Detection device, communication system and door width adjustment method

Abstract

The invention provides detection equipment, a communication system and a gate width adjustment method. The detection equipment comprises a wavelength division multiplexer, a beam splitter, a fluorescence detector, at least one polarization module and at least one receiving module, the first end of the wavelength division multiplexer is connected with transmitting end equipment, the second end of the wavelength division multiplexer is connected with the first end of the beam splitter, and the third end of the wavelength division multiplexer is connected with the first end of the fluorescence detector; the second end of the beam splitter is connected with the input end of each polarization module, and the output end of each polarization module is connected with the input end of the corresponding receiving module. According to the detection equipment provided by the embodiment of the invention, when the fluorescence photons are generated in the detection equipment, the fluorescence photons can enter the fluorescence detector through the wavelength division multiplexer, so that the generated fluorescence photons are detected through the fluorescence detector, and the safety of the detection equipment can be determined according to the detection result; the security of the detection equipment in the data transmission process can be improved, and data leakage is avoided.

Description

Technical Field

[0001] The present application relates to the field of quantum communication technology, and in particular to a detection device, a communication system and a gate width adjustment method. Background Art

[0002] With the continuous development of communication technology, the security of data transmission is becoming more and more important. Therefore, data can be transmitted through quantum key distribution technology, which can give full play to the characteristics of unconditional security, thereby ensuring the security of data transmission.

[0003] In the related art, a quantum key distribution (QKD) system includes: a transmitter and a receiver. The transmitter can send a single-photon laser pulse to the receiver through a quantum channel and encode information on the polarization state of the single photon, wherein the laser pulse can include four polarization states. Correspondingly, the receiver can receive the laser pulse and perform operations based on a pre-stored basis consisting of two polarization states to achieve data transmission and decoding.

[0004] However, in actual applications, the receiving end will generate an avalanche current after receiving the signal photon, and may also generate fluorescent photons. The fluorescent photons will be transmitted from the receiving end to the transmitting end, and will carry information corresponding to the polarization state when passing through the polarization device, thereby causing data leakage. Summary of the invention

[0005] The embodiments of the present application provide a detection device, a communication system and a gate width adjustment method, which can solve the problem that fluorescent photons may be generated at the receiving end. When the fluorescent photons pass through the polarization device, they will carry information corresponding to the polarization state, thereby causing data leakage.

[0006] In a first aspect, an embodiment of the present application provides a detection device, comprising: a wavelength division multiplexer, a beam splitter, a fluorescence detector, at least one polarization module and at least one receiving module;

[0007] The first end of the wavelength division multiplexer is connected to the transmitting end device, the second end of the wavelength division multiplexer is connected to the first end of the beam splitter, and the third end of the wavelength division multiplexer is connected to the first end of the fluorescence detector;

[0008] The second end of the beam splitter is connected to the input end of each polarization module, and the output end of the polarization module is connected to the input end of the corresponding receiving module;

[0009] If the receiving module generates fluorescent photons while receiving the laser pulse signal generated by the transmitting device, the fluorescent photons will enter the fluorescent detector through the polarization module, beam splitter and wavelength division multiplexer.

[0010] In a possible implementation manner of the first aspect, the polarization module includes: a polarization controller and a polarization beam splitter;

[0011] The first end of the polarization controller is the first end of the polarization module, the second end of the polarization controller is connected to the first end of the polarization beam splitter, and the second end of the polarization beam splitter is the second end of the polarization module.

[0012] In a possible implementation of the first aspect, the detection device further includes: a single photon counter;

[0013] The first end of the single photon counter is connected to the second end of the fluorescence detector, and the single photon counter is used to count the number of fluorescence photons.

[0014] In a possible implementation of the first aspect, the detection device further includes: a waveform generator;

[0015] The waveform generator is respectively connected to the second end of the single photon counter and the output end of each receiving module. The waveform generator generates a rectangular square wave electrical signal. The rectangular square wave electrical signal generated by the waveform generator is used as a synchronization signal of the single photon counter and is used to trigger each receiving module so that the receiving module enters the Geiger mode.

[0016] In a possible implementation manner of the first aspect, the number of polarization modules is 2.

[0017] In a possible implementation manner of the first aspect, the number of receiving modules is 4.

