What size heat shrink tubing should be used for the fiber optic coil

Choose heat shrink tubing with an expanded diameter slightly larger than the coil's maximum diameter and a shrink ratio that ensures a snug fit without over-compressing the fiber.

Key Considerations

1. Measure the Fiber Optic Coil: Use a digital caliper to measure the largest diameter of the fiber optic coil, including any connectors or loops. Also, note the smallest diameter where the tubing will terminate to ensure proper compression and sealing . 2. Determine the Shrink Ratio: Common shrink ratios are 2:1, 3:1, and 4:1. For delicate fiber optics, a 2:1 or 3:1 ratio is typically preferred to avoid excessive compression that could damage the fibers . 3. Calculate the Required Expanded Diameter: Use the formula: Supplied Diameter = Maximum Coil Diameter × Shrink Ratio × Clearance Factor

• For 2:1 ratio, add ~15% clearance
• For 3:1 ratio, add ~10% clearance Example: If the coil's maximum diameter is 8 mm and using a 2:1 ratio: 8 mm × 2 × 1.15 ≈ 18.4 mm expanded diameter . 4. Check Recovered Diameter: The tubing's recovered (shrunk) diameter should be 10–20% smaller than the maximum coil diameter to ensure a secure fit without over-compression . 5. Wall Thickness and Material: Select tubing with a thin wall for fiber optics to avoid excessive pressure on the fibers. Polyolefin is commonly used for flexibility and protection, while dual-wall tubing can provide additional moisture sealing if needed . 6. Installation Tips:
• Do not force the tubing over the coil; it should slide easily.
• Apply heat evenly using a heat gun or oven to avoid wrinkles or uneven shrinkage .
• Cut the tubing slightly longer than the coil to account for longitudinal shrinkage . By following these steps, you can select heat shrink tubing that fits securely, protects the fiber optic coil, and maintains long-term reliability.