Communication and encryption integrated key distribution system and method based on coherent light communication

Abstract

The invention belongs to but is not limited to the technical field of optical key distribution, and discloses a communication and encryption integrated key distribution system and method based on channel reciprocity and coherent optical communication, which utilizes a scrambler to enable the tap coefficient of a time-varying depolarization algorithm to change quickly, thereby improving the key generation rate and improving the key transmission efficiency. And the method is combined with a channel reciprocity characteristic and is applied to secure key distribution. According to the invention, key distribution and secure coherent light communication can be carried out simultaneously. And during digital signal processing of the signal receiving module, on one hand, key generation is carried out, and on the other hand, secure optical communication is carried out. It is guaranteed that two legal parties obtain consistent secret keys through dynamic reciprocity of channels, and safety is guaranteed through mutual disturbance of the channel reciprocity and a time-varying cross-polarization state. The system does not need additional devices and is highly compatible with the current coherent communication system, so that the deployment cost of the key distribution module can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of coherent optical communication and physical layer key distribution, and in particular relates to a key distribution system and method that integrates communication and encryption based on channel reciprocity and cascaded multimode algorithm (CMMA). Background Technology

[0002] As optical access networks continue to expand in scale and increase in communication capacity, the demand for secure communication in fiber optic communication systems is becoming increasingly urgent. Physical layer key distribution (PLKD), as one of the key technologies for achieving secure transmission, faces numerous challenges. Traditional key distribution systems mainly rely on the complexity of algorithms to ensure their security, but this also leads to limitations in key generation rate, affecting their practical application.

[0003] Quantum key distribution (QKD) uses the quantum no-cloning principle to generate keys, theoretically enabling absolutely secure communication. However, due to the complexity of single-photon detection technology, the key generation rate of QKD systems is relatively low, and they have poor compatibility with existing fiber optic communication systems, limiting their practical deployment.

[0004] Current research focuses on chaotic optical synchronization and channel-characteristic-based key distribution systems. Chaotic optical synchronization generates keys by deploying two similar chaotic optical systems. Optical chaos possesses characteristics such as high bandwidth and unpredictability, meeting the requirements for high-speed key generation and randomness. Symmetrically deployed chaotic optical sources provide additional security guarantees. However, this approach is difficult and costly to deploy, and places extremely high demands on device consistency, limiting its widespread application.

[0005] On the other hand, channel-characteristic-based key distribution systems utilize the inherent reciprocity and randomness (such as polarization dispersion) of fiber optic channels to extract keys, satisfying the randomness and consistency required for key distribution. However, static channel characteristics change slowly, failing to provide high-speed key generation and being easily eavesdropped upon. Therefore, introducing dynamic perturbations to alter channel characteristics becomes an effective way to improve the key generation rate.

[0006] While existing key distribution technologies each have their own advantages and disadvantages, most schemes suffer from drawbacks such as overly complex algorithms or excessively high requirements for device consistency. Furthermore, current research largely focuses on standalone key distribution systems and has not yet delved into key distribution within coherent optical communication. Therefore, achieving efficient and secure key distribution in coherent optical communication systems remains a pressing issue that needs to be addressed.

[0007] Among the closest existing technologies, some studies have proposed a key distribution scheme based on fiber optic channel feature extraction. This scheme generates keys by measuring certain statistical characteristics of the channel (such as signal-to-noise ratio and bit error rate), thereby achieving physical layer secure key distribution between communicating parties. Experiments show that this scheme can obtain a certain consistency key sequence by quantizing and encoding the fiber optic channel features. However, the key generation process is relatively independent of the communication demodulation process. Furthermore, under dynamic channel conditions, the consistency of the extracted features is constrained by the time-varying characteristics of the fiber, leading to a significant increase in the probability of key inconsistency between the two parties, which affects the reliability and real-time performance of practical applications.

