Optical modules complying with SFP (Small Form-factor Pluggable) standard are devices converting electrical signal to the optical form and optical signal to the electrical form.
Usage media converters with the ability to exchange SFP modules is particularly preferred because of its versatility, for example if you change the network configuration rather than replace the entire unit or add new media converters simply select the appropriate SFP module. Modules complying with most of switches and routers with SFP socket.