Research On Random Fiber Lasers Based On Weak-reflected Fiber Bragg Grating Array

The random fiber laser is a new type of fiber laser,which is different from the traditional laser,without fixed resonant cavities and getting random feedback from scattering.The advantages like the high efficiency,the compact structure and the low excitation threshold make it an important light source in military,technology and other fields.The reported random fiber laser mainly obtains feedback through the Rayleigh scattering of the single mode fiber.Due to the extremely low scattering coefficient of the backward Rayleigh,it is often necessary to exploit the fiber of up to thousands of meters to ensure sufficient mode suppression effect.In this paper,a random fiber laser based on the weak-reflected fiber Bragg grating array was designed.The main contents are as follows:(1)Research on the random distributed feedback weak-reflected fiber Bragg grating arrays.The photon localization theory of random fiber laser is analyzed,and the transmission rate of fiber Bragg grating array with the number of grating is studied based on the transmission matrix method.The passive reflection spectrum of the array was simulated to obtain the production parameters.Random distributed feedback weak-reflected fiber Bragg grating arrays with different number of grating were fabricated based on the traditional phase mask method and the drawing tower respectively.(2)Design of the random fiber laser based on the weak-reflected fiber Bragg grating array.Based on the Giles energy level model,the simulation of erbium-doped fiber gain system was realized,and the proper pump source was selected and the length of erbium-doped fiber was optimized.The theoretical models of semiconductor optical amplifier were established to compare the advantages and disadvantages of each gain.The proper gain was chosen and the theoretical basis was provided for the design of random fiber laser.(3)Experimental research of the random fiber laser based on the weak-reflected fiber Bragg grating array.The experimental optical path of the ring cavity random fiber laser was built with the erbium-doped fiber as the gain and the weak-reflected fiber Bragg grating array as the feedback device.The output of the laser was tested.The measurement method of each parameter was described,and the performance of the laser system was evaluated according to the experimental results,with the corresponding improvement scheme proposed.(4)Research on other random fiber lasers.Attached a narrow-band tunable optical filter to the random fiber laser with the weak-reflected fiber Bragg grating array,the laser output wavelength could be tuned in some range by adjusting the wavelength of the filter in the laser system,which met the needs of the tunable light source for the sensing system.Taking advantage of the polarization-maintaining fiber biaxial refractive index,the random fiber laser with weak-reflected fiber Bragg grating array on the polarization-maintaining fiber achieved the dual-wavelength output or the single wavelength switching over two different wavelengths.