Polarization control chip, polarization control system and polarization control method

Abstract

The invention provides a polarization control chip, a polarization control system and a polarization control method. The polarization control chip comprises an input end optical switch, a phase shifter and an output end optical switch, the output end of the beam splitter is respectively connected with the input end of the primary polarization regulation and control unit and the second input end of the primary coupler; the output end of the first-stage polarization regulation and control unit is connected with the first input end of the first-stage coupler; the output end of the primary coupler is respectively connected with the input end of the secondary polarization regulation and control unit and the second input end of the secondary coupler; the output end of the secondary polarization regulation and control unit is connected with the first input end of the secondary coupler; and the output end of the secondary coupler is connected with the input end of the beam combiner. By changing the state of the optical switch, the optical path is switched to the passive waveguide when the phase of the phase shifter reaches the boundary phase, so that the output light is ensured to be continuous when the phase shifter is reset, and the state switching efficiency of the optical switch is high, so that the regulation and control period is not increased; the problem that an existing polarization control chip is long in period for achieving continuous non-reset polarization control is solved.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a polarization control chip, system, and control method. Background Art

[0002] In some applications, such as optical communications and optical sensing, continuous and long-term locking of polarized light is required. For example, in integrated silicon photonic chip lidars, manufactured using silicon-based photonics technology, the emitted light has an outgoing polarization state of TE mode. When the laser is reflected by an object, the polarization state of the reflected light is uncertain. Therefore, a polarization control chip is required to actively lock the polarization state, converting all reflected light to TE mode. This avoids power loss caused by the inability to receive TM mode and improves the signal-to-noise ratio. This application requires the polarization control chip to lock the polarization state of the reflected light in real time. Regardless of how the polarization state of the reflected light changes, the locking process must remain continuous, without any sudden changes in optical power.

[0003] To meet these application requirements, current polarization control chips typically employ a two-stage phase shifter-Mach-Zehnder interferometer structure. The first-stage phase shifter rotates the polarization state about the S1 axis on the Poincare sphere. The second-stage phase shifter, along with two 3dB couplers, forms a Mach-Zehnder interferometer structure, effectively rotating the polarization state about the S3 axis on the Poincare sphere. Because the S1 and S3 axes are orthogonal, this polarization control chip possesses two-dimensional control capabilities on the Poincare sphere, theoretically enabling conversion between arbitrary polarization states.

[0004] However, in existing polarization control chips with a two-stage phase shifter-Mach-Zehnder interference structure, the phase shifter uses a thermo-optical phase shifter. This thermo-optical phase shifter has phase modulation boundaries and requires a reset operation when reaching the boundary. Therefore, this polarization control chip cannot achieve continuous polarization control without reset. To achieve continuous polarization control without reset, the current common practice is to add multiple control units through redundant design, introducing more control degrees of freedom to search for convergence directions that do not reach the boundaries, thereby avoiding reset operations. However, this approach not only increases the cost of the polarization control chip, but also, due to the introduction of more degrees of freedom, the control cycle becomes longer, the control speed becomes slower, and the overall performance of the device is reduced. Summary of the Invention

[0005] The object of the present invention is to provide a polarization control chip, system and control method to solve the problems of high cost and long control period in existing polarization control chips for achieving continuous polarization control without reset.

[0006] To solve the above technical problems, the present invention provides a polarization control chip, comprising 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 optically connected in sequence; 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 combiner, and the second output end of the second-level coupler is connected to the second input end of the combiner.

[0007] Optionally, in the polarization control chip, 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; 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.

[0008] 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 as the phase shifter.

[0009] Optionally, in the polarization control chip, when the second coupler and the third coupler are multimode 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.

[0010] Optionally, in the polarization control chip, the second output end of the beam splitter is connected to the second input end of the first-level coupler through a passive waveguide; the second output end of the first-level coupler is connected to the second input end of the second-level coupler through a passive waveguide.

[0011] Optionally, in the polarization control chip, 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.

[0012] Optionally, in the polarization control chip, the first-level polarization control unit and the second-level 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.

[0013] To solve the above technical problems, the present invention also provides a polarization control system, comprising a polarization analysis module, a control module, and a polarization control chip as described in any one of the above items; 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 state of the input optical switch and the output optical switch, and to control the reset of the phase shifter.

