Short answer
Fiber optic geohazard monitoring uses a single cable as thousands of sensors along a slope, road, rail line, dam or tunnel. DAS detects dynamic events such as rockfall and slope cracking, FBG sensors measure precise point strain, tilt and pore pressure, and Brillouin distributed strain tracks slow ground movement. DuyuSense develops FBG and DAS systems for these early warning applications.
Can fiber optics detect landslides and rockfall on roads and railways?
Yes. A fiber cable laid along a cut slope, retaining wall or catch fence acts as a continuous sensor, and Distributed Acoustic Sensing (DAS) picks up the impact and rolling signature of falling blocks along the whole line. Because DAS spatial resolution is typically a few metres over tens of kilometres, an alarm points operators to the affected section rather than a whole valley.
Slow landslides behave differently: they creep millimetres per day before accelerating. For these, strain along the cable (Brillouin) and FBG point sensors at key locations reveal the build-up long before a dynamic event occurs.
- Rockfall impact and debris flow along road and rail corridors
- Slope cracking and toe movement in cuts and embankments
- Catch fence and rockfall net loading
- Ground movement under track or pavement
How do DAS, FBG and distributed strain sensing complement each other?
Each technology covers a different time scale and spatial pattern, so robust geohazard systems combine them. DAS listens for fast dynamic events, Brillouin distributed strain sensing (DSS) maps slow deformation along kilometres of cable, and Fiber Bragg Grating (FBG) sensors deliver high-precision readings where the geotechnical model says movement matters most.
FBG strain resolution is typically around 1 microstrain, and FBG sensors can be packaged as strain gauges, tiltmeters, piezometers and displacement transducers. Many FBGs can share one fiber, so a borehole or slope can be instrumented with a single cable back to the interrogator.
- DAS: rockfall, cracking, microseismic activity, third-party intrusion
- DSS (Brillouin): slow creep and settlement along the full cable length
- FBG: point strain, tilt, pore pressure and in-place inclinometer chains
- DTS (Raman): temperature profiles, used alongside the others for seepage
How are dams, embankments and tailings dams monitored with fiber optics?
Dams and embankments are monitored for deformation, pore pressure and seepage, and fiber optics address all three. FBG piezometers and strain sensors track pore pressure and structural response at critical sections, while distributed strain cables embedded in the crest or foundation reveal differential settlement and cracking.
Seepage is usually detected with Distributed Temperature Sensing (DTS), a complementary Raman based technique: water flowing through the fill changes the local temperature profile along the cable. Mine tailings dams, which can fail with little visible warning, benefit from the same combination of pore pressure, deformation and seepage data in one fiber network.
How is tunnel convergence monitored with FBG or distributed strain?
Tunnel convergence is measured by fixing FBG strain or displacement sensors, or a distributed strain cable, around the lining circumference. Changes in hoop strain reveal how the ring deforms as the surrounding rock or soil loads it, both during excavation and over the service life.
Fiber is well suited to tunnels because it is immune to electromagnetic interference from traction power and needs no electronics inside the tunnel. A single cable can also carry DAS for rockfall and train detection in adjacent portals and cuttings.
Can fiber optics detect sinkholes and ground subsidence?
Yes, distributed strain sensing is the main tool for sinkhole and subsidence detection. A cable buried under a road, railway or pipeline stretches as a void forms beneath it, and the strain profile shows both the location and the growth of the anomaly.
FBG sensors can then be added at suspect zones for higher precision, and DAS can flag the sudden collapse itself. This layered approach is useful over karst terrain, old mine workings and areas with ground water extraction.
How early can fiber sensing warn of slope failure?
Warning time depends on the failure type: slow landslides often give days to weeks of accelerating movement, while rockfall gives seconds. Fiber systems cover both ends, trending slow strain for planning and raising real-time alarms for sudden events.
Early warning thresholds are usually staged: an attention level based on displacement or strain rate, an alert level when the rate accelerates, and an alarm level that triggers speed restrictions or road closure. Thresholds are set with the geotechnical engineer and refined as baseline data accumulates.
