connected to a larger network. This term is normally used in reference to Internet services. Thus, it usually refers to a facility where a number of end-users are interfaced with the Internet. In this context, its function is analogous to that of a CO in a telephony network. It should be noted many dial-up Internet users connect to their POP via a CO.

Point-to-Multi-Point (P2MP) In the context of an optical access network, this term describes an architecture in which an OLT is optically linked to multiple ONUs through entirely passive means. There are no intermediate active devices, although some sort of passive device is required at the “branching” point. This term is often used as a synonym for a Passive Optical Network (see definition above).

Point-to-Point (P2P) : In the context of an optical access network, this term describes an architecture in which all optical links are from one point to another, without optical branching. However, branching can be (and usually is) done at an intermediate point by way of an active device (see definition for O/E/O). The intermediate active device can be located anywhere in the network, including the Central Office or a curb-side enclosure.

PON See Passive Optical Network

POP Also PoP. See Point of Presence

POTS Plain Old Telephone Service. A term used to describe basic Telephony.

Protocol Set of rules defining how data transmission equipment and/or software will communicate and interact.

Public Switched Telephone Network (PSTN)

The network that is normally thought of as the incumbent telephone system. It is considered Public because of open-access requirements. It is considered switched because dedicated connections or circuits are set up during calls, in contrast to IP or other networks that are connectionless.

Quality of Service (QoS) A term that describes the ability of a network to provide a particular level of service availability. QoS levels can range from best-effort to dedicated bandwidth. QoS is a


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technical term associated with ATM, but is commonly used to describe the concept of guaranteed availability for a wider range of technologies.

Radio Frequency Interference (RFI)

Radio frequency is the electromagnetic spectrum from 3 KHz to 300 GHz.

Rain fade Electromagnetic signal loss due to absorption and reflections caused by raindrops within the signal path. The wavelength of a system’s electromagnetic radiation determines its susceptibility to rain fade.

Rate Adaptive Digital Subscriber Line (RADSL)

ADSL modem that adjusts to varying lengths and qualities of lines. This type of modem can be designed to select their connection speed during a connection, or upon signal from the central office.

Regional Bell Operating Company (RBOC)

Any one of the large companies that emerged from the 1984 divestiture of AT&T with a charter to provide local telephone service over large regions of the United States. The scope of the original RBOCs has been changed in some cases by mergers and by their entry into other business segments. However, they are still easily identifiable by their lineage and status as the largest ILECs (see definition) in the United States.

Rehabilitation (Rehab) A term used to describe the upgrade or outright replacement of an existing network. The new network may be capable of delivering new or better services than the old network. For example, old copper telephony networks are often upgraded in order to provide DSL. By definition, this type of construction does not increase the number of operational networks.

Remote Termination Unit Device installed at the customer premise that connects to the local loop to provide high-speed connectivity.

RJ-11 Six-conductor modular jack used with four-wire cabling and is used commonly on phones, modems, and fax machines.

RJ-45 Eight-pin connector used to attach data transmission devices to standard telephone wiring.

Router A multi-port data communications device that transfer data packets from one port to any of the other ports according to address data included in the Overhead. Routers are differentiated from data communications Switches by the ability to perform higher-level functions necessary to the interconnection of different networks.

SAN See Storage Area Network

Scrambling In cable television, the process of modifying an analog TV signal so that it cannot be correctly displayed by a television receiver. In data transmission, scrambling refers to the process of randomizing the bit pattern of a transmitted signal to prevent peaks in the spectrum of the modulated signal. Note that the cable television and data transmission definitions are NOT equivalent.

SCTE Society of Cable Telecommunications Engineers. A professional organization of technologists interested in cable telecommunications technology.

Service User The end user at the customer premise.

Serving Central Office The central office in the local communications network that is directly connected to the end user location.

Set Top Box Also known as a Set Top terminal or Set Top Converter. A device used with an end-user’s TV to allow reception of television programs. It may tune channels the TV does not tune, and may include descrambling circuitry. It also may decode digital video signals for viewing on an analog television and provide auxiliary functions such as an electronic program guide.

