Method for gain equalization, and device and system for use in carrying out the method

Abstract

The present invention relates to a method for gain equalization, for example. First, an optical transmission line including an optical amplifier having a gain changing nonlinearly with wavelength is provided (step (a)). Secondly, gain equalization of the optical transmission line is performed so as to obtain a gain changing substantially linearly with wavelength (step (b)). Finally, gain equalization of the optical transmission line is performed so as to obtain a gain remaining substantially unchanged with wavelength (step (c)). According to this method, gain equalization of the optical transmission line is performed so as to obtain a gain changing substantially linearly with wavelength. Accordingly, variations in equalization error due to changes in system condition can be easily suppressed.

1 . An apparatus comprising: 
 an optical amplifier amplifying a light;    a fixed gain equalizer equalizing the amplified light; and    a variable gain equalizer having a changeable optical transmittance versus wavelength characteristic curve to variably equalize the amplified light and thereby compensate for equalization error remaining after equalization by the fixed gain equalizer, the curve maintaining a fixed optical transmittance at a specific wavelength as the curve changes.    
   
   
       2 - 40 . (canceled)