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How Optical Fibers are Manufactured



A glass optical fiber is a flexible, transparent fiber made by drawing glass. It consists of a core surrounded by a cladding layer. Light and image travel through the core from one end to the other. Since the diameter of thin glass fibers is about a half of the typical human hair, fiber cores are made from very high purity optical glass materials.



For fiber fabrication, a double crucible is used of which the inner crucible contains molten core glass and the outer one contains the cladding glass. Fibers are drawn from the molten state through orifices in the bottom of the two concentric crucibles in a continuous production process.



Drawn glass optical fibers are bundled in some tens or in hundreds, then coated with resin to make up like a wire. At Sumita, we draw fibers with diameters starting from 30 um and have monthly production capacity of 500 thousand kilometers of optical fibers.