WO2023246089A1

WO2023246089A1 - Mobile fronthaul system and method, and storage medium

Info

Publication number: WO2023246089A1
Application number: PCT/CN2023/072280
Authority: WO
Inventors: 吕凯林; 朱晓光; 陈文娟; 范忱
Original assignee: 中兴通讯股份有限公司
Priority date: 2022-06-20
Filing date: 2023-01-16
Publication date: 2023-12-28
Also published as: CN117318814A

Abstract

The present invention relates to the technical field of mobile communications. Disclosed are a mobile fronthaul system and method, and a storage medium. The system comprises a transmitting end and a receiving end; the transmitting end is connected to the receiving end by means of a single-mode optical fiber; the transmitting end converts a first analog signal into a first digital signal, and loads the first digital signal onto an optical carrier to obtain a modulated first optical signal; the receiving end performs self-coherent detection on the first optical signal, detects same to obtain a second digital signal, amplifies the second digital signal, and filters out-of-band quantization noise of the amplified second digital signal to obtain a second analog signal; the single-mode optical fiber transmits the first optical signal to the receiving end.

Description

Mobile fronthaul system, method and storage medium

Cross-references to related applications

This disclosure claims the priority of Chinese patent application CN202210698800.

Technical field

The present disclosure relates to the field of mobile communication technology, and in particular, to a mobile fronthaul system, method and storage medium.

Background technique

In recent years, with the development of the mobile Internet, smart devices have been constantly updated, the number of mobile terminals has increased dramatically, and mobile users' demands for transmission speed and latency experience have also increased. Currently, mobile fronthaul solutions can be divided into analog mobile fronthaul and digital mobile fronthaul.

Contents of the invention

Embodiments of the present disclosure provide a mobile fronthaul system, method and storage medium.

According to an aspect of an embodiment of the present disclosure, a mobile fronthaul system is provided, including: a transmitting end and a receiving end, the transmitting end and the receiving end are connected through a single-mode optical fiber, wherein the transmitting end transmits a first analog The signal is converted into a first digital signal, and the first digital signal is loaded onto an optical carrier to obtain a modulated first optical signal; the receiving end performs self-coherent detection on the first optical signal, and detects a second digital signal, amplify the second digital signal, filter out the out-of-band quantization noise of the amplified second digital signal, and obtain a second analog signal; the single-mode optical fiber transmits the first optical signal to the receiving end.

According to another aspect of the embodiment of the present disclosure, a mobile fronthaul method is also provided, including: converting a first analog signal into a first digital signal, wherein the first analog signal is an up-converted orthogonal frequency signal. OFDM analog signals are multiplexed, and the first digital signal is a DSM signal; the first digital signal is loaded onto the optical carrier generated by the laser diode to obtain a modulated first optical signal; the self-coherent receiver module The first optical signal is self-coherently detected to detect a second digital signal; after the second digital signal is amplified by a digital power amplifier, the out-of-band quantization noise of the amplified second digital signal is filtered out to obtain Second analog signal.

According to another aspect of the embodiments of the present disclosure, a storage medium is also provided. A computer program is stored on the storage medium. When the computer program is executed by a processor, the mobile fronthaul method as described above is implemented.

According to another aspect of the embodiments of the present disclosure, there is also provided a computer program product containing instructions, which when run on a computer, causes the computer to perform the above method.

Description of the drawings

The drawings described here are used to provide a further understanding of the present disclosure and constitute a part of the present disclosure. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation of the present disclosure. In the attached picture:

Figure 1 is a schematic structural diagram of a mobile fronthaul system in an embodiment of the present disclosure;

Figure 2 is a schematic structural diagram of the transmitting end of the mobile fronthaul system in an embodiment of the present disclosure;

Figure 3 is a schematic structural diagram of the receiving end of the mobile fronthaul system in an embodiment of the present disclosure;

Figure 4 is a schematic structural diagram of a self-coherent receiver module in an embodiment of the present disclosure;

Figure 5 is a schematic diagram of the structure and signal transmission of a mobile fronthaul system in an embodiment of the present disclosure;

Figure 6 is a schematic flowchart of a mobile fronthaul method according to an embodiment of the present disclosure;

Figure 7 is a schematic diagram of the self-coherence detection spectrum in an embodiment of the present disclosure; and

Figure 8 is a schematic diagram of the correction of the Delta Sigma modulated signal in the embodiment of the present disclosure.

