What's the use of optical fiber?

The fine fiber is encapsulated in a plastic sheath so that it can bend without breaking. Typically, a transmitter on one end of the fiber uses a light-emitting diode (light emitting diode,led) or a laser beam to transmit the light pulses to the optical fiber, and the receiving device on the other end of the optical fiber detects the pulse with the photosensitive element.

In daily life, optical fiber is used as a long-distance information transmission because the conduction loss of light in optical fiber is much lower than that of electric wire conduction.

Usually two nouns of fiber and optical cable will be confused. Most optical fibers must be covered by several layers of protection before they are used, and the cables that are covered are known as optical cables. The protective structure of the outer layer of the fiber can prevent the damage of the surrounding environment to the optical fiber, such as water, fire, electric shock, etc. fiber optic cable is divided into: Buffer layer and drape. Fiber is similar to coaxial cable, except that there is no mesh shielding layer. The center is a glass core of light transmission.

In multimode fiber, the diameter of the core is 15μm~50μm, roughly the same as the weight of the human hair. The diameter of single mode fiber core is 8μm~10μm. The core is surrounded by a glass envelope with a lower refractive index than the core to keep the light in the core. Then there is a thin plastic coat to protect the envelope. The fiber is usually tied to a bundle and the outer shell is protected. Fiber core is usually made of quartz glass cross section of a small double concentric cylindrical body, which is brittle, easy to break, and therefore need a protective layer.

　　Fiber structure

Fiber bare fiber is generally divided into three layers: the center of the high refractive index glass core (the core diameter is generally 50 or 62.5μm), the middle of the low refractive index of silicon glass cladding (diameter is generally 125μm), the most external is to strengthen the resin coating.

　　Numerical aperture

The light that is incident to the end of the fiber is not all transmitted by the optical fiber, only the incident light in a certain angle range can be. This angle is called the numerical aperture of the optical fiber. The numerical aperture of optical fiber is more advantageous to the connection of optical fiber. The numerical aperture of optical fibers produced by different manufacturers is different (at&t CORNING).

　　Quartz fiber

Quartz fiber (silica Fiber) is a fiber that controls the refractive index of the core and cladding by using silica (SIO2) as the main raw material and according to different doping quantities. Quartz (glass) series of optical fiber, with low consumption, broadband characteristics, has been widely used in cable television and communication systems.

The advantage of quartz glass optical fiber is low loss, when the light wavelength is 1.0~1.7μm (around 1.4μm), the loss is only 1db/km, the lowest in 1.55μm place, only 0.2db/km.

　　Fluorine-doped fiber

Fluorine-doped fiber (fluorine doped Fiber) is one of the typical products of quartz fiber. Usually, as a 1.3Pm optical fiber for communication, the doping of the control core is germanium dioxide (GeO2), and the cladding is made by Sio. But the core of fluorine fiber, most of the use of SiO2, but in the coating is mixed with fluorine. The Rayleigh scattering loss is a light scattering phenomenon caused by the change of refractive index. Therefore, the hope that the formation of refractive index changes in the doping, less good. The main function of fluorine is to reduce the refractive index of SIO2. Therefore, it is often used in cladding doping. Because of the fluorine-doped fiber, the core does not contain fluorine doping which affects the refractive index. Because its Rayleigh scattering is very small, and the loss is also close to the theoretical minimum value. So much for long-distance optical signal transmission.

Quartz fiber and other raw materials, compared to optical fiber, but also from ultraviolet light to near-infrared light transmission spectrum, in addition to the use of communications, but also for guided light and conduction of images and other fields.