Polarization control chip and system, control method

Abstract

The application provides a polarization control chip and system, a control method, which comprises an input optical switch, a phase shifter and an output optical switch; a beam splitter output is connected with a first polarization control unit input and a first coupler second input respectively; the first polarization control unit output is connected with the first coupler first input; the first coupler output is connected with a second polarization control unit input and a second coupler second input respectively; the second polarization control unit output is connected with the second coupler first input; and the second coupler output is connected with a beam combiner input. Through the state change of the optical switch, when the phase of the phase shifter reaches the boundary phase, the optical path is switched to the passive waveguide, so that the output light is continuous when the phase shifter resets, and because the state switching efficiency of the optical switch is high, the control period is not increased, and the problem that the existing polarization control chip has a long control period to realize continuous and no-reset polarization control is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication, in particular to a polarization control chip and system, and a control method. BACKGROUND

[0002] In some applications such as optical communication and optical sensing, it is necessary to lock the polarization light continuously and for a long time. For example, an integrated silicon optical chip laser radar made by using silicon-based photon technology has a TE mode of the outgoing polarization state of the emitted light, and when the laser is reflected by a reflecting object, the polarization state of the reflected light is uncertain. Therefore, it is necessary to actively lock the polarization state by using a polarization control chip to convert all the reflected light to the TE mode, so as to avoid the power loss caused by the TM mode which cannot be received and to improve the signal-to-noise ratio. Such an application requires that the polarization control chip can lock the polarization state of the reflected light in real time, and the locking process should be continuous regardless of the change of the polarization state of the reflected light, and the light power should not be suddenly changed.

[0003] To meet the above application requirements, the current polarization control chip is usually a two-stage phase shifter-Mach-Zehnder interference structure, wherein the first stage phase shifter can rotate the polarization state on the Poincare sphere around the S1 axis, and the second stage phase shifter and two 3dB couplers constitute a Mach-Zehnder interference structure, which has the effect of rotating the polarization state on the Poincare sphere around the S3 axis. Since the S1 axis is orthogonal to the S3 axis, the polarization control chip of this structure has two-dimensional control capability on the Poincare sphere, and can theoretically realize the conversion between any polarization states.

[0004] However, in the existing polarization control chip of the two-stage phase shifter-Mach-Zehnder interference structure, the phase shifter is a thermo-optic phase shifter, and the thermo-optic phase shifter has a phase modulation boundary. When the boundary is reached, a reset operation is required. Therefore, the polarization control chip cannot realize continuous and reset-free polarization control. To realize continuous and reset-free polarization control, the current common method is to increase the number of control units by redundant design, introduce more control degrees of freedom to search for a converging direction that will not reach the boundary, so as to avoid the reset operation. However, this method not only increases the cost of the polarization control chip, but also makes the control period longer and the control speed slower due to the introduction of more degrees of freedom, thereby reducing the overall performance of the device. SUMMARY

[0005] The present application aims to provide a polarization control chip and system, and a control method, to solve the problems of high cost and long control period in the existing polarization control chip for realizing continuous and reset-free polarization control.

[0006] To solve the above technical problems, the present application provides a polarization control chip, comprising a beam splitter, a first polarization regulation unit, a first coupler, a second polarization regulation unit, a second coupler and a beam combiner; the first polarization regulation unit and the second polarization regulation unit each comprise an input optical switch, a phase shifter and an output optical switch connected in sequence;

[0007] The input end of the first polarization regulation unit is connected with the first output end of the beam splitter, and the output end of the first polarization regulation unit is connected with the first input end of the first coupler; the second output end of the beam splitter is connected with the second input end of the first coupler; the input end of the second polarization regulation unit is connected with the first output end of the first coupler, and the output end of the second polarization regulation unit is connected with the first input end of the second coupler; the second output end of the first coupler is connected with the second input end of the second coupler; the first output end of the second coupler is connected with the first input end of the beam combiner, and the second output end of the second coupler is connected with the second input end of the beam combiner.

[0008] Optionally, in the polarization control chip, the input optical switch comprises a first coupler, a first sub-phase shifter and a second coupler; the output optical switch comprises a third coupler, a second sub-phase shifter and a fourth coupler;

[0009] The input end of the first coupler in the first polarization regulation unit is connected with the first output end of the beam splitter, and the input end of the first coupler in the second polarization regulation unit is connected with the first output end of the first coupler; the input end of the first sub-phase shifter is connected with the first output end of the first coupler, and the output end of the first sub-phase shifter is connected with the first input end of the second coupler; the second output end of the first coupler is connected with the second input end of the second coupler; the first output end of the second coupler is connected with the input end of the phase shifter; the second output end of the second coupler is connected with the second input end of the third coupler; the output end of the phase shifter is connected with the first input end of the third coupler; the first output end of the third coupler is connected with the first input end of the fourth coupler, and the second output end of the third coupler is connected with the input end of the second sub-phase shifter; the output end of the second sub-phase shifter is connected with the second input end of the fourth coupler; the output end of the fourth coupler in the first polarization regulation unit is connected with the first input end of the first coupler, and the output end of the fourth coupler in the second polarization regulation unit is connected with the first input end of the second coupler.

[0010] Optionally, in the polarization control chip, when the second coupler and the third coupler are directional couplers, the first sub-phase shifter and the second sub-phase shifter are located on the same side of the phase shifter.

[0011] Optionally, in the polarization control chip, when the second coupler and the third coupler are multi-mode interferometers, the first sub-phase shifter is located on the same side of the phase shifter, and the second sub-phase shifter is located on the different side of the phase shifter.

[0012] Optionally, in the polarization control chip, the second output end of the beam splitter is connected to the second input end of the first-order coupler through a passive waveguide; and the second output end of the first-order coupler is connected to the second input end of the second-order coupler through a passive waveguide.

[0013] Optionally, in the polarization control chip, the first-order polarization control unit and the second-order polarization control unit each further include at least one photodetector; the photodetector is used to acquire light intensity, so as to perform phase calibration on the first sub-phase shifter, the phase shifter and the second sub-phase shifter according to the light intensity.

