High-speed switching N-bit path selection type silicon-based integrated microwave photon delay line structure

Abstract

A high-speed switching N-bit path selection type silicon-based integrated microwave photon delay line comprises a wavelength tunable external cavity laser, an electro-optical modulator, an N-bit wavelength selection delay line and a photoelectric detector, and the wavelength selection delay line is composed of N + 1 2 * 2 wavelength interleavers and N groups of delay and reference waveguide pairs. After being modulated by a microwave signal, light output by the external cavity laser is input into the N-bit wavelength selection delay line and finally converted into a microwave signal through the photoelectric detector to be output. By switching the wavelength of the laser, high-speed switching of a delay light path can be realized, and then high-speed phase shifting of a microwave signal is realized. According to the scheme, the wavelength selection type delay line adopts a passive device design, and compared with a traditional optical switch type delay line, the wavelength selection type delay line is easy to realize low loss, does not need voltage regulation and control, and is low in overall system power consumption.

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 photon signal processing, such as beamforming, microwave photon filtering, etc., due to their large bandwidth, low loss, and no electromagnetic interference. Silicon-based optoelectronic integration has the advantages of high integration, CMOS process compatibility, and low cost, and is suitable for the production of highly integrated optical delay line array chips.

[0003] However, existing silicon photonic adjustable delay line structures, including cascaded Mach-Zehnder Switch (MZS) and Microring Resonator (MRR), have certain limitations. The MZS adjustable delay line is composed of multiple 2×2 MZS and delay optical waveguides in cascade, and the adjustable delay is achieved by adjusting the MZS switch state to switch different delay paths. This scheme has a large delay adjustment range, and the delay accuracy depends on the unit delay amount; the MRR adjustable delay line achieves adjustable delay by adjusting the resonance of the microring. This scheme has a compact structure and continuously adjustable delay, but its adjustment range is small and requires complex feedback control to stabilize the resonant wavelength.

[0004] At present, most of the silicon-based optical delay chips reported in the literature use the thermo-optic effect to achieve delay control, and the switching time is generally in the order of 10 microseconds, which is difficult to meet the needs of high-speed beamforming / deflection and microwave signal processing. If a high-speed adjustable delay line is to be realized, an electro-optical phase shifter based on the free carrier dispersion effect is generally used on a silicon photonic platform to control the switching state of the MZS. Although this solution can achieve nanosecond response, it introduces significant carrier absorption losses, which increase significantly as the scale of the delay line increases. Optical delay lines with nanosecond switching speeds can also be realized based on a thin-film lithium niobate platform. However, due to the large size of the unit device, it is not conducive to the large-scale integration of optical delay lines.

[0005] High-performance on-chip laser sources are an indispensable part of microwave photon signal processing. Single crystal silicon is an indirect bandgap material. The recombination of electrons and holes cannot generate photons, so it cannot be directly used 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 ways 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 and the output end is directly connected to the silicon photonic waveguide; the other is that the III-V gain chip and the silicon photonic chip form a hybrid cavity, and 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.). Using them in external cavity lasers is beneficial to reducing the laser line width and achieving large-range tuning.

[0006] The change of laser output wavelength is mainly achieved by changing the phase in the laser cavity. Thermo-optical effect is limited by the speed of heat diffusion and can only achieve a switching speed of microseconds. In order to achieve a higher switching speed, on the one hand, an electro-optical phase shifter based on PN or PIN diodes can be introduced into the cavity to achieve nanosecond wavelength switching.

[0007] Near-infrared photodetection on silicon substrates is mainly achieved by epitaxially growing germanium materials on silicon substrates. Germanium-silicon photodetectors can adopt waveguide-coupled lateral or longitudinal PIN structures. Compared with metal-semiconductor-metal (MSM) structures, PIN detectors have higher quantum efficiency and lower dark current. Summary of the invention

[0008] In order to realize an adjustable delay scheme supporting high-speed switching, the present invention proposes an N-bit path selection integrated microwave photonic delay line chip supporting high-speed optical path switching, which is composed of a wavelength-tunable laser, a modulator, an N-bit wavelength selection optical delay line and a photodetector. High-speed wavelength tuning of the external cavity laser is achieved by means of electro-optical effect or piezoelectric effect. The optical signal generated by the laser is modulated by the modulator and input into the N-bit wavelength selection optical delay line. The delay path selection of the wavelength selection delay line is realized by means of a passive wavelength interleaver, which eliminates the disadvantages of high control power consumption and high active regulation thermal crosstalk required by traditional path selection integrated optical delay lines. It also avoids the complex state calibration process required for the series optical switch array in the traditional path selection integrated optical delay line. In addition, traditional nanosecond 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, which introduces additional and step-by-step cumulative carrier absorption losses. It is only necessary to use a passive wavelength interleaver to adjust the input wavelength of the external cavity laser through the carrier injection effect to achieve the switching of the delay path, while taking into account the nanosecond switching speed while avoiding the deterioration of the delay chip performance caused by carrier absorption losses.

