Multi-dimensional optical parameter fusion underwater encryption communication method and device

Abstract

The invention belongs to the technical field of optical communication, and particularly discloses an underwater encryption communication method and device for multi-dimensional optical parameter fusion, and the method comprises the steps: mapping to-be-transmitted real information (real codes) and false information (virtual codes) to a plurality of physical parameters of an optical carrier at a transmitting end; and a brand-new and high-concealment composite signal is constructed through fusion of the two signals. And the composite signal is decoded at a receiving end, so that real information is obtained. The invention aims to solve the problems that the existing underwater laser communication is easy to intercept, the anti-interference capability is poor and the safety is insufficient.

Description

Technical Field

[0001] This invention relates to the field of laser communication, and in particular to an optical encrypted communication technology for underwater environments, specifically an underwater encrypted communication method and device based on multidimensional optical parametric fusion. Background Technology

[0002] Underwater communication plays a vital role in marine exploration, environmental monitoring, and national defense. Currently, mainstream underwater communication technologies include underwater acoustic communication, radio wave communication, and blue-green laser communication. Among these, blue-green laser communication, due to its short wavelength, good directionality, and high bandwidth, can achieve high-speed data transmission underwater. However, blue-green laser communication typically uses single-dimensional information encoding and relies on complex mathematical encryption. Once this encryption method is cracked, the communication content will be completely exposed. Furthermore, the complex underwater environment, due to turbulence and suspended particles, causes severe signal absorption and scattering, resulting in significant signal attenuation and distortion. These factors limit the reliability and security of communication. Therefore, developing highly secure underwater information encryption methods is crucial for information communication. Summary of the Invention

[0003] In view of the shortcomings of existing technologies, the purpose of this invention is to provide a multi-dimensional optical parameter fusion underwater encrypted communication method and device. This method utilizes optical parameters such as light intensity, wavelength, and polarization to perform mixed encryption on the transmitting end information. Real codes are assigned to multiple specified optical parameter dimensions (light intensity, wavelength, polarization), and virtual codes for different signals are also loaded onto the same optical parameter dimensions. At the receiving end, using specific decoding techniques, the received signal is decoded to obtain the real code information. This encryption method effectively prevents the decryption of real information and can significantly improve the security and reliability of underwater communication.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides a multi-dimensional optical parametric fusion underwater encrypted communication method, comprising:

[0006] At the transmitting end, the real information to be transmitted is mapped to a real code, and false information used for encryption and cover is generated as a virtual code; the real code and the virtual code are respectively modulated onto the physical parameters of the optical carrier, the physical parameters including at least two of light intensity, wavelength, and polarization; multiple optical signals modulated with the real code and the virtual code are combined to form a composite encrypted optical signal; the composite encrypted optical signal is transmitted to an underwater channel for transmission;

[0007] At the receiving end, the composite encrypted optical signal is received and separated to extract the optical signal corresponding to the target physical parameters carrying the real code; the extracted optical signal is decoded to obtain the real information.

[0008] Furthermore, the real code and the virtual code are modulated onto different physical parameters of the optical carrier, specifically including:

[0009] Assign optical signals with multiple physical parameter dimensions to the real code;

[0010] Assign optical signals of the same physical parameter dimension but different from those of the real code to the virtual code.

[0011] Furthermore, the transmitting end also includes:

[0012] The combined encrypted optical signal is subjected to polarization state conversion, so that the output polarization state is associated with the wavelength of the optical signal currently carrying the real code, thus forming the first key rule.

[0013] Furthermore, at the transmitting end, it also includes: setting a correspondence between light intensity and modulation period for the optical signal carrying the real code, forming a second key rule.

[0014] Furthermore, the step of receiving and separating the composite encrypted optical signal at the receiving end specifically includes:

[0015] The polarization state of the received composite encrypted optical signal is detected, and the wavelength of the optical signal currently carrying the real code is determined according to the preset first key rule;

[0016] Based on the determined wavelength, the optical signal of the corresponding wavelength is filtered and separated from the composite encrypted optical signal.

[0017] Furthermore, the decoding of the extracted optical signal specifically includes:

[0018] The separated optical signal is converted into an It curve;

[0019] The modulation period is determined from the light intensity-time curve according to the second key rule;

[0020] The time-domain encoded data corresponding to the modulation period is extracted as the real code.

