Data transmission method and device for constructing underwater quantum key distribution, equipment and storage medium

Abstract

The invention discloses a classical channel construction method for an underwater quantum key distribution system, and the method comprises the steps: caching data generated by a source end through an FPGA, carrying out the RS coding and 8B / 10B coding, carrying out the Manchester coding after the parallel-serial conversion output, and outputting an LVTTL level signal; the FPGA judges a transmission distance based on the detected information, modulates an LVTTL level signal to an LD driving circuit and receives the LVTTL level signal by an APD photoelectric detector through an underwater channel when the transmission distance is smaller than a first threshold value, otherwise, modulates the LVTTL level signal to an LED driving circuit and receives the LVTTL level signal by a PMT photoelectric detector; the FPGA receiving module receives the modulated LVTTL level signal, the received modulated LVTTL level signal is subjected to photoelectric conversion and then sent to the signal amplification processing circuit, an LVTTL level pulse sequence is obtained, and the LVTTL level pulse sequence is demodulated and decoded by the FPGA receiving module to recover information and is stored in the storage unit. The invention also discloses an underwater quantum key distribution device, corresponding equipment and a storage medium. According to the invention, the problems of signal transmission and reception in underwater quantum key distribution are solved, and the reliability and security of the system are improved.

Description

Technical Field

[0001] The present application relates to the technical field of quantum key distribution, and more specifically, to a data transmission method, device, equipment and storage medium for constructing underwater quantum key distribution. Background Art

[0002] With the continuous development of ocean exploration technology, underwater wireless communication technology plays an increasingly important role in systems such as underwater vehicles and underwater sensor networks. Underwater quantum key distribution (QKD) technology, as a new means of underwater communication security, aims to achieve the absolutely secure distribution of keys through the principles of quantum mechanics. However, the complexity of the underwater environment, such as the optical properties of seawater absorption and scattering, poses severe challenges to the efficiency and security of quantum key distribution.

[0003] Although existing underwater optical communication technologies can achieve high-speed data transmission over short distances, there are still deficiencies in long-distance transmission and signal stability. In addition, underwater quantum key distribution systems also face technical problems such as the synchronization problem of hardware devices, the complexity of signal encoding and decoding, and how to maintain the stability of quantum states in a complex underwater environment. Summary of the Invention

[0004] In view of at least one defect or improvement requirement of the prior art, the present invention provides a data transmission method, device, equipment and storage medium for constructing underwater quantum key distribution, which can solve at least one of the problems existing in the above background art.

[0005] To achieve the above object, according to the first aspect of the present invention, there is provided a data transmission method for constructing underwater quantum key distribution, the method comprising:

[0006] Data generated by a source end is buffered by an FPGA, encoded by RS and 8B / 10B encoding, and after serial-to-parallel conversion output, Manchester encoding is performed to output an LVTTL level signal;

[0007] The FPGA determines the transmission distance based on the detected information. When the transmission distance is less than a first threshold, the LVTTL level signal is modulated onto an LD drive circuit, and via an underwater channel, is received by an APD photodetector. When the transmission distance is not less than the first threshold, the LVTTL level signal is modulated onto an LED drive circuit, and via an underwater channel, is received by a PMT photodetector;

[0008] The received and modulated LVTTL level signal is subjected to optoelectronic conversion and then sent to a signal amplification processing circuit to obtain an LVTTL level pulse sequence, and the information is restored by demodulation and decoding by an FPGA receiving module and stored in a storage unit.

[0009] Further, for the above-mentioned data transmission method for constructing underwater quantum key distribution, the photon count detected by the FPGA receiver is obtained. If the photon count is greater than the second threshold, the transmission distance is less than the first threshold. If the photon count is not greater than the second threshold, the transmission distance is not less than the first threshold.

[0010] Further, for the above-mentioned data transmission method for constructing underwater quantum key distribution, before the data generated by the source end is cached by the FPGA, the source end information generated by the FPGA of the quantum key distribution key board is stored in the FIFO of the optical communication board for clock conversion.

