OPGW cable installation is a critical component in optical cable line construction, directly related to communication quality and operational safety. Compared to ordinary optical cables, OPGW cable installation has higher technical requirements: the cable must maintain constant tension during stringing, avoid twisting and excessive bending, while preventing damage to the outer sheath and fiber compression. The tension stringing method used in construction keeps the cable suspended at all times, effectively protecting the fiber from damage and ensuring long-term stable operation of the communication system. This guide introduces the construction procedures for OPGW stringing and sagging, including pulling rope deployment, key technical points of cable stringing, and sagging methods under different tension tower configurations, providing technical guidance and operational standards for OPGW cable installation.
Pulling Rope Stringing
- The pulling rope generally adopts non-twisted steel wire rope, gradually converted through guide rope traction. The guide rope generally uses Dyneema rope, deployed by aircraft.
- When manual deployment is used, the pulling rope is coiled and deployed in sections manually. After each section is deployed, it is connected with anti-bending connectors.
- When aircraft deployment is used, the aircraft performs aerial deployment of Dyneema rope, utilizing small traction and small tension to pull the steel wire rope with Dyneema rope.
- The connection sequence between pulling ropes is: pulling rope - anti-bending/swivel connector - pulling rope (as shown in Figure).
Pulling Rope Connection Diagram
OPGW Cable Stringing
① The connection sequence between pulling rope and cable is: anti-twist steel wire rope (pulling rope) - swivel connector - pulling grip - OPGW, as shown in Figure.
Pulling Rope and Cable Connection Diagram
② After connecting the pulling rope and cable, first release the pulling rope temporary anchor device, hang the grounding traveler, and start after confirming the entire line is normal. Starting sequence: start tensioner first, then puller; stopping sequence: stop puller first, then tensioner.
③ Pulling speed: The puller should slowly accelerate to a low speed of 5m/min. If everything is confirmed normal, it can accelerate smoothly. The pulling speed should be around 25m/min, with a maximum not exceeding 35m/min. The actual pulling speed should be determined by construction commanders based on actual conditions.
④ Stringing blocks at angle tower positions should be pre-offset using guy wires, with continuous offset adjustment during the pulling process to ensure the cable does not jump out of the sheave groove during stringing, as shown in Figure.
Pre-offset Adjustment Diagram
⑤ When only 5-6 turns of cable remain on the tensioner spool, pulling should stop. Temporarily anchor in front of the tensioner using OPGW special clamps or tension preformed armor rods, adding balance weights each time. Remove the remaining cable from the drum and tensioner. If pulling is about to reach position, install tension preformed armor rods (with balance weights) at the cable end, tighten with motorized winch, remove temporary anchor, and the pulling field slowly pulls while the motorized winch slowly releases.
⑥ If the cable will be pulled for a distance after releasing from the tensioner, when 5-6 turns remain in the drum, stop and remove the remaining cable, install special grips, anti-bending swivel connectors, and pulling rope, then wind back onto the drum and continue slow deployment. Stop when the cable end is about to exit the tension wheel, install tension preformed armor rods (with balance weights), use winch assistance to release 5-10m, replace the special connector with a swivel connector, and deploy pulling rope on the tensioner.
⑦ When the cable end is pulled through the stringing section and reaches the designed end length, stop pulling. OPGW cable installation stringing is complete. The reserved length at both ends of OPGW stringing should be at least 15m after reaching ground level.
⑧ When the puller-tensioner is installed inside the tension tower, after pulling is complete, temporary anchoring must be done on tangent towers at both ends before coiling the remaining OPGW in the drum into large loops, then hoisting the tail rope to the tower.
OPGW Cable Sagging
OPGW cable sagging is usually divided into the following two scenarios based on actual conditions, with steps for each as follows:
Tension Section Without Tension Towers
Sagging when there are no tension towers in the middle of the tension section is shown in Figure.
Sagging Diagram When No Tension Tower in Middle of Tension Section
① After cable stringing is complete, mark according to designed end length on N2 tension tower and install tension clamp.
② After the tension clamp is installed on N2 tension tower, slowly pull at the pulling field. When the sag in the N1-N2 tension section is 2-3m greater than the designed installation sag (observation span sag), stop pulling.
③ Install sagging preformed armor rods (with balance weights) 4-5m outside the line at N1 tension tower, use sagging equipment to adjust N1-N2 sag. When it reaches the standard, mark and install tension clamp to complete sagging. After marking each tangent tower between N1-N2, tangent tower hardware installation can proceed.
Tension Section With Connected Tension Towers (N3 Without Splice Box)
Sagging Diagram When Tension Tower in Middle of Tension Section
① Mark according to designed end length on N2 tower and install tension clamp.
② Perform N2-N3 section sagging. Connect sagging preformed armor rods and chain hoists on both sides of N3 tower simultaneously and slightly tighten, then tighten the chain hoist on the N2 side for sagging.
③ When N2-N3 sag reaches standard, mark each tangent tower and install tension hardware on the N2 side of N3 tower.
