科技论文-Optical fiber communication technology, history and status of development.doc

无锡科技职业学院科技论文optical fiber communication technology, history and status of development科技论文题 目optical fiber communication technology, history and status of development 系 别 尚德光伏学院 专 业 应用电子技术（光电子技术方向） 班 级 0901 学生姓名 学 号 090281 指导教师 2012年4 月optical fiber communication technology, history and status of developmentabstract：optical fiber communication line with the high-speed, large capacity, high security, etc., but the practical application of optical fiber communications can transmit information in the human is not easy, their development has experienced many technical difficulties to solve these technical problems, optical fiber communications can be further development.this article from the light source and transmission medium, optoelectronic devices, optical fiber communication systems to demonstrate the development of optical communication technology. key words ：optical fiber cable optical fiber communication technology active devices passive components fiber communication system【body】the inherent advantages of light it is destined to serve as human history, the role can not be ignored, with the development of human technology, its application more widely; the advantages are becoming more prominent.optical fiber communication is to send the image, and data to the optical carrier signal modulation to optical fiber as the transmission medium of communication. as a carrier wave frequency is much higher than the radio frequency as the transmission medium off than coaxial cable or fiber-optic waveguide loss is much lower, so relative to cable communications or microwave communications, optical fiber communication has many unique advantages.highlight the advantages of real applications of optical fiber communications to human life, and many technologies, requires a process of development. first, the formation of optical fiber communication technology (a), the early optical communications light everywhere, this sentence is no exaggeration. early in human development, human beings have begun to use light to transmit information, and there are many such examples.gestures are a form of visual communication, can not be in the dark. the transmission system during the day and the sun as light source, solar radiation carry the senders information transmitted to the recipient, hand movements modulated light, the human eye as detector. in addition, there is a beacon 3000 years ago until now still use the lights, semaphore and so can be regarded as primitive forms of optical communications. the emergence of the telescope and greatly extend the light of these visual forms of communication distance. such optical communication has a significant disadvantage is that they can transport capacity is extremely limited. modern history, as early as 1880, the united states bell (bell) invented the optical telephone. this light telephone use of sunlight or arc lamp as light source, the beam is focused through a lens in front of the vibration transmitter lens, so that the light intensity changes with the voice, to achieve light intensity modulated voice. at the receiving end, with the parabolic reflector came into the beam reflected from the atmosphere into the silicon photo-pool, so that the light signal is transformed into the current transmitted to the receiver. light phone and not get in the lives of actual use, mainly because there was no suitable light source and transmission medium. their use of natural light for non-coherent light, directional well, not easy to modulation and transmission; the air as transmission medium, the loss will be great, can not achieve long-distance transmission, but also vulnerable to weather, traffic and extremely unstable and reliable. it seems that this light the phone and not much practical value, however, we have to say, light phone is still a great invention, its appearance as the carrier proved that transmit information using light waves is possible, therefore, to bell telephone as modern optical communication optical prototype without too much.(b), the formation of modern optical fiber communication technology with the development of society, increasing the amount of information transmission and exchange, the traditional means of communication can not meet peoples needs. in order to expand the communication capacity, communication from wave and short wave developed to microwave, millimeter wave, which is in fact the carrier frequency by increasing communication through communication capacity to expand. continue to improve the frequency band to light, light is the most familiar of electromagnetic waves, the wavelength at the micron level, and the frequency of magnitude compared to hz, which higher than the commonly used microwave frequency times. in view of this, using light as the carrier for communication, communication capacity will greatly exceed the traditional means of communication.to the development of optical communications, the most important issue is to find a light source for optical communications and transmission media. in 1970, fiber optics and laser research at the same time the two come out opened the curtain of optical fiber communication, so we called the optical fiber communication 1970, the year one. 1, light source in 1960, the united states, mailman (thiamin) invented the ruby laser, which can produce coherent monochromatic light that light modulation of high-speed information as possible.and compared to ordinary light, laser with narrow spectral width, direction excellent, high brightness, and the frequency and phase characteristics of a more consistent sound. laser is a highly coherent light, its characteristics and radio wave similar to an ideal optical carrier.however, the ruby laser beam emitted is not easy to transfer coupled into the fiber, the coupling