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

Abstract

The application discloses a kind of based on time-domain ghost imaging mid-infrared data encryption optical communication system and method, the system includes: continuous light laser, for producing tunable near-infrared continuous light;Signal encryption module, for generating target data signal and generating key pair target data signal encryption, obtain encrypted signal;Near-infrared high-speed light modulation module, for responding to encrypted signal, tunable near-infrared continuous light is time-domain high-speed modulation, generates near-infrared modulation light signal;Dispersion optical fiber module, for introducing dispersion compensation optical fiber to near-infrared modulation light signal time-domain stretch, after physical encryption, send to nonlinear frequency down-conversion module;Near-infrared single-frequency laser, for outputting near-infrared single-frequency continuous light;Nonlinear frequency down-conversion module, for near-infrared modulation light signal and near-infrared single-frequency continuous light beam combination, through frequency down-conversion generation carries encrypted signal's mid-infrared light signal;Mid-infrared low-speed light detection module, for detecting mid-infrared light signal and recording signal integral intensity;Time-domain ghost imaging data decryption module, for signal integral intensity and key cross-correlation, decryption obtains target data signal, realizes mid-infrared waveband data encryption transmission.The application solves the problem of mid-infrared detector bandwidth limitation by combining frequency down-conversion technology and computing time-domain ghost imaging, and improves encryption rate.

Description

Technical Field

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

[0002] Temporal ghost imaging systems employ low temporal coherence light sources with random intensity fluctuations in the temporal domain as probe light. By correlating the temporal intensity fluctuations of the light source itself with the integrated power of the light source after interaction with a temporal object (such as a high-speed electro-optic modulator signal), the ultrafast optical modulation signal can be reconstructed. Since only the integrated optical power needs to be measured after interaction with the temporal object, temporal ghost imaging significantly reduces the intensity requirement of the measured optical signal compared to direct detection. Furthermore, the reconstruction effect of temporal ghost imaging on the temporal object is insensitive to potential temporal signal distortion introduced in the optical detection link. In addition, a known random signal can be generated using an arbitrary waveform generator and a high-speed optical modulator to pre-modulate the temporal intensity of the light source, constructing a computational temporal ghost imaging system. This allows for the detection of high-speed temporal modulation signals using only a single slow detector. Computational temporal ghost imaging has important applications in long-distance underwater communication, high-speed and secure communication, and quantum communication in the visible and near-infrared spectral regions. Furthermore, free-space optical communication systems based on computational time-domain ghost imaging possess strong resistance to atmospheric turbulence, providing a reliable alternative for transmission in free-space optical communication systems. Since computational time-domain ghost imaging allows for the retrieval of fast-moving time objects using high-sensitivity, low-bandwidth photodetectors and the encryption of transmitted data, this novel concept can enable high-speed, secure communication in high-loss and turbulent transmission channels.

[0003] However, current data encryption optical communication based on computational time-domain ghost imaging is still limited to the visible and near-infrared bands, while its application in the mid-infrared band remains unexplored. The mid-infrared spectral region, especially in the 3-5μm and 8-12μm atmospheric windows, is particularly advantageous for free-space optical communication due to its high transparency and low scattering loss. However, current technology faces two major bottlenecks: (1) Detector bandwidth limitation: Commercial mid-infrared detectors (such as mercury cadmium telluride detectors) have a bandwidth on the order of 100MHz, limiting the ability to conduct high-speed free-space encrypted optical communication in the mid-infrared band; (2) Insufficient encryption rate: Mid-infrared encryption schemes based on chaotic quantum cascade lasers are limited to a data encryption transmission rate of less than 10Mbps due to the small chaotic bandwidth. Therefore, compared with the visible and near-infrared regions, achieving high-speed data encryption optical communication in the mid-infrared region remains challenging. Summary of the Invention

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

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

[0006] Continuous light lasers are used to generate tunable near-infrared continuous light with wavelengths within a specific range.

[0007] The signal encryption module is used 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 is used to perform time-domain high-speed modulation of the tunable near-infrared continuous light in response to the encryption signal, thereby generating a near-infrared modulated optical signal. The near-infrared high-speed optical modulation module employs an electro-optic modulator with a modulation bandwidth smaller than the encryption signal rate.

