Online concentration monitoring system for gases in cable tunnel based on optical fiber sensing

The invention relates to an online concentration monitoring system for gases in a cable tunnel based on optical fiber sensing. The system comprise a tunable laser, a circulator, 1*N photoswitches, an optical cable, sensor probes, a photoelectric detector, and a control module. An output end of the tunable laser is connected with an input end of the circulator. An output end of the circulator is connected with an input end of each of the 1*N photoswitches. Each of the 1*N photoswitches is connected with one sensor probe through a single-core single-mode optical fiber. Another output end of the circulator is connected with an input end of the photoelectric detector, and an output end of the photoelectric detector is connected with a corresponding input end of the control module. Two output ends of the control module are connected with the tunable laser and the corresponding input end of the 1*N photoswitches. The system has the advantages that the passive sensor probes are adaptive to multiple gases, potential safety hazards caused by power supply equipment are avoided, the probes are distributed along the cable, the coverage is wide, calibration can be performed in a machine room, and the troubles of field calibration are omitted.