An optical modulator compensation method and compensation device

Abstract

The application discloses an optical modulator compensation method and a compensation device, and relates to the field of optical communication.The method comprises the following steps: acquiring the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value; acquiring the first phase shifter voltage of each optical modulator when the phase difference of two arms of the optical modulator is 180 degrees; keeping the phase difference of two optical signals of the optical modulator at 90 degrees when the first phase shifter voltage is acquired each time; calculating the absolute value of the difference between the two first phase shifter voltages obtained by each optical modulator; continuously performing the above steps; and adjusting the optical power of another optical modulator when the absolute value of one of the optical modulators is greater than or equal to a corresponding preset threshold value, so that the absolute value is less than the corresponding preset threshold value. The application solves the problem that the non-ideal characteristics of the MZ modulator cannot be compensated in real time in the prior art.

Description

Technical Field

[0001] This application relates to the field of optical communication, specifically to an optical modulator compensation method and compensation device. Background Technology

[0002] With the development of optical communication technology, communication capacity has gradually increased, and the integration of optical devices has also become increasingly sophisticated. Integrated optical devices have advantages such as low power consumption, high bandwidth, and ultra-high spectral efficiency. Therefore, they have replaced many electrical devices in various fields, such as optical interconnects, optical sensing, optical communication, and quantum communication. IQ optical modulators are one such core device, capable of intensity and phase modulation of light. They are typically composed of multiple nested Mach-Zehnder (MZ) modulators. The I-path modulator and Q-path modulator are located on the upper and lower arms of an MZ modulator, respectively. This MZ modulator is called the mother MZ modulator or outer MZ modulator. The I-path and Q-path modulators themselves are two independent MZ modulators, also known as child MZ modulators or inner MZ modulators.

[0003] MZ modulators typically consist of beam splitters, waveguides, phase shifters, traveling-wave electrodes, and beam combiners. An ideal MZ modulator has perfectly symmetrical upper and lower arms, exhibiting excellent performance. However, in actual manufacturing, process errors exist, resulting in imperfections in the upper and lower arms of a real MZ modulator. These imperfections include variations in loss, beam splitter / combiner ratios, and modulation efficiency. These variations lead to suboptimal modulator characteristics, finite extinction ratios, and non-zero chirp coefficients. The non-ideal nature of MZ modulators degrades system performance in applications such as reduced optical power and worsened signal-to-noise ratio, and can severely limit their application range, including single-sideband modulation and microwave photonics.

[0004] Existing hardware solutions for compensating for non-ideal MZ modulators primarily utilize Variable Optical Attenuators (VOA) or adjustable beam splitters / combiners to adjust the optical power ratio between the upper and lower arms of the MZ modulator. Compensation methods typically employ a factory calibration to generate a lookup table, which is then consulted during application. This method involves a very time-consuming calibration process at the factory, and because it is not real-time, the error in the lookup table increases with chip aging, rendering it meaningless for compensation. Summary of the Invention

[0005] This application provides an optical modulator compensation method and compensation device, which can solve the problem that the non-ideal characteristics of MZ modulators cannot be compensated in real time in the prior art.

[0006] In a first aspect, embodiments of this application provide an optical modulator compensation method, the optical modulator including two optical modulators, each optical modulator having two arms, and a first phase shifter disposed in one arm of each optical modulator, the method comprising:

[0007] Obtain the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value; obtain the first phase shifter voltage of each optical modulator when the phase difference between the two arms is 180 degrees; keep the phase difference between the optical signals of the two optical modulators at 90 degrees each time the first phase shifter voltage is obtained; calculate the absolute value of the difference between the two first phase shifter voltages obtained for each optical modulator.

[0008] By continuously performing the above steps, when the absolute value of one optical modulator is greater than or equal to the corresponding preset threshold, the optical power of the other optical modulator is adjusted so that the absolute value is less than the corresponding preset threshold.

[0009] In conjunction with the first aspect, in one embodiment, acquiring the first phase shifter voltage when the phase difference between the two arms of each optical modulator is 180 degrees includes:

[0010] A portion of the optical power is extracted from the output of one optical modulator and converted into an electrical signal. After processing, a low-frequency electrical signal is obtained. The voltage of the first phase shifter of the optical modulator is adjusted until the low-frequency electrical signal reaches its extreme value, and the voltage of the first phase shifter at this time is obtained.

