The transmission of video signals and digital data via conventional "copper" cables can no longer keep up with the ever-increasing demands for the transmission of signals of ever higher quality at ever greater speeds over ever greater distances. The problem is that the resistance and impedance of coaxial cables and twisted pairs limit the distance over which signals can be transmitted. Moreover, in any system, long-distance data conductors act like a giant antenna, which is subject to interference from a variety of sources, including interference from nearby conductors, currents induced by stray magnetic fields, and other extraneous sources of electrical noise.
An elegant and inexpensive solution to this problem is fiber optics. Optical fiber has a much wider bandwidth and lower loss than coaxial cable, which allows high-resolution images to be transmitted over very long distances without the use of route amplifiers or repeaters. And since the signal is transmitted in the form of a light beam, and not an electric current, the system becomes completely immune to any kind of electrical interference, including interference from neighboring conductors or high-voltage power lines
Unfortunately, working with a fiber the thickness of a human hair will never be as easy as connecting two wires with a crimp terminal, and of course, cleanliness is paramount. In addition, an interface is required at each end of the line to convert the electrical signal to light and vice versa.
Why, in spite of this, is there an ever-growing interest in the use of fiber optics in closed-loop TV systems and security systems?
Benefits of Fiber Optic Signaling
For many applications, fiber optics is preferred for a number of advantages. Not all of them, however, are created equal for different users. The most important from the point of view of applications in closed-loop TV systems are summarized below:
Low transmission loss . Low loss fiber optic cables allow the transmission of image signals over long distances without the use of route amplifiers or repeaters. This is especially useful for long-distance transmission schemes - for example, highway or railway surveillance systems, where 20 km of repeater-free sections are not uncommon.
Broadband signal transmission . The wide transmission bandwidth of optical fiber allows high quality video, audio and digital data to be transmitted simultaneously over a single fiber optic cable.
Immunity to interference and interference . The complete insensitivity of the fiber optic cable to external electrical noise and interference ensures stable operation of the systems even in cases where the installers did not pay sufficient attention to the location of nearby power networks, etc.
Electrical insulation . The lack of electrical conductivity for fiber optic cable means that the problems associated with changes in ground potential, such as those in power plants or railways, are gone. This property also eliminates the risk of damage to equipment caused by current surges from lightning, etc.
Lightweight and compact cables . The extremely small dimensions of optical fibers and fiber optic cables bring a new lease of life to jam-packed cable ducts. For example, a single coaxial cable takes up as much space as 24 optical cables, each of which can presumably carry 64 video channels and 128 audio or video signals simultaneously.
Timeless communication line . By simply replacing the terminal equipment, rather than the cables themselves, fiber optic networks can be upgraded to carry more information. On the other hand, part or even the entire network can be used for a completely different task, for example, combining a local area network and a closed-loop TV system in one cable.
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