WO2018094650A1

WO2018094650A1 - Modulation method and apparatus

Info

Publication number: WO2018094650A1
Application number: PCT/CN2016/107114
Authority: WO
Inventors: 周恩波
Original assignee: 华为技术有限公司
Priority date: 2016-11-24
Filing date: 2016-11-24
Publication date: 2018-05-31

Abstract

A modulation method and apparatus. The modulation method comprises: a transmission end performing time-frequency conversion on a first time domain digital signal to obtain a first frequency domain digital signal, the first time domain digital signal being an electrical signal to be modulated at the transmission end; according to a channel fading feature of an optical fibre communication system, the transmission end adjusting a parameter of at least one sub-carrier among sub-carriers included in the first frequency domain digital signal to obtain a second frequency domain digital signal; the transmission end performing inverse time-frequency conversion on the second frequency domain digital signal to obtain a second time domain digital signal; and the transmission end performing electrical-to-optical conversion on the second time domain digital signal to obtain an optical signal, and transmitting the optical signal to a receiving end.

Description

Modulation method and device

Technical field

The present invention relates to the field of optical communication technologies, and in particular, to a modulation method and apparatus.

Background technique

In recent years, as the demand for telecommunication services continues to increase, there is an urgent need for transmission systems to provide high-speed, large-capacity data transmission. Optical fiber communication systems are widely used in data transmission processes due to their high speed and large capacity.

In optical fiber communication systems, channel fading occurs in Direct Detection (DD) systems due to the effects of chromatic dispersion effects of fiber links. Channel fading refers to the transmission of signals in the system. Subcarriers at different frequencies will produce different degrees of power fading during transmission, which is referred to as frequency power fading. The frequency power fading causes distortion of the signal received by the receiving end of the optical fiber communication system, and the bit error rate (BER) of the signal becomes large. For example, in addition to the dispersion of the fiber link, factors such as the characteristics of the optical device, the nonlinear characteristics of the modulator, and the nonlinear characteristics of the demodulator can cause frequency power fading. Especially with the accumulation of dispersion in the fiber link, the frequency power fading caused by the dispersion of the fiber link becomes more and more serious.

In the existing signal modulation scheme, the problem of frequency power fading is usually solved by compensating for the dispersion of the fiber link during signal modulation. For example, a time-domain compensation algorithm such as Maximum Likelihood Sequence Estimation (MLSE) algorithm performs sequence detection and decision on a signal that is time-domain-distorted due to dispersion, thereby compensating for dispersion. When the frequency domain power fading problem is solved by the time domain compensation algorithm, since the time domain compensation algorithm is based on the estimation of the sequence, it is difficult to completely avoid the influence of power fading, and thus the existing signal modulation scheme cannot solve the frequency point well. The problem of power fading.

In summary, in the field of optical fiber communication technology, there is a need for a modulation method that can better solve the problem of frequency power fading, so as to better solve the problem of frequency power fading in optical fiber communication systems and reduce the error of optical communication systems. Code rate.

Summary of the invention

In view of this, a modulation method and apparatus are provided to better solve the frequency power fading problem in the optical fiber communication system and reduce the bit error rate of the optical fiber communication system.

In a first aspect, an embodiment of the present invention provides a modulation method, which is performed by a transmitting end of a fiber optic communication system, and includes the following steps: performing time-frequency conversion on a first time domain digital signal to obtain a first frequency domain digital signal, where The first time domain digital signal is an electrical signal to be modulated by the transmitting end; and the parameters of at least one of the subcarriers included in the first frequency domain digital signal are adjusted according to a channel fading characteristic of the optical fiber communication system, to obtain a second frequency domain. a digital signal, wherein the adjusted subcarrier is all or part of subcarriers included in the first frequency domain digital signal, and which subcarrier needs to be adjusted according to channel fading characteristics; and then, the transmitting end reverses the second frequency domain digital signal The time-frequency conversion obtains the second time domain digital signal; finally, the transmitting end performs electro-optical conversion on the second time domain digital signal to obtain an optical signal, and transmits the optical signal to the receiving end.

The channel fading characteristic of the optical fiber communication system refers to the fading of the received power of the subcarriers at different frequency points relative to the transmission power in the signal transmitted in the optical fiber communication system. The channel fading characteristics of a fiber-optic communication system are independent of the signals transmitted in the fiber link and are only related to the channel performance of the fiber-optic communication system. For example, if the channel fading characteristic of a fiber-optic communication system indicates that the received power of the sub-carrier with a frequency of 20 GHz is 50% relative to the fading of the transmission power, then when the signal A is transmitted in the optical fiber communication system, the IF of the signal A is The received power of the 20 GHz subcarrier is fading to 50% of the transmit power. When the signal B is transmitted in the optical fiber communication system, the received power of the subcarrier of the signal B with a frequency of 20 GHz is also fading to 50% of the transmit power.

In the above solution, the parameters of at least one of the subcarriers included in the first frequency domain digital signal are adjusted according to the channel fading characteristic of the optical fiber communication system to obtain a second frequency domain digital signal. Since the channel fading characteristic of the optical fiber communication system is used as a basis for adjustment when adjusting parameters of at least one of the subcarriers included in the first frequency domain digital signal, the channel fading characteristic indicates power fading of subcarriers at different frequency points. In the case, the parameters of at least one of the subcarriers included in the first frequency domain digital signal are adjusted according to the channel fading characteristic, and the first frequency can be accurately compensated The frequency power fading of the subcarriers contained in the domain digital signal. The adjusted second frequency domain digital signal is processed to obtain an optical signal, and the optical signal is transmitted to the receiving end via the optical fiber, and the optical signal received by the receiving end is an optical signal converted by the adjusted electrical signal, and thus the receiving end After the optical signal is reduced to an electrical signal, the recovered electrical signal has a low bit error rate.

In summary, the modulation method provided by the above first aspect can more accurately solve the frequency power fading problem in the optical fiber communication system and reduce the bit error rate of the optical fiber communication system.

In a possible design, after the inverse frequency conversion of the second frequency domain digital signal, the transmitting end can also perform digital-to-analog conversion on the second time domain digital signal to obtain a time domain analog signal; When the second time domain digital signal is subjected to electro-optical conversion, the time domain analog signal is actually subjected to electro-optical conversion.

In one possible design, the channel fading characteristic is used to indicate the percentage of received power of each subcarrier contained in the first frequency domain digital signal relative to the transmit power fading.

It should be noted that, when the channel fading characteristic indicates the power fading condition of the subcarrier, it is not limited to the indication manner of the percentage of the received power relative to the fading of the transmit power, as long as the power fading condition of the subcarrier can be indicated.

In a possible design, the parameters of the at least one subcarrier include: a transmit power and/or a frequency point of each of the at least one subcarrier;

The transmitting end adjusts parameters of at least one of the subcarriers included in the first frequency domain digital signal according to the channel fading characteristic, and specifically includes: for each subcarrier in the at least one subcarrier: if the channel fading characteristic indicates a certain subcarrier The percentage of the received power relative to the transmit power fading is a fixed value greater than the first threshold, and the transmit power of the subcarrier is increased by a set multiple; if the channel fading characteristic indicates the percentage of the received power of a certain subcarrier relative to the transmit power fading If it is greater than the second threshold, the frequency of the subcarrier is changed.

