Fibre Optic Sensing
Distributed Strain and Temperature Measurement Over Long Distances
Distributed fibre optic sensing (DFOS) uses standard optical fibres as continuous sensors, measuring strain and temperature at every point along the fibre length. Unlike conventional point sensors (strain gauges, tiltmeters), which measure at discrete locations, DFOS provides a continuous measurement profile, capturing structural behaviour along the full length of every instrumented element with spatial resolution as fine as 1mm.
The technology works by analysing changes in the backscattered light signal within the fibre. When the fibre is strained or its temperature changes, the characteristics of the backscattered light change measurably. Brillouin scattering techniques provide distributed measurement over distances up to 50km with metre-scale spatial resolution. Fibre Bragg gratings (FBGs) provide high-precision point measurements at pre-defined locations along the fibre.
For structural investigation, DFOS is particularly valuable for monitoring large or linear structures, bridge decks, tunnel linings, pipelines, retaining walls, and building facades, where installing hundreds of conventional point sensors would be impractical and expensive. A single fibre optic cable bonded to a structure provides the equivalent of thousands of strain gauges, detecting and locating structural anomalies (cracks, settlement, overloading) along the entire instrumented length.
TRSC deploys DFOS for complex monitoring applications where continuous spatial measurement is required to capture structural behaviour that point sensors might miss. The ability to detect and locate new crack formation anywhere along an instrumented element, without knowing in advance where cracks will appear, is a capability that no other monitoring technology provides.
Speak with an RPEQ-qualified structural engineer about deploying this technology on your asset.
Applications
Crack Detection & Location
Detecting new crack formation and locating existing cracks along the full length of instrumented structural elements, without prior knowledge of crack locations.
Bridge Monitoring
Continuous strain monitoring of bridge decks, girders, and cables, measuring load distribution, deflection profiles, and structural response to traffic loading.
Tunnel Lining Monitoring
Distributed strain measurement around tunnel circumference to detect ground movement, lining distortion, and joint opening in segmental tunnel linings.
Pipeline Monitoring
Continuous strain and temperature monitoring of pipelines for ground movement detection, thermal expansion tracking, and leak detection.
Pile Load Testing
Measuring strain distribution along the full length of test piles during load testing, determining load transfer characteristics and shaft friction distribution.
Facade Monitoring
Distributed strain monitoring of building facades to detect differential movement, thermal cycling effects, and developing structural distress across large panel areas.
Frequently Asked Questions
When does TRSC recommend fibre optic sensing over conventional sensors?
DFOS is recommended when continuous spatial measurement is required along large or linear structural elements, when the location of future cracking or distress is unknown, or when the number of conventional point sensors required would be impractical. For localised monitoring at known locations, conventional vibrating wire or tiltmeter sensors are more cost-effective.
Is fibre optic sensing durable enough for long-term use?
Yes. Optical fibres are glass-based, chemically inert, and immune to electromagnetic interference, making them exceptionally durable in harsh environments (marine, chemical, high-voltage). Properly protected and installed, fibre optic sensors have operational lives exceeding 25 years. The primary vulnerability is physical damage to the fibre cable, which is managed through appropriate cable protection during installation.
Can fibre optic sensors be installed on existing structures?
Yes. Fibre optic cables can be surface-bonded to concrete, steel, and masonry structures using structural adhesive. For embedded applications in existing concrete, fibres can be installed in saw-cut grooves and sealed. Surface-bonded installation is non-destructive and typically takes one to two days for a standard monitoring array.
Deploy DFOS on your asset
Every investigation begins with a direct conversation with an RPEQ-qualified structural engineer. No sales intermediary, contact TRSC to discuss whether fibre optic sensing is appropriate for your structural question.