What is XFP 10G?

The XFP (10 Gigabit Small Form Factor Pluggable) is a standard for transceivers for high-speedcomputer network and telecommunication links that use optical fiber. It was defined by an industry group in 2002, along with its interface to other electrical components which is called XFI.
Description
XFP modules are hot-swappable and protocol-independent. They typically operate at optical wavelengths (colors) of 850 nm, 1310 nm or 1550 nm. Principal applications include 10 Gigabit Ethernet, 10 Gbit/s Fibre Channel, Synchronous optical networking (SONET) at OC-192 rates, Synchronous optical networkingSTM-64, 10 Gbit/s Optical Transport Network (OTN) OTU-2, and parallel optics links. They can operate over a single wavelength or use dense wavelength-division multiplexing techniques. They include digital diagnostics that provide management that were added to the SFF-8472 standard. XFP modules use an LC fiber connector type to achieve high density.
The XFP specification was developed by the XFP Multi Source Agreement Group. It is an informal agreement of an industry group, not officially endorsed by any standards body. The first preliminary specification was published on March 27, 2002. The first public release was on July 19, 2002. It was adopted on March 3, 2003, and updated with minor updates through August 31, 2005. The chair of the XFP group was Robert Snively of Brocade Communications Systems, and technical editor was Ali Ghiasi of Broadcom.[2] The organization's web site was maintained until 2009.
XFI
The XFI electrical interface specification was a 10 gigabit per second chip-to-chip electrical interface specification defined as part of the XFP multi-source agreement. It was also developed by the XFP MSA group. XFI provides a single lane running at 10.3125 Gbit/s when using a 64B/66B encoding scheme. A serializer/deserializer is often used to convert from a wider interface such as XAUI that has four lanes running at 3.125 Gbit/s using 8B/10B encoding. XFI is sometimes pronounced as "X" "F" "I" and other times as "ziffie".
Dimensions
The physical dimensions of the XFP transceiver are slightly larger than the original small form-factor pluggable transceiver (SFP). One of the reasons for the increase in size is to allow for on-board heat sinks for greater cooling.
XFP dimensions are:
Height: 0.33 inches (8.5 mm)
Width: 0.72 inches (18.3 mm)
Depth: 3.1 inches (78 mm)
The XFP packaging was smaller than the XENPAK form-factor which had been published earlier (by almost a year). Some vendors supported both, or the XENPAK follow-ons called XPAK and X2.