Multi-fiber testing is not new – it has been a part of networking for nearly a decade. What is new, however, is the scale at which it is reshaping the way data centers are built and operated. A major industry challenge is understanding the evolving role of fiber testing – its purpose, the right way to conduct it, and how to verify its accuracy.

The timing is critical. As artificial intelligence and machine learning drive unprecedented demand on cloud providers, data center expansion has become one of the most capital-intensive priorities in telecommunications. Meeting that demand depends on robust networks, making multi-fiber testing not just an established practice, but a key enabler of the next era of connectivity.

From his early days as a technician, through years of leading product strategy and technician training programs, Ed Gastle, director of product line marketing and management at Viavi, has seen firsthand how testing practices have grown alongside the networks themselves. Today, he continues to help guide that progression – not only within Viavi, but also globally through the Standards Council of Canada, where he represents the country at the IEC and helps define the international standards for fiber optic testing.

At Viavi, Gastle leads the essential fiber and access solutions team, which spans everything from fiber-to-the-home to the complex architectures powering today’s data centers. For them, fiber testing and sensing are not just tools, but essential capabilities.

The multi-fiber wave

Technologies like the multi-fiber push-on (MPO) connector have been in use for more than two decades, traditionally serving as a way to bundle large groups of fibers together for backbone cabling. Up to now, they served as a means to split fibers into smaller two-fiber (duplex) connections at the optical layer, supporting the direct links that carry data traffic.

Today’s data centers, driven by the explosive demands of AI and machine learning, are rapidly scaling to operate at speeds of 400G, 800G, 1.6T, and beyond – bandwidths that can only be supported by multi-fiber connectivity running directly to the optics themselves. Not long ago, most new fiber installations began using Lucent (LC) connectors. Now, MPO connectors are becoming the standard, and data center cabling is adapting to keep up, with newer options like miniature multi-fiber connectors (MMCs) also starting to appear. As Gastle explains, the implications are profound:

“In a single rack unit, small-form-factor connectors can now pack more than 6,000 fibers, delivering the density required by hyperscale environments. High-performance computing, particularly the need for ultra-fast connections between GPUs, is accelerating this trend, pushing data centers into a new multi-fiber era.”

Legacy testing reconsidered

Historically, fiber testing in data centers relied on what Gastle describes as the fan-out method, using a duplex tester to measure two fibers at a time. In smaller deployments, this approach worked well, but in today’s hyperscale data centers – where tens of thousands of multi-fiber links are the norm – the sheer volume of required tests has rendered legacy methods unsustainable.

With legacy testing, collating and processing massive amounts of data quickly becomes a bottleneck, potentially putting pressure on teams to cut corners. Yet, as the last step before a network goes live, testing is critical and skipping or rushing this process risks costly troubleshooting and delays when problems inevitably surface.

The urgency of this shift was made clear during the Covid-19 pandemic, when remote work drove unprecedented demand for platforms like Microsoft Teams. Operators were forced to scale data center capacity faster than ever before.

Gastle recalls one facility on the verge of going live, only to find that legacy testing methods couldn’t keep pace with the timeline. By deploying Viavi’s multi-fiber tester, the contractor could speed up validation across all fibers simultaneously, enabling the data center to come online on schedule – proving that speed and accuracy in testing can be mission-critical. These real-world demands highlight Gastle’s straightforward but essential principle:

“Number one, test everything. Don’t cut corners on the testing – that causes problems later.”

Moreover, the complexity of modern multi-fiber infrastructure introduces new challenges – they are validating 12, 16, or 24 fibers at a time, dramatically increasing throughput. When different connectivity types exist at opposite ends of a link, standard test procedures aren’t sufficient, as each scenario requires a customized approach. Any cloud provider, contractor, or cabling vendor can encounter issues if these non-standard setups aren’t handled properly.

Gastle’s team at Viavi leverages deep standards expertise and decades of hands-on experience to bridge that gap. By developing practical testing methodologies, providing training and job aids, and supporting contractors on-site, they ensure that multi-fiber networks are validated efficiently and accurately – helping data centers go live quickly without compromising reliability.

How high are your standards?

In modern data centers, technicians strive for 100 percent testing – validating every link installed, which can mean tens of thousands of individual connections. Testing typically involves a loss test aligned with Tier 1 certification standards, measuring loss, length, and polarity, while also accounting for fiber end-face inspections. These results are not just for network operators; they are often shared with cabling vendors and can form the basis of infrastructure warranties, highlighting just how critical thorough testing is.

