An adjustable time-domain sampling filter and a computational spectrometer

Abstract

This invention discloses an adjustable time-domain sampling filter and a computational spectrometer, relating to the technical fields of filters and computational spectrometers. The adjustable time-domain sampling filter includes an optical input port, an optical output port group, and a spectral perturbation structure. The spectral perturbation structure includes multiple cascaded active tunable spectral perturbation units. Each active tunable spectral perturbation unit includes at least a first active tunable spectral perturbation unit and a second active tunable spectral perturbation unit of different types. The multiple cascaded active tunable spectral perturbation units are formed by alternating cascades of the first and second active tunable spectral perturbation units. Each active tunable spectral perturbation unit is equipped with a phase modulator, which can improve the randomness of the spectral response function.

Description

Technical Field

[0001] This invention relates to the field of filters and computational spectrometers, specifically to an adjustable time-domain sampling filter and a computational spectrometer. Background Technology

[0002] The basic principle of computational (reconstruction) spectrometers is to input the unknown spectrum into several pre-calibrated sampling filters (either non-modulotable or modulotable), then use photodetectors to measure the signal intensity after filtering each filter, and finally use relevant algorithms to inversely solve for the input spectrum. Mathematically, this process can be described as follows: Assume a computational spectrometer has M filtered sampling channels, where the spectral response function of each channel is T. i (λ)(i=1,2,...,M), the output of the photodetector is:

[0003] I i =∫T i (λ)Φ(λ)dλ

[0004] Multiple response functions can be represented as a single perturbation characteristic matrix (transmission characteristic matrix), and multiple photodetector results can also be represented as a column vector:

[0005] I M×1 =T M×N Φ N×1

[0006] Where N is the number of wavelength pixels.

[0007] Given column vector I M×1 and transmission characteristic matrix T M×N In this case, the above formula is an underdetermined system of equations. Mathematical algorithms such as convex optimization, greedy algorithms, or machine learning are used to solve this system of equations in reverse, reconstructing the input spectrum Φ(λ), thereby achieving the purpose of spectral detection.

[0008] To achieve good reconstruction results, the perturbation characteristic matrix T_(M×N) needs to satisfy the requirement that the spectral response function of each row, i.e., each channel, is as random as possible. Existing computational spectrometers typically employ cascaded multiple identical structures for perturbation, such as cascaded Mach-Zehnder interferometers, cascaded microring resonators, cascaded grating structures, fiber arrays, etc. The randomness of the spectral response function can be improved by adjusting the structural parameters of each structure individually or through modulation. However, the inventors discovered that the randomness of the spectral response function in computational spectrometers composed of such cascaded or arranged structures is limited. Summary of the Invention

[0009] This invention aims to address, to a certain extent, one of the technical problems in related technologies. To this end, this invention provides an adjustable time-domain sampling filter and a computational spectrometer, which can improve the randomness of the spectral response function.

[0010] To achieve the above objectives, the present invention adopts the following technical solution in the first aspect:

[0011] An adjustable time-domain sampling filter includes an optical input port, an optical output port group, and a spectral perturbation structure. The optical output port group includes at least one optical output port. The spectral perturbation structure includes multiple cascaded active tunable spectral perturbation units. Each active tunable spectral perturbation unit includes at least a first active tunable spectral perturbation unit and a second active tunable spectral perturbation unit of different types. The multiple cascaded active tunable spectral perturbation units are formed by alternating cascades of the first and second active tunable spectral perturbation units. Each active tunable spectral perturbation unit is equipped with a phase modulator. The multiple cascaded active tunable spectral perturbation units are used to receive the input optical signal input through the optical input port and generate different perturbations in time according to the tuning of the phase modulator, so that the optical output port outputs multiple different output optical signals at different times. The different output optical signals have different power distributions in the frequency domain.

[0012] Optionally, the active tunable spectral perturbation unit may be of at least three types: active asymmetric Mach-Zehnder interferometer, microring resonator, and Bragg grating perturbation structure, and the first active tunable spectral perturbation unit and the second active tunable spectral perturbation unit may be at least any two of these three types.

[0013] Optionally, multiple active asymmetric Mach-Zehnder interferometers may be included in the multiple cascaded active tunable spectral perturbation units; there may be an arm length difference between the two tuning arms of the active asymmetric Mach-Zehnder interferometers; and each of the multiple active asymmetric Mach-Zehnder interferometers may have a different arm length difference.

