CN113517933A - Optical signal transmission method and device - Google Patents
Optical signal transmission method and device Download PDFInfo
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- CN113517933A CN113517933A CN202110444322.5A CN202110444322A CN113517933A CN 113517933 A CN113517933 A CN 113517933A CN 202110444322 A CN202110444322 A CN 202110444322A CN 113517933 A CN113517933 A CN 113517933A
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Abstract
The embodiment of the application discloses an optical signal transmission method and device. The method comprises the following steps: and the transmitting end is used for respectively inputting each path of subcarrier baseband digital signals into a digital-to-analog converter for digital-to-analog conversion, and carrying out frequency shift and multiplexing on the converted analog signals. And the receiving end demultiplexes the composite analog electrical signal, and respectively inputs the demultiplexed multi-channel signals into an analog-to-digital converter for analog-to-digital conversion after frequency shift operation. The embodiment of the application adopts the multi-channel digital-to-analog converter with low sampling rate to complete digital-to-analog conversion and complete subcarrier multiplexing in the analog domain, so that the requirement on the sampling rate of the digital-to-analog converter can be reduced. Meanwhile, the electric power distributor is used in the analog domain to complete subcarrier demultiplexing, and the multi-path analog-to-digital converter with low sampling rate is used for completing sampling, so that the requirement on the sampling rate of the analog-to-digital converter can be reduced.
Description
Technical Field
The present application relates to the field of communications technologies, and in particular, to a method and an apparatus for transmitting an optical signal.
Background
The transmission requirements of ultra-high speed, ultra-large capacity and ultra-long distance brought by the high-speed growth of diversified large-bandwidth services such as a fifth generation new wireless system 5G (5th generation), large data, cloud computing and the like push the performance of an optical network in the aspects of transmission speed, transmission capacity and transmission distance to be continuously improved, and the requirements can be effectively met by the comprehensive application of high-speed large-capacity transmission technologies such as a high-order modulation format with high wave specificity and high spectral efficiency.
High baud rate transmission requires the use of high sampling rate and high throughput digital-to-analog converters and analog-to-digital converters, while high-order modulation formats require the use of high resolution digital-to-analog converters and analog-to-digital converters, but in hardware implementations the two indices, high sampling rate and high resolution, are often contradictory.
At present, a digital signal processing technology is adopted to multiplex a plurality of subcarriers into a high baud rate signal, and then digital-to-analog conversion is completed through a digital-to-analog converter, the processing mode has higher requirement on the sampling rate of the digital-to-analog converter, and is still limited by the dilemma that the high sampling rate and the high resolution are difficult to be obtained simultaneously.
Disclosure of Invention
Because the existing methods have the above problems, embodiments of the present application provide an optical signal transmission method and apparatus.
Specifically, the embodiment of the present application provides the following technical solutions:
in a first aspect, an embodiment of the present application provides an optical signal transmission method, including:
a transmitting end:
converting a bit stream to be transmitted into M paths of subcarrier baseband digital signals, and respectively inputting each path of subcarrier baseband digital signals into a digital-to-analog converter (DAC) for digital-to-analog conversion to obtain subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals; wherein M is more than or equal to 2;
frequency-shifting the M paths of subcarrier baseband analog signals to a specified subcarrier frequency to obtain M paths of subcarrier frequency band analog signals, and multiplexing the M paths of subcarrier frequency band analog signals to obtain a composite analog electrical signal in a subcarrier multiplexing state;
performing optical modulation on the composite analog electrical signal to obtain an optical signal;
receiving end:
carrying out balanced photoelectric conversion on the optical signal to obtain a composite analog electrical signal in a subcarrier multiplexing state;
demultiplexing the composite analog electrical signal to obtain M paths of subcarrier frequency band analog signals, and respectively frequency-shifting the M paths of subcarrier frequency band analog signals to a baseband to obtain M paths of subcarrier baseband analog signals;
and respectively inputting the M paths of subcarrier baseband analog signals into an analog-to-digital converter (ADC) for analog-to-digital conversion to obtain subcarrier baseband digital signals corresponding to each path of subcarrier baseband analog signals.
Optionally, the converting the bit stream to be transmitted into M subcarrier baseband digital signals includes:
and dividing the bit stream to be transmitted into M paths of branch bit streams, and carrying out coding, mapping and forming filtering processing on the M paths of branch bit streams to obtain M paths of subcarrier baseband digital signals.
