On-chip adaptive combining method and feedback system for polarization diversity MZM

Abstract

The application relates to the field of silicon-based optoelectronic integration, and particularly discloses an on-chip adaptive combining method and a feedback system for polarization diversity MZM, which comprises the following steps: optical coupling and mode conversion, polarization diversity electro-optical modulation, optical power collection and photoelectric conversion, signal processing and feedback control, and a tunable combining module; after the coupling conversion and modulation, two-way optical power is collected and photoelectrically converted, a power difference voltage is obtained through an analog circuit, a control voltage is generated by superimposing a bias voltage, and a tunable combiner is driven to dynamically adjust a beam splitting ratio to complete combining. The application solves the problems that the output power of the polarization diversity MZM randomly fluctuates with the polarization state, the existing polarization control scheme has slow response, a complex structure and is difficult to integrate with a silicon-based process, realizes real-time and accurate compensation of power fluctuation, guarantees stable combining output power, and has a simple system structure, low power consumption, is easy to monolithically integrate with a silicon-based chip, and improves the performance and compatibility of an integrated photonic link.

Description

Technical Field

[0001] This invention relates to the field of silicon-based optoelectronic integration technology, specifically to an on-chip adaptive multiplexing method and feedback system for polarization diversity MZM. Background Technology

[0002] Silicon-based optoelectronic integration technology is a core supporting technology for high-speed coherent optical communication and optical interconnect systems. The polarization sensitivity of photonic devices is a key issue restricting the development and integrated application of this technology, while polarization diversity technology is the core means to overcome this polarization sensitivity. The polarization diversity Mach-Zehnder modulator (MZM), as a key core device in this field, is usually used in conjunction with a dual polarization grating coupler. It can decompose arbitrary polarization light input from an optical fiber into two orthogonally polarized light states, and convert them into TE modes for electro-optic modulation, thereby achieving robust modulation of the randomness of the input light polarization. This is an important foundation for building high-performance integrated photonic transmission links.

[0003] However, the power distribution ratio of the two output optical signals of polarization diversity MZM fluctuates randomly with the original polarization state of the input light. This characteristic makes it impossible for the output to be efficiently coupled directly with back-end photonic functional devices (such as multiplexers, wavelength division multiplexers, optical switches, etc.) designed with a fixed beam splitting ratio. In integrated links, this can easily lead to significant power mismatch, a surge in insertion loss, and deterioration in noise performance, which seriously restricts the overall performance, operational stability, and integration of silicon-based optoelectronic integrated systems. Therefore, developing an on-chip adaptive multiplexing system that can sense changes in the input polarization state in real time and automatically adjust to stabilize the multiplexing output power has become a key technical challenge that urgently needs to be addressed to promote the development of high-performance integrated photonic links.

[0004] To address the dynamic changes in optical polarization state, various adaptive control schemes based on photoelectric feedback have been proposed. The core objective of these schemes is primarily focused on the measurement, conversion, and stabilization of the optical polarization state itself. The aim is to convert any input polarization state into a stable and controllable output polarization state, typically employing digital signal processing, matrix operations, or complex iterative algorithms to control the polarization state by manipulating multiple phase shifters. Among these, one scheme proposes a general-purpose on-chip polarization state control system based on digital control and time-series multiplexing. This system uses time-series multiplexing technology to drive multiple phase shifters in a time-division multiplexing manner through a single digital-to-analog converter and a digital control module, achieving polarization state modulation. Another scheme proposes a polarization control system based on a thin-film lithium niobate platform and transmission matrix calculation, achieving polarization control through complete measurement of the optical polarization state and real-time transmission matrix operations. Yet another scheme designs a polarization-independent feedback control system for optical switches, employing a gradient descent algorithm to optimize the polarization-independent characteristics of the optical switch.

[0005] However, the aforementioned existing technical solutions all have obvious limitations when applied to solve the specific system-level compatibility problem of adaptive power combining at the back end of polarization diversity MZM, and are not the optimal solutions for this application scenario. Specifically, polarization state control systems based on digital control and time-series multiplexing introduce inherent periodic delays in their "time-division detection and regulation" operating mode, limiting system response speed. They cannot provide instantaneous and continuous compensation for power fluctuations caused by rapid random changes in polarization state. Furthermore, their reliance on digital processors such as FPGAs increases system power consumption, area, and cost, hindering compact integration with MZM transmitter chips. Polarization control systems based on thin-film lithium niobate platforms and transmission matrix calculations require complete measurement of polarization state and complex matrix operations, resulting in high computational load, response delays, and poor real-time performance. Moreover, their compatibility with mainstream silicon-based optoelectronic integration processes is poor due to their specific material platform of thin-film lithium niobate, limiting their widespread application. Polarization-independent feedback control systems used for optical switches aim to optimize the optical switch state, which is incompatible with the requirement for stable combined power. The convergence time of the iterative algorithm limits response speed, and the intermittent feedback loop cannot provide continuous and uninterrupted stable compensation for the real-time rapid power fluctuations of the MZM output, easily causing periodic fluctuations in output power.

