Frequency Response Range Expanded Slope-Assisted BOTDA Sensor Using Randomized Sampling Technique

A novel frequency response range expanded slope-assisted Brillouin optical time domain analysis (SA-BOTDA) sensor is proposed and demonstrated using randomized sampling technique. In contrast to uniform sampling with fixed periods, randomized sampling employs different sampling intervals, which manages to achieves ultra-high detectable frequency range, and it breaks the limitation imposed by the round-trip time of the pulses in conventional systems. In addition, the massive averaging is no longer required in long range sensing scenario for the proposed scheme since randomized sampling accomplishes higher frequency signal measurement with similar signal-to-noise ratio (SNR) compared to uniform sampling, while it is indispensable for the traditional SA-BOTDA sensors using uniform sampling in order to compensate for the SNR, which however severely restricting the detectable frequency range. For proof of concept, 3.5kHz vibration signal is successfully detected adopting randomized sampling in 7 km sensing fiber with the pulse repetition rate of 10kHz, surpassing the theoretical maximum frequency limit of 500 Hz with 10 averages of the traditional uniform sampling scheme.