Study On Tunable And Switchable Multi-wavelength Erbium–Brillouin Random Fiber Laser

Random fiber laser is a new type of fiber laser device developed in recent years.Random fiber laser has the characteristics of simple structure,low spatial coherence,stable output,etc.,which is considered as a new type of light source.The research of multi-wavelength random fiber laser not only enriches the research of nonlinear effect,but also has important application value in the fields of wavelength division multiplexing,fiber sensing and microwave.Tunable and switchable multi-wavelength Erbium–Brillouin random fiber laser is mainly studied in this paper,including the following aspects :(1)This paper introduces the research background of random fiber laser,and briefly expounds its research status,development trend and application prospect at home and abroad.(2)The Rayleigh scattering effect and nonlinear effect in fiber are analyzed,and the working principle,structure classification and gain mode of random fiber laser are introduced.Finally,the implementation scheme of multi-wavelength random fiber laser is briefly analyzed.(3)A tunable and switchable multi-wavelength Erbium–Brillouin random fiber laser with a half-open cavity structure and incorporating a segment of highly nonlinear fiber is proposed and experimentally demonstrated.Due to HNLF being with high nonlinear coefficient,high Brillouin gain coefficient and high Rayleigh scattering coefficient,a reduced length of HNLF can provide a strong random distributed feedback and high stimulated Brillouin scattering gain.Using the presented MW-EBRFL,up to 11 orders of stable Stokes laser lines with a wavelength spacing of 0.074 nm and the minimum optical signal-to-noise ratio of 41.22 d B are obtained.By adjusting BP wavelength,multi-wavelength output with 6–11 channel numbers can be tuned in a wide wavelength range spanning 36 nm.The proposed MW-EBRFL also can realize switchable multi-wavelength generation of 1?11 order Stokes with an increasing wavelength number in turn,only by simply adjusting HP-EDFA pump power.Furthermore,when a polarization-maintaining fiber loop mirror filter is cascaded with output port of the cavity,it can be very convenient to achieve wavelength switching between single-and double-Brillouin frequency spacing,only by tuning polarization controller in PMF-LMF.(4)On this basis,the above schemes are further optimized and adjusted,a wavelength-interval switchable wide-band multi-wavelength Brillouin-erbium fiber laser is proposed and experimentally demonstrated.Using the presented scheme,up to 118 stable Stokes laser lines with a power deviation of less than 15 d B,70 stable Stokes laser lines with a power deviation of less than 5 d B and a fix wavelength spacing of 0.075 nm are obtained.Furthermore,when a polarization-maintaining fiber loop mirror is cascaded with the free end of the HNLF via an optical isolator,wavelength-interval switchable laser can be conveniently achieved.