ABSTRACT
Strain measurements using optical ber sensors in both embedded and surface-mounted congurations have been reported by researchers in the past [2]. Fiber-optic sensors are small in size and immune to electromagnetic interference and can be easily integrated with existing optical ber communication links. Such sensors can typically be easily multiplexed, resulting in distributed networks that can be used for health monitoring of integrated, high-performance materials and structures. Optical ber sensors for strain measurements should possess certain important characteristics. ese sensors should either be insensitive to ambient uctuations in temperature and pressure or should have demodulation techniques
33.1 Extrinsic Fabry-Perot Interferometric Sensor ........................... 33-2 33.2 Intrinsic Fabry-Perot Interferometric Sensor ............................33-4 33.3 Fiber Bragg-Grating Sensor ..........................................................33-5
33.5 Comparison of Sensing Schemes ............................................... 33-14 33.6 Conclusion ..................................................................................... 33-14 References .................................................................................................. 33-14 Further Readings ...................................................................................... 33-15
that compensate for changes in the output signal due to the undesired perturbations. In the embedded conguration, the sensors for axial strain measurements should have minimum cross sensitivity to other strain states. e sensor signal should itself be simple and easy to demodulate. Nonlinearities in the output demand expensive decoding procedures or require precalibrating the sensor. e sensor should ideally provide an absolute and real-time strain measurement in a form that can be easily processed. For environments where large strain magnitudes are expected, the sensor should have a large dynamic range while at the same time maintaining the desired sensitivity. A discussion of each of the four sensing schemes individually, along with their relative merits and demerits, follows.
