Photo-generated microwave frequency modulation signal generation system

Abstract

The invention discloses a photo-generated microwave frequency-modulated signal generation system, relates to the technical field of microwave photonics, and can solve the problems of poor tunability and high phase noise of a microwave frequency-modulated signal generated by a microwave photon technology. The system comprises a mode-locked laser used for generating a laser pulse signal; the polarization controller is arranged on an emergent light path of the mode-locked laser and is used for adjusting the polarization state of the laser pulse signal to obtain a polarized laser signal; the modulator is arranged on an emergent light path of the polarization controller and is used for modulating the polarization laser signal according to different loaded radio frequency signals so as to output a modulated light signal with linearly changed frequency; the photoelectric detector is used for converting the modulated optical signal into a microwave signal to obtain a microwave linear frequency modulation signal; and the band-pass filter is used for carrying out filtering processing on the microwave linear frequency modulation signal so as to select a microwave signal of a target frequency band.

Description

Technical Field

[0001] This application relates to the field of microwave photonics technology, and particularly to an optical microwave frequency modulation signal generation system. Background Art

[0002] With the rapid development of communication technology and radar technology, the requirements for microwave signal sources are increasing day by day. Traditional microwave signal sources are based on electronic methods and have problems such as low carrier frequency, narrow frequency modulation bandwidth, and high phase noise, and gradually cannot meet the needs of modern communication and radar systems.

[0003] Microwave photon technology, as an emerging technology that combines the advantages of traditional microwave technology and photon technology, provides a new way to solve the above problems. By means of optical methods, the generation, modulation, transmission, reception, and demodulation of microwave signals are realized, which has the advantages of high carrier frequency, large working bandwidth, and strong anti-electromagnetic interference ability. However, the existing microwave photon technology for generating microwave frequency modulation signals still has problems such as poor tunability and high phase noise. Summary of the Invention

[0004] This application provides an optical microwave frequency modulation signal generation system, which can solve the problems of poor tunability and high phase noise of microwave frequency modulation signals generated by microwave photon technology.

[0005] In order to achieve the above object, this application adopts the following technical solutions:

[0006] An embodiment of this application provides an optical microwave frequency modulation signal generation system, and the system includes;

[0007] A mode-locked laser for generating a laser pulse signal;

[0008] A polarization controller is arranged on the outgoing optical path of the mode-locked laser and is used to adjust the polarization state of the laser pulse signal to obtain a polarized laser signal;

[0009] A modulator is arranged on the outgoing optical path of the polarization controller and is used to modulate the polarized laser signal according to different loaded radio frequency signals to output a modulation optical signal with linearly varying frequency;

[0010] A photodetector is used to convert the modulation optical signal into a microwave signal to obtain a microwave linear frequency modulation signal;

[0011] A band-pass filter is used to filter the microwave linear frequency modulation signal to select a microwave signal in a target frequency band.

[0012] As a possible implementation manner, the system further includes: a first coupler and a second coupler, the first coupler is arranged on the outgoing optical path of the polarization controller, and the second coupler is arranged on the incoming optical path of the photodetector;

[0013] The first coupler is configured to divide the polarized laser signal into a main optical path and a sub-optical path, and the polarized laser signal in the main optical path is incident on the modulator;

[0014] The second coupler is configured to perform beat frequency processing on the modulated optical signal and the polarized laser signal in the sub-optical path to obtain a beat frequency signal.

[0015] As a possible implementation, the photodetector is further configured to convert the beat frequency signal into a microwave signal to obtain a beat frequency microwave linear frequency modulation signal;

[0016] The band-pass filter is further configured to perform filtering processing on the beat frequency microwave linear frequency modulation signal to select a microwave signal in a target frequency band.

[0017] As a possible implementation, the sub-optical path is divided into a first sub-optical path and a second sub-optical path, there are two second couplers, and the system further includes an optical switch;

[0018] The optical switch is configured to divide the modulated optical signal into a first light beam and a second light beam;

[0019] One of the second couplers is configured to perform beat frequency processing on the modulated optical signal of the first light beam and the polarized laser signal in the first sub-optical path to obtain a first beat frequency signal;

[0020] The other second coupler is configured to perform beat frequency processing on the modulated optical signal of the second light beam and the polarized laser signal in the second sub-optical path to obtain a second beat frequency signal.

