Optical filter and multi-frequency receiving system

Abstract

An optical filter and a multi-frequency receiving system. The optical filter comprises: a first MZI structure (11), a first micro-ring structure (121), a second micro-ring structure (122) and a third micro-ring structure (123); the first MZI structure (11) comprises a first arm (111) and a second arm (112); the first micro-ring structure (121) is coupled to the first arm (111) to form a first micro-ring resonator (A); the second micro-ring structure (122) is coupled to the second arm (112) to form a second micro-ring resonator (B); the third micro-ring structure (123) is coupled to the second arm (112) to form a third micro-ring resonator (C). The sum of the additional phases of the second micro-ring resonator (B) and the third micro-ring resonator (C) is twice the additional phase of the first micro-ring resonator (A), and / or the central wavelength (λ2) of the second micro-ring resonator (B) and the central wavelength (λ3) of the third micro-ring resonator (C) are symmetrically distributed on both sides of the central wavelength (λ1) of the first micro-ring resonator (A). The optical filter can achieve coherent destructive interference near the central wavelengths of the two arms of the first MZI structure (11) and coherent constructive interference at the central wavelength of the whole optical filter, so that the optical filter has a good shape factor.

Description

Optical filter, multi-frequency receiving system

[0001] Cross-reference to related applications

[0002] This application claims priority to the Chinese patent application No. 202410669493.1, filed on May 23, 2024, entitled "Optical filter, multi-frequency receiving system", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of optics, in particular to an optical filter and a multi-frequency receiving system. BACKGROUND

[0004] The optical filter is one of the key basic subsystems in the integrated microwave photonic chip, which is an optical frequency (or optical wavelength) selector. It can select the required wavelength from a large number of wavelengths, and the light other than the wavelength will be filtered out. It can be used for wavelength selection, noise filtering of optical amplifiers, gain equalization, optical multiplexing, optical demultiplexing, etc.

[0005] The common optical filter in silicon-based optoelectronics includes a micro-ring optical filter (structure as shown in FIG. 1A) and a Mach-Zehnder interferometer (MZI) optical filter (structure as shown in FIG. 2A). The micro-ring optical filter and the MZI optical filter have their own shortcomings in terms of process implementation difficulty and comprehensive filtering performance. Therefore, the ring-assisted Mach-Zehnder interferometer (RAMZI) optical filter, which combines the narrow-band characteristics of the micro-ring optical filter and the stability and programmability of the MZI optical filter, is a research hotspot (structure as shown in FIG. 4A, the upper and lower arms of the MZI are coupled with a micro-ring, respectively).

[0006] The next generation of wireless communication field requires more stringent requirements for the performance of microwave photonic signal processing, such as good rectangular coefficient (i.e. narrow transition band and large suppression ratio). However, the existing filter scheme cannot meet this demand. SUMMARY

[0007] The present application provides an optical filter and a multi-frequency receiving system for narrowing the transition band of the optical filter, improving the suppression ratio, and achieving good rectangular coefficient.

[0008] In a first aspect, an optical filter is provided, comprising: a first MZI structure, a first micro-ring structure, a second micro-ring structure, and a third micro-ring structure; the first MZI structure comprises a first arm and a second arm; the first arm is an upper arm, and the second arm is a lower arm, or the second arm is an upper arm, and the first arm is a lower arm; the first micro-ring structure is coupled to the first arm to form a first micro-ring resonator; the second micro-ring structure is coupled to the second arm to form a second micro-ring resonator; the third micro-ring structure is coupled to the second arm to form a third micro-ring resonator; a sum of additional phases of the second micro-ring resonator and the third micro-ring resonator is equal to twice an additional phase of the first micro-ring resonator; and / or center wavelengths of the second micro-ring resonator and the third micro-ring resonator are symmetrically distributed on both sides of a center wavelength of the first micro-ring resonator.

[0009] In the embodiment, three micro-ring structures are coupled to the two arms of the first MZI structure to form a three-micro-ring assisted MZI, and the center wavelengths of two of the micro-ring resonators are symmetrically distributed on both sides of the center wavelength of the other micro-ring resonator, so that a phase difference of ±π can be introduced near the center wavelengths of the two arms of the first MZI structure to achieve coherent cancellation, and a phase difference of 2mπ (m is an integer) can be introduced at the center wavelength of the entire optical filter to achieve coherent addition, so that the output spectrum curve of the entire optical filter is lowered near the center wavelength of the entire optical filter, a large amplitude transition band is compressed, the suppression ratio is improved, and the effect of the rectangular coefficient of the filter is improved.

[0010] In a possible design, the optical filter can further comprise more micro-ring structures, for example, further comprising: a fourth micro-ring structure coupled to the second arm to form a fourth micro-ring resonator; and a fifth micro-ring structure coupled to the second arm to form a fifth micro-ring resonator; wherein the center wavelength of the fourth micro-ring resonator is aligned with the center wavelength of the second micro-ring resonator, and the center wavelength of the fifth micro-ring resonator is aligned with the center wavelength of the third micro-ring resonator. This design can further improve the suppression ratio.

[0011] In a possible design, in the coupling region between the first micro-ring structure and the first MZI structure, the first micro-ring structure and the first arm form a first sub-MZI structure with adjustable coupling coefficient; in the coupling region between the second micro-ring structure and the first MZI structure, the second micro-ring structure and the first arm form a second sub-MZI structure with adjustable coupling coefficient; and in the coupling region between the third micro-ring structure and the first MZI structure, the third micro-ring structure and the first arm form a third sub-MZI structure with adjustable coupling coefficient.

[0012] In this design, the coupling structure is designed as a sub-MZI structure, so that the bandwidth of the optical filter can be tuned by tuning the coupling coefficient of the MZI structure, and the optical filter has good bandwidth reconfigurability.

[0013] In a possible design, at least one of the first micro-ring structure, the second micro-ring structure or the third micro-ring structure is provided with an electrode, and the electrode on the micro-ring structure is used to tune the additional phase of the corresponding micro-ring resonator of the micro-ring structure.

[0014] In this design, the micro-ring structure is designed to be tunable in the additional phase, and the center wavelength (or center frequency) of the optical filter can be tuned by tuning the additional phase of the corresponding micro-ring resonator of the micro-ring structure, so that the optical filter has good center wavelength reconfigurability.

[0015] In a possible design, a phase shifter is arranged on the first arm or the second arm, and the additional phase of the phase shifter can be tuned.

[0016] In this way, the optical filter has good bandpass / trap reconfigurability by tuning the additional phase of the phase shifter. For example, the value of the tuned additional phase is ±Nπ, N is a natural number, and the switching of the bandpass and the trap of the optical filter can be realized.

[0017] In a possible design, the phase shifter is arranged on the first arm. Because the number of micro-rings coupled on the first arm is smaller, arranging the phase shifter on the first arm can improve the space utilization and reduce the device size.

[0018] In a possible design, the optical filter can further include a second MZI structure; two output ends of the second MZI structure are respectively connected to two input ends of the first MZI structure; an electrode is arranged on the first arm and / or the second arm of the second MZI structure, and the electrode arranged on the first arm and / or the second arm of the second MZI structure is used to tune the power difference between the first arm and the second arm of the second MZI structure.

[0019] In this way, the power difference between the first arm and the second arm of the first MZI structure can be tuned by tuning the power difference between the first arm and the second arm of the second MZI structure, so that the power of the two arms of the first MZI structure is as symmetrical as possible, for example, the power difference between the first arm and the second arm of the first MZI structure is less than or equal to a preset value. Thus, the problem that the power of the two arms of the first MZI structure is not symmetrical due to the difference in the introduced insertion loss and thus the filter characteristics are degraded can be improved or avoided.

