The majority of loose tube fiber optic cables are available in a gel-free or gel-filled configuration. Although the end result is essentially the same, there are some significant differences in construction. Hopefully this post can help you decide on which product is best suited for your application.
Let’s start off by going over the similarities. Both gel-filled and gel-free cables pass all industry standard requirements. They are also both designed and manufactured to withstand the rigors of outdoor installations. And lastly, both types of cables are built to operate within performance parameters when installed in harsh environments.
With all that taken into consideration, let’s look at the differences between the two cables. The only thing that varies between the two types of construction is the method used to block water from entering into the cable.
Gel-free cables use a “water swellable” material between the fibers and the outer jacket. Typically this is tape, but could also be foam or string. Whatever the material is, it is treated with an absorbent material to help keep water away from the actual fibers. There are some pro’s to using this type of water blocking. Number one, installers love it. It’s much less mess for them to have to deal with when splicing or terminating the fibers. The second biggest benefit is that, because of the less involved prep for splicing and terminating, labor costs can be significantly reduced. As for the downside of using this type of water blocking, the only significant one we can come up with is that the water absorbing materials used in these cables do not “fill” the entire tube (like a gel does), therefore possibly allowing some amount of water to permeate the tube and exposing the fiber to damage.
Gel-filled cables have their own set of pros and cons. In a gel-filled cable, any space in a tube that is not occupied by a fiber, is filled with impenetrable gel. Some of the benefits of using this water-blocking method are: 1) loose tube cable that is gel-filled has fibers that are free floating meaning there is less tension on the fibers; and 2) The gel in gel-filled cable adds an additional layer of protection against any element that might cause damage to the fiber. The most significant drawback to using this type of cable is that is can be a timely (read: costly) mess for installers. Having to clean the gel from the fibers can significantly slow down the installation process and just be a plain mess for the lucky technician that has to splice or terminate this cable.
So what do these differences mean to you when trying to decide which cable is best? Unfortunately, there is no magic bullet or one fiber cable that is suitable for every application. You must first ask yourself a few questions to determine which is right for you. The most important question is; “What amount of water is the cable likely to be exposed?” and another important issue to consider is time: not only the time you will need to complete the installation, but the lead time from the manufacturer.