No one doesn't know the Internet right now, but if you ask what it is exactly further, few people will answer it well. It is known that it can do a lot of things online, and a lot of super-big companies appeared based on the Internet. This is our impression of the Internet. Is the Internet really like a cell phone signal which we can’t see it or touch it?
In fact, in addition to the base stations we know, there are also optical cables that are transmitted over long distances. The submarine cables connected between the continents currently have more than 380 submarine cables around the world, responsible for 95% of data transmission between continents. Looking at a foreign football game, TV programs, calling overseas phones, and using the network are all transmitted through submarine cables.
The optical cable is a communication cable composed of two or more glass, plastic optical fiber core and wrapping layer. The internal signal transmission of the optical fiber generally uses 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 cable reaches an astonishing 160 TBps, and the transmission distance can reach several tens of kilometers without using a signal amplifier. （1G＝1024M 1T＝1024G）
Fiber development history
There was no internet or fiber optic cable in ancient times, and people used flying pigeons to quickly transmit information. With the rapid development of science and technology, human beings have entered the information age. As the number 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, and the loss is higher. Fiber optic communication was born, and humans have entered the era of light.
In 1870, British physicists discovered the principle of total reflection of light, which laid the foundation for future fiber transmission signals.
In 1880, the invention of the "optical phone" is to use the beam to transmit sound waves.
In 1970 Corning developed a quartz glass fiber with less attenuation.
In 1980, the first fiber optic cable began commercial use.
In 1988, the transatlantic submarine cable connecting Yingmei 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 in Shanghai to Hangzhou.
How fiber works
If the Internet is regarded as an information superhighway, then the optical cable is the cornerstone of the expressway. So how is the high-capacity information optical cable transmitted at a high speed and long distance?
Firstly, the information to be transmitted (such as voice) will be converted into an electrical signal at the transmitting end, and then transmitted to the laser beam through the laser. The intensity of the light changes with the frequency of the electrical signal and is transmitted through the optical fiber. At the receiving end, the detector receives the optical signal and turns it into an electrical signal, which is processed to restore the original information.
The optical fiber made of glass fiber inside the fiber can transmit optical signals to thousands of kilometers, and combine hundreds of thousands of optical fibers to form a cable with the same cable, which improves the strength of the optical fiber. and greatly increased the communication capacity.
The speed of light propagation in different materials is different, so when one substance is shot to another, the intersection of the two substances will refract and reflect, 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 an angle, the refracted light will disappear and the incident light will be reflected back. This is the total reflection of the light.
The optical signal is transmitted to the endpoint after repeated refraction in the optical fiber. The optical signal is dispersed or attenuated after the primary refraction, and the optical signal needs to be amplified every 50 kilometers.