The set multiple may be a ratio of a difference between the transmit power and the received power and the received power.

It should be noted that, if the channel fading characteristic indicates that the percentage of the received power of a certain subcarrier relative to the transmit power fading is greater than the second threshold, the frequency of the subcarrier is changed, and the frequency of the subcarrier is changed. When the subcarrier is transmitted, the received power of the subcarrier is relative to the transmit power The percentage of rate fading will be less than the second threshold.

When the channel fading characteristic indicates that the percentage of the received power of the certain subcarrier relative to the transmit power fading is greater than the second threshold, the parameter of the adjusted subcarrier may be the frequency point of the subcarrier. The transmitting end can adjust the frequency of the subcarrier to prevent the subcarrier from transmitting at a frequency at which the percentage of the received power relative to the transmit power fading is greater than the second threshold, thereby avoiding the received power of the subcarrier relative to the transmit power. The percentage of fading is greater than the second threshold.

When the signal fading characteristic indicates that the percentage of the received power of the frequency point of the certain subcarrier relative to the transmit power fading is a fixed value greater than the first threshold, the transmitting end may increase the transmit power of the subcarrier by a set multiple at the transmitting end. The subcarrier transmitted at the frequency point is subjected to power fading, and the received power is the same as the original transmit power of the subcarrier.

In a possible design, the transmitting end may also encode the original bit information to obtain the first time domain digital signal before performing time-frequency conversion on the first time domain digital signal.

Wherein, the original bit signal can be converted into bit information represented by binary, quaternary, octal, hexadecimal or the like by encoding, that is, converted into the first time domain digital signal.

In a second aspect, an embodiment of the present invention provides a modulation apparatus that can be placed at a transmitting end of a fiber optic communication system and can be used to perform the modulation method provided by the above first aspect. The device comprises a time-frequency conversion module, a sub-carrier adjustment module, an inverse time-frequency conversion module, an electro-optical conversion module and a transmission module. among them,

The time-frequency conversion module is configured to perform time-frequency conversion on the first time domain digital signal to obtain a first frequency domain digital signal, where the first time domain digital signal is an electrical signal to be modulated;

The subcarrier adjustment module is configured to adjust a parameter of at least one of the subcarriers included in the first frequency domain digital signal according to a channel fading characteristic of the optical fiber communication system, to obtain a second frequency domain digital signal, where adjustment is needed. The subcarriers may be determined according to channel fading characteristics of the fiber communication system;

The inverse time-frequency conversion module is configured to perform inverse time-frequency conversion on the second frequency domain digital signal to obtain a second time domain digital signal;

The electro-optical conversion module is configured to perform electro-optical conversion on the second time domain digital signal to obtain an optical signal;

The transmission module is configured to transmit the optical signal obtained by electro-optical conversion of the electro-optical conversion module to the receiving end.

According to the above solution, since the channel fading characteristic of the optical fiber communication system is used as a basis for adjustment when the subcarrier adjustment module adjusts the parameters of at least one of the subcarriers included in the first frequency domain digital signal, the channel fading characteristic indicates The power fading condition of the subcarriers at different frequency points, so the subcarrier adjustment module adjusts the parameters of at least one of the subcarriers included in the first frequency domain digital signal according to the channel fading characteristic, and can accurately compensate the first frequency domain. The frequency power fading of the subcarriers contained in the digital signal. The electro-optical conversion module performs electro-optic conversion on the adjusted second frequency domain digital signal to obtain an optical signal, and the optical signal is transmitted by the transmission module to the receiving end via the optical fiber, and the optical signal received by the receiving end is the adjusted electrical signal. The optical signal converted into the optical signal, and thus the optical signal restored by the receiving end to the electrical signal, the error rate of the restored electrical signal is low.

In summary, the modulation apparatus provided by the above second aspect can more accurately solve the frequency power fading problem in the optical fiber communication system and reduce the error rate of the optical fiber communication system.

In a possible design, the above modulation device further includes a digital to analog conversion module. The digital-to-analog conversion module is configured to perform digital-to-analog conversion on the second time domain digital signal after the inverse time-frequency conversion module performs inverse time-frequency conversion on the second frequency domain digital signal to obtain a time domain analog signal; When the second time domain digital signal is subjected to electro-optical conversion, the time domain analog signal obtained after the digital-to-analog conversion is subjected to electro-optical conversion.

The subcarrier adjustment module is configured to: adjust, for the at least one subcarrier, the parameter of the at least one subcarrier included in the first frequency domain digital signal according to the channel fading characteristic Each subcarrier: if the channel fading characteristic indicates that the percentage of the received power of the subcarrier relative to the transmit power fading is a fixed value greater than the first threshold, the transmit power of the subcarrier is increased by a set multiple; if the channel fading characteristic indicates the subcarrier The percentage of received power relative to the transmit power fading is greater than the second threshold, and the frequency of the subcarrier is changed.

It should be noted that, if the channel fading characteristic indicates that the percentage of the received power of the certain subcarrier relative to the transmit power fading is greater than the second threshold, the subcarrier adjustment module changes the frequency of the subcarrier after the subcarrier is changed. When the subcarrier is transmitted at the frequency point, the percentage of the received power of the subcarrier relative to the transmit power fading will be less than the second threshold.

When the channel fading characteristic indicates that the percentage of the received power of the certain subcarrier relative to the transmit power fading is greater than the second threshold, the parameter of the subcarrier adjusted by the subcarrier adjustment module may be the frequency of the subcarrier. The subcarrier adjustment module can prevent the subcarrier from transmitting at a frequency point where the percentage of the received power relative to the transmit power fading is greater than the second threshold by changing the frequency of the subcarrier, thereby preventing the received power of the subcarrier from being opposite to the received power. The percentage of transmit power fading is greater than the second threshold.

When the signal fading characteristic indicates that the percentage of the received power of the frequency point of the certain subcarrier relative to the transmit power fading is a fixed value greater than the first threshold, the subcarrier adjustment module may increase the transmit power of the subcarrier at the transmitting end. The multiple is such that the subcarrier transmitted at the frequency is subjected to power fading, and the received power is the same as the original transmit power of the subcarrier.

In a possible design, the above modulation device further comprises an encoding module. The encoding module is configured to encode the original bit information to obtain a first time domain digital signal before the time-frequency conversion module performs time-frequency conversion on the first time domain digital signal.

The encoding module converts the original bit signal into bit information represented by binary, quaternary, octal, hexadecimal, etc. by encoding, that is, into the first time domain digital signal.

In a third aspect, an embodiment of the present invention provides a demodulation method, which can implement demodulation of a modulated signal obtained by the modulation method provided by the above first aspect. At the transmitting end of the optical fiber communication system, the first time domain digital signal is processed by the modulation method provided by the first aspect to obtain an optical signal, and the optical signal is transmitted to the receiving end, and the receiving end of the optical fiber communication system adopts a third party. The demodulation method provided by the surface can restore the first time domain digital signal.

