Distributed fiber optic sensing uses the fiber as a passive sensing medium and returns a position-resolved profile from an interrogator. Depending on the architecture, the system measures dynamic axial strain or vibration, temperature, strain, or a dense local strain/temperature map.
Start with the measurement decision
- Dynamic activity and event location: DAS.
- Continuous temperature and heat detection: Raman DTS.
- Long-route strain and temperature: Brillouin or interferometric DSS/DTSS.
- Dense strain/temperature mapping on a specimen: ODiSI HD-FOS.
- High-resolution fiber/component reflectometry: OBR.
- Selected high-speed measurement points: multiplexed FBG/FP with HYPERION.
Send us the route or specimen length, measured quantity and required spatial granularity →
The secret is in light scattering
How does the interrogator “know” what is happening along the fiber? As the laser pulse travels through the glass, a small fraction of the light is scattered backwards — back towards the transmitter. That light is not uniform: it arises from three different physical effects, and each of them carries different information. This is the heart of the whole technology.
Rayleigh scattering → DAS Distributed Acoustic Sensing
An elastic scattering process: the light returns without a frequency shift from frozen-in micro-inhomogeneities in the glass. DAS measures phase changes associated with dynamic axial strain or strain rate transferred into the fiber. It is often described as a distributed microphone, although its response to acoustic sources depends strongly on cable construction and mechanical coupling.
Brillouin scattering → DTSS Temperature & Strain Sensing
An inelastic interaction with acoustic waves in the glass. Around a selected operating point, the Brillouin frequency shift (BFS) changes approximately with both temperature and strain. Typical silica-fiber values are shown below; measurement coefficients require calibration for the actual fiber and system.
~0.05 MHz/µεsensitivity
Raman scattering → DTS Distributed Temperature Sensing
An inelastic interaction associated with molecular vibrations. The anti-Stokes/Stokes ratio is strongly temperature-sensitive. The illustrative relative sensitivities shown below are local values around 20 °C, not constants over the full temperature range. A calibrated DTS converts that ratio into temperature while accounting for differential attenuation, connectors, bends and cable transitions.
Stokes ≈0.096%/Krelative sensitivity near 20 °C
Note: the Brillouin peaks sit ~10.8 GHz from the laser line, while the Raman bands are as far as ~13 THz (~1000× further) — at true scale they would not fit on one chart. The axis is deliberately schematic (as in textbooks).
Three technologies, three effects
Because each scattering effect carries different information, three families of measurement systems grew out of them. Each has its own detailed article — here is the short version:
Detects vibration and sound: digging near a pipeline, an intruder at a fence, a train passing.
More: how DAS works →The temperature profile along a cable: hotspots on power lines, detecting a fire in a tunnel.
More: how DTS works →Deformation of structures and ground: soil movement, pipeline integrity, well monitoring.
More: how DTSS works →Coverage versus measurement density
Route-scale DFOS uses several read-out architectures: phase-OTDR and Raman OTDR, Brillouin BOTDA/BOTDR, and frequency-domain BOFDA/BOFDR. OFDR is optimised for dense local measurements. The practical choice balances coverage, spatial granularity, acquisition time and uncertainty — it is not a simple time-domain-versus-frequency-domain split.
This is not one “dial” but two separate families of systems — pick one to compare. The figures are indicative and depend on the system and its configuration.
More: how OFDR works — ODiSI and OBR (high-density sensing) →
Selected points versus a distributed profile
Point and multiplexed FBG/FP sensors measure selected locations; distributed sensing returns a quasi-continuous profile defined by sampling interval, gauge length and spatial resolution. Both approaches can use passive sensors, and they are often complementary.
One fiber, many applications
The same technology — depending on the need — protects pipelines, borders, power networks and wells. Click an area on the map to see what is monitored, and how:
Pipeline — interference and optional leak detection* DAS
DAS can identify signatures associated with excavation, third-party interference (TPI) and — when selected — leaks through the configured and licensed detector set. Operational use requires route-specific tuning and validation; leak performance also depends on pipe construction and the transported medium.*
Perimeter — protecting fences and borders DAS
A fence-mounted or buried sensing cable can detect and locate configured event classes. Route-specific detector tuning can reduce nuisance alarms from benign activity such as wind or animals.*
Power cable — hotspots and ampacity DTS
DTS provides a continuous temperature profile for hotspot detection and can supply measured temperature to dynamic cable-rating or RTTR software using an appropriate thermal model.
