Folding type electro-optical modulator and optical communication system

Abstract

The invention discloses a folding type electro-optical modulator and an optical communication system, and relates to the technical field of optical waveguides, the folding type electro-optical modulator comprises a first modulation area, a third modulation area and a second modulation area, the second modulation area is arranged between the first modulation area and the third modulation area, and the third modulation area is arranged between the first modulation area and the third modulation area. The second modulation region is perpendicular to the first modulation region and the third modulation region; two ends of the second modulation area are respectively connected with the first modulation area and the third modulation area through bending areas; the first waveguide and the second waveguide sequentially penetrate through the first modulation area, the second modulation area and the third modulation area; and the multimode interference coupler is connected with the first waveguide and the second waveguide. According to the invention, the second modulation area is additionally arranged, so that the crosstalk between the first modulation area and the third modulation area is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of optical waveguide technology, specifically to a folded electro-optic modulator and an optical communication system. Background Technology

[0002] Currently, with the continuous development of the information age, the transmission demands of optical communication systems are increasing. Electro-optic modulators are core components in optical communication, primarily responsible for converting electro-optic signals. To date, various silicon photonics-based optical modules have been widely applied in optical communication, including data center intranets and silicon photonics chip interconnects. In practical optical communication systems, Mach-Zehnder (MZ) structure electro-optic modulators are often only a few millimeters long, wasting layout area and hindering large-scale integration. Therefore, it is necessary to reduce the modulator length and the required layout area through folding methods.

[0003] However, when using GS traveling wave electrode routing, the RF signal will be lost during propagation, the modulation length will be long and occupy a large layout area, and severe crosstalk will occur between the upper and lower modulation areas after folding. Using ground electrode shielding will greatly increase the area and is not conducive to impedance matching, which severely limits the bandwidth performance of electro-optic modulator. Summary of the Invention

[0004] This invention provides a foldable electro-optic modulator and an optical communication system, which can solve the problem of severe crosstalk between the upper and lower modulation regions after the electro-optic modulator is folded.

[0005] In a first aspect, embodiments of the present invention provide a folded electro-optic modulator, comprising: First modulation region; The third modulation region is set parallel to the first modulation region at a preset distance; The second modulation region is located between the first modulation region and the third modulation region, and is perpendicular to the first modulation region and the third modulation region. The second modulation region is connected to the first modulation region and the third modulation region at both ends through curved regions, respectively; The first waveguide and the second waveguide pass through the first modulation region, the second modulation region, and the third modulation region in sequence. A multimode interference coupler is connected to the first waveguide and the second waveguide.

[0006] In conjunction with the first aspect, in one implementation method: The first waveguide and the second waveguide are arranged in parallel within the first modulation region, the second modulation region, and the third modulation region.

[0007] In conjunction with the first aspect, in one implementation method: The first waveguide includes a first curved waveguide segment and a second curved waveguide segment disposed in the curved region; The second waveguide includes a third curved waveguide segment and a fourth curved waveguide segment located in the curved region.

[0008] In conjunction with the first aspect, in one implementation, it includes: Multiple first-layer couplers are disposed at both ends of the first curved waveguide segment and the second curved waveguide segment; The first and second curved waveguide segments are made of materials with different refractive indices than the third and fourth curved waveguide segments, so that the light passing through the first and second waveguides has the same propagation time in the curved region.

[0009] In conjunction with the first aspect, in one implementation, it includes: Multiple second-layer couplers are disposed at both ends of the third and fourth curved waveguide segments; The third and fourth curved waveguide segments are made of materials with different refractive indices than the first and second curved waveguide segments, so that the light passing through the first and second waveguides has the same propagation time in the curved region.

[0010] In conjunction with the first aspect, in one implementation, it includes: Multiple third-layer couplers are disposed at both ends of the first curved waveguide segment, the second curved waveguide segment, the third curved waveguide segment, and the fourth curved waveguide segment; The first and second curved waveguide segments are made of materials with different refractive indices than the third and fourth curved waveguide segments, so that the light passing through the first and second waveguides has the same propagation time in the curved region.

