A high-speed switching N-bit path-selective silicon-based integrated microwave photonic delay line structure

Abstract

A high-speed switching N-bit path selection silicon-based integrated microwave photonic delay line includes a wavelength-tunable external cavity laser, an electro-optical modulator, an N-bit wavelength selective delay line, and a photodetector. The wavelength selective delay line consists of N+1 2×2 wavelength interleavers and N groups of delay and reference waveguide pairs. The output light of the external cavity laser is modulated by a microwave signal and input into the N-bit wavelength selective delay line. Finally, it is converted into a microwave signal output by a photodetector. By switching the laser wavelength, high-speed switching of the delay light path can be achieved, thereby achieving high-speed phase shifting of the microwave signal. In this solution, the wavelength selective delay line adopts a passive device design. Compared with traditional optical switching delay lines, it is easy to achieve low loss and does not require voltage regulation, and the overall system power consumption is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated optoelectronic devices, and in particular relates to an N-bit path-selective silicon-based integrated microwave photonic delay line structure that utilizes a tunable external cavity laser to achieve high-speed switching. Background Art

[0002] In recent years, optical delay lines have been widely used in microwave photonic signal processing, such as beamforming and microwave photonic filtering, due to their wide bandwidth, low loss, and resistance to electromagnetic interference. Silicon-based optoelectronics integration, with its advantages of high integration density, CMOS process compatibility, and low cost, is suitable for the fabrication of highly integrated optical delay line array chips.

[0003] However, existing silicon photonics tunable delay line structures, including cascaded Mach-Zehnder switches (MZS) and microring resonators (MRR), both have limitations. The MZS tunable delay line, constructed by cascading multiple 2×2 MZSs and delay optical waveguides, achieves adjustable delay by switching between different delay paths through the MZS switching state. This scheme offers a wide delay adjustment range, but the delay accuracy depends on the unit delay. The MRR tunable delay line achieves adjustable delay by adjusting the resonance of the microring. While this scheme is compact and offers continuously adjustable delay, it has a narrow adjustment range and requires complex feedback control to stabilize the resonant wavelength.

[0004] Currently, most silicon-based optical delay chips reported in the literature use the thermo-optic effect to achieve delay control, with switching times generally on the order of 10 microseconds, making them difficult to meet the requirements of high-speed beamforming / deflection and microwave signal processing. To achieve a high-speed adjustable delay line, electro-optical phase shifters based on the free-carrier dispersion effect are generally used on a silicon photonics platform to control the switching state of the MZS. Although this approach can achieve nanosecond response, it introduces significant carrier absorption losses, which increase significantly as the delay line scales up. Optical delay lines with nanosecond switching speeds can also be achieved based on thin-film lithium niobate platforms. However, the large size of the unit devices makes large-scale integration of optical delay lines unfavorable.

[0005] High-performance on-chip laser sources are an indispensable part of microwave photonic signal processing. Single-crystal silicon is an indirect bandgap material. The recombination of electrons and holes cannot generate photons, so it cannot be used directly to make lasers. Usually, III-V and silicon materials need to be hybrid integrated to make lasers on a silicon photonics platform. There are two main methods of hybrid integration: one is the direct coupling integration of III-V lasers and silicon photonics chips, in which the III-V lasers are independent chips with the output directly connected to the silicon photonic waveguide; the other is the III-V gain chip and the silicon photonic chip forming a hybrid cavity, in which the laser cavity is composed of III-V waveguides and silicon photonic waveguides. Silicon waveguides have low transmission loss and can form high-performance tunable filters (including gratings, microring resonators, multi-arm interference structures, etc.). Their use in external cavity lasers is conducive to reducing the laser linewidth and achieving wide-range tuning.

[0006] Changing the laser's output wavelength is primarily achieved by shifting the phase within the laser cavity. Thermo-optical effects are limited by the speed of heat diffusion, and can only achieve switching speeds on the order of microseconds. To achieve even higher switching speeds, electro-optical phase shifters based on PN or PIN diodes can be introduced within the cavity to achieve nanosecond wavelength switching.