[0011] Further, for the above-mentioned data transmission method for constructing underwater quantum key distribution, a frame synchronization identification header is added to the data after 8B / 10B encoding conversion.

[0012] Further, for the above-mentioned data transmission method for constructing underwater quantum key distribution, the LVTTL level pulse sequence is obtained, and the information is restored through demodulation and decoding by the FPGA receiving module, including performing FIFO cross-domain conversion on the obtained LVTTL level pulse sequence by the FPGA to eliminate the asynchronous of the transceiver FPGA clocks.

[0013] Further, for the above-mentioned method for constructing the classical channel of underwater quantum key distribution, the data after cross-domain conversion is subjected to Manchester encoding, the frame synchronization identification header is identified, and the valid data of the current frame is decoded.

[0014] Further, for the above-mentioned data transmission method for constructing underwater quantum key distribution, the data after cross-domain conversion and Manchester encoding is subjected to serial-to-parallel conversion, 10B / 8B decoding, and then RS decoding, and is stored in the memory.

[0015] According to the second aspect of the present invention, there is also provided a data transmission device for constructing underwater quantum key distribution, which includes:

[0016] An encoding module, configured to, after the data generated by the source end is cached by the FPGA, perform RS encoding and 8B / 10B encoding, perform Manchester encoding after output through serial-to-parallel conversion, and output an LVTTL level signal;

[0017] A transmission module, configured to judge the transmission distance by the FPGA based on the detected information. When the transmission distance is less than the first threshold, modulate the LVTTL level signal to the LD drive circuit, and receive it through the underwater channel by the APD photodetector. When the transmission distance is not less than the first threshold, modulate the LVTTL level signal to the LED drive circuit, and receive it through the underwater channel by the PMT photodetector;

[0018] A decoding module is used to perform optoelectronic conversion on the received and modulated LVTTL level signal and send it to a signal amplification processing circuit to obtain an LVTTL level pulse sequence. The information is demodulated and decoded by an FPGA receiving module and stored in a storage unit.

[0019] According to the third aspect of the present invention, there is also provided a data transmission device for constructing an underwater quantum key distribution, which includes at least one processing unit and at least one storage unit. Wherein, the storage unit stores a computer program, and when the computer program is executed by the processing unit, the processing unit executes the steps of the method described in any one of the above.

[0020] According to the fourth aspect of the present invention, there is also provided a storage medium, which stores a computer program executable by a data transmission device for constructing an underwater quantum key distribution. When the computer program runs on the data transmission device for constructing an underwater quantum key distribution, the data transmission device for constructing an underwater quantum key distribution executes the steps of the method described in any one of the above.

[0021] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0022] A data transmission method for constructing an underwater quantum key distribution provided by the present invention, by selecting the schemes of RS coding, 8B / 10B coding and Manchester coding, is more suitable for an underwater communication system, preventing the limitations that the receiving end cannot recover the clock and extract valid data in the case of long-term presence or absence of light, ensuring signal synchronization and DC balance, and optimizing the hardware configuration by dynamically selecting an LD or LED driving circuit and an APD or PMT photodetector, improving communication efficiency and stability, effectively solving the problems of signal transmission and reception in underwater quantum key distribution, and improving the reliability and security of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a schematic flowchart of a data transmission method for constructing an underwater quantum key distribution provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] The terms "first", "second", "third", etc. in the specification, claims and above-mentioned drawings of this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0027] Figure 1 It is a schematic flow chart of a data transmission method for constructing underwater quantum key distribution provided by an embodiment of this application, as Figure 1 shown, a data transmission method for constructing underwater quantum key distribution provided by an embodiment of this application includes the following steps:

[0028] After the data generated by the source end is cached by the FPGA, it is encoded by RS and 8B / 10B encoding, and after serial-to-parallel conversion output, it is Manchester encoded to output an LVTTL level signal;

[0029] The FPGA judges the transmission distance based on the detected information. When the transmission distance is less than the first threshold, the LVTTL level signal is modulated to the LD drive circuit, and via the underwater channel, it is received by the APD photodetector. When the transmission distance is not less than the first threshold, the LVTTL level signal is modulated to the LED drive circuit, and via the underwater channel, it is received by the PMT photodetector;

[0030] The received modulated LVTTL level signal is subjected to optoelectronic conversion and then sent to the signal amplification processing circuit to obtain an LVTTL level pulse sequence. The information is restored by demodulation and decoding by the FPGA receiving module and stored in the storage unit.

