A high-speed optoelectronic communication signal transmission method based on terahertz waves

Abstract

The application discloses a high-speed optoelectronic communication signal transmission method based on terahertz waves, and relates to the technical field of optoelectronic communication, constructs a full-link reference transmission model, realizes super-high-speed and high-reliability terahertz optoelectronic communication transmission through full-link loss pre-compensation of a transmitting end, dynamic closed-loop updating and residual loss sparse equalization of a receiving end, and has the advantages that a device and channel joint reference transmission model covering a full link of terahertz optoelectronic communication is constructed, reverse pre-distortion processing of full-link linear and nonlinear transmission loss is completed at a signal transmitting source, and a model dynamic closed-loop updating mechanism based on real-time states in a transmission process is simultaneously used, so that a long-standing technical prejudice of single-link discrete optimization in the field is broken through, a serial discrete transmission architecture commonly used in the prior art is completely abandoned, and inherent technical contradictions that transmission rate improvement is inevitably accompanied by signal-to-noise ratio deterioration, error code rate soaring and transmission distance sharply decreasing are fundamentally broken.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic communication technology, specifically to a high-speed optoelectronic communication signal transmission method based on terahertz waves. Background Technology

[0002] The current generation of information and communication technologies is in a critical stage of accelerated evolution from 5G to 6G. With the rapid implementation of emerging scenarios such as real-time transmission of ultra-high-definition video, immersive interaction in the metaverse, integrated space-ground communication, high-reliability real-time interconnection of the industrial internet, and high-speed interconnection of large-scale data centers, the global communication industry has put forward unprecedented high-level requirements for the transmission rate, bandwidth capacity, transmission latency, and anti-interference capability of wireless transmission systems. Terahertz waves, as electromagnetic waves with frequencies in the range of 0.1THz-10THz, are located in the spectrum gap between microwaves and infrared light waves. They combine the strong penetration and anti-interference of microwave communication with the ultra-large bandwidth, low transmission latency, and high security of optical communication. They are the core carrier for realizing Tbps-level ultra-high-speed wireless communication and are also recognized as one of the core candidate technologies in the global 6G communication technology standardization process. Existing terahertz high-speed optoelectronic communication signal transmission technologies mainly achieve terahertz frequency band optoelectronic communication signal transmission by performing discrete optimization of core components such as transmitter modulation, channel transmission, and receiver demodulation. This is achieved using a serial discrete architecture of electro-optic modulation-terahertz transmission-photoelectric detection-electric domain compensation. However, this approach has certain drawbacks. First, the existing schemes are limited by the serial discrete architecture and the single-stage optimization approach. Increasing the transmission rate inevitably leads to a deterioration in the signal-to-noise ratio, a surge in the bit error rate, and a sharp drop in transmission distance. Performance improvements are highly dependent on upgrades to the specifications of core hardware components, making it difficult to achieve low-cost, ultra-high-speed, long-distance stable transmission. Second, existing schemes only perform full transmission impairment compensation at the receiver, lacking a closed-loop collaborative design mechanism at the transmitter and receiver. This results in high signal processing complexity and power consumption at the receiver, insufficient signal recovery accuracy, and weak resistance to time-varying channel interference, making it unsuitable for stable transmission requirements in complex scenarios. Therefore, we propose a high-speed optoelectronic communication signal transmission method based on terahertz waves. Summary of the Invention

[0003] The purpose of this invention is to provide a high-speed optoelectronic communication signal transmission method based on terahertz waves.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a high-speed optoelectronic communication signal transmission method based on terahertz waves, the signal transmission method comprising the following steps: Step 1: Collect the device response parameters of the electro-optic modulator and photodetector of the entire terahertz opto-communication link, as well as the transmission characteristic parameters of the terahertz wireless channel. Fit and establish a frequency-domain discretized full-link reference transmission model, and output the comprehensive transmission response and nonlinear distortion coefficient of each frequency point of the entire link to provide a calculation benchmark for transmission impairment pre-cancellation. Step 2: Calculate the full-link integrated transmission function based on the full-link reference transmission model, obtain the perfectly matched predistortion transmission function through inverse fitting, calculate and generate the predistortion baseband signal, and achieve pre-cancellation of full-link linear and nonlinear transmission impairments from the signal transmission source; Step 3: Perform cyclic redundancy check coding, low-density parity check forward error correction coding, high-order orthogonal amplitude modulation mapping and root raised cosine shaping filtering on the predistorted baseband signal in sequence to generate a modulated baseband electrical signal that meets the requirements of electro-optic modulation input. Step 4: Generate two coherent single-frequency optical signals with a frequency difference matching the target terahertz carrier frequency through an optical frequency comb generator, load the modulation baseband electrical signal onto an electro-optic modulator to complete optical domain modulation, and generate a terahertz carrier signal carrying modulation information through difference frequency processing, which is then transmitted to the wireless channel through an antenna. Step 5: The receiver collects channel status parameters and received signal performance parameters in real time, and transmits them back to the transmitter through a low-bandwidth reverse control channel. The receiver updates the full-link reference transmission model and predistortion calculation parameters in real time to ensure that the predistortion processing is accurately matched with the actual transmission characteristics of the link. Step 6: The receiving end receives the transmitted terahertz carrier signal through the terahertz antenna, completes photoelectric conversion through coherent detection, and outputs the received baseband electrical signal corresponding to the modulated baseband electrical signal of the transmitting end. Step 7: After completing carrier and symbol synchronization compensation for the received baseband electrical signal, construct a sparse equalization matrix based on the reference parameters of the predistortion processing at the transmitting end. Optimize the matrix weights through iterative calculation with sparse constraints, and perform low-complexity compensation only for residual transmission impairments across the entire link to output a high-fidelity baseband signal. Step 8: Demodulate, decode, and perform cyclic redundancy check on the equalized high-fidelity baseband signal in sequence. After removing the check bits and encoding redundancy bits, output the original transmission data to complete the entire signal transmission process.

