Intermediate infrared data encryption optical communication system and method based on time domain ghost imaging

Abstract

The invention discloses an intermediate infrared data encryption optical communication system and method based on time domain ghost imaging, and the system comprises a continuous light laser which is used for generating tunable near-infrared continuous light; the signal encryption module is used for generating a target data signal and generating a key to encrypt the target data signal to obtain an encrypted signal; the near-infrared high-speed light modulation module is used for performing time-domain high-speed modulation on tunable near-infrared continuous light in response to the encrypted signal to generate a near-infrared modulated light signal; the dispersion optical fiber module is used for introducing a dispersion compensation optical fiber to carry out time domain stretching and physical encryption on the near-infrared modulation optical signal and then sending the near-infrared modulation optical signal to the nonlinear frequency down-conversion module; the near-infrared single-frequency laser is used for outputting near-infrared single-frequency continuous light; the nonlinear frequency down-conversion module is used for performing beam combination on the near-infrared modulated light signal and the near-infrared single-frequency continuous light, and generating a mid-infrared light signal carrying an encrypted signal through frequency down-conversion; the mid-infrared low-speed light detection module is used for detecting mid-infrared light signals and recording signal integral intensity; and the time domain ghost imaging data decryption module is used for carrying out cross-correlation on the signal integral intensity and the secret key and carrying out decryption to obtain a target data signal so as to realize mid-infrared band data encryption transmission. By combining the frequency down-conversion technology and the calculation time domain ghost imaging, the problem of bandwidth limitation of the intermediate infrared detector is solved, and the encryption rate is improved.

Description

Technical Field

[0001] The present invention relates to the field of mid-infrared optical communications, and in particular to a mid-infrared data encryption optical communication system and method based on time-domain ghost imaging. Background Art

[0002] A time-domain ghost imaging system uses a low-temporal-coherence light source with random intensity fluctuations in the time domain as the probe light. By correlating multiple measurements of the light source's own temporal intensity fluctuations with the integrated power after the light source is subjected to a temporal object (such as an intensity modulation signal from a high-speed electro-optical modulator), the ultrafast optical modulation signal can be reconstructed. Since only the integrated optical power needs to be detected after the interaction with the temporal object, time-domain ghost imaging significantly reduces the requirements for the measured optical signal intensity compared to direct detection. Furthermore, the reconstruction of the temporal object by time-domain ghost imaging is insensitive to optical time-domain signal distortion that may be introduced in the optical detection link. Furthermore, an arbitrary waveform generator and a high-speed optical modulator can be used to generate a known random signal to pre-modulate the light source's temporal intensity, thus constructing a computational time-domain ghost imaging system. This system can detect high-speed time-domain modulated signals using only a slow detector. Computational time-domain ghost imaging has important applications in long-distance underwater communications, high-speed and secure communications, and quantum communications in the visible and near-infrared spectral regions. Furthermore, free-space optical communication systems based on computational time-domain ghost imaging are highly resistant to atmospheric turbulence, offering an alternative for reliable transmission in free-space optical communication systems. Because computational time-domain ghost imaging allows the use of highly sensitive, low-bandwidth photodetectors to retrieve fast-time objects and encrypt transmitted data, this new concept could provide a path for high-speed, secure communication in highly lossy and turbulent transmission channels.

[0003] However, data encryption optical communications based on computational time-domain ghost imaging are still limited to the visible and near-infrared bands, while applications in the mid-infrared band are still blank. The mid-infrared spectral region, especially in the 3-5μm and 8-12μm atmospheric windows, is particularly advantageous for the application of free-space optical communications due to its high transparency and low scattering loss. However, current technology faces two major bottlenecks: (1) detector bandwidth limitations. Commercial mid-infrared detectors (such as mercury cadmium telluride detectors) have only a bandwidth of the order of 100MHz, which limits the ability to carry out high-speed free-space encrypted optical communications in the mid-infrared band; (2) insufficient encryption rate. The mid-infrared encryption scheme based on chaotic quantum cascade lasers has a data encryption transmission rate of less than 10Mbps due to its small chaotic bandwidth. Therefore, compared with the visible and near-infrared regions, it is still challenging to achieve high-speed data encryption optical communications in the mid-infrared region. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a mid-infrared data encryption high-speed optical communication system and method based on time-domain ghost imaging that can break through the limitations of detector bandwidth and encryption rate.