[0009] The dispersion fiber module is used to stretch the near-infrared modulated light signal output by the near-infrared high-speed optical modulation module in the time domain by introducing dispersion compensation fiber, and then send it 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 light signal with the near-infrared single-frequency continuous light beam, and generate a mid-infrared light signal carrying the encrypted signal through frequency down-conversion.

[0012] The mid-infrared low-speed light detection module is used to detect mid-infrared light signals carrying encrypted signals and record the integrated signal intensity.

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

[0014] Furthermore, the signal encryption module includes:

[0015] A computer is used to generate a randomized Hadamard matrix as a key and multiply the generated target data signal with the key to generate an encrypted signal in the form of a digital signal;

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

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

[0018] Dichroic mirrors are used to combine near-infrared modulated light signals with near-infrared single-frequency continuous light.

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

[0020] A long-pass filter is used to filter out near-infrared light from mid-infrared light to obtain mid-infrared light carrying encrypted signals.

[0021] Furthermore, the nonlinear crystal can be a periodically polarized lithium niobate crystal, used to generate mid-infrared light signals with a wavelength range of 3-5 μm; the nonlinear crystal can also be a zinc germanium phosphorus crystal or a BaGa4Se7 crystal, used to generate mid-infrared light signals with a wavelength range of 8-12 μm.

[0022] Furthermore, it also includes a mid-infrared light transmission channel. The mid-infrared light signal carrying the encrypted signal generated by the nonlinear frequency down-conversion module is then transmitted through the mid-infrared light transmission channel.

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

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

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

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

[0027] To solve the above-mentioned 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] Acquire tunable near-infrared continuous light with wavelengths within a specific range;

[0029] A target data signal is generated and encrypted to obtain an encrypted signal;

[0030] In response to the encrypted signal, the tunable near-infrared continuous light is temporally high-speed modulated using an electro-optic modulator with a modulation bandwidth smaller than the rate of the encrypted signal to generate a near-infrared modulated light signal.

[0031] Dispersion-compensating fiber is introduced to stretch the near-infrared modulated optical signal output by the near-infrared high-speed optical modulation module in the time domain, and then physically encrypts it before sending it to the nonlinear frequency down-conversion module.

[0032] A near-infrared single-frequency laser is used to output single-frequency continuous light, and the physically encrypted near-infrared modulated light signal is combined with the single-frequency continuous light. The mid-infrared light signal carrying the encrypted signal is generated by frequency down-conversion.

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

[0034] The integrated signal strength is cross-correlated with the key to decrypt the target data signal, thereby achieving encrypted data transmission in the mid-infrared band.

[0035] The mid-infrared data encryption optical communication system and method based on time-domain ghost imaging of the present invention has at least the following beneficial effects: The present invention combines frequency down-conversion technology with computational time-domain ghost imaging, and uses a nonlinear frequency down-conversion module to losslessly transfer high-speed near-infrared encryption signals to the mid-infrared band, solving the problem of insufficient bandwidth in commercial mid-infrared detectors. It can still achieve high-precision decryption at a data rate of 64Mbps, significantly surpassing traditional mid-infrared encryption schemes. A randomized Hadamard matrix is ​​used as the key to encrypt the target data signal. An electro-optic modulator with a modulation bandwidth smaller than the encryption signal rate and dispersion-compensating fiber are used to perform time-domain stretching of the near-infrared modulated light signal, introducing signal distortion. Dual encryption, combining digital and physical encryption, enhances security. Combining frequency down-conversion and computational time-domain ghost imaging technology, mid-infrared light carrying encryption signals can be generated, and a detection and decryption module can be used to detect and decrypt high-speed encryption signals in the mid-infrared band. Utilizing the time-domain ghost imaging technology of frequency down-conversion, by 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. Attached Figure Description

[0036] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

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

[0038] Figure 2 The time-domain waveforms of the target data signal, the key, and the encrypted signal are shown.

[0039] Figure 3The graph shows the time-resolved intensity curve of the 1.5μm near-infrared modulated light as the modulation speed increases from 1Mbps to 64Mbps.

