Wavelength Assignment and Upgrading Strategies for WDM Rings

We investigate the performance improvements imparted by some wavelength assignment algorithms to optical path WDM rings. A computationally inexpensive algorithm is presented that minimizes: a) the blocking probability immediately after each assignment; and b) the increment of the channel blocking probability at the assigned wavelength. Simple metrics are proposed for the choice of the best wavelength assignment that are based totally on local information. We also discuss upgrading strategies for the WDM ring, showing that a modest wavelength pool size excess with respect to fiber load can produce almost the same improvement as full wavelength conversion.