[0006] In summary, existing polarization control technologies either suffer from slow response, high power consumption and cost due to complex architecture, poor compatibility with silicon-based processes due to complex technical paths and platform specificity, or low control efficiency due to discrepancies between application objectives and control logic. None of these solutions can efficiently and appropriately solve the problem of adaptive and stable combining of polarization diversity MZM output optical power.

[0007] Therefore, there is an urgent need to develop a highly specialized, simple, fast-responding, and highly compatible on-chip adaptive multiplexing feedback system to achieve real-time, accurate, and stable compensation for polarization diversity MZM output power fluctuations, overcome key compatibility bottlenecks in high-performance integrated photonic links, and promote the monolithic and practical development of silicon-based optoelectronic integrated systems. Summary of the Invention

[0008] To address the aforementioned problems in the prior art, this invention provides an on-chip adaptive multiplexing method and feedback system for polarization diversity MZM, which solves the problems of output power fluctuation in polarization diversity MZM, slow response and integration difficulties in existing solutions, and achieves real-time stable power multiplexing and efficient on-chip integration of the system.

[0009] To achieve the above objectives, this invention proposes an on-chip adaptive multiplexing feedback system for polarization diversity MZM, comprising:

[0010] The optical coupling and mode conversion module and the polarization diversity electro-optic modulation module are connected in sequence. The optical power acquisition and photoelectric conversion module is connected to the output end of the polarization diversity electro-optic modulation module. The signal processing and feedback control module is connected to the optical power acquisition and photoelectric conversion module. The tunable wave combiner module is connected to the polarization diversity electro-optic modulation module and the signal processing and feedback control module respectively.

[0011] The optical coupling and mode conversion module is a dual polarization grating coupler, used to decompose input light of arbitrary polarization state into two orthogonal linearly polarized lights and convert them into TE mode output;

[0012] The polarization diversity electro-optic modulation module is a polarization diversity Mach-Zehnder single-drive modulator, used to electro-optically modulate the TE mode optical paths of two orthogonal linearly polarized lights.

[0013] The optical power acquisition and photoelectric conversion module is used to extract the monitoring light of the two modulated lights and convert it into an electrical signal;

[0014] The signal processing and feedback control module includes a low-noise amplifier optoelectronic monolithic integrated circuit, a subtractor optoelectronic monolithic integrated circuit, and an adder optoelectronic monolithic integrated circuit connected in sequence. The subtractor optoelectronic monolithic integrated circuit is used to perform differential operations on the two amplified electrical signals to obtain the optical power difference voltage V. diff The adder optoelectronic monolithic integrated circuit is used to convert V diff With preset bias voltage V bias Superimposed to generate control voltage V ctrl And V ctrl =V bias +V diff ;

[0015] The tunable multiplexing module is a power-splitting-ratio controllable multiplexer, including a multimode interference coupler and an integrated optical phase shifter. The optical phase shifter receives a control voltage V. ctrl And achieve phase tuning.

[0016] Preferably, the optical power acquisition and photoelectric conversion module includes a directional coupler and a photodetector. The directional coupler is a non-invasive optical coupling device, and the photodetector is a photodiode that is monolithically heterogeneously integrated with a silicon-based optoelectronic device.

[0017] Preferably, the control voltage V output by the adder optoelectronic monolithic integrated circuit in the signal processing and feedback control module is... ctrl Within the preset linear control range [V min V max The V min The voltage boundary value corresponding to the extreme polarization state where the input optical power is zero is V.max This is the voltage boundary value corresponding to the extreme polarization state where the power of the other input optical path is zero.

[0018] Preferably, the power splitting ratio controllable multiplexer is composed of a first-stage 2×2 multimode interference coupler, an optical phase shifter integrated on one output arm of the 2×2 multimode interference coupler, and a second-stage 2×1 multimode interference coupler cascaded with the output end of the first-stage 2×2 multimode interference coupler.

