With the variety of splice options that fiber network planners have today, identifying the best connectors can be a bit overwhelming. Consequently, not much thought is often given to the connector selection, and many make choices based solely on cost, availability, or what they’ve used previously.
However, fiber connector types have unique designs and advantages and disadvantages. Your fiber connector choice can have a significant impact on costs and deployment speed.
Related: Fiber Optic Cable Buyer’s Guide
Fiber Connector Types & Their Differences
Fiber connectors are what make remateable connections possible and generally get used when flexibility is necessary at termination points where the optical signal gets routed. First, let’s look at the different options of fiber connector types.
Polish & Epoxy Fiber Connectors
Polish and epoxy fiber connector types were initially used for termination and still see extensive use today. They offer a wide range of choices, like ST, SC, FC, LC, SMA, MT-RJ, D4, and MU connectors. Their advantages include:
- Sturdiness. These connectors can endure high levels of mechanical and environmental stress.
- Cable size. You can use these connectors for cables of various diameters.
- Numerous connectors. They can handle multiple cables in a single connector (up to 24).
Polish & No Epoxy Fiber Connectors
The main advantage of polish and no epoxy fiber connector types are that they are extremely easy to install, which translates into a lower skill level necessary to handle them. These connectors come in two types:
- Connectors without epoxy.
- Connectors with preloaded epoxy.
The fiber in these connectors gets stabilized by internal crimp mechanisms, and they are available in FC, SC, and ST styles.
No Polish & No Epoxy Fiber Connectors
No polish and no epoxy fiber connectors are of simple design and low cost. As a result, the training and installation costs are much less, and fast restorations are still possible. These connectors are available in ST, LC, SC, FC, and MT-RJ styles.
Fiber Count: Simplex & Duplex Fiber Connectors
Simplex connections mean that signals only get sent in one direction. For example, if it transmits a signal from device A to device B, it cannot return from device B to device A through the same route. Duplex connectors allow the signal to travel either direction. Also, simplex fiber connections often use one trans of fiber, while duplex connectors use two.
Fiber Mode: Single and Multi-Fiber Connectors
Single-mode fiber lets one light mode pass through at a time, and multi-mode fiber can handle multiple modes at once. Diversity impacts both single and multi-mode fiber connectors on account of the combination of corresponding optical fiber types. However, as technology advances, fiber connectors like LC, FC, and SC are compatible with both types of cables.
Fiber Polishment: APC, PC, & UPC
Depending on the polishing type, you can divide fiber cable connectors into three categories: APC, PC, and UPC. You can identify each type by its color code: APC connectors are green, PC connectors are black, and UPC connectors are blue. The structure and performance of each one varies, which affects the insertion and return loss of each type.
For applications that require high precision for optical fiber signaling, APC is typically the best choice. For digital systems that are less sensitive, PC and UPC polish types are typically acceptable.
Field Termination vs. Factory Termination Fiber Connector Types
Field termination terminates the end of the fiber cable in the field. This procedure includes stripping the cable, prepping the epoxy, applying the connector, polishing, inspection, and testing the connection. Field termination requires a large number of tools and skilled technicians to properly conduct the termination.
Pros of field termination include:
- Cable length precision and flexibility
- Easy cable routing
- Standard procedure
Cons of field termination include:
- Time-consuming
- Requires a kit
- Quality depends on the technician’s skill
- Consumes more materials
- Can fail testing
Factory termination, also known as factory pre-termination, is when the fibers and cables get terminated with the connector at the factory. Pre-terminated cables come in a pre-measured length with connectors already installed.
Pros of factory termination include:
- Factory polish quality
- Minimal insertion loss
- Almost always passes testing
Cons of factory termination include:
- You must know the exact lengths
- It can be bulky for cable tracks
Most Common Fiber Connector Types
Fiber connectors, both proprietary and standard, get used in telecom equipment, television and cable, data lines, and other industrial fields.
Let’s look at the most common fiber connector types. We’ll start with the most widely used and take an in-depth look at them. Next, we’ll cover some of the lesser-used (or now obsolete) connectors in less detail.
Related: Fiber Optics: What Is it & How Does it Work?
- Standard (SC) Connector
The SC connector, developed by Nippon Telegraph and Telephone in the mid-eighties, was one of the first fiber connectors to come to the market following the development of ceramic ferrules. It’s also referred to as a square connector, and it has a push-pull end face containing a spring-loaded ceramic ferrule. Designed initially for ethernet networking, it became a standard in the telecommunications industry in 1991 and continued to grow in popularity as its manufacturing costs continued to fall. Because of the SC connector’s exceptional performance, it dominated the fiber connector market for over a decade, rivaled only by the ST connector. Today, it still remains one of the top choices for polarization maintenance applications. SC connectors are ideal for telecom and datacom applications, including passive optical networking and point-to-point networking.
- Lucent (LC) Connector
The LC connector, often considered the modern replacement of the standard SC connector, didn’t have the most successful introduction, partially because of the initially high license fees implemented by its inventor, Lucent Corporation. Like the SC connector, this one is a push-pull connector, but it uses a latch rather than a locking tab like the SC. Its smaller ferrule gives it a small form factor. With half of the footprint of the SC connector, the LC is widely popular in datacoms and high-density patch applications because of the small size and latch feature. It’s ideal for densely populated panels and. The LC connector is steadily seeing more use in the FTTH arena as more active networking components, and transceivers introduce LC compatibility.
