Orthogonal Imbalance Compensation Method of Φ-OTDR System Based on RLS Algorithm

Aiming at the quadrature unbalance phenomenon in the phase-sensitive optical time domain reflectometry ($\Phi $-OTDR) system, a method of quadrature unbalance compensation for the$\Phi $-OTDR system based on the recursive least square (RLS) algorithm is studied and demonstrated to improve the accuracy of the demodulated phase waveform. Firstly, the DC residual term of the quadrature imbalance is eliminated by calculating the mean value of the envelope. Further, the cyclic symmetry of the AC orthogonal unbalance is tracked to complete parameter estimation, and then the orthogonal unbalance correction is completed through an adaptive filtering method. The experimental results show that under the condition of the detection light pulse with a repetition frequency of 5 KHz and a pulse width of 100 ns, the RLS compensation algorithm greatly improves the demodulation characteristics of the system and suppresses the quadrature imbalance. It is of great significance to the practical process of the$\Phi $-OTDR system.