Two-Parameter Distributed Sensor Base On Coherent Detected BOTDR Signal

The Brillouin Scattering Distributed Sensor works at long wavelength, and its attenuation and scattering are both smaller, which make it to be fit for long distance sensing. And For the normal single-mode optical-fiber, the frequency shift and optical power of Brillouin scattering light are the functions of the temperature and strain. So, the temperature and strain of the optical-fiber can be detected together, as Brillouin frequency shift and the optical power are able to be obtained simultaneously. But, Brillouin scattering signal has some disadvantages, such as its light-power is weak, and we have to face the problem of the polarization relative detecting signal. This system collect data by high-speed acquisition card, take logic control by FPGA, demodulate the scattering optical signal's amplitude with generalized S transform, solve the polarization relative problem by orthogonal polarization control ,in order to gain frequency and power spectrum for compute sensing information. We have completed the job of design a Brillouin Optical Time Domain Reflectometer Dual-Parameter Sensing System, and made it work with 25-km standard single-mode optical-fiber in lab.