Two-channel grating-assisted counter-directive coupler type dispersion compensator

Abstract

The application provides a two-channel grating-assisted reverse coupler type dispersion compensator, comprising a mode division multiplexer, a reverse coupler, a straight waveguide, a tapered waveguide and a curved waveguide; the mode division multiplexer is a micro-ring-based mode division multiplexer, and the reverse coupler is a chirped grating-assisted reverse coupler; the straight waveguide is connected with the mode division multiplexer through the curved waveguide; the straight waveguide is connected with the mode division multiplexer through the tapered waveguide; the mode division multiplexer is connected with the reverse coupler through the tapered waveguide; and the straight waveguide is connected with the reverse coupler through the curved waveguide. The application separates the input light and the reflected output light by using the reverse coupling between two waveguides based on the Bragg condition, is equivalent in function to a Bragg grating with input and output separation, does not need an additional optical circulator or other light splitting devices, and reduces the integration difficulty of the device.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and more specifically, to a two-channel grating-assisted reverse coupler type dispersion compensator. Background Technology

[0002] As optical communication systems evolve towards high speed and high capacity, dispersion has gradually become a key limiting factor. To improve chip compactness, miniaturized and highly integrated on-chip dispersion compensation schemes have attracted widespread attention, such as chirped Bragg gratings, micro-ring filters, and finite impulse response filters composed of Mach-Zehnder interferometers. Chirped Bragg gratings offer numerous advantages, including high integration, low loss, and bandwidth flexibility. However, traditional Bragg gratings have a single port for input and output, requiring a separate optical circulator or on-chip beam splitter to separate the input and output light, increasing integration complexity and introducing additional insertion loss. Furthermore, unlike the periodic filters of micro-ring or finite impulse response filters, chirped Bragg grating dispersion compensators can only compensate for a single bandwidth; in wavelength division multiplexing (WDM) systems, multiple devices are typically needed to compensate for multiple wavelengths separately.

[0003] Patent document CN112684541A discloses a cascaded tunable silicon-based Bragg grating dispersion compensator. Multiple stages of optical switches are connected in series via straight waveguides and Bragg grating dispersion compensators. The input terminal of the first-stage optical switch is connected to the input straight waveguide, and the output terminal of the last-stage optical switch is connected to the output straight waveguide. In each stage of the Bragg grating dispersion compensator, the input terminal of the compensator's input waveguide is connected to the output terminal of the optical switch, the output terminal of the compensator's input waveguide is connected to the input terminal of the chirped Bragg grating, the input terminal of the compensator's output waveguide is connected to the output terminal of the chirped Bragg grating, and the output terminal of the compensator's output waveguide is connected to the input terminal of the optical switch. Heating electrodes are located on the chirped Bragg grating. However, this patent document still suffers from the drawback of only being able to compensate for a single bandwidth, which typically requires multiple devices to compensate for multiple wavelengths in wavelength division multiplexing systems.

[0004] Patent document CN102590952B discloses a multi-channel dynamic optical dispersion compensator, including a dual-fiber collimator, a roof prism, a polarization conversion component, a prism pair, a Fourier lens, a transmissive phase grating, a mirror, and a silicon-based liquid crystal chip. The transmissive phase grating and the silicon-based liquid crystal chip are located on the front and rear focal planes of the Fourier lens, respectively, forming a 2f system. The two pigtails of the dual-fiber collimator serve as the input and output terminals of the multi-channel dynamic optical dispersion compensator, respectively. However, this patent document still has the drawback of only being able to compensate for a single bandwidth, which typically requires multiple devices to compensate for multiple wavelengths in wavelength division multiplexing systems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a two-channel grating-assisted reverse coupler type dispersion compensator.

[0006] A two-channel grating-assisted reverse coupler type dispersion compensator according to the present invention includes: a mode division multiplexer, a reverse coupler, a straight waveguide, a tapered waveguide, and a curved waveguide;

[0007] The mode divider is a micro-ring based mode divider, and the reverse coupler is a chirped grating-assisted reverse coupler.

