It is known that there exist various similarities between CFP and CXP optical transceiver. For example, both of them are hot-pluggable, available for 40Gb/s and 100Gb/s as well as support transmitting and receiving function, etc. On the surface, it seems that there are no differences between CFP and CXP optical transceiver.
What Is CFP Optical Transceiver?
CFP, short for C Form-factor Pluggable, is designed after the Small Form-factor Pluggable transceiver (SFP) interface but is significantly larger to support 100Gbps. The C stands for the Latin letter C used to express the number 100 (centum), on account that the standard is primarily developed for 100 Gigabit Ethernet systems. In fact, CFP also supports 40GbE. When it comes into CFP optics, CFP is always defined as multipurpose CFP.
The CFP form factor(including three form factors: CFP, CFP2, CFP4, shown as the pic), as detailed in the MSA, supports both single-mode and multi-mode fiber and a variety of data rates, protocols, and link lengths, including all the physical media-dependent (PMD) interfaces in the IEEE 802.3ba standard. At 40GE, target optical interfaces include the 40GBase-SR4 for 100 meters (m) and the 40GBase-LR4 for 10 kilometers (km). Simultaneously, there are three PMDs for 100GE: 100GBase-SR10 for 100ms, 100GBase-LR4 for 10kms, and 100GBase-ER4 for 40kms. Moreover, the electrical connection of a CFP uses 10 x 10Gbps lanes in each direction (RX, TX). The optical connection can support both 10 x 10Gbps and 4 x 25Gbps variants. CFP transceivers can support a single 100Gbps signal like 100GE or OTU4 or one or more 40Gbps signals like 40GE, OTU3, or STM-256/OC-768.
What Is CXP Optical Transceiver?
CXP optical transceiver is targeted at the clustering and high-speed computing markets, thus CXP optical transceiver is usually called as high-density CXP optics. Technically, the CFP will work with multimode fiber for short-reach applications, but it is not really optimized in size for the multimode fiber market, mostly due to that high interface density is required in the multimode fiber market. The CXP is created to satisfy the requirements of the data center for high density, targeting parallel interconnections for 12x QDR InfiniBand (120Gbps), 100GbE, as well as all links between systems collocated in the same facility. The InfiniBand Trade Association is currently standardizing the CXP.
The CXP is 45mm in length and 27mm in width, slightly larger than an XFP. It consists of 12 transmitting and 12 receiving channels in its compact form factor, which is achieved via a connector configuration similar to that of the CFP. Besides, the CXP enables a front panel density that is greater than that of an SFP+ running at 10Gbps. And its transmission distance can reach up to 100ms.
CFP vs. CXP Optical Transceiver：What Are the Differences?
When it comes to the differences between CFP and CXP optic transceiver module, it seems that the similarities of them are more than differences of them. Thus, the similarities will be first introduced before the differences are involved in. In terms of form factors, both CFP and CXP optical transceiver are hot-pluggable. In the aspect of design, both are with transmitting and receiving functions. With respect to data rate, both support data rates of 40Gbps and 100Gbps. Although CFP is similar to CXP in the acronym and the time of emerging, and the form factor of CFP and CXP optical transceiver is markedly different in size, density, and application. The differences in the density and size actually shown in the separate introductions to CFP and CXP. Therefore, the next content will mainly be focused on the introduction of the difference in applications.
In applications, the CFP supports both single-mode and multimode fiber and can accommodate a host of data rates, protocols, and link lengths, primarily aimed at 40G and 100G Ethernet applications. While the CXP, by contrast, is targeted at the clustering and high-speed computing markets. Furthermore, CFP is for long-reach applications, while CXP is for short-reach applications. Thus, the existence of CXP does not mean the replacing of CFP.
To sum up, there are many similarities and differences between CFP and CXP optical transceivers. In some sense, there is a competition between CFP optical transceivers and CXP optical transceivers, which is due to that CFP optics can also be used with multimode optic fibers. Well, the actual applications depend on the users’ choices. For example, if one needs to build a network available for various data speeds, CFP optical transceiver can be used; if it is mainly used for short-distance transmission, the CXP optical transceiver will be a better choice.
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