[0021] As a possible implementation, both the photodetector and the band-pass filter are two;

[0022] One of the photodetectors is configured to convert the first beat frequency signal into a microwave signal to obtain a first microwave linear frequency modulation signal, and the other photodetector is configured to convert the second beat frequency signal into a microwave signal to obtain a second microwave linear frequency modulation signal;

[0023] One of the band-pass filters is configured to perform filtering processing on the first microwave linear frequency modulation signal to select a microwave signal in a first target frequency band; the other band-pass filter is configured to perform filtering processing on the second microwave linear frequency modulation signal to select a microwave signal in a second target frequency band.

[0024] As a possible implementation, the system further includes: a third coupler, and the third coupler is disposed between the modulator and the optical switch;

[0025] The third coupler is configured to divide the modulated optical signal output by the modulator into a main optical beam and a sub-optical beam. Wherein, the optical switch is disposed on the optical path of the main optical beam, and the main optical beam is input into the optical switch.

[0026] As a possible implementation, the system further includes: a bias controller, and the sub-optical beam is input into the bias controller;

[0027] The bias controller is configured to convert the sub-optical beam into an electrical signal and then input the electrical signal into the modulator;

[0028] The modulator is further configured to control the DC voltage of the modulator to be stabilized within a preset range according to the electrical signal.

[0029] As a possible implementation, the modulator is a Mach-Zehnder modulator.

[0030] The beneficial effects brought by the technical solution provided by the embodiments of the present application at least include:

[0031] The optical microwave frequency modulation signal generation system provided by the embodiments of the present application includes: a mode-locked laser, a polarization controller, a modulator, a photodetector, and a band-pass filter. Among them, the mode-locked laser is configured to generate a laser pulse signal; the polarization controller is disposed on the output optical path of the mode-locked laser and is configured to adjust the polarization state of the laser pulse signal to obtain a polarized laser signal; the modulator is disposed on the output optical path of the polarization controller and is configured to modulate the polarized laser signal according to different loaded radio frequency signals to output a modulated optical signal with a linearly changing frequency; the photodetector is configured to convert the modulated optical signal into a microwave signal to obtain a microwave linear frequency modulation signal; the band-pass filter is configured to perform filtering processing on the microwave linear frequency modulation signal to select a microwave signal in a target frequency band. The optical microwave frequency modulation signal generation system provided by the embodiments of the present application utilizes the characteristics of electro-optic modulation, uses the pulsed laser generated by the mode-locked laser as the carrier signal in the modulation process, makes full use of the rich frequency components of the optical comb signal to load the tunable radio frequency signal at the radio frequency signal end of the modulator, realizes the linear change of the frequency of the output microwave signal, and the obtained microwave linear frequency modulation signal can achieve free switching between different carrier frequencies through different band-pass filters, improving the selectivity of the carrier frequency of the output signal and the utilization rate of the frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the structure of an optical microwave frequency modulation signal generation system provided by an embodiment of the present application Figure 1 ;

[0033] Figure 2 is the structure of an optical microwave frequency modulation signal generation system provided by an embodiment of the present application Figure 2 ;

[0034] Figure 3 Spectrum diagram of the laser pulse signal output by a mode-locked laser provided by an embodiment of the present application;

[0035] Figure 4 Frequency components of the laser pulse signal output by a mode-locked laser provided by an embodiment of the present application near 1 GHz at point (a) and 5 GHz at point (b);

[0036] Figure 5 Spectral diagram of the laser pulse signal output by a mode-locked laser provided by an embodiment of the present application;

[0037] Figure 6 Spectrum of a microwave chirp signal provided by an embodiment of the present application Figure 1 ;

[0038] Figure 7 Spectrum of a microwave chirp signal provided by an embodiment of the present application Figure 2 ;

[0039] Figure 8 Measurement result of the phase noise of a microwave chirp signal provided by an embodiment of the present application Figure 1 ;

[0040] Figure 9 Measurement result of the phase noise of a microwave chirp signal provided by an embodiment of the present application Figure 2 。

[0041] Reference numerals:

[0042] 01 - Mode-locked laser, 02 - Polarization controller, 03 - Modulator, 04 - Photoelectric detector, 05 - Band-pass filter, 06 - First coupler, 07 - Third coupler, 08 - Bias controller, 09 - Optical switch, 10 - Second coupler. Detailed implementation manners

[0043] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0044] Hereinafter, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present disclosure, unless otherwise specified, the meaning of "a plurality" is two or more.

