CN111049613A - Time Division Multiplexing (TDM) removing device and method - Google Patents
Time Division Multiplexing (TDM) removing device and method Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/16—Time-division multiplex systems in which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals, to vary number of channels transmitted
- H04J3/1676—Time-division multiplex with pulse-position, pulse-interval, or pulse-width modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/524—Pulse modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
- H04B10/69—Electrical arrangements in the receiver
- H04B10/691—Arrangements for optimizing the photodetector in the receiver
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0852—Quantum cryptography
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Abstract
The invention discloses a time division multiplexing de-multiplexing device and a time division multiplexing de-multiplexing method. The time division multiplexing de-multiplexing device comprises an optical detection unit, a time division multiplexing optical detection unit and a time division multiplexing optical detection unit, wherein the optical detection unit is used for receiving and detecting the time division multiplexing optical and converting the time division multiplexing optical into a time division multiplexing electric signal; the clock distribution unit comprises a signal input port and two or more signal output ports, and can output the input electric signals through different output ports after frequency division; a programmable unit configured to emit a first control signal for detecting a synchronous electrical signal, a second control signal for detecting a classical electrical signal; the first logic unit and the second logic unit respectively comprise two or more than two signal input ports, and one signal output port can carry out logic operation. The system of the invention has simple structure and reduces the application cost; the code rate of classical signals and synchronous signals is improved; the influence of system Raman scattering on quantum light is effectively reduced, and therefore the coding rate of the quantum key is improved.
Description
Technical Field
The invention relates to the technical field of quantum secret communication, in particular to a Time Division Multiplexing (TDM) device and a time division multiplexing method.
Background
As a new technology developed on the basis of quantum mechanics, modern communication, modern cryptography and the like, the quantum secret communication technology encrypts information by using a one-time pad mode based on the basic principle of quantum mechanics, has the characteristic of indecipherability and has incomparable security advantages. Quantum Key Distribution (QKD) technology is a Key technology for Quantum secret communication. One of the issues of intensive research on quantum key distribution technology at present is how to implement quantum key distribution by using the existing optical fiber communication network.
In the prior art, a quantum key distribution technology using a time division multiplexing technology realizes quantum key distribution using an existing optical fiber communication network, a receiving end of the prior art needs to perform time division multiplexing by a time division multiplexing apparatus after receiving signal light of a transmitting end, and fig. 1 shows a schematic structural diagram of the time division multiplexing apparatus of the prior art. After receiving the optical signal at the transmitting end, the time division multiplexing apparatus at the receiving end in the prior art shown in fig. 1 splits the time division multiplexing light by the optical splitting apparatus, and then transmits the split signal light to the synchronous optical detector, the classical optical detector and the quantum key detector through the channel, so as to obtain the synchronous signal, the classical signal and the quantum key by respectively detecting the signal light. Such a time division multiplex apparatus has the following problems. Firstly, the time division multiplexing device in the prior art needs a light splitting device, and synchronous light and classical light need different light detectors to detect respectively, so that the device has a complex structure and higher cost; secondly, in the prior art, light splitting is performed first, and then synchronous light and classical light are detected respectively to obtain synchronous signals and classical signals, and due to attenuation or phase shift of light caused by the light splitting process, the resultant code rate of the synchronous signals and the classical signals is reduced; thirdly, a large attenuation effect is generated on the light intensity in the light splitting process, so that a transmitting end is required to emit strong light, and the Raman scattering noise and the light intensity are in a positive correlation relationship, so that a strong Raman scattering effect is generated, and the quantum key composition rate is low.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a Time Division Multiplexing (TDM) demultiplexing device, which comprises: a light detection unit configured to receive and detect time division multiplexed light and convert the time division multiplexed light into a time division multiplexed electrical signal; the clock distribution unit comprises a signal input port and two or more signal output ports, and is configured to receive the time division multiplexing electric signals, distribute the time division multiplexing electric signals to form a first time division multiplexing signal and a second time division multiplexing signal, and output the first time division multiplexing signal and the second time division multiplexing signal; a programmable unit configured to emit a first control signal for detecting a synchronous electrical signal, a second control signal for detecting a classical electrical signal; a first logic unit including two or more signal input ports, one signal output port having a logic operation function, configured to receive the first time division multiplexing signal, the first control signal, and to process the first control signal to send out the synchronous electrical signal; and the second logic unit comprises two or more signal input ports and one signal output port, has a logic operation function, is configured to receive the second time division multiplexing signal and the second control signal, and sends out the classical electric signal after processing.
