CN110749956B - Reconfigurable optical mode converter compatible with wavelength division multiplexing - Google Patents

Abstract

The invention provides a reconfigurable optical mode converter compatible with wavelength division multiplexing, which includes a multi-ring cascade and a mode converter that are connected to each other; and n-1 tunable microring resonators, where n is a positive integer greater than or equal to 2. The optical mode converter applies multi-ring cascade to the mode converter. By changing the resonant state of each tunable micro-ring resonator, the light in the active micro-ring is divided into x equal parts, and the light in the active micro-ring is divided into x parts, and the light in the active micro-ring is divided into x parts through the resonant micro-ring resonator. The ring resonator is downloaded into the corresponding waveguide, and the fundamental mode can be converted into any high-order mode at the same time through the mode converter, that is, multiple modes are generated at the same time, so as to solve the problem of too many lasers required in the optical communication system. . The invention has good expansibility and can be combined with wavelength division multiplexing, thereby improving the flexibility of the optical communication system.

Description

A Reconfigurable Optical Mode Converter Compatible with Wavelength Division Multiplexing

technical field

The invention belongs to the technical field of optical mode multiplexing, and relates to a reconfigurable optical mode converter compatible with wavelength division multiplexing.

Background technique

With the advent of the era of big data, people's requirements for information processing speed and processing capacity have been further improved. By applying advanced optical multiplexing technology to high-speed optical communication systems, researchers have improved the information transmission capacity of optical networks. At present, the most mature multiplexing technology is wavelength division multiplexing. With the increase of data communication capacity, the number of laser sources required by wavelength division technology will increase proportionally, which makes the cost of optical communication systems also greatly increased. rise. To this end, the researchers introduced optical mode multiplexing technology in the transmission of light. The mode of light is the wavelength of light, a dimension outside the polarization, and different modes of light propagate independently of each other in a waveguide or fiber. Therefore, the transmission signal can be carried on different modes of the same wavelength, data transmission can be carried out by using the orthogonality of the modes, and the mode demultiplexer can be used at the receiving end to demultiplex different optical modes into different ports. In this way, different modes of one wavelength can be used to replace more required wavelengths through the optical mode multiplexing technology, thereby greatly reducing the number of on-chip laser sources, and at the same time improving the information processing capability in the optical communication system.

The current optical mode converters and mode multiplexers generally convert one mode into another specific mode. In 2014, L. W. Luo et al. published an article in the famous journal Nature Communications "WDM-compatible mode-division multiplexing on a silicon chip” (Nature Communications, Vol. 5, pp. 3069). The pattern multiplexer based on microring was proposed for the first time. Since then, the research on patterns has attracted more and more researchers' attention. In 2019, X.Han et al. published the technical paper "Reconfigurable On-Chip Mode Exchange for Mode-Division Multiplexing Optical Networks" in the Journal of Lightwave Technology (Journal of Lightwave Technology, Vol.37, Issue 3, pp. 1008- 1013) proposed a mode-selective switch between fundamental and higher-order modes based on a micro-ring mode converter. However, these devices cannot realize the conversion from one mode to multiple modes at the same time, that is, cannot generate multiple modes at the same time. For wavelength division multiplexing, different wavelengths can be input into the same waveguide or fiber at the same time. However, the above devices cannot generate multiple modes at the same time, and cannot perform parallel processing on the required modes, which greatly reduces the information processing capability of the optical communication system and cannot meet the demands of the increasingly large optical communication system.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a reconfigurable optical mode converter compatible with wavelength division multiplexing, which can realize mode conversion from the fundamental mode to any number of high-order modes at the same time, and reduce the number of laser sources in the optical communication system by using the mode division multiplexing. Thereby, the power consumption of the optical communication system is reduced.

In order to achieve the above object, the technical solution adopted in the present invention is: a reconfigurable optical mode converter compatible with wavelength division multiplexing, comprising a multi-ring cascade and a mode converter connected; the multi-ring cascade is composed of It consists of a straight waveguide, a passive microring and n tunable microring resonators.

