laser com. a prob w/diode creating a ringing in signal

I am using a 200mW laser at gigabit speeds and have seen a ringing that distorts my transmited signal. has anyone else seen this or have a way to prevent it? It keeps me from increasing my tx power over 30mW.

did you consider the nonlinear effects in the fiber?

Do you actually expect people to offer an answer from that sparse bit of info? What type of laser, what type of modulator and are you stabilizing it somehow, what are you doing to control polarization, what type of detector, what type of fiber/length, are you using optical isolators,.........ad nauseum