[0014] Optionally, in the polarization control chip, the first-order polarization control unit and the second-order polarization control unit each include a first photodetector, a second photodetector and a third photodetector; the first photodetector is connected to the second output end of the second coupler, so as to perform phase calibration on the first sub-phase shifter; the second photodetector is connected to the second output end of the third coupler, so as to perform phase calibration on the phase shifter; and the third photodetector is connected to the output end of the fourth coupler, so as to perform phase calibration on the second sub-phase shifter.

[0015] To solve the above technical problems, the application further provides a polarization control system, which comprises a polarization analysis module, a control module and the polarization control chip as any one of the above.

[0016] To solve the above technical problems, the application further provides a polarization control method applied to the polarization control chip as any one of the above, which comprises the following steps.

[0017] initializing the polarization control chip;

[0018] inputting a polarized light into the polarization control chip;

[0019] The polarization control chip modulates the input polarized light in phase and intensity, and outputs the modulated polarized light, wherein the phase of the phase shifter continuously changes under the convergence algorithm of polarization control;

[0020] When the phase of the phase shifter reaches the boundary phase, the states of the input optical switch and the output optical switch are simultaneously switched to change the polarized light path in the polarization control chip;

[0021] The phase shifter is reset to the initial phase;

[0022] The input optical switch and the output optical switch are reset to the initial state;

[0023] The polarization control chip continues to modulate the input polarized light in phase and intensity, and outputs the modulated polarized light.

[0024] Optionally, in the polarization control method, the method of initializing the polarization control chip comprises:

[0025] The phase modulation range of the phase shifter is set to [0, 4k ] and the initial phase is set to 2k ;

[0026] The input optical switch and the output optical switch are set to the on state.

[0027] Optionally, in the polarization control method, the states of the input optical switch and the output optical switch are simultaneously switched in the form of pulse charging.

[0028] Optionally, in the polarization control method, before initializing the polarization control chip, the polarization control method comprises:

[0029] Phase calibration is performed on the input optical switch, the phase shifter and the output optical switch.

[0030] Optionally, in the polarization control method, the input optical switch comprises a first coupler, a first sub-phase shifter and a second coupler; the output optical switch comprises a third coupler, a second sub-phase shifter and a fourth coupler; and the method of performing phase calibration on the input optical switch, the phase shifter and the output optical switch comprises:

[0031] A first photodetector is connected to the second output end of the second coupler, a second photodetector is connected to the second output end of the third coupler, and a third photodetector is connected to the output end of the fourth coupler;

[0032] In the first preset voltage range, the first sub-phase shifter is scanned with a first step; when the light intensity detected by the first photodetector is the minimum, the voltage at this time is corresponded to the first off voltage of the first sub-phase shifter; when the light intensity detected by the first photodetector is the maximum, the voltage at this time is corresponded to the first on voltage of the first sub-phase shifter;

[0033] In the second preset voltage range, the first sub-phase shifter is scanned with a second step and the phase shifter is scanned with a third step; the light intensity detected by the second photodetector is used to calculate the variance of the light power of the phase shifter in each third step range; when the variance is 0, the voltage at this time is corresponded to the 0 phase and 4k phase of the phase shifter;

[0034] The phase of the first sub-phase shifter is set to the phase corresponding to the first off voltage, and the second sub-phase shifter is scanned with a fourth step in the third preset voltage range; when the light intensity detected by the third photodetector is the minimum, the voltage at this time is corresponded to the second off voltage of the second sub-phase shifter; when the light intensity detected by the third photodetector is the maximum, the voltage at this time is corresponded to the second on voltage of the second sub-phase shifter.

[0035] Optionally, in the polarization control method, the method of scanning the first sub-phase shifter with the second step and scanning the phase shifter with the third step comprises:

[0036] When the first sub-phase shifter is scanned with the second step for one period of scanning, the voltage of the phase shifter is increased by a third step, wherein the second step is greater than the third step.

[0037] The polarization control chip, system and control method provided by the present invention include a beam splitter, a first-level polarization control unit, a first-level coupler, a second-level polarization control unit, a second-level coupler and a beam combiner; the first-level polarization control unit and the second-level polarization control unit both include an input optical switch, a phase shifter and an output optical switch connected in sequence by optical paths; the input end of the first-level polarization control unit is connected to the first output end of the beam splitter, and the output end of the first-level polarization control unit is connected to the first input end of the first-level coupler; the second output end of the beam splitter is connected to the second input end of the first-level coupler; the input end of the second-level polarization control unit is connected to the first output end of the first-level coupler, and the output end of the second-level polarization control unit is connected to the first input end of the second-level coupler; the second output end of the first-level coupler is connected to the second input end of the second-level coupler; the first output end of the second-level coupler is connected to the first input end of the beam combiner, and the second output end of the second-level coupler is connected to the second input end of the beam combiner. By adding an input optical switch and an output optical switch at both ends of the phase shifter based on the structure of an existing polarization control chip, the path states of the input optical switch and the output optical switch can be changed so that when the phase of the phase shifter reaches the boundary phase, the polarized light path is switched to the passive waveguide, thereby ensuring the continuity of the output polarized light when the phase shifter is reset. Since no additional control unit is added, the cost is controlled, and the high efficiency of the optical switch state switching does not increase the control cycle, thus solving the problems of high cost and long control cycle in existing polarization control chips for achieving continuous polarization control without reset. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic structural diagram of the polarization control chip provided in this embodiment;

[0039] Figure 2 A schematic structural diagram of the phase shifter provided in this embodiment;

[0040] Figure 3 A schematic diagram of the structure of the input optical switch provided in this embodiment;

[0041] Figure 4 A schematic diagram of the structure of the output optical switch provided in this embodiment;

[0042] Figure 5 A schematic structural diagram of a polarization control unit when the second coupler and the third coupler provided in this embodiment are directional couplers;

[0043] Figure 6 A schematic structural diagram of a polarization control unit when the second coupler and the third coupler provided in this embodiment are multi-mode interferometers;

[0044] Figure 7A structure schematic diagram of the polarization control unit with a photoelectric detector provided for the embodiment is shown in FIG. 1;

[0045] Figure 8 A structure schematic diagram of the polarization control system provided for the embodiment is shown in FIG. 2;

