Single- and dual-band dispersion compensation unit using apodized chirped fiber Bragg grating

In this study, a wideband dispersion compensation (WBDC) profile that effectively covers the entire C- and/or part of the L-band is designed and evaluated. Several apodizations with different apodization strengths applied to a chirp fiber Bragg grating (CFBG), different CFBG lengths (L), and different refractive index modulation amplitudes (\(\Delta n\)) are investigated during the design and evaluation process. The design and optimization processes target parameters including a maximum full width at half maximum (FWHM), minimum group delay ripples (GDR) and an acceptable reflectivity and sidelobe suppression ratio (SLSR). A wavelength shift of no more than 2 nm is observed as a result of investigating the effect of temperature in the WBDC scenario. During single-stage operation, the results shows that a hyper-tanh with L = 15 cm and \(\Delta n\) = 4e−4 is the optimum design choice that provides an FWHM of 36.9378 nm, a GDR of 0.85 ps, a reflectivity of \(-4.46706\) dB and an SLSR of 42.08 dB. Optimization indicates that a tanh apodization with \(L =\) 15 cm and \(\Delta n=\) 4e−4 is the optimum choice for dual-stage operation that achieves an FWHM of 37.2244 nm, a GDR of 0.85 ps, a reflectivity of −5.36151 dB and an SLSR of 43.59 dB. Small variations in the SLSR level (e.g., 0.8 dB) are observed while investigating the effect of temperature on the dual-stage operation even in the worst-case operating scenario.