Delay interferometer

摘要

In a delay interferometer in which a Michelson delay interferometer unit is mounted in a package, the delay interferometer includes: a Michelson delay interferometer unit in which A-channel interference output light obtained by optically processing input light that is formed by splitting input light received through an input port, into A and B channels through a splitting portion is output from an A-channel first output port and an A-channel second output port disposed, and B-channel interference output light is output from a B-channel first output port and a B-channel second output port; and a first optical path length compensating member which is interposed between the A-channel interference output light or the B-channel interference output light, and the A-channel first output port or the B-channel first output port.