Impact of nonlinear spectral broadening in ultra-long Raman fibre lasers

We present an experimental study of the impact of FWM-induced nonlinear spectral broadening on the effective reflectivity of ultra-long Raman fiber laser cavities of diverse lengths and fiber bases. We observe an exponential decay of the effective reflectivity with growing power. In standard single-mode fiber, effective reflectivity drops of up to 50% for shorter cavity lengths are observed, while the longest cavity length of 82.4km displays power leakage amounting to an effective reduction of reflectivity of approximately 30%. Using different types of fiber we examine the effect of chromatic dispersion on the Stokes wave broadening. © 2007 Optical Society of America.J. D. Ania-Castañón and S. K. Turitsyn would like to acknowledge the support the Engineering and Physical Sciences Research Council (EPSRC). Paul Harper would like to acknowledge support from The Nuffield Foundation Grant Ref: NAL/32796.Peer Reviewe