Tag Archives: FC connectors

Know Enough About Fiber Connectors?

As there exists a wide range of splice options for fiber network available on the market, selecting the right connector for your application can sometimes be tough and confusing. While choosing the fiber connector, various factors like cost and availability should be considered, which naturally lead to even less thought goes to connector itself. Since each connector has its own unique design as well as merits and demerits, it can pose a significant influence on deployment speeds and costs in the long run. So before making your decision, you’d better have an overall understanding of fiber connectors, and this is what we will talk about.

Fiber Connectors Overview

In this part, we will introduce some fiber connectors that are commonly used in the network applications. The following diagram directly explains the differences among them in performance.

Name Mating Cycles Ferrule Size Typical Insertion Loss (db) Application Features
SC 1000 2.5 mm Ceramic 0.25-0.5 Mainstream, Reliable, Fast deployment, Field fit
LC 500 1.25 mm Ceramic 0.25-0.5 High density, Cost effective, Field fit
FC 500 2.5 mm Ceramic 0.25-0.5 High precision, Vibration environments, Field fit
ST 500 2.5 mm Ceramic 0.25-0.5 Military (legacy), Field fit
MTP/MPO 1000 6.4*2.5 mm molded 0.25-0.75 High density, Aggregate networking, Fast deployment
SC Connector

SC connector was one of the first connectors presented on the market following the advent of ceramic ferrules. It has a push-pull coupling end face with a spring loaded ceramic ferrule. Initially intended for Gigabit Ethernet networking, it became increasingly popular as manufacturing costs came down. The SC connector has held a dominated position in fiber optics for over a decade with only the ST rivaling it. And it still remains the second most common connector for polarization maintaining applications. The SC is ideally suited for datacoms and telecoms applications including point to point and passive optical networking.

SC fiber connectors

LC Connector

Considered to be the modern replacement of the SC connector, LC connector is also a push-pull connector, but it utilizes a latch as opposed to the SC locking tab and with a smaller ferrule it is known as a small form factor connector. LC connector shares huge popularity in datacoms and other high-density patch applications. And its small size and latch feature make it an ideal alternative for densely populated racks and panels. Since LC compatible transceivers and active networking components have been introduced, LC connector is likely to continue to grow steadily.

LC fiber connectors

FC Connector

FC connector leads the trend 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. In spite that the manufacturing and installation of FC connector are much more complex, it’s still an optimum option for precise measuring equipment such as OTDRs. Moreover, FC connector is particularly effective in high vibration environments, ensuring that the spring-loaded ferrule is firmly mated.

FC connectors

ST Connector

ST connector looks much like FC connector, but it uses a bayonet fitment rather than a screw thread. 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. However, it cannot be terminated with an angled polish, which limits use in single mode fiber and FTTH applications.

ST connectors

MTP/MPO connector

MTP and MPO connector falls into the category of multiple fiber push-on/pull-off connector. It is larger than other connectors since it can support up to 24 fibers in a single ferrule. It is currently extensively used in high density patch environments such as data centers, both at single mode and multi-mode wavelengths. MTP/MPO 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.

MTP/MPO connectors

Conclusion

Getting to know the differences between various types of fiber connectors simply contribute to the primary stage of selecting the right one. And when it comes to the planning process of fiber deployments, the differences can be much more clearly. So, make sure to invest enough time to select the right fiber connector, which will do you a good return in the long run.

How Does Fiber Connector Polish Type Influence Termination?

Connectors are used to mate two fibers to create a temporary joint and/or connect the fiber to a piece of network device. That’s one of fiber termination ways. The primary specification of connector termination is loss or the amount of light lost in the connection. Connector loss can be caused by a number of factors. This article will talk about the influence of fiber connector polish type on connector termination.

fiber-connector-termination

When the cone of light emerges from the connector, it will spill over the core of the receiving fiber and be lost. In addition, the end gaps can arouse the other problem called reflectance. The air gap in the joint between the fibers causes a reflection when the light encounters the change of refractive index from the glass fiber to the air in the gap. This reflection is called to as reflectance or optical return loss, which can be a problem in laser based systems.

Nowadays the fiber optic connectors have several different ferrule shapes or finishes, usually referred to as end finish or polish types. The connector end face preparation will determine the connectors’ return loss, also known as back reflection. Different end face causes different back reflection.

PC Polish

The Physical Contact (PC) polish results in a slightly curved connector surface, forcing the fiber ends of mating connector pairs into physical contact with each other. This eliminates the fiber-to-air interface and results in back reflections of -30 to -40 dB. The PC polish is the most popular connector end face, used in most applications.

UPC Polish

In the Ultra PC (UPC) polish, an extended polishing cycle enhances the surface quality of the connector, resulting in back reflections of -40 to -55 dB and < -55dB, respectively. These polish types are used in high-speed, digital fiber optic transmission systems.

APC Polish

Later, it was determined that polishing the connector ferrules to a convex end face would produce an even better connection. The convex ferrule guaranteed the fiber cores were in contact. Losses were under 0.3dB and reflectance -40 dB or better. This solution is to angle the end of the ferrule 8 degrees to create APC or angled PC connector. Then any reflected light is at an angle that is absorbed in the cladding of the fiber, resulting in reflectance  of >-60 dB.

FC-APC-Connector

As the introduction of fiber optic technology, numerous connector styles have been developed – probably over 100 designs. Each connector style is designed to offer better performance (less light loss and reflectance) and easier, faster and/or more inexpensive termination. For example, FC–“Ferrule Connector”. The following are three common types of FC connectors:

  • FC/PC–It’s the most common of the FC connectors. The tip is slightly curved to ensure only the fiber cores make connection during mating not the ferrules themselves. The return loss is 25-40 dB.
  • FC/UPC–The higher quality polish with rounder edges than FC/PC ensures better core mating. The return loss is 45-50 dB. It can mate with FC/PC connectors.
  • FC/APC–Common in most single mode applications where back reflection is critical to be minimized. Identified by the 8 degree of angle present in the ferrule tip along with a typical green colored strain relief boot. The return loss is 55-70 dB. It can only mate with other FC/APC fibers.

From this article, you can see the connector with APC polish type can provide the best connection. Later when you face many different types of fiber optic connectors, you may take polish type as one of the factors to make your decision.