Optionally, the sampling rate of the digital-to-analog converter DAC is a composite baud rate × 2/N, and the bandwidth is a composite baud rate/(2N).
Optionally, the frequency-shifting the M-channel subcarrier baseband analog signals to the designated subcarrier frequency to obtain M-channel subcarrier baseband analog signals includes:
and shifting the M paths of subcarrier baseband analog signals to the appointed subcarrier frequency by adopting a phase shift method single-sideband subcarrier modulation and/or a filtering method single-sideband subcarrier modulation mode to obtain M paths of subcarrier frequency band analog signals.
Optionally, the performing optical modulation on the composite analog electrical signal to obtain an optical signal includes:
and inputting the composite analog electric signal to an IQ modulator for optical modulation to obtain an optical signal.
In a second aspect, an embodiment of the present application provides an optical signal transmission apparatus, including:
the first processing module is used for converting a bit stream to be transmitted into M paths of subcarrier baseband digital signals, and inputting each path of subcarrier baseband digital signals into a digital-to-analog converter (DAC) for digital-to-analog conversion to obtain subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals; wherein M is more than or equal to 2;
the second processing module is used for frequency shifting the M paths of subcarrier baseband analog signals to a specified subcarrier frequency to obtain M paths of subcarrier frequency band analog signals, and multiplexing the M paths of subcarrier frequency band analog signals to obtain a composite analog electrical signal in a subcarrier multiplexing state;
the third processing module is used for carrying out optical modulation on the composite analog electric signal to obtain an optical signal;
the fourth processing module is used for carrying out balanced photoelectric conversion on the optical signal to obtain a composite analog electrical signal in a subcarrier multiplexing state;
a fifth processing module, configured to demultiplex the composite analog electrical signal to obtain M channels of subcarrier band analog signals, and frequency shift the M channels of subcarrier band analog signals to a baseband respectively to obtain M channels of subcarrier baseband analog signals;
and the sixth processing module is used for respectively inputting the M paths of subcarrier baseband analog signals into an analog-to-digital converter (ADC) for analog-to-digital conversion to obtain subcarrier baseband digital signals corresponding to each path of subcarrier baseband analog signals.
According to the technical scheme, the bit stream to be transmitted is converted into multiple paths of subcarrier baseband digital signals at the transmitting end, and each path of subcarrier baseband digital signal is respectively input into a digital-to-analog converter (DAC) for digital-to-analog conversion, so that a subcarrier baseband analog signal corresponding to each path of subcarrier baseband digital signal is obtained; and then frequency-shifting the multi-channel subcarrier baseband analog signal to a designated subcarrier frequency, and then carrying out subcarrier multiplexing to obtain a composite analog electrical signal in a multiplexing state and complete optical carrier modulation to obtain an optical signal. At a receiving end, carrying out balanced photoelectric conversion on the optical signal to obtain a composite analog electrical signal in a subcarrier multiplexing state; demultiplexing the composite analog electrical signal to obtain multi-channel subcarrier frequency band analog signals, and respectively frequency-shifting the multi-channel subcarrier frequency band analog signals to a baseband to obtain multi-channel subcarrier baseband analog signals; and respectively inputting the multi-channel subcarrier baseband analog signals into an analog-to-digital converter (ADC) for analog-to-digital conversion to obtain subcarrier baseband digital signals corresponding to each channel of subcarrier baseband analog signals. Therefore, the embodiment of the application adopts the multi-path digital-to-analog converter with low sampling rate to complete digital-to-analog conversion and complete subcarrier multiplexing in the analog domain, so that the requirement on the sampling rate of the digital-to-analog converter can be reduced. Meanwhile, an electric power distributor is used in an analog domain to complete subcarrier demultiplexing, a plurality of paths of analog-to-digital converters with low sampling rate are used to complete sampling, the requirement on the sampling rate of the analog-to-digital converters can be reduced, and therefore high-bit-rate optical signal transmission of a high-order modulation format is achieved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a flowchart of an optical signal transmission method provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram of an emitting end of an optical signal transmission system provided in an embodiment of the present application;
fig. 3 is a schematic structural diagram of a receiving end of an optical signal transmission system according to an embodiment of the present disclosure;
FIG. 4 is a flowchart of a frequency shift operation provided by an embodiment of the present application;
FIG. 5 is a second flowchart of a frequency shift operation provided by an embodiment of the present application;
fig. 6 is a schematic diagram of an optical signal transmission method according to an embodiment of the present application;
fig. 7 is a flowchart of digital signal processing on a demodulated optical signal according to an embodiment of the present application;
fig. 8 is a schematic structural diagram of an optical signal transmission apparatus provided in an embodiment of the present application;
fig. 9 is a schematic structural diagram of a communication device according to an embodiment of the present application.
