A novel chaotic lidar with high resolution is proposed and studied theoretically. In chaotic lidar system, the
chaotic laser emitted from chaotic laser diode is split into two beams: the probe and the reference light. The
ranging is achieved by correlating the reference waveform with the delayed probe waveform backscattered from
the target. In chaotic lidar systems presented previously, the chaotic signal source is laser diode with optical
feedback or with optical injection by another one. The ranging resolution is limited by the bandwidth of chaotic
laser which determined by the configuration of chaotic signal source. We proposed a novel chaotic lidar which
ranging resolution is enhanced significantly by external optical injected chaotic laser diode. With the
bandwidth-enhanced chaotic laser, the range resolution of the chaotic lidar system with optical injection is
roughly two times compared with that of without optical injection. The resolution increases with injection
strength increasing in a certain frequency detuning range.
We numerically study the message filtering characteristics of semiconductor laser as a receiver in optical chaos
communication. The transmitter is an external-cavity laser subjecting to optical feedback that operates in a chaotic
regime. The receiver can operate at a chaotic regime either similar to the transmitter (closed-loop scheme) or without
optical feedback (open-loop scheme). We study the effects of frequency detuning and parameters mismatch between
transmitter and receiver on quality of the recovered signal in both open and closed loop schemes. We find that the
closed-loop scheme has, in general, a higher quality of recovered signal compared with the open-loop. We also study the
effects of message frequency on quality of the recovered signal in the two types of schemes. The results demonstrate that
the filtering effect of semiconductor laser receiver is larger for low frequency message and decreases as the message
frequency approaches the relaxation oscillation frequency of semiconductor laser. The SNR of the recovered signal of the
open-loop scheme remains higher than that of the closed-loop scheme when the message frequency is in high frequency
region.
The effects of dispersion on optical fiber chaotic secure communication are numerically investigated. A theoretical model
for fiber chaotic secure communication system which is consisted of a pair of synchronized chaotic lasers and an optical
fiber channel is presented. Chaotic secure communication for a 1-GHz sinusoidal message after propagating several
hundred kilometers is numerically analyzed. By numerically studying the effects of dispersion on the system's
performance, we show that the synchronization progressively degrades and the signal-to-noise ratio of the recovered
message decreases as the fiber length increases. We also find that the signal-to-noise ratio descends when the modulation
frequency of the encoding message increases. We propose a dispersion management scheme to compensate the
dispersion in fiber chaotic secure communication system. The proposed dispersion management map is consisted of a
segment of 5-km dispersion-compensating fiber with value of dispersion β2=-49ps2/km, a segment of 245-km nonzero dispersion-shifted fiber with value of dispersion β2=1ps2/km and optical amplifiers. The results show that the
signal-to-noise ratio of the extracted 1-GHz sinusoidal message increases from 2.75dB to 14.02dB when the length of
fiber is set to 500km.
Range finding with continuous-wave chaotic laser train generated from laser diode with optical feedback is investigated
theoretically. Chaotic laser is split into probe beam flighting to target and reference beam, and then, the distance of target
can be calculated from the flight time obtained by correlating the time-delayed probe beam with the reference one.
Effects of noise and waveform error on correlation performances for different chaotic states are investigated to study the
system tolerance of environmental noise. Simultaneously, the effects of chaotic state characterized by the largest
Lyapunov exponent and correlation dimension on correlation performances are demonstrated theoretically to select
satisfying chaotic laser used as probe light. Simulated results indicate that ideal chaotic laser train should have high
dimension and have smooth spectrum with broad bandwidth for ranging with high resolution. For the simulated system,
ranging resolution within 1.5cm range independent of target location can be achieved using the chaotic lasers generated
in middle of the chaos-generated regime of feedback level.
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