An Overall Understanding of Fiber Optic Connectors

When installing a brand new fiber optic network, it is necessary to join two fibers together with low signal attenuation. Typically, there are two ways to link optical fibers: fusion splicing by using splicing machines and mechanical splicing by using of connectors. The fusion splice is a permanent connection which directly links two fibers by welding with an electric arc and aligning best possible both fiber cores. While by using connectors, you can connect two fibers more easily and quickly than splicing. Fiber optic connectors adopt the mechanical and optical means for cross connecting fibers and linking to fiber optic transmission equipment. They are the most widely used optical passive components in fiber optical transmission, optical distribution frame, optical test instruments and instrument panels. This paper will make a review of fiber optic connectors from the structure, advantages and common types.


Since 1980s, various manufacturers have developed a dozen types of fiber optic connectors. Although the mechanical design varies a lot among different connector types, the most common elements in a fiber connector are the same, such as dust cap, connector housing, ferrule, crimp eyelet and boot bare buffer, etc, as shown in following diagram. Among them, the ferrule, body and mating adapter are the most components in a fiber optic connector.

Ferrules are made of ceramic, metal, glass or plastic, among which ceramic ferrules or ceramic ferrules with metal inserts are most widely deployed. It is the most crucial element of the connector plug used for the precise alignment and centering of the optical fiber. Typical ferrule size is the 2.5 mm used in the SC, ST, and the FC plugs. The 1.25 mm ferrule is used in the small form factor LC plug. But in MTP and MPO connectors based on MT ferrule, it can allow quick and reliable connections for up to 96 fibers.

The body of the plug holds the ferrule, the coupling mechanism, and the boot. The coupling mechanism mates the plug with the mating adapter, allowing the connector to mate in only one position. At the end of the plug body is the boot which serves as a bend radius limiter for the cable entering the plug body.

The mating adapter is also an essential component in a fiber optic connector. It can hold the connector bodies and let them snap into place. For example, when mating two MTO connectors. the MPO connectors form a “plug and jack” style connector, where the plug is a no-pin connector and a jack is a pin connector with mating adapter. The adapter also aligns the MPO connector keys, which may be up or down in relation to the numbering of the fibers.


Due to the demands of fast, efficient and safe performance in communication networks, more accurate and precise connections of the fiber ends are required. Fiber optic connectors just provide the right solution for complex systems. There are many advantages of fiber optic connectors. First of all, you can choose any types of connectors according to the application field of the system. Besides, the connection is removable that you can either connect and disconnect two fibers hundreds to thousands times without damaging the connectors.

Common Types

There are numerous types of fiber optic connectors available today. The most common are ST, SC, FC, MT-RJ and LC style connectors. Generally, there are three methods for the classification of fiber optic connectors according to transmission media, head structure, and end face preparation.

According to the transmission media, fiber optic connectors can be divided into common silicon-based single-mode and multimode optical fiber connectors. As the name implies, the single-mode connector is connected with SM (single-mode) patch cable, while the multimode optical fiber connector is used for MM (multimode) cable. Of course, they can have other options, for example, single-mode LC to ST fiber patch cable or multimode FC to SC fiber patch cable.

In addition, we can get various connectors based on head structure, such as FC, SC, ST, LC, MT, etc. ST, SC, FC fiber optic connectors are the standard form which are developed earlier than other connectors. They have different applications. ST connector is commonly used in wiring device, SC and MT for network equipment, FC for telecommunication network, etc.

In accordance with connector end face preparation, the connectors can be classified into PC polish, UPC/SPC polish, and APC polish connectors. The connector end face preparation can determine what the connector return loss, known as back reflection, will be. The back reflection is the ratio between the light propagating through the connector in the forward direction and the light reflected back into the light source by the connector surface. Minimizing back reflection can provide high-speed and analog fiber optic links. The following picture shows the difference between PC polish, UPC/SPC polish, and APC polish connectors.


It is not an easy task to select the right connector for different applications because there are so many choices available today. Choosing the suitable fiber optic connector for any installation not only provides perfect performs for your job, but also saves time. Next time when you make a selection of fiber optic connectors, this article may give you a general idea of how to choose them.

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