A robust large air fill fraction holey fibre

Holey fibres have an array of holes around the core which run along the entire length of the fibre. This reduces the effective index of the cladding and provides the light guiding mechanism. This new type of fibre offers a wide range of unique optical properties which make them of great interest for a wide range of applications including telecommunications and sensing. Holey fibres are produced by stacking pure silica capillaries in a hexagonal pattern, with a solid silica rod as the core, as shown in figure 1, step 1. This stack is then drawn down to fibre in a single, or two stage, process. Around 300 capillaries are required to produce an appropriately microstructured fibre of 30 - 40 µm diameter. Whilst high quality fibres of such dimensions can be made they are extremely fragile and difficult to handle in appreciable lengths, severely compromising their practicality. Therefore means for scaling the fibre to practical dimensions and protecting the fragile mechanical structure are required. Both theory and experiment show that the guidance properties of the fibre are defined predominantly by the inner-most rings of capillaries. This gives considerable scope for simplification and improvements in fibre design