Integration of BOTDA and φ-OTDR distributed fiber sensing for multiple parameters monitoring

In this article, the integration of the Brillouin optical time-domain analysis (BOTDA) and the phase-sensitive optical time domain reflectometry (phi-OTDR) distributed fiber sensing systems is discussed. By combining the two systems and sharing common instruments, the cost of the experiments is minimized, enabling the sensing of three parameters: temperature, strain, and vibration on the same 18.7 km fiber. In the BOTDA part, the focus is on temperature and strain analysis. Two 4 m dispersion shifted fibers (DSF) are used to simulate strain at different positions, causing the Brillouin frequency shift (BFS) to shift from 10.88 GHz to 10.52 GHz, allowing for strain sensing. The two 4 m single mode fibers and DSF are separately heated from room temperature to 200 degrees C, resulting in an R2 value of 0.97654 and 0.99958, respectively, indicating a good linear relationship. In the phi-OTDR section, vibration point frequencies were demodulated using an external interferometer system based on Mach-Zehnder interferometer (MZI). This article presents comprehensive experiments that demonstrate the ability to achieve multi-parameter sensing on a single fiber using a hybrid system, all within a low-cost framework.