| 摘要 |
PROBLEM TO BE SOLVED: To reduce the influence of a zero-order diffraction light beam from a diffraction grating, being unwanted light in an optical multiplexer- demultiplexer, affecting an optical multiplexer-demultiplexer system and to reduce a noise. SOLUTION: By setting zero-order diffracted light 10, not diffracted but reflected by a diffraction grating 4, free from a light passing portion 11 provided in the propagating direction of the zero-order diffracted light to the outside of a module casing 51 on the side face of the module casing 51 between the diffraction grating 4 and a collimator lens 3, it is prevented that the zero-order diffracted light 10 becomes a stray light beam and scattering from inside the module casing 51. |
