Half-wave voltage measuring method and measuring system based on pulse signal

Abstract

The invention discloses a half-wave voltage measurement method based on a pulse signal, which comprises the following steps: driving a phase modulator to be measured by using a pulse modulation electric signal, adjusting the delay and amplitude of the pulse modulation electric signal, and calculating the half-wave voltage of the phase modulator to be measured according to the amplitude of the pulse modulation electric signal. The invention further discloses a half-wave voltage measuring system based on the pulse signals, and the half-wave voltage measuring system is used for achieving the half-wave voltage measuring method based on the pulse signals. According to the invention, the to-be-measured phase modulator is driven by using the pulse modulation electric signal, and then the half-wave voltage of the to-be-measured phase modulator is calculated according to the amplitude of the corresponding pulse modulation electric signal when the adjacent waveform amplitudes of the interference optical signal are continuously equal. The method can effectively eliminate the adverse effect of interference optical signal phase drift on half-wave voltage measurement, thereby accurately measuring the half-wave voltage of the to-be-measured phase modulator, and is widely applied to a QKD system and a quantum measurement and metering system.

Description

Technical Field

[0001] The invention relates to the technical field of quantum information and optical communication, and in particular to a half-wave voltage measurement method and a measurement system based on a pulse signal. Background Art

[0002] Quantum Key Distribution (QKD) is one of the main candidates for providing data security in the quantum era. Existing QKD frameworks include Figure 1 As shown, QKD securely exchanges keys between two remote parties through the principles of quantum mechanics. Half-wave voltage phase modulation and intensity modulation are one of the key technologies in the development of QKD systems.

[0003] Half-wave voltage refers to the electric field amplitude when the phase of the optical carrier changes by π due to the applied electric field of the phase modulator. It is an important parameter to describe the working efficiency and energy consumption of the phase modulator. In the quantum key distribution system based on phase coding, the half-wave voltage of the phase modulator directly affects the overall performance of the system. Therefore, accurate measurement of the half-wave voltage of the phase modulator is crucial for optimizing the system.

[0004] The existing method for measuring the half-wave voltage of a phase modulator is to construct a Mach-Zehnder interferometer, place the phase modulator in one of the arms of the Mach-Zehnder interferometer, and then apply a DC voltage to the phase modulator. According to the interference theory, the phase difference of the optical signal passing through the two arms of the interferometer will change with the change of the DC voltage, causing the light intensity of the output optical signal to change accordingly. Therefore, the half-wave voltage is obtained according to the difference in DC voltages corresponding to adjacent maximum or minimum values ​​of the light intensity of the output optical signal.

[0005] However, changes in the external environment can easily cause the phase of the interference light signal to drift, making it difficult to maintain a stable signal intensity output by the interferometer. Therefore, existing measurement methods are difficult to accurately measure the half-wave voltage of the phase modulator. Summary of the invention

[0006] In order to solve the problem that the existing measurement method is difficult to accurately measure the half-wave voltage of a phase modulator, the present invention provides a half-wave voltage measurement method and a measurement system based on a pulse signal.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A half-wave voltage measurement method based on a pulse signal comprises the following steps:

[0009] S1: Generates pulsed optical signals and pulse modulated electrical signals;

[0010] S2: Splitting the pulse light signal to obtain a first pulse light signal and a second pulse light signal;

[0011] S3: using the pulse modulated electrical signal to drive the phase modulator to be tested to phase modulate the first pulse optical signal to obtain a phase modulated optical signal;

[0012] S4: interfering the phase modulated optical signal with the second pulse optical signal, and performing photoelectric conversion on the optical signal obtained by interference to obtain an electrical signal to be measured;

[0013] S5: adjusting the relative time delay between the pulse modulated electrical signal and the pulsed optical signal so that the amplitude difference between adjacent waveforms of the electrical signal to be measured displayed on the oscilloscope is maximized, and the amplitude difference between adjacent waveforms remains unchanged during the duration of the high level;

[0014] S6: Adjust the amplitude of the pulse modulated electrical signal, and record the amplitude of the pulse modulated electrical signal corresponding to the continuous equality of the amplitudes of adjacent waveforms displayed by the electrical signal to be tested on the oscilloscope; calculate the half-wave voltage of the phase modulator to be tested based on the recorded amplitude of the pulse modulated electrical signal.

