Optical true time delay based rof communication method and system

Abstract

This application provides a true optical delay-based ROF communication method and system, belonging to the field of communication technology. The method includes the following steps: At the transmitting end, a multiplexed signal is used by an RoF system to generate an optical carrier signal carrying IQ modulation information, which is then coupled with an optical carrier used for heterodyne beat frequency to generate a coupled optical signal; different time delays are applied to each channel through an optical true delay network to generate multiple time-delay-modulated optical signals, which are then converted into beam-directive radio signals via photoelectric conversion; at the receiving end, the received signal is down-converted to an intermediate frequency signal and remodulated onto the optical carrier for long-distance transmission via optical fiber. This application combines optical domain beamforming with optical fiber transmission to achieve directional transmission of multi-user signals and ultra-long-distance reliable relay, effectively improving spectral efficiency and system anti-interference capability.

Description

Technical Field

[0001] This application relates to the field of communication technology, specifically to a ROF communication method and system based on optical true delay. Background Technology

[0002] ROF (Radio-over-Fiber) technology is a transmission scheme that integrates the advantages of optical fiber communication and wireless communication, and is considered a strong contender for future broadband mobile data communication. Specifically, the ROF architecture, based on optical heterodyne, modulates the signal onto an optical carrier, couples it with a reference light, and transmits it via optical fiber to a remote base station. The base station then performs photoelectric conversion to generate millimeter-wave / terahertz signals, which are ultimately radiated to the user terminal via an antenna.

[0003] However, the RoF architecture in related technologies can only achieve point-to-point information transmission, making it difficult to meet the simultaneous access needs of multiple users. In conventional wireless communication systems, multi-user communication usually relies on phased array technology based on electrical phase shifters. However, since electrical phase shifters introduce fixed phase shifts to different frequency components of the signal, beam squint effect is inevitably generated in broadband signal transmission, which contradicts the broadband transmission characteristics of RoF.

[0004] To address the aforementioned issues, the relevant technologies have not yet offered effective solutions and can no longer meet people's needs, thus requiring urgent improvement. Summary of the Invention

[0005] The main objective of this application is to provide a ROF communication method and system based on an optical true delay network and a simulated beamformer, so as to realize beamless slant-look directional transmission of broadband signals and solve the problem that the ROF architecture in related technologies only supports point-to-point communication.

[0006] The embodiments of this application are implemented using the following technical solutions:

[0007] According to one aspect of the embodiments of this application, a ROF communication method based on optical true delay is provided, comprising: a communication transmitter sending a multiplexed signal to a RoF system; the RoF system generating an IQ modulated coupled optical signal based on the multiplexed signal; amplifying the IQ modulated coupled optical signal and coupling it with an optical carrier signal to generate a coupled optical signal; inputting the coupled optical signal into an optical true delay network; applying different optical true delays to different optical true delay channels to output corresponding time delay modulated optical signals; the time delay modulated optical signals undergoing photoelectric conversion through a photodetector to generate corresponding radio signals; and inputting the coupled optical signals to an analog beamformer to determine the optical true delay of each channel according to preset beam pointing parameters. The delay configuration value of the time channel is set, and the optical transmission path of each optical true delay channel is adjusted based on the delay configuration value. The corresponding physical delay is applied to the optical carrier signal, and the multiple optical carrier signals after delay adjustment are converted into radio signals respectively. The delay data of each optical true delay channel is monitored in real time, and the delay data is compared with the preset theoretical value to obtain calibration parameters. The delay configuration value of each optical true delay channel is adjusted according to the calibration parameters to maintain the delay accuracy of the optical true delay network. The communication receiver receives the radio signal, amplifies and mixes the radio signal to generate the corresponding intermediate frequency signal, re-modulates the intermediate frequency signal, and then amplifies the re-modulated optical signal through an erbium-doped fiber amplifier before transmitting it through an optical fiber for long-distance transmission.

[0008] According to at least one specific embodiment of the present application, the communication transmitter sends a multiplexed signal to the RoF system, and the RoF system generates an IQ modulated coupled optical signal based on the multiplexed signal. The method further includes: the communication transmitter sending the multiplexed signal to the RoF system via digital multicarrier technology; an optical IQ modulator in the RoF system modulating the in-phase component I and quadrature component Q of the multiplexed signal onto an optical carrier, which is generated by a first laser; an optical amplifier amplifying the information-carrying optical signal generated by the IQ modulation; a second laser generating an optical carrier signal; and a polarization-maintaining coupler coupling the optical carrier signal with the IQ modulated coupled optical signal to generate a coupled optical signal.

[0009] According to at least one specific embodiment of the present application, the coupled optical signal is input into an optical true delay network. By applying different optical true delays to different optical true delay channels, a corresponding time delay-modulated optical signal is output. The time delay-modulated optical signal is photoelectrically converted by a photodetector to generate a corresponding radio signal. The method further includes: inputting the coupled optical signal into an analog beamformer; sending the coupled optical signal to different optical true delay channels through the optical beamsplitter of the analog beamformer; applying optical true delay to the coupled optical signal for phase adjustment; and the signals output from the optical true delay channels are photoelectrically converted by photodetectors to generate corresponding millimeter-wave / terahertz signals.

[0010] According to at least one specific embodiment of the present application, the step of inputting the coupled optical signal into a simulated beamformer, sending the coupled optical signal to different optical true delay channels through the optical beam splitter of the simulated beamformer, and applying optical true delay to the coupled optical signal for phase adjustment further includes: the output end of the optical true delay channel is connected to an antenna array through a photodetector; the antenna array is divided into subarrays; the time delay coefficient corresponding to each subarray is calculated; the time delay coefficient is configured into the corresponding optical true delay channel; the optical true delay channels of the subarrays are set according to their respective time delay coefficients, so that the beams generated by each subarray are respectively aligned with the direction of the specified target user.

[0011] According to at least one specific embodiment of the present application, the time delay coefficient is calculated by the formula τ=(n-1)·d·sinθ / c, where n is the array element index, d is the array element interval, θ is the target azimuth angle, and c is the speed of light.

[0012] According to at least one specific embodiment of the present application, the output end of the optical true delay channel is connected to an antenna array via a photodetector. The antenna array is divided into subarrays, and the time delay coefficient corresponding to each subarray is calculated. The antenna array is 1. A 16-antenna array is divided into two subarrays, each with a resolution of 1. 8 uniform linear arrays, with element spacing d =c / ( f s 2), where c is the speed of light. f s for The carrier frequency of millimeter-wave / terahertz signals.

