A photon terahertz communication system based on non-uniform probability shaping

Abstract

This invention discloses a photonic terahertz communication system based on non-uniform probabilistic shaping, belonging to the field of terahertz communication. Specifically, it includes a transmitter and a receiver. The transmitter incorporates non-uniform probabilistic shaping and phase fuzzy encryption techniques, using photonic beat frequency generation to produce a terahertz signal. This signal is then transmitted wirelessly via single-mode fiber to the receiver, where it is mixed with a frequency-multiplied local oscillator signal to achieve down-conversion of the terahertz signal, obtaining an intermediate frequency (IF) signal. The IF signal is then sampled and input to an RX-DSP module for digital signal processing, ultimately obtaining the original data and calculating the bit error rate (BER). This invention improves the system's BER performance and significantly enhances the security of the photonic terahertz communication system.

Description

Technical Field

[0001] This invention relates to a photonic terahertz communication system based on non-uniform probability shaping, belonging to the field of terahertz communication. Background Technology

[0002] Applications of the sixth-generation (6G) wireless access network include ubiquitous virtual reality / augmented reality (VR / AR), artificial intelligence, and 4K / 8K high-definition video, which will bring explosive data traffic and place higher demands on data rates.

[0003] Therefore, researchers are working to find ways to achieve mobile data transmission at the highest possible data rates. The terahertz band (0.1-10 THz) is a promising candidate for 6G due to its vast bandwidth, which can support even higher data rates.

[0004] However, communication in the millimeter-wide / terahertz band faces limitations in wireless range and data rate, primarily due to the challenges posed by the outdoor environment, including atmospheric penetration loss and moisture absorption. Improving the bit error rate performance of terahertz communication links under conditions of high loss and low signal-to-noise ratio remains a major challenge.

[0005] In optical and wireless communications, probabilistic shaping techniques, by increasing the frequency of lower-energy constellation points, bring the signal amplitude distribution closer to the theoretically optimal Gaussian distribution, significantly improving spectral efficiency and bringing system performance closer to the Shannon limit. Simultaneously, it reduces the peak-to-average power ratio of the signal, helping to mitigate nonlinear effects in fiber optic communication and enabling longer-distance transmission. Therefore, probabilistic shaping techniques can be applied to photonic terahertz communication systems to reduce the impact of atmospheric loss and moisture absorption, thereby improving the bit error rate performance at the receiver.

[0006] However, while current probabilistic shaping schemes based on distributed matchers offer near-optimal performance close to the Shannon limit, their high system complexity, signal-to-noise ratio sensitivity, and high hardware resource consumption limit their application in photonic terahertz communication systems. Therefore, there is a need to develop a probabilistic shaping scheme with low algorithmic complexity and insensitivity to signal-to-noise ratio.

[0007] Furthermore, the short wavelength and strong directionality of terahertz signals also present unique security challenges. Their high spatial resolution and narrow beam propagation characteristics mean that even during directional transmission, signals can be precisely intercepted by malicious devices through sidelobes or environmental reflections, significantly increasing the risk of covert eavesdropping and data breaches.

[0008] Digital chaotic encryption is widely used in physical layer secure communication due to its nonlinearity, randomness, complex key sequences, and unpredictability. Summary of the Invention

[0009] To address the limitations of current probabilistic shaping schemes based on distributed matchers in low signal-to-noise ratio (SNR) applications of photonic terahertz communication, and the data security issues arising from the potential interception of terahertz signals by unauthorized devices during directional transmission, this invention proposes a photonic terahertz communication system based on non-uniform probabilistic shaping. By utilizing the non-uniform distribution characteristics of the mapped symbols after segmentation at the transmitting end for probabilistic shaping, the system's bit error rate performance is improved. Simultaneously, the Nose-Hoover improved chaotic system is used to perform XOR encryption and phase fuzzy encryption on the transmitted signal, significantly enhancing the security of the photonic terahertz communication system.

[0010] The aforementioned photonic terahertz communication system includes a transmitter and a receiver. The transmitter incorporates non-uniform probability shaping and phase fuzzy encryption techniques, and uses photonic beat frequency generation to generate terahertz signals, which are then transmitted wirelessly via single-mode fiber. The receiver uses digital signal processing to receive the signals.

