WO2018121053A1 - 一种用于量子通信系统的光源及编码装置 - Google Patents

一种用于量子通信系统的光源及编码装置 Download PDF

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Publication number
WO2018121053A1
WO2018121053A1 PCT/CN2017/109242 CN2017109242W WO2018121053A1 WO 2018121053 A1 WO2018121053 A1 WO 2018121053A1 CN 2017109242 W CN2017109242 W CN 2017109242W WO 2018121053 A1 WO2018121053 A1 WO 2018121053A1
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laser
slave
pulse
light source
master
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PCT/CN2017/109242
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English (en)
French (fr)
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汤艳琳
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科大国盾量子技术股份有限公司
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Priority to US16/472,854 priority Critical patent/US10972187B1/en
Priority to JP2019555534A priority patent/JP6906628B2/ja
Priority to EP17886886.5A priority patent/EP3562068A4/en
Publication of WO2018121053A1 publication Critical patent/WO2018121053A1/zh

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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
    • 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
    • H04B10/508—Pulse generation, e.g. generation of solitons
    • 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
    • H04B10/54—Intensity modulation
    • H04B10/541—Digital intensity or amplitude modulation
    • 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
    • H04B10/548—Phase or frequency modulation
    • H04B10/556—Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK]
    • H04B10/5561—Digital phase modulation
    • 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
    • H04B10/70—Photonic quantum communication
    • 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
    • H04L9/001—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols using chaotic signals
    • 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
    • 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
    • H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding

Definitions

  • the present application relates to the field of quantum secure communication technologies, and in particular to a light source for a coding device and a corresponding coding device.
  • Quantum secure communication is an emerging technology with great application prospects in the field of communication technology.
  • Quantum key distribution is one of the most commonly used and most popular ones in many subdivisions covered by quantum secure communication.
  • Quantum key distribution is based on the basic principle of quantum mechanics. It encrypts information by means of “one time and one secret”, which guarantees the unbreakable characteristics of confidential communication in principle. This is a defense unit and financial institution with high confidentiality requirements.
  • the government sector, and even the fast-growing Internet finance are all technological advances.
  • the BB84 protocol Since its inception in 1984, as the first quantum key distribution protocol, the BB84 protocol has been increasingly developed. It has become the world's most widely used, most mature and best-in-class quantum key distribution protocol.
  • the BB84 protocol is based on four-state coding.
  • the polarization or phase is used to encode the information, and the polarized or phase-encoded photons are transmitted through a set of devices including wave plates, beam splitters, photocells, and corresponding circuits.
  • a simple decoding device decodes the information.
  • the structure is simple, the system technical requirements are not high, the maintenance is easy and large-scale production, the process is mature, and the coding rate and the code distance are incomparable compared with other protocols.
  • the coding scheme of the decoy BB84 quantum key distribution system mainly uses polarization coding, phase coding and time bit-phase coding.
  • polarization coding the advantage is low cost and simple structure, and the disadvantage is that the polarization system is susceptible to the polarization of the fiber, which directly affects the bit error rate. The resulting compensation for polarization causes time. Waste is so that the code rate is reduced or unstable.
  • the phase encoding method is used to prepare optical pulses by unequal-arm interferometer, and the phase difference of the front and rear optical pulses is used as the information carrier, and the polarization change of the optical fiber has little influence on the phase difference, so the polarization change is not It will cause an increase in the bit error rate, which is conducive to long-distance transmission or use in environments with strong external interference.
  • the disadvantage is that the receiving end of the conventional phase system has a large insertion loss, resulting in a lower rate of code and a farther coded distance than the polarization system.
  • time-bit-phase coding method developed under the above background is encoded by two basis vectors, namely: time base vector (Z-based vector, whose eigenstate is
  • Figure 1 shows an encoding device for implementing time bit-phase encoding.
  • the laser pulse outputted by the light source generates two time-separated pulse components via an unequal arm Mach-Zehnder (MZ) interferometer, and the two pulse components successively enter the isobaric interference.
  • the equal-arm interferometer includes two phase modulators (PMs), which can obtain different interference output light intensity and phase results by adjusting the relative phase differences of the two phase modulators, and the pulse components arriving at different times. Different light intensity and phase results can be modulated by switching the modulation voltage value.
  • the encoding device of Fig. 1 is capable of encoding three kinds of base vectors.
  • the phase difference of the equal-arm interferometer is 0, ⁇ , the corresponding output is the extinction and the luminescent result.
  • the Z-base vector is encoded; when the phase difference is ⁇ /2, - ⁇ /2, the pulse is output, between the pulses.
  • the phase difference is determined to be X-based vector coding or Y-based vector coding.
  • Fig. 2 shows another encoding apparatus for implementing time bit-phase encoding.
  • the laser pulse output from the light source generates two time-separated pulse components via the unequal arm MZ interferometer.
  • four phases 0, ⁇ , ⁇ /2 and 3 ⁇ /2 are loaded between the two pulse components by the phase modulator.
  • the front or rear pulse components are separately modulated by an intensity modulator (IM), and the pass or extinction is controlled to retain the previous or next pulse component to obtain a time state
  • IM intensity modulator
  • the intensity modulator is 1/2 light-passed for both pulse components. Since the intensity modulator can be regarded as an equal-arm interferometer, the coding apparatus of Figures 1 and 2 is identical in coding principle.
  • the known encoding apparatus for time bit-phase encoding has shortcomings in base vector stability, code rate and stability thereof, and particularly requires frequent intensity feedback for stable time coding in a poor coding environment.
  • phase feedback is used to stabilize the phase encoding, which also leads to the need to introduce other feedback devices and structures, which will increase the cost of the system, and the information transmission effect is not good, so the practical range is limited.
  • an encoding device that can be used for both time encoding and phase encoding has a problem of unstable encoding and poor extinction ratio, which directly leads to a low communication transmission efficiency and a limited transmission distance.
  • many existing related literatures have not proposed a good solution to this problem. Even if the structure is simplified or the coding scheme is improved, the overall communication system is optimized, and the final communication effect is improved to a certain extent. Without a cure, the above problems are still in the throat and are subject to this.
  • Toshiba has proposed a pulse injection method using a pulse injection locking technique in a quantum communication system.
  • the light source scheme based on the pulse injection locking technology can make the optical pulse spectral performance better, can improve the interference performance of the encoded state, and finally improve the coding performance.
  • the solution disclosed by Toshiba Corporation it adopts the polarization coding method, which is affected by the polarization change of the fiber during transmission, and the polarization feedback is needed to compensate for the deviation.
  • the light source output is still a phase random light pulse, and the improvement is only to improve the spectral performance of the light pulse and reduce the time jitter of the light pulse ( Time jitter), the final interference effect is enhanced.
  • Such a light source scheme cannot solve the above-mentioned deficiencies in the encoding apparatus for time bit-phase encoding, but only to some extent, the optical pulse interference effect is enhanced, and the improvement of the overall communication system performance is still limited.
  • the present invention provides a light source that can be used for both time encoding and phase encoding, and an encoding apparatus that uses such a light source, which is capable of allowing time-phase encoding with high stability and high extinction ratio.
  • the light source according to the present invention may include: a main laser that outputs a main laser pulse for forming a seed light based on a driving of a main driving signal supplied from a main driving signal source in one system period; and a slave laser based on the slave driving
  • the drive from the drive signal provided by the signal source is outputted in an injection-locked manner by the excitation of the seed light for encoding the signal light pulse.
  • the slave drive signal may include first, second, and third slave drive signals, and one of the first, second, and third slave drive signals may be randomly outputted during one system cycle To drive the slave laser.
  • the slave laser in one system cycle, the slave laser can output only one first slave laser pulse driven by the first slave drive signal, and the first slave laser pulse is derived from one of the master laser pulses The pulse at the first time position is partially excited; during one system cycle, the slave laser can output only one second slave laser pulse driven by the second slave drive signal, and the second slave laser The pulse is partially excited by a pulse at a second time position of the primary laser pulse; and, in one system cycle, the slave laser outputs two consecutive pulses driven by the third slave drive signal The three slave laser pulses are excited by the pulse portions of the one of the master laser pulses at the third time position and the fourth time position, respectively.
  • the light source of the present invention can provide a high and stable extinction ratio when applied to Z-based vector encoding, and can provide two consecutive optical pulses having a stable phase relationship
  • the master and slave lasers may be connected by an optical transmission element, wherein the main laser pulse enters the first port of the optical transmission element and exits from the second port and is injected from the laser, from the laser pulse into the second port of the optical transmission element and from The third port leaves to provide an output of the light source.
  • the number of primary lasers is one and its operating frequency is the system frequency.
  • the number of slave lasers is one and its operating frequency can be at least twice the operating frequency of the primary laser.
  • the width of the main laser pulse may be greater than or equal to the total width of the two consecutive third slave laser pulses.
  • the relative delay between the master and slave lasers can be set such that, during one system cycle, the primary laser pulse injected into the slave laser can temporally cover two consecutive third slave laser pulses.
  • the light source may further comprise providing another seed light to the primary laser to cause the primary laser to be injected A laser that generates a master laser pulse in a locked mode.
  • the number of primary and secondary lasers may each be one, and an unequal arm interferometer may be provided between the primary laser and the optical transmission element.
  • the arm length difference of the unequal arm interferometer may be set such that a time difference between successive pulse portions through which the main laser pulse is divided coincides with an interval time between the third slave laser pulses.