[0046] Figure 9 A flow chart of the polarization control method provided for the embodiment is shown in FIG. 3;

[0047] Figure 10 A control schematic diagram of the optical switch control pulse and response time provided for the embodiment is shown in FIG. 4;

[0048] In the drawings, the reference signs are explained as follows:

[0049] 110-beamsplitter; 120-first polarization control unit; 130-first coupler; 140-second polarization control unit; 150-second coupler; 160-beam combiner;

[0050] 210-input optical switch; 220-phase shifter; 230-output optical switch;

[0051] 211-first coupler; 212-first sub-phase shifter; 213-second coupler;

[0052] 231-third coupler; 232-second sub-phase shifter; 233-fourth coupler. DETAILED DESCRIPTION

[0053] The polarization control chip and system, and the control method provided by the present application are further described in detail below in combination with the drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and all use non-precise proportions, only to facilitate and clarify the purpose of assisting in the description of the embodiments of the present application. In addition, the structures shown in the drawings are often part of the actual structure. In particular, the emphasis of each drawing needs to be different, sometimes different proportions are used.

[0054] It should be noted that "first", "second", and the like in the description and claims of the present application and the drawings are used to distinguish similar objects in order to describe the embodiments of the present application, and are not intended to describe a specific order or sequence. It should be understood that the structures used in this way can be interchanged under appropriate circumstances. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0055] The present embodiment provides a polarization control chip, as shown in FIG. 1.Figure 1 As shown, it comprises a beam splitter 110, a first polarization control unit 120, a first coupler 130, a second polarization control unit 140, a second coupler 150 and a beam combiner 160; the first polarization control unit 120 and the second polarization control unit 140 each comprises an input optical switch 210, a phase shifter 220 and an output optical switch 230 connected in sequence.

[0056] The input end of the first polarization control unit 120 is connected with the first output end of the beam splitter 110, and the output end of the first polarization control unit 120 is connected with the first input end of the first coupler 130; the second output end of the beam splitter 110 is connected with the second input end of the first coupler 130; the input end of the second polarization control unit 140 is connected with the first output end of the first coupler 130, and the output end of the second polarization control unit 140 is connected with the first input end of the second coupler 150; the second output end of the first coupler 130 is connected with the second input end of the second coupler 150; the first output end of the second coupler 150 is connected with the first input end of the beam combiner 160, and the second output end of the second coupler 150 is connected with the second input end of the beam combiner 160.

[0057] The polarization control chip provided by the embodiment can change the pass state of the input optical switch and the output optical switch, so that when the phase of the phase shifter reaches the boundary phase, the polarization light path is switched to the passive waveguide, thereby ensuring the continuity of the output polarization light when the phase shifter is reset. Since no additional control unit is added, the cost is controlled, and since the state switching efficiency of the optical switch is high, the control period will not be increased, thereby solving the problems of high cost and long control period in the existing polarization control chip for realizing continuous and reset-free polarization control.

[0058] Specifically, in the embodiment, the beam splitter 110, the first polarization control unit 120, the first coupler 130, the second polarization control unit 140, the second coupler 150 and the beam combiner 160 are arranged in sequence along the optical path direction. The first coupler 130, the second polarization control unit 140 and the second coupler 150 constitute a Mach-Zehnder interference structure.

[0059] In actual application, for example, Figure 1As shown, the beam splitter 110 is a 1x2 beam splitter, thereby splitting the input polarized light into two paths; the first polarization control unit 120 is located on the upper arm branch of the beam splitter 110, and the lower arm branch of the beam splitter 110 is a passive waveguide; the first coupler 130 can be a 2x2 3dB coupler, thereby coupling the two input light and then splitting into two output light; the second polarization control unit 140 is located on the same side as the first polarization control unit 120, i.e. on the upper arm branch, and the corresponding lower arm branch is also a passive waveguide; the second coupler 150 is consistent with the first coupler 130, which can be a 2x2 3dB coupler, thereby coupling the two input light and then splitting into two output light; the beam combiner 160 corresponds to the beam splitter 110, which is a 2x1 beam combiner, thereby combining the two output light from the second coupler 150 and then outputting.

[0060] Further, as shown in Figure 2 The phase shifters in the first polarization control unit 120 and the second polarization control unit 140 include two branch waveguides with the same length, i.e. the upper arm and the lower arm, wherein the refractive index of the upper arm waveguide region can change based on the thermo-optic effect and the electro-optic effect according to the applied voltage signal. The change in refractive index causes the speed of light transmission in the upper arm waveguide to be different from the speed of light transmission in the lower arm waveguide, thereby causing the time required for the polarized light to pass through the upper arm waveguide and the lower arm waveguide with the same length to be different, and thus a phase difference is generated.

[0061] And, as shown in Figure 3 The input end optical switch 210 includes a first coupler 211, a first sub-phase shifter 212, and a second coupler 213 arranged in sequence along the optical path.

[0062] In actual application, the first coupler 211 can be a 1x2 coupler, thereby splitting the optical path into two paths, one of which is sent to the upper arm of the first sub-phase shifter 212 for phase shifting, and the other of which is sent to the passive waveguide of the lower arm of the first sub-phase shifter 212; the second coupler 213 can be a 2x2 3dB coupler, and the second coupler 213 couples and outputs the two light output by the first sub-phase shifter 212 into the phase shifter 220.

[0063] And, as shown in Figure 4 The output end optical switch 230 includes a third coupler 231, a second sub-phase shifter 232, and a fourth coupler 233 arranged in sequence along the optical path.

[0064] In actual application, the third coupler 231 can be a 2x2 3dB coupler, the third coupler 231 couples two light paths output by the phase shifter 220 and outputs two light paths into the second sub-phase shifter 232, one of the two light paths is sent into the upper arm of the second sub-phase shifter 232 to be phase shifted, and the other is sent into the passive waveguide of the lower arm of the second sub-phase shifter 232; the fourth coupler 233 can be a 2x1 coupler, so as to combine the two light paths into one light path for output.

