Chaotic generation device based on dispersion optoelectronic oscillation loop

Abstract

The application discloses a kind of time delay characteristic suppression type chaos generating device based on dispersion optoelectronic oscillation loop, and optoelectronic loop is divided into two parts of dispersion optical path and feedback circuit, laser is emitted by semiconductor laser, enters Mach-Zehnder modulator after polarization controller, is modulated by Mach-Zehnder modulator, and the modulated optical signal is then passed through chirped fiber Bragg grating, then enters optical power amplifier to increase power, and is received by photodetector again and converted into electrical signal, electrical signal is divided into two ways by power divider, one way is fed back to drive Mach-Zehnder modulator by radio frequency amplifier, and the other way is used as oscillator output.The application utilizes the reflection effect of grating to form loop to realize chaos generation, and utilizes group velocity dispersion caused by chirp effect to realize time delay characteristic suppression, and the system is simple, has higher operability, and is low in cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic oscillators, and in particular relates to a time delay characteristic suppression type chaos generating device based on a dispersive optoelectronic oscillation loop. Background Art

[0002] Chaos is a significant discovery in physics of the 20th century, and research related to it was awarded the 2021 Nobel Prize in Physics. Laser chaos combines the ultra-high-speed characteristics of lasers with the unique properties of chaotic dynamics, such as waveform randomness, high dimensionality, and synchronizability. It has been widely adopted in numerous popular research fields, including lidar, secure communications, high-speed physical random number generation, dynamic Brillouin grating sensing, secure key distribution, and photon reservoir computing.

[0003] Optoelectronic oscillators (OEOs) are a microwave signal generation technology that uses an optoelectronic feedback loop to achieve photon-to-microwave energy conversion. Thanks to their significant advantages in signal phase noise and bandwidth, OEOs have overcome bottlenecks in electronic microwave generation technology and significantly improved the performance of microwave systems. Optoelectronic modulation devices typically exhibit nonlinear characteristics, making OEOs based on optoelectronic modulation a popular device for generating laser chaos. Unlike optical feedback chaotic semiconductor lasers, OEOs offer advantages such as wide bandwidth and a flat power spectrum. However, OEOs share the same drawbacks as optical feedback chaotic lasers: the time delay information of the feedback loop can be easily obtained by eavesdroppers using time series analysis, allowing them to reconstruct the chaotic system, which in turn has a significant negative impact on the application of laser chaos. Therefore, addressing the issue of exposing chaotic time delay information and effectively suppressing the time delay characteristics has become a top priority in laser chaos research.

[0004] To address the delay characteristics of laser chaos generated by optoelectronic oscillators, the existing technology is to introduce additional loops. This solution increases the complexity of the system by increasing the number of delay parameters. By adjusting the system parameters, the delay characteristics can be suppressed to a certain extent. The device of this method is as follows Figure 1 shown.

[0005] Figure 1 The scheme shown mainly consists of a laser, an optical coupler, a Mach-Zehnder modulator, a photodetector, a radio frequency amplifier, and an optical isolator.

[0006] The implementation steps of this solution are as follows: First, laser light is emitted from a semiconductor laser and modulated by a Mach-Zehnder modulator. After passing through an optical coupler, the modulated optical signal is split into two paths. One optical signal passes through Delay Line 1, where it is converted into an electrical signal by a photodetector. This signal then passes through an RF amplifier to drive the Mach-Zehnder modulator. The other optical signal passes through an optical isolator, then passes through Delay Line 2 and is coupled to the laser input via an optical coupler to serve as the input signal for the Mach-Zehnder modulator.

[0007] This existing solution introduces an additional optical feedback loop. When the delay of the optical feedback loop and the delay of the optoelectronic loop meet a specific relationship, the delay characteristics of the two loops will exhibit a mutually suppressive effect. By adjusting the energy distribution of the two loops, the overall delay characteristic is suppressed. This solution requires high precision in matching the lengths of the two loops, and the specific loop energy distribution narrows the parameter space of the chaotic state. Summary of the Invention

[0008] In view of the problems of the prior art, the present invention provides a time-delay characteristic suppression type chaos generating device based on a dispersive photoelectric oscillation loop.

[0009] The present invention is a time delay characteristic suppression type chaos generating device based on a dispersive photoelectric oscillation loop. The photoelectric loop is divided into two parts: a dispersive optical path and a feedback circuit. The dispersive optical path is composed of a semiconductor laser, a polarization controller, a Mach-Zehnder modulator, a chirped fiber Bragg grating, a circulator, an optical fiber jumper and an optical power amplifier, and realizes chaos intensity modulation and group delay dispersion processing of the input laser; the feedback circuit is composed of a photodetector, a power divider and a radio frequency amplifier, and realizes the extraction, output and feedback modulation of the chaos intensity signal.

