DEVICE AND METHOD FOR REDUCING SELF-PHASE MODULATION/ GROUP VELOCITY DIFFUSION IN OPTICAL SYSTEM

摘要

PROBLEM TO BE SOLVED: To reduce the non-linear distortion of an optical transmission system by rounding the edge part of an optical pulse to be received from the transmitter of the system so that a pulse to be used for modulation can be similar to a Gaussian pulse. SOLUTION: In order to promote the reduction of SPM/GVD distortion from an optical communication link, a transponder 43 is provided with an electric attenuator 44 placed between a photodiode 36 and an amplifier 38. This electric attenuator 44 smoothes the signal pulse of a sharp edge part by attenuating the said signal received by the amplifier 38. Especially, in order not to operate the amplifier 38 in deep saturated state, a predetermined attenuation level is applied to the electric signal received from the photodiode 36. When the electric attenuator 44 is placed in front of the amplifier 38, the electric signal to be inputted to the amplifier 38 is attenuated into power level lower than a power level for operating the amplifier 38 in the deep saturated state.