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How To Encode 2.05 Bits Per Photon, By Using Twisted Light
Thorfinn.au writes Researchers at the University of Rochester and their collaborators have developed a way to transfer 2.05 bits per photon by using "twisted light." [Abstract here.]This remarkable achievement is possible because the researchers used the orbital angular momentum of the photons to encode information, rather than the more commonly used polarization of light. The new approach doubles the 1 bit per photon that is possible with current systems that rely on light polarization and could help increase the efficiency of quantum cryptography systems.
205 bits per 100 photons.
Infinite-capacity wireless vortex beams carry 2.5 terabits per second
American and Israeli researchers have used twisted vortex beams to transmit data at 2.5 terabits per second. As far as we can discern, this is the fastest wireless network ever created — by some margin. This technique is likely to be used in the next few years to vastly increase the throughput of both wireless and fiber-optic networks.
These twisted signals use orbital angular momentum (OAM) to cram much more data into a single stream. In current state-of-the-art transmission protocols (WiFi, LTE, COFDM), we only modulate the spin angular momentum (SAM) of radio waves, not the OAM. If you picture the Earth, SAM is our planet spinning on its axis, while OAM is our movement around the Sun. Basically, the breakthrough here is that researchers have created a wireless network protocol that uses both OAM and SAM.
New Optical Fiber Puts a Twist on Data Transmission
“For several decades since optical fibers were deployed, the conventional assumption has been that OAM-carrying beams are inherently unstable in fibers,” said BU engineering professor Siddharth Ramachandran, who designed the new fiber. “Our discovery of design classes in which they are stable has profound implications for a variety of scientific and technological fields that have exploited the unique properties of OAM-carrying light, including the use of such beams for enhancing data capacity in fibers.”
The strategy by Ramachandran, Willner and colleagues, OAM mode-division multiplexing, combines both approaches. They packed several colors into each mode and used multiple modes. Unlike in conventional fibers, OAM modes in these specially designed fibers can carry data streams across an optical fiber while remaining separate at the receiving end.
Ramachandran’s OAM fiber had four modes (an optical fiber typically has two), and he and Willner showed that for each OAM mode, they could transmit 400 Gb/s in just a single wavelength of light — or 1.6 Tb/s across 10 wavelengths — over the course of 0.68 miles (1.1 km).