[0020] In a possible design, the waveguide of at least one of the first micro-ring structure, the second micro-ring structure or the third micro-ring structure is a multimode wide waveguide.

[0021] In this design, the multimode wide waveguide is used to design the micro-ring structure with ultra-low loss, so that the sensitivity of the transmission loss of the micro-ring structure to the roughness of the waveguide sidewall is reduced, the narrowband characteristics are more easily realized, and the robustness of the processing is increased.

[0022] In a possible design, the curved portion of at least one of the first micro-ring structure, the second micro-ring structure, or the third micro-ring structure adopts Euler bending or Bezier bending.

[0023] In this design, the curved portion of the micro-ring structure is designed by using Euler bending or Bezier bending, so that the overall structure of the device is more compact, and a larger free spectral range (FSR) can be obtained.

[0024] In a second aspect, a multi-frequency receiving system is provided, including a signal path, a carrier path, a combiner, and an optical filter as described in the first aspect or any possible design of the first aspect; the signal path is configured to convert a plurality of frequency band antenna signals from an electrical domain to an optical domain to obtain optical domain antenna signals; the carrier path is configured to generate a carrier signal; the combiner is configured to combine the optical domain antenna signals and the carrier signal to output a combined signal; and the optical filter is configured to filter the combined signal.

[0025] In a third aspect, a manufacturing method of an optical filter is provided, including: coupling a first micro-ring structure with a first arm of a first mach-zehnder interferometer (MZI) structure to form a first micro-ring resonator; coupling a second micro-ring structure with a second arm of the first MZI structure to form a second micro-ring resonator; and coupling a third micro-ring structure with the second arm of the first MZI structure to form a third micro-ring resonator; wherein the first arm is an upper arm and the second arm is a lower arm, or the second arm is an upper arm and the first arm is a lower arm; wherein a sum of additional phases of the second micro-ring resonator and the third micro-ring resonator is equal to twice an additional phase of the first micro-ring resonator; and / or, a center wavelength of the second micro-ring resonator and a center wavelength of the third micro-ring resonator are symmetrically distributed on two sides of a center wavelength of the first micro-ring resonator.

[0026] In a fourth aspect, a filtering method is provided, which filters an optical signal by using an optical filter as described in the first aspect or any possible design of the first aspect.

[0027] In a fifth aspect, a control method is provided, which is applied to a controller and includes: obtaining an optical signal output by an optical filter; and tuning an operating parameter of at least one device in the optical filter according to the optical signal output by the optical filter, so that a parameter of the optical signal output by the optical filter reaches or approaches a target parameter; wherein the optical filter includes a first MZI structure, a first micro-ring structure, a second micro-ring structure, and a third micro-ring structure; the first MZI structure includes a first arm and a second arm; the first arm is an upper arm, and the second arm is a lower arm, or the second arm is the upper arm, and the first arm is the lower arm; the first micro-ring structure is coupled to the first arm to form a first micro-ring resonator; the second micro-ring structure is coupled to the second arm to form a second micro-ring resonator; the third micro-ring structure is coupled to the second arm to form a third micro-ring resonator; a sum of additional phases of the second micro-ring resonator and the third micro-ring resonator is equal to twice an additional phase of the first micro-ring resonator; and / or a center wavelength of the second micro-ring resonator and a center wavelength of the third micro-ring resonator are symmetrically distributed on two sides of a center wavelength of the first micro-ring resonator.

[0028] In a possible design, in a coupling region between the first micro-ring structure and the first MZI structure, the first micro-ring structure and the first arm form a first sub-MZI structure with a tunable coupling coefficient; in a coupling region between the second micro-ring structure and the first MZI structure, the second micro-ring structure and the first arm form a second sub-MZI structure with a tunable coupling coefficient; and in a coupling region between the third micro-ring structure and the first MZI structure, the third micro-ring structure and the first arm form a third sub-MZI structure with a tunable coupling coefficient. Correspondingly, the tuning of the operating parameter of the at least one device in the optical filter according to the optical signal output by the optical filter includes: tuning a coupling coefficient of at least one of the first sub-MZI structure, the second sub-MZI structure, or the third sub-MZI structure according to the optical signal output by the optical filter, so that a bandwidth of the optical signal output by the optical filter reaches or approaches a target bandwidth.

[0029] In a possible design, at least one of the first micro-ring structure, the second micro-ring structure, or the third micro-ring structure is provided with an electrode, and the electrode on the micro-ring structure is used to tune an additional phase of a corresponding micro-ring resonator of the micro-ring structure. Correspondingly, the tuning of the operating parameter of the at least one device in the optical filter according to the optical signal output by the optical filter includes: tuning the additional phase of the corresponding micro-ring resonator of the at least one micro-ring structure according to the optical signal output by the optical filter, so that a center wavelength of the optical signal output by the optical filter reaches or approaches a target center wavelength.

[0030] In a possible design, a phase shifter is arranged on the first arm or the second arm. Correspondingly, the tuning of the operating parameter of the at least one device in the optical filter according to the optical signal output by the optical filter includes: tuning an additional phase of the phase shifter, so that the optical filter switches between a band-pass and a band-stop, where a value of the tuned additional phase is ±Nπ, and N is a natural number.

[0031] In a possible design, the optical filter further includes a second MZI structure; two output ends of the second MZI structure are connected to two input ends of the first MZI structure respectively; an electrode is arranged on a first arm and / or a second arm of the second MZI structure, and the electrode arranged on the first arm and / or the second arm of the second MZI structure is configured to tune a power difference between the first arm and the second arm of the second MZI structure. Correspondingly, the method of tuning the working parameter of at least one device in the optical filter according to the optical signal output by the optical filter includes: tuning the power difference between the first arm and the second arm of the second MZI structure according to the optical signal output by the optical filter, so as to tune the power difference between the first arm and the second arm of the first MZI structure, so that the power difference between the first arm and the second arm of the first MZI structure is less than or equal to a preset value.

[0032] In a sixth aspect, a computer readable storage medium is provided, and the readable storage medium is configured to store instructions, when the instructions are executed, causing the method in the fifth aspect or any possible design of the fifth aspect to be implemented.

[0033] In a seventh aspect, a computer program product is provided, and the computer program product has instructions stored therein, when the instructions are executed on a computer, causing the computer to execute the method in the fifth aspect or any possible design of the fifth aspect.

