CN115296749A - Envelope detection photon millimeter wave terahertz communication system and method - Google Patents
Envelope detection photon millimeter wave terahertz communication system and method Download PDFInfo
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- CN115296749A CN115296749A CN202211194630.8A CN202211194630A CN115296749A CN 115296749 A CN115296749 A CN 115296749A CN 202211194630 A CN202211194630 A CN 202211194630A CN 115296749 A CN115296749 A CN 115296749A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/90—Non-optical transmission systems, e.g. transmission systems employing non-photonic corpuscular radiation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
- H04B10/25752—Optical arrangements for wireless networks
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/5165—Carrier suppressed; Single sideband; Double sideband or vestigial
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
Abstract
The invention discloses an envelope detection photon millimeter wave terahertz communication system and method. The system comprises: the optical transmitter is used for generating a polarization multiplexing optical twin single sideband vector signal without carrier; the optical wireless conversion module is used for carrying out carrier coupling and optical heterodyne beat frequency on polarization multiplexing signals of the left sideband and the right sideband of the optical twin single-sideband vector signals after optical fiber transmission to generate millimeter wave terahertz single-sideband vector signals on X polarization and Y polarization; and the wireless receiving module is used for carrying out down-conversion, vector reconstruction, polarization crosstalk elimination and demodulation on the millimeter wave terahertz single-sideband vector signals on the X polarization and the Y polarization of the left sideband and the right sideband in an envelope detection direct detection mode to obtain the X polarization signal and the Y polarization signal of the left sideband and the right sideband. According to the technical scheme of the embodiment of the invention, the frequency spectrum efficiency and the transmission capacity of the low-cost envelope detection photon millimeter wave terahertz communication system are improved, and the problem of optical carrier fading caused by the transmission of the traditional polarization multiplexing single-sideband vector signal with the carrier through the optical fiber is avoided.
Description
Technical Field
The invention relates to the technical field of millimeter wave terahertz communication, in particular to an envelope detection photon millimeter wave terahertz communication system and method.
Background
The photonic millimeter wave terahertz communication system can better cooperate with optical fiber transmission and millimeter wave terahertz wave wireless transmission, not only exerts the advantages of the photonic millimeter wave terahertz communication system in wireless communication, but also can combine the advantages of optical fiber communication, and plays an important role in the development of remote, large-capacity and wide-coverage mobile communication.
At present, the envelope detection millimeter wave terahertz receiver based on direct detection has relatively low cost and simple system structure, and the passive device can obviously reduce power consumption, so the envelope detection photon millimeter wave terahertz communication system has more advantages in the aspects of wide deployment and practicability. However, current envelope detection photonic millimeter wave terahertz communication systems are limited in envelope detection characteristics, carry information mainly through amplitude modulation, result in low spectral efficiency and limited system capacity, and are not sufficient to support high-speed wireless communication scenarios of B5G/6G ultra-bandwidth, large capacity and wide coverage.
In order to improve the transmission capacity of the system, the high-order vector signal modulation and polarization multiplexing technology is an effective means. However, the current mainstream scheme of polarization multiplexing of the traditional optical fiber communication direct detection system is realized, or the traditional optical fiber communication direct detection system cannot be popularized and applied in an envelope detection photon millimeter wave terahertz communication system, or the traditional optical fiber communication direct detection system is applicable but has extremely high hardware cost, and is not suitable for large-scale deployment; or the transmitting end is based on a single-sideband modulation mode of light with carrier, after optical fiber transmission, due to the problem of optical carrier fading brought by random polarization rotation, the transmission capacity of the system can be effectively improved only by artificial active polarization control.
Disclosure of Invention
The invention provides an envelope detection photon millimeter wave terahertz communication system and method, which are used for improving the spectrum efficiency and the transmission capacity of a low-cost envelope detection photon millimeter wave terahertz communication system and avoiding the problem of optical carrier fading caused by random polarization rotation of a polarization multiplexing single-sideband vector signal with a carrier after optical fiber transmission.
According to an aspect of the invention, an envelope detection photonic millimeter wave terahertz communication system is provided, which includes:
the optical transmitter is used for generating a polarization multiplexing optical twin single sideband vector signal without carrier and transmitting the signal to the optical wireless conversion module through an optical fiber;
the optical wireless conversion module is used for extracting a left side polarization multiplexing signal and a right side polarization multiplexing signal of the polarization multiplexing optical twin single sideband vector signal, respectively performing carrier coupling and optical heterodyne beat frequency aiming at the polarization multiplexing signals of the left side band and the right side band, and generating millimeter wave terahertz single sideband vector signals with carriers in the X polarization direction and the Y polarization direction;
and the wireless receiving module is used for performing down-conversion operation on the millimeter wave terahertz single-sideband vector signals in the X and Y polarization directions of the left and right sidebands in an envelope detection direct detection mode, and performing vector reconstruction, polarization crosstalk elimination and demodulation operation on the signals subjected to the down-conversion operation to obtain the X polarization signals and the Y polarization signals of the left and right sidebands.
Optionally, the optical transmitter includes:
a transmitting laser for outputting an optical wave;
the first optical polarization beam splitter is used for dividing the light wave output by the transmitting laser into two polarization directions of X and Y;
the first optical twin single sideband modulation module is used for carrying out high-order vector signal modulation operation in the X polarization direction and generating an X polarization optical twin single sideband vector signal without a carrier;
the second light twin single sideband modulation module is used for carrying out high-order vector signal modulation operation in the Y polarization direction to generate a Y polarization light twin single sideband vector signal without a carrier;
and the first optical polarization coupler is used for coupling the X polarized light twin single sideband vector signal without the carrier and the Y polarized light twin single sideband vector signal without the carrier and outputting a polarization multiplexing light twin single sideband vector signal without the carrier.
Optionally, the first optical twin single sideband modulation module and the second optical twin single sideband modulation module employ IQ modulators.
