Outside plant installation (OSP) of fiber optic cables can be a more diverse process than premises installations. OSP installs may include placing aerial or underwater cable, direct-buried cable, cable in conduit or installing conduit or innerduct and then pulling cable. A single link may use several types of installation. Cables may end when pulled into buildings or terminated at the top of poles where surveillance cameras or wireless access points are located. Splices where cables are concatenated can be placed in pedestals, buried underground or hung in aerial splice closures.
(Ed. Note: Part 3 is here.)
The diversity of OSP installation makes it extremely important for the contractor to know the route of the cable to be installed. Like the estimator, who should walk the route before beginning the estimating process, the contractor must see challenges before they arise. This inspection allows the contractor to determine what special equipment may be needed and even double check that all the permits needed are in order. Long cable pulls in conduit will require lubricants to reduce friction. Longer pulls may require intermediate pulls in both directions. An intermediate pull will require your installers to “figure eight” the cable at the midpoint to prevent kinking.
Hardware and equipment
OSP installations may require positioning of supporting structures before the cable placement can begin. New conduit or innerduct may need to be buried, or conduit already in place may need to be checked, old cables removed and new innerduct installed. Some buried cables even may require the installation of manholes or controlled-environment vaults for equipment and conduit.
Not only does the contractor need to consider all the hardware that may need to be installed, but he or she has to schedule the specialized equipment needed: trenchers or cable plows, backhoes, bucket trucks, cable winches, etc., and ensure that personnel are well-trained in their use.
Once the infrastructure is in place and the cabling pulled, the fiber optic splicing work begins. Now, scheduling the availability of appropriate fiber optic equipment is the concern. If the cable is to be spliced outdoors, a splice trailer is normally used, unless splices are being made on a pole or in a bucket, where a tent may be required in bad weather.
Each splice must be verified with an optical time-domain reflectometer (OTDR) test. Preferably, testing is done as each splice is made. To be efficient, a splicer will be on the job site, and a test tech will be at the other end of the cable with an OTDR to verify each splice. Splicing machines give an estimate of splice loss, but going back later, opening a splice closure and resplicing is an expensive proposition.
Care should be taken to ensure each fiber is placed carefully in the splice closure to prevent damage, and the closure needs to be sealed carefully to prevent long term degradation. And, as we always warn splicers, careful identification marking inside the closure makes identifying fibers much easier if a later problem requires re-entry.
Cables will be terminated inside facilities where they will connect to communications equipment. OSP cables generally do not meet National Electrical Code flammability requirements, so the cable entering a building must be terminated or spliced to indoor cables soon after entry. Some OSP cables have double jackets, an outer one for outdoors and an inner one rated for indoor use, so the outer jacket can be stripped off inside the building and the cable run to the equipment room. Cables terminated in pedestals or vaults do not have this requirement.
Generally, single-mode OSP cables will be terminated by splicing pigtails onto each fiber, and splices will be placed in a splice closure. Multimode fibers can be handled the same way or terminated directly onto the fibers. Most OSP cables will require installing a breakout kit, which sleeves each fiber in a tube rugged enough for direct termination.
OSP safety is a very important issue, well beyond the usual fiber issues of protecting your eyes from fiber shards. Routes should be cleared with “One Call” or “Call Before You Dig” services to ensure no buried cables or pipes are in the proposed route. Installers working with cable-placing machinery need to be well trained in how to operate them safely. Aerial installations are particularly dangerous, since poles usually have electrical cables too close for comfort. Every OSP job should have posted safety procedures and all personnel should be briefed in their use.
HAYES is a VDV writer and educator and the president of The Fiber Optic Association. Find him at www.jimhayes.com.
(Ed. Note: Part 5 is here.)