[0005] As a further aspect of the present invention: Step one specifically involves: completing the acquisition of transmission characteristic parameters of the entire terahertz optoelectronic communication link and constructing a benchmark transmission model. First, through the built-in test signal source at the transmitter, a frequency sweep test signal covering the target operating frequency band is transmitted to the entire link. Simultaneously, the amplitude frequency response parameters, phase frequency response parameters, and input-output nonlinear response parameters of the transmitter's electro-optic modulator in the target operating frequency band are acquired. The atmospheric attenuation parameters, frequency selective fading parameters, and multipath transmission response parameters of the terahertz wireless channel in the current transmission environment are also acquired. The response bandwidth parameters, photoelectric conversion efficiency parameters, and floor noise parameters of the receiver's photodetector in the target operating frequency band are also acquired. Then, the acquired parameters of the entire link are discretized and fitted to establish a frequency-domain discretized benchmark transmission model corresponding to the target transmission scenario. The model output values ​​are the comprehensive transmission response and comprehensive nonlinear distortion coefficient of the entire link at the corresponding frequency point, providing a benchmark calculation basis for the subsequent pre-cancellation processing of the entire link transmission impairment.

[0006] As a further aspect of the present invention: Step two specifically involves: based on the end-to-end reference transmission model established in step one, performing reverse pre-distortion calculation of end-to-end transmission impairment; firstly, calculating the integrated transmission function of the entire link within the target operating frequency band based on the integrated transmission response and integrated nonlinear distortion coefficients at each frequency point output by the end-to-end reference transmission model. ,in For operating frequency, It simultaneously includes quantitative characterizations of both linear and nonlinear transmission impairments across the entire link. Then, through inverse fitting calculations, a predistorted transmission function that perfectly inversely matches the overall transmission function of the entire link is obtained. The formula for calculating the predistorted transmission function is as follows: ; in, For predistorted transfer functions, is the regularization coefficient, which is taken as the maximum value of the full-link baseband noise power within the target operating frequency band, used to avoid noise amplification. Finally, based on the predistortion transfer function, the time-domain expression of the corresponding original baseband signal is calculated. The time-domain calculation formula for the predistortion baseband signal is as follows: ; in, For predistorted baseband signals, The raw baseband signal to be transmitted. For Fast Fourier Transform operations, To perform the fast inverse Fourier transform operation and generate the predistorted baseband signal, pre-cancellation of linear and nonlinear transmission impairments across the entire transmission link is achieved from the signal transmission source.

[0007] As a further aspect of the present invention: Step three specifically involves: completing the forward error correction coding and high-order modulation mapping processing of the predistorted baseband signal. First, the predistorted baseband signal generated in step two is cyclic redundancy check coding, and then forward error correction coding is completed using low-density parity check codes. The coding rate is fixedly configured according to the full-link signal-to-noise ratio parameters collected in step one. Subsequently, the coded baseband signal is symbol mapped, and the mapping method adopts a high-order orthogonal amplitude modulation method that matches the target transmission rate. After completing the symbol mapping, the baseband symbols are subjected to root-raised cosine shaping filtering processing, and the filter roll-off coefficient is fixed at a constant value between 0.15 and 0.3. Finally, a modulated baseband electrical signal adapted to the input requirements of the electro-optic modulator is generated, ensuring that the baseband signal after predistortion processing completely retains the characteristics of reverse-matched full-link transmission impairment.

[0008] As a further aspect of the present invention: Step four specifically involves: completing the generation of the terahertz carrier and the electro-optical conversion and transmission of the predistorted modulation signal. First, two coherent single-frequency optical signals with a frequency difference consistent with the target terahertz carrier frequency are generated by the optical frequency comb generator at the transmitting end. The two coherent single-frequency optical signals are respectively input to the two input ports of the Mach-Zehnder electro-optic modulator. At the same time, the modulation baseband electrical signal generated in step three is loaded onto the radio frequency drive port of the Mach-Zehnder electro-optic modulator. The predistorted modulation baseband signal is completely mapped onto the optical domain amplitude and phase of the two coherent optical signals through electro-optic modulation. Then, the two modulated coherent optical signals are input to a single-row carrier photodiode for difference frequency processing to generate a terahertz carrier signal carrying predistorted modulation information. Finally, the terahertz carrier signal is transmitted to the terahertz wireless channel through a terahertz high-gain antenna.

[0009] As a further aspect of the present invention: Step five specifically involves: completing real-time status monitoring of the terahertz wireless channel and closed-loop updating of the full-link reference transmission model. During the continuous transmission of the terahertz signal, the receiver collects the signal-to-noise ratio, bit error rate, and channel attenuation parameters of the currently received signal in real time, and simultaneously collects the atmospheric temperature, relative humidity, and atmospheric pressure parameters of the current transmission environment. All collected parameters are transmitted back to the transmitter in real time through a low-bandwidth reverse control channel. Based on the transmitted parameters, the transmitter updates the full-link reference transmission model established in step one in real time, and synchronously updates the predistortion transmission function and predistortion baseband signal calculation parameters in step two, ensuring that the predistortion processing always maintains a precise match with the actual transmission characteristics of the current full link, and avoiding a decrease in the pre-cancellation effect caused by the time-varying characteristics of the channel.

[0010] As a further aspect of the present invention: Step six specifically involves: completing the coherent reception and photoelectric conversion processing of the terahertz wireless signal. The receiving end receives the terahertz carrier signal transmitted through the terahertz wireless channel via a terahertz high-gain antenna of the same specifications as the transmitting end. The received terahertz carrier signal is divided into two paths. One path is used as the signal light input to the signal input port of the coherent receiver, and the other path is mixed with the terahertz local oscillator signal generated locally at the receiving end to generate a reference optical signal coherent with the optical frequency comb of the transmitting end. The reference optical signal is input to the local oscillator input port of the coherent receiver. The photoelectric conversion of the terahertz signal is completed through coherent detection, and the received baseband electrical signal corresponding to the modulated baseband electrical signal of the transmitting end is output, thus completing the lossless conversion of the terahertz signal from the optical domain to the electrical domain.

