CN110519043A - Polarization feedback compensation method and system based on mode division multiplexing in a kind of quantum secret communication - Google Patents
Polarization feedback compensation method and system based on mode division multiplexing in a kind of quantum secret communication Download PDFInfo
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- CN110519043A CN110519043A CN201810489070.6A CN201810489070A CN110519043A CN 110519043 A CN110519043 A CN 110519043A CN 201810489070 A CN201810489070 A CN 201810489070A CN 110519043 A CN110519043 A CN 110519043A
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- 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
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6162—Compensation of polarization related effects, e.g., PMD, PDL
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- 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
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- 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
- H04B10/70—Photonic quantum communication
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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
- H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding
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Abstract
The present invention provides polarization feedback compensation method and system based on mode division multiplexing in a kind of quantum secret communication, comprising steps of S1, output signal light and reference light；S2, by signal light and with reference to after optical coupling by same root less fundamental mode optical fibre transmission；S3, the signal light after coupling and reference light are received and signal light and reference light are subjected to a beam splitting；S4, detectable signal light and real-time detection reference light, and judge whether reference light meets preset condition；If meeting, continue to test；If not meeting, S5 is entered step；The polarization state of S5, feedback reference light, and be adjusted according to polarization state of the polarization state of reference light to signal light.Without frequently interrupting QKD business, guarantees that quantum key distribution persistently carries out, improve system working efficiency, have positive promotion meaning for the construction of high speed quantum key distribution network.Additional wavelength channel resource will not be occupied, when setting up extensive quantum secret communication network, there is objective economic benefit.
Description
Technical field
The present invention relates to Technique on Quantum Communication field, more particularly in a kind of quantum secret communication based on mode division multiplexing
Polarize feedback compensation method and system.
Background technique
Quantum secret communication is compared with classical encryption and decryption, the characteristic with unconditional security.With related key technical
It continues to develop, quantum secret communication gradually moves towards Practical Project application from laboratory, is finance, electric power, government affairs and state
The realm informations business such as family's safety provide quantum safety guarantee.
Quantum secret communication is using single mode optical fiber channel as transmission medium at present, and quantum signal light is in the form of single mode in light
It is transmitted in fibre.
Quantum secret communication includes transmitting terminal Alice and receiving end Bob.Transmitting terminal (Alice) to quantum signal light into
Row polarization encoder, polarization encoder uses four non-orthogonal states as quantum information state, and four states are belonging respectively to two groups of conjugated radicles
It swears, two states in every group of basic vector are all mutually orthogonal.This four quantum information states are respectively that horizontal state of polarization H (is denoted as
→), perpendicular polarisation state V (being denoted as ↑) ,+45 ° of polarization state P (Ji Zuo ↗), -45 ° of polarization state N (Ji Zuo ↘).Horizontal state of polarization H and
Perpendicular polarisation state V each other one group of measurement basic vector+,+45 ° of polarization state P and -45 ° of polarization state N each other one group of measurement basic vector ×.It is based on
It is as follows that BB84 agreement carries out quantum secret communication process:
(1) single photon that Alice randomly chooses any polarization state in tetra- kinds of polarization states of H, V, P, N is sent to receiving end
Bob。
(2) Bob is randomly choosed+or × basic vector is measured to measure the photon polarization state received.
(3) which measurement of Bob told to Alice, Alice for used measurement basic vector when Bob announces its detection polarization state
Basic vector is correct, and is remained, remaining whole discards.
(4) Alice and Bob retains the polarization state for selecting identical basic vector, is translated into binary sequence according to agreement.Water
Flat polarization state H and+45 ° of polarization state P represents " 0 " bit, and perpendicular polarisation state V and -45 ° of polarization state N represent " 1 " bit.
(5) processes such as error correction, privacy amplification are then carried out and generate secure quantum key.
