Why does an OPGW optical cable need to install an OPGW suspension Clamp (a fiber optic suspension clamp / suspension clamp for fiber optic cable)?
During OPGW installation, as the OPGW line is strung over a long distance, the accumulated weight becomes considerable. This makes the gravity load-bearing capacity of the OPGW suspension Clamp very important. The larger the span, the greater the tension formed by the catenary. The OPGW suspension Clamp transfers the vertical load to the tower, preventing the OPGW cable from bearing excessive bending stress. If there is no intermediate support point, an excessively large bending radius will form at the crossing point. Without a suspension clamp, the OPGW cable will sag under its own weight until it breaks.
The role of OPGW suspension Clamp on the optical cable
Before understanding the role, we need to know that a transmission line is a continuous tension system:
Tower ← Dead-end clamp ← OPGW ← suspension clamp ← OPGW ← Dead-end clamp → Tower
The OPGW suspension Clamp does not fix the tension direction. It allows the cable to freely expand and contract with temperature changes, and it bears the vertical component of the load in that span section while maintaining continuity of horizontal tension. Without the suspension clamp, the cable can only span between dead-end towers; the cable cannot freely expand/contract and will generate stress. Intermediate towers lose their supporting function, causing a significant decline in line economy.
In terms of mechanical protection, it provides wear protection. Without a suspension clamp, the OPGW cable would directly contact the metal components of the tower, and wind-induced vibration would cause repeated friction.
In vibration control, it mainly changes the boundary conditions and vibration frequency characteristics of the cable, limiting the propagation of vibration along the longitudinal direction of the cable.
Optical performance protection by OPGW suspension Clamp
The position of the OPGW suspension Clamp is the most likely location to produce bending loss. Long-term influence will gradually become unstable, so it is necessary to use preformed rods together with the clamp (a preformed suspension clamp system). The preformed rods must completely cover the clamp edges to form a flexible transition zone. The wrapping tension must be uniform-neither too tight nor too loose-and testing must be performed after installation (especially for OPGW fiber, OPGW fiber optic, and OPGW fiber optic performance verification).
Micro-bending stress release
In common wind-induced vibration, if the cable is rigidly fixed at the tower, vibration will concentrate at the fixed point. The OPGW suspension Clamp allows limited displacement, which can effectively disperse vibration energy. In terms of temperature, the sliding function of the OPGW suspension Clamp also allows thermal expansion and contraction.
Electrical function of OPGW suspension Clamp
OPGW has both communication and ground wire functions (as an OPGW earth wire, i.e., an optical ground wire OPGW / OPGW optical ground wire). The electrical role of the OPGW suspension Clamp is to provide reliable electrical contact and ensure a lightning-current path. It is a key node that transfers lightning current to the tower. Through the U-shaped shackle, the OPGW is electrically connected to the tower, forming a complete grounding system. Each suspension point is a current shunt point, reducing the lightning current amplitude at any single point.
If the electrical connection is poor, it can lead to protection failure during lightning strikes; contact resistance generates heat, burning the OPGW cable; and induced electromagnetic current cannot be effectively conducted into the ground.
The importance of OPGW suspension Clamp among optical cable accessories
The hub role of the suspension clamp for the vibration damper:
Vibration damper
↓
Preformed rods ← Suspension clamp→ Preformed rods
↓
U-shaped shackle
↓
Insulator string
↓
Tower
It is the physical connection point and the mechanical convergence point of multiple accessories. The OPGW suspension Clamp can serve as a reference point: all accessory installation positions are referenced to the OPGW suspension Clamp; it can determine the sag and ground clearance of the OPGW cable; and it determines the tension distribution of the span section. If the OPGW suspension Clamp is installed later, the cable needs to be moved; the already-installed preformed rods may twist and become misaligned, and the position of the vibration damper cannot be accurately located.