[0013] According to at least one specific embodiment of the present application, a communication receiver receives a radio signal, amplifies and mixes the radio signal to generate a corresponding intermediate frequency (IF) signal, remodulates the IF signal, and transmits the remodulated IF signal into an optical fiber for long-distance transmission. The method further includes: the communication receiver receives the radio signal, amplifies the radio signal using a low-noise amplifier, inputs the amplified radio signal into a mixer and mixes it with a local oscillator signal to obtain a corresponding IF signal; the IF signal is amplified by an electrical amplifier and input into an intensity modulator, modulated onto an optical carrier generated by a laser to generate a corresponding optical double-sideband signal; the optical double-sideband signal is amplified by an erbium-doped fiber amplifier and then transmitted into a single-mode optical fiber for long-distance transmission.

[0014] According to at least one specific embodiment of the present application, the communication receiving end receives a radio signal, amplifies the radio signal using a low-noise amplifier, and inputs the amplified radio signal into a mixer for mixing with a local oscillator signal to obtain a corresponding intermediate frequency (IF) signal. The method further includes: at the wireless receiving end, capturing a directionally transmitted radio signal using a receiving antenna located at a specified position; performing primary amplification of the radio signal using a low-noise amplifier, and inputting the amplified signal into a mixer for mixing with a local oscillator signal; obtaining an IF signal through down-conversion; enhancing the power of the IF signal using an electrical amplifier, and then modulating it onto an optical carrier using an intensity modulator; adjusting the frequency of the input optical carrier to ensure that the center frequency of the output optical carrier carrying user information is consistent with the transmitter's optical carrier; enhancing the power of the modulated optical signal using an erbium-doped fiber amplifier; and then injecting it into a single-mode fiber for long-distance transmission.

[0015] According to at least one specific embodiment of the present application, the method further includes: the communication receiving end filters the received optical signal through an optical bandpass filter, performs coherent detection with the filtered optical signal using the optical carrier generated by the local optical oscillator signal to generate an IQ baseband signal, samples and digitizes the IQ baseband signal through an analog-to-digital converter, and recovers the original transmitted information based on digital signal processing technology.

[0016] According to another aspect of the embodiments of this application, a ROF communication system based on optical true delay is provided for implementing the aforementioned ROF communication method based on optical true delay, comprising: a coupled optical signal generation module, wherein a communication transmitter sends a multiplexed signal to the RoF system, the RoF system generates an IQ modulated coupled optical signal based on the multiplexed signal, amplifies the IQ modulated coupled optical signal, and couples it with an optical carrier signal to generate a coupled optical signal; a photoelectric conversion module, wherein the coupled optical signal is input into an optical true delay network, and by applying different optical true delays to different optical true delay channels, outputs a corresponding time delay modulated optical signal, the time delay modulated optical signal is photoelectrically converted by a photodetector to generate a corresponding radio signal; and the coupled optical signal is input to an analog beamformer, which, according to a preset... The beam pointing parameters determine the delay configuration value of each optical true delay channel. Based on the delay configuration value, the optical transmission path of each optical true delay channel is adjusted, and a corresponding physical delay is applied to the optical carrier signal. The multiple optical carrier signals after delay adjustment are converted into radio signals respectively. The delay data of each optical true delay channel is monitored in real time. The delay data is compared with the preset theoretical value to obtain calibration parameters. The delay configuration value of each optical true delay channel is adjusted according to the calibration parameters to maintain the delay accuracy of the optical true delay network. In the radio signal modulation and transmission module, the communication receiver receives the radio signal, amplifies and mixes the radio signal to generate the corresponding intermediate frequency signal, re-modulates the intermediate frequency signal, and then amplifies the re-modulated optical signal through an erbium-doped fiber amplifier before transmitting it through an optical fiber for long-distance transmission.

[0017] The beneficial technical effects of the embodiments of this application are: The ROF communication method and system based on optical true delay provided in this application integrates the RoF architecture on the basis of related technologies. It utilizes the optical true delay and beamforming characteristics of the RoF architecture to form a complete wireless communication system. By performing complex signal generation, frequency conversion and beam orientation processing in the optical domain, it realizes long-distance directional transmission of signals. Moreover, by adjusting the coefficient of the optical true delay channel, different directional orientations can be achieved. Through the post-electro-optical hybrid architecture, it can achieve reliable signal transmission over ultra-long distances. By combining architectural innovation with digital multi-carrier multiplexing technology, it realizes simultaneous transmission of multiple broadband signals for multiple users. It can also adjust the signal modulation format according to the channel characteristics of different users to achieve stable and reliable signal transmission.

[0018] This application embodiment realizes the directional transmission of high-frequency radio signals (millimeter wave / terahertz), enabling the signals to coherently superimpose in a specific direction in space. Based on this, other directions can cancel each other out, forming a sharp beam, which improves the signal strength in the target direction, extends the transmission distance, and also improves the spectrum utilization and system anti-interference capability through spatial beamforming.

[0019] This application combines optoelectronic integration with fiber optic transmission, integrating the flexibility of wireless communication with the massive capacity, ultra-low loss, and electromagnetic interference resistance of fiber optic communication. At the transmitting end, the RoF (RoboF) architecture modulates the high-frequency wireless signal onto an optical carrier, which is then transmitted to the base station via fiber optics, reducing the deployment cost of complex RF components. At the receiving end, the wireless signal is down-converted to an intermediate frequency (IF) and then modulated back onto the optical carrier for long-distance transmission via single-mode fiber, solving the technical problem of excessive loss when directly transmitting high-frequency wireless signals over long distances. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the specific implementation methods or related technologies of this application, the accompanying drawings used in the description of the specific implementation methods or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some implementation methods of the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the method flow provided in the embodiments of this application.

[0022] Figure 2 This is a schematic diagram of the system architecture provided in the embodiments of this application.

[0023] Figure 3 This is a flowchart of digital signal processing at the transmitting end.

[0024] Figure 4 This is a schematic diagram of the transmitter structure of an RoF system based on optical true delay beamformer.

[0025] Figure 5 This is a schematic diagram of the receiver structure of an RoF system based on an optical true delay beamformer.

[0026] Figure 6 This is a schematic diagram of the digital signal processing structure at the user receiver end. Detailed Implementation

[0027] To enable those skilled in the art to better understand the embodiments of this application, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the implementation methods of the embodiments of this application, and not all of the implementation methods. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the protection scope of the embodiments of this application.

[0028] The RoF architecture, after photoelectric conversion, typically transmits signals directly to users via horn antennas, enabling only point-to-point communication and failing to meet the needs of simultaneous multi-user access. In conventional wireless communication systems, multi-user communication generally relies on phased array technology based on electrical phase shifters. These beamformers apply different phase shifts to multiple electrical signals, causing the outputs of multiple antennas to coherently superimpose in the target direction, thus achieving directional transmission and multi-user access. However, because electrical phase shifters introduce a fixed phase shift to all frequency components, accurate beam pointing can only be formed at the center frequency. In broadband signal transmission, the pointing of different frequency components will deviate, resulting in beam squinting (i.e., beams far from the center frequency cannot be accurately aligned with users, causing a decrease in reception quality), which clearly contradicts the broadband transmission characteristics of RoF.

[0029] In contrast, beamforming technology based on optical true delay networks adjusts the beam direction by introducing precise and controllable time delays in each channel, achieving consistent directional pointing across the entire frequency band and enabling beam-free, look-ahead transmission of broadband signals. Furthermore, the optical approach offers significant advantages in terms of low loss and resistance to electromagnetic interference.

[0030] Based on the aforementioned integrated and innovative architecture, this application's embodiments achieve point-to-multipoint communication based on frequency division multiplexing through algorithm and hardware co-design. At the transmitting end, digital multi-subcarrier multiplexing technology is employed to modulate multiple user signals onto an optical carrier, which is then coupled with a reference light and input to an analog beamformer. At the hardware level, a beamformer codebook based on a dual-uniform subarray configuration flexibly adjusts the optical true delay channel coefficients, thereby enabling simultaneous pointing by multiple users. At the receiving end, the pointed-to user can accurately recover the required information from the received signal through receiver algorithm processing.

[0031] Definitions: Beamforming is a technique that uses array antenna technology to spatially concentrate the energy of transmitted or received signals in a certain direction. By artificially introducing phase differences or time delays in different elements of the array antenna, multiple signals coherently superimpose in the target direction.

[0032] Phase shifter: A device that can adjust the phase of a wave. When a signal passes through a phase shifter, the signal at the output terminal produces a specific phase shift relative to the input terminal.

[0033] Optical True Delay Channel: An optical true delay channel is a transmission path that uses optical devices to achieve a true time delay of a signal. It directly delays the signal in the time domain, thereby changing its phase.

[0034] like Figure 1 The ROF communication method based on true optical delay shown includes: Step S1: The communication transmitter sends a multiplexed signal to the RoF system. The RoF system generates an IQ modulated coupled optical signal based on the multiplexed signal, amplifies the IQ modulated coupled optical signal, and couples it with an optical carrier signal to generate a coupled optical signal.

[0035] Step S2: The coupled optical signal is input into the optical true delay network. By applying different optical true delays to different optical true delay channels, a corresponding time-delay modulated optical signal is output. The time-delay modulated optical signal undergoes photoelectric conversion through a photodetector to generate a corresponding radio signal, and / or: Step S3: Input the coupled optical signal into the analog beamformer, determine the delay configuration value of each optical true delay channel according to the preset beam pointing parameters, adjust the optical transmission path of each optical true delay channel based on the delay configuration value, apply the corresponding physical delay to the optical carrier signal, convert the delay-controlled multi-channel optical carrier signals into radio signals respectively, monitor the delay data of each optical true delay channel in real time, compare the delay data with the preset theoretical value to obtain calibration parameters, and adjust the delay configuration value of each optical true delay channel according to the calibration parameters to maintain the delay accuracy of the optical true delay network.

[0036] Step S4: The communication receiver receives the radio signal, amplifies and mixes the radio signal to generate the corresponding intermediate frequency signal, re-modulates the intermediate frequency signal, and then amplifies the re-modulated optical signal through an erbium-doped fiber amplifier before transmitting it through an optical fiber for long-distance transmission.

[0037] The technical solutions provided in steps S1 to S4 achieve high-precision beamforming and signal transmission through IQ modulation of multiplexed signals, optical carrier coupling, and modulation / demodulation. Based on the synergy of optical domain processing and radio signals, the signal at the communication transmitter is converted into a radio signal that can be transmitted over long distances, ensuring the directionality, accuracy, and stability of the signal transmission process.

[0038] In step S1, the transmitting end generates an optical signal through IQ modulation, providing the foundation signal for subsequent optical true delay network control. Steps S2 and S3 collaboratively or selectively apply adjustable optical true delay, converting the optical signal into a radio signal with a specific beam direction, thus achieving communication directionality. To ensure the stability of the optical true delay, step S3 also dynamically adjusts the delay configuration by real-time monitoring of delay data and comparison with theoretical values, overcoming errors caused by environmental fluctuations or device limitations, and ensuring reliable accuracy in the beamforming process. Steps S2 and S3 utilize the high bandwidth and low loss characteristics of the optical carrier and combine them with the parallel processing capabilities of the optical true delay network to achieve high-fidelity conversion of multiple signals. Step S4 further adapts the signal to long-distance transmission over optical fiber through mixing and remodulation, realizing the coordinated operation from optical signal to electrical signal and back to optical signal.

[0039] The overall technical solution from steps S1 to S4 achieves point-to-multipoint communication based on frequency division multiplexing through algorithm and hardware co-design. At the transmitting end, digital multi-subcarrier multiplexing technology is used to modulate multiple user signals onto an optical carrier, which is then coupled with a reference light and input to an analog beamformer. At the hardware level, this embodiment adjusts the optical true delay channel coefficients based on a beamformer codebook configured with dual or multiple sub-arrays, thereby enabling simultaneous pointing by two or more users. At the receiving end, the pointed user can accurately recover the required information from the received signal through receiving algorithm processing. In summary, the solution provided by steps S1 to S4, with an optical true delay network at its core, achieves both beamforming accuracy and signal transmission efficiency. Furthermore, the dynamic calibration operation in step S3 introduces different time delays in each optical true delay channel to adjust the beam direction, enabling consistent directional pointing of the signal across the entire frequency band. This achieves beam-free, angle-of-sight transmission of broadband signals and also offers significant advantages in terms of low loss and electromagnetic interference resistance.

[0040] To prevent beamforming issues that may occur during system initialization, this application provides a further optimization of step S3. The delay configuration value determined based on preset beam pointing parameters in step S3 is further limited to prevent each optical true delay channel from failing to determine its initial position, thus avoiding initial beam pointing errors caused by starting from a random, uncalibrated state. This provides a correct reference for subsequent beam calibration. Step S31: Calculate the initial delay configuration value of each optical true delay channel based on the preset beam pointing parameters, generate the corresponding first control instruction set, use the first control instruction set to drive each optical true delay channel in the network, apply the specified initial physical delay to the input coupled optical signal by adjusting the physical characteristics of its optical transmission path, and output the pre-modulated multi-channel optical signal.

