Heating pipelines are buried underground, making it difficult for manual inspections to detect issues promptly, such as insulation moisture, joint cracking, or pipeline leaks during operation. A fiber-optic temperature sensing system functions by equipping the pipeline network with a "nervous system" capable of continuous temperature monitoring. The principle behind distributed fiber-optic temperature sensing is straightforward.
After the sensing fiber is laid along the pipeline, a master unit transmits laser pulses into it, generating continuous backscattered light; the intensity of the Raman scattering signal correlates with the temperature at the fiber's location. By analyzing and demodulating these scattering signals, temperature data for every point along the fiber can be obtained.
Under normal operating conditions, the temperature distribution along the pipeline remains stable; however, if a leak occurs, the escaping hot water or steam alters the temperature field around the leak site. The system detects this temperature change, triggers an automatic alarm, and identifies the leak's location.
A fiber-optic temperature sensing system typically consists of three components: the sensing fiber, the temperature-sensing master unit, and a backend monitoring platform. The sensing fiber acts as the sensor and is laid along the entire length of the heating pipeline; the master unit handles laser transmission as well as the reception and analysis of scattering signals; and the monitoring platform visualizes the temperature data and issues automatic alarms in the event of anomalies. Regarding performance, key technical specifications outlined in the group standard T/SSM 24-2025, *General Technical Specifications for Distributed Fiber-Optic Temperature Sensing Systems for Thermal Pipelines*, include: a temperature measurement range of -20°C to 130°C, spatial resolution of 1 meter or better (within a 15 km detection range), temperature accuracy of ±1°C, positioning accuracy of ±1 meter, and a maximum monitoring distance of at least 10 km. As the optical fiber itself is an insulator immune to electromagnetic interference, it is well-suited for long-distance deployment.
Compared to traditional electrical leak detection systems, fiber-optic temperature sensing offers advantages such as longer monitoring ranges, higher positioning accuracy, and superior resistance to interference. Electrical systems require signal cables to be embedded alongside the pipeline and rely on changes in resistance or impedance to detect leaks; consequently, they are susceptible to electromagnetic interference and offer relatively limited positioning accuracy. Once buried alongside the pipeline, fiber-optic temperature sensing systems require minimal maintenance and boast a long service life. Regarding industry standards, the standard T/CDHA 11-2022, *Technical Specifications for Fiber-Optic Monitoring Systems for Directly Buried Heating Pipelines*, issued by the China District Heating Association in 2022, applies to fiber-optic monitoring systems based on temperature-sensing technology installed on the exterior of directly buried heating pipelines. The national standard GB/T 47547-2026, *Technical Specifications for Fiber-Optic Monitoring Systems for the Safe Operation of Directly Buried Insulated Heating Pipelines*, was released in April 2026 and is scheduled for implementation in November 2026.
This technology is already being utilized in practical projects. The "situational awareness system" deployed in the Shiyan district heating network comprises three components-high-precision optical fiber, a distributed fiber-optic temperature-sensing host unit, and a backend monitoring platform-supporting a temperature measurement accuracy of ±1°C. The intelligent fiber-optic leak detection system for pipeline networks, jointly developed by Tangshan Xingbang Pipeline and the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, features temperature-sensing fiber laid alongside the pipeline; it is capable of pinpointing leak locations and providing real-time early warnings. In June 2025, the International Organization for Standardization (ISO) officially initiated the project *Technical Requirements for Fiber-Optic Leak Monitoring Systems for Directly Buried Heating Pipelines*, with Xingbang Pipeline serving as the lead drafting organization. Fiber-optic temperature-sensing systems transform leaks in heating networks from "invisible" to "visible." For new or renovated heating projects, this represents a fundamental investment worth considering.