Spectral broadening in tight confinement geometry of a random fiber laser.

We present a random Raman fiber laser pumped by a continuous-wave 1480 nm source. The backward pumping feedback loop allows a single direction of 1584 nm wave propagation under tighter confinement of dispersion compensating fiber (DCF). This geometry that implies a stronger Kerr-lensing effect supports two types of nonlinear broadening that were achieved in the stable output power generation. The first that agrees well to wave kinetics theory favors 1.76–3.37 nm spectral progress. Against this flow, another type of wider broadening begun at 4.88 nm before reducing gradually to 4.05 nm with the increase in pump power. The former corresponds to a maximum of 6.3 times broadening ratio with respect to the pump linewidth. In contrast without the tighter confinement geometry, fluctuations in the nonlinearity growth from 1.58 to 3.53 nm bandwidth was realized. These ascertain the double roles of DCF as a stabilizing factor as well as for dispersion management. [ABSTRACT FROM AUTHOR]