In a fourth aspect, an embodiment of the present invention provides a demodulating apparatus, where the demodulating apparatus is configured to perform the demodulation method provided by the foregoing third aspect. The demodulation device can be regarded as a demodulation device corresponding to the modulation device provided by the above second aspect, that is, the operation performed by the modulation device provided by the second aspect described above can realize converting the first time domain digital signal into an optical signal. After the demodulation device receives the optical signal transmitted by the modulation device provided by the second aspect, the optical signal can be restored to the first time domain by performing an operation reciprocal with the modulation device provided by the second aspect. Digital signal.

In a fifth aspect, a computer readable storage medium is provided, where computer execution instructions are stored, and when at least one processor of a computing node executes the computer to execute an instruction, the computing node executes the first aspect or the first Various possible aspects of the aspect provide a method of providing, or performing the methods provided by the various possible designs of the third aspect or the third aspect above.

In a sixth aspect, a computer program product is provided, the computer program product comprising computer executed instructions stored in a computer readable storage medium. At least one processor of the computing node can read the computer-executable instructions from a computer-readable storage medium, the at least one processor executing the computer-executing instructions, such that the computing node implements the first aspect or the methods provided by the various possible designs of the first aspect Or implementing the methods provided by the various possible designs of the third aspect or the third aspect above.

DRAWINGS

FIG. 1 is a schematic diagram of channel fading characteristics according to an embodiment of the present invention;

2 is a schematic flowchart of a modulation method according to an embodiment of the present invention;

3 is a schematic diagram of frequency spectrum characteristics of a first frequency domain digital signal according to an embodiment of the present invention;

4 is a schematic diagram of spectrum characteristics of a second frequency domain digital signal according to an embodiment of the present invention;

FIG. 5 is a schematic diagram showing a comparison of signal power density spectra in a transmitting end and a receiving end when using the modulation method shown in FIG. 2 and the modulation method in the prior art according to an embodiment of the present invention; FIG.

FIG. 6 is a schematic flowchart diagram of a demodulation method according to an embodiment of the present disclosure;

FIG. 7 is a schematic flowchart diagram of another modulation method according to an embodiment of the present disclosure;

FIG. 8 is a schematic flowchart diagram of another demodulation method according to an embodiment of the present disclosure;

FIG. 9 is a schematic structural diagram of a modulation apparatus according to an embodiment of the present invention;

FIG. 10 is a schematic structural diagram of another modulation apparatus according to an embodiment of the present disclosure;

FIG. 11 is a schematic structural diagram of a demodulation apparatus according to an embodiment of the present invention;

FIG. 12 is a schematic structural diagram of another demodulation apparatus according to an embodiment of the present invention.

detailed description

For a better understanding of the above objects, aspects and advantages of the present invention, a detailed description is provided below. The detailed description sets forth various embodiments of the devices and/or methods in the <RTIgt; In these block diagrams, flowcharts, and/or examples, one or more functions and/or operations are included. Those skilled in the art will appreciate that the various functions and/or operations within the block diagrams, flowcharts or examples can be implemented individually or collectively by various hardware, software, firmware, or by any of hardware, software and firmware. Combined implementation.

The basic concepts involved in the embodiments of the present invention are explained below. It should be noted that the explanations are intended to make the embodiments of the present invention easier to understand, and should not be construed as limiting the scope of the invention as claimed.

First, optical fiber communication system

The optical fiber communication system includes a transmitting end and a receiving end, and the transmitting end and the receiving end are connected by a fiber link. The transmitting end is used for encoding and electro-optical converting the original bit information to obtain an optical signal, and transmitting the optical signal to the optical fiber link; the optical fiber link is used for transmitting the optical signal transmitted by the transmitting end to the receiving end; and the receiving end is used for receiving the optical signal transmitted by the transmitting end; The received optical signal is photoelectrically converted and decoded to restore original bit information. The original bit information is transmitted from the transmitting end to the receiving end through the optical fiber communication system.

Second, time-frequency conversion and inverse time-frequency conversion

In the embodiment of the present invention, time-frequency conversion refers to converting a time domain signal into a frequency domain signal, and inverse time-frequency conversion refers to converting a frequency domain signal into a time domain signal.

In the time-frequency conversion, serial-to-parallel conversion is required, that is, one serial time domain signal is converted into multiple parallel time domain signals, and then discrete Fourier transform is performed on the multi-channel parallel time domain signals. (Discrete Fourier Transform, DFT) or Fast Fourier Transformation (FFT) transforms to convert multiple parallel time domain signals into multiple parallel frequency domain signals.

In inverse time-frequency conversion, it is necessary to convert multiple parallel frequency domain signals into multiples by using Inverse Discrete Fourier Transform (IDFT) or Inverse Fast Fourier Transform (IFFT). The parallel time domain signal is parallel-converted and converted into a serial time domain signal.

It should be noted that after performing time-frequency conversion or inverse time-frequency conversion, only the domain of the signal description changes for the signal, but does not change any characteristics of the signal.

Third, channel fading characteristics

The channel fading characteristic is used to indicate the fading of the received power of the subcarriers at different frequency points with respect to the transmitted power for the transmitted signal in the optical fiber communication system. In a specific implementation, the channel fading characteristic may indicate a fading condition of the received power relative to the transmit power in a percentage manner, that is, the channel fading characteristic is used to indicate that the received power of each subcarrier included in the first frequency domain digital signal is fading relative to the transmit power. percentage.

It should be noted that, when the channel fading characteristic indicates the power fading condition of the subcarrier, it is not limited to the indication manner of the percentage of the received power relative to the fading of the transmit power, as long as the power fading condition of the subcarrier can be indicated. For ease of understanding, the present invention is an embodiment in which the channel fading characteristics are all indicated by the percentage of received power relative to the fading of the transmit power.

The fading in the channel fading characteristic refers to the decrease of the received power of the subcarrier relative to the transmit power. For example, the transmit power of a certain subcarrier in a certain signal is A. After the transmission through the optical link, the receiving end receives the subcarrier. The received power is B (B<A), then the power fading value of the subcarrier is AB, and the percentage of the received power of the subcarrier with respect to the transmit power fading is [(AB)/A]*100%.

Channel fading characteristics are related to many factors, such as transmission distance, link dispersion accumulation, 啁啾 characteristics, transmitter and receiver linearity. For example, in a fiber-optic communication system, when the transmission distance of the signal is 15 km, the percentage of the received power of the frequency carrier 1 and the frequency-frequency sub-carrier in the signal is 90% relative to the transmission power fading, and the frequency is 3 Receive power of subcarriers is fading relative to transmit power The percentage is 50%, and this characteristic can be called channel fading characteristics.