The optical mode converter of the present invention is based on the mode conversion principle in the prior art, and the cascaded micro-ring is applied to the mode converter. The passive micro-ring R1 and the micro-ring R2 and the micro-ring in the optical mode converter are R3 and microring R4 are cascaded, and by adjusting the effective refractive index of active microrings such as microring R2, microring R3 and microring R4, the resonance state of active microrings such as R2, R3 and R4 can be changed to realize the fundamental mode. Conversion to any number of higher-order modes at the same time. The optical mode converter can be well combined with mature CMOS process technology, and the device has good scalability and can be combined with wavelength division multiplexing technology to improve the flexibility of optical networks. important role in the communication system.

Description of drawings

FIG. 1 is a schematic diagram of an optical mode converter of the present invention.

FIG. 2 is a schematic diagram of a multi-loop cascade in an embodiment of the optical mode converter of the present invention.

FIG. 3 is a schematic diagram of a mode conversion structure in an embodiment of the optical mode converter of the present invention.

FIG. 4 is an output spectrum diagram of the fundamental mode converted into any high-order mode in the optical mode converter of the present invention.

FIG. 5 is an output spectrum diagram of the fundamental mode converted into any two high-order modes in the optical mode converter of the present invention.

6 is an output spectrum diagram of the fundamental mode converted into any three high-order modes in the optical mode converter of the present invention.

Figure 7 is a schematic diagram of the cross-sectional structure of a silicon-based thermo-optically modulated microring resonator or straight waveguide.

FIG. 8 is a schematic diagram of the cross-sectional structure of a silicon-based electro-optically modulated microring resonator or straight waveguide.

Figure 9 is a graph of the spectral response of a microring resonator, taking silicon-based thermo-optic modulation as an example.

In the figure: 1. Multi-loop cascade, 2. Mode converter, 2-1. The first straight waveguide, 2-2. The first curved waveguide, 2-3. The second straight waveguide, 2-4. The second Curved waveguide, 2-5. Third curved waveguide, 2-6. Third straight waveguide, 2-7. Fourth curved waveguide, 2-8. Fifth curved waveguide, 2-9. Fourth straight waveguide, 2- 10. The sixth curved waveguide, 2-11. The seventh curved waveguide, 2-12. The fifth straight waveguide, 2-13. The eighth curved waveguide, 2-14. The sixth straight waveguide, 2-15. The seventh straight waveguide Waveguide, 2-16. Eighth straight waveguide;

1-1. The ninth straight waveguide, 1-2. The tenth straight waveguide, 1-3. The ninth curved waveguide, 1-4. The tenth straight waveguide, 1-5. The tenth curved waveguide, 1-6. Twelfth straight waveguide, 1-7. Eleventh curved waveguide, 1-8. Thirteenth straight waveguide, 1-9. Fourteenth straight waveguide, 1-10. Twelfth curved waveguide, 1-11. The fifteenth straight waveguide, 1-12. The sixteenth straight waveguide, 1-13. The thirteenth curved waveguide, 1-14. The seventeenth straight waveguide, and 1-15. The eighteenth straight waveguide.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1, the reconfigurable optical mode converter of the present invention includes a multi-ring cascade 1 and a mode converter 2 connected to each other; the multi-ring cascade 1 consists of a straight waveguide, a passive micro-ring and It consists of n tunable microring resonators.

The mode converter 2 in the reconfigurable optical mode converter of the present invention includes a plurality of straight waveguides for mode converters arranged in sequence, the straight waveguides for adjacent mode converters are connected through adiabatic cones, and the plurality of mode converters use the width of the straight waveguides. Decrease in turn; a mode converter is coupled with a straight waveguide with a curved structure waveguide, the curved structure waveguide is composed of a straight waveguide for a curved structure waveguide and two curved waveguides for a curved structure waveguide, and the two curved structure waveguides pass through the curved waveguide The curved structure waveguide is connected by a straight waveguide, and the straight waveguide for the curved structure waveguide is arranged in parallel with the straight waveguide for the coupled mode converter; in the same curved structure waveguide, the curved structure waveguide with the smallest width among the straight waveguides for the mode converter is used for the curved structure waveguide. The other ends of are connected to the multi-ring cascade 1. The width of the straight waveguide for the curved structure waveguide and the curved waveguide for the curved structure waveguide are the same in all the curved structure waveguides.