In the apparatus for demultiplexing as described above, the clock distribution unit is further a clock distributor.
The apparatus for demultiplexing time division multiplexing as described above, the programmable unit may further include: a control chip configured to issue an operation instruction to the signal generation device or the delay device; the signal generating device is configured to receive an operation instruction of the control chip and generate an electric signal; the time delay device is configured to receive an operation instruction of the control chip, and the electric signal generated by the signal generation device carries out time delay operation on the received electric signal according to the received operation instruction.
In the apparatus for demultiplexing time division multiplexing as described above, the optical detection unit is further a PN junction type photodetector, or a PIN type photodetector, or an Avalanche Photodiode (APD) detector, or a pull-on avalanche photodiode (RAPD) detector.
In the apparatus for demultiplexing as described above, the first logic unit or the second logic unit is further a logic chip.
In the apparatus for demultiplexing time division multiplexing, the first logic unit or the second logic unit may be any one of an and circuit, an or circuit, a nor circuit, an exclusive or circuit, and an exclusive or circuit.
In the above apparatus for demultiplexing time division multiplexing, the first logic unit or the second logic unit is further an and circuit.
In the apparatus for demultiplexing as described above, the signal characteristics of the first time-division multiplexed electrical signal and the second time-division multiplexed electrical signal are consistent with the signal characteristics of the time-division multiplexed electrical signal.
According to another aspect of the present invention, a method for time division multiplexing includes: the optical detection unit receives and detects the time division multiplexing light, and converts the time division multiplexing light into a time division multiplexing electric signal; receiving the time division multiplexing electric signals by the clock distribution unit and distributing to form a first time division multiplexing electric signal and a second time division multiplexing electric signal; sending out a first control signal for detecting a synchronous electrical signal and a second control signal for detecting a classical electrical signal by the programmable unit; the first time division multiplexing electric signal and the first control signal are input into the first logic unit, and after being processed, a synchronous electric signal is output; and the second time division multiplexing electric signal and the second control signal are input into the second logic unit, and after being processed, a classical electric signal is output.
The device and the method for demultiplexing and time division multiplexing provided by the invention have the advantages that a light splitting device in the prior art is eliminated, the detection of classical light and synchronous light can be realized by one light detection unit, the system structure is simple, and the application cost is reduced. Compared with the prior art, the invention firstly detects the time division multiplexing light to obtain the time division multiplexing electric signal, then obtains the synchronous electric signal and the classical electric signal through the processing of the logic unit, and the processed electric signal is simpler and more convenient and has higher precision compared with the optical signal, thereby improving the code rate of the signal. In addition, due to the elimination of the light splitting device, the light intensity of the sending end when sending the signal light can be reduced compared with the prior art, so that the influence of system Raman scattering on the quantum light can be effectively reduced, and the resultant code rate of the quantum key is improved.
Drawings
Fig. 1 shows a schematic structure diagram of a time division multiplexing apparatus of a time division multiplexing quantum key distribution system in the prior art;
fig. 2 is a schematic structural diagram illustrating an exemplary embodiment of a transmitting end according to the present invention;
fig. 3 shows a signal slot modulation diagram of a transmitting end according to the present invention;
fig. 4 shows a schematic structural diagram of an exemplary embodiment of a receiving end according to the present invention;
FIG. 5 shows a schematic structural diagram of an exemplary embodiment of a de-time division multiplexing apparatus according to the present invention;
fig. 6 shows a schematic diagram of the initialization phase of the de-time division multiplexing device according to the invention;
fig. 7 shows a signal diagram of an initialization phase of a de-time division multiplexing device according to the invention;
fig. 8 shows a schematic diagram of the working phases of a de-time division multiplex apparatus according to the invention;
fig. 9 shows a signal diagram of the operating phase of a de-time division multiplex device according to the invention;
fig. 10 shows a flow chart of a method of demultiplexing according to the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof and in which is shown by way of illustration specific embodiments of the application. In the drawings, like numerals describe substantially similar components throughout the different views. Various specific embodiments of the present application are described in sufficient detail below to enable those skilled in the art to practice the teachings of the present application.
