broadband optical networks
TRANSCRIPT
Broadband Optical Networks
Delivered by
Dr. Erna Sri Sugesti
22 November 2018
Agenda
• Fiber Optics System- Overview
• PON Technologies and Developments
Fiber optics - overview
PONs Slide 4
© = sin¯ (n2/n1)1
V =c/n
t = L·n/c
t = Propagation Time
t Vacuum: n=1, t=3.336ns/m
t Water : n=1.33, t=4.446ns/m
Total Internal Reflection
in Step-Index Multimode Fiber
Multimode Graded-
Index Fiber
Single-mode
Fiber
Types of Optical Fiber
Popular Fiber
Sizes
• Click to edit Master text styles
– Second level
• Third level– Fourth level
Optical Loss versus Wavelength
Total Dispersion
Multimode Dispersion
Chromatic Dispersion
Material Dispersion
Sources of Dispersion
1 0 11
Multimode Dispersion
1 11 11 11
Dispersion limits bandwidth in optical fiber
1 0 11
Graded-index Dispersion
1 10
PONs Slide 10
1 0 1 1 10
In SM the limit bandwidth is caused by chromatic dispersion.
1
Single-Mode Dispersion
How to calculate bandwidth?
Tc = (20ps/nm * km) * 5nm * 15km = 1.5ns
Tc = Dmat * * L
Tc = (20ps/nm * km) * 0.2nm * 60km = 0.24ns
For Laser 1550nm Fabry Perot
For Laser 1550nm DFB
For a 1.25 Gb/s we need a BW of 0.7 BitRate = 1.143ns
System Design Consideration
Material Dispersion (Dmat)
PONs Slide 13
LASER/laser diode: Light Amplification by Stimulated Emission of Radiation. Done of the wide range of
devices that generates light by that principle. Laser light is directional, covers a narrow range of
wavelengths, and is more coherent than ordinary light. Semiconductor diode lasers are the standard light
sources in fiber optic systems. Lasers emit light by stimulated emission.
Spectral Characteristics
Laser
W
Laser Optical Power Output vs. Forward Current
PIN DIODES (PD)
- Operation simular to LEDs, but in reverse, photon are converted to electrons
- Simple, relatively low- cost
- Limited in sensitivity and operating range
- Used for lower- speed or short distance applications
AVALANCHE PHOTODIODES (APD)
- Use more complex design and higher operating voltage than PIN diodes
to produce amplification effect
- Significantly more sensitive than PIN diodes
- More complex design increases cost
- Used for long-haul/higher bit rate systems
Light Detectors
Wavelength-Division Multiplexing
WDM Duplexing
PASSIVE OPTICAL NETWORKS (PON) TECHNOLOGY AND DEVELOPMENTS
BMCDR = Burst Mode Clock Data Recovery
OLT = Optical Line Termination
ONU = Optical Network Unit
Basic Configuration of PON
Typical PON Configuration and Optical Packets
Access network bottleneckhard for end users to get high datarates because of the access bottleneck
local area networks
• use copper cable• get high datarates over short distances
core networks
• use fiber optics• get high datarate over long distances• small number of active network elements
access networks (first/last mile)
• long distances– so fiber would be the best choice
• many network elements and large number of endpoints – if fiber is used then need multiple optical transceivers– so copper is the best choice– this severely limits the datarates
coreaccess
LAN
Fiber To The CurbHybrid Fiber Coax and VDSL
• switch/transceiver/miniDSLAM located at curb or in basement• need only 2 optical transceivers but not pure optical solution• lower BW from transceiver to end users• need complex converter in constrained environment
N end userscore
access network
feeder fiber
copper
Fiber To The Premiseswe can implement point-to-multipoint topology purely in optics
• but we need a fiber (pair) to each end user
• requires 2 N optical transceivers
• complex and costly to maintain
N end userscore
access network
An obvious solutiondeploy intermediate switches • (active) switch located at curb or in basement• saves space at central office• need 2 N + 2 optical transceivers
N end userscore
access network
feeder fiber
fiber
The PON solutionanother alternative - implement point-to-multipoint topology purely in optics• avoid costly optic-electronic conversions • use passive splitters – no power needed, unlimited MTBF• only N+1 optical transceivers (minimum possible) !
