Key points for construction and acceptance of lightweight self-supporting overhead cable

In rural areas lacking self built poles, using light self-supporting optical overhead cables attached to power poles can greatly reduce the construction cost of rural broadband. In article “How to attach the lightweight self supporting aerial cable to electric pole?”

Yingda introduces the structural characteristics and performance of light self-supporting optical aerial cables, as well as the key points of engineering design. So, what are the precautions during the construction and acceptance stages.

For the convenience of understanding in the following text, let’s first review the structure of lightweight self-supporting aerial cables.

Testing of FTTH Cable Fitting

There are three main types of fasteners for light self-supporting aerial cable: steel band clamps, C-ring fasteners, and wedge clamps.

Metal structural components should have no cracks, a smooth surface, and uniform color. The galvanized layer should be firm and free from bubbles, peeling, pinholes, and zinc deficiency.

The load tension of the steel band clamps should not be less than 6kN, and the product should have no deformation, defects or other adverse phenomena after tensile testing.

The load tension of the plastic wedge clamps should not be less than 3kN, and the product should have no cracks or deformations after tensile testing. The displacement of the clamped cable should not exceed 5mm. Plastic parts are free from defects such as burrs, bubbles, cracks, voids, warping, and impurities.

Laying of Optical Fiber Aerial Cables

Due to the poor flexibility of the reinforcement components in lightweight self-supporting cable materials, the cable curvature radius is relatively large; The bending radius during the construction process/after installation and fixation should not be less than 30 times/20 times the outer diameter of the cable.

Before laying the cable, the position of the fixing point should be determined based on factors such as the laying span, verticality, and installation height, and steel band clamps or C-shaped fasteners should be installed.

Due to the strong rigidity of the reinforcing components in lightweight self-supporting cable materials, the cable cannot be laid upside down like ordinary cables. Instead, a pay off rack or pay off cart can be used to prevent problems such as cable back buckling and twisting. After the optical cable is successfully laid out, it can be coiled and stored in an “figure-8” manner like ordinary overhead cables.           

When laying optical cables, fixed points can be used to attach pulleys first, and the optical cables are pre wired by being pulled by the pulleys. After the pre wiring is completed, install wedge-shaped fixtures at fixed points; Place the fiber optic cable messenger wire into the wedge-shaped groove of the clamp, tighten the clamp and the cable, and adjust it to the appropriate verticality.

 The optical cable is only reserved in a U-shape at each fixed point on the power pole, and is not reserved at other locations.

Stripping of Optical Cables

The messenger wire should be cut off firstly before self-supporting aerial cable terminated, entering the fiber distribution box or cable cross cabinets, then strip the cable sheath and following steps.

The cutting operation of the messenger wire can refer to the following steps.

(1) At a distance of 15cm to 20cm from the cross-section of the cable, slowly cut with the utility knife (with the blade facing the cross-section of the cable) into the sling between the messenger wire and the optical cable, and separate them.

(2) Change the direction of the blade and use the knife to cut the sling to the appropriate length towards the messenger wire.

(3) Separate the messenger wire and optical cable into the character “person”, and use cable pliers to cut off the messenger wire.

(4) Wrap the cut section of the messenger wire with electrical tape.

When peeling off the cable sheath, you can choose the side of the cable with a sling, and use a utility knife to diagonally cut into the fiber optic cable sheath to the surface of the glass fiber (reinforcement). Then hold the knife in your right hand and pull the fiber optic cable back evenly with your left hand. Attention should be paid to the angle of the blade and the speed of pulling the left hand backwards to avoid cutting the casing.

After open the cable sheath, slowly separate the sheath from the fiberglass tape opening, and use diagonal pliers to remove excess sheath and fiberglass tape, being careful not to prick the fiberglass tape into your hands.

 Fixing of Optical Cables In Joint Closures ( Splice Boxes) and Fiber Splitting Box

Light self-supporting cables should be mainly fixed with cable reinforcement as an auxiliary in ordinary cable splice boxes and fiber splitting boxes. Generally, the fiberglass tape is twisted into strands for auxiliary fixation, and then the optical cable is clamped with a fixing fixture and tightened with a hose clamp.

In addition to using specialized fixtures, the fixation of optical cables can also be achieved by wrapping electrical tape around the cable sheath to a suitable thickness before fixing.

 When the fiberglass tape cannot penetrate the fiber optic cable reinforcement core and fix the column, the fiberglass tape can be twisted into a rope shape, wrapped around the fixing screw a few times, and then assisted in fixing.

Safe Production

When attaching lightweight self-supporting cables to electric poles, construction operations should be strictly carried out in accordance with the provisions of the “Safety Production Operation Specification for Communication Construction Projects” regarding “overhead operations near power supply lines”.

Acceptance of lightweight self-supporting cable lines

The acceptance of lightweight self-supporting optical cable lines should be inspected according to the contents and methods listed in the table below.