Single Mode Fiber (SMF) Optical fiber that support only a single optical propagation mode, and thus exhibits no Modal Dispersion. Single Mode Fiber (SMF) is typically capable of uninterrupted transmission distances that are orders of magnitude longer than Multimode Fiber (MMF).

Society of Cable Telecommunications Engineers (SCTE)

A professional organization of technologists interested in cable telecommunications technology.

SONET Synchronous Optical Network. An optical networking standard. SONET defines specific aspects of how the network will be automatically restored during service


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outages via redundant links, as well as how it will be synchronized to facilitate TDM. Splitter A device having three or more ports, used to divide RF signal power between two or

more paths. If the device is bi-directional, it can also be used to combine two or more signals.

SSP See Storage Service Provider

Statistical Multiplexing In multiplexed video compression systems, the process of assigning more or less of the available channel bandwidth to each of the several signals being multiplexed,according to the instantaneous needs of each.

Storage Area Network (SAN)

A network created for the purpose of providing shared data storage capabilities to a group of users.

Storage Service Provider (SSP)

A company that provides data storage facilities. These services often provide added security, in addition to storage capacity.

Strand A heavy wire attached to utility poles, to which coaxial and fiber optic cables can be attached.

Streaming The process of downloading video and/or audio while the user is watching/listening at the same time. This allows the user to start enjoying the content before it is fully downloaded, saving time before beginning playout of a movie.

STS-1 ATM physical layer implementation supporting 51 Mbps.

STS-3 ATM physical layer implementation supporting 155 Mbps.

Switch In telephony, the device used to connect one circuit for the duration of a call. In data communication, a multi-port device that transfers discrete pieces of data from one port to any of the others, according to address data included in the Overhead.

Symmetrical Digital Subscriber Line

DSL connection that provides equivalent upstream and downstream transmission rates.

Synchronization In data transmission, the process of ensuring that data recovery at the receiver is timed properly with the data being transmitted. In video, the process of ensuring that the camera pickup and the receiver display are scanning the same part of the image at the same time.

Synchronous Digital Hierarchy (SDH)

The international standard for transmitting digital information over optical networks, a version of SONET

Synchronous Optical Network (SONET)

An optical networking standard. SONET defines specific aspects of how the network will be automatically restored during service outages via redundant links, as well as how it will be synchronized to facilitate TDM.

Synchronous Optical Network (SONET)

Standards for transmitting digital information over optical networks. Fiber optic transmission rates range from 51.84 Mbps to 13.22 Gbps. It defines a physical interface, optical line rates known as Optical Carrier (OC) signals, frame formats, and an OAM&P (Operations, Administration, Maintenance, and Provisioning) protocol. The base rate is known as OC-1 and runs at 51.84 Mbps. Higher rates are a multiple of this such that OC-12 is equal to 622 Mbps (12 times 51.84 Mbps).

Synchronous Transmission Data transmission using synchronization bytes, instead of star/stop bits, to control the transmission.

T-1 A data exchange protocol used in North America for constant bit rate systems. It operates at 1.544 Mb/s and can handle up to 24 telephone calls or other data. The corresponding protocol in Europe and elsewhere is E1, 2.048 Mb/s, handling up to 30 telephone calls or other data. T-1 is also used to describe the actual service, as provided by telephone system operators.

T-3 The US equivalent of an E-3. This is a Bell system term for a digital carrier facility used for transmission of data through the telephone hierarchy at a transmission rate of 45 Mbps.

Telco Generic term for the local telephone company operator in a given area.

Telephony over Passive Optical Network

Telephony using a PON as all or part of the transmission system between telephone switch and subscriber.

Time Division Multiple Access (TDMA)

A data transmission method in which a number of individual transmitters in different locations share a transmission channel, each occupying the channel for a portion of the total time.


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Transmission Control Protocol/Internet Protocol (TCP/IP)

The protocols (TCP/IP) are the result of the Defense Advanced Research Projects Agency (DARPA) project to interconnect disparate computer networks of the 1970s. Today the protocols are the basis of the Internet.

Trunk (1) The untapped portion of a coaxial distribution network. (2) The segment of a Distribution Network closest to the central facilities (Headend or CO).

