Design Principles of Fiber Optic Aerial Pole Route

Fiber optic aerial pole route mainly consists of aerial fiber optic cables, required number of poles, guys, stranded metallic wires, braced poles, and other necessary components that are required for installation.

Aerial cable poleThe aerial fiber optic pole route is arranged to keep the standards of pole span and sag and shall be designed to limit the strain of optical fibers even under the worst case environmental conditions such as storm and temperature extremes. The nominal span length for an aerial fiber optic plant in urban regions is 50 meters. Some installers take this span length to a maximum of 70 meters also. The sag for aerial fiber optic plant is nominally 1% of the span length at the time of installation.

This means, if the span length is 50 meters, the sag at the installation temperature is kept at 0.5 meters. Under temperature extremes, this sag level can go up to 2%. Also note that as the sag increases, the cable experiences less strain.

In order to reduce the number of poles and the length of aerial fiber optic cables, fiber optic cable installers go for dialogue with the local authorities and landowner. A good amount of installation cost can be saved by doing this. Wherever possible, the aerial fiber optic pole route shall go straight.

The environmental and physical requirements of the fiber optic aerial pole routes are wind pressure, temperature, and the strength of cable materials.

Different fiber optic installers have different standards for installation. However, for reference purposes we can assume a transverse wind pressure of about 400N/sq.meter of the projected area on the pole facility surface and 500N/sq.meter on fiber optic cables and stranded wires, etc. On flat surfaces, the transverse wind pressure of 800N/sq.meter can be assumed.

The maximum ambient temperature can be taken as 40 deg C, but under normal circumstances, the ambient temperature is considered as 30 deg C. At the time of maximum loading of stresses on the aerial fiber optic cables, the temperature to be considered is 10 deg C.

The design strength of materials used for the pole route shall be less than 50% of the ultimate tensile strength.

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