However in actual fiber communication link, paving mode is complicated, and optical fiber is vulnerable to external environment influence.It is especially aerial
Optical cable, since aerial optical cable is generally all laid on, liftoff more than ten even tens of meters of height are aerial, and optical cable is highly prone to strong wind, sleet
The interference of the weathers such as hail, frequent environmental perturbation cause fiber birefringence effect, so that polarization state generation can not in optical fiber
The acute variation of prediction, to cause to seriously affect to quantum key distribution (QKD) system based on polarization encoder, system is even
It can not work normally.Accordingly, it is desirable to provide a kind of polarization feedback compensating system solves the above problems.Polarize feedback compensating system
The polarization state that can guarantee the photon received by fiber channel is consistent with the photon polarization state of transmitting or almost consistent (fair
Perhaps lesser error rate), so as to guarantee that quantum secret communication system is suitable in the environment of all weather conditions and full geographical conditions
Ying Xing.Existing QKD polarization feedback compensation method mainly includes two kinds, and one is time-division multiplex technology is based on, another kind is to be based on
Wavelength-division multiplex technique.
For the QKD system using the polarization feedback compensation that is time-multiplexed, system needs frequent starting to polarize feedback compensation, from
And it can frequently interrupt QKD business.A kind of QKD system based on time division multiplexing polarization feedback compensation that the prior art is announced.Firstly,
System can set error rate threshold, and QKD system can be judged according to the error rate during quantum key distribution, if mistake
Rate is repeatedly more than set error rate threshold, can enable time division multiplexing polarization feedback.HV basic vector feedback is carried out first, and polarization is anti-
Feedback module request laser issues single H light, by adjusting receiving end electricity Polarization Controller until feedback is reached to H/V contrast
Until setting value.Carry out +/- basic vector feedback later, polarization feedback module request laser issues single+light, passes through adjusting
Until feedback until +/- contrast reaches setting value, feedback procedure terminates receiving end electricity Polarization Controller.Then be further continued for into
The quantum key distribution business in row new period.
Feedback compensation technique is polarized for wavelength-division multiplex, system will not frequently interrupt QKD business.G B Xavier et al. exists
Propose within 2009 a kind of method based on wavelength-division multiplex polarization feedback compensation.QKD sender, which increases, refers to radiant, reference light
Optical source wavelength and quantum signal optical wavelength interval 0.8nm, it is inclined with reference to polarization state and quantum signal light because of wavelength interval very little
Polarization state has very strong correlation.It is logical that quantum optical transport is coupled by wavelength division multiplexer after decaying with reference to radiant
Road.Reference light is separated with quantum signal light by solution wavelength division multiplexer in receiving end, reference light prepares module by reference to light
Beam splitting is tetra- tunnel PH, PV, PP, PN, is acquired respectively by PIN pipe, electric Polarization Controller is adjusted by polarization feedback algorithm, to adjust
It is whole to refer to polarization state.Because reference light wavelength and quantum signal optical wavelength are closely spaced, the variation of quantum signal polarization state and ginseng
It examines polarization state variation holding to synchronize, therefore adjusting also can the change of synchronous adjustment quantum signal polarization state with reference to polarization state variation
Change, achievees the purpose that feed back quantum signal light polarization.It needs frequently to interrupt QKD industry compared to time division multiplexing polarization feedback compensation
Business, wavelength-division multiplex polarization feedback compensating system can monitor to real-time online polarization state and change and corrected, reduction system into
The frequency of row polarization feedback compensation, improves the working efficiency of QKD business.
Feedback compensation technique is polarized for time division multiplexing, needs frequently to interrupt QKD business, it is close that this measure can significantly affect quantum
Key distributes efficiency, is unfavorable for the development of high speed quantum key distribution technology.
Feedback compensation technique is polarized for wavelength-division multiplex, needs additionally to increase reference light all the way, that is, needs to occupy optical-fiber network
In a channel.Under the conditions of wavelength resource is limited, busy channel both will affect the transmission of teledata business, also be unfavorable for
Multichannel quantum signal optical coupling is transmitted to improve quantum key distribution rate.
Summary of the invention
In view of the foregoing deficiencies of prior art, the purpose of the present invention is to provide be based in a kind of quantum secret communication
The polarization feedback compensation method and device of mode division multiplexing, for solving existing time division multiplexing polarization feedback compensation technique and wavelength-division
The problem of multiplexing polarization feedback compensation technique is individually present.Feedback compensation technique is polarized for time division multiplexing, needs frequently to interrupt
QKD business, this measure can significantly affect quantum key distribution efficiency, be unfavorable for the development of high speed quantum key distribution technology；For
Wavelength-division multiplex polarizes feedback compensation technique, needs additionally to increase reference light all the way, that is, needs to occupy a channel in optical-fiber network.In
Under the conditions of wavelength resource is limited, busy channel both will affect the transmission of teledata business, also be unfavorable for multichannel quantum signal
Optical coupling is transmitted to improve quantum key distribution rate.
The present invention provides the polarization feedback compensation method based on mode division multiplexing in a kind of quantum secret communication, comprising steps of
S1, output signal light and reference light；S2, by the signal light and it is described with reference to after optical coupling by same root less fundamental mode optical fibre channel
Transmission；S3, the signal light after coupling and the reference light are received and is carried out the signal light and the reference light primary
Beam splitting；Reference light described in S4, the detection signal light and real-time detection, and judge whether the reference light meets preset condition；
If meeting, continue to test；If not meeting, S5 is entered step；The polarization state of S5, the feedback reference light, and according to described
The polarization state of reference light is adjusted the polarization state of the signal light.
In one embodiment of the invention, the step S1 further comprises the steps of: S11, carries out the reference light of outgoing
Decaying；S12, the mode of the reference light after decaying is converted into higher order mode by basic mode.
In one embodiment of the invention, the step S3 further comprises the steps of: S31, by the reference after a beam splitting
Light progress is secondary to be beamed into reference light described in two beams；S32, reference light described in two beams after secondary beam splitting is divided three times respectively
Beam is divided into reference light described in four beams.
In one embodiment of the invention, the step S4 further comprise the steps of: S41, respectively the reference light described in four beams into
Row detection；S42, detection counting ratio is calculated, and judges that the detection is counted than whether not less than preset judgment threshold；If
It is, then return step S41；If it is not, then entering step S5.
In one embodiment of the invention, the step S5 further comprises the steps of: S51, progress voltage control signal issues, right
The polarization state of the reference light carries out correction compensation；S52, synchronization is compensated according to the correction that the polarization state to the reference light carries out
Correction compensation is carried out to the polarization state of the signal light.
The present invention also provides the polarization feedback compensating systems in a kind of quantum secret communication based on mode division multiplexing, comprising:
Transmitting terminal is used for output signal light；With reference to light emitting devices, for being emitted reference light；Pattern multiplexer is used for the signal
By same root less fundamental mode optical fibre transmission after light and the reference optical coupling；Pattern demultiplexer, after receiving coupling
The signal light and the reference light are simultaneously carried out a beam splitting by the signal light and the reference light；Receiving end, for receiving
The signal light after beam splitting；Reference light Polarization Detection module, for reference light described in real-time detection；Polarization control
Module for judging whether the reference light meets preset condition, and feeds back the polarization state of the reference light；Electric Polarization Control
Device, for being adjusted according to the polarization state of the reference light to the polarization state of the signal light.
In one embodiment of the invention, the light emitting devices that refers to includes: with reference to optical transmitting set, for being emitted reference
Light；Attenuator, for the reference light of outgoing to be decayed；Mode converter, for the reference light after decaying
Mode higher order mode is converted to by basic mode.
In one embodiment of the invention, the reference light Polarization Detection module includes: beam splitter, is used for a beam splitting
Reference light progress afterwards is secondary to be beamed into reference light described in two beams；Polarization-maintaining polarization beam apparatus, for will be after secondary beam splitting
Reference light described in two beams carries out beam splitting three times respectively, is divided into reference light described in four beams.