Detailed Description
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 shows a flowchart of an optical signal transmission method provided in an embodiment of the present application, fig. 2 is a schematic structural diagram of an emitting end of an optical signal transmission system provided in the embodiment of the present application, fig. 3 is a schematic structural diagram of a receiving end of the optical signal transmission system provided in the embodiment of the present application, fig. 4 is a flowchart of a frequency shift operation provided in the embodiment of the present application, fig. 5 is a flowchart of another frequency shift operation provided in the embodiment of the present application, fig. 6 is a schematic diagram of a path of the optical signal transmission method provided in the embodiment of the present application, and fig. 7 is a flowchart of digital signal processing performed on a demodulated optical signal provided in the embodiment of the present application. The following explains and explains the optical signal transmission method provided in the embodiment of the present application in detail with reference to fig. 1 to 7, and as shown in fig. 1, the optical signal transmission method provided in the embodiment of the present application includes:
a transmitting end:
step 101: converting bit stream to be transmitted into M paths of transmitted subcarrier baseband digital signals with the same data length, and respectively inputting each path of subcarrier baseband digital signals into a digital-to-analog converter (DAC) for digital-to-analog conversion to obtain subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals; wherein M is more than or equal to 2;
in this step, it should be noted that the bit stream carrying the service signal is divided into multiple groups, and each group is allocated to N subcarrier branches for transmission. And coding, mapping and forming filtering processing is carried out on the N subcarrier branches to obtain M subcarrier baseband digital signals. Specifically, bits may be mapped to a symbol of quadrature amplitude modulation, and then the mapped symbol is subjected to nyquist shaping filtering processing, so as to improve spectrum resource utilization efficiency.
In this step, each path of subcarrier baseband digital signals obtained after the nyquist shaping filtering processing is respectively input to a digital-to-analog converter DAC with high resolution and a sampling rate of composite baud rate × 2/N to complete digital-to-analog conversion, and subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals are obtained.
Step 102: frequency-shifting the M paths of subcarrier baseband analog signals to a specified subcarrier frequency to obtain M paths of subcarrier frequency band analog signals, and multiplexing the M paths of subcarrier frequency band analog signals to obtain a composite analog electrical signal in a subcarrier multiplexing state;
in this step, it should be noted that, frequency shift operation is performed on the baseband analog signals of each subcarrier branch, and the frequency shift operation may adopt phase shift single-sideband subcarrier modulation and filtering single-sideband subcarrier modulation. The baseband analog signals of each subcarrier branch are respectively frequency shifted to the designated frequency in the frequency spectrum to obtain the frequency band analog signals of each subcarrier branch, and then each subcarrier branch is multiplexed by using an electric beam combiner to obtain the composite analog electric signal in the subcarrier multiplexing state.
Step 103: and carrying out optical modulation on the composite analog electric signal to obtain an optical signal.
In this step, the analog point model after subcarrier multiplexing is output to an optical modulator for optical modulation, and a polarization multiplexed optical signal is obtained.
Receiving end:
step 104: carrying out balanced photoelectric conversion on the optical signal to obtain a composite analog electrical signal in a subcarrier multiplexing state;
in this step, it should be noted that, after being transmitted back to back or through an optical fiber, the optical signal is subjected to 90-degree frequency mixing and balanced photoelectric conversion to obtain a composite baud rate analog electrical signal in a subcarrier multiplexing state. The 90-degree mixing is used for mixing the optical signal and the local oscillator optical signal. And the balanced photoelectric detector is used for balanced reception of the mixed optical signal.
