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25 Most Important Types of Fiber Optic Connectors

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Since the 1970s, telecommunication transmission technology has been dramatically advanced; accordingly, fiber optic connectors have undergone significant breakthroughs, and hundreds of types of fiber connectors have been introduced into the market. Yet only a handful of them makes a long-lasting success. Do you wonder what types are the most seen? And What’s the difference between them? And what qualifies one type of fiber connector as a suitable fiber connector? Regarding these questions, we’d like to talk a bit more about the details of the common types of fiber connectors; also, the newly introduced types of fiber connectors and the obsolete ones will be discussed shortly.

various types of fiber optic connectors
various types of fiber optic connectors

Common types being in use: FC, ST, SC, LC, MTP/MPO

Generally speaking, we can classify these fiber optic connectors in their individual size, namely, Standard Fiber Connectors, Small Form Factors, and Ribbon Fiber Connectors (also called Multifiber Connectors).

nameLong-formCoupling typeFerrule diameterstandardapplications
FC Ferrule ConnectorScrew-on nut2.5 mmIEC 61754-13; TIA-604-4 (FOCIS-4)Datacom, telecom, measurement equipment, and singlemode lasers; becoming less common
STStraight Tipbayonet mount2.5 mmIEC 61754-2; TIA-604-2 (FOCIS-2)Multimode, rarely singlemode; APC not compatible
SCSubscriber Connector, or Square Connectorsnap-in push/pull2.5 mmIEC 61754-4; TIA-604-3(FOCIS 3)Datacom and telecom; are ubiquitous
LCLucent Connectorpush/pull with a latch1.25 mmIEC 61754-20; TIA-604-10 (FOCIS-10)High-density connections, SFP/SFP+ transceivers, and XFP transceivers; are prevalent
MTP/MPOMultiple Fiber Push-On (MPO); Multifiber Termination Push-on (MTP)Snap (multiplex push/pull coupling)2.5*6.4 mmIEC 61754-7; TIA-604-5(FOCIS 5)High-density networks, such as data centers and LANs, often used in 40G and 100G high-bandwidth parallel optical connections. MTP is a registered trademark of MPO.
MUMiniature Unitsnap-in push/pull1.25 mmIEC 61754-6; TIA-604-17(FOCIS 17)SONET, SDH, LAN, WDM, CATV, and ATM applications.
E2000 (aka LSH)Laser Shock HardeningSnap, with light and dust-cap2.5 mmIEC 61754-15; TIA/EIA-604-16(FOCIS 16)broadband applications, telecommunication networks, LAN, CATV, FTTx, and data networks.  
LX-5 Latch, integral light- and dust-cap1.25 mmIEC 61754-23; FOCIS-13 (TIA-604-13).High-density connections; rarely used
MTMechanically TransferableSnap (multiplex push/pull coupling)2.5*6.4 mmTIA-604-5(FOCIS 5)factory terminated cable assemblies and cabling systems
Q-RMCRosenberger Multifiber Connectorpush/pull closing  Industrial site, minefield, mobile communication, 5G Base Station, broadcast, smart grid cabling, etc.
CSCorning/Senko           Latch, push-pull1.25 mm             
SN  1.25mm data center 400 G optimization
MDC push/pull coupling1.25 mmTelcordia GR-326 carrier or data center applications.
MT-RJMechanical Transfer Registered Jack, or Media Termination recommended jackLatch, gendered2.45×4.4 mm     IEC 61754-18Duplex multimode connections  
Deutsch 1000 Screw  Telecom; obsolete
BICONIC Screw2.5 mm           FOCIS-1 (TIA-604-1)military fiber optic applications; obsolete
VolitionVolition Fiber plug-and-jackNone, V-grooves as guidanceFOCIS-7 (TIA-604-7)Datacom; obsolete
Opti-Jack snap-lock plug and socket2.5 mm           FOCIS-6 (TIA-604-6).Building wiring, wall outlets
ESCONEnterprise Systems ConnectionLatch, integral shroud2.5 mm IBM mainframe computers and peripherals
FDDIFiber distributed data interfaceSnap   2.5 mm  
AMP Optimate Screw-on Nut  Plastic fiber; obsolete
SMASub MiniatureScrew, optionally keyed3.17 mmIEC 60874-2Industrial lasers, optical spectrometers, military; telecom multimode
NEC D4 Screw2.0 mm            Japanese telecom in the 1970s and 1980s

