At present, Broadband Metropolitan Area Network (BMAN) is becoming a hot spot in informatization construction. The huge bandwidth and transparency of data transmission of DWDM (Dense Wavelength Division Multiplexing) are undoubtedly the preferred technology in today's optical fiber applications. . However, MAN has the characteristics of short transmission distance, flexible topology and multiple access types. If you copy DWDM, which is mainly used for long-distance transmission, the cost will be too high. At the same time, early DWDM is also difficult to adapt to the flexibility and diversity of MAN. Faced with this low-cost metropolitan-wide broadband demand, CWDM (Coarse Wavelength Division Multiplexing) technology came into being and quickly became a practical device. For optical communications, its technology is basically mature, but business needs are relatively insufficient. Take FTTH, known as the "ultimate goal of broadband access," as an example. Its implementation technology, EPON, is fully mature. However, due to the low bandwidth required by ordinary users to access the Internet, the commercial use of FTTH is limited to some pilot areas. However, in 2006, with the development of triple play services such as IPTV, the bandwidth provided by operators could no longer meet users' requirements for high-definition TV, and the deployment of FTTH was also put on the agenda. Coincidentally, ASON has flexible control over the transmission network and can provide personalized services for enterprise customers. In order to develop and maintain enterprise customers, many operators have invested heavily in the construction of ASON.
All-optical network The ultimate goal of future transmission networks is to build an all-optical network, that is, to fully realize "fiber transmission instead of copper wire transmission" in access networks, metropolitan area networks, and backbone networks. All current research and development progress is a process of "approaching" this goal. In the 1930s, someone put forward this view: "One day optical communications will replace wired and microwave communications and become the mainstream of communications." This view reflects the importance that optical fiber communication technology has shown in future communications. Today, optical communication technology is very mature. Optical fiber communication has become the main transmission method of various communication networks. Optical fiber communication plays a vital role in the construction of information highways. Developed countries such as Europe and the United States have placed optical fiber communication on strategic position for national development. Nowadays, the use of optical fiber is not limited to land. Optical fiber cables have been widely laid to the bottom of the Atlantic and Pacific Oceans. These submarine optical cables make global communications very simple and fast. Many developed countries are now laying optical cables in front of homes, realizing optical fiber to the office and fiber to the home. The reason why optical fiber communication technology develops so rapidly is mainly determined by the advantages of optical fiber communication itself, in addition to people's growing needs for information transmission and exchange.
Big events in optical communications
—In 1880, American telephone inventor Bell had researched and successfully sent and received optical telephones. In 1881, Bell read out a paper entitled "On the Generation and Reproduction of Sound by Light," reporting on his photophone device.
——Between 1930 and 1932, Japan achieved 3.6 kilometers of optical communication between the Nippon Telegraph Company in Tokyo and the Mainichi News Agency, but the effect was very poor in foggy and rainy weather. During World War II, optical telephones developed into infrared telephones because infrared rays are invisible to the naked eye and are more conducive to confidentiality.
--In 1854, the British Tyndall pointed out in a lecture at the Royal Society that light can be reflected and transmitted along a curved pipe filled with water, and confirmed this idea with experiments.
--In 1927, Baird of the United Kingdom used the phenomenon of total light reflection for the first time to make quartz fiber resolvable images, and obtained two patents.
——In 1951, the Netherlands and the United Kingdom began to develop soft fiberscopes.
--In 1953, the Dutchman Van Hel coated a plastic with a refractive index of 1.47 on the glass fiber to form a jacket layer with a lower refractive index than the glass fiber core, and obtained a single optical insulation. root fiber. However, due to the uneven plastic coating, the loss of light energy is too great.
——In July 1960, the world’s first ruby ??laser appeared. In September 1961, China's first ruby ??laser was successfully developed by the Changchun Institute of Optics and Precision Mechanics of the Chinese Academy of Sciences.
——In the 1960s, some laboratories used helium-neon gas lasers to conduct experiments on transmitting television signals and 20-way telephone calls. Some companies have also developed language channel experimental communication systems with a maximum transmission distance of 600 meters. By the early 1980s, laser communications had entered the application development stage.
--In 1966, Dr. Kun Gao, a British-Chinese, first proposed the idea of ??using optical fibers for laser communications, and for this he won the International Ilysin Communications Prize awarded by the King of Switzerland in May 1979.
--In 1968, two Japanese companies jointly announced the development of a new type of unjacketed optical fiber that could focus and image, called focusing fiber. At the same time, the United States announced the creation of liquid fiber, which is composed of quartz capillary tubes filled with highly transparent liquid. The optical loss of these two types of optical fibers is difficult to reduce, so they have little practical value.
--In 1970, the American Corning Company used high-purity quartz to produce the world's first jacketed optical fiber with a loss rate of 20 decibels per kilometer, which opened a new chapter in optical fiber communications and made a leap forward in communication optical fiber research. A big step forward. One optical fiber can transmit 1.5 million telephone lines and 20,000 television sets.
