The most common fiber optic connectors usedTIA
Optical fiber connectors are mechanical devices that are placed at the end of a fiber cable, allowing it to be connected to telecommunication equipment such as another cable, a receiver or a light source. They align the core of microscopic fibers together so light pulses can travel through them and allow communication. These devices make temporary links, which means they can be easily joined and detached.
Over the course of optical fiber technology development and improvement, several communication companies have created and introduced more than 100 connectors to the market, but just a few of them made it to the present days. And even fewer are considered the most used.
OPTICAL FIBER CONNECTORS TYPES
Optical fiber connectors are used in premises installations, inside and outside plant applications, in CATV and telephony systems to join cables and equipment where a connect/disconnect capability is needed. Connectors are considered the weakest link in a fiber optic system, because they mark a spot in which signal power can be lost. So for optical fiber systems to have an outstanding performance, well designed connectors, good terminations and an installer with skills are needed.
There are several types of optical fiber connectors and they are all integrated by three main mechanisms:
- The ferrule
This is the most important component of fiber optic connectors because it holds, protects and aligns the glass fiber. Ferrules are usually made of ceramic, high-quality plastic or metal. Of all those materials, zirconia ferrules are the ones that offer the highest performance and durability after several mating cycles.
- Coupling mechanism
It keeps the connector in place when it is joined to another device. It could be push-pull or bayonet style.
- Connector body
Is the structure that holds the ferrule, the coupling mechanism and the boot. It is made of plastic or metal.
The connectors’ end-face determines what the return loss, also known as back reflection, of a fiber optic cable will be.
Return loss is the loss of power that happens when light returns from the fiber to the light source device due to discontinuities or airs gaps caused in the ferrule’s end-face. It is measured in decibels.
Ferrules are polished in different ways, which classifies connectors as:
- PC (Physical Contact):
PC connectors are polished with a slight curvature, which reduces the air gaps between fibers. These connectors’ back reflection is between 30dB and 40dB.
- UPC (Ultra Physical Contact):
UPC connectors also have a convex end-face, but have a finer surface finish. Their return loss goes from -40dB from -55dB, which makes them reliable for transmitting TV and data signals.
- APC (Angled Physical Contact):
APC connectors have an 8° angle cut in their ferrules, which makes connections between optical fibers even tighter. Industry standards indicate that APC connectors back reflection is -60dB.
Optical fiber connector’s types
Hundreds of types of optical connectors have been created over the course of the years by telecommunication companies, but not all of them acquired great popularity in the marketplace.
Connectors that prevailed comply with TIA Fiber Optic Connector Intermateability Standards (FOCIS), the specifications manufacturers need to follow to assure their connectors will be intermateable with other manufacturer’s connector.
SC (Stander Connector)
The SC was created in the mid-eighties by the Japanese telecommunication company Nippon Telegraph and Telephone, but it wasn’t widely used at the beginning because it was considered highly expensive. SC connector has a typical connection loss of 0.25 dB and is rated for 1000 connect-disconnect cycles.
SC connector aligns fibers with precision due to its 2.5mm spring-loaded ceramic ferrule, which uses a push-pull joining system that has given it the name of “Set and Click” and “Stab and Click” connector. It was initially used in Gigabit Internet applications, but was replaced by smaller connectors. It is currently used with single mode and multimode cables in CATV applications and telephony environments.
LC (Lucent Connector)
The LC, also known as Little Connector, was created by Lucent Technologies and is widely used in single mode applications because it has an excellent performance and it can be simply terminated with any adhesive. It has a 1.25mm ceramic ferrule that uses push-pull mechanism and has a typical insertion loss of 0.10 dB.
LC connector smallsize reduces space needed for patch panels in 50% compared with SC or ST connectors, thus it is used in high density telecommunication applications such as racks and panels, FTTH, premises distribution, Local Area Networks, Data processing networks and CATV. It can be used with both single mode and multimode cables, but is favored for single mode fiber applications.
ST (Straight Tip)
The ST was created and licensed by AT&T and is still one of the most popular connectors used in networking applications. It has an insertion loss of about 0.25 dB and holds the fiber with a ceramic, spring-loaded 2.5mm ferrule that stays in place with a half-twist bayonet mount, which has made common for technicians to also call them “Set and Twist”, “Stab and Twist” or “Single Twist” connector. ST connector is used in both long and short distance applications such as campuses or corporate network environments and military applications. It can be easily attached and detached due to its flexibility and is rated for roughly 500 mating cycles.
FC (Ferrule Connector)
Designed by Nippon Telephone and Telegraph (NTT), the FC is a 2.5mm zirconia ceramic ferrule, which stays in place with a screw-on nut mechanism. It is available for both single and multimode fiber, but it’s widely used in single mode applications and in high-speed optical fiber communication networks.It is also used in high-vibration environments due to its threaded body. Its insertion loss is of 0.3 dB.
MTRJ (Mechanical Transfer-Registered Jack)
MTRJ is duplex connector, meaning it holds two fibers at the same time. Its body and ferrule are made of plastic and it has male and female versions that stay in place with pins. MTRJ only works with multimode optical fiber.
MPO (Multi-fiber Push-on)
Is a multi-fiber connector that brings together from 12 to 24 fibers in a single rectangular ferrule and is used for building 40Gb to 100Gb optical parallel connections. It comes in UPC and APC versions. A male MPO connector has two pins on its ferrule tip, while females has two holes. Its typical insertion lost is 0.25dB.
Thanks to its different technologies, mechanical and optical interfaces, the E-2000™ fiber optic connector family can cover the most standard and customized requirements in response to the increasingly customer demands. The family includes: simplex, compact and backplane connectors and adapters, as well as a series of network accessories such as: attenuators, hybrid adapters, transition adapters, terminators, reflectors and receptacles.
No stores or technicians seem to agree when asked “What are the most popular optical fiber connectors?”
There isn’t any verified information for such a frequently asked question. Therefore, we decided to investigate it searching over every optical fiber equipment store that would let us check which ones were their most popular products. Using Beyondtech’s information and the data we collected, we found that SC connector is the most popular connector in 34% of the visited online stores, LC connector in 32%, ST connector in 28% and FC connector in 6%.
The characteristics that made these connectors the most popular ones are:
- SC connectors are low cost, simple and durable. They offer accurate fiber alignment thanks to their ceramic ferrule.
- LC connectors’ small size makes them perfect for high density environments.
- ST connectors are still the most used in campuses and building multimode fiber applications.
- FC connectors provide more reliable real-time data transmission in high vibration scenarios.