2 is a mode converter 2 in an embodiment of the reconfigurable optical mode converter of the present invention, including a first straight waveguide 2-1, an eighth straight waveguide 2-16, and a seventh straight waveguide 2-15 arranged in sequence and the sixth straight waveguide 2-14, the first straight waveguide 2-1 is connected to the eighth straight waveguide 2-16 through the first adiabatic cone, and the eighth straight waveguide 2-16 is connected to the seventh straight waveguide through the second adiabatic cone 2-15 are connected, the seventh straight waveguide 2-15 is connected with the sixth straight waveguide 2-14 through the third adiabatic cone; the width of the first straight waveguide 2-1 is smaller than the width of the eighth straight waveguide 2-16, the eighth The width of the straight waveguide 2-16 is smaller than the width of the seventh straight waveguide 2-15, and the width of the seventh straight waveguide 2-15 is smaller than the width of the sixth straight waveguide 2-14;

The mode converter 2 shown in FIG. 2 further includes a second straight waveguide 2-3, a third straight waveguide 2-6, a fourth straight waveguide 2-9 and a fifth straight waveguide 2-12, the second straight waveguide 2-3 parallel to and coupled with the first straight waveguide 2-1, the third straight waveguide 2-6 parallel to and coupled with the eighth straight waveguide 2-16, the fourth straight waveguide 2-9 parallel to and coupled with the seventh straight waveguide 2-15, The fifth straight waveguide 2-12 is parallel to and coupled with the sixth straight waveguide 2-14; the two ends of the second straight waveguide 2-3 are respectively connected with the first curved waveguide 2-2 and the second curved waveguide 2-4, the third Two ends of the straight waveguide 2-6 are respectively connected with a third curved waveguide 2-5 and a fourth curved waveguide 2-7, and two ends of the fourth straight waveguide 2-9 are respectively connected with a fifth curved waveguide 2-8 and a sixth curved waveguide Both ends of the curved waveguide 2-10 and the fifth straight waveguide 2-12 are respectively connected with a seventh curved waveguide 2-11 and an eighth curved waveguide 2-13;

The first curved waveguide 2-2, the third curved waveguide 2-5, the fifth curved waveguide 2-8 and the seventh curved waveguide 2-11 all face the direction of the first straight waveguide 2-1, and the first curved waveguide 2- The other end of connected.

The width of the first curved waveguide 2-2, the width of the second straight waveguide 2-3, the width of the second curved waveguide 2-4, the width of the third curved waveguide 2-5, the width of the third straight waveguide 2-6, The width of the fourth curved waveguide 2-7, the width of the fifth curved waveguide 2-8, the width of the fourth straight waveguide 2-9, the width of the sixth curved waveguide 2-10, the width of the seventh curved waveguide 2-11, The width of the fifth straight waveguide 2-12 is the same as the width of the eighth curved waveguide 2-13.

The multi-ring cascade element 1 in the reconfigurable optical mode converter of the present invention includes a ring-shaped structure composed of a ninth straight waveguide 1-1 and n tunable micro-ring resonators, and each device constituting the ring-shaped structure Not in contact with each other, the n tunable micro-ring resonators are micro-ring resonators R2, micro-ring resonators R3, micro-ring resonators R4, ... and micro-ring resonators Rn arranged in sequence, and the tunable micro-ring resonators are Active microring; the ring structure is provided with a microring resonator R1, and the microring resonator R1 is a passive microring; the number of active microrings is the same as that of the curved structure waveguides in the mode converter 2. The radius of all active microrings is the same and smaller than that of passive microrings.

Each active micro-ring is coupled with a straight waveguide for the multi-ring cascade, and the active micro-ring is located between the straight waveguide for the multi-ring cascade coupled to the active micro-ring and the micro-ring resonator R1 During the period, all straight waveguides for multi-ring cascades coupled with active micro-rings do not intersect, and a straight waveguide for multi-ring cascades coupled with active micro-rings is connected to the mode converter through a connecting waveguide 2 One of the curved-structure waveguides is connected, that is, the straight waveguide for the multi-loop cascade coupled with the active micro-ring passes through a curved-structure waveguide connecting the waveguide and the mode converter 2 toward the straight waveguide for the mode converter. The curved structure waveguide with the smallest width straight waveguide is connected with the other end of the curved waveguide.

The structure of the connecting waveguide is determined according to the distance between the straight waveguide for the multi-loop cascade coupled with the active micro-ring and the curved waveguide in the mode converter 2 to which the straight waveguide is to be connected, and can be two curved waveguides and two curved waveguides. The root straight waveguides are arranged and connected in sequence, and can be formed by connecting two straight waveguides with a curved waveguide, or a straight waveguide, and all the connecting waveguides do not intersect.

