Distributed fibre-optic strain sensors

The development of distributed fibre-optic strain sensors has resulted in new techniques for monitoring structures and infrastructure such as foundations, embankments and tunnel linings. They offer the opportunity for cost-effectively sensing strain and temperature with a spatial resolution of around 1 metre using conventional fibre-optic cable, either attached to or embedded in a structure. Bending in the cable creates strain in the fibre which can be measured with a fibre optic analyser using the BOTDR (Brillouin Optical Time Domain Reflectometer) or BOTDA (Brillouin Optical Time Domain Analysis) technique. There is no wiring and no electromagnetic interference.

Distributed fibre-optic strain sensors can be used for:

• The measurement of strain in foundations.
• Failure prediction in tunnels and bridges.
• The measurement of strain in oil, gas, and water pipelines.
• Monitoring embankments to predict landslides.
• Measuring structural deformation in nuclear facilities.

Crucial to the effectiveness of this technique of monitoring is the method of attachment to structures. It is important to avoid unintentional twisting or damage to the fibre optic cable and to make sure that the sensor does not creep from attachment points, producing measurement errors. This involves not only the selection of suitable attachment technologies, but also appropriate installation training.

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[edit] External references

• Cambridge Smart Infrastructure and Construction (CSIC), Distributed fibre-optic strain sensors.