By Ed Cady, contributing editor
The CFP—C = 100G Form-factor Pluggable—interconnect product family includes CFP connectors, cages, active optical modules and cables. The associated cables are primarily passive optical MPO or dual LC types that plug into the outboard side of the CFP module. Some low-volume copper twin-axial system failover and test cables are also used.
CFP is an established primary type of high-speed I/O interface interconnect system primarily used in telecommunication networks systems. CFP is a hot swappable 10 or 4 lane Link I/O system broadly used to connect WAN, Metro, wireless base-stations, telephony server, storage, CARRIER switch, video and other communication systems. Major market segment implementations include varying volume implementations within some cloud datacenters, enterprise datacenters, HPC (high performance computing) labs and Internet provider systems.
The CFP interconnect system has largely supplanted the use of older active optical modular interconnects like XPAK and Xenpak. CFP has had several of its own evolving iterations of smaller and faster product variants. Long-distance active optical modules with embedded DSP and host board interconnects needed more power and function controls which the established smaller size CXP and QSFP modular short length rack systems interconnects did not provide back in 2005.
10×10 Gbps and 4×25 Gbps CFP interconnect products have been used for OTU-4 and OIF-CEI-25 standard interfaces as well as:
- Campus Ethernet 100GBaseSR10 and 100GBaseSR4 100M MMF links
- Metro area Ethernet 100GBaseLR10 and 100GBaseLR4 10KM SMF links
- Wide area Ethernet 100GBaseER10 and 100GBaseER4 40KM SMF links
- WAN InfiniBand EDR and FC ISL cloud links
CFP has been used for a few older I/O interface cable serial I/O link aggregation and multi-link trunks for SONET, SDH, ATM, MPLS and other open and proprietary interfaces.
CFP is a two-piece, copper, 148-pin, dual-row edge connector system; it’s 82-m wide and handles 24 W to power the module. This interconnect system includes the use of various reach and data speed rate active transceiver modules that plug into the receptacle edge style connector that is inboard from the box bulkhead and under a CFP metal shield cage. The back end of the module is flush with the box bulkhead or back-panel. The CFP module outboard end usually has a MPO or dual LC receptacle port that provides mating connection with different types of external MMF or SMF fiber-optic cables relative to link reach requirements.
An extensive variety of CFP AOMs (Active Optical Modules) is available to select from relative to power consumption, cost, speed rates, reaches and photonic technologies employed. There have been custom active copper and active optical CFP to CXP cable assemblies, switch-to-switch links and uplinks.
CFP custom copper cables are usually constructed using 20 individually shielded twin-axial transmission elements within an outer shielding layer for controlling EMI and achieving EMC regulations. The copper wire conductors and differential pair shields and system shield are carefully laser trimmed prepped, processed and terminated with reflow soldering or laser welded to the Module Plug PCB’s pad fields. Increases of higher speed data rates once caused temporary use of awkwardly large 24-28 AWG wire size cables for longest length copper reaches, usually done using three cabled legs for achieving bend radius requirements. Over time, copper reach length requirements have been greatly reduced and some short applications now use very small 30-34 AWG wire size twin-axial elements, making the outer diameter cable size more acceptable.
CFP2 is the second-generation half-size module and interconnect system. This generation does not have the DSP chip on the module but is on the host board so a smaller module package only needed 104 electrical pins and is 41.5 mm wide while using only 12 W. CFP2 has been used for 10x10G, 4x25G and 8x25G interface applications. You can Google CFP MSA CFP2 for many more details.
CFP4 is the third generation quarter-size module and interconnect system that has been in production volume since 2013. Transceiver chip advances and more miniaturization have enabled the use of a 21.5 mm wide module that only needs 56 electrical pins and 6 W of power. This small module allows for many more ports on a switch box front panel versus CFP and CFP2. CFP4 is primarily used for 4x25G and 4x28G applications. There have been CFP4 to CFP2 and CFP4 to CFP inter-generational optical and copper cables as well as CFP4 to QSFP+ custom cables. Current popular applications are the 100GBaseSR4 100M MMF and 100GBaseLR4 10KM SMF. Manufacturer’s CFP4 modules and connectors have been rigorously tested per telephony industry’s Telecordia requirements. Go to www.cfp-msa.org for a full CFP4 specification. See IEEE802.3bj, InfiniBand EDR, OIF CEI-28, FC PI-6, OTL4.4 and CAUI-4 related specifications.
Next week, I’ll delve into more modern developments of CFP technologies, including CDFP, CFP8, CFP16 and CFPxx.