Server optical modules are typically small pluggable devices inserted into network adapters (NICs), with sizes depending on the form factor such as SFP, QSFP, or OSFP, rather than being directly installed in the server chassis.

Physical Size and Form Factors

Optical modules used in servers are pluggable transceivers that convert electrical signals to optical signals and vice versa. They are not directly installed in server ports; instead, they are inserted into network adapters (NICs), which then connect to the server via PCIe slots . Common form factors include:

• SFP (Small Form-factor Pluggable): Compact modules typically around 13.4 mm × 56.5 mm × 8.5 mm, used for 1G–10G connections .
• QSFP (Quad Small Form-factor Pluggable): Larger modules supporting 40G–400G, roughly 18.35 mm × 72.4 mm × 13.5 mm .
• OSFP (Octal Small Form-factor Pluggable) and OSFP-XD: Designed for 400G–1.6T speeds, slightly larger to accommodate higher power and heat dissipation requirements . The size of the module is determined by the number of lanes, power requirements, and cooling needs. For example, 400G QSFP-DD modules are double-density, while 800G OSFP-XD modules are larger to handle higher bandwidth and thermal loads .

Server Integration

Servers themselves do not have direct optical ports. Instead, optical modules are installed in NICs, which are then plugged into the server's PCIe slots. This allows servers to connect to switches or other network devices via fiber optics . The NIC form factor and manufacturer determine compatibility with specific optical modules, so selecting the correct module requires checking the NIC specifications .

Summary

• Server optical modules are small, pluggable devices inserted into NICs, not directly into the server chassis.
• Form factors vary by speed: SFP (1–10G), QSFP (40–400G), OSFP/OSFP-XD (400G–1.6T).
• Physical dimensions depend on the form factor and thermal/power requirements.
• Integration relies on NICs, which connect to the server via PCIe, ensuring fiber connectivity to switches and data center networks . This modular approach allows servers to support high-speed optical connections while maintaining flexibility and compatibility with evolving data center standards.