Broadband orbital angular momentum transmission using a hollow-core photonic bandgap fiber

We present the viability of exploiting a current hollow-core photonic bandgap fiber (HC-PBGF) to support orbital angular momentum (OAM) states. The photonic bandgap intrinsically provides a large refractive index spacing for guiding light, leading to OAM transmission with low crosstalk. From numerical simulations, a broad OAM_±1 mode transmission window with satisfied effective index separations between vector modes (>10^-4) and low confinement loss (<3 dB/km) covering 240 nm bandwidth is observed. The OAM purity (defined as normalized power weight for OAM mode) is found to be affected by the modal effective area. Simulation results also show HC-PBGF based OAM transmission is immune to fabrication inaccuracies near the hollow core. This work illustrates that HC-PBGF is a competitive candidate for high-capacity communication harnessing OAM multiplexing.