Optical Modules Usage in DATA CENTER

The current data center is no longer just one or a few computer rooms, but a group of data centers. Mass interaction, which means that a data center interconnection network is required, and optical fiber communication becomes a necessary means to achieve interconnection by the optical modules and cables.
Optical modules in Data center can be divided into three categories according to the connection type:
(1) From the data center to the user, it is generated by terminal user behaviors such as accessing the cloud to browse webpages, send and receive emails, and video streams;
(2) Data center interconnection, mainly used for data replication, software and system upgrades;
(3) Inside the data center, it is mainly used for information storage, generation and mining.
According to forecasts, data center internal communications account for more than 70% of data center communications. The great development of data center construction has also given birth to the development of high-speed optical modules
The growing data traffic, the large-scale and flat data centers trend drives the development of optical modules in two aspects:
–Increased transmission rate demand
–Increase in quantity demand
The large-scale trend of data centers has led to an increase in transmission distance requirements. The multimode fiber transmission distance is limited by the increase in signal rate, and it is expected to be gradually replaced by single-mode fiber. The cost of an optical fiber link consists of an optical module and an optical fiber, and there are different applicable solutions for different distances. As to the medium and long-distance interconnection requirement leads to two revolutionary solutions born from MSA:
PSM4（Parallel Single Mode 4 lanes）and CWDM4（Coarse Wavelength Division Multiplexer 4 lanes） Among them, PSM4 fiber usage is 4 times that of CWDM4. When the link distance is long, the cost of the CWDM4 solution is relatively low.

The application of optical modules in data centers In China and other countries is different.
The interconnection of internal switches in the US data center is mainly single-mode optical fiber. In the 100G era, CWDM4/PSM4 optical modules are widely used, and in the 400G era, DR4 is currently the mainstay; most servers and switches are interconnected by DAC cable. The DAC cable and MM cable usage will be lower and lower due to the actual data rate speed up requirement
The interconnection of internal switches in China’s data centers is dominated by multi-mode fiber, and the proportion of single-mode fiber is gradually increasing. At present, there is little domestic demand for 400G. In the 100G era, SR4/CWDM4 modules are used, and most of the interconnections between servers and switches use active optical cable AOC.