800G Optical Module Packaging

With the continuous advancement of technology, the packaging form of optical modules has undergone significant evolution. From early GBIC packaging, to smaller SFP packaging, and now to 800G QSFP-DD and OSFP packaging. This development trend not only reflects the continuous improvement in speed of optical modules, but also demonstrates their progress towards miniaturization and hot plugging. The application scenarios of 800G optical modules are becoming increasingly widespread, covering multiple fields such as Ethernet, CWDM/DWDM, connectors, fiber channel, and wired/wireless access.

800G QSFP-DD external specifications:

Dual density four channel small pluggable high-speed module. QSFP-DD is currently the preferred packaging for 800G optical modules, enabling data centers to efficiently grow and expand cloud capacity as needed. The QSFP-DD module adopts an 8-channel electrical interface, with a rate of up to 25Gb/s (NRZ modulation) or 50Gb/s (PAM4 modulation) per channel, providing aggregation solutions of up to 200Gb/s or 400Gb/s.

Advantages of 800G QSFP-DD:

1. Compatible with QSFP+/QSFP28/QSFP56 QSFP packages.
2. Adopting a 2x1 stacked integrated cage connector, it can support both single height and double height cage connector systems.
3. At least 12 watts of thermal capacity can be achieved for each module through SMT connectors and 1xN cages. A higher heat capacity can reduce the heat dissipation requirements of the optical module, thereby reducing some unnecessary costs.
4. In the design of QSFP-DD, the MSA working group fully considers the flexibility of user use, adopts ASIC design, supports multiple interface rates, and can be backward compatible (compatible with QSFP+/QSFP28), thereby reducing port costs and device deployment costs.

800G OSFP external specifications:
OSFP is a new type of optical module that is much smaller than CFP8 but slightly larger than QSFP-DD. It has 8 high-speed electrical channels and still supports 32 OSFP ports on each 1U front panel. Combined with integrated heat sinks, it can greatly improve heat dissipation performance.

Advantages of 800G OSFP:
1. The OSFP module is designed with 8 channels, directly supporting a total throughput of up to 800G, thereby achieving higher bandwidth density.
2. Due to OSFP encapsulation supporting more channels and higher data transmission rates, it can provide higher performance and longer transmission distances.
3. The OSFP module has excellent heat dissipation design and can handle higher power consumption.
4. OSFP aims to support higher speeds in the future. Due to the larger size of OSFP modules, it is possible to support higher power consumption and thus higher rates, such as 1.6T or higher.

Comparison of external parameters of 800G optical module:

QSFP-DD is usually the preferred choice in telecommunications applications, while OSFP is more suitable for data center environments. The main difference between the two is:
1. Size: OSFP size is slightly larger; 2. Power consumption: OSFP has slightly higher power consumption than QSFP-DD; 3. Compatibility: QSFP-DD is perfectly compatible with QSFP28 and QSFP+, while OSFP is not compatible.

Types of 800G optical modules：

800G=8 x 100G=4 x 200G, therefore it can be divided into two categories based on single channel rate, namely single channel 100G and 200G. The corresponding architecture is shown in the following figure. A single channel 100G optical module can be quickly implemented, while 200G requires higher optical components. Due to the current maximum speed supported by the electrical interface being 112Gbps PAM4, for a single channel 200G, a gearbox is required for conversion.

For multi-mode situations, there are two main standards for 800G optical modules, corresponding to transmission distances less than 100m. 

The 800G SR8 adopts VCSEL scheme with a wavelength of 850nm and a single channel rate of 100Gbps PAM4, requiring 16 optical fibers. This can be seen as an upgraded version of the 400G SR4, doubling the number of channels. Its optical interface is MPO-16 or 2-row MPO-12, as shown in the following figure. The 800G SR8 optical module is generally used for 800G Ethernet, data center links, or 800G-800G interconnects.

The 800G SR4 scheme uses 850nm/910nm wavelengths for bidirectional transmission, and utilizes DeMux in the module to separate the two wavelengths. A single channel speed of 100Gbps PAM4 requires 8 optical fibers. Compared with SR8, the number of optical fibers in this scheme has been reduced by half. The block diagram is shown in the following figure:

The fiber optic interface is shown in the figure below, using MPO-12 interface.

For single-mode situations, there are multiple standards for 800G optical modules:

800G DR8, 800G 2xDR4, and 800G PSM8 The internal architecture of these three standards is similar, with 8 transmitters and 8 receivers, a single channel speed of 100Gbps, and the need for 16 optical fibers. The 800G DR8 optical module adopts 100G PAM4 and 8-channel single-mode parallel technology, with a transmission distance of up to 500m through single-mode fiber. It is commonly used in data centers, 800G-800G, 800G-400G, and 800G-100G interconnects. The 800G PSM8 adopts CWDM technology and has 8 optical channels, each with a transmission rate of 100Gbps. It supports a transmission distance of 100m and is very suitable for long-distance transmission and fiber resource sharing.

800G 2DR4 refers to two "400G-DR4" interfaces. The optical interface of 2DR4 is two MPO-12, as shown in the figure below. It can be interconnected with 400G DR4 optical modules without the need for fiber optic branch cables and supports a transmission distance of 500m, making it convenient for data center upgrades. The optical interface of PSM8 and DR8 is MPO-16.

800G 2xFR4 and 2xLR4
The internal structures of these two standards are similar, both containing 4 wavelengths and a single channel rate of 100Gbps. To reduce the number of optical fibers through Mux, 4 optical fibers are required, as shown in the following figure.

These two solutions are upgrades to 400G FR4 and LR4 optical modules, using CWDM4 wavelengths of 1271/1291/1311/1331nm. 2xFR4 supports a transmission distance of 2km, while 2xLR4 supports a transmission distance of 10km. Its optical interface adopts dual CS or dual LC interface.