Detailed ways

In order to enable those skilled in the art to better understand the present disclosure, the following will clearly and completely describe the technical solutions in the present disclosure embodiments in conjunction with the accompanying drawings. Obviously, the described embodiments are only These are part of the embodiments of this disclosure, not all of them. Based on the embodiments in this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the scope of protection of this disclosure. It should be noted that, as long as there is no conflict, the embodiments and features in the embodiments of the present disclosure can be combined with each other.

It should be noted that the terms "first", "second", etc. in the description and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It is to be understood that the data so used are interchangeable under appropriate circumstances so that the embodiments of the disclosure described herein can be practiced in sequences other than those illustrated or described herein. Furthermore, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, e.g., a process, method, product or apparatus that encompasses a series of steps or units need not be limited to those steps explicitly listed or units, but may include other steps or units not expressly listed or inherent to such processes, methods, products or devices.

Analog mobile fronthaul based on optical radio frequency technology has the advantages of large transmission capacity and high spectrum efficiency. However, due to the continuous waveform and peak-to-average power ratio of analog signals, they are easily affected by nonlinear distortion introduced by optical devices, electrical devices, and optical fiber links, resulting in limitations in their receiving sensitivity, transmission performance, and transmission distance. Digital mobile fronthaul usually uses CPRI (Common Public Radio Interface, Common Public Radio Interface) to sample and quantize the continuous waveform of analog signals, which can provide excellent transmission impairment tolerance, but the spectrum efficiency is relatively low and requires a large data bandwidth .

Mobile fronthaul usually uses the IMDD (Intensity-modulation with Direct-detection, intensity modulation direct detection) system. Although this solution has a simple structure, the receiving sensitivity of optical signals is low. The traditional coherent detection system can be used for simultaneous demodulation of amplitude and phase, and the receiving sensitivity can be effectively improved through the local oscillator. But in traditional optical coherent receivers, phase noise and frequency offset require complex digital signal processing to compensate and estimate. At the same time, components such as local lasers and balanced light detectors will significantly increase system cost and complexity.

In summary, in order to overcome the bottleneck problem of CPRI and the cost problem of traditional coherent detection systems, a mobile fronthaul solution with large fronthaul capacity, high receiving sensitivity and low system complexity is urgently needed.

An embodiment of the present disclosure provides a mobile fronthaul system. Refer to Figure 1. Figure 1 is a schematic structural diagram of a mobile fronthaul system in an embodiment of the present disclosure. The mobile fronthaul system includes: a transmitting end 10 and a receiving end 20. The transmitting end 10 and the receiving end 20 connected via single mode fiber 30. The transmitting end 10 converts the first analog signal into a first digital signal; loads the first digital signal onto the optical carrier to obtain a modulated first optical signal. The receiving end 20 performs self-coherent detection on the first optical signal to detect the second digital signal; amplifies the second digital signal and filters out the out-of-band quantization noise of the amplified second digital signal to obtain the second analog signal. The single-mode optical fiber 30 transmits the first optical signal to the receiving end.

In the embodiment of the present disclosure, the original signal is an analog signal. The transmitting end converts the analog signal into a digital signal and loads it onto the optical carrier to obtain a modulated optical signal. The modulated optical signal is transmitted to the receiving end through a standard single-mode optical fiber. The receiving end performs self-coherence detection on the optical signal, detects the digital signal carried in the optical signal, and then amplifies the digital signal, filters out the out-of-band quantization noise of the amplified digital signal, and converts the digital signal into an analog signal. Finally, Analog signals are transmitted through the antenna to achieve mobile fronthaul.

Analog signals are easily affected by nonlinear distortion. In the embodiment of the present disclosure, the original analog signal is converted into a digital signal for signal transmission, which can improve the system's ability to resist nonlinear noise. By performing self-coherent detection on the modulated optical signal, the detection Digital signal; amplify the digital signal, filter out the out-of-band quantization noise of the amplified digital signal, and restore the analog signal, realizing the conversion of digital-to-analog signals without the need for a digital-to-analog converter, reducing the cost of the mobile fronthaul system the complexity.

