Alphabet soup of fiber optic acronyms or what means what?


BX-D and BX-U (BiDi) – These optical transceivers use one optical fiber instead of two for standards which are mentioned above. It is a cost-effective solution for Data Centers and other infrastructure. BIDI SFP optical modules must be matched in pairs because there is one port only for transmitting or receiving. These optical transceivers use SMF from 10 to 120 km to support bi-directional links.

CFP – CFP is an acronym from 100G (C = 100 in Roman numerals; Centum) Form factor Pluggable. CFP is introduced to serve as an optical transceiver for 100G interfaces. Electrical connection of the CFP modules use 10×10 Gbps lanes in each direction (Tx and Rx) and optical connection support 10×10 Gbps for 100GBASE-SR10 and 4×25 Gbps for 100GBASE-LR4 and 100GBASE-ER4. CFP Form factor is larger in size and requires higher power consumption. 100G CFP optical transceivers are used by Internet Service Providers, Mobile Operators and Data Center globally. 

CFP2 – CFP2 module has a form factor of 1/2 the size of a CFP module. Electrical interfaces vary by application, but the nominal signaling lane rate is 25 Gbit/s per lane. The electrical interface has been specified to allow for supplier-specific customization around various 4 x 25 Gbit/s interfaces, nevertheless, it can support 8×25 Gbit/s, 10 x 10 Gbit/s, and 8×50 Gbit/s. CFP2 is more efficient than the CFP optical module and it is ideal for line-side trunk DWDM data center interconnection, metro carriers, and regional/long-haul applications.

CFP4 – CFP4 is designed to support a 40/100G interface for Ethernet, Telecommunication and other applications. dentical to CFP2 module, the electrical interface of CFP4 will vary by application, the nominal signaling lane rate is also 25 Gbit/s. With 1/4 the size of the CFP module, CFP4 can be used to support SMF and MMF optics. CFP4 electrical interface is specified to allow for supplier-specific customization with various 4 x 25 Gbit/s and 4 x 10Gbit/s interfaces.

CFP8 – CFP MSA designed CFP8 as a 400G form factor type.  It is the same size as the CFP2 transceiver but uses a new 16x25G electrical I/O connector. As for bandwidth density, it respectively supports eight times and four times the bandwidth density of CFP and CFP2 transceivers. The interfaces of the four CFP8 transceivers are generally specified to allow for 8 x 50 Gb/s, 16 x 25 Gb/s, 4x100Gb/s modes.

Copper SFP – This kind of  transceiver supports copper connection over CAT5 cable maximum up to 100m and it has RJ45 connector. Copper modules are used for different places today’s networking where existing copper connections are still available.

Copper SFP+ – Copper SFP+ is common for communications links, which requires 10 Gigabit over Cat6a/7 cables and RJ45 connector. Transmission distance depends on the speed, for example, it can reach 30 m at 10Gb/s. Advantage of these transceivers is that it can be compatible with legacy networks and plan copper networks using existing ports. Also copper cables are less expensive than fiber cables.

cSFP – cSFP is a Compact Small Form-Factor Pluggable. By using Compact SFP (cSFP) we can achieve double throughput in the same SFP port by having 2 BiDi bidirectional streams of traffic, thus we can get 2xGE out from one SFP port. Most commonly cSFP is used in Central Office/Aggregation site operating at Tx1&Tx2:1490nm Rx1&Rx2:1310nm and it gets connected to 2 CPE sites which have simple BiDi SFP operating in Tx:1310nm Rx:1490 at each site. 

CWDM4 – The CWDM4 is designed for low-cost  optical interfaces that run up to 2 km in data center applications.  CWDM4 modules adopt WDM technology that enables four wavelengths (input wavelengths of 25Gb/s) to be multiplexed to transmit on a single fiber, which greatly saves optical fiber resources. On the other end of the connection, the CWDM4 de-multiplexes a 100Gb/s (for example) optical input into 4 channels of CWDM optical signals and then converts them to 4 output channels of electrical data on the receiver.


DR4 – DR4 supports a maximum transmission distance of 500 meters on 1310 nm center wavelength. DR4 module converts 8 channels of 50Gb/s (PAM4) electrical signal into 4 channels of parallel optical output data, each capable of 100Gb/s data rate for an aggregated bandwidth of 400Gbls. On the receiver side, the optic transceiver converts 4 lanes of parallel optical data of 100Gbp/s each lane for an aggregate of 400 Gbp/s to support 8 lanes of 50Gb/s PAM4 electrical output signal.

ER – ER (Extended Range) works in distance up to 40km on SMF and 1550nm laser. These optical transceivers are in different applications such as for Data Centers, Enterprise and Internet Service Providers networks.

ER4- EX (Extended Wavelength)  supports the dense wavelength division multiplexing technology to transmit signals by the single-mode fiber optic cables, which can reach a distance of 40km on SMF. The ER4 optical module transmitters are operating at the LAN WDM wavelength (1295 nm, 1300 nm, 1305 nm, and 1310 nm).

