Crosstalk Limitation in Optical Cross-Connect Node with Filters

Crosstalk is an important limiting factor in optical wavelength division multiplexing (WDM) networks with optical cross-connect (OXC) nodes. The impact of coherent and incoherent crosstalk on an optical signal passing through a typical OXC architecture is studied in this paper. We give the analytical power penalty expressions for both coherent and incoherent cases. Through simulation calculation, the coherent crosstalk is found to be the most important limitation in the OXC. In order to relax the total crosstalk specification requirement for components, the use of filters is proposed. On the other hand, the power penalty depends less on the number of input fibers N compared with the number of multiplexing wavelengths m for the ideal performance of mechanical switch. If the number of links must to be increased due to traffic demand, we can gracefully adapt to the demand by adding modular units one by one to the design maximum of N.