[0005] To solve the above technical problems, the present invention adopts a technical solution: to provide a mid-infrared data encryption optical communication system based on time-domain ghost imaging, comprising:

[0006] Continuous-wave lasers, used to generate tunable near-infrared continuous light with a wavelength within a specific range;

[0007] A signal encryption module, configured to generate a target data signal and generate a key to encrypt the target data signal to obtain an encrypted signal;

[0008] a near-infrared high-speed optical modulation module, configured to perform time-domain high-speed modulation on the tunable near-infrared continuous light in response to the encrypted signal to generate a near-infrared modulated optical signal, wherein the near-infrared high-speed optical modulation module uses an electro-optical modulator with a modulation bandwidth smaller than the encryption signal rate;

[0009] a dispersion optical fiber module, configured to perform time domain stretching on the near-infrared modulated optical signal output by the near-infrared high-speed optical modulation module by introducing a dispersion-compensating optical fiber, and to send the signal to the nonlinear frequency down-conversion module after physical encryption;

[0010] Near-infrared single-frequency laser, used to output near-infrared single-frequency continuous light;

[0011] A nonlinear frequency down-conversion module is used to combine the physically encrypted near-infrared modulated optical signal with the near-infrared single-frequency continuous light beam, and generate a mid-infrared optical signal carrying the encrypted signal through frequency down-conversion;

[0012] Mid-infrared low-speed light detection module, used to detect mid-infrared light signals carrying encrypted signals and record the signal integrated intensity;

[0013] The time-domain ghost imaging data decryption module is used to cross-correlate the signal integrated intensity with the key, decrypt the signal to obtain the target data signal, and realize encrypted transmission of mid-infrared band data.

[0014] Furthermore, the signal encryption module includes:

[0015] a computer for generating a randomized Hadamard matrix as a key and multiplying the generated target data signal by the key to generate an encrypted signal in the form of a digital signal;

[0016] The arbitrary waveform generator is used to convert the encrypted signal in the form of a digital signal output by the computer into an encrypted signal in the form of an electrical signal to drive the near-infrared high-speed light modulation module.

[0017] Furthermore, the nonlinear frequency down-conversion module includes:

[0018] A dichroic mirror is used to combine the near-infrared modulated light signal with the near-infrared single-frequency continuous light;

[0019] Nonlinear crystals are used to generate mid-infrared light carrying encrypted signals through the difference frequency effect, thus enabling the transfer of encrypted signals from the near-infrared to the mid-infrared band.

[0020] The long-pass filter is used to filter out the near-infrared light in the mid-infrared light and obtain the mid-infrared light carrying the encrypted signal.

[0021] Furthermore, the nonlinear crystal may be a periodically poled lithium niobate crystal for generating a mid-infrared light signal with a wavelength range of 3-5 μm; the nonlinear crystal may also be a phosphorus germanium zinc crystal or a BaGa4Se7 crystal for generating a mid-infrared light signal with a wavelength range of 8-12 μm.

[0022] Furthermore, it also includes a mid-infrared light transmission channel, and the mid-infrared light signal carrying the encrypted signal generated by the nonlinear frequency down-conversion module will be output and then introduced into the mid-infrared light transmission channel for transmission;

[0023] The mid-infrared light transmission channel includes a first lens, a second lens, and a free-space optical channel. The generated mid-infrared light carrying the encrypted signal is collimated by the first lens, propagates in the free-space optical channel, and is focused by the second lens to the mid-infrared low-speed light detection module.

[0024] Furthermore, the mid-infrared low-speed light detection module includes:

[0025] A photodetector, used to convert mid-infrared light signals into electrical signals and measure their integrated signal intensity;

[0026] An oscilloscope is used to record the integrated intensity of the signal output by the photodetector.

