Hybrid Distributed Fiber-Optic Sensing System by Using Rayleigh Backscattering Lightwave as Probe of Stimulated Brillouin Scattering

Distributed fiber-optic sensing system has been employed for temperature and strain measurement in health monitoring of various structures, and current systems are mainly designed for static-only or dynamic-only parameters. To combine these functions, we propose and experimentally demonstrate a single-end multi-parameter distributed sensing system which can simultaneously measure static parameters and dynamic parameters by integrating Brillouin optical time domain analyzer (BOTDA) for static parameters and phase-sensitive optical time domain reflectometry ( $\varphi$ -OTDR) for dynamic parameters. The probe pulse of $\varphi$ -OTDR and the pump pulse of BOTDA are successively injected into the sensing fiber. The first pulse is used as the probe pulse of a regular $\varphi$ -OTDR for vibration measurement, and its Rayleigh backscattering (RBS) lightwave is used as the probe of BOTDA. The second pulse is used to amplify the RBS lightwave for the measurement of static-parameters. The interaction of the pulse pair is analyzed in detail, and the hybrid system is experimentally demonstrated. The experimental results show that 3 kHz vibration sensing with 10 m spatial resolution at 14 km standard single mode fiber can be realized, and the temperature of the sensing fiber can be measured simultaneously with 5 m spatial resolution and 1.29 MHz measurement accuracy of Brillouin frequency shift.