Rod Breakdown Machine Line
Single, Dual Wire Drawing Machine Line
Multi-wire Drawing Machine
Online Annealing Unit
Take-up Machine
Wire Tinning Machine
Wire Enamelling Machine
Wire Electro-plating Machine
Copper Cladding Machine (CCA)
Insulated Wire Stranding Machine
Double Twisting Machine
Bow Type Double Twisting Machine
Rigid Stranding Machine
Tubular Stranding Machine
Drum Stranding Machine
Cage Stranding Machine
News
What is the difference between tight buffer and loose tube
2025-06-05
Loose-Tube Structure & Process
The loose-tube manufacturing process (known as secondary coating) involves:
- Fiber grouping: Multiple optical fibers are stranded together
- Filling: Fibers immersed in thixotropic water-blocking gel within extruded PBT tube
- Key features:
- Fibers free-floating in gel (radial movement ±0.5mm)
- PBT tube cavity diameter ≥3× fiber diameter
- Gel provides <0.001% microbend loss and hydrogen protection
Core Structural Comparison
| Parameter | Loose-Tube Cable | Tight-Buffered Cable |
|---|---|---|
| Primary Design | Fibers suspended in gel-filled cavity | Fibers bonded to coating layer |
| Tube Dimensions | OD≥2.0mm; ID/fiber dia. ratio≥3 | OD≤0.9mm (e.g., 900μm coating) |
| Filling Medium | Hydrophobic gel (>80% tube volume) | No filling (dry water-blocking yarn in some types) |
| Stress Isolation | >95% external stress attenuation | Partial stress transmission to fibers |
Reinforcement Configuration
| Component | Loose-Tube Construction | Tight-Buffered Construction |
|---|---|---|
| Central Strength Member | FRP rod (ø2-3mm) at core | No central member |
| Tensile Element Position | Tubes helically stranded around FRP | Aramid yarn braided over buffer layer |
| Load Distribution | FRP carries >90% tensile load | Aramid carries 60-70% tensile load |
Structural Sequence:
- Loose-Tube: FRP core → PBT tubes (helically stranded) → Gel → Fibers
- Tight-Buffered: Fiber → UV-cured polymer coating (bonded) → Aramid braiding
Key Performance Advantages
| Property | Loose-Tube Cable | Tight-Buffered Cable |
|---|---|---|
| Tensile Resistance | >3000N load capacity | <1000N load capacity |
| Temp Range | -40°C to +70°C (ΔT=110°C) | -20°C to +60°C (ΔT=80°C) |
| Fiber Strain | <0.05% at 0.7% cable strain | Direct strain transfer to fibers |
| Water Protection | IEC 60794-1 F1 standard | No standardized water-blocking |
Critical Applications:
- Loose-tube: Long-haul networks (>80km), aerial/direct-burial installations
- Tight-buffered: Intra-building risers, patch cords, equipment jumpers
Source: Telecommunications Industry Association (TIA-598-D), IEC 60794-1-2
