CN117478238A - Device and method for detecting interception of fiber channel - Google Patents
Device and method for detecting interception of fiber channel Download PDFInfo
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Abstract
The invention belongs to the technical field of optical encryption communication, and discloses a device and a method for detecting interception of a fiber channel, wherein the device comprises an interception detection module and a reflection type polarization self-compensation module which are respectively arranged at two ends of the fiber channel to be detected, and the interception detection module comprises a laser, an attenuator, a circulator, a reflection type polarization modulation module, an orthogonal polarization interferometer, a first polarization beam splitter, a beam splitter and two single photon detectors. Compared with the prior art, the invention uses the reflective polarization self-compensation module to transmit the time-phase coded quantum state transmitted by the sender through the optical fiber channel and reflect the time-phase coded quantum state back to the sender for measurement, and judges whether the channel has eavesdropping according to the error rate. The method not only can automatically compensate the polarization conversion of the channel, but also can automatically compensate the phase change in the receiving and transmitting optical path, and does not need to actively control and communicate with a sender, so that the complexity and the power consumption of a receiver are not increased, and the communication bandwidth is not additionally occupied.
Description
Technical Field
The invention relates to the technical field of optical encryption communication, in particular to a device and a method for detecting interception of a fiber channel.
Background
With the development of society and technology, the demand for communication security is increasing. Eavesdropping techniques for fiber optic communication systems are diverse and are commonly categorized as invasive and non-invasive. The main method adopted by the intrusion method is a beam splitting method, namely, directly cutting off the optical fiber and connecting the optical coupler to separate out information data to be intercepted, which can cause short-term communication interruption; the non-invasive method mainly comprises a bending coupling method, an evanescent wave coupling method, a V-shaped groove method and the like, mainly comprises the steps of invading an optical fiber communication system under the condition of not interrupting communication, separating out part of optical signals, and stealing information, and has strong concealment, large threat and difficult discovery. Therefore, there is a need to develop a channel eavesdropping detection technique for optical fiber communication.
At present, conventional channel eavesdropping detection methods are mainly divided into two types, namely, statistical analysis is carried out on some characteristics of communication signals, such as light intensity monitoring, bit error rate measurement, spectral analysis and the like, the detection speed of the method is low, and short eavesdropping behaviors cannot be detected; and secondly, measuring the Rayleigh scattering and Fresnel reflection signals of the reflected strong classical optical signals by using a time domain reflection technology, such as patent CN110855373A, CN114884570A and the like. However, these methods are incapable of intercepting the eavesdropping modes such as retransmission attack, associated interference attack, etc., the former can intercept an optical signal and retransmit a completely consistent optical signal, and the latter can steal information while keeping the optical power in the channel unchanged, so that eavesdropping cannot be found.
With the development of quantum technology, more sensitive and reliable eavesdropping detection can be realized by utilizing the characteristics of unclonable quantum state, uncertainty and the like. Patent CN107370546B proposes a method for detecting eavesdropping using a quantum state, in which a sender sends the quantum state to a receiver for measurement, and determines whether eavesdropping exists according to the change condition of the measurement result of the quantum state. The patent CN110719128A adopts the quantum key distribution device more directly on both sides of the transceiver, the cost and complexity are both greatly improved, and the two sides are required to communicate to perform post-processing negotiation, so that a larger channel bandwidth is occupied. The patent CN115955280B adopts a round trip structure, does not occupy channel bandwidth, and has higher stability. However, the scheme adopts phase coding, so that the round-trip optical pulse signals are required to be subjected to phase modulation, and the transmitted optical pulse signals are required to be subjected to 4 kinds of phase modulation, thereby increasing the complexity of the system.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a device and a method for detecting the interception of a fiber channel.
The technical scheme of the invention is realized as follows:
the utility model provides a fibre channel eavesdropping detection device, includes eavesdropping detection module and reflective polarization self-compensating module of deploying respectively at waiting to detect fibre channel both ends, eavesdropping detection module includes:
a Laser for generating horizontally polarized light pulses;
an attenuator ATT for attenuating the light pulse to a preset intensity;
the circulator CIR is used for multi-directional transmission of different light pulses, and specifically comprises the following steps: transmitting the light pulses attenuated therefrom to a reflective polarization modulation module; and transmitting the light pulses reflected by the reflective polarization modulation module to the orthogonal polarization interferometer; and for transmitting the light pulses output from the orthogonal polarization interferometer to the first polarization beam splitter PBS1;
the reflective polarization modulation module is connected with the corresponding port of the circulator CIR through 45-degree fusion connection of the polarization maintaining fiber; the reflection type polarization modulation module is used for randomly modulating the polarization state of the light pulse into horizontal polarization, vertical polarization or 45-degree polarization;
an orthogonal polarization interferometer having long and short arms for converting light pulses of different polarizations into a time phase encoded quantum state light signal;
The reflection type polarization self-compensation module is used for reflecting the quantum state optical signal transmitted through the optical fiber channel to be detected, rotating the polarization state of the quantum state optical signal by 90 degrees and carrying out polarization self-compensation on the optical fiber channel to be detected;
the beam splitter BS is used for splitting the quantum state optical signal returned from the optical fiber channel to be detected to generate a first quantum state component and a second quantum state component;
the first polarization beam splitter PBS1 is connected with the corresponding port of the circulator CIR through 45-degree fusion connection of the polarization maintaining fiber and is used for reflecting the vertical polarization component of the second quantum state component subjected to orthogonal polarization interferometer and 45-degree polarization rotation;
the first single photon detector SPD1 and the second single photon detector SPD2 are respectively configured to detect a first quantum state component and a vertically polarized component of a second quantum state component reflected by the first polarizing beam splitter PBS 1.
Preferably, the reflective polarization modulation module includes a first phase modulator PM1 and a quarter-wave plate mirror QM, one end of the first phase modulator PM1 serves as an input port and an output port of the reflective polarization self-compensation module, and the other end is connected to the quarter-wave plate mirror QM.
Preferably, the reflective polarization modulation module comprises a second phase modulator PM2 and a first Faraday mirror FM1, wherein one end of the second phase modulator PM2 is used as an input port and an output port of the reflective polarization self-compensation module, and the other end of the second phase modulator PM2 is connected with the first Faraday mirror FM 1.
