In this study, a novel tubular hollow-core fiber design with extended cladding structures aiming low transmission losses and dominant single-mode guidance in the infrared region is proposed. The fiber parameters are optimized to achieve low-loss operation at the target wavelength of $2\mathrm{\mu }\mathrm{m}$, at which the emission spectrum of thulium-doped fiber lasers are centered. The confinement loss of the fundamental mode is found to be less than 0.02 dB/km in the near- and mid-infrared region, which makes the proposed design a strong alternative for conventional step-index silica optical fibers. Strong suppression of the higher order modes, and low bending sensitivity are also observed in the proposed design. The proposed fiber shows promising results to achieve low-loss transmission in the infrared spectrum.

在这项研究中，提出了一种具有扩展包层结构的新型管状空心光纤设计，旨在降低传输损耗并在红外区域实现单模主导。优化光纤参数以在目标波长下实现低损耗操作$2\mathrm{\mu }\mathrm{米}$，其中掺铥光纤激光器的发射光谱居中。在近红外和中红外区域发现基模的限制损耗小于 0.02 dB/km，这使得所提出的设计成为传统阶跃折射率石英光纤的有力替代方案。在所提出的设计中还观察到对高阶模式的强烈抑制和低弯曲敏感性。所提出的光纤显示出在红外光谱中实现低损耗传输的有希望的结果。