In the wave of artificial intelligence (AI) advancement, data centers worldwide are undergoing a profound architectural transformation. From training large language models like ChatGPT to real-time inference, massive data processing imposes extreme demands on interconnect bandwidth, latency, and energy efficiency. Traditional copper-based electrical interconnects can no longer support the exponential growth needs of AI data centers. Against this backdrop, Silicon Photonics and Co-Packaged Optics (CPO) have emerged as core solutions for next-generation high-performance computing and networking infrastructure. Within this technological ecosystem, Fiber Arrays (also known as FAU - Fiber Array Units) play an indispensable role as the critical bridge for achieving efficient optical coupling and system-level connectivity. This article provides a comprehensive analysis of this technology system and explores its evolution path under the drive of AI.

Why AI Is Driving the Rapid Development of Silicon Photonics
The explosive growth of AI applications, particularly generative AI and large-scale model training, has posed unprecedented challenges to computing infrastructure. A single AI training cluster may contain tens of thousands or even hundreds of thousands of GPUs, requiring continuous exchange of massive parameters and gradients. Traditional copper interconnects face severe signal attenuation, surging power consumption, and limited transmission distance at high speeds. For example, while NVIDIA’s NVLink copper solutions deliver high bandwidth, their effective range is typically limited to about two meters, making it difficult to support large-scale “scale-out” cluster expansion.

Silicon Photonics technology integrates photonic components (such as lasers, modulators, detectors, and waveguides) on a silicon platform, using light as the information carrier to achieve revolutionary improvements in bandwidth density and energy efficiency. It is highly compatible with mature CMOS processes, enabling large-scale production using existing semiconductor manufacturing equipment and significantly reducing costs. It also supports technologies like wavelength division multiplexing (WDM) to further amplify per-fiber bandwidth.

In AI data centers, silicon photonics not only dramatically lowers power consumption per bit (reaching pJ/bit levels or lower) but also supports longer interconnect distances and higher port densities. This directly alleviates the “power wall” and “bandwidth wall” challenges. Leading companies such as NVIDIA have launched CPO switches based on silicon photonics, reducing power consumption by approximately 3.5 times compared to traditional pluggable optical modules while significantly enhancing network resilience—laying the foundation for building million-GPU-scale AI factories.

CPO technology takes this further by co-packaging the optical engine with high-performance ASIC chips in the same package, greatly shortening electrical signal paths (from centimeters to millimeters), reducing SerDes power consumption, and minimizing signal distortion. This not only improves overall system performance but also provides a critical pathway for the sustainable expansion of AI infrastructure.

Why Silicon Photonics Needs Fiber Arrays
Although PICs (Photonic Integrated Circuits) in silicon photonics can efficiently process optical signals at the chip scale, reliably transmitting these signals to external networks requires Fiber Arrays. Silicon waveguides on PICs are extremely small (sub-micron scale), while standard single-mode fiber cores are about 9μm, creating a significant mismatch in mode field diameter and size. Direct coupling would result in losses as high as tens of dB, rendering it impractical.

Fiber Arrays precisely arrange multiple fibers (from a few to hundreds of channels) into a high-density array, enabling one-to-one alignment with PIC waveguide arrays. They serve as the bridge connecting silicon photonics from “on-chip” to “inter-system.” In CPO architectures, optical engines must handle aggregate bandwidths at TB/s levels, demanding interfaces with extremely high channel density and stability. Without reliable fiber arrays, the advantages of silicon photonics cannot be fully realized.

Additionally, fiber arrays support various coupling methods, including edge coupling and grating coupling, and can integrate auxiliary structures like spot size converters to further optimize coupling efficiency. In the high-density rack environments of AI data centers, they also adapt to complex conditions such as thermal expansion and mechanical vibration, ensuring long-term reliable operation.

How Fiber Arrays Achieve High-Precision Coupling
High-precision coupling in fiber arrays relies on a combination of materials science, precision manufacturing, and alignment technologies:
· Precision V-Groove Substrates: Silicon, glass, or quartz substrates are used, with photolithography and etching processes forming V-groove arrays to precisely fix fiber positions and ensure consistent core spacing.
· Fiber Processing Techniques: These include grinding, polishing, and end-face coating to achieve optical-grade flatness. Fibers can also be tapered or etched for pitch conversion.
· Advanced Alignment Technologies: Combining active alignment (real-time optical power monitoring) and passive alignment (machine vision + precision mechanics) achieves sub-micron or even sub-100-nanometer accuracy. High-end solutions integrate Planar Lightwave Circuit (PLC) technology to bridge mode field differences.
· Specialty Fiber Integration: Supports single-mode fibers, polarization-maintaining fibers (PMF), and hybrid configurations for coherent communications and polarization-sensitive applications.

