FOTAS DTS FAQs

FOTAS DTS is the temperature-sensing branch of the FOTAS fiber optic sensing family. It turns optical fiber into a continuous linear temperature sensor for real-time, long-range monitoring. The branch includes two product lines built on the same DTS core: FOTAS APEX for fire detection and Linear Heat Detection, and FOTAS INTEGRITY for asset condition monitoring, thermal trend analysis, and predictive maintenance.

A DTS controller sends laser pulses into an optical fiber and analyzes the Raman backscatter returning from every point along the cable. The ratio between the temperature-sensitive anti-Stokes signal and the Stokes signal is used to calculate temperature. The return time of the light identifies the position of each reading, using the known speed of light in fiber. Temperature is typically reported at approximately one-meter intervals, creating a continuous thermal profile along the route.

FOTAS APEX and FOTAS INTEGRITY share the same distributed temperature sensing principle but serve different objectives. FOTAS APEX is the fire-focused product line, used as a continuous Linear Heat Detector for fire detection and alarm applications. FOTAS INTEGRITY is the condition-monitoring product line, used for thermal mapping, trend deviation analysis, asset integrity monitoring, predictive maintenance, and dynamic rating applications.

Linear Heat Detection provides continuous heat monitoring along a protected route rather than relying only on individual point detectors. FOTAS APEX uses DTS to produce digital temperature measurements and a complete thermal profile along the fiber, allowing abnormal heat to be located precisely. Traditional LHD cables generally provide a binary alarm when a temperature-dependent element is triggered. APEX provides measured temperature data, profile-based alarm logic, and precise event location, and its sensing principle does not rely on polymer-cable degradation.

FOTAS APEX is designed for compliance with EN 54-22 requirements for linear heat detection, VdS approval requirements, and SIL 2. These statements describe the product’s compliance design targets. The current approval and certification status for a specific product version or project should be confirmed through the latest official FOTAS documentation.

FOTAS INTEGRITY is available with nominal sensing ranges of 10, 20, 30, and 40 kilometres. Depending on the project configuration, it can be supplied with 2, 4, 8, or 16 channels. These options support both long linear assets and multi-route monitoring projects.

FOTAS DTS typically provides temperature readings at approximately one-meter intervals. Spatial resolution is generally between 1 and 4 metres, depending on the application and configuration. Temperature resolution is typically 0.1°C, and tunnel deployments can provide temperature accuracy of ±1°C. Thermal anomalies can be localised to approximately one metre under suitable system and installation conditions.

FOTAS APEX is intended for continuous fire and heat monitoring in applications such as:

• Road, rail, and metro tunnels
• Car parks and electric vehicle charging infrastructure
• Warehouses, storage and logistics facilities, including cold storage and battery charging areas
• Conveyor belts
• Manufacturing and industrial facilities
• Rooftop and utility-scale solar PV installations
• Cable trays
• Data centres

FOTAS INTEGRITY is intended for continuous thermal condition monitoring in applications such as:

• High-voltage power cables
• Transformers, substations, and battery energy storage systems
• Oil and gas pipelines and multi-utility pipelines
• Conveyor and drive-station components, including bearings, rollers, and gearboxes
• Busbar and switchgear connections
• Data centre cooling and power infrastructure

Yes. FOTAS INTEGRITY can provide continuous temperature data for dynamic or real-time thermal rating of power cables. Through integration with SCADA, OMS, or EMS platforms, the system can support load-management decisions and help maximise power-transfer capacity while remaining within thermal limits.

Yes. FOTAS DTS can identify leak-related thermal anomalies along a pipeline. Gas leaks can produce local cooling through the Joule-Thomson effect, while liquid leaks can create temperature changes through interaction between the released product and the surrounding soil. The distributed thermal profile allows these anomalies to be detected and located along the monitored route.

FOTAS DTS can integrate with fire alarm panels through hard-wired relay outputs and with SCADA, BMS, DCS, and EMS platforms. Supported project interfaces can include IEC 61850, OPC UA, and Modbus TCP/IP. This allows temperature data, alarms, zones, and system status information to be incorporated into existing operational and safety workflows.

No. The fiber optic sensing cable is a passive element and requires no electrical power along the monitored route. It is immune to electromagnetic and radio-frequency interference. Suitable sensing cables are designed for a service life of more than 25 years and require minimal field maintenance, while the controller and system health should be maintained according to the project plan.

Yes. FOTAS DTS can use sensing cable options designed for demanding environments, including LSZH, fire-resistant, and armoured constructions. The passive fiber is immune to EMI and RFI and can be deployed in environments exposed to dust, humidity, and vibration. This makes the system suitable for tunnels, mining, industrial facilities, and other challenging sites.

Choose FOTAS APEX when the main requirement is fire detection, Linear Heat Detection, alarm generation, and compliance-oriented fire protection. Choose FOTAS INTEGRITY when the objective is asset-health monitoring, thermal trending, predictive maintenance, anomaly localisation, or dynamic rating. Both objectives can coexist in the same project, but the system architecture and alarm strategy should be selected according to the application. Contact FOTAS for a project assessment.

Yes. FOTAS DTS and FOTAS DAS can be combined within one project to provide thermal, operational, acoustic, and security monitoring along the same route. See the FOTAS FAQs for the combined DTS and DAS deployment approach.