Modeling the suppression of stimulated Raman scattering in active and passive fibers by lumped spectral filtering elements

Stimulated Raman scattering in optical fibers can be suppressed by different techniques, which include the use of special fiber designs (that work as distributed spectral filters) or the use of lumped filtering elements. Fiber designs like the w-type profile are limited in maximum fiber core size and provide Raman attenuations of a few dB/m. These characteristics imply that these designs are not suitable for high power fiber amplifiers with short fiber lengths. In these applications lumped filters could provide a better and more flexible solution. Thus, in this work lumped filters will be evaluated as Raman suppression elements in passive fibers as well as in active Yb-doped fibers for amplifier and laser applications. Both the influence of the number of equidistant discrete filters in various setups and the impact of their insertion losses will be theoretically studied.