[0021] Secondly, the present invention provides a transmitter device for implementing the method described above, comprising:

[0022] Multiple lasers are used to generate optical carriers with different physical parameters;

[0023] Multiple modulators, correspondingly connected to the multiple lasers, are used to modulate the real code onto an optical carrier generated by one of the lasers, and to modulate the virtual code onto an optical carrier generated by at least one other laser;

[0024] A beam combiner is used to combine modulated multiple optical signals into a single composite encrypted optical signal.

[0025] An optical transmission system is used to shape the composite encrypted optical signal and transmit it to an underwater channel.

[0026] Furthermore, the transmitting device also includes:

[0027] A polarization conversion device is disposed on the output optical path of the beam combiner and is used to perform polarization state conversion on the composite encrypted optical signal;

[0028] The polarization conversion device is configured to have a preset correspondence between the output polarization state and the wavelength of the optical signal currently carrying the real code.

[0029] Thirdly, the present invention provides a receiving device for implementing the method described above, comprising:

[0030] An optical parametric separation device is used to receive composite encrypted optical signals from an underwater channel and separate optical signals of different physical parameter dimensions from them.

[0031] At least one photodetector is used to convert the separated optical signal into an electrical signal;

[0032] The signal processing and decoding module is used to process the electrical signal and decode the real code according to a preset key rule.

[0033] Furthermore, the optical parametric separation device includes:

[0034] A polarization filtering detection module is used to detect the polarization state of the composite encrypted optical signal;

[0035] The wavelength filtering module filters out the optical signal of the corresponding wavelength from the composite encrypted optical signal based on the wavelength of the optical signal carrying the real code, which is determined by the polarization state.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) Encryption light has rich dimensions: The introduction of multiple optical parameters such as light intensity, wavelength, and polarization greatly increases the complexity of encryption and effectively improves communication security.

[0038] (2) Strong resistance to environmental interference: Through multi-parameter fusion, even if the intensity signal attenuates severely in the underwater environment, the system can demodulate information from optical parameters such as wavelength and polarization, which improves the link reliability in harsh underwater environments such as turbidity and turbulence.

[0039] (3) It is expected to improve transmission capacity: Loading multiple dimensions of information onto the same optical carrier is equivalent to multiple communication channels. Transmitting information through multiple channels in parallel can effectively improve data transmission rate and capacity. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the multi-dimensional optical parameter fusion encrypted communication described in this invention, where A, B, and C are the sender, the eavesdropper, and the receiver, respectively.

[0041] Figure 2 The diagram illustrates a specific solution in this invention, using encrypted communication with three lasers of different wavelengths as an example. The components are: 1. First laser; 2. Second laser; 3. Third laser; 4. First modulator; 5. Second modulator; 6. Third modulator; 7. Voltage drive module; 8. First beam combiner; 9. Second beam combiner; 10. Polarization conversion device; 11. Beam expander; 12. Collimating lens; 13. Underwater transmission environment; 14. Polarization state filtering and detection module; 15. Wavelength filter; 16. Focusing lens; 17. APD; 18. Display screen.

[0042] Figure 3 for Figure 2 The key rules of an encrypted communication system at a certain moment include decoding rules in three dimensions: wavelength, polarization state, and light intensity;

[0043] Figure 4 for Figure 2 The real-code modulation and coding photocurrent time-domain response curve of the encrypted communication system has a modulation period of 40s. The resulting signal is 010000110100100101000111010010010101 0100, and the corresponding character is CIGIT.

[0044] Figure 5 for Figure 2 The time-domain response curve of the photocurrent of the virtual code modulation encoding of the encrypted communication system has a modulation period of 40s. The resulting signal is 1011110010110110101110001011011010101011, and the corresponding character is ¼¶¸¶«.

[0045] Figure 6 For carrying Figure 4 Real code laser and portable Figure 5The photocurrent time-domain response curve after virtual code laser beam combining and 45° linear polarization state conversion has a response period of 40s. The resulting signal is 111111111111111111111111111111111111111111, which is just a pulse with consistent light intensity and does not carry any information.

[0046] Figure 7 for Figure 6 The signal is obtained by polarization / wavelength dual filtering and decoding. Figure 4 The photocurrent time-domain response curve has a decoding period of 40s (according to the key protocol, the decoding period is 40s under the light intensity corresponding to the maximum photocurrent of 9 μA). The obtained signal is 010000110100100101000111010010010101 0100, and the corresponding character is CIGIT.