Optionally, the optical wireless conversion module includes:
the first optical filter and the second optical filter are used for respectively extracting a left side band polarization multiplexing signal and a right side band polarization multiplexing signal of the polarization multiplexing light twin single sideband vector signal which are transmitted by the optical fiber;
the first polarization diversity photoelectric conversion module is used for respectively carrying out carrier coupling and optical heterodyne beat frequency on the left polarization multiplexing signal to generate millimeter wave terahertz left side band vector signals with carriers in the X and Y polarization directions;
and the second polarization diversity photoelectric conversion module is used for respectively carrying out carrier coupling and optical heterodyne beat frequency on the polarization multiplexing signals with the right side to generate millimeter wave terahertz right side band vector signals with carriers in the X and Y polarization directions.
Optionally, the first polarization diversity photoelectric conversion module includes:
the second optical polarization beam splitter is used for splitting the left polarization multiplexing signal into signal light waves in the X and Y polarization directions;
the first optical coupler is used for coupling the carrier light output by the carrier laser and the local oscillator light output by the local oscillator laser;
the third optical polarization beam splitter is used for splitting the signal output by the first optical coupler into a synthesized double carrier wave in the X and Y polarization directions;
the second optical coupler is used for coupling the synthesized double carrier waves in the X polarization direction with the signal light waves and sending the coupled double carrier waves to the first photoelectric detector to complete photoelectric conversion so as to generate millimeter wave terahertz left-side band vector signals with the carrier waves in the X polarization direction;
and the third optical coupler is used for coupling the synthesized double carrier waves in the Y polarization direction with the signal light waves and sending the coupled double carrier waves to the second photoelectric detector to complete photoelectric conversion so as to generate millimeter wave terahertz left-side band vector signals with the carrier waves in the Y polarization direction.
Optionally, the carrier light output by the carrier laser has the same center frequency as the signal light wave;
the center frequency interval between the local oscillator light output by the local oscillator laser and the signal light wave is as follows: and the carrier frequency of the millimeter wave terahertz single-sideband vector signal with the carrier wave in the X or Y polarization direction.
Optionally, the wireless receiving module includes:
the first envelope detector is used for performing down-conversion operation from the millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-side band vector signal in the X polarization direction of the left band;
the first analog-to-digital converter is used for carrying out digital sampling on the signal output by the first envelope detector;
the second envelope detector is used for performing down-conversion operation from the millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-sideband vector signal in the Y polarization direction of the left side band;
the second analog-to-digital converter is used for carrying out digital sampling on the signal output by the second envelope detector;
and the first DSP processing module is used for carrying out vector reconstruction, polarization crosstalk elimination and demodulation operations on the two paths of digital signals output by the first analog-to-digital converter and the second analog-to-digital converter to obtain an X polarization signal and a Y polarization signal of a left sideband.
Optionally, the first DSP processing module is configured to:
reconstructing left-side band vector signals of two paths of digital signals output by the first analog-to-digital converter and the second analog-to-digital converter by respectively adopting a Kramers-Kronig (KK) algorithm;
carrying out depolarization multiplexing processing on the reconstructed left sideband vector signals in the X polarization direction and the reconstructed left sideband vector signals in the Y polarization direction in a combined manner so as to eliminate polarization crosstalk;
and performing baseband recovery, channel equalization and symbol demapping on the two paths of signals subjected to the depolarization multiplexing processing to obtain an X polarization signal and a Y polarization signal of a left sideband.
Optionally, the system further includes:
and the MIMO antenna module is used for wirelessly transmitting the millimeter wave terahertz single sideband vector signals in the X and Y polarization directions of the left and right sidebands output by the optical wireless conversion module to the wireless receiving module.
According to another aspect of the invention, an envelope detection photonic millimeter wave terahertz communication method is provided, and includes:
generating a polarization multiplexing optical twin single sideband vector signal without carrier waves through an optical transmitter, and transmitting the signal to an optical wireless conversion module through an optical fiber;
extracting a left side band polarization multiplexing signal and a right side band polarization multiplexing signal of the polarization multiplexing optical twin single sideband vector signal through an optical wireless conversion module, and respectively carrying out carrier coupling and optical heterodyne beat frequency on the polarization multiplexing signals of the left side band and the right side band to generate millimeter wave terahertz single sideband vector signals with carriers in the X polarization direction and the Y polarization direction;
through a wireless receiving module, millimeter wave terahertz single-sideband vector signals in the X and Y polarization directions of the left and right sidebands are subjected to down-conversion operation in an envelope detection direct detection mode, and the signals subjected to down-conversion operation are subjected to vector reconstruction, polarization crosstalk elimination and demodulation operation to obtain X polarization signals and Y polarization signals of the left and right sidebands.
According to the technical scheme of the embodiment of the invention, a polarization multiplexing optical twin single sideband vector signal without carrier is generated by an optical transmitter and is transmitted to an optical wireless conversion module through an optical fiber; extracting a left side polarization multiplexing signal and a right side polarization multiplexing signal of the polarization multiplexing optical twin single sideband vector signal through an optical wireless conversion module, and respectively carrying out carrier coupling and optical heterodyne beat frequency aiming at the polarization multiplexing signals of the left side band and the right side band to generate millimeter wave terahertz single sideband vector signals with carriers in the X polarization direction and the Y polarization direction; through a wireless receiving module, through an envelope detection direct detection mode, down-conversion operation is carried out on millimeter wave terahertz single-sideband vector signals in the X and Y polarization directions of a left sideband and a right sideband, vector reconstruction, polarization crosstalk elimination and demodulation operation are carried out on the signals after down-conversion operation, and X polarization signals and Y polarization signals of the left sideband and the right sideband are obtained, so that the problem that the transmission capacity of a system cannot be effectively improved in the prior art is solved, high-order vector light twin single-sideband modulation is realized through an optical wireless conversion module, and polarization demultiplexing of high-order vector signals is realized through the wireless receiving module, so that the spectral efficiency and the transmission capacity of a low-cost envelope detection photon millimeter wave terahertz communication system are improved; by adding the optical carrier at the optical wireless conversion end, random polarization rotation caused by optical fiber transmission is avoided, and the problem of optical carrier fading caused by random polarization rotation of the traditional polarization multiplexing single-sideband vector signal with the carrier after optical fiber transmission is avoided.