The channel fading characteristics are independent of the signals transmitted in the fiber link and are only related to the channel performance of the fiber-optic communication system. For example, if the channel fading characteristic of the optical fiber communication system indicates that the received power of the subcarrier of the frequency point 4 in the signal of the frequency point 4 is 90% relative to the fading of the transmission power, the received power of the subcarrier of the frequency point 5 is relative to the fading of the transmission power. 20%; then, when the signal A is transmitted through the optical fiber communication system, the percentage of the received power of the subcarrier of the signal A in the signal A is 90% relative to the transmit power, and the received power of the subcarrier of the frequency 5 is relative to the transmission. The percentage of power fading is 20%; when the signal B is transmitted through the optical fiber communication system, the received power of the subcarrier of the signal B in the intermediate frequency of the signal B is 90% relative to the fading of the transmission power, and the received power of the subcarrier of the frequency 5 is relatively The percentage of emission power fading is 20%.

The channel fading characteristics of fiber-optic communication systems can be obtained through experimental tests, digital signal processing (DSP) calculations, and the like.

Figure 1 shows the channel fading characteristics at different transmission distances. The abscissa in Figure 1 represents the frequency of the subcarriers in the signal transmitted in the fiber link, and the ordinate represents the relative power fading of the signal transmitted in the fiber link. From Figure 1, the following two conclusions can be drawn:

First, the farther the signal transmission distance is, the more serious the power fading of the signal is;

2. For the same signal at different transmission distances, the frequency of the subcarriers with larger power fading in the channel is generally different. For example, a subcarrier with a large power fading distance of 10 km has a frequency of about 19 GHz (GigaHertz, gigahertz) and 33 GHz, and a subcarrier with a large power fading at a transmission distance of 40 km has a frequency of about 10 GHz and 17GHz.

Fourth, electro-optical conversion

Electro-optical conversion refers to modulating a continuous wave (CW) by an electrical signal, and outputting an optical signal, and the output optical signal carries source information contained in the electrical signal. The output optical signal can be transmitted to the receiving end through the optical fiber, so that the source information carried in the optical signal can be transmitted to the receiving end. Electro-optic conversion is usually achieved by an electro-optic modulator having two inputs, one CW and the other an electrical signal containing source information.

Fifth, encoding and decoding

Encoding refers to converting the original bit information into bit information in binary, quaternary, octal, hexadecimal, etc. at the transmitting end to obtain a coded digital signal. In the embodiment of the present invention, the code can pass Non-Return to Zero (NRZ), Pulse Amplitude Modulation (PAM), Four Level Pulse Amplitude Modulation (PAM4), Realized by Quadrature Amplitude Modulation (QAM).

Reciprocal with the encoding, the digital signal in the time domain is decoded at the receiving end, and the original bit information can be restored. Similarly, decoding can also be implemented by NRZ, PAM, PAM4, QAM, and the like.

The embodiment of the invention provides a modulation method for better solving the frequency power fading problem in the optical fiber communication system and reducing the bit error rate of the optical fiber communication system. As shown in Figure 2, the method includes:

S201: The transmitting end performs time-frequency conversion on the first time domain digital signal to obtain a first frequency domain digital signal.

The first time domain digital signal is an electrical signal to be modulated at the transmitting end.

Optionally, before the transmitting end performs time-frequency conversion on the first time domain digital signal, the original bit information may be encoded to obtain a first time domain digital signal, where the original bit information is represented by a binary sequence. A digital signal consisting of "0" and "1".

Wherein, the coding can be implemented by means of non-return to zero code NRZ, PAM, PAM4, QAM, and the like.

When performing time-frequency conversion on the first time domain digital signal in S201, in addition to FFT and DFT, digital filter bank technology may be used to isolate the subcarriers of different frequency points in the first time domain digital signal. Crosstalk enhances the system's ability to resist signal distortion.

S202: The transmitting end adjusts parameters of at least one of the subcarriers included in the first frequency domain digital signal according to a channel fading characteristic of the optical fiber communication system, to obtain a second frequency domain digital signal.

In S202, the channel fading characteristic can be used to indicate a percentage of the received power of each subcarrier included in the first frequency domain digital signal relative to the transmit power fading. The parameters of the at least one subcarrier may include: transmit power and/or frequency of the frequency of each of the at least one subcarrier. Then, the manner in which the transmitting end adjusts the parameters of at least one of the subcarriers included in the first frequency domain digital signal according to the channel fading characteristic of the optical fiber communication system may be as follows:

method one

If the channel fading characteristic of the optical fiber communication system indicates that the percentage of the received power of the subcarrier at a certain frequency point relative to the transmit power fading is greater than a second threshold, for example, 40%, the frequency in the first frequency domain digital signal may be adjusted. The frequency of the subcarrier at the point, so as to avoid the phenomenon that the percentage of received power relative to the transmit power fading is greater than the second threshold when transmitting the subcarrier.

Way two

If the channel fading characteristic of the optical fiber communication system indicates that the percentage of the received power of the subcarrier at a certain frequency point relative to the fading of the transmission power is a fixed value greater than a first threshold (a value between 0 and 1, for example, 10%), The transmit power of the subcarrier corresponding to the frequency point in the first frequency domain digital signal may be increased by a set multiple, and the set multiple may be a ratio of a difference between the transmit power and the received power and the received power, so that the frequency is The subcarriers are after power fading, and the received power is the same as the original transmit power. For example, if the received power of a subcarrier is 40% relative to the transmit power fading, the transmit power of the subcarrier corresponding to the frequency may be increased by 2/3 times, that is, the transmit power of the subcarrier corresponding to the frequency is increased. It is 5/3 times of the original transmit power, so that the subcarriers at this frequency point are after power fading, and the received power is the same as the original transmit power.

It should be noted that, in the foregoing two methods, when the first threshold and the second threshold are selected, they may be selected according to experience or selected by using a test manner. Taking the second threshold value as an example, when the selection is based on experience, the second threshold is preferably 40% to 60%; when the test mode is selected, the maximum value of the percentage of the received power of the subcarrier relative to the transmit power fading can be tested. The error rate of the optical signal does not cause the first time domain digital signal transmitted by the transmitting end to be restored, and this maximum value can be used as the second threshold. In actual implementation, the first threshold and the second threshold may be the same or different.

Considering the above two ways, an example is given to explain in more detail how the transmitting end adjusts the parameters of at least one of the subcarriers included in the first frequency domain digital signal according to the channel fading characteristics of the optical fiber communication system:

Assuming that the channel fading characteristic of the optical fiber communication system indicates that the signal transmission through the optical fiber communication system is performed, the percentage of the received power of the subcarriers at the frequency point f3, the frequency point f4 and the frequency point f10 is 95% relative to the transmission power fading, that is, reception The power will fade to approximately zero, and the sub-loads at frequency points f1 and f11 The percentage of the received power of the wave relative to the transmit power fading is 20%. If the spectrum characteristic of the first frequency domain digital signal is as shown in FIG. 3, that is, the first frequency domain digital signal includes seven subcarriers, and the frequency points of each of the seven subcarriers are f1, f2, f3, f4, and f5, respectively. F6 and f7, the power of the seven subcarriers are a, b, c, d, e, f, and g, respectively. Among them, f1, f2, f3, f4, f5, f6, and f7 are frequency points that are sequentially incremented.

