Optical fiber modal birefringence measurement based on Lyot-Sagnac interferometer

We propose and demonstrate a simple and accurate optical fiber modal birefringence measurement technique based on a two-segment Lyot-Sagnac fiber interferometer. We have conducted accurate measurements for several low birefringence fibers and the results are consistent with published data. This measurement method is allowed in the birefringence-length product ranging from 10/sup -3/ to 10/sup -6/ m within the resolution of the optical spectrum analyzer used.