CN107733637B - Quantum key distribution device used in duplex quantum key distribution system - Google Patents

Quantum key distribution device used in duplex quantum key distribution system Download PDF

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Publication number
CN107733637B
CN107733637B CN201610658812.4A CN201610658812A CN107733637B CN 107733637 B CN107733637 B CN 107733637B CN 201610658812 A CN201610658812 A CN 201610658812A CN 107733637 B CN107733637 B CN 107733637B
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optical
locked loop
qkd
synchronous
port
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CN107733637A (en
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姚海涛
贾云
唐世彪
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Quantumctek Shanghai Co ltd
Quantumctek Co Ltd
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Quantumctek Shanghai Co ltd
Quantumctek Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0852—Quantum cryptography
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/66—Non-coherent receivers, e.g. using direct detection
    • H04B10/69—Electrical arrangements in the receiver
    • H04B10/691—Arrangements for optimizing the photodetector in the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
    • H04L7/033—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Theoretical Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Optical Communication System (AREA)

Abstract

A crystal oscillator of a synchronous optical device is connected to a transmitting-end phase-locked loop, an output end of the transmitting-end phase-locked loop is connected with a synchronous optical laser, an output end of the synchronous optical laser is connected to an input end of an optical beam splitter, one end of the optical beam splitter with the proportion of N is connected with a circulator port 1 through a tunable optical attenuator, a circulator port 2 is an input/output port of synchronous light, one end of the optical beam splitter with the proportion of 1 is connected with a port 1 of an optical switch, a circulator port 3 is connected with a port 2 of the optical switch, an output end of the optical switch is connected with a receiving-end phase-locked loop through a PIN tube, and the receiving-end phase-locked loop is connected with the transmitting-end phase-locked loop. The invention also discloses two simplified QKD devices. The invention has the following advantages: the optical path is formed by the connection between common optical devices, and the duplex QKD by using one synchronous light can be realized by matching two QKD devices of the invention, so that the method has the characteristics of simplicity and easiness.

Description

Quantum key distribution device used in duplex quantum key distribution system
Technical Field
The invention relates to the field of quantum secret communication, in particular to a quantum key distribution device used in a duplex quantum key distribution system.
Background
Duplex quantum key distribution (Quantum Key Distribution, QKD) systems, each comprising a sender Alice and a receiver Bob, can operate two QKD links simultaneously, as schematically illustrated in fig. 1.
One key technology in QKD systems is the synchronization of information at the system sender (Alice) and the system receiver (Bob). Only when the photon pulse detected by the receiver is synchronous with the photon pulse sent by the sender, the two sides of the system can extract the quantum key which is safe and consistent.
In the prior art, each link of a duplex system is synchronized using separate synchronization lights. Considering a large-scale application, the design of each QKD apparatus is identical, i.e., the two devices that work in pairs are identical. So, the individual parameters (wavelength, frequency, etc.) of the synchronous light on both links are also identical and transmitted in the same fiber. Because the actual optical fiber link environment is not ideal, the reflection phenomenon of the optical fiber end face exists. For example, when QKD link 1 is started, there may be a reflection of the synchronization light from Alice of the link, and the reflection enters Bob of link 2, which may cause erroneous discrimination of the synchronization signal in link 2; thus, when link 2 is started, the synchronization light emitted by Alice of link 2 is disturbed, so that the link cannot operate normally.
As shown in fig. 2, in order to solve the problem of synchronous light reflection in the "a method and apparatus for synchronizing a quantum key distribution system" of the prior application No. 201410472681.1, two synchronous light lasers with different wavelengths are configured in a duplex QKD device, and when the duplex QKD operates, two links use synchronous light with one of the wavelengths.
In the art, there are what are defined as "two-way QKD systems," which refers to implementations in which signal light is sent from a first QKD end to a second QKD end and then back to the first QKD end along the original optical path. In general, the signal light from the first QKD end to the second QKD end is strong, averages hundreds or thousands of photons per pulse, and is attenuated to a single photon magnitude (averaging one photon per pulse or less) at the second QKD end before returning to the first QKD end. Only one QKD link on the fiber optic link of the system is a two-way, simplex process.
The first QKD station of a comparison document, such as MAGIQ technologies inc (application No. 200580025415.3), has a laser source that emits light at a different wavelength, and a plurality of single-photon detector (SPD) units. In a two-way QKD system, backscattered light is typically generated by the stronger output signal light in the fiber link connecting the first and second QKD stations. To reduce or avoid back-scattered light interfering with the detection of signal light returned from the second QKD station to the first QKD station, the patent sequentially activates different light sources while sequentially activating pairs of SPDs in the SPD units in the first QKD station. The patent aims to solve the problem that the detection of signal light in a two-way QKD system is easy to be interfered by backward scattered light, the requirement on a related control system is high, the expected arrival time of the signal light needs to be calculated according to the length of an actual optical fiber link, different light sources and the activation control of an SPD unit are carried out at the expected arrival time, the control precision requirement is high, and the sequential activation process is continuously carried out.