Tunneling Protocol Technology that enables one network to send its data via another network's connections.

Twisted Pair A type of cable used extensively for transmission of electrically balanced audio or data signals. The cable consists of two insulated conductors twisted together in order to achieve specific electrical properties. These electrical properties and the performance of the cable may be compromised if the twist rate is disturbed by handling or installation. There may or may not be a shield over the twisted pair.

User Network Interface (UNI)

The user’s end of an access or distribution network. This is more generic than an ONU, since it is not necessarily Optical. However, it is the same in all other respects.

Video Compression The removal of signal information from a Video signal in order to reduce the bandwidth necessary to transmit that signal. Video Compression can be done in such a way that there is little or no perceptible change in the Video quality. It can also be done at the expense of Video quality, when higher compression rates are necessary for bandwidth limited systems.

Video Over IP The transmission of video programming over an IP network. If the source programming is digital, it is simply encapsulated into IP packets. Otherwise, it is first digitized and usually compressed. The signal can be converted back to an analog signal by equipment at the customer’s premises, or viewed by a digital-capable TV. One attraction of Video Over IP and VOIP (see below) is that they could allow a single network protocol to handle voice, video and data services.

Video-On-Demand (VoD) A video service which allows users to select a program and begin viewing it at any time. In some embodiments, it allows VCR-like control of the playback (e.g. pause, rewind, fast-forward) without use of a PVR.

Virtual Private Network (VPN)

A logical (as opposed to physical) grouping of users in a network which has many functional attributes of a dedicated or private network. VPNs provide the convenience and security of dedicated networks, while allowing more than one VPN (or set of users) to share the same infrastructure.

Voice Over IP (VoIP) The transmission of telephone calls over an IP network. See also Video Over IP.

Wavelength (1) The size of an electromagnetic wave as it travels through a transmission medium. Wavelength is equal to the speed of propagation in a medium divided by the frequency, and thus is inversely proportional to frequency. (2) A term used to describe an individual channel in a WDM system.

Wavelength Division Multiplexing (WDM)

Multiplexing in which a unique optical wavelength is used for each signal, thereby allowing two or more signals to be transmitted through the same medium simultaneously without interference.

Wavelength Overlay The insertion of an additional wavelength or channel onto an existing optical link. Strictly speaking, this is WDM (see below), but the term is often used to describe the expansion of capacity in a PON.

WDM Over PON The expansion of capacity in a Passive Optical Network through the use of Wavelength Division Muliplexing. The additional wavelengths or channels can be accessible to one, some, or all of the end-users who are physically connected to that PON. It is often used to provide a dedicated channel for a single user (e.g. a large business), expand capacity for a limited subset of end-users, or broadcast analog video.

Wide Area Network (WAN) A network of individual PCs and servers that are geographically dispersed and are using a common communication protocol. See also Local Area Network.


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FTTP Glossary/Acronyms – For Relay Racks and Fiber Frames within the Central Office. Block -- Short for fiber termination block. Cross Connect -- Means by which two network elements are connected to each other. One network element is connected to the rear of one FTB, and the other network element is connected to the rear of another FTB. The two network elements are then connected to one another by means of a patch cord, which is connected at the front of each FTB. This method of connecting network elements is recommended when expecting many moves, adds, and changes in the network. Edge Protector -- Device designed to protect a jumper from being routed over a rough or sharp edge, thereby eliminating the possibility of signal attenuation at this point. End Guard -- A device that is placed at the beginning and end of line-ups to protect the fiber frames and the cables within from damage. The NGF end guard is 5” wide and matches the height and depth of the adjacent FMDF. There are two types of FMDF that accommodate an end guard: the standard FMDF and the front-facing FMDF. Equipment -- The transmission components of a network. Fiber Storage Area -- Vertical area in the center of the FMDF frame which contains slack storage spools. FMDF -- Fiber Main Distribution Frame. FOT -- Fiber Optic Terminal. Network element that transmits and receives optical signals through fiber optic cable. FOTSB -- Fiber Optic Terminal Storage Bay. 12” wide free standing panel that functions as a storage area for equipment patch cord slack. Frame Section -- Individual NGF bay framework. Includes base guard boxes, uprights, patch cord storage area, horizontal and vertical troughways, and 12 module mounting positions. FTB -- Fiber Termination Block. Horizontal Trough --Trough which resides just below the FTB on the FMDF. Guides jumpers from front of FTB to vertical cable guides or from front of FTB to rear horizontal cable trough. IFC -- Intrafacility Cable. Multi-fiber in-building cable used between the termination frame and OSP splice point. Interconnect -- Means by which two network elements are connected to each other. One network element is connected to the rear of an FTB, and the other is connected to the front of the same FTB. This method of connecting network elements is recommended for low fiber counts and a small number of moves, adds, and changes in the network. Jumper -- Cable assembly containing one or two fibers. Also called patch cord. LHS -- Left Hand Side. Refers to the vertical on the left side of the FMDF as seen from front of frame section. Lower Trough -- Trough which rests on the base of the front-facing FMDF. Its function is to guide cross-connect patch cords from one side of the frame to the other or from one frame to another.


