5G optical module solution for 5G bearer network

Now that 5G has officially entered the commercialization process, the industry is paying more and more attention to the construction of 5G bearer networks. Compared with the previous 3G/4G, 5G has more business scenarios, including some new services, which puts forward higher requirements on the bearer network architecture and technical transmission solutions at various layers, and the requirements for optical modules are also corresponding. Promote. This article will focus on the 5G optical module solutions in the 5G bearer network architecture and 5G pre- and mid-backhaul technical solutions.

5G bearer network architecture

The 5G bearer network is a basic network that provides network connections for the 5G wireless access network and the core network. Compared with 4G networks, 5G bearer networks have undergone major changes in network architecture and bandwidth in order to adapt to large bandwidth, low latency, and massive connection services.

5G moves part of the physical layer of the BBU (baseband processing unit) in the original 4G to the AAU (active antenna unit). After moving down, the fronthaul interface changes from the original 100Gbit/s CPRI to the 25 Gbit/s eCPRI; and the BBU Some of the non-real-time functions of the BBU are moved up to the CU (centralized unit) to make sufficient preparations for network cloudification; after the separation, the BBU only leaves the DU (distributed unit). As shown in the figure below, in the 5G bearer network, the part from AAU to DU is divided into fronthaul, the part from DU to CU is divided into intermediate transmission, and the part from CU to core network is divided into backhaul.

In other words, the 5G access network has evolved from a two-level architecture of BBU and RRU of a 4G access network to a three-level architecture of CU, DU, and AAU. Doing so can not only obtain performance guarantees such as large bandwidth and low latency, but also play a role in flexible scheduling, network protection, and management control.

5G bearer network technical solution

It can be seen from the above that the 5G bearer network is divided into three parts: fronthaul, midhaul and backhaul. Each part has different applications, and its technical solutions and requirements for 5G optical modules are also different. details as follows:

5G fronthaul technical solution

5G fronthaul imposes more stringent requirements on bandwidth and delay (less than 100µs). Therefore, 5G fronthaul will give priority to the 25Gbps eCPRI interface. The current 5G fronthaul technical solutions mainly include optical fiber direct connection, passive WDM, active WDM/OTN, etc. The comparison of technical solutions is shown in the figure below. Among them, the optical fiber direct connection network is simple and easy to maintain, but consumes a lot of optical fibers; while the WDM solution can reduce the use of optical fibers, but its cost is relatively high.

• When deploying a 5G fronthaul network with a direct fiber connection solution, a 25Gbit/s gray optical module is generally used. The module of this rate can support dual-fiber bidirectional and single-fiber bidirectional transmission, and the transmission distance can reach 300 meters and 10 kilometers, respectively. The optical fiber direct connection solution is a common solution in the early 5G fronthaul network deployment.

• WDM solutions include point-to-point passive WDM solutions and active WDM/OTN. When using a point-to-point passive WDM solution to deploy a 5G fronthaul network, a 10Gbit/s or 25Gbit/s color optical module is generally used to connect multiple AAUs to DUs through a pair or a single fiber. This scheme can effectively save optical fiber, but the complexity of WDM technology will also increase a certain degree of difficulty for network management. When using active WDM/OTN solutions to deploy 5G fronthaul networks, 10Gbit/s or 25Gbit/s short-distance gray optical modules are usually used to connect AAU/DU to WDM/OTN/SPN equipment, while WDM/OTN/SPN equipment The connection between generally uses N*10/25/50/100Gbit/s dual fiber bidirectional or single fiber bidirectional color light module. Compared with the passive WDM solution, the network of this solution is more flexible, and with the deep coverage of high frequency network and low frequency increase point, this solution is likely to be widely used in 5G gradually.

In the early stage of 5G fronthaul deployment, considering cost reasons, some 5G network service providers may use 10Gbit/s optical modules for network deployment, but due to module rate limitations, the industry now prefers 25Gbit/s optical modules, which means 5G The optical modules of the fronthaul network will be mainly based on 25Gbit/s and 100Gbit/s. The following table shows 5G fronthaul optical modules.

Note: All the optical modules mentioned above must meet the reliability requirements of industrial temperature (-40℃~+85℃) and dustproof.

5G midstream and backhaul technical solutions

Since 5G intermediate transmission and backhaul have basically the same requirements in terms of bandwidth, networking flexibility, and network slicing, the same technical solutions can be used for 5G intermediate transmission and backhaul, which are currently mainly concentrated in IPRAN (IP-based radio access network) , PTN and OTN and other technical applications, among which IPRAN is more economical and practical. At present, there are two main technical solutions for 5G transmission and backhaul:

• Packet-enhanced OTN+IPRAN-5G Zhongchuan uses packet-enhanced OTN equipment with routing and forwarding functions to build a network, and 5G backhaul will continue to use IPRAN. BGP protocol is used for routing and forwarding between OTN and IPRAN. In order to meet the large capacity and network slicing requirements of 5G bearers, IPRAN will introduce high-speed interface technologies such as 25Gbit/s, 50 Gbit/s, and 100Gbit/s, and consider adopting new interface technologies such as FlexE (Flexible Ethernet) to achieve physical isolation. , Provide better quality assurance of bearing.

• End-to-end packet-enhanced OTN-5G midhaul and backhaul networks all use end-to-end packet-enhanced OTN equipment for networking. Compared with the above solutions, this solution has powerful networking capabilities and end-to-end maintenance The management ability can effectively avoid the problems of OTN and IPRAN interconnection and inter-professional coordination.

In addition, 5G intermediate transmission and backhaul cover the access layer, convergence layer and core layer of the metropolitan area network, and the optical modules used in the metropolitan area network are not much different from those used in the existing transmission network and data center. Among them, the metro access layer will mainly adopt gray optical modules or color optical modules with rates of 25Gbit/s, 50Gbit/s, and 100Gbit/s. The metro aggregation layer and metro core layer will mainly adopt 100Gbit/s, 200Gbit/s. s and 400Gbit/s DWDM color light module. That is to say, 5G intermediate transmission and backhaul will mainly be based on optical modules with a rate of 25/50/100/200/400Gbit/s. The following table shows the 5G mid-transmission and return-transmission optical modules.

to sum up

With the official commercialization of 5G networks, 5G will become a key milestone in the history of network communications. 5G fronthaul, midhaul and backhaul put forward differentiated requirements for new optical modules. At present, there are multiple optical module technical solutions and types for each application scenario. This has great potential for the optical module market, but the accompanying challenges are not small. The industry predicts that the demand for optical modules in the 5G period will reach tens of millions, far exceeding the 4G period. At present, due to the short development cycle of 5G optical modules , the price is temporarily relatively high, but it is believed that as 5G technology and applications continue to mature, the price of 5G optical modules in the future will gradually decrease, just like 4G optical modules.