It has been a while since my last blog, as I was busy preparing for and attending OFC. Afterward, I needed time to digest all the valuable insights I gathered. To be honest, getting started on this blog was daunting—I wasn’t sure which topic to address first, given the wealth of fascinating discussions at OFC. Unlike previous years, the focus wasn’t primarily on broadband; instead, AI connectivity took center stage, along with its vast bandwidth and low latency requirements.

I’ll cover topics such as Co-Packaged Optics, Multi-Core Fiber, and lens-based connectors in future blogs. But right now, the technology that impressed me the most in terms of maturity and potential is Hollow Core Fibers (HCF).

The Progress and Potential of HCF

HCF has come a long way from a technical, production, and deployment perspective. Cable production has now reached lengths of 100km, with projections exceeding 200km soon, at a quality and price point that makes commercial viability a reality. The NAND-R design appears to enable consistent production, achieving sub 0.1dB/km insertion loss (IL) and excellent non-linearity, making it possible to utilize a broader bandwidth spectrum.

Deployment limitations are now well understood, allowing us to define optimal application scenarios. For instance:

• Gas absorption constraints limit long-haul applications, as they affect usable bandwidth.
• Higher bending radius requirements impact connectivity solutions and must be considered during integration.
• Mode filtering to standard SMF** is necessary, since no direct HCF-compatible transceiver solutions exist yet.

Despite these challenges, major hyperscalers are recognizing HCF’s advantages for data center interconnectivity (DCI), while telecom service providers see its potential for extending metro and rural links.

Key Application Scenarios

Given current limitations in fiber length and gas absorption effects on long-distance applications, the most promising use cases are inter-data-center (IDC) connectivity. HCF’s low latency and improved non-linearity allow data centers to be placed farther apart while staying within acceptable delay limits for application replication. Additionally, HCF offers future-proofing benefits, enabling increased bandwidth without requiring compensation for linearity limitations at high speeds.

An exciting advantage of HCF is its compatibility with standard arc splicers—though it requires extra care, making deployment significantly easier. This same principle supports its use in broadband metro networks and remote rural networks, where it allows active equipment to be installed farther from end applications. This approach simplifies network architecture while reducing costs, all while ensuring scalability for future bandwidth demands.

Current Challenges

Of course, HCF is not without its drawbacks:

• It has a higher minimum bending radius than conventional solid-core SMF, meaning all intermediary connections—splice enclosure domes, street cabinets, patch panels, and ducting—must accommodate this requirement.
• Existing market transceivers are designed for solid-core fibers, necessitating mode conversion when transferring signals to and from HCF. Special pigtails are needed to manage this transition, requiring careful splicing at connection points.
• Direct connectors for HCF are still in development, meaning fiber terminations currently rely on workaround solutions.

Final Thoughts

I’m genuinely excited about the potential of HCF and eager to explore product development in this space. This technology offers immense benefits—from reducing CAPEX and OPEX for service providers to minimizing reliance on central offices and active equipment, all while contributing to the development of a more resilient AI infrastructure.

Have you worked with HCF? I’d love to hear your experiences—feel free to share your thoughts, whether you agree or disagree with my perspective!