Researchers at Chalmers University of Technology have developed an optical amplifier that they expect will revolutionize both space and fiber communication. The new amplifier offers high performance, is compact enough to integrate into a chip just millimeters in size, and crucially, does not generate excess noise.
Optical communication makes it possible to send information over very long distances. The technology is useful in a range of applications, such as space communication and in fiber optic cables for internet traffic.
With communication based on light, rather than radio waves, we could, for example, quickly send high-resolution images from Mars. The information, carried by laser beams, could be sent with high speed from a transmitter on the planet to a receiver on Earth or on the Moon. Optical communication also allows us to use the internet around the world — whether the signal is transferred in optical fiber cables under the seabed or transmitted wirelessly.
Because the light — carrying the information between two distant points — loses power along the way, a large number of optical amplifiers are needed. Without amplifiers, up to 99 percent of the signal in an optical fiber cable would disappear within 100 kilometers.
A well-known problem in optical communication, however, is that these amplifiers add excess noise that significantly impairs the quality of the signal you want to send or receive. The light amplification in the Chalmers project is based on a principle known as the Kerr effect, which so far is the only known approach that amplifies light without causing significant excess noise. The principle has been demonstrated before, but never in such a compact format — previous versions were too bulky to be useful. The new amplifier fits in a small chip just a few millimeters in size, compared to previous amplifiers that have been several thousand times larger.
Additionally, the new amplifiers offer a level of performance high enough that they can be placed more sparingly, making them a more cost-effective option. They also work in a continuous wave (CW) operation rather than a pulsed operation only.
“What we demonstrate here represents the first CW operation with an extremely low noise in a compact integrated chip. This provides a realistic opportunity for practical use in a variety of applications. Since it’s possible to integrate the amplifier into very small modules, you can get cheaper solutions with much better performance, making this very interesting for commercial players in the long run,” said Professor Peter Andrekson. “It can have many practical uses, not only in communication, but in areas including quantum computers, various sensor systems, and in metrology when making atmospheric measurements from satellites for Earth monitoring.”