专业英语翻译-(13).doc

optic-fiber communication;fiber-optic communications
optical fiber communications From the optical communication talent showing itself, has become one of the main pillars of modern communication in the modern telecommunications network, play a decisive role in the. Optical fiber communication as a new technology, its rapid development in recent years, applications broad range of communications in history, but also the important symbol of revolution of world new technology and the future information society information main transfer tool.
Optical fiber for optical fiber abbreviation. Optical fiber communication is to light as the carrier of information, with the optical fiber as transmission medium is a means of communication. In principle, constitute the basic elements of optical fiber communication optical fiber, a light source and a light detector. Optical fiber in addition to the manufacturing process, material composition and optical properties for classification, in the application of the optical fiber, used to use for classification, can be divided into communication and optical fiber sensor with optical fiber. Transmission medium optical fiber is divided into general and special two, and functional devices for optical fiber refers to the amplification, shaping, frequency divider, frequency, modulation and optical oscillation features such as optical fiber, and often a function of the device appeared in the form of.
The characteristics of optical fiber communication

( 1) the communications capacity, transmission distance; a fiber potential bandwidth of up to 20THz. The bandwidth, just one second, then human at all times and in all countries all text data. The 400Gbit / s system has been put into commercial use. The optical loss is extremely low, in light with a wavelength of 1.55 m nearby, quartz fiber loss lower than 0.2dB / km, the ratio of any current transmission medium loss is low. Therefore, transmission distance can reach tens, even hundreds of kilometers. ( 2) small signal interference, good secrecy performance; ( 3) resistant to electromagnetic interference, the transmission quality is good, the electric communication cannot solve all kinds of electromagnetic interference, optical fiber communication is not only affected by all kinds of electromagnetic interference. ( 4) fiber of small size, light weight, convenient installation and transportation; ( 5) and rich material source, good environmental protection, is in favor of saving nonferrous metals copper. ( 6) no radiation, difficult to eavesdropping, because optical fiber transmission light cannot run fiber outside. ( 7) cable strong adaptability, long life. ( 8) a brittle texture, poor mechanical strength. ( 9) fiber cut off and continue to require certain tools, equipment and technology. ( 10) shunt, coupling flexible. ( 11) fiber optic cable bending radius can not be too small ( > 20cm ) ( 12) have the power supply problem. The use of light in optical fiber communication. Because the laser has high directivity, high coherence, high monochromaticity and other significant advantages in optical fiber communication, light is a laser, so they called the laser optical fiber communication.
Principle
Optical fiber communication principle is: the sending end first to transmit information ( such as voice ) into electrical signals, and then the modulation to the laser beam emitted from the laser, causing the light intensity with the electric signal amplitude ( frequency ) changes, and transmitted through optical fiber; at the receiving end, the light signals are received after the detector transform it into an electrical signal, the demodulation after the restoration of the original information.
Editor this paragraph development
Optical fiber communication is the main transmission means in the modern communication network, its development history of only ten or twenty years, has experienced three generations: the short wavelength multimode optical fiber, a multimode fiber and long wavelength of long wavelength single mode fiber. By using optical fiber communication is the communication history great change, beautiful, day, flower, law to wait for 20 many countries have announced no longer construction cable communication line, and committed to the development of optical fiber communication optical fiber communication. China has entered a practical stage. The birth and development of optical fiber communication is an important history of the telecommunications revolution and satellite communications, mobile communications and tied for the nineteen ninties technology. Enter after twenty-first Century, because of the Internet, the rapid development of business and audio, video, data, multimedia application on growth, large capacity (ultra high speed and long distance ) optical transmission systems and networks have more pressing needs. Optical fiber communication is the use of light as a carrier to transmit information, and to optical fiber as transmission medium to realize information transmission, to achieve communication purposes a new communication technology. The development of communication process is to improve the carrier frequency to expand the capacity of communication process, optical frequency as the carrier of communication carrier cap, because the light is a kind of extremely high frequency electromagnetic wave, so the light as a carrier for communication capacity greatly, is the last communication mode for thousands of times, has great appeal, optical communication it is long pursuit of the goal, but also the inevitable trend of development of communication. Optical fiber communication and the electrical communication, the main difference is that there are many advantages: it transmission bandwidth, communication capacity; low transmission loss, long distance relay; line small size, light weight, raw material for the quartz, metal material saving, is conducive to the rational use of resources; insulation, strong electromagnetic interference resisting performance; also has strong corrosion resistance, strong ability of resisting radiation, can rotate around the well, no spark, small leakage, confidentiality and strong advantages, but in special environments or military use.
Application fields
Optical fiber communication application field is very extensive, mainly used for telephone trunk line, optical fiber communication here can give full play to advantages, gradually replacing the cable, widely used. Also used for long-distance communication past mainly by cable, microwave, satellite communication, is to gradually use of optical fiber communication and the formation of a global advantage bit transmission method; used for global communication network, national public telecommunication network ( such as the national level, provincial level and the county route two route following the branch line ); it also for high quality color television transmission, industrial production site monitoring and scheduling, traffic surveillance and control command, urban cable TV network, the antenna ( CATV ) system for optical fiber LAN, and other such as in aircraft, spacecraft, ships within within within, mine, electric power department, military and corrosion and radiation used in. Optical fiber transmission system mainly consists of: optical transmitter, optical receiver, optical cable transmission line, optical repeater and a variety of passive optical components. Communication is to be achieved, the baseband signal must pass through the electric machine to process the signals sent to the optical fiber transmission system to complete the communication process. It is suitable for fiber optic communication system, but also suitable for optical fiber digital communication system and data communication system. In fiber optic communication system, signal processing refers to the baseband signal is amplified, the modulation of such treatment, and the electrical signal processing is the originator of the processing of the inverse process, namely, amplification, demodulation processing. In optical fiber digital communication system, signal processing refers to the baseband signal is amplified, sampling, quantization, namely the pulse code modulation ( PCM ) and line code type code processing, and signal processing is also the originator of the inverse process of anti. The data of optical fiber communication, signal processing includes the signal amplification, and digital communication system is that it does not need code converter.
