Micro-ring wavelength locking system and method based on digital perturbation signal

Abstract

This invention discloses a micro-ring wavelength locking system and method based on digital perturbation signals. The method includes a global scanning stage and a local locking stage. In the global scanning stage, the optimal digital value of the global DC bias voltage is obtained by increasing the thermal power in equal steps. In the local locking stage, a digital array of periodic sinusoidal perturbation signals is constructed based on the optimal digital value of the global DC bias. After being applied to the micro-ring, an array of photovoltages is obtained at the through-hole. This array is multiplied by the sinusoidal perturbation signal to obtain a mixed signal. The mixed signal is then summed to obtain an error signal. The sign of the error signal is used to determine whether the DC bias voltage has increased or decreased. This invention uses a digital method to generate the perturbation signal and directly converts the micro-ring through-hole signal into a digital signal via an ADC. Digital signal processing is performed inside the processor to extract the error signal. It features low cost, high reliability, and high compatibility with micro-ring wavelength locking requirements of different parameters.

Description

Technical Field

[0001] This invention belongs to the field of micro-ring wavelength control technology, specifically relating to a micro-ring wavelength locking system and method based on digital perturbation signals. Background Technology

[0002] Currently, photonic devices such as lasers, filters, optical switches, and modulators have been designed based on microring resonators. However, due to the high thermo-optic coefficient of silicon, silicon-based microring resonators are highly susceptible to wavelength detuning caused by changes in ambient temperature, leading to a deviation from the optimal operating wavelength. Furthermore, manufacturing errors can also cause deviations between the actual resonant wavelength and the designed wavelength. To address the impact of ambient temperature fluctuations and manufacturing errors on the microring resonant wavelength, a common wavelength-locking method involves monitoring parameter changes caused by wavelength detuning and applying appropriate heating power to a microheater integrated on the microring to counteract the effects of ambient temperature. This closed-loop control system maintains constant alignment between the resonant wavelength and the target wavelength.

[0003] Monitoring parameter changes caused by microring wavelength misalignment can include bit error rate, temperature, optical power, etc. Monitoring optical power changes is commonly used, but these methods often lead to locking deviations due to the instability of the input optical power. At the same time, since the transmission spectrum of the microring is a symmetrical spectrum, the direction of temperature shift cannot be directly determined during locking, which makes it impossible to correctly change the heating power to ensure real-time wavelength locking, resulting in low locking efficiency.

[0004] The method of generating a perturbation signal using a signal generator on the peripheral circuit and performing a series of signal processing steps to extract the first derivative information of the microring heating power and spectrum, and accurately determining the temperature offset direction by using the sign of the first derivative, is a mature control technique with a simple control algorithm. However, this method has some problems. First, it requires generating a signal generator with adjustable amplitude, frequency, and waveform, increasing the cost of wavelength locking. Second, when performing analog signal processing on the circuit, it is necessary to construct related analog circuits such as multipliers, amplifiers, and low-pass filters. Different perturbation signals are required for different microring resonators, making the modification of related parameters on the analog circuit too cumbersome. In summary, this method increases the cost of wavelength locking to some extent, has poor flexibility in signal processing on the analog circuit, and poor compatibility with wavelength locking of microrings with different parameters. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and propose a micro-loop wavelength locking system and method based on digital perturbation signals. Compared with the scheme of implementing perturbation signals on analog circuits, it has lower cost and higher compatibility with micro-loop wavelength locking of different parameters.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A micro-ring wavelength locking system based on digital perturbation signals includes a laser, a micro-ring system under test, a photodetector, and an MCU control unit.

[0008] The MCU control unit integrates a 16-bit DAC and a 16-bit ADC.

[0009] The microring system under test includes a microring body integrating a microheater, a straight waveguide, an input terminal, and a through terminal;

[0010] During operation, the laser generates a single-wavelength optical signal, which is coupled into the micro-ring system under test through the input terminal. The optical signal at the through-end is converted into an electrical signal by a photodetector and acquired by a 16-bit ADC. Based on the output DC bias voltage, the 16-bit ADC generates a periodic sinusoidal perturbation signal in a digital manner, which is superimposed on the DC bias voltage and applied to the micro heater. The output photovoltage signal at the through-end is acquired and multiplied with the sinusoidal perturbation signal to obtain a mixed signal. The sign of the error signal is used to determine whether the heating power of the micro heater has increased or decreased.