[0007] Near-infrared photodetection on silicon is primarily achieved by epitaxially growing germanium on a silicon substrate. Germanium-silicon photodetectors can utilize either a waveguide-coupled lateral or longitudinal PIN structure. Compared to metal-semiconductor-metal (MSM) structures, PIN detectors offer higher quantum efficiency and lower dark current. Summary of the Invention

[0008] To implement an adjustable delay solution that supports high-speed switching, the present invention proposes an N-bit path-selective integrated microwave photonic delay line chip that supports high-speed optical path switching. The chip consists of a wavelength-tunable laser, a modulator, an N-bit wavelength-selective optical delay line, and a photodetector. High-speed wavelength tuning of the external cavity laser is achieved using the electro-optical effect or the piezoelectric effect. The optical signal generated by the laser is modulated by the modulator and then input into the N-bit wavelength-selective optical delay line. The delay path selection of the wavelength-selective delay line is achieved using a passive wavelength interleaver, eliminating the shortcomings of traditional path-selective integrated optical delay lines, such as high control power consumption and high thermal crosstalk caused by active regulation. Furthermore, the complex state calibration process required for the series-connected optical switch array in traditional path-selective integrated optical delay lines is avoided. In addition, traditional nanosecond-level high-speed delay switching requires that the optical switch needs to inject carriers into the waveguide inside the switch to achieve high-speed phase shift during switching. At the same time, additional and step-by-step cumulative carrier absorption losses are introduced during the phase shift. Only a passive wavelength interleaver is needed to adjust the input wavelength of the external cavity laser through the carrier injection effect to achieve delay path switching, achieving nanosecond switching speed while avoiding the deterioration of delay chip performance caused by carrier absorption loss.

[0009] The technical solutions of the present invention are as follows:

[0010] A high-speed wavelength switching N-bit path selective integrated microwave photonic delay line is characterized by comprising a wavelength tunable external cavity laser, an electro-optical modulator, an N-bit wavelength selective delay line and a photodetector.

[0011] Assume that the first channel center wavelength of the kth (k=1, 2, ..., N+1) 2×2 wavelength interleaver is λ k , free spectral range is FSR k , the passband bandwidth is B k , after design, the following conditions are met: (1) The center wavelength of the first channel of the k+1th 2×2 wavelength interleaver is equal to the center wavelength λ of the kth 2×2 wavelength interleaver k Plus its bandwidth B k half of (2) Free Spectral Range (FSR) of the k+1th 2×2 wavelength interleaver k+1 ) is equal to the free spectral range (FSR) of the kth 2×2 wavelength interleaver k ), which is twice the FSR k+1 =2FSR k (3) The bandwidth of the k+1th 2×2 wavelength interleaver is equal to twice the bandwidth of the kth 1×2 wavelength interleaver, that is, B k+1 =2B k .

[0012] The N-bit wavelength selective delay line includes N+1 2×2 wavelength interleavers, N groups of delays and reference waveguide pairs.

[0013] A delay waveguide (length L) is connected between the kth (k=1, 2, ..., N) and k+1th 2×2 wavelength interleavers. k ) and a reference waveguide (length L0), where the length difference between the delay waveguide and the reference waveguide is ΔL k =L k -L0=2 k-1 ΔL, where ΔL is the unit delay length, and the unit delay introduced by the unit delay length is Δτ. To this end, 2 is formed by N+1 wavelength interleavers. N wavelength channels, with a central wavelength of λ k Belong to the set Each wavelength channel experiences a unique delay path, and thus the delay amount can be generated to belong to the set {Δτ k |Δτ k =kΔτ,k∈0,1,2,...,2 N -1}.

[0014] The longitudinal mode spacing Δv of the wavelength tunable laser and the adjacent wavelength channel spacing of the corresponding N-bit wavelength selective delay line Alignment, by tuning the wavelength of the external cavity laser, optical path switching is achieved to obtain different optical delays.

[0015] The high-speed switching N-bit path selective silicon-based integrated microwave photonic delay line is characterized in that the N-bit wavelength interleaver includes structures such as a microring-assisted Mach-Zehnder filter, an unbalanced Mach-Zehnder filter, a cascaded unbalanced Mach-Zehnder filter, a microring resonator filter, a cascaded microring resonator filter, and an arrayed waveguide grating; the input and output waveguides, delay waveguide, reference waveguide, and wavelength interleaver can all be implemented on integrated platforms such as SOI, silicon oxide, silicon oxynitride, silicon nitride, lithium niobate, barium titanate, and lithium tantalate.

[0016] The high-speed switching N-bit path selection silicon-based integrated microwave photonic delay line is characterized in that the N-bit wavelength interleaver can integrate phase change material as a non-volatile phase shifter to achieve a one-time correction of the phase error caused by the manufacturing process deviation.

