400G Transceiver Form Factors Explained

Rapid demand for bandwidth has led datacenters to upgrade networks from 10G and 40G to 100G and now 400G. Cisco predicts that by 2020 global cloud IP traffic will meet or exceed 14 zettabytes. To meet this continuously growing demand of IP traffic, transceiver manufacturers have been working on viable 400G interconnects.

Here, we look at two popular 400G form factors – QSFP-DD and OSFP.

400G Transceiver Form Factors Explained


QSFP-DD stands for Quad Small Form Factor Pluggable Double Density. It adapts the same basic concept as the 40G QSFP and 100G QSFP28, the one difference being electrical contact density. The QSFP-DD supports 8 lanes of 50Gb/s to achieve 400Gb/s in contrast to the 4 lanes by QSFP and QSFP28.

The main advantage of the 400G QDFP-DD is its backward compatibility. QSFP-DD ports support 40G and 100G pluggables enabling easier migration to 400GbE. The QSFP-DD form factor is slightly longer than lower speed quad form factors to accommodate extra rows of contacts in the connector. The QSFP-DD specification defines both single-height and stacked configurations of the cage/connector system, each supporting QSFP modules with the original rows of contacts, plus supporting QSFP-DD modules via the additional recessed row of contacts.


OSFP stands for Octal Small Form Factor Pluggable. Like the QSFP-DD, the OSFP supports 8 lanes of 50Gb/s for an aggregate data rate of 400Gb/s. It is designed for maximum thermal and electrical performance. OSFP is slightly longer and wider than the QSFP and does not offer backwards compatibility. Cooling is achieved by integrating heat sink directly into the form factor.

In conclusion, OSFP and QSFP-DD offer different benefits to the end user. The choice of one over the depends on the customer’s priorities with regards to thermal management, density, backwards compatibility etc.

Vitex recently introduced 400G QSFP-DD and OSFP transceivers with partner, Innolight. For more information go to our 400G page here.

Related Products

Group working together

Subscribe and stay informed

Your job is easier with a fiber optic expert for a friend.