After the Spring Festival, China Telecom organized the first domestic 100G system technology test. Industry insiders expect that after the test is completed, 100G commercial trials will be launched soon. The reason why telecommunications operators conduct 100G system technology testing at this point in time is on the one hand to cope with the rapid growth of network traffic. On the other hand, because the technology is maturing, commercial opportunities have already arrived. The application of 100G optical network is mainly in the inter-provincial and inter-city trunk network, so the realization of long-distance transmission is one of the key points. The reason for limiting the long-distance transmission is that the quality of the optical fiber is not ideal, and there are optical losses such as dispersion and polarization dispersion, and ultimately it cannot be transmitted. It is therefore self-evident and practical to realize the remote transmission of the 100G optical network. .
Signal regeneration is a remedy for the drawbacks caused by optical fiber quality limitations in optical transmission. In traditional networks, signal regeneration is usually used to solve the problem.
A few days ago, Alcatel-Lucent claimed that its new solution can get rid of fiber quality limitations and achieve long-distance transmission. For this reason, the reporter conducted an in-depth interview on its solution.
“A major objective of optical transmission in the long run is to improve the efficiency of transmission and the distance of transmission. The main aspect of limiting long-distance transmission is that the quality of optical fiber is not very satisfactory. There are dispersion, polarization dispersion, and loss. These factors eventually make The signal gradually weakens, noise gradually increases, the signal is submerged in the noise and cannot be transmitted far away.†said Ding Hao, Director of Advanced Tendering Solutions at Shanghai Bell's Cable Product Capability Center at Alcatel-Lucent China flagship company. “This situation is common to all high-speed transmissions. Existence, 10G, 40G optical transmission has already appeared this kind of situation, the greater the transmission bandwidth is in the future, the more obvious this kind of situation. This kind of situation is mainly caused by the limitation of the optic fibre quality, this is a few defects of the optic fibre itself.
In traditional networks, it is a common practice to perform signal regeneration. The process of regeneration is to convert the optical signal into an electrical signal, and then convert the electrical signal to an optical signal, and an optical-electrical-optical conversion occurs so that the damaged signal becomes the original signal. “Actually, we thought for many years and hope to be able to do regeneration in the optical domain, but the actual situation is still far from this solution. There is no way to do the conversion of light-electricity-light, and the benefits are light. The signal-to-noise ratio is back to a relatively high level, but the cost is the increase in cost and power consumption." Ding Hao said.
In addition to signal regeneration, dispersion compensation is also required on some older 10G and 40G systems. Many old systems do not use related optical technologies. After a certain distance is transmitted, dispersion and positive dispersion are unbearable. This situation is particularly evident in 40G transmission, and it is necessary to add negative dispersion fibers. The actual transmission distance of the optical fiber and the dispersion compensation fiber ratio is 7:1, which means that more than ten kilometers of dispersion compensation fiber needs to be added for transmission of 100 kilometers.
The new modulation technology has been recognized as relatively uniform in 100G optical communication modulation methods. After the expansion of 100G production, it will help reduce costs and accelerate the overall development of the industry.
On 10G or 40G, the modulation method of the previous light is direct modulation or phase modulation. If 100G continues to use phase modulation, the baud rate of transmission will be 50G or even higher, resulting in serious loss of the optical signal noise ratio. Positive-polarity-multiplexing four-phase correlated optical modulation makes the actual baud rate of 100G information rate in the transmission drop to 25G. With the introduction of coherent optical technology, the receiver's optical signal to noise ratio can be improved, and high-speed electrical signal processing can be used at the receiving end to effectively compensate for polarization dispersion and dispersion, thereby minimizing those factors that affect long-distance transmission. "These technologies will increase the transmission distance of 100G optical networks." Ding Hao said, "Alcatel-Lucent's recently introduced enhanced equipment has made finer choices in the choice of devices and adjustment of key receiver parameters. And nonlinear dispersion is more effective, the optical signal can go further.
