A Digital Phase Resolving Method for Fiber Optic Sensing

Phase is of great significance in many fields, which can be used to carry important information. In a fiber optic sensing system, phase is crucial for extracting environment information along fiber link. Therefore, the accuracy of the phase resolving result significantly influences the performance of a fiber optic sensing system. There are some widely used phase demodulation method like 3 × 3 coupler demodulation method, in-phase quadrature (IQ) demodulation method and phase generated carrier (PGC) demodulation method, which usually have an imbalance error or distortion problem. In this paper, a novel phase resolving method is proposed and used in an interferometric fiber optic sensing system. Comparison between proposed method and commercial IQ demodulator is carried out. The proposed method is proved to have a better orthogonality performance. Furthermore, the proposed method has less bandwidth limits compared with a digital IQ demodulation method, giving it a broader application.