Device and method for measuring half-wave voltage of phase modulator

Abstract

The invention discloses a device for measuring the half-wave voltage of a phase modulator. The device comprises a laser light source, a beam splitter, a phase modulator to be measured, a signal generator, a beam combiner, photoelectric detection equipment and measurement equipment. The invention also discloses a method for measuring the half-wave voltage of the phase modulator. The method is realized based on the device for measuring the half-wave voltage of the phase modulator. The invention discloses a device and method for measuring the half-wave voltage of a phase modulator, and the method comprises the steps: driving a to-be-measured phase modulator to carry out phase modulation through employing a pulse modulation electric signal, and carrying out the calculation according to the amplitude of the corresponding pulse modulation electric signal when the waveform of an interference optical signal is a specified waveform, and obtaining the half-wave voltage of the to-be-measured phase modulator. 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 present invention relates to the field of quantum information and optical communication technology, and in particular to a device and method for measuring the half-wave voltage of a phase modulator. Background Art

[0002] The application of quantum technology industry is one of the hot spots of global technology competition. Quantum Key Distribution (QKD) is expanding towards quantum network architecture and large-scale application. Figure 1 Shown is the existing QKD system framework; phase, polarization and other degree of freedom modulation are key technologies for QKD systems, quantum measurement and metrology.

[0003] Phase modulator is a type of device that uses the electro-optical effect of crystal to realize optical carrier modulation. Its main function is to convert signals from the electrical domain to the optical domain for processing. It has wide and practical applications in optical communications, optical sensing, optical computing, lidar and other fields.

[0004] In a quantum key distribution system based on phase encoding, 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.

[0005] At present, the half-wave voltage of the phase modulator is mostly measured by placing the phase modulator in one of the arms of the Mach-Zehnder interferometer, and then applying a DC voltage to the phase modulator. Since the phase difference of the optical signals output by the two arms of the interferometer will change with the change of the DC voltage, the light intensity of the optical signal output by the interferometer will also change accordingly. Therefore, the half-wave voltage can be obtained according to the difference in DC voltages corresponding to the adjacent maximum or minimum values ​​of the light intensity of the output optical signal. However, considering that the phase of the interference optical signal is easily affected by changes in the external environment and drifts, it is difficult to keep the signal intensity output by the interferometer stable. Therefore, this method has certain limitations in terms of measurement accuracy, and it is difficult to accurately measure the half-wave voltage of the phase modulator.

[0006] Therefore, it is necessary to improve the current technology for measuring the half-wave voltage of the phase modulator and propose a more accurate method for measuring the half-wave voltage of the phase modulator. Summary of the invention

[0007] In order to solve the problem that it is difficult to accurately measure the half-wave voltage of a phase modulator at present, the present invention provides a device and method for measuring the half-wave voltage of a phase modulator.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] A device for measuring the half-wave voltage of a phase modulator, comprising a laser light source, a beam splitter, a phase modulator to be measured, a signal generator, a beam combiner, a photoelectric detection device and a measuring device;

[0010] The optical signal generated by the laser light source is input into the beam splitter and then divided into a first optical signal and a second optical signal for output, wherein the first optical signal is input into the phase modulator to be measured, and the second optical signal is directly input into the beam combiner;

[0011] The signal generator generates a pulse modulated electrical signal to drive the phase modulator to be tested to perform phase modulation on the first optical signal to obtain a phase modulated signal;

[0012] The phase modulated signal is input into the beam combiner and interferes with the second optical signal, and the optical signal output by the interference is input into the photoelectric detection device for photoelectric conversion to obtain the electrical signal to be measured;

[0013] Adjust the amplitude of the pulse modulated electrical signal, and record the amplitude of the pulse modulated electrical signal corresponding to the electrical signal to be tested when the electrical signal to be tested continuously displays a specified waveform in the measuring device; calculate the half-wave voltage of the phase modulator to be tested based on the recorded amplitude of the pulse modulated electrical signal;

[0014] The specified waveform is specifically: a waveform with double peaks and double valleys within one cycle, and the peak values ​​of the double peaks are equal, the duration of the double peaks is respectively equal to the high level duration and the low level duration of the pulse modulated electrical signal, and the duration of the double valley is respectively equal to the rise time and the fall time of the pulse modulated electrical signal.

