Faseroptischer Verstärker

摘要

Pumping light from an optical pumping source (24) is incident on an Er-doped fiber (22) through a multiplexer (26) to pump Er. When signal light is incident on the Er-doped fiber (22) through the multiplexer (26) in this state, the signal light is amplified by stimulated emission of pumped Er. This amplified signal light is attenuated by a high-loss optical fiber (30) and is output externally through a splitter (36) and the like. Meanwhile, part of the amplified signal light is fed back to a driving source (42) of the optical pumping source (24) through the splitter (36) so as to be used to adjust the gain of the optical fiber amplifier. With this operation, the output signal power is kept constant. In this case, since the high-loss optical fiber is connected to the output terminal of the Er-doped fiber, the noise figure of the optical fiber amplifier can be kept small over a wide range of input light intensities.