A Multi-Frequency RF Optical Backhaul Method and System Based on DWDM Dynamic Wavelength Mapping

Abstract

This application discloses a multi-frequency radio frequency optical backhaul method and system based on DWDM dynamic wavelength mapping, relating to the field of optical carrier multiplexing technology. The method includes: digitizing multiple radio frequency signals of different frequency bands and performing orthogonal mapping processing based on a preset orthogonal vector group to convert each frequency band signal into mutually orthogonal vectorized sub-signals, forming a composite baseband signal; dynamically selecting a suitable DWDM transmission wavelength according to real-time link crosstalk strength and optical power constraints to optimize signal transmission performance and reduce crosstalk; performing pre-distortion compensation on the composite baseband signal using a nonlinear model of the optical fiber link to offset nonlinear distortion during optical fiber transmission; optically modulating the pre-compensated signal at a dynamically determined wavelength and coupling the signal to a single optical fiber link for transmission using a DWDM optical multiplexer. Through dynamic wavelength allocation and nonlinear compensation, the multi-frequency signal transmission performance is improved, and the capacity and stability of the optical fiber system are optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical carrier multiplexing, and in particular to a multi-frequency radio frequency optical backhaul method and system based on DWDM dynamic wavelength mapping. BACKGROUND

[0002] In modern communication networks, mobile communication has increasingly higher requirements for transmission bandwidth and signal fidelity. Radio over Fiber (RoF) technology carries radio frequency signals through optical fibers, which can realize centralized processing of remote wireless signals, thereby saving base station hardware costs and improving flexibility. The RoF system usually adopts an external modulation structure to load radio frequency signals onto optical carriers, and relies on the advantages of low loss and anti-electromagnetic interference of optical fibers to realize long-distance transmission. However, the traditional RoF system mainly targets a single frequency band (such as millimeter wave) or a small number of frequency bands, and lacks effective isolation and collaborative transmission capabilities for multi-frequency radio frequency signals.

[0003] To improve the transmission capacity of optical fibers, Dense Wavelength Division Multiplexing (DWDM) technology has emerged. DWDM uses lasers of different wavelengths to multiplex multiple signals into a single optical fiber, greatly improving the capacity of a single fiber. After the DWDM multiplexer combines the signals of different wavelengths and transmits them into the optical fiber, the central device uses a demultiplexer to separate each wavelength and send it to the corresponding optical-electric converter, thereby realizing the transmission effect of one fiber with multiple waves. In theory, DWDM can divide the entire 20 THz of spectral bandwidth into hundreds of wavelength channels, greatly improving the utilization rate of optical fibers.

[0004] However, in the process of multi-wavelength parallel transmission, the nonlinear effects, dispersion in optical fibers, and physical limitations of devices can cause inter-channel crosstalk and signal distortion. Especially in radio frequency optical systems, when different radio frequency bands are mapped to adjacent optical wavelengths, changes in optical intensity can cause phase modulation through the Kerr effect, which is then converted into intensity noise through dispersion, forming cross-channel crosstalk. When the transmission distance increases or the optical power increases, the Cross-Phase Modulation (XPM) effect becomes more serious, and traditional compensation methods such as Dispersion Compensating Fiber (DCF) and Erbium-Doped Fiber Amplifier (EDFA) mainly solve the problems of loss and dispersion, and are difficult to suppress nonlinear crosstalk. SUMMARY

[0005] The application provides a multi-frequency radio frequency optical backhaul method and system based on DWDM dynamic wavelength mapping, a storage medium, a computer program product and an electronic device, to at least solve the problem that multi-wavelength radio frequency optical transmission is prone to nonlinear crosstalk and difficult to maintain the independence of multi-frequency signals.

[0006] In a first aspect, the embodiments of the application provide a multi-frequency radio frequency optical backhaul method based on DWDM dynamic wavelength mapping, applied to a remote wireless node, the method comprising: collecting radio frequency signals of multiple different frequency bands, and performing digital processing on the radio frequency signals to generate multi-frequency digital baseband signals; performing orthogonal mapping processing on the multi-frequency digital baseband signals based on a preset orthogonal vector group, expanding each frequency band signal into a vectorized sub-signal orthogonal to each other, and superimposing to form a composite baseband signal; dynamically determining a DWDM transmission wavelength of the composite baseband signal according to a real-time measured link crosstalk strength and an optical power constraint; performing pre-distortion compensation processing on the composite baseband signal based on a nonlinear model of a fiber link to generate a pre-compensation signal for offsetting fiber transmission nonlinear distortion; and modulating the pre-compensation signal in an optical domain at the dynamically determined DWDM transmission wavelength, and coupling to a single fiber link through a DWDM optical multiplexer for transmission to a central device.

[0007] In a second aspect, the embodiments of the application provide a multi-frequency radio frequency optical backhaul system based on DWDM dynamic wavelength mapping, deployed in a remote wireless node, the system comprising: a radio frequency signal collection unit configured to collect radio frequency signals of multiple different frequency bands, and perform digital processing on the radio frequency signals to generate multi-frequency digital baseband signals; an orthogonal mapping unit configured to perform orthogonal mapping processing on the multi-frequency digital baseband signals based on a preset orthogonal vector group, expand each frequency band signal into a vectorized sub-signal orthogonal to each other, and superimpose to form a composite baseband signal; a wavelength allocation unit configured to dynamically determine a DWDM transmission wavelength of the composite baseband signal according to a real-time measured link crosstalk strength and an optical power constraint; a pre-distortion compensation unit configured to perform pre-distortion compensation processing on the composite baseband signal based on a nonlinear model of a fiber link to generate a pre-compensation signal for offsetting fiber transmission nonlinear distortion; and an optical domain modulation unit configured to modulate the pre-compensation signal in an optical domain at the dynamically determined DWDM transmission wavelength, and couple to a single fiber link through a DWDM optical multiplexer for transmission to a central device.

[0008] In a third aspect, an electronic device is provided, comprising at least one processor, and a memory connected to the at least one processor in communication, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the steps of the multi-frequency radio frequency optical backhaul method based on DWDM dynamic wavelength mapping of any embodiment of the application.

[0009] In a fourth aspect, an embodiment of the present application provides a storage medium having stored thereon a computer program, wherein the program, when executed by a processor, implements the steps of the method for multi-frequency radio frequency optical backhaul based on DWDM dynamic wavelength mapping according to any one of the embodiments of the present application.

[0010] In a fifth aspect, an embodiment of the present application provides a computer program product, comprising computer programs / instructions, which, when executed by a processor, implement the steps of the method for multi-frequency radio frequency optical backhaul based on DWDM dynamic wavelength mapping according to any one of the embodiments of the present application.

[0011] The method and system for multi-frequency radio frequency optical backhaul based on DWDM dynamic wavelength mapping provided by the present application can at least produce the following technical effects:

[0012] (1) The traditional DWDM system usually adopts fixed wavelength allocation, which is prone to inter-frequency crosstalk or cannot optimize wavelength allocation according to the actual link conditions. However, the present application dynamically selects appropriate DWDM transmission wavelengths by real-time measurement of the crosstalk intensity and optical power constraints in the link, optimizes the transmission conditions of each signal, and realizes effective transmission of multi-frequency radio frequency signals through the dynamic wavelength mapping method based on DWDM. Based on flexible wavelength selection, different frequency bands of signals are effectively isolated, and the transmission performance of signals is greatly improved by adaptively adjusting according to the changes in the link environment and avoiding the interference risk caused by fixed wavelengths.

[0013] (2) When multi-frequency signals are transmitted through optical fibers, nonlinear effects (such as cross-phase modulation) can cause signal distortion and crosstalk, especially when the transmission distance of the optical fiber increases or the optical power increases, the nonlinear distortion is more serious. The traditional solution relies on dispersion compensation optical fiber and optical fiber amplifier to alleviate the loss and dispersion problem, but it is not directly effective in dealing with nonlinear effects. By introducing pre-distortion compensation based on the nonlinear model of the optical fiber link, the signal is compensated in advance to accurately offset the nonlinear distortion, so that the signal can maintain higher integrity during transmission in the optical fiber, reducing the bit error and signal distortion caused by nonlinear effects, thereby improving the overall performance and reliability of the system.