[0034] The technical effects of the second aspect to the seventh aspect can refer to the technical effects of the first aspect, and will not be described again. BRIEF DESCRIPTION OF DRAWINGS

[0035] FIG. 1A is a structural schematic diagram of a conventional micro-ring optical filter;

[0036] FIG. 1B is an optical response schematic diagram of the conventional micro-ring optical filter;

[0037] FIG. 2A is a structural schematic diagram of a conventional MZI optical filter;

[0038] FIG. 2B is an optical response schematic diagram of the conventional MZI optical filter;

[0039] FIG. 3 is a schematic diagram of a microwave photonic filter;

[0040] FIG. 4A is a schematic diagram of a RAMZI type optical filter;

[0041] FIG. 4B is a schematic diagram of an output spectrum of the RAMZI type optical filter;

[0042] FIG. 5 is a structural schematic diagram of an optical filter 1 provided by an embodiment of the present application;

[0043] FIG. 6A is an amplitude-frequency response schematic diagram of the optical filter 1 provided by an embodiment of the present application;

[0044] Figure 6B is a schematic diagram showing the performance comparison between the optical filter 1 and a conventional RAMZI optical filter according to an embodiment of the present application;

[0045] Figure 7A is a schematic diagram showing a specific structure of the optical filter 1;

[0046] Figure 7B is a schematic diagram showing the output bandwidth of the optical filter 1;

[0047] Figure 8A is a schematic diagram showing a specific structure of the optical filter 1;

[0048] Figure 8B is a schematic diagram showing the center frequency of the optical filter 1;

[0049] Figure 8C is a schematic diagram showing a specific structure of the optical filter 1;

[0050] Figure 9A is a schematic diagram showing a specific structure of the optical filter 1;

[0051] Figure 9B is a schematic diagram showing the switching of the bandpass and bandstop responses;

[0052] Figure 9C is a schematic diagram showing the bandpass and bandstop responses;

[0053] Figure 10 is a schematic diagram showing the Euler or Bezier bending of the bending section of the micro-ring structure;

[0054] Figure 11 is a schematic diagram showing a specific structure of the optical filter 1;

[0055] Figure 12 is a schematic diagram showing the use of a multi-mode wide waveguide in the two arms of the first MZI structure 11;

[0056] Figure 13 is a schematic diagram showing a specific structure of the optical filter 1;

[0057] Figure 14 is a schematic diagram showing the structure of a multi-frequency receiving system according to an embodiment of the present application;

[0058] Figure 15 is a specific structure example of the multi-frequency receiving system;

[0059] Figure 16 is a schematic diagram showing the principle of receiving a multi-frequency signal based on post-injection of a carrier wave;

[0060] Figure 17 is a flow chart showing a manufacturing method of an optical filter according to an embodiment of the present application;

[0061] Figure 18 is a flow chart showing a control method according to an embodiment of the present application. DETAILED DESCRIPTION

[0062] With the development and evolution of wireless communication technology, the generation, reception and processing of ultra-wideband microwave signals of wireless radio frequency front end are facing great opportunities and challenges. Among them, integrated microwave photonics technology has become an important scheme. This is because integrated microwave photonics technology has the advantages of making full use of optical signal processing, large bandwidth, large range of tunable, good reconfigurability, and using mature complementary metal oxide semiconductor (CMOS) process to integrate the entire microwave photonics system on a chip (i.e. microwave photonics chip), which can reduce cost, reduce size and improve system signal processing performance.

[0063] The optical filter is one of the key basic subsystems in the integrated microwave photonics chip, which is an optical frequency (or wavelength) selector. It can select the required wavelength from a large number of wavelengths, and the light other than this wavelength will be filtered out. It can be used for wavelength selection, noise filtering of optical amplifiers, gain equalization, optical multiplexing, optical demultiplexing, etc.

[0064] The optical filter used in silicon-based optoelectronics includes micro-ring resonant type, mach-zehnder interferometer (MZI) type, waveguide Bragg grating type, arrayed waveguide grating type, etc. Among them, the micro-ring resonant type optical filter can be called micro-ring optical filter or microring resonator (MRR), and the MZI type optical filter can be called MZI optical filter.

[0065] FIG. 1A is a structural schematic diagram of a conventional micro-ring optical filter, which includes two straight waveguides (one is an input waveguide and the other is an output waveguide) and a micro-ring waveguide (referred to as a micro-ring) arranged between the two straight waveguides. The optical signal containing multiple wavelengths is input from the input waveguide. When the optical signal passes through the micro-ring, the resonant wavelength optical signal will be coupled into the micro-ring. The optical wave resonates in the micro-ring, and the resonant optical wave is coupled into the output waveguide again when passing through the output waveguide. It can be understood that in FIG. 1A, the input waveguide can be a straight waveguide located above the micro-ring, and the output waveguide can be a straight waveguide located below the micro-ring. Then the optical signal of multiple wavelengths can be input from the input end, the resonant light can be output from the download end, and the other non-resonant light can be output from the straight-through end. Alternatively, the output waveguide can be a straight waveguide located above the micro-ring, and the input waveguide can be a straight waveguide located below the micro-ring. Then the optical signal of multiple wavelengths can be input from the upload end, the resonant light can be output from the straight-through end, and the other non-resonant light can be output from the download end. Among them, k1, k2, -k1*, -k2* represent the coupling coefficient, and t1, t2, t1*, t2* are the transmission coefficient.

[0066] Fig. 1B is a schematic diagram of the optical response of the micro-ring optical filter shown in Fig. 1A. Fig. 1B is an example in which a plurality of wavelength optical signals are input from the input end, resonant light is output from the download end, and other non-resonant light is output from the through end. The solid line represents a notch filter (i.e., the output of the through end), which suppresses interference signals, and the dashed line represents a bandpass (i.e., the output of the download end), which selects useful signals. As can be seen from Fig. 1B, the output spectrum of the micro-ring optical filter is of a Lorentz type, and the micro-ring optical filter has obvious advantages in narrow bandwidth characteristics and compact structure compared to other types of optical filters.

[0067] Fig. 2A is a schematic diagram of the structure of a conventional MZI optical filter. The MZI is composed of two 3dB splitting structures (such as a multimode interference coupler) and two arms. The wavelength splitting principle is as follows: light enters the input waveguide of the MZI (e.g., Ein), is split by the first 3dB coupler, and uniformly enters the two arms. The light waves in the two arms have a path difference at the second 3dB coupler, resulting in interference. By designing the length difference between the two arms, the filterable wavelength is placed at the position of maximum interference, and the desired filter wavelength is selected.

[0068] Fig. 2B is a schematic diagram of the optical response of the MZI optical filter shown in Fig. 2A. In Fig. 2B, the solid line and the dashed line represent the outputs of the two output ports out1 and out2, respectively. As can be seen from Fig. 2B, the output spectrum of the MZI optical filter is of a cosine type, and the MZI optical filter has advantages in multi-channel filtering, programmability, stability, etc. compared to other types of optical filters. The bandwidth of the MZI optical filter can be adjusted by adjusting the coupling coefficient of the coupler of the MZI optical filter, and the center frequency (or center wavelength) of the MZI optical filter can be adjusted by adjusting the additional phase or delay of one arm of the MZI optical filter. Therefore, the MZI optical filter has excellent bandwidth and frequency reconfigurability.

[0069] In the field of next-generation wireless communication, microwave photon signal processing has more stringent requirements for filter performance, such as high precision, good rectangular coefficient, and good reconfigurability. High precision refers to a Sub-GHz narrow bandwidth, good rectangular coefficient refers to a large suppression ratio and a narrow transition band, and reconfigurability refers to the switching between bandpass and notch. It can be understood that Sub-GHz refers to a radio frequency band below one gigahertz, and the Sub-GHz frequency band generally refers to a frequency band between 300 MHz and 1 GHz. These frequency bands have the characteristics of long transmission distance, strong penetration ability, and narrow bandwidth.

[0070] However, the above single micro-ring optical filter or MZI optical filter scheme cannot meet the demand. Therefore, it is crucial to develop a high-precision reconfigurable rectangular optical filter with excellent performance for the mature application of wireless radio frequency front-end, especially integrated microwave photonic chip system. The representative high-precision reconfigurable rectangular optical filter is mainly based on high-quality factor micro-ring resonator type optical filter and ring assist mach-zehnder interferometer (RAMZI) type optical filter.