3 is a multi-ring cascade component 1 in an embodiment of the reconfigurable optical mode converter of the present invention, including a ninth straight waveguide 1-1, a micro-ring resonator R2, a micro-ring resonator R3, a micro-ring resonator The ring structure formed by the resonator R4 and the micro-ring resonator R5, the ninth straight waveguide 1-1, the micro-ring resonator R2, the micro-ring resonator R3, the micro-ring resonator R4 and the micro-ring resonator R5 are not in contact. The ring structure is provided with a micro-ring resonator R1, the micro-ring resonator R1 is a passive micro-ring, and the micro-ring resonator R2, the micro-ring resonator R3, the micro-ring resonator R4 and the micro-ring resonator R5 are active micro-rings. Ring; the radius of the micro-ring resonator R2, the radius of the micro-ring resonator R3, the radius of the micro-ring resonator R4 and the radius of the micro-ring resonator R5 are the same and smaller than the radius of the micro-ring resonator R1.

The micro-ring resonator R2 is coupled to the tenth straight waveguide 1-2 arranged vertically, and the upper end of the tenth straight waveguide 1-2 is connected to one end of the tenth straight waveguide 1-4 through the ninth curved waveguide 1-3. The other end of the tenth straight waveguide 1-4 is connected to the upper end of the twelfth straight waveguide 1-6 through the tenth curved waveguide 1-5, and the lower end of the twelfth straight waveguide 1-6 is connected to the first curved waveguide 2-2. The other ends are connected; here, the ninth curved waveguide 1-3, the tenth straight waveguide 1-4, the tenth curved waveguide 1-5 and the twelfth straight waveguide 1-6, which are connected in sequence, constitute the connecting waveguide.

The micro-ring resonator R3 is coupled with the vertically arranged fifteenth straight waveguide 1-11, and the upper end of the fifteenth straight waveguide 1-11 passes through the twelfth curved waveguide 1-10 and one end of the fourteenth straight waveguide 1-9 connected, the other end of the fourteenth straight waveguide 1-9 is connected to the upper end of the thirteenth straight waveguide 1-8 through the eleventh curved waveguide 1-7, and the lower end of the thirteenth straight waveguide 1-8 is connected to the third curved waveguide The other ends of 2-5 are connected; here, the twelfth curved waveguide 1-10, the fourteenth straight waveguide 1-9, the thirteenth straight waveguide 1-8 and the eleventh curved waveguide 1-7, which are connected in sequence, form a connection waveguide.

The microring resonator R4 is coupled with the seventeenth straight waveguide 1-14 arranged horizontally, and one end of the seventeenth straight waveguide 1-14 is connected to the upper end of the sixteenth straight waveguide 1-12 through the thirteenth curved waveguide 1-13 , the lower end of the sixteenth straight waveguide 1-12 is connected to the other end of the fifth curved waveguide 2-8; here, the connected thirteenth curved waveguide 1-13 and the sixteenth straight waveguide 1-12 constitute a connecting waveguide.

The microring resonator R5 is coupled to the eighteenth straight waveguide 1-15 arranged vertically, and the lower end of the eighteenth straight waveguide 1-15 is connected to the other end of the seventh curved waveguide 2-11. Here, the eighteenth straight waveguides 1-15 are connecting waveguides.

All waveguides in Figure 3 (both straight and curved) have the same width.

The resonant wavelength of the microring resonator is changed by changing the effective refractive index of the microring resonator.

In the reconfigurable optical mode converter of the present invention, the straight waveguides of different widths connected in sequence in the mode converter 2 are connected by a sufficiently long adiabatic cone to form an output waveguide, wherein the width of the adiabatic cone changes linearly and gradually, Changing from a narrower waveguide width to a wider waveguide width ensures that the lower-order mode optical signal propagates in the adiabatic cone without mode switching. Since the effective refractive index of different modes is related to the width of the waveguide and the order of the modes, to realize the mode conversion, the effective refractive index of the converted modes must be the same. conversion.