It should be understood that the statements in this section are not intended to identify key or critical features of the embodiments of the present invention, nor are they intended to limit the scope of the invention. Other features of the present invention will become apparent from the following description.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an envelope detection photonic millimeter wave terahertz communication system according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an envelope detection photonic millimeter wave terahertz communication system based on polarization multiplexing optical twin single sideband signal modulation provided by an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a vector signal polarization multiplexing optical transmitter according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a polarization diversity photoelectric conversion module according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a frequency spectrum of a dual polarization vector signal envelope detection process according to an embodiment of the present invention;
fig. 6 is an example diagram of an envelope detection photonic millimeter wave terahertz communication system supporting polarization multiplexing optical twin single sideband vector signals according to an embodiment of the present invention;
fig. 7 is a flowchart of a method for envelope detection photonic millimeter wave terahertz communication according to an embodiment of the present invention.
Description of the reference numerals
Each symbol in fig. 2 represents: the optical fiber polarization multiplexing device comprises a vector signal polarization multiplexing optical transmitter 11, a standard single-mode optical fiber 12, a first optical filter 13, a first polarization diversity photoelectric conversion module 15, a first MIMO antenna module 17, a first wireless receiving module 19, a second optical filter 14, a second polarization diversity photoelectric conversion module 16, a second MIMO antenna module 18 and a second wireless receiving module 20. The first wireless receiving module 19 includes: a first envelope detector 191, a second envelope detector 192, a first analog-to-digital converter 193, a second analog-to-digital converter 194, and a first DSP processing module 195. The second wireless receiving module 20 includes: a third envelope detector 201, a fourth envelope detector 202, a third analog-to-digital converter 203, a fourth analog-to-digital converter 204 and a second DSP processing block 205.
Each symbol in fig. 3 represents: a transmitting laser 111, a first optical polarization beam splitter 112, a first optical twin single sideband modulation module 113 and a second optical twin single sideband modulation module 114, a first optical polarization coupler 115.
Each symbol in fig. 4 represents: a second optical polarization beam splitter 151, a carrier laser 152, a local oscillator laser 153, a first optical coupler 154, a third optical polarization beam splitter 155, second and third optical couplers 156 and 157, and first and second photodetectors 158 and 159.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Fig. 1 is a schematic structural diagram of an envelope detection photonic millimeter wave terahertz communication system according to an embodiment of the present invention. The embodiment can be applied to the situation that the spectrum efficiency and the transmission capacity of the envelope detection photon millimeter wave terahertz communication system with low cost are improved through a twin single-sideband and vector signal polarization multiplexing technology. The system comprises:
the optical transmitter 11 is used for generating a polarization multiplexing optical twin single sideband vector signal without a carrier and transmitting the signal to the optical wireless conversion module through an optical fiber;
the optical wireless conversion module 120 is configured to extract a left-side polarization multiplexing signal and a right-side polarization multiplexing signal of the polarization multiplexing optical twin single sideband vector signal, and perform carrier coupling and optical heterodyne beat frequency on the left-side polarization multiplexing signal and the right-side polarization multiplexing signal, respectively, to generate millimeter wave terahertz single sideband vector signals with carriers in the X and Y polarization directions;
the wireless receiving module 130 is configured to perform down-conversion operation on the millimeter wave terahertz single-sideband vector signals in the X and Y polarization directions of the left and right sidebands in a direct envelope detection manner, and perform vector reconstruction, polarization crosstalk cancellation, and demodulation operation on the down-converted signals to obtain X-polarized signals and Y-polarized signals of the left and right sidebands.
In the present embodiment, as shown in fig. 2, the specific structure of the envelope detection photon terahertz communication system, the optical transmitter 11 generates a single sideband vector signal of polarization multiplexing light twin without carrier, and the detailed structure of the optical transmitter 11 is shown in fig. 3. The polarization multiplexing light twin single sideband vector signal without carrier generated by the optical transmitter 11 is divided into two branches after being transmitted by the standard single mode fiber 12, and the two branches respectively correspond to the signal processing flow of the left polarization multiplexing signal and the right polarization multiplexing signal. The left sideband polarization multiplexed signal is extracted by the first optical filter 13 in the optical wireless conversion module 120, and the right sideband polarization multiplexed signal is extracted by the second optical filter 14 in the optical wireless conversion module 120.
Taking the polarization multiplexing signal of the left sideband as an example, the polarization multiplexing signal of the left sideband extracted by the first optical filter 13 is subjected to carrier coupling and optical heterodyne beat frequency by the first polarization diversity photoelectric conversion module 15 in the optical wireless conversion module 120, so as to generate a millimeter wave terahertz left sideband vector signal with a carrier. The detailed structure of the first polarization diversity photoelectric conversion module 15 is shown in fig. 4. The first polarization diversity photoelectric conversion module 15 can generate millimeter wave terahertz left side band vector signals in the X and Y polarization directions, the two paths of left side band millimeter wave terahertz signals complete wireless path transmission through the first MIMO antenna module 17, and are received and processed by the first wireless receiving module 19 in an envelope detection direct detection mode.
The left and right sideband signal processing flows are basically the same, and the difference is that the signal frequency spectrums are distributed in the optical domain, one is the left sideband signal, and the other is the right sideband signal, so the processing flow of the polarization multiplexing signal of the right sideband is not described herein again.
In an alternative embodiment, as shown in fig. 3, the optical transmitter 11 includes: a transmission laser 111 for outputting an optical wave; a first optical polarization beam splitter 112 for splitting the light wave output by the transmitting laser 111 into two polarization directions X and Y; the first optical twin single sideband modulation module 113 is configured to perform a high-order vector signal modulation operation in the X polarization direction to generate an X polarization optical twin single sideband vector signal without a carrier; the second optical twin single sideband modulation module 114 is used for performing high-order vector signal modulation operation in the Y polarization direction to generate a Y polarization optical twin single sideband vector signal without a carrier; the first optical polarization coupler 115 is configured to couple the X-polarized light twin single sideband vector signal without the carrier with the Y-polarized light twin single sideband vector signal without the carrier, and output a polarization multiplexed light twin single sideband vector signal without the carrier, that is, a dual-polarization multiplexed light twin single sideband signal with high spectral efficiency.