[0031] Specifically, the data generated by the source end first passes through the FPGA cache to ensure the stability and continuity of the data. Subsequently, the data undergoes error correction processing through RS coding. The RS coding uses Reed-Solomon coding with a code length of 255 bits and can correct up to 16-bit errors. The data is encoded by 8B / 10B to ensure DC balance and prevent signal errors caused by long 0 or long 1 sequences. After parallel-to-serial conversion, the data is Manchester encoded to ensure that there is a level change within each bit period to achieve signal synchronization and DC balance. Finally, an LVTTL level signal is output to prepare for subsequent signal modulation.

[0032] The FPGA determines the transmission distance based on the detected information. When the transmission distance is less than the first threshold, the LVTTL level signal is modulated to the LD drive circuit and received by the APD photodetector via the underwater channel. The APD photodetector is suitable for short-distance high-rate communication and can efficiently receive and convert optical signals. When the transmission distance is not less than the first threshold, the LVTTL level signal is modulated to the LED drive circuit and received by the PMT photodetector via the underwater channel. The PMT photodetector is suitable for long-distance low-rate communication and can effectively detect optical signals in a low light intensity environment. Through this dynamic switching mechanism, the system can optimize the hardware configuration according to the actual transmission distance, improving communication efficiency and stability. The first threshold can be determined based on the requirements of the actual application, and this application does not make a limitation here.

[0033] The receiving end performs optoelectronic conversion on the modulated LVTTL level signal, and the converted signal is sent to the signal amplification processing circuit to obtain an LVTTL level pulse sequence. The signal amplification processing circuit amplifies and processes the signal to ensure the integrity and readability of the signal. Subsequently, the signal is demodulated and decoded through the FPGA receiving module to restore the original information. The FPGA receiving module solves the data transmission rate matching problem and the cross-clock domain problem through the FIFO buffer to ensure data synchronization and stability. The decoded valid data is stored in a storage unit, such as a ROM or DDR3, for subsequent processing and use. The embodiments of this application can effectively restore and store key information, ensuring the reliability and security of underwater quantum key distribution.

[0034] A classical channel communication method for underwater quantum key distribution provided by an embodiment of the present application, by selecting the schemes of RS coding, 8B / 10B coding, and Manchester coding, is more suitable for underwater communication systems, preventing the limitation that the receiving end cannot recover the clock and extract valid data in the case of long-term presence or absence of light, ensuring signal synchronization and DC balance, and optimizing the hardware configuration by dynamically selecting LD or LED drive circuits and APD or PMT photodetectors, improving communication efficiency and stability, effectively solving the problems of signal transmission and reception in the classical channel of underwater quantum key distribution, and improving the reliability and security of the system.

[0035] Optionally, a classical channel communication method for underwater quantum key distribution provided by an embodiment of the present application obtains the photon count detected by the FPGA receiving end. If the photon count is greater than the second threshold, the transmission distance is less than the first threshold; if the photon count is not greater than the second threshold, the transmission distance is not less than the first threshold.

[0036] Specifically, in an underwater quantum key distribution system, there is a close relationship between the photon count detected by the FPGA receiving end and the transmission distance. When the photon count is too low, it usually means that the transmission distance is far and the signal attenuation is large, resulting in a decrease in the number of photons detected by the receiving end. On the contrary, when the photon count is too high, it usually means that the transmission distance is close and the signal strength is strong, and the receiving end detects more photons. This relationship enables the system to dynamically adjust the hardware scheme according to the photon count to adapt to different transmission distances and signal strengths.

