CN104092538B - Multi-user wavelength division multiplexing QKD network system and secret key distributing and sharing method thereof - Google Patents
Multi-user wavelength division multiplexing QKD network system and secret key distributing and sharing method thereof Download PDFInfo
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Abstract
The invention discloses a multi-user wavelength division multiplexing quantum key distribution network system and a secret key distributing and sharing method thereof. The system comprises an Alice control end, a pulse conveying line and a Bob user end. The secret key distributing and sharing method comprises two stages of secret key distributing and sharing, wherein Alice and a plurality of Bob users carry out quantum secret key distributing and storing, and secret key priority is set; and Alice uses a secret key with low priority for encrypting a secret key with high priority into a ciphertext, then the ciphertext is sent to a user with low priority, the user with the low priority uses the secret key with low priority for decrypting the ciphertext, and the secret key with high priority is obtained. The system is reasonable, convenient to operate and low in cost, users in a network are relatively independent, the stability of the secret key generating rate of a single user is guaranteed, the secret key generating rate cannot be decreased along with increasing of users, meanwhile, a two-level equal-difference frequency space wave length planning scheme and an accurate pulse delaying technology are used, and mutual interference of pulses between different users is removed.
Description
Technical field
The present invention relates to fiber optic communication and quantum communication network field, more particularly, to a kind of multi-user's wavelength-division multiplex
QKD (quantum key distribution) network systems and its key distribution and sharing method.
Background technology
The safety of conventional cipher technology is ensured by mathematical computation complexity, but the calculating energy in the face of becoming stronger day by day
Power, its safety are subject to grave danger.The safety of quanta cryptology technique does not rely on the complexity of calculating, but is based on quantum
Mechanics ultimate principle, i.e. Heisenberg uncertainty principle and the unclonable principle of unknown quantum state.Quantum key distribution (Quantum
Key Distribution, QKD) in the way of being perfectly safe, the legal participant in diverse geographic location can be allowed (generally to use
Alice is represented with Bob) share key, it can be free space or optical fiber that the key of both sides sends channel, using optical fiber conduct
The QKD of transmission channel has made significant headway.
The QKD that great majority are realized at present adopts the polarization or phase place of faint light pulse as the carrier of information.But by
In the impact of the birefringence and environment of optical fiber, it is difficult to be deployed to actual fiber optic network link based on the system of Polarization Modulation enterprising
The remote key distribution of row, even if the system based on phase-modulation also can be affected by fiber birefringence.Plug and play system
A kind of system --- round QKD system, eliminates the shadow brought to system by which with by automatic compensated optical fiber birefringence effect
Ring, therefore in transmitting procedure, do not need any polarization control system to ensure that operation of the system in longer period of time
Stability.But optical fiber QKD major parts are all point-to-point applications at present, it is impossible to directly extend multiple-user network application, this is to limit
Which moves towards one of major obstacle of large-scale application.
Existing QKD networks mainly adopt two kinds of technologies at present：A kind of is the QKD networks based on optical nodes, optics section
Point can be beam splitter, photoswitch, wavelength division multiplexer or other PASSIVE OPTICAL devices；Another kind is based on credible relaying
QKD networks, its difficult point are the reliability for keeping relaying.Compared to second QKD network, the QKD networks based on optical nodes
The absolute reliability of optical nodes need not be must assure that.Based on the quantum key distribution network of beam splitter have safety it is good, hold
The advantage easily realized, but an obviously shortcoming is there is also, it is exactly that its network extension can have a strong impact on the life of single user key
Into rate and transmission range.The average photon number of Alice transmittings is divided into N parts for the light pulse device that is split of μ, and wherein N is number of users,
The average photon number for being so sent to each receiving terminal Bob is μ/N, then final key production rate can subtracting because of number of photons
N/mono- of single user key production rate is reduced to less.With the increase of number of users N, the transmission range and single user key of network
Production rate all can reduce therewith at double.Based on early wavelength-division multiplex technique (Wavelength Division Multiplexing,
WDM) although tunable wavelength light source multi-user QKD schemes can no longer by launch party Alice launch pulse give not
Same user, but the pulse that synchronization laser instrument is produced remains as single wavelength pulse, can only serve sole user, and this makes
Into the predicament that multi-user can not work simultaneously, and from the point of view of length of a game, the key production rate of single user is still locked into
Userbase, i.e., with the increase of number of users, the key production rate of single user can reduce.Although all trying in follow-up improvement project
Diagram is determined the problem that reduces with the increase of number of users of key production rate, but new problem occurs therewith, such as different user it
Between interfere, this increased unnecessary error code to user in network, and the practical feasibility of these schemes also needs
Further verify.
