ODAC (Optical Digital-to-Analog Converter) implementation system and method based on five-segment thermo-optical phase modulator

Abstract

The invention discloses an ODAC implementation system and method based on a five-segment thermo-optical phase modulator, and relates to the technical field of optical communication, and the method comprises the following steps: obtaining single-mode laser input, dividing the single-mode laser input into two paths through a multi-mode interference device beam splitter, and transmitting the single-mode laser input into an upper arm and a lower arm of a Mach-Zehnder modulator; the current is adjusted through the thermo-optic phase modulator to control the temperature, the refractive index is changed to introduce phase delay, and the phase difference of two arms of the Mach-Zehnder modulator is calibrated; on the basis of a five-segment thermo-optical modulator, hierarchical amplitude modulation is carried out on beam splitting light according to digital input, a phase space is constructed by utilizing weight combination, and a linear optimal discrete state is screened; the modulated light is combined by a multi-mode interference device beam combiner, and digital-analog mapping output of light intensity is carried out; a detector installed at an output port of the five-segment thermo-optical phase modulator is used for monitoring output optical power in real time, the output optical power is fed back to a control circuit to calculate errors, thermo-optical modulation current is dynamically adjusted to compensate offset point drift, and optical digital analog conversion is achieved.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to an ODAC implementation system and method based on a 5-segment thermo-optical phase modulator. Background Art

[0002] As optical communication technology develops towards high speed and high precision, optical digital-to-analog converters, as core components of optical signal processing, have placed higher demands on the quantization accuracy, linearity, and environmental robustness of optical digital-to-analog conversion in scenarios such as optical transmission and optical quantum computing. Traditional optical digital-to-analog conversion solutions based on 4-segment Mach-Zehnder modulators can no longer meet these requirements.

[0003] However, traditional optical digital-to-analog conversion implementation methods often face the following problems when dealing with high-precision optical signal processing, multi-dimensional phase modulation, and dynamic environment adaptation: First, insufficient quantization accuracy and segmented modulation limitations. The traditional 4-segment Mach-Zehnder modulator can only provide 16 phase states. When processing 4-bit digital signals, the standard deviation of the light intensity interval is large, which cannot meet the light intensity quantization requirements in high-precision scenarios. Second, bias point drift and dynamic calibration capabilities are insufficient. Traditional solutions rely on fixed resistor heating calibration and lack a closed-loop feedback mechanism. In long-term operation, resistance drift caused by device aging further exacerbates bias point offset, affecting system stability. In addition, linearity optimization and multi-segment collaborative design are lacking. Traditional 4-segment modulators cannot construct sufficient phase modulation space and can only filter linear states from the edge areas. The nonlinear error of the light intensity-phase curve is large. When processing multi-level modulated signals in complex optical communication protocols, traditional solutions have difficulty in selecting the optimal operating point from the multi-dimensional phase-intensity correlation, which cannot meet the requirements of high-speed coherent communication. Summary of the Invention

[0004] The object of the present invention is to provide an ODAC implementation system and method based on a 5-segment thermo-optical phase modulator to solve the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an ODAC implementation method based on a 5-segment thermo-optical phase modulator, the method comprising the following steps:

[0006] Obtain single-mode laser input, split it into two paths through a multi-mode interferometer beam splitter and send it to the upper and lower arms of the Mach-Zehnder modulator;

[0007] Using a thermo-optical phase modulator, the temperature change is controlled by adjusting the current, changing the refractive index of the waveguide material, introducing a controllable phase delay, and calibrating the phase difference between the two arms of the Mach-Zehnder modulator when there is no modulation voltage.

[0008] The 5-segment thermo-optical phase modulator performs hierarchical amplitude modulation on the split optical signal according to the digital input signal. The phase modulation space is constructed using segmented weight combinations, and the discrete state set with the best linearity is selected from the full amount of modulation states.

[0009] The modulated optical signals of the two arms are combined by a multi-mode interferometer combiner to perform digital-to-analog mapping output of the optical intensity signal;

[0010] The output optical power is monitored in real time by a detector installed at the output port of the 5-segment thermo-optical phase modulator. The data is fed back to the automatic bias control circuit to calculate the error between the current optical power and the target power, and the current of the thermo-optical phase modulator is dynamically adjusted to compensate for the bias point drift.

