Polarization-independent coherent detection photon terahertz communication method and system

Abstract

The invention discloses a polarization-independent coherent detection photon terahertz communication method, and relates to the technical field of terahertz communication, and the method comprises the steps: mapping an original data stream to be transmitted into an original vector signal, carrying out the Alamouti coding of the original vector signal to generate two paths of signals, and enabling the two paths of signals to generate a dual-polarization signal through a dual-polarization IQ modulator; after the dual-polarization signal is coupled with the local oscillation optical signal, a terahertz signal is generated through optical heterodyne beat frequency; the terahertz signals are mixed with the radio-frequency signals after being converged, down-conversion of the terahertz signals is achieved, and intermediate-frequency signals are obtained; performing down-conversion, matched filtering and carrier phase recovery on the acquired intermediate frequency signal to obtain a correction signal; and according to the correction signal, adopting an Alamouti-MIMO decoding method to obtain a transmitted original data stream. The invention also discloses a polarization-independent coherent detection photon terahertz communication system. The polarization-independent coherent detection photon terahertz communication system supports polarization-insensitive photon-assisted terahertz communication with low complexity and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz communication, and in particular to a polarization-independent coherent detection photon terahertz communication method and system. Background Art

[0002] In the 6G development vision and technical route, terahertz communication is generally considered to be the core component of the future 6G mobile communication system, and the photon-assisted terahertz communication system (i.e., photon terahertz communication system) has become the focus of research due to its ability to seamlessly integrate optical fiber and terahertz links, and its advantages of large capacity and ultra-bandwidth. The photon-assisted terahertz communication system uses optical heterodyne beat frequency (i.e., the coupled signal light and the local oscillator light are sent to the photodetector for beat frequency) to generate terahertz signals. The adjustable signal frequency range covers the entire terahertz frequency band, and the spectrum resource utilization rate is high. It has broad application prospects in future large-capacity communications, intersatellite communications, and integrated space-ground communications.

[0003] However, for traditional photon-assisted terahertz communication systems, when performing optical heterodyne beat frequency, it is necessary to focus on the polarization alignment between the two beams. During the transmission process, the signal light will have a polarization mismatch with the local oscillator light due to factors such as optical fiber transmission, mechanical stress, and temperature changes. When entering the coupler, it will have an angle deviation from the direction of the local oscillator light, causing the generated terahertz signal power to degrade, thereby causing polarization sensitivity problems (such as Figure 2 (a) in Figure 1), even in extreme cases, when the two beams are orthogonal, the terahertz signal power generated by the beat frequency will be completely lost and cannot carry any effective information. Therefore, at the current communication system architecture level, it is inevitable to use a polarization controller or polarization tracking algorithm to actively control the polarization state of the signal to be consistent with the direction of the local oscillator light, or to use a polarization diversity optical heterodyne detection system to maintain system performance and solve the polarization sensitivity problem.

[0004] Although the above two methods can solve the polarization sensitivity problem, the application of polarization controller cannot guarantee the long-term stability of the system. It requires manual real-time monitoring of the signal polarization state and cannot solve the problem once and for all. The polarization tracking algorithm usually involves complex tracking algorithm processes and feedback mechanisms, which will significantly increase the complexity of the system and reduce the robustness of the system; and the polarization diversity optical heterodyne detection system requires the introduction of additional optical devices (such as polarization beam splitters, optical couplers, etc.), which will not only increase the system cost, but also reduce the light detection sensitivity. Therefore, in the current photon-assisted terahertz communication system, a low-complexity and cost-effective polarization-insensitive solution is urgently needed to improve the reliability and operability of the system. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a polarization-independent coherent detection photon terahertz communication method and system. Based on the Alamouti coding technology and combined with the proposed Alamouti-multiple-input-multiple-output (Alamouti-MIMO) decoding algorithm based on polarization-independent theory, the present invention can realize polarization-insensitive transmission of terahertz signals without using any active polarization control means or introducing additional optical devices, simplify the communication system while maintaining the long-term stability of the communication performance, improve the reliability and operability of the system, and thus support low-complexity, low-cost polarization-insensitive photon-assisted terahertz communication.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] A polarization-independent coherent detection photon terahertz communication method proposed in the present invention includes:

[0008] The original data stream to be transmitted is mapped into an original vector signal, and then the original vector signal is Alamouti-encoded to generate two signals, and the two signals are passed through a dual-polarization IQ modulator to generate a dual-polarization signal;

