Colin Yao asked:
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
1. 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.
2. 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.
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
1. 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.
2. 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 asked:
The two most common outdoor fiber optic cable installations are pole line aerial installation and underground cable installation. Underground cable installation can be buried directly underground or placed into a buried duct.
Direct burial installation:
Direct burial installations are most common for long cross-country installations. The cables are plowed in or buried in a trench; the installation process can be very quick. The most common cables used for direct burial are steel armored outdoor fiber cables.
Underground duct installation:
Fiber optic cables can also be pulled through underground ducts, which protect the cables from harsh environment. Underground duct installation also provides opportunity for future expansion without the need to dig. This is the most common practice in urban areas. Another benefit is that fiber cables without armor can be used which makes the installation even easier.
Preparation before underground cable installation:
1. Obtain proper right-of-way permits
2. Identify existing underground utilities such as buried cables, pipes
3. Investigate the soil condition in order to determine the installation depth, whether duct should be used, the type of fiber cable should be used and plowing equipment needed
Cable Burial techniques:
1. Plowed under
Plowing in a fiber cable is faster than trenched. But this process has to be carefully monitored to prevent from damaging the cable.
2. Trenched
The fiber cable can also be trenched. This process is slower than plowing in; however, it allows a much more controlled cable installation. Trenches can be dug by hand or by machine.
3. Directional boring
Directional boring technique is used where the surface cannot be worked on such as high, railway crossings, etc. Instead, a boring machine is used to bore a several inches diameter hole underneath the surface, a duct is pulling through the hole and then fiber cables pulled into the duct.
Important factors:
1. Cable installation depth: up to 40 inches
The depth that fiber cables should be buried is determined by the soil conditions and surface usage. In colder areas, fiber cables are typically buried below the frost line to prevent the cables from being damaged by ground frost heaves.
2. Keep the trenches as straight as possible
Fiber cable trenches should be straight, and the trench bottom should be flat and level. Backfill can also be used to distribute the cable load evenly and protect the cables.
3. Fiber cable warning labels should be buried directly above the cable
Fiber optic warning cables are typically buried directly above the cables to warn future digging operations. Or concrete slabs can be buried below the warning label but above the cables to provide even more protection.
4. Whenever conducting armored fiber cables are used, they should be properly grounded
In direct burial installations, steel armored fiber cables are often chosen for their strength and protection from rodent bites. A very important thing to keep in mind is to properly ground the cables. They should be grounded at all termination points, splices and building entrances. The cable steel armor should be connected to a ground wire using a compression-type clamp. The cable ground wire is then bolted to a nearby ground terminal strip.
5. Fiber optic cable minimum bending radius should always be observed during installation.
The two most common outdoor fiber optic cable installations are pole line aerial installation and underground cable installation. Underground cable installation can be buried directly underground or placed into a buried duct.
Direct burial installation:
Direct burial installations are most common for long cross-country installations. The cables are plowed in or buried in a trench; the installation process can be very quick. The most common cables used for direct burial are steel armored outdoor fiber cables.
Underground duct installation:
Fiber optic cables can also be pulled through underground ducts, which protect the cables from harsh environment. Underground duct installation also provides opportunity for future expansion without the need to dig. This is the most common practice in urban areas. Another benefit is that fiber cables without armor can be used which makes the installation even easier.
Preparation before underground cable installation:
1. Obtain proper right-of-way permits
2. Identify existing underground utilities such as buried cables, pipes
3. Investigate the soil condition in order to determine the installation depth, whether duct should be used, the type of fiber cable should be used and plowing equipment needed
Cable Burial techniques:
1. Plowed under
Plowing in a fiber cable is faster than trenched. But this process has to be carefully monitored to prevent from damaging the cable.
2. Trenched
The fiber cable can also be trenched. This process is slower than plowing in; however, it allows a much more controlled cable installation. Trenches can be dug by hand or by machine.
3. Directional boring
Directional boring technique is used where the surface cannot be worked on such as high, railway crossings, etc. Instead, a boring machine is used to bore a several inches diameter hole underneath the surface, a duct is pulling through the hole and then fiber cables pulled into the duct.
Important factors:
1. Cable installation depth: up to 40 inches
The depth that fiber cables should be buried is determined by the soil conditions and surface usage. In colder areas, fiber cables are typically buried below the frost line to prevent the cables from being damaged by ground frost heaves.
2. Keep the trenches as straight as possible
Fiber cable trenches should be straight, and the trench bottom should be flat and level. Backfill can also be used to distribute the cable load evenly and protect the cables.
3. Fiber cable warning labels should be buried directly above the cable
Fiber optic warning cables are typically buried directly above the cables to warn future digging operations. Or concrete slabs can be buried below the warning label but above the cables to provide even more protection.
4. Whenever conducting armored fiber cables are used, they should be properly grounded
In direct burial installations, steel armored fiber cables are often chosen for their strength and protection from rodent bites. A very important thing to keep in mind is to properly ground the cables. They should be grounded at all termination points, splices and building entrances. The cable steel armor should be connected to a ground wire using a compression-type clamp. The cable ground wire is then bolted to a nearby ground terminal strip.
5. Fiber optic cable minimum bending radius should always be observed during installation.