CN110635895A - CVQKD (constant velocity quantum key distribution) sending device and method based on self-stabilization intensity modulation and CVQKD system - Google Patents
CVQKD (constant velocity quantum key distribution) sending device and method based on self-stabilization intensity modulation and CVQKD system Download PDFInfo
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
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- H04B10/516—Details of coding or modulation
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- H04B10/541—Digital intensity or amplitude modulation
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Abstract
The invention provides a CVQKD (constant velocity quantum key distribution) sending device and method based on self-stabilizing intensity modulation and a CVQKD system, which comprise a pulse laser, a first beam splitter, an adjustable optical attenuator, a self-stabilizing intensity modulation device, a first phase modulator, a time delay device and a first polarization beam splitter; the pulse laser is used for generating a periodic pulse sequence; the first beam splitter is used for splitting the pulse sequence; the variable optical attenuator is used for attenuating signals and inputting the signals into the self-stabilizing intensity modulation device; the self-stabilization intensity modulation device comprises a second beam splitter and a second phase modulator; the first phase modulator generates Gaussian modulated signal light from the signal light; the delay device delays the Gaussian modulated signal light and inputs the delayed signal light into the first polarization beam splitter; and the first polarization beam splitter combines the delayed Gaussian modulated signal light and the local oscillator light and outputs the combined signal light and the local oscillator light. The CVQKD transmitting device and method based on the self-stabilizing intensity modulation and the CVQKD system realize the modulation of the orthogonal amplitude of the optical field.
Description
Technical Field
The invention relates to the technical field of Continuous Variable Quantum Key Distribution (CVQKD), in particular to a CVQKD transmitting device and method based on self-stabilizing intensity modulation and a CVQKD system.
Background
In the GG02 scheme commonly used in the CVQKD protocol, a transmitting end needs to perform two-dimensional gaussian modulation with a zero mean value on quadrature components (position and momentum components) of coherent states, and a commonly used method is to implement two-dimensional gaussian modulation on two quadrature components by using an amplitude modulator and a phase modulator.
It is common in the art to implement an amplitude (or intensity) modulator in a CVQKD distribution device using a lithium niobate modulator based on a mach-zehnder structure. However, in practical applications, the arm lengths of the two arms of the mach-zehnder interferometer are difficult to be strictly consistent, so that the interference contrast of the amplitude modulator is poor, and the effect of modulating the orthogonal amplitude of the optical field in the CVQKD system is finally poor.
In addition, the phase difference between the two arms cannot be kept stable for a long time during interference, for example, the length of the two arms of the interferometer is easily changed by the influence of external environment such as temperature, and the conversion introduces an undesired and unknown phase difference on the final composite signal, thereby causing the amplitude modulation result to drift. Therefore, it is usually necessary to add a corresponding intensity feedback device in the signal light path to compensate for the unknown variation. Therefore, the actual intensity modulation effect is poor, the stability is poor, the structure is complex, the cost is high, and the popularization and the application of large-scale integration are not facilitated.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a CVQKD transmission apparatus and method based on self-stabilizing intensity modulation, and a CVQKD system, which use a self-stabilizing intensity modulation apparatus based on Sagnac Effect (Sagnac Effect) to perform amplitude modulation, provide two light components for interference with identical optical paths, and perform different phase modulation on the two light components to form a modulation phase difference between the two light components, thereby generating different interference results and realizing modulation of orthogonal amplitude of an optical field. In addition, the general Mach-Zehnder amplitude modulator usually adopts an X-cut amplitude modulator, and does not generate an additional phase modulation effect, but the invention considers the non-zero phase modulation effect generated by the intensity modulation device based on the Sagnac structure and corrects the phase modulation required by the CVQKD.