The "duplex QKD system" in this proposal is different from the "two-way QKD system" described above. As defined above, a "two-way QKD system" is a "two-way" or "simplex" system, and a "one-way" or "duplex" system is a system that can operate in "full duplex", where each end of the duplex system includes Alice and Bob, and two QKD links can be established simultaneously.
In the prior art, each link of a duplex system uses independent synchronization light for synchronization, which leads to the occurrence of synchronization light reflection problems. In addition, although the existing technical scheme can solve the problem, the two links still use a scheme of independently synchronizing light, and the scheme greatly increases the development cost of the system.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a scheme capable of solving the synchronous light reflection problem, so that two QKD links can be used in a duplex quantum key distribution system which normally operates.
The invention solves the technical problems through the following technical scheme: the synchronous optical device of the QKD device comprises a crystal oscillator, a sending end phase-locked loop, a synchronous optical laser, an optical beam splitter, an adjustable optical attenuator, a circulator, an optical switch, a PIN tube and a receiving end phase-locked loop;
the crystal oscillator is connected to the sending end phase-locked loop, the output end of the sending end phase-locked loop is connected with the synchronous optical laser, the output end of the synchronous optical laser is connected to the input end of the optical beam splitter, the light splitting proportion of the optical beam splitter is N1, one end of the optical beam splitter with the proportion of N is connected with the circulator port 1 through the adjustable optical attenuator, the circulator port 2 is an input/output port of synchronous light, one end of the optical beam splitter with the proportion of 1 is connected with the port 1 of the optical switch, the circulator port 3 is connected with the port 2 of the optical switch, the output end of the optical switch is connected with the receiving end phase-locked loop through the PIN tube, and the receiving end phase-locked loop is connected with the sending end phase-locked loop.
The invention also provides a quantum key distribution device used in the simpler duplex quantum key distribution system, the quantum key distribution device can only be used as a synchronous light sender, the synchronous light device of the QKD device comprises a crystal oscillator, a sending end phase-locked loop, a synchronous light laser, an optical beam splitter, an adjustable light attenuator, a circulator, an optical switch, a PIN tube and a receiving end phase-locked loop, wherein the crystal oscillator is connected to the sending end phase-locked loop, the output end of the sending end phase-locked loop is connected with the synchronous light laser, the synchronous light laser generates synchronous light and enters the optical beam splitter, the optical beam splitter splits the synchronous light according to the splitting proportion of N:1, the synchronous light output by the synchronous light laser enters the circulator port 1 through the optical beam splitter at one end with the proportion of N, the circulator port 2 is an output port of the synchronous light, the synchronous light output by the synchronous light laser is connected with the port 1 of the optical switch through the PIN tube, and the output end of the optical switch is connected with the receiving end phase-locked loop.
The invention also provides a quantum key distribution device used in the simpler duplex quantum key distribution system, the quantum key distribution device can only be used as a synchronous light receiver and can not transmit synchronous light, and the synchronous light device of the QKD device comprises a crystal oscillator, a transmitting-end phase-locked loop, a circulator, an optical switch, a PIN tube and a receiving-end phase-locked loop, wherein the crystal oscillator is connected to the transmitting-end phase-locked loop, a port 2 of the circulator is an input port of synchronous light, a port 3 of the circulator is connected with a port 2 of the optical switch, an output end of the optical switch is connected with the receiving-end phase-locked loop through the PIN tube, and the receiving-end phase-locked loop is connected with the transmitting-end phase-locked loop.
In the above three technical solutions, the optical switch is optimized to be a 1*2 matrix optical switch.
In the above three technical solutions, the light beam splitter is optimized to have a splitting ratio of 9:1.
Compared with the prior art, the invention has the following advantages:
1. the optical path is formed by the connection between common optical devices, and the duplex QKD by using one synchronous light can be realized by matching two QKD devices of the invention, so that the method has the characteristics of simplicity and easiness.
2. The optical path connection is constructed through devices such as an optical beam splitter, an optical circulator and an optical switch, so that duplex QKD is realized by using one path of synchronous light, and the problem that the QKD system cannot operate in full duplex due to synchronous light reflection caused by that each link of the existing duplex QKD system uses independent synchronous light for synchronization can be solved.
3. The optical path connection is constructed through devices such as an optical beam splitter, an optical circulator and an optical switch, so that duplex QKD is realized by using one path of synchronous light, and compared with the scheme of configuring two synchronous optical lasers with different wavelengths in the prior art, the system has low development cost and does not need to add a channel with another wavelength.