After analysis, among the seven subcarriers included in the first frequency domain digital signal, the frequency points of the third subcarrier and the fourth subcarrier are f3 and f4, respectively, which are just the received power indicated by the channel fading characteristic with respect to The percentage of transmit power fading is 95% of the frequency; the frequency of the first subcarrier is f1, which is just the frequency of the received power of the channel fading characteristic as a percentage of the transmit power fading of 20%.

Therefore, when S202 is executed, the subcarriers corresponding to the frequency point f3 and the frequency point f4 of the first frequency domain digital signal can be respectively adjusted to the frequency point f8 and the frequency point f9, thereby avoiding the sub-frequency point f3 and the frequency point f4 corresponding to the sub-carrier. The received power of the carrier is fading to 5% of the transmit power; and the transmit power of the subcarrier corresponding to the frequency point f1 of the first frequency domain digital signal is increased by 0.25 times, that is, 1.25 times of the original transmit power, thereby corresponding to the frequency point f1. After the received power of the subcarrier is fading to 80% of the increased transmit power, the received power is the same as the original transmit power. The spectral characteristics of the adjusted first frequency domain digital signal (ie, the second frequency domain digital signal) can be as shown in FIG.

It should be noted that when the transmitting end adjusts the frequency of the subcarrier, the frequency of the subcarrier is adjusted to which frequency point can be determined according to factors such as the bandwidth of the optical fiber transmission system, the system transmission rate, and the transmission distance; In power, the multiple of the increase can be a real number or a complex number. If the multiplier is a real number, the complex electric field on the subcarrier has only a change in amplitude; if the multiplier is a complex number, the complex electric field on the subcarrier has not only a change in amplitude but also a phase change.

In addition, if the parameter of at least one of the subcarriers included in the first frequency domain digital signal is adjusted in S202, the channel fading characteristic of the optical fiber communication system indicates that the subcarriers at many frequency points in the optical fiber communication system The percentage of the received power relative to the transmit power fading is greater than the second threshold, and then the frequency point of the subcarrier corresponding to the corresponding frequency point in the first frequency domain digital signal needs to be adjusted. When the transmission rate of the system is constant, the number of frequency points (referred to as available frequency points) that can be used for signal transmission per unit time is fixed. Therefore, if it is necessary to adjust the number of subcarriers at the frequency point, the unit time is The number of available frequency points required also increases accordingly. At this time, the transmission rate of the system can be appropriately reduced, thereby increasing the number of available frequency points per unit time, and more fully satisfying the requirement of the system for the number of available frequency points per unit time after executing S202, thereby more accurately compensating for the frequency. Point power fading reduces the bit error rate of fiber-optic communication systems.

S203: The transmitting end performs inverse time-frequency conversion on the second frequency domain digital signal to obtain a second time domain digital signal.

Optionally, after the transmitting end performs inverse time-frequency conversion on the second frequency domain digital signal in S203, the second time domain digital signal is digital-to-analog converted by the digital-to-analog converter to obtain a time domain analog signal.

S204: The transmitting end performs electro-optical conversion on the second time domain digital signal, obtains an optical signal, and transmits the optical signal to the receiving end.

In the modulation method shown in FIG. 2, parameters of at least one of the subcarriers included in the first frequency domain digital signal are adjusted according to channel fading characteristics of the optical fiber communication system to obtain a second frequency domain digital signal. Since the channel fading characteristic of the optical fiber communication system is used as a basis for adjustment when adjusting parameters of at least one of the subcarriers included in the first frequency domain digital signal, the channel fading characteristic indicates power fading of subcarriers at different frequency points. In this case, the parameters of at least one of the subcarriers included in the first frequency domain digital signal are adjusted according to the channel fading characteristic, so that the frequency power fading of the subcarriers included in the first frequency domain digital signal can be accurately compensated. The adjusted second frequency domain digital signal is processed to obtain an optical signal, and the optical signal is transmitted to the receiving end via the optical fiber, and the optical signal received by the receiving end is an optical signal converted by the adjusted electrical signal, and thus the receiving end After the optical signal is reduced to an electrical signal, the recovered electrical signal has a low bit error rate. In summary, the modulation method shown in FIG. 2 can more accurately solve the frequency power fading problem in the optical fiber communication system and reduce the bit error rate of the optical fiber communication system.

5 is a power density spectrum of a signal in a transmitting end and a receiving end when a modulation method according to an embodiment of the present invention is used, and a signal in a transmitting end and a receiving end when modulated by an algorithm for compensating frequency point power fading in the prior art; Power density spectrum. It can be seen from the comparison of the two modulation methods in Figure 5, The modulation method provided by the embodiment of the present invention is more similar to the frequency modulation characteristic of the signal at the transmitting end than the modulation method in the prior art. Therefore, the modulation method provided by the embodiment of the present invention can be further used. Effectively reduce the bit error rate of fiber-optic communication systems.

At the same time, considering the modulation of the signal in the frequency domain, the modulation of the signal in the time domain has the advantages of strong phase noise tolerance, small peak-to-average ratio, and strong anti-signal distortion capability of the system. Therefore, in the modulation method shown in FIG. 2, the first time domain digital signal is time-frequency converted, and the parameters of at least one of the subcarriers included in the first frequency domain digital signal in the frequency domain are adjusted, and After the adjustment, the inverse time-frequency conversion is performed to obtain the second time domain digital signal, and then the modulation is performed, that is, the time domain signal after the inverse time-frequency conversion is modulated by the transmitting end. Therefore, the problem of frequency point power fading can be solved by performing subcarrier parameter adjustment in the frequency domain. At the same time, the modulation method provided by the embodiment of the present invention modulates the inverse frequency conversion after the inverse frequency conversion is performed. The time domain signal is thus compared with the prior art, and the optical signal obtained by the modulation method provided by the embodiment of the present invention has a strong phase noise tolerance, a smaller peak-to-average ratio, and a more anti-signal distortion capability of the system. Strong.

In summary, the modulation method provided by the present invention can reduce the frequency power fading of the optical signal caused by channel fading, thereby reducing the bit error rate of the optical fiber communication system; at the same time, having a strong phase noise tolerance and a small peak-to-average ratio, the system The advantage of strong resistance to signal distortion.

After the modulation method provided by the embodiment of the present invention is adopted at the transmitting end, a demodulation method that is inversely related to the modulation method is needed at the receiving end of the optical fiber communication system. The demodulation method corresponding to the modulation method shown in FIG. 2 can be as shown in FIG. 6.

S601: The receiving end photoelectrically converts the received optical signal to obtain a second time domain digital signal.

For example, the manner in which the receiving end photoelectrically converts the optical signal may be: detecting the optical signal through the photodetector, and converting the detected signal into a second time domain digital signal through an analog to digital converter.

S602: The receiving end performs time-frequency conversion on the second time domain digital signal to obtain a second frequency domain digital signal.

Optionally, after performing photoelectric conversion on the received optical signal to obtain a second time domain digital signal, the second time domain digital signal may also be subjected to analog-to-digital conversion to obtain a time domain analog signal. Then, in S602, the time-frequency conversion of the second time domain digital signal by the receiving end is actually time-frequency conversion of the time domain analog signal. Change to obtain the second frequency domain digital signal.

