Fibre Bragg gratings are used to reflect light back to the Interrogator. As the grating is stretched, the wavelength it reflects changes. This is what the Interrogator uses to determine the strain at each sensor location.
The fibre optic cable is encased in a glass fibre patch. This protects the fibre, and the similar material types makes it easy to install into a blade. They are normally laminated over in the blade to ensure they are fully bonded and protected.
Sensors are IPx5 rated, and are typically 180 x 140mm.
Connecting to sensors inside blades
Insensys use heavily armoured optical cables to connect the sensors inside the blade to the FSI. These are routed to pass through the centre of pitch rotation of the blade so that the cables don't stretch.