A range of optical fibre-based sensors for the measurement of ethanol, primarily in aqueous solution, have been developed and are reviewed here. The sensing approaches can be classified into four groups according to the measurement techniques used, namely absorption (or absorbance), external interferometric, internal fibre grating and plasmonic sensing. The sensors within these groupings can be compared in terms of their characteristic performance indicators, which include sensitivity, resolution and measurement range. Here, particular attention is paid to the potential application areas of these sensors as ethanol production is globally viewed as an important industrial activity. Potential industrial applications are highlighted in the context of the emergence of the internet of things (IoT), which is driving widespread utilization of these sensors in the commercially significant industrial and medical sectors. The review concludes with a summary of the current status and future prospects of optical fibre ethanol sensors for industrial use.

There has of late been a call among language practitioners for the sophisticated new markup language XML to be used in Web-based tools for language learning (Mills, 1999; Riley, 2001; Godwin-Jones, 2000). This paper describes just such an application: the development of an interactive electronic resource book of learning tasks for English Language Teaching (ELT). The electronic resource book incorporates an authenticity-centred approach to language learning materials design, viz language learning based on authentic texts complemented by authentic tasks. The paper covers a general introduction to XML, describes the pedagogical model (i.e. the authenticity-centred approach) that it was used to realise, and describes the development of the XML-based system operating the electronic resource book. Among the conclusions of this paper are that this trial application reveals XML to be ideally suited to the realisation of such pedagogical models and that its greatly enhanced information management and linking potential promises an exciting future in the field of language teaching by providing the possibility for pedagogy-led technology rather than technology-led pedagogy.

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A unique side-polished balloon shaped heterocore structure plastic optical fibre (POF) sensor for real-time measurement of very low to high ethanol concentration in water is reported. The sensor is designed as a large core-small core-large core heterocore structure where small core fibre (SCF) acts as a sensing region, whereas large core fibre (LCFs) are used as input and output light waveguide s as well as to introduce the light leakage in the cladding of SCF at the heterocore structure’s input interface and hence generate the significant evanescent field. The principle of operation of the sensor is based on evanescent field interaction at the interface of modif ied SCF and the liquid boundary. The sensor is characterized for ethanol-water solutions in the ethanol concentration ranges of 20 %v/v to 80 %v/v, 1 %v/v to 10 %v/v, and 0.1 %v/v to 1 %v/v, demonstrating a maximum sensitivity of 54673 %/RIU. The experimentally evaluated high sensitivity of this sensor design for real-time measurement of ethanol concentration in water at different ranges makes it a potential candidate for implementation in the industry as a low-cost and real-time solution for ethanol sensing as well as other RI sensing applications.

A novel long period grating (LPG) inscribed balloon-shaped heterocore-structured plastic optical fibre (POF) sensor is described and experimentally demonstrated for real-time measurement of the ultra-low concentrations of ethanol in microalgal bioethanol production applications. The heterocore structure is established by coupling a 250 μm core diameter POF between two 1000 μm diameter POFs, thus representing a large core—small core—large core configuration. Before coupling as a heterocore structure, the sensing region or small core fibre (SCF; i.e., 250 μm POF) is modified by polishing, LPG inscription, and macro bending into a balloon shape to enhance the sensitivity of the sensor. The sensor was characterized for ethanol–water solutions in the ethanol concentration ranges of 20 to 80 %v/v, 1 to 10 %v/v, 0.1 to 1 %v/v, and 0.00633 to 0.0633 %v/v demonstrating a maximum sensitivity of 3 × 106 %/RIU, a resolution of 7.9 × 10−6 RIU, and a limit of detection (LOD) of 9.7 × 10−6 RIU. The experimental results are included for the intended application of bioethanol production using microalgae. The characterization was performed in the ultra-low-level ethanol concentration range, i.e., 0.00633 to 0.03165 %v/v, that is present in real culturing and production conditions, e.g., ethanol-producing blue-green microalgae mixtures. The sensor demonstrated a maximum sensitivity of 210,632.8 %T/%v/v (or 5 × 106 %/RIU as referenced from the RI values of ethanol–water solutions), resolution of 2 × 10−4%v/v (or 9.4 × 10−6 RIU), and LOD of 4.9 × 10−4%v/v (or 2.3 × 10−5 RIU). Additionally, the response and recovery times of the sensor were investigated in the case of measurement in the air and the ethanol-microalgae mixtures. The experimentally verified, extremely high sensitivity and resolution and very low LOD corresponding to the initial rate of bioethanol production using microalgae of this sensor design, combined with ease of fabrication, low cost, and wide measurement range, makes it a promising candidate to be incorporated into the bioethanol production industry as a real-time sensing solution as well as in other ethanol sensing and/or RI sensing applications.