Ultra‐Low Loss Weakly Coupled Few‐Mode Hollow‐Core Anti‐Resonant Fiber Enabling Eight Channels via Differential Wall Thickness and Truncated Tubes

We propose and analyze a novel, ultra‐low loss, weakly coupled few‐mode hollow‐core anti‐resonant fiber that supports eight spatial modes as independent channels. The design features an optimized, simplified cladding structure with differentiated tube thicknesses. This configuration effectively suppresses coupling between the guided core modes and cladding modes, significantly reducing confinement loss (CL), and mitigating loss fluctuations caused by nesting nodes, while also minimizing surface scattering loss (SSL). Simulation results demonstrate that within the wavelength range of 1460–1680 nm, the effective refractive index difference between adjacent core modes consistently exceeds 1.0 × 10 −4 , ensuring weak mode coupling. The intrinsic loss (CL + SSL) for all eight modes remains below 1.27 × 10 −4 dB/m across this band, reaching a minimum loss of less than 9.92 × 10 −5 dB/m at 1550 nm. The loss ratio between higher‐order modes and the fundamental mode is maintained below 15.38 in the operating band. Furthermore, with a bending radius of just 5 cm, the loss of all eight modes does not exceed 1.35 × 10 −4 dB/m. This work employs a simplified fiber structure that may be easier to manufacture and represents a significant step forward toward practical, low‐loss, high‐capacity, low‐latency mode‐division multiplexing systems.