CN107947930B - Continuous variable quantum key distribution modulation compensation system and implementation method thereof - Google Patents
Continuous variable quantum key distribution modulation compensation system and implementation method thereof Download PDFInfo
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Abstract
The invention discloses a continuous variable quantum key distribution modulation compensation system and an implementation method thereof.A quantum key sending end modulates a quantum signal, changes the quantum signal into a plurality of subcarrier forms and sends the subcarrier forms to a quantum key receiving end; the quantum key receiving end collects and processes the sent signals and sends the results to an I/Q correction compensation post-processing module; and the I/Q correction compensation post-processing module processes the received signals by adopting a least mean square algorithm. The invention can overcome the modulation defects in the quantum key distribution system, particularly aims at I/Q imbalance, and further improves the actual safety of the continuous variable quantum key distribution system based on orthogonal frequency division multiplexing.
Description
Technical Field
The invention belongs to the technical field of optical fiber quantum communication, and relates to a continuous variable quantum key distribution modulation compensation system based on orthogonal frequency division multiplexing and an implementation method thereof.
Background
The quantum key distribution can ensure that two long-distance keys are safely shared in an untrusted quantum channel, and the safety of the two long-distance keys is ensured by the inaccuracy measurement principle of quantum mechanics and the quantum unclonable theorem. Currently, quantum key distribution is mainly divided into two types, namely discrete variable and continuous variable. Compared with discrete variable quantum key distribution, the quantum state of the continuous variable quantum key distribution is easier to prepare, the continuous variable quantum key distribution can be integrated into the existing optical fiber system, and a homodyne detection or heterodyne detection technology with high efficiency and low cost can be used, so that the continuous variable quantum key distribution system can more easily enter the commercialization field. However, the continuous variable quantum key distribution is inefficient in negotiation in long distance communication, and the key rate thereof is to be further improved in a considerable range of communication distance. OFDM (Orthogonal Frequency Division Multiplexing) has been developed in the field of quantum communication. The continuous variable quantum key distribution system based on orthogonal frequency division multiplexing can effectively improve the security key rate of the quantum communication network. However, this scheme also has many unavoidable modulation defects, such as amplitude imbalance and phase quadrature error (I/Q imbalance) that occur during modulation. Therefore, it is important to measure and compensate for the signal defect generated by the modulation process.
Disclosure of Invention
In order to achieve the above object, the present invention provides a continuous variable quantum key distribution modulation compensation system and an implementation method thereof, which solve the problem of modulation defects in the orthogonal frequency division multiplexing continuous variable quantum key distribution system in the prior art.
The technical scheme adopted by the invention is that the continuous variable quantum key distribution modulation compensation system comprises:
the quantum key sending end is used for generating a key, modulating a quantum signal, sending the modulated signal to a quantum key receiving end through a quantum channel and sending a modulation defect signal generated in the modulation process to the I/Q correction compensation post-processing module;
the quantum key receiving end is used for receiving and detecting quantum signals and transmitting feedback information to the I/Q correction compensation post-processing module;
and the I/Q correction compensation post-processing module is used for acquiring modulation defect signals sent by the quantum key sending end and feedback information sent by the quantum key receiving end, detecting and correcting the I/Q imbalance degree by adopting a least mean square algorithm, and finally compensating the modulation defects.
Further, the quantum key sending end includes:
a pulsed laser for generating pulsed coherent light;
the beam splitter is used for separating the pulse coherent light into signal light with the quantum level of 1% and local oscillator light with the quantum level of 99%;
the radio frequency OFDM transmitting end is used for mapping input binary serial data through quadrature amplitude modulation, performing serial-parallel conversion, and loading the binary serial data to an orthogonal subcarrier through Fourier transform to form an OFDM signal;
the Mach-Zehnder modulator is used for modulating a radio frequency OFDM signal sent by a radio frequency OFDM sending end to an optical domain with 1% quantum light intensity generated by the beam splitter, the signal light is divided into two beams of light with identical amplitude and phase on a Y-branch device of the Mach-Zehnder modulator, and the two beams of light are transmitted on an upper branch and a lower branch along with an optical waveguide, and the Mach-Zehnder modulator inevitably has the defect of I/Q imbalance in the modulation process;
the adjustable attenuator is used for attenuating the signal light sent by the Mach-Zehnder modulator to a proper light intensity level, the light intensity level is set according to different processed signal lights, and the attenuated signal light is sent to the polarization coupler;
the field programmable gate array signal acquisition card is used for receiving the modulation defect signal of the Mach-Zehnder modulator, taking the modulation defect signal as a training sequence symbol and sending the training sequence symbol to I/Q correction and channel equalization;
and the polarization coupler is used for coupling the received signal light and the local oscillator light separated by the beam splitter into a quantum signal and transmitting the quantum signal to a quantum key receiving end through a quantum channel.
