CN210007714U

CN210007714U - Quantum key distribution phase codec, corresponding codec device and system

Info

Publication number: CN210007714U
Application number: CN201920296070.4U
Authority: CN
Inventors: 许华醒
Original assignee: China Electronics Technology Group Corp CETC
Current assignee: China Electronics Technology Group Corp CETC; Electronic Science Research Institute of CTEC
Priority date: 2019-03-08
Filing date: 2019-03-08
Publication date: 2020-01-31
Anticipated expiration: 2029-03-08

Abstract

The utility model provides an quantum key distribution phase codec and corresponding coding and decoding device and system, this phase codec includes the beam splitter, respectively through two polarization quadrature rotatory reflection device of two arms and beam splitter optical coupling, set up the phase modulator on in two arms, among two reflection device or every reflection device include the polarization beam splitter who has input port and two output ports, and couple to corresponding arm through the input port of polarization beam splitter, two output ports of every polarization beam splitter are through the polarization maintaining optical fiber who contains odd number 90 degrees welding point optical coupling each other, the light pulse of two output port outputs of polarization beam splitter couples to corresponding polarization maintaining optical fiber's slow axis and fast axis respectively.

Description

Quantum key distribution phase codec, corresponding codec device and system

Technical Field

The utility model relates to a secret communication technology field of optical transmission especially relates to kinds of quantum key distribution phase codec based on polarization quadrature rotation reflection, including this phase codec's corresponding coding and decoding device and quantum key distribution system.

Background

The quantum secret communication technology is the leading-edge hotspot field combining quantum physics with information science, the quantum secret communication can realize the safe transmission of information on a public channel based on the quantum key distribution technology and times of secret code principles, the quantum key distribution is based on the physical principles of quantum mechanics Heisebang uncertain relation, quantum unclonable theorem and the like, the secret key can be safely shared among users, potential eavesdropping behaviors can be detected, and the quantum secret communication technology can be applied to the fields of high-safety information transmission requirements of national defense, government affairs, finance, electric power and the like.

The ground quantum key distribution is mainly based on optical fiber channel transmission, and because phase encoding adopts the phase difference of front and back optical pulses to encode information and can be stably maintained in the long-distance optical fiber channel transmission process, the phase encoding and the time bit-phase encoding based on the unequal arm interferometer are the main encoding schemes for quantum key distribution application. However, the manufacturing of the optical fiber has non-ideal conditions such as non-circular symmetry of the cross section, nonuniform distribution of the refractive index of the fiber core along the radial direction, and the like, and the optical fiber is influenced by temperature, strain, bending, and the like in the actual environment, and can generate random birefringence effect. Therefore, after the optical pulse is transmitted by the long-distance optical fiber and transmitted by the two-arm optical fiber of the unequal-arm interferometer, the problem of polarization-induced fading exists when the unequal-arm interferometer is used for phase decoding interference, so that the decoding interference is unstable, and the error rate is increased. If use the equipment of rectifying, can increase system complexity and cost, and to strong interference condition such as aerial fiber cable, road bridge optical cable difficult to realize stable application.

For quantum key distribution phase encoding and time bit-phase encoding schemes, how to stably and efficiently perform interferometric decoding is a hotspot and difficult problem for quantum secret communication application based on the existing optical cable infrastructure.

SUMMERY OF THE UTILITY MODEL

The utility model discloses a main aim at provides kinds of quantum key distribution phase place codecs based on polarization quadrature rotation reflection, including this phase place codec's corresponding codec and quantum key distribution system to solve the unstable difficult problem of phase place decoding interference that polarization induction fading arouses in phase place coding and time bit-phase place coding quantum key distribution application.

The utility model provides an at least following technical scheme:

the quantum key distribution phase codec comprises a beam splitter, two reflecting devices which are respectively optically coupled with the beam splitter through two arms, wherein each reflecting device is a polarization orthogonal rotation reflecting device, or each reflecting device in the two reflecting devices comprises a polarization beam splitter with an input port and two output ports, and is coupled to the corresponding arm in the two arms through the input port of the polarization beam splitter, the two output ports of each polarization beam splitter are optically coupled with each other through a transmission optical path, and for at least reflecting devices comprising polarization beam splitters, the transmission optical path of the reflecting devices is formed by polarization-maintaining optical fibers containing odd number of 90-degree fusion-splicing points, optical pulses output by output ports in the two output ports of the polarization beam splitter are coupled to the slow axis of the polarization-maintaining optical fibers, and optical pulses output by another output ports in the two output ports of the polarization beam splitter are coupled to the fast axis of the polarization-maintaining optical fibers.

2. The phase codec of claim 1, wherein the two reflective devices are identically constructed polarization orthogonal rotating reflective devices or differently constructed polarization orthogonal rotating reflective devices.

3. The phase codec of claim 1, wherein the odd number of 90-degree weld points comprises 1 90-degree weld point or more odd number of 90-degree weld points.

4. The phase codec of claim 1, wherein the beam splitter is a polarization maintaining beam splitter.

5. The phase codec of claim 1, wherein the two arms are each polarization-maintaining optical paths, and the optical devices on the two arms are polarization-maintaining optical devices and/or non-birefringent optical devices.

6. The phase codec of , wherein the phase codec further comprises a phase modulator disposed on the beam splitter front end or on at least of the two arms.

7, dc modulation quantum key distribution phase codec, comprising a pre-splitter and two phase codecs according to any in schemes 1-6, where the two phase codecs are optically coupled to the pre-splitter via two sub-optical paths, respectively, and of the splitter of each phase codec, which is not coupled to the ports of the two arms of the phase codec, is optically coupled to a corresponding sub-optical path of the two sub-optical paths, and each sub-optical path is provided with optical circulators.