ER8 – ER8 is designed for  400GBASE-ER8 Ethernet. Modules can reach up to 40km over dual SMF with FEC.  On the transmission side, it converts 8x 50G 400GAUI-8 PAM4 electrical input channels (each 53.125Gbps) into 8 Single Lambda 50G PAM4 LAN-WDM optical signals which are multiplexed for transmission over single fiber. On the other side of the connection, an optical signal is received and demultiplexed and then it converts 8 Single Lambda 50G PAM4 LAN-WDM optical signals into 8x 50G 400GAUI-8 electrical inputs.

eSR4 – eSR4 is designed for use in 40 Gigabit Ethernet (40GE) applications over multi-mode fiber. The QSFP+ eSR4 transceiver integrates four data lanes in each direction with each lane to give an aggregated 40 Gbps bandwidth. Each lane supports link lengths of 300m on OM3 multimode fiber or 400m on OM4 multimode fiber.

EX – EX (Extended Wavelength) can reach a longer distance up to 40km over SMF and 1310 or 1550nm. There are different networking places where these distance modules are used. For example most popular are for Internet Service Providers, Gigabit Ethernet Communications, Ethernet and Data Center Networks and other optical links.

FR4 – FR refers to 2km reach using single-mode fiber, and “4” implies there are 4 optical channels. FR4 transceiver incorporates 4 independent lanes on CWDM4 center wavelengths of 1271/1291/1311/1331nm running at 100 Gbps per lane. The FR4 module uses a duplex LC connector to connect to a single fiber pair.


GBIC The gigabit interface converter (GBIC) is the forefather of all optical transceiver form factors. It was created in 1995 and is used to link gigabit Ethernet connections over short distances up to hundreds of kilometers. It has been superseded by the SFP form factor and is now outdated, however some customers still use GBIC optical transceivers on occasion.


LR – LR (Long Range) helps to connect network equipment from a distance of up to 10km. LR, unlike SR, is connected over SMF and uses a 1310nm laser. Transceivers are suitable for Data Centers, Enterprise and Internet Server Provider networks. As LR has no minimal distance then it can be used for short connections over SMF.

LR4 – LR4 (Long Range 4 channels) is designed for long-distance transmission up to 10km in the 100G Ethernet network with a working bandwidth of 1295 nm to 1310 nm. The 100G QSFP28 LR4 optical module converts four 25Gbps electrical signals into four LAN WDM optical signals and multiplexes them into a single channel for 100G optical transmission. At the receiver side, the module reuses 100G light input demultiplexing into four LAN WDM optical signals and then converts them into four electrical channel signal output channels.

LR8 – LR8 (Long Range 8 channels) is designed for 400GBASE-ER8 Ethernet. LR8 is meant for links up to 10km over single mode fiber. The 400GBASE-LR8 module supports eight electrical interface lanes which operate in 50G PAM4 encoding mode resulting in 400G (8x50G) data rate.

LRM – LRM (Long Reach Multimode) operates with the same 1310nm laser as LR but distance is only till 220m over MMF which is enough for LAN networks inside the building. This is popular for the high speed in the short distance where legacy OM1 fiber is used.

LW – LW (Long Wavelength) supports links up to 10km over SMF. LW expression is designed for usage in Fiber Channel links, with its central wavelength of 1310 nm.

LX – LX supports link up to 10km over SMF (single mode fiber) or 550m on MMF.  SMF LX works at 1310nm, it is more affected by waveguide dispersion, and it is more affected by micro bends, twists and stress in the fiber. These modules are used for Ethernet switches and routers to connect it in the different buildings.

SFP – SFP stands for small form-factor pluggable. A hot-swappable optical transceiver designed for data rates from 1.063 to 1.25 Gbps. SFPs are interchangeable fiber connectors that can adapt to any existing network. They can be intermixed in combinations of 1000BASE-SX, 1000BASE-LX/LH, 1000BASE-EX, 1000BASE-ZX, or 1000BASE-BX10-D/U on a port-by-port basis.

SFP+ – SFP+ (also known as Small Form Factor Pluggable Enhanced) is a hot-swappable optical transceiver, and is a type of transceiver used in high-speed networking applications. It is designed for data rates from 8.5 Gbps up to 10.3 Gbps and is commonly used in 10 Gigabit Ethernet and Fibre Channel applications. SFP+ transceivers provide the uplink interfaces, laser transmission (Tx) and receiver (Rx), and it supports 850 to 1610 nm nominal wavelengths, depending on the used transceiver.

SFP28 – Same Form Factor With Different Speed – SFP28 and SFP+ transceivers are both small form-factor pluggable transceivers, meaning they have a similar physical size and shape. However, the main difference between the two is the data rate they support. An SFP28 transceiver can achieve higher data rates than an SFP+ transceiver (up to 25 Gbps), but it is not backwards compatible with SFP+ ports. Additionally, SFP28 transceivers are typically smaller in size compared to SFP+ transceivers. It is important to use the correct transceiver type for the intended application to ensure optimal performance.