[0037] By obtaining the photon count detected by the FPGA receiving end, the distance of the transmission can be effectively judged. Specifically, if the photon count is greater than the second threshold, the transmission distance is less than the first threshold; if the photon count is not greater than the second threshold, the transmission distance is not less than the first threshold. The second threshold can be determined based on the requirements of the actual application, and the present application does not limit it here. This method can dynamically adjust the transmission strategy according to the change of the photon count to ensure the reliability and accuracy of underwater quantum key distribution. In practical applications, this method can effectively cope with the complexity of the underwater environment and improve the adaptability and stability of the system.

[0038] Optionally, a classical channel communication method for underwater quantum key distribution provided by an embodiment of the present application stores the source information generated by the FPGA of the quantum key distribution key board into the FIFO of the optical communication board for clock conversion before the data generated by the source end is cached by the FPGA.

[0039] Specifically, in the FPGA, the FIFO buffer is used to solve the problem of data transfer rate matching between FPGAs and the problem of cross-clock domain within the FPGA. The information of the sending end generated by the FPGA of the quantum key distribution key board is stored in the FIFO of the optical communication board for clock conversion, solving the problem of asynchrony between different FPGA boards. In this way, when the data enters the FPGA buffer, it can ensure the smooth progress of subsequent encoding, modulation, and transmission processes, improving the reliability and efficiency of the entire system.

[0040] Optionally, for an underwater quantum key distribution classical channel communication method provided by an embodiment of the present application, a frame synchronization identification header is added to the data after 8B / 10B encoding conversion.

[0041] Specifically, after the data undergoes 8B / 10B encoding conversion, a frame synchronization identification header is added to ensure the accuracy and synchronization of data transmission. 8B / 10B encoding is a coding method that converts every 8 bits of data into a 10-bit codeword. This conversion can maintain the DC balance of the signal while increasing the data transfer rate, reducing long strings of consecutive identical bits, and thus reducing transmission errors. In high-speed data communication, 8B / 10B encoding can effectively avoid long strings of consecutive identical bits and reduce transmission errors by decomposing the data into two groups and encoding it. In addition, the addition of the frame synchronization identification header helps the receiving end accurately identify the starting position of the data frame, thereby achieving synchronous reception of the data. In the 8B / 10B interface implemented by the FPGA, the link layer encapsulation will add a frame header and a frame tail to ensure the integrity and synchronization of the data frame, effectively improving the performance and reliability of the underwater quantum key distribution system.

[0042] Optionally, for the underwater quantum key distribution classical channel communication method provided by an embodiment of the present application, the obtaining of the LVTTL level pulse sequence, demodulating and decoding the information through the FPGA receiving module includes performing FIFO cross-domain conversion on the obtained LVTTL level pulse sequence through the FPGA to eliminate the asynchrony of the transceiver FPGA clocks.

[0043] Specifically, in the underwater quantum key distribution system, the LVTTL level pulse sequence obtained by the receiving end is first demodulated and decoded through the FPGA receiving module. Since the FPGAs of the sending end and the receiving end may work in different clock domains, resulting in asynchronous data transfer clocks, FIFO cross-domain conversion is required. The FIFO buffer can temporarily store data and achieve data transfer between different rates or clock domains. Through FIFO cross-domain conversion, the problem of asynchrony of the transceiver FPGA clocks can be effectively eliminated, ensuring the accuracy and integrity of the data.

[0044] Optionally, for the classical channel communication method of underwater quantum key distribution provided by the embodiments of the present application, the data after cross-domain conversion is subjected to Manchester coding, the frame synchronization identification header is identified, and the valid data of the current frame is decoded.

[0045] Specifically, after the FIFO cross-domain conversion is completed, the data enters the Manchester coding stage. Manchester coding represents data by introducing a level transition within each bit period. This coding method not only provides the synchronization function of the data but also ensures the DC balance of the signal, avoiding transmission errors caused by long strings of consecutive identical bits.