Further, the quantum key receiving end includes:
the OFDM demodulator is used for converting optical signals transmitted by the quantum channels into electric signals, further converting the signals into digital signals through an analog-to-digital converter in the OFDM demodulator, performing fast Fourier transform, processing the signals according to compensation quantity obtained by decision feedback, and finally demodulating the signals and transmitting the demodulated signals to the polarization beam splitter;
the polarization beam splitter is used for dividing the quantum signals sent by the OFDM demodulator into 10% of signal light and 90% of local oscillation light;
the local oscillator laser is used for generating local oscillator light, interfering with the signal light sent by the polarization beam splitter, realizing difference through the path difference of the local oscillator light and the signal light, and sending the difference to the homodyne detector;
the homodyne detector is used for carrying out homodyne detection on coherent light obtained by interference between local oscillator light generated by the local oscillator laser and signal light received by the polarization beam splitter to obtain a measurement result of randomly selected orthogonal components and sending the detection result to the field programmable gate array data acquisition card;
the field programmable gate array data acquisition card is used for sending signals acquired by the homodyne detector to I/Q correction and channel equalization, using the signals as known feedback signals, solving IQ imbalance parameters and channel transmission functions at the current moment, and using the IQ imbalance parameters and the channel transmission functions for IQ correction and channel equalization of the next OFDM data symbol.
Further, the I/Q correction based compensation post-processing module comprises:
the I/Q correction and channel equalization are used for receiving training sequence symbols sent by a field programmable gate array signal acquisition card and known feedback signals sent by the field programmable gate array data acquisition card, estimating the imbalance degree of modulation signals by using a least mean square algorithm, finally carrying out constellation point judgment on the obtained complex signals, taking the latest value as a judgment value, calculating corresponding compensation quantity and sending the corresponding compensation quantity to judgment feedback;
and the decision feedback is used for receiving the compensation quantity information and transmitting the compensation quantity information to the OFDM demodulator.
Furthermore, the pulse laser is a Thorlabs OPG1015 picosecond optical pulse generator, the Mach-Zehnder modulator is a BP-ABC bias controller, the field programmable gate array signal acquisition card is formed by combining Xilinx VC707 and FMC176, and the polarization coupler is a Thorlabs PBC980PM-FC polarization beam coupler.
Furthermore, the type of the homodyne detector is a Thorlabs PDA435A balanced amplification photoelectric detector, and the field programmable gate array data acquisition card is formed by combining Xilinx VC707 and FMC 176.