[0008] The straight waveguide is connected to the mode divider multiplexer via the curved waveguide; the straight waveguide is connected to the mode divider multiplexer via the tapered waveguide; the mode divider multiplexer is connected to the reverse coupler via the tapered waveguide; and the straight waveguide is connected to the reverse coupler via the curved waveguide.

[0009] Preferably, the mode division multiplexer includes an upper straight waveguide, a ring resonant cavity, and a lower straight waveguide;

[0010] The annular resonant cavity is located between the upper straight waveguide and the lower straight waveguide;

[0011] The straight waveguide is connected to one end of the upper straight waveguide via the curved waveguide;

[0012] The straight waveguide is connected to one end of the lower straight waveguide via the tapered waveguide; the other end of the lower straight waveguide is connected to the reverse coupler via the tapered waveguide.

[0013] Preferably, the upper straight waveguide and the ring resonant cavity are single-mode waveguides, and the lower straight waveguide is a multimode waveguide.

[0014] Preferably, the reverse coupler includes an incident waveguide and a reflecting waveguide;

[0015] The lower straight waveguide is connected to one end of the incident waveguide via the tapered waveguide;

[0016] The straight waveguide is connected to one end of the reflective waveguide via the curved waveguide.

[0017] Preferably, the incident waveguide is a single-mode waveguide supporting multiple modes, and the reflecting waveguide is a double-sidewall modulation waveguide grating supporting a single mode.

[0018] Preferably, the double sidewalls of the reflecting waveguide are modulated into a transversely misaligned grating with an antisymmetric structure.

[0019] Preferably, the reflecting waveguide is abutted on one side near the curved waveguide;

[0020] Apodization functions include cosine functions, and apodization methods include changing the grating period, changing the duty cycle, changing the width, and changing the waveguide spacing.

[0021] Preferably, the straight waveguide includes a first straight waveguide, a second straight waveguide, a third straight waveguide, a fourth straight waveguide, and a fifth straight waveguide;

[0022] The first straight waveguide is connected to the upper straight waveguide via the curved waveguide, the second straight waveguide is connected to one end of the lower straight waveguide via the tapered waveguide, and the fifth straight waveguide is connected to one end of the reflective waveguide via the curved waveguide.

[0023] The third straight waveguide connection is located at the other end of the incident waveguide; the fourth straight waveguide connection is located at the other end of the reflection waveguide.

[0024] Preferably, the tapered waveguide includes a first tapered waveguide and a second tapered waveguide;

[0025] The second straight waveguide is connected to the lower straight waveguide through the first tapered waveguide, and the two ends of the first tapered waveguide are respectively connected to one end of the second straight waveguide and one end of the lower straight waveguide;

[0026] The lower straight waveguide is connected to the incident waveguide via the second tapered waveguide, and the two ends of the second tapered waveguide are respectively connected to one end of the lower straight waveguide and one end of the incident waveguide.

[0027] Preferably, the curved waveguide includes a semi-circular curved waveguide and an S-shaped curved waveguide;

[0028] The first straight waveguide is connected to the upper straight waveguide through the semi-circular curved waveguide, and the two ends of the semi-circular curved waveguide are respectively connected to one end of the first straight waveguide and one end of the upper straight waveguide;

[0029] The fifth straight waveguide is connected to the reflecting waveguide via the S-shaped curved waveguide, and the two ends of the S-shaped curved waveguide are respectively connected to one end of the fifth straight waveguide and one end of the reflecting waveguide.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The grating-assisted reverse coupler of the present invention utilizes the reverse coupling between two waveguides based on the Bragg condition to separate the input light from the reflected output light. Functionally equivalent to an input-output separated Bragg grating, it does not require an additional optical circulator or other beam splitting device, thus reducing the integration difficulty of the device.