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Lowest Spool Position -- Spool that is offset from the slack storage spools in the fiber storage area of frame. Resides at very bottom of frame below the first slack storage spool. Provides edge protection for patch cords that are routed to and from the fiber storage area. NGF -- Next Generation Frame. ADC product line that includes the standard FMDF, the F3MDF, the Slim Rack, the associated FTB blocks, and various accessories. OSP -- Outside plant cable. Multi-fiber cable used outdoors to interconnect network elements from one building to another. Patch Cord -- Cable assembly containing one or two fibers. Also called jumper. Radius Limiter -- Device designed to protect the minimum bend radius of a jumper, thereby minimizing the possibility of signal attenuation at this point. Rear Trough -- The path through which jumpers are routed on the rear of the standard FMDF. The dimensions of each rear trough are 2” H x 5” D. The FMDF has six rear troughs. Also called rear horizontal trough. RHS -- Right Hand Side. Refers to vertical on the right side of the FMDF as seen from front of frame section. Slack Storage Spool -- Radiused device designed to support fiber jumper and protect the minimum bend radius of jumpers at the frame section. Sliding Adapter Pack -- Sliding housing that contains fiber adapters. Resides within the FTB. Terminate -- To mate a connector with an adapter. VCG -- Short for Vertical Cable Guide. Vertical -- Area of frame that accepts fiber termination blocks. A vertical accepts up to six FTBs or three Fiber Combination Blocks. The standard frame and the front facing frame each have two verticals (LHS and RHS). The slim rack has one (LHS vertical). Vertical Cable Guide -- Device designed to protect and guide jumpers vertically from one area of frame section to another.


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Link Loss Budget Calculations

Abstract For optical fiber point-to-point passive optical networks (PONs), oOne of the biggest concerns for the Outside Plant Design Engineer today is how do I calculate the link loss budget? What components do I consider when calculating the link loss budgets? The assumption for all design engineers regarding the Link Loss Budget Calculations is to design for the worst case scenario. Simply put, the design engineer should design for the highest loss values on component structures that are determined by the individual "Standards Bodies." With that said, let us look at the link loss budget for an FTTP Network with the Video services provided over IP. What impacts Passive Optical Network (PON) distances and link budgets? 1st, we have the physical aspects of the PON network, the quality and quantity of the splice points, the number and types of connectors, the split ratios, and finally the fiber. 2nd, we have the optical power considerations of the lasers, the class of the PON optics in the network we are designing and the receiver sensitivity. And finally, we have the physics, the types of dispersion (i.e. PMD and chromatic). Today, the dispersion effects do not greatly effect the link loss budgets. In the future, dispersion will play a greater role when bandwidths greater than 10 Gbps and longer distances greater than 20 km are the norm.