The invention adopts another technical scheme that the implementation method of the continuous variable quantum key distribution modulation compensation system is specifically carried out according to the following steps:
firstly, pulse coherent light generated by a pulse laser is separated into signal light and local oscillation light through a beam splitter; meanwhile, an input serial data is subjected to quadrature amplitude modulation mapping and serial-to-parallel conversion by a radio frequency OFDM sending end, an OFDM signal is formed by loading Fourier transform on an orthogonal subcarrier, a multi-carrier signal from the radio frequency OFDM sending end and a quantum optical signal from a beam splitter are received by a Mach-Zehnder modulator, the radio frequency OFDM signal is modulated on an optical domain with 1% quantum light intensity generated by the beam splitter in the Mach-Zehnder modulator, a plurality of subcarrier-form optical signals are formed, the defect of I/Q imbalance is inevitably generated in the modulation process, and a received modulation defect signal is transmitted to I/Q correction and channel equalization by a field programmable gate array signal acquisition card to compensate the modulation defect; the signal light sent by the Mach-Zehnder modulator is attenuated to a proper light intensity level through the adjustable attenuator, then coupled with the local oscillation light sent by the beam splitter in the polarization coupler, and sent to the quantum key receiving end through a quantum channel;
at a quantum signal receiving end, recovering the modulation state of a signal by a quantum signal through an OFDM demodulator, dividing the signal into signal light and local oscillator light through a polarization beam splitter, coupling the signal light and the local oscillator light emitted by a local oscillator laser, detecting the signal light and the local oscillator light through a homodyne detector, sending a detection result to a field programmable gate array data acquisition card, and transmitting the data serving as a feedback signal to an I/Q correction and channel equalization channel and a training sequence symbol of the field programmable gate array signal acquisition card for comparison and detection;
thirdly, the I/Q correction compensation module sends the signals acquired by the field programmable gate array signal acquisition card to I/Q correction and channel equalization; the I/Q correction and the channel equalization process the acquired modulation defect signals by adopting a minimum mean square algorithm, then transmit the obtained compensated result to a decision feedback, and the decision feedback transmits the received correction result to an OFDM demodulator at a quantum signal receiving end through a classical channel so as to compensate the defects of a Mach-Zehnder modulator in a key distribution modulation compensation system.
The invention has the advantages that the Field Programmable Gate Array (FPGA) signal acquisition card acquires the modulation signal distributed by the continuous variable quantum key based on the orthogonal frequency division multiplexing technology, the I/Q correction compensation post-processing module is used for receiving the I/Q modulation signal, firstly, the modulation signal deviation is estimated, and then, the data is processed by the least mean square algorithm. And the processed data stream is transmitted to decision feedback, and the signal is demodulated and compensated at a quantum key receiving end. The invention has the advantages of real-time feedback and low compensation delay, effectively reduces the influence of modulation defects existing in continuous variable quantum key distribution on a communication system by utilizing the I/Q correction compensation post-processing module, and improves the maximum transmission distance of communication and the system security key rate.
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 the drawings without creative efforts.
FIG. 1 is a block diagram of the architecture of an embodiment of the present invention;
fig. 2 is a schematic diagram of a quantum key transmitting end and a quantum key receiving end according to an embodiment of the present invention.
In the figure, 1, a pulse laser, 2, a beam splitter, 3, a radio frequency OFDM transmitting end, 4, a Mach-Zehnder modulator, 5, an adjustable attenuator, 6, a Field Programmable Gate Array (FPGA) signal acquisition card, 7, a polarization coupler, 8, an OFDM demodulator, 9, a polarization beam splitter, 10, a local oscillator laser, 11, a homodyne detector, 12, a Field Programmable Gate Array (FPGA) data acquisition card, 13, I/Q correction and channel equalization, and 14, decision feedback.
Detailed Description
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.
A continuous variable quantum key distribution modulation compensation system based on orthogonal frequency division multiplexing, as shown in fig. 1-2, includes:
the quantum key sending end is used for generating a key, modulating a quantum signal, sending the modulated signal to a quantum key receiving end through a quantum channel and sending a modulation defect signal generated in the modulation process to the I/Q correction compensation post-processing module;
the quantum key receiving end is used for receiving and detecting quantum signals and transmitting feedback information to the I/Q correction compensation post-processing module;
and the I/Q correction compensation post-processing module is used for acquiring modulation defect signals sent by the quantum key sending end and feedback information sent by the quantum key receiving end, detecting and correcting the I/Q imbalance degree by adopting a least mean square algorithm, and finally compensating the modulation defects.