[0014] (3) By performing orthogonal mapping on the multi-frequency radio frequency signals to form mutually orthogonal vectorized sub-signals, effective modulation is performed in the optical domain, avoiding the interference and crosstalk between frequency bands in the traditional method. The orthogonal mapping technology makes each frequency band signal not interfere with each other, thereby improving the parallel transmission capability of multi-frequency signals in the optical fiber and significantly increasing the transmission efficiency of the system. Therefore, combined with the dynamic wavelength mapping and pre-distortion compensation technologies, the utilization efficiency and signal quality of the transmission link are further improved.

[0015] Through the technical scheme, the efficient transmission of the multi-frequency radio frequency signal in the DWDM system is successfully realized by combining the dynamic wavelength mapping, the orthogonal signal processing and the nonlinear pre-compensation technology, the bandwidth utilization and the signal quality are significantly improved, and the long-distance remote transmission performance of the high-bandwidth multi-frequency signal is especially optimized. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] Figure 1 A flow chart of an example of a multi-frequency radio frequency optical backhaul method based on DWDM dynamic wavelength mapping according to an embodiment of the present application is shown;

[0018] Figure 2 An example of an operation flow chart of generating a composite baseband signal by orthogonal mapping according to an embodiment of the present application is shown;

[0019] Figure 3 An example of an operation flow chart of dynamically determining the DWDM transmission wavelength of the composite baseband signal according to an embodiment of the present application is shown;

[0020] Figure 4 An example of an operation flow chart of generating a pre-compensation signal based on a weighted asymmetric Volterra pre-compensation model according to an embodiment of the present application is shown;

[0021] Figure 5 An example of an operation flow chart of DWDM system optical domain modulation according to an embodiment of the present application is shown;

[0022] Figure 6 A comparative effect diagram of an example of the inter-channel crosstalk level of the DWDM channel of different methods is shown;

[0023] Figure 7 A comparative effect diagram of an example of the bit error rate change with the fiber length of different methods is shown;

[0024] Figure 8 A structure block diagram of an example of a multi-frequency radio frequency optical backhaul system based on DWDM dynamic wavelength mapping according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, 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 some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] It should be noted that the paper "Enhancement on the performance of Radio-over-FiberROF technology" points out that for millimeter-wave RoF modulation and compensation, adjusting the switching voltage of the Mach-Zehnder modulator can optimize the eye diagram opening of the SCM-ASK (Subcarrier Multiplexed Amplitude Shift Keying) modulated signal. Furthermore, inserting erbium-doped fiber amplifiers (EDFAs) at intervals along the transmission link enhances the signal, thus achieving the optimal switching voltage. This approach demonstrates the impact of external modulator parameters on RoF performance; however, this research still focuses on a single millimeter-wave frequency band and primarily improves modulation efficiency without addressing the crosstalk problem associated with multi-frequency co-transmission.

[0027] The paper "Performance Evaluation of DWDM for Radio over Fiber System with Dispersion Compensation and EDFA" proposes that, for the application of DWDM systems in RoF, the introduction of EDFA and dispersion-compensating fiber (DCF) can compensate for fiber attenuation and dispersion, thereby improving system performance at different fiber lengths and bit rates. The study points out that EDFA is used to compensate for attenuation and scattering loss in the optical path, while DCF is used to compensate for dispersion; the combination of the two can significantly increase the transmission distance of the DWDM RoF system, reducing the bit error rate to within 10-1. -9 The fiber length has been significantly increased. Furthermore, the paper points out that WDM (Wavelength Division Multiplexing) technology improves fiber utilization by carrying multiple signals of different wavelengths on a single fiber. However, these schemes primarily focus on loss and dispersion compensation, neglecting deeper issues such as nonlinear crosstalk, channel isolation, and multi-frequency sharing. The paper also notes that the design of wavelength division multiplexers and demultiplexers should balance reducing crosstalk and increasing channel isolation; however, in practical systems, due to device filtering characteristics and optical power limitations, adjacent-channel crosstalk is still difficult to completely suppress, especially in high-power, multi-channel scenarios.

[0028] Early theoretical and experimental studies on XPM showed that the degree of cross-phase modulation crosstalk is closely related to fiber dispersion and channel spacing. When fiber dispersion is large or channel spacing is small, XPM crosstalk is significantly enhanced. Furthermore, when propagating across multiple fiber amplification sections, XPM crosstalk generated by different amplification sections interferes with each other, affecting the frequency response of the entire system. Although phase noise in a single optical channel does not directly degrade the performance of the IM-DD system, dispersion converts phase noise into intensity noise, leading to an increase in the bit error rate. Therefore, suppressing crosstalk requires not only optimizing wavelength spacing and power but also designing new signal mapping and compensation methods.

[0029] Some studies have also proposed an improved tandem single-sideband (TSSB) modulation scheme for 60 GHz millimeter-wave RoF. This scheme utilizes a dual-electrode Mach-Zehnder modulator to generate two optical sidebands and suppress the optical carrier, obtaining the millimeter-wave signal at the receiver through optical beat frequency. This scheme achieves frequency doubling and avoids dispersion-induced fading, while supporting high-spectral-efficiency vector modulation signals. By removing the original optical carrier and utilizing the beat frequencies of both sidebands, a carrier-free 60 GHz RF signal can be generated, avoiding the dispersion fading present in traditional double-sideband schemes. However, this technology is mainly designed for a specific frequency band (60 GHz) and single-channel transmission, lacking flexibility when facing multi-band and multi-service requirements. Furthermore, the high-frequency modulator is costly and the system structure is complex.

[0030] It should be understood that the above description of the relevant technologies is intended only to help the public better understand the inventive spirit and motivation of this application, and is not intended to limit this application. Furthermore, the technical solutions described in the above-mentioned relevant technologies are not prior art, and may also be undisclosed technical solutions, such as those under research or in the laboratory stage.

[0031] The technical solutions in this application, including the collection, storage, use, processing, transmission, provision, and disclosure of users' personal information, comply with relevant laws and regulations and do not violate public order and good morals.

[0032] Figure 1 A flowchart illustrating an example of a multi-frequency radio frequency optical backhaul method based on DWDM dynamic wavelength mapping according to an embodiment of this application is shown.

[0033] Regarding the execution subject of the method in this application embodiment, it can be any controller or processor with computing or processing capabilities, such as the signal processing controller of a remote wireless node. This controller has functions such as signal acquisition, processing, wavelength mapping selection, and distortion compensation. Specifically, the DWDM transmission wavelength of the composite baseband signal can be dynamically adjusted according to the real-time measured link status (such as crosstalk intensity, optical power, etc.), and combined with orthogonal signal processing and nonlinear distortion pre-compensation technology, to ensure efficient signal transmission and minimal distortion during optical fiber transmission.

[0034] Regarding remote wireless communication nodes, they can be applied to high-bandwidth communication scenarios requiring parallel transmission of signals across multiple frequency bands. Specifically, remote wireless nodes can optimize signal transmission paths in complex fiber optic transmission environments, effectively address issues such as fiber nonlinearity and crosstalk, ensure stable backhaul transmission of multi-frequency radio frequency signals, and improve the overall system's communication capabilities and reliability.

[0035] In some examples, it may be integrated into an electronic device or terminal through software, hardware, or a combination of both, and the type of terminal or electronic device may be diverse.

[0036] like Figure 1 As shown, in step S110, multiple radio frequency signals of different frequency bands are acquired and the radio frequency signals are digitally processed to generate multi-frequency digital baseband signals.

[0037] It should be noted that the radio frequency receiving system collects signals from different radio frequency bands. Each radio frequency signal is typically an analog signal containing useful communication data. The signals from different radio frequency bands can be radio frequency signals from different wireless standards (such as 5G low-frequency, millimeter wave, Wi-Fi, satellite links, etc.), which need to be digitally converted. For example, the radio frequency signals are digitized through a broadband analog-to-digital converter, and amplitude normalization and digital filtering are performed.

[0038] In some implementations, multiple radio frequency (RF) signals in different frequency bands are acquired from multiple wireless nodes via antennas at remote wireless nodes. These RF signals may originate from multiple base stations or wireless devices, covering different frequency bands, such as 2.4 GHz, 5 GHz, or even millimeter-wave bands (e.g., 28 GHz or higher). Since these RF signals differ in their spectral distribution, the acquired RF signals undergo analog-to-digital conversion (ADC) before entering a digital signal processing unit (DSP). At this point, the RF signal of each frequency band is digitized and converted into a corresponding digital baseband signal. The digital baseband signal is a discrete representation of each frequency band signal in its original frequency domain. This enables the synchronous acquisition and digitization of multiple RF signals, ensuring that all RF signals can be accurately processed and scheduled in the digital domain.

