“…When write fiber Bragg gratings in photosensitive fibers with UV light, photo-induced birefringence can split the transmission and reflection spectra of gratings and can thus induce undesired polarizationmode dispersion and polarization-dependent loss, which will produce harmful effect on communication systems, especially for high-speed systems. On the other hand, photo-induced birefringence can be used to fabricate rocking filter, comb rocking filters, polarization mode dispersion compensators, and so on [4][5][6][7][8]. Therefore, the study on photo-induced birefringence of photosensitive fibers is needed.…”