[0027] To solve the above technical problems, another technical solution adopted by the present invention is to provide a mid-infrared data encryption optical communication method based on time-domain ghost imaging, comprising the following steps:

[0028] Obtaining tunable near-infrared continuous light with a wavelength within a specific range;

[0029] generating a target data signal and encrypting the target data signal to obtain an encrypted signal;

[0030] In response to the encrypted signal, the tunable near-infrared continuous light is subjected to time-domain high-speed modulation using an electro-optical modulator having a modulation bandwidth smaller than the encryption signal rate to generate a near-infrared modulated optical signal;

[0031] Introducing dispersion-compensating optical fiber to perform time domain stretching on the near-infrared modulated optical signal output by the near-infrared high-speed optical modulation module, and sending it to the nonlinear frequency down-conversion module after physical encryption;

[0032] Utilizing a near-infrared single-frequency laser to output single-frequency continuous light, combining the physically encrypted near-infrared modulated optical signal with the single-frequency continuous light, and generating a mid-infrared optical signal carrying the encrypted signal through frequency down-conversion;

[0033] Detect the mid-infrared light signal carrying the encrypted signal and record the signal integrated intensity;

[0034] The signal integrated intensity is cross-correlated with the key, and the target data signal is decrypted to achieve encrypted transmission of mid-infrared band data.

[0035] The mid-infrared data encryption optical communication system and method based on time-domain ghost imaging of the present invention have at least the following beneficial effects: by combining frequency down-conversion technology with computational time-domain ghost imaging, the present invention losslessly transfers high-speed near-infrared encrypted signals to the mid-infrared band through a nonlinear frequency down-conversion module, thereby solving the problem of insufficient bandwidth of commercial mid-infrared detectors and achieving high-precision decryption at a data rate of 64Mbps, significantly surpassing traditional mid-infrared encryption schemes; a randomized Hadamard matrix is used as a key to encrypt the target data signal, and then an electro-optical modulator with a modulation bandwidth less than the encryption signal rate is used and a dispersion-compensating optical fiber is used to time-domain stretch the near-infrared modulated optical signal, introducing signal distortion, and dual encryption of digital encryption and physical encryption to enhance security; by combining frequency down-conversion and computational time-domain ghost imaging technology, mid-infrared light carrying encrypted signals can be generated, and a detection and decryption module is used to realize detection and decryption of high-speed encrypted signals in the mid-infrared band; by utilizing the time-domain ghost imaging technology of frequency down-conversion and adjusting the near-infrared laser wavelength and nonlinear crystal, the system can flexibly output in the 35μm or 812μm mid-infrared band, and flexibly tune the operating wavelength of the mid-infrared data encryption optical communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0037] Figure 1 This is a structural diagram of the mid-infrared data encryption optical communication system based on time-domain ghost imaging of the present invention.

[0038] Figure 2 The figure shows the time domain waveform of the target data signal, key and encrypted signal.

[0039] Figure 3This is a time-resolved intensity curve of 1.5μm near-infrared modulated light measured when the modulation speed increases from 1Mbps to 64Mbps.

[0040] Figure 4 This is a comparison chart of the time-resolved intensity curves of 1.5μm near-infrared continuous light modulated by encrypted signals and 3μm mid-infrared light generated by frequency down-conversion.

[0041] Figure 5 The figure is a comparison diagram of signal waveforms obtained by using the method of the present invention and not using the method of the present invention at different data transmission rates.

[0042] Figure 6 A test chart of the tuning capability and encrypted communication performance of the PPLN-based frequency down-conversion time-domain ghost imaging method in the mid-infrared band.

[0043] Figure 7 The present invention is a flowchart of a method for mid-infrared data encryption optical communication based on time-domain ghost imaging in an implementation manner.

[0044] The meanings of the reference numerals in the accompanying drawings are:

[0045] Continuous light laser 100, signal encryption module 200, computer 210, arbitrary waveform generator 220, near-infrared high-speed optical modulation module 300, near-infrared single-frequency laser 400, nonlinear frequency down-conversion module 500, dichroic mirror 510, nonlinear crystal 520, long-pass filter 530, dispersive fiber module 700, mid-infrared low-speed optical detection module 700, photodetector 710, oscilloscope 720, time-domain ghost imaging data decryption module 800, mid-infrared optical transmission channel 900. DETAILED DESCRIPTION

[0046] The present invention will be further described below with reference to the accompanying drawings.