[0065] In combination Figure 3 The working principle of the optical switch provided in the embodiment is described as follows: the first sub-phase shifter 212 in the input end optical switch 210 is used to cause phase delay of two light paths, and then the coupling interference of the second coupler 213 is used to cause additional phase 1 and 0, so that the light path is completely conducted upward or completely conducted downward. The complete upward conduction is defined as the conduction state (off state) of the optical switch, and the complete downward conduction is defined as the disconnection state (on state) of the optical switch. The voltage applied to the optical switch is switched between the voltage V1 and V0 corresponding to the phase 1 and 0, so as to realize the conversion of the on-off state of the optical switch.

[0066] Since the structure of the input end optical switch 210 is symmetrical to the structure of the output end optical switch 230, the working principle of the optical switch is described only by taking the input end optical switch 210 as an example, and the working principle of the output end optical switch 230 is similar, which will not be described herein.

[0067] Specifically, in the embodiment, in combination Figure 1As shown, the input end of the first coupler 211 in the first polarization control unit 120 is connected with the first output end of the beam splitter 110, and the input end of the first coupler 211 in the second polarization control unit 140 is connected with the first output end of the first coupler 130; the input end of the first sub-phase shifter 212 is connected with the first output end of the first coupler 211, and the output end of the first sub-phase shifter 212 is connected with the first input end of the second coupler 213; the second output end of the first coupler 211 is connected with the second input end of the second coupler 213; the first output end of the second coupler 213 is connected with the input end of the phase shifter 220; the second output end of the second coupler 213 is connected with the second input end of the third coupler 231; the output end of the phase shifter 220 is connected with the first input end of the third coupler 231; the first output end of the third coupler 231 is connected with the first input end of the fourth coupler 233, and the second output end of the third coupler 231 is connected with the input end of the second sub-phase shifter 232; the output end of the second sub-phase shifter 232 is connected with the second input end of the fourth coupler 233; the output end of the fourth coupler 233 in the first polarization control unit 120 is connected with the first input end of the first coupler 130, and the output end of the fourth coupler 233 in the second polarization control unit 140 is connected with the first input end of the second coupler 150.

[0068] Further, in the embodiment, when the second coupler 213 and the third coupler 231 are directional couplers, the first sub-phase shifter 212 and the second sub-phase shifter 232 are located on the same side of the phase shifter 220. As shown, the first sub-phase shifter 212 and the second sub-phase shifter 232 are located on the upper arm branch of the phase shifter 220. Figure 5

[0069] In another specific embodiment, when the second coupler 213 and the third coupler 231 are multi-mode interferometers, the first sub-phase shifter 212 is located on the same side of the phase shifter 220, and the second sub-phase shifter 232 is located on the different side of the phase shifter 220. As shown, the first sub-phase shifter 212 is located on the upper arm branch of the phase shifter 220, and the second sub-phase shifter 232 is located on the lower arm branch of the phase shifter 220. Figure 6

[0070] It should be noted that, in order to clearly show the connection relationship of each optical element, the above-mentioned first sub-phase shifter 212, phase shifter 220 and second sub-phase shifter 232 all refer to one branch of the phase shifter in which phase shift occurs.

[0071] ​​Further, in order to facilitate phase calibration of the first sub-phase shifter 212, the second sub-phase shifter 232 and the phase shifter 220, thereby facilitating state control of the input optical switch 210 and the output optical switch 230, and reset control of the phase shifter 220, in the embodiment, the first polarization control unit 120 and the second polarization control unit 140 each further include at least one photodetector; the photodetector is used to obtain light intensity, so as to perform phase calibration on the first sub-phase shifter 212, the phase shifter 220 and the second sub-phase shifter 232 according to the light intensity.

[0072] Specifically, in the embodiment, as shown in Figure 7 , the first polarization control unit 120 and the second polarization control unit 140 each include a first photodetector pd1, a second photodetector pd2 and a third photodetector pd3; the first photodetector pd1 is connected to the second output end of the second coupler 213, so as to perform phase calibration on the first sub-phase shifter 212; the second photodetector pd2 is connected to the second output end of the third coupler 231, so as to perform phase calibration on the phase shifter 220; and the third photodetector pd3 is connected to the output end of the fourth coupler 233, so as to perform phase calibration on the second sub-phase shifter 232.

[0073] Hereinafter, the working principle of the polarization control chip provided in the embodiment for realizing continuous reset-free polarization control is described in combination with Figure 1 , Figure 5 and Figure 6 .

[0074] In the embodiment, the polarization control chip is made of silicon material and is manufactured by using a silicon optical process.

[0075] When the polarization control chip starts to work, the conduction direction of the input optical switch 210 and the output optical switch 230 is the active waveguide where the phase shifter 220 is located, and the initial phase of the phase shifter 220 is set to 2 , the lower boundary of the phase adjustment is set to 0, and the upper boundary is set to .

[0076] All the phase shifters (including the first sub-phase shifter 212, the phase shifter 220 and the second sub-phase shifter 232) are based on the thermo-optic effect and have a linear relationship with the applied power, and the transmission matrix is represented as .

[0077] When the 2x2 coupler (including the second coupler 213, the third coupler 231, etc.) is a directional coupler, as shown in Figure 5 , the transmission matrix is When the input light is incident only from the lower port (second input end), the directional coupler is a 1x2 beam splitter.

[0078] The transmission matrix of the polarization control unit composed of the input optical switch 210, the phase shifter 220 and the output optical switch 230 is wherein, φ1 represents the phase of the first sub-phase shifter 212, φ2 represents the phase of the phase shifter 220, φ3 represents the phase of the second sub-phase shifter 232.

[0079] When , the transmission matrix is At this time, the input optical switch 210 and the output optical switch 230 make all the light pass through the active waveguide of the upper arm branch, so that the phase shifter 220 can realize continuous phase modulation.

[0080] When reaches the boundary 0 or 4 , at this time, the state of the input optical switch 210 and the output optical switch 230 is switched, so that , at this time, the transmission matrix is , all the light is guided out from the passive waveguide. At this time, the output result of the polarization control chip is independent of the change of , and is reset to the initial phase , and the output light intensity and phase will not change.

