Single sideband modulator based on on-chip integrated optical Hilbert converter and method
Through a single-sideband modulator based on an on-chip integrated optical Hilbert converter, the complex structure and high cost of traditional single-sideband modulators are solved, and efficient spectrum utilization and low-power single-sideband modulation are achieved, which is suitable for high-speed optical communication and wireless transmission.
Patent Information
- Application Number
- CN202510362997.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-26
- Publication Date
- 2025-07-08
AI Technical Summary
Traditional single-sideband modulators have complex structures and high cost, and traditional optical Hilbert converters are difficult to embed in other systems for real-time signal processing.
Using a single sideband modulator based on an on-chip integrated optical Hilbert converter, precise phase adjustment is achieved through the combination of the first coupler, phase modulator and optical Hilbert converter, separation of the upper or lower sidebands, and reducing spectrum overlap and signal distortion.
It improves spectrum utilization, reduces power consumption, and has higher spectrum purity and stability. It is suitable for high-speed optical communication, wireless transmission and radio frequency signal processing.
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Figure CN120276092A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a single-sideband modulator, and in particular to a single-sideband modulator and method based on an on-chip integrated optical Hilbert transformer, belonging to the fields of optical integration and optical communication technologies. Background Art
[0002] Single-sideband modulation (SSB) is an efficient communication modulation technology that improves spectrum utilization by suppressing the carrier and one sideband, and is widely used in fields such as wireless communication, broadcasting, and radar. Traditional single-sideband modulation methods mainly include the filtering method and the phase-shift method. Among them, the filtering method has high requirements for the performance of the filter, while the phase-shift method has strict requirements for the accuracy of the phase-shift network. Among them, the main structures of the electro-optic modulator that generates single-sideband signals by the phase-shift method are as follows: The first is based on, for example, Figure 1 the dual-drive Mach-Zehnder modulator (DD-MZM) shown as follows. By precisely controlling the amplitudes and phase differences of two independent radio-frequency drive signals to modulate the two arms of the optical signal respectively, a single-sideband signal is generated. The second method is, for example, Figure 2 the dual-parallel Mach-Zehnder modulator (DP-MZM) shown as follows, which consists of two parallel sub-Mach-Zehnder modulators (MZMs) and a main interferometer. By separately adjusting the bias points of the two sub-MZMs and the phase differences of the radio-frequency drive signals, two optically generated sideband signals with orthogonal phases can be generated at the output. When these two sideband signals are recombined in the main interferometer, through the interference effect, one sideband will be enhanced and the other sideband will be suppressed, thereby realizing single-sideband modulation. However, these two structures require precise modulation of radio-frequency signals or adjustment of multiple bias points and phase parameters, resulting in high system complexity and high cost.
[0003] As an important signal processing tool, the Hilbert transformer can accurately shift the phase of a signal by 90°, thereby generating a single-sideband signal. However, the traditional optically constructed Hilbert transformer using a lens system has poor reproducibility and portability and is difficult to be embedded in other systems for real-time signal processing. Summary of the Invention
[0004] The purpose of the present invention is to solve the above problems of the prior art, and provide a single-sideband modulator based on an on-chip integrated optical Hilbert transformer, which can efficiently suppress carrier and sideband interference, improve bandwidth utilization, reduce power consumption, and have higher spectral purity and stability.
[0005] Another object of the present invention is to provide a single-sideband modulation method implemented based on the above single-sideband modulator.
[0006] The object of the present invention can be achieved by adopting the following technical solutions:
[0007] A single-sideband modulator based on an on-chip integrated optical Hilbert transformer, comprising a first coupler, a second coupler, a first phase modulator, a second phase modulator, and an optical Hilbert transformer. The first coupler has one input end and two output ends. The second coupler has two input ends and one output end. The first output end of the first coupler is respectively connected to the input end of the first phase modulator. The second output end of the first coupler is connected to the input end of the second phase modulator. The output end of the first phase modulator is connected to the input end of the optical Hilbert transformer. The output end of the optical Hilbert transformer is connected to the first input end of the second coupler. The output end of the second phase modulator is connected to the second input end of the second coupler.