[0011] Obtain single-mode laser input, split it into two paths through a multimode interferometer beam splitter and send it to the upper and lower arms of the Mach-Zehnder modulator. The specific steps include:

[0012] A single-mode optical signal of a laser light source that needs to be converted from analog to digital is obtained as input light, and the input light is used as an analog signal carrier of the optical digital-to-analog converter; wherein the wavelength of the single-mode optical signal of the laser light source is 1550 nm;

[0013] The input light is evenly divided into two paths by a 2*2 multimode interferometer beam splitter and sent to the upper and lower arms of the Mach-Zehnder modulator respectively.

[0014] Using a thermo-optical phase modulator, the temperature change is controlled by adjusting the current, changing the refractive index of the waveguide material, introducing a controllable phase delay, and calibrating the phase difference between the two arms of the Mach-Zehnder modulator when there is no modulation voltage. The specific steps include:

[0015] The heating components are integrated around the upper and lower arm waveguides of the Mach-Zehnder modulator. When powered on, the local temperature changes, causing the effective refractive index of the waveguide to change, thereby introducing a controllable phase delay. Where Δφ represents the phase difference, Δn eff is the refractive index change caused by temperature change, L is the length of the heated area, and λ represents the wavelength of light;

[0016] When power is applied, the local temperature changes, causing the waveguide refractive index to change. Specifically:

[0017] At a wavelength of 1550nm, the refractive index of silicon material changes with temperature at a rate of n represents the refractive index of the material, and t represents the temperature;

[0018] Phase difference calibration is implemented in stages, specifically:

[0019] After the modulator is first used or packaged, an adjustable current is applied to the thermo-optical modulator, the output light intensity of the Herz-Zehnder modulator is monitored, and the phase difference between the two arms is compared with the calibration reference of the phase difference between the two arms, and the phase difference between the two arms is calibrated to the calibration reference of the phase difference between the two arms to achieve phase balance between the two arms in the absence of modulation, wherein the phase difference between the two arms is calibrated to π / 2;

[0020] During long-term operation or in an environment with temperature changes, the output optical power is monitored in real time through a light detector. When the error exceeds the set threshold, the current regulation amount is calculated based on the PID algorithm.

[0021] The split optical signal is hierarchically amplitude modulated based on the digital input signal using a five-segment thermo-optical phase modulator. A phase modulation space is constructed using segmented weight combinations. The set of discrete states with the optimal linearity is selected from the full modulation state. The modulated optical signals from both arms are combined using a multimode interferometer combiner to perform digital-to-analog mapping of the optical intensity signal. The specific steps include:

[0022] A 32-order phase modulation space is constructed based on the segmented weight combination, where the segmented weight combination is 1:2:4:8:16. The linear optimal discrete state set is screened by the following method:

[0023] The 5-segment modulator forms 32 phase combinations through independent current control, corresponding to the cumulative phase value φ k =k·Δφ, k=0,1,…,31, the output light intensity satisfies Among them, I k represents the light intensity value output by the Mach-Zehnder modulator when the five-segment modulator combination forms an accumulated phase difference; k represents the phase state index; I0 represents the initial light signal intensity input to the Mach-Zehnder modulator;

[0024] From these 32 levels, 16 equally spaced, approximately linearly responding points are selected as modulation values. From the most linear region in the middle, i.e., the 32 discrete phase points near φ = π / 2, k = 8 to 23 is selected. The corresponding output is

[0025] The modulated optical signals of the two arms are combined through a 2*2 multimode interferometer combiner, and the output intensity is controlled by the interference principle. Specifically:

[0026] The electric fields of the two interferometer arms are Where A is the amplitude of the optical field, φ1 and φ2 represent the phases of the upper and lower modulation arms, respectively, and E1 and E2 represent the electric fields of the upper and lower modulation arms, respectively. j is the unit of the imaginary part of the imaginary number, defined as j^2 = -1.

[0027] The output electric field after beam combining is Among them, E out represents the output electric field after beam combining;

[0028] The output light intensity is I out =|E out | 2 =2A 2 [1+cos(φ1-φ2)]; where I out Indicates the output light intensity after beam combining.

[0029] The detector installed at the output port of the 5-segment thermo-optical phase modulator monitors the output optical power in real time. The data is fed back to the automatic bias control circuit to calculate the error between the current optical power and the target power. The current of the thermo-optical phase modulator is dynamically adjusted to compensate for bias point drift. The specific steps include:

[0030] Add an optical power monitoring detector to the other port of the Mach-Zehnder modulator output to monitor the changes in the output light intensity in real time, calculate the error between the current output optical power and the target optical power in real time, and determine whether the modulator deviates from the ideal bias point:

[0031] Compare the calculated error between the current output optical power and the target optical power with the set error threshold to determine whether the modulator deviates from the ideal bias point. If exceeded, bias point calibration is triggered.

