Optical fiber can be used for optical communication. The laser has strong directionality and high frequency, making it an ideal light source for optical fiber communication. Compared with radio wave communication, optical fiber communication can provide more communication channels, which can meet the needs of high-capacity communication systems.
Optical fiber is generally composed of two layers. The inner layer is called the inner core, with a diameter of dozens of microns, but its refractive index is relatively high. The outer layer of the fiber optic cable is called the cladding, and its refractive index is relatively low.
The light incident from one end of the optical fiber is repeatedly refracted by the inner core and then is transmitted to the end. Due to the different refractive indexes of the two layers, the light entering the inner core is always transmitted in the inner core.
The transmission distance of light is related to the optical loss of the optical fiber. If the optical loss is small, the transmission distance is long. Otherwise, a repeater is needed to amplify the attenuated signal.
The fiber optic cable made of the latest fluorine glass can transmit optical signals to the other side of the Pacific Ocean without any relay station.
In actual use, hundreds of optical fibers are often combined and reinforced to form a cable-like optical cable, which not only improves the strength of the optical fiber, but also greatly increases the communication capacity.
Replacing communication cables with optical cables can save a lot of non-ferrous metals, such as 1.1 tons of copper and 2 to 3 tons of lead per kilometer.
Fiber optic cables have the advantages of light weight, small size, compact structure, good insulation performance, long life, long transmission distance, good security, and low cost.
The combination of optical fiber communication with digital technology and computers can be used to transmit telephones, images, data and to control electronic equipment and intelligent terminals and so on, partially replacing the role of communications satellites.
Optical fibers with high optical loss can be used over short distances, especially suitable for making various human endoscopes, such as gastroscopes, cystoscopes, proctoscopes, hysteroscopes, etc., which are extremely beneficial for diagnosis and treatment of various diseases.
The optical fiber used in practice is a very thin special glass filament with a diameter of only a few micrometers to a hundred micrometers, consisting of two layers: an inner core and an outer jacket.
The refractive index of the inner core is larger than that of the outer jacket, and total reflection occurs at the interface between the inner core and the outer jacket when light travels.
If the optical fibers are gathered into a bundle so that the relative position of the fibers at each end is the same, then the image with bright and dark colors can be transmitted from one end to the other. Medically, fiber optic cables are used to make endoscopes to examine the interior of the human viscera, like stomach, intestines, and trachea.
The actual endoscope is equipped with two sets of optical fibers. One is used to transmit light to the inside of the human body and the other is used for observation.
We know that light is also an electromagnetic wave and that it can be used as a carrier to transmit information like radio waves.
The laser carrying sound, image, and various digital signals is input from one end of the fiber optic cable, and then it can be transmitted to the other end thousands of miles away along the optical fiber to realize optical fiber communication.
(1) Large communication capacity and long transmission distance;
(2) The signal crosstalk is small, and the security performance is good;
(3) Anti-electromagnetic interference and good transmission quality;
(4) The fiber optic cable is small in size and light in weight, which is easy to be laid and transported;
(5) Rich sources of materials and good environmental protection;
(6) No radiation and not easy to be tapped;
(7) The optical cable has strong adaptability and long life.