Broadband Linearization of Dispersive Delay Line Using a Chirped Fiber Bragg Grating

A design of chirped fiber Bragg gratings (CFBGs) for the compensation of higher order dispersion in dispersive delay lines of microwave photonic (MWP) filters driven by broadband sources is presented. It is shown that the modification of the dispersion slope of a nonlinearly CFBG can compensate for third-order dispersion in relatively broad optical bands, resulting in a linear correspondence between group delay and optical frequency. The concept is demonstrated by use of a custom modification of a commercial, low-ripple CFBG for dispersion compensation in 20 nm of the C-band. This broadband linear dispersive delay line is used to provide shape invariance in both the resonance's amplitude and phase responses of single-passband MWP filters based on double-sideband modulation. The dispersion of the delay line is shown to be tunable in the range -170.0 to -143.3 ps/nm by the addition to the CFBG of different lengths of single-mode fiber, without compromising shape invariance.