[0011] In conjunction with the first aspect, in one implementation method: The preset distance between the first modulation region and the second modulation region is not less than 500um.

[0012] In conjunction with the first aspect, in one implementation method: The first and second curved waveguide segments are made of silicon nitride.

[0013] In conjunction with the first aspect, in one implementation method: The first interlayer coupler has a silicon substrate layer, a silicon oxide layer, and a metal electrode layer arranged from bottom to top. The silicon oxide layer also has a first modulation layer and a second modulation layer.

[0014] Secondly, embodiments of the present invention provide an optical communication system including the folded electro-optic modulator.

[0015] This invention discloses a foldable electro-optic modulator and an optical communication system. The foldable electro-optic modulator includes: a first modulation region; a third modulation region, which is parallel to the first modulation region at a predetermined distance; a second modulation region, which is located between the first and third modulation regions and perpendicular to both of them; the two ends of the second modulation region are respectively connected to the first and third modulation regions via curved regions; a first waveguide and a second waveguide, which sequentially pass through the first, second, and third modulation regions; and a multimode interference coupler connected to the first and second waveguides. This invention effectively reduces crosstalk between the first and third modulation regions by adding a second modulation region. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a top view of the first embodiment of the foldable electro-optic modulator of the present invention; Figure 2 This is a top view of the second embodiment of the foldable electro-optic modulator of the present invention; Figure 3 This is a top view of the third embodiment of the foldable electro-optic modulator of the present invention; Figure 4 This is a top view of the interlayer coupler according to an embodiment of the present invention; Figure 5 This is a cross-sectional structural diagram of the interlayer coupler according to an embodiment of the present invention; Figure 6 This is a graph showing the relationship between the microwave loss curve and the electrode distance in an embodiment of the present invention.

[0018] In the figure: 10, multimode interference coupler; 101, first multimode interference coupler; 102, second multimode interference coupler; 201, first modulation region; 202, second modulation region; 203, third modulation region; 301, first waveguide; 302, second waveguide; 303, first curved waveguide segment; 304, second curved waveguide segment; 305, third curved waveguide segment; 306, fourth curved waveguide segment; 40, interlayer coupler; 401, first interlayer coupler; 402, second interlayer coupler; 403, third interlayer coupler; 501, first curved region; 502, second curved region. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] When electro-optic modulators use GS traveling wave electrodes, the modulation length is typically quite long due to signal loss during propagation, which is detrimental to layout integration. Existing technologies use folding to reduce the area occupied by the electro-optic modulator. However, after folding, the first and third modulation regions are too close together, leading to severe crosstalk between them. Ground electrode shielding is usually used to eliminate crosstalk, but this requires adding ground electrodes above and below the GS, transforming the entire system from GS electrodes to GSSG electrodes. This results in a larger outermost bend radius, causing a sharp increase in area. Furthermore, the increased number of electrodes introduces additional parasitic parameters, especially at bends where the difference between the innermost and outermost paths is too large, leading to uneven electric field distribution and affecting impedance matching, severely limiting the bandwidth performance of the electro-optic modulator. Increasing the bend radius to increase the distance between the first and third modulation regions to eliminate crosstalk further increases the area occupied by the bend.

[0021] like Figure 6 As shown, when the metal electrodes are designed using traveling wave electrodes, severe signal crosstalk occurs when the signal electrodes of the first and third modulation regions of the folded electro-optic modulator are too close together due to voltage imbalance. Crosstalk gradually decreases as the distance increases. The horizontal axis in the figure represents microwave frequency, and the vertical axis represents microwave loss. The curves in the figure show the relationship between microwave frequency and microwave loss for the signal electrodes of the first and third modulation regions at a fixed distance. From the figure and experimental data, it can be seen that when the distance between the signal electrodes of the first and third modulation regions is constant, microwave loss increases with increasing microwave frequency. When the microwave frequency is constant, and the distance is within 500 μm, microwave loss decreases as the distance between the signal electrodes of the first and third modulation regions increases. When the distance is greater than 500 μm, the effect of the distance between the signal electrodes of the first and third modulation regions on microwave loss is negligible. That is, the preset distance between the signal electrodes of the first and third modulation regions can be set to no less than 500 μm. Thus, when the first and third modulation regions do not use ground electrode shielding, the crosstalk between the two modulation regions can also be ignored.

