Choosing a Pre-Terminated Fiber Optic Assembly


Choosing a Pre-Terminated Fiber Optic Assembly for your Needs

Choosing a fiber cable for your installation can sometimes be confusing given all of the choices. In this article, we will attempt to clear up some of the confusion. Basically there are two attributes that you will need to consider and those are “cable material and construction” and “fiber type”. First we will talk about cable material and construction. The types of material and construction include the following:

Cable Material and Construction

Indoor Plenum

Use this for all indoor installations. The cable can be run directly in all indoor applications. Installation in conduit or innerduct is not required but does offer additional security for the possibility of the cable from being cut. Most installations do not use conduit of innerduct. A cable rated for plenum installation will have low-smoke characteristics as defined by the NFPA (National Fire Protection Agency).


Outdoor cables are filled with a water blocking jell and are rated for all outdoor applications except for "direct bury". This cable is suitable for underground installation in conduit, overhead lashed to a guy wire, or secured to a building or other permanent outdoor structure. The drawback of the jell-filled cable is that it is mandated at a maximum of 50 feet run indoors due to fire-code regulations.


Please note that the only difference between outdoor (jell-filled) and direct bury cable is that the latter has an added overall metallic sheath which gives it protection from rodents. If you require a direct bury cable, please contact sales for a quote.



Indoor/Outdoor cables are approved for use in underground conduits, even if the possibility of water infiltration exists. Indoor/Outdoor cables are not recommended for aerial installations. The advantage of using Indoor/Outdoor over standard Outdoor cable is that it does not have the 50 foot restriction for indoor installation that standard outdoor cable has. This cable has an overall PVC sheath and is not rated for plenum spaces.

Interlock Armor Indoor Plenum

This cable has all of the attributes of Indoor Plenum cable with the additional benefit of the armor which protects it from accidental cutting.

Interlock Armor Indoor/Outdoor Plenum

This cable has all of the attributes of Indoor Plenum and Indoor/Outdoor cable with the additional benefit of the armor which makes it suitable for direct bury.

Outdoor Aerial with Messenger

This cable has a steel messenger for use spanning from building to building or pole to pole etc. Due to the fact that it contains a jell-filled cable, it is limited to a maximum of 50 feet running indoors.

Fiber Type

The 62.5/125 µm (AKA: OM1) has been the most popular multimode fiber choice throughout the 80's, 90's and into the early 2000's and was the most common multimode fiber used and yet it has the lowest data carrying capacity and shortest distance limitations as compared with other Multimode fiber types. It is generally accepted that 62.5/125 Multimode will soon be obsolete for the purpose of new installations.

NOTE: If you currently have 62.5/125 µm fiber installed in your office, building or campus you need to continue to use 62.5/125 µm fiber patch cables to connect to it. Attempting to mate two different fiber core sizes can lead to high loss and is therefore strongly not recommended. We recommend at least OM2 or higher for new installations.

The 50/125 µm core size comes in three different classifications (OM2, OM3 and OM4). Below are the types of fiber available


OM1 will soon be rendered obsolete because in contrast 50/125 fibers have a much higher bandwidth capacity. Also consider the fact that OM2 is usually about the same price as OM1. The only practical use for OM1 cables would be for use in extending and existing OM1 cable run. OM1 typically has an orange jacket.


OM2 will become the cable of choice for those who have no intention of upgrading to 10 Gb. OM2 can run 1 Gb Ethernet for a maximum distance of 220 meters. OM2 typically has an orange jacket.

Category Fast Ethernet 100BASE-FX 1 Gb (1000 Mb) Ethernet 1000BASE-SX 10 Gb Ethernet 10GBASE-SR 40 Gb Ethernet 40GBASE-SR4 100 Gb Ethernet 100GBASE-SR10
OM1 (62.5/125) 2000 m 220 m 33m Not supported Not supported
OM2 (50/125) 550 m
(mode-conditioning patch cord required over 300m)
82m Not supported Not supported
OM3 (50/125) (Laser Optimized) 300m 100m (330m) 100m
OM4 (50/125) (Laser Optimized) 400m 150m (550m) 150m

* NOTE: Check with equipment manufacturers to verify the above distances and speeds.


OM3 will become the cable of choice for those who seek to run 10 Gb Ethernet either now or in the near future. OM3 will soon be the most popular Multimode choice especially for Data Centers. OM3 typically has an aqua color jacket.


OM4 will be the cable of choice for Data Centers due to its ability to run 100 Gb at greater distances. OM4 typically has an aqua color jacket.

Frequently Asked Questions
Use OM1 only to extend existing fiber runs. Otherwise use a minimum of OM2.
OM1 is 62.5/125 and OM2 is 50/125. The 50/125 core of OM2 has a higher bandwidth capacity.
If you wish to run a 10 Gb network now or in the future, choose OM3.
Choosing a fiber type is normally dictated by the equipment that you wish to use. For example, if you choose media converters that are designed for distances on 15 Km or greater, they would be Singlemode. You would then choose and install Singlemode fiber to connect the equipment.
OM 4 just like OM2 & 3, has a 50 micron core. OM4 has a laser optimized core (like OM3) and is rated for higher distances than OM3. Few users need the extra distance so it is not a popular choice.
The answer depends on your anticipated future needs. Most people get at least 2 or more extra pairs.
It is OK to use a 2 strand assembly like a long patch cord and go straight into the equipment. However it would not be advisable with any strand count higher than two. The reason is because the unused strands would be hanging down in a sloppy fashion. If you have a strand count higher than two, we recommend a fiber termination box. The termination box is easy to install and makes for a much more professional installation (even if all of the strands were used).
If you are installing it in a conduit, PVC Riser rated cable is ok to use in a plenum space.
Fiber Optic cabling has a very small difference in price for PVC verses plenum comparing it to copper cable. By stocking only one cable type, we are able to sell it at the same cost as non-plenum cable.
Yes, installing the cable in a conduit would serve the same purpose as installing Interlocking Armor cable. The installation of the Interlocking Armor cable would be much easier. In either case, the fiber optic cable would be protected from the harshest environments and be relatively safe from accidental cutting.
MTP systems use a single head to terminate 12 fibers. In a typical installation, the 12 fiber connector plugs into a cassette that breaks out the 12 fibers to traditional LC or SC connectors. Because of its high density, it is very popular in data centers. The MTP assembly is not expensive but the cassettes are somewhat. If high density is not important to you than you would be better off with traditional Pre-Terminated fiber assemblies.
The most common reason would be the polarity. Be sure to swap the polarity on one side only so that the transmit of one unit connects to the receive of the other unit and vice-versa. If you are unsure, just reverse the polarity. If the pull was difficult and a lot of force was required to pull in the cable, it is possible that one or more fibers, or connectors may have broken. Multimode fiber can be checked by shining a flashlight into one of the connectors (one at a time) and seeing if it comes through on the other side. If you have Singlemode fiber than you will need to use a VFL (visual fault locator) to check continuity. Another cause for failure can be dirty connectors which can become contaminated during the installation. Be sure to use fiber cleaning systems that are designed for the purpose. For additional information please see the following article: Pre-Terminated Assemblies