Hengtong's FPOD Process Breaks Through Highly Fluorine-Doped Tube and Rod Technology

C114 News, midday September 11 (Jiang Junmu) — As the AI computing wave sweeps the globe, specialty optical fiber, the strategic material at the "pinnacle of the pyramid" of the optical communications supply chain, is entering an unprecedented demand surge. Yet the long-standing bottleneck holding back the performance and mass production of high-end specialty fiber in China — octagonal fluorine-doped tubes and fluorine-doped rods — has remained a formidable barrier.

At the 2026 China International Optoelectronic Exposition (CIOE), Hengtong Optic-Electric showcased a complete set of self-developed octagonal fluorine-doped tubes and rods, and disclosed its proprietary FPOD (fluorinated plasma vapor deposition) process technology for the first time. The breakthrough not only fills a gap in China's core substrate materials for high-end optical fiber, but also marks a pivotal leap for China's specialty fiber industry from "following" to "leading."

Octagonal fluorine-doped tubes and rods: indispensable key substrates

Octagonal fluorine-doped tubes and rods are key substrates for producing high-power active fibers and power-delivery fibers, and their quality directly determines the damage threshold, optical stability and finished-product yield of laser fibers. However, this key substrate has long depended on imports. The preparation technology and core equipment for large-size, heavily fluorine-doped specialty optical fiber preforms are monopolized by foreign players, leaving critical raw materials at the mercy of others.

The industry's mainstream PCVD fluorine tube + RIC process route now shows increasingly pronounced drawbacks. On one hand, specifications are limited: inherent constraints of the substrate tube make it hard to meet the demand of high-end, high-power fiber for large-size octagonal tubes and large-format rods. On the other hand, costs are high: cumbersome steps and a lengthy process chain keep overall manufacturing costs elevated, seriously constraining the scaled, low-cost mass production of high-end specialty fiber.

Industry experts told C114 that achieving domestic control of this material is the core lever for China's specialty fiber industry to further break through overseas technical barriers and achieve an industrial breakout, with strategic significance no less than the earlier domestication breakthrough in optical fiber preforms.

From Bottleneck to Breakthrough: A Comprehensive Technical Overhaul of the FPOD Process

Faced with industry challenges, Hengtong Optic-Electric chose an innovation path starting from the underlying process. Its in-house FPOD process delivers a comprehensive technical overhaul compared with the conventional PCVD fluorine tube + RIC route.

First, one-step curing eliminates fluorine loss: the FPOD process uses one-step fluorine-doped curing technology, avoiding the fluorine volatilization caused by the conventional two-stage high-temperature process and ensuring the stability of material doping at the source.

Second, streamlined workflow and sharply higher efficiency: the FPOD process significantly simplifies production steps, boosting overall manufacturing efficiency by 150%. With demand for specialty optical fiber growing rapidly, this efficiency gain translates directly into greater capacity and lower costs, laying a solid foundation for large-scale, high-efficiency volume production.

Third, performance breakthroughs and precise shape control: the FPOD process pushes the numerical aperture beyond conventional limits, enabling precise replication of the octagonal geometric profile and tight control of cladding shape accuracy, while achieving uniform fluorine doping inside. This effectively optimizes the pump light reflection path and improves the fiber's thermal management performance.

From "Rod-Fiber-Cable Integration" to a Full-Chain "Materials-Process-Application" Closed Loop

The breakthrough in the FPOD process is not an isolated event, but a key milestone in Hengtong Optic-Electric's long-term commitment to core upstream optical communication technologies and the building of vertically integrated capabilities.

Hengtong is one of the few domestic manufacturers with integrated preform, fiber and cable capabilities. It has built the world's largest green optical preform R&D and industrialization base, successfully achieving domestic substitution for high-end preform products. The launch of the FPOD process further extends its independent and controllable reach into fluorine-doped tubes/rods, a more upstream key substrate material.

According to C114, Hengtong Optic-Electric has recently made advances on multiple fronts in specialty fiber. For example, it has successfully developed a fluorine-doped quartz tube at the industry's highest technical level, with a maximum diameter exceeding 60 mm, meeting the high-end needs of rare-earth-doped specialty fiber and polarization-maintaining fiber. In CPO polarization-maintaining fiber, its HPPD high-precision polarization-maintaining fiber drawing technology has improved bare fiber diameter control accuracy to ±0.1 μm, far surpassing conventional processes. Notably, the company has also invested in expanding its AI Advanced Fiber Materials R&D and Manufacturing Center, focusing on the R&D and manufacturing of specialty fibers such as ultra-low-loss hollow-core fiber, ultra-low-loss multi-core fiber and high-performance multi-band multimode fiber.

As AI computing power drives a new growth cycle for the optical communication industry, the strategic value of specialty fiber is being redefined. The breakthrough in the FPOD process is more than the announcement of a technical achievement; it sends a clear signal: China's specialty fiber industry is moving from "product substitution" to "process definition," and from "passive catch-up" to "active leadership."

As seen at this year's CIOE, Hengtong Optic-Electric continues to make in-house process development the core of its growth, deepening materials research upstream while precisely matching diversified market demand downstream for active fiber, power-delivery fiber and computing communication fiber. It keeps improving its integrated upstream-to-downstream industrial layout, comprehensively strengthening the core competitiveness of domestic specialty fiber in the global market.