Identical Weak Fiber Bragg Grating Sensing Detection Based On Fiber Chaotic Laser

Fiber Bragg grating (FBG) has the advantages of high sensitivity, lightquality, small size, easy fabrication, resis tance to electro-magnetic interferenceand easy to realize multiplex. FBGs are widely used in structure detection oflarge composite materials and concrete, safety testing of the aerospace, reservoirdetection of oil and gas and the temperature and loadin g of electric transmissionline.In the dissertation, a novel type of quasi-distributed fiber Bragg gratingsensing system based on fiber chaotic laser is demonstrated. The light source isthe wavelength tunable fiber chaotic laser. The identical weak fibe r Bragggratings are utilized as sensors. According to delta function characteristics of thecorrelation of chaotic light sources, the correlation peaks of the cross-correlationbetween the reflected light from sensors and reference light from chaotic fibe rlaser can locate the positions of the sensors. The center wavelength of theidentical weak fiber Bragg grating with stress can be demodulated using tunableoptical fiber grating filter and the quasi-distributed fiber Bragg grating sensingsystem is realized.For the sensing detection technology, the dissertation mainly includes thefollowing contents:1. The development of the quasi-distributed sensing detection systems with FBGs and demodulation technologies of sensing information of domestic andforeign is summarized. The advantages and disadvantages of these techniques areanalyzed.2. The classification and production methods of FBG are theoreticallyanalyzed. The sensing principle of FBG is included.3. The experiment of the erbium-doped fiber chaotic laser with tunablewavelengths is carried out. The wavelengths from the laser can match with thecenter wavelength of the FBG. The output characteristic of chaotic laser withdifferent wavelengths is studied. The experimental results show that thewavelength-tunable chaotic laser can be used for demodulating the sensinginformation of FBG. What’s more, the system can obtain the accurate positions ofthe FBG sensors with correlation method.4. Based on quasi-distributed weak reflection FBG sensors array, t heexperiment can detect the stress and determine the sensors’ locations. The resultsshow that the wavelength of the chaotic fiber laser can be continuously tuned forfiber Bragg grating sensor demodulation. According to the correlation curves ofreflected light and signal light, sensors’ position can be achieved.5. At last, The summaries and analysis of the results is analyzed and then welook forward to the future of our work.