Application Note 03

Installing Fiber Optic Cable

As the number of commercial and industrial users of fiber optic equipment grows, the amount of optical cable permanently installed will also grow. By careful planning, the installation of fiber optic cable can be as easy as the installation of copper wire. The suggestions that follow should act as a guideline when installing or planning to install such cable and should give the prospective installer some tips on how to achieve professional results.

Install more conductors than you initially require.

Every installer stresses this and for good reason. Most installations are only planned for the equipment currently on hand or on order. With the rapid progress of electronics however, new systems are constantly being developed and the costs for re-cabling an industrial plant or office building in the future could be prohibitive. The small differential cost for a few spare fiber conductors is a very small price to pay for insurance.

Be aware of National as well as Regional and Local Electrical Codes

Although fiber optic cables do not conduct electricity in any way, shape or form, the strength members used in some cables may contain steel or other materials that do. If this is the case, then parts of the various codes may apply. For example, if the cable is of the all-dielectric type and will be installed in existing conduits with actual electrical conductors, the "fill factor" may impose certain restraints. As a result, it is always a good idea to check local fire codes, the National Fire Protection Association standards, the Uniform Building Code and whatever FCC RFI/EMI requirements you feel might apply.

Choose the correct outer jacket construction for the cable used

Local fire codes and the National Electrical Code all require the use of special cables specifically designed for use in plenums or air ducts. The reason for this, of course, is because of how the cable reacts during a fire. Ordinary PVC as well as many common cable jacket materials burn quickly and produce poisonous gasses. Plenum cable, on the other hand, burns very slowly, produces little or no smoke and no toxic gasses. Fiber optic plenum cable is readily available for these applications when required and the additional cost is similar to that incurred with conventional copper wire plenum cable.

Know exactly where the cable will be installed

Fiber optic cable is perfectly safe to install alongside live electrical wiring as long as only dielectric, or totally non-conducting cable is used. Furthermore, it is not necessary to be overly concerned about electrical noise pickup. The cable is virtually totally immune to just about any form of RFI or EMI. Caution in this instance refers to disturbing existing electrical wiring when installing the fiber optic cable.

Carefully calculate the amount of cable you will require

Most installers look at blueprints or floor plans and often measure the actual space by hand. This is of particular importance with fiber optic cables as it is more difficult to splice than conventional copper wire. When in doubt, err on the high side. You can always coil a few additional feet somewhere along the installation path. In addition, be sure there is additional cable at the ends of a link for breakout boxes or patch panels if they are to be used.

Understand the environment the cable will operate in

Since fiber optic cable is virtually immune to interference, it can be placed in dropped ceilings, tie-wrapped along the outside of existing power lines, placed inside conduits with existing power lines, run in air conditioning ducts and even stapled to baseboards. Be certain however, that excessive temperatures will not occur that might melt the outer jacket of the cable or that situations will not occur that could crush the cable. Also be sure that all cables installed overhead are mechanically secure to prevent them from dropping on people or damaging ceiling tiles.

Use the correct personnel for the job

Inform the architect that you will be using fiber optics and that you require plenty of space for the installation of the cables. Also indicate that personnel assigned to the project have some practical knowledge or experience in the installation of such cable. Make doubly sure that they have the resources to do the job quickly and properly. If connectors are to be installed as part of the job be certain that the installer has the proper tools, training and experience to do this phase. Also be certain that all cables are properly tagged at each end and that all bends around corners are gradual. Fiber optic cable needs a radius of at least 10 times the diameter of the cable around a bend. The use of sharp, 90 degree bends can be a disaster. Also be sure that the installer has the appropriate liability and workman's compensation insurance. You don't want to be liable for injury or damage incurred during installation.

Make sure you clearly designate the person in charge of the installation

If you plan to install the cable yourself, then you are the one. If it is to be installed professionally, then have someone in your organization become very familiar with the details. Then, if and when problems arise, or when it is necessary to repair or expand the operation, the person responsible should be in a good position to handle the situation.

Check all costs carefully and know what you are, and are not getting

Many times fiber optic vendors will offer a total, installed package price. Pin them down on what's what. Insist on itemized prices and check with at least one other supplier to determine that what is quoted is reasonably priced.

By following the "tips" given in this article, as well as by employing some good common sense, you can assure that your fiber optic cable installation goes smoothly and is "up and running" in minimum time.

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