Quantum classical converged communication system based on Sagnac-Mach-Zehnder interference structure

Abstract

The utility model discloses a quantum classical converged communication system based on a Sagnac-Mach-Zehnder interference structure. The quantum classical converged communication system comprises a sender, a first DWDM module, a second DWDM module and a receiver which are connected in sequence, wherein the receiver comprises a quantum signal receiving module; the quantum signal receiving module is of a Sagnac-Mach-Zehnder interference structure and comprises a circulator, a first polarization beam splitter, a second polarization beam splitter, a first beam splitter, a second beam splitter, a first phase modulator, a first single-photon detector and a second single-photon detector. The utility model discloses a quantum classical converged communication system based on a Sagnac-Mach-Zehnder interference structure, and through a quantum signal receiving module of the Sagnac-Mach-Zehnder interference structure, a QKD (quantum key distribution) system has the characteristics of insensitivity to a polarization state and compatibility with high-speed modulation, so that the stability and robustness of the system are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to quantum information and optical communication technical field, concretely relates to a kind of quantum classical fusion communication system based on Sagnac-Mach-Zehnder interference structure. BACKGROUND

[0002] Quantum Key Distribution (QKD) is one of the main candidates for providing data security in the quantum era. Traditional encryption methods are mainly based on computational complexity, while QKD securely exchanges keys between remote parties through quantum mechanics principles.

[0003] In optical fiber communication, one of the main technologies that enables the transmission of multiple optical signals over the same optical fiber is Dense Wavelength Division Multiplexing (DWDM). However, one challenge for quantum and classical network fusion based on DWDM is that strong data signals can generate background noise. Since quantum signals are usually weak, even a small amount of background noise can have a significant impact on the operation of the QKD link. These noises mainly include four-wave mixing, Raman scattering, and crosstalk between adjacent channels, etc.

[0004] In the prior art, such as Chinese patent CN209170378U, a quantum classical fusion transmission noise processing system can eliminate backward Raman scattering and filter channel crosstalk. However, the double MZI structure used in this system is very sensitive to the polarization state change of the transmitted photons, which leads to an increase in the bit error rate, thereby reducing the stability and robustness of the system. UTILITY MODEL CONTENT

[0005] The utility model discloses to solve the problem that the existing quantum classical fusion transmission noise processing system adopts double MZI structure and is very sensitive to the polarization state change of the transmitted photons, reduces the stability and robustness of the system, and proposes a quantum classical fusion communication system based on Sagnac-Mach-Zehnder interference structure.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the utility model is as follows:

[0007] A quantum classical fusion communication system based on Sagnac-Mach-Zehnder interference structure, comprising a sender, a first DWDM module, a second DWDM module and a receiver connected in sequence; wherein the receiver comprises a quantum signal receiving module;

[0008] The quantum signal receiving module is a Sagnac-Mach-Zehnder interference structure, comprising a circulator, a first polarization beam splitter, a second polarization beam splitter, a first beam splitter, a second beam splitter, a first phase modulator, a first single-photon detector and a second single-photon detector.

[0009] The first port of the circulator is connected with the output end of the second DWDM module, the second port of the circulator is connected with the input end of the first single photon detector, the third port of the circulator is connected with the input end of the first polarization beam splitter, different output ends of the first polarization beam splitter are connected with the first port of the first beam splitter and the first port of the second beam splitter respectively, the second port of the first beam splitter is connected with the second port of the second beam splitter, the third port of the first beam splitter and the third port of the second beam splitter are connected with different ports of the first phase modulator respectively, the fourth port of the first beam splitter and the fourth port of the second beam splitter are connected with different input ends of the second polarization beam splitter respectively, and the output end of the second polarization beam splitter is connected with the input end of the second single photon detector.

[0010] In the above scheme, the quantum signal receiving module with the Sagnac-Mach-Zehnder interference structure is used to realize the characteristics of being insensitive to polarization state and compatible with high-speed modulation, thereby increasing the stability and robustness of the system.

[0011] Preferably, one of the output ends of the first polarization beam splitter is connected with the first port of the first beam splitter through a first polarization maintaining optical fiber, and the other output end of the first polarization beam splitter is connected with the first port of the second beam splitter through a second polarization maintaining optical fiber; the fourth port of the first beam splitter is connected with one of the input ends of the second polarization beam splitter through a third polarization maintaining optical fiber, and the fourth port of the second beam splitter is connected with the other input end of the second polarization beam splitter through a fourth polarization maintaining optical fiber.