The first optical twin single sideband modulation module and the second optical twin single sideband modulation module adopt IQ modulators, and the generated polarization multiplexing optical twin single sideband vector signals do not carry optical carriers, so that the carrier fading effect of the signals after the signals are transmitted through optical fibers is avoided.
In an alternative embodiment, as shown in fig. 2, the optical wireless conversion module 120 includes: a first optical filter 13 and a second optical filter 14 for extracting a left-side band polarization multiplexed signal and a right-side band polarization multiplexed signal of the polarization multiplexed light twin single sideband vector signal transmitted through the optical fiber, respectively; the first polarization diversity photoelectric conversion module 15 is configured to perform carrier coupling and optical heterodyne beat frequency on the left-side band polarization multiplexing signal, respectively, and generate millimeter wave terahertz left-side band vector signals with carriers in the X and Y polarization directions; and the second polarization diversity photoelectric conversion module 16 is configured to perform carrier coupling and optical heterodyne beat frequency on the right-side polarization multiplexed signal, respectively, and generate millimeter wave terahertz right-side vector signals with carriers in the X and Y polarization directions.
In an alternative embodiment, as shown in fig. 4, the first polarization diversity photoelectric conversion module 15 includes: a second optical polarization beam splitter 151, configured to split the left polarization multiplexed signal into signal light waves in two polarization directions, X and Y; a first optical coupler 154, configured to couple carrier light output by the carrier laser 152 and local oscillator light output by the local oscillator laser 153; a third optical polarization beam splitter 155 for splitting the signal output by the first optical coupler into a combined dual carrier in both X and Y polarization directions; the second optical coupler 156 is configured to couple the synthesized dual carrier in the X polarization direction with the signal light wave in the X polarization direction, and send the coupled dual carrier to the first photodetector 158 to complete photoelectric conversion, so as to generate a millimeter wave terahertz left-band vector signal with a carrier in the X polarization direction; and the third optical coupler 157 is configured to couple the synthesized dual carrier in the Y polarization direction with the signal light wave in the Y polarization direction, and send the coupled dual carrier to the second photodetector 159 to complete photoelectric conversion, so as to generate a millimeter wave terahertz left-band vector signal with a carrier in the Y polarization direction.
In an alternative embodiment, the carrier laser outputs carrier light with the same center frequency as the signal light wave; the center frequency interval between the local oscillator light output by the local oscillator laser and the signal light wave is as follows: and the carrier frequency of the millimeter wave terahertz single-sideband vector signal with the carrier wave in the X or Y polarization direction.
The carrier light and the signal light wave are set to have the same central frequency, and light carrier components are provided for the light twin single sideband vector signals; the center frequency interval between the local oscillator light and the signal light wave is set as follows: and the carrier frequency of the millimeter wave terahertz single side band vector signal with the carrier wave in the X or Y polarization direction is larger, so that heterodyne beat frequency of the single-ended photoelectric detector is facilitated, and the required millimeter wave terahertz single side band vector signal is generated.
The signal processing flows of the first polarization diversity photoelectric conversion module 15 and the second polarization diversity photoelectric conversion module 16 are basically the same, and the difference is that the first polarization diversity photoelectric conversion module 15 processes a left-side band polarization multiplexing signal and generates a millimeter wave terahertz left-side band vector signal, the second polarization diversity photoelectric conversion module 16 processes a right-side band polarization multiplexing signal and generates a millimeter wave terahertz right-side band vector signal, and therefore the processing flow of the second polarization diversity photoelectric conversion module 16 on the right-side band polarization multiplexing signal is not described herein again.
It should be noted that, since the carrier light and the local oscillator light are added in the optical wireless conversion module 120 and are not subjected to random polarization rotation caused by optical fiber transmission, the carrier light and the local oscillator light can be equally added to the two polarization directions of X and Y, so that the problem of optical carrier fading existing in the scheme of generating/adding optical carrier waves at the transmitting end can be avoided. This lays a favorable foundation for the present embodiment to support polarization demultiplexing of vector signals under the condition of transmission of any fiber length, and active polarization control operation is not required, thereby greatly simplifying the operational complexity of the high-order vector signal modulation and polarization multiplexing technology applied in the envelope detection photonic millimeter wave terahertz communication system.
In an optional embodiment, the system further comprises: and the MIMO antenna module is used for wirelessly transmitting the millimeter wave terahertz single sideband vector signals in the X and Y polarization directions of the left and right sidebands output by the optical wireless conversion module to the wireless receiving module.
In this embodiment, as shown in fig. 2, the MIMO antenna module may include a first MIMO antenna module 17 and a second MIMO antenna module 18. The first MIMO antenna module 17 is configured to transmit the millimeter wave terahertz left-band vector signal with carrier waves in the two polarization directions X and Y generated by the first polarization diversity photoelectric conversion module 15 to the first wireless receiving module 19 in the wireless receiving module. And the second MIMO antenna module 18 is configured to transmit the millimeter wave terahertz right sideband vector signals with carriers in the two polarization directions of X and Y, which are generated by the second polarization diversity photoelectric conversion module 16, to a second wireless receiving module 20 in the wireless receiving module.
In an optional embodiment, the wireless receiving module 130 includes: the first envelope detector 191 is used for performing down-conversion operation from the millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-side band vector signal in the X polarization direction of the left band; a first analog-to-digital converter 193 for digitally sampling a signal output from the first envelope detector; the second envelope detector 192 is configured to perform down-conversion operation from the millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-sideband vector signal in the Y polarization direction of the left-side band; a second analog-to-digital converter 194, configured to perform digital sampling on a signal output by the second envelope detector; the first DSP processing module 195 is configured to perform vector reconstruction, polarization crosstalk cancellation, and demodulation operations on the two paths of digital signals output by the first analog-to-digital converter and the second analog-to-digital converter to obtain an X polarization signal and a Y polarization signal of a left sideband.
