Research On Structural Design Of Low Loss Single Mode Hollow Core Antiresonant Fiber

In recent years,hollow-core anti-resonant fiber(HC-ARF)has broken through the limitation of surface scattering loss on the loss of hollow core photonic crystal fiber by virtue of its simple cladding structure and unique light guiding characteristics,and has become a research hotspot in the field of fiber optics.Compared with the traditional optical fiber that transmits light in the glass core based on the principle of total reflection,the HC-ARF transmits light in the air-core region by combining the anti-resonant reflection principle and the mode coupling suppression principle.Therefore,it has the advantages of low latency,low nonlinearity and high damage threshold.HC-ARF has a broad application prospect in many fields,such as long-distance high speed communication,polarization filter,and optical sensor,etc.Starting from the correlation between the light-guiding principle,transmission characteristics,and the cladding structure of HC-ARF,this paper designs and optimizes the cladding structure of HC-ARF to minimize the transmission loss and improve the single-mode characteristics of the fiber.The research content is divided into the following parts:First,the light-guiding mechanism of HC-ARF is analyzed.Taking single-layer HC-ARF and double-layer nested HC-ARF as the experiment objects.The influence of the HC-ARF cladding tube thickness on the fiber transmission loss is explained by the anti-resonant reflected optical waveguide model,and the influence of cladding structure change on fiber loss and single-mode characteristics is analyzed by the mode coupling model of core modes and cladding modes.Second,the transmission loss of the optical fiber is further reduced,and the single-mode and bending characteristics of the optical fiber are improved by adding a flat glass layer between the anti-resonance tubes of 5-tube double-layer nested HC-ARF.The loss error by the curvature change of the glass layer,the deformation of the outer tube,and the inclination of the glass layer during the preparation of the designed optical fiber are analyzed.And the manufacturing tolerance is given.Third,the 4-tube HC-ARF with larger cladding space was investigated.The low-loss single-mode transmission of the 4-tube HC-ARF is realized by adding four adjacent nested inner tubes in the outer anti-resonant tube.Change the cladding geometry to analyze the effect of adjacent nested inner tube size and position on the fundamental mode loss and minimum higher-order mode loss of the fiber.In addition,the optical fiber has high birefringence at a communication wavelength of 1.55 μm by changing the wall thickness of the outer tube in the vertical direction.Fourth,combined with the light-guiding mechanism of HC-ARF,an HC-ARF with negative curvature triangular-core is proposed.Replacing the cladding capillary with three negative-curvature suspending glass layers simplifies 5-tube double-layer nested HC-ARF cladding structure.By comparing with other design schemes,the significance of the negative curvature core boundary on the transmission performance of HC-ARF is analyzed.