PISA, ITALY — Scientists at the Sant’Anna School of Advanced Studies in Pisa, Italy, say they successfully tested what they are calling “the world’s fastest WiFi network.”The experiment transmitted data uninterrupted for 12-hours at speeds above 1.2 terabits per second using a technology called “free-space optical communications.” Unlike traditional broadband over fiber-optic cable or WiFi transmission which employs radio waves, free-space optical communication uses light to send and receive data.

According to the Harvard Broadband Communication Laboratory, “Free-space optical communications is a line-of-sight technology that transmits a modulated beam of visible or infrared light through the atmosphere for broadband communications. In a manner similar to fiber-optical communications, free-space optics uses a light-emitting diode or laser (light amplification by stimulated emission of radiation) point source for data transmission. However, in free-space optics, an energy beam is collimated and transmitted through space rather than being guided through an optical cable. These beams of light, operating in the TeraHertz portion of the spectrum, are focused on a receiving lens connected to a high-sensitivity receiver through an optical fiber.”

Scientists have theorized free-space optical communications could be used for inter-satellite communications and communication with spacecraft.

“It is possible to transmit tens of megabits per second or more over many thousands of kilometers, using moderate laser average powers of the order of a few watts” in the vacuum of space, the Harvard lab notes. Such transmission is not quite as easy on Earth, however, because of atmospheric limitations (primarily fog and turbulence) that constrain distances to only a few kilometers. Water in Earth’s atmosphere “can modify light characteristics or completely hinder the passage of light,” according to the lab’s explanation. In addition, wind eddies can bend or otherwise displace light beams.

Perhaps the most significant limiter of effective free-space optical transmission is physical obstacles, since light beams cannot bend around objects.

The previous record, set by Korean scientists using radio waves, was 160 gigabits per second. Until the Pisa experiment, it was thought that speeds in the terabits range could be accomplished only over fiber-optic cable.