| 摘要 |
PROBLEM TO BE SOLVED: To improve an amplification characteristic by effectively utilizing excitation light from an optical amplifier. SOLUTION: Excitation lightλp projected from an excitation light source 13 is made incident upon an erbium dope optical fiber(EDF) 14 through an wavelength multiplexer (WDM) coupler 12 and absorbed to generate sufficient inversion distribution. When signal lightλs is made incident upon the EDF 14 in the incident state of the excitation lightλp, The lightλs is gradually amplified by induction emission action and the amplified signal light is discharged as an output optical signalλS. When the EDF 14 is sufficiently short against the intensity of the excitation lightλp, the excitation lightλp may be discharged to the output end of the EDF 14 as remaining excitation light (r). The light (r) is made incident upon a total reflection film 19 successively through a WDM coupler 15 and a fiber 18 and reflected by the film 19 and the reflected light is returned into the EDF 14 successively through the fiber 18 and the coupler 15, so that the amplification characteristic of the EDF 14 is improved.
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