Different types of transceivers

Different types of transceivers

There’s a lot to consider when building a fiber optic network. There are so many different ways to approach optical communication, and every device has its own list of pros and cons. In modern, dense networks, small form factors are a constant necessity. Without such interfaces, you simply can’t pack enough networking components into the limited space that is always constricting the network’s design. That’s why so many form factors have emerged. This simple guide is going to help you map the differences between GBIC, SFP, SFP+, SFP28, QSFP, QSFP+, QSFP28 and CFP. With it, at least some of your networking decisions should come a little more easily.

GBIC (Gigabit Interface Converter)

A gigabit interface converter (GBIC) is a transceiver that converts electric currents (digital highs and lows) to optical signals, and optical signals to digital electric currents. The GBIC is typically employed in fiber optic and Ethernet systems as an interface for high-speed networking. The data transfer rate is one gigabit per second (1 Gbps) or more. This is the first generation of all transceiver modules which was invented in the year 2000.

GBIC modules allow technicians to easily configure and upgrade electro-optical communications networks. The typical GBIC transceiver is a plug-in module that is hot-swappable (it can be removed and replaced without turning off the system). The devices are economical because they eliminate the necessity for replacing entire boards at the system level. Upgrading can be done with any number of units at a time, from an individual module to all the modules in a system.

SFP (Small Form-factor Pluggable)

Usually, SFP is considered an upgraded version of the GBIC module. However, GBIC and SFP are equal in performance. The only major difference between them is their size. SFP module is much smaller than the GBIC module. For this reason, the SFP is also called mini GBIC which was developed in 2001. These years, due to the small size of SFP, GBIC module is being replaced by SFP. Why is this happening? In fact, the most common reason is that the big size of the GBIC module was not feasible to provide a number of interfaces on a line card or a switch since it occupies more space.

In my previous article, you might have seen basics of SFP transceivers available in the market. The evolution of these transceivers didn’t stop here too. Even though SFPs are the most widely used transceivers there is many more SFP varieties are available which is based on the data transfer rate and maximum distance it can cover. Let us have a look at these models also.

SFP+

SFP+ takes the benefits of the SFP design and improves on their data capacity. SFP+ still functions with copper and optical cabling, but it can achieve much higher speeds. SFP+ is made to operate at 10Gb/s. Classified by the host interface, the SFP+ fiber optic transceiver can be divided into linear and limiting transceivers. The linear SFP+ module is most appropriate for 10GBase-LRM; otherwise, a limiting module is preferred with the reason that it contains a signal amplifier to re-shape the degraded (received) signal whereas linear does not.

SFP 28

SFP28 stands for Small Form-Factor Pluggable 28. It is the third generation of the SFP interconnect systems designed for 25G performance per the IEEE 802.3by specification (25GBASE-CR). SFP28 has the same common form factor as the SFP+ but supports 25Gbps electrical interfaces per channel. SFP+ and SFP28 transceiver has the same pinouts and they are mating compatible.

Given the fact that SFP28 is compatible with SFP+ ports, here comes the question: is it possible to connect SFP28 ports with SFP+? The answer is definitely yes: SFP28 adopts the same form factor as SFP+, just running at 25 Gb/s instead of 10Gb/s, which offers better performance and higher speed. So SFP28 will work sufficiently on SFP+ ports, and SFP+ cables can be plugged into SFP28 ports although they are not designed for 25Gb/s data rates. When it comes to copper cable, SFP28 copper cable possesses significantly greater bandwidth and lower loss compared with the SFP+ version.

XFP

XFP has appeared before the SFP+. It is also a standardized form factor for serial 10 Gb/s fiber optic transceivers. Principal applications include 10 Gigabit Ethernet, 10 Gbit/s Fiber Channel, synchronous optical networking (SONET) at OC-192 rates, synchronous optical networking STM-64, 10 Gbit/s Optical Transport Network (OTN) OTU-2, and parallel optics links.. XFP transceivers are used in data communication and telecommunication optical links and offer a smaller footprint and lower power consumption than other 10 Gb/s transponders. The electrical interface to the host board is a standardized serial 10 Gb/s interface called XFI. XFPs are slightly bigger than SFP modules in size.

QSFP(Quad Small Form-factor Pluggable)

Another expansion on the original SFP concept, QSFP uses double fiber pairs. The Q stands for “quad,” and the additional pair allows for substantially more powerful data transmission. QSFP data rates get up to 1 Gbps per channel, allowing for 4X1 G cables and stackable networking designs that achieve better throughput. QSFP connectors are still small(slightly bigger than SFPs) and hot-pluggable, and they still support Ethernet and fiber optics. Added to the supported list is InfiniBand.

QSFP+( Quad Small Form-factor pluggable plus)

QSFP+ is the modern incarnation of QSFP. The difference is only the data transfer rate in QSFP+ is much higher than QSFP. In most data centers, it has completely replaced its predecessor. QSFP+ can reach speeds of 10 Gbps per line. QSFP+ has four-channel SFP+ interfaces that can transfer rates up to 4x10Gbps or 1x40Gbps depending on the transceiver used.

QSFP28(Quad Small Form-factor pluggable 28)

The latest advance on QSFP connections is QSFP28. The 100G QSFP28 transceiver module is a high-density, high-speed product designed for 100Gbps applications. It has the same form factor as the QSFP+ transceivers. QSFP28 100G optics offers four channels of high-speed differential signals with data rates ranging from 25 Gbps up to potentially 40 Gbps, and finally, meet 100 Gbps Ethernet (4×25 Gbps) and 100 Gbps 4X InfiniBand Enhanced Data Rate (EDR) requirements. QSFP28 transceiver recently is typically available in several standards—100GBASE-SR4, 100GBASE-LR4, 100GbASE-PSM4 and 100GBASE-CWDM4. QSFP28-100G-SR4 operates over multimode fiber for a distance of 100 m. While 100GBASE-LR4 QSFP28 supports a much longer distance of 10 km. Compared with CFP form factors, QSFP28 optics are more popular on the 100G optics market.

CFP(C form-factor pluggable)

CFP 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. It can support a wide range of 40Gb/s, 100Gb/s and 400Gb/s applications, including next-generation High-Speed Ethernet (40GE, 100GE and 400GE). Pluggable CFP, CFP2, CFP4 and CFP8 transceivers will support the ultra-high bandwidth requirements of data communication networks that form the backbone of the internet. The most recent CFP8 transceiver form factor provides for a very versatile platform that can support a broad range of PMD’s at 400G and importantly offers a path to products in the future that are capable of supporting 800Gb/s.

Classified by application, which means that all of the above transceivers can be used with multiple fiber optics technologies such as BiDi, CWDM, DWDM the data transfer rate and distance can be maximized. For this purpose, various BiDi modules, CWDM modules, DWDM modules of all of the above transceivers can be purchased.

Knowledge & picture Credits: www.fs.com

Have a comment or points to be reviewed? Let us grow together. Feel free to comment.