Well — reservoir and integrity monitoring DAS DTS
A fiber-optic installation can support acoustic and temperature measurements for flow profiling, VSP and integrity monitoring. Sharing one individual fiber requires compatible multiplexing and coexistence validation.
Choose a system configuration with INTERLAB
INTERLAB supplies complementary distributed and multiplexed fiber sensing platforms from OptaSense, LIOS, Silixa, fibrisTerre and Luna Innovations. The table separates verified configuration examples instead of combining incompatible maxima:
| Measurement objective | INTERLAB option | Verified configuration examples* |
|---|---|---|
| Dynamic route events | OptaSense ATLAS / Silixa DAS | Route-scale DAS; at 205.4 m gauge length, selected ATLAS configurations specify either 1 × 100 km or 190 km total as 2 × 95 km — not metre-scale localisation |
| Power-cable temperature | LIOS OTS3 Raman | 1 m spatial resolution; 4–20 km per channel, depending on model and fiber |
| Linear heat detection | LIOS DE.TECT | Sampling from 0.25 m; up to 10 km, or 6 km for four channels |
| Brillouin strain + temperature | fibrisTerre fTB 5020 | Mode-dependent alternatives: 0.2 m over up to 2 km, OR 0.5–16 m over a 25 km full loop, OR 2.5 m over an 80 km full loop |
| Interferometric strain | Silixa iDSS | Mode-dependent specifications: sampling from 10 cm, spatial resolution from 60 cm and range above 50 km; these extrema are not simultaneous |
| Dense strain + temperature | ODiSI 7100 | 0.65 mm gage pitch to 20 m; 2.6/5.2 mm to 100 m; up to 8 channels |
| Fiber/component reflectometry | OBR 4600 | 10 µm/30 m, 20 µm/70 m, or 1 mm/2 km; distributed sensing typically to 70 m |
| Point/multipoint sensing | HYPERION | Mode/variant-dependent: nearly 1,000 sensors on up to 16 channels, OR up to 5 kHz in the dedicated High Speed variant; these maxima are not simultaneous |
* 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.
- OptaSense — DAS systems for pipeline protection, perimeter security and infrastructure monitoring.
- LIOS — DTS and linear heat detection (LHD) systems for power cables, tunnels and industry.
- Silixa — ultra-sensitive DAS plus distributed temperature and strain sensing (DTS/DSS) for the most demanding applications (wells, seismics, CCS).
- ODiSI 7100 provides dense strain and temperature mapping with gage pitch down to 0.65 mm in compatible modes. OBR provides high-resolution reflectometry; sampling is not measurement accuracy.
- fibrisTerre — distributed strain and temperature sensing using Brillouin (DTSS) over long distances.
- HYPERION provides multiplexed FBG/FP measurement at selected points: up to 16 channels and up to 5 kHz in the dedicated High Speed variant; full-spectrum data is 10 Hz.
Ready application solutions: Pipeline monitoring · Perimeter security · Geotechnical monitoring · Power line monitoring · all fiber optic sensors →
For an actionable shortlist, send the route or specimen length, measured quantity, required spatial granularity, update rate, available fibers and operating environment.
Each technology in detail
Every technology has its own interactive article — with step-by-step animations:
Frequently asked questions
How do I choose between DAS, DTS, DSS/DTSS and OFDR?
How far does one distributed sensing system reach?
Can existing dark fiber be reused?
Can DAS, DTS and DSS share one cable or one fiber?
Which sensing architecture fits your project?
Send us the route or specimen length, the quantity to measure, required spatial granularity, update rate and available fibers. An INTERLAB application engineer will shortlist the interrogator, sensing cable and software configuration.
Request a system recommendation →