[0047] Figure 8 for Figure 6 The signal is obtained by polarization / wavelength dual filtering and decoding. Figure 5 The photocurrent time-domain response curve has a decoding period of 40s (according to the key protocol, the decoding period is 40s under the light intensity corresponding to the maximum photocurrent of 9 μA). The obtained signal is 1011110010110110101110001011011010101011, which corresponds to the character ¼¶¸¶«. Detailed Implementation

[0048] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0049] The invention will now be further described with reference to the accompanying drawings.

[0050] Example 1:

[0051] This invention provides a multi-dimensional optical parametric fusion underwater encrypted communication method. Its core lies in utilizing multiple physical dimensions of an optical carrier to encrypt and hide information, aiming to solve the problems of easy interception and poor security in existing underwater laser communication. Specifically, this multi-dimensional optical parametric fusion underwater encrypted communication method includes the following two steps.

[0052] Step 1: At the transmitting end, the real information to be transmitted is mapped to a real code, and false information used for encryption and cover is generated as a virtual code; the real code and the virtual code are modulated onto different physical parameters of the optical carrier, the physical parameters including at least two of light intensity, wavelength, and polarization; multiple optical signals modulated with the real code and the virtual code are combined to form a composite encrypted optical signal; the composite encrypted optical signal is transmitted to the underwater channel for transmission.

[0053] In this embodiment, step 1 specifically includes two sub-steps: transmitter information processing and encryption modulation, and composite signal generation and transmission.

[0054] For information processing and encryption modulation at the transmitting end, firstly, the real information to be transmitted (i.e., real code) and the false information used to cover up the real transmission (i.e., virtual code) are determined. The real code and virtual code can be binary bit streams. Next, this information is mapped to different physical parameters of the optical carrier. Available physical parameters include, but are not limited to, light intensity, wavelength, and polarization. In this invention, only the real code is loaded onto multiple optical parameter dimensions (wavelength, polarization, light intensity, etc.), while virtual codes for different signals are also loaded onto the same type of optical parameter dimension, thereby achieving information mixing and concealment.

[0055] For the generation and transmission of the composite signal, multiple optical signals carrying real and imaginary codes are combined into a single composite encrypted optical signal using a beam combiner (such as a beam combiner prism or dichroic plate). This process integrates multi-dimensional information. Furthermore, the polarization state of the composite beam is controlled using polarization conversion devices (such as waveplates or polarizers) to increase the encryption dimension. Finally, a transmitting lens group is used to expand and collimate the composite encrypted beam to reduce its divergence angle during underwater transmission, and then it is transmitted into an underwater channel (such as seawater).

[0056] Step 2: At the receiving end, the composite encrypted optical signal is received and separated to extract the optical signal corresponding to the target physical parameter value carrying the real code; the extracted optical signal is decoded to obtain the real information.

[0057] In this embodiment, step 2 can be implemented through two sub-steps: receiving and separating signals at the receiving end, and decoding and acquiring information.

[0058] For signal reception and separation at the receiving end, the receiving end collects and focuses the composite encrypted optical signal from underwater through a receiving focusing lens. The key is that the receiving end is equipped with an optical parameter separation device (such as a device composed of metasurface structures, optical filters, analyzers, phase selectors, etc.) to efficiently separate the different physical parameters (such as wavelength, light intensity, polarization) information that are fused together in space or spectrum.

[0059] For information decoding and acquisition, the separated optical parameter information is detected by the corresponding photodetector (such as an avalanche photodiode APD) and converted into electrical signals. The signal processing and decoding module amplifies and filters the electrical signals, and then, according to the preset key rules, identifies and demodulates the information loaded on the target physical parameter value (i.e., the parameter value carrying the real code) from the mixed signal, filters out the false code, and finally obtains the real information carried by the real code.

[0060] In some embodiments, modulating the real code and the virtual code onto multiple physical parameters of an optical carrier specifically includes: allocating optical signals of multiple physical parameter dimensions to the real code; and allocating optical signals of the same physical parameter dimensions but different from the real code to the virtual code.

[0061] This embodiment further defines the specific allocation strategy for information modulation to different optical parameters. At the transmitting end, in order to implement effective encryption, it is necessary to clearly allocate the carrying dimensions of real code and virtual code, including real code allocation and virtual code allocation.

[0062] Real code allocation: From the multiple available physical parameter values ​​(e.g., different wavelengths λ1, λ2, λ3; different polarization states P1, P2, P3; different light intensities I1, I2), a unique set of physical parameter values ​​(e.g., wavelength λ2, polarization state P2, and light intensity I2) is designated as the channel carrying the real code at the current moment.

[0063] Virtual code allocation: Random combinations other than the single set of physical parameter values ​​mentioned above are allocated to carry virtual codes.