[0011] As a further aspect of the present invention: Step seven specifically involves: completing low-complexity sparse equalization compensation for residual transmission impairment of the received baseband electrical signal. First, the received baseband electrical signal output in step six is ​​synchronized to complete carrier frequency offset compensation and symbol timing synchronization. Then, based on the reference parameters of the transmitter pre-distortion processing, a sparse equalization matrix is ​​constructed that is only for residual transmission impairment across the entire link. The residual transmission impairment is the non-stationary impairment remaining after the transmitter pre-cancellation processing, caused by channel time-varying errors and device random noise. The formula for updating the weight coefficients of the sparse equalization matrix is: ; in, For the first The weight coefficients of the sparse equilibrium matrix in the next iteration. The iteration step size, For the first The equalization error signal of the next iteration. To receive the baseband signal after synchronization with the input. For symbolic functions, The sparse constraint threshold is set to the root mean square value of the baseband signal's basis noise. The optimization of the sparse equalization matrix is ​​completed through iterative calculation. Only the non-zero sparse components corresponding to residual damage are compensated, and the high-fidelity baseband signal after equalization is finally output.

[0012] As a further aspect of the present invention: Step eight specifically involves: demodulating, decoding, and outputting the original transmission data of the equalized baseband signal. First, the equalized baseband signal output in step seven is subjected to quadrature amplitude modulation demodulation to complete the symbol-to-bit stream mapping conversion. Then, the demodulated bit stream is subjected to low-density parity check decoding and cyclic redundancy check. After the check passes, the check bits and coding redundancy bits are removed, and the transmission data that is completely consistent with the original baseband signal input at the transmitter is output, thus completing the entire high-speed optoelectronic communication signal transmission process based on terahertz waves.

[0013] Compared with the prior art, the beneficial effects of the present invention by adopting the above technical solution are as follows: 1. This invention constructs a joint reference transmission model of devices and channels covering the entire terahertz optoelectronic communication link, and completes the inverse predistortion processing of linear and nonlinear transmission impairments at the signal transmission source. At the same time, it is combined with a dynamic closed-loop update mechanism of the model based on the real-time channel status during transmission. This invention breaks through the technical bias of single-link discrete optimization that has long existed in the field, completely abandons the serial discrete transmission architecture commonly used in existing technologies, and fundamentally breaks the inherent technical contradiction that increasing the transmission rate will inevitably lead to a deterioration in the signal-to-noise ratio, a surge in the bit error rate, and a sharp drop in the transmission distance. It can achieve stable long-distance transmission of ultra-high-speed terahertz optoelectronic communication signals without relying on the performance upgrade of core hardware devices, which greatly reduces the system implementation threshold and deployment cost, and significantly improves the transmission performance limit and adaptability to complex scenarios of the terahertz communication system. 2. This invention addresses the industry pain points of existing technologies that only perform full-link transmission impairment pre-cancellation at the receiving end, which is based on the completion of full-link transmission impairment pre-cancellation at the transmitting end. This mechanism focuses on low-complexity sparse equalization compensation for residual transmission impairment at the receiving end. Combined with a closed-loop collaborative design of full-link synchronous calibration and dynamic channel state adaptation at both the transmitting and receiving ends, this invention solves the problems of high signal processing complexity, high power consumption, and insufficient signal recovery accuracy caused by full impairment compensation at the receiving end in existing technologies. It also breaks through the inherent limitations of the separate design of the transmitting and receiving ends in existing technologies, achieving precise collaboration between transmitting end pre-compensation and receiving end post-processing. This significantly reduces the signal processing pressure at the receiving end, while significantly improving the fidelity of signal recovery and the system's resistance to time-varying interference. It ensures the continuous stability of the link in ultra-high-speed transmission scenarios and effectively expands the industrial application space of terahertz optoelectronic communication technology. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the method steps in an embodiment of the present invention. Detailed Implementation

[0015] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0016] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0017] Please see the appendix Figure 1 This invention discloses a high-speed optoelectronic communication signal transmission method based on terahertz waves. The signal transmission method includes the following steps: Step 1: Collect the device response parameters of the electro-optic modulator and photodetector of the entire terahertz opto-communication link, as well as the transmission characteristic parameters of the terahertz wireless channel. Fit and establish a frequency-domain discretized full-link reference transmission model, and output the comprehensive transmission response and nonlinear distortion coefficient of each frequency point of the entire link to provide a calculation benchmark for transmission impairment pre-cancellation. Step 2: Calculate the full-link integrated transmission function based on the full-link reference transmission model, obtain the perfectly matched predistortion transmission function through inverse fitting, calculate and generate the predistortion baseband signal, and achieve pre-cancellation of full-link linear and nonlinear transmission impairments from the signal transmission source; Step 3: Perform cyclic redundancy check coding, low-density parity check forward error correction coding, high-order orthogonal amplitude modulation mapping and root raised cosine shaping filtering on the predistorted baseband signal in sequence to generate a modulated baseband electrical signal that meets the requirements of electro-optic modulation input. Step 4: Generate two coherent single-frequency optical signals with a frequency difference matching the target terahertz carrier frequency through an optical frequency comb generator, load the modulation baseband electrical signal onto an electro-optic modulator to complete optical domain modulation, and generate a terahertz carrier signal carrying modulation information through difference frequency processing, which is then transmitted to the wireless channel through an antenna. Step 5: The receiver collects channel status parameters and received signal performance parameters in real time, and transmits them back to the transmitter through a low-bandwidth reverse control channel. The receiver updates the full-link reference transmission model and predistortion calculation parameters in real time to ensure that the predistortion processing is accurately matched with the actual transmission characteristics of the link. Step 6: The receiving end receives the transmitted terahertz carrier signal through the terahertz antenna, completes photoelectric conversion through coherent detection, and outputs the received baseband electrical signal corresponding to the modulated baseband electrical signal of the transmitting end. Step 7: After completing carrier and symbol synchronization compensation for the received baseband electrical signal, construct a sparse equalization matrix based on the reference parameters of the predistortion processing at the transmitting end. Optimize the matrix weights through iterative calculation with sparse constraints, and perform low-complexity compensation only for residual transmission impairments across the entire link to output a high-fidelity baseband signal. Step 8: Demodulate, decode, and perform cyclic redundancy check on the equalized high-fidelity baseband signal in sequence. After removing the check bits and encoding redundancy bits, output the original transmission data to complete the entire signal transmission process.

