A MZI silicon optical modulator phase locking method and device

Abstract

This invention discloses a phase locking method for an MZI silicon optical modulator, comprising the following steps: S1, initialization and data acquisition; S2, calculation of target and initial values for a PID algorithm; and S3, acquisition of various parameters of the PID algorithm to achieve phase locking. This method uses a PID algorithm to adjust and control the MZI silicon optical modulator, rapidly achieving rough phase locking using proportional parameters. The differential phase predicts and adjusts the control variable in advance to reduce oscillations, while the integral phase eliminates steady-state errors and enhances accuracy. Furthermore, the method possesses dynamic update capabilities, enabling real-time phase locking and adapting to a wide range of operating environments.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a method and device for phase locking of an MZI silicon optical modulator. Background Art

[0002] With the development of AI, the demand for communication capacity is also growing. High-speed optical communication technologies such as 800G, 1.6T, 3.2T, and 6.4T are constantly emerging. With the increase in communication capacity and speed, traditional optical modules are becoming increasingly difficult to control in terms of speed, power consumption, volume, and cost. Silicon photonics has obvious advantages in these aspects. Therefore, it is generally believed that silicon photonics technology solutions are one of the core technologies of the next generation of optical communications.

[0003] The MZI silicon optical modulator (MZI) is an optical device based on the Mach-Zehnder interferometer principle. It typically consists of two beamsplitters and two optical paths. An MZI silicon optical modulator modulates the intensity of the output light by changing the phase of one of the optical paths, typically using electro-optical or thermo-optical effects to control the phase of one of the optical paths. MZI silicon optical modulators can be used in both direct-modulation optical communications and coherent optical communications, with different phase control options tailored to the specific needs of the operation. The 90° phase point is typically referred to as the Quad point, while the 180° phase point is the Null point. The Quad point is the center of the linear region of the modulator's output optical power intensity curve. In direct-modulation optical modules, the Quad point represents the operating point, while the Null point represents the minimum output optical power and serves as the module's optical shutdown operating point.

[0004] Due to the thermo-optical effect, the MZI silicon optical modulator is very sensitive to temperature. Therefore, in order to ensure the stable operation of the silicon optical solution module, the phase point of the MZI silicon optical modulator needs to be precisely controlled in real time. This indicator is also an important indicator for evaluating the performance of silicon optical modules. It directly affects the ER parameter of the optical module and is an important parameter for evaluating the quality of the optical module.

[0005] Currently, the main method for controlling the phase lock of an MZI silicon optical modulator (SiO2) is to perform proportional adjustments based on the direction of the MZI SiO2's output optical power error, thereby correcting the phase offset. Specifically, this involves comparing the difference between the previously recorded sampled value (which can be voltage, current, or power) and the current sampled value. If the comparison result is less than 0, the adjustment value is increased; otherwise, the adjustment value is decreased.

[0006] However, adjusting the phase of the MZI silicon optical modulator simply by comparing the results with the previous one can easily cause the output of the MZI silicon optical modulator to oscillate at the phase point. This has low accuracy and cannot meet the stability requirements of the MZI modulator's operating point, making it prone to oscillation. Summary of the Invention

[0007] In response to the above problems, the purpose of the present invention is to propose a phase locking method and device for an MZI silicon optical modulator. The MZI silicon optical modulator is adjusted and controlled by a PID algorithm, and the proportional parameter is used to quickly complete the rough phase locking. The control amount is predicted and adjusted in advance based on the differential link to reduce oscillation, and the integral link can eliminate steady-state errors and enhance accuracy. At the same time, it has the ability to dynamically update, lock the phase in real time, and can adapt to more working environments.

