The words distribution, dry loose tube, gel filled loose tub, breakout, simplex and ADSS - what do they all have in common - well they are all different types of fiber optic cable constructions that you could possibly see on a fiber optic job site. Each of these cable types offers different protections, constructions and qualifications for different applications. There are cables that are only meant to be installed inside of buildings, and have no added protections for outside conditions. There are cables such as gel filled loose tube and ADSS cables that are never meant to be installed within buildings - they are only meant for outdoor conditions. Then there is the happy medium, an indoor/outdoor cable that can go in both indoor and outdoor installations. In the following paragraphs we will take a look at what makes each cable construction different from the others. Also, an important note – when using armored fiber optic cable it is necessary to bond and ground the cable to protect against electrical charges.

Simplex and Duplex

Simplex cable is a single optical fiber cable that is encased in a riser, plenum or low smoke zero halogen (LSZH) outer jacket, then aramid yarn is used to provide tensile strength, and finally a tight buffered optical fiber. A duplex cable, is just as it sounds, it is a two fiber cable that is typically a zip cord construction, but can also be a round construction in some cases. Duplex cable also contains aramid yarn and tight buffered fiber. Both of these cable styles can be found in various outer diameter sizes such as 3mm, 2mm or even 1.6mm and 1.2mm. Simplex and duplex cable is most often used to build fiber optic cable assemblies or patch cords.

Ribbon Cables

Ribbon cables are comprised of multiple bare fibers that are “glued” together as a flat “ribbon”, hence the name. They are typically available in a configuration of 12 and sometimes but rarely, 16 fiber counts, but sometimes even as high as a 144 or 288 fiber count. The higher fiber counts are achieved by including multiple 12 fiber ribbons inside the outer jacket. So a 144 fiber ribbon cable would contain (12) 12 fiber ribbons inside. These cables are usually installed indoors but there are some manufacturers that do make them for outdoor applications. Ribbon cables save on space and are ideal for high density solutions.

Distribution Cable

Distribution cable is the most popular style of indoor fiber optic cable. Fiber counts can range from 2 fibers to 288 fibers, and it can be constructed with a riser or plenum outer jacket. In some cases you will see a distribution type cable that is suitable for Indoor/Outdoor applications. Inside the outer jacket there are multiple color coded subunits, each containing a set of 900um color coded tight buffered fibers, and each of these subunits is surrounded by aramid yarn, usually with a central bend strength member for support and pulling strength. These cables can also be armored if necessary. .

Breakout Cables

A breakout cable is a cable construction where each individual fiber is 900um tight buffered and includes Kevlar or aramid yarn strength members, all encased in a single 2.0mm or 3.0mm jacket within the primary outer jacket. The entire construction is supported by a central bend strength member. Each of the individual fibers can be broken out on their own, and the fiber counts typically range from 2-24 fibers. This cable is essentially constructed of multiple simplex cables bundled together inside an outer jacket. Breakout cables are usually heavier, more expensive and bulkier (because of the extra jacketing), than distribution cable, making it a much less popular style.

Micro Distribution

Micro Distribution cable is the perfect solution for tight fits such as data center applications, because these cables are some of the smallest multi-fiber indoor cables on the market. Micro Distribution is usually comprised of a single outer cable jacket and a layer of aramid yarn with multiple smaller color coded subunits encasing the 250 micron color coded bare fibers, and there may or may not be a central strength member within the cable construction. Fiber counts on these cables can range up to 288 fibers and many times higher. These cables are ideal for high fiber count applications where there might not be enough space for a larger diameter cable. These cables are also perfect for use with MTP/MPO multi-fiber connectors.

Loose Tube Cable

Loose Tube Cable comes in two constructions – Dry loose tube, or in a petroleum based water blocking gel filled (Icky Pic) construction. Both of these options can be armored and they both come in various fiber counts.

In regards to gel filled loose tube, this cable construction provides superior protection in outdoor environments, especially where it is very cold. These cables are commonly double jacketed, with water blocking gel materials (commonly called Icky Pic) that help protect the fiber strands from moisture which can cause long term damage. Loose tube cable can be installed underground, but for the best protection, cables that are direct buried should be armored for rodent protection, and to make sure that they can be located once they are buried. Gel filled cable limits the installer to a maximum 50 foot distance inside a building. The 50 foot rule pertains to the fact that the gel is petroleum based and can burn, giving off toxic fumes.

Dry loose tube is an indoor and outdoor cable because there is no petroleum gel in the construction, only water swellable yarn or water absorbent powder for water blocking protection, eliminating the 50 foot rule. Also, no gel makes this cable easier to terminate or fusion splice as it eliminates a cleaning step in the termination process. Dry loose tube should not be direct buried on its own, but rather it should be placed in conduit or duct if it is necessary to install this type of cable in the ground.

Indoor/Outdoor Cable

Indoor/outdoor cables can be utilized both in indoor and outdoor spaces, without distance limits; they are created to be able to withstand some of the harsh outdoor conditions while still meeting the indoor cable standards. These cables are usually either a dry loose tube construction or a tight buffer construction - they do not have gel (Icky Pic) like a traditional loose tube cable. These cables can also be armored for additional protection if necessary for the application. They usually have a durable UV Resistant black jacket that is either riser or plenum rated and water blocking aramid yarn or water absorbing powder.


ADSS or All Dielectric Self Supporting cable is used in outdoor transmission environments. There is no messenger wire in this cable, nor are there any conductive materials in this cable type. The construction of this cable allows ADSS to be installed in a single pass for quick and relatively easy installation by technicians. ADSS comes in a variety of fiber counts, and these fibers are usually encased in an ultra rugged polyethylene outer jacket which is usually gel filled for water blocking purposes.


Optical Ground Wire Cable (OPGW) is most commonly used in the electric utility industry, and it is installed at the top of the electrical transmission lines or the top of the pole position. OPGW is a dual purpose cable that houses fibers for telecommunications, but it also serves to protect the cable from lightening because it shields conductors on the lines by providing a grounding wire.

So, as you can see from the above there are hundreds of different ways to configure a cable. Factors include: the construction type, the mode of the fiber, the fiber counts and also, a very important factor, the location of the installation, such as whether it will be going inside or outside of the building. All of these are characteristics and details that must be taken into account when trying to find the right cable construction for your application.