[0011] The present invention also includes a microring wavelength locking method based on the provided microring wavelength locking system, comprising:

[0012] During the global scan phase, the optimal digital value of the global DC bias voltage is obtained by increasing the thermal power in equal steps.

[0013] In the local locking phase, a digital array of periodic sinusoidal perturbation signals is constructed based on the globally optimal DC bias digital value. After being applied to the micro-ring, a photovoltage array is obtained at the through-hole. This array is multiplied by the sinusoidal perturbation signal to obtain a mixed signal. The mixed signal is then summed to obtain an error signal. The sign of the error signal is used to determine whether the DC bias voltage increases or decreases.

[0014] Furthermore, the global scanning phase specifically includes:

[0015] Construct a DAC digital value array with equal heating power steps, and determine the globally optimal DC bias voltage digital value:

[0016] Set maximum heating power P max If the heating power step size is ΔP, then the heating power array is [0, ΔP, 2ΔP...P]. max The heating voltage array with equal heating power step size is [0, U1, U2, ... U]. max ];

[0017] When an n-bit DAC is used to output the heating voltage, the corresponding digital value of the DAC is DAC. val for:

[0018] DAC val =U*2 n / U ref ;

[0019] Among them, U ref It is the maximum output voltage of the DAC; the DAC digital value array with equal heating power step size. val The range is [0, X1, X2, ...].

[0020] The constructed DAC digital value array with equal heating power step size is sequentially output to the DAC, amplified by the thermal adjustment drive circuit and applied to the micro heater. The photovoltage value of the through terminal after each change of the DAC digital value is recorded as [Y1, Y2, ...].

[0021] When the resonant wavelength of the microring is aligned with the signal wavelength, the photovoltage value at the through-hole is minimized. By comparing the photovoltage values ​​at the through-hole during the process, the minimum value Y is obtained. m Its corresponding DAC digital value X m This is the globally optimal DC bias voltage digital value.

[0022] Furthermore, the local locking phase specifically includes:

[0023] Construct an array of digital values ​​for the perturbation signal at the globally optimal digital value of the DC bias voltage;

[0024] The optical power at the through-end is collected to obtain the optical voltage array at the through-end;

[0025] The error signal is obtained by multiplying the direct-end optical voltage array with the perturbation signal and summing the results.

[0026] The optimal DC bias voltage digital value is adjusted based on the error signal.

[0027] Furthermore, an array of digital values ​​for the perturbation signal is constructed at the globally optimal digital value of the DC bias voltage, specifically as follows:

[0028] Constructing a digital array of perturbation signals for a DAC

[0029] Where A is the amplitude of the perturbation signal, i max It is the maximum number of points, i is incremented from 0 to i max To ensure that the perturbation signal is a complete sine cycle, It is a constant that converts angles to radians;

[0030] The perturbation signal DAC digital value array plus the globally optimal DC bias digital value X m This refers to the array of perturbation signals during this local locking process.

[0031] Furthermore, the optical power at the through-end is collected to obtain the through-end optical voltage array, specifically:

[0032] The constructed perturbation signal digital value array is sequentially output to the DAC, amplified and applied to the micro heater. Each time the DAC digital value is changed, the through-end optical signal is converted into a photovoltage signal by photodetector and directly converted into a digital signal by ADC to obtain the through-end photovoltage array V_Th[i].

[0033] Furthermore, the error signal is obtained by multiplying the direct-end photovoltage array with the perturbation signal and summing the results, specifically:

[0034] The smoothed through-end photovoltage array V_Th[i] and the perturbation signal array are compared. Multiplying them together yields the mixed signal Raw[i], which contains the modulation part influenced by the DC bias voltage and the sinusoidal perturbation signal. Since the sinusoidal perturbation signal is a complete periodic signal, the modulation affecting the micro-ring is also a complete periodic part. Summing the mixed signal eliminates the AC component in the mixed signal, resulting in the DC signal of the mixed signal, i.e., the error signal ε.

[0035] Furthermore, the optimal DC bias voltage digital value is adjusted based on the error signal, specifically as follows:

[0036] When the error signal is less than 0, it indicates that the DC bias voltage is too low, causing the resonant wavelength of the micro-ring resonator to be to the left of the signal wavelength, and the digital value of the DC bias voltage needs to be increased; when the error signal is greater than 0, it indicates that the DC bias voltage is too high, causing the resonant wavelength of the micro-ring resonator to be to the right of the signal wavelength, and the digital value of the DC bias voltage needs to be decreased.

