Technical Route Analysis of the Fiber Through Hole Plate in MEMS-Based OCS Solutions

Amid the explosive growth of AI computing power and the restructuring of hyperscale data centers, Optical Circuit Switches (OCS) are rapidly moving from laboratories into large-scale commercial deployment. Cloud providers such as Google have already deployed MEMS-based OCS at scale in their TPU clusters, enabling millisecond-level optical path reconfiguration, ultra-low latency, and significant power savings. The MEMS approach currently dominates the OCS market thanks to its high maturity, low insertion loss, and strong port scalability. Within this technical route, one seemingly modest yet critically important component—the Fiber Through Hole Plate (also known as the fiber hole plate or fiber through-hole array plate)—has emerged as a key technology that determines the upper limits of system performance and reliability.

1. The Fiber Through Hole Plate: The Precision Foundation of MEMS OCSThe operating principle of a MEMS OCS is straightforward: light from input fibers is converted into collimated free-space beams by a lens array and directed onto a first two-dimensional array of tiltable MEMS micromirrors. The mirrors deflect according to control instructions, steering the beams toward a second micromirror array, which reflects them into the target output fibers—achieving any-to-any all-optical switching without optoelectronic conversion. The system is protocol- and rate-transparent.

To support high-density switching at hundreds of ports, the optical fibers must be precisely fixed in a two-dimensional grid that matches the MEMS micromirror array one-to-one. The Fiber Through Hole Plate performs exactly this function: it is a substrate containing a high-precision array of through-holes through which the fibers pass and are secured. The plate is then precisely aligned with a microlens array to form the fiber collimator.

The accuracy of the hole plate directly governs:
· Fiber positioning and pointing errors,
· Alignment margin between the optical spots and the micromirrors,
· System insertion loss, crosstalk, and long-term stability.

If hole-position deviations exceed tolerance, even the most precise MEMS mirror control cannot fully compensate, and overall optical performance suffers. Far from being a simple “perforated plate,” the Fiber Through Hole Plate is one of the highest-precision components in the entire MEMS OCS optical system.

2. Technical Challenges: The Triple Demands of High Precision, High Density, and High ReliabilityAs port counts scale from tens toward 136×136 and beyond, the hole plate faces stringent requirements:
· Positional accuracy and verticality — Hole-center positioning errors must typically be controlled to the micron or even sub-micron level; hole walls must be highly vertical and smooth to ensure consistent fiber axial alignment and pointing after insertion.
· Material compatibility — The substrate must match the thermal expansion coefficients of the fibers and lens array to minimize temperature-induced misalignment.
· Mechanical strength versus manufacturability — The plate must be sufficiently thick to provide mechanical support and reliable fiber retention, while still allowing the fabrication of high-aspect-ratio precision through-holes.
· Batch consistency — Hundreds of holes must simultaneously meet both global and local error budgets; yield directly impacts cost.

Traditional processes have relied on silicon deep reactive-ion etching (DRIE), precision mechanical drilling, or polymer substrates combined with micro-ferrules. These approaches can meet the needs of moderate port counts, but struggle with high-density, high-reliability applications due to rough hole walls, limited aspect ratios, suboptimal thermal stability, or high assembly complexity.

3. Evolution of Mainstream Technical Routes: From Silicon to Glass FLICECurrent Fiber Through Hole Plate technology is advancing along two main axes—material and process:

1. Silicon-based hole arrays
Early and some existing solutions use silicon, forming through-hole arrays via semiconductor processes. Silicon offers high processing precision and good compatibility with MEMS fabrication, yet its brittleness, thermal expansion characteristics, and fiber-retention constraints limit performance in thick-plate, high-aspect-ratio scenarios.

2. Glass-based hole plates fabricated by femtosecond laser irradiation followed by chemical etching (FLICE)
A more advanced route that has gained significant attention employs fused silica or similar glass materials processed by FLICE.The process involves first irradiating the glass with a femtosecond laser to create precise three-dimensional modified regions, then immersing the plate in a selective chemical etchant (typically a hydrofluoric-acid-based solution). Only the laser-modified volumes are etched, forming high-precision fiber pathways that extend completely from one side of the plate to the other.