  • the operating frequency of the primary laser may be the system frequency, the operating frequency of the laser is at least twice the operating frequency of the primary laser, and the width of the primary laser pulse is greater than the width of the secondary laser pulse.
  • the relative delay between the master and slave lasers can be set such that, in one system cycle, when the main laser pulse is injected into the slave laser by the two pulse portions divided by the unequal arm interferometer, it is possible in time The two consecutive third slave laser pulses are respectively covered.
  • the number of primary lasers may be one, and the number of optical transmission elements connected from the laser and the same may be two, and the primary laser passes through the first beam splitter respectively.
  • An optical transmission element connects the two slave lasers.
  • the two slave lasers are respectively connected to the second beam splitter through two optical transmission elements to synthesize two slave laser pulses output from the laser.
  • the first beam splitter is used to split the main laser pulse into two pulse portions.
  • the operating frequencies of the master and slave lasers may all be system frequencies, and the width of the master laser pulse is greater than the width of the slave laser pulse.
  • the relative delay between the master and slave lasers can be set such that, in one system cycle, the two pulse portions of the main laser pulse divided by the first beam splitter can be separately injected into the slave laser.
  • One of the third slave laser pulses is covered at different time positions.
  • an adjustable time delay element may be disposed between the optical transmission element and the second beam splitter.
  • the optical transmission element can be a circulator or a beam splitter.
  • the first and third time positions may be the same and the second and fourth time positions may be the same.
  • the intensity of the first and second slave laser pulses may be the same and may be one time the intensity of the third slave laser pulse.
  • Another aspect of the present invention provides an encoding apparatus that can perform both time encoding and phase encoding, which can include the light source of the present invention.
  • the encoding device may further comprise an intensity modulator and/or a phase modulator, wherein the phase modulator modulates a phase difference between successive two third slave laser pulses, the intensity modulator modulates the first slave laser pulse, the second The relative light intensity between the laser pulse and the third slave laser pulse.
  • the light source provided by the invention combines the injection locking technology and the laser internal modulation technology to form a novel pulse light source structure, which is particularly suitable for applications requiring both time encoding and phase encoding.
  • the pulsed light source of the invention can provide a time state (Z-based vector) with a high and stable extinction ratio through laser internal modulation technology, and can also provide two time and phase relationships at the same time by laser internal modulation technology.
  • Non-random pulses are used for phase encoding (X-based vectors), which subtly solves the laser internal modulation technique because it can only generate random pulses of phase relationship with each other and cannot be directly used for phase (X-vector) coding bias.
  • Fig. 1 schematically shows a prior art encoding apparatus for time bit-phase encoding
  • FIG. 2 schematically shows another encoding device for time bit-phase encoding of the prior art
  • FIG. 3A is a view schematically showing a light source and an encoding apparatus according to a first embodiment of the present invention
  • FIG. 3B is a view schematically showing a process of forming a light pulse in the light source of the first embodiment of the present invention
  • FIG. 4A is a view schematically showing a light source and an encoding device according to a second embodiment of the present invention.
  • 4B is a view schematically showing a process of forming a light pulse in a light source according to a second embodiment of the present invention
  • FIG. 5A is a view schematically showing a light source and an encoding apparatus according to a third embodiment of the present invention.
  • FIG. 5B is a view schematically showing a process of forming a light pulse in a light source according to a third embodiment of the present invention.
  • FIG. 6A is a view schematically showing a light source and an encoding apparatus according to a fourth embodiment of the present invention.
  • Fig. 6B schematically shows a process of forming a light pulse in a light source of a fourth embodiment of the present invention.
  • the light source may include: a main laser that outputs a main laser pulse for driving the seed light under the driving of the main driving signal supplied from the main driving signal source; and a slave laser that is driven from the driving signal source.
  • the signal is driven to output a pulse from the laser for encoding.
  • the slave drive signal may include first, second, and third slave drive signals, and one of the first, second, and third slave drive signals may be randomly output from the drive signal source.
  • only one first slave laser pulse is output from the laser driven by the first slave drive signal, and the first slave laser pulse is partially excited by a pulse at a first time position of a master laser pulse. .
  • only one second slave laser pulse is output from the laser driven by the second slave drive signal, and the second slave laser is partially excited by a pulse located at a second time position of a master laser pulse.
  • the slave laser outputs three consecutive third slave laser pulses driven by the third slave drive signal, and the two third slave laser pulses are respectively derived from a master laser pulse at a third time position. And the pulse portion of the fourth time position is excited.
  • the seed light for exciting the two third slave laser pulses is derived from two pulse portions of the same master laser pulse, a fixed phase relationship can be formed between the two seed lights, so that under the injection locking illumination mechanism
  • the two second slave laser pulses generated by the two seed light excitations consisting of two pulse portions of the same master laser pulse will also form a fixed rather than random phase relationship.
  • time positions such as first, second, third or fourth time positions may be used to indicate relative time positions within one system period.
  • the light source of the invention is particularly suitable for time bit-phase encoding, wherein the first and second slave laser pulses can be used for encoding under the Z-based vector, ie time coding; two consecutive third slave laser pulses can be used for X The coding under the base vector, ie phase encoding.
  • one of the first and second slave drive signals can be output from the drive signal source such that the slave laser outputs a fixed time characteristic based on the excitation of one master laser pulse (eg, temporally Pre- or post-) slave laser pulses for time encoding; when performing X
  • the third slave drive signal can be output from the drive signal source, so that the slave laser outputs two consecutive slave pulse with stable time and phase relationship based on one master laser pulse to satisfy the phase encoding requirement.
  • the first and second slave laser pulses may be arranged to have the same intensity, and the intensity of each of the two consecutive third slave laser pulses may be set to be half of the first and second slave laser pulses.
  • the first time position can be the same as the third time position.
  • the second time position can be the same as the fourth time position.
  • the slave drive signal may not be limited to the first, second, and third slave drive signals, but may also have other slave drive signals.
  • the output of the slave laser may be not limited to the first, second, and third slave laser pulses, but may also output a single slave laser pulse at other time positions, or the output may be more excited by a primary laser pulse. Multiple consecutive slave laser pulses with stable time and phase relationships.
  • Figures 3-6 illustrate several embodiments of the light source of the present invention.
  • first, second, and third slave drive signals are output from the drive signal source, and the first and third time positions are the same and the second and fourth time positions are The same is an example.
  • the specific embodiments are merely exemplary and are not intended to limit the invention to the specific embodiments.
  • the light source according to the first embodiment of the present invention includes a master laser 11 and a slave laser 12, and the master laser 11 and the slave laser 12 are connected by an optical transmission element 13.
  • the optical transmission element 13 may comprise three ports 1-3 and is arranged such that light entering from port 1 can exit from port 2 and light entering from port 2 can exit from port 3.
  • the master laser 11 is connected to the port 1 of the optical transmission element 13
  • the port 2 of the optical transmission element 13 is connected from the laser 12, and the port 3 of the optical transmission element 13 is used as the output port of the light source.
  • the optical transmission element can be a circulator or a beam splitter.
  • the circulator is selected for use as an optical transmission element in this embodiment.
  • the operating frequency of the master laser 11 can be the system frequency.
  • the operating frequency of the slave laser 12 can be at least twice the operating frequency of the main laser 11, and the total width of the two consecutive slave laser pulses (the sum of the pulse width and the interval time) is smaller than the main laser pulse width, so that one master laser Two slave laser pulses can be generated under excitation of the pulse, see Figure 3B.
  • the master laser 11 outputs a main laser pulse, which is here directly injected as seed light into the slave laser 12 via port 2 of the circulator 13.
  • the primary laser pulse injected into the slave laser can temporally cover two consecutive slave laser pulses in one system cycle, thereby applying the primary laser pulse as seed light through the injection.
  • the manner of locking produces two consecutive slave laser pulses in excitation from laser 12.
  • Output from the laser pulse from port 3 of the circulator 13 provides an output pulse of the source.
  • the third slave drive signal is output from the drive signal source in one system cycle such that at the third (first) time position and the fourth (second) time Position, from The laser generates two third slave laser pulses in an injection-locked manner under excitation of the injected main laser pulse.
  • the seed light for the two third slave laser pulses is respectively a pulse portion corresponding to the third and fourth time positions in the main laser pulse injected from the laser; the output times of the two third slave laser pulses respectively correspond to The third and fourth time positions, the output time difference between the two is the time difference corresponding to the third and fourth time positions.
  • phase relationship (phase difference) of the pulse portion corresponding to the third and fourth time positions on one main laser pulse is stable. Therefore, there is also a fixed phase difference between the two consecutive third slave laser pulses outputted in one system cycle at this time, instead of the random phase relationship in the non-injection locking mode, nor the conventional injection locking mode.
  • the random phase relationship under the excitation of different main laser pulses is used, and this phase difference can be determined by the third and fourth time positions.
  • the two third slave laser pulses can be directly passed through a phase modulator 14 when necessary, and the modulation is loaded between the two pulses. Phase 0 or ⁇ , thus completing the X-based vector coding.
  • at least the spectroscopic elements for providing two optical pulses having a fixed time and phase relationship such as an unequal arm interferometer, or by means of a beam splitter and a delay line, are omitted on the optical path for encoding.
  • the formed beam splitting element simplifies the optical path structure of the encoding device.
  • the requirement for the laser power is also reduced, so that the system requirements and costs are reduced.
  • conventional phase encoding and/or time bit-phase encoding can be omitted.
