Introduction to Optical Communication

With the rapid development of society, it seems that optical communication plays a key part in nearly all industry. Whether in one’ daily life or in one’ work, it exists everywhere. Although it’s commonly utilized, and maybe most people haven’t had a detailed knowledge of it. Then this article will have an introduction to optical communication in these aspects, such as optical communication definition, types of optical communication, and advantages of optical communication.



What’ s Optical Communication?
Optical communication, also known as optical telecommunication, is one type of communications in which light is used to carry the signal to the remote end, instead of electrical current. Optical communication relies on optical fibers to carry signals to their destinations. It can be performed visually or by using electronic devices. An optical communication system uses a transmitter for encoding a message into an optical signal, a channel for carrying the signal to its destination, and a receiver for  reproducing the message from the received optical signal. These form the blocks of the optical communications system. When electronic equipment is not employed, the 'receiver' is a person visually observing and interpreting a signal, which may be either simple (such as the presence of a beacon fire) or complex (such as lights using color codes or flashed in a Morse code sequence).

Types of Optical Communication
Optical communication can be divided into laser communication and non laser communication according to the characteristics of light source. At the same time, according to the different transmission media, optical communication can be divided into wired optical communication and wireless optical communication (also known as atmospheric optical communication). The commonly used types include those:
Atmospheric laser communications:  the information is transmitted along the atmosphere by a laser beam. It’s unnecessary to lay the line; the equipment is light in weight and convenient to maneuver; it’s with good confidentiality, with large-capacity information transmission. These information can be transmitted such as sound, data, image and so on. Atmospheric laser communication is easily influenced by climate and external environment, and is commonly used as the horizon communication among river and lake, valley, desert area and island.
Optical fiber communication: It is a kind of wired communication. The light wave transmits along optical fiber. The light source can be a laser (also called as a semiconductor laser diode) or a light-emitting diode. Optical fibre communication, which is with low transmission attenuation, large capacity, good confidentiality and is free from external interference, can be used in large capacity defense trunk communication and field operation communication.
Blue-green light communication: it’s a kind of communication way in which information is transmitted under the sea by utilizing a kind of laser whose wavelength is between the blue light and green light. At present, it’s the best communication method under the water.
Infrared communication: it transmits information by infrared(wavelength is 300～0.76 micron). These information can be transmitted, such as language, character, data, image and so on. It’s available in coastal islands, remote control at short range, interior of air vehicle and so on. It’s with these advantages such as with large capacity, good confidentiality, with high performance in anti-electromagnetic interference. Simultaneously, the device is with simple architecture, small in size, light in weight, low in price. However, it’s easy to get influenced by climate when transmitted in the atmosphere channel, and the transmission distance is only 4000m.
Ultraviolet communication: It transmits information via  ultraviolet (wavelength is 0.39～60×10 micron). Its communication theory is similar to that of infrared, and both belong to non-laser communication.

Advantages of Optical Communication
The main benefits of optical communication include high bandwidth, low loss, wide transmission range and no electromagnetic interference. Besides, it’s also with these merits as below:

1. Long Distance Transmission & Economic and Energy-saving

When 10Gb information(10 billions of signals) need to be transmitted in on second, if using telecommunication, the signal need to be adjusted every 100m. By comparison, if applying the optic communication, it's adjusted every over 100kms. The less the signals are adjusted, the less the machines are needed. Therefore, to some degree, it's economic and energy-saving.

2. Large-capacity Information Transmission at One Time

Lots of users can simultaneously receive the information they need, such as movies, news and so on. In one second, at most 10Gb information can be transmitted via the telecommunication. While at most 1Tb information can be transmitted via optic communication.

3. With High-speed Transmission Rate

Telecommunication will bring about mistakes due to electronic noises, which leads to the dropping of transmission rate. While the optic communication will not have such kind of troubles so that it can transmit signals at high speed.

Conclusion
In current society, more industries can hardly work without optical communication, especially IT industry, communication industry and so on. Meanwhile, the communication tech is always keeping improved and keeping pace with the market demands, in which the fiber optical communication is widely used among these optical communications. Maybe the introduction to fiber optic communication can be made in next article.