Polarization coding modulator and polarization coding method for quantum key distribution

Abstract

The present invention provides a polarization coding modulator and polarization coding method for quantum key distribution. The polarization coding modulator includes a first beam splitter for splitting an input optical signal to obtain a first optical signal and a second optical signal; a first interferometer for modulating the first optical signal to obtain a first modulated signal, wherein the polarization of the first modulated signal is parallel to the slow axis of the polarization beam splitter; a second interferometer for modulating the second optical signal to obtain a second modulated signal, wherein both the first interferometer and the second interferometer have phase modulation parameters, and the polarization of the second modulated signal is parallel to the fast axis of the polarization beam splitter; and a polarization beam splitter for combining the first modulated signal and the second modulated signal to obtain an output optical signal. The phase modulation parameters of the first interferometer and the second interferometer are adjusted to achieve coding modulation of different polarization states.

Description

Technical Field

[0001] The present invention relates to the field of quantum communication technology, and more specifically, to a polarization coding modulator and a polarization coding method for quantum key distribution. Background Art

[0002] Quantum key distribution can achieve unconditional and secure key distribution by encoding key information in physical dimensions such as polarization or phase of photons. For example, in polarization-encoded quantum key distribution, it is usually necessary to modulate the horizontal polarization state. , vertical polarization state , 45 degrees polarization state , 135 degrees polarization state . In addition, quantum key distribution generally uses weak coherent state light sources. To ensure security and key generation rate, the weak coherent state needs to be modulated by light intensity, which is called the decoy state method. Therefore, a practical quantum key distribution system needs to meet the two requirements of photon coding dimension modulation and light intensity modulation. Currently, the coding dimension modulation and light intensity modulation tasks are usually completed independently by multiple devices, which lacks integration and stability. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a polarization coding modulator and a polarization coding method for quantum key distribution.

[0004] One aspect of an embodiment of the present invention provides a polarization coded modulator for quantum key distribution, including:

[0005] a first beam splitter, configured to perform beam splitting processing on an input optical signal to obtain a first optical signal and a second optical signal;

[0006] a first interferometer, configured to perform signal modulation on the first optical signal to obtain a first modulated signal, wherein the polarization of the first modulated signal is parallel to the slow axis of the polarization beam splitter;

[0007] a second interferometer, configured to perform signal modulation on the second optical signal to obtain a second modulated signal, wherein both the first interferometer and the second interferometer have phase modulation parameters, and the polarization of the second modulated signal is parallel to the fast axis of the polarization beam splitter;

[0008] The polarization beam splitter is used to combine the first modulated signal and the second modulated signal to obtain an output optical signal;

[0009] Wherein, the coded modulation of different polarization states is achieved by adjusting the phase modulation parameters of the first interferometer and the second interferometer.

[0010] According to an embodiment of the present invention, the first interferometer includes:

[0011] a second beam splitter, configured to perform beam splitting processing on the first optical signal to obtain a third optical signal and a fourth optical signal;

[0012] a first phase modulator, configured to perform phase modulation processing on the third optical signal to obtain a first initial modulated signal, wherein the first phase modulator has a first phase modulation parameter;

[0013] a second phase modulator, configured to perform phase modulation processing on the fourth optical signal to obtain a second initial modulated signal, wherein the second phase modulator has a second phase modulation parameter;

[0014] The third beam splitter is used to combine the first initial modulated signal and the second initial modulated signal to obtain the first modulated signal.

[0015] According to an embodiment of the present invention, the second interferometer includes:

[0016] a fourth beam splitter, configured to perform beam splitting processing on the second optical signal to obtain a fifth optical signal and a sixth optical signal;

[0017] a third phase modulator, configured to perform phase modulation processing on the fifth optical signal to obtain a third initial modulated signal, wherein the third phase modulator has a third phase modulation parameter;

[0018] a fourth phase modulator, configured to perform phase modulation processing on the sixth optical signal to obtain a fourth initial modulated signal, wherein the fourth phase modulator has a fourth phase modulation parameter;

[0019] The fifth beam splitter is used to combine the third initial modulated signal and the fourth initial modulated signal to obtain the second modulated signal.