Gastle explains that Tier 1 certification has existed for decades and covers fundamental fiber testing. Tier 2 certification goes further, incorporating optical time domain reflectometer (OTDR) testing to pinpoint faults, splices, or bends – but it is more commonly applied in campus networks than inside hyperscale data centers.

“Tier 1 has been in the standards since the mid-90s. Those standards were written for duplex or simplex fiber runs, not for multi-fiber systems. The industry has had to create new standards specifically for multi-fiber deployments,” Gastle points out, adding:

“The rise of MPO connectors – and now MMC connectors with even higher fiber counts – has pushed the industry beyond existing standards. Updating standards can take three to five years, but data center operators can’t afford to wait. They need to adopt best practices that make operational sense, even before formal standards catch up.”

In this rapidly evolving environment, flexibility, expertise, and practical testing approaches are essential to ensuring reliable, high-density fiber infrastructure while standards continue to evolve.

Bringing fiber testing into the 21st century

Welcome to 2025, where automation is transforming fiber testing and data center build-outs. Today, multi-fiber testers perform rapid, high-volume testing without the need for fan-out cables – but testing speed is only one part of the equation.

Even as technology advances, the technician remains central. Many engineers and technicians may not have specialized fiber experience, yet they are now tasked with managing vast amounts of fiber. According to Gastle, test process automation (TPA) acts as a virtual project manager, coordinating jobs through online systems, dispatching tasks to technicians, and handling time-consuming elements like labeling each individual link. This dramatically reduces manual effort, allowing technicians to focus on testing itself rather than setup. Gastle explains the impact:

“Instead of taking a tester, connecting it to a computer, and manually transferring results, all test data now flows to the cloud. Data center managers – who may be in a different city or even continent – can access results in real time, verify them, and generate closeout reports. By automating this process, every small step flows smoothly, visibility is continuous, and data centers can be turned up faster.”

In essence, automation doesn’t replace the technician – it amplifies their effectiveness, enabling faster, more accurate testing, streamlined reporting, and ultimately, quicker deployment of high-density data center networks.

As part of its operational design, Viavi emphasizes creating systems that make the testing process as smooth and intuitive as possible, reducing the need for unnecessary interactions with the instrument. Gastle explains:

“A test cycle starts when you save one result and ends when you save the next. Traditionally, a technician would have to move physically to the next port, set up the tester, initiate the test, and save the result. Each cycle could involve six or more steps, which adds frustration and slows progress. By automating functions like auto-saving results and auto-incrementing labels, you make the process cleaner and easier. Technicians go home feeling productive instead of frustrated.”

In data centers, time is money. A single error out of thousands of fiber tests can cause costly delays and rework. Streamlining the technician’s workflow doesn’t just improve morale – it has tangible operational and financial impacts.

“The impact for data center owners and operators is clear – projects are completed faster and more efficiently. Multi-fiber testers combined with test process automation enable data centers to be delivered more quickly than with legacy methods. Contractors are increasingly expected to use these tools – it’s becoming the industry standard.”

By bringing the human into the design, automation and advanced testing systems allow technicians to work efficiently, accurately, and confidently, while data centers benefit from faster, more reliable deployment.

Dear contractors, cloud providers, and consultants…

The multi-fiber wave is here, and data centers can no longer rely on methods that are 15 to 20 years old. To keep pace with today’s multi-fiber, high-speed networks, testing approaches must modernize, balancing speed, accuracy, and operational efficiency. Gastle’s message resonates across all corners of the data center ecosystem:

For contractors to compete in cloud provider environments, mastering multi-fiber testers and adopting test process automation is essential. Without these capabilities, securing projects in high-speed, high-density networks becomes increasingly challenging.

For cloud providers, while the largest players already understand the stakes, legacy testing methods are no longer sufficient for second- and third-tier providers entering multi-fiber environments.

And for consultants, who often draft the standards and specifications for network deployment: embrace multi-fiber testing techniques and the automation systems that make testing faster, more accurate, and future-proof, ensuring that guidelines reflect the realities of today’s data center infrastructure.

For more information, visit viavisolutions.com/en-us/solutions/hyperscale.