Modulation instability of femtosecond pulses in dispersion-decreasing fibers

Modulation instability (MI) to generate femtosecond pulse in dispersion-dec reasing fibers (DDF) is investigated. Higher-order dispersion effect and hi gher-order nonlinear effects are taken into account when continuous wave or quasi-continuous wave evolves into sub-picosecond or femtosecond pulses by MI in optical fibers. Our research results show that the gain spectrum of the DDF is much wider than that in conventional fibers. The third-order dis persion effect has no contribution to gain spectrum, self-steepening effect reduces the maximum value and gain bandwidth of gain spectrum, and Raman s elf-scattering effect widens the extent where MI occurs. (C) 2001 Published by Elsevier Science B.V.