[0011] In conjunction with the first aspect, in one embodiment, obtaining the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value includes:

[0012] A portion of the optical power is extracted from the output optical waveguide of the optical modulator and converted into an electrical signal. After processing, a low-frequency electrical signal is obtained. The voltages of the first phase shifters of the two optical modulators are adjusted until the low-frequency electrical signal reaches its extreme value. The voltages of the first phase shifters of the two optical modulators at this time are then obtained.

[0013] In conjunction with the first aspect, in one embodiment, the extreme value is a maximum or a minimum value. When the modulation signal loaded on the optical modulator is greater than a set interface value, the extreme value is a maximum value; when the modulation signal loaded on the optical modulator is less than the set interface value, the extreme value is a minimum value.

[0014] In conjunction with the first aspect, in one embodiment, adjusting the optical power of the other optical modulator includes: reducing or increasing the optical power of one or both arms, or adjusting the splitting ratio of the two arms of the optical modulator.

[0015] Secondly, embodiments of this application provide an optical modulator compensation device, the optical modulator including two optical modulators, the device comprising:

[0016] The phase shift adjustment module includes a second phase shifter and two first phase shifters. The two first phase shifters are respectively disposed in one arm of each optical modulator. The second phase shifter is disposed after one of the optical modulators and is used to adjust the phase difference between the optical signals of the two optical modulators to 90 degrees.

[0017] The control module is used to acquire the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value; it is also used to acquire the first phase shifter voltage of each optical modulator when the phase difference between the two arms is 180 degrees; and it is also used to calculate the absolute value of the difference between the two first phase shifter voltages acquired by each optical modulator.

[0018] An optical power adjustment module is used to adjust the optical power of another optical modulator so that the absolute value is less than the corresponding preset threshold when the absolute value of one optical modulator is greater than or equal to the corresponding preset threshold.

[0019] In conjunction with the second aspect, in one embodiment, each optical modulator includes an adjustable beam combiner and / or beam splitter, and the optical power adjustment module adjusts the splitting ratio of the two arms of the optical modulator in its respective optical path through the adjustable beam combiner and / or beam splitter, thereby adjusting the optical power.

[0020] In conjunction with the second aspect, in one embodiment, each optical modulator has an adjustable optical attenuator in one arm, and the optical power adjustment module reduces the optical power of the arm by adjusting the adjustable optical attenuator.

[0021] Alternatively, an optical amplifier can be installed in one arm of each optical modulator, and the optical power adjustment module can increase the optical power of the arm by adjusting the optical amplifier.

[0022] In conjunction with the second aspect, in one embodiment, acquiring the first phase shifter voltage when the phase difference between the two arms of each optical modulator is 180 degrees includes:

[0023] A portion of the optical power is extracted from the output of one optical modulator by a photodetector, converted into an electrical signal by a control module, and processed to obtain a low-frequency electrical signal. The voltage of the first phase shifter of the optical modulator is adjusted so that the low-frequency electrical signal reaches its extreme value, and the voltage of the first phase shifter at this time is obtained.

[0024] In conjunction with the second aspect, in one embodiment, obtaining the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value includes:

[0025] A portion of the optical power is extracted from the output waveguide of the optical modulator by a photodetector. The low-frequency electrical signal is obtained through processing by the control module. The voltages of the first phase shifter and the second phase shifter of the two optical modulators are adjusted respectively until the low-frequency electrical signal reaches its extreme value. The voltages of the first phase shifter of the two optical modulators at this time are then obtained.

[0026] The beneficial effects of the technical solutions provided in this application include at least the following:

[0027] When the phase difference between the optical signals of the two optical modulators is 90 degrees, the first phase shifter voltage of each optical modulator is acquired when the phase difference between the two arms is 180 degrees. The first phase shifter voltage of each optical modulator is also acquired when the output optical signal of the optical modulator reaches an extreme value. The absolute value of the difference between the two first phase shifter voltages acquired for each optical modulator is calculated. This absolute value is continuously calculated, and when the absolute value of one optical modulator is greater than or equal to a corresponding preset threshold, the optical power of the other optical modulator is adjusted to make the absolute value less than the preset threshold. Throughout the modulator's entire lifecycle, phase shifter modulation can compensate for the non-ideal characteristics of the optical modulator in real time, thereby improving device performance; it avoids lookup table errors and improves compensation performance. By adjusting the ratio of the optical power of the two arms in real time, the signal degradation introduced by the extinction ratio ER and chirp coefficient is compensated, significantly improving performance. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart of the optical modulator compensation method of this application;

[0029] Figure 2 The curve shows the relationship between the absolute value of the voltage difference of the first phase shifter and the ratio of the optical power of the two arms.