4. The duplex QKD with one synchronous light can be realized by upgrading and reforming the light path by using a passive optical device without changing a laser, a detector and an electronic board card in the original duplex QKD system.
Drawings
Fig. 1 is a duplex QKD system schematic;
FIG. 2 is a prior art synchronization scheme diagram;
fig. 3 is a schematic diagram of a single QKD apparatus according to a first embodiment of the present invention;
fig. 4 is a schematic diagram of two QKD links of a first embodiment of the present invention synchronized using one synchronization light;
fig. 5 is a schematic diagram of a duplex QKD system reception control system according to a first embodiment of the present invention;
fig. 6 is a scheme diagram of a duplex QKD system-L of embodiment two of the present invention;
fig. 7 is a scheme diagram of a duplex QKD system-R of embodiment two of the present invention;
fig. 8 is a schematic diagram of a duplex QKD system reception control system according to a second embodiment of the present invention.
Detailed Description
The following describes in detail the examples of the present invention, which are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of protection of the present invention is not limited to the following examples.
The invention provides a QKD device used in a duplex quantum key distribution system, two QKD devices are paired into the duplex quantum key distribution system, the paired two QKD devices use one synchronous light, and each QKD device comprises a sending end Alice and a receiving end Bob. Wherein the synchronous light generated by the transmitting end of the first station QKD device is output to the receiving end of the second station QKD device, and the synchronous light generated by the transmitting end of the first station QKD device is simultaneously transmitted to the receiving end of the first station QKD device, and the synchronous signal received by the receiving end of the second station QKD device is transmitted to the transmitting end of the second station QKD device.
Example 1
As shown in fig. 3, in this embodiment, in the duplex QKD system, two QKD devices paired together have the same structure, and the synchronous light generating and receiving device of each QKD device includes a crystal Oscillator (OSC), a transmitting-side phase-locked loop (Phase Locked Loop, PLL), a synchronous optical Laser (LD, laser Diode), an optical splitter BS (Beam Splitter), an adjustable optical attenuator, a circulator, an optical switch OSW (Optical Switch), a PIN tube, and a receiving-side phase-locked loop.
The crystal oscillator is connected to the sending end phase-locked loop, the output end of the sending end phase-locked loop is connected with the synchronous optical laser, the output end of the synchronous optical laser is connected to the input end of the optical beam splitter, the light splitting proportion of the optical beam splitter is N1, one end of the optical beam splitter with the proportion of N is connected with the circulator port 1 through the adjustable optical attenuator, the circulator port 2 is an input/output port of synchronous light, one end of the optical beam splitter with the proportion of 1 is connected with the port 1 of the optical switch, the circulator port 3 is connected with the port 2 of the optical switch, and the output end of the optical switch is connected with the receiving end phase-locked loop through the PIN tube. The receiving end phase-locked loop is connected with the transmitting end phase-locked loop.
QKD systems are driven with a clock generated by a crystal oscillator. The phase-locked loop utilizes an externally input clock reference signal to control the frequency and the phase of an oscillation signal in the loop, so that the frequency of an output signal can be automatically tracked to the frequency of an input signal, and clock signals with different frequencies can be generated according to the clock signal of the frequency of an input end to be output.
In the technical scheme, signals output by a local crystal oscillator are firstly connected into a phase-locked loop, and after passing through the phase-locked loop, signal light driving signals and synchronous light driving signals are generated. The frequency of the signal light driving signal is different from that of the synchronous light driving signal, and in many cases, the frequency of the signal light driving signal is greater than that of the synchronous light signal.
The signal light driving signal and the synchronous light driving signal are respectively applied to the signal light laser and the synchronous light laser to generate signal light and synchronous light required by the system. The signal light is used for generating a quantum key, and the synchronous light is used for realizing the synchronization of a system transmitting end and a system receiving end. The invention is mainly a synchronous mode of the system, so only follow-up processing of synchronous light is concerned, and the signal light is not repeated.
The beam splitting ratio of the beam splitter is N:1, where N is a positive integer, for example, BS with a beam splitting ratio of 9:1 is used, and of course, the beam splitting ratio may be freely selected according to practical situations. The output end with the proportion of N is connected with an adjustable optical attenuator, then is connected into the circulator port 1 and is output from the circulator port 2, and the circulator port 2 is an external optical input/output (I/O) port of the duplex QKD system.
The synchronous light output by the synchronous light laser is connected into the input port 1 of the optical switch through the output end with the proportion of 1 of the optical beam splitter. Wherein the optical switch is of a 1*2 matrix format, and the output of the circulator port 3 is connected to the other input port 2 of the optical switch.