[0012] Preferably, the length of the first polarization maintaining optical fiber is equal to the length of the second polarization maintaining optical fiber; and the length of the third polarization maintaining optical fiber is equal to the length of the fourth polarization maintaining optical fiber.

[0013] Preferably, the sender comprises a quantum signal generating module.

[0014] The quantum signal generating module is an AMZI structure, comprising a laser, an intensity modulator, a second phase modulator, a third beam splitter and a fourth beam splitter.

[0015] The output end of the laser is connected with the input end of the third beam splitter through the intensity modulator, one of the output ends of the third beam splitter is connected with one of the input ends of the fourth beam splitter, the other output end of the third beam splitter is connected with the other input end of the fourth beam splitter through the second phase modulator, and the output end of the fourth beam splitter is connected with the input end of the first DWDM module.

[0016] Preferably, the other output end of the third beam splitter is connected with the second phase modulator through a delay line.

[0017] Preferably, the quantum signal generating module has three, and the channel wavelengths of the three quantum signal generating modules are 1548.0nm, 1548.8nm and 1550.4nm respectively.

[0018] Preferably, the quantum signal receiving module has three.

[0019] Preferably, the quantum signal receiving module further comprises an optical isolator and a filter; the output end of the second DWDM module is connected with the input end of the optical isolator, and the output end of the optical isolator is connected with the first port of the circulator through the filter.

[0020] Preferably, the sender and the receiver are respectively provided with a classical signal transceiver; wherein the classical signal transceiver of the sender is connected with the first DWDM module through an attenuator, and the classical signal transceiver of the receiver is connected with the second DWDM module through another attenuator.

[0021] Preferably, the channel wavelength of the classical signal transceiver is 1556.0nm.

[0022] The utility model has beneficial technical effect:

[0023] The utility model provides a quantum classic fusion communication system based on Sagnac -Mach -Zehnder interference structure, realizes system to have the characteristics of being insensitive to polarization state and being compatible with high -speed modulation through quantum signal receiving module of Sagnac -Mach -Zehnder interference structure, to increase the stability and robustness of system. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is whole structural schematic diagram of the utility model;

[0025] Figure 2 It is structure schematic diagram of quantum signal receiving module in the utility model;

[0026] Figure 3 It is structure schematic diagram of quantum signal generating module in the utility model;

[0027] Wherein: 1, sender; 10, quantum signal generating module; 100, laser; 101, intensity modulator; 102, second phase modulator; 103, third beam splitter; 104, fourth beam splitter; 2, first DWDM module; 3, second DWDM module; 4, receiver; 40, quantum signal receiving module; 400, circulator; 401, first polarization beam splitter; 402, second polarization beam splitter; 403, first beam splitter; 404, second beam splitter; 405, first phase modulator; 406, first single-photon detector; 407, second single-photon detector; 408, optical isolator; 409, filter; 5, classical signal transceiver device; 6, attenuator. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the utility model more clearly, the following will be further described in detail with examples, but the scope of the utility model claimed is not limited to the following specific examples.

[0029] Example 1

[0030] As Figures 1-2 shown, a quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure, comprising sequentially connected sender 1, first DWDM module 2, second DWDM module 3 and receiver 4; wherein the receiver 4 includes quantum signal receiving module 40;

[0031] The quantum signal receiving module 40 is a Sagnac-Mach-Zehnder interference structure, comprising circulator 400, first polarization beam splitter 401, second polarization beam splitter 402, first beam splitter 403, second beam splitter 404, first phase modulator 405, first single-photon detector 406 and second single-photon detector 407;

[0032] The first port of the circulator 400 is connected with the output end of the second DWDM module 3, the second port of the circulator 400 is connected with the input end of the first single-photon detector 406, the third port of the circulator 400 is connected with the input end of the first polarization beam splitter 401, different output ends of the first polarization beam splitter 401 are connected with the first port of the first beam splitter 403 and the first port of the second beam splitter 404 respectively, the second port of the first beam splitter 403 is connected with the second port of the second beam splitter 404, the third port of the first beam splitter 403 and the third port of the second beam splitter 404 are connected with different ports of the first phase modulator 405 respectively, the fourth port of the first beam splitter 403 and the fourth port of the second beam splitter 404 are connected with different input ends of the second polarization beam splitter 402 respectively, and the output end of the second polarization beam splitter 402 is connected with the input end of the second single-photon detector 407.

