LAUSR

Abstracts The influence of pump pulse spectrum launched into the sensing fiber on the spontaneous Brillouin scattering and Brillouin Optical Time Domain Reflectometry (BOTDR) sensing system, is investigated both theoretically and experimentally. The pump pulse power spectrum is the essential factor for the Brillouin scattering from physical mechanism, and it includes two ingredients: the laser linewidth and the modulated pulse waveform; they both subsequently affect the performance of the BOTDR system. Two different pump pulse spectra are generated in the experiment: (1) the output light of a distributed feedback (DFB) laser with 3 MHz linewidth, modulated to a rectangular pulse; and (2) the continuous output of a fiber laser with 4 KHz linewidth, modulated to a Lorentzian pulse. Experimental results indicate that the signal-noise-ratio (SNR) of the Brillouin scattering spectrum for the second pulse spectrum is 4 dB larger than that of the first, then the corresponding frequency fluctuation of the whole sensing fiber in BOTDR for the second pulse spectrum is 2 MHz smaller than that of the first. This is in accordance with numerical simulations. This study will likely prove to be beneficial for the design optimization of BOTDR sensing systems.