Fig. 2 shows a schematic structural diagram of an exemplary embodiment of a transmitting end according to the present invention. The basic structure of the transmitting end of the present invention can be briefly explained by the embodiment of fig. 2. As shown in fig. 2, the transmitting end of the present invention may include a quantum key encoding unit 101, a first laser 103, and a first wavelength division multiplexing unit 201.
In some embodiments, the quantum key encoding unit 101 may receive the optical signal, perform quantum key encoding, and transmit the encoded quantum signal in the form of quantum light, and the quantum key encoding unit 101 may be a polarization encoding device, a time encoding device, a phase encoding device, or a time phase encoding device, preferably a time phase encoding device. The probability of quantum key encoding by the quantum key encoding unit 101 is random, and after quantum key encoding is completed, the wavelength λ is t1The period t is within the range of 5ns to 60 ns. The quantum key encoding unit 101 may include an encoding preparation device that receives the optical signal to perform quantum key encoding; a decoy state preparation device can be included to perform decoy state preparation; can comprise a single-photon preparation device for preparing single photons.
In some embodiments, the firstThe lasers 103 may emit light having the same wavelength λ2Wherein the synchronization light is operable to transmit the encoded synchronization signal and the classical light is operable to transmit the encoded classical signal. The first laser 103 may send a sync light during the initialization phase of the present invention and send a sync light or a classical light during the operation phase of the present invention. The synchronous light emitted by the first laser 103 can transmit synchronous frames meeting the requirements of synchronous digital transmission, the digital synchronous transmission can adopt an optical fiber channel to realize the functions of multi-node synchronous information transmission, multiplexing, add-drop multiplexing, cross connection and the like, the synchronous light emitted by the first laser 103 can be narrow pulses with the duty ratio less than or equal to 1 percent, and further narrow pulses with the duty ratio less than or equal to 1 per thousand, the period of the synchronous light emitted by the first laser 103 is T1, and the numerical range of the period T1 is 5 us-T1-30 us; the classical light emitted by the first laser 103 can be a classical light pulse with a pulse width capable of being modulated, and the classical light is a narrow pulse with a duty cycle less than or equal to 30%; preferably, the pulse is a narrow pulse with a duty ratio of 20% or less; further preferably a narrow pulse having a duty ratio of 10% or less; the period of the classical light emitted by the first laser 103 is T2, and the value range of the period T2 is T < T2 < T1.
The first laser 103 adopts time division multiplexing technology in the process of emitting the classical light and the synchronous light, the channel transmission time is divided into different time slots, and the system allocates the different time slots after division to the synchronous light and the classical light, thereby realizing the time division multiplexing of the synchronous light and the classical light. The first laser 103 modulates the synchronous light and the classical light emitted by it according to the time slot modulation diagram shown in fig. 3. The first laser 103 modulates the synchronization light according to the time slot diagram shown in the first row of fig. 3, the synchronization light wavelength being λ as shown in the first row of fig. 32The period is T1, T1 is more than or equal to 5us and less than or equal to 30 us; the first laser 103 modulates the classical light according to the time slot diagram shown in the second row of fig. 3, the classical light wavelength being λ as shown in the second row of fig. 32The period is T2, T is more than or equal to T2 and more than or equal to T1; the first laser 103 time-division multiplexes the synchronous light and the classical light according to the time slot diagram shown in the third row of fig. 3, realizes time-division multiplexing of the classical light and the synchronous light, andand emitting time division multiplexing light, wherein the time difference between the synchronous light and the adjacent classical light is delta T, and the value range of the time difference is T less than or equal to delta T less than or equal to T1/2.
In some embodiments, the first wavelength division multiplexing unit 201 includes a first port C, a second port R, and a third port T. The first wavelength division multiplexing unit 201 is a bidirectional optical element, and can be set in the following mode: when light in the first frequency range is incident from the second port R and/or light in the second frequency range is incident at the third port T, the incident light of the second port R and the incident light of the third port T are combined into one path of output at the first port C; when light is incident on the first port C, the second port R outputs light in the first frequency range, and the third port T outputs light in the second frequency range. Wherein the first frequency range may be different from the second frequency range.