[0033] In the implementation process, the quantum signal receiving module 40 of the Sagnac-Mach-Zehnder interference structure is used to realize the characteristics of being insensitive to polarization states and compatible with high-speed modulation, thereby increasing the stability and robustness of the system.

[0034] Embodiment 2

[0035] A quantum-classical fusion communication system based on a Sagnac-Mach-Zehnder interference structure, comprising a sender 1, a first DWDM module 2, a second DWDM module 3 and a receiver 4 connected in sequence; wherein the receiver 4 comprises a quantum signal receiving module 40;

[0036] The quantum signal receiving module 40 is a Sagnac-Mach-Zehnder interference structure, comprising a circulator 400, a first polarization beam splitter 401, a second polarization beam splitter 402, a first beam splitter 403, a second beam splitter 404, a first phase modulator 405, a first single-photon detector 406 and a second single-photon detector 407.

[0037] The first port of the circulator 400 is connected with the output end of the second DWDM module 3, the second port of the circulator 400 is connected with the input end of the first single-photon detector 406, the third port of the circulator 400 is connected with the input end of the first polarization beam splitter 401, the different output ends of the first polarization beam splitter 401 are respectively connected with the first port of the first beam splitter 403 and the first port of the second beam splitter 404, the second port of the first beam splitter 403 is connected with the second port of the second beam splitter 404, the third port of the first beam splitter 403 and the third port of the second beam splitter 404 are respectively connected with different ports of the first phase modulator 405, the fourth port of the first beam splitter 403 and the fourth port of the second beam splitter 404 are respectively connected with different input ends of the second polarization beam splitter 402, and the output end of the second polarization beam splitter 402 is connected with the input end of the second single-photon detector 407.

[0038] In the implementation process, the photon polarization direction of the third port of the first polarization beam splitter 401 forms a 90° angle with the slow axis of the polarization maintaining optical fiber, and the Jones matrix of the rotation operation is

[0039]

[0040] It should be noted that the rotation operation is the same for the Jones matrix of forward and reverse propagation.

[0041] Since the Jones matrix of the PM fiber can be regarded as a unit matrix, the following analysis omits the influence of the PM fiber in the Sagnac-Mach-Zehnder interferometer structure and also omits the loss of all optical devices.

[0042] The Jones matrix expressions of the PBS (Polarization Beam Splitter) and BS (Beam Splitter) are

[0043]

[0044] wherein, is the Jones matrix of the nth BS (PBS), and the subscript indicates that the photon enters from the jth port and exits from the kth port.

[0045] When the two light pulses emitted from the sender 1 (Alice) reach the receiver 4 (Bob) through the channel, due to the optical fiber birefringence effect and various disturbances of the real environment, the polarization state changes unpredictably, and thus the Jones vector is written in the normalized form

[0046]

[0047] Here θ is the horizontal polarization angle, and β represents the phase delay between the horizontal polarization light and the vertical polarization light. For the output port of the first polarization beam splitter 401, the transmission matrices of the two interference light pulses through the long and short paths are respectively:

[0048]

[0049] wherein, T L (T S ) is the propagation matrix of the light pulse along the long arm (short arm) path of the AMZI (Asymmetric Mach-Zehnder Interferometer), is the modulation phase of the second phase modulator 102φ B .

[0050] Considering that the phase difference between the two light pulses caused by the modulation of the second phase modulator 102φ A is Then the final output Jones vector of the first polarization beam splitter 401 can be written as

[0051]

[0052] Thus the light intensity expression output by the first polarization beam splitter 401 is

[0053]

[0054] Similarly, the final output Jones vector of the second polarization beam splitter 402 can be written as

[0055]

[0056] The light intensity expression output by the second polarization beam splitter 402 is

[0057]

[0058] As can be seen from the light intensity expressions output by the first polarization beam splitter 401 and the second polarization beam splitter 402, the light intensity expression of the final output is irrelevant to the input polarization state. Therefore, the Sagnac-Mach-Zehnder interference structure has the characteristic of polarization insensitivity.

[0059] In the specific implementation process, the first DWDM module 2 and the second DWDM module 3 both adopt a multiplexer / demultiplexer with 25 channels, 100 GHz and a channel spacing of 0.8 nm.