[0008] Further, the optical Hilbert transformer is an optical Hilbert transformer based on a waveguide grating, comprising a waveguide, a directional coupler, and an asymmetric sidewall phase-shifted Bragg grating. The waveguide includes an input waveguide, a connecting waveguide, and an output waveguide. The input waveguide is connected to the directional coupler. The directional coupler is connected to the asymmetric sidewall phase-shifted Bragg grating through the connecting waveguide. The asymmetric sidewall phase-shifted Bragg grating is connected to the output waveguide.
[0009] Further, the input waveguide is a first tapered waveguide, the connecting waveguide is a second tapered waveguide, and the output waveguide is a third tapered waveguide.
[0010] Further, the waveguide further includes a fourth tapered waveguide, a first curved waveguide, a second curved waveguide, a third curved waveguide, a fourth curved waveguide, and a first straight waveguide. The fourth tapered waveguide, the first straight waveguide, the fourth curved waveguide, the third curved waveguide, and the first curved waveguide are connected in sequence. The directional coupler includes a second straight waveguide and a fifth tapered waveguide. The two ends of the second straight waveguide are respectively connected to the first curved waveguide and the second curved waveguide. One end of the fifth tapered waveguide is connected to the input waveguide, and the other end of the fifth tapered waveguide is connected to the asymmetric sidewall phase-shifted Bragg grating through the connecting waveguide.
[0011] Further, the asymmetric sidewall phase-shifted Bragg grating includes a first asymmetric sidewall Bragg grating, a third straight waveguide, and a second asymmetric sidewall Bragg grating. One end of the first asymmetric sidewall Bragg grating is connected to the connecting waveguide. The other end of the first asymmetric sidewall Bragg grating is connected to one end of the second asymmetric sidewall Bragg grating through the third straight waveguide. The other end of the second asymmetric sidewall Bragg grating is connected to the output waveguide.
[0012] Further, the optical Hilbert transformer is an optical Hilbert transformer based on a microring resonator, including a microring resonator. The ring resonator includes a curved waveguide, a Mach-Zehnder modulator, and a single-arm phase shifter. The Mach-Zehnder modulator has two input terminals and two output terminals. The first input terminal and the first output terminal of the Mach-Zehnder modulator are respectively connected to both ends of the single-arm phase shifter through the curved waveguide. The second input terminal and the second output terminal of the Mach-Zehnder modulator are respectively connected to the input waveguide and the output waveguide.
[0013] Further, the optical Hilbert transformer is a Hilbert transformer based on a wavelength division multiplexer, including a splitter, a combiner, and a plurality of Mach-Zehnder interferometers. Each Mach-Zehnder interferometer includes two couplers and a Mach-Zehnder modulator. Both ends of the Mach-Zehnder modulator are respectively connected to the two couplers, and the two couplers are respectively connected to the splitter and the combiner.
[0014] Further, the optical Hilbert transformer is an optical Hilbert transformer based on a delay line. By using the optical path difference and the interference effect, a fixed time delay is introduced through the optical delay line, so that different frequency components of the input optical signal experience specific phase shifts, thereby realizing the Hilbert transform at the output end.
[0015] Another object of the present invention can be achieved by adopting the following technical solutions:
[0016] A single-sideband modulation method is implemented based on the above single-sideband modulator. The method includes:
[0017] The input light is split into two beams by the first coupler, and the optical signal is modulated with the signal through the first phase modulator and the second phase modulator. The optical signal output by the first phase modulator enters the optical Hilbert transformer. The optical Hilbert transformer generates a relative phase shift of π on both sides of the center wavelength, and the lower sideband generates a relative phase shift of π relative to the upper sideband signal. The optical signal output by the optical Hilbert transformer interferes with the optical signal output by the second phase modulator. The lower sidebands of the two optical signals cancel each other out coherently, and the upper sidebands of the two optical signals add up coherently.
