In a promising breakthrough in the future of communications, researchers at EPFL (Federal Polytechnic School of Lausanne, Switzerland) have developed technology that can amplify light in the latest hollow-core optical fibers. The results of the discovery of scientists are reported by the journal Nature Photonics.
Luc Thévenaz, the head of the fiber optics group at the EPFL School of Engineering, admitted that the idea “hovered” in his head for about 15 years, but he did not have the time or resources to do something with it. Now his laboratory has developed technology to amplify light inside the latest hollow-core optical fibers.
Modern optical fibers usually have a strong glass core with no air inside. Light can propagate along fibers, but after 15 km it loses half of its intensity. It continues to weaken until it is difficult to detect and from a distance of 300 km. Therefore, in order for the light to continue to move, it must be regularly amplified.
Thevenaz’s approach is based on new hollow-core optical fibers filled with air or gas. Air means less signal attenuation, so light can travel a greater distance. This is a real advantage. But in a substance as “thin” as air, it is more difficult to amplify light. This is the crux of the problem: light travels faster when there is less resistance, but at the same time it is more difficult to act on it. However, the discovery of scientists solved this problem.
So what did the researchers do? They simply added pressure to the air in the fiber to create controlled resistance. It works in a similar way to optical tweezers – air molecules are compressed and form clusters with a regular distance between them. This creates a sound wave that increases in amplitude and effectively diffracts light from the powerful source towards the attenuated beam so that it is amplified up to 100,000 times. Thus, the technique of scientists makes the light much more powerful.
The new technology can be applied to any type of light, from infrared to ultraviolet, as well as any gas, the scientists conclude.
In the future, this technology may serve other purposes besides light amplification. For example, hollow-core or compressed gas optical fibers can be used to make ultra-precise thermometers. The technology can also be used to create temporary optical memory by stopping light in a fiber for a microsecond – ten times longer than is currently possible.