The synchronous light output by the optical switch is to be sent to the receiving end of the duplex QKD system, the synchronous light needs to be subjected to photoelectric conversion through a PIN tube to obtain an electric signal, and then the electric signal is sent to a phase-locked loop of the receiving end, and the phase-locked loop generates a detection clock for a single photon detector according to the input synchronous electric signal.
Referring to FIG. 4, two QKD devices paired are represented by a duplex QKD system-L and a duplex QKD system-R, respectively. The sending end Alice of the duplex QKD system-L and the receiving end Bob of the duplex QKD system-R are paired into a QKD link 1; the sender Alice of the duplex QKD system-R and the receiver Bob of the duplex QKD system-L pair into a QKD link 2.
The specific synchronization method of duplex QKD system-L and duplex QKD system-R is as follows:
the sending end Alice of the duplex QKD system-L sends the synchronization light, the synchronization light transmission is shown by the solid line path in fig. 4, and the other link (Alice of the duplex QKD system-R does not send the synchronization light) synchronization light transmission is shown by the dashed line path in fig. 4. Wherein in this embodiment part of the connection lines are unused during actual operation of the system, this unused part is not shown in fig. 4.
Links transmitting synchronous light, synchronous optical paths such as solid line paths: firstly, a signal output by a local crystal oscillator is connected into a phase-locked loop of a sending end Alice in a duplex QKD system-L, after passing through the phase-locked loop, a synchronous optical drive signal is generated, the synchronous optical drive signal output by the phase-locked loop acts on a synchronous optical laser, synchronous light output by the synchronous optical laser passes through one end with the proportion of N of an optical beam splitter, then enters a circulator port 1, is output from the circulator port 2, passes through optical fiber transmission, reaches the circulator port 2 in a duplex QKD system-R, is output from the circulator port 3, enters the port 2 of an optical switch, passes through a PIN tube, is converted into an electric signal and then is sent to a phase-locked loop of a receiving end Bob, and synchronization of the sending end Alice of the duplex QKD system-L of the QKD link 1 and the receiving end Bob of the duplex QKD system-R is completed.
The synchronous optical path of the other link is shown as a dashed path: the phase-locked loop of the sending end Alice in the duplex QKD system-R takes the phase-locked loop output of the receiving end Bob in the duplex QKD system-R as a driving signal, so that the synchronous signal input by the phase-locked loop of the sending end Alice can be homologous to the synchronous signal output by the phase-locked loop of the receiving end Bob, but the sending end Alice of the duplex QKD system-R does not generate synchronous light additionally. The output end of the optical beam splitter BS with the proportion of 1 of the duplex QKD system-L is connected with the port 1 of the optical switch, and the synchronous optical signal output by the optical switch enters the PIN tube to be subjected to photoelectric conversion, so that the synchronous electric signal is sent to the phase-locked loop of the receiving end Bob. Thereby completing the synchronization of the sender Alice of the duplex QKD system-R and the receiver Bob of the duplex QKD system-L of QKD link 2.
The adjustable optical attenuator has the function of combining attenuation on an optical fiber link and setting different values so that the synchronous light generated by the duplex QKD system-L meets the condition of photoelectric conversion of a PIN tube when reaching the receiving end Bob of the duplex QKD system-R of the link.
Referring to fig. 5, in practice, two QKD devices operating in a pairing mode may receive control of an upper "control system". The "control system" is connected to the two QKD devices that operate in pairing, respectively, and can configure which duplex QKD system's transmitting end Alice transmits the synchronization light. If the duplex QKD system-L on the left side of fig. 5 is configured to send synchronous light, then the optical switch in that system is simultaneously set to port 1 gating, while the optical switch in the other duplex QKD system-R is simultaneously set to port 2 gating.
In this embodiment, the QKD devices with the same structure are paired to form a duplex QKD system, which has the advantage that two QKD devices can be paired to form a duplex QKD system that can synchronize using the same path of synchronization light without considering the situation of the paired two QKD devices.
Example two
Duplex QKD systems, two devices working in pairs adopt unequal designs, i.e. two QKD systems working in pairs in embodiment one, each end only designs the part involved in the work and no redundant part. Duplex QKD system-L and duplex QKD system-R were designed as follows:
as shown in fig. 6, the synchronous light generating device of one of the paired duplex QKD systems-L includes a crystal Oscillator (OSC), a transmitting-side phase-locked loop (Phase Locked Loop, PLL), a synchronous optical Laser (LD), an optical splitter BS (Beam Splitter), a tunable optical attenuator, a circulator, an optical switch OSW (Optical Switch), a PIN tube, and a receiving-side phase-locked loop. The crystal oscillator is connected to the sending end phase-locked loop, the output end of the sending end phase-locked loop is connected with the synchronous optical laser, the synchronous optical laser generates synchronous light to enter the optical beam splitter BS, the optical beam splitter splits the synchronous light according to the splitting proportion of N:1, the synchronous light output by the synchronous optical laser passes through one end of the optical beam splitter with the proportion of N and then enters the circulator port 1 through the adjustable optical attenuator, the circulator port 2 is an output port of the synchronous light, the synchronous light output by the synchronous optical laser passes through one end of the optical beam splitter with the proportion of 1 and is connected with the port 1 of the optical switch, and the output end of the optical switch is connected with the receiving end phase-locked loop through the PIN tube.