[0014] Optionally, multiple cascaded active tunable spectral perturbation units may include multiple microring resonators; the microrings of the microring resonators have a certain perimeter, and the microrings in the multiple microring resonators have different perimeters.

[0015] Optionally, the multiple cascaded active tunable spectral perturbation units may include multiple Bragg grating perturbation structures, wherein the Bragg gratings in the Bragg grating perturbation structures have grating periods or duty cycles, and the multiple Bragg grating perturbation structures have different grating periods or different duty cycles.

[0016] Optionally, the spectral perturbation structure includes multiple optical path components, which are connected to the optical input port via an optical splitter; each optical path component includes multiple cascaded active tunable spectral perturbation units; the optical output port group includes multiple optical output ports, which correspond one-to-one with each of the multiple optical path components to output different output optical signals.

[0017] Optionally, the spectral perturbation structure includes 2 to 8 cascaded active tunable spectral perturbation units.

[0018] Optionally, the phase modulator has at least two different phase adjustment states.

[0019] Furthermore, in a second aspect, the present invention provides a computational spectrometer, including a light source, a photodetector, and an adjustable time-domain sampling filter as described in the first aspect; the computational spectrometer further includes a signal processing circuit; the light source is used to provide an input optical signal to the adjustable time-domain sampling filter, the input optical signal being transmitted light or reflected light; the photodetector is used to convert the optical power of the output optical signal into a corresponding electrical signal;

[0020] The signal processing circuit is used to generate control signals to tune the phase modulator and to acquire spectral correlation data with the input optical signal based on a plurality of the output optical signals.

[0021] Optionally, it may also include a driving circuit for amplifying the control signal to drive the phase modulator.

[0022] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and accompanying drawings. The preferred embodiments or means of the present invention will be shown in detail in conjunction with the accompanying drawings, but are not intended to limit the technical solutions of the present invention. In addition, each of these features, elements and components appearing in the following text and drawings is a plurality of, and different symbols or numbers are used for convenience of representation, but all represent parts with the same or similar construction or function. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings:

[0024] Figure 1 This is a simplified structural diagram of the adjustable time-domain sampling filter described in one embodiment.

[0025] Figure 2 This is a simplified structural diagram of the tunable time-domain sampling filter described in one embodiment, showing multiple cascaded active tunable spectral perturbation units on its two optical transmission channels.

[0026] Figure 3This is a simplified structural diagram of the adjustable time-domain sampling filter in one embodiment, showing an arrangement in which the first active tunable spectral perturbation unit and the second active tunable spectral perturbation unit are alternately cascaded.

[0027] Figure 4 This is a schematic diagram of the adjustable time-domain sampling filter in one embodiment, showing the active asymmetric Mach-Zehnder interferometer and microring resonator therein.

[0028] Figure 5 To utilize Figure 4 The adjustable time-domain sampling filter in the figure has spectral response functions for 10 channels in the time domain, and the spectral waveforms of 10 different output spectra are shown.

[0029] Figure 6 This is a schematic diagram of the active asymmetric Mach-Zehnder interferometer of the adjustable time-domain sampling filter described in one embodiment.

[0030] Figure 7 This is a schematic diagram of the microring resonator of the adjustable time-domain sampling filter described in one embodiment.

[0031] Figure 8 This is a schematic diagram of the adjustable time-domain sampling filter in one embodiment, showing the Bragg grating perturbation structure and microring resonator therein.

[0032] Figure 9 This is a schematic diagram of the adjustable time-domain sampling filter in one embodiment, showing multiple optical path components therein.

[0033] Figure 10-12 This is a schematic diagram of the structure of the computational spectrometer described in some embodiments.

[0034] Figure 13 This is a schematic diagram of the filter structure of a computational spectrometer composed of four cascaded microring resonators.

[0035] Figure 14 for Figure 13 The filter in the image has spectral response functions for 10 channels in the time domain, and the spectral waveforms of 10 different output spectra are shown.

[0036] Figure 15 This is a schematic diagram of the filter structure of a computational spectrometer composed of four cascaded Mach-Zehnder interferometers.