--In 1976, Japan began to prepare to build the world's first experimental area for optical communication using optical cables in Nara County near Dagu. By July 1978, it had 300 users. (In fact, the optical communication system does not use a single optical fiber, but an optical cable composed of many optical fibers gathered together. An optical cable with a diameter of 1 cm has nearly a hundred optical fibers in it. Optical cables can be installed just like electrical cables. In the air, buried underground, or laid on the seabed, its emergence has brought laser communication into the practical application stage)
——Many countries in the world have begun to use optical communication technology on a large scale to increase transmission capacity. and transmission distance have been greatly improved. At present, our country has also laid a large number of optical fiber networks. The data transfer rate has reached 100Gb/ps. After foreign breakthroughs in low-loss optical fibers in the 1970s, my country began research on low-loss optical fibers and optical communications in 1974, and developed low-loss optical fibers and semiconductor lasers that can emit continuous light at room temperature in the mid-1970s. In 1979, local optical cable communication test systems were built in Beijing and Shanghai respectively, which was only more than two years later than the first field test in the world. These achievements became a good start for my country's optical communication research and made our country one of the few countries with experimental sections for optical cable communication systems at that time. By the end of the 1980s, my country's key technologies for optical fiber communications had reached the international advanced level.
Since 1991, my country has no longer built long-distance cable communication systems, but has vigorously developed optical fiber communications. During the "Eighth Five-Year Plan" period, an "eight horizontal and eight vertical" large-capacity optical fiber communication trunk transmission network containing 22 optical cable trunk lines and a total length of 33,000 kilometers was built. In January 1999, my country's first national first-level trunk line (Jinan-Qingdao) with the highest transmission rate, an 8×2.5Gb/s dense wavelength division multiplexing (DWDM) system, was completed, which expanded the communication capacity of a pair of optical fibers. 8 times.
At present, many countries in the world have begun to apply optical communication technology on a large scale, and transmission capacity and transmission distance have made great progress. In the Chinese market, in the field of Internet access, Internet users of basic telecommunications companies are further moving toward broadband. As of 2012, China's Internet broadband users are expected to reach 176 million, with an annual growth rate of 17. In terms of mobile broadband, 3G has entered a stage of large-scale development. It is expected that China's 3G users will grow to 226 million by the end of 2012, exceeding the number of Internet broadband access users. At the same time, my country has also laid a large number of optical fiber networks. The data transfer rate has reached 100Gb/ps. For optical communications, its technology is basically mature, but business needs are relatively insufficient. Take FTTH, known as the "ultimate goal of broadband access," as an example. Its implementation technology, EPON, is fully mature. However, due to the low bandwidth required by ordinary users to access the Internet, the commercial use of FTTH is limited to some pilot areas.
However, after 2006, with the development of triple play services such as IPTV, the bandwidth provided by operators can no longer meet users' requirements for high-definition TV, and the deployment of FTTH has also been put on the agenda. Coincidentally, ASON has flexible control over the transmission network and can provide personalized services for enterprise customers. Many operators have invested heavily in the construction of ASON in order to develop and maintain enterprise customers.
According to media reports, as of 2010, my country’s average broadband access rate ranked 71st in the world, with an average downlink rate of only 1.8Mbps, only 1/3 of the global average broadband access rate of 5.6Mbps. It is less than 1/10 of that of developed countries such as the United States and Japan, but the average broadband access cost is 3-4 times that of developed countries.
Although my country's broadband development currently lags far behind that of developed countries, data shows that my country's optical fiber communication technology and product equipment are already at the world's leading level, with the world's largest and most complete optical communication industry chain. Become a major player in the global optical communication device market and product output.
The optical fiber communication system mainly includes three parts: optical communication equipment, optical fiber cables and optical communication devices. Optical communication devices are the basis for building optical communication systems and networks, determining high-speed optical transmission equipment and long-distance optical transmission equipment. and the development, upgrade, promotion and application of intelligent optical networks.
According to the analysis of "China Optical Communication Device Industry Market Forecast and Investment Strategic Planning Analysis Report", with the acceleration of infrastructure construction in my country's optical communication industry, the optical communication device industry has gradually transferred to China, and our country has also become An important production and sales base in the world. In 2010, the devices manufactured in China accounted for more than 25% of the global market share. my country's optical device market share in the global market also increased from 17% in 2008 to about 26% in 2010, with a scale of 9.3 billion yuan, a year-on-year growth rate 30. The ultimate goal of the future transmission network is to build an all-optical network, that is, to fully realize "fiber transmission instead of copper wire transmission" in the access network, metropolitan area network, and backbone network. All current research and development progress is a process of "approaching" this goal.
The backbone network is a part of the network that has the highest requirements for speed, distance and capacity. Applying ASON technology to the backbone network is an important step in realizing the intelligence of optical networks. The basic idea is that in the past optical transmission network An intelligent control plane is introduced to realize on-demand allocation of resources. DWDM will also play a role in the backbone network, and may completely replace SDH in the future, thereby realizing IPOVERDWDM.
The metropolitan area network will become a bottleneck for operators to provide bandwidth and services. At the same time, the metropolitan area network will also become the largest market opportunity. At present, MSTP technology based on SDH is mature and has good compatibility. Especially after adopting new standards such as RPR, GFP, LCAS and MPLS, it can support various data services flexibly and effectively.
For access networks, FTTH (fiber to the home) is an ideal long-term solution. The evolution route of FTTx will be the process of gradually bringing optical fiber closer to users, that is, from FTTN (fiber to the community) to FTTC (fiber to the roadside) and FTTB (fiber to the apartment building) and finally to FTTP (fiber to the premises) . Of course, this will be a long transition period, during which fiber access will coexist with ADSL/ADSL2.
There are many core technologies based on the above-mentioned all-optical network architecture, which will lead the future development of optical communications. The following focuses on the four most important technologies of ASON, FTTH, DWM, and RPR.