Just the other day, I was reminiscing about some exploits from the past. One that came to mind was when I had to put together a mock-up to analyze how much Cat6a we could responsibly manage in an 800mm wide 42RU rack. At that time, we established that anything beyond 240 patches would significantly increase the operational risk during moves, adds, and changes. It was also around that time that we created a calculator to determine the amount of copper twisted pair cables that could be installed in a cable tray with specific dimensions.

When I currently look at the high fiber count cable assemblies required to support the bandwidth and connections in the data center for network connectivity, I can’t help but draw a parallel with those previous challenges. Increasing fiber cable sizes in the cable trays and the vast amounts of fiber patchcords in the racks sound very familiar.

And looking at the industry’s forecast, it seems this amount of cables to manage in the racks and data center is only going to increase.

So, I started thinking about how we could deal with this. I looked at some of the solutions that emerged when we faced the copper conundrum, such as the solutions with AWG27 and even AWG28. Why not do the same with fiber?

What if we could use the same fiber but reduce the cladding and coating? This would provide three main advantages:

• It would reduce the diameter of the fiber and thus also the overall diameter for multi-fiber cable assemblies, allowing the installation of more cables in the cable tray or rack.
• It would also improve bending insensitivity, making it better suited for constrained environments, such as racks.
• It would reduce the amount of materials used to produce a cable, thus having an impact on their sustainability footprint.

However, there are a few challenges with producing pre-terminated fiber cable assemblies with reduced cladding and coating. The processes to produce the cable, terminate the connector, and test the assembly are more fragile and demanding. Given the number of fibers per cable and connectors to be terminated, the quality of the termination and getting it right the first time become important factors to reduce cost, lead times, and waste. Furthermore, I can only imagine that the increase in density will most likely use a mix of standard MPO and very small form factor (VSFF) connectors with up to 16 fibers [1].

The use of reduced cladding and coating fibers is not new. 200μm cables can be found in the outside plant (OSP) world for high fiber count blow-in cables and the transceiver world for micro-optic fiber arrays (FA).

Looking at the future, the use of reduced cladding and coating fiber could further lead to a reduction in the connector size, where the current pitch is 250μm.

So what do you think, are you struggling to fit all cables in the cable tray you need to share with the increased space requirements for (liquid)cooling and power?

Which advantages from reduced cladding and coating fiber appeal most to your use case, reduced cable size, increased bend insensitivity, reduced carbon footprint or all three?

I am looking forward to exchanging thoughts about this topic and whether this is something that is currently a challenge you are facing and would need a solution for.

[1] Next Generation Multi-Fiber Ferrule Using 165 Micron Pitch Optical Fiber

Source: Fraunhofer Vision: Machine Vision for Quality Assurance

Source: Rollable Ribbon High Density Optical Fiber Cable | Underground | Optical Fiber Cable | Communications Solutions Division | Furukawa Electric Co., Ltd.