MZI silicon light modulator phase locking method and device

Abstract

The invention discloses a phase locking method for an MZI silicon optical modulator. The phase locking method comprises the steps of S1, initialization and data acquisition; s2, calculating a target value and an initial value of a PID algorithm; and S3, multiple parameters of a PID algorithm are obtained, and phase locking is completed. According to the method, the MZI silicon light modulator is adjusted and controlled through a PID algorithm, phase rough locking is rapidly completed through proportional parameters, the control quantity is predicted and adjusted in advance based on a differential link to reduce oscillation, and steady-state errors can be eliminated through an integral link to enhance accuracy; meanwhile, the dynamic updating capability is achieved, the phase can be locked in real time, and the method can adapt to more working environments.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technologies, and particularly 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 continuously increasing. High-speed optical communication technologies such as 800G, 1.6T, 3.2T, and 6.4T have emerged one after another. As the communication capacity and rate increase, it becomes increasingly difficult to control the rate, power consumption, volume, and cost of traditional optical modules. Silicon photonics technology has obvious advantages in these aspects. Therefore, it is generally believed that the silicon photonics technology solution is one of the core technologies for the next generation of optical communication.

[0003] An MZI silicon optical modulator is an optical device based on the Mach-Zehnder interferometer principle. MZI stands for Mach-Zehnder Interferometer, that is, the Mach-Zehnder interferometer. It usually consists of two beam splitters and two optical paths. The MZI silicon optical modulator can modulate the intensity of the output light by changing the phase of one of the optical paths. Usually, the electro-optic effect or the thermo-optic effect is used to control the phase of one of the optical paths. The MZI silicon optical modulator can be used in direct modulation optical communication and coherent optical communication, and different phase controls are performed according to different working requirements. Usually, the point with a phase of 90° is called the Quad point, and the point with a phase of 180° is called the Null point. The Quad point is in the middle of the linear region of the output optical power intensity curve of the modulator. In a direct modulation optical module, Quad is the working point, and the Null point is the point with the minimum output optical power, which is the optical off working point of the module.

[0004] Due to the thermo-optic effect, the MZI silicon optical modulator is very sensitive to temperature. Therefore, in order to ensure the stable operation of the silicon photonics solution module, it is necessary to accurately control the phase point of the MZI silicon optical modulator in real time. This index is also an important index for evaluating the performance of the silicon photonics module, directly affecting 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 phase locking control of an MZI silicon optical modulator is: according to the direction of the output optical power error of the MZI silicon optical modulator, corresponding proportional adjustment is performed to complete the correction of the phase offset. The specific operation is to perform a difference comparison between the sampled value recorded at the previous moment and the sampled value at the current moment. The sampled value can be voltage, current, or power. If the comparison result is less than 0, the adjustment value is increased, otherwise it is decreased.

[0006] However, simply adjusting the phase of the MZI silicon optical modulator by comparing the results with the previous ones is likely to cause the output of the MZI silicon optical modulator to oscillate at the phase point, with low precision, unable to meet the stability requirements of the operating point of the MZI modulator, and prone to oscillation. Summary of the Invention

[0007] Aiming at the above problems, the object of the present invention is to propose a phase locking method and device for an MZI silicon optical modulator. By using the PID algorithm to adjust and control the MZI silicon optical modulator, the proportional parameter is used to quickly complete the rough phase locking. Based on the differential link, the control quantity is predicted and adjusted in advance to reduce oscillation, and the integral link can eliminate the steady-state error and enhance the accuracy. At the same time, it has the ability of dynamic update, locks the phase in real time, and can adapt to more working environments.