[0019] Preferably, the optical phase shifter is a phase shifter based on the thermo-optical effect, and the phase difference it generates satisfies the formula:

[0020] ;

[0021] in, The wavelength of light in a vacuum. The thermo-optical coefficient of the effective refractive index of the waveguide. This represents the change in the effective refractive index of the waveguide. The operating temperature of the waveguide. For waveguide temperature rise, This is the length of the heated waveguide arm.

[0022] Preferably, the optical phase shifter is a phase shifter based on carrier dispersion effect, and the phase difference it generates satisfies the formula:

[0023] ;

[0024] in, The wavelength of light in a vacuum. The length of the doped modulation waveguide arm;

[0025] The change in effective refractive index of the waveguide Satisfying the formula:

[0026] ;

[0027] in, For electron charge, At the speed of light, The vacuum permittivity, For the refractive index of the material, This represents the change in electron concentration. This represents the change in hole concentration. For the effective mass of electrons, The effective mass of the hole.

[0028] An on-chip adaptive multiplexing method for polarization diversity MZM is also proposed, applicable to any of the aforementioned on-chip adaptive multiplexing feedback systems for polarization diversity MZM, comprising the following steps:

[0029] S1, Optical Coupling and Mode Conversion: The input light of arbitrary polarization state is decomposed into two orthogonal linearly polarized lights through a dual polarization grating coupler, and both polarized lights are converted into TE modes and output to the polarization diversity Mach-Zehnder single-drive modulator.

[0030] S2, Polarization diversity electro-optic modulation, synchronous electro-optic modulation of two TE mode beams is performed by a polarization diversity Mach-Zehnder single-drive modulator.

[0031] S3. Optical power acquisition and photoelectric conversion: Extract the monitoring light of the two modulated lights, convert the monitoring light into photocurrent signals, and then amplify them to obtain the two corresponding voltage signals.

[0032] S4. Signal processing and feedback control: The two voltage signals are differentially processed in real time using a subtractor-based optoelectronic monolithic integrated circuit to obtain V. diff Then, the V is converted into an adder by a single-chip optoelectronic integrated circuit. diff With the preset V bias Superimposed to generate control voltage V ctrl =V bias +V diff ;

[0033] S5, tunable combiner, controls the voltage V ctrl Phase modulation is achieved by applying phase to an optical phase shifter, and the interference conditions of the multimode interference coupler are changed by phase change, thereby dynamically adjusting its power splitting ratio and performing wave combining on the two modulated beams.

[0034] Preferably, in S3, a non-invasive optical coupling method is used to extract the monitoring light of the two modulation lights, and the power of the extracted monitoring light is in a fixed ratio to the power of the main modulation light.

[0035] Preferably, in S4, the generated control voltage V ctrl Within the preset linear control range [V min V max The V bias The preset DC reference voltage is used to make the power split ratio controllable combiner operate in a 50:50 split state when the two modulated optical powers are equal.

[0036] Preferably, in S5, the optical phase shifter is driven by the thermo-optical effect or the carrier dispersion effect to generate a compensated phase difference. The interference conditions of the multimode interference coupler are changed by the compensated phase difference, and the power splitting ratio is dynamically adjusted to achieve dynamic compensation for the power imbalance of the two modulated optical paths.

[0037] Therefore, this invention proposes an on-chip adaptive multiplexing method and feedback system for polarization diversity MZM, the advantages of which are as follows:

[0038] (1) The control architecture of analog direct feedback is adopted, which eliminates complex operations such as digital processing and algorithm iteration, eliminates inherent processing delay, realizes rapid dynamic compensation for power fluctuations caused by polarization state changes, achieves sub-microsecond real-time response, and ensures instantaneous stability of combined output power.

[0039] (2) The system architecture is greatly simplified. The core control is completed by relying on basic analog circuits. No digital processing module is required, which significantly reduces power consumption, chip area and manufacturing cost. It is easy to achieve monolithic integration with polarization diversity MZM. The control logic is highly matched with the power equalization target. The closed-loop control has high efficiency and good stability, and accurately solves the problem of wave combination compatibility between polarization diversity MZM and back-end photonic devices.

[0040] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0041] Figure 1 This is an overall structural diagram of the invention;

[0042] Figure 2 This is a flowchart of the workflow of the present invention;

[0043] Figure 3 This is a cross-sectional view of the present invention along line A-A';

[0044] Figure 4 This is a phase shifter based on the thermo-optic effect, as shown in the B-B' cross-sectional view of the present invention;

[0045] Figure 5 This is a phase shifter based on carrier dispersion effect in the B-B' cross-sectional view of the present invention.

