Hollow-Core Fiber: Three Major Challenges (Part 1) | Materials, Performance, Engineering
Sep 25, 2025| Hollow-Core Fiber: Three Major Challenges (Part 1) | Materials, Performance, Engineering: Three Technical Highpoints from Laboratory to Industrialization
When the attenuation coefficient of hollow-core fiber (HCF) broke through the 0.1 dB/km mark, surpassing the theoretical limit of traditional solid-core fiber, the entire industry was thrilled. However, this brilliant milestone is not the end but the starting point for an even more arduous climb. What technical barriers must be overcome for hollow-core fiber to move from a performance "singularity" to large-scale commercial use?
1. The Foundation of Materials: A "Purity" Revolution in Glass Tubes
The breakthrough begins at the source. As one expert from a university research institute pointedly noted, "What deserves focused attention in the future is actually the quality and stability control of glass tube raw materials."
This seemingly basic aspect is precisely the critical factor determining the performance consistency and yield of hollow-core fibers. Whether based on photonic bandgap or anti-resonant structures, their precise optical properties are built upon microscopic glass materials and glass tubes. Any minor material defects or dimensional inconsistencies can be amplified during high-speed fiber drawing, ultimately affecting the fiber's performance. The relentless pursuit of material "purity" and "consistency" is the first major hurdle for hollow-core fiber to transition from laboratory samples to stable, mass-produced products.
2. Performance Optimization: Addressing Three Major "Internal Loss" Challenges-Gas Absorption, Loss Spectrum, and Mode Interference
A representative from an operator application perspective raised more specific challenges: "Currently, three key technical issues urgently need resolution: gas absorption, loss spectrum flatness, and mode interference."
Gas Absorption: Trace residual gas molecules such as water vapor/hydroxyl (H₂O) and carbon dioxide (CO₂) in the hollow channel form absorption peaks at specific wavelengths, eroding the advantage of ultra-low loss.
Loss Spectrum Flatness: Achieving uniform and extremely low loss across the entire communication window (e.g., from O-band to C/L-band), rather than excelling only in isolated bands, is crucial for wavelength-division multiplexing (WDM) systems.
Mode Interference: Ensuring stable transmission of optical signals within the hollow core and suppressing mode coupling and crosstalk are fundamental to guaranteeing the reliability of high-capacity, long-distance transmission.
Addressing these three "internal loss" challenges requires collaborative innovation across the entire chain-from mechanistic research and structural design to preparation processes and encapsulation testing.
3. Engineering Enablement: Urgent Need for "Adapter" Solutions in Testing and Splicing
Technological maturity depends on supporting tools. Experts in testing and splicing highlighted the practical challenges of engineering implementation.
Testing Challenges: A testing expert noted that while most existing instruments can be reused, the absence of single-ended OTDR (Optical Time-Domain Reflectometer) is currently the biggest pain point for engineering maintenance. Due to extremely weak air scattering, traditional OTDRs struggle to accurately locate fault points. Developing high-performance single-ended OTDRs will become a "necessity" for the efficient deployment and maintenance of hollow-core fiber optic cable lines.
Splicing Processes: A splicing expert emphasized the need to enhance fiber consistency through standardization and optimize fusion splicer performance and the working environment to minimize the entry of moisture and other contaminants into the hollow core during splicing. This is a critical step in ensuring end-to-end system performance.
The technological of hollow-core fiber has entered the "deep water zone," shifting from macroscopic structural design to microscopic material science, gas dynamics, and process control. As industry experts have stated, this requires collaboration among fiber manufacturers, equipment suppliers, and operators. Every small step forward paves the way for the large-scale future of hollow-core fiber. Academic and research institutions must also play a pivotal role by addressing fundamental questions and exploring creative applications of new methods in the hollow-core fiber field, driven by curiosity.