The University of Southampton

Distributed Optical Fibre Sensors

The Distributed Optical Fibre Sensors Research Group investigates novel distributed optical fibre sensors and laser designs for sensing applications. With over 30 publications in the last four years it is one of the leading players in the technological development of Distributed Optical Fibre Sensors.

Distributed Fibre Optic sensors offer unique possibilities for monitoring a wide range of variables such as temperature, strain, acoustic perturbations, etc. The distinctive property of such sensors is their ability to spatially resolve measurands along the entire length of their sensing fibre simultaneously.

During the 1990s, the two main areas of interest were distributed temperature and strain measurements. During this period, the University of Southampton enjoyed a very successful collaboration with York Sensors Ltd, a local Southampton company that led the world in distributed temperature sensing and later acquired by the Schlumberger group.

In the late 1990s, Dr Newson and his research team demonstrated the first distributed optical fibre sensor capable of measuring the strain and temperature independently using spontaneous Brillouin optical time domain reflectometry (BOTDR). This sensing technique was later combined with in-line Raman amplification to demonstrate a long-range distributed temperature and strain optical fibre sensor with a sensing range of over 100km, temperature sensitivity of 1°C and spatial resolution of 1m. Typical applications include monitoring chemical processes in unfriendly environments such as pressure vessels, brick lined reactors ovens and driers, maximising efficiency in electrical power transmission, fire detection particularly in underground or concealed locations, and general management of oil, liquid gas and chemical flows. Furthermore, due to the growing demand for high spatial resolution distributed temperature and strain sensors, a sensing technique was developed capable of measuring temperature and strain with a spatial resolution of 5cm. This sensing technique demonstrated a temperature and strain resolution of 2°C and 60με respectively.

In recent years, the focus of the research group has shifted towards distributed sensors capable of detecting dynamic phenomena including dynamic strains, sound waves, and electromagnetic fields. The first distributed optical fibre dynamic strain sensor capable of fully quantifying multiple dynamic strains along 1km sensing fibre was demonstrated by this research group in 2013. It was shown that using the phase of the backscattered Rayleigh trace, strain as low as 100nε within the frequency range of 100Hz~5000Hz can be measured. The application of such sensor includes borehole and well monitoring in geophysical sciences as well as oil and gas industry, structural health monitoring of civil structures, perimeter security monitoring, etc. Using a similar sensing technique, other distributed optical fibre sensors such as distributed magnetic field sensor and distributed acoustic sensor have recently been demonstrated.

Present research is now directed towards two main objectives. The first objective is to extend the sensing and frequency range of the sensor. The second objective is to improve the sensitivity of the sensor beyond its current 100nε.

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