The content of the invention
The primary and foremost purpose of the present invention is to provide a kind of multi-user's wavelength-division multiplex quantum key distribution network system, and the system will
The carrier that the multi-Wavelength Pulses that single light source multiple-wavelength laser is produced simultaneously are transmitted as multi-user information, by each wavelength pulse
Different validated users are sent to, each user is relatively independent, it is ensured that the key production rate of single user is stable, will not be with user's
Increase and reduce.
A further object of the present invention is a kind of the close of application multi-user wavelength-division multiplex quantum key distribution network system of proposition
Key is distributed and sharing method.
For achieving the above object, the present invention takes technical scheme below：
A kind of multi-user's wavelength-division multiplex quantum key distribution network system, including Alice control ends, pulse conveying circuit and
Bob user sides, Alice control ends are connected with Bob user sides by pulse conveying circuit.
The Alice control ends include multi-Wavelength Pulses generator, circulator, bonder, non-equilibrium interferometer and
Two multi-wavelength single photon detecting elements；Multi-Wavelength Pulses generator output pulse group after circulator, by coupling
Device is injected into non-equilibrium interferometer, sequentially includes short delay line, single phase-modulator and partially on non-equilibrium interferometer is long-armed
Shake beam splitter, and non-equilibrium interferometer galianconism connects polarization beam apparatus, and a multi-wavelength single photon detecting element connects coupling by circulator
The input of device, another multi-wavelength single photon detecting element connect the coupled end of bonder；
The Bob user sides include beam splitter, the upper branch road for modulating pulse loading phase information and for for upper
Road provides the lower branch road of reference information and system security monitoring, and the polarization beam apparatus in Alice control ends pass through pulse pipeline
Road connects the beam splitter of Bob user sides, and the outfan of beam splitter connects upper and lower branch road respectively；
Variable optical attenuator that the upper branch road includes being sequentially connected with, pulse delay apparatus, fibre delay line, phase-modulation
Device and reflection unit, the upper output termination variable optical attenuator of beam splitter；
The lower branch road includes the variable optical attenuator being sequentially connected with and classical detector, and the lower output termination of beam splitter is another
One variable optical attenuator.
Multi-Wavelength Pulses generator can be produced and meet multiple users while the required multiwavelength laser pulse of communication, is somebody's turn to do
Pulse generation schemes can both reduce pulses generation and control cost, can abandon pulse produced by single wavelength light source prescription case again
Diversity.The long-armed single phase-modulator of non-equilibrium interferometer loads phase information for all users in network simultaneously,
Single phase-modulator replaces conventional multi-phase modulator structure, it is ensured that while phase-modulation concordance and stability,
Also reduce system cost.Two multi-wavelength single photon detecting elements according to return pulse interferometer outfan interference feelings
Condition, records result of interference respectively, and in multi-wavelength single photon detecting element the response of a certain wavelength detection device whether, be with
Corresponding wavelength pulse whether there occurs constructive interference.Multi-wavelength single photon detecting element can enter after each detection event
Enter dormancy time, i.e., the interference caused by afterpulse is eliminated by adding the dead time and counted, reduce error rate of system.
Incident pulse is divided into strong and weak two-way by every Bob user, and upper branch road (weaker all the way) is for modulating pulse loading
Phase information, lower branch road (relatively by force all the way) are mainly used in providing reference information and system security monitoring for upper branch road.Upper branch road leads to
Extra pulse time-delay mechanism arranges the pulse delay of each Bob user, enables the pulse of each user almost while returning to
Alice ends.Fibre delay line is arranged to the Rayleigh scattering light of high power pulse before then aiming at elimination, allows return pulse to stagger stronger
The Rayleigh scattering light that forward direction high power pulse is produced.The incident pulse of lower branch road by variable optical attenuator which is carried out suitably decay in case
Only detector saturation, is finally received by classical detector, provides time reference for upper branch road displacement modulation, and foundation enters
Penetrate the information such as the strong and weak change of pulse security monitoring service is provided for system.
The multi-wavelength single photon detecting element includes multiple single-photon detectors and a wavelength division multiplexer, multiple monochromatic lights
Sub- detector is connected with wavelength division multiplexer.
In a kind of preferred scheme, the multi-Wavelength Pulses generator includes that the single light source multi-Wavelength Pulses for connecting swash
Light device and wavelength selector.Single light source multi-wavelength pulse laser is required for producing the simultaneously communication that disclosure satisfy that multiple users
Multiwavelength laser pulse.Wavelength selector selects the wavelength pulse for being suitable for that each Bob user uses according to Wavelength Assignment planning, and
The motility that its wavelength is selected provides possibility for the change of user's wavelength and user's increase and decrease of multiple-user network, increased network
Expansibility.
