Mode order converter, optical module and optical network equipment

Abstract

The invention provides a mode order converter, an optical module and optical network equipment, relates to the technical field of communication, and aims to solve the technical problem of poor working performance of the mode order converter. The mode order converter provided by the invention comprises a first port, a second port, a waveguide structure and a phase shift structure, the waveguide structure and the phase shift structure are respectively connected between the first port and the second port; the phase shift structure comprises a waveguide substrate, the waveguide substrate comprises a first section, a middle section and a second section which are sequentially connected, the peripheral surface of the first section comprises a first chirp grating, the peripheral surface of the second section comprises a second chirp grating, the peripheral surface of the middle section comprises a uniform grating, the width of the first chirp grating is gradually increased from one end of the first section to the middle section, and the width of the second chirp grating is gradually increased from the other end of the first section to the middle section. And the width of the second chirp grating is gradually increased from one end of the second section to the middle section. The mode order converter provided by the invention can realize effective mode order conversion on transverse electric waves and transverse magnetic waves.

Description

Technical Field

[0001] This application relates to the field of communication technologies, and in particular, to a mode-order converter, an optical module, and an optical network device. Background Art

[0002] In the field of optical communication, the signal transmission capacity can be improved by adopting the mode division multiplexing (MDM) technology. Mode division multiplexing refers to a technology in which optical signals of multiple orthogonal modes with different paths and mode field distributions and carrying different information propagate together in the same multimode optical waveguide. As an important mode division multiplexing device, a mode-order converter (MDM) can realize the mutual conversion between the fundamental mode and the high-order mode of a signal, so as to facilitate the transmission of the signal in a few-mode optical fiber. For example, in the currently adopted mode division multiplexing technology, the common transmission of two different modes, namely, the transverse electric wave (TE) and the transverse magnetic wave (TM), can be realized. Among them, there is a need for mutual conversion between the fundamental mode and the high-order mode for both the transverse electric wave and the transverse magnetic wave. However, in the current mode-order converter, it is difficult to effectively realize the mode-order conversion for both the above-mentioned transverse electric wave and transverse magnetic wave. Summary of the Invention

[0003] This application provides a mode-order converter, an optical module, and an optical network device that can realize mode-order conversion for transverse electric waves and transverse magnetic waves.

[0004] In a first aspect, this application provides a mode-order converter, including a first port, a second port, a waveguide structure, and a phase shift structure. The waveguide structure is connected between the first port and the second port. The phase shift structure includes a waveguide substrate, and the waveguide substrate includes a first section, a middle section, and a second section that are connected in sequence. Moreover, the waveguide substrate is connected between the first port and the second port. The outer peripheral surface of the first section includes a first chirped grating, the outer peripheral surface of the second section includes a second chirped grating, and the outer peripheral surface of the middle section includes a uniform grating. Among them, the width of the first chirped grating gradually increases from one end of the first section to the middle section, and the width of the second chirped grating gradually increases from one end of the second section to the middle section. In practical applications, the first port can be used as the input port of the optical wave, and the second port can be used as the output port of the optical wave. When the optical wave propagates in the waveguide structure, a phase change will occur. The phase shift structure can be regarded as a combined structure of the waveguide structure and the grating. When the optical wave propagates in the phase shift structure, a phase change will also occur. Moreover, an additional phase difference will be added under the action of the refractive index change of the phase shift structure. When two optical waves are combined at the second port, the conversion of the optical wave mode can be realized. Moreover, effective mode-order conversion can be realized for both transverse electric waves and transverse magnetic waves.

[0005] In one example, the cross-sections of the first section, the middle section, and the second section are the same. Through this structure with the same cross-section, the structure of the waveguide substrate is effectively simplified, which can improve the convenience in manufacturing the phase shift structure. In addition, regions with relatively small cross-sections in the waveguide substrate can be avoided, making the mode order converter insensitive to manufacturing precision, which is beneficial to ensuring the stability of the mode order converter.

[0006] In one example, the cross-sections of the waveguide substrate and the waveguide structure are the same, which can reduce the complexity in calculating and designing the mode order converter.

[0007] In one example, the width dimension of the uniform grating is greater than the maximum width dimensions of the first chirped grating and the second chirped grating, which can achieve an effective transition between the uniform grating, the first chirped grating, and the second chirped grating.

[0008] In one example, the first chirped grating includes a plurality of grating teeth arranged at intervals along the extending direction of the first section, the second chirped grating includes a plurality of grating teeth arranged at intervals along the extending direction of the second section, and the uniform grating includes a plurality of grating teeth arranged at intervals along the extending direction of the middle section. Among them, the distance between two adjacent grating teeth is the same. That is, the plurality of grating teeth are arranged with the same period, which can effectively simplify the structure of the mode order converter, thereby reducing the complexity in calculating and designing the mode order converter.

[0009] In one example, the length dimensions of each grating tooth are the same, which can effectively simplify the structure of the mode order converter, thereby reducing the complexity in calculating and designing the mode order converter.

[0010] In one example, the distance between adjacent grating teeth in each chain is less than the operating wavelength of the mode order converter, that is, the uniform grating, the first chirped grating, and the second chirped grating are all sub-wavelength structures, which can effectively improve the applicability of the mode order converter.

[0011] In one example, the first chirped grating and the second chirped grating are symmetrically arranged with respect to the middle section, thereby reducing the complexity in calculating and designing the mode order converter.

