基于光脉冲延迟法的光纤长度测量方法

Method of Measuring Fiber Length Based on Optical Pulse Delaying

提出了一种基于光脉冲延迟的光纤长度测量新方法。该方法中，光源被调制后经光纤耦合器分成两路，分别经过被测光纤和参考光纤，调节调制信号的频率使两路信号重合，通过调制频率分析计算出被测光纤的光纤长度。该技术与传统的光时域反射计（OTDR）相比，测量精度由米级提高到厘米级；与光频域反射计（OFDR）、光相干域反射测量仪（OCDR）及基于频移不对称Sagnac干涉仪相比，其对光源的稳定性和相干性要求较低，系统易于实现。实验结果表明，基于光脉冲延迟的光纤长度测量方法不仅测量动态范围大而且测量精度也很高，850 nm波段和1300 nm波段测得的多模光纤最大长度分别为10 km和20 km，测量精度可以达到厘米级。

Using the method of optical pulse delaying, a novel fiber length measurement method is proposed. The method is that the modulated light source is divided into two parts by the optical fiber coupler and goes through the measured optical fiber and the reference optical fiber. The frequency of modulation signal is regulated so that the two signals can coincide, and then the measured optical fiber length is calculated by analyzing the modulation frequency. Compared with the traditional optical time domain reflectometer, the measurement precision is improved from the meter scale to the centimeter scale. Compared with the optical frequency domain reflectometer, optical coherence domain reflectometer and frequency-shifted asymmetrical Sagnac interferometer, the requirement of stability and coherence properties of light source is lower and the system is more easier to be achieved. The experimental result indicates that fiber length measurement method based on optical pulse delaying has a large dynamic range and a high precision. The maximal multimode optical fiber lengths measured by this method at 850 nm and 1300 nm are 10 km and 20 km, respectively, and the measurement accuracy can reach centimeter magnitude.