The invention relates to compensating for the wavelength dependent loss
(WDL) in a variable optical attenuator (VOA) system by using a chromatic
dispersion wedge, which is inserted between the mirror and the lens.
Different wavelength components, e.g. shorter blue and longer red
wavelengths, are redirected at different angles by the chromatic
dispersion wedge and now arrive at the output fiber at different
positions. Thus the smaller mode field diameter (MFD) or mode spot size
of the blue light, overlaps more of the core of the output fiber by being
closer thereto and now has less insertion loss (IL) as compared to a VOA
without WDL compensator.