We investigate six different methods presented in litera-ture to estimate eye-opening penalty for dispersion-com-pensating fiber Bragg gratings with aid of the grating’s ripple function. The investigation is based on theoretical ripple functions as well on measurement results of three continuously chirped gratings. The gratings in question offer full wavelength coverage between 1530 nm and 1565 nm. We will show that the eye-opening penalty de-pends on the phase and frequency of the grating’s ripple function as well as to pattern length and to pulse form of the signal used. Since the estimation methods do not ac-count for these properties, their accuracy is shown to be limited.