[0030] Figure 3 This is a schematic diagram of an embodiment of the optical modulator compensation method of this application;

[0031] Figure 4 This is a schematic diagram of another embodiment in which the optical power of each optical modulator is adjusted by means of two arms;

[0032] Figure 5 This is a schematic diagram of another embodiment of the optical modulator compensation method of this application.

[0033] In the picture:

[0034] 1. First optical modulator; 2. Second optical modulator; 3. Beam splitter; 4. Beam combiner; 5. First phase shifter; 6. Second phase shifter; 71. First photodetector; 72. Second photodetector; 73. Third photodetector; 8. Adjustable optical attenuator; 9. Optical amplifier; 10. Controller; 11. First polarization state optical modulator; 12. Second polarization state optical modulator; 13. Polarization rotation beam combiner; 14. Fourth photodetector. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0036] The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus. The terms "first," "second," and "third," etc., are used to distinguish different objects, etc., and do not indicate a sequence, nor do they limit "first," "second," and "third" to different types.

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0038] In the first aspect, embodiments of this application provide an optical modulator compensation method that can solve the problem in the prior art where the compensation for non-ideal characteristics of MZ modulators is done using a lookup table, which cannot provide real-time compensation.

[0039] The optical modulator used in this application includes two optical modulators, each with two arms. A first phase shifter is set in one arm of each optical modulator. The process includes the following steps:

[0040] Obtain the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value; obtain the first phase shifter voltage of each optical modulator when the phase difference between the two arms is 180 degrees; keep the phase difference between the optical signals of the two optical modulators at 90 degrees each time the first phase shifter voltage is obtained; calculate the absolute value of the difference between the two first phase shifter voltages obtained for each optical modulator.

[0041] The absolute value is continuously calculated through the above steps. When the absolute value of one optical modulator is greater than or equal to the corresponding preset threshold, the optical power of the other optical modulator is adjusted so that the absolute value is less than the corresponding preset threshold.

[0042] like Figure 1 As shown, the specific steps of the above optical modulator compensation method are as follows:

[0043] S101. Obtain the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at its extreme value; obtain the first phase shifter voltage of each optical modulator when the phase difference between the two arms is 180 degrees; each time the first phase shifter voltage is obtained, maintain the phase difference between the optical signals of the two optical modulators at 90 degrees. Calculate the absolute value of the difference between the two first phase shifter voltages obtained for each optical modulator.

[0044] S102. Determine whether the absolute value calculated by each optical modulator is less than the corresponding preset threshold. If yes, proceed to S101; otherwise, proceed to S103.

[0045] S103. If the absolute value calculated by one optical modulator is greater than or equal to the corresponding preset threshold, adjust the optical power of the other optical modulator and proceed to S101.

[0046] Throughout the adjustment process, if the optical power of another optical modulator was increased in the previous step S103, and the absolute value calculated in this step S101 is found to be greater than or equal to the corresponding preset threshold, then the optical power of the other optical modulator will be reduced in this step S103, and vice versa. By continuously calculating and adjusting through the above steps, the absolute value of each optical modulator is modulated below the corresponding preset threshold, avoiding lookup table errors and improving compensation performance.

[0047] In step S101 above, the order of acquiring the first phase shifter voltage twice can be interchanged. Before acquiring the voltage, the phase difference between the optical signals of the two optical modulators can be adjusted to 90 degrees.

[0048] In the above steps, the two optical modulators are divided into a first optical modulator and a second optical modulator. In S101, when the output optical signal of the optical modulator is at an extreme value, the first phase shifter voltage of the first optical modulator is V1, and the first phase shifter voltage of the second optical modulator is V2. When the phase difference between the two arms of the two optical modulators is 180 degrees, the first phase shifter voltage of the first optical modulator is V10, and the first phase shifter voltage of the second optical modulator is V20. A first threshold and a second threshold are preset. In S102, the optical power of the first optical modulator is adjusted so that |V2-V20| is less than the first threshold; the optical power of the second optical modulator is adjusted so that the absolute value of |V1-V10| is less than the second threshold.