It is as faraday mirror is capable of the birefringence effect of compensated optical fiber automatically, then in a kind of preferred scheme, described anti-
Injection device is faraday mirror, that is, go up branch road by faraday mirror to change pulse transmission direction.
In a kind of preferred scheme, the pulse conveying circuit includes first connected by wavelength routing apparatus
Optical fiber and some the second optical fiber, the quantity of the second optical fiber are identical with Bob user side quantity.
Wherein the first optical fiber is common optical fiber, and the second optical fiber is special optic fibre.As each Bob user distributions are disperseed, it is impossible to
Only pulse is conveyed using a circuit, therefore the system takes two-stage conveying circuit.According to user distribution, common optical fiber and dedicated optical
Fine length ratio can be adjusted, and usually, common optical fiber is long as far as possible, and special optic fibre is short as far as possible, it is therefore intended that allow
Each Bob user's pulse paths traversed difference is as little as possible, reduces the time jitter and difference for returning that pulse reaches Alice ends
Step difference.
Wavelength routing apparatus control the Path selection of each wavelength pulse signal, in a kind of preferred scheme, the wavelength
Route device is any one in wavelength division multiplexer, array waveguide grating, Bragg grating or wavelength-selective switches.
In a kind of preferred scheme, the long-armed and galianconism of the non-equilibrium interferometer is polarization maintaining optical fibre, inclined using protecting
Optical fiber is suppressing polarization effect.
Due to the weak signal feature of quantum communication system, the wavelength planning of quantum communication network is meeting this ITU-T wavelength
While standard, it is also necessary to take into full account four-wave mixing effect.One important starting point of wavelength planning seeks to allow four ripples to mix
Wavelength of the new frequencies of light that frequency is produced far as possible from this four pulse signals.Select one kind effectively reduce in the present invention
The wavelength programme that four-wave mixing effect affects, wavelength selector select wavelength by the way of two grades of equal difference frequency intervals.
The wavelength channel planning and designing of this appropriate unequal-interval, can make the new frequencies of light of generation most of away from other letters
Number wavelength, and the efficiency of four-wave mixing reduced as wavelength interval increases, and systematic influence is further reduced.With following several
As a example by individual wavelength, fi、fi+1=fi+Δf、fi+2=fi+2Δf、fi+3=fi+3Δf、fi+4=fi+4Δf、fi+5=fi+5Δf、
fi+6=fi+6Δf、fi+7=fi+7Δf、fi+8=fi+8Δf、fi+9=fi+ 9 Δ f ... Δs f are to meet ITU-T standards of wavelength
Frequency interval, fiWith fi+1、fi+3And fi+6The new frequencies of light for producing is respectively fi+2、fi+6And fi+12, fi+1With fi+3And fi+6Produce
New frequencies of light be respectively fi+5And fi+11, fi+3With fi+6The new frequencies of light for producing is fi+9, due to fiWith fi+3Interval it is larger, produce
Raw new frequencies of light fi+6It is relatively weak, therefore frequency is adopted for f in the present inventioni、fi+1、fi+3、fi+6、fi+10Deng light pulse conduct
The physical support of information transfer.
A kind of key distribution of application multi-user wavelength-division multiplex quantum key distribution network system and sharing method, the method
Comprise the following steps：
S1. system initialization：Alice and each Bob subscriber software-hardwares facility are checked, check whether equipment can run well,
Set the primary conditions such as correct running voltage, suitable operating temperature；
S2. system noise test：On the premise of Alice does not launch laser pulse train, i.e., when train of pulse number is zero, test
System noise levels, it is ensured that below the zone of reasonableness of design；
S3. fiber lengths test and pulse delay are arranged：Alice sends one group of high power pulse, and each Bob user is by measuring arteries and veins
Due in is rushed, fiber lengths in link are determined, according to the length relation of optical fiber between each Bob user and Alice, arranges each
Bob user's time delay；
Alice launches one group of high power pulse again, and Alice is returned after being decayed by Bob user, measures due in, comes and goes adjustment
Bob user's time delay is arranged, to reach pulse that each Bob user returns again to almost arrival Alice ends simultaneously；
S4. key sends：Alice sends train of pulse to Bob user in units of frame, sends the frame of certain amount every time,
Time interval between frame and frame is referred to as frame rate, frame by burst blocks into；Bob user is modulated and is decayed after receiving pulse
Return to after single photon level, the pulse returned from different Bob users reaches Alice simultaneously and is loaded same phase information；
Voltage and pulsing previous existence needed for modulation pulse into real random code it is corresponding, as the selection of respective base, Alice and
Bob user is needed according to each own coding, selects different phase voltage modulation impulse phases；
S5. testing keys with into code：Alice records the probe response event of multi-wavelength detection device, public with each Bob user
Comparison base is opened, screening key is formed；Then some data of random choose in screening key, judge whether eavesdropping, judge
Afterwards, selected data are rejected；Again remaining data are carried out with data harmonization and close property is amplified, obtain final safe key；
Safe key step-by-step is stored, and plus storage prefix before every group of safe key, the storage prefix of safe key is sent out using key
Send the time；Priority settings are carried out to safe key；The setting of priority can be entered from high to low according to the number order of Bob
OK.
