Multiwavelength Coherent Brillouin Random Fiber Laser With Ultrahigh Optical Signal-to-Noise Ratio

A narrow-linewidth multiwavelength Brillouin random fiber laser (MW-BRFL) was experimentally demonstrated and characterized, which was achieved by mutually combining Brillouin amplification with randomly distributed Rayleigh feedback in optical fibers. By cascading process through a sub-fiber loop, up to six orders Stokes emissions simultaneously resonate in a coherent lasing fashion under the acoustic coupling of stimulated Brillouin scattering in the presence of coherent Rayleigh scattered random feedback, which acts as an optical filter with the high reflection coefficient for lowest order longitudinal mode of each Stokes line to ensure single longitudinal mode operation. Consequently, random laser output with an unprecedented ultra-high optical signal-to-noise ratio of ∼47 dB and an optimal peak power discrepancy of 1.8 dB were obtained. Furthermore, each Stokes random lasing emission with narrow linewidth of ∼1 kHz was achieved thanks to coherent random lasing. Relative intensity noise transfer was observed in sequence from the first-to sixth-order Stokes emission. In this MW-BRFL, a wide tunable range over 30 nm of the operating wavelength was validated by shifting the central wavelength of the input pump from 1530 to 1560 nm. Meanwhile, the statistical properties of the MW-BRFL and the performance optimization were also experimentally investigated.