| 摘要 |
PROBLEM TO BE SOLVED: To prevent input beam input through an optical input port of a port group in a wavelength selection switch including a plurality of port groups from returning to an optical input port of other port groups.SOLUTION: A wavelength selection switch 1A includes a light input/output unit, a wavelength dispersion element, a light deflecting element, and an optical system. The optical system includes an optical component 41. In the optical component 41, input beams Ba1, Ba2 input through first and second light input ports of the light input/output unit, respectively, are incident at angles &thetas;1, &thetas;2 with respect to a predetermined axial line A1. Signs of the angles &thetas;1, &thetas;2 are opposite to each other. An optical axis A2 of the optical component 41 is inclined with respect to the predetermined axial line A1 in such a manner that reflected light beams of the input beams Ba1, Ba2 in the optical component 41 are reflected at angles &thetas;3, &thetas;4, respectively, with respect to the predetermined axial line A1. The angles &thetas;3, &thetas;4 are different from any of the angles &thetas;1, &thetas;2. Signs of the angles &thetas;3, &thetas;4 are the same. |