[0071] Example based on high-quality factor micro-ring resonator type optical filter: as shown in FIG. 3, it is a schematic diagram of a tunable sub-gigahertz bandwidth microwave photonic filter (MPF) based on high-quality factor micro-ring resonator type. The overall performance of the MPF is relatively balanced. Due to the ultra-high quality factor of 1.14×106 of the micro-ring resonator, a half-width full-width of 170MHz is achieved, and the corresponding rejection ratio of the band-pass filter is 26.5dB. In addition, by manufacturing a micro-heater on the micro-ring, the center frequency of the filter can be continuously tuned in the range of 2.0 to 18.4GHz, and a tuning range of 16.4GHz is achieved, with a maximum power consumption of 14.4mW and a device area of only about 0.05mm2. Overall, the filter based on high-quality factor micro-ring resonator type is difficult to achieve a rejection ratio of 35dB, and the transition band is often more than several times the bandwidth. Although the rejection ratio of this type of filter can be improved to some extent by cascading and other schemes, and the rectangular coefficient can be improved, the free spectral range (FSR) is limited, the resonant frequency alignment between rings is difficult, and the process tolerance is small, so it is difficult to realize.

[0072] An example of RAMZI-type optical filter: As shown in FIG. 4A, it is a high-precision high-rectangular-coefficient filter chip on a low-loss silicon nitride photonic integrated platform, which adopts an optical Nyquist filter function, promotes a Sub-GHz bandwidth and a nearly rectangular passband with an 8% roll-off, and the output spectrum of the filter chip is shown in FIG. 4B (the dashed line and the solid line represent the output spectrum of the two output ports, respectively). Such performance is very promising for high-spectral-efficiency Nyquist wavelength division multiplexing superchannels. The chip provides a simple dual-ring resonator-assisted MZI, which has a chip area of sub-square centimeter due to the high refractive index contrast Si3N4 / SiO2 waveguide, and at the same time shows low wavelength dependence, making the 1550 nm communication band cover more than 160 effective FSRs of 25 GHz. In this structure, its excellent performance depends on the ultra-low-loss Si3N4 photonic platform, which is difficult to achieve in conventional SOI due to the relatively large loss of silicon waveguides. As can be seen from FIG. 4A, the bandwidth of the RAMZI filter is generally greater than 1 GHz, which is difficult to balance the large suppression ratio and narrow band performance. In some designs, special physical properties are applied, such as using the stimulated Brillouin scattering effect of the waveguide, to obtain a bandwidth of less than 1 GHz and a suppression ratio of more than 35 dB to a certain extent, but it cannot meet the needs of wireless communication radio frequency front-end and other scenarios in terms of CMOS compatibility and other aspects, and the process is difficult.

[0073] To solve one or more of the above technical problems, the technical solutions of the embodiments of the present application are provided. It can be understood that the embodiments of the present application can be applied to optical filters, and can also be applied to other various technical fields containing optical filters, such as microwave photonic filters (a kind of microwave filter based on optical technology, which converts microwave signals into optical signals for processing. By modulating the microwave signal onto the light, then processing through the optical device, and finally converting the optical signal into the microwave signal, the filtering function is realized), signal processing systems containing optical filters (such as multi-frequency receiving systems), and the like.

[0074] As shown in FIG. 5, it is a structural schematic diagram of an optical filter 1 provided by the embodiments of the present application, which comprises a first MZI structure 11, a first micro-ring structure 121, a second micro-ring structure 122, and a third micro-ring structure 123.

[0075] The first MZI structure 11 comprises two arms, i.e. a first arm 111 and a second arm 112. The first arm 111 can be an upper arm, and the second arm 112 is a lower arm; or the second arm 112 can be an upper arm, and the first arm 111 is a lower arm. For the convenience of showing, in the figures given in the text, the first arm 111 is taken as a lower arm and the second arm 112 is taken as an upper arm as an example, which is not limited in practice.

[0076] The first MZI structure 11, the first micro-ring structure 121, the second micro-ring structure 122, the third micro-ring structure 123 and the first MZI structure 11 can constitute a three-micro-ring assisted MZI structure. As shown in FIG. 5, the first micro-ring structure 121 is coupled with the first arm 111 of the first MZI structure 11 to form a first micro-ring resonator A; the second micro-ring structure 122 and the third micro-ring structure 123 are both coupled with the second arm 112 of the first MZI structure 11, wherein the second micro-ring structure 122 is coupled with the second arm 112 of the first MZI structure 11 to form a second micro-ring resonator B, and the third micro-ring structure 123 is coupled with the second arm 112 of the first MZI structure 11 to form a third micro-ring resonator C.

[0077] In the embodiment of the present application, the center wavelength of the first micro-ring resonator A is set as the center wavelength of the entire optical filter 1, and the center wavelength (such as λ2) of the second micro-ring resonator B and the center wavelength (such as λ3) of the third micro-ring resonator C are symmetrically distributed on both sides of the center wavelength (such as λ1) of the first micro-ring resonator A, so that the phase difference of ±π can be introduced near the center wavelengths of the two arms of the first MZI structure 11 (i.e. the center wavelength of the entire optical filter 1) to realize coherent cancellation, and the phase difference of 2mπ (m is an integer) is realized at the center wavelength of the entire optical filter 1 to realize coherent addition, so that the output spectrum curve of the entire optical filter 1 is reduced near the center wavelength of the entire optical filter 1, a large amplitude transition band is realized, and the effect of improving the filter rectangular coefficient is improved.

[0078] Specifically, the center wavelength (such as λ2) of the second micro-ring resonator B and the center wavelength (such as λ3) of the third micro-ring resonator C are symmetrically distributed on both sides of the center wavelength (such as λ1) of the first micro-ring resonator A, and the sum of the additional phases of the second micro-ring resonator B and the third micro-ring resonator C needs to be equal to twice the additional phase of the first micro-ring resonator A, that is Of course, in actual application, there may be some errors in the device, so There can be other variations, for example k is an error coefficient introduced.

[0079] It can be understood that the additional phase of the micro-ring resonator refers to the phase generated by the propagation of the light wave in the micro-ring resonator, that is, the difference between the phase of the light wave emitted from the micro-ring resonator and the phase of the light wave incident on the micro-ring resonator.

[0080] As an example, the design process of the embodiments of the present application can be as follows: by referring to the design theory of digital filter, the rectangular digital filter needs to meet the specific zero-pole distribution. Among the common digital filters, the elliptical filter has the smallest transition bandwidth, and has better rectangular coefficient under the same order and ripple. Therefore, first of all, it is necessary to verify in Python whether the three-micro-ring assisted MZI structure can achieve the target and the minimum order required. The scipy.signal library is used in Python to assist in the design, and the specific performance of the required 500MHz band-pass filter (passband frequency, stopband attenuation, cutoff frequency, etc.) is defined to return the minimum order, wherein the passband frequency corresponds to the 13dB bandwidth of the optical filter, the stopband attenuation corresponds to the 35dB out-of-band rejection ratio of the optical filter 1, and the cutoff frequency corresponds to the transition bandwidth of the optical filter 1. Here, the transition bandwidth corresponding to the 500MHz bandwidth is about 1.5GHz. Then, according to the target performance, considering the transmission loss of the waveguide under the existing process is α (dB / cm), the coefficient of the corresponding transmission function is returned through Python. The transmission function is decomposed to obtain the coupling coefficient and the additional phase value of the three micro-rings. Further, the transmittance of the entire filter can be obtained according to the transfer function, which can comply with the following formula:

[0081] wherein, E j is the output light field distribution of the jth micro-ring, k j is the power coupling coefficient of the jth micro-ring, is the additional phase of the jth micro-ring (j=1, 2, 3), is the additional phase introduced by the lower arm of the MZI, L is the circumference of the micro-ring, α is the transmission loss of the micro-ring, and β is the optical propagation constant.