[0018] In a possible implementation manner of the first aspect, the splitting ratio of the beam splitter is 50:50.

[0019] In a possible implementation manner of the first aspect, the fluorescence detector and each receiving module are avalanche single photon detectors.

[0020] In a second aspect, an embodiment of the present application provides a communication system, including: a transmitting end device and any detection device as described in the first aspect above;

[0021] The output end of the transmitting end device is connected to the first end of the wavelength division multiplexer in the detection device;

[0022] The sending end device is used to generate and send a laser pulse signal to the detection device, and the detection device is used to obtain data information according to the laser pulse signal and detect the generated fluorescent photons.

[0023] In a possible implementation manner of the second aspect, the sending end device is connected to the detection device through an optical fiber.

[0024] In a third aspect, an embodiment of the present application provides a door width adjustment method, the method comprising:

[0025] Activate the communication system;

[0026] Controlling delayed scanning of each receiving module of the detection device in the communication system;

[0027] According to the detection efficiency of each receiving module, the gate width of each receiving module is adjusted to a minimum gate width.

[0028] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0029] An embodiment of the present application proposes a detection device. A wavelength division multiplexer is set in the detection device, and the wavelength division multiplexer is connected to a fluorescence detector. When fluorescent photons are generated in the detection device, the fluorescent photons can enter the fluorescence detector through the wavelength division multiplexer, so that the generated fluorescent photons are detected by the fluorescence detector. The security of the detection device can be determined based on the detection results, which can improve the security of the detection device during data transmission and avoid data leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A system schematic diagram of a QKD system provided in an embodiment of the present application;

[0032] Figure 2A A schematic diagram of the structure of a detection device provided in an embodiment of the present application;

[0033] Figure 2B is a structural schematic diagram of another detection device provided in an embodiment of the present application;

[0034] Figure 2C is a structural schematic diagram of another detection device provided in an embodiment of the present application;

[0035] Figure 3 It is a flow chart of a door width adjustment method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0036] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known methods and terminal devices are omitted to prevent unnecessary details from obstructing the description of the present application.

[0037] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be limiting of the present application. As used in the specification and appended claims of the present application, the singular expressions "a", "said", "above", and "the" are intended to also include expressions such as "one or more", unless the context clearly indicates otherwise.

[0038] With the continuous development of communication technology, the security of data transmission is becoming more and more important. Therefore, data can be transmitted through quantum key distribution technology, which can give full play to the characteristics of unconditional security, thereby ensuring the security of data transmission.

[0039] In the related art, the quantum key distribution (QKD) system includes: a transmitter and a receiver. The transmitter can send a single-photon laser pulse to the receiver through a quantum channel and encode the information in the polarization state of the single photon, where the laser pulse can include four polarization states. (The horizontal polarization state |H> and the vertical polarization state |V> are two polarization states on the horizontal basis, one of which represents 0 and the other 1; the π / 4 polarization state |+> and the -π / 4 polarization state |-> are two polarization states on the diagonal basis, which are also 0 and 1 respectively). Correspondingly, the receiver can receive the laser pulse and randomly select a set of bases from the horizontal basis and the diagonal basis to measure it. Then the communicating parties announce the basis selection information in the classical channel, and only retain the measurement results of the correct basis. The communicating parties jointly hold this part of information, thus realizing key transmission.

[0040] However, in actual applications, the receiving end will generate an avalanche current after receiving a photon, and may also generate fluorescent photons. The fluorescent photons will be transmitted from the receiving end to the transmitting end, and will carry information corresponding to the polarization state when passing through the polarization device, thereby causing data leakage.

[0041] Therefore, an embodiment of the present application proposes a detection device, which provides a wavelength division multiplexer in the detection device and connects the wavelength division multiplexer to a fluorescence detector. When fluorescence photons are generated in the detection device, since the wavelength of the fluorescence photons is inconsistent with the wavelength of the signal light photons sent by the transmitting device, the fluorescence photons can enter the fluorescence detector through the wavelength division multiplexer, and the generated fluorescence photons are detected by the fluorescence detector. Then, the security of the detection device can be determined based on the detection results, which can improve the security of the detection device during data transmission and avoid data leakage.

