Design of a distributed Brillouin optical fiber sensing system based on high efficiency and cost-effective consideration

A distributed Brillouin optical fiber sensing system scheme is proposed and experimentally demonstrated. It adopts a digital down-conversion module to replace the traditionally used radio frequency (RF) power amplifier, local oscillator (LO) and mixer for Brillouin spectrum sweeping and sampling, which makes the new sensing system cost-effective with good performance. And a Brillouin spectrum extraction method that is based on cubic Spline interpolation is also employed in the proposed sensing system to enhance the efficiency for the Brillouin center frequency extraction. According to the feature of Brillouin spectrum such as waveform and bandwidth, the peak power point is searched first, and then the range of Brillouin spectrum for data interpolation is determined, and finally by cubic Spline interpolation, the center frequency of Brillouin spectrum can be accurately extracted. In the experiment, with probe pulse peak power of 20dBm and pulse width of 10 microseconds, the sensing system obtains a 40dB double way dynamic range, and it just takes about 8 seconds to extract the center frequency of the Brillouin spectrum along an optical fiber with length of 25.2km. The accuracy for the Brillouin center frequency extraction along the whole optical fiber is about +/- 1.0MHz, which agrees well with the expectation for practical application.