TheC form-factor pluggable (CFP,100G form factor pluggable, whereC isLatin:centum "hundred")[1] is amulti-source agreement to produce a common form-factor for the transmission of high-speed digital signals. The c stands for the Latin letter C used to express the number 100 (centum), since the standard was primarily developed for100 Gigabit Ethernet systems.
The CFP transceiver is specified by amulti-source agreement (MSA) among competing manufacturers.[2] The CFP was designed after theSmall Form-factor Pluggable transceiver (SFP) interface, but is significantly larger to support 100 Gbit/s. While the electrical connection of a CFP uses10 × 10 Gbit/s lanes in each direction (RX, TX),[1] the optical connection can support both10 × 10 Gbit/s and4 × 25 Gbit/s variants of 100 Gbit/s interconnects (typically referred to as 100GBASE-SR10 in 100 meterMMF, 100GBASE-LR10 and 100GBASE-LR4 in 10 kmSMF reach, and 100GBASE-ER10 and 100GBASE-ER4 in 40 km SMF reach respectively.)[3]
In March 2009,Santur Corporation demonstrated a 100 Gigabit pluggable CFP transceiver prototype.[4]
CFP transceivers can support a single 100 Gbit/s signal like100GbE orOTU4 or one or more 40 Gbit/s signals like 40GbE,OTU3, orSTM-256/OC-768.
TheOptical Internetworking Forum in 2016 published the CFP2-ACO or CFP2 - Analog Coherent Optics Module Interoperability Agreement (IA). This IA supports a configuration where thedigital signal processor (DSP) is on the main board and analog optical components are on the module. This IA is useful in the case when the DSP exceeds the module power envelope.[5]
The ACO interface can be used in coherent optics applications when the link delivers a flexible amount of bandwidth to the system, for example when combined withFlexE. The initial ACO IA is for the CFP2 module.
The original CFP specification was proposed at a time when 10 Gbit/s signals were far more achievable than 25 Gbit/s signals. As such to achieve 100 Gbit/s line rate, the most affordable solution was based on 10 lanes of 10 Gbit/s. However, as expected, improvements in technology have allowed higher performance and higher density. Hence the development of the CFP2 and CFP4 specifications. While electrically similar, they specify a form-factor of 1/2 and 1/4 respectively in size of the original specification. Note that CFP, CFP2 and CFP4 modules are not interchangeable (but are inter-operable at the optical interface with appropriate connectors).
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