Research On Fiber Bragg Grating Demodulator Based On Static Tunable Light Source

Fiber Bragg Grating(FBG)sensor has many advantages,such as simple structure,strong anti-electromagnetic interference capability,high sensitivity and low cost.It has been widely studied and applied in scientific research and industry in recent years.The key technology of FBG sensing lies in the accurate demodulation of the Bragg reflection wavelength.We can say that the measuring accuracy of the demodulation module directly determines the detection precision of the sensor system.Therefore,as a demodulator for FBG sensors,a fiber grating demodulator has also received a high degree of attention.In this paper,we go deep into understanding and researching on fiber grating sensing principle,and demodulation technology and use the tunable DFB(Distributed Feedback)laser array as the static tunable source.A new type of fiber grating sensing system and method have been researched and designed.The system and method do not need to perform full-peak scanning of the FBG like the traditional demodulation technology,and only need to scan part of the spectrum to achieve accurate demodulation,so that the system and method greatly reduce the cost of the fiber grating demodulator.This article firstly introduced the sensing fundamental of FBG including analysis of strain sensing and temperature sensing characteristics,and carried on an analysis of FBG wavelength demodulation technology.The advantages and disadvantages of the existing commercial demodulation system have been analyzed.The overall scheme of the demodulation system and the corresponding demodulation algorithm have been designed.The light source drive of the demodulator has been designed by using a 4-channel tunable laser,including the temperature control circuit and the current control circuit.Finally,the reason for limiting the yield of DFB laser has been analyzed.Based on the original packaging process,a low thermal conductivity tunable DFB laser has been proposed,which could solve the tuning range to a certain extent.It could achieve large capacity of the demodulation system in theory.The demodulation algorithm has been simulated by MATLAB,and the accuracy of the demodulation system and algorithm has been verified.The demodulation error of the algorithm is less than 2 pm,and the sampling and demodulation time of the demodulation algorithm is greatly shortened.The text of scanninng FBG has been verified the feasibility of the demodulation system in practical applications,and the error of the full-peak scan is only 5pm.The high precision,high stability and low cost demodulator can be achieved in theory.The development of low thermal conductivity tunable lasers shows that this method has high stability and reliability.The resilience of demodulation system is very good which can meetthe needs of the project.