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

摘要

The present invention relates to a diffraction grating device in which a diffraction grating based on perturbation of refractive index is formed through a predetermined range in a light guide direction in an optical waveguide and in which the diffraction grating selectively reflects light in a reflection band out of light guided through the optical waveguide. In the diffraction grating device, where a first band is defined as a band with a maximum bandwidth out of continuous wavelength bands for which the transmittance is not more than T0 and where a second band is defined as a wavelength band between a maximum wavelength and a minimum wavelength out of wavelengths for which the reflectance is R0, T0 is not more than -20 dB and R0 is not more than -20 dB. A ratio (B1/B2) of a width B1 of the first band to a width B2 of the second band is not less than 0.3. A maximum group delay difference caused by reflection of the light in the first band by the diffraction grating is not more than a predetermined limit, 0.011×exp(7.86×B1/B2-0.045×R0)/B1.