Tuning Rate Estimation for Improving Positioning Accuracy in OFDR System

A necessary tuning rate estimation method to correct the positioning error caused by nonlinear effects in optical frequency-domain reflectometry (OFDR) systems is proposed. Unlike previous studies on nonlinear effects in OFDR systems, this article focuses on the adverse effects of nonlinear tuning on positioning accuracy, rather than on the spatial resolution of the system. Based on the nonlinear noise model of the tunable laser source (TLS), the mechanism of its effect on the positioning capability is discussed in this article, and the specific effects of each parameter in the noise model on the positioning accuracy are further investigated. In the proposed method, the common auxiliary reference signal is employed to estimate the phase information, and the correction of OFDR system positioning is achieved using the short-time Fourier transform (STFT) and the sine-fit algorithm. In this article, the effect of different kinds of nonlinear noise on the positioning capability of the system is discussed, and the possibility of using the proposed method to eliminate the positioning error is verified. Comparing the positioning capacity before and after correction, we can achieve a positioning accuracy enhancement of about 2.36% on a 310-m fiber under test (FUT).