Exhibit 1. Single Fiber Architecture – Passive Optical Network (PON) Exhibit 1. Key:

OLT – Optical Line Termination ONT – Optical Network Termination ODN – Optical Distribution Network AT – Access terminal FDH/FDT – Fiber Distribution Hub/Terminal VAM – Value Added Module

1310 nm US digital1490 nm DS digital

1590 nm US Analog 1550 nm DS Overlay


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When looking at the Link Loss Budget, please use the following: Active Component Vendor Selection and Class of Optics Optical link budgets are determined by individual vendor’s active components; PON chips within the electronics, the lasers, and the receivers. The PON Optics Classes have been defined as Class A, B, & C. Traditional BPON equipment has always used the Class B Optics. When we look at the link budget for the Class B optics, we see that the maximum link is set at 25 dB. It was determined that some of the PON Networks of 20 km were actually stretching these budgets to the limit, and the active equipment manufacturers were force to increase these budgets to 26.5 dB. With the advent of these increased budgets and the possible need to increase the split ratios of GPON, the Class B Optics were given an increase in the receiver photo detectors to allow for a 28 dB loss budget. While still not in the Class C optics range, these components were given the distinction of Class B+ optics. The key differentiation is that the cost of these Class B+ optics have not increased to the Class C pricing while maintaining better PON loss characteristics. This is not to say that in the future, the need to transport to longer reaches (say 30 km or 40 km) and even higher split ratios (1:128) will force the equipment manufacturers to the Class C optics. For the Point to Point (P2P) Ethernet in the First Mile (EFM) and GEPON systems, the IEEE has defined the optics classifications as P10 & P20. Initially, the EPON ONTs were provided with P10 optics which would lead to only a 1:16 split ration with a 10km reach. The current generation of GEPON electronics are using the P20 optics which allow for the full 1x32 split ratios with a 20km reach capability.

Optics Class Min Optical Link Budget Max Optical Link Budget

A 5 dB 20dB

P10 5 dB 20 dB

P20 10 dB 25 dB

B 10dB 25dB

B+ 10dB 28dB

C 15dB 30dB

Exhibit 2. Optical Link Budgets and PON Optics

Central Office Connectorization Losses: The connector loss table in Exhibit 3 are the maximum losses allowed for connectors in the "field." The field is defined to be within the outside plant (OSP), and the standards were put into place to cover the environmental conditions due to temperature changes. Realistically, in looking at connector manufacturing, the measured losses may be quite low (on the order of 0.05 to 0.15 db per connector) regardless of the connector type used; Ultra Physical Contact (UPC) or Angled Physical Contact (APC).


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As long as the connectors are placed in the Central Office, as this is a controlled environment and the temperatures should not vary greatly, the design engineer may use 0.25 dB per connector or 0.5 dB per connector mated pair for all CO connectors. However, the loss value for all Outside Plant connectors should use the standards table below. For the PON systems designed, the preferred connector used in the central office and in the field are the APC connectors where in the field, the design engineer should use 0.35 dB or 0.7 dB per connector mated pair for all OSP connections. Again, these are the "worst case" losses which is what the design engineer should be designing for on paper. Telcordia GR326 Standard Connector Loss Table Type Loss (dB) Fusion Splice Loss (dB) SC/UPC 0.20 – 0.25 0.1 ((± 0.05dB) SC/APC 0.30 – 0.35

Exhibit 3. Optical Parameters – Connector/Splice Loss Exhibit 4 below shows what a typical Central Office layout should look like. In determining the link loss budget for a particular system, the CO typically only accounts for less than 100 meters (328 feet) if fiber, and may be omitted in the overall link loss budget calculations. However, when experiencing a budget calculation close to the manufacturer’s maximum link loss budget, this value should be considered.

Exhibit 4. FTTH/P Central Office Layout

Active Components P/V-OLT Video WDM

Fiber Distribution Frames Fiber Entrance Cabinet (FEC)


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The other consideration is to look at Central Office connection method; There are three connection method strategies, and each has its own advantages and disadvantages. For the most part, we will use the cross connection method as this method offers greater flexibility in how we test and turn up networks. With the cross connection method used, the Connectorization Loss within the Central Office would be three connected mated pairs maximum or 1.5 dB. From the Central Office perspective, we will also have at least one (1) splice where the OSP fiber will transition to the CO Fiber, and again we will be using the worst case of 0.1 dB per splice (inside plant or outside plant). So for the first total, we will have 1.6 dB for our Central Office losses.