[0046] Figure Labels

[0047] 101. Dual-polarization grating coupler; 102. TE single-mode optical waveguide; 103. Polarization diversity silicon-based Mach-Zehnder single-drive modulator; 104. Modulator signal electrode; 105. Directional coupler; 106. Photodetector; 107. Low-noise amplifier optoelectronic monolithic integrated circuit; 108. Subtractor optoelectronic monolithic integrated circuit; 109. Adder optoelectronic monolithic integrated circuit; 110. Power beam-splitting ratio controllable multiplexer; 111. Multimode interference coupler; 112. Optical phase shifter; 201. Waveguide upper cladding; 202. Waveguide core layer; 203. Waveguide lower cladding; 204. Chip substrate; 205. Miniature resistance heater; 206. Metal signal electrode; 207. Metal via; 208. PN junction doped waveguide. Detailed Implementation

[0048] To make the technical solutions, advantages, and objectives of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of this application.

[0049] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0050] like Figures 1-5 As shown, the present invention provides an on-chip adaptive multiplexing feedback system for polarization diversity MZM, comprising:

[0051] The optical coupling and mode conversion module and the polarization diversity electro-optic modulation module are connected in sequence. The optical power acquisition and photoelectric conversion module is connected to the output of the polarization diversity electro-optic modulation module. The signal processing and feedback control module is connected to the optical power acquisition and photoelectric conversion module. The tunable wave combiner module is connected to the polarization diversity electro-optic modulation module and the signal processing and feedback control module, respectively.

[0052] The optical coupling and mode conversion module is a dual polarization grating coupler 101, which is used to decompose input light of arbitrary polarization state into two orthogonal linearly polarized lights and convert them into TE mode output.

[0053] The polarization diversity electro-optic modulation module is a polarization diversity Mach-Zehnder single-drive modulator 103, used to electro-optically modulate the TE mode optical paths of two orthogonal linearly polarized lights.

[0054] The optical power acquisition and photoelectric conversion module is used to extract the monitoring light of two modulated lights and convert it into an electrical signal. The optical power acquisition and photoelectric conversion module includes a directional coupler 105 and a photodetector 106. The directional coupler 105 is a non-invasive optical coupling device, and the photodetector 106 is a photodiode that is monolithically heterogeneously integrated with a silicon-based optoelectronic device.

[0055] The signal processing and feedback control module includes a low-noise amplifier optoelectronic monolithic integrated circuit 107, a subtractor optoelectronic monolithic integrated circuit 108, and an adder optoelectronic monolithic integrated circuit 109 connected in sequence to the subtractor optoelectronic monolithic integrated circuit 108. The subtractor optoelectronic monolithic integrated circuit 108 is used to perform differential operations on the two amplified electrical signals to obtain the optical power difference voltage V. diff The adder optoelectronic monolithic integrated circuit 109 is used to convert V diff With preset bias voltage V bias Superimposed to generate control voltage V ctrl And Vctrl =V bias +V diff .

[0056] The control voltage V output by the adder optoelectronic monolithic integrated circuit 109 in the signal processing and feedback control module is... ctrl Within the preset linear control range [V min V max ], V min V is the voltage boundary value corresponding to the extreme polarization state where the input optical power is zero. max This is the voltage boundary value corresponding to the extreme polarization state where the power of the other input optical path is zero.

[0057] The tunable multiplexer module is a power-splitting-ratio controllable multiplexer 110, including a multimode interference coupler 111 and an optical phase shifter 112 integrated thereon. The optical phase shifter 112 receives a control voltage V. ctrl And achieve phase tuning.

[0058] The power beam splitting ratio controllable multiplexer is composed of a first-stage 2×2 multimode interference coupler 111, an optical phase shifter 112 integrated on an output arm of the first-stage 2×2 multimode interference coupler 111, and a second-stage 2×1 multimode interference coupler 111 cascaded together and connected to the output terminal of the first-stage 2×2 multimode interference coupler 111.

[0059] An optical phase shifter is a phase shifter based on the thermo-optical effect, and the phase difference it generates satisfies the formula:

[0060] ;

[0061] in, The wavelength of light in a vacuum. The thermo-optical coefficient of the effective refractive index of the waveguide. This represents the change in the effective refractive index of the waveguide. For waveguide temperature rise, The operating temperature of the waveguide. This is the length of the heated waveguide arm.

