Fiber Optic Connectors and its pros and cons

1, Lucent Connectors (LC)

LC Connectors were invented by Lucent Technologies (hence the LC name). This is a member of what is referred to as the small form factor (SFF) line of connectors. These SFF connectors were initially invented to fill a need for large fiber count applications. In some installations there are dozens of connectors being plugged in and these connectors make life much easier. LC is a push-pull connector, the LC utilizes a latch as opposed to the SC locking tab and with a smaller ferrule, measuring 1 1/4 mm, which is approximately half the size of an ST connector, it is known as a small form factor connector. Having half the footprint of the SC connector gives it huge popularity in datacoms and other high-density patch applications, as its combination of small size and latch feature make it ideal for densely populated racks/panels. These connectors work well for multimode transceivers and single-mode cables.

Advantages

The small footprint of LC connectors makes them ideal for use in crowded spaces, such as for transceivers and networking. You can quickly convert these instruments from a simplex connector to a duplex connector with the use of a clip and the ease of adding a connector to the end of a cable. They are low loss connectors and are also pull proof. LC connectors can quickly be terminated and have a couple different methods to achieve that. The SFF design makes this the perfect connection for a high-density application, which is why this is the connection of choice for networking and transceivers.

Disadvantages

The small size can pose a problem when removing them, especially in high-density sites. Most people have difficulty reaching the clip to disconnect these terminations due to the tiny size of the ferrule and the cramped space these connectors often appear in. It is probably a good idea to order an extraction tool when ordering this type of connector.

2. Standard Connectors (SC)

The SC was developed by the laboratories at Nippon Telegraph and Telephone (NTT) in the mid-'80s, and was one of the first connectors to hit the market following the advent of ceramic ferrules. Sometimes referred to as the ‘square connector’ the SC has a push-pull coupling end face with a spring-loaded ceramic ferrule. Initially intended for Gigabit Ethernet networking, it was standardized into the telecommunications specification TIA-568-A in 1991 and slowly grew in popularity as manufacturing costs came down. Due to its excellent performance, it dominated fiber optics for over a decade with only the ST rivalling it. The SC connector was invented to directly replace the ST connectors and, as a result, has become one of the most common fiber connectors in the world. Similar to the ST connector, this SC style also utilizes a 2.5mm ferrule. Using a push and pull motion secures the connector. These types of terminations have high levels of performance, which along with a price drop since their introduction, has contributed to their vast popularity in multiple applications. In fact, many formerly ST connectors applications now use SC connectors instead.

Advantages

The SC connector is what is called a non-optical disconnect connector. This term means that once the connector has been installed, any pushing or pulling on the jacket of the cable will not cause the ferrule to disconnect, which is a prevalent problem with the ST model connectors. This ensures that the signal is not to be interrupted. Plus, its sturdy hold prevents connection problems, even if someone pulls the cable. This advantage solves an issue with ST connectors that can interrupt fiber optic signals if someone pulls on the cable.
The square shape of these connectors offers a more compact design which in turn means that more of these connectors can be installed in a smaller footprint of a space. Sometimes there just is not enough room for the pull and twist connectors and that is where the SC connector becomes a life saver. Since the SC has a standard 2 1/2 mm size, it can pair with an FC or ST connector with a hybrid adapter.
SC connectors are perfectly suited for datacoms and telecoms.

Disadvantages

The disadvantage of using SC connectors is the size of their ferrules and SC connector is although its square body is easier to insert/take out, the body is larger than the LC connector which means it will take up more room than its newer cousin. Therefore, for the most compact spaces or crowded areas, LC connectors might provide a better solution.

3. ST Connectors

ST connectors are among the oldest of fiber cable connector types. The ST connecter was developed by AT&T shortly after the arrival of the FC. At a glance, they can be mistaken for one another but the ST uses a bayonet fitment rather than a screw thread. The design of ST connectors is a 2 1/2 mm ferrule that has a bayonet-style connection between the fibers through an adapter. Until 2005, this proprietary AT&T brand of connector ranked as one of the most popular fiber terminations. Usage has declined in recent decades, for the same reasons as the FC. Today, their cost is low due to their age, making them a choice for budget-mindful projects.

Deployed predominately in multi-mode datacoms, it is most common in network environments such as campuses, corporate networks and in military applications where the quick connecting bayonet had its advantages at the time. It is typically installed into infrastructures that were built at the turn of the century; when retro-fitting, STs are typically swapped out for more cost-effective SC and LC connectors.

