Multimode Nested Antiresonant Hollow Core Fiber

A novel centro-symmetric nested antiresonant fiber (CNAF) design is proposed and investigated numerically for low-loss, multimode applications. Conventional single tube-lattice and nested antiresonant hollow core fibers (ARHCFs) inherently support multiple core modes, but the higher order modes are more prone to coupling to lossy cladding modes, thereby dissipating power along the length of the fiber. In the proposed CNAF design, coupling of higher order modes to leaky cladding modes is inhibited by bifurcating the airy region of the cladding capillaries with centrosymmetric nested tubes. The designed fiber is shown to support 5 to 9 spatially distinct core mode groups, having confinement loss less than 0.002 dB/m to 0.01 dB/m respectively. We present detailed numerical investigation into the multimode operation of the proposed fiber and its superiority over conventional asymmetric nested tube designs.