Adaptive Nonlinear Tuning Compensation Method for OFDR System Based on Phase Prediction

The nonlinearity of the tunable laser source (TLS) can significantly impair the accuracy and spatial resolution of the OFDR system. Therefore, nonlinear tuning compensation is a key technology for OFDR systems. However, in the conventional compensation method, the delay fiber length of the auxiliary interferometer significantly restricts the optimal compensation effects. This paper proposes an adaptive compensation method based on phase prediction. The instantaneous optical frequency of the TLS is obtained using an interferometer with a short-delay fiber. Then, the beat signals with different delay times are generated to meet different measurement distances by delaying the instantaneous optical frequency of the TLS in the calculation. Finally, optimal compensations for different measurement positions are achieved simultaneously with the generated beat signals. This method breaks the limitation of the length of the delayed fiber in the conventional compensation method. The experimental results show that the proposed method can achieve a resolution of 0.6 mm over a 100 m range with a 20 m-long delayed fiber in the auxiliary interferometer. The compensation result is better than conventional compensation methods with five times the length of the delay fiber. Meanwhile, optimal compensation can be achieved simultaneously at different locations within a range of 200 m using this method.