CN211406034U - Free space quantum key distribution system for aircraft - Google Patents
Free space quantum key distribution system for aircraft Download PDFInfo
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- CN211406034U CN211406034U CN202020144581.7U CN202020144581U CN211406034U CN 211406034 U CN211406034 U CN 211406034U CN 202020144581 U CN202020144581 U CN 202020144581U CN 211406034 U CN211406034 U CN 211406034U
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Abstract
The utility model discloses a free space quantum key distribution system for aircraft. Carry the utility model discloses the aircraft of well quantum key distribution equipment and arbitrary aircraft or the ground satellite station that carry this equipment equally can realize the secret communication of point-to-point quantum of absolute safety in theory between. The method comprises the steps that a communication sender firstly attenuates strong laser to obtain quasi-single photon laser with the average photon number being single photon level, then carries out polarization state modulation on the quasi-single photon laser according to a polarization BB84 protocol, and sends single photon carrying key information after modulation to a receiver through an optical antenna via free space. And the receiver receives the single photons from the sender through the optical antenna and demodulates the key information carried by the single photons through the quantum signal receiving system. Because the single photon of the unknown quantum state has the characteristics of irreproducibility and inseparability, a third party cannot steal the key information of both communication parties under the condition of not being discovered, and the safety of aircraft communication information is ensured.
Description
Technical Field
The utility model relates to a quantum key distribution field, concretely relates to free space quantum key distribution system for aircraft
Background
With the wide-range popularization of the internet, the information transmission reaches unprecedented amount and frequency, and various privacy information is increasingly exposed on the internet, so that the demand of people for secret communication also reaches unprecedented height. The quantum key distribution uses quantum state as information carrier, based on quantum mechanics's uncertainty relation and quantum unclonable theorem, makes both communication parties share the key through quantum channel, is the product of combining cryptology and quantum mechanics. The quantum key distribution technology does not transmit a cipher text in communication, and only transmits a key by using a quantum channel to distribute the key to both communication parties.
The BB84 protocol is the first quantum key distribution protocol proposed in 1984 by IBM corporation's c.h.bennett and g.brassard, university of Montreal, canada. The realization of ultra-long distance quantum communication based on the BB84 protocol, B92 protocol and other protocols has been one of the difficulties in the field of quantum information. Due to the influence of optical attenuation caused by optical fiber itself, not deformation, purity and defects, the transmission loss of optical signals in an optical fiber channel is difficult to further reduce greatly along with the development of a preparation process, and the distance of quantum communication realized through the optical fiber channel is close to a limit distance. In contrast, photons of partial frequencies transmit in the atmosphere with losses much smaller than those transmitted in fiber channels, and especially in outer space above the atmosphere of 40Km, the optical power attenuation is almost zero. Therefore, the free space optical communication technology can effectively solve the problem of high loss of long-distance optical communication of an optical fiber channel, and the satellite, the airplane and the like are applied to the field of quantum key distribution, so that quantum secret communication in a metropolitan area or even a global area is expected to be realized.
Due to the birefringence of the optical fiber, the polarization state of the optical signal transmitted in the optical fiber will change continuously during the transmission process. Although polarization-maintaining optical fiber can be used in practical applications to realize the polarization state transmission of optical waves, the polarization state of optical waves also has a certain change with the increase of transmission distance, and the change is enough to cause the increase of bit errors in practical communication and reduce the communication rate. In free-space optical transmission, however, the polarization state of optical waves hardly changes even if the optical waves are transmitted over a long distance. This property makes free space more suitable for quantum key distribution systems implementing polarization modulation.
Patent technology 201810955173.7 discloses an aviation quantum encryption communication method based on autonomous feedback, which is applied between any two aircrafts, and the aircrafts carry out aviation quantum communication through quantum channels and classical channels, so that quantum encryption of data information sent by the aircrafts is realized. But only relates to quantum secret communication between two aircrafts and does not relate to secret communication between the aircrafts and a fixed ground station, a mobile ground or a sea surface carrier.
SUMMERY OF THE UTILITY MODEL
In order to solve the technical problem, the utility model provides a can be applied to aircraft, make the aircraft realize the secret communication of quantum through the mode that utilizes free space to carry out the distribution of quantum key. Any aircraft carrying this device can establish a real-time quantum key distribution communication link with a ground station or another aircraft.
