The communications industry is in an exciting period of innovation and change.
Among them, the mobile Internet can be said to be one of the most eye-catching hotspots in this round of changes. The emergence of a series of intelligent terminals and the popularity of 3G have enabled all ordinary people to truly realize the dream of accessing the Internet anytime and anywhere. Under the support of 3G networks, people can not only obtain information through intelligent terminals, but also realize many functions that were previously unimaginable, such as video browsing, location services, online games, and so on.
According to Bell Labs' analysis, by 2014, there will be 1.2 billion connected mobile terminals represented by iPad and 2.5 billion smartphones worldwide. The data growth brought by all these terminals is explosive. According to statistics, the monthly traffic of smartphones is 35 times that of ordinary function phones, while the data traffic of a tablet computer is 121 times that of ordinary mobile phones. Laptops with Internet cards. The traffic even reached 498 times that of ordinary mobile phones.
Driven by these new intelligent terminals, by 2014, the mobile Internet business will account for 70% of all mobile data; by 2015, the total mobile data will be 30 times that of 2010; by 2017, the world will have The 107EB data comes from a variety of mobile terminals. Therefore, some people say that we are facing a data tsunami, then is our basic network ready to respond?
The response of optical networks
As a basic network, optical networks need to be prepared for bandwidth growth in advance. At present, the optical transport network has evolved from today's 10G, 40G to 100G. From InfoneTIc's statistics, it can be seen that by 2014, the number of 100G boards based on coherent detection technology will account for 40% of all rates.
From the current situation, the 100G standard is fully mature. IEEE, ITU-T, OIF and CCSA have made a perfect definition of the 100G system architecture, module interface, link standard, and device technical specifications and test specifications. In the fields of routers, optical transmission, optical modules and test instruments, there are already many manufacturers that can provide mature commercial products. Therefore, it can be said that the entire ecosystem of 100G has been perfected.
Compared with the diversity of 40G coding methods, the 100G technology route is quite clear, and the industry-recognized PDM-QPSK+ coherent detection is the best solution for 100G. However, 100G is not the end of optical network bandwidth evolution. At present, various manufacturers have begun research on 400G or even 1T systems. However, we can see from Figure 1 that the development of systems above 100G is limited by Shannon's law and must be balanced in terms of spectrum efficiency, performance and capacity.
As shown in Figure 1, if the modulation phase is developed from the current 4-phase of 100G to 16-phase of 400G, the OSNR requirement of the system will increase by 3.8dB; if it is further increased to 256-phase, the system OSNR will reach 19dB or more. Undoubtedly, the transmission distance of the system will be greatly shortened.
If you want to achieve 400G or even T-bit transmission, we can improve in the following aspects.
1. Higher performance DSP processing chip. It gives us the ability to introduce SD-FEC, which can roughly improve the system OSNR performance by about 1.5dB compared to HD-FEC, that is, the purple point in Figure 1 is 1.5dB to the limit of the Shannon curve. Of course, SD-FEC will bring more overhead bytes, higher cost and longer delay. We need to adopt flexible according to the actual needs of the network. For 100G systems, HD-FEC-based technology can already achieve 2000 km of non-electrical relay transmission, which can meet the needs of most networks; but for systems above 400G, SD-FEC is a technology that must be adopted.
2. Flexible grid technology. The transmission rate after 100G generally requires a spectrum larger than 50 GHz. For example, the theoretical spectrum bandwidth of 400G using dual carrier frequency and 16 phase multiplexing is 100 GHz. After some technical processing, the spectrum bandwidth can be compressed to 75 GHz, which brings a signal problem of how to effectively arrange different spectral widths in the C-band. Flexible grid technology defines a spectral width of at least 12.5 GHz, allowing flexible routing of different signals in this unit to maximize spectrum utilization.
3.Raman light. Raman light is not a new technology. When we enter the speed above 100G, we need to get better system OSNR. The low noise figure of Raman light is very helpful.
4. Super channel (superchannel). A high-speed signal of a T bit level can be obtained by modulating several 100G signals together. Usually these sub-signals are modulated by OFDM to obtain the best spectral efficiency. Since each sub-signal is a 100G channel, the 100G DSP and related processing techniques can be seen as the basic module for building higher rate signals.
5. Advanced power control technology. It is well known that higher fiber-input power results in better OSNR performance, but at the same time leads to greater nonlinearity. In systems above 100G, we need to better control the fiber input power of each channel, achieving the best point between OSNR and nonlinearity.
Alcatel-Lucent's high-speed delivery solution
As early as June 2010, Alcatel-Lucent took the lead in launching a single-carrier 100G correlation detection commercial system on the OTN platform 1830PSS. So far, it has been widely used in more than 60 customer networks around the world. The cumulative number of 100G OTU shipments exceeds 2,300, accounting for more than 69% of the global 100G market share, and it is an undisputed leader.
In December 2011, Alcatel-Lucent announced an enhanced 100G solution that increased the distance from 1,500 km to 2,000 km. In March 2012, Alcatel-Lucent once again released a new generation of PSE-Photonic Service Engine for 100G and 400G. The engine uses four key technologies to further enhance performance.
1. Introducing SD-FEC to improve system performance by 1.5dB, so that the 100G system's unpowered relay transmission distance is further extended to 3000 kilometers.
2. Advanced wavelength shaping technology compresses the 400G spectrum bandwidth to 75GHz, and can accommodate up to 58 channels in the C band, thus increasing the maximum capacity of the system from the original 8.8T (88x10G) to 23T (58x400G). , expanded by 2.6 times the network capacity.
3. Higher sampling rate and ultra-fast digital-to-analog conversion make the decision of the signal more accurate.
4. Enhanced frequency and phase control techniques to suppress slip codes.
In addition to continuously improving network transmission capacity, Alcatel-Lucent is also constantly innovating in the transmission network architecture. Alcatel-Lucent is the first to propose the concept of CBT (Convergent Backbone Transport), that is, use low-level bypass high-rises as much as possible, and use high-rises only when necessary; try to bypass the electrical layer with light layer and use the electrical layer only when necessary.
This is because the lower the processing level, the higher the transmission efficiency and the lower the power consumption per bit. For large granular services such as 100G in the backbone network, because the convergence requirements are usually completed in the aggregation layer, and the service destination is clear and single, the ROADM-based optical layer scheduling can best achieve efficient transmission. In the aggregation layer, in order to increase the bandwidth filling rate, an ODU cross-matrix can be introduced to complete aggregation based on small-particle services. The router is introduced only at a site that really needs to open a packet for more than three layers.
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