Research On Mode Locked Laser Based On High Concentration Erbium Doped Fiber

Mode locked lasers have attracted widespread attention from scientists due to their advantages such as simple structure,low cost,and stable output.The ultrashort pulses generated by mode-locked lasers can not only serve as the main information carrier for future ultra long distance and ultra large capacity communication systems,but also have important applications in communication system detection,biomedical and other fields.Therefore,the research on mode-locked lasers has important practical significance.This article mainly studies mode-locked lasers based on high concentration erbium-doped fibers.The gain characteristics of erbium-doped fibers and the mode-locked characteristics of lasers are theoretically analyzed.Theoretical analysis combined with practical experiments is used to study mode-locked lasers.The main research work of the thesis is as follows:(1)Designed an erbium-doped fiber amplifier scheme based on high concentration erbium-doped fibers.Firstly,based on the energy level structure of erbium ion,its Rate equation and transmission equation are deduced and simulated,and the factors affecting the gain of high concentration erbium-doped fiber amplifier are explored.The optimal length of the erbium-doped fiber and the minimum pump power it needs are obtained.Based on the simulation results,an experimental platform is built for experimental verification,and an erbium-doped fiber amplifier with a spectral broadening of 110 nm and a maximum output power of 23 dBm is realized.(2)A passive mode-locked laser scheme based on the erbium-doped fiber amplifier mentioned above has been studied and designed.By using high concentration erbium doped fibers,the resonant cavity length of the laser was shortened,and a semiconductor saturable absorption mirror was used as a mode-locked device.A mode-locked laser based on high concentration erbium doped fibers was constructed,achieving stable mode-locked pulse output with a central wavelength of 1550 nm and an average power of 32.1 mW.(3)In order to achieve fast and real-time resolution of the characteristics and types of pulses,a pulse recognition scheme based on Gate Recurrent Unit(GRU)is proposed.The Gaussian pulse evolution process and single soliton pulse evolution process of different pulse widths,input power signals,and signal noise were trained on a dataset.After simulation testing,it was proven that the accuracy of this recognition scheme can reach 100%,This provides a new approach for the design of an intelligent and stable mode-locked laser.(4)A linear light sampling system based on passive mode-locked lasers was constructed,and the effects of balanced detector response characteristics,pulse light power and signal light power,as well as pulse spectral width and signal spectral width on the linear light sampling system were investigated.It was found that high-power,narrow pulse width pulse light sources have a certain degree of improvement in the performance of the linear light sampling system.