Value of fiber overlays in WDM metro networks

In wavelength-division-multiplexing (WDM) networks, multiple fibers can be used to provide the needed capacity for highly congested WDM routes. Such fiber overlays effectively serve to reduce wavelength blocking in transparent optical networks. In this letter we show, by performing wavelength allocation simulations, that the use of fiber overlays on the central ring of a typical interconnected-ring transparent metro network can significantly reduce wavelength blocking. We derive the optimum number of overlays and show that connection churn has negligible effect on blocking.