In order to achieve the purpose, the utility model adopts the following technical scheme: a free space quantum key distribution system for aircraft includes aircraft FnWith ground station GmDevice, said aircraft FnWith ground station GmThe devices are each provided with a quantum key distribution system, the quantum key distribution system is used for sending and receiving quantum communication signals, the quantum key distribution system is a sender when sending the quantum communication signals and is a receiver when receiving the quantum communication signals, wherein:
the quantum key distribution system comprises a communication signal generation module, a communication signal transceiving module, a communication signal receiving selection module, a polarization basis vector detection module, a quantum signal detection module, a fine tracking beacon generation module, a fine tracking beacon detection module, a fine tracking beacon transceiving module and an optical antenna module;
the communication signal generation module is used for generating a quantum signal and a polarization basis vector signal;
the communication signal transceiver module is used for coupling the generated quantum signal/polarization basis vector signal to a free-space (representing a propagation space without any attenuation, any blockage and any multipath) from an optical fiber and transmitting the quantum signal/polarization basis vector signal to the optical antenna module; the optical antenna module is used for receiving the quantum signals/polarization basis vector signals from the optical fiber, and transmitting the quantum signals/polarization basis vector signals to the polarization basis vector detection module and the quantum signal detection module;
the polarization basis vector detection module is used for detecting the received polarization basis vector signals;
the quantum signal detection module is used for detecting the polarization state of the received quantum signal;
the communication signal receiving and selecting module is used for carrying out polarization basis vector compensation on the quantum signals and controlling the polarization basis vector detection module and the quantum signal detection module to switch between detection modes;
the fine tracking beacon generating module is used for generating a fine tracking beacon;
the fine tracking beacon detection module is used for carrying out imaging detection on the received fine tracking beacon;
when the fine tracking beacon transceiver module is in a fine tracking beacon receiving mode, the receiving optical antenna module receives the fine tracking beacon and transmits the fine tracking beacon to the fine tracking beacon detection module; when the optical antenna module is in a mode of transmitting the fine tracking beacon, the optical antenna module is used for transmitting the fine tracking beacon generated by the fine tracking beacon generating module;
the optical antenna module is used for transmitting the signal light transmitted by the communication signal transceiving module and the fine tracking beacon transceiving module to a receiving party; and transmitting the quantum signal/polarization basis vector signal received by the receiver to a quantum communication signal transceiver module and transmitting the fine tracking beacon received by the receiver to a fine tracking beacon transceiver module.
Preferably, the communication signal generating module includes a fiber laser, a first fiber splitter, an intensity modulator, a fixed optical attenuator, a variable optical attenuator, a second fiber splitter, an optical power detector, a fiber coupler, and a first polarization modulator;
the output of the optical fiber laser is connected with the input end of a first optical fiber beam splitter, and a first output port of the first optical fiber beam splitter is sequentially connected with a second optical fiber beam splitter and an optical power detector through optical fibers; the second output port of the first optical fiber beam splitter is sequentially connected with an intensity modulator, a fixed optical attenuator, a variable optical attenuator, an optical fiber coupler and a first polarization modulator through optical fibers; the second optical fiber beam splitter is connected with the optical fiber coupler through the first optical switch.
Preferably, the communication signal transceiver module includes a beam shaper, a laser beam expander, a first ultra-narrow band filter, a fiber collimator, and a fiber circulator;
the first port of the optical fiber circulator is connected with the polarization modulator, the second port of the optical fiber circulator is connected with the optical fiber collimator through a single mode optical fiber, and the optical fiber collimator is sequentially connected with the ultra-narrow band optical filter, the laser beam expander and the beam shaper.
Preferably, the communication signal receiving selection module comprises a second polarization modulator and a second optical switch, and the second switch has two output ports, namely a first output port and a second output port;
the second polarization modulator is connected with a third port of the optical fiber circulator, and the second optical switch is connected with the second polarization modulator.
Preferably, the polarization basis vector detection module comprises an analyzer, an optical amplifier and an optical power detector;
the analyzer is connected with a first output port of the second optical switch, and the analyzer is sequentially connected with the optical amplifier and the optical power detector.
Preferably, the quantum signal detection module comprises a third optical fiber beam splitter, two optical fiber polarization controllers, two optical fiber polarization beam splitters and four single-photon detectors;
the third optical fiber beam splitter is connected with the second output port of the second optical switch, two output ports of the third optical fiber beam splitter are respectively connected with an optical fiber polarization controller and an optical fiber polarization beam splitter in sequence, and two single photon detectors are connected to one optical fiber polarization beam splitter.
Preferably, the fine tracking beacon transceiver module comprises a second ultra-narrow band optical filter and a rotating reflector which are connected in sequence;
the fine tracking beacon generation module comprises a light beam shaper and a semiconductor laser which are connected in sequence.
Preferably, the fine tracking beacon detection module comprises an imaging lens and a CMOS camera tube which are connected in sequence.
Preferably, the optical antenna module includes a convex mirror, a concave mirror, a third planar mirror, a convex lens, a second planar mirror, a first planar mirror, a fast tilting mirror, and a dichroic mirror;
the dichroic mirror is respectively connected with the beam shaper and the second ultra-narrow band filter, and the dichroic mirror is sequentially connected with the rapid tilting reflector, the third plane reflector, the second plane reflector, the convex lens, the first plane reflector, the convex reflector and the concave reflector.
The utility model discloses profitable technological effect: the utility model discloses well sender of communication at first attenuates strong laser and obtains the quasi single photon laser that the average photon number is the single photon rank, then carries out polarization state modulation to it to the single photon that will carry key information after the modulation sends for the receiver via free space through optical antenna. And the receiver receives the single photons from the sender through the optical antenna and demodulates the key information carried by the single photons through the quantum signal receiving system. Because the single photon of the unknown quantum state has the characteristics of non-duplicability and non-segmentability, a third party can not steal the key information of both communication parties under the condition of not being discovered theoretically, and the safety of the communication information of the aircraft is ensured.