[0008] Therefore, existing technologies cannot effectively solve the technical problem of achieving coordinated operation of communication demodulation and high-consistency key extraction under dynamic optical fiber channel conditions, which is also the core technical pain point that the independent claims of this invention address. Summary of the Invention

[0009] To address the shortcomings and gaps in existing technologies, this invention provides a key distribution system device, method, and integrated information processing terminal technology that combines communication and security, in order to solve the problems of complex encryption algorithms and the separation of key distribution and secure communication in existing key distribution technologies, and to realize key distribution in coherent optical communication systems.

[0010] This invention is implemented as follows: a unified key distribution system for communication and confidentiality based on dynamic channel reciprocity and CMMA, comprising:

[0011] The first signal transmission module is used to modulate and transmit the information bit sequence signal, and to divide the polarization direction of the signal light into mutually perpendicular X and Y directions for subsequent mutual perturbation of the two polarization directions. The first signal transmission module includes a first information bit register, a first random signal generator, a first laser, a first Mach-Zehnder modulator, a second Mach-Zehnder modulator, and a first polarization beam combiner;

[0012] The second signal transmission module is used to modulate and transmit the information bit sequence signal, and to divide the polarization direction of the signal light into mutually perpendicular X and Y directions for subsequent mutual perturbation of the two polarization directions. The second signal transmission module includes a second information bit register, a second random signal generator, a second laser, a third Mach-Zehnder modulator, a fourth Mach-Zehnder modulator, and a second polarization beam combiner;

[0013] The channel transmission module is used to transmit the optical signals generated by the first and second signal transmission modules, artificially and uniformly perturb the polarization state of the laser using a polarization scrambler, and finally perform key distribution using the tap characteristics of its time-varying CMMA. The fiber optic transmission module includes standard single-mode fiber, a first polarization scrambler, a second polarization scrambler, and...

[0014] The first signal receiving module is used for coherent reception and digital signal processing of optical signals transmitted through the channel, as well as extraction of CMMA tap features. The first signal receiving module includes a first polarization beam splitter, a first photodetector, a second photodetector, and a first digital signal processing module.

[0015] The second signal receiving module is used for coherent reception and digital signal processing of optical signals transmitted through the channel, as well as extraction of CMMA tap features. The second signal receiving module includes a second polarization beam splitter, a third photodetector, a fourth photodetector, and a second digital signal processing module.

[0016] Furthermore, in the first signal generation module, the information bit sequence in the first information bit register is stored in a buffer to form a signal frame, which is then loaded onto the first random signal generator. The first laser emits a DC optical signal, which is modulated by the random signal generator to form a coherent transmitter. The transmitter emits two mutually orthogonal polarized beams, and the modulated optical signals are transmitted into a channel with reciprocal polarization states, generating polarization crosstalk.

[0017] Furthermore, in the second signal generation module, the information bit sequence in the second information bit register is stored in a buffer to form a signal frame, which is then loaded onto the second random signal generator. The information bit sequence in the second information bit register may differ from the information bit sequence in the first information bit register. The second laser emits a DC optical signal, which is modulated by the random signal generator to form a coherent transmitter. The transmitter emits two mutually orthogonal polarized beams, and the modulated optical signals are transmitted into a channel with reciprocal polarization states, generating polarization crosstalk.

[0018] Furthermore, in the channel transmission module, a first polarization scrambler and a second polarization scrambler are used to artificially and uniformly perturb the polarization states in the channel, making the crosstalk between the two polarization states more severe. The rate of perturbation determines the rate of key production. Therefore, the signal-to-noise ratio (SNR) characteristics of the dynamic reciprocal channel are time-varying. This time-varying SNR characteristic will cause the tap characteristics of the CMMA (Channel Motion Modeling) to also be time-varying when the received signal undergoes digital signal processing. To utilize channel reciprocity, the optical signals generated by the first and second signal transmission modules are transmitted in opposite directions through standard single-mode optical fiber in adjacent or identical time slots.

