Do You Have Any Idea of Water-Resistant Fiber Optic Cable?


There is no doubt that fiber optic cables play an integral role in the telecommunication industry. Applications like data centers, local area networks, telecommunication networks, industrial Ethernet, and wireless network are all needing fiber optics to ensure smooth connectivity. Each application requires a specific cable design based on performance requirements, environmental conditions, and installation type. The common fiber optic cables like LC to LC patch cord cannot adapt to the harsh environment (e.g. moisture environment or underground deployment), thus water-resistant fiber optic cables are highly demanded on the market due to their waterproof nature. Here is what you should know about the water-resistant fiber optic cable.

Overview of Water-resistant Fiber Optic Cables

Water-resistant fiber optic cable refers to the special type of fiber optic cable that is designed and specified for installations where the cable will come in contact with water or moisture, such as aerial, direct buried, or in conduit. The cables in these applications are exposed to or can be temporarily submerged in water, so they contain either a water-resistant gel-filled or gel-free (dry gel) polymer.

Generally, fiber optic cables can be divided into three types—outside plant cable (OSP), indoor/outdoor, and indoor, which are specified based on the environment and location where they are installed. With the exception of indoor cables, all cables contain water-resistant gel-filled or gel-free material to protect them from water and moisture. Before the use of gel-filled and gel-free materials, the flooded core was another water-blocking method that is rarely used today (it has been replaced with gel-filled). The following image shows the gel-filled cables.

a diagram showing how water resistance properties are achieved in tight buffered fiber optic cables

The gel is a gooey substance that must be removed when accessing and installing the cable. Gel-free cables, which are now more widely used, contain a super-absorbent polymer powder that is activated when it comes in contact with water or moisture. This blocks the water from penetrating the cable and allows for some expansion and contraction with temperature changes. Indoor cables do not contain water-resistant material since they are not typically exposed to water. Indoor (and indoor/outdoor) cables must meet additional flammability requirements dictated by local codes, such as the National Electrical Code.

Tight-Buffered & Loose Tube Cable Construction Provides Excellent Moisture Resistance

Water-resistant materials and cables are included in many industry specifications and standards. Generally, there are two basic water-resistant cable designs: Tight-buffer cables (primarily used inside buildings), Loose tube cables (used for OSP and indoor/outdoor).

It is known to all that most tight-buffered cable designs (seen in the image below) are specified for indoor use, but some of them are designed with water-resistant powder and yarn, making them suitable for indoor/outdoor applications. This tight-buffered cable utilizes a different design approach to deal with the moisture issue. Buffer materials are low-porosity plastics with excellent moisture resistance. This construction very effectively minimizes the water molecule and OH-ion concentration level at the glass surface and virtually eliminates the stress corrosion phenomenon.

cross section of an armored tight buffer fiber optic cable

In loose-tube cables (seen in the image below), in order to prevent the water from reaching the 250μm coated fibers, the tubes surrounding the fibers must be filled with water-absorbent powder or gel that withstands high-moisture conditions, making them excellent for outside plant applications. This approach is specially made to waterproof the cable by filling the empty spaces in the cable with gel. The gel-filled tubes can also expand and contract with temperature changes, which makes loose-tube cable great for harsh, high-humidity environments where water or condensation can be a problem. However, gels can move, flow, and settle, leaves an uncertainty of the fill level of any particular point of a loose-tube gel-filled cable. Because the loose-tube cable is typically 250 microns, you’ll need a fan-out kit to build up the individual fiber strands to 900 microns when making the transition at the entrance point from outdoor loose-tube to indoor to tight-buffered cable.

cross section of fiber optic cables

The same level of protection remains in place all along the fiber, regardless of installation conditions, environment, or time. The balance of the tight-buffered, tight bound cable designs is such that it minimizes the open spaces available in the cable structure in which water can reside. Even if an outer cable jacket is cut, or water otherwise enters the cable structure, only a very small percentage of the cross-sectional area is open to the water.


When selecting the suitable fiber optic cables, one must consider the application, the installation location, and the appropriate cable design and type according to specifications and standards. The water-resistant optic cable is specially made for moisture environment to ensure smooth connectivity. However, whether to have the loose tube fiber optic cable or tight-buffered cable, it depends on the installation location. FS.COM offers a full range of fiber optic cables at very economical rates. These cables are widely used and are highly demanded on the market due to their waterproof nature. In addition to this, we offer these cables in various fiber optic cable specifications, such as duplex/simplex fiber cable, single-mode/multimode fiber optic cable, LC/FC/SC/ST fiber optic cable and so on. LC to FC patch cord is absolutely high quality and low price, just like the other fiber optic cables. If you want to know more about our products, please contact us directly.

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