[0018] Another object of the present invention can also be achieved by adopting the following technical solutions:
[0019] A single-side modulation method is implemented based on the above single-sideband modulator. The method includes:
[0020] The input light is split into two beams by the first coupler, and the optical signals are modulated with signals through the first phase modulator and the second phase modulator; the optical signal output by the first phase modulator enters the optical Hilbert transformer, which generates a relative phase shift of π on both sides of the central wavelength, and a relative phase shift of π between the upper sideband and the lower sideband signals. The optical signal output by the optical Hilbert transformer interferes with the optical signal output by the second phase modulator. The lower sidebands of the two optical signals interfere constructively, and the upper sidebands of the two optical signals interfere destructively.
[0021] The present invention has the following beneficial effects compared with the prior art:
[0022] The single-sideband modulator of the present invention has problems of higher complexity and higher power consumption compared with the existing single-sideband modulators. By using the Hilbert transformer to achieve precise phase adjustment, the upper sideband or the lower sideband can be effectively separated, reducing spectral overlap and signal distortion, capable of efficiently suppressing carrier and sideband interference, improving bandwidth utilization, reducing power consumption, and having a single-sideband modulation with higher spectral purity and stability, enabling the single-sideband modulator to have better performance and application value in fields such as high-speed optical communication, wireless transmission, and radio frequency signal processing. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.
[0024] Figure 1 It is a schematic structural diagram of an existing double-drive Mach-Zehnder modulator.
[0025] Figure 2 It is a schematic structural diagram of an existing double-parallel Mach-Zehnder modulator.
[0026] Figure 3 It is a structural diagram of the single-sideband modulator based on the on-chip integrated optical Hilbert transformer in Embodiment 1 of the present invention.
[0027] Figure 4 It is a schematic structural diagram of the on-chip integrated Hilbert transformer based on waveguide gratings in Embodiment 2 of the present invention
[0028] Figure 5 It is a graph showing the variation of the insertion loss of the optical Hilbert transformer based on waveguide gratings in Embodiment 2 of the present invention with wavelength.
[0029] Figure 6It is a diagram showing the variation of the phase with wavelength of the optical Hilbert transformer based on waveguide gratings in Embodiment 2 of the present invention.
[0030] Figure 7 It is a schematic structural diagram of the optical Hilbert transformer based on waveguide gratings with adjustable central wavelength in Embodiment 2 of the present invention.
[0031] Figure 8 It is a schematic structural diagram of the optical Hilbert transformer based on microring resonators in Embodiment 3 of the present invention.
[0032] Figure 9 It is a schematic structural diagram of the Hilbert transformer based on wavelength division multiplexers in Embodiment 4 of the present invention.
[0033] Figure 10 It is a schematic structural diagram of the optical Hilbert transformer based on delay lines in Embodiment 5 of the present invention. Detailed implementation manners
[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0035] Embodiment 1:
[0036] This embodiment provides a single-sideband modulator based on an on-chip integrated optical Hilbert transformer. The single-sideband modulator based on the Hilbert transformer avoids the dependence on high-precision filters or complex phase-shift networks in traditional methods by combining Hilbert transform and quadrature carrier modulation, and has the advantages of simple implementation, high spectral efficiency, and strong adaptability. Compared with traditional electrical single-sideband modulators, it has ultra-high bandwidth (in the THz range), high modulation speed, low transmission loss, strong parallel processing ability, and strong anti-electromagnetic interference ability.
[0037] As Figure 3As shown, the single-sideband modulator of this embodiment includes a first coupler 101, a second coupler 102, a first phase modulator 103, a second phase modulator 104, and an optical Hilbert transformer 105. The first coupler 101 has one input end and two output ends, and the second coupler 102 has two input ends and one output end. That is, both the first coupler 102 and the second coupler 103 are 1×2 couplers. The first output end of the first coupler 101 is respectively connected to the input end of the first phase modulator 103, the second output end of the first coupler 102 is connected to the input end of the second phase modulator 103, the output end of the first phase modulator 103 is connected to the input end of the optical Hilbert transformer 105, the output end of the optical Hilbert transformer 105 is connected to the first input end of the second coupler 102, the output end of the second phase modulator 104 is connected to the second input end of the second coupler 102, and each device is connected by a connecting waveguide.