Advantages

The ST connector, while older, is still commonly in use in today’s fiber installations due to it being extremely easy to install and its relatively low cost compared to some other connectors. This connector has a keyed “slot” on the end of the connector that helps keep it tightly mated to the fibers and in alignment when they are decoupled and recoupled.

Disadvantages

ST connector cannot be terminated with an angled polish, which limits its use in single-mode fiber and FTTH applications. These ferrules use a spring-load design that can make installation difficult unless the parts have precise seating, though a keyed slot assists with aligning the ferrules for connection. ST Connectors have a round shape to them and are not as compact as more modern square body connections. Also, with this being a spring-loaded connection, the installers must push the connector with quite a bit of force and turn the nut to use these connectors. If there is a tray with lots of connections this can get tedious as it may become hard to get into the tight spaces to decouple/recouple the connectors.

4. Ferrule Core (FC) Connectors

The FC was the first optical fiber connector to use a ceramic ferrule, but unlike the plastic-bodied SC and LC, it utilizes a round screw-type fitment made from nickel-plated or stainless steel. The connector end face relies on an alignment key for correct insertion and is then tightened into the adapter/jack using a threaded collet. Despite the additional complexity both in manufacturing and installation, it’s still the connector of choice for precise measuring equipment such as OTDRs. FC connectors rank as some of the most popular for use with single-mode connections before the introduction of LC and SC connectors. These use a keyed, screw-in type ferrule. However, the process of screwing in the ferrule requires extra time and effort compared to snap-in SC connectors.

Like ST and SC connectors, The FC connector also utilizes a 2.5mm ferrule. With a hybrid adapter, anyone can create a bridge between these connector types.

Advantages

The screw-in design prevents the connection from interruptions, even when someone pulls the cable or the system has applications in areas with a lot of movement. Video over fiber is one use for these types of connectors due to the constant flow of data through the cable and the security of the connector.Like the SC connector, the FC connector also has a non-optical disconnect advantage. Because this connector threads onto a connection, you can be sure that this connector will stay stable and mated to its connection, even during rougher environments.

Disadvantages

Very similarly to the ST, this connector can be hard to grab and twist to thread or unthread from a connection if there are lots of connectors in one receptacle.

5. Multi-Position Optical (MPO) Connectors

The MT ferrule connector is another of NTT’s inventions and has been around since the 1980s, although the technology has only recently become popular under branded versions of the Multiple Fiber Push-On/Pull-Off connector, such as MTP and MPO. MTP is the commercial brand of MPO connectors. MTP and MPO connectors are the same, except the MTP brand has a specific use for high-performance applications, whereas MPO works on more mechanical situations. These two connectors usually connect ribbon cables with multiple fibers.It is larger than the other connectors but for good reason - it can support up to 24 fibers in a single ferrule.

Multi-fiber connectors are not currently designed for field-fit applications so must be lab terminated. In high-density patch environments such as data centers, they are used extensively, both at single-mode and multi-mode wavelengths. On a ‘per-fiber’ basis the costs are relatively inexpensive. However as might be expected, the attenuation loss can be higher than a single ceramic ferrule connector. In single mode use these will typically get about .25dB loss and about .20dB loss in multi-mode. These are also available in the smaller 8 fiber connectors in this configuration. Single mode ferrules are angled at 8°. This is mostly used in very high-density applications with ribbon cable to reduce the connector space that may be required.

Network planners should also consider that while still using an adapter much like other connectors, the MTP/MPO must also be mated to an opposing male or female connector. This may require more than one connector specification or type within inventory, adding to cost and complexity.

Because the sequence of the fibers cannot physically be changed after termination, the connector is often supplied with a fan-out assembly at the opposing end (such as LC, SC, FC etc.). This allows the operator to change channels simply by re-patching the fanned-out side of the cable. The consequence of this is that the small form high density design of the MTP/MPO will only benefit one side of the assembly.

More common in datacoms, these connectors are starting to appear in FTTH applications. They should therefore be considered if drivers include quick deployment of aggregate fibers, high-density patching or where smaller ODFs and nodes might be crucial.

MTP connectors are usually considered a high-performance option while MPO are better for mechanical uses.

MTP connectors are equipped with a housing that is removeable so you can change, re polish or even change the gender of the connection from male to female.

Advantages

MPO/MTP connectors combine 8, 12 or 24 fibers into one single and compact interface. They can put this amount of cable in the same space an SC connector would take up. This very effectively saves rack space on a high-density rack.

Disadvantages

An MPO/MTP connector is not the easiest to clean on account of there being so many fibers in one connection.

3GOTEK offers bespoke optical fiber solution slip rings for defense, communication, satcom, tracking system, survey system and medical system etc. some of our cases for review as below.