[0037] The global optimal DC bias voltage digital value X is changed according to the sign of the error signal. m Then proceed with the next locking process.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] 1. This invention proposes a micro-loop wavelength locking method based on digital perturbation signals. The perturbation signals are generated digitally, eliminating the need for a signal generator and reducing the cost of micro-loop wavelength locking. The relevant signal processing is performed inside the processor, which is more flexible than signal processing based on analog circuits. Micro-loop wavelength locking with different parameters can be achieved by making corresponding modifications to the program. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the system of the present invention;

[0041] Figure 2 This is a flowchart of the method of the present invention;

[0042] Figure 3 This is a transmission spectrum diagram of the straight-through end;

[0043] Figure 4 This is a schematic diagram of the error signal and the photovoltage signal at the through end. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0045] Example

[0046] like Figure 1 As shown, the micro-ring wavelength locking system based on digital perturbation signals includes a laser, a micro-ring under test system, a photodetector, and an MCU control unit.

[0047] The MCU control unit integrates a 16-bit DAC and a 16-bit ADC.

[0048] The microring system under test includes a microring body integrating a microheater, a straight waveguide, an input terminal, and a through terminal;

[0049] During operation, the laser generates a single-wavelength optical signal, which is coupled into the micro-ring test system at the input end. The optical signal at the direct-through end is converted into an electrical signal by a photodetector and acquired by a 16-bit ADC. Based on the output DC bias voltage, the 16-bit ADC digitally generates a periodic sinusoidal perturbation signal, which is then superimposed on the DC bias voltage. It acts on the micro heater;

[0050] Where V is the DC bias voltage and A is the amplitude of the sinusoidal perturbation signal. Since the modulated perturbation AC signal is sufficiently small relative to the DC bias voltage, the nonlinear part introduced by the process is not considered, and the photoelectric conversion signal at the through end is still a sinusoidal signal.

[0051] Let the change in the center wavelength of the microring be... Where α is the modulation efficiency of the voltage signal applied to the microheater to the center wavelength, and B is the amplitude of the signal. Since the perturbation AC signal is sufficiently small relative to the DC bias voltage, α is approximately equal to the slope ε of the DC bias voltage with respect to the wavelength measured at the through-hole. Therefore, the photovoltage signal output from the through-hole is a sinusoidal signal. The hybrid signal is obtained by multiplying the direct-end optical signal with the sinusoidal perturbation signal. The AC component can be filtered out by summing the mixed signals over time. The DC component A·ε·α·B, which includes the slope ε, is the error signal. A, α, and B are all positive numbers, and the sign of the error signal is determined by the slope ε of the DC bias voltage with respect to the wavelength. For example... Figure 3 As shown, the spectrum of the microring through end indicates that when the error signal is equal to 0, it means that the microring resonator is in a locked state. When the error signal is less than zero, it means that the resonant wavelength is less than the target wavelength, and the heating power needs to be increased. Similarly, when the error signal is greater than zero, it means that the resonant wavelength is greater than the target wavelength, and the heating power needs to be reduced.

[0052] like Figure 2 As shown, in another embodiment, a micro-ring wavelength locking method for the system described in the above embodiments is provided, comprising:

[0053] Global scan phase:

[0054] Construct a DAC digital value array with equal heating power step size to determine the globally optimal DC bias voltage digital value. First, determine the maximum heating power P. max If the heating power step size ΔP is determined, then the heating power array is [0, ΔP, 2ΔP…P]. max Then the heating voltage array with equal heating power step size is [0, U1, U2, ..., Y]. max When an n-bit DAC is used to output the heating voltage, the corresponding digital value of the DAC is... val For: DAC val =U*2 n / U ref U ref If it is the maximum output voltage of the DAC, then the DAC digital value array with equal heating power step size is... val The array of DAC digital values ​​with equal heating power steps is [0, X1, X2, ...]. The constructed array of DAC digital values ​​with equal heating power steps is sequentially output to the DAC, amplified by a thermally adjustable drive circuit, and applied to the micro-ring heater. The photovoltage value at the through-hole is recorded as [Y1, Y2, ...] after each change in the DAC digital value. When the resonant wavelength of the micro-ring is aligned with the signal wavelength, the photovoltage value at the through-hole is minimized. The minimum value Y is obtained by comparing the array of through-hole photovoltage values ​​during the process. m Its corresponding DAC digital value X m This is the globally optimal DC bias voltage digital value.