[0014] To solve the above technical problems, the present invention further provides a polarization control method, which is applied to the polarization control chip as described in any one of the above items. The polarization control method includes: 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.

[0015] Optionally, in the polarization control method, the method of 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.

[0016] Optionally, in the polarization control method, the states of the input end optical switch and the output end optical switch are controlled to switch simultaneously by pulse powering.

[0017] Optionally, in the polarization control method, 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.

[0018] Optionally, in the polarization control method, 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.

[0019] Optionally, in the polarization control method, the method of scanning the first sub-phase shifter with the second step size and scanning the phase shifter with the third step size 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.

[0020] 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

[0021] Figure 1 A schematic structural diagram of the polarization control chip provided in this embodiment; Figure 2 A schematic structural diagram of the phase shifter provided in this embodiment; Figure 3A schematic diagram of the structure of the input optical switch provided in this embodiment; Figure 4 A schematic diagram of the structure of the output optical switch provided in this embodiment; 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; 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; Figure 7 A schematic structural diagram of a polarization control unit with a photodetector provided in this embodiment; Figure 8 A schematic structural diagram of the polarization control system provided in this embodiment; Figure 9 A flow chart of the polarization control method provided in this embodiment; Figure 10 A schematic diagram comparing the control pulse and response time of the optical switch provided in this embodiment; The descriptions of the reference numerals are as follows: 110-beam splitter; 120-primary polarization control unit; 130-primary coupler; 140-secondary polarization control unit; 150-secondary coupler; 160-beam combiner; 210-input optical switch; 220-phase shifter; 230-output optical switch; 211 - first coupler; 212 - first sub-phase shifter; 213 - second coupler; 231 - third coupler; 232 - second sub-phase shifter; 233 - fourth coupler. DETAILED DESCRIPTION

[0022] The polarization control chip, system, and control method proposed in the present invention are further described in detail below, using the accompanying drawings and specific embodiments. It should be noted that the drawings are highly simplified and not precisely scaled, serving only to facilitate and clearly illustrate the embodiments of the present invention. Furthermore, the structures shown in the drawings are often partial to the actual structures. In particular, different drawings may use different scales to illustrate different aspects of the illustration.

[0023] It should be noted that the terms "first", "second", etc. in the specification, claims, and accompanying drawings of the present invention are used to distinguish similar objects in order to describe the embodiments of the present invention, and are not used 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 "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, products, or apparatuses.

[0024] This embodiment provides a polarization control chip, such as Figure 1 As shown, it includes a beam splitter 110, a primary polarization control unit 120, a primary coupler 130, a secondary polarization control unit 140, a secondary coupler 150 and a combiner 160; the primary polarization control unit 120 and the secondary polarization control unit 140 both include an input end optical switch 210, a phase shifter 220 and an output end optical switch 230 that are optically connected in sequence.

[0025] The input end of the first-level polarization control unit 120 is connected to the first output end of the beam splitter 110, and the output end of the first-level polarization control unit 120 is connected to the first input end of the first-level coupler 130; the second output end of the beam splitter 110 is connected to the second input end of the first-level coupler 130; the input end of the second-level polarization control unit 140 is connected to the first output end of the first-level coupler 130, and the output end of the second-level polarization control unit 140 is connected to the first input end of the second-level coupler 150; the second output end of the first-level coupler 130 is connected to the second input end of the second-level coupler 150; the first output end of the second-level coupler 150 is connected to the first input end of the combiner 160, and the second output end of the second-level coupler 150 is connected to the second input end of the combiner 160.

[0026] The polarization control chip provided in this embodiment adds 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. By changing the path states of the input and output optical switches, the polarized light path is switched to a passive waveguide when the phase of the phase shifter reaches a boundary phase, thereby ensuring the continuity of the output polarized light when the phase shifter is reset. Because no additional control unit is added, 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 polarization control without reset.

[0027] Specifically, in this embodiment, the beam splitter 110, the primary polarization control unit 120, the primary coupler 130, the secondary polarization control unit 140, the secondary coupler 150, and the beam combiner 160 are sequentially arranged along the optical path. The primary coupler 130, the secondary polarization control unit 140, and the secondary coupler 150 form a Mach-Zehnder interferometer structure.

