Optical chaos

Professor Alan Shore of the

School of Informatics and colleagues within an EU-funded project, have shown that embedding light-based signals in chaos is an effective means of transmitting sensitive data.

The demonstration of this capability involved sending light-based signals over a distance of 120 km using a commercial fibre-optic telecommunication network in the metropolitan area of Athens, Greece.

There are several benefits of sending information encoded in chaotic signals. For one thing, the chaos serves as a good encryption system: at face value, the signal looks like pure noise, and it's only when the receiver generates its own chaotic output signal, which can be synchronized with that of the transmitter, that the chaos can be removed to recover the true signal.

This approach enables the communication of sensitive information with no risk of 'eavesdropper' access. This technology could therefore be used, for example, to support secure trading via the web.

 "The basic idea is that a chaotic light signal is generated by a transmitting laser. The receiver contains a second laser that can be induced by a feedback circuit to produce a chaotic output synchronized with that of the transmitter. The information-laden optical signal is mixed in with the chaotic signal in the transmitter, but can be decoded by subtracting the synchronized chaos of the receiver. This process had been demonstrated previously over very short distances in the laboratory, but this recent work proves that it will work in the real world," explained Professor Shore.