Drawings
Fig. 1 is a schematic diagram of a free space quantum key distribution system for an aircraft according to the present invention.
Fig. 2 is a schematic diagram of aircraft position parameters in a free space quantum key distribution system for an aircraft according to the present invention.
Fig. 3 is a schematic diagram of aircraft attitude parameters in a free space quantum key distribution system for an aircraft according to the present invention.
Fig. 4 is a schematic diagram of antenna attitude parameters in a free space quantum key distribution system for an aircraft.
Fig. 5 is a schematic diagram of the overall structure of a quantum key distribution system of the free space quantum key distribution system for an aircraft according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments, but the scope of the present invention is not limited to the following specific embodiments.
1-5, a free space quantum key distribution system for an aircraft includes an aircraft FnWith ground station GmDevice, said aircraft FnWith ground station GmThe equipment comprises quantum key distribution systems, wherein the quantum key distribution systems are used for sending and receiving quantum communication signals, the quantum key distribution systems are sender Alice when sending the quantum communication signals, and receiver Bob when receiving the quantum communication signals.
In practical application, one or both of the two communication parties are aircrafts, or one of the two communication parties is an aircraft and the other one is ground station equipment. Aircraft FnIn the quantum key distribution process, the roles of the sender Alice and the receiver Bob can be flexibly selected and switched according to the actual situation. Both sender Alice and receiver Bob have an ATP familyAnd a quantum communication system capable of transmitting and detecting coarse tracking and fine tracking beacons; the system has the capabilities of generating single-photon pulses, carrying out polarization modulation on the generated single photons and carrying out polarization state detection on single-photon signals. Besides the capability of sending quantum signals, the system also has the capability of sending polarization basis vector signals with the same frequency as the quantum signals for detecting the atmospheric environment of the transmission path and the polarization basis vector calibration.
The sender Alice and the receiver Bob have radio communication functions and can access an existing communication network for radio communication. Meanwhile, the positioning system is arranged, so that the positioning information of the positioning system can be acquired in real time, and the positioning information can be shared with another party in communication through the radio communication system.
The quantum key communication protocol of the two communication parties is a decoy state BB84 protocol.
The Alice sender modulates the single photon polarization state in a mode following a BB84 protocol, and randomly and equally probability modulates the single photon polarization state to a 0-degree horizontal polarization state | →>＝|0>90 DEG vertical polarization state |1>＝|1>Polarization state of 45 °
Or-45 ° polarization state
The receiver Bob is able to distinguish the horizontal polarization state | → of the photons>Perpendicular polarization state
Polarization state of 45 DEG
Or-45 ° polarization state
And the polarization state information is converted into the responses of different detectors, and code values corresponding to the responses of the different detectors are used as communication keys.
As shown in fig. 1, an aircraft FnCan be within practical safety distance of quantum key distribution to any ground station GmOr aircraft FnPerforming quantum key distribution and only having one ground station G at the same timemOr aircraft FnAnd carrying out quantum key distribution.
As shown in FIG. 1, a ground station G in the systemmMay be a ground-based fixed communication base station, a mobile ground or marine vehicle. Aircraft FnWith ground station GmCarry respectively the utility model provides a quantum key distribution equipment can realize the function of sender and receiver simultaneously. Aircraft FnWith ground station GmThe method can flexibly select to act as a sender or a receiver in the communication process according to the actual situation.
As shown in FIG. 2, the aircraft location parameters include longitude θ, latitude λ, and altitude L. The ground station location parameters include longitude θ, latitude λ, and altitude L.
As shown in FIG. 3, the attitude parameters of the aircraft include roll angle γ and pitch angle
And a heading angle ω. The attitude parameters of the ground station include roll angle gamma and longitudinal roll angle
And a heading angle ω. Fixed ground station attitude parameters roll angle gamma and pitch angle
And the heading angle ω is generally constant.
As shown in FIG. 4, the aircraft antenna attitude parameters include azimuth α, pitch β, ground station GmThe device antenna attitude parameters include azimuth α, pitch β.
As shown in fig. 5, the quantum key distribution system includes a communication signal generation module 01, a communication signal transceiver module 02, a communication signal reception selection module 03, a polarization basis vector detection module 04, a quantum signal detection module 05, a fine tracking beacon generation module 07, a fine tracking beacon detection module 08, a fine tracking beacon transceiver module 06, and an optical antenna module 09;
the communication signal generation module 01 is used for generating a quantum signal and a polarization basis vector signal;
the communication signal transceiver module 02 is used for coupling the generated quantum signal/polarization basis vector signal from the optical fiber to the free space and transmitting the signal to the optical antenna module; the optical antenna module is used for receiving the quantum signals/polarization basis vector signals from the optical fiber, and transmitting the quantum signals/polarization basis vector signals to the polarization basis vector detection module and the quantum signal detection module;
the communication signal receiving and selecting module 03 is used for performing polarization basis vector compensation on the quantum signal and controlling the polarization basis vector detection module and the quantum signal detection module to switch between detection modes;
the polarization basis vector detection module 04 is configured to detect a received polarization basis vector signal;
the quantum signal detection module 05 is configured to perform polarization state detection on the received quantum signal;
when the fine tracking beacon transceiver module 06 is in the fine tracking beacon receiving mode, the receiving optical antenna module receives the fine tracking beacon and transmits the fine tracking beacon to the fine tracking beacon detection module; when the optical antenna module is in a mode of transmitting the fine tracking beacon, the optical antenna module is used for transmitting the fine tracking beacon generated by the fine tracking beacon generating module;
the fine tracking beacon generation module 07 is configured to generate a fine tracking beacon;
the fine tracking beacon detection module 08 is configured to perform imaging detection on the received fine tracking beacon;
the optical antenna module 09 is configured to transmit the signal light transmitted by the communication signal transceiver module and the fine tracking beacon transceiver module to a receiving party; and transmitting the quantum signal/polarization basis vector signal received by the receiver to the communication signal transceiver module and transmitting the fine tracking beacon received by the receiver to the fine tracking beacon transceiver module.