S603: The receiving end adjusts parameters of at least one of the subcarriers included in the second frequency domain digital signal by using an adjustment scheme that is reciprocal with S202, to obtain a first frequency domain digital signal.

The receiving end adjusts the parameters of at least one of the subcarriers included in the second frequency domain digital signal by using an adjustment scheme that is reciprocal to the S202, and adjusts the manner of each subcarrier in the at least one subcarrier. Divided into the following two types:

method one

If the channel fading characteristic indicates that the percentage of the received power of the certain subcarrier relative to the transmit power fading is a fixed value greater than the first threshold, the transmitting end of the subcarrier increases the transmit power of the subcarrier by a multiple of the transmit power in S202, then, since the transmitting end When the transmit power is increased by a set multiple, the received power is the same as the transmit power before the set multiple (ie, the original transmit power), so the receiving end does not adjust the subcarrier when performing S603.

Way two

If the channel fading characteristic indicates that the percentage of the received power of the certain subcarrier relative to the transmit power fading is greater than the second threshold, the transmitting end of the S202 changes the frequency of the subcarrier, and the receiving end needs the subcarrier when performing S603. The frequency of the frequency is adjusted to the original frequency. For example, in S202, the transmitting end changes the frequency of a certain subcarrier from A to B. Then, in S603, the receiving end needs to adjust the frequency of the subcarrier from B to A.

Combining the above two methods, an example is given to explain in more detail how the receiving end adjusts the parameters of at least one of the subcarriers included in the second frequency domain digital signal by using an adjustment scheme that is reciprocal with S202:

Assuming that the subcarriers corresponding to the frequency domain f3 and the frequency f4 of the first frequency domain digital signal are respectively adjusted to the frequency point f8 and the frequency point f9 in S202, in S603, the intermediate frequency domain f8 of the second frequency domain digital signal is required. The subcarriers corresponding to the frequency point f9 are respectively adjusted to the frequency point f3 and the frequency point f4; if it is assumed in S202 that the transmission power of the subcarrier corresponding to the frequency point f1 of the first frequency domain digital signal is doubled, then in S603, There is no need to adjust the received power of the subcarrier corresponding to the frequency point f1 of the second frequency domain digital signal, because the subcarrier corresponding to the frequency point f1 of the second frequency domain digital signal passes through the frequency in the optical fiber link. After the point power is degraded, the received power is the transmit power (ie, the original transmit power) before the transmitter adjusts.

In S603, the parameter of at least one of the subcarriers included in the second frequency domain digital signal is adjusted according to the parameter of the at least one subcarrier included in the first frequency domain digital signal in S202. Means, and adopts an adjustment scheme that is reciprocal with the adjustment scheme in S202. The adjustment scheme adopted in S202 may be agreed by the transmitting end and the receiving end in advance, or the transmitting end may send the adjustment scheme to the receiving end. In the embodiment of the present invention, there is no limitation on how the receiving end knows the adjustment scheme of the transmitting end.

S604: The receiving end performs inverse time-frequency conversion on the first frequency domain digital signal to obtain a first time domain digital signal.

It should be noted that the demodulation method shown in FIG. 6 is the inverse of the modulation method shown in FIG. 2. In the case of ignoring the interference factors such as phase noise and signal distortion of the system, each step of the demodulation method shown in FIG. 6 is a process of gradually reducing the signal received by the receiving end to the electrical signal before modulation. In the modulation method shown in FIG. 2, the signal conversion process is: first time domain digital signal→first frequency domain digital signal→second frequency domain digital signal→second time domain digital signal; then the solution shown in FIG. In the modulation method, the signal conversion process is: a second time domain digital signal → a second frequency domain digital signal → a first frequency domain digital signal → a first time domain digital signal.

Optionally, after performing inverse time-frequency conversion on the first frequency domain digital signal, the method further includes: decoding the first time domain digital signal to obtain original bit information, where the original bit information is a digital signal represented by a binary sequence. , that is, the signal before the transmitting end performs the encoding operation.

It should be noted that when the modulation method shown in FIG. 2 is employed, the signal is modulated in the time domain instead of modulating the signal in the frequency domain. Therefore, when the demodulation method shown in FIG. 6 is adopted, the processing for adjusting the subcarriers at the frequency point is different from the scheme for modulating the signals in the frequency domain: if the transmitting end is in the frequency domain If the sub-carriers of the frequency point are adjusted, it is not necessary to separately adjust the sub-carriers back to the original frequency point, and only need to demodulate each sub-carrier separately; In the middle, the transmitting end modulates the signal in the time domain, and when the receiving end performs demodulation, for the subcarriers whose frequency points are adjusted, the subcarriers need to be respectively adjusted back to the original frequency point, and then the frequency domain signal is adjusted. Demodulation after conversion to a time domain signal, if Without adjusting these subcarriers back to the original frequency point, the electrical signal before modulation cannot be restored. In the embodiment of the present invention, in consideration of various advantages of modulating a signal in a time domain (strong phase noise tolerance, small peak-to-average ratio, and strong anti-signal distortion capability), a method of modulating a signal in a time domain is adopted. . Therefore, in the demodulation, the corresponding subcarrier needs to be adjusted back to the original frequency point, and then demodulated.

In combination with the above, the flow of the modulation method of the transmitting end in an optical fiber communication system can be as shown in FIG. 7. The flow of the demodulation method of the receiving end in an optical fiber communication system can be as shown in FIG. 8. Among them, the method shown in FIG. 7 and the method shown in FIG. 8 need to be used together in a fiber-optic communication system. The original bit information restored after the processing of FIG. 8 is the original bit information input by the transmitting end before the processing shown in FIG. 7 is performed.

The modulation method shown in FIG. 7 is adopted at the transmitting end, and the demodulation method shown in FIG. 8 is adopted at the receiving end, which can reduce the frequency power fading of the optical signal caused by channel fading, thereby reducing the bit error rate of the optical fiber communication system. At the same time, the optical fiber transmission system has the advantages of strong phase noise tolerance, small signal peak-to-average ratio, and strong anti-signal distortion capability.

The embodiment of the present invention further provides a modulating device, which can be used to perform the method shown in FIG. 2. As shown in FIG. 9, the modulating device 900 includes:

The time-frequency conversion module 901 is configured to perform time-frequency conversion on the first time domain digital signal to obtain a first frequency domain digital signal, where the first time domain digital signal is an electrical signal to be modulated at a transmitting end;

The subcarrier adjustment module 902 is configured to adjust, according to a channel fading characteristic of the optical fiber communication system, a parameter of at least one of the subcarriers included in the first frequency domain digital signal to obtain a second frequency domain digital signal;

The inverse time-frequency conversion module 903 is configured to perform inverse time-frequency conversion on the second frequency domain digital signal to obtain a second time domain digital signal;

The electro-optical conversion module 904 is configured to perform electro-optical conversion on the second time domain digital signal to obtain an optical signal.

The transmission module 905 is configured to transmit the optical signal to the receiving end.