[0019] Furthermore, in the first signal receiving module, the signal is coherently received by two polarization-splitting parts. On one hand, after digital signal processing such as mode conversion, IQ orthogonality, dispersion compensation, clock recovery, channel equalization, frequency offset and phase compensation, the signal is used for normal secure coherent optical communication. On the other hand, since the two mutually orthogonal polarization states have mutual crosstalk, time-varying tap coefficients are extracted during depolarization to extract the key and complete key distribution.

[0020] Furthermore, in the second signal receiving module, the signal is coherently received by two polarization-splitting parts. On one hand, after digital signal processing such as mode conversion, IQ orthogonality, dispersion compensation, clock recovery, channel equalization, frequency offset and phase compensation, the signal is used for normal secure coherent optical communication. On the other hand, since the two mutually orthogonal polarization states have mutual crosstalk, time-varying tap coefficients are extracted during depolarization to extract the key and complete key distribution.

[0021] This invention also provides a key distribution method for realizing dynamic channel reciprocity and CMMA tap coefficient estimation based on polarization perturbation, comprising the following steps:

[0022] a. The first signal transmission module is used to modulate the information bit sequence, perform orthogonal processing on the polarization state, and achieve coherent transmission of the optical signal.

[0023] b. The second signal transmission module is used to modulate the information bit sequence, perform orthogonal processing on the polarization state, and achieve coherent transmission of the optical signal.

[0024] c. The channel transmission module transmits optical signals with orthogonal polarization states generated by the first signal transmission module and the second signal transmission module, and artificially and rapidly perturbs the optical polarization state in the channel so that the tap coefficients of its CMMA are time-varying.

[0025] d. The first signal receiving module is used to coherently receive and digitally process the signal transmitted through the channel, as well as extract the time-varying tap coefficients that vary with the polarization state and perform secure demodulation.

[0026] e. The second signal receiving module is used to coherently receive and digitally process the signal transmitted through the channel, as well as extract the time-varying tap coefficients that vary with polarization state and perform secure demodulation.

[0027] f. Extract the consistency key based on the time-varying tap coefficients generated by the first signal receiving module and the second signal receiving module.

[0028] This invention also provides a method for implementing unified communication and confidentiality key distribution based on channel reciprocity and tap coefficient estimation, comprising the following steps:

[0029] a. The first signal generation module and the second signal generation module perform coherent modulation on the information bit sequence.

[0030] b. These optical signals are transmitted bidirectionally using an optical fiber transmission module, which includes a polarization scrambler;

[0031] c. At both receiving ends, the polarization state of the signal light is divided into two intersecting parts. One part is the secure communication module, which transmits information bits through coherent demodulation and digital signal processing. The other part is the key distribution module, which extracts consistent time-varying tap coefficients.

[0032] d. Extract the consensus key by using the time-varying tap coefficients of the threshold decision.

[0033] This invention provides a high-speed key generation method based on channel reciprocity, wherein the key generation rate is related to the scrambling speed of the scrambling device.

[0034] This invention provides a method for extracting time-varying depolarization tap coefficients from changes in polarization state and then extracting the key.

[0035] Through the above technical solution, the present invention has the following advantages compared with existing key distribution technologies:

[0036] This invention proposes a key distribution scheme based on dynamic channel reciprocity and depolarization tap coefficient estimation using artificial perturbation. A polarization scrambler is placed at the fiber optic channel to artificially interfere with the polarization state of light in the channel, thereby extracting the consensus key through time-varying tap coefficients. High-speed polarization scramblers enable high-speed key distribution. Channel reciprocity and threshold decision-making for tap coefficients provide security guarantees; even if an unauthorized party eavesdrops on the channel, they will be unable to extract the consensus key due to the difficulty in perceiving channel integrity and the decision threshold. This invention's key distribution system based on channel reciprocity and tap coefficient estimation solves several existing technical problems and achieves improved performance.

[0037] Solve existing technical problems:

[0038] 1. Security issues: Traditional key distribution systems use complex algorithms to ensure their security, but leakage of these algorithms can lead to the complete cracking of the keys.