[0015] In the above scheme, the phase modulator to be tested is driven to perform phase modulation 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 of the interference light signal when the specified conditions are reached. 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 laser light source is a continuous laser.

[0017] Preferably, the pulse modulated electrical signal is a square wave electrical signal, and the low level is 0V.

[0018] Preferably, the amplitude of the pulse modulated electrical signal is increased according to equal gradient values.

[0019] Preferably, the half-wave voltage of the phase modulator to be tested is calculated based on the amplitudes of any two adjacent pulse modulated electrical signals recorded.

[0020] Preferably, the measuring device is an oscilloscope.

[0021] A method for measuring a half-wave voltage of a phase modulator is implemented based on the device for measuring a half-wave voltage of a phase modulator, and comprises the following steps:

[0022] S1: Generates optical signal and pulse modulated electrical signal;

[0023] S2: Splitting the optical signal to obtain a first optical signal and a second optical signal;

[0024] S3: using the pulse modulated electrical signal to drive the phase modulator to be tested to perform phase modulation on the first optical signal to obtain a phase modulated optical signal;

[0025] S4: interfering the phase modulated optical signal with the second optical signal, and performing photoelectric conversion on the optical signal output by the interference to obtain an electrical signal to be measured;

[0026] S5: adjusting the amplitude of the pulse modulated electrical signal, and recording the amplitude of the pulse modulated electrical signal corresponding to when the electrical signal to be measured continuously displays a specified waveform in the measuring device;

[0027] The specified waveform is specifically: a waveform with double peaks and double valleys in one cycle, wherein the peak values ​​of the double peaks are equal, the durations of the double peaks are respectively equal to the high level duration and the low level duration of the pulse modulated electrical signal, and the durations of the double valleys are respectively equal to the rise time and the fall time of the pulse modulated electrical signal;

[0028] S6: Calculate the half-wave voltage of the phase modulator to be tested according to the amplitude of the recorded pulse modulated electrical signal.

[0029] Preferably, the optical signal is a continuous optical signal.

[0030] Preferably, in step S5, the amplitude of the pulse modulated electrical signal is increased according to an equal gradient value.

[0031] Preferably, in step S6, the half-wave voltage V of the phase modulator to be tested is calculated by the following formula: π :

[0032]

[0033] Among them, V 1 and V 2 It is the amplitude of any two adjacent pulse modulated electrical signals recorded.

[0034] Beneficial technical effects of the present invention:

[0035] The present invention provides a device and method for measuring the half-wave voltage of a phase modulator. The device and method utilize a pulse modulated electrical signal to drive the phase modulator to be measured to perform phase modulation, and then calculate 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 of the interference light signal when the waveform of the interference light signal is a specified waveform. The device and 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 schematic diagram of module connection of the present invention;

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

[0039] Figure 4 It is a flowchart of the implementation steps of the technical solution of the present invention;

[0040] Among them: 1. Laser light source; 2. Beam splitter; 3. Phase modulator to be measured; 4. Signal generator; 5. Beam combiner; 6. Photoelectric detection equipment; 7. Measurement equipment. 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 device for measuring the half-wave voltage of a phase modulator includes a laser light source 1, a beam splitter 2, a phase modulator to be measured 3, a signal generator 4, a beam combiner 5, a photoelectric detection device 6 and a measuring device 7;

[0044] The optical signal generated by the laser light source 1 is input into the beam splitter 2 and then divided into a first optical signal and a second optical signal for output, wherein the first optical signal is input into the phase modulator 3 to be measured, and the second optical signal is directly input into the beam combiner 5;

