Optical access network plays an important role in the communication network and realizes the comprehensive access and carrying of various services. The development of business needs, such as hd video business large bandwidth demand, virtual reality (Virtual Reality) of low delay demand and optical fiber further extended to the room / workshop demand, promote optical access network evolution, the result is that optical access network can provide greater bandwidth, lower delay and more intelligent services, to meet the needs of new business.
In February 2020, the European Telecommunications Standardization Association (ETSI) established the fifth-generation The 5th Generation Fixed Network (F5G) working group. Through the research and development of F5G standards and white papers, the traditional optical access network is promoted to the three key features of ultra-wide (eFBB, Enhanced Fixed Broadband), ubiquitous (FFC, Full-Fiber Connection) and guaranteed experience (GRE, Guaranteed Reliable Experience).
After more than two years of exploration, Operators have carried out a lot of applications and practices for the three key features of the all-optical intelligent access network: in the scenario facing large bandwidth requirements, 10G PON (Passive Optical Network) networks with Gigabit bandwidth support are deployed for specific large bandwidth access scenarios, Expand the access technology beyond 10G, Continuous excavating of pipeline capacity and value; In terms of the ubiquitous connectivity, Proposed home user fiber extension to the room (FTTR, Fiber To The Room) Technology, At the same time, for the industry expansion, The landing application of government-enterprise all-optical networking, optical fiber sensing (i. e., “sensory joint knowledge and control”) and intelligent detection mainly realizes the ubiquitous connection of multiple scenarios; In terms of ensuring the experience, By building intelligent network capabilities based on SDN (Software Defined Network) technology, And through hierarchical modeling, telemetry Telemetry technology, industrial PON self-service management capabilities and deterministic technology, To improve the intelligent level of the all-optical intelligent access network, It provides a solid foundation for the guaranteed experience.
This paper will introduce several key technologies for the main characteristics of the all-optical intelligent access network.
Key technology of all-optical intelligent access network
Ultra-wide access to 50G PON
In 2018, ITU-T SG15 started the high-speed PON technology research of the 50 Gbit/s single-wavelength channel, and completed and released the 50 G PON G in 2021. First edition of the 9804 Series Standard.50G PON provides 5 times the bandwidth of 10G PON, in order to achieve the smooth evolution of 10G PON to 50G PON, ITU-T SG15 proposed “a set of systems for two generations (10G PON and 50G PON coexist)” way. In the implementation process of 50G PON system, the difficulties are high speed, high power budget and low cost. Key technologies include high power and high speed transmitter, high sensitivity and high bandwidth optical receiver, high gain FEC (Forward Error Correction) and high speed DSP (Digital Signal Processing). Among them, DSP is the key enabling technology to realize the 50G rate through the 25G rate optical module, which can compensate for the bandwidth limit and the optical fiber dispersion loss, improve the sensitivity of the receiver, and reduce the bandwidth requirements of the optical devices.
In principle, the coexistence, evolution and upgrade of 50G PON and 10G PON adopts the wave division coexistence technology. The capacity of the two-generation PON systems does not affect each other, supporting the smooth upgrade by replacing the ONU. The 10G PON and 50G PON coexistence technology architecture is shown in Figure 1, with external integrated wave components coexisting and MPM (Multi PON Model) multi-mode integrated wave components. Among them, MPM method has been applied in the scale, which is an important technical solution to upgrade 10G PON to 50G PON in the future, mainly because it can save cost. In the ONU smooth upgrade process, the system needs to support 12.5G/50G, 25G / 50G, 50G / 50G and other rate combinations to match the differentiated business requirements.
Figure 1 10G PON and 50G PON coexistence technical architecture
The 50G PON industry chain can make use of the 25G mature industrial ecology, including 25G TIA, 25G DML and APD, so as to effectively control costs and reduce the difficulty of upgrading. With the expansion of 50G PON industry investment, 50G PON also needs to increase the exploration of DSP and MAC chip technology, to promote the maturity of key components and device industry technology.
The FTTR is a technology proposed around 2020. The goal is to extend the optical fiber to every room within the home / government and enterprise. After more than two years of development, FTTR has made significant progress in the technology industry, scenario application, and standardization at home and abroad.
At present, the three major domestic operators are providing gigabit access capacity to home users by deploying 10G PON. Home new business continues to emerge, putting forward the requirements of large bandwidth, stable connection and low latency. However, the home internal network is limited by the connection media and networking factors, which cannot meet the user experience. FTTR consists of three parts: main FTTR device, FTTR equipment and indoor fiber distributed network. Based on the fiber P2MP (Point to Multiple Point) physical topology, the FTTR deploys the main FTTR device at the home access point location, and provides network coverage for each area as the center, realizing the non-perceptual switching of the whole-house network. Among them, home users have the characteristics of ultra-short distance, so the optical fiber distribution distance is generally less than 100 meters.
Since 2021, China’s three major operators will promote FTTR technology, build brands such as “whole-house optical broadband”, and provide users with three-gigabit network capabilities through FTTR technology.
The traditional enterprise network generally adopts the networking scheme of Etheric switch, which generally has the problems such as transformation and upgrading difficulties, management difficulties, non-standard construction and deployment, and insufficient network broadband capacity. FTTR technology can not only solve the above problems, but also can be well applied in some commercial office scenarios, such as hospitals, exhibition halls, micro, small and medium-sized enterprise office areas, street shops, dormitory classrooms, etc. The FTTR technical architecture is shown in Figure 2.