Specifically, the fine tracking beacon generation module 07, the fine tracking beacon transceiver module 06, and the optical antenna module 09 cooperate to form a fine tracking beacon transmission system.
The communication signal generating module 01, the communication signal transceiving module 02 and the optical antenna module 09 form a quantum signal/polarization basis vector signal transmitting system in a matching manner.
The optical antenna module 09, the fine tracking beacon transceiver module 06 and the fine tracking beacon detection module 08 cooperate to form a fine tracking beacon detection system.
The optical antenna module 09, the communication signal transceiver module 02, the communication signal receiving selection module 03, and the polarization basis vector signal detection module 04 cooperate to form a polarization basis vector signal detection system.
The optical antenna module 09, the communication signal transceiver module 02, the communication signal receiving selection module 03 and the quantum signal detection module 05 are matched to form a quantum signal detection system.
The optical antenna modules constitute an optical antenna system.
Specifically, the communication signal generation module includes a fiber laser 101, a first fiber splitter 102, an intensity modulator 103, a fixed optical attenuator 104, a variable optical attenuator 105, a second fiber splitter 106, an optical power detector 107, a first optical switch 108, a fiber coupler 109, and a first polarization modulator 110;
the output of the fiber laser 101 is connected with the input end of a first fiber beam splitter 102, and a first output port of the first fiber beam splitter 102 is sequentially connected with a second fiber beam splitter 106 and an optical power detector 107; a second output port of the first optical fiber beam splitter 102 is sequentially connected with an intensity modulator 103, a fixed optical attenuator 104, a variable optical attenuator 105, an optical fiber coupler 109 and a first polarization modulator 110; the second fiber splitter 106 is in turn connected to a fiber coupler 109 via a first optical switch 108.
Preferably, the communication signal transceiving module 02 comprises a beam shaper 116, a laser beam expander 115, a first ultra-narrow band filter 114, a fiber collimator 113 and a fiber circulator 111;
a first port of the optical fiber circulator 111 is connected to the polarization modulator 110, a second port of the optical fiber circulator 111 is connected to the optical fiber collimator 113 through a single-mode optical fiber 112, and the optical fiber collimator 113 is further connected to a first ultra-narrow band filter 114, a laser beam expander 115, and a beam shaper 116 in sequence.
Preferably, the communication signal receiving selection module 03 includes a second polarization modulator 201 and a second optical switch 202, and the second switched light 202 has two output ports, i.e., a first output port and a second output port;
the second polarization modulator 201 is connected to the third port of the fiber circulator 111, and the second optical switch 202 is connected to the second polarization modulator 201.
Preferably, the polarization basis vector detection module 04 comprises an analyzer 203, an optical amplifier 204 and an optical power detector 205;
the analyzer 203 is connected to a first output port of the second optical switch 202, and the analyzer 203 is in turn connected to an optical amplifier 204 and an optical power detector 205.
Preferably, the quantum signal detection module 05 comprises a third fiber beam splitter 206, two fiber polarization controllers (207,208), two fiber polarization beam splitters (209,210) and four single photon detectors (211,212,213, 214);
the third optical fiber beam splitter 206 is connected to the second output port of the second optical switch 202, two output ports of the third optical fiber beam splitter 206 are respectively connected to an optical fiber polarization controller and an optical fiber polarization beam splitter in sequence, and two single photon detectors are connected to one optical fiber polarization beam splitter.
Preferably, the fine tracking beacon transceiver module 06 includes a second ultra-narrow band filter 301 and a rotating mirror 302 connected in sequence;
the fine tracking beacon generating module 07 comprises a beam shaper 305 and a semiconductor laser 306 which are connected in sequence; the beam shaper 305 is connected to the rotating mirror 302.
Preferably, the fine tracking beacon detection module 08 comprises an imaging lens 303 and a CMOS camera tube 304 which are connected in sequence, and the imaging lens 303 is connected with the rotating reflector 302.
Preferably, the optical antenna module 09 includes a convex mirror 001, a concave mirror 002, a first planar mirror 003, a convex lens 004, a second planar mirror 005, a third planar mirror 006, a fast tilting mirror 007, and a dichroic mirror 008;
the dichroic mirror 008 is connected to the beam shaper 116 and the second ultra-narrow band filter 301, and the dichroic mirror 008 is further connected to the fast tilting mirror 007, the third planar mirror 006, the second planar mirror 005, the convex lens 004, the first planar mirror 003, the convex mirror 001, and the concave mirror 002 in sequence.