[0028] In practical applications, such as Figure 1 As shown, the beam splitter 110 is a 1×2 beam splitter, thereby splitting the input polarized light into two paths; the first-level polarization control unit 120 is located in 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-level coupler 130 can be specifically a 2×2 3dB coupler, thereby coupling the two input lights and then splitting them into two output paths; the second-level polarization control unit 140 is located on the same side as the first-level polarization control unit 120, that is, located in the upper arm branch, and the corresponding lower arm branch is also a passive waveguide; the second-level coupler 150 is consistent with the first-level coupler 130, and can be a 2×2 3dB coupler, thereby coupling the two input lights and then splitting them into two output paths; the beam combiner 160 corresponds to the beam splitter 110 and is a 2×1 beam combiner, thereby combining the two lights output by the second-level coupler 150 and outputting them.

[0029] Further, such as Figure 2 As shown, the phase shifters in the primary polarization control unit 120 and the secondary polarization control unit 140 include two branch waveguides, an upper arm and a lower arm, of equal length. The refractive index of the upper arm waveguide region can change in response to an applied voltage signal, based on thermo-optical and electro-optical effects. This change in refractive index causes the speed of light propagating in the upper arm waveguide to differ from that in the lower arm waveguide. Consequently, polarized light takes different amounts of time to travel through the upper and lower arm waveguides of equal length, resulting in a phase difference.

[0030] As well as Figure 3 As shown, the input optical switch 210 includes a first coupler 211 , a first sub-phase shifter 212 , and a second coupler 213 which are sequentially arranged along the optical path.

[0031] In practical applications, the first coupler 211 can be a 1×2 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 is sent to the passive waveguide of the lower arm of the first sub-phase shifter 212; the second coupler 213 can be a 2×2 3dB coupler, which couples the two light paths output by the first sub-phase shifter 212 and outputs the two light paths into the phase shifter 220.

[0032] As well as Figure 4As shown, the output optical switch 230 includes a third coupler 231 , a second sub-phase shifter 232 and a fourth coupler 233 which are sequentially arranged along the optical path.

[0033] In practical applications, the third coupler 231 can be a 2×2 3dB coupler, which couples the two light paths output by the phase shifter 220 and outputs the two light paths into the second sub-phase shifter 232, one of which is sent to the upper arm of the second sub-phase shifter 232 for phase shifting, and the other is sent to the passive waveguide of the lower arm of the second sub-phase shifter 232; the fourth coupler 233 can be a 2×1 coupler, thereby combining the two light paths into one output.

[0034] Combine Figure 3 The working principle of the optical switch provided in this embodiment is described as follows: the first sub-phase shifter 212 in the input optical switch 210 is used to cause phase delay in the two paths of light, and then the coupling interference after passing through the second coupler 213 causes an additional phase delay. 1 and 0, so that the optical path is fully conductive upward or fully conductive downward. Fully conductive upward is defined as the conductive state (off state) of the optical switch, and fully conductive downward is defined as the disconnected state (on state) of the optical switch. 1 and By switching between the voltages V1 and V0 corresponding to 0, the switching state of the optical switch can be converted.

[0035] Since the structure of the input-end optical switch 210 is symmetrical to that of the output-end optical switch 230 , this embodiment only takes the input-end optical switch 210 as an example to illustrate the working principle of the optical switch. The working principle of the output-end optical switch 230 is similar and will not be described in detail in this application.

[0036] Specifically, in this embodiment, combined with Figure 1As shown, the input end of the first coupler 211 in the primary polarization control unit 120 is connected to the first output end of the beam splitter 110, and the input end of the first coupler 211 in the secondary polarization control unit 140 is connected to the first output end of the primary coupler 130; the input end of the first sub-phase shifter 212 is connected to the first output end of the first coupler 211, and the output end of the first sub-phase shifter 212 is connected to the first input end of the second coupler 213; the second output end of the first coupler 211 is connected to the second input end of the second coupler 213; the first output end of the second coupler 213 is connected to the input end of the phase shifter 220; the second output end of the second coupler 213 is connected to the The second input end of the third coupler 231 is connected; the output end of the phase shifter 220 is connected to the first input end of the third coupler 231; the first output end of the third coupler 231 is connected to the first input end of the fourth coupler 233, and the second output end of the third coupler 231 is connected to the input end of the second sub-phase shifter 232; the output end of the second sub-phase shifter 232 is connected to the second input end of the fourth coupler 233; the output end of the fourth coupler 233 in the primary polarization control unit 120 is connected to the first input end of the primary coupler 130, and the output end of the fourth coupler 233 in the secondary polarization control unit 140 is connected to the first input end of the secondary coupler 150.

