双绞线、同轴电缆、光纤的区别及如何使用(国外英文资料).docVIP

双绞线、同轴电缆、光纤的区别及如何使用(国外英文资料)The difference between twisted pair, coaxial cable and optical fiber and how to use.TxtThe difference between twisted pair cable, coaxial cable and optical fiber and how to use themRelease time: 2010-3-29 source: China Wire Cable Network1 coaxial cableThe coaxial cable has the advantages of low cost, convenient laying (relative to the optical fiber), so the general monitoring system in small range, the transmission distance is very close, the use of coaxial cable transmission directly monitoring image with little damage on the image quality, can satisfy the actual request.However, according to the analysis of the coaxial cables own characteristics, when the signal is transmitted in coaxial cable, its attenuation is related to the transmission distance and the frequency of the signal itself. Generally speaking, the higher the signal frequency, the greater the attenuation. Video signal bandwidth is large, up to 6MHz, and the color image part is modulated at high frequency, so that the video signal transmission in a coaxial cable not only signal amplitude of each frequency component is attenuated and the attenuation varies greatly, especially the color part of the maximum attenuation. Therefore, coaxial cable is only suitable for transmitting image signals at short distance. When the transmission distance is about 200 meters, the image quality will decrease obviously, especially the color becomes dim and distorted.In engineering practice, coaxial amplifiers are used to extend transmission distances. The coaxial amplifier has a certain amplification to the video signal, and also can compensate different frequency components with different sizes by balanced adjustment, so that the video signal produced by the receiver is as small as possible. However, the coaxial amplifier cannot limit and cascade, generally in a coaxial point-to-point system amplifier can only cascade 2 to 3, otherwise it is impossible to ensure the quality of video transmiss