Optionally, the modulating device 900 further includes: a digital-to-analog conversion module, configured to perform digital-to-analog conversion on the second time domain digital signal after the inverse time-frequency conversion module 903 performs inverse time-frequency conversion on the second frequency domain digital signal, Obtaining a time domain analog signal; the electro-optical conversion module 904 is specifically configured to: perform electro-optical conversion on the time domain analog signal when performing electro-optical conversion on the second time domain digital signal.

Optionally, the channel fading characteristic is used to indicate a percentage of received power of each subcarrier included in the first frequency domain digital signal with respect to transmit power fading.

Optionally, the parameter of the at least one subcarrier includes: a transmit power and/or a frequency point of each of the at least one subcarrier;

The transmitting end adjusts parameters of at least one of the subcarriers included in the first frequency domain digital signal according to the channel fading characteristic, and specifically includes: for each subcarrier in the at least one subcarrier: if the channel fading characteristic indicates the subcarrier The percentage of the received power relative to the transmit power fading is a fixed value greater than the first threshold, and the transmit power of the subcarrier is increased by a set multiple; if the channel fading characteristic indicates that the received power of the subcarrier is greater than the second of the transmit power fading is greater than the second The threshold changes the frequency of the subcarrier.

Optionally, the modulating device 900 further includes: an encoding module, configured to: before the time-frequency conversion module 901 performs time-frequency conversion on the first time domain digital signal, encode the original bit information to obtain a first time domain digital signal.

In actual implementation, the functions of the time-frequency conversion module 901, the sub-carrier adjustment module 902, and the inverse time-frequency conversion module 903 can be implemented by a DSP, and the function of the electro-optical conversion module 904 can be implemented by an electro-optical converter, and the function of the transmission module 905 can be transmitted and received. The function of the digital-to-analog conversion module can be realized by a digital-to-analog converter, and the function of the coding module can be realized by an encoder.

The modulating device 900 provided by the embodiment of the present invention may be used to perform the operations performed by the transmitting end in the modulating method shown in FIG. 2, and the implementation manner not explained and described in detail by the modulating device 900 may refer to the related description in the modulating method shown in FIG. .

It should be noted that the division of the module in the embodiment of the present invention is schematic, and is only a logical function division, and the actual implementation may have another division manner. In addition, each functional module in each embodiment of the present application may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules.

Based on the above embodiments, the embodiment of the present invention further provides a modulating device that can perform the method provided by the embodiment corresponding to FIG. 2, which can be the same as the modulating device 900 shown in FIG.

Referring to FIG. 10, the apparatus 1000 includes at least one processor 1001, a memory 1002, and a communication interface 1003; the at least one processor 1001, the memory 1002, and the communication interface 1003 are each connected by a bus 1004;

The memory 1002 is configured to store a computer execution instruction;

The at least one processor 1001 is configured to execute a computer-executed instruction stored by the memory 1002, so that the device 1000 performs data interaction with other devices through the communication interface 1003 to perform the modulation method provided by the foregoing embodiment.

At least one processor 1001 may include different types of processors 1001, or include the same type of processor 1001; the processor 1001 may be any one of the following: a central processing unit (CPU), an ARM processor , Field Programmable Gate Array (FPGA), dedicated processor and other devices with computational processing capabilities. In an optional implementation manner, the at least one processor 1001 may also be integrated into a many-core processor.

The memory 1002 may be any one or any combination of the following: a random access memory (RAM), a read only memory (ROM), and a non-volatile memory (Non-volatile memory). (NVM), Solid State Drives (SSD), mechanical hard disks, disks, disk arrays and other storage media.

Communication interface 1003 is for device 1000 to perform data interaction with other devices, such as demodulation devices of fiber optic communication systems. The communication interface 1003 may be any one or any combination of the following: a network interface (such as an Ethernet interface), a wireless network card, and the like having a network access function.

The bus 1004 can include an address bus, a data bus, a control bus, etc., for ease of representation, Figure 10 shows the bus with a thick line. The bus 1004 may be any one or any combination of the following: an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, and an extended industry standard structure ( Extended Industry Standard Architecture (EISA) bus and other devices for wired data transmission.

Corresponding to the modulating device 900, the embodiment of the present invention further provides a demodulating device for performing The demodulation method shown in FIG. As shown in FIG. 11, the demodulation device 1100 includes:

The photoelectric conversion module 1101 is configured to perform photoelectric conversion on the received optical signal to obtain a second time domain digital signal;

The time-frequency conversion module 1102 is configured to perform time-frequency conversion on the second time domain digital signal to obtain a second frequency domain digital signal;

The subcarrier adjustment module 1103 is configured to adjust parameters of at least one of the subcarriers included in the second frequency domain digital signal by using an adjustment scheme that is reciprocal to the subcarrier adjustment module 903 in the modulation apparatus 900, to obtain the first Frequency domain digital signal.

The inverse time-frequency conversion module 1104 is configured to perform inverse time-frequency conversion on the first frequency domain digital signal to obtain a first time domain digital signal.

Optionally, the demodulation device 1100 further includes: an analog-to-digital conversion module, configured to perform analog-to-digital conversion on the second time domain digital signal after performing photoelectric conversion on the received optical signal to obtain the second time domain digital signal, Get the time domain analog signal.

Optionally, the demodulation device 1100 further includes: a decoding module, configured to decode the first time domain digital signal to obtain original bit information, where the original bit information is a digital signal represented by a binary sequence, that is, the transmitting end encodes Signal before operation.

In actual implementation, the function of the photoelectric conversion module 1101 can be implemented by a photodetector, and the time-frequency conversion module 1102, the sub-carrier adjustment module 1103, and the inverse time-frequency conversion module 1104 can be implemented by a DSP, and the function of the analog-to-digital conversion module can pass the modulus. The converter is implemented, and the function of the decoding module can be implemented by a decoder.

The demodulation device 1100 provided by the embodiment of the present invention can be used to perform the demodulation method shown in FIG. 6. The implementation manner not explained and described in detail by the demodulation device 1100 can be referred to the related description in the demodulation method shown in FIG. 6.

Based on the above embodiment, the embodiment of the present invention further provides a demodulation device, which can perform the method provided by the embodiment corresponding to FIG. 6, and can be the same as the demodulation device 1100 shown in FIG.

Referring to FIG. 12, the apparatus 1200 includes at least one processor 1201, a memory 1202, and a communication interface 1203; the at least one processor 1201, the memory 1202, and the communication interface 1203. Both are connected by bus 1204;

The memory 1202 is configured to store a computer execution instruction;

The at least one processor 1201 is configured to execute a computer-executed instruction stored by the memory 1202, so that the apparatus 1200 performs data interaction with other devices through the communication interface 1203 to perform the demodulation method provided by the foregoing embodiment.

At least one processor 1201 may include different types of processors 1201, or include the same type of processor 1201; the processor 1201 may be any of the following: CPU, ARM processor, FPGA, dedicated processor, etc. with calculation processing Capable device. In an optional implementation manner, the at least one processor 1201 may also be integrated into a many-core processor.

The memory 1202 may be any one or any combination of the following: a storage medium such as a RAM, a ROM, an NVM, an SSD, a mechanical hard disk, a magnetic disk, a disk array, or the like.