In order to achieve the above and other related objects, the present invention provides a CVQKD transmitting apparatus and method based on self-stabilizing intensity modulation, and a CVQKD system, including a pulse laser, a first beam splitter, an adjustable optical attenuator, a self-stabilizing intensity modulation apparatus, a first phase modulator, a time delay apparatus, and a first polarization beam splitter; the pulse laser is used for generating a periodic pulse sequence; the first beam splitter is connected with the pulse laser and used for splitting the pulse sequence to generate local oscillation light and signal light; the local oscillator light is input into the first polarization beam splitter, and the signal light is input into the variable optical attenuator; the variable optical attenuator is connected with the first beam splitter and used for attenuating the signal light and inputting the signal light to the self-stabilizing intensity modulation device; the self-stabilizing intensity modulation device comprises a second beam splitter and a second phase modulator; the second beam splitter comprises a first port, a second port, a third port and a fourth port, and the second port and the third port are connected to form a bidirectional ring optical path; the first port or the fourth port is connected with the adjustable optical attenuator to obtain the attenuated signal light, the second port and the third port respectively output a first component and a second component which are split by the second beam splitter, and the fourth port or the first port outputs the signal light after intensity modulation; the second phase modulator is connected with the second port and the third port and is used for performing phase modulation on the first component and/or the second component so that the first component and the second component have a phase difference; the first phase modulator is used for generating the signal light with the intensity modulated into the signal light with the Gaussian modulated optical field orthogonal component; the delay device is connected with the first phase modulator and used for delaying the Gaussian modulated signal light and inputting the delayed Gaussian modulated signal light into the first polarization beam splitter; and the first polarization beam splitter is used for combining the delayed modulated signal light and the local oscillator light and then outputting the combined light.
In an embodiment of the present invention, the splitting ratio of the first beam splitter is 99: 1; the splitting ratio of the second beam splitter is 50: 50.
In an embodiment of the present invention, the first phase modulator and the second phase modulator are respectively controlled by two quantum random number generators or different channels of one quantum random number generator, the two quantum random number generators or the different channels of one quantum random number generator generate a series of random arrays satisfying a gaussian distribution with a modulation variance VN and a mean value zero, and each array modulates one signal light pulse to generate a gaussian modulated signal light; v is the self-defined coefficient, and N is shot noise.
In an embodiment of the present invention, the optical transmission unit further includes an optical transmission unit connected to the second beam splitter; the optical transmission unit comprises a first port, a second port and a third port, wherein the first port is used for receiving the attenuated signal light, the second port is connected to the first port of the second beam splitter through a polarization maintaining optical fiber, and the third port is used for outputting the intensity-modulated signal light; the first phase modulator is connected with a third port of the optical transmission unit or a first port or a fourth port of the second beam splitter; the optical transmission unit adopts a circulator or a beam splitter.
In an embodiment of the present invention, the delay device includes a faraday rotator, an optical fiber delay line, and a second polarization beam splitter, which are connected in sequence, the gaussian modulated signal light is input to the second polarization beam splitter, and the output light of the second polarization beam splitter is output to the first polarization beam splitter.
In an embodiment of the present invention, the optical fiber laser further includes an amplitude modulator, and the amplitude modulator is connected to the pulse laser and the first beam splitter, and is configured to perform amplitude modulation on the pulse sequence and input the pulse sequence to the first beam splitter.
In an embodiment of the invention, the amplitude modulator employs the self-stabilizing intensity modulation apparatus.
In an embodiment of the present invention, the first beam splitter and the second beam splitter are both polarization maintaining beam splitters; the first phase modulator and the second phase modulator are both polarization maintaining phase modulators.
In an embodiment of the invention, the signal light is generated when the self-stabilizing intensity modulation device performs modulation
Phase shift of (2); deduction when the first phase modulator is modulating
Phase shift of (2); vsVoltage V of the clockwise pulse light obtained by beam splitting of the second beam splitternIs the voltage V of the pulse light in the counterclockwise direction obtained by beam splitting of the second beam splitterπIs a half-wave voltage across the second phase modulator.
In an embodiment of the present invention, when the second beam splitter adopts the first port as the output port, voltages of the pulsed light in the counterclockwise direction and the clockwise direction obtained after beam splitting by the second beam splitter are both 2kVπWherein k is 0,1,2 …; when the second beam splitter adopts the fourth port as the output port, the modulation voltage needs to be additionally increased by (1+2k) VπWhere k is 0,1,2 …, VπIs the half-wave voltage of the second phase modulator.
