| 摘要 |
PROBLEM TO BE SOLVED: To effectively reduce light surges with a simple and also economical configuration by serially connecting an optical fiber, which is doped with rare earth elements that do not have an amplifying characteristic in an optical signal wavelength band, to a light amplifier. SOLUTION: A light surge reduction optical fiber 3 is serially connected to an input side of a normal erbium-doped optical fiber amplifier 1 that amplifies an optical signal of a signal wavelength area of 1.5 micron band. The fiber 3 has an absorption characteristic in 1,520 to 1,570 nm signal wavelength region and is constituted of an optical fiber which is doped with rare earth elements that do not have an amplification characteristic. As the absorption characteristic, absorption quantity becomes small when input power is large. Also, when the input power is small or when the input power is disconnected due to light switch disconnection, the absorption quantity becomes large, and also when the input power is changed from being. small to large and from large to small, the absorption quantity cannot be changed abruptly but changes gradually. |