  • the real-time phase calibration feedback device required by the system and the additional optical channel for the feedback light the initial phase difference only needs the measurement terminal of the MDIQKD Charlie to inform the measured base error rate of the X-based vector through the classic channel to the sender of the MDIQKD.
  • Bob, Alice and Bob can adjust their initial phase, and no phase feedback is needed later.
  • one of the first and second slave drive signals is randomly outputted from the source of the drive signal during a system cycle such that the first time position or the second time position is correspondingly
  • the laser generates a first slave laser pulse or a second slave laser pulse in an injection-locked manner under excitation of the injected primary laser pulse.
  • the seed light for the first or second slave laser pulses is respectively a pulse portion corresponding to the first or second time position injected into the primary laser pulse from the laser, the output of the first or second slave laser pulse The time corresponds to the first or second time position, respectively.
  • the first and second slave laser pulses having respective different output time characteristics can be used directly to represent different time encodings, such as when the source outputs only the first slave laser pulse in one system cycle, the first slave laser.
  • the pulse can be used to indicate the phenomenon of passing light at the first time position and extinction at the second time position, ie, can be used to represent time code 1; when the light source outputs only the second slave laser pulse in one system cycle,
  • the second slave laser pulse can be used to indicate the phenomenon of extinction at the first time position and the light at the second time position, i.e., can be used to represent time coded 0; and vice versa.
  • the contrast of the Z-based vector generated at this time is determined by the degree to which the laser does not trigger the extinction of the light pulse, and the degree of extinction can be high and stable from the environment.
  • the interference principle (the principle inside the intensity modulator is also an equal arm interferometer) is used for extinction, and Interference is affected by the external environment's interference phase, resulting in an extinction ratio that is not high and unstable.
  • the elements for providing Z-based sub-glare are omitted on the optical path for encoding, which simplifies the optical path structure of the encoding device, while at the same time providing high and stable extinction, thereby omitting
  • the intensity feedback device that guarantees the extinction stability of the Z-base vector greatly improves the code rate and its stability.
  • the amplitude of the slave drive signal such that the first and second slave laser pulses for the Z-based vector have the same intensity for the third slave laser pulse of the X-based vector
  • the intensity is half of the pulse intensity of the first or second slave laser.
  • the first, second, and third slave laser pulses can also be set to have the same intensity, and the pulsed light intensity for the Z-based vector and the pulsed light intensity for the X-based vector are also inconsistent, in the X-based Since the vector outputs two slave laser pulses and only one slave laser pulse is output under the Z base vector, the light intensity corresponding to the X base vector is twice the intensity of the Z base vector, and therefore, the encoded optical path There is still a need to provide an intensity modulator 15 for attenuating the pulse intensity for the X-based vector by half so that the final intensity at different base vectors remains the same.
  • the intensity modulator here may also have a state change, but does not affect the extinction ratio of the Z-based vector, and does not affect the Z-base stability of the encoding device.
  • FIG. 4A shows a second exemplary embodiment of a light source in accordance with the present invention, which is a further improvement to the light source structure of FIG. 3A.
  • the light source shown in FIG. 4A differs from the light source shown in FIG. 3A in that a main laser 20 is added.
  • the first main laser 20 and the second main laser 21 are connected by an optical transmission element 26.
  • the second master laser 21 outputs a pulse in an injection-locking manner under the excitation of the seed light supplied from the first master laser 20 to provide seed light for the slave laser 22; the optical transmission element is passed between the second master laser 21 and the slave laser 22 23 is connected, and pulses are output in an injection-locked manner from the excitation of the seed light supplied from the laser 22 by the second main laser 21 to provide a signal light pulse such as that used for encoding, as can be seen with reference to FIG. 4B.
  • the structure and arrangement of the optical transmission elements 23, 26, and the manner of connection between the lasers 20 and 21, 21 and 22 are the same as those described for the optical transmission element 13 in the first embodiment, from the laser 22
  • the manner of generating the pulse by the action of the second master laser 21, and the subsequent time encoding and phase encoding structure and process are also the same as those described in the first embodiment, and therefore will not be described herein again. The differences are described in detail.
  • the laser pulse output from the second master laser 21 is also generated by the seed light excitation provided by the first master laser 20 based on the injection locking mode. Therefore, the spectral performance of the seed light supplied from the laser 22 by the second master laser 21 is further improved. Specifically, compared with the first embodiment, the light source in this embodiment outputs a better wavelength consistency between two consecutive third slave laser pulses in one system cycle, which can improve the decoding of the X-based vector. Interference contrast, thereby reducing the decoding error rate of the X-based vector.
  • FIG. 5A shows a third exemplary embodiment of a light source in accordance with the present invention.
  • the light source of this embodiment includes a master laser 31 and a slave laser 32.
  • the master laser 31 is coupled to the optical transmission component 33 via an unequal arm interferometer 37, and is coupled to the slave laser 32 via the optical transmission component 33.
  • the optical transmission element 33 can likewise comprise three ports 1-3 and is arranged such that light entering from port 1 can exit from port 2 and light entering from port 2 can exit from port 3.
  • the master laser 31 is connected to the port 1 of the optical transmission element 33 via the unequal arm interferometer 37
  • the port 2 of the optical transmission element 33 is connected from the laser 32
  • the port 3 of the optical transmission element 33 serves as the output port of the light source.
  • the optical transmission element can be a circulator or a beam splitter.
  • the circulator is selected for use as an optical transmission element in this embodiment.
  • the unequal arm interferometer 37 can be, for example, an unequal arm Mach-Zehnder (MZ) interferometer or a Michelson interferometer.
  • MZ Mach-Zehnder
  • Michelson interferometer Preferably, an MZ interferometer is taken as an example in this embodiment.
  • this embodiment differs from the first embodiment in that the main laser pulse is no longer directly injected as seed light into the slave laser 32, but is first divided into two successive pulse portions by the unequal arm interferometer 37. These two pulse portions are injected into the slave laser 32 via ports 1, 2 of the optical transmission element 33.
  • the two pulse portions of the master laser pulse are in time (in the first (third) time position and the second (fourth) time position, respectively, in one system cycle)
  • the two adjacent slave laser pulses can be separately covered, thereby generating two consecutive slave laser pulses in excitation from the laser 32 as seed light, respectively, by injection locking.
  • Output from the laser pulse from port 3 of circulator 33 provides an output pulse of the source.
  • the two main laser pulse portions used as seed light are divided by a main laser pulse through an unequal arm interferometer, the two main laser pulse portions have exactly the same wavelength characteristics and a fixed phase relationship. Accordingly, there is also a fixed phase relationship between the two slave laser pulses output from the excitation of the two seed lights by the laser 32.
  • the operation principle and mode of the light source of the present embodiment under the X and Z base vectors similar to the first embodiment in which the portion of the main laser pulse at different time positions is used as the seed light, the time and phase are performed by the pulse output from the light source.
  • the principle and manner of coding are similar to those of the first embodiment, and therefore will not be described again. Only the differences between the two are described in detail.
  • the arm length difference of the unequal arm interferometer 37 requires that the time difference between successive pulse portions of its output coincide with the interval between successive two slave laser pulses in the laser 32.
  • the width of the main laser pulse is not required to be greater than or equal to the total width of two consecutive slave laser pulses, and only the width of the main laser pulse is required to be greater than or equal to the width of one slave laser pulse. The requirement for the performance of the master laser 31 is thus significantly reduced.
  • the two seed lights for exciting two consecutive slave laser pulses correspond to the pulse portions of two different time positions on one master laser pulse due to the erbium phenomenon.
  • the presence of the pulse portions of the two different time positions may not be exactly the same, but in the present embodiment, since the two seed lights are split by the same pulse through the unequal arm interferometer, they will be identical.
  • Wavelength characteristics That is, the light source of the present embodiment is superior to the foregoing embodiment in terms of wavelength uniformity for exciting two seed lights of two consecutive slave laser pulses.
  • the wavelength consistency of the two consecutive third slave laser pulses output by the light source under the X-based vector is better, thereby improving the interference contrast of the decoding of the X-based vector in the codec application and reducing the decoding error of the X-based vector. rate.
  • phase difference of the two consecutive third slave laser pulses output by the light source of the present embodiment under the X-based vector is affected by the phase of the unequal arm interferometer.
  • the effect of the change, while in the light source of the first embodiment, this phase difference is stable.
  • Figure 6A shows a fourth exemplary embodiment of a light source in accordance with the present invention.
  • the light source of this embodiment includes a master laser 41 and two slave lasers 42, 49.
  • the main laser pulse is split into two pulse portions via the first beam splitter 47.
  • the two pulse portions are injected into the first slave laser 42 and the second slave laser 49 via the first optical transmission element 43 and the second optical transmission component 46, respectively, to serve as seed light.
  • the slave laser pulses output by the first slave laser 42 and the second slave laser 49 pass through the first optical transmission component 43 and the second optical transmission component 46, respectively, and are coupled together at the second beam splitter 48 as an output pulse of the light source.
  • To provide signal light pulses such as for encoding.
  • the structure and arrangement of the optical transmission elements 43, 46, and the connection manner between the master and slave lasers by means of the optical transmission elements are the same as those described in the first embodiment, and thus Let me repeat.
  • the optical transmission element can be a circulator or a beam splitter, and a circulator is preferably employed in this embodiment.
  • the present embodiment is different from the first embodiment in that two slave lasers are used; the main laser pulse is no longer directly injected as seed light into the slave laser, but first
  • the first beam splitter 47 is split into two pulse portions which are respectively injected into the respective slave lasers via different optical paths.