[0045] The signal generator 4 generates a pulse modulated electrical signal to drive the phase modulator 3 to be tested to perform phase modulation on the first optical signal to obtain a phase modulated signal;

[0046] The phase modulated signal is input into the beam combiner 5 and interferes with the second optical signal. The optical signal output by the interference is input into the photoelectric detection device 6 for photoelectric conversion to obtain the electrical signal to be measured;

[0047] Adjust the amplitude of the pulse modulated electrical signal, and record the amplitude of the pulse modulated electrical signal corresponding to the specified waveform displayed continuously in the measuring device 7; calculate the half-wave voltage of the phase modulator 3 to be tested according to the recorded amplitude of the pulse modulated electrical signal;

[0048] The specified waveform is specifically: a waveform with double peaks and double valleys within one cycle, and the peak values ​​of the double peaks are equal, the duration of the double peaks is respectively equal to the high level duration and the low level duration of the pulse modulated electrical signal, and the duration of the double valley is respectively equal to the rise time and the fall time of the pulse modulated electrical signal.

[0049] In the specific implementation process, the phase modulator 3 to be tested is driven by a pulse modulated electrical signal to perform phase modulation, and then the half-wave voltage of the phase modulator 3 to be tested is calculated according to the amplitude of the pulse modulated electrical signal corresponding to the specified waveform of the interference light signal. 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 3 to be tested.

[0050] Example 2

[0051] A device for measuring the half-wave voltage of a phase modulator, comprising a laser light source 1, a beam splitter 2, a phase modulator to be measured 3, a signal generator 4, a beam combiner 5, a photoelectric detection device 6 and a measuring device 7;

[0052] The optical signal generated by the laser light source 1 is input into the beam splitter 2 and then divided into a first optical signal and a second optical signal for output, wherein the first optical signal is input into the phase modulator 3 to be measured, and the second optical signal is directly input into the beam combiner 5;

[0053] More specifically, the optical signal generated by the laser light source 1 is a continuous optical signal;

[0054] More specifically, the laser light source 1 is a continuous laser;

[0055] Preferably, the pulse modulated electrical signal is a square wave electrical signal, and the low level is 0V;

[0056] The signal generator 4 generates a pulse modulated electrical signal to drive the phase modulator 3 to be tested to perform phase modulation on the first optical signal to obtain a phase modulated signal;

[0057] The phase modulated signal is input into the beam combiner 5 and interferes with the second optical signal. The optical signal output by the interference is input into the photoelectric detection device 6 for photoelectric conversion to obtain the electrical signal to be measured;

[0058] Adjust the amplitude of the pulse modulated electrical signal,

[0059] More specifically, the amplitude of the pulse modulated electrical signal is increased according to an equal gradient value;

[0060] and recording the amplitude of the pulse modulated electrical signal corresponding to when the electrical signal to be measured continuously displays the specified waveform in the measuring device 7;

[0061] The specified waveform is specifically: a waveform with double peaks and double valleys in one cycle, wherein the peak values ​​of the double peaks are equal, the durations of the double peaks are respectively equal to the high level duration and the low level duration of the pulse modulated electrical signal, and the durations of the double valleys are respectively equal to the rise time and the fall time of the pulse modulated electrical signal;

[0062] The half-wave voltage of the phase modulator 3 to be tested is calculated based on the amplitude of the recorded pulse modulated electrical signal;

[0063] More specifically, the half-wave voltage of the phase modulator 3 to be tested is calculated according to the amplitudes of any two adjacent pulse modulated electrical signals recorded.

[0064] More specifically, the measuring device 7 is an oscilloscope.

