Multi-path polarization control system for coherent combination and control method thereof

Abstract

The invention provides a multi-path polarization control system for coherent synthesis and a control method thereof, the control system comprises a beam splitter, N phase modulators, N polarization controllers, N amplifiers, a polarization beam splitter and a 90-degree optical mixer, the N polarization controllers are respectively used for modulating polarization states of N paths of sub-beams after phase modulation, the N amplifiers are respectively used for modulating polarization states of N paths of sub-beams after phase modulation, and the N polarization controllers are respectively used for modulating polarization states of N paths of sub-beams after phase modulation. The N amplifiers are respectively used for amplifying the optical power of the N paths of sub-light beams after polarization state modulation, the polarization beam splitter is used for obtaining a required feedback signal, and the 90-degree optical mixer is used for performing coherent frequency mixing processing on one path of sub-light beams after beam splitting by the beam splitter and part of CBC synthetic light # imgabs0 #. The polarization controller outputs a polarization feedback to the phase modulator. The 90-degree frequency mixer is additionally arranged at the feedback position, any polarization state of all paths can be quickly recovered to expected linear polarization output, and the time required by polarization control is not influenced by the number of beam splitting light paths.

Description

Technical Field

[0001] The present invention relates to the technical field of coherent combination, and particularly to a multi-channel polarization control system for coherent combination and a control method thereof. Background Art

[0002] In the field of coherent combination, for a non-polarization-maintaining combination system, each path of light is amplified by a non-polarization-maintaining amplifier and then combined. To output linearly polarized light in a non-polarization-maintaining combination system, polarization control needs to be performed on each sub-beam, which is generally achieved by adjusting a polarization controller (EPC).

[0003] Currently, the control method for multi-channel polarization (as Figure 1 shown) is to split the combined light into two orthogonally polarized light beams through a polarization beam splitter (PBS), where a photodetector (PD) is used to convert the optical intensity signal into an electrical signal. By setting the light intensity as the objective function, a small perturbation is applied to the EPC of the light beam in each channel simultaneously through the stochastic parallel gradient descent method to detect the gradient, and the objective function is optimized according to the gradient feedback to achieve the search and stabilization of the linearly polarized state.

[0004] Existing multi-channel polarization control methods include: 1. The stochastic parallel gradient descent method (i.e., a non-polarization-maintaining coherent combination system, as Figure 2 shown). Under the condition of ensuring phase locking, the light after the combined light beam passes through the PBS is used as the feedback quantity. A small voltage perturbation is applied to the EPS in each channel to detect the change of the feedback quantity and calculate the gradient. Iterative feedback is performed according to the calculated gradient. Finally, when the optical power of the combined light beam after passing through the PBS is maximized, it is considered that the polarization states of all paths of light are locked to linearly polarized light. However, the stochastic parallel gradient descent method relies on random gradient exploration for multiple-step iteration to perform polarization control. The number of iteration steps is large and the path is completely random and unpredictable and increases with the increase of the number of channels N, resulting in low polarization control efficiency (low efficiency in the iterative process). The stochastic parallel gradient descent method requires multiple-step iteration, and the number of iteration steps is affected by different initial polarization states, and each step requires waiting for the EPC to respond (the response time of the EPC is generally about 50 μs), thus resulting in a low control bandwidth. The stochastic parallel gradient descent method needs to continuously apply a small voltage perturbation to the EPC to explore the gradient, and the exploration process will cause the polarization extinction ratio to decrease; 2. The polarization tracking and stabilization control method only models two wave plates and cannot traverse all polarization states. The derived method is only for single-channel polarization recovery and cannot be directly extended to the multi-channel coherent combination field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to solve the technical problem that the control bandwidth of the existing random parallel gradient descent method decreases with the increase of the optical path. The present invention provides a multi-channel polarization control system for coherent synthesis and its control method. Through the improvement of the multi-channel polarization control method, it can quickly restore any polarization state of all channels to the expected linearly polarized output, and the time required for polarization control is not affected by the number of beam splitting optical paths.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a multi-channel polarization control system for coherent synthesis, including: a beam splitter, N phase modulators, N polarization controllers, N amplifiers, a polarization beam splitter, and a 90° optical mixer. The beam splitter is used to split the input seed light into N + 1 sub-beams. The N phase modulators are respectively used to modulate the phases of the N sub-beams. The N polarization controllers are respectively used to modulate the polarization states of the N sub-beams after phase modulation. The N amplifiers are respectively used to amplify the optical powers of the N sub-beams after polarization state modulation. The polarization beam splitter is used to obtain the required feedback signal. The 90° optical mixer is used to perform coherent mixing processing on 1 sub-beam after being split by the beam splitter and part of the CBC combined light to output phase feedback to the phase modulator and polarization feedback to the polarization controller.