In one embodiment of the invention, the reference light Polarization Detection module further includes four detectors；It is multiple described
Detector is respectively used to the reference light described in four beams and detects；The polarization control module is also used to calculate detection and counts
Than, and judge that the detection is counted than whether being lower than preset judgment threshold, and count than lower than described in the detection
Voltage control signal is issued to the electric Polarization Controller when judgment threshold.
In one embodiment of the invention, the electricity Polarization Controller is also used to entangle the polarization state of the reference light
Positive compensation；And the correction compensation carried out according to the polarization state to the reference light is synchronized and is entangled to the polarization state of the signal light
Positive compensation.
As described above, polarization feedback compensation method in a kind of quantum secret communication of the invention based on mode division multiplexing and being
System, has the advantages that
Polarization feedback compensation is carried out to reference light in real time online, synchronizes and polarization feedback compensation is carried out to quantum signal light,
Therefore entirely during polarization feedback compensation, without frequently interrupting QKD business, guarantees that quantum key distribution persistently carries out, improve
System working efficiency has positive promotion meaning for the construction of high speed quantum key distribution network.
The wavelength of reference light is consistent with quantum signal optical wavelength, and only the two mode is different, will not occupy additional wavelength
Channel resource.So polarizing feedback technique compared to wavelength-division multiplex, a wavelength channel can be saved, is setting up extensive quantum
When secret communication network, there is objective economic benefit.
Detailed description of the invention
Fig. 1 is shown as in the present invention process side of the polarization feedback compensation method in quantum secret communication based on mode division multiplexing
Frame schematic diagram.
The structure that Fig. 2 is shown as in the present invention in quantum secret communication the polarization feedback compensating system based on mode division multiplexing is shown
It is intended to.
Fig. 3 is shown as the structural schematic diagram of an embodiment in Fig. 2.
Component label instructions:
1 transmitting terminal
2 refer to light emitting devices
3 pattern multiplexers
4 pattern demultiplexers
5 less fundamental mode optical fibres
6 receiving ends
7 reference light Polarization Detection modules
8 polarization control modules
9 electric Polarization Controllers
21 refer to optical transmitting set
22 attenuators
23 mode converters
71 beam splitters
72 polarization-maintaining polarization beam apparatus
D0~D3 detector
Specific embodiment
Illustrate embodiments of the present invention below by way of specific specific example, those skilled in the art can be by this specification
Other advantages and efficacy of the present invention can be easily understood for disclosed content.The present invention can also pass through in addition different specific realities
The mode of applying is embodied or practiced, the various details in this specification can also based on different viewpoints and application, without departing from
Various modifications or alterations are carried out under spirit of the invention.It should be noted that in the absence of conflict, following embodiment and implementation
Feature in example can be combined with each other.
It should be noted that illustrating the basic structure that only the invention is illustrated in a schematic way provided in following embodiment
Think, only shown in diagram then with related component in the present invention rather than component count, shape and size when according to actual implementation
Draw, when actual implementation kenel, quantity and the ratio of each component can arbitrarily change for one kind, and its assembly layout kenel
It is likely more complexity.
Referring to Fig. 1 to Fig. 3, it should however be clear that the appended diagram of this specification depicted structure, ratio, size etc., only to match
The revealed content of specification is closed, so that those skilled in the art understands and reads, is not intended to limit the invention implementable
Qualifications, therefore do not have technical essential meaning, the modification of any structure, the change of proportionate relationship or the adjustment of size,
In the case where not influencing the effect of present invention can be generated and the purpose that can reach, should all still fall in disclosed technology
In the range of Rong get Neng is covered.Meanwhile it is cited such as "upper", "lower", "left", "right", " centre " and " one " in this specification
Deng term, be merely convenient to being illustrated for narration, rather than to limit the scope of the invention, the change of relativeness
Or adjustment, under the content of no substantial changes in technology, when being also considered as the enforceable scope of the present invention.