Development trend
Fiber to the home ( FTTH ) development
FTTH may be provided to the user in a very rich bandwidth, it has been considered the ideal way of access, for the realization of information society has an important role, also need to large-scale promotion and construction. FTTH needed for fiber may be an existing application fiber 2 ~ 3 times. Due to the high cost of FTTH, the lack of broadband video service and broadband content and other reasons, the FTTH also failed to mention program to come up, only a small amount of test. Recently, due to the progress of optoelectronic devices, optical transceiver module and optical fiber is greatly reduced price; plus broadband content to alleviate somewhat, have accelerated the process of practical FTTH. Developed on the FTTH view is not exactly the same: the United States AT&T think FTTH market is smaller, at the 0F62003 FTTH 20-50 said: in the years after the market. The United States of America operators Verizon and Sprint positive, in 10 - 12 years with FTTH transformation network. Japan NTT development FTTH originally, now has nearly 2000000 users. At present, China is in the pilot phase of the FTTH. The FTTH [ challenges: now widely used ADSL technology to provide broadband business still has certain advantages. Compared with FTTH : the cheap price of using the original copper net so construction simple, the 1Mbps - 500kbps video transmission which can meet the needs of. FTTH is currently a large number of promotion limited. In the near future to development of broadband business, such as: online education, online office, video conferencing, online games, remote diagnosis, two-way business and HDTV high-definition digital TV, uplink and downlink transmission asymmetry business, ADSL is difficult to satisfy. Especially HDTV, after compression, the transmission rate is 19.2Mbps. Using H.264 technology development, which can be compressed to 5 ~ 6Mbps. Usually think about QOS guarantee ADSL maximum transmission speed is 2Mbps, is still difficult to transmit HDTV. HDTV can be regarded as the main driving force of FTTH. HDTV business comes, FTTH can not be. The FTTH solution: usually have a point P2P point and PON passive optical network two categories. F2P one one advantages: the user independent transmission, mutual influence, system changes flexible; can use inexpensive low-speed optoelectronic module; long transmission distance. Disadvantages: in order to reduce the user directly to the optical fiber and the pipeline bureau, required in the user area user placement of 1 Summary of active node. PON scheme -- advantages: passive network maintenance is simple; in principle can save photoelectron devices and optical fiber. Disadvantages: the need to use the expensive high-speed optoelectronic module; need to use user to distinguish from different electronic module, in order to avoid various user uplink signal conflict with each other; the transmission distance by PON than shorter; the user downlink bandwidth occupied bandwidth to each other, if the user does not guarantee, is not only to the network expansion, also need the replacement of PON and replace user modules to solve the. ( according to the current market price, PEP than PON economy ). PON has a variety of, usually has the following several kinds: ( 1) APON: ATM-PON, for ATM switching network. ( 2) BPON: i.e. broadband PON. ( 3) OPON: using general frame processing OFP-PON. ( 4) EPON: using Ethernet technology PON, 0EPON Gigabit Ethernet PON. ( 5) WDM-PON: using wavelength division multiplexing is used to distinguish the user PON, because the user and the wavelength, so that the maintenance is inconvenient, in FTTH are rarely used in. The developed country develops the FTTH plan and technical scheme, according to the concrete conditions vary. The United States mainly uses the A-PON, because the ATM exchange in the United States of America wide application. Japan NTT having a B-FLETts program, using P2P-MC, B-PON, G-EPON, SCM-PON and other techniques. SCM-PON: is the sub-carrier modulation as multiplexing PON. Chinese ATM use STM SDH is less than APON, are generally not considered. We can account for the P2P, GPON and EPON. P2P scheme have been told, the economy, the use of flexible, far transmission distance should be adopted. The comparison of GPON and EPON, each have advantages and disadvantages. GPON: using the technology of GFP high efficiency network; can have a telephone, suitable for SDH network, combined with IP not EPON good, but the current GPON technology is not very mature. EPON: combined with IP, can the user telephone, such as using the phone with lAD technology. At present, China 's FTTH pilot using EPON more. FTTH technical scheme adopted, also need according to the user's specific situation is different. In recent years, the rapid development of wireless access technology. Can be used as WLAN IEEE802.11g protocol, the transmission bandwidth of up to 54Mbps, coverage of more than 100 meters, has been available commercially. If the wireless access WLAN user data transfer, including: uplink and downlink data and on-demand TV VOD uplink data, for the general user the ascending little, IEEE802.11g can be satisfied. And the use of optical fiber FTTH mainly solves the HDTV broadband video downlink transmission, of course, in need can also contain some downlink data. This form of" fibre to the home + wireless access" ( FTTH + wireless access ) family network. The home network, if the PON, very simple, because the PON does not uplink signal, do not need ranging electronic module, greatly reduced cost, simple maintenance. If, the PON user groups, is a wireless metropolitan area network ( 1EEE802.16 WiMAX ) coverage and can use, so do not have a dedicated WLAN construction. Access network using wireless is a trend, but the wireless access network still needs the clouds on the user near the optical fiber network to support, not much difference between a and FTTH. FTTH + wireless access is the future trend of development.
Photonic switching technology
In fact can be expressed as: communication transmission + exchange. Optical fiber only solves the transmission problem, still need to solve the problem of optical switching. In the past, communication network is formed by metal cable, transmission is the electronic signal, switching is the use of electronic switch. Now, in addition to a user terminal in