How Are Optical Fibers Made?

- Oct 23, 2020-

How Are Optical Fibers Made?


The process of optical fiber manufacturing determines the mechanical strength, transmission characteristics and service life of the optical fiber, which is very important to ensure the quality of the optical fiber. The manufacturing of communication optical fiber is divided into two processes: rod making and wire drawing.


The manufacturing process of optical fiber is mainly divided into three processes: preform preparation, optical fiber drawing and testing.


Preform Preparation

The production of preforms mainly includes MCVD, OVD, VAD and PCVD processes. This article only introduces the MCVD process.


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The MCVD (modified chemical vapor deposition) process was developed by Bell Labs in 1974. It introduces a gaseous mixture composed of SiCl4 (silicon chloride), GeCl4 (germanium chloride) and other chemical substances into a quartz glass tube (cladding), and rotates and heats outside the quartz tube to oxidize silicon and germanium to form SiO2 (Silica) and GeO2 (germanium dioxide), and reside in the quartz tube to form the main part of the optical fiber.


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The refractive index, expansion coefficient, and melting point of the optical fiber can be controlled by the component concentration of the gaseous mixture. After the preform has cooled down, a quality (refractive index) test is performed.

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Fiber Drawing

Put the preform into the fiber drawing tower for drawing. The preform is drawn into an optical fiber with a thickness of 125μm and coated with two layers of resin to protect the strength of the optical fiber.

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There is a graphite furnace in the fiber drawing tower, which can generate a high temperature of 17000-2000 degrees to soften the preform, and then it is wound by a drawing wheel to draw a slender fiber. The drawing tower has an information feedback system, which is used to feedback the furnace temperature and winding speed, etc., so as to accurately control the fiber diameter through the laser micrometer.

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In order to enhance the strength of the optical fiber, it is necessary to coat the optical fiber with a thin layer of resin in time during the drawing process and dry it in time to avoid mutual adhesion.

After the drawing is completed, the finished fiber needs to be tested. The content mainly includes: tensile strength, refractive index, fiber structure, attenuation, information carrying capacity (bandwidth), dispersion, operating temperature and humidity range, etc.

This is how optical fiber is made!

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With the rise and development of fiber optic communication and the construction and promotion of 5G, the market demand for optical communication products and devices is exploding, and higher requirements are placed on quality and performance.


OPTICO COMMUNICATION ( focuses on the development of fiber optic network communication product lines and provides a comprehensive solution to the fiber connectivity system components. We supply fiber optic components, such as fiber patch cord, PLC splitter, SFP transceiver, MTP/MPO, CWDM/DWDM, FTTH solution, Data center wiring solution, etc. All the products adopt strict quality standards in the production and inspection, ensuring excellent operation performance and good product stability, and safely and reliably ensuring the long-term use of products.

For more details, pls visit OPTICO website: