The complete name of the optical fiber is called optical fiber. The English name is OPTIC FIBER, also called OPTICAL FIBER. It is made of pure quartz (glass) and drawn into a glass tube with a medium in the middle that is thinner than a hair by a special process. It can be used in a short period of time. convey enormous amounts of information.

This is a process diagram of high temperature drawing of preform rods (that is, high-purity glass rods), and the shiny part in the middle is melted glass.

We can see from the picture that a preform rod is drawn into an optical fiber after being melted at high temperature on the drawing tower. The optical fiber drawn from the picture below is still very thick. When the drawing speed reaches the normal standard, the drawn optical fiber will become a finished optical fiber with uniform thickness.

During the fiber drawing process of a preform, a certain amount of substandard optical fibers will be produced in the front and rear parts. If the process is not well controlled in the middle, waste fibers or low-grade optical fibers will also be produced. The optical cables produced have adverse reactions such as large attenuation and easy breakage.

Optical fibers for communication are made of glass that transmits light signals by total internal reflection. Glass optical fibers have a standard diameter of 125 microns (0.125 mm) and are covered with a protective resin coating of 250 microns or 900 microns in diameter. The light-carrying central portion of a glass fiber is called the "core," and the surrounding cladding has a lower index of refraction than the core, limiting light loss.

Features

The characteristics of optical fiber: fast transmission speed, long distance, large transmission data, and it is not subject to electromagnetic interference, not afraid of lightning strikes, it is difficult to eavesdrop on the outside, non-conductive, and there is no trouble of grounding between devices, etc.

Type

According to the transmission mode of light in the optical fiber, it can be divided into: single-mode optical fiber and multi-mode optical fiber.

Single-mode generally uses a laser with a wavelength of 1310nm (nanometer) or 1550nm to transmit signals. The optical fiber is made of high-purity quartz glass material, and the attenuation reaches the minimum near the wavelength of 1550nm (close to the theoretical limit of 0.18dB/Km)

Multimode fiber can transmit multiple modes of light. However, its intermodal dispersion is relatively large, which limits the frequency of digital signal transmission, and it will be more serious with the increase of distance. Therefore, the transmission distance of multimode optical fiber is relatively short, generally only 2 kilometers.