8, quantum key distribution time bit-phase codec, comprising a front splitter and phase codecs according to of schemes 1-6, the phase codecs being optically coupled to the front splitter via sub-optical paths, wherein of the ports of the splitter of the phase codecs not coupled to the two arms are optically coupled to sub-optical paths.

9, dc modulation quantum key distribution time bit-phase codec, comprising a front beam splitter and phase codecs according to in schemes 1 to 6, the phase codecs are optically coupled to the front beam splitter via sub-optical paths, wherein of the beam splitters of the phase codecs, which are not coupled to the two arms, are optically coupled to sub-optical paths, and optical circulators are disposed on the sub-optical paths.

10. The codec according to claim 8 or 9, further comprising a splitter coupled to the front splitter via another sub-optical paths.

11, a quantum key distribution system, comprising:

the phase codec according to of any one of claims 1 to 6 or the codec device according to of any one of claims 7 to 10, which is provided at a receiving end of the quantum key distribution system for decoding, and/or

The phase codec according to of any one of schemes 1 to 6 or the codec device according to of any one of schemes 7 to 10, which is provided at a transmitting end of the quantum key distribution system for encoding.

The utility model discloses an unexpected beneficial effect has been realized from this to the creative structure for can encode and decode the interference to the input light pulse of arbitrary polarization state steadily, utilize the utility model discloses a scheme can realize the stable interference output of interferometer department at the phase decoding to the input light pulse of arbitrary polarization state, has solved phase coding and time bit-phase place code quantum key distribution and has used the induced decline of polarization and cause the unable problem of stable work of system, the utility model provides kinds of anti-polarization induced decline phase coding and time bit-phase place code quantum key distribution decoding scheme of easily realizing and using.

Drawings

Fig. 1 is a schematic structural diagram of a quantum key distribution phase codec based on polarization orthogonal rotation reflection according to a preferred embodiment of the present invention ;

fig. 2 is a schematic structural diagram of another preferred embodiment of the present invention illustrating a structure of a quantum key distribution phase codec based on polarization orthogonal rotation reflection;

FIG. 3 is a schematic diagram of the structure of polarization orthogonal rotation reflectors that can be used in the phase encoder/decoder of the present invention;

FIG. 4 is a schematic diagram of another polarization orthogonal rotation reflectors that can be used in the phase encoder/decoder of the present invention;

FIG. 5 is a schematic diagram of another polarization orthogonal rotation reflectors that can be used in the phase encoder/decoder of the present invention;

fig. 6 is a schematic structural diagram of a dc modulation quantum key distribution phase encoding and decoding device based on polarization orthogonal rotation reflection according to a preferred embodiment of the present invention ;

fig. 7 is a schematic structural diagram of a quantum key distribution time bit-phase encoding and decoding device based on polarization orthogonal rotation reflection according to a preferred embodiment of the present invention ;

fig. 8 is a schematic structural diagram of a dc modulation quantum key distribution time bit-phase encoding and decoding device based on polarization orthogonal rotation reflection according to a preferred embodiment of the present invention .

Detailed Description

The following detailed description of the preferred embodiments of the invention, which is incorporated in and constitutes part of this application , and together with embodiment of the invention serves to explain the principles of the invention, a detailed description of known functions and structures of devices described herein will be omitted for clarity and simplicity.

The quantum key distribution phase codec based on polarization orthogonal rotation reflection of the preferred embodiment of the present invention is shown in fig. 1, and comprises a beam splitter 101, a phase modulator 102, and two

reflection devices

103 and 104.

Two reflecting

devices

103 and 104 are optically coupled to the beam splitter 101 via two arms (upper and lower arms in fig. 1), respectively, and a phase modulator 102 is inserted into (upper arm in fig. 1) of the two arms.

According to the present invention, both reflecting

devices

103 and 104 are polarization orthogonal rotating reflecting devices.

For example, assuming that the two orthogonal polarization states are x-polarization state and y-polarization state respectively, the x-polarization state transmitted to polarization orthogonal rotating reflection devices along the optical path is converted into the y-polarization state orthogonal thereto after being reflected by the polarization orthogonal rotating reflection at the reflection device, and the y-polarization state transmitted to the reflection device along the optical path is converted into the x-polarization state orthogonal thereto after being reflected by the polarization orthogonal rotating reflection at the reflection device.

The beam splitter 101 is used to split the incoming input optical pulses of any polarization state into two optical pulses for transmission along the two arms, respectively.

The two arms are used for respectively transmitting the two paths of light pulses.

The phase modulator 102 is configured to phase modulate the optical pulses transmitted by the arm (i.e., of the two optical pulses) according to a quantum key distribution protocol, the phase modulation performed by the phase modulator 102 is determined by the quantum key distribution protocol, depending on the particular application, for example, in possible applications, the phase modulator 102 may randomly modulate either a 0 degree phase or a 90 degree phase.

The phase modulator 102 may be a polarization independent phase modulator or a birefringent phase modulator. The birefringent phase modulator is adapted to apply different adjustable phase modulations to two orthogonal polarization states passing therethrough. For example, the birefringent phase modulator may be a lithium niobate phase modulator, and by controlling the voltage applied to the lithium niobate crystal, the phase modulation experienced by each of the two orthogonal polarization states passing through the lithium niobate phase modulator may be controlled and adjusted.