According to reports, with the new modulation technology and enhanced equipment, the transmission distance can be increased from 1,500 to 1,600 kilometers to 2000 to 2,500 kilometers, an increase of 30%.
Currently, optical communication companies are strengthening their research on QPSK. In 100G optical communications, the industry will adopt more uniform modulation technologies. In 10G and 40G transmission, there are multiple modulation technologies. Each of these modulation methods has its own advantages and disadvantages. Operators face a variety of solutions. Although there are many solutions, each solution has a limited scale and prices cannot be further reduced. The relative unification of 100G optical communication modulation methods will increase the output of 100G and reduce the cost, which is conducive to the overall development of the industry.
100G All-optical Network Benefits Obviously 100G optical transmission, after getting rid of fiber quality limitations, has practical significance for operators.
100G optical transmission to get rid of fiber quality limitations, the operator's practical significance is reflected in two aspects: First, can significantly reduce the cost per bit and power consumption; Second, can significantly improve the transmission efficiency.
In general, all signal processing at the optical level is more cost-effective than at the electrical level. For each bit, the optical network will be better in terms of power consumption, cost, and floor space of the equipment room. “Alcatel-Lucent proposed to be able to do at the optical level as far as possible on the optical level, only on the optical level can not be handled, must be handled at the electrical level before entering the electrical level.†Ding Hao told reporters. To get rid of optical fiber quality restrictions and reduce the need for regeneration, it is to solve the problem at the optical level in solving the transmission distance.
At present, the service traffic of China's operator backbone network, provincial network and metropolitan area network grows very fast. Wei Leping, director of the China Telecom Science and Technology Commission, believes that network traffic is growing at a rate of 40% to 60%. The flow of a connection between a national trunk line and a metropolitan area network has reached the order of 10G to 1T, and the transmission particles are getting larger and larger. This magnitude is comparable to or even larger than the one that can be carried by a single wavelength of 100G. Therefore, 100G transmission, the efficiency has improved significantly.
“We have done a lot of analysis, including metropolitan area networks, provincial networks, and backbone networks. We have also done many projects abroad. If the network is as close as possible to the optical layer and 100G level, only CAPEX (capital expenditures) can save 20 From 5% to 50%, OPEX (Operational Expenditure) has a more pronounced reduction effect. Usually, the investment in a provincial backbone network is on the order of US$10 million. If CAPEX can save 30%, there will be very huge benefits, and the significance is also very significant. big."
Signal regeneration is a remedy for the drawbacks caused by optical fiber quality limitations in optical transmission. In traditional networks, signal regeneration is usually used to solve the problem.
A few days ago, Alcatel-Lucent claimed that its new solution can get rid of fiber quality limitations and achieve long-distance transmission. For this reason, the reporter conducted an in-depth interview on its solution.
“A major objective of optical transmission in the long run is to improve the efficiency of transmission and the distance of transmission. The main aspect of limiting long-distance transmission is that the quality of optical fiber is not very satisfactory. There are dispersion, polarization dispersion, and loss. These factors eventually make The signal gradually weakens, noise gradually increases, the signal is submerged in the noise and cannot be transmitted far away.†said Ding Hao, Director of Advanced Tendering Solutions at Shanghai Bell's Cable Product Capability Center at Alcatel-Lucent China flagship company. “This situation is common to all high-speed transmissions. Existence, 10G, 40G optical transmission has already appeared this kind of situation, the greater the transmission bandwidth is in the future, the more obvious this kind of situation. This kind of situation is mainly caused by the limitation of the optic fibre quality, this is a few defects of the optic fibre itself.
In traditional networks, it is a common practice to perform signal regeneration. The process of regeneration is to convert the optical signal into an electrical signal, and then convert the electrical signal to an optical signal, and an optical-electrical-optical conversion occurs so that the damaged signal becomes the original signal. “Actually, we thought for many years and hope to be able to do regeneration in the optical domain, but the actual situation is still far from this solution. There is no way to do the conversion of light-electricity-light, and the benefits are light. The signal-to-noise ratio is back to a relatively high level, but the cost is the increase in cost and power consumption." Ding Hao said.
