Generation of Pulse Trains with High-Repetition-rate in Anomalous Dispersion Decreasing Fibers

Optical pulse generation and compression have been numerically studied in anomalous dispersion decreasing fibers (DDF). We show that evolution of modulation instability (MI) observed with chirped wave packets in tapered fibers produces the mechanism for generation of ultra-short pulses with high repetition rates. The role of modulation instability and Raman self-scattering has been also discussed. The simulations show that pulse chirping enhances self-Raman scattering at early stages of pulse propagation and improves compression of the generated pulses. It is also shown that the presence of amplitude and frequency modulation of the seed wave provide essential impact on the pulse train formation. The new method for increasing the pulse train repetition rate through frequency modulation of the seed wave has been proposed.