[0060] More specifically, one output end of the first polarization beam splitter 401 is connected with the first port of the first beam splitter 403 through a first polarization maintaining optical fiber, and the other output end of the first polarization beam splitter 401 is connected with the first port of the second beam splitter 404 through a second polarization maintaining optical fiber; the fourth port of the first beam splitter 403 is connected with one input end of the second polarization beam splitter 402 through a third polarization maintaining optical fiber, and the fourth port of the second beam splitter 404 is connected with the other input end of the second polarization beam splitter 402 through a fourth polarization maintaining optical fiber.

[0061] More specifically, the length of the first polarization maintaining optical fiber is equal to the length of the second polarization maintaining optical fiber; the length of the third polarization maintaining optical fiber is equal to the length of the fourth polarization maintaining optical fiber.

[0062] More specifically, the sender 1 includes a quantum signal generation module 10, as shown in Figure 3

[0063] The quantum signal generation module 10 is an AMZI structure, which includes a laser 100, an intensity modulator 101, a second phase modulator 102, a third beam splitter 103 and a fourth beam splitter 104.

[0064] The output end of the laser 100 is connected with the input end of the third beam splitter 103 through the intensity modulator 101, one output end of the third beam splitter 103 is connected with one input end of the fourth beam splitter 104, the other output end of the third beam splitter 103 is connected with the other input end of the fourth beam splitter 104 through the second phase modulator 102, and the output end of the fourth beam splitter 104 is connected with the input end of the first DWDM module 2.

[0065] ​In the implementation process, the laser 100, the intensity modulator 101, the second phase modulator 102, the third beam splitter 103 and the fourth beam splitter 104 are connected through polarization maintaining optical fiber, and the fourth beam splitter 104 is connected with the first DWDM module 2 through single-mode optical fiber.

[0066] More specifically, the other output end of the third beam splitter 103 is connected with the second phase modulator 102 through a delay line.

[0067] More specifically, the quantum signal generation module 10 has three (Alice1, Alice2, Alice3 respectively), and the channel wavelengths of the three quantum signal generation modules 10 are 1548.0nm, 1548.8nm and 1550.4nm respectively.

[0068] More specifically, the quantum signal receiving module 40 has three (Bob1, Bob2, Bob3 respectively).

[0069] More specifically, the quantum signal receiving module 40 further comprises an optical isolator 408 and a filter 409; the output end of the second DWDM module 3 is connected with the input end of the optical isolator 408, and the output end of the optical isolator 408 is connected with the first port of the circulator 400 through the filter 409.

[0070] More specifically, the sender 1 and the receiver 4 are respectively provided with a classical signal transceiver 5; wherein the classical signal transceiver 5 of the sender 1 is connected with the first DWDM module 2 through an attenuator 6, and the classical signal transceiver 5 of the receiver 4 is connected with the second DWDM module 3 through another attenuator 6.

[0071] In the implementation process, the signal sent by the classical signal transceiver 5 is reduced in transmission power by the attenuator 6, and then sent to the second (first) DWDM module through the first (second) DWDM module connected therewith, and received by the corresponding classical signal transceiver 5.

[0072] More specifically, the channel wavelength of the classical signal transceiver 5 is 1556.0nm.

[0073] In the implementation process, the classical signal sent by the classical signal transceiver 5 includes a data signal and a synchronization signal.

[0074] In the specific implementation process, Alice 1 sends a weak laser pulse, and the average photon number is usually 0.1. The key bits of Alice 1 are encoded by the phase parameter ΦA of the AMZI, the base selection is (0, π) or (π / 2, 3π / 2), and two continuous output pulses with a phase difference of ΦA are output. The channel wavelength of Alice 1 is 1548.0 nm, the channel wavelength of Alice 2 is 1548.8 nm, the channel wavelength of Alice 3 is 1550.4 nm, and the channel wavelength of the classical signal transceiver 5 is 1556.0 nm. The quantum signal, the synchronization signal and the data signal are multiplexed in the optical fiber through the DWDM module, and the four-wave mixing and the crosstalk of adjacent channels caused by the nonlinear effect of the optical fiber. In the embodiment, a non-equidistant channel wavelength division method is adopted, wherein the wavelength interval between Alice 1 and Alice 2 is one standard wavelength interval of ITU, the wavelength interval between Alice 1 and Alice 3 is two standard wavelength intervals, and the wavelength interval between Alice 1 and the classical signal is ten standard wavelength intervals. This method can eliminate four-wave mixing and reduce crosstalk of adjacent channels. The intensity modulator 101 is used in the phase encoding-based decoy state protocol, and the decoy state with different intensities is modulated and sent to the receiver 4 (Bob), so that the attacker cannot distinguish the signal state and the decoy state, thereby avoiding multi-photon number attacks. The receiver 4 (Bob) allows the signal to be detected only in the pulse arrival time according to the synchronization signal, avoids noise entering the detector in the non-detection period, and reduces Raman noise.