Standard Fiber Connectors

These Standard fiber connectors are assorted according to their 2.5 mm ferrule. Either simplex or duplex, these fiber connectors are available both in singlemode or multimode. FC, ST, and SC fiber connectors are the common types of moderate size.

FC Fiber Connector

Known as Ferrule Connector, invented by JP NTT, FC was the first fiber connector that utilizes a 2.5mm ferrule made of ceramic to replace stainless alloy. It is a round threaded connector featuring a screw-on nut mechanism and a stainless-steel housing around the ceramic ferrule. FC is a non-optical disconnect connector, firmly tightened by screwing using a threaded collet; therefore, it is ideally suitable for high-vibration environments.

It was simplex only, available both in singlemode and multimode, but widely used in singlemode applications. Once one of the most popular singlemode connectors, its use has significantly declined due to its high cost and complex design, and it has been replaced by SC and LC fiber connectors.

Covered by TIA-604-4 (FOCIS-4), it has an insertion loss of 0.3 dB and 500 mating cycles. FC is still deployed in singlemode cables in high-vibration environments due to its vibration resistance.

FC Fiber Connectors
FC Fiber Connectors

ST Fiber Connector

ST stands for Straight Tip and was designed by AT&T in the late 1980s, following the release of FC. Arguably the most popular connector for multimode networks till around 2005, ST features a bayonet mount design, keyed and spring-loaded. Like FC, it uses a long cylindrical 2.5 mm ferrule, most made of ceramic, while some of stainless alloy or plastic. It is simplex only, available both in singlemode and multimode. However, as it doesn’t support APC, its use has dwindled remarkably. Although it used to be commonly seen on campuses, corporate networks, and military applications, today, it’s been phasing out in favor of SC and LC.

Covered by TIA-604-2 (FOCIS-2), It has an insertion loss of about 0.25 dB and 500 mating cycles.

ST Simplex Fibre Connector
ST Simplex Fibre Connector

SC Fiber Connector

SC stands for Subscriber Connector or Square Connector. It was invented by JP NTT in the mid-eighties, aiming to replace the ST fiber connector. SC features a snap-in push/pull coupling mechanism with a locking tab. It also uses a 2.5 mm ceramic ferrule and is one of the first connectors to enter the market following the advent of ceramic ferrules.

Compared with ST, the SC, like FC mentioned above, is a non-optical disconnect connector. It’s easy to use and rugged. Besides, It was the first connector standardized in the telecommunications specification TIA-568-standard in 1991. As its cost gradually decreases, it is increasingly popular and widely used in singlemode fiber optic cable, CATV, GPON, GBIC, Fiber Media Converters, datacoms, and telecom applications, such as point-to-point and PON.

Due to its excellent performance and fast deployment, it was the best connector until the release of the LC connector. Thirty years after its release, it remains the second-best fiber connector choice for simplex applications, duplex applications, and polarization-maintaining applications.

SC connector has a typical connection loss of 0.25 dB and 1000 mating cycles.

SC APC Connector
SC APC Connector

E2000 Fiber Connector

E2000 connector, also called LSH (laser shock hardening), features a push/pull latching mechanism and a spring-loaded automatic metal shutter. When fully inserted, it clicks, and the shutter opens automatically; when disconnected, the shutter closes automatically to keep the connector from dust, dirt, scratch, or laser beam.

It uses a 1.25 mm ferrule and has one of the lowest insert losses at 0.1 dB. E2000 is a registered trademark of Diamond SA, based in Losone, Switzerland.

