The annual China Optical Network Symposium did not come as scheduled, but was postponed to this week for some well-known special reasons. But better late than never! Every year, the industry expects to get the latest development status, problems and future development trend of optical communication industry from Wei Leping.

In the special year of 2020, China Optical Network seminar also ushered in the 20th session. All kinds of elites in the optical communication industry chain gathered in Beijing again in such a special period to talk about the future of optical communication industry. At the “2020 China Optical Network seminar” held today, with “the development trend and thinking of trunk optical communication” as the theme, Wei Leping, executive deputy director of the communication science and Technology Commission of the Ministry of industry and information technology, director of the science and Technology Committee of China Telecom Group Corporation, and chairman of the China Optical Network seminar, shared the following views with us:

“Capacity crisis” will emerge eventually

China Telecom launches the world's largest all-optical backbone network -- all optical network 2.0

In Wei Leping’s view, the biggest driving force of all-optical network is capacity, and the demand and improvement of capacity are endless.

Ten years ago, it was predicted that the Shannon limit of single fiber capacity would be exceeded by 2020, and the existing technology would be difficult to cope with, and there might be a capacity crisis, but this prediction did not come true ten years later. Wei Leping thinks that there are three main reasons for the absence of “capacity crisis”

First, the demand side slowed down. The growth rate of global Internet traffic dropped from 40% to 24%, easing the pressure of network expansion.

Second, supply side progress. DWDM direction: first of all, the current C-band 80 wave can be expanded to C-band 96 wave at a very low cost, with 20% expansion gain; at the same time, there is no insurmountable technical barrier to further expand to ultra wideband C-band 120 wave, and even 192 wave in C + L band, but it needs the support of ecosystem, including laser and newly doped fiber amplifier; the latter two steps of technical improvement still need to be improved Only with the support of economic feasibility and in line with the law of significantly reducing the cost per bit can it be popularized; TDM direction – since PDH system, TDM direction has always been developing according to the rule that the rate is increased by 4 times, and the cost is only increased by 2.5 times, that is, the transmission cost of single bit transmission should be reduced by about 35% when the rate is upgraded by 4 times; the transmission distance of single wave 400gbps can be extended from 600km to 1000km with the new odsp More than km, meeting the requirements of trunk line application.

Third, China’s trunk line expansion strategy choice in the near and medium term. In order to avoid frequent upgrade and expansion of trunk network, trunk system should continue to follow the expansion rhythm of 4 times of capacity step in principle, that is, upgrade directly from the current n * 100gbps to the n * 400gbps system; in the local congestion section, it can be upgraded to the n * 200gbps system first.

The trend of the maximum link capacity of China Telecom transmission network is as follows: from 2008 to 2018, the maximum link capacity of the actual transmission network will increase by 42%; the growth rate from 2018 to 2023 may still reach 18%; the maximum capacity will exceed 100TB / s in 2019 and 200tb / s in 2023.

From the perspective of the trend of the largest node capacity of China Telecom transmission network, the annual average growth rate of the largest node capacity of the actual transmission network from 2008 to 2018 is 40%; the growth rate from 2018 to 2023 may still reach 20%, but the growth rate will be halved; the maximum capacity will exceed 300tb / s in 2019 and 600tb / s in 2023. In terms of the capacity evolution of all-optical nodes, 20-dimensional WSS will be implemented in 2017, 32-dimensional WSS in 2019, and 64 dimensional WSS may be made in 2023.

Wei Leping believes that the “capacity crisis” will eventually emerge: first, from the overall view of the expansion path, the basic dimension resources of optical communication expansion include amplitude, phase, frequency / wavelength, polarization, time, and airspace. The development of WDM dimension expansion and TDM dimension technology selection progress mentioned above is limited, so it is difficult to cope with the long-term capacity pressure; secondly, at present, the only one The only space resources that have not been fully exploited and utilized are airspace resources, that is, the capacity can be expanded by increasing the number of space parallel transmission channels; at the same time, in the medium and long term, more optical fibers, especially routing fiber shortage areas, are used; in addition, in the long run, the development of multi-core and small mode fiber and even angular momentum multiplexing technology is still in the early stage of research, and its economy is not clear, and there is also application level capacity Moderation and coding progress are still necessary.