[0045] In addition, the use of "based on" or "according to" implies openness and inclusiveness, because a process, step, calculation, or other action "based on" or "according to" one or more conditions or values can, in practice, be based on additional conditions or values beyond those stated.

[0046] With the rapid development of communication technology and radar technology, the requirements for microwave signal sources are increasing day by day. Traditional microwave signal sources are based on electronic methods and have problems such as low carrier frequency, narrow frequency modulation bandwidth, and high phase noise, and gradually cannot meet the needs of modern communication and radar systems. Microwave photonics technology, as an emerging technology that combines the advantages of traditional microwave technology and photon technology, provides a new way to solve the above problems. By means of optical methods, the generation, modulation, transmission, reception, and demodulation of microwave signals are realized, which have the advantages of high carrier frequency, large working bandwidth, and strong anti-electromagnetic interference ability.

[0047] The existing methods for generating microwave frequency modulation signals by microwave photonics technology still have deficiencies. The direct modulation method has a bandwidth limited by the response frequency of the semiconductor laser and poor tunability; the optical heterodyne method has high phase noise and requires an additional phase-locked loop, resulting in a high system complexity; the mode-locked laser method has a fixed frequency and cannot be flexibly tuned, relying on the repetition frequency. Therefore, the existing microwave photonics technology for generating microwave frequency modulation signals still has problems such as poor tunability and high phase noise.

[0048] To solve the above problems, the present application provides an optical generation system for microwave frequency modulation signals, as Figure 1 shown, the system includes;

[0049] A mode-locked laser 01 for generating a laser pulse signal;

[0050] A polarization controller 02 is arranged on the output optical path of the mode-locked laser 01 for adjusting the polarization state of the laser pulse signal to obtain a polarized laser signal;

[0051] A modulator 03 is arranged on the output optical path of the polarization controller 02 for modulating the polarized laser signal according to different loaded radio frequency signals to output a modulation optical signal with a linearly changing frequency;

[0052] A photodetector 04 for converting the modulation optical signal into a microwave signal to obtain a microwave linear frequency modulation signal;

[0053] A band-pass filter 05 is used to filter the microwave chirp signal to select microwave signals in the target frequency band.

[0054] Among them, the mode-locked laser 01 is a kind of ultra-short pulse laser device that can emit laser with narrow pulse width and high peak power. The mode-locking technology adopted by the mode-locked laser 01 is to use a certain modulation method to make the laser oscillation have a definite phase relationship between different longitudinal modes with different frequencies. The mode-locked laser 01 in this application can be a fiber laser built by using the passive mode-locking method, and the output optical signal is stable. The repetition frequency of the laser pulse signal output by the mode-locked laser 01 is 107 MHz.

[0055] After the mode-locked laser 01 generates a laser pulse signal, the polarization controller 02 adjusts the polarization state of the laser pulse signal to ensure that the laser pulse signal maintains a stable polarization characteristic during long-distance transmission and ensures the optimal modulation efficiency.

[0056] Optionally, the modulator 03 can be a Mach-Zehnder Modulator (MZM). The Mach-Zehnder Modulator is a device that modulates the radio frequency signal S(t) with the polarized laser signal adjusted by the polarization controller 02. The radio frequency signal S(t) with a sine wave waveform is loaded on the signal driving end of the MZM, and the output microwave chirp signal is controlled by changing the sweep bandwidth and sweep speed of the radio frequency signal.

