This paper studies the influence of random phase and amplitude fabrication
errors on the performance of optical filters based on fiber Bragg gratings
(FBG's), In particular, we analyze two effects of particular importance for
optical communications: the excess crosstalk. induced in apodized gratings
commonly used in wavelength-division-multiplexing (WDM) systems, and the t
ime-delay fluctuations that appear in chirped gratings employed to compensa
te the fiber dispersion. A statistical model is presented to explain these
effects in terms of the coherence length, of the grating fabrication proced
ure.