The first wavelength division multiplexing unit 201 may be a sparse wavelength division multiplexer, a dense wavelength division multiplexer, a band pass wavelength division multiplexer, or a fiber bragg grating, but is not limited thereto. Since the sparse wavelength division multiplexer, the dense wavelength division multiplexer, and the band pass wavelength division multiplexer have a common port, a reflection port, and a transmission port, and the isolation of the transmission port is greater than that of the reflection port, it is preferable to use these three wavelength division multiplexers, and set the common port to the first port C, the reflection port to the second port R, and the transmission port to the third port T. Preferably, the first wavelength division multiplexing unit 201 may be a wavelength division multiplexer having an isolation degree of 60dB or more.
The quantum light emitted by the quantum key encoding unit 101 and the time division multiplexing light emitted by the first laser 103 may be input through the second port R of the first wavelength division multiplexing unit 201 or may be input through the third port T of the first wavelength division multiplexing unit 201, and further the quantum light emitted by the quantum key encoding unit 101 may be input through the third port T of the first wavelength division multiplexing unit 201, which may facilitate the transmission port with the maximum isolation degree to eliminate the influence of local fluorescence on the quantum light.
In the present invention, the first laser 103 may emit light having a wavelength λ2Synchronous light with period T1 and wavelength of λ2Of period T2 and according to FIG. 3Modulating the synchronous light according to the time slot diagram shown in one row, modulating the classical light according to the time slot diagram shown in the second row of fig. 3, and time-division multiplexing the classical light and the synchronous light according to the time slot diagram shown in the third row of fig. 3, thereby realizing the time-division multiplexing of the classical light and the synchronous light and emitting light with the wavelength of lambda2The time-division multiplexed light of (1), in the emitted time-division multiplexed light, the numerical range of the time difference Δ T between the synchronous light and the adjacent classical light is not less than the period T of the quantum light and not more than T1/2; the quantum key encoding unit 101 may perform quantum key encoding and emit light with a wavelength λ1Quantum light of period t; wavelength lambda of the time division multiplexed light2With wavelength lambda of quantum light1Are not equal; the first wavelength division multiplexing unit 201 may receive the wavelength λ emitted by the first laser 1032The wavelength emitted by the time division multiplexing optical and quantum key encoding unit 101 is lambda1And wavelength division multiplexing the time division multiplexing light and the quantum light, and then sending out the wavelength division multiplexing light and transmitting the wavelength division multiplexing light through a channel.
In the invention, the quantum light and the time division multiplexing light, namely the quantum light and the classical light or the synchronous light have different wavelengths, and the wavelength division multiplexing can be carried out, which means that the quantum light is not subjected to time division multiplexing, so that the problem that a relatively long 'clearing period' is required before the quantum light is emitted in the prior art can not be generated, the sending frequency of the quantum light is not influenced by the time division multiplexing, and the high-speed sending of the quantum key can be realized. In addition, the transmitting end of the invention does not need to use a plurality of modulators to modulate the classical light and the synchronous light during time division multiplexing, thereby simplifying the system structure and reducing the cost.
Fig. 4 shows a schematic structural diagram of an exemplary embodiment of a receiving end according to the present invention. As shown in fig. 4, the receiving end of the present invention may include a second wavelength division multiplexing unit 203, a time division demultiplexing device 301, and a quantum key decoding unit 303.
In some embodiments, the second wavelength division multiplexing unit 203 is a bidirectional optical element having a similar structure to the first wavelength division multiplexing unit 201, and the second wavelength division multiplexing unit 203 receives the wavelength division multiplexed light transmitted from the transmitting end of the present invention and demultiplexes the received wavelength division multiplexed light, wherein the resulting quantum light is transmitted to the quantum key decoding unit 303, and the resulting time division multiplexed light is transmitted to the demultiplexing device 301.
In some embodiments, the de-time division multiplexing device 301 may receive the time division multiplexing light transmitted by the second wavelength division multiplexing unit 203, detect the received time division multiplexing light, convert the time division multiplexing light into a time division multiplexing electrical signal, and further process the time division multiplexing electrical signal to obtain a synchronous electrical signal and a classical electrical signal.