The

reflection devices

103 and 104 are respectively used for reflecting the two light pulses transmitted from the beam splitter 101 through the two arms back to the beam splitter 101 to be combined and output by the beam splitter 101.

Because the two

reflection devices

103 and 104 are polarization orthogonal rotation reflection devices, for each paths of optical pulses in the two paths of optical pulses, when the path of optical pulse is reflected by the corresponding reflection device in the two reflection devices, the two orthogonal polarization states of the path of optical pulse are subjected to polarization orthogonal rotation reflection, so that after the reflection by the corresponding reflection device, each orthogonal polarization state of the path of optical pulse is converted into a polarization state orthogonal to the orthogonal polarization state.

Although only phase modulators 102 are shown in fig. 1 as being arranged on of the two arms, it is also possible to arrange phase modulators on each of the two arms, in which case the two phase modulators are so arranged, the difference in phase modulated by the two phase modulators is determined by the quantum key distribution protocol, depending on the specific application, in addition, instead of arranging a phase modulator on or both of the two arms, a phase modulator may be arranged before the beam splitter 101 for phase modulating the input light pulses before splitting according to the quantum key distribution protocol or phase modulating the output light pulses after splitting according to the quantum key distribution protocol.

The present invention proposes three inventive configurations of polarization orthogonal rotating reflective devices, namely configuration 1, configuration 2 and configuration 3 described below.

According to configuration 1, the polarization orthogonal rotation reflection apparatus includes a polarization beam splitter having an input port and two output ports, the two output ports of the polarization beam splitter being optically coupled to each other via transmission optical paths, the transmission optical paths being formed by polarization maintaining fibers, the transmission optical paths being provided with half-wave plates, the polarization directions of optical pulses input to the half-wave plates being at 45 degrees to the fast axis or the slow axis of the half-wave plates, the polarization orthogonal rotation reflection apparatus having configuration 1, when used in the phase codec of the present invention, can be coupled to the arm by coupling the input port of its polarization beam splitter to arm of the phase codec.

According to configuration 2, the polarization quadrature rotation reflection device comprises a polarization beam splitter having an input port and two output ports, the two output ports of the polarization beam splitter being optically coupled to each other via transmission optical paths, said transmission optical paths being formed by a polarization maintaining fiber, the slow axis and the fast axis of said polarization maintaining fiber respectively maintaining stable transmission of the two orthogonal polarization states of the optical pulses input into the polarization maintaining fiber, i.e. the polarization states are unchanged, and the two output ports of the polarization beam splitter and the polarization maintaining fiber being configured such that the optical pulses output by the two output ports of the polarization beam splitter are both coupled to the slow axis of the polarization maintaining fiber for transmission or are both coupled to the fast axis of the polarization maintaining fiber for transmission by the polarization maintaining fiber twisting 90 degrees or twisting (90+ n 180 degrees), where n is an integer, the optical pulses output by the two output ports of the polarization beam splitter are both coupled to the slow axis of the polarization maintaining fiber for transmission or are both coupled to the fast axis of the polarization maintaining fiber for transmission by the polarization maintaining fiber twisting (90+ n 180 degrees), the polarization maintaining fiber is configured to always transmit the optical pulses along the polarization maintaining fiber, the polarization beam splitter, and the polarization decoder is configured to always transmit the fast axis of the polarization maintaining fiber for transmission along the polarization encoding device ().

According to configuration 3, the polarization quadrature rotating reflective device comprises a polarization beam splitter having an input port and two output ports, the two output ports of the polarization beam splitter being optically coupled to each other via transmission light paths, the transmission light path being formed by a polarization maintaining fiber comprising an odd number of 90 degree fusion splices, each 90 degree fusion splice being formed by fusion splicing a slow axis of the polarization maintaining fiber in alignment with a fast axis of the polarization maintaining fiber, the polarization quadrature rotating reflective device having configuration 3 when used in a phase codec may be coupled to the phase codec by coupling the input port of its polarization beam splitter to the arm of the phase codec.

Returning to the phase codec of fig. 1, at least of the reflecting

means

103 and 104 may be a polarization orthogonal rotation reflecting means employing in configuration 1, configuration 2 and configuration 3 above, when 0 of the reflecting

means

103 and 104 are polarization orthogonal rotation reflecting means employing 1 in configuration 1, configuration 2 and configuration 3 above, another of the reflecting means may be polarization orthogonal rotation reflecting means employing 3 in configuration 1, configuration 2 and configuration 3 above, or polarization orthogonal rotation reflecting means of other configurations, such as a quarter wave plate mirror "a quarter wave plate mirror" may also include a mirror and a quarter mirror, which is formed integrally with the quarter wave plate 82 at the rear end of the quarter wave plate, wherein the two orthogonal polarization states of the input quarter-wave plate have a phase difference in direction from the fast axis of the quarter-wave plate , and the slow axis of the quarter-wave plate may be phase-shifted by a quarter-wave plate 3690 after the quarter-wave plate 3690.

For the phase codec of fig. 1, the relative delay of the two optical pulses may be achieved by adjusting the lengths of the two arms and/or adjusting the transmission optical paths in or two reflecting devices of the two reflecting

devices

103 and 104 using configurations selected from configurations 1, 2, and 3.

Thus, for each light pulse in the split two light pulses, the two orthogonal polarization states of the light pulse may be maintained constant during the time the beam splitter splits to the respective reflecting device for reflection and during the time the respective reflecting device reflects to the beam splitter for combination.

Further, the beam splitter 101 of the phase codec may be a polarization maintaining beam splitter.

