Single Frequency Brillouin Fiber Laser And Its Application In Microwave Photonics

Single-frequency Brillouin fiber lasers(SBFL)have been attracting extensive interests because of their compactness,narrow linewidth,low noise and stableness.They have important potential applications in many fields,such as fiber sensing systems,high-resolution spectroscopy and microwave photonics,and so on.Although great improvement of their single-frequency ability has been achieved nowadays,the tunability of the laser is needs further studied for exploring more applications.The main work of this thesis is to develop a tunable single-frequency Brillouin fiber laser.The influence of the fiber length on the threshold power of the laser is analyzed theoretically and experimentally,and the output laser power,wavelength stability and the line width of the laser are measured by experiments.Based on the laser,we have studied its application in the field of high quality microwave photonics generation.The main research content of this article as follows:(1)Based on the fiber-optic stimulated Brillouin scattering effect,a ring cavity Brillouin single-frequency fiber laser is designed.the laser uses single-mode fiber as gain fiber,and the influence of cavity length on the laser threshold and linewidth is experimentally studied.The experimental results show that the threshold value of the laser decreases with the increase of the ring cavity length.when the gain fiber length of the ring cavity is 100 m,70 m,50 m,20 m and 0 m,the linewidth of the laser is 496.5 Hz,457.2 Hz,567.8 Hz,523.1 Hz and 639.8 Hz.The experiment also measured the stability of the laser.The results showed that the stability of the laser was good,and the wavelength range of change is between ± 0.01 nm,the laser output was within the range of ±0.5dB power fluctuation.(2)By using the single-frequency Brillouin fiber laser and the output laser of the tunable narrow linewidth laser,the effect of the gain fiber length on the line width of the laser is analyzed experimentally.When the length of the gain fiber is 100m,70m,50m,20m and 0m,the line width of the microwave signals is 63.18MHz,64.47MHz,53.59MHz,98.86MHz and 64.15MHz respectively.The microwave signal can be tuned by temperature control of the gain fiber in the cavity.The experimental results show that the frequency range of the generated microwave signals is from 10.7GHz to 11GHz,and the tuning accuracy is determined by the temperature coefficient of fiber Brillouin frequency shift(1.08MHz/?),about 1.0MHz/?.The experiment also shows that the microwave signals generated are stable at-20?and 30?.