The quantum key transmitting terminal comprises:
a pulse laser 1 for generating pulse coherent light;
the beam splitter 2 is used for splitting the pulse coherent light into signal light with a 1% quantum level and local oscillation light with a 99% quantum level, and the local oscillation light has the effect of amplifying the intensity of the signal light;
the radio frequency OFDM transmitting end 3 is used for mapping input binary serial data through quadrature amplitude modulation, performing serial-parallel conversion, and loading the binary serial data to an orthogonal subcarrier through Fourier transform to form an OFDM signal;
the Mach-Zehnder modulator 4 is used for modulating a radio frequency OFDM signal sent by the radio frequency OFDM sending end 3 to an optical domain with 1% quantum light intensity generated by the beam splitter 2, the signal light is divided into two beams of light with identical amplitude and phase on a Y-branch device of the Mach-Zehnder modulator 4, and the two beams of light are transmitted on an upper branch and a lower branch along with an optical waveguide, and in the modulation process, the Mach-Zehnder modulator 4 inevitably has the defect of I/Q unbalance due to the influence of factors such as precision error, temperature drift and the like of an analog device;
an adjustable attenuator 5 for attenuating the signal light sent from the mach-zehnder modulator 4 to a suitable light intensity level, the light intensity level being set according to the difference of the processed signal light, and sending the attenuated signal light to the polarization coupler 7;
the field programmable gate array signal acquisition card 6 is used for receiving the modulation defect signal of the Mach-Zehnder modulator 4, taking the modulation defect signal as a training sequence symbol and sending the training sequence symbol to the I/Q correction and channel equalization 13;
and the polarization coupler 7 is used for coupling the received signal light and the local oscillator light separated by the beam splitter 2 into a quantum signal and transmitting the quantum signal to a quantum key receiving end through a quantum channel.
Quantum key receiving end, including:
the OFDM demodulator 8 is configured to perform an optical signal to electrical signal conversion operation on an optical signal transmitted by a quantum channel, further convert the signal into a digital signal through an analog-to-digital converter inside the OFDM demodulator 8, perform fast fourier transform, process the signal according to a compensation amount obtained by the decision feedback 14, and finally demodulate the signal and send the signal to the polarization beam splitter 9;
the polarization beam splitter 9 is configured to split the quantum signal sent by the OFDM demodulator 8 into 10% of signal light and 90% of local oscillation light;
the local oscillator laser 10 is configured to generate local oscillator light, interfere with the signal light sent by the polarization beam splitter 9, and send a path difference, which is realized by the path difference between the local oscillator light and the signal light, to the homodyne detector 11;
a homodyne detector 11, configured to perform homodyne detection on coherent light obtained by interference between local oscillation light generated by the local oscillation laser 10 and signal light received by the polarization beam splitter 9, obtain a measurement result of a randomly selected orthogonal component, and send the detection result to the field programmable gate array data acquisition card 12;
and the field programmable gate array data acquisition card 12 is used for sending the signals acquired by the homodyne detector 11 to the I/Q correction and channel equalization 13, and taking the signals as known feedback signals to calculate IQ imbalance parameters and channel transmission functions at the current moment for IQ correction and channel equalization of the next OFDM data symbol.
An I/Q correction compensation based post-processing module comprising:
an I/Q correction and channel equalization 13 for receiving training sequence symbols sent by a field programmable gate array signal acquisition card 6 and known feedback signals sent by a field programmable gate array data acquisition card 12 and estimating the degree of signal imbalance by using a least mean square algorithm, wherein the I/Q correction and channel equalization 13 utilizes the values of the known training sequence symbols on the programmable gate array signal acquisition card 6 and the values of the known feedback signals on the field programmable gate array data acquisition card 12 to obtain an initial estimation value H of an I/Q imbalance parameter G and a channel transmission function, then the I/Q correction and channel equalization 13 performs I/Q correction and channel equalization on OFDM data symbols according to the G and H obtained by the initial estimation, finally performs constellation point judgment on the obtained complex signals, and takes the latest value as a judgment value, and calculates the corresponding compensation amount and sends the compensation amount to the decision feedback 14;
and a decision feedback 14 for receiving the compensation amount information and delivering it to the OFDM demodulator 8.
The quantum channel is a transmission medium formed by a single-mode fiber or a free space, the single-mode fiber has stable attenuation coefficient which is about 0.2dB/km, the anti-interference capability is strong, and the cost is low; a classical channel is a transmission medium formed by classical wireless, wire line, or optical fiber.