[0049] Specifically, in the above steps, V1 and V2 each have multiple values ​​that can satisfy the requirement that the phase difference between the optical signals of the two optical modulators is 90 degrees, and that the output optical signal of the optical modulator is an extreme value. V10 and V20 also have multiple values ​​that can satisfy the requirement that the phase difference between the optical signals of the two optical modulators is 90 degrees, and that the phase difference between the two arms of the same optical modulator is 180 degrees. The first threshold and the second threshold are set according to the noise floor level, and they can be the same or different.

[0050] In some embodiments, in S101 above, the extreme value can be either a maximum or a minimum value, determined by the magnitude of the modulation electrical signal applied to the optical modulator. When the modulation electrical signal is greater than a set interface value, the extreme value is a maximum; when the modulation electrical signal is less than the set interface value, the extreme value is a minimum.

[0051] In S103 above, adjusting the optical power of each optical modulator can be done by increasing or decreasing the optical power of one or both arms of the optical modulator, or by adjusting the splitting ratio of the two arms of the optical modulator.

[0052] like Figure 3 As shown, a specific embodiment of an optical modulator compensation method is provided, and the principle of the above method is explained in detail. In this embodiment, the optical modulator is an IQ optical modulator, and both the first optical modulator 1 and the second optical modulator 2 are MZ modulators.

[0053] In the optical modulator of this embodiment, both the first optical modulator 1 and the second optical modulator 2 include a beam splitter 3 and a beam combiner 4. The lower arm of both the first optical modulator 1 and the lower arm of the second optical modulator 2 are equipped with a first phase shifter 5. The output of the second optical modulator 2 is also equipped with a second phase shifter 6. A portion of the optical power of the first optical modulator 1 is extracted through a first photodetector 71; a portion of the optical power of the second optical modulator 2 is extracted through a second photodetector 72; and the entire portion of the optical power is extracted from the output waveguide of the optical modulator through a third photodetector 73.

[0054] Preferably, the photodetector can be an on-chip detector integrated with the optical modulator, or it can be an external detector. The entire control process can be implemented by a controller 10.

[0055] The expression for the output optical field of the output waveguide of the optical modulator is as follows:

[0056]

[0057] Where ω0 is the frequency of the optical carrier, V i,RF (i = I, Q) is the radio frequency voltage (e.g., ... Figure 3 V i,DC (i = I, Q) is the phase shifter voltage (e.g., ... Figure 3 (V1 voltage of the first phase shifter of the first optical modulator and the first phase shifter of the second optical modulator) π,RF It is the voltage required by the RF electrodes when the modulator generates a 180-degree phase shift, V. π,DC This is the voltage required by the phase shifter to generate a 180-degree phase shift. The coefficient M i (i = I, Q) characterizes the intrinsic extinction ratio ER of the modulator. i (i = I, Q), that is

[0058]

[0059] To simplify the derivation, assume the radio frequency voltage is 0. When the optical modulator outputs a minimum optical signal, i.e., E... out =0, we can get V1 and V2, as follows:

[0060]

[0061]

[0062] V10 is the first phase shifter voltage of the first optical modulator 1 when the phase difference between the two arms is 180 degrees; V20 is the first phase shifter voltage of the second optical modulator 2 when the phase difference between the two arms is 180 degrees. We can obtain V10 = -Vpi,DC and V20 = Vpi,DC. Therefore, we can calculate the absolute value of the difference between the two first phase shifter voltages obtained for each optical modulator:

[0063]

[0064]

[0065] As can be seen from formulas (5)-(6), when V1-V10=0 and V2-V20=0, the extinction ratio of the first optical modulator 1 and the second optical modulator 2 reaches the optimal value.

[0066] In fact, when there is an RF voltage, V1-V10 and V2-V20 can also be used as target values ​​to adjust the upper and / or lower arm optical power of the first optical modulator 1 and the upper and / or lower arm optical power of the second optical modulator 2.

[0067] like Figure 2 The diagram shows the relationship between the absolute value of the voltage difference of the first phase shifter and the ratio of the optical power of the two arms. Adjusting the ratio of the optical power of the upper and lower arms of the first optical modulator 1 results in almost no change in |V1-V10|, but a significant change in |V2-V20|. When the optical power of the upper and lower arms of the first modulator 1 is the same, |V2-V20| equals 0. That is, by approaching |V2-V20| to zero, the optical power of the upper and / or lower arms of the first optical modulator 1 can be adjusted via feedback; similarly, by approaching |V1-V10| to zero, the optical power of the upper and / or lower arms of the second optical modulator 2 can be adjusted via feedback.

