Various classification criteriaExamples are as follows:
(1) According to the operating wavelength: ultraviolet optical fiber, observable optical fiber, near-infrared optical fiber, infrared optical fiber (0.85 μm, 1.3 μm, 1.55 μm).
(2) According to the refractive index distribution: step (SI) type optical fiber, near-step fiber, gradient (GI) type optical fiber, others (such as triangular, W-type, concave, etc.).
(3) According to the transmission mode: single-mode fiber (including polarization maintaining fiber, non-polarization maintaining fiber), multi-mode fiber.
(4) According to the raw materials: quartz optical fiber, multi-component glass optical fiber, plastic optical fiber, composite optical fiber (such as plastic cladding, liquid core, etc.), infrared materials. According to the cladding material can also be divided into inorganic materials (carbon, etc.), metal materials (copper, nickel, etc.) and plastics.
(5) in accordance with the manufacturing method: pre-plasticization of vapor-phase axial deposition (VAD), chemical vapor deposition (CVD), etc., drawing method has a tube law (Rod intube) and double crucible method.
One, fiber optics
Fiber optics, fiber optics, is the abbreviation of optical fibers, is a use of light in glass or plastic made of fibers in the principle of total reflection and reached the light conduction tools. Optical fiber was invented by Charles Kao, former president of the Chinese University of Hong Kong. The microscopic fiber is encapsulated in a plastic sheath that allows it to be bent without breaking. Typically, a transmitting device at one end of the fiber transmits pulses of light into the fiber using light emitting diodes (LEDs) or a beam of laser light, and a receiving device at the other end of the fiber detects the pulses using a photosensitive element. In everyday life, optical fibers are used as a means of transmitting information over long distances because the conduction loss of light in optical fibers is much lower than the loss of electricity conducted through wires.
Second, the principle of optical fiber
Because the propagation speed of light in different substances is different, so the light from one substance to another substance, in the two substances at the interface will produce refraction and reflection. 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 all the incident light will be reflected back, which is the total reflection of light. The angle of refraction of different substances for the same wavelength of light is different, and the angle of refraction of the same substances for different wavelengths of light is also different. Fiber optic communication is based on the above principle.
Three, optical fiber structure
Optical fiber bare fiber is generally divided into three layers: the center of the high refractive index glass core (core diameter is generally 50 or 62.5 μm), the middle of the low refractive index silica glass cladding (diameter of 125 μm), the most outwardly reinforced with a resin coating.