The pulse laser 1 adopts a Thorlabs OPG1015 picosecond optical pulse generator, and can generate laser pulses with the frequency of 10GHz and less than or equal to 3 ps.
The Mach-Zehnder modulator 4 adopts a BP-ABC bias controller, can support a common single polarization intensity modulator or an IQ modulator, provides SPCI standard control instructions, and is suitable for analog modulation and digital modulation at the same time.
Polarization coupler 7 uses a Thorlabs PBC980PM-FC polarization beam coupler to couple two orthogonally polarized light beams into one fiber. High extinction ratio (>18dB), low loss (<2 dB).
The homodyne detector 11 adopts a Thorlabs PDA435A balanced amplification photoelectric detector, the common mode rejection ratio is more than 20dB, and the bandwidth can reach 350 MHz.
The field programmable gate array signal acquisition card 6 and the field programmable gate array data acquisition card 12 are both formed by combining Xilinx VC707 and FMC176, can flexibly change the clock frequency, can meet the requirement of high-speed real-time data stream transmission, and have the characteristics of good real-time performance, high speed, high precision and the like.
A realization method of a continuous variable quantum key distribution modulation compensation system applies the continuous variable quantum key distribution modulation compensation system, and specifically comprises the following steps:
firstly, pulse coherent light generated by a pulse laser 1 is separated into signal light and local oscillation light through a beam splitter 2; meanwhile, the radio frequency OFDM sending end 3 carries out quadrature amplitude modulation mapping on input serial data, then carries out serial-to-parallel conversion, and loads the serial data onto orthogonal subcarriers through Fourier transformation to form OFDM signals, the Mach-Zehnder modulator 4 receives multi-carrier signals from the radio frequency OFDM sending end 3 and quantum optical signals from the beam splitter 2, the radio frequency OFDM signals are modulated onto an optical domain with 1% quantum light intensity generated by the beam splitter 2 in the Mach-Zehnder modulator 4 to form a plurality of subcarrier-form optical signals, the I/Q imbalance defect is inevitably generated in the modulation process, and the received modulation defect signals are transmitted to the I/Q correction and channel equalization 13 by the field programmable gate array signal acquisition card 6 to compensate the modulation defect; the signal light sent by the Mach-Zehnder modulator 4 is attenuated to a proper light intensity level through the adjustable attenuator 5, then coupled with the local oscillation light sent by the beam splitter 2 in the polarization coupler 7, and sent to the quantum key receiving end through a quantum channel;
at a quantum signal receiving end, recovering the modulation state of a signal by a quantum signal through an OFDM demodulator 8, dividing the signal into signal light and local oscillator light through a polarization beam splitter 9, coupling the signal light and the local oscillator light emitted by a local oscillator laser 10, detecting the signal light and the local oscillator light through a homodyne detector 11, sending a detection result to a field programmable gate array data acquisition card 12, and transmitting the data serving as a feedback signal to an I/Q correction and channel equalization 13 through a classical channel to compare and detect with a training sequence symbol of the field programmable gate array signal acquisition card 6;
thirdly, the I/Q correction compensation module sends the signals acquired by the field programmable gate array signal acquisition card 12 to an I/Q correction and channel equalization module 13; the I/Q correction and channel equalization 13 processes the acquired modulation defect signal by using a least mean square algorithm, and then transmits the obtained compensated result to the decision feedback 14, and the decision feedback 14 transmits the received correction result to the OFDM demodulator 8 at the quantum signal receiving end through a classical channel, so as to compensate the defect occurring in the mach-zehnder modulator 4 in the key distribution modulation compensation system.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.