In addition, the invention provides a CVQKD sending method based on self-stabilizing intensity modulation, which is applied to a CVQKD sending device based on self-stabilizing intensity modulation, wherein the CVQKD sending device based on self-stabilizing intensity modulation comprises a pulse laser, a first beam splitter, an adjustable optical attenuator, a self-stabilizing intensity modulation device, a first phase modulator, a time delay device and a first polarization beam splitter; the CVQKD sending method based on the self-stabilizing intensity modulation comprises the following steps:
generating a periodic pulse sequence based on the pulsed laser;
splitting the pulse sequence based on the first beam splitter to generate local oscillation light and signal light; the local oscillator light is input into a first polarization beam splitter, and the signal light is input into a variable optical attenuator;
the signal is input into a self-stabilizing intensity modulation device after being attenuated by the variable optical attenuator;
performing intensity modulation on the attenuated signal light based on the self-stabilization intensity modulation device, wherein the self-stabilization intensity modulation device comprises a second beam splitter and a second phase modulator; the second beam splitter comprises a first port, a second port, a third port and a fourth port, and the second port and the third port are connected to form a bidirectional ring optical path; the first port or the fourth port is connected with the adjustable optical attenuator to obtain the attenuated signal light, the second port and the third port respectively output a first component and a second component which are split by the second beam splitter, and the fourth port or the first port outputs the signal light after intensity modulation; the second phase modulator is connected with the second port and the third port and is used for modulating the phase of the first component and/or the second component so that the first component and the second component have a phase difference;
generating signal light with Gaussian modulated light field orthogonal components based on the signal light after intensity modulation by the first phase modulator;
delaying the Gaussian modulated signal light based on the delay device and inputting the delayed signal light into a first polarization beam splitter;
and combining the delayed Gaussian modulated signal light and the local oscillator beam based on the first polarization beam splitter and then outputting the combined signal light and the local oscillator beam.
Finally, the invention provides a CVQKD system based on self-stabilizing intensity modulation, which comprises the CVQKD transmitting device and the CVQKD receiving device based on self-stabilizing intensity modulation.
As described above, the CVQKD transmitting apparatus and method and CVQKD system based on self-stabilized intensity modulation according to the present invention have the following advantageous effects:
(1) the amplitude modulation is carried out by adopting a self-stabilizing intensity modulation device based on the Sagnac effect, and completely consistent light paths are provided for two light components used for interference;
(2) the two light components are subjected to different phase modulation to form a modulation phase difference between the two light components, so that different interference results are generated, and the modulation of the orthogonal amplitude of the light field is realized;
(3) the phase modulation effect generated by the self-stabilizing intensity modulation device with the Sagnac effect can realize the modulation of the optical field quadrature phase together by matching with another phase modulator;
(4) good stability and simple structure, and is beneficial to the popularization and application of large-scale integration.
Drawings
Fig. 1 is a schematic diagram illustrating an exemplary embodiment of a self-stabilizing intensity modulation-based CVQKD transmitting apparatus according to the present invention;
FIG. 2 is a schematic structural diagram of a self-stabilizing intensity modulation apparatus according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a self-stabilizing intensity modulation apparatus according to another embodiment of the present invention;
FIG. 4 is a schematic diagram of a self-stabilized intensity modulation based CVQKD system according to an embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating variation of voltage-related parameters of the self-stabilized intensity modulation apparatus according to the present invention;
fig. 6 is a flowchart of a self-stabilizing intensity modulation based CVQKD transmission method according to an embodiment of the present invention;
fig. 7 is a schematic diagram of a CVQKD system according to an embodiment of the invention.
