A Straight-Line Type Sagnac Optical Fiber Acoustic Sensing System Suitable for Sound Detection in Harsh Natural Environment

A straight-line type Sagnac optic fiber acoustic sensing system is proposed in this paper. The Sagnac interference fiber loop is replaced by a straight-line fiber and a 1×2 coupler to enhance the environmental adaptability, and the length of Sagnac interference fiber loop is shortened close to 50%. The key parameters are analyzed by theory calculating and simulation. Experimental results show that the sensing system has a well response to 50-8000Hz, 70dB sinusoidal acoustical signal and can distinguish them with different frequency. Using a small-scale helicopter audio signal as acoustical signal, the test response curve is consistent with the simulation results, and the sensitivity reaches 30.67mV/Pa