As shown in Figure 1, Fig. 1 is shown as in the present invention polarization feedback compensation side in quantum secret communication based on mode division multiplexing
The process blocks schematic diagram of method.The present invention provides the polarization feedback compensation sides in a kind of quantum secret communication based on mode division multiplexing
Method, comprising steps of
S1, output signal light and reference light；In the present invention, it is basic mode that signal light, which goes out emission mode, by signal light polarization
Preparation and attenuation module prepare other H, V, P, N polarised light of required single-photon-level.Reference optical signal is identical as signal optical signal,
Mode is similarly basic mode.The signal light and reference light for selecting phase co-wavelength and mode, will not occupy additional wavelength resource.One
In preferred embodiment, step S1 further comprises the steps of: S11, the reference light of outgoing is decayed；S12, by the reference light after decaying
Mode higher order mode is converted to by basic mode.It is in order to avoid too strong reference light is to quantum to the purpose that reference light is decayed
Signal light generates interference.In the present embodiment, higher order mode can be LP11Mode or other high-order modes.
S2, by signal light and with reference to after optical coupling by same root less fundamental mode optical fibre transmission；In one embodiment, basic mode
Quantum signal light is coupled into same root less fundamental mode optical fibre channel by pattern multiplexer with high-order mode reference light and is transmitted.Few mould
Optical fiber supports limited several transmission modes, can improve effectiveness by mode multiplexing.Compared with single mode optical fiber, few mould
Optical fiber attenuation is suitable, and mode field diameter is bigger, and nonlinear effect is lower, and the mode of support is more, and channel capacity is bigger.With multimode light
Fibre is compared, and is decayed smaller, and transmission range is farther, and is interfered between mode less, and different mode is convenient for individually control.
S3, the signal light after coupling and reference light are received and signal light and reference light are subjected to a beam splitting；In general, primary
Beam splitting is by pattern demultiplexer by signal light and reference light beam splitting.Further, step S3 further comprises the steps of: S31, by one
Reference light after secondary beam splitting carries out secondary being beamed into two beam reference lights；S32, two beam reference lights after secondary beam splitting are carried out respectively
Beam splitting three times is divided into four beam reference lights.In general, reference light is divided into two beams by beam splitter, using two polarization-maintaining polarizations point
After beam device, be divided into PH, PV, PP, PN four bundles light, respectively by the 0th detector D0, the first detector D1, the second detector D2,
Tetra- detector detections of third detector D3.
S4, detectable signal light and real-time detection reference light, and judge whether reference light meets preset condition；If meeting,
It continues to test；If not meeting, S5 is entered step；In the preferred embodiment of the present invention, step S4 further comprise the steps of: S41,
Four beam reference lights are detected respectively；S42, calculating, which detect, counts ratio, and judges whether detection counting ratio is not less than and set in advance
Fixed judgment threshold；If so, return step S41；If it is not, then entering step S5.
The polarization state of S5, feedback reference light, and be adjusted according to polarization state of the polarization state of reference light to signal light.In
In a preferred embodiment of the present invention, step S5 further comprises the steps of: S51, progress voltage control signal issues, to the inclined of reference light
Polarization state carries out correction compensation；S52, according to the correction compensation that the polarization state of reference light is carried out synchronize to the polarization state of signal light into
Row corrects compensation.Detection by detecting reference light counts ratio, when counting than lower than given threshold, carries out voltage control signal
It issues, voltage control signal is to be handed down to electric Polarization Controller, is corrected by electric Polarization Controller to reference polarization state.
It in the present embodiment, can be by being visited to the 0th detector D0, the first detector D1, the second detector D2, third
It surveys device D3 detection and counts than D0/D1, D2/D3 and judge optical fiber link polarization variations.If detection counts lower than D0/D1, D2/D3
In decision threshold set in advance, then electric Polarization Controller is carried out under voltage control signal by polarization control module
Hair guarantees that detection is counted than D0/D1, D2/D3 on decision threshold set in advance.In this manner it is possible to complete to reference
The correction compensation of polarization state variation.Because reference light wavelength is identical with signal light wavelength, only mode is different, according to ginseng
It examines polarization state variation and adjusts electric Polarization Controller to change progress feedback compensation to optical fiber link polarization state, so that synchronous correct
The variation of quantum signal polarization state achievees the effect that synchronization carries out polarization feedback compensation to quantum signal light in real time.
