| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain stable quality even in the case of deterioration with the lapse of time while utilizing an advantage of a Raman amplifier. <P>SOLUTION: An optical transmission system 10 comprising Raman amplification relay spans 11, 12 to 1N and an EDFA relay span 21, wherein the single EDFA relay section 21 is disposed in a subsequent stage of the N Raman amplification relay sections 11 to 1N. The Raman amplifier 115 operates at an input signal level where a pumping gain becomes constant, while an EDFA 217 operates at an input signal level where an output signal level becomes constant. Even if a signal level of a signal having passed through the N Raman amplification relay sections 11 to 1N deviates significantly from a setting value, the EDFA relay section 21 in the subsequent stage can control the output signal level to return to the setting level. <P>COPYRIGHT: (C)2004,JPO |
