Lightwave path allocation for lightwave network with cut-throughs in fiber layer

In this paper, we report results of our study with respect to the number of wavelength division multiplexer/demultiplexers that should be provided in optical cross-connect switches (optical XCs) installed in the nodes of optical wavelength multiplexed transmission networks. Optical XCs perform the switching and add/drop operations of optical signal routes in the nodes, as well as establish lightwave paths between two arbitrary nodes. In many cases, the optical XCs proposed in the past had wavelength division multiplexer/demultiplexers connected to all input/output optical fibers that, after separating all lightwave paths transmitting wavelength multiplexed signals, performed switch and add/drop operations. However, when all lightwave paths input in an optical XC from an optical fiber are relayed to only one different output optical fiber, there is no need to perform wavelength demultiplexing between the input and output optical fibers. If a lightwave path passes through a node without separation of optical signals as they were multiplexed in the optical fiber (cut-through), the number of wavelength division multiplexer/demultiplexers can be reduced. The authors considered two algorithms for lightwave path allocations whose purpose is to minimize the number of wavelength division multiplexer/demultiplexers and evaluated them on an example of an m×n mesh network. The results of evaluation suggest that it is possible to reduce the number of wavelength division multiplexer/demultiplexers that must be installed by 10% to several dozen percent compared to the case when the dividers are installed on all input fibers.