Patent ID: 8259390

Claim:
An optical amplifier apparatus comprising: an optical amplifier including an amplification medium to amplify an optical signal and to output a first optical signal, the amplification medium being doped with an active substance for exciting itself; a semiconductor optical amplifier, arranged after the optical amplifier, to amplify the first optical signal and to output a second optical signal; a photo diode to receive the second optical signal; a driver including a memory medium to store data for a correspondence relationship between an absolute maximum rating of a light-receiving level according to a type of the photo diode and a drive current value, such that a maximum level of the second optical signal is within the absolute maximum rating, the driver being configured to supply a drive current to drive the semiconductor optical amplifier in order that the semiconductor optical amplifier has an amplification characteristic with respect to an input optical signal, the amplification characteristic including a gain non-saturated region and a gain saturated region, an amount of the drive current corresponding to being within the absolute maximum rating of the light-receiving level for the type of the photo diode based on the data stored in the memory medium; and an input-light level adjuster to adjust the first optical signal to an input optical signal light level of the semiconductor optical amplifier, the input optical signal light level being set up in the gain non-saturated region close to a boundary between the gain non-saturated region and the gain saturated region, so that when an optical surge is added into the input optical signal, an output optical signal level of the semiconductor optical amplifier has a designated region in which an optical signal to which the surge is added, is output.