Choosing the Right Fiber Optic Cable
There are so many fiber optic cable options available that one might wonder where to start. This article will set you on the right path in the decision process. Let’s begin by focusing on the broad categories of fiber optic cable. Below you can make “either/or” decisions. A handy reference chart that summarizes key cable features can be found below.
Multimode or Single Mode?
Multimode Cable - Applications: Multimode fiber is used to transport high volumes of data over relatively short distances (compared to single mode fiber). Common applications include Data Centers and other Local Area Network (LAN) applications. Note that multimode distance capabilities have increased over the years. Multimode fiber cable now offers an economical alternative to single mode cable for certain applications. Design: Multimode cable has a relatively large core (either 50 or 62.5µm) that enables multiple streams of data to be transported simultaneously.
Single Mode Cable - Applications: Telcos and CATV companies use single mode cable to transport signals over long distances. Business campuses and other institutions also use single mode cable for longer cable runs, such as links between buildings. Design: The core diameter of single mode fiber is so small (9µm) that it permits only one mode of light to pass through it at any given time. This characteristic reduces attenuation and enables light to be transmitted over great distances. While the purchase price of single mode cable is less than multimode cable in general, single mode transceivers and network interfaces are generally more expensive than those used for multimode systems.
Simplex or Duplex?
Applications: Simplex and Duplex cables are typically used for fiber optic patch cables and desktop installations that don’t require a high fiber count. Design: Simplex cables contain a single 900µm coated fiber or a combination of a 900µm coated fiber surrounded by an aramid yarn strength member with an outer jacket diameter varying between 3, 2, 1.8 and 1.6mm. Duplex cables contain two 900µm coated fibers surrounded by an aramid yarn strength member with an outer jacket diameter varying from 3, 2, 1.6 and 1.2mm.
Loose Tube or Tight Buffer?
Loose Tube Cable: Applications: Loose tube cable is ideal for use in long distance outside plant applications that require a high fiber count. The cable is designed to withstand harsh outdoor environments; the cable’s unjacketed fibers are free to expand and contract with temperature changes. Design: Fibers within loose tube cables are surrounded by a water blocking component (either gel or a dry water-blocking material). Although loose tube cables are engineered to withstand damp outdoor environments, they are not designed to be submerged in water, but can come in contact with water. Terminating Loose Tube Fibers – The fibers within the gel-filled tubes of the cable have a very thin acrylate coating which is 250µm in diameter. Before terminating, the fibers must be put into small plastic tubes (called a breakout kit or box). The tubes protect the thin fibers and make them easier to handle when terminating and connecting to network equipment.
Tight Buffer Cable: Applications: Tight buffer cable is typically used indoors. A tight buffer (cable jacket) encapsulates each fiber. The 900 micron buffer enables the fibers to be directly terminated without requiring a breakout kit, which saves substantial time. These cables do not typically provide protection from water migration and do not isolate fibers well from the expansion and contraction of other materials due to temperature extremes. Tight-buffered cables, often called premise or distribution cables, are ideally suited for indoor-cable runs. Design: Tight buffer cables have two protective coatings; a 900 micron PVC jacket and 250 micron acrylate coating, all encased in an outer PVC jacket.
Distribution or Breakout?
Distribution Cable: Applications: Distribution cable is ideal for networks that terminate multiple fibers at a common location, such as a patch panel or communications closet. Fibers within a distribution cable have their own 900 micron individual cable jackets. This space-saving feature enables up to 144 fibers to be bundled within the cable. Fibers in a “Micro Distribution” cable do not have the 900 micron tight buffered PVC jacket, instead they contain color coded 250 micron acrylate coated fibers. Because of the decreased diameter of the individual fibers in the cable, a micro distribution cable may contain up to 432 or more fibers. A disadvantage of micro distribution cable is that the unjacketed fibers require the use of a breakout kit for termination. Design - Distribution cable contains a number of 250µm - 900µm fibers that are color-coded for easy identification. The cable includes an aramid yarn strength member and a thick outer jacket that provides protection and strength during cable installation. If required, the cables can be purchased with interlocking armor.
Breakout Cable: Applications: Breakout cable is ideal for applications where fibers are connected directly to equipment, including local hubs. Also, the robust design of breakout cable makes it well suited for use as drop cables. Design - Breakout cable differs from distribution cable in that each of the fibers in a breakout cable is 900 micron tight buffered and surrounded by aramid yarn all encased in a 2mm or 3mm PVC jacket. Then all of these 2 or 3mm jacketed fibers are encased in an outer jacket. This additional jacketing can save substantial time and installation cost, especially if the fibers are being terminated with connectors. One disadvantage of breakout cable is that the fiber jackets take up room within the cable, so breakout cable cannot contain as many fibers as distribution cable. Fiber counts for breakout cable are typically 2-24 fibers (maximum is 48 fibers).
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