[0011] The transmitter includes: a TX-DSP module, an I / Q modulator, two external cavity lasers ECL1 and ECL2, a 10km single-mode fiber, an erbium-doped fiber amplifier, a 1:1 optical coupler, a tunable optical attenuator, a single-line carrier photodetector, and a terahertz antenna.

[0012] The I / Q modulator is connected to both the TX-DSP module and the external cavity laser ECL1. The output of the external cavity laser ECL1 serves as the optical carrier. The TX-DSP module uses non-uniform probabilistic shaping and a Nose-Hoover improved chaotic system to generate a encrypted and shaped baseband RF signal, which drives the I / Q modulator to modulate the input optical carrier and output the optical signal for transmission in a single-mode fiber. The transmitted optical signal is amplified by an erbium-doped fiber amplifier and then coupled to the output of the external cavity laser ECL2 via an optical coupler. The coupled signal is then fed to a single-row carrier photodetector for beat frequency adjustment after the power is adjusted by an adjustable optical attenuator. The resulting terahertz signal is then transmitted into free space via a terahertz antenna.

[0013] The receiver includes: a terahertz antenna, a frequency multiplier, a mixer, a local oscillator, and an RX-DSP module;

[0014] The terahertz signal in free space is received by the terahertz antenna at the receiving end, and then input into a mixer to mix with the local oscillator signal that has been multiplied by a frequency multiplier. This down-conversion of the terahertz signal yields an intermediate frequency (IF) signal. The IF signal is then sampled and input into the RX-DSP module for digital signal processing, ultimately yielding the original data from which the bit error rate is calculated.

[0015] The working principle of the photonic terahertz communication system is as follows:

[0016] Step 1: Define the initial key in the TX-DSP module By using a three-dimensional chaotic system based on the Nose-Hoover model, a set of chaotic sequences is obtained by solving the three-dimensional Nose-Hoover chaotic equations. ;

[0017] Step 2: Process the chaotic sequence Data processing is performed to obtain binary data. and sequence;

[0018] Among them, for , Sequence The operation yields values ​​from 0 and 1. ;

[0019] for Sequence The operation yields values ​​from 0, 1, and 2. .

[0020] This represents the modulo operation. Indicate extraction The integer obtained from the m-th decimal place.

[0021] Step 3: Use a pseudo-random binary code generator to generate a binary sequence PRBS and a binary... The sequence is XORed to achieve the first level of bit-level chaotic encryption; then, the encrypted PRBS is QAM mapped to generate a digital baseband signal. .

[0022] Step 4: Using binary and Sequence generates constellation conjugate rotation vectors and For digital baseband signals Perform phase fuzzy encryption to obtain the phase fuzzy encrypted signal. .

[0023] The specific encryption method for phase fuzzing encryption is as follows:

[0024] ;

[0025] ;

[0026] ;

[0027] in It is a symbolic function.

[0028] Step 5: Encrypt the phase-blurred signal Divide the blocks into blocks according to the specified length, and count the number of QAM symbols in each block.

[0029] The block division formula is: ; Signal after phase fuzzing encryption Length; The length of the block; To transmit the signal The total number of blocks into which the length is divided.

[0030] Step 6: Perform probabilistic shaping encoding based on the number of QAM symbols in each block to obtain the shaped signal. .

[0031] The specific method is as follows:

[0032] First, set the target 16QAM constellation shaping matrix ( , , , , , , , , , , , , , , , );

[0033] in , , , Corresponding to the four constellation points in the inner ring of the 16QAM symbol; , , , , , , , Corresponding to the 8 constellation points in the middle ring of the 16QAM symbol; , , , These correspond to the four constellation points in the outer ring of the 16QAM symbol.

[0034] Then, based on the number of QAM symbols in each block, they are sorted in descending order, and so on. Constellation Points Exchange , , , , , , , , , , , , , , , This means implementing the probability shaping process;

[0035] Finally, the information after the exchange is completed is recorded, which is the shaping signal. .

[0036] Step 7: Shaping the signal After upsampling and root-raised-cosine filtering, the real and imaginary parts of the baseband signal are separated and fed into the in-phase I and quadrature-phase Q inputs of the same dual-channel digital-to-analog converter, respectively, to generate the drive signals for the I / Q modulator. .

[0037] Step 8: Use the external cavity laser ECL1 to generate a center frequency of A continuous optical carrier is input to an I / Q modulator; the drive signal The in-phase and quadrature components driving the I / Q modulator are such that the center frequency of the I / Q modulator output is... The carrier signal.