Referring to Figure 2, Figure 2 is a schematic structural diagram of the transmitter end of the mobile fronthaul system in an embodiment of the present disclosure. In the embodiment of the present disclosure, the transmitter end 10 includes an analog signal generation module 11, a Delta Sigma modulator module 12, and an electro-optical conversion module 13.

The analog signal generation module 11 generates a first analog signal, where the first analog signal is an up-converted orthogonal frequency division multiplexing OFDM analog signal.

In the embodiment of the present disclosure, the analog signal is generated by the analog signal generation module, and the generated analog signal is an orthogonal frequency division multiplexing OFDM (Orthogonal Frequency Division Multiplexing, orthogonal frequency division multiplexing) analog signal after upconversion.

Delta Sigma Modulator (DSM) module 12 converts the first analog signal into a first digital signal.

Delta Sigma modulation is a digital method based on oversampling and noise shaping. It samples the signal at a frequency much greater than twice the signal bandwidth, and moves most of the quantization noise frequency components to high frequencies through a loop filter. The traditional PCM (Pulse Code Modulation) linear pulse code modulation ADC (Analog-to-digital converter, analog-to-digital converter) is limited by the manufacturing process and cannot achieve high resolution, while the ADC based on Delta Sigma modulation technology can High resolution is achieved under relevant processes, and the structure is simple and easy to implement. Therefore, embodiments of the present disclosure use a Delta Sigma modulator module to convert analog signals into digital signals.

The original analog signal is converted into a digital signal after passing through the bandpass Delta Sigma modulator module, and the resulting digital signal is the Delta Sigma modulated signal. The digital signal is usually a two-level or four-level signal.

The electro-optical conversion module 13 loads the first digital signal onto the optical carrier to obtain a modulated first optical signal.

In the embodiment of the present disclosure, a digital signal is loaded onto an optical carrier through an electro-optical conversion module to obtain a modulated optical signal. In the embodiment, the electro-optical conversion module is a MZM (Mach-Zehnder Modulator), and the optical carrier Generated by LD (Laser Diode, laser diode), the Delta Sigma modulated signal is loaded onto the optical carrier generated by LD (Laser Diode, laser diode) through MZM (Mach-Zehnder Modulator, Mach-Zehnder modulator), and then passed through SSMF (Standard Single Mode Fiber, standard single-mode fiber) transmits the optical signal carrying the Delta Sigma modulated signal to the receiving end of the mobile fronthaul system.

The transmitting end of the embodiment of the present disclosure includes an analog signal generation module, a Delta Sigma modulator module, and an electro-optical conversion module, which converts the original analog signal into a digital signal, and then loads the digital signal onto the optical carrier to obtain a modulated optical signal. By using the Delta Sigma modulator module to convert analog signals into digital signals, the system's ability to resist nonlinear noise can be improved. Compared with using CPRI to sample and quantize the continuous waveform of analog signals, it can improve spectrum utilization.

Referring to FIG. 3 , FIG. 3 is a schematic structural diagram of the receiving end of the mobile fronthaul system in an embodiment of the disclosure. In the embodiment of the disclosure, the receiving end 20 includes a self-coherent receiver module 21 , a digital power amplifier module 22 , and a bandpass filter module 23 .

The self-coherent receiver module 21 performs self-coherent detection on the first optical signal, and detects the second digital signal.

In this disclosed embodiment, the optical signal modulated by the transmitting end is transmitted to the receiving end through a standard single-mode optical fiber. The self-coherent receiver module in the receiving end converts the optical signal into an electrical signal, and detects the Delta Sigma modulated signal carried in the optical signal. .

The digital power amplifier module 22 amplifies the second digital signal.

The digital signal detected by the self-coherent receiver module is amplified by a DPA (Digital Power Amplifier), and its efficiency is much higher than that of an analog power amplifier.

The bandpass filter module 23 filters out-of-band quantization noise of the amplified second digital signal to obtain a second analog signal.

The embodiment of the present disclosure uses a BPF (Band-pass Filter) to filter out the out-of-band quantization noise of the Delta Sigma modulated signal, thereby recovering the digital signal to obtain an OFDM analog signal.