[0039] 2. Distribution rate problem: Existing deployable key distribution schemes rely on complex structures to improve the key distribution rate.

[0040] 3. System complexity issues: In order to achieve better security and higher distribution rate, existing systems are based on chaotic synchronization, but chaotic synchronization systems are complex and costly.

[0041] Achieve significant performance improvements:

[0042] 1. Enhanced Security: This invention addresses the reciprocity of bidirectional transmission of polarization state changes within the channel, as well as the reciprocity of crosstalk between two orthogonal polarization states. This prevents eavesdroppers from simulating complete channel characteristics and thus from obtaining the key. Furthermore, when extracting the key from time-varying tap coefficients, the eavesdropper's inability to obtain the decision threshold further strengthens the system's security.

[0043] 2. Theoretically higher key distribution rate: This invention uses a polarization scrambler to artificially perturb the polarization state of light in the channel. The rapid change in polarization state causes the tap coefficients of the depolarization algorithm to change rapidly in the key distribution module due to the crosstalk between the two orthogonal polarization states. Theoretically, the polarization speed of the scrambling device determines the key distribution rate.

[0044] 3. Lower system complexity: This invention employs coherent modulation and coherent reception techniques, and the random source is a time-varying tap coefficient, eliminating the need for other devices to generate it, thus resulting in low system complexity. This not only reduces the difficulty of deploying key distribution in existing optical networks but also significantly reduces the cost of key distribution.

[0045] This invention implements a key distribution scheme integrating key distribution and secure optical communication, generating a one-time key. In the optical receiving module, the secure communication channel performs normal coherent reception with a very low bit error rate, and the rate of change over time corresponds to the slowly varying channel characteristics, without affecting the reception of information bits. In the key acquisition channel, due to the polarization scrambler, the output optical power changes with the polarization, and the tap coefficients of the depolarization algorithm change rapidly, making it suitable for extracting random keys. Since the information bit sequence transmitted in each secure communication is different, the extracted consistency key is one-time, meeting the "one-time pad" requirement.

[0046] (1) The expected benefits and commercial value of the technical solution of the present invention after transformation are as follows: After the technical solution of the present invention is transformed, it can be directly applied to the existing coherent optical communication system without adding any other devices. Key distribution can be completed at extremely low cost, which has great commercial potential.

[0047] (2) The technical solution of this invention solves a technical problem that people have long desired to solve but have never been able to achieve: the traditional key distribution scheme based on the reciprocity of optical fiber channels utilizes static reciprocity. In order to obtain dynamic reciprocity, the currently popular method is key distribution based on optical chaotic synchronization, but chaotic sources are generally complex in structure and costly. Therefore, designing a simple dynamic reciprocity key distribution scheme is a problem that needs to be solved. Attached Figure Description

[0048] Figure 1This is a block diagram of a key distribution system integrating communication and encryption based on channel reciprocity and bit error rate estimation, provided in an embodiment of the present invention.

[0049] Figure 2 This is a waveform diagram of the legitimate signals acquired by both parties according to an embodiment of the present invention;

[0050] Figure 3 This is a line graph of the tap coefficients extracted by the legitimate communicating parties according to an embodiment of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be noted that the description of these embodiments is for the purpose of aiding understanding the invention, but does not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.

[0052] like Figure 1 As shown, the unified key distribution system for communication and encryption based on channel reciprocity and bit error rate estimation provided in this embodiment of the invention includes:

[0053] S1, the first signal transmitting module, is used to modulate and transmit the information bit sequence signal, and to divide the polarization direction of the signal light into mutually perpendicular X and Y directions for subsequent mutual perturbation of the two polarization directions. The first signal transmitting module includes a first information bit register 11, a first random signal generator 12, a first laser 13, a first Mach-Zehnder modulator 14, a second Mach-Zehnder modulator 15, and a first polarization beam combiner 16;

