Hi DEMAS,According to your first question ,you have to work on gain flatness.For this you can see optisystem samples.Otherwise you can work on many parameters for gain flattening e.g pump power,pumping techniques (co,counter and bi directional),core radius ,length of raman amplifier etc.
According to your 2nd question you can use various advanced modulation formats like CSRZ DRZ MDRZ .here i have given a link for these formats .check this link
Advanced Modulation Formats
Moreover these formats are good to mitigate the effect of dispersion and bandwidth efficient.
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