Method for optimizing receiving optical signal noise ratio in optical fibre transmission system

The present invention relates to the method of optimizing the S/N ratio of received light in fiber transmission system, especially in wide band long distance or very long distance WDM system. In all or partial nodes, the output powers of various WDM wavelength signals are multiple stage strengthening controlled to make the WDM wavelength signals in the receiving end in the specified power range have extremely great and balanced OSNR. The present invention makes the fiber transmission system, especially the wide band long distance or very long distance WDM system possess optimized balance target via solving the unbalanced OSNR problem, and is favorable to raise the capacity and distance of fiber transmission system.