A series of advantages of optical communication equipment such as immunity, high capacitance and confidentiality make optical communication system more and more the first choice for communication system (especially backbone network), and as the "skeleton" of optical communication system, optical fiber products Due to the current classification regulations on the list of optical fiber products and industry habits, there are certain differences, so it is easy to cause disputes in import and export declarations.
In principle, no matter what kind of information is transmitted in optical fiber products, it is realized by light as the carrier, so its basic structure is exactly the same: the core made of transparent material and the refraction of the fiber core around it. The cladding is made of a material with a slightly lower rate, and the optical signal injected into the core is reflected by the interface of the cladding, so that the optical signal propagates forward in the core. It is generally a symmetrical cylinder of a multilayer dielectric structure consisting of a core, cladding and coating layers.
On this basis, optical fibers have derived a series of different products with different characteristics according to their use and cost considerations.
Optical fibers are usually attached with a thin layer of plastic that is invisible to the naked eye, so that the fibers are not easily broken. They are usually wound on reels when importing and exporting, and the length can reach several kilometers. Most of the fields belong to the concept of "semi-finished products". However, in some cases, a single optical fiber can also be used directly with a sheath (sheath). For example, the access end of the currently popular "fiber to the home" uses a single-core optical fiber with a sheath.
As the name implies, many optical fibers are grouped together to form an optical fiber bundle like single mode fiber bundle, linear fiber bundle. Because the cross-section of a single optical fiber is too thin, it is not suitable for transmitting images or light, so this function is achieved by sticking multiple optical fibers together.
Of course, making a glass rod with a large cross-sectional area can also achieve the same ability, but in this way, the unique flexibility of the optical fiber is lost, it cannot be made very long, and the cost is greatly increased. Fiber optic bundle is divided into two types in the industry: rigid fiber optic bundles and flexible fiber optic bundles.
Rigid optical fiber bundles are bonded together by adhesive. Each optical fiber is in exactly the same order at both ends. This ordered optical fiber bundle can be used to transmit images. Commonly used in image transmission lines such as endoscopes.
The flexible optical fiber bundle only bundles the ends of the fiber bundle into a bundle, and the order of each optical fiber at both ends is random. This disordered optical fiber bundle can only be used to transmit illumination light and cannot transmit images. . At present, many hotel lobbies (atriums) abandon electric lights and use optical fiber bundles to introduce sunlight for daytime lighting. This environmentally friendly model takes advantage of the characteristics of flexible optical fiber bundles.
In theory, using wavelength division multiplexing technology, a single fiber can hold an infinite amount of information. However, from the perspective of the prior art, optical cables are common connecting lines in current optical communication equipment. In order to save wiring space and expand communication capacity, people often integrate multiple optical fibers into the same casing (sheath).