[0081] At the same time, considering the change of the output phase and intensity during the switching of the input optical switch 210 and the output optical switch 230: when reaches the boundary 0 or 4 , the transmission matrix is When changes from to , synchronously changes from 0 to , and always keeps , the transmission matrix becomes , that is, the output light intensity and phase of the polarization control chip do not change during the switching of the input optical switch 210 and the output optical switch 230, and continuous infinite phase modulation is realized.

[0082] When the 2x2 coupler (including the second coupler 213, the third coupler 231, etc.) is a multimode interferometer, such as Figure 6As shown, the transmission matrix of the polarization control unit composed of the input optical switch 210, the phase shifter 220 and the output optical switch 230 is .

[0083] When , , the transmission matrix is For the phase shifter 220, at this time, the input optical switch 210 and the output optical switch 230 make all the light pass through the active waveguide of the upper arm branch, so that the phase shifter 220 can realize continuous phase modulation.

[0084] When reaches the boundary 0 or 4 , , at this time, the state of the input optical switch 210 and the output optical switch 230 is switched, so that , , at this time, the transmission matrix is , all the light is guided out from the passive waveguide. At this time, the output result of the polarization control chip is independent of the change of , and is reset to the initial phase , and the light intensity and phase of the output end will not change.

[0085] At the same time, considering the change of the output phase and intensity during the switching process of the input optical switch 210 and the output optical switch 230: when reaches the boundary 0 or 4 , the transmission matrix is When changes from to , synchronously changes from to , and always keeps , the transmission matrix becomes , that is, the light intensity and phase of the output end of the polarization control chip do not change during the switching process of the input optical switch 210 and the output optical switch 230, and continuous infinite phase modulation is realized.

[0086] Based on this, the embodiment further provides a polarization control system, as shown in Figure 8 , comprising a polarization analysis module, a control module and the polarization control chip as described above; the polarization analysis module is used for analyzing and processing the light signal output by the secondary coupler to obtain a feedback signal; the control module is used for generating a control signal according to the feedback signal, so as to control the on-off state of the input optical switch and the output optical switch by using the control signal, and control the reset of the phase shifter.

[0087] Specifically, in this embodiment, the polarization analysis module obtains the optical signal I from the two output ends of the secondary coupler 150. x and I y , through I x and I y The control module generates two sets of control signals based on the feedback signals to control the on / off states of the input optical switch 210 and the output optical switch 230 in the primary polarization control unit 120 and the secondary polarization control unit 140, respectively, and to reset the phase shifter 220.

[0088] The polarization control system provided in this embodiment is particularly suitable for laser radar application scenarios, and can achieve continuous polarization control without reset while controlling costs.

[0089] Furthermore, this embodiment also provides a polarization control method, which is applied to the polarization control chip as described above. Figure 9 As shown, the polarization control method includes:

[0090] S1, initialize the polarization control chip;

[0091] S2, input polarized light to the polarization control chip;

[0092] S3, the polarization control chip modulates the phase and intensity of the input polarized light and outputs the modulated polarized light. The phase of the phase shifter changes continuously under the convergence algorithm of the polarization control.

[0093] S4, when the phase of the phase shifter reaches the boundary phase, the states of the input optical switch and the output optical switch are switched simultaneously to change the polarization light path in the polarization control chip;

[0094] S5, the phase shifter is reset to the initial phase;

[0095] S6, the input optical switch and the output optical switch are reset to the initial state;

[0096] In step S7, the polarization control chip continues to perform phase and intensity modulation on the input polarized light and outputs the modulated polarized light.

[0097] The polarization control method provided in this embodiment changes the path states of the input and output optical switches so that when the phase of the phase shifter reaches a boundary phase, the polarized light path is switched to the passive waveguide, thereby ensuring the continuity of the output polarized light when the phase shifter is reset. Because no additional control unit is required, costs are controlled, and the high switching efficiency of the optical switch does not increase the control cycle. This solves the high cost and long control cycle problems of existing polarization control chips for achieving continuous, reset-free polarization control.

[0098] Specifically, in the embodiment, step S1, initializing the polarization control chip.

[0099] In a specific embodiment, initializing the polarization control chip includes setting the phase-shifting range and the initial phase of the phase shifter 220, for example, setting the phase-shifting range of the phase shifter to [0, 4k ] and the initial phase to 2k . And initializing the polarization control chip also includes setting the initial states of the input optical switch 210 and the output optical switch 230, for example, setting the states of the input optical switch 210 and the output optical switch 230 to the on state, that is, when the polarization control chip starts to work, the light is transmitted through the active waveguide.

[0100] Further, in the embodiment, step S2, inputting the polarized light to the polarization control chip.

[0101] Specifically, the polarized light is input to the input end of the beam splitter 110 and is orthogonally decomposed into two beams of TE mode light entering the upper arm active waveguide and the lower arm passive waveguide for transmission.

[0102] And, in the embodiment, step S3, the polarization control chip modulates the phase and intensity of the input polarized light, and outputs the modulated polarized light, wherein the phase of the phase shifter continuously changes under the convergence algorithm of polarization control.

[0103] Specifically, the phase and intensity modulation of the polarized light is realized through the first polarization control unit 120, the first coupler 130, the second polarization control unit 140, and the second coupler 150. The specific modulation method is not the focus of the present application, and those skilled in the art can learn the working principle of the phase and intensity modulation of the polarization control chip based on the working principle of the existing polarization control chip, and the present application will not be described again.

[0104] Further, in the embodiment, step S4, when the phase of the phase shifter reaches the boundary phase, the states of the input optical switch and the output optical switch are simultaneously switched to change the polarized light path in the polarization control chip.

[0105] Specifically, as analyzed above, when the phase of the phase shifter 220 reaches the boundary phase 0 or 4k , the states of the input optical switch 210 and the output optical switch 230 are changed from the on state to the off state, so that the light path transmission path in the first polarization control unit 120 and the second polarization control unit 140 is changed from the active waveguide path to the passive waveguide path.

[0106] And, in the embodiment, step S5, the phase shifter 220 is reset to the initial phase.

[0107] Specifically, when the optical path transmission path is changed to the passive waveguide path, the phase change of the phase shifter 220 will not affect the phase and intensity of the output light, and thus the phase shifter 220 can be reset to the initial phase 2k at this time .