Communication interface 1203 is for device 1200 to perform data interaction with other devices, such as modulation device 900 or modulation device 1000. The communication interface 1203 may be any one or any combination of the following: a network interface (such as an Ethernet interface), a wireless network card, and the like having a network access function.

The bus 1204 can include an address bus, a data bus, a control bus, etc., for ease of representation, Figure 12 shows the bus with a thick line. The bus 1204 may be any one or any combination of the following: a device for wired data transmission such as an ISA bus, a PCI bus, or an EISA bus.

In summary, the embodiment of the present invention provides a modulation method and apparatus. The modulation scheme provided by the present invention can reduce the frequency power fading of an optical signal caused by channel fading, thereby reducing the bit error rate of the optical fiber communication system; It has the advantages of small phase noise, small peak-to-average ratio, and strong anti-signal distortion capability of the system.

Those skilled in the art will appreciate that embodiments of the present invention can be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or a combination of software and hardware. Moreover, the invention can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) including computer usable program code.

The present invention is directed to a method, apparatus (system), and computer program according to an embodiment of the present invention. The flow chart and/or block diagram of the product is described. It will be understood that each flow and/or block of the flowchart illustrations and/or FIG. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine for the execution of instructions for execution by a processor of a computer or other programmable data processing device. Means for implementing the functions specified in one or more of the flow or in a block or blocks of the flow chart.

The computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture comprising the instruction device. The apparatus implements the functions specified in one or more blocks of a flow or a flow and/or block diagram of the flowchart.

These computer program instructions can also be loaded onto a computer or other programmable data processing device such that a series of operational steps are performed on a computer or other programmable device to produce computer-implemented processing for execution on a computer or other programmable device. The instructions provide steps for implementing the functions specified in one or more of the flow or in a block or blocks of a flow diagram.

Although the preferred embodiment of the invention has been described, it will be apparent to those skilled in the < Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and the modifications and It is apparent that those skilled in the art can make various modifications and variations to the embodiments of the invention without departing from the spirit and scope of the embodiments of the invention. Thus, it is intended that the present invention cover the modifications and modifications of the embodiments of the invention.

Claims

A modulation method, comprising:

The transmitting end performs time-frequency conversion on the first time domain digital signal to obtain a first frequency domain digital signal, where the first time domain digital signal is an electrical signal to be modulated by the transmitting end;

The transmitting end adjusts parameters of at least one of the subcarriers included in the first frequency domain digital signal according to a channel fading characteristic of the optical fiber communication system, to obtain a second frequency domain digital signal;

Transmitting, by the transmitting end, inverse frequency conversion of the second frequency domain digital signal to obtain a second time domain digital signal;

The transmitting end performs electro-optical conversion on the second time domain digital signal to obtain an optical signal, and transmits the optical signal to the receiving end.
The method of claim 1, wherein the transmitting end, after performing inverse time-frequency conversion on the second frequency domain digital signal, further comprises:

The transmitting end performs digital-to-analog conversion on the second time domain digital signal to obtain a time domain analog signal;

The transmitting end performs electro-optical conversion on the second time domain digital signal, and specifically includes:

The transmitting end performs electro-optical conversion on the time domain analog signal.
The method according to claim 1 or 2, wherein the channel fading characteristic is used to indicate a percentage of received power of each subcarrier included in the first frequency domain digital signal with respect to transmit power fading.
The method according to claim 3, wherein the parameter of the at least one subcarrier comprises: a transmit power of each of the at least one subcarrier;

The transmitting end adjusts parameters of at least one of the subcarriers included in the first frequency domain digital signal according to the channel fading characteristic, and specifically includes:

For each of the at least one subcarrier: if the channel fading characteristic indicates that the percentage of received power of the subcarrier with respect to transmit power fading is a fixed value greater than a first threshold, then the subcarrier is The transmit power is increased by a set multiple.
The method of claim 3, wherein the parameters of the at least one subcarrier Include: a frequency point of each of the at least one subcarrier;

The transmitting end adjusts parameters of at least one of the subcarriers included in the first frequency domain digital signal according to the channel fading characteristic, and specifically includes:

For each of the at least one subcarrier: if the channel fading characteristic indicates that the percentage of the received power of the subcarrier relative to the transmit power fading is greater than a second threshold, changing the frequency point of the subcarrier.
The method according to any one of claims 1 to 5, wherein before the transmitting end performs time-frequency conversion on the first time domain digital signal, the method further includes:

The transmitting end encodes the original bit information to obtain the first time domain digital signal.
A modulation device, comprising:

a time-frequency conversion module, configured to perform time-frequency conversion on the first time domain digital signal to obtain a first frequency domain digital signal, where the first time domain digital signal is an electrical signal to be modulated;

a subcarrier adjustment module, configured to adjust a parameter of at least one of the subcarriers included in the first frequency domain digital signal according to a channel fading characteristic of the optical fiber communication system, to obtain a second frequency domain digital signal;

An inverse time-frequency conversion module, configured to perform inverse time-frequency conversion on the second frequency domain digital signal to obtain a second time domain digital signal;

An electro-optical conversion module, configured to perform electro-optical conversion on the second time domain digital signal to obtain an optical signal;

And a transmission module, configured to transmit the optical signal to the receiving end.
The device of claim 7 further comprising:

a digital-to-analog conversion module, configured to perform digital-to-analog conversion on the second time domain digital signal after the inverse time-frequency conversion module performs inverse time-frequency conversion on the second frequency domain digital signal to obtain a time domain analog signal ;

The electro-optical conversion module is specifically configured to: when performing electro-optical conversion on the second time domain digital signal:

Performing electro-optic conversion on the time domain analog signal.
The apparatus according to claim 7 or 8, wherein the channel fading characteristic is used to indicate a percentage of received power of each subcarrier included in the first frequency domain digital signal with respect to transmit power fading.
The apparatus according to claim 9, wherein the parameter of the at least one subcarrier comprises: a transmit power of each of the at least one subcarrier;

When the subcarrier adjustment module adjusts parameters of at least one of the subcarriers included in the first frequency domain digital signal according to the channel fading characteristic, the subcarrier adjustment module is specifically configured to:

For each of the at least one subcarrier: if the channel fading characteristic indicates that the percentage of received power of the subcarrier with respect to transmit power fading is a fixed value greater than a first threshold, then the subcarrier is The transmit power is increased by a set multiple.
The apparatus according to claim 9, wherein the parameter of the at least one subcarrier comprises: a frequency point of each of the at least one subcarrier;

When the subcarrier adjustment module adjusts parameters of at least one of the subcarriers included in the first frequency domain digital signal according to the channel fading characteristic, the subcarrier adjustment module is specifically configured to:

For each of the at least one subcarrier: if the channel fading characteristic indicates that the percentage of the received power of the subcarrier relative to the transmit power fading is greater than a second threshold, changing the frequency point of the subcarrier.
The device according to any one of claims 7 to 11, further comprising:

And an encoding module, configured to encode the original bit information to obtain the first time domain digital signal before the time-frequency conversion module performs time-frequency conversion on the first time domain digital signal.