Wherein: the convex reflector 001, the concave reflector 002, the first plane reflector 003 and the convex lens 004 together form a Cassegrain telescope system, and the Cassegrain telescope system transmits local signal light to a free space and receives the signal light from the free space. The first plane mirror 003, the second plane mirror 005, the third plane mirror 006 and the fast tilting mirror 007 together form a kuide optical path, and the light beam is turned to a light guide optical path rotating along with the axis system, so that the light beam can be emitted in a predetermined direction without being influenced by the rotation of the turntable.
Specifically, the utility model discloses the concrete working process of system as follows:
according to the requirement of user secret communication, a sending party firstly sends a request quantum communication signal to the other party (receiving party) of communication through a classical communication network. The receiving party receives the communication request signal from the sending party, and the receiving party responds to the request of the sending party and sends the online signal of the communication system to the sending party.
And the sender and the receiver perform identity authentication to confirm that the two parties are legal users. And if the identity authentication fails, giving up the communication and responding to the alarm signal. And if the identity authentication is successful, the sender and the receiver carry out position and attitude information interaction through a classical communication network.
Program tracking is performed by both communication parties. The computer processes, calculates and compares the position and posture information of the two parties to obtain the angle error of the two parties in the standard time relative to the actual angle of the antenna, and then feeds the value back to the ATP rough tracking systemAnd the servo system drives the antenna rotating platform to eliminate the angle error. Regardless of roll angle gamma and pitch angle of both communication parties
And a heading angle omega, the sender position parameters are longitude theta, latitude lambda and height L, and the position coordinates are expressed as (theta, lambda and L). The receiver position parameters are longitude theta ', latitude lambda', height L ', and the position coordinates are expressed as (theta', lambda ', L').
Theoretical azimuth of the receiving device antenna:
theoretical pitch angle of the receiving antenna:
theoretical azimuth of the transmitter antenna:
theoretical pitch angle of the antenna of the sender device:
then compensating the roll angle gamma and the pitch angle of the self postures of the two communication parties
And a heading angle ω.
And the sender and the receiver complete program tracking. The transmitting side transmits a coarse tracking beacon to the receiving side. And the receiver receives the coarse tracking beacon by the coarse tracking camera to capture the target. The receiver feeds back the detection result to the sender through the classical communication network. And the receiver and the sender control the rotating platform of the optical antenna to adjust the attitude through the ATP system according to the detection result of the receiver on the rough tracking beacon.
The sender and the receiver finish coarse tracking capture, and the two communication parties perform fine tracking. And the transmitting direction transmits a fine tracking beacon with the wavelength of 532nm to the receiving party, and the receiving party receives the fine tracking beacon and detects the fine tracking beacon through the CMOS imaging tube.
The specific transmission process of the fine tracking beacon is as follows:
the transmitting party fine tracks the direction of reflected beam transmission from the rotating mirror 302 in the beacon transceiver module 06 towards the beam shaper mirror 305. First, the semiconductor laser 306 emits fine tracking beacon light having a wavelength of 532 nm. The fine tracking beacon passes through the beam shaping mirror 305, and the fine tracking beacon is converted from the original Gaussian spot into an annular spot. The fine tracking beacon after wave front shaping is reflected by a rotating mirror 302 to a second ultra-narrow band filter 301 with a center wavelength of 532nm and a bandwidth of about 5 nm. The filtered fine tracking beacon is transmitted to the optical antenna module 09 through the dichroic mirror 008 with the transmission center wavelength of 532 nm. And finally, transmitting the fine tracking beacon to a receiving party through the optical antenna module 09.
The fine tracking beacon specifically receives and detects as follows:
the transmission direction of the reflected light beam of the rotating mirror 302 in the receiving fine tracking beacon transceiver module 06 is directed to the imaging lens 303. The optical antenna module 09 receives the fine tracking beacon from the sender and transmits the fine tracking beacon to the dichroic mirror 008. The fine tracking beacon is transmitted through the dichroic mirror 008, is firstly transmitted to the second ultra-narrow band filter 301 of the fine tracking beacon transceiver module, and is then reflected to the fine tracking beacon detection module 08 through the rotary mirror 302. The fine tracking beacon is imaged on the CMOS pickup tube 304 through the imaging lens 303.
The receiver feeds back the detection result to the sender through the classical communication network. The receiver and the sender adjust the fast tilting mirror 007 through the ATP system according to the detection result of the receiver on the fine tracking beacon.
Degradation of polarization contrast due to atmospheric transmission channels, and changes in the polarization basis vector due to changes in the attitude of the ground station and aircraft antennas, transmitters and receiversThe receiver needs to perform polarization basis vector alignment. Communication error rate due to polarization contrast ER
Can be expressed as
For linearly polarized light, ER > 1 is typical, so
Deviation of the polarization basis vector, which is denoted as α, can be equated to a decrease in polarization contrast ratio
After the two communication sides complete the fine tracking, the two communication sides carry out the polarization basis vector calibration. And the transmitting direction transmits the polarization basis vector signal to the receiving party, and the receiving party receives the polarization basis vector signal and detects the polarization basis vector signal through the optical power detector.