[0108] In addition, in the embodiment, in step S6, the input optical switch 210 and the output optical switch 230 are reset to the initial state.

[0109] Specifically, after the phase shifter 220 is reset, the phase thereof can continue to change continuously under the convergence algorithm of polarization control, so as to realize phase and intensity modulation of the input polarized light, and thus the state of the input optical switch 210 and the output optical switch 230 can be restored to the on state, so that the optical path transmission path is changed from the passive waveguide path to the active waveguide path.

[0110] Finally, in the embodiment, in step S7, the polarization control chip continues to perform phase and intensity modulation on the input polarized light and outputs the modulated polarized light.

[0111] Specifically, step S7 repeats the process of step S3 and circulates to realize phase and intensity modulation of the input light.

[0112] Preferably, considering that the phase of the phase shifter 220 is reset when reaching the boundary to realize continuous control of polarization and to ensure that the phase and intensity of the light do not change, but the input polarization state will still change to cause the output polarization state to deviate from the locked position. Therefore, the reset process needs to be completed as soon as possible. To this end, in the embodiment, the response speed of the silicon optical thermal phase shifter is improved in the form of pulse charging, and then the state of the input optical switch 210 and the output optical switch 230 is switched at the same time in a very short time.

[0113] In actual application, it is assumed that the switch voltages of the optical switches after calibration are V0 and V1 respectively, wherein V1 > V0. When the switch is switched, the voltage is switched from V0 to V1. In the initial stage of switching, the voltage generates a pulse to make the heat accumulate quickly, and the size of the pulse is determined by the experimental value, which is usually 2 times of V1 and does not exceed the voltage resistance range of the polarization control chip; the pulse duration is about 5% of the response time.

[0114] As shown in Figure 10 , the left side is the voltage used by the existing conventional control optical switch switching and the time required for the state of the optical switch to switch completely under the voltage, and the right side is the voltage used by the embodiment and the time required for the state of the optical switch to switch completely under the voltage. From Figure 10It can be seen that, under the existing conventional control voltage, the optical switch needs 30 μs to complete the state switching; while the control mode of pulse charging adopted in the embodiment needs only 0.5 μs for the optical switch to complete the state switching, greatly improving the response speed of the thermo-optic phase shifter, thereby ensuring that the change of the input polarization state is very small and can be ignored during the resetting of the phase shifter 220, and further ensuring that the output polarization state will not deviate from the locked position.

[0115] Preferably, in order to ensure that the states of the input optical switch 210 and the output optical switch 230 can be switched in time and accurately, and in order to ensure that the phase shifter 220 can be reset in time and accurately, the phases of the first sub-phase shifter 212 in the input optical switch 210, the second sub-phase shifter 232 in the output optical switch 230, and the phase shifter 220 need to be calibrated. Therefore, before initializing the polarization control chip in step S1, the polarization control method provided in the embodiment further comprises:

[0116] S0, phase calibration is performed on the input optical switch, the phase shifter, and the output optical switch.

[0117] Specifically, in the embodiment, a plurality of photoelectric detectors are added for detecting light intensity. In a specific embodiment, as shown in FIG. 2, a first photoelectric detector pd1 is connected to the second output end of the second coupler 213, a second photoelectric detector pd2 is connected to the second output end of the third coupler 231, and a third photoelectric detector pd3 is connected to the output end of the fourth coupler 233. Figure 7

[0118] In actual application, a 1% light splitting link can be introduced at the position where the photoelectric detector needs to be connected in the polarization control unit, and the photoelectric detector is connected to the light splitting link, so that the corresponding light intensity can be detected without affecting the normal function of the polarization control chip, ensuring that the optical path loss is within an acceptable range.

[0119] Taking the second coupler 213 and the third coupler 231 as directional couplers as an example, the phase calibration method of the first sub-phase shifter 212, the second sub-phase shifter 232, and the phase shifter 220 provided in the embodiment is described.

[0120] For the first sub-phase shifter 212, in order to achieve accurate switching of the state of the input optical switch 210, 0 and Thus, the control voltages for the on and off states of the input optical switch 210 are obtained. Specifically, within a first preset voltage range (for example, 0~Vmax), the first sub-phase shifter 212 is scanned with a first step size, and the change of the light intensity monitored by the first photoelectric detector pd1 is observed. Assuming that the input light intensity is E, the light intensity expression of the first photoelectric detector pd1 is ​When the light intensity detected by the first photodetector pd1 is the minimum, the voltage at this time is corresponded to the 0 phase of the first sub-phase shifter 212, i.e. the voltage is the first off voltage of the first sub-phase shifter 212; when the light intensity detected by the first photodetector pd1 is the maximum, the voltage at this time is corresponded to the 4k phase of the first sub-phase shifter 212, i.e. the voltage is the first on voltage of the first sub-phase shifter 212. The voltages corresponding to the 0 and 4k phases are recorded to complete the calibration of the first sub-phase shifter 212.

[0121] For the phase shifter 220, in order to achieve accurate reset, the voltages at the phase shifting boundaries (0 and 4k phases) need to be obtained. Specifically, in the second preset voltage range, the first sub-phase shifter 212 is scanned with the second step and the phase shifter 220 is scanned with the third step, wherein the first sub-phase shifter 212 can be quickly scanned with a sawtooth wave and the phase shifter 220 can be slowly scanned, i.e. the second step is greater than the third step, and specifically, when the first sub-phase shifter 212 completes a period of scanning with the second step, the voltage of the phase shifter 220 is increased by a third step. In the scanning process, the light intensity of the second photodetector pd2 is expressed as When , the light intensity of the second photodetector pd2 is , which is independent of the state of the first sub-phase shifter 212. Therefore, by calculating the light power variance of the phase shifter 220 in each third step range (one scanning period of the first sub-phase shifter 212), when the light power variance is 0, the voltage at this time is corresponded to the 0 phase and the 4k phase of the phase shifter 220. The voltage at this time is recorded to complete the calibration of the phase shifter 220.