[0009] The dual polarization signal is coupled with the local oscillator optical signal and then subjected to optical heterodyne beat frequency to generate a terahertz signal;

[0010] After the terahertz signal is converged, it is mixed with the radio frequency signal to achieve down-conversion of the terahertz signal to obtain an intermediate frequency signal;

[0011] The collected intermediate frequency signal is subjected to down-conversion, matched filtering, and carrier phase recovery to obtain a correction signal;

[0012] According to the correction signal, an Alamouti-MIMO decoding method is used to obtain the original data stream for transmission; wherein the Alamouti-MIMO decoding method includes:

[0013] The correction signal is separated into odd and even data blocks to obtain odd block signals and even block signals; the even block signal is conjugated and the original vector signal is restored together with the odd block signal using the Volterra-MIMO equalization method, and then demapped to obtain the original data stream for transmission.

[0014] A polarization-independent coherent detection photon terahertz communication system, comprising:

[0015] The optical transmitter is used to map the original data stream to be transmitted into an original vector signal, and then generate two signals through Alamouti encoding. The two signals are passed through a dual-polarization IQ modulator to generate dual-polarization signals, and the dual-polarization signals are output to the optical-wireless conversion module;

[0016] An optical-to-wireless conversion module is used to couple the dual-polarization signal with the local oscillator optical signal and generate a terahertz signal through optical heterodyne beat frequency, and the terahertz signal is output to a terahertz wireless receiver;

[0017] The terahertz wireless receiver is used to converge the terahertz signal and mix it with the radio frequency signal to achieve down-conversion of the terahertz signal, obtain the intermediate frequency signal and output it to the processing module;

[0018] The processing module is used to perform down-conversion, matched filtering and carrier phase recovery on the collected intermediate frequency signal to obtain a correction signal, separate the correction signal into odd and even data blocks to obtain an odd block signal and an even block signal; conjugate the even block signal, and use the Volterra-MIMO equalization method to restore the original vector signal together with the odd block signal, and demap it to obtain the original data stream for transmission.

[0019] As a further optimization scheme of the polarization-independent coherent detection photon terahertz communication system described in the present invention, in the optical-wireless conversion module, the dual-polarization signal generated based on Alamouti coding is coupled with the local oscillator light signal and then subjected to optical heterodyne beat frequency to generate a terahertz signal, which is amplified by a terahertz low-noise amplifier and then transmitted through a high-gain antenna to complete the conversion of light into a terahertz wireless signal, and then transmitted to the terahertz wireless receiver via a wireless link.

[0020] As a further optimization scheme of the polarization-independent coherent detection photon terahertz communication system described in the present invention, in a terahertz wireless receiver, the terahertz signal is gathered and received by a horn antenna, then amplified by a low-noise amplifier and mixed with a frequency-doubled radio frequency signal in a terahertz mixer to achieve down-conversion of the terahertz signal to obtain an intermediate frequency signal, which is then amplified by an electrical amplifier and input into a processing module.

[0021] As a further optimization scheme of a polarization-independent coherent detection photon terahertz communication system described in the present invention, the processing module includes a receiving end signal acquisition module, a down-conversion module, a matched filtering module, a carrier phase recovery module, an odd-even data separation module, an even-block signal conjugation module, a Volterra-MIMO equalization module, and a signal demapping module;

[0022] A receiving end signal acquisition module is used to collect the intermediate frequency signal amplified by the electric amplifier;

[0023] A down-conversion module is used to convert the intermediate frequency signal to baseband and output the baseband signal to the matched filter module;

[0024] The matched filtering module and the carrier phase recovery module are used to perform matched filtering and carrier phase recovery on the baseband signal to obtain a correction signal;

[0025] The parity data separation module is used to separate the parity data blocks of the correction signal to obtain odd block signals and even block signals;

[0026] An even-numbered block signal conjugation module is used to conjugate the even-numbered block signal and use it and the odd-numbered block signal as two inputs of the Volterra-MIMO equalization module;

[0027] The Volterra-MIMO equalization module is used to restore the original vector signal by using a linear equalization method, and the original vector signal is output to the signal demapping module;

[0028] The signal demapping module is used to demap the original vector signal to obtain the original data stream for transmission.

[0029] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0030] (1) On the one hand, the polarization-independent coherent detection photon terahertz communication system proposed in the present invention can realize signal decoding under different polarization states through the designed Alamouti-MIMO decoding algorithm to restore the original vector signal.

