Multiresolution Phase Compensation for Phase-Sensitive OTDR

In order to suppress the phase distortion caused by fading in phase-sensitive optical time-domain reflectometer ( $\varphi $ -OTDR) system, a new multi-resolution phase compensation algorithm is proposed in this paper. When the intensity of the beat signal approaches the system floor noise, the phase variation will gradually follow the uniform distribution, and fading occurs. The fading region in the spatiotemporal phase plane would be determined subsequently by synthesizing the differential section intensity. The redundancy and local correlation of the phase plane is thoroughly utilized by the patch searching algorithm in multi-resolution. Hence, the marked fading region would be compensated by the fading free region in the phase plane. The proposed method has been proved and analyzed that the fading can be effectively suppressed in the $\varphi $ -OTDR system in the experiment. The fading region can be accurately compensated whether the disturbance exists. The disturbance can be restructured effectively with SNR of 31.2 dB. Furthermore, the strain resolution was achieved to 7.685 $\text{p}\varepsilon /\surd $ Hz. Therefore, the proposed method provides a promising approach to realizing fading elimination without additional structure in the $\varphi $ -OTDR system.