To ensure the installation quality of fiber optic joint closures, you need to strictly control pre-installation preparation, on-site operation standards, sealing reliability verification, and post-installation testing & maintenance.

• Verify Material & Equipment Eligibility

  • Check the joint closure’s factory qualification certificate and performance test report; confirm it complies with standards like YD/T 814 or IEC 61753-1. Reject products with cracks, deformation, or damaged sealing gaskets.
  • Inspect auxiliary materials: Ensure heat-shrinkable splice protectors, waterproof tapes, and rubber seals are within their shelf life, free from aging or adhesion failure.
  • Calibrate tools: Confirm the fusion splicer, optical power meter, and torque wrench are calibrated and accurate (e.g., the splicer’s loss measurement function must be valid).

• Confirm Cable & Site Matching

  • Check the cable core count, diameter, and sheath type match the joint closure’s port specifications (e.g., avoid forcing a thick cable into a small port, which can damage the seal).
  • Evaluate the installation site: For aerial applications, ensure the mounting bracket is firm; for direct burial, clear the pit of sharp stones to prevent piercing the closure shell.

• Control Cable Stripping & Fiber Handling

  • Use a dedicated cable stripper to remove the outer sheath, armor, and buffer tubes—avoid scratching the bare fiber or breaking the fiber coating, which can cause hidden transmission losses.
  • Clean fibers with lint-free alcohol wipes (≥95% anhydrous ethanol) before splicing; prevent dust, oil, or moisture from contaminating the fiber end faces.

• Ensure Splicing Quality of Fibers

  • Cleave fiber ends at a 12° angle (standard for single-mode fibers) to ensure a flat, perpendicular end face—poor cleaving will lead to high splice loss.
  • After fusion splicing, check the splice loss value immediately via the splicer: The loss of single-mode fiber splices should be ≤0.05 dB; discard and re-splice any splice with loss exceeding 0.1 dB.
  • Heat the splice protector evenly with a heat gun—avoid overheating (which can melt the fiber coating) or underheating (which can cause loose protection).

• Follow Structural Installation Norms

  • Arrange fibers in the splice tray with a minimum bending radius ≥40 mm (for single-mode fibers) to prevent microbending loss. Ensure no fibers are pinched between the tray and closure shell.
  • Fix cables with tension-resistant brackets: Use a torque wrench to tighten clamps according to the manufacturer’s specs (usually 8–12 N·m). Over-tightening can damage the cable sheath; under-tightening may cause cable slippage.
  • Install the sealing gasket correctly: Place it in the dedicated groove without twisting or stretching, and clean the closure’s sealing surface with alcohol to remove dust and debris.

Sealing is critical to prevent moisture and dust intrusion—directly related to the closure’s long-term stability.

• Standardize Sealing Operation

  • For bolt-locked closures, tighten bolts in a crisscross order to ensure uniform pressure on the sealing surface; avoid uneven tightening that causes gaps.
  • For direct burial or underwater closures, add an extra layer of waterproof tape (e.g., butyl rubber tape) around the port and lid edges after closing the shell.

• On-Site Sealing Leak Test

  • Use the pressure test method (applicable to closures with pressure test valves): Inject dry air or nitrogen into the closure to a pressure of 0.05–0.1 MPa, immerse it in water for 30 minutes, and check for no air bubbles—bubbles indicate sealing failure.
  • For small-sized closures without test valves, wrap the sealed area with plastic film and observe for no condensation inside after 24 hours.

• Transmission Performance Testing

  • Conduct end-to-end optical loss testing with an optical power meter and light source: Compare the total loss before and after installation—any sudden loss increase indicates a problem (e.g., pinched fibers, poor splices).
  • Perform an OTDR (Optical Time Domain Reflectometer) test to locate hidden faults: Check for abnormal loss peaks in the splice section; ensure no reflection events (which can cause signal interference).

• Standardize Labeling & Documentation

  • Attach a durable label to the closure, marking key information: cable route, core count, installation date, operator, and splice loss data.
  • Record the installation process in detail (including test reports and material batches) for future maintenance tracing.

• For aerial closures, check the mounting bracket’s tightness every 6 months to prevent wind-induced shaking.
• For direct burial closures, avoid heavy pressure on the burial area; regularly inspect the ground for subsidence or damage.