In addition to signal regeneration, dispersion compensation is also required on some older 10G and 40G systems. Many old systems do not use related optical technologies. After a certain distance is transmitted, dispersion and positive dispersion are unbearable. This situation is particularly evident in 40G transmission, and it is necessary to add negative dispersion fibers. The actual transmission distance of the optical fiber and the dispersion compensation fiber ratio is 7:1, which means that more than ten kilometers of dispersion compensation fiber needs to be added for transmission of 100 kilometers.
The new modulation technology has been recognized as relatively uniform in 100G optical communication modulation methods. After the expansion of 100G production, it will help reduce costs and accelerate the overall development of the industry.
On 10G or 40G, the modulation method of the previous light is direct modulation or phase modulation. If 100G continues to use phase modulation, the baud rate of transmission will be 50G or even higher, resulting in serious loss of the optical signal noise ratio. Positive-polarity-multiplexing four-phase correlated optical modulation makes the actual baud rate of 100G information rate in the transmission drop to 25G. With the introduction of coherent optical technology, the receiver's optical signal to noise ratio can be improved, and high-speed electrical signal processing can be used at the receiving end to effectively compensate for polarization dispersion and dispersion, thereby minimizing those factors that affect long-distance transmission. "These technologies will increase the transmission distance of 100G optical networks." Ding Hao said, "Alcatel-Lucent's recently introduced enhanced equipment has made finer choices in the choice of devices and adjustment of key receiver parameters. And nonlinear dispersion is more effective, the optical signal can go further.
According to reports, with the new modulation technology and enhanced equipment, the transmission distance can be increased from 1,500 to 1,600 kilometers to 2000 to 2,500 kilometers, an increase of 30%.
Currently, optical communication companies are strengthening their research on QPSK. In 100G optical communications, the industry will adopt more uniform modulation technologies. In 10G and 40G transmission, there are multiple modulation technologies. Each of these modulation methods has its own advantages and disadvantages. Operators face a variety of solutions. Although there are many solutions, each solution has a limited scale and prices cannot be further reduced. The relative unification of 100G optical communication modulation methods will increase the output of 100G and reduce the cost, which is conducive to the overall development of the industry.
100G All-optical Network Benefits Obviously 100G optical transmission, after getting rid of fiber quality limitations, has practical significance for operators.
100G optical transmission to get rid of fiber quality limitations, the operator's practical significance is reflected in two aspects: First, can significantly reduce the cost per bit and power consumption; Second, can significantly improve the transmission efficiency.
In general, all signal processing at the optical level is more cost-effective than at the electrical level. For each bit, the optical network will be better in terms of power consumption, cost, and floor space of the equipment room. “Alcatel-Lucent proposed to be able to do at the optical level as far as possible on the optical level, only on the optical level can not be handled, must be handled at the electrical level before entering the electrical level.†Ding Hao told reporters. To get rid of optical fiber quality restrictions and reduce the need for regeneration, it is to solve the problem at the optical level in solving the transmission distance.
At present, the service traffic of China's operator backbone network, provincial network and metropolitan area network grows very fast. Wei Leping, director of the China Telecom Science and Technology Commission, believes that network traffic is growing at a rate of 40% to 60%. The flow of a connection between a national trunk line and a metropolitan area network has reached the order of 10G to 1T, and the transmission particles are getting larger and larger. This magnitude is comparable to or even larger than the one that can be carried by a single wavelength of 100G. Therefore, 100G transmission, the efficiency has improved significantly.
“We have done a lot of analysis, including metropolitan area networks, provincial networks, and backbone networks. We have also done many projects abroad. If the network is as close as possible to the optical layer and 100G level, only CAPEX (capital expenditures) can save 20 From 5% to 50%, OPEX (Operational Expenditure) has a more pronounced reduction effect. Usually, the investment in a provincial backbone network is on the order of US$10 million. If CAPEX can save 30%, there will be very huge benefits, and the significance is also very significant. big."
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