[0122] For the second sub-phase shifter 232, in order to achieve accurate switching of the state of the output optical switch 230, the voltages corresponding to the 2k and phases need to be obtained, so as to obtain the control voltages of the on and off states of the output optical switch 230. Specifically, the phase of the first sub-phase shifter 212 is set to the phase corresponding to the first off voltage, i.e. the 0 phase, and the phase of the phase shifter 220 can be any value, the second sub-phase shifter 232 is scanned with the fourth step in the third preset voltage range (for example, 0~Vmax), and the change of the light intensity monitored by the third photodetector pd3 is observed. At this time, the light intensity of the third photodetector pd3 is expressed as When the light intensity detected by the third photodetector pd3 is the minimum, the voltage at this time is corresponded to the 2k The phase corresponding to the voltage is the second closing voltage of the second sub-phase shifter 232. When the light intensity detected by the third photoelectric detector pd3 is the maximum, the voltage at this time is corresponded to the second opening voltage of the second sub-phase shifter 232 The phase corresponding to the voltage is the second closing voltage of the second sub-phase shifter 232. When the light intensity detected by the third photoelectric detector pd3 is the maximum, the voltage at this time is corresponded to the second opening voltage of the second sub-phase shifter 232 And The phase corresponding to the voltage is the second closing voltage of the second sub-phase shifter 232. When the light intensity detected by the third photoelectric detector pd3 is the maximum, the voltage at this time is corresponded to the second opening voltage of the second sub-phase shifter 232

[0123] In actual application, the first preset voltage range, the second preset voltage range, the third preset voltage range, the first step, the second step, the third step, and the fourth step used in the calibration process can be reasonably set according to actual needs, and the application does not limit this. Wherein, the smaller the step size is set, the more accurate the voltage value obtained is, although the calibration process may take longer. Of course, in some specific embodiments, a variable step size can also be used, that is, a larger step size is used for rough scanning, and a smaller step size is used for fine scanning in the range close to the target voltage.

[0124] And, when the second coupler 213 and the third coupler 231 are a multimode interferometer, the above calibration method can be referred to, when the light intensity detected by the first photoelectric detector pd1 is the minimum, the voltage corresponding to the phase of the first sub-phase shifter 212 is obtained When the light intensity detected by the first photoelectric detector pd1 is the maximum, the voltage corresponding to the phase of the first sub-phase shifter 212 is obtained And, when the second coupler 213 and the third coupler 231 are a multimode interferometer, the above calibration method can be referred to, when the light intensity detected by the first photoelectric detector pd1 is the minimum, the voltage corresponding to the phase of the first sub-phase shifter 212 is obtained When the light intensity detected by the first photoelectric detector pd1 is the maximum, the voltage corresponding to the phase of the first sub-phase shifter 212 is obtained When the light intensity detected by the third photoelectric detector pd3 is the minimum, the voltage corresponding to the phase of the second sub-phase shifter 232 is obtained

[0125] The polarization control method provided by the embodiment can change the path state of the input end optical switch and the output end optical switch, so that when the phase of the phase shifter reaches the boundary phase, the polarization light path is switched to the passive waveguide, thereby ensuring the continuity of the output polarization light when the phase shifter is reset. The polarization control method provided by the embodiment uses pulse charging to control the change of the path state of the input end optical switch and the output end optical switch, which can complete the state switching with fast response speed, thereby ensuring that the input polarization state does not change during the reset process of the phase shifter, and further ensuring that the output polarization state does not deviate from the locked position.

[0126] It should be noted that the various embodiments in the specification are described in a progressive manner, each embodiment focuses on the differences from other embodiments, and the same or similar parts between embodiments can be referred to each other, and in addition, the different parts between the embodiments can also be used in combination with each other, and the application does not limit this.

[0127] The polarization control chip and system and the control method provided by the embodiment comprise a beam splitter, a first polarization control unit, a first coupler, a second polarization control unit, a second coupler and a beam combiner; the first polarization control unit and the second polarization control unit both comprise an input optical switch, a phase shifter and an output optical switch connected in sequence; the input end of the first polarization control unit is connected with the first output end of the beam splitter, and the output end of the first polarization control unit is connected with the first input end of the first coupler; the second output end of the beam splitter is connected with the second input end of the first coupler; the input end of the second polarization control unit is connected with the first output end of the first coupler, and the output end of the second polarization control unit is connected with the first input end of the second coupler; the second output end of the first coupler is connected with the second input end of the second coupler; the first output end of the second coupler is connected with the first input end of the beam combiner, and the second output end of the second coupler is connected with the second input end of the beam combiner. By adding the input optical switch and the output optical switch at both ends of the phase shifter on the basis of the structure of the existing polarization control chip, the polarization light path can be switched to the passive waveguide when the phase of the phase shifter reaches the boundary phase by changing the pass state of the input optical switch and the output optical switch, so that the output polarization light is continuous when the phase shifter resets; since no additional control unit is added, the cost is controlled, and since the state switching efficiency of the optical switch is high, the control period will not increase, solving the problems of high cost and long control period in the existing polarization control chip for realizing continuous and reset-free polarization control.

[0128] The above description is only a description of the preferred embodiments of the application, and does not limit the scope of the application in any way, and any modification or modification of the application by a person skilled in the art according to the above disclosure is within the protection scope of the claims.

Claims

1. A polarization control chip, characterized in that: The optical fiber optical device comprises a beam splitter, a primary polarization control unit, a primary coupler, a secondary polarization control unit, a secondary coupler and a beam combiner; the primary polarization control unit and the secondary polarization control unit each comprise an input optical switch, a phase shifter and an output optical switch connected in sequence by optical paths; The input end of the primary polarization control unit is connected to the first output end of the beam splitter, and the output end of the primary polarization control unit is connected to the first input end of the primary coupler; the second output end of the beam splitter is connected to the second input end of the primary coupler through a passive waveguide; the input end of the secondary polarization control unit is connected to the first output end of the primary coupler, and the output end of the secondary polarization control unit is connected to the first input end of the secondary coupler; the second output end of the primary coupler is connected to the second input end of the secondary coupler through a passive waveguide; the first output end of the secondary coupler is connected to the first input end of the beam combiner, and the second output end of the secondary coupler is connected to the second input end of the beam combiner; The input optical switch and the output optical switch in the primary polarization control unit and the secondary polarization control unit are configured to: when the phase of the phase shifter reaches a boundary phase, simultaneously switch the states of the input optical switch and the output optical switch to change the polarization light path in the polarization control chip, and reset the input optical switch and the output optical switch to their initial states after the phase shifter is reset to an initial phase.

