chapter  33
Optical Fiber Displacement Sensors
Pages 16

Strain measurements using optical Ÿber sensors in both embedded and surface-mounted conŸgurations 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 Ÿber 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 Ÿber sensors for strain measurements should possess certain important characteristics. œese sensors should either be insensitive to ambient žuctuations 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 conŸguration, the sensors for axial strain measurements should have minimum crosssensitivity to other strain states. œe sensor signal should itself be simple and easy to demodulate. Nonlinearities in the output demand expensive decoding procedures or require precalibrating thesensor.œe 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.