[0007] Therefore, a 90° mixer is added at the feedback, and 1 reference path is added during beam splitting. The part of the combined light of the polarization beam splitter is input into the 90° mixer together. The phase feedback of the 90° mixer is input into the phase modulator, and the polarization feedback is input into the polarization controller. According to the fixed sampling times of the polarization control feedback, a polarization digital twin model of each beam is established, so as to optimize the polarization in the digital domain, so that the optical power is stabilized at the maximum value after passing through the polarization controller, and the polarization states of each beam are kept consistent at the synthesis, so as to obtain a high-power linearly polarized light output with a high extinction ratio. In addition, any polarization state of all channels can be quickly restored to the expected linearly polarized output, and the time required for polarization control is not affected by the number of beam splitting optical paths.

[0008] Further, the polarization controller includes: four wave plates, and the azimuth angles of the four wave plates are 0°, 45°, 0°, and 45° respectively.

[0009] A control method for a multi-channel polarization control system for coherent synthesis includes the following steps: S1. According to the reference path and the optical field after synthesis and passing through the polarization beam splitter are used as the input of the 90° optical mixer together to obtain the light intensity of the polarization feedback ; S2. Obtain the light intensity of the polarization feedback in S1 , to obtain a polarization feedback signal ; S3. Set M different sets of polarization control amounts in N polarization controllers and load them on N sub-beams simultaneously to obtain the feedback amount after beam demodulation , and calculate to obtain the first row vector ; S4. Obtain the first row vector in S3 , and model to obtain the polarization feedback signals of all paths ; S5. Obtain the polarization feedback signals of all paths in S4 , and optimize the polarization feedback signal to solve for the phase delay corresponding to the maximum output optical power of the th path , and apply the solved phase delay to each of the polarization controllers on each path, then the target output linearly polarized light with the highest power can be obtained; S7 continuously repeats S2 - S5, thereby realizing the polarization tracking and stable output of the CBC composite light in real time; Where: .

[0010] Furthermore, in S1, the calculation formula for the reference path optical field is: ; Where: represents the amplitude of the sine perturbation applied to the th path beam, represents the optical frequency, represents the time, represents the initial phase of the sine perturbation applied to the th path beam.

[0011] Furthermore, in S1, the calculation formula for the optical field is: ; Where: represents the amplitude of the th path beam without sine perturbation, represents the initial phase of the th path beam without sine perturbation, represents the amplitude of the perturbation signal of the th path, represents the frequency of the perturbation signal of the th path.

[0012] Further, in S1, the light intensity of the polarization feedback is calculated by the formula: ; where: represents the vacuum permittivity, represents the vacuum permeability.

[0013] Further, in S2, the polarization feedback signal is calculated by the formula: ; where: represents the amplitude of the th path of light, represents the phase of the th path of light.

[0014] Further, in S2, the coefficient is calculated by the formula: ; The coefficient is calculated by the formula: ; where: represents the signal amplitude, represents the responsivity of the photodetector, represents the photosensitive area of the photodetector, represents the first-order Bessel function of the first kind, represents the zero-order Bessel function of the first kind, represents the small perturbation amplitude of the th path of light.

[0015] Further, in S3, three wave plates arranged in 0°, 45°, and 0° in the polarization controller are selected, and the polarization control amount of the wave plates is controlled. Let the phase delays of the wave plates loaded with the th path of light beam be: ; For the th path of light beam, according to the derivation of the Stocks vector and the Muller matrix, the expression of the feedback amount after beam demodulation is: .