[0075] According to the disclosure and teaching of the above description, those skilled in the art of the present application can also change and modify the above embodiments. Therefore, the present application is not limited to the specific embodiments disclosed and described above, and some modifications and changes of the present application should fall within the protection scope of the claims of the present application. In addition, although some specific terms are used in the specification, these terms are only for convenience and do not constitute any limitation on the present application.

Claims

1. A quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure, characterized in that, The sender, the first DWDM module, the second DWDM module and the receiver are sequentially connected; wherein the receiver comprises a quantum signal receiving module; The quantum signal receiving module is a Sagnac-Mach-Zehnder interference structure, comprising a circulator, a first polarization beam splitter, a second polarization beam splitter, a first beam splitter, a second beam splitter, a first phase modulator, a first single-photon detector and a second single-photon detector; The first port of the circulator is connected with the output end of the second DWDM module, the second port of the circulator is connected with the input end of the first single-photon detector, the third port of the circulator is connected with the input end of the first polarization beam splitter, different output ends of the first polarization beam splitter are connected with the first port of the first beam splitter and the first port of the second beam splitter respectively, the second port of the first beam splitter is connected with the second port of the second beam splitter, the third port of the first beam splitter and the third port of the second beam splitter are connected with different ports of the first phase modulator respectively, the fourth port of the first beam splitter and the fourth port of the second beam splitter are connected with different input ends of the second polarization beam splitter respectively, and the output end of the second polarization beam splitter is connected with the input end of the second single-photon detector.

2. The quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure according to claim 1, characterized in that, One of the output ends of the first polarization beam splitter is connected with the first port of the first beam splitter through a first polarization maintaining optical fiber, the other output end of the first polarization beam splitter is connected with the first port of the second beam splitter through a second polarization maintaining optical fiber, the fourth port of the first beam splitter is connected with one of the input ends of the second polarization beam splitter through a third polarization maintaining optical fiber, and the fourth port of the second beam splitter is connected with the other input end of the second polarization beam splitter through a fourth polarization maintaining optical fiber.

3. The quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure according to claim 2, characterized in that, The length of the first polarization maintaining optical fiber is equal to the length of the second polarization maintaining optical fiber, and the length of the third polarization maintaining optical fiber is equal to the length of the fourth polarization maintaining optical fiber.

4. The quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure according to claim 1, characterized in that, The sender comprises a quantum signal generating module. The quantum signal generating module is an AMZI structure, comprising a laser, an intensity modulator, a second phase modulator, a third beam splitter and a fourth beam splitter. The output end of the laser is connected with the input end of the third beam splitter through the intensity modulator, one of the output ends of the third beam splitter is connected with one of the input ends of the fourth beam splitter, the other output end of the third beam splitter is connected with the other input end of the fourth beam splitter through the second phase modulator, and the output end of the fourth beam splitter is connected with the input end of the first DWDM module.

5. The quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure according to claim 4, characterized in that, The other output end of the third beam splitter is connected with the second phase modulator through a delay line.

6. The quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure according to claim 4, characterized in that, There are three quantum signal generating modules, and the channel wavelengths of the three quantum signal generating modules are 1548.0 nm, 1548.8 nm and 1550.4 nm respectively.

7. The quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure according to claim 1, characterized in that, There are three quantum signal receiving modules.

8. The quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure according to claim 1 or 7, characterized in that, The quantum signal receiving module further comprises an optical isolator and a filter, the output end of the second DWDM module is connected with the input end of the optical isolator, the output end of the optical isolator is connected with the first port of the circulator through the filter.

9. The quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure according to claim 1, characterized in that, The sender and the receiver are respectively provided with a classical signal transceiving device; wherein the classical signal transceiving device of the sender is connected with the first DWDM module through an attenuator, and the classical signal transceiving device of the receiver is connected with the second DWDM module through another attenuator.

10. The quantum-classical fusion communication system based on Sagnac-Mach-Zehnder interference structure according to claim 9, characterized in that, The channel wavelength of the classical signal transceiving device is 1556.0 nm.

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