[0047] See also Figure 1The mid-infrared data encryption optical communication system based on time-domain ghost imaging of the present invention includes a continuous light laser 100, a signal encryption module 200, a near-infrared high-speed optical modulation module 300, a near-infrared single-frequency laser 400, a nonlinear frequency down-conversion module 500, a dispersive optical fiber module 600, a mid-infrared low-speed optical detection module 700 and a time-domain ghost imaging data decryption module 800. During communication, the signal encryption module 200 generates a target data signal and generates a key to encrypt the target data signal, obtains an encrypted signal and sends it to the near-infrared high-speed optical modulation module 300; the continuous light laser 100 generates tunable near-infrared continuous light with a wavelength within a specific range and transmits it to the near-infrared high-speed optical modulation module 300; the near-infrared high-speed optical modulation module 300 responds to the encrypted signal, performs time-domain high-speed modulation on the tunable near-infrared continuous light generated by the continuous light laser 100, generates a near-infrared modulated optical signal and sends it to the dispersion optical fiber module 600; the dispersion optical fiber module 600 introduces a dispersion-compensating optical fiber to perform time-domain stretching on the near-infrared modulated optical signal output by the near-infrared high-speed optical modulation module 300 and sends it to the nonlinear frequency down-conversion module 500. The near-infrared single-frequency laser 400 outputs near-infrared single-frequency continuous light and transmits it to the nonlinear frequency down-conversion module 500; the nonlinear frequency down-conversion module 500 combines the received near-infrared modulated light signal with the near-infrared single-frequency continuous light, generates a mid-infrared light signal carrying an encrypted signal through frequency down-conversion, and transmits it; the mid-infrared low-speed light detection module 700 detects the mid-infrared light signal carrying the encrypted signal and records the signal integral intensity, and the time-domain ghost imaging data decryption module 800 cross-correlates the signal integral intensity with the key, decrypts and obtains the target data signal, thereby realizing encrypted transmission of mid-infrared band data.

[0048] In this embodiment, the continuous light laser 100 is a 1.5 μm band continuous light laser 100 to generate tunable near-infrared continuous light in the range of 1520-1560 nm.

[0049] The signal encryption module 200 includes a computer 210 and an arbitrary waveform generator 220. The specific working process of the signal encryption module 200 is that the computer 210 generates a randomized Hadamard matrix as a key and multiplies the generated target data signal with the key to generate an encrypted signal in the form of a digital signal and load it into the arbitrary waveform generator 220; the arbitrary waveform generator 220 converts the encrypted signal in the form of a digital signal output by the computer 210 into an encrypted signal in the form of an electrical signal to drive the near-infrared high-speed optical modulation module 300. In this embodiment, the target data signal is composed of a 64-bit pseudo-random binary sequence (PRBS), the key is a 64-order randomized Hadamard matrix, and the rate of the encrypted signal can reach up to 64 Mbps. Please refer to Figure 2, is the time domain waveform of the target data signal, key and encrypted signal. Figure 2 (a) is the time domain waveform of the target data signal composed of a 64-bit pseudo-random binary sequence signal. Figure 2 (b) is the randomized Hadamard matrix generated as the key, Figure 2 (c) shows three randomly selected encrypted signals. It can be seen that their time domain waveforms are completely different from those of the target data signal, verifying that the encryption of the target data signal is successful.

[0050] The near-infrared high-speed optical modulation module 300 is used to perform high-speed temporal modulation on the tunable near-infrared continuous light generated by the continuous light laser 100 to generate a near-infrared modulated optical signal. The near-infrared high-speed optical modulation module 300 is configured as an electro-optical modulator. To achieve physical encryption of the target data signal, in this embodiment, the electro-optical modulator uses an electro-optical modulator with a modulation bandwidth less than the encryption signal rate. In this embodiment, the modulation bandwidth of the electro-optical modulator corresponds to a rise time of approximately 35ns. Figure 3 Time-resolved intensity curves of 1.5μm near-infrared modulated light were obtained at EO modulation speeds of 1, 10, 20, and 64 Mbps, respectively. Due to the limited modulation bandwidth of the EO modulator, the temporal pattern of the modulated 1.5μm near-infrared light closely follows the ciphertext at modulation speeds of 1 Mbps and 10 Mbps. Due to the limited modulation bandwidth of the EO modulator, the temporal pattern of the modulated 1.5μm near-infrared light closely follows the ciphertext. However, due to the limited modulation bandwidth of the EO modulator, the temporal pattern is severely distorted at a modulation speed of 64 Mbps, making it impossible to discern the ciphertext pattern. This provides additional physical encryption for the target data signal.