Preferably, the reflective polarization modulation module includes a second polarization beam splitter PBS2 and a third phase modulator PM3, where an input port of the second polarization beam splitter PBS2 is used as an input port and an output port of the reflective polarization self-compensating module, and the two output ports are respectively connected with two ends of the third phase modulator PM3 through polarization-preserving fibers.
Preferably, the orthogonal polarization interferometer comprises a third polarization beam splitter PBS3 and a fourth polarization beam splitter PBS4, wherein two output ports of the third polarization beam splitter PBS3 are respectively connected with two input ports of the fourth polarization beam splitter PBS4 through polarization maintaining optical fibers with different lengths to respectively form a long arm and a short arm of the orthogonal polarization interferometer; the input port of the third polarizing beam splitter PBS3 and the output port of the fourth polarizing beam splitter PBS4 are respectively the input port and the output port of the orthogonal polarization interferometer.
Preferably, the orthogonal polarization interferometer includes a fifth polarization beam splitter PBS5, a second faraday mirror FM2, and a third faraday mirror FM3, and one input port and one output port of the fifth polarization beam splitter PBS5 are respectively connected to the second faraday mirror FM2 and the third faraday mirror FM3, and the other input port and the other output port thereof are respectively used as an input port and an output port of the orthogonal polarization interferometer.
Preferably, the orthogonal polarization interferometer is a sixth polarization beam splitter PBS6, one input port and one output port of the sixth polarization beam splitter PBS6 are directly connected through a polarization maintaining fiber, and the other input port and the other output port of the sixth polarization beam splitter PBS are respectively used as an input port and an output port of the orthogonal polarization interferometer.
Preferably, the reflective polarization self-compensating module comprises a seventh polarization beam splitter PBS7 and a faraday rotator FR, wherein two output ports of the seventh polarization beam splitter PBS7 are respectively connected with two ends of the faraday rotator FR through polarization maintaining fibers to form an annular structure; the polarization rotation angle of the Faraday rotator FR is 90 degrees, and the polarization directions of the two ends of the Faraday rotator FR are aligned with the slow axis of the polarization maintaining fiber.
Preferably, the reflective polarization self-compensation module is a fourth faraday mirror FM4.
Preferably, the reflective polarization self-compensating module includes an eighth polarization beam splitter PBS8 and a fifth faraday mirror FM5, wherein one output port of the eighth polarization beam splitter PBS8 is connected to the fifth faraday mirror FM5, and the other output port thereof is connected to one input port thereof through a polarization maintaining fiber.
Preferably, the orthogonal polarization interferometer is used for converting light pulses with different polarizations into a time phase encoded quantum state light signal, specifically: wherein a horizontally polarized light pulse incident on an input port of an orthogonal polarization interferometer is converted into a first time encoded state The method comprises the steps of carrying out a first treatment on the surface of the Converting a vertically polarized light pulse incident to an input port of an orthogonal polarization interferometer into a second time-encoded state +.>The method comprises the steps of carrying out a first treatment on the surface of the Converting 45 DEG polarized light pulses incident to an input port of an orthogonal polarization interferometer into phase encoded statesThe method comprises the steps of carrying out a first treatment on the surface of the First time encoding state->And a second temporal coding state->The polarizations of (2) are perpendicular to each other and have a predetermined time difference.
The invention also discloses a method for detecting the interception of the optical fiber channel, which comprises the following steps:
step 1: the Laser generates horizontal polarized light pulse, and the light pulse is attenuated to preset intensity through an attenuator ATT; randomly modulating the polarization state of the light pulse into horizontal polarization, vertical polarization or 45-degree polarization by using a polarization modulation module;
step 2: the polarized light pulse enters the orthogonal polarization interferometer to complete the time-phase quantum state coding, and a first time coding state is randomly generatedSecond temporal coding state->Phase encoding state->；
Step 3: the quantum state is transmitted to a reflective polarization self-compensation module through a fiber channel, reflected and returned through the fiber channel again, polarization is rotated by 90 degrees and then enters a beam splitter to perform basis vector selection, so that the quantum state enters a first single photon detector SPD1 with a certain probability r to perform time state measurement, and enters an orthogonal polarization interferometer with a probability of 1-r to perform phase state measurement;
Step 4: counting detection counts C00 and C01 of a time window corresponding to two time coding states of the first single photon detector SPD1 and detection count C02 of the second single photon detector SPD2 when the first time coding state is sent; counting detection counts C10 and C11 of a time window corresponding to two time coding states of the first single photon detector SPD1 and detection count C12 of the second single photon detector SPD2 when the second time coding state is transmitted; counting a detection count C2 of the second single photon detector SPD2 when the phase encoding state is sent;
step 5: calculating a first error rate e1= (c01+c10)/(c00+c01+c10+c11) and a second error rate e2=c2/(2×c02+2×c12); and when at least one of the first error rate and the second error rate is larger than a corresponding preset threshold value, determining that the channel is eavesdropped.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a device and a method for detecting optical fiber channel eavesdropping, which use a reflective polarization self-compensation module to transmit time-phase coded quantum states transmitted by a sender through the optical fiber channel and then reflect the transmitted time-phase coded quantum states back to the sender for measurement, and judge whether the channel eavesdrop exists or not according to an error rate. The method not only can automatically compensate the polarization conversion of the channel, but also can automatically compensate the phase change in the receiving and transmitting optical path, and the module of the receiving end is a simple passive device, and does not need to actively control and communicate with the transmitting party, so that the complexity and the power consumption of the receiving party are not increased, and the communication bandwidth is not additionally occupied. In addition, 3 polarization states are generated through polarization modulation to prepare 3 time phase quantum states, only 3 phases are required to be adjusted, and the returned optical signals do not need to be subjected to phase modulation, so that the complexity of the system is greatly reduced.
Drawings
FIG. 1 is a schematic block diagram of a fibre channel eavesdropping detection device of the present invention;
FIG. 2 is a block diagram of a first embodiment of a fiber channel eavesdropping detection device according to the present invention;
FIG. 3 is a block diagram of a second embodiment of a fiber channel eavesdropping detection device according to the present invention;
fig. 4 is a block diagram of a third embodiment of a device for detecting a fibre channel tap according to the present invention.
Detailed Description
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.