[0016] Further, in S3, the expression of the first row vector is: ; For the th subsampling, the feedback amount is demodulated , to form the second row vector , the phase retardation amounts of the three wave plates of the polarization controller corresponding to the ; to obtain a column vector , sample times to obtain a matrix , solve the equation through the least squares method, then the first row vector can be obtained, so that the coefficients corresponding to each path can be solved in parallel; wherein: the column vector is ten parameters obtained by multiplying the Muller matrices of the three wave plates, represents the inverse matrix.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: A 90° mixer is added at the feedback, and one reference path and a part of the combined light of the polarization beam splitter are added during beam splitting and input into the 90° mixer together. The phase feedback of the 90° mixer is input into the phase modulator, and the polarization feedback is input into the polarization controller. According to the fixed sampling times of the polarization control feedback, a polarization digital twin model of each path of light beam is established, so as to optimize the polarization in the digital domain, so that the optical power is stabilized at the maximum value after passing through the polarization controller, and the polarization states of each path of light beam are kept consistent at the synthesis, so as to obtain a high-power linearly polarized light output with a high extinction ratio. In addition, any polarization state of all paths can be quickly restored to the expected linearly polarized output, and the time required for polarization control is not affected by the number of beam splitting optical paths. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below with reference to the drawings and embodiments.

[0019] Figure 1 is a framework diagram of a multi-path polarization control system for coherent synthesis in the prior art; Figure 2 is a framework diagram of a multi-path polarization control system for coherent synthesis of the present invention; Figure 3 is a schematic structural diagram of the polarization controller of the present invention; Figure 4 is a flowchart of the control method of the multi-path polarization control system for coherent synthesis of the present invention; Figure 5 is a convergence diagram of the multi-path polarization control system for coherent synthesis of the present invention.

[0020] In the figure: 1. Beam splitter; 2. Phase modulator; 3. Polarization controller; 301. Wave plate; 4. Amplifier; 5. Polarizing beam splitter; 6. 90° optical mixer. Detailed implementation mode

[0021] Now, the present invention will be further described in detail with reference to the accompanying drawings. These drawings are all simplified schematic diagrams, only showing the basic structure of the present invention in a schematic manner, so they only show the components related to the present invention.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present invention. In addition, the features defined as "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0023] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0024] As Figures 2 to 3 shown, a multi-channel polarization control system for coherent combination includes: a beam splitter 1, N phase modulators 2, N polarization controllers 3, N amplifiers 4, a polarizing beam splitter 5, and a 90° optical mixer 6. The beam splitter 1 is used to split the input seed light into N + 1 sub-beams. The N phase modulators 2 are respectively used to modulate the phases of the N sub-beams. The N polarization controllers 3 are respectively used to modulate the polarization states of the N sub-beams after phase modulation. The N amplifiers 4 are respectively used to amplify the optical powers of the N sub-beams after polarization state modulation. The polarizing beam splitter 5 is used to obtain the required feedback signal. The 90° optical mixer 6 is used to mix 1 sub-beam after being split by the beam splitter 1 and part of the CBC combined light Perform coherent mixing processing to output phase feedback to the phase modulator 2 and polarization feedback to the polarization controller 3. Thus, a 90° mixer is added at the feedback, and at the beam splitting, one reference path and a part of the combined light of the polarization beam splitter 5 are input into the 90° mixer together. The phase feedback of the 90° mixer is input into the phase modulator 2, and the polarization feedback is input into the polarization controller 3. According to the fixed number of sampling times of the polarization control feedback, a polarization digital twin model of each beam is established, so as to optimize the polarization in the digital domain, so that the optical power is stabilized at the maximum value after passing through the polarization controller 3, and the polarization states of each beam are kept consistent at the synthesis, so as to obtain a high-power linearly polarized light output with a high extinction ratio. In addition, it can quickly restore the arbitrary polarization state of all paths to the expected linearly polarized output, and the time required for polarization control is not affected by the number of beam splitting optical paths.

