Better path-optimization algorithm for WDM fiber-optic networks speeds up calculations by 10,000 times

June 28, 2011
For today's wavelength-division multiplexing (WDM) systems, calculating the best route and wavelength assignments for each signal path is a challenge.

Raleigh, NC--For today's wavelength-division multiplexing (WDM) systems, calculating the best route and wavelength assignments for each signal path is a challenge. Not only are WDM SONET (synchronous optical network) rings becoming more complicated, but a single optical fiber can support 100 or more wavelengths; in addition, the difficulty of the path-assignment calculations grows exponentially with the network size. Researchers at North Carolina State University have developed a more efficient algorithm that should speed up the path-calculating process by 10,000 times.1

Using existing techniques, finding the optimal solution for a SONET ring network can take days, even for smaller rings. And a ring's connections are modified on an ongoing basis, to respond to changing use patterns and constantly increasing traffic demands.

In contrast, the new model identifies the exact optimal routes and wavelengths for ring network designers, creating a large graph of all the paths in a ring and where those paths overlap. The model then breaks that graph into smaller units, with each unit consisting of the paths in a ring that do not overlap. Because these paths do not overlap, they can use the same wavelengths. (Naturally, paths that do overlap cannot use the same wavelengths.)

"Problems that used to take days to solve can now be solved in just a few seconds," says George Rouskas, one of the researchers. He notes that ring design work can also be done using fewer computer resources, lowering costs.


1. Emre Yetginer et al., Journal of Optical Communications and Networking, Vol. 3, No. 7, p. 577 (2011); doi:10.1364/JOCN.3.000577.

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About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

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