[0008] This is achieved through the following technical solutions:

[0009] First, a phase locking method for an MZI silicon optical modulator is proposed, which includes the following steps:

[0010] S1. Initialization and data acquisition: Initialize the acquisition control unit, power on the laser and MZI silicon optical modulator; apply the phase modulation module in the MZI silicon optical modulator from 0 to V multiple times. DD The voltage is applied in steps of V step ; Corresponding photodetectors and external resistors are set at the input and output ends of the MZI silicon optical modulator. After each voltage is applied, the corresponding voltage V on the external resistor is collected. in and V out , V out and V in The ratio is recorded as K ratio ;

[0011] S2, calculate the target value and initial value of the PID algorithm: from each K in step S1 ratio In the above example, we select a set of adjacent minimum values K that appear periodically. ratio_min and the maximum value K ratio_max Record, and then record the minimum value K ratio_min and the maximum value K ratio_max The corresponding applied voltage is V ratio_min and V ratio_max ; S3, obtain various parameters of the PID algorithm to complete phase locking: based on the minimum value K in step S2 ratio_min and the maximum value K ratio_max , calculate the target value K of the PID algorithm ratio_target , and according to the corresponding applied voltage V ratio_min and V ratio_max Calculate the initial value V of the PID algorithm start_target; Set the current moment K ratio Denoted as K ratio_now , the K corresponding to the moment before the current moment ratio Denoted as K ratio_last , according to K ratio_now and target value K ratio_target , calculate the proportional link parameter E of the PID algorithm at the current moment now At the same time, the proportional link parameter E corresponding to the previous moment now Update record to E last ; Then according to the proportional link parameter E now and E last Calculate the integral parameter S of the PID algorithm at the current moment error and the differential link parameter D error ; Set the initial value V start_target The various parameters are substituted into the PID algorithm to output the applied voltage V that needs to be updated to the MZI silicon optical modulator at the current moment. now , the acquisition control unit will apply voltage V now The phase modulation module applied to the MZI silicon optical modulator achieves phase locking.

[0012] Preferably, after power is turned on in step S1, the optical power at the input end of the recording laser when the light enters the MZI silicon optical modulator is P in , record the optical power at the output of the MZI silicon optical modulator as P out ; Collection voltage V in and V out , V in =P in ×α in ×R esp1 ×R in , where α in R is the splitting ratio of the optical beam splitter built into the MZI silicon optical modulator to the photodetector corresponding to the input end, in is the resistance of the external resistor at the input of the MZI silicon optical modulator, R esp1 is the responsivity of the photodetector at the input end; V out =P out ×[α out / (1-α out )]×R esp2 ×R out , where α out R is the splitting ratio of the optical beam splitter built into the MZI silicon optical modulator to the photodetector corresponding to the output end, out is the resistance of the external resistor at the output end of the MZI silicon optical modulator, R esp2 is the responsivity of the photodetector at the output.

[0013] Preferably, in step S3, the proportional link parameter E is calculated now When E now =K ratio_target -K ratio_now .

[0014] Preferably, in step S3, the differential link parameter D is calculated error When D error =E now -E last .

[0015] Preferably, in step S3, the integral link parameter S at the current moment is calculated error When S error =S error_last +E now , used to characterize the total historical error, S error_last represents the S at the previous moment error .

[0016] Preferably, after completing the phase lock corresponding to the current moment in step S3, return to step S3 to obtain the K corresponding to the next moment. ratio_now Loop and continue to calculate the applied voltage V that needs to be updated to the MZI silicon optical modulator at the next moment next .

[0017] In addition, an MZI silicon optical modulator phase locking device is proposed, which operates using the above-mentioned MZI silicon optical modulator phase locking method. The device includes a stable light source, an optical fiber or a lens, an MZI silicon optical modulator, a first resistor, an acquisition control unit, a second resistor, a first photodetector, and a second photodetector; wherein, the light provided by the stable light source is optically coupled through the optical fiber or the lens and input into the input optical port of the MZI silicon optical modulator; the first photodetector is used to convert the light at the input optical port into a corresponding photocurrent I, and the first resistor is used to convert the photocurrent I into a voltage I and transmit it to the acquisition control unit; the second photodetector is used to convert the light before entering the output optical port into a corresponding photocurrent II, and the second resistor is used to convert the photocurrent II into a voltage II and transmit it to the acquisition control unit; the acquisition control unit performs phase-locked control on the MZI silicon optical modulator based on voltages I and II.

