Optical sensors for aerospace structural monitoring

Sensor systems based on optical fibre Bragg gratings embedded in thermo-set, carbon-epoxy composite material are being investigated. The systems under consideration are based on the following concept: an array of fibre gratings each with slightly differing nominal reflection wavelengths is illuminated by a broad-band semiconductor light source via a 3 dB coupler. The narrow band reflections from the grating array are channelled back through the coupler into spectral analysis hardware. Strain measurements are made by measuring the reflection wavelengths of each grating and assuming proportionality between change in reflection wavelength and strain. The grating array is sandwiched between plies within carbon fibre material