a method and device is disclosed for dispersion compensation of an optical signal having periodic dispersion within a multi - channels system . for example interleaved optical channels often exhibit dispersion having a characteristic that is repeated in adjacent channels . by providing a periodic device that allows for polarization dependent routing of an interleaved signal to allow for multiple passes of said signal through a multi - cavity gt etalon , having a free - spectral range that corresponds to the channel spacing , the dispersion in the interleaved signal can be lessened and practically obviated or balanced to a desired level . this invention provides a device and method to achieve that end .