The Intensity Demodulation System Of FBG Time Division Multiplexing Based On Polarization Maintaining Fiber Sagnac Ring

Fiber bragg grating has many advantages such as small size,high sensitivity,antielectromagnetic interference,and strong operability,which have developed rapidly relying on its own numerous advantages and a wide range of applications.That is also the reason why it is widely used in many sensing and testing areas.Sensing demodulation technology is the key technology of FBG sensors and sensing systems.It converts FBG sensing signals(the Gaussian type)characterized by changes in central wavelength or signal strength into electrical signal forms,including optical signal processing and optical signal processing,sensing signal(wavelength information or intensity information)to electrical signal conversion and electrical signal processing.The traditional demodulation methods include spectrometer OSA measurement,unbalanced Mach-Zehnder(MZ)interferometer method,CCD spectrum demodulation technology and tunable FP filter demodulation technology.But the above technologies are usually susceptible to environmental influences and costly.The complex structure,the limited number of FBG sensors that can be demodulated,etc,limit the wide application of FBG sensing technology.Therefore,the ability to develop a demodulation system with lower cost,faster demodulation speed,and higher detection accuracy is of great significance to the practical application of sensing in various industries.This paper proposes a FBG time-division multiplexing intensity demodulation system based on a polarization maintaining fiber Sagnac loop and mainly introduces five aspects: research background and current status at home and abroad,demodulation system theories,demodulation system hardware introduction,data processing algorithm principle as well as summary and prospects.Among them,the intensity filter uses the Sagnac ring based on the polarization maintaining fiber.Different lengths of polarization maintaining fiber in the Sagnac ring can change the filtering range of the filter.Thus,the length of the polarization fiber in the Sagnac can be designed depending on the sensing application;What's more,in the signal processing module,a combined algorithm with wavelet analysis algorithm and LM(Levenberg-Marquardt)Gaussian algorithm is used to denoise and filter the signal,optimizing the traditional wavelet threshold denoising algorithm,and greatly improving the demodulation accuracy and signal noise of the system signal ratio.After the experiments,the SNR of the system has been increased from 8.06 d B to 11.7d B,which means the SNR of the demodulation system has increased by about 45%,effectively improving the anti-interference ability of the system signal and the accuracy of sensor detection.The subject of this article is based on the current industry demodulation situation.While improving the system's signal-to-noise ratio and demodulation efficiency,it greatly increases the number of multiplexed FBG sensors in the system.This demodulation system is expected to be widely used in sensing systems in all walks of life.