[0068] Based on the above principles, such as Figure 3 As shown, this embodiment specifically includes the following steps:

[0069] A101. Adjust the second phase shifter 6 so that the phase difference between the optical signals of the first optical modulator 1 and the second optical modulator 2 is 90 degrees.

[0070] Specifically, the first photodetector 71 extracts a portion of the optical power from the output of the first optical modulator 1, converts the optical signal into an electrical signal, and processes it to obtain a low-frequency electrical signal. This processing involves amplification and filtering. The first phase shifter 5 of the first optical modulator 1 is adjusted. When the phase difference between the two arms of the first optical modulator 1 is 180 degrees, the low-frequency electrical signal reaches its minimum value. The voltage V10 of the first phase shifter of the first optical modulator 1 (i.e., the voltage of the first phase shifter 5 of the first optical modulator 1) is then determined.

[0071] The second photodetector 72 extracts a portion of the optical power from the output of the second optical modulator 2, converts the optical signal into an electrical signal, and obtains a low-frequency electrical signal after amplification and filtering. The first phase shifter 5 of the second optical modulator 2 is adjusted. When the phase difference between the two arms of the second optical modulator 2 is 180 degrees, the low-frequency electrical signal is at its minimum value. The voltage V20 of the first phase shifter of the second optical modulator 2 (i.e., the voltage of the first phase shifter 5 of the second optical modulator 1) is then determined.

[0072] The third photodetector 73 extracts a portion of the optical power from the output waveguide of the optical modulator, converts the optical signal into an electrical signal, and obtains a low-frequency electrical signal after amplification and filtering. The first phase shifter 5 of the two optical modulators and the second phase shifter 6 of the entire optical modulator are adjusted. When the phase difference between the first optical signal (generated by the first optical modulator 1) and the second optical signal (generated by the second optical modulator 2) is 90 degrees, and the output optical signal of the optical modulator is at its minimum value, the first phase shifter voltage V1 of the first optical modulator 1 and the first phase shifter voltage V2 of the second optical modulator 1 are determined at this time.

[0073] Calculate |V1-V10| for the first optical modulator 1, and calculate |V2-V20| for the second optical modulator 2.

[0074] In this embodiment, the extreme values ​​of the low-frequency electrical signals output by the two optical modulators and the optical signals output by the optical modulator are both minimum values. In other embodiments, the extreme values ​​can also be maximum values. In this embodiment, the minimum value can be set as follows: given a suitable threshold, if it is less than the threshold, it is considered to have reached the minimum value; or, the initial voltage of the phase shifter is V, the adjustment direction is positive, and the phase shifter voltage is adjusted according to a certain step dv, i.e., V+dv. The low-frequency voltage signal is recorded, and by comparing the magnitudes of the low-frequency voltage signals before and after, it is determined whether the low-frequency signal is being adjusted in the direction of decreasing (if the low-frequency voltage signal decreases, the adjustment direction remains unchanged; if the low-frequency voltage signal increases, the adjustment direction is reversed). When the adjustment direction is reversed multiple times, it is considered to have reached the minimum value. The minimum value of the optical signal output by the optical modulator is also set according to this method.

[0075] A102. Determine whether |V1-V10| is less than the preset second threshold, and whether |V2-V20| is less than the first threshold. If yes, that is, |V1-V10| is less than the second threshold and |V2-V20| is less than the first threshold, make no adjustment and proceed to A101. If no, proceed to A103.

[0076] A103. If |V2-V20| is less than the first threshold, adjust the optical power of the first optical modulator 1; or if |V1-V10| is less than the second threshold, adjust the optical power of the second optical modulator 2, and then proceed to A101. The principle of adjustment is to control the absolute value of each optical modulator below the corresponding preset threshold.

[0077] In some embodiments, such as Figure 2 As shown, by adjusting the beam splitter 3 of each optical modulator, the splitting ratio of the upper and lower arms of that optical modulator is changed; or by adjusting the beam combiner 4 of each optical modulator, the splitting ratio of the upper and lower arms of that optical modulator is changed, and the optical power is adjusted by the splitting ratio.