The specific process of transmitting the polarization basis vector signal is as follows:
the first optical switch 108 in the communication signal generation module 01 of the transmission side is turned on. The fiber laser 101 emits pulsed laser with a wavelength of 850nm, the laser is split into two beams with unequal energy by the first fiber beam splitter 102, a strong light signal with energy accounting for 90% of incident light is output from the port 1, and a weak light with energy accounting for 10% of incident light energy is output from the output port 1. The strong light signal is split by the second fiber splitter 106, and the strong light signal with energy accounting for 90% of the incident light is used as a polarization basis vector signal. The polarization-basis-vector signal is optically coupled with the quantum signal by the first optical switch 108 via the fiber coupler 109. Since the intensity of the quantum signal light is much weaker than that of the polarization basis vector signal light, when the polarization basis vector signal is coupled with the quantum signal, the influence of the quantum signal on the detection result of the polarization basis vector signal is negligible. The polarization basis vector signal is modulated into a stable horizontal polarization by the polarization modulator 110, and is input from port 1 and output from port 2 of the optical fiber circulator 111 in the communication signal transceiver module 02. The polarization basis vector signal then passes through a fiber collimator 113 to convert the fiber light into parallel light transmitted in free space. The polarization basis vector signal light is converted into free space and transmitted, then expanded and collimated by a laser beam expander 115, and then wave front shaping is performed by a beam shaping mirror 116. And finally, the light is reflected by a dichroic mirror 008 in the optical antenna module 09 to enter a Kudet optical path and is finally transmitted to a receiving party through a telescope.
The polarization basis vector signal receiving and detecting process is as follows:
the second optical switch 202 in the receiving party is directed to port 1. The receiving side receives the polarization basis vector signal from the transmitting side through the optical antenna module 09. The polarization basis vector signal is shaped by the beam shaping mirror 116 through the Kude optical path, then reversely contracted by the laser beam expander 115, filtered by the first ultra-narrow band filter 114 to remove spatial stray light, coupled to the single-mode fiber 112 through the fiber collimator 113, and finally input through the port 2 of the optical circulator 111 and output from the port 3 to the polarization basis vector signal detection module. The polarization-basis-vector signal enters the second optical switch 202 after being subjected to polarization-basis-vector compensation by the polarization modulator 201 and is output from the port 1. The polarization basis vector signal passes through an analyzer 203 which only allows horizontal polarization transmission, then passes through an optical amplifier 204 for optical power amplification, and finally is detected by an optical power detector 205 for optical power detection. The receiving side controls the polarization modulator 201 according to the detection result of the detector until the polarization compensation added by the polarization modulator can make the optical power detector 205 stabilize near the optical power detection peak.
And after the two communication sides finish the polarization basis vector calibration, the two communication side systems distribute the quantum key. The transmitting side transmits the quantum signal to the receiving side, and the receiving side receives the quantum signal and detects the polarization state of the quantum signal.
The specific process of sending quantum signals by the sender is as follows:
the fiber laser 101 emits a pulsed laser having a wavelength of 850nm, a frequency of 50MHz, and a pulse width of 500 ps. The pulse laser is split into two beams of unequal energy by the first fiber beam splitter 102, and weak light with energy accounting for 10% of incident light energy is output from the port 2 as a quantum signal. The quantum signal is first modulated in intensity by the intensity modulator 103, and there are three modulation parameters, which are the quantum signal (0.125hv), the decoy state signal, and the (0.5hv) vacuum signal (0 hv). Then passes through a fixed optical attenuator 104 and then is attenuated by an adjustable optical attenuator 105 controlled by an electric signal in real time to obtain a stable quantum signal with the output intensity equivalent to the single photon level. The strong light which is split by the first optical fiber beam splitter 102 and has energy accounting for 90% of incident light energy is output from the port 1, then enters the second optical fiber beam splitter 106 and is split into light beams with energy accounting for 10% and 90% of the incident light energy respectively, wherein the light beam with energy accounting for 10% is output from the port 1, then the optical power is detected by the optical power detector 107, the detection result is fed back to a local computer to serve as a control signal of the adjustable optical attenuator 105, the attenuation coefficient of the attenuator is controlled, and the energy of the attenuated quantum signal is kept stable. The quantum signal modulated to the single photon level is input to the fiber coupler 109 and output from port 2 to port 1 of the fiber circulator 111 and output from port 2 of the fiber circulator 111. Then, the quantum signal is transmitted to the receiving side through the communication signal transceiving module 02 and the optical antenna module 09.
At this time, the first optical switch 108 in the transmitting-side communication signal generation module 01 is closed, and the unpolarized basis vector signal is input to the optical fiber coupler 109. Therefore, port 2 of the fiber coupler 109 outputs only quantum signal light at this time.
