Optical modulator compensation method and compensation device

Abstract

An optical modulator compensation method and compensation device, relating to the field of optical communications. The method comprises: separately acquiring a first phase shifter voltage of each light modulator when an output optical signal of an optical modulator is an extreme value; separately acquiring a first phase shifter voltage when the phase difference of two arms of each light modulator is 180 degrees; each time when the first phase shifter voltage is acquired, keeping the phase difference of optical signals of the two-path light modulators to be 90 degrees; calculating the absolute value of the difference between the two obtained first phase shifter voltages of each light modulator; and, continuously carrying out said steps, and when the absolute value of one light modulator is greater than or equal to a corresponding preset threshold value, adjusting the optical power of the other light modulator, so as to cause the absolute value to be less than the corresponding preset threshold value. The present application solves the problem in the prior art of incapability of real-time compensation for non-ideal characteristics of MZ modulators.

Description

Optical modulator compensation method and compensation device Technical Field

[0001] The present application relates to the field of optical communications, and in particular to an optical modulator compensation method and compensation device. Background Art

[0002] With the development of optical communication technology, communication capacity has gradually increased, and the integration of optical devices has become increasingly higher. Integrated optical devices have the advantages of low energy consumption, high bandwidth, and ultra-high spectrum utilization. Therefore, they have replaced many electrical devices in many fields, such as optical interconnection, optical sensing, optical communication, quantum communication, etc. The IQ optical modulator is one of the core devices that can realize intensity modulation and phase modulation of light. It is usually composed of multiple nested Mach-Zehnder (MZ) modulators. Among them, the I-channel modulator and the Q-channel modulator are respectively in the upper and lower arms of an MZ modulator. This MZ modulator is called a mother MZ modulator, or an outer MZ modulator. The I-channel and Q-channel modulators themselves are two independent MZ modulators, which can also be called sub-MZ modulators, or inner MZ modulators.

[0003] An MZ modulator typically consists of a beam splitter, waveguide, phase shifter, traveling-wave electrode, and beam combiner. An ideal MZ modulator has completely symmetrical upper and lower arms, exhibiting exceptional performance. However, due to process errors in actual manufacturing, the upper and lower arms of a real MZ modulator are not completely symmetrical. These errors, such as varying losses, different beam splitter or combiner ratios, and varying modulation efficiencies, result in suboptimal modulator characteristics, a finite extinction ratio, and a non-zero chirp coefficient. These non-idealities can degrade system performance, such as reduced optical power and a degraded signal-to-noise ratio, and can even severely limit its 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 (VOAs) or adjustable beam splitters / combiners to adjust the optical power ratio between the upper and lower arms of the MZ modulator. This compensation method typically uses a factory calibration to generate a lookup table, which is then queried during application. This method involves a very time-consuming factory calibration process. Furthermore, because it is not real-time, the lookup table's error increases as the chip ages, rendering the compensation ineffective.

[0005] Summary of the Invention

[0006] The present application provides an optical modulator compensation method and compensation device, which can solve the problem in the prior art that the non-ideal characteristics of the MZ modulator cannot be compensated in real time.

[0007] In a first aspect, embodiments of the present application provide a method for compensating an optical modulator, wherein the optical modulator includes two optical modulators, each optical modulator having two arms, and a first phase shifter is provided in one arm of each optical modulator. The method includes:

[0008] Obtaining the first phase shifter voltage of each optical modulator when the optical modulator output optical signal is at an extreme value; obtaining the first phase shifter voltage of each optical modulator when the phase difference between the two arms is 180 degrees; maintaining the phase difference of the optical signals of the two optical modulators at 90 degrees each time the first phase shifter voltage is obtained; and calculating the absolute value of the difference between the two first phase shifter voltages obtained for each optical modulator;

[0009] The above steps are continuously performed. 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 to make the absolute value less than the corresponding preset threshold.

[0010] In combination with the first aspect, in one embodiment, obtaining the first phase shifter voltage when the phase difference between the two arms of each optical modulator is 180 degrees includes:

[0011] A portion of optical power is extracted from the output of an optical modulator, converted into an electrical signal, and processed to obtain a low-frequency electrical signal. The voltage of the first phase shifter of the optical modulator is adjusted until the low-frequency electrical signal reaches an extreme value, and the first phase shifter voltage at this time is obtained.