[0022]

[0023] like Figure 1 As shown, the present invention discloses a foldable electro-optic modulator, comprising: a first modulation region 201; a third modulation region 203, which is parallel to the first modulation region 201 at a predetermined distance; a second modulation region 202, which is disposed between the first modulation region 201 and the third modulation region 203, and is perpendicular to the first modulation region 201 and the third modulation region 203; both ends of the second modulation region 202 are respectively connected to the first modulation region 201 and the third modulation region 203 through curved regions; a first waveguide 301 and a second waveguide 302, which sequentially pass through the first modulation region 201, the second modulation region 202, and the third modulation region 203; and a multimode interference coupler 10, which is connected to the first waveguide 301 and the second waveguide 302.

[0024] The first modulation region 201 and the third modulation region 203 are set parallel to each other at a preset distance, and the second modulation region 202 is set perpendicular to the first modulation region 201 and the third modulation region 203. The three modulation regions are on the same plane.

[0025] The multimode interference coupler 10 has two parts: a first multimode interference coupler 101 and a second multimode interference coupler 102.

[0026] The input terminals of the first waveguide 301 and the second waveguide 302 are connected to the output terminal of the first multimode interference coupler 101.

[0027] The output terminals of the first waveguide 301 and the second waveguide 302 are connected to the input terminal of the second multimode interference coupler 102.

[0028] In use, the optical signal enters the first multimode interference coupler 101 through the input optical waveguide and enters the first modulation region 201. The first waveguide 301 and the second waveguide 302 in the first modulation region 201 have equal lengths within the modulation region. After the optical signal completes its first electro-optic modulation in the first modulation region 201, it enters the first bending region 501, completes a 90-degree bend, and then enters the second modulation region 202 for a second electro-optic modulation. After the second modulation, the optical signal enters the second bending region 502, completes another 90-degree bend to achieve a 180-degree reversal, and then enters the third modulation region 203 for a third electro-optic modulation. The first waveguide 301 and the second waveguide 302 in the three modulation regions have the same electric field direction, ensuring the accumulation of the modulation phase. The signal is then output through the second multimode interference coupler 102.

[0029] This invention adds a second modulation region between the first and third modulation regions, which makes the spacing between the first and third modulation regions after folding negligible, allowing the crosstalk between the signal electrodes of the first and third modulation regions to be negligible. By setting the second modulation region, the bending radius of the curved region is greatly reduced, and the area occupied by the curved region is also greatly reduced. To achieve the modulation effect, the total length of the modulation region is fixed, and by setting the second modulation region, the area occupied by the first and third modulation regions can be further reduced.

[0030] like Figure 1 As shown, in one embodiment, the first waveguide 301 and the second waveguide 302 are arranged in parallel within the first modulation region 201, the second modulation region 202, and the third modulation region 203.

[0031] like Figure 1 As shown, in one embodiment, the first waveguide 301 includes a first curved waveguide segment 303 and a second curved waveguide segment 304 disposed in the curved region; the second waveguide 302 includes a third curved waveguide segment 305 and a fourth curved waveguide segment 306 disposed in the curved region.

[0032] The first waveguide 301 achieves the purpose of reversing the direction of light propagation by bending the input light twice by 90 degrees through the first curved waveguide section 303 and the second curved waveguide section 304 located in the curved region.

[0033] The second waveguide 302 achieves the purpose of reversing the direction of light propagation by bending the input light twice by bending the third curved waveguide section 305 and the fourth curved waveguide section 306 in the curved region.