[0041] Step S32: The optical sampling unit integrated into the output of the optical true delay network periodically collects the optical signal after time delay processing and converts the optical signal into an electrical signal. The timing characteristics contained in the electrical signal are analyzed to obtain the actual time delay measurement value of each channel. The actual time delay measurement value is compared with the pre-stored theoretical time delay value to calculate the calibration parameter set characterizing the time delay deviation.

[0042] Step S33: Based on the calibration parameter set, generate a second control command set to correct the current working state of each optical true delay channel in order to compensate for the measured time delay deviation.

[0043] The optimization techniques provided in steps S31 to S33 automate the calibration of delay settings for each optical true delay channel in the optical true delay network, transforming the static delay settings in related technologies into a dynamic, self-optimizing management process. Step S31 provides an initial accuracy benchmark; the initial delay set according to the theoretical model ensures that the optical true delay network can quickly enter a roughly correct working state. However, due to unpredictable factors such as temperature fluctuations and transmission medium aging, the initial accuracy may gradually be lost. Therefore, step S32 is needed to detect potential initial deviations and continuously monitor the actual delay of each channel. Once step S32 detects a delay deviation, step S33 compensates and corrects the comparison between the theoretical and actual values, enabling the system to actively combat internal and external interference and maintain delay accuracy at a relatively stable level over a long period, thereby ensuring the accuracy and stability of beam pointing. The optimization techniques provided in steps S31 to S33 transform an open-loop delay control system into a closed-loop, stable system with optimization capabilities, preventing it from being affected by external interference.

[0044] Preferably, in step S1, the communication transmitter sends a multiplexed signal to the RoF system, and the RoF system generates an IQ modulated coupled optical signal based on the multiplexed signal, further including: In step S11, the communication transmitter sends a multiplexed signal to the RoF system using digital multicarrier technology. The optical IQ modulator in the RoF system decomposes the multiplexed signal into an in-phase component I and a quadrature component Q, and modulates them onto an optical carrier. The optical carrier is generated by the first laser ECL1. For example, the multiplexed signal is orthogonally decomposed to generate two baseband electrical signals, in-phase (I) and quadrature (Q), which are then modulated onto two optical carriers generated by the first laser ECL1, respectively. One of the optical carriers is orthogonalized through a phase shifter.

[0045] In step S12, the optical signal carrying information generated by IQ modulation is amplified by an optical amplifier, an optical carrier signal is generated by a second laser, and the optical carrier signal is coupled with the IQ modulation coupled optical signal by a polarization maintaining coupler to generate a coupled optical signal.

[0046] In the optimized technical solution provided in steps S11 to S12, the transmitting end of the RoF system generates a coupled optical signal suitable for long-distance transmission by optically modulating the multiplexed signal with IQ modulation in the optical domain and coupling it with a coherent carrier. This allows a single optical carrier to carry multiple information streams, improving spectral efficiency. The first laser ECL1 provides the optical carrier, and the optical IQ modulator completes the modulation of electrical data to the optical domain. Step S12 plays a crucial role in signal enhancement and spectral shaping. The optical amplifier, the second laser ECL2, and the polarization-maintaining coupler first address the issues of signal strength and signal format. The optical amplifier amplifies the modulated weak optical signal to ensure sufficient power for subsequent processing and transmission. Then, the second laser ECL2 generates a new optical carrier, which is coupled with the amplified IQ modulated signal through the polarization-maintaining coupler to generate a coupled optical signal. This converts multiple electrical signals into optical signals, providing the basic signal for subsequent fiber optic transmission.

[0047] Preferably, in step S2, the coupled optical signal is input into the optical true delay network, and different optical true delays are applied to different optical true delay channels to output corresponding time-delay modulated optical signals. The time-delay modulated optical signals are then converted into corresponding radio signals by a photodetector, further comprising: Step S21: Input the coupled optical signal into the simulated beamformer, and send the coupled optical signal to different optical true delay channels through the optical beam splitter of the simulated beamformer to apply optical true delay to the coupled optical signal for phase adjustment. In step S22, the signals output from the optical true delay channel are respectively passed through a photodetector PD for photoelectric conversion to generate corresponding millimeter-wave / terahertz signals. The radio signals generated in step S22 are millimeter-wave / terahertz signals ( f s The radio signal still retains the phase difference formed by the delay of different optical paths, so that after being transmitted by multiple antennas, it can achieve coherent enhancement in a specified direction and realize the directional transmission of the signal.

[0048] The optimized technical solution provided in steps S21 to S22 uses an optical true delay network to apply optical true delay to the coupled optical signal in the optical domain for phase adjustment, and then converts it into a high-frequency radio signal through photoelectric detection. The time delay difference of the optical path is directly mapped to the phase difference of the spatial wavefront, and finally the directional shaping of the beam in the spatial domain is realized.

[0049] Step S21 involves the optical beamsplitter working in conjunction with multiple optical true delay channels. The beamsplitter distributes the signal to each optical true delay channel, which independently applies a precise and realistic physical time delay to the signal. The beam directivity achieved in the optical domain in step S21 is stable over a wide bandwidth, overcoming the beam tilt problem of traditional electronic phased arrays. The optical beamsplitter ensures synchronous signal distribution to each optical true delay channel, while the multiple optical true delay channels provide parallel and independent phase control capabilities, laying the optical foundation for beamforming in subsequent steps.

[0050] Step S22 receives the time-delay-modulated optical signal from step S21 and completes the crucial conversion from optical signal to radio signal via a photodetector PD. The photodetector not only converts the optical signal into an electrical signal but also incorporates the true optical delay characteristics applied to each channel into the phase of the output millimeter-wave / terahertz signal. The different optical path delays set in step S21, after conversion by the photodetector PD, form a precise phase gradient between radiating elements. Based on this phase gradient, the signals emitted by multiple antennas achieve coherent enhancement in a specific direction in space, while canceling each other out in other directions, thus enabling directional signal transmission.

