Patent Number: 7,085,043

Title: Optical amplifier

Abstract: An optical amplifier of the invention comprises first and second optical amplification sections connected in a cascade manner between an input terminal and an output terminal. Optical isolators which block C-band ASE travelling in an opposite direction to L-band signal light, are inserted on the amplification medium of each of the optical amplification sections. A constant gain control section calculates the number of wavelengths based on the input power of signal light, and controls the pumping light power of each optical amplification section at a constant slope with respect to the number of wavelengths, so that the respective gains in the optical amplification sections corresponding to the number of wavelengths each become constant. As a result, it is possible to maintain flat gain wavelength characteristics even when receiving input of WDM light where the number of wavelengths varies rapidly over a wide range.

Inventors: Takeyama; Tomoaki (Kawasaki, JP), Inagaki; Shinya (Kawasaki, JP), Sasaki; Keiko (Kawasaki, JP)

Assignee: Fujitsu Limited

International Classification: H04B 10/12 (20060101)

Expiration Date: 8/01/02018