[0031] (2) The present invention simplifies the coherent detection photon terahertz communication scheme on the basis of realizing polarization-independent transmission. The system transmitter only needs a set of photodetectors and no longer needs additional polarization-related devices (such as polarization controllers, polarization beam splitters, etc.), which reduces system costs and improves receiving sensitivity. This scheme no longer needs to consider the polarization state of the system, can maintain the performance of the system under long-term operation, has high stability and robustness, and can well adapt to the development of future long-distance communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The key modulation and demodulation processing flow of the polarization-independent coherent detection photon terahertz communication system based on Alamouti coding provided by the example of the present invention;

[0033] Figure 2 A schematic diagram of the formation principle of polarization sensitivity problem of the traditional solution provided in the example of the present invention and a schematic diagram of the polarization-independent realization principle based on Alamouti coding; wherein (a) is a schematic diagram of the formation principle of polarization sensitivity problem of the traditional solution, and (b) is a schematic diagram of the polarization-independent realization principle based on Alamouti coding;

[0034] Figure 3 A schematic diagram of the structure of a polarization-independent coherent detection photon terahertz communication system based on Alamouti coding provided by an example of the present invention;

[0035] Figure 4A schematic diagram of the structure of an optical transmitter of a polarization-independent coherent detection photon terahertz communication system provided by an example of the present invention;

[0036] Figure 5 A schematic diagram of the algorithm flow of the DSP processing module of the polarization-independent coherent detection photon terahertz communication system provided by the example of the present invention;

[0037] Figure 6 A simplified structure diagram of a polarization-independent coherent detection photon terahertz communication system based on Alamouti coding is provided as an example of the present invention.

[0038] The reference numerals are explained as follows: 11-polarization-independent system optical transmitter based on Alamouti coding, 12-optical fiber link, 13-optical-terahertz conversion module, 21-terahertz signal wireless receiver, 22-polarization-independent system DSP processing module based on Alamouti coding, 131-optical coupler, 132-local oscillator laser, 133-photodetector, 134-terahertz low noise amplifier, 135-high gain antenna, 211-horn antenna, 212-terahertz low noise amplifier, 213-radio frequency source, 214-terahertz mixer, 215-electric amplifier;

[0039] 111- vector signal generation module, 112- Alamouti coding processing module, 113- dual polarization IQ modulator, 114- transmitting end laser;

[0040] 221 - receiving end signal acquisition module, 222 - down conversion module, 223 - matched filtering module, 224 - carrier phase recovery module, 225 - odd and even data separation module, 226 - even block signal conjugation module, 227 - Volterra-MIMO equalization module, 228 - signal demapping module. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] The processing flow of the polarization-independent coherent detection photon terahertz communication system based on Alamouti coding provided by the example of the present invention is as follows: Figure 1As shown in the figure, in the optical transmitter, the original data stream to be transmitted is mapped into the original vector signal through the Matlab offline program, and then two signals carrying the same information content but in different forms are generated through Alamouti coding. These signals are then passed through the dual polarization IQ modulator (DP-IQ modulator) to generate dual polarization signals. When encoding, considering the different responses of the modulator to odd and even signals, a more serious inter-code crosstalk that is difficult to be compensated by the equalizer will be introduced at the junction of the odd and even data blocks. Block coding is used to reduce the performance impact caused by the inter-code crosstalk. The dual polarization signals obtained in this coding and modulation method can be carried on the same optical carrier, and can compensate for each other's performance losses when projecting to the local oscillator light, thereby solving the polarization sensitivity problem.

[0043] In the optical-to-wireless conversion module, the dual-polarization signal generated based on Alamouti coding is coupled with the local oscillator optical signal and then subjected to optical heterodyne beat frequency to generate a terahertz signal, which is amplified by a terahertz low-noise amplifier and then transmitted through a high-gain antenna to complete the conversion of light into a terahertz wireless signal, which is then transmitted via a wireless link.

[0044] In the terahertz wireless receiver, the divergent terahertz signal is gathered and received by the horn antenna, then amplified by a low-noise amplifier to compensate for the free space path loss, and then mixed with the frequency-doubled RF signal in the terahertz mixer to achieve down-conversion of the terahertz signal to obtain an intermediate frequency signal. The intermediate frequency signal is then amplified by an electrical amplifier and received and collected by a digital storage oscilloscope.