[0051] The dispersion fiber module 600 is disposed between the near-infrared high-speed optical modulation module 300 and the nonlinear frequency down-conversion module 500. It is used to time-stretch the near-infrared modulated optical signal output by the near-infrared high-speed optical modulation module 300 by introducing a dispersion-compensating optical fiber, and then transmit the result to the nonlinear frequency down-conversion module 500. In this embodiment, the dispersion-compensating optical fiber is longer than 10 km. Using this dispersion-compensating optical fiber to time-stretch the near-infrared modulated optical signal makes the target data signal difficult to identify, thereby achieving physical encryption and further enhancing the strength of the physical encryption.

[0052] The near-infrared single-frequency laser 400 is used to generate 1 μm near-infrared single-frequency continuous light. It should be understood that the near-infrared single-frequency laser 400 can be replaced with a near-infrared single-frequency laser 400 of other wavelengths according to actual needs to generate near-infrared single-frequency continuous light of other wavelengths, such as 2 μm near-infrared single-frequency continuous light.

[0053] The nonlinear frequency down-conversion module 500 includes a dichroic mirror 510, a nonlinear crystal 520, and a long-pass filter 530. The specific working process of nonlinear frequency down-conversion is as follows: the dichroic mirror 510 combines the near-infrared modulated optical signal with the near-infrared single-frequency continuous optical signal and transmits it to the nonlinear crystal 520; the nonlinear crystal 520 generates mid-infrared light carrying the encrypted signal through the difference frequency effect, achieving the transfer of the encrypted signal from the near-infrared to the mid-infrared band; the long-pass filter 530 filters out the near-infrared light from the mid-infrared light to obtain the mid-infrared light carrying the encrypted signal. The nonlinear crystal 520 can be a periodically poled lithium niobate (PPLN) crystal to generate mid-infrared optical signals in the wavelength range of 3-5μm; it can also be a phosphorus germanium zinc crystal or BaGa4Se7 crystal to generate mid-infrared optical signals in the wavelength range of 8-12μm. In this embodiment, the nonlinear crystal 520 is a PPLN crystal with a period of 30.49μm and a temperature control range of 26.85126.85°C. After down-conversion through the PPLN crystal, the generated mid-infrared continuous light is separated from the near-infrared modulated light signal and the near-infrared single-frequency continuous light by a long-pass filter 530 with a cutoff wavelength of 2.4 μm. Figure 4 The time-resolved intensity curves of three randomly selected sets of 1.5μm near-infrared continuous light modulated with an encrypted signal (dashed lines) are compared with the temporal waveforms of 3μm mid-infrared light (solid lines) generated by frequency down-conversion using a periodically poled lithium niobate (PPLN) crystal. The results in the figure show that the temporal distributions of the 1.5μm modulated signal light and the 3μm idler light maintain a high degree of consistency, demonstrating that the encrypted signal was successfully transferred from the 1.5μm band to the 3μm band.

[0054] To improve transmission efficiency, as a preferred embodiment, a mid-infrared optical transmission channel 900 is provided between the nonlinear frequency down-conversion module 500 and the mid-infrared low-speed optical detection module 700. The mid-infrared optical signal carrying the encrypted signal generated by the nonlinear frequency down-conversion module 500 is then output and directed into the mid-infrared optical transmission channel 900 for transmission. The mid-infrared optical transmission channel 900 includes a first lens, a second lens, and a free-space optical channel. The generated mid-infrared light carrying the encrypted signal is collimated by the first lens, propagates within the free-space optical channel, and is focused by the second lens onto the mid-infrared low-speed optical detection module 700.

[0055] The mid-infrared low-speed light detection module 700 is used to detect the mid-infrared light signal carrying the encrypted signal and record the integrated signal intensity. It includes a photodetector 710 and an oscilloscope 720. The photodetector 710 has a bandwidth in the MHz range. The specific operation of the mid-infrared low-speed light detection module 700 is as follows: the photodetector 710 converts the mid-infrared light signal into an electrical signal and measures its integrated signal intensity, while the oscilloscope 720 records the integrated signal intensity output by the detector. The time-domain ghost imaging data decryption module 800 is used to cross-correlate the integrated signal intensity with the key to decrypt the target data signal, enabling encrypted data transmission in the mid-infrared band.

