光纤双干涉在线绝对测量技术研究

Research on optical fiber dual-interferometry for on-line and absolute measurement

研究了一种新的兼融低相干干涉和高相干干涉的光纤在线绝对测量技术,可对能转换成位移变化的静态及准静态任意物理量进行测量。利用宽带光谱光源作为光源,以及光纤光栅只反射布拉格波长的特性,使光纤迈克尔逊干涉仪同时工作于低相干干涉和高相干干涉状态。用低相干干涉信号决定被测量的幅值,使测量的最大跨距不受光波波长限制,并且实现绝对测量;同时,用高相干干涉信号测量被测量的量值,使测量结果保持高相干干涉测量的高精度。利用高相干干涉信号对环境干扰进行修正,使该测量技术适合在线测量。分别研究并实验了单光源光纤测量系统以及由双光源组成的复合光源光纤测量系统,利用这两种系统对位移进行测量,测量结果的线性相关性分别为0.996和0.999 9,测量量程均为6 mm,均可对0～6 mm范围内任意跨距的位移进行测量。

A novel on-line and absolute measurement technology with optical fiber,which has both low coherence interferometry and high coherence interferometry,is presented. The technology is suitable for the measurement of any measurand that can be converted into the variation of displacement. Using broadband light sources and based on the characteristic of a fiber Bragg grating that reflects Bragg wavelength, the optical fiber Michelson interferometer is working in both modes of low coherence interferometry and high coherence interferometry. The signal of low coherence interferometry is used to determine the amplitude of the measurand and absolute measurement can be realized,while the signal of high coherence interferometry is used to measure the value of the measurand precisely. The maximum step of the measurand is no longer limited by the optical wavelength. The signal of high coherence interferometry is also used to correct the errors resulting from the environmental disturbances, therefore the technology is suitable for on-line measurement. A measurement system with a single broadband light source and another measurement system with synthesizing light source including two broadband light sources are studied and experimented respectively. And the linear regression coefficient of absolute displacement measurement result of each system is 0. 996 and 0. 999 9. The measurement ranges of the two systems are 6 mm, and any measurement step of measurement displacement during 0 -6 mm can be chosen.