[0037] Figure 16 for Figure 15 The filter in the image has spectral response functions for 10 channels in the time domain, and the spectral waveforms of 10 different output spectra are shown.

[0038] Among them, 1. Asymmetric Mach-Zehnder interferometer; 12. Tuning arm; 13. First waveguide beam splitter; 14. Second waveguide beam splitter; 2. Micro-ring resonator; 21. Resonant structure; 22. Third waveguide beam splitter; 3. Phase modulator; 4. Bragg grating perturbation structure. Detailed Implementation

[0039] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are intended to explain the present invention and should not be construed as limiting the invention.

[0040] The terms "an embodiment," "example," or "trademark" used in this specification refer to a particular feature, structure, or characteristic described in connection with the embodiment itself that may be included in at least one embodiment disclosed in this patent. The phrase "in an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0041] Existing computational spectrometers typically employ cascaded multiple identical structures for perturbation, such as cascaded Mach-Zehnder interferometers, cascaded microring resonators, cascaded grating structures, fiber arrays, and so on. The inventors discovered that although the randomness of the spectral response function can be improved by adjusting structural parameters or through modulation, the randomness of the spectral response function of such computational spectrometers, composed of cascaded or arranged single structures, is limited because the filters in the spectrometer are cascaded with multiple similar structures (perturbation structures based on the same principle), and the spectral response characteristics of these structures follow the same rules.

[0042] like Figure 13 and Figure 14 The image shows a filter for a computational spectrometer consisting of only four cascaded microring resonators, and the spectral response functions (i.e., spectral waveforms of 10 different output spectra for the same input light signal) of this (microring resonator) filter after tuning, forming 10 channels in the time domain. It can be seen that the spectral response functions still exhibit a certain periodicity, and the waveforms in the three (red) boxes show a high degree of similarity. This further demonstrates that the randomness of the spectral response function of this computational spectrometer (filter) is limited.

[0043] like Figure 15 and 16The diagram illustrates a filter for a computational spectrometer consisting of only four cascaded Mach-Zehnder interferometers. It also shows the spectral response functions (i.e., spectral waveforms of ten different output spectra for the same input light signal) of the 10 channels formed by the tuned Mach-Zehnder interferometer filter in the time domain. A clear periodicity is observed in the spectral response functions. This demonstrates that the randomness of the spectral response function of a filter constructed using only a single cascaded Mach-Zehnder interferometer is also limited.

[0044] To address this, the inventors replaced the original cascaded single-type filter with a hybrid design of multiple different structures, thereby reducing the periodicity of the spectral response function and significantly improving its randomness. This will be illustrated with an example below.

[0045] Example:

[0046] In the first aspect, this embodiment proposes an adjustable time-domain sampling filter that can be applied to a computational reconstruction spectrometer. During use, the randomness of the spectral response of the sampling filter can be improved by tuning, thereby improving the spectral reconstruction effect when using a computational reconstruction spectrometer employing this adjustable time-domain sampling filter.

[0047] like Figure 1 As shown, the tunable time-domain sampling filter includes an optical input port, an optical output port group, and a spectral perturbation structure. The optical input port receives optical signals through an optical waveguide. The spectral perturbation structure receives the input optical signal through the optical input port, perturbs the input optical signal to obtain multiple output optical signals with different optical characteristics, and outputs them through the optical output port group. The tunable time-domain sampling filter is applied in a computational reconstruction spectrometer. Its input optical signal can be the optical signal from a light source, or the transmitted or reflected light from the light source after passing through the analyte. The specific input signal can be determined according to the structure of the computational reconstruction spectrometer and is not limited.

[0048] The optical output port group includes at least one optical output port, and multiple output optical signals can be output from the same optical output port or from different optical output ports. For a single-channel tunable time-domain sampling filter, the optical output port group includes only one optical output port. Spatially, there is only one optical transmission channel (i.e., the transmission path of the optical signal) between the optical input port and the optical output port. For a multi-channel tunable time-domain sampling filter, the optical output port group includes only multiple optical output ports. Spatially, there are multiple optical transmission channels between the optical input port and the multiple optical output ports. The input optical signal from the optical input port can be split into multiple optical transmission channels by a beam splitter, and the number of optical transmission channels is determined by the number of optical output ports in the optical output port group. For example... Figure 2 The adjustable time-domain sampling filter has two optical channels. The number of optical transmission channels in the adjustable time-domain sampling filter can be flexibly set by those skilled in the art according to the actual situation, without limitation.

