| 摘要 |
PROBLEM TO BE SOLVED: To collectively amplify a plurality of signal beams which are subjected to wavelength multiplexing with a constant gain, simplify a device configuration in comparison with an obtained gain, and improve the noise figure. SOLUTION: Optical fibers 11 and 21 to amplify three-level system are connected in cascade, the optical fiber 11 for amplification at a previous stage is set so that the optical fiber 21 for amplification at a later stage operates while gain is saturated by applying light which is naturally discharged from the optical fiber 11 for amplification at the previous stage, and the saturated gain state of the optical fiber 21 for amplification at the later stage is controlled, thus constantly maintaining an entire gain. |
