Fusion Distributed Optical Fiber Sensing System With Multi-parameter Synchronous Detection Capability

In recent years,China's large-scale infrastructure construction in the fields of national defense,energy,transportation,and communications has grown significantly,and the scale of infrastructure construction has reached the world's largest.These large-scale infrastructures have a long service life and will inevitably be affected by factors such as structural aging,natural disasters,and man-made destruction.Once an accident occurs,it will seriously threaten the lives of the people and cause great losses.Distributed optical fiber sensing technology has the advantages of long sensing distance,continuous measurement without blind spots,high sensitivity,multi-physical quantity sensitivity and anti-electromagnetic interference.It has broad application prospects in structural health and safety monitoring of large facilities.However,the current distributed optical fiber sensing system still has many limitations: on the one hand,the traditional distributed optical fiber sensing system can usually only monitor one kind of environmental parameters,which may easily lead to missed reports and false alarms.Large-scale infrastructures have various types of hidden health risks and complex working environments,and they often produce abnormal changes in multiple physical parameters such as temperature,strain,and vibration.If only one of these parameters is monitored,it is not only difficult to distinguish the specific types of health risks,but the monitoring results are also susceptible to environmental noise.On the other hand,the device parameters of the sensor will drift with time,and calibration is needed to maintain the measurement accuracy.Sensor calibration is a test conducted to determine its performance indicators and is a necessary process to improve the quality of sensor data.At present,the calibration of optical fiber sensors generally depends on returning to the factory for calibration.After the measurement accuracy deteriorates,it is necessary to return to the manufacturer to recalibrate the device parameters,which greatly affects the efficiency of the sensor.In response to the above problems,this paper designed the fusion distributed fiber sensing system based on Rayleigh and Brillouin scattering by using the characteristics of different scattered light in optical fiber sensitive to different physical parameters.The fusion system fully reuses devices such as lasers,modulators,and optical amplifiers,and selects and configures the operating parameters and modes of the devices reasonably to achieve simultaneous sensing of temperature,strain,and vibration.A self-calibration method of instrument fusion sensor system is proposed.The self-calibration method can quickly determine whether the fusion system is in a normal working state through a programmed inspection process,and set device parameters reasonably so that the fusion system is in an optimal working state.An optical fiber calibration device is designed,which can not only calibrate the initial temperature of the optical fiber to be tested,but also assist in the self-calibration of the fusion system,which is helpful for the rapid inspection and debugging of the sensor system and reduces the error of manual calibration of the optical fiber temperature.Based on the fusion system design scheme and self-calibration method,this paper completes the development of a prototype of a fusion-type distributed optical fiber sensor system with self-calibration capabilities.The experimental results show that the system can achieve a spatial resolution of 10 m within a sensing distance of 10 km,temperature and strain measurement uncertainties of ± 1? and ± 20??,and a vibration response range of 10 Hz to 1k Hz,which can accurately locate vibration events.The fusion system realizes the simultaneous measurement of three parameters of temperature,strain and vibration.The fusion-type distributed optical fiber sensing system proposed in this paper uses only a single optical fiber to achieve simultaneous monitoring of multiple parameters of temperature,strain and vibration,and provides a self-calibrating,highly fused,easy-to-implement distributed optical fiber sensing technology solution.It has important potential application value in largescale infrastructure health monitoring.