Understanding The Basic Terms
1.
Dead end pole: Dead end pole is a utility pole on which self-supporting figure 8 aerial cable or a steel messenger is tensioned and terminated into a dead-end fixture.
2.
Messenger span: Messenger span refers to the length of continuous steel messenger tensioned between two dead-end poles.
3.
Intermediate poles: Intermediate poles are all the poles between two dead-end poles.
Planning
1.
Careful planning and preparation are necessary before any aerial cable installations. During the cable route survey, representatives from all necessary parties including utilities, street depart, etc should be present. Before even detailed planning begins, approval should be get from all involved parties. Sufficient clearance for new cable along the right of way should be confirmed during the route survey.
2.
Existing poles should be used whenever possible in order to save cost.
3.
Where on a pole to place the aerial fiber optic cable? Fiber optic cables weigh less than equivalent copper cables and also sag less, so fiber optic cables should occupy the uppermost available communications space on a pole.
4.
Sufficient clearances must be maintained between fiber optic cables and electrical power cables on joint-use poles. You need to refer to current National Electrical Safety Code for the proper clearances.
5.
Existing dead-end pole must be evaluated to see whether they can withstand the stresses during aerial cable installation. You have to evaluate whether temporary guying is needed in order to relieve the temporary unbalanced loading during cable installation.
6.
Splice locations. Splice locations are usually selected during the cable route survey. They are chosen to allow for the longest possible continuous cable spans and a minimum number of splices. They should be easily accessible to a splicing vehicle.
7.
Aerial installation should never be done in wet conditions. And make sure all personnel are properly trained for pole line work.
8.
Fiber optic cables (including all dielectric cables) should be properly grounded when installed in the vicinity of high-voltage power cables.
Installation:
Fiber optic cable aerial installation can be done in two ways
Lashing a fiber optic cable to a steel messenger
A steel messenger is first installed between the poles. Then a cable reel trailer and truck are used to pull the cable along the messenger. A cable guide and cable lasher are used to wrap around both the messenger and the fiber cable to secure the fiber cable to the messenger. Following the cable lasher is an aerial bucket truck which makes necessary adjustments.
At each pole, the fiber optic cable forms an expansion loop to allow for expansion of the messenger. The expansion loop's sizes have both a length and a depth, its length should be larger than twice its depth. The fiber cable should also maintain its minimum bending radius at all times.
Direct installation of self-supporting figure 8 aerial fiber optic cables
Self-supporting (Figure-8) optical fiber cables greatly simplifies the task of placing fiber optic cables onto a aerial plant. The self-supporting figure-8 cable incorporates both a steel messenger and the fiber cable into a single jacket of Figure-8 cross section.
The combination of strand and optical fiber into a single cable allows rapid one-step installation and results in a more durable aerial plant.
Colin Yao is an expert on fiber optic communication technologies and products. Learn more about loose tube cable, loose tube fiber cable and loose tube fiber optic cable on Fiber Optics For Sale Co. web site.
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