[0064] Through this allocation, the real code is hidden within a signal cluster composed of multiple imaginary code signals. For example... Figure 6 As shown, when the real and imaginary signals are combined within the same period, what is directly detected is a mixed pulse with consistent light intensity, making it impossible to directly distinguish the effective information and effectively deceiving the eavesdropper. Figure 1 (B in the middle).

[0065] In some embodiments, at the transmitting end, the method further includes: performing polarization state conversion on the combined encrypted optical signal, such that the output polarization state is associated with the wavelength of the optical signal currently carrying the real code, thereby forming a first key rule.

[0066] This embodiment, based on the above embodiment, adds a first layer of key protection, involving the encryption application of polarization states. Specifically, after the multi-wavelength optical signals are combined at the transmitting end, a polarization conversion device 10 is provided at the output end of the combining device. This device performs polarization state conversion on the combined laser beam. The preset encryption rule (i.e., the first key rule) is: the output polarization states (P1, P2, P3) correspond one-to-one with the wavelengths (λ1, λ2, λ3) of the laser currently carrying the real code. For example, the rule can be set as follows: if the real code is loaded on the laser with wavelength λ1, the polarization converter is adjusted to make the output beam horizontally polarized P1; if the real code is on λ2, the output polarization state is P2; if the real code is on λ3, the output polarization state is P3 (this correspondence can be found in [reference needed]). Figure 3 (The intended meaning is unclear). In one instance, if the real code wavelength is λ2, then the final output hybrid laser polarization state is adjusted to P2. This step makes the polarization state a key used at the receiver to indicate which wavelength is the valid real code carrier.

[0067] In some embodiments, at the transmitting end, the method further includes: setting a correspondence between light intensity and modulation period for the optical signal carrying the real code, thereby forming a second key rule.

[0068] This implementation adds a second layer of key protection based on the first key rule, involving the encryption application of the light intensity modulation period. During time-domain coding modulation at the transmitting end, in addition to allocating wavelength and polarization, encryption rules are set for the laser intensity dimension carrying the real code, forming the second key rule. Specifically, the driving voltage of the laser is controlled by the voltage driving module 7 (e.g., selecting only U1 or U2), with different voltages corresponding to different laser output intensities (e.g., U1 corresponds to intensity I1, and U2 corresponds to intensity I2).

[0069] Furthermore, a predefined correspondence between light intensity and modulation period is established: for example, light intensity I1 corresponds to a shorter modulation period T1, and light intensity I2 corresponds to a longer modulation period T2 (where T1 < T2), as follows. Figure 3 As shown.

[0070] Therefore, at the receiving end, it is necessary to measure the light intensity value to deduce the modulation period used by the transmitting end in order to correctly parse the time-domain coded data within the corresponding time period.

[0071] In some embodiments, receiving and separating the composite encrypted optical signal at the receiving end specifically includes: detecting the polarization state of the received composite encrypted optical signal; determining the wavelength of the optical signal currently carrying the real code according to a preset first key rule; and filtering and separating the optical signal of the corresponding wavelength from the composite encrypted optical signal according to the determined wavelength.

[0072] This embodiment describes the specific steps for separating the composite signal at the receiving end, incorporating the application of the first key rule (polarization-wavelength correspondence). After receiving the composite encrypted optical signal, the receiving end separates the real code signal according to the following steps:

[0073] (1) Polarization state filtering detection and real-code wavelength recognition: A polarization state detection module 14 is set at the input end of the receiver to first detect the polarization state of the received mixed laser (e.g., detecting P2). Then, according to the first key rule preset by the transmitter (i.e., the polarization state-real-code wavelength correspondence, such as...), the polarization state is detected. Figure 3 The laser wavelength (λ2) carrying the real code is deduced from the detected polarization state (P2). This is the crucial first step in decoding.

[0074] (2) Wavelength Filtering: Based on the identified real-code wavelength (λ2), the wavelength filtering module (e.g., an adjustable filter or a dichroic filter) is controlled to operate. This module filters out light of other wavelengths (i.e., virtual-code wavelengths, such as λ1 and λ3) in the mixed laser, allowing only the real-code wavelength (λ2) to pass through. Figure 7 and Figure 8 As shown, after filtering, the real and imaginary codes can be decoded and restored to their respective independent time-domain signals.

[0075] In some embodiments, decoding the extracted optical signal specifically includes: converting the separated optical signal into an It curve; determining the modulation period from the It curve according to the second key rule; and extracting the time-domain encoded data corresponding to the modulation period as the real code.