[0049] The perturbation processing here refers to the alteration of some optical characteristics of the input optical signal during transmission (through an optical transmission channel) by passing through a spectral perturbation structure and changing it according to a preset spectral response function, thereby changing the power distribution of the output optical signal in the frequency domain. The spectral perturbation structure, by setting spectral perturbation units with adjustable spectral response functions in the time domain, allows different output optical signals to have different power distributions in the frequency domain, meaning each output optical signal is unique. The spectral response function can be achieved by designing different parameters of the spectral perturbation structure.

[0050] The perturbation process can be performed once or multiple times. By setting parameters during multiple perturbations, each perturbation produces a different output. As the number of perturbations (under different parameter settings, including the order of perturbations) accumulates, the power distribution of each output optical signal in the frequency domain exhibits high-intensity randomness, and the multiple output optical signals also exhibit high independence from each other. Furthermore, to ensure that the spectral perturbation structure can alter the power distribution of the output optical signal across its entire frequency domain (bandwidth), the bandwidth of the spectral perturbation structure is greater than or equal to the entire bandwidth of the optical signal.

[0051] This embodiment uses a single-channel tunable time-domain sampling filter as an example. The spectral perturbation structure includes multiple cascaded active tunable spectral perturbation units, for example, 2-8 stages. These multiple cascaded active tunable spectral perturbation units are disposed on the optical transmission channel between the optical input port and the optical output port. Each active tunable spectral perturbation unit includes at least a first active tunable spectral perturbation unit and a second active tunable spectral perturbation unit of different types. The multiple cascaded active tunable spectral perturbation units are formed by alternating cascades of first and second active tunable spectral perturbation units.

[0052] It should be noted that the alternating cascade arrangement refers to the alternating arrangement of two or more different types of active tunable spectral perturbation units, but it does not require that active tunable spectral perturbation units of the same type cannot be adjacent. For example Figure 1 The first and second active tunable spectral perturbation units are arranged in a 1-2-2-2 configuration, for example... Figure 3 The first and second active tunable spectral perturbation units are arranged in a 1-2-1-2-2 configuration, for example... Figure 2In one optical channel, the first active tunable spectral perturbation unit and the second active tunable spectral perturbation unit are arranged in an alternating pattern of one-two-one-two.

[0053] When there are three or more different types of active tunable spectral perturbation units, those skilled in the art can insert one or more third active tunable spectral perturbation units (or fourth active tunable spectral perturbation units, etc.) into any two active tunable spectral perturbation units (referring to the first active tunable spectral perturbation unit and / or the second active tunable spectral perturbation unit) among the above two different types of active tunable spectral perturbation units. The first active tunable spectral perturbation unit, the second active tunable spectral perturbation unit, and the third active tunable spectral perturbation unit belong to three different types.

[0054] Each of the active tunable spectral perturbation units is equipped with a phase modulator. Each phase modulator has at least two different phase adjustment states. The number of phase adjustment states is generally related to the number of cascaded active tunable spectral perturbation units. The product of the number of phase adjustment states of the phase modulator and the number of active tunable spectral perturbation units should satisfy the number of underdetermined equations required by the computational spectrometer when constructing the spectral reconstruction matrix. Those skilled in the art can flexibly set this according to actual conditions without limitation. Multiple cascaded active tunable spectral perturbation units are used to receive the input optical signal through the optical input port and generate different perturbations in time sequence according to the tuning of the phase modulator, so that the optical output port outputs multiple different output optical signals at different times. The different output optical signals have different power distributions in the frequency domain.

[0055] For example, in three cascaded active tunable spectral perturbation units, each active tunable spectral perturbation unit's phase modulator has three different phase adjustment states, which can enable the optical output port of the spectral perturbation structure to output 27 different output optical signals.

[0056] Multiple cascaded active tunable spectral perturbation units generate different perturbations in timing according to the tuning of the control signal, so that the optical output port outputs multiple different output optical signals at different times. The active tunable spectral perturbation units include at least three types: active asymmetric Mach-Zehnder interferometer, microring resonator, and Bragg grating perturbation structure, and the first and second active tunable spectral perturbation units are at least any two of these three types.