[0039] In step S120, the multi-frequency digital baseband signal is orthogonally mapped based on a preset orthogonal vector group, expanding each frequency band signal into mutually orthogonal vectorized sub-signals, and superimposing them to form a composite baseband signal.

[0040] Specifically, the frequency domain information of each frequency band signal is transformed into a corresponding vector using specific orthogonal coding rules. The orthogonal mapping process ensures that the signal in each frequency band can be decoded independently during transmission, without crosstalk effects causing mutual interference. Multiple orthogonal sub-signals are superimposed into a composite baseband signal, forming a comprehensive digital signal stream.

[0041] In some implementations, orthogonal frequency division multiplexing (OFDM) or similar orthogonal mapping techniques can be used to map the digital signal of each frequency band to a high-dimensional orthogonal space. Each frequency band signal is expanded into multiple independent sub-signals through a set of orthogonal vectors, and these sub-signals are mutually orthogonal in the frequency domain. Then, these orthogonal sub-signals are superimposed to form a composite baseband signal.

[0042] As a result, multiple frequency band signals maintain an orthogonal relationship, remain independent during transmission, avoid interference or crosstalk between signals, and can efficiently utilize available bandwidth.

[0043] In step S130, the DWDM transmission wavelength of the composite baseband signal is dynamically determined based on the real-time measured link crosstalk intensity and optical power constraints.

[0044] Here, the system selects the most suitable wavelength based on the real-time operating status of the fiber optic link (such as optical power and link crosstalk) to ensure the stability and quality of signal transmission.

[0045] In some implementations, real-time monitoring data from remote wireless nodes is used to monitor the optical power and crosstalk intensity of the fiber optic link, including optical power, link noise, inter-channel crosstalk, and other factors that may affect signal quality. Based on this real-time data, the transmission capacity of each possible DWDM wavelength under the current link conditions is calculated. When a change in link status or an increase in system load is detected, the transmission wavelength can be adjusted in real time to avoid exacerbating crosstalk.

[0046] Therefore, by utilizing dynamic wavelength mapping technology, the system can automatically adapt to different link conditions. Through dynamic wavelength adjustment, it can effectively reduce link crosstalk and signal distortion crosstalk caused by improper wavelength selection between different signals, optimize the utilization of fiber bandwidth, maintain high-efficiency transmission performance under constantly changing transmission conditions, and improve the system's adaptive capability to changes in fiber optic links.

[0047] In step S140, pre-distortion compensation processing is performed on the composite baseband signal based on the nonlinear model of the optical fiber link to generate a pre-compensated signal to offset the nonlinear distortion of optical fiber transmission.

[0048] During fiber optic transmission, nonlinear effects (such as XPM and four-wave mixing) can cause signal distortion and affect transmission quality. To reduce the impact of these nonlinear effects, this embodiment employs a pre-distortion compensation technique based on a fiber optic link nonlinear model to adjust the signal before transmission and counteract nonlinear distortion in fiber optic transmission.

[0049] In some implementations, a nonlinear model for the fiber optic link is established, capable of predicting and describing the impact of nonlinear effects in the fiber on the signal. By simulating the nonlinear behavior of signal transmission in the fiber, the system can calculate a distortion compensation function for each composite baseband signal. This model is then used to pre-compensate the composite baseband signal, compensating for nonlinear distortion during transmission. Furthermore, the generated pre-compensated signal undergoes further processing to ensure it adapts to the nonlinear characteristics of the fiber optic link, enabling the signal to cancel out distortion caused by nonlinearity after transmission through the fiber, particularly effectively optimizing signal distortion over long distances or high power transmissions.

[0050] In step S150, the pre-compensated signal is optically modulated on the dynamically determined DWDM transmission wavelength and coupled to a single optical fiber link through a DWDM optical multiplexer for transmission to the central device.

[0051] Here, various modulation or amplitude modulation techniques can be employed to optically modulate the pre-compensated signal at a defined DWDM wavelength. For example, an external modulator can be used to modulate the electrical signal onto an optical carrier, forming a transmittable optical signal. A DWDM optical multiplexer then multiplexes multiple signal wavelengths onto a single optical fiber for parallel transmission, maximizing the fiber's bandwidth utilization. Each signal corresponds to a specific DWDM wavelength, and after precise modulation, it is transmitted via an optical fiber link to the central receiving device. The central device then performs demultiplexing and demodulation processing, completing the overall RF signal backhaul transmission link.

[0052] Through the embodiments of this application, dynamic wavelength mapping and orthogonal mapping processing significantly improve the transmission efficiency of multi-frequency radio frequency signals, reduce crosstalk between signals, and enhance the anti-interference capability of the signals. Dynamically selecting the transmission wavelength not only optimizes the bandwidth utilization of the link but also improves the system's adaptability to changes in the fiber optic link state, enhancing the system's flexibility and stability. Through nonlinear pre-compensation processing, the impact of fiber nonlinear effects is successfully reduced, especially in long-distance or high-power transmission, ensuring signal integrity and reliability. Therefore, the backhaul transmission performance of the DWDM system in the remote radio unit (RU) for multi-band radio frequency light is effectively improved.

[0053] Figure 2 An example operation flowchart is shown for generating a composite baseband signal by orthogonal mapping according to an embodiment of this application.

[0054] like Figure 2 As shown, in step S210, energy allocation parameters are calculated for the multi-frequency digital baseband signal set based on the service priority, RF power requirements, and fiber optic link predicted attenuation of each frequency band, in order to generate normalized weights for controlling the energy proportion of different frequency bands in the vector space.

[0055] Here, by calculating the energy normalization weight of each frequency band, it is ensured that the energy allocation of all frequency bands can meet the attenuation characteristics of the optical fiber link and the service priority requirements.

[0056] Equation (1)

[0057] In the formula, For the first The energy normalization weights of each frequency band mapped to the vector space For the first Service priority coefficient for each frequency band; For the first The frequency band power requirement parameter for each frequency band represents the baseband power required to demodulate the signal in the corresponding frequency band. For the first The fiber optic link loss factor for each frequency band represents the estimated attenuation intensity of the corresponding frequency band signal in the optical fiber. For the planned fiber optic link transmission distance, This represents the total number of frequency bands in the set of multi-frequency digital baseband signals. The normalization term represents the sum of the weighted loss factors across all frequency bands.

[0058] In equation (1), appropriate energy weights are allocated to the multi-frequency digital baseband signal set based on the service priority, RF power requirements, and attenuation characteristics of each frequency band. By performing normalized weight calculations on signals of different frequency bands, energy can be accurately allocated to each frequency band. Taking into account the priority, power requirements, and link attenuation of each frequency band, performance bottlenecks caused by unreasonable power allocation in some frequency bands are avoided, while also preventing the waste of link resources.

[0059] In step S220, each frequency band is expanded into a vector form to avoid optical domain intermodulation. An orthogonal vector group with a length equal to the total number of frequency bands is constructed to satisfy the mutual orthogonality constraint, so that the signals of each frequency band occupy mutually orthogonal dimensions in the vector space, and the discrete baseband symbol sequence of each frequency band is mapped into a vectorized sub-signal.

[0060] Specifically, the signal of each frequency band is sampled in the time domain and mapped through orthogonal basis vectors to transform it into a high-dimensional vector form. The orthogonal basis vectors of each frequency band need to satisfy the mutual orthogonality constraint condition to ensure the independence of signals in different frequency bands. The discrete baseband symbol sequence of each frequency band is transformed into a vectorized signal through the mapping of orthogonal basis vectors, and the symbol sequence reflects the time domain information of the frequency band signal.

[0061] Equation (2)

[0062] In the formula, For the first Vectorized sub-signals of each frequency band in vector space For discrete-time indexing, For the first A discrete baseband symbol sequence for each frequency band, representing the time-domain symbol of that frequency band after sampling and digitization; For the first The orthogonal basis vectors corresponding to each frequency band, and any two distinct vectors satisfy the following: , and Frequency band index; The Hermitian transpose operation is used to represent the conjugate transpose of a complex vector.

[0063] By using orthogonal mapping, each frequency band signal is transformed into a sub-signal that does not interfere with each other in the vector space, effectively avoiding intermodulation and cross-modulation effects in the optical domain, and ensuring that multi-frequency signals can be transmitted in parallel in optical fiber without mutual interference.

