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 25 publications in the last five years it is one of the leading players in the technological development of Distributed Optical Fibre Sensors.

Distributed Fibre Optic sensors (DOFSs) 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 harsh 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. The advances in this technology led to a joint research project between the University and National Grid to for temperature monitoring and hot-spot detection along high-voltage cables.

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 (also known as Distributed Acoustic Sensor (DAS)) capable of fully quantifying high-frequency 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, submarine cable condition monitoring, etc.

Our current research activities are directed towards the following areas:

  • Distributed optical fibre 3D shape sensing: In this project, the aim is to use a multi-core fibre (MCF) to develop a distributed 3D shape and twist sensor. The concept is based on interrogating the strain levels at different cores of a MCF through BOTDR analysis and measure the fibre curvature based on the difference in strain between different cores.
  • Distributed Acoustic Sensor or DAS: The main aim of this project is to further develop this sensing technology in terms of the sensing range, frequency range, and strain sensitivity.
  • Distributed Magnetic Field Sensor: The aim of this project is to develop a speciality optical fibre for measurement of sub-Gauss magnetic field.

Moreover, we have developed a portable DAS unit to carry out field trials. So far, we have conducted several field trials for subsea cable condition monitoring, train and railway condition monitoring, structural health monitoring (SHM). For more information regarding our project or if you are interested using our DAS system in any field trials, please contact Dr Ali Masoudi via A.Masoudi@soton.ac.uk.

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