Claims (3)
1. A realization method of a continuous variable quantum key distribution modulation compensation system is characterized in that,
a system for distributed modulation compensation using a continuously variable quantum key, comprising:
the quantum key sending end is used for generating a key, modulating a quantum signal, sending the modulated signal to a quantum key receiving end through a quantum channel and sending a modulation defect signal generated in the modulation process to the I/Q correction compensation post-processing module;
the quantum key receiving end is used for receiving and detecting quantum signals and transmitting feedback information to the I/Q correction compensation post-processing module;
the I/Q correction compensation post-processing module is used for acquiring a modulation defect signal sent by the quantum key sending end and feedback information sent by the quantum key receiving end, detecting and correcting the I/Q imbalance degree by adopting a least mean square algorithm, and finally compensating the modulation defect;
the quantum key transmitting terminal comprises:
a pulsed laser (1) for generating pulsed coherent light;
the beam splitter (2) is used for splitting the pulse coherent light into signal light with a quantum level of 1% and local oscillation light with a quantum level of 99%;
the radio frequency OFDM transmitting end (3) is used for mapping input binary serial data through quadrature amplitude modulation, performing serial-parallel conversion, and loading the binary serial data to an orthogonal subcarrier through Fourier transform to form an OFDM signal;
the Mach-Zehnder modulator (4) is used for modulating a radio frequency OFDM signal sent by a radio frequency OFDM sending end (3) to an optical domain with 1% quantum light intensity generated by the beam splitter (2), the signal light is divided into two beams with identical amplitude and phase on a Y splitter of the Mach-Zehnder modulator (4), and the two beams are transmitted on an upper branch and a lower branch along with an optical waveguide, and the Mach-Zehnder modulator (4) inevitably has the defect of I/Q imbalance in the modulation process;
the adjustable attenuator (5) is used for attenuating the signal light sent by the Mach-Zehnder modulator (4) to a proper light intensity level, setting the light intensity level according to different processed signal lights and sending the attenuated signal light to the polarization coupler (7);
the field programmable gate array signal acquisition card (6) is used for receiving the modulation defect signal of the Mach-Zehnder modulator (4), taking the modulation defect signal as a training sequence symbol and sending the training sequence symbol to the I/Q correction and channel equalization (13);
the polarization coupler (7) is used for coupling the received signal light and the local oscillator light separated by the beam splitter (2) into a quantum signal and transmitting the quantum signal to a quantum key receiving end through a quantum channel;
the quantum key receiving end comprises:
the OFDM demodulator (8) is used for performing optical signal to electrical signal conversion operation on an optical signal transmitted by a quantum channel, further converting the signal into a digital signal through an analog-to-digital converter in the OFDM demodulator (8), performing fast Fourier transform, processing the signal according to a compensation quantity obtained by decision feedback (14), and finally demodulating the signal and sending the demodulated signal to the polarization beam splitter (9);
the polarization beam splitter (9) is used for splitting the quantum signals sent by the OFDM demodulator (8) into 10% of signal light and 90% of local oscillator light;
the local oscillator laser (10) is used for generating local oscillator light, interfering with the signal light sent by the polarization beam splitter (9), realizing difference through the path difference of the local oscillator light and the signal light, and sending the difference to the homodyne detector (11);
the homodyne detector (11) is used for carrying out homodyne detection on coherent light obtained by interference between local oscillation light generated by the local oscillation laser (10) and signal light received by the polarization beam splitter (9) to obtain a measurement result of randomly selected orthogonal components, and sending the detection result to the field programmable gate array data acquisition card (12);
the field programmable gate array data acquisition card (12) is used for sending the signals acquired by the homodyne detector (11) to the I/Q correction and channel equalization (13), taking the signals as known feedback signals, solving IQ imbalance parameters and channel transmission functions at the current moment, and using the IQ imbalance parameters and the channel transmission functions for IQ correction and channel equalization of the next OFDM data symbol;
the I/Q correction compensation post-processing module comprises:
