NAS server with optical connector

SFP (optics)

— the server has at least one SFP connector for connecting to the Internet (or other external network) via fibre optic cable.

Note that initially the SFP standard covers different types of connections, however, in NAS servers, it is “optics” that is most widely used. The speed of such a connection can reach 2.5 Gbps, while the fibre is maximally protected from electromagnetic interference (more precisely, it is absolutely insensitive to them). As a result, the SFP is well suited for professional applications and is mainly used in this area. However, nowadays, this standard is gradually falling into disuse, being replaced by more advanced SFP + (see the relevant paragraph).