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Tags: Innovation, Optical
July 24, 2019

The Solution to the Toughest Problem Is Often the Simplest – A Lesson Learned from a Boy Scout

By Fady Masoud
Principal, Solutions Marketing


Having spent most of my youth as a Boy Scout, I’ve had the chance to learn numerous tips and techniques to help overcome a challenge or solve a problem. A quick example comes to mind: when lost in the woods, look to see which direction the trees – especially pines – are permanantly leaning in. This gives you an indication of the regular wind direction, and from it you can determine the four cardinal directions if you know your area’s normal wind patterns. You could also follow the water stream, as water goes from higher to lower ground and people tend to settle in valleys because they are close to water.

Ultimately, what I learned as a Boy Scout can be distilled down into these words of wisdom: Look around, observe, analyze, and the solution to your problem is often the simplest one.

Decades later and after spending 23 years (and counting!) in telecom, I’ve come to the conclusion that the Boy Scout way of solving a problem is still the right one. Let me explain.

Unfortunately, there is a common perception across many industries, not only in telecom, that powerful and advanced technologies have to be complicated to use and operate, or else they are just ordinary. Somehow the degree of complexity is a metric of how sophisticated and advanced a technology is!  I’ve seen this pattern over and over again, where hardware and software engineers burn the midnight oil to tackle complex customer problems and create a solution that everybody cheers for, only to later realize that it is complex and hard to operate. Complex solutions for complex problems – but it doesn’t have to be that way.

A few years ago, I was thrilled to witness firsthand the Boy Scout mantra being used to evolving the optical network to improve capacity-reach performance. Once again, I realized the merit and value of such an approach.

As we move to higher wavelength speeds with higher-order modulation (bits per symbol) and higher baud rates (symbols per second), non-linear effects, including self-phase modulation (SPM) and cross-phase modulation (XPM), have an increasingly significant impact on the maximum possible reach for a given level of capacity.  If we look at what happens to these non-linear effects in the 0 to 30 gigabaud (Gbaud) range, we see that as SPM decreases, XPM increases, creating a natural baud rate sweet spot between 4 Gbaud and 12 Gbaud. The problem is that as we increase the baud rate to maximize wavelength speed and reduce the cost per bit, we move further and further away from this sweet spot.

 Figure 1: XPM and SPM Penalties vs. Baud Rate

Infinera’s engineers somehow used the same Boy Scout mantra by observing, analysing, and coming up with the simplest solution to the toughest problem – Nyquist subcarriers. Nyquist subcarriers divide a high-baud-rate carrier into multiple subcarriers, each with a baud rate, you guessed it, in this sweet spot. For example, Infinera’s fourth-generation Infinite Capacity Engine (ICE4) optical engine divides a ~32 Gbaud wavelength into four 8 Gbaud subcarriers, while Infinera’s ICE6 optical engine will divide an ~88 Gbaud wavelength into eight 11 Gbaud subcarriers.

 

Figure 2: Nyquist Subcarriers

This not only solved the problem, it also opened the door for new world records in optical performance. Nyquist subcarriers, along with other performance-enhancing features like pulse shaping and spacing, have led Infinera to set two new industry records in spectral efficiency. We achieved 6.21 bits (b) per second (s) per hertz (Hz) over 6,644 kilometers (km) over the MAREA subsea cable from Virginia Beach, Virginia to Bilbao, Spain using 16 quadrature amplitude modulation (16QAM) for a total of 26.2 terabits per second (Tb/s) per fiber. We also demonstrated 4.5 b/s/Hz over 10,600 km over the Seabras-1 subsea cable from New York City to São Paulo, Brazil, using 8QAM and achieving 18.2 Tb/s total capacity per fiber. Both these achievements were made possible due to breakthrough innovation on our current generation of optical engine, ICE4, which will be further enhanced for the next generation, ICE6.

No matter how many years later and no matter what industry or application they are applied to, some words of wisdom (and ways of thinking) never lose their sparkle. The Boy Scout was right!