Development of photonic crystal fiber supporting 124 OAM modes with flat dispersion and low confinement loss

A ring core photonic crystal fiber (RC-PCF) is proposed and studied. The RC-PCF supports 124 orbital angular momentum modes at 1.55 μm. The RC-PCF is optimised in the range of 1.3–1.6 μm. The proposed PCF is composed of a high index ring of lithium niobate (LiNbO 3 ) in the background layer of silica. The circular air holes are distributed among the four rings in the cladding region. The central core region is composed of elliptical air holes arranged in an optimised configuration. The RC-PCF features flat dispersion (~ 0.5 ps/nm/km) in the tested wavelength range and low confinement loss (< 10 −5 dB/km). The large effective index difference helps to lower the crosstalk among optical modes. The fiber bend tolerance is also analysed to check its sustainability. The fiber is bend insensitive (∆n eff > 10 −4 ) to high bend radius (B R ~ 2 cm). The proposed PCF is a potential candidate for multimode applications.