A Ge-doped sandwiched ring-core photonic crystal fiber supporting orbital angular momentum modes for broadband dispersion compensation

Abstract In order to solve the limitation of data transmission speed and transmission distances of the communication system due to the accumulated dispersion in orbital angular momentum(OAM) transmission system, a Ge-doped sandwich ring-core photonic crystal fiber(SR-PCF) is proposed for OAM modes’ broadband dispersion compensation. SR-PCF is divided by the Ge-doped sandwich ring-core into two regions of the inner and outer claddings with periodic triangular lattice air holes, which is conducive to negative dispersion. By optimizing the cladding air-hole diameter, air-hole spacing, sandwich ring-core’s thickness and mole fraction of GeO 2 , the dispersion compensation properties of SR-PCF are improved. The proposed SR-PCF are numerically analyzed by the finite element method. The results show that SR-PCF has broadband negative dispersion values of −57.87 ∼ −65.60 ps/(nm·km) and negative dispersion slope values of the OAM 1,1∼3,1 modes in the range of 1530 ∼ 1570 nm. The high negative dispersion values of −63.31, −62.14 and −60.11 ps/(nm·km) at 1550 nm can be used to compensate dispersion with 1:15.8, 1:6.9 and 1:3.8 length ratios in OAM modes fiber optic transmission links. In addition, it has the confinement loss as low as 2.18 × 10 −7 dB·km −1 , the effective mold field area as high as 123.92 μm 2 , and the nonlinear coefficient as low as 0.89/W·km. The proposed SR-PCF can be used for low-order of OAM modes’ broadband dispersion compensation in the mode division multiplexing systems and the construction of passive all-optical networks.