(Optical fiber network engineer training materials Chinese version 1. Light is an electromagnetic wave. The wavelength range of visible light is: 390~760nm (nanometers), the part greater than 760nm is infrared light, and the part less than 390nm is ultraviolet light. The optical fibers used are: 850nm, 1300nm, and 1550nm. 2. Refraction, reflection and total reflection of light. Because the propagation speed of light in different substances is different, when light is emitted from one substance to another substance, refraction and reflection will occur at the interface of the two substances. Moreover, the angle of the refracted light will change with the angle of the incident light. When the angle of the incident light reaches or exceeds a certain angle, the refracted light will disappear, and the incident light will be fully reflected back, which is the total reflection of light. Different substances have different refraction angles for the same wavelength of light (that is, different substances have different refractive indices of light), and the same substance has different refraction angles for different wavelengths of light. Optical fiber communication is formed based on the above principles. .........)
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