efficiency is very low, so the need to develop miniaturized laser light sources. in 1970, the united states, bell labs, nec corporation (nec) and the former soviet union has broken through the semiconductor laser at low temperature (-200) or under pulsed excitation conditions of work restrictions, the successful development of room temperature continuous operation of the gallium aluminum arsenide (galas) double-heterostructure semiconductor laser (short wavelength). although the life span of only a few hours, but its meaning is significant, it is the development of semiconductor laser basis. in 1973, the semiconductor laser life up to 100,000 hours (about 11.4 years), the extrapolated life of 100 million hours, fully meet the practical requirements. during this period, 1976 ntt developed emission wavelength of 1.3 of indium gallium arsenide phosphorus (inga asp) laser, in 1979 the united states telegraph and telephone (at & t) company, and ntt developed the emission wavelength of 155 consecutive oscillation semiconductor lasers.the invention and application of lasers to make sleeping a 80-year optical communications into a new stage. 2, the transmission medium 1) atmospheric 1961 to 1970, people mainly use of atmospheric transport of optical signals. massachusetts institute of technology use he-ne lasers and lasers for atmospheric laser communication. test proved that carry information using light waves spread through the atmosphere to achieve point to point communication is possible, but there are many atmospheric optical communication transmission serious problems: (1) communication capacity and quality very seriously affected by climate. as rain, fog, snow and atmospheric dust absorption and scattering, light attenuation great. for example, rain can cause 30db/km attenuation, fog attenuation up to 120db/km. (2) the density and temperature of the atmosphere is very uneven, resulting in changes in the refractive index, coupled with the impact of atmospheric turbulence, beam position shift may occur, and jitter. thus the distance and stability of communication are severely limited, can not be achieved all weather communication. (3) atmospheric transmission equipment located at a height requirement, the sending and receiving devices must be a straight line visible. the geographical conditions make the application of atmospheric transport communication has great limitations. although solid-state lasers (for example, neodymium-doped yttrium aluminum garnet (nd: yag) laser) of the invention enhanced the launch optical power, to extend the transmission distance, so that optical communication can cross rivers, islands, and some specific occasions between use, but the atmospheric stability and reliability of laser communication is still not resolved. in order to overcome the impact of climate on laser communication, people naturally think of the laser beam is limited to a particular space transmission. have proposed a waveguide lens and mirror light waveguide transmission system. lens waveguide is a metal tube at regular intervals from the installation of a lens, each lens the beam transmitted through the next lens convergence achieved. mirror waveguide and waveguide transmission similar to that used with the beam propagation direction at the angle of two parallel mirrors instead of lenses and composition. the two waveguides is theoretically feasible, but in practical applications encountered insurmountable difficulties. first of all, on-site calibration and installation of construction is very complicated; secondly, in order to prevent the impact of ground movements on the waveguide, the waveguide must be buried or select vehicles scarce regions.in the absence of finding reliable and low-loss transmission medium, optical communication, once the research into the downturn. 2) fiber to develop the optical communication technology, people have considered and tried a variety of transmission media, including the use made of glass optical fiber to transmit light signals, but the best was the loss of optical glass material in 1000db/km above, such a high transmission loss can not be used simply to communicate. in 1966, the chinese-american kao (ckkao) and hawke hamm (cahockham) published a new concept on the transmission medium paper; it points out the possibility of optical fiber to transmit information and technical approach, and laid a fiber optic communication basis. in 1970, a major breakthrough in fiber development. corning (corning) loss 20db/km company successfully developed the quartz fiber. therefore, the optical fiber and coaxial cable communication can start to compete around the world have invested a lot of manpower and material resources to research and development of optical fiber communication to a new stage. 1972, with the fiber preparation process in the purification of raw materials, rods, and wire drawing technology continues to improve, then the graded-index multimode fiber of the attenuation coefficient decreased 4db/km. in 1973, bell labs developed the fiber loss down to 2.5db/km. 1974 dropped to 1.1db/km. 1976 nippon telegraph and telephone (ntt) company and other units to reduce fiber loss to 0.47db/km (wavelength 1.2). 