A broadband chaotic source generation method with dual intensity and phase coupling

Abstract

This invention discloses a method for generating a broadband chaotic source with dual intensity and phase coupling. Specifically, the method combines electro-optical feedback intensity chaos with photoelectric oscillation phase chaos. Intensity chaos and phase chaos are generated by splitting the laser signal emitted by a semiconductor laser into two paths, each entering a delay loop with a phase modulator and an intensity modulator. The chaotic laser signals output by the two electro-optical feedback delay loops are coupled and used as feedback optical signals. The chaotic laser signals output by the two electro-optical feedback delay loops are the output light of the phase modulator and the intensity modulator, respectively. The coupled chaotic laser signal is a broadband chaotic laser signal. This method can generate a broadband chaotic signal source, substantially eliminates the time delay signature present in traditional electro-optical delay systems, and significantly improves the complexity of the chaotic laser signal.

Description

Technical Field

[0001] The invention belongs to the technical field of chaotic secure optical communication, and in particular relates to a method for generating a broadband chaotic source with dual intensity and phase coupling. Background Art

[0002] Chaotic signals possess characteristics such as determinism, boundedness, sensitivity to initial conditions, broadband nature, and pseudo-randomness. They can be used to mask information signals to be transmitted, thereby enhancing the security of such signals during transmission. Chaotic secure optical communication technology is designed to leverage these characteristics. Chaotic lasers, due to their wide bandwidth and high-amplitude noise-like properties, are being used as a new generation of physical entropy sources to address the issue of insufficient real-time random number generation rates. Radar systems using broadband chaotic lasers as signal sources can effectively improve the range resolution of target detection.

[0003] Chaotic lasers have a wide range of applications in secure communications, high-speed physical random number generation, and secure key distribution. Previous studies have shown that in chaotic secure communications, laser chaotic sources carry system characteristics, posing certain security risks. In principle, a chaotic system with a feedback loop can generate an infinite-dimensional chaotic carrier, with the feedback delay parameter serving as a critical security key. However, various methods, such as autocorrelation functions, mutual information, and extreme value statistics, can successfully extract the delay time. The delay time can then be used to easily estimate other hardware parameters. Once an eavesdropper has cracked all hardware keys, they can use techniques such as artificial neural networks to reconstruct the chaotic system. Therefore, addressing the issue of chaotic delay information exposure and effectively suppressing delay characteristics have become urgent priorities in laser chaos research.

[0004] In 2010, Johanne Hizanidis's team proposed a cascaded system of all-optical chaos and electro-optical chaos. The chaotic optical signal output by the all-optical system replaces the constant light output by the laser as the input of the electro-optical chaotic system. The output light of the subsequent electro-optical chaotic system serves as the chaotic carrier signal propagating along the link during actual communication. The chaotic light output by the preceding stage of both systems replaces the continuous light output as the light source of the subsequent stage, causing the feedback gain coefficient of the system to vary constantly. This change in the system gain coefficient also changes the overall dynamic characteristics of the system, increasing its complexity, making the output signal more complex, and reducing its temporal correlation. In 2015, Cheng from Huazhong University of Science and Technology proposed an electro-optical chaotic source capable of hiding time delay. This system consists of three coupled intensity chaotic systems, with the sum of the chaotic voltages of each two stages serving as the driving voltage for the third modulator. Compared to traditional electro-optical chaotic sources, the output signal of this chaotic source undergoes more nonlinear transformations, significantly increasing its complexity and reducing its temporal correlation. This allows for delay label hiding under conditions of high feedback gain. In 2017, Cheng from Huazhong University of Science and Technology proposed a new type of electro-optical chaos source, which solved the problem of exposing the system delay label in the cross-correlation function of the previous system. The system used a special optical coupler to realize the nonlinear coupling of three chaotic signals. Summary of the Invention

[0005] Aiming at the problems of limited bandwidth and time delay tag in chaotic laser signal generated by traditional electro-optical feedback, the present invention provides a broadband chaotic source generation method with intensity-phase dual coupling.

[0006] The present invention provides a method for generating a broadband chaotic source with dual intensity and phase coupling. This method combines electro-optical feedback intensity chaos with photoelectric oscillation phase chaos. Intensity chaos and phase chaos are generated by splitting the laser signal emitted by a semiconductor laser into two paths, each entering a delay loop with a phase modulator and an intensity modulator. The chaotic laser signals output by the two electro-optical feedback delay loops are coupled and used as feedback optical signals. The chaotic laser signals output by the two electro-optical feedback delay loops are the output light of the phase modulator and the intensity modulator, respectively. The coupled chaotic laser signal is a broadband chaotic laser signal. The method specifically includes the following steps:

[0007] Step 1: First, intensity chaos and phase chaos are generated by dividing the laser signal emitted by the semiconductor laser into two paths and entering the delay loop with a phase modulator and an intensity modulator respectively; including: the output light of the semiconductor laser passes through a beam splitter and is input into the phase modulator and the intensity modulator respectively for electro-optical phase modulation and electro-optical intensity modulation.