[0012] In combination with the first aspect, in one embodiment, obtaining the first phase shifter voltage of each optical modulator when the optical modulator outputs an optical signal at an extreme value includes:

[0013] A portion of the optical power is extracted from the optical modulator output optical waveguide and converted into an electrical signal. After processing, a low-frequency electrical signal is obtained. The first phase shifter voltages of the two optical modulators are adjusted respectively until the low-frequency electrical signal reaches an extreme value. At this time, the first phase shifter voltages of the two optical modulators are respectively obtained.

[0014] In combination with the first aspect, in one embodiment, the extreme value is a maximum value or a minimum value. When the modulated electrical signal loaded on the optical modulator is greater than the set interface value, the extreme value is a maximum value; when the modulated electrical signal loaded on the optical modulator is less than the set interface value, the extreme value is a minimum value.

[0015] In combination with the first aspect, in one embodiment, 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.

[0016] In a second aspect, an embodiment of the present application provides an optical modulator compensation device, wherein the optical modulator includes two optical modulators, and the device includes:

[0017] The phase shift adjustment module includes a second phase shifter and two first phase shifters, wherein the two first phase shifters are respectively arranged in one arm of each optical modulator; the second phase shifter is arranged 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;

[0018] a control module, configured to obtain a first phase shifter voltage of each optical modulator when the optical modulator output optical signal is at an extreme value; further configured to obtain a first phase shifter voltage of each optical modulator when the phase difference between the two arms of the optical modulator is 180 degrees; and further configured to calculate the absolute value of the difference between the two first phase shifter voltages obtained for each optical modulator;

[0019] The 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.

[0020] In combination with the second aspect, in one embodiment, each optical modulator includes an adjustable combiner and / or beam splitter, and the optical power adjustment module adjusts the splitting ratio of the two arms of the optical path modulator through the adjustable combiner and / or beam splitter, thereby adjusting the optical power.

[0021] In conjunction with the second aspect, in one embodiment, an adjustable optical attenuator is provided in one arm of each optical modulator, and the optical power adjustment module reduces the optical power of the arm by adjusting the adjustable optical attenuator;

[0022] Alternatively, an optical amplifier is provided in one arm of each optical modulator, and the optical power adjustment module increases the optical power of the arm by adjusting the optical amplifier.

[0023] In conjunction with the second aspect, in one embodiment, respectively obtaining the first phase shifter voltage when the phase difference between the two arms of each optical modulator is 180 degrees includes:

[0024] A portion of the optical power is extracted from the output of an optical modulator through a photodetector, converted into an electrical signal through a control module, and processed to obtain a low-frequency electrical signal. The first phase shifter voltage of the optical modulator is adjusted to achieve the extreme value of the low-frequency electrical signal, and the first phase shifter voltage at this time is obtained.

[0025] In conjunction with the second aspect, in one embodiment, obtaining the first phase shifter voltage of each optical modulator when the optical modulator output optical signal is an extreme value includes:

[0026] A portion of the optical power is extracted from the optical modulator output optical waveguide via a photodetector, and processed by a control module to obtain a low-frequency electrical signal. The first phase shifter voltage and the second phase shifter voltage of the two optical modulators are adjusted respectively until the low-frequency electrical signal reaches an extreme value, and the first phase shifter voltage of the two optical modulators at this time is obtained.

[0027] The beneficial effects of the technical solutions provided in the embodiments of the present application include at least:

[0028] 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 obtained when the phase difference between the two arms is 180 degrees; the first phase shifter voltage of each optical modulator is obtained when the optical signal output by the optical modulator is at an extreme value; the absolute value of the difference between the two first phase shifter voltages obtained by each optical modulator is calculated; the above absolute values ​​are continuously calculated, and 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 preset threshold. During the entire life cycle of the modulator, the use of phase shifter modulation can compensate for the non-ideal characteristics of the optical modulator in real time, thereby improving device performance; avoiding errors in the lookup table and improving compensation performance. By adjusting the optical power ratio of the two arms in real time, the signal degradation introduced by the extinction ratio ER and the chirp coefficient chirp is compensated, significantly improving performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a schematic flow chart of the optical modulator compensation method of the present application;

[0030] FIG2 is a curve showing the relationship between the absolute value of the voltage difference of the first phase shifter and the ratio of the optical powers of the two arms;

[0031] FIG3 is a schematic diagram of an embodiment of an optical modulator compensation method of the present application;

[0032] FIG4 is a schematic diagram of another embodiment of adjusting the optical power of each optical modulator through two arms;

[0033] FIG. 5 is a schematic diagram of another embodiment of the optical modulator compensation method of the present application.