Description of the element reference numerals
1 pulse laser
2 first beam splitter
3 variable optical attenuator
4 self-stabilization intensity modulation device
41 second beam splitter
42 second phase modulator
43 optical transmission unit
5 first phase modulator
6 time delay device
61 Faraday rotator mirror
62 optical fiber delay line
63 second polarization beam splitter
7 first polarization beam splitter
8 amplitude modulator
9 polarization controller
10 third polarization beam splitter
11 fourth polarization beam splitter
12 optical fiber delay line
13 Faraday rotator mirror
14 balance detector
15 third phase modulator
71 CVQKD transmitting device based on self-stabilization intensity modulation
72 CVQKD receiving device
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions of the present invention, so that the present invention has no technical significance. In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention. In addition, in the present invention, unless otherwise expressly specified or limited, the terms "connected" and "connecting" are to be construed broadly and may include, for example, direct connection, indirect connection via an intermediate, and communication between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
As shown in fig. 1, in an embodiment, the CVQKD transmitting apparatus based on self-stabilized intensity modulation of the present invention includes a pulsed laser 1, a first beam splitter 2, a variable optical attenuator 3, a self-stabilized intensity modulation apparatus 4, a first phase modulator 5, a time delay apparatus 6 and a first polarization beam splitter 7.
The pulsed laser 1 is used to generate a periodic pulse train. The periodic pulse train may be generated by the pulse laser 1 through internal modulation, or may be generated by chopping the light output from the pulse laser 1 with a chopper. Preferably, the chopper is an amplitude modulator, preferably the amplitude modulator is a self-stabilizing intensity modulation device.
The first beam splitter 2 is connected with the pulse laser 1 and is used for splitting the pulse sequence to generate local oscillation light and signal light; the local oscillator light is input to the first polarization beam splitter 7, and the signal light is input to the variable optical attenuator 3.
Preferably, the first beam splitter 2 splits light by using a beam splitter with a high splitting ratio, such as 99:1, wherein a stronger beam of light is input to one port of the first polarization beam splitter 7 as local oscillation light; a weaker beam of light is input to the variable optical attenuator 3 as signal light.
The adjustable optical attenuator 3 is connected with the first beam splitter 2, and is used for attenuating the signal light and inputting the attenuated signal light to the self-stabilization intensity modulation device 4.
The self-stabilizing intensity modulation device 4 comprises a second beam splitter 41 and a second phase modulator 42; the second beam splitter 41 includes a first port, a second port, a third port and a fourth port, and the second port and the third port are connected to form a bidirectional ring optical path; the first port or the fourth port is connected with the adjustable optical attenuator 3 to obtain the attenuated signal light, the second port and the third port respectively output a first component and a second component which are split by the second beam splitter 2, and the fourth port or the first port outputs the signal light after intensity modulation; the second phase modulator 42 is connected to the second port and the third port for phase modulating the first component and/or the second component such that the first component and the second component have a phase difference Δ θ. It should be noted that the functions of the first port and the fourth port of the second beam splitter 41 may be interchanged, that is, the attenuated signal light is input to the fourth port, and the intensity-modulated signal light is output from the first port; or the first port inputs the attenuated signal light, and the fourth port outputs the signal light after intensity modulation.
As shown in fig. 2, in an embodiment, the second splitter 41 includes a first port 1A, a second port 1B, a third port 1C and a fourth port 1D. The second port 1B and the third port 1C are connected through a polarization-maintaining optical fiber to form a bidirectional ring optical path. The second phase modulator is connected to the second port 1B and the third port 1C. When the first port 1A is an input port, the second port 1B and the third port 1C may be a reflection output port and a transmission output port, respectively; when the second port 1B is an input port, the first port 1A and the fourth port 1D may be a reflective output port and a transmissive output port, respectively.
Preferably, the second beam splitter 41 adopts a beam splitter with a beam splitting ratio of 50: 50.
The first phase modulator 5 is configured to generate the signal light with the intensity modulated into the signal light with the gaussian modulated optical field orthogonal component. Wherein the light field orthogonal components are position and momentum components.
Specifically, the first phase modulator 5 and the second phase modulator 42 are respectively controlled by two quantum random number generators or different channels of one quantum random number generator, the two quantum random number generators or the different channels of one quantum random number generator generate a series of random arrays (x, p) satisfying gaussian distribution with a modulation variance VN and a mean value zero, each array modulates one signal light pulse, and finally modulates the signal light into a coherent state of | x + ip >, that is, generates signal light satisfying gaussian modulation. Wherein V is a self-defined coefficient, and N is shot noise.
