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The C form-factor pluggable (CFP) is a multi-source agreement to produce a common form-factor for the transmission of high-speed digital signals. C stands for the Latin letter C used to express the number 100, since the standard was primarily developed for 100 Gigabit Ethernet systems. While the electrical connection of a CFP uses 10 x 10 Gbit/s lanes in each direction (RX, TX), the optical connection can support both 10 x 10 Gbit/s and 4 x 25 Gbit/s variants of 100 Gbit/s interconnects. With improvements in technology allowing higher performance and higher density, CFP2 and CFP4 optical transceivers emerged and gradually replaced CFP transceiver. CFP2 optical transceiver and CFP4 optical module specify a form-factor of 1/2 and 1/4 respectively in size of the CFP transceiver module (see below figure). This article will have an introduction to CFP2 optical transceiver and CFP4 optical module from some aspects.
CFP2 optical transceiver has 8 x 25G TX and RX I/O pairs, while CFP4 optical module has 4 x 25G TX and RX I/O pairs. In addition, CFP2 can be reconfigured to support 10 x10G TX and RX I/O pairs. All the form factors have an optional reference clock input as well as optional TX and RX monitor clock inputs.
CFP is locked into the host system with two screws which engage the host connector cover, minimizing tolerance stack up between connector plug and receptacle. Because screws take up front panel width, CFP2 and CFP4 optical transceiver modules are locked in with latch bails similar to other pluggable form factors like XFP and SFP+.
CFP2 has 83.3V power pins and supports 4 power classes with 3, 6, 9 and 12 Watt limits. However, CFP4 has 43.3V power pins and supports 4 power classes with 1.5, 3, 4.5 and 6 Watt limits. The lowest power density limit permits operation without a heat sink. The four power limits correspond to progressively higher top surface power densities requiring more advanced cooling techniques.
CFP2 and CFP4 optical modules are defined to support existing and future SMF applications. The primary application is 100GE-LR4 10km duplex SMF, with CAUI-4 electrical I/O to be defined in. CFP2 will support 100GE-ER4 40km and 100G DWDM optics when integration technology matures. CFP2 and CFP4 can also support the future 100G structured data center 1000m duplex SMF application.
CFP2 and CFP4 optical transceivers are defined to support existing and future parallel MMF applications. The primary application is 100GE-SR4 100m on parallel MMF. CFP2 and CFP4 optical modules can also support 100GE-SR10 with CAUI-4 electrical I/O by using a 4:10 Gearbox IC. An extension of the 100GE-SR10 application is break out of the parallel MMF cable into ten duplex MMF fiber pairs to enable high 10GE-SR front panel density. 10 x 10G electrical I/O can directly support this functionality. However, CAUI-4 electrical I/O does not support this because it breaks up 10GE lanes into 5G virtual lanes. To preserve 10GE lanes, the OIF is defining a Muli Link Gearbox (MLG) standard which will support 10:4 multiplexing and 4:10 de-multiplexing of ten 10GE asynchronous streams across a 4 x 25G electrical I/O interface.
CFP2 optical transceiver and CFP4 optical module are going to light up a new generation of 100GbE interfaces. Fiberstore, a leading and professional manufacturer and supplier of optical components, offers lots of 100G transceivers like 100GBASE-LR4 CFP2, 100G CFP2, CFP4 LR4, etc. For more information, please visit Fiberstore.