Fiber cabling has come a long way from it's humble beginnings, and has more than broken the image of a delicate, fragile data communications transfer technology. Fiber cable of today has much higher pulling tensions and bend radii in addition to being more secure and efficient in transferring data. Fiber and traditional copper cabling have many differences and similarities when it comes to installation safeties and precautions.
Mohawk has been in the copper and fiber cabling business for over 60 years and is a leader in design and manufacturing of cable. Courtesy of their vast cabling knowledge repertoire, we will take a look at the specific concerns and cautions that installers or contractors should be aware of as they work with and install fiber cabling.
One of the biggest impacts a switch from copper to fiber has is that there is a much smaller risk of injury to anyone who may be installing or even just nearby the cable. Fiber has no electrical conductivity, meaning it is immune to electrical interference like lightning and can be used in close proximity's to electrical lines. Copper, on the other hand, transmits information via electricity, meaning there is a very real risk of injury or even death due to electrocution.
This is not to say that fiber is 100% safe at all times, but by following these 3 quick tips, you can ensure your safety when working around fiber installations:
Do not stare into connector endface or view directly with optical instruments (when installed on a live system, invisible laser radiation may be present).
Wear safety glasses when working with optical fiber.
Dispose of all scrap fibers to avoid getting fiber slivers.
There are two different types of tension in fiber optic cables, the more important of the two being the 'maximum load installation' tension, which is what the cable can be subjected to without causing permanent damage. It is also known as 'short term tension', 'dynamic load', 'installation load' or 'installation tension' and is measured in Newton's or pounds.
Whenever possible, the tension of the installation should be monitored. Tension can be measured with a dynamometer, or with a pulling wheel. Breakaway pulling eyes are available which separate if the tension reaches a preset level. Use of a swivel is recommended when pulling the cable in tray, because the swivel allows the cable and pulling rope to twist independently.
If pulling a cable in an outside plant conduit, the use of lubricants can help minimize friction. The use of corrugated innerducts can also help reduce the amount of tension needed to pull the cable. When installing loose-tube cables, the use of sealer is recommended to prevent gel migration.
There are two types of bend radius: Short term minimum bend radius (dynamic bend radius) and long term bend radius (static bend radius).
Short term minimum bend radius is the tightest recommended bend while installing cable at the maximum rated tension. It is the larger of the two specified bend radii. Throughout the pull, the minimum bend radius must be strictly followed. If a location exists in the middle of a run where a relatively tight bend is unavoidable, the cable should be hand-fed around the bend or a pulley can be used.
Long term bend radius is the tightest recommended bend while the cable is under a minimum tension. It is the smaller of the two specified bend radii. After the pull is complete, the cable can be bent more tightly to fit into existing space, but not to exceed the long term minimum bend radius.
Always follow the manufacturer's guidelines for minimum bend radius and tension. Failure to do so may result in high attenuation (macrobends) and possible damage to the cable and fiber. Guidelines are normally supplied with the cable manufacturer specification sheets. If the bend radius specifications are unknown, the industry de facto standard is to maintain a minimum radius of 20X the diameter of the cable. The minimum bend radius must also be adhered to when using service loops. Fiber optic splice trays and patch panels are designed to accommodate the bend radii of the individual fibers, but outside of the hardware, extra care must be taken.
Pulling eyes and cable netting are highly recommended for cable pulling as the eye will facilitate the installation as well as protect the pre-terminated ends during a pull. For both regular and pre-connectorized cables, the maximum pull force is identified with the “installation maximum load” cable specification on a cables specific datasheets.
The installation of a cable, which is pre-connectorized on both ends, requires special raceway considerations and pulling grips. A typical fiber optic connector is 0.5 in. (1.25 cm) in diameter, has a limited pull-off rating and must be protected during cable placement. A pulling grip for a pre-connectorized cable must successfully isolate the connectors from any tensile load by placing the load on the cable itself. The pulling grip must also protect the connectors from abrasion and damage. In medium fiber counts (6 to 24 fibers) the connectors must be staggered when installed to reduce the diameter of the pulling grip. In high-fiber counts (greater than 24 fibers), installation of a connectorized cable may not be possible due to the conduit size that would be required.
In many cases, pulling is not done from point to point, but rather from an intermediate point pulling back in each direction to each termination location. It is then important to make sure that the cable is ordered with two pulling eyes, one at each end.
Testing Prior To Installation
Most manufacturers of optical fiber cables test said cables before they leave the manufacturing plant. Before installing the cable, it is recommended to test the cable on your reel for continuity. This ensures that no damage occurred during shipment.
Since the cost of installation is usually higher than the cost of materials, testing the fibers before installation can avoid additional expenses and help meet important deadlines. At a minimum, continuity testing can be done on the reel with a visual fault locator or a simple fiber tracer such as a flashlight, a modified flashlight to properly hold the fibers, a microscope or a bright red light (LED lookalike). With this simple test, you should be able to identify broken fibers, if any, within the optical fiber cable. Also, it is recommended to double-check the actual fiber count and the actual cable length, to avoid any inconvenience.
All in all, the hazards to an installer have been heavily mitigated with telecommunications changing focus to fiber from copper cabling. For those that are interested in a more in-depth guide to either copper or fiber installation, take a look at these guides developed by Mohawk.
To learn more about free installation resources, Mohawk, Mohawk cable products or about telecommunications in general, contact your local Accu-Tech representative today.