[0034] The present invention achieves the reversal of the light propagation direction by setting a first curved waveguide segment, a second curved waveguide segment, a third curved waveguide segment, and a fourth curved waveguide segment, thereby reducing the area occupied by the layout.

[0035] In practical optical communication systems, Mach-Zehnder (MZ) electro-optic modulators are typically a few millimeters long and several hundred micrometers wide, occupying a large layout area and hindering large-scale integration. Existing solutions reduce the modulator length and thus the layout area occupied by a single electro-optic modulator through folding. However, the bending radii of the upper and lower layers at the bend in the folded electro-optic modulator are different, leading to inconsistent light propagation times in the waveguide of the bend region, ultimately resulting in a speed mismatch in light reaching the second modulation region. Although cross-waveguides have been used to reduce speed mismatch, the design of passive components remains complex.

[0036] like Figure 1As shown, in one embodiment, it includes: a plurality of first interlayer couplers 401 disposed at both ends of the first curved waveguide segment 303 and the second curved waveguide segment 304; the first curved waveguide segment 303 and the second curved waveguide segment 304 are made of materials with different refractive indices than the third curved waveguide segment 305 and the fourth curved waveguide segment 306, so that the light passing through the first waveguide 301 and the second waveguide 302 has the same propagation time in the curved region.

[0037] In use, the optical signal enters the first multimode interference coupler 101 through the input optical waveguide and enters the first modulation region 201. The first electro-optic modulation is completed through the first waveguide 301 and the second waveguide 302 in the first modulation region 201. After modulation, the optical signal is input into the first bending region 501. The light in the first waveguide enters the first bent waveguide segment 303 of the first bending region 501 through the first interlayer coupler 401, completing a 90-degree bend before entering the second modulation region 202, completing the second electro-optic modulation. Subsequently, it enters the second bent waveguide segment 304 of the second bending region 502 through the first interlayer coupler 401, completing a 90-degree bend before entering the second modulation region 202, completing the second electro-optic modulation. Then, it enters the second bent waveguide segment 304 of the second bending region 502 through the first interlayer coupler 401, completing a 90-degree bend before entering the first interlayer coupler 302. The inter-coupler 401 completes a 180-degree reversal and re-enters the third modulation region 203 to complete the third electro-optic modulation. The light in the second waveguide 302 directly passes through the third curved waveguide segment 405, which is made of the same material as the modulation region, and enters the second modulation region 202 after completing a 90-degree bend in the first curved region 501 to complete the second electro-optic modulation. After completing a 90-degree bend in the second curved region 502, it enters the third modulation region 203 to complete the third electro-optic modulation. The first waveguide 301 and the second waveguide 302 in the third modulation region have the same electric field direction, which ensures the accumulation of the modulation phase. Then, it is output through the second multimode interference coupler 102.

[0038] This invention utilizes the difference in group refractive index of two materials to overcome optical wave velocity delay. The basic principle is as follows: In the curved section, due to the unequal path lengths of the inner and outer optical waveguides, a certain velocity delay will occur, resulting in optical loss and reducing the performance of the modulator. Therefore, the lengths of two materials with different refractive indices are set in the curved region to offset the optical delay.

[0039] The key to reducing optical delay using this method lies in setting the lengths of the two waveguides in the curved region. The relationship between the time of optical waveguide passage and the refractive index and length is τ = nL / c; Where n represents the refractive index of the waveguide group, and L represents the length of the first curved waveguide segment. Let the refractive index, length, and time of light passing through the curved waveguide segment of the first curved waveguide segment be n1, L1, and τ1, respectively, and let the refractive index, length, and time of light passing through the waveguide segment of the third curved waveguide segment be n2, L2, and τ2, respectively.

[0040] Optical delay cancellation is achieved by using curved waveguide segments with different refractive indices and materials as compensation structures. The specific steps are as follows: S1 obtains the refractive index n1 of the first curved waveguide segment and the refractive index n2 of the third curved waveguide segment through simulation. S2 calculates the segmental optical delay τ1 of the third curved waveguide segment based on the length L1 of the first curved waveguide segment: τ1 = n1L1 / c; S3 calculates the length L2 of the third curved waveguide segment based on the optical delay τ1, which is cτ1 / n2.

