To implement different 10GbE physical layer standards, many interfaces consist of a standard socket into which different PHY modules may be plugged. Physical layer modules are not specified in an official standards body but by multi-source agreements
(MSAs) that can be negotiated more quickly. Relevant MSAs for 10GbE include XENPAK
(and related X2 and XPAK), XFP
. When choosing a PHY module, a designer considers cost, reach, media type, power consumption, and size (form factor). A single point-to-point link can have different MSA pluggable formats on either end (e.g. XPAK and SFP+) as long as the 10GbE optical or copper port type (e.g. 10GBASE-SR) supported by the pluggable is identical.
XENPAK was the first MSA for 10GE and had the largest form factor. X2 and XPAK were later competing standards with smaller form factors. X2 and XPAK have not been as successful in the market as XENPAK. XFP came after X2 and XPAK and it is also smaller.
The newest module standard is the enhanced small form-factor pluggable transceiver
, generally called SFP+. Based on the small form-factor pluggable transceiver
(SFP) and developed by the ANSI T11 fibre channel
group, it is smaller still and lower power than XFP. SFP+ has become the most popular socket on 10GE systems. SFP+ modules do only optical to electrical conversion, no clock and data recovery, putting a higher burden on the host's channel equalization. SFP+ modules share a common physical form factor with legacy SFP modules, allowing higher port density than XFP and the re-use of existing designs for 24 or 48 ports in a 19-inch rack
width blade. Read more...