| 摘要 |
PURPOSE:To allow automatic power control by optical signals at levels in a wider range without deteriorating noise characteristics. CONSTITUTION:Front excitation beams generated by a front excitation beam source 2 are applied from one edge of an amplifying optical fiber 1, and rear excitation beams generated by a rear excitation beam source 5 are applied from the other edge of the amplifying optical fiber 1. A front excitation drive circuit 14 increases and reduces the emission strength of the front excitation beam source 2 so as to allow the power at a level which corresponds to a first reference level generated by a level setting part 13 within the prescribed maximum strength. The rear excitation drive circuit 15 controls the emission strength of the rear excitation beam source 5 so as to allow the power at a level which corresponds to a second reference level. The second reference level is generated by the reference level setting part 13 and is lower than the first reference level. |