[0025] In other words, by sampling the output of the 90° mixer to establish the relationship between the polarization phase delay and the combined optical signal after the beam splitter 1, it is ensured that the output optical power after the polarization controller 3 is always stabilized at the maximum value (or the minimum value), so that the non-polarization-maintaining coherent synthesis system can output linearly polarized light with a relatively high polarization extinction ratio; by establishing a polarization digital twin model for multi-path coherent synthesis, the optimal control voltage of the polarization controller 3 can be directly optimized in the digital domain, so that the arbitrary polarization state of all paths can be quickly restored to the expected linearly polarized output, and the time required for polarization control is the same for any number of paths, and it can ensure that the number of sampling times is fixed for any number of channels and will not change.

[0026] Specifically, the 90° optical mixer 6 can have two-port output or four-port output. Only two balanced photodetectors are needed for the four-port output to obtain two feedback electrical signals; the polarization controller 3 can be of the type with variable delay and fixed azimuth angle, or of the type with variable azimuth angle and fixed delay; the polarization controller 3 can be of the crystal type or the extrusion type; the seed sources applicable to this scheme include: continuous light, and the pulse seed source can perform the same architecture synthesis for high-repetition-rate pulse signals or continuous light signals; this scheme is applicable to adding spectral broadening before beam splitting, or optical paths such as adding optical path adjustment for each path; the phase modulator 2 can be either an electro-optic phase modulator 2 or a piezoelectric ceramic fiber phase modulator 2; the synthesis method can be sub-aperture synthesis or common-aperture synthesis; this scheme is applicable to systems with amplification (generally, coherent synthesis systems have an amplification stage for power amplification), and is also applicable to optical path systems with an amplification stage.

[0027] In this embodiment, the polarization controller 3 includes: four wave plates 301, and the azimuth angles of the four wave plates 301 are 0°, 45°, 0°, and 45° respectively. Specifically, as Figure 3As shown, the azimuth angles of the four wave plates 301 are arranged alternately. By changing the voltage of each wave plate 301, the phase delay amount can be changed, and thus the polarization state of the input light can be changed. In addition, the azimuth angles of the four wave plates 301 can also be 0°, 45°, -45°, 0°. When in use, only 0°, 45°, 0° need to be selected.

[0028] As Figures 4 to 5 shown, a control method for a multi-channel polarization control system for coherent combination includes the following steps: S1. Use the reference path and the optical field after synthesis and passing through the polarization beam splitter 5 together as the input of the 90° optical mixer 6 to obtain the light intensity of the polarization feedback ; S2. Obtain the light intensity of the polarization feedback in S1 to obtain a polarization feedback signal ; S3. Set M groups of different polarization control amounts in the N polarization controllers 3 and load them on the N sub-beams simultaneously to obtain the feedback amount after beam demodulation and calculate to obtain the first row vector ; S4. Obtain the first row vector in S3 and model to obtain the polarization feedback signals of all paths ; S5. Obtain the polarization feedback signals of all paths in S4 and optimize the polarization feedback signal to solve for the phase delay corresponding to the maximum output optical power of the th path and apply the solved phase delay to the polarization controller 3 of each path respectively, then the target output linearly polarized light with the highest power can be obtained; S7. Continuously repeat S2 - S5 to realize the polarization tracking and stable output of the CBC combined light in real time; Among them: . Specifically, because there are ten undetermined coefficients in the first row vector and the optimal solution is .

[0029] In this embodiment, in S1, the calculation formula for the reference path optical field is: ; Among them: represents the amplitude of the sine perturbation applied to the th path beam represents the optical frequency, represents the time, represents the initial phase of the sinusoidal perturbation applied to the optical field is calculated as: ; where: represents the amplitude of the th beam without the sinusoidal perturbation, represents the initial phase of the th beam without the sinusoidal perturbation, represents the amplitude of the th perturbation signal, represents the frequency of the th perturbation signal; ; where: represents the vacuum permittivity, represents the vacuum permeability.

