System impairment of birefringence in fiber Bragg gratings in optical networks

Abstract

Considering the presence of birefringence in fiber Bragg gratings (FBGs), the spectral polarization mode dispersion and polarization-dependent-loss-induced power penalty of eye opening is simulated for a network consisting of cascaded FBGs with various index apodization profiles. It is shown that with the same FBG length, 3dB bandwidth, and the birefringence value, FBGs with Gaussian index apodization profiles introduce the highest power penalty compared to FBGs with other apodization profiles, such as raised cosine, Blackman, etc. When there is wavelength misalignment up to 0.1nm between the central FBG's resonance and the wavelength of the laser source, the birefringence-induced power penalty can be up to a few times higher than the case with no wavelength misalignment.