ch2-e3-e4 ews-dwdm & oxc concepts

E3-E4 (E&WS)

DWDM & OXC

For internal circulation of BSNL only

AGENDA

The Challenges of Today's

Telecommunications Network

Resolving the Capacity Crisis

Capacity Expansion and Flexibility

Capacity Expansion Potential

Optical Layer as the Unifying Layer

Optical Cross Connect

MEMS


DWDM

Definition

Dense wavelength division multiplexing (DWDM)

is a fiber-optic transmission technique that

employs multiple light wavelengths to transmit

data in parallel through a single fiber.


BLOCK SCHEMATIC

Tx RxMUX DEMUX

OFA W

D

M

W

D

M

λ2

.

.

.

.

λ1

λ16

TRANSPONDERS

OPTICALSIGNALS.

STM-1STM-4STM-16

ATMIP


CHALLENGES OF TODAY'S

TELECOMMUNICATIONS NETWORK

The forecasts of the amount of bandwidth

capacity needed for networks were calculated

on the presumption

Challenge of deploying and integrating diverse

technologies in one physical infrastructure.


CHALLENGES OF TODAY'S

TELECOMMUNICATIONS NETWORK

DWDM provides unique bandwidth management

capabilities by offering services such as e-mail,

video, and multimedia carried as IP data over

ATM and voice carried over SDH.


RESOLVING THE CAPACITY CRISIS

Challenges of increased bandwidth needs as

well as of laying new fiber after fiber exhaust.

By increasing the bit rate using time division

multiplexing (TDM), service providers purchase

more capacity than they initially need and it may

remain unutilized in the near future.


CAPACITY EXPANSION AND

FLEXIBILITY

By combining multiple optical signals and

transporting over a single fiber of different rate

and of different format (SDH, ATM, data, etc.)

i.e. DWDM can carry 80 wavelengths, each of

STM-16 capacity i.e. total of 200 Gbps.


CAPACITY EXPANSION AND

FLEXIBILITY

High-speed, high-volume transmission is

possible through deployment of optical amplifier.

Optical amplifiers operate in a specific band of

the frequency spectrum while ultra wideband

optical-fiber amplifiers can boost light wave

signals carrying over 100 channels (or

wavelengths) of light.


CAPACITY EXPANSION POTENTIAL

Flexibility to expand capacity in networks.

Compared with repeater-based applications it

increases the distances between nodes.

Using fewer regenerators in long-distance

networks results in fewer interruptions and

improved efficiency.


© for BSNL internal circulation only

OPTICAL LAYER AS THE

UNIFYING LAYER

Optical layer integrates the diverse technologies

of their existing networks into one physical

infrastructure

DWDM is Bit-rate and format independent and

can accept any combination of interface rates

Optical layer carries signals without any

additional multiplexing, i.e. ATM or IP without

deploying an overlay network

DWDM SYSTEM

CHARACTERISTICS

Well-engineered DWDM systems offer

component reliability, system availability, and

system margin.

Automatic adjustment of the optical amplifiers

when channels are added or removed ensures

optimal system performance.


DWDM SYSTEM

CHARACTERISTICS

In the 1530- to 1565-nm range, silica-based optical

amplifiers with filters and fluoride-based optical

amplifiers perform equally well. However, fluoride-

based optical amplifiers are intrinsically more costly

to implement


WHY OPTICAL (DWDM)

NETWORKING

Fibre Exhaust : Tapping the unlimited bandwidth

on a fibre pair

Bit Rate Transparency

Format/Protocol Transparency : IP, ATM etc


ECONOMICS OF DWDM

Saving of regeneration costs by multiplexing

multiple wavelengths on a single fiber, can

decrease the number of amplifiers by a huge

factor at each regenerator site.

Cost effective compared to laying new fibers


EDFA

Erbium Doped Fiber Amplifier (EDFA)

Optical fiber that is doped with the element

erbium and the amplifier. When a pump laser is

used to energize the erbium with light at a

specific wavelength, the erbium acts as a gain

medium that amplifies the in coming optical

signal.


OPTICAL CROSS CONNECT

Optical cross connects (OXC):Light in one fiber can be

moved into a different fiber i.e. redirecting the light.

An optical cross-connects (OXCs) is also referred to

as a wavelength cross-connect (WXC) or a

wavelength router. It is an optical device that can route

an input wavelength on an input port to an output port.


MICRO-ELECTRO-MECHANICAL

SYSTEMS (MEMS)

MEMS consist tiny moveable mirrors no larger in

diameter than a human hair. They can be

arranged on special pivots so that they can be

moved in three dimensions, and several

hundred such mirrors can be placed together on

mirror arrays no larger than a few centimeters

square


MEMS Mirror

MEMS Optical Cross Connect


MEMS OPTICAL CROSS

CONNECT

Light from an input fiber is put at a mirror, which

is directed to move the light to another mirror on

a facing array. This mirror then reflects the light

down towards the desired output optical fiber.

Most advanced optical switching technology is

MEMS, with tiny moveable mirrors


© for BSNL internal circulation only

SUMMARY

Cross connects forward signals to their destination

by specific routes

Traditional cross connects convert light to

electricity then back to light

OXC has many advantages including less cost,

smaller size, and bit-rate transparency as it

redirects the light from one optical fiber to another,

without electrical conversion

THANKS