Between S6.Bob user, key is shared：According to the key priority set in step S5, when safe key priority is：
Bob_i>Bob_j>Bob_k>During Bob_l, Bob_i and Bob_k carries out key and shares.
The key priority of Bob_i is more than Bob_k, so Bob_k to be shared the key of Bob_i；Alice is used as middle node
Point, is encrypted to the key of Alice and Bob_i first by the key of Alice and Bob_k, then will be the Bob_i of encryption close
Key is sent to Bob_k, and Bob_k is decrypted after receiving ciphertext, obtained the key of Bob_i, so just have shared key with Bob_i；Its
His situation is identical with this.
Between Bob user, the shared key with exclusiveness, i.e. Bob user of key can only be entered with other some Bob user
Row is shared, after sharing can not again with other Bob users to share.
It is a kind of technology that data security is improved by open communication that wherein close property is amplified, through above-mentioned data harmonization
Afterwards, sender Alice is highly consistent with the data that recipient Bob possesses, and the bit error rate is very low, but listener-in Eve may know that portion
Divided data, in order to improve the confidentiality of data, Alice and Bob makes what Eve knew to reduce information that they possess as cost
Quantity of information is changed into invalid.
Compared with prior art, beneficial effects of the present invention are：
1), wavelength-division multiplex technique ensure that relatively independent between each user, and the key production rate of single user will not be with
The increase of user and reduce；2), the wavelength programme of two grades of equal difference frequency intervals and accurately pulse delay technology, eliminate
Pulse between different user is interfered, and reduces error rate of system；3), single light source multiple-wavelength laser replaces multiple light courcess
Structure, reduces the cost of sender unit, and single phase-modulator replaces multi-phase modulator structure, it is ensured that phase-modulation
While concordance and stability, system cost is also reduced；4), user terminal adopts Variable delay device, adjusts each user
Between return pulse the return moment, it is ensured that the motility of network；5) each device for, adopting in system is ripe, overall plan
Can increase with higher exploitativeness, and number of users, with good expansion.
Description of the drawings
Fig. 1 is wavelength-division multiplex quantum key distribution network diagram.
Fig. 2 is multi-user's wavelength-division multiplex quantum key distribution network system of the present invention.
Fig. 3 is phase modulation process schematic diagram.
Fig. 4 is the flow chart of key distribution and shared procedure.
Fig. 5 is quantum bit error rate and number of users and the graph of a relation of transmission range.
Fig. 6 is the graph of a relation for screening key rate and quantum bit error rate with distance change.
Specific embodiment
Accompanying drawing being for illustration only property explanation, it is impossible to be interpreted as the restriction to this patent；
In Fig. 1：101- common optical fibers；102- wavelength routing apparatus；103rd, 104,105,106- special optic fibres；
In Fig. 2：201- multiple-wavelength laser MW-LD；202- wavelength screening washer WS；203- light path circulator CIR；204、
205- multi-wavelength single photon detecting element MW-SPD；206- bonder C；207th, 221,229,237,245- delay line DL；208、
222nd, 230,238,246- phase-modulator PM；209- is long-armed；210- polarization beam apparatus PBS；211- galianconism；212、214、215、
216th, 217- single-mode fibers SMF；213- wavelength division multiplexer MUX；218th, 226,234,242- beam splitter S；219、224、227、
232nd, 235,240,243,248- variable optical attenuator VOA；220th, 228,236,244- chronotron TD；223、231、239、247-
Faraday mirror FM；225th, 233,241,249- classics detectors；250- multi-Wavelength Pulses generators；251- phase-modulations are filled
Put；252- pulse transmission lines road；
In Fig. 3：301-Alice ends phase signal；1 reference pulses of 302- λ；2 reference pulses of 303- λ；304- λ 3 refer to arteries and veins
Punching；4 reference pulses of 305- λ；1 signal pulses of 306- λ；307-Bob ends phase signal reference pulse.
With reference to the accompanying drawings and examples technical scheme is described further.
The present invention is a kind of networking mode of point-to-multipoint, can especially further extend into multi-multipoint side
Formula.Described embodiment is the one kind in one-to-many manner of the present invention, it is thus evident that it can relatively easily expand to more answering
With a more representative wavelength-division multiplex quantum key distribution network diagram is as shown in Figure 1.
