Measurement of two-dimensional bending in a structural element using intrinsic optical fibre strain gauges would normally require three sensors to be attached to, or embedded within, the structure. The same measurement can now be made using a single multi-core optical fibre, reducing deployment cost and increasing practicality.Fabrication of a novel three-core photonic crystal fibre is described. The ability of the fibre sensor to measure bend in two dimensions is demonstrated in the laboratory using interferometric interrogation at a single wavelength. Deployment of the sensor to measure the deformation of a bridge undergoing loading trials is described.

In this work we report the design and implementation of a very high speed retro-reflective free space communication system between a ground station and a commercial unmanned aerial vehicle (UAV). The system uses a pixelated electro-absorption modulator (EAM) modulating retroreflector (MRR) to establish a data link operating at 500 Mbps at a range of 560 m and a bit error rate (BER) of 7.6•10 -4 . The MRR provides an effective aperture of 11mm and full field of view (FFOV) of 6.4°. To the best of our knowledge, this is the fastest demonstration of an outdoor link of this type. In this paper the design and implementation of the system is described, as well as results from experimental trials.

Weight reduction and low power consumption are key requirements in the next generation of unmanned aerial vehicles (UAVs). To communicate with an operator, a secured link between the UAV and a ground-based station is desirable. To realize these links, retroreflecting free-space optics is potentially attractive as it offers light weight and low complexity at the UAV. However, the base station requires a high-performance tracking module to enable a steady illumination of the UAV retroreflector. In this paper, we present the design and implementation of a tracking system, which consists of coarse tracking and holographic fine tracking modules working cooperatively. Using this system, experimental field trials were carried out by mounting a multiple-quantum-well-based modulated retroreflector on a commercial UAV. A 2 Mbps optical link was achieved with a bit error rate of ∼2×10^-4 at a link range of 300 m.

In this work we present the design and implementation of a pixelated electro-absorption modulator (EAM) based modulating retroreflector (MRR) for high speed optical wireless communications. The modulator is based on a multiple quantum well (MQW) structure embedded in an asymmetric Fabry-Perot (FP) cavity. This MRR was used in an outdoor link, operating at 150 Mbps with a bit error rate (BER) of 1.22 x 10 -6 at a range of 200 m. The system was also tested in laboratory controlled conditions achieving a data rate of 200 Mbps with a BER of 2 x 10 -4 . To the best of our knowledge, this is the fastest retroreflective free space optics (RFSO) demonstration in both indoor and outdoor environments.

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