The RaySense LGDS is a buried fiber optic intrusion detection system that turns the ground itself into a sensor. A single underground fiber optic cable detects footsteps, vehicles, and digging along up to 100 km (62 miles) of perimeter, and pinpoints each event to within a few meters, while remaining completely invisible to intruders.
Known in U.S. government and border security programs as a Linear Ground Detection System (LGDS), this class of underground perimeter intrusion detection delivers something cameras, radar and fence sensors do not: a detection line with nothing visible above ground, so intruders have no cue where it runs and no exposed equipment to disable.
A buried fiber optic intrusion detection system uses the seismic vibrations created by walking, running, driving, or digging above the cable. Every meter of buried fiber listens continuously, and one Alarm Processing Unit (APU) reports the precise location of every disturbance, with no in-ground devices to space, power, or maintain. The cable is the detector.
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The buried cable creates a completely covert
and invisible security perimeter. -
The AI detects people or vehicles crossing
within 3 to 10 meters (9.8 to 32.8 feet). -
The underground sensor requires
no field power or electronics in the field. -
The same cable and controller can be used for
both fence-mounted and underground applications.
Key Features of the RaySense Buried Security Sensor
- 100% covert. Nothing above grade: no poles, cameras, cabinets, or cable runs to reveal your detection line.
- Up to 100 km (62 mi) per APU across two independent detection channels.
- Location. 3 m (10 ft) detection resolution along the fiber; simultaneous disturbances are reported individually when at least 40 m (130 ft) apart.
- Wide detection corridor. Detects people and vehicles within 3–10 m (10–33 ft) of the buried line.
- Zero field infrastructure. No power or electronics in the ground; the passive fiber is not affected by EMI, RFI or lightning-induced surges.
- AI nuisance rejection. Deep-learning classification filters wind, rain, and animal activity before an alarm is raised.
- Software-defined zones. Create, resize, or re-map detection zones in software, no digging required.
- Cut supervision. A cable break is detected and located by the APU. With a redundant loop, detection continues to within 10 m (30 ft) on either side of a cut; with a single-ended run, detection continues from the APU to within 10 m (30 ft) of the cut.
- Hybrid-ready. The same APU runs buried and fence-mounted zones with application-specific algorithms.
- Open integration. TCP/IP and relay outputs connect to any VMS, alarm panel, or command-and-control platform.
How RaySense Underground Perimeter Intrusion Detection Works
1. Install the sensing cable underground. A direct-burial-rated single-mode fiber optic cable follows an engineered route along the protection line. Burial depth, trench method and backfill follow RBtec burial guidelines; soil type, compaction and nearby activity (roads, rail, machinery) are recorded in the site survey and shape the installation and commissioning plan. There is no power and no electronics in the ground; the cable is the detector.
2. Measure ground vibration (COTDR). The Alarm Processing Unit sends laser pulses through the fiber and measures changes in the backscattered light using Coherent Optical Time Domain Reflectometry. Footsteps, vehicles or digging above the line create vibrations that couple through the soil into the buried cable and change the light pattern at that point.
3. Report the event and its location. The AI engine applies the buried-application detection algorithm and the configured zones, filters wind, rain and typical animal activity, and reports alarms with a location through the monitoring interface. Detection resolution is 3 m (10 ft) between detection points along the fiber; simultaneous disturbances are reported individually when at least 40 m (130 ft) of cable separates them. Detection performance is validated on site against the threat scenarios (walking, running, driving, digging) during commissioning. A buried RaySense detects walking and digging over the cable line, including someone standing behind a barrier without touching it; it is more labor-intensive to install than a fence-mounted sensor. For fence lines, see the fence-mounted RaySense.
What Is a Buried Fiber Optic Intrusion Detection System?
A buried fiber optic intrusion detection system is a covert perimeter security solution that uses an underground fiber optic sensor cable to detect the seismic vibrations created by walking, running, driving, or digging above it. Because the sensor is hidden below the surface, intruders get no visual cue that detection exists.
Unlike discrete ground sensors, RaySense is a distributed sensor: every meter of the buried cable listens continuously, and one Alarm Processing Unit (APU) reports the precise location of every disturbance. There are no in-ground devices to space, power, or maintain: the cable is the detector.
Why Governments Call It LGDS: Linear Ground Detection System
In border security procurement, buried fiber optic detection is known as a Linear Ground Detection System: “linear” because one continuous sensing line replaces thousands of individual point sensors along the boundary.
The same buried line registers pedestrian crossings, vehicle movement, and shallow digging, then hands verified alarm locations to command-and-control platforms, cameras, or patrol units in real time. RaySense brings that government-grade approach to substations, solar farms, data centers, correctional facilities, and airports.
Innovative Solutions for Every Need
Purpose built perimeter detection for the industries where a breach costs the most.