Step 105: demultiplexing the composite analog electrical signal to obtain M paths of subcarrier frequency band analog signals, and respectively frequency-shifting the M paths of subcarrier frequency band analog signals to a baseband to obtain M paths of subcarrier baseband analog signals; wherein M is more than or equal to 2;
in this step, the analog electrical signal in the multiplexing state is first subjected to a shunt demultiplexing process to obtain a multi-channel band analog subcarrier signal, and the subcarrier signal in the band state is further down-converted into a baseband signal, which is demultiplexed from the high baud rate signal in the multiplexing state to the low baud rate baseband signal that is not multiplexed. The demultiplexing may adopt single-sideband subcarrier demodulation (as shown in fig. 6), and after demultiplexing, frequency-shifts the analog subcarriers of each branch to the baseband (at 0 frequency), respectively, to obtain a multi-subcarrier baseband analog signal.
Step 106: and respectively inputting the M paths of subcarrier baseband analog signals into an analog-to-digital converter (ADC) for analog-to-digital conversion to obtain subcarrier baseband digital signals corresponding to each path of subcarrier baseband analog signals.
In this step, it should be noted that the obtained multiple paths of subcarrier baseband analog signals are respectively input to an analog-to-digital converter ADC for analog-to-digital conversion, so as to obtain subcarrier baseband digital signals corresponding to each path of subcarrier baseband analog signals. The sampling rate of the analog-to-digital converter is a composite baud rate multiplied by 2/N, and the bandwidth is a composite baud rate/(2N).
In this step, optionally, after obtaining the sampled data, the sampled data may be subjected to damage compensation processing by using a device such as an application specific integrated circuit, a field programmable gate array, or the like, including but not limited to: quadrature in-phase imbalance compensation, chromatic dispersion compensation (after optical fiber transmission), adaptive equalization and polarization demultiplexing, carrier phase recovery, and the like.
According to the technical scheme, when optical signals are transmitted, the bit stream to be transmitted is converted into multiple paths of subcarrier baseband digital signals, and each path of subcarrier baseband digital signal is respectively input into a digital-to-analog converter (DAC) for digital-to-analog conversion, so that subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals are obtained; and then frequency-shifting the multi-channel subcarrier baseband analog signal to a designated subcarrier frequency, and then carrying out subcarrier multiplexing to obtain a composite analog electrical signal in a multiplexing state and complete optical carrier modulation to obtain an optical signal. Therefore, in the embodiment of the application, the bit stream is divided into the multiple paths of digital signals in the digital domain, then the multiple paths of digital signals are converted into the analog domain, and frequency shifting and multiplexing are performed in the analog domain, so that the requirements on the sampling rate and the resolution of the digital-to-analog converter can be reduced to a great extent, and high-bit-rate optical signal transmission in a high-order modulation format is realized.
According to the technical scheme, when the optical signal is received, the optical signal is balanced and photoelectrically converted to obtain the composite analog electrical signal in the subcarrier multiplexing state, then the signals in the multiplexing state are respectively subjected to frequency shift to the baseband signals with the low baud rate, and the data sampling and receiving are completed by adopting the analog-to-digital converter with the low sampling rate. Therefore, the receiving end of the embodiment of the application also adopts the analog-to-digital converter with the low sampling rate in the analog domain to complete subcarrier multiplexing, and compared with the prior art that the analog signal after balanced photoelectric conversion is directly input into the analog-to-digital converter, the requirement on the sampling rate of the analog-to-digital converter can be effectively reduced, and high-bit-rate optical signal transmission in a high-order modulation format is realized.
Based on the content of the foregoing embodiment, in this embodiment, the converting the bitstream to be transmitted into M subcarrier baseband digital signals includes:
and dividing the bit stream to be transmitted into M paths of branch bit streams, and carrying out coding, mapping and forming filtering processing on the M paths of branch bit streams to obtain M paths of subcarrier baseband digital signals.
In this embodiment, it should be noted that the bit stream carrying the service signal is divided into multiple groups, and each group is allocated to N subcarrier branches for transmission. And coding, mapping and forming filtering processing is carried out on the N subcarrier branches to obtain M subcarrier baseband digital signals. Specifically, bits may be mapped to a symbol of quadrature amplitude modulation, and then the mapped symbol is subjected to nyquist shaping filtering processing, so as to improve spectrum resource utilization efficiency.
Based on the content of the above embodiment, in this embodiment, the sampling rate of the digital-to-analog converter DAC is the composite baud rate × 2/N, and the bandwidth is the composite baud rate/(2N).
In this embodiment, it should be noted that the digital-to-analog converter DAC is configured to perform digital-to-analog conversion on the symbol sequence to obtain a corresponding baseband analog signal, where a sampling rate is a composite baud rate × 2/N, and a bandwidth is a composite baud rate/(2N).
