chirped soliton is a sech temporal profile with chirp.
Any pulse that propagate in nonlinear fiber will experiences chirp. so I expect if you input a sech function in nonlinear fiber the output would be sech with chirp.
ok thanks and i have another question that for soliton condition is that dispersive length is less then non-linear length please explain this condition ? and what happen if dispersive length is greater than non-linear length?
In general in the soliton propagation the dispersion length and the soliton length are comparable to the fiber length. that means both dispersion and nonlinearity are included in the calculations.
if dispersive length is little longer or shorter than nonlinear length is no matter. the main concept is that the dispersion would be ignored or the nonlinearity will be ignored if their effective length is too longer than the length of propagation!!
Hope that clears,