Its main draw lies in the enhanced safety and good performance and is used in broadband applications, telecommunication networks, LAN, CATV, FTTx, and data networks.

Covered by TIA/EIA-604-16(FOCIS 16), E2000 connectors are available in singlemode and multimode.

E2000 Fiber Optic Connector
E2000 Fiber Optic Connector

SFF: Small Form Factor fiber optic connectors

To satisfy the need for a high-density packaged system, small size connectors are invented, such as LC, MU, E2000, and LX-5. These connectors typically have a 1.25 mm ferrule, half the size of SC.

LC Fiber Connector

LC refers to Lucent Connector, named after its designer Lucent Technologies. LC uses a 1.25 mm ferrule, half the size of SC, FC, or ST. Therefore it is also called the “little connector,” widely used in high-density telecommunication applications such as racks and panels, FTTH, LAN, SFP/SFP+ transceivers, and XFP transceivers.

LC resembles a miniature version of SC. It features a push/pull with a latch design. Simplex and duplex, LC is available both in singlemode and multimode. Like the introduction of SC, at first, its cost was relatively high due to the high license fees charged by Lucent. Due to its small dimension and excellent performance, LC gradually dominates both singlemode and multimode deployments, partly because of its proliferation in the active network equipment.

 Covered by TIA-604-10 (FOCIS-10), LC has a typical insertion loss of 0.10 dB and 500 mating cycles.

LC Fiber Connector
LC Fiber Connector

MU Fiber Connector

MU is the acronym for Miniature Unit. Developed by JP NTT, it resembles a miniature SC and comes in simplex and duplex designs, singlemode and multimode. Like SC, Mu features a simple snap-in push/pull design with a 1.25mm ferrule. Mu is more prevalent in Japan, and widely applied to SONET, SDH, LAN, WDM, CATV, and ATM applications.

Covered by TIA-604-17(FOCIS 17), MU has a low insertion loss and 500 mating cycles.

MU Duplex Connector
MU Duplex Connector

LX-5 Fiber Connector

Like E2000, Lx-5 also employs a flap to attenuate the beam when disconnected. It is the European version of LC and has a 1.25 mm ferrule. Designed for use in CATV applications as well as in high-performance telecommunication networks. Like E2000, LX-5 offers high density, excellent performance, and reliable connection. However, it’s kind of fiddly and not robust.

Covered by TIA-604-13(FOCIS-13), it has one of the lowest insertion losses at 0.1 dB.

LX-5 Fiber Connector
LX-5 Fiber Connector

Ribbon Fiber Connector or Multiple Fiber Connector

Besides the standard 2.5 mm ferrule fiber connectors and the tiny 1.25 mm ferrule fiber connectors, another Ribbon Fiber Connector, also known as Multiple Fiber Connector, could carry up to 72 fibers into one single ferrule to provide maximum connectivity in a very tight space.

MT ferrules

MT stands for Mechanically Transferable. It was invented by the JP NTT in the early 1980s, aiming to provide a design of splicing of high-density and high-count cables in the joint cable closures.  The technicians called the high-speed mechanical transfer switching of fiber ribbons the MT ferrules. It’s larger than other connectors and can contain up to 24 fibers in a single ferrule. In the following years, they advanced this technology and developed MPO in 1986 and APC-MPO in 1991.

Covered by TIA-604-5(FOCIS 5), MT ferrules are used for factory terminated cable assemblies and cabling systems.

MT Fiber Connector
MT Fiber Connector


As mentioned above, MPO/MTP is the application of MT ferrules; that is to say, they’re ribbon fiber connectors based on MT ferrule. They belong to the same series, except that MPO/MTP have been popular recently.

MPO stands for Multiple Fiber Push-On. MTP is a registered trademark of MPO type fiber connector of US Conec. MTP refers to Multifiber Termination Push-on”, an upgraded version of MPO with higher specifications, some of them covered by patents. The two resemble each other.