[0040] Figure 4 A comparison of 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 diagram shows a comparison of signal waveforms obtained using the method of this invention and those not using the method of this invention at different data transmission rates.

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

[0043] Figure 7 This is a flowchart of an actual implementation of the mid-infrared data encryption optical communication method based on time-domain ghost imaging according to the present invention.

[0044] The meanings of the labels in the attached diagram are as follows:

[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 600, mid-infrared low-speed light detection module 700, photodetector 710, oscilloscope 720, time-domain ghost imaging data decryption module 800, mid-infrared optical transmission channel 900. Detailed Implementation

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

[0047] Please see 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 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, obtaining an encrypted signal, which is then sent 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. In response to the encrypted signal, the near-infrared high-speed optical modulation module 300 performs time-domain high-speed modulation on the tunable near-infrared continuous light generated by the continuous light laser 100, generating a near-infrared modulated optical signal, which is then sent to the dispersion fiber module 600. The dispersion fiber module 600 introduces a dispersion compensation 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. A near-infrared single-frequency laser 400 outputs near-infrared single-frequency continuous light and transmits it to a 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. A mid-infrared low-speed light detection module 700 detects the mid-infrared light signal carrying the encrypted signal and records the signal integration intensity. A time-domain ghost imaging data decryption module 800 cross-correlates the signal integration intensity with the key to decrypt and obtain the target data signal, thereby realizing encrypted transmission of mid-infrared band data.

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

[0049] The signal encryption module 200 includes a computer 210 and an arbitrary waveform generator 220. The specific operation of the signal encryption module 200 is as follows: 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 digital form, which is then loaded into the arbitrary waveform generator 220; the arbitrary waveform generator 220 converts the encrypted signal in digital form output by the computer 210 into an encrypted signal in electrical form to drive the near-infrared high-speed optical modulation module 300. In this embodiment, the target data signal consists of a 64-bit pseudo-random binary sequence (PRBS), the key is a 64-order randomized Hadamard matrix, and the encryption signal rate can reach up to 64 Mbps. Please refer to [link to relevant documentation]. Figure 2This is a time-domain waveform diagram of the target data signal, the key, and the 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 generated randomized Hadamard matrix that serves 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, which verifies that the encryption of the target data signal was successful.

[0050] The near-infrared high-speed optical modulation module 300 is used to perform high-speed time-domain modulation of 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-optic modulator. To achieve physical encryption of the target data signal, in this embodiment, the electro-optic modulator uses an electro-optic modulator with a modulation bandwidth smaller than the encryption signal rate. In this embodiment, the modulation bandwidth of the electro-optic modulator corresponds to a rise time of approximately 35 ns. Please refer to [link to relevant documentation]. Figure 3 Time-resolved intensity curves of 1.5μm near-infrared modulated light were obtained at modulation speeds of 1, 10, 20, and 64 Mbps using the electro-optic modulator. Due to the limited modulation bandwidth of the electro-optic modulator, the temporal pattern of the modulated 1.5μm near-infrared light closely followed the ciphertext at modulation speeds of 1 Mbps and 10 Mbps. However, due to the limited modulation bandwidth of the electro-optic modulator, the time distortion was severe at a modulation speed of 64 Mbps, making it impossible to distinguish the ciphertext pattern. This provides additional physical encryption for the target data signal.

[0051] A dispersion-compensating 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 temporally stretch the near-infrared modulated optical signal output from the near-infrared high-speed optical modulation module 300 by introducing dispersion-compensating fiber and then transmit it to the nonlinear frequency down-conversion module 500. In this embodiment, the dispersion-compensating fiber is longer than 10 km. Using this dispersion-compensating fiber to temporally stretch the near-infrared modulated optical signal makes the target data signal difficult to identify, achieving a physical encryption effect and further enhancing the strength of the physical encryption.

[0052] The near-infrared single-frequency laser 400 is used to generate 1μm 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 to generate near-infrared single-frequency continuous light of other wavelengths, such as 2μm near-infrared single-frequency continuous light, according to actual needs.