[0008] It is achieved through the following technical solutions: First, a phase locking method for an MZI silicon optical modulator is proposed, including the following steps: S1. Initialization and data acquisition: Initialize the acquisition control unit, power on the laser and the MZI silicon optical modulator; apply the voltage from 0 to V to the phase modulation module in the MZI silicon optical modulator multiple times with a step of V each time; respectively set corresponding photodetectors and external resistors at the input end and output end of the MZI silicon optical modulator. After each voltage application, collect the corresponding voltages V and V on the external resistor, and record the ratio of V to V as K; DD of the voltage and the step of each voltage application is V step ; at both the input end and output end of the MZI silicon optical modulator, corresponding photodetectors and external resistors are respectively set. After each voltage application, collect the corresponding voltages V in and V out , and record the ratio of V out to V in as K ratio ; S2. Calculate the target value and initial value of the PID algorithm: From each K in step S1, select a set of adjacent minimum values K ratio and maximum values K ratio_min that appear periodically for recording, and then record the applied voltages corresponding to the minimum value K ratio_max and the maximum value K ratio_min as V ratio_max and V ratio_min respectively; S3. Obtain various parameters of the PID algorithm to complete phase locking: According to the minimum value K ratio_max and the maximum value K ratio_min in step S2, calculate the target value K ratio_max of the PID algorithm, and at the same time calculate the initial value V ratio_target of the PID algorithm according to the corresponding applied voltages V ratio_min and V ratio_max ; Record the current K start_target as K ratio and record it as K ratio_now, denote the K corresponding to the previous moment of the current moment as K ratio ; Record it as K ratio_last , based on K ratio_now and the target value K ratio_target , calculate the proportional link parameter E of the PID algorithm at the current moment now , and at the same time update and record the proportional link parameter E corresponding to the previous moment as E now ; Then, based on the proportional link parameter E last and E now and E last , calculate the integral link parameter S error and the derivative link parameter D of the PID algorithm at the current moment error ; Substitute the initial value V start_target and various parameters into the PID algorithm, and output the applied voltage V to be updated to the MZI silicon optical modulator at the current moment now , and the acquisition control unit applies the applied voltage V now to the phase modulation module of the MZI silicon optical modulator to complete phase locking.

[0009] Preferably, after power-on in step S1, record the optical power at the input end when the light emitted by the laser enters the MZI silicon optical modulator as P in , and record the optical power at the output end of the MZI silicon optical modulator as P out ; Collect the voltages V in and V out , V in = P in × α in × R esp1 × R in , where α in is the splitting ratio of the optical splitter built in the MZI silicon optical modulator to the photodetector corresponding to the input end, R in is the resistance value of the resistor externally connected to the input end 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 is the splitting ratio of the optical splitter built in the MZI silicon optical modulator to the photodetector corresponding to the output end, R out is the resistance value of the resistor externally connected to the output end of the MZI silicon optical modulator, R esp2 is the responsivity of the photodetector at the output end.

[0010] Preferably, in step S3, when calculating the proportional link parameter E now , E now=K ratio_target -K ratio_now 。

[0011] Preferably, in step S3, calculate the differential link parameter D error When error =E now -E last 。

[0012] Preferably, in step S3, calculate the integral link parameter S at the current moment error When error =S error_last +E now , which is used to represent the total historical error, and S error_last represents the S at the previous moment error 。

[0013] Preferably, after completing the phase locking corresponding to the current moment in step S3, return to step S3 to obtain the K corresponding to the next moment ratio_now for cycling, and continue to calculate the applied voltage V to be updated to the MZI silicon optical modulator at the next moment next 。

[0014] In addition, a phase locking device for an MZI silicon optical modulator is proposed, which operates using the above-mentioned phase locking method for an MZI silicon optical modulator. 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 input into the input optical port of the MZI silicon optical modulator after optical coupling through the optical fiber or the lens; 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 the voltages I and II.

[0015] Preferably, the stable light source uses a laser, and the MZI silicon optical modulator includes an input optical port, a phase modulation module, an optical splitter, and an output optical port connected in sequence.

[0016] Preferably, the optical splitter is used to split the light in the MZI silicon optical modulator and transmit it to the output optical port and two photodetectors respectively. The first photodetector is connected to the first resistor, and the second photodetector is connected to the second resistor.