[0065] In the specific implementation process, the phase of the first optical signal depends on the amplitude of the pulse modulated electrical signal, and the phase difference between the two components of the continuous optical signal will change with the waveform of the pulse modulated electrical signal. Therefore, considering that the pulse modulated electrical signal has a rise and fall time, as well as the influence of external environmental factors, it is usually observed on the oscilloscope that there is a single peak and a single valley in one cycle, and the duration of the single peak is equal to the high level duration of the pulse modulated electrical signal, and the duration of the single valley is equal to the low level duration of the pulse modulated electrical signal, or the duration of the single peak is equal to the low level duration of the pulse modulated electrical signal, and the duration of the single valley is equal to the high level duration of the pulse modulated electrical signal (such as Figure 3 1) or a waveform with double peaks and double valleys in one cycle, and the duration of the double peaks is equal to the high level and low level duration of the pulse modulated electrical signal, and the duration of the double valleys is equal to the rise time and fall time of the pulse modulated electrical signal, but the peak values ​​of the double peaks are not equal (such as Figure 3 Example 2 in the example);

[0066] Only when the phase difference between the two components of the continuous optical signal is 2kπ (k = 0, 1, 2, 3...), that is, the amplitude of the pulse modulated electrical signal is the half-wave voltage V π The oscilloscope will continue to display a waveform with double peaks and double valleys in one cycle only when the value is an even multiple of , and the peak values ​​of the double peaks are equal, the duration of the double peaks is respectively equal to the high level duration and low level duration of the pulse modulated electrical signal, and the duration of the double valley is respectively equal to the rise time and fall time of the pulse modulated electrical signal (such as Figure 3 Otherwise, the waveform displayed by the oscilloscope will continue to change with the fluctuation of the external environment.

[0067] Example 3

[0068] like Figure 4 As shown, a method for measuring the half-wave voltage of a phase modulator is implemented based on the device for measuring the half-wave voltage of a phase modulator, and includes the following steps:

[0069] S1: Generates optical signal and pulse modulated electrical signal;

[0070] S2: Splitting the optical signal to obtain a first optical signal and a second optical signal;

[0071] S3: using the pulse modulated electrical signal to drive the phase modulator 3 to be tested to perform phase modulation on the first optical signal to obtain a phase modulated optical signal;

[0072] S4: interfering the phase modulated optical signal with the second optical signal, and performing photoelectric conversion on the optical signal output by the interference to obtain an electrical signal to be measured;

[0073] S5: adjusting the amplitude of the pulse modulated electrical signal, and recording the amplitude of the pulse modulated electrical signal corresponding to when the electrical signal to be measured continuously displays a specified waveform in the measuring device 7;

[0074] The specified waveform is specifically: a waveform with double peaks and double valleys in one cycle, wherein the peak values ​​of the double peaks are equal, the durations of the double peaks are respectively equal to the high level duration and the low level duration of the pulse modulated electrical signal, and the durations of the double valleys are respectively equal to the rise time and the fall time of the pulse modulated electrical signal;

[0075] S6: Calculate the half-wave voltage of the phase modulator 3 to be tested according to the amplitude of the recorded pulse modulated electrical signal.

[0076] More specifically, the optical signal is a continuous optical signal.

[0077] More specifically, in step S5, the amplitude of the pulse modulated electrical signal is increased according to an equal gradient value.

[0078] More specifically, in step S6, the half-wave voltage V of the phase modulator 3 to be tested is calculated by the following formula: π :

[0079]

[0080] Among them, V 1 and V 2 It is the amplitude of any two adjacent pulse modulated electrical signals recorded.

[0081] In the specific implementation process, starting from 0, the amplitude of the pulse modulated electrical signal is increased according to the equal gradient value. When the measured electrical signal is continuously displayed as a specified waveform in the measuring device 7 for the first time, the amplitude of the pulse modulated electrical signal corresponding to the measured electrical signal is 0V. The half-wave voltage V of the phase modulator 3 to be measured is calculated. π The formula is:

[0082]

[0083] Among them, V 2 It is the amplitude of the pulse modulated electrical signal corresponding to the second time when the electrical signal to be measured continues to display as a specified waveform in the measuring device 7.

