An all-optical chaotic spatial synchronization generating device and method

Abstract

The application provides a full-optical chaotic space synchronization generating device, comprising a chaotic signal generating module, a free space channel and a signal receiving module; the chaotic signal generating module comprises a first laser and an optical reflector; laser signals emitted by the first laser are reflected by the optical reflector and then injected into the first laser to generate a main chaotic signal; the free space channel is used for transmission of the main chaotic signal; the signal receiving module comprises an optical fiber delay line and a second laser; the signal receiving module is used for receiving the main chaotic signal transmitted by the free space channel and dividing the main chaotic signal into a first main chaotic signal and a second main chaotic signal. The device provided by the application has a simple structure, does not need a complex optical path, is easy to operate, can realize high-quality chaotic space synchronization, and has important significance for realizing large-capacity, high-speed and high-security chaotic space secure communication.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser technology, in particular to a full-optical chaotic spatial synchronization generating device and method. BACKGROUND

[0002] Chaotic laser secure communication is a hardware encryption technology at the physical layer, which transmits information by hiding it in a chaotic signal similar to noise. In the practical application of chaotic secure communication, the receiving end must generate a chaotic signal synchronized with the given chaotic system to enable effective demodulation and recovery of the signal. However, without control, two independent chaotic systems cannot generate synchronized chaotic signals, so how to perform chaotic synchronization is the key to chaotic secure communication.

[0003] At the same time, with the surge in demand for Internet data and network bandwidth, current microwave communication is difficult to meet the demand for future broadband data transmission. Free space communication, with its fast transmission rate and abundant spectrum resources, has become an important technical means for the construction of new-generation information networks. However, in actual free space communication, the transmission of signals in the atmospheric channel is often affected by atmospheric turbulence and background noise, making it difficult to achieve synchronization of the chaotic carrier between the transmitter and receiver. Therefore, for a free space chaotic laser secure communication system, the key technology to improve communication performance lies in the suppression of atmospheric turbulence and the improvement of chaotic spatial synchronization quality.

[0004] Current research on key technologies for free space chaotic laser communication mainly focuses on atmospheric turbulence suppression, while research on chaotic laser spatial synchronization technology is limited and the system structure is complex. Chinese patent CN113890723A proposes adding a dispersion compensation device at the receiving end to use the nonlinear effect caused by dispersion compensation to make the two slave chaotic signals generated by the slave laser flat in frequency spectrum and have no time delay characteristics, achieving high-quality chaotic synchronization. However, this technology only verifies the high-quality chaotic synchronization achieved under the same table and short distance conditions, and cannot guarantee the synchronization performance under long-distance free space conditions. SUMMARY

[0005] Based on the problems existing in the prior art, the present application provides a full-optical chaotic spatial synchronization generating device with simple structure and high chaotic synchronization performance, which can achieve high-quality chaotic synchronization.

[0006] To solve the above technical problems, the present application adopts the following technical solutions:

[0007] A full-optical chaotic spatial synchronization generating device, comprising,

[0008] The chaotic signal generation module comprises a first laser (Distributed Feedback Laser, DFB1) and a mirror (Mirror, M), wherein the laser signal emitted by the DFB1 is reflected by the mirror and then injected into the DFB1, thereby disturbing the steady state of the DFB1 and used for generating a main chaotic signal;

[0009] A free space channel (Free Space Optical Communication, FSO) is used for transmission of the main chaotic signal.

[0010] The signal receiving module comprises a delay line (Delay line, DL) and a second laser (DFB2),

[0011] The signal receiving module is used for receiving the main chaotic signal transmitted by the free space channel and dividing the main chaotic signal into a first main chaotic signal and a second main chaotic signal,

[0012] The first main chaotic signal generates a main chaotic laser I1(t) after passing through the delay line.

[0013] The second main chaotic signal is injected into the second laser and then emitted again to generate a slave chaotic laser I2(t).

[0014] The signal acquisition module comprises a first photodetector (Photodetector, PD1), a second photodetector (Photodetector, PD2), and a high-speed oscilloscope (Oscilloscope, OSC).

[0015] The first photodetector is used for receiving the main chaotic laser I1(t), and the second photodetector is used for receiving the slave chaotic laser I2(t).

