| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical amplifier which suppresses the fluctuation of a distortion characteristic with lapse of time and which substantially prevents the occurrence of a large distortion. SOLUTION: This optical amplifier has a signal light source 8, an optical fiber 6 added with an active material for amplifying signal light, an exciting light source 10 for making the exciting light for exciting this active material incident on this optical fiber 6, an optical coupler 2 which is optically connected to the respective output ends of the signal light source 8 and the exciting light source 10, outputs the light coupling the signal light and the exciting light and makes this light incident on the optical fiber 6 and an optical isolator 4 which is installed on the optical path between the optical fiber 6 and the signal light source by making the progressing direction of the light heading the optical fiber 6 from the signal light source 8 as a forward direction. Quarter- wave plates 14, 12 are respectively installed at the respective output ends of the signal light source 8 and the optical isolator 4 so that the incident signal light on the optical fiber 6, the optical coupler 2 and the optical isolator 4 is made into a circularly polarized wave. |