[0064] In step S230, each vectorized sub-signal is superimposed item by item according to the vector dimension to generate a composite baseband signal vector.

[0065] Specifically, by superimposing orthogonal signals from each frequency band, the vectorized sub-signals of each frequency band are superimposed in the vector space to form a composite baseband signal that can carry signal information from multiple frequency bands.

[0066] Equation (3)

[0067] In the formula, It is a composite baseband signal vector to reduce the intermodulation and cross-modulation effects generated after multi-frequency radio frequency signals are optically modulated.

[0068] By superimposing signals from different frequency bands, a composite baseband signal is generated, containing complete information from all frequency bands. Furthermore, because the signals have been orthogonally mapped, interference-free transmission is ensured. Thus, the generation of this composite signal provides a foundation for the parallel transmission of multiple frequency band signals in the same transmission medium, reduces intermodulation and cross-modulation effects between multiple frequency signals, and supports efficient utilization of fiber optic bandwidth.

[0069] Figure 3 A flowchart illustrating an example of dynamically determining the DWDM transmission wavelength of a composite baseband signal according to an embodiment of this application is shown.

[0070] like Figure 3 As shown, in step S310, a candidate wavelength set containing multiple candidate wavelengths is constructed based on the wavelength tuning range of the tunable laser, and the wavelength interval matrix between any two candidate wavelengths is calculated.

[0071] Specifically, based on the wavelength tuning range of the tunable laser, a set of candidate wavelengths suitable for DWDM transmission is determined. For example, this set may include M candidate wavelengths, each selected according to the spectral allocation requirements of the fiber optic system. Since the tunable laser can adjust its output wavelength within a certain range, the tuning capability of the laser must be considered when constructing the candidate wavelength set to ensure that the selected wavelengths are within the laser's effective tuning range.

[0072] Next, the spectral separation between these candidate wavelengths is evaluated by calculating the wavelength spacing matrix between them.

[0073] Equation (4)

[0074] In the formula, and The first The candidate wavelength and the first One candidate wavelength These are elements in the wavelength spacing matrix, used to characterize the wavelength. With wavelength Spectral separation between them.

[0075] In the calculation of the wavelength spacing matrix in equation (4), each element represents the spectral separation between different candidate wavelengths. By constructing the candidate wavelength set and the wavelength spacing matrix, it is ensured that the candidate wavelengths can meet the modulation requirements of signals in different frequency bands, and reliable data support is provided for wavelength allocation and cross-phase modulation calculation.

[0076] In step S320, based on the current transmit power of each frequency band and the link dispersion parameters obtained by real-time measurement, the cross-phase modulation intensity of signals in different frequency bands at each candidate wavelength is estimated, and the instantaneous crosstalk intensity between different candidate wavelengths is defined according to the fiber nonlinear theory.

[0077] Specifically, cross-phase modulation is caused by the nonlinear interaction between adjacent wavelengths, typically manifesting as phase interference, thus affecting signal quality. Based on the nonlinear theory of optical fibers, the cross-phase modulation intensity between different candidate wavelengths is calculated:

[0078] Equation (5)

[0079] In the formula, wavelength With wavelength Cross-phase modulation crosstalk intensity between them and Mapped to wavelength respectively and wavelength The optical power of the signal, is the fiber nonlinearity coefficient, representing the sensitivity of the fiber material to the nonlinearity of optical power coupling; This represents the measured group velocity dispersion parameter of the link. This is the dispersion correlation function, used to describe the degree of influence of dispersion on the cross-phase modulation effect.

[0080] In equation (5), the cross-phase modulation intensity is calculated using the real-time measured signal power and the dispersion parameters of the link, and the fiber nonlinear theory model is used. The XPM intensity depends on the optical power of the signal, the nonlinear coefficient of the fiber, and the dispersion parameters of the link. The calculation of the cross-phase modulation intensity helps to assess the crosstalk risk that may occur during signal transmission in advance.

[0081] In step S330, a mapping function is constructed to map each frequency band to the candidate wavelength set, and an optimization model is established with the goal of minimizing the overall optical domain crosstalk intensity.

[0082] Here, a wavelength allocation optimization model is constructed with the goal of minimizing the overall crosstalk intensity in the optical domain. To achieve this goal, the system needs to map signals of different frequency bands to a set of candidate wavelengths and ensure that the crosstalk intensity between wavelengths is minimized.

[0083] Equation (6)

[0084] In the formula, The wavelength allocation strategy mapping function represents mapping the set of frequency bands to the set of candidate wavelengths; Wavelength allocation strategy for all frequency bands Total crosstalk accumulation, and They represent the first The frequency band and the first Wavelength allocation strategy for each frequency band The corresponding candidate wavelength index.

[0085] The wavelength of each frequency band is selected by an optimization algorithm to ensure that the mutual interference between signals of different frequency bands is minimized. A wavelength allocation optimization model is constructed based on Equation (6). The wavelength allocation strategy mapping function represents the mapping relationship between the set of frequency bands and the set of candidate wavelengths. By calculating all possible wavelength allocation schemes one by one, the optimization objective is to minimize the total crosstalk of all frequency bands on the candidate wavelengths, thereby improving the signal transmission quality.

[0086] In step S340, the optimal wavelength allocation strategy is solved based on the single-shot constraint and the minimum wavelength spacing constraint.

[0087] Here, the single-shot constraint ensures that each frequency band signal is allocated only one wavelength, avoiding the situation where frequency band signals share channels. The minimum wavelength spacing constraint guarantees that the spacing between any two allocated wavelengths is not less than the minimum safe wavelength spacing that the system can support. Thus, the rationality and security of wavelength allocation are further ensured.

[0088] Specifically, single-shot constraints are used to ensure that only one wavelength is allocated to each frequency band, and that they do not share the same channel:

[0089] Equation (7)

[0090] The minimum wavelength spacing constraint is used to ensure that the wavelength spacing between any two assigned wavelengths is not less than the minimum safe wavelength spacing that the DWDM system can support:

[0091] Equation (8)

[0092] In the formula, This indicates a wavelength allocation strategy. Assigned to the The frequency band and the first The actual wavelength spacing between candidate wavelengths in each frequency band. This is the minimum safe wavelength interval.

[0093] In this embodiment, wavelength allocation optimization reduces crosstalk and interference between different frequency bands, thereby improving signal transmission quality. The optimization model based on minimizing optical domain crosstalk intensity ensures efficient transmission of multi-band signals in the fiber optic system while avoiding signal interference and waste of fiber optic resources, effectively improving the transmission performance of multi-frequency radio frequency signals in the DWDM system.

[0094] Regarding the details of solving the optimal wavelength allocation strategy, in some examples of the embodiments of this application, under the condition of satisfying the single-shot constraint and the minimum wavelength spacing constraint, a greedy solution strategy of dynamic wavelength allocation is adopted for iterative optimization.

[0095] More specifically, all frequency bands to be allocated are comprehensively sorted according to the service priority coefficient of each frequency band and the transmit power of each frequency band to generate a frequency band sequence in descending order, so that high-power and high-priority frequency bands are given priority in the wavelength allocation process.

[0096] Here, based on the service priority and transmit power requirements of each frequency band, the wavelengths of each band are rationally selected, minimizing the crosstalk increment during wavelength allocation. First, all frequency bands to be allocated are comprehensively ranked according to their service priority coefficient and transmit power. Frequency bands with high power and high priority are allocated first to ensure priority processing of important frequency bands. Then, by evaluating the cross-phase modulation crosstalk increment between wavelengths in the candidate wavelength set and the already allocated wavelength set, the optimal wavelength is selected for allocation.

[0097] For example, initialize the set of unassigned frequency bands. and initialize the allocated wavelength set. During the iteration process, for each frequency band to be allocated... All candidate wavelengths not included in the assigned wavelength set will be included. Candidate wavelengths Each frequency band will be evaluated individually. Mapped to candidate wavelength The time-related increase in crosstalk relative to the currently allocated wavelength set.

[0098] Here, for each frequency band to be allocated All unassigned wavelengths in the candidate wavelength set are evaluated one by one, and the frequency bands are... Mapped to a candidate wavelength It calculates the crosstalk increment introduced when the frequency band is mapped to wavelength, and uses this crosstalk increment to quantize the frequency band. The effect of mapping to a certain wavelength on the currently assigned set of wavelengths.