[0038] Step Nine: The center frequency is The continuous optical carrier, after transmission through single-mode fiber and amplification by an erbium-doped fiber amplifier, is coupled with the output center frequency of the external cavity laser ECL2. The optical signal is coupled 1:1 and sent to a single-row carrier photodetector for beat frequency generation, producing a frequency of... Terahertz signals are transmitted to the receiving end.

[0039] Step 10: The receiver inputs the terahertz signal into the mixer, mixes it with the local oscillator signal that has been multiplied by the frequency multiplier, realizes the down-conversion of the terahertz signal, obtains the intermediate frequency signal, inputs it into the RX-DSP module for digital signal processing, and finally obtains the original data and calculates the bit error rate.

[0040] Specific digital signal processing includes digital downconversion, power normalization, optimal downsampling, radius decision equalization algorithm, FFT frequency offset estimation, blind phase search, deprobabilistic integer coding, phase ambiguity decryption, demapping, XOR decryption, bit error rate calculation, etc.

[0041] The advantages of this invention are:

[0042] 1. The photonic terahertz communication system based on non-uniform probability shaping proposed in this invention has lower algorithm complexity and improves the feasibility of the algorithm compared with the traditional probability shaping system based on distributed matchers.

[0043] 2. The photonic terahertz communication system based on non-uniform probabilistic shaping proposed in this invention can still achieve probabilistic shaping decoding under low signal-to-noise ratio conditions, and has better robustness than the common CCDM probabilistic shaping scheme.

[0044] 3. The photonic terahertz communication system based on non-uniform probabilistic shaping proposed in this invention combines chaotic encryption with probabilistic shaping methods, which improves system security while reducing the bit error rate. Attached Figure Description

[0045] Figure 1 This is a structural diagram of the photonic terahertz communication system based on non-uniform probability shaping according to the present invention;

[0046] Figure 2 This is a flowchart of the workflow of the photonic terahertz secure communication system based on non-uniform probability shaping of the present invention;

[0047] Figure 3 This is an optional phase diagram of the Nose-Hoover improved chaotic system according to an embodiment of the present invention;

[0048] Figure 4 This is a schematic diagram of an optional phase fuzzy encryption embodiment of the present invention;

[0049] Figure 5 This is a schematic diagram of an optional non-uniform probability shaping according to an embodiment of the present invention;

[0050] Figure 6 This is a schematic diagram of probability shaping under optional different block lengths according to an embodiment of the present invention; Detailed Implementation

[0051] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0052] This invention proposes a photonic terahertz communication system based on non-uniform probability shaping. Non-uniform probability shaping technology is introduced at the transmitting end to reduce the system's bit error rate. At the same time, the Nose-Hoover improved chaotic system is used to perform digital chaotic encryption on the transmitting end signal, thereby improving the security of the photonic terahertz communication system.

[0053] like Figure 1 As shown, the photonic terahertz communication system includes a transmitter and a receiver. The transmitter introduces non-uniform probability shaping and phase fuzzy encryption technology, and uses photonic beat frequency method to generate terahertz signals. Then, it is transmitted through 10km single-mode optical fiber and 5m wireless transmission. The receiver uses digital signal processing to receive the signals.

[0054] The transmitter includes: a TX-DSP module, an I / Q modulator, two external cavity lasers ECL1 and ECL2, a 10km single-mode fiber, an erbium-doped fiber amplifier, a 1:1 optical coupler, a tunable optical attenuator, a single-line carrier photodetector, and a terahertz antenna.

[0055] Two external cavity lasers, ECL1 and ECL2: the output of ECL1 serves as the input optical carrier of the I / Q modulator; the output of ECL2 serves as another optical signal required for optical heterodyne beat frequency.

[0056] TX-DSP module: It uses non-uniform probability shaping and Nose-Hoover improved chaotic system to generate encrypted and shaped 16QAM baseband signal, which is used to drive I / Q modulator to modulate optical carrier.

[0057] I / Q modulator: Loads the modulated signal onto the optical carrier.

[0058] 10km single-mode optical fiber: used to transmit modulated optical signals.

[0059] Erbium-doped fiber amplifier: amplifies optical signals transmitted through single-mode fiber.

[0060] Optical coupler: Couples the output signal of the I / Q modulator and the output signal of ECL2 into a single signal.