For example, the mode of the light input into the ninth straight waveguide 1-1 is the fundamental mode TE ₀ , and the input light conforming to the resonance wavelength λ of the microring resonator R1 is coupled into the microring resonator R1 through the coupling region. The micro-ring resonator R1 is cascaded with a plurality of micro-ring resonators R2, R3, R4, ..., Rn whose radius is smaller than the radius of the micro-ring resonator R1. Change the waveguide temperature of the micro-ring resonators R2, R3, R4,..., Rn, so as to change the effective refractive index of the micro-ring resonators R2, R3, R4,..., Rn, correspondingly, the micro-ring resonator is realized. Tuning effect of R2, R3, R4, ..., Rn. If the light with wavelength λ is downloaded to the output waveguide of the micro-ring resonator R2, it is only necessary to adjust the resonance wavelength of the micro-ring resonator R2 to λ. Similarly, any micro-ring resonator such as R3 and R4 can be adjusted to any The resonant wavelength of one or more resonators can realize that the light with wavelength λ is evenly divided and output from the desired output waveguide. If the input wavelength is changed to λ1 and the number of resonant microrings is correspondingly increased, the simultaneous conversion of multiple modes in the two wavelengths of λ and λ1 can be realized at the same time. By analogy, the reconfigurable optical mode converter of the present invention has the function of being compatible with wavelength division multiplexing.

Figure 4 is a spectrum diagram of the download end obtained when any one of the micro-ring resonators R2, R3, R4, ..., Rn resonates, the ordinate is the light intensity of the download end, and the abscissa is the wavelength. When only one of the microring resonators R2, R3, R4,...Rn resonates, the light coupled from the input waveguide into the microring resonator R1 will be directly downloaded to the corresponding microring resonator through the resonating microring resonator into the waveguide and into the mode converter. Since the effective refractive index of the fundamental mode in the fundamental mode waveguide is the same as the effective refractive index of the mode to be converted in the waveguide width of its conversion region, the fundamental mode in the fundamental mode waveguide will be converted into the corresponding mode.

As shown in Figure 5, it is the download end spectrum obtained when any two microring resonators in the microrings R2, R3, R4, ... Rn resonate, the ordinate is the light intensity of the download end, and the abscissa is the wavelength. The two curves in Fig. 5 basically overlap. Due to the slight difference in the coupling conditions of each microring resonator, the tops of the two curves are slightly different. In the curve, when there are two micro-ring resonators in R2, R3, R4, ..., Rn, the light coupled from the input waveguide to the micro-ring resonator R1 will be divided into two parts, respectively, passing through the micro-ring resonator in the resonant state. The ring resonator is downloaded into the corresponding waveguide and converted into the corresponding mode by the mode converter 2, and the converted mode can be transmitted in the multi-mode waveguide at the same time.

Figure 6 is a spectrum diagram of the download end obtained when any three micro-ring resonators in the micro-rings R2, R3, R4, ... Rn resonate, the ordinate is the light intensity of the download end, and the abscissa is the wavelength. The three curves in Fig. 6 basically overlap, and the tops of the three curves are slightly different due to the slight difference in the coupling conditions of each microring resonator. When there are three microring resonators in R2, R3, R4, ..., Rn to resonate, the light coupled from the input waveguide to the microring resonator R1 will be equally divided into three equal parts, respectively passing through the resonating microrings Downloaded to the corresponding waveguide, and then converted into the corresponding mode through the mode converter 2, the converted mode can be transmitted in the multi-mode waveguide at the same time.

The device of the present invention is based on SOI material. Since the refractive index difference between the waveguide core layer Si (refractive index: 3.45) made of SOI material and the substrate SiO ₂ (refractive index: 1.44) is large, it has a strong effect on the optical field. Therefore, the size of the device is small, and the radius of the microring resonator can also be small. At the same time, the reconfigurable optical mode converter of the present invention can also be realized by using materials such as SIN and III-V groups.

The resonant frequency of the microring resonator in the reconfigurable optical mode converter of the present invention can be tuned based on the thermo-optic effect, or can be tuned by the plasmon dispersion effect. Figure 7 is a cross-sectional view of a silicon-based thermo-optically modulated microring resonator or straight waveguide, whose substrate is Si, with a layer of _SiO2 material _on the substrate, and a waveguide core layer (Si material) and tuning electrodes, the waveguide core layer and tuning electrodes are surrounded by _SiO2 material. The width of the waveguide core layer is W, the height is H, and the distance between the top of the core region and the bottom of the tuning electrode is d _SiO2 . Figure 8 shows a cross-sectional view of a silicon-based electro-optical modulation microring resonator or straight waveguide. The electro-optical modulation structure has high modulation efficiency and fast modulation speed. The injection and extraction of carriers in the waveguide can be changed by an applied voltage, thereby changing the effective refractive index of the waveguide. When a forward bias is applied, carriers will be injected into the waveguide SI from the P and N regions, and when a reverse bias is applied, the electrons and holes in the waveguide SI will be extracted.

