Temperature Sensing

Temperature sensing with optical fibers is a well-established and growing market. Numerous installations of optical fiber systems to monitor temperature for fire detection, leak detection and system health monitoring have been made in the following applications:

Fire detection:
Road and Rail Tunnels

Mineshafts

Car Parks

Public Buildings

Leak detection:
Oil and Gas Pipelines
LNG transport and storage tanks

System Health Monitoring:
Production Wellholes
Power Cables
Petrochemical Plants

Gasification Plants

Cable stays

The primary benefits of optical sensor technologies that have attracted such a market demand are:

• multi km range
• zero power, intrinsically safe sensors
• immunity from electromagnetic interference
• ease and cost of installation
• highly multiplexed solutions
  
  

Classically, the type of optical fiber sensor technology that has been deployed into the majority of these applications is so-called distributed temperature sensing or DTS. In a DTS system, a single complex instrument is able to detect thermal variations along lengths of standard optical fiber by injecting laser light into the fiber and measuring a property known as Raman backscatter. Such instruments are well developed and can offer continuous temperature measurement with spatial resolutions of 1m or less on multi-km length structures.

DTS instrumentation is very sophisticated and relatively expensive compared to modern FBG interrogators. However, for a DTS system the multi-point sensor is simply optical fiber which is very inexpensive, whereas for an FBG system, each measurement location requires a discrete sensor. Clearly, the number of measurement locations required determines the relative cost of each system.

The simple graph below shows our interpretation of how the cost of an FBG system (interrogator and sensors) compares with an equivalent performance DTS system for varying measurement locations. It makes this comparison for FBG technology today and for what FBG technology was available some 5 years ago.

This analysis suggests that for sensor locations numbering less than 500, an FBG temperature measurement system may offer significant cost advantage.

Consider for instance a few examples:

Please contact us with your distributed temperature sensing requirements and, through our close collaboration with DTS system suppliers, we shall offer a balanced assessment of the most appropriate technology for your application.