Embodiment 1
In Fig. 1, launch parties of the Alice as pulse signal possesses a multi wave length illuminating source, can produce and meet multiple
Bob user is while the pulse signal of the used different wave length that communicates.Each Bob user can be assigned to the letter of a certain wavelength
Number, and which has the wider suitability to pulse wavelength, i.e., the distribution of signal wavelength between each Bob is adjusted in wavelength planning process
Afterwards, Bob still can be with normal work.In Fig. 1, optical fiber 101 is used in conjunction with for each user, and optical fiber 103,104,105 and 106 is every
The special optic fibre of individual user, the special optic fibre and 101 sum of common optical fiber of each user are defined as the distance of each user.Wavelength
Route device 102 is used between control end Alice and user side Bob, controls the Path selection of each wavelength pulse signal, and it can be with
It is the devices such as wavelength division multiplexer, array waveguide grating, Bragg grating, wavelength-selective switches, but same requirement is to transmission
Business has the transparency, and has the features such as little loss, reaction fast, stable performance.
The embodiment schematic diagram of multi-user's wavelength-division multiplex quantum key distribution network system of Fig. 2 present invention.The system is adopted
Reciprocation type structure is used, is related to five users, wherein Alice produces the pulse group comprising four kinds of wavelength, sends out respectively as control end
It is sent to four independent user Bob.Pulse transmission line road is special comprising one section of common optical fiber, a wavelength division multiplexer and four sections
The effector of optical fiber, wherein wavelength division multiplexer as pulse Path selection.Each Bob receives the arteries and veins that Alice control stations send
After punching, as needed, carry out phase-modulation to pulse, load information, and according to total range difference of each Bob and Alice control stations
Relation, arranges time delay, and pulse is returned Alice control stations then.Pulse transmittance process is described specifically below.
Alice produces the train of pulse with multiple wavelength, four wavelength pulse strings therein using multiple-wavelength laser 201
Use being picked out by the requirement that wavelength is planned by wavelength screening washer 202 for four Bob.Pulse is led to after circulator 203
Cross 50：50 bonder 206 is injected into non-equilibrium interferometer.So each pulse group is divided into two parts, and a part will be worn
Comprising short delay line 207, phase-modulator 208 and polarization beam apparatus 210 long-armed 209 are crossed, another part is then by lower section
Galianconism 211, such two parts pulse from 210 outgoing of polarization beam apparatus when have a time difference, embodiment has one in position
Individual range difference, the former is referred to as reference pulse, and the latter is referred to as signal pulse.It is pointed out that long-armed the 209 of non-equilibrium interferometer
With galianconism 211 using polarization maintaining optical fibre suppressing polarization effect.On pulse transmission line road 252, two-stage circuit conveying arteries and veins is taken
Punching, first passes through first order quantum channel, i.e. common optical fiber 212 from the pulse group of 210 outgoing of polarization beam apparatus, then multiple by wavelength-division
Separated in the way of wave length addressing with device 213, the train of pulse of each wavelength is each through next stage quantum channel, i.e. special optic fibre
214th, 215,216 and 217, reach respective Bob ends.Due to each Bob it is different from the distance of wavelength division multiplexer 213, second level quantum
Channel length is different.
Below by taking Bob1 as an example, wavelength X1Pulse group reach Bob1 after, first by 10：90 beam splitter 218 is divided into two
Branch road is gone down in part, stronger part, and Jing variable optical attenuators 224 are received by classical detector 225 after decaying, this part arteries and veins
The effect of punching mainly has two：One is time action, and classical detector 225 detects the time of pulse and is recorded and is passed to control
System processed, provides time reference to apply modulation voltage to upper branch road displacement modulation；Two is safety effect, classical detector
225, by monitoring the information such as the intensity of incident pulse, determine whether external signal attacking system, and such as Trojan Horse is attacked
Hit.
And branch road is gone in weaker part, equally decayed by variable optical attenuator 219, pass by delay line and (also referred to as store
Ring) 221, then through phase-modulator 222, the signal in two parts pulse is divided into by the non-equilibrium interferometer in Alice ends before
Pulse will be loaded phase information, select corresponding to the base of Bob, and the reference pulse for going before is not modulated, final pulse
Reflected by faraday mirror 223, suitable time-delay is given after chronotron 220, return Alice control ends.Each Bob ends are according to them
From the distance at Alice ends and be provided with different time delays, therefore the pulse returned from each Bob ends almost simultaneously can be reached
The non-equilibrium interferometer at Alice ends.
It is pointed out that Bob user sides do not use common light reflecting device in the present embodiment, but adopt farad
Mirror, this is because faraday mirror can compensated optical fiber automatically birefringence effect.