④ Measure the required downlead length as designed, install tension hardware on the N1 side of N3 tower, and release the chain hoist on that side. If the remaining cable length after N2-N3 sagging is insufficient for downlead length, tighten the chain hoist on the N1 tower side to meet downlead length requirements.
⑤ Then perform N3-N1 section sagging.
Common Problems and Solutions
Cable Twisting Problems
How to determine if OPGW has twisted?
Three signs: ① Change in strand direction on cable surface. ② Connector rotated more than 3 turns. ③ Cable shows "twisted rope" appearance.
After how many turns of twisting must work stop?
Must immediately stop when twisting exceeds 3 turns, strictly prohibited to continue pulling.
How to prevent cable twisting?
① Use anti-twist whip (3.5m long, 20kg weight). ② Install swivel connector at each connection point. ③ Control pulling speed at 25-35m/min.④ Assign dedicated personnel for monitoring.
How to handle twisting when discovered?
① Immediately stop. ② Release tension. ③ Manually release twist at angle tower.④ Check swivel connector.⑤ Use OTDR to confirm fiber is undamaged.
How long to maintain after sagging to eliminate torsional stress?
Maintain for 1 hour after reaching designed sag to allow internal torsional stress to completely dissipate.
Over-Pulling Problems
What is the safe limit for OPGW pulling tension?
≤15% of breaking strength, actual construction controlled at 0.8-1.2T, maximum not exceeding 1.3T.
What are the consequences of over-pulling?
① Fiber experiences tensile stress causing microbend loss ② Metal strands undergo plastic deformation ③ Severe cases cause fiber breakage
What is the start-stop sequence for tensioner and puller?
Starting: start tensioner first, then puller; Stopping: stop puller first, then tensioner.
When cable remains how many turns on tensioner should pulling stop?
Must stop pulling for temporary anchoring when 5-6 turns remain.
How to control pulling speed?
① Slowly accelerate to 5m/min low speed to confirm normal ② Smoothly accelerate to 25m/min ③ Maximum not exceeding 35m/min ④ Reduce speed when passing angle towers and crossing points
What are the requirements for tensioner wheel diameter?
≥70 times OPGW outer diameter, and ≥1000mm
Sheave Jumping Problems
What are the main causes of sheave jumping?
① Insufficient pre-offset at angle tower.② Pulling speed too fast.③ Sheave wheel diameter too small.④ Windy weather.
What are the specifications for stringing blocks?
Groove bottom diameter ≥40 times OPGW outer diameter, and ≥450mm (commonly 560mm), must have nylon or rubber lining.
How to prevent jumping at angle towers?
① Install pre-offset guy wire (direction opposite to angle bisector).② Continuously adjust during pulling.③ Assign tower climbing monitoring personnel.④ Reduce speed when passing.
What are the handling steps after discovering jumping?
① Immediately notify to stop.② Maintain status quo without unauthorized movement.③ Technical supervisor assessment.④ OTDR testing.⑤ Carefully return to groove and secure.
What weather conditions prohibit construction?
Must stop construction in wind force ≥5, thunderstorms, heavy fog.
How to handle outer layer scratches after cable jumping?
Minor abrasion wrap with tape; outer layer deformation requires re-spooling; fiber damage must be replaced or spliced.
Temporary Anchoring Problems
When is temporary anchoring needed?
① During reel change operations ② Construction interruption (lunch break/night/severe weather) ③ Waiting for sagging ④ Cable testing
What equipment must be used for temporary anchoring?
OPGW special clamps or tension preformed armor rods (manufacturer-matched), strictly prohibited to use ordinary clamps.
What accessories must be equipped during temporary anchoring?
Balance weights must be added each time (generally 20-50kg) to maintain cable force balance.
Where can temporary anchor points be located?
Only at tangent towers or tension towers, strictly prohibited at angle towers.
How many times can preformed armor rods be reused?
Not exceeding 2 times.
How often to inspect during temporary anchoring?
Inspect every 4 hours, handle abnormalities promptly.
What testing is needed before and after temporary anchoring?
OTDR test fiber before temporary anchoring, test again after, compare to confirm no damage.
Can temporary anchoring operations be performed in strong winds?
High-altitude temporary anchoring operations prohibited when wind force ≥5.
Comprehensive Quality Control
What are the "Five Preventions" in OPGW cable installation?
Prevention of pulling damage, abrasion damage, twisting damage, compression damage, bending damage.
What is the minimum bending radius requirement during construction?
≥20 times cable outer diameter (during construction); ≥30 times after installation complete.
What is the acceptance standard for fiber splice loss?
Average loss ≤0.08dB per splice.
What is the allowable sag deviation?
110kV: +5%/-2.5%; 220kV: ±2.5%; Long span ≤±1%.
When is OTDR testing required?
① Baseline testing before construction ② Before/after jumping/twisting/temporary anchoring ③ After sagging complete ④ Final acceptance
Related articles