In an embodiment of the present invention, as shown in fig. 3, the self-stabilized intensity modulation apparatus 4 of the present invention further includes an optical transmission unit 43 connected to the second beam splitter; the optical transmission unit 43 includes a first port 3A, a second port 3B, and a third port 3C, the first port 3A is configured to receive the attenuated signal light, the second port 3B is connected to the first port of the second beam splitter 41 through a polarization maintaining fiber, and the third port 3C is configured to output the intensity-modulated signal light; the first phase modulator 5 is connected to the third port 3C of the optical transmission unit 43 or the first port or the fourth port of the second beam splitter 41. Preferably, in the optical transmission unit 43, the light input from the first port may be output from the second port, but may not be output from the third port; light input from the second port may be output from the third port. Specifically, the optical transmission unit employs a circulator or a beam splitter.
The delay device 6 is connected to the first phase modulator 5, and configured to delay the gaussian modulated signal light and input the delayed gaussian modulated signal light to the first polarization beam splitter 7.
Preferably, as shown in fig. 4, the time delay device 6 includes a faraday rotator mirror (FM2)61, an optical fiber delay line 62, and a second polarization beam splitter 63 connected in sequence, the gaussian modulated signal light is input to the second polarization beam splitter 63, and the output light of the second polarization beam splitter 63 is output to the first polarization beam splitter 7. And after passing through the time delay device, the Gaussian modulated signal light generates a certain time difference with the local oscillation light pulse.
And the first polarization beam splitter 7 is configured to combine the delayed gaussian modulated signal light and the local oscillator light for output.
In an embodiment of the present invention, the CVQKD transmitting apparatus based on self-stabilizing intensity modulation further includes an amplitude modulator 8, where the amplitude modulator 8 is connected to the pulse laser 1 and the first beam splitter 2, and is configured to amplitude modulate the pulse sequence and input the modulated pulse sequence to the first beam splitter 2. A higher extinction ratio is generally required in CVQKD systems, and if the extinction ratio of a pulse train generated by a pulse laser is not sufficient, the extinction ratio of the pulse train needs to be further improved by amplitude modulation of an amplitude modulator before being input to the first beam splitter.
Preferably, the amplitude modulator employs the self-stabilizing intensity modulation device.
Preferably, the first beam splitter and the second beam splitter are both polarization-maintaining beam splitters; the first phase modulator and the second phase modulator are both polarization maintaining phase modulators.
The operation principle of the CVQKD receiving apparatus corresponding to the CVQKD transmitting apparatus based on self-stabilized intensity modulation according to the present invention will be briefly described below. As shown in fig. 4, the delayed gaussian modulated signal light and the local oscillator light are combined by the first polarization beam splitter 7 and then transmitted to the CVQKD receiving apparatus through an optical fiber. Due to the birefringence effect of light transmitted in the optical fiber, it is necessary to perform polarization correction and compensation on the light through the polarization controller 9, and then the light separates the local oscillation light from the signal light again through the third polarization beam splitter 10, where the local oscillation light meets the signal light right at the balanced detector (BHD)14 through the delay device formed by the fourth polarization beam splitter 11, the optical fiber delay line 12, and the faraday rotator (FM2)13, that is, the timing is re-synchronized. The local oscillation light is subjected to phase modulation through the third phase modulator 15, the third phase modulator 15 is controlled by a quantum random number generator, and the orthogonal component x or p of the light field can be measured according to different outputs of the quantum random number generator. The signal light and the local oscillation light separated by the receiving device enter a balance detector (BHD) to be measured at the same time, if a heterodyne detector is adopted for detection, a third phase modulator is not needed, and orthogonal components x and p of a light field can be measured at the same time.
Since the CVQKD system involves phase modulation, the self-stabilizing intensity modulation apparatus of the present invention includes a phase modulator, and therefore, the effect of the self-stabilizing intensity modulation apparatus on the phase modulation is not negligible, and calculation and compensation are required.
