The first of the five trends in optical communications

communication technology in wired communication, and the optical transmission network built around it, to see how optical communication is coping with the huge challenges of the digital revolution. At present, our society is in the take-off stage of the second digital revolution (Digital Intelligence Revolution). Based on the great success of the consumer Internet, we have opened up a new blue ocean of industry Internet, and accordingly put forward the digital economy and digital transformation strategy. As a result, countless industry digitalization scenarios (e.g. smart factories, smart logistics, smart tourism, etc.) have emerged, accelerating the generation of massive amounts of data. According to the forecast, human data production is growing rapidly at the rate of 50% per year. Around this huge amount of data, we urgently need more powerful computing and communication power to cope with it. This is the source of ICT technology development. How should we cope with it? We're looking at 5G for wireless and fiber optics for wired. In this article, we're going to talk about wired, and analyze in detail the most important optical communication technology in wired communication, as well as the optical transmission network built around optical communication technology, to see how optical communication can cope with the huge challenges of the digital revolution. When it comes to optical communication, we still have to silently thank Dr. Charles Kao for his founding paper in 1966. It was his persistence and perseverance that brought us such an almost perfect communication medium as optical fiber. With its large bandwidth, high performance, and low cost, it laid the foundation for the subsequent start of informationization in human society. We cannot imagine how many precious resources would have been consumed and how much damage would have been done to the environment if we had not relied solely on metal media to build the huge communication network that now covers the world. Not to mention the unbelievably high communication costs we would face if these costs were passed on to the average user. Optical Fiber Today, fiber optics is the cornerstone of our entire digital society. It is like a blood vessel, constantly transporting EBs and ZBs of data, connecting the world and creating value. The future development trend of optical communication technology closely revolves around performance and cost, which is summarized in three points. Development trend one: the evolution of all-optical network All-optical network is a term that we are very familiar with. The first task of optical communication is to transmit data. As mentioned earlier, human society is facing data growth every day. In order to avoid congestion, optical communication must keep up with the development of demand and continue to expand its bandwidth and capacity. The way to expand the transmission capacity of optical communication is very clear: one, to continue to improve the single-wave capacity, which is equivalent to widening the road. Second, upgrade all the routing exchange nodes to realize the highway point-to-point direct access (to avoid interchange). Single-wave capacity upgrade After decades of painstaking operation, the current backbone network of domestic operators has reached the level of 100Gbps per wave. The next development target is 400Gbps single-wave, and the main obstacle to this target is the cost, especially the cost of core components such as optical modules. In addition to 400G, in the research and development and testing stage, is 800G and 1.2T. Want to achieve a single-wave rate increase, there are two main ways: the use of higher-order modulation, improve the baud rate. Although the higher-order modulation can multiply the speed, but the noise resistance is poor. That is, as with wireless airports, the external environment deteriorates, or the transmission distance is far, you can not use high-order modulation, only down-order. High baud rate is more useful than high level modulation. It can increase the speed without affecting the transmission distance. However, the high baud rate is very demanding for optoelectronic devices. To be frank, it is a process issue. Optical Communication Spectrum Bandwidth Extension In addition to increasing the capacity of a single wave, if you want to increase the transmission rate of a single fiber, you have to let the fiber transmit more waves. If you want more waves, you can only further extend the spectrum bandwidth of optical communication. Optical communication is actually the same as wireless communication in that it also relies on spectrum resources. We transmit different frequency bands of light in a single fiber, and the larger the available spectrum bandwidth, the more waves of light can be transmitted and the larger the capacity, taking into account the protection interval. In general, the spectrum resource is 4 THz when the C-band is used, and it increases by 20% to 4.8 THz when the CE-band is used, and 6 THz when the C++-band is used, and 11 THz when the C+L-band is used, which is a 175% increase compared to the C-band. (Extended reading: Links). If the rate is 400G for a single wave, C++ band (80 waves), then the backbone transmission capacity can be increased to 400G x 80 waves = 32Tbps. In order to further enhance the rate, experts have not