In fact, in addition to the base stations we know, the transmission of the Internet also includes long-distance optical cables, and submarine optical cables connected between continents. At present, there are as many as 380 submarine optical cables in the world, responsible for 95% of language and data transmission between continents. , We are watching a football game abroad, a TV program, making transoceanic phone calls, and other useful networks are all transmitted through submarine optical cables.
Optical cable is a kind of communication cable, which consists of two or more glass, plastic optical fiber cores and wrapping layers. The internal signal transmission of optical fiber generally adopts laser, which has the characteristics of higher speed, larger capacity and long-distance transmission.
The data transmission rate of a single fiber can reach several Gbps, and the transmission of submarine optical cables can reach an astonishing 160TBps, and the transmission distance can reach tens of kilometers each time without using a signal amplifier. (1G=1024M 1T=1024G)
Optical fiber and cable
Optical fiber development history
In ancient times, there was no Internet and no optical cable. To transmit information quickly, only flying pigeons were used. With the rapid development of science and technology, human beings have entered the information age. As the amount of information increases, it is necessary to find a new transmission method. After years of research, the transmission speed is faster and the transmission volume is larger. Optical fiber communication was born, and since then mankind has entered the era of light.
In 1870, British physicists discovered the principle of total reflection of light, which laid the foundation for later optical fiber transmission of signals.
In 1880, the "optical telephone" was invented by using light beams to transmit sound waves.
In 1970, Corning developed a silica glass fiber with less attenuation.
In 1980, the first optical cable was commercialized
In 1988, the transatlantic submarine optical cable connecting the United Kingdom and the United States was successfully laid
In 1978, China developed its own communication fiber
In 2005, the ultra-large-capacity optical fiber communication was opened from Shanghai to Hangzhou
How Fiber Works
If the Internet is compared to the information highway, the optical cable is like the cornerstone of the highway, so how does the large-capacity information optical cable transmit at high speed and long distance?
At the transmitting end, the information to be transmitted (such as voice) is first converted into an electrical signal, and then transmitted to the laser beam through a laser. The intensity of the light will change with the frequency of the electrical signal, and it will be emitted through an optical fiber. At the receiving end, the detection After receiving the optical signal, the device converts it into an electrical signal, and restores the original information after processing.
The optical fiber made of glass fiber inside the optical fiber can transmit optical signals to thousands of kilometers away, and combine hundreds of thousands of optical fibers to make an optical cable like a cable, which not only improves the strength of the optical fiber , and greatly increased the communication capacity.
The propagation speed of light in different substances is different, so when shooting from one substance to another substance, refraction and reflection will occur at the junction of the two substances, and the angle of the refracted light will change with the angle of the incident light. However, when the angle of the incident light reaches or exceeds a certain angle, the refracted 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 repeated refraction in the fiber. The optical signal will be scattered or attenuated after repeated refraction, and the optical signal needs to be amplified every 50 kilometers.
Fiber Manufacturing Process
First, the embryonic body of the optical fiber preform, which is mainly composed of high-purity silica, is fired into the optical fiber preform at a temperature of 1500 degrees.
After 20 hours, the high-purity light rod was successfully fired. Hang the light rod with a length of 3 meters and a diameter of 20 cm into the wire drawing furnace, and the wire can be drawn continuously for 7,500 kilometers within 48 hours. To prevent impurities and dust from falling on the optical fiber, the light rod is melted into a soft embryo at a high temperature of 2200 degrees Celsius. After passing through a 1-meter-long annealing tube, it gradually cools into a glass fiber with a diameter of 0.1 mm. The take-up machine rotates to drive the optical fiber to draw and complete the optical fiber. collection.
The difference between optical cable and optical fiber
As I said so much before, it's a bit confusing to see the optical fiber and the optical cable for a while. What is the difference between them?
The optical cable is composed of a certain number of optical fibers, which are wrapped with a sheath and a protective layer, which are used for communication and long-distance large-capacity information transmission.
Optical fiber is a transmission tool, just like a thin plastic wire. The very thin optical fiber will be encapsulated in a plastic sleeve and used for long-distance information transmission. So fiber optic cables contain optical fibers.
Finally, let's talk about a cable. The cable is composed of a conductive wire core, an insulating layer, and a sealing protective layer. It uses a metal material (mostly copper, aluminum) as a conductor, and is used to transmit power or information. Wires are twisted, and cables are mostly used in transportation hubs, substations and other places. In fact, there is no strict boundary between wires and cables. Usually we call those with small diameter and few cells as wires, and those with large diameter, many cells and complex structure as cables. .
In recent years, Huawei's mobile phone business has developed rapidly, and now it has surpassed Apple as the world's second largest mobile phone manufacturer. Perhaps because Huawei's mobile phone business has developed so well that it has overshadowed the company's main business: information and communication business. In the field of submarine cable engineering, many communication technologies are provided by Huawei. Huawei currently has dozens of submarine optical cable projects. From 2015 to 2020, the submarine optical cables laid by Huawei accounted for 1/4 of the world. Marvel! In addition to making mobile phones, Huawei also There is such a great technology.
With the development of 5G technology, it uses next-generation cellular technology, using microwave transmission, with fast speed and large coverage, and 5G download speeds of up to 10Gbps are faster than the current 1000-megabit fiber. With the reduction of 5G commercial network costs, some people It is predicted that 5G will not only eliminate WIFI but also fiber with faster transmission speed, what do you think?