[0018] Preferably, the stable light source is a laser, and the MZI silicon optical modulator includes an input optical port, a phase modulation module, an optical beam splitter and an output optical port connected in sequence.

[0019] Preferably, the optical beam splitter is used to split the light in the MZI silicon optical modulator and transmit the light to the output light port and two photodetectors respectively, the first photodetector is connected to the first resistor, and the second photodetector is connected to the second resistor.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The technical solution of the present invention adjusts and controls the MZI silicon optical modulator through the PID algorithm, uses the proportional parameter to quickly complete the rough phase locking, predicts and adjusts the control amount in advance based on the differential link to reduce oscillation, and the integral link can eliminate steady-state errors and enhance accuracy; at the same time, it has the ability to dynamically update and lock the phase in real time, and can adapt to more working environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of a phase locking method for an MZI silicon optical modulator;

[0023] Figure 2 A detailed flowchart of a phase locking method for an MZI silicon optical modulator;

[0024] Figure 3 This is a schematic diagram of the structure of a MZI silicon optical modulator phase locking device;

[0025] Figure 4 P is the normalized value after applying 0 to VDD voltage to the phase modulation module. out or K ratio Graph of

[0026] Reference numerals: stable light source 1 , MZI silicon optical modulator 2 , optical fiber or lens 3 , first photodetector 41 , second photodetector 42 , first resistor 51 , second resistor 52 , acquisition control unit 6 , phase modulation module 7 , optical beam splitter 8 . DETAILED DESCRIPTION

[0027] The following will be combined with the present invention Figures 1 to 4 , the technical solutions in the embodiments of the present invention are described in detail.

[0028] like Figure 1 As shown in FIG, it is a flow chart of a phase locking method of an MZI silicon optical modulator; Figure 2 As shown, it is a detailed flow chart of the phase locking method of MZI silicon optical modulator; combined with Figure 1 and Figure 2 As shown in the figure, this method first applies voltage to the phase modulation module of the MZI silicon optical modulator in a specific step, thereby determining various parameters of the PID algorithm, and then determining the exact voltage that needs to be applied at the current moment based on these various parameters, thereby achieving precise locking of the phase modulation module. Phase locking is performed specifically through the following steps:

[0029] S1. Initialization and data acquisition: First, initialize the acquisition control unit, power on the laser and MZI silicon optical modulator, and input the light into the input end of the MZI silicon optical modulator. Then, apply the phase modulation module in the MZI silicon optical modulator multiple times from 0 to V. DD The voltage is applied in steps of V step At the input and output ends of the MZI silicon optical modulator, corresponding photodetectors and external resistors are respectively set. Each photodetector is used to convert the corresponding light into photocurrent, so that the corresponding resistor generates voltage and transmits it to the acquisition control unit. After each voltage is applied, the corresponding voltage V on the external resistor is collected. in and V out , voltage V out is the voltage on the resistor close to the output terminal, voltage V in is the voltage on the resistor close to the input terminal. out and V in The ratio is recorded as K ratio , the suffix ratio means proportion.

[0030] In this embodiment, in step S1, the two photodetectors provided at the input and output of the MZI silicon optical modulator can be identical or different; as long as their respective responsivities are known, subsequent calculations can be performed using them. The two external resistors provided at the input and output of the MZI silicon optical modulator can be identical or different; as long as their respective resistance values are known, subsequent calculations can be performed using them. Furthermore, using identical devices at both ends facilitates experimental analysis and cost control, particularly facilitating actual device procurement.

[0031] In this embodiment, the optical power at the input end of the recording laser when the light enters the MZI silicon optical modulator is P in , record the optical power at the output of the MZI silicon optical modulator as P out ; Therefore, the acquisition voltage V in and V out When V in =P in ×α in ×R esp1 ×R in , where α in R is the splitting ratio of the optical beam splitter built into the MZI silicon optical modulator to the photodetector corresponding to the input end, in is the resistance of the external resistor at the input of the MZI silicon optical modulator, R esp1 is the responsivity of the photodetector at the input.

