What 5G Transceivers Are Used in 5G Networks

The 5G network is thriving and it promotes the huge demands for related 5G optical transceivers. It is known the 5G network architecture includes three parts, namely 5G fronthaul, midhaul, and backhaul. What types of  5G network transceivers are used in each part? Which optical transceiver is cost-effective for your future 5G network deployments? You will find answers in the following post.

5G Network Architecture Explained

The previous 4G base station generally consists of BBU (Building Base Band Unite), RRU (Remote Radio Unit), feeder, and aerial. Different from the 4G network, in 5G network architecture, the RRU and aerial integrate into AAU. Also, the BBU evolves into CU (Centralized Unit) and DU (Distributed Unit). Simply put, 5G network architecture reconstructed from BBU-RRU architecture of 4G into CU-DU-AAU. 

The CU and DU are distinguished by the real-time processing tasks. The CU focuses on non-real-time functions, some core network functions, and the MEC function while DU focuses on the physical layer and real-time L2 functions. Since CU and DU are separately deployed in 5G networks, the 5G network from the previous fronthaul-backhaul evolution to fronthaul-midhaul-backhaul. The evolution from the 4G network to the 5G network architecture diagram is shown in the following figure.

Fig. 1 - 4G vs 5G Network Architecture

5G Transceivers Are in High Demand

5G optical transceivers are the basic components of the 5G networks, even accounting for more than 50% ~ 70% of the total cost in some 5G projects. Especially in the 5G fronthaul, there may be tens of millions of demands for 5G network transceivers. Due to the different rate requirements, transmission distance, working environment, optical fiber resources and etc.

Accordingly, 5G fronthaul, midhaul, and backhaul put forward specific requirements for optical modules. The 5G optical module should meet the higher speed requirements, longer distance, wider temperature range, and lower cost. Next, this paper will detailedly introduce which 5G transceivers are used in 5G fronthaul, midhaul, and backhaul respectively.

5G Transceivers Used in 5G Fronthaul

The typical optical transceivers application scenarios include fiber direct connection, passive WDM, semi-active WDM, and active WDM. The four typical 5G fronthaul application scenarios are shown in fig.2.

The 5G fiber direct connection is the main solution in the short term for 5G deployment because the solution features low delay and easy deployment. It generally uses 25G grey optical transceivers and 25G BiDi (Bidirectional) transceivers. Although the 25G BiDi transceiver is helpful in reducing the optical fiber consumption. However, with the gradually increasing of 5G base stations, the shortage of optical fiber resources will become more urgent. Therefore, various WDM solutions are developed.

The passive WDM application scenario generally includes point-to-point passive WDM and WDM-PON. Since one pair or one optical fiber is used to connect multiple AAUs and DUs, this solution saves optical fiber resources to a great extent. 10G or 25G colored optical transceivers are typically used in the passive WDM solution.

The active WDM application scenario usually uses 10G or 25G short-range grey optical transceivers between AAU/DU to WDM/OTN/SPN devices. And 10/25/50/100G dual fiber bidirectional and single-fiber bidirectional colored transceivers are generally used within WDM/OTN/SPN devices.

The semi-active WDM application combines the above passive WDM and active WDM solutions. On the DU side, active WDM/OTN/SPN devices are used, and passive wavelength division multiplexing devices are used on the AAU side.

Fig.2 - 4 Typical Application Scenarios of 5G Fronthaul

It should be noticed that since the AAU is located outdoor environment, 5G fronthaul transceivers must meet specific environmental requirements, such as the industrial-grade temperature (-40℃~+85℃) and dustproof.

Why Is 25G BiDi Crucial to 5G Fronthaul?

In the 4G era, the fronthaul network mainly uses 10G duplex single-mode optical transceivers. In the early stage of the 5G fronthaul, the fronthaul network is still dominated by optical fiber direct drive, but it has higher requirements for the speed and optical port of the optical module. Considering saving optical fiber resources and ensuring low delay, the BiDi transceiver type is superior to the duplex transceiver type.

On the other hand, 5G has at least a 10 times higher download rate than 4G. Also, with the launch of the enhanced Common Public Radio Interface (eCPRI) protocol, the rate of 25Gbit/s has also become necessary. Based on the above two considerations, there is no doubt that the 25G BiDi optical module can better meet the requirements of the 5G fronthaul. The transmission distance of 10km can cover most application scenarios. In terms of wavelength selection, the 1270/1330 nm wavelengths combination is more cost-effective.

5G Transceivers Used in 5G Midhaul and Backhaul

5G midhaul and backhaul cover the MAN (Metropolitan Area Network) access layer, distribution layer, and core layer. The required optical transceivers are similar to the transceivers used in existing transport networks and data centers. The bearing capacity can be improved by increasing the date rate of transceiver modules or using WDM technology. The access layer mainly adopts 25G/50G gray or colored optical transceivers. The distribution layer mainly uses 25G colored optical transceivers and 100G grey optical transceivers.  And the core layer and above mostly adopt 100G/200G/400G DWDM colored optical transceivers.

5G Midhaul Demand for 50G PAM4 Transceivers

The access layer and distribution layer of the 5G network will have a large demand for 25G/50G interfaces. To save 5G deployment costs, based on 25G optical devices and PAM4 modulation format, 50G PAM4 optical transceivers will become the main solution in the 5G midhaul. 50G PAM4 optical transceiver has two main specifications, 10km and 40km. The 10km type can be realized by directly modulating the laser at a 25G baud rate and ensuring low cost. The 40km type requires a 25g baud rate electro-absorption modulated laser and avalanche photodetector.

5G Midhaul Demand for Low-cost 100G Coherent Transceivers

The distribution layer and core layer of the 5G backhaul have demands for coherent 100G, 200G, and 400G optical modules. The coherent transceivers typically enable transmission distance within 200km and the wavelength is in C-band. The low-cost coherent 100G optical module is regarded as a unit technology. Based on this unit technology, higher transmission bandwidth can be achieved by using wavelength division multiplexing technology.

Conclusion

Compared with the transceivers for the 4G network, the 5G optical transceiver will occupy a more important position in the whole optical module market. Being aware of what 5G transceivers are suitable for the 5G network is vital. QSFPTEK is a professional optical transceiver manufacturer, we can provide customized 5G transceivers such as 25G CWDM, 25G LWDM, and 25G DWDM transceivers for your 5G network deployments. welcome to consult via sales@qsfptek.com.