Design of an OFDR-based full-area intelligent and precise temperature measurement system for belt conveyors

Rapid and precise measurement of temperature along the belt conveyor plays a core role in preventing external fire hazards in coal mines. Distributed optical fiber temperature measurement based on Optical Time-Domain Reflectometry (OTDR) is currently the mainstream technology for temperature measurement along belt conveyors, but it suffers from low temperature measurement accuracy and large positioning errors. To address this issue, an Optical Frequency Domain Reflectometry (OFDR)-based full-area intelligent and precise temperature measurement system for belt conveyors was proposed. By analyzing the system's technical route and architecture, Raman scattering was determined as the theoretical basis, fast Fourier transform as the signal processing algorithm, and a tunable semiconductor laser was selected. A four-layer composite-structured OFDR optical cable with a diameter of 4 mm was designed, with the diameter reduced by 50% compared with traditional OTDR optical cables, the maximum tensile strength increased by 33%, and the maximum compressive strength improved by 233%. An industrial test was carried out along the No.1 South Wing belt conveyor of Shanxi Gaohe Energy Co., Ltd. The results showed that the system operated stably for one year, with a system inspection cycle of 12.5 s, a temperature measurement accuracy of 0.5 ℃, and a positioning accuracy of 0.25 m, all meeting the requirements of NB/T 10183—2019 Distributed Optical Fiber Temperature Measuring Device for Mine and surpassing the current advanced industry level. At the same time, the system reliably provided alarm functions for temperature over-limit, temperature rise, and temperature difference.