High purity fused silica rods generally serve one of following purposes in specialty fiber production:
- As a material which later forms the light-conducting core of the fiber. These rods should be made of a material which has a low absorption in the desired wavelength region. This rod must then be provided with a cladding. This fiber either is a plastic clad pure silica core fiber (PCS) or the rod is given a quartz glass cladding with a lower refractive index (multi-mode fiber).
- For forming a preform for photonic crystal fibers (PCF) (stacking of different glass pieces, or drilling holes into the rods).
- For locally adjusting the refractive index or the generation of mechanical stress in the fibers. One possibility for producing polarization-maintaining fibers is to use two stress inducing Boron doped rods..
- As an aid for the production of specialty fibers.