[0010] The specific implementation process is as follows: the laser is emitted by a semiconductor laser, enters a Mach-Zehnder modulator after passing through a polarization controller, and is modulated by the Mach-Zehnder modulator. The modulated optical signal then passes through a chirped fiber Bragg grating, enters an optical power amplifier to increase the power, and is then received by a photodetector and converted into an electrical signal. The electrical signal is divided into two paths by a power divider. One path passes through a radio frequency amplifier to feedback drive the Mach-Zehnder modulator, and the other path is output as an oscillator.

[0011] Compared with the traditional dual-loop optoelectronic oscillator, the present invention has no special requirements for feedback delay and the chaotic parameter space is expanded. The theoretical model of the scheme is described by the following formula:

[0012]

[0013] Where v(t) is the AC modulation voltage of the Mach-Zehnder modulator, V πRFis the alternating current half-wave voltage of the Mach-Zehnder modulator; t and θ are the response time corresponding to the high frequency and low frequency cut-off frequency of the equivalent bandwidth filter, r(t) is the time-domain pulse response of the chirped fiber Bragg grating; φ=πV B / (2V πB ), V B is the direct current modulation voltage of the Mach-Zehnder modulator, V πB is the direct current half-wave voltage of the Mach-Zehnder modulator; γ=αGP, wherein α is the responsivity of the optoelectronic oscillator, and G and P are the gain of the radio frequency and the optoelectronic oscillator respectively; τ is the time delay of the feedback loop.

[0014] The reflection spectrum frequency response of the chirped fiber Bragg grating is obtained by the method of transmission matrix. Firstly, the whole chirped fiber Bragg grating is divided into N segments, each segment of the grating is considered as a uniform fiber Bragg grating, and the transmission matrix of the mth segment of the grating can be expressed by a 2*2 matrix T m .

[0015]

[0016] Among them, κ m =2πf m ρ<δ n > / 2c, f m =c / 2n eff Λ m , f m is the Bragg frequency, n eff is the effective factor, Λ m is the grating period of the mth segment of the uniform grating; the length of each segment of the grating is ΔL; <δ n > is the average variation factor, ρ is the edge visibility factor, and c is the propagation speed of light in vacuum.

[0017] Finally, the forward R N and the backward S N light field of the whole chirped Bragg grating can be calculated by the following formula:

[0018]

[0019] Further, the reflection spectrum frequency response of the chirped fiber Bragg grating can be obtained by S N / R N .

[0020] The beneficial technical effects of the present application are:

[0021] The present invention proposes a dispersive loop solution whose resonant duration is non-unique and continuously distributed, thereby incorporating a delay suppression mechanism into chaos generation. This solution incorporates an inexpensive chirped fiber Bragg grating (FBG) passive optical device into the dispersive loop implementation. This device utilizes the grating's reflection effect to form a loop in the optical path to generate chaos, while simultaneously utilizing the group velocity dispersion caused by the grating's chirp effect to suppress delay characteristics. This type of grating is a highly mature and inexpensive passive optical device, resulting in a simple system with high operability and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the traditional dual-loop optoelectronic oscillator system.

[0023] Figure 2 This is a schematic diagram of the time delay characteristic suppression type chaos generation based on the dispersive photoelectric oscillation loop of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0025] The present invention is a time delay characteristic suppression type chaos generating device based on a dispersive photoelectric oscillation loop, such as Figure 2 As shown in the figure, the optoelectronic loop is divided into two parts: the dispersive optical path and the feedback circuit. The dispersive optical path consists of a semiconductor laser, a polarization controller, a Mach-Zehnder modulator, a chirped fiber Bragg grating, a circulator, an optical fiber jumper and an optical power amplifier, which realizes the chaotic intensity modulation and group delay dispersion processing of the input laser; the feedback circuit consists of a photodetector, a power divider and a radio frequency amplifier, which realizes the extraction, output and feedback modulation of the chaotic intensity signal.

[0026] The specific principle and implementation process are as follows: laser light is emitted by a semiconductor laser, passes through a polarization controller, and then enters a Mach-Zehnder modulator for modulation. The modulated optical signal then passes through a chirped fiber Bragg grating (FBG), before entering an optical power amplifier to increase its power. It is then received by a photodetector and converted into an electrical signal. The electrical signal is split into two paths by a power splitter: one for output and one for feedback through an RF amplifier to drive the FBG. Chaos is generated by forming a loop using the reflection effect of the chirped fiber Bragg grating (FBG), and the dispersion effect of the chirped grating is used to suppress time delay characteristics. Under specific feedback parameters, the laser can exhibit a chaotic dynamic state. Through the dispersion effect of the chirped fiber Bragg grating, the time delay characteristics of the generated laser chaos can be effectively suppressed.

