A universal fiber-optic high-resolution point sensor system, based upon singal recoversy by dual-wayelength low coherence interferometry, has been developed and demonstrated ofor quasistatic absolute measurements of multiparameters. This system is coapable of multiplexing up to 32 fiber-optic point sensors which can be fiber optic interfermoeters or fiber Bragg gratings or any combination of the two. The topology of this system isbased on a spatially multiplexd scheme with low coherence singal recovery that we have reported previously.A range of mutiparameter point sensors, including a medium pressure sneor, a high pressure sensor, a miniature temperature sensor, a displacemnt sensor, and a fiber Bragg grating strain sensor with drift-compensation, have been developd and incorporated into thsi netowrk and demonstrated. A range to resolution of better than 104:1 and 2

We report a novel technique in which by combining the output from two multimode laser diodes a synthesized source with an extremely short coherence length is produced for use in white-light interferometric sensingsystems. Experimentally and theoretically it is demonstrated that, by summing the autocorrelation function of two multimode laser diodes with a wavelength difference of 108nm, a synthesized source with an equivalentcoherence length of ～4μm is generated, greatly reducing the signal-to-noise ratio required to identify the centralfringe position.

A spatialywavelength-division multiplexing topology with combination of a tunable-wavelength filter and an interferometric wavelength scanner is used to interrogate a range of fiber Bragg grating (FBG) strain sensors embedded in modern composite materials. A nine-element FBG sensor system based on this topology is demonstrated for quasi-static strain sensing of a carbon fiber reinforced plastic plate for aerospace applications. Preliminary experimental results show that a strain resolution of ～1.8μεrms with an ～30-Hz bandwidth (～0.32με√Hz) for quasi-static strain measurement has been achieved.

Simultaneous strain and temperature measurement for advanced 3-D braided composite materials using fibre-optic sensor technology is demonstrated, for the first time. These advanced 3-D braided composites can virtually eliminate the most serious problem of delamination for conventional composites. A tandem in-fibre Bragg-grating (FBG)/extrinsic Fabry-Perot interferometric sensor (EFPI) system with improved accuracy has been used to facilitate simultaneous temperature and strain measurement in this work. The non-symmetric distortion of the optical spectrum of the FBG, due to the combination of the FBG and the EFPI, is observed for the first time. Experimental and theoretical studies indicate that this type of distortion can affect the measurement accuracy seriously and it is mainly caused by the modulation of the periodic output of the EFPI. A simple method has been demonstrated to improve the accuracy for detection of the wavelength-shift of the FBG induced by temperature change. A strain accuracy of ～±20με and a temperature accuracy of ～±1℃ have been achieved, which can meet the requirements for practical applications of 3-D braided composites.

A simultaneous spatial, time and wavelength division multiplexing topology, with combination of a tunable wavelength filter and an interferometric wavelength scanner, os proposed to interrogate a range of in-fibre Bragg grating (FBG) sensors. An eleven-element FBG sensor network based upon this topology is demonstrated for quasi-static strain sensing. Preliminary experimental results show that a strain resolution of ～7μεwith a～30Hz bandwidth (～1.3με/√Hz) for quasi-static strain measurement has been obtained.