[0054] S2, the second signal transmission module, is used to modulate and transmit the information bit sequence signal, and to divide the polarization direction of the signal light into mutually perpendicular X and Y directions for subsequent mutual perturbation of the two polarization directions. The second signal transmission module includes a second information bit register 21, a second random signal generator 22, a second laser 23, a third Mach-Zehnder modulator 24, a fourth Mach-Zehnder modulator 25, and a second polarization beam combiner 26;

[0055] S3, the channel transmission module, is used to transmit the optical signals generated by the first and second signal transmission modules, artificially and uniformly perturb the polarization state of the laser using a polarization scrambler, and finally perform key distribution using the tap characteristics of its time-varying CMMA. The fiber optic transmission module includes a standard single-mode fiber 31, a first polarization scrambler 32, and a second polarization scrambler 33.

[0056] S4, the first signal receiving module, is used for coherent reception and digital signal processing of optical signals transmitted through the channel, as well as extracting the tap features of the CMMA. The first signal receiving module includes a first polarization beam splitter 41, a first photodetector 42, a second photodetector 43, and a first digital signal processing module 44;

[0057] S5, the second signal receiving module, is used for coherent reception and digital signal processing of optical signals transmitted through the channel, as well as extracting the tap features of the CMMA. The second signal receiving module includes a second polarization beam splitter 51, a third photodetector 52, a fourth photodetector 53, and a second digital signal processing module 54;

[0058] The communication and key distribution system based on channel reciprocity and bit error rate estimation described in this embodiment of the invention works on the physical layer reciprocity of the optical fiber channel, the time-varying polarization perturbation characteristics, and the coherent receiving digital signal processing capability. It generates a consistent key by synchronously extracting channel state information during communication, thereby achieving the integration of communication and key distribution.

[0059] During system operation, the first and second signal transmission modules modulate the information bit sequences on both communication sides. Each module introduces a random perturbation factor through a random signal generator, and then uses a Mach-Zehnder modulator to modulate the amplitude and phase of the optical carrier. A polarization combiner decomposes the modulated signal and maps it to mutually orthogonal X and Y polarization directions, thus forming independent and correlated optical signal components in the two polarization dimensions. This provides a foundation for subsequent polarization perturbation and channel characterization.

[0060] The modulated optical signal enters the channel transmission module and is transmitted to the other end via standard single-mode fiber. During transmission, artificial, synchronous, and time-varying uniform perturbations are applied to the polarization state of the optical signal by a first and second polarization scrambler, causing the optical signal to exhibit random but highly correlated changes in both the polarization and time domains within the same time slot. Simultaneously, the random perturbations and dispersion effects of the fiber channel itself cause the channel tap coefficients to change dynamically over time, forming statistically consistent but instantaneously unpredictable channel state information. The first and second signal receiving modules perform coherent reception processing on the received optical signals. At the receiving end, the optical signal is separated according to polarization direction by a polarization beamsplitter, and after photoelectric conversion by a photodetector, it enters the digital signal processing module. The received signal undergoes carrier recovery, channel equalization, and bit error rate estimation, and the CMMA tap characteristic parameters of the channel are extracted. Because the channel satisfies reciprocity within a short timescale, the tap characteristics extracted by both communicating parties at the same time are statistically highly consistent, and can therefore be quantized and mapped to local key sequences.

[0061] Subsequently, the two communicating parties perform quantization, error correction, and consistency correction based on the extracted tap features and bit error rate information to generate a highly consistent key. This key is used to encrypt the current communication data or update encryption parameters, achieving synchronous key distribution and information transmission. Because the key originates from the physical characteristics of the channel and the time-varying perturbation process, it is difficult for external eavesdroppers to simultaneously obtain the same channel state information, thus ensuring the security and unpredictability of the key.

[0062] Therefore, by combining polarization perturbation and channel reciprocity, this invention achieves deep integration of communication and key generation without introducing an additional key distribution channel, thereby improving the system's security, real-time performance, and engineering feasibility.