the I/Q correction and channel equalization (13) is used for receiving training sequence symbols sent by a field programmable gate array signal acquisition card (6) and known feedback signals sent by a field programmable gate array data acquisition card (12), estimating the imbalance degree of a modulation signal by using a least mean square algorithm, finally carrying out constellation point judgment on the obtained complex signals, taking the latest value as a judgment value, calculating corresponding compensation and sending the corresponding compensation to a judgment feedback (14);
a decision feedback (14) for receiving the compensation amount information and passing it to the OFDM demodulator (8);
the method specifically comprises the following steps:
firstly, pulse coherent light generated by a pulse laser (1) is separated into signal light and local oscillation light through a beam splitter (2); meanwhile, an input serial data is subjected to quadrature amplitude modulation mapping by a radio frequency OFDM sending end (3), then serial-to-parallel conversion is carried out, Fourier transform is carried out on the serial data and loaded on orthogonal subcarriers to form OFDM signals, a Mach-Zehnder modulator (4) receives multi-carrier signals from the radio frequency OFDM sending end (3) and quantum optical signals from a beam splitter (2), the radio frequency OFDM signals are modulated on an optical domain with 1% quantum light intensity generated by the beam splitter (2) in the Mach-Zehnder modulator (4) to form a plurality of optical signals in a subcarrier mode, the I/Q imbalance defect is inevitably generated in the modulation process, and a received modulation defect signal is transmitted to an I/Q correction and channel equalization (13) by a field programmable gate array signal acquisition card (6) to compensate the modulation defect; the signal light sent by the Mach-Zehnder modulator (4) is attenuated to a proper light intensity level through the adjustable attenuator (5), then is coupled with the local oscillation light sent by the beam splitter (2) in the polarization coupler (7), and is sent to a quantum key receiving end through a quantum channel;
at a quantum signal receiving end, recovering the modulation state of a signal by a quantum signal through an OFDM demodulator (8), dividing the signal into signal light and local oscillator light through a polarization beam splitter (9), coupling the signal light and the local oscillator light emitted by a local oscillator laser (10), detecting the signal light and the local oscillator light through a homodyne detector (11), sending a detection result to a field programmable gate array data acquisition card (12), and transmitting the data serving as a feedback signal to an I/Q correction and channel equalization (13) through a classical channel to compare and detect a training sequence symbol of the field programmable gate array signal acquisition card (6);
thirdly, the I/Q correction compensation module sends the signals acquired by the field programmable gate array signal acquisition card (12) to I/Q correction and channel equalization (13); the I/Q correction and channel equalization (13) adopts a least mean square algorithm to process the acquired modulation defect signals, then transmits the obtained compensated result to a decision feedback (14), and the decision feedback (14) transmits the received correction result to an OFDM demodulator (8) at a quantum signal receiving end through a classical channel so as to compensate the defects of the Mach-Zehnder modulator (4) in the key distribution modulation compensation system.
2. The implementation method of the continuous variable quantum key distribution modulation compensation system according to claim 1, wherein the pulse laser (1) is a Thorlabs OPG1015 picosecond optical pulse generator, the mach-zehnder modulator (4) is a BP-ABC bias voltage controller, the field programmable gate array signal acquisition card (6) is formed by combining Xilinx VC707 and FMC176, and the polarization coupler (7) is a Thorlabs PBC980PM-FC polarization beam coupler.
3. The implementation method of the continuous variable quantum key distribution modulation compensation system according to claim 1, wherein the homodyne detector (11) is a Thorlabs PDA435A balanced amplification photodetector, and the field programmable gate array data acquisition card (12) is formed by combining Xilinx VC707 and FMC 176.
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| CN111541536B (en) * | 2020-04-21 | 2021-09-28 | 中山大学 | Continuous variable quantum key distribution system enhanced by phase sensitive amplification technology |
| CN111786732B (en) * | 2020-06-08 | 2021-06-04 | 中国电子科技集团公司第三十研究所 | High-speed local oscillator continuous variable quantum key distribution system and method |
| CN111970280B (en) * | 2020-08-18 | 2022-05-06 | 中南大学 | Attack detection method of continuous variable quantum key distribution system |
| CN112702162B (en) * | 2020-12-25 | 2021-12-17 | 中南大学 | One-dimensional continuous variable quantum key distribution system based on discrete state and implementation method thereof |
| CN114268433B (en) * | 2021-12-27 | 2024-04-16 | 中南大学 | Nonlinear compensation method of high-speed continuous variable quantum key distribution system |
| CN114897171B (en) * | 2022-03-29 | 2023-05-02 | 顾中建 | Superconducting quantum bit low-delay feedback control circuit and superconducting quantum feedback control method |
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