[0015] In the above scheme, since the phase drift rate of the interference light signal is smaller than the rate of high-low level conversion of the modulated electrical signal, the phase modulator to be tested is driven by using a pulse modulated electrical signal, and then the half-wave voltage of the phase modulator to be tested is calculated according to the amplitude of the pulse modulated electrical signal corresponding to the waveform amplitudes of adjacent interference light signals that are continuously equal. This can effectively eliminate the adverse effect of the phase drift of the interference light signal on the half-wave voltage measurement, thereby accurately measuring the half-wave voltage of the phase modulator to be tested.

[0016] Preferably, the frequency of the pulse light signal is twice the frequency of the pulse modulated electrical signal.

[0017] Preferably, the pulse modulated electrical signal is a rectangular wave electrical signal.

[0018] Preferably, the high level duration of the rectangular wave electrical signal is greater than the width of the pulse light signal and less than the period of the pulse light signal.

[0019] Preferably, the pulse modulated electrical signal is a square wave electrical signal.

[0020] Preferably, the low level of the pulse modulated electrical signal is 0V.

[0021] Preferably, starting from 0, the relative time delay between the pulse modulated electrical signal and the pulse optical signal is increased according to an equal gradient value.

[0022] Preferably, in step S6, starting from 0, the amplitude of the pulse modulated electrical signal is increased according to an equal gradient value.

[0023] Preferably, the half-wave voltage V of the phase modulator to be tested is calculated by the following formula: π :

[0024]

[0025] Wherein, V1 and V2 are the amplitudes of any two adjacent pulse modulated electrical signals recorded.

[0026] A half-wave voltage measurement system based on a pulse signal, used to implement the half-wave voltage measurement method based on a pulse signal, characterized in that it includes a laser light source, a signal generator, a first optical beam splitter, a phase modulator to be measured, a second optical beam splitter, a photodetector and an oscilloscope;

[0027] The laser light source is used to generate a pulse light signal;

[0028] The signal generator is used to generate a pulse modulated electrical signal and adjust the amplitude of the pulse modulated electrical signal; and send a trigger signal to the laser light source to adjust the relative delay between the pulse modulated electrical signal and the pulse light signal;

[0029] The first optical beam splitter is used to split the pulse light signal into a first pulse light signal and a second pulse light signal;

[0030] The phase modulator to be tested is used to be driven by the pulse modulated electrical signal to perform phase modulation on the first pulse optical signal to obtain a phase modulated optical signal;

[0031] The second optical beam splitter is used to interfere the phase modulated optical signal with the second pulse optical signal;

[0032] The photoelectric detector is used to perform photoelectric conversion on the optical signal obtained by interference to obtain an electrical signal to be measured;

[0033] The oscilloscope is used to detect the electrical signal to be tested and display a waveform curve showing the amplitude of the electrical signal to be tested changing with time.

[0034] Beneficial technical effects of the present invention:

[0035] The present invention provides a half-wave voltage measurement method and measurement system based on pulse signals. The method drives a phase modulator to be measured by using a pulse modulated electrical signal, and then calculates the half-wave voltage of the phase modulator to be measured according to the amplitude of the pulse modulated electrical signal corresponding to the waveform amplitudes of adjacent interference light signals that are continuously equal. The method can effectively eliminate the adverse effect of the phase drift of the interference light signal on the half-wave voltage measurement, thereby accurately measuring the half-wave voltage of the phase modulator to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the QKD framework;

[0037] Figure 2 It is a flowchart of the implementation steps of the technical solution of the present invention;

[0038] Figure 3 It is a waveform comparison schematic diagram of the present invention;

[0039] Figure 4 It is a schematic diagram of module connection of the present invention;

[0040] Among them: 1. laser light source; 2. signal generator; 3. first optical beam splitter; 4. phase modulator to be measured; 5. second optical beam splitter; 6. photoelectric detector; 7. oscilloscope. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments, but the scope of protection claimed in the present invention is not limited to the following specific embodiments.