[0076] This embodiment describes the specific steps of decoding at the receiving end, incorporating the application of the second key rule (light intensity-period correspondence). After separating the optical signal of the real code wavelength through filtering, decoding is performed, including the following steps:

[0077] (1) Photoelectric conversion and It curve acquisition: The filtered real-wavelength laser is focused onto the photosensitive surface of the APD 17. The APD converts the optical signal into an electrical signal, which is then sampled by a high-speed data acquisition card to generate the It curve.

[0078] (2) Determine the modulation period: Analyze the It curve according to the second key rule preset by the transmitter (i.e., the correspondence between light intensity and modulation period). For example, by identifying the maximum light intensity value (I1 or I2) in the curve, it can be determined whether the modulation period used by the transmitter is T1 or T2 (see...). Figure 3 rule).

[0079] (3) Data Extraction and Analysis: Knowing the correct modulation period (e.g., T1), extract the time-domain coded data segment synchronized with that period from the It curve. Decoding this data segment yields the original real-code bitstream. For example... Figure 7 and Figure 8 As shown.

[0080] This embodiment also provides a transmitter device for implementing the method described above, such as... Figure 2 As shown, it includes:

[0081] Multiple lasers, for example, three lasers, namely a first laser 1, a second laser 2, and a third laser 3, are used to generate lasers with different physical parameter values ​​(in this embodiment, different wavelengths λ1, λ2, and λ3). The wavelengths of these lasers are preferably located in the blue-green light band, where underwater transmission loss is relatively low.

[0082] Multiple modulators, for example, three, namely a first modulator 4, a second modulator 5, and a third modulator 6, are connected to corresponding lasers. One modulator (e.g., the second modulator 5) is used to load real code onto the optical parameters (such as light intensity) of a certain laser (e.g., the second laser 2 corresponding to λ2); the other modulators (e.g., the first modulator 4 and the third modulator 6) are used to load virtual code onto specified optical parameters of other lasers. The modulators perform time-domain encoding under the synchronous control of the voltage drive module 7.

[0083] The beam combiner, for example, is configured as two beam combiners, the first beam combiner 8 and the second beam combiner 9, which can be implemented as two beam combining prisms to combine three modulated optical signals of different wavelengths into a single beam of light.

[0084] The transmitting optical system includes a beam expander 11 and a collimator 12, which are used to expand and collimate the combined encrypted optical signal to form a beam suitable for long-distance transmission in an underwater environment, and then transmit it underwater.

[0085] In some embodiments, the transmitting device further includes a polarization conversion device 10, which is disposed in the output optical path of the first beam combiner 8 and the second beam combiner 9. The polarization conversion device 10 may include a waveplate and a polarizer for polarization state conversion of the composite encrypted optical signal. A key configuration of the polarization device 10 is that its angle is controlled and adjusted so that the polarization state (P1, P2, P3) of the final output beam forms a fixed, preset correspondence (i.e., a first key rule) with the wavelength of the laser currently carrying the real code. Figure 2 As shown, when the real code is on λ2, the polarization device 10 is set to output the P2 polarization state.

[0086] This invention also provides a receiving device for implementing the method described above, such as... Figure 2 As shown, it includes:

[0087] An optical parametric separator is used to physically separate received composite encrypted optical signals. This device can be an integrated module containing... Figure 2 The polarization filtering detection device 14 and filter 15 are used in the system. Their function is to perform polarization state detection and wavelength selection sequentially.

[0088] The photodetector 17, preferably an avalanche photodiode (APD), is used to efficiently convert the optical signal of the separated target physical parameter value (such as the real code wavelength) into an electrical signal.

[0089] The signal processing and decoding module (integrated into the display screen 18) is used to receive the electrical signal output by the APD. This module first generates an It curve using a high-speed data acquisition card and then uses signal processing algorithms to repair signal distortion caused by underwater turbulence and scattering. Next, based on the key rules (including the first and second key rules) obtained in advance from a secure channel, it parses the modulation period and extracts the time-domain encoded data, finally decoding and restoring the actual code information, which can then be displayed on the display screen 18.

[0090] In some embodiments, the optical parametric separation device includes a polarization detection module 14 and a wavelength filtering module 15. The polarization detection module 14 is located at the front end of the receiving optical path and is used to first detect the polarization state of the incident composite encrypted optical signal. This can be accomplished by using a rotating analyzer in conjunction with photoelectric detection. The wavelength filtering module 15 determines the wavelength to be extracted based on the result of the polarization detection module and a preset polarization state-real code wavelength correspondence rule. Subsequently, the wavelength filtering module 15 (e.g., a switchable narrowband filter or an acousto-optic tunable filter) is configured to allow only a set wavelength of optical signal to pass through, while blocking other wavelengths, thereby completing the crucial step of separating the real code carrier from the composite signal.