given up on the fiber. New fiber optic transmission technologies, such as MCF, FMF and PCF, are now becoming industry hotspots. Fiber-optic headquarter enterprises are stepping up their technology development. All-optical switching In addition to increasing bandwidth, another means to improve capacity is to upgrade and expand switching nodes, which is also the essence of All-Optical Network 2.0. The development goal of optical communication is to replace all electrical pathways. In other words, all data transmission should be completed by the optical channel. Optical fiber should not only be laid to the home, but also to each room, each PC, each TV, each refrigerator. All fixed network access, all replaced by optical, eliminating the network port. In addition, in the device's internal, also to abandon the conversion of optical power, direct optical path to the components, to the chip. Between the chip and the chip, between the internal chip, all optical path. This is the ultimate development goal of optical communications. For ordinary people, this goal is unimaginable, is not it? On the subscriber side, we have now reached the FTTR (Fiber to the Home) stage. On the backbone side, with the popularization of ROADM and OXC, we have already achieved all-optical wavelength switching in China. In the future, the development idea of all-optical wavelength switching is - up and down. On the one hand, to meet the exchange and dispatch of small particle size (industry-oriented demand, slicing). On the other hand, to meet the exchange and dispatch of large granularity (for backbone network capacity expansion). To realize the upgrade of ROADM dispatching capability, it is necessary to study the WSS technology and process. This is also one of the most noteworthy research directions in the optical communication industry chain. Development trend two: decoupling & white-boxing In addition to the continuous refinement of communication capabilities, the second concern of optical communication development is cost compression. After all, enterprises need to survive, and survival cannot be separated from profits. If you want to make profits, you can only tighten your belt and reduce expenses in addition to increasing revenue. As the largest party in the industry, the most effective means for operators to control costs is to support the industry chain. To put it plainly, the more mature a technology is, the more open it is, and the more manufacturers do it, the more likely it is to keep prices down and eventually achieve "cabbage prices". The sad thing is that in the field of optical communication, the three domestic carriers do not give way to each other and have chosen different technology systems, making the industrial chain difficult. At present, the competition for technical standards is becoming increasingly fierce, the industry chain is still waiting to see, indecisive. The company's main goal is to provide the best possible service to its customers. The money saved is the country's money. The company's main goal is to provide a comprehensive solution to the problem. Under the banner of "open source and decoupling" of operators, it is inevitable that optical communication equipment will be gray-boxed and white-boxed. All the equipment is open and decoupled, so that manufacturers are reduced to "low-end" manufacturing plants. In this way, more B-parties can join, further reducing the purchase cost of equipment and maximizing the interests of operators. The Open RAN on the side of access network is actually the same idea. Development Trend 3: Network Flattening CAPEX (construction cost) depends on the industry chain, OPEX (maintenance cost) can only depend on the internal strength of the enterprise. The maintenance cost of operators has been very high, the most important components of which are staff wages, equipment maintenance, energy consumption expenses (electricity). How to reduce the overall energy consumption of the network, how to reduce the complexity of network operations and maintenance, and further reduce the investment in manpower, is the number one issue that operators need to consider. From the perspective of optical communication, it is to consider the further potential of energy consumption per unit bit of metric transmission and unit bit of switching. Light is originally an energy-saving technology. The higher the percentage of optical domain in the transmission network, the lower the overall energy consumption. Especially after the evolution of WDM to ROADM all-optical switching, energy consumption can be further reduced. Optical communication technology itself has limited potential to reduce energy consumption. Therefore, operators have come up with another solution, which is to simplify the network. That is, to make the entire transmission network as simple as possible, reduce the number of equipment, improve the capacity of equipment, in order to reduce operating and maintenance costs. The most important measure to simplify the network - network flattening. Take China Telecom for example. The current China Telecom transmission network is macroscopically divided into four layers, from top to bottom, they are national trunk (a trunk), provincial trunk (second trunk), metro area, access. Telecom's idea is to directly trunk them into two layers - national and provincial trunk integration, metro and access integration, into a "backbone + metro" two-tier structure. In this way, the number of equipment is definitely reduced, not only to save hardware costs, but also to reduce the space occupation and electricity expenses, as well as human input. The flattened transmission network will change from a tree-like architecture to a MESH network architecture. This is a revolutionary innovation, but also a difficult challenge. For the network, it is equivalent to an operation to change the bone. Development trend 4: The changing role of MANET When it comes to metro area network, I think it is necessary to talk about it specifically. The development route of all-optical network 2.0 is to first backbone all-optical, and then metro all-optical. A feature of the metro area all-optical, OTN such expensive equipment under Shen, from only used in the backbone, into the metro area also have. City WDM, will also be further reduced in cost, down to the edge of the city. The metro area all-optical network, including the metro area core, convergence, access three layers. High-performance equipment down, meaning that the positioning of the metro network and service targets, will be obvious changes. All along, operators have been hoping to leverage the success of metro access technology (PON, passive optical network) in the C-side to replicate the experience to the B-side and open up new markets. In other words, carriers believe that the home broadband market is already saturated (now pushing Gigabit, in the future pushing 50G-PON, although the demand is not large), and now hope to vigorously promote the broadband access market for government and enterprise users to meet the demand for full-service transmission. After the upgrade, the carrier's metropolitan all-optical network will realize the comprehensive integration of mobile (base stations), home broadband, government and enterprise users, cloud services (data centers), that is, "one network to eat". Among the optical access needs of government and enterprise industry users, it is worth noting the industrial interconnection scenario. These scenarios have the highest requirements for transmission bandwidth, deterministic latency, security and reliability, and are complex and challenging. The OSU-based M-OTN technology system is based on the needs of government and enterprise user scenarios and is proposed. It can support small-bandwidth particle multi-service carrier and meet the small-particle low-cost transmission for industrial applications. The metro area all-optical network and cloud network convergence are closely related. It not only intersects with data centers, but is also a grip for operators to enter the cloud business of government and enterprise customers. For example, carriers can provide optical broadband access with cloud leased line services, and even sell their own cloud services. Development trend 5: AI intelligent operation and maintenance In addition to architectural changes, if you want to simplify the network, you can only introduce the support of advanced operation and maintenance technologies. SDN, SDON, it goes without saying that operators require manufacturers to decouple forwarding and control, centralize the management and business scheduling capabilities of all devices, and achieve unified control. The vendors are definitely not willing to do so, and then, both sides are in a stalemate. After centralized management, the operator can realize intelligent operation of the entire transmission network by introducing AI artificial intelligence technology and big data technology. This is like a national traffic dispatch center, and the center is based on artificial intelligence algorithms, which has a lot of potential. The company's newest product, the "AI+SDN", will enable network traffic prediction, performance degradation prediction, root cause failure analysis, and fiber situational awareness. The network itself will be able to provide a lot of information about the network. With the help of AI, the network itself will have a strong self-healing capability. When a problem occurs, AI can provide rapid response and link scheduling to reduce the length of business interruptions, so that customers do not even perceive that a failure has occurred. In addition to cost reduction, the introduction of intelligent operation and maintenance has another benefit, which is green energy saving. Green energy saving of communication network is no longer a public service slogan. It involves an important political task for operators - that is, to serve the country's "dual carbon" strategy. In a sense, its importance is even higher than saving money. Conclusion This is a great opportunity to learn more about the future direction of optical communications. I have not introduced some of the technologies, such as DCI, WSON, ZR, etc., because of the space limitation. In the future, I will have the opportunity to explain in detail through special topics. I still say that the optical transmission network is the base of the entire digital society, the importance is extremely high, much higher than 5G. Optical communication technology is one of the few communication fields worthy of in-depth study. I hope that all young people can join the research of optical communication and participate in building a more powerful and intelligent all-optical 3.0 or even 4.0, so as to lay the foundation for the digital intelligence revolution.