Dynamical characterisation of a laser diode subject to double optical feedback for chaotic optical communications

Abstract

[eng] A chaotic semiconductor laser subject to double optical feedback is characterised in terms of the statistical analysis, power spectrum analysis and forecast error analysis of thechaotic dynamics. Varying the relative lengths of the two external cavities, the dynamics areobserved and compared to that of a single cavity. We show that in the case of integer multipleexternal-cavity lengths the round-trip time delays can be deduced from the forecast erroranalysis. In the case of fractional multiple cavity lengths, only the mean value of the cavity resonance frequencies can be deduced from the power spectra and hence the cavity time delays cannot be found. Cavity time delays that differ more than 0.4 ns can be obtained from the forecast error analysis. In the case of similar cavity lengths, the cavity time delays cannot be extracted. The results show that double optical feedback may offer particular advantages for enhancing security in chaos encryption.