[0038] Input light E in has a spectrum as shown in Figure 3 (a). The input light is split into two beams by the first coupler 101. The optical signals are modulated with signals by the first phase modulator 103 and the second phase modulator 104. Then, the spectrum at the output end of the first phase modulator 103 is as shown in Figure 3 (b), which is a double-sideband signal; the spectrum at the output end of the second phase modulator 104 is as shown in Figure 3 (c), which is also a double-sideband signal; the optical signal output by the first phase modulator 103 enters the optical Hilbert transformer 105. The optical Hilbert transformer 105 will generate a relative phase shift of π on both sides of the central wavelength, which will result in two cases: The first case is that the lower sideband generates a relative phase shift of π relative to the upper sideband signal. The output spectrum of the corresponding optical Hilbert transformer is as shown in Figure 3 (e1). In this case, the optical signal output by the optical Hilbert transformer 105 interferes with the optical signal output by the second phase modulator 104. The lower sidebands of the two optical signals cancel each other out coherently, and the upper sidebands of the two optical signals add up coherently. Therefore, only the upper sideband exists in the optical signal at the output end, as shown in Figure 3 (f1); The second case is that the upper sideband generates a relative phase shift of π relative to the lower sideband signal. The output spectrum of the corresponding optical Hilbert transformer is as shown in Figure 3 (e2). In this case, the optical signal output by the optical Hilbert transformer 105 interferes with the optical signal output by the second phase modulator 104. The lower sidebands of the two optical signals add up coherently, and the upper sidebands of the two optical signals cancel each other out coherently. Therefore, only the lower sideband exists in the optical signal at the output end, as shown in Figure 3 (f2). Regardless of which of the above two cases, this modulator can successfully generate a single-sideband modulation signal.
[0039] Embodiment 2:
[0040] The optical Hilbert transformer in this embodiment is an optical Hilbert transformer based on a waveguide grating. The optical Hilbert transformer is provided with a sidewall waveguide grating with a π phase shift, as Figure 4 shown. It includes a waveguide, a directional coupler, and an asymmetric sidewall phase-shifted Bragg grating. The waveguide includes an input waveguide, a connecting waveguide, and an output waveguide. The input waveguide is connected to the directional coupler. The directional coupler is connected to the asymmetric sidewall phase-shifted Bragg grating through the connecting waveguide. The asymmetric sidewall phase-shifted Bragg grating is connected to the output waveguide.
[0041] Furthermore, the input waveguide is a first tapered waveguide 201, the connecting waveguide is a second tapered waveguide 202, and the output waveguide is a third tapered waveguide 203. The waveguide further includes a fourth tapered waveguide 204, a first curved waveguide 205, a second curved waveguide 206, a third curved waveguide 207, a fourth curved waveguide 208, and a first straight waveguide 209. The fourth tapered waveguide 204, the first straight waveguide 209, the fourth curved waveguide 208, the third curved waveguide 207, and the first curved waveguide 205 are connected in sequence. The directional coupler includes a second straight waveguide 211 and a fifth tapered waveguide 212. Two ends of the second straight waveguide 211 are respectively connected to the first curved waveguide 205 and the second curved waveguide 206. One end of the fifth tapered waveguide 212 is connected to the first tapered waveguide 201. The other end of the fifth tapered waveguide 212 is connected to the asymmetric sidewall phase-shifted Bragg grating through the second tapered waveguide 202. The asymmetric sidewall phase-shifted Bragg grating is connected to the third tapered waveguide 203.
[0042] Furthermore, the asymmetric sidewall phase-shifted Bragg grating includes a first asymmetric sidewall Bragg grating 221, a third straight waveguide 222, and a second asymmetric sidewall Bragg grating 223. One end of the first asymmetric sidewall Bragg grating 221 is connected to the second tapered waveguide 202. The other end of the first asymmetric sidewall Bragg grating 221 is connected to one end of the second asymmetric sidewall Bragg grating 223 through the third straight waveguide 222. The other end of the second asymmetric sidewall Bragg grating 223 is connected to the third tapered waveguide 203.