[0042] Example 1

[0043] like Figure 2-3 As shown, a half-wave voltage measurement method based on a pulse signal comprises the following steps:

[0044] S1: Generates pulsed optical signals and pulse modulated electrical signals;

[0045] S2: Splitting the pulse light signal to obtain a first pulse light signal and a second pulse light signal;

[0046] S3: using the pulse modulated electrical signal to drive the phase modulator 4 to be tested to perform phase modulation on the first pulse optical signal to obtain a phase modulated optical signal;

[0047] S4: interfering the phase modulated optical signal with the second pulse optical signal, and performing photoelectric conversion on the optical signal obtained by interference to obtain an electrical signal to be measured;

[0048] S5: adjusting the relative time delay between the pulse modulated electrical signal and the pulse optical signal so that the amplitude difference between adjacent waveforms of the electrical signal to be measured displayed on the oscilloscope 7 is maximized, and the amplitude difference between adjacent waveforms remains unchanged during the duration of the high level;

[0049] S6: Adjust the amplitude of the pulse modulated electrical signal, and record the amplitude of the pulse modulated electrical signal corresponding to the continuous equality of the amplitudes of adjacent waveforms displayed by the electrical signal to be tested on the oscilloscope 7; calculate the half-wave voltage of the phase modulator 4 to be tested based on the recorded amplitude of the pulse modulated electrical signal.

[0050] In the specific implementation process, since the phase drift rate of the interference light signal is smaller than the rate of high-low level conversion of the modulated electrical signal, the phase modulator 4 to be tested is driven by a pulse modulated electrical signal, and then the half-wave voltage of the phase modulator 4 to be tested is calculated according to the amplitude of the pulse modulated electrical signal corresponding to the waveform amplitudes of adjacent interference light signals that are continuously equal. This can effectively eliminate the adverse effect of the phase drift of the interference light signal on the half-wave voltage measurement, thereby accurately measuring the half-wave voltage of the phase modulator 4 to be tested.

[0051] Example 2

[0052] A half-wave voltage measurement method based on a pulse signal comprises the following steps:

[0053] S1: Generates pulsed optical signals and pulse modulated electrical signals;

[0054] More specifically, the frequency of the pulse optical signal and the frequency of the pulse modulated electrical signal satisfy an integer multiple relationship, and the high-low level conversion rate of the pulse modulated electrical signal must be greater than the phase drift rate of the interferometer (composed of the first optical beam splitter 3, the phase modulator to be measured 4 and the second optical beam splitter 5) caused by external environmental factors;

[0055] More specifically, the frequency of the pulsed optical signal is twice the frequency of the pulse modulated electrical signal;

[0056] More specifically, the pulse modulated electrical signal is a rectangular wave electrical signal;

[0057] More specifically, the high level duration of the rectangular wave electrical signal is greater than the width of the pulse light signal and less than the period of the pulse light signal;

[0058] More specifically, the pulse modulated electrical signal is a square wave electrical signal;

[0059] More specifically, the low level of the pulse modulated electrical signal is 0V;

[0060] S2: Splitting the pulse light signal to obtain a first pulse light signal and a second pulse light signal;

[0061] S3: using the pulse modulated electrical signal to drive the phase modulator 4 to be tested to perform phase modulation on the first pulse optical signal to obtain a phase modulated optical signal;

[0062] S4: interfering the phase modulated optical signal with the second pulse optical signal, and performing photoelectric conversion on the optical signal obtained by interference to obtain an electrical signal to be measured;

[0063] S5: adjusting the relative time delay between the pulse modulated electrical signal and the pulse optical signal so that the amplitude difference between adjacent waveforms of the electrical signal to be measured displayed on the oscilloscope 7 is maximized, and the amplitude difference between adjacent waveforms remains unchanged during the duration of the high level;

[0064] More specifically, in step S5, starting from 0, the relative time delay between the pulse modulated electrical signal and the pulse optical signal is increased according to an equal gradient value.