[0099] Crosstalk increment is calculated using the following formula:

[0100] Equation (9)

[0101] In the formula, Indicates frequency band Mapped to wavelength Increased crosstalk For the allocated frequency band The corresponding candidate wavelength index, wavelength With wavelength The cross-phase modulation crosstalk intensity between them.

[0102] Under the condition of satisfying the minimum wavelength spacing constraint Of all candidate wavelengths, select the one that makes The smallest candidate wavelength is given priority for allocation.

[0103] This ensures that wavelengths are allocated according to priority order within the frequency bands, and fully considers the impact of crosstalk increments calculated as in equation (9) when selecting candidate wavelengths, always selecting the candidate wavelength with the smallest crosstalk increment for allocation. Thus, by evaluating the crosstalk introduced when each frequency band is mapped to different wavelengths, the wavelength allocation with the least impact on performance can be selected, thereby optimizing the use of fiber bandwidth and minimizing interference between signals.

[0104] In some cases, if multiple candidate wavelengths have the same minimum crosstalk increment, the candidate wavelength with the largest interval between it and the wavelength closest to it in the already assigned wavelength set is further selected. By selecting the wavelength with the largest interval between it and the already assigned wavelengths, it helps to improve the uniformity of the spectrum, avoid excessive concentration and spectral crowding in the spectral region, thereby maintaining a better spectral distribution and reducing the performance degradation caused by spectral interference.

[0105] Selected candidate wavelengths Then, this frequency band With wavelength Establish mapping relationship and update the assigned wavelength set. And the set of unassigned frequency bands, until all frequency bands have been mapped.

[0106] Here, once a candidate wavelength is selected and mapped, a mapping relationship is established between the frequency band and the selected wavelength. Subsequently, the allocated wavelength set and the unallocated frequency band set are updated, the mapping relationship is added to the allocated wavelength set, and the frequency band is removed from the unallocated frequency band set. This iterative allocation operation continues until all frequency bands are mapped to suitable wavelengths. While ensuring minimal crosstalk increments, the gradual iterative allocation of wavelengths for all frequency bands maximizes the utilization of fiber resources and minimizes crosstalk and interference.

[0107] This application's embodiments employ dynamic wavelength allocation and a greedy optimization strategy to solve the optimal matching problem between frequency bands and wavelengths. First, frequency bands are prioritized based on their transmission power, and the crosstalk increment introduced when mapping each frequency band to a wavelength is evaluated during wavelength selection. By selecting candidate wavelengths with the minimum crosstalk increment and further considering the spacing between wavelengths, the system can optimize the spectral distribution and reduce the impact of nonlinear crosstalk. Finally, by iteratively updating the allocated wavelength set and the unallocated frequency band set, an efficient and optimal wavelength allocation scheme is achieved, ensuring maximum utilization of fiber optic resources and optimization of signal transmission quality.

[0108] Regarding the details of generating the pre-compensation signal, in some examples of embodiments of this application, a weighted asymmetric Volterra pre-distortion model (WAVPM) can be used to construct the nonlinear response model of the optical fiber link, and a pre-compensation signal for offsetting the nonlinear distortion of the link can be generated based on the nonlinear response model.

[0109] Figure 4 A flowchart illustrating an example of generating a pre-compensation signal based on a weighted asymmetric Volterra pre-compensation model according to an embodiment of this application is shown.

[0110] like Figure 4 As shown, in step S410, based on the nonlinear transmission mechanism of the optical fiber link, the output optical field corresponding to the input optical field of the link is approximately represented as a Volterra series model with memory effect and nonlinear interaction.

[0111] Specifically, the Volterra series approximates the input-output relationship of an optical fiber link using kernel functions of different orders. Each kernel function represents the contribution of different nonlinear effects and takes into account the impact of time delay.

[0112] Equation (10)

[0113] In the formula, It is the highest order of the Voltaire series. For the first The first-order Volterra kernel function characterizes the memory effect, dispersion effect, and nonlinear coupling effect between different wavelengths in an optical fiber link. This represents the convolution time delay variable of the Volterra kernel. and These represent the input optical field and output optical field of the fiber optic link as a function of time, respectively. The complex envelope is represented as follows: Indicates the first Volterra kernel function The integration region.

[0114] As shown in Equation (10), in the modeling process of the optical fiber link, the nonlinear relationship between the input and output optical fields is represented by a series of recursive kernel functions using the Voltaire series. Each kernel function reflects the influence of different nonlinear effects (such as memory effect, dispersion effect, and nonlinear interaction). During modeling, the convolution time delay variable is used. This is used to represent the delay relationship between the historical moment of the input signal and the response of the fiber optic link. These time delays determine how the input optical field affects the amplitude and phase of the output optical field.

[0115] By convolving the input signal with Voltara kernels of various orders, the output optical field of the optical fiber link can be obtained, which can accurately describe the influence of various nonlinear effects in the link on the optical signal.

[0116] In step S420, during the Volterra kernel modeling process, the amplitude and phase response of each order of Volterra kernel function are estimated based on real-time monitoring data during link operation, and weighting coefficients are constructed for each order of kernel function.

[0117] Specifically, based on real-time monitoring data during link operation, the amplitude and phase responses of different-order Volterra kernel functions are estimated. For example, real-time operating parameters such as the link's bit error rate, dispersion variation, and cross-wavelength cross-phase modulation intensity are monitored to estimate the amplitude and phase responses of each-order Volterra kernel function, and weighting coefficients are constructed for each kernel function. These weighting coefficients are used to adjust the contribution of different kernel functions to nonlinear compensation, ensuring the accuracy and efficiency of the compensation effect.

[0118] Equation (11)

[0119] In the formula, The wavelength combination index selected from the DWDM candidate wavelength set is used to indicate the wavelength combination index. The wavelength group involved in the order nucleus; and They represent time respectively and Iterative wavelength combination For the first The weighting coefficients of the Volterra kernel; In order to be with the first The step size factor corresponding to the order kernel function; For time The nonlinear distortion error metric is calculated based on the link bit error rate, cross-phase modulation intensity, and amplifier gain compression. For wavelength combination in time The normalized modulation factor is composed of the average power, minimum wavelength spacing, and equivalent dispersion slope of the iteration.

[0120] about The calculation example can collect real-time monitoring data of the link, including the link's bit error rate (BER) and the strength of cross-phase modulation (XPM). For example, the link's BER might be 10. -5 The intensity of cross-phase modulation may be 0.05. These data provide basic information about the current state of the link, reflecting the distortion caused by nonlinear effects in signal transmission. Next, these data are combined with pre-set weighting coefficients to calculate the error metric of the link state. For example, the weighting coefficients for bit error rate and cross-phase modulation intensity might be 0.8 and 0.2, respectively, to represent the contribution of these two factors to the total error metric.

[0121] about A calculation example can be used to calculate the total power of a specific wavelength combination in a link, for example, assuming the power of a certain wavelength combination is 1.2 watts. Next, the minimum wavelength spacing between any two wavelengths in that wavelength combination is calculated, which can be determined based on the physical characteristics of the optical fiber; for example, assuming the calculated minimum wavelength spacing is 0.2 nm. Then, based on the dispersion characteristics of the link, the effect of the dispersion slope on phase modulation is further estimated; for example, the dispersion slope might be... This indicates how the dispersion effect of optical fiber affects signal transmission. Finally, these calculation results are fused together to reflect the degree of influence of this wavelength combination on signal nonlinear distortion in the link.

[0122] In equation (11), The weighting factor, constructed as a weighting factor for each order kernel function, reflects the magnitude of the contribution of different wavelength combinations to the nonlinear effect.

[0123] By dynamically adjusting the weighting coefficients based on real-time monitoring data, the compensation effect of the Volterra kernel can be optimized according to the current state of the link. This ensures that the system can adapt to different link states and dynamically adjust the amplitude and accuracy of nonlinear compensation, thereby improving the transmission stability and signal quality of the system.

[0124] In step S430, the target kernel function is constructed based on the weighted kernel function.

[0125] Specifically, the system constructs the target kernel function by weighted superposition of Volterra kernel functions of different orders. This calculation process is based on the previously estimated weighting coefficients and takes into account the influence of each order of Volterra kernel on the nonlinear distortion of the link.

[0126] Equation (12)

[0127] In step S440, a pre-compensation signal is generated to offset link nonlinear distortion based on the link nonlinearity compensation principle and the target kernel function. .