[0018] Example 1 This embodiment provides a high-speed optoelectronic communication signal transmission method based on terahertz waves, applied to an ultra-high-speed wireless interconnection scenario between data center racks. The environment is a static setting with a constant indoor temperature of 25℃ and relative humidity of 40%, a transmission distance of 10m, a target peak transmission rate of 1.2Tbps, a target operating frequency band of 0.3THz-0.5THz, and a center carrier frequency of 0.4THz. The specific implementation steps are as follows: Step 1: Complete the acquisition of transmission characteristic parameters of the entire terahertz optoelectronic communication link and build the reference transmission model. Through the built-in test signal source of the transmitter, transmit a linear frequency modulation sweep test signal covering the target working frequency band of 0.3THz-0.5THz to the entire link. The sweep bandwidth is 200GHz, the sweep period is 10μs, and the transmission power is 0dBm. The amplitude frequency response parameters, phase frequency response parameters, and input-output nonlinear response parameters of the Mach-Zehnder electro-optic modulator at the transmitter were synchronously acquired in the target operating frequency band. The measured modulator had a 3dB bandwidth of 220GHz, a 1dB compression point of 5dBm, an in-band amplitude frequency fluctuation of ≤±1.5dB, and an insertion loss of 6dB at the center frequency of 0.4THz. Atmospheric attenuation parameters, frequency selective fading parameters, and multipath transmission response parameters of an indoor terahertz wireless channel were collected. Measured data showed that at a transmission distance of 10m, the atmospheric attenuation in the 0.4THz band was 0.8dB, the peak-to-peak frequency selective fading was 1.2dB, the multipath delay spread was ≤1ns, and the direct path power ratio was ≥95%. The response bandwidth, photoelectric conversion efficiency, and floor noise parameters of the single-row carrier photodetector at the receiving end were collected within the target operating frequency band. The measured 3dB bandwidth of the detector was 200 GHz, the photoelectric conversion efficiency was 0.8 A / W, and the maximum in-band floor noise power was -110 dBm / Hz, which translates to a linearity of 1 × 10⁻⁶. -14 W; The collected parameters of the entire link were discretized in the frequency domain at 1024 points and calculated using least squares fitting. A frequency-discrete full-link benchmark transmission model corresponding to the indoor static transmission scenario was established. The output values ​​of the model are the comprehensive transmission response and comprehensive nonlinear distortion coefficient of the entire link at the corresponding frequency points. The linear amplitude of the comprehensive transmission function of the entire link at the center frequency of 0.4THz is 0.3, and the phase offset is 15° (π / 12rad). This provides a benchmark calculation basis for the subsequent pre-cancellation processing of transmission impairments in the entire link.

[0019] Step 2: Based on the end-to-end reference transmission model established in Step 1, perform inverse predistortion calculation of end-to-end transmission impairment. First, calculate the integrated transmission function of the entire link in the target operating frequency band based on the integrated transmission response and integrated nonlinear distortion coefficients at each frequency point output by the end-to-end reference transmission model. ,in For operating frequency, It includes quantitative representations of both linear and nonlinear transmission impairments across the entire link, presented as frequency-domain complex values, covering 1024 discrete frequency points across the entire 0.3THz-0.5THz frequency band. The specific expression for the center frequency point at 0.4THz is as follows: ; Then, through inverse fitting calculation, a predistorted transmission function that perfectly matches the end-to-end integrated transmission function is obtained. The calculation formula for the predistorted transmission function is as follows: ; In the formula, For predistorted transfer functions, The regularization coefficient is the maximum value of the end-to-end noise power within the target operating frequency band, and in this embodiment, it is fixed at 1×10. -14 W is used to prevent noise amplification; because The value is much smaller than The linear amplitude value is negligible, therefore the specific calculation result of the predistortion transfer function at the center frequency is: ; That is, the center frequency signal is compensated by 3.333 times amplitude and -15° reverse phase compensation, which completely cancels the amplitude attenuation and phase shift at the center frequency of the entire link. All 1024 discrete frequency points across the entire frequency band are calculated point-by-point using this formula, with the lowest in-band amplitude | |=0.25 corresponds to a compensation coefficient of 4, the highest amplitude| |=0.35 corresponds to a compensation coefficient of 2.857; Finally, based on the predistorted transfer function, a 4096-point Fast Fourier Transform / Inverse Transform was used, with the system sampling rate set to 250 GSa / s and the frequency resolution to 61.035 MHz. The time-domain expression of the predistorted baseband signal corresponding to the original baseband signal was calculated. The time-domain calculation formula for the predistorted baseband signal is as follows: ; In the formula, For predistorted baseband signals, The raw baseband signal to be transmitted. For Fast Fourier Transform operations, This is the inverse fast Fourier transform operation; In this embodiment, the original baseband signal is a 1.2Tbps dual-polarization 256QAM signal with a single-polarization symbol rate of 125GBaud. Each symbol corresponds to 2 sampling points. After calculation using the above formula, the pre-distortion baseband signal is generated, achieving pre-cancellation of linear and nonlinear transmission impairments across the entire link from the signal transmission source.

[0020] Step 3: Perform cyclic redundancy check encoding on the predistorted baseband signal generated in Step 2. Use CRC32 encoding to generate 32-bit check bits, and the check polynomial is 0x04C11DB7. Then, a low-density parity-check code compatible with the 5GNR standard is used to complete the forward error correction coding. The coding rate is fixed at 0.6, the code length is 64800, and the base map is BG2. Subsequently, the encoded baseband signal is subjected to dual-polarization 256QAM high-order orthogonal amplitude modulation symbol mapping, with a single-polarization symbol rate of 125 GBaud. After symbol mapping, the baseband symbols are subjected to root-raised cosine shaping filtering with a fixed roll-off factor of 0.2, occupying a baseband bandwidth of 150 GHz. Finally, a dual-polarization modulated baseband electrical signal adapted to the input requirements of the Mach-Zehnder electro-optic modulator is generated, ensuring that the baseband signal after pre-distortion processing fully retains the characteristics of reverse-matched end-link transmission impairment. The theoretical peak transmission rate that this step can support is 125 GBaud × 8 bits × 0.6 code rate × 2 polarizations = 1200 Gbps = 1.2 Tbps, which is perfectly matched with the target transmission rate.

