Brief Introduction on Connectors

The Connector is a mechanical device mounted on the end of a fiber optic cable, light source, Receiver or housing. It allows it to be mated to a similar device. The Transmitter provides the Information bearing light to the fiber optic cable through a connector. The Receiver gets the Information bearing light from the fiber optic cablethrough a connector. The connector must direct light and collect light. It must also be easily attached and detached from equipment. This is a key point. The connector is disconnected. With this feature it is different than a splice which will be discussed in the next sub-chapter.

A connector marks a place in the premises fiber optic data link where signal power can be lost and the BER can be affected. It marks a place in the premisesfiber optic cablelink where reliability can be affected by a mechanical connection.

There are many different connector types. The ones for glass fiber optic cableare briefly described below and put in perspective. This is followed by discussion of connectors for plastic fiber optic cable. However, it must be noted that the ST connector is the most widely used connector for premise data communications

Connectors to be used with glass fiber optic cableare listed below in alphabetical order.

Biconic - One of the earliest connector types used in fiber optic data links. It has a tapered sleeve that is fixed to the fiber optic cable. When this plug is inserted into its receptacle the tapered end is a means for locating the fiber optic cable in the proper position. With this connector, caps fit over the ferrules, rest against guided rings and screw onto the threaded sleeve to secure the connection. This connector is in little use today.

D4 - It is very similar to the FC connector with its threaded coupling, keying and PC end finish. The main difference is its 2.0mm diameter ferrule. Designed originally by the Nippon Electric Corp.

FC/PC - Used for single-mode fiber optic cable. It offers extremely precise positioning of the single-mode fiber optic cable with respect to the Transmitter's optical source emitter and the Receiver's optical detector. It features a position locatable notch and a threaded receptacle. Once installed the position is maintained with absolute accuracy.

SC - Used primarily with single-mode fiber optic cables. It offers low cost, simplicity and durability. It provides for accurate alignment via its ceramic ferrule. It is a push on-pull off connector with a locking tab.

SMA - The predecessor of the ST connector. It features a threaded cap and housing. The use of this connector has decreased markedly in recent years being replaced by ST and SC connectors.

ST - A keyed bayonet type similar to a BNC connector. It is used for both multi-mode and single-mode fiber optic cables. Its use is wide spread. It has the ability both to be inserted into and removed from a fiber optic cable both quickly and easily. Method of location is also easy. There are two versions ST and ST-II. These are keyed and spring loaded. They are push-in and twist types.

Photographs of several of these connectors are provided in Figure 1-1.

Figure 1-1: Common connectors for glass fiber optic cable (Courtesy of AMP Incorporated)


Plastic Fiber Optic Cable Connectors - Connectors that are exclusively used for plastic fiber optic cable stress very low cost and easy application. Often used in applications with no polishing or epoxy. Figure 1-2 illustrates such a connector. Connectors for plastic fiber optic cable include both proprietary designs and standard designs. Connectors used for glass fiber optic cable, such as ST or SMA are also available for use with plastic fiber optic cable. As plastic fiber optic cable gains in popularity in the data communications world there will be undoubtedly greater standardization.

 

Figure 1-2: Plastic fiber optic cable connector (Illustration courtesy of AMP Incorporated)