[0042] The following first introduces a QKD system involved in a detection device provided in an embodiment of the present application, see Figure 1 , Figure 1 A system diagram of a QKD system provided in an embodiment of the present application is shown in FIG. Figure 1 As shown, the QKD system may include: a transmitting device 110 and a receiving device 120.

[0043] The output end of the transmitting device 110 is connected to the first end of the wavelength division multiplexer in the receiving device 120. The transmitting device 110 is used to generate and send a laser pulse signal to the receiving device 120. The receiving device 120 is used to obtain data information according to the laser pulse signal and detect the generated fluorescent photons. Therefore, the receiving device 120 is also a detection device.

[0044] Moreover, in actual applications, the transmitting device 110 can be connected to the detection device via an optical fiber, and the embodiment of the present application does not specifically limit the connection method between the transmitting device 110 and the receiving device 120.

[0045] In the above QKD system, the detection device can detect the fluorescent photons generated by the detection device through a pre-set wavelength division multiplexer, thereby determining the security of the QKD system. The structure of the detection device is introduced as follows.

[0046] Figure 2A This is a schematic diagram of a detection device provided in an embodiment of the present application. As an example but not a limitation, the detection device can be applied to the above-mentioned QKD system. Figure 2A The detection device may include: a wavelength division multiplexer 1201, a beam splitter 1202, a fluorescence detector 1203, at least one polarization module 1204 and at least one receiving module 1205.

[0047] The first end of the wavelength division multiplexer 1201 is connected to the transmitting end device 110, the second end of the wavelength division multiplexer 1201 is connected to the first end of the beam splitter 1202, and the third end of the wavelength division multiplexer 1201 is connected to the first end of the fluorescence detector 1203. The first end of the fluorescence detector 1203 can input signal photons and output fluorescence photons.

[0048] For example, the first end of the wavelength division multiplexer 1201 is a pass port, the second end of the wavelength division multiplexer 1201 is a common port, and the third end of the wavelength division multiplexer 1201 is a reflect port.

[0049] Moreover, the second end of the beam splitter 1202 is connected to the input end of each polarization module 1204, and the output end of the polarization module 1204 is connected to the input end of the corresponding receiving module 1205. Figure 2A Two receiving modules 1205 are shown in the figure) and are connected to corresponding multiple receiving modules 1205.

[0050] In addition, the number of polarization modules 1204 can be determined according to the number of bases composed of polarization states. Preferably, the data of the polarization module is the same as the number of bases composed of polarization states. In the embodiment of the present application, four polarization states constitute two groups of bases, and the number of polarization modules 1204 is 2. Among them, each polarization module 1204 corresponds to a group of bases, and each group of bases corresponds to two polarization states. In other words, each group of bases corresponds to two receiving modules.

[0051] For example, if the beam splitter 1202 has a splitting ratio of 50:50, the beam splitter can split the laser pulse signal into two paths, which are then connected to two polarization modules 1204. It should be noted that one laser pulse signal photon can randomly enter one of the two paths split by the beam splitter.

[0052] Accordingly, during operation of the detection device, the detection device can receive the laser pulse signal generated and emitted by the transmitting end device through the wavelength division multiplexer 1201, so that the laser pulse signal can be screened through the wavelength division multiplexer 1201, so that the photons of the laser pulse signal can enter the beam splitter 1202 through the second end of the wavelength division multiplexer 1201, and the laser pulse signal is randomly split by the beam splitter 1202, then the split laser pulse signal can randomly enter each polarization module 1204, and the polarization state of the laser pulse signal is measured by the polarization module 1204, and the measured laser pulse signal enters the corresponding receiving module 1205, so as to complete the decoding of the laser pulse signal.

[0053] However, when the detection device receives the laser pulse signal to trigger the avalanche, it may generate fluorescent photons. Moreover, the generated fluorescent photons can enter the fluorescent detector 1203 in the order of the polarization module 1204, the beam splitter 1202 and the wavelength division multiplexer 1201. When the fluorescent photons enter the fluorescent detector 1203, it can be determined that the detection device will generate fluorescent photons, and there is a problem with the security of the QKD system.