[0012] In one example, the ratio of the effective refractive index difference when the transverse electric wave propagates in the phase shift structure to the effective refractive index difference when the transverse magnetic wave propagates in the phase shift structure is an odd number. This is to facilitate effective mode conversion for both the transverse electric wave and the transverse magnetic wave.

[0013] In one example, the mode-order converter further includes a first splitter and a second splitter. The first splitter has a first input port and two first output ports. The first input port constitutes the first port, and the two first output ports are respectively connected to the waveguide structure and the waveguide substrate. The second splitter has two second input ports and a second output port. The two second input ports are respectively connected to the waveguide structure and the waveguide substrate, and the second output port constitutes the second port.

[0014] In one example, the mode-order converter includes a plurality of pairs of waveguide structures and phase-shift structures. The mode-order converter further includes a first splitter and a second splitter. The first splitter has a first input port and a plurality of first output ports. The first input port constitutes the first port, and the plurality of first output ports are respectively and correspondingly connected to the plurality of waveguide structures and the plurality of waveguide substrates. The second splitter has a plurality of second input ports and a second output port. The plurality of second input ports are respectively and correspondingly connected to the plurality of waveguide structures and the plurality of waveguide substrates, and the second output port constitutes the second port. In practical applications, the number of waveguide structures and phase-shift structures can be reasonably increased or decreased according to actual needs, having good design flexibility and scalability.

[0015] In a second aspect, the present application further provides an optical module, including a laser component and the above-mentioned mode-order converter. The laser component is used to input an optical signal into the first port, and the optical signal is output from the second port after being subjected to mode-order conversion by the mode-order converter. In the optical module provided by the present application, by configuring the above-mentioned mode-order converter, effective mode-order conversion can be performed on the light wave emitted by the laser component, thereby effectively improving the transmission capacity of the optical module.

[0016] In a third aspect, the present application further provides an optical network device, including a controller and the above-mentioned optical module. The controller is electrically connected to the laser component and is used to regulate the mode of the optical signal input into the first port by the laser component. By configuring the above-mentioned optical module in the optical network device, the transmission capacity of the optical network device can be effectively improved. Description of the Drawings

[0017] Figure 1 It is a schematic diagram of a scenario where a mode-order converter provided by an embodiment of the present application is applied to an optical module;

[0018] Figure 2 It is a schematic plan view of a mode-order converter provided by an embodiment of the present application;

[0019] Figure 3 It is a schematic diagram of a TE0 mode and a TM0 mode input into a mode-order converter provided by an embodiment of the present application;

[0020] Figure 4 It is a schematic plan view of a waveguide structure in a mode-order converter provided by an embodiment of the present application;

[0021] Figure 5 Schematic diagram of the planar structure of a phase shift structure in a mode order converter provided by an embodiment of the present application;

[0022] Figure 6 Schematic diagram of the planar structure of a phase shift structure in a mode order converter provided by an embodiment of the present application;

[0023] Figure 7 Simulation diagram of the effective refractive indices of TE mode and TM mode in a waveguide structure varying with the width dimension of the waveguide structure;

[0024] Figure 8 Simulation diagram of the effective refractive indices of TE mode and TM mode in a phase shift structure varying with the duty cycle;

[0025] Figure 9 Schematic diagram of inputting TE0 mode and TM0 mode into a mode order converter provided by an embodiment of the present application;

[0026] Figure 10 Schematic diagram of inputting TE1 mode and TM1 mode into a mode order converter provided by an embodiment of the present application;

[0027] Figure 11 Schematic diagram of inputting TE0 mode and TM0 mode into a mode order converter provided by an embodiment of the present application;

[0028] Figure 12 Schematic diagram of inputting TE1 mode and TM1 mode into a mode order converter provided by an embodiment of the present application;

[0029] Figure 13 Block diagram of the structure of an optical module provided by an embodiment of the present application. Specific embodiments

[0030] In order to make the objectives, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings.

[0031] To facilitate the understanding of the mode order converter provided by the embodiment of the present application, its application scenario will be introduced first below.

[0032] The mode order converter provided by the embodiment of the present application can be applied in a communication link or a communication device to achieve an effective conversion between the fundamental mode and the high-order mode of an optical signal.

[0033] Such as Figure 1As shown in the figure, taking an optical module as an example, the optical module may include a laser diode (LD), a mode order converter (MOC), and an arrayed waveguide gratings (AWG). Figure 1 Eight lasers are shown in Figure 1 , namely LD1, LD2, LD3, LD4, LD5, LD6, LD7, and LD8. Among them, the wavelengths of the optical signals emitted by LD1 and LD2 are both λ1. The wavelengths of the optical signals emitted by LD3 and LD4 are both λ2. The wavelengths of the optical signals emitted by LD5 and LD6 are both λ3. The wavelengths of the optical signals emitted by LD7 and LD8 are both λ4. The optical module includes four mode order converters, namely MOC1, MOC2, MOC3, and MOC4. Among them, the optical signals emitted by LD1, LD3, LD5, and LD7 are directly input into the arrayed waveguide gratings. The optical signal emitted by LD2 is input into the arrayed waveguide gratings after mode order conversion by MOC1. The optical signal emitted by LD4 is input into the arrayed waveguide gratings after mode order conversion by MOC2. The optical signal emitted by LD6 is input into the arrayed waveguide gratings after mode order conversion by MOC3. The optical signal emitted by LD8 is input into the arrayed waveguide gratings after mode order conversion by MOC4. That is, the above optical module can achieve hybrid multiplexing of wavelength division multiplexing (WDM) and mode division multiplexing (MDM), effectively improving the transmission capacity of the optical module. Of course, in actual applications, the number of lasers and mode order converters can be flexibly set according to the actual situation, and the present application does not limit the number of lasers and mode order converters.