In an alternative embodiment, the first DSP processing module 195 is configured to: reconstructing the left-side band vector signals of the two paths of digital signals output by the first analog-to-digital converter 193 and the second analog-to-digital converter 194 by respectively adopting a KK algorithm; carrying out depolarization multiplexing processing on the reconstructed left sideband vector signals in the X and Y polarization directions in a combined manner so as to eliminate polarization crosstalk; and performing baseband recovery, channel equalization and symbol demapping on the two paths of signals subjected to the depolarization multiplexing processing to obtain an X polarization signal and a Y polarization signal of a left sideband.
It should be noted that, as shown in fig. 2, the wireless receiving module is actually divided into a first wireless receiving module 19 and a second wireless receiving module 20, which are used for respectively processing the millimeter wave terahertz single-sideband vector signals of the left and right sidebands. Since the first wireless receiving module 19 and the second wireless receiving module 20 have the same structure, that is, both modules include two envelope detectors, two analog-to-digital converters, and one DSP processing module, the processing flows of the two modules for the millimeter wave terahertz single-sideband vector signal are also substantially the same.
In an alternative embodiment, as shown in fig. 2, the wireless receiving module 130 includes: the third envelope detector 201 is configured to perform down-conversion operation from the millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-side band vector signal in the X polarization direction of the right band; a third analog-to-digital converter 203, configured to perform digital sampling on a signal output by the third envelope detector; the fourth envelope detector 202 is used for performing down-conversion operation from the millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-side band vector signal in the Y polarization direction of the right band; a fourth analog-to-digital converter 204 for digitally sampling a signal output by the fourth envelope detector; the second DSP processing module 205 is configured to perform vector reconstruction, polarization crosstalk cancellation, and demodulation operations on the two paths of digital signals output by the third analog-to-digital converter and the fourth analog-to-digital converter to obtain an X polarization signal and a Y polarization signal of the right sideband.
In an optional embodiment, the second DSP processing module 205 is specifically configured to: reconstructing the right side band vector signals of the two paths of digital signals output by the third analog-to-digital converter 203 and the fourth analog-to-digital converter 204 by adopting a KK algorithm respectively; carrying out depolarization multiplexing processing on the reconstructed right sideband vector signals in the X and Y polarization directions in a combined manner so as to eliminate polarization crosstalk; and performing baseband recovery, channel equalization and symbol demapping on the two paths of signals subjected to the depolarization multiplexing processing to obtain an X polarization signal and a Y polarization signal of a right sideband.
To further illustrate the working principle of the first DSP processing module 195, a frequency spectrum diagram of key steps from envelope detection to DSP signal processing is given by taking the dual-polarization left-sideband millimeter wave terahertz signal as an example, as shown in fig. 5. First, due to random polarization rotation of the optical fiber transmission, the signal received by the first wireless receiving module 19 from the first polarization diversity photoelectric conversion module 15 is actually a mixture of the X-polarization left-band millimeter wave terahertz signal and the Y-polarization left-band signal. The mixed signals on the two polarizations are subjected to signal down-conversion through an envelope detector, under the action of square law characteristics of envelope detection, two paths of output signals both comprise five components, and taking X polarization envelope detection output as an example, the two paths of output signals comprise 1) X polarization signals per se, 2) Y polarization signal crosstalk, 3) X polarization signal and signal beat frequency crosstalk (X-SSBI), 4) Y polarization signal and signal beat frequency crosstalk (Y-SSBI) and 5) X polarization signal and Y polarization signal cross beat frequency crosstalk (C-SSBI). For X-polarization, only the first term is expected, the second term belongs to the first-order crosstalk, and the third, fourth and fifth terms belong to the second-order crosstalk, which are all unwanted crosstalk terms, and their existence degrades the signal-to-noise ratio of the X-polarization signal, thereby degrading the demodulation performance of the system. Accordingly, the same is true for the Y polarization.
To eliminate these crosstalk, the first DSP processing module 195 performs the following DSP signal processing flow: (1) And respectively reconstructing the signals of the X and Y polarization signals with crosstalk by adopting a KK algorithm. By utilizing a KK algorithm, three second-order crosstalk terms of X-SSBI, Y-SSBI and C-SSBI can be perfectly eliminated, and the recovered left side band vector signal only has another polarized first-order crosstalk term. (2) And jointly performing 2X 2 MIMO depolarization multiplexing on the X and Y polarization left sideband vector signals reconstructed by the KK algorithm. The depolarization multiplexing can adopt a constant modulus algorithm or a cascade multimode algorithm, and the operation can eliminate a first-order crosstalk term caused by polarization rotation and output two pure left-side band signals. (3) Demodulating the two acquired left sideband signals, including: and recovering a baseband, equalizing a channel and demapping a symbol to obtain an X polarized signal and a Y polarized signal of a left sideband, and calculating the error rate.
The baseband recovery means that a single sideband signal of an intermediate frequency is converted into a baseband signal through frequency shift processing, the channel equalization means that a direct decision least mean square algorithm equalizer is adopted to perform channel equalization on the baseband signal, and the symbol demapping means that the baseband signal subjected to the signal equalization is mapped onto a binary code element from a QAM symbol, so that the error rate can be calculated conveniently.
According to the envelope detection photon millimeter wave terahertz communication system, the high-order vector light twin single-sideband modulation is adopted, the bandwidth of an analog-digital/digital-analog converter at a transmitting and receiving end can be fully utilized, the vector field signal can be recovered from the signal amplitude information obtained by envelope detection based on a KK algorithm, and meanwhile, the beat frequency crosstalk of the signal introduced by square law detection is eliminated, so that the envelope detection photon millimeter terahertz communication system can be expanded to two-dimensional vector field modulation from the traditional one-dimensional amplitude modulation, meanwhile, the envelope detection photon millimeter wave terahertz communication system has the vector signal polarization demultiplexing capability, and the capacity potential of the envelope detection photon millimeter terahertz communication system is remarkably improved. In addition, by coupling the carrier light and the local oscillator light at the optical wireless conversion end, the problem of carrier fading existing in the single-side band signal of the light with the carrier at the traditional sending end is solved, and the polarization demultiplexing of the vector signal after transmission at any optical fiber length can be realized without active polarization control. Therefore, the envelope detection photon millimeter terahertz communication system with low cost can be similar to a mixing coherent photon millimeter wave terahertz communication system, can provide high-speed and high-capacity communication capability by fully utilizing multi-dimensional modulation such as amplitude, phase and polarization state of light, and is beneficial to promoting the practical development of the B5G/6G photon millimeter wave terahertz system.
