Distributed birefringence measurement of a polarization maintaining fiber with a 20 cm resolution over a 500 m range based on Brillouin dynamic grating

We demonstrate a distributed birefringence measurement of a polarization-maintaining fiber with a 20 cm resolution over a 500 m fiber based on Brillouin dynamic grating with the scheme including a CW pump1, a 20 ns square pump2 pulse, and a 2 ns square probe pulse. The measurement results show similar to 3% fluctuation of the birefringence over the entire 500 m fiber. We also observed the birefringence change caused by the uneven stress as winding the fiber around a spool with a spatial period of 49 cm and the residual stress during the fiber drawing and coating processes.