[0032] 2. This invention uses a multimode waveguide as the input waveguide of the grating, which enables a single device to perform multi-channel dispersion compensation through mode division multiplexing;

[0033] 3. This invention uses a grating-assisted reverse coupler, which eliminates the need for an additional optical circulator to separate the input and output, making it easy to integrate;

[0034] 4. In the grating-assisted reverse coupler of the present invention, the waveguide adopts an antisymmetric design to suppress the reflection of the waveguide itself. Attached Figure Description

[0035] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0036] Figure 1 This is a schematic diagram of the structure of the two-channel grating-assisted reverse coupler type dispersion compensator of the present invention;

[0037] Figure 2 This is a schematic diagram of the micro-ring-based module multiplexer of the present invention;

[0038] Figure 3 This is a schematic diagram of the micro-ring-based modulus multiplexer of the present invention;

[0039] Figure 4 This is a schematic diagram of the chirped grating-assisted reverse coupler of the present invention;

[0040] Figure 5 This is a schematic diagram of the chirped grating-assisted reverse coupler of the present invention;

[0041] Figure 6 This is a cross-sectional view of the waveguide of the thin-film lithium niobate platform.

[0042] Figure 7 The simulation results of the micro-ring-based mode demultiplexer are shown in the figure.

[0043] Figure 8 and Figure 9 The simulation results are shown in the figure for the grating-assisted reverse coupler.

[0044] The diagram shows:

[0045] Mode division multiplexer 1 Third straight waveguide 303

[0046] Upper straight waveguide 101, fourth straight waveguide 304

[0047] Lower straight waveguide 102, fifth straight waveguide 305

[0048] 103 ring resonator and 4 tapered waveguide

[0049] Reverse Coupler 2 First Tapered Waveguide 401

[0050] Incident waveguide 201, second conical waveguide 402

[0051] Reflecting waveguide 202, Bending waveguide 5

[0052] Straight waveguide 3, semi-circular curved waveguide 501

[0053] First straight waveguide 301, S-shaped curved waveguide 502

[0054] Second straight waveguide 302 Detailed Implementation

[0055] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0056] Example 1:

[0057] like Figures 1-5 As shown, this embodiment provides a two-channel grating-assisted reverse coupler type dispersion compensator, including: a mode division multiplexer 1, a reverse coupler 2, a straight waveguide 3, a tapered waveguide 4, and a curved waveguide 5. The mode division multiplexer 1 is a micro-ring-based mode division multiplexer, and the reverse coupler 2 is a chirped grating-assisted reverse coupler. The straight waveguide 3 is connected to the mode division multiplexer 1 through the curved waveguide 5, and the straight waveguide 3 is connected to the mode division multiplexer 1 through the tapered waveguide 4. The mode division multiplexer 1 is connected to the reverse coupler 2 through the tapered waveguide 4. The straight waveguide 3 is connected to the reverse coupler 2 through the curved waveguide 5.

[0058] The mode division multiplexer 1 includes an upper straight waveguide 101, a ring resonant cavity 103, and a lower straight waveguide 102.

[0059] The reverse coupler 2 includes an incident waveguide 201 and a reflection waveguide 202.

[0060] Straight waveguide 3 includes a first straight waveguide 301, a second straight waveguide 302, a third straight waveguide 303, a fourth straight waveguide 304, and a fifth straight waveguide 305.

[0061] The tapered waveguide 4 includes a first tapered waveguide 401 and a second tapered waveguide 402.

[0062] The curved waveguide 5 includes a semi-circular curved waveguide 501 and an S-shaped curved waveguide 502.

[0063] The ring resonator 103 is located between the upper straight waveguide 101 and the lower straight waveguide 102. The straight waveguide 3 is connected to one end of the upper straight waveguide 101 through a bent waveguide 5, and the straight waveguide 3 is connected to one end of the lower straight waveguide 102 through a tapered waveguide 4. The other end of the lower straight waveguide 102 is connected to the reverse coupler 2 through the tapered waveguide 4. The upper straight waveguide 101 and the ring resonator 103 are single-mode waveguides, and the lower straight waveguide 102 is a multimode waveguide.

[0064] The first straight waveguide 301 is connected to the upper straight waveguide 101 via a bent waveguide 5; the second straight waveguide 302 is connected to one end of the lower straight waveguide 102 via a tapered waveguide 4; the fifth straight waveguide 305 is connected to one end of the reflecting waveguide 202 via a bent waveguide 5; the third straight waveguide 303 is connected to the other end of the incident waveguide 201; and the fourth straight waveguide 304 is connected to the other end of the reflecting waveguide 202.

