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 refractive index modulation is disposed in a predetermined area in the direction of propagation of light along the optical waveguide and the light in a reflection band out of the light propagated through the optical waveguide is selectively reflected by the diffraction grating. If the band having the maximum bandwidth out of the continuous wavelength bands the transmittance o f which is T0 or less is made a first band and if the wavelength band between the maximum and minimum wavelength out of the wavelengths the reflectance to which is R0 is made a second band, T0 is -20 dB or less, R0 is 20 dB or less , and the ratio (B1/B2) of the bandwidth B1 of the first band to the bandwidth B2 of the second band is 0.3 or more. The maximum group delay difference caused by reflection of the light in the first band by the diffraction grati ng is a predetermined limit value 0.011 .times. exp(7.86 .times. B1/B2-0.045 .times. R0)/B1 or less.