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A novel self-referencing fiber optic intensity sensor based on bending losses of a partially polished polymer optical fiber (POF) coupler is presented. The coupling ratio (K) depends on the external liquid in which the sensor is immersed. It is possible to distinguish between different liquids and to detect their presence. Experimental results for the most usual liquids found in industry, like water and oil, are given. K value increases up to 10% from the nominal value depending on the liquid. Sensor temperature dependence has also been studied for a range from 25 °C (environmental condition) to 50 °C. Any sector requiring liquid level measurements in flammable atmospheres can benefit from this intrinsically safe technology.

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Parker, M.; Walker, SD.; Llorente, R.; Morant, M.; Beltrán, M.; Möllers, I.; Jäger, D.... (2010). Radio-over-fibre technologies arising from the Building the future Optical Network in Europe (BONE) project. IET Optoelectronics. 4(6):247-259. https://doi.Abstract: This paper describes a wide range of salient radio-over-fibre (RoF) system issues. Impulse radio (IR) and multi-band (MB) ultra-wideband (UWB) signal distribution, over both single-mode fibre (SMF) and multimode fibre (MMF) implementations are considered. Carrier frequencies ranging from 3.1-10.6 GHz, up to 60 GHz are featured, and the use of microring laser transmitters is discussed. A cost-performance comparative analysis of competing distributed antenna system (DAS) topologies is presented, and a theoretical approach to understanding the factors underlying radio-over-MMF performance for within-building applications is discussed. Finally, techniques to minimise thermal impacts on performance are described and novel energyefficient schemes introduced. Overall, this paper provides a snap-shot of research being undertaken by European institutes involved in the Building the future Optical Network in Europe (BONE) project.The paper is arranged as follows: Section 2 discusses the development of lower carrier frequency (3.1 to 10.6 GHz) RoF technologies using standard single mode fibre (SMF) to distribute ultra wideband (UWB) signals.Section 3 presents results on more advanced RoF technologies, including the use of higher carrier frequencies (60 GHz) to distribute impulse radio (IR) UWB signals, and the use of microring laser transmitters. Energy efficiency gains for RoF systems via software-defined antennas (cloning and holographic technologies) are also discussed. Section 4 presents radio-over-multimode fibre (RoMMF) theory for within-building applications, a cost-performance comparative analysis of different distributed antenna systems (DAS's), and the distribution of IR and multi-band (MB) UWB over RoMMF systems. Section 5 considers RoF impairment mitigation, and conclusions are given in section 6. 3.1 -10.6 GHz RoF technologiesUWB is a radio technology for replacing cables within picocells, with high definition (HD) video and audio [2] a typical candidate application. UWB radio offers: low self-interference, low interception probability and tolerance to multi-path fading, and comes in two main implementations: multi-band orthogonal frequency division multiplexing (MB-OFDM) and impulse radio (IR). The ECMA standard [3] uses MB-OFDM in 528MHz individual sub-bands, whilst the IR implementation employs short pulses to fill a desired bandwidth. MB-OFDM generally shows superior performance to the IR approach in terms of multi-path fading and intersymbol interference (ISI) tolerance. Currently, UWB uses the 3.1 to 10.6 GHz band [3][4][5]; with bandwidth significantly wider than 50 MHz as in ETSI regulations [6]. RoF distribution of UWB signals in standard single-mode fibreUWB RoF distribution over SMF has been proposed in [7] for RoF high-definition audio-v...

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