Phase Demodulation Based on DCM Algorithm in Φ-OTDR With Self-Interference Balance Detection

A phase demodulation algorithm in phase-sensitive optical time domain reflectometry (φ-OTDR) with self-interference balance detection is proposed. With a simple differentiate-and-cross-multiply (DCM) operation to acquire the perturbation waveform, and a further second-order operation to compensate the amplitude fluctuation of the phase, the phase can be extracted accurately. The self-interference balance detection structure can equivalently achieve the function of dual-pulse detection, but avoid the negative impact of the common-mode noise and the difference between the dual pulses on the demodulation. In experiment, several types of vibrations are retrieved correctly under the condition of single channel and low sampling rate, which demonstrates the validity of this demodulation approach.