1,370 research outputs found
Synchronization of spatiotemporal semiconductor lasers and its application in color image encryption
Optical chaos is a topic of current research characterized by
high-dimensional nonlinearity which is attributed to the delay-induced
dynamics, high bandwidth and easy modular implementation of optical feedback.
In light of these facts, which adds enough confusion and diffusion properties
for secure communications, we explore the synchronization phenomena in
spatiotemporal semiconductor laser systems. The novel system is used in a
two-phase colored image encryption process. The high-dimensional chaotic
attractor generated by the system produces a completely randomized chaotic time
series, which is ideal in the secure encoding of messages. The scheme thus
illustrated is a two-phase encryption method, which provides sufficiently high
confusion and diffusion properties of chaotic cryptosystem employed with unique
data sets of processed chaotic sequences. In this novel method of cryptography,
the chaotic phase masks are represented as images using the chaotic sequences
as the elements of the image. The scheme drastically permutes the positions of
the picture elements. The next additional layer of security further alters the
statistical information of the original image to a great extent along the
three-color planes. The intermediate results during encryption demonstrate the
infeasibility for an unauthorized user to decipher the cipher image. Exhaustive
statistical tests conducted validate that the scheme is robust against noise
and resistant to common attacks due to the double shield of encryption and the
infinite dimensionality of the relevant system of partial differential
equations.Comment: 20 pages, 11 figures; Article in press, Optics Communications (2011
Physics and Applications of Laser Diode Chaos
An overview of chaos in laser diodes is provided which surveys experimental
achievements in the area and explains the theory behind the phenomenon. The
fundamental physics underpinning this behaviour and also the opportunities for
harnessing laser diode chaos for potential applications are discussed. The
availability and ease of operation of laser diodes, in a wide range of
configurations, make them a convenient test-bed for exploring basic aspects of
nonlinear and chaotic dynamics. It also makes them attractive for practical
tasks, such as chaos-based secure communications and random number generation.
Avenues for future research and development of chaotic laser diodes are also
identified.Comment: Published in Nature Photonic
Synchronization in semiconductor laser rings
We examine the dynamics of semiconductor lasers coupled in a ring
configuration. The lasers, which have stable output intensity when isolated,
behave chaotically when coupled unidirectionally in a closed chain. In this
way, we show that neither feedback nor bidirectional coupling is necessary to
induce chaotic dynamics at the laser output. We study the synchronization
phenomena arising in this particular coupling architecture, and discuss its
possible application to chaos-based communications. Next, we extend the study
to bidirectional coupling and propose an appropriate technique to optical chaos
encryption/decryption in closed chains of mutually coupled semiconductor
lasers.Comment: 15 pages, 7 figure
Synchronised laser chaos communication: statistical investigation of an experimental system
The paper is concerned with analyzing data from an experimental antipodal laser-based chaos shift-keying communication system. Binary messages are embedded in a chaotically behaving laser wave which is transmitted through a fiber-optic cable and are decoded at the receiver using a second laser synchronized with the emitter laser. Instrumentation in the experimental system makes it particularly interesting to be able to empirically analyze both optical noise and synchronization error as well as bit error rate. Both the noise and error are found to significantly depart in distribution from independent Gaussian. The conclusion from bit error rate results is that the antipodal laser chaos shift-keying system can offer a feasible approach to optical communication. The non-Gaussian optical noise and synchronous error results are a challenge to current theoretical modelling
Experimental demonstration of 25 GHz wideband chaos in symmetric dual port EDFRL
We study dynamics of chaos in dual port erbium-doped fiber ring laser (EDFRL). The laser consists of
two erbium-doped fibers, intracavity filters at 1549.30 nm, isolators, and couplers. At both ports, the laser
transitions into the chaotic regime for pump currents greater than 100 mA via period doubling route. We
calculate the Lyapunov exponents using Rosenstein’s algorithm. We obtain positive values for the largest
Lyapunov exponent (≈0.2) for embedding dimensions 5, 7, 9 and 11 indicating chaos. We compute the
power spectrum of the photocurrents at the output ports of the laser. We observe a bandwidth of ≈ 25
GHz at both ports. This ultra wideband nature of chaos obtained has potential applications in high speed
random number generation and communication
Lag time and parameter mismatches in synchronization of unidirectionally coupled chaotic external cavity semiconductor lasers
We report an analysis of synchronization between two unidirectionally coupled
chaotic external cavity master/slave semiconductor lasers with two
characteristic delay times, where the delay time in the coupling is different
from the delay time in the coupled systems themselves. We demonstrate for the
first time that parameter mismatches in photon decay rates for the master and
slave lasers can explain the experimental observation that the lag time is
equal to the coupling delay time.Comment: LaTex, 5 pages, submitted to PRE(R
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