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The infusion, flow and cure of RTM6 resin in a carbon fibre reinforced composite preform have been monitored using a variety of multiplexed fibre optic sensors. Optical fibre Fresnel sensors and tilted fibre Bragg grating (TFBG) sensors were configured to monitor resin infusion/flow in-plane of the component. The results obtained from the different sensors were in good agreement with visual observations. The degree of cure was monitored by Fresnel sensors via a measurement of the refractive index of the resin which was converted to degree of cure using a calibration determined from Differential Scanning Calorimetry. Fibre Bragg grating sensors fabricated in highly linearly birefringent fibre were used to monitor the development of transverse strain during the cure process, revealing through-thickness material shrinkage of about 712 μe and residual strain of 223 μe. An alternative approach to infusion monitoring, based on an array of multiplexed tapered optical fibre sensors interrogated using optical frequency domain reflectometry, was also investigated in a separate carbon fibre preform that was infused with RTM6 resin.

Coherent optical frequency domain reflectometry is used to multiplex a serial array of tapered optical fibre sensors. By monitoring changes in the Rayleigh backscattered signal from tapered regions of a single mode optical fibre, the refractive index of the medium surrounding each taper can be determined. The approach is used to demonstrate a liquid flow sensor.

Tapered optical fibers with nano-assembled coatings of thicknesses of order tens of nanometres were used for the detection of ammonia gas. The film coating was composed of alternate layers of tetrakis-(4-sulfophenyl) porphine (TSPP) and poly(allylamine hydrochloride) (PAH), which were deposited using the electrostatic self-assembly process (ESA). Exposure of a PAH/TSPP nano-assembled non-adiabatic tapered optical fiber with a waist diameter of 10 µm to ammonia induced significant optical changes in the transmission spectrum of the optical fiber. The fiber optic sensor showed a linear sensitivity to the concentration of ammonia in the range of 10–100 ppm, with response and recovery times less than 100 and 240 sec, respectively. The 3σ limit of detection (LOD) was estimated to be ca. 2 ppm.

An optical fibre surface pressure sensor capable of measuring the changes in the meniscus forming properties of a liquid is presented. The sensor consists of a tapered single mode silica fibre, mounted with a small curvature and positioned with the tapered region of the fibre immersed in the water. The low angle curve formed by the fibre acts to enhance the movement of the meniscus along the fibre by creating a capillary channel between the fibre and the surface of the water. As the surface pressure of the water changed a concomitant change in the intensity of features within the transmission spectrum of the tapered fibre was observed. The performance of the fibre optic sensor compares well with that of the conventional Wilhelmy plate surface pressure sensor.

Nanostructured coatings have been deposited onto tapered optical fibres using the Langmuir Blodgett technique. The response of the transmission spectrum of the tapered fibres to changes in thickness of the coating has been analysed. The effects observed are shown to be dependent on the diameter of the tapered region.

The subject of the study was transportation of glucose molecules through a cuprophase membrane by the earlier devised method based on the phenomenon of light interference sensitive to changes in the optical density in two neighbouring chambers separated by a membrane. In the experiment the number of light and dark interference fringes and the rate of their movement through the observation slit were recorded. The analysis of time changes in the concentration of the solutions in the two chambers brings information on the dynamics and mechanism of glucose molecules transportation through the membrane.

The use of high spatial resolution optical frequency domain reflectometry (OFDR) to facilitate the multiplexing of a serial array of tapered optical fibre sensors is presented. Changes in the attenuation of the Rayleigh backscattered signal from the tapered regions are used to monitor the refractive index of the surrounding medium. The use of an array of five tapered regions to monitor liquid flow is demonstrated. An analysis of the performance of the system shows that, for tapers of diameter 50??m, up to nine tapers could be multiplexed using commercial OFDR instrumentation.

Nanostructured coatings have been deposited onto tapered optical fibres using the Langmuir–Blodgett technique. The response of the transmission spectrum of the tapered fibres to changes in thickness of the coating has been analysed. The effects observed are shown to be dependent on the diameter of the tapered region.