  • one of the two pulse portions of the master laser pulse can cover one of the first slave lasers 42 at the first (third) time position during one system cycle.
  • the other can cover one of the second slave lasers 49 from the laser pulse at the second (fourth) time position, thereby respectively acting as a seed light from the corresponding time at a predetermined time position by injection locking.
  • the excitation in the laser produces a pulse from the laser.
  • a slave pulse from the laser output and a second slave laser output is ultimately coupled to an output at a second beam splitter 48 to provide an output pulse of the source.
  • a third slave drive signal is output from the drive signal source during a system period such that the first slave laser 42 generates a stimulus at the third time position under the excitation of the injected main laser pulse portion.
  • a third slave laser pulse, and a second slave laser 49 generates a third slave laser pulse at the fourth time position under excitation of the injected master laser pulse portion, the two third slave laser pulses at the second beam splitter Coupled into one output to provide two consecutive pulses with predetermined time intervals. Since the seed light respectively injected into the two slave lasers is divided into two pulse portions formed by a main laser pulse and splitter in one system cycle, the two seed lights have exactly the same wavelength characteristics and are fixed. The phase relationship, correspondingly, also has a fixed phase relationship between successive two third slave laser pulses ultimately output by the source.
  • the first and the first are randomly output from the drive signal source in one system cycle. And driving one of the first or second slave lasers such that the first or second slave laser is excited by the injected main laser pulse portion, respectively, at the first time position or the second time position A first slave laser pulse or a second slave laser pulse is generated in an injection locked manner.
  • the output times of the first or second slave laser pulses respectively correspond to the first or second time position.
  • the first and second slave laser pulses having respective different output time characteristics can be directly used to represent different time encodings, such as when the source outputs only the first slave laser pulse in one system cycle, the first slave laser.
  • the pulse can be used to represent the phenomenon of passing light at the first time position and extinction at the second time position, ie can be used to represent time code 1; when the light source shows only the second slave laser pulse in one system cycle
  • the second slave laser pulse can be used to indicate the phenomenon of extinction at the first time position and the pass at the second time position, ie can be used to represent time code 0; and vice versa.
  • the width of the main laser pulse is not required to be greater than or equal to the total width of two consecutive slave laser pulses, and only the width of the main laser pulse is required to be greater than or equal to one. From the width of the laser pulse, the performance requirements for the main laser are also reduced. Also, the slave laser in this embodiment may have the same operating frequency as the master laser.
  • the wavelengths of the two seed lights for exciting the two consecutive slave laser pulses in the first embodiment are not completely identical, and in the present embodiment, since the two seed lights are caused by the same pulse They are divided by the beam splitter and they will have exactly the same wavelength characteristics. That is, the light source of the present embodiment is also superior to the first embodiment in terms of wavelength uniformity for exciting two seed lights of two consecutive slave laser pulses.
  • the wavelength consistency of the two consecutive third slave laser pulses output by the light source under the X-based vector is better, thereby improving the interference contrast of the decoding of the X-based vector in the codec application and reducing the decoding error of the X-based vector. rate.
  • the two time modes can be flexibly adjusted by additionally providing delay elements 40 (for example, electrically adjustable delays) on the output optical paths of the two slave lasers.
  • delay elements 40 for example, electrically adjustable delays
  • the time interval between light pulses Since different decoding devices may have different time interval requirements, the adjustability of such time intervals enables the light source of this embodiment to be flexibly applied to encoding devices corresponding to various decoding devices.
