| 摘要 |
PROBLEM TO BE SOLVED: To prevent a gain from fluctuating even if the outside temperature is changed by detecting the temperature of a light amplifying medium, and permitting a current supply control means to control current applied to a conductive coating layer based on the detected temperature. SOLUTION: An Er added quartz optical fiber is used as an Er added optical fiber 1 being a light amplifying medium. A coating layer formed of three layers is formed on the outer side of the Er added optical fiber 1. In the three layers of the coating layer, the innermost layer is a carbon coating layer, the intermediate layer is a metallic coating layer and the outermost layer is an insulating coating layer. Lead wires 7a and 7b from a current supply control circuit 7 are connected to the metallic coating layer. A temperature detection means 5 formed of a thermocouple 6a and a voltmeter 6b detects the temperature of the metallic coating layer of the Er addition optical fiber 1. A current supply control means 7 controls applied current and therefore it is kept to be constant. Thus, the prescribed gain can be obtained. |
