Breakthroughs in Laser Research

Since the fiber industry relies on laser technology, I periodically look to see the latest breakthroughs and news in the field of laser research.

Beaming Lasers Through Tubes. Luc Thévenaz and a team from the Fiber Optics Group at the École Polytechnique Fédérale de Lausanne in Switzerland have developed a technology that amplifies light through hollow-tube fiber cables.

Today’s fiber has a core of solid glass. As light moves through the glass, the light signal naturally loses intensity due to impurities in the glass, losses at splice points, and light that bounces astray. Eventually, the light signal must be amplified and renewed if the signal is to be beamed for great distances.

Thévenaz and his team reasoned that the light signal would travel further if it could pass through a medium with less resistance than glass. They created hollow fiber glass tubes with the center filled with air. They found that there was less attenuation and resistance as the light traveled through the air tube and that they could beam signals for a much greater distance before needing to amplify the signal. However, at normal air pressure, they found that it was challenging to intercept and amplify the light signal.

They finally struck on the idea of adding pressure to the air in the tube. They found that as air is compressed in the tiny tubes that the air molecules form into regularly spaced clusters, and the compressed air acts to strengthen the light signal, similar to the manner that sound waves propagate through the air. The results were astounding, and they found that they could amplify the light signal as much as 100,000 times. Best of all, this can be done at room temperatures. It works for all frequencies of light from infrared to ultraviolet and it seems to work with any gas.

The implications for the breakthrough is that light signals will be able to be sent for great distances without amplification. The challenge will be to find ways to pressurize the fiber cable (something that we used to do fifty years ago with air-filled copper cable). The original paper is available for purchase in nature photonics.

Bending the Laws of Refraction. Ayman Abouraddy, a professor in the College of Optics and Photonics at the University of Central Florida, along with a team has developed a new kind of laser that doesn’t obey the understood principles of how light refracts and travels through different substances.

Light normally slows down when it travels through denser materials. This is something we all instinctively understand, and it can be seen by putting a spoon into a glass of water. To the eye, it looks like the spoon bends at that point where the water and air meet. This phenomenon is described by Snell’s Law, and if you took physics you probably recall calculating the angles of incidence and refraction predicted by the law.

The new lasers don’t follow Snell’s law. Light is arranged into what the researchers call spacetime wave packets. The packets can be arranged in such a way that they don’t slow down or speed up as they pass through materials of different density. That means that the light signals taking different paths can be timed to arrive at the destination at the same time.

The scientists created the light packets using a device known as a spatial  light modulator which arranges the energy of a pulse of light in a way that the normal properties if space and time are no longer separate. I’m sure like me that you have no idea what that means.

This creates a mind-boggling result in that light can pass through different mediums and yet act as if there is no resistance. The packets still follow another age-old rule in Fermat’s Principle that says that light always travels to take the shortest path. The findings are lading scientists to look at light in a new way and develop new concepts for the best way to transmit light beams. The scientists say this feels as if the old restrictions of physics have been lifted and has given them a host of new avenues of light and laser research.

 The research was funded by the U.S. Office of Naval Research. One of the most immediate uses of the technology would be the ability to communicate simultaneously from planes or satellites with submarines in different locations.  The research paper is also available from nature photonics.

 

The Fragile Supply Chain

The recent outbreak of the coronavirus reminded us how fragile the supply chain is for telecom. As it turns out, the Hubei province of China is where much of the world’s optics and lasers are built that are the key component in every device that is used to communicate in a fiber network. Within days after the reality of the virus become apparent, the stocks of tech companies that rely on lasers took a hit.

The supply chain for electronics manufacturing stretches worldwide. The lasers are made in one place. The chips in devices are made somewhere else. Other electronic components come from a third geographic source. Components like cellphone screens and other non-electric components come from yet a different place. And the raw materials to make all of these devices come from markets all over the world.

The virus scare made the world wake up to the fragility of the supply chain. Without lasers, there would be no fiber-to-the-home devices manufactured. There would be no new servers in data centers. There would be no new small cell sites built or activated. Major industries could be brought to their knees within weeks.

It’s not hard to understand why I say the supply chain is fragile. Consider smartphones. There are probably a dozen components in a smartphone that must be delivered on time to a smartphone factory to keep the manufacturing process going. If any one of those components can’t be delivered, smartphone manufacturing comes to a halt. The manufacturing floor can be crippled by a lack of screens just as much as it can suffer if the chips, antennas, or other key electronic components become unavailable.

It’s impossible to know if the coronavirus will cause any major disruption in the supply chain for fiber optics – but the point is that it could. If it’s not a virus today, disruptions could come from a wide range of natural disasters and manmade problems. I remember a fire that destroyed a fiber optic cable factory a few decades ago that created a major shortfall of optic cables for a year. Floods, fires, earthquakes, and other disasters can knock out key manufacturing sites.

Manmade disruptions to the supply chain are even easier to imagine. We saw the price of electronics components shoot up over the last year due to tariff battles between the US and China. The supply chain can be quickly cut if the country making devices goes to war, or even undergoes an ugly regime change. It’s also now possible to weaponize the supply chain and threaten to cut off key components when negotiating other issues.

I’m sure that very few Americans realized that the Wuhan region has a near-monopoly on the manufacture of lasers. A worldwide economy rewards the creation of monopolies because components are cheapest when an industry takes the most advantage of the economy of scale. The companies in the Wuhan region can likely manufacture lasers cheaper than anybody else.

From a strategic position, countries like the US should foster their own industries to manufacture vital components. But that’s not easy or practical to achieve. A new US company trying to compete on the world stage by making lasers is likely to be more expensive and unable to compete when the supply chain is humming at normal capacity. It’s hard to picture creating a competitor to the Wuhan region that can manufacture lasers in the quantities, and at a price the market is willing to pay.

In the long run, the world always finds alternate solutions to any permanent changes in the supply chain. For example, if China is ever unable to export lasers, within a few years other countries would pick up the slack. But the fiber industry would be devastated during the lull needed to find a new source of components. Bank of America reported last year that 3,000 major manufacturing companies were already reconsidering their supply chain due to tariff and other concerns. Some of these companies, particularly electronics companies have been considering bringing production back to the US now that factories can be heavily robotized. I’m sure the coronavirus has accelerated these decisions.