[0032] The setting rules for the ideal bias point are as follows:

[0033] The ideal bias point refers to the linear operating point of the Mach-Zehnder modulator, that is, the phase difference between the two modulation arms is π / 2, so that the modulation response is at the position with the maximum linear slope in the light intensity-voltage curve;

[0034] The controller executes the PID algorithm to calculate the phase compensation value that needs to be adjusted. The controller outputs a control current to control the thermo-optical phase modulator, thereby adjusting the phase difference of the Mach-Zehnder modulator and maintaining the bias point at π / 2.

[0035] The ODAC implementation system based on a 5-segment thermo-optical phase modulator includes: an optical input and beam splitting module, a phase calibration module, a modulation module and an optical signal beam combining and output module. The optical input and beam splitting module is used to obtain a single-mode laser input, which is evenly divided into two paths through a multi-mode interferometer beam splitter and sent to the upper and lower arms of the Mach-Zehnder modulator; the phase calibration module is used to adjust the current through the thermo-optical phase modulator to control the temperature, change the refractive index to introduce phase delay, and calibrate the phase difference between the two arms of the Mach-Zehnder modulator; the modulation module is used to hierarchically modulate the amplitude of the split light according to the digital input based on the 5-segment thermo-optical modulator, and use the weighted group The phase space is constructed and the linear optimal discrete state is screened; the optical signal combining and output module is used to combine the modulated light through the multimode interferometer combiner and perform digital-to-analog mapping output of the light intensity; the output optical power is monitored in real time by a detector installed at the output port of the 5-segment thermo-optical phase modulator, and the error is fed back to the control circuit to dynamically adjust the thermo-optical modulation current to compensate for the bias point drift; the output end of the optical input and beam splitting module is connected to the input end of the phase calibration module, the output end of the phase calibration module is connected to the input end of the modulation module, and the output end of the modulation module is connected to the input end of the optical signal combining and output module.

[0036] The optical input and beam splitting module includes a laser input light source unit and a beam splitting unit. The laser input light source unit is used to obtain a single-mode optical signal of a laser light source that needs to be converted from analog to digital as input light, and use the input light as the analog signal carrier of the optical digital-to-analog converter; the beam splitting unit is used to evenly split the input light into two paths through a 2*2 multimode interferometer beam splitter, and send them to the upper and lower arms of the Mach-Zehnder modulator respectively.

[0037] The phase calibration module includes a thermo-optical phase modulator unit, a phase calibration unit, and a dynamic bias control unit. The thermo-optical phase modulator unit is used to introduce controllable phase delay by controlling temperature changes through current based on the thermo-optic effect of silicon material; the phase calibration unit is used to implement phase difference calibration in stages; and the dynamic bias control unit is used to calculate the current adjustment amount based on the PID algorithm.

[0038] The modulation module includes a segmentation unit and a linear state screening unit. The segmentation unit is used to perform hierarchical amplitude modulation on the split optical signal according to the digital input signal through a 5-segment thermo-optical phase modulator, and construct a phase modulation space using a segmented weight combination, wherein the segmented weight combination is 1:2:4:8:16; the linear state screening unit is used to select points with equal intervals and approximately linear responses as modulation values.

[0039] The optical signal combining and output module includes a combining unit, an optical power output unit and an optical power monitoring unit; the combining unit is used to combine the optical signals modulated by the two arms through a multimode interferometer combiner; the optical power output unit is used to integrate a monitoring port and realize real-time monitoring of the output light intensity by connecting a detector; the optical power monitoring unit is used to calculate the error between the current optical power and the target power, dynamically adjust the current of the thermo-optical phase modulator, and compensate for the bias point drift.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. A 32-order phase modulation space is constructed by using five thermo-optical modulator arms. 16 optimal states are selected from the intermediate linear region to map a 4-bit digital signal. Compared with the existing four-segment modulator (which only has 16 phase states), this invention reduces quantization error. This solution breaks through the dimensional limitations of traditional single-segment modulation and achieves high-precision hierarchical modulation of the optical signal amplitude through binary weight combination and multi-dimensional phase-intensity correlation analysis.