As shown in Figure 2 to Figure 3, Fig. 2 is shown as in the present invention feedback of the polarization in quantum secret communication based on mode division multiplexing
The structural schematic diagram of compensation system.Fig. 3 is shown as the structural schematic diagram of an embodiment in Fig. 2.The present invention also provides a kind of amounts
Polarization feedback compensating system in sub- secret communication based on mode division multiplexing, comprising: transmitting terminal 1 is used for output signal light；Reference light
Emitter 2, for being emitted reference light；Pattern multiplexer 3, for lacking mould by same root by signal light and with reference to after optical coupling
5 transmission of optical fiber；Pattern demultiplexer 4, for receiving the signal light after coupling and reference light and by signal light and reference light
Carry out a beam splitting；Receiving end 6, for receiving the signal light after a beam splitting；Reference light Polarization Detection module 7, for real-time
Detect reference light；Polarization control module 8, for judging whether reference light meets preset condition, and feedback reference light is inclined
Polarization state；Electric Polarization Controller 9, for being adjusted according to the polarization state of reference light to the polarization state of signal light.
In use, 1 output signal light of transmitting terminal, is emitted reference light with reference to light emitting devices 2；In the present invention, signal light
Emission mode is basic mode out, prepares required single-photon-level other H, V, P, N by the preparation of signal light polarization and attenuation module and polarizes
Light.The reference optical signal launched with reference to light emitting devices 2 is identical with signal optical signal, and mode is similarly basic mode.Joining
Light is examined after mode converter is converted into higher order mode, wavelength is still identical as signal light holding, will not occupy additional wave
Long channel.Pattern multiplexer 3 by signal light and with reference to after optical coupling by 5 transmission of same root less fundamental mode optical fibre；Implement one
In example, basic mode quantum signal light and high-order mode reference light by pattern multiplexer 3 be coupled into 5 channel of same root less fundamental mode optical fibre into
Row transmission.Less fundamental mode optical fibre 5 supports limited several transmission modes, can improve effectiveness by mode multiplexing.With single mode
Optical fiber is compared, and less fundamental mode optical fibre 5 is decayed quite, and mode field diameter is bigger, and nonlinear effect is lower, and the mode of support is more, and channel holds
It measures bigger.Compared with multimode fibre, decay smaller, transmission range is farther, and interferes less between mode, and different mode is convenient for
Individually control.Pattern demultiplexer 4 is reached after first passing through electric Polarization Controller 9, pattern demultiplexer 4 receives the signal after coupling
Signal light and reference light are simultaneously carried out a beam splitting by light and reference light；In general, a beam splitting will be believed by pattern demultiplexer 4
Number light and reference light beam splitting.Receiving end 6 receives the signal light after a beam splitting；Reference light Polarization Detection module 7 receives primary point
Reference light after beam is simultaneously detected.Polarization control module 8 judges whether reference light meets default item according to detection result
Part, and the polarization state of feedback reference light gives electric Polarization Controller 9.Electric Polarization Controller 9 is fed back according to polarization control module 8
The polarization state of reference light the polarization state of signal light is adjusted.
It in one embodiment of this invention, include: with reference to optical transmitting set 21, for being emitted reference with reference to light emitting devices 2
Light；
Attenuator 22, for the reference light of outgoing to be decayed；Mode converter 23, for the reference light after decaying
Mode higher order mode is converted to by basic mode.It is in order to avoid too strong reference light is to quantum to the purpose that reference light is decayed
Signal light generates interference.In the present embodiment, higher order mode can be LP11 mode or other high-order modes.
