Optical Spectrum Characteristics of Phase-Only Sampled Chirp Gratings with Manufacturing Errors

Abstract

Due to strong coupling among multi-channels of phase-only sampled gratings, the effects of manufacturing errors on sampled grating are different from fiber gratings with a single reflection peak. The influence was investigated by numerical simulation. When group delay and reflectivity ripples are caused by random phase and amplitude errors, inside a grating channel, the ripple amplitude at short wavelength is larger than the one at long wavelength, and this phenomenon was qualitatively explained using the principle that the reflecting position varies with the wavelength of incident light in a chirp grating. The sub-grating length of the transfer matrix method, which is decided by the accuracy of phase mask and UV writing, exerts an influence on the ripple amplitude. For multi-channel fiber gratings, stitch error impairs the periodicity of sampling function, so this kind of fabrication error leads to unequal performance reduction in different channels, and the reduction is more serious for channels at two sides.