[0051] Preferably, in step S3, the coupled optical signal is input to the analog beamformer, the time delay configuration value of each optical true delay channel is determined according to the preset beam pointing parameters, and the coupled optical signal is sent to different optical true delay channels through the optical beam splitter of the analog beamformer, and the phase of the coupled optical signal is adjusted, further including: Step S31: The output of the optical true delay channel is connected to the antenna array via a photodetector. The antenna array is divided into subarrays, and the time delay coefficient corresponding to each subarray is calculated. For example, the time delay coefficient is calculated using the formula τ=(n-1)·d·sinθ / c, where n is the element index, d is the element spacing, θ is the target azimuth angle, and c is the speed of light. The antenna array is 1... A 16-antenna array is divided into two subarrays, each with a resolution of 1. A uniform linear array of 8 elements with varying element spacing. d =c / ( f s 2), where c is the speed of light. f s for Millimeter wave / terahertz signal.

[0052] Step S32: Configure the time delay coefficients into the corresponding optical true delay channels. The optical true delay channels of the subarrays are set according to their respective time delay coefficients so that the beams generated by each subarray are aligned with the designated target user direction.

[0053] The optimized technical solution provided in steps S31 to S32 divides the large-scale antenna array into multiple subarrays and independently configures the corresponding time delay coefficient for each subarray in the optical true delay network, thereby realizing synchronous control and directional control of multiple beams in different spatial directions. By utilizing subarray division and independent time delay control, single beamforming is extended into parallel, multi-target beamforming.

[0054] Step S3 by 1 The 16-antenna array is logically divided into two 16-antenna arrays. An 8-eight linear array is used, and the corresponding time delay coefficient is independently calculated for each subarray, giving the system multiple independent beam control units. The time delay calculation formula τ=(n-1)·d·sinθ / c applied in step S31 provides a theoretical basis for each subarray to independently point to different angles θ. Step S32 receives the calculated time delay coefficients from step S31 and configures the time delay coefficients into the corresponding optical true delay channels, driving the hardware to generate the expected beam shape. The optical true delay channels of the optical true delay network are grouped according to subarrays, and the optical true delay channels within each subarray work together to achieve coherent enhancement of the generated beam in the specified user direction. Steps S31 to S32 work together to utilize the same set of antennas and optical network infrastructure to simultaneously generate multiple independent beams with high gain, covering multiple users in different directions, significantly improving spatial multiplexing efficiency and system capacity.

[0055] Preferably, in step S4, the communication receiver receives a radio signal, amplifies and mixes the radio signal to generate a corresponding intermediate frequency (IF) signal, re-modulates the IF signal optically, and then amplifies the re-modulated optical signal again via an erbium-doped fiber amplifier before transmitting it through an optical fiber for long-distance transmission. This further includes: Step S41: The communication receiver receives the radio signal, amplifies the radio signal through a low-noise amplifier, and inputs the amplified radio signal into a mixer to mix it with a local oscillator signal to obtain the corresponding intermediate frequency signal. In step S42, the intermediate frequency signal is amplified by an electrical amplifier and then input into the intensity modulator MZM, which modulates it onto the optical carrier generated by the laser to generate the corresponding optical double-sideband signal. Step S43: The optical double-sideband signal is transmitted to a single-mode fiber for long-distance transmission via an erbium-doped fiber amplifier (EDFA).

[0056] For example, in step S41, at the wireless receiver, a directionally transmitted radio signal is captured by a receiving antenna located at a specified position, the radio signal is initially amplified using a low-noise amplifier, and the amplified signal is input into a mixer along with a local oscillator signal (frequency f). LO The intermediate frequency signal f is obtained by performing frequency mixing and down-conversion.IF , where f IF =fs-f LO After the intermediate frequency signal is amplified by an electrical amplifier, it is input to an intensity modulator and modulated onto an optical carrier generated by the third laser ECL3 (the frequency of the optical carrier is configured to f). c1 -f IF This ensures that the center frequency corresponding to the user information is located at the optical carrier f generated by the first laser ECL1. c1 The modulated signal is then boosted by an erbium-doped fiber amplifier and injected into a single-mode fiber for long-distance transmission.

[0057] The optimized technical solution provided in steps S41 to S43 converts the received high-frequency radio signal into an optical signal format suitable for transmission in standard single-mode fiber through cascaded down-conversion and optical remodulation at the communication receiver. Step S41 amplifies the weak high-frequency radio frequency signal and suppresses noise through the coordinated use of a low-noise amplifier and a mixer, then converts it into a lower-frequency, more easily processed intermediate frequency (IF) signal via down-conversion. Step S42 uses an intensity modulator to remodulate the IF signal onto a new optical carrier by setting the optical carrier frequency to f0. c1 -f IF This allows the center frequency of the modulated signal to return to the original optical carrier f at the transmitting end. c1 At the specified frequencies, the spectral alignment design ensures optimal compatibility of the signal format with standard fiber optic transmission links, enabling long-distance transmission. The optical double-sideband signal format generated in step S42 is suitable for transmission in optical fiber. The erbium-doped fiber amplifier in step S43 boosts the power of the suitable optical signal, compensating for transmission losses caused by the fiber optic link. This allows the signal carrying user information to be transmitted over ultra-long distances in single-mode fiber without sacrificing signal-to-noise ratio and signal quality.

[0058] Preferably, in addition to steps S1 to S4, step S5 is further included: The communication receiver filters the received optical signal using an optical bandpass filter, performs coherent detection between the optical carrier generated by the local optical oscillator signal and the filtered optical signal to generate an IQ baseband signal, samples and digitizes the IQ baseband signal using an analog-to-digital converter, and recovers the original transmitted information based on digital signal processing technology.

[0059] Step S5 at the communication receiving end uses coherent optical communication technology to demodulate the long-distance transmitted optical signal with high sensitivity, and finally recovers the original transmitted information completely through digital signal processing. Step S5 uses a filter to remove out-of-band noise and amplifier spontaneous emission noise accumulated during transmission, providing a clean signal for subsequent processing. Then, the optical carrier generated by the local optical oscillator is used to perform coherent detection with the filtered signal, down-converting the signal to baseband, which can effectively extract and amplify weak optical signals. The analog-to-digital converter digitizes the analog IQ baseband signal, and then performs a series of DSP algorithm processing on the digitized IQ baseband signal to finally recover the original transmitted information. Step S5 completely and accurately extracts the information carried by the signals transmitted in steps S1 to S4, realizing the final completion of the entire communication process.

[0060] For the method steps disclosed in the above embodiments, the method steps are described as a series of actions for the purpose of simplicity. However, those skilled in the art should understand that the embodiments of this application are not limited to the described order of actions, because according to the embodiments of this application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also understand that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily necessary for the embodiments of this application.

