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What is the difference between 100G, 200G, 400G, and 800G Optical Module?

June 30,2023

The optical module is composed of optoelectronic devices, functional circuits and optical interfaces, etc. The optoelectronic devices include transmitting and receiving. General speaking, the function of the optical module is to convert the electrical signal into an optical signal, after being transmitted through an optical fiber, the receiving end converts the optical signal into an electrical signal.

What is the difference between 100G, 200G 400G, and 800G?
Simply put, a 100G optical module is an optical module with a rate of 100G. G is the unit of optical signal transmission rate (Gbps). The commonly used package is QSFP28, which has 4 independent transmission channels for optical signal transmission and reception, and the transmission rate of each channel is 25G.

200G QSFP56 optical modules can be divided into QSFP56 CR, SR, DR, FR, LR, which can realize different distance transmission on single-mode and multi-mode optical fibers. QSFP56 optical module, that is, four small channel hot-swappable optical modules, can support 4x50G transmission, so as to achieve a transmission rate of 200G, adopt PAM4 modulation technology, can transmit more data on existing optical fibers, and is suitable for ultra-large-scale data center network.

The "DD" in the 200G QSFP-DD optical module refers to double density, that is to say, the number of channels changes from 4 to 8, and it adopts a hot-swappable QSFP-DD package, which is forward and backward compatible with QSFP , compatible with QSFP28 optical modules and AOC/DAC high-speed cables, etc.

The 200G QSFP-DD SR8 optical module is an 8-channel full-duplex high-performance optical module. Each channel runs at a rate of 25.78Gbps. When used with OM3 optical fiber, the transmission distance is 70m. When used with OM4 optical fiber jumper, the transmission distance is 100m for short distance multi-channel data communication and interconnection applications.

The 200G QSFP-DD PSM8 optical module is a high-speed product of single-mode parallel technology. It adopts 8 channels of 1310nm single-mode fiber parallel scheme, and the transmission distance can reach 10km.

The 400G optical module is mainly used for photoelectric conversion . The electrical signal is converted into an optical signal at the sending end, and then transmitted through an optical fiber. At the receiving end, the optical signal is converted into an electrical signal. The transmission rate of the 400G optical module is 400G, which was born to adapt to the network market from 100M, 1G, 25G, 40G to 100G, 200G, 400G, and even 1T. 400G optical modules play a vital role and influence in building 400G network systems. The main function of the 400G optical transceiver is to increase data throughput and maximize the bandwidth and port density of the data center. The future trend of 400G optical modules is to achieve wide gain, low noise, miniaturization and integration, and to provide high-quality optical communication modules for next-generation wireless networks and ultra-large data centers.

The 800G optical module is an optical module with a transmission rate of 800G. In the 800G pluggable MSA, two solutions are firstly defined, namely 800G-SR8 and 800G-FR4. In the SR8 scenario, in order to consider more technological advances, a competitive SMF solution can be obtained. Therefore, the power consumption of OMA and ER will be relaxed, and the reference receiver used in TDECQ measurements will be redefined. Experiments and simulations show that a low-power, low-latency FEC sub-layer should be added in the optical module to achieve the target power budget. Details of the new FEC will be introduced in the 800G-FR4 standard specification to ensure interoperability. Meanwhile, bandwidth improvement of components and optimization of package design are two other issues that need to be thoroughly studied.

In short-distance application scenarios, cost is the focus of attention. 800G optical modules can use 800G SR8. In the evolution from 400G-SR8 to 800G-SR8, the rate of single-channel 100G may limit the solution. The 800G rate optical module and coherent long-distance optical module are the core unit modules to realize the optical interconnection within and between data centers , and are the necessary foundation for building a high-quality computing power network. Therefore, the launch of high-speed optical modules will continue to promote the construction of cloud computing data centers to meet their massive data exchange needs.

As the 400GbE generation prepares to launch in the market, 800G pluggable modules are ready. This new ecosystem will be leveraged to deliver higher density and cost-optimized single-lane 100G and single-lane 200G interconnects for next-generation 25.6T and 51.2T switches .

Looking ahead to 800G to 1.6T, the industry is starting to see the possible limitations of pluggable modules. SerDes for C2M interconnects are not likely to scale to single-lane 200G using conventional PCBs, which may require bringing analog electronics and optics closer to switching ASICs. But the single-lane 200G interconnect defined in the MSA will be an important part of the 800G and 1.6T interconnect generations , whether it is the evolution to co-packaged optics , on-board optics or pluggable devices.

Based on the above, the obvious difference between 100G, 200G, 400G, and 800G is that the transmission rate is different, and the higher the rate supports the greater the data transmission.