[0078] In other embodiments, such as Figure 4 As shown, each optical modulator can be equipped with an adjustable optical attenuator 8 and an optical amplifier 9 on both arms. By adjusting the adjustable optical attenuator 8 of the upper arm and / or the lower arm, the optical power of the upper arm and / or the lower arm can be reduced; or, by adjusting the optical amplifier of the upper arm and / or the lower arm, the optical power of the upper arm and / or the lower arm can be increased.

[0079] like Figure 5 The diagram shown is a schematic representation of another embodiment of the optical modulator compensation method of this application. This embodiment involves two optical polarization states and is a polarization-multiplexed optical modulator, including a first polarization state optical modulator 11 and a second polarization state optical modulator 12. The output waveguides of the two polarization state optical modulators have the same polarization state. A polarization rotation beam combiner 13 rotates the polarization state of the output light from the first polarization state optical modulator 11 or the output light from the second polarization state optical modulator 12 and combines it with the output light from the other polarization state optical modulator. The first polarization state optical modulator 11 includes... Figure 1 The first optical modulator 1 and the second optical modulator 2, and the first polarization state optical modulator 12 also include Figure 1 The first optical modulator 1 and the second optical modulator 2 are in the middle.

[0080] The compensation principle and method used in this embodiment are the same as those in the above embodiments. A portion of the optical power is extracted from the output of the first optical modulator 1 of the first polarization-state optical modulator 11 via the first photodetector 71. After photoelectric conversion, amplification, and filtering, a low-frequency electrical signal is obtained. The first phase shifter 5 of the first optical modulator 11 is adjusted to obtain the phase shifter voltage V10 of the first phase shifter 5 when the low-frequency electrical signal reaches its minimum value. A portion of the optical power is extracted from the output of the second optical modulator 2 of the first polarization-state optical modulator 11 via the second photodetector 72. After photoelectric conversion, amplification, and filtering, a low-frequency electrical signal is obtained. The first phase shifter 5 of the second optical modulator 2 is adjusted to obtain the phase shifter voltage V20 of the first phase shifter 5 when the low-frequency electrical signal reaches its minimum value. Then, a portion of the optical power is extracted from the output optical waveguide of the first polarization-state optical modulator 11 via the third photodetector 73. After photoelectric conversion, amplification, and filtering, a low-frequency electrical signal is obtained. By adjusting the two first phase shifters 5 and one second phase shifter 6, the voltages V1 and V2 of the first phase shifters of the two optical modulators of the first polarization state optical modulator 11 are obtained.

[0081] For the first polarization modulator 11, it is determined whether |V1-V10| is less than a preset second threshold and whether |V2-V20| is less than a first threshold. If yes, that is, |V1-V10| is less than the second threshold and |V2-V20| is less than the first threshold, no adjustment is made, and the acquisition and determination of V10, V20, V1, and V2 in the above steps are repeated. If no, |V2-V20| is less than the first threshold, and the optical power of the first optical modulator 1 is adjusted; or |V1-V10| is less than the second threshold, and the optical power of the second optical modulator 2 is adjusted.

[0082] The same method can be used to adjust the second polarization state light modulator 12, which will not be described in detail here.

[0083] like Figure 5 As shown, another modulation compensation method can also be used in this embodiment. It is basically the same as the compensation method described above. A portion of the optical power is extracted from the output of the first optical modulator 1 of the first polarization-state optical modulator 11 using the first photodetector 71, processed to obtain a low-frequency electrical signal, and the phase shifter voltage V10 of the first phase shifter 5 of the first optical modulator 1 is determined by the minimum value of the low-frequency electrical signal. Similarly, a portion of the optical power is extracted from the output of the second optical modulator 2 of the first polarization-state optical modulator 11 using the second photodetector 72, processed to obtain a low-frequency electrical signal, and the phase shifter voltage V20 of the first phase shifter 5 of the second optical modulator 2 is determined by the minimum value of the low-frequency electrical signal. Unlike the compensation method described above, in this embodiment, a portion of the optical power is extracted from the output waveguide of the entire polarization-multiplexed optical modulator using a fourth photodetector 13, and after photoelectric conversion, amplification, and filtering, a low-frequency electrical signal is obtained. By adjusting the two first phase shifters 5 and one second phase shifter 6 of the first polarization state optical modulator 11, the voltages V1 and V2 of the first phase shifters of the two optical modulators of the first polarization state optical modulator 11 can be obtained in real time according to the minimum value of the low-frequency electrical signal.