[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 the nonlinear frequency down-conversion is as follows: the dichroic mirror 510 combines the near-infrared modulated light signal with the near-infrared single-frequency continuous light 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, realizing 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 polarized lithium niobate (PPLN) crystal to generate mid-infrared light signals with a wavelength range of 3-5 μm; it can also be a zinc germanium phosphorus crystal or a BaGa4Se7 crystal to generate mid-infrared light signals with a wavelength range of 8-12 μm. In this embodiment, the nonlinear crystal 520 is a PPLN crystal with a period of 30.49 μm and a temperature control range of 26.85-126.85℃. After down-conversion via a 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. Please refer to [link / reference]. Figure 4 The temporal resolution intensity curves (dashed lines) of three randomly selected sets of 1.5 μm near-infrared continuous light modulated by an encrypted signal were compared with the temporal waveforms of 3 μm mid-infrared light (solid lines) generated by frequency down-conversion using a periodically polarized lithium niobate crystal (PPLN). The results in the figure show that the temporal distributions of the 1.5 μm modulated signal light and the 3 μm idle light maintain a high degree of consistency, proving that the encrypted signal was successfully transferred from the 1.5 μm band to the 3 μm band.

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

[0055] A mid-infrared low-speed light detection module 700 is used to detect mid-infrared light signals carrying encrypted signals and record the signal integration intensity. The mid-infrared low-speed light detection module 700 includes a photodetector 710 and an oscilloscope 720. The bandwidth of the photodetector 710 is on the order of MHz. The specific working process 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 signal integration intensity; the oscilloscope 720 records the signal integration intensity output by the detector. A time-domain ghost imaging data decryption module 800 is used to cross-correlate the signal integration intensity with the key to decrypt and obtain the target data signal, realizing encrypted data transmission in the mid-infrared band.

[0056] Please see Figure 5 , Figure 5 (a) is an experimental signal reconstruction diagram of time-domain ghost imaging (solid line) and target data signal (dashed line) calculated by frequency downconversion when data rates of 1, 10, 20 and 64 Mbps are selected respectively. Figure 5 (b) shows the time-domain plots of signals directly detected using a 1MHz bandwidth photodetector at data rates of 1, 10, 20, and 64 Mbps. It is clear that direct detection can only effectively retrieve the target signal at a data rate of 1 Mbps. However, when the data rate exceeds the bandwidth of the mid-infrared detector, significant distortion is observed, and the directly transmitted signal received at 64 Mbps is completely different from the ciphertext. The data rate demonstrated is limited by the bandwidth of the electro-optic modulator used. Figure 5 (a) and Figure 5 (b) By comparison, it can be seen that the computational time-domain ghost imaging based on frequency downconversion 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 communication in spectrum regions with ultra-fast modulation or detection challenges such as mid-infrared and terahertz.

[0057] Please see Figure 6 , Figure 6 (a) is the mid-infrared spectral tuning pattern generated by the frequency down-conversion process obtained by changing the phase matching condition of the PPLN crystal, which realizes mid-infrared output in the range of 3.3-3.5μm; Figure 6 (b) Experimental results of frequency down-conversion computational time-domain ghost imaging at a data rate of 64 Mbps, operating at three mid-infrared wavelengths: 3323 nm, 3393 nm, and 3493 nm. The results demonstrate that the down-conversion computational time-domain ghost imaging method of this invention successfully achieves data encryption and free-space communication across the entire 3.3–3.5 μm region.

[0058] To further improve the data encryption transmission rate in the mid-infrared region, as a preferred implementation, a wavelength division multiplexer and an upconversion detector are added to the above scheme. Multiple near-infrared laser sources of different wavelengths are modulated, for example, N wavelengths in the 1.5μm band, each independently carrying an encrypted signal. A chirped PPLN crystal is used to achieve broadband nonlinear frequency downconversion, generating multi-wavelength mid-infrared light signals, such as in the 3-5μm or 8-12μm bands. In the aforementioned scheme, the single-channel transmission rate is limited by the bandwidth of the mid-infrared detector; wavelength division multiplexing, through multi-channel parallel transmission, significantly improves the overall system capacity and rate. The multi-wavelength mid-infrared light carrying the encrypted information is transmitted via a free-space link and then re-transferred to the near-infrared band (1.5μm region) using frequency upconversion technology. Detection using a high-sensitivity, high-bandwidth near-infrared InGaAs detector can further increase the data encryption transmission rate in the mid-infrared region to 10Gbps. The aforementioned scheme relies on a mid-infrared low-speed detector, resulting in severe distortion of high-speed signals. Upconversion detection bypasses the bandwidth bottleneck of the mid-infrared detector by converting multi-wavelength mid-infrared light to the near-infrared band. By extending channel capacity through wavelength division multiplexing and overcoming the bandwidth limitation of the mid-infrared detector using upconversion detection, high-speed, high-capacity, and highly reliable encrypted transmission of mid-infrared data is ultimately achieved.

