Research On Fiber Bragg Grating Flow Sensing

Optical fiber sensor has been widely studied for its unique advantages,such as high sensitivity and small volume.Fiber Bragg gratin(FBG)is one of the most widely used passive devices.In all fields of industrial control,flow has been needed to be monitored and analyzed in order to ensure the safe operation of the production.Compared with the traditional flow meters having some problems,such as large volume and low sensitivity,we can design new flow-meters based on fiber grating which has high sensitivity,which has great significance to the modern industrial process control.This paper is closely combined with the research and development direction of FBG flow sensor,we design and produce new FBG flow measurement system in basing on the analysis of fiber Bragg gratin theory,and put forward to Mach-Zehnder interferometer cascading with fiber Bragg gratin to achieve flow measurement.The main research is as follows:1?Basing on the structure of fiber Bragg grating and target,we design that double FBGs with different center wavelengths are symmetrical sticker on both sides of the target to measure the flow.Meanwhile,the flow measurement of the sensor at different positions of the pipe is also studied.In this design,the temperature is compensated by two gratings,and the influence of temperature for the flow measurement is eliminated due to double FBG having same temperature characteristics,so the on-line measurement of the flow is realized.2?Based on fiber taper and fiber Bragg grating,a new structure based on single-mode fiber(SMF)-taper-FBG is designed.Compared with double FBGs,FBG cladding has excitation modes due to fiber taper,so that FBG reflection spectrum has high order modes exist.In this design,the influence of the taper size on the FBG reflection spectrum is analyzed.The response of the sensing system to the corresponding force is also studied.3?A new flow sensing system base on Inline Mach-Zehnder Interferometer(MZI)cascading with FBG is proposed.In this design,the influence of fiber dislocation and the length of the interference arm on the transmission spectrum of the MZI sensor are analyzed.The advantage of the sensing system is to transform flow detection into stress measurement to eliminate the effect of fluid temperature on the transmission spectrum of sensors.4?A distributed monitoring system based on fiber Bragg grating for oil and gas pipeline transportation is proposed.The shortcomings of current monitoring oil and gas pipeline transportation and the protection methods of pipeline are expounded,and the key technologies of distributed monitoring of FBG is put forward,including packaging technology,multiplexing technology and demodulation technology.Finally,the pipeline monitoring system and the sensor layout process are designed.