2. The polarization control chip according to claim 1, wherein: The input-end optical switch includes a first coupler, a first sub-phase shifter, and a second coupler; the output-end optical switch includes a third coupler, a second sub-phase shifter, and a fourth coupler; The input end of the first coupler in the primary polarization control unit is connected to the first output end of the beam splitter, and the input end of the first coupler in the secondary polarization control unit is connected to the first output end of the primary coupler; the input end of the first sub-phase shifter is connected to the first output end of the first coupler, and the output end of the first sub-phase shifter is connected to the first input end of the second coupler; the second output end of the first coupler is connected to the second input end of the second coupler; the first output end of the second coupler is connected to the input end of the phase shifter; the second output end of the second coupler is connected to the second input end of the third coupler; the output end of the phase shifter is connected to the first input end of the third coupler; the first output end of the third coupler is connected to the first input end of the fourth coupler, and the second output end of the third coupler is connected to the input end of the second sub-phase shifter; the output end of the second sub-phase shifter is connected to the second input end of the fourth coupler; the output end of the fourth coupler in the primary polarization control unit is connected to the first input end of the primary coupler, and the output end of the fourth coupler in the secondary polarization control unit is connected to the first input end of the secondary coupler.

3. The polarization control chip according to claim 2, characterized in that: When the second coupler and the third coupler are directional couplers, the first sub-phase shifter and the second sub-phase shifter are located on the same side as the phase shifter.

4. The polarization control chip according to claim 2, wherein: When the second coupler and the third coupler are multi-mode interferometers, the first sub-phase shifter and the phase shifter are located on the same side, and the second sub-phase shifter and the phase shifter are located on different sides.

5. The polarization control chip according to claim 2, characterized in that: The primary polarization control unit and the secondary polarization control unit also include at least one photodetector; the photodetector is used to obtain light intensity to perform phase calibration on the first sub-phase shifter, the phase shifter and the second sub-phase shifter according to the light intensity.

6. The polarization control chip according to claim 5, characterized in that: The primary polarization control unit and the secondary polarization control unit both include a first photodetector, a second photodetector, and a third photodetector; the first photodetector is connected to the second output end of the second coupler to perform phase calibration on the first sub-phase shifter; the second photodetector is connected to the second output end of the third coupler to perform phase calibration on the phase shifter; the third photodetector is connected to the output end of the fourth coupler to perform phase calibration on the second sub-phase shifter.

7. A polarization control system, characterized in that: The device comprises a polarization analysis module, a control module, and a polarization control chip according to any one of claims 1 to 6; the polarization analysis module is used to analyze and process the optical signal output by the secondary coupler to obtain a feedback signal; the control module is used to generate a control signal based on the feedback signal, so as to use the control signal to control the on / off states of the input optical switch and the output optical switch, and to control the reset of the phase shifter.

8. A polarization control method, applied to the polarization control chip according to any one of claims 1 to 6, characterized in that: The polarization control method comprises: Initialize the polarization control chip; Input polarized light to the polarization control chip; The polarization control chip modulates the phase and intensity of the input polarized light and outputs the modulated polarized light. The phase of the phase shifter changes continuously under the convergence algorithm of the polarization control. When the phase of the phase shifter reaches the boundary phase, the states of the input optical switch and the output optical switch are switched simultaneously to change the polarization light path in the polarization control chip; The phase shifter is reset to the initial phase; The input optical switch and the output optical switch are reset to the initial state; The polarization control chip continues to modulate the phase and intensity of the input polarized light and outputs the modulated polarized light.

9. The polarization control method according to claim 8, wherein: The method for initializing the polarization control chip includes: Set the phase shifter's phase modulation range to [0,4k ], the initial phase is 2k ; Set the input optical switch and the output optical switch to the on state.

10. The polarization control method according to claim 8, wherein: By pulse power-on, the states of the input optical switch and the output optical switch are controlled to switch simultaneously.

11. The polarization control method according to claim 8, wherein: Before initializing the polarization control chip, the polarization control method includes: Perform phase calibration on the input optical switch, phase shifter and output optical switch.

12. The polarization control method according to claim 11, wherein: The input optical switch includes a first coupler, a first sub-phase shifter, and a second coupler; the output optical switch includes a third coupler, a second sub-phase shifter, and a fourth coupler; and the method for performing phase calibration on the input optical switch, the phase shifter, and the output optical switch includes: Connecting the first photodetector to the second output end of the second coupler, connecting the second photodetector to the second output end of the third coupler, and connecting the third photodetector to the output end of the fourth coupler; Scanning the first sub-phase shifter with a first step length within a first preset voltage range; when the light intensity detected by the first photodetector is minimum, the voltage at that time is corresponded to a first off-voltage of the first sub-phase shifter; and when the light intensity detected by the first photodetector is maximum, the voltage at that time is corresponded to a first on-voltage of the first sub-phase shifter; In the second preset voltage range, the first sub-phase shifter is scanned with a second step length and the phase shifter is scanned with a third step length; the light intensity detected by the second photodetector is used to calculate the optical power variance of the phase shifter within each third step range; when the variance is 0, the voltage at this time is corresponded to the 0 phase and 4k phase; The phase of the first sub-phase shifter is set to the phase corresponding to the first off voltage, and the second sub-phase shifter is scanned with a fourth step size within a third preset voltage range; when the light intensity detected by the third photodetector is minimum, the voltage at this time is corresponded to the second off voltage of the second sub-phase shifter; when the light intensity detected by the third photodetector is maximum, the voltage at this time is corresponded to the second on voltage of the second sub-phase shifter.

13. The polarization control method according to claim 12, wherein: The method of scanning the first sub-phase shifter with the second step length and scanning the phase shifter with the third step length includes: When the first sub-phase shifter completes one cycle of scanning with the second step length, the voltage of the phase shifter increases by a third step length, wherein the second step length is greater than the third step length.

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