As shown in fig. 1, the optical fiber channel eavesdropping detection device comprises an eavesdropping detection module and a reflective polarization self-compensation module which are respectively arranged at two ends of an optical fiber channel to be detected, wherein the eavesdropping detection module comprises a Laser, an attenuator ATT, a circulator CIR, a reflective polarization modulation module, an orthogonal polarization interferometer, a first polarization beam splitter PBS1, a beam splitter BS, a first single photon detector SPD1 and a second single photon detector SPD2,
the Laser is used for generating light pulses with horizontal polarization;
the attenuator ATT is used for attenuating the light pulse to preset intensity;
the circulator CIR is used for transmitting the light pulse attenuated by the circulator CIR to the reflective polarization modulation module; and transmitting the light pulses reflected by the reflective polarization modulation module to the orthogonal polarization interferometer; and for transmitting the light pulses output from the orthogonal polarization interferometer to the first polarization beam splitter PBS1;
The reflective polarization modulation module and the first polarization beam splitter PBS1 are connected with corresponding ports of the circulator CIR through 45-degree fusion welding of the polarization maintaining fiber;
the reflection type polarization modulation module is used for randomly modulating the polarization state of the light pulse into horizontal polarization, vertical polarization or 45-degree polarization;
the orthogonal polarization interferometer is provided with a long arm and a short arm and is used for converting light pulses with different polarizations into a time phase coded quantum state light signal; in which a horizontally polarized light pulse incident on its input port is converted into a first time-encoded stateThe method comprises the steps of carrying out a first treatment on the surface of the Converting a vertically polarized light pulse incident on its input port into a second time-encoded state +.>The method comprises the steps of carrying out a first treatment on the surface of the Converting a 45 DEG polarized light pulse incident on its input port into a phase encoded state +.>The method comprises the steps of carrying out a first treatment on the surface of the First time encoding state->And a second temporal coding state->The polarizations of (2) are perpendicular to each other and have a predetermined time difference;
the reflection type polarization self-compensation module is used for reflecting the quantum state optical signal transmitted through the optical fiber channel to be detected, rotating the polarization state of the quantum state optical signal by 90 degrees and carrying out polarization self-compensation on the optical fiber channel;
the beam splitter BS is configured to split a quantum state optical signal returned from the optical fiber channel, and generate a first quantum state component and a second quantum state component;
The first polarization beam splitter PBS1 is used for reflecting a vertical polarization component of the second quantum state component subjected to the orthogonal polarization interferometer and the 45 ° polarization rotation;
the first single photon detector SPD1 and the second single photon detector SPD2 are respectively configured to detect a first quantum state component and a vertically polarized component of a second quantum state component reflected by the first polarizing beam splitter PBS 1.
The specific working process is as follows:
the laser generates light pulse with horizontal polarization, the light pulse is attenuated to the single photon magnitude by the attenuator, then reaches a 45-degree fusion point by the circulator CIR, and enters the reflective polarization modulation module after the polarization is rotated by 45 degrees. The 45 polarization state of the light pulse can be written as
。
The reflection type polarization modulation module rotates the horizontal polarization component and the vertical polarization component by 90 degrees respectively, randomly modulates the phase difference between the two components to j=0, pi/2 and pi, and generates the polarization state of
。
The polarization state becomes after the polarization rotation of 45 degrees again
。
It can be seen that when j=0, the above polarization state is horizontal polarization; when j=pi, the above polarization state is vertical polarization; when j=pi/2, the above polarization state is 45 ° polarization.
The polarized light pulse enters the input port of the orthogonal polarization interferometer through the circulator CIR, if the polarized light pulse is horizontally polarized, the short arm of the interferometer is moved away, the polarized light pulse still is horizontally polarized when the polarized light pulse exits from the output port of the interferometer, and the polarized light pulse is in the former time mode, namely the first time coding state The method comprises the steps of carrying out a first treatment on the surface of the If the polarization is vertical, the long arm of the interferometer is moved, the polarization is still vertical when the long arm exits from the output port of the interferometer, and the long arm is in the latter time mode, namely the second time coding state->The method comprises the steps of carrying out a first treatment on the surface of the If the polarization is 45 DEG, the horizontal polarization component and the vertical polarization component respectively go through the short arm and the long arm of the interferometer, and the probability of being in the previous time mode and the next time mode when exiting from the output port of the interferometer is equal, namely the phase coding state->The method comprises the steps of carrying out a first treatment on the surface of the First time encoding state->And a second temporal coding state->The polarizations of (2) are perpendicular to each other and have a predetermined time difference.
The quantum state of the time phase code then enters the optical fiber channel through the beam splitter BS, reaches the reflective polarization self-compensation module after being transmitted, is reflected by the module and outputs the polarized state, and rotates 90 degrees, and returns to the sender after being transmitted through the optical fiber channel again, at the moment, the polarization of the quantum state is mutually perpendicular to the polarization when exiting from the sender, and is irrelevant to channel disturbance, so that the reflective polarization self-compensation module can perform polarization self-compensation on the optical fiber channel.
The returned quantum state enters a beam splitter BS for beam splitting, and a first quantum state component and a second quantum state component are generated. The first quantum state component directly enters the first single photon detector SPD1 to be detected, and the first single photon detector SPD1 needs to have two time windows due to the existence of two time modes. Counting detection counts C00 and C01 of a time window of the first single photon detector SPD1 corresponding to two time coding states when the first quantum state component is in the first time coding state, and detection counts C10 and C11 of a time window of the first single photon detector SPD1 corresponding to two time coding states when the first quantum state component is in the second time coding state. Wherein, C00 and C11 are correct counts, and C01 and C10 are error counts, so that the first error rate is e1= (c01+c10)/(c00+c01+c10+c11), and the second quantum state component enters the orthogonal polarization interferometer, and as the polarization state is rotated by 90 °, different paths can be taken in the interferometer according to the polarization states. Specifically, the first time encoding state is changed from horizontal polarization to vertical polarization, and the long arm is walked in the interferometer; the second time encoding state is changed from vertical polarization to horizontal polarization, and a short arm is moved in the interferometer; so that both are in the same time window. The polarization states of the previous time mode and the next time mode of the phase coding state are respectively vertical polarization and horizontal polarization, and a long arm and a short arm are respectively moved in the interferometer, so that when the two polarization modes are emitted from an input port of the interferometer, polarization beam combination is carried out, and the polarization beam combination is identical with the time windows when the two time coding states are emitted, namely, only one time window is generated under the 3 conditions, and no non-interference peak exists.