[0063] Furthermore, in the first signal generation module S1, the information bit sequence in the first information bit register 11 is stored in a buffer to form a signal frame, which is then loaded onto the first random signal generator 12. The first laser 13 emits a DC optical signal, which is modulated by the random signal generator to form a coherent transmitter. The transmitter emits two beams of mutually orthogonal polarized light, and the modulated optical signal is transmitted into a channel with reciprocal polarization states, generating polarization crosstalk.

[0064] Furthermore, in the second signal generation module S2, the information bit sequence in the second information bit register 21 is stored in a buffer to form a signal frame, which is then loaded onto the second random signal generator 22. The information bit sequence in the second information bit register may differ from the information bit sequence in the first information bit register 11. The second laser 23 emits a DC optical signal, which is modulated by the random signal generator to form a coherent transmitter. The transmitter emits two mutually orthogonal polarized beams, and the modulated optical signals are transmitted into a channel with reciprocal polarization states, generating polarization crosstalk.

[0065] Furthermore, in the channel transmission module S3, the first polarization scrambler 32 and the second polarization scrambler 33 are used to artificially and uniformly perturb the polarization states in the channel, making the crosstalk between the two polarization states more severe. The rate of perturbation determines the rate of key production. Therefore, the signal-to-noise ratio (SNR) characteristics of the dynamic reciprocal channel are time-varying. The time-varying SNR characteristics will cause the tap characteristics of the CMMA (Channel Motion Model) to also be time-varying when the received signal is processed digitally. To utilize the channel reciprocity, the optical signals generated by the first signal transmission module and the second signal transmission module are transmitted in opposite directions through the standard single-mode fiber 31 in adjacent or identical time slots.

[0066] Furthermore, in the first signal receiving module S4, the signal is coherently received by two polarization-splitting parts. On one hand, after digital signal processing such as mode conversion, IQ orthogonality, dispersion compensation, clock recovery, channel equalization, frequency offset and phase compensation, the signal is used for normal secure coherent optical communication. On the other hand, since the two mutually orthogonal polarization states have mutual crosstalk, time-varying tap coefficients are extracted during depolarization to extract the key and complete key distribution.

[0067] Furthermore, in the second signal receiving module S5, the signal is coherently received by two polarization-splitting parts. On one hand, after digital signal processing such as mode conversion, IQ orthogonality, dispersion compensation, clock recovery, channel equalization, frequency offset and phase compensation, the signal is used for normal secure coherent optical communication. On the other hand, since the two mutually orthogonal polarization states have mutual crosstalk, time-varying tap coefficients are extracted during depolarization to extract the key and complete key distribution.

[0068] The secure key distribution device provided in this embodiment of the invention has a first signal receiving module S4 and a second signal receiving module S5. The first digital signal processing module 44 and the second digital signal processing module 54 respectively perform coherent reception, and subsequently estimate the tap coefficients of their depolarization algorithm. This allows two legitimate parties to obtain consistent normalized signal changes. The correlation diagram of the digital key stream signals generated by the first digital signal processing module 44 and the second digital signal processing module 54 is shown below. Figure 2 As shown, the correlation coefficient between the two is 0.995, which is close to the theoretical maximum value of 1. This indicates that the analog key stream signals received by the two legitimate parties have good consistency, providing a foundation for high-quality secure key distribution.

[0069] In the secure optical communication device provided in this embodiment of the invention, the first digital signal processing module 44 and the second digital signal processing module 54 respectively perform coherent reception in the first signal receiving module S4 and the second signal receiving module S5 to complete secure coherent optical communication.

[0070] To verify the effectiveness of the secure key distribution device provided in this embodiment of the invention, relevant experiments were conducted. The experimental results show that, in the first signal receiving module S4 and the second signal receiving module S5, the tap coefficient line graphs generated by the first digital signal processing module 44 and the second digital signal processing module 54 during coherent reception are as follows: Figure 3 As shown, two legitimate parties can obtain consistent normalized signal changes.

