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

Abstract

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.