[0017] The high-speed switching N-bit path selection integrated optical delay line structure is characterized in that N+1 wavelength interleavers are connected in series in pairs, that is, the two output terminals O of the previous wavelength interleaver are connected in series in pairs. k ,P k , respectively connected to the two output ports I of the next stage wavelength interleaver k+1 ,J k+1 . The O k End and I k+1 Between the two ends, a delay waveguide (length L k ) connection; the P k Duan and J k+1 The delay waveguide and the reference waveguide are connected by a reference waveguide (length L0). k -L0 is 2 of the unit delay length ΔL k-1 times.

[0018] The central wavelength and free spectral range of the first channel of the first-level wavelength interleaver are λ1 and FSR1 respectively, and the central wavelength and free spectral range of the first channel of the k-th level wavelength interleaver are and 2 k-1 FSR1.

[0019] The tunable laser output wavelength λ k , after modulating the microwave signal, it is input into the N-bit wavelength selection delay line structure, and the kth delay channel is selected by the N+1 wavelength interleaver. The delay generated is Where Δτ0 is the unit delay, Γ k ∈{0,1} is the control factor. When the optical signal passes through the k-th delay waveguide, Γ k Take 1; when the optical signal passes through the k-th reference waveguide, Γ k Take 0. By configuring different sequences Γ={Γ k |k=1,2,...,N}, the output waveguide of the N-bit wavelength selective delay line is used to delay the input signal, and the set of delay amounts is T={kΔτ0|k=0,1,2,...,2 N -1}.

[0020] The modulator is integrated into the wavelength tunable laser to realize internal modulation, or is located between the wavelength tunable laser and the N-bit wavelength selective delay line to realize external modulation.

[0021] The technical routes of the modulator include but are not limited to Mach-Zehnder modulator, micro-ring modulator, micro-ring coupled Mach-Zehnder modulator, etc.

[0022] The photodetector can be made by growing single crystal germanium on silicon and adopting a transverse or longitudinal PIN junction structure.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] To achieve a low-loss, nanosecond-level, high-speed adjustable delay line, this paper proposes an N-bit path-selective integrated microwave photonic delay line chip that supports high-speed optical path switching. The technical effects are as follows:

[0025] (1) The output signal wavelength of the tunable laser is switched at nanosecond speeds and then modulated and input into an N-bit path-selective integrated optical delay line structure: On the one hand, this enables high-speed delayed optical path switching and eliminates the carrier absorption loss introduced by traditional high-speed electro-optical switch arrays during high-speed switching. On the other hand, optical path switching is achieved by changing the output optical signal wavelength of the tunable laser rather than adjusting the state of the optical switch. This also eliminates the complex switch state calibration process of traditional path-selective integrated optical delay lines and the complex switch array drive circuit.

[0026] (2) By using a passive design to achieve a wavelength interleaver with target filtering characteristics, or by using phase change materials to achieve a wavelength interleaver with adjustable filtering characteristics, it is possible to achieve near-zero power consumption and non-volatile state retention for each wavelength channel (i.e., delay path), while avoiding the chip performance degradation caused by thermal crosstalk. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the high-speed switching N-bit path-selective silicon-based integrated microwave photonic delay line structure of the present invention;

[0028] Figure 2 is a schematic diagram of an N-bit wavelength selective optical delay line of the present invention;

[0029] Figure 3 A schematic diagram of a Mach-Zehnder wavelength interleaver based on tunable coupled microrings;

[0030] Figure 4 It is a schematic diagram of a cascaded unbalanced Mach-Zehnder wavelength interleaver;

[0031] Figure 5 Schematic diagram of the working principle of a 5-bit wavelength selective optical delay line in an embodiment;

[0032] Figure 6 is a delay state lookup table of a 5-bit wavelength selective optical delay line in an embodiment;

[0033] Figure 7 This is a schematic diagram of an external cavity laser based on the double micro-ring Vernier effect;

[0034] Figure 8 This is a schematic diagram of a Mach-Zehnder modulator;

[0035] Figure 9 This is a schematic diagram of a photodetector. DETAILED DESCRIPTION

[0036] The present invention is further defined below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention should not be limited thereby.

[0037] Figure 1 This is a schematic diagram of the high-speed switching N-bit path-selective silicon-based integrated microwave photonic delay line structure of the present invention, as shown in the figure, including: a tunable laser 1.1, a modulator 1.2, an N-bit wavelength-selective optical delay line 1.3 and a photodetector 1.4.

