Photonic Cipher

Sending sensitive communications (no matter the method) usually is accompanied by a lingering fear that somehow the information could be compromised.

A bank’s message about fiscal policy, for example, easily could be misused if it fell into the wrong hands.

How does one guarantee a high level of security for such confidential data? A group of European researchers thinks that chaos might be the answer.

The team is seeking to develop a communications system where chaotic waveforms — in the form of randomly varying light power transmitted through a single fibre — are used to deliver information that is decoded on the receiving end. Intercepting, let alone deciphering, such a message would be close to impossible.

Using more than 140 km of fibre optic network in Athens, researchers tested a communications system that relies on chaotic waveforms.

The ongoing research effort, led by Dimitris Syvridis, a professor at the National and Kapodistrian University of Athens, is entering a new phase known as PICASSO (Photonic Integrated Components Applied to Secure chaoS encoded Optical communications systems), which will seek to develop the components necessary to make such a network viable. The main goal of PICASSO is the development of chaotic transmitters and receivers in the form of photonic integrated circuits that are capable of seamless integration into the existing telecommunications infrastructure. Another objective is the experimental investigation of the security of the chaos-encoding communications systems.

In 2005, the researchers successfully sent a message using lasers that transmitted chaotic pulses of light. The technique was demonstrated by the optical communications group of the University of Athens, where chaotic information was transmitted 140 km over the city’s installed fibre optic telecommunications network. They sent the information at a rate of about 1 Gb/s. At that time the project was known as OCCULT (Optical Chaos Communications Using Laser-Diode Transmitters).

A lucid message was embedded amid the disordered signals generated by a semiconductor laser. When the incoming blur of information arrived at its destination, the receiver used a laser essentially identical to the emitter to cancel the chaos portion of the transmission and to reveal the message implanted within.

The latest research, which again is being funded by the European Commission, is seeking to achieve transmission rates of tens of gigabits per second. In addition, the researchers said that they will seek to overcome the problem of changes in temperature, which can cause wavelengths to deviate and can affect the transmission of information. By using integrated sources, they will seek to resolve mechanical instabilities as well.