An optical module is composed of optoelectronic devices, functional circuits and optical interfaces. Optoelectronic devices include two parts: transmitting and receiving. Simply put, the function of an optical module is to convert electrical signals into optical signals at the transmitting end, and then convert the optical signals into electrical signals at the receiving end after being transmitted through optical fibers.
What are the differences between 100G, 400G, and 800G?
Simply put, a 100G optical module is an optical module with a rate of 100G. Here, G is the unit of optical signal transmission rate, i.e. Gbps). The commonly used package is QSFP28, which has 4 independent optical signal transmission channels, and the transmission rate of each channel is 25G.
400G optical modules are mainly used for photoelectric conversion. Electrical signals are converted into optical signals at the transmitting end and then transmitted through optical fibers. At the receiving end, optical signals are converted into electrical signals. The transmission rate of 400G optical modules is 400G. They are designed to adapt to the network market from 100M, 1G, 25G, 40G to 100G, 400G, and even 1T. 400G optical modules play a vital role and influence in building 400G network systems. The main function of 400G optical modules is to increase data throughput and maximize the bandwidth and port density of data centers. The future trend of 400G optical modules is to achieve wide gain, low noise, miniaturization and integration, and provide high-quality optical communication modules for next-generation wireless networks and ultra-large data centers.
800G optical module is an optical module with a transmission rate of 800G. Two schemes are first defined in the 800G pluggable MSA, namely 800G-SR8 and 800G-FR4. In the SR8 scenario, in order to consider more technological advancements and obtain a competitive SMF solution. Therefore, the power consumption of OMA and ER will be relaxed, and the reference receiver used in TDECQ measurement will be redefined. Experiments and simulations show that a low-power, low-latency FEC sublayer should be added to the optical module to achieve the target power budget. The details of the new FEC will be introduced in the 800G-FR4 standard specification to ensure interoperability. At the same time, the bandwidth improvement of components and the optimization of packaging design are two other issues that need to be thoroughly studied.
The 800G pluggable MSA aims to release the first specification in Q4 2020, and several sub-components in the MSA have been prototyped. As the 400GbE generation is ready to be launched in the market, the 800G pluggable modules are ready. This new ecosystem will be used to provide higher density and cost-optimized single-channel 100G and single-channel 200G interconnects for the next generation of 25.6T and 51.2T switches.
Looking ahead to 800G to 1.6T, the industry is beginning to see the possible limits of pluggable modules. Using traditional PCBs, SerDes for C2M interconnects cannot be extended to single-lane 200G, which may require bringing analog electronics and optics closer to the switching ASIC. However, whether it is an evolution to co-packaged optics, on-board optics, or pluggables, the single-lane 200G interconnect defined in the MSA will be an important part of the 800G and 1.6T interconnect generations.