Exhibit 5. Optical Parameters – Cross Connect Method Spectral Attenuation The spectral attenuation is simply the loss characteristics built into the fiber optic cable given over a particular optical wave length. The lower the wavelength, the higher the spectral attenuation. You will see this applied to link loss budget calculations where we will take the worst case and apply those numbers for the end-to-end loss budget. Not shown in the graph is the fact that after the 1600 nm wavelength, the intrinsic attenuation actually goes back up. Therefore, it is not logical to say that we can keep extending the wavelength to achieve lower and lower losses. For PON, the equipment operates in the ranges between 1310 nm and 1590 nm. The fact that we are using CWDM transceivers, the total bandwidth variants can be between plus/minus 10 nm to a plus/minus 50 nm. In telecommunications, the spectral bandwidth for single peak devices is the difference between wavelengths at which the radiant intensity is 50%, or 3 dB down from the maximum value. In looking at the link budget for an FTTP Network with the Video services provided over IP, we are only going to use the 1310 & 1490nm wavelength spectral attenuations.

Jumper or IFC

SPLICE

FDF P-OLT

1 2

2

3

3 IFC

FEC


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When applying to distances and calculating the link loss budget for a given architecture, Fiber Optic Cable manufacture must specify the Spectral Attenuation for their products. In designing the FTTP network, the design engineer, will initially design for the wavelength with the highest loss characteristics. For BPON and GPON, this will always be 1310 nm. The loss will vary from manufacturer to manufactures. Some of the ranges are from 0.31 db/km for premium fiber to 0.34 db/km for standard SMF-28e (corning) to a high of 0.40 dB/km. When we start increasing the split ratios in a given network, the Spectral Attenuation will need to be closely monitored.

Exhibit 6. Optical Parameters – Operating Windows

Wavelength Loss dB/km Loss dB/mi Band

1590 nm 0.25 dB 0.40 dB C* 1550 nm 0.25 dB 0.40 dB C* 1490 nm 0.28 dB 0.48 dB S* 1310 nm 0.40 dB 0.64 dB O*

1535 -1559 nm 0.25 dB 0.40 dB C** 1427 – 1450 nm 0.28 dB 0.48 dB E**

( * NOTE1: Wavelengths used in BPON, EPON, GPON & EFM.) (** NOTE2: Wavelengths used in WDM PON.)

Exhibit 7. Optical Parameters – Loss Table

Spectral Attenuation

n m d B / k m a 850 1.81 b 1300 0.35 c 1310 0.34 d 1380 0.40 e 1550 0.25 f 1490 0.28 g 1590 0.25

a

f g


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Splitter Loss Regardless of the splitting architectures or PON Technologies used (Centralized vs. Distributed Architectures), when calculating the link loss budget, you want to account for the following splitter loss configurations (SC/APC connectors in/out are included): 1x2 3.70 dB, 1x3 5.10 dB, 1x4 7.25 dB, 1x8 10.38 dB, 1x16 14.10 dB, and 1x32 17.45 dB. (ITU Standards) These losses include connectors and are the maximum losses defined by the International Telecommunications Union (ITU) G.671 and Telcordia GR-1209. When GPON requires the 1x64 split ratio we were originally forced to use a single 1x2 splitter interfacing two 1x32 splitters to make up the 1x64 configuration. With today’s packaging, this is allowable, however for the design engineer, we are taking the 1x2 maximum of 3.7 dB and the 1x32 maximum 17.45 dB and adding = 21.15 dB. When we do this, and we only are using Class B Optics (at 26.5 dB Loss) we are left with 5.35 dB of what we call “head room.” Even with the best fiber manufactured, where the Spectral Attenuation is 0.31 dB per kilometer, we are only able to design for a 17.25 km PON network. All this, and we still have not included any of the connectors within the Central office or Head End or the splices in the OSP. The FSANS standards body and splitter manufacturers using newer planer techniques are pushing the loss of the 1x64 splitter to around 20.4 dB. Remember, these are the maximum allowable loses per the applicable standards that cover optical couplers; G.671 from the ITU and GR-1209 from Telcordia. The design engineer does have some options. In designing the network, we can use premium splitters and ensure that low loss connectors are used in the network, and also ensure that our fusion splices are well below 0.05 dB/splice. There are other techniques we can use until the standards have caught up the technology for 1x64 and higher split ratios.