Fig. 6 is a diagram showing an example of an envelope detection photonic millimeter wave terahertz communication system supporting a polarization multiplexing optical twin single sideband vector signal according to an embodiment of the present invention.
Wherein, two paths of signals adopt a 16QAM modulation format, the baud rate is 5.75Gbaud/s, and the signals are transmitted back to back through 60 kilometers of optical fibers and wirelessly. The whole system consists of a plurality of modules of an optical transmitter, an optical fiber transmission link, an optical beam splitter (OS), a left/right sideband optical filter, a left/right sideband optical wireless conversion module, an MIMO antenna module and a left/right sideband wireless receiver.
In an optical transmitter, two IQMZMs are used for generating optical twin single sideband vector signals without carriers, polarization multiplexing is carried out through an optical polarization coupler (PBC), then the signals are transmitted to an optical wireless conversion end through optical fibers, and optical left/right side band polarization multiplexing signals are filtered through two band-pass filters with different center frequencies respectively. The two signals are respectively subjected to the same processing, for example, one of the two signals is coupled with carrier light and local oscillator light, a needed millimeter wave terahertz single sideband vector signal is generated by an optical heterodyne detection technology based on polarization diversity, and the carrier frequency of the obtained millimeter wave terahertz signal can be portable and adjustable according to the central wavelength of the local oscillator light. In the left/right side band wireless receiver, a target millimeter wave terahertz signal is subjected to down-conversion by using an envelope detector, passes through an amplifier and an analog-to-digital conversion module and then is sent to a receiving DSP processing module for processing. And reconstructing a vector signal by using a KK algorithm in the DSP, eliminating polarization crosstalk by using a polarization demultiplexing algorithm, and finally demodulating to obtain an X polarization signal and a Y polarization signal.
The system avoids the problem of optical carrier fading caused by random polarization rotation of optical fiber transmission by adding the optical carrier at the optical wireless conversion end, and greatly improves the capacity potential of the envelope detection photon millimeter wave terahertz communication system by using a twin single side band and vector signal polarization multiplexing technology.
Fig. 7 is a flowchart of an envelope detection photonic millimeter wave terahertz communication method according to an embodiment of the present invention, where the embodiment is applicable to a case where the spectrum efficiency and the transmission capacity of a low-cost envelope detection photonic millimeter wave terahertz communication system are improved by a twinning single sideband and vector signal polarization multiplexing technique, and the method may be implemented by the envelope detection photonic millimeter wave terahertz communication system. As shown in fig. 7, the method includes:
and S710, generating a polarization multiplexing optical twin single sideband vector signal without a carrier by an optical transmitter, and transmitting the signal to an optical wireless conversion module by an optical fiber.
S720, extracting the left side band polarization multiplexing signal and the right side band polarization multiplexing signal of the polarization multiplexing optical twin single sideband vector signal through an optical wireless conversion module, and respectively carrying out carrier coupling and optical heterodyne beat frequency aiming at the polarization multiplexing signals of the left side band and the right side band to generate millimeter wave terahertz single sideband vector signals with carriers in the X polarization direction and the Y polarization direction.
And S730, performing down-conversion operation on the millimeter wave terahertz single-sideband vector signals in the X and Y polarization directions of the left and right sidebands through a wireless receiving module in an envelope detection direct detection mode, and performing vector reconstruction, polarization crosstalk elimination and demodulation operation on the signals subjected to the down-conversion operation to obtain the X polarization signals and the Y polarization signals of the left and right sidebands.
According to the technical scheme of the embodiment of the invention, a polarization multiplexing optical twin single sideband vector signal without carrier is generated by an optical transmitter and is transmitted to an optical wireless conversion module through an optical fiber; extracting a left side polarization multiplexing signal and a right side polarization multiplexing signal of the polarization multiplexing optical twin single sideband vector signal through an optical wireless conversion module, and respectively carrying out carrier coupling and optical heterodyne beat frequency aiming at the polarization multiplexing signals of the left side band and the right side band to generate millimeter wave terahertz single sideband vector signals with carriers in the X polarization direction and the Y polarization direction; through the wireless receiving module, through an envelope detection direct detection mode, down-conversion operation is carried out on millimeter wave terahertz single-sideband vector signals in X and Y polarization directions of a left sideband and a right sideband, vector reconstruction, polarization crosstalk elimination and demodulation operation are carried out on the signals after down-conversion operation, X polarization signals and Y polarization signals of the left sideband and the right sideband are obtained, the problem that the transmission capacity of a system cannot be effectively improved in the prior art is solved, the spectral efficiency and the transmission capacity of a low-cost envelope detection photon millimeter wave terahertz communication system are improved, and the problem of optical carrier fading caused by random polarization rotation of the polarization multiplexing single-sideband vector signals of the traditional carrier after optical fiber transmission is solved.
In an alternative embodiment, generating a polarization multiplexed optical twin single sideband vector signal without a carrier by an optical transmitter comprises:
outputting light waves through a transmitting laser;
dividing the light wave output by the transmitting laser into two polarization directions of X and Y by a first light polarization beam splitter;
performing high-order vector signal modulation operation in the X polarization direction through a first light twin single sideband modulation module to generate an X polarization light twin single sideband vector signal without a carrier;
performing high-order vector signal modulation operation in the Y polarization direction through a second light twin single sideband modulation module to generate a Y polarization light twin single sideband vector signal without a carrier;
and coupling the X polarized light twin single sideband vector signal without the carrier and the Y polarized light twin single sideband vector signal without the carrier through a first optical polarization coupler, and outputting a polarization multiplexing light twin single sideband vector signal without the carrier.