[0091] Example 2:

[0092] Based on the underwater encrypted communication method and device with multidimensional optical parameter fusion provided in the various embodiments of Example 1, a specific method for implementing underwater encrypted communication is provided. Figure 1Schematic diagram of an encryption communication coding system for multi-optical parameter fusion, including a sender module A, an eavesdropper module B, and a partner module C; the sender module A includes multiple laser diodes for generating optical signals with different optical parameters. Each optical parameter is generated by the corresponding laser diode and then input into a beam combiner for fusion; the sender A generates optical signals with four optical parameters through the laser diodes respectively, fuses these four optical parameters through the beam combiner, and edits the real signal into one of the optical parameters. The eavesdropper module B includes an eavesdropping device (only containing one APD for directly detecting the unseparated fused optical parameter signal) and a display device (for displaying the pseudo-code signal obtained by eavesdropping); the eavesdropping device of the eavesdropper B does not separate the fusion parameters, directly uses one APD to detect the fused optical signal, the obtained signal is a pseudo-code, and is displayed on the display device; the partner module C includes an optical parameter separator (for separating the four fused optical parameters), multiple photodiodes (for detecting each separated optical parameter signal one by one), and a comparison display device (for comparing and displaying the real signal); the partner C inputs the four fused optical parameters into the separator for separation, then detects each parameter signal with a photodiode one by one, compares the detected signals, so as to obtain the real signal, and displays it on the comparison display device.

[0093] Figure 2 Shown is a specific case of the encryption communication system using the three dimensions of wavelength, polarization, and optical intensity of the present invention, including a transmitting end and a receiving end. The specific implementation steps of each part are as follows:

[0094] 1. Transmitting end

[0095] The transmitting end is used to generate a laser beam carrying multi-dimensional encrypted information and transmit it in an underwater environment. The specific steps are as follows:

[0096] ① Laser source voltage drive and parameter matching

[0097] Prepare three lasers with different wavelengths, the first laser 1, the second laser 2, and the third laser 3. The initial laser wavelengths of the three beams are λ1, λ2, and λ3 (λ1≠λ2≠λ3) respectively. Use a voltage drive module 7 to provide drive voltages for the three lasers synchronously. The drive voltage is only selected from U1 or U2 (where U1>U2); preset the corresponding relationships between voltage and optical intensity, and between optical intensity and modulation period: voltage U1 corresponds to laser optical intensity I1, voltage U2 corresponds to laser optical intensity I2; optical intensity I1 corresponds to modulation period T1, optical intensity I2 corresponds to modulation period T2 (where T1<T2), and ensure that the voltage, optical intensity, and modulation period of each laser beam are in one-to-one correspondence.

[0098] ② Time-domain coding modulation and beam combination

[0099] Three independent time-domain modulators, modulator 4, modulator 5, and modulator 6, are used to perform time-domain coded modulation on three laser beams of different wavelengths, with only one laser beam using real code ( Figure 2 Select the second laser (2) for modulation, and use virtual code (2 lasers) for the remaining two laser beams. Figure 2 The first laser 1 and the third laser 3 are selected for modulation, and the modulation process of the three lasers is started synchronously; a wavelength switching module is configured to adjust the wavelength of the laser carrying the real code (any one of wavelengths λ1, λ2, and λ3) in real time; the first beam combiner 8 and the second beam combiner 9 are used to combine the three modulated lasers into a single hybrid laser.

[0100] ③ Polarization state conversion

[0101] A polarization conversion device 10 is installed at the output end of the beam combining device to convert the polarization state of the combined laser beam. There are three polarization states P1, P2, and P3. The correspondence between the polarization state and the actual wavelength is preset: the actual wavelength λ1 corresponds to polarization state P1, the actual wavelength λ2 corresponds to polarization state P2, and the actual wavelength λ3 corresponds to polarization state P3. By adjusting the angle between the polarizer and the waveplate, the polarization state of the final output of the combined laser is matched with the current actual wavelength. Figure 2 The wavelength of the real code is λ2, and the output polarization state is P2), ensuring that each polarization state uniquely identifies the laser wavelength currently carrying the real code.