[0034] In the figure: 1. First optical modulator; 2. Second optical modulator; 3. Beam splitter; 4. 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 combiner; 14. Fourth photodetector. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0036] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit the "first", "second" and "third" to different types.

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

[0038] In a first aspect, embodiments of the present application provide an optical modulator compensation method that can solve the problem in the prior art that compensation for non-ideal characteristics of an MZ modulator uses a lookup table approach and cannot be compensated in real time.

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

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

[0041] The absolute value is calculated continuously 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 to make the absolute value less than the corresponding preset threshold.

[0042] As shown in FIG1 , specifically, the steps of the optical modulator compensation method are as follows:

[0043] S101. Obtain a first phase shifter voltage for each optical modulator when the optical modulator output optical signal is at an extreme value. Obtain a first phase shifter voltage for each optical modulator when the phase difference between the two arms of the optical modulator is 180 degrees. Maintain a 90-degree phase difference between the optical signals of the two optical modulators 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.

[0044] S102. Determine whether the absolute value calculated by each optical modulator is less than the corresponding preset threshold. If so, proceed to S101; if not, proceed to S103.

[0045] S103 . Indicate that 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] During the entire adjustment process, if the optical power of another optical modulator was increased in the previous step S103, and the absolute value calculated in the current step S101 is found to be greater than or equal to the corresponding preset threshold, then the optical power of the other optical modulator is correspondingly reduced in the current step S103, and vice versa. By continuously calculating and adjusting through these steps, the absolute value of each optical modulator is modulated below the corresponding preset threshold, avoiding errors in the lookup table and improving compensation performance.

[0047] In the above step S101, the order of obtaining the first phase shifter voltage twice can be interchanged. Before obtaining, the phase difference of 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 the above S101, when the optical modulator outputs an extreme optical signal, 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. The first threshold and the second threshold are pre-set. In the above 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 a 90-degree phase difference between the optical signals of the two optical modulators and an extreme optical signal output by the optical modulator. V10 and V20 also have multiple values ​​that can satisfy a 90-degree phase difference between the optical signals of the two optical modulators and a 180-degree phase difference between the two arms of the optical modulator. The first and second thresholds are set based on the noise floor level and can be the same or different.

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

[0051] In the above S103, adjusting the optical power of each optical modulator may be to increase or decrease the optical power of one or both arms of the optical modulator, or to adjust the splitting ratio of the two arms of the optical modulator.

[0052] As shown in Figure 3, a specific embodiment of an optical modulator compensation method is provided to explain the principle of the method 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 arms of the first optical modulator 1 and the second optical modulator 2 are each equipped with a first phase shifter 5. A second phase shifter 6 is also provided at the output of the second optical modulator 2. A portion of the optical power of the first optical modulator 1 is extracted via a first photodetector 71; a portion of the optical power of the second optical modulator 2 is extracted via a second photodetector 72; and a portion of the optical power is extracted from the output optical waveguide of the optical modulator via a third photodetector 73.

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

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

[0056] Where ω0 is the frequency of the optical carrier, V i,RF (i=I,Q) is the RF voltage (as shown in Figure 3), V i,DC (i=I,Q) is the phase shifter voltage (such as the first phase shifter voltage of the first optical modulator and the first phase shifter voltage of the second optical modulator in FIG3 ), V π,RFis the voltage required by the RF electrode when the modulator produces a 180-degree phase shift, V π,DC The voltage required by the phase shifter when the modulator produces a 180-degree phase shift. i (i=I,Q) represents the intrinsic extinction ratio ER of the modulator i (i=I,Q), that is

[0057] To simplify the derivation, assume that the RF voltage is 0. When the optical modulator outputs the optical signal at the minimum value, that is, E out =0, we can get V1 and V2 as follows:

[0058] V10 is the first phase shifter voltage of optical modulator 1 when the phase difference between its two arms is 180 degrees. V20 is the first phase shifter voltage of optical modulator 2 when the phase difference between its two arms is 180 degrees. It can be seen that V10 = -Vpi,DC and V20 = Vpi,DC. Therefore, the absolute value of the difference between the two first phase shifter voltages obtained by each optical modulator can be calculated:

[0059] It can be seen from formulas (5)-(6) that 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.