Building all optical network in five dimensions

Since the “capacity crisis” will eventually appear, all optical network will become the only way. However, what are the challenges facing all optical networks? How to deal with it? Wei Leping put forward the following points:

First, it is necessary to reduce the recovery time of all-optical network. At present, the recovery time of all-optical network is several minutes, which is expected to be reduced to 10 seconds or even seconds. There are four ways to reduce network recovery time: one is to implement service classification according to service value to ensure the recovery time of high-value service, and even issue protection route link table in advance; the second is centralized routing + distributed control architecture, which introduces centralized routing PCE to effectively avoid wavelength conflict of rerouting and reduce recovery time; the third is to introduce SDN, which is expected to be the best With the bandwidth resources of the whole network, the convergence speed can be shortened and the delay can be reduced. SDN can also obtain the shortest delay service path according to the reported link conditions. Fourthly, ML is introduced to realize the prediction of optical performance degradation, optical fiber or equipment failure, saving the service debugging and recovery time and even active rerouting.

Second, we need to reduce the cost of all-optical network. Whether ROADM can further expand to the edge of the network is the key to cost, and the key to reduce the cost is technological innovation and economies of scale. In terms of physical layer innovation, the first is to remove unnecessary functions and unnecessary temperature requirements at the network edge, relax device requirements, omit heaters and coolers, etc.; the second is to innovate and design a new generation of optical switching devices; in terms of network layer innovation, SDN controlled “gray box” or even “white box” of software and hardware decoupling, open and standardized interface, data interface interoperability, so as to promote optical In order to obtain the benefits of global cellular economy and reduce fragmentation, it is necessary to standardize a F5G with unified definition, architecture, function, capacity and performance.

Thirdly, the all-optical network also needs to be programmable, which requires the setting of rate, modulation format and wavelength interval at minute level.

Fourth, all optical networks should also move towards open ecology. In order to cope with the increasingly severe situation of weak development of the industry and increasing external competition pressure, reducing costs and innovating a more healthy and active industrial ecology have become the key to the sustainable development of the industry. Although there are still some controversies about the open wireless access network industry, in Wei Leping’s opinion: “from the beginning of wireless access network, all fields of network will gradually open up, interface standardization, software and hardware decoupling, hardware white box, software open source, all-optical transmission network based on all-optical will be no exception, and all-optical network will also move towards open ecology.” For example, at & T opened the world’s first ROADM commercial white box system. In 2019, it realized a flexible and low-cost optical connection from Atlanta to Dallas with a total length of 1300 km and a speed of 400 Gbps. The system is based on the decoupling distributed (DDC) white box design of openroadm specification.

Fifthly, all-optical network needs artificial intelligence to promote the development of all-optical network from three aspects of algorithm, computing power and data.

The coverage and scale of China Telecom all optical backbone network 2.0 is the largest in the world

In terms of all-optical network construction, China Telecom has been moving faster.

Talking about the progress of all-optical backbone network 2.0 of China Telecom, Wei Leping said: the coverage and scale of China Telecom all-optical backbone network 2.0 is the largest in the world: five regions, with a total system length of 220000 km, 470 ROADM nodes, 2357 OA nodes, with a total network capacity of 590t; 5039 100g, regional WSON control, recovery time less than 2 minutes; CD based on 20 dimensional WSS; direct optical layer with minimum delay.

Wei Leping also looks forward to the future goals of China Telecom all optical backbone 2.0: minute level distribution, second level priority recovery, 30 millisecond delay, automatic topology discovery and routing.

Editor in charge: PJ

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