Transportation Structural Health Monitoring
Rail intrusion, tunnel and bridge monitoring — DAS + DTSS-BOTDR with laser ranging, one fiber base for three sensing methods.
What is distributed fiber optic monitoring for transportation infrastructure?
Distributed fiber optic monitoring for transportation applies fiber sensing to rail lines, tunnels and bridges — long structures where point sensors are too costly to deploy densely. DTSS-BOTDR measures strain distribution along tunnel linings and bridge girders at ±5 με accuracy with ≤1 s measurement time, revealing deformation and crack growth over years of service; DAS reuses the co-located railway communication fiber to detect track intrusion and slope movement in real time across up to 160 km (dual channel). One fiber base supports both long-term structural health assessment and day-to-day operational safety, with single-ended access that suits existing, already-in-service structures.
Four safety challenges of transport infrastructure
Rail intrusion
Falling rocks, clearance violations and people entering the track directly threaten train safety; manual patrol can't provide round-the-clock coverage.
Slope instability
Rail and road slopes face landslide risk from rainfall and construction, with subtle precursors that are hard to catch in time.
Structural degradation
Tunnel convergence, lining cracks and bridge strain evolve slowly and need long-term continuous data for sound assessment.
Long-structure monitoring is hard
Tunnels and bridges span wide; point sensors cost too much for full coverage with many failure points, and fragmented data can't form a full picture.
Architecture: three sensing methods together
DAS + DTSS-BOTDR + laser ranging share one fiber base, covering intrusion, deformation and convergence.
Rail intrusion & slope monitoring
DAS uses existing co-located fiber to identify rail intrusion, abnormal vibration and slope-movement precursors in real time — 160 km (dual channel) covering long sections with meter-level localization.
Tunnel & bridge strain monitoring
DTSS-BOTDR measures tunnel-lining and bridge-girder strain distribution at ±5 με accuracy and ≤1 s measurement time; single-ended access suits existing structures with no blind zones.
Tunnel convergence monitoring
Laser range-finding complements the fiber strain data to monitor cross-section convergence, forming a complete structural health picture.
How a typical deployment works
From asset classification to long-term structural records — with minimal impact on operations.
- Classify the assets. Separate rail sections (intrusion and slope focus) from tunnels and bridges (strain and convergence focus) — each needs a different sensing emphasis.
- Design the sensing mix. DAS on the spare core of co-located communication fiber (up to 160 km dual channel); DTSS-BOTDR strain cable on linings and girders; laser range-finding added for tunnel convergence.
- Install with minimal traffic impact. Single-ended access suits already-buried fiber; strain cable is surface-bonded or groove-embedded on the existing structure.
- Record baselines and thresholds. Capture the initial strain distribution of each structure and set deformation-rate and intrusion alert policies.
- Operate long-term. Continuous, automated measurement accumulates into a structural health record that supports maintenance planning and periodic assessment.
Benchmark projects & key metrics
A major highway operator
Structural health monitoring for the largest cross-section highway tunnel at the time of construction — continuous structural data via DTSS-BOTDR.
View caseHow the sensing approach compares
A factual comparison of common approaches for long-structure monitoring.
| Dimension | Periodic manual inspection | Traditional point-based sensors | Distributed fiber monitoring |
|---|---|---|---|
| Coverage | Samples of the structure at inspection time | Discrete points; long structures need too many to be practical | Continuous along the full structure, strain at ±5 με with ≤1 s measurement |
| Data continuity | Snapshots separated by months | Continuous per point, sparse in between | 24/7 automated strain and vibration records |
| Operational impact | Track possession or lane closure usually required | Retrofit wiring on in-service structures is disruptive | Single-ended access and surface bonding suit already-in-service structures |
| Event response | Issues found at the next inspection | Alarm only at the instrumented point | Real-time DAS intrusion alerts with meter-level localization |
Frequently Asked Questions
Get a transportation monitoring solution & quote
Tell us your rail, tunnel or bridge scenario — we'll design the sensing architecture.