Exhibit 8. ADC Mini Plug-N-Play Splitter Confiburation

Central Office

Plug -N -Play Splitter Chassis

Parking Lot for unused output

splitter

Splice

Plug-N-Play Splitter

1:32 Planer

Strain Relief 72-Port

Distribution Panel

Splice

FDH3000

F1 Fiber from CO

F2 Fiber to Subscribers


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Optical Distribution Network (ODN) and the Outside Plant (OSP) We have already reviewed the splitter loss within the PON network, and in most instances these losses occur in the ODN (Connector loss is included in the splitter loss). For the total ODN losses, we take the total length of the fiber and use the spectral attenuation, all splices in the ODN, and all connectors in the ODN. What does this all add up in the link loss budget. From the rule of taking the worst case scenario: we normally take into account the ONT 1310 nm upstream wavelength loss on the fiber distance, and the mated pair of connectors within the ONT. At the access terminal, we can either provide a splice or connectorize drop (at least one splice here). We have one splice at the fiber distribution Hub (FDH) splice case for the distribution fiber F2, and one splice for the feeder fiber F1.

Exhibit 10. Optical Distribution Network (ODN)

Allianc

Fiber Distributio

n

Splice Case

Splice Case

ONT

ONT Drop Cable

Drop Cable

Access Terminal

OSP Feeder Cable (F1) From CO

Distribution Cable (F2)

Access Terminal

Access Terminal

Mounted in Hand-Hole

FTTP FDH Cabinet

Distribution Cable (F2)


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Link Loss Budget Totals In reviewing how we look at the TOTAL Link Loss Budget, we are calculating for the physical aspects of the PON network; the quality and quantity of the splice points, the number and types of connectors, the split ratios, and finally the fiber. Use the following: Central Office (CO)- If we are doing cross connect to the active components (preferred method) there are three (3) mated pairs and a single splice at the Fiber entrance cabinet. (3-APC Connector Mated Pairs at 0.5 dB/Mated Pair, and 0.1 dB/splice) 3x0.5 + 0.1 = 1.6 dB Spectral Attenuation (SA) - For 20.0 km, the SA for 1310 nm is 0.4 dB. .4 x 20 = 8.0 db. Splitter Loss - When using the standard 1x32 splitter, the loss = 17.45 dB. (Loss Calculations taken from ITU Standards Body for Optical Fiber, Optical Techniques and Connectivity Products.) ODN Splices - Using the total number of Feeder Fiber (F1) Splices to equal 4 (worst case) > 0.1 x 4 = 0.4 dB. Using the total number of Distribution Fiber Splices to equal 3 (worst case) > 0.1 x 3 = 0.3 dB. ODN APC Connectors - (We are using connectorization techniques at the Access Terminal [MSTs]). We have seven (2) mated pairs of connectors (1 in the MST, 1 in the ONT) for > 2 X 0.7 = 1.4 dB. We are using the Telcordia GR-326 Standard for APC connectors in the OSP (worst case) for 0.35 dB/connector or 0.7 dB/mated pair. Now, let us add all this up. (CO Loss + SA Loss + Splitter Loss + ODN Splice Loss + ODN Connector Loss = Total Link Loss Budget Loss) 1.6 + 8.0 + 17.45 + 0.7 + 1.4 = 29.15 dB of loss NOT VERY GOOD........However, these calculations "ON PAPER" are worst case calculations based upon the standards bodies. It can be argued that these losses are way too high, but over time......, dirty connectors......, macro bends......, micro bends......, laser degradation......, fiber aging......, additional splices...... Not an easy task for the design engineer. Now,....., let us look at ways we can reduce the total link loss budget. The CO losses will be the same (1.6 dB). We can infer from best practices that the fiber loss will be at minimal 0.34 dB/km for 1310 nm . 0.34 x 20 = 6.8 dB (maybe we do not go the 20 km, say we go 15 km 15 x 0.34 db = 5.1 dB). Again, using the total number of F1 splices at 4, and most good splicers can get the loss down to about 0.02 dB/fusion splice > 0.02 x 4 = 0.08 dB and the F2 Splices at 3 > 0.02 x 3 = 0.06 (0.05 dB by many service providers are the minimum requirements based upon the Fusion Splice "Machine" Reading.). For the 1x32 splitter, we will use the high performance 1x32 where the loss is 16.2 dB. And, we will use the GR-326 maximum loss for OSP connectors at the Access Terminal and ONT to be the same. Now, let us add all this up. (CO Loss + SA Loss (15 km) + Splitter Loss + ODN Splice Loss + ODN Connector Loss = Total Link Loss Budget Loss) 1.6 + 5.1 + 16.2 + 0.14 + 1.4 = 24.44 dB of loss (BETTER BUT NOT GREAT.....) If using the GPON B+ Optics which tells us that the receiver sensitivity (maximum link loss) is 28 dB, then the 15 km links will work. If we use a 1x64 splitter in the solution, we will need to add around 2.5 to 3.0 dB which will put us very close to the maximum for GPON B+ optics.