[0042] 2. The output optical power is monitored in real time using a photodetector, and the thermo-optical modulation current is dynamically adjusted by executing a PID algorithm through an automatic bias control circuit. Compared with the static resistance heating calibration in the prior art, the present invention can compensate for bias point drift caused by temperature fluctuations and device aging in real time. The adaptive adjustment module automatically optimizes the thermo-optical modulation power distribution through a "monitoring-calculation-adjustment" closed loop, avoiding the modulation curve offset caused by environmental changes in traditional solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the flow of the ODAC implementation method based on a 5-segment thermo-optical phase modulator of the present invention;

[0044] Figure 2 This is a structural diagram of the ODAC implementation system based on a 5-segment thermo-optical phase modulator of the present invention. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Example: Figure 1-Figure 2 As shown, the present invention provides a technical solution, an ODAC implementation method based on a 5-segment thermo-optical phase modulator, the method comprising the following steps:

[0047] Obtain single-mode laser input, split it into two paths through a multi-mode interferometer beam splitter and send it to the upper and lower arms of the Mach-Zehnder modulator;

[0048] Using a thermo-optical phase modulator, the temperature change is controlled by adjusting the current, changing the refractive index of the waveguide material, introducing a controllable phase delay, and calibrating the phase difference between the two arms of the Mach-Zehnder modulator when there is no modulation voltage.

[0049] The 5-segment thermo-optical phase modulator performs hierarchical amplitude modulation on the split optical signal according to the digital input signal. The phase modulation space is constructed using segmented weight combinations, and the discrete state set with the best linearity is selected from the full amount of modulation states.

[0050] The modulated optical signals of the two arms are combined by a multi-mode interferometer combiner to perform digital-to-analog mapping output of the optical intensity signal;

[0051] The output optical power is monitored in real time by a detector installed at the output port of the 5-segment thermo-optical phase modulator. The data is fed back to the automatic bias control circuit to calculate the error between the current optical power and the target power, and the current of the thermo-optical phase modulator is dynamically adjusted to compensate for the bias point drift.

[0052] Obtain single-mode laser input, split it into two paths through a multimode interferometer beam splitter and send it to the upper and lower arms of the Mach-Zehnder modulator. The specific steps include:

[0053] A single-mode optical signal of a laser light source that needs to be converted from analog to digital is obtained as input light, and the input light is used as an analog signal carrier of the optical digital-to-analog converter; wherein the wavelength of the single-mode optical signal of the laser light source is 1550 nm;

[0054] The input light is evenly divided into two paths by a 2*2 multimode interferometer beam splitter and sent to the upper and lower arms of the Mach-Zehnder modulator respectively.

[0055] Using a thermo-optical phase modulator, the temperature change is controlled by adjusting the current, changing the refractive index of the waveguide material, introducing a controllable phase delay, and calibrating the phase difference between the two arms of the Mach-Zehnder modulator when there is no modulation voltage. The specific steps include:

[0056] The heating components are integrated around the upper and lower arm waveguides of the Mach-Zehnder modulator. When powered on, the local temperature changes, causing the effective refractive index of the waveguide to change, thereby introducing a controllable phase delay. Where Δφ represents the phase difference, Δn eff is the refractive index change caused by temperature change, L is the length of the heated area, and λ represents the wavelength of light;

[0057] When power is applied, the local temperature changes, causing the waveguide refractive index to change. Specifically:

[0058] At a wavelength of 1550nm, the refractive index of silicon material changes with temperature at a rate of n represents the refractive index of the material, and t represents the temperature;

[0059] Phase difference calibration is implemented in stages, specifically:

[0060] After the modulator is first used or packaged, an adjustable current is applied to the thermo-optical modulator, the output light intensity of the Herz-Zehnder modulator is monitored, and the phase difference between the two arms is compared with the calibration reference of the phase difference between the two arms, and the phase difference between the two arms is calibrated to the calibration reference of the phase difference between the two arms to achieve phase balance between the two arms in the absence of modulation, wherein the phase difference between the two arms is calibrated to π / 2;

[0061] During long-term operation or in an environment with temperature changes, the output optical power is monitored in real time through a light detector. When the error exceeds the set threshold, the current regulation amount is calculated based on the PID algorithm.

[0062] The split optical signal is hierarchically amplitude modulated based on the digital input signal using a five-segment thermo-optical phase modulator. A phase modulation space is constructed using segmented weight combinations. The set of discrete states with the optimal linearity is selected from the full modulation state. The modulated optical signals from both arms are combined using a multimode interferometer combiner to perform digital-to-analog mapping of the optical intensity signal. The specific steps include:

[0063] A 32-order phase modulation space is constructed based on the segmented weight combination, where the segmented weight combination is 1:2:4:8:16. The linear optimal discrete state set is screened by the following method:

[0064] The 5-segment modulator forms 32 phase combinations through independent current control, corresponding to the cumulative phase value φ k =k·Δφ, k=0,1,…,31, the output light intensity satisfies Among them, I k represents the light intensity value output by the Mach-Zehnder modulator when the five-segment modulator combination forms an accumulated phase difference; k represents the phase state index; I0 represents the initial light signal intensity input to the Mach-Zehnder modulator;

[0065] From these 32 levels, 16 equally spaced, approximately linearly responding points are selected as modulation values. From the most linear region in the middle, i.e., the 32 discrete phase points near φ = π / 2, k = 8 to 23 is selected. The corresponding output is

[0066] The modulated optical signals of the two arms are combined through a 2*2 multimode interferometer combiner, and the output intensity is controlled by the interference principle. Specifically:

[0067] The electric fields of the two interferometer arms are Where A is the amplitude of the optical field, φ1 and φ2 represent the phases of the upper and lower modulation arms, respectively, and E1 and E2 represent the electric fields of the upper and lower modulation arms, respectively. j is the unit of the imaginary part of the imaginary number, defined as j^2 = -1.

[0068] The output electric field after beam combining is Among them, E out represents the output electric field after beam combining;

[0069] The output light intensity is I out =|E out | 2 =2A 2 [1+cos(φ1-φ2)]; where I out Indicates the output light intensity after beam combining.

[0070] Specifically, for four-segment and five-segment modulators, the difference in the number of segments directly affects the accuracy, error, and robustness;

[0071] Compared with the segmented Mach-Zehnder modulator, when the modulation efficiency of the modulator is the same, the adjustment range of each segment is proportional to the length of each segment. The modulation error of the five-segment Mach-Zehnder modulator is lower than that of the four-segment Mach-Zehnder modulator. The reduction of the error is estimated by the adjustment step of each segment. The four-segment and five-segment modulators have the same total adjustment range V in The adjustment step length under is calculated as follows. The adjustment step length of the four segments is The error step of optical digital-to-analog conversion is the minimum interval between the discrete levels output by the modulator. The error step of the four-segment modulator is ΔE4 = 1 / 15, and the adjustment step of the five-segment modulator is The error step of the five-segment modulator is ΔE5 = 1 / 31;

[0072] Evaluate the modulation error advantage of the five-segment modulator over the four-segment modulator by calculating the error reduction percentage. It can be concluded that the error of the five-segment modulator is reduced by about 51.6% compared with the four-segment modulator;

[0073] Compared with the 4-segment optical digital-to-analog conversion, the 5-segment optimized optical digital-to-analog conversion reduces the linear fitting residual RMS by 79.5%, the light intensity interval standard deviation by 78.9%, and the maximum modulation error by 77%.

[0074] Linear fit residual RMS: measures the average deviation between the actual output and the linear fit. Among them I i The actual output intensity of the i-th is 0 is the i-th linear fitting value, N is the total number of points 16,

[0075] Standard deviation of light intensity: indicates the degree of change between adjacent output light intensities, reflecting whether the codeword distribution is uniform, and the light intensity interval ΔI between two adjacent codewords i =I i+1 -I i , the standard deviation σ of all intervals ΔI =std({ΔI1,ΔI2,…,ΔI N-1}), the smaller the standard deviation, the more uniform the spacing between each codeword, and the stronger the robustness.

[0076] Maximum modulation error: The maximum deviation between a single codeword and its ideal linear value, reflecting the worst point of modulation accuracy.

[0077] The detector installed at the output port of the 5-segment thermo-optical phase modulator monitors the output optical power in real time. The data is fed back to the automatic bias control circuit to calculate the error between the current optical power and the target power. The current of the thermo-optical phase modulator is dynamically adjusted to compensate for bias point drift. The specific steps include:

[0078] Add an optical power monitoring detector to the other port of the Mach-Zehnder modulator output to monitor the changes in the output light intensity in real time, calculate the error between the current output optical power and the target optical power in real time, and determine whether the modulator deviates from the ideal bias point:

[0079] Compare the calculated error between the current output optical power and the target optical power with the set error threshold to determine whether the modulator deviates from the ideal bias point. If exceeded, bias point calibration is triggered.

[0080] The setting rules for the ideal bias point are as follows:

[0081] The ideal bias point refers to the linear operating point of the Mach-Zehnder modulator, that is, the phase difference between the two modulation arms is π / 2, so that the modulation response is at the position with the maximum linear slope in the light intensity-voltage curve;

[0082] The controller executes the PID algorithm to calculate the phase compensation value that needs to be adjusted. The controller outputs a control current to control the thermo-optical phase modulator, thereby adjusting the phase difference of the Mach-Zehnder modulator and maintaining the bias point at π / 2.

