Increasing the Numerical Aperture of Large-Core Microstructured Polymer Optical Fibers Using a ‘Y’-Bridge Cladding

There has been considerable recent success in fabricating large-core highly multimoded polymer air-clad fibers suspended by thin bridges. These thin bridges are constructed by surrounding a solid core preform by many capillary tubes, the adjacent walls of the capillary tubes fuse together and form bridges when the preform is drawn to fiber. Recently a different cladding technique has been demonstrated experimentally where the interstitial holes between capillary walls do not completely collapse and leave a gap at the core or cladding side of the bridge forming a ´Y´-shape. This paper investigates this ´Y´-bridge microstructured cladding and the potential for increased numerical aperture of different geometries of the bridge.