[0041] Similarly, the length of the fourth curved waveguide segment can be calculated for S4.

[0042] This invention utilizes the characteristic that light travels at different speeds in media with different refractive indices. By selecting curved waveguide segments with different refractive indices in the curved region, and matching them, the time of light entering and exiting the curved region in the first and second waveguides is synchronized, so that the light in the first and second waveguides travels for the same time in the curved region. This overcomes the problem of light delay caused by curvature. Compared with using cross waveguides, it occupies less area and is more flexible.

[0043] like Figure 2 As shown, in one embodiment, it includes: a plurality of second interlayer couplers 402 disposed at both ends of the third curved waveguide segment 305 and the fourth curved waveguide segment 306; the third curved waveguide segment 305 and the fourth curved waveguide segment 306 are made of materials with different refractive indices than the first curved waveguide segment 303 and the second curved waveguide segment 304, so that the light passing through the first waveguide 301 and the second waveguide 302 has the same propagation time in the curved region.

[0044] like Figure 3 As shown, in one embodiment, it includes: a plurality of third interlayer couplers 403 disposed at both ends of the first curved waveguide segment 303, the second curved waveguide segment 304, the third curved waveguide segment 305, and the fourth curved waveguide segment 306; the first curved waveguide segment 303 and the second curved waveguide segment 304 are made of materials with different refractive indices than the third curved waveguide segment 305 and the fourth curved waveguide segment 306, so that the light passing through the first waveguide 301 and the second waveguide 302 has the same propagation time in the curved region.

[0045] In use, the optical signal enters the first multimode interference coupler 101 through the input optical waveguide and enters the first modulation region 201. It then passes through the first waveguide 301 and the second waveguide 302 in the first modulation region 201, where the first waveguide 301 and the second waveguide 302 have equal lengths within the modulation region. After completing the first electro-optic modulation in the first modulation region 201, the optical signal enters the first bending region 501, completes a 90-degree bend, and then enters the second modulation region 202 for the second electro-optic modulation. After the second modulation, the optical signal enters the second bending region 502, completes another 90-degree bend to achieve a 180-degree reversal, and then enters the third modulation region 203 for the third electro-optic modulation. The first waveguide 301 and the second waveguide 302 in the three modulation regions have the same electric field direction, ensuring the accumulation of the modulation phase. Finally, the signal is output through the second multimode interference coupler 102.

[0046] To ensure that the light propagation time in the first and second waveguides remains consistent in the curved region, the same waveguide material is used in both the first and second waveguides in the modulation region, thus maintaining a consistent light propagation rate in the modulation region. Three possible solutions to address the light velocity mismatch in the curved region are: 1. Use materials with different refractive indices in the first and second curved waveguide segments compared to those in the modulation region, and use materials with the same refractive index in the first and second waveguide segments compared to those in the modulation region, so that the light in the first and second waveguides travels for the same time in the curved region; 2. Use materials with the same refractive index in the first and second waveguide segments compared to those in the modulation region, and use materials with different refractive indices in the third and fourth curved waveguide segments compared to those in the modulation region, so that the light in the first and second waveguides travels for the same time in the curved region; 3. Use materials with different refractive indices in the first and second waveguide segments compared to those in the modulation region, and use materials with different refractive indices in the third and fourth curved waveguide segments compared to those in the modulation region, so that the light in the first and second waveguides travels for the same time in the curved region.

[0047] Preferably, in one embodiment, the preset distance between the first modulation region 201 and the second modulation region 202 is not less than 500 μm.

[0048] Preferably, in one embodiment, the first bent waveguide segment 303 and the second bent waveguide segment 304 are made of silicon nitride.