[0083] Specifically, the error between the current output optical power and the target optical power is determined by the effective least bit (LSB) of the optical digital-to-analog conversion. The error should be controlled within ±0.5LSB. If the error exceeds ±0.5LSB, the codeword will be mapped to the wrong output level, resulting in an incorrect quantization result. The 5-segment modulator proposed in this patent realizes 4-bit digital-to-analog conversion, and its effective minimum is 1LSB = 1 / 32, and the error range is ±0.5LSB = ±1 / 64LSB, which is generally approximately ±1.6%P in , P in is the input optical power

[0084] The ODAC implementation system based on a 5-segment thermo-optical phase modulator includes: an optical input and beam splitting module, a phase calibration module, a modulation module and an optical signal beam combining and output module. The optical input and beam splitting module is used to obtain a single-mode laser input, which is evenly divided into two paths through a multi-mode interferometer beam splitter and sent to the upper and lower arms of the Mach-Zehnder modulator; the phase calibration module is used to adjust the current through the thermo-optical phase modulator to control the temperature, change the refractive index to introduce phase delay, and calibrate the phase difference between the two arms of the Mach-Zehnder modulator; the modulation module is used to hierarchically modulate the amplitude of the split light according to the digital input based on the 5-segment thermo-optical modulator, and use the weighted group The phase space is constructed and the linear optimal discrete state is screened; the optical signal combining and output module is used to combine the modulated light through the multimode interferometer combiner and perform digital-to-analog mapping output of the light intensity; the output optical power is monitored in real time by a detector installed at the output port of the 5-segment thermo-optical phase modulator, and the error is fed back to the control circuit to dynamically adjust the thermo-optical modulation current to compensate for the bias point drift; the output end of the optical input and beam splitting module is connected to the input end of the phase calibration module, the output end of the phase calibration module is connected to the input end of the modulation module, and the output end of the modulation module is connected to the input end of the optical signal combining and output module.

[0085] The optical input and beam splitting module includes a laser input light source unit and a beam splitting unit. The laser input light source unit is used to obtain a single-mode optical signal of a laser light source that needs to be converted from analog to digital as input light, and use the input light as the analog signal carrier of the optical digital-to-analog converter; the beam splitting unit is used to evenly split the input light into two paths through a 2*2 multimode interferometer beam splitter, and send them to the upper and lower arms of the Mach-Zehnder modulator respectively.

[0086] The phase calibration module includes a thermo-optical phase modulator unit, a phase calibration unit, and a dynamic bias control unit. The thermo-optical phase modulator unit is used to introduce controllable phase delay by controlling temperature changes through current based on the thermo-optic effect of silicon material; the phase calibration unit is used to implement phase difference calibration in stages; and the dynamic bias control unit is used to calculate the current adjustment amount based on the PID algorithm.

[0087] The modulation module includes a segmentation unit and a linear state screening unit. The segmentation unit is used to perform hierarchical amplitude modulation on the split optical signal according to the digital input signal through a 5-segment thermo-optical phase modulator, and construct a phase modulation space using a segmented weight combination, wherein the segmented weight combination is 1:2:4:8:16; the linear state screening unit is used to select points with equal intervals and approximately linear responses as modulation values.

[0088] The optical signal combining and output module includes a combining unit, an optical power output unit and an optical power monitoring unit; the combining unit is used to combine the optical signals modulated by the two arms through a multimode interferometer combiner; the optical power output unit is used to integrate a monitoring port and realize real-time monitoring of the output light intensity by connecting a detector; the optical power monitoring unit is used to calculate the error between the current optical power and the target power, dynamically adjust the current of the thermo-optical phase modulator, and compensate for the bias point drift.

[0089] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. An ODAC implementation method based on a 5-segment thermo-optical phase modulator is characterized by: The method comprises the following steps: Obtain single-mode laser input, split it into two paths through a multi-mode interferometer beam splitter and send it to the upper and lower arms of the Mach-Zehnder modulator; Using a thermo-optical phase modulator, the temperature change is controlled by adjusting the current, changing the refractive index of the waveguide material, introducing a controllable phase delay, and calibrating the phase difference between the two arms of the Mach-Zehnder modulator when there is no modulation voltage. The 5-segment thermo-optical phase modulator performs hierarchical amplitude modulation on the split optical signal according to the digital input signal. The phase modulation space is constructed using segmented weight combinations, and the discrete state set with the best linearity is selected from the full amount of modulation states. The modulated optical signals of the two arms are combined by a multi-mode interferometer combiner to perform digital-to-analog mapping output of the optical intensity signal; The output optical power is monitored in real time by a detector installed at the output port of the 5-segment thermo-optical phase modulator. The data is fed back to the automatic bias control circuit to calculate the error between the current optical power and the target power, and the current of the thermo-optical phase modulator is dynamically adjusted to compensate for the bias point drift.