In some embodiments, the quantum key decoding unit 303 may receive the quantum light transmitted by the second wavelength division multiplexing unit 203, and detect the quantum light to decode the quantum key to obtain the encoded information therein.
Fig. 5 shows a schematic structural diagram of an exemplary embodiment of a device for time division multiplexing according to the present invention. As shown in fig. 5, the apparatus for demultiplexing time division multiplexing according to the present invention may include an optical detection unit 401, a clock distribution unit 501, a programmable unit 601, a first logic unit 603, and a second logic unit 605, where the programmable unit 601 may include a control chip 6011, a signal generation device 6013, and a delay device 6015.
In some embodiments, the optical detection unit 401 may receive and detect an optical signal and obtain a corresponding electrical signal, and the optical detection unit 401 may be a PN junction type photodetector, a PIN type photodetector, an Avalanche Photodiode (APD) detector, or a pull-through avalanche photodiode (RAPD) detector. The clock distribution unit 501 may include one signal input port, may include two or more signal output ports, and may output the input electrical signals through different output ports after being distributed according to system requirements. Preferably, the clock distribution unit 501 may be a clock distributor.
In some embodiments, the programmable unit 601 may issue different signals according to different working phases of the present invention, may issue a scan signal during the initialization phase, and may issue a control signal during the working phase. The programmable unit 601 may include a control chip 6011, and may issue an operation instruction to the signal generation device 6013 or the delay device 6015; the signal generating device 6013 may receive an operation instruction of the control chip 6011, generate different electrical signals in different working stages of the present invention, send a scanning signal in an initialization stage, and send a control signal in a working stage; the delay device 6015 may receive an operation instruction of the control chip 6011 and the electrical signal generated by the signal generation device 6013, and perform a delay operation on the received electrical signal according to the received operation instruction.
In some embodiments, the first logic unit 603 is a circuit capable of performing a logic operation, and may be an and gate circuit, an or gate circuit, or an nor gate circuit, an xor gate circuit, or an xnor gate circuit. The first logic unit 603 may include two or more signal input ports and may include one signal output port. Preferably, the first logic unit 603 may be a logic chip. The second logic unit 605 has a similar structure and function to the first logic unit 603. Preferably, the first logic unit 603 and the second logic unit 605 may be and circuits.
The inventive de-time division multiplexing device can have different operation modes in the inventive initialization phase or working phase.
Fig. 6 shows a schematic diagram of an initialization phase of the time division multiplexing apparatus according to the present invention, and fig. 7 shows a signal diagram of an initialization phase of the time division multiplexing apparatus according to the present invention. During the initialization phase of the present invention, the first laser 103 emits a synchronization light, which is transmitted to the time division multiplexing apparatus of the present invention through a channel. The light detection unit 401 receives and detects the synchronization light, and converts the synchronization light into a synchronization electrical signal shown in the first row of fig. 7, where the synchronization electrical signal and the synchronization light have the same signal characteristics of period, wavelength, pulse width, duty cycle, frequency, and the like. The clock distribution unit 501 receives the synchronization electrical signal and distributes it to the first logic unit 603. In the initialization stage, the sending end of the invention can send the information such as the period, the pulse width and the like of the synchronous light to the time division multiplexing device at the receiving end through a classical channel. After receiving the information of the period, pulse width, etc. of the synchronizing light, the programmable unit 601 sends a signal generating instruction to the signal generating device 6013 from the control chip 6011, randomly generates a scanning signal as shown in the second row of fig. 7, which has the same period as the synchronizing electrical signal and has a pulse width 1.5 to 3 times as large as the pulse width of the synchronizing electrical signal, and sends the scanning signal to the first logic unit 603 through the delay device 6015. After receiving the synchronization signal and the scan signal, the first logic unit 603 performs an and gate logic operation. If the first logic unit 603 does not output high level after the and gate operation, that is, the scanning signal does not scan the synchronous electrical signal, the control chip 6011 instructs the delay device 6015 to perform a delay operation for a certain time on the scanning signal generated by the signal generation device 6013 to obtain the scanning signal shown in the third row of fig. 7, and sends the scanning signal to the first logic unit 603, and then the first logic unit 603 performs the and gate operation on the received synchronous electrical signal and the scanning signal until there is a high level output, at this time, the programmable unit 601 may generate a first control signal 705 which has the same period and the same frequency as the synchronous electrical signal and has a pulse width 1.5 to 3 times as long as the pulse width of the synchronous electrical signal, as shown in the fourth row of fig. 7, so as to detect the synchronous electrical signal, perform the negation operation on the first control signal 705 and generate a second control signal 707 shown in the fifth row of fig. 7, for detecting classical electrical signals.
