Jun 26, 2026News & Insights
Inner Winding vs. Outer Winding for UAV Fiber Optics: Which Should You Choose?
UAV Fiber Guide: Use Outer Winding for 1-30km (simple, low cost). For 30-60km, Inner Winding is crucial; its zero-tension, center-pull coil prevents mid-flight breakage.
Inner Winding vs. Outer Winding for UAV Fiber Optics: Which Should You Choose?
Recently, we’ve received many inquiries from UAV manufacturers and defense contractors regarding the differences between Inner Winding (Center-pull) and Outer Winding (Conventional Spooling) for fiber optic dispensing.
Choosing the right winding technology is critical for UAV operations. The wrong choice can lead to high payout tension, fiber tangling, or even mid-flight breakage. In this technical insight, we break down the mechanics, pros, and cons of each method, and provide a practical rule of thumb to help you choose the right solution based on your flight distance.
1. Outer Winding (Conventional Spooling)
Mechanism:
The fiber is wound externally onto a spool and unwinds from the outermost layer, much like a traditional spool of thread.
The Pros: The machinery required for outer winding is mechanically simple and the technology is highly mature. This results in generally lower manufacturing costs and a highly accessible process.
The Cons for UAVs: During payout, the entire spool must rotate (or the fiber is forcefully pulled from the end). This creates high rotational inertia and significant tension fluctuations, which increases the risk of the fiber breaking or tangling during flight.
2. Inner Winding (Center-pull Winding)
Mechanism:
The fiber is wound into a self-supporting coil (typically housed in a protective fiber canister). During payout, the coil remains completely stationary, and the fiber is pulled smoothly from the center (inside) out.
The Pros (UAV-Optimized):
Zero Rotational Inertia: Because the coil doesn't move, it ensures ultra-low and constant payout tension. This prevents fiber breakage even during high-speed or highly maneuverable UAV flights.
Tangle-Free Reliability: The center-pull design completely eliminates the risk of twisting or knotting.
Integration-Friendly: It allows for easy pre-routing, leaving the Air Unit cables exposed for convenient soldering to the Flight Controller (FC) during UAV assembly.
The Technical Barrier: Manufacturing center-pull coils is highly complex. It requires ultra-precise tension control and advanced dispensing/curing technologies to ensure the inner layers of the coil do not collapse under pressure.
Expert Recommendation: The "30km Rule" for Fiber Coils
If you are unsure which technology suits your project, our engineering team recommends making the decision based on flight distance and manufacturing experience:
Scenario A: 1km to 30km Distance
Recommendation: Outer Winding
If your UAV operation requires a fiber length between 1km and 30km, and your team lacks prior experience with complex fiber winding processes, Outer Winding is sufficient. The shorter distance and lighter payload mean that rotational inertia is manageable, making the simpler, more cost-effective outer winding method the smartest choice for rapid deployment.
Scenario B: 30km to 60km Distance
Recommendation: Inner Winding
For long-range tactical or industrial operations requiring 30km to 60km of fiber, Inner Winding is strictly recommended. At these lengths, a conventional spool becomes too heavy, and the rotational inertia would almost certainly cause tension spikes and fiber breakage. Inner winding ensures the coil remains stationary, guaranteeing a flawless, zero-tension payout over extreme distances.
Quick Comparison Table
Feature | Outer Winding (Conventional) | Inner Winding (Center-pull) |
Payout Mechanism | Spool rotates; unwinds from the outside. | Coil is stationary; unwinds from the inside. |
Rotational Inertia | High (increases tension risks). | Zero (constant, low tension). |
Ideal Distance | 1km – 30km | 30km – 60km |
Experience Needed | Beginner-friendly; standard machinery. | Advanced; requires precise curing tech. |
Best For | Short-to-medium range, commercial UAVs. | High-speed, long-range tactical UAVs. |
Looking for the Right Winding Solution?
Whether you are building short-range commercial drones or long-range tactical UAVs, selecting the right winding machine is the first step to success. Contact WhatsApp +86-13510219832 today to discuss your specific payload and distance requirements.