[0017] The beneficial effects of the present invention compared with the prior art are: 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 the oscillation, and the integral link can eliminate the steady-state error and enhance the accuracy; at the same time, it has the ability of dynamic update, locks the phase in real time, and can adapt to more working environments. Description of the Drawings

[0018] Figure 1 It is a flowchart of a method for phase locking of an MZI silicon optical modulator; Figure 2 It is a detailed step flowchart of a method for phase locking of an MZI silicon optical modulator; Figure 3 It is a structural schematic diagram of a device for phase locking of an MZI silicon optical modulator; Figure 4 It is the P out or K ratio curve graph after normalization processing after applying a voltage of 0 to VDD to the phase modulation module; 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 and control unit 6, phase modulation module 7, optical beam splitter 8. Detailed Embodiment

[0019] Next, in combination with the Figures 1 to 4 in the present invention, the technical solutions in the embodiments of the present invention will be described in detail.

[0020] As Figure 1 shown, it is a flowchart of a method for phase locking of an MZI silicon optical modulator; as Figure 2 shown, it is a detailed step flowchart of a method for phase locking of an MZI silicon optical modulator; in combination with Figure 1 and Figure 2 shown, this method first applies a voltage to the phase modulation module of the MZI silicon optical modulator in a specific step, and then determines various parameters of the PID algorithm, and then determines the accurate voltage to be applied at the current moment based on various parameters, so as to complete the precise locking of the phase modulation module. The phase locking is specifically carried out through the following steps: S1. Initialization and data acquisition: First, initialize the acquisition and control unit, power on the laser and the MZI silicon optical modulator, and the laser inputs light to the input end of the MZI silicon optical modulator. Then, apply a voltage from 0 to V DD to the phase modulation module in the MZI silicon optical modulator multiple times, and the step of applying the voltage each time is V step; At both the input end and the output end of the MZI silicon optical modulator, corresponding photodetectors and external resistors are respectively arranged. Each photodetector is used to convert the corresponding light into photocurrent, so that the corresponding resistor generates a voltage and transmits it to the acquisition and control unit. After each voltage application, the corresponding voltages V in and V out are respectively collected. The voltage V out is the voltage corresponding to the resistor near the output end, and the voltage V in is the voltage corresponding to the resistor near the input end. The ratio of V out and V in is denoted as K ratio . The suffix "ratio" means ratio.

[0021] In this embodiment, in step S1, the two photodetectors respectively arranged at the input end and the output end of the MZI silicon optical modulator can be the same or different. As long as the responsivities of the two are known, subsequent calculations can be carried out; the two external resistors respectively arranged at the input end and the output end of the MZI silicon optical modulator can be the same or different. As long as the resistance values of the two are known, subsequent calculations can be carried out. In addition, if the same devices are used at both ends, it is convenient for experimental analysis and cost control, especially for actual device procurement.

[0022] In this embodiment, the optical power at the input end when the light emitted by the laser enters the MZI silicon optical modulator is recorded as P in , and the optical power at the output end of the MZI silicon optical modulator is recorded as P out ; Therefore, when collecting the voltages V in and V out , V in =P in ×α in ×R esp1 ×R in , where α in is the splitting ratio of the built-in optical splitter in the MZI silicon optical modulator to the photodetector corresponding to the input end, R in is the resistance value of the external resistor at the input end of the MZI silicon optical modulator, and R esp1 is the responsivity of the photodetector at the input end.

[0023] At the same time, V out =P out ×[α out / (1 - α out )]×R esp2 ×R out , where α out is the splitting ratio of the built-in optical splitter in the MZI silicon optical modulator to the photodetector corresponding to the output end, R outis the resistance value of the resistor externally connected to the output end of the MZI silicon optical modulator, R esp2 is the responsivity of the photodetector at the output end.

[0024] It should be noted that the MZI silicon optical modulator is internally equipped with an optical splitter, which can split part of the light at the input end to the corresponding photodetector according to the splitting ratio of α in and can also split part of the light at the output end to the corresponding photodetector according to the splitting ratio of α out and.

[0025] Such as Figure 4 shown, is the curve graph of P out or K ratio after normalization processing after the phase modulation module applies a voltage from 0 to VDD. Normalization is to unify the data size for easy calculation and comparison. Ratio is K ratio , and this graph shows the relationship between P out and K ratio at the output end of the MZI silicon optical modulator. Therefore, it shows that the voltage to be applied can be calculated based on K ratio to affect P out .

