BASIC WDM OPTICAL NETWORK What is WDM WDM

BASIC WDM OPTICAL NETWORK

What is WDM ? ? ? • WDM (Wavelength Division Multiplexing) is multiplex technique used in optical network. It’s used to multipex some of wavelength that come in optical network • In WDM, one channel is used for only one wavelength like FDM that only pass one frequency in one channel. ג 1 ג 2 ג 3 ג 4

WDM ARCHITECTURE • Generally, WDM architecture is classified in two categories : 1. Broadcast and select WDM network 2. Wavelength routed WDM network.

Broadcast and select WDM network • It’s the architecture of WDM network that have a simple broadcast system • Star topology is a popular topology used in this architecture. Another topology in this network is bus topology.

How does Broadcast and select WDM network? ? Different node transmit messages on different wavelength simultaneously. The star coupler combines all these messages and then broadcasts the combined message to all the nodes. A node selects a desired wavelength to receive the desired message by tuning its receiver to that wavelength.

Advantages and Disadvantages of Broadcast and select WDM network • Advantages: Having a simple broadcast system • Disadvantages: They have limitations such as large number of wavelength are required, there is no wavelength reuse in the network. they cannot span long distances since the transmitted power is split among various nodes and each node receives only a small fraction of the transmitted power, which becomes smaller as the number of nodes increases

Wavelength Routed WDM Network • There are two main components : Routing node and access node. • Routing node route the sent messages • Access node has function as O-E-O converter

How does Routed WDM Network? ? A message is sent from one node to another node using a wavelength continuous route called a light path. A light path is an all-optical communication path between two nodes, established by allocating the same wavelength throughout the route of the transmitted data.

The Requirements of Light Path • Wavelength continuity constraint: The requirement that the same wavelength must be used on all the links along the selected route • Distinct wavelength assignment constraint : Two light paths cannot be assigned the same wavelength on any fiber.

Advantages and Disadvantages of Broadcast and select WDM network • Advantages: A same wavelength can be used in other different link or we can say a wavelength can be reused in this network. • Disadvantages: Inefficient utilization of wavelength channel, bandwidth loss caused by the wavelength continuity constraint.

References • Gond , Vitthal J. and Aditya Goel. “Performance Evaluation of Wavelength Routed Optical Network with Wavelength Conversion”. Journal of Telecommunication, vol. 2, issue 1, April 2010 • Zheng, Jun and Hussein T. Mouftah. 2004. “Optical WDM Networks: Concepts and Design Principles”. Institute of Electrical and Electronic Engineers, Inc.

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