Low Loss and High Polarization-Maintaining Single-Mode Hollow-Core Anti-Resonant Fibers with the S+C+L+U Communication Bands

In this paper, a low loss and high polarization-maintaining single-mode hollow-core anti-resonant fiber (PM-HC-ARF) is designed. The elliptical core in the PM-HC-ARF is formed by strategically enlarging selected cladding air holes along the y-axis. Additionally, the variations in the wall thickness in both the x and y directions generate the distinct surface modes. We have effectively enhanced the birefringence performance of the fiber structure design by introducing the combined effect of the two. Theoretical analysis results show that the proposed PM-HC-ARF achieves a transmission loss of 0.82 dB/km at wavelength 1450 nm, along with a birefringence of 1.38 × 10-4, it demonstrates CL levels an order of magnitude below state-of-the-art polarization-maintaining HC-ARFs. Moreover, within the S+C+L+U communication bands, it achieves a bandwidth exceeding 380 nm(1420-1800nm) while maintaining a birefringence of greater than1.45 × 10-4. Especially, this PM-HC-ARF demonstrates a maximum higher-order mode extinction ratio of over 32,070, the single-mode transmission characteristics are excellent. along with exceptional bending resistance characteristic. When the bending radius exceeds 3 cm, the impacts on the loss and birefringence are negligible, this also demonstrates that the fiber structure shows good robustness when subjected to harsh environment interference. The proposed PM-HC-ARF is believed to have important applications in the fiber optic gyroscopes, optical amplifiers, and hydrophones.