[0062] An optical phase shifter is a phase shifter based on the carrier dispersion effect, and the phase difference it produces satisfies the formula:

[0063] ;

[0064] in, The wavelength of light in a vacuum. The length of the doped modulation waveguide arm;

[0065] Waveguide effective refractive index change Satisfying the formula:

[0066] ;

[0067] in, For electron charge, At the speed of light, The vacuum permittivity, For the refractive index of the material, This represents the change in electron concentration. This represents the change in hole concentration. For the effective mass of electrons, The effective mass of the hole.

[0068] An on-chip adaptive multiplexing method for polarization diversity MZM is also proposed, applied to an on-chip adaptive multiplexing feedback system for polarization diversity MZM, including the following steps:

[0069] S1. Optical coupling and mode conversion: The input light of arbitrary polarization state is decomposed into two orthogonal linear polarized lights by the dual polarization grating coupler 101, and both polarized lights are converted into TE mode and output to the polarization diversity Mach-Zehnder single-drive modulator 103.

[0070] S2, Polarization diversity electro-optic modulation, synchronous electro-optic modulation of two TE mode beams is performed by polarization diversity Mach-Zehnder single-drive modulator 103.

[0071] S3. Optical power acquisition and photoelectric conversion: Extract the monitoring light of the two modulated lights, convert the monitoring light into photocurrent signals, and then amplify them to obtain the two corresponding voltage signals.

[0072] The monitoring light of the two modulated lights is extracted using a non-invasive optical coupling method, and the power of the extracted monitoring light is in a fixed ratio to the power of the main modulated light.

[0073] S4. Signal processing and feedback control: The two voltage signals are differentially processed in real time using a subtractor-based optoelectronic monolithic integrated circuit 108 to obtain V. diff Then, the V is added via the adder optoelectronic monolithic integrated circuit 109. diff With the preset V bias Superimposed to generate control voltage V ctrl =V bias +V diff ;

[0074] S5, tunable combiner, controls the voltage V ctrl Phase modulation is achieved by applying phase to an optical phase shifter, and the interference conditions of the multimode interference coupler are changed by phase change, thereby dynamically adjusting its power splitting ratio and performing wave combining on the two modulated beams.

[0075] The generated control voltage V ctrl Within the preset linear control range [Vmin V max ], V bias The preset DC reference voltage is used to make the power split ratio controllable combiner operate in a 50:50 split state when the two modulated optical powers are equal.

[0076] The optical phase shifter is driven by thermo-optical effect or carrier dispersion effect to generate a compensated phase difference. The interference conditions of the multimode interference coupler are changed by the compensated phase difference, and the power splitting ratio is dynamically adjusted to achieve dynamic compensation for the power imbalance of the two modulated optical paths.

[0077] This invention employs the thermo-optical effect and the carrier dispersion effect to achieve phase tuning of the optical phase shifter 112, forming two core embodiments, which are described in detail below.

[0078] Example 1: On-chip adaptive multiplexing method and feedback system for optical phase shifters based on thermo-optical effect;

[0079] This embodiment is applicable to silicon-based optoelectronic integrated link scenarios with high requirements for optical efficiency and control stability. The optical phase shifter 112 is a thermo-optical effect-based thermally tuned phase shifter (corresponding to...). Figure 4 The specific modules of the system are as follows:

[0080] The optical coupling and mode conversion module is a dual polarization grating coupler 101; the polarization diversity electro-optic modulation module is a polarization diversity silicon-based Mach-Zehnder single-drive modulator 103; the optical power acquisition and photoelectric conversion module consists of an S / P polarization directional coupler 105 and a photodetector 106; the signal processing and feedback control module consists of a low-noise amplifier optoelectronic monolithic integrated circuit 107, a subtractor optoelectronic monolithic integrated circuit 108, and an adder optoelectronic monolithic integrated circuit 109; and the tunable multiplexing module is a power beam-splitting ratio controllable multiplexer 110, which is composed of a cascaded 2×2 multimode interference coupler 111, a thermo-optical tuning phase shifter 112, and a 2×1 multimode interference coupler 111.

[0081] The on-chip adaptive multiplexing method in this embodiment includes the following steps:

[0082] S1. Optical Coupling and Mode Conversion: Input light of arbitrary polarization state is incident on dual polarization grating coupler 101. The coupler couples the S-polarization component and P-polarization component in the optical fiber to two independent S / P polarization TE single-mode optical waveguides 102, respectively, which excite the TE mode and complete the conversion from spatial polarization to waveguide mode. The two TE mode lights are transmitted along the waveguide with low loss.

