"Right now, sensors of different types are present in almost any environment such as industry, the automotive sector, buildings or consumer electronics," explained Daniel Leandro. "One example of their huge importance in everyday life are smartphones that have more than ten or so built into them. The growing demand for the monitoring of various parameters, or for more features, which boils down to the need for new and better sensors, has driven new technologies, such as fibre optics, so that the field of application of sensors can be expanded from telecommunications to sensorics".
A fibre optic sensor can be defined as a device that has been manufactured using fibre optics and which transfers the external changes of the parameter one is intending to measure (be it physical, chemical or biological) into the modulation or one or more light parameters. These changes are finally picked up by a detector that measures the variations.
"Fibre optic sensors have emerged as a flexible solution to solve some of the main limitations affecting conventional ones," he pointed out. "For example, fibre optics is chemically inert and electromagnetically passive. So it can work in explosive environments such as fuel tanks or gas pipelines or with electromagnetic fields or intense radiation. Another important feature of fibre optic sensors is that they are compact, small and lightweight. What is more, multiple sensors can monitor from a great distance --up to hundreds of kilometres--, which is of particular interest in the case of sensors built into large structures such as bridges, tunnels or oil pipelines".
From safety to space
All these properties mean that fibre optic sensors are "perfect candidates for a whole host of applications, in particular, for those relating to safety, such as the monitoring of the structural health of large infrastructure, such as nuclear power plants, bridges, tunnels, oil pipelines or gas pipelines, apart from aerospace applications, geotechnical ones, ones relating to mining and gas detection, among others".
The research has focussed on the development of new setups for multiplexing fibre optic sensors. "The term multiplexing refers to the including of a whole range of sensors into a single network for the purpose of sharing the equipment needed for interrogation, be it of the light source, channel or receiver, or several of them or even all of them. The main outcome of sensor multiplexing in one and the same network is the cost-cutting of the system; the reason is that equipment is shared, so the cost per sensor falls," added Daniel Leandro, who went on a research stay at City University London (United Kingdom) during the writing up of his thesis.