[0032] At the same time, V out =P out ×[αout / (1-α out )]×R esp2 ×R out , where α out R is the splitting ratio of the optical beam splitter built into the MZI silicon optical modulator to the photodetector corresponding to the output end, out is the resistance of the external resistor at the output end of the MZI silicon optical modulator, R esp2 is the responsivity of the photodetector at the output.

[0033] It should be noted that the MZI silicon optical modulator has a built-in optical beam splitter, which can split the light at the input end into two parts according to α in The splitting ratio can split part of the light to the corresponding photodetector, or the light at the output end can be split according to α out The splitting ratio splits part of the light to the corresponding photodetector.

[0034] like Figure 4 The figure shows the normalized P after the phase modulation module applies a voltage from 0 to VDD. out or K ratio Normalization is to unify the data size to facilitate calculation and comparison. Ratio is K ratio , the figure shows the P at the output of the MZI silicon optical modulator out With K ratio Therefore, it is possible to ratio To calculate the voltage that needs to be applied to affect P out .

[0035] S2, calculate the target value and initial value of the PID algorithm: from each K in step S1 ratio In the example, select a set of adjacent minimum values K that appear periodically. ratio_min and the maximum value K ratio_max Record, and then record the minimum value K ratio_min and the maximum value K ratio_max The corresponding applied voltage is V ratio_min and V ratio_max .

[0036] S3, obtain various parameters of PID algorithm and complete phase locking: according to the minimum value K in step S2 ratio_min and the maximum value K ratio_max , calculate the target value K of the PID algorithm ratio_target , and according to the corresponding applied voltage V ratio_min and V ratio_max Calculate the initial value V of the PID algorithm start_target . The current K ratio Denoted as K ratio_now, and at the same time, the K corresponding to the previous moment of the current moment ratio Denoted as K ratio_last , according to K ratio_now and K ratio_target , we can calculate the proportional link parameter E of the PID algorithm at the current moment now At the same time, the proportional link parameter E corresponding to the previous moment now Update record to E last Then, according to the proportional link parameter E now and E last , continue to calculate the integral parameter S of the PID algorithm at the current moment error and the differential link parameter D error .

[0037] by Figure 4 Taking the Quad point phase in the figure as an example, the average optical power at the output end at the Quad point is half of the maximum optical power. Therefore, it can be seen that K at the Quad point is Quad_target =(K ratio_min +K ratio_max ) / 2; At the same time, at the Quad point, V start_targe =(V ratio_min +V ratio_max ) / 2 is the starting point of the algorithm. It should be noted that this starting point is not the voltage point corresponding to the Quad point, but the starting point for calculating the voltage corresponding to the Quad point.

[0038] Then the initial value V start_target Each of the above parameters is substituted into the PID algorithm for calculation, and the output is the applied voltage V that needs to be updated to the MZI silicon optical modulator at the current moment. now , the acquisition control unit will apply voltage V now The phase modulation module applied to the MZI silicon optical modulator is adjusted to achieve phase locking.

[0039] In this embodiment, the proportional link parameter can quickly complete the rough locking of the phase; when calculating the proportional link parameter E now When E now =K ratio_target -K ratio_now , and the E of the previous moment last = K corresponding to the previous moment ratio_target -K corresponding to the previous moment ratio_now , and each data will be recorded in the processor's memory, waiting for subsequent use. The differential link parameter is a sensitive response to the error change rate, which can predict and adjust the control amount in advance, thereby speeding up the system's response speed and reducing the overshoot, which is the maximum deviation value. When calculating the differential link parameter D error When D error =Enow -E last , where E last Indicates the proportional link parameter of the previous moment at the current moment, and is used to calculate the proportional link parameter E at the current moment. now When the previous moment's proportional link parameter E now Update record to E last The integral link can eliminate the steady-state error by accumulating and correcting the error to make the result more accurate, thereby making the phase lock more accurate; when calculating the integral link parameter S at the current moment error When the previous moment's integral parameter S error Update record to S error_last , so the integral parameter S at the current moment error =S error_last +E now , so that the corresponding calculation at each moment can use the previous historical data, which can be used to represent the total historical error.