These processes collectively ensure coupling losses below 1 dB, or even approaching 0.5 dB, while supporting 200G per channel or higher data rates. In high-volume production, process stability and yield control are key indicators of a supplier’s capability.

Why Pitch Accuracy Is Critically Important
Pitch Accuracy—the deviation in center-to-center spacing between adjacent fiber cores—is a core technical parameter of fiber arrays, typically controlled within ±0.5μm or better. Why is it so critical? Silicon waveguide arrays are often designed with very tight pitches (30–125μm) to achieve high-density integration. Any minor pitch deviation can lead to:
· Sharp Drop in Coupling Efficiency: The light spot fails to align precisely with the waveguide entrance, causing severe power loss.
· Increased Crosstalk: Interference between adjacent channels degrades signal-to-noise ratio and impacts high-speed transmission quality.
· Thermo-Mechanical Reliability Issues: In the high-temperature environments of CPO packages, differences in material thermal expansion coefficients amplify initial deviations, leading to long-term drift.

In AI data center applications, systems may contain thousands or tens of thousands of optical channels, where cumulative errors can have catastrophic consequences. High pitch accuracy not only ensures per-channel performance but also provides the foundation for WDM and parallel transmission. It is a prerequisite for the large-scale commercialization of CPO. Leading industry solutions can control cumulative deviations in multi-channel arrays to extremely low levels, supporting future higher-density evolution.

The Role of Fiber Arrays in CPO
In CPO architectures, fiber arrays undertake the critical task of the “last-mile” connection between the optical engine and external fiber infrastructure. They support high-channel-count fiber bundles for precise docking with PICs, providing detachable or permanent fixed interfaces for easier maintenance and service. At the same time, in CPO, fiber arrays must address more stringent environmental challenges: thermal crosstalk near high-power ASICs, limited package space, and high reliability requirements.

Through fiber arrays, CPO systems can easily integrate WDM, higher-order modulation, and other technologies to further increase bandwidth density. In the future, as silicon photonics advances toward 3D and heterogeneous integration, fiber arrays will evolve into intelligent components integrating more functional modules (such as microlens arrays or power monitoring), supporting deeper “opto-electronic co-packaging” in AI data centers.

GLSUN Fiber Array Solutions
As a trusted supplier in the optical communications field, GLSUN specializes in high-performance fiber array solutions. Its product line covers a wide range of channel configurations, standard and custom pitches (such as 127μm, 165μm, 250μm), and supports various types including polarization-maintaining fibers, optimized specifically for silicon photonics packaging and CPO applications.

GLSUN Fiber Arrays feature low insertion loss, high pitch precision, and high reliability. They are widely used in optical communication modules, silicon photonics PIC packaging, MEMS systems, optical sensors, and AI data center interconnects. Leveraging its in-house chip and device R&D capabilities, GLSUN offers end-to-end support from design to mass production, helping customers accelerate product iteration and reduce overall system costs. Its solutions emphasize production consistency and environmental adaptability, making them a preferred choice for many high-end optical modules and CPO projects.

Challenges and Future Outlook
Despite the bright prospects, the application of fiber arrays in CPO still faces challenges in thermal management, alignment automation, and cost control. In the future, with advanced packaging technologies (such as TSMC COUPE) and new materials, fiber arrays will evolve toward higher density, lower cost, and smarter integration. The continued expansion of AI data centers will further accelerate the maturation and adoption of this technology.

Conclusion
Fiber Arrays are not only the “unsung heroes” in silicon photonics and CPO technology systems but also the key enablers connecting the chip world with fiber networks. In today’s era where AI is reshaping the global computing landscape, choosing high-quality fiber array solutions—such as those from GLSUN—will provide solid support for data center construction. Looking ahead, optical interconnect technologies will continue to drive AI innovation, making computing more efficient and greener.