Another preferred embodiment of the phase codec of of the present invention is shown in fig. 2, and comprises a polarization maintaining beam splitter 203, a phase modulator 204, and polarization quadrature rotating reflective devices 205 and 206.

of two ports 201 and 202 on the side of a polarization-maintaining beam splitter 203 serves as an input port of a phase codec, the polarization-maintaining beam splitter 203 and polarization quadrature rotation reflection devices 205 and 206 constitute an unequal arm Michelson interferometer, and two arms therebetween are polarization-maintaining fiber optical paths, a phase modulator 204 is inserted into any arm of two arms of the unequal arm Michelson interferometer, and the port 201 or 202 of the polarization-maintaining beam splitter 203 can serve as an output port of the phase codec.

During operation, an optical pulse enters the polarization maintaining beam splitter 203 through the port 201 or 202 of the polarization maintaining beam splitter 203 and is divided into two optical pulses by the polarization maintaining beam splitter 203, optical pulses from the polarization maintaining beam splitter 203 are subjected to phase modulation by the phase modulator 204 and then reflected back by the polarization orthogonal rotating reflection device 205, another optical pulses are directly transmitted to the polarization orthogonal rotating reflection device 206 through the polarization maintaining optical fiber and reflected back by the polarization orthogonal rotating reflection device 206, and the two reflected optical pulses after relative delay are combined by the polarization maintaining beam splitter 203 and then output through the port 201 or 202.

Where the at the input and output ports of the polarization maintaining beam splitter 203 are the same ports, the phase codec may also include an optical circulator, which may be located in front of the polarization maintaining beam splitter 203. an incoming loop input optical pulse of any polarization state may be input from the port of the optical circulator and output from the second port of the optical circulator to the polarization maintaining beam splitter 203, and the combined beam output from the polarization maintaining beam splitter 203 is input to the second port of the optical circulator and output from the third port of the optical circulator.

Fig. 3 is a schematic diagram showing the structure of polarization orthogonal rotation reflectors that can be used in the phase codec of the present invention.

The polarization orthogonal rotating reflective device shown in fig. 3 includes the following components: a polarization beam splitter 302, and a polarization maintaining fiber 303.

The polarization beam splitter 302 includes three ports, port A, port B, and port C, which can be referred to as an input port, an th output port, and a second output port, respectively, the port 301 connected to the port A of the polarization beam splitter 302 serves as both an input port and an output port of a reflection device, the port B and the port C of the polarization beam splitter 302 are connected by a polarization maintaining fiber 303, and optical pulses output by the port B and the port C of the polarization beam splitter 302 are coupled to a slow axis transmission of the polarization maintaining fiber 303 or are coupled to a fast axis transmission of the polarization maintaining fiber.

When the polarization beam splitter device works, an input optical pulse is input into the polarization beam splitter 302 through a port 301, namely a port A of the polarization beam splitter 302, the input optical pulse can be regarded as being composed of two orthogonal polarization states, the two orthogonal polarization states can be respectively marked as an x polarization state and a y polarization state, the polarization beam splitter 302 splits the input optical pulse into a second path optical pulse in the x polarization state and a second path optical pulse in the y polarization state, the second path optical pulse in the x polarization state output by the port B of the polarization beam splitter 302 and is output by the port C of the polarization beam splitter 302, the second path optical pulse in the x polarization state output by the port B of the polarization beam splitter 302 is coupled to a slow axis of the polarization maintaining optical fiber 303 and is transmitted to a port C of the polarization beam splitter 302 along the slow axis of the polarization maintaining optical fiber 303, the second path optical pulse at the port C is coupled to the polarization beam splitter 302 by the slow axis of the polarization maintaining optical fiber 303, namely, the polarization state of the second path optical pulse coupled to the y polarization state is converted into a polarization state by a port A of the polarization beam splitter 302, the polarization state output by the polarization beam splitter 302, the polarization state is converted into a polarization state by the polarization state of the polarization state reflected by the polarization beam splitter device, the polarization beam splitter after the polarization state of the polarization beam splitter, the polarization state of the polarization beam splitter, the polarization state input optical pulse is reflected by the polarization state A, the polarization state of the polarization beam splitter 302, the polarization state of the polarization beam splitter 302, the polarization beam splitter, the polarization state is reflected by the polarization state of the polarization state, the polarization state of the polarization state, the polarization state polarization beam splitter 302, the polarization state of the polarization beam splitter, the polarization state of the polarization state polarization beam splitter 302, the polarization beam splitter, the polarization state of the polarization beam splitter, the polarization state of the polarization state, the polarization state of the polarization beam splitter, the polarization beam splitter 302, the polarization state of the polarization beam splitter, the.

Port B and port C of polarization splitter 302 may both be coupled to the fast axis of polarization maintaining fiber 303, with the results unaffected.

Fig. 4 is a schematic diagram showing the structure of another polarization orthogonal rotation reflection devices that can be used in the phase codec of the present invention.

The polarization orthogonal rotating reflective device shown in fig. 4 includes the following components: a polarization beam splitter 402, a polarization maintaining fiber 403, and a 90 degree splice point 404.

The polarization beam splitter 402 includes three ports, port A, port B, port C may be referred to as an input port, an th output port, and a second output port, respectively, port 401 connected to port A of the polarization beam splitter 402 serves as both an input port and an output port of the device, port B and port C of the polarization beam splitter 402 are connected by a polarization maintaining fiber 403, a light pulse output by port B of the polarization beam splitter 402 is coupled to a slow axis of the polarization maintaining fiber 403 and a light pulse output by port C of the polarization beam splitter 402 is coupled to a fast axis of the polarization maintaining fiber 403, or a light pulse output by port B of the polarization beam splitter 402 is coupled to a fast axis of the polarization maintaining fiber 403 and a light pulse output by port C of the polarization beam splitter 402 is coupled to a slow axis of the polarization maintaining fiber 403. the polarization maintaining fiber 403 includes a 90 degree fusion splice point 404, and the 90 degree fusion splice point 404 is formed by aligning the slow axis of the polarization maintaining fiber and the fast axis of the polarization maintaining fiber.