MPO connectors could support up to 72 fibers into one single ferrule. They’re typically available with 8, 12, or 24 fiber arrays; therefore, they’re ideal for building 40 Gb to 100 Gb parallel optical connections. MPO features a plug-and-jack format, i.e., male and female, using pins to align and two 0.7 mm diameter holes to hold precision metal guide pins; that’s why MPO connectors are not fit for on-site termination and need to be appropriately positioned to assure that the transmit fibers match up to the appropriate receive fiber at the other end.  It comes in UPC and APC versions.

Covered by TIA-604-5(FOCIS 5), the MPO connector typically has a 0.25 dB insertion loss in singlemode and about 0.20 dB in multimode. MPO is suitable for high-density networks, such as data centers and LANs, both in singlemode and multimode deployments, and is also often used in 40G and 100G high-bandwidth parallel optical connections.

These mentions above are the common types seen currently. Next, we’d like to shortly introduce several newly released types of fiber connectors. In the final part, we’ll also talk a little about some kinds of fiber connectors that were common but have become obsolete nowadays.

MPO/MTP Fiber Connector
MPO/MTP Fiber Connector

Newly introduced types of fiber connectors

Rosenberger Q-RMC Fiber Connector

Q-RMC, an abbreviation for Rosenberger Multifiber Connector, is one type of MPO connector that can support 24 fibers. It features a push/pull closing mechanism and is resistant to water, dust, and corrosion. It’s suitable for harsh environments, like extreme temperatures, and is applied to industrial sites, minefields, mobile communication, 5G Base Station, broadcast, smart grid cabling, etc.

Q-RMC (Rosenberger Multifiber Connector)
Q-RMC (Rosenberger Multifiber Connector)

Senko CS

Senko CS is a duplex connector. It features a push/pull tab using an LC 1.25 mm ferrule. CS® is designed for next-generation 200/400 G transceiver QSFP-DD and OSFP. Compared to the LC duplex, it has a 40% reduction dimension and twice the density of a patch panel.

The Senko CS Fiber Connector
The Senko CS Fiber Connector


SN® also is a duplex connector, using two LC style 1.25mm O.D. Zirconia ferrules in a single housing pitched 3.1 mm apart vs. 6.25 mm in a duplex LC connector. Designed for data center 400 G optimization. SN® supports up to a 1.6 mm jacketed cable.

LC vs CS vs SN fiber Connectors
LC vs. CS vs. SN fiber Connectors


The US MDC is a duplex connector using an LC 1.25 mm ferrule. It takes a push/pull coupling mechanism. Designed for optimal stability exceeding the requirements of Telcordia GR-326 for carrier or data center applications.

The US Conec MDC Fiber Connector
The US Conec MDC Fiber Connector

Two expanded beam connectors: 3M Expanded beam and the R&M QXB

These two expanded beam connectors have been introduced to the market, aiming to compete with the MPO.

3M™ Expanded Beam Optical Connectors are designed to reduce the need for maintenance and cleaning with exceptional performance. Compared with conventional physical contact connectors, 3M’s design has expanded the light beam and changed the light angle to reduce risk in alignment and dirt, yet with a higher cost.

3M Expanded beam fiber connectors
3M Expanded beam fiber connectors

R&M QXB, like an MPO connector, holds 12, 24, or 32 parallel fibers. With the expanded beam technology, the QXB connectors no longer need to clean the contact surfaces for the light signals transmitted without any physical contact. Also, visual inspections and the search for transmission errors are unnecessary, claimed by the  R&M’s market manager.

R&M QXB Connectors in their 12 fiber MM and 32 Fiber MM versions
R&M QXB Connectors in their 12 fiber MM and 32 Fiber MM versions

Obsolete Fiber Optic Connector

Below are those commonly used in the past, now obsolete fiber types.

MT-RJ Fiber Connector

MT-RJ refers to Mechanical Transfer Registered Jack, is a duplex connector using a polymer ferrule, only available in multimode. It was designed by AMP, using pins for alignment, and has male/female polarity or plug/jack formats. As its ferrule is made of polymer, it has higher insertion loss than the mainstream ceramic ferrule. Meanwhile, its alignment pins make it more difficult to clean. Besides, it’s difficult to test.

