Patent ID: 7133581

Claim:
An optical switch comprising: first, second, third, and fourth polarization-maintaining single-mode fibers, each having first and second ends; an optical coupler in said third polarization-maintaining single-mode fiber, between the first and second ends thereof; a first polarization splitting/combining module having a first input/output terminal into which a signal light is input, a second input/output terminal on a side of said first polarization splitting/combining module opposite said first input/output terminal, to which the first end of the first polarization-maintaining single-mode fiber is connected, and a third input/output terminal for outputting a switched signal light; a second polarization splitting/combining module having a first input/output terminal to which the second end of the second polarization-maintaining single-mode fiber is connected, a second input/output terminal on a side of said second polarization splitting/combining module opposite said first input/output terminal, to which the first end of the third polarization-maintaining single-mode fiber is connected, and a third input/output terminal to which the first end of the fourth polarization-maintaining single-mode fiber is connected; a first polarization plane conversion portion connecting the second end of said first polarization-maintaining single-mode fiber and the first end of said second polarization-maintaining single-mode fiber; and a second polarization plane conversion portion connecting the second end of said third polarization-maintaining single-mode fiber and the second end of said fourth polarization-maintaining single-mode fiber.