Optical Fiber consist of core and cladding which differ in refractive index. hence two different materials are required. this can be realized with glasses (or glass like materials) and monocrystalline structure (certain plastics). glasses exhibit the best overall materials charasteristics for use in the fabrication of low loss optical fibre. they are therefore used almost exclusivelly in the preparation of fiber for telecomunication. plastic-cald and all plastic fiber find some use in short haul low bandwith application. we will discuss the preparation of only glass fiber.
there are two-stage process in which initially the pure glass is produced and converted into a form (rod or preform) suitable for making the fiber. a drawing or pulling technique is then employed to acquire the end product. the methods of preparing the extremely pure optical glasses generally fall, in two major categories wich are :
a. Conventional Glass Refining techniques in which the glass is processed in the molten state (melting methods) producing a multi component glass structure. one example of method in this category is the double crucible method.
b. Vapor Phase Deposition methods producing silica-rich glasses which have melting temperature that are too high to allow the conventional melt process. techniques for the fabrication of glass by means of the vapor phase deposition methods are :
- The outside vapor phase oxidation (OVPO) process
- The vapor axial deposition (VAD) process
- The modified chemical vapor deposition (MCVD) process
- The plasma-activated chemical vapor deposition (PCVD) process
The drawing of high quality silica fiber require a clean heat source capable of achieving 2200 Celcius with good temperatue control and a stable enviroment. one example is the zirconia induction furnance.
there are two-stage process in which initially the pure glass is produced and converted into a form (rod or preform) suitable for making the fiber. a drawing or pulling technique is then employed to acquire the end product. the methods of preparing the extremely pure optical glasses generally fall, in two major categories wich are :
a. Conventional Glass Refining techniques in which the glass is processed in the molten state (melting methods) producing a multi component glass structure. one example of method in this category is the double crucible method.
b. Vapor Phase Deposition methods producing silica-rich glasses which have melting temperature that are too high to allow the conventional melt process. techniques for the fabrication of glass by means of the vapor phase deposition methods are :
- The outside vapor phase oxidation (OVPO) process
- The vapor axial deposition (VAD) process
- The modified chemical vapor deposition (MCVD) process
- The plasma-activated chemical vapor deposition (PCVD) process
The drawing of high quality silica fiber require a clean heat source capable of achieving 2200 Celcius with good temperatue control and a stable enviroment. one example is the zirconia induction furnance.
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