Surface-mode induced high birefringence in a low-loss 7-cell photonic bandgap hollow-core fiber

• We demonstrate that high birefringence could be achieved in PBG-HCF by shifting the SM to the outside of transmission band. • SM engineering could solve the counter-balance between narrow bandwidth and high birefringence. • The new method request no complex design or fabrication. In this paper, a low-loss high-birefringence 7-cell photonic-bandgap hollow-core fiber (PBG-HCF) is designed and fabricated based on the method of surface mode engineering. Within a smooth transmission band from 1472 nm to 1560 nm, a minimum attenuation of 39 dB/km is measured where up to 3.29 × 10 −3 group birefringence is achieved. The windowed Fourier transform (WFT) is applied in the analysis of spectral beating measurement results. The wavelength dependence of group birefringence of fundamental and higher-order modes is resolved.