[0056] See also Figure 5 , Figure 5 (a) Experimental signal reconstruction diagram of the time-domain ghost imaging (solid line) and the target data signal (dashed line) calculated by frequency down-conversion when the data rates are 1, 10, 20, and 64 Mbps, respectively. Figure 5 (b) is a time domain diagram of the signal directly detected by a photodetector with a bandwidth of 1 MHz at data rates of 1, 10, 20, and 64 Mbps. It can be clearly seen that direct detection can only effectively retrieve the target signal when the data rate is 1 Mbps. However, when the data rate exceeds the bandwidth of the mid-infrared detector, obvious distortion can be observed, and the directly transmitted signal received at 64 Mbps is completely different from the ciphertext. The demonstrated data rate is limited by the bandwidth of the electro-optic modulator used. Figure 5 (a) with Figure 5 (b) By comparison, the computational time-domain ghost imaging based on frequency down-conversion of the present invention can not only realize data encryption and decryption in the mid-infrared region, but also significantly alleviate the bandwidth requirements of mid-infrared detectors, opening up new possibilities for dedicated communications in spectral regions such as the mid-infrared and terahertz regions with ultrafast modulation or detection challenges.

[0057] See also Figure 6 , Figure 6 (a) Mid-infrared spectrum tuning diagram generated by the frequency down-conversion process by changing the phase matching conditions of the PPLN crystal, achieving mid-infrared output in the 3.3-3.5 μm range; Figure 6 (b) Experimental results of frequency down-conversion computational time-domain ghost imaging at a data rate of 64 Mbps at three mid-infrared wavelengths: 3323 nm, 3393 nm, and 3493 nm. These results demonstrate that the proposed down-conversion computational time-domain ghost imaging method successfully achieves data encryption and free-space communication across the entire 3.3-3.5 μm range.

[0058] In order to further improve the rate of encrypted transmission of mid-infrared data, as a preferred embodiment, a wavelength division multiplexer and an up-conversion detector are added to the above scheme. Multiple near-infrared laser sources of different wavelengths are modulated, such as N wavelengths in the 1.5μm band, and each wavelength independently carries the encrypted signal. Chirped PPLN crystals are used to achieve broadband nonlinear frequency down-conversion to generate multi-wavelength mid-infrared light signals, such as 3-5μm or 8-12μm bands. In the above scheme, the single-channel transmission rate is limited by the bandwidth of the mid-infrared detector. Wavelength division multiplexing significantly improves the total capacity and rate of the system through multi-channel parallel transmission. After the multi-wavelength mid-infrared light carrying ciphertext information is transmitted through a free-space link, it is re-transferred to the near-infrared band (1.5μm region) through frequency up-conversion technology. The detection is then carried out using a near-infrared InGaAs detector with high sensitivity and high bandwidth, which can increase the rate of encrypted transmission of mid-infrared data to 10Gbps. Previous solutions relied on slow mid-infrared detectors, resulting in severe distortion of high-speed signals. Upconversion detection, however, bypasses the bandwidth bottleneck of mid-infrared detectors by converting multi-wavelength mid-infrared light into the near-infrared band. By expanding channel capacity through wavelength division multiplexing and utilizing upconversion detection to overcome the bandwidth limitations of mid-infrared detectors, this ultimately enables high-speed, high-capacity, and highly reliable encrypted transmission of mid-infrared data.

[0059] The present invention also discloses a mid-infrared data encryption optical communication method based on time-domain ghost imaging, which is implemented based on the mid-infrared data encryption optical communication system based on time-domain ghost imaging of the above embodiment. Figure 7 , is a flow chart of an implementation method of a mid-infrared data encryption optical communication method based on time-domain ghost imaging of the present invention. This implementation method specifically includes the following steps:

[0060] S1. Obtain tunable near-infrared continuous light.

[0061] Specifically, a continuous light laser 100 is used to generate tunable near-infrared continuous light with a wavelength within a specific range. In this embodiment, a 1.5 μm band continuous light laser 100 is used to generate tunable near-infrared continuous light within the range of 1520-1560 nm.

[0062] S2. Signal encryption.

[0063] Specifically, a target data signal is generated and encrypted to obtain an encrypted signal. The operation process is: generating a randomized Hadamard matrix as a key and multiplying the generated target data signal with the key to obtain an encrypted signal.

