An optical packet switching system includes an optical packet transmitter, an optical packet switching apparatus, an optical amplifier, an optical packet receiver, an information gathering unit, and a peak power calculation unit. The information gathering unit collects the packet density, time-averaged power and extinction ratio from the optical packet transmitter, collects the packet density, time-averaged power and noise figure from the optical amplifier, collects the packet density, time-averaged power, switch on/off time ratio and extinction ratio from the optical packet switching apparatus, and collects the packet density and time-averaged power from the optical packet receiver. The peak power calculation unit calculates the peak power of an optical packet signal outputted from each apparatus/device based on the collected information. The device control unit control each apparatus/device based on the calculated peak power such that the optical packet signal having a peak power according to a predetermined optical level diagram is outputted.