Research On Tunable Multi-wavelength And Single-longitudinal-mode Fiber Laser Based On SBS

With the improvements in the optical communication networks and fiber materialproduction process, the development of fiber laser technology is advancing rapidly. Theapplication fields of fiber laser have penetrated into various fields, such as laser marking,laser welding, laser cutting, and laser medical. Although most types of fiber lasers are still inthe laboratory research stage, but we believe that as the technology matures, the benefits theytake to us will be unimaginable.Based on stimulated Brillouin scattering effect, this paper designed and explored thetunable multiwavelength fiber laser and single-longitudinal-mode Brillouin fiber laser. At first,the implementation mechanisms of two kinds of fiber lasers are theoretical analysed. And then,with the aim to simplify structure, reduce costs and achieve stable output at room temperature,the experimental studies and analysis of them were conducted. The followings are the detaildescriptions of the work:1. A brief background of the processes of fiber lasers was introduced, and then thedevelopments and applications in various fields of multi-wavelength Brillouin fiber lasers andsingle-longitudinal-mode Brillouin fiber lasers were described.2. Stimulated Brillouin scattering (SBS) in the fibers was described in detail, includingits physical mechanism, gain spectrum and threshold. Then the mode competition phenomenain multi-wavelength erbium-doped fiber lasers and the basic principles of SBS in stabilizingthe output at a room temperature were discussed. Several techniques to achieve singlelongitudinal mode were introduced. The mode linewidth narrowing effect and the effect ofnoise suppression technology in brillouin fiber lasers were analysed. At last, a briefintroduction of laser linewidth measurement technique was given.3. A wideband tunable double Brillouin frequency shifts multi-wavelength fiber laserswas proposed. In the structure, a piece of200m long HNLF was used as a Brillouin gainmedium. Two three-port circulators were incorporated in the laser configuration to circulatethe odd-order Brillouin Stokes in the cavity and couple out the initial Brillouin pump andeven-order Stokes, which provided the multi-wavelength output with double Brillouinfrequency spacing. An advantage of this scheme was that it did not use any active gainmedium in the cavity for amplification of pumping signals, which realized a tuning range of69nm between1536nm and1605nm by eliminating the affection of the self-lasing cavitymodes.4. An Ultra-widely tunable double-Brillouin-frequency spaced multiwavelength fiberlaser with110nm tuning range was realized. By introducing a tunable bandpass filter (TBF),the gain property of the ring cavity can be manipulated. By eliminating the effect of theself-lasing cavity modes to the tuning range of the cavity laser, the laser can obtain a range of110nm. 5. A single-longitudinal-mode Brillouin fiber laser based on F-P fiber ring and saturableabsorber was proposed. The F-P fiber ring, consisted by two couplers and a piece of SMF,combined with a saturable absorber to ensure a stable single longitudinal mode oscillationoutput. The linewidth of the Brillouin laser was0.58KHz. Besides, the Brillouin fiber laserhad a good noise suppression effect; the SNR of the output BFL was70dB, increased bynearly20dB compared with the Brillouin pump signal. And also, the laser had a good stability,during the observation of one hour; the maximum power fluctuation was0.6mW.