The second quantum state component reaches the first polarization beam splitter PBS1 after passing through the circulator CIR and polarization rotation of 45 degrees, when the second quantum state component is in a first time coding state and a second time coding state, the polarization states are respectively changed into 45 degrees and 135 degrees, so that the probability of being reflected by the first polarization beam splitter PBS1 is 50 percent, and the detection counts of the second single photon detector SPD2 are respectively C02 and C12 under the two conditions; when the two time modes are in a phase encoding state, as the optical path changes experienced by the two time modes are the same, namely the phase difference between the two time modes is 0, the two time modes are polarized and combined and rotated for 45 degrees to become horizontal polarization, wherein if a vertical polarization component exists, an error light signal caused by factors such as polarization extinction ratio and the like is generated correspondingly, and the detection count of the second single photon detector SPD2 is counted as C2. Assuming that the sum of probabilities of preparing the first time encoding state and the second time encoding state is equal to the probability of preparing the phase encoding state, the phase decoding result of the phase encoding state may be approximately 2 (c02+c12), and thus the bit error rate of the phase encoding state is C2/(2c02+2c12).
And when at least one of the first error rate and the second error rate is larger than a corresponding preset threshold value, determining that the channel is eavesdropped.
As shown in fig. 2, a first embodiment of a device for detecting optical fiber channel interception according to the present invention:
the reflective polarization modulation module comprises a first phase modulator PM1 and a quarter-wave plate reflector QM, wherein one end of the first phase modulator PM1 is used as an input port and an output port of the reflective polarization self-compensation module, and the other end of the first phase modulator PM1 is connected with the quarter-wave plate reflector QM.
The orthogonal polarization interferometer comprises a third polarization beam splitter PBS3 and a fourth polarization beam splitter PBS4, wherein two output ports of the third polarization beam splitter PBS3 are respectively connected with two input ports of the fourth polarization beam splitter PBS4 through polarization-preserving optical fibers with different lengths to respectively form a long arm and a short arm of the orthogonal polarization interferometer; the input port of the third polarizing beam splitter PBS3 and the output port of the fourth polarizing beam splitter PBS4 are respectively the input port and the output port of the orthogonal polarization interferometer.
The reflective polarization self-compensation module comprises a seventh polarization beam splitter PBS7 and a Faraday rotator FR, wherein two output ports of the seventh polarization beam splitter PBS7 are respectively connected with two ends of the Faraday rotator FR through polarization maintaining fibers to form an annular structure; the polarization rotation angle of the Faraday rotator FR is 90 degrees, and the polarization directions of the two ends of the Faraday rotator FR are aligned with the slow axis of the polarization maintaining fiber.
The specific working procedure of the first embodiment is as follows:
the laser generates a light pulse with horizontal polarization, the light pulse is attenuated to the single photon magnitude by an attenuator, then reaches a 45 DEG fusion point by a circulator CIR, and enters a first phase modulator PM1 after the polarization is rotated by 45 deg. The 45 polarization state of the light pulse can be written as
。
The horizontal polarization component and the vertical polarization component of the light pulse are modulated by phase difference when the light pulse passes through the first phase modulator PM1 in the forward direction, then the light pulse is respectively rotated by 90 DEG by the quarter-wave plate reflector QM, the phase difference between the two components is modulated again when the light pulse passes through the first phase modulator PM1 again, the randomly modulated phases are obtained as j=0, pi/2 and pi, and the generated polarization state is as follows
。
The polarization state becomes after the polarization rotation of 45 degrees again
。
It can be seen that when j=0, the above polarization state is horizontal polarization; when j=pi, the above polarization state is vertical polarization; when j=pi/2, the above polarization state is 45 ° polarization.
The polarized light pulse enters the input port of the third polarization beam splitter PBS3 through the circulator CIR, if the polarized light pulse is horizontally polarized, the short arm of the interferometer is moved away, the polarized light pulse still is horizontally polarized when the polarized light pulse exits from the output port of the fourth polarization beam splitter PBS4, and the polarized light pulse is in the former time mode, namely the first time coding stateThe method comprises the steps of carrying out a first treatment on the surface of the If the polarization is vertical, the long arm of the interferometer is moved away, the polarization is still vertical when the polarization exits from the output port of the fourth polarization beam splitter PBS4, and the polarization is in the latter time mode, namely the second time coding state +. >The method comprises the steps of carrying out a first treatment on the surface of the If the polarization is 45 DEG, the horizontal polarization component and the vertical polarization component respectively go through the short arm and the long arm of the interferometer, and the probability of being in the previous time mode and the next time mode when exiting from the output port of the fourth polarization beam splitter PBS4 is equal, namely the phase coding state ∈>The method comprises the steps of carrying out a first treatment on the surface of the First time encoding state->And a second temporal coding state->The polarizations of (2) are perpendicular to each other and have a predetermined time difference.
The quantum state of the time phase code enters an optical fiber channel through a beam splitter BS, reaches an input port of a seventh polarization beam splitter PBS7 after being transmitted, and propagates clockwise along a polarization-maintaining optical fiber slow axis in an annular structure after the horizontal polarization component of the quantum state is transmitted, propagates along the polarization-maintaining optical fiber slow axis after being rotated by 90 degrees through a Faraday rotator FR, and then exits from the input port of the seventh polarization beam splitter PBS7 to become vertical polarization; the vertical polarization component of the quantum state propagates along the slow axis of the polarization maintaining fiber anticlockwise in the annular structure, propagates along the slow axis of the polarization maintaining fiber after being rotated by 90 degrees by the Faraday rotator FR, and then exits from the input port of the seventh polarization beam splitter PBS7 to become horizontal polarization. Therefore, the polarization of the horizontal polarization component and the vertical polarization component of the quantum state is rotated by 90 degrees after being acted by the reflective polarization self-compensation module formed by the seventh polarization beam splitter PBS7 and the Faraday rotator FR and is transmitted again through the optical fiber channel and then returned to the sender, and at the moment, the polarization of the quantum state is mutually perpendicular to the polarization when the quantum state exits from the sender and is irrelevant to channel disturbance, so that the reflective polarization self-compensation module can carry out polarization self-compensation on the optical fiber channel.