Further, reference light Polarization Detection module 7 includes: beam splitter 71, for by the reference light after a beam splitting into
Row is secondary to be beamed into two beam reference lights；Polarization-maintaining polarization beam apparatus 72, for carrying out two beam reference lights after secondary beam splitting respectively
Beam splitting three times is divided into four beam reference lights.
Preferably, reference light Polarization Detection module 7 further includes four detectors；Multiple detectors are respectively used to join four beams
Light is examined to be detected；Polarization control module 8 is also used to calculate detection and counts ratio, and judges that detection is counted than whether lower than pre-
The judgment threshold first set, and voltage control signal is issued to electricity polarization control when the detection is counted than lower than judgment threshold
Device 9 processed.
Further, electric Polarization Controller 9 is also used to carry out correction compensation to the polarization state of reference light；And according to reference
The correction compensation that the polarization state of light carries out, which is synchronized, carries out correction compensation to the polarization state of signal light.In general, reference light passes through beam splitting
Device 71 is divided into two beams, after two polarization-maintaining polarization beam apparatus 72, is divided into PH, PV, PP, PN four bundles light, respectively by the 0th
Tetra- detector D0, the first detector D1, the second detector D2, third detector D3 detector detections.In the present embodiment, may be used
With by the 0th detector D0, the first detector D1, the second detector D2, third detector D3 detection count than D0/D1,
D2/D3 judges optical fiber link polarization variations.If detection is counted than D0/D1, D2/D3 lower than decision threshold set in advance
Value then carries out voltage control signal by 8 pairs of polarization control module electric Polarization Controllers 9 and issues, guarantees that detection counts ratio
D0/D1, D2/D3 are on decision threshold set in advance.In this manner it is possible to complete the correction changed to reference polarization state
Compensation.Because reference light wavelength is identical with signal light wavelength, only mode is different, is changed according to reference polarization state and is adjusted
Electric Polarization Controller 9 carries out feedback compensation to change to optical fiber link polarization state, so that synchronous correct quantum signal polarization state
Variation achievees the effect that synchronization carries out polarization feedback compensation to quantum signal light in real time.
In conclusion polarization feedback compensation method and system in quantum secret communication of the invention based on mode division multiplexing,
Polarization feedback compensation is carried out to reference light in real time online, synchronizes and polarization feedback compensation is carried out to quantum signal light, thus it is entire inclined
It shakes during feedback compensation, without frequently interrupting QKD business, guarantees that quantum key distribution persistently carries out, improve system work
Efficiency has positive promotion meaning for the construction of high speed quantum key distribution network.The wavelength and quantum signal light of reference light
Wavelength is consistent, and only the two mode is different, will not occupy additional wavelength channel resource.So anti-compared to wavelength-division multiplex polarization
Feedback technology can save a wavelength channel, when setting up extensive quantum secret communication network, have objectively economic effect
Benefit.So the present invention effectively overcomes various shortcoming in the prior art and has high industrial utilization value.
The above-described embodiments merely illustrate the principles and effects of the present invention, and is not intended to limit the present invention.It is any ripe
The personage for knowing this technology all without departing from the spirit and scope of the present invention, carries out modifications and changes to above-described embodiment.Cause
This, institute is complete without departing from the spirit and technical ideas disclosed in the present invention by those of ordinary skill in the art such as
At all equivalent modifications or change, should be covered by the claims of the present invention.
Claims (10)
1. the polarization feedback compensation method in a kind of quantum secret communication based on mode division multiplexing, which is characterized in that comprising steps of
S1, output signal light and reference light；
S2, by the signal light and it is described with reference to after optical coupling by same root less fundamental mode optical fibre transmission；
S3, the signal light after coupling and the reference light are received and is once divided the signal light and the reference light
Beam；
Reference light described in S4, the detection signal light and real-time detection, and judge whether the reference light meets preset condition；If
Meet, then continues to test；If not meeting, S5 is entered step；
The polarization state of S5, the feedback reference light, and according to the polarization state of the reference light to the polarization state of the signal light into
Row adjustment.
