Improved Differential Phase Detecting Optical Fiber Interferometer With a Low-Frequency Compensation Scheme

To overcome the poor low-frequency response sensitivity of differential phase detecting interferometer, an improved differential phase detecting optical fiber interferometer with a time domain low frequency compensation scheme is designed and implemented, effectively compensating the low frequency loss of the system by means of recursive accumulation method. Theoretical derivation and experimental verification are conducted in this paper. The experimental results indicate that the improved system can significantly enhance the amplitude of 10 Hz signal and signals with high fidelity can be obtained because the compensated system responds equally both to the high and low frequency signals. Further experiments in the buried pipelines monitoring reveal that the signal-to-noise ratio is obviously improved by 22 dB approximately compared with the traditional system. The positioning error of the proposed system is within ±20 m along a 40 km sensing fiber. The differential phase detection interferometer compensated by the proposed scheme has potential application in low-frequency fields such as seismic wave detection, hydrophones, sonar, pipeline monitor and geological detection.