Hi Vikas,
I would suggest you to go for hybrid amplifier (raman and EDFA) for long haul DWDM system.
As soliton is a new topic, as The existence of an optical soliton in
fibers is made by deriving the evolution equation for the complex
light wave envelope (or the slowly varying Fourier
amplitude) by retaining the lowest order of the group dispersion
(variation of the group velocity as a function of the light
wave frequency) and the nonlinearity, which for a glass fiber
is cubic and originates from the Kerr effect.
i also have very less interest in soliton transmission.