The Evolution of Fiber Connectors in Networks

 Mar 31, 2021   |    Steve Molek

Fiber Optic Cable Connectors in Networks: Then and Now

The media for most networks, regardless of their size, typically is copper or fiber cabling used to connect servers, computers, and devices together. For copper connectivity, most people are familiar with the RJ-45 connector. Developed in the early 90s when 10BASE-T networks first came on the market, it is still used today and is considered the de-facto copper connector, even for high-speed Gigabit and 10 Gigabit Ethernet networks. But the same is not true with fiber connectivity.

Humble Beginnings Featured No Standard Fiber Optic Cable Connector

In the late 70s and early 80s, equipment manufacturers did not use a standard connector for fiber. Some of the old legacy fiber connectors from this time included the “Biconic,” “E2000,” “SMA,” “FC,” and “D4” fiber connectors. Most used some form of “threading” to secure the fiber connector to the equipment.

“Biconics” “E2000” “SMA” “FC” “D4”
fiber-connector_r1_BICONICS fiber-connector_r1_E2000 fiber-connector_r1_SMA fiber-connector_r1_FC fiber-connector_r1_D4

The “ESCON” and “FDDI” fiber connector systems used a keying style method to make connectivity. These were typically deployed in fiber ring topologies that used a keying system to correctly form the fiber infrastructure.

“ESCON” “FDDI”
Fiber Data Distribution Interface
fiber-connector_r2_ESCON fiber-connector_r2_FDDI

These all basically did the same thing, although the size, shape, and how they connect to the equipment varied widely. Modern networks no longer use most of these legacy fiber connectors today.

Enter ST and SC Fiber Optic Cable Connectors

In the 90s, fiber became more popular and the number of fiber optic cable connectors in use by the industry started to narrow down. “ST” and “SC” fiber connectors were commonly used at that time.

“ST” “SC”
fiber-connector_r3_ST fiber-connector_r3_SC

The “ST” connector came first. It has a 2.5-mm ceramic ferrule and uses a spring-loaded “push on” ¼ turn latching system. This connector is very secure but can be somewhat difficult to make connections.

The “SC” fiber connector soon followed the “ST” connector as the fiber connector of choice. The “SC” fiber connector also uses a 2.5-mm ceramic ferrule and has an improved mating system for making connections onto equipment. It uses a “push/pull” style of mating to equipment that is much easier and faster than the “ST” connector. Although the physical size of the “ST” and “SC” are very similar, the “SC” connector’s main advantage is that it is easier to connect.

These two fiber connectors dominated the industry throughout the 90s and in many cases they are still in use today. But around the year 2000 with fiber demands and density increasing, manufacturers introduced a new style of fiber connectors to the industry to account for these changing issues.

Three Types of Small-Form Factor (SFF) Connectors Dominated the Early 2000s

These new fiber connectors were called the “SFF” or Small Form Factor style of connectors. These “SFF” connectors basically perform the same functions as any other fiber optic cable connectors, but their major advantage is that each is about ½ the size of the popular “ST” and “SC” that were in use at the time. Several manufacturers introduced their version of a “SFF” fiber connector. Each was a little different, but all did the same thing.

“VF-45” “MT-RJ” “LC”
fiber-connector_r4_VF45 fiber-connector_r4_MTRJ fiber-connector_r4_LC

VF-45 Fiber Optic Cable Connector Enters the Market

One of the first “SFF” fiber connectors that came on the market in the early 2000s was the “VF-45” fiber connector. Manufactured by the 3M Corporation, it was called the (3M Volition) fiber connector. The “VF-45” connector held two fiber strands in a housing that resembled the same latching as the RJ-45 plug used in copper cabling systems. One major disadvantage of the VF-45 connector was that fiber assemblies could not be made out in the field.

MT-RJ Fiber Optic Cable Connector Came Next

The next “SFF” fiber connector was the “MT-RJ” fiber connector, introduced by AMP Corporation. This connector also held two fiber strands in an all-plastic housing with a similar latching system as the RJ-45 plug used in copper cabling systems. One very unique thing about the MT-RJ fiber connector was that it used two metal “guide pins” to keep the fiber strands aligned. Typically, the male MT-RJ fiber connectors had guide pins and the female MT-RJ fiber connectors did not.

Lucent’s LC Fiber Optic Cable Connector Takes Hold

The final SFF fiber connector that was introduced to the industry at this time was the “LC” fiber connector. Developed by the Lucent Corporation, the LC fiber connector held a single fiber strand and used a much smaller 1.25-mm ceramic ferrule than the ferrule used in the ST and SC connector. This connector also used a similar latching system as the RJ-45 plug in copper cabling systems. Commonly, two LC fiber connectors were used side by side.

Within a very short period of time, these three SFF fiber connectors were introduced to the industry. The industry did not have room for three SFF fiber connectors, so one of these connectors was surely going to dominate the market over time. Usually the leading equipment manufacturers indirectly choose which connector will dominate the market. Today, the LC fiber connector is found in nearly all data centers on practically all equipment.

MPO Connectors for Optical Fiber Support Increased Density

Finally, the need for even more fiber in the data center still continues to grow demanding that more fiber strands be packed into tighter and smaller spaces. The SFF fiber connectors, although very good, still cannot meet these demands. The “MPO” (“Multi-Fiber Push On”) fiber optic cable connector supports 12 or 24 fiber strands in one single connector. The MPO connectors are similar to the MT-RJ fiber connector because they use guide alignment pins and a “push/pull” mating system similar to the SC fiber connector. The fiber strands are arranged in a single 12-strand fiber row or two rows when using 24 strands.  

“Male — MPO ” “Female — MPO”
fiber-connector_r5_MPO-male fiber-connector_r5_MPO-female

This connector is almost always found in large data centers on high-end server and switch equipment where high speed bandwidth parallel processing applications are required.

While the standard RJ-45 twisted-pair cable connector has been used for decades, fiber optic cable connectors have gone through many changes. From legacy fiber optic connectors to today’s LC and MPO fiber connectors, fiber optic connectivity has changed over the years. In the beginning, there was no standard fiber optic cable connector. The industry introduced several types of legacy connectors in the 70s and 80s, followed by the SC and ST connectors in the 90s. Small Form Factor (SFF) connectors, including VF-45, MT-RJ, LC, began to dominate the market in the early 2000s. The ST and SC fiber connectors are slowing beginning to be phased out or not used on new networking equipment, thus causing them to slowly fade away. MPO is the newest connector and it supports high fiber optic cable density. LC is the most common fiber optic cable connector used in current installations. The MPO fiber optic cable connector is mainly found in the data center where large fiber trucks are needed to connect equipment together. Today, LC and MPO fiber optic cable connectors are the most widely used types of fiber optic cable connectors.

About the Author

Steve Molek

Product Engineer

Steve Molek has 27 years’ experience in the cabling and connectivity data communication industry. He started his career as a Technical Support Representative and now works as a Project Engineer for Black Box. As a Product Engineer, his primary focus is evaluating and testing all new cabling and connectivity products for sale by Black Box and training our inside technical support and sales teams. Steve also works directly with our domestic and international OEM suppliers as well as several nationally recognized third-party testing labs. Steve holds a B.S. degree in Mathematics and Computer Science from California University of Pennsylvania and an MBA from Waynesburg University.

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