Key advantages of this approach include:
· Ultra-high precision and controllable geometry — Cylindrical or variable-cross-section holes with highly vertical, smooth sidewalls can be formed, enabling tighter fiber-to-wall contact.
· Support for thicker substrates — Overcomes the limitations of traditional thin plates, improving mechanical strength and fiber retention reliability while reducing the risk of fiber loosening.
· Excellent optical and thermal stability — Glass offers low birefringence and a thermal expansion coefficient better matched to optical fiber, helping suppress temperature drift.
· High batch consistency — Laser direct writing combined with selective etching is inherently well-suited to complex arrays, allowing simultaneous control of global and local errors.

Patent literature and technical disclosures indicate that fiber collimators built with FLICE glass hole plates achieve significantly tighter alignment of fibers to their intended positions. This enables smaller MEMS mirrors, longer free-space optical paths, or higher port density within the same volume—ultimately improving overall OCS performance and scalability.In addition, the hole plate can incorporate alignment features that facilitate passive alignment with the lens array, further reducing assembly difficulty and cost.

4. System-Level Value Delivered by Advances in the Hole PlateImprovements in the Fiber Through Hole Plate are not isolated; they amplify the competitiveness of the entire MEMS OCS:
· Lower insertion loss and higher reliability — Better alignment precision translates into reduced coupling loss and crosstalk, supporting long-term stable operation.
· Enhanced port scalability — Higher port counts become feasible within the same physical footprint, or more compact designs become possible at a given port count.
· Cost and supply-chain optimization — As processes such as glass FLICE mature, the manufacturing barrier for high-port-count collimators is lowered, accelerating the transition of OCS from customized to volume production.
· Alignment with AI data-center requirements — Proven 136-port-class MEMS OCS deployments (e.g., Google’s) place extremely tight demands on optical alignment margins; advanced hole plates are one of the key enabling technologies supporting this scale.

5. GLSUN 3D MEMS OCS: Exploring Next-Generation Optical Interconnects
As a company focused on optical switching and optical communication technologies, GLSUN continues to develop 3D MEMS optical switching solutions for applications such as data center interconnects, AI computing networks, and other scenarios requiring flexible optical path management.

3D MEMS OCS uses micromirrors to establish optical connections between different ports, providing flexible optical path connectivity. Compared with switching approaches that require optical-electrical conversion, OCS can eliminate unnecessary conversion stages in suitable applications, offering new possibilities for network architecture optimization.

As OCS systems scale to higher port counts, the key engineering challenges extend beyond individual component performance to encompass overall optical design, precision structures, assembly processes, control systems, and scalable manufacturing capabilities.

For precision positioning technologies such as Fiber Through Hole Plates, their real value lies not simply in adopting a particular structure, but in how effectively that structure integrates with the MEMS optical system to support stable optical alignment, reliable channel performance, and repeatable manufacturing quality.

GLSUN will continue to explore optical switching technologies and related optical communication products, providing more solution options for the development of AI data centers and high-speed optical interconnects.

6. Outlook: The Hole Plate as a Differentiating Element in the OCS Supply ChainAs AI training clusters push optical interconnects toward extreme bandwidth, latency, and energy-efficiency requirements, OCS is evolving from an optional technology into a necessity. MEMS solutions will remain dominant in the near term, and the Fiber Through Hole Plate—serving as the precision bridge between the fiber domain and the micromirror domain—will directly influence system performance, cost, and supply capability.

Advanced processes such as glass FLICE are transforming the hole plate from a precision bottleneck into a performance lever. Looking ahead, the organizations that best balance hole-position accuracy, material stability, batch yield, and cost will be best positioned to capture advantageous roles in the OCS value chain.

Though small in size, the Fiber Through Hole Plate carries the large future of all-optical switching. In the ongoing evolution of computing networks toward all-optical architectures, this micron-scale precision technology is quietly determining the reliability and scalability of multi-terabit optical paths.