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A Comprehensive Understanding of CFP Transceiver Modules

July 22, 2015

To achieve 100 Gbit/s line rate, one of the solutions is based on 10 lanes of 10 Gbit/s. Hence there emerges the CFP transceiver module, the carrier of the transformation from 10G to 100G. What is CFP? What does CFP stand for? This article will expound on the gadget.

CFP Wiki

The CFP, short for C form-factor pluggable, is a multi-source agreement to define the form-factor of the optical transceiver for the transmission of high-speed digital signals. CFP modules are defined by CFP MSA to enable 40 Gb/s, 100 Gb/s and 400 Gb/s applications. The CFP transceivers feature a new concept known as the riding heat sink, which makes it very easy for the operator to insert the module into the host board. The CFP module offers Ethernet users another option for 100G connectivity.


Types of CFP Transceiver Module

CFP transceiver includes pluggable CFP, CFP2, CFP4 and CFP8 transceivers to support the high bandwidth requirements of data communication networks. One thing that needs to be noted is that although not interchangeable, they could be interoperable at the optical interface with appropriate connectors.

CFP Transceiver Module for 40/100G

CFP (C=100 in Roman numerals; Centum) refers to 100G form-factor pluggable, which features as a new ultra high speed pluggable I/O interface. The optical connection can support both 4 x 10Gbps, 10 x 10Gbps and 4 x 25Gbps variants. 100G CFP modules include 100GBASE-SR10 CFP for 100m on MMF, 100GBASE-LR10 CFP and 100GBASE-LR4 CFP for 10km via SMF, and 100GBASE-ER10 CFP and 100GBASE-ER4 CFP for 40km on SMF. They are an ideal choice for data center applications.

CFP2 Transceiver Module for 40/100G

CFP2 was specified by CFP MSA in a form factor of 1/2 in size of the CFP module. The module electrical interface has been generally specified to allow for supplier-specific customization around various 4 x 25 Gbit/s interfaces, but it can also support 10 x 10 Gbit/s, 4 x 25 Gbit/s, 8 x 2 5 Gbit/s, or 8 x 50 Gbit/s lanes. 200G CFP2 and 400G CFP2, however, are not being put into use so far. CFP2 has been chosen to accommodate a wide range of power dissipations and applications.

CFP4 Transceiver Module for 40/100G

CFP4 form factor is the half size of CFP2 module, which is designed to support Singlemode (SMF) and Multimode Fiber (MMF) Ethernet optics. CFP4 has 4 x25G TX and RX I/O electrical pairs, so its nominal signaling lane rate is 25 Gbit/s. Its electrical interface is specified to support both 4 x 25 Gbit/s and 4 x 10 Gbit/s interfaces. CFP MSA defined the CFP4 to apply for 40G/100G Ethernet, telecommunication and other applications.

CFP8 Transceiver Module for 400G

Following CFP2 and CFP4 naming, CFP8 module was proposed in the year 2015, and its form factor is similar to CFP2 module. Featuring a small 40mm x 102mm x 9.5mm form factor, the new CFP8 module delivers four times more bandwidth than existing 100G solutions. Its electrical interface has been generally specified to allow for 16 x 25 Gb/s and 8 x 50 Gb/s mode. CFP MSA demonstrated CFP8 (16 x 25 Gb/s) form factor for 400 Gigabit Ethernet at OFC 2017. 400G CFP8 transceiver provides Ethernet users with a dense-port and high-throughput solution with its compact size and low power consumption. From the point of bandwidth density, the CFP8 module is eight times larger than the CFP module and four times larger than the CFP2 module.

Applications of CFP Transceiver Module

CFP is an established primary type of high-speed I/O interface interconnect system primarily used in WAN, Metro, wireless base-stations, video and other telecommunication networks systems. Major market segment implementations include varying volume implementations within some cloud data centers, enterprise data centers, HPC (high performance computing) labs and Internet provider systems. Here we illustrate two Metro network applications involving CFP transceiver module.

100G Coherent CFP Module for Metro Network Applications

Coherent 100G CFP can overcome optical transmission impairments and still achieve acceptable performance, and more importantly, it can realize data transmission between sites over 1000 km. To satisfy the high capacity and long distance of 100G metro networks, DWDM technology is utilized and coherent CFP transceiver is deployed.

Scenario 1: 100G Multi-Channel DWDM Networking

Since the 100G rates are more susceptible to dispersion, extra dispersion compensation and optical power boost would be required. Thus an extra 100 GHz DWDM multiplexer is first used to combine all the 100G rates together followed by a combined dispersion compensation and amplification stage. This architecture conveniently supports the ‘pay-as-you-grow’ model for service providers. When the bandwidth is exhausted, the existing legacy 10G channels may be seamlessly interchanged with 100G services. The same remaining components can even be reused to extend the data rate up to 2.4 Tb/s.


This scenario would require 24 differently colored CFP modules deployed together with the 48 channel 100 GHz DWDM multiplexer. All the 100G services are first multiplexed together such that only one dispersion compensation and amplification stage suffices. Clearly, such a network architecture provides higher density with the capability to reuse existing infrastructure with flexibility while remaining cost friendly.

Scenario 2: 100G Distance Extension Solutions

In this scenario, the switch was tested with SFP+ OEO transponders for simple distance extension solutions. The 100G output signals from the switch are converted to DWDM signals that can be transmitted over longer distances. The solution removes the distance limitations by using a coherent CFP module to connect the output signal to the line fiber and carry the signal over longer distances.


To achieve higher cabling density with Cisco CFP 100G optics, the architecture mixed a 16 channels dual fiber DWDM Mux Demux which can be used for CWDM/DWDM hybrid and 8 channels dual fiber CWDM Mux Demux, by adding MTP harness cable and WDM SFP+ OEO converter to transfer the regular SR wavelength to DWDM wavelengths. Therefore, building a long distance 2500 km DWDM networks in 100G coherent CFP modules and cost effective way will be achieved.


CFP was designed after the Small Form-factor Pluggable transceiver (SFP) interface but is significantly larger to support 100Gbps. The electrical connection of a CFP uses 10 x 10 Gbps lanes in each direction (RX, TX). The optical connection can support both 10 x 10 Gbps and 4 x 25 Gbps variants. CFP has had several of its own evolving iterations of smaller and faster product variants. Coherent 100G CFP can ensure desired performance with less optical transmission impairments, representing as an effective solution for 100G metro networks.


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