[0082] According to the transmittance curve, the amplitude-frequency response of the filter can be obtained as shown in FIG. 6A, wherein the left graph of FIG. 6A is the phase response, and the right graph is the amplitude response.

[0083] As can be seen from FIG. 6A, through the above scheme, an optical filter response with a target bandwidth of 500MHz, a rejection ratio of 35dB and a transition band of about 1.5GHz can be obtained. Compared with the conventional RAMZI scheme (such as the RAMZI shown in FIG. 4A), the 35dB rejection ratio and the transition band comparable to the bandwidth can be simultaneously achieved, and in particular, the quality factor of the single ring is reduced by nearly half, which relatively greatly reduces the process implementation difficulty.

[0084] As shown in FIG. 6B, a performance comparison diagram of the optical filter 1 provided by the embodiment of the present application and a conventional RAMZI optical filter (a double-ring resonator auxiliary MZI as shown in FIG. 4A) is provided. The filter bandwidth of the conventional RAMZI optical filter is generally greater than 1 GHz, and no special optimization design is made for the transition band; while the optical filter 1 provided by the embodiment of the present application can realize a large amplitude compression of the transition band (the transition bandwidth from -3 dB to -35 dB is about 3 times of the 3 dB bandwidth, far lower than 10 times of the conventional RMZI), while the narrow bandwidth and high suppression ratio can be taken into account.

[0085] It can be understood that the micro-ring filter belongs to an infinite impulse response (IIR) type optical filter, and the MZI filter belongs to a finite impulse response (FIR) type optical filter, and thus the optical filter 1 provided by the embodiment of the present application can belong to a hybrid type optical filter of IIR and FIR.

[0086] In a possible design, the coupling coefficients of at least one of the first micro-ring structure 121, the second micro-ring structure 122, the third micro-ring structure 123 and the first MZI structure 11 are adjustable. By adjusting the coupling coefficients of at least one of the first micro-ring structure 121, the second micro-ring structure 122, the third micro-ring structure 123 and the first MZI structure 11, the output bandwidth of the optical filter 1 can be adjusted.

[0087] In a specific example, as shown in FIG. 7A, in the coupling region of the first micro-ring structure 121 and the first MZI structure 11, the first micro-ring structure 121 and the first arm form a first sub-MZI structure 113a with adjustable coupling coefficient; in the coupling region of the second micro-ring structure 122 and the first MZI structure 11, the second micro-ring structure 122 and the first arm form a second sub-MZI structure 113b with adjustable coupling coefficient; and in the coupling region of the third micro-ring structure 123 and the first MZI structure 11, the third micro-ring structure 123 and the first arm form a third sub-MZI structure 113c with adjustable coupling coefficient. By adjusting the coupling coefficient of at least one of the first sub-MZI structure 113a, the second sub-MZI structure 113b or the third sub-MZI structure 113c, the bandwidth of the optical filter 1 can be adjusted.

[0088] For example, as shown in FIG. 7A, k1, k2, k3 represent the coupling coefficients of the first sub-MZI structure 113a, the second sub-MZI structure 113b or the third sub-MZI structure 113c respectively, and each sub-MZI structure is provided with an electrode, VDD-1, VDD-2, VDD-3. By adjusting the working parameters (such as voltage) of the electrode, the coupling coefficient of the sub-MZI structure where the electrode is located can be adjusted. It can be understood that the electrode is represented by VDD in FIG. 7A, which is not limited in practice. In FIG. 7A, three coupling structures are all sub-MZI structures coupled as an example, which is not limited in practice.

[0089] For example, the cases of different coupling coefficients near the wavelength of 1550 nm in the optical communication band are simulated, and the simulation results are shown in FIG. 7B: the operating bandwidth at the center wavelength can be changed between 250 MHz and 875 MHz, and the filter shape and suppression ratio do not deteriorate significantly.

[0090] In a possible design, at least one of the first micro-ring structure 121, the second micro-ring structure 122 or the third micro-ring structure 123 is provided with an electrode, and the electrode on the micro-ring structure is used to tune the additional phase of the micro-ring resonator corresponding to the micro-ring structure. The center wavelength of the optical filter 1 is tuned by tuning the additional phase of the micro-ring resonator corresponding to the at least one micro-ring structure.

[0091] In a specific example, as shown in FIG. 8A, each of the first micro-ring structure 121, the second micro-ring structure 122 or the third micro-ring structure 123 is provided with an electrode, such as VDD-4, VDD-5, VDD-6. By tuning the working parameters (such as voltage) of the electrode on each micro-ring structure, the additional phase corresponding to the micro-ring structure can be tuned, such as

[0092] It can be understood that the speed of light = center wavelength x center frequency, so in some embodiments, the center wavelength can be replaced by the center frequency.

[0093] For example, the cases of different additional phases near the wavelength of 1550 nm in the optical communication band are simulated, and the simulation results are shown in FIG. 8B: the maximum tunable range of the center frequency is 100 GHz, which is limited by the circumference of the micro-ring in the filter and has met the application requirements of most wireless base station radio frequency front-end systems.

[0094] It can be understood that the schemes shown in FIG. 8A and FIG. 7A above can be implemented respectively, or can be combined for implementation. When combined for implementation, for example, as shown in FIG. 8C, by tuning the coupling coefficient of at least one of the first sub-MZI structure 113a, the second sub-MZI structure 113b or the third sub-MZI structure 113c, the bandwidth of the optical filter 1 can be tuned; by tuning the additional phase of the corresponding micro-ring resonator of at least one of the first micro-ring structure 121, the second micro-ring structure 122 or the third micro-ring structure 123, the center wavelength of the optical filter 1 can be tuned.

[0095] Through the above design, the center wavelength of the optical filter 1 can be tuned.

[0096] In a possible design, a phase shifter 114 is arranged on the first arm and / or the second arm of the first MZI structure 11. By tuning the additional phase of the phase shifter 114, the optical filter 1 can realize switching between bandpass and bandstop. The value of the overall tuned additional phase is ±Nπ, where N is a natural number. The phase shifter 114 can be a thermal phase shifter (such as an electrode), an electro-optic phase shifter, etc., without limitation.

[0097] For example, referring to FIG. 9A, a phase shifter 114 is arranged on the first arm of the first MZI structure 11, and the value of the additional phase of the phase shifter 114 that can be tuned is ±Nπ, where N is a natural number. By arranging the phase shifter on the first arm with fewer micro-ring structures, the space utilization can be improved.

[0098] As shown in FIG. 9B, a schematic diagram of switching between bandpass and bandstop responses under the same output port. By changing or switching the additional phase of the lower arm of the MZI The filtering response can be switched between bandpass and bandstop. For example, When it is bandpass, When it is bandstop. At the same time, the bandwidth of the bandstop response is smaller than that of the bandpass, and has a narrower transition bandwidth under the same condition. This means that in the case of suppressing the interference signal, there will be no excessive impact on the adjacent useful signal. As shown in FIG. 9C, a schematic diagram of bandpass filtering and bandstop filtering, the left diagram in FIG. 9C is bandstop filtering, which can effectively suppress the stray light, and the right diagram is bandpass filtering, which can realize multi-channel frequency selection.

