Quantum classical common fiber transmission signal receiving device

Abstract

The invention relates to a quantum classical common-fiber transmission signal receiving device, and the device comprises a filtering module which is used for filtering signal light, and separating quantum signal light and classical signal light; the quantum state analysis module is connected with the filtering module, and the quantum state analysis module is used for receiving the quantum signal light and performing projection measurement on the quantum state subjected to time phase encoding; and the coherent detection module is connected with the filtering module, and the coherent detection module is used for receiving the classical signal light and the local oscillation light and carrying out coherent detection on the IQ modulated classical signal. According to the invention, the filtering module is arranged to realize efficient separation of the classical signal and the quantum signal, and the coherent detection module and the quantum state analysis module can detect and analyze the classical signal and the quantum signal at the same time, so that the problem of noise crosstalk in a quantum classical co-transmission scene is solved; and moreover, the quantum signal does not need to be migrated to an O wave band, a novel optical fiber does not need to be deployed, relatively high optical fiber link loss is not introduced, and the cost can be reduced.

Description

Technical Field

[0001] This application relates to the field of quantum communication technology, specifically to a quantum classical co-fiber transmission signal receiving device. Background Technology

[0002] Quantum key distribution technology can guarantee unconditional secure transmission of information between legitimate communicating parties, and it has now moved from the laboratory stage to the field deployment stage. However, the co-transmission of quantum signals and classical signals in existing fiber optic networks has become a major obstacle to the further large-scale deployment of this technology. This is because classical signals generate nonlinear noise when transmitted in optical fibers, which interferes with quantum signals.

[0003] In related technologies, the industry has proposed a variety of solutions, including migrating quantum signals to the O-band while keeping classical signals in the C-band to reduce the impact of nonlinear noise on quantum signals; and using new types of optical fibers such as multi-core optical fibers, hollow-core optical fibers, and few-mode optical fibers to increase the isolation from nonlinear noise or generate less noise.

[0004] However, the above technical solutions still have some drawbacks. For example, migrating quantum signals to the O-band will introduce higher optical fiber link loss, resulting in a low security key rate. Deploying new optical fibers into existing optical fiber networks is costly, time-consuming, and difficult to implement.

[0005] Therefore, it is necessary to design a quantum classical co-fiber transmission signal receiving device to overcome the above problems. Summary of the Invention

[0006] This application provides a quantum classical co-fiber transmission signal receiving device, which can solve the technical problems of fiber optic link loss and high cost in related technologies.

[0007] In a first aspect, embodiments of this application provide a quantum-classical co-fiber transmission signal receiving device, comprising: a filtering module for filtering signal light to separate quantum signal light and classical signal light; a quantum state analysis module connected to the filtering module, wherein the quantum state analysis module is used to receive quantum signal light and perform projection measurement on time-phase encoded quantum states; and a coherent detection module connected to the filtering module, wherein the coherent detection module is used to receive classical signal light and local oscillator light and perform coherent detection on IQ modulated classical signals.

[0008] In conjunction with the first aspect, in one embodiment, the filtering module includes a cascaded microring. The download end of the cascaded microring is connected to the quantum state analysis module, and the transmission end of the cascaded microring is connected to the coherent detection module. In this embodiment, the cascaded microring is connected to a spot size converter. The signal light is coupled into the cascaded microring through the spot size converter. The cascaded microring is used for filtering, which can separate the quantum signal light and the classical signal light.

[0009] In conjunction with the first aspect, in one embodiment, the cascaded microrings include a plurality of microrings arranged sequentially and a first waveguide disposed on opposite sides of each microring. The first waveguide located at the download end is connected to the quantum state analysis module, and the first waveguide located at the transmission end is connected to the coherent detection module. In this embodiment, the cascaded microrings can achieve resonance of a specific wavelength of light field within the microrings, which is then output from the download end of the microrings. Light fields of other wavelengths, not satisfying the resonance condition, are output from the transmission end of the microrings via the first waveguides, thereby achieving filtering characteristics. The filtering bandwidth and center wavelength can be adjusted by designing the diameter of the microrings and the spacing between the microrings and the first waveguides. This cascaded microring structure can be further repeated to improve the isolation of the filter.

[0010] In conjunction with the first aspect, in one embodiment, a heating electrode is disposed on the cascaded microrings. In this embodiment, the heating electrode can be used to dynamically adjust the resonant wavelength of the microrings.

