Patent ID: 6888681
Filing Date: 2005-05-03
Classification: G02B

Abstract:
1. An optical demultiplexer comprising: a light input unit for inputting incident light rays having a plurality of optical signals different in wavelength as a multiplex signal; a light collimating element for converting said incident light rays input by said light input unit into parallel light rays; a diffraction grating for demultiplexing said parallel light rays collimated by said light collimating element in accordance with wavelengths; and a plurality of photo acceptance units provided in different positions where a plurality of light rays at different wavelengths demultiplexed by said diffraction grating are converged and image-formed in accordance with the wavelengths by said collimating element; wherein distances h in which j is an integer of 0 to n, A is equal to sin(θg+tan −1 (h 0 /f)), f is a focal length of said light collimating element, θg is an angle between the optical axis of said light collimating element and a line normal to a diffraction surface of said diffraction grating, h 0 , is a distance between said light input unit and the optical axis of said light collimating element, N is a number of grooves in said diffraction grating, m is order of diffraction, and λ 0 , λ 1 , . . . , λ n are demultiplexed wavelengths.