The specific process of receiving and detecting the quantum signal by the receiving party is as follows:
the second optical switch 202 in the receiver's quantum signal detection module 05 is directed to port 2. And the receiving party receives the quantum signal from the transmitting party through the optical antenna module. The quantum signal is shaped by the beam shaping mirror 116 through the kurdu optical path, then reversely contracted by the laser beam expander 115, filtered by the first ultra-narrow band filter 114 to remove spatial stray light, coupled to the single mode fiber 112 through the fiber collimator 113, and then input through the port 2 of the optical circulator 111 and output from the port 3 to enter the quantum signal detection module 05. The quantum signal enters the second optical switch 202 after being subjected to polarization compensation by the polarization modulator 201 and is output from the port 2. The quantum signal then enters the third fiber splitter 206 and randomly exits either port 1 or port 2 with equal probability. If the quantum signal exits from port 1 of 206 fiber beam splitter, the quantum signal maintains the polarization state before incidence after passing through the fiber polarization controller 207, and then passes through the polarization beam splitter 211 for beam splitting, the horizontal polarization state is output from port 1 and received by the single photon detector 213, and the vertical polarization state is output from port 2 and received by the single photon detector 214. If the quantum signal exits from port 2 of the third fiber beam splitter 206, the polarization state of the quantum signal after passing through the fiber polarization controller 208 is rotated by 45 °, and then the quantum signal is split by the polarization beam splitter 211, the horizontal polarization state is output from port 1 and received by the single photon detector 211, and the vertical polarization state is output from port 2 and received by the single photon detector 212. And respectively generating a corresponding code value 0 or a corresponding code value 1 as an initial key according to the response condition of the detector in a single pulse period.
And the two communication parties continuously track and aim the target in the communication process, and when the deviation of the target exceeds a threshold value in the communication process, quantum communication is suspended, distributed key information is reserved, and the tracking system quickly adjusts the posture of the antenna. When the tracking error has rested below the threshold, quantum key distribution continues.
Because the aircraft can move constantly in the communication process, the antenna attitude of the aircraft can change constantly along with the movement of the aircraft, and the polarization basis vectors of two communication parties are deviated. Therefore, after the initial polarization basis vector calibration is completed by the transmitting side and the receiving side, the polarization basis vector calibration needs to be continuously performed during the transmission of the quantum signals. At this time, the first optical switch 108 of the sender and the second optical switch 202 of the receiver are kept in an on state at a frequency of 100Hz during the transmission of the quantum signal, and simultaneously, the rising edge and the falling edge of the optical switches should be respectively less than 15ns, and the switching time of the first optical switch of the sender and the switching time of the second optical switch of the receiver should be kept synchronous.
After the sub-key distribution is completed, the sender and the receiver perform basis vector comparison through a classical communication network, abandon data with different basis vectors, and reserve the data with the same basis vectors as an initial key of communication.
And after the basis vector comparison is completed, carrying out error code detection on both communication sides, judging whether eavesdropping exists or not, if so, abandoning the quantum key distribution, discarding the key obtained by the communication, and stopping the communication. If no eavesdropping exists, the initial key is reserved, error correction and confidentiality enhancement are carried out on the key, and a final security key is obtained.
Variations and modifications to the above-described embodiments may occur to those skilled in the art, in light of the above teachings and teachings. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should fall within the protection scope of the claims of the present invention. In addition, although specific terms are used in the specification, the terms are used for convenience of description and do not limit the utility model in any way.
Claims (9)
1. A free space quantum key distribution system for aircraft includes aircraft FnWith ground station
Device characterized in that said aircraft FnWith ground station
The devices each include a quantum key distribution system, the quantum key distribution system is used for sending and receiving quantum communication signals, the quantum key distribution system is a sender when sending the quantum communication signals and is a receiver when receiving the quantum communication signals, wherein:
the quantum key distribution system comprises a communication signal generation module, a communication signal transceiving module, a communication signal receiving selection module, a polarization basis vector detection module, a quantum signal detection module, a fine tracking beacon generation module, a fine tracking beacon detection module, a fine tracking beacon transceiving module and an optical antenna module;
the communication signal generation module is used for generating a quantum signal and a polarization basis vector signal;
the communication signal transceiving module is used for coupling the generated quantum signal/polarization basis vector signal to free space from an optical fiber and transmitting the quantum signal/polarization basis vector signal to the optical antenna module; the optical antenna module is used for receiving the quantum signals/polarization basis vector signals from the optical fiber, and transmitting the quantum signals/polarization basis vector signals to the polarization basis vector detection module and the quantum signal detection module;
the polarization basis vector detection module is used for detecting the received polarization basis vector signals;
the quantum signal detection module is used for detecting the polarization state of the received quantum signal;
the communication signal receiving and selecting module is used for carrying out polarization basis vector compensation on the quantum signals and controlling the polarization basis vector detection module and the quantum signal detection module to switch between detection modes;
the fine tracking beacon generating module is used for generating a fine tracking beacon;
the fine tracking beacon detection module is used for carrying out imaging detection on the received fine tracking beacon;
when the fine tracking beacon transceiver module is in a fine tracking beacon receiving mode, the receiving optical antenna module receives the fine tracking beacon and transmits the fine tracking beacon to the fine tracking beacon detection module; when the optical antenna module is in a mode of transmitting the fine tracking beacon, the optical antenna module is used for transmitting the fine tracking beacon generated by the fine tracking beacon generating module;
the optical antenna module is used for transmitting the signal light transmitted by the communication signal transceiving module and the fine tracking beacon transceiving module to a receiving party; and transmitting the quantum signal/polarization basis vector signal received by the receiver to a quantum communication signal transceiver module and transmitting the fine tracking beacon received by the receiver to a fine tracking beacon transceiver module.
