Abstract
In this study, we have proposed and numerically demonstrated that the bias current of a semiconductor laser cannot be used as a key for optical chaos communication, using external-cavity lasers. This is because the chaotic carrier has a signature of relaxation oscillation, whose period can be extracted by the first side peak of the carrier’s autocorrelation function. Then, the bias current can be approximately cracked, according to the well-known relationship between the bias current and relaxation period of a solitary laser. Our simulated results have shown that the cracked current eavesdropper could successfully crack an encrypted message, by means of a unidirectional locking injection or a bidirectional coupling. In addition, the cracked bias current was closer to the real value as the bias current increased, meaning that a large bias current brought a big risk to the security.
Highlights
The secure optical chaos communication process has received considerable attention due to its excellent features, such as hardware encryption, high transmission rate, long transmission distance, and compatibility with the existing fiber networks
Plots the RF spectrum of laser intensity chaos, which was obtained with a fixed bias current I1 = 1.6Ith
The spectrum obviously had a dominant peak around around the relaxation frequency. This meant that the chaotic carrier had a signature of laser relaxation the relaxation frequency
Summary
The secure optical chaos communication process has received considerable attention due to its excellent features, such as hardware encryption, high transmission rate, long transmission distance, and compatibility with the existing fiber networks. Considering the robustness and cost, external-cavity semiconductor laser (ECL) is a promising chaotic transceiver, due to its simple structure, which is capable of integration. Chaos-based communication can be realized only when the parameters of chaotic transceivers are matched. The parameters of chaotic lasers are generally considered to be key in optical chaos communication [9]. For ECLs like chaotic transceivers, the controllable external parameters, including bias current, external-cavity length, and feedback strength should be selected as the keys, to ensure security. Paul et al proposed the external-cavity length as a key [10]. This is unsafe because the laser chaotic oscillation contains external-cavity
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