[0021] Step 4: Generate two coherent single-frequency optical signals with a frequency difference matching the target terahertz carrier frequency using the optical frequency comb generator at the transmitting end. The optical frequency comb has a repetition frequency of 100MHz, a comb line count of ≥100, and a comb line power flatness of ≤±1dB. The center frequencies of the two coherent single-frequency optical signals are 193.1THz and 193.5THz, respectively, with a frequency difference of 0.4THz, which perfectly matches the target terahertz carrier frequency. The power of each optical signal is 3dBm. Two coherent single-frequency optical signals are input to the two input ports of the Mach-Zehnder electro-optic modulator, respectively. At the same time, the dual-polarization modulation baseband electrical signal generated in step three is loaded onto the radio frequency drive port of the Mach-Zehnder electro-optic modulator. The modulator has a half-wave voltage of 3.5V and an extinction ratio of 30dB. The pre-distorted modulation baseband signal is completely mapped onto the optical domain amplitude and phase of the two coherent optical signals through electro-optic modulation. The modulated coherent optical signals are then input into a single-row carrier photodiode for difference frequency processing. The photodiode has a saturation optical power of 10dBm and a 3dB bandwidth of 200GHz, generating a 0.4THz terahertz carrier signal carrying predistortion modulation information. Finally, a terahertz carrier signal with an equivalent isotropic radiated power of 10 dBm was transmitted into the terahertz wireless channel through a terahertz high-gain horn antenna with a gain of 25 dBi, and the antenna half-power beamwidth was 10°.

[0022] Step 5: During the continuous transmission of the terahertz signal, the receiver continuously collects the signal-to-noise ratio (SNR), bit error rate (BER), and channel attenuation parameters of the received signal in real time. Simultaneously, it collects the ambient atmospheric temperature and relative humidity parameters. All collected parameters are transmitted back to the transmitter in real time via a low-bandwidth reverse control channel. The reverse control channel has a bandwidth of 1MHz, a transmission rate of 1Mbps, and a fixed parameter update period of 1ms. When the channel attenuation change exceeds 0.5dB or the system BER exceeds 1×10⁻⁶, the transmitter will be notified. -9 In such cases, an emergency update will be triggered immediately. Based on the returned parameters, the transmitter updates the end-to-end reference transmission model established in step one in real time, and synchronously updates the predistortion transmission function and predistortion baseband signal calculation parameters in step two to ensure that the predistortion processing always maintains a precise match with the actual transmission characteristics of the current end link, and avoids the decline in pre-cancellation effect caused by slight changes in the environment.

[0023] Step Six: The receiver uses a 25dBi gain terahertz high-gain horn antenna of the same specifications as the transmitter to receive the terahertz carrier signal transmitted via the terahertz wireless channel. The received terahertz carrier signal is split into two paths. One path is used as the signal light input to the signal input port of the coherent receiver. The other path is mixed with a 0.4THz terahertz local oscillator signal generated locally at the receiver. The local oscillator signal power is 0dBm and the phase noise is ≤-110dBc / Hz@10kHz. A reference optical signal coherent with the optical frequency comb of the transmitter is generated. The reference optical signal is input to the local oscillator input port of the coherent receiver. The photoelectric conversion of the terahertz signal is completed through balanced coherent detection. The output is a dual-polarization receiving baseband electrical signal corresponding to the modulated baseband electrical signal of the transmitter, completing the lossless conversion of the terahertz signal from the optical domain to the electrical domain.

[0024] Step 7: Perform synchronization processing on the received baseband electrical signal output in Step 6 to complete carrier frequency offset compensation and symbol timing synchronization. The carrier synchronization accuracy is ≤100Hz and the symbol timing synchronization error is ≤0.01 symbol cycles. Based on the baseline parameters of the pre-distortion processing at the transmitter, a 32-tap sparse equalization matrix is ​​constructed that is only for the residual transmission impairment of the entire link. The residual transmission impairment is the non-stationary impairment caused by channel time-varying error and device random noise that remains after the pre-cancellation processing at the transmitter. Specifically, it is a small amplitude impairment with amplitude distortion ≤1dB and phase distortion ≤5°. The formula for updating the weight coefficients of the sparse equilibrium matrix is ​​as follows: ; Initial weights in this embodiment It is an identity matrix, with only the center tap having a weight of 1, and the remaining 31 taps having an initial weight of 0. The iteration step size is fixed at 0.005 in this embodiment. For the first The equalization error signal of the next iteration, the initial error of the first iteration. =0.001V, To receive the baseband signal after synchronization, the amplitude of the input signal in the first iteration is... =0.02V, For symbolic functions, The sparsity constraint threshold is set to the root mean square value of the received baseband signal's basis noise; in this embodiment, the measured value is 1×10⁻⁶. -3 V; Taking the first iteration as an example, let's calculate by substituting specific parameters: ,therefore The final weights calculated after the first iteration are: ; After 10 iterations of calculation, the sparse equalization matrix was optimized. Finally, only 5 taps had non-zero weights, while the weights of the remaining 27 taps converged to 0. Only the non-zero sparse components corresponding to the residual damage were compensated, and the high-fidelity baseband signal after equalization was finally output.

[0025] Step 8: Perform 256QAM quadrature amplitude modulation and demodulation on the equalized baseband signal output from Step 7 to complete the symbol-to-bit stream mapping conversion. Then, perform low-density parity check decoding and cyclic redundancy check on the demodulated bit stream. After the check passes, remove the check bits and coding redundancy bits, and output transmission data that is completely consistent with the original baseband signal input from the transmitter, thus completing the entire signal transmission process.