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Video Overlay (VOLT) Below are some additional considerations for the RF Overlay.... Link Loss Budget Calculations with RF Overlay (V-OLT) Considerations For the Video Overlay considerations, what happens at the OLT and ONT? If the video overlay is used, at the OLT, there is an external WDM (ADC's) that takes the 1550 nm wavelength from the V-OLT (video overlay) and 1490 nm wavelength from the OLT (Packet/digital - voice/data) combines or multiplexes the two wavelengths, and sends them downstream. We are only to consider the implications of the link loss budget in this context. The downstream 1550 & 1490 nm wavelengths are then de-muxed at the ONT Triplexer, where the 1550 nm wavelength is sent to an optical to electrical converter where the raw RF (54Mhz - 1.2Ghz) is sent to the F-connector on the ONT. The 1490 nm wavelength is sent to an optical to electrical converter (digital) where the electronics (SLIC Chips) take the voice component (TDM) and process for delivery via TR-57 standard RJ-11 jacks on the ONT. The data component is IP based and is handled using Ethernet IEEE 802.3 (10/100 Mbps Base-T) standard and is sent to the RJ-45 jack on the ONT . The voice and data components are combined electrically within the ONT, and converted to an optical 1310 nm signal for upstream delivery. The 1310 nm wavelength is mixed internally at the ONT WDM and sent upstream. The 1310 nm wavelength travels the same path as the 1490 nm wavelength (only upstream). At the OLT (packet/digital), an internal diplexer un-combines (de-muxes) the upstream signal and processes the same voice and data applications to the OLT electronics. ADC's current WDM configuration utilizes two (2) input ports as the 1490 nm downstream wavelength and the 1310nm upstream wavelength travel the same path. For the link loss budget calculations, the typical loss characteristics for the WDM is 1.2 dB. (0.7 dB for the muxing/de-muxing mirrors, and 0.5 dB insertion connector loss). For the triplexer within the ONT, the typical loss characteristic is 0.5 dB (The ONT manufacturer should confirm the loss within the Tri-plexer). However, most active component manufacturers simply place the ONT tri-plexer loss and WDM loss within the receiver sensitivity, and is not typically used when calculating the link loss budgets. Today, there is a 4th wavelength to consider when using the RF Overlay. This 4th wavelength is an upstream wavelength from the ONT. The 4th wavelength is the 1590 nm wavelength used for the RF Return or RFoG (RF Over Glass) for video on demand (VOD) applications. When using the 4th wavelength, a CWDM is required, and depending upon the specifications, 0.5 dB may be added to the link loss budget. The combined total loss for these two components is 1.7 dB. The ADC Specifications for the CWDM is the same as the WDM when Calculating the link loss budget (1.2 dB).

pon design

Documents

electronic

slack storage

private property

personal video

wholesale

asynchronous

link loss

minimum bend