<title>Fiber optic sensor considerations and developments for smart structures</title>

Abstract

The potential suitability of the Fabry-Perot and Bragg grating fiber optic sensors will be considered against a set of criteria for practical use with Smart Structures. Particular attention will be given to a number of key issues, such as: interrupt immunity, apparent strain, sensitivity, response tune, structural integration, optical inteifacing ininitnalperturbation and sensorpeifonnance lifetime. Some of our development of fiber optic sensors for use with Smart Structures will he reviewed in the light of these considerations.

Bragg grating-based laser sensors systems with interferometric interrogation and wavelength division multiplexing

“…If the laser is multimode (laser cavity length >> 5 cm) the interference signal at the output of the MZI will comprise multiple component interference signals arising from each laser mode. In this case, the OPD of the MZI must match a length corresponding to an integer multiple of the round trip path length of the fiber laser cavity according to (6) …”

“…These sensors provide a "quasi-point'' sensing capability, and are particularly attractive for distributed sensing [2], [3], as many gratings can be incorporatedwritten into a length of fiber and addressed using either wavelength division multiplexing or time division addressing [4], [5]. These devices are useful for a variety of applications, in particularly in "smart structures," where fibers can be embedded into the structural material to allow real time evaluation of load, strain, temperature, vibration etc., for sensing in both the manufacturing and in-service use of materials or structural components [ 6 ] . Fiber Bragg gratings are also ideal for use as spectrally narrowband reflectors for creating in-fiber cavities for fiber lasers [7], [8].…”

Compensation of hysteresis in magnetic field sensors employing Fiber Bragg Grating and magneto-elastic materials

“…Moreover, thanks to the small dimensions, they can be integrated in host structures to monitor location that are not accessible to other sensors (i.e. strain gages) [2,3]. Simultaneous multi-parameter measures can also be performed by these devices, able to work in very harsh conditions [4,5].…”