[0034] It should be noted that as a tool for transmitting signals, there are currently five physical dimensions that can be utilized for optical carriers, namely time, frequency, polarization, orthogonality, and space. Among them, wavelength division multiplexing (WDM), which is commonly used in optical modules, utilizes the frequency dimension and can simultaneously transmit multiple optical signals with different wavelengths in the optical module, thereby significantly enhancing the communication capacity. To further improve the transmission capacity of optical modules, based on the current use of wavelength division multiplexing, mode division multiplexing (MDM) technology based on the space dimension can be adopted to form a hybrid multiplexing technology. In a mode division multiplexing system, data signals are mainly transmitted simultaneously through the use of multiple eigenmode channels in a multimode waveguide. Among them, a mode order converter (MOC), as an important mode division multiplexing device, can convert the fundamental mode of the loaded signal (or optical wave) into a higher-order mode, so as to be transmitted in a few-mode fiber (FMF). Among them, a few-mode fiber is a fiber with a core area large enough to utilize several independent spatial modes to transmit parallel data streams.

[0035] To meet the requirements of high integration, high performance, and low cost, on-chip mode division multiplexing technology has become a solution that is expected to address the growing demand for ultra-high bandwidth and transmission capacity. However, existing silicon-based mode devices are difficult to achieve our goals. First of all, due to the inherent birefringence effect of silicon materials, the effective refractive indices of the modes of the two polarization states transmitted in the silicon waveguide differ greatly, which makes it very difficult to achieve efficient parallel mode order conversion for the two polarizations with a single mode order converter under the same device geometry. Therefore, most existing silicon-based mode devices are only targeted at the modes in one polarization state and are difficult to apply to the two polarization states simultaneously. Specifically, in an optical signal, there are two polarization states, namely the transverse electric wave (TE) and the transverse magnetic wave (TM). TE waves and TM waves are two basic modes when electromagnetic waves propagate in a medium. A TE wave means that the electric field of the electromagnetic wave is perpendicular to the propagation direction and the magnetic field is parallel to the propagation direction. A TM wave means that the magnetic field of the electromagnetic wave is perpendicular to the propagation direction and the electric field is parallel to the propagation direction. Currently, some mode order converters can only effectively convert the mode order of the transverse electric wave or the transverse magnetic wave, and cannot effectively take both waves into account.

[0036] In addition, existing silicon-based mode devices are also subject to the problem of bandwidth limitation. If wavelength division multiplexing is used to expand the communication capacity, it is necessary for the device to operate at a larger bandwidth. In summary, large-bandwidth and dual-polarization mode order conversion devices have great application prospects in the future and are also the difficulties that need to be overcome in current research.

[0037] Based on this, the present application provides a mode-order converter that can effectively achieve mode-order conversion for both transverse electric waves and transverse magnetic waves.

[0038] In order to make the objectives, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] As Figure 2 shown, in an example provided by the present application, the mode-order converter 10 includes a first port 101, a second port 102, a waveguide structure 11, and a phase-shift structure 12. The waveguide structure 11 is connected between the first port 101 and the second port 102, and the phase-shift structure 12 is also connected between the first port 101 and the second port 102. It can be considered that the waveguide structure 11 and the phase-shift structure 12 are connected in parallel between the first port 101 and the second port 102. Among them, the waveguide structure 11 is a traditional waveguide structure 11, and a phase change will occur when light waves propagate in the waveguide structure 11. The phase-shift structure 12 can be considered as a combined structure of the waveguide structure 11 and multiple grating teeth 103. A phase transformation will also occur when light waves propagate in the phase-shift structure 12, and an additional phase difference will be added under the action of the refractive index change in the phase-shift structure 12. When light waves enter from the first port 101, one beam of light waves will propagate along the waveguide structure 11, and the other beam of light waves will propagate along the phase-shift structure 12. When the two beams of light waves are combined at the second port 102, the conversion of the light wave mode can be achieved.

[0040] For example, as Figure 3 shown, when light waves (or optical signals) in TE0 and TM0 modes are input into the mode-order converter 10 from the first port 101, they are evenly divided into two paths. One path of light waves passes through the waveguide structure 11, and the other path of light waves passes through the phase-shift structure 12. A phase difference of π will be generated between the two paths of light waves. After the two paths of light waves are combined, they are converted into light waves in TE1 and TM1 modes. That is, through the mode-order converter 10, an effective conversion between light waves in TE0 mode and light waves in TE1 mode can be achieved, and at the same time, an effective conversion between light waves in TM0 mode and light waves in TM1 mode can be achieved.