The returned quantum state enters a beam splitter BS for beam splitting, and a first quantum state component and a second quantum state component are generated. The first quantum state component directly enters the first single photon detector SPD1 to be detected, and the first single photon detector SPD1 needs to have two time windows due to the existence of two time modes. Counting detection counts C00 and C01 of a time window of the first single photon detector SPD1 corresponding to two time coding states when the first quantum state component is in the first time coding state, and detection counts C10 and C11 of a time window of the first single photon detector SPD1 corresponding to two time coding states when the first quantum state component is in the second time coding state. Wherein, C00 and C11 are correct counts, and C01 and C10 are error counts, so that the first error rate is e1= (c01+c10)/(c00+c01+c10+c11), and the second quantum state component enters the output port of the fourth polarization beam splitter PBS4, and as the polarization state is rotated by 90 °, different paths can be taken in the interferometer according to the polarization states. Specifically, the first time encoding state is changed from horizontal polarization to vertical polarization, and the long arm is walked in the interferometer; the second time encoding state is changed from vertical polarization to horizontal polarization, and a short arm is moved in the interferometer; so that both are in the same time window. The polarization states of the previous time mode and the next time mode of the phase coding state are respectively vertical polarization and horizontal polarization, and the long arm and the short arm are respectively moved in the interferometer, so that when the two polarization states are emitted from the input port of the third polarization beam splitter PBS3, the polarization beam combination is performed, and the time windows are the same as those when the two time coding states are emitted, namely, only one time window is generated under the 3 conditions, and no non-interference peak exists.
The second quantum state component reaches the first polarization beam splitter PBS1 after passing through the circulator CIR and polarization rotation of 45 degrees, when the second quantum state component is in a first time coding state and a second time coding state, the polarization states are respectively changed into 45 degrees and 135 degrees, so that the probability of being reflected by the first polarization beam splitter PBS1 is 50 percent, and the detection counts of the second single photon detector SPD2 are respectively C02 and C12 under the two conditions; when the two time modes are in a phase encoding state, as the optical path changes experienced by the two time modes are the same, namely the phase difference between the two time modes is 0, the two time modes are polarized and combined and rotated for 45 degrees to become horizontal polarization, wherein if a vertical polarization component exists, an error light signal caused by factors such as polarization extinction ratio and the like is generated correspondingly, and the detection count of the second single photon detector SPD2 is counted as C2. Assuming that the sum of probabilities of preparing the first time encoding state and the second time encoding state is equal to the probability of preparing the phase encoding state, the phase decoding result of the phase encoding state may be approximately 2 (c02+c12), and thus the bit error rate of the phase encoding state is C2/(2c02+2c12).
And when at least one of the first error rate and the second error rate is larger than a corresponding preset threshold value, determining that the channel is eavesdropped.
As shown in fig. 3, a second embodiment of a device for detecting optical fiber channel interception according to the present invention:
the reflective polarization modulation module comprises a second phase modulator PM2 and a first Faraday mirror FM1, wherein one end of the second phase modulator PM2 is used as an input port and an output port of the reflective polarization self-compensation module, and the other end of the second phase modulator PM2 is connected with the first Faraday mirror FM 1.
The orthogonal polarization interferometer comprises a fifth polarization beam splitter PBS5, a second Faraday mirror FM2 and a third Faraday mirror FM3, wherein one input port and one output port of the fifth polarization beam splitter PBS5 are respectively connected with the second Faraday mirror FM2 and the third Faraday mirror FM3, and the other input port and the other output port of the fifth polarization beam splitter PBS are respectively used as an input port and an output port of the orthogonal polarization interferometer.
The reflective polarization self-compensation module is a fourth faraday mirror FM4.
The specific working procedure of the second embodiment is as follows:
the laser generates a light pulse with horizontal polarization, the light pulse is attenuated to the single photon magnitude by an attenuator, then reaches a 45 DEG fusion point by a circulator CIR, and enters a second phase modulator PM2 after the polarization is rotated by 45 deg. The 45 polarization state of the light pulse can be written as
。
The horizontal polarization component and the vertical polarization component of the light pulse are modulated by the phase difference when the light pulse passes through the second phase modulator PM2 in the forward direction, then the light pulse is respectively rotated by 90 degrees by the first Faraday mirror FM1, the phase difference between the two components is modulated again when the light pulse passes through the first phase modulator PM1 again, the randomly modulated phases are obtained as j=0, pi/2 and pi, and the generated polarization state is as follows
。
The polarization state becomes after the polarization rotation of 45 degrees again
。
It can be seen that when j=0, the above polarization state is horizontal polarization; when j=pi, the above polarization state is vertical polarization; when j=pi/2, the above polarization state is 45 ° polarization.
The polarized light pulse enters one input port of the fifth polarization beam splitter PBS5 through the circulator CIR, if the polarized light pulse is horizontally polarized, the polarized light pulse directly exits from one output port of the fifth polarization beam splitter PBS5, namely a short arm of the interferometer, still horizontally polarized, and is in the former time mode, namely the first time coding stateThe method comprises the steps of carrying out a first treatment on the surface of the If the polarization is vertical polarization, the polarization is reflected by the fifth polarization beam splitter PBS5, reaches the third Faraday mirror FM3, then reaches the second Faraday mirror FM2 through the fifth polarization beam splitter PBS5, finally exits from one output port of the fifth polarization beam splitter PBS5, the path taken by the polarization is the long arm of the interferometer, the polarization is still vertical polarization, and the polarization is in the latter time mode, namely the second time coding state>The method comprises the steps of carrying out a first treatment on the surface of the If the polarization is 45 DEG, the horizontal polarization component and the vertical polarization component respectively go through the short arm and the long arm of the interferometer, and the probability of being in the previous time mode and the next time mode when exiting from the output port of the fourth polarization beam splitter PBS4 is equal, namely the phase coding state ∈ >The method comprises the steps of carrying out a first treatment on the surface of the First time encoding state->And a second temporal coding state->The polarizations of (2) are perpendicular to each other and have a predetermined time difference.
The quantum state of the time phase code then enters the optical fiber channel through the beam splitter BS, reaches the fourth Faraday mirror FM4 after transmission, and returns to the sender after being transmitted again through the optical fiber channel after the reflected polarization is rotated by 90 degrees, and the polarization of the quantum state is mutually perpendicular to the polarization when the quantum state exits from the sender and is irrelevant to channel disturbance, so that the polarization self-compensation of the optical fiber channel can be carried out.