As shown in fig. 5, it is assumed that the signal light input from the steady intensity modulation device is periodic pulse light having a period Tp. And the time difference Tsn between the S pulse light and the N pulse light reaching the second phase modulator is obtained by splitting the light by the second beam splitter. Setting the first port 1A as the output port of the self-stabilizing intensity modulation device, and the voltage loaded on the N pulse light is VnHalf-wave voltage of the second phase modulator is VπAccording to the principle of the phase modulator, the phase of the modulated N pulse light is known to be
Setting the voltage applied to the S pulse light to VsThe phase of the S pulse light is modulated to be
Assuming that the initial light field incident on the self-stabilized intensity modulation device is EinThe initial phase is zero, and the optical fields in the S and N directions after passing through the second beam splitter are the same by neglecting the insertion loss of each device
After being modulated by the second phase modulator, the light field emitted by the second beam splitter is
From the above, it can be seen that there occurs between the outgoing light field and the incoming light field
The phase shift of (2). The second phase modulator modulates the phase-to-voltage relationship of
Where v (t) is a time varying voltage signal applied to the second phase modulator. The self-stabilizing intensity modulation device is adopted to carry out quadrature amplitude modulation on the optical field so as to generate phase
Drift of (2). Therefore, the first phase modulator is used to modulate the optical field quadrature phase and need to be subtracted
A phase shift section. Generally for simplicity, V may be sets(t) 0 or Vn(t) is 0. Setting the first port 1A as the output port of the self-stabilizing intensity modulation device, the voltages loaded on the N pulse light and the S pulse light are both 2kVπWhere k is 0,1,2 …. Preferably, k is 0. If the fourth port 1D is used as the output port, the original modulation voltage needs to be increased by (1+2k) V to obtain the same result as the first port 1AπWhere k is 0,1,2 …. Preferably k is 0.
In addition, the above results do not take the insertion loss of each device into consideration, and the corresponding voltage can be easily calculated based on the above results when the insertion loss is taken into consideration.
As shown in fig. 6, in an embodiment, the CVQKD transmission method based on self-stabilizing intensity modulation according to the present invention is applied to a CVQKD transmission apparatus based on self-stabilizing intensity modulation, where the CVQKD transmission apparatus based on self-stabilizing intensity modulation includes a pulse laser, a first beam splitter, an adjustable optical attenuator, a self-stabilizing intensity modulation apparatus, a first phase modulator, a time delay apparatus, and a first polarization beam splitter; the CVQKD sending method based on the self-stabilizing intensity modulation comprises the following steps:
step S61, generating a periodic pulse sequence based on the pulsed laser.
Step S62, splitting the pulse sequence based on the first beam splitter to generate local oscillation light and signal light; the local oscillator light is input into a first polarization beam splitter, and the signal light is input into a variable optical attenuator.
And step S63, attenuating the signal light based on the variable optical attenuator and inputting the signal light to a self-stabilizing intensity modulation device.
Step S64, performing intensity modulation on the attenuated signal light based on the self-stabilization intensity modulation apparatus, where the self-stabilization intensity modulation apparatus includes a second beam splitter and a second phase modulator; the second beam splitter comprises a first port, a second port, a third port and a fourth port, and the second port and the third port are connected to form a bidirectional ring optical path; the first port or the fourth port is connected with the adjustable optical attenuator to obtain the attenuated signal light, the second port and the third port respectively output a first component and a second component which are split by the second beam splitter, and the fourth port or the first port outputs the signal light after intensity modulation; the second phase modulator is connected to the second port and the third port, and phase-modulates the first component and/or the second component so that the first component and the second component have a phase difference.
Step S65, based on the first phase modulator, generating the signal light with the intensity modulated, light field orthogonal component being gaussian modulated.
And step S66, delaying the Gaussian modulated signal light based on the delay device and inputting the delayed signal light into a first polarization beam splitter.
And step S67, combining the delayed gaussian modulated signal light and the local oscillator beam based on the first polarization beam splitter, and outputting the combined signal light and local oscillator beam.
As shown in fig. 7, in an embodiment, the CVQKD system based on self-stabilizing intensity modulation of the present invention includes the above-mentioned CVQKD transmitting device 71 and CVQKD receiving device 72 based on self-stabilizing intensity modulation.