[0038] Among them, N-bit wavelength selective optical delay line, such as Figure 2 As shown, it includes an input waveguide (2.1), N+1 wavelength interleavers (2.2), N delay waveguides (2.3), N reference waveguides (2.4) and an output waveguide (2.5). A wavelength interleaver k (k = 1, 2, ..., N) and a wavelength interleaver k+1 are connected to each other with a length of L. k The delay waveguide (2.3) and a reference waveguide (2.4) with a length of L0, the length difference between the delay waveguide and the reference waveguide is ΔL k =L k -L0=2 k-1 ΔL, where ΔL is the unit delay length, corresponding to the unit delay amount Δτ0.

[0039] 2 is composed of N+1 wavelength interleavers N wavelength routing channels, with a central wavelength λ k Belong to the set Each routing channel corresponds to a delay state. If the modulation bandwidth of the modulator for the laser is B L , the allowed bandwidth of the wavelength interleaver is B I , then the maximum operating bandwidth allowed by the device is B=min{B L ,B I Theoretically, the maximum number of N bits of path-selective integrated optical delay lines allowed is N. max =[log2(B / FSR1)], where [·] represents the maximum integer not exceeding ·.

[0040] Figure 3 An embodiment of a tunable coupled microring-assisted Mach-Zehnder wavelength interleaver is presented. The embodiment includes a set of input waveguides (3.1) I and J, a set of output waveguides (3.4) O and P, two 3-dB couplers (3.2), and modulation arms connecting them, one of which is a straight waveguide and the other is a microring with adjustable coupling. This forms a microring-coupled Mach-Zehnder filter. By adjusting the coupling factor of the microring and the phase of the two arms through a phase shifter (3.3), a flat-top filter can be obtained, and the center wavelength and passband shape of the filter can be adjusted. Phase change materials can be used to implement the near-zero power consumption and non-volatile phase shifter (3.3), thereby enabling non-volatile configuration and correction of the filtering characteristics of each wavelength interleaver. The on-chip heater that excites the phase change of the phase change material includes, but is not limited to, TiN based on the thermo-optical effect, a waveguide-doped thermal resistor scheme, and a pin junction scheme based on the carrier dispersion effect.

[0041] Figure 4 Another embodiment of a cascaded unbalanced Mach-Zehnder wavelength interleaver is presented, comprising a set of input waveguides (4.1) I and J, a set of output waveguides (4.7) O and P, three broadband couplers (4.2, 4.3, 4.4) with a defined splitting ratio, and two phase-shifting waveguides (4.5, 4.6). By precisely setting the coupling coefficients of the three broadband couplers and the phase shifts of the two phase-shifting waveguides, a set of flat-top filters can also be obtained. Phase-change material phase shifters (4.8, 4.9) can be used to non-volatilely correct the phase shifts of the phase-shifting waveguides to modify the filtering shape of the interleaver.

[0042] The two wavelength interleavers described above are only used to illustrate the principles and available technical solutions of the wavelength interleaver. Other technologies not described include microring filters, cascaded multi-microring filters, multi-microring assisted Mach-Zehnder filters, waveguide array gratings, etc.

[0043] Figure 5 The following diagram shows the working principle of a 5-bit wavelength selective delay line. The 6 wavelength interleavers included in it divide the operating bandwidth into 32 wavelength channels, and each wavelength experiences a unique delay path. Assume that the center wavelength and bandwidth of wavelength interleaver 1 are λ1 and B1 respectively, and the FSR is twice the bandwidth B1. Then the center wavelength λ of the first channel of interleaver k (k = 1, 2, 3, ..., 6) is k and bandwidth B k They are and 2 k-1 B1. Taking wavelength channel λ1 as an example, the five wavelength interleavers it passes through are all in the straight-through state (bar state), so it passes through T={Δτ0,2Δτ0,2 2 Δτ0,...,2 4 The delay waveguide of Δτ0}, so the relative delay experienced by this wavelength channel is (1+2+2 2 +...+2 4 )Δτ0, that is, 31Δτ0. The lookup table of the working state of the 5-bit wavelength selection delay line in this embodiment is as follows Figure 6 When the output wavelength of the tunable laser is switched at high speed, the delay of the optical path can be adjusted at high speed.