  • the pulsed light source of the invention can provide a time state (Z-based vector) with a high and stable extinction ratio through laser internal modulation technology, and can also provide two time and phase relationships at the same time by laser internal modulation technology.
  • Non-random pulses are used for phase encoding (X-based vectors), which subtly solves the laser internal modulation technique because it can only generate random pulses of phase relationship with each other and cannot be directly used for phase (X-vector) coding bias.
  • the light source of the present embodiment can be used in time and/or phase encoding schemes, particularly for schemes that require both time and phase encoding (such as time bit-phase encoding schemes), including but not Limited to the coding scheme based on the decoy BB84 protocol, the reference-frame-independent quantum key distribution (RFIQKD) protocol, and the three-state protocol (Loss-tolerant), wherein the advantages when applied to the MDIQKD system are More obvious.
  • time bit-phase encoding schemes including but not Limited to the coding scheme based on the decoy BB84 protocol, the reference-frame-independent quantum key distribution (RFIQKD) protocol, and the three-state protocol (Loss-tolerant), wherein the advantages when applied to the MDIQKD system are More obvious.
  • Another aspect of the present invention also provides an encoding apparatus capable of simultaneously performing time encoding and phase encoding, the encoding apparatus comprising a light source according to the present invention for outputting a phase having a fixed time and phase relationship under an X-based vector Two light pulses are adjacent, and one of the adjacent two light pulses is output under the Z-based vector.
  • the encoding device may further comprise a phase modulator for loading a modulation phase between adjacent two optical pulses under the X-based vector.
  • the encoding device may further include an intensity modulator for attenuating the intensities of adjacent two optical pulses under the X-based vector such that a sum of the intensities of the adjacent two optical pulses is equal to the The intensity of one of the two adjacent optical pulses output under the Z-base.
  • an intensity modulator for attenuating the intensities of adjacent two optical pulses under the X-based vector such that a sum of the intensities of the adjacent two optical pulses is equal to the The intensity of one of the two adjacent optical pulses output under the Z-base.
  • the encoding device of the present invention requires fewer optical components and does not require an additional feedback mechanism, and the structure is simpler. Meanwhile, since the light pulse provided by the light source for encoding is wavelength uniform, The phase stability is better, so the encoding device can have a higher code rate and stability.

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Abstract

本发明提供了一种用于量子通信领域的光源及采用该光源的编码装置。本发明的光源在应用于Z基矢编码时可以提供高且稳定的消光比，并且可以提供具有稳定相位关系的连续两个光脉冲以用于X基矢下的编码。

Description

一种用于量子通信系统的光源及编码装置
本申请要求于2016年12月26日提交中国专利局、申请号为201611217678.0、申请名称为“一种用于量子通信系统的光源及编码装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及量子保密通信技术领域，特别涉及用于编码装置的光源及相应的编码装置。
背景技术
通信技术作为当代社会不可或缺的关键技术，其发展迅猛，日新月异。量子保密通信就是通信技术领域中极有应用前景的新兴技术。作为量子力学、现代通信和现代密码学的结晶，量子保密通信相较于经典通信方式有无可比拟的安全性优势。量子密钥分发就是量子保密通信所涵盖的诸多细分领域中，最为常用且最易推广的一个方向。量子密钥分发基于量子力学的基本原理，利用“一次一密”的方式对信息进行加密，从原理上保证了保密通信的不可破译的特性，这对保密性要求较高的国防单位、金融机构、政府部门，乃至高速发展的互联网金融都是开创性的一大进步。
自从1984年诞生以来，作为第一套量子密钥分发协议，BB84协议就日益发展，目前已经成为世界上应用最广泛，技术最成熟，综合效果最好的一套量子密钥分发协议。BB84协议基于四态编码，利用偏振或者相位的方式，对信息进行编码，将经过偏振或者相位编码的光子传输，再通过一套由波片、分束器、光电管、相应电路等器件组成的简单的解码装置对信息进行解码。其结构简单，系统技术要求不高，易于维护和大规模生产，工艺成熟，在成码率、成码距离上，相比其他协议有着无可比拟的优势。
然而，随着量子密钥分发系统的发展和理论的完善，人们发现，量子密钥分发所确保的所谓理论上的绝对安全性到了实际应用中，就会出现不少不符合理论假设的情况，从而使安全性大打折扣，系统的缺陷也逐渐暴露出来，成为量子黑客攻击的目标。其中，较为著名的是光子数分离攻击，它通过对非理想单光子源中的多光子成分进行截取和攻击，达到窃听的效果。应对的措施是利用诱骗态理论，通过调节发送端的光强来防止光子数分离攻击，也即诱骗态BB84量子密钥分发系统。
诱骗态BB84量子密钥分发系统的编码方案中主要采用偏振编码、相位编码和时间比特-相位编码等编码方式。对于偏振编码，其优势为成本低廉且结构简单，而其劣势为偏振系统容易受到光纤偏振扰动的影响，直接影响其误码率，由此而导致的对偏振的补偿措施，造成了时间上的浪费以致成码率降低或者不稳定。
相比于偏振编码，采用相位编码方式的方案通过不等臂干涉仪制备光脉冲，利用前后光脉冲的相位差作为信息载体，而光纤的偏振变化对相位差的影响较小，因此偏振变化不会造成误码率上升，有利于远距离传输或在有强烈外界干扰的环境使用。其劣势为传统相位系统的接收端插损很大，导致成码率以及最远成码距离低于偏振系统。
在上述背景下发展出的时间比特-相位编码方式，采用了2个基矢来编码，即：时间基矢(Z基矢，其本征态为|t0>、|t1>)；以及相位基矢(X或Y基矢，其本征态为
Figure PCTCN2017109242-appb-000001
或
Figure PCTCN2017109242-appb-000002
)。
图1示出了一种用于实现时间比特-相位编码的编码装置。如图1中所示，光源输出的激光脉冲经不等臂马赫-曾德(Mach-Zehnder，简称MZ)干涉仪产生两个时间上分离的脉冲分量，这两个脉冲分量先后进入等臂干涉仪中。等臂干涉仪中包括两个相位调制器(Phase Modulator，PM)，通过调节这两个相位调制器的相对相位差可以获得不同的干涉输出光强和相位结果，而且对于不同时间到达的脉冲分量，通过切换调制电压值可以调制出不同的光强和相位结果。图1中的编码装置能够进行3种基矢的编码。例如，等臂干涉仪的相位差为0、π时对应输出为消光和有光结果，此时为Z基矢编码；相位差为π/2、-π/2时都输出脉冲，脉冲之间的相位差则决定是X基矢编码或Y基矢编码。
