In-Service OTDR Fiber Monitoring (RFTS)
24/7 automatic cable health monitoring — 100 km range, ±1 m fault location, degradation before interruption.
What is in-service fiber optic cable monitoring?
In-service fiber optic cable monitoring (RFTS) watches live communication fiber without interrupting it. The monitoring unit reads the fiber's attenuation curve around the clock through a spare core or a non-disruptive access method — 100 km range per unit with ±1 m fault localization on the fiber-link coordinate. When a fiber is cut or degraded, the event is alarmed in seconds and the location is handed directly to repair crews, instead of technicians driving the route with a portable OTDR section by section. Continuous curve archives also turn each cable route into a living asset ledger of joints, loss points and degradation trends, so weak spots are addressed before they interrupt service.
Four pain points of conventional cable O&M
Slow fault localization
After a fiber cut, crews carry an OTDR to locate the break section by section — long repair cycles and growing business-interruption losses.
Degradation invisible
Bending, crushing and water ingress degrade gradually; traditional O&M only responds after the fiber breaks.
No asset inventory
Long cable routes are complex; joints and loss points lack an online ledger, so fault diagnosis has no data to rely on.
Multi-owner complexity
Cable assets belong to many owners (carriers, private networks, self-built); O&M responsibility needs objective monitoring data.
Architecture: 24/7 automatic monitoring loop
Monitor → localize → archive: a closed loop that upgrades cable O&M from firefighting to prevention.
In-Service OTDR Fiber Monitoring (RFTS)
The RFTS unit automatically patrols in-service fiber 24/7 — 100 km range (industry avg 80 km), real-time attenuation curve and event-point tracking for the full route.
±1 m fault location
±1 m on the fiber-link coordinate plus ±5 m field location (using cable route records) guides repair crews straight to the real fault point — no section-by-section search.
Fiber health archive
Continuous attenuation-curve accumulation builds an online ledger of joints, loss points and degradation trends, turning O&M from after-the-fact repair to before-degradation warning.
Installation without disruption: how a typical deployment works
From route inventory to 24/7 automatic patrol — with live traffic physically untouched.
- Step 1 — Inventory routes and cores. List cable routes, lengths and available spare cores, or determine the appropriate non-disruptive access method for each route.
- Step 2 — Design the monitoring layout. Allocate RFTS units — 100 km range each — across the route network, and plan integration with the existing network management system.
- Step 3 — Connect without disruption. Monitoring uses a spare core or physically isolated access, so in-service communication traffic is never touched.
- Step 4 — Capture the baseline. Record reference attenuation curves and event points (joints, splices, loss points) for every monitored fiber.
- Step 5 — Operate 7×24. The system patrols automatically, alarms fiber cuts and degradation in seconds with ±1 m localization, and trends attenuation changes before they become outages.
Core metrics: measurement accuracy & fault detection
Ecosystem backing
Landsub Global is a DICT partner in a leading telecom operator's ecosystem, with cable-monitoring capability integrated into carrier-grade digital services — and adapts to transport, power, petrochemical private networks and enterprise self-built cable.
Operations: long-distance distributed monitoring at carrier scale
What running RFTS across a multi-route network involves day to day.
At network scale, RFTS is operated as a standing capability rather than a test campaign. A monitoring station of coordinated units covers the route inventory — 100 km per unit — and the day-to-day workflow concentrates on three things:
- Alarm handling. Fiber cuts are localized to ±1 m on the fiber coordinate and ±5 m on the ground, so dispatch sends the crew to a point, not a segment.
- Degradation trending. The curve archive surfaces slowly worsening loss points — joints under stress, sections with water ingress — while they are still planned-work items rather than outages.
- Asset ledger maintenance. After each splice or repair, the updated curve becomes the new baseline entry in the route's health record, keeping the ledger current without manual surveys.
For multi-owner environments, the same monitoring data provides an objective basis for O&M responsibility discussions: when a fault is localized and time-stamped automatically, the question of whose section failed is answered by the record rather than by negotiation.
Two practical boundaries are worth stating plainly. First, monitoring quality depends on route records: the ±1 m fiber-coordinate reading becomes a real-world location only when the cable-route documentation is accurate, so keeping that database current is part of the operating discipline. Second, RFTS watches the fiber itself — it does not interpret the services the fiber carries — so it complements, rather than replaces, the traffic-management tooling operators already run. Within those boundaries, the capability is owner-agnostic: the same deployment pattern serves carrier backbones, transport and energy private networks, and campus or factory self-built cable.
Offline OTDR vs in-service monitoring: how the O&M approach compares
A factual comparison of common approaches to fiber cable operation and maintenance.
| Dimension | Offline OTDR testing | Reactive break-fix O&M | In-service fiber monitoring |
|---|---|---|---|
| Coverage | Tested only when a crew schedules a visit | The whole route, but only after an outage | 100 km per unit, 7×24 automatic patrol |
| Response | Depends on test scheduling | Begins after customers report the fault | Second-level alarms on cuts and degradation |
| Localization | Section by section, from the access point | Walk-down search along the route | ±1 m on the fiber coordinate, ±5 m in the field |
| In-service operation | Test light must be injected on the working route, often during a window | Repair windows only — no visibility in between | Spare-core or isolated access; live traffic untouched |
| Asset records | One-off test reports, hard to compare over time | None until failure | Continuous curve archive: joints, loss points and degradation trends |
Frequently Asked Questions
Further reading
- Optical time-domain reflectometer — the measurement technique behind attenuation curves and ±1 m fault location.
- Fiber optic sensor — background on distributed fiber sensing for cable health monitoring.
- Distributed acoustic sensing — how the same fiber infrastructure supports acoustic event detection.
- Distributed temperature sensing — the companion technology for temperature monitoring on cabled assets.
Last updated: September 2026
By the Landsub Global Engineering Team
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