When the polarization beam splitter device works, an input optical pulse is input into the polarization beam splitter 402 through a port 401, namely a port A of the polarization beam splitter 402, the input optical pulse can be regarded as being composed of two orthogonal polarization states, the two orthogonal polarization states can be respectively recorded as an x polarization state and a y polarization state, the polarization beam splitter 402 splits the polarization of the input optical pulse into a second -path optical pulse in the x polarization state and a second path optical pulse in the y polarization state, the second -path optical pulse in the x polarization state output by the port B of the polarization beam splitter 402 is coupled to a slow axis of the polarization-maintaining optical fiber 403 and is transmitted to a 90-degree fusion splice point 404, the second -path optical pulse in the x polarization state output by the port B of the polarization beam splitter 402 is transmitted to a port C of the polarization beam splitter 402 along a fast axis of the polarization-maintaining optical fiber 404 after passing through the 90-degree fusion splice point 404, the second -path optical pulse in the x polarization state, namely the fast axis of the polarization-maintaining optical fiber 403, at the port C, the polarization beam splitter 402 is coupled to the polarization state, the polarization beam splitter 402, the polarization beam splitter 404 is converted into the y polarization state by the polarization state input optical pulse, the polarization state, the polarization beam splitter 403, the polarization state is reflected by the polarization beam splitter 403, the polarization state of the polarization beam splitter 402, the polarization beam splitter 402 is reflected by the polarization beam splitter, the polarization beam splitter 402, the polarization beam splitter 402 is reflected by the polarization beam splitter, the polarization state of the polarization beam splitter, the polarization beam splitter 402 is reflected by the polarization state of the polarization beam splitter, the polarization beam splitter 402, the polarization beam splitter 404 is reflected by the polarization beam splitter, the polarization state of the polarization beam splitter, the polarization beam splitter.

Although only degree fusion splices 404 are shown in FIG. 4, this is exemplary only, and the polarization maintaining fiber 403 may contain any odd number of 90 degree fusion splices, each 90 degree fusion splice being made by fusion splicing the polarization maintaining fiber slow axis in alignment with the polarization maintaining fiber fast axis, where the polarization maintaining fiber 403 contains more than 1 odd number of 90 degree fusion splices, the results are unaffected, except that the second optical pulses and the second optical pulses output by ports B and C of the polarization beam splitter 402 each alternate between traveling along the polarization maintaining fiber slow axis and traveling along the polarization maintaining fiber fast axis more times as they travel along the polarization maintaining fiber 403, the number of transitions being equal to the number of 90 degree fusion splices.

Polarization orthogonal rotation is performed on two orthogonal polarization states by using the polarization maintaining fiber 403 containing an odd number of 90-degree fusion points, so that the phase between the x-polarization state and the y-polarization state of the input light pulse and the phase between the y-polarization state and the x-polarization state of the output light pulse are kept the same.

When port B of the polarization beam splitter 402 is coupled to the fast axis of the polarization maintaining fiber 403 and port C of the polarization beam splitter 402 is coupled to the slow axis of the polarization maintaining fiber 403, the above result is not affected.

Fig. 5 is a schematic diagram showing the structure of another polarization orthogonal rotation reflection devices that can be used in the phase codec of the present invention.

The polarization orthogonal rotating reflective device shown in fig. 5 includes the following components: a polarizing beam splitter 502, a half wave plate 503.

The polarization beam splitter 502 includes three ports, port A, port B, and port C may be referred to as an input port, an th output port, and a second output port, respectively, port 501 connected to port A of the polarization beam splitter 502 may be used as both an input port and an output port of the apparatus, port B of the polarization beam splitter 502 is connected to port D of the half-wave plate 503 through a transmission optical path, and port C of the polarization beam splitter 502 is connected to port E of the half-wave plate 503 through a transmission optical path, the transmission optical path connecting port B of the polarization beam splitter 502 to port D of the half-wave plate 503 and the transmission optical path connecting port C of the polarization beam splitter 502 to port E of the half-wave plate 503 are both polarization maintaining optical paths, such as polarization maintaining fiber optical paths, and the polarization direction of the polarization state of the optical pulses input to the half-wave plate 503 by port D and port E of the half-wave plate 503 forms an angle of 45 degrees with the slow axis.

When the polarization beam splitter 502 is operated, an input optical pulse is input into the polarization beam splitter 502 through the port 501, that is, the port a of the polarization beam splitter 502, the input optical pulse can be regarded as being composed of two orthogonal polarization states, which can be respectively marked as an x-polarization state and a y-polarization state, the polarization beam splitter 502 transmits the input optical pulse in a polarization beam splitting manner into a th optical pulse in the x-polarization state and a second optical pulse in the y-polarization state, which are output through the port B and the port C of the polarization beam splitter 502, respectively, the th optical pulse in the x-polarization state output through the port B of the polarization beam splitter 502 is transmitted to the half wave plate 503, the polarization state of the second th optical pulse in the orthogonal polarization state is converted into the y-polarization state through the half wave plate 503, the th optical pulse in the y-polarization state output through the port E of the half wave plate 503 is transmitted to the port C of the polarization beam splitter and is input into the polarization beam splitter 502, and the polarization beam splitter 502 is transmitted to the polarization beam splitter 503, the polarization beam splitter outputs the polarization beam splitter, the polarization optical pulse in the orthogonal polarization state, the polarization beam splitter is converted into the polarization state, the polarization beam splitter is transmitted to the polarization beam splitter, the polarization beam splitter is transmitted to the polarization state of the polarization beam splitter, the polarization beam splitter is orthogonal polarization beam splitter, the polarization state of the polarization beam splitter is orthogonal polarization beam splitter, the polarization beam splitter is orthogonal polarization beam splitter, the polarization state of the polarization beam splitter is orthogonal polarization beam splitter, the polarization state of the polarization beam splitter.