[0041] As Figure 2As shown, in the example provided by this application, the mode-order converter 10 realizes the splitting and combining of optical waves through a Y-branch. Specifically, the mode-order converter 10 includes a first brancher 13 and a second brancher 14. The first brancher 13 has a first input port 131, a first output port 132a, and a first output port 132b. The first input port 131 constitutes the first port 101. The first output port 132a is connected to the waveguide structure 11, and the first output port 132b is connected to the waveguide substrate 121. The optical wave input from the first input port 131 is evenly split into two paths. One path propagates from the first output port 132a to the waveguide structure 11. The other path propagates from the first output port 132b to the phase-shift structure 12. The second brancher 14 has a second input port 142a, a second input port 142b, and a second output port 141. The second output port 141 constitutes the second port 102. The second input port 142a is connected to the waveguide structure 11, and the second input port 142b is connected to the waveguide substrate 121. The optical wave propagating from the waveguide structure 11 is input into the second brancher 14 from the second input port 142a, and the optical wave propagating from the phase-shift structure 12 is input into the second brancher 14 from the second input port 142b. And, the two optical waves are combined in the second brancher 14 and output from the second output port 141.

[0042] Alternatively, it can be understood that Figure 2 the first brancher 13 and the second brancher 14 shown in can form a Mach-Zehnder interferometer (MZI) structure. The two arms of the first brancher 13 and the second brancher 14 are respectively connected through the waveguide structure 11 and the phase-shift structure 12.

[0043] In other examples, the first brancher 13 can also be other devices with a wave-splitting function. The second brancher 14 can also be other devices with a wave-combining function, which will not be elaborated here.

[0044] As Figure 4 shown, in specific settings, the waveguide structure 11 can specifically be a substrate integrated waveguide. Its cross-section can be in the shape of a rectangle, a square, etc. In specific applications, the specific structure type of the waveguide structure 11 can be reasonably set according to actual requirements, which will not be elaborated here.

[0045] In specific settings, the specific structure type of the phase-shift structure 12 can be diverse.

[0046] For example, as Figure 5As shown, in an example provided by the present application, the phase shift structure 12 includes a waveguide substrate 121. For the convenience of description and distinction, different segments of the waveguide substrate 121 are respectively defined as a first segment 1211, an intermediate segment 1212, and a second segment 1213. The first segment 1211, the intermediate segment 1212, and the second segment 1213 are connected in sequence. The outer peripheral surface of the first segment 1211 includes a first chirped grating 122, the outer peripheral surface of the second segment 1213 includes a second chirped grating 124, and the outer peripheral surface of the intermediate segment 1212 includes a uniform grating 123. Among them, the width dimension of the first chirped grating 122 gradually increases from one end of the first segment 1211 to the intermediate segment 1212, and the width dimension of the second chirped grating 124 gradually increases from one end of the second segment 1213 to the intermediate segment 1212.

[0047] Among them, the specific materials of the waveguide structure 11 and the phase shift structure 12 can be silicon, silicon dioxide, polymer, etc. In actual applications, a suitable manufacturing platform and materials can be adopted, which will not be elaborated here.

[0048] It should be noted that the structure type of the waveguide substrate 121 is basically the same as that of the above-mentioned waveguide structure 11. For example, the width dimensions of the waveguide structure 11 and the waveguide substrate 121 can both be w1. In the example provided by the present application, based on the waveguide substrate 121, an effective phase shift function for light waves can be achieved by configuring the first chirped grating 122, the uniform grating 123, and the second chirped grating 124. The first chirped grating 122, the second chirped grating 124, and the uniform grating 123 are all sub-wavelength grating structures. Among them, the first chirped grating 122 and the second chirped grating 124 can achieve an adiabatic transition from the waveguide to the sub-wavelength uniform grating 123 structure, preventing the increase in insertion loss and non-target mode conversion caused by sudden size changes. On the other hand, through the sub-wavelength uniform grating 123 structure, the effective refractive index of the waveguide substrate 121 can be adjusted. By designing appropriate grating periods and duty cycles (DC), equal phase differences can be added to the modes of both TE and TM polarizations simultaneously. By combining the phase shift structure 12 with the first splitter 13, the second splitter 14, and the waveguide structure 11, it can be used as a dual-polarization arbitrary mode order converter. In addition, the sub-wavelength uniform grating 123 in the phase shift structure 12 itself has a wavelength-insensitive characteristic, so the mode order converter 10 fabricated based on this has a large bandwidth characteristic. It can be understood that in actual applications, the first chirped grating 122 and the second chirped grating 124 also have the function of adjusting the effective refractive index of the waveguide substrate 121. Therefore, when designing the overall effective refractive index of the phase shift structure 12, the first chirped grating 122 and the second chirped grating 124 can also be regarded as one of the parameters to be considered.

[0049] In addition, in practical applications, the performance of the phase shift structure 12 depends on various dimensional parameters of itself. For example, the length dimension of the waveguide substrate 121, the length dimension of the first chirped grating 122, the length dimension of the second chirped grating 124, the length dimension of the uniform grating 123, the dimensional parameters and the position arrangement of each grating tooth 103 all have obvious effects on the performance of the phase shift structure 12. That is to say, the performance of the phase shift structure 12 is jointly affected by multiple parameters. Therefore, in practical applications, various parameters of the phase shift structure 12 can be reasonably adjusted according to actual requirements.

[0050] To facilitate the understanding of the technical solution of this application, several structural deformations of the phase shift structure 12 will be exemplarily described below.