[0045] In the DSP processing module, the collected intermediate frequency signal is first down-converted to obtain a baseband signal, the baseband signal is matched filtered, and then a carrier phase recovery algorithm (CPE) is used to perform frequency offset and phase compensation; finally, the processed signal is sent to the Alamouti-MIMO decoding algorithm module designed according to the polarization-independent theory of the present invention, the original vector signal is recovered and demapped to obtain the transmitted original data stream, and the bit error rate and other related results are calculated.

[0046] The polarization-independent photonic terahertz communication system proposed in the present invention is a polarization-insensitive solution with low complexity and high cost-effectiveness. It can maintain the stability of system performance for a long time under the premise that the system polarization state is insensitive, thereby improving the reliability and operability of the system.

[0047] The polarization-independent photonic terahertz communication system proposed in the present invention can maintain the stability of system performance for a long time without considering the polarization state of the system. The relevant principles are as follows: Figure 2As shown in (b) in the figure. In the traditional single polarization system, the signal light is affected by optical devices, temperature, etc. during transmission, resulting in polarization rotation. When it enters the coupler, it is not in the same plane as the local oscillator signal and needs to be projected onto the local oscillator signal, resulting in power loss of the generated terahertz signal. Figure 2 (a) shows the power changes of four different polarization states in the traditional single polarization system after coupling with the local oscillator light. After Alamouti encoding, the two signals with the same information but different forms are generated. When coupled with the local oscillator light, both polarization signals are projected in the direction of the local oscillator light signal, which can be seen from Figure 2 (b) in the figure shows intuitively that the two groups of signals can compensate for each other's power loss.

[0048] In order to further improve the credibility of the scheme, the polarization-independent principle is theoretically derived. The original vector signal is Alamouti-encoded and then the DP-IQ modulator generates a dual-polarization signal. Assume that the original vector signal SP = [S1 S2 S3S4 ... S i ], the signal E carried on two different polarizations (denoted as X polarization and Y polarization) after Alamouti encoding x and E y It can be expressed as E x =[S1-S2 * S3-S4 * ……], E y =[S2 S1 * S4S3 * ……], for the sake of simplicity, the following will take the first two symbol blocks as an example. xx h xy ;h yx h yy ] represents the channel response of the optical fiber, where h xx represents the influence coefficient between signals on X polarization, h xy It represents the influence coefficient of the X-polarization signal on the Y-polarization signal, h yx It represents the influence coefficient of the Y polarization signal on the X polarization signal, h yy represents the influence coefficient between the signals on the Y polarization, then the signal reaching the optical coupler 131 after being transmitted through the optical fiber can be expressed as:

[0049]

[0050] Among them, S i represents the i-th vector signal block, i=1,3,5,... represents odd blocks, i=2,4,6,... represents even blocks, E x ′ , E y′ Represents the signals carried on two polarizations after being affected by polarization rotation during transmission. The Alamouti coded data pair [S1-S2] with intrinsic orthogonality * ] and [S2 S1 * ] transmits on both X and Y polarizations, the '*' indicates conjugation.

[0051] When coupling with the local oscillator light, it is assumed that the angle between the local oscillator light and the X polarization direction of the incident signal is θ (θ∈[-90°,90°]), such as Figure 2 As shown in (b), after simple optical heterodyne detection without polarization diversity based on a single photodetector UTC-PD, the signals in the two polarization states will be projected onto the local oscillator direction with coefficients related to the polarization rotation angle θ, and a superimposed terahertz signal can be obtained: E oc =cosθ×E x ′ +sinθ×E y ′ . Based on this, the generated terahertz signal (i.e. E oc ) can be expressed as:

[0052]

[0053] Among them, S odd is the odd block of the signal after projection accumulation, S even is the even block of the signal after projection accumulation, 'T' represents transposition, and '×' represents multiplication.

[0054]

[0055] As shown in the above formula, the even block signal is conjugated. After sorting, it can be found that the conjugated signal and the original vector signal present a matrix transformation relationship, and H1 is the transformation matrix. It can be further found that the determinant result of H1 |H1|=-|h xx cosθ+h yx sinθ| 2 -|h xy cosθ+h yy sinθ| 2 If it is not zero, it means that the processed signal and the original vector signal are linearly transformed, and the original vector signal can be restored through the equalizer.

[0056] Thus, the feasibility of using Alamouti coding to achieve polarization-independent transmission is theoretically proved. Under any polarization state of angle θ, the received [S odd S even * ] TThe original vector signal is restored from [S1 S2].

