Research On Multiwavelength Brillouin Erbium-Doped Random Fiber Lasers

As a new type of fiber laser,random fiber laser has a novel feature that the feedback mechanism of laser formation is provided by the inherent or artificial random scattering in the fiber,which no longer relies on the well-defined resonator in the traditional fiber laser,and simplifies the construction of the laser cavity.Therefore,the random fiber laser has some unique advantages of simple experimental device,easy maintenance,flexible design and so on.Since the structure of random distributed feedback based on Rayleigh scattering in fiber was first proposed in 2010,the research direction of the random fiber laser has covered multi wavelength output,narrow linewidth,high efficiency,high power,wavelength tunability and other aspects,and further expanding its functionality.In recent years,the research shows that this new laser is expected to play an important role in the fields of fiber communication system,fiber sensing and optical imaging.The main work of this thesis is to design a variety of multi wavelength random fiber lasers based on Brillouin erbium-doped gain.The influence of erbium-doped gain position on the output characteristics of a single Brillouin frequency shift interval random fiber laser is studied systematically through experiments,which provides a reference for further improving the performance of the laser;By increasing the interval between the output wavelengths,the output characteristics of random fiber laser with double Brillouin frequency shift interval are studied in detail;Furthermore,a random fiber laser with switchable wavelength interval is realized,which increases the flexibility of laser application.The specific contents of this thesis are as follows:(1)The research background and classification of random fiber lasers are described.Combined with the literature,the current research status of multi wavelength random fiber lasers and wavelength tunable random fiber lasers are summarized and introduced.(2)A random fiber laser based on Brillouin erbium-doped gain is proposed.The effect of the position of erbium-doped gain on the output spectrum is studied.It is found that the erbium-doped fiber amplifier(EDFA)has a strong amplification effect on the Brillouin pump light and Stokes light when it is located at the port 2 of the circulator,and the laser can output 18 order Stokes light.However,the tunable range of the laser is up to54 nm when it is located at the port 1 of the circulator.This research provides a new idea for the design of high performance multi wavelength tunable random fiber laser.(3)A random fiber laser with double Brillouin frequency shift interval is proposed,which simplifies the double branch structure proposed by our group before,and realizes the separation of odd order and even orders Stokes light.Four Stokes lines with a wavelength interval of about 0.176 nm can be obtained,and the wavelength tunable range is as high as 60 nm.(4)To further optimize the structure of the random fiber laser,a random fiber laser with a wavelength interval that can be flexibly switched is designed.The wavelength interval can be switched by controlling whether the EDFA is in working state,the laser output characteristics at the wavelength intervals of 0.088 nm and 0.176 nm are studied,respectively.In addition,by studying the effect of two EDFAs on the laser,it is found that the output wavelength interval can be switched by controlling the gain of the EDFA reasonably.