[0059] This invention also discloses a mid-infrared data encryption optical communication method based on temporal ghost imaging. This method is implemented based on the mid-infrared data encryption optical communication system based on temporal ghost imaging described above. Please refer to... Figure 7 This is a flowchart of an embodiment of the mid-infrared data encryption optical communication method based on time-domain ghost imaging according to the present invention. This embodiment specifically includes the following steps:

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

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

[0062] S2, Signal Encryption.

[0063] Specifically, a target data signal is generated and encrypted to obtain an encrypted signal. The operation process is as follows: a randomized Hadamard matrix is ​​generated as a key, and the generated target data signal is multiplied by the key to obtain the encrypted signal.

[0064] S3. High-speed temporal modulation of 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 light signal. To achieve physical encryption of the target data signal, in this embodiment, an electro-optic modulator with a modulation bandwidth smaller than the encryption signal rate is used to perform high-speed temporal modulation of the tunable near-infrared continuous light.

[0066] S4, physical encryption.

[0067] Specifically, dispersion-compensating fiber is introduced to perform temporal stretching of the near-infrared modulated optical signal. In this embodiment, the dispersion-compensating fiber is longer than 10 km. By using this dispersion-compensating fiber to perform temporal stretching of the near-infrared modulated optical signal, the target data signal becomes difficult to identify, thus achieving a physical encryption effect and further enhancing the strength of the 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 used to generate a mid-infrared light signal carrying an encrypted signal. The operation process is as follows: first, the near-infrared modulated light signal and the near-infrared single-frequency continuous light are combined; then, a mid-infrared light carrying an encrypted signal is generated through a difference frequency effect; finally, the near-infrared light in the mid-infrared light is filtered out, thus achieving the transfer of the encrypted signal from the near-infrared to the mid-infrared band.

[0070] S6, Detection and Decryption.

[0071] Specifically, the method involves detecting mid-infrared light signals carrying encrypted signals and recovering the target data signal using a key, thereby achieving encrypted data transmission in the mid-infrared band. The operation process is as follows: the mid-infrared light signal carrying the encrypted signal is detected and its integrated intensity is recorded; the integrated intensity is cross-correlated with the key to decrypt and obtain the target data signal.

[0072] This invention combines frequency down-conversion technology with computational time-domain ghost imaging. By using a nonlinear frequency down-conversion module, it losslessly transfers high-speed near-infrared encrypted signals to the mid-infrared band, solving the problem of insufficient bandwidth in commercial mid-infrared detectors. It achieves high-precision decryption at a data rate of 64 Mbps, significantly surpassing the encryption rates below 10 Mbps in traditional mid-infrared encryption. A randomized Hadamard matrix is ​​used as the key to encrypt the target data signal. An electro-optic modulator with a modulation bandwidth smaller than the encryption signal rate and dispersion-compensating fiber are used to temporally stretch the near-infrared modulated light signal, introducing signal distortion. This dual encryption of digital and physical encryption enhances security. Combining frequency down-conversion and computational time-domain ghost imaging, mid-infrared light carrying encrypted signals can be generated. 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. Utilizing the frequency down-conversion time-domain ghost imaging technology, by adjusting the near-infrared laser wavelength and nonlinear crystal, the system can flexibly output in the 35 μm or 812 μm mid-infrared band, flexibly tuning the operating wavelength of the mid-infrared data encryption optical communication system.