[0083] S2, Polarization diversity electro-optic modulation: The two TE mode beams are guided to the polarization diversity silicon-based Mach-Zehnder single-drive modulator 103. The modulator is driven by the same signal modulator signal electrode 104 through push-pull, so as to complete synchronous and independent electro-optic modulation of the two orthogonally polarized TE mode beams.

[0084] S3. Optical power acquisition and photoelectric conversion: While the two modulated optical signals are transmitted on the main path, 10% of the optical power is extracted non-invasively by a -10dB directional coupler as monitoring light. The monitoring light is incident on the germanium-silicon photodetector and is converted into a photocurrent signal that is linearly proportional to the optical power. The photocurrent is amplified by the low-noise amplifier photoelectric monolithic integrated circuit 107 to obtain two corresponding voltage signals.

[0085] S4. Signal Processing and Feedback Control: The subtractor optoelectronic monolithic integrated circuit 108 performs real-time differential calculations on the two voltage signals, outputting the optical power difference voltage V, which characterizes the imbalance between the two optical power signals. diff The adder optoelectronic monolithic integrated circuit 109 will V diff With the preset DC bias voltage V bias Superimposed to generate control voltage V ctrl And V ctrl =V bias +V diff Preset V bias V min V max Three voltage thresholds, V bias V is the voltage required to operate the power splitting ratio controllable multiplexer 110 in a 50:50 splitting state when the two optical powers are equal. min V max To ensure the voltage boundary value corresponding to the extreme polarization state where the single-channel optical power is zero, V ctrl Always within the linear control range [V min V max ]Inside;

[0086] S5, Tunable Wavelength Combining: A control voltage Vctrl is applied to the miniature resistive heater 205 of the thermo-optically tuned optical phase shifter 112. The heater generates Joule heating, causing a temperature rise in the region of the lower S / P polarized TE single-mode optical waveguide 102. The effective refractive index of silicon waveguide materials changes with temperature rise, satisfying the formula: ,in The thermo-optic coefficient of the effective refractive index of the waveguide;

[0087] Light waves at a length of When propagating in the heated waveguide arm, the resulting compensated phase difference satisfies the formula: ;

[0088] in, The wavelength of light in a vacuum. The electrothermal conversion coefficient and ( It is the reciprocal of thermal conductivity. (where G is the heater resistance) and G is the total gain of the feedback system. The difference in power between the two optical paths;

[0089] The compensated phase difference changes the interference conditions of the multimode interference coupler 111, causing its power splitting ratio to be dynamically adjusted, accurately offsetting the power imbalance introduced by the random change of polarization state at the front end. Finally, after the two modulated beams are combined by the power splitting ratio controllable combiner 110, a single channel beam with stable power is output, completing the closed-loop control of adaptive beam combining.

[0090] This embodiment achieves phase tuning through the thermo-optical effect, resulting in good tuning linearity, no additional optical absorption loss, and effectively ensuring the optical efficiency of the system, as well as high stability of the combined output power.

[0091] Example 2: On-chip adaptive multiplexing method and feedback system for optical phase shifters based on carrier dispersion effect;

[0092] This embodiment is suitable for applications with stringent requirements for system response speed and power consumption, and which can tolerate a certain amount of additional optical loss, such as high-speed coherent optical communication. The optical phase shifter 112 is a doped waveguide phase shifter based on carrier dispersion effect (corresponding to...). Figure 5 The system's module composition is completely consistent with that of Embodiment 1, except that the implementation of the optical phase shifter 112 is different. It consists of a PN junction doped waveguide 208 formed by ion implantation, a metal signal electrode 206, and a metal via 207.

[0093] In the on-chip adaptive multiplexing method of this embodiment, steps S1-S4 are exactly the same as in Embodiment 1. The core difference lies in the tunable multiplexing stage in step S5, which is as follows:

[0094] S5, Tunable Combined Wave: This allows the linear control interval [V] to be... min V max The control voltage Vctrl within is applied to the PN junction-doped waveguide 208 through the metal signal electrode 206. The metal via 207 achieves ohmic contact between the electrode and the doped waveguide. ctrl The changes alter the width of the PN junction depletion layer and the internal carrier concentration distribution, resulting in changes in electron concentration within the space charge region overlapping with the optical mode field. and changes in hole concentration ;

[0095] Changes in carrier concentration cause changes in the real part of the effective refractive index of the waveguide according to the Soref relation, satisfying the formula: ;

[0096] in, For electron charge, At the speed of light, The vacuum permittivity, For the refractive index of the material, This represents the change in electron concentration. This represents the change in hole concentration. For the effective mass of electrons, The effective mass of the hole;

[0097] When a light wave propagates in a doped modulation waveguide arm of length L, the compensated phase difference caused by the change in effective refractive index satisfies the following formula: ,in This represents the change in the effective refractive index of the waveguide. The wavelength of light in a vacuum;

[0098] After the compensated phase difference is transmitted to the multimode interference coupler 111, its interference conditions and power splitting ratio are dynamically changed to realize real-time compensation for the power imbalance of the two modulated optical paths. Finally, the combined output power of the single-channel light is stable, thus completing the closed-loop feedback control.