[0128] Equation (13)

[0129] In this process, by weighting and superimposing Volterra kernels of different orders, the higher-order nonlinear terms generated by different wavelength combinations in the link are canceled out before transmission.

[0130] By weighted superposition of Volterra kernels of different orders, the system can effectively pre-compensate for the nonlinearity of the input signal. This allows for early compensation of distortion caused by nonlinear effects (such as cross-phase modulation) at the fiber optic link front-end, thereby reducing signal distortion and bit error rate during subsequent transmission. Ultimately, the generated pre-compensated signal will help improve the transmission quality of the signal in the link and reduce the negative impact of nonlinear effects.

[0131] Figure 5 An example operation flowchart of optical domain modulation of a DWDM system according to an embodiment of this application is shown.

[0132] like Figure 5 As shown, in step S510, each wavelength channel in the DWDM optical multiplexer is constructed based on the micro-ring resonator, so that each micro-ring resonator corresponds to an independent wavelength multiplexing path.

[0133] Here, microring resonators are used as a key component in the DWDM system to achieve wavelength selection and multiplexing. The core function of the microring resonator is to select and modulate different wavelengths through its free spectral range (FSR). In this process, each microring resonator corresponds to an independent wavelength multiplexing path, and each wavelength is selected and transmitted through a different microring resonator. The free spectral range of the microring resonator ensures the effective separation and multiplexing of different wavelength signals, thereby supporting the requirements of high-density wavelength division multiplexing.

[0134] Specifically, the free spectral range of each microring resonator satisfies:

[0135] Equation (14)

[0136] In the formula, This refers to the free spectral range of the microring resonator. The speed of light in a vacuum. The group refractive index of the waveguide material for the microring resonator. Let be the circumference of the microring resonator.

[0137] The design of microring resonators ensures that each device can independently respond to a specific transmission wavelength, thereby avoiding mutual interference between different wavelengths and ensuring efficient multiplexing of each wavelength. By independently selecting the wavelength for each microring resonator, crosstalk between signals of different wavelengths can be effectively avoided.

[0138] In step S520, for each microring resonator, the radius of the microring resonator is adjusted to adjust the ring circumference, so that the adjusted free spectral range matches the DWDM transmission wavelength of the microring resonator.

[0139] Here, initial wavelength range matching is performed to ensure that each microring resonator can select and transmit wavelengths within a general range, but precise wavelength matching has not yet been performed.

[0140] Specifically, by adjusting the radius of the micro-ring resonator, the circumference of the ring is changed. To affect its free spectral range It should be noted that this adjustment process is preliminary, as it only ensures that each microring resonator can cover a general range of the target wavelength range. By adjusting the radius, each microring resonator can be roughly matched to multiple transmission wavelength ranges, ensuring that each wavelength signal can enter the appropriate multiplexing path. Through the above initial matching process, it is ensured that each microring resonator in the DWDM system can initially adapt to the target wavelength range.

[0141] In step S530, the pre-compensation signal is modulated to multiple DWDM transmission wavelengths corresponding to the center wavelength of each microring resonator, so that different pre-compensation signal copies are mapped to the corresponding wavelength multiplexing paths.

[0142] Here, fine wavelength matching is further performed on each microring resonator to ensure that different pre-compensated signal copies are accurately mapped to different wavelength multiplexing paths. Specifically, each microring resonator is finely tuned to accurately correspond to the target DWDM wavelength. After fine wavelength matching, the pre-compensated signal is modulated onto the precisely selected wavelength of each microring resonator, so that different signal copies are mapped to different multiplexing paths. This ensures that each signal copy does not experience wavelength cross-interference or distortion during transmission, thereby improving the signal transmission quality.

[0143] In step S540, the multi-wavelength pre-compensated optical signals, after wavelength selection and multiplexing by each micro-ring resonator, are aggregated at the output port of the DWDM optical multiplexer, and the aggregated multi-wavelength multiplexed pre-compensated optical signals are coupled to a single optical fiber link for transmission to the central device.

[0144] Here, multiplexed optical signals from multiple micro-ring resonators are converged into a single optical fiber signal, enabling the transmission of multi-wavelength signals within the same fiber. The converged multi-wavelength signal is then coupled into a single optical fiber link and transmitted to a central device (e.g., a central equipment room). Thus, multiple frequency band signals can share the same optical fiber link for long-distance transmission, maximizing fiber utilization efficiency.

[0145] In some implementations, at the output port of the DWDM optical multiplexer, pre-compensated optical signals of different wavelengths are aggregated into a single multiplexed signal stream, each signal having been modulated and compensated at its specific wavelength. The aggregated optical signal is then transmitted to a central device via a single fiber optic link through an optical fiber coupling device, allowing the central device to perform further demodulation and signal processing.

[0146] This application's embodiments employ a DWDM optical multiplexer design using microring resonators. Leveraging the high-precision wavelength selectivity and tunable free spectral range of the microring resonator, different DWDM transmission wavelengths are matched by precisely adjusting the radius of the microring resonator, achieving efficient multi-wavelength multiplexing and signal transmission. Through the microring resonator design, combined with both coarse and fine wavelength matching processes, accurate multiplexing and transmission of signals at various wavelengths in the DWDM system are ensured, enabling the system to transmit multiple wavelength signals efficiently and without interference.

[0147] Regarding the details of fine wavelength matching in step S530, in some examples of embodiments of this application, a slit waveguide structure is constructed within the waveguide cross-section of each microring resonator to improve the mode constraint ratio of the optical field in the slit region.

[0148] It should be noted that the resonant center wavelength of each microring resonator is closely related to the physical structure and material properties of the microring. Therefore, the design and adjustment of the microring resonator are crucial to ensuring that each signal in the DWDM system can be accurately matched to the corresponding transmission wavelength.

[0149] By constructing a slit waveguide structure within the waveguide cross-section of a microring resonator, the mode confinement ratio of the optical field in the slit region can be significantly improved, thereby precisely controlling the signal transmission characteristics. The resonant center wavelength of the microring resonator is determined by the ring circumference, the effective refractive index of the slit waveguide structure, and the order of the resonant modes. More specifically, the resonant center wavelength of the microring resonator satisfies the following equation:

[0150] Equation (15)

[0151] In the formula, This is the resonant center wavelength of the microring resonator. Let be the circumference of the microring resonator. The effective refractive index of the slit waveguide structure, The order of the resonant mode.

[0152] The design of the microring resonator ensures that it can accurately select signals across different wavelength ranges. In some implementations, this is achieved by adjusting the ring circumference of the microring resonator. Initial matching of the free spectral range was achieved, and the effective refractive index of the waveguide material was further adjusted. This makes the resonant wavelength of each microring resonator... It can be precisely calculated or adjusted according to system requirements, and can accurately match the target transmission wavelength.

[0153] Furthermore, a thermally tuned tuner is integrated on each micro-ring resonator, and the effective refractive index of the waveguide material is updated by adjusting the driving current to control the offset of the resonant center wavelength, so that the tuned resonant center wavelength can be dynamically aligned with the corresponding DWDM transmission wavelength.

[0154] Specifically, a thermally tuned tuner is integrated on each microring resonator to update the effective refractive index of the waveguide material by adjusting the thermally driven current, and to ensure dynamic alignment with the corresponding DWDM transmission wavelength by precisely adjusting the offset of the resonant center wavelength.

[0155] Equation (16)

[0156] In the formula, Indicates the offset. This represents the amount of adjustment or change in the effective refractive index.

[0157] Through the embodiments of this application, by introducing a slit waveguide structure within the micro-ring resonator, the mode constraint ratio of the optical field within the micro-ring resonator is significantly improved, enhancing signal selectivity and transmission accuracy. The dynamic adjustment of the thermally tuned fine-tuner ensures that the micro-ring resonator can adapt to changes in the link environment in real time, precisely aligning with the target DWDM transmission wavelength and avoiding signal interference and distortion caused by wavelength mismatch. Ultimately, through precise wavelength matching, the system can significantly improve bandwidth utilization and transmission stability, ensuring efficient and interference-free transmission of multi-band signals and significantly enhancing the overall performance of the optical fiber communication system.

[0158] To verify the effectiveness of the proposed multi-frequency radio frequency optical backhaul method, this paper compares the performance of the DWDM RoF system and the proposed scheme in terms of crosstalk suppression and bit error rate through simulation.

