This blog will introduce the features of 800G QSFP-DD and 800G OSFP transceivers and explain the differences between them.

QSFP-DD Transceivers

QSFP-DD stands for Quad Small Form Factor Pluggable Double Density. What Double Density means? What’s the difference with the QSFP, QSFP28, QSFP56 and QSFP112?

The 800G QSFP-DD and 400G QSFP-DD transceivers follow the same port densities system as the QSFP, QSFP28 and QSFP56 but the QSFP-DD supports eight lanes instead of four lanes for the others QSFPs, which double the density.
For the 800G QSFP-DD transceiver, each of the eight lanes will operate a data rate up to 100Gb/s providing a 800Gb/s data speed. It increases the capacity of the 400G QSFP-DD by two and the 100G QSFP28 by eight.
The 800G QSFP-DD transceiver is also called 800G QSFP-DD800, but for simplicity it is often called 800G QSFP-DD.

The next level is reached with the QSFP112 module. It complies with the latest QSFP112 MSA specification and supports 112G-PAM4 electrical and optical signaling. Four transmit and receive channels each transmit 106.25 Gbit/s, achieving a total data rate of 425 Gbit/s.

OSFP Transceivers

The OSFP is a new pluggable form factor, which is slightly wider and deeper than the QSFP family. OSFP stands for Octal Small Form factor Pluggable. As the QSFP-DD, the OSFP has 8 lanes supporting.
The OSFP transceivers family started with the development of the 400G OSFP transceiver, and thus only have two data speed rate available at the moment: 400G and 800G.
To know more about the OSFP MSA click here.

The differences between the 800G QSFP-DD and the 800G OSFP Transceivers

QSFP-DD vs OSFP: Size

The width, length and thickness of 800G QSFP-DD are 18.35mm, 103mm and 8.5mm, while those of 800G OSFP are 22.58mm, 107.8mm and 13.0mm. It is obvious that the OSFP form factor is slightly wider and deeper than the QSFP-DD, but it still enables to put 36 ports in one switch slot, accumulating 14.4 Tbp/s in one slot.

Thermal Capacity and Power Consumption

Due to its slightly bigger size, the 800G OSFP transceiver has a better thermal capacity. However, a larger thermal capacity also means a higher power consumption. Obviously, the 800G QSFP-DD has a lower thermal capacity, but a better power consumption.

Backwards Compatibility

The great advantage of the 800G QSFP-DD transceiver is its backward compatibility with the QSFP, QSFP28, QSFP56 and 400G QSFP-DD. Indeed the 800G QSFP-DD ports will also support 40G, 100G, 200G and 400G which will facilitate and reduce the cost of the network migration toward the 800G.
The larger size of the 800G OSFP transceiver won’t enable the backward compatibility with the QSFP family. However, it is possible to find an adaptor (OSFP to QSFP) that supports other QSFP transceivers. The 800G OSFP is backward compatible with the 400G OSFP transceiver.

Confused about the different versions of OSFP design?

The OSFP transceivers are available in three form factor variants. Notably, some 400G network interface cards (NICs) may only support the Flat Top OSFP, not the Finned OSFP. In 2024, we expect to witness more than 800G OSFP Finned-top transceivers. Additionally, 400G pluggable module implementations are becoming more complex, with more instances of 400G implemented in OSFP112 or QSFP112 in addition to the traditional QSFP56-DD/QSFP-DD and OSFP. Exercise caution when selecting optical transceivers.

OSFP Finned Top: A finned top OSFP transceiver has a heat sink attached to the top of the module. The heat sink is made up of thin, extended fins that increase the surface area and pull heat away, allowing the transceiver to operate at higher temperatures without overheating. The finned-top design allows for more efficient cooling, which helps maintain the optimal temperature for the transceiver to function.
OSFP Flat Top/RHS: Developed by NVIDIA and primarily used in their network cards (NICs). A flat top/riding heat sink (RHS) OSFP transceiver design caters to low-profile environments. The heat sink is removed from the transceiver and integrated into the network adapter's cage, "riding" on top of the inserted transceiver. It stands out with its unique design, setting a new standard in the industry.
OSFP Closed Top: A closed top OSFP transceiver design enhances heat dissipation due to the addition of a metal cover on top of the fins. This enables increased airflow along the entire length of the transceiver, creating an efficient pathway for heat dispersion. The closed top surface allows for better conduction of heat from the fins, leading to an improved transfer of heat away from the transceiver.

Both finned top and closed top are designed to be installed in switches. OSFP flat top, also known as RHS transceivers, are designed to be installed in network cards that have the heat sink built into the top of the OSFP cage.

At LightOptics, we are advancing the optical transceiver industry with quality-driven global supply chain, offered in three unique form factors. Each design is meticulously tailored to meet the specific needs of clients' equipment. For more information about our products you can visit our website: https://www.lightoptics.co.uk/collections/800g