In short: distributed strain sensing measures relative deformation, expressed in µε — not mechanical stress in Pa. A validated reference state, temperature compensation and engineering thresholds turn the profile into actionable condition information.

Brillouin systems provide long-route strain and temperature profiles. Interferometric and OFDR systems offer different reach, spatial granularity and update-rate trade-offs. INTERLAB selects the architecture from the engineering objective rather than from one headline maximum.

Brillouin frequency shift (BFS)

In a selected reference state, the Brillouin peak is typically near 10.8 GHz at 1550 nm. Around an operating point, BFS changes approximately with strain and temperature. Typical silica-fiber coefficients are about 0.05 MHz/µε and 1.1 MHz/°C; coefficients used for measurement require calibration for the actual fiber and system.

frequency [GHz] 10.80 (at rest) 10.72 10.96
BFS (measured)
10.800 GHz
Strain
0 µε
Temperature
20 °C

Note (the crux of DTSS): the same BFS shift can come from strain or from temperature. Separating the two is a topic of its own (an additional measurement, purpose-built cables, combining Brillouin with Rayleigh). Values are schematic.

Frequency carries strain and temperature information. After calibration and temperature compensation, the BFS profile is converted into strain along the monitored length. The same raw shift cannot be assigned uniquely to strain without resolving temperature influence.

The strain profile along a structure

Measurements at successive locations defined by the selected spatial-resolution mode form a strain profile. Local changes can support earlier inspection and trend-based condition assessment; they do not by themselves guarantee that damage will be predicted.

● strain within limits
monitored structure: illustrative threshold: 600 µε 0 m distance along the structure → 10 km
A localised strain trend for engineering review. DSS/DTSS shows where the measured strain profile changes, according to the selected spatial configuration. Engineering interpretation, temperature compensation and validated thresholds determine the operational response.

Where DTSS earns its keep

🛢️

Pipelines and ground

A measured strain-profile change can indicate ground movement, landslide-related deformation or pipeline deformation when strain transfer from the ground or asset to the sensing cable has been verified.

🏗️

Structures

Bridges, dams, tunnels and buildings — continuous strain measurement (SHM) wherever individual strain gauges are not enough.

⛏️

Wells and geotechnics

Well integrity, CCS and geothermal monitoring, reservoir behaviour — including with ultra-sensitive systems.

DTSS at INTERLAB

INTERLAB supplies distributed strain and temperature sensing systems:

More on high-density measurement: how OFDR works →

* Manufacturer maxima refer to specific products, operating modes and channel counts; they are not necessarily available simultaneously. Coverage, spatial granularity, measurement rate and uncertainty are confirmed for the selected configuration and application conditions.

Strain is relative deformation in µε, not mechanical stress in Pa. Stress can only be inferred using material properties, geometry, boundary conditions and a validated structural model. The 600 µε animation threshold is illustrative.

For selection, provide monitored length, one- or two-ended access, required spatial resolution, strain range, temperature-compensation strategy, acquisition time and cable installation or bonding method.

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Frequently asked questions

If BFS depends on strain and temperature, how are they separated?
Common approaches include a temperature-only loose-fiber reference, purpose-built cable constructions, an independent temperature measurement, or combined sensing architectures. The correct method depends on installation, required uncertainty and operating conditions.
What range and spatial resolution does Brillouin DSS/DTSS offer?
fibrisTerre fTB 5020 examples include 0.5–16 m spatial resolution over a 25 km full loop, 2.5 m over an 80 km ultra-long-range loop, and 0.2 m over up to 2 km in enhanced-resolution mode. Single-ended BOFDR is specified above 25 km at 1.5 m. These are different modes, not simultaneous maxima.
Does distributed strain sensing measure mechanical stress?
No. It measures relative deformation (strain), usually in µε or µm/m. Mechanical stress in Pa can only be inferred using material properties, geometry, boundary conditions and a validated structural model.
How is DSS/DTSS different from DAS?
DAS measures dynamic axial strain or strain rate and is optimised for vibration and events. DSS/DTSS measures slower or quasi-static strain and, depending on the architecture, temperature. They answer different operational questions and can be complementary.

Need a strain profile for engineering decisions?

Send the monitored length, access topology, required spatial resolution, strain range, temperature conditions and cable installation method. We will compare the appropriate Brillouin, interferometric or high-definition sensing configuration.

Request a strain-sensing configuration →