Parts of the fiber optic connectors include the connector body, the cable, and the coupling device. The connector body, also called housing, holds the ferrule. It is usually made of metal or plastic and includes one or more assemblies which hold the fiber in place. The ferrule extends past the connector body to slip into the coupling device.
The cable is attached to the connector body and acts as a point of entry for the fiber. Extra strength is provided by a strain-relief boot added over the junction between the cable and connector body. A coupling device is used instead of a male-female configuration. The video below gives a great brief description of the types of connectors. More detailed description can be found in the next section.
Types of Fiber Optic Connectors
Common types of fiber optic connectors include:
- Biconic connectors have precision tapered ends for low insertion loss. It has a glass - filled plastic molded and started with the fiber being molded into the ferrule. Biconic connectors are becoming obsolete.
- D4 connectors are made from a composite zirconia ceramic ferrule for durability. They have a high-performance threading mounting system and a keyed body for repeatability and intermateability. It uses a smaller ferrule than SCs or FCs. D4 connectors were widely used in telco networks in the 80s to early 90s but they are becoming an obsolete technology.
- ESCON’s name derives from its application in IBM's ESCON channel interface. It is similar to the FDDI connector-a duplex connector using 2.5-mm ferrules. The main difference is its retractable shroud as opposed to a fixed shroud. The shroud is over the ferrule is spring-loaded and retracts. ESCON connectors are used to connect to the equipment from a wall outlet.
- An FC, or fixed connection, connector is constructed of an all-zirconia ceramic ferrule for durability. They have a high-performance threading mounting system and a keyed body for repeatability and intermateability. They are primarily used with single mode fibers and used in telephone, instruments, and high-speed communication links. The style is similar to that of an ST connector, but it uses a threaded connection which makes it better suited for high vibration environments.
- FDDI connectors are designed by ANSI for use in FDDI networks. This connector is a duplex connector using two 2.5-mm ferrules and has a fixed shroud over the ferrules. This connector has a fixed shroud that protects the ferrules from damage. They are usually used to connect to the equipment from a wall outlet, but the rest of the network will have ST or SC connectors. Image Credit: Fiber-optics.info
- LC, also known as Lucent Connector, Little Connector, or Local Connectors, connectors have precision PC polished zirconia ceramic ferrules. They have an RJ45 push-pull style housing and latching. They are half the size of standard connectors, resembling a smaller version of the SC. This design increases packaging density by 50% with its narrow footprint and push/pull snap-lock design. LC connectors are used in private and public networks, and are gaining in popularity due to their small form factor (SFF) optical transmitter/receiver assemblies.
- Loopback connectors are used in testing transceiver systems. Loopback describes a way of routing electronic signals from their originating facility to the receiving end of the source without processing or modification. This is best used as a way to test the transmission of transportation infrastructure.
- MTP, the abbreviation for Multi-Fiber Push On/Pull Off, connectors are a threaded type fiber optic connector. They are ideal for high-density applications. MTP connectors is the commercial name for MT connectors, which are 12 fiber connectors for rubber cable. It is used for preterminated cable assemblies and cabling systems.
- The MT-RJ uses a ferrule smaller than the standard MT to hold two fibers. MT stands for Mechanical Transfer and RJ stands for Register Jack. It also uses a press to release latch quite similar to that found on the modular jack to make its operation familiar. MT-RJ use pins for alignment and has male and female versions. They are multimode only, and are field terminated by prepolished/splice method.
- An MU connectors is a 1.25mm diameter ferrule for compact multiple optical connectors and self-retentive mechanism for backplane applications. These "miniature units" are utilized in high-speed data communications, voice networks, telecommunications and high-density DWDM applications. MU connectors are more popular in Japan.
- SC, or Subscriber Connector, connectors are high-precision ceramic ferrules. They feature a snap-in locking mechanism for positive latching. SC connectors use a push-pull design and can be used for simplex or multiplex applications. They have a keyed body for repeatability and intermateability and are ideal for high-density applications. SCs are referred to as a premises connector since they are used for premises installations. Although it has a compact hard plastic design, they do not have the smallest footprint, requiring 0.378 square inches.
- SMA connectors have a low cost multimode coupling with approval for military applications. SMA, which stands for Subminiature A, is a microwave connector.
- ST, or Straight - Tip, connectors are composed of a precise zirconia ceramic ferrule. They have an easy-to-assemble, one-piece bayonet mounting system. They can be used for both single mode and multimode fibers. This type of connector is very popular in communication applications, such as LANs and CCTV systems. ST connectors are also referred to as a BFOC - Bayonet Fiber Optical Connector. They have a ceramic tip which extends past the connector body. This is also known as a simplex bayonet-style twist-lock connector and it requires special care since the ferrule is unprotected. While the ST connector is still popular in many industrial applications, it is losing favor to more compact, keyable form factors.
Connector Color Codes:
Since the earliest days of fiber optics, orange, black or gray was multimode and yellow singlemode. However, the advent of metallic connectors like the FC and ST made color coding difficult, so colored boots were often used. The TIA 568 color code for connector bodies and/or boots has been Beige for multimode fiber, Blue for singlemode fiber, and Green for APC (angled) connectors. With the advent of new types of fiber, the choices were widened as shown in the table below.
|Fiber type||Connector Body||Strain Relief/ |
|50/125 laser optimized||Aqua||Aqua|