[0061] like Figure 2 As shown, this application embodiment, based on the ROF communication method based on optical true delay, also provides a corresponding ROF communication system based on optical true delay, including: The coupled optical signal generation module transmits a multiplexed signal to the RoF system from the communication transmitter. The RoF system generates an IQ modulated coupled optical signal based on the multiplexed signal, amplifies the IQ modulated coupled optical signal, and couples it with an optical carrier signal to generate a coupled optical signal. The photoelectric conversion module inputs the coupled optical signal into the optical true delay network, applies different optical true delays to different optical true delay channels, and outputs corresponding time-delay-controlled optical signals. These time-delay-controlled optical signals undergo photoelectric conversion through a photodetector to generate corresponding radio signals, and / or: The coupled optical signal is input to the analog beamformer. The delay configuration value of each optical true delay channel is determined according to the preset beam pointing parameters. The optical transmission path of each optical true delay channel is adjusted based on the delay configuration value. The corresponding physical delay is applied to the optical carrier signal. The multi-channel optical carrier signal with delay control is converted into radio signals respectively. The delay data of each optical true delay channel is monitored in real time. The delay data is compared with the preset theoretical value to obtain calibration parameters. The delay configuration value of each optical true delay channel is adjusted according to the calibration parameters to maintain the delay accuracy of the optical true delay network. The radio signal modulation and transmission module receives radio signals, amplifies and mixes them to generate corresponding intermediate frequency (IF) signals, re-modulates the IF signals, and then amplifies the re-modulated optical signals again through an erbium-doped fiber amplifier before transmitting them over long distances through an optical fiber.

[0062] The implementation methods of the system described above are merely illustrative. For example, the various functional modules, units, or subsystems within the system may or may not be physically separate, or they may or may not be physical units; that is, they may be located in the same place or distributed across multiple different systems and their subsystems or modules. Those skilled in the art can select some or all of the functional modules, units, or subsystems to achieve the objectives of the embodiments of the present invention according to actual needs. Those skilled in the art can understand and implement the above-described situations without any creative effort.

[0063] The technical solutions (including their optimized solutions) provided in steps S1 to S5 are implemented below through specific embodiments: The transmitter uses digital multicarrier technology to generate two user signals, specifically including: like Figure 3 The digital signal processing procedure shown at the transmitting end includes: Step 1. Generate two pseudo-random binary encoded sequences to represent the transmitted information in the actual communication system.

[0064] Step 2. The two generated binary encoded sequences are used to generate two independent complex baseband signals using QAM quadrature amplitude modulation technology (the QAM modulation format of different users' signals can be flexibly adjusted according to their respective channel characteristics).

[0065] Step 3. The two independent complex baseband signals are upsampled and root-raised cosine filtered respectively, so that the signals can meet the sampling requirements of the DAC and realize the pulse shaping of the signals.

[0066] Step 4. Upconvert the two pulse-shaped signals to different signal frequencies (f). s1 and f s2 This ensures that the signal spectrum does not overlap, and subcarrier multiplexing is achieved through time-domain superposition. To improve spectrum utilization, the signal frequency interval is set as small as possible. Specifically, the signal frequency f... s1 = - BW (1 + α) / 2, f s2 =BW (1 + α) / 2, where BW is the signal bandwidth and α is the roll-off factor of the root-raised cosine filter.

[0067] exist Figure 3In Chinese: PRBS - Pseudo-random binary sequence, refers to a random sequence of 0s and 1s generated by an algorithm.

[0068] QAM Modulation: Converts binary bits into radio waveforms, transmitting multiple bits within a symbol by simultaneously changing the amplitude and phase of the carrier wave.

[0069] Up-Sampling: Increases the sampling rate of the signal by inserting several zero values ​​between each point of the original QAM symbol sequence.

[0070] RC Filter - Root-Raised Cosine Filter: A pulse shaping filter used to limit signal bandwidth, confining the signal's spectrum within a preset bandwidth to prevent interference with adjacent channels. RC filters can also be used to eliminate inter-symbol interference, ensuring that when the receiver samples correctly, the waveform of each symbol does not interfere with the sampling points of other symbols, guaranteeing distortion-free signal transmission in bandwidth-constrained channels.

[0071] Up conv. to f s1 - Up-convert to f s1 The spectrum of the baseband signal (center frequency around 0Hz) processed by this specific embodiment is shifted to a high-frequency carrier frequency f. s1 The upper part is used for antenna radiation.

[0072] like Figure 4 The RoF system transmitter, illustrated by the analog beamformer based on an optical true delay network, demonstrates the specific process of generating the transmitter signal and feeding it into the analog beamformer for beamforming. The real part I and imaginary part Q of the complex signal generated by the transmitter's digital signal processing are respectively fed into two sampling rate-matched digital-to-analog converters (DACs) to generate two analog signals. These two analog signals are then amplified by two electrical amplifiers and fed into an optical IQ modulator. The modulator modulates the two signals onto the optical carrier f generated by the laser ECL1. c1 One of the signals passes through a 90° phase shifter, thus achieving orthogonality between the two optical signals. The two orthogonal optical signals are then coupled into a single optical signal via a coupler. This optical signal is then amplified by an optical amplifier (EDFA) and coupled with the optical carrier (f) generated by ECL2. c1 +fs) is coupled to output one optical signal via a polarization-maintaining coupler. The coupled optical signal is then fed into an analog beamformer based on an optical true delay network. The optical true delay network includes multiple optical true delay channels, and the phase of the signals in different channels is adjusted by regulating the delay of different optical paths. The signals output from the optical true delay channels are then photoelectrically converted by photodetectors (PDs) to generate millimeter-wave / terahertz signals f. sThe signals generated by the multi-channel photodetectors still retain the phase difference formed by the time delay of different optical paths, so that after being transmitted by multiple antennas, coherent enhancement can be achieved in a specified direction, thus realizing the directional transmission of the signal.

[0073] Specific implementation of an analog beamformer based on optical true delay: To achieve simultaneous pointing by two users, 1 The 16-antenna array is divided into two subarrays, and different pointing methods are achieved by independently adjusting the coefficients of the time delay channels of the two subarrays (where each subarray is 1). 8-line array, element spacing d =c / ( f s 2), where c is the speed of light); assuming user 1's angle is θ1, then the phase difference brought about by this directional path (with the first array element as a reference) is an = exp(-j 2 pi f (n-1) d sinθ1 / c), where n is the antenna element index; to achieve coherent enhancement of the signal in this direction, the delay of the nth channel is set to (n-1). d sinθ1 / c. The setup of subarray 2 is the same as that of subarray 1.