How to install OPGW suspension Clamp
① After OPGW tensioning is completed, the OPGW suspension Clamp should be installed in time. Under special circumstances, if it cannot be installed in time, the sheave and OPGW must be fixed in the stringing block with a nylon rope to prevent OPGW wear, as shown in Figure.
Figure:Diagram of fixing OPGW inside the stringing block
② On both sides of the large and small sizes, use the cable tensioning preformed rods and chain hoists to tighten and lift the OPGW on both sides, and remove the stringing block, as shown in Figure.
Figure:Diagram of lifting the optical cable
③ Align the mark of the inner-layer armor rods with the marked point, as shown in Figure.
Figure:Align the inner-layer armor rod mark with the marked point
Following the lay direction of the armor rods, wrap from the center mark point to both ends. The armor rods should be wrapped one by one, as shown in Figure.
Figure:Wrap the armor rods one by one
Leave 25–30 cm at both ends temporarily unwrapped so that the armor rods can be removed if reinstallation is needed. All rods should be evenly spaced.
④ After all inner-layer armor rods are installed, twist all rods to the tail end with both hands at the same time to seat them. All rod tail ends should be aligned, and the deviation should not exceed 50 mm.
⑤ Install the rubber sleeves (pads). Wrap the OPGW with two rubber sleeves from the upper and lower directions. Align the center mark of the rubber sleeve with the center mark of the installed inner-layer armor rods, and temporarily fix them, as shown in Figure.
Figure:Align the rubber sleeve center mark with the inner-layer armor rod center mark
⑥ Install the outer-layer armor rods. Place the first outer-layer armor rod on the rubber sleeve, with the color mark facing outward. Following the lay direction, wrap it around the rubber sleeve and the grounding plate. The wrapping length should ensure the rubber sleeve is stable. Install the remaining rods at equal intervals. The outer-layer armor rods should conform to the curved outer contour of the rubber sleeve. For double suspension clamps, the center of the outer-layer armor rods should be located between the two rubber sleeves.
⑦ Connect the clamp plate of the OPGW suspension Clamp to the suspension hardware and tighten the screws. Release the chain hoist so that the suspension hardware string is loaded, as shown in Figure.
Figure:Diagram of straight-line suspension string
FAQ
Q: What Risks Does The Suspension Clamp Mainly Address?
A: It mainly targets three types of risks:
Bending stress and clamping/compressive stress (most concentrated at support points)
Dynamic fatigue caused by aeolian vibration and galloping
Support-point wear/abrasion
Q: Why Do Installation Instructions Always Emphasize "Center Marking, Alignment, And Symmetrical Wrapping"?
A: Because once it is not aligned, the support point will have eccentric loading, causing local stress concentration. AFL OPGW suspension clamp installation instructions clearly require: mark the clamp center position on the OPGW with ink (not tape), and align the center mark of the armor rods with it.
Q: What Is The Direct Relationship Between The Suspension Clamp And The "Fatigue Life" Of OPGW?
A: Wind vibration/galloping repeatedly applies dynamic stress at the support point, causing fatigue accumulation. Many "preformed/armor-rod" suspension clamps explicitly claim that by dispersing stress at the suspension point and reducing static pressure and dynamic stress, they improve fatigue resistance and extend service life.
Q: Will The Suspension Clamp Affect The Optical Attenuation Of OPGW Fiber?
A: Under correct selection and installation, it will not cause issues. However, if the following occur-too small a bending radius at the support point; abnormal clamping force, flattening, or local squeezing; misinstalled armor rods or pads causing eccentric stress-micro-bending risk may increase, leading to additional loss or hidden hazards (especially for OPGW fiber / OPGW fiber optic).
Q: What Are The Most Common Failures/Hidden Hazards At OPGW Suspension Points?
A: Support-point wear (slip, fretting wear)
Misaligned or loose armor rods causing local stress concentration
Loose clamp body, missing pins/cotter pins
Material mismatch leading to corrosion or galling
Long-term insufficient vibration control leading to fatigue cracks