In the embodiment of the present disclosure, the receiving end includes a self-coherent receiver module, a digital power amplifier module, and a bandpass filter module. The receiving end uses the self-coherent receiver module to perform self-coherent detection of optical signals, detect digital signals, and uses a digital power amplifier. Amplify the digital signal, use a bandpass filter to convert the digital signal into the original analog signal, and finally transmit the analog signal through the antenna. Compared with the traditional coherent detection system, the embodiment of the present disclosure does not require the use of complex digital signal processing. Compensation and estimation of phase noise and frequency offset reduce system complexity.

Referring to Figure 4, Figure 4 is a schematic structural diagram of a self-coherent receiver module in an embodiment of the present disclosure. The self-coherent receiver module consists of a DFB (Distributed Feedback, distributed feedback) laser and an EAM (Electro-absorption Modulator, electro-absorption modulator) Composed, the distributed feedback laser provides the local oscillator light required in the self-coherent receiver module. When the wavelength difference between the first wavelength of the first optical signal and the second wavelength of the local oscillator light is less than a preset threshold, the local oscillator light and The first optical signal injected into the electroabsorption modulator is locked and synchronized; the electroabsorption modulator detects the second optical signal coupled with the local oscillator light provided by the distributed feedback laser to obtain a second digital signal.

The self-coherent receiver module in the disclosed embodiment is EML (Electro-absorption Modulated Laser, electro-absorption modulated laser). EML is an integrated device of EAM and DFB laser. It is a high-speed optical fiber transmission network with small size and low wavelength chirp integrated by an electroabsorption modulator that utilizes the quantum confinement Stark effect (QCSE) and a DFB laser that uses internal grating coupling to determine the wavelength. A high-performance optical communication light source for medium-sized information transmission carriers. In coherent detection, DFB serves as the local oscillator and EAM serves as the detector. Part of the signal light injected into the EML is injected into the EAM detector and part into the DFB laser. The EAM has a similar structure to the photodiode and can be used as a detector when working in the absorption state. DFB The laser acts as an injection-locked slave laser, providing the local oscillator light required in an autocoherent receiver. When the carrier wavelength of the injected signal light is similar to the wavelength of the laser generated by the DFB, and the wavelength difference between the first wavelength of the first optical signal and the second wavelength of the local oscillator light is less than the preset threshold, using injection locking technology, the wavelength of the laser generated by the DFB laser Can be migrated to the signal light, which is the same wavelength as the signal light, and the output power remains unchanged. At the same time, injection-locked lasers can effectively suppress amplitude noise and phase noise without requiring frequency offset estimation, thus simplifying the processing of received signals. In addition, the line width of the output light of the slave laser is only determined by the master light and has nothing to do with the original line width of the slave laser, thereby reducing the line width of the DFB laser and improving the stability of the DFB laser.

In the embodiment of the present disclosure, a polarization controller and an optical circulator are further provided between the transmitting end and the receiving end, wherein the polarization controller adjusts the polarization state of the first optical signal to be consistent with the polarization state of the local light in the self-coherent receiver module. Consistent; the optical circulator blocks the output light of the self-coherent receiver module from flowing back to the transmitter.

In some examples, the polarization state of the signal light can be adjusted by manually adjusting a PC (Polarization controller) so that it is consistent with the polarization state of the local oscillator light in coherent detection. In some examples, optical circulators use multi-port non-reciprocal optical devices to complete the separation task of forward and reverse transmission signal light. The signal light whose polarization state is adjusted by the polarization controller is injected into the EML self-coherent receiver through an OC (Optical Circulator) to prevent the EML output light from flowing back to the transmitter.

Using the above solution of the embodiment of the present disclosure, the polarization state of the first optical signal is adjusted and the output light of the self-coherent receiver module is blocked from flowing back to the transmitter.

Refer to FIG. 5 , which is a schematic diagram of the structure and signal transmission of a mobile fronthaul system in an embodiment of the present disclosure. Refer to FIG. 5 for a complete explanation of the mobile fronthaul system in an embodiment of the present disclosure.

As shown in Figure 5(1), the mobile fronthaul system in the embodiment of the present disclosure consists of an analog signal generation module, a Delta Sigma modulator module, an electro-optical conversion module, a single-mode optical fiber, an autocoherent receiver module, a digital power amplifier module, and a band-pass filtering module. It consists of a polarization controller module, a polarization controller, and an optical circulator.

