Jacks, Panels, & Hardware > Connectors

In a fiber optic adapter, the internal ferrule sleeve holds the fiber in place and aligns the filament of one fiber ferrule with its mate. The ferrule sleeve is the most expensive component to manufacture in a fiber optic adapter, accounting for approximately 80% of the total adapter cost.

The ferrule alignment sleeves are also the most critical part of a fiber optic connection process. They provide the bridge between one cable’s ferrule and another cable’s ferrule interface. The precision of the ferrule sleeve and its hole determines how well the fibers align, which affects the light signal transmission.

Fiber optic adapters are generally made with ceramic or metal ferrule sleeves. Some adapters also feature ferrule sleeves that are a combination of these materials.

Ceramic ferrule sleeves are more precisely molded and fit close to the fiber ferrule. This precise molding gives the fiber optic connection a lower optical loss. As a general rule, use ceramic ferrule sleeves for critical network connections, such as backbone runs in highly secure networks or for connections that will be changed frequently, like those in wiring closets. Ceramic ferrule sleeves best suit single-mode cable connections.

Ferrule sleeves made of metal, such as bronze ferrules, offer more durability than ceramic sleeves, but they may not offer the same precision alignment as ceramic ferrule sleeves. Drilling an accurate hole through the metal ferrule sleeve can be difficult, and that can result in less accurate fiber alignment. The use of watch-jeweled centering improves alignment. But overall, metal ferrule sleeves are better suited for multimode fiber applications where absolute alignment isn’t crucial.

• The ST® connector, which uses a bayonet locking system, is the most common connector.

• The SC connector features a molded body and a push- pull locking system.

• The FDDI connector comes with a 2.5-mm free-floating ferrule and a fixed shroud to minimize light loss.

• The MT-RJ connector, a small-form RJ-style connector, features a molded body and uses cleave-and-leave splicing.

• The LC connector, a small-form factor connector, features a ceramic ferrule and looks like a mini SC connector.

• The VF-45™connector is another small-form factor connector. It uses a unique “V-groove“ design.

• The FC connector is a threaded body connector. Secure it by screwing the connector body to the mating threads. Used in high-vibration environments.

• The MTO/MTP connector is a fiber connector that uses high-fiber-count ribbon cable. It’s used in high-density fiber applications.

• The MU connector resembles the larger SC connector. It uses a simple push-pull latching connection and is well suited for high-density applications.

Terminating fiber cable used to be a job for experts only. But today, prepolished connectors make it possible for anyone to terminate multimode fiber—all you need is a bit of patience and the right tools. Here’s how to terminate fiber with ST connectors:

Step 1 — Slide the connector strain-relief boot, small end first, onto the cable.

Step 2 — Using a template, mark the jacket dimensions to be stripped (40 mm and 52 mm from the end).

Step 3 — Remove the outer jacket from the cable end to the 40 mm mark. Cut the exposed Kevlar. Carefully remove the jacket to the 52-mm mark, exposing the remaining length of Kevlar.

Step 4 — Fan out the Kevlar fibers and slide the crimp ring of the connector approximately 5 mm over the fibers to hold them out of the way. Mark the fiber buffer 11 mm from the end of the cable jacket. Also, mark the buffer where it meets the jacket.

Step 5 — Bit by bit, strip off the buffering until you reach the 11-mm mark. Check the mark you made on the buffer at the jacket. If it’s moved, carefully work the buffer back into the jacket to its original position.

Step 6 — Clean the glass fiber with an alcohol wipe. Cleave the fiber to an 8-mm length.

Step 7 — Carefully insert the fiber into the connector until you feel it bottom out and a bow forms between the connector and the clamp. Cam the connector with the appropriate tool.

Step 8 — Crimp the connector.

Step 9 — Slide the crimp ring up the jacket away from the connector, releasing the Kevlar fibers. Fan the fiber so they encircle the buffer. The ends of the fibers should just touch the rear of the connector—if they’re too long, trim them now.

Step 10 — Crimp the connector again.

Step 11 — Slide the strain-relief boot over the rear of the connector. You might want to put a bead of 411 Loctite adhesive for extra strength on the rear of the boot where it meets the jacket.

Although the details may vary slightly with different connectors and termination kits, the basic termination procedure is the same.

There are different categories of graded-index multimode fiber optic cable. The ISO/IEC 11801 Ed 2.1:2009 standard specifies categories OM1, OM2, and OM3. The TIA/EIA recognizes OM1, OM2, OM3, and OM4. The TIA/EIA ratified OM4 in August 2009 (TIA/EIA 492-AAAD). The IEEE ratified OM4 (802.ba) in June 2010.

OM1 specifies 62.5-micron cable and OM2 specifies 50-micron cable. These are commonly used in premises applications supporting Ethernet rates of 10 Mbps to 1 Gbps. They are also typically used with LED transmitters. OM1 and OM2 cable are not suitable though for today's higher-speed networks.

OM3 and OM4 are both laser-optimized multimode fiber (LOMMF) and were developed to accommodate faster networks such as 10, 40, and 100 Gbps. Both are designed for use with 850-nm VCSELS (vertical-cavity surface-emitting lasers) and have aqua sheaths.

OM3 specifies an 850-nm laser-optimized 50-micron cable with a effective modal bandwidth (EMB) of 2000 MHz/km. It can support 10-Gbps link distances up to 300 meters. OM4 specifies a high-bandwidth 850-nm laser-optimized 50-micron cable an effective modal bandwidth of 4700 MHz/km. It can support 10-Gbps link distances of 550 meters. 100-Gbps distances are 100 meters and 150 meters, respectively. Both rival single-mode fiber in performance while being significantly less expensive to implement.

OM1 and 2 are made with a different process than OM3 and 4. Non-laser-optimized fiber cable is made with a small defect in the core, called an index depression. LED light sources are commonly used with these cables.

OM3 and 4 are manufactured without the center defect. As networks migrated to higher speeds, VCSELS became more commonly used rather than LEDs, which have a maximum modulation rate of 622 Mbps. Because of that, LEDs can’t be turned on and off fast enough to support higher-speed applications. VCSELS provided the speed, but unfortunately when used with older OM1 and 2 cables, required mode-conditioning launch cables. Thus manufacturers changed the production process to eliminate the center defect and enable OM3 and OM4 cables to be used directly with the VCSELS. OM3/OM4 Comparison
850 nm High Performance EMB (MHz/km)



850-nm Ethernet Distance
1-GbE



10-GbE



40-GbE



100-GbE