Design And Characterization Of Hollow-Core Anti-Resonant Fibers

Hollow core anti resonant fiber（HC-ARF）carries out optical transmission in the air core.Compared with the traditional solid core fiber,it overcomes the intrinsic losses such as material loss and scattering loss,and has the characteristics of low loss,wide bandwidth,high damage threshold,low time delay,low nonlinearity and low dispersion.HC-ARF has broad application prospects in the fields of optical communication,sensors,lasers,material detection and optoelectronic devices.In this paper,the finite-element modeling is used to study the influence of the change of cladding tube and nested tube on the transmission characteristics,and the dispersion characteristics and polarization maintaining characteristics of HC-ARF.The main research contents are as follows:HC-ARF with different numbers of cladding tubes is designed,and the long half axis of the cladding tube is fixed.It is found that the short half axis of the cladding tube when the fundamental mode loss and single-mode characteristics reach the best is similar,and the HC-ARF with 7 cladding tubes achieves the lowest fundamental mode loss and the best single-mode characteristics.The semi elliptical cladding tube HC-ARF is designed.It is found that the curvature change of the cladding tube has a significant effect on the transmission characteristics of the optical fiber.It is found that the vertical movement of the nested tube within 0-2μm can reduce the fundamental mode loss.The rotation movement of nested tube will increase the fundamental mode loss.When the distance between the edge of the nested tube and the fiber core remains unchanged,the change of the nested tube diameter within a certain range has little effect on the fundamental mode loss of the fiber.The change of the elliptical curvature of nested tube has a great impact on the fundamental mode loss and single-mode characteristics of the fiber.For the wavelength 1.19μm,the fiber obtains low loss and good single-mode characteristics.HC-ARF with single mode,low loss,wide bandwidth and near-zero flat dispersion transmission characteristics was investigated.In the wavelength range of 1.32μm to 1.57μm,the dispersion is always in the range of 0–1 ps/（nm·km）,and the FM confinement loss is less than 0.01 d B/km,the higher-order modes extinction ratio（HOMER）being greater than 1000.For the fiber dispersion research,the core diameter and tube wall thickness have a significant effect on the fiber dispersion.By increasing the core diameter,a near-zero flat dispersion with a larger wavelength range can be obtained.Changing the tube wall thickness can control the zero-dispersion wavelength of the fiber.And zero-dispersion can be adjusted to any wavelength by changing the tube wall thickness.The tube wall thickness also can control dispersion curve of fiber to achieve near-zero flat characteristics in a wide wavelength range.Moreover,the fiber has large negative dispersion characteristics,which can be used for dispersion compensation.A novel HC-ARF with a cladding ring,two nested resonant tubes and two nested silicon tubes was designed.The cladding ring in the fiber contributes to decrease the fundamental mode（FM）loss of x-polarization and enlarge polarization-extinction ratio（PER）.In addition,the nested silicon tubes can improve birefringence greatly.The combination of cladding ring,nested resonant tubes and nested silicon tubes can make the fiber obtain low FM loss,single-polarization,and high birefringence.Specifically,the proposed HC-ARF exhibits total FM loss of x-polarization,PER,and birefringence of0.89 d B/km,4432,3.07×10^-4 respectively at 1.55μm.Moreover,the y-bend direction has a great influence on the propagation properties of the fiber.The fiber in the x-bend direction has low total bend-loss of 0.004 d B/m for a small bend radius of 5.8 cm.