[0037] Furthermore, in this 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 as the phase shifter 220. Figure 5 As shown, the first sub-phase shifter 212 , the second sub-phase shifter 232 and the phase shifter 220 are all located in the upper arm branch.

[0038] In another specific embodiment, when the second coupler 213 and the third coupler 231 are multimode interferometers, the first sub-phase shifter 212 and the phase shifter 220 are located on the same side, and the second sub-phase shifter 232 and the phase shifter 220 are located on different sides. Figure 6 As shown, the first sub-phase shifter 212 and the phase shifter 220 are located in the upper arm branch, and the second sub-phase shifter 232 is located in the lower arm branch.

[0039] It should be noted that, in order to clearly illustrate the connection relationship between the optical elements, the first sub-phase shifter 212, the phase shifter 220 and the second sub-phase shifter 232 all refer to a branch of the phase shifter where phase shifting occurs.

[0040] Furthermore, 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, as well as reset control of the phase shifter 220, in this embodiment, the primary polarization control unit 120 and the secondary polarization control unit 140 each further include at least one photodetector; the photodetector is used to obtain light intensity to perform phase calibration on the first sub-phase shifter 212, the phase shifter 220, and the second sub-phase shifter 232 based on the light intensity.

[0041] Specifically, in this embodiment, Figure 7 As shown, the primary polarization control unit 120 and the secondary polarization control unit 140 both 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 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 to perform phase calibration on the phase shifter 220; the third photodetector pd3 is connected to the output end of the fourth coupler 233 to perform phase calibration on the second sub-phase shifter 232.

[0042] The following, combined Figure 1 、 Figure 5 and Figure 6 , the working principle of the polarization control chip provided in this embodiment to achieve continuous polarization control without reset is explained.

[0043] In this embodiment, the polarization control chip is based on silicon material and is manufactured using silicon photonics technology.

[0044] When the polarization control chip starts working, 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 .

[0045] All 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 are linearly related to the applied power. The transmission matrix is expressed as .

[0046] When the 2×2 couplers (including the second coupler 213, the third coupler 231, etc.) are directional couplers, such as Figure 5 As shown, the transmission matrix is , when the input light is incident only from the lower port (the second input port), the directional coupler is a 1×2 beam splitter.

[0047] 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: ,in, represents the phase of the first sub-phase shifter 212, represents the phase of the phase shifter 220, represents the phase of the second sub-phase shifter 232 .

[0048] when , When , the transfer matrix is For the phase shifter 220, the input optical switch 210 and the output optical switch 230 allow all light to pass through the active waveguide of the upper arm branch, so that the phase shifter 220 can achieve continuous phase modulation.

[0049] when Reaching boundary 0 or 4 hour, , at this time, the states of the input optical switch 210 and the output optical switch 230 are switched so that 、 , then the transmission matrix is , all light is extracted from the passive waveguide. At this time, the output result of the polarization control chip is the same as Regardless of the changes in Reset to initial phase , will not change the light intensity and phase at the output.

[0050] At the same time, consider the changes in the output phase and intensity during the switching process of the input optical switch 210 and the output optical switch 230: Reaching boundary 0 or 4 , the transfer matrix is .when Depend on Towards When changes, Synchronization from 0 to Change and always maintain , then the transfer matrix becomes That is, during the switching process between the input optical switch 210 and the output optical switch 230 , the light intensity and phase at the output end of the polarization control chip do not change, thus achieving continuous and infinite phase modulation.

[0051] When the 2×2 coupler (including the second coupler 213, the third coupler 231, etc.) is a multi-mode 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 .

[0052] when , When , the transfer matrix is For the phase shifter 220, the input optical switch 210 and the output optical switch 230 allow all light to pass through the active waveguide of the upper arm branch, so that the phase shifter 220 can achieve continuous phase modulation.