[0159] The system model used in the comparative experiment was a DWDM RoF system, which modulates each frequency band independently to a fixed wavelength without using pre-compensation or dynamic wavelength allocation.

[0160] Regarding signal parameters, the total number of frequency bands can be selected as K = 4, corresponding to 3.5 GHz, 6 GHz, 28 GHz and 60 GHz respectively. The baseband signal of each frequency band adopts 16-QAM modulation and the sampling rate is 2 GHz. The orthogonal vector length of the MFOM (Multi-Frequency Orthogonal Mapping) module in this paper is 4, and the weight is set according to the service priority as [0.3,0.2,0.3,0.2].

[0161] Regarding wavelength resources, a total of 8 wavelengths are available for simulation, spaced 50 GHz apart, with a center wavelength range of 1549~1552nm. DWAM-RF dynamically allocates wavelengths based on power and real-time measured XPM intensity.

[0162] Regarding link parameters, the selected fiber length range is 0~200 km, and a standard single-mode fiber model is adopted; nonlinear coefficients... Dispersion parameters Relay stations, each containing an EDFA (noise figure 4.5 dB) and a dispersion compensation module, are set up every 50 km.

[0163] The evaluation metrics used in the experiment mainly include bit error rate (BER), crosstalk intensity, and power utilization, with crosstalk intensity expressed as optical margin loss.

[0164] Figure 6 This diagram illustrates a comparison of the inter-channel crosstalk levels of different DWDM methods.

[0165] like Figure 6 As shown, the crosstalk levels of the two schemes were compared across eight DWDM channels. The baseline RoF system, lacking dynamic wavelength allocation and pre-compensation techniques, resulted in a crosstalk level of approximately -32 dB between adjacent channels. In contrast, the proposed DWDM isolation scheme, incorporating dynamic wavelength allocation and pre-compensation techniques, significantly reduced the crosstalk level to -50 dB, with minimal differences in crosstalk between channels.

[0166] Experimental results show that by dynamically adjusting the wavelength spacing and applying pre-compensated nonlinearity, interference caused by cross-phase modulation (XPM) can be effectively suppressed, thereby significantly improving the signal quality of the system and enhancing the isolation between channels. This also proves that DWDM systems, combined with dynamic wavelength allocation and nonlinear compensation techniques, can significantly improve the spectral efficiency of the system, reduce signal interference, and effectively increase system capacity.

[0167] Figure 7 A schematic diagram showing the comparison of bit error rate variations of different methods with fiber length is presented as an example.

[0168] Figure 7 The paper presents a comparison of the bit error rate (BER) of the baseline DWDM system and the proposed scheme at different fiber transmission distances. In the baseline DWDM RoF system, due to the lack of nonlinear compensation technology, the BER shows a steady upward trend with increasing fiber length, exceeding 10^6 BER at a transmission distance of 200 km. -4 .

[0169] In contrast, the proposed scheme, after employing WAVP (Wideband Adaptive Compensation) and DWAM-RF (Dynamic Wavelength Allocation and Nonlinear Compensation) techniques, significantly suppresses the bit error rate. Even at a transmission distance of 200 km, the bit error rate remains at 10%. -7 The magnitude is [missing information], and the rate of increase in the bit error rate is relatively slow.

[0170] Experiments show that the baseline bit error rate (BER) rises rapidly with increasing fiber optic transmission distance; however, the proposed scheme exhibits a slower BER increase and maintains a low BER even over longer distances. Therefore, through effective pre-compensation and dynamic wavelength allocation strategies, nonlinear effects and crosstalk in the fiber optic link can be suppressed, thereby maintaining a low BER over long distances and effectively ensuring the transmission distance and signal quality of high-capacity DWDM systems.

[0171] To address the limitations of existing RF optical backhaul systems in effectively supporting multi-band signals and their susceptibility to nonlinear crosstalk, this paper proposes a multi-frequency RF optical backhaul method based on DWDM channel isolation. This method comprehensively applies multi-frequency orthogonal mapping, dynamic wavelength allocation, weighted asymmetric Voltaire pre-compensation, and high-Q microring resonators, theoretically and practically solving the core challenges of multi-frequency RoF systems. Comparative simulations demonstrate that, compared to baseline DWDM RoF systems, the proposed scheme exhibits significant advantages in crosstalk suppression, bit error rate, transmission distance, and system flexibility.

[0172] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of combined actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Secondly, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application. In the above embodiments, the descriptions of each embodiment have their own emphasis; for parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0173] Figure 8A structural block diagram of an example of a multi-frequency radio frequency optical backhaul system based on DWDM dynamic wavelength mapping according to an embodiment of this application is shown. The system is deployed at a remote wireless node.

[0174] like Figure 8 As shown, the multi-frequency radio frequency optical backhaul system 800 based on DWDM dynamic wavelength mapping includes a radio frequency signal acquisition unit 810, an orthogonal mapping unit 820, a wavelength allocation unit 830, a predistortion compensation unit 840, and an optical domain modulation unit 850.

[0175] The radio frequency signal acquisition unit 810 is used to acquire multiple radio frequency signals of different frequency bands and to perform digital processing on the radio frequency signals to generate multi-frequency digital baseband signals.

[0176] The orthogonal mapping unit 820 is used to perform orthogonal mapping processing on the multi-frequency digital baseband signal based on a preset orthogonal vector group, expand each frequency band signal into mutually orthogonal vectorized sub-signals, and superimpose them to form a composite baseband signal.

[0177] The wavelength allocation unit 830 is used to dynamically determine the DWDM transmission wavelength of the composite baseband signal based on the real-time measured link crosstalk intensity and optical power constraints.

[0178] The predistortion compensation unit 840 is used to perform predistortion compensation processing on the composite baseband signal based on the nonlinear model of the optical fiber link to generate a pre-compensated signal to offset the nonlinear distortion of optical fiber transmission.

[0179] The optical modulation unit 850 is used to optically modulate the pre-compensated signal on the dynamically determined DWDM transmission wavelength and couple it to a single optical fiber link through a DWDM optical multiplexer for transmission to the central device.

[0180] In some embodiments, this application provides a non-volatile computer-readable storage medium storing one or more programs including execution instructions. The execution instructions can be read and executed by an electronic device (including but not limited to a computer, server, or network device) to perform the steps of any of the above-described multi-frequency radio frequency optical backhaul methods based on DWDM dynamic wavelength mapping.

[0181] In some embodiments, this application also provides a computer program product, the computer program product including a computer program stored on a non-volatile computer-readable storage medium, the computer program including program instructions, which, when executed by a computer, cause the computer to perform the steps of any of the above-described multi-frequency radio frequency optical backhaul methods based on DWDM dynamic wavelength mapping.

[0182] In some embodiments, this application also provides an electronic device, which includes: at least one processor and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the steps of a multi-frequency radio frequency optical backhaul method based on DWDM dynamic wavelength mapping.

[0183] The above-described product can perform the methods provided in the embodiments of this application, and has the corresponding functional modules and beneficial effects for performing the methods. Technical details not described in detail in this embodiment can be found in the methods provided in the embodiments of this application.

[0184] The electronic devices in this application can exist in various forms, including but not limited to: mobile communication devices, ultra-mobile personal computer devices, portable entertainment devices, or other airborne electronic devices with data interaction functions.

