Fiber optics technology has come a long way since 1965, when the first working fiber-optics data transmission system was developed at the Telefunken Research Labs in Ulm, Germany. Since then, these fibers made from pure glass have revolutionized the world of network communications and information exchange. In fact, optical fibers have practically made metallic wires and cables obsolete—just ask those who are already experiencing ultra-fast internet speeds through fiber optics.
But how are these ultra-fine fibers made? Can you simply use just any kind of glass? In this article, we’ll take a closer look into how optical fibers are made in three simple steps.
Making the Fiber Optic Preform
The preform is a cylindrical glass blank from which the glass fiber will be drawn in one continuous strand. This is basically the source material of the optical fiber.
The preform is made through a process called modified chemical vapor deposition or MCVD, where oxygen is bubbled through various chemical solutions, primarily silicon chloride (SiCl4) and germanium chloride (GeCl4). The vapors produced will then be directed into a rotating tube made of synthetic silica or quartz, as a high-powered torch is moved up and down the tube. The high heat from the torch causes the silicon and germanium to react with oxygen, forming silicon dioxide (SiO2) and germanium dioxide (GeO2). These two compounds stick to the inside of the rotating tube, where they then fuse together to form the glass that will become the optical fibers.
Once cooled, the glass is then subjected to different quality tests to ensure that it has no impurities, which can interfere with the transmission of light and data.
Drawing the Optical Fiber from the Preform
After the preform has passed the quality tests, it will be loaded onto a fiber drawing tower. One end of the preform will then be loaded into an in-line graphite furnace, with temperatures of up to 3,992 degrees Fahrenheit. As the preform begins to melt, a molten lump of glass gets pulled downward by gravity. Behind the glob is a fine glass strand that quickly cools and solidifies.
The operator threads this glass strand through a series of devices in the tower, which include buffer coatings and UV curing ovens, and onto a spool. This spool is controlled by a tractor equipped with a linear stage, so that the fiber is aligned correctly when pulled from the heated preform and onto a spool. Low profile linear bearings also help ensure photonic alignment, while a laser micrometer continuously monitors the fiber’s diameter for consistency.
The tractor pulls the glass strand at a rate of 33 to 66 feet per second. This usually results to at least 1.5 miles (2.5 kilometers) of optical fiber per spool.
The finished optical fiber will be subjected to a battery of tests to determine its quality. Some of the assessments involve the following:
- Tensile Strength – the fiber must be able to withstand 100,000 psi or more
- Fiber Geometry – to ensure that the core diameter, cladding, and coating are uniform
- Attenuation – help determine the amount of degradation of light signals over distance
- Bandwidth – the fiber’s information carrying capacity at any given time
- Operating Temperature and Humidity
- Refractive Index Profile – screening for optical defects
Several factors may influence the overall quality and purity of the optical fiber. In particular, the chemical composition of the various chemicals used in creating the preform, the materials used for the valves and tubes that comes into contact with the vapors , and the consistency of motion and temperature of the cylinder are among the most important elements of the process.
A majority of telephone and cable companies and network providers have now shifted or are currently shifting to fiber-optics-based systems for improved speed, capacity, and clarity. Not only are fiber optic fibers less expensive, they are also more lightweight and flexible, have a higher carrying capacity, and have lower power requirements. They also experience less signal degradation, resulting in clearer signals and better overall customer experience and optimized operational efficiency for providers.