Tag Archives: CXP Transceiver

Knowledge of Multi-source Agreement

We usually see some products that are compliant with MSA when refers to fiber optic transceivers, but what does MSA mean? It seems like a standard that is used to define the optical transceiver. In fact, MSAs are not official standards organizations. Instead, they are agreements that equipment vendors assume when developing form factors for communications interfaces. These form factors, usually called the transceiver modules, are typically deployed in active electronics such as switches, servers and multiplexers. In this text, some knowledge of the MSA will be introduced.

What is Multi-source Agreement?

MSA stands for multi-source agreement, which is an agreement between multiple manufacturers to make products which are compatible across vendors, acting as de facto standards, establishing a competitive market for interoperable products. Products that adhere to MSAs include optical transceivers (SFP, SFP+, XENPAK, QSFP, XFP, etc), fiber optic cables, and other networking devices. MSAs strictly define the operating characteristics of these optical transceivers so that system vendors may implement ports in their devices that allow MSA compliant transceivers produced by name brand, as well a third party vendors, to function properly. That is, transceivers may be purchased from any of the multiple sources in the open market, like Fiberstore. MSAs are also important in the cabling industry as the density, line speed, power consumption and typical costs of a MSA can strongly impact its success in the marketplace. This, in turn, can drive the choice for both connector and media type.

Why is Multi-source Agreement so Important?

Equipment vendors all rely on MSAs when designing their systems, ensuring interoperability and interchangeability between interface modules, that is every supplier can produce the transceiver modules with the same functions. For this reason, there are many module suppliers from which customers can choose freely. As we all know, freedom of choice is the foundation of the efficient operation of markets. In order to gain a bigger share of the market, suppliers may act as efficiently as possible, which may drive down costs and offer the widest options to customers. Besides, since there are so many excellent 3rd party optical transceiver module suppliers in the market that network operators don’t need to purchase optical transceivers directly from system (original brand) vendors, which will also save huge costs. Finally, there is no doubt that all these will help support and encourage creation and adherence to standards at the same time. Over the past decade, the MSA process has helped accelerate the acceptance of modules such as SFP+ and CFP, which allow optical transceivers to support greater bandwidth such as 40G and 100G.

Approved Fiber Optica Transceiver Multi-source Agreements

MSA is a popular industry format jointly developed and supported by many network component vendors, most common optical transceivers are specified by it at present. MSAs usually specify parameters for optical transceivers and their guideline values, such as the electrical and optical interfaces (e.g. SX, LX, EX, ZX, etc), mechanical dimensions, electro-magnetic values and other data. This data is accessible by the host system over the I2C interface, as is the status of the optional DDM functions. Some approved fiber optica transceiver multi-source agreements are listed in the table below:

Name	Year	Brief Description	Keywords/Applications
GBIC	2000	GigaBit Interface Converter	Designed for Gigabit Ethernet, SDH/SONET (2.5 Gb/s) and Fibre Channel (4Gb/s). Superseded by SFP
SFP	2001	Small Form-factor Pluggable	Designed for Gigabit Ethernet, SDH/SONET (2.5 Gb/s) and Fibre Channel (4Gb/s)
XENPAK	2001	Fiber optic transceiver for 10Gb Ethernet	Superseded by X2 and SFP+
X2	2005	Fiber optic transceiver for 10Gb Ethernet	Superseded by SFP+
XFP	2005	Fiber optic transceiver for 10Gb Ethernet	Designed for 10Gb/s. Supports 8Gb/s Fibre Channel, 10 Gb/s Ethernet and Optical Transport Network
SFP+	2013	Fiber optic transceiver for 10Gb Ethernet	Designed for 10Gb/s. Supports 8Gb/s Fibre Channel, 10 Gb/s Ethernet and Optical Transport Network standard OTU2
QSFP/QSFP+	2013	Quad Small Form-factor Pluggable 40G	Supports Ethernet, Fibre Channel, InfiniBand and SONET/SDH standards up to 40GB/s and 100Gb/s
CFP	2013	C Form Factor Pluggable (100G)	Optical transceiver form factors supporting 40Gb/s and 100Gb/s. CFP, CFP2 and CFP4
CXP	In Progress	C Form Factor Pluggable	Supports Infiniband and Ethernet to 100G. CXP and CXP2

40 Gigabit Ethernet Options Guideline

When the IEEE introduced the 802.3ba Ethernet standard, this was in response to the increasing bandwidth demands facing data centers, paving the way for the introduction of 40Gb/s and 100Gb/s Ethernet operations. Believe it or not, the 40 Gigabit Ethernet era is already upon us. This text put together a brief overview of the current 40 Gigabit Ethernet optics types and form factors to aid in planning for future high-performance Ethernet needs.

