Wavelength Division Multiplexing (WDM)

WDM is a technique where multiple light signals are transmitted in a single optical fiber. Each signal uses unique wavelength and the routing in nodes is based on this. The same wavelength can be used at most once in any link, or a wavelength conflict occurs. The configuration of given set of logical connections into a WDM network consists of:

Routing (R)
Wavelength Assignment (WA)

Once the lightpath routes are fixed the remaining wavelength assignment problem can be represented as a graph coloring problem. Each lightpath corresponds to a node in WA graph, and two nodes are set as neighbours only if the respective lightpaths share at least one common link. The graph coloring problem is shown to be NP-hard.

This applet demonstrates a simple algorithm to solve a static RWA problem.

The objective is to configure a lightpath between each node pair, i.e. to create a fully connected logical topology.
First the algorithm finds the shortest path for each node pair.
Then a greedy algorithm assigns the smallest feasible wavelength channel to each lightpath in the descending order of node degree in WA graph.

Download the source code.

Back to java demos page.

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