[0064] S3. Perform high-speed temporal modulation on near-infrared continuous light.

[0065] Specifically, in response to the encryption signal, the tunable near-infrared continuous light generated by the continuous light laser 100 is subjected to high-speed temporal modulation to generate a near-infrared modulated optical signal. To achieve physical encryption of the target data signal, in this embodiment, an electro-optical modulator with a modulation bandwidth smaller than the encryption signal rate is used to perform high-speed temporal modulation on the tunable near-infrared continuous light.

[0066] S4. Physical encryption.

[0067] Specifically, a dispersion-compensating fiber is introduced to time-stretch the near-infrared modulated optical signal. In this embodiment, the dispersion-compensating fiber is longer than 10 km. Using this dispersion-compensating fiber to time-stretch the near-infrared modulated optical signal makes the target data signal difficult to identify, thereby achieving the effect of physical encryption and further enhancing the strength of physical encryption.

[0068] S5. Generate a mid-infrared light signal carrying an encrypted signal.

[0069] Specifically, a near-infrared single-frequency laser 400 outputs single-frequency continuous light, and a near-infrared modulated light signal is combined with the single-frequency continuous light. Frequency down-conversion is then performed to generate a mid-infrared light signal carrying the encrypted signal. The process involves combining the near-infrared modulated light signal with the near-infrared single-frequency continuous light, then generating mid-infrared light carrying the encrypted signal through the difference frequency effect. Finally, near-infrared light is filtered out of the mid-infrared light, achieving the transfer of the encrypted signal from the near-infrared to the mid-infrared band.

[0070] S6. Detection and decryption.

[0071] Specifically, the system detects the mid-infrared light signal carrying the encrypted signal and uses the key to recover the target data signal, achieving encrypted data transmission in the mid-infrared band. The process involves detecting the mid-infrared light signal carrying the encrypted signal, recording the integrated signal intensity, and then cross-correlating the integrated signal intensity with the key to decrypt the target data signal.

[0072] The present invention combines frequency down-conversion technology with computational time-domain ghost imaging to losslessly transfer high-speed near-infrared encrypted signals to the mid-infrared band through a nonlinear frequency down-conversion module, solving the problem of insufficient bandwidth of commercial mid-infrared detectors. High-precision decryption can still be achieved at a data rate of 64Mbps, significantly exceeding the encryption rate of less than 10Mbps in traditional mid-infrared encryption. A randomized Hadamard matrix is used as a key to encrypt the target data signal. An electro-optical modulator with a modulation bandwidth less than the encryption signal rate and dispersion-compensating optical fiber are then used to time-domain stretch the near-infrared modulated optical signal, introducing signal distortion. Dual encryption of digital encryption and physical encryption enhances security. Combining frequency down-conversion and computational time-domain ghost imaging technology can generate mid-infrared light carrying the encrypted signal, and a mid-infrared low-speed light detection module and a time-domain ghost imaging data decryption module are used to detect and decrypt high-speed encrypted signals in the mid-infrared band. By utilizing the time-domain ghost imaging technology of frequency down-conversion and adjusting the near-infrared laser wavelength and nonlinear crystal, the system can flexibly output in the 35μm or 812μm mid-infrared band, flexibly tuning the operating wavelength of the mid-infrared data encryption optical communication system.

[0073] The above description merely expresses the preferred embodiments of the present invention, and its description is relatively specific and detailed, but it should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art may make a number of variations and improvements without departing from the concept of the present invention, and these variations and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent of the present invention shall be based on the appended claims.

Claims

1. A mid-infrared data encryption optical communication system based on time-domain ghost imaging, characterized in that: include: Continuous-wave lasers, used to generate tunable near-infrared continuous light with a wavelength within a specific range; A signal encryption module, configured to generate a target data signal and generate a key to encrypt the target data signal to obtain an encrypted signal; a near-infrared high-speed optical modulation module, configured to perform time-domain high-speed modulation on the tunable near-infrared continuous light in response to the encrypted signal to generate a near-infrared modulated optical signal, wherein the near-infrared high-speed optical modulation module uses an electro-optical modulator with a modulation bandwidth smaller than the encryption signal rate; a dispersion optical fiber module, configured to perform time domain stretching on the near-infrared modulated optical signal output by the near-infrared high-speed optical modulation module by introducing a dispersion-compensating optical fiber, and to send the signal to the nonlinear frequency down-conversion module after physical encryption; Near-infrared single-frequency laser, used to output near-infrared single-frequency continuous light; A nonlinear frequency down-conversion module is used to combine the physically encrypted near-infrared modulated optical signal with the near-infrared single-frequency continuous light beam, and generate a mid-infrared optical signal carrying the encrypted signal through frequency down-conversion; Mid-infrared low-speed light detection module, used to detect mid-infrared light signals carrying encrypted signals and record the signal integrated intensity; The time-domain ghost imaging data decryption module is used to cross-correlate the signal integrated intensity with the key, decrypt the signal to obtain the target data signal, and realize encrypted transmission of mid-infrared band data.

