Characterization of Stimulated Brillouin Scattering in Polymer Optical Fibers Based on Lock-in-Free Pump–Probe Technique

We observe stimulated Brillouin scattering (SBS) in polymer optical fibers (POFs) using a pump-probe technique without lock-in detection, and fully investigate the dependences of the Brillouin gain spectrum on the POF length, pump power, probe power, and temperature. Since the POF has relatively high propagation loss of 250 dB/km at 1.55 μm, an optimal POF length exists for SBS observation, which is found to be approximately 3.8 m with 21.1-dBm pump and 22.2-dBm probe waves. As the probe and pump powers are increased, the Stokes power is also raised but nonlinearly. The temperature dependence of the Brillouin frequency shift is -4.02 MHz/K, which agrees well with the previous report. These results indicate that the Brillouin signal in POFs observed with this technique can be directly applied to the development of POF-based Brillouin optical time-domain analysis systems for high-precision temperature sensing.