[0057] The photodetector 04 can be a high-speed photodetector 04. The high-speed photodetector 04 converts the modulated optical signal output by the modulator 03 into a microwave signal through photoelectric conversion, so as to obtain a microwave chirp signal. Different microwave chirp signals in different frequency bands are filtered and selected through band-pass filters 05 with different center wavelengths and adapted passband bandwidths, and the influence of part of the classical noise and high-frequency noise on the output signal is filtered. By passing through different band-pass filters 05, the switching of the microwave chirp signal between different carrier frequencies can be realized.

[0058] As Figure 2 shown, the system further includes: a first coupler 06 and a second coupler 10. The first coupler 06 is arranged on the outgoing optical path of the polarization controller 02, and the second coupler 10 is arranged on the incoming optical path of the photodetector 04;

[0059] The first coupler 06 is used to divide the polarized laser signal into a main optical path and a sub-optical path, and the polarized laser signal on the main optical path is incident on the modulator 03; the second coupler 10 is used to perform beat frequency processing on the modulated optical signal and the polarized laser signal on the sub-optical path to obtain a beat frequency signal.

[0060] Optionally, the photodetector 04 is further configured to convert the beat signal into a microwave signal to obtain a beat microwave linear frequency modulation signal; the band-pass filter 05 is further configured to perform filtering on the beat microwave linear frequency modulation signal to select microwave signals in a target frequency band.

[0061] Among them, the distribution ratio of the main optical path to the sub-optical path can be 4:1. That is to say, 80% of the polarized laser signals enter the main optical path, and 20% of the polarized laser signals enter the sub-optical path. Of course, the distribution ratio of the main optical path to the sub-optical path can be set as needed, and the embodiments of the present application do not make specific limitations in this regard.

[0062] Optionally, the sub-optical path is divided into a first sub-optical path and a second sub-optical path, there are two second couplers 10, and the system further includes an optical switch 09;

[0063] The optical switch 09 is configured to divide the modulated optical signal into a first light beam and a second light beam; one of the second couplers 10 is configured to perform beat processing on the modulated optical signal of the first light beam and the polarized laser signal of the first sub-optical path to obtain a first beat signal; the other second coupler 10 is configured to perform beat processing on the modulated optical signal of the second light beam and the polarized laser signal of the second sub-optical path to obtain a second beat signal.

[0064] Among them, the distribution ratio of the first sub-optical path to the second sub-optical path can be 1:1. That is to say, 10% of the polarized laser signals enter the first sub-optical path, and 10% of the polarized laser signals enter the first sub-optical path. Of course, the distribution ratio of the first sub-optical path to the second sub-optical path can be set as needed, and the embodiments of the present application do not make specific limitations in this regard.

[0065] It can be understood that after performing beat processing on the modulated optical signal and the polarized laser signal of the sub-optical path as a carrier, compared with using a single-frequency optical signal as a carrier, the signal quality is effectively improved, the signal has good phase noise characteristics, and it is suitable for the high-frequency and large-bandwidth requirements of modern communication and radar systems.

[0066] Optionally, there are two photodetectors 04 and two band-pass filters 05; one of the photodetectors 04 is configured to convert the first beat signal into a microwave signal to obtain a first microwave linear frequency modulation signal, and the other photodetector 04 is configured to convert the second beat signal into a microwave signal to obtain a second microwave linear frequency modulation signal; one of the band-pass filters 05 is configured to perform filtering on the first microwave linear frequency modulation signal to select microwave signals in a first target frequency band; the other band-pass filter 05 is configured to perform filtering on the second microwave linear frequency modulation signal to select microwave signals in a second target frequency band.

[0067] That is to say, a band - pass filter 05 with different central wavelengths and adapted pass - band bandwidths is used to filter and select microwave linear frequency - modulated signals in different frequency bands, and filter the influence of part of the classical noise and high - frequency noise on the output signal. By passing through different band - pass filters 05, the switching of microwave linear frequency - modulated signals between different carrier frequencies can be realized.

[0068] Optionally, the system further includes: a third coupler 07. The third coupler 07 is disposed between the modulator 03 and the optical switch 09. The third coupler 07 is configured to divide the modulated optical signal output by the modulator 03 into a main beam and a sub - beam. Among them, the optical switch 09 is disposed on the optical path of the main beam, and the main beam is input to the optical switch.

