Research On Compact Sensing Systems Based On Optical Fiber Sensor And Underwater Temperature Measurement

Fiber grating sensor has become an important direction in the field of sensing research due to its superior performance.The interrogation system restores the optical signal to the measured information,and its accuracy and stability directly affect the quality of the sensing,which is an important part of the sensing system.Among the currently developed interrogation methods,the filter interrogation method has small size and fast interrogation speed,but it has the disadvantages of being susceptible to temperature and low sensitivity,which limits the application of this interrogation method.In order to solve the defects of the filter interrogation system,realize the system with automatic temperature compensation and high sensitivity,and give full play to the advantages of the filter interrogation method,this work focuses on the following research:The edge filtering system based on long period grating filter is studied to improve the sensitivity and anti-temperature interference ability of the system.The sensitivity of the edge filtering system is related to the edge slope.By increasing the number of long-period grating periods to 45,the spectral bandwidth of the long-period grating is reduced.Combined with the pre-stressed packaging,the edge slope is successfully improved to-2.24 d B/nm,and the system sensitivity is increased by 15 times.An automatic temperature compensation scheme based on edge filtering is designed.The two Bragg gratings in the system have similar temperature response,and the temperature interference of the system is reduced by about 80% by differential method.A double Bragg grating center wavelength matching interrogation method is proposed,and the interrogation range of the system is optimized.The Bragg grating is used to replace the long period grating filtering,and the strain is measured by the center wavelength difference of two Bragg gratings.The central wavelength difference does not change significantly when the temperature changes,achieving temperature compensation.At the same time,the edge slope of the Bragg grating is larger,and a higher resolution is achieved.The minimum resolution in the experiment is 0.6 με.The chirped Bragg grating is used to improve the measurement range of the system,which solves the problem that the range is inversely proportional to the sensitivity,and the sensitivity of system is 0.261 m V/με and 0.447 m V/°C.A tunable filter interrogation system driven by piezoelectric transducers is designed.The spectrum to be measured is scanned by the right-side spectrum of the chirped Bragg grating,which provides an idea for the large bandwidth filter to interrogate the small bandwidth sensor.The underwater temperature quasi-distributed sensing system is designed by using tunable light source interrogation.The tensile and compressive packaging of the sensor is designed and verified.The optical path of the sensing system is designed.By sending the data to the network,the temperature data can be observed in real time and the test is completed under laboratory conditions.This paper starts with the basic edge filter interrogation,analyzes the influence of filter properties on the interrogation system,optimizes the design according to the problems exposed in the experiment,and realizes automatic temperature compensation and high sensitivity.Finally,a quasi-distributed temperature measurement system is designed according to the actual needs.This paper has certain reference significance for solving the temperature interference in the edge filter interrogation system and the design of underwater temperature sensing based on fiber grating.