2. The free-space quantum key distribution system for aircraft according to claim 1, wherein the communication signal generation module comprises a fiber laser, a first fiber splitter, an intensity modulator, a fixed optical attenuator, a variable optical attenuator, a second fiber splitter, an optical power detector, a fiber coupler, and a first polarization modulator;
the output of the optical fiber laser is connected with the input end of a first optical fiber beam splitter, and a first output port of the first optical fiber beam splitter is sequentially connected with a second optical fiber beam splitter and an optical power detector through optical fibers; the second output port of the first optical fiber beam splitter is sequentially connected with an intensity modulator, a fixed optical attenuator, a variable optical attenuator, an optical fiber coupler and a first polarization modulator through optical fibers; the second optical fiber beam splitter is connected with the optical fiber coupler through the first optical switch.
3. The free-space quantum key distribution system for aircraft according to claim 2, wherein the communication signal transceiver module comprises a beam shaper, a laser beam expander, a first ultra-narrow band filter, a fiber collimator, and a fiber circulator;
the first port of the optical fiber circulator is connected with the polarization modulator, the second port of the optical fiber circulator is connected with the optical fiber collimator through a single mode fiber, and the optical fiber collimator is sequentially connected with the first ultra-narrow band filter, the laser beam expander and the beam shaper.
4. The free-space quantum key distribution system for aircraft according to claim 3, wherein the communication signal reception selection module comprises a second polarization modulator and a second optical switch, the second optical switch having two output ports, a first output port and a second output port;
the second polarization modulator is connected with a third port of the optical fiber circulator, and the second optical switch is connected with the second polarization modulator.
5. The free-space quantum key distribution system for aircraft according to claim 4, wherein the polarization basis vector detection module comprises an analyzer, an optical amplifier, and an optical power detector;
the analyzer is connected with a first output port of the second optical switch, and the analyzer is sequentially connected with the optical amplifier and the optical power detector.
6. The free-space quantum key distribution system for aircraft according to claim 5, wherein the quantum signal detection module comprises a third fiber splitter, two fiber polarization controllers, two fiber polarization splitters, and four single photon detectors;
the third optical fiber beam splitter is connected with the second output port of the second optical switch, two output ports of the third optical fiber beam splitter are respectively connected with an optical fiber polarization controller and an optical fiber polarization beam splitter in sequence, and two single photon detectors are connected to one optical fiber polarization beam splitter.
7. The free-space quantum key distribution system for aircraft according to claim 6, wherein the fine tracking beacon transceiver module comprises a second ultra narrow band filter and a rotating mirror connected in sequence;
the fine tracking beacon generation module comprises a light beam shaper and a semiconductor laser which are connected in sequence.
8. The free-space quantum key distribution system for aircraft according to claim 7, wherein the fine tracking beacon detection module comprises an imaging lens and a CMOS camera tube connected in sequence.
9. The free-space quantum key distribution system for aircraft according to claim 7, wherein the optical antenna module comprises a convex mirror, a concave mirror, a third planar mirror, a convex lens, a second planar mirror, a first planar mirror, a fast-tilt mirror, and a dichroic mirror;
the dichroic mirror is respectively connected with the beam shaper and the second ultra-narrow band filter, and the dichroic mirror is sequentially connected with the rapid tilting reflector, the third plane reflector, the second plane reflector, the convex lens, the first plane reflector, the convex reflector and the concave reflector.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111162903A (en) * | 2020-01-22 | 2020-05-15 | 华南师范大学 | Free space quantum key distribution system and method for aircraft |
| CN112578573A (en) * | 2021-02-24 | 2021-03-30 | 北京中创为南京量子通信技术有限公司 | Portable free space quantum communication optical axis calibration system |
| CN116027539A (en) * | 2022-12-15 | 2023-04-28 | 北京极光星通科技有限公司 | Laser communication advanced aiming system and method |
| GB2615354A (en) * | 2022-02-07 | 2023-08-09 | Aegiq Ltd | Free space quantum key distribution |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111162903A (en) * | 2020-01-22 | 2020-05-15 | 华南师范大学 | Free space quantum key distribution system and method for aircraft |
| CN111162903B (en) * | 2020-01-22 | 2024-03-15 | 广东尤科泊得科技发展有限公司 | Free space quantum key distribution system and method for aircraft |
| CN112578573A (en) * | 2021-02-24 | 2021-03-30 | 北京中创为南京量子通信技术有限公司 | Portable free space quantum communication optical axis calibration system |
| GB2615354A (en) * | 2022-02-07 | 2023-08-09 | Aegiq Ltd | Free space quantum key distribution |
| CN116027539A (en) * | 2022-12-15 | 2023-04-28 | 北京极光星通科技有限公司 | Laser communication advanced aiming system and method |
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