The utility model discloses a phase place codec can be used as direct current modulation quantum key distribution phase place codec's component, can be used as quantum key distribution time bit-phase place codec's component, also can be used as direct current modulation quantum key distribution time bit-phase place codec's component.

kinds of direct current modulation quantum key distribution phase encoding and decoding devices based on polarization orthogonal rotation reflection of the phase encoder and decoder are shown in figure 6, which comprises a preposed beam splitter 603,

optical circulators

604 and 611, polarization maintaining

beam splitters

605 and 612, direct

current phase modulators

606 and 613 and polarization orthogonal

rotation reflection devices

607, 608, 614 and 615.

Polarization maintaining beam splitter 605, two polarization quadrature rotating

reflective devices

607 and 608, and two arms between polarization maintaining beam splitter 605 and the two polarization quadrature rotating reflective devices constitute polarization maintaining unequal arm michelson interferometer, i.e. phase codec according to the present invention, two arms of phase codec are polarization maintaining fiber optical paths, dc phase modulator 606 is located on any arms of the two arms of phase codec.

Similarly, polarization maintaining beam splitter 612, two polarization orthogonal

rotating mirrors

614 and 615, and two arms between polarization maintaining beam splitter 612 and the two polarization orthogonal rotating mirrors form a second polarization maintaining unequal arm Michelson interferometer, i.e., a second phase codec according to the present invention.

The following describes an example of the codec device of fig. 6 for decoding.

The two

ports

601 and 602 on the side of the pre-splitter 603 (left side in fig. 6) are used as input ports of the apparatus, the th port a and the second port B of the optical circulator 604 are connected to the output ports of the pre-splitter 603 and the th input ports of the polarization maintaining splitter 605 respectively, the optical pulses input to the second phase codec are decoded and then output by the 4 output ports 609 of the polarization maintaining splitter 605, or are transmitted to the port B of the optical circulator 604 via the other output ports of the polarization maintaining splitter 605 (i.e., the input ports of the polarization maintaining splitter 605) and output from the third port C of the optical circulator 604, the port a and the second port B of the optical circulator 611 are connected to the other output ports of the pre-splitter 603 and the input ports of the polarization maintaining splitter 612 respectively, the second port B input to the second phase codec is decoded and then output by the 3 output ports of the polarization maintaining splitter 612, or is transmitted to the third port B of the polarization maintaining splitter via the polarization maintaining splitter 611, the third port B of the polarization maintaining splitter 611 and then output ports of the optical circulator 612.

During operation, optical pulses enter the beam splitter 603 through a port 601 or 602 of the beam splitter 603 and are split into a th optical pulse and a second optical pulse by the beam splitter 603, the th optical pulse is input through a port a of the optical circulator 604 and is output to the polarization maintaining beam splitter 605 through a port B of the optical circulator 604, the polarization maintaining beam splitter 605 splits the input th optical pulse into two paths of 1 st sub optical pulses, th th sub optical pulses are phase-modulated by the direct current phase modulator 606 and are reflected back by the polarization orthogonal rotating reflection device 607, the th 634 th sub optical pulse is directly transmitted to the polarization orthogonal rotating reflection device 608 through the polarization maintaining optical fiber and is reflected back by the polarization orthogonal rotating reflection device 608, the two paths of the th sub optical pulses reflected back through the relative delay are combined by the polarization maintaining beam splitter 605 and output through a port 611 after being output to a port B609 of the optical circulator 604 and transmitted to a port C through a port 610 and output a second optical pulse through a port B613, the optical pulse is directly transmitted to a phase maintaining beam splitter 611 after being phase-modulated by the polarization maintaining beam splitter 611, and is output to a phase-modulated by a phase maintaining beam splitter 611, and is output through a port B612, and is directly transmitted to a phase-modulated by a port B612, and is output through a polarization rotating optical pulse phase maintaining beam splitter 611 after being output through a port B of the polarization rotating optical fiber 612, and is directly transmitted through a polarization maintaining optical pulse phase-.

Next, the encoding and decoding apparatus of fig. 6 will be described by way of example for encoding.

The optical pulses input from the third port C of the optical circulator 604 are input to the second port B of the optical circulator 604 via the second port B of the optical circulator 604, the second phase codec from the third port C of the optical circulator 604, the optical pulses output from the polarization splitter 605 to the second port B of the optical circulator 604 after being encoded by the phase codec of the third port and the optical pulse encoder 603 are output to the optical circulator 604 via the polarization splitter 605 and transmitted from the third port B of the optical circulator 603 to the front polarization splitter 603 via the third port B of the optical circulator 603 and the front polarization splitter 603 via the polarization splitter 603 and the optical pulse encoder 603 and encoder 603, and the optical pulses input from the optical circulator 603 and encoder 603 to the front polarization splitter 611C via the optical circulator 603 and encoder, the optical pulses are output from the front polarization splitter 603 and encoder, the optical pulses input to the optical circulator 603 and encoder, the optical transmitters, the optical circulator 603, the optical circulator, the optical splitter, the optical circulator, the optical transmitter.

