Optical fiber, short for optical conductive fiber, is a fiber made of glass or plastic that can be used as a light conduction tool. The transmission principle is "total reflection of light". Former Chinese University of Hong Kong President Charles Kao and George A. Hockham first proposed the idea that optical fiber can be used for communication transmission, and Charles Kao won the Nobel Prize in Physics in 2009.
Optical fiber is a kind of thin, soft solid glass material, which is composed of fiber core, cladding layer and coating layer. It can be used as a light conduction tool.
· Core: located in the center of the optical fiber, the composition of high purity silica is glass.
· Cladding: located around the core, its composition is also high purity silica. The cladding provides a reflective surface and optical isolation for light transmission, and plays a certain role in mechanical protection.
· Coating layer: the outermost layer of the fiber, consisting of acrylate, silicone rubber and nylon. The coating layer protects the fiber from water vapor erosion and mechanical abrasion.
The implementation of optical fiber communication is based on the principle of total reflection of light. When the light propagates into the center of the fiber, the refractive index n1 of the fiber core is higher than that of the cladding n2, and the loss of the fiber core is lower than that of the cladding, so that the light will occur total reflection phenomenon, the light energy is mainly transmitted in the fiber core, with the help of continuous total reflection, light can be conducted from one end to the other end.
The working principle of optical fiber: at the transmitting end, the information to be transmitted (such as voice) is first turned into an electrical signal, and then transmitted to the laser beam through the laser. The intensity of the light will change with the frequency of the electrical signal, and is transmitted out through the fiber. At the receiving end, the detector is turned into an electrical signal after receiving the optical signal, and the original information is recovered after processing.
The optical fiber made of glass fiber inside the optical fiber can transmit the optical signal to thousands of kilometers away, and combine hundreds of thousands of optical fiber together to make optical cable like cable, which not only improves the strength of optical fiber, but also greatly increases the communication capacity.
The propagation speed of light in different substances is not the same, so when from one substance to another, the junction of the two substances will be refrected and reflected, and the Angle of the refrected light will change with the Angle of the incident light. When the Angle of the incident light reaches or exceeds a certain Angle, the refrected light will disappear, and all the incident light will be reflected back, which is the total reflection of light.
The optical signal is transmitted to the end point after a refraction in the fiber. The optical signal will be dispersed or attenuated after a refraction, so it is necessary to amplify the optical signal every 50 kilometers.