[0008] Step 2: coupling the chaotic laser signals outputted by the two electro-optical feedback delay loops; including: coupling the output lights of the phase modulator and the intensity modulator into a chaotic optical signal via an optical coupler.

[0009] Step 3: The chaotic laser signals output from the two electro-optical feedback delay loops are coupled and used as feedback optical signals; the process includes: the coupled optical signal is divided into two optical signals by a beam splitter, one signal passes through a delay line and enters an interferometer, converting the phase chaos part of the coupled chaotic signal into intensity chaos, the optical signal is converted into an electrical signal by a photodetector, and then enters a radio frequency amplifier and is fed back to an intensity modulator as its excitation signal; the other signal passes through a delay line and enters a photodetector and a radio frequency amplifier and is fed back to a phase modulator as its excitation signal.

[0010] An intensity-phase dual-coupled broadband chaotic source generation system includes a first signal loop and a second signal loop: the first signal loop includes a semiconductor laser, a beam splitter, an optical coupler, a phase modulator, a photodetector, a radio frequency amplifier, and a delay line; the second signal loop includes a semiconductor laser, a beam splitter, an optical coupler, an intensity modulator, a photodetector, a radio frequency amplifier, an interferometer, and a delay line.

[0011] The output light of the semiconductor laser passes through a beam splitter and is input into a phase modulator and an intensity modulator respectively for electro-optical phase modulation and electro-optical intensity modulation. The output light of the phase modulator and the intensity modulator is coupled into one optical signal by an optical coupler and then divided into two optical signals by a beam splitter. One signal passes through a delay line, enters the interferometer, and is fed back to the intensity modulator through a photodetector and a radio frequency amplifier; the other signal passes through a delay line, a photodetector, and a radio frequency amplifier, and is fed back to the phase modulator.

[0012] The present invention can be applied as a chaotic signal source.

[0013] The beneficial technical effects of the present invention are:

[0014] 1. The present invention not only enhances the bandwidth of chaotic laser signals, but also effectively hides the delay label of chaotic laser signals.

[0015] 2. This invention can generate a broadband chaotic signal source, essentially eliminating the time delay signature present in traditional electro-optical delay systems. Simultaneously, the complexity of the chaotic laser signal is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a structural diagram of the intensity-phase dual-coupled broadband chaotic source generation method of the present invention.

[0017] Figure 2 This is the time domain waveform of the traditional electro-optical feedback chaotic laser signal.

[0018] Figure 3 This is the power spectrum of the traditional electro-optical feedback chaotic laser signal.

[0019] Figure 4 This is the time domain waveform of the broadband chaotic source with dual intensity and phase coupling of the present invention.

[0020] Figure 5 This is the power spectrum of the broadband chaotic source with dual intensity and phase coupling according to the present invention.

[0021] Figure 6 This is the autocorrelation function curve of the traditional electro-optical feedback chaotic laser signal.

[0022] Figure 7 This is a graph showing the autocorrelation function of the broadband chaotic source with dual intensity and phase coupling according to the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0024] The broadband chaotic source generation system of the present invention with dual intensity and phase coupling is as follows: Figure 1 As shown, it includes a first signal loop and a second signal loop: the first signal loop includes a semiconductor laser, a beam splitter, an optical coupler, a phase modulator, a photodetector, a radio frequency amplifier and a delay line; the second signal loop includes a semiconductor laser, a beam splitter, an optical coupler, an intensity modulator, a photodetector, a radio frequency amplifier, an interferometer and a delay line.

[0025] Among them, the semiconductor laser is used to generate continuous laser; the optical coupler facilitates the generation of a loop, so that the feedback light passes through the coupler and is fed back into the phase modulator or intensity modulator; the interferometer can convert the phase characteristics of the chaotic signal into intensity characteristics. The present invention uses this characteristic to achieve the effect of simultaneously exciting the phase modulator and intensity modulator after coupling the intensity chaos and phase chaos.

[0026] like Figure 1As shown, the present invention uses a semiconductor laser module 101 to generate a laser signal, which is divided into two beams by a beam splitter module 1021 and respectively input into a phase modulator 105 module and an intensity modulator 103 module for electro-optical phase modulation and electro-optical intensity modulation. The output light of the phase modulator 105 module and the intensity modulator 103 module is synthesized into one optical signal by an optical coupler 104 module, and then divided into two optical signals by beam splitters 1022 modules and 1023 modules. One signal passes through the delay line 1061 module, enters the interferometer 107 module, and is fed back to the intensity modulator 103 module through the photodetector 1081 module and the radio frequency amplifier 1091 module; the other signal passes through the delay line 1062 module, the photodetector 1082 module and the radio frequency amplifier 1092 module, and is fed back to the phase modulator 105 module.