[0057] For example, such as Figure 4The single-channel tunable time-domain sampling filter shown employs four cascaded active tunable spectral perturbation units in its spectral perturbation structure. These active tunable spectral perturbation units include two types: active asymmetric Mach-Zehnder interferometers and microring resonators. The first stage is the first active tunable spectral perturbation unit, and stages 2-4 are all second active tunable spectral perturbation units.

[0058] Specifically, the first active tunable spectral perturbation unit is a Mach-Zehnder interferometer, the second active tunable spectral perturbation unit is a microring resonator, and the microring resonators of the 2nd to 4th stages are set with different (optical) parameters.

[0059] This tunable time-domain sampling filter can be viewed as a filter based on an existing micro-ring resonator structure, in which an active asymmetric Mach-Zehnder interferometer is used to replace one of the (first-stage) pure micro-ring resonators, thereby changing the original multi-stage cascaded single-type active tunable spectral perturbation units into a tunable time-domain sampling filter with a hybrid (spectral perturbation) structure.

[0060] like Figure 5 The image shows the spectral response functions (i.e., the spectral waveforms of 10 different output spectra for the same input optical signal) of the tunable time-domain sampling filter with this hybrid (spectral perturbation) structure applied to a computational spectrometer. Figure 5 Separately and Figure 14 , Figure 16 By comparison, it can be seen that... Figure 5 The periodicity of the spectral response function is significantly reduced, meaning that the waveform has no obvious periodicity. In other words, compared with existing single-structure filters, the spectral response function of this hybrid structure filter has higher randomness.

[0061] Specifically, such as Figure 4 As shown, the first active tunable spectral perturbation unit is an active asymmetric Mach-Zehnder interferometer 1, and the second active tunable spectral perturbation unit is a microring resonator.

[0062] The active asymmetric Mach-Zehnder interferometer has two tuning arms 12 of unequal length and a phase modulator 3 disposed on at least one of the tuning arms 12. The asymmetric Mach-Zehnder interferometer forms an asymmetric structure through the two tuning arms of unequal length. The phase modulator actively tunes the phase of the optical signal entering the tuning arm according to the control signal to adjust the power distribution of the output optical signal in the frequency domain.

[0063] It should be noted that there is a difference in arm length between the two tuning arms of the active asymmetric Mach-Zehnder interferometer, and if there are multiple active asymmetric Mach-Zehnder interferometers, each of the multiple active asymmetric Mach-Zehnder interferometers has a different difference in arm length. For example, the difference in arm length between two interference arms in three (adjacent or non-adjacent) asymmetric Mach-Zehnder interferometers can be set to 300µm, 500µm, and 800µm respectively to improve the effect of random perturbation.

[0064] More specifically, such as Figure 6 As shown, the active asymmetric Mach-Zehnder interferometer includes a first waveguide beam splitter 13 disposed on the input side of the tuning arm and a second waveguide beam splitter 14 disposed on the output side of the tuning arm. The first waveguide beam splitter 13 is used to split the input optical signal into two paths according to a preset splitting ratio and input them into the two tuning arms 12 respectively. The second waveguide beam splitter 14 is used to combine the output light of the two tuning arms 12 (also known as interferometer arms) to produce optical interference (i.e., to form a disturbance).

[0065] The first waveguide splitter 13 has two input ports. During use, the input optical signal can be selected to enter the tuning arm through one of these input ports. The second waveguide splitter 14 has two output ports. The input of the next-stage active tunable spectral perturbation unit can be connected to one of the output ports of the second waveguide splitter 14.

[0066] The splitting ratio of the first waveguide splitter 13 and the second waveguide splitter 14 is between 0.05 and 0.5. The splitting ratios of the first waveguide splitter 13 and the second waveguide splitter 14 located in different Mach-Zehnder interferometers can be the same or different. The first and second waveguide splitters can be implemented in various ways, such as multimode interferometers, directional couplers, or Y-splitters, without limitation.