[0026] Example 2 This embodiment provides a high-speed optoelectronic communication signal transmission method based on terahertz waves, applied to a 6G outdoor base station wireless backhaul scenario in a dynamic outdoor atmospheric environment. The specific implementation steps are as follows: Step 1: Complete the acquisition of transmission characteristic parameters of the entire terahertz optoelectronic communication link and construct the benchmark transmission model. Through the built-in test signal source of the transmitter, transmit a frequency sweep test signal covering the target operating frequency band of 0.22THz-0.24THz to the entire link. Simultaneously acquire the amplitude frequency response parameters, phase frequency response parameters, and input-output nonlinear response parameters of the Mach-Zehnder electro-optic modulator at the transmitter in the target operating frequency band. Acquire atmospheric attenuation parameters, frequency selective fading parameters, multipath transmission response parameters, and atmospheric turbulence influence parameters of the outdoor terahertz wireless channel. Acquire the response bandwidth parameters, photoelectric conversion efficiency parameters, and floor noise parameters of the single-carrier photodetector at the receiver in the target operating frequency band. Discretize and fit the acquired parameters of the entire link to establish a frequency-domain discretized benchmark transmission model corresponding to the outdoor dynamic transmission scenario. The model outputs the comprehensive transmission response and comprehensive nonlinear distortion coefficient of the entire link at the corresponding frequency point, providing a benchmark calculation basis for the subsequent pre-cancellation processing of the entire link transmission impairment. Step 2: Based on the end-to-end reference transmission model established in Step 1, perform inverse predistortion calculation of end-to-end transmission impairment. Based on the comprehensive transmission response and comprehensive nonlinear distortion coefficient of each frequency point output by the end-to-end reference transmission model, calculate the comprehensive transmission function of the end-to-end in the target operating frequency band. Calculate the predistortion transmission function that is completely inversely matched with the comprehensive transmission function of the end-to-end through inverse fitting. Then, calculate the predistortion baseband signal corresponding to the original baseband signal based on the predistortion transmission function. This achieves pre-cancellation of linear and nonlinear transmission impairments of the end-to-end from the signal transmission source. Step 3: Perform cyclic redundancy check coding on the predistorted baseband signal generated in Step 2. Use low-density parity check code to complete forward error correction coding. The coding rate is fixed at 0.5. Perform 64QAM high-order quadrature amplitude modulation symbol mapping on the encoded baseband signal. After completing the symbol mapping, perform root raised cosine shaping filtering on the baseband symbols. The filter roll-off factor is fixed at 0.25. Finally, generate a modulated baseband electrical signal that meets the input requirements of the Mach-Zehnder electro-optic modulator to ensure that the baseband signal after predistortion processing completely retains the characteristics of reverse matching full-link transmission impairment. Step 4: Generate two coherent single-frequency optical signals with a frequency difference of 0.23 THz using the optical frequency comb generator at the transmitter. Input the two coherent single-frequency optical signals to the two input ports of the Mach-Zehnder electro-optic modulator, respectively. At the same time, load the modulation baseband electrical signal generated in Step 3 onto the RF drive port of the Mach-Zehnder electro-optic modulator. Through electro-optic modulation, the pre-distorted modulation baseband signal is completely mapped onto the optical domain amplitude and phase of the two coherent optical signals. Then, input the two modulated coherent optical signals into a single-row carrier photodiode for difference frequency processing to generate a 0.23 THz terahertz carrier signal carrying pre-distortion modulation information. Finally, transmit the terahertz carrier signal into the terahertz wireless channel through a terahertz high-gain directional antenna. Step 5: During the continuous transmission of the terahertz signal, the receiver collects the signal-to-noise ratio, bit error rate, and channel attenuation parameters of the received signal in real time. At the same time, it collects the atmospheric temperature, relative humidity, and atmospheric pressure parameters of the outdoor environment. All collected parameters are transmitted back to the transmitter in real time through the low-bandwidth reverse control channel. Based on the transmitted parameters, the transmitter updates the full-link reference transmission model established in Step 1 in real time and updates the predistortion transmission function and predistortion baseband signal calculation parameters in Step 2 in a synchronous manner. This ensures that the predistortion processing always maintains a precise match with the actual transmission characteristics of the current full link and avoids the decrease in pre-cancellation effect caused by changes in the atmospheric environment. Step 6: The receiver receives the terahertz carrier signal transmitted via the terahertz wireless channel through a terahertz high-gain directional antenna of the same specifications as the transmitter. The received terahertz carrier signal is split into two paths. One path is used as the signal light input to the signal input port of the coherent receiver. The other path is mixed with the terahertz local oscillator signal generated locally at the receiver to generate a reference optical signal coherent with the optical frequency comb of the transmitter. The reference optical signal is input to the local oscillator input port of the coherent receiver. The photoelectric conversion of the terahertz signal is completed through coherent detection, and the received baseband electrical signal corresponding to the modulated baseband electrical signal of the transmitter is output. Step 7: Perform synchronization processing on the received baseband electrical signal output from Step 6 to complete carrier frequency offset compensation and symbol timing synchronization. Based on the reference parameters of the pre-distortion processing at the transmitter, construct a sparse equalization matrix that only addresses the residual transmission impairments of the entire link. The residual transmission impairments are the non-stationary impairments remaining after the pre-cancellation processing at the transmitter, caused by channel time-varying errors, atmospheric turbulence disturbances, and device random noise. The sparse equalization matrix is ​​optimized through iterative calculation with sparse constraints. Only the non-zero sparse components corresponding to the residual impairments are compensated. Finally, a high-fidelity baseband signal after equalization processing is output. Step 8: Perform 64QAM quadrature amplitude modulation and demodulation on the equalized baseband signal output from Step 7 to complete the symbol-to-bit stream mapping conversion. Then, perform low-density parity check decoding and cyclic redundancy check on the demodulated bit stream. After the check passes, remove the check bits and coding redundancy bits, and output transmission data that is completely consistent with the original baseband signal input from the transmitter, thus completing the entire signal transmission process.

[0027] Comparative Example This comparative example employs a conventional terahertz high-speed optoelectronic communication signal transmission method, using the exact same hardware test platform, core component specifications, indoor static transmission environment, transmission distance of 10m, target operating frequency band of 0.3THz-0.5THz, and center carrier frequency of 0.4THz as Example 1. The only difference is that this comparative example does not construct a full-link device-channel joint reference transmission model, and the transmitting end does not perform inverse pre-distortion processing for full-link transmission impairments. It only performs the same CRC test on the original baseband signal to be transmitted as in Example 1. The system employs 32-cycle redundancy check coding, low-density parity check coding with a code rate of 0.6, dual-polarization 256QAM modulation, and root-raised cosine shaping filtering with a roll-off factor of 0.2. It lacks a channel state parameter backhaul and transmission model closed-loop update mechanism. The receiver uses a commonly used 128-tap full-order linear equalization scheme to fully compensate for all linear and nonlinear transmission impairments across the entire link. The remaining processes—terahertz carrier generation, optical frequency comb configuration, electro-optic modulation, difference frequency transmission, coherent reception, photoelectric conversion, and demodulation / decoding—are completely consistent with those in Example 1.