As shown in fig. 7, the synchronous optical receiver of another duplex QKD system-R of the pair includes a crystal Oscillator (OSC), a transmit-side phase-locked loop (Phase Locked Loop, PLL), a circulator, an optical switch OSW (Optical Switch), a PIN tube, and a receive-side phase-locked loop. The crystal oscillator is connected to the phase-locked loop at the transmitting end, the circulator port 2 is an input port of synchronous light, the circulator port 3 is connected with the port 2 of the optical switch, and the output end of the optical switch is connected with the phase-locked loop at the receiving end through the PIN tube. The receiving end phase-locked loop is connected with the transmitting end phase-locked loop.
Referring to FIG. 8, two QKD devices are paired, and the transmitting end Alice of duplex QKD system-L and the receiving end Bob of duplex QKD system-R are paired to form a QKD link 1; the sender Alice of the duplex QKD system-R and the receiver Bob of the duplex QKD system-L pair into a QKD link 2.
In this embodiment, the specific synchronization method of duplex QKD system-L and duplex QKD system-R is as follows:
the sending end Alice of the duplex QKD system-L sends the synchronization light, as shown by the solid line path in fig. 8, and the other link (Alice of the duplex QKD system-R does not send the synchronization light), as shown by the dashed line path in fig. 8.
Links transmitting synchronous light, synchronous optical paths such as solid line paths: firstly, a signal output by a local crystal oscillator is connected into a phase-locked loop of a sending end Alice in a duplex QKD system-L, after passing through the phase-locked loop, a synchronous optical drive signal is generated, the synchronous optical drive signal output by the phase-locked loop acts on a synchronous optical laser, synchronous light output by the synchronous optical laser passes through one end with the proportion of N of an optical beam splitter, then enters a circulator port 1, is output from the circulator port 2, passes through optical fiber transmission, reaches the circulator port 2 in a duplex QKD system-R, is output from the circulator port 3, enters the port 2 of an optical switch, passes through a PIN tube, is converted into an electric signal and then is sent to a phase-locked loop of a receiving end Bob, and synchronization of the sending end Alice of the duplex QKD system-L of the QKD link 1 and the receiving end Bob of the duplex QKD system-R is completed.
The synchronous optical path of the other link is shown as a dashed path: the phase-locked loop of the sending end Alice in the duplex QKD system-R takes the phase-locked loop output of the receiving end Bob in the duplex QKD system-R as a driving signal, so that the synchronous signal input by the phase-locked loop of the sending end Alice can be homologous to the synchronous signal output by the phase-locked loop of the receiving end Bob, but the sending end Alice of the duplex QKD system-R does not generate synchronous light additionally. The output end of the optical beam splitter BS with the proportion of 1 of the duplex QKD system-L is connected with the port 1 of the optical switch, and the synchronous optical signal output by the optical switch enters the PIN tube to be subjected to photoelectric conversion, so that the synchronous electric signal is sent to the phase-locked loop of the receiving end Bob. Thereby completing the synchronization of the sender Alice of the duplex QKD system-R and the receiver Bob of the duplex QKD system-L of QKD link 2.
Referring also to fig. 8, in practical applications, two QKD devices operating in a pairing operation may receive control of an upper "control system". The control system is respectively connected to the two QKD devices in pairing operation, and is configured to send synchronous light by the sending end Alice of the duplex QKD system-L. The optical switch in this system is simultaneously set to port 1 gating while the optical switch in another duplex QKD system-R is set to port 2 gating.
The QKD devices with simplified structures are adopted for pairing in the embodiment to form the duplex QKD system, and the advantages are that parts which are not needed in synchronous production are not needed, the production process is simplified, and the cost is reduced.
Example III
For convenience of description, each QKD device of the same configuration in the first embodiment is referred to as a "full QKD device", each QKD device of the second embodiment in which only a part participating in the operation is designed, each QKD device in which no redundant part is designed is referred to as a "simplest QKD device", and a "simplest QKD device" transmitting synchronous light is referred to as a "simplest synchronous light transmitting QKD device", and a "simplest QKD device" receiving synchronous light is referred to as a "simplest synchronous light receiving QKD device".