[0054] It should be noted that, in practical applications, each receiving module 1205 includes an avalanche single photon detector, or each receiving module 1205 can be an avalanche single photon detector, and the fluorescence detector 1203 can be an avalanche single photon detector or a superconducting single photon detector, which is not specifically limited in the embodiments of the present application. Among them, the avalanche single photon detector can generate fluorescent photons as a monitored object, and the superconducting single photon detector is used to detect the existence and characteristics of a single photon.

[0055] It should be noted that the input end of the avalanche single-photon detector inputs fluorescent photons and the output end outputs electrical pulse signals.

[0056] Furthermore, if Figure 2A As shown, the polarization module 1204 may include: a polarization controller 1204a and a polarization beam splitter 1204b.

[0057] The first end of the polarization controller 1204 a is the first end of the polarization module 1204 , the second end of the polarization controller 1204 a is connected to the first end of the polarization beam splitter 1204 b , and the second end of the polarization beam splitter 1204 b is the second end of the polarization module 1204 .

[0058] Correspondingly, the beam splitter 1202 can be connected to the first end of the polarization controller 1204a, and the split laser pulse signal can enter the polarization controller 1204a, and the split laser pulse signal is polarized by the polarization beam splitter 1204b to obtain a polarized laser pulse signal, thereby sending the polarized laser pulse signal to each receiving module 1205.

[0059] In addition, if Figure 2B As shown, the detection device may further include: a single photon counter 1206 .

[0060] The first end of the single photon counter 1206 is connected to the second end of the fluorescence detector 1203, and the single photon counter 1206 is used to count the number of fluorescence photons. It should be noted that the fluorescence detector 1203 can be an avalanche single photon detector or a superconducting single photon detector. The second end of the fluorescence detector 1203 is used to output an electrical signal.

[0061] Specifically, the transmitting device 110 in the QKD system can be turned on first, and the receiving device 120 can be turned off. At this time, no fluorescent photons are generated, and the background noise received by the fluorescent detector is measured by the single photon counter 1206. The background noise is the average number of counts of the fluorescent detector when the QKD system does not receive any photons, also known as dark counts.

[0062] Afterwards, the receiving device 120 can be turned on, and the single photon counter 1206 can be used to measure and determine the first average number of current fluorescent photons. If the first average number is less than or equal to the dark count, it can be determined that the receiving device 120 does not generate fluorescent photons to cause security threats, and data transmission can be performed through the QKD system.

[0063] However, if the first average number is greater than the dark count, it can be determined that the receiving device 120 will generate fluorescent photons and cause a security threat, thereby determining that there is a security threat to the QKD system and security maintenance should be performed on the QKD system.

[0064] Moreover, if Figure 2C As shown, the detection device may further include: a waveform generator 1207 .

[0065] The waveform generator 1207 is respectively connected to the third end of the fluorescence detector 1203 and the trigger signal input port of each receiving module 1205, and the waveform generator 1207 is used to generate an electrical pulse signal to trigger the receiving module 1205. The third end of the fluorescence detector 1203 is used as the input end of the avalanche single photon detector electrical signal.

[0066] It should be noted that the receiving mode 1205 enters the Geiger mode when receiving the electrical pulse signal sent by the waveform generator 1207. When the receiving module 1205 works in the Geiger mode, the receiving module 1205 is highly sensitive to single photons. Since fluorescent photons are single photons, the receiving module 1205 can have good detection sensitivity to fluorescent photons.

[0067] It should also be noted that since the single-photon counter 1206 can not only count fluorescence photons but also count signal light photons, the single-photon counter 1206 can also be connected to each receiving module 1205 so that each receiving module 1205 and the fluorescence detector 1203 multiplex the single-photon counter 1206.

[0068] It should also be noted that the single photon counter 1206 can also be connected to the waveform generator 1207, so that the single photon counter 1206 receives the electrical signal transmitted by the waveform generator 1207, and the electrical signal transmitted to the single photon counter 1206 is used as the synchronization signal of the single photon counter 1206 to ensure the time synchronization of the fluorescence detector 1203 and the QKD system.

[0069] To summarize, a detection device provided in an embodiment of the present application, by setting a wavelength division multiplexer in the detection device and connecting the wavelength division multiplexer to a fluorescence detector, when fluorescent photons are generated in the detection device, the fluorescent photons can enter the fluorescence detector through the wavelength division multiplexer, and the generated fluorescent photons are detected by the fluorescence detector, and then the security of the detection device can be determined based on the detection results, which can improve the security of the detection device during data transmission and avoid data leakage.

