Fast Phase Demodulation Method for Heterodyne Phase-Sensitive OTDR

We propose a fast and effective phase demodulation method based on the spatial phase shifting technique for heterodyne phase-sensitive OTDR. An orthogonal signal can be directly obtained using the spatially shifted original signal, without the need for digital I/Q demodulation or Hilbert transform. The proposed method has experimentally demonstrated at least 30% phase demodulation speed improvement with no deterioration in the demodulation results compared to the conventional methods. This technique may prove useful for practical distributed acoustic sensing applications, because of its simpler computation process and faster computation speed.