[0074] Figure 4 In the TX DSP, it refers to the digital signal processing at the transmitting end; IQ Modulator refers to the IQ modulator; and EA is an electrical amplifier.

[0075] like Figure 5 The RoF system receiver shown is based on an optical true delay beamformer. The signal transmitted by the transmitter is directionally transmitted and then received by a receiving antenna located at a specified position. To achieve long-distance signal transmission, this architecture first amplifies the received wireless signal using a low-noise amplifier (LNA), and then inputs it into a mixer along with a local oscillator signal (f...). LO The intermediate frequency signal (f) carrying the transmitted information is obtained by mixing the frequencies. IF = f s -f LO The intermediate frequency signal is amplified by an electrical amplifier and then remodulated by an intensity modulator MZM onto the optical carrier generated by ECL3 (f). c1 -f IF At this point, the center frequency corresponding to the user information is fc1. After passing through the long-distance erbium-doped fiber amplifier (EDFA), the signal is transmitted to the single-mode fiber (SMF) to deliver the signal to the long-distance receiving user. At the receiving end, the signal passes through the optical bandpass filter (OBPF) and utilizes the optical carrier fc1 generated by the local optical oscillator (ECL4).c1 The received signal is coherently detected by an integrated coherent receiver (ICR). The IQ signal from the coherent detection is then fed into an analog-to-digital converter (ADC) for signal sampling and digitization processing. Subsequently, a digital DSP is used to recover the transmitted information.

[0076] like Figure 6 The digital signal processing flow at the user receiver end is shown. After receiving signals from both users, the signals are sampled and digitized by an analog-to-digital converter (ADC) to generate digital signals. These digital signals are then subjected to down-conversion, low-pass filtering, downsampling, clock recovery, channel equalization, and phase recovery to recover the information transmitted by the transmitter. The implementation of down-conversion varies slightly for different users; for user 1, the down-conversion frequency is f. s1 For user 2, the frequency of the downconverter is f. s2 Below is Figure 6 Definitions of terms in Chinese: Downconversion, or down-conversion, is used to shift the digital intermediate frequency signal sampled by the ADC back to the baseband (i.e., the center frequency is 0Hz) through digital mixing. User 1 and User 2 will use different frequencies (f... s1 and f s2 The signal is down-converted to separate the signals of the two users.

[0077] The LPF (Low-Pass Filter) is used after down-conversion to filter out high-frequency image components and out-of-band noise generated during the mixing process, retaining only the required baseband signal.

[0078] Down sampling reduces the data rate to the optimal rate corresponding to one or two sampling points per symbol, which is equivalent to the reverse process of up sampling at the transmitting end.

[0079] Clock Recovery is the process by which a receiver accurately locates the start and end times of each symbol in the received data stream to determine the optimal time to sample the signal and minimize bit errors. Therefore, it is necessary to recover the clock at the transmitting end.

[0080] CMA & RDE – Constant Modulus Equalization (CMA) and Radius-Oriented Equalization (RDE) – are two channel equalization algorithms used to compensate for signal distortion and inter-symbol interference during channel transmission. The system needs to use either these algorithms in combination or adaptively select them to cope with different channel conditions and modulation formats.

[0081] CPR (Carrier Phase Recovery) corrects carrier phase noise and frequency offset generated by the transmitting laser, the receiving local laser, and during transmission, ensuring that the constellation diagram is stable and clear during demodulation at the receiving end.

[0082] BER (Bit Error Rate) is the ratio of the number of bits recovered from errors at the receiver to the total number of bits. BER = Number of erroneous bits / Total bits. A lower BER indicates better system performance and higher reliability.

[0083] As can be seen from the specific embodiments described above, the fiber-optic wireless hybrid system architecture based on an optical true delay beamformer provided in this application can achieve both directional transmission of broadband signals and different directional orientations by adjusting the coefficients of the optical true delay channel. The post-electro-optical hybrid architecture enables reliable signal transmission over ultra-long distances. By combining the above innovative architecture with digital multi-carrier multiplexing technology, this application embodiment can achieve simultaneous transmission of multiple broadband signals to two users. Furthermore, the signal modulation format can be adjusted according to the channel characteristics of different users to achieve stable and reliable transmission. This application embodiment can be applied to future 6G high-capacity long-distance multi-user real-time communication systems to achieve directional transmission of broadband signals, solving the problem that RoF in related technologies can only achieve point-to-point transmission.

[0084] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the specification of the embodiments of this application.

[0085] In the description of the embodiments of this application, the reference to terms such as "an embodiment," "example," "specific example," etc., means that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0086] Furthermore, the technical solutions of the various implementation methods in this application can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the embodiments of this application.

[0087] All features disclosed in the embodiments of this application, or all steps in the disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps. Any feature disclosed in the specification of the embodiments of this application, unless specifically stated otherwise, may be replaced by other equivalent or similar alternative features. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features. Throughout the specification, the same reference numerals indicate the same elements.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of this application, and are not intended to limit them. Although the embodiments of this application have been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing specific embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this invention.

Claims

1. A ROF communication method based on optical true delay, characterized in that, include: The communication transmitter sends a multiplexed signal to the RoF system. The RoF system generates an IQ modulated coupled optical signal based on the multiplexed signal, amplifies the IQ modulated coupled optical signal, and couples it with an optical carrier signal to generate a coupled optical signal. The coupled optical signal is input into the optical true delay network. By applying different optical true delays to different optical true delay channels, a corresponding time delay modulated optical signal is output. The time delay modulated optical signal is photoelectrically converted by a photodetector to generate a corresponding radio signal. The coupled optical signal is input to the analog beamformer. The delay configuration value of each optical true delay channel is determined according to the preset beam pointing parameters. The optical transmission path of each optical true delay channel is adjusted based on the delay configuration value. The corresponding physical delay is applied to the optical carrier signal. The multi-channel optical carrier signal with delay control is converted into radio signals respectively. The delay data of each optical true delay channel is monitored in real time. The delay data is compared with the preset theoretical value to obtain calibration parameters. The delay configuration value of each optical true delay channel is adjusted according to the calibration parameters to maintain the delay accuracy of the optical true delay network. The communication receiver receives the radio signal, amplifies and mixes the radio signal to generate the corresponding intermediate frequency signal, re-modulates the intermediate frequency signal, and then amplifies the re-modulated optical signal through an erbium-doped fiber amplifier before transmitting it through an optical fiber for long-distance transmission.

