| 摘要 |
PURPOSE:To reduce an accumulated spontaneous emission light in a transmission line and a receiver input or to flatten a frequency characteristic by providing an optical filter constituted by shifting the center frequency from a signal frequency in accordance with an optical amplifier. CONSTITUTION:By connecting repeaters 1, 2,...N in a multistage, an optical transmission line is constituted. Each repeater 1, 2,...N is constituted of optical amplifiers 11, 21,... and optical filters 12, 22,..., a signal light attenuated in the transmission line is amplified by the optical amplifiers 11, 21,..., and the signal light of a desired band is transmitted through the optical filters 12, 22,.... That is, the signal line emitted from a transmitting station passes through the repeaters 1-N, and an optical fiber between them, and a loss by the optical fiber is compensated by gain of the repeater. In this case, the optical amplifiers 11, 21,... constitute one block and in one block, the same optical filters 12, 22,... are provided, and two kinds of optical filters 12, 22,... in which the band width is the same and the center frequency is shifted to the high frequency side and the low frequency side, respectively of the signal frequency are arranged alternately in each block. |
