Making optical cables out of air could boost communication in space

Under our feet, cables carry data between our homes, offices and data centers at a pace that can match the speed of light. The data travels as light that runs through strings made of materials like glass and plastic.

Researchers at the University of Maryland want to do away with the cable altogether and just use air to guide the light. That’s not as simple as it sounds, because a laser sent through air will spread apart and interact with particles, gradually losing its intensity over time.

The research team instead caused patches of air to mimic a fiber optic cable by creating tubes of dense air surrounded by low-density air. In a fiber optic cable, a laser travels through a string of glass. When it tries to leave the glass, it hits a wall that reflects it back into the center, guiding it along the length of the cable. The cable made of air works in the same way.

Traditional fiber optic cables. Photo courtesy of Flickr / pasukaru76.
Traditional fiber optic cables. Photo courtesy of Flickr / pasukaru76.

“It’s like you could just take a physical optical fiber and unreel it at the speed of light, put it next to this thing that you want to measure remotely, and then have the signal come all the way back to where you are,” University of Maryland team lead Howard Milchberg said in a release.

To create the air cable, the team sent short pulses of a high-power laser, which causes particles in the air to collapse into a dense string. The air around it expands, leaving a low-density tube around the core. While the cable only lasts for a few milliseconds, that is a million times longer than the pulse it takes to create it. And Milchberg said for many uses for laser communications, “milliseconds is infinity.”

Signals that traveled through the air cable were 1.5 times stronger than when they were sent through plain air. The team was able to send them over a distance of three feet and is now interested in pushing the range to 150 feet.

If the University of Maryland team succeeds, the air cables could be used for communication in remote locations on Earth where laying fiber optic cables is extremely difficult, or places where it actually is impossible like space. NASA is already experimenting with laser communication between the International Space Station and Earth. The technique could also be used to probe the Earth to make topographic maps or examine the chemicals present in hard-to-reach places like the atmosphere or a nuclear plant.