The returned quantum state enters a beam splitter BS for beam splitting, and a first quantum state component and a second quantum state component are generated. The first quantum state component directly enters the first single photon detector SPD1 to be detected, and the first single photon detector SPD1 needs to have two time windows due to the existence of two time modes. Counting detection counts C00 and C01 of a time window of the first single photon detector SPD1 corresponding to two time coding states when the first quantum state component is in the first time coding state, and detection counts C10 and C11 of a time window of the first single photon detector SPD1 corresponding to two time coding states when the first quantum state component is in the second time coding state. Wherein, C00 and C11 are correct counts, and C01 and C10 are error counts, so that the first error rate is e1= (c01+c10)/(c00+c01+c10+c11), and the second quantum state component enters the fifth polarization beam splitter PBS5, and as the polarization state is rotated by 90 °, different paths are taken in the interferometer according to the polarization state. Specifically, the first time coding state is changed from horizontal polarization to vertical polarization, and then reflected by the fifth polarization beam splitter PBS5, reaches the second Faraday mirror FM2, then reaches the third Faraday mirror FM3 through the fifth polarization beam splitter PBS5, and finally exits from one input port of the fifth polarization beam splitter PBS5, and the path taken by the first time coding state is the long arm of the interferometer; the second time encoding state is changed from vertical polarization to horizontal polarization and is directly transmitted from the fifth polarization beam splitter PBS5, which is equivalent to walking a short arm in the interferometer; so that both are in the same time window. The polarization states of the previous time mode and the next time mode of the phase coding state are respectively vertical polarization and horizontal polarization, and the long arm and the short arm are respectively moved in the interferometer, so that when the two polarization states are emitted from the input port of the third polarization beam splitter PBS3, the polarization beam combination is performed, and the time windows are the same as those when the two time coding states are emitted, namely, only one time window is generated under the 3 conditions, and no non-interference peak exists.
The second quantum state component reaches the first polarization beam splitter PBS1 after passing through the circulator CIR and polarization rotation of 45 degrees, when the second quantum state component is in a first time coding state and a second time coding state, the polarization states are respectively changed into 45 degrees and 135 degrees, so that the probability of being reflected by the first polarization beam splitter PBS1 is 50 percent, and the detection counts of the second single photon detector SPD2 are respectively C02 and C12 under the two conditions; when the two time modes are in a phase encoding state, as the optical path changes experienced by the two time modes are the same, namely the phase difference between the two time modes is 0, the two time modes are polarized and combined and rotated for 45 degrees to become horizontal polarization, wherein if a vertical polarization component exists, an error light signal caused by factors such as polarization extinction ratio and the like is generated correspondingly, and the detection count of the second single photon detector SPD2 is counted as C2. Assuming that the sum of probabilities of preparing the first time encoding state and the second time encoding state is equal to the probability of preparing the phase encoding state, the phase decoding result of the phase encoding state may be approximately 2 (c02+c12), and thus the bit error rate of the phase encoding state is C2/(2c02+2c12).
And when at least one of the first error rate and the second error rate is larger than a corresponding preset threshold value, determining that the channel is eavesdropped.
As shown in fig. 4, a third embodiment of a device for detecting optical fiber channel interception according to the present invention:
the reflective polarization modulation module comprises a second polarization beam splitter PBS2 and a third phase modulator PM3, wherein an input port of the second polarization beam splitter PBS2 is used as an input port and an output port of the reflective polarization self-compensation module, and the two output ports of the second polarization beam splitter PBS2 are respectively connected with two ends of the third phase modulator PM3 through polarization maintaining optical fibers.
The orthogonal polarization interferometer is a sixth polarization beam splitter PBS6, one input port and one output port of the sixth polarization beam splitter PBS6 are directly connected through a polarization maintaining fiber, and the other input port and the other output port of the sixth polarization beam splitter PBS6 are respectively used as an input port and an output port of the orthogonal polarization interferometer.
The reflective polarization self-compensation module comprises an eighth polarization beam splitter PBS8 and a fifth Faraday mirror FM5, wherein one output port of the eighth polarization beam splitter PBS8 is connected with the fifth Faraday mirror FM5, and the other output port of the eighth polarization beam splitter PBS is connected with one input port through a polarization maintaining optical fiber.
The specific working procedure of the third embodiment is as follows:
the laser generates a light pulse with horizontal polarization, the light pulse is attenuated to the single photon magnitude by an attenuator, then reaches a 45 DEG fusion point by a circulator CIR, and enters a second polarization beam splitter PBS2 after the polarization is rotated by 45 deg. The 45 polarization state of the light pulse can be written as
。
The light pulse is polarized by the second polarization beam splitter PBS2, the plane polarized component and the vertical polarized component of the Shu Chengshui component, the two components pass through the third phase modulator PM3 from opposite directions respectively, are randomly modulated to be in phase j=0, pi/2 and pi, and then pass through the second polarization beam splitter PBS2 for polarization beam combination, and the generated polarization state is that
。
The polarization state becomes after the polarization rotation of 45 degrees again
。
It can be seen that when j=0, the above polarization state is horizontal polarization; when j=pi, the above polarization state is vertical polarization; when j=pi/2, the above polarization state is 45 ° polarization.
The polarized light pulse enters one input port of the sixth polarization beam splitter PBS6 through the circulator CIR, if the polarized light pulse is horizontally polarized, the polarized light pulse is directly transmitted from the sixth polarization beam splitter PBS6, which is equivalent to walking the short arm of the interferometer, is still horizontally polarized, and is in the former time mode, namely the first time coding stateThe method comprises the steps of carrying out a first treatment on the surface of the If the polarization is vertical polarization, the polarization is reflected by the sixth polarization beam splitter PBS6, and after the polarization maintaining fiber propagates, the polarization is reflected from the sixth polarization beam splitter PBS6, which is equivalent to the long arm of the interferometer, and still is vertical polarization, and in the latter time mode, the second time coding state +.>The method comprises the steps of carrying out a first treatment on the surface of the If the polarization is 45 DEG, the horizontal polarization component and the vertical polarization component respectively go through the short arm and the long arm of the interferometer, and the probability of being in the previous time mode and the next time mode when exiting from the output port of the fourth polarization beam splitter PBS4 is equal, namely the phase coding state ∈ >The method comprises the steps of carrying out a first treatment on the surface of the First time encoding state->And a second temporal coding state->The polarizations of (2) are perpendicular to each other and have a predetermined time difference.