[0060] In fact, in the presence of RF voltage, V1-V10 and V2-V20 can also be used as target values ​​to feedback-regulate the upper arm and / or lower arm optical power of the first optical modulator 1 and the upper arm and / or lower arm optical power of the second optical modulator 2.

[0061] Figure 2 shows a graph showing the relationship between the absolute value of the voltage difference across the first phase shifter and the optical power ratio between the two arms. Adjusting the optical power ratio between the upper and lower arms of the first optical modulator 1 results in almost no change in |V1-V10|, while a significant change in |V2-V20| occurs. When the optical powers of the upper and lower arms of the first optical modulator 1 are the same, |V2-V20| equals 0. This means that the optical power of the upper and / or lower arms of the first optical modulator 1 can be adjusted by feedback, by making |V2-V20| approach zero. Similarly, the optical power of the upper and / or lower arms of the second optical modulator 2 can be adjusted by feedback, by making |V1-V10| approach zero.

[0062] According to the above principle, as shown in FIG3 , this embodiment specifically includes the following steps:

[0063] 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.

[0064] 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 includes 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 first phase shifter voltage V10 of the first optical modulator 1 (i.e., the voltage of the first phase shifter 5 of the first optical modulator 1) is determined.

[0065] 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 then amplifies and filters it to produce a low-frequency electrical signal. 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 reaches 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 determined.

[0066] The third photodetector 73 extracts a portion of the optical power from the optical modulator's output optical waveguide, converts the optical signal into an electrical signal, and then amplifies and filters it to obtain a low-frequency electrical signal. The first phase shifters 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 optical modulator output optical signal 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.

[0067] Calculate |V1-V10| of the first optical modulator 1 and calculate |V2-V20| of the second optical modulator 2.

[0068] 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 ​​may also be maximum values. In this embodiment, the minimum value can be set by assigning a suitable threshold value; if it is less than the threshold value, the minimum value is considered to be reached; or, the initial voltage of the phase shifter is V, the adjustment direction is forward, 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 magnitude of the low-frequency voltage signal before and after, it is determined whether the low-frequency signal is adjusting in a decreasing direction (if the low-frequency voltage signal decreases, the adjustment direction remains unchanged; if the low-frequency voltage signal increases, the adjustment direction is reversed). If the adjustment direction reverses multiple times, the minimum value is considered to be reached. The minimum value of the optical modulator output optical signal is also set according to this method.

[0069] A102. Determine whether |V1-V10| is less than the preset second threshold, and whether |V2-V20| is less than the first threshold. If so, that is, |V1-V10| is less than the second threshold, and |V2-V20| is less than the first threshold, proceed to A101 without making any adjustments. If not, proceed to A103.

[0070] A103. If |V2 - V20| is less than the first threshold, adjust the optical power of optical modulator 1. Alternatively, if |V1 - V10| is less than the second threshold, adjust the optical power of optical modulator 2. After these adjustments, proceed to A101. The principle of adjustment is to keep the absolute value of each optical modulator below the corresponding preset threshold.

[0071] In some embodiments, as shown in FIG2 , the splitting ratio of the upper and lower arms of each optical modulator is changed by adjusting the beam splitter 3 of each optical modulator; or the splitting ratio of the upper and lower arms of each optical modulator is changed by adjusting the beam combiner 4 of each optical modulator, and the optical power is adjusted by the splitting ratio.

[0072] In other embodiments, as shown in FIG4 , an adjustable optical attenuator 8 and an optical amplifier 9 may be provided on the two arms of each optical modulator. 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 may 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 may be increased.

[0073] As shown in Figure 5, it is a schematic diagram of another embodiment of the optical modulator compensation method of the present application. This embodiment involves two optical polarization states, which is a polarization multiplexed optical modulator, including a first polarization state optical modulator 11 and a second polarization state optical modulator 12. The polarization states of the output waveguides of the two polarization state optical modulators are the same. The polarization state of the output light of the first polarization state optical modulator 11 or the output light of the second polarization state optical modulator 12 is rotated through a polarization rotation combiner 13 and combined with the output light of the other polarization state optical modulator. Among them, the first polarization state optical modulator 11 includes the first optical modulator 1 and the second optical modulator 2 in Figure 1, and the first polarization state optical modulator 12 also includes the first optical modulator 1 and the second optical modulator 2 in Figure 1.

