Time-Delay Signature Characteristics Of The Chaotic Output From An Optoelectronic Oscillator By Introducing An Optical Feedback

Optoelectronic oscillators?OEOs?not only have the advantages of good adjustability,high reliability,easily controllability,good robustness,and wide bandwidth,but also can produce a rich variety of dynamical behaviors.OEOs can be used as high-quality chaotic entropy sources and widely used in the fields of optical chaos communications and high-speed physical random bits generation,thus OEOs have emerged as universal and particularly efficient systems now.Up to now,the chaotic output signals based on OEOs have been extensively studied.However,due to the limitation of the architectures of OEOs,the delay time will inevitably be introduced in chaotic output.This will have a negative impact on the randomness of chaotic signals and security of chaos communication systems.Therefore,many researchers have done a lot of researches on how to suppress the time delay signatures?TDS?existing in the chaotic output of OEOs.In this paper,we numerically simulate a scheme by introducing an extra optical feedback loop into the traditional OEO-based chaotic system to suppress time delay signatures.Because the traditional OEOs system originally has a delay time T₁,a new delay time T₂ is bound to be added after adding an extra optical feedback.As a result,the TDS should be inspected within a large time window including T₁ and T₂.First of all,under the fixed injected optical power,the two delay times will be changed regularly as the optical feedback strength increases.We can confirm that it is necessary for the TDS of the chaotic output to be determined by the TDS at two delay times.Then,the influence of the optical feedback strength on the TDS of chaotic output is observed in detail through calculated map,it is found that there is an optimized range that can suppress the TDS of chaotic output.The optimal optical feedback strength and the lowest TDS at different injected optical powers are studied.Then the TDS of chaotic output signal are observed in the parameter space of optical feedback strength and T₂.The three-dimensional map shows the above rules at different injected optical powers.Finally,the TDS of chaotic output signal are observed in the parameter space of T₁ and T₂ under the fixed injected optical power,and then the relationship between the two delay times suitable for suppressing TDS of chaotic output signals is determined.