2. the polarization feedback compensation method in quantum secret communication according to claim 1 based on mode division multiplexing, feature
It is, the step S1 is further comprised the steps of:
S11, the reference light of outgoing is decayed；
S12, the mode of the reference light after decaying is converted into higher order mode by basic mode.
3. the polarization feedback compensation method in quantum secret communication according to claim 1 based on mode division multiplexing, feature
It is, the step S3 is further comprised the steps of:
S31, the reference light after a beam splitting is carried out secondary to be beamed into reference light described in two beams；
S32, reference light described in two beams after secondary beam splitting is subjected to beam splitting three times respectively, is divided into reference light described in four beams.
4. the polarization feedback compensation method in quantum secret communication according to claim 3 based on mode division multiplexing, feature
It is, the step S4 is further comprised the steps of:
S41, the reference light described in four beams detects respectively；
S42, detection counting ratio is calculated, and judges that the detection is counted than whether not less than preset judgment threshold；If so,
Then return step S41；If it is not, then entering step S5.
5. the polarization feedback compensation in quantum secret communication according to any one of claims 1 to 4 based on mode division multiplexing
Method, which is characterized in that the step S5 is further comprised the steps of:
S51, progress voltage control signal issue, and carry out correction compensation to the polarization state of the reference light；
S52, the correction compensation carried out according to the polarization state to the reference light are synchronized and are entangled to the polarization state of the signal light
Positive compensation.
6. the polarization feedback compensating system in a kind of quantum secret communication based on mode division multiplexing characterized by comprising
Transmitting terminal (1) is used for output signal light；
With reference to light emitting devices (2), for being emitted reference light；
Pattern multiplexer (3), for by the signal light and it is described with reference to after optical coupling by same root less fundamental mode optical fibre (5) channel
Transmission；
Pattern demultiplexer (4), for receiving the signal light after coupling and the reference light and by the signal light and institute
It states reference light and carries out a beam splitting；
Receiving end (6), for receiving the signal light after a beam splitting；
Reference light Polarization Detection module (7), for reference light described in real-time detection；
Polarization control module (8) for judging whether the reference light meets preset condition, and feeds back the reference light
Polarization state；
Electric Polarization Controller (9), for being adjusted according to the polarization state of the reference light to the polarization state of the signal light.
7. the polarization feedback compensating system in quantum secret communication according to claim 6 based on mode division multiplexing, feature
It is, it is described to include: with reference to light emitting devices (2)
With reference to optical transmitting set (21), for being emitted reference light；
Attenuator (22), for the reference light of outgoing to be decayed；
Mode converter (23), for the mode of the reference light after decaying to be converted to higher order mode by basic mode.
8. the polarization feedback compensating system in quantum secret communication according to claim 6 based on mode division multiplexing, feature
It is, the reference light Polarization Detection module (7) includes:
Beam splitter (71) secondary is beamed into reference light described in two beams for carrying out the reference light after a beam splitting；
Polarization-maintaining polarization beam apparatus (72) is divided into for reference light described in two beams after secondary beam splitting to be carried out beam splitting three times respectively
At reference light described in four beams.
9. the polarization feedback compensating system in quantum secret communication according to claim 8 based on mode division multiplexing, feature
It is, the reference light Polarization Detection module (7) further includes four detectors；Multiple detectors are respectively used to four beam institutes
Reference light is stated to be detected；
The polarization control module (8) is also used to calculate detection and counts ratio, and judges that whether the detection counting than is lower than
Preset judgment threshold, and voltage control signal is issued to institute when the detection is counted than being lower than the judgment threshold
State electric Polarization Controller (9).
10. according to the polarization feedback compensation in quantum secret communication described in claim 6 to 9 any one based on mode division multiplexing
System, which is characterized in that the electricity Polarization Controller (9) is also used to carry out correction compensation to the polarization state of the reference light；And
The correction compensation carried out according to the polarization state to the reference light, which is synchronized, carries out correction compensation to the polarization state of the signal light.
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