[0067] If two or more active asymmetric Mach-Zehnder interferometers exist, in two adjacent asymmetric Mach-Zehnder interferometers, the output light of the second waveguide splitter in the previous stage is entirely used as the input light of the first waveguide splitter in the next stage. In this case, there are no restrictions on the splitting ratio of the second waveguide splitter in the previous stage and the first waveguide splitter in the next stage. It should be noted that in two adjacent asymmetric Mach-Zehnder interferometers, the second waveguide splitter in the preceding asymmetric Mach-Zehnder interferometer and the first waveguide splitter in the following asymmetric Mach-Zehnder interferometer can reuse the same waveguide splitter.

[0068] like Figure 4 and Figure 7 As shown, the second active tunable spectral perturbation unit is a microring resonator 2 with a resonant structure 21. The resonant structure of the microring resonator includes a phase modulator 3. The phase modulator tunes the phase of the optical signal entering the resonant structure according to the control signal, thereby adjusting the power distribution of the output optical signal in the frequency domain. The resonant structure of the microring resonator is a microring of a certain size. If there are multiple microring resonators, the microrings of the multiple microring resonators will each have a different perimeter.

[0069] Specifically, the microring resonator 2 includes a third waveguide beam splitter 22, a microring, and a phase modulator 3 disposed on the microring. The microring resonator 2 acquires the output optical signal of the previous stage active tunable spectral perturbation unit through an input port of the third waveguide beam splitter 22. The microring is connected to the third waveguide beam splitter 22, and the optical signal is output to the next stage active tunable spectral perturbation unit through an output port of the third waveguide beam splitter 22 after passing through the microring.

[0070] In an exemplary embodiment, the first active tunable spectral perturbation unit can also employ a Bragg grating perturbation structure 4, and the second active tunable spectral perturbation unit can employ a microring resonator 2. For example... Figure 8 As shown, the spectral perturbation structure employs four cascaded active tunable spectral perturbation units, where stages 1, 2, and 4 are Bragg grating perturbation structures 4, and stage 3 is a microring resonator 2. This tunable time-domain sampling filter includes a waveguide bus with three Bragg grating perturbation structures 4 mounted on it, and a microring resonator located between the second and third Bragg grating perturbation structures. The Bragg gratings in the perturbation structures have grating periods or duty cycles, and the multiple perturbation structures have different grating periods or different duty cycles.

[0071] Furthermore, in some embodiments, such as Figure 9 As shown, the spectral perturbation structure includes multiple optical path components. These components are connected to the optical input port via optical splitters. The optical input port and the multiple optical path components are connected in parallel via a 1*N splitter, where N is the number of optical path components. Each optical path component includes multiple cascaded active tunable spectral perturbation units. The optical output port group includes multiple optical output ports, each corresponding one-to-one with a specific optical path component to output different output optical signals.

[0072] like Figure 10As shown, this embodiment also provides a computational spectrometer in a second aspect, including a light source, a photodetector, a driving circuit, a signal processing circuit, and an adjustable time-domain sampling filter as described in the first aspect. The adjustable time-domain sampling filter can be integrated on a spectral modulation chip. The computational spectrometer also includes optical components such as mirrors and convex lenses.

[0073] The light source is used to provide an input optical signal for the adjustable time-domain sampling filter, and the input optical signal is transmitted light or reflected light.

[0074] It should be noted that computational spectrometers are divided into transmission type and reflection type. For the reflection type, please refer to [link to relevant documentation]. Figure 10 and 12 The computational spectrometer in the text, for transmission type, see [link to relevant documentation]. Figure 11 The computational spectrometer in this context refers to a computational spectrometer. The adjustable time-domain sampling filter in a computational spectrometer can be set either before or after the analyte, without restriction. For computational spectrometers where the adjustable time-domain sampling filter is set before the analyte, see [link to relevant documentation]. Figure 10 and 11 For computational spectrometers with adjustable time-domain sampling filters set after the analyte, see [link to relevant documentation]. Figure 11 .

[0075] The signal processing circuit is used to generate control signals to tune the phase modulator and to acquire spectral correlation data with the input optical signal based on a plurality of the output optical signals.

[0076] The driving circuit is used to amplify the power of the control signal to drive the phase modulator.

[0077] The photodetector receives the highly random output optical signal from the optical output port and converts the optical power of the output optical signal into a corresponding electrical signal. There is no limitation on whether a photodetector corresponds one-to-one with an optical output port, or multiple optical output ports can time-division multiplex the same photodetector.

