top of page
telekom fiber.png

Telecom   Fiber Infrastructure

Underground Fiber Optic Cable Installation


Underground Fiber Optic Cable Installation


The practice of using fiber optic cables has become much more common in recent years. Fiber optic cables are designed to withstand all the typical installation and environmental stresses expected in a particular application. However, it can still be damaged if not used properly during the installation process. The two most common outdoor fiber optic cable harnesses are pole line aerial harness and underground cable harness.

Underground wiring can be buried directly underground or placed in a buried conduit. When buried directly, cables are driven into a ditch or buried and the installation process can be very quick. The most common cables used for direct burial are steel armored outdoor fiber cables. Underground conduit installation can protect cables from harsh environments and provides the opportunity for future expansion without the need for digging. And this is the most common practice in many areas today. Another benefit is that unarmored fiber cables can be used, making installation even easier.


Preparations and Precautions Before Underground Cable Installation


To ensure a successful job, some preparation steps are needed before the installation process. Receives appropriate right of way permits.

Identify existing underground utilities such as buried cables, pipes.

Investigate the soil condition to determine the depth of installation, the type of fiber cable to be used, and the driving equipment required.

Except for the above preparatory work, all personnel should be fully familiar with the following general precautions when delivering the fiber optic cable.


DO NOT exceed the specified maximum tensile tension for the cable.

DO NOT exceed the specified minimum bend radius of the cable.

DO NOT exceed the maximum crushing load of the cable

DO NOT use detergents or petroleum-based compounds as cable lubricants.

NEVER install a cable reel on the flange side (to avoid cable routing at the exit point).


Cable Placement Steps


The methods used to lay fiber optic cables in conduits are essentially the same as those used to lay copper cables. However, fiber optic cable is a high capacity transmission medium that can degrade its transmission properties when subjected to excessive pulling force, sharp bends, and crushing forces. These losses may not occur long after setup is complete. For these reasons, extra care must be taken throughout the entire installation procedure.

First, determine the inner channel where the fiber optic cable will be placed. Once the correct inner conduit has been identified, the cable must be connected to prevent it from "creeping" while it is pulled into it. Any redundant conduit should be sealed so that it does not interfere with cable pulling.


Prepare draw manholes. This includes removing the inner channel from the rack and removing the gap caused by the rack, placing lubricant where appropriate, preparing the dragline, and generally reconnecting the inner channel to provide a continuous path for the cable to follow. The amount of lubricant used in intermediate manholes depends on the length between manholes, type of inner channel, etc. It will depend.

Place the towing equipment (winch or capstan) in the towing manhole. The towing equipment should be equipped with a tension controller and operated according to the manufacturer's recommendations. Never exceed the 600 pound pull limit for the cable.


Install the appropriate guides in the draw end manhole as specified by your company's practice. These guides are to ensure that the drawline and fiber optic cable can enter and exit the inner conduit in a straight way. And intermediate manholes should be prepared for cable pulling with any problems observed during the pre-towing survey already solved.

Place the cable reel near the feed manhole so that the cable can be manually fed from the manhole. To reduce tensile stresses, the cable should be pulled from the reel manually and fed into the manhole by hand. Then connect the towline with a swivel connector to the towing eye / handle attached to the fiber optic cable.


Use approved cable grease to lubricate the entire channel to reduce pull stress. Apply lubricant to the cable before it is fed into the inner conduit according to standard company practices. The lubricant application method will vary depending on the company application. Before towing operations begin, a communication link must be established between the feed and pull manholes (and any intermediate manholes through which the cable can pass).

Start pulling by engaging the winch / winch at a slow speed. Turn the spool by hand when the pull starts to reduce the initial tension. After the draw eye / grip enters the channel in the feed manhole, the drawing speed can be increased. Speed ​​should be built up slowly up to a maximum speed of about 100 feet per minute (30 meters per minute).

The winch / capstan operator in the draw shaft controls the cable pulling speed. Each intermediate should be informed about the progress of the cable as it passes through the manhole. A constant pulling speed is the desired method of inserting the cable into the inner conduit. Changes in draw speeds, starts and stops should be avoided. If it is necessary to stop the towing at any point, the winch / capstan operator should stop the towing but not release the tension on the rope. If tension is maintained in the hauling rope and the rope, it is easier to continue pulling.

When the cable appears in the pull shaft, the diameter of the pulley or block can be pulled over a pulley or quarter block as long as it meets the minimum bending radius of the cable under tension. It should not be attempted to run the cable up to the last manhole length. This may cause undesirable curvature in the end of the cable.


Post-Installation Inspection


The final part of completing the underground wiring is a comprehensive study of the entire route from start to finish. Engineering personnel and interested parties should inspect the construction site above the ground to ensure:

The restoration is complete.

Permanent markers are placed right next to the cables.

Path holes, if used, are properly finished and will not collapse part of the path.

Debris and garbage are removed from the construction site.

Other specific installation instructions have been completed according to the features of the drawing.




In fact, the cable assembly process is most likely the most aggressive event the cable will be subjected to, and only specially trained people can do this. Even for these professionals, they cannot guarantee that the whole process is smooth and smooth. But adhering to the above steps and precautions can help maximize the chances of the cable working properly over the entire design life of the cable.

bottom of page