The influence of interferometer initial phase angle to fiber-optic acoustic emission detection

In fiber-optic acoustic emission testing system,the initial phase of the coherent light directly impacts the output signal. We analyze the relationship between the initial phase and the output signal. The theoretical calculation results were simulated by computer. The Sagnac interferometer acoustic emission detection system was designed and experimental verification was done. Experimental results verifies the correctness of the theoretical calculation. It reasonably interprets the reason of that frequency doubling phenomenon appears in the optical fiber acoustic emission detection. This work lays a foundation for further study.