[0099] Through the above design, the switching between bandpass and bandstop of the optical filter 1 can be realized, and the bandpass / bandstop reconfigurability of the optical filter 1 is realized.

[0100] In a possible design, the waveguide of at least one of the first micro-ring structure 121, the second micro-ring structure 122 or the third micro-ring structure 123 can be a multi-mode wide waveguide. The multi-mode wide waveguide refers to that the transmission mode of the waveguide has multiple modes.

[0101] In a specific implementation, the key to realizing low loss by the multi-mode wide waveguide micro-ring is to design a low-loss curved waveguide, while ensuring compact structure to obtain a large FSR. In one possible example, the curved portion of at least one of the first micro-ring structure 121, the second micro-ring structure 122, or the third micro-ring structure 123 can adopt Euler bending or Bezier bending. For example, FIG. 10 schematically shows that the curved portion of the second micro-ring structure 122 in the extension direction of the two arms of the first MZI structure adopts Euler bending or Bezier bending.

[0102] The above design uses a multi-mode wide waveguide to design an ultra-low loss micro-ring structure, which reduces the sensitivity of micro-ring structure transmission loss to waveguide sidewall roughness, makes it easier to achieve narrowband characteristics, and increases the robustness of processing.

[0103] As shown in FIG. 11, the optical filter 1 can further include a second MZI structure 13; two output ends of the second MZI structure 13 are respectively connected to two input ends of the first MZI structure 11; and an electrode is arranged on the first arm 131 and / or the second arm 132 of the second MZI structure 13. The electrode arranged on the first arm and / or the second arm of the second MZI structure 13 is used to tune the power difference between the first arm and the second arm of the second MZI structure 13. By tuning the power difference between the first arm and the second arm of the second MZI structure 13, the power difference 13 between the first arm and the second arm of the first MZI structure 11 can be tuned. For example, the first arm 131 of the second MZI structure 13 is in communication with the first arm 111 of the first MZI structure 11, the second arm 132 of the second MZI structure 13 is in communication with the second arm 112 of the first MZI structure 11, and an electrode is arranged on the first arm 131 and the second arm 132 of the second MZI structure 13.

[0104] By tuning the power difference between the first arm and the second arm of the second MZI structure 13, the power difference between the first arm and the second arm of the first MZI structure 11 can be made as close as possible, such as the power difference 13 between the first arm and the second arm of the first MZI structure 11 being less than or equal to a preset value.

[0105] In this way, the problem of power asymmetry of the two arms of the first MZI structure 11 due to the difference in introduced insertion loss and the resulting filter performance degradation can be improved or avoided.

[0106] In one possible design, the two arms (i.e., the first arm 111 and the second arm 112) of the first MZI structure 11 can be implemented using a multimode wide waveguide. As shown in FIG. 12, by introducing a multimode wide waveguide design on the two arms of the first MZI structure 11, the normalized phase noise of the first MZI structure 11 is 2 orders of magnitude lower than that of a conventional single-mode waveguide design. The low random phase noise means that the first MZI structure 11 has greater process tolerance, is less sensitive to processing errors, and has lower insertion loss. As shown in Table 1, this is an example of a comparison of the phase noise of the first MZI structure 11 and a conventional MZI structure:

[0107] Table 1. Comparison of phase noise of the first MZI structure 11 and a conventional MZI structure

[0108] Of course, in addition to the first MZI structure 11, the two arms of other MZI structures (such as the second MZI structure 13, the first sub-MZI structure 113a, the second sub-MZI structure 113b, the third sub-MZI structure 113c, etc.) in the embodiments of the present application can also be implemented using a multimode wide waveguide.

[0109] The conventional RAMZI optical filter is not particularly designed for process implementation robustness, and is mostly limited to a specific photonic integrated platform, such as ultra-low-loss silicon nitride (SiN). However, in the optical filter 1 of the embodiments of the present application, a large-tolerance design is introduced on the two arms of the MZI, making it easier for the device performance to be implemented through a CMOS standard flow process, not just limited to low-loss silicon nitride and thin-film lithium niobate platforms, but also applicable to standard silicon-on-insulator platforms.

[0110] In one possible design, more microrings can also be coupled to the first MZI structure 11. For example, as shown in FIG. 13, the optical filter 1 further includes: a fourth microring structure 124 coupled to the second arm to form a fourth microring resonator D; and a fifth microring structure 125 coupled to the second arm to form a fifth microring resonator E; wherein the center wavelength of the fourth microring resonator D is aligned (i.e., the same or close) to the center wavelength of the second microring resonator B, and the center wavelength of the fifth microring resonator E is aligned (i.e., the same or close) to the center wavelength of the third microring resonator C. For example, the additional phase of the fourth microring resonator D the additional phase of the second microring resonator B satisfies: n is a natural number; the additional phase of the fifth microring resonator E the additional phase of the third microring resonator C satisfies: n is a natural number. In this way, the suppression ratio of the optical filter 1 can be further improved.

[0111] It can be understood that the above-mentioned implementation manners can be implemented separately or in combination, without limitation.

[0112] Based on the same technical concept, the embodiment of the present application also provides a filtering method, which comprises: filtering an optical signal using the optical filter 1.

[0113] It can be understood that the optical filter 1 provided by the embodiment of the present application can be applied to various filtering scenarios, and one possible example is listed below.

[0114] Referring to FIG. 14, the embodiment of the present application provides a multi-frequency receiving system, which comprises a signal path 2, a carrier path 3, a combiner 4, and the optical filter 1 as described above; the signal path 2 is configured to convert antenna signals of multiple frequency bands from an electrical domain to an optical domain to obtain optical domain antenna signals; the carrier path 3 is configured to generate carrier signals; the combiner 4 is configured to combine the optical domain antenna signals and the carrier signals to output a combined signal; and the optical filter 1 is configured to filter the combined signal.

[0115] Referring to FIG. 15, which is a specific structural example of a multi-frequency receiving system, the carrier of the carrier path in the system adopts a post-injection mode (as shown in FIG. 16, which is a schematic diagram of a multi-frequency signal receiving principle based on post-injection of a carrier). In the system, after multi-band signals sm1, sm2, …, smN are received by an antenna array and modulated to an optical domain by array optical modulators 1-M, and after a series of operations such as optical amplitude and phase control in the optical domain, optical domain antenna signals are obtained; at the same time, local oscillator radio frequency signals RF1-RFN are modulated to the optical domain and then combined to serve as post-injection carriers cm1-cmM. After the signals of the signal path and the carrier path are combined, the combined signal is sent to the optical filter 1 for filtering, and the signal output by the optical filter 1 is sent to a photodetector for frequency mixing, so that the received wide-band signals can be modulated on microwave signals with frequencies of sm1, sm2, …, smN. After the microwave signals pass through an electrical domain anti-aliasing filter and an ADC converter, subsequent signal processing is performed.

[0116] It can be understood that in the above-mentioned system, the multi-frequency signals received by the antenna array often contain a lot of spurious signals, high-order harmonic signals generated due to the nonlinearity of the modulator, and amplified spontaneous emission (ASE) noise that may be generated in the optical link. These interference signals will limit the signal-to-noise ratio of the system and ultimately cause the beamforming effect to deteriorate. By adding a high-precision reconfigurable optical rectangular filter, i.e., the filter 1, at the end of the optical link, the interference signals can be largely filtered out, the signal-to-noise ratio of the useful signals can be increased, the complexity and difficulty of subsequent electrical domain signal processing can be reduced, and the system performance can be improved.

