Tunable and Switchable Multi-Wavelength Erbium-Brillouin Random Fiber Laser Incorporating a Highly Nonlinear Fiber

A tunable and switchable multi-wavelength Erbium–Brillouin random fiber laser (MW-EBRFL) with a half-open cavity structure and incorporating a segment of highly nonlinear fiber (HNLF) is proposed and experimentally demonstrated. Due to HNLF being with high nonlinear coefficient, high Brillouin gain coefficient and high Rayleigh scattering (RS) coefficient, a reduced length of HNLF can provide a strong random distributed feedback (RDFB) and high stimulated Brillouin scattering (SBS) gain. In addition, an optical fiber amplify loop (OFAL) including a high-power erbium-doped fiber amplifier (HP-EDFA) and an optical attenuator (ATT) is constructed to provide a strong Brillouin pump (BP) and controllable optical feedback. 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 (OSNR) of 41.22 dB are obtained. System parameters including BP power and HP-EDFA pump power influence on output of MW-EBRFL are also investigated. 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 (PMF-LMF) is cascaded with output port of the cavity, it can be very convenient to achieve wavelength switching between single- and double-Brillouin frequency spacing (BFS), only by tuning polarization controller in PMF-LMF.