Optical amplifier

摘要

The present invention provide an optical amplifier that excites a rare earth element dopant in a light transmitting medium with exciting light generated from a semiconductor laser such that the light propagating through the light transmitting medium is amplified, wherein drive power being supplied to drive the semiconductor laser is modulated with an AC component having a higher frequency than the frequency corresponding to the lifetime of the excited state of the ion of the rare earth element, and the drive current from the drive power has an amplitude which is higher than the threshold value of the semiconductor laser.