[0011] In conjunction with the first aspect, in one embodiment, the quantum state analysis module includes a Mach-Zehnder interferometer connected to the filtering module, and the two outputs of the Mach-Zehnder interferometer are respectively connected to a second waveguide and a third waveguide, the second waveguide and the third waveguide being connected to a first multimode interferometer; wherein the length of the second waveguide is greater than the length of the third waveguide.

[0012] In conjunction with the first aspect, in one embodiment, both the second waveguide and the third waveguide include thermal phase shifters, and the second waveguide includes a delay line waveguide.

[0013] In conjunction with the first aspect, in one embodiment, the Mach-Zehnder interferometer includes a second multimode interferometer and a third multimode interferometer. The second multimode interferometer is connected to the filtering module, and the second multimode interferometer is connected to the third multimode interferometer via a fourth waveguide, wherein the fourth waveguide contains a thermal phase shifter. In this embodiment, the Mach-Zehnder interferometer in the quantum state analysis module is used to equalize the optical power of the subsequent long-arm and short-arm waveguides, because the optical delay line in the long-arm waveguide introduces additional losses. By controlling the thermal phase shifter on one arm of the Mach-Zehnder interferometer, the phase difference between the two arms of the interferometer can be changed, thereby changing the ratio of the light intensity at the two output ports of the interferometer due to interference, ultimately achieving optical power equalization.

[0014] In conjunction with the first aspect, in one embodiment, the coherent detection module includes a fourth multimode interferometer, an optical cross-waveguide, a first balanced detector, a second balanced detector, and a fifth multimode interferometer. The fourth multimode interferometer is connected to the filtering module and the optical cross-waveguide. The first balanced detector is connected to the optical cross-waveguide and the fourth multimode interferometer. The second balanced detector is connected to the optical cross-waveguide and the fifth multimode interferometer.

[0015] In conjunction with the first aspect, in one embodiment, the first balanced detector includes a sixth multimode interferometer, which is connected to the fourth multimode interferometer and the optical cross waveguide via a fifth waveguide, and the sixth multimode interferometer is also connected to two photodetectors.

[0016] In conjunction with the first aspect, in one embodiment, the fifth waveguide includes a thermal phase shifter. In this embodiment, the first balanced detector and the second balanced detector in the coherent detection module are denoted as the I-path and Q-path, respectively, and are used to coherently detect the I-component signal and the Q-component signal in the classical signal. Thermal-optical phase shifters are respectively provided at the two input ports of the balanced detectors of the I-path and Q-path to control the phase of the signal light and the local oscillator light.

[0017] The beneficial effects of the technical solutions provided in this application include: By setting up a filtering module, the classical and quantum signals can be efficiently separated. Furthermore, the coherent detection module and the quantum state analysis module can simultaneously detect and analyze both classical and quantum signals, thus solving the noise crosstalk problem in the quantum-classical co-transmission scenario. Moreover, it does not require the quantum signal to be migrated to the O-band, nor does it require the deployment of new optical fibers. It does not introduce high optical fiber link loss and can also reduce costs, thus solving the technical problems of introducing optical fiber link loss and high cost in related technologies. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the architecture of a quantum classical co-fiber transmission signal receiving device provided in this application embodiment; Figure 2 This is a schematic diagram of the architecture of another quantum classical co-fiber transmission signal receiving device provided in an embodiment of this application.

[0020] In the picture: 1. Filtering module; 11. Cascaded micro-ring; 111. Micro-ring; 112. First waveguide; 2. Quantum state analysis module; 21. Mach-Zehnder interferometer; 211. Second multimode interferometer; 212. Third multimode interferometer; 22. Second waveguide; 23. Third waveguide; 24. Delay line waveguide; 25. First multimode interferometer; 3. Coherent detection module; 31. Fourth multimode interferometer; 32. Optical cross-waveguide; 33. First balanced detector; 34. Second balanced detector; 35. Fifth multimode interferometer; 36. Sixth multimode interferometer; 37. Photodetector; 4. Thermal phase shifter; 5. Spot size converter. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0022] This application provides a quantum classical co-fiber transmission signal receiving device, which can solve the technical problems of fiber optic link loss and high cost in related technologies.

[0023] See Figure 1As shown in the figure, a quantum classical co-fiber transmission signal receiving device provided in this application embodiment may include: a filtering module 1, which is used to filter the signal light and separate the quantum signal light and the classical signal light; a quantum state analysis module 2, which is connected to the filtering module 1, and the quantum state analysis module 2 is used to receive the quantum signal light and perform projection measurement on the time phase encoded quantum state; and a coherent detection module 3, which is connected to the filtering module 1, and the coherent detection module 3 is used to receive the classical signal light and the local oscillator light, and perform coherent detection on the IQ modulated classical signal.