The quantum state of the time phase code then enters the optical fiber channel through the beam splitter BS, and reaches an input port of the eighth polarization beam splitter PBS8 after being transmitted, the horizontal polarization component of the quantum state is transmitted, then reaches the fifth Faraday mirror FM5 to be reflected, reaches the eighth polarization beam splitter PBS8 to be reflected after the polarization is rotated by 90 degrees, and exits from the eighth polarization beam splitter PBS8 to be vertical polarization after being transmitted along the polarization maintaining optical fiber; the vertical polarization component of the quantum state is reflected by the eighth polarization beam splitter PBS8, propagates along the polarization maintaining fiber, exits from the eighth polarization beam splitter PBS8, then reaches the fifth faraday mirror FM5 to be reflected, and is transmitted from the eighth polarization beam splitter PBS8 after polarization is rotated by 90 ° to become horizontal polarization. Therefore, the polarization of the horizontal polarization component and the vertical polarization component of the quantum state is rotated by 90 degrees after being acted by the reflective polarization self-compensation module formed by the eighth polarization beam splitter PBS8 and the fifth Faraday mirror FM5 and is transmitted again through the optical fiber channel and then returned to the sender, and at the moment, the polarization of the quantum state is mutually perpendicular to the polarization when the quantum state exits from the sender and is irrelevant to channel disturbance, so that the reflective polarization self-compensation module can carry out polarization self-compensation on the optical fiber channel.
The returned quantum state enters a beam splitter BS for beam splitting, and a first quantum state component and a second quantum state component are generated. The first quantum state component directly enters the first single photon detector SPD1 to be detected, and the first single photon detector SPD1 needs to have two time windows due to the existence of two time modes. Counting detection counts C00 and C01 of a time window of the first single photon detector SPD1 corresponding to two time coding states when the first quantum state component is in the first time coding state, and detection counts C10 and C11 of a time window of the first single photon detector SPD1 corresponding to two time coding states when the first quantum state component is in the second time coding state. Wherein C00 and C11 are correct counts, and C01 and C10 are error counts, so that the first error rate is e1= (c01+c10)/(c00+c01+c10+c11), and the second quantum state component enters an output port of the sixth polarization beam splitter PBS6, and as the polarization state is rotated by 90 °, different paths are taken in the interferometer according to the polarization state. Specifically, the first time encoding state is changed from horizontal polarization to vertical polarization, and then reflected by the sixth polarization beam splitter PBS6, and reflected from the sixth polarization beam splitter PBS6 after propagating along the polarization maintaining fiber, which is equivalent to walking a long arm in the interferometer; the second time encoding state is changed from vertical polarization to horizontal polarization, and is directly transmitted from the sixth polarization beam splitter PBS6, which is equivalent to walking a short arm in the interferometer; so that both are in the same time window. The polarization states of the previous time mode and the next time mode of the phase coding state are respectively vertical polarization and horizontal polarization, and the long arm and the short arm are respectively moved in the interferometer, so that when the two polarization states are emitted from the input port of the third polarization beam splitter PBS3, the polarization beam combination is performed, and the time windows are the same as those when the two time coding states are emitted, namely, only one time window is generated under the 3 conditions, and no non-interference peak exists.
The second quantum state component reaches the first polarization beam splitter PBS1 after passing through the circulator CIR and polarization rotation of 45 degrees, when the second quantum state component is in a first time coding state and a second time coding state, the polarization states are respectively changed into 45 degrees and 135 degrees, so that the probability of being reflected by the first polarization beam splitter PBS1 is 50 percent, and the detection counts of the second single photon detector SPD2 are respectively C02 and C12 under the two conditions; when the two time modes are in a phase encoding state, as the optical path changes experienced by the two time modes are the same, namely the phase difference between the two time modes is 0, the two time modes are polarized and combined and rotated for 45 degrees to become horizontal polarization, wherein if a vertical polarization component exists, an error light signal caused by factors such as polarization extinction ratio and the like is generated correspondingly, and the detection count of the second single photon detector SPD2 is counted as C2. Assuming that the sum of probabilities of preparing the first time encoding state and the second time encoding state is equal to the probability of preparing the phase encoding state, the phase decoding result of the phase encoding state may be approximately 2 (c02+c12), and thus the bit error rate of the phase encoding state is C2/(2c02+2c12).
And when at least one of the first error rate and the second error rate is larger than a corresponding preset threshold value, determining that the channel is eavesdropped.
As can be seen from the embodiments of the present invention, the present invention provides a device and a method for detecting optical fiber channel eavesdropping, which uses a reflective polarization self-compensation module to transmit a time-phase encoded quantum state transmitted by a sender through an optical fiber channel, and then reflect the transmitted time-phase encoded quantum state back to the sender for measurement, and determines whether the channel eavesdropping exists according to an error rate. The method not only can automatically compensate the polarization conversion of the channel, but also can automatically compensate the phase change in the receiving and transmitting optical path, and the module of the receiving end is a simple passive device, and does not need to actively control and communicate with the transmitting party, so that the complexity and the power consumption of the receiving party are not increased, and the communication bandwidth is not additionally occupied. In addition, 3 polarization states are generated through polarization modulation to prepare 3 time phase quantum states, only 3 phases are required to be adjusted, and the returned optical signals do not need to be subjected to phase modulation, so that the complexity of the system is greatly reduced.
Claims (12)
1. The utility model provides a fibre channel eavesdropping detection device, includes eavesdropping detection module and reflective polarization self-compensating module of deploying respectively at waiting to detect fibre channel both ends, its characterized in that, eavesdropping detection module includes:
a laser for generating horizontally polarized light pulses;
An attenuator for attenuating the light pulse to a preset intensity;
the circulator is used for multi-direction transmission of different light pulses;
the reflective polarization modulation module is connected with the corresponding port of the circulator through 45-degree fusion connection of the polarization maintaining fiber; the reflection type polarization modulation module is used for randomly modulating the polarization state of the light pulse into horizontal polarization, vertical polarization or 45-degree polarization;
an orthogonal polarization interferometer having long and short arms for converting light pulses of different polarizations into a time phase encoded quantum state light signal;
the reflection type polarization self-compensation module is used for reflecting the quantum state optical signal transmitted through the optical fiber channel to be detected, rotating the polarization state of the quantum state optical signal by 90 degrees and carrying out polarization self-compensation on the optical fiber channel to be detected;
the beam splitter is used for splitting the quantum state optical signal returned from the optical fiber channel to be detected to generate a first quantum state component and a second quantum state component;
the first polarization beam splitter is connected with the corresponding port of the circulator through 45-degree fusion connection of the polarization maintaining fiber and is used for reflecting the vertical polarization component of the second quantum state component subjected to orthogonal polarization interferometer and 45-degree polarization rotation;
the first single photon detector and the second single photon detector are respectively used for detecting the first quantum state component and the vertical polarization component of the second quantum state component reflected by the first polarization beam splitter.