[0065] The lower straight waveguide 102 is connected to one end of the incident waveguide 201 via a tapered waveguide 4, and the straight waveguide 3 is connected to one end of the reflecting waveguide 202 via a bent waveguide 5. The incident waveguide 201 is a single-mode waveguide supporting multiple modes, and the reflecting waveguide 202 is a double-sidewall modulation waveguide grating supporting a single mode.

[0066] The second straight waveguide 302 is connected to the lower straight waveguide 102 through the first tapered waveguide 401. The two ends of the first tapered waveguide 401 are respectively connected to one end of the second straight waveguide 302 and one end of the lower straight waveguide 102. The lower straight waveguide 102 is connected to the incident waveguide 201 through the second tapered waveguide 402. The two ends of the second tapered waveguide 402 are respectively connected to one end of the lower straight waveguide 102 and one end of the incident waveguide 201.

[0067] The double sidewalls of the reflecting waveguide 202 are modulated into a transversely misaligned grating with an antisymmetric structure. The side of the reflecting waveguide 202 closest to the curved waveguide 5 is abutted on one side. The abutment function includes a cosine function, and the abutment method includes changing the grating period, changing the duty cycle, changing the width, and changing the waveguide spacing.

[0068] The first straight waveguide 301 is connected to the upper straight waveguide 101 via a semi-circular curved waveguide 501. The two ends of the semi-circular curved waveguide 501 are respectively connected to one end of the first straight waveguide 301 and one end of the upper straight waveguide 101. The fifth straight waveguide 305 is connected to the reflection waveguide 202 via an S-shaped curved waveguide 502. The two ends of the S-shaped curved waveguide 502 are respectively connected to one end of the fifth straight waveguide 305 and one end of the reflection waveguide 202.

[0069] Example 2:

[0070] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0071] This embodiment provides a two-channel grating-assisted reverse coupler type dispersion compensator, including a micro-ring-based mode division multiplexer 1, a chirped grating-assisted reverse coupler 2, a straight waveguide 3, a tapered waveguide 4, and a curved waveguide 5.

[0072] There are two signal input ports and one signal output port. The two channels of signals are input through the first straight waveguide 301 and the second straight waveguide 302 and enter the micro-ring-based mode division multiplexer 1. The tapered waveguide 4, which supports multiple modes, connects the micro-ring-based mode division multiplexer 1 and the chirped grating-assisted reverse coupler 2. The lower left S-shaped curved waveguide 502 and the fifth straight waveguide 305 serve as the output.

[0073] The upper straight waveguide 101 and the microring resonator 102 of the microring-based mode divider 1 are single-mode waveguides, and the lower straight waveguide 102 is a multimode waveguide.

[0074] The incident waveguide 201 is a single-mode waveguide that supports multiple modes, and the reflecting waveguide 202 is a double-sidewall modulation waveguide grating that supports a single mode.

[0075] The double sidewalls of the reflecting waveguide 202 are modulated into a transversely misaligned grating with an antisymmetric structure, and a single-sided apodization is performed on the left side. The apodization function includes, but is not limited to, a cosine function, and the apodization method includes, but is not limited to, changing the grating period, duty cycle, width, and waveguide spacing.

[0076] The two-channel grating-assisted reverse coupler dispersion compensation device in this embodiment mainly includes a micro-ring-based mode divider multiplexer 1 and a chirped grating-assisted reverse coupler 2. The chirped grating-assisted reverse coupling consists of a multimode waveguide and the chirped grating-assisted reverse coupler forming the reverse coupling region. The grating combs on both sides of the waveguide grating, modulated by double sidewalls, have an anti-symmetrical structure with a 180-degree phase difference, are staggered laterally, and their effective width changes linearly along the waveguide length; the two are connected by a tapered waveguide. This embodiment achieves dispersion compensation for multi-channel input optical signals, utilizing mode divider multiplexing and a single grating-assisted reverse coupler to provide high dispersion compensation for two wavelength channels, demonstrating great potential in wavelength division multiplexing systems.

