We propose a method for encrypting a signal within the high dimensional chaotic fluctuations of the wavelength from a delayed feedback tunable laser diode. Decoding is performed remotely by using a slave laser diode fully synchronized with the master one. No additional synchronization channel is required. [S0031-9007(98) PACS numbers: 89.70. + c, 05.45. + b Secure communications based on chaos have been investigated for some years, especially in the area of radiofrequency transmissions. Signal encoding and decoding is achieved using a carrier whose amplitude fluctuates chaotically. Compared with conventional data encryption techniques in which the key is a pseudorandom binary number that controls the encryption algorithm, but which is slow, chaos is used as a coding key embodied directly in the structure of the carrier. At least two classical methods have been demonstrated for communicating with chaos [1]. The first method due to Ott, Grebogi, and Yorke [1] utilizes controlling chaos. The dynamics of a chaotic oscillator is made to follow prescribed orbits in the attractor by using small perturbations, thus allowing a message to be encoded in the chaotic wave form. A very different concept developed by Pecora and Carroll [1] uses the idea of synchronized chaos for secure communications. In this case, a small information-bearing signal is masked by a large chaotic signal. The chaotic codegenerating system is divided in two subsystems, namely, the master and the slave. The slave is replicated at the receiver. The master subsystem is used to synchronize the two slave subsystems. The message signal is added to the chaotic signal generated by the slave subsystem at the transmitter and this composite signal is transmitted to the receiver. When the two subsystems are synchronized, the message can be reproduced by subtracting the chaotic part of the composite signal. So far most of the studies were implemented with electrical circuits featuring low dimensional attractors, such as the double scroll or Chua's attractor that has a single positive Lyapunov exponent [2]. The simple chaotic processes thus obtained can, however, be defeated by an eavesdropper without the synchronized receiver, using unmasking signal processing techniques which work well for simple chaotic systems [3]. One way to solve this security problem is by using hyperchaotic systems with multiple positive Lyapunov exponents to mask the message. A recent theoretical work [4] indicates the possibility of synchronizing hyperchaotic chaos with just one transmitted signal. Practical realizations remain, however, to be developed. The question of optical synchronization of chaos has also been studied in optics, but results deal mostly with numerical simulations [5] except some unique demonstrations of control of laser chaos and digital encoded transmission [6]. When talking about chaos in optics, it looks natural to look for nonlinearities induced by optical power. It is probably the reason why implementing optical chaotic cryptosystems poses severe problems...
Abstract-Silicon photonics is poised to revolutionise several data communication applications. The development of high performance optical modulators formed in silicon is essential for the technology to be viable. In this paper we review our recent work on carrier depletion silicon Mach Zehnder based optical modulators which have formed part of the work within the UK Silicon Photonics and HELIOS projects, as well as including some recent new data. A concept for the self-aligned formation of the pn junction which is flexible in the capability to produce a number of device configurations is presented. This process is key in having performance repeatability, a high production yield and large extinction ratios. Experimental results from devices which are formed though such processes are presented with operation up to and beyond 40Gbit/s. The potential for silicon photonics to fulfil longer haul applications is also explored in the analysis of the chirp produced from these devices and the ability to produce large extinction ratios at high speed. It is shown that the chirp produced with the modulator operated in dual drive configuration is negligible and that a 18dB dynamic modulation depth is obtainable at a data rate of 10Gbit/s.
We describe a new method for quantum key distribution that utilizes phase modulation of sidebands of modulation by use of integrated electro-optic modulators at the transmitting and receiving modules. The system is shown to produce constructive or destructive interference with unity visibility, which should allow quantum cryptography to be carried out with high flexibility by use of conventional devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.