In the second embodiment, the two QKD devices paired are both QKD devices with simplified structures, so that in the practical application process, the failure of one QKD device is unavoidable, and if there is no simplified QKD device with the same structure in the field, the use of the duplex QKD system is affected.
In this embodiment, a duplex QKD system is formed using a complete QKD device paired with a simplest synchronous light-receiving QKD device.
In the duplex QKD system, the synchronous optical generation and reception apparatus of the complete QKD apparatus is shown in fig. 3, and includes a crystal Oscillator (OSC), a transmitting-side phase-locked loop (Phase Locked Loop, PLL), a synchronous optical Laser (LD), an optical splitter BS (Beam Splitter), a tunable optical attenuator, a circulator, an optical switch OSW (Optical Switch), a PIN tube, and a receiving-side phase-locked loop.
The crystal oscillator is connected to the sending end phase-locked loop, the output end of the sending end phase-locked loop is connected with the synchronous optical laser, the output end of the synchronous optical laser is connected to the input end of the optical beam splitter, the light splitting proportion of the optical beam splitter is N1, one end of the optical beam splitter with the proportion of N is connected with the circulator port 1 through the adjustable optical attenuator, the circulator port 2 is an input/output port of synchronous light, one end of the optical beam splitter with the proportion of 1 is connected with the port 1 of the optical switch, the circulator port 3 is connected with the port 2 of the optical switch, and the output end of the optical switch is connected with the receiving end phase-locked loop through the PIN tube. The receiving end phase-locked loop is connected with the transmitting end phase-locked loop.
The synchronous optical receiver of the simplest synchronous optical receiver QKD apparatus is shown in fig. 7, and includes a crystal Oscillator (OSC), a transmitting-side phase-locked loop (Phase Locked Loop, PLL), a circulator, an optical switch OSW (Optical Switch), a PIN tube, and a receiving-side phase-locked loop. The crystal oscillator is connected to the phase-locked loop at the transmitting end, the circulator port 2 is an input port of synchronous light, the circulator port 3 is connected with the port 2 of the optical switch, and the output end of the optical switch is connected with the phase-locked loop at the receiving end through the PIN tube. The receiving end phase-locked loop is connected with the transmitting end phase-locked loop.
A link transmitting synchronization light, a synchronization light route: firstly, a signal output by a local crystal oscillator is connected into a phase-locked loop of a transmitting end Alice in a complete QKD device, after passing through the phase-locked loop, a synchronous optical driving signal is generated, the synchronous optical driving signal output by the phase-locked loop acts on a synchronous optical laser, synchronous light output by the synchronous optical laser passes through one end with the proportion of N by an optical beam splitter, then enters a circulator port 1, is output from the circulator port 2, is transmitted through an optical fiber, reaches the port 2 of the circulator in a simplest synchronous optical receiving QKD device, is output from a port 3 of the circulator, enters a port 2 of an optical switch, passes through a PIN tube, is converted into an electric signal and then is transmitted to a phase-locked loop of a receiving end Bob, and synchronization of the transmitting end Alice of the complete QKD device of the QKD link 1 and the receiving end Bob of the simplest synchronous optical receiving QKD device is completed.
Synchronous optical path of another link: the phase-locked loop of the transmitting end Alice in the simplest synchronous light receiving QKD device takes the phase-locked loop output of the receiving end Bob of the simplest synchronous light receiving QKD device as a driving signal, so that the synchronous signal input by the phase-locked loop of the transmitting end Alice can be homologous to the synchronous signal output by the phase-locked loop of the receiving end Bob, but the transmitting end Alice of the simplest synchronous light receiving QKD device does not generate synchronous light additionally. The output end of the optical beam splitter BS of the complete QKD device with the proportion of 1 is connected with the port 1 of the optical switch, and the synchronous optical signal output by the optical switch enters the PIN tube to be subjected to photoelectric conversion, so that the synchronous electric signal is sent to the phase-locked loop of the receiving end Bob. Thereby completing the synchronization of the sender Alice of the simplest synchronous optical receiving QKD device of QKD link 2 and the receiver Bob of the full QKD device.
In practice, two QKD devices operating in a pairing operation can receive upper layer "control system" control. The control system is respectively connected to the two QKD devices in pairing operation, and the transmitting end Alice of the complete QKD device is configured to transmit synchronous light. The optical switch in the system is simultaneously set to port 1 gating while the optical switch in the other simplest synchronous light-receiving QKD device is set to port 2 gating.
Example IV
For convenience of description, each QKD device of the same configuration in the first embodiment is referred to as a "full QKD device", each QKD device of the second embodiment in which only a part participating in the operation is designed, each QKD device in which no redundant part is designed is referred to as a "simplest QKD device", and a "simplest QKD device" transmitting synchronous light is referred to as a "simplest synchronous light transmitting QKD device", and a "simplest QKD device" receiving synchronous light is referred to as a "simplest synchronous light receiving QKD device".