[0065] In the specific implementation process, the amplitude difference of adjacent waveforms of the measured electrical signal displayed on the oscilloscope is the largest, and the difference remains unchanged during the high level duration, so as to achieve that the measured phase modulator 4 only phase modulates one of the two adjacent first pulse light signals while the other one is not phase modulated.

[0066] S6: Adjust the amplitude of the pulse modulated electrical signal, and record the amplitude of the pulse modulated electrical signal corresponding to the continuous equality of the amplitudes of adjacent waveforms displayed by the electrical signal to be tested on the oscilloscope 7; calculate the half-wave voltage of the phase modulator 4 to be tested based on the recorded amplitude of the pulse modulated electrical signal.

[0067] More specifically, in step S6, starting from 0, the amplitude of the pulse modulated electrical signal is increased according to an equal gradient value.

[0068] More specifically, the half-wave voltage V of the phase modulator 4 to be tested is calculated by the following formula: π :

[0069]

[0070] Wherein, V1 and V2 are the amplitudes of any two adjacent pulse modulated electrical signals recorded.

[0071] In the specific implementation process, only the difference in the phase difference between the two components of the adjacent pulse light signal (k=0,1,2,3…), that is, the amplitude of the pulse modulated electrical signal is the half-wave voltage V π The amplitudes of adjacent waveforms displayed on the oscilloscope 7 will remain equal only when the amplitudes are even multiples of Figure 3 Otherwise, as the external environment fluctuates, the amplitudes of adjacent waveforms displayed in the oscilloscope 7 fluctuate, and there are cases where the waveform amplitudes are not equal (such as Figure 3 as shown in Example 1).

[0072] In the specific implementation process, when the amplitude of the pulse modulated electrical signal is 0, the oscilloscope 7 displays the amplitudes of adjacent waveforms as being equal for the first time, and then gradually increases the amplitude of the pulse modulated electrical signal until the oscilloscope 7 displays the amplitudes of adjacent waveforms as being equal for the second time, and records the amplitude V2 of the pulse modulated electrical signal, which can be directly calculated according to the formula: The half-wave voltage of the phase modulator 4 to be tested is obtained by calculation.

[0073] Example 3

[0074] like Figure 4 As shown, a half-wave voltage measurement system based on a pulse signal is used to implement the half-wave voltage measurement method based on a pulse signal, characterized in that it includes a laser light source 1, a signal generator 2, a first optical beam splitter 3, a phase modulator to be measured 4, a second optical beam splitter 5, a photodetector 6 and an oscilloscope 7;

[0075] The laser light source 1 is used to generate a pulse light signal;

[0076] The signal generator 2 is used to generate a pulse modulated electrical signal and adjust the amplitude of the pulse modulated electrical signal; and send a trigger signal to the laser light source to adjust the relative delay between the pulse modulated electrical signal and the pulse light signal;

[0077] The first optical beam splitter 3 is used to split the pulse light signal into a first pulse light signal and a second pulse light signal;

[0078] The phase modulator to be tested 4 is used to be driven by the pulse modulated electrical signal to perform phase modulation on the first pulse optical signal to obtain a phase modulated optical signal;

[0079] The second optical beam splitter 5 is used to interfere the phase modulated optical signal with the second pulse optical signal;

[0080] The photoelectric detector 6 is used to perform photoelectric conversion on the optical signal obtained by interference to obtain an electrical signal to be measured;

[0081] The oscilloscope 7 is used to detect the electrical signal to be tested and display a waveform curve showing the change of the amplitude of the electrical signal to be tested over time.

