Optical fibre is drawn by inserting the preform into a high temperature graphite resistance furnace at 2100 C. Explore the optical cable manufacturing process. Is your digital life lagging? Slow streams, dropped calls? The unsung hero of our connected world, the optical cable, might be the key, and. The raw materials used in the initial stages of optical fibre manufacture include high quality synthetic quartz substrate tubes, ultra-pure halides such as silicon tetrachloride (SiCl 4 ) and germanium tetrachloride (GeCl 4 ), as well as the gaseous forms of pure oxygen (O 2 ), Helium (He). Attenuation Test: Measures how much signal loss occurs as light travels through the fiber. Geometrical Measurements: Confirms fiber diameter, concentricity, and coating thickness.