SR – SR (Short Range) is a very popular optical transceiver for high speed in the short distance (till 300m) via OM3 fiber and operating at 850nm. It is an option for Data Centers, Enterprise Networks, Internet Service Providers and for other optical links.

SR4 – SR4 is designed for 4-channel pluggable optical transceivers for short-range data communication and interconnects applications. The maximum distance of SR4 is up to 100 meters. Mostly used for 40 Gbps and 100 Gbps applications.

SR8 – SR8 (Short Range 8 channel) is designed for 400GBASE-ER8 Ethernet with a maximum link length of 100m on OM4 multimode fiber. The module supports eight electrical interface lanes which operate in 50G PAM4 encoding mode resulting in 400G (8x50G) data rate. The SR8 high-speed optical transceivers find applications in cloud computing, Big Data and other technologies associated with the construction of data centers.  

SW – SW (Short Wavelength) supports links up to 100m over MMF. SW expression is designed for usage in Fiber Channel links, with its central wavelength of 850 nm.

SX – SX (Short Wavelength) operates over MMF (multimode fiber) up to 550m with LC connectors. SX modules work with 850nm lasers. These standard transceivers are popular for networks inside the one building. As the MMF core is thicker, it allows it to reach higher speeds at short distances. These transceivers are more affected by modal dispersion because light rays have different paths through the fiber and it arrives at different times at the other end. This is the reason why distance is limited.


QSFP, QSFP+ – QSFP, or quad small form factor pluggable, is another type of compact, hot-swappable transceiver. It supports Ethernet, Fibre Channel, InfiniBand and SONET/SDH standards with different data rate options. QSFP modules are commonly available in several different types: 4 x 1 Gbps QSFP, 4 x 10 Gbps QSFP+. QSFP+ modules integrate 4 transmit and 4 receiver channels and support 4 x 10 Gbps or 1 x 40 Gbps. The specifications for QSFP are based on SFF-8436.

QSFP-DD – The QSFP-DD (Quad Small Form Pluggable Double Density) transceiver form factor leverages the manufacturing capability and cost structure that supports QSFP+ and QSFP28. The QSFP-DD specification defines a pluggable form factor that supports 8 high speed electrical interfaces connecting to the host. QSFP-DD can support 36 ports of 400GbE in a single Rack Unit (RU) providing over 14Tb/s of bandwidth. The QSFP-DD has become the most popular form-factor for 400G due to its small size as compared to competing solutions in QSFP or CFP2 formats.

QSFP28 – 100G QSFP28 (Quad Small Form-Factor Pluggable 28) optical transceivers are widely used by Internet Service Providers, Mobile Operators and Data Centers globally as QSFP28 transceivers have become the dominant form factor of 100G. QSFP28 transceiver portfolio consists of transceivers which can operate over Single Mode or Multi Mode optical fiber, can be used for connections from couple of meters up to 80 kilometers and are suitable for 100G Ethernet, Optical Transport Network OTU4 and 128G Generation 6 Fiber Channel applications. Additionally, Single Fiber 100G QSFP28 transceivers are available for 10km to 40km connecting distances.

QSFP56 – QSFP56 (Quad Small Form-Factor Pluggable 56) transceivers use the same physical specifications as the QSFP28 form factor and still have 4 electrical lane signals (same as QSFP28), but instead of carrying 4x25G NRZ modulated signal (QSFP28), QSFP56 transceivers support 4x50G PAM-4 (Pulse Amplitude Modulation 4-level) signals, which effectively doubles the network’s data rate to 200G.


XFP – The XFP (10 Gigabit Small Form Factor Pluggable) is a standard for modules for high-speed network and telecommunication links that use optical fiber. XFP modules are hot-swappable and they typically operate at 850nm, 1310nm or 1550nm. These transceivers can operate over a single wavelength or use dense wavelength-division multiplexing techniques. Principal applications of XFP modules include SONET OC-192, SDH STM-64, 10 Gbit/s Optical Transport Network (OTN) OTU-2, and parallel optics links.

ZR – ZR transmission distance reaches up to 80 km over SMF with a 1550nm laser. Modules are used for optical network applications. 

ZR4 – ZR4 transceivers are used to connect switches, routers and transmission equipment in the data center, and the transmission distance is up to 80 km over single-mode fiber (SMF). ZR4 optical module is fully compliant with the QSFP28 industry standard and associated MSA as described in the latest SFF-8665/8636, and is available with digital diagnostics via the I2C interface.

ZX – ZX also stands for Extended Wavelength but it can reach 80 km over SFP and works with a 1550nm laser. These transceivers are used in similar networks where 40km optical modules only distance between devices are longer.

One more option is EZX standard with extended distance up to 120km.


4WDM – 4WDM optics are designed to support 100G Ethernet, suitable for data center links up to 30 km (without FEC) or 40 km (with FEC) over single mode fiber. 4WDM modules operate at four LWDM (short for LAN-WDM) wavelengths of 1295.56nm, 1300.05nm, 1304.58nm and 1309.14nm.