[0077] Example 3:

[0078] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0079] This embodiment provides a two-channel grating-assisted reverse coupler type dispersion compensator, including: a mode division multiplexer, a reverse coupler, a straight waveguide, a tapered waveguide, and a curved waveguide.

[0080] The mode division multiplexer includes an upper straight waveguide, a ring resonator, and a lower straight waveguide. The reverse coupler includes an incident waveguide and a reflecting waveguide. Straight waveguides include a first, second, third, fourth, and fifth straight waveguide. Tapered waveguides include a first and second tapered waveguide. Bending waveguides include semi-circular bending waveguides and S-shaped bending waveguides.

[0081] Using a microring-based mode division multiplexing device, input signals of different wavelengths are coupled into different modes in a multimode waveguide. The upper waveguide and ring resonant cavity of the microring are single-mode waveguides, the lower waveguide is a multimode waveguide, and the lower left and upper right of the microring are two input ports.

[0082] The input signals are all fundamental modes. The input of the multimode waveguide is directly connected to the lower right output waveguide because the wave vector of the multimode waveguide is mismatched with that of the single-mode waveguide of the ring resonant cavity. The upper right single-mode waveguide has the same width as the single-mode waveguide of the ring resonant cavity, and the fundamental mode refractive index is matched, so it is coupled into the resonant cavity.

[0083] By designing the waveguide width, the refractive index of the higher-order modes of the multimode waveguide is matched with that of the fundamental mode of the single-mode waveguide. Ultimately, the fundamental mode in the single-mode waveguide of the ring resonator is coupled to the higher-order mode of the multimode waveguide. The two fundamental mode signals at the two input ports are coupled to the fundamental mode and the higher-order mode of the multimode waveguide in the lower right corner, respectively, thus realizing mode division multiplexing.

[0084] The light in these modes enters a waveguide grating with sidewall modulation as the input waveguide, and a multimode waveguide-assisted reverse coupler as the output waveguide. When the wavelength of the input optical signal satisfies the reverse coupling condition, the input end, after passing through the chirped grating-assisted reverse coupler, is reverse-coupled to the output end. Different modes, due to their different effective refractive indices, will satisfy the Bragg condition for reverse coupling at different wavelengths, and will be coupled into the single-mode waveguide as the fundamental mode for output. Dispersion compensation is achieved through mode division multiplexing (MDF). The waveguide grating achieves chirping by linearly changing its width, duty cycle, or period, resulting in a linearly varying delay in the output signal, thus achieving dispersion compensation.

[0085] Furthermore, for the width design of the multimode waveguide and the sidewall modulation waveguide grating of the chirped grating-assisted reverse coupler, the refractive indices of the fundamental and higher-order modes used in the multimode waveguide should be mismatched with the fundamental mode of the sidewall modulation waveguide grating in order to suppress co-directional coupling between waveguides.

[0086] Furthermore, for the waveguide grating of the chirped grating-assisted reverse coupler, an antisymmetric double-sidewall modulation is adopted, with the two gratings having a 180-degree phase shift to suppress their self-reflection.

[0087] Furthermore, the longitudinal grating tooth width of the sidewall modulated waveguide grating is weighted by a cosine apodization function at the beginning of the reverse coupling region, while the remaining grating tooth width is fixed to the maximum tooth width of the apodization region, thereby reducing group delay jitter.

[0088] This embodiment solves the problem that dispersion compensation chips based on chirped gratings can only compensate for a single wavelength.

[0089] Example 4:

[0090] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0091] like Figure 1 As shown, this embodiment provides a two-channel grating-assisted reverse coupler type dispersion compensator, which mainly includes a micro-ring-based mode division multiplexer 1, a chirped grating-assisted reverse coupler 2, a straight waveguide 3, a tapered waveguide 4, and a curved waveguide 5.