Explore how RBtec fits yours:
Substations and Electrical Utilities
Government & Classified Networks
The Hidden Advantage: Why RaySense LGDS Outperforms the Competition
Unlike Radar units or Thermal Cameras that must be mounted on poles, making them easy targets for sabotage or "blind spot" mapping, RaySense is completely covert.
Thermal cameras lose significant range in heavy fog, rain, or high humidity (which "scatters" infrared signals). Radar can be affected by "clutter" from heavy snow or moving vegetation.
Radars and Cameras require a clear "Line of Sight" (LoS) to work. Hills, trees, or curved perimeter walls create "dead zones" where an intruder can hide.
A 10 km (6.2 miles) perimeter using cameras or radar requires miles of power cabling, expensive trenching for electricity, and dozens of active electronic points that can fail during a lightning strike.
Radar often struggles to detect without false alarms when it doesn't have a camera for video verification.
Buried Fiber vs. Other Underground Detection Technologies
| Capability | RaySense buried fiber (DAS) | Discrete seismic point sensors | Leaky coax / RF cable |
|---|---|---|---|
| Coverage per controller | Up to 100 km on one APU | Small radius per unit; large sites need hundreds of devices | Short zones chained together, each with field electronics |
| Power in the field | None, fully passive cable | Batteries or wiring at every sensor | Powered electronics per zone |
| Location accuracy | ~3 m point location | To the nearest sensor | To the zone |
| Threat classification | AI vibration-signature analysis (person / vehicle / digging) | Threshold-based presence alerts | Presence within the RF field |
| EMI / lightning exposure | Immune, glass fiber with no metal required | Field electronics at risk | Field electronics at risk |
| Cost at long distances | Scales efficiently per km | Grows with every added sensor | Grows with every added zone |
Where a Linear Ground Detection System Fits Best
Anywhere the perimeter is long, sensitive, or impossible to watch line-of-sight: the buried line disappears into the terrain and keeps listening.
Borders & national perimeters
Tens of kilometers of covert, multi-threat detection with no field power, the environment the LGDS was named for.
Substations & utilities
A glass sensor immune to the EMI that disrupts electronic sensors in high-voltage environments.
Solar farms & PV plants
Long, remote perimeters protected against panel and copper theft without running power to the field.
Data centers
An invisible early-warning ring ahead of the fence: defense-in-depth without changing the campus appearance.
Correctional facilities
Covert sterile-zone detection that cannot be located or bridged.
Airports & seaports
Continuous detection across huge perimeters full of line-of-sight obstacles.
One Platform for Buried and Fence Detection
Most large sites need both covert ground detection across open approaches and sensing on the physical barrier itself. Because RaySense runs application-specific AI algorithms per zone, a single APU can monitor buried and fence-mounted fiber segments at the same time: one processor, one interface, one integration.
Buried Fiber Optic Intrusion Detection FAQ
How is the buried sensor cable installed?
The direct-burial fiber cable is laid in a trench along the protection line following RBtec burial guidelines for depth and backfill. Detection depends on how well ground vibration couples into the cable, so soil type, compaction, frozen ground and nearby vibration sources are assessed in the site survey and verified during commissioning. No power or electronics are added to the field. RBtec provides a site-specific cable route and zone layout as part of every project design.
What is a Linear Ground Detection System (LGDS)?
LGDS is the term used in U.S. government and border security programs for buried linear sensing: a continuous underground sensor line that detects people, vehicles, and digging along its full length. RaySense is RBtec’s Linear Ground Detection System.
Can it tell people apart from animals and weather?
Yes. Every event creates a distinct vibration signature, and the two-layer AI engine classifies each one in real time. Long-wave environmental vibration from wind and rain, and typical animal activity, are filtered out; only classified threats such as footsteps, vehicles, and digging raise an alarm.
How accurately does it locate an intrusion?
RaySense reports events with a 3 m (10 ft) detection resolution anywhere along up to 100 km (62 miles) of cable per APU. Simultaneous disturbances are reported as separate events when at least 40 m (130 ft) of cable separates them.
What happens if someone cuts the cable?
A cut is an alarm in itself: the Alarm Processing Unit detects the break and reports its location. Detection continues on the APU side of the cut to within 10 m (30 ft) of the break, and with a redundant-loop layout on both sides of it. Because the cable is buried, an intruder first has to find it.
Does it integrate with cameras and VMS platforms?
Yes. The APU offers TCP/IP and dry-contact relay outputs, so alarms can cue PTZ cameras, VMS platforms, alarm panels, and command-and-control systems. RBtec’s Vidalert alarm management software is available for unified monitoring.
Can one system protect both open ground and a fence?
Yes. The same APU runs buried and fence-mounted fiber zones simultaneously, applying a purpose-built detection algorithm to each zone type.
Design Your Invisible Perimeter
Every terrain is different: soil, layout, and threat profile all shape where the cable should run. Send RBtec your site plan and our engineers will return a buried fiber optic intrusion detection system layout with cable route, detection zones, and APU configuration for your exact site.