[0024] See Figure 1 As shown, the quantum-classical co-fiber transmission signal receiving device provided in this embodiment mainly includes three modules: a filtering module 1, a quantum state analysis module 2, and a coherent detection module 3. The filtering module 1 filters the signal light, separating the quantum signal light and the classical signal light, which then enter the quantum state analysis module 2 and the coherent detection module 3, respectively. The quantum state analysis module 2 performs projection measurements on the time-phase encoded quantum state. The coherent detection module 3 measures the IQ-modulated classical signal. The local oscillator light is simultaneously input into the coherent detection module 3 to achieve coherent detection.

[0025] This embodiment achieves efficient separation of classical and quantum signals by setting up a filtering module 1. Furthermore, the coherent detection module 3 and the quantum state analysis module 2 can simultaneously detect and analyze classical and quantum signals, solving the noise crosstalk problem in the quantum-classical co-transmission scenario. Moreover, it does not require the quantum signal to be migrated to the O-band, nor does it require the deployment of new optical fibers. It does not introduce high optical fiber link loss and can also reduce costs, thus solving the technical problems of introducing optical fiber link loss and high cost in related technologies.

[0026] Related technologies also employ optical filters to filter nonlinear noise, reducing its entry into the quantum channel. However, optical filters suffer from insufficient bandwidth, inadequate isolation, and an inability to adjust the center wavelength. Compared to traditional optical filtering schemes, the quantum classical co-fiber transmission signal receiving device provided in this embodiment offers advantages such as narrow filtering bandwidth, adjustable center wavelength, and high integration.

[0027] Further, in one embodiment, the filtering module 1 includes a cascaded microring 11, the download end of which is connected to the quantum state analysis module 2, and the transmission end of which is connected to the coherent detection module 3. See also Figure 2 As shown, the cascaded microring 11 is connected to the spot size converter 5. The signal light is coupled into the cascaded microring 11 through the spot size converter 5. The cascaded microring 11 is used for filtering, which can separate the quantum signal light and the classical signal light.

[0028] Further, in some optional embodiments, the cascaded microrings 11 include a plurality of microrings 111 arranged in sequence and a first waveguide 112 disposed on opposite sides of each microring 111. The first waveguide 112 located at the download end is connected to the quantum state analysis module 2, and the first waveguide 112 located at the transmission end is connected to the coherent detection module 3. See also Figure 2 As shown, the cascaded microring 11 in this embodiment comprises two microrings 111, each with a first waveguide 112 on both sides. One of the first waveguides 112 is connected to a spot size converter 5. The signal light is coupled into the first waveguide 112 through the spot size converter 5, and then enters the cascaded microring 11, separating the quantum signal light and the classical signal light. The quantum light signal is output from the download end of the cascaded microring 11 and enters the quantum state analysis module 2, while the classical signal light is output from the transmission end of the cascaded microring 11 and enters the coherent detection module 3.

[0029] In the above embodiments, the cascaded microrings 11 can achieve resonance of a specific wavelength of light field within the microrings 111, which is then output from the receiving end of the microrings 111. Light fields of other wavelengths, not satisfying the resonance condition, are output from the transmitting end of the microrings 111 via the first waveguide 112, thus achieving filtering characteristics. The filtering bandwidth and center wavelength can be adjusted by designing the diameter of the microrings 111 and the spacing between the microrings 111 and the first waveguide 112. This cascaded microring structure 11 can be further repeated to improve the isolation of the filter.

[0030] Preferably, a heating electrode is provided on the cascaded microring 11. In this embodiment, the heating electrode can be used to dynamically adjust the resonant wavelength of the microring 111.

[0031] Further, in one embodiment, the quantum state analysis module 2 includes a Mach-Zehnder interferometer 21, which is connected to the filtering module 1. The two outputs of the Mach-Zehnder interferometer 21 are respectively connected to a second waveguide 22 and a third waveguide 23. The second waveguide 22 and the third waveguide 23 are connected to a first multimode interferometer 25; wherein the length of the second waveguide 22 is greater than the length of the third waveguide 23. See also... Figure 2 As shown, the second waveguide 22 is a micro long-arm waveguide, the third waveguide 23 is a short-arm waveguide, and the first multimode interferometer 25 is a 2×2 multimode interferometer. The output of this 2×2 multimode interferometer is also connected to two spot size converters 5. After the quantum signal light is transmitted through the long-arm and short-arm waveguides, it is then interfered with by a 2×2 multimode interferometer. The interfered quantum signal is output from the two spot size converters 5, completing the time-phase quantum state analysis.