Due to the polarization selection function of polarization beam apparatus 210, the signal pulse through interferometer long-armed 209 now will before
Galianconism 211 of the meeting through interferometer, and before now will be through the length of interferometer through the reference pulse of interferometer galianconism 211
Arm 209, phase-modulator 208 can be to the return pulse loading phase informations through long-armed 209, and this is selected corresponding to the base of Alice
Select, different from Alice ends phase place loading procedure in point-to-point link, the now return pulse of four Bob will be modulated simultaneously.
Through interferometer two-arm pulse at bonder 206 further in conjunction with, according to added by Alice is from Bob, phase information is different,
There are different interference events.When two-way pulse has 180 ° of phase contrasts, multi-wavelength single photon detecting element 204 can be responded, and
Record detection event.When two-way pulse phase difference is zero, multi-wavelength single photon detecting element 205 can be responded, and record detection
Event.The difference of interference pulse wavelength, can cause a pair of detecting modules of certain wavelength in multi-wavelength single photon detecting element
Response.
It is pointed out that due to the weak signal feature of quantum communication system, the wavelength planning of quantum communication network is full
While foot this ITU-T standards of wavelength, it is also necessary to take into full account four-wave mixing effect.One important starting point of wavelength planning is just
Be to be allowed four-wave mixing produce new frequencies of light far as possible from this four pulse signals wavelength.In actual use,
In order to effectively reduce four-wave mixing effect impact, wavelength selector selects wavelength by the way of two grades of equal difference frequency intervals.
Fig. 3 is phase modulation process schematic diagram.By arranging rational time delay, the corresponding wavelength arteries and veins of each position at Bob ends
Punching almost can reach Alice ends simultaneously.But transmission speed is trembled to the dependency of wavelength, fiber lengths in a fiber due to light
The factor such as dynamic, device is undesirable, the corresponding wavelength pulse of each position reach the Alice moment and difference occur, but in certain limit
Time difference not only do not interfere with systematic function, and time-multiplexed mode can also reduce four-wave mixing effect.
Maximum time difference is 20ns in the present embodiment, but this does not reach the maximum time difference allowed by system.
The time difference of 20ns is about 4m equivalent to pulse transfer path difference, and, for the optical fiber of tens kms, a key divides for this
The length fluctuations for occurring 4m in the cycle of sending out are impossible.Shown in Fig. 3 (a), the persistent period of Alice ends phase modulated signal is
90ns, the maximum time span that each pulse group is likely to occur are 60ns.Can either be avoided using single phase-modulator 208 many
The modulation deviation that individual phase-modulator causes, also significantly reduces Alice control complexities and system cost.Fig. 3 (b) show
Bob1 ends phase place loading procedure, adjacent λ1Reference pulse 302 time interval be 200ns, that is to say Alice ends original pulse
Transmission interval, and the time interval between the same pulse two parts caused due to non-equilibrium interferometer is 50ns, i.e. λ1Reference
The close λ therewith of pulse 3021306 time interval of signal pulse be 50ns, due to Bob1 every time one pulse of modulation, be carried in
The phase signal persistent period of its phase-modulator 222 is 35ns.
Key distribution and shared procedure, such as Fig. 4 is described specifically below：
Step 401：System initialization.Alice and each Bob software and hardware facilities are checked, check whether equipment can run well,
Set the primary conditions such as correct running voltage, suitable operating temperature；
Step 402：System noise is tested.On the premise of Alice does not launch laser pulse train, i.e., train of pulse number is zero,
Test System Noise level, it is ensured that below the zone of reasonableness of design；
Step 403：Fiber lengths are tested and pulse delay is arranged.Alice sends one group of high power pulse, and each Bob is by measurement
Pulse due in, determines fiber lengths in link, according to the length relation of optical fiber between each Bob and Alice, arranges each Bob
End time delay.Alice launches one group of high power pulse again, and Alice is returned after suitably being decayed by Bob, measures due in, comes and goes adjustment
Bob ends time delays is arranged, to reach pulse that each Bob ends return again to almost arrival Alice ends simultaneously；
Step 404：Key sends.Alice sends train of pulse to Bob in units of frame, sends the frame of certain amount every time,
Time interval between frame and frame is referred to as frame rate, and frame by burst blocks into impulse ejection frequency of the pulse by user's setting
Rate sends.Bob is modulated after receiving pulse and is returned after decaying to single photon level, from the pulse that different Bob ends return
Alice ends are reached simultaneously is loaded same phase information.Voltage and pulsing previous existence needed for modulation pulse into it is truly random
Code-phase correspondence, used as the selection of respective base, Alice and Bob is needed according to each own coding, selects different phase voltage modulation arteries and veins
Rush phase place.