[0020] According to an embodiment of the present invention, the intensity coefficient of the first modulation signal is , the phase is ,in, is the first phase modulation parameter, is the second phase modulation parameter.

[0021] According to an embodiment of the present invention, the intensity coefficient of the second modulation signal is , the phase is ,in, is the third phase modulation parameter, is the fourth phase modulation parameter.

[0022] According to an embodiment of the present invention, when preparing a polarization state intensity In the case of the output optical signal, the first phase modulation parameter , the second phase modulation parameter , the third phase modulation parameter , the fourth phase modulation parameter The following constraints are met:

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029] in, is the strength coefficient, , is the horizontal polarization state, is the vertical polarization state, The polarization state is 45 degrees. The polarization state is 135 degrees. is left-handed polarization state, is the right-hand polarization state.

[0030] According to an embodiment of the present invention, the different polarization states include a horizontal polarization state, a vertical polarization state, a 45-degree polarization state, a 135-degree polarization state, a left-handed polarization state, and a right-handed polarization state.

[0031] Another aspect of an embodiment of the present invention provides a polarization encoding method for quantum key distribution, including:

[0032] Performing beam splitting processing on the input optical signal using the first beam splitter to obtain a first optical signal and a second optical signal;

[0033] Modulating the first optical signal using a first interferometer to obtain a first modulated signal, wherein the polarization of the first modulated signal is parallel to the slow axis of the polarization beam splitter;

[0034] Modulating the second optical signal using a second interferometer to obtain a second modulated signal, wherein both the first interferometer and the second interferometer have phase modulation parameters, and the polarization of the second modulated signal is parallel to the fast axis of the polarization beam splitter;

[0035] Combining the first modulated signal and the second modulated signal using the polarization beam splitter to obtain an output optical signal;

[0036] Wherein, the coded modulation of different polarization states is achieved by adjusting the phase modulation parameters of the first interferometer and the second interferometer.

[0037] According to an embodiment of the present invention, using a first interferometer to modulate the first optical signal to obtain a first modulated signal includes:

[0038] Using a second beam splitter to split the first optical signal to obtain a third optical signal and a fourth optical signal;

[0039] Performing phase modulation processing on the third optical signal using a first phase modulator to obtain a first initial modulated signal, wherein the first phase modulator has a first phase modulation parameter;

[0040] Performing phase modulation processing on the fourth optical signal using a second phase modulator to obtain a second initial modulated signal, wherein the second phase modulator has a second phase modulation parameter;

[0041] The first initial modulated signal and the second initial modulated signal are combined by using a third beam splitter to obtain the first modulated signal.

[0042] According to an embodiment of the present invention, using a second interferometer to modulate the second optical signal to obtain a second modulated signal includes:

[0043] Splitting the second optical signal using a fourth beam splitter to obtain a fifth optical signal and a sixth optical signal;

[0044] performing phase modulation processing on the fifth optical signal using a third phase modulator to obtain a third initial modulated signal, wherein the third phase modulator has a third phase modulation parameter;

[0045] performing phase modulation processing on the sixth optical signal using a fourth phase modulator to obtain a fourth initial modulated signal, wherein the fourth phase modulator has a fourth phase modulation parameter;

[0046] The third initial modulated signal and the fourth initial modulated signal are combined by using a fifth beam splitter to obtain the second modulated signal.

[0047] According to an embodiment of the present invention, a first beam splitter is used to split an input optical signal to obtain a first optical signal and a second optical signal. The first and second optical signals are modulated using a first interferometer and a second interferometer, respectively, to obtain a first modulated signal and a second modulated signal. The first and second modulated signals are then combined using a polarization beam splitter to obtain an output optical signal. The polarization-coded modulator of this embodiment of the present invention can achieve modulation in both intensity and polarization dimensions using a single device, thereby improving the integration and stability of the quantum key distribution system. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0049] Figure 1 A schematic structural diagram of a polarization coded modulator for quantum key distribution according to an embodiment of the present invention is shown;

[0050] Figure 2 A flow chart of a polarization encoding method for quantum key distribution according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0051] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0052] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the presence of the features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0053] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0054] When expressions such as "at least one of A, B, and C, etc." are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0055] Figure 1 A schematic structural diagram of a polarization coded modulator for quantum key distribution according to an embodiment of the present invention is shown.