[0026] S2. Calculate the target value and initial value of the PID algorithm: From each K ratio in step S1, select a set of adjacent minimum values K ratio_min and maximum values K ratio_max that appear periodically for recording, and then record the applied voltages corresponding to the minimum value K ratio_min and the maximum value K ratio_max respectively as V ratio_min and V ratio_max .

[0027] S3. Obtain various parameters of the PID algorithm to complete phase locking: According to the minimum value K ratio_min and the maximum value K ratio_max in step S2, calculate the target value K ratio_target of the PID algorithm, and at the same time calculate the initial value V ratio_min and V ratio_max of the PID algorithm according to the corresponding applied voltages V start_target . Denote the K ratio at the current moment as K ratio_now , and at the same time denote the K ratio corresponding to the previous moment of the current moment as K ratio_last . According to K ratio_now and K ratio_target , the proportional link parameter E now of the PID algorithm at the current moment can be calculated, and at the same time the proportional link parameter E corresponding to the previous momentnow The update record is E last . Then, based on the proportional link parameter E now and E last , continue to calculate the integral link parameter S error and the derivative link parameter D error of the PID algorithm at the current moment.

[0028] Taking the Quad point phase in Figure 4 as an example, the average optical power at the output end at the Quad point is half of the maximum output optical power. Therefore, it can be known that the K Quad_target =(K ratio_min +K ratio_max ) / 2 at the Quad point; meanwhile, at the Quad point, V start_targe =(V ratio_min +V ratio_max ) / 2 can be used as 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.

[0029] Substitute the initial value V start_target and each of the above parameters into the PID algorithm for calculation, and output the applied voltage V now to be updated to the MZI silicon optical modulator at the current moment. The acquisition control unit applies the applied voltage V now to the phase modulation module of the MZI silicon optical modulator for adjustment to complete phase locking.

[0030] In this embodiment, the proportional link parameter can quickly complete the rough locking of the phase; when calculating the proportional link parameter E now , E now =K ratio_target -K ratio_now , and the E last at the previous moment = the K ratio_target corresponding to the previous moment - the K ratio_now corresponding to the previous moment. Moreover, each data will be recorded in the memory of the processor for use at subsequent moments. The derivative link parameter is sensitive to the rate of change of the error, can predict and adjust the control quantity in advance, thereby accelerating the response speed of the system and reducing the overshoot, and the overshoot is the maximum deviation value. When calculating the derivative link parameter D error , D error =E now -E last , where E last represents the proportional link parameter at the previous moment of the current moment. When calculating the proportional link parameter E now at the current moment, the proportional link parameter E now at the previous moment will be updated and recorded as Elast 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 phase parameter S error Update record to S error_last , so the integral link 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 characterize the total historical error.

[0031] In this embodiment, after completing the phase lock corresponding to the current moment in step S3, at the next moment, step S3 can be returned to obtain the K corresponding to the next moment. ratio_now The loop continues 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.

[0032] like Figure 3 The figure is a schematic diagram of the structure of a MZI silicon optical modulator phase locking device. Figure 3 The present application also proposes a MZI silicon optical modulator phase locking device, which is operated by the above-mentioned MZI silicon optical modulator phase locking method. The device includes 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; wherein the light provided by the stable light source 1 is input into the input optical port of the MZI silicon optical modulator 2 after optical coupling through the optical fiber or the lens 3; 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 according to the voltages I and II.

[0033] In this embodiment, the stable light source 1 adopts 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.

[0034] In summary, 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 quantity in advance based on the differential link to reduce oscillation, and the integral link can eliminate the steady-state error and enhance the accuracy; at the same time, it has the ability of dynamic update, locks the phase in real time, can adapt to more working environments, and has remarkable progressiveness.

[0035] The above embodiments are only used to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the present invention.

