Fig. 1. Structure of the POFDR system. SSB: single-side band; RF, radio frequency; EPC, electrical polarization controller; PDR, polarization diversity receiver; BPD, balanced photodetector; FUT, fiber under test; L_ref, reference fiber.

Fig. 2. Experimental results. (a) POFDR curves for two polarization directions. (b) Comparison of forward SOP results calculated by POFDR and POTDR systems when the birefringence changes abruptly within a range of 4.11 m. POTDR: black points; POFDR: red line.

Fig. 3. Comparison of birefringence measurement results between POFDR and POTDR systems.

Fig. 4. Simulation results. (a) Process of deviation accumulation of forward SOP. (b) Histogram of DSOP at the fiber end.

Fig. 5. Contrast of absolute DSOP value for approximately 100 points. DSOP1: DSOP between the collected backward SOP and the calculated SOP using the improved algorithm. DSOP2: DSOP of the backward SOP and the calculated SOP using the original algorithm.