The original signal is usually an up-converted OFDM (Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing) analog signal. The analog signal is converted into a digital signal, that is, a Delta Sigma modulated signal, after passing through a bandpass Delta Sigma modulator, as shown in the figure As shown in 5(2), the Delta Sigma modulated signal is modulated onto the optical carrier generated by LD (Laser Diode) through MZM (Mach-Zehnder Modulator), and the signal light is transmitted through SSMF (Standard Single Mode) Fiber, standard single-mode optical fiber), the polarization state of the signal light is adjusted by manually adjusting the PC (Polarization controller, polarization controller), so that it is consistent with the polarization state of the local oscillation light in coherent detection, and passes through the OC (Optical Circulator, optical circulator) is injected into the EML self-coherent receiver, where OC is used to prevent the EML output light from flowing back to the transmitter. The Delta Sigma modulated signal detected by EML is amplified by a DPA (Digital Power Amplifier, digital power amplifier), and a BPF (Band-pass Filter, band-pass filter) is used to filter out the out-of-band quantization noise of the Delta Sigma modulated signal, thereby restoring The OFDM analog signal is obtained, and finally the OFDM analog signal is transmitted through the antenna to achieve mobile fronthaul.

A mobile fronthaul system proposed in an embodiment of the present disclosure includes: a transmitting end and a receiving end, and the transmitting end and the receiving end are connected through a single-mode optical fiber. The transmitting end converts the first analog signal into a first digital signal; loads the first digital signal onto the optical carrier to obtain a modulated first optical signal. The receiving end performs self-coherence detection on the first optical signal to detect the second digital signal; amplifies the second digital signal and filters out the out-of-band quantization noise of the amplified second digital signal to obtain the second analog signal. The single-mode optical fiber transmits the first optical signal to the receiving end. Since analog signals are easily affected by nonlinear distortion, in the embodiment of the present disclosure, the original analog signal is converted into a digital signal for signal transmission, which can improve the system's ability to resist nonlinear noise and perform self-coherent detection on the modulated optical signal. , detect the digital signal; amplify the digital signal, filter out the out-of-band quantization noise of the amplified digital signal, and restore the analog signal, realizing the conversion of digital-to-analog signals without the need for a digital-to-analog converter, reducing the cost Mobile fronthaul system complexity.

An embodiment of the present disclosure also proposes a mobile fronthaul method. Refer to FIG. 6 . FIG. 6 is a schematic flowchart of a mobile fronthaul method according to an embodiment of the present disclosure. The method includes steps S10 to S40.

S10. Convert the first analog signal into a first digital signal, where the first analog signal is an upconverted orthogonal frequency division multiplexing OFDM analog signal, and the first digital signal is a Delta Sigma modulated signal.

In this disclosed embodiment, the original signal is an up-converted OFDM (Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing) analog signal. The analog signal is converted into a digital signal after passing through a bandpass Delta Sigma modulator.

S20: Load the first digital signal onto the optical carrier generated by the laser diode to obtain a modulated first optical signal.

In this step, the first digital signal, that is, the Delta Sigma modulated signal, is loaded onto the optical carrier generated by the LD (Laser Diode, laser diode) through the MZM (Mach-Zehnder Modulator) to obtain a signal containing Delta Sigma A light signal that modulates the signal.

S30, perform self-coherence detection on the first optical signal through the self-coherence receiver module, and detect the second digital signal.

The optical signal is transmitted in SSMF (Standard Single Mode Fiber, standard single-mode fiber) and injected into the EML self-coherent receiver. The self-coherent receiver performs self-coherent detection on the optical signal and detects the Delta Sigma modulation in the optical signal. Signal.

S40: After amplifying the second digital signal through a digital power amplifier, filter out-of-band quantization noise of the amplified second digital signal to obtain a second analog signal.

The Delta Sigma modulated signal detected by EML is amplified by a DPA (Digital Power Amplifier), which is much more efficient than an analog power amplifier, and then a BPF (Band-pass Filter) is used to filter out the Delta Sigma modulated signal. The out-of-band quantization noise is recovered to recover the OFDM analog signal, and finally the recovered OFDM analog signal is transmitted through the antenna to realize the mobile fronthaul solution.

In this disclosed embodiment, the original analog signal is converted into a Delta Sigma digital signal, which can improve the system's ability to resist nonlinear noise and improve spectrum utilization. The self-coherent receiver module is used to perform self-coherent detection on the digital signal at the receiving end, which can improve the system's ability to resist nonlinear noise. Receiving sensitivity, reducing system complexity and power consumption.