[0051] For example, please refer to Figure 5 and Figure 6 , in an example provided by this application, the waveguide substrate 121 is divided into three segments, namely the first segment 1211, the middle segment 1212, and the second segment 1213. Along the extension direction of the waveguide substrate 121, the cross-sections of different regions of the waveguide substrate 121 are the same. That is, the cross-sections of the first segment 1211, the middle segment 1212, and the second segment 1213 are all the same. The first chirped grating 122 is provided on the outer peripheral surface of the first segment 1211, the second chirped grating 124 is provided on the outer peripheral surface of the second segment 1213, and the uniform grating 123 is provided on the outer peripheral surface of the middle segment 1212. Among them, the first chirped grating 122 includes multiple ( Figure 6 five are shown in Figure 6 ) grating teeth 103. From the end of the first segment 1211 towards the middle segment 1212, the width of the grating teeth 103 increases linearly. The second chirped grating 124 includes multiple ( Figure 6 five are shown in Figure 6 ) grating teeth 103. From the end of the second segment 1213 towards the middle segment 1212, the width dimension of the grating teeth 103 increases linearly. The uniform grating 123 includes multiple ( Figure 6 five are shown in Figure 6The width dimension of the grating teeth 103 at the right end in [description] is slightly larger than the width dimension of the waveguide substrate 121, and the width dimension of the grating teeth 103 in the second chirped grating 124 adjacent to the uniform grating 123 is slightly smaller than the width dimension of the grating teeth 103 in the uniform grating 123. Therefore, the second chirped grating 124 can achieve an adiabatic transition from one end of the waveguide substrate 121 (such as Figure 6 the right end in [description]) to the structure of the uniform grating 123. This prevents the increase in insertion loss and non-target mode conversion caused by sudden changes in dimensions.

[0052] It should be noted that when setting the grating teeth 103, the layout of the grating teeth 103 can be diverse. For example, when the cross-section of the waveguide substrate 121 is rectangular, the grating teeth 103 can be set only on two opposite sides of the waveguide substrate 121. Or, the grating teeth 103 can also be set on four sides of the waveguide substrate 121. Or, the grating teeth 103 can also be set on at least any one side of the waveguide substrate 121. Or, it can be understood that the grating teeth 103 can be a closed structure arranged circumferentially around the waveguide substrate 121 or a non-closed structure.

[0053] In the example provided in this application, the cross-sectional shapes of different segments of the waveguide substrate 121 are the same, which has the advantage of being easy to fabricate. Or it can be understood that there is no region with a small cross-sectional size in the waveguide substrate 121. Therefore, it is not sensitive to fabrication accuracy, which can effectively improve the convenience during fabrication and the reliability of the mode order converter 10. Or, it can be understood that in some current mode order converters 10, their structural designs are unreasonable, resulting in being greatly affected by processing errors, high processing costs, and low yields.

[0054] In other examples, in the first chirped grating 122, the width of the grating teeth 103 can also increase non-linearly from the end of the first segment 1211 to the middle segment 1212. Or, in the second chirped grating 124, the width of the grating teeth 103 can also increase non-linearly from the end of the second segment 1213 to the middle segment 1212. When specifically setting, the specific structures of the first chirped grating 122 and the second chirped grating 124 can be reasonably set according to actual requirements, which will not be elaborated here.

[0055] In addition, as Figure 6 shown, in the example provided in this application, the length dimensions of each grating tooth 103 are basically the same. That is, the length dimension of each grating tooth 103 is a. In other ways, the length dimensions of the grating teeth 103 can also be different, which will not be elaborated here.

[0056] In addition, as Figure 6As shown, multiple grating teeth 103 are arranged in a fixed period Λ. Moreover, the distance between two adjacent grating teeth 103 is less than the operating wavelength of the mode-order converter 10, that is, the first chirped grating 122, the uniform grating 123, and the second chirped grating 124 are all sub-wavelength structures.

[0057] In addition, in the example provided in this application, the first chirped grating 122 and the second chirped grating 124 are symmetrically arranged with respect to the middle section 1212. Therefore, it can effectively improve the convenience in manufacturing the mode-order phase shift structure 12. In addition, when setting or debugging the design parameters of the phase shift structure 12, it is also beneficial to reduce the complexity of calculation and debugging, facilitating the low-cost manufacturing and wide application of the mode-order converter 10.

[0058] Generally speaking, as Figure 6 shown, in the example provided in this application, the length dimension of each grating tooth 103 is the same, all being a, and multiple grating teeth 103 are arranged in a fixed period Λ. The width dimension of the waveguide substrate 121 is w1, and the width dimension of the grating teeth 103 in the uniform grating 123 is w2. n2 is the number of periods of the grating teeth 103 in the first chirped grating 122 and the second chirped grating 124, and n3 is the number of periods of the grating teeth 103 in the uniform grating 123. n1 is the total number of periods of the grating teeth 103 in the middle phase shift structure 12. Therefore, the distance between the two end grating teeth 103 in the phase shift structure 12 is n1*Λ. Among them, n1, n2, and n3 can be integers or decimals.

[0059] In addition, as Figure 6 shown, in the example provided in this application, the width dimension of the waveguide structure 11 is w1, and the length dimension is n1*Λ.

[0060] It should be noted that Figure 4 what is shown is the planar structure of the waveguide structure 11. Actually, in the direction perpendicular to the drawing plane, the waveguide structure 11 has a certain thickness dimension. Correspondingly, Figure 5 and 6 what is shown is the planar structure of the phase shift structure 12. Actually, in the direction perpendicular to the drawing plane, the phase shift structure 12 also has a certain thickness dimension. Among them, the thickness dimension of the waveguide structure 11 and the thickness dimension of the phase shift structure 12 can be basically the same.

