Patent ID: 7209661

Claim:
A wavelength multiplexing method wherein a plurality of optical signals, each being assigned a unique wavelength, are input to and output from a plurality of variable optical attenuators, respectively, wavelength-multiplexed by a multiplexer, and output from said multiplexer; said wavelength-multiplexed output is spectrum-analyzed by an optical monitor unit, and a spectrum-analyzed level of each of said optical signals is measured; and an input level of each of said optical signals input from said respective variable optical attenuator to said multiplexer is adjusted by said respective variable optical attenuator such that the spectrum-analyzed levels of all said optical signals become the same, the method comprising the steps of: detecting said input level of each of said optical signals from said respective variable optical attenuator to said multiplexer, and controlling an attenuation amount of each of said variable optical attenuators based on a difference between said input level of said respective optical signal from said variable optical attenuator to said multiplexer and said spectrum-analyzed level measured by said optical monitor unit.