US Patent 7599587 Wavelength selective switch

In a wavelength selective switch according to the present invention, an isolator is disposed between a lens array and a first lens. The isolator includes an isolator element and a transmitting means. The isolator is disposed so that the isolator element is on light paths of input lights and that the transmitting element is on a light path of an output light. The isolator element is shared among the light paths of the plurality of input lights. The isolator element intercepts lights propagating in an opposite direction to the input lights and prevents coupling of the lights to input ports. The transmitting element transmits the output light and couples it to an output port.