Patent ID: 7272278

Claim:
An optical multiplexer/demultiplexer which, when light is fed into any one of a plurality of ports, causes any one of said plurality of ports to output a wavelength component included in the light, said optical multiplexer/demultiplexer comprising: a first optical system for outputting light fed into any one of said plurality of ports; a first wavelength branching device for spatially splitting wavelength components included in the light and outputting the split wavelength components into respective optical paths different from each other; a second optical system for condensing the wavelength components outputted from said first wavelength branching device; a plurality of optical path changing parts for inputting the wavelength components condensed by said second optical system and outputting the wavelength components onto an output optical path not located on the same line as an input optical path of the inputted wavelength components, the output optical path being changeable; a third optical system for inputting the light outputted from said optical path changing parts and outputting the light; a second wavelength branching device for inputting the wavelength components outputted from said third optical system, changing a traveling direction of each inputted wavelength component according to the wavelength, and then outputting the wavelength components; and a fourth optical system for inputting the wavelength components outputted from said second wavelength branching device, condensing the wavelength components, and causing any one of said plurality of ports to output the wavelength components, wherein at least one of said first and third optical systems collimates the inputted light and outputs the collimated light, wherein said optical path changing parts include first and second reflecting surfaces substantially perpendicular to each other, wherein the optical axis of the first optical system is not parallel to the optical axis of the second optical system, wherein each of the first and second reflecting surfaces of said optical path changing part is movable in a direction substantially perpendicular to a plane including principal rays of the wavelength components having traveled through said first optical system, first wavelength branching device and second optical system after being outputted from the same port, and changes the output optical path by the movement, and wherein, when f 1 is the focal length of said first optical system, f 2 is the focal length of said second system and Δx f is the pitch of arrangement of said plurality of ports, Δx m is the pitch of arrangement of said optical path changing parts and the foregoing parameters satisfy the expression: Δx f f 1 =Δx m /f 2 .