[0028] Experimental verification Experimental conditions All tests in this experiment were completed on a unified terahertz optoelectronic communication hardware test platform. The core transmitting, receiving, and baseband processing devices were completely identical in specifications. The test environments were an indoor constant temperature and humidity static environment matching that of Example 1 and the comparative example, and an outdoor dynamic atmospheric environment matching that of Example 2. All test indicators were tested 10 times using standardized communication test instruments such as a 40GHz bandwidth real-time oscilloscope, a terahertz spectrum analyzer, a bit error rate tester, and an optical power meter. The average value was taken as the final test result to ensure the accuracy and repeatability of the test data.

[0029] Core test metrics This test covers three core dimensions: transmission performance, system power consumption, and link stability. The core test indicators include: peak transmission rate, maximum error-free transmission distance, receiver baseband processing power consumption, system average bit error rate, and probability of link interruption during 24-hour continuous testing.

[0030] Experimental Results Table

[0031] Summarize The invention addresses the technical biases and industry pain points in the field of terahertz high-speed optoelectronic communication, breaks through the inherent limitations of existing serial discrete transmission architectures, abandons the conventional approach of single-stage discrete optimization, and constructs a closed-loop collaborative transmission method covering the entire signal transmission and reception process, achieving a leap in overall system performance.

[0032] This invention breaks the inherent technical contradiction of signal quality degradation and transmission distance reduction accompanying the increase in transmission rate by using a joint transmission model of the entire link device and channel and a reverse pre-cancellation design for the full-link impairment at the transmitter. It can achieve ultra-high-speed signal transmission without upgrading the core hardware, which greatly reduces the system implementation threshold and deployment cost. Through dynamic closed-loop collaboration between the transceiver and receiver and low-complexity sparse equalization design for residual impairment at the receiver, it achieves precise collaboration of transceiver processing, solves the high complexity and high power consumption problems caused by full compensation at the receiver in the existing technology, and significantly improves the signal recovery fidelity and the system's anti-interference capability.

[0033] The solution of this invention has strong adaptability to various scenarios and can be flexibly adapted to diverse transmission scenarios. It is compatible with existing 5G / 6G communication standards and can be widely used in core fields such as 6G mobile communication, space-ground integrated communication, and high-speed interconnection of data centers, providing core technical support for the industrialization of terahertz optoelectronic communication technology.

[0034] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A high-speed optoelectronic communication signal transmission method based on terahertz waves, characterized in that, The signal transmission method includes the following steps: Step 1: Collect the device response parameters of the electro-optic modulator and photodetector of the entire terahertz opto-communication link, as well as the transmission characteristic parameters of the terahertz wireless channel. Fit and establish a frequency-domain discretized full-link reference transmission model, and output the comprehensive transmission response and nonlinear distortion coefficient of each frequency point of the entire link to provide a calculation benchmark for transmission impairment pre-cancellation. Step 2: Calculate the full-link integrated transmission function based on the full-link reference transmission model, obtain the perfectly matched predistortion transmission function through inverse fitting, calculate and generate the predistortion baseband signal, and achieve pre-cancellation of full-link linear and nonlinear transmission impairments from the signal transmission source; Step 3: Perform cyclic redundancy check coding, low-density parity check forward error correction coding, high-order orthogonal amplitude modulation mapping and root raised cosine shaping filtering on the predistorted baseband signal in sequence to generate a modulated baseband electrical signal that meets the requirements of electro-optic modulation input. Step 4: Generate two coherent single-frequency optical signals with a frequency difference matching the target terahertz carrier frequency through an optical frequency comb generator, load the modulation baseband electrical signal onto an electro-optic modulator to complete optical domain modulation, and generate a terahertz carrier signal carrying modulation information through difference frequency processing, which is then transmitted to the wireless channel through an antenna. Step 5: The receiver collects channel status parameters and received signal performance parameters in real time, and transmits them back to the transmitter through a low-bandwidth reverse control channel. The receiver updates the full-link reference transmission model and predistortion calculation parameters in real time to ensure that the predistortion processing is accurately matched with the actual transmission characteristics of the link. Step 6: The receiving end receives the transmitted terahertz carrier signal through the terahertz antenna, completes photoelectric conversion through coherent detection, and outputs the received baseband electrical signal corresponding to the modulated baseband electrical signal of the transmitting end. Step 7: After completing carrier and symbol synchronization compensation for the received baseband electrical signal, construct a sparse equalization matrix based on the reference parameters of the predistortion processing at the transmitting end. Optimize the matrix weights through iterative calculation with sparse constraints, and perform low-complexity compensation only for residual transmission impairments across the entire link to output a high-fidelity baseband signal. Step 8: Demodulate, decode, and perform cyclic redundancy check on the equalized high-fidelity baseband signal in sequence. After removing the check bits and encoding redundancy bits, output the original transmission data to complete the entire signal transmission process.

2. The high-speed optoelectronic communication signal transmission method based on terahertz waves according to claim 1, characterized in that: Step one specifically involves: collecting the transmission characteristic parameters of the entire terahertz optoelectronic communication link and constructing a benchmark transmission model. First, a frequency sweep test signal covering the target operating frequency band is transmitted to the entire link through the built-in test signal source at the transmitter. Simultaneously, the amplitude frequency response parameters, phase frequency response parameters, and input-output nonlinear response parameters of the transmitter's electro-optic modulator in the target operating frequency band are collected. The atmospheric attenuation parameters, frequency selective fading parameters, and multipath transmission response parameters of the terahertz wireless channel in the current transmission environment are also collected. The response bandwidth parameters, photoelectric conversion efficiency parameters, and floor noise parameters of the receiver's photodetector in the target operating frequency band are also collected. Then, the collected parameters of the entire link are discretized and fitted to establish a frequency-domain discretized benchmark transmission model corresponding to the target transmission scenario. The model output values ​​are the comprehensive transmission response and comprehensive nonlinear distortion coefficient of the entire link at the corresponding frequency point, providing a benchmark calculation basis for subsequent pre-cancellation processing of the entire link transmission impairment.

