What Will the Fiber Optic Access Network Reform in the 5G Era?
We have seen 5G’s bandwidth increase, delay reduction and stronger support for the Internet of Things. It also poses a huge challenge to the traditional optical access network. First, for traditional Internet services, the bandwidth of mobile users is increased to 1~10Gbps. The delay is reduced to 1~10ms, which is basically equivalent to the fixed-line optical access performance. The bandwidth and delay advantages of traditional optical access are lost in the face of 5G, and the convenience of mobility will increase the transfer of more traffic to the 5G wireless network. Secondly, For the IoT service, the 5G IoT has a wide coverage, convenient service delivery, standardized interfaces, easier operation and maintenance, and lower costs than the IoT gateway.

Challenges and opportunities for optical access networks in the 5G era
As the most important information and communication infrastructure for the digital transformation of the whole society, 5G will realize the interconnection of all things, and connect people and machines, environment, etc. more closely and efficiently, and it is convenient, fast, intelligent and reliable. The communication connection will lead to innovation and evolution of the whole society’s production mode, business model and lifestyle.
Compared with 4G, 5G can provide stronger services, subdivided into three telecom business scenarios, one is enhanced mobile broadband (eMBB) with a peak rate of up to 10Gbps, and the other is that the number of connections can reach 1 million per square kilometer. Connected to the Internet of Things (mMTC), the third is low-latency, high-reliability communication (URLLC) with an end-to-end delay of 1ms, such as the Internet of Vehicles.
We have seen 5G’s bandwidth increase, delay reduction and stronger support for the Internet of Things. It also poses a huge challenge to the traditional optical access network. First, for traditional Internet services, the bandwidth of mobile users is increased to 1~10Gbps. The delay is reduced to 1~10ms, which is basically equivalent to the fixed-line optical access performance. The bandwidth and delay advantage of traditional optical access is lost in the face of 5G, and the convenience of mobility will increase the transfer of more traffic to the 5G wireless network. Secondly, For the IoT service, the 5G IoT has a wide coverage, convenient service delivery, standardized interfaces, easier operation and maintenance, and lower costs than the IoT gateway.
On the other hand, the development of 5G brings new opportunities to optical access networks. First, 5G using AAU and DU separation architecture, and because of such high frequency introducing 5G AAU huge number, a 4G times 2 or more times, so 5G before the transmission network becomes very important, the key to the optical fiber resources become deployed; this has been built a high-density coverage ODN network, low cost and easy access on demand. 5G AAUs, WDM-PON technologies provide a wide range of applications. Secondly, 5G uses high-frequency signals, which has the weak wall-to-wall capability, and there is also a problem of bandwidth degradation and unstable access quality at the edge of the wireless network. In contrast, the bandwidth and quality of service of optical access fixed-line users are independent of distance. Is a huge advantage.
Operators can consider the advantages of integrated 5G wireless access and optical access to form a supplement. They rely on the large ODN fiber resources and stable large-bandwidth access that has been built on the existing network to provide users with stable and reliable 5G+FTTH dual-gigabit access.