[0061] In addition, Figure 2 and Figure 3 what is shown is the planar structure of the mode-order converter 10. Actually, in the direction perpendicular to the drawing plane, the mode-order converter 10 also has a certain thickness dimension. In actual applications, the thickness dimensions of different structures in the mode-order converter 10 can be basically the same.

[0062] For what is shown as Figure 3For the shown mode-order converter 10, after two light waves pass through the waveguide structure 11 and the phase-shift structure 12, the phase difference between the two light waves can be expressed as:

[0063]

[0064] where λ is the wavelength of the light wave when propagating in the waveguide structure 11. n ps represents the effective refractive index of the fundamental mode when propagating in the phase-shift structure 12, and n wire represents the effective refractive index of the fundamental mode when propagating in the waveguide structure 11. L ps = n1*Λ represents the total length of the phase-shift structure 12.

[0065] Essentially, the bandwidth size of the mode-order converter 10 is the sensitivity of the phase difference to the wavelength. Therefore, taking the derivative of the above formula (1) gives:

[0066]

[0067] If the mode-order converter 10 has a phase-shift function and is insensitive to the wavelength, then it is required that the parameters of the mode-order converter 10 satisfy the following formulas (3) and (4):

[0068]

[0069] Solving this system of equations gives:

[0070]

[0071] And Δn eff (λ) = n PS (λ) - n wire (λ), n wire (λ) is the effective refractive index of the straight waveguide, which is almost constant. The refractive index of the chirped sub-wavelength grating can be written as:

[0072]

[0073] where n xx and n zz are tensors, which represent the components of the effective refractive index of the fundamental mode in the grating in different directions and are affected by the period Λ of the sub-wavelength grating and the duty cycle f = a / Λ. Therefore, the parameters can be controlled to make the solutions of the above equations hold. It should be noted that since the mode-order converter 10 is designed to work in a dual-polarization state, the above equations and solutions need to hold for both the TE mode and the TM mode.

[0074] In practical applications, when designing the mode-order converter 10, the following steps can be referred to:

[0075] Step 1: First, calculate the specific numerical values of the effective refractive indices of the TE mode and TM mode in the waveguide structure 11 through simulation software.

[0076] As Figure 7 shown, the variation of the effective refractive indices of the TE mode and TM mode in the waveguide structure 11 with the width dimension of the waveguide structure 11 is shown. Figure 7 In Figure 7 , the abscissa represents the width dimension of the waveguide structure 11, with the unit of nm; the ordinate represents the effective refractive index. S1 represents the simulation curve of the effective refractive index of the TE mode varying with the width dimension of the waveguide structure 11. S2 represents the simulation curve of the effective refractive index of the TM mode varying with the width dimension of the waveguide structure 11. It should be noted that, as a specific example,

[0077] in the measured simulation data, the thickness dimension of the waveguide structure 11 is 220 nm. Of course, in other examples, the thickness dimension of the waveguide structure 11 can also be other values, which will not be elaborated here.

[0078] As Figure 8 shown, the variation of the effective refractive indices of the TE mode and TM mode in the phase shift structure 12 with the duty cycle f is shown when x = 400 nm and y = 750 nm. Figure 8 In

[0079] the abscissa represents the duty cycle, and the ordinate represents the effective refractive index. S3 represents the simulation curve of the effective refractive index of the TE mode varying with the duty cycle. S4 represents the simulation curve of the effective refractive index of the TM mode varying with the duty cycle. Figure 7 and Figure 8 Based on the calculated numerical values given, find the duty cycle f corresponding to when the ratio of the effective refractive index difference of the transverse electric (TE mode) wave during propagation in the phase shift structure 12 to the effective refractive index difference of the transverse magnetic wave (TM mode) during propagation in the phase shift structure 12 is odd. For example, this ratio of the effective refractive index difference can be (2m + 1):(2n + 1), so as to add a phase shift of (2m + 1)π to the TE fundamental mode and a phase shift of (2n + 1)π to the TM fundamental mode.

[0080] For example, in Figure 8 , when f = 0.5, it satisfies adding a phase shift of 3π to the TE fundamental mode and a phase shift of 5π to the TM fundamental mode.

[0081] Step 4: As long as the grating period Λ satisfies the sub-wavelength condition (i.e., Λ << λ), the function of the sub-wavelength grating holds for any period Λ that meets the condition for the given f. After selecting the specific value of Λ, the length dimension a of the grating teeth 103 is a = f * Λ.

[0082] Step 5: According to:

[0083]

[0084] Substitute Figure 7 and 8 the effective refractive index of the TE mode or TM mode into it. According to the phase shift of the TE mode (2m + 1)π or the phase shift of the TM mode (2n + 1)π, the length of L can be calculated. PS This is the theoretical length of the sub-wavelength grating straight waveguide.

[0085] Step 6: Consider the first chirped grating 122 and the second chirped grating 124 parts. According to the simulation, calculate the equivalent situation of the phase shift introduced by the first chirped grating 122 and the second chirped grating 124 parts and the phase shift introduced by the uniform grating 123 part, so as to calculate the values of n1, n2, and n3 and determine all the structural parameters.

[0086] It can be understood that the steps shown above are only for illustrative purposes. In practical applications, appropriate methods can be selected according to the actual situation to reasonably set the parameters of the mode order converter 10, and this application does not limit this.

[0087] In addition, in the above example, an illustrative description is given taking the mode order converter 10 including one waveguide structure 11 and one phase shift structure 12 as an example. However, in other examples, the mode order converter 10 may also include multiple waveguide structures 11 and phase shift structures 12.

