A lossless switching magneto-optical switch and a wave plate angle adjustment method

Abstract

The present application discloses a lossless magneto-optical switch and a wave plate angle adjustment method, belonging to the field of optics. A first polarization beam splitter decomposes parallel light into p-light and s-light. A first half-