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介绍了一种基于相位调制干涉仪解调光链路的新型光纤长度测量系统。推导了光链路增益理论模型,分析了光纤干涉仪的两臂光程差和增益自由频谱范围(FSR)的关系,得出利用长度已标定光纤来计算待测光纤长度的方法。该测量方法和传统的光时域反射(OTDR)方法相比,无测量盲区且可以将测量精度由米量级提高到毫米量级;与光频域反射法(OFDR)和光相干域反射法(OCDR)相比,对光源的相干性要求显著降低。通过理论分析和实验验证,采用现有的67GHz安捷伦网络分析仪可以测试的光纤最小相对长度为3mm,在相对光纤长度100m的情况下,测量误差小于0.05mm。该系统的原理及结构都很简单,是一种具有实用价值的光纤长度测量方法。
A new fiber length measurement system based on phase modulation interferometer to demodulate optical link is introduced. The theoretical model of the optical link gain is deduced. The relationship between the optical path difference of the two arms and the gain-free spectral range (FSR) of the optical fiber interferometer is analyzed. The method for calculating the length of the optical fiber to be tested by using the length-calibrated optical fiber is obtained. Compared with the traditional OTDR method, the measurement method has no measurement blind spot and can improve the measurement accuracy from the order of magnitude to the order of millimeters. Compared with the optical frequency domain reflectometry (OFDR) and the optical coherence domain reflectometry OCDR), the coherence requirements for light sources are significantly reduced. Through theoretical analysis and experimental verification, the minimum relative fiber length that can be tested with the existing 67GHz Agilent network analyzer is 3mm, and the measurement error is less than 0.05mm when the relative fiber length is 100m. The principle and structure of the system are very simple, is a practical method of fiber length measurement.