Temperature-compensated fibre optic strain gauge

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 right-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.