Info on Fiber

7/30/2019 Info on Fiber

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Fiber Connector Guide

Fiber optic connectors are unique. Fiber cables transmit pulses oflight instead of electrical signals, so the terminations must be muchmore precise. Instead of merely allowing pins to make metal-to-metalcontact, fiber optic connectors must align microscopic glass fibers perfectly in order to allow forcommunication. While there are many different types of fiber connectors, they share similar designcharacteristics. There are three major components of a fiber connector: the ferrule, the connector body, and

the coupling mechanism.

Ferrule this is a thin structure (often cylindrical) that actually holds the glass fiber. It has a hollowed-outcenter that forms a tight grip on the fiber. Ferrules are usually made from ceramic, metal, or high-qualityplastic, and typically will hold one strand of fiber.

Connector body this is a plastic or metal structure that holds the ferrule and attaches to the jacket andstrength members of the fiber cable itself.

Coupling mechanism this is a part of the connector body that holds the connector in place when itgets attached to another device (a switch, NIC, bulkhead coupler, etc.). It may be a latch clip, a bayonet-

style nut, or similar device.

ST Straight TipThe ST connector was one of the first connector types widely implemented in fiberoptic networking applications. Originally developed by AT&T, it stands for StraightTip connector. ST connections use a 2.5mm ferrule with a round plastic or metalbody. The connector stays in place with a twist-on/twist-off bayonet-stylemechanism. Although extremely popular for many years, the ST connector is slowlybeing supplanted by smaller, denser connections in many installations.

SC Subscriber ConnectorSC connectors also use a round 2.5mm ferrule to hold a single fiber. They use a

push-on/pull-off mating mechanism which is generally easier to use than the twist-style ST connector when in tight spaces. The connector body of an SC connector issquarish, and two SC connectors are usually held together with a plastic clip (this isreferred to as a duplex connection). The SC connector was developed in Japan byNTT (the Japanese telecommunications company), and is believed to be anabbreviation for Subscriber Connector, or possibly Standard Connector.

LC Lucent ConnectorOne popular SFF connector is the LC type. This interface was developed by LucentTechnologies (hence, Lucent Connector). It uses a push-pull mechanism, similar tothe SC, and the connector body resembles the squarish shape of SC connectors aswell. LC connectors are normally held together in a duplex configuration with a

plastic clip. The ferrule of an LC connector is 1.25mm.

MTRJ Mechanical Transfer Registered JackThis is another popular SFF connector. Based on a specification by NTT, it wasdeveloped by AMP/Tyco and Corning, and stands for Mechanical Transfer-Registered Jack. The MT-RJ connector closely resembles an RJ-style modular plug,even getting part of its name from the resemblance. MT-RJ connectors are alwaysduplex in that they hold two fibers. The body and ferrule are normally made fromplastic or plastic composite, and lock into place with a tab (just like a modular RJ-style plug).

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FDDIFDDI stands for Fiber Distributed Data Interface, and it actually refers to a localarea network standard such as Ethernet or Token Ring. The termination on the fiber

optic cable itself is called an FDDI connector, or is also known as an MIC (MediaInterface Connector) connector. It contains two ferrules in a large, bulky plastichousing that uses a squeeze-tab retention mechanism.

MTPMTP is a special type of fiber optic connector. Made by US Conec, it is animprovement of the original MPO (Multi-fiber Push-On) connector designed by NTT.The MTP connector is designed to terminate several fibersup to 12 strandsina single ferrule. MTP connections are held in place by a push-on/pull-off latch,and can also be distinguished by a pair of metal guide pins that protrude from thefront of the connector. Because of the high number of fiber strands available in asmall connection, MTP assemblies are used for backbone, cross-connect, andbreak-out applications.

Small Form Factor connectors (SFF)SFF connectors grew from the effort to make fiber connections smaller. In a rack orcloset environment, space for several connections is limited, and thusmanufacturers sought a way to increase port density. A standard was developedfor smaller connectors called SFF (Small Form Factor). There are many differenttypes of SFF connectors, but they are all smaller than normal ST or SC connections.

Other SFF ConnectorsThere are some other SFF connectors in the marketplace, which are not widely popular as the LC and MT-

RJ. These include the Volition VF-45 by 3M, the Opti-Jack by Panduit, the SC-DC, and the MU.



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How to Select the Right Fiber Cable for Your Application

Step 1 - Select The Fiber Type:

The type of fiber needed depends on your equipment and application overall. Thisinformation may be written on the equipment, an existing cable or in the equipmentsoperation manual.

If your equipment uses a single mode laser diode for signal transmission, then select9/125.

If your equipment uses multimode LEDs for signal transmission then select 50/125 or62.5/125.

Please note: Although some 62.5/125 applications are backwards compatible with50/125, it is recommended that you use the size suggested by your equipmentsmanufacturer. Mixing different core sizes in the application can affect the performance ofyour network.

If your equipment uses a multimode laser diode 10Gbs (Sometimes referred to as VCSEL)select 50/125 LOMM. The cable used is also known as Aqua Fiber because of theouter jackets unique Aqua color.

Step 2 - Select The Fiber Count:

Examine the equipment to determine how many fiber strands are needed.

Applications which require one strand of fiber are known as Simplex. Applications which require two strands of fiber are known as Duplex.

Simplex Connector Duplex Connector



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Step 3 - Select The Connector Types:

Select the connectors required for each end of the equipment. Keep in mind that the

connectors do not have to be identical on both ends of the cable.

LC SC MTRJ ST

Step 4 - Select The Length:

Select the length of cable that is required for your application.


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