图2示出了另一种用于实现时间比特-相位编码的编码装置。如图2所示，光源输出的激光脉冲经不等臂MZ干涉仪产生两个时间上分离的脉冲分量。为了获得X和Y基矢下的相位编码，通过相位调制器在两个脉冲分量之间加载四种相位0、π、π/2和3π/2.为了获得Z基矢下的时间比特编码，通过强度调制器(Intensity Modulator，IM)对前或后脉冲分量分别调制，控制通过或消光，保留前一个或者后一个脉冲分量以得到时间态|t0>或|t1>。如果是X或Y基矢编码，则强度调制器对两个脉冲分量均通光1/2。由于强度调制器可以看做是一个等臂干涉仪，因此，图1和图2的编码装置在编码原理上是一致的。
由此可见，在已知的用于实现时间比特-相位编码的编码装置中均需要基于等臂干涉仪原理的元件参与到编码过程中，其时间和相位基矢的稳定性、成码率及成码率的稳定性均要依赖于这种等臂干涉仪元件的稳定性。然而，光纤搭建的等臂干涉仪由于相位变化会受到环境温度、应力、震动等各种影响，无法保证其干涉结果的稳定性，从而导致诸如Z基矢和X基矢的不稳定性和消光比不佳等问题。因此，已知的用于时间比特-相位编码的编码装置在基矢稳定性、成码率及其稳定性方面存在不足，特别在恶劣的编码环境下需要频繁的强度反馈用于稳定时间编码，或相位反馈用于稳定相位编码，而这也导致需要引入其他反馈装置和结构，会增加系统的成本，信息传输效果不佳，因此实用范围有所限制。
目前的可同时用于时间编码和相位编码的编码装置存在编码不稳定、消光比不佳的问题，这直接导致最终的通信传输效率低下，传输距离有限。而现有的诸多相关文献也未能对此问题提出很好的解决方法，即使简化了结构或是改进了编码方案，优化了整体通信系统，在一定程度上提升了最终的通信效果，但是治标不治本，对于上述问题仍然如鲠在喉，受制于此。
例如东芝公司曾经提出过在量子通信系统中采用脉冲注入锁定技术来实现脉冲光源的方案。这种基于脉冲注入锁定技术的光源方案可以使得光脉冲光谱性能更好，能提高编码态的干涉性能，最终提高成码性能。然而，在东芝公司所公开的方案中，其采用的是偏振编码方式，这种编码方式会受到传输过程中光纤的偏振变化影响，需要通过偏振反馈来补偿偏差。此外，在这种基于脉冲注入锁定技术的脉冲光源方案中，光源输出的仍然是相位随机的光脉冲，其改进之处仅在于提高了光脉冲的光谱性能，减小了光脉冲的时间抖动(time jitter)现象，使得最终的干涉效果得到增强。这种光源方案不能解决上面提及的用于时间比特-相位编码的编码装置中的不足，只是在一定程度上使得光脉冲干涉效果增强，对整体通信系统效能的提升仍然有限。
发明内容
针对现有技术的不足，本发明提供了一种可同时用于时间编码和相位编码的光源以及应用这种光源的编码装置，其能够允许进行高稳定性和高消光比的时间-相位编码。
根据本发明的光源可以包括：主激光器，其在一个系统周期内基于主驱动信号源提供的主驱动信号的驱动输出一个主激光器脉冲，以用于形成种子光；以及从激光器，其基于从驱动信号源提供的从驱动信号的驱动在所述种子光的激励下以注入锁定的方式输出从激光器脉冲，用于编码信号光脉冲。
在本发明中，从驱动信号可以包括第一、第二和第三从驱动信号，且在一个系统周期内，所述第一、第二和第三从驱动信号中的一个可以被随机地输出以驱动所述从激光器。其中，在一个系统周期内，所述从激光器可以在所述第一从驱动信号的驱动下仅输出一个第一从激光器脉冲，且所述第一从激光器脉冲是源于一个所述主激光器脉冲的位于第一时间位置的脉冲部分激励的；在一个系统周期内，所述从激光器可以在所述第二从驱动信号的驱动下仅输出一个第二从激光器脉冲，且所述第二从激光器脉冲是源于一个所述主激光器脉冲的位于第二时间位置的脉冲部分激励的；并且，在一个系统周期内，所述从激光器在所述第三从驱动信号的驱动下输出连续两个第三从激光器脉冲，且所述两个第三从激光器脉冲是分别源于一个所述主激光器脉冲的位于第三时间位置和第四时间位置的脉冲部分激励的。由此，本发明的光源在应用于Z基矢编码时可以提供高且稳定的消光比，并且可以提供具有稳定相位关系的连续两个光脉冲以用于X基矢下的编码。
进一步地，主、从激光器可以通过光学传输元件连接，其中主激光器脉冲进入光学传输元件的第一端口并从第二端口离开以及注入从激光器，从激光器脉冲进入光学传输元件的第二端口并从第三端口离开，从而提供光源的输出。
在本发明的一个示例性方面，主激光器的数量为1个，且其工作频率为系统频率。从激光器的数量为1个，且其工作频率可以至少为主激光器的工作频率的两倍。主激光器脉冲的宽度可以大于或等于连续两个第三从激光器脉冲的总宽度。
进一步地，主、从激光器之间的相对延时可以被设置成使得，在一个系统周期内，注入到从激光器中的主激光器脉冲在时间上能够覆盖连续两个第三从激光器脉冲。
更进一步地，光源还可以包括用于向主激光器提供另一个种子光以使主激光器以注 入锁定方式生成主激光器脉冲的激光器。
在本发明的另一示例性方面，主、从激光器的数量可以均为1个，且可以在主激光器与光学传输元件之间设有不等臂干涉仪。其中，不等臂干涉仪的臂长差可以被设置成使得，主激光器脉冲经其分成的先后两个脉冲部分之间的时间差与所述第三从激光器脉冲之间的间隔时间一致。
进一步地，主激光器的工作频率可以为系统频率，从激光器的工作频率至少为主激光器的工作频率的两倍，且主激光器脉冲的宽度大于从激光器脉冲的宽度。
进一步地，主、从激光器之间的相对延时可以被设置成使得，在一个系统周期内，主激光器脉冲被不等臂干涉仪分成的两个脉冲部分注入到从激光器时，在时间上能够分别覆盖连续的两个第三从激光器脉冲。
在本发明的又一示例性方面，主激光器的数量可以为1个，而从激光器及与之相连的光学传输元件的数量可均为2个，且主激光器经第一分束器分别通过两个光学传输元件连接两个从激光器。两个从激光器分别通过两个光学传输元件连接第二分束器，以便将两个从激光器输出的从激光器脉冲合成一路输出。其中，第一分束器被用于将主激光器脉冲分成两个脉冲部分。
进一步地，主、从激光器的工作频率可均为系统频率，且主激光器脉冲的宽度大于从激光器脉冲的宽度。
进一步地，主、从激光器之间的相对延时可以被设置成使得，在一个系统周期内，主激光器脉冲被第一分束器分成的两个脉冲部分在被注入到从激光器中时能够分别在不同的时间位置上覆盖第三从激光器脉冲中的一个。
进一步地，光学传输元件与第二分束器之间还可以设有可调的时间延时元件。
优选地，光学传输元件可以为环形器或分束器。
优选地，第一和第三时间位置可以是相同的，第二和第四时间位置可以是相同的。
优选地，第一和第二从激光器脉冲的强度可以是相同的，且可以为第三从激光器脉冲的强度的一倍。
本发明的另一方面提供了一种可同时进行时间编码和相位编码的编码装置，其可以包括本发明的光源。
可选地，编码装置还可以包括强度调制器和/或相位调制器，其中相位调制器调制连续两个第三从激光器脉冲之间的相位差，强度调制器调制第一从激光器脉冲、第二从激光器脉冲、第三从激光器脉冲之间的相对光强。
本发明提供的光源，将注入锁定技术与激光器内调技术有机结合形成一种新颖的脉冲光源结构，该结构特别适合同时需要进行时间编码和相位编码的应用场合。本发明的脉冲光源一方面通过激光器内调技术能够提供具有高且稳定的消光比的时间态(Z基矢)，另一方面也能够通过激光器内调技术同时提供两个时间和相位关系固定而非随机的脉冲以用于相位编码(X基矢)，巧妙地解决了激光器内调技术因为只能产生彼此之间相位关系随机的脉冲而不能直接用于相位(X基矢)编码的偏见。
附图说明
图1示意性地示出了现有技术的用于时间比特-相位编码的编码装置；
图2示意性地示出了现有技术的用于时间比特-相位编码的另一编码装置；
图3A示意性地示出了本发明第一实施例的光源及编码装置；
图3B示意性地示出了本发明第一实施例的光源中光脉冲的形成过程；
图4A示意性地示出了本发明第二实施例的光源及编码装置；
图4B示意性地示出了本发明第二实施例的光源中光脉冲的形成过程；
图5A示意性地示出了本发明第三实施例的光源及编码装置；
图5B示意性地示出了本发明第三实施例的光源中光脉冲的形成过程；
图6A示意性地示出了本发明第四实施例的光源及编码装置；以及
图6B示意性地示出了本发明第四实施例的光源中光脉冲的形成过程。
具体实施方式
在下文中，本发明的示例性实施例将参照附图来详细描述。下面的实施例以举例的方式提供，以便充分传达本发明的精神给本发明所属领域的技术人员。因此，本发明不限于本文公开的实施例。
根据本发明，光源可以包括：主激光器，其在主驱动信号源提供的主驱动信号驱动下输出主激光器脉冲，以用于形成种子光；以及从激光器，其在从驱动信号源提供的从驱动信号驱动下输出从激光器脉冲，以用于进行编码。从驱动信号可以包括第一、第二和第三从驱动信号，且从驱动信号源可以随机地输出第一、第二和第三从驱动信号中的一个。在一个系统周期内，从激光器在第一从驱动信号的驱动下仅输出一个第一从激光器脉冲，且第一从激光器脉冲是源于一个主激光器脉冲的位于第一时间位置的脉冲部分激励的。在一个系统周期内，从激光器在第二从驱动信号的驱动下仅输出一个第二从激光器脉冲，且第二从激光器是源于一个主激光器脉冲的位于第二时间位置的脉冲部分激励的。在一个系统周期内，从激光器在第三从驱动信号的驱动下输出连续两个第三从激光器脉冲，且这两个第三从激光器脉冲是分别源于一个主激光器脉冲的位于第三时间位置和第四时间位置的脉冲部分激励的。由于用于激励这两个第三从激光器脉冲的种子光是源自同一个主激光器脉冲的两个脉冲部分，两个种子光之间可以形成固定的相位关系，因此在注入锁定的发光机制下，由同一个主激光器脉冲的两个脉冲部分构成的这两个种子光激励产生的连续两个第三从激光器脉冲之间也将形成固定而非随机的相位关系。
在本文中，诸如第一、第二、第三或第四时间位置等时间位置可以被用于指示一个系统周期内的相对时间位置。
本发明的光源特别适合用于时间比特-相位编码，其中，第一和第二从激光器脉冲可以用于Z基矢下的编码，即时间编码；连续两个第三从激光器脉冲可以用于X基矢下的编码，即相位编码。换言之，当进行Z基矢编码时，从驱动信号源可以输出第一、第二从驱动信号中的一个，以使从激光器基于一个主激光器脉冲的激励输出一个具有固定时间特征(例如时间上在前或者在后)的从激光器脉冲，用于时间编码；当进行X 基矢编码时，从驱动信号源可以输出第三从驱动信号，以使从激光器基于一个主激光器脉冲输出连续两个具有稳定时间和相位关系的从激光器脉冲，以满足相位编码之需。
优选地，第一、第二从激光器脉冲可以被设置成具有相同的强度，而连续两个第三从激光器脉冲的每一个的强度可以被设置成是第一和第二从激光器脉冲的一半。第一时间位置可以与第三时间位置相同。第二时间位置可以与第四时间位置相同。
本领域技术人员容易认识到，从驱动信号可以不限于第一、第二和第三从驱动信号，而是还可以有其他从驱动信号。相应地，在一个主激光器脉冲的激励下，从激光器的输出可以不限于第一、第二和第三从激光器脉冲，而是还可以在其他时间位置上输出唯一一个从激光器脉冲，或者输出更多个连续的具有稳定时间和相位关系的从激光器脉冲。
为了更好地理解本发明的原理，以在时间比特-相位编码方案中的应用为例，图3-6示出了本发明的光源的几个具体实施方式。在这些具体实施方式中，出于说明性的目的，仅以从驱动信号源输出第一、第二和第三从驱动信号，且第一、第三时间位置相同及第二、第四时间位置相同为例。然而，本领域技术人员能够认识到，这些具体实施方式仅是示例性的，并不期望将本发明限制为这些具体实施方式。
<实施例一>