[0099] This embodiment achieves phase tuning based on carrier dispersion effect, with modulation speed reaching the GHz level and power consumption only in the microwatt level. It also avoids thermal crosstalk issues and can quickly respond to rapid random changes in the polarization state of the input light, meeting the real-time compensation requirements of high-speed optical communication systems.

[0100] Both of the above embodiments are designed around the core objective of adaptive beam combining of polarization diversity MZM output power. They can be flexibly selected according to the performance priority of silicon-based optoelectronic integrated systems. Both can achieve accurate and real-time compensation for power fluctuations caused by changes in input polarization state, solving the beam combining compatibility problem between polarization diversity MZM and back-end fixed beam splitting ratio photonic devices.

[0101] Therefore, this invention provides an on-chip adaptive multiplexing method and feedback system for polarization diversity MZM, which solves the technical problems of the output power of polarization diversity MZM fluctuating randomly with the input polarization state, and the existing polarization control schemes having slow response, complex architecture, high integration difficulty, and low control efficiency. It achieves real-time and accurate compensation for power fluctuations, ensures stable multiplexing output power, and the system is easy to integrate on a single chip, which greatly improves the performance and compatibility of integrated photonic links.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An on-chip adaptive multiplexing feedback system for polarization diversity MZM, characterized in that, It includes an optical coupling and mode conversion module and a polarization diversity electro-optic modulation module connected in sequence, as well as an optical power acquisition and photoelectric conversion module connected to the output end of the polarization diversity electro-optic modulation module, a signal processing and feedback control module connected to the optical power acquisition and photoelectric conversion module, and a tunable wave combiner module; The optical coupling and mode conversion module is a dual polarization grating coupler, used to decompose input light of arbitrary polarization state into two orthogonal linearly polarized lights and convert them into TE mode output; The polarization diversity electro-optic modulation module is a polarization diversity Mach-Zehnder single-drive modulator used to electro-optically modulate the TE mode optical paths of two orthogonal linearly polarized lights. The output of the polarization diversity electro-optic modulation module is divided into two paths: one path is connected to the optical power acquisition and photoelectric conversion module, and the other path is used as the main optical waveguide transmission link to connect to the tunable multiplexing module. The optical power acquisition and photoelectric conversion module is used to extract the monitoring light of the two modulated lights and convert it into an electrical signal; The signal processing and feedback control module includes a low-noise amplifier optoelectronic monolithic integrated circuit, a subtractor optoelectronic monolithic integrated circuit, and an adder optoelectronic monolithic integrated circuit connected in sequence. The subtractor optoelectronic monolithic integrated circuit is used to perform differential operations on the two amplified electrical signals to obtain the optical power difference voltage V. diff The adder optoelectronic monolithic integrated circuit is used to convert V diff With preset bias voltage V bias Superimposed to generate control voltage V ctrl And V ctrl =V bias +V diff ; The tunable multiplexing module is a power-splitting-ratio controllable multiplexer, including a multimode interference coupler and an integrated optical phase shifter. The optical phase shifter receives a control voltage V. ctrl And achieve phase tuning, controlling the voltage V ctrl A miniature resistive heater is applied to the thermo-optically tuned phase shifter. The heater generates Joule heat, causing a temperature rise in the S / P polarized TE single-mode waveguide region below. The effective refractive index of silicon waveguide materials changes with temperature rise, satisfying the formula: ,in The thermo-optic coefficient of the effective refractive index of the waveguide; Light waves at a length of When propagating in the heated waveguide arm, the resulting compensated phase difference satisfies the formula: ; in, The wavelength of light in a vacuum. The electrothermal conversion coefficient and , It is the reciprocal of thermal conductivity. Where is the heater resistance, and G is the total gain of the feedback system. This represents the power difference between the two optical paths.

2. The on-chip adaptive multiplexing feedback system for polarization diversity MZM according to claim 1, characterized in that, The optical power acquisition and photoelectric conversion module includes a directional coupler and a photodetector. The directional coupler is a non-invasive optical coupling device, and the photodetector is a photodiode that is monolithically heterogeneously integrated with a silicon-based optoelectronic device.