[0092] The device has two input channels: a first straight waveguide 301 and a second straight waveguide 302. The input wavelength of the first straight waveguide 301 is λ1, and the input wavelength of the second straight waveguide 302 is λ2. The output channel is a fifth straight waveguide 305, which simultaneously outputs the dispersion-compensated optical signal results from both channels λ1 and λ2.

[0093] The first straight waveguide 301, the second straight waveguide 302, the third straight waveguide 303 and the fifth straight waveguide 305 are single-mode waveguides, and the fourth straight waveguide 304 is a multimode waveguide.

[0094] Micro-ring-based pattern multiplexer 1, such as Figure 2 As shown, it includes an upper straight waveguide 101, a lower straight waveguide 102, and a ring resonator 103, wherein the lower waveguide 102 is a multimode waveguide with a width of W. b The lower straight waveguide 102 and the ring resonator 103 are both single-mode waveguides with a width of W. a The radius of the annular portion in the ring resonator is R, the length of the coupling region is L, and the spacing between the coupling regions is G1. A suitable width is designed to match the wave vectors of the TE1 mode of the multimode waveguide with those of the TE1 mode of the single-mode waveguide.

[0095] The second tapered waveguide 402 connects the output of the microring mode multiplexer 1 to the input of the chirped grating-assisted reverse coupler 2.

[0096] Chirped grating-assisted reverse coupler 2, such as Figure 4 As shown, it includes an incident waveguide 201 and a reflecting waveguide 202. The incident waveguide 201 is a tapered multimode waveguide with no sidewall modulation and an initial width of W. b1 The reflecting waveguide 202 is a single-mode waveguide grating with an initial width of W. a1 The waveguide grating is an antisymmetric structure with double sidewall modulation, and there is a 180° phase difference between the two gratings to suppress self-reflection of the waveguide. The grating period is fixed at Λ. The grating width is W. gThe spacing between the incident waveguide 201 and the reflecting waveguide 202 is G2, and their widths decrease linearly. The effective widths on the right side are W... b2 and W a2 .

[0097] The principle behind this embodiment for achieving dispersion compensation in two channels is as follows:

[0098] The micro-ring-based mode multiplexer 1 has four ports: input, pass-through, upload, and download. For example... Figure 3 As shown: The TE0 signal from the upload end, due to the different waveguide widths of the lower straight waveguide 102 of the microring and the ring resonant cavity 103, has a mismatched fundamental mode and will not couple into the ring resonant cavity. It is directly transmitted to the download end through the lower straight waveguide 102. The TE0 signal from the input end, however, has the same width as the upper straight waveguide 101 of the ring resonant cavity 103, resulting in mode matching. It will be coupled to the TE0 mode of the ring resonant cavity 103. Furthermore, the TE0 mode of the ring resonant cavity 103 has the same refractive index as the TE1 mode of the lower straight waveguide 102, also resulting in mode matching. It will be coupled into the lower straight waveguide 102. Finally, the TE0 signal from the input end will be coupled to the TE1 mode of the download end at the resonant wavelength of the microring. The mode multiplexer 1 ultimately couples the TE0 modes from input port 1 and input port 2 to the TE0 mode and TE1 mode of the second tapered waveguide 402, respectively, and they enter the incident waveguide 201 of the reverse coupler 2, achieving mode division multiplexing.

[0099] For reverse coupler 2, a chirped grating-assisted reverse coupler, such as Figure 5 As shown, when the wavelength of light incident into the reverse coupling region satisfies the local Bragg condition (n effa + effb )Λ=λ c At this time, light of this wavelength can be coupled into the reflection waveguide 202 by the incident waveguide 201 of the chirped grating-assisted reverse coupler, and the output signal propagation direction is opposite to the incident direction. Due to the linear change in waveguide width, its effective refractive index also changes linearly, thus causing the wavelength of the reflected light satisfying the Bragg condition to change linearly along the light wave propagation direction of the reverse coupler. Since the group delay is proportional to the propagation length, the group delay of the optical signal ultimately changes linearly with the wavelength. Because the refractive indices of the modes TE0 and TE1 of the multimode waveguide are different, the wavelengths at which the two modes satisfy the Bragg condition are also different. Relying on the design of the waveguide width, the difference between λ1 and λ2 is much larger than the wavelength range of the chirped change of a single mode, and is ultimately compensated for by the dispersion of the two output channels λ1 and λ2 in the reflection waveguide 202. Finally, the fifth straight waveguide 305 will output the dispersion-compensated result of the two wavelength signals from output port 1 and input port 2.

