Optical Communications

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Definition

Optical communication is a type of communication in which light is used to carry the signal to the remote end instead of electrical current. Optical communication relies on fiber optic cables to carry the light signals to their destinations. In addition, a complete optical communication network is also including a modulator/demodulator, a transmitter/receiver, a light signal and a transparent channel. They are the building blocks of the optical communications system. Furthermore, to increase the bandwidth of the optical path, there are two methods: One is to increase the fiber single-channel transmission rate, and the other is to increase the number of single fiber transmission wavelength. The fact that the wavelength division multiplexing technology (WDM), optical communication equipment is only suitable in the last few km distance.

Compared to the electrical transmission, optical communication has more advantages and now has largely replaced copper wire communications in core networks in many developed countries. Optical communication is becoming a trend in the next period of time.

Transmission Mmedium of Optical Communication – Optical Fiber

Optical fiber is the most common type of channel for optical communications. In addition to the manufacturing process, material composition and optical properties, applications, optical fiber is often classified by purpose so that optical fiber can be divided into communication with fiber-optic and sensing fiber. Transmission medium, optical fiber is divided into two kinds of general and special-purpose, functional devices optical fiber means for the completion of the amplification of light waves, the plastic divider, multiplier, modulation as well as light oscillation function of the fiber, and often some kind of functional devices form.

Principle

The principle of optical communication will simply be described as following: Firstly, the sender sends the information (eg, voice, image or data etc.) into electrical signals, and then modulated onto the laser emits a laser beam, so that the change of light intensity with the signal amplitude (frequency) as well as sending via optical fiber. In the receiving end, detector receives the optical signal to transform it into an electrical signal by demodulation after reinstatement.

All-Optical Network

The ultimate goal of the transmission network is to build all-optical networks including the access network, MAN, backbone network and so on. In a word, we will make a full realization of the optical transmission instead of copper wires.

The backbone network is the highest part of the network speed, distance and capacity requirements of ASON technology used in backbone networks is an important step in the intelligent optical network, the basic idea is the introduction of intelligent control plane in the optical transmission network, which realization of resources according to need. DWDM is also in the backbone network show their skills, the future may be completely replaced by SDH, in order to achieve IP OVER DWDM.

MAN will become the operator to provide bandwidth and services and bottlenecks. At the same time, MAN will become the largest market opportunities. SDH-based MSTP technology is mature and has good compatibility and flexibly and effectively support a variety of data services.

About access network, FTTx (fiber to the x) is a long-term ideal solution. FTTx evolutionary path will gradually be fiber to the user to push close to the process, from FTTH (Fiber to the home) or FTTN (Fiber to the neighborhood) to FTTC (fiber to the curb) and FTTB (fiber to the building) and even finally to FTTP (fiber to the premises). Of course, it’s still a very long period to make it universally apply. In this process, fiber access will coexist with ADSL/ADSL2+.

Technical field
  • communication capacity, transmission distance; the potential bandwidth of an optical fiber up to 20THz. This bandwidth, just about one second, can be human at all times all the text data transfer is completed. 400Gbit / s systems have been put into commercial use. Low-loss optical fiber in the wavelength of 1.55μm near the quartz fiber loss may be less than 0.2dB/km, which is lower than the loss of any transmission medium. Therefore, no relay transmission distance up to tens or even hundreds of kilometers.
  • signal interference, the performance of confidentiality.
  • anti-electromagnetic interference, good transmission quality of radio communications can not solve the problem of electromagnetic interference, only the optical fiber communication from a variety of electromagnetic interference.
  • fiber small size, light weight, ease of laying and transportation.
  • a rich source of materials, environmental protection, conservation non-ferrous metal copper.
  • no radiation is difficult to eavesdropping, because the optical fiber transmission of light waves can not run out of the fiber outside.
  • fiber optic cable is adaptable, long life.
  • crisp texture, and poor mechanical strength.
  • fiber cut and splice need some tools, equipment and technology.
  • shunt, the coupling is not flexible.
  • fiber optic cable bend radius can not be too small (> 20cm)
  • supply difficulties.The use of light waves in optical fiber transmission means of communication. Laser with high directivity, high coherency, high monochromaticity significant advantages of the light waves in optical fiber communication laser, also known as laser – Optical Fiber Communication.
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