[0016] The high-speed oscilloscope OSC acquires the I1(t) and I2(t) in real time and analyzes a cross correlation coefficient CC, wherein the cross correlation coefficient CC is the maximum value of the absolute value of a cross correlation function (Crosscorrelation function, CCF), and the calculation method of the cross correlation function CCF is shown in Formula 1.

[0017]

[0018] The I1(t) is the intensity of the main chaotic laser, <I1(t)> is the average value of the intensity of the main chaotic laser, I2(t) is the intensity of the slave chaotic laser, and <I2(t)> is the average value of the intensity of the slave chaotic laser.

[0019] By adjusting the parameters of the chaotic signal generation module and the signal receiving module, 0.9≤CC≤1 is controlled.

[0020] As an optimization scheme, the all-optical chaotic spatial synchronization generation device further comprises a filtering module. After the OSC collects I1(t) and I2(t) in real time, the filtering module is used as an initial input for offline processing, and then CC is calculated.

[0021] Preferably, the filtering module comprises a low-pass filter.

[0022] Further, the low-pass filter is a 4th order Butterworth filter, and the filter bandwidth of the low-pass filter needs to be reasonably set.

[0023] As a preferred scheme, the chaotic signal generation module further comprises,

[0024] a first fiber coupler (FC1) and a variable optical attenuator (VOA);

[0025] The laser generated by the first laser DFB1 is split into two paths after being incident on the first fiber coupler FC1. One of the two paths is incident on a light reflector after passing through the VOA. The light reflector reflects the incident laser into the DFB1 again, thereby disturbing the steady state of the DFB1 and causing the laser to enter a chaotic state. The main chaotic signal is then emitted again through the FC1.

[0026] As a preferred scheme, the chaotic signal generation module further comprises, in sequence along the direction of emission of the main chaotic signal,

[0027] a first optical isolator (OI1), a first polarization controller (PC1), a fiber amplifier (FA), a first collimator (Col.1), and a telescope (Tel.1);

[0028] The OI1 is used to control the unidirectional passage of the main chaotic signal.

[0029] The PC1 is used to adjust the polarization state of the main chaotic signal during transmission, which is conducive to achieving high-quality chaotic synchronization at the back end.

[0030] The FA is used to adjust the optical power of the main chaotic signal emitted by the PC1; and to compensate for the energy loss caused by coupling at the receiving end.

[0031] The Col.1 is used to collimate the main chaotic signal emitted by the FA.

[0032] Tel.1 is used to expand the main chaotic signal laser beam emitted from Col.1.

[0033] As a preferred embodiment, the fiber amplifier is an erbium-doped fiber amplifier (EDFA).

[0034] As a preferred embodiment, the signal receiving module further includes components connected sequentially along the incident direction of the main chaotic signal.

[0035] Telescope (Tel.2), Collimator (Col.2), Optical Isolator (OI2), Fiber Coupler (FC2), Polarization Controller (PC2)

[0036] The functions of each component in the signal receiving module are similar to those in the chaotic signal generation module.

[0037] Tel.2 is used to receive the main chaotic signal transmitted via FSO;

[0038] Col.2 is used to couple the main chaotic signal transmitted via the space channel into the optical fiber;

[0039] OI2 is used to control the unidirectional passage of the main chaotic signal;

[0040] FC2 is used to split the received main chaotic signal into two beams, namely the first main chaotic signal and the second main chaotic signal. The first main chaotic signal is directly incident on the signal receiving module, and the second main chaotic signal is incident on DFB2.

[0041] After receiving the second main chaotic signal, DFB2 processes it and emits it again to generate chaotic laser I2(t);

[0042] I2(t) passes through PC2 again and is then injected into FC2. After exiting again, it is injected into DL and then received by the signal receiving module.

[0043] PC2 is used to adjust the polarization state of I2(t) during transmission. The output of PC2 is connected to the input of DFB2, and the output of FC2 is connected to the input of DL.

[0044] As a preferred embodiment, the parameter settings of DFB2 are the same as those of DFB1.

[0045] As a preferred embodiment, the multiple of Tel.1 is 5 times and the multiple of Tel.2 is 8 times.