[0009] The technical solution of the present invention is as follows:

[0010] A high-speed wavelength switching N-bit path selective integrated microwave photonic delay line, characterized in that it includes a wavelength tunable external cavity laser, an electro-optic 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) The 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 L 0 ), where the length difference between the delay waveguide and the reference waveguide is ΔL k =L k -L 0 =2 k-1 ΔL, where ΔL is the unit delay length, and the unit delay introduced by the unit delay length is Δτ. Therefore, N+1 wavelength interleavers form a 2 N wavelength channels, with a central wavelength of λ k Belongs to the collection 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,...,2N -1}.

[0014] The longitudinal mode spacing Δv of a wavelength tunable laser and the spacing between adjacent wavelength channels 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 selection silicon-based integrated microwave photonic delay line is characterized in that the N-bit wavelength interleaver includes micro-ring assisted Mach-Zehnder filter, unbalanced Mach-Zehnder filter, cascaded unbalanced Mach-Zehnder filter, micro-ring resonant filter, cascaded micro-ring resonant filter, array waveguide grating and other structures; the input and output waveguides, delay waveguides, reference waveguides and wavelength interleavers 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 materials as non-volatile phase shifters 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 ports 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 Terminal and I k+1 Between the two ends, a delay waveguide (length L) is passed. k ) connection; the P k Duan and J k+1 Between the two ends, a reference waveguide (length L) is passed. 0 ) connection. The length difference L between the delay waveguide and the reference waveguide k -L 0 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-stage wavelength interleaver are λ 1 and FSR 1 , the central wavelength and free spectral range of the first channel of the k-th wavelength interleaver are and 2 k-1 FSR 1 .

[0019] The tunable laser output wavelength λ k , the modulated microwave signal is input into the N-bit wavelength selection delay line structure, and the kth delay channel is selected through the N+1 wavelength interleavers, and the delay generated is where Δτ 0 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}, in the output waveguide of the N-bit wavelength selective delay line, the delay of the input signal is realized, and the set of delay amounts is T={kΔτ 0 |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 adopts a lateral or vertical PIN junction structure.

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

[0024] In order to realize a low-loss nanosecond-level high-speed adjustable delay line, the present invention proposes an N-bit path selection integrated microwave photonic delay line chip that supports high-speed optical path switching, and its technical effects are as follows:

[0025] (1) The output signal wavelength of the tunable laser is switched at a speed of nanoseconds, and after modulation, it is input into the N-bit path-selective integrated optical delay line structure: On the one hand, this can realize high-speed delayed optical path switching and eliminate the carrier absorption loss introduced by the traditional high-speed electro-optical switch array during the high-speed switching process. On the other hand, the optical path switching is achieved by changing the output optical signal wavelength of the tunable laser, rather than by adjusting the state of the optical switch, which also eliminates the complex switch state calibration process of the traditional path-selective integrated optical delay line and the complex switch array drive circuit.

[0026] (2) By using 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 chip performance degradation caused by thermal crosstalk. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a high-speed switching N-bit path selection 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 It is a schematic diagram of an external cavity laser based on the double micro-ring Vernier effect;

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

[0035] Fig. 9 It is a schematic diagram of a photoelectric detector. DETAILED DESCRIPTION

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

[0037] Figure 1 It is a schematic diagram of the high-speed switching N-bit path selection type silicon-based integrated microwave photonic delay line structure of the present invention, as shown in the figure, including: an adjustable 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 2As 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 respectively connected to each other with a length of L. k The delay waveguide (2.3) and a length of L 0 The reference waveguide (2.4) has a length difference of ΔL between the delay waveguide and the reference waveguide. k =L k -L 0 =2 k-1 ΔL, where ΔL is the unit delay length, corresponding to the unit delay amount Δτ 0 .

[0039] The 2 N wavelength routing channels, with a central wavelength λ k Belongs to the collection 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 =[log 2 (B / FSR 1 )], where [·] represents the largest integer not exceeding ·.

[0040] Figure 3 An embodiment of an adjustable coupled micro-ring assisted Mach-Zehnder wavelength interleaver is presented, which 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, wherein one modulation arm is a straight waveguide and the other modulation arm is a coupled adjustable micro-ring. Thus, a micro-ring coupled-Mach-Zehnder filter is formed. By adjusting the coupling factor of the micro-ring 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. A phase change material can be used to realize a near-zero power consumption and non-volatile phase shifter (3.3), so as to non-volatilely configure and correct 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 4Another embodiment based on cascaded unbalanced Mach-Zehnder wavelength interleaver is presented, which includes 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 determined splitting ratio, and two phase-shifting waveguides (4.5, 4.6). When the coupling coefficients of the three broadband couplers and the phase shifts of the two phase-shifting waveguides are accurately set, a set of flat-top filters can also be obtained. The phase shifts of the phase-shifting waveguides can be non-volatilely corrected using phase-change material phase shifters (4.8, 4.9) to correct the filtering shape of the interleaver.

[0042] The two wavelength interleaving embodiments given above are only used to illustrate the principle and available technical solutions of the wavelength interleaver. Other technologies not described, such as microring filter, cascaded multi-microring filter, multi-microring assisted Mach-Zehnder filter, waveguide array grating, etc.