Fig. 8 shows a schematic diagram of the operating phases of the de-time division multiplex device according to the invention. Fig. 9 shows a signal diagram of the operating phases of a de-time division multiplex device according to the invention. As shown in fig. 9, the first row is a time-division multiplexed electrical signal, the second row is a first time-division multiplexed electrical signal 701, the third row is a second time-division multiplexed electrical signal 703, the fourth row is a first control signal 705, the fifth row is a second control signal 707, the sixth row is a synchronous electrical signal, and the seventh row is a classical electrical signal.
In the working phase of the present invention, the optical detection unit 401 receives the time division multiplexing light transmitted by the transmitting end of the present invention, detects the received time division multiplexing light, converts the time division multiplexing light into a time division multiplexing electrical signal, and obtains the time division multiplexing electrical signal as shown in the first line of fig. 9, where the obtained time division multiplexing electrical signal has the same signal characteristics as the time division multiplexing light, such as period, frequency, wavelength, duty cycle, and pulse width. The clock distribution unit 501 may receive the time-division multiplexed electrical signal shown in the first row of fig. 9, distribute the received time-division multiplexed electrical signal, and output a first time-division multiplexed electrical signal 701 shown in the second row of fig. 9 and a second time-division multiplexed electrical signal 703 shown in the third row of fig. 9, where signal characteristics and values of the first time-division multiplexed electrical signal 701 and the second time-division multiplexed electrical signal 703 are consistent with the time-division multiplexed electrical signal. The first logic unit 603 receives a first time division multiplexed electrical signal 701 as shown in the second row of fig. 9 and a first control signal 705 sent by the programmable unit 601 as shown in the fourth row of fig. 9. The first logic unit 603 may receive the first time division multiplexing electrical signal 701 and the first control signal 705, perform an and gate logic operation, and output a synchronous electrical signal as shown in the sixth row of fig. 9, where the obtained synchronous electrical signal has the same signal characteristics as the synchronous light, such as period, frequency, wavelength, duty cycle, and pulse width. The second logic unit 605 receives the second time-division-multiplexed electrical signal 703 shown in the third row of fig. 9 and the second control signal 707 sent by the programmable unit 601 shown in the fifth row of fig. 9. The second logic unit 605 may receive the second time-division multiplexing electrical signal 703 and the second control signal 707, perform an and gate logic operation, and output a classical electrical signal as shown in the seventh row of fig. 9, where the obtained classical electrical signal has the same signal characteristics as the classical light, such as period, frequency, wavelength, duty cycle, and pulse width.
Fig. 10 shows a flow chart of a method of demultiplexing according to the invention. As shown in fig. 10, the time division multiplexing method of the present invention may include the steps of:
s1001: the optical detection unit 401 receives and detects the time division multiplexing light, and converts the time division multiplexing light into a time division multiplexing electrical signal;
s1002: the clock distribution unit 501 receives the time division multiplexed electrical signal and distributes the time division multiplexed electrical signal to form a first time division multiplexed electrical signal 701 and a second time division multiplexed electrical signal 703;
s1003: the programmable unit 601 generates a first control signal 705 for detecting a synchronous electrical signal, a second control signal 707 for detecting a classical electrical signal;
s1004: the first time division multiplexing electrical signal 701 and the first control signal 705 are input to the first logic unit 603, and after performing and gate logic operation, a synchronous electrical signal is output; the second time-division multiplexed electrical signal 703 and the second control signal 707 are input to the second logic unit 605, and subjected to and gate logic operation, and then output as a classical electrical signal.