2. The mid-infrared data encryption optical communication system based on time-domain ghost imaging according to claim 1, characterized in that: The signal encryption module includes: a computer for generating a randomized Hadamard matrix as a key and multiplying the generated target data signal by the key to generate an encrypted signal in the form of a digital signal; The arbitrary waveform generator is used to convert the encrypted signal in the form of a digital signal output by the computer into an encrypted signal in the form of an electrical signal to drive the near-infrared high-speed light modulation module.

3. The mid-infrared data encryption optical communication system based on time-domain ghost imaging according to claim 1, characterized in that: The nonlinear frequency down-conversion module comprises: A dichroic mirror is used to combine the near-infrared modulated light signal with the near-infrared single-frequency continuous light; Nonlinear crystals are used to generate mid-infrared light carrying encrypted signals through the difference frequency effect, thus enabling the transfer of encrypted signals from the near-infrared to the mid-infrared band. The long-pass filter is used to filter out the near-infrared light in the mid-infrared light and obtain the mid-infrared light carrying the encrypted signal.

4. The mid-infrared data encryption optical communication system based on time-domain ghost imaging according to claim 3, characterized in that: The nonlinear crystal may be a periodically poled lithium niobate crystal, which is used to generate a mid-infrared light signal with a wavelength range of 3-5 μm; the nonlinear crystal may also be a phosphorus germanium zinc crystal or a BaGa4Se7 crystal, which is used to generate a mid-infrared light signal with a wavelength range of 8-12 μm.

5. The mid-infrared data encryption optical communication system based on time-domain ghost imaging according to claim 1, characterized in that: It also includes a mid-infrared light transmission channel, and the mid-infrared light signal carrying the encrypted signal generated by the nonlinear frequency down-conversion module will be output and then introduced into the mid-infrared light transmission channel for transmission; The mid-infrared light transmission channel includes a first lens, a second lens, and a free-space optical channel. The generated mid-infrared light carrying the encrypted signal is collimated by the first lens, propagates in the free-space optical channel, and is focused by the second lens to the mid-infrared low-speed light detection module.

6. The mid-infrared data encryption optical communication system based on time-domain ghost imaging according to claim 1, characterized in that: The mid-infrared low-speed light detection module includes: A photodetector, used to convert mid-infrared light signals into electrical signals and measure their integrated signal intensity; An oscilloscope is used to record the integrated intensity of the signal output by the photodetector.

7. A mid-infrared data encryption optical communication method based on time-domain ghost imaging, characterized in that: The following steps are involved: Obtaining tunable near-infrared continuous light with a wavelength within a specific range; generating a target data signal and encrypting the target data signal to obtain an encrypted signal; In response to the encrypted signal, the tunable near-infrared continuous light is subjected to time-domain high-speed modulation using an electro-optical modulator having a modulation bandwidth smaller than the encryption signal rate to generate a near-infrared modulated optical signal; Introducing dispersion-compensating optical fiber to perform time domain stretching on the near-infrared modulated optical signal output by the near-infrared high-speed optical modulation module, and sending it to the nonlinear frequency down-conversion module after physical encryption; Utilizing a near-infrared single-frequency laser to output single-frequency continuous light, combining the physically encrypted near-infrared modulated optical signal with the single-frequency continuous light, and generating a mid-infrared optical signal carrying the encrypted signal through frequency down-conversion; Detect the mid-infrared light signal carrying the encrypted signal and record the signal integrated intensity; The signal integrated intensity is cross-correlated with the key, and the target data signal is decrypted to achieve encrypted transmission of mid-infrared band data.

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