Figure 2. F T T R technical architecture
The government-enterprise all-optical network is similar to the home FTTR. The difference is that the distance between the government-enterprise scenario is generally large (500 ~ 1000m), and the overall number of point information required is large. Considering the factors such as performance, redundancy coverage and uneven distribution of users, the main gateway needs to provide more access points than the home FTTR. In FTTR deployment, from the gateway is generally top suction type, it is difficult to get power. In the case of local power is difficult from the gateway equipment, remote power supply introduced the new ODN (Optical Distribution Network) device —— small fiber number photoelectric composite cable, photoelectric composite connector, photoelectric shunt. The ODN mode of remote power supply is shown in Figure 3, which requires remote power supply along the direction of the optical fiber. Previously, the passive photoelectric distributor required local power supply from the subgateway. Currently, active devices are used. Through power supply to the photoelectric distributor, the local power supply from the subgateway is removed, and the photoelectric composite interface and connector are used in the interface of the subgateway. At present, CCSA has carried out standardization work for the new ODN to promote the gradual maturity of devices and promote the ecological development of the whole industry.
Figure 3. The ODN mode of the remote power supply
FTTR system shall support inductive roaming from FTTR gateway Wi-Fi: avoid interference from FTTR gateway via automatic planning through Wi-Fi channel band; support visitor network isolation to provide excellent broadband service experience; realize seamless roaming switching with Easy Mesh protocol.
In addition, under the government-enterprise all-optical network, it is necessary to provide corresponding processing strategies and capabilities for the flow of differentiated business flow. In addition to the north-south upper cloud and Internet access, it is also necessary to consider the east-west network internal traffic, such as file sharing, internal server access, monitoring and so on.
Access network to build edge intelligence
In the application and deployment of the traditional optical access network, the OLT (Optical Line Terminal) equipment management interface is differentiated. Therefore, the manufacturer-specific EMS management mode is mostly adopted in the current network deployment, and the unified control of the OLT equipment of different manufacturers cannot be realized. The network based on SDN architecture is open and intelligent, providing a unified control interface and a better performance Telemetry data acquisition interface for the automated operation and maintenance of OLT and ONU (Optical Network Unit) devices.
Multi-level computing power facilities are shown in Figure 4. In industrial PON, operators can deploy computing power on OLT and ONU, which can build a collaborative edge intelligent network architecture and give full play to the advantages of “connection + computing power” integration. Among them, open programmable side equipment OLT provides moderate computing power resources, supports rich application loading and edge control model training through container architecture; end side equipment ONU provides lightweight computing power, can flexibly load various light industrial applications, support industrial field data acquisition and extremely low delay data processing; SDN-based self-service management platform supports internal computing power management and real-time detection for OLT / ONU devices, and can effectively realize computing network collaborative configuration.
Figure 4 Multi-level computing power facilities
For the needs of industrial field-level computing power, the industrial PON fusion gateway (namely ONU) has both network, data acquisition and computing capabilities. ONU can realize local computing processing and forwarding by flexibly loading third-party applications, such as docking with industrial equipment such as PLC (Programmable Logic Controller) controllers and robotic arms in industrial sites, collect information about registers in the lower equipment and report data after completing protocol conversion, or load video detection models in machine vision scenarios.
The architecture of industrial PON side cloud collaboration is shown in Figure 5. Factory SCADA system is deployed in the cloud data center in the factory, allowing managers can see the equipment operation in the factory in real time remotely; Side is generally deployed in the central room, OLT can manage ONU and report ONU information to the cloud management platform; ONU is deployed in the plant closest to the equipment, support real-time collection of plant equipment information.
Figure 5 Architecture of industrial PON side cloud collaboration
OLT can insert different computing levels to provide medium computing power. The OLT computing power card can load different applications through an open container architecture, and the industrial PON self-service platform can meet the needs of remote site management in the industrial industry. At the same time, DPI and DFI algorithms can also be loaded on the OLT computing power board to perceive user business experience, identify poor quality users, and bound and locate poor quality service network segments.
Gigabit industry applications are booming
Since March 2020, the Ministry of Industry and Information Technology has successively issued a series of policies on gigabit optical networks, such as the “Double gigabit” Network Collaborative Development Action Plan (2021-2023), to encourage the application of new gigabit optical networks. In 2022, the first “Guanghua Cup” Gigabit Optical Network Application Innovation Competition was launched, with special industry integration and application topics, and mining the case of deep integration of gigabit optical network and application scenarios.
In the case of “Guanghua Cup”, the gigabit optical network capability is outstanding, with the characteristics of large bandwidth, low latency, wide coverage and full access. It integrates with the industry demand cloud network, and effectively builds the industry private network capability of “sense connection, knowledge and control”. It has been applied on a large scale in many fields, such as people’s livelihood, medical care, education and industry. For example, in the industrial industry, to build the “double Gigabit” optical network base of solid shift integration, through the hierarchical cloud resource deployment and edge cloud application collaboration, and the use of cloud network fusion to build the “sensory connection, knowledge and control” industry private network capability.
Facing the needs of new business development and the continuous evolution of the network, operators constantly promote the development of F5G all-optical intelligent access network, strengthen the deep integration of Gigabit optical network and the industry; and constantly explore new technical solutions and business applications in the fields of ultra-wide, ubiquitous and intelligent network, to realize the integration of cloud and network integration.