Coherent multipath crosstalk in Benes and dilated Benes optical switches

Optical space switches are expected to play a key role in future transparent optical networks. Crosstalk due to finite isolation of switching elements is an important parameter for optical switches. Coherent crosstalk in particular can be very damaging, originating even bit error floors. Multipath crosstalk associated with multiple propagation paths inside the switch is one form of coherent crosstalk. This crosstalk is a single source interference and, in this way, it is always present even when only one data channel is routed by the switch. An additional feature of multipath crosstalk is that, the different terms interfere coherently, making its analysis particularly difficult. In this paper, the problem of coherent multipath crosstalk is discussed and its influence on optical space switches is analyzed, considering both Benes and dilated Benes architectures