Whether it is indoor or outdoor fiber-optic (FO) cable, using a step-by-step approach reduces the chance of fiber damage while ensuring the performance of fibers.
In our continuing discussion of installing FO cables, let's use a step-by-step approach in detailing how to strip and clean indoor and outdoor FO cables. Please refer to the noted FO cable cross-section diagrams as you read through the guidelines.
To strip and clean indoor FO cable preparation, follow this procedure.
Step 1: Decide how much cable you want in the termination cabinet, so you know how much jacket to remove at the slack end. Mark the jacket. Be sure you allow enough length. Some like to put a piece of shrink sleeve, about 2 in. or 3 in. long, over this point in the cable. These are available with your cable identification imprinted on them.
Step 2: Put a circular score around the outer jacket at 7 in. to 10 in. away form the cable's end. Be careful not to cut through the jacket and cut off the ripcord. Strip back and remove the 7-in. to 10-in. long piece of outer jacket to expose the ripcord, which you'll use to remove the rest of the jacket to the Step 1 mark. Make sure you have enough length on the ripcord to get a good grip. You can use a knife with a hook blade or one of a variety of other outer jacket cutters.
Generally, the jacket's outer part of the plastic is soft, and the inner part is hard or brittle. So, you should be able to bend the jacket, and the plastic will break off.
Step 3: Score the cable at the Step 1 mark, being careful not to cut through the jacket.
Step 4: Strip the jacket down to the mark with the ripcord, and remove it from the cable. Your best bet is to put a little nick in the jacket at the ripcord's location with the hook blade knife. This provides a good starting location for the ripcord and reduces the possibility of it breaking.
Step 5: Remove the outer jacket from the point where it will enter the termination cabinet to the slack end, making sure you leave a few inches of the jacket in the enclosure. Use cable ties to fasten the cable to a fastening part inside the enclosure.
Step 6: If the buffered fibers are in a sub-group jacket, you'll have to remove this, too, again making sure you don't cut too deeply through the jacket. If there are no sub-groups, just individual buffered fibers, unwrap them from around the strength member.
Step 7: Cut the strength member to length, and fasten it solidly to the enclosure. This will prevent the cable from pulling out of the enclosure and putting damaging strain on the fibers. If the strength member is a solid fiberglass rod, you may have to use a set-screw lug to attach it to the enclosure. If it is aramid yarn, then fasten it to the enclosure by wrapping it around a screw (manufacturers' recommendation). This writer finds crimping it in a lug is neater and more secure.
To strip and clean outdoor FO cable, you have to start with the outer jacket.
Removing the outer jacket. Step 1: Mark the armor (if the cable has armor) with the tip of your knife to note a length sufficient to expose the cable's ripcord, being careful not to go through the armor and cut the ripcords.
Step 2: Cut and remove the armor at this mark to expose the two ripcords (usually one each on opposite sides of cable).
Step 3: Nick the armor on each side with your knife to provide a starting point for the ripcords. Get a good grip on one ripcord and pull at 90 degrees to the cable; it will cut through the armor and jacket with ease. Do the same with the other ripcord, and the outer jacket and armor will come off in two pieces, with no strain on the cable itself. (With some cables, you'll find a gel-type adhesive on the cable under the armor, which you'll need to clean off at this point. There are many products on the market; make sure you use a safe, environmentally friendly, and effective product.)
Now you can move onto the inner jacket.
Removing the inner jacket. Step 1: Cut and remove a few inches of the inner jacket at the end of the cable to expose one or two ripcords.
Step 2: Nick the jacket and mark it to the length you want removed. Remember, the fibers inside have little protection, so use the knife sparingly.
Step 3: Grip the ripcords and pull to remove the inner jacket. This will expose nylon binding strings and a plastic covering over the fiber units.
Step 4: Using a small binder cord cutter (which is quite similar to a seam ripper), cut the cords. Cutting every second or third is enough.
Step 5: Using a wipe well soaked with gel remover, wipe the cable. As the gel dissolves, the binder threads will come off. Make sure you remove all of the gel.
Step 6: Unwind the loose tubes from around the center strength member. Cut off the filled tubes and discard them. Loose tubes have a bend memory; to make a neat bundle some technicians prefer to heat them with a heat gun or even a hair dryer to straighten them out. This writer's preference is to leave well enough alone and not look for trouble.
Step 7: Attach the strength member to the enclosure.
Step 8: Remove the buffer tube. You'll find the same gel on the fibers in this tube. This buffer tube is extremely hard plastic; if you over bend this tube, it will kink and break the fibers inside. Using a small cutter, cut around the tube, being careful not to cut through it. Then, grasp the tube on each side of the cut with the thumb and forefinger of each hand. Bend it each way carefully to make it snap.
Step 9: Carefully clean the gel from the fibers using an appropriate cleaner. Make sure you have good ventilation and a way of disposing your wipes.
One type of indoor FO cable, called "non-breakout" cable, is usually used indoors. As shown in Fig. 1 (on page 42), this type of cable has a PVC outer jacket, if the cable is riser rated. Under this jacket is a binder of some type (usually cellophane or plastic) that holds the fibers in tight bundles. Under the binder are the buffered fibers, which may be individual fibers or fibers in separate jacketed sub-groups. For the latter grouping, these sub-groups surround a central strength member, which is usually made of a dielectric type material such as fiberglass or aramid yarn. Generally, there will be one nylon ripcord on this type of cable.
The fiber unit, or buffered fiber, itself is usually 900 mm. You can connectorize this size fiber but probably don't want to run it more than a very few feet between cabinets because of its small size. And, you should never run this size fiber in a raceway because you'll surely damage it.
The other type of indoor cable, called "breakout" cable, is 50% larger in diameter than non-breakout cable. It can withstand rougher handling and generally slightly greater pulling tension.
The sub-unit jacket is only enclosing one fiber (surrounded by an aramid yarn). This sub-unit jacket can be anywhere from 2.0 mm to 3.0 mm (.08 in. to .12 in.). Under this jacket is, again, aramid yarn. If you're connectorizing the fiber, use this strength member and fasten it into the connector. If you're splicing instead, fasten these pieces of yarn to some attachment point in the enclosure. This type of cable is rugged enough to run from one cabinet to another without damage.
One product commonly used to remove gel from fibers and tools (d'Gel) consists of petroleum distillates and monocyclic terpene hydrocarbon. You dissolve the gel with this cleaner and then clear the residue left on the cable with alcohol. A similar product (PF cleaner) doesn't leave the residue behind so alcohol is not required for the final cleaning.