2. The ODAC implementation method based on a 5-segment thermo-optical phase modulator according to claim 1, characterized in that: Obtain single-mode laser input, split it into two paths through a multimode interferometer beam splitter and send it to the upper and lower arms of the Mach-Zehnder modulator. The specific steps include: A single-mode optical signal of a laser light source that needs to be converted from analog to digital is obtained as input light, and the input light is used as an analog signal carrier of an optical digital-to-analog converter; The input light is evenly divided into two paths by a 2*2 multimode interferometer beam splitter and sent to the upper and lower arms of the Mach-Zehnder modulator respectively.

3. The ODAC implementation method based on a 5-segment thermo-optical phase modulator according to claim 2, characterized in that: Using a thermo-optical phase modulator, the temperature change is controlled by adjusting the current, changing the refractive index of the waveguide material, introducing a controllable phase delay, and calibrating the phase difference between the two arms of the Mach-Zehnder modulator when there is no modulation voltage. The specific steps include: The heating components are integrated around the upper and lower arm waveguides of the Mach-Zehnder modulator. When powered on, the local temperature changes, causing the effective refractive index of the waveguide to change, thereby introducing a controllable phase delay. Where Δφ represents the phase difference, Δn eff is the refractive index change caused by temperature change, L is the length of the heated area, and λ represents the wavelength of light; Phase difference calibration is implemented in stages, specifically: After the modulator is first used or packaged, an adjustable current is applied to the thermo-optical modulator, the output light intensity of the Hertz-Zehnder modulator is monitored, and the phase difference between the two arms is compared with the calibration reference of the phase difference between the two arms, and the phase difference between the two arms is calibrated to the calibration reference of the phase difference between the two arms to achieve phase balance between the two arms when there is no modulation; During long-term operation or in an environment with temperature changes, the output optical power is monitored in real time through a light detector. When the error exceeds the set threshold, the current regulation amount is calculated based on the PID algorithm.

4. The ODAC implementation method based on a 5-segment thermo-optical phase modulator according to claim 3, characterized in that: The split optical signal is hierarchically amplitude modulated based on the digital input signal using a five-segment thermo-optical phase modulator. A phase modulation space is constructed using segmented weight combinations. The set of discrete states with the optimal linearity is selected from the full modulation state. The modulated optical signals from both arms are combined using a multimode interferometer combiner to perform digital-to-analog mapping of the optical intensity signal. The specific steps include: A 32-order phase modulation space is constructed based on the segmented weight combination, where the segmented weight combination is 1:2:4:8:

16. The linear optimal discrete state set is screened by the following method: The 5-segment modulator forms 32 phase combinations through independent current control, corresponding to the cumulative phase value φ k =k·Δφ, k=0,1,…,31, the output light intensity satisfies Among them, I k represents the light intensity value output by the Mach-Zehnder modulator when the five-segment modulator combination forms an accumulated phase difference; k represents the phase state index; I0 represents the initial light signal intensity input to the Mach-Zehnder modulator; From these 32 levels, 16 equally spaced, approximately linearly responding points are selected as modulation values. From the most linear region in the middle, i.e., the 32 discrete phase points near φ = π / 2, k = 8 to 23 is selected. The corresponding output is The modulated optical signals of the two arms are combined through a 2*2 multimode interferometer combiner, and the output intensity is controlled by the interference principle. Specifically: The electric fields of the two interferometer arms are Where A is the amplitude of the optical field, φ1 and φ2 represent the phases of the upper and lower modulation arms, respectively, and E1 and E2 represent the electric fields of the upper and lower modulation arms, respectively. j is the unit of the imaginary part of the imaginary number, defined as j^2 = -1. The output electric field after beam combining is Among them, E out represents the output electric field after beam combining; The output light intensity is I out =|E out | 2 =2A 2 [1+cos(φ1-φ2)]; where I out Indicates the output light intensity after beam combining.