The CVQKD receiving device 72 is a CVQKD receiving device that is conventional in the art, and therefore, is not described herein again.
In summary, the CVQKD transmitting apparatus and method and the CVQKD system based on the self-stabilizing intensity modulation of the present invention use the self-stabilizing intensity modulation apparatus based on the sagnac effect to perform amplitude modulation, so as to provide a completely consistent optical path for two optical components used for interference; the two light components are subjected to different phase modulation to form a modulation phase difference between the two light components, so that different interference results are generated, and the modulation of the orthogonal amplitude of the light field is realized; the phase modulation effect generated by the self-stabilizing intensity modulation device with the Sagnac effect can realize the modulation of the optical field quadrature phase together by matching with another phase modulator; good stability and simple structure, and is beneficial to the popularization and application of large-scale integration. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (12)
1. A CVQKD transmission apparatus based on self-stabilized intensity modulation, characterized by: the self-stabilizing optical fiber laser comprises a pulse laser, a first beam splitter, a variable optical attenuator, a self-stabilizing intensity modulation device, a first phase modulator, a time delay device and a first polarization beam splitter;
the pulse laser is used for generating a periodic pulse sequence;
the first beam splitter is connected with the pulse laser and used for splitting the pulse sequence to generate local oscillation light and signal light; the local oscillator light is input into the first polarization beam splitter, and the signal light is input into the variable optical attenuator;
the variable optical attenuator is connected with the first beam splitter and used for attenuating the signal light and inputting the signal light to the self-stabilizing intensity modulation device;
the self-stabilizing intensity modulation device comprises a second beam splitter and a second phase modulator; the second beam splitter comprises a first port, a second port, a third port and a fourth port, and the second port and the third port are connected to form a bidirectional ring optical path; the first port or the fourth port is connected with the adjustable optical attenuator to obtain the attenuated signal light, the second port and the third port respectively output a first component and a second component which are split by the second beam splitter, and the fourth port or the first port outputs the signal light after intensity modulation; the second phase modulator is connected with the second port and the third port and is used for performing phase modulation on the first component and/or the second component so that the first component and the second component have a phase difference;
the first phase modulator is used for generating the signal light with the intensity modulated into the signal light with the Gaussian modulated optical field orthogonal component;
the delay device is connected with the first phase modulator and used for delaying the Gaussian modulated signal light and inputting the delayed Gaussian modulated signal light into the first polarization beam splitter;
and the first polarization beam splitter is used for combining the delayed Gaussian modulated signal light and the local oscillator beam and outputting the combined signal light and the local oscillator beam.
2. A self-stabilizing intensity modulation-based CVQKD transmission apparatus according to claim 1, wherein: the splitting ratio of the first beam splitter is 99: 1; the splitting ratio of the second beam splitter is 50: 50.
3. A self-stabilizing intensity modulation-based CVQKD transmission apparatus according to claim 1, wherein: the first phase modulator and the second phase modulator are respectively controlled by different channels of two quantum random number generators or one quantum random number generator, different channels of the two quantum random number generators or one quantum random number generator generate a series of random arrays meeting Gaussian distribution with modulation variance V x N and mean value zero, and each array modulates one signal light pulse to generate signal light meeting Gaussian modulation requirements; v is the self-defined coefficient, and N is shot noise.
4. A self-stabilizing intensity modulation-based CVQKD transmission apparatus according to claim 1, wherein: the optical transmission unit is connected with the second beam splitter; the optical transmission unit comprises a first port, a second port and a third port, wherein the first port is used for receiving the attenuated signal light, the second port is connected to the first port of the second beam splitter through a polarization maintaining optical fiber, and the third port is used for outputting the intensity-modulated signal light; the first phase modulator is connected with a third port of the optical transmission unit or a first port or a fourth port of the second beam splitter; the optical transmission unit adopts a circulator or a beam splitter.