[0055] The local locking phase includes:

[0056] Construct an array of digital values ​​for the perturbation signal at the globally optimal digital value of the DC bias voltage;

[0057] First, construct the DAC digital value array for the perturbation signal. Where A is the amplitude of the perturbation signal, and the amplitude of the perturbation signal is kept as small as possible to avoid affecting the thermo-optic modulation effect of the DC bias voltage on the micro-ring. max It is the maximum number of points, i is incremented from 0 to i max To ensure that the perturbation signal is a complete sine cycle, It is a constant for converting angles to radians. The perturbation signal DAC digital value array is added to the globally optimal DC bias digital value X. m This refers to the array of perturbation signals during this local locking process.

[0058] The optical power at the through-end is collected to obtain the optical voltage array at the through-end;

[0059] The constructed perturbation signal digital value array is sequentially output to the DAC, amplified by the thermal adjustment drive circuit and applied to the micro ring heater. Each time the DAC digital value is changed, the through-end optical signal is converted into a photovoltage signal by photodetector and directly converted into a digital signal by the 16-bit ADC to obtain the through-end photovoltage array V_Th[i].

[0060] The error signal is obtained by multiplying the direct-end optical voltage array with the perturbation signal and summing the results.

[0061] The smoothed through-end photovoltage array V_Th[i] and the perturbation signal array are compared. Multiplying them together yields the mixed signal Raw[i], which contains the modulation part influenced by the DC bias voltage and the sinusoidal perturbation signal. Since the sinusoidal perturbation signal is a complete periodic signal, the modulation affecting the micro-ring is also a complete periodic part. Summing the mixed signal eliminates the AC component in the mixed signal, resulting in the DC signal of the mixed signal, i.e., the error signal ε.

[0062] Adjust the optimal DC bias voltage digital value according to the error signal;

[0063] When the error signal is less than 0, it indicates that the DC bias voltage is too low, causing the resonant wavelength of the micro-ring resonator to be to the left of the signal wavelength, requiring an increase in the DC bias voltage value. When the error signal is greater than 0, it indicates that the DC bias voltage is too high, causing the resonant wavelength of the micro-ring resonator to be to the right of the signal wavelength, requiring a decrease in the DC bias voltage value. The globally optimal DC bias voltage value X is adjusted according to the sign of the error signal. m To proceed with the next locking process.

[0064] In this embodiment, the maximum heating power P is set during the global scan phase. max The power was set to 50mW, the heating power step size ΔP was 0.05mW, the resistance R of the micro-ring heater was 400Ω, and the process was divided into 1000 steps to ensure that the globally optimal DC bias digital value X could be obtained.m During the local locking phase, the amplitude A of the perturbation signal is set to 30mV, and the maximum number of points i max The value is set to 100 to ensure the generated sinusoidal perturbation signal has a complete cycle. A 16-bit DAC is used for digital-to-analog signal conversion, and the maximum output voltage U of the DAC is... ref The voltage is 3.0V. The result is as follows: Figure 4 As shown, when the heating power gradually increases from 0 to P max During the process, the photovoltage signal at the direct end of the microring exhibits a symmetrical spectral distribution. When the photovoltage signal at the direct end is at its lowest, the error signal is equal to 0. When the heating power is adjusted so that the resonant wavelength of the microring is to the left of the signal wavelength, the error signal is less than 0. When the heating power is adjusted so that the resonant wavelength of the microring is to the right of the signal wavelength, the error signal is greater than 0. The direction of heating power movement can be determined based on the sign of the error signal, thereby improving the locking efficiency of the microring wavelength locking.