Compared with the prior art in which different optical detectors respectively detect the classical light and the synchronous light, the invention cancels the light splitting device in the prior art, and can realize the detection of the classical light and the synchronous light by one optical detection unit, thereby leading the system structure to be greatly simple compared with the prior art and effectively reducing the application cost. In addition, compared with the prior art that light splitting is firstly carried out and then synchronous signals and classical signals are detected from split signal light, the method and the device firstly detect time-division multiplexing light to obtain time-division multiplexing electric signals and then obtain synchronous electric signals and classical electric signals through processing of a first logic unit and a second logic unit which can carry out logic operation. The light intensity of the sending end when sending the signal light can be reduced to one third to one half of the light intensity of the time division multiplexing in the prior art due to the elimination of the light splitting device, and the influence of the system Raman scattering on the quantum light can be effectively reduced due to the fact that the Raman scattering effect and the light intensity are in a positive correlation relationship, and therefore the forming code rate of the quantum key is improved.
The above embodiments are provided only for illustrating the present invention and not for limiting the present invention, and those skilled in the art can make various changes and modifications without departing from the scope of the present invention, and therefore, all equivalent technical solutions should fall within the scope of the present invention.
Claims (9)
1. An apparatus for time division multiplexing, comprising:
a light detection unit configured to receive and detect time division multiplexed light and convert the time division multiplexed light into a time division multiplexed electrical signal;
the clock distribution unit comprises a signal input port and two or more signal output ports, and is configured to receive the time division multiplexing electric signals, distribute the time division multiplexing electric signals to form a first time division multiplexing signal and a second time division multiplexing signal, and output the first time division multiplexing signal and the second time division multiplexing signal;
a programmable unit configured to emit a first control signal for detecting a synchronous electrical signal, a second control signal for detecting a classical electrical signal;
a first logic unit including two or more signal input ports, one signal output port having a logic operation function, configured to receive the first time division multiplexing signal, the first control signal, and to process the first control signal to send out the synchronous electrical signal;
and the second logic unit comprises two or more signal input ports and one signal output port, has a logic operation function, is configured to receive the second time division multiplexing signal and the second control signal, and sends out the classical electric signal after processing.
2. The apparatus for time division multiplexing according to claim 1, the clock distribution unit further being a clock distributor.
3. The apparatus for time division multiplexing according to claim 1, the programmable unit further comprising:
a control chip configured to issue an operation instruction to the signal generation device or the delay device;
the signal generating device is configured to receive an operation instruction of the control chip and generate an electric signal;
the time delay device is configured to receive an operation instruction of the control chip, and the electric signal generated by the signal generation device carries out time delay operation on the received electric signal according to the received operation instruction.
4. The apparatus for time division multiplexing according to claim 1, wherein the light detection unit is further a PN junction photodetector, or a PIN photodetector, or an Avalanche Photodiode (APD) detector, or a pull-through avalanche photodiode (RAPD) detector.
5. The apparatus for demultiplexing according to claim 1, the first logic unit or the second logic unit further being a logic chip.
6. The apparatus for time division multiplexing according to claim 1, wherein the first logic unit or the second logic unit is any one of an AND gate circuit, an OR gate circuit, an NOR gate circuit, a NAND gate circuit, a NOR gate circuit, an XOR gate circuit, and an XNOR gate circuit.
7. The de-time division multiplexing device of claim 1, the first logic unit or the second logic unit further being an and gate circuit.
8. The apparatus according to claim 1, wherein the signal characteristics of the first time-division multiplexed electrical signal and the second time-division multiplexed electrical signal are consistent with the signal characteristics of the time-division multiplexed electrical signal.
9. A method of time division multiplexing, comprising:
the optical detection unit receives and detects the time division multiplexing light, and converts the time division multiplexing light into a time division multiplexing electric signal;
receiving the time division multiplexing electric signals by the clock distribution unit and distributing to form a first time division multiplexing electric signal and a second time division multiplexing electric signal;
sending out a first control signal for detecting a synchronous electrical signal and a second control signal for detecting a classical electrical signal by the programmable unit;
the first time division multiplexing electric signal and the first control signal are input into the first logic unit, and after being processed, a synchronous electric signal is output;
and the second time division multiplexing electric signal and the second control signal are input into the second logic unit, and after being processed, a classical electric signal is output.
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