Simultaneous temperature and vibration sensing based on hybrid BOTDR and Φ-OTDR

A novel hybrid BOTDR and Φ-OTDR system for simultaneous static and dynamic measurements is proposed. Employing the division of both backscattering light and local light, a double coherent detection configuration is achieved to extend the sensing range and demodulate the phase quantitively. With the independent detection of Brillouin scattering light and Rayleigh scattering light, the demodulation error in BOTDR is avoided while the signal-to-noise ratio of Φ-OTDR is enhanced. Experiment for simultaneously measuring temperature and vibration is carried out, which proves the sensing range of the hybrid system is 49.5km with 20m spatial resolution. The measurement uncertainty of BOTDR is verified to be 2.821MHz, and the maximum frequency response range of Φ-OTDR is 900Hz. Experimental results indicate the proposed system is specialized in dealing with both static and dynamic situations simultaneously.