[0046] Further, the length of the FSO is 7.5-8.5m.

[0047] A method for generating full-optical chaotic spatial synchronization, characterized in that the method comprises:

[0048] S1: generating a master chaotic signal, and dividing the master chaotic signal into a first master chaotic signal and a second master chaotic signal;

[0049] S2: processing the first master chaotic signal and the second master chaotic signal to generate a master chaotic laser I1(t) and a slave chaotic laser I2(t);

[0050] S3: adjusting device parameters to control 0.9≤CC≤1, so as to realize chaotic synchronization.

[0051] Compared with the prior art, the beneficial effects of the present application are:

[0052] 1. The full-optical chaotic spatial synchronization device based on the one-way injection locking mechanism provided by the present application has a simple structure, does not require a complex optical path, is simple to operate, and can realize high-quality chaotic spatial synchronization, which is of great significance for realizing large-capacity, high-speed, and high-security chaotic spatial secure communication.

[0053] 2. The filtering module in the present application is simple and effective, can further eliminate the influence of system noise, increase the CC value, and improve the chaotic spatial synchronization performance. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 The structure diagram of the filtering module provided in an embodiment of the present application;

[0055] Figure 2 The structure diagram of the full-optical chaotic spatial synchronization generating device provided in an embodiment of the present application;

[0056] Figure 3 The time-domain waveform and power spectrum of the chaotic signal provided in an embodiment of the present application;

[0057] Figure 4 The master and slave chaotic laser synchronization scatter point diagram provided in an embodiment of the present application. DETAILED DESCRIPTION

[0058] The features and exemplary embodiments of various aspects of the present application will be described below in detail, in order to make the purposes, technical solutions and advantages of the present application more clear and apparent, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, but not to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by showing examples of the present application.

[0059] In an embodiment of the present application, a full-optical chaotic spatial synchronization generating device is provided, comprising,

[0060] A chaotic signal generating module, comprising a first laser and an optical mirror, is configured to generate a main chaotic signal;

[0061] A free space channel is configured to transmit the main chaotic signal;

[0062] A signal receiving module, comprising an optical fiber delay line and a second laser,

[0063] The signal receiving module is configured to receive the main chaotic signal transmitted by the free space channel, and divide the main chaotic signal into a first main chaotic signal and a second main chaotic signal,

[0064] The first main chaotic signal generates a main chaotic laser I1(t) after passing through the optical fiber delay line;

[0065] The second main chaotic signal generates a slave chaotic laser I2(t) after being incident on the second laser and then being emitted again;

[0066] A signal collecting module, comprising a first photodetector, a second photodetector, and a high-speed oscilloscope;

[0067] The first photodetector is configured to receive the main chaotic laser I1(t), and the second photodetector is configured to receive the slave chaotic laser I2(t);

[0068] The high-speed oscilloscope OSC collects the I1(t) and I2(t) in real time and analyzes a cross correlation coefficient CC, wherein the cross correlation coefficient CC is a maximum value of an absolute value of a cross correlation function (CCF), and the CCF is calculated in a manner shown in Formula 1,

[0069]

[0070] The I1(t) is the intensity of the main chaotic laser, <I1(t)> is the average value of the main chaotic laser intensity, I2(t) is the intensity of the slave chaotic laser, and <I2(t)> is the average value of the intensity of the slave chaotic laser;

[0071] By adjusting the parameters of the chaotic signal generation module and the signal receiving module, 0.9≤CC≤1 is controlled.

[0072] The all-optical chaotic spatial synchronization generation device provided in the application generates main chaotic laser by using an external light feedback type structure at the sending end, generates slave chaotic laser based on a one-way injection structure at the receiving end, and realizes the output of the synchronized main chaotic laser signal and slave chaotic laser signal in a spatial channel.

[0073] In the synchronization generation device, because the main and slave chaotic lasers generated by the first laser and the second laser experience different optical paths when reaching the signal acquisition module, a large synchronization delay is caused, and a single-mode optical fiber needs to be introduced as an optical fiber delay line to compensate for the synchronization delay of the receiving end. The optical fiber delay line can eliminate the synchronization errors introduced by the optical fiber link, the spatial link and various devices, so that the synchronization of the sending end and the receiving end can be realized when a small data length is acquired when acquiring the waveform.