[0061] Adjustable optical attenuator: Adjusts the optical power entering the single-row carrier photodetector.

[0062] Single-carrier photodetector: The coupled signal is subjected to optical heterodyne beat frequency to obtain a terahertz signal.

[0063] Terahertz antenna: amplifies and transmits terahertz signals into free space.

[0064] An external cavity laser (ECL1) is connected to an I / Q modulator, whose output optical carrier is input to the I / Q modulator. The I / Q modulator is also connected to a TX-DSP module. The TX-DSP module uses non-uniform probabilistic shaping and a Nose-Hoover improved chaotic system to generate a encrypted and shaped 16QAM baseband RF signal, which drives the I / Q modulator to modulate the input optical carrier. The optical signal output from the I / Q modulator is then transmitted through a 10km single-mode fiber. The transmitted optical signal is amplified by an erbium-doped fiber amplifier. The amplified optical signal and the output of the external cavity laser (ECL2) are coupled through an optical coupler. The coupled signal is then adjusted in power by an adjustable optical attenuator and input to a single-row carrier photodetector for beat frequency generation. The resulting terahertz signal is then transmitted into free space through a terahertz antenna.

[0065] The receiver includes: a terahertz antenna, a frequency multiplier, a mixer, a local oscillator, and an RX-DSP module;

[0066] Terahertz antenna: receives terahertz signals.

[0067] Local oscillator: used as input to the frequency multiplier.

[0068] Frequency multiplier: multiplies the frequency of the local oscillator signal.

[0069] Mixer: Mixes the received signal with the frequency multiplier signal to obtain the down-converted intermediate frequency signal.

[0070] RX-DSP module: Digital signal processing at the receiver.

[0071] Terahertz signals in free space are wirelessly transmitted over a 5m radius and received by a terahertz antenna at the receiving end. The received terahertz signal is then input into a mixer and mixed with a local oscillator signal that has been multiplied by a frequency multiplier to achieve down-conversion of the terahertz signal and obtain an intermediate frequency (IF) signal. The IF signal is sampled and then input into the RX-DSP module for digital signal processing. This includes digital down-conversion, power normalization, optimal downsampling, radius decision equalization algorithm, FFT frequency offset estimation, blind phase search, deprobabilistic shaping coding, phase ambiguity decryption, demapping, XOR decryption, and other digital signal processing operations. Finally, the original data is obtained, and the bit error rate is calculated.

[0072] like Figure 2 As shown, the working principle of the photonic terahertz communication system is as follows:

[0073] Step 1: Define the initial key in the TX-DSP module By using a three-dimensional chaotic system based on the Nose-Hoover model, a set of chaotic sequences is obtained by solving the three-dimensional Nose-Hoover chaotic equations. ;

[0074] This chaotic system can be described by a set of ordinary differential equations:

[0075]

[0076] in , , There are three state variables. It is the time step. It is a constant system parameter.

[0077] Step 2: Process the chaotic sequence Data processing is performed to obtain binary data. and sequence;

[0078] Among them, for , Sequence The operation yields values ​​from 0 and 1. ;

[0079] for Sequence The operation yields values ​​from 0, 1, and 2. .

[0080] This represents the modulo operation. Indicate extraction The integer obtained from the m-th decimal place.

[0081] Step 3: Use a pseudo-random binary code generator to generate a binary sequence PRBS and a binary... The sequence is XORed to achieve the first level of bit-level chaotic encryption; then, the encrypted PRBS is mapped using 16QAM to generate a digital baseband signal. .

[0082] Step 4: Using binary and Sequence generates constellation conjugate rotation vectors and For digital baseband signals Perform phase fuzzy encryption to obtain the phase fuzzy encrypted signal. .

[0083] The specific encryption method for phase fuzzing encryption is as follows:

[0084] ;

[0085] ;

[0086] ;

[0087] in It is a symbolic function.

[0088] Step 5: Encrypt the phase-blurred signal Divide the blocks into blocks according to the specified length, and count the number of QAM symbols in each block.

[0089] The block division formula is: ; Signal after phase fuzzing encryption Length; The length of the block; To transmit the signal The total number of blocks into which the length is divided.

[0090] Step 6: Perform probabilistic shaping encoding based on the number of QAM symbols in each block to obtain the shaped signal. .

