Gain dispersion induced subpicosecond pulse breakup in a fiber and semiconductor laser amplifier combined system

We observe pulse breakup for 650‐fs pulses propagating through 9 m of optical fiber followed by an InGaAsP amplifier. The pulses are broadened by a factor of two, and a second peak appears at about 2 ps after the main peak. To identify the responsible mechanisms, we solve numerically the propagation equations including nonlinear carrier dynamics and gain dispersion. We attribute the broadening to two photon absorption and the breakup to the interplay between linear gain dispersion and frequency chirp in the amplifier. These pulse distortions could impact devices involving fibers and semiconductor amplifiers for high speed (>200 Gb/s) optical switching or transmission.