| 摘要 |
PURPOSE:To keep the amplification factor of a total apparatus and the amplification of optical output signal constant independently of characteristics change and the like of not only a pumping light supply source but also the other optical components, by obtaining optical power ratio by monitoring optical signals before and after amplification, and controlling the optical power of the pumping light, based on the above optical power ratio. CONSTITUTION:From scattered light generating at a connection point (a) of an incidence optical path 1 and an optical branching apparatus 2, optical power proportional to optical signal before amplification is detected; from scattered light generating at a connection point (b) of an optical fiber 3 and an output optical path 7, optical power proportional to optical signal after amplification is detected; driving current for a semiconductor laser 4 is controlled so as to keep the ratio of the above optical power constant. Thereby the amplification factor of a total apparatus can be kept constant not only when the optical power of pumping light from the semiconductor laser 4 changes but also when characteristics of the optical branching apparatus 2 and the optical fiber 3 change. |