The quantum key distribution time bit-phase encoding and decoding device based on polarization orthogonal rotation reflection using the phase encoder and decoder of the present invention is shown in fig. 7, and comprises

beam splitters

703 and 704, polarization maintaining beam splitter 707, phase modulator 708, and polarization orthogonal

rotation reflection devices

709 and 710.

Polarization maintaining beam splitter 707, two polarization quadrature rotating

reflective devices

709 and 710, and two arms between polarization maintaining beam splitter 707 and the two polarization quadrature rotating reflective devices constitute a polarization maintaining unequal arm michelson interferometer, i.e., a phase codec according to the present invention.

The following describes an example of the codec device of fig. 7 for decoding.

The splitter 703 is a pre-splitter, and its side two ports 701 and of 702 are input ports of the device, the splitter 704 splits optical pulses from the splitter 703 and outputs them through

ports

705 and 706, and the optical pulses input to the polarization maintaining unequal arm michelson interferometer are decoded and output through port 711.

During operation, an input optical pulse enters the beam splitter 703 through a

port

701 or 702 of the beam splitter 703, and is split into two optical pulses by the beam splitter 703 for transmission, optical pulses from the beam splitter 703 are input to the beam splitter 704, and are output through a

port

705 or 706 after being split by the beam splitter 704 for time bit decoding, another optical pulses from the beam splitter 703 are input to a polarization maintaining beam splitter 707 and are split into two sub optical pulses by the polarization maintaining beam splitter 707, sub optical pulses are randomly modulated in phase by the phase modulator 708 at 0 degree or 180 degree and then reflected back by the polarization orthogonal rotating reflection device 709, another sub optical pulses are directly transmitted to the polarization orthogonal rotating reflection device 710 through the polarization maintaining fiber and reflected back by the polarization orthogonal rotating reflection device 710, and the two sub optical pulses reflected back after being relatively delayed are combined by the polarization maintaining beam splitter 707 and then output through a port 711.

Here, it should be noted that the splitter 704 is optional, and it is possible to directly output the optical pulses for time-bit decoding by the pre-splitter 703.

Next, the encoding and decoding apparatus of fig. 7 will be described by way of example for encoding.

The optical pulse input from the port 711 is encoded by a polarization maintaining unequal arm michelson interferometer and then output to the pre-splitter 703 from the polarization maintaining splitter 707, and two phase encodings are realized by the modulation phase modulator 708 therebetween, and the ports 701 and of the pre-splitter 703 are output as output ports of the apparatus, and the optical pulse output from the splitter 704 and the optical pulse output from the polarization maintaining splitter 707 are combined by the splitter 703 and then output from the

ports

701 and 702 by the splitter 703.

The splitter 704 is optional, it is possible to use the port of the splitter 703 connected to the splitter 704 directly as an input port for time bit encoding.

The kinds of direct current modulation quantum key distribution time bit-phase encoding and decoding device based on polarization orthogonal rotation reflection of the phase encoder and decoder of the utility model is shown in figure 8, and comprises beam splitters 803 and 804, an optical circulator 807, a polarization-maintaining beam splitter 808, a direct current phase modulator 809 and polarization orthogonal rotation reflection devices 810 and 811.

Polarization maintaining beam splitter 808, two polarization orthogonal rotating reflectors 810 and 811, and two arms between polarization maintaining beam splitter 808 and the two polarization orthogonal rotating reflectors constitute a polarization maintaining unequal arm michelson interferometer, i.e., a phase codec according to the present invention.

The following describes an example of the codec device of fig. 8 for decoding.

The beam splitter 803 acts as a pre-splitter, with the two ports 801 on the side and on the 802 side acting as input ports for the device, the beam splitter 804 splits optical pulses from the beam splitter 803 for output by either port 805 or 806, the optical pulse input from the th port a of the optical circulator 807 is output by the second port B of the optical circulator 807, the optical pulse input from the second port B of the optical circulator 807 is output by the third port C of the optical circulator 807, the optical pulse input to the polarization maintaining unequal arm michelson interferometer is decoded for output by port 812, or transmitted to the second port B of the optical circulator 807 via another output port of the polarization maintaining beam splitter 808 and output by the third port C of the optical circulator 807 for output by port 813.

paths of optical pulses from the beam splitter 803 are input to the beam splitter 804 and output from the port 805 or 806 after being split by the beam splitter 804 for time bit decoding, another paths of optical pulses from the beam splitter 803 are input through the second port A of the optical circulator 807 and output to the polarization-preserving beam splitter 808 from the second port B of the optical circulator 807, the polarization-preserving beam splitter 808 splits the another paths of optical pulses into two paths of sub-optical pulses, paths of sub-optical pulses are modulated by the direct-current phase modulator 809 to have a phase of 0 degree or a phase of 180 degree and then reflected back by the polarization orthogonal rotating and reflecting device 810, another paths of sub-optical pulses are directly transmitted to the polarization orthogonal rotating and reflecting device 811 through the polarization-preserving fiber and reflected back by the polarization orthogonal rotating and reflecting device 811, and the reflected two paths of relatively delayed sub-optical pulses 808 are combined by the polarization-preserving beam splitter 812 and output from the second port C of the optical circulator 807 and output from the third port 813 of the optical circulator 807.

Here, it should be noted that the splitter 804 is optional, and it is possible that the optical pulses are directly output by the pre-splitter 803 for time-bit decoding.

