For artists and romantics, flashing stars is visual poetry. A dance of distant light as it turns and bends across a turbulent ocean of air above our heads.
Not everyone is so fascinated by our atmospheric distortions. For many scientists and engineers, a large amount of research and communications from Earth to the satellite would be a lot easier if there were no air.
Losing a protective gas bubble on our planet is not an entirely common option. But Australian and French researchers teamed up to design the next best thing – a system that directs light through stormy currents of corrugated air by flicking a mirror.
The result is a laser link that is able to maintain stability through the atmosphere with unprecedented stability.
While astronomers have a few tricks up their sleeve to correct it Atmospheric distortions For incoming light, it was difficult to send a coherent beam of photons from the ground to a distant receiver so that they remained together and on a point.
Keeping the transmissions on target and coherent – with their phases remaining precisely – across hundreds of kilometers of air diversion will allow us to connect high-precision measuring instruments and communication systems.
Satellites can search for materials or assess water levels with improved accuracy. High-speed data transfer may require less power and contain more information.
Lead author Ben Dicks Matthews, an electrical engineer at the International Center for Radio Astronomy Research in Australia, explained the technology to ScienceAlert.
“The active terminal mainly uses a small quad-pixel camera, which measures the lateral motion of the received beam,” says Dix-Matthews.
“This position measurement is then used to effectively control a steerable mirror that maintains the received beam in the center and eliminates the sideways motion caused by the atmosphere.”
In fact, the system can be used to compensate for the twisting effects of moving air in three dimensions – not just up and down, or left and right, but along the beam path, while keeping the link centered and its phases in order.
So far, it has only been tested over a relatively short distance of 265 meters (about 870 feet). About 715 meters (just under half a mile) of underground fiber-optic cable ran between the transmitter and receiver to carry a beam for comparison.
The results were so stable that they could be used to relate the types of optical atomic clocks used to test basic physics, such as Einstein’s theories of relativity.
With proof of concept being correct, there is no reason to believe that a similar approach will one day never aim at heaven and beyond. Although there are some hurdles that have to be overcome first.
“During this experiment we had to do the initial alignment manually, using a visible pointing laser aligned with the stable infrared beam,” Dix-Matthews told ScienceAlert.
“When creating bonds between optical atomic clocks, it would be nice to have a way to do this rough alignment more easily.”
Fortunately, the French collaborators are working with Dix-Matthews on a device that will speed up the rough initial alignment process, promising a second generation of laser-linking technology that won’t require such setup included.
The team also found that temperature differences in the equipment affected phase stability, limiting the signal duration to around 100 seconds. This obstacle will also be the focus of future improvements.
We may not need to wait long. Researchers are already making progress with upgrades to their systems.
“We are starting to use a high-powered laser amplifier that should help us deal with the larger energy losses expected over longer distances, such as space,” says Dix-Matthews.
“We have also completely rebuilt our active terminal to make it more sensitive to the low energies received and to make it more effective in canceling the motion of the received beam.”
As orbital technology is rapidly becoming a major focus of many data providers, and it is likely to fill our skies with satellites, the innovations that make connecting communications systems across our atmosphere will become even more demanding.
As useful as our atmosphere is, well, to keep us all alive, there are definitely some downsides to being buried under a blanket of warm gas.
This research was published in Nature Communications.