[0091] The specific method is as follows:

[0092] First, set a target 16QAM constellation integer matrix ( , , , , , , , , , , , , , , , );

[0093] in , , , Corresponding to the four constellation points in the inner ring of the 16QAM symbol; , , , , , , , Corresponding to the 8 constellation points in the middle ring of the 16QAM symbol; , , , These correspond to the four constellation points in the outer ring of the 16QAM symbol.

[0094] Then, based on the number of QAM symbols in each block, they are sorted in descending order, and so on. Constellation Points Exchange , , , , , , , , , , , , , , , This means implementing the probability shaping process;

[0095] Finally, the information after the exchange is completed is recorded, which is the shaping signal. .

[0096] Step 7: Analyze the encrypted and shaped digital baseband signal. After upsampling and root-raised-cosine filtering, the real and imaginary parts of the baseband signal are separated and fed into the in-phase I and quadrature-phase Q inputs of the same dual-channel digital-to-analog converter, respectively, to generate the drive signals for the I / Q modulator. .

[0097] Step 8: Use the external cavity laser ECL1 to generate a center frequency of A continuous optical carrier is input to an I / Q modulator. The signal... The in-phase and quadrature components driving the I / Q modulator are such that the center frequency of the I / Q modulator output is... The carrier signal.

[0098] Step 9, center frequency is The continuous optical carrier, after transmission through single-mode fiber and amplification by an erbium-doped fiber amplifier, is coupled with the output center frequency of the external cavity laser ECL2. The optical signal is coupled 1:1 and sent to a single-row carrier photodetector for beat frequency generation, producing a frequency of... Terahertz signals are transmitted to the receiving end.

[0099] Step 10: The receiver inputs the terahertz signal into the mixer, mixes it with the local oscillator signal that has been multiplied by the frequency multiplier, realizes the down-conversion of the terahertz signal, obtains the intermediate frequency signal, inputs it into the RX-DSP module for digital signal processing, and finally obtains the original data and calculates the bit error rate.

[0100] The specific implementation method is as follows:

[0101] Step 1: In the TX-DSP module, first set the initial key. Time step System parameters By using a three-dimensional chaotic system based on the Nose-Hoover model, a set of chaotic sequences was obtained by solving the chaotic equations. .

[0102] The phase diagram of a three-dimensional chaotic system in the Nose-Hoover model is shown below. Figure 3 As shown.

[0103] Step 2: Process the chaotic sequence , , Data processing is performed to obtain binary data. and sequence;

[0104] Indicate extraction The integer obtained from the m-th decimal place, where m=15 in this example.

[0105] Step 3: Use a pseudo-random binary code generator to generate a binary sequence PRBS and a binary... The sequence is XORed to achieve the first level of bit-level chaotic encryption. Then, the encrypted PRBS is mapped using 16QAM to generate a digital baseband signal. .

[0106] Step 4: Utilize and Sequence generates constellation conjugate rotation vectors and For digital baseband signals Phase fuzzing encryption is performed, and the signal after phase fuzzing encryption is represented as follows: .

[0107] Taking the constellation point at coordinates (1, 3) as an example, the encryption process is illustrated as follows: Figure 4 As shown in (ac).

[0108] Step 5: Encrypt the phase-blurred signal Divide the block into blocks according to its length, and count the number of QAM symbols in each block.

[0109] The process of performing non-uniform probability shaping is as follows: Figure 5 As shown, assume the signal after phase ambiguity encryption The length is L = 16384 (L is an integer multiple of M), for If the symbol sequence is divided into blocks of length 32, then it will be divided into 32 blocks. piece.

[0110] Step 6: Count the number of QAM symbols in each block and perform probabilistic integer encoding.

[0111] The specific method is as follows:

[0112] First, define a target 16QAM constellation integer matrix (-1+1i, 1+1i, 1-1i, -1-1i, -3+1i, -1+3i, 1+3i, 3+1i, 3-1i, 1-3i, -1-3i, -3-1i, -3+3i, 3+3i, 3-3i, -3-3i), where -1+1i, 1+1i, 1-1i, and -1-1i correspond to the four constellation points in the inner ring of the 16QAM symbol; -3+1i, -1+3i, 1+3i, 3+1i, 3-1i, 1-3i, -1-3i, and -3-1i correspond to the eight constellation points in the middle ring of the 16QAM symbol; and -3+3i, 3+3i, 3-3i, and -3-3i correspond to the four constellation points in the outer ring of the 16QAM symbol. like Figure 5 As shown in (c).

