Temperature Measuring & Environmental Monitoring


AP Sensing can monitor temperature under harsh conditions over long distances to optimize maintenance, detect fires and overheating, and measuring environmental temperature.

AP Sensing’s linear heat series minimizes your operational costs and performs extremely reliable by using a standard fiber optic cable which has no active components or electronic sensors within the exposed zone. Fiber optic cable is also immune to electromagnetic interference.

Up to 10km of Fiber Optic Cable can be used to sense heat on each 1m section to 1°C accuracy enabling users to monitor 10 000 temperature readings from one central point using one 10km fiber optic cable.

Depending on cable grade, the fiber cable can also be directly exposed to flames while still measuring accurately. Firefighting effectiveness can hence be monitored throughout the fire event.

Distributed Temperature Sensing (DTS) utilizes laser light and fiber optic cables to measure temperature. An infrared laser pulse is sent through the fiber. The incident energy is back-scattered from the glass molecules throughout the entire length of the fiber. These minute light signals contain information about the temperature of the glass at any given point in the fiber, in accordance with the Raman Effect . The back scattered light is measured and then analysed for temperature.

( A quantum mechanical effect first discovered by CV Raman in 1922. Wavelength of light scattered from optical crystals changes and varies as per the temperature of the crystal.)

The position of the temperature reading (along the fiber length) is determined by measuring the time delay of the returning light pulse, similar to a radar echo.





One of the most famous applications of the Linear Heat Series in Europe is the Eurotunnel fire monitoring system to activate and control the suppression system. The Channel Tunnel is 38km long, the longest undersea tunnel in the world; it connects the United Kingdom with France. After experiencing a devastating fire in September 2008 the safety requirements were reviewed. Full-scale qualification tests were carried out in Germany. These tests were performed under live fire conditions with intense temperatures from 5MW fire loads, which equates to a fire involving 40 cars. The results were extremely convincing, resulting in full UL and FM approvals.

*More case studies and detailed information available from the Sperosens office

The system offers many benefits including fast activation and good control capability. This allows easy access for rescue services and enables effective firefighting. AP Sensing’s Linear Heat Series was installed as the fire monitoring system of choice taking road and rail tunnel safety to a new level.