5. A self-stabilizing intensity modulation-based CVQKD transmission apparatus according to claim 1, wherein: the time delay device comprises a Faraday rotating mirror, an optical fiber time delay line and a second polarization beam splitter which are sequentially connected, the Gaussian modulated signal light is input into the second polarization beam splitter, and the output light of the second polarization beam splitter is output to the first polarization beam splitter.
6. A self-stabilizing intensity modulation-based CVQKD transmission apparatus according to claim 1, wherein: the pulse laser device further comprises an amplitude modulator, wherein the amplitude modulator is connected with the pulse laser device and the first beam splitter and is used for inputting the pulse sequence into the first beam splitter after amplitude modulation is carried out on the pulse sequence.
7. A self-stabilizing intensity modulation-based CVQKD transmission apparatus according to claim 6, wherein: the amplitude modulator adopts the self-stabilization intensity modulation device.
8. A self-stabilizing intensity modulation-based CVQKD transmission apparatus according to claim 1, wherein: the first beam splitter and the second beam splitter are both polarization-maintaining beam splitters; the first phase modulator and the second phase modulator are both polarization maintaining phase modulators.
9. A self-stabilizing intensity modulation-based CVQKD transmission apparatus according to claim 1, wherein: the signal light is generated when the self-stabilization intensity modulation device is used for modulation
Phase shift of (2); deduction when the first phase modulator is modulating
Phase shift of (2); vsVoltage V of the clockwise pulse light obtained by beam splitting of the second beam splitternIs the voltage V of the pulse light in the counterclockwise direction obtained by beam splitting of the second beam splitterπIs a half-wave voltage across the second phase modulator.
10. A self-stabilizing intensity modulation-based CVQKD transmission apparatus according to claim 1, wherein: when the first port of the second beam splitter is used as an output port, the voltages on the pulse light in the anticlockwise direction and the pulse light in the clockwise direction obtained after beam splitting of the second beam splitter are both 2kVπWherein k is 0,1,2 …; when the second beam splitter adopts the fourth port as the output port, the modulation voltage needs to be additionally increased by (1+2k) VπWhere k is 0,1,2 …, VπIs the half-wave voltage of the second phase modulator.
11. A CVQKD sending method based on self-stabilizing intensity modulation is characterized in that: the CVQKD transmitting device based on the self-stabilizing intensity modulation comprises a pulse laser, a first beam splitter, an adjustable optical attenuator, a self-stabilizing intensity modulation device, a first phase modulator, a time delay device and a first polarization beam splitter; the CVQKD sending method based on the self-stabilizing intensity modulation comprises the following steps:
generating a periodic pulse sequence based on the pulsed laser;
splitting the pulse sequence based on the first beam splitter to generate local oscillation light and signal light; the local oscillator light is input into a first polarization beam splitter, and the signal light is input into a variable optical attenuator;
the signal is input into a self-stabilizing intensity modulation device after being attenuated by the variable optical attenuator;
performing intensity modulation on the attenuated signal light based on the self-stabilization intensity modulation device, wherein the self-stabilization intensity modulation device comprises a second beam splitter and a second phase modulator; the second beam splitter comprises a first port, a second port, a third port and a fourth port, and the second port and the third port are connected to form a bidirectional ring optical path; the first port or the fourth port is connected with the adjustable optical attenuator to obtain the attenuated signal light, the second port and the third port respectively output a first component and a second component which are split by the second beam splitter, and the fourth port or the first port outputs the signal light after intensity modulation; the second phase modulator is connected with the second port and the third port and is used for modulating the phase of the first component and/or the second component so that the first component and the second component have a phase difference;
generating signal light with Gaussian modulated light field orthogonal components based on the signal light after intensity modulation by the first phase modulator;
delaying the Gaussian modulated signal light based on the delay device and inputting the delayed signal light into a first polarization beam splitter;
and combining the delayed Gaussian modulated signal light and the local oscillator beam based on the first polarization beam splitter and then outputting the combined signal light and the local oscillator beam.
12. A CVQKD system based on self-stabilizing intensity modulation, characterized by: comprising the self-stabilizing intensity modulation based CVQKD transmitting device and the CVQKD receiving device of one of claims 1-10.
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