[0056] like Figure 1 As shown, the polarization coded modulator for quantum key distribution includes:

[0057] a first beam splitter, configured to perform beam splitting processing on an input optical signal to obtain a first optical signal and a second optical signal;

[0058] a first interferometer, configured to perform signal modulation on the first optical signal to obtain a first modulated signal, wherein the polarization of the first modulated signal is parallel to the slow axis of the polarization beam splitter;

[0059] a second interferometer, configured to perform signal modulation on the second optical signal to obtain a second modulated signal, wherein both the first interferometer and the second interferometer have phase modulation parameters, and the polarization of the second modulated signal is parallel to the fast axis of the polarization beam splitter;

[0060] a polarization beam splitter, configured to combine the first modulated signal and the second modulated signal to obtain an output optical signal;

[0061] The coded modulation of different polarization states is achieved by adjusting the phase modulation parameters of the first interferometer and the second interferometer.

[0062] According to an embodiment of the present invention, the first beam splitter BS1 is a 50:50 polarization-maintaining beam splitter. The polarization coding modulators are internally connected via polarization-maintaining optical fibers. The first interferometer and the second interferometer can both be Mach-Zehnder interferometers.

[0063] According to an embodiment of the present invention, the different polarization states may include a horizontal polarization state. , vertical polarization state , 45 degree polarization state , 135 degrees polarization state , left-handed polarization state and right-handed polarization state .

[0064] According to an embodiment of the present invention, any polarization state can be obtained by and Combination generation: , where A and B are and The strength coefficient, for and For a 45-degree polarization state , 135 degrees polarization state , left-handed polarization state and right-handed polarization state ,That Corresponding to 0, 、 、 ,at the same time .

[0065] According to an embodiment of the present invention, when the user determines the output optical signal of the polarization state that he wants to modulate, the corresponding input optical signal can be input at the input end of the first beam splitter, wherein the intensity of the input optical signal must be more than twice the modulated light intensity required by the user.

[0066] According to an embodiment of the present invention, an input optical signal is split into a first optical signal and a second optical signal by a first beam splitter, and the first optical signal and the second optical signal are modulated by a first interferometer and a second interferometer, respectively, to obtain a first modulated signal and a second modulated signal. Thereafter, the first modulated signal and the second modulated signal are combined by a polarization beam splitter (PBS) to obtain a desired output optical signal, wherein signal modulation refers to modulation of phase and intensity.

[0067] According to an embodiment of the present invention, the first modulated signal output by the first interferometer contributes to the horizontal polarization of the output optical signal. Part (the quantum state of the outgoing light parallel to the slow axis is the horizontal polarization state ), the second modulated signal output by the second interferometer contributes to the vertical polarization of the output optical signal Part (polarization parallel to the fast axis of the outgoing light quantum state is vertical polarization state ). According to the horizontal polarization Partial and vertical polarization The output optical signal of any polarization state can be obtained.

[0068] According to an embodiment of the present invention, a first beam splitter is used to split an input optical signal to obtain a first optical signal and a second optical signal. The first and second optical signals are modulated using a first interferometer and a second interferometer, respectively, to obtain a first modulated signal and a second modulated signal. The first and second modulated signals are then combined using a polarization beam splitter to obtain an output optical signal. The polarization-coded modulator of this embodiment of the present invention can achieve modulation in both intensity and polarization dimensions using a single device, thereby improving the integration and stability of the quantum key distribution system.

[0069] According to an embodiment of the present invention, Figure 1 As shown, the first interferometer includes:

[0070] a second beam splitter, configured to perform beam splitting processing on the first optical signal to obtain a third optical signal and a fourth optical signal;

[0071] a first phase modulator, configured to perform phase modulation processing on the third optical signal to obtain a first initial modulated signal, wherein the first phase modulator has a first phase modulation parameter;

[0072] a second phase modulator, configured to perform phase modulation processing on the fourth optical signal to obtain a second initial modulated signal, wherein the second phase modulator has a second phase modulation parameter;

[0073] The third beam splitter is used to perform beam combining processing on the first initial modulated signal and the second initial modulated signal to obtain a first modulated signal.

