A method comprises receiving an output signal of one of multiple detection channels. The method further includes color separating the output signal and generating a color-separated signal substantially only with the peaks corresponding to the detected signals with the principle emission in the emission spectrum range of the detection channel. The method further includes estimating a time-variant amplitude of the gradually decaying tail and removing the time-variant amplitude from the color-separated signal. The method further includes generating a corrected colored-separated signal with substantially only the peaks corresponding to the fluorescent dyes attached to the fragments in the sample.