[0074] The compensation principles and methods employed in this embodiment are the same as those in the previous embodiment. A first photodetector 71 extracts a portion of the optical power from the output of the first optical modulator 1 of the first polarization state optical modulator 11. After photoelectric conversion, amplification, and filtering, a low-frequency electrical signal is obtained. The first phase shifter 5 of the first optical modulator 1 of the first polarization state optical modulator 11 is adjusted to obtain a phase shifter voltage V10 of the first phase shifter 5 when the low-frequency electrical signal is at its minimum. A second photodetector 72 extracts a portion of the optical power from the output of the second optical modulator 2 of the first polarization state optical modulator 11. After photoelectric conversion, amplification, and filtering, a low-frequency electrical signal is obtained. The first phase shifter 5 of the second optical modulator 2 of the first polarization state optical modulator 11 is adjusted to obtain a phase shifter voltage V20 of the first phase shifter 5 when the low-frequency electrical signal is at its minimum. Then, a third photodetector 73 extracts a portion of the optical power from the output optical waveguide of the first polarization state optical modulator 11. After photoelectric conversion, amplification, and filtering, a low-frequency electrical signal is obtained. By adjusting the two first phase shifters 5 and the 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.

[0075] For the first polarization state optical modulator 11, determine whether |V1-V10| is less than a preset second threshold, and determine whether |V2-V20| is less than a first threshold. If so, 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 not, |V2-V20| is less than the first threshold, and the optical power of the first optical modulator 1 is adjusted; or if |V1-V10| is less than the second threshold, the optical power of the second optical modulator 2 is adjusted.

[0076] The same method can be used to adjust the second polarization state light modulator 12, which will not be described in detail here.

[0077] As shown in FIG5 , another modulation compensation method can also be used in this embodiment. This method is essentially the same as the compensation method described above. A first photodetector 71 extracts a portion of the optical power from the output of the first optical modulator 1 of the first polarization state optical modulator 11. After processing, a low-frequency electrical signal is obtained. 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. A second photodetector 72 extracts a portion of the optical power from the output of the second optical modulator 2 of the first polarization state optical modulator 11. After processing, a low-frequency electrical signal is obtained. 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 fourth photodetector 13 is used to extract a portion of the optical power from the output optical waveguide of the entire polarization-multiplexed optical modulator. 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 are obtained in real time according to the minimum value of the low-frequency electrical signal.

[0078] That is, in this embodiment, the fourth photodetector 13 extracts a portion of the optical power from the output optical waveguide of the entire polarization-multiplexed optical modulator 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 method for the first polarization-state optical modulator 11 and the second polarization-state optical modulator 12 is the same as in the above embodiment and will not be further described here.

[0079] It can be understood that in this embodiment, the minimum value of the low-frequency electrical signal is used to obtain the voltage of the corresponding phase shifter in real time. In other embodiments, the maximum value of the low-frequency electrical signal can also be used to obtain the voltage of the corresponding phase shifter in real time.

[0080] On the other hand, the present application provides an optical modulator compensation device that can implement the above 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.

[0081] The phase shift adjustment module includes a second phase shifter and two first phase shifters. The two first phase shifters are respectively arranged in one arm of each optical modulator; the second phase shifter is arranged 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.

[0082] The control module is used to obtain the first phase shifter voltage of each optical modulator when the phase difference between the two arms is 180 degrees; further used to obtain the first phase shifter voltage of each optical modulator when the output optical signal of the optical modulator is at an extreme value; and further used to calculate the absolute value of the difference between the two first phase shifter voltages obtained by each optical modulator.

[0083] The 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.

[0084] In some embodiments, the control module and the optical power adjustment module can be implemented together by the controller in the above embodiments.

[0085] In some implementations, each optical modulator includes an adjustable combiner and / or beam splitter, and the optical power adjustment module adjusts the splitting ratio of the two arms of the optical modulator in the optical path through the adjustable combiner and / or beam splitter, thereby adjusting the optical power.