[0185] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0186] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented using software plus a general-purpose hardware platform, or of course, using hardware. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the related technology, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0187] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A multi-frequency radio frequency optical backhaul method based on DWDM dynamic wavelength mapping, applied to a remote radio node, characterized in that, The method comprises: Collecting a plurality of radio frequency signals of different frequency bands, and performing digital processing on the radio frequency signals to generate multi-frequency digital baseband signals; Based on a preset orthogonal vector group, the multi-frequency digital baseband signals are subjected to orthogonal mapping processing, each frequency band signal is expanded into a vectorized sub-signal which is mutually orthogonal, and a composite baseband signal is formed by superposition, specifically comprising: According to the service priority, radio frequency power requirement and optical fiber link predicted loss of each frequency band, energy distribution parameter calculation is performed on the multi-frequency digital baseband signal set to generate a normalization weight for controlling the energy proportion of different frequency bands in the vector space: ， wherein, is the energy normalization weight of the th frequency band mapped to the vector space, is the service priority coefficient of the th frequency band; is the frequency band power demand parameter of the th frequency band, which represents the baseband power required for the demodulation quality of the corresponding frequency band signal; is the fiber link loss coefficient of the th frequency band, which represents the estimated attenuation intensity of the corresponding frequency band signal in the optical fiber; is the planned fiber link transmission distance, is the total number of frequency bands in the multi-frequency digital baseband signal set; andis the normalization term, representing the sum of the weighted loss factors of all frequency bands.​​​​ Each frequency band is expanded into a vector form to avoid optical domain intermodulation, an orthogonal vector group with a length of the total number of frequency bands is constructed to satisfy the mutual orthogonal constraint, so that each frequency band signal occupies mutually orthogonal dimensions in the vector space, and the discrete baseband symbol sequence of each frequency band is mapped into a vectorized sub-signal: ， wherein is the vectorized sub-signal of the th frequency band in the vector space, is the discrete time index, is the discrete baseband symbol sequence of the th frequency band, representing the time domain symbols after sampling and digitizing the frequency band; is the orthogonal basis vector corresponding to the th frequency band, and any two different vectors satisfy , and is the frequency band index; is the Hermitian transpose operation, used to represent the conjugate transpose of a complex vector; Each vectorized sub-signal is superimposed item by item according to the vector dimension to generate a composite baseband signal vector: ， In the formula, is a complex baseband signal vector, so as to reduce the intermodulation and cross modulation effects generated after the multi-frequency radio frequency signal is modulated through the optical domain. According to the real-time measured link crosstalk strength and optical power constraint, the DWDM transmission wavelength of the composite baseband signal is dynamically determined, specifically comprising: Based on the wavelength tuning range of a tunable laser, a candidate wavelength set containing a plurality of candidate wavelengths is constructed, and a wavelength interval matrix between any two candidate wavelengths is calculated: ， wherein and are the first and the second candidate wavelengths, respectively, is an element of the wavelength spacing matrix, characterizing the spectral separation between the wavelength and the wavelength ; Based on the current transmission power of each frequency band and the link dispersion parameter obtained by real-time measurement, the cross-phase modulation intensity of different frequency band signals under each candidate wavelength is estimated, and the instantaneous crosstalk strength between different candidate wavelengths is defined according to the optical fiber nonlinear theory: ， wherein is the wavelength is the wavelength is the cross-phase modulation crosstalk strength between the wavelengths and are the optical powers of the signals mapped to the wavelengths and the wavelength respectively, is the fiber nonlinear coefficient, representing the sensitivity of the fiber material to optical power coupling nonlinearity; represents the measured group velocity dispersion parameter of the link, is the dispersion correlation function, used to describe the degree of influence of dispersion on the cross-phase modulation effect; A mapping function for mapping each frequency band to the candidate wavelength set is constructed, and an optimization model is established with the objective of minimizing the overall optical domain crosstalk strength: ， In the formula, The wavelength allocation strategy mapping function represents mapping the set of frequency bands to the set of candidate wavelengths; Wavelength allocation strategy for all frequency bands Total crosstalk accumulation, and They represent the first The frequency band and the first Wavelength allocation strategy for each frequency band The corresponding candidate wavelength index; Based on the single shot constraint condition and the minimum wavelength interval constraint condition, an optimal wavelength allocation strategy is solved; The single shot constraint is used to ensure that each frequency band is allocated only one wavelength and does not share the same channel: ； The minimum wavelength interval constraint is used to ensure that the wavelength interval between any two allocated wavelengths is not less than the minimum safe wavelength interval: ， wherein indicates the wavelength allocation strategy allocated to the first band and the first band candidate wavelength, is the minimum safe wavelength interval; Based on the nonlinear model of the optical fiber link, pre-distortion compensation processing is performed on the composite baseband signal to generate a pre-compensation signal for offsetting the nonlinear distortion of the optical fiber transmission; The pre-compensation signal is modulated in the optical domain at the dynamically determined DWDM transmission wavelength, and is coupled to a single optical fiber link through a DWDM optical multiplexer for transmission to a central device.

2. The method of claim 1, wherein, The solving of the optimal wavelength allocation strategy based on the single shot constraint condition and the minimum wavelength interval constraint condition comprises: In the case of satisfying the single shot constraint condition and the minimum wavelength interval constraint condition, a dynamic wavelength allocation greedy solving strategy is used for iterative optimization, specifically comprising: According to the service priority coefficient of each frequency band and the transmission power of each frequency band, all the to-be-allocated frequency bands are comprehensively sorted to generate a descendingly arranged frequency band sequence, so that the frequency bands with high power and high priority are preferentially entered into the wavelength allocation process; Initialize the set of unassigned frequency bands and initialize the allocated wavelength set. During the iteration process, for each frequency band to be allocated... All candidate wavelengths not included in the allocated wavelength set will be selected. Candidate wavelengths Each frequency band will be evaluated individually. Mapped to candidate wavelength The increase in crosstalk introduced relative to the currently allocated wavelength set: ， In the formula, indicates mapping the frequency band to the wavelength Increased crosstalk amount, is the candidate wavelength index corresponding to the allocated frequency band , is the wavelength , is the cross-phase modulation crosstalk intensity between the wavelength Under the condition of satisfying the minimum wavelength spacing constraint Of all candidate wavelengths, select the one that makes The candidate wavelength with the smallest crosstalk increment is selected as the priority for allocation; if multiple candidate wavelengths have the same minimum crosstalk increment, the candidate wavelength with the largest interval between it and the wavelength with the closest interval to it in the already allocated wavelength set is further selected. In the selected candidate wavelength After the frequency band With the wavelength The mapping relationship is established And the allocated wavelength set is updated And the unallocated frequency band set until all frequency bands are completed mapping.

3. The method of claim 1, wherein, The pre-distortion compensation processing of the composite baseband signal based on the nonlinear model of the optical fiber link to generate a pre-compensation signal for offsetting the nonlinear distortion of the optical fiber transmission comprises: The nonlinear response model of the optical fiber link is constructed by using a weighted asymmetric Volterra pre-compensation model, and a pre-compensation signal for offsetting the nonlinear distortion of the link is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, 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generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre-compensation signal is generated according to the nonlinear response model, and the pre ​ ， wherein, is the highest order of the Volterra series, is the first order Volterra kernel function, representing the memory effect, dispersion effect and nonlinear coupling effect between different wavelengths of the fiber link; denotes the convolution time delay variable of the Volterra kernel, and denote the complex envelope representation of the input optical field of the fiber link and the output optical field of the fiber link, respectively, as a function of time denotes the integration region of the first order Volterra kernel function ​​ ​ ， wherein, is the index of the wavelength combination selected from the set of DWDM candidate wavelengths, used to indicate the wavelength group involved in the order Volterra kernel; and respectively represent the time and iterative wavelength combination the weighting coefficient of the order Volterra kernel; is the step factor corresponding to the order kernel function; is the time nonlinear distortion error metric calculated according to the link bit error rate, cross-phase modulation intensity and the degree of amplifier gain compression; is the normalized modulation factor composed of the average power, minimum wavelength interval and equivalent dispersion slope of the wavelength combination at time iteration; ​ ， According to the link nonlinearity compensation principle and the target kernel function, a pre-compensation signal for offsetting the link nonlinearity distortion is generated : ， ​ 4. The method of claim 1, wherein, ​ ​ ， wherein is the free spectral range of the micro-ring resonator, is the vacuum speed of light, is the group refractive index of the micro-ring resonator waveguide material, is the circumference of the micro-ring resonator; ​ ​ ​ 5. The method of claim 4, wherein, ​ ​ ， wherein is the resonant center wavelength of the microring resonator, is the circumference of the microring resonator, is the effective index of the slot waveguide structure, is the resonant mode order; ​ ， In the formula, represents the offset amount, represents the adjustment amount of the effective refractive index.

6. A multi-frequency radio-over-fiber backhaul system based on DWDM dynamic wavelength mapping, deployed at a remote radio node, for implementing the method of any one of claims 1-5; characterized in that, ​ ​ ​ ​ a pre-distortion compensation unit configured to perform a pre-distortion compensation process on the composite baseband signal based on a nonlinearity model of the fiber link to generate a pre-compensated signal for counteracting fiber transmission nonlinearity distortion; an optical domain modulation unit configured to modulate the pre-compensated signal in an optical domain at a dynamically determined DWDM transmission wavelength and couple to a single fiber link through a DWDM optical multiplexer for transmission to a central facility.

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