- Ferrule Core (FC) Connector
The FC connector was the first one to use a ceramic ferrule. Unlike the SC and LC that have plastic bodies, the FC uses a screw-type, round fitment made with either nickel or stainless steel. The end face relies on using an alignment key for the correct connection and gets tightened into the adaptor with a threaded collet. Despite its additional complexity in manufacturing and installation, it’s the connector of choice for equipment like OTDRs that rely on precision. Initially created for telecom and datacom applications, it has not been used as often since the SC and LC connectors were introduced. The FCs deliver similar performance, but SC and LC connectors are quicker to connect and less expensive. But, because of the FC’s screw-on collet, they are effective in high vibration environments to ensure that it stays firmly connected.
- ST Connector
The ST connector, developed by AT&T, came out shortly after the FC. The two are quite similar, but the ST has a bayonet fitment rather than the screw thread found in the FC. Its usage has gone down for the same reasons as the FC connectors, plus the ST has limited uses in FTTH and single-mode fiber applications due to its inability to be terminated with an angled polish. ST connectors mostly get used in corporate networks, campuses, and military applications because of the quick connecting bayonet. When retro-fitting, these connectors typically get swapped out with SC and LC connectors for their cost-effectiveness.
- MTP/MPO Connector
Another invention of Nippon Telegraph and Telephone, the MTP and MPO connectors have been around for years, but the technology has only recently become popular. These connectors are much larger than others, but they can support 24 fibers in each ferrule. These multi-fiber connectors must get lab terminated, as they are not designed for field-fit applications. MTP and MPO connectors frequently get used in high-density patch environments like datacenters at both multi-mode and single-mode wavelengths. The costs are relatively inexpensive on a per-fiber basis, but the attenuation loss can be higher. With that said, low loss MTP and MPO connectors have a comparable insertion loss performance but come with a higher initial cost.
- E2000 Connector
Many modern day telecom networks use E2000 connectors. They have integrated spring-loaded shutters that protect the ferrule from dust, dirt, and scratches. These connectors use a monobloc ceramic ferrule, and the problems associated with the coefficient of expansion are nonexistent. It’s a latched push-pull connector and trademarked by Diamond SA. The two advantages of E2000 connectors are the safety and high performance offered by the monobloc ferrule and shutter mechanism. It supports color keying and has minimal return loss. These connectors typically see use in LAN, broadband, telecom, and data networks.
- Bionic Connector
Bionic connectors, which are basically obsolete at this point, were one of the first used in fiber optic communication links. You can identify these connectors by their tapering sleeves fixed onto them. The connector’s narrowing ends enable those sleeves to sit properly and, along with guided rings and caps, helps secure the connection.
- SMA Connector
Another mostly obsolete connector is the SMA connector, and it was the forerunner to the aforementioned ST model. It was eventually replaced by both ST and SC connectors.
- Plastic Fiber Optic Cable Connector
While most connectors are made of glass fiber, these plastic fiber optic connectors are much cheaper and are sufficient for some easy applications. Plastic connectors typically don’t have a polished or epoxy option. They are available in both proprietary and standard designs, and although SMA and ST connectors are made for use with glass, you can also use them with plastic connectors.
- Enterprise Systems Connection (ESCON) Connector
These ESCON connectors, developed by IBM, get used for interfacing peripheral storage devices, like tape drives, to a mainframe. It’s a half-duplex serial interface and uses fiber optic cable.
- Fiber Distributed Data Interface (FDDI) Connector
FDDI connectors provide data transmission at speeds up to 100 Mbps in dual ring token local area networks and work within a 200 km range. These connectors connect different network equipment into wall plugs and contain a 2.5 mm ferrule, which can mate onto SC and ST connectors with an adapter.
- Opti-Jack Connector
The Opti-Jack duplex connectors resemble the universal RJ-45 connectors. They contain two ST ferrules and a rugged female to male connector.
- LX-5 Connector
LX-5 connectors provide reliable, high-performance, and high-density connections. These connectors use automatic metal shutter technology and come in a standardized small form factor with a 1.25 mm ferrule. LX-5’s mainly see use in CATV applications and high-performance telecom networks. It achieves high packing density thanks to its small form factor, and the automatic metal shutter delivers better safety and performance. Its insertion loss of 0.1 dB is one of the lowest of all fiber optic connectors.
- Volition Connector
Volition connectors are unique in that they do not use a ferrule. It’s a plug and jack duplex connector that uses “V” shaped grooves to align the fibers.
- MT-RJ Connector
MT-RJ connectors use a single polymer ferrule duplex and include alignment. It’s available in both plug and jack or female and male format.
- MU Connector
MU connectors have a lower carbon footprint and are a new generation of fiber connectors that mainly get used in dense applications. It’s a square connector that uses a push-pull mating mechanism. MU connectors get used for SDH, SONET, LAN, CATV, WDM, and ATM applications, and they come in the following variations:
- Single Mode APC
- Single Mode UPC
- Multi-Mode UPC
- MT Connector
MT connectors use a ribbon cable with 12 fiber connectors. They mainly get used for cabling systems and factory terminated cable assemblies.
Planning a data center or smart building and looking for the best fiber optic cabling and structured cabling design? Get in touch with C&C Technology Group today for all of your fiber cabling needs!
Related: Cable & Network Testers Buyer’s Guide
Last Updated on January 21, 2023 by Josh Mahan