[0088] For example, as Figure 9 and Figure 10 shown, in an example provided by this application, a dual-polarization high-order mode converter is composed of multiple cascaded Y-branchers combined with two waveguide structures 11 and two phase shift structures 12. Among them, the waveguide structures 11 and the phase shift structures 12 are arranged in pairs, and the two groups of waveguide structures 11 and phase shift structures 12 are symmetric up and down.

[0089] As Figure 9As shown in the figure, the first port 101 can be used as an input port, and the second port 102 can be used as an output port. Light waves in TE0 mode and TM0 mode are input from the first port 101 into the mode-order converter 10. After passing through the first splitter 13 formed by two cascaded Y-branch splitters, the light waves are evenly divided into four paths, and the initial phases of the light waves in each path are the same. The four paths of light waves are respectively transmitted through the waveguide structure 11 and the phase-shift structure 12. The two paths of light waves output from the paired waveguide structure 11 and phase-shift structure 12 will have a phase difference of π. After the two pairs of paired waveguide structures 11 and phase-shift structures 12 are combined, TE1 mode and TM1 mode with opposite phases are respectively generated. Finally, after being combined in front of the second port 102, TE2 mode and TM2 mode are formed. That is to say, the mode-order converter 10 provided in the embodiment of the present application can simultaneously achieve effective conversion between TE0 mode and TE2 mode and effective conversion between TM0 mode and TM2 mode.

[0090] In addition, as Figure 10 shown, the first port 101 can be used as an input port, and the second port 102 can be used as an output port. Light waves in TE1 mode and TM1 mode are input from the first port 101 into the mode-order converter 10. After passing through the first splitter 13 formed by two cascaded Y-branch splitters, the light waves are evenly divided into four paths. Among them, the phases of the light waves entering the upper two arms are opposite to the phases of the light waves entering the lower two arms. The four paths of light waves are respectively transmitted through the waveguide structure 11 and the phase-shift structure 12. The two paths of light waves output from the paired waveguide structure 11 and phase-shift structure 12 will have a phase difference of π. After the two pairs of paired waveguide structures 11 and phase-shift structures 12 are combined, TE1 mode and TM1 mode with opposite phases are respectively generated. Finally, after being combined in front of the second port 102, TE3 mode and TM3 mode are formed. That is to say, the mode-order converter 10 provided in the embodiment of the present application can simultaneously achieve effective conversion between TE1 mode and TE3 mode and effective conversion between TM1 mode and TM3 mode.

[0091] In addition, as Figure 11 and Figure 12 shown, in an example provided by the present application, a dual-polarization high-order mode converter is formed by cascading multiple Y-branch splitters and combining two waveguide structures 11 and two phase-shift structures 12. Among them, the waveguide structure 11 and the phase-shift structure 12 are paired, and in the group of waveguide structure 11 and phase-shift structure 12, the phase-shift structure 12 is located in the lower arm.

[0092] As Figure 11As shown, the first port 101 can be used as an input port, and the second port 102 can be used as an output port. Light waves in TE0 mode and TM0 mode are input from the first port 101 into the mode order converter 10. After passing through the first splitter 13 formed by two cascaded Y-branchers, the light waves are evenly divided into four paths, and the initial phases of the light waves in each path are the same. The four paths of light waves are respectively transmitted through the waveguide structure 11 and the phase shift structure 12. The two paths of light waves output from the paired waveguide structure 11 and phase shift structure 12 will have a phase difference of π. After the two pairs of paired waveguide structure 11 and phase shift structure 12 are combined, TE1 mode and TM1 mode with opposite phases are respectively generated, and finally, after being combined in front of the second port 102, TE3 mode and TM3 mode are formed. That is to say, the mode order converter 10 provided by the embodiment of the present application can simultaneously achieve effective conversion between TE0 mode and TE3 mode and effective conversion between TM0 mode and TM3 mode.

[0093] In addition, as Figure 12 shown, the first port 101 can be used as an input port, and the second port 102 can be used as an output port. Light waves in TE1 mode and TM1 mode are input from the first port 101 into the mode order converter 10. After passing through the first splitter 13 formed by two cascaded Y-branchers, the light waves are evenly divided into four paths. Among them, the phases of the light waves entering the upper two arms are opposite to the phases of the light waves entering the lower two arms. The four paths of light waves are respectively transmitted through the waveguide structure 11 and the phase shift structure 12. The two paths of light waves output from the paired waveguide structure 11 and phase shift structure 12 will have a phase difference of π. After the two pairs of paired waveguide structure 11 and phase shift structure 12 are combined, TE1 mode and TM1 mode with opposite phases are respectively generated, and finally, after being combined in front of the second port 102, TE2 mode and TM2 mode are formed. That is to say, the mode order converter 10 provided by the embodiment of the present application can simultaneously achieve effective conversion between TE1 mode and TE2 mode and effective conversion between TM1 mode and TM2 mode.

[0094] In Figures 9 to 12 the example provided, an exemplary description is made with the mode order converter 10 including two pairs of paired waveguide structure 11 and phase shift structure 12. In other examples, the mode order converter 10 may also include three or more pairs of paired waveguide structure 11 and phase shift structure 12. Generally speaking, the mode order converter 10 may include multiple pairs of paired waveguide structure 11 and phase shift structure 12.

[0095] In practical applications, the mode order converter 10 can be independently applied in a communication link or integrated with other devices.