[0030] In this embodiment, in S2, the polarization feedback signal is calculated as: ; where: represents the amplitude of the th light, represents the phase of the th light; The coefficient ; The coefficient is calculated as: ; where: represents the signal amplitude, represents the responsivity of the photodetector, represents the photosensitive area of the photodetector, represents the first kind of Bessel function of the first order, represents the first kind of Bessel function of the zero order, represents the The small disturbance amplitude of the optical path. Specifically, after removing the DC component and high-frequency terms that the detector cannot respond to, and finally obtaining an effective optical intensity signal, multiplying it with the disturbance signal and integrating to obtain the polarization control signal, which is only valid when the integration time is an integer multiple of the disturbance signal period or much larger than the difference frequency period; through the polarization feedback signal The calculation formula of, when the phase part is locked, , These terms all tend to zero, and the final demodulation feedback amounts of each path only depend on the amplitude of its own path (i.e., the optical power of its own beam splitting to the beam splitter), then there is , that is, the power levels of each path are demodulated.

[0031] In this embodiment, in S3, three wave plates 301 arranged in 0°, 45°, and 0° in the polarization controller 3 are selected, and the polarization control amount of the wave plate 301 is controlled. Let the phase delays of the wave plate 301 loaded with the path beam be respectively: ; For the path beam, according to the derivation of the Stocks vector and the Muller matrix, the expression of the feedback amount after beam demodulation is: ; The expression of the first row vector is: ; For the th sampling, the feedback amount is demodulated to form the second row vector . The phase delay amounts of the three wave plates 301 corresponding to the path beam in the polarization controller 3 are respectively denoted as: ; To obtain the column vector , sampling times to obtain the matrix , and solving the equation by the least squares method, then the first row vector can be obtained, so that the coefficients corresponding to each path can be solved in parallel; where: the column vector is ten parameters obtained by multiplying the Muller matrices of the three wave plates 301, represents the inverse matrix. Specifically, the Stocks vector is the Stokes vector, which is used to represent the polarization state, and the Muller matrix is used to represent the transformation effect of the device on the incident light Stocks vector.

[0032] It should be noted that: as Figure 5 shown (the vertical axis represents the change in the optical intensity of the synthesized light output during the algorithm execution process), by setting different voltages 10 times (i.e., ), sampling the results by the polarization controller 3, and finally restoring to the state where the polarization of all paths is consistent and linearly polarized (i.e., the optical intensity reaches the maximum value after synthesis), and finally the synthesized light reaches the maximum value of 1.

[0033] In summary, the present invention adds a 90° mixer at the feedback, and adds one reference path during beam splitting. A part of the synthesized light of the polarization beam splitter 5 is input into the 90° mixer together. The phase feedback of the 90° mixer is input into the phase modulator 2, and the polarization feedback is input into the polarization controller 3. According to the fixed sampling times of the polarization control feedback, a polarization digital twin model of each beam is established, so as to optimize the polarization in the digital domain, so that the optical power is stabilized at the maximum value after passing through the polarization controller 3, and the polarization states of each beam are kept consistent at the synthesis, so as to obtain a high-power linearly polarized light output with a high extinction ratio. In addition, it can quickly restore any polarization state of all paths to the expected linearly polarized output, and the time required for polarization control is not affected by the number of beam splitting optical paths.

[0034] The above is based on the ideal embodiments of the present invention as an inspiration. Through the above description, relevant staff can make various changes and modifications completely within the scope without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A multi-channel polarization control system for coherent synthesis, characterized in that Comprising: A beam splitter (1) for splitting the input seed light into N + 1 sub - beams; N phase modulators (2), each of the N phase modulators (2) being used to modulate the phase of one of the N sub - beams; N polarization controllers (3), each of the N polarization controllers (3) being used to modulate the polarization state of one of the N sub - beams after phase modulation; N amplifiers (4), each of the N amplifiers (4) being used to amplify the optical power of one of the N sub - beams after polarization state modulation; A polarization beam splitter (5) for obtaining the required feedback signal; 90° optical mixer (6), and the 90° optical mixer (6) is configured to perform coherent mixing processing on one sub-beam and part of the CBC composite light after being split by the beam splitter (1), so as to output phase feedback to the phase modulator (2) and polarization feedback to the polarization controller (3). ​ 2. The multi-channel polarization control system for coherent combination according to claim 1, wherein The polarization controller (3) comprises: Four wave plates (301) with azimuth angles of 0°, 45°, 0° and 45° respectively.

