10 most popular optical transceivers

Transceivers are lasers that are wavelength specific and convert electrical data signals from data switches into optical signals. Once this process has been performed the data signals can then be transmitted over optical fiber. Each stream of data is transformed into a signal with a unique wavelength.  The signals can be 850nm, 1310nm or 1550nm (where nm is nanometer) – these wavelengths are known as wideband; or CWDM or DWDM – these wavelengths are known as narrow band. 

GBIC (gigabit interface converter) is a standard for transceivers, commonly used with Gigabit Ethernet setups and fibre channel data networks in the 2000s. The standard offers hot swappable electrical interface, which supports a wide range of physical media, from copper to long-wave single-mode optical fiber, at lengths of hundreds of kilometers. 

A GBIC module acts as a transceiver that converts between electrical and optical signals for high-speed networking. The module plugs directly into a system without turning off the computer. This flexibility eliminates the need to replace entire system networking boards. 

SFP, also called mini-GBIC, was designed to replace GBIC because of its smaller size. A SFP module can link equipment like routers and switches. SFP specifications are based on IEEE802.3 and SFF-8472. They are capable of supporting speeds up to 4.25 Gbps. It supports other communication equipment like 100/1000Mbps Ethernet, Fibre Channel, SONET, among other communication standards. 

SFP+ transceiver is virtually identical to SFP in size and appearance. In fact, SFP+ is an enhanced version of the SFP. The main difference is in data rate, which accounts for a difference in transmission distance—SFP typically has a longer transmission distance. SFP+ supports 8 Gbit/s Fibre Channel, 10-Gigabit Ethernet and Optical Transport Network standard OTU2. The applications have expanded to include SONET OC-192, SDH STM-64, OTN G.709, CPRI wireless, 16G Fibre Channel, and the emerging 32G Fibre Channel application. 

XENPAK is a multi-source agreement (MSA) for a 10 Gigabit Ethernet (10GbE) transceiver package. It’s the oldest 10G fiber optic transceiver. XENPAK transceivers are designed with XAUI interface and Digital Diagnostic Monitor Interface, which comply with the XENPAK MSA protocol and satisfy the application of 802.3ae Ethernet protocol 10GB. XENPAK transceivers are supplied for physical layer interfaces supporting multi-mode and single mode fiber optic cables and InfiniBand copper cables with connectors like as CX4. Transmission distances vary from 100 meters (330 ft) to 80 kilometers (50 mi) on fiber and up to 15 meters (49 ft) on CX4 cable. Newer XENPAKs using the 10GBase-LX4 standard operated using multiple wavelengths on legacy multimode fibers at distances of up to 300 meters (980 ft), eliminating the need to reinstall cable in a building when upgrading certain 1 Gbit/s circuits to 10 Gbit/s. 

Like the move from GBIC to SFP, XENPAK was replaced by X2 or SFP+ transceiver that providing higher port density and most of the transceiver vendors stop to provide to the market. 

X2 Optics are a standardized form factor for 10 Gbps fiber optics transponders. Both 10G Ethernet and 10G Fibre Channel versions are available. X2 optics are used in datacom optical links only (not telecom), and they are smaller than XENPAK transponder. The electrical interface to the host board is also standardized and is called XAuI (4 x 3.125 Gbps). X2 optics are essentially an enhanced version of the Xenpak. It also has the same connector as a Xenpak (SC). The X2 optics come in 4 different versions: SX, LX, EX and ZX. The SX version will work on Multi Mode fiber, the LX, EX and ZX work only on Single Mode fiber. The LX will reach a maximum range of 10km, the EX of 40km and the ZX of 80km. X2 optics always have a Tx (sending laser) and a Rx side (receiver). The difference between the sending power (in dB) and the receiving power (in dB) is called the power budget and will determine the distance an optic can cover, where the laser light (in nanometers) also has an important role. Recently, Cisco offered the X2-10GB-T with has a normal RJ45 / Copper port and can produce speeds of 10G over CAT7 cable. 

XFP transceiver module is a 10-Gigabit small form factor pluggable. It generally operates at wavelengths (colors) of 850 nm, 1310 nm or 1550 nm. Principal applications include 10G Ethernet, 10G Fibre Channel, SONET OC-192, SDH STM-64 and OTN G.709, and parallel optics links. 

10G XFP and SFP+ transceivers can be inter-compatible in one Ethernet network on condition that their protocols and standards are consistent. That is to say, they can be used at opposite ends of a physical link and talk with each other, as long as they conform to the same wavelength and signaling rate. 

 XFP technology is relatively older but more expensive, that's also the reason 10G SFP+ modules have been gaining more market share. However, XFP transceiver module still cannot be replaced by SFP+ modules in some 10G network applications. That is due to SFP+ moves some functions to motherboard, including signal modulation function, MAC, CDR and EDC, which makes SFP+ smaller than XFP in size. 

 CFP, short for 100G Form factor Pluggable, is introduced by CFP MSA primarily for 100 Gigabit Ethernet systems. It can support a wide range of 40 and 100 Gb/s applications such as 40G and 100G Ethernet, OC-768/STM-256, OTU3, and OTU4. The electrical interface will vary by application, but the nominal signaling lane rate is 10Gbit/s per lane and documentation is provided for CAUI, XLAUI, OTL4.10, OTL3.4, and STL256.4 electrical interface specifications.  

CFP was designed after the 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.  

There are several CFP types – CFP, CFP2 and CFP4. CFP, CFP2 and CFP4 modules are not interchangeable, but would be inter-operable at the optical interface with appropriate connectors. 

CFP2 is more efficient than the CFP optical module, and its smaller size gives it an advantage over high-density cabling. 

CFP2 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. 

CFP4 module is the half size of CFP2, a quarter of the width of the first generation of CFP, which is less efficient in port utilization. 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 module to apply for 40G/100G Ethernet, telecommunication and other applications. 

The 100G QSFP28 transceiver module is a high-density, high-speed product designed for 100Gbps applications.   

The 100G QSFP28 SR4 is a four-channel, pluggable, parallel, fiber-optic QSFP+ SR4 optical transceiver module for 100/40 Gigabit Ethernet, InfiniBand DDR/EDR and 32GFC applications. This transceiver is a high-performance module for short-range multi-lane data communication and interconnects applications. It integrates 4 data lanes in each direction with 112.2 Gbps bandwidth. Each lane can operate at 8.055Gbps up to 70M using OM3 fiber or 100M using OM4 fiber. The module is designed to operate over multimode fiber system using a nominal wavelength of 850nm. The electrical interface uses a 38-contact edge type connector. The optical interface uses a 12 fiber MTP (MPO) connector. 

Compared with 100G CFP/CFP2/CFP4 transceivers, the 100G QSFP28 module surpasses them with the strong ability to increase density, decrease power consumption, and decrease the price per bit. 

There are different variants for QSFP28 form factor.