June 6, 2013
An Ultra Secure Optical Communications Network With Temporal Cloaking
redOrbit Staff & Wire Reports - Your Universe Online
Researchers at Purdue University have demonstrated a temporal cloaking device for optical communications that bends light to create holes in time, something that could have important implications for sending secret messages over fiber optic cables or thwarting would-be eavesdroppers.
"More work has to be done before this approach finds practical application, but it does use technology that could integrate smoothly into the existing telecommunications infrastructure,” said Joseph Lukens, a Purdue University graduate student working with Andrew Weiner, Professor of Electrical and Computer Engineering.
The new device is capable of hiding a continuous stream of events at rates of 12.7 Gigabits per second (Gbps), dramatically higher than a similar invention unveiled last year that cloaked events at only a tiny fraction — about one-10,000th of a percent — of the time available for sending data in optical communications. In other words, while last year´s invention could cloak events lasting only picoseconds, the current breakthrough can hide nearly half the total bandwidth of the light.
Furthermore, while the previous research in temporal cloaking required the use of a complex, ultrafast-pulsing "femtosecond" laser, the Purdue researchers only required off-the-shelf equipment commonly found in commercial optical communications.
The effect is called temporal cloaking because it hides data being transmitted over time, as opposed to "spatial" cloaking that conceals physical objects.
The technique used by the Purdue researchers works by manipulating the phase, or timing, of light pulses. If we think of the propagation of light as waves in the ocean, when one wave is going up and interacts with another wave that's going down, they cancel each other out and the light has zero intensity. The phase determines the level of interference between these waves.
"By letting them interfere with each other you are able to make them add up to a one or a zero," Lukens said. "The zero is a hole where there is nothing."
Any data in regions where the signal is zero would be cloaked. Controlling phase allows the transmission of signals in ones and zeros to send data over optical fibers.
A critical piece of hardware is a component known as a phase modulator, which is commonly found in optical communications to modify signals. In temporal cloaking, two phase modulators are used to create the holes and two more are used to cover them up, making it appear as though nothing was done to the signal.
"It's a potentially higher level of security because it doesn't even look like you are communicating," Lukens explained. "Eavesdroppers won't realize the signal is cloaked because it looks like no signal is being sent."
The technology could also have implications for the military, homeland security or law enforcement.
"It might be used to prevent communication between people, to corrupt their communication links without them knowing," Lukens said. "And you can turn it on and off, so if they suspected something strange was going on you could return it to normal communication."
Lukens said the technique could be improved to increase its operational bandwidth and the percentage of cloaking beyond 46 percent.
The technology is somewhat comparable to recent advances in cloaking using new "metamaterials," assemblies that contain features, patterns or elements such as tiny antennas or alternating layers of oxides that enable an unprecedented control of light and that could make possible a cloak of invisibility. However, temporal cloaking does not require metamaterials, just commercially available phase modulators and optical fibers.
The findings are published online June 5 in the journal Nature.