[0053] when Reaching boundary 0 or 4 hour, , at this time, the states of the input optical switch 210 and the output optical switch 230 are switched so that 、 , then the transmission matrix is , all light is extracted from the passive waveguide. At this time, the output result of the polarization control chip is the same as Regardless of the changes in Reset to initial phase , will not change the light intensity and phase at the output.

[0054] At the same time, consider the changes in the output phase and intensity during the switching process of the input optical switch 210 and the output optical switch 230: Reaching boundary 0 or 4 When , the transfer matrix is .when Depend on Towards When changes, Synchronization by Towards Change and always maintain , then the transfer matrix becomes That is, during the switching process between the input optical switch 210 and the output optical switch 230 , the light intensity and phase at the output end of the polarization control chip do not change, thus achieving continuous and infinite phase modulation.

[0055] Based on this, this embodiment also provides a polarization control system, such as Figure 8 As shown, it includes a polarization analysis module, a control module and the polarization control chip as described above; 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 according to the feedback signal, so as to use the control signal to control the on and off states of the input end optical switch and the output end optical switch, and to control the reset of the phase shifter.

[0056] 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.

[0057] 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.

[0058] 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: S1, initialize the polarization control chip; S2, input polarized light to the polarization control chip; 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. 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; S5, the phase shifter is reset to the initial phase; S6, the input optical switch and the output optical switch are reset to the initial state; 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.

[0059] 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.

[0060] Specifically, in this embodiment, step S1 is to initialize the polarization control chip.

[0061] In a specific embodiment, initializing the polarization control chip includes setting the phase modulation range and initial phase of the phase shifter 220. For example, the phase modulation range of the phase shifter is set to [0, 4k ], the initial phase is 2k Furthermore, initializing the polarization control chip further includes setting the initial states of the input optical switch 210 and the output optical switch 230. For example, the states of the input optical switch 210 and the output optical switch 230 are set to be on. That is, when the polarization control chip starts working, all light is transmitted through the active waveguide.

[0062] Furthermore, in this embodiment, in step S2 , polarized light is input to the polarization control chip.

[0063] 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 by the beam splitter 110 and enters the upper arm active waveguide and the lower arm passive waveguide for transmission.

[0064] And, in this embodiment, in step S3, the polarization control chip performs phase and intensity modulation on the input polarized light and outputs the modulated polarized light, wherein the phase of the phase shifter changes continuously under the convergence algorithm of the polarization control.

[0065] Specifically, phase and intensity modulation of polarized light is achieved through the primary polarization control unit 120, the primary coupler 130, the secondary polarization control unit 140, and the secondary coupler 150. The specific modulation method is not the focus of this application, and those skilled in the art can understand the working principle of phase and intensity modulation of the polarization control chip of this application based on the working principle of existing polarization control chips, so this application will not elaborate on it.

[0066] Furthermore, in this embodiment, in 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 switched simultaneously to change the polarization light path in the polarization control chip.

[0067] Specifically, as analyzed above, when the phase of the phase shifter 220 reaches the boundary phase 0 or 4k When the optical switch 210 at the input end and the optical switch 230 at the output end are changed in state, that is, switched from the on state to the off state, the optical transmission path in the primary polarization control unit 120 and the secondary polarization control unit 140 is changed from an active waveguide path to a passive waveguide path.

[0068] Furthermore, in this embodiment, in step S5 , the phase shifter 220 is reset to the initial phase.

[0069] Specifically, when the optical transmission path is changed to a passive waveguide path, the phase change of the phase shifter 220 will not affect the phase and intensity of the output light. Therefore, the phase shifter 220 can be reset to the initial phase 2k .

[0070] Furthermore, in this embodiment, in step S6 , the input optical switch 210 and the output optical switch 230 are reset to their initial states.

[0071] Specifically, after the phase shifter 220 is reset, its phase can continue to change continuously under the convergence algorithm of polarization control, thereby achieving phase and intensity modulation of the input polarized light. Therefore, the state of the input end optical switch 210 and the output end optical switch 230 can be restored to the on state, thereby changing the optical path transmission path from a passive waveguide path to an active waveguide path.