[0043] Figure 5 A schematic diagram showing the working principle of a 5-bit wavelength selective delay line is shown. The 6 wavelength interleavers included in the diagram divide the working bandwidth into 32 wavelength channels, and each wavelength undergoes a unique delay path. Assume that the central wavelength and bandwidth of wavelength interleaver 1 are λ 1 and B 1 , and FSR is the bandwidth B 1 Then the central 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 B 1 . With wavelength channel λ 1 For example, the five wavelength interleavers it passes through are all in the through state (bar state), so after T = {Δτ 0 ,2Δτ 0 ,2 2 Δτ 0 ,...,2 4 Δτ 0} delay waveguide, so the relative delay experienced by this wavelength channel is (1+2+2 2 +...+2 4 )Δτ 0 , that is, 31Δτ 0 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] The wavelength tunable laser can be integrated with the wavelength selection routing array on the same chip or realized separately. The materials used, in addition to the III-V group gain materials, include but are not limited to silicon, silicon nitride, silicon oxide, lithium niobate, barium titanate, silicon carbide and other common materials or combinations thereof. The generation of laser can be achieved by electrical pumping or optical pumping (mainly using some nonlinear effects, including but not limited to stimulated Raman effect and stimulated Brillouin effect). The laser can be an independent monolithic integrated laser (Monolithic laser), the output of which is directly supplied to the silicon-based waveguide, including but not limited to Fabry-Perot (FP) laser, distributed feedback laser (DFB), distributed Bragg reflector laser (DBR), vertical cavity surface emitting laser (VCSEL); it can also be a hybrid cavity composed of III-V group active parts and silicon-based chips, and the longitudinal mode selection structure of the laser includes but is not limited to gratings, microring resonators, multi-arm interference structures and other common 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 electro-optical effect and piezoelectric effect, the laser can be used at wavelength λ i , single-mode output and high-speed switching are realized between i=1,2,...,N.

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

[0046] like Figure 7An embodiment of an adjustable laser is shown. The laser connects the gain 7.1 and the lithium niobate external cavity chip 7.2 by end face coupling. The external cavity chip mainly includes a spot converter 7.3, a phase shifter 7.4, and two microrings 7.5 and 7.6 with phase shifters. The spot converter 7.3 can be used to improve the coupling efficiency of the gain and the external cavity. In addition, the spot converter 7.3 has a tilt angle, which is mainly used to reduce the reflection of the contact end face. The Vernier filter composed of the two microrings 7.5 and 7.6 is mainly used for mode selection. By design, the circumferences of the two microrings are slightly different, which leads to differences in the transmission spectra of the two microrings. When one of the resonance peaks of the transmission spectra of the two microrings is aligned, the other resonance peaks will not be aligned, thereby ensuring single-mode output. By changing the phase of one of the microrings through the phase shifter, the transmission spectrum of the microring can be moved, and then the two transmission spectra will be aligned at another resonance peak, thus realizing the switching of the laser wavelength. The phase shifter 7.4 is mainly used to compensate for the phase difference between the filter center wavelength and the laser longitudinal mode.

[0047] like Figure 8 An embodiment of a modulator is shown, which is composed of two 1×2 multimode interferometers 8.1, 8.2 and two phase shifters 8.3, 8.4. When a signal is applied to the two-arm phase shifter and there is a phase difference between the two arms, the input light intensity will change, thereby achieving light intensity modulation.

[0048] like Fig. 9 An embodiment of a photodetector is shown. It is mainly composed of an input waveguide 9.1, a tapered structure 9.2 with a gradually varying width, a germanium absorption region 9.3, and an electrode 9.4. The laser is input from a single-mode waveguide 9.1, and passes through a tapered structure 9.2 with a gradually varying width, and the light is input into a silicon multimode waveguide below the germanium. Under the effect of interlayer evanescent wave coupling, the light is continuously coupled into the 9.3Ge absorption region to generate photogenerated carriers. The bias voltage can be loaded and the photogenerated current can be read through the electrode 9.4.

Claims

1. A high-speed switching N-bit path selection 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-optic 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 of length L0 are connected, 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 wavelength channels, the channel center wavelength, free spectrum range FSR and passband bandwidth B of each 2×2 wavelength interleaver meet the following conditions: (a) 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 (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) The 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; Among them, by adjusting the wavelength of the external cavity laser, the passive characteristics of the wavelength interleaver are used to achieve fast switching of the optical path, thereby obtaining different optical delays and avoiding carrier absorption loss. The longitudinal mode spacing Δv of a wavelength tunable laser and the spacing between adjacent wavelength channels 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 selection 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 selection 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 selection 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 claims 1-3, 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 selection 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 through the N+1 wavelength interleavers, and 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 selection silicon-based integrated microwave photonic delay line according to claim 1, characterized in that: The modulator may be integrated into the external cavity laser to realize internal modulation, or may 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 selection 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 adopts a lateral or vertical 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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