1:2 passive splitter
1:4 passive splitter
N end users
feeder fiber
core
access network
typically N=32
max defined 128
PONs Slide 26
PON advantagesShared infrastructure translates to lower cost per customer
• minimal number of optical transceivers
• feeder fiber and transceiver costs divided by N customers
• greenfield per-customer cost similar to UTP
Passive splitters translate to lower cost
• can be installed anywhere
• no power needed
• essentially unlimited MTBF
Fiber data-rates can be upgraded as technology improves
• initially 155 Mbps
• then 622 Mbps
• now 1.25 Gbps
• soon 2.5 Gbps and higher
PONs Slide 27
PON
architecture
PONs Slide 28
TerminologyLike every other field, PON technology has its own terminology
• the CO head-end is called an OLT
• ONUs are the CPE devices (sometimes called ONTs in ITU)
• the entire fiber tree (incl. feeder, splitters, distribution fibers) is an ODN
• all trees emanating from the same OLT form an OAN
• downstream is from OLT to ONU (upstream is the opposite direction)
downstream
Optical Network Units
upstream
Optical Distribution NetworkNNI
Terminal Equipment
UNI
coresplitter
Optical Line Terminal
Optical Access Network
PON types
many types of PONs have been defined
APON ATM PON
BPON Broadband PON
GPON Gigabit PON
EPON Ethernet PON
GEPON Gigabit Ethernet PON
CPON CDMA PON
WPON WDM PON
in this course we will focus on GPON and EPON (including GEPON) with a touch of BPON thrown in for the flavor
Bibliography• BPON is explained in ITU-T G.983.x
• GPON is explained in ITU-T G.984.x
• EPON is explained in IEEE 802.3-2005 clauses 64 and 65– (but other 802.3 clauses are also needed)
EPONBPONGPON
PON principles(Almost) all PON types obey the same basic principles
OLT and ONU consist of
• Layer 2 (Ethernet MAC, ATM adapter, etc.)• optical transceiver using different s for transmit and receive• optionally: Wavelength Division Multiplexer
downstream transmission
• OLT broadcasts data downstream to all ONUs in ODN• ONU captures data destined for its address, discards all other data• encryption needed to ensure privacy
upstream transmission
• ONUs share bandwidth using Time Division Multiple Access• OLT manages the ONU timeslots• ranging is performed to determine ONU-OLT propagation time
additional functionality
• Physical Layer OAM• Autodiscovery• Dynamic Bandwidth Allocation
GPON, xGPON, Radio over Fiber
Dr. Erna Sri Sugesti
BACKGROUND
PON TECHNOLOGY DEVELOPMENT
APON/BPON AND G-PON
ATM-PON and ITU-T G.983
All ITU PON standards feature three classes of optical transmission layer designs with different ODN (Optical Distribution Network) attenuations between ONU and OLT. The three classes are specified in ITU-T G.982 as:• Class A: 5–20 dB• Class B: 10–25 dB• Class C: 15–30 dBClass C design is a very demanding power budget requirement for a passive fiber plant. For practical implementation yield and cost reasons, Class B+ with 28-dB attenuation was later introduced by most PON transceiver vendors
G-PON and ITU-T G.984To better cope with the changes in communication technologies and meet fast-growing demand, ITU-T created the G.984 series standards for PONs with Gigabit capabilities, or G-PON
ITU-T G.984.1 gives a high-level overview of G-PON components and reference structure. G-PON PMD layer or transceiver requirements are covered by the ITU-TG.984.2 standard. Similar to APON, G-PON also defined single-fiber and dual-fiber PMDs. The bit rates defined in G.984 are:• Downstream: 1244.16 Mbps/2488.32 Mbps• Upstream: 155.52 Mbps/622.08 Mbps/1244.16 Mbps/2488.32
Mbps
As the bit rate advances into the gigabit regime, PON optical layer starts to become challenging. First, to cover the full 20-km transmission distance, multilongitudinal-mode (MLM) lasers cannot be used at ONU any more in order toavoid excessive dispersion penalty.
Second, to cover the loss budget requirements for Class B (10–25 dB) and Class C (15–30 dB) fiber plants, more sensitive avalanche photo-diodes (APDs) are required instead of the lower cost PIN receivers. Without proper protection circuits, APDs are susceptible to damages due to avalanche breakdown if the inputs optical power becomes too high.
XGPON
XG-PON means• Full compatibility with G-PON — by virtue of a wavelength
plan, blocking filters and loss budget that allow coexistence on a common PON infrastructure
• Support for single-sided and mid-span reach extension, with reach of up to 60 km
• Full service support — including voice, TDM, Ethernet (up to Gigabit rates), xDSL, wireless backhaul
• Powerful Operation Administration Maintenance and Provisioning (OAM&P) capabilities providing a feature-rich service management system
• Advanced security features including authentication, rogue detection and information privacy
• Power-saving features on top of the already considerable power-efficient nature of fibre access
G.987 — 10-Gigabit-capable passive optical network (XG-PON) systems: Definitions, abbreviations and acronyms
Establishes common terms and acronyms used in the G.987 series, as well as delineates various optical access topologies.
G.987.1 — 10-Gigabit-capable passive optical network (XG-PON) systems: General requirements Lists system-level requirements for XG-PON systems. Most significantly, the XG-PON system can coexist with a G-PON system on the same ODN. Provides examples of the wide variety of SNIs, UNIs and system configurations possible.
G.987.2 — 10-Gigabit-capable passive optical network (XG-PON) systems: Physical media dependent (PMD) layer specification
Defines the physical layer interface specifications for the system operating at the nominal data rates of 10 Gbit/s downstream, 2.5 Gbit/s upstream.
RADIO OVER FIBER
F. Aurzada, M. Scheutzow, M. Reisslein, N. Ghazisaidi, and M. Maier, IEEECapacity and Delay Analysis of Next-GenerationPassive Optical Networks (NG-PONs), IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 59, NO. 5, May 2011
References:
• C. F. Lam, Passive optical networks : principles and practice, Elsevier, 2007.
• Fiber in The Data Center II: Another Lightwave Study, Webinar, May 7, 2014
• Some figures are downloaded from several sources in the internet