Typical Application Scenarios of 400G Transceiver

With the maturity of industry standards and the real demand of the network, 400G has become the propeller of ICT (Information and Communications Technology) industry upgrading, getting more and more attention and application. It has a very broad application prospect in the scenario of data center networking, metropolitan bearer network and long-distance and large-capacity transmission network. This article will introduce these three major application scenarios of 400G transceivers: data center network, metropolitan bearer network and long-distance high capacity transmission network from their backgrounds and trends.

400G Transceiver Data Center Interconnection Application

Background: Rapid Growth of East-west Traffic

According to IDC, nearly 80% of the world's data traffic will be retained in core and edge servers by 2025 and the growth rates of data center east-west traffic are expected to be much higher than north-south traffic and traffic between data centers. With the penetration of cloud computing, traditional data centers are being replaced by cloud data centers, which significantly increases the necessity for 400G optical modules .

Table1：The Comparison of Different Types of Data Centers

Trends: Lower Cost per Bit and Power Consumption

Generally, when the application scenarios change, the demands for users will convert at the same time. In long-distance WDM transmission, the performance is a key point for those who want a higher capacity and longer transmission distance. In contrast, the cost is more important for short-distance transmission in the data center.

In order to achieve a higher capacity, there are three major ways for 400G transceivers to reduce the transmission cost per bit:

PAM4(Pulse Amplitude Modulation 4) technology: PAM4 can greatly improve the efficiency of bandwidth utilization. Under the same baud rate conditions, the PAM4 signal bit rate is twice as high as the NRZ signal, which doubles the transmission efficiency and reduces the cost at the same time.

Multi-lanes: The 8 lanes solution also balances cost and power consumption compared to 4 lanes.

Higher baud rate opto chip: It can boost the rate without affecting the transmission distance. A variety of 25Gbaud optical chips (DML, EML, VSCEL) are evolving to 56Gbaud.

The application of 400G optic modules in data centers is very common. The 400G QSFP-DD XDR4 can be used as a 4x100G breakout application to QSFP-FR-100G. 400G QSFP-DD FR4 module can reach a distance of 2km over SMF for DCI application. 400G QSFP-DD LR8 and LR4 support link lengths of up to 10km by transmitting over four CWDM grid optical wavelengths. While400G QSFP-DD ER8 is suitable for long-distance transmission with a link length of 40km over G.652 single-mode fiber. The picture below shows FS 400G Data Center Network Optical Module Solution .

400G Optical Transceiver Application in Metropolitan Bearer Network

Background: New Services Drive Traffic Growth in the 5G Era

Ultra-high bandwidth, massive connectivity, ultra-low power latency and high reliability have become the new demands for bearer networks in the 5G era, the existing 100G ports in metro networks can't meet the requirement for the aggregation layer and core layer. The 400G transceiver solution plays an important role in 5G bearer network.

Trends: Reduce Transmission Cost per Bit for Reliability & Distance

As the estimated usage of optical modules in 5G base stations is in the tens of millions, operators urgently need to reduce the cost of optical modules in network construction investment. In addition, the service life of the module in the telecom bearer network is over 10 years and the transmission distance is up to 80km, which requires higher reliability and performance of modules in bearer network scenario.

400G transceivers for integrated metro bearers are implemented in similar technologies to data center networking scenarios in order to achieve higher rates and lower costs:

          Higher reliability transceiver: Using hermetically sealed packages to meet 10 years of service life and 0~70℃ working temperature.

          High-performance LWDM transmitter: Low dispersion cost and high transmission performance.

          High-performance APD receiver: Enhancing the receiving sensitivity.

          Coherent technology: In order to transmit a longer distance like 80km, coherent technology is adopted for the 400G transceiver solution. At the same time, the development of SiP and INP integration technology and the continuous evolution of CMOS technology support the continuous evolution of coherent optics toward miniaturization and low power consumption. As 400G ZR has the advantage of low power consumption and small size, this technology is expected to be used in metro edge access scenarios.

400G Transceiver Long-Distance High-Capacity Transmission Application

Background: Traffic Growth Increases Bandwidth Pressure for Long-Distance Transmission

Network traffic growth leads to increased port bandwidth on the transmission network. For long-haul and high-bandwidth transmission, Wavelength Division Multiplexer (WDM)-based coherent transmission technology provides the best solution.

With the introduction of Flexible Modulation and Flexible Grid technologies, DWDM can improve spectral efficiency and transmission capacity by selecting the most appropriate code pattern and channel width for each port's capacity and transmission distance, such as FS DWDM-400CFP2-DCO .

Trends: Higher Spectrum Efficiency

Coherent optical modules are moving in three directions：

Spectral Efficiency: increase spectral efficiency and single fiber capacity based on oDSP algorithm advances.

Baud rate: increase single-wavelength baud rate for higher single-port bandwidth, resulting in lower cost per bit and lower power consumption.

Smaller size and lower power consumption: adopt integrated optoelectronic components, advanced manufacturing processes and specialized oDSP algorithms to reduce the size and power consumption of 400G transceivers.

Conclusion

At present, mainstream 400G transceivers have been used in various network scenarios, such as data center networks, metropolitan integrated bearer networks, and long-distance and large-capacity transmission networks. The demand for higher capacity, lower unit bit cost and lower power consumption is driving higher transmission rates of transceivers.