Claims

1. A phase locking method for an MZI silicon optical modulator, characterized in that It includes the following steps: S1. Initialization and data acquisition: Initialize the acquisition control unit, and power on the laser and the MZI silicon optical modulator; apply a voltage from 0 to V to the phase modulation module in the MZI silicon optical modulator multiple times, with a voltage step of V each time DD step ;​ A corresponding photodetector and an external resistor are respectively arranged at the input end and the output end of the MZI silicon optical modulator. After each voltage application, the corresponding voltages V in and V out across the external resistor are respectively collected, and the ratio of V out to V in is denoted as K ratio ; S2. Calculate the target value and initial value of the PID algorithm: From each K in step S1 ratio select a group of adjacent minimum values K that appear periodically ratio_min and maximum values K ratio_max for recording. Then record the applied voltages V ratio_min and V ratio_max corresponding to the minimum value K ratio_min and the maximum value K respectively ratio_max ; S3. Obtain various parameters of the PID algorithm to 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 . At the same time, according to the corresponding applied voltages V ratio_min and V ratio_max , calculate the initial value V of the PID algorithm start_target ; Denote the K at the current moment as K ratio ; denote the K corresponding to the previous moment of the current moment as K ratio_now ; according to K ratio and the target value K ratio_last , calculate the proportional link parameter E of the PID algorithm at the current moment ratio_now ; at the same time, update and record the proportional link parameter E corresponding to the previous moment as E ratio_target ; then, according to the proportional link parameters E now and E now , calculate the integral link parameter S last and the derivative link parameter D of the PID algorithm at the current moment now ; last ; error error error ​ Substitute the initial value V start_target and a variety of parameters into the PID algorithm, and output the applied voltage V that needs to be updated to the MZI silicon optical modulator at the current moment now , and the acquisition control unit applies the applied voltage V now to the phase modulation module of the MZI silicon optical modulator to complete phase locking.

2. A phase locking method for an MZI silicon optical modulator according to claim 1, characterized in that After power-on in step S1, record the optical power at the input end when the light emitted by the laser enters the MZI silicon optical modulator as P in , and record the optical power at the output end of the MZI silicon optical modulator as P out ; Sampling voltage V in and V out ,V in =P in ×α in ×R esp1 ×R in where α in is the splitting ratio of the optical splitter built in the MZI silicon optical modulator to the photodetector corresponding to the input end, R in is the resistance value of the resistor externally connected to the input end 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 is the splitting ratio of the optical splitter built in the MZI silicon optical modulator to the photodetector corresponding to the output end, R out is the resistance value of the resistor externally connected to the output end of the MZI silicon optical modulator, R esp2 is the responsivity of the photodetector at the output end.

3. A phase locking method for an MZI silicon optical modulator according to claim 1, characterized in that, In step S3, calculate the proportional link parameter E now When now E ratio_target = K ratio_now - K 4. A phase locking method for an MZI silicon optical modulator according to claim 1, characterized in that In step S3, calculate the differential link parameter D error When error D now = E last .

5. A phase locking method for an MZI silicon optical modulator according to claim 1, characterized in that, In step S3, calculate the integral link parameter S at the current moment error When error =S error_last +E now , which is used to represent the total historical error, and S error_last represents the S at the previous moment error .

6. A phase locking method for an MZI silicon optical modulator according to claim 1, characterized in that After completing the phase locking corresponding to the current moment in step S3, return to step S3 to obtain the K corresponding to the next moment again ratio_now Perform a loop to continue calculating the applied voltage V that needs to be updated to the MZI silicon optical modulator at the next moment next .

7. An MZI silicon optical modulator phase locking device operates by using an MZI silicon optical modulator phase locking method described in any one of the above claims 1 to 6, characterized in that, The device includes 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); Among them, the light provided by the stable light source (1) is input into the input optical port of the MZI silicon optical modulator (2) after being optically coupled by the optical fiber or the lens (3); 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 (6); the acquisition control unit (6) performs phase-locked control on the MZI silicon optical modulator (2) according to the voltages I and II.

8. A phase-locking device for an MZI silicon optical modulator according to claim 7, characterized in that, The stable light source (1) uses a laser, and the MZI silicon optical modulator (2) includes an input optical port, a phase modulation module (7), an optical splitter (8), and an output optical port connected in sequence.

9. The phase-locking device of an MZI silicon optical modulator according to claim 8, wherein, The optical splitter (8) is used to split the light in the MZI silicon optical 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).

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