[0044] Wavelength-tunable lasers can be integrated with wavelength-selective routing arrays on the same chip or implemented separately. In addition to III-V gain materials, the materials used include, but are not limited to, common materials such as silicon, silicon nitride, silicon oxide, lithium niobate, barium titanate, and silicon carbide, or combinations thereof. Laser generation can be achieved through electrical or optical pumping (primarily utilizing nonlinear effects, including but not limited to the stimulated Raman effect and the stimulated Brillouin effect). The laser can be an independent monolithic laser whose output is directly fed into a silicon-based waveguide, including but not limited to Fabry-Perot (FP) lasers, distributed feedback lasers (DFB), distributed Bragg reflector lasers (DBR), and vertical-cavity surface-emitting lasers (VCSELs). It can also be a hybrid cavity consisting of a III-V active component and a silicon-based chip. The longitudinal mode selection structure of the laser includes, but is not limited to, common structures such as gratings, microring resonators, and multi-arm interferometer structures. Hybrid cavity lasers include but are not limited to external cavity lasers (ECL) and self-injection locked lasers (SIL). Integration methods include but are not limited to common integration methods such as epitaxial growth, heterogeneous integration, and hybrid integration. The external cavity laser can be designed so that its longitudinal mode spacing Δv is aligned with the adjacent wavelength spacing Δλ of the wavelength selection routing, and with the help of effects such as electro-optical effect and piezoelectric effect, the laser can be used at wavelength λ. i , i=1,2,...,N to achieve single-mode output and high-speed switching.

[0045] A modulator can be integrated into the laser to achieve internal modulation, or can be interposed between the laser and the N×N wavelength selection routing array to achieve external modulation; the modulator can be prepared based on commonly used integration platforms including but not limited to silicon-based, lithium niobate, lithium tantalate, barium titanate, etc.

[0046] like Figure 7An embodiment of a tunable laser is presented. The laser connects a gain element 7.1 and a lithium niobate external cavity chip 7.2 via end-face coupling. The external cavity chip primarily comprises a spot size converter 7.3, a phase shifter 7.4, and two microrings 7.5 and 7.6 with phase shifters. The spot size converter 7.3 can be used to improve the coupling efficiency between the gain and the external cavity. Furthermore, the spot size converter 7.3 has a tilt angle, primarily to reduce reflections from the contact end faces. The Vernier filter formed by the two microrings 7.5 and 7.6 is primarily used for mode selection. By design, the circumferences of the two microrings differ slightly, resulting in differences in their transmission spectra. When one of the resonance peaks of the transmission spectra of the two microrings aligns, the other resonance peaks do not, thus ensuring single-mode output. By changing the phase of one of the microrings using a phase shifter, the transmission spectrum of that microring shifts, and the two transmission spectra then align at another resonance peak, thus achieving laser wavelength switching. The phase shifter 7.4 is mainly used to compensate for the phase difference between the center wavelength of the filter and the longitudinal mode of the laser.

[0047] like Figure 8 An embodiment of a modulator is shown, comprising two 1×2 multimode interferometers 8.1 and 8.2 and two phase shifters 8.3 and 8.4. When a signal is applied to the two phase shifters and there is a phase difference between the two arms, the input light intensity changes, thus achieving light intensity modulation.

[0048] like Figure 9 An embodiment of a photodetector is shown. It primarily consists of an input waveguide 9.1, a tapered width structure 9.2, a germanium absorption region 9.3, and an electrode 9.4. Laser light is input through a single-mode waveguide 9.1, passing through a tapered width structure 9.2, which then directs the light into a silicon multimode waveguide beneath the germanium. Through interlayer evanescent wave coupling, the light is continuously coupled into the Ge absorption region 9.3, generating photogenerated carriers. Electrode 9.4 allows for bias voltage application and reading of the photogenerated current.