5. The ODAC implementation method based on a 5-segment thermo-optical phase modulator according to claim 4, characterized in that: The detector installed at the output port of the 5-segment thermo-optical phase modulator monitors the output optical power in real time. The data is fed back to the automatic bias control circuit to calculate the error between the current optical power and the target power. The current of the thermo-optical phase modulator is dynamically adjusted to compensate for bias point drift. The specific steps include: Add an optical power monitoring detector to the other port of the Mach-Zehnder modulator output to monitor the changes in the output light intensity in real time, calculate the error between the current output optical power and the target optical power in real time, and determine whether the modulator deviates from the ideal bias point: Compare the calculated error between the current output optical power and the target optical power with the set error threshold to determine whether the modulator deviates from the ideal bias point. If exceeded, bias point calibration is triggered. The setting rules for the ideal bias point are as follows: The ideal bias point refers to the linear operating point of the Mach-Zehnder modulator, that is, the phase difference between the two modulation arms is π / 2, so that the modulation response is at the position with the maximum linear slope in the light intensity-voltage curve; The controller executes the PID algorithm to calculate the phase compensation value that needs to be adjusted. The controller outputs a control current to control the thermo-optical phase modulator, thereby adjusting the phase difference of the Mach-Zehnder modulator and maintaining the bias point at π / 2.

6. An ODAC implementation system based on a 5-segment thermo-optical phase modulator, applied to the ODAC implementation method based on a 5-segment thermo-optical phase modulator according to any one of claims 1 to 5, characterized in that: The system includes: an optical input and beam splitting module, a phase calibration module, a modulation module and an optical signal beam combining and output module. The optical input and beam splitting module is used to obtain single-mode laser input, which is evenly divided into two paths through a multi-mode interferometer beam splitter and sent to the upper and lower arms of the Mach-Zehnder modulator; the phase calibration module is used to adjust the current and control the temperature through a thermo-optical phase modulator, change the refractive index to introduce phase delay, and calibrate the phase difference between the two arms of the Mach-Zehnder modulator; the modulation module is used to hierarchically modulate the split light amplitude according to the digital input based on a 5-segment thermo-optical modulator, construct the phase space by weight combination, and screen the line The optical signal combining and output module is used to combine the modulated light through the multimode interferometer combiner and perform digital-to-analog mapping output of the light intensity; the output optical power is monitored in real time by a detector installed at the output port of the 5-segment thermo-optical phase modulator, and the error is fed back to the control circuit to calculate the error, and the thermo-optical modulation current is dynamically adjusted to compensate for the bias point drift. The output end of the optical input and beam splitting module is connected to the input end of the phase calibration module, the output end of the phase calibration module is connected to the input end of the modulation module, and the output end of the modulation module is connected to the input end of the optical signal combining and output module.

7. The ODAC implementation system based on a 5-segment thermo-optical phase modulator according to claim 6, characterized in that: The optical input and beam splitting module includes a laser input light source unit and a beam splitting unit. The laser input light source unit is used to obtain a single-mode optical signal of a laser light source that needs to be converted from analog to digital as input light, and use the input light as the analog signal carrier of the optical digital-to-analog converter; the beam splitting unit is used to evenly split the input light into two paths through a 2*2 multimode interferometer beam splitter, and send them to the upper and lower arms of the Mach-Zehnder modulator respectively.

8. The ODAC implementation system based on a 5-segment thermo-optical phase modulator according to claim 7, characterized in that: The phase calibration module includes a thermo-optical phase modulator unit, a phase calibration unit, and a dynamic bias control unit. The thermo-optical phase modulator unit is used to introduce controllable phase delay by controlling temperature changes through current based on the thermo-optic effect of silicon material; the phase calibration unit is used to implement phase difference calibration in stages; and the dynamic bias control unit is used to calculate the current adjustment amount based on the PID algorithm.

9. The ODAC implementation system based on a 5-segment thermo-optical phase modulator according to claim 8, characterized in that: The modulation module includes a segmentation unit and a linear state screening unit. The segmentation unit is used to perform hierarchical amplitude modulation on the split optical signal according to the digital input signal through a 5-segment thermo-optical phase modulator, and construct a phase modulation space using a segmented weight combination, wherein the segmented weight combination is 1:2:4:8:16; the linear state screening unit is used to select points with equal intervals and approximately linear responses as modulation values.

10. The ODAC implementation system based on a 5-segment thermo-optical phase modulator according to claim 9, characterized in that: The optical signal combining and output module includes a combining unit, an optical power output unit and an optical power monitoring unit; the combining unit is used to combine the optical signals modulated by the two arms through a multimode interferometer combiner; the optical power output unit is used to integrate a monitoring port and realize real-time monitoring of the output light intensity by connecting a detector; the optical power monitoring unit is used to calculate the error between the current optical power and the target power, dynamically adjust the current of the thermo-optical phase modulator, and compensate for the bias point drift.

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