In the second embodiment, the two QKD devices paired are both QKD devices with simplified structures, so that in the practical application process, the failure of one QKD device is unavoidable, and if there is no simplified QKD device with the same structure in the field, the use of the duplex QKD system is affected.
In this embodiment, a duplex QKD system is formed by pairing a simplest synchronous optical transmit QKD device with a full QKD device.
As shown in fig. 6, the synchronous light generating device of the simplest synchronous light transmitting QKD device includes a crystal Oscillator (OSC), a transmitting-side phase locked loop (Phase Locked Loop, PLL), a synchronous light Laser (LD), an optical splitter BS (Beam Splitter), a tunable optical attenuator, a circulator, an optical switch OSW (Optical Switch), a PIN tube, and a receiving-side phase locked loop. The crystal oscillator is connected to the sending end phase-locked loop, the output end of the sending end phase-locked loop is connected with the synchronous optical laser, the synchronous optical laser generates synchronous light to enter the optical beam splitter BS, the optical beam splitter splits the synchronous light according to the splitting proportion of N:1, the synchronous light output by the synchronous optical laser passes through one end of the optical beam splitter with the proportion of N and then enters the circulator port 1 through the adjustable optical attenuator, the circulator port 2 is an output port of the synchronous light, the synchronous light output by the synchronous optical laser passes through one end of the optical beam splitter with the proportion of 1 and is connected with the port 1 of the optical switch, and the output end of the optical switch is connected with the receiving end phase-locked loop through the PIN tube.
In the duplex QKD system, the synchronous optical generation and reception apparatus of the complete QKD apparatus is shown in fig. 3, and includes a crystal Oscillator (OSC), a transmitting-side phase-locked loop (Phase Locked Loop, PLL), a synchronous optical Laser (LD), an optical splitter BS (Beam Splitter), a tunable optical attenuator, a circulator, an optical switch OSW (Optical Switch), a PIN tube, and a receiving-side phase-locked loop.
The crystal oscillator is connected to the sending end phase-locked loop, the output end of the sending end phase-locked loop is connected with the synchronous optical laser, the output end of the synchronous optical laser is connected to the input end of the optical beam splitter, the light splitting proportion of the optical beam splitter is N1, one end of the optical beam splitter with the proportion of N is connected with the circulator port 1 through the adjustable optical attenuator, the circulator port 2 is an input/output port of synchronous light, one end of the optical beam splitter with the proportion of 1 is connected with the port 1 of the optical switch, the circulator port 3 is connected with the port 2 of the optical switch, and the output end of the optical switch is connected with the receiving end phase-locked loop through the PIN tube. The receiving end phase-locked loop is connected with the transmitting end phase-locked loop.
A link transmitting synchronization light, a synchronization light route: firstly, a signal output by a local crystal oscillator is connected into a phase-locked loop of a transmitting end Alice in a simplest synchronous optical transmitting QKD device, and after passing through the phase-locked loop, a synchronous optical driving signal is generated, the synchronous optical driving signal output by the phase-locked loop acts on a synchronous optical laser, synchronous light output by the synchronous optical laser passes through one end with the proportion of N of an optical beam splitter, then enters a circulator port 1, is output from the circulator port 2, passes through an optical fiber transmission, reaches the port 2 of the circulator in a complete QKD device, is output from the port 3 of the circulator, enters the port 2 of an optical switch, passes through a PIN tube, is converted into an electric signal and then is transmitted to a phase-locked loop of a receiving end Bob, and synchronization of the transmitting end Alice of the simplest synchronous optical transmitting QKD device of the QKD link 1 and the receiving end Bob of the complete QKD device is completed.
Synchronous optical path of another link: the phase-locked loop of the transmitting end Alice in the complete QKD device takes the phase-locked loop output of the receiving end Bob of the complete QKD device as a driving signal, so that the synchronous signal input by the phase-locked loop of the transmitting end Alice can be homologous to the synchronous signal output by the phase-locked loop of the receiving end Bob, but the transmitting end Alice of the complete QKD device does not generate synchronous light additionally. The output end of the optical beam splitter BS of the simplest synchronous optical transmission QKD device with the proportion of 1 is connected with the port 1 of the optical switch, and synchronous optical signals output by the optical switch enter a PIN tube for photoelectric conversion to obtain synchronous electric signals which are sent to a phase-locked loop of the receiving end Bob. Thereby completing the synchronization of the sender Alice of the complete QKD device of QKD link 2 and the receiver Bob of the simplest synchronous optical transmission QKD device.