[0072] Finally, in this 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.

[0073] Specifically, step S7 repeats the process of step S3 and repeats it over and over again to achieve phase and intensity modulation of the input light.

[0074] While resetting the phase of phase shifter 220 upon reaching a boundary can achieve continuous polarization control and ensure that both the phase and intensity of the light remain unchanged, this process still causes the input polarization state to change, causing the output polarization state to deviate from the locked position. Therefore, the reset process needs to be completed as quickly as possible. To this end, in this embodiment, pulsed power is used to increase the response speed of the silicon photothermal phase modulator, thereby controlling the states of the input optical switch 210 and the output optical switch 230 to switch simultaneously within a very short time.

[0075] In practical applications, assume that the switching voltages of the optical switch after calibration are V0 and V1, respectively, where V1 > V0. During switching, the voltage switches from V0 to V1. Initially, a voltage pulse is generated, causing rapid heat accumulation. The pulse size is determined experimentally, typically twice V1, and does not exceed the withstand voltage of the polarization control chip. The pulse duration is approximately 5% of the response time.

[0076] like Figure 10 As shown, the left side shows the voltage used in conventional optical switch control and the time required for the optical switch state to switch completely under this voltage, and the right side shows the voltage used in pulse powering in this embodiment and the time required for the optical switch state to switch completely under this voltage. Figure 10It can be seen that under conventional control voltages, the optical switch requires 30 μs to complete state switching. However, with the pulsed power control method adopted in this embodiment, the optical switch completes state switching in only 0.5 μs, greatly improving the response speed of the thermo-optical phase shifter. This ensures that during the resetting process of the phase shifter 220, the change in the input polarization state is extremely small and can be ignored, thereby ensuring that the output polarization state does not deviate from the locked position.

[0077] Preferably, to ensure that the states of the input optical switch 210 and the output optical switch 230 can be switched promptly and accurately, and to ensure that the phase shifter 220 can be reset promptly and accurately, it is necessary to calibrate 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. To this end, before initializing the polarization control chip in step S1, the polarization control method provided in this embodiment further includes: S0, phase calibration is performed on the input optical switch, phase shifter and output optical switch.

[0078] Specifically, in this embodiment, a number of photoelectric detectors are added to detect light intensity. Figure 7 As shown, the first photodetector pd1 is connected to the second output end of the second coupler 213 , the second photodetector pd2 is connected to the second output end of the third coupler 231 , and the third photodetector pd3 is connected to the output end of the fourth coupler 233 .

[0079] In practical applications, a 1% splitter link can be introduced at the location where a photodetector needs to be connected in the polarization control unit. The photodetector is connected to the splitter link, so that while being able to detect the corresponding light intensity, it will not affect the normal function of the polarization control chip, ensuring that the optical path loss is within an acceptable range.

[0080] 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 this embodiment is described: For the first sub-phase shifter 212, in order to achieve accurate switching of the state of the input optical switch 210, it is necessary to obtain 0 and Thus, the control voltage for the on and off states of the input optical switch 210 is obtained. Specifically, within a first preset voltage range (e.g., 0 to Vmax), the first sub-phase shifter 212 is scanned with a first step length to observe the change in light intensity detected by the first photodetector pd1. Assuming that the light intensity of the input light is E, the light intensity expression of the first photodetector pd1 is: When the light intensity detected by the first photodetector pd1 is the minimum, the voltage at this time corresponds to the 0 phase of the first sub-phase shifter 212, that is, 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 corresponds to the 0 phase of the first sub-phase shifter 212. Phase, that is, the voltage is the first on voltage of the first sub-phase shifter 212. Record 0 and The voltage corresponding to the phase is used to complete the calibration of the first sub-phase shifter 212.

[0081] For the phase shifter 220, in order to achieve accurate reset, it is necessary to obtain the phase boundary (0 and 4 Specifically, within the second preset voltage range, the first sub-phase shifter 212 is scanned at a second step length and the phase shifter 220 is scanned at a third step length. The first sub-phase shifter 212 can be scanned quickly with a sawtooth wave, and the phase shifter 220 can be scanned slowly, i.e., the second step length is greater than the third step length. Furthermore, the specific scanning method can be: when the first sub-phase shifter 212 completes a cycle of scanning with the second step length, the voltage of the phase shifter 220 increases by a third step length. During the scanning process, the light intensity expression of the second photodetector pd2 is: .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 optical power variance of the phase shifter 220 within each third step range (one scanning cycle of the first sub-phase shifter 212); when the optical power variance is 0, the voltage at this time is corresponding to the 0 phase and 4k of the phase shifter 220. The voltage at this time is recorded to complete the calibration of the phase shifter 220.