3. The on-chip adaptive multiplexing feedback system for polarization diversity MZM according to claim 1, characterized in that, The control voltage V output by the adder optoelectronic monolithic integrated circuit in the signal processing and feedback control module is... ctrl Within the preset linear control range [V min V max The V min The voltage boundary value corresponding to the extreme polarization state where the input optical power is zero is V. max This is the voltage boundary value corresponding to the extreme polarization state where the power of the other input optical path is zero.

4. The on-chip adaptive multiplexing feedback system for polarization diversity MZM according to claim 1, characterized in that, The power splitting ratio controllable multiplexer is composed of a first-stage 2×2 multimode interference coupler, an optical phase shifter integrated on one output arm of the 2×2 multimode interference coupler, and a second-stage 2×1 multimode interference coupler cascaded together and connected to the output end of the first-stage 2×2 multimode interference coupler.

5. An on-chip adaptive multiplexing feedback system for polarization diversity MZM according to claim 4, characterized in that, The optical phase shifter is a phase shifter based on the thermo-optical effect, and the phase difference it generates satisfies the formula: ； in, The wavelength of light in a vacuum. The thermo-optical coefficient of the effective refractive index of the waveguide. This represents the change in the effective refractive index of the waveguide. The operating temperature of the waveguide. For waveguide temperature rise, This is the length of the heated waveguide arm.

6. An on-chip adaptive multiplexing feedback system for polarization diversity MZM according to claim 4, characterized in that, The optical phase shifter is a phase shifter based on the carrier dispersion effect, and the phase difference it generates satisfies the formula: ； in, The wavelength of light in a vacuum. The length of the doped modulation waveguide arm; The change in effective refractive index of the waveguide Satisfying the formula: ； in, For electron charge, At the speed of light, The vacuum permittivity, For the refractive index of the material, This represents the change in electron concentration. This represents the change in hole concentration. For the effective mass of electrons, The effective mass of the hole.

7. An on-chip adaptive multiplexing method for polarization diversity MZM, characterized in that, An on-chip adaptive multiplexing feedback system for polarization diversity MZM as described in any one of claims 1-6 includes the following steps: S1, Optical Coupling and Mode Conversion: The input light of arbitrary polarization state is decomposed into two orthogonal linearly polarized lights through a dual polarization grating coupler, and both polarized lights are converted into TE modes and output to the polarization diversity Mach-Zehnder single-drive modulator. S2, Polarization diversity electro-optic modulation, synchronous electro-optic modulation of two TE mode beams is performed by a polarization diversity Mach-Zehnder single-drive modulator. S3. Optical power acquisition and photoelectric conversion: Extract the monitoring light of the two modulated lights, convert the monitoring light into photocurrent signals, and then amplify them to obtain two corresponding voltage signals. S4. Signal processing and feedback control: The two voltage signals are differentially processed in real time using a subtractor-based optoelectronic monolithic integrated circuit to obtain V. diff Then, the V is converted into an adder by a single-chip optoelectronic integrated circuit. diff With the preset V bias Superimposed to generate control voltage V ctrl =V bias +V diff ; S5, tunable combiner, controls the voltage V ctrl Phase modulation is achieved by applying phase to an optical phase shifter, and the interference conditions of the multimode interference coupler are changed by phase change, thereby dynamically adjusting its power splitting ratio and performing wave combining on the two modulated beams.

8. The on-chip adaptive multiplexing method for polarization diversity MZM according to claim 7, characterized in that, In S3, a non-invasive optical coupling method is used to extract the monitoring light of the two modulation lights, and the power of the extracted monitoring light is in a fixed ratio with the power of the main modulation light.

9. The on-chip adaptive multiplexing method for polarization diversity MZM according to claim 7, characterized in that, In S4, the generated control voltage V ctrl Within the preset linear control range [V min V max The V bias The preset DC reference voltage is used to make the power splitting ratio controllable multiplexer operate in a 50:50 splitting state when the two modulated optical powers are equal.

10. The on-chip adaptive multiplexing method for polarization diversity MZM according to claim 7, characterized in that, In S5, the optical phase shifter is driven by the thermo-optical effect or the carrier dispersion effect to generate a compensated phase difference. The interference conditions of the multimode interference coupler are changed by the compensated phase difference, and the power splitting ratio is dynamically adjusted to achieve dynamic compensation for the power imbalance of the two modulated optical paths.

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