Novel design of broadband dispersion compensating photonic crystal fiber with all solid structure and low index difference

By employing germanium up-doped and fluorine/boron down-doped cylindrical inclusions instead of air-holes in pure silica, a novel kind of broadband dual concentric core dispersion compensating photonic crystal fiber (DCC-DCPCF) with all solid structure and low index difference is proposed. By analyzing the kappa value's influences on the dispersion compensating behavior, it is found that the DCC-DCPCF whose kappa curve intersects twice with that of compensated fiber in the targeted band is most preferable for ultra-broadband dispersion compensation. The bandwidth of the DCC-DCPCF can be readily managed by tuning the position and the interval of the two kappa matched wavelength. Following the design procedure of broadband DCC-DCPCF given in this paper, an all solid DCC-DCPCF aims at compensating the accumulated dispersion of Corning SMF28 fiber in entire S + C band are designed. Negative dispersion ranging from −183 to −281 ps/(nm km) in S + C bands is achieved with the refractive index differences between matrical material and cylindrical inclusions no more than 0.03. Numerical results show that the DCC-DCPCF can compensate 15.43 times its length of Corning SMF28 fiber with small residual dispersion in the range of ±0.15 ps/(nm km). The calculated effective mode area is 16.01 μm2 at 1550 nm, corresponding to a coupling loss of 1.35 dB to the Corning SMF28 fiber, the confinement loss and bending loss with 1 cm bending radius less than 0.058 dB/km and 0.315 dB/km at 1550  nm, respectively.