Wraparound optical switch matrix

Abstract

An optical switch matrix connects N input waveguides to M output waveguides via M rows of switch sets. Each row of switch sets includes a first switch set that has one input port and two output ports, N&minus;2 intermediate switch sets that have two input ports and two output ports, and a last switch set that has two input ports and one or two output ports. One output port of each first or intermediate switch set is optically coupled to an input port of a succeeding switch set in the same row, and the other output port is optically coupled to an input port of a respective switch set in a cyclically succeeding row, by intermediate waveguides that do not cross each other. The only exceptions are the intermediate waveguides that connect the last row to the first row. These intermediate waveguides may cross other waveguides. Preferably, however, no intermediate waveguides cross each other: the intermediate waveguides that connect the last row to the first row either cross the input waveguides or cross the output waveguides or cross no waveguides. Preferably, each switch set includes a 1&times;2 switch and a 2&times;1 combiner coupled optically to each other and to the input and output ports of the switch set. Optionally, in an N&times;N optical switch matrix, yet another switch set with two input ports and one output port is appended to each of L<N&minus;1 of the rows, starting from the next to last row and working upwards. The first L switch sets of the last row are optically coupled to respective appended switch sets instead of to respective switch sets of the first row.