[0084] In other words, in this embodiment, a portion of the optical power is extracted from the output waveguide of the entire polarization-multiplexed optical modulator using a fourth photodetector 13 to obtain the voltages V1 and V2 of the first phase shifters of the two optical modulators of the first polarization-state optical modulator 11. The compensation methods for the first polarization-state optical modulator 11 and the second polarization-state optical modulator 12 are the same as in the above embodiments, and will not be repeated here.

[0085] It is understood that in this embodiment, the voltage of the corresponding phase shifter is obtained in real time using the minimum value of the low-frequency electrical signal. In other embodiments, the voltage of the corresponding phase shifter can also be obtained in real time using the maximum value of the low-frequency electrical signal.

[0086] On the other hand, this application provides an optical modulator compensation device that can implement the above-described compensation method embodiment. The optical modulator includes two optical modulators, and the compensation device includes a phase shift adjustment module, a control module, and an optical power adjustment module.

[0087] The phase shift adjustment module includes a second phase shifter and two first phase shifters. The two first phase shifters are respectively set in one arm of each optical modulator. The second phase shifter is set after one of the optical modulators and is used to adjust the phase difference of the optical signals of the two optical modulators to 90 degrees.

[0088] The control module is used to acquire the first phase shifter voltage when the phase difference between the two arms of each optical modulator is 180 degrees; it is also used to acquire the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value; and it is also used to calculate the absolute value of the difference between the two first phase shifter voltages acquired by each optical modulator.

[0089] An optical power adjustment module is used to adjust the optical power of another optical modulator so that the absolute value is less than the preset threshold when the absolute value of one optical modulator is greater than or equal to the corresponding preset threshold.

[0090] In some embodiments, the control module and the optical power adjustment module can be jointly implemented by the controller in the above embodiments.

[0091] In some implementations, each optical modulator includes an adjustable beam combiner and / or beam splitter. The optical power adjustment module adjusts the splitting ratio of the two arms of the modulator in the optical path through the adjustable beam combiner and / or beam splitter, thereby adjusting the optical power.

[0092] Each optical modulator has an adjustable optical attenuator in one arm, and the optical power adjustment module reduces the optical power of that arm by adjusting the adjustable optical attenuator; alternatively, each optical modulator has an optical amplifier in one arm, and the optical power adjustment module increases the optical power of that arm by adjusting the optical amplifier. This allows for adjustment of the splitting ratio between the two arms of each optical modulator.

[0093] The above-mentioned acquisition of the first phase shifter voltage when the phase difference between the two arms of each optical modulator is 180 degrees includes: extracting a portion of the optical power from the output of one optical modulator through a photodetector, converting it into an electrical signal through a control module, processing it to obtain a low-frequency electrical signal, adjusting the first phase shifter voltage of that optical modulator until the low-frequency electrical signal reaches its extreme value, and acquiring the first phase shifter voltage at this time.

[0094] When the output optical signal of the optical modulator is at an extreme value, the first phase shifter voltage of each optical modulator includes: extracting a portion of optical power from the output optical waveguide of the optical modulator through a photodetector, processing it through a control module to obtain a low-frequency electrical signal, adjusting the first phase shifter voltage of the two optical modulators and adjusting the second phase shifter voltage respectively, until the low-frequency electrical signal reaches an extreme value, and obtaining the first phase shifter voltage of the two optical modulators at this time.

[0095] It should be noted that the sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0096] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0097] In some processes described in the embodiments of this application, multiple operations or steps are included in a specific order. However, it should be understood that these operations or steps may not be executed in the order they appear in the embodiments of this application, or they may be executed in parallel. The sequence number of the operation is only used to distinguish different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed sequentially or in parallel, and these operations or steps may be combined.

[0098] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. An optical modulator compensation method, the optical modulator comprising two optical modulators, each optical modulator having two arms, characterized in that, The method includes setting a first phase shifter in one arm of each optical modulator, wherein the method comprises: Obtain the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value; obtain the first phase shifter voltage of each optical modulator when the phase difference between the two arms is 180 degrees; keep the phase difference between the optical signals of the two optical modulators at 90 degrees each time the first phase shifter voltage is obtained; calculate the absolute value of the difference between the two first phase shifter voltages obtained for each optical modulator. By continuously performing the above steps, when the absolute value of one optical modulator is greater than or equal to the corresponding preset threshold, the optical power of the other optical modulator is adjusted so that the absolute value is less than the corresponding preset threshold.

