Interfermetric fiber sensors based on triangular phase modulation

This work presents three novel signal processing methods capable of accurately detecting the optical phase delay in optical inter-ferometric sensors. In the proposed methods, a triangular waveform modulation signal is used to modulate the optical phase of an optical interferometer for measuring optical phase delay. The optical phase delay in the first method is obtained by integrating the interferometric output signals with the gated-in signal. The optical phase delay in the second method can be measured from the time delay difference between the interferometric signals during the gated-in period. For the third method, the pseudo-heterodyne technique is applied, and the optical phase delay is measured from the phase difference between two output signals. Moreover, a fiber Sagnac interferometric rotation sensor is adopted to demonstrate the effectiveness of the proposed methods. Furthermore, experimental results confirm that the proposed methods have an extreme degree of sensitivity and good linearity.