In practice, two QKD devices operating in a pairing operation can receive upper layer "control system" control. The "control system" is connected to the two QKD devices that operate in pairing, respectively, and is configured to transmit the synchronization light by the transmitting end Alice of the simplest synchronization light transmitting QKD device. The optical switch in this system is set to port 1 gating at the same time as the optical switch in the other full QKD device is set to port 2 gating.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (8)

1. The quantum key distribution device used in the duplex quantum key distribution system is characterized by being a QKD device capable of being used as a sender or a receiver, wherein a synchronous optical device of the QKD device comprises a crystal oscillator, a sending-end phase-locked loop, a synchronous optical laser, an optical beam splitter, an adjustable optical attenuator, a circulator, an optical switch, a PIN tube and a receiving-end phase-locked loop;
the crystal oscillator is connected to the sending end phase-locked loop, the output end of the sending end phase-locked loop is connected with the synchronous optical laser, the output end of the synchronous optical laser is connected to the input end of the optical beam splitter, the light splitting proportion of the optical beam splitter is N1, one end of the optical beam splitter with the proportion of N is connected with the circulator port 1 through the adjustable optical attenuator, the circulator port 2 is an input/output port of synchronous light, one end of the optical beam splitter with the proportion of 1 is connected with the port 1 of the optical switch, the circulator port 3 is connected with the port 2 of the optical switch, the output end of the optical switch is connected with the receiving end phase-locked loop through the PIN tube, and the receiving end phase-locked loop is connected with the sending end phase-locked loop.
2. A quantum key distribution device for use in a duplex quantum key distribution system according to claim 1, wherein the optical switch is a 1*2 matrix optical switch.
3. A quantum key distribution device for use in a duplex quantum key distribution system according to claim 1, wherein the splitting ratio of the optical splitter is 9:1.
4. The quantum key distribution device used in the duplex quantum key distribution system is characterized in that the quantum key distribution device is used as a QKD device of a sender, the synchronous light device of the QKD device comprises a crystal oscillator, a sending end phase-locked loop, a synchronous light laser, an optical beam splitter, an adjustable optical attenuator, a circulator, an optical switch, a PIN tube and a receiving end phase-locked loop, wherein the crystal oscillator is connected to the sending end phase-locked loop, the output end of the sending end phase-locked loop is connected with the synchronous light laser, the synchronous light laser generates synchronous light to enter the optical beam splitter, the optical beam splitter splits the synchronous light according to the splitting proportion of N1, the synchronous light output by the synchronous light laser enters a circulator port 1 through one end of the optical beam splitter with the proportion of N and then enters the circulator port 2 through the adjustable optical attenuator, the synchronous light output by the synchronous light laser is connected with a port 1 of the optical switch through one end of the optical beam splitter with the proportion of 1, and the output end of the optical switch is connected with the receiving end phase-locked loop through the PIN tube.
5. A quantum key distribution device for use in a duplex quantum key distribution system according to claim 4, wherein the optical switch is a 1*2 matrix optical switch.
6. A quantum key distribution device for use in a duplex quantum key distribution system according to claim 4, wherein the splitting ratio of the optical splitter is 9:1.
7. The quantum key distribution device used in the duplex quantum key distribution system is characterized in that the quantum key distribution device is taken as a QKD device of a receiving party, a synchronous optical device of the QKD device comprises a crystal oscillator, a sending-end phase-locked loop, a circulator, an optical switch, a PIN tube and a receiving-end phase-locked loop, wherein the crystal oscillator is connected to the sending-end phase-locked loop, a port 2 of the circulator is an input port of synchronous light, a port 3 of the circulator is connected with a port 2 of the optical switch, an output end of the optical switch is connected with the receiving-end phase-locked loop through the PIN tube, and the receiving-end phase-locked loop is connected with the sending-end phase-locked loop.
8. A quantum key distribution device for use in a duplex quantum key distribution system according to claim 7, wherein the optical switch is a 1*2 matrix optical switch.
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JP2010206459A (en) * 2009-03-03 2010-09-16 Nec Corp Quantum key distribution system and method
CN104202157A (en) * 2014-09-16 2014-12-10 安徽量子通信技术有限公司 Quantum key distribution (QKD) system synchronization method and device
CN206060783U (en) * 2016-08-12 2017-03-29 上海国盾量子信息技术有限公司 Quantum key distribution device used in duplexing quantum key distribution system

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JP2010206459A (en) * 2009-03-03 2010-09-16 Nec Corp Quantum key distribution system and method
CN101764648A (en) * 2010-02-10 2010-06-30 南通墨禾量子科技发展有限公司 Polarization-preserving plug-and-play quantum secret communication system
CN104202157A (en) * 2014-09-16 2014-12-10 安徽量子通信技术有限公司 Quantum key distribution (QKD) system synchronization method and device
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