We report an ultra-long Raman laser that implemented a variable pumping scheme in backward and forward configurations. Rayleigh backscattering effects were realized in the 51 km fiber length that functioned as a virtual mirror at one fiber end. With the employment of a fiber Bragg grating that has a peak reflection wavelength at 1553.3 nm, spectral broadening effects were observed. These occurred as the pump power level was diverted more to the forward direction. Owing to this fact, a maximum width of 0.9 nm was measured at 100% forward pumping. The obtained results show that the efficient exploitation of four-wave mixing interactions as well as strong Rayleigh backscattering are beneficial to influence the lasing performances. Both of these nonlinear responses can be adjusted by varying pumping distributions along the fiber longitudinal dimension.
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"Since, then, RDF-FLs have been widely studied, due to its simple structure without any " mirrors " and unique output characteristics. These studies related to RDF-FLs include basic emission characteristics – , noise and gain optimization , , high-order and tunable emission –, broadband, multi-wavelength, and narrow linewidth outputs –. It is believed that RDF-FL is a good candidate of fiber-optic communication and sensing source, due to its stable output with little thermal sensitivity, wide wavelength tenability, excellent noise and modulation characteristics, spatial incoherence while with a high photonic density of states –. "
[Show abstract][Hide abstract] ABSTRACT: Random distributed feedback fiber laser (RDF-FL) based on combination of Er-doped fiber (EDF) and single-mode fiber (SMF) is proposed in this paper. Through pumping of both the EDF (i.e., 1480 nm pump) and the SMF (i.e., 1455 nm pump), random lasing is obtained. With increase of pump powers, different transitions between chaotic and stable status of the output spectrum are observed. Especially, single-peak random lasing can be obtained under the stable operation regime.
Full-text · Article · Jan 2015 · IEEE Journal of Selected Topics in Quantum Electronics
"Compared with other random lasers, the RFL has the outstanding features of high power output, stable output, long-distance emission and wide wavelength tenability, which would be of significant impact on optical sensing and communication. A great deal of valuable research work has been carried out regarding the design and analysis of RFLs      . Dual-wavelength ultra-long fiber laser was realized through random distributed feedback and two different FBGs . "
[Show abstract][Hide abstract] ABSTRACT: In this paper, we report realization of a spectrum-adjustable random fiber laser (RFL) though central pumping in a single mode fiber (SMF), wherein a fiber Bragg grating (FBG) is mounted in the middle to control the laser output. By adjusting the feedback of the FBG bi-directionally, random lasing with adjustable spectra is realized. A unique hybrid dual-peak lasing spectrum with one peak regulated by the FBG and the other peak determined by distributed Rayleigh scattering (RS) feedback is achieved. It is also revealed that the FBG defining lasing peak is sensitive to temperature variation while the other peak is insensitive to temperature variation.
[Show abstract][Hide abstract] ABSTRACT: The work presented in this paper details the changes in continuous-wave laser characteristics that were affected by the orientation of pumping separation. The Raman laser was constructed in forward and backward pumping schemes with respect to the 1553.3-nm fiber Bragg grating location. The laser cavity was formed by the induction of Rayleigh backscattering effects in the 51-km fiber length that served as a virtual mirror. From the results obtained, it can be concluded that low threshold operation around 788 mW was satisfied at a coupling ratio of 0 (forward pumping scheme). Moreover, the best output power attainment of 220 mW was realized when 60% of pump powers were delivered via a backward pumping scheme. Thus, the success of this research provides a basis to further understand the principle of backscattered wave interactions along the fiber longitudinal structure.