A dispersion compensator having relatively uniform transmission characteristics over the bandwidth of a communication channel. The compensator is designed to process an optical signal corresponding to the communication channel by decomposing that signal into spectral components, routing different components along different optical paths that impart relative delays between the components, and recombining the delayed components spatially and directionally to generate a processed optical signal with reduced chromatic dispersion. In one embodiment, the compensator is a waveguide circuit that includes four diffraction gratings operating in transmission and optically coupled to a tunable lens array, in which different tunable lenses receive light corresponding to different communication channels. For each channel, a desired group delay value is produced by selecting magnification strength of the corresponding tunable lens.