Jay Tourigny discusses the challenges of cleaning high-density fibre connections in giant data centres and how they can be overcome
Today, the demand for fast, flawless connectivity is expanding around the globe. High-speed networks allow instant access to data-intensive apps on billions of devices worldwide while the Internet of Things allows them to seamlessly interact with one another. Autonomous vehicles, augmented reality and fully automated home systems including virtual assistants and smart appliances will soon be the norm. In addition, online selling, social media and tele-education continue to make our lives more convenient and connected.
The one thing that makes this connectivity possible is an effective and reliable network to manage the large volume, or big data, required to operate it all. Data-driven companies are constantly developing ways to manage their users’ data demand and the high traffic associated with it. One current solution is to use very large, or hyperscale, data centres.
On average, the footprint of a hyperscale data centre is 200,000 square metres or larger. Millions of servers inside the centres operate together via fibre optic networks to control the massive amount of data traffic that users require. The networks typically comprise hundreds of thousands of metres of fibre optic cable and hundreds of thousands of optical connections. The data centres allow fast and efficient data handling. However, they do have some drawbacks.
Data centre concerns
Since the data centres are so large, they are often built in remote areas where there are more wide-open spaces and land is less expensive. However, locating a data centre far away can cause performance problems including latency delays. These time degraded responses are unacceptable for many critical applications such as GPS responses for military systems, remote medical monitoring and diagnostic results or vital financial transactions.
Also, because of the mass volume of servers, hyperscale data centres run very hot and require extensive cooling. In an attempt to keep hyperscale data centres cool, companies often employ power-hungry climate control systems that use enormous quantities of electricity and emit large quantities of greenhouse gases.
More fibre, smaller footprint
One solution to these concerns is to make data centres smaller, closer, and more energy efficient. Achieving these goals requires squeezing more fibre into a smaller footprint. Fortunately, fibre optic cable makers have changed cable construction in a way that enables them to pack thousands more optical fibres into a single cable. Just a few years ago, an 864-fibre cable was considered a huge trunk. Today, typical fibre counts are 1,728, 3,456, and 5,184.
Recently, a UHCF (ultra-high-count fibre cable) with 6,912 fibres was introduced into the industry and a 7,776-fibre version is on the horizon. The result is UHCF cables that carry double or triple the data in the same or even less space. This reduces the size of the data centre, allowing for more accessible data centre locations and better energy efficiency.
Fibre connectors
However, the higher the fibre count of the cable, the more vulnerable the connectors and end faces are to contamination. All connectors are inherently dirty because of the moving parts like springs, connectors, and latches, all of which generate wear debris. Therefore, to get absolute reliability and uninterrupted service from any UHCF network it is important that all connectors are cleaned and inspected to meet IEC 61300-3-35 standards prior to installation. This helps avoid potential fibre network problems such as insertion loss (weakened signal), back-reflection (signal is diverted back to its source) or a complete system shut down.
There are three newer types of connector options used with UHCF cables that aggregate more fibre into a smaller footprint: CS duplex connector system for the next-generation QSFP-DD transceivers, the 16 fibre-array MT-based connector, and lens-array ferrules for parallel optic and silicon photonics applications. All have their advantages and all bring their own cleaning challenges.
These connectors utilise the standard 1.25mm LC form factor ferrule, but with tighter spacing between the ferrules. With the CS design, pitch is reduced to 3.8mm from the LC standard of 6.25 mm. The result is a theoretical capacity increase of 80 per cent. The small size of these connectors along with very tight clearances on CS adapters makes it difficult for many cleaning tools to get inside the ferrule. Use high absorbency, non-linting fibre cleaning sticks with a high-purity fibre cleaning fluid to clean these connectors. Or, for cleaning large numbers of connectors a mini click-to-clean tool typically works best.
Multi-fibre connectors
Some cable manufacturers are migrating from the traditional 12-fibre arrays to a 16-fibre array using the same 2.5mm x 6.4mm standard MT ferrule footprint. These connectors are most often used on optical backplanes, where the data jumps from the fibre transport into the switch for routing. Not only are these connectors denser, they are 80 per cent glass to improve thermal expansion control. These connectors often retain more static electricity than other connectors making dust particles cling to the connector. The use of an optical-grade, static-dissipating cleaning fluid is important to dissipate the static-cling and significantly improve cleaning performance of task-built clickers.
The lens array connectors basically are expanded beam lenses on a microscopic scale. These designs collimate the optical signal and eliminate the need for physical contact. They use a very small, tightly focused ‘spot size’ beam to pass the signal into the receiving lens. This design minimises problems associated with scratching and contamination between the lenses. However, these connectors are typically made from very soft, easily-scratched moulded plastics that over time tend to attract dust in the form of a hazy film into the central signal ‘spot-zone’ and can be difficult to clean.
To prevent scratching the plastic, the most effective cleaning method uses a ‘touchless’ process of applying a small dose of high purity cleaning fluid that is fast-evaporating, plastic-safe and static-dissipating to gently rinse away surface contamination, and then follow-up by blow-drying the connector using a can of optical-grade duster.
The increasing demand for more connectivity spurred the rise of remote hyperscale data centres. However, with the introduction of UHCF cables, smaller local data centres may now be able to deliver the data speeds and reliability that end-users require. But to obtain the best fibre optic performance, cleaning the fibre end-faces prior to installation will always remain a priority.
Jay Tourigny is senior vice president at MicroCare
