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A double cladding nested antiresonant hollow core fiber is reported in this article. We demonstrated that the addition of nested elements in the second cladding ring and the proper optimization of structural parameters lead to the loss reduction by more than five orders. The numerical simulation exhibits a loss of less than ∼ 0.1 dB/km over the O, E, S, C, L telecom bands, with the minimum loss of 0.001 dB/km at 1.40 µm wavelength with a fiber core diameter of 33 µm. The fiber also shows a better performance in terms of bending loss as well as single modeness, and may have effective applications in a telecommunication system.

We explain the effects of cladding geometries on conjoined tube hollow-core negative curvature fibers and offer a modified conjoined tube negative curvature fiber with appropriate positioning of an additional negative curvature D-shaped layer joining the flat bar to reveal attractive performances over existing recent related fibers. The proposed fiber ensures the least loss of 0.003 dB/km at 1.43 µm, a ∼ 0.04 d B / k m loss covering the wide bandwidth of approximately 300 nm, the lowest surface scattering loss of ∼ 0.02 d B / k m , and the lowest microbending loss of ∼ 0.04 d B / k m , thus providing a propagation loss of 0.10 dB/km at the 1.55 µm wavelength and also offering excellent bend loss performance ( ∼ 0.015 d B / k m loss at a 7 cm bend radius). The fiber, with a core diameter of 30.50 µm, also shows a higher-order mode extinction ratio of ∼ 1600 and maintains greater than 100 over most of the telecom bands; hence, it effectively provides single-mode operation. We show the potential of conjoined tube hollow-core negative curvature fibers in optical communications systems.

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In this paper, a highly birefringent polarization maintaining low losses and a single mode antiresonant hollow core fiber is proposed and analyzed, that is able to exhibit better performances compared to the recent related structures. The usage of bi-thickness cladding tubes with additional high refractive index layers on our geometrically optimized structure improves birefringence nearly by one order: the highest birefringence is 4.7 × 10−4 at 1.51 µm and sustains > 1 × 10−4 for a wide bandwidth of 100 nm with a larger core diameter of 26 µm. Elliptical nesting on our proposed structure lowers the confinement loss to 0.007 dB/m at 1.51 µm and maintains a loss of < 1 dB/m for a wide range of 210 nm. A polarization extinction ratio of 300 and higher order mode extinction ratio of 63, for our fiber, ensure a single polarization and single mode operation at 1.51 µm. Moreover, the proposed fiber exhibits a bend robust performance with a very low bend loss of 0.009 dB/m at a small bend radius of 6 cm and sustains a bend loss of < 0.01 dB/m from a bend radius of 4 cm and above. Hence, our presented fiber, containing the above excellent characteristics, may be fruitful for designing polarization-controlled devices (fiber optic sensors, fiber optic amplifiers, fiber optic gyroscope, etc.) in the field of optical communication.