2. The ROF communication method based on true optical delay according to claim 1, characterized in that, The communication transmitter sends a multiplexed signal to the RoF system, and the RoF system generates an IQ modulated coupled optical signal based on the multiplexed signal, further including: The communication transmitter sends a multiplexed signal to the RoF system through digital multicarrier technology. The optical IQ modulator in the RoF system modulates the in-phase component I and quadrature component Q of the multiplexed signal onto the optical carrier, which is generated by the first laser. The optical signal carrying information generated by IQ modulation is amplified by an optical amplifier, and an optical carrier signal is generated by a second laser. The optical carrier signal is coupled with the IQ modulated coupled optical signal through a polarization-maintaining coupler to generate a coupled optical signal.

3. The ROF communication method based on true optical delay according to claim 1, characterized in that, The coupled optical signal is input into an optical true delay network. By applying different optical true delays to different optical true delay channels, a corresponding time-delay modulated optical signal is output. The time-delay modulated optical signal undergoes photoelectric conversion through a photodetector to generate a corresponding radio signal. The network further includes: The coupled optical signal is input into the simulated beamformer, and the optical beam splitter of the simulated beamformer sends the coupled optical signal to different optical true delay channels. The optical true delay is applied to the coupled optical signal to adjust the phase. The signals output from the optical true delay channel are converted into corresponding millimeter-wave / terahertz signals by photodetectors.

4. The ROF communication method based on true optical delay according to claim 3, characterized in that, The step of inputting the coupled optical signal into a simulated beamformer, sending the coupled optical signal to different optical true delay channels through the optical beam splitter of the simulated beamformer, and applying an optical true delay to the coupled optical signal for phase adjustment further includes: The output of the optical true delay channel is connected to the antenna array through a photodetector. The antenna array is divided into subarrays, and the time delay coefficient corresponding to each subarray is calculated. The time delay coefficient is configured into the corresponding optical true delay channel. The optical true delay channels of the subarray are set according to their respective time delay coefficients, so that the beams generated by each subarray are respectively aligned with the designated target user direction.

5. The ROF communication method based on true optical delay according to claim 4, characterized in that, The time delay coefficient is calculated using the formula τ=(n-1)·d·sinθ / c, where n is the array element index, d is the array element interval, θ is the target azimuth angle, and c is the speed of light.

6. The ROF communication method based on true optical delay according to claim 4, characterized in that, The output of the optical true delay channel is connected to the antenna array via a photodetector. The antenna array is divided into subarrays, and the time delay coefficient corresponding to each subarray is calculated. The antenna array is 1. A 16-antenna array is divided into two subarrays, each with a resolution of 1. 8 uniform linear arrays, with element spacing d =c / ( f s 2), where c is the speed of light. f s for The carrier frequency of millimeter-wave / terahertz signals.

7. The ROF communication method based on true optical delay according to claim 1, characterized in that, The communication receiver receives a radio signal, amplifies and mixes the radio signal to generate a corresponding intermediate frequency (IF) signal, remodulates the IF signal, and transmits the remodulated IF signal through an optical fiber for long-distance transmission. This further includes: The communication receiver receives a radio signal, amplifies the radio signal through a low-noise amplifier, and then inputs the amplified radio signal into a mixer to mix it with a local oscillator signal to obtain the corresponding intermediate frequency signal. The intermediate frequency signal is amplified by an electrical amplifier and then input into an intensity modulator, which modulates it onto the optical carrier generated by the laser to generate a corresponding optical double-sideband signal. The signal is amplified by an erbium-doped fiber amplifier and then transmitted over long distances through a single-mode fiber via a double-sideband optical fiber.

8. The ROF communication method based on optical true delay according to claim 7, characterized in that, The communication receiver receives a radio signal, amplifies the radio signal using a low-noise amplifier, and then inputs the amplified radio signal into a mixer to mix it with a local oscillator signal to obtain the corresponding intermediate frequency signal. The process further includes: At the wireless receiver, the directional radio signal is captured by the receiving antenna located at a specified position; the radio signal is amplified by a low-noise amplifier, and the amplified signal is input into a mixer to be mixed with the local oscillator signal. The intermediate frequency signal is obtained by down-conversion. After the intermediate frequency signal is amplified by an electrical amplifier, it is input to an intensity modulator and modulated onto an optical carrier. By adjusting the frequency of the input optical carrier to the intensity modulator, the center frequency of the output optical carrier carrying user information is made consistent with the optical carrier of the transmitter. After the modulated signal is amplified by an erbium-doped fiber amplifier, it is injected into a single-mode fiber for long-distance transmission.

9. The ROF communication method based on true optical delay according to claim 1, characterized in that, Also includes: The communication receiver filters the received optical signal using an optical bandpass filter, performs coherent detection between the optical carrier generated by the local optical oscillator signal and the filtered optical signal to generate an IQ baseband signal, samples and digitizes the IQ baseband signal using an analog-to-digital converter, and recovers the original transmitted information based on digital signal processing technology.

10. A true optical delay-based ROF communication system for implementing the true optical delay-based ROF communication method according to any one of claims 1 to 9, characterized in that, include: The coupled optical signal generation module transmits a multiplexed signal to the RoF system from the communication transmitter. The RoF system generates an IQ modulated coupled optical signal based on the multiplexed signal, amplifies the IQ modulated coupled optical signal, and couples it with an optical carrier signal to generate a coupled optical signal. The photoelectric conversion module inputs the coupled optical signal into the optical true delay network, applies different optical true delays to different optical true delay channels, and outputs corresponding time delay modulated optical signals. The time delay modulated optical signals are photoelectrically converted by a photodetector to generate corresponding radio signals. The coupled optical signal is input to the analog beamformer. The delay configuration value of each optical true delay channel is determined according to the preset beam pointing parameters. The optical transmission path of each optical true delay channel is adjusted based on the delay configuration value. The corresponding physical delay is applied to the optical carrier signal. The multi-channel optical carrier signal with delay control is converted into radio signals respectively. The delay data of each optical true delay channel is monitored in real time. The delay data is compared with the preset theoretical value to obtain calibration parameters. The delay configuration value of each optical true delay channel is adjusted according to the calibration parameters to maintain the delay accuracy of the optical true delay network. The radio signal modulation and transmission module receives radio signals, amplifies and mixes them to generate corresponding intermediate frequency (IF) signals, re-modulates the IF signals, and then amplifies the re-modulated optical signals again through an erbium-doped fiber amplifier before transmitting them over long distances through an optical fiber.

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