[0113] Then, based on the number of QAM symbols in each block, they are sorted in descending order, and so on. The constellation points are swapped to -1+1i, 1+1i, 1-1i, -1-1i, -3+1i, -1+3i, 1+3i, 3+1i, 3-1i, 1-3i, -1-3i, -3-1i, -3+3i, 3+3i, 3-3i, -3-3i, and the swap information is recorded after the swap is completed. This performs a probability shaping process to obtain the signal. ,like Figure 5 As shown in (a)-(e);

[0114] Figure 6 This demonstrates the non-uniform probability shaping effect under different block lengths.

[0115] Step 7: Probabilistically shaped digital baseband signal After being upsampled by 4 times and passed through a root-raised cosine filter with a roll-off factor of 0.01, the real and imaginary parts of the baseband signal are separated and fed into the in-phase I and quadrature-phase Q inputs of the same dual-channel digital-to-analog converter, respectively, to generate the drive signals for the I / Q modulator. .

[0116] Step 8: Generate a continuous optical carrier with a center frequency of 193.765 THz using the external cavity laser ECL1, and input it into the I / Q modulator. Simultaneously, the signal... The in-phase and quadrature components driving the I / Q modulator produce a carrier signal with a center frequency of 193.765 THz. This signal is transmitted through a 10 km single-mode fiber, amplified by an erbium-doped fiber amplifier, and then coupled to an optical signal with a center frequency of 193.415 THz output from the external cavity laser ECL2 via a 1:1 optical coupler. The coupled signal is then sent to a single-row carrier photodetector for beat frequency generation, producing a 320 GHz terahertz signal. This terahertz signal is amplified by a terahertz antenna and emitted into free space.

[0117] Step Nine: The terahertz signal, after 5m wireless transmission, is received by the terahertz antenna at the receiving end and input into a mixer. It is then mixed with the local oscillator signal, which has been multiplied by a frequency multiplier, to achieve down-conversion of the terahertz signal and obtain an intermediate frequency (IF) signal. The IF signal is then input into the RX-DSP module for digital down-conversion, power normalization, optimal 4x downsampling, radius decision equalization algorithm, FFT frequency offset estimation, blind phase search, deprobabilistic shaping coding, phase ambiguity decryption, demapping, XOR decryption, and other operations to finally obtain the original data and calculate the bit error rate.

Claims

1. A photonic terahertz communication system based on non-uniform probability shaping, comprising a transmitter and a receiver, characterized in that, The transmitting end introduces non-uniform probability shaping and phase fuzzy encryption technology, uses photonic beat frequency method to generate terahertz signal, and then transmits it to the receiving end via single-mode fiber and wireless transmission. The receiving end uses digital signal processing to receive the signal, obtain the raw data, and calculate the bit error rate. The working principle of the photonic terahertz communication system is as follows: Step 1: Define the initial key in the TX-DSP module at the transmitting end. By using a three-dimensional chaotic system based on the Nose-Hoover model, a set of chaotic sequences is obtained by solving the three-dimensional Nose-Hoover chaotic equations. ; Step 2: Process the chaotic sequence Data processing is performed to obtain binary data. and sequence; Step 3: Use a pseudo-random binary code generator to generate a binary sequence PRBS and a binary... The sequence is XORed to achieve the first level of bit-level chaotic encryption; then, the encrypted PRBS is QAM mapped to generate a digital baseband signal. ; Step 4: Using binary and Sequence generates constellation conjugate rotation vectors and For digital baseband signals Perform phase fuzzy encryption to obtain the phase fuzzy encrypted signal. ; The specific encryption method for phase fuzzing encryption is as follows: ； ； ； in It is a symbolic function; Step 5: Encrypt the phase-blurred signal Divide the block into blocks according to the specified length, and count the number of QAM symbols in each block. Step 6: Perform probabilistic shaping encoding based on the number of QAM symbols in each block to obtain the shaped signal. ; Step 7: Shaping the signal After upsampling and root-raised-cosine filtering, the real and imaginary parts of the baseband signal are separated and fed into the in-phase I and quadrature-phase Q inputs of the same dual-channel digital-to-analog converter, respectively, to generate the drive signals for the I / Q modulator. ; Step 8: Use the external cavity laser ECL1 to generate a center frequency of A continuous optical carrier is input to an I / Q modulator; the drive signal The in-phase and quadrature components driving the I / Q modulator are such that the center frequency of the I / Q modulator output is... The carrier signal; Step Nine: The center frequency is The continuous optical carrier, after transmission through single-mode fiber and amplification by an erbium-doped fiber amplifier, is coupled with the output center frequency of the external cavity laser ECL2. The optical signal is coupled 1:1 and sent to a single-row carrier photodetector for beat frequency generation, producing a frequency of... Terahertz signals are transmitted to the receiving end; Step 10: The receiver inputs the terahertz signal into the mixer, mixes it with the local oscillator signal that has been multiplied by the frequency multiplier, realizes the down-conversion of the terahertz signal, obtains the intermediate frequency signal, inputs it into the RX-DSP module for digital signal processing, and finally obtains the original data and calculates the bit error rate.