Step 405：Testing keys with into code.The spy of a certain wavelength detection module in Alice record multi-wavelength detection devices
Response events are surveyed, is disclosed with each Bob and is compared base, form screening key.Then some data of random choose in screening key, sentence
Disconnected to whether there is eavesdropping, after judgement, the data selected are dropped.Remaining data are carried out with data harmonization again and close property is put
Greatly, obtain final safe key.The storage step-by-step of safe key is carried out, and is used for convenience, is added before every group of safe key
Storage prefix, such as sends the time as labelling with key, while will also set key priority, the setting of priority can be according to
The number order of Bob is carried out from high to low.
Step 406：Between Bob, key is shared.According to the key priority set in step 405, with priority Bob1>Bob2
>Bob3>As a example by Bob4, Bob1 and Bob3 carries out key and shares, as the key priority of Bob1 is more than Bob3, so Bob3 will
The key of shared Bob1.Alice as intermediate node, first by the key of the key to Alice and Bob1 of Alice and Bob3
It is encrypted, the Bob1 keys of encryption is sent to into Bob3 then, Bob3 is decrypted after receiving ciphertext, obtains the key of Bob1, this
Sample just have shared key with Bob1.Other situations are similar, but the shared key with exclusiveness, i.e. Bob of key between Bob
Can be shared with other some Bob, can not be shared with other Bob again after sharing.
Hereinafter the systematic function of embodiment is analyzed.
Screening secret-key rate and quantum bit error rate are two important parameters for weighing QKD system performance.Suitable for this
The screening secret-key rate R of QKD networkssiftedIt is expressed as：
In above formula, frepAlice impulse ejection frequencies are represented, μ represents Bob ends and returns average pulse number of photons, tABRepresent
The percent of pass of fibre circuit, t between Alice and BobARepresent the percent of pass of Alice terminals, ηARepresent the effect of Alice end detectors
Rate.
Quantum bit error rate represents the ratio between the error count that detector receives and detection sum, it is adaptable to this
The quantum bit error rate QBER of QKD networks is expressed as
In above formula, V represents the interference contrast of Alice ends interferometer, pdarkRepresent that dark counting causes explorer count
Probability, pdetRepresent the probability of explorer count, pafterRepresent that afterpulse causes the probability of explorer count.
Embodiment adopts following parameter：Impulse ejection frequency 5MHz, average photon number 0.1, single photon detection efficiency 10%,
Dark counting probability 10-5, afterpulse probability 4.25%, Alice transmitances 0.51, fiber transmission attenuation 0.25dB/km, interferometer point
Resolution 99%, wavelength division multiplexer transmitance 0.85.
Fig. 5 is quantum bit error rate and number of users and the graph of a relation of transmission range.The QBER of four users has identical
Trend, and independently of one another.Similarly as shown in fig. 6, the key production rate of each user is also with identical trend, and each other
It is independent.So multi-user has very strong independence in the QKD networks of the present invention, the performance of each user will not be because of the increasing of user
Subtract generation large change, especially better than scheme before, user key production rate no longer because user increase and exponentially
Reduce.
The corresponding same or analogous part of same or analogous label；
Position relationship for the explanation of being for illustration only property described in accompanying drawing, it is impossible to be interpreted as the restriction to this patent；
Obviously, the above embodiment of the present invention is only intended to clearly illustrate example of the present invention, and is not right
The restriction of embodiments of the present invention.For those of ordinary skill in the field, may be used also on the basis of the above description
To make other changes in different forms.There is no need to be exhaustive to all of embodiment.It is all this
Any modification, equivalent and improvement made within the spirit and principle of invention etc., should be included in the claims in the present invention
Protection domain within.
Claims (10)
1. a kind of multi-user's wavelength-division multiplex quantum key distribution network system, including Alice control ends, pulse conveying circuit and
Bob user sides, Alice control ends are connected with Bob user sides by pulse conveying circuit, it is characterised in that
The Alice control ends include multi-Wavelength Pulses generator, circulator, bonder, non-equilibrium interferometer and two
Multi-wavelength single photon detecting element；The pulse group of multi-Wavelength Pulses generator output is noted by bonder after circulator
Enter to non-equilibrium interferometer, sequentially include short delay line, single phase-modulator and polarization point on non-equilibrium interferometer is long-armed
Beam device, non-equilibrium interferometer galianconism connect polarization beam apparatus, and a multi-wavelength single photon detecting element connects bonder by circulator
Input, another multi-wavelength single photon detecting element connect the coupled end of bonder；
The Bob user sides include beam splitter, the upper branch road for modulating pulse loading phase information and for carrying for upper branch road
The lower branch road of information and system security monitoring for reference, the polarization beam apparatus in Alice control ends are connect by pulse conveying circuit
The beam splitter of Bob user sides, the outfan of beam splitter connect upper and lower branch road respectively；
Variable optical attenuator that the upper branch road includes being sequentially connected with, pulse delay apparatus, fibre delay line, phase-modulator with
And reflection unit, the upper output termination variable optical attenuator of beam splitter；
The lower branch road includes the variable optical attenuator being sequentially connected with and classical detector, and the lower output of beam splitter terminates variable light
Attenuator.
