OPTICAL WAVEGUIDE DIFFRACTION GRATING DEVICE, METHOD FOR FABRICATING OPTICAL WAVEGUIDE DIFFRACTION GRATING DEVICE, MULTIPLEXING/DEMULTIPLEXING MODULE, AND OPTICAL TRANSMISSION SYSTEM

摘要

An optical waveguide diffraction grating device in which a diffraction grati ng by diffractive index modulation is provided over a predetermined length in t he direction of propagation of light along an optical waveguide and the light i n a reflection band out of the light propagated through the optical waveguide is selectively reflected by the diffraction grating. The reflection band is divided into K (K = 2) wavelength bands. The refractive index modulation .DELTA.nall within the predetermined length is the sum of the refractive ind ex modulations .DELTA.nk (k=1 to K) of the periods .LAMBDA.k corresponding to t he K wavelength bands. At least a pair of phases out of the phases .PHI.k (k=1 to K) of the diffractive index modulation .DELTA.nk at the central position of the predetermined length are different from each other. In such way, an optical waveguide diffraction grating device which is short as a whole, is manufactured at low cost, and has excellent reflection/transmission characteristics is provided.