Figure 9 shows the spectral response of the thermo-optically modulated micro-ring resonator. When no voltage is applied, the resonant wavelength of the micro-ring resonator is located at λ1. At this time, only the light with wavelength λ1 can be downloaded by the micro-ring resonator. As shown in Figure 9a; when an appropriate voltage is applied, the resonant wavelength of the microring resonator will move to λ2 due to the thermo-optic effect, and only the light with wavelength λ2 can be downloaded by the microring resonator, as shown in Figure 9b.

The optical mode converter of the invention applies multi-ring cascade to the mode converter, and by changing the resonance state of each tunable micro-ring resonator (active micro-ring), the light in the passive micro-ring is equally divided into x The optical mode converter of the present invention can realize the conversion of the fundamental mode to any variety of high-order modes at the same time, that is, to generate multiple modes at the same time, Thus, the problem that the number of lasers required in the optical communication system is too large is solved. The invention has good expansibility, can be combined with wavelength division multiplexing, and improves the flexibility of the optical communication system.

Claims (4)

1. A reconfigurable optical mode converter compatible with wavelength division multiplexing, characterized in that it comprises a connected multi-ring cascade (1) and a mode converter (2); the multi-ring cascade (1) It consists of a straight waveguide, a passive micro-ring and n tunable micro-ring resonators. The passive micro-ring in the optical mode converter is cascaded with n active tunable micro-rings. The effective refractive index of the ring, thereby changing the resonance state of the active microring; and n≥2. 2 . The reconfigurable optical mode converter compatible with wavelength division multiplexing according to claim 1 , wherein the mode converter ( 2 ) comprises a plurality of straight waveguides for mode converters arranged in sequence, and adjacent to 2 . The mode converters are connected by straight waveguides through adiabatic cones, and the widths of the multiple mode converters are successively decreased by the straight waveguides; one mode converter is coupled with a straight waveguide with a curved structure waveguide, and the curved structure waveguide is composed of a straight waveguide with a curved structure waveguide. It is composed of two curved waveguides using curved waveguides, and the two curved waveguides are connected by straight waveguides through the curved waveguides, and the straight waveguides for the curved waveguides are arranged in parallel with the coupled mode converters using straight waveguides; the same curved structure The other ends of the curved waveguides of the straight waveguides with the smallest width in the straight waveguides facing the mode converter are all connected with the multi-loop cascade (1); all the curved waveguides are straight waveguides and curved waveguides in the curved waveguides The widths of the curved waveguides are all the same. 3. The reconfigurable optical mode converter compatible with wavelength division multiplexing according to claim 2, characterized in that the multi-ring cascade (1) comprises a ninth straight waveguide (1-1) and a A ring structure composed of n tunable micro-ring resonators, the devices constituting the ring structure are not in contact, the ring structure is provided with a micro-ring resonator R1, and the micro-ring resonator R1 is a passive micro-ring; The number of active microrings is the same as the number of curved waveguides in the mode converter (2); the radii of all active microrings are the same and smaller than that of passive microrings; Each active micro-ring is coupled with a straight waveguide for the multi-ring cascade, and the active micro-ring is located between the straight waveguide for the multi-ring cascade coupled to the active micro-ring and the micro-ring resonator R1 During the period, all straight waveguides for multi-ring cascades coupled with active micro-rings do not intersect, and one straight waveguide for multi-ring cascades coupled with active micro-rings connects the waveguide with the mode converter ( 2) In one of the curved structure waveguides facing the mode converter, the curved structure waveguides of the straight waveguides with the smallest width in the straight waveguides are connected with the other end of the curved waveguides; all the connecting waveguides do not intersect. 4. The reconfigurable optical mode converter compatible with wavelength division multiplexing according to claim 3, wherein the connecting waveguide is formed by connecting two curved waveguides and two straight waveguides in sequence; or , is a curved waveguide connecting two straight waveguides; or, is a straight waveguide.

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