一种基于动态参考瑞利散射谱的分布式光纤大应变解调方法

A large strain demodulation method based on dynamic reference Rayleigh backscattering spectrum in distributed optical fiber strain measurement

基于光频域反射计(OFDR)的分布式光纤系统在结构健康监测领域得到广泛关注,通过对参考瑞利散射谱和测量瑞利散射谱进行互相关分析来确定谱偏移量,进而转化为结构应变。这种分布式光纤的应变解调方法具有较高的空间分辨率和测量精度,但在光纤受到较大应变时(超过3000με)会出现瑞利散射谱信号急剧衰减,从而导致互相关分析无法解调应变。本文提出了一种OFDR分布式光纤的大应变分步解调方法,采用动态参考瑞利散射谱取代固定参考瑞利散射谱的方法来突破大应变测量的限制。通过对复合材料层合板拉伸实验的大应变测量表明,本文所提出的光纤应变解调方法能稳定和可靠地测量10000με以上的大应变情况。

Distributed optical fiber strain measurement based on optical frequency domain reflectometry (OFDR) has attracted extensive attention in the field of structural health monitoring. The spectral offset is determined by the cross-correlation analysis of reference Rayleigh backscattering spectrum and measurement Rayleigh backscattering spectrum, which can be transformed into the structural strain. The strain demodulation method of distributed optical fibers has high spatial resolution and measurement accuracy. However, when the fiber is subjected to a large strain (more than 3000με), the amplitude of the Rayleigh backscattering signal will be drastically attenuated, which leads to the failure of cross-correlation analysis and cannot demodulate the strain. In this study, a large strain demodulation method for OFDR distributed optical fibers is proposed. The dynamic reference Rayleigh backscattering spectrum is used instead of the traditional fixed one to break through the limitation of large strain measurement. The large strain measurement of composite laminates in the tension testing shows that the proposed fiber optic strain demodulation method can measure the large strain of more than 10000με steadily and reliably.