[0032] Furthermore, preferably, both the second waveguide 22 and the third waveguide 23 include a thermal phase shifter 4, and the second waveguide 22 includes a delay line waveguide 24.

[0033] See Figure 2 As shown, in one embodiment, the Mach-Zehnder interferometer 21 includes a second multimode interferometer 211 and a third multimode interferometer 212. The second multimode interferometer 211 is connected to the filter module 1, and the second multimode interferometer 211 is connected to the third multimode interferometer 212 through a fourth waveguide, and the fourth waveguide contains a thermal phase shifter 4. In this embodiment, the second multimode interferometer 211 is a 1×2 multimode interferometer, and the third multimode interferometer 212 is a 2×2 multimode interferometer. The quantum signal light is output from the download end of the cascaded microring 11 and enters the 1×2 multimode interferometer, then enters the 2×2 multimode interferometer through the fourth waveguide. The two outputs of the 2×2 multimode interferometer are respectively connected to the long-arm waveguide and the short-arm waveguide.

[0034] In the above embodiment, the Mach-Zehnder interferometer 21 in the quantum state analysis module 2 is used to equalize the optical power of the subsequent long-arm waveguide and short-arm waveguide, because the optical delay line in the long-arm waveguide introduces additional losses. By controlling the thermal phase shifter 4 on one arm of the Mach-Zehnder interferometer 21, the phase difference between the two arms of the interferometer can be changed, thereby changing the ratio of the light intensity at the two output ports of the interferometer due to interference, ultimately achieving optical power equalization. For time-phase encoded quantum states, they exhibit two pulse distributions in time, denoted as... and The quantum state, after being transmitted through the long-arm and short-arm waveguides in quantum state analysis module 2 and then re-beamed, exhibits a time-varying distribution of three pulses, denoted as... and The middle pulse Interference will occur, at which point the output time-phase encoded quantum state will be analyzed.

[0035] Further, in one embodiment, the coherent detection module 3 includes a fourth multimode interferometer 31, an optical cross-waveguide 32, a first balanced detector 33, a second balanced detector 34, and a fifth multimode interferometer 35. The fourth multimode interferometer 31 connects the filtering module 1 to the optical cross-waveguide 32, the first balanced detector 33 connects the optical cross-waveguide 32 to the fourth multimode interferometer 31, and the second balanced detector 34 connects the optical cross-waveguide 32 to the fifth multimode interferometer 35. See also Figure 2As shown, in this embodiment, both the fourth multimode interferometer 31 and the fifth multimode interferometer 35 are 1×2 multimode interferometers. The classical signal light is output from the transmission end of the cascaded microring 11 and enters the 1×2 multimode interferometer (fourth multimode interferometer 31), where it is split into two paths. These paths then pass through the optical cross-waveguide 32 and enter the first balanced detector 33 and the second balanced detector 34, respectively. The local oscillator light is input from another spot size converter 5, split into two paths by the 1×2 multimode interferometer (fifth multimode interferometer 35), and then enters the first balanced detector 33 and the second balanced detector 34 via the optical cross-waveguide 32. By measuring the differential current detected in the first balanced detector 33 and the second balanced detector 34, the detection of the classical signal can be completed.

[0036] Further, in one embodiment, the first balanced detector 33 includes a sixth multimode interferometer 36, which is connected to the fourth multimode interferometer 31 and the optical cross-waveguide 32 via a fifth waveguide. The sixth multimode interferometer 36 is also connected to two photodetectors 37. See also... Figure 2 As shown, in this embodiment, the first balanced detector 33 and the second balanced detector 34 have the same structure, both including the aforementioned sixth multimode interferometer 36, fifth waveguide, and two photodetectors 37.

