Effect of the initial chirp on picosecond pulse breakup in the presence of noise is analyzed through numerically solving
the modified nonlinear Schrödinger equation, using the standard split-step Fourier method. It is found that, for shorter
pulses, the pulse breakup is caused by pulse collapse resulted from high-order soliton compression, even in the presence
of noise. For longer pulse, pulse breakup is triggered by nonlinear amplification of noise caused by modulation
instability. The effect of initial chirp on pulse breakup is closely related to the mechanism of pulse breakup, and the
process of short pulse breakup depends strongly on the strength of negative initial chirp.