| 摘要 |
First and second independent optical fiber amplifiers, which preferably include first and second rare-earth doped optical fibers, respectively, are provided in a two-stage series or parallel configuration. An optical divider for dividing and taking out pumping light to a side opposite where the pumping light is combined, is coupled to the first optical fiber. An optical combiner combines the divided pumping light with the second optical fiber from a side opposite to a pumping light source. The amplification efficiency is promoted by using the pumping light which has not been used in the one optical fiber amplifier by inputting it to the other, and vice versa. Preferably, wavelength filters block naturally emitting light to first and second optical combining and dividing instruments. Alternatively, wavelength filters block signal light in inputting the divided pumping light to the optical fiber amplifier on the other side.
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