Based on the content of the foregoing embodiment, in this embodiment, the frequency-shifting the M-channel subcarrier baseband analog signals to a designated subcarrier frequency to obtain M-channel subcarrier frequency band analog signals includes:
and shifting the M paths of subcarrier baseband analog signals to the appointed subcarrier frequency by adopting a phase shift method single-sideband subcarrier modulation and/or a filtering method single-sideband subcarrier modulation mode to obtain M paths of subcarrier frequency band analog signals.
In the present embodiment, the baseband analog signals of the respective subcarrier branches are subjected to frequency shift operation, and the frequency shift operation may employ single-sideband subcarrier modulation (fig. 5) by phase shift method and single-sideband subcarrier modulation (fig. 4) by filtering method. And respectively frequency-shifting the baseband analog signals of each subcarrier branch to a specified frequency in a frequency spectrum to obtain the frequency band analog signals of each subcarrier branch.
Based on the content of the foregoing embodiment, in this embodiment, the performing optical modulation on the composite analog electrical signal to obtain an optical signal includes:
and inputting the composite analog electric signal to an IQ modulator for optical modulation to obtain an optical signal.
In this embodiment, it should be noted that the analog point model after subcarrier multiplexing is output to an optical IQ modulator for optical modulation, so as to obtain a polarization-multiplexed optical signal. The IQ modulator is used for carrying out optical IQ modulation and polarization multiplexing on the multiplexed composite baud rate signal and carrying the multiplexed composite baud rate signal on an optical carrier.
The present application will be specifically described below with reference to specific examples.
The first embodiment:
in this embodiment, the 128GBaud bit sequence to be transmitted is divided into M channels (assuming that M is 8), and then the 128GBaud bit sequence is divided into 8 channels of 16GBaud digital signals, each channel is input into a DAC, and then the sampling rate of the DAC is 32 GSa/s. And D/A conversion is carried out by using a DAC to obtain a 16GBaud analog signal, and frequency shifting operation is carried out. Specifically, the 16GBaud baseband analog domain signal of each subcarrier branch is frequency-shifted to a specific frequency, specifically, the subcarriers 1 to 8 are frequency-shifted to 0GHz, 8GHz, 16GHz, 24GHz, 32GHz, 40GHz, 48GHz, and 56GHz, respectively, the frequency-shifted specific implementation may be as shown in fig. 2 and fig. 3, and then each subcarrier is multiplexed by using an electric power combiner, so as to obtain a 128GBaud composite signal with a bandwidth of 64 GHz. And then enters an IQ modulator to complete modulation, and a polarization-multiplexed 128GBaud optical signal is obtained. In the currently reported scheme, the 128GBaud bit sequence is divided into 8 channels in the digital signal processing unit, i.e., in the digital domain, and frequency shifted and multiplexed. The baud rate of the multiplexed digital signal is 128GBaud, then the 128GBaud is input into a DAC with the sampling rate of 256GSa/s to obtain a 128GBaud analog electric signal, and the 128GBaud analog electric signal is input into an IQ modulator to complete optical modulation. It can be seen that the sampling rate of the digital-to-analog converter of the embodiment of the present application can be reduced by eight times compared with the prior art.
Second embodiment:
in the embodiment, a 128GBaud signal in an analog state is obtained after Balanced Photoelectric Detection (BPD), the signal is decomposed into 8 paths of 16GBaud analog signals by using an electric power distributor, then the 8 paths of 16GBaud analog signals are respectively subjected to frequency shift to 0 frequency in an analog domain, and finally sampling is carried out by using an ADC with a 32GSa/s rate. In the reported scheme, the 128GBaud analog signal after BPD is directly input into the ADC, which requires the ADC to sample at a rate of 256 GSa/s. Therefore, the embodiment of the application can adopt the digital-to-analog converter/analog-to-digital converter with low sampling rate and high resolution to transmit the high-order modulation format optical signal with high baud rate.
In addition, the processing speed of the chip circuit can be reduced in the embodiments of the present application, for example, in the embodiments, the signal baud in the digital domainThe rate is 16GBaud, meaning that the chip processes 1.6X 10 chips per second10And (6) operation. Whereas the prior art requires processing of 128GBaud signals in the digital domain, meaning that the chip processes 2.56 x 10 signals per second12The required processing rate and throughput are greatly increased.