In some implementations of the embodiments of the present disclosure, the first optical signal is self-coherently detected through an autocoherent receiver, and the second digital signal is detected, that is, S30, which includes steps S31 to S32.

S31. Adjust the polarization state of the first optical signal to be consistent with the polarization state of the local oscillation light provided in the self-coherent receiver module.

In the embodiment of the present disclosure, the way to adjust the polarization state of the first optical signal may be to adjust the polarization state of the signal light by adjusting the PC (Polarization controller, polarization controller) so that it maintains the polarization state of the local light in coherent detection. consistent.

S32. Detect the second optical signal after coupling the first optical signal and the local oscillator light to obtain a second digital signal.

The EML autocoherent receiver is composed of a DFB (Distributed Feedback) laser and an EAM (Electro-absorption Modulator). In coherent detection, DFB serves as the local oscillator and EAM serves as the detector. Part of the signal light injected into the EML is injected into the EAM detector and part into the DFB laser. The EAM has a similar structure to the photodiode and can be used as a detector when working in the absorption state. DFB The laser acts as an injection-locked slave laser to provide the local oscillator light required in the autocoherent receiver. When the injected signal light carrier wavelength is consistent with the DFB The wavelength of the laser generated is similar. When the wavelength difference between the first wavelength of the first optical signal and the second wavelength of the local oscillator light is less than the preset threshold, using injection locking technology, the wavelength of the laser generated by the DFB laser can be migrated to the same wavelength as the signal light. , and the output power remains unchanged. At the same time, injection-locked lasers can effectively suppress amplitude noise and phase noise without requiring frequency offset estimation, thus simplifying the processing of received signals. In addition, the line width of the output light of the slave laser is only determined by the master light and has nothing to do with the original line width of the slave laser, thereby reducing the line width of the DFB laser and improving the stability of the DFB laser.

Referring to Figure 7, Figure 7 is a schematic diagram of the self-coherent detection spectrum in an embodiment of the present disclosure, where Figure 7(1) is the first optical signal spectrum, Figure 7(2) is the DFB laser emission spectrum, and Figure 7(3) is the EAM reception signal spectrum. The first optical signal spectrum of the Delta Sigma modulated signal modulated onto the optical carrier through MZM is shown in Figure 7(1). The optical carrier is generated by LD, its wavelength is λ _LD and the line width is narrow. The laser spectrum generated by DFB is shown in Figure 4(2), and its wavelength is λ _DFB . A part of the first optical signal is injected into the DFB. When the difference between λ _LD and λ _DFB is less than the locking range of the DFB laser, the laser wavelength generated by the DFB laser is locked and synchronized to the wavelength of the injected light wave λ _LD , and the line width is only determined by the injected light wave. The light wave determines, thus providing the local oscillator light required in an autocoherent receiver. The local oscillator light provided by the DFB laser is coupled with the first optical signal injected into the EAM and detected by the EAM. The spectrum of the EAM received signal is shown in Figure 4(3). The carrier power of this signal is higher than the carrier power of the injected first optical signal, and the carrier power of this signal will not decrease as the received optical power decreases, so It can improve the receiving sensitivity of the system.

The embodiment of the present disclosure uses an EML autocoherent receiver to detect the Delta Sigma modulated signal carried by the first optical signal to achieve photoelectric conversion of the signal.

In addition, since injection locking technology usually uses pure optical carriers for injection, in this embodiment, an optical signal carrying a Delta Sigma modulation signal is used for injection. Therefore, in order to better achieve injection locking, the embodiment of the present disclosure can also use two methods To correct the Delta Sigma modulated signal, refer to Figure 8. Figure 8 is a schematic diagram of the correction of the Delta Sigma modulated signal in an embodiment of the present disclosure.

In some embodiments, before performing autocoherent detection on the first optical signal through an autocoherent receiver and detecting the second digital signal, the method further includes: extracting the analog-to-digital signal conversion according to the first digital signal and the first analog signal. the quantization noise at the time; multiply the quantization noise by the preset factor to obtain the attenuated quantization noise; and subtract the attenuated quantization noise from the first digital signal to obtain the modified first digital signal.