In an optional embodiment, the first optical twin single sideband modulation module and the second optical twin single sideband modulation module adopt IQ modulators.
In an optional embodiment, an optical wireless conversion module is used to extract a left-side polarization multiplexing signal and a right-side polarization multiplexing signal of the polarization multiplexing optical twin single sideband vector signal, and carrier coupling and optical heterodyne beat frequency are respectively performed on the left-side polarization multiplexing signal and the right-side polarization multiplexing signal to generate millimeter wave terahertz single sideband vector signals with carriers in two polarization directions of X and Y, including:
respectively extracting a left polarization multiplexing signal and a right polarization multiplexing signal of the polarization multiplexing light twin single sideband vector signal transmitted by the optical fiber through a first optical filter and a second optical filter;
respectively carrying out carrier coupling and optical heterodyne beat frequency on the polarization multiplexing signal with the left side through a first polarization diversity photoelectric conversion module to generate a millimeter wave terahertz vector signal with a carrier wave in the X and Y polarization directions;
and respectively carrying out carrier coupling and optical heterodyne beat frequency on the polarization multiplexing signal with the right side through a second polarization diversity photoelectric conversion module to generate a millimeter wave terahertz vector signal with a carrier wave on the X polarization direction and the Y polarization direction.
In an optional embodiment, the carrier coupling and optical heterodyne beat frequency are respectively performed on the left-side band polarization multiplexing signal through the first polarization diversity photoelectric conversion module, so as to generate millimeter wave terahertz left-side band vector signals with carriers in two polarization directions of X and Y, including:
dividing the left polarization multiplexing signal into signal light waves in X and Y polarization directions by a second light polarization beam splitter;
coupling carrier light output by a carrier laser and local oscillator light output by a local oscillator laser through a first optical coupler;
dividing the signal output by the first optical coupler into a synthetic dual carrier in X and Y polarization directions by a third optical polarization beam splitter;
coupling the synthesized double carrier waves in the X polarization direction with signal light waves through a second optical coupler, and sending the coupled double carrier waves to a first photoelectric detector to complete photoelectric conversion so as to generate millimeter wave terahertz left side band vector signals with carrier waves in the X polarization direction;
and coupling the synthesized double-carrier wave in the Y polarization direction with the signal light wave through a third optical coupler, and sending the coupled double-carrier wave to a second photoelectric detector to complete photoelectric conversion so as to generate a millimeter wave terahertz left side band vector signal with the carrier wave in the Y polarization direction.
In an alternative embodiment, the carrier laser outputs carrier light with the same center frequency as the signal light wave;
the center frequency interval between the local oscillator light output by the local oscillator laser and the signal light wave is as follows: and the carrier frequency of the millimeter wave terahertz single-sideband vector signal with the carrier wave in the X or Y polarization direction.
In an optional embodiment, through a wireless receiving module, performing down-conversion operation on millimeter wave terahertz single-sideband vector signals in the X and Y polarization directions of the left and right sidebands in a direct envelope detection manner, and performing vector reconstruction, polarization crosstalk cancellation, and demodulation operation on the down-converted signals to obtain X-polarized signals and Y-polarized signals of the left and right sidebands, including:
performing down-conversion operation from a millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-side band vector signal in the X polarization direction of the left band through a first envelope detector;
performing digital sampling on the signal output by the first envelope detector through a first analog-to-digital converter;
performing down-conversion operation from the millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-side-band vector signal in the Y polarization direction of the left band through a second envelope detector;
performing digital sampling on the signal output by the second envelope detector through a second analog-to-digital converter;
and performing vector reconstruction, polarization crosstalk elimination and demodulation operations on the two paths of digital signals output by the first analog-to-digital converter and the second analog-to-digital converter through the first DSP processing module to obtain an X polarization signal and a Y polarization signal of a left sideband.
In an optional embodiment, the performing, by the first DSP processing module, polarization crosstalk cancellation and demodulation operations on the two paths of digital signals output by the first analog-to-digital converter and the second analog-to-digital converter to obtain an X-polarized signal and a Y-polarized signal of a left sideband, includes:
reconstructing left-side vector signals of two paths of digital signals output by the first analog-to-digital converter and the second analog-to-digital converter by adopting a KK algorithm respectively;
carrying out depolarization multiplexing processing on the reconstructed left sideband vector signals in the X polarization direction and the reconstructed left sideband vector signals in the Y polarization direction in a combined manner so as to eliminate polarization crosstalk;
and performing baseband recovery, channel equalization and symbol demapping on the two paths of signals subjected to the depolarization multiplexing processing to obtain an X polarization signal and a Y polarization signal of a left sideband.
In an optional embodiment, the method further comprises:
and through an MIMO antenna module, millimeter wave terahertz single sideband vector signals in the X and Y polarization directions of the left and right sidebands output by the optical wireless conversion module are wirelessly transmitted to the wireless receiving module.
It should be understood that various forms of the flows shown above may be used, with steps reordered, added, or deleted. For example, the steps described in the present invention may be executed in parallel, sequentially, or in different orders, and are not limited herein as long as the desired results of the technical solution of the present invention can be achieved.
The above-described embodiments should not be construed as limiting the scope of the invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may be made, depending on design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. An envelope detection photonic millimeter wave terahertz communication system is characterized by comprising:
the optical transmitter is used for generating a polarization multiplexing optical twin single sideband vector signal without a carrier and transmitting the signal to the optical wireless conversion module through an optical fiber;
the optical wireless conversion module is used for extracting a left side polarization multiplexing signal and a right side polarization multiplexing signal of the polarization multiplexing optical twin single sideband vector signal, respectively performing carrier coupling and optical heterodyne beat frequency aiming at the polarization multiplexing signals of the left side band and the right side band, and generating millimeter wave terahertz single sideband vector signals with carriers in the X polarization direction and the Y polarization direction;
and the wireless receiving module is used for carrying out down-conversion operation on the millimeter wave terahertz single-sideband vector signals in the X and Y polarization directions of the left and right sidebands in an envelope detection direct detection mode, and carrying out vector reconstruction, polarization crosstalk elimination and demodulation operation on the signals subjected to the down-conversion operation to obtain the X polarization signals and the Y polarization signals of the left and right sidebands.