Claims

1. A high-speed switching N-bit path-selective silicon-based integrated microwave photonic delay line, characterized in that: include: a wavelength-tunable external cavity laser for generating a tunable optical signal; an electro-optical modulator for modulating the optical signal generated by the external cavity laser; An N-bit wavelength selective delay line includes N+1 2×2 wavelength interleavers and N groups of delay waveguides and reference waveguides. That is, a line of length L is connected between the kth and k+1th 2×2 wavelength interleavers. k The delay waveguide and the reference waveguide are of length L0, where the length difference between the delay waveguide and the reference waveguide is ΔL k =L k -L0=2 k-1 ΔL, where ΔL is the unit delay length, and the delay introduced by the unit delay length is Δτ; the N+1 2×2 wavelength interleavers constitute 2 N The channel center wavelength, free spectrum range (FSR), and passband bandwidth (B) of each 2×2 wavelength interleaver meet the following conditions: (a) The central wavelength of the first channel of the k+1th 2×2 wavelength interleaver is equal to the central wavelength λ of the kth 2×2 wavelength interleaver. k Plus its bandwidth B k half of (b) FSR of the k+1th 2×2 wavelength interleaver k+1 Equal to the kth 2×2 wavelength interleaver FSR k twice, that is, FSR k+1 =2FSR k ; (c) Bandwidth B of the k+1th 2×2 wavelength interleaver k+1 Equal to the bandwidth B of the kth 1×2 wavelength interleaver k twice, that is, B k+1 =2B k ;as well as, a photodetector for receiving and detecting the optical signal processed by the N-bit wavelength selective delay line; The wavelength of the external cavity laser is adjusted and the passive characteristics of the wavelength interleaver are utilized to achieve fast switching of the optical path, thereby obtaining different optical delays and avoiding carrier absorption loss. The longitudinal mode spacing Δv of the wavelength tunable laser and the adjacent wavelength channel spacing of the corresponding N-bit wavelength selective delay line Alignment, by tuning the wavelength of the external cavity laser, optical path switching is achieved to obtain different optical delays.

2. The high-speed switching N-bit path selective silicon-based integrated microwave photonic delay line according to claim 1, characterized in that: The wavelength interleaver includes an unbalanced Mach-Zehnder filter, a cascaded unbalanced Mach-Zehnder filter, and a micro-ring assisted Mach-Zehnder filter.

3. The high-speed switching N-bit path selective silicon-based integrated microwave photonic delay line according to claim 1 or 2, characterized in that: The wavelength interleaver can integrate phase change materials to achieve non-volatile phase shifting, and can be used to correct phase errors caused by manufacturing process deviations.

4. The high-speed switching N-bit path selective silicon-based integrated microwave photonic delay line according to claim 1 or 2, characterized in that: The N+1 wavelength interleavers are connected in series in pairs, and the two output ends of the kth 2×2 wavelength interleaver are connected to the two input ends of the k+1th 2×2 wavelength interleaver through a delay waveguide and a reference waveguide, respectively, wherein the length difference between the delay waveguide and the reference waveguide is 2 times the unit delay length ΔL k-1 times.

5. The high-speed switching N-bit path selective silicon-based integrated microwave photonic delay line according to any one of claims 1 to 3, characterized in that: The central wavelength and free spectral range of the first channel of the first-level wavelength interleaver are λ1 and FSR1 respectively, and the central wavelength and free spectral range of the first channel of the k-th level wavelength interleaver are and 2 k-1 FSR1.

6. The high-speed switching N-bit path selective silicon-based integrated microwave photonic delay line according to claim 1, characterized in that: The external cavity laser output wavelength λ k , the modulated microwave signal is input into the N-bit wavelength selection delay line, and the kth delay channel is selected by the N+1 wavelength interleaver. The delay generated is Where Δτ0 is the unit delay, Γ k ∈{0,1} is the control factor. When the optical signal passes through the k-th delay waveguide, Γ k Take 1; when the optical signal passes through the k-th reference waveguide, Γ k Take 0; by configuring different sequences Γ={Γ k |k=1,2,...,N}, the output waveguide of the N-bit wavelength selective delay line is used to delay the input signal, and the set of delay amounts is T={kΔτ0|k=0,1,2,...,2 N -1}.

7. The high-speed switching N-bit path selective silicon-based integrated microwave photonic delay line according to claim 6, characterized in that: By configuring different sequences of delay waveguides and reference waveguide combinations, the input signal is delayed on the output waveguide of the N-bit wavelength selective delay line. The set of delay amounts is determined by the unit delay amount and the control factor. When the optical signal passes through the delay waveguide, the control factor is 1; when the optical signal passes through the reference waveguide, the control factor is 0.

8. The high-speed switching N-bit path selective silicon-based integrated microwave photonic delay line according to claim 1, characterized in that: The modulator can be integrated into the external cavity laser to realize internal modulation, or be located between the external cavity laser and the N-bit wavelength selective delay line to realize external modulation.

9. The high-speed switching N-bit path selective silicon-based integrated microwave photonic delay line according to claim 6, characterized in that: The photodetector can be made by growing single crystal germanium on silicon and adopting a transverse or longitudinal PIN junction structure.

10. The high-speed switching N-bit path selection integrated microwave photonic delay line according to any one of claims 1 to 9, characterized in that: The external cavity laser utilizes electro-optic effect or piezoelectric effect to achieve high-speed wavelength tuning.

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