- Level 1, attention: movement or strain rate above the baseline trend
- Level 2, alert: sustained acceleration, inspection and closer monitoring
- Level 3, alarm: rate or event above limit, closure or speed restriction
- Instant alarm: DAS detected rockfall or impact on the protected line
Why does geohazard monitoring matter in Turkey?
Turkey combines high seismicity, steep topography and heavy rainfall zones, which makes geohazards a recurring infrastructure risk. The Black Sea region is known for frequent landslides, mountainous highways and rail lines cross unstable slopes and rock cuts, and a large portfolio of dams requires long-term deformation and seepage monitoring.
DuyuSense, based at ITU Teknopark in Istanbul, develops FBG and DAS sensing systems and offers custom sensor design, system integration and pilot projects for road, rail and dam operators. Contact contact@duyusense.com to discuss a monitoring concept.
| Feature | DAS | FBG | DSS (Brillouin) | Conventional inclinometer / extensometer |
|---|---|---|---|---|
| Measurement | Dynamic vibration and acoustic events | Point strain, tilt, pore pressure, displacement | Distributed static strain (and temperature) | Point or profile displacement |
| Coverage | Continuous, typically tens of km per channel | Multiple points on one fiber | Continuous along the cable, km scale | Single borehole or anchor |
| Best for | Rockfall, cracking, sudden events | High-precision readings at critical spots | Slow creep, settlement, sinkholes | Established reference measurements |
| Response | Real time | Real time, high speed | Minutes per scan | Manual or periodic readings in many cases |
| Field electronics | None along the cable | None along the cable | None along the cable | Sensors, cabling and loggers at each site |
| EMI and lightning | Immune | Immune | Immune | Susceptible |
Frequently asked questions
Can DAS detect rockfall on a railway line?
Yes. DAS converts a fiber along the track or slope into a continuous vibration sensor and recognises the impact signature of falling rock. The alarm is located to within a few metres, so the operator can stop or slow trains before they reach the affected section and send an inspection team.
What is the difference between an FBG inclinometer and a conventional inclinometer?
A conventional probe inclinometer is lowered through a borehole casing for periodic manual readings. An FBG in-place inclinometer chain stays installed and reports tilt at many depths continuously, with no electronics in the borehole and immunity to lightning, which suits remote slopes and automated early warning.
What is Brillouin distributed strain sensing used for in geotechnics?
Brillouin DSS measures strain along the entire length of a fiber cable, so it maps slow ground movement over long distances. Typical uses include landslide creep, embankment and dam settlement, sinkhole formation, pipeline ground movement and tunnel lining deformation, where the location of movement is not known in advance.
How is seepage in a dam detected with fiber optics?
Seepage is usually detected with DTS, which measures temperature along the cable. Water flowing through an embankment carries heat differently from the surrounding fill, creating a temperature anomaly at the leak. DTS complements FBG piezometers and strain sensing for a complete dam safety picture.
How early can fiber optic monitoring warn of a landslide?
For slow moving landslides, strain and tilt trends often show acceleration days or weeks before failure, giving time for closures and remediation. For rockfall and sudden collapses the warning is seconds, but DAS delivers it in real time, which is enough to stop traffic approaching the zone.
Can existing telecom fiber be used for geohazard monitoring?
Existing fiber along roads and railways can often be used for DAS, since DAS works on standard single-mode fiber. Coupling to the ground and cable routing affect sensitivity, so a site trial is recommended. FBG sensors and strain cables are usually installed specifically at critical slopes and structures.
Does DuyuSense offer geohazard monitoring solutions?
DuyuSense develops FBG and DAS fiber optic sensing systems, including a patented FBG interrogation system and patented DAS signal processing. The company offers custom sensor design, system integration and pilot projects for slope, road, rail, dam and tunnel monitoring from ITU Teknopark, Istanbul.