[0100] To verify that the present invention can achieve this function, verification examples are provided below:

[0101] This verification example uses the Lumerical Finite-Difference Time-Domain (FDTD) method for calculation and analysis. The simulation test parameters are as follows: the waveguide layer is a 300nm thick X-cut lithium niobate layer, with the lateral direction being the Z direction. The bottom consists of a 300nm thick lithium niobate layer and a 3μm thick silicon dioxide layer, as shown below. Figure 6 As shown. The width is set to: W b =1.1μm, W a =0.8μm, W b1 =1.24μm, W b2 =1.1μmW a1 =W a2 =0.8μm.

[0102] The microring radius R is 50 μm, the coupling region length L is 5 μm, and the coupling region spacing G1 is 0.9 μm. The grating period Λ is 390 nm, the number of periods is 2500, the duty cycle is 20%, the lithium niobate sidewall tilt angle is 70°, and the final equivalent duty cycle is approximately 50%. The grating spacing is 0.3 μm. A single-sided apodization is used, with the apodized portion accounting for 70%.

[0103] Figure 7 Simulation results of a microring-based mode divider (MDD) multiplexer are presented. The solid line represents the transmission spectrum from the fundamental mode at the upper right input port of the microring to the higher-order mode at the lower right, and the dashed line represents the transmission spectrum from the fundamental mode at the upper right input port to the fundamental mode at the lower right. The free spectral range is 5.2 nm, and the bandwidth is 0.1 nm. The insertion loss at channel 1 is 3.8 dB, the extinction ratio is 33 dB, and the crosstalk with the TE0 mode is 30 dB. The transmission from the fundamental mode at the lower left input port of the microring to the fundamental mode at the lower right is almost passband, while the crosstalk to the higher-order modes is above 40 dB, thus achieving the function of mode divider multiplexing.

[0104] Figure 8 , Figure 9 The figures show simulation results for dispersion compensation in single-mode and multi-mode modes, respectively. The dashed lines in the figures represent transmission spectral lines, which are implemented as group delay spectral lines.

[0105] Since only the reflecting waveguide 202 is linearly chirped, the bandwidths of both channels remain essentially unchanged at 3 nm, with insertion losses of 2.54 dB and 2.7 dB, respectively. The center wavelengths of channels 1 and 2 are 1583 nm and 1553 nm, respectively, with a spacing of 30 nm. The maximum dispersion values ​​are 17 ps and 18 ps, and the dispersion values ​​are -2.8 ps / nm and -3.8 ps / nm, respectively. Increasing the device length can achieve higher dispersion values.

[0106] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

[0107] In summary, the cascaded chirped grating-assisted reverse coupler type optical dispersion delay line provided by this invention can achieve dispersion compensation for optical signal inputs of two wavelength channels. It has greater potential in wavelength division multiplexing systems than conventional single-channel signals, and can provide high dispersion values ​​in a compact chip size. It can be better applied to integrated dispersion compensation, optical buffering, and optical true delay networks.

[0108] This invention utilizes the reverse coupling between two waveguides based on the Bragg condition to separate the input light from the reflected output light, which is functionally equivalent to an input-output separated Bragg grating. It does not require additional optical circulators or other beam splitters, thus reducing the integration difficulty of the device.