[0027] Figure 2 、 Figure 3 The following are the time domain waveform and power spectrum of the traditional electro-optical feedback chaotic laser signal. Figure 3 As can be seen from the inset diagram, the power spectrum has obvious periodic frequency intervals, which are 0.05GHz, corresponding to the delay of the delay loop 1 / t ns -1 , exposing the time delay characteristics of the chaotic signal.

[0028] Figure 4 、 Figure 5 The following are the time domain waveform and power spectrum of broadband chaotic laser signal. Figure 5 It can be seen that the spectrum of this scheme is flatter, and there is no obvious periodic frequency interval in the inset diagram, which indicates that the chaotic signal generated by this method has its delay signature weakened or eliminated, and the effective bandwidth has also been significantly improved.

[0029] Figure 6 、 Figure 7 The following are the autocorrelation function curves of the traditional electro-optical feedback chaotic laser signal and the broadband chaotic laser signal. The autocorrelation function (ACF) analysis method is one of the commonly used methods for analyzing the time delay characteristics of chaotic signals. Figure 6 It can be seen that the ACF curve of the traditional electro-optical feedback chaotic laser signal has an obvious peak at the 20ns oscillation ring delay, exposing the system's delay signature. Figure 7 It can be seen that the ACF curve of the broadband chaotic laser signal has no peak at the oscillation ring delay of 20ns, and has an inconspicuous peak at the introduced phase chaos feedback loop delay of 35ns, indicating that the delay label of the chaotic signal has been effectively suppressed.

[0030] In summary, the broadband chaotic laser signal generation scheme proposed in this invention has the following benefits: (1) the spectrum is flatter and has a larger bandwidth; (2) the delay label existing in the traditional electro-optical delay system is basically eliminated; (3) the complexity of the chaotic laser signal is significantly improved.

Claims

1. A method for generating a broadband chaotic source with dual intensity and phase coupling, characterized in that: The electro-optical feedback intensity chaos is combined with the photoelectric oscillation phase chaos; the intensity chaos and phase chaos are generated by dividing the laser signal emitted by the semiconductor laser into two paths and entering the delay loop with a phase modulator and an intensity modulator respectively; the chaotic laser signals output by the two electro-optical feedback delay loops are coupled and used as feedback optical signals; the chaotic laser signals output by the two electro-optical feedback delay loops are the output lights of the phase modulator and the intensity modulator respectively, and the coupled chaotic laser signal is a broadband chaotic laser signal; the specific steps include: Step 1: First, intensity chaos and phase chaos are generated by splitting the laser signal emitted by a semiconductor laser into two paths and respectively entering a delay loop with a phase modulator and an intensity modulator. This includes: the output light of the semiconductor laser passes through a beam splitter and is respectively input into the phase modulator and the intensity modulator for electro-optical phase modulation and electro-optical intensity modulation; Step 2: coupling the chaotic laser signals output by the two electro-optical feedback delay loops; including: coupling the output light of the phase modulator and the intensity modulator into a chaotic optical signal via an optical coupler; Step 3: The chaotic laser signals output from the two electro-optical feedback delay loops are coupled and used as feedback optical signals; the process includes: the coupled optical signal is divided into two optical signals by a beam splitter, one signal passes through a delay line and enters an interferometer, converting the phase chaos part of the coupled chaotic signal into intensity chaos, the optical signal is converted into an electrical signal by a photodetector, and then enters a radio frequency amplifier and is fed back to an intensity modulator as its excitation signal; the other signal passes through a delay line and enters a photodetector and a radio frequency amplifier and is fed back to a phase modulator as its excitation signal.

2. A broadband chaotic source generation system with dual intensity and phase coupling, characterized in that: The invention comprises a first signal circuit and a second signal circuit: the first signal circuit comprises a semiconductor laser, a beam splitter, an optical coupler, a phase modulator, a photodetector, a radio frequency amplifier and a delay line; the second signal circuit comprises a semiconductor laser, a beam splitter, an optical coupler, an intensity modulator, a photodetector, a radio frequency amplifier, an interferometer and a delay line; The output light of the semiconductor laser passes through a beam splitter and is input into a phase modulator and an intensity modulator respectively for electro-optical phase modulation and electro-optical intensity modulation. The output light of the phase modulator and the intensity modulator is coupled into one optical signal by an optical coupler and then divided into two optical signals by a beam splitter. One signal passes through a delay line, enters the interferometer, and is fed back to the intensity modulator through a photodetector and a radio frequency amplifier; the other signal passes through a delay line, a photodetector, and a radio frequency amplifier, and is fed back to the phase modulator.

3. The method for generating a broadband chaotic source with dual intensity and phase coupling according to claim 1, characterized in that: Application is chaotic signal source.

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