2. multi-user's wavelength-division multiplex quantum key distribution network system according to claim 1, it is characterised in that described many
Wavelength pulse generator includes single light source multi-wavelength pulse laser and the wavelength selector for connecting.
3. multi-user's wavelength-division multiplex quantum key distribution network system according to claim 2, it is characterised in that described anti-
Injection device is faraday mirror.
4. multi-user's wavelength-division multiplex quantum key distribution network system according to claim 3, it is characterised in that the arteries and veins
Rush conveying circuit include by wavelength routing apparatus connect first optical fiber and some the second optical fiber, the number of the second optical fiber
Amount is identical with Bob user side quantity.
5. multi-user's wavelength-division multiplex quantum key distribution network system according to claim 4, it is characterised in that the ripple
Long route device is any one in wavelength division multiplexer, array waveguide grating, Bragg grating or wavelength-selective switches.
6. the multi-user's wavelength-division multiplex quantum key distribution network system according to claim 1,2 or 3, it is characterised in that
The long-armed and galianconism of the non-equilibrium interferometer adopts polarization maintaining optical fibre.
7. the multi-user's wavelength-division multiplex quantum key distribution network system according to Claims 2 or 3, it is characterised in that institute
State wavelength selector wavelength is selected by the way of two grades of equal difference frequency intervals.
8. the key of the multi-user's wavelength-division multiplex quantum key distribution network system described in a kind of any one of application claim 1-7
Distribution and sharing method, it is characterised in that comprise the following steps：
S1. system initialization：Alice and each Bob user facilities are checked, checks whether equipment can run well, set initial strip
Part；
S2. system noise test：On the premise of Alice does not launch laser pulse train, i.e., when train of pulse number is zero, test system
Noise level；
S3. fiber lengths test and pulse delay are arranged：Alice sends one group of high power pulse, and each Bob user is arrived by measuring pulse
Up to the moment, fiber lengths in link are determined, according to the length relation of optical fiber between each Bob user and Alice, each Bob is set and is used
Family time delay；
Alice launches one group of high power pulse again, and Alice is returned after being decayed by Bob user, measures due in, comes and goes adjustment Bob and uses
Family time delay is arranged, to reach pulse that each Bob user returns again to almost arrival Alice ends simultaneously；
S4. key sends：Alice sends train of pulse to Bob user in units of frame, sends the frame of certain amount every time；Bob is used
Family is modulated after receiving pulse and is returned after decaying to single photon level, and the pulse returned from different Bob users is arrived simultaneously
Same phase information is loaded up to Alice；Voltage and pulsing previous existence needed for modulation pulse into real random code it is corresponding,
Used as the selection of respective base, Alice and Bob user are needed according to each own coding, select different phase voltage modulation pulsion phases
Position；
S5. testing keys with into code：Alice records the probe response event of multi-wavelength detection device, discloses ratio with each Bob user
To base, screening key is formed；Then some data of random choose in screening key, judge whether eavesdropping, after judgement,
The data that rejecting is selected；Again remaining data are carried out with data harmonization and close property is amplified, obtain final safe key；To safety
Key carries out priority settings；
Between S6.Bob user, key is shared：According to the key priority set in step S5, when safe key priority is：Bob_
i>Bob_j>Bob_k>During Bob_l, Bob_i and Bob_k carries out key and shares；
The key priority of Bob_i is more than Bob_k, so Bob_k to be shared the key of Bob_i；Alice as intermediate node,
The key of Alice and Bob_i is encrypted first by the key of Alice and Bob_k, then by the Bob_i keys of encryption
Bob_k is sent to, and Bob_k is decrypted after receiving ciphertext, obtained the key of Bob_i, so just key is have shared with Bob_i；Other
Situation is identical with this；
Between Bob user, the shared key with exclusiveness, i.e. Bob user of key can only be carried out altogether with other some Bob user
Enjoy, share after can not again with other Bob users to share.
9. key according to claim 8 is distributed and sharing method, it is characterised in that the safe key obtained by step S5
Step-by-step is stored, plus storage prefix before every group of safe key.
10. key according to claim 9 is distributed and sharing method, it is characterised in that the storage prefix energy of safe key
The time is sent using key enough.
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