[0040] In this embodiment, after completing the phase lock corresponding to the current moment in step S3, at the next moment, you can return to step S3 to obtain the K corresponding to the next moment. ratio_now Loop and continue to calculate the applied voltage V that needs to be updated to the MZI silicon optical modulator at the next moment next , so that it can be dynamically updated in real time and can adapt to a variety of application scenarios, especially those with more interference and higher requirements for real-time output.

[0041] like Figure 3 The figure shows a schematic diagram of the structure of a MZI silicon optical modulator phase locking device, combined with Figure 3 The present application also proposes an MZI silicon optical modulator phase locking device, which operates using the above-mentioned MZI silicon optical modulator phase locking method. The device includes a stable light source 1, an optical fiber or lens 3, an MZI silicon optical modulator 2, a first resistor 51, an acquisition control unit 6, a second resistor 52, a first photodetector 41 and a second photodetector 42; wherein, the light provided by the stable light source 1 is optically coupled by the optical fiber or lens 3 and input into the input optical port of the MZI silicon optical modulator 2; the first photodetector 41 is used to convert the light at the input optical port into a corresponding photocurrent I, and the first resistor 51 is used to convert the photocurrent I into a voltage I and transmit it to the acquisition control unit 6; the second photodetector 42 is used to convert the light before entering the output optical port into a corresponding photocurrent II, and the second resistor 52 is used to convert the photocurrent II into a voltage II and transmit it to the acquisition control unit; the acquisition control unit 6 performs phase-locked control on the MZI silicon optical modulator 2 based on the voltages I and II.

[0042] In this embodiment, the stable light source 1 uses a laser, and the MZI silicon light modulator 2 includes an input optical port, a phase modulation module 7, an optical beam splitter 8, and an output optical port connected in sequence; the optical beam splitter 8 is used to split the light in the MZI silicon light modulator 2 and transmit it to the output optical port and two photodetectors respectively. The first photodetector 41 is connected to the first resistor 51, and the second photodetector 42 is connected to the second resistor 52.

[0043] In summary, the present invention adjusts and controls the MZI silicon optical modulator through the PID algorithm, quickly completes coarse phase locking using proportional parameters, predicts and adjusts the control amount in advance based on the differential link to reduce oscillation, and the integral link can eliminate steady-state errors and enhance accuracy. At the same time, it has dynamic update capabilities, locks the phase in real time, can adapt to more working environments, and is significantly progressive.

