The University of Southampton

Distributed Optical Fibre Sensors

The Distributed Optical Fibre Sensors Research Group investigates novel distributed optical fibre sensors for sensing applications. With over 35 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 the sensing fibre at once.

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 journal paper on distributed optical fibre dynamic strain sensor, also known as Distributed Acoustic Sensor (DAS) or Distributed Vibration Sensor (DVS), capable of fully quantifying the frequency and amplitude of dynamic strains was published by this research group in 2013. The most recent version of the DAS sensing system, developed at the ORC, has demonstrated a sub-nε strain sensitivity of vibrations as low as 0.1Hz. In addition, using a speciality fibre known as Ultra-Low Loss Enhanced Backscattering (ULEB) fibre, designed and developed at the ORC, the range of the DAS system is extended to 150km.

The application of such sensor includes borehole and well monitoring in oil and gas industry, structural health monitoring of civil engineering, perimeter security monitoring, submarine cable condition monitoring, and monitoring of seismic activities in geophysical science to name a few.

Recently, a commercial version of the DAS system has been developed. The system is capable of mapping vibrations and visualise it in a real-time waterfall plot. So far, the system has been used in a number of field trials from monitoring train and track along railway lines, traffic monitoring along a dual carriageway, and surface wave and seismic activity analysis.

For more information regarding the current projects of the group or if you are interested to use or purchase the DAS system, please contact Dr Ali Masoudi via A.Masoudi@soton.ac.uk.

 

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