[0117] For example, for the multi-band reception of several typical telecommunication spectrums, 1.8G, 4.9G, 6.9G, etc., since the optical carrier radio frequency signals to be processed are narrow in bandwidth (e.g., 150MHz-400MHz) and narrow in frequency interval (e.g., 1.5GHz), and there are various nonlinear harmonics, spurs and noise components around the signals, an ultra-narrow filter with a filter bandwidth matching the signal bandwidth is needed to directly extract the characteristic signals in the optical domain while suppressing the interference signals at nearby frequencies, thereby greatly simplifying the subsequent processing process. In the specific implementation, the target parameters of the filter system are simply decomposed, mainly including the band-stop filtering of the strong interference signals less than 300MHz and the band-pass filtering of the narrow-band signals of 400MHz-700MHz. The optical filtering problem in the optical domain can be implemented by the optical filter 1.

[0118] Based on the use of the optical filter 1 to filter the combined signals of the signal path and the carrier path in the multi-frequency receiving system provided by the embodiments of the present application, the interference signals can be effectively filtered out, the signal-to-noise ratio of the useful signals is increased, the complexity and difficulty of the subsequent electrical domain signal processing are reduced, and the performance of the entire system is improved.

[0119] It can be understood that the optical filter 1 can also have other application scenarios in actual applications, and the embodiments of the present application will not be enumerated one by one.

[0120] Based on the same technical concept, the embodiments of the present application also provide a manufacturing method of an optical filter, as shown in FIG. 17, the method includes the following steps:

[0121] S101, coupling the first micro-ring structure with the first arm of the first MZI structure to form a first micro-ring resonator;

[0122] S102, coupling the second micro-ring structure with the second arm of the first MZI structure to form a second micro-ring resonator;

[0123] S103, coupling the third micro-ring structure with the second arm of the first MZI structure to form a third micro-ring resonator.

[0124] The first arm is the upper arm, and the second arm is the lower arm, or the second arm is the upper arm, and the first arm is the lower arm.

[0125] The sum of the additional phases of the second micro-ring resonator and the third micro-ring resonator is equal to twice the additional phase of the first micro-ring resonator; and / or the center wavelengths of the second micro-ring resonator and the third micro-ring resonator are symmetrically distributed on both sides of the center wavelength of the first micro-ring resonator.

[0126] It can be understood that the steps S101, S102 and S103 are not in a specific order.

[0127] More manufacturing details can be referred to the above description of the structure of the optical filter 1, and will not be expanded here.

[0128] The optical filter manufactured by the above method can have a structure of a three-micro-ring assisted MZI (see the structure diagram of the filter 1 in the above description for details). Since the center wavelengths of the two micro-ring resonators are symmetrically distributed on both sides of the center wavelength of the other micro-ring resonator, a phase difference of ±π can be introduced near the center wavelengths of the two arms of the first MZI structure to realize coherent cancellation, and a phase difference of 2mπ (m is an integer) can be introduced at the center wavelength of the entire optical filter to realize coherent addition, so that the output spectrum curve of the entire optical filter is reduced near the center wavelength of the entire optical filter, a large amplitude transition band is compressed, the suppression ratio is improved, and the effect of the filter rectangular coefficient is improved.

[0129] Based on the same technical concept, the embodiment of the present application also provides a control method applied to a controller. The controller can be any device with control capability, such as a host computer, a field programmable gate array (FPGA), a single-chip microcomputer (such as TSM32), or a logic circuit. The controller forms a dynamic closed-loop control system by acquiring the optical signal output by the optical filter and feeding back the control electrical signal to the electrode on the optical filter. For the specific structure of the optical filter, refer to the description of the optical filter 1 in the above description, which will not be expanded here.

[0130] As shown in FIG. 18, the control method can include:

[0131] S1801, acquiring an optical signal output by an optical filter;

[0132] S1802, tuning the working parameter of at least one device in the optical filter according to the optical signal output by the optical filter, so that the parameter of the optical signal output by the optical filter reaches or approaches the target parameter.

[0133] For example, the target parameter includes a target bandwidth. The controller can tune the coupling coefficient of at least one of the first sub-MZI structure, the second sub-MZI structure, or the third sub-MZI structure according to the optical signal output by the optical filter, so that the bandwidth of the optical signal output by the optical filter reaches or approaches the target bandwidth.

[0134] For example, the target parameter includes a target center wavelength. The controller can tune the additional phase of the corresponding micro-ring resonator of at least one micro-ring structure according to the optical signal output by the optical filter, so that the center wavelength of the optical signal output by the optical filter reaches or approaches the target center wavelength.

[0135] For example, the controller can also tune the additional phase of the phase shifter such that the optical filter implements switching between bandpass and bandstop, wherein the value of the tuned additional phase is ±Nπ, N being a natural number.

[0136] For example, the controller can also tune the power difference between the first arm and the second arm of the second MZI structure according to the optical signal output by the optical filter, to tune the power difference between the first arm and the second arm of the first MZI structure, so that the power difference between the first arm and the second arm of the first MZI structure is less than or equal to a preset value.

[0137] Of course, the above are only some examples, and the actual control method is not limited thereto.

[0138] Based on the same technical concept, the embodiments of the present application also provide a computer readable storage medium for storing instructions, when the instructions are executed, the control method as shown in FIG. 18 is implemented.

[0139] Based on the same technical concept, the embodiments of the present application also provide a computer program product containing instructions, the computer program product stores instructions, when it runs on a computer, the computer executes the control method as shown in FIG. 18.

[0140] It can be understood that the above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art can make various modifications and changes to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and changes of the present application fall within the scope of the claims of the present application and the equivalent technology thereof, the present application also intends to include these modifications and changes.

Claims

1. An optical filter, characterized by, Comprise: A first Mach-Zehnder interferometer (MZI) structure, a first micro-ring structure, a second micro-ring structure, a third micro-ring structure; the first MZI structure comprises a first arm and a second arm; the first arm is an upper arm, and the second arm is a lower arm, or the second arm is an upper arm, and the first arm is a lower arm; The first micro-ring structure is coupled with the first arm to form a first micro-ring resonator; the second micro-ring structure is coupled with the second arm to form a second micro-ring resonator; The third micro-ring structure is coupled with the second arm to form a third micro-ring resonator; Wherein, the sum of the additional phases of the second micro-ring resonator and the third micro-ring resonator is equal to twice the additional phase of the first micro-ring resonator; and / or, the center wavelengths of the second micro-ring resonator and the third micro-ring resonator are symmetrically distributed on both sides of the center wavelength of the first micro-ring resonator.

2. The optical filter of claim 1, wherein, Also comprise: A fourth micro-ring structure coupled with the second arm to form a fourth micro-ring resonator; A fifth micro-ring structure coupled with the second arm to form a fifth micro-ring resonator; Wherein, the center wavelength of the fourth micro-ring resonator is aligned with the center wavelength of the second micro-ring resonator, and the center wavelength of the fifth micro-ring resonator is aligned with the center wavelength of the third micro-ring resonator.

3. The optical filter of claim 1 or 2, wherein In the coupling region of the first micro-ring structure and the first MZI structure, the first micro-ring structure and the first arm constitute a first sub-MZI structure with adjustable coupling coefficient; In the coupling region of the second micro-ring structure and the first MZI structure, the second micro-ring structure and the first arm constitute a second sub-MZI structure with adjustable coupling coefficient; In the coupling region of the third micro-ring structure and the first MZI structure, the third micro-ring structure and the first arm constitute a third sub-MZI structure with adjustable coupling coefficient; By tuning the coupling coefficient of at least one of the first sub-MZI structure, the second sub-MZI structure or the third sub-MZI structure, the bandwidth of the optical filter is tuned.