[0073] The above description merely illustrates preferred embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A mid-infrared data encryption optical communication system based on time-domain ghost imaging, characterized in that, include: Continuous light lasers are used to generate tunable near-infrared continuous light with wavelengths within a specific range. The signal encryption module is used 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 is used to perform time-domain high-speed modulation of the tunable near-infrared continuous light in response to the encryption signal, thereby generating a near-infrared modulated optical signal. The near-infrared high-speed optical modulation module employs an electro-optic modulator with a modulation bandwidth smaller than the encryption signal rate. The dispersion fiber module is used to stretch the near-infrared modulated light signal output by the near-infrared high-speed optical modulation module in the time domain by introducing dispersion compensation fiber, and then send it 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 light signal with the near-infrared single-frequency continuous light beam, and generate a mid-infrared light signal carrying the encrypted signal through frequency down-conversion. The mid-infrared low-speed light detection module is used to detect mid-infrared light signals carrying encrypted signals and record the integrated signal intensity. The time-domain ghost imaging data decryption module is used to cross-correlate the integrated signal strength with the key to decrypt the target data signal and realize encrypted transmission of mid-infrared band data. The signal encryption module includes: a computer, used to generate a randomized Hadamard matrix as a key and multiply the generated target data signal with the key to generate an encrypted signal in digital signal form; and an arbitrary waveform generator, used to convert the encrypted signal in digital signal form output by the computer into an encrypted signal in electrical signal form to drive the near-infrared high-speed optical modulation module.

2. The mid-infrared data encryption optical communication system based on time-domain ghost imaging as described in claim 1, characterized in that, The nonlinear frequency down-conversion module includes: Dichroic mirrors are used to combine near-infrared modulated light signals with near-infrared single-frequency continuous light. Nonlinear crystals are used to generate mid-infrared light carrying encrypted signals through the difference frequency effect, thereby enabling the transfer of encrypted signals from the near-infrared to the mid-infrared band. A long-pass filter is used to filter out near-infrared light from mid-infrared light to obtain mid-infrared light carrying encrypted signals.

3. The mid-infrared data encryption optical communication system based on time-domain ghost imaging as described in claim 2, characterized in that, The nonlinear crystal can be a periodically polarized lithium niobate crystal, used to generate mid-infrared light signals with a wavelength range of 3-5 μm; the nonlinear crystal can also be a zinc germanium phosphorus crystal or a BaGa4Se7 crystal, used to generate mid-infrared light signals with a wavelength range of 8-12 μm.

4. The mid-infrared data encryption optical communication system based on time-domain ghost imaging as described in claim 1, characterized in that: It also includes a mid-infrared light transmission channel, where the mid-infrared light signal carrying the encrypted signal generated by the nonlinear frequency down-conversion module is transmitted through the mid-infrared light transmission channel. The mid-infrared light transmission channel includes a first lens, a second lens, and a free-space light channel. The generated mid-infrared light carrying the encrypted signal is collimated by the first lens and propagates in the free-space light channel, and is focused by the second lens onto the mid-infrared low-speed light detection module.

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

6. A mid-infrared data encryption optical communication method based on time-domain ghost imaging, characterized in that, Includes the following steps: Acquire tunable near-infrared continuous light with wavelengths within a specific range; The process involves generating a target data signal and encrypting it to obtain an encrypted signal. This step includes: generating a randomized Hadamard matrix as a key and multiplying the generated target data signal with the key to generate an encrypted signal in digital form; and converting the encrypted signal in digital form into an encrypted signal in electrical form. In response to the encrypted signal, the tunable near-infrared continuous light is temporally high-speed modulated using an electro-optic modulator with a modulation bandwidth smaller than the rate of the encrypted signal to generate a near-infrared modulated light signal. The near-infrared modulated optical signal is stretched in the time domain by introducing dispersion compensation fiber, and then physically encrypted before being sent to the nonlinear frequency down-conversion module. A near-infrared single-frequency laser is used to output single-frequency continuous light, and the physically encrypted near-infrared modulated light signal is combined with the single-frequency continuous light. The mid-infrared light signal carrying the encrypted signal is generated by frequency down-conversion. Detect mid-infrared light signals carrying encrypted signals and record the integrated signal intensity; The integrated signal strength is cross-correlated with the key to decrypt the target data signal, thereby achieving encrypted data transmission in the mid-infrared band.

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