Patent ID: 7343063

Claim:
A light signal switching apparatus which comprises a plurality of input ports to which an input light signal is input and a plurality of output ports which output an output light signal, wherein the light signal switching apparatus outputs the output light signal from a desired output port out of the plurality of output ports, comprising: a splitting element which polarizes an input light signal fed from the input port into a first component comprising a first polarized light signal and a second component comprising a second polarized light signal, whose polarization planes are different mutually by 90 degrees, to output the first polarized light signal and the second polarized light signal; a first polarization controlling element which rotates a polarization plane of the second polarized light signal by 90 degrees to output a third polarized light signal; a first optical switch which switches a path of the first polarized light signal fed from the splitting element to the desired output port side, to output the first polarized light signal; a second optical switch which switches a path of the third polarized light signal fed from the first polarization controlling element to the desired output port side, to output the third polarized light signal; a second polarization controlling element which rotates a polarization plane of the first polarized light signal fed from the first optical switch by 90 degrees to output a fourth polarized light signal; and a combiner which combines the third polarized light signal fed from the second optical switch with the fourth polarized light signal fed from the second polarization controlling element, to output a combined light signal to the desired output port, wherein the first polarization controlling element is provided at every input port.