[0096] For example, as Figure 13As shown in the figure, an embodiment of the present application further provides an optical module, which includes a laser component and any one of the above-mentioned mode-order converters. The laser component is used to input an optical wave signal to the input port of the mode-order converter, so that the mode-order converter can perform mode-order conversion on the optical wave emitted by the laser component.

[0097] In addition, as Figure 13 shown in the figure, an arrayed waveguide grating may further be included in the optical module. The arrayed waveguide grating is generally used as an optical multiplexing device in a wavelength division multiplexing system, and the arrayed waveguide grating can multiplex optical waves of many wavelengths into a single optical fiber for transmission.

[0098] It can be understood that in practical applications, the laser component in the optical module may include multiple laser emitters and multiple mode-order converters, and the wavelengths of the optical waves emitted by different laser emitters may be the same or different.

[0099] In practical applications, the mode-order converter or the optical module integrated with the mode-order converter can be applied to various different types of optical network devices. A controller may be included in the optical network device. The controller may be electrically connected to the laser component and is used to regulate the mode of the optical signal emitted by the laser component to effectively improve the transmission capacity of the optical network device.

[0100] Among them, the optical network device may specifically be an optical modem or a router, etc. The present application does not limit the specific type of the optical network device.

[0101] In each embodiment of the present application, if there is no special description and logical conflict, the terms and / or descriptions between different embodiments are consistent and can be mutually referred to, and the technical features in different embodiments can be combined to form new embodiments according to their internal logical relationships.

[0102] In the present application, "a plurality of" means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone, where A and B may be singular or plural.

[0103] It can be understood that the various numerical numbers involved in the embodiments of the present application are only for the convenience of description and are not used to limit the scope of the embodiments of the present application. The magnitude of the serial numbers of the above processes does not mean the sequence of execution, and the execution sequence of each process should be determined according to its function and internal logic.

Claims

1. A modulus converter, characterized in that, It includes a first port, a second port, a waveguide structure, and a phase shift structure; The waveguide structure is connected between the first port and the second port; The phase shift structure includes a waveguide substrate, the waveguide substrate includes a first section, a middle section, and a second section connected in sequence, and the waveguide substrate is connected between the first port and the second port; The outer peripheral surface of the first section includes a first chirped grating, the outer peripheral surface of the second section includes a second chirped grating, and the outer peripheral surface of the middle section includes a uniform grating; Wherein, the width of the first chirped grating gradually increases from one end of the first section towards the middle section, and the width of the second chirped grating gradually increases from one end of the second section towards the middle section.

2. The modulo-order converter according to claim 1, characterized in that, The cross-sections of the first section, the middle section, and the second section are the same.

3. The modulus converter according to claim 1 or 2, characterized in that, The cross-section of the waveguide substrate and the waveguide structure is the same.

4. The modulus converter according to any one of claims 1 to 3, characterized in that, The width dimension of the uniform grating is greater than the maximum width dimensions of the first chirped grating and the second chirped grating.

5. The modulus converter according to any one of claims 1 to 4, characterized in that The first chirped grating includes a plurality of grating teeth spaced along the extending direction of the first section, the second chirped grating includes a plurality of grating teeth spaced along the extending direction of the second section, and the uniform grating includes a plurality of grating teeth spaced along the extending direction of the middle section; Wherein, the distance between adjacent two grating teeth is the same.

6. The modulo-rank converter according to claim 5, characterized in that, The length dimensions of each of the grating teeth are the same.

7. The modulo-step converter according to claim 5 or 6, characterized in that, The distance between adjacent two of the grating teeth is less than the operating wavelength of the mode order converter.

8. The modulus converter according to any one of claims 1 to 7, characterized in that The first chirped grating and the second chirped grating are symmetrically arranged with respect to the middle section.

9. The modulo converter according to any one of claims 1 to 8, characterized in that, The ratio of the effective refractive index difference when the transverse electric wave propagates in the phase shift structure to the effective refractive index difference when the transverse magnetic wave propagates in the phase shift structure is an odd number.

10. The modulus converter according to any one of claims 1 to 9, characterized in that, The mode order converter further includes a first splitter and a second splitter; The first splitter has a first input port and two first output ports, the first input port constitutes the first port, and the two first output ports are respectively connected to the waveguide structure and the waveguide substrate; The second splitter has two second input ports and a second output port, the two second input ports are respectively connected to the waveguide structure and the waveguide substrate, and the second output port constitutes the second port.

11. The modulo converter according to any one of claims 1 to 9, characterized in that, The mode order converter includes a plurality of pairs of the waveguide structures and the phase shift structures arranged; The mode order converter further includes a first splitter and a second splitter; The first splitter has a first input port and a plurality of first output ports, the first input port constitutes the first port, and the plurality of first output ports are respectively connected to the plurality of waveguide structures and the plurality of waveguide substrates in one-to-one correspondence; The second splitter has a plurality of second input ports and a second output port, the plurality of second input ports are respectively connected to the plurality of waveguide structures and the plurality of waveguide substrates in one-to-one correspondence, and the second output port constitutes the second port.

12. An optical module, characterized in that, It includes a laser component and the mode order converter according to any one of claims 1 to 11, the laser component is used to input an optical signal to the first port, and the optical signal is output from the second port after passing through the mode order converter.

13. An optical network device, characterized in that, Comprising a controller and an optical module as described in claim 12, the controller is electrically connected to the laser component and is used to regulate the mode of the optical signal input by the laser component to the first port.

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