[0074] According to an embodiment of the present invention, before the first interferometer processes the first optical signal, the first phase modulation parameter and the second phase modulation parameter The arrangement is performed such that after the second beam splitter BS2 splits the first optical signal into a third optical signal and a fourth optical signal, the first phase modulator PM1 and the second phase modulator PM2 are used to perform set phase modulation processing on the third optical signal and the fourth optical signal, thereby obtaining a first initial modulation signal and a second initial modulation signal, and finally the first initial modulation signal and the second initial modulation signal are combined using the third beam splitter BS3 to obtain a first modulated signal.

[0075] According to an embodiment of the present invention, Figure 1 As shown, the second interferometer includes:

[0076] a fourth beam splitter, configured to perform beam splitting processing on the second optical signal to obtain a fifth optical signal and a sixth optical signal;

[0077] a third phase modulator, configured to perform phase modulation processing on the fifth optical signal to obtain a third initial modulated signal, wherein the third phase modulator has a third phase modulation parameter;

[0078] a fourth phase modulator, configured to perform phase modulation processing on the sixth optical signal to obtain a fourth initial modulated signal, wherein the fourth phase modulator has a fourth phase modulation parameter;

[0079] The fifth beam splitter is used to perform beam combining processing on the third initial modulated signal and the fourth initial modulated signal to obtain a second modulated signal.

[0080] According to an embodiment of the present invention, before the second interferometer processes the second optical signal, the third phase modulation parameter is first and the fourth phase modulation parameter The arrangement is performed such that, after the fourth beam splitter BS4 splits the second optical signal into a fifth optical signal and a sixth optical signal, the third phase modulator PM3 and the fourth phase modulator PM4 are respectively used to perform set phase modulation processing on the fifth optical signal and the sixth optical signal, thereby obtaining a third initial modulated signal and a fourth initial modulated signal, and finally, the fifth beam splitter BS5 is used to combine the third initial modulated signal and the fourth initial modulated signal, thereby obtaining a second modulated signal.

[0081] According to an embodiment of the present invention, the intensity coefficient of the first modulation signal is , the phase is ,in, is the first phase modulation parameter, is the second phase modulation parameter.

[0082] According to an embodiment of the present invention, the intensity coefficient of the second modulation signal is , the phase is ,in, is the third phase modulation parameter, is the fourth phase modulation parameter.

[0083] According to an embodiment of the present invention, the relative phase between the first modulated signal and the second modulated signal outputted by the first interferometer and the second interferometer is .

[0084] According to an embodiment of the present invention, appropriate electrical signals are loaded on the first interferometer and the second interferometer respectively so that the modulation phases of the first phase modulator, the second phase modulator, the third phase modulator and the fourth phase modulator are respectively 、 、 、 , thereby obtaining an output optical signal, wherein the polarization and intensity of the output optical signal are the desired polarization state.

[0085] It should be noted that 、 、 、 The specific value needs to be calculated based on the polarization and intensity of the output optical signal desired by the user.

[0086] According to an embodiment of the present invention, when preparing a polarization state intensity of In the case of the output optical signal, the first phase modulation parameter , the second phase modulation parameter , the third phase modulation parameter , the fourth phase modulation parameter The following constraints are met:

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] in, is the strength coefficient, , is the horizontal polarization state, is the vertical polarization state, The polarization state is 45 degrees. The polarization state is 135 degrees. is left-handed polarization state, is the right-hand polarization state.

[0094] According to an embodiment of the present invention, the The modulation of the corresponding state can be achieved, and the scheme is not unique. The following table is a specific example.

[0095]

[0096] Figure 2 A flow chart of a polarization encoding method for quantum key distribution according to an embodiment of the present invention is shown.

[0097] like Figure 2 As shown, the polarization encoding method for quantum key distribution includes operations S201 to S204.