The embodiment of the present disclosure corrects the Delta Sigma modulated signal through quantization and noise reduction. Referring to Figure 8(1), the input is first subtracted from the analog-to-digital converted Delta Sigma modulated signal, that is, the original analog signal is subtracted to extract the quantization noise, and then the quantization noise is multiplied by the factor α (0<α<1 ) is attenuated, and finally, the attenuated quantization noise is subtracted from the Delta Sigma modulated signal again to obtain the corrected "Delta Sigma modulated signal".

Multi-bit quantization is a common method to reduce quantization noise, but it will cause the data rate to be too high. However, the embodiment of the present disclosure removes a part of the quantization noise from the Delta Sigma modulated signal and controls the noise reduction level through the quantization noise reduction factor α, which can Reduce the quantization noise around the optical carrier of the Delta Sigma modulated signal and ensure that the increase in the remaining carrier component does allow a larger locking range to achieve the injection locking technology of the Delta Sigma modulated signal.

In other embodiments, before performing self-coherent detection on the first optical signal through an autocoherent receiver and detecting the second digital signal, the method further includes: using a first-order high-pass Butterworth digital with a cutoff frequency F ₀ of β The filter filters out low-frequency noise near the optical carrier of the first digital signal to obtain a larger residual carrier component, and obtains the modified first digital signal.

The embodiment of the present disclosure corrects the Delta Sigma modulated signal through high-pass filtering. Referring to Figure 8(2), a first-order high-pass Butterworth digital filter with a cutoff frequency F ₀ of β (0<β<1) is used to filter out the low-frequency noise near the Delta Sigma modulated signal optical carrier through high-pass filtering to obtain a better Large residual carrier component, thereby greatly increasing the locking range to achieve injection locking technology for Delta Sigma modulated signals.

The Delta Sigma modulated signal is corrected through the above two methods to better realize the injection locking of the Delta Sigma modulated signal.

Through the description of the above embodiments, those skilled in the art can clearly understand that the method according to the above embodiments can be implemented by means of software plus the necessary general hardware platform. Of course, it can also be implemented by hardware, but in many cases the former is Better implementation. Based on this understanding, the technical solution of the present disclosure can be embodied in the form of a software product in essence or that contributes to related technologies. The computer software product is stored in a storage medium (such as ROM/RAM, magnetic disk, optical disk). ), includes several instructions to cause a terminal device (which can be a mobile phone, computer, server, or network device, etc.) to execute the methods of various embodiments of the present disclosure.

An embodiment of the present disclosure also provides a computer-readable storage medium on which a computer program is stored. The computer-readable storage medium can be at least one of ROM (Read-Only Memory)/RAM (Random Access Memory), a magnetic disk, and an optical disk. The computer-readable storage medium includes a number of instructions. It is used to cause a terminal device with a control module (which can be a television, a car, a mobile phone, a computer, a server, a terminal, or a network device, etc.) to execute the methods described in the above embodiments of the present disclosure.

In yet another embodiment provided by the present disclosure, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to execute the methods described in the above embodiments of the present disclosure.

The above serial numbers of the embodiments of the present disclosure are only for description and do not represent the advantages and disadvantages of the embodiments.

In the above-mentioned embodiments of the present disclosure, each embodiment is described with its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

In the several embodiments provided in this disclosure, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only illustrative, such as the division of units, which is only a Logical function division can be divided in other ways in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. On the other hand, the coupling or direct coupling or communication connection between each other shown or discussed may be through some interfaces, and the indirect coupling or communication connection of the units or modules may be in electrical or other forms.

A unit described as a separate component may or may not be physically separate. A component shown as a unit may or may not be a physical unit, that is, it may be located in one place, or it may be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in various embodiments of the present disclosure may be integrated into one processing unit, or each unit may exist physically alone, or two or more units may be integrated into one unit. The above integrated units can be implemented in the form of hardware or software functional units.

Integrated units may be stored in a computer-readable storage medium if they are implemented in the form of software functional units and sold or used as independent products. Based on this understanding, the technical solution of the present disclosure is essentially or contributes to the relevant technology, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, It includes several instructions to cause a computer device (which can be a personal computer, a server or a network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present disclosure. The aforementioned storage media include: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program code. .

The above are only optional implementations of the present disclosure. It should be noted that those of ordinary skill in the art can also make several improvements and modifications without departing from the principles of the present disclosure. These improvements and modifications It should also be regarded as the protection scope of this disclosure.