[0044] The above embodiments are only for illustrating the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A phase locking method for an MZI silicon optical modulator, characterized in that: The steps include: S1. Initialization and data collection: Initialize the acquisition control unit and power on the laser and MZI silicon optical modulator. After powering on, record the optical power at the input end when the light emitted by the laser enters the MZI silicon optical modulator as P. in , record the optical power at the output of the MZI silicon optical modulator as P out ; Collection voltage V in and V out , V in =P in ×α in ×R esp1 ×R in , where α in R is the splitting ratio of the optical beam splitter built into the MZI silicon optical modulator to the photodetector corresponding to the input end, in is the resistance of the external resistor at the input of the MZI silicon optical modulator, R esp1 is the responsivity of the photodetector at the input end; V out =P out ×[α out / (1-α out )]×R esp2 ×R out , where α out R is the splitting ratio of the optical beam splitter built into the MZI silicon optical modulator to the photodetector corresponding to the output end, out is the resistance of the external resistor at the output end of the MZI silicon optical modulator, R esp2 is the responsivity of the photodetector at the output end; the phase modulation module in the MZI silicon optical modulator is repeatedly applied from 0 to V DD The voltage is applied in steps of V step ; The input and output ends of the MZI silicon optical modulator are respectively provided with corresponding photodetectors and external resistors. After each voltage is applied, the corresponding voltage V on the external resistor is collected. in and V out , V out and V in The ratio is recorded as K ratio ; S2. Calculate the target value and initial value of the PID algorithm: From each K in step S1 ratio In the above example, we select a set of adjacent minimum values K that appear periodically. ratio_min and the maximum value K ratio_max Record, and then record the minimum value K ratio_min and the maximum value K ratio_max The corresponding applied voltage is V ratio_min and V ratio_max ; S3. Obtain various parameters of the PID algorithm and complete phase locking: According to the minimum value K in step S2 ratio_min and the maximum value K ratio_max , calculate the target value K of the PID algorithm ratio_target , and according to the corresponding applied voltage V ratio_min and V ratio_max Calculate the initial value V of the PID algorithm start_target ; The current moment K ratio Denoted as K ratio_now , the K corresponding to the moment before the current moment ratio Denoted as K ratio_last , according to K ratio_now and target value K ratio_target , calculate the proportional link parameter E of the PID algorithm at the current moment now At the same time, the proportional link parameter E corresponding to the previous moment now Update record to E last ; Then according to the proportional link parameter E now and E last Calculate the integral parameter S of the PID algorithm at the current moment error and the differential link parameter D error ; Set the initial value V start_target The various parameters are substituted into the PID algorithm to output the applied voltage V that needs to be updated to the MZI silicon optical modulator at the current moment. now , the acquisition control unit will apply voltage V now The phase modulation module applied to the MZI silicon optical modulator achieves phase locking.

2. The MZI silicon optical modulator phase locking method according to claim 1, characterized in that: In step S3, the proportional link parameter E is calculated now When E now =K ratio_target -K ratio_now .

3. The MZI silicon optical modulator phase locking method according to claim 1, characterized in that: In step S3, the differential parameter D is calculated error When D error =E now -E last .

4. The MZI silicon optical modulator phase locking method according to claim 1, wherein: In step S3, the integral parameter S at the current moment is calculated. error When S error =S error_last +E now , used to characterize the total historical error, S error_last represents the S at the previous moment error .

5. The MZI silicon optical modulator phase locking method according to claim 1, characterized in that: After completing the phase lock corresponding to the current moment in step S3, return to step S3 to obtain the K corresponding to the next moment ratio_now Loop and continue to calculate the applied voltage V that needs to be updated to the MZI silicon optical modulator at the next moment next .

6. A MZI silicon optical modulator phase locking device, operating using a MZI silicon optical modulator phase locking method according to any one of claims 1 to 5, characterized in that: The device comprises a stable light source (1), an optical fiber or a lens (3), an MZI silicon optical modulator (2), a first resistor (51), an acquisition control unit (6), a second resistor (52), a first photodetector (41), and a second photodetector (42); The light provided by the stable light source (1) is optically coupled through an optical fiber or a lens (3) and then input into the input optical port of the MZI silicon optical modulator (2); the first photodetector (41) is used to convert the light of the input optical port into a corresponding photocurrent I, and the first resistor (51) is used to convert the photocurrent I into a voltage I and transmit it to the acquisition control unit (6); the second photodetector (42) is used to convert the light before entering the output optical port into a corresponding photocurrent II, and the second resistor (52) is used to convert the photocurrent II into a voltage II and transmit it to the acquisition control unit (6); the acquisition control unit (6) performs phase-locked control on the MZI silicon optical modulator (2) based on the voltages I and II.

7. The MZI silicon optical modulator phase locking device according to claim 6, characterized in that: The stable light source (1) adopts a laser, and the MZI silicon optical modulator (2) comprises an input optical port, a phase modulation module (7), an optical beam splitter (8), and an output optical port which are connected in sequence.

8. The MZI silicon optical modulator phase locking device according to claim 7, characterized in that: The optical beam splitter (8) is used to split the light in the MZI silicon optical modulator (2) and transmit the light to the output light port and two photodetectors respectively. The first photodetector (41) is connected to the first resistor (51), and the second photodetector (42) is connected to the second resistor (52).

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