Aerial Cable

In the construction of communication networks, overhead optical cables are a very common laying method.
It is suitable for areas with complex terrain or existing power poles, especially in open areas such as towns and rural areas. Overhead optical cables not only have relatively low construction costs and short construction periods, but also can fully utilize the existing overhead bare wire pole resources. However, overhead optical cables are exposed and are greatly affected by weather, traffic, and human damage. The construction quality directly affects the stability of subsequent operation. Today, we will systematically review the technical key points of the entire process of overhead optical cable laying to help frontline construction personnel do the job quickly and standardly.
1. Pre-construction preparation: Selecting the right materials is the first step to do a good job. Before the formal construction, the preparation of materials and tools must be in place.
Optical cable selection: Overhead optical cables should use outdoor optical cables with high strength and UV resistance. Currently, common models include GYTA and GYTS. These optical cables have good tensile performance and weather resistance, and can adapt to the complex outdoor environment.
Hanging wire materials: The hanging wire should use galvanized steel wire with a specification of 7/2.2mm. The steel wire should have no scars, rust, or other defects, and the twisting should be tight and uniform.
Tools preparation: Including optical cable reels, traction ropes, pulleys, hooks, communication phones, and safety protection equipment (safety helmets, insulating gloves, insulating shoes, etc.). Before construction, each piece of personal protective equipment must be checked to ensure it meets safety standards and is intact.
Optical cable inspection: Before laying the optical cable, the optical fibers should be inspected to confirm that there are no breaks, the attenuation value meets the design requirements, and the length of the optical cable should be checked and selected according to the laying length in the construction drawing. The splices should be placed away from rivers, traffic arteries, and other obstacles.

2. Route re-measurement and pole line construction: Building a solid foundation before laying the optical cable. Before laying the communication optical cable overhead, the pole line construction must be completed.
Communication optical cable overhead construction usually follows eight steps: erecting poles, installing guy wires, laying hanging wires, lightning protection wires and ground wires, laying optical cables, splicing optical cables, completing the end of the optical cable and testing, and project acceptance.
Route re-measurement: The construction unit should base on the construction drawing provided by the design unit to re-measure the specific location, accurate length of the pole line, and the pole position of each pole, determine the specific location of the line crossing obstacles and the corresponding protection measures. If there is a discrepancy between the design document and the actual situation, a design change must be made before proceeding to the next process of construction.
Erecting poles: The basic pole height is 7m, the taper diameter is 150mm. In special sections, pole heights of 8m or 9m can be selected. The pole spacing is generally controlled within 50 meters, with a ±5m deviation. The depth of the pole holes varies depending on the soil type. It is strictly prohibited to arbitrarily increase or decrease the depth. For a 7m pole, the normal soil hole depth is 1.3m, hard soil 1.2m, waterlogged land or wetlands 1.4m, and stone soil 1.0m. Straight poles should be vertical and located on the center line of the route, with a deviation of ≤50mm to the left or right. Angle poles should be moved inward 100-150mm towards the line turning point, and terminal poles should be inclined 100-200mm towards the tension side.
Installing guy wires: Angle pole guy wires should be on the extension line of the internal angle bisector. Straight poles should have one guy wire every 16 spans, and one guy wire every 32 poles.
3. Laying hanging wires: The "railway track" of the optical cable is the load-bearing foundation of the overhead optical cable. The original sag and span of the hanging wire should meet the design requirements. After laying the hanging wire, no more than three hanging wires should be erected on the pole line. Generally, only one optical cable should be hung on each hanging wire.

4. Optical cable laying: Two mainstream methods are detailed. The overhead optical cable laying methods mainly include two: fixed pulley traction method and optical cable reel moving release method.
(1) Fixed pulley traction method This is the most commonly used method in China at present, including manual traction and mechanical traction. Manual traction method: First, set up the cable reel to be released. Fix large pulleys on the poles at the upper and lower sections, and install small pulleys every 10 to 20 meters, and thread the traction rope through the small pulleys. Manually push the cable reel to gradually release the cable. Have one person on each pole to assist in the traction. To ensure safety, set up 3 communication phones at the release end, the collection end, and the cable traction head to maintain constant communication. When the single cable reel is long, it is generally laid out in two stages: after laying the first half reel, make an "8" shape and then lay the second half reel in the opposite direction. Mechanical traction method: Place the mechanical traction machine at the collection end, and the auxiliary traction machine at an appropriate position along the laid route. The traction force mainly acts on the reinforcement core of the cable, and the traction force should not exceed 150 kg. The traction speed should be controlled at around 10 m/min. When the traction tension exceeds the standard, there should be an automatic cut-off or alarm device.
(2) Cable reel moving and release method: Place the cable reel on a truck and lay it along the overhead pole line while hanging the cable on the suspension lines. This method is simple to operate, but it is limited by road conditions and is suitable for sections where the road width is allowed, the overhead pole line is no more than 3 meters away from the roadside, and there are no obstructions.
V. Cable hanging and fixation: After the cable is laid, use hooks to fix it on the suspension lines. During construction, pay attention to the following key parameters:
Hook spacing: The spacing of the cable hooks should be 500 mm, with an allowable deviation of ±30 mm. The hook buckles on the suspension lines should be consistent in direction, and the hook trays should be complete and neat.
On both sides of the poles: The first hook on each side of the pole should be 250 mm away from the pole, with an allowable deviation of ±20 mm.
Expansion预留： When laying the suspended overhead cable, make an expansion预留 at every 1 to 3 poles. The expansion预留 should be 200 mm below the zip ties on both sides of the poles and a protective pipe (polyethylene corrugated pipe) should be installed at the crossing point of the poles.
Special treatment： Protective pipes should be installed at the places where the cable passes through the cross or T-shaped suspension lines. At the suspension line joints, the cable should be hanged and fixed.
Residual cable management： After laying, leave the required length of cable for the joints and the length of cable reserved on each pole. Hang the wrapped end of the residual cable on the pole.