[0037] See Figure 2 As shown, in this embodiment, the fifth waveguide includes a thermal phase shifter 4. The first balanced detector 33 and the second balanced detector 34 in the coherent detection module 3 are denoted as the I-path and Q-path, respectively, and are used for coherent detection of the I-component and Q-component signals in the classical signal. Thermal-optical phase shifters are respectively installed at the two input ports of the balanced detectors of the I-path and Q-path to control the phase of the signal light and the local oscillator light. When performing coherent detection on the IQ modulated classical signal, the phase difference between the local oscillator lights of the I-path and Q-path needs to be adjusted to 90°, which can be achieved by controlling the thermal-optical phase shifters on the waveguide where the local oscillator light is located. By applying bias voltages of +V and -V to the two electrodes of these two sets of balanced detectors, differential photocurrents Signal_I and Signal_Q can be output on the intermediate electrode, thus obtaining the I-component and Q-component signals in the classical signal.

[0038] This application provides a quantum classical co-fiber transmission signal receiving device, which achieves efficient separation of classical and quantum signals based on an integrated optical platform, and can simultaneously detect and analyze classical and quantum signals. It solves the noise crosstalk problem in quantum classical co-transmission scenarios, and has the advantages of narrow filtering bandwidth, adjustable center wavelength, and high integration compared with traditional optical filtering schemes.

[0039] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0040] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0041] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A quantum classical co-fiber transmission signal receiving device, characterized in that, It includes: The filtering module (1) is used to filter the signal light and separate the quantum signal light and the classical signal light; A quantum state analysis module (2) is connected to the filtering module (1), and the quantum state analysis module (2) is used to receive quantum signal light and perform projection measurement on the time phase encoded quantum state; The coherent detection module (3) is connected to the filtering module (1). The coherent detection module (3) is used to receive classical signal light and local oscillator light, and to perform coherent detection on the classical signal modulated by IQ.

2. The quantum classical co-fiber transmission signal receiving device as described in claim 1, characterized in that, The filtering module (1) includes a cascaded microring (11), the download end of the cascaded microring (11) is connected to the quantum state analysis module (2), and the transmission end of the cascaded microring (11) is connected to the coherent detection module (3).

3. The quantum classical co-fiber transmission signal receiving device as described in claim 2, characterized in that, The cascaded microrings (11) include a plurality of microrings (111) arranged in sequence and a first waveguide (112) disposed on opposite sides of each microring (111). The first waveguide (112) located at the download end is connected to the quantum state analysis module (2), and the first waveguide (112) located at the transmission end is connected to the coherent detection module (3).

4. The quantum classical co-fiber transmission signal receiving device as described in claim 2, characterized in that, Heating electrodes are provided on the cascaded microrings (11).

5. The quantum classical co-fiber transmission signal receiving device as described in claim 1, characterized in that, The quantum state analysis module (2) includes a Mach-Zehnder interferometer (21), which is connected to the filter module (1). The two outputs of the Mach-Zehnder interferometer (21) are connected to the second waveguide (22) and the third waveguide (23), respectively. The second waveguide (22) and the third waveguide (23) are connected to the first multimode interferometer (25). The length of the second waveguide (22) is greater than the length of the third waveguide (23).

6. The quantum classical co-fiber transmission signal receiving device as described in claim 5, characterized in that, Both the second waveguide (22) and the third waveguide (23) contain thermal phase shifters (4), and the second waveguide (22) contains a delay line waveguide (24).

7. The quantum classical co-fiber transmission signal receiving device as described in claim 5, characterized in that, The Mach-Zehnder interferometer (21) includes a second multimode interferometer (211) and a third multimode interferometer (212). The second multimode interferometer (211) is connected to the filter module (1). The second multimode interferometer (211) is connected to the third multimode interferometer (212) through a fourth waveguide. The fourth waveguide contains a thermal phase shifter (4).

8. The quantum classical co-fiber transmission signal receiving device as described in claim 1, characterized in that, The coherent detection module (3) includes a fourth multimode interferometer (31), an optical cross-waveguide (32), a first balanced detector (33), a second balanced detector (34), and a fifth multimode interferometer (35). The fourth multimode interferometer (31) connects the filtering module (1) to the optical cross-waveguide (32). The first balanced detector (33) connects the optical cross-waveguide (32) to the fourth multimode interferometer (31). The second balanced detector (34) connects the optical cross-waveguide (32) to the fifth multimode interferometer (35).

9. The quantum classical co-fiber transmission signal receiving device as described in claim 8, characterized in that, The first balanced detector (33) includes a sixth multimode interferometer (36), which is connected to the fourth multimode interferometer (31) and the optical cross waveguide (32) respectively through a fifth waveguide. The sixth multimode interferometer (36) is also connected to two photodetectors (37).

10. The quantum classical co-fiber transmission signal receiving device as described in claim 9, characterized in that, The fifth waveguide includes a thermal phase shifter (4).

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