[0057] The polarization-independent transmission scheme proposed in the present invention can maintain the long-term stability of system performance without polarization control or the introduction of additional optical devices. The schematic diagram of the structure of the polarization-independent coherent detection photon terahertz communication system based on Alamouti coding is shown in the figure. Figure 3 It is mainly composed of a polarization-independent system optical transmitter 11 based on Alamouti coding, an optical fiber link 12, an optical-terahertz conversion module 13, a terahertz signal wireless receiver 21, and a polarization-independent system DSP processing module 22 based on Alamouti coding.

[0058] The polarization-independent system optical transmitter 11 based on Alamouti coding is used to generate dual-polarization signals after Alamouti coding. The two polarizations carry signals with the same information but in different forms. The detailed structure is as follows: Figure 4 As shown. The original first vector signal is generated by the vector signal generation module 111 and sent to the Alamouti coding processing module 112 to generate the second vector signal and the third vector signal according to the coding rule. Among them, due to the different responses of the dual-polarization modulator to the parity symbols, a more serious inter-code interference will be introduced at the junction of the parity and even data blocks. In order to reduce the performance impact caused by the inter-code interference, the Alamouti block coding scheme is adopted, that is, a symbol block contains multiple symbols, and the encoding is performed in blocks. The two generated vector signals are sent to the dual-polarization IQ modulator 113, and together with the transmitting end laser 114, the dual-polarization IQ modulator 113 is driven to generate a dual-polarization signal.

[0059] After the dual polarization signal is transmitted over a long distance through the optical fiber link 12, it is coupled with the local oscillator light from the local oscillator laser 132 in the optical coupler 131 of the optical-wireless conversion end 13, and then the terahertz signal is generated by the beat frequency in the photodetector 133, completing the conversion of light to terahertz. In this process, the signals in the two polarization states will be projected in the direction of the local oscillator light. The carrier frequency of the generated terahertz signal is equal to the center frequency interval between the transmitting end laser 114 and the local oscillator laser 132. Subsequently, the terahertz signal generated by the beat frequency is amplified by the terahertz low noise amplifier 134, transmitted through the high gain antenna 135, and received and collected by the wireless receiver 21 after passing through the wireless link.

[0060] In the wireless receiver 21, the terahertz signal received by the horn antenna 211 is first amplified by the terahertz low noise amplifier 212 to compensate for the more serious free path loss in long-distance transmission. The RF signal generated by the RF source 213 is mixed with the terahertz signal in the terahertz mixer 214 after frequency doubling and down-converted into an intermediate frequency signal. It is then amplified by the electrical amplifier 215 and sent to the polarization-independent system DSP processing module 22 based on Alamouti coding to complete the recovery of the original vector signal and the calculation of related results such as bit error rate. Figure 6 A simplified structure diagram of a polarization-independent coherent detection photon terahertz communication system based on Alamouti coding is provided as an example of the present invention.

[0061] The algorithm flow of the DSP processing module of the polarization-independent coherent detection photon terahertz communication system provided by the embodiment of the present invention is as follows: Figure 5 As shown. First, the intermediate frequency signal amplified by the electric amplifier 215 is collected by the receiving end signal acquisition module 221, and the down-conversion module 222 converts the frequency to the baseband for subsequent processing. Subsequently, the signal is sent to the matched filter module 223 for matched filtering, and then the carrier phase recovery module 224 compensates for the frequency deviation and phase noise during the transmission process. According to the polarization-independent theoretical derivation process, the present invention designs an Alamouti-MIMO decoding module, which mainly includes an odd-even data separation module 225, an even block signal conjugation module 226, a Volterra-MIMO equalization module 227, and a signal demapping module 228. The data processed by the carrier phase recovery module 224 is sent to the parity data separation module 225 to separate the odd block signal and the even block signal, and the even block signal to be processed is sent to the even block signal conjugation module 226 to take conjugation, and together with the odd block signal to be processed, it is used as the input of the Volterra-MIMO equalization module 227. The Volterra-MIMO equalization module 227 uses the characteristic that the conjugate processed signal and the original vector signal present a linear relationship, and uses the odd block signal S based on part of the original vector signal. 2k+1 and the even block signal S 2k+2 (k=0,1,2,3,...) training data is used to assist in estimating the channel response H1, and the original vector signal is restored by the linear equalization method. Finally, the original vector signal obtained by equalization is sent to the signal demapping module 228 to obtain the original data stream transmitted by the polarization-independent system optical transmitter 11 based on Alamouti coding, and the bit error rate and other related results are calculated.

