Temperature-compensated fibre optic strain gauge

Abstract

A temperature-compensated fibre optic strain gauge (10) for measuring strain of a host structure, the strain gauge (10) comprising: a mount (20) to be operatively attached to the host structure, the mount (20) having a void (19) separating a first section (17) of the mount (20) from a second section (18) of the mount (20); a first fiber Bragg grating (FBG) (30) recorded within a core of an optical fiber (11) to measure strain and temperature, the first FBG (30) being located transverse to the void (19) and a first end portion of the first FBG (30) is operatively attached to the first section (17) of the mount (20) and a second end portion of the first FBG (30) is operatively attached to the second section (18) of the mount (20), the end portions of the first FBG (30) being pre-strained by an amount larger than a predetermined operational range of the first FBG (30); a second fiber Bragg grating (FBG) (40) recorded within the core of the optical fiber (11) to measure temperature, the temperature measurement of the second FBG (40) being used to eliminate temperature as an influence on the strain measurement of the first FBG (30), a first end portion of the second FBG (40) is operatively attached to the first FBG (30) and a second end portion of the second FBG (40) is operatively attached to the mount (20) so that the second FBG (40) is free from strain; and removable bridging portions (24) adjacent to the void (19) to connect the first section (17) to the second section (18) of the mount (20), the bridging portions (24) being removed after the mount (20) is operatively attached to the host structure; wherein a safe-side failure proof feature is provided by detecting whether a reflection wavelength reverts to an original Bragg wavelength of the first FBG (40) to indicate whether the first FBG (40) has broken. 一种用于测量主体结构的应变的温度补偿光纤应变仪(10)，所述应变仪(10)包括：支座(20)，其操作地连接到所述主体结构，所述支座(20)具有使得支座(20)的第一部分(17)与支座(20)的第二部分(18)分隔开的空隙(19)；第一光纤布拉格光栅(FBG)(30)，其记录在光纤(11)的芯部内，用于测量应变和温度，所述第一FBG(30)横过所述空隙(19)定位，所述第一FBG(30)的第一端部操作地连接到所述支座(20)的第一部分(17)，所述第一FBG(30)的第二端部操作地连接到所述支座(20)的第二部分(18)，所述第一FBG(30)的这两个端部被预加载应变的量大于所述第一FBG(30)的预定操作范围；第二光纤布拉格光栅(FBG)(40)，其记录在光纤(11)的芯部内，用于测量温度，所述第二FBG(40)的温度测量用来消除温度对第一FBG(30)的应变测量的影响，所述第二FBG(40)的第一端部操作地连接到所述第一FBG(30)，所述第二FBG(40)的第二端部操作地连接到所述支座(20)，使得所述第二FBG(40)没有应变；以及能被移除的桥接部分(24)，其与所述空隙(19)相邻，以将所述支座(20)的第一部分(17)连接到所述支座(20)的第二部分(18)，所述桥接部分(24)可在所述支座(20)操作地连接到所述主体结构之后移除，其中，通过检测反射波长是否恢复到第一FBG(40)的原始布拉格波长来提供右侧故障验证特征，从而指示第一FBG(40)是否断裂。