[0102] ④ Beam expansion, collimation, and underwater transmission

[0103] The hybrid laser, after polarization conversion, is fed into beam expander 11 to expand the laser beam and reduce beam divergence during transmission. The expanded laser beam is then fed into collimator 12 to collimate the beam and reduce interference from underwater suspended particles on the beam propagation direction. The collimated laser beam is then transmitted in the target underwater environment 13, with the emission direction towards the receiver.

[0104] 2. Receiving end

[0105] The receiver receives the laser beam transmitted underwater, according to Figure 3 The key rules in the code are used to sequentially parse the encrypted information in three dimensions: polarization, wavelength, and light intensity, and finally recover the original transmitted data. The specific steps are as follows:

[0106] ① Polarization state detection and real-code wavelength recognition

[0107] A polarization state detection module 14 is set at the input end of the receiver to detect the polarization state of the received mixed laser and determine the current polarization state of the laser (one of P1, P2, and P3); according to Figure 3 The polarization state-to-real code wavelength correspondence preset at the transmitter is used to infer the current laser wavelength carrying the real code from the detected polarization state. Figure 2 If polarization state P2 is detected, then the real code wavelength is λ2.

[0108] ② Wavelength filtering and beam focusing

[0109] Based on the identified real wavelength, the virtual wavelength laser in the mixed laser is filtered out by the corresponding filter 15. Figure 2 The actual wavelength is λ2, and the laser wavelengths λ1 and λ3 are filtered out, retaining only the laser with the actual wavelength. The filtered laser with the actual wavelength is then fed into the focusing lens 16 and focused onto the photosensitive surface of the APD17 to ensure that the APD17 can efficiently receive the optical signal.

[0110] ③ Photoelectric conversion and It curve acquisition

[0111] The APD and high-speed data acquisition card are activated. The APD converts the focused light signal into an electrical signal, and the high-speed data acquisition card samples and processes the electrical signal to generate the It curve. The generated It curve is then transmitted to the display screen 18 for real-time display, facilitating subsequent data analysis.

[0112] ④ Data repair and encrypted information decryption

[0113] Signal processing algorithms are used to repair the distorted It curve caused by underwater disturbances, compensating for light intensity fluctuations caused by water flow and signal attenuation caused by suspended particles; according to Figure 3 The transmitter has a preset light intensity-modulation period correspondence. The modulation period of the current laser is determined by the maximum light intensity value in the It curve (e.g., if the maximum light intensity is I1, then the modulation period is T1). The time-domain encoded data corresponding to the modulation period (e.g., the data segment corresponding to the period T1) is extracted. This data is the encrypted information transmitted by the transmitter, and the information parsing is completed.

[0114] Figures 4 to 8 To adopt Figure 2 The experimentally measured time-domain optical signal obtained by the encrypted optical communication system. In the experiment, the transmitting end used dual-band, linearly polarized lasers for mixed time-domain optical intensity modulation with a modulation period of 40s. The real code signal was modulated using the ASCII binary code corresponding to the character "CIGIT", and the imaginary code corresponding to the character "¼¶¸¶«". The dual-band beam was then combined and subjected to a 45-degree linear polarization state conversion. The receiving end used polarization detection devices, filters, and an APD to detect polarization, wavelength, and light intensity, respectively, and finally decoded to recover the real code. Figure 4 and Figure 5 The It curves are the original signals in real and imaginary code, respectively. Figure 6 The It curve is the result of combining real and imaginary codes within the same period and undergoing a 45° linear polarization state conversion. Figure 7 and Figure 8The images show the It curves of the real and imaginary codes obtained after decryption and restoration through polarization / wavelength dual filtering (according to the key protocol, the decoding period is 40s under the light intensity corresponding to a maximum photocurrent of 9 μA).

[0115] This implementation scheme enhances anti-eavesdropping capabilities through three-dimensional key rules based on wavelength, polarization, and light intensity, as detailed below:

[0116] ① Polarization-real-code wavelength key protection

[0117] The eavesdropper does not know the correspondence between polarization state and real code wavelength. Even if the detector receives the mixed laser, it cannot distinguish between real code wavelength and virtual code wavelength, and cannot obtain effective optical signal. If it tries to detect it, it can only obtain virtual code data and cannot crack the information.

[0118] ② Light intensity-modulation period key protection

[0119] Even if the eavesdropper obtains the actual wavelength through illegal means, due to the unknown correspondence between light intensity and modulation period, they cannot determine the modulation period from the optical signal, and therefore cannot extract the time-domain encoded data corresponding to the period; moreover, underwater disturbances will cause the It curve obtained by the eavesdropper to be distorted, further increasing the difficulty of cracking.