[0086] Each optical modulator has an adjustable optical attenuator in one arm, and the optical power adjustment module adjusts the adjustable optical attenuator to reduce the optical power in that arm. Alternatively, each optical modulator has an optical amplifier in one arm, and the optical power adjustment module adjusts the optical amplifier to increase the optical power in that arm. This allows for adjustment of the splitting ratio between the two arms of each optical modulator.

[0087] The above-mentioned method of respectively obtaining the first phase shifter voltage of each optical modulator when the phase difference between the two arms is 180 degrees includes: extracting a portion of 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 the optical modulator to achieve an extreme value of the low-frequency electrical signal, and obtaining the first phase shifter voltage at this time.

[0088] The above-mentioned method of obtaining the first phase shifter voltage of each optical modulator when the optical signal output by the optical modulator reaches an extreme value includes: extracting a portion of optical power from the optical modulator output optical waveguide through a photodetector, processing the obtained low-frequency electrical signal through a control module, and adjusting the first phase shifter voltage and the second phase shifter voltage of the two optical modulators 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.

[0089] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0090] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0091] In some processes described in the embodiments of the present application, multiple operations or steps are included that appear in a specific order. However, it should be understood that these operations or steps may not be performed in the order in which they appear in the embodiments of the present application or may be performed in parallel. The sequence numbers of the operations are only used to distinguish between different operations, and the sequence numbers themselves do not represent any order of execution. In addition, these processes may include more or fewer operations, and these operations or steps may be performed in sequence or in parallel, and these operations or steps may be combined.

[0092] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A compensation method for an optical modulator, the optical modulator comprising two optical modulators, each optical modulator having two arms, characterized in that: A first phase shifter is arranged in one arm of each optical modulator, and the method comprises: Respectively obtain the first phase shifter voltage of each optical modulator when the optical signal output by the optical modulator is an extreme value; respectively 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, the phase difference of the optical signals of the two optical modulators is maintained at 90 degrees; calculate the absolute value of the difference between the two first phase shifter voltages obtained by each optical modulator; The above steps are performed continuously, and when the absolute value of one optical modulator is greater than or equal to the corresponding preset threshold, the optical power of another optical modulator is adjusted to make the absolute value less than the corresponding preset threshold.

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

3. The optical modulator compensation method according to claim 1, wherein: The first phase shifter voltage of each optical modulator is obtained when the optical modulator output optical signal is an extreme value, including: A portion of the optical power is extracted from the optical modulator output optical waveguide 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 respectively until the low-frequency electrical signal reaches an extreme value. The first phase shifters of the two optical modulators at this time are obtained respectively. Shifter voltage.

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

5. The optical modulator compensation method according to claim 1, wherein: The 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 comprises: The phase shift adjustment module includes a second phase shifter and two first phase shifters, wherein the two first phase shifters are respectively arranged in one arm of each optical modulator; the second phase shifter is arranged 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; A control module, used to respectively obtain the first phase shifter voltage of each optical modulator when the optical modulator outputs an optical signal of an extreme value; also used to respectively obtain the first phase shifter voltage of each optical modulator when the phase difference between the two arms of each optical modulator is 180 degrees; and also used to calculate the absolute value of the difference between the two first phase shifter voltages obtained by each optical modulator; The 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 according to 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 in the optical path through the adjustable beam combiner and / or beam splitter, thereby adjusting the optical power.

8. The optical modulator compensation device according to claim 6, characterized in that: An adjustable optical attenuator is arranged in one arm of each optical modulator, and the optical power adjustment module reduces the optical power of the arm by adjusting the adjustable optical attenuator; Alternatively, an optical amplifier is provided in one arm of each optical modulator, and the optical power regulating module increases the optical power of the arm by regulating the optical amplifier.

9. The optical modulator compensation device according to claim 6, characterized in that: The method of respectively obtaining the first phase shifter voltage when the phase difference between the two arms of each optical modulator is 180 degrees comprises: A portion of optical power is extracted from the output of an optical modulator through a photodetector, converted into an electrical signal through a control module, and processed to obtain a low-frequency electrical signal. The first phase shifter voltage of the optical modulator is adjusted to achieve an extreme value of the low-frequency electrical signal, and the first phase shifter voltage at this time is obtained.

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

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