[0043] The working principle of this embodiment is as follows: The incident light containing the TE0 mode enters the Hilbert transformer through the first tapered waveguide 201, passes through the fifth tapered waveguide 212 of the directional coupler in the forward direction, and then passes through a band-pass filter formed by the second tapered waveguide 202, the first asymmetric sidewall Bragg grating 221, and the second asymmetric sidewall Bragg grating 223. The middle third straight waveguide 222 realizes the function of phase shift, and its effect is as Figure 5As shown, the center wavelength is 1.55 um, and a band - pass filter is formed between 1.543 um and 1.557 um. At the same time, the device introduces the phase for negative - frequency signals and the phase for positive - frequency signals, thus generating a 180° phase change at the center - wavelength position, as Figure 6 shown; The light in the TE0 mode passes through the asymmetric - side - wall phase - shift Bragg grating and reflects the light in the TE1 mode backward. The backward - propagating reflected light will be coupled from the fifth tapered waveguide 212 of the directional coupler to the second straight waveguide 211, and after passing through the first curved waveguide 205, the third curved waveguide 207, the fourth curved waveguide 208, and the first straight waveguide 209, it is output through the fourth tapered waveguide 204.
[0044] The ordinary signal x(t) as the real - part signal can obtain the imaginary - part signal after Hilbert transform The real - part signal and the imaginary - part signal can form an analytic signal z(t), as shown in the following formula:
[0045]
[0046] The ordinary signal only contains amplitude information, while the analytic signal obtained by the Hilbert transformer contains the complete signal information (amplitude and phase). It can be used for the complete reconstruction of the signal without losing any information of the original signal, which is an important advantage in signal processing, especially in scenarios where high - precision signal reconstruction is required.
[0047] Optionally, two resistors 301 are added on both sides of the optical Hilbert transformer to adjust the center wavelength of the Hilbert transformer, as Figure 7 shown.
[0048] Those skilled in the art can easily understand that in addition to the above - mentioned methods, the following transformations can also be made in this embodiment: The material for manufacturing the device can specifically be lithium niobate (including thin - film lithium niobate), silicon, lithium tantalate (including thin - film lithium tantalate), indium phosphide, and other materials; The directional coupler can be replaced with other couplers such as X - couplers.
[0049] Embodiment 3:
[0050] The optical Hilbert transformer in this embodiment is an optical Hilbert transformer based on a microring resonator. The optical Hilbert transformer is specifically a microring resonator, as Figure 8As shown, it includes a bent waveguide 410, a Mach-Zehnder modulator 420, and a single-arm phase shifter 430. The Mach-Zehnder modulator 420 has two input terminals and two output terminals. The first input terminal and the first output terminal of the Mach-Zehnder modulator 420 are respectively connected to both ends of the single-arm phase shifter 430 through the bent waveguide 410. The second input terminal and the second output terminal of the Mach-Zehnder modulator 420 are respectively connected to the input waveguide and the output waveguide.
[0051] Specifically, the Mach-Zehnder modulator 420 can be an electro-optic modulator, a thermo-optic modulator, or other modulators based on various optical effects, including two 2×2 multimode interferometers and a phase shifter. The phase shifter includes two straight waveguides and three electrodes. The single-arm phase shifter 430 includes a straight waveguide and two electrodes. The input waveguide is the first straight waveguide 440, and the output waveguide is the second straight waveguide 441.
[0052] The working principle of this embodiment is as follows: The incident light is input through the first straight waveguide 440. An ideal ring resonator is a first-order all-pass filter that can make light of a specific frequency resonate. The frequency of resonance is adjusted through the thermo-optic modulator 430, and the power coupling coefficient between the ring resonator 410 and the second straight waveguide 441 is adjusted through the Mach-Zehnder modulator 420. The coupled output light is output through the second straight waveguide 441.
[0053] Those skilled in the art can easily understand that in addition to the above-mentioned methods, the following transformations can also be made in this embodiment: The 2×2 multimode interferometer can be transformed into a coupler such as a 2×2 directional coupler; the three electrodes of the Mach-Zehnder modulation can be transformed into two electrodes.