[0046] During the coding process, a specific synchronization sequence, that is, the frame synchronization identification header, is first added at the beginning of the data frame to help the receiving end identify the starting position of the data frame. Subsequently, each data bit is subjected to Manchester coding to ensure that there is a level transition at the middle moment of each bit, thereby realizing the synchronous transmission of the data.

[0047] At the receiving end, the original data can be accurately restored by detecting the level transitions in the Manchester-coded signal. Specifically, the receiving end detects the level changes within each bit period and determines whether the data bit is "0" or "1" according to the direction of the transition. At the same time, by identifying the frame synchronization identification header, the receiving end can determine the starting position of the data frame, thereby correctly decoding the entire data frame.

[0048] Optionally, for the classical channel communication method of underwater quantum key distribution provided by the embodiments of the present application, the data after the cross-domain conversion and Manchester coding is subjected to serial-to-parallel conversion, 10B / 8B decoding, and then RS decoding, and is stored in the memory.

[0049] Specifically, for the data after the FIFO cross-domain conversion and Manchester coding, serial-to-parallel conversion is first performed to convert the serial data into parallel data for subsequent processing and decoding. Then, 10B / 8B decoding is performed to restore the encoded data to the original 8-bit data. This process not only ensures the DC balance of the data but also effectively reduces transmission errors. Subsequently, RS decoding is performed. By using the error correction ability of Reed-Solomon coding, the errors that may occur during transmission are corrected to ensure the integrity and accuracy of the data. Finally, the decoded data is stored in the memory for subsequent processing and use. The embodiments of the present application can effectively achieve data synchronization, decoding, and storage in underwater quantum key distribution, improving the reliability of the system and the accuracy of data transmission.

[0050] The embodiments of the present application also provide a classical channel communication device for an underwater quantum key distribution system, including:

[0051] An encoding module, which is used to perform RS encoding and 8B / 10B encoding on the data generated at the source end after being cached by the FPGA, and perform Manchester encoding after serial-to-parallel conversion output, and output an LVTTL level signal;

[0052] A transmission module, which is used for the FPGA to judge the transmission distance based on the detected information. When the transmission distance is less than the first threshold, the LVTTL level signal is modulated to the LD drive circuit, and is received by the APD photodetector via the underwater channel. When the transmission distance is not less than the first threshold, the LVTTL level signal is modulated to the LED drive circuit, and is received by the PMT photodetector via the underwater channel;

[0053] A decoding module, which is used to perform photoelectric conversion on the received modulated LVTTL level signal and send it to the signal amplification processing circuit to obtain an LVTTL level pulse sequence, and restore the information through demodulation and decoding by the FPGA receiving module and store it in the storage unit.

[0054] This application also provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, the steps of the above method are implemented. Among them, the computer-readable storage medium may include, but is not limited to, any type of disk, including floppy disks, optical disks, DVDs, CD-ROMs, microdrives, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic cards or optical cards, nano-systems (including molecular memory ICs), or any type of medium or device suitable for storing instructions and / or data.

[0055] It should be noted that for the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that this application is not limited by the described action sequence, because according to this application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0056] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0057] In several embodiments provided by the present application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection to each other can be through some service interfaces. The indirect coupling or communication connection of the device or unit can be in an electrical or other form.

[0058] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0059] In addition, in each embodiment of the present application, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0060] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The aforementioned memory includes: USB flash drives, read-only memories (ROM), random access memories (RAM), mobile hard disks, magnetic disks, or optical discs, etc., which can store program codes.

[0061] Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing relevant hardware through a program. This program can be stored in a computer-readable memory. The memory can include: flash drives, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs, etc.

[0062] The above are only exemplary embodiments of the present disclosure, and the scope of the present disclosure cannot be limited thereby. That is, any equivalent changes and modifications made according to the teachings of the present disclosure still fall within the scope covered by the present disclosure. Those skilled in the art will readily conceive of other embodiments of the present disclosure after considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common general knowledge or conventional technical means in the technical field not recorded in the present disclosure. The specification and examples are only regarded as exemplary, and the scope and spirit of the present disclosure are defined by the claims.