[0098] In operation S201, a first beam splitter is used to split an input optical signal to obtain a first optical signal and a second optical signal;

[0099] In operation S202, a first interferometer is used to modulate the first optical signal to obtain a first modulated signal, wherein the polarization of the first modulated signal is parallel to the slow axis of the polarization beam splitter;

[0100] In operation S203, a second interferometer is used to modulate the second optical signal to obtain a second modulated signal, wherein both the first interferometer and the second interferometer have phase modulation parameters, and the polarization of the second modulated signal is parallel to the fast axis of the polarization beam splitter;

[0101] In operation S204, the first modulated signal and the second modulated signal are combined using a polarization beam splitter to obtain an output optical signal.

[0102] The coded modulation of different polarization states is achieved by adjusting the phase modulation parameters of the first interferometer and the second interferometer.

[0103] According to the embodiment of the present invention, the polarization encoding method part corresponds to the polarization encoding modulator part in the embodiment of the present invention. The description of the polarization encoding method part specifically refers to the polarization encoding modulator part, which will not be repeated here.

[0104] According to an embodiment of the present invention, a first beam splitter is used to split an input optical signal to obtain a first optical signal and a second optical signal. The first and second optical signals are modulated using a first interferometer and a second interferometer, respectively, to obtain a first modulated signal and a second modulated signal. The first and second modulated signals are then combined using a polarization beam splitter to obtain an output optical signal. The polarization-coded modulator of this embodiment of the present invention can achieve modulation in both intensity and polarization dimensions using a single device, thereby improving the integration and stability of the quantum key distribution system.

[0105] According to an embodiment of the present invention, using a first interferometer to modulate a first optical signal to obtain a first modulated signal includes:

[0106] Splitting the first optical signal using a second beam splitter to obtain a third optical signal and a fourth optical signal;

[0107] Performing phase modulation processing on the third optical signal using a first phase modulator to obtain a first initial modulated signal, wherein the first phase modulator has a first phase modulation parameter;

[0108] performing phase modulation processing on the fourth optical signal by using a second phase modulator to obtain a second initial modulated signal, wherein the second phase modulator has a second phase modulation parameter;

[0109] The first initial modulated signal and the second initial modulated signal are combined by using a third beam splitter to obtain a first modulated signal.

[0110] According to an embodiment of the present invention, using a second interferometer to modulate the second optical signal to obtain a second modulated signal includes:

[0111] performing beam splitting processing on the second optical signal using a fourth beam splitter to obtain a fifth optical signal and a sixth optical signal;

[0112] performing phase modulation processing on the fifth optical signal by using a third phase modulator to obtain a third initial modulated signal, wherein the third phase modulator has a third phase modulation parameter;

[0113] performing phase modulation processing on the sixth optical signal using a fourth phase modulator to obtain a fourth initial modulated signal, wherein the fourth phase modulator has a fourth phase modulation parameter;

[0114] The third initial modulated signal and the fourth initial modulated signal are combined by using a fifth beam splitter to obtain a second modulated signal.

[0115] The embodiments of the present invention have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be advantageously used in combination. The scope of the present invention is defined by the embodiments and their equivalents. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A polarization coded modulator for quantum key distribution, characterized in that: include: a first beam splitter, configured to perform beam splitting processing on an input optical signal to obtain a first optical signal and a second optical signal; a first interferometer, configured to perform signal modulation on the first optical signal to obtain a first modulated signal, wherein the polarization of the first modulated signal is parallel to the slow axis of the polarization beam splitter; a second interferometer, configured to perform signal modulation on the second optical signal to obtain a second modulated signal, wherein both the first interferometer and the second interferometer have phase modulation parameters, and the polarization of the second modulated signal is parallel to the fast axis of the polarization beam splitter; The polarization beam splitter is used to combine the first modulated signal and the second modulated signal to obtain an output optical signal; Wherein, the coded modulation of different polarization states is achieved by adjusting the phase modulation parameters of the first interferometer and the second interferometer.

2. The polarization coded modulator according to claim 1, wherein: The first interferometer comprises: a second beam splitter, configured to perform beam splitting processing on the first optical signal to obtain a third optical signal and a fourth optical signal; a first phase modulator, configured to perform phase modulation processing on the third optical signal to obtain a first initial modulated signal, wherein the first phase modulator has a first phase modulation parameter; a second phase modulator, configured to perform phase modulation processing on the fourth optical signal to obtain a second initial modulated signal, wherein the second phase modulator has a second phase modulation parameter; The third beam splitter is used to combine the first initial modulated signal and the second initial modulated signal to obtain the first modulated signal.