[0062] The above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A polarization-independent coherent detection photon terahertz communication method, characterized in that: include: The original data stream to be transmitted is mapped into an original vector signal, and then the original vector signal is Alamouti-encoded to generate two signals, and the two signals are passed through a dual-polarization IQ modulator to generate a dual-polarization signal; The dual polarization signal is coupled with the local oscillator optical signal and then subjected to optical heterodyne beat frequency to generate a terahertz signal; After the terahertz signal is converged, it is mixed with the radio frequency signal to achieve down-conversion of the terahertz signal to obtain an intermediate frequency signal; The collected intermediate frequency signal is subjected to down-conversion, matched filtering, and carrier phase recovery to obtain a correction signal; According to the correction signal, an Alamouti-MIMO decoding method is used to obtain the original data stream for transmission; wherein the Alamouti-MIMO decoding method includes: The correction signal is separated into odd and even data blocks to obtain odd block signals and even block signals; the even block signal is conjugated and the original vector signal is restored together with the odd block signal using the Volterra-MIMO equalization method, and then demapped to obtain the original data stream for transmission.

2. A polarization-independent coherent detection photon terahertz communication system, characterized in that: include: The optical transmitter is used to map the original data stream to be transmitted into an original vector signal, and then generate two signals through Alamouti encoding. The two signals are passed through a dual-polarization IQ modulator to generate dual-polarization signals, and the dual-polarization signals are output to the optical-wireless conversion module; An optical-to-wireless conversion module is used to couple the dual-polarization signal with the local oscillator optical signal and generate a terahertz signal through optical heterodyne beat frequency, and the terahertz signal is output to a terahertz wireless receiver; The terahertz wireless receiver is used to converge the terahertz signal and mix it with the radio frequency signal to achieve down-conversion of the terahertz signal, obtain the intermediate frequency signal and output it to the processing module; The processing module is used to perform down-conversion, matched filtering and carrier phase recovery on the collected intermediate frequency signal to obtain a correction signal, separate the correction signal into odd and even data blocks to obtain an odd block signal and an even block signal; conjugate the even block signal, and use the Volterra-MIMO equalization method to restore the original vector signal together with the odd block signal, and demap it to obtain the original data stream for transmission.

3. The polarization-independent coherent detection photon terahertz communication system according to claim 2, characterized in that: In the optical-to-wireless conversion module, the dual-polarization signal generated based on Alamouti coding is coupled with the local oscillator optical signal and then subjected to optical heterodyne beat frequency to generate a terahertz signal, which is amplified by a terahertz low-noise amplifier and then transmitted through a high-gain antenna to complete the conversion of light into a terahertz wireless signal, and then transmitted to the terahertz wireless receiver via a wireless link.

4. The polarization-independent coherent detection photon terahertz communication system according to claim 2, characterized in that: In the terahertz wireless receiver, the terahertz signal is gathered and received by the horn antenna, then amplified by a low-noise amplifier and mixed with the frequency-doubled RF signal in a terahertz mixer to achieve down-conversion of the terahertz signal to obtain an intermediate frequency signal. The intermediate frequency signal is then amplified by an electrical amplifier and input into the processing module.

5. The polarization-independent coherent detection photon terahertz communication system according to claim 2, characterized in that: The processing module includes a receiving end signal acquisition module, a down-conversion module, a matched filtering module, a carrier phase recovery module, an odd-even data separation module, an even-block signal conjugation module, a Volterra-MIMO equalization module, and a signal demapping module; A receiving end signal acquisition module is used to collect the intermediate frequency signal amplified by the electric amplifier; A down-conversion module is used to convert the intermediate frequency signal to baseband and output the baseband signal to the matched filter module; The matched filtering module and the carrier phase recovery module are used to perform matched filtering and carrier phase recovery on the baseband signal to obtain a correction signal; The parity data separation module is used to separate the parity data blocks of the correction signal to obtain odd block signals and even block signals; An even-numbered block signal conjugation module is used to conjugate the even-numbered block signal and use it and the odd-numbered block signal as two inputs of the Volterra-MIMO equalization module; The Volterra-MIMO equalization module is used to restore the original vector signal by using a linear equalization method, and the original vector signal is output to the signal demapping module; The signal demapping module is used to demap the original vector signal to obtain the original data stream for transmission.

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