2. The device of claim 1, wherein the reflective polarization modulation module comprises a first phase modulator and a quarter wave plate mirror, one end of the first phase modulator being used as an input port and an output port of the reflective polarization self-compensating module, and the other end of the first phase modulator being connected to the quarter wave plate mirror.
3. The device of claim 1, wherein the reflective polarization modulation module comprises a second phase modulator and a first faraday mirror, one end of the second phase modulator being an input port and an output port of the reflective polarization self-compensation module, and the other end of the second phase modulator being connected to the first faraday mirror.
4. The optical fiber channel eavesdropping detection device according to claim 1, wherein the reflective polarization modulation module comprises a second polarization beam splitter and a third phase modulator, an input port of the second polarization beam splitter is used as an input port and an output port of the reflective polarization self-compensation module, and the two output ports of the second polarization beam splitter are respectively connected with two ends of the third phase modulator through polarization-maintaining optical fibers.
5. The optical fiber channel eavesdropping detection device according to claim 1 or 2 or 3 or 4, wherein the orthogonal polarization interferometer comprises a third polarization beam splitter and a fourth polarization beam splitter, and two output ports of the third polarization beam splitter are respectively connected with two input ports of the fourth polarization beam splitter through polarization-preserving optical fibers with different lengths, so as to respectively form a long arm and a short arm of the orthogonal polarization interferometer; the input port of the third polarizing beam splitter and the output port of the fourth polarizing beam splitter are respectively used as the input port and the output port of the orthogonal polarization interferometer.
6. The optical fiber channel eavesdropping detection device according to claim 1 or 2 or 3 or 4, wherein the orthogonal polarization interferometer includes a fifth polarization beam splitter, a second faraday mirror, and a third faraday mirror, and one input port and one output port of the fifth polarization beam splitter are connected to the second faraday mirror and the third faraday mirror, respectively, and the other input port and the other output port thereof are respectively used as the input port and the output port of the orthogonal polarization interferometer.
7. The optical fiber channel eavesdropping detection device according to claim 1 or 2 or 3 or 4, wherein the orthogonal polarization interferometer is a sixth polarization beam splitter, one input port and one output port of the sixth polarization beam splitter are directly connected through a polarization maintaining fiber, and the other input port and the other output port of the sixth polarization beam splitter are respectively used as an input port and an output port of the orthogonal polarization interferometer.
8. The optical fiber channel eavesdropping detection device according to claim 1, wherein the reflective polarization self-compensation module comprises a seventh polarization beam splitter and a Faraday rotator, and two output ports of the seventh polarization beam splitter are respectively connected with two ends of the Faraday rotator through polarization maintaining fibers to form an annular structure; the polarization rotation angle of the Faraday rotator is 90 degrees, and the polarization directions of the two ends of the Faraday rotator are aligned with the slow axis of the polarization maintaining optical fiber.
9. The device of claim 1, wherein the reflective polarization self-compensating module is a fourth faraday mirror.
10. The optical fiber channel eavesdropping detection device according to claim 1, wherein the reflective polarization self-compensation module comprises an eighth polarization beam splitter and a fifth faraday mirror, one output port of the eighth polarization beam splitter is connected with the fifth faraday mirror, and the other output port of the eighth polarization beam splitter is connected with one input port of the eighth polarization beam splitter through a polarization maintaining fiber.
11. The device according to claim 1, wherein the orthogonal polarization interferometer is configured to convert light pulses of different polarizations into time-phase encoded quantum state light signals, specifically: wherein a horizontally polarized light pulse incident on an input port of an orthogonal polarization interferometer is converted into a first time encoded stateThe method comprises the steps of carrying out a first treatment on the surface of the Converting a vertically polarized light pulse incident to an input port of an orthogonal polarization interferometer into a second time-encoded state +.>The method comprises the steps of carrying out a first treatment on the surface of the Converting 45 DEG polarized light pulses incident to an input port of an orthogonal polarization interferometer into a phase encoded state +.>The method comprises the steps of carrying out a first treatment on the surface of the First time encoding state->And a second timeCoding state->The polarizations of (2) are perpendicular to each other and have a predetermined time difference.
12. A method for detecting a fibre channel tap, comprising the steps of:
step 1: the laser generates light pulses with horizontal polarization, and the light pulses are attenuated to preset intensity through the attenuator; randomly modulating the polarization state of the light pulse into horizontal polarization, vertical polarization or 45-degree polarization by using a polarization modulation module;
step 2: the polarized light pulse enters the orthogonal polarization interferometer to complete the time-phase quantum state coding, and a first time coding state is randomly generatedSecond temporal coding state->Phase encoding state->；
Step 3: the quantum state is transmitted to a reflective polarization self-compensation module through a fiber channel, reflected and returned through the fiber channel again, polarization is rotated by 90 degrees and then enters a beam splitter to perform basis vector selection, so that the quantum state enters a first single photon detector with a certain probability r to perform time state measurement, and enters an orthogonal polarization interferometer with a probability of 1-r to perform phase state measurement;
step 4: counting detection counts C00 and C01 of a time window corresponding to two time coding states of the first single photon detector and detection count C02 of the second single photon detector when the first time coding state is sent; counting detection counts C10 and C11 of a time window corresponding to the two time coding states of the first single photon detector and detection count C12 of the second single photon detector when the second time coding state is sent; counting the detection count C2 of the second single photon detector when the phase encoding state is sent;
Step 5: calculating a first error rate e1= (c01+c10)/(c00+c01+c10+c11) and a second error rate e2=c2/(2×c02+2×c12); and when at least one of the first error rate and the second error rate is larger than a corresponding preset threshold value, determining that the channel is eavesdropped.
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