2. The photonic terahertz communication system based on non-uniform probability shaping as described in claim 1, characterized in that, The transmitting end includes: a TX-DSP module, an I / Q modulator, two external cavity lasers ECL1 and ECL2, a single-mode fiber, an erbium-doped fiber amplifier, a 1:1 optical coupler, a tunable optical attenuator, a single-row carrier photodetector, and a terahertz antenna. The I / Q modulator is connected to both the TX-DSP module and the external cavity laser ECL1. The output of the external cavity laser ECL1 serves as the optical carrier. The TX-DSP module uses non-uniform probabilistic shaping and a Nose-Hoover improved chaotic system to generate a encrypted and shaped baseband RF signal, which drives the I / Q modulator to modulate the input optical carrier and output the optical signal for transmission in a single-mode fiber. The transmitted optical signal is amplified by an erbium-doped fiber amplifier and then coupled to the output of the external cavity laser ECL2 via an optical coupler. The coupled signal is then fed to a single-row carrier photodetector for beat frequency adjustment after the power is adjusted by an adjustable optical attenuator. The resulting terahertz signal is then transmitted into free space via a terahertz antenna.

3. The photonic terahertz communication system based on non-uniform probability shaping as described in claim 1, characterized in that, The receiver includes: a terahertz antenna, a frequency multiplier, a mixer, a local oscillator, and an RX-DSP module; The terahertz signal in free space is received by the terahertz antenna at the receiving end, and input into the mixer to mix with the local oscillator signal that has been multiplied by the frequency multiplier, thereby realizing the down-conversion of the terahertz signal to obtain the intermediate frequency signal. Then, the intermediate frequency signal is sampled and input into the RX-DSP module for digital signal processing, and finally the original data is obtained to calculate the bit error rate.

4. The photonic terahertz communication system based on non-uniform probability shaping as described in claim 1, characterized in that, Step two specifically involves: For , Sequence The operation yields values ​​from 0 and 1. ; for Sequence The operation yields values ​​from 0, 1, and 2. ; This represents the modulo operation. Indicate extraction The integer obtained from the m-th decimal place.

5. The photonic terahertz communication system based on non-uniform probability shaping as described in claim 1, characterized in that, The block division formula for step five is as follows: ; Signal after phase fuzzing encryption Length; The specified block length; To transmit the signal The total number of blocks into which the length is divided.

6. The photonic terahertz communication system based on non-uniform probability shaping as described in claim 1, characterized in that, Step six specifically involves: First, set the target 16QAM constellation shaping matrix ( , , , , , , , , , , , , , , , ); in , , , Corresponding to the four constellation points in the inner ring of the 16QAM symbol; , , , , , , , Corresponding to the 8 constellation points in the middle ring of the 16QAM symbol; , , , Corresponding to the four constellation points in the outer ring of the 16QAM symbol; Then, based on the number of QAM symbols in each block, they are sorted in descending order, and so on. Constellation Points Exchange , , , , , , , , , , , , , , , This means implementing the probability shaping process; Finally, the information after the exchange is completed is recorded, which is the shaping signal. .

7. The photonic terahertz communication system based on non-uniform probability shaping as described in claim 1, characterized in that, The specific digital signal processing in step ten includes digital downconversion, power normalization, optimal downsampling, radius decision equalization algorithm, FFT frequency offset estimation, blind phase search, deprobabilistic integer coding, phase ambiguity decryption, demapping, XOR decryption, and bit error rate calculation.

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