Claims

A mobile fronthaul system, including: a transmitting end and a receiving end, the transmitting end and the receiving end are connected through a single-mode optical fiber, wherein,

The transmitting end converts the first analog signal into a first digital signal; loads the first digital signal onto an optical carrier to obtain a modulated first optical signal;

The receiving end performs self-coherence detection on the first optical signal to detect a second digital signal; amplifies the second digital signal to filter out out-of-band quantization of the amplified second digital signal. noise to obtain a second analog signal; and

The single-mode optical fiber transmits the first optical signal to the receiving end.
The mobile fronthaul system of claim 1, wherein the transmitter includes an analog signal generation module, a DSM module, and an electro-optical conversion module;

The analog signal generation module generates a first analog signal, wherein the first analog signal is an up-converted orthogonal frequency division multiplexing OFDM analog signal;

The DSM module converts the first analog signal into a first digital signal; and

The electro-optical conversion module loads the first digital signal onto an optical carrier to obtain a modulated first optical signal.
The mobile fronthaul system of claim 1, wherein the receiving end includes an autocoherent receiver module, a digital power amplifier module, and a bandpass filter module; wherein,

The self-coherent receiver module performs self-coherent detection on the first optical signal and detects the second digital signal;

The digital power amplifier module amplifies the second digital signal; and

The bandpass filter module filters out-of-band quantization noise of the amplified second digital signal to obtain a second analog signal.
The mobile fronthaul system of claim 3, wherein the self-coherent receiver module is composed of a distributed feedback laser and an electroabsorption modulator,

The distributed feedback laser provides the local oscillator light required in the self-coherent receiver module, when the wavelength difference between the first wavelength of the first optical signal and the second wavelength of the local oscillator light is less than a preset threshold. In this case, the local oscillator light is locked and synchronized with the first optical signal injected into the electroabsorption modulator; and

The electroabsorption modulator couples the first optical signal and the local oscillator optical coupler provided by the distributed feedback laser. The combined second optical signal is detected to obtain a second digital signal.
The mobile fronthaul system according to claim 3, wherein a polarization controller and an optical circulator are further provided between the transmitting end and the receiving end, wherein,

The polarization controller adjusts the polarization state of the first optical signal to be consistent with the polarization state of the local light in the self-coherent receiver module; and

The optical circulator blocks the output light of the self-coherent receiver module from flowing back to the transmitter.
A mobile fronthaul method including:

Convert the first analog signal into a first digital signal, wherein the first analog signal is an upconverted orthogonal frequency division multiplexing OFDM analog signal, and the first digital signal is a DSM signal;

Load the first digital signal onto the optical carrier generated by the laser diode to obtain a modulated first optical signal;

The first optical signal is self-coherently detected through the self-coherent receiver module, and the second digital signal is detected; and

After the second digital signal is amplified by a digital power amplifier, the out-of-band quantization noise of the amplified second digital signal is filtered to obtain a second analog signal.
The mobile fronthaul method according to claim 6, wherein the self-coherence detection of the first optical signal by the self-coherence receiver, and detecting the second digital signal includes:

Adjusting the polarization state of the first optical signal to be consistent with the polarization state of the local oscillator light provided in the self-coherent receiver module; and

The first optical signal and the second optical signal coupled to the local oscillator are detected to obtain a second digital signal.
The mobile fronthaul method according to claim 7, wherein the first optical signal is self-coherently detected by the self-coherent receiver, and before the second digital signal is detected, the method further includes:

According to the first digital signal and the first analog signal, extract the quantization noise during analog-to-digital signal conversion;

Multiply the quantization noise by a preset factor to obtain attenuated quantization noise; and

Subtract the attenuated quantization noise from the first digital signal to obtain a modified first digital signal.
The mobile fronthaul method according to claim 7, wherein the first The optical signal is subjected to self-coherence detection, and before the second digital signal is detected, the method further includes:

A first-order high-pass Butterworth digital filter with a cutoff frequency F0 of β is used to filter out the low-frequency noise near the optical carrier of the first digital signal to obtain a larger residual carrier component and obtain the modified first digital signal.
A storage medium. A computer program is stored on the storage medium. When the computer program is executed by a processor, the mobile fronthaul method according to any one of claims 7 to 9 is implemented.