Research On Multi-Wavelength Brillouin Random Fiber Laser

In recent years,due to the application potential of random fiber laser(RFL)in optical sensing and optical communication systems,it has attracted widespread attention.The research focus of early random fiber lasers is mainly based on ordinary single-mode fiber Raman random lasers.The laser threshold of this random laser is generally in the order of watts.For random lasers based on Brillouin scattering,the gain coefficient is much higher than Raman scattering,and the threshold can be reduced to tens of milliwatts.Therefore,this paper proposes a dual-end pumped random fiber laser model that provides an amplification mechanism through stimulated Brillouin scattering and provides a randomly distributed feedback mechanism for backward Rayleigh scattering in long fibers,and designs a Multi-wavelength Brillouin random fiber laser(MW-BRFL)based on this model.the main research content is divided into the following three parts:1.A model of a dual-end pumped Brillouin random laser is proposed,and the power coupling equation of the laser is established and numerically solved.By changing the pump power,the output power distribution of pump and stokes with different coupling coefficients and fiber lengths and corresponding laser output characteristics such as corresponding threshold values are simulated.According to the simulation results,the pump power at both ends of the fiber is exponentially attenuated under different fiber lengths and coupling coefficients,and the Stokes power increases exponentially.The larger the coupling coefficient,the higher the Stokes power generated at both ends of the fiber,and the greater the effective length of the fiber,the lower the threshold of multiwavelength laser output.2.A MW-BRFL based on the above model is designed.The MW-BRFL adopts a dual-end pump structure,a common single-mode fiber as the gain medium,and a Brillouin gain mechanism in the single-mode fiber and a randomly distributed Rayleigh Scatter feedback is realized by combining with each other.When the fiber length is 10 km,the pump power is 54.07 mW,and the coupling coefficients are 0.1,0.5,and 0.9,respectively,the first,fifth,and third-order Stokes optical outputs are obtained;when the fiber length is 20 km,the pump power is at 54.07 mW,the Stokes light output of order 1,5,and 8 was obtained when the coupling coefficients were 0.1,0.5,and 0.9,respectively,and the 7th order Stokes light output was obtained when the coupling coefficient was 0.9.Regardless of the length of the fiber,a stable 5th-order Stokes light output can be obtained when the coupling coefficient is 0.5,the wavelength interval between each order is about 0.088 nm,the optimal peak power difference is 0.569 dB,and the optical signal-to-noise ratio is greater than 44 dB,and the resulting Stokes has a linewidth as narrow as 986.13 Hz.In addition,the MW-BRFL also has high output power stability,and the maximum peak difference is only 1.72 dB within 1 hour.3.Based on the dual-end pump structure,an enhanced distributed feedback MWBRFL is proposed.The MW-BRFL uses another section of single-mode fiber for distributed feedback,so that the generated Stokes light is enhanced by Rayleigh scattering feedback.In this case,the Stokes optical output power is effectively compensated to achieve higher-order Stokes optical output.