图3A中示出了根据本发明的光源的第一示例性实施例。如图所示，根据本发明的第一实施例的光源包括一个主激光器11和一个从激光器12，主激光器11和从激光器12之间通过光学传输元件13连接。光学传输元件13可以包括三个端口1-3，且被设置成：从端口1进入的光可以从端口2离开，从端口2进入的光可以从端口3离开。在该实施例中，主激光器11连接光学传输元件13的端口1，从激光器12连接光学传输元件13的端口2，光学传输元件13的端口3作为光源的输出端口。
光学传输元件可以为环形器或分束器。优选地，在该实施例中选择环形器作为光学传输元件来使用。
主激光器11的工作频率可以为系统频率。从激光器12的工作频率可以至少为主激光器11的工作频率的2倍，且两个连续从激光器脉冲的总宽度(脉冲宽度与间隔时间之和)要小于主激光器脉冲宽度，使得在一个主激光器脉冲的激励下可以生成两个从激光器脉冲，参见图3B。
如图3A和3B所示，主激光器11输出主激光器脉冲，在此其直接作为种子光经由环形器13的端口2注入到从激光器12中。通过调节主、从激光器的相对延时，使得在一个系统周期内，注入到从激光器中的主激光器脉冲在时间上能够覆盖连续两个从激光器脉冲，从而以该主激光器脉冲为种子光通过注入锁定的方式在从激光器12中激励产生连续两个从激光器脉冲。从激光器脉冲从环形器13的端口3处输出，提供光源的输出脉冲。
对于本发明的光源，当要进行X基矢编码时，在一个系统周期内，从驱动信号源输出第三从驱动信号，使得在第三(第一)时间位置和第四(第二)时间位置上，从 激光器在注入的主激光器脉冲的激励下以注入锁定的方式生成两个第三从激光器脉冲。用于这两个第三从激光器脉冲的种子光分别为注入从激光器的主激光器脉冲中的对应于第三和第四时间位置的脉冲部分；两个第三从激光器脉冲的输出时间分别对应于第三和第四时间位置，两者的输出时间差即为第三和第四时间位置对应的时间差。由于在注入锁定条件下，从激光器脉冲与相应种子光之间存在固定的相位关系，而一个主激光器脉冲上对应于第三和第四时间位置的脉冲部分在相位上的关系(相位差)是固定的。因此，此时在一个系统周期内输出的两个连续的第三从激光器脉冲之间也存在固定的相位差，而不再是非注入锁定方式下的随机相位关系，也不是传统的在注入锁定方式下由不同的主激光器脉冲激励下的随机相位关系，且这种相位差可以由第三和第四时间位置决定。
由于此时输出的两个第三从激光器脉冲之间存在固定的相位关系，因此，必要时可以直接让这两个第三从激光器脉冲通过一个相位调制器14，在两个脉冲之间加载调制相位0或者π，从而完成X基矢编码。相比于现有技术，在用于编码的光路上至少省略了用于提供两个具有固定时间和相位关系的光脉冲的分光元件，诸如不等臂干涉仪，或者借助分束器和延迟线形成的分光元件，简化了编码装置的光路结构。同时，由于在编码光路上无需再对信号光分光，因此，对于激光器功率的要求也降低了，使得系统要求及成本减小。此外，由于X基矢的稳定性，特别对于测量设备无关的量子密钥分发(measurement-device-independent quantum key distribution，简称MDIQKD)协议，可以省去传统的相位编码和/或时间比特-相位编码系统所要求的实时相位校准反馈装置以及额外的供反馈光使用的光通道，初始的相位差只需要MDIQKD的测量端Charlie将测得的X基矢误码率通过经典信道告知MDIQKD的发送端Alice、Bob，由Alice和Bob调节各自的初始相位即可，后续无需再进行相位反馈。
当要进行Z基矢编码时，在一个系统周期内，由从驱动信号源随机输出第一和第二从驱动信号中的一个，使得相应地在第一时间位置或第二时间位置上，从激光器在注入的主激光器脉冲的激励下以注入锁定的方式生成一个第一从激光器脉冲或者一个第二从激光器脉冲。类似地，用于第一或第二从激光器脉冲的种子光分别为注入从激光器的主激光器脉冲中的对应于第一或第二时间位置的脉冲部分，第一或第二从激光器脉冲的输出时间分别对应于第一或第二时间位置。因此，具有各自不同的输出时间特征的第一和第二从激光器脉冲可以被直接用来代表不同的时间编码，例如当光源在一个系统周期内只输出第一从激光器脉冲时，第一从激光器脉冲可以被用来表示在第一时间位置上通光且第二时间位置上消光的现象，即可以被用于代表时间编码1；当光源在一个系统周期内只输出第二从激光器脉冲时，第二从激光器脉冲可以被用来表示在第一时间位置上消光且第二时间位置上通光的现象，即可以被用于代表时间编码0；反之亦然。
可以注意到，此时所产生的Z基矢的对比度是由激光器不触发光脉冲的消光程度决定的，这种消光程度可以很高而且稳定不受环境影响。而在现有的时间比特-相位编码方案中，都是通过干涉原理(强度调制器内部的原理也是等臂干涉仪)来消光，其 干涉都会受到外界环境对干涉相位的影响从而导致消光比不高而且会不稳定。相比之下，在用于编码的光路上至少省略了用于提供Z基矢下消光的元件，简化了编码装置的光路结构，与此同时还能够提供高而且稳定的消光从而省略了用于保证Z基矢下消光稳定性的强度反馈装置，使得成码率及其稳定性得到极大改善。
进一步地，在本发明中，还可以通过设置从驱动信号的幅度，使得用于Z基矢的第一和第二从激光器脉冲具有相同的强度，用于X基矢的第三从激光器脉冲的强度是第一或第二从激光器脉冲强度的一半。此时，Z基矢下的脉冲光强和X基矢下的脉冲光强保持一致，从而能够在用于编码的光路上省略用于强度归一化的强度调制元件IM，进一步简化了编码装置的光路结构，并且改善了编码装置的稳定性。
当然，也可以将第一、第二、第三从激光器脉冲设置成具有相同的强度，此时用于Z基矢的脉冲光强和用于X基矢的脉冲光强还不一致，在X基矢下由于要输出2个从激光器脉冲，而在Z基矢下只输出了一个从激光器脉冲，所以对应X基矢的光强是对应Z基矢光强的两倍，因此，在编码的光路中仍然还需要设置一个强度调制器15，用于将用于X基矢的脉冲光强衰减一半，使得最终的不同基矢下的光强保持一致。这里的强度调制器也可能存在状态变化，然而并不影响Z基矢的消光比，不会对编码装置的Z基矢稳定性造成影响。
<实施例二>
图4A示出了根据本发明的光源的第二示例性实施例，其是对图3A的光源结构的进一步改进。图4A所示的光源与图3A所示的光源相比，其区别在于增加了一个主激光器20。第一主激光器20与第二主激光器21之间通过一个光学传输元件26连接。第二主激光器21在第一主激光器20提供的种子光的激励下以注入锁定方式输出脉冲，提供用于从激光器22的种子光；第二主激光器21和从激光器22之间通过光学传输元件23连接，从激光器22在第二主激光器21提供的种子光的激励下以注入锁定方式输出脉冲，以提供诸如用于编码的信号光脉冲，如参见图4B可以看到的那样。
在该实施例中，光学传输元件23、26的结构和设置、以及激光器20与21、21与22之间的连接方式与第一实施例中有关光学传输元件13的描述相同，从激光器22在第二主激光器21的作用下产生脉冲的方式、以及后续的时间编码和相位编码结构及过程亦与第一实施例中的相关描述相同，因此在此不再赘述，此处仅针对两者的不同之处进行详细说明。
与第一实施例不同的是，第二主激光器21输出的激光脉冲也是基于注入锁定方式由第一主激光器20提供的种子光激励产生的。因此，第二主激光器21所提供的用于从激光器22的种子光的光谱性能得到进一步提高。具体而言，与第一实施例相比，该实施例中的光源在一个系统周期内输出的连续两个第三从激光器脉冲之间的波长一致性更好，这样可以提高X基矢的解码的干涉对比度，从而降低X基矢的解码误码率。
<实施例三>
图5A示出了根据本发明的光源的第三示例性实施例。该实施例的光源包括一个主激光器31和一个从激光器32，主激光器31经不等臂干涉仪37与光学传输元件33连接，再经该光学传输元件33连接从激光器32。光学传输元件33同样可以包括三个端口1-3，且被设置成：从端口1进入的光可以从端口2离开，从端口2进入的光可以从端口3离开。在该实施例中，主激光器31经不等臂干涉仪37连接光学传输元件33的端口1，从激光器32连接光学传输元件33的端口2，光学传输元件33的端口3作为光源的输出端口。
光学传输元件可以为环形器或分束器。优选地，在该实施例中选择环形器作为光学传输元件来使用。不等臂干涉仪37可以例如为不等臂马赫曾德(MZ)干涉仪或迈克尔逊干涉仪。优选地，在该实施例中以MZ干涉仪为例。
参见图5B，该实施例与第一实施例不同之处在于：主激光器脉冲不再直接作为种子光注入到从激光器32中，而是先经过不等臂干涉仪37分成先后两个脉冲部分。这两个脉冲部分经光学传输元件33的端口1、2注入到从激光器32中。通过调节主、从激光器的相对延时，使得在一个系统周期内，主激光器脉冲的这两个脉冲部分在时间上(分别位于第一(第三)时间位置和第二(第四)时间位置)能够分别覆盖相邻的两个从激光器脉冲，从而分别作为种子光通过注入锁定的方式在从激光器32中激励产生连续两个从激光器脉冲。从激光器脉冲从环形器33的端口3处输出，提供光源的输出脉冲。
由于用作种子光的这两个主激光器脉冲部分是由一个主激光器脉冲经不等臂干涉仪分成的，因此，这两个主激光器脉冲部分具有完全相同的波长特性和固定的相位关系。相应地，从激光器32在这两个种子光的激励下输出的两个从激光器脉冲之间也存在固定的相位关系。
至于本实施例的光源在X和Z基矢下的工作原理及方式，与以一个主激光器脉冲上不同时间位置的部分作为种子光的第一实施例类似，利用光源输出的脉冲进行时间和相位编码的原理及方式亦与第一实施例类似，因此不再赘述，文中仅针对两者不同之处进行详细说明。
在该实施例中，不等臂干涉仪37的臂长差要求其输出的先后两个脉冲部分之间的时间差与从激光器32中的连续两个从激光器脉冲之间的间隔时间一致。在此，由于引入了不等臂干涉仪，因此无需主激光器脉冲的宽度大于或等于连续两个从激光器脉冲的总宽度，而仅需要主激光器脉冲的宽度大于或等于一个从激光器脉冲的宽度，从而明显降低了对主激光器31的性能的要求。
此外，本领域技术人员能够理解，在第一实施例中，用于激励连续两个从激光器脉冲的两个种子光对应于一个主激光器脉冲上两个不同时间位置的脉冲部分，由于啁啾现象的存在，这两个不同时间位置的脉冲部分的波长可能并非完全一致，而在本实施例中，由于两个种子光是由同一个脉冲经不等臂干涉仪分成的，它们将具有完全相同的波长特性。即，就用于激励连续两个从激光器脉冲的两个种子光的波长一致性而言，本实施例的光源优于前述实施例，
相应地，光源在X基矢下输出的两个连续第三从激光器脉冲的波长一致性更佳，从而可以提高编解码应用中X基矢的解码的干涉对比度，降低X基矢的解码误码率。
当然，也要注意到的是，由于引入了不等臂干涉仪，本实施例的光源在X基矢下输出的两个连续第三从激光器脉冲的相位差会受到不等臂干涉仪的相位变化的影响，而在第一实施例的光源中，这种相位差是稳定不变的。
<实施例四>
图6A示出了根据本发明的光源的第四示例性实施例。如图所示，该实施例的光源包括一个主激光器41和两个从激光器42、49。主激光器脉冲经第一分束器47分成两个脉冲部分。这两个脉冲部分分别经第一光学传输元件43和第二光学传输元件46注入到第一从激光器42和第二从激光器49中，以用作种子光。第一从激光器42和第二从激光器49输出的从激光器脉冲分别经过第一光学传输元件43和第二光学传输元件46，并在第二分束器48处耦合成一路，作为光源的输出脉冲，以提供诸如用于编码的信号光脉冲。