Based on the same inventive concept, another embodiment of the present invention provides an optical signal transmission apparatus, as shown in fig. 8, including:
the first processing module 1 is configured to convert a bit stream to be transmitted into M channels of subcarrier baseband digital signals, and input each channel of subcarrier baseband digital signals into one digital-to-analog converter DAC for digital-to-analog conversion, so as to obtain subcarrier baseband analog signals corresponding to each channel of subcarrier baseband digital signals; wherein M is more than or equal to 2;
the second processing module 2 is configured to frequency-shift the M paths of subcarrier baseband analog signals to a designated subcarrier frequency to obtain M paths of subcarrier frequency band analog signals, and multiplex the M paths of subcarrier frequency band analog signals to obtain a composite analog electrical signal in a subcarrier multiplexing state;
the third processing module 3 is used for performing optical modulation on the composite analog electrical signal to obtain an optical signal;
the fourth processing module 4 is configured to perform balanced photoelectric conversion on the optical signal to obtain a composite analog electrical signal in a subcarrier multiplexing state;
a fifth processing module 5, configured to demultiplex the composite analog electrical signal to obtain M channels of subcarrier band analog signals, and frequency shift the M channels of subcarrier band analog signals to a baseband respectively to obtain M channels of subcarrier baseband analog signals; wherein M is more than or equal to 2;
and a sixth processing module 6, configured to input the M paths of subcarrier baseband analog signals to an analog-to-digital converter ADC respectively for analog-to-digital conversion, so as to obtain a subcarrier baseband digital signal corresponding to each path of subcarrier baseband analog signals.
In this embodiment, it should be noted that the bit stream carrying the service signal is divided into multiple groups, and each group is allocated to N subcarrier branches for transmission. And coding, mapping and forming filtering processing is carried out on the N subcarrier branches to obtain M subcarrier baseband digital signals. Specifically, bits may be mapped to a symbol of quadrature amplitude modulation, and then the mapped symbol is subjected to nyquist shaping filtering processing, so as to improve spectrum resource utilization efficiency.
In this embodiment, each path of subcarrier baseband digital signals obtained after the nyquist shaping filtering processing is respectively input to a digital-to-analog converter DAC with high resolution and a sampling rate of composite baud rate × 2/N to complete digital-to-analog conversion, so as to obtain subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals.
In this embodiment, it should be noted that, the frequency shift operation is performed on the baseband analog signals of each subcarrier branch, and the frequency shift operation may employ phase shift single-sideband subcarrier modulation and filtering single-sideband subcarrier modulation. The baseband analog signals of each subcarrier branch are respectively frequency shifted to the designated frequency in the frequency spectrum to obtain the frequency band analog signals of each subcarrier branch, and then each subcarrier branch is multiplexed by using an electric beam combiner to obtain the composite analog electric signal in the subcarrier multiplexing state.
In this embodiment, the analog point model after subcarrier multiplexing is output to an optical modulator for optical modulation, and a polarization-multiplexed optical signal is obtained.
In this embodiment, it should be noted that, after being transmitted through an optical fiber or in a back-to-back condition, the optical signal is subjected to 90-degree frequency mixing and balanced photoelectric conversion, so as to obtain a composite baud rate analog electrical signal in a subcarrier multiplexing state. The 90-degree mixing is used for mixing the optical signal and the local oscillator optical signal. And the balanced photoelectric detector is used for balanced reception of the mixed optical signal.
In this embodiment, first, the analog electrical signal in the multiplexing state is subjected to a demultiplexing process to obtain a multi-channel band analog subcarrier signal, and then the subcarrier signal in the band state is down-converted into a baseband signal, and the high-baud-rate signal in the multiplexing state is demultiplexed into an un-multiplexed low-baud-rate baseband signal. The demultiplexing may adopt single-sideband subcarrier demodulation (as shown in fig. 7), and after demultiplexing, frequency-shifts the analog subcarriers of each branch to the baseband (at 0 frequency), respectively, to obtain a multi-subcarrier baseband analog signal.
In this embodiment, it should be noted that the obtained multiple paths of subcarrier baseband analog signals are respectively input to an analog-to-digital converter ADC for analog-to-digital conversion, so as to obtain subcarrier baseband digital signals corresponding to each path of subcarrier baseband analog signals. The sampling rate of the analog-to-digital converter is a composite baud rate multiplied by 2/N, and the bandwidth is a composite baud rate/(2N).