2. The optical modulator compensation method as described in claim 1, characterized in that, The voltage of the first phase shifter is obtained when the phase difference between the two arms of each optical modulator is 180 degrees, including: A portion of the optical power is extracted from the output of one optical modulator and converted into an electrical signal. After processing, a low-frequency electrical signal is obtained. The voltage of the first phase shifter of the optical modulator is adjusted until the low-frequency electrical signal reaches its extreme value, and the voltage of the first phase shifter at this time is obtained.

3. The optical modulator compensation method as described in claim 1, characterized in that, When the output optical signal of the optical modulator is at an extreme value, the first phase shifter voltage of each optical modulator includes: A portion of the optical power is extracted from the output optical waveguide of the optical modulator and converted into an electrical signal. After processing, a low-frequency electrical signal is obtained. The voltages of the first phase shifters of the two optical modulators are adjusted until the low-frequency electrical signal reaches its extreme value. The voltages of the first phase shifters of the two optical modulators at this time are then obtained.

4. The optical modulator compensation method according to any one of claims 1-3, characterized in that, The extreme value is either a maximum or a minimum value. When the modulation signal applied to the optical modulator is greater than the set interface value, the extreme value is a maximum value; when the modulation signal applied to the optical modulator is less than the set interface value, the extreme value is a minimum value.

5. The optical modulator compensation method as described in claim 1, characterized in that, Adjusting the optical power of another optical modulator includes: reducing or increasing the optical power of one or both arms, or adjusting the splitting ratio of the two arms of the optical modulator.

6. An optical modulator compensation device, the optical modulator comprising two optical modulators, characterized in that, The device includes: The phase shift adjustment module includes a second phase shifter and two first phase shifters. The two first phase shifters are respectively disposed in one arm of each optical modulator. The second phase shifter is disposed after one of the optical modulators and is used to adjust the phase difference between the optical signals of the two optical modulators to 90 degrees. The control module is used to acquire the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value; it is also used to acquire the first phase shifter voltage of each optical modulator when the phase difference between the two arms is 180 degrees; and it is also used to calculate the absolute value of the difference between the two first phase shifter voltages acquired by each optical modulator. An optical power adjustment module is used to adjust the optical power of another optical modulator so that the absolute value is less than the corresponding preset threshold when the absolute value of one optical modulator is greater than or equal to the corresponding preset threshold.

7. The optical modulator compensation device as described in claim 6, characterized in that, Each optical modulator includes an adjustable beam combiner and / or beam splitter. The optical power adjustment module adjusts the splitting ratio of the two arms of the optical modulator through the adjustable beam combiner and / or beam splitter, thereby adjusting the optical power.

8. The optical modulator compensation device as described in claim 6, characterized in that, Each optical modulator has an adjustable optical attenuator in one arm, and the optical power adjustment module reduces the optical power of the arm by adjusting the adjustable optical attenuator. Alternatively, an optical amplifier can be installed in one arm of each optical modulator, and the optical power adjustment module can increase the optical power of the arm by adjusting the optical amplifier.

9. The optical modulator compensation device as described in claim 6, characterized in that, The step of acquiring the first phase shifter voltage when the phase difference between the two arms of each optical modulator is 180 degrees includes: A portion of the optical power is extracted from the output of one optical modulator by a photodetector, converted into an electrical signal by a control module, and processed to obtain a low-frequency electrical signal. The voltage of the first phase shifter of the optical modulator is adjusted so that the low-frequency electrical signal reaches its extreme value, and the voltage of the first phase shifter at this time is obtained.

10. The optical modulator compensation device as described in claim 6, characterized in that, When the output optical signal of the optical modulator is at an extreme value, the first phase shifter voltage of each optical modulator includes: A portion of the optical power is extracted from the output waveguide of the optical modulator by a photodetector. The low-frequency electrical signal is obtained through processing by the control module. The voltages of the first phase shifter and the second phase shifter of the two optical modulators are adjusted respectively until the low-frequency electrical signal reaches its extreme value. The voltages of the first phase shifter of the two optical modulators at this time are then obtained.

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