双折射光纤环镜应变传感器在线测量方法研究

Research on the on-line measurement of a birefringence fiber loop mirror strain sensor

为了实现双折射光纤环镜(Bi-FLM)传感器的在线测量,采用推导得出的基于波长解调双折射光纤环镜应变传感器在线测量的理论表达式,选取典型通讯波长1550nm和1310nm附近的2组波长进行了计算,所得应变均与给定应变基本吻合。结果表明,利用干涉光谱任意连续4个相邻的波谷波长及其双折射光纤初始长度、初始双折射率和初始双折射应变系数便可计算出双折射光纤受应变后的绝对长度,并以此计算所受应变唯一大小;根据干涉光谱任意4个相邻波谷波长相对位置蕴含着应变信息的特点,区分是干扰还是外界传感量导致干涉光谱变化,以此剔除外界干扰,提高了测量精度。该研究对Bi-FLM应变、振动等各类传感器实现计算机在线测量,提高测量精度具有指导意义。

In order to realize the on-line measurement of a birefringence fiber(BF)loop mirror(Bi-FLM)strain sensor,the theoretical wavelength-demodulation on-line measurements expression of a Bi-FLM strain sensor was deduced.Two different groups of four-adjacent-wave-valley wavelengths near 1550nm and 1310nm were chosen and substituted into the theoretical expression.Both the calculated strains were basically consistent with the given strains.The result shows that the absolute BF length can be calculated by the random four-adjacent-wave-valley wavelengths,the initial BF length,the initial BF birefringence,and the initial strain dependent birefringence coefficient.Then the strain can be calculated according to the absolute BF length after axial strain and the initial BF length.According to the relative positions of any four-adjacent-wave-valley wavelengths which contained strain information,the noises or external sensing can be distinguished when the interference spectrum changes.By this way,the noises can be eliminated,and the measurement accuracy can be improved.These results can provide guidance for realizing the on-line measurement and improving measurement accuracy of the strain,vibration and other sensors of Bi-FLM.