In this embodiment, optionally, after obtaining the sampled data, the sampled data may be subjected to damage compensation processing by using a device such as an application specific integrated circuit or a field programmable gate array, including but not limited to: quadrature in-phase imbalance compensation, chromatic dispersion compensation (after optical fiber transmission), adaptive equalization and polarization demultiplexing, carrier phase recovery, and the like.
According to the technical scheme, when optical signals are transmitted, the bit stream to be transmitted is converted into multiple paths of subcarrier baseband digital signals, and each path of subcarrier baseband digital signal is respectively input into a digital-to-analog converter (DAC) for digital-to-analog conversion, so that subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals are obtained; and then frequency-shifting the multi-channel subcarrier baseband analog signal to a designated subcarrier frequency, and then carrying out subcarrier multiplexing to obtain a composite analog electrical signal in a multiplexing state and complete optical carrier modulation to obtain an optical signal. Therefore, in the embodiment of the application, the bit stream is divided into the multiple paths of digital signals in the digital domain, then the multiple paths of digital signals are converted into the analog domain, and frequency shifting and multiplexing are performed in the analog domain, so that the requirements on the sampling rate and the resolution of the digital-to-analog converter can be reduced to a great extent, and high-bit-rate optical signal transmission in a high-order modulation format is realized.
According to the technical scheme, when the optical signal is received, the optical signal is balanced and photoelectrically converted to obtain the composite analog electrical signal in the subcarrier multiplexing state, then the signals in the multiplexing state are respectively subjected to frequency shift to the baseband signals with the low baud rate, and the data sampling and receiving are completed by adopting the analog-to-digital converter with the low sampling rate. Therefore, the receiving end of the embodiment of the application also adopts the analog-to-digital converter with the low sampling rate in the analog domain to complete subcarrier multiplexing, and compared with the prior art that the analog signal after balanced photoelectric conversion is directly input into the analog-to-digital converter, the requirement on the sampling rate of the analog-to-digital converter can be effectively reduced, and high-bit-rate optical signal transmission in a high-order modulation format is realized.
The optical signal transmission apparatus described in this embodiment may be used to implement the above method embodiments, and the principle and technical effect are similar, which are not described herein again.
Based on the same inventive concept, another embodiment of the present invention provides a communication device, which refers to the schematic structural diagram of the communication device shown in fig. 9, and specifically includes the following contents: a processor 901, memory 902, communication interface 903, and communication bus 904;
the processor 901, the memory 902 and the communication interface 903 complete mutual communication through the communication bus 904; the communication interface 903 is used for realizing information transmission among the devices;
the processor 901 is configured to call the program in the memory 902 to execute in real time, and when executing the program, the processor implements all the steps of the above-mentioned optical signal transmission method, for example: a transmitting end: converting a bit stream to be transmitted into M paths of subcarrier baseband digital signals, and respectively inputting each path of subcarrier baseband digital signals into a digital-to-analog converter (DAC) for digital-to-analog conversion to obtain subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals; wherein M is more than or equal to 2; frequency-shifting the M paths of subcarrier baseband analog signals to a specified subcarrier frequency to obtain M paths of subcarrier frequency band analog signals, and multiplexing the M paths of subcarrier frequency band analog signals to obtain a composite analog electrical signal in a subcarrier multiplexing state; performing optical modulation on the composite analog electrical signal to obtain an optical signal; receiving end: carrying out balanced photoelectric conversion on the optical signal to obtain a composite analog electrical signal in a subcarrier multiplexing state; demultiplexing the composite analog electrical signal to obtain M paths of subcarrier frequency band analog signals, and respectively frequency-shifting the M paths of subcarrier frequency band analog signals to a baseband to obtain M paths of subcarrier baseband analog signals; wherein M is more than or equal to 2; and respectively inputting the M paths of subcarrier baseband analog signals into an analog-to-digital converter (ADC) for analog-to-digital conversion to obtain subcarrier baseband digital signals corresponding to each path of subcarrier baseband analog signals.