3. The polarization coded modulator according to claim 2, wherein: The second interferometer comprises: a fourth beam splitter, configured to perform beam splitting processing on the second optical signal to obtain a fifth optical signal and a sixth optical signal; a third phase modulator, configured to perform phase modulation processing on the fifth optical signal to obtain a third initial modulated signal, wherein the third phase modulator has a third phase modulation parameter; a fourth phase modulator, configured to perform phase modulation processing on the sixth optical signal to obtain a fourth initial modulated signal, wherein the fourth phase modulator has a fourth phase modulation parameter; The fifth beam splitter is used to combine the third initial modulated signal and the fourth initial modulated signal to obtain the second modulated signal.

4. The polarization coded modulator according to claim 2, wherein: The intensity coefficient of the first modulation signal is , the phase is ,in, is the first phase modulation parameter, is the second phase modulation parameter.

5. The polarization coded modulator according to claim 3, wherein: The intensity coefficient of the second modulation signal is , the phase is ,in, is the third phase modulation parameter, is the fourth phase modulation parameter.

6. The polarization coded modulator according to claim 1, wherein: In the preparation of polarization state intensity In the case of the output optical signal, the first phase modulation parameter , the second phase modulation parameter , the third phase modulation parameter , the fourth phase modulation parameter The following constraints are met: ； ； ； ； ； ； in, is the strength coefficient, , is the horizontal polarization state, is the vertical polarization state, The polarization state is 45 degrees. The polarization state is 135 degrees. is left-handed polarization state, is the right-hand polarization state.

7. The polarization coded modulator according to claim 1, wherein: The different polarization states include a horizontal polarization state, a vertical polarization state, a 45-degree polarization state, a 135-degree polarization state, a left-hand polarization state, and a right-hand polarization state.

8. A polarization encoding method for quantum key distribution, characterized in that: include: Performing beam splitting processing on the input optical signal using the first beam splitter to obtain a first optical signal and a second optical signal; Modulating the first optical signal using a first interferometer to obtain a first modulated signal, wherein the polarization of the first modulated signal is parallel to the slow axis of the polarization beam splitter; Modulating the second optical signal using a second interferometer to obtain a second modulated signal, wherein both the first interferometer and the second interferometer have phase modulation parameters, and the polarization of the second modulated signal is parallel to the fast axis of the polarization beam splitter; Combining the first modulated signal and the second modulated signal using the polarization beam splitter to obtain an output optical signal; Wherein, the coded modulation of different polarization states is achieved by adjusting the phase modulation parameters of the first interferometer and the second interferometer.

9. The polarization encoding method according to claim 8, wherein: Modulating the first optical signal using a first interferometer to obtain a first modulated signal includes: Performing beam splitting processing on the first optical signal using a second beam splitter to obtain a third optical signal and a fourth optical signal; Performing phase modulation processing on the third optical signal using a first phase modulator to obtain a first initial modulated signal, wherein the first phase modulator has a first phase modulation parameter; performing phase modulation processing on the fourth optical signal using a second phase modulator to obtain a second initial modulated signal, wherein the second phase modulator has a second phase modulation parameter; The first initial modulated signal and the second initial modulated signal are combined by using a third beam splitter to obtain the first modulated signal.

10. The polarization encoding method according to claim 9, wherein: Modulating the second optical signal using a second interferometer to obtain a second modulated signal includes: performing beam splitting processing on the second optical signal using a fourth beam splitter to obtain a fifth optical signal and a sixth optical signal; performing phase modulation processing on the fifth optical signal by using a third phase modulator to obtain a third initial modulated signal, wherein the third phase modulator has a third phase modulation parameter; performing phase modulation processing on the sixth optical signal using a fourth phase modulator to obtain a fourth initial modulated signal, wherein the fourth phase modulator has a fourth phase modulation parameter; The third initial modulated signal and the fourth initial modulated signal are combined by using a fifth beam splitter to obtain the second modulated signal.

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