[0074] In order to quantitatively analyze the synchronization quality, the maximum absolute value of CCF, that is, the cross-correlation coefficient CC, is usually selected to represent the cross-correlation degree of the chaotic signal. The larger the CC value is, the higher the correlation of the two time series is, the closer the CC value is to 1, the better the synchronization quality is, and the closer the CC value is to 0, the worse the synchronization quality is. When the injection intensity is within a certain range, high-quality chaotic synchronization can be formed.

[0075] In an embodiment of the application, as shown in Figure 1 The filter module includes a low-pass filter.

[0076] Further, the low-pass filter adopts a 4th-order Butterworth filter, and the filter bandwidth of the low-pass filter needs to be reasonably set, so that the high-frequency noise can be well filtered out, thereby retaining the chaotic signal with a lower frequency

[0077] Figure 1 A schematic diagram of the filter module is given. When the chaotic signal is transmitted in the optical fiber link and the free space channel, it will be affected by multiple devices and free space disturbances. These background noises will disturb the waveform of the chaotic laser and affect the synchronization of the chaotic system. The filter module is used to filter out the real noise in the chaotic laser similar to the noise.

[0078] The signal collected by the high-speed oscilloscope OSC is set as the initial input, the low-pass filter is set, that is, the high-frequency noise in the signal is filtered out, and the chaotic signal with a lower frequency is allowed to pass, so as to obtain the filtered signal. Then, the main and slave chaotic lasers after filtering are calculated to obtain the cross-correlation coefficient CC.

[0079] In an embodiment of the present application, the chaotic signal generation module further comprises,

[0080] a first fiber coupler (FC1), a variable optical attenuator (VOA),

[0081] The laser generated by the first laser DFB1 is split into two paths after being incident on the first fiber coupler FC1, one of which is incident on the optical reflector after passing through the VOA, and the optical reflector reflects the incident laser into the DFB1 again, thereby disturbing the steady state of the DFB1 and causing the laser to enter a chaotic state, generating a main chaotic signal which is then emitted again through the FC1.

[0082] In an embodiment of the present application, the chaotic signal generation module further comprises, connected in sequence along the direction of emission of the main chaotic signal,

[0083] a first optical isolator, a first polarization controller, a fiber amplifier, a first collimator, and a beam expander;

[0084] The OI1 is used to control the unidirectional passage of the main chaotic signal;

[0085] The PC1 is used to adjust the polarization state of the main chaotic signal during transmission, which is conducive to realizing high-quality chaotic synchronization at the back end;

[0086] The FA is used to adjust the optical power of the main chaotic signal emitted by the PC1; to compensate for the energy loss caused by coupling at the receiving end;

[0087] The Col.1 is used to collimate the main chaotic signal emitted by the FA;

[0088] The Tel.1 is used to change the laser beam emitted by the Col.1 into a collimated parallel light beam.

[0089] In an embodiment of the present application, as shown in Figure 2 the signal receiving module further comprises, connected in sequence along the direction of incidence of the main chaotic signal,

[0090] a telescope (Tel.2), a second collimator (Col.2), a second optical isolator (OI2), a second fiber coupler (FC2), and a second polarization controller (PC2),

[0091] The functions of the components in the signal receiving module are similar to those in the chaotic signal generation module,

[0092] Tel.2 is used for receiving the main chaotic signal transmitted by FSO;

[0093] Col.2 is used for coupling the main chaotic signal transmitted by space channel into optical fiber;

[0094] OI2 is used for controlling the unidirectional transmission of the main chaotic signal;

[0095] FC2 is used for dividing the received main chaotic signal into two beams, i.e. the first main chaotic signal and the second main chaotic signal, wherein the first main chaotic signal is directly incident into the signal receiving module, and the second main chaotic signal is incident into DFB2;

[0096] DFB2 receives the second main chaotic signal and processes it, and then generates the slave chaotic laser I2(t) after the second emission;

[0097] I2(t) is incident into FC2 after passing through PC2 again, and then is incident into DL after the second emission, and is received by the signal receiving module after the third emission; wherein PC2 is used for adjusting the polarization state of I2(t) in the transmission process, the output end of PC2 is connected with the input end of DFB2, and the output end of FC2 is connected with the input end of DL.

