The Strain Sensor

A strain sensor comprising a strain sensing element whose response to interrogation is dependent on the force to which it is subjected, the strain sensing element having a long axis, wherein, in use, the application of a given force to the strain sensing element in a direction substantially aparallel to the long axis induces a greater strain in the strain sensing element than the given force would induce when applied in a direction substantially parallel to the long axis wherein the strain sensing element is a wavelength selective element, the wavelength selective element being disposed within an optic fibre, the long axis of the strain sensing element being defined as being the longitudinal axis of the optic fibre in the locality of the strain sensing element wherein the optic fibre is tethered to a substrate at a first and second point such that the optic fibre therebetween is substantially strain-relieved from the application of force to the optic fibre external of the first and second points, the wavelength selective element being disposed therebetween, wherein, in use, a force is applied between the first and second attachment points.