Temporal Invisibility Cloak For Fiber Optic Communications Developed

“Blue Fiber” by Michael Wyszomierski via flickr, CC BY-NC 2.0

With electronic communication quickly taking over all traditional methods of sharing information, privacy has become of paramount importance. A team of researchers have developed a technique that is able to temporally cloak a signal when attempted spying is taking place along a fiber optic network. The research was led by Julien Fatome from the Université de Bourgogne and the paper was published in an open access format in Nature Communications.

This is not the first attempt at concealing sensitive information sent electronically, though this appears to be the most complete. Previous methods have only been able to obscure part of the communication signal for a short amount of time, whereas Fatome’s new method blocks all traces of the data signal for a designated amount of time.

The key to the technique relies on the principle of light polarization, which refers to the directionality of the light’s electric and magnetic fields. Polarized lenses—which can be found in sunglasses—are designed to allow only certain orientations of light through, which cuts down on the amount of light allowed to pass through. Fatome’s lab developed a device back in 2012 called an Omnipolarizer, which doesn’t block out certain polarizations, but instead converts them into uniform polarization states.

The team was able to use the Omnipolarizer to completely shield data from a fiber optic cable from being read by unsecured sources. To test this, they set up a network involving a data source, an end user, and an Omnipolarizer on either side of an “indiscreet eye” using a continuous wave probe (CW probe) to try to pick up on the information. 

The polarization used in (a) allows the CW probe to copy the information that is being sent. In (b), the first Omnipolarizer makes the probe completely blind to the data being transmitted. Credit: Bony et al.

As the signal comes down the fiber optic cable, it is run through the first Omnipolarizer which forces all of the light to adopt the same polarization state that makes it completely invisible to the CW probe. During testing, the method was able to cloak 100% of the information from prying eyes, though the cable had been transmitting about 10 gigabits per second.

However, the light cannot stay in this state if it is to be read by the intended target on the other end of the line. Once the signal has successfully passed the point of being read by spying eyes, the second Omnipolarizer returns the light to random polarization. Because of this technique, there are no constraints with how far or how long this can be used. 

The researchers note that returning the signal to its randomly polarized state may cause a brief latent period before the signal is completely restored. However, the extent of this effect is dependent on the materials used within the fiber optic cable and the wavelength at which the signal is moving. 

[Hat tip: Neomatica]

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