[0063] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered that the scope described in this specification is covered.

[0064] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A data transmission method for constructing underwater quantum key distribution, characterized in that It includes the following steps: After the data generated by the source end is cached by the FPGA, it undergoes RS coding and 8B / 10B coding, and after serial-to-parallel conversion output, it undergoes Manchester coding to output an LVTTL level signal; The FPGA determines the transmission distance based on the detected information. When the transmission distance is less than the first threshold, the LVTTL level signal is modulated to the LD drive circuit, and is received by the APD photodetector via the underwater channel. When the transmission distance is not less than the first threshold, the LVTTL level signal is modulated to the LED drive circuit, and is received by the PMT photodetector via the underwater channel; The received and modulated LVTTL level signal is subjected to photoelectric conversion and then sent to the signal amplification processing circuit to obtain an LVTTL level pulse sequence. The information is restored through demodulation and decoding by the FPGA receiving module and stored in the storage unit.

2. The data transmission method for constructing underwater quantum key distribution according to claim 1, characterized in that, Obtain the photon count detected by the FPGA receiving end. If the photon count is greater than the second threshold, the transmission distance is less than the first threshold. If the photon count is not greater than the second threshold, the transmission distance is not less than the first threshold.

3. A data transmission method for constructing underwater quantum key distribution according to claim 1, characterized in that Before the data generated by the source end is cached by the FPGA, the source end information generated by the FPGA of the quantum key distribution key board is stored in the FIFO of the optical communication board for clock conversion.

4. The data transmission method for constructing underwater quantum key distribution according to claim 1, wherein Add a frame synchronization identification header to the data after 8B / 10B coding conversion.

5. The data transmission method for constructing underwater quantum key distribution according to claim 1, characterized in that, The step of obtaining the LVTTL level pulse sequence, and restoring the information through demodulation and decoding by the FPGA receiving module includes performing FIFO cross-domain conversion on the obtained LVTTL level pulse sequence by the FPGA to eliminate the asynchronization of the transceiver FPGA clocks.

6. The data transmission method for constructing underwater quantum key distribution according to claim 5, wherein Perform Manchester coding on the data after cross-domain conversion, identify the frame synchronization identification header, and decode the valid data of the current frame.

7. The data transmission method for constructing underwater quantum key distribution according to claim 6, characterized in that, Perform serial-to-parallel conversion on the data after cross-domain conversion and Manchester coding, perform 10B / 8B decoding, and then perform RS decoding and store it in the memory.

8. A data transmission device for constructing underwater quantum key distribution, characterized in that, It includes: An encoding module, which is used to perform RS coding and 8B / 10B coding on the data generated by the source end after being cached by the FPGA, and perform Manchester coding after serial-to-parallel conversion output to output an LVTTL level signal; A transmission module, which is used for the FPGA to determine the transmission distance based on the detected information. When the transmission distance is less than the first threshold, the LVTTL level signal is modulated to the LD drive circuit, and is received by the APD photodetector via the underwater channel. When the transmission distance is not less than the first threshold, the LVTTL level signal is modulated to the LED drive circuit, and is received by the PMT photodetector via the underwater channel; A decoding module, which is used to perform photoelectric conversion on the received and modulated LVTTL level signal and then send it to the signal amplification processing circuit to obtain an LVTTL level pulse sequence. The information is restored through demodulation and decoding by the FPGA receiving module and stored in the storage unit.

9. A data transmission device for constructing underwater quantum key distribution, characterized in that, It includes at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program. When the computer program is executed by the processing unit, the processing unit executes the steps of the method according to any one of claims 1 to 7.

10. A storage medium, characterized in that, It stores a computer program executable by a data transmission device for constructing an underwater quantum key distribution. When the computer program runs on the data transmission device for constructing an underwater quantum key distribution, it causes the data transmission device for constructing an underwater quantum key distribution to execute the steps of the method according to any one of claims 1 to 7.

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