4. The optical filter of any one of claims 1-3, wherein, At least one of the first micro-ring structure, the second micro-ring structure or the third micro-ring structure is provided with an electrode, and the electrode on the micro-ring structure is used to tune the additional phase of the corresponding micro-ring resonator of the micro-ring structure; By tuning the additional phase of the corresponding micro-ring resonator of the at least one micro-ring structure, the center wavelength of the optical filter is tuned.

5. The optical filter of any one of claims 1-4, wherein, A phase shifter is arranged on the first arm or the second arm; By tuning the additional phase of the phase shifter, the optical filter realizes the switching of bandpass and bandstop, and the value of the tuned additional phase is ±Nπ, where N is a natural number.

6. The optical filter of claim 5, wherein, The phase shifter is arranged on the first arm.

7. The optical filter of any one of claims 1-6, wherein, Also comprise a second MZI structure; two output ends of the second MZI structure are connected with two input ends of the first MZI structure respectively; an electrode is arranged on a first arm and / or a second arm of the second MZI structure, and the electrode arranged on the first arm and / or the second arm of the second MZI structure is used for tuning a power difference between the first arm and the second arm of the second MZI structure; by tuning the power difference between the first arm and the second arm of the second MZI structure, the power difference between the first arm and the second arm of the first MZI structure is tuned, and the power difference between the first arm and the second arm of the first MZI structure is less than or equal to a preset value.

8. The optical filter of any one of claims 1-6, wherein, The waveguide of at least one of the first micro-ring structure, the second micro-ring structure or the third micro-ring structure is a multimode wide waveguide.

9. The optical filter of any one of claims 1-8, wherein, The bending part of at least one of the first micro-ring structure, the second micro-ring structure or the third micro-ring structure adopts Euler bending or Bezier bending.

10. A multi-frequency receiving system, characterized by The optical filter comprises a signal path, a carrier path, a combiner and the optical filter according to any one of claims 1-9. The signal path is used for converting antenna signals of multiple frequency bands from an electrical domain to an optical domain to obtain optical domain antenna signals. The carrier path is used for generating a carrier signal. The combiner is used for combining the optical domain antenna signals and the carrier signal to output a combined signal. The optical filter is used for filtering the combined signal.

11. A method of manufacturing an optical filter, characterized by, The method comprises: coupling a first micro-ring structure with a first arm of a first mach-zehnder interferometer (MZI) structure to form a first micro-ring resonator; coupling a second micro-ring structure with a second arm of the first MZI structure to form a second micro-ring resonator; coupling a third micro-ring structure with the second arm of the first MZI structure to form a third micro-ring resonator; wherein the first arm is an upper arm and the second arm is a lower arm, or the second arm is an upper arm and the first arm is a lower arm; wherein a sum of additional phases of the second micro-ring resonator and the third micro-ring resonator is equal to twice an additional phase of the first micro-ring resonator; and / or, a center wavelength of the second micro-ring resonator and a center wavelength of the third micro-ring resonator are symmetrically distributed on two sides of a center wavelength of the first micro-ring resonator.

12. A filtering method, characterized by, The optical filter according to any one of claims 1-9 is used for filtering an optical signal.

13. A control method characterized by, The method is applied to a controller, and the method comprises: obtaining an optical signal output by an optical filter; tuning a working parameter of at least one device in the optical filter according to the optical signal output by the optical filter, so that a parameter of the optical signal output by the optical filter reaches or approaches a target parameter; and obtaining an optical signal output by an optical filter; The optical filter comprises a first MZI structure, a first micro-ring structure, a second micro-ring structure and a third micro-ring structure. The first MZI structure comprises a first arm and a second arm. The first arm is an upper arm, and the second arm is a lower arm, or the second arm is an upper arm, and the first arm is a lower arm. The first micro-ring structure is coupled with the first arm to form a first micro-ring resonator. The second micro-ring structure is coupled with the second arm to form a second micro-ring resonator. The third micro-ring structure is coupled with the second arm to form a third micro-ring resonator. The sum of the additional phases of the second micro-ring resonator and the third micro-ring resonator is equal to twice the additional phase of the first micro-ring resonator. The center wavelength of the second micro-ring resonator and the center wavelength of the third micro-ring resonator are symmetrically distributed on both sides of the center wavelength of the first micro-ring resonator.

14. The method of claim 13, wherein, In the coupling region of the first micro-ring structure and the first MZI structure, the first micro-ring structure and the first arm form a first sub-MZI structure with adjustable coupling coefficient. In the coupling region of the second micro-ring structure and the first MZI structure, the second micro-ring structure and the first arm form a second sub-MZI structure with adjustable coupling coefficient. In the coupling region of the third micro-ring structure and the first MZI structure, the third micro-ring structure and the first arm form a third sub-MZI structure with adjustable coupling coefficient. The working parameters of at least one device in the optical filter are tuned according to the optical signal output by the optical filter, including: The coupling coefficient of at least one of the first sub-MZI structure, the second sub-MZI structure or the third sub-MZI structure is tuned according to the optical signal output by the optical filter, so that the bandwidth of the optical signal output by the optical filter reaches or approaches the target bandwidth.

15. The method of claim 13 or 14, wherein, At least one of the first micro-ring structure, the second micro-ring structure or the third micro-ring structure is provided with an electrode, and the electrode on the micro-ring structure is used to tune the additional phase of the corresponding micro-ring resonator of the micro-ring structure. The working parameters of at least one device in the optical filter are tuned according to the optical signal output by the optical filter, including: The additional phase of the corresponding micro-ring resonator of the at least one micro-ring structure is tuned according to the optical signal output by the optical filter, so that the center wavelength of the optical signal output by the optical filter reaches or approaches the target center wavelength.

16. The method according to any one of claims 13 to 15, wherein, A phase shifter is arranged on the first arm or the second arm. The working parameters of at least one device in the optical filter are tuned according to the optical signal output by the optical filter, including: The additional phase of the phase shifter is tuned so that the optical filter realizes the switching of bandpass and bandstop, and the value of the tuned additional phase is ±Nπ, where N is a natural number.

17. The method of any one of claims 13-16, wherein, The optical filter further comprises a second MZI structure; two output ends of the second MZI structure are respectively connected with two input ends of the first MZI structure; an electrode is arranged on a first arm and / or a second arm of the second MZI structure, and the electrode arranged on the first arm and / or the second arm of the second MZI structure is used for tuning a power difference between the first arm and the second arm of the second MZI structure; The working parameters of at least one device in the optical filter are tuned according to the optical signal output by the optical filter, comprising: The power difference between the first arm and the second arm of the second MZI structure is tuned according to the optical signal output by the optical filter, so as to tune the power difference between the first arm and the second arm of the first MZI structure, so that the power difference between the first arm and the second arm of the first MZI structure is less than or equal to a preset value.

18. A computer-readable storage medium, characterized in that, The readable storage medium is used for storing instructions, when the instructions are executed, the method as claimed in any one of claims 13-17 is realized.

19. A computer program product comprising instructions, characterized in that, The computer program product stores instructions, when the instructions are executed on the computer, the computer executes the method as claimed in any one of claims 13-17.

Images