Optical fibers, short for optical fibers, are light-conducting tools that use the principle of total reflection of light in fibers made of glass or plastic. The optical fiber was invented by the former president of the Chinese University of Hong Kong. The fine fiber is encapsulated in a plastic sheath that allows it to bend without breaking. In general, an emitting device at one end of an optical fiber transmits a light pulse to an optical fiber using a light emitting diode (LED, LED) or a laser beam, and a receiving device at the other end of the optical fiber uses a photosensitive element detection pulse. In daily life, optical fiber is used as a long-distance information transmission because the conduction loss of light on the optical fiber is much lower than the loss of electricity on the electric wire.
1. Light is an electromagnetic wave Visible light part of the wavelength range is: 390 ~ 760nm (nano) greater than 760nm part of the infrared light, less than 390nm part of the ultraviolet light fiber applications are:. 850 nm, 1310, 1550 three. 2. The refraction, reflection and total reflection of light. Because the speed of light propagation in different materials is different, when light is emitted from one material to another, refraction and reflection will occur at the interface between the two materials. Moreover, the angle of the refracted light changes with the angle of the incident light. When the angle of incident light reaches or exceeds a certain angle, the refracted light will disappear and the incident light will be reflected back. This is the total reflection of light. Different materials have different refraction angles for light of the same wavelength (that is, different materials have different light refraction indexes), and the same material has different refraction angles for different wavelengths of light. Optical fiber communication is based on the above principles.
1. Fiber structure:
Fiber bare fiber is generally divided into three layers: the central high-index glass core (core diameter is generally 50 or 62.5μm), the middle is a low refractive index silica glass cladding (diameter is generally 125μm), the outermost is the strengthening of the resin coating Floor.
2. Numerical aperture:
The light incident on the end face of the fiber cannot be completely transmitted by the fiber, but only incident light within a certain range of angles. This angle is called the numerical aperture of the fiber. The larger numerical aperture of the fiber is advantageous for the mating of optical fibers. The numerical aperture of the fibers produced by different manufacturers is different (AT&T CORNING).
3. The type of fiber:
There are many types of optical fibers, and depending on the application, the required functions and performance vary. However, the principle of designing and manufacturing optical fibers for cable television and communication is basically the same, such as: 1 low loss; 2 has a certain bandwidth and small dispersion; 3 easy wiring; 4 easy to establish; 5 high reliability; 6 manufacturing comparison Simple; 7 cheap and so on. The classification of optical fibers is mainly based on the working wavelength, refractive index distribution, transmission mode, raw materials and manufacturing methods. Various classification examples are as follows.
(1) Operating wavelengths: UV fiber, visible fiber, near-infrared fiber, infrared fiber (0.85 μm, 1.3 μm, 1.55 μm). (2) Refractive index distribution: Step (SI) fiber, near-step fiber, gradient (GI) fiber, and others (such as triangular, W, depressed, etc.). (3) Transmission mode: Single mode fiber (including polarization maintaining fiber, non-polarization maintaining fiber), multimode fiber. (4) Raw materials: quartz fiber, multi-component glass fiber, plastic fiber, composite fiber (such as plastic clad, liquid fiber core, etc.), infrared materials, etc. The covering materials can also be classified into inorganic materials (carbon, etc.), metal materials (copper, nickel, etc.) and plastics. (5) Manufacturing methods: Vapor-phase axial deposition (VAD), chemical vapor deposition (CVD), etc., wire drawing method (Rod intube) and double crucible method.