[0070] The QKD system and the detection device are introduced above, so that the fluorescence photons can be detected by setting a fluorescence detector in the detection device to avoid data leakage. In practical applications, the gate width of each receiving module 1205 in the detection device can also be adjusted based on the above-mentioned QKD system or the receiving end device in the QKD system, so as to reduce the time spent on the quenching of the generation circuit of each receiving module 1205, thereby reducing the probability of each receiving module 1205 generating fluorescent photons. It should be noted that in the process of adjusting the gate width of each receiving module 1205 in the detection device using the gate width adjustment method provided in the embodiment of the present application, the receiving module 1205 needs to work in Geiger mode.

[0071] The following is an introduction to the method of adjusting the door width of each receiving module 1205. Figure 3 A schematic diagram of a flow chart of a door width adjustment method provided in an embodiment of the present application, such as Figure 3 As shown, the method may include:

[0072] Step 301: Start the QKD system.

[0073] In the process of adjusting the gate width, the QKD system can be started according to the operation triggered by the user, that is, the transmitting device and the receiving device of the QKD system are started. In the process of starting the receiving device, the frequency of the waveform generator can be set so that the transmitting device and the receiving device can synchronously receive the pulse signal.

[0074] Specifically, the waveform generator can be turned on first and set according to the preset system frequency so that the frequency of the pulse signal output by the waveform generator is consistent with the system frequency, thereby ensuring that the transmitting device and the receiving device can synchronously receive the pulse signal.

[0075] Moreover, after the transmitting end device is turned on, the transmitting end device can randomly transmit pulse signals of multiple polarization states. For example, the transmitting end device can transmit a pulse signal of one of the polarization states of |H>, |V>, |+>, and |->.

[0076] In addition, when starting the receiving end device, each receiving module can be set to an external trigger mode and the parameters of each receiving module can be adjusted. For example, when each receiving module is an avalanche single photon detector, the detection efficiency, gate width and dead time of each avalanche single photon detector can be set.

[0077] Step 302: Control each receiving module in the detection device to delay scanning.

[0078] Since it takes a certain amount of time for the pulse signal sent by the transmitting device to reach the receiving device, the timing of scanning each receiving module can be adjusted so that the scanning time of each receiving module is consistent with the time when the pulse signal reaches the receiving device, thereby completing the scanning of the pulse signal.

[0079] The waveform generator transmits a pulse electrical signal to trigger the receiving module. The delay time for the waveform generator to send the pulse electrical signal to the receiving module can be set. The delayed scanning of each receiving module is achieved by the waveform generator sending the pulse electrical signal to each receiving module with different delay times.

[0080] Specifically, the receiving device can first scan according to the pre-set initial delay time. If no pulse signal is scanned, the initial delay time is adjusted until each receiving module can complete the scanning of the pulse signal, so that the gate position of each single-photon detector can completely cover the signal light pulse.

[0081] Furthermore, each receiving module may record the detection efficiency of each receiving module during the process of receiving the pulse signal, so that in subsequent steps, the gate width of the receiving module may be adjusted according to the recorded detection efficiency.

[0082] Step 303: Adjust the door width of each receiving module until the door width of each receiving module is adjusted.

[0083] After determining the detection efficiency, the receiving device can adjust the gate width of each receiving module so that each receiving module can reduce the opening time, thereby reducing the probability of the receiving module generating fluorescent photons to improve the security of the QKD system. The above step 303 can be performed by the receiving module in the receiving device. Specifically, the above step 303 is set on the avalanche single photon detector in the receiving device.

[0084] For each receiving module, the receiving end device can continuously reduce the gate width of the receiving module, and receive pulse signals according to the reduced gate width, so as to determine the detection efficiency after the gate width is reduced. If the detection efficiency does not change, the gate width can be adjusted again according to the preset step size. If it is detected that the detection efficiency is reduced, the gate width adjusted last time can be used as the minimum gate width, so as to reduce the gate width of the receiving module on the basis of ensuring the detection efficiency.

[0085] Similarly, the gate width of each receiving module can be adjusted in the above manner, so that the receiving modules for receiving pulse signals of each polarization state are all adjusted to the minimum gate width, thereby reducing the probability of the receiving end device generating fluorescent photons.