Covered by TIA-604-12 (FOCIS 12), MT-RJ has a typical insertion loss of 0.25 dB for SMF (singlemode fiber) and 0.35 dB for MMF (multimode fiber).

MT-RJ vs SC connector
MT-RJ vs. SC connector

Deutsch 1000 Fiber Connector

Probably the first commercially successful fiber connector in the late 70s, Deutsch 1000 features a screw coupling mechanism and has a typical insertion loss of 3 dB.

Deutsch 1000 Fiber Connector
Deutsch 1000 Fiber Connector


The bionic connector, one of the first connectors, was designed by Bell Labs. It features a tapering sleeve that fixes onto the fiber connector. The air gap between mated ferrules causes the Fresnel reflection, which means no connector with an air gap can have less than 0.3 dB loss.

Covered by TIA-604-1 (FOCIS-1), the Bionic connector is simplex only. Available in singlemode and multimode.

BICONIC Fiber Connector
BICONIC Fiber Connector

Volition Fiber Connector

A volition connector is a duplex connector. Instead of using a ferrule, Volition employs a V-shaped groove to align the fibers. Plug and jack formats, while field terminate jacks only.

It was covered by TIA-604-7 (FOCIS-7).

3M Volition Fiber Connector
3M Volition Fiber Connector


Opti-Jack is a duplex connection using two ST 2.5 mm ferrules. It is a version of the Fiber Jack connector designed by Panduit Corporation. It features a snap-lock plug and Jack formats. It’s neat and rugged. It strongly resembles the well-known RJ-45 connector.

Opti-Jack is covered in the TIA connector intermateability standard FOCIS-6 (TIA-604-6).

Panduit Opti-Jack Fiber Connector
Panduit Opti-Jack Fiber Connector


ESCON, short for IBM’s Enterprise Systems Connection Connector, was a half-duplex serial interface that uses FOC, developed by IBM for interfacing peripheral storage devices, including tape drives, to their mainframes. It has two 2.5 mm ceramic ferrules featuring a spring-loaded retractable shroud over the ferrules.

ESCON Fiber Connector
ESCON Fiber Connector


FDDI stands for Fiber Distributed Data Interface Connector. Designed by ANSI, the FDDI connector is a duplex multimode connector applied in FDDI networks, using two 2.5 mm ferrules protected by a fixed shroud. Generally, FDDI connectors connect to the equipment from a wall plug. It provides data transmission at 100 Mbps in a dual ring token LAN within a 200-kilometer range.

FDDI Fiber Connector
FDDI Fiber Connector


Once widespread in the early 1980s, AMP Optimate features a conical plastic ferrule and screw-on nut. It was one of the critical industry fiber connector solutions for digital communications data links at the time. Soon it was replaced by ST.

AMP OPTIMATE Fiber Connectors
AMP OPTIMATE Fiber Connectors

SMA Fiber Connector

Designed by Amphenol, the SMA stands for the “Subminiature A.” The models 905 and 906 are simplex multimode connectors, using ferrules made of stainless alloy or stainless steel. They used threaded connections, and due to their low-cost coupling, they were suitable for military applications. Eventually, it was replaced by ST.

sma905 fc st fiber coupler metal with high temperature resistance
SMA-905 vs FC vs ST connector


The NEC D4 is a simplex singlemode connector using a 2.0 mm ferrule. It was probably the first connector using a ferrule made of ceramic or hybrid ceramic/stainless steel. It features a threaded nickel-plated brass body, widely used in telco networks from the 1980s till the early 1990s.

NEC D4 connector
NEC D4 connector

Final Words

After finishing a wordy introduction of the common types of fiber connectors, finally, we could get our breath back. Maybe there’re still some problems with which this document is not concerned. If you have any questions in mind, no matter what the question is, please don’t hesitate and feel free to tell us. Either leave a reply or directly contact us via email. Here is Our email: [email protected].

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