[0049] The commonly used waveguide is the silicon waveguide. By selecting silicon nitride as the material for the first and second curved waveguide sections, the propagation speed delay caused by the different bending radii of light in the silicon and silicon nitride waveguides can be overcome by taking advantage of the different propagation speeds of light in the first and second waveguides in the curved region.

[0050] like Figure 5 As shown, the first interlayer coupler 401 is provided with a silicon substrate layer, a silicon oxide layer, and a metal electrode layer from bottom to top. The silicon oxide layer is also provided with a first modulation layer and a second modulation layer.

[0051] The present invention also discloses an optical communication system, including the aforementioned folded electro-optic modulator.

[0052] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention 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, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0053] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0054] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A folded electro-optic modulator, characterized in that, It includes: First modulation region (201); The third modulation region (203) is set parallel to the first modulation region (201) at a preset distance; The second modulation region (202) is located between the first modulation region (201) and the third modulation region (203), and is perpendicular to the first modulation region (201) and the third modulation region (203); the two ends of the second modulation region (202) are respectively connected to the first modulation region (201) and the third modulation region (203) through curved regions; The first waveguide (301) and the second waveguide (302) pass through the first modulation region (201), the second modulation region (202) and the third modulation region (203) in sequence. A multimode interference coupler (10) is connected to the first waveguide (301) and the second waveguide (302).

2. The folded electro-optic modulator according to claim 1, characterized in that: The first waveguide (301) and the second waveguide (302) are arranged in parallel within the first modulation region (201), the second modulation region (202), and the third modulation region (203).

3. A folded electro-optic modulator according to claim 2, characterized in that: The first waveguide (301) includes a first curved waveguide segment (303) and a second curved waveguide segment (304) disposed in the curved region. The second waveguide (302) includes a third curved waveguide segment (305) and a fourth curved waveguide segment (306) located in the curved region.

4. A folded electro-optic modulator according to claim 3, characterized in that, include: Multiple first interlayer couplers (401) are disposed at both ends of the first curved waveguide segment (303) and the second curved waveguide segment (304); The first curved waveguide segment (303) and the second curved waveguide segment (304) are made of materials with different refractive indices than the third curved waveguide segment (305) and the fourth curved waveguide segment (306) so that the light passing through the first waveguide (301) and the second waveguide (302) has the same propagation time in the curved region.

5. A folded electro-optic modulator according to claim 3, characterized in that, include: Multiple second interlayer couplers (402) are disposed at both ends of the third curved waveguide segment (305) and the fourth curved waveguide segment (306); The third curved waveguide segment (305) and the fourth curved waveguide segment (306) are made of materials with different refractive indices than the first curved waveguide segment (303) and the second curved waveguide segment (304) so ​​that the light passing through the first waveguide (301) and the second waveguide (302) has the same propagation time in the curved region.

6. A folded electro-optic modulator according to claim 3, characterized in that, include: Multiple third-layer couplers (403) are disposed at both ends of the first curved waveguide segment (303), the second curved waveguide segment (304), the third curved waveguide segment (305), and the fourth curved waveguide segment (306); The first curved waveguide segment (303) and the second curved waveguide segment (304) are made of materials with different refractive indices than the third curved waveguide segment (305) and the fourth curved waveguide segment (306) so that the light passing through the first waveguide (301) and the second waveguide (302) has the same propagation time in the curved region.

7. A folded electro-optic modulator according to claim 1, characterized in that: The preset distance between the first modulation region (201) and the second modulation region (202) is not less than 500um.

8. A folded electro-optic modulator according to claim 4, characterized in that: The first curved waveguide segment (303) and the second curved waveguide segment (304) are made of silicon nitride material.

9. A folded electro-optic modulator according to claim 4, characterized in that: The first interlayer coupler (401) is provided with a silicon substrate layer, an oxygen silicon layer and a metal electrode layer from bottom to top. The oxygen silicon layer is also provided with a first modulation layer and a second modulation layer.

10. An optical communication system, characterized in that... Includes a folded electro-optic modulator as described in any one of claims 1-9.

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