Designing suitable dispersion decreasing active fibers to generate parabolic pulses in presence of macrobending

Abstract

The present work deals with the performances of straight and bent active normal dispersion decreasing fibers (NDDFs) to create parabolic pulses. Since these optical fibers are generally kept in the form of fiber rolls, they may suffer from unavoidable bend losses. For the NDDFs, the core radius and hence transverse field distribution inevitably change along the fiber length; thereby bend loss is no longer an invariable quantity throughout the NDDF length. The spatial variation of bend loss for a parabolic index NDDF is incorporated for the first time to investigate the effect of bend loss analytically and numerically on parabolic pulse generation. It is illustrated that suitable choice of relative refractive index difference and bend radius of curvature of the fibers would lead to parabolic pulse formation by a bent NDDF. The comparative study on the straight and bent NDDFs will be helpful for the fiber optic manufacturers to design and fabricate NDDFs with proper choice of optimized parameters and index differences so that parabolic pulses can be generated even under the influence of practically unavoidable bending.