[0065] It should also be noted that, in this specification, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0066] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A micro-ring wavelength locking system based on digital perturbation signals, characterized in that, This includes a laser, a micro-ring test system, a photodetector, and an MCU control unit; The MCU control unit integrates a 16-bit DAC and a 16-bit ADC. The microring system under test includes a microring body integrating a microheater, a straight waveguide, an input terminal, and a through terminal; During operation, the laser generates a single-wavelength optical signal, which is coupled into the micro-ring test system through the input terminal. The optical signal at the through-end is converted into an electrical signal by a photodetector and acquired by a 16-bit ADC. Based on the output DC bias voltage, the 16-bit ADC generates a periodic sinusoidal perturbation signal in a digital manner, which is superimposed on the DC bias voltage and applied to the micro-heater. The output photovoltage signal at the through-end is acquired and multiplied with the sinusoidal perturbation signal to obtain a mixed signal. The sign of the error signal is used to determine whether the heating power of the micro-heater has increased or decreased. The micro-ring wavelength locking system specifically includes the following steps for micro-ring wavelength locking: During the global scan phase, the optimal digital value of the global DC bias voltage is obtained by increasing the thermal power in equal steps. In the local locking phase, a digital array of periodic sinusoidal perturbation signals is constructed based on the globally optimal DC bias digital value. This array, applied to the micro-ring, yields a photovoltage array at the through-hole. This photovoltage array is multiplied by the sinusoidal perturbation signal to obtain a mixed signal. The mixed signal is then summed to obtain an error signal. The sign of the error signal is used to determine whether the DC bias voltage has increased or decreased. Specifically, this includes: Construct an array of digital values ​​for the perturbation signal at the globally optimal digital value of the DC bias voltage; The optical power at the through-end is collected to obtain the optical voltage array at the through-end; The error signal is obtained by multiplying the direct-end optical voltage array with the perturbation signal and summing the results. The optimal DC bias voltage digital value is adjusted based on the error signal, specifically as follows: When the error signal is less than 0, it indicates that the DC bias voltage is too low, causing the resonant wavelength of the micro-ring resonator to be to the left of the signal wavelength, and the digital value of the DC bias voltage needs to be increased; when the error signal is greater than 0, it indicates that the DC bias voltage is too high, causing the resonant wavelength of the micro-ring resonator to be to the right of the signal wavelength, and the digital value of the DC bias voltage needs to be decreased. Changing the global optimum dc bias voltage digital value depending on the sign of the error signal to proceed with the next locking procedure.

2. The digital micro-kicks based micro-ring wavelength locking system of claim 1, wherein, The global scan phase specifically includes: Construct a DAC digital value array with equal heating power steps, and determine the globally optimal DC bias voltage digital value: Set maximum heating power Heating power step Then the heating power array is [0, ,2 … ] and the heating voltage array with equal heating power step is [0, , ,… ] When using an n-bit DAC to output the heating voltage, the corresponding digital value of the DAC is... for: ； in, It is the maximum output voltage of the DAC; the DAC digital value array with equal heating power steps. For [0, , ,…]; The constructed DAC digital value array with equal heating power step size is sequentially output to the DAC, amplified by the thermal adjustment drive circuit, and applied to the micro-heater. The photovoltage value at the through-terminal is recorded after each change of the DAC digital value. , , …]; When the resonant wavelength of the microring is aligned with the signal wavelength, the photovoltage value at the through-hole is minimized. The minimum value is obtained by comparing the array of photovoltage values ​​at the through-hole during the process. Its corresponding DAC digital value This is the globally optimal DC bias voltage digital value.

3. The micro-ring wavelength locking system based on digital perturbation signals according to claim 1, characterized in that, A digital array of perturbation signals is constructed at the globally optimal digital value of the DC bias voltage, specifically as follows: Constructing a digital array of perturbation signals for a DAC ; in, It is the amplitude of the perturbation signal. It is the maximum number of points. Add from 0 to To ensure that the perturbation signal is a complete sine cycle, It is a constant that converts angles into radians; Perturbation signal DAC digital value array plus globally optimal DC bias digital value This refers to the array of perturbation signals during this local locking process. .

4. The micro-ring wavelength locking system based on digital perturbation signals according to claim 3, characterized in that, The optical power at the through-end is collected to obtain the through-end optical voltage array, specifically: The constructed digital array of perturbation signals is sequentially output to the DAC, amplified, and applied to the micro-heater. Each time the DAC digital value is changed, the direct-end optical signal is converted into a photovoltage signal via photodetector, which is then directly converted into a digital signal by the ADC to obtain the direct-end photovoltage array. .

5. The micro-ring wavelength locking system based on digital perturbation signals according to claim 4, characterized in that, The error signal is obtained by multiplying the direct-end optical voltage array with the perturbation signal and summing the results: The smoothed through-end photovoltage array With perturbation signal array Multiplication yields a mixed signal The signal contains a modulation component influenced by a DC bias voltage and a sinusoidal perturbation signal. Since the sinusoidal perturbation signal is a complete periodic signal, the modulation affecting the micro-loop is also a complete periodic component. Summing the mixed signals eliminates the AC component, yielding the DC signal of the mixed signal, which is the error signal. .

Images