We report fabrication of a Nested Antiresonant Nodeless hollow-core Fibre (NANF) with a minimum loss of 1.3dB/km at 1450nm and a 65nm bandwidth below 1.5dB/km. The 0.5-km long fibre is effectively single moded and is shown capable of data transmission.

Using hollow-core NANFs with 5-nested-tubes, we achieve the lowest loss ever reported in a hollow core fiber at 1300 and 1625nm (0.22dB/km), and in any type of optical fiber at 850nm (0.6dB/km) and 1060nm (0.3dB/km).

Abstract:We systematically study different approaches to introduce high birefringence and high polarization extinction ratio in hollow core antiresonant fibers. Having shown the ineffectiveness of elliptical cores to induce large birefringence in hollow core fibers, we focus on designing and optimizing polarization maintaining Hollow Core Nested Antiresonant Nodeless Fibers (HC-NANF). In a first approach, we create and exploit anti-crossings with glass modes at different wavelengths for the two polarizations. We show that suitable low loss high birefringence regions can be obtained by appropriately modifying the thickness of tubes along one direction while leaving the tubes in the orthogonal direction unchanged and in antiresonance. Using this concept, we propose a new birefringent NANF design providing low loss (~40dB/km) and high birefringence (>10 −4 ) over a record bandwidth of ~550nm, and discuss how bandwidth can be traded off to further reduce the loss to a few dB/km. Finally, we propose a polarization mode-stripping technique in the birefringent NANF. As a demonstration, we propose a polarizing birefringent NANF design that can achieve orthogonal polarization loss ratios as large as 30dB over the C-band while eliminating any undesirable polarization coupling effect thereby resulting in a single polarization output in a hollow core fiber regardless of the input polarization state.

We report the first double-nested antiresonant hollow core fiber. The fiber matches the loss of commercial solid core fibers in the C-band (0.174 dB/km) and fundamentally improves it (0.22 dB/km) in the O-band.

Hollow-core-photonic-bandgap fiber, fabricated from high-purity synthetic silica, with a wide operating bandwidth between 3.1 and 3.7 μm, is reported. A minimum attenuation of 0.13 dB/m is achieved through a 19-cell core design with a thin core wall surround. The loss is reduced further to 0.05 dB/m following a purging process to remove hydrogen chloride gas from the fiber-representing more than an order of magnitude loss reduction as compared to previously reported bandgap-guiding fibers operating in the mid-infrared. The fiber also offers a low bend sensitivity of <0.25 dB per 5 cm diameter turn over a 300 nm bandwidth. Simulations are in good agreement with the achieved losses and indicate that a further loss reduction of more than a factor of 2 should be possible by enlarging the core using a 37-cell design.