3. A control method for a multi-channel polarization control system for coherent combination according to any one of claims 1-2, characterized in that, Comprising the following steps: S1. According to the reference path and the optical field after synthesis and passing through the polarization beam splitter (5) are used together as the input of the 90° optical mixer (6) to obtain the light intensity of the polarization feedback ; S2. Obtain the light intensity of the polarization feedback in S1 to obtain a polarization feedback signal ; S3. Set M different polarization control amounts in N polarization controllers (3) and simultaneously load them on N sub-beams to obtain the feedback amount after beam demodulation , and calculate to obtain the first row vector ; S4. Obtain the first row vector in S3 and model to obtain the polarization feedback signals of all paths ; S5. Obtain polarization feedback signals of all paths in S4 , and the polarization feedback signal Optimize to solve the The phase delay corresponding to the maximum output optical power of the path , and the solved phase delay When applied to the polarization controller (3) of each path respectively, the target output linear polarization light with the highest power can be obtained; S7 continuously repeats S2 - S5 to achieve real-time polarization tracking and stable output of the CBC synthetic light ; Wherein: .

4. The control method of the multi-channel polarization control system for coherent combination according to claim 3, characterized in that, In S1, the reference path optical field The calculation formula is as follows: ； Wherein: represents the amplitude of the sine perturbation applied to the th optical beam, represents the optical frequency, represents the time, represents the initial phase of the sine perturbation applied to the th optical beam.

5. The control method of the multi-channel polarization control system for coherent combination according to claim 3, characterized in that, In S1, the optical field is calculated by the formula: ； Wherein: represents the amplitude of the th path of light beam without applying a sine perturbation, represents the initial phase of the th path of light beam without applying a sine perturbation, represents the amplitude of the th path of perturbation signal, represents the frequency of the th path of perturbation signal.

6. The control method of the multi-channel polarization control system for coherent combination according to claim 3, wherein In S1, the optical intensity of the polarization feedback The calculation formula is as follows: ； Wherein: represents the vacuum permittivity, represents the vacuum permeability.

7. The control method of the multi-channel polarization control system for coherent combination according to claim 3, characterized in that, In S2, the polarization feedback signal has the following calculation formula: ； Wherein: represents the amplitude of the th path of light, and represents the phase of the 8. The control method of the multi-channel polarization control system for coherent combination according to claim 3, characterized in that In S2, the calculation formula for the coefficient is as follows: ； Coefficient The calculation formula is as follows: ； Wherein: represents the signal amplitude, represents the responsivity of the photodetector, represents the photosensitive area of the photodetector, represents the Bessel function of the first kind of the first order, represents the Bessel function of the first kind of the zero order, represents the small perturbation amplitude of the light on the 9. The control method of the multi-channel polarization control system for coherent combination according to claim 3, characterized in that, In S3, three wave plates (301) arranged in the order of 0°, 45°, and 0° in the polarization controller (3) are selected, and the polarization control amount of the wave plate (301) is controlled. Let the phase delays of the wave plates (301) loaded with the light beams of the ； For the th optical path beam, according to the derivation of the Stocks vector and the Muller matrix, the expression of the feedback quantity after beam demodulation is: 。 10. The control method of the multi-channel polarization control system for coherent combination according to claim 9, characterized in that, In S3, the first row vector has the following expression: ； For the subsampling, the feedback quantity is demodulated to form the second row vector , and for the th optical beam, the phase delays of the three wave plates (301) corresponding to the polarization controller (3) are respectively denoted as: ； To obtain a column vector , sample times to obtain a matrix , solve the equation by the least squares method, then the first row vector can be obtained, so that the coefficients corresponding to each path can be solved in parallel ; where: the column vector are ten parameters obtained by multiplying the Muller matrices of three of the said wave plates (301), represents the inverse matrix.

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