Distributed Fibre Optic Sensing (DFOS) is flipping the SHM play book: one hair thin glass fibre can replace thousands of discrete gauges, streaming a continuous strain or temperature profile every few millimetres along kilometres of asset. Owners move from "four gauges on a bridge" to a real time, 3D health twin that spots cracks as they breathe — a leap in risk visibility and life cycle value.
What makes DFOS different?
| Classic gauges | DFOS cable |
|---|---|
| Hand picked hotspots | Wall to wall coverage |
| 10–20 points / span | 10,000+ points / span |
| Electrical, corrosion prone | Dielectric, embed ready |
| Manual readout cycles | Live data stream |
The four sensing "dialects"
| Family | Best for | Spatial res. | Range |
|---|---|---|---|
| OFDR (Rayleigh) | µ strain / mm scale cracks | 1 mm | ≤10 km |
| BOTDR / BOTDA (Brillouin) | long, quasi static strain | 20–50 cm | ≤70 km |
| DTS (Raman) | pure temperature | 25 cm | ≤70 km |
| DAS (ϕ OTDR) | vibrations & acoustics | 1–10 m | ≤100 km |
Some hybrid interrogators can now mix between Rayleigh + Brillouin to separate thermal & mechanical effects in one fibre or achieve high sensitivity or high frequency over long distances.
Cables built for site reality
- Polyimide coated fibres – high temp lab work
- Tight buffer "strain" cables – direct embed, bridges & slabs
- Armoured loose tube – long haul DTS/DAS in tunnels & pipelines
Who makes what? — quick supplier map
- Cables: Solifos (CH), SHM System (PL), NBG (AT), Thorlabs (US).
- Interrogators: Luna (US), AP Sensing (DE), Omnisens (CH), Neubrex (JA).
Explore the interactive Europe map to see 30+ DFOS leaders, tech focus and flagship gear.
From cable to cloud — getting it right
- Pick the right pair: tight buffer + OFDR for strain and crack width; armoured cable + DAS for intrusion/vibration.
- Budget the stack: interrogator < 40% of lifetime cost; installation & analytics dominate.
- Mind the craft: poor bonding or loose jackets kill strain transfer and hide defects.
- Plan the data path: DFOS is only valuable when the 2 TB/year stream lands in dashboards that engineers can trust.
The takeaway
DFOS has vaulted from niche R&D to a multi‑billion‑euro ecosystem where cable makers, interrogator vendors and AI analysts converge. For owners, that means swapping periodic, labour‑heavy inspections for continuous, data‑driven asset management — and spotting the next crack before it matters.