Investigation of interstice collapse for hollow-core photonic bandgap fiber fabrication

Hollow-core photonic bandgap fibers (PBGF) have low loss in theory; hence, they have great potential for many applications, such as high-speed big-data fiber communication and fiber sensors. They are fabricated using a two-step fiber drawing method. For PBGF optical properties, fabrication is an important factor. Most studies for microstructure fiber fabrication consider gas pressure, tension, and temperature control in the fiber drawing progress without considering the hexagon fillet in the honeycomb cladding, which could have a significant effect on the bandgap width. This letter focuses on the interstice's impacts among capillaries in the hexagon fillet forming process via the hydrodynamic mode. Research shows that small interstices could collapse totally when the heating temperature is high enough, and the collapse of interstice can help the honeycomb holes restrain collapse slightly. Interstices might be advantageous for controlling the honeycomb holes and hexagon fillets.