[0027] Compared with the traditional dual-loop optoelectronic oscillator, the present invention has no special requirements for feedback delay and the chaotic parameter space is expanded. The theoretical model of the scheme is described by the following formula:

[0028]

[0029] Where v(t) is the AC modulation voltage of the Mach-Zehnder modulator, V πRF is the AC half-wave voltage of the Mach-Zehnder modulator; t and θ are the response times corresponding to the high-frequency and low-frequency cutoff frequencies of the equivalent bandwidth filter, r(t) is the time-domain impulse response of the chirped fiber Bragg grating; φ = πV B / (2V πB ), V B is the DC modulation voltage of the Mach-Zehnder modulator, V πB is the DC half-wave voltage of the Mach-Zehnder modulator; γ = αGP, where α is the responsivity of the optoelectronic oscillator, G and P are the gains of the RF and optoelectronic oscillators, respectively; τ is the delay of the feedback loop.

[0030] r(t) is the time domain impulse response of the chirped fiber Bragg grating, which can be obtained by first obtaining its frequency response and then performing an inverse Fourier transform.

[0031] The reflection spectrum frequency response of the chirped fiber Bragg grating is obtained by the transmission matrix method. First, the entire chirped fiber Bragg grating is divided into N segments. Each segment is considered to be a uniform fiber Bragg grating. The transmission matrix of the mth segment grating can be obtained by the 2×2 matrix T m Expressed as:

[0032]

[0033] in, κ m =2πf m ρ<δ n > / 2c,f m =c / 2n eff Λ m , f m is the Bragg frequency, n eff is the effective factor, Λ m is the grating period of the mth segment of uniform grating; the length of each grating segment is ΔL; <δ n > is the average variation factor, ρ is the edge visibility factor, and c is the speed of light in vacuum.

[0034] Finally, the forward R of the entire chirped Bragg grating N and backward S N The light field can be calculated as follows:

[0035]

[0036] Furthermore, the reflection spectrum frequency response of the chirped fiber Bragg grating can be obtained by S N / RN get.

Claims

1. A time delay characteristic suppression type chaos generating device based on a dispersive photoelectric oscillation loop, characterized in that: The optoelectronic loop is divided into two parts: the dispersive optical path and the feedback circuit. The dispersive optical path consists of a semiconductor laser, a polarization controller, a Mach-Zehnder modulator, a chirped fiber Bragg grating, a circulator, a fiber jumper, and an optical power amplifier, which realizes chaotic intensity modulation and group delay dispersion processing of the input laser. The feedback circuit consists of a photodetector, a power divider, and a radio frequency amplifier, which realizes the extraction, output, and feedback modulation of the chaotic intensity signal. The specific implementation process is as follows: laser light is emitted by a semiconductor laser, passes through a polarization controller, and then enters a Mach-Zehnder modulator for modulation. The modulated optical signal then passes through a chirped fiber Bragg grating (FBG) and then enters an optical power amplifier to increase its power. The optical signal is then received by a photodetector and converted into an electrical signal. The electrical signal is then split into two paths by a power splitter. One path is fed back through an RF amplifier to drive the Mach-Zehnder modulator, and the other path is output as an oscillator. The theoretical model of the time-delay characteristic suppression type chaos generation is described by the following formula: Where v(t) is the AC modulation voltage of the Mach-Zehnder modulator, V πRF is the AC half-wave voltage of the Mach-Zehnder modulator; t and θ are the response times corresponding to the high-frequency and low-frequency cutoff frequencies of the equivalent bandwidth filter, r(t) is the time-domain impulse response of the chirped fiber Bragg grating; φ = πV B / (2V πB ), V B is the DC modulation voltage of the Mach-Zehnder modulator, V πB is the DC half-wave voltage of the Mach-Zehnder modulator; γ = αGP, where α is the responsivity of the optoelectronic oscillator, G and P are the gains of the RF and optoelectronic oscillators, respectively; τ is the delay of the feedback loop; The reflection spectrum frequency response of a chirped fiber Bragg grating is obtained using the transmission matrix method. First, the entire chirped fiber Bragg grating is divided into N segments. Each segment is considered to be a uniform fiber Bragg grating. The transmission matrix of the mth segment is expressed as a 2×2 matrix: in, κ m =2πf m ρ<δ n > / 2c,f m =c / 2n eff Λ m , f m is the Bragg frequency, n eff is the effective factor, Λ m is the grating period of the mth segment of uniform grating; the length of each segment of uniform grating is ΔL; <δ n > is the average variation factor, ρ is the edge visibility factor, and c is the speed of light in vacuum; Finally, the forward R of the entire chirped Bragg grating N and backward S t The light field is calculated as follows: Furthermore, the reflection spectrum frequency response of the chirped fiber Bragg grating can be obtained by S N / R N get.

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