[0069] Optionally, the system further includes: a bias controller 08. The sub - beam is input to the bias controller 08. The bias controller 08 is configured to convert the sub - beam into an electrical signal and then input the electrical signal to the modulator 03. The modulator 03 is further configured to control the DC voltage of the modulator 03 to be stabilized within a preset range according to the electrical signal.

[0070] Among them, the distribution ratio of the main beam and the sub - beam can be: 99:1. That is to say, 99% of the modulated optical signal is input to the optical switch 09, and 1% of the modulated optical signal is input to the bias controller 08. Of course, the distribution ratio of the main beam and the sub - beam can be set as needed, and the embodiments of the present application do not make specific limitations in this regard.

[0071] It can be understood that 1% of the modulated optical signal output by the modulator 03 passes through the bias controller 08 (Bias Controller, BC). After converting the optical signal into an electrical signal, the bias controller 08 uses it as the negative feedback signal of the MZM to control and stabilize the DC voltage at both ends of the MZM, stabilize the DC operating point of the MZM, and stabilize the operating mode of the MZM at the Q point.

[0072] The optoelectronic microwave frequency modulation signal generation system provided by the embodiment of the present application includes: a mode-locked laser 01, a polarization controller 02, a modulator 03, a photodetector 04, and a bandpass filter 05. Among them, the mode-locked laser 01 is used to generate a laser pulse signal; the polarization controller 02 is arranged on the outgoing optical path of the mode-locked laser 01 and is used to adjust the polarization state of the laser pulse signal to obtain a polarized laser signal; the modulator 03 is arranged on the outgoing optical path of the polarization controller 02 and is used to modulate the polarized laser signal according to different loaded radio frequency signals to output a modulation optical signal with a linearly changing frequency; the photodetector 04 is used to convert the modulation optical signal into a microwave signal to obtain a microwave linear frequency modulation signal; the bandpass filter 05 is used to perform filtering processing on the microwave linear frequency modulation signal to select a microwave signal in a target frequency band. The optoelectronic microwave frequency modulation signal generation system provided by the embodiment of the present application utilizes the characteristics of electro-optical modulation, uses the pulsed laser generated by the mode-locked laser 01 as the carrier signal in the modulation process, makes full use of the rich frequency components of the optical comb signal, loads the tunable radio frequency signal at the radio frequency signal end of the modulator 03, realizes the linear change of the frequency of the output microwave signal, and the obtained microwave linear frequency modulation signal can realize the free switching between different carrier frequencies through different bandpass filters 05, improving the selectivity of the carrier frequency of the output signal and the utilization rate of the frequency band.

[0073] Figure 3 is the spectrogram of the laser pulse signal output by the mode-locked laser, Figure 4 are the frequency components of the laser pulse signal output by the mode-locked laser near 1 GHz at point (a) and 5 GHz at point (b). From Figure 3 and Figure 4 it can be seen that the signal-to-noise ratios between the frequency components are different, and the signal-to-noise ratio of the frequency components gradually decreases as the frequency increases. This is mainly determined by the gain spectral width in the resonant cavity of the mode-locked laser. From Figure 4 it can also be seen that the signal-to-noise ratio of the frequency components near 1 GHz of the output light reaches 50 dB, while the signal-to-noise ratio of the frequency components near 5 GHz reaches 42 dB.

[0074] Figure 5 is the spectrogram of the laser pulse signal output by the mode-locked laser. During the test, the laser pulse signal output by the mode-locked laser is directly connected to a spectrum analyzer with a resolution (YOKOGAWA AQ6370D). The resolution of the spectrum analyzer is 0.02 nm, and the spectrogram of the laser pulse signal is obtained. From Figure 5 it can be seen that the central wavelength of the laser pulse signal output by the mode-locked laser is 1566.66 nm, and the 3 dB bandwidth is 9.22 nm.

[0075] Figure 6It is the spectrogram of the microwave chirp signal when the frequency of the laser pulse signal output by the mode-locked laser is 10 GHz and the radio frequency signals loaded by the modulator are 30 MHz respectively. Figure 7 It is the spectrogram of the microwave chirp signal when the frequency of the laser pulse signal output by the mode-locked laser is 10 GHz and the radio frequency signals loaded by the modulator are 40 MHz respectively. From Figure 6 and Figure 7 it can be seen that when the frequency of the laser pulse signal output by the mode-locked laser is 10 GHz and the radio frequency signals loaded by the modulator are 30 MHz and 40 MHz respectively, the signal-to-noise ratios of the microwave chirp signals are both above 12 dB, and the phase noise is not higher than -112.24 dBc / Hz@10 kHz.

[0076] Figure 8 It is the measurement result of the phase noise of the microwave chirp signal of the 1 GHz channel. Figure 9 It is the measurement result of the phase noise of the microwave chirp signal of the 5 GHz channel. From Figure 8 it can be seen that the phase noise of the signal at the frequency point of 10 kHz near 1.07 GHz is about -110 dBc / Hz, and from Figure 9 it can be seen that the phase noise of the signal at the frequency point of 10 kHz near 5.35 GHz is about -101 dBc / Hz.

[0077] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0078] The above embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be understood as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A photogenerated microwave frequency modulation signal generation system, characterized in that The system includes: A mode-locked laser for generating a laser pulse signal; A polarization controller disposed on the output optical path of the mode-locked laser for adjusting the polarization state of the laser pulse signal to obtain a polarized laser signal; A modulator disposed on the output optical path of the polarization controller for modulating the polarized laser signal according to different loaded radio frequency signals to output a modulated optical signal with linearly varying frequency; A photodetector for converting the modulated optical signal into a microwave signal to obtain a microwave chirp signal; A band-pass filter for filtering the microwave chirp signal to select a microwave signal in a target frequency band.

2. The system according to claim 1, wherein The system further includes: a first coupler and a second coupler. The first coupler is disposed on the output optical path of the polarization controller, and the second coupler is disposed on the input optical path of the photodetector; The first coupler is configured to divide the polarized laser signal into a main optical path and a sub-optical path, and the polarized laser signal on the main optical path is incident on the modulator; The second coupler is configured to perform beat frequency processing on the modulated optical signal and the polarized laser signal on the sub-optical path to obtain a beat frequency signal.

3. The system according to claim 2, wherein The photodetector is further configured to convert the beat frequency signal into a microwave signal to obtain a beat frequency microwave chirp signal; The band-pass filter is further configured to filter the beat frequency microwave chirp signal to select a microwave signal in a target frequency band.

4. The system according to claim 2, wherein The sub-optical path is divided into a first sub-optical path and a second sub-optical path. There are two second couplers, and the system further includes an optical switch; The optical switch is configured to divide the modulated optical signal into a first light beam and a second light beam; One of the second couplers is configured to perform beat frequency processing on the modulated optical signal of the first light beam and the polarized laser signal on the first sub-optical path to obtain a first beat frequency signal; The other second coupler is configured to perform beat frequency processing on the modulated optical signal of the second light beam and the polarized laser signal on the second sub-optical path to obtain a second beat frequency signal.

5. The system according to claim 4, characterized in that, Both the photodetector and the band-pass filter are two; One of the photodetectors is configured to convert the first beat frequency signal into a microwave signal to obtain a first microwave chirp signal, and the other photodetector is configured to convert the second beat frequency signal into a microwave signal to obtain a second microwave chirp signal; One of the band-pass filters is configured to filter the first microwave chirp signal to select a microwave signal in a first target frequency band; the other band-pass filter is configured to filter the second microwave chirp signal to select a microwave signal in a second target frequency band.

6. The system according to claim 4, wherein The system further includes: a third coupler. The third coupler is disposed between the modulator and the optical switch; The third coupler is configured to divide the modulated optical signal output by the modulator into a main light beam and a sub-light beam. Among them, the optical switch is disposed on the optical path of the main light beam, and the main light beam is input to the optical switch.

7. The system according to claim 6, characterized in that, The system further includes: a bias controller, and the sub-light beam is input to the bias controller; The bias controller is configured to convert the sub-beam into an electrical signal and input the electrical signal into the modulator; The modulator is further configured to control the DC voltage of the modulator to be stabilized within a preset range according to the electrical signal.

8. The system according to claim 1, wherein The modulator is a Mach-Zehnder modulator.

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