[0082] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A half-wave voltage measurement method based on a pulse signal, characterized in that: The following steps are involved: S1: Generates pulsed optical signals and pulse modulated electrical signals; S2: Splitting the pulse light signal to obtain a first pulse light signal and a second pulse light signal; S3: using the pulse modulated electrical signal to drive the phase modulator to be tested to phase modulate the first pulse optical signal to obtain a phase modulated optical signal; S4: interfering the phase modulated optical signal with the second pulse optical signal, and performing photoelectric conversion on the optical signal obtained by interference to obtain an electrical signal to be measured; S5: adjusting the relative time delay between the pulse modulated electrical signal and the pulsed optical signal so that the amplitude difference between adjacent waveforms of the electrical signal to be measured displayed on the oscilloscope is maximized, and the amplitude difference between adjacent waveforms remains unchanged during the duration of the high level; S6: Adjust the amplitude of the pulse modulated electrical signal, and record the amplitude of the pulse modulated electrical signal corresponding to the continuous equality of the amplitudes of adjacent waveforms displayed by the electrical signal to be tested on the oscilloscope; calculate the half-wave voltage of the phase modulator to be tested based on the recorded amplitude of the pulse modulated electrical signal.

2. A half-wave voltage measurement method based on a pulse signal according to claim 1, characterized in that: The frequency of the pulse light signal is twice the frequency of the pulse modulated electrical signal.

3. A half-wave voltage measurement method based on a pulse signal according to claim 1, characterized in that: The pulse modulated electrical signal is a rectangular wave electrical signal.

4. A half-wave voltage measurement method based on a pulse signal according to claim 3, characterized in that: The high level duration of the rectangular wave electrical signal is greater than the width of the pulse light signal and less than the period of the pulse light signal.

5. The half-wave voltage measurement method based on pulse signal according to claim 3 is characterized in that: The pulse modulated electrical signal is a square wave electrical signal.

6. A half-wave voltage measurement method based on a pulse signal according to claim 1, characterized in that: The low level of the pulse modulated electrical signal is 0V.

7. A half-wave voltage measurement method based on a pulse signal according to claim 1, characterized in that: In step S5, starting from 0, the relative time delay between the pulse modulated electrical signal and the pulse optical signal is increased according to an equal gradient value.

8. The half-wave voltage measurement method based on pulse signal according to claim 1 is characterized in that: In step S6, starting from 0, the amplitude of the pulse modulated electrical signal is increased according to the equal gradient value.

9. The half-wave voltage measurement method based on pulse signal according to claim 1, characterized in that: The half-wave voltage V of the phase modulator to be tested is calculated by the following formula π : Wherein, V1 and V2 are the amplitudes of any two adjacent pulse modulated electrical signals recorded.

10. A measurement system for a half-wave voltage measurement method based on a pulse signal according to any one of claims 1 to 9, characterized in that: It includes a laser light source, a signal generator, a first optical beam splitter, a phase modulator to be measured, a second optical beam splitter, a photodetector and an oscilloscope; The laser light source is used to generate a pulse light signal; The signal generator is used to generate a pulse modulated electrical signal and adjust the amplitude of the pulse modulated electrical signal; and sending a trigger signal to the laser light source to adjust the relative time delay between the pulse modulated electrical signal and the pulsed optical signal; The first optical beam splitter is used to split the pulse light signal into a first pulse light signal and a second pulse light signal; The phase modulator to be tested is used to be driven by the pulse modulated electrical signal to perform phase modulation on the first pulse optical signal to obtain a phase modulated optical signal; The second optical beam splitter is used to interfere the phase modulated optical signal with the second pulse optical signal; The photoelectric detector is used to perform photoelectric conversion on the optical signal obtained by interference to obtain an electrical signal to be measured; The oscilloscope is used to detect the electrical signal to be tested and display a waveform curve showing the amplitude of the electrical signal to be tested changing with time.

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