Next, the encoding and decoding apparatus of fig. 8 will be described by way of example for encoding.

Optical pulses input from the third port C of the optical circulator 807 are output from the second port B of the optical circulator 807, optical pulses input from the second port B of the optical circulator 807 are output from the third port a of the optical circulator 807, time-bit-encoding is achieved by outputting the optical pulses input from the port 812 and optical pulses input from the third port C of the optical circulator 807 and output from the second port B of the optical circulator 807 to the polarization beam splitter 808, optical pulses encoded by the polarization unequal arm michelson interferometer are output from the polarization beam splitter 808 to the second port B of the optical circulator 807 and transmitted from the third port B of the polarization beam splitter 807 to the pre-polarization beam splitter 803 via the third port C of the polarization beam splitter 807, and output from the polarization beam splitter 801 to the third port B of the optical circulator 807 via the third port B of the polarization beam splitter 807 and output from the third port B of the optical circulator 807 to the pre-polarization beam splitter 803 via the third port a of the optical circulator 807, and output from the optical circulator 802 to the output port 801 and the optical pulse output port 802 of the optical circulator 807, and output from the polarization beam splitter 803 via the third port B of the polarization beam splitter 803, and output port B of the optical circulator 802 and of the optical circulator 807, and output port 802, 83, respectively, and output from the polarization beam splitter 803, and output port 802 of the optical circulator 804, and .

The splitter 804 is optional, it is possible to directly use the port of the splitter 803 connected to the splitter 804 as an input port for time bit encoding.

Although phase modulators are shown in fig. 1-2 and 6-8, it is possible that the phase codec and codec devices of the present invention do not include phase modulators.

Herein, the terms "beam splitter" and "beam combiner" are used interchangeably, and a beam splitter may also be referred to and used as a beam combiner, and vice versa. Herein, the term "polarization maintaining fiber optical path" refers to an optical path formed by connecting polarization maintaining fibers or an optical path formed by transmitting optical pulses by using polarization maintaining fibers.

For the phase codec or corresponding codec of the present invention, which when used in the receiving end or transmitting end of a quantum key distribution system, may include a phase modulator as exemplarily described above in connection with fig. 1-2 and 6-8 or may not include a phase modulator, additionally, in case of both the receiving end and the transmitting end of a quantum key distribution system, the phase codec or codec used for at least of the receiving end and the transmitting end may include a phase modulator.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the preferred embodiments, as illustrated in the accompanying drawings.

Claims

Quantum key distribution phase codec, comprising a beam splitter, two reflection devices optically coupled to the beam splitter via two arms, respectively, each of the reflection devices being polarization orthogonal rotating reflection devices, of the two reflection devices or each of the reflection devices comprising a polarization beam splitter having an input port and two output ports and being coupled to a respective one of the two arms via the input port of the polarization beam splitter, wherein the two output ports of each polarization beam splitter are optically coupled to each other via a transmission optical path, for at least reflection devices comprising polarization beam splitters whose transmission optical path is formed by polarization maintaining fibers containing an odd number of 90 degree fusion splices, the optical pulses output by of the two output ports of the polarization beam splitter are coupled to the slow axis of the polarization maintaining fiber, and the optical pulses output by the other of the two output ports of the polarization beam splitter are coupled to the fast axis of the polarization maintaining fiber.
2. The phase codec of claim 1, wherein the two reflective devices are identically constructed polarization quadrature rotating reflective devices or differently constructed polarization quadrature rotating reflective devices.
3. The phase codec of claim 1, wherein the odd number of 90-degree weld points comprises 1 90-degree weld point or more odd number of 90-degree weld points.
4. The phase codec of claim 1, wherein the beam splitter is a polarization maintaining beam splitter.
5. The phase codec of claim 1, wherein the two arms are each polarization-maintaining optical paths, and the optical devices on the two arms are polarization-maintaining optical devices and/or non-birefringent optical devices.
6. The phase codec of , further comprising a phase modulator disposed at the front end of the beam splitter or on at least of the two arms.
7, DC-modulated quantum key distribution phase codec device, comprising a front splitter and two phase codecs according to any of claims 1-6, the two phase codecs being optically coupled to the front splitter via two sub-optical paths, respectively, wherein of the splitter of each phase codec not coupled to the ports of the two arms of the phase codec is optically coupled to a corresponding sub-optical path of the two sub-optical paths, and optical circulators are disposed on each sub-optical path.
8, quantum key distribution time bit-phase codec device, comprising a pre-splitter and phase codecs according to of claims 1-6, the phase codecs being optically coupled to the pre-splitter via sub-paths, wherein of the ports of the splitter of the phase codecs not coupled to the two arms are optically coupled to sub-paths.
The apparatus of DC-modulated quantum key distribution time bit-phase codec, wherein the apparatus comprises a front splitter and phase codecs according to of claims 1-6, the phase codecs is optically coupled to the front splitter via sub-optical paths, wherein of the splitter of the phase codecs, which are not coupled to the ports of the two arms, are optically coupled to sub-optical paths, and optical circulators are disposed on the sub-optical paths.
10. The codec of claim 8 or 9, further comprising a splitter coupled to the front splitter via another sub-paths.
11, a quantum key distribution system, characterized in that the quantum key distribution system comprises:

the phase codec according to any of claims 1-6 or the codec according to any of claims 7-10, which is arranged at a receiving end of the quantum key distribution system for decoding, and/or

The phase codec according to any of claims 1-6 or the codec according to any of claims 7-10, provided at a transmitting end of the quantum key distribution system for encoding.