40 Gigabit Ethernet Standards
The IEEE 802.3ba introduced the 40 Gigabit and 100 Gigabit Ethernet standards in 2010. 802.3ba is the designation given to the higher speed Ethernet task force which completed its work to modify the 802.3 standard to support speeds higher than 10 Gbit/s. This was the first time two different Ethernet speeds were specified in a single standard. The table below gives detailed specifications for 40 Gigabit Ethernet standards.

40 Gigabit Ethernet QSFPTransceiver Options
As with any new generation of technology, one design goal was to leverage as much existing technology as possible. By minimizing the number of new interfaces, the interfaces become less expensive and take advantage of volume production and simplicity. To meet this design goal, there are three media modules will be used in the first generation of 40 Gigabit Ethernet: QSFP, CXP and CFP.

QSFP
The Quad Small-Form-Factor Pluggable (QSFP) is similar in size to the CXP and provides four transmit and four receive lanes to support 40 Gigabit Ethernet applications for multimode fiber and copper today and may serve single-mode in the future. Another future role for the QSFP may be to serve 100 Gigabit Ethernet when lane rates increase to 25 Gbps.

CXP
The CXP transceiver features 12 transmit and 12 receive 10-Gbps lanes to support one 100 Gigabit Ethernet port, or up to three 40 Gigabit Ethernet ports. It can achieve rates up to 120 Gbps of pluggable data over 12 lanes in one assembly while enhanced-footprint connectors transmit signals over 10 lanes for up to 100 Gbps.

CFP
The C Form-Factor Pluggable (CFP) is a new media module that was designed for longer-reach applications, with up to 24 watts of power dissipation. Its dense electrical connectors and integrated, riding heat sink enable a range of interfaces. This module is used for 40GBASE-SR4, 40GBASE-LR4.

40GbE Cabling Options

The most common 40GbE cable is the QSFP+ Cable. Such as QSFP direct attach copper cable (DAC) and QSFP active optical cable (AOC). Besides, the MPO/MTP cable is considered the best solution for 40GbE. Since MPO/MTP connectors have either 12 fibres or 24 fibres array, which can allow data transmission across multiple fibres simultaneously.

Direct Attach Copper Cable

Transmitting 40 GbE over short distances of parallel coaxial copper cabling (also referred to as twinax cabling) is accomplished using a special cabling assembly with four lanes of coaxial cabling (eight pairs). Four pairs each transmit 10 Gbps in one direction and four transmit 10 Gbps in the other direction for a total data rate of 40 Gbps. The two common DACs used in 40g Ethernet are QSFP to QSFP and QSFP to 4 SFP+ copper direct-attach cables.

40G DAC

Active Optical Cable

In the market, there are two common 40g fiber cable: QSFP to 4 SFP+ breakout AOC and QSFP to QSFP AOC. The former is a 4×10 Gb/s parallel active optical cable which transmits four separate streams of 10 Gb/s data over ribbon cables in a point-to-multipoint configuration. The cable contains a QSFP+ module on one end and four separate SFP+ modules at the other ends. The latter is a 40 Gb/s parallel active optical cable which transmits error-free parallel 4×10 Gb/s data over multimode fiber (MMF) ribbon cables.

40G AOC

MPO/MTP Cable

Current multi-mode optics standards for 40GbE optics use multiple 10Gbps lasers, simultaneously transmitting across multiple fiber strands to achieve high data rates. Because of the multi-lane nature of these optics, 40GbE multi-mode optics use a different style of fiber cabling, known as MPO or MTP cabling. As with 10GbE optics over multi-mode fiber, an OM3 or OM4 grade MMF is needed to be able to cover longer distances. For 40g Ethernet, we can use 8 fibers MPO/MTP harness cables or 12 fibers MPO/MTP trunk cables. The former is to directly connect a QSFP port to other 4 SFP+ ports. The latter is to directly connect one QSFP port to another QSFP port.

MPO/MTP cable

40G Network Connectivity Solutions
MTP Fiber Cable Solutions
Three Types MTP Harness Cables Used in Today’s Data Center

What’s Difference Between CFP and CXP Transceivers?