[0082] For the second sub-phase shifter 232, in order to achieve accurate switching of the state of the output optical switch 230, it is necessary to obtain 2 and The voltage corresponding to the phase is obtained to obtain the control voltage for 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, that is, the 0 phase. The phase of the phase shifter 220 can be any value. Within the third preset voltage range (for example, 0~Vmax), the second sub-phase shifter 232 is scanned with a fourth step size to observe the change in the light intensity monitored by the third photodetector pd3. At this time, the light intensity expression of the third photodetector pd3 is When the light intensity detected by the third photodetector pd3 is the minimum, the voltage at this time is corresponding to the 2 of the second sub-phase shifter 232. Phase, that is, the voltage is the second off voltage of the second sub-phase shifter 232; when the light intensity detected by the third photodetector pd3 is the maximum, the voltage at this time corresponds to the second sub-phase shifter 232 Phase, that is, the voltage is the second on voltage of the second sub-phase shifter 232. Record 2 and The voltage corresponding to the phase is used to complete the calibration of the second sub-phase shifter 232.

[0083] In actual applications, the first preset voltage range, the second preset voltage range, the third preset voltage range, and the first step size, the second step size, the third step size, and the fourth step size used in the calibration process can be reasonable according to actual needs, and this application does not impose any restrictions on this. Among them, the smaller the step size is set, the longer the calibration process may take, but the more accurate the voltage value obtained. Of course, in some specific embodiments, a variable step size method can also be used, that is, a larger step size is used for coarse scanning, and a smaller step size is used for fine scanning within a range close to the target voltage.

[0084] Furthermore, when the second coupler 213 and the third coupler 231 are multimode interferometers, the calibration method described above can be used to obtain the first phase shifter 212 when the light intensity detected by the first photodetector pd1 is the minimum. When the light intensity detected by the first photodetector pd1 is the maximum, the first sub-phase shifter 212 is obtained. And, when the light intensity detected by the third photodetector pd3 is minimum, the second sub-shifter 232 is obtained. When the light intensity detected by the third photodetector pd3 is the maximum, the second sub-shifter 232 is obtained. The voltage corresponding to the phase.

[0085] The polarization control method provided by this embodiment utilizes the polarization control chip provided by this embodiment. By altering the path states of the input and output optical switches, the polarized light path is switched to the passive waveguide when the phase of the phase shifter reaches a boundary phase. This ensures the continuity of the output polarization when the phase shifter is reset. The polarization control method provided by this embodiment uses a pulsed voltage to control the path states of the input and output optical switches, enabling rapid state switching and ensuring that the input polarization state remains unchanged during the phase shifter reset process, thereby ensuring that the output polarization state does not deviate from the locked position.

[0086] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other. In addition, the different parts between the various embodiments can also be used in combination with each other, and the present invention is not limited to this.

[0087] The polarization control chip, system, and control method provided in this embodiment 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.

[0088] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection 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 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 combiner, and the second output end of the second-level coupler is connected to the second input end of the combiner.

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, wherein: 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, characterized in that: 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 1, wherein: The second output end of the beam splitter is connected to the second input end of the first-level coupler through a passive waveguide; the second output end of the first-level coupler is connected to the second input end of the second-level coupler through a passive waveguide.

6. 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.

7. The polarization control chip according to claim 6, 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.

8. 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 7; 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.

9. A polarization control method, applied to the polarization control chip according to any one of claims 1 to 7, 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.

10. The polarization control method according to claim 9, 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.

11. The polarization control method according to claim 9, wherein: By pulse power-on, the states of the input optical switch and the output optical switch are controlled to switch simultaneously.

12. The polarization control method according to claim 9, 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.

13. The polarization control method according to claim 12, 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.

14. The polarization control method according to claim 13, 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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