3. The high-speed optoelectronic communication signal transmission method based on terahertz waves according to claim 1, characterized in that: In step two, specifically: based on the end-to-end reference transmission model established in step one, the reverse pre-distortion calculation of end-to-end transmission impairment is completed. First, based on the integrated transmission response and integrated nonlinear distortion coefficients at each frequency point output by the end-to-end reference transmission model, the integrated transmission function of the end-to-end in the target operating frequency band is calculated. ,in For operating frequency, It simultaneously includes quantitative characterizations of both linear and nonlinear transmission impairments across the entire link. Then, through inverse fitting calculations, a predistorted transmission function that perfectly inversely matches the overall transmission function of the entire link is obtained. The formula for calculating the predistorted transmission function is as follows: ； in, For predistorted transfer functions, The regularization coefficient is set to the maximum value of the full-link baseband noise power within the target operating frequency band. Finally, based on the predistortion transfer function, the time-domain expression of the predistorted baseband signal corresponding to the original baseband signal is calculated. The time-domain calculation formula for the predistorted baseband signal is as follows: ； in, For predistorted baseband signals, The raw baseband signal to be transmitted. For Fast Fourier Transform operation, To perform the fast inverse Fourier transform operation and generate the predistorted baseband signal, pre-cancellation of linear and nonlinear transmission impairments across the entire transmission link is achieved from the signal transmission source.

4. The high-speed optoelectronic communication signal transmission method based on terahertz waves according to claim 1, characterized in that: In step three, specifically: the forward error correction coding and high-order modulation mapping of the predistorted baseband signal are completed. First, the predistorted baseband signal generated in step two is cyclic redundancy check coding, and then forward error correction coding is completed using low-density parity check code. The coding code rate is fixedly configured according to the full-link signal-to-noise ratio parameters collected in step one. Then, the coded baseband signal is symbol mapped. The mapping method adopts a high-order orthogonal amplitude modulation method that matches the target transmission rate. After the symbol mapping is completed, the baseband symbol is subjected to root-raised cosine shaping filtering. The filter roll-off coefficient is fixed at a constant value between 0.15 and 0.

3. Finally, a modulated baseband electrical signal adapted to the input requirements of the electro-optic modulator is generated.

5. The high-speed optoelectronic communication signal transmission method based on terahertz waves according to claim 1, characterized in that: In step four, specifically: the generation of the terahertz carrier and the electro-optical conversion and transmission of the predistorted modulation signal are completed. First, two coherent single-frequency optical signals with a frequency difference consistent with the target terahertz carrier frequency are generated by the optical frequency comb generator at the transmitting end. The two coherent single-frequency optical signals are respectively input to the two input ports of the Mach-Zehnder electro-optic modulator. At the same time, the modulation baseband electrical signal generated in step three is loaded onto the radio frequency drive port of the Mach-Zehnder electro-optic modulator. The predistorted modulation baseband signal is completely mapped onto the optical domain amplitude and phase of the two coherent optical signals through electro-optic modulation. Then, the two modulated coherent optical signals are input to a single-row carrier photodiode for difference frequency processing to generate a terahertz carrier signal carrying predistorted modulation information. Finally, the terahertz carrier signal is transmitted to the terahertz wireless channel through a terahertz high-gain antenna.

6. The high-speed optoelectronic communication signal transmission method based on terahertz waves according to claim 1, characterized in that: Step five specifically involves: completing real-time status monitoring of the terahertz wireless channel and closed-loop updating of the full-link reference transmission model. During the continuous transmission of the terahertz signal, the receiver collects the signal-to-noise ratio, bit error rate, and channel attenuation parameters of the currently received signal in real time, and simultaneously collects the atmospheric temperature, relative humidity, and atmospheric pressure parameters of the current transmission environment. All collected parameters are transmitted back to the transmitter in real time through a low-bandwidth reverse control channel. The transmitter updates the full-link reference transmission model established in step one in real time based on the transmitted parameters, and synchronously updates the predistortion transmission function and predistortion baseband signal calculation parameters in step two.

7. The high-speed optoelectronic communication signal transmission method based on terahertz waves according to claim 1, characterized in that: Step six specifically involves: completing the coherent reception and photoelectric conversion of the terahertz wireless signal. The receiver receives the terahertz carrier signal transmitted via the terahertz wireless channel through a terahertz high-gain antenna of the same specifications as the transmitter. The received terahertz carrier signal is split into two paths. One path is used as the signal light input to the signal input port of the coherent receiver, and the other path is mixed with the terahertz local oscillator signal generated locally at the receiver to generate a reference optical signal coherent with the optical frequency comb of the transmitter. The reference optical signal is input to the local oscillator input port of the coherent receiver. The photoelectric conversion of the terahertz signal is completed through coherent detection, and the received baseband electrical signal corresponding to the modulated baseband electrical signal of the transmitter is output, thus completing the lossless conversion of the terahertz signal from the optical domain to the electrical domain.

8. The high-speed optoelectronic communication signal transmission method based on terahertz waves according to claim 1, characterized in that: Step seven specifically involves: completing low-complexity sparse equalization compensation for residual transmission impairments of the received baseband electrical signal. First, the received baseband electrical signal output from step six is ​​synchronized to complete carrier frequency offset compensation and symbol timing synchronization. Then, based on the reference parameters from the transmitter's pre-distortion processing, a sparse equalization matrix is ​​constructed specifically for residual transmission impairments across the entire link. The residual transmission impairments are the non-stationary impairments remaining after the transmitter's pre-cancellation processing, caused by channel time-varying errors and device random noise. The formula for updating the weight coefficients of the sparse equalization matrix is ​​as follows: ； in, For the first The weight coefficients of the sparse equilibrium matrix in the next iteration. The iteration step size, For the first The equalization error signal of the next iteration. To receive the baseband signal after synchronization with the input. For symbolic functions, The sparse constraint threshold is set to the root mean square value of the baseband signal's basis noise. The sparse equalization matrix is ​​optimized through iterative calculation, compensating only the non-zero sparse components corresponding to residual damage, and finally outputting a high-fidelity baseband signal after equalization processing.

9. The high-speed optoelectronic communication signal transmission method based on terahertz waves according to claim 1, characterized in that: In step eight, specifically: after completing the demodulation, decoding, and output of the original transmission data of the equalized baseband signal, firstly, the equalized baseband signal output in step seven is subjected to quadrature amplitude modulation demodulation to complete the symbol-to-bit stream mapping conversion, and then the demodulated bit stream is subjected to low-density parity check decoding and cyclic redundancy check. After the check passes, the check bits and coding redundancy bits are removed, and the transmission data that is completely consistent with the original baseband signal input at the transmitter is output, thus completing the entire high-speed optoelectronic communication signal transmission process based on terahertz waves.

Images