400G Optical Module Application Scenarios

NADDOD Jason Data Center Architect Jan 18, 2023

In the previous article “200G vs 400G: Who will dominate the next step of the data center network?” it was mentioned that since the cost of data center optical devices accounts for more than half of the cost of the entire data center network equipment, the cost per bit of 400G optical devices is higher than that of 200G optical modules. It has advantages, and the momentum of 400G transmission is obvious on the whole. This article will introduce the full application scenarios of 400G optical transceivers: data centers, metro bearer networks, and long-distance large-capacity transmission networks.

400G Data Center Optical Module Solution

Background: East-west Traffic Far Exceeds North-south Traffic

In 2021, about 70% of data center east-west traffic will remain within the data center, and the growth rate is expected to be much higher than that of north-south traffic and traffic between data centers. The penetration of cloud computing has led to the replacement of traditional data centers by cloud data centers, greatly increasing the demand for high-speed optical modules

Typically, user experience varies with application scenarios. In long-distance WDM scenarios, users are more sensitive to performance and expect longer transmission distances and higher spectral efficiency. On the contrary, considering distance, volume and power consumption, users in short-distance data center solutions are more sensitive to cost.

400G Optical Module Solution for MAN

With the rapid development of 5G, new services including IoT, ultra-high-definition video, VR and Internet of Vehicles (IoV) put forward the following new requirements for the bearer network: ultra-high bandwidth, multiple connection channels, ultra-low latency and high reliability sex. Since the 100GE ports of the metropolitan area network cannot support the aggregation layer and core words that require ultra-broadband, a 400GE-based optical interconnection solution is necessary.

Taking the 5G bearer network as an example, according to the bandwidth evaluation of the Next Generation Mobile Network Alliance, during the large-scale 5G commercialization of the metropolitan area network, the access layer bandwidth will be developed to 50GE, and the core word bandwidth will be developed to 200GE/400GE.

At the same time, data centers are migrating from the backbone layer to the edge of the metropolitan area network. Therefore, the rapid growth of data center traffic puts forward higher bandwidth requirements, thus accelerating the bandwidth upgrade of data center interconnection interfaces from 100G to 400G.

Data Center Connection

In the 5G era, it is expected that 5G sites will be 1.5 to 2 times more than 4G sites, and the number of optical modules used in the metropolitan area network is expected to reach tens of millions. The ratio of optical module cost to equipment cost is also increasing, leading operators to prioritize lower optical module costs in network construction investment. Operators also urgently need 400GE optical modules to only require half the power consumption and unit bit cost of 100GE optical modules. In addition, the carrier network has higher reliability and performance requirements than the data center.

Contrary to the data center network with short transmission distance, the metropolitan integrated bearer network with long transmission distance has higher requirements on the transmission performance of optical modules. The metro integrated bearer network adopts the technology in the data center networking scenario to achieve a higher transmission rate of 400G and reduce the transmission cost per unit bit.

400G Optical Module Solution for DWDM Network

The increase in network traffic results in an increase in port bandwidth on the transport network. For long-distance and high-bandwidth transmission, coherent transmission technology based on wavelength division multiplexer WDM provides the best solution.

As 400G coherent solutions mature, the requirements for 400G coherent ports will grow rapidly beyond 2020. There are two driving forces for the growth of 400G consistent ports: the increase in network bandwidth and the increase in the number of 400GE ports on clients. Facts have proved that using a 400G wavelength to carry 400GE services is the most cost-effective solution. According to Light Counting’s forecast report, 400G coherent ports will be used in more and more networks and will see the fastest growth in the next 5 years.

Trend: Higher Spectral Efficiency

Coherent Optical Modules Are Developing in Three Directions:
Spectrum efficiency: Improve spectrum efficiency and single-fiber capacity based on the advancement of DSP algorithms.

Baud rate: Increase the single-wavelength baud rate to obtain higher single-port bandwidth, thereby reducing unit bit cost and power consumption.

Smaller size and lower power consumption: using integrated optoelectronic components, advanced manufacturing process and dedicated oDSP algorithm.


The demand for higher capacity, lower cost per bit and lower power consumption is driving the transmission rate of optical modules higher and higher. Like the mainstream technology of the previous generation, 100G has entered the mature and stable stage of its life cycle, and the reduction of unit bit cost is greatly limited. At present, mainstream 400G optical modules have been used in various network scenarios, such as data center networks, metropolitan integrated bearer networks, and large-capacity and long-distance transmission networks.

Related Resources:
400G Optical Transceiver Module Types
Typical Solutions for 400G Data Center
Typical Connection Solutions of 400G Optical Transceivers and Cables
The Next Station of Data Center Networks—200G vs 400G
100G & 400G Optical Transceiver Marketing
Four Types of Typical 400G Network Solution Plan Explained
400G Solutions Changes High-Bandwidth DCI Architecture
400G QSFP-DD FR4 vs 400G QSFP-DD FR8
A Beginner Guide: What is 400G Optical Module?
FAQs for 400G Transceivers and Cables