[0071] Based on the above technical solutions, the embodiments of the present invention provide illustrative descriptions of a unified key distribution system from multiple levels, including system architecture, signal processing flow, and key extraction mechanism. Those skilled in the art should understand that the following embodiments are only used to illustrate the technical concept of the present invention and do not constitute a limitation on the scope of protection.

[0072] In one exemplary embodiment, the system includes a coherent optical transmitter and a coherent optical receiver arranged opposite each other, connected by a polarization-reciprocal optical fiber channel. The coherent optical transmitter can be implemented in different configurations, such as a transmitter structure based on an integrated photonic chip, a transmitter structure composed of discrete optical devices, or a transmitter structure based on a programmable optical modulation module. All of these different configurations can functionally achieve coherent emission of orthogonally polarized light.

[0073] Preferably, the transmitting end can use a DC continuous laser source, the center wavelength of which can be selected as C-band or L-band, such as 1530nm, 1550nm, or 1565nm; the modulation rate can be in the range of 10Gb / s, 25Gb / s, or 50Gb / s to cover different system bandwidth requirements. Information bits can be buffered in a frame structure before transmission, with a frame length selectable as 2^10, 2^12, or 2^14 bits to improve the system's adaptability to time-varying channels.

[0074] During channel transmission, the polarization reciprocal optical channel can include standard single-mode optical fiber, with fiber lengths ranging from hundreds of meters to tens of kilometers. To enhance the physical randomness of the channel, a polarization scrambling device is preferably installed in the optical fiber link. The polarization scrambling device can be a mechanical rotation type, an electro-optic type, or a stress modulation-based polarization scrambling structure, and its scrambling rate can be in the low-speed, medium-speed, or high-speed range, such as 1Hz, 10Hz, or 100Hz, to correspond to different key generation rate requirements.

[0075] In an exemplary embodiment at the receiving end, the coherent optical signal enters the coherent receiving link after polarization separation. The receiving structure can employ either a dual-polarization coherent receiving module or an equivalent multi-channel photodetector structure. Subsequently, the digital signal processing module performs processing steps on the received signal, including but not limited to mode conversion, IQ quadrature correction, dispersion compensation, timing recovery, frequency offset compensation, and phase recovery.

[0076] Furthermore, during the depolarization process, the channel equalization algorithm adaptively estimates the crosstalk relationship between orthogonal polarizations to obtain time-varying equalization tap parameters. The equalization algorithm can employ a multi-tap structure, with the number of taps selectable as 3, 5, or 7 to adapt to different channel conditions. The tap parameters can be further normalized, filtered, or quantized to form a simulated feature sequence for key generation.

[0077] Preferably, the two communicating parties extract the tap features within adjacent or identical time windows. Due to the channel polarization reciprocity, the feature sequences obtained by both parties are highly correlated. This feature sequence can be used in parallel for key negotiation without affecting the original information communication demodulation, thereby achieving coordinated operation of communication and key distribution.

[0078] The embodiments of the present invention can be implemented through hardware, software, or a combination of both, and are particularly suitable for signal processing and transmission modules in coherent optical communication systems. The hardware portion can be implemented using application-specific integrated circuits (ASICs) or optical devices; the software portion can be stored in memory and executed by a suitable signal processing system, such as a microprocessor or dedicated hardware, by controlling the modulation, demodulation, and other processes of the coherent optical signal.

[0079] Those skilled in the art will understand that the devices and methods mentioned above can be implemented by computer-executable instructions and / or processor control code, especially in coherent optical communication systems. This code can be stored on a carrier medium such as a disk, CD or DVD-ROM, or in the form of a read-only memory (such as firmware), or in a data carrier of an optical or electronic signal carrier.