Optical access network evolution trend and technology hotspot
In order to achieve 5G+FTTH dual Gigabit access, the optical access network needs to uniformly consider the evolution of wired and wireless convergence, which is embodied in planning and construction, network architecture, and technical path.
From the perspective of planning and construction, in planning fiber network coverage and computer room construction, it is necessary to consider current business coverage and future business expansion. Establishing an integrated service access area is an effective method, which is based on the division of the fixed network, wireless base station, and government business services, combined with the division of administrative areas and natural areas, the structure of the road network, and the distribution of customers. Each of the integrated service access areas includes an intensively covered ODN network and an integrated access equipment room. The integrated access equipment room uniformly deploys fixed-line OLT, wireless BBU/DU, and cable transmission equipment. , to achieve a fixed shift station.
From the perspective of network architecture, the integrated access room is a POP portal accessed by users and is an important node for realizing service identification and offloading to the cloud. The large-capacity integrated access room reduces the number of machine rooms and meets the requirements of the operator network simplification. By establishing a comprehensive access equipment room, unified service model, equipment room specifications, technical routes, and networking solutions, the future evolution to the SDN network and the introduction of AI intelligent operation and maintenance will greatly simplify the construction and operation of the entire optical access network and reduce operations. Business cost.
On the technical route, in order to meet the extreme experience requirements of new services such as 4K/8K/VR/AR, the cable is upgraded to 10G PON technology, and wireless adds 5G access to achieve more than 1Gbps bandwidth per user. Through the NFVI infrastructure sinking access to the equipment room and MEC technology, to meet the real-time low-latency business needs, carry out new services such as VR, car networking, remote control.
Focusing on the more efficient use of ODN fiber resources, PON technology based on point-to-multipoint architecture presents multiple hotspot directions, including WDM-PON technology for 5G pre-transmission and 50G PON technology for a larger bandwidth.
WDM-PON is a point -to- multipoint technology architecture (refer to the figure below). It uses independent wavelengths to provide rigid pipes for each user, and the speed is up to 25Gbps, which meets the requirements of 5G pre-transmission. At the same time, WDM-PON matches the existing ODN network saves backbone fiber resources, and is suitable for 5G coverage in dense urban areas. It is one of the important choices for 5G forward transmission technology. At present, WDM-PON still has problems such as high cost and low reliability of working temperature conditions, which needs to be solved through the industrial chain.

The next-generation PON adopts 50G PON technology, and ITU-T has been established in 2018. 50G PON adopts single-wavelength technology, is compatible with XG (S) PON and GPON, and greatly improves uplink delay performance through low-latency DBA technology. It can meet the needs of home wide bandwidth increase, and can also be used for government and enterprise and 5G small base station backhaul. The new field has greatly expanded the application range of PON and is the best technology evolution path for operators to make full use of existing ODN networks.
Thoughts on the Construction of Optical Access Network in the 5G Era
The core of the optical access network construction in the 5G era is to build an integrated access room into an intelligent fixed-mobile integration room, meeting the technical requirements of speed, easy, flexible, intelligent and reliable. Reference test the FIG., While retaining the original power supply system (including backup power), the case where the air-conditioning cooling system, control system, and routing channels, the access network is divided into four internal room functional modules.

- Connection function: refers to the internal network of the access room, refer to the Spine-Leaf architecture of the data center, establish a large bandwidth, scalable, and reliable internal communication system to meet the wireless DU / wired OLT / uplink transmission/access room NFVI Complex business communication and QoS guarantees between infrastructures ;
- Access network: refers to wireless DU and wired OLT, which are responsible for wireless and wired access processing respectively;
- NFVI infrastructure ( computing storage function): As a remote module of the edge data center EDC, the service NFV running on it is managed by the 5G core network to ensure fast processing of low-latency real-time services and improve user experience;
- Transmission function: Provides a network-side interface to uniformly carry wired and wireless traffic; the transmission device can be OTN, IPRAN or SPN.
In reality, the number of access to the computer room is large, and the hardware conditions and environment are also quite different. The capital investment and equipment of the entire equipment transformation are large and the workload is large. In the specific implementation, the following three principles should be fully considered and implemented step by step. Gradually evolved.
- Openness principle: The access function, connection function, NFVI infrastructure (computing storage function) and transmission function in the access room network should support the open interface; the NFVI infrastructure device is shared with all functions and users in the equipment room. .
- Scalability principle: The specific conditions of access to the equipment room are quite different, such as hardware conditions such as equipment room area, power supply, and heat dissipation; access function, connection function, NFVI infrastructure (computing storage function), and transmission function in the access room Crop based on actual business needs and support smooth expansion by function and capacity.
- The principle of flexibility: The network transformation of the access equipment room should be based on the smooth verification of the existing access equipment architecture. Under the premise of ensuring the normal operation of the existing services, the relevant functions can be flexibly collected according to the conditions of the equipment room.
The optical access network in the 5G era still has great value. Based on the ubiquitous ODN fiber resources, through the construction of the integrated service access area, the wired and wireless access services can be matched with the equipment room area, and resource sharing such as the equipment room and MEC can be realized. Combined with the continuous evolution of PON technology and the introduction of SDN&NFV technology. To realize the intelligent transformation of the integrated access equipment room and simplify service deployment and operation and maintenance.