Two years ago, though everyone is talking about the 100G Ethernet as the next generation, it had still faced a lot of problems to be solved, seeming to be a long way off. But, technologies are developed very rapidly, and now 100G Ethernet is becoming more and more closer to us. Fiber connectivity in higher-speed active equipment is being condensed and simplified with plug-and-play, hot-swap transceiver miniaturization. Thus, optical transceiver technology is one of the basic but important technology to achieve the realiable and effective 100G Ethernet. Interfaces for 100G active equipment include CFP and CXP. So, what are CFP and CXP? And what’s the difference between CFP and CXP? Is CXP transceiver designed to replace the CFP? … You might be interested in them and have a lot of questions in your mind. Today, you will find the answer in this post.

About CFP
CFP, short for C form-factor pluggable, is a multi-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 for 100 Gigabit Ethernet systems. In fact, CFP also supports the 40GbE. When talking about CFP, we always define it as multipurpose CFP, compared to the CXP which is discussed later.

The CFP MSA was formally launched at OFC/NFOEC 2009 in March by founding members Finisar, Opnext, and Sumitomo/ExceLight. The CFP form factor, 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 encompassed 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). There are three PMDs for 100 GE: 100GBase-SR10 for 100 m, 100GBase-LR4 for 10 km, and 100GBase-ER4 for 40 km.

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 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.

The CFP-MSA Committee has defined three form factors:

CFP – Currently at standard revision 1.4 and is widely available in the market
CFP2 – Currently at draft revision 0.3 is half the size of the CFP transceiver; these are recently available in the market
CFP4 – Standard is not yet available, is half the size of a CFP2 transceiver, not yet available

CFP transceiver today to future

The original CFP specification was proposed at a time when 10Gbps signals were far more achievable than 25Gbps signals. As such to achieve 100Gbps line rate, the most affordable solution was based on 10 lanes of 10Gbps. However as expected, improvements in technology has allowed higher performance and higher density. Hence the development of the CFP2 and CFP4 specifications. While electrical 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 interchangable (but would be interoperable at the optical interface with approriate connectors).

About CXP
CXP is targeted at the clustering and high-speed computing markets, so we usually called it high-density CXP. 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, most notably because the multimode fiber market requires high faceplate density. The CXP was created to satisfy the high-density requirements of the data center, targeting parallel interconnections for 12x QDR InfiniBand (120 Gbps), 100 GbE, and proprietary links between systems collocated in the same facility. The InfiniBand Trade Association is currently standardizing the CXP.

The CXP is 45 mm in length and 27 mm in width, making it slightly larger than an XFP. It includes 12 transmit and 12 receive channels in its compact package. This is achieved via a connector configuration similar to that of the CFP. For perspective, the CXP enables a front panel density that is greater than that of an SFP+ running at 10 Gbps.

Typical applications of CXP in the data center include 100GE over Copper (CXP): 7m (23ft) and 100GE over multimode fiber: CXP for short reach applications (CFP is used for longer reach applications).

What’s the Difference Between CFP and CXP?
Despite having a similar acronym and emerging at roughly the same time, the CFP and CXP form factors are markedly different in terms of size, density, and intended application. The CFP and CXP optical transceiver form factors are hot pluggable, both feature transmit and receive functions, and both support data rates of 40 and 100 Gbps. But the similarities begin and end there. Aimed primarily at 40- and 100-Gigabit Ethernet (GbE) applications, the CFP supports both singlemode and multimode fiber and can accommodate a host of data rates, protocols, and link lengths. The CXP, by contrast, is targeted at the clustering and high-speed computing markets. The two are therefore complementary, not competitive, according to several sources. Thus, the existence of CXP does not mean the replacing of CFP.

However, things are never black and white. In some case, there is a competition between CFP and CXP, as CFP can also be used with multimode fiber. It becomes more of a choice for system vendors. Do they need to build a box that can adapt to any interface? If so, they would probably use CFP. If it’s a box that is just focused on the short-reach market, then they would probably use something more like CXP.

I hope this post will let you more understanding the 100GbE transceivers, whether CFP or CXP. Similarly, you could kown the 40GbE transceiver through this post as the CFP and CXP also support the 40GbE. If you want to have a further study on this subject, I suggest you to learn the related refference of MSA.

Article Source: http://www.fiber-optic-transceiver-module.com/whats-difference-between-cfp-and-cxp-transceivers.html

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