Giuseppe Aromataris

Private Message Transmission by Common Driving of Two Chaotic Lasers

In this paper, we numerically demonstrate private data transmission using twin semiconductor lasers in which chaotic dynamics and synchronization are achieved by optical injection into the laser pair of a common, chaotic driving-signal, generated by a third laser subject to delayed optical feedback. This laser is selected with different parameters with respect to the twin pair, so that the emissions of the synchronized, matched lasers are highly correlated, whereas their correlation with the driver is low. The digital message modulates the emission of the transmitter, as in a standard CM scheme. Message recovery is then obtained by subtracting, from the transmitted chaos-masked message, the chaos, locally generated by the synchronized receiver laser. Simulations have been performed with the Lang-Kobayashi model, keeping into account both laser and photodetector noise. Private transmission has been demonstrated by investigating the effect of the parameter mismatch, between transmitter and receiver, on synchronization and message recovery.

Secure Chaotic Transmission on a Free-Space Optics Data Link

In this paper, we numerically demonstrate secure data transmission, using synchronized ldquotwinrdquo semiconductor lasers working in the chaotic regime, which represent the transmitter and receiver of a cryptographic scheme, compatible with free-space optics technology for line-of-sight communication links. Chaotic dynamics and synchronization are obtained by current injection into the laser pair of a common, chaotic driving-signal. Results of simulations are reported for the configuration in which the chaotic driving-current is obtained by photodetection of the emission of a third laser (driver), chaotic by delayed optical feedback in a short cavity scheme, selected with different parameters with respect to the laser pair. The emissions of the synchronized, matched lasers are highly correlated, whereas their correlation with the driver is low. The digital message modulates the pumping current of the transmitter. Message recovery is performed by subtracting the chaos, locally generated by the synchronized receiver laser, from the signal obtained by photodetection (at the receiver side) of the chaos-masked message transmitted in free space. Simulations have been performed with the Lang-Kobayashi model, keeping into account both attenuation of the optical signal in a line-of-sight configuration, and noise. Security has been investigated and demonstrated by considering the effect, on synchronization and message recovery, of the parameter mismatch between transmitter and receiver.

Multi-User Private Transmission With Chaotic Lasers

In this paper, we propose a scheme for private data transmission using chaotic lasers, which is derived from the well-known public key cryptography. With this new approach, it is possible to exchange data between any couple of subscribers in a network, while schemes based on chaotic lasers are usually restricted to transmission between two specific users, sharing a twin laser pair. This is possible by introducing a provider, who is responsible of the network security. For each subscriber a couple of twin chaotic lasers is required, one being held by the provider and the other by the subscriber himself. The basic two-laser scheme of chaotic transmission is then used for secure data exchange, both between two subscribers and between a subscriber and the provider. Several arrangements can be considered, based on this architecture, including the use of an electro-optical repeater, which is studied in detail in this paper. More advanced solutions can be also implemented, e.g., using a three-laser scheme. The Lang-Kobayashi model is used for simulations. Experiments are performed using InP-integrated modules.

All-Optical Wavelength Conversion of a Chaos Masked Signal

Wavelength conversion in the transmission of a message masked by optical chaos is experimentally demonstrated. In our setup, chaos is generated by a distributed-feedback laser subject to delayed optical feedback, and hides a message by additive chaos masking. The optical wavelength is converted, along the transmission line, by four-wave mixing in a semiconductor optical amplifier. At the receiver, the message is extracted by master-slave synchronization. Our experiments demonstrate that secure communications based on chaos are compatible with channel switching as required in reconfigurable optical networks.

Sound representation in higher language areas during language generation

Significance The results of our experiments show that a special representation of sound is actually exploited by the brain during language generation, even in the absence of speech. Taking advantage of data collected during neurosurgical operations on awake patients, here we cross-correlated the cortical activity in the frontal and temporal language areas of a person reading aloud or mentally with the envelope of the sound of the corresponding utterances. In both cases, cortical activity and the envelope of the sound of the utterances were significantly correlated. This suggests that in hearing people, sound representation deeply informs generation of linguistic expressions at a much higher level than previously thought. This may help in designing new strategies to help people with language disorders such as aphasia. How language is encoded by neural activity in the higher-level language areas of humans is still largely unknown. We investigated whether the electrophysiological activity of Broca’s area correlates with the sound of the utterances produced. During speech perception, the electric cortical activity of the auditory areas correlates with the sound envelope of the utterances. In our experiment, we compared the electrocorticogram recorded during awake neurosurgical operations in Broca’s area and in the dominant temporal lobe with the sound envelope of single words versus sentences read aloud or mentally by the patients. Our results indicate that the electrocorticogram correlates with the sound envelope of the utterances, starting before any sound is produced and even in the absence of speech, when the patient is reading mentally. No correlations were found when the electrocorticogram was recorded in the superior parietal gyrus, an area not directly involved in language generation, or in Broca’s area when the participants were executing a repetitive motor task, which did not include any linguistic content, with their dominant hand. The distribution of suprathreshold correlations across frequencies of cortical activities varied whether the sound envelope derived from words or sentences. Our results suggest the activity of language areas is organized by sound when language is generated before any utterance is produced or heard.

Privacy in Two-Laser and Three-Laser Chaos Communications

In this paper, we compare the performances of the well-known two-laser and three-laser chaos communications schemes, in terms of privacy. It is found by numerical analysis that in optimized conditions both methods are well suited for private transmission. However, while the three-laser scheme gives its optimum performance with the twin laser pair, the two-laser scheme reaches its best performance using two slightly different lasers (the optimum pair). This results in an easier device selection and in a slightly higher privacy level of the three-laser scheme. Using a twin pair with the two-laser scheme still offers a good level of privacy in most cases; however, in principle the eavesdropper has a chance to extract the message, by selecting a suitable laser.

Error Analysis of a Digital Message Impaired by Optical Chaos

In this letter, we numerically investigate the statistical properties of the optical chaos hiding a digital message in secure transmission schemes. It is found that even if chaos statistics are usually not Gaussian, the statistics of the residual chaos, over the extracted message, are nearly Gaussian. Thus, assessing the bit-error rate from the Q parameter, as it is often done in the numerical analysis of such schemes, is a viable approach.

Secure transmission network using chaotic lasers

In this paper, we propose a scheme for multi-user secure data transmission using chaotic lasers. While schemes based on optical chaos are usually restricted to point-to-point transmission, with this new approach, which is derived from the well-known public key cryptography, it is possible to exchange data between any couple of nodes in a network. For each user, a pair of twin chaotic lasers is required, one being held by the user himself and the other by a provider, who is responsible of the network security. The basic two-laser or three-laser schemes of chaotic transmission are then used for secure data exchange, both between two subscribers and between a subscriber and the provider.

Secure transmission with chaotic lasers synchronized by electrical injection

In this paper, we numerically demonstrate secure data transmission using “twin” semiconductor lasers in which chaotic dynamics and synchronization are achieved by electrical injection into the laser pair of a common, chaotic driving-signal, obtained by photodetection of the emission of a third chaotic laser.

Transmission of a chaos-masked signal with in-line all-optical wavelength conversion

In this paper we demonstrate wavelength-conversion, of a message masked by additive chaos, along a transmission line. This result shows that chaos-based communications are compatible with channel-switching and wavelength-conversion as required in reconfigurable networks.