[0080] The device and its modules of this invention can be implemented using optical integrated circuits, semiconductor materials (such as photodiodes, optical modulators, etc.), and dedicated hardware (such as coherent optical demodulators, optical filters, fiber optic modules, etc.). Alternatively, digital signal processors (DSPs) or dedicated hardware devices based on FPGAs or ASICs can be used to process signals in coherent optical communication. Furthermore, the combination of the hardware circuitry and software (such as firmware) can also realize operations such as the transmission and decoding of coherent optical signals, thereby improving the system's performance and flexibility.

[0081] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A unified optical communication key distribution system based on channel reciprocity, characterized in that, include: At least one pair of coherent optical transmitting units for counter-communication, used to transmit coherent optical signals containing information bits to the same polarization reciprocal optical channel in the same or adjacent time slots; The polarization reciprocal optical channel is used to introduce time-varying polarization crosstalk characteristics during signal transmission. At least one pair of coherent optical receiving and processing units respectively perform depolarization processing on the coherent optical signal transmitted through the polarization reciprocal optical channel; The coherent optical receiving and processing unit, while completing information communication demodulation, generates a consistent key feature sequence based on the time-varying channel equalization tap coefficients obtained during the depolarization process, and uses the key feature sequence to realize the synchronous completion of key distribution and secure optical communication.

2. The system as described in claim 1, characterized in that, The coherent optical transmitting unit is configured to decompose the emitted coherent optical signal into at least two mutually orthogonal polarization states, so as to form polarization crosstalk characteristics in the polarization reciprocal optical channel that can be identified by depolarization processing, thereby supporting the acquisition of the channel equalization tap coefficients.

3. The system as described in claim 1, characterized in that, The polarization reciprocal optical channel includes an optical fiber transmission medium and at least one polarization scrambling unit. The polarization scrambling unit is used to make the polarization crosstalk characteristics change over time, so as to enhance the distinguishability of the channel equalization tap coefficients in the time dimension.

4. The system as described in claim 3, characterized in that, The perturbation rate of the scrambling unit is matched with the update rate of the key feature sequence to support the stable operation of the continuous key generation process.

5. A method for integrated communication and confidentiality key distribution based on a polarization reciprocal optical channel, characterized in that, include: Within the same or adjacent time slots, at least two coherent optical signals are directed to pass through the same polarization reciprocal optical channel. This causes the polarization reciprocal optical channel to exhibit time-varying polarization crosstalk characteristics during transmission; While performing depolarization processing at the receiver, the channel equalization tap coefficients that vary over time are estimated. Extract the key feature sequence based on the channel equalization tap coefficients; To achieve synchronous execution of key distribution and information communication without affecting information communication demodulation.

6. The method as described in claim 5, characterized in that, The channel equalization tap coefficients are adaptively updated during the depolarization processing and participate in the generation of the key feature sequence as channel features characterizing the instantaneous state of the polarization reciprocal optical channel.

7. The method as described in claim 5, characterized in that, Both communicating parties generate corresponding key feature sequences based on the channel equalization tap coefficients obtained in the same or adjacent time slots, so as to improve the consistency of the key feature sequences between the two communicating parties.

8. A coherent receiving and key extraction device for a unified optical communication system, characterized in that, include: The depolarization processing unit is used to demultiplex coherent optical signals containing orthogonal polarization crosstalk; The equalization parameter estimation unit is used to obtain the time-varying channel equalization tap coefficients during the depolarization process; A key generation unit is used to generate a key feature sequence based on the channel equalization tap coefficients; The device is configured to output the key feature sequence for key distribution in parallel while performing coherent optical communication demodulation.

9. The apparatus as claimed in claim 8, characterized in that, The device includes a digital signal processing module, which synchronously outputs intermediate signal results for depolarization processing during the information communication demodulation process, so as to realize the coordinated execution of communication demodulation and channel equalization tap coefficient extraction.

10. The apparatus as claimed in claim 8, characterized in that, The key generation unit includes a module for normalizing and quantizing the channel equalization tap coefficients to convert the channel equalization tap coefficients into a digital key stream for key distribution.

Images