PULLING FIBER OPTIC CABLES Fiber Optics PULLING FIBER OPTIC CABLES

Fiber Optics One of the most critical steps before pulling fiber is to get an accurate measure of the distance of the cable pull, we usually add approximately 20% to this total for a fudge factor. Because fiber pulls are typically long runs it would be disastrous to come up short, if that happens you’ll end up with a nickname like “shorty” and possibly fired.

Fiber Optics The goal is to limit the amount of splices because of the insertion loss and limit the number of bends especially sharp bends that can cause micro fracturing and reflection problems. Two factors to consider when installing fiber are the pulling force and bend radius during the pull.

Fiber Optics If the fiber optic cable is going to be installed in conduit (indoors or outdoors) a mule tape can be dragged through the conduit and used as a pull rope. Mule tape is extremely strong (1800-2500lbs) and has footage markings on it that can be used to gauge the overall footage of the pull.

Fiber Optics Once the total distance has been determined the fiber can be ordered and delivered to the site. What is the first thing you should do as a technician with the cable reel when it shows up on site? SHINE LIGHT THROUGH ALL OF THE STRANDS

Fiber Optics Once you’ve determined there are no dark fibers you can set up for the cable pull. Fiber should always be pulled directly off the reel not spun over the edge of reel, this will eliminate cable twists. Indoor rated fiber like distribution or breakout cable should never be pulled by the jacketing.

Fiber Optics When pulling fiber it should always be pulled by the aramid yarn, this will require some cable prep. The steps for prepping a fiber for a pull are as follows; ARAMID YARN IS TYPICALLY YELLOW AND IS REFERED TO AS THE STRENGTH MEMBER

Fiber Optics Strip back the outer jacketing approximately 2 to 3 feet. Cut away all fiber strands. Cut away the fiberglass rod(s) and filler strands where applicable. This will leave you with aramid yarn strength members only.

Fiber Optics Tie a swivel hook to the aramid yarn. Tape the aramid yarn and your knot. Then tie your string or rope to the swivel hook

Fiber Optics Do not pull fiber by half hitching to the outer jacket unless the fiber is specifically designed for that application. During the cable pull it is important to maintain a 20 times the diameter radius through out the pull. Indoor cable pulled by the aramid yarn has a pulling force of 300lbs.

Fiber Optics When the fiber emerges from the conduit a mandrel should be used to pull the extra length needed in the closet. By using a mandrel you don’t grab the jacketing and exert pulling force on the strands. A mandrel distributes the force amongst the whole cable and strength member.

Fiber Optics

Fiber Optics When the fiber is placed such as dressing it into ladder racks or fiber panels a 10 times the diameter radius needs to be maintained. If the cable is pulled by the jacket it will cause stress on the strands and create rippled fiber that will micro fracture.

Fiber Optics Fiber optic cables rated for outdoor use, such as direct burial or underground cable will not require the same prep as indoor cables. A pulling grip with a swivel eye is typically used when working with cables in an OSP application.

Fiber Optics Using a swivel head to pull fiber optic cable ensures that the fiber strands will not twist up inside the jacketing and increase the overall attenuation of the fiber. Outdoor cables are rated to about 600 pounds of pulling force.

Fiber Optics When pulling long runs of fiber it will become necessary to pull slack off of the reels, this is done by making a figure 8.

Fiber Optics The figure helps to maintain the concentricity of the cable and keeps it from getting knotted up and kinked. If fiber gets kinked it becomes unusable, as you can imagine the glass would crack within the jacket leaving dark fiber. In some cases you may have to flip the figure 8 so that the cable feeds off the top.

Fiber Optics In some instances innerduct will be installed before installing the fiber, in OSP applications the conduit in the manhole is loaded with innerduct.

Fiber Optics Innerduct is a plastic conduit used to protect fiber optic cable and it is common knowledge that if there is innerduct in the ceiling it is strictly for a fiber optic backbone. Innerduct comes on 5 to 6 foot rolls preloaded with mule tape or poly rope.

Fiber Optics Innerduct being installed through manholes before the fiber is installed, 3 ducts are installed in one 4” conduit. 6 FOOT REELS, YOU WOULDN’T WANT ONE OF THESE REELS TO ROLL AWAY FROM YOU, THEY’RE HARD TO STOP ONCE THEY GAIN MOMENTUM.

Fiber Optics When cutting innerduct the technician has to be careful to not lose the rope in the duct, it is under a lot tension especially after a pull. Make a circular cut around the innerduct.

Fiber Optics Separate the two sections and slit approximately 18” of innerduct on both sides of your cut. Force the rope through the slits you made.

Fiber Optics Cut the rope in the middle fold it back onto the innerduct and tape it down, the rope will still have a lot of tension on it so be careful to not let it slip back into the innerduct.

Fiber Optics After the cable is pulled you will need to install a service loop at each end. The minimum service loop should be 20 to 25 feet (at both ends). Indoor pathways for fiber are similar to pathways for copper.

Fiber Optics A separate J hook run should be established for the fiber backbones. How far apart should J-hooks be spaced? 4 TO 5 FEET APART

Fiber Optics Conduit runs must contain no more than 2 90 degree bends per 100 feet. There should be a pull box every hundred feet. Minimum size for a conduit containing fiber should be 2”.

Fiber Optics The maximum distance a multimode fiber can be pulled is 2000 meters. The maximum distance a single-mode fiber can be pulled is 3000 meters. If our MM backbone is to exceed 2000 meters than we should install SM fiber to allow up to 3000 meters for use with led based systems.

Fiber Optics Single-mode fiber used in OSP applications can be pulled at least 26 kilometers or 15 miles before the signal needs to be repeated. This is based on a laser transmission system and distances are dependent on laser output power.