[0120] ③ Multi-dimensional combined protection effect

[0121] The three-dimensional key rules are interconnected and indispensable. The eavesdropper needs to crack all three dimensions of the key simultaneously to obtain the encrypted information, which greatly increases the threshold for cracking. At the same time, the neural network algorithm's ability to repair distorted data further ensures the accuracy of information from the legitimate receiving end, while the eavesdropper lacks the support of repair algorithms and has difficulty processing distorted data.

[0122] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A multi-dimensional optical parametric fusion underwater encrypted communication method, characterized in that, include: At the transmitting end, the real information to be transmitted is mapped to real code, and fake information used for encryption and cover is generated as virtual code; The real code and the virtual code are respectively modulated onto the physical parameters of the optical carrier, the physical parameters including at least two of light intensity, wavelength, and polarization; multiple optical signals modulated with the real code and the virtual code are combined to form a composite encrypted optical signal; the composite encrypted optical signal is transmitted to an underwater channel for transmission. At the receiving end, the composite encrypted optical signal is received and separated to extract the optical signal corresponding to the target physical parameters carrying the real code; the extracted optical signal is decoded to obtain the real information.

2. The underwater encrypted communication method based on multidimensional optical parametric fusion according to claim 1, characterized in that, The step of modulating the real code and the virtual code onto different physical parameters of the optical carrier specifically includes: Assign optical signals with multiple physical parameter dimensions to the real code; Assign optical signals of the same physical parameter dimension but different from those of the real code to the virtual code.

3. The underwater encrypted communication method based on multidimensional optical parametric fusion according to claim 1 or 2, characterized in that, The transmitting end also includes: The combined encrypted optical signal is subjected to polarization state conversion, so that the output polarization state is associated with the wavelength of the optical signal currently carrying the real code, thus forming the first key rule.

4. The underwater encrypted communication method based on multidimensional optical parametric fusion according to claim 3, characterized in that, At the transmitting end, it also includes: setting a correspondence between light intensity and modulation period for the optical signal carrying the real code, forming a second key rule.

5. The underwater encrypted communication method based on multidimensional optical parametric fusion according to claim 1, characterized in that, The step of receiving and separating the composite encrypted optical signal at the receiving end specifically includes: The polarization state of the received composite encrypted optical signal is detected, and the wavelength of the optical signal currently carrying the real code is determined according to the preset first key rule; Based on the determined wavelength, the optical signal of the corresponding wavelength is filtered and separated from the composite encrypted optical signal.

6. The underwater encrypted communication method based on multidimensional optical parametric fusion according to claim 4, characterized in that, The decoding of the extracted optical signal specifically includes: The separated optical signal is converted into an intensity-time (It) curve; The modulation period is determined from the It curve according to the second key rule; The time-domain encoded data corresponding to the modulation period is extracted as the real code.

7. A transmitting device for implementing the method according to any one of claims 1-6, characterized in that, include: Multiple lasers are used to generate optical carriers with different physical parameters; Multiple modulators, correspondingly connected to the multiple lasers, are used to modulate the real code onto an optical carrier generated by one of the lasers, and to modulate the virtual code onto an optical carrier generated by at least one other laser; A beam combiner is used to combine modulated multiple optical signals into a single composite encrypted optical signal. An optical transmission system is used to shape the composite encrypted optical signal and transmit it to an underwater channel.

8. The transmitting device according to claim 7, characterized in that, Also includes: A polarization conversion device is disposed on the output optical path of the beam combiner and is used to perform polarization state conversion on the composite encrypted optical signal; The polarization conversion device is configured to have a preset correspondence between the output polarization state and the wavelength of the optical signal currently carrying the real code.

9. A receiving device for implementing the method according to any one of claims 1-6, characterized in that, include: An optical parametric separation device is used to receive composite encrypted optical signals from an underwater channel and separate optical signals of different physical parameter dimensions from them. At least one photodetector is used to convert the separated optical signal into an electrical signal; The signal processing and decoding module is used to process the electrical signal and decode the real code according to a preset key rule.

10. The receiving end device according to claim 9, characterized in that, The optical parameter separation device includes: A polarization filtering detection module is used to detect the polarization state of the composite encrypted optical signal; The wavelength filtering module filters out the optical signal of the corresponding wavelength from the composite encrypted optical signal based on the wavelength of the optical signal carrying the real code, which is determined by the polarization state.

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