[0098] Preferably, the parameter setting of DFB2 is consistent with that of DFB1.

[0099] In the actual use of the present application, the injection light intensity and wavelength detuning of the main laser injected into the receiving end are regulated by adjusting the rotation angle of the polarization controller PC1, the temperature control setting of the main laser DFB1 and the amplification multiple of the EDFA, in a specific embodiment, the adjustable range of the EDFA is 10dBm-20dBm, the wavelength detuning range of the main and slave lasers is 0nm-0.35nm, combined with the setting of the driving current of the two emitting lasers, the synchronous main and slave chaotic lasers I1(t), I2(t) are finally generated.

[0100] In a specific embodiment of the present application, the multiple of Tel.1 is 5 times, and the multiple of Tel.2 is 8 times.

[0101] Preferably, the length of FSO is 7.5-8.5m.

[0102] The present application also provides a method for generating all-optical chaotic spatial synchronization, which comprises:

[0103] S1: generating a main chaotic signal, and dividing the main chaotic signal into a first main chaotic signal and a second main chaotic signal;

[0104] S2: processing the first main chaotic signal and the second main chaotic signal to generate a main chaotic laser I1(t) and a slave chaotic laser I2(t);

[0105] S3: Adjusting the device parameters to control 0.9≤CC≤1 to realize chaos synchronization.

[0106] In one embodiment, the driving current of DFB1 and DFB2 is set to 20 mA, the control temperature is set to 25℃, and the output power of the two lasers is 3 dBm and 1.72 dBm, respectively. The center wavelength of the intrinsic laser spectrum output by DFB1 and DFB2 is 1549.56 nm and 1549.47 nm, respectively, and the 3 dB bandwidth is 0.017 nm and 0.016 nm, respectively. The 3 dB bandwidth of the chaotic laser generated after adding the external optical feedback structure at the transmitting end is expanded to 0.08 nm, and the center wavelength remains unchanged. The 3 dB bandwidth of the chaotic laser generated after the external optical injection structure at the receiving end is expanded to 0.07 nm, and the center wavelength is red-shifted to 1549.58 nm, which is almost consistent with the spectrum of the transmitting end chaotic laser.

[0107] The EDFA is set to 16 dBm, and the coupling efficiency of the receiving end is fixed at 9%, at which time the power after the coupler of the receiving end is 5.5 dBm, and the power injected into DFB2 is 2.5 dBm.

[0108] The chaotic synchronization is adjusted, and the time-domain waveform and power spectrum of the master and slave chaotic lasers are as shown in Figure 3 The time-domain waveforms of the master and slave lasers show a high degree of similarity. The effective bandwidths of the transmitting end and receiving end chaotic lasers are 8.5 GHz and 13.5 GHz, respectively.

[0109] The collected waveforms are filtered. The low-pass filter uses a 4th order Butterworth filter.

[0110] 500 points are taken into the cross-correlation function, and the correlation point diagram of the output signals of the master and slave lasers is as shown in Figure 4 The synchronization coefficient CC value is 0.922, indicating that under the current parameter setting, the chaotic laser can achieve high-quality synchronization performance after free-space transmission.

[0111] A single-mode optical fiber with a length of 15 m is introduced as a time delay line in the signal acquisition device, so the synchronization time delay of the master and slave chaotic lasers is 2.1 ns.

