The recoverable linear fiber optic differential temperature fire detector BHG-FGCW is a continuous distributed fiber optic temperature sensing system. Utilizing OTDR technology and the temperature-sensitive characteristic of Raman scattering light, it detects temperature variations along different positions of the fiber, achieving truly distributed measurements. In addition to timely warning of fire hazards, the linear fiber optic differential temperature fire detector can also locate the fire's origin. As a mature distributed temperature measurement method, it boasts advantages such as long measurement distance, high measurement accuracy, fast response speed, resistance to electromagnetic interference, and suitability for flammable and explosive hazardous environments. It is widely applicable in fields such as online monitoring of high-voltage cables, power load flow analysis, fire monitoring in traffic tunnels, oil and gas storage tank fire monitoring, coal conveyor belt fire monitoring, and dam leakage monitoring.