Influence of nonlinear effects on forward stimulated Brillouin scattering distributed sensing

Abstract

The impacts of nonlinear effects on sensing performance of forward stimulated Brillouin scattering (FSBS) were investigated, using opto-mechanical time-domain analysis (OMTDA) sensor as an example. The excitation of FSBS often requires high pulse power (Watt level) because of the lower gain coefficient. Due to the copropagation of reading pulse and scattered light, high-power activation pulses will induce various nonlinear effects in FSBS sensing system. Using the reported method based on activation-reading time-domain separation, the influence of nonlinear effects due to activation pulses can be effectively avoided. However, the nonlinear effects of reading pulses have direct impact on sensing performance. Based on this consideration, we studied the influence of nonlinear effects on FSBS sensing and its physical mechanism under different peak power of reading pulses; the variation process of the 1st- and 2nd-order FSBS spectrums along~4.7 km standard single-mode fiber (SMF) was shown in detail. Finally, the optimization region was found, inside which a perfect FSBS local spectrum was obtained, and the sensing distance extension can be achieved.