AFTER its successful role in the telecommunications revolution, optical fibre is poised to cut costs and improve safety in other industries, such as power transmission and petrochemicals, which rely on temperature sensing to ensure the safe and efficient operation of factories and equipment.
The technique works by sending a laser pulse of light down an optical fibre and measuring changes in its properties when it is reflected back. Variations in the reflected light translate into temperature readings, while the time between injecting the pulse and receiving the reflected signal pinpoints the location of the temperature reading.
Traditional temperature sensing relies on discrete sensors, such as thermocouples, which provide information only from their own location. They must be linked to a data acquisition unit, which often causes complex wiring problems.
When there is a need for multiple-point or shifting monitoring, discrete sensors are inflexible and expensive. Optical fibre sensors can discriminate between temperature readings only a metre apart for distances of up to 40km - long enough to reach across the English Channel.
Users can monitor thousands of points without needing to decide where to take the measurements.
Adopting optical fibre to monitor temperatures is the work of York Sensors, a Southampton company with close links to Southampton University, which has pioneered many developments in optical fibres. Peter Orrell, sales and marketing manager of York Sensors, says it might cost around pounds 10 per point to install discrete sensors, whereas an optical fibre system costing pounds 50,000 could measure up to 10,000 points.
"Not only can an optical fibre system provide information from thousands of points, it can respond to temperature changes in less than a second and continues to measure even if the fibre is broken," Mr Orrell says.
This makes the technique very powerful in fire detection. It also has an advantage over infra-red fire detection systems, which cannot distinguish between smoke and fire, in being able to pinpoint the seat of a fire. …