Abstract: A temperature-compensated fibre optic strain gauge (10) for measuring strain of a host structure (5), the strain gauge (10) comprising: a mount (20) to be operatively attached to the host structure (5), 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 measur