The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the embodiment of the present invention. One of ordinary skill in the art can understand and implement it without inventive effort.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (8)
1. An optical signal transmission method, comprising:
a transmitting end:
converting a bit stream to be transmitted into M paths of subcarrier baseband digital signals, and respectively inputting each path of subcarrier baseband digital signals into a digital-to-analog converter (DAC) for digital-to-analog conversion to obtain subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals; wherein M is more than or equal to 2;
frequency-shifting the M paths of subcarrier baseband analog signals to a specified subcarrier frequency to obtain M paths of subcarrier frequency band analog signals, and multiplexing the M paths of subcarrier frequency band analog signals to obtain a composite analog electrical signal in a subcarrier multiplexing state;
performing optical modulation on the composite analog electrical signal to obtain an optical signal;
receiving end:
carrying out balanced photoelectric conversion on the optical signal to obtain a composite analog electrical signal in a subcarrier multiplexing state;
demultiplexing the composite analog electrical signal to obtain M paths of subcarrier frequency band analog signals, and respectively frequency-shifting the M paths of subcarrier frequency band analog signals to a baseband to obtain M paths of subcarrier baseband analog signals;
and respectively inputting the M paths of subcarrier baseband analog signals into an analog-to-digital converter (ADC) for analog-to-digital conversion to obtain subcarrier baseband digital signals corresponding to each path of subcarrier baseband analog signals.
2. The method according to claim 1, wherein said converting the bitstream to be transmitted into M subcarrier baseband digital signals comprises:
and dividing the bit stream to be transmitted into M paths of branch bit streams, and carrying out coding, mapping and forming filtering processing on the M paths of branch bit streams to obtain M paths of subcarrier baseband digital signals.
3. The method of claim 1, wherein the sampling rate of the DAC is composite baud rate x 2/N and the bandwidth is composite baud rate/(2N).
4. The method according to claim 1, wherein the frequency-shifting the M-channel sub-carrier baseband analog signals to a designated sub-carrier frequency to obtain M-channel sub-carrier band analog signals comprises:
and shifting the M paths of subcarrier baseband analog signals to the appointed subcarrier frequency by adopting a phase shift method single-sideband subcarrier modulation and/or a filtering method single-sideband subcarrier modulation mode to obtain M paths of subcarrier frequency band analog signals.
5. The method of claim 1, wherein the optically modulating the composite analog electrical signal to obtain an optical signal comprises:
and inputting the composite analog electric signal to an IQ modulator for optical modulation to obtain an optical signal.
6. The method according to claim 1, wherein the frequency-shifting the M subcarrier band analog signals to baseband respectively to obtain M subcarrier baseband analog signals comprises:
and respectively frequency-shifting the M paths of subcarrier frequency band analog signals to a baseband by adopting a phase-shifting method single-sideband subcarrier demodulation and/or a filtering method single-sideband subcarrier demodulation mode to obtain M paths of subcarrier baseband analog signals.
7. An optical signal transmission apparatus, comprising:
the first processing module is used for converting a bit stream to be transmitted into M paths of subcarrier baseband digital signals, and inputting each path of subcarrier baseband digital signals into a digital-to-analog converter (DAC) for digital-to-analog conversion to obtain subcarrier baseband analog signals corresponding to each path of subcarrier baseband digital signals; wherein M is more than or equal to 2;
the second processing module is used for frequency shifting the M paths of subcarrier baseband analog signals to a specified subcarrier frequency to obtain M paths of subcarrier frequency band analog signals, and multiplexing the M paths of subcarrier frequency band analog signals to obtain a composite analog electrical signal in a subcarrier multiplexing state;
the third processing module is used for carrying out optical modulation on the composite analog electric signal to obtain an optical signal;
the fourth processing module is used for carrying out balanced photoelectric conversion on the optical signal to obtain a composite analog electrical signal in a subcarrier multiplexing state;
a fifth processing module, configured to demultiplex the composite analog electrical signal to obtain M channels of subcarrier band analog signals, and frequency shift the M channels of subcarrier band analog signals to a baseband respectively to obtain M channels of subcarrier baseband analog signals;
and the sixth processing module is used for respectively inputting the M paths of subcarrier baseband analog signals into an analog-to-digital converter (ADC) for analog-to-digital conversion to obtain subcarrier baseband digital signals corresponding to each path of subcarrier baseband analog signals.
8. The optical signal transmission apparatus according to claim 7, wherein the first processing module is specifically configured to:
and dividing the bit stream to be transmitted into M paths of branch bit streams, and carrying out coding, mapping and forming filtering processing on the M paths of branch bit streams to obtain M paths of subcarrier baseband digital signals.
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