10 years later, the fiber loss of 1.55 nm (figure 2): 1979 is the 20db/km, 1984 years 0.157db/km, 1986 years 0.154db/km, close to the lowest-loss optical fiber theoretical limit.in 1976, further to lower the glass (oh) content, we found that the attenuation of optical fiber in the long wavelength region is 1.31 and 1.55 the two low-loss windows. in 1976, the united states in atlanta for the worlds first practical optical fiber communication system field test, the system uses galas laser as light source, multi-mode optical fiber as transmission medium, the rate for the 44.736mbit / s, transmission distance of about 10km, so that this test optical fiber communication to the practical first step. in 1980, raw materials, purification and fiber preparation process has been continuously improved; thereby speeding up the fiber transmission window is moved to 1.31 from 0.85 and 1.55 in the process. in particular, made out of low attenuation optical fiber, and its attenuation coefficient of 1.55 0.20db/km, close to the theoretical value. at the same time, to promote practical optical fiber communication systems, people and in a timely manner for the development of long wavelength light source, ice laser, led and light detector. emerged into the fiber cables, optical passive devices, performance testing and engineering instruments, such as technology matures, both for optical fiber transmission medium of communication as a new laid a good foundation. 1981, the worlds developed countries, large-scale fiber-optic communication technology into the business. after 20 years of rapid development, optical fiber communication rate from 1978 to 45mbit / s (such as the u.s. opened in 1991, mci chicago to st.louis length of 275 miles of the 4 10gbit / s optical fiber communication systems for commercial, etc.). second, the development of optical communication technology and its from a macro point of view, including fiber optic cable optical fiber communication, optoelectronic devices and optical communication system equipment such as three parts. (a), optical fiber cable the advantages of optical fiber and its inherent technological advances to become the main medium of social information transmission. figure 3 shows the consumption of fiber optic cable in north america more, accounting for nearly 25% of the world, followed by europe. the amount of global fiber consumption increased year by year, which shows that the fiber market demand is increasing, its application more widely. figure 4 shows the single mode, multimode fiber to increase overall spending, combined with figure 5, figure 6 and can know the market share of single-mode fiber has declined, while multimode fiber applications become more widespread. (b), optoelectronic devices1, optical active devices 1) optical detector common optical detector includes: pn photodiode, pin photodiode and avalanche photodiode (apd). the current optical detector can basically meet the requirements of the optical fiber transmission, in the actual optical receiver, optical signals coming from its weak, sometimes only about 1mw. in order to obtain a larger signal current, it is hoped that the sensitivity as high as possible. photoelectric detectors work, the signal delay is completely impossible, but must be limited to a range; otherwise the photo detector will not work. as the transmission rate of optical fiber communication systems continue to improve the transmission of high-speed photo detector response speed of the increasingly high demand of its manufacturing technology put forward higher requirements. the photoelectric detector is in an extremely weak signal conditions, work, and it is in the forefront of optical receiver, if the optical noise introduced during the transformation is too large, then the signal to noise ratio will reduce the impact to reproduce the original signal. therefore, the photoelectric detector noise requirement is small. in addition, the requirement of the main properties of the detector is not possible or less susceptible to external temperature changes and environmental changes. 2) optical amplifiers the emergence of optical amplifiers so that we can save the traditional long-distance optical fiber transmission systems indispensable light - electricity - light conversion process, making the circuit becomes relatively simple, reliability becomes higher. laser invented as early as 1960 soon, people began to study the optical amplifier, but the real beginning of the study is practical after 1980. with the improvement of semiconductor lasers, first appeared in fabry - perot semiconductor laser amplifier, and then embarked on a traveling wave semiconductor laser amplifier research. on the other hand, the development of optical fiber technology with the emergence of fiber raman amplifiers. late 80s, rare earth doped fiber amplifier stand out, and soon reached the practical level, applied in overseas long-distance optical communication systems. present to the optical amplifier for optical fiber communication semiconductor laser amplifier and the main rare earth doped fiber amplifier, in particular, erbium-doped fiber amplifier (edfa) favorites. university of southampton in 1985 for the development of erbium-doped fiber for the first time since 1989 of erbium-doped fiber amplifier continuously made significant breakthroughs. since the advent of optical amplifiers, in 1990 and 1992 less than two years, the fiber optic system capacity actually increased by an order of magnitude. in 1982 to 1990, 8 years, the capacity of optical fiber system was only increased by an order of magnitude. the role of optical amplifiers and fiber optic transmission capacity by leaps and bounds, in order to show the infinite optical fiber communication broad prospects for development. the current optical fiber communication systems operating in two low-loss window: 1.55-band and 1.31 bands. select a different doping element, the amplifier can work in a different window. erbium-doped fiber amplifier in the 1.55 window that window is the fiber loss coefficient lower than 1.31 (only 0.2db/km). edfa is a commercial low noise, good gain curve, the amplifier bandwidth, and wavelength division multiplexing (wdm) compatible, pump, high efficiency, stable performance, mature technology, in the modern long-distance high-speed optical communication systems become widely accepted. praseodymium-doped fiber amplifier operating in 1.31m band has been laying fiber 90% work in the window. pdfa optical c