Claims

1. A fully optical chaotic spatial synchronization generator, characterized in that, The application relates to a method for generating chaotic signals, and belongs to the field of chaotic signal generation. The method comprises the following steps: a chaotic signal generation module, a free space channel, a signal receiving module, a signal collection module and a filter module. The chaotic signal generation module comprises a first laser and an optical reflector, wherein laser signals emitted by the first laser are reflected by the optical reflector and then injected into the first laser to generate a main chaotic signal; The free space channel is used for transmission of the main chaotic signal; The signal receiving module comprises an optical fiber delay line and a second laser; The signal receiving module is used for receiving the main chaotic signal transmitted by the free space channel and dividing the main chaotic signal into a first main chaotic signal and a second main chaotic signal, wherein, the first main chaotic signal generates main chaotic laser I1(t) after passing through the optical fiber delay line; the second main chaotic signal generates slave chaotic laser I2(t) after being injected into the second laser and then emitted again; The signal collection module comprises a first photodetector, a second photodetector and a high-speed oscilloscope; The first photodetector is used for receiving the main chaotic laser I1(t), and the second photodetector is used for receiving the slave chaotic laser I2(t); ； The high-speed oscilloscope collects the I1(t) and I2(t) in real time and analyzes a cross-correlation coefficient CC, wherein the cross-correlation coefficient CC is the maximum value of an absolute value of a cross-correlation function CCF, the calculation mode of the CCF is shown in formula 1, 2. The all-optical chaotic spatial synchronization generating device according to claim 1, characterized in that: the I1(t) is the intensity of the main chaotic laser, <I1(t)> is the average value of the intensity of the main chaotic laser, I2(t) is the intensity of the slave chaotic laser, and <I2(t)> is the average value of the intensity of the slave chaotic laser, 3. The all-optical chaotic spatial synchronization generating device according to claim 2, characterized in that: the parameter of the chaotic signal generation module and the parameter of the signal receiving module are adjusted to control 0.9<=CC<=1.

4. The all-optical chaotic spatial synchronization generating device according to claim 3, wherein: The filter module is further included, and after the high-speed oscilloscope collects the I1(t) and I2(t) in real time, the I1(t) and I2(t) are taken as initial inputs of the filter module to be processed offline, and then the CC is calculated.

5. The all-optical chaotic spatial synchronization generating device according to claim 1, wherein: The filter module comprises a low-pass filter. The low-pass filter is a fourth-order Butterworth filter. The chaotic signal generation module further comprises a first optical fiber coupler and an adjustable attenuator. The laser generated by the first laser is divided into two paths after being incident to the first optical fiber coupler, 6. The all-optical chaotic spatial synchronization generating device according to claim 5, wherein: one of the two paths is incident to the optical reflector through the adjustable attenuator, the optical reflector reflects the incident laser into the first laser again, thereby disturbing the steady state of the first laser, making the laser enter a chaotic state, generating the main chaotic signal, and then emitting the main chaotic signal through the first optical fiber coupler again.

7. The all-optical chaotic spatial synchronization generating device according to claim 1, wherein: The chaotic signal generation module further comprises a first optical fiber isolator, a first polarization controller, an optical fiber amplifier and a first collimator which are connected in sequence along the emission direction of the main chaotic signal. The signal receiving module further comprises a beam reducer, a second collimator, a second optical fiber isolator, a second optical fiber coupler and a second polarization controller which are connected in sequence along the incident direction of the main chaotic signal.

8. The all-optical chaotic spatial synchronization generating device according to claim 1, wherein: The output end of the second polarization controller is connected with the input end of the second laser, and the output end of the second optical fiber coupler is connected with the input end of the optical fiber delay line.

9. A method for all-optical chaotic spatiotemporal synchronization, applied to the apparatus of any one of claims 1-8, characterized in that, The parameter setting of the second laser is the same as that of the first laser. The method comprises the following steps: S1: generating a main chaotic signal and dividing the main chaotic signal into a first main chaotic signal and a second main chaotic signal; S2: collecting the first main chaotic signal and the second main chaotic signal through the signal collection module; S3: calculating a cross-correlation coefficient CC of the first main chaotic signal and the second main chaotic signal through the high-speed oscilloscope; S4: adjusting the parameter of the chaotic signal generation module and the parameter of the signal receiving module to control 0.9<=CC<=1. S2: processing the first master chaotic signal and the second master chaotic signal to generate a master chaotic laser I1(t) and a slave chaotic laser I2(t); S3: adjusting the device parameters to control a cross-correlation coefficient CC0.9≤CC≤1, the cross-correlation coefficient CC being a maximum value of an absolute value of a cross-correlation function CCF, The calculation method of the CCF is shown in formula 1, ； The I1(t) is the intensity of the master chaotic laser, <I1(t)> is the average value of the intensity of the master chaotic laser, I2(t) is the intensity of the slave chaotic laser, and <I2(t)> is the average value of the intensity of the slave chaotic laser.

Images