如图6A所示，在本实施例中，光学传输元件43、46的结构和设置、以及主从激光器之间借助光学传输元件的连接方式均与第一实施例中的相关描述相同，因此不再赘述。
同样地，光学传输元件可以为环形器或分束器，本实施例中优选采用环形器。
结合图6A和6B可以更清楚地理解，本实施例与第一实施例的不同之处在于：采用了两个从激光器；主激光器脉冲不再直接作为种子光注入到从激光器中，而是先经过第一分束器47分成两个脉冲部分，这两个脉冲部分经不同光路分别注入到相应的从激光器中。通过调节主、从激光器的相对延时，使得在一个系统周期内，主激光器脉冲的这两个脉冲部分中的一个能够在第一(第三)时间位置上覆盖第一从激光器42中的一个从激光器脉冲，另一个能够在第二(第四)时间位置上覆盖第二从激光器49中的一个从激光器脉冲，从而分别作为种子光通过注入锁定的方式在预定的时间位置上从相应的从激光器中激励产生一个从激光器脉冲。第一从激光器输出的一个从激光器脉冲和第二从激光器输出的一个从激光器脉冲最终在第二分束器48处耦合成一路输出，提供光源的输出脉冲。
当要进行X基矢编码时，在一个系统周期内，从驱动信号源输出第三从驱动信号，使得第一从激光器42在第三时间位置上在注入的主激光器脉冲部分的激励下生成一个第三从激光器脉冲，以及第二从激光器49在第四时间位置上在注入的主激光器脉冲部分的激励下生成一个第三从激光器脉冲，两个第三从激光器脉冲在第二分束器处耦合成一路输出，从而提供连续两个具有预定时间间隔的脉冲。由于在一个系统周期内，分别注入两个从激光器的种子光是由一个主激光器脉冲经分束器分而成的两个脉冲部分，因此这两个种子光具有完全相同的波长特性和固定的相位关系，相应地，光源最终输出的连续两个第三从激光器脉冲之间也存在固定的相位关系。
当要进行Z基矢编码时，在一个系统周期内，由从驱动信号源随机输出第一和第 二从驱动信号中的一个，以驱动第一或第二从激光器，使得相应地在第一时间位置或者第二时间位置上，第一或第二从激光器在注入的主激光器脉冲部分的激励下以注入锁定的方式生成一个第一从激光器脉冲或者一个第二从激光器脉冲。因此，第一或第二从激光器脉冲的输出时间分别对应于第一或第二时间位置。因此，具有各自不同的输出时间特征的第一和第二从激光器脉冲可以直接被用于代表不同的时间编码，例如当光源在一个系统周期内只输出第一从激光器脉冲时，第一从激光器脉冲可以被用来表示在第一时间位置上通光且第二时间位置上消光的现象，即可以被用于代表时间编码1；当光源在一个系统周期内只示出第二从激光器脉冲时，第二从激光器脉冲可以被用来表示在第一时间位置上消光且第二时间位置上通光的现象，即可以被用于代表时间编码0；反之亦然。
在该实施例中，由于引入了分束器和两个从激光器，因此无需主激光器脉冲的宽度大于或等于连续两个从激光器脉冲的总宽度，而仅需要主激光器脉冲的宽度大于或等于一个从激光器脉冲的宽度，同样降低了对主激光器性能的要求。并且，本实施例中的从激光器可以具有与主激光器相同的工作频率相同。
此外，正如前面讨论的那样，第一实施例中用于激励连续两个从激光器脉冲的两个种子光的波长并非完全一致，而在本实施例中，由于两个种子光是由同一个脉冲经由分束器分成的，它们将具有完全相同的波长特性。即，就用于激励连续两个从激光器脉冲的两个种子光的波长一致性而言，本实施例的光源同样优于第一实施例。
相应地，光源在X基矢下输出的两个连续第三从激光器脉冲的波长一致性更佳，从而可以提高编解码应用中X基矢的解码的干涉对比度，降低X基矢的解码误码率。
进一步地，由于本实施例中设有两个从激光器，因此，可以通过在两个从激光器的输出光路上额外设置延迟元件40(例如电可调延时器)来调节灵活调节2个时间模式光脉冲之间的时间间隔。由于不同的解码装置可能具有不同的时间间隔要求，因此，这种时间间隔的可调节性使得该实施例的光源能够灵活地应用于与各种解码装置对应的编码装置。
结合上述示例性实施例可以更加全面地理解本发明的构思，即，将注入锁定技术与激光器内调技术有机结合形成一种新颖的脉冲光源结构，该结构特别适合同时需要进行时间编码和相位编码的应用场合，例如采用时间比特-相位编码方案的量子通信系统。本发明的脉冲光源一方面通过激光器内调技术能够提供具有高且稳定的消光比的时间态(Z基矢)，另一方面也能够通过激光器内调技术同时提供两个时间和相位关系固定而非随机的脉冲以用于相位编码(X基矢)，巧妙地解决了激光器内调技术因为只能产生彼此之间相位关系随机的脉冲而不能直接用于相位(X基矢)编码的偏见。
本领域技术人员能够认识到，本实施例的光源可用于时间和/或相位编码方案中，尤其适用于同时需要进行时间和相位编码的方案(诸如时间比特-相位编码方案)，其包括但不限于基于诱骗态BB84协议、参考系无关量子密钥分发(reference-frame-independent quantum key distribution，简称RFIQKD)协议、三态协议(Loss-tolerant)的编码方案，其中当应用于MDIQKD系统时优点则更为明显。
<编码装置>
本发明的另一方面还提出了一种可同时进行时间编码和相位编码的编码装置，该编码装置包括根据本发明的光源，其用于在X基矢下输出具有固定时间和相位关系的相邻两个光脉冲，以及在Z基矢下输出相邻两个光脉冲中的一个。在诱骗态BB84协议和/或RFIQKD协议下，该编码装置还可以包括相位调制器，其用于在所述X基矢下的相邻两个光脉冲之间加载调制相位。可选地，该编码装置还可以包括强度调制器，其用于衰减所述X基矢下的相邻两个光脉冲的强度，使得所述相邻两个光脉冲的强度之和等于所述Z基矢下输出的相邻两个光脉冲中的一个的强度。
与现有技术的编码装置相比，本发明的编码装置需要更少的光学元件且无需额外的反馈机构，结构更为简单；同时，由于光源提供的用于编码的光脉冲在波长一致性、相位稳定性更好，因此该编码装置能够具有更高的成码率和稳定性。
以上所述仅是本发明的实施方式，应该指出对于本领域的普通技术人员来说，在不脱离本发明技术原理的前提下，还可以做出若干改进和变型，这些改进和变型也应视为本发明的保护范围。

Claims (17)

  1. 一种可同时用于时间编码和相位编码的光源，其包括：
    主激光器，其在一个系统周期内基于主驱动信号源提供的主驱动信号的驱动输出一个主激光器脉冲，以用于形成种子光；
    从激光器，其基于从驱动信号源提供的从驱动信号的驱动在所述种子光的激励下以注入锁定的方式输出从激光器脉冲，用于编码信号光脉冲；
    其特征在于：
    所述从驱动信号包括第一、第二和第三从驱动信号，且在一个所述系统周期内，所述第一、第二和第三从驱动信号中的一个被随机地输出以驱动所述从激光器；
    其中，在一个所述系统周期内，所述从激光器在所述第一从驱动信号的驱动下仅输出一个第一从激光器脉冲，且所述第一从激光器脉冲是源于一个所述主激光器脉冲的位于第一时间位置的脉冲部分激励的；
    在一个所述系统周期内，所述从激光器在所述第二从驱动信号的驱动下仅输出一个第二从激光器脉冲，且所述第二从激光器脉冲是源于一个所述主激光器脉冲的位于第二时间位置的脉冲部分激励的；
    以及，在一个所述系统周期内，所述从激光器在所述第三从驱动信号的驱动下输出连续两个第三从激光器脉冲，且所述两个第三从激光器脉冲是分别源于一个所述主激光器脉冲的位于第三时间位置和第四时间位置的脉冲部分激励的。
  2. 如权利要求1所述的光源，其中所述主激光器和所述从激光器通过光学传输元件连接；所述主激光器脉冲进入所述光学传输元件的第一端口，并从第二端口离开以及注入所述从激光器，所述从激光器脉冲进入所述光学传输元件的所述第二端口，并从第三端口离开。
  3. 如权利要求2所述的光源，其中，所述主激光器的数量为1个，且其工作频率为系统频率，所述从激光器的数量为1个，且其工作频率至少为所述主激光器的工作频率的两倍；所述主激光器脉冲的宽度大于或等于所述连续两个第三从激光器脉冲的总宽度。
  4. 如权利要求3所述的光源，其中，所述主激光器与所述从激光器之间的相对延时被设置成使得，在一个所述系统周期内，注入到所述从激光器中的所述主激光器脉冲在时间上能够覆盖所述连续两个第三从激光器脉冲。
  5. 如权利要求3或4所述的光源，其还包括用于向所述主激光器提供另一个种子光，以使所述主激光器以注入锁定方式生成所述主激光器脉冲的激光器。
  6. 如权利要求2所述的光源，其中，所述主激光器和所述从激光器的数量均为1个；所述主激光器与所述光学传输元件之间还设有不等臂干涉仪；并且
    所述不等臂干涉仪的臂长差被设置成使得，所述主激光器脉冲经其分成的先后两个脉冲部分之间的时间差与所述两个第三从激光器脉冲之间的间隔时间一致。
  7. 如权利要求6所述的光源，其中，所述主激光器的工作频率为系统频率，所述从激光器的工作频率至少为所述主激光器的工作频率的两倍；并且，所述主激光器脉 冲的宽度大于所述从激光器脉冲的宽度。
  8. 如权利要求7所述的光源，其中所述主激光器与所述从激光器之间的相对延时被设置成使得，在一个所述系统周期内，所述主激光器脉冲被所述不等臂干涉仪分成的所述两个脉冲部分在被注入到所述从激光器中时，在时间上能够分别覆盖所述连续的两个第三从激光器脉冲。
  9. 如权利要求2所述的光源，其中所述主激光器的数量为1个，所述从激光器及与之相连的所述光学传输元件的数量均为2个；所述主激光器经第一分束器分别通过所述两个光学传输元件连接所述两个从激光器，其中所述第一分束器用于将所述主激光器脉冲分成两个脉冲部分；并且，所述两个从激光器分别通过所述两个光学传输元件连接第二分束器，以便将所述两个从激光器输出的从激光器脉冲合成一路输出。
  10. 如权利要求9所述的光源，其中所述主激光器和所述从激光器的工作频率均为系统频率；并且，所述主激光器脉冲的宽度大于所述从激光器脉冲的宽度。
  11. 如权利要求10所述的光源，其中所述主激光器与所述从激光器之间的相对延时被设置成使得，在一个所述系统周期内，所述主激光器脉冲被所述第一分束器分成的所述两个脉冲部分在被注入到所述从激光器中时能够分别在不同的时间位置上覆盖所述第三从激光器脉冲中的一个。
  12. 如权利要求11所述的光源，其中在所述光学传输元件与所述第二分束器之间还设有可调的时间延时元件。
  13. 如权利要求4、8或11所述的光源，其中所述光学传输元件为环形器或分束器。
  14. 如权利要求4、8或11所述的光源，其中所述第一时间位置与所述第三时间位置相同，所述第二时间位置与所述第四时间位置相同。
  15. 如权利要求4、8或11所述的光源，其中所述第一从激光器脉冲的强度与所述第二从激光器脉冲的强度相同，且为所述第三从激光器脉冲的强度的一倍。
  16. 一种可同时进行时间编码和相位编码的编码装置，其包括如权利要求1-15所述的光源。
  17. 如权利要求16所述的编码装置，其还进一步包括相位调制器和/或强度调制器，其中所述相位调制器用于调制所述连续两个第三从激光器脉冲之间的相位差，所述强度调制器用于调制所述第一从激光器脉冲、所述第二从激光器脉冲、所述第三从激光器脉冲之间的相对光强。
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