YOFC Polarization-Maintaining Fiber Enters AI Optical Interconnect Applications

C114, September 17 (Liu Dingzhou) — Polarization-maintaining fiber, a category of specialty fiber, has suddenly taken off this year, becoming a darling of both industry and capital markets.

The reason is that AI is driving rapid iteration in computing infrastructure, while new optical interconnect technologies such as CPO (co-packaged optics) continue to emerge. With its ability to transmit light in a stable polarization state, polarization-maintaining fiber is ideally suited for connecting external light sources to silicon photonic chips. It has leapt from a specialty fiber for niche applications to a key component of computing infrastructure, seizing the new market opportunities brought by AI.

YOFC, the first company in China to bring polarization-maintaining fiber into volume production, held a product launch during CIOE China International Optoelectronic Exposition on September 10, unveiling specialty fibers dedicated to CPO/NPO and the CopackAlign brand. YOFC's polarization-maintaining fiber, under its own brand, has formally taken the stage in AI optical interconnects.

Polarization-Maintaining Fiber: A Strategic Fit for AI Optical Interconnects

AI clusters are scaling from tens of thousands to hundreds of thousands of GPUs, and single data centers are increasingly constrained by physical factors such as power supply, cooling, land, and facility capacity. Multi-campus distributed deployment is becoming a major trend. Emerging technologies continue to appear, and progress in optical interconnect technologies such as CPO and NPO has become a focus of industry attention. In August this year, NVIDIA announced that its Spectrum-X series of co-packaged optics (CPO) switches have entered full-scale production, opening the era of large-scale CPO commercialization.

CPO uses an external light source architecture that transforms traditional optical module design, making fiber interconnects indispensable for delivering the external light source to the silicon photonics chip. In real-world data center deployments, ordinary single-mode fiber is subject to temperature changes, mechanical vibration, fiber bending and other factors that cause the polarization state of light to drift randomly and continuously. The technical characteristics of polarization-maintaining fiber make it an indispensable part of CPO systems.

“Over the next one to two years, demand for polarization-maintaining fiber in CPO/NPO scenarios will grow several-fold,” said Yangtze Optical Fibre and Cable executive director and president Zhuang Dan in a speech at the launch event. The company has been deeply engaged in polarization-maintaining fiber for many years, becoming the first to launch commercial panda-type polarization-maintaining fiber products and ranking first in domestic market share for five consecutive years. “From component-level polarization-maintaining fiber to full CPO/NPO scenarios, YOFC has established a complete technology and product portfolio and won recognition from leading global customers.”

According to reports, major global CPO vendors have adopted YOFC's polarization-maintaining fiber connection solutions in the links from external light sources to silicon photonic engines, embedding domestically produced polarization-maintaining fiber deeply into the global AI advanced packaging supply chain.

“Our polarization-maintaining fiber production lines are also preparing capacity for the explosive demand for AI optical interconnects,” Zhuang added. All of the company's preparations revolve around AI computing infrastructure demand, with a customer-centric focus on delivering strong products and solutions.

Dr. Scott Wilkinson, principal analyst at Cignal-AI, also noted at the event that NVIDIA and TSMC are driving CPO from concept to large-scale commercial deployment. The high sensitivity of silicon photonic modulators to polarization means the entire link from ELSFP to the silicon photonic engine must rely on high-quality polarization-maintaining fiber. Dr. Scott Wilkinson forecast that global annual CPO/NPO port shipments will approach 35 million units by 2030, with polarization-maintaining fiber a core beneficiary.

Five core capabilities: in-house technology built on years of accumulated expertise

Why was YOFC the first company in China to launch panda-type polarization-maintaining fiber, and how has it maintained its lead? According to earlier YOFC materials, manufacturing polarization-maintaining fiber is far more difficult than ordinary communication fiber. The key is to symmetrically embed stress-applying parts on both sides of the core to create a birefringent structure that “locks” the polarization direction. This process involves three major stages — preform drilling, high-temperature drawing, and stress control — each presenting extremely high technical barriers.

Among the world's mainstream optical fiber preform manufacturing processes, PCVD offers inherent advantages in complex precision control, enabling nanometer-level tuning of the radial and axial refractive index profiles. It is therefore also the core process for producing polarization-maintaining fiber preforms. Yangtze Optical Fibre and Cable is one of very few manufacturers to master the PCVD process, allowing precise control of key polarization-maintaining fiber parameters and stable polarization-maintaining performance across a wide temperature range of -45℃ to +85℃.

At the launch event, Mo Qi, chief specialist of YOFC's specialty product line and manager of the specialty fiber R&D department, presented the five core capabilities behind YOFC's polarization-maintaining fiber: PCVD preforms, waveguide structures, multi-element doping, stress-region forming, and coating formulation with volume manufacturing. Together, these five capabilities deliver PCVD consistency and manufacturability, batch stability, and large-scale supply capability in YOFC's polarization-maintaining fiber.

Building on these five capabilities, YOFC officially launched CopackAlign, a new brand for CPO/NPO applications. It comprises two sub-brands, Polalign polarization-maintaining fiber and EzAlign single-mode fiber, forming a paired fiber platform developed under a single geometric control system to ensure that core-height consistency comes from structural design rather than screening. At the event, YOFC announced the official release of the CopackAlign Prime series, covering two products: Polalign CUP0012 and EzAlign CUE0023.

YOFC's "paired delivery" product concept carries significant industry value. AI compute clusters demand extremely high system stability; even a minor fault can cost millions of dollars. As an entirely new technology architecture, CPO requires every subsystem to deliver high reliability. While other suppliers sell two separate fibers, YOFC delivers them as a matched pair with the same cladding specification, the same concentricity specification, and the same core height, upgrading mode-field matching and significantly improving long-term reliability — adding another layer of "insurance" for CPO system stability.

The new CopackAlign brand reflects YOFC's strategic determination to refine and strengthen its polarization-maintaining fiber business. Zhuang Dan emphasized, "What YOFC is launching this time is not just a fiber product, but a precision connection solution focused on advanced packaging optics scenarios, and an important implementation of YOFC's 'AI-2030' strategy."