[0086] To summarize, the gate width adjustment method provided in the embodiment of the present application receives the pulse signal through the receiving end device, determines the detection efficiency, and then continuously reduces the gate width of each receiving module. On the basis of ensuring the detection efficiency, the gate width of each receiving module is adjusted to the minimum gate width, thereby reducing the scanning time of each receiving module, and then reducing the probability of each receiving module generating fluorescent photons, which can improve the security of the QKD system and avoid data leakage.

[0087] It should be noted that the information interaction, execution process, etc. between the above-mentioned devices / units are based on the same concept as the method embodiment of the present application. Their specific functions and technical effects can be found in the method embodiment part and will not be repeated here.

[0088] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0089] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, which can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium can at least include: any entity or device that can carry the computer program code to the camera / terminal device, recording medium, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, RandomAccess Memory), electric carrier signal, telecommunication signal and software distribution medium. For example, a USB flash drive, a mobile hard disk, a magnetic disk or an optical disk. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electric carrier signals and telecommunication signals.

[0090] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0091] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0092] In the embodiments provided in the present application, it should be understood that the disclosed devices / communication systems and methods can be implemented in other ways. For example, the device / communication system embodiments described above are merely schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or modules, which can be electrical, mechanical or other forms.

[0093] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0094] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A detection device, characterized in that: The detection device comprises: a wavelength division multiplexer, a beam splitter, a fluorescence detector, at least one polarization module and at least one receiving module; The first end of the wavelength division multiplexer is connected to the transmitting end device, the second end of the wavelength division multiplexer is connected to the first end of the beam splitter, and the third end of the wavelength division multiplexer is connected to the first end of the fluorescence detector; The second end of the beam splitter is connected to the input end of each polarization module, and the output end of the polarization module is connected to the input end of the corresponding receiving module; If the receiving module generates fluorescent photons simultaneously when receiving the laser pulse signal generated by the transmitting device, the fluorescent photons pass through the polarization module, the beam splitter and the wavelength division multiplexer and enter the fluorescent detector.

2. The detection device according to claim 1, characterized in that: The polarization module includes: a polarization controller and a polarization beam splitter; The first end of the polarization controller is the first end of the polarization module, the second end of the polarization controller is connected to the first end of the polarization beam splitter, and the second end of the polarization beam splitter is the second end of the polarization module.

3. The detection device according to claim 1, characterized in that: The detection device also includes: a single photon counter; The first end of the single-photon counter is connected to the second end of the fluorescence detector, and the single-photon counter is used to count the number of the fluorescence photons.

4. The detection device according to claim 3, characterized in that: The detection device also includes: a waveform generator; The waveform generator is respectively connected to the second end of the single photon counter and the output end of each receiving module, and generates a rectangular square wave electrical signal. The rectangular square wave electrical signal generated by the waveform generator is used as a synchronization signal of the single photon counter and is used to trigger each receiving module so that the receiving module enters the Geiger mode.

5. The detection device according to any one of claims 1 to 4, characterized in that: The number of the polarization modules is 2.

6. The detection device according to any one of claims 1 to 4, characterized in that: The number of the receiving modules is 4.

7. The detection device according to any one of claims 1 to 4, characterized in that: The beam splitter has a splitting ratio of 50:

50.

8. The detection device according to any one of claims 1 to 4, characterized in that: The fluorescence detector and each of the receiving modules are avalanche single-photon detectors.

9. A communication system, characterized in that: The communication system comprises: a transmitting end device and a detection device as claimed in any one of claims 1 to 8; The output end of the transmitting end device is connected to the first end of the wavelength division multiplexer in the detection device; The transmitting device is used to generate and send a laser pulse signal to the detecting device, and the detecting device is used to obtain data information according to the laser pulse signal and detect the generated fluorescent photons.

10. The communication system according to claim 9, characterized in that: The sending end device is connected to the detection device via an optical fiber.

11. A door width adjustment method, characterized in that: The method comprises: Activate the communication system; Controlling delayed scanning of each receiving module of the detection device in the communication system; According to the detection efficiency of each receiving module, the gate width of each receiving module is adjusted to a minimum gate width.

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