[0084] 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 device for measuring the half-wave voltage of a phase modulator, characterized in that: It includes laser light source, beam splitter, phase modulator to be tested, signal generator, beam combiner, photoelectric detection equipment and measurement equipment; The optical signal generated by the laser light source is input into the beam splitter and then divided into a first optical signal and a second optical signal for output, wherein the first optical signal is input into the phase modulator to be measured, and the second optical signal is directly input into the beam combiner; The signal generator generates a pulse modulated electrical signal to drive the phase modulator to be tested to perform phase modulation on the first optical signal to obtain a phase modulated signal; The phase modulated signal is input into the beam combiner and interferes with the second optical signal, and the optical signal output by the interference is input into the photoelectric detection device for photoelectric conversion to obtain the electrical signal to be measured; Adjust the amplitude of the pulse modulated electrical signal, and record the amplitude of the pulse modulated electrical signal corresponding to the electrical signal to be tested when the electrical signal to be tested continuously displays a specified waveform in the measuring device; calculate the half-wave voltage of the phase modulator to be tested based on the recorded amplitude of the pulse modulated electrical signal; The specified waveform is specifically: a waveform with double peaks and double valleys within one cycle, and the peak values ​​of the double peaks are equal, the duration of the double peaks is respectively equal to the high level duration and the low level duration of the pulse modulated electrical signal, and the duration of the double valley is respectively equal to the rise time and the fall time of the pulse modulated electrical signal.

2. The device for measuring the half-wave voltage of a phase modulator according to claim 1, characterized in that: The laser light source is a continuous laser.

3. The device for measuring the half-wave voltage of a phase modulator according to claim 1, characterized in that: The pulse modulated electrical signal is a square wave electrical signal, and the low level is 0V.

4. The device for measuring the half-wave voltage of a phase modulator according to claim 1, characterized in that: Increase the amplitude of the pulse modulated electrical signal at equal gradient values.

5. The device for measuring the half-wave voltage of a phase modulator according to claim 1, characterized in that: The half-wave voltage of the phase modulator to be tested is calculated according to the amplitudes of any two adjacent pulse modulation electrical signals obtained by recording.

6. The device for measuring the half-wave voltage of a phase modulator according to claim 1, characterized in that: The measuring device is an oscilloscope.

7. A method for measuring the half-wave voltage of a phase modulator, characterized in that: The following steps are involved: S1: Generates optical signal and pulse modulated electrical signal; S2: Splitting the optical signal to obtain a first optical signal and a second optical signal; S3: using the pulse modulated electrical signal to drive the phase modulator to be tested to perform phase modulation on the first optical signal to obtain a phase modulated optical signal; S4: interfering the phase modulated optical signal with the second optical signal, and performing photoelectric conversion on the optical signal output by the interference to obtain an electrical signal to be measured; S5: adjusting the amplitude of the pulse modulated electrical signal, and recording the amplitude of the pulse modulated electrical signal corresponding to when the electrical signal to be measured continuously displays a specified waveform in the measuring device; The specified waveform is specifically: a waveform with double peaks and double valleys in one cycle, wherein the peak values ​​of the double peaks are equal, the durations of the double peaks are respectively equal to the high level duration and the low level duration of the pulse modulated electrical signal, and the durations of the double valleys are respectively equal to the rise time and the fall time of the pulse modulated electrical signal; S6: Calculate the half-wave voltage of the phase modulator to be tested according to the amplitude of the recorded pulse modulated electrical signal.

8. The method for measuring the half-wave voltage of a phase modulator according to claim 7, characterized in that: The optical signal is a continuous optical signal.

9. The method for measuring the half-wave voltage of a phase modulator according to claim 7, characterized in that: In step S5, the amplitude of the pulse modulated electrical signal is increased according to the equal gradient value.

10. The method for measuring the half-wave voltage of a phase modulator according to claim 7, characterized in that: In step S6, 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.

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