[0109] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0110] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A two-channel grating-assisted reverse coupler type dispersion compensator, characterized in that, include: The mode division multiplexer (1), the reverse coupler (2), the straight waveguide (3), the tapered waveguide (4), and the curved waveguide (5); The mode divider (1) is a micro-ring-based mode divider, and the reverse coupler (2) is a chirped grating-assisted reverse coupler. The straight waveguide (3) is connected to the mode division multiplexer (1) through the curved waveguide (5); the straight waveguide (3) is connected to the mode division multiplexer (1) through the tapered waveguide (4); the mode division multiplexer (1) is connected to the reverse coupler (2) through the tapered waveguide (4); the straight waveguide (3) is connected to the reverse coupler (2) through the curved waveguide (5). The mode division multiplexer (1) includes an upper straight waveguide (101), a ring resonant cavity (103), and a lower straight waveguide (102). The straight waveguide (3) includes a first straight waveguide (301), a second straight waveguide (302), a third straight waveguide (303), a fourth straight waveguide (304), and a fifth straight waveguide (305). The tapered waveguide (4) includes a first tapered waveguide (401) and a second tapered waveguide (402); The curved waveguide (5) includes a semi-circular curved waveguide (501) and an S-shaped curved waveguide (502). The ring resonant cavity (103) is located between the upper straight waveguide (101) and the lower straight waveguide (102); The straight waveguide (3) is connected to one end of the upper straight waveguide (101) through the curved waveguide (5); The straight waveguide (3) is connected to one end of the lower straight waveguide (102) through the tapered waveguide (4); the other end of the lower straight waveguide (102) is connected to the reverse coupler (2) through the tapered waveguide (4); The upper straight waveguide (101) and the ring resonant cavity (103) are single-mode waveguides, and the lower straight waveguide (102) is a multimode waveguide; The reverse coupler (2) includes an incident waveguide (201) and a reflection waveguide (202). The lower straight waveguide (102) is connected to one end of the incident waveguide (201) through the tapered waveguide (4); The straight waveguide (3) is connected to one end of the reflective waveguide (202) through the curved waveguide (5); The incident waveguide (201) is a single-mode waveguide that supports multiple modes, and the reflection waveguide (202) is a double-sidewall modulation waveguide grating that supports a single mode. The double sidewalls of the reflective waveguide (202) are modulated into a transversely misaligned grating with an antisymmetric structure; The reflecting waveguide (202) is unilaterally abutted on one side near the curved waveguide (5).

2. The two-channel grating-assisted reverse coupler type dispersion compensator according to claim 1, characterized in that, Apodization functions include cosine functions, and apodization methods include changing the grating period, changing the duty cycle, changing the width, and changing the waveguide spacing.

3. The two-channel grating-assisted reverse coupler type dispersion compensator according to claim 1, characterized in that, The first straight waveguide (301) is connected to the upper straight waveguide (101) through the curved waveguide (5), the second straight waveguide (302) is connected to one end of the lower straight waveguide (102) through the tapered waveguide (4), and the fifth straight waveguide (305) is connected to one end of the reflecting waveguide (202) through the curved waveguide (5). The third straight waveguide (303) is connected to the other end of the incident waveguide (201); the fourth straight waveguide (304) is connected to the other end of the reflection waveguide (202).

4. The two-channel grating-assisted reverse coupler type dispersion compensator according to claim 3, characterized in that, The second straight waveguide (302) is connected to the lower straight waveguide (102) through the first tapered waveguide (401), and the two ends of the first tapered waveguide (401) are respectively connected to one end of the second straight waveguide (302) and one end of the lower straight waveguide (102); The lower straight waveguide (102) is connected to the incident waveguide (201) through the second tapered waveguide (402), and the two ends of the second tapered waveguide (402) are respectively connected to one end of the lower straight waveguide (102) and one end of the incident waveguide (201).

5. The two-channel grating-assisted reverse coupler type dispersion compensator according to claim 4, characterized in that, The first straight waveguide (301) is connected to the upper straight waveguide (101) through the semi-circular curved waveguide (501), and the two ends of the semi-circular curved waveguide (501) are respectively connected to one end of the first straight waveguide (301) and one end of the upper straight waveguide (101); The fifth straight waveguide (305) is connected to the reflection waveguide (202) through the S-shaped curved waveguide (502), and the two ends of the S-shaped curved waveguide (502) are respectively connected to one end of the fifth straight waveguide (305) and one end of the reflection waveguide (202).

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