[0054] Embodiment 3:
[0055] The optical Hilbert transformer of this embodiment is a Hilbert transformer based on a wavelength division multiplexer, as Figure 9 shown, which includes a splitter 501, a combiner 502, and multiple Mach-Zehnder interferometers 503. Each Mach-Zehnder interferometer 503 includes two couplers and a Mach-Zehnder modulator. Both ends of the Mach-Zehnder modulator 503 are respectively connected to the two couplers, and the two couplers are respectively connected to the splitter 501 and the combiner 502.
[0056] The working principle of this embodiment is as follows: The input optical signal is decomposed into multiple wavelength channels (corresponding to different frequency components of the signal) through the splitter 501. Then, the Mach-Zehnder interferometer is used to perform phase and amplitude modulation on the optical signals of different frequency components. The modulated different wavelength components are combined through the combiner. By reasonably designing the phase shift distribution of each channel, an approximate overall Hilbert transform can be achieved. The target sideband (upper sideband or lower sideband) is retained, while the other sideband and the carrier are suppressed, thereby realizing single-sideband signal output.
[0057] Embodiment 4:
[0058] The optical Hilbert transformer in this embodiment is a delay-line-based optical Hilbert transformer. This optical Hilbert transformer utilizes the optical path difference and interference effect, introduces a fixed time delay through an optical delay line, enables different frequency components of the input optical signal to experience specific phase shifts, and thus approximately realizes the Hilbert transform at the output end.
[0059] As Figure 10 shown, the single-sideband modulator in this embodiment includes a first coupler 601, a second coupler 602, a first phase modulator 603, a second phase modulator 604, and an optical delay line 605. The first coupler 601 has one input end and two output ends, and the second coupler 602 has two input ends and one output end. That is, both the first coupler 601 and the second coupler 602 are 1×2 couplers. The first output end of the first coupler 601 is respectively connected to the input end of the first phase modulator 603, the second output end of the first coupler 601 is connected to the input end of the second phase modulator 604, the output end of the first phase modulator 603 is connected to the input end of the optical delay line 605, the output end of the optical delay line 605 is connected to the first input end of the second coupler 602, and the output end of the second phase modulator 604 is connected to the second input end of the second coupler 602. Each device is connected by a connecting waveguide.
[0060] In summary, compared with the existing single-sideband modulators, the single-sideband modulator of the present invention has the problems of higher complexity and higher power consumption. By using a Hilbert transformer to achieve precise phase adjustment, it can effectively separate the upper sideband or the lower sideband, reduce spectral overlap and signal distortion, can efficiently suppress carrier and sideband interference, improve bandwidth utilization, reduce power consumption, and has a single-sideband modulation with higher spectral purity and stability, enabling the single-sideband modulator to have better performance and application value in the fields of high-speed optical communication, wireless transmission, and radio frequency signal processing.
[0061] The above are only preferred embodiments of the present invention patent, but the implementation manners of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement manners and are all included in the protection scope of the present invention.
Claims
1. A single-sideband modulator based on an on-chip integrated optical Hilbert transformer, characterized in that, It includes a first coupler, a second coupler, a first phase modulator, a second phase modulator and an optical Hilbert transformer. The first coupler has one input end and two output ends. The second coupler has two input ends and one output end. The first output end of the first coupler is respectively connected to the input end of the first phase modulator. The second output end of the first coupler is connected to the input end of the second phase modulator. The output end of the first phase modulator is connected to the input end of the optical Hilbert transformer. The output end of the optical Hilbert transformer is connected to the first input end of the second coupler. The output end of the second phase modulator is connected to the second input end of the second coupler.
2. The single-sideband modulator according to claim 1, wherein The optical Hilbert transformer is an optical Hilbert transformer based on a waveguide grating, and includes a waveguide, a directional coupler and an asymmetric sidewall phase-shifted Bragg grating. The waveguide includes an input waveguide, a connecting waveguide and an output waveguide. The input waveguide is connected to the directional coupler. The directional coupler is connected to the asymmetric sidewall phase-shifted Bragg grating through the connecting waveguide. The asymmetric sidewall phase-shifted Bragg grating is connected to the output waveguide.