2. The system of claim 1, wherein the optical transmitter comprises:
a transmitting laser for outputting a light wave;
the first optical polarization beam splitter is used for dividing the light wave output by the transmitting laser into two polarization directions of X and Y;
the first optical twin single sideband modulation module is used for carrying out high-order vector signal modulation operation in the X polarization direction and generating an X polarization optical twin single sideband vector signal without a carrier;
the second light twin single sideband modulation module is used for carrying out high-order vector signal modulation operation in the Y polarization direction to generate a Y polarization light twin single sideband vector signal without a carrier;
and the first optical polarization coupler is used for coupling the X polarized light twin single sideband vector signal without the carrier wave with the Y polarized light twin single sideband vector signal without the carrier wave and outputting a polarized multiplexing light twin single sideband vector signal without the carrier wave.
3. The system of claim 2, wherein the first optical twin single sideband modulation module and the second optical twin single sideband modulation module employ IQ modulators.
4. The system of claim 1, wherein the optical wireless conversion module comprises:
the first optical filter and the second optical filter are used for respectively extracting a left side band polarization multiplexing signal and a right side band polarization multiplexing signal of the polarization multiplexing light twin single sideband vector signal which are transmitted by the optical fiber;
the first polarization diversity photoelectric conversion module is used for respectively carrying out carrier coupling and optical heterodyne beat frequency on the polarization multiplexing signals with the left side to generate millimeter wave terahertz vector signals with carriers in the X and Y polarization directions;
and the second polarization diversity photoelectric conversion module is used for respectively carrying out carrier coupling and optical heterodyne beat frequency on the polarization multiplexing signals with the right side to generate millimeter wave terahertz right side band vector signals with carriers in the X and Y polarization directions.
5. The system of claim 4, wherein the first polarization diversity optical-to-electrical conversion module comprises:
the second optical polarization beam splitter is used for splitting the left polarization multiplexing signal into signal light waves in the X and Y polarization directions;
the first optical coupler is used for coupling the carrier light output by the carrier laser and the local oscillator light output by the local oscillator laser;
the third optical polarization beam splitter is used for splitting the signal output by the first optical coupler into synthetic dual carriers in the X and Y polarization directions;
the second optical coupler is used for coupling the synthesized double-carrier wave in the X polarization direction with the signal light wave and sending the coupled double-carrier wave to the first photoelectric detector to complete photoelectric conversion so as to generate a millimeter wave terahertz left side band vector signal with the carrier wave in the X polarization direction;
and the third optical coupler is used for coupling the synthesized double carriers in the Y polarization direction with the signal light waves and sending the coupled double carriers to the second photoelectric detector to complete photoelectric conversion so as to generate millimeter wave terahertz left side band vector signals with the carriers in the Y polarization direction.
6. The system of claim 5,
the carrier light output by the carrier laser has the same center frequency as the signal light wave;
the center frequency interval between the local oscillator light output by the local oscillator laser and the signal light wave is as follows: and the carrier frequency of the millimeter wave terahertz single-sideband vector signal with the carrier wave in the X or Y polarization direction.
7. The system of claim 1, wherein the wireless receiving module comprises:
the first envelope detector is used for performing down-conversion operation from the millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-side band vector signal in the X polarization direction of the left band;
the first analog-to-digital converter is used for digitally sampling the signal output by the first envelope detector;
the second envelope detector is used for performing down-conversion operation from the millimeter wave terahertz signal to a low-frequency signal on the millimeter wave terahertz single-sideband vector signal in the Y polarization direction of the left side band;
the second analog-to-digital converter is used for carrying out digital sampling on the signal output by the second envelope detector;
and the first DSP processing module is used for carrying out vector reconstruction, polarization crosstalk elimination and demodulation operations on the two paths of digital signals output by the first analog-to-digital converter and the second analog-to-digital converter to obtain an X polarization signal and a Y polarization signal of a left sideband.
8. The system of claim 7, wherein the first DSP processing module is configured to:
reconstructing left-side vector signals of two paths of digital signals output by the first analog-to-digital converter and the second analog-to-digital converter by adopting a KK algorithm respectively;
carrying out depolarization multiplexing processing on the reconstructed left sideband vector signals in the X and Y polarization directions in a combined manner so as to eliminate polarization crosstalk;
and performing baseband recovery, channel equalization and symbol demapping on the two paths of signals subjected to the depolarization multiplexing processing to obtain an X polarization signal and a Y polarization signal of a left sideband.
9. The system of claim 1, further comprising:
and the MIMO antenna module is used for wirelessly transmitting the millimeter wave terahertz single sideband vector signals in the X and Y polarization directions of the left and right sidebands output by the optical wireless conversion module to the wireless receiving module.
10. An envelope detection photon millimeter wave terahertz communication method is characterized by comprising the following steps:
generating a polarization multiplexing optical twin single sideband vector signal without carrier waves through an optical transmitter, and transmitting the signal to an optical wireless conversion module through an optical fiber;
extracting a left side polarization multiplexing signal and a right side polarization multiplexing signal of the polarization multiplexing optical twin single sideband vector signal through an optical wireless conversion module, and respectively carrying out carrier coupling and optical heterodyne beat frequency aiming at the polarization multiplexing signals of the left side band and the right side band to generate millimeter wave terahertz single sideband vector signals with carriers in the X polarization direction and the Y polarization direction;
through a wireless receiving module, through an envelope detection direct detection mode, down-conversion operation is carried out on millimeter wave terahertz single-sideband vector signals in the X and Y polarization directions of the left and right sidebands, vector reconstruction, polarization crosstalk elimination and demodulation operation are carried out on the signals after down-conversion operation, and X polarization signals and Y polarization signals of the left and right sidebands are obtained.
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| WO2024066213A1 (en) * | 2022-09-29 | 2024-04-04 | 网络通信与安全紫金山实验室 | Envelope detection photon millimeter wave terahertz communication system and method |
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