[0078] The photodetector can be either an InGaAs detector or a germanium detector. For germanium detectors, they can be integrated onto the same monolithic chip as a spectral modulation chip, without any restrictions.

[0079] It should be noted that the input terminals of the signal processor are used to process the output signal of the photodetector (equipped with signal amplification circuits, analog-to-digital conversion circuits, etc.). The signal processor can integrate computing functions and can be used to reconstruct and recover the spectrum of the optical signal without limitation. Similarly, the signal processor can be integrated with the photodetector and the spectral modulation chip on the same monolithic chip.

[0080] It should be noted that the spectral modulation chip uses a planar optical waveguide chip. The waveguide materials of the chip include silicon nitride waveguides, silicon waveguides, silicon oxide waveguides, thin-film lithium niobate waveguides, polymer waveguides, etc. The aforementioned tunable time-domain sampling filter can be fabricated on the chip using these materials.

[0081] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. An adjustable time-domain sampling filter, characterized in that, The tunable time-domain sampling filter includes an optical input port, an optical output port group, and a spectral perturbation structure. The optical output port group includes at least one optical output port. The spectral perturbation structure includes multiple cascaded active tunable spectral perturbation units, each comprising multiple optical path components connected to the optical input port via an optical splitter. Each optical path component includes multiple cascaded active tunable spectral perturbation units. The optical output port group includes multiple optical output ports, each corresponding one-to-one with one of the optical path components to output different output optical signals. The active tunable spectral perturbation units include at least a few different types of... The optical output port is equipped with a first active tunable spectral perturbation unit and a second active tunable spectral perturbation unit. The plurality of cascaded active tunable spectral perturbation units are formed by alternating cascades of the first active tunable spectral perturbation unit and the second active tunable spectral perturbation unit. Each active tunable spectral perturbation unit is equipped with a phase modulator. The plurality of cascaded active tunable spectral perturbation units are used to receive the input optical signal input through the optical input port and generate different perturbations in timing according to the tuning of the phase modulator, so that the optical output port outputs a plurality of different output optical signals at different times. The different output optical signals have different power distributions in the frequency domain.

2. The adjustable time-domain sampling filter according to claim 1, characterized in that, The active tunable spectral perturbation unit includes at least three types: active asymmetric Mach-Zehnder interferometer, microring resonator, and Bragg grating perturbation structure, and the first active tunable spectral perturbation unit and the second active tunable spectral perturbation unit are at least any two of these three types.

3. The adjustable time-domain sampling filter according to claim 2, characterized in that, The multiple cascaded active tunable spectral perturbation units contain multiple active asymmetric Mach-Zehnder interferometers; there is an arm length difference between the two tuning arms of the active asymmetric Mach-Zehnder interferometers; The various active asymmetric Mach-Zehnder interferometers described above each have different arm length differences.

4. The adjustable time-domain sampling filter according to claim 2, characterized in that, The multiple cascaded active tunable spectral perturbation units contain multiple microring resonators; the microrings of the microring resonators have a certain perimeter, and the microrings in the multiple microring resonators have different perimeters.

5. The adjustable time-domain sampling filter according to claim 2, characterized in that, The multiple cascaded active tunable spectral perturbation units contain multiple Bragg grating perturbation structures. The Bragg gratings in the perturbation structures have grating periods or duty cycles, and the multiple Bragg grating perturbation structures have different grating periods or different duty cycles.

6. The adjustable time-domain sampling filter according to claim 1, characterized in that, The spectral perturbation structure comprises 2 to 8 cascaded active tunable spectral perturbation units.

7. The adjustable time-domain sampling filter according to claim 1, characterized in that, The phase modulator has at least two different phase adjustment states.

8. A computational spectrometer, comprising a light source, a photodetector, and an adjustable time-domain sampling filter as described in any one of claims 1-7; characterized in that, The computational spectrometer further includes a signal processing circuit; the light source is used to provide an input optical signal to the adjustable time-domain sampling filter, the input optical signal being transmitted light or reflected light; the photodetector is used to convert the optical power of the output optical signal into a corresponding electrical signal; The signal processing circuit is used to generate control signals to tune the phase modulator and to acquire spectral correlation data with the input optical signal based on a plurality of the output optical signals.

9. The computational spectrometer according to claim 8, characterized in that, It also includes a driving circuit, which amplifies the control signal to drive the phase modulator.

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