Examination of Chaotic Signal Encryption, Synchronization and Retrieval Using Hybrid Acousto-Optic Feedback

Chatterjee, Monish Ranjan; Alsaedi, Mohammed

doi:10.1364/fio.2008.fwc3

Cited by 5 publications

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“…In 2008, Chatterjee and Al-Saedi demonstrated that the chaotic signal in hybrid A-O feedback can be used for encryption and retrieval of signals through preliminary simulations. 25 The work presented in this paper expands on the earlier findings by driving the hybrid A-O system into chaos with a proper choice of the parametersβ,α 0 and TD, and then encrypting the chaotic waveform with a message wave applied through the acoustic driver bias input. At the receiver end, a chaotic waveform is locally generated and multiplied by the modulated chaotic waveform coming from the transmitter.…”

Section: Signal Encryption In Chaotic Circuit Andmentioning

confidence: 70%

Examination of chaotic signal encryption and recovery for secure communication using hybrid acousto-optic feedback

Chatterjee

Alsaedi

2011

Opt. Eng

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Generation of chaos from acousto-optic (A-O)Bragg cell modulators with an electronic feedback has been studied for over 3 decades. Since an acousto-optic Bragg cell with zeroth-and first-order feedback exhibits chaotic behavior past the threshold for bistability, such a system was recently examined for possible chaotic encryption of simple messages (such as a low-amplitude sinusoidal signal) applied via the bias input of the sound cell driver. Subsequent recovery of the message signal was carried out via a heterodyne-type strategy employing a locally generated chaotic carrier, with threshold parameters matched to the transmitting Bragg cell. In this paper, we present numerical results and detailed interpretations for signal encryption and recovery under hybrid A-O electronic feedback using a heterodyne strategy. Important features of this setup, such as the system robustness in terms of parameter matching (feedback gain, dc bias, and time delay) are also examined in some detail. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). IntroductionIn an acousto-optic (A-O) modulator, an RF signal applied to a piezo-electric transducer, bonded to a suitable crystal, will generate an acoustic wave. It is well known that the acoustic wave acts like a "phase grating" that diffracts any incident laser beam into a number of diffracted orders. The Raman-Nath regime is characterized by multiple scattered orders while in the Bragg regime there are typically only two scattered orders (zeroth-and first-orders). 1 Around 1978, it was reported that A-O devices with positive feedback gain exhibit bistability characteristics. 2 In an A-O device, the amplitude of the diffracted fields that operate in the Bragg regime, i.e., the zeroth-and first-orders, which appear at the output of the Bragg cell, are related through a set of coupled differential equations. In Refs. 3 and 4, Chrostowski and co-workers present experimental results for A-O bistability and chaos using an equivalent circuit model of the Bragg cell with feedback. In a standard setup, a Bragg cell is driven by an ultrasonic sound wave from an RF generator at 40 MHz, and the resulting sound grating diffracts an incident He-Ne laser beam into the first Bragg order under Bragg condition. The first-order is then picked up by a linear photodetector, fed to an amplifier, and then returned to the bias input of the RF generator. The arrangement is shown in Fig. 1. Nominally, the scattered light beam is intrinsically frequency or phase modulated (with the acoustic frequency). In typical waveform sources, the external bias input amplitude modulates the RF waveform. A plot of the first order intensity (I 1 ) versus the bias inputα 0 yields the well known bistable and hysteretic behavior. 3,4 The bistability and hysteresis characteristics depend strongly on the feedback gain (β), the feedback time delay (TD), and the amplitude (I inc ) of the incident

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Section: Signal Encryption In Chaotic Circuit Andmentioning

confidence: 70%