Fiber optic grating and etalon sensor systems
US 5646401 A

Fiber optic grating and etalon based fiber sensor systems are described that include an all solid state demodulation system with no moving parts. This demodulation system is based on using interference patterns generated by reflections from fiber gratings or etalons and measurements using an optical detector array. This demodulation system is applied to dual overlaid fiber optic gratings that have been written onto noncircularly symmetric birefringent optical fibers. These fiber grating based sensors may be used to measure transverse strain, longitudinal strain and temperature at a single location simultaneously and their nonsymmetric nature allows accurate placement and alignment of the strain sensing axes in materials.