3. The single-sideband modulator according to claim 2, wherein The input waveguide is a first tapered waveguide. The connecting waveguide is a second tapered waveguide. The output waveguide is a third tapered waveguide.
4. The single-sideband modulator according to claim 2, wherein The waveguide further includes a fourth tapered waveguide, a first curved waveguide, a second curved waveguide, a third curved waveguide, a fourth curved waveguide and a first straight waveguide. The fourth tapered waveguide, the first straight waveguide, the fourth curved waveguide, the third curved waveguide and the first curved waveguide are connected in sequence. The directional coupler includes a second straight waveguide and a fifth tapered waveguide. The two ends of the second straight waveguide are respectively connected to the first curved waveguide and the second curved waveguide. One end of the fifth tapered waveguide is connected to the input waveguide, and the other end of the fifth tapered waveguide is connected to the asymmetric sidewall phase-shifted Bragg grating through the connecting waveguide.
5. The single-sideband modulator according to claim 2, wherein The asymmetric sidewall phase-shifted Bragg grating includes a first asymmetric sidewall Bragg grating, a third straight waveguide and a second asymmetric sidewall Bragg grating. One end of the first asymmetric sidewall Bragg grating is connected to the connecting waveguide, and the other end of the first asymmetric sidewall Bragg grating is connected to one end of the second asymmetric sidewall Bragg grating through the third straight waveguide. The other end of the second asymmetric sidewall Bragg grating is connected to the output waveguide.
6. The single-sideband modulator according to claim 1, wherein The optical Hilbert transformer is an optical Hilbert transformer based on a microring resonator, and includes a microring resonator. The ring resonator includes a curved waveguide, a Mach-Zehnder modulator and a single-arm phase shifter. The Mach-Zehnder modulator has two input ends and two output ends. The first input end and the first output end of the Mach-Zehnder modulator are respectively connected to the two ends of the single-arm phase shifter through the curved waveguide. The second input end and the second output end of the Mach-Zehnder modulator are respectively connected to the input waveguide and the output waveguide.
7. The single-sideband modulator according to claim 1, characterized in that, The optical Hilbert transformer is a wavelength-division multiplexer-based Hilbert transformer, which includes a splitter, a combiner, and multiple Mach-Zehnder interferometers. Each Mach-Zehnder interferometer includes two couplers and a Mach-Zehnder modulator. The two ends of the Mach-Zehnder modulator are respectively connected to the two couplers, and the two couplers are respectively connected to the splitter and the combiner.
8. The single-sideband modulator according to claim 1, wherein The optical Hilbert transformer is a delay-line-based optical Hilbert transformer. By using the optical path difference and interference effect, a fixed time delay is introduced through an optical delay line, so that different frequency components of the input optical signal experience specific phase shifts, thereby realizing the Hilbert transform at the output end.
9. A single-sideband modulation method implemented based on the single-sideband modulator according to any one of claims 1-8, characterized in that, The method includes: The input light is split into two beams by a first coupler, and the optical signal is modulated with a signal through a first phase modulator and a second phase modulator; the optical signal output by the first phase modulator enters the optical Hilbert transformer, and the optical Hilbert transformer generates a relative phase shift of π on both sides of the central wavelength, and the lower sideband generates a relative phase shift of π relative to the upper sideband signal. The optical signal output by the optical Hilbert transformer interferes with the optical signal output by the second phase modulator, and the lower sidebands of the two optical signals cancel each other out coherently, and the upper sidebands of the two optical signals add up coherently.
10. A single-sideband modulation method, implemented based on the single-sideband modulator according to any one of claims 1-8, characterized in that, The method includes: The input light is split into two beams by a first coupler, and the optical signal is modulated with a signal through a first phase modulator and a second phase modulator; the optical signal output by the first phase modulator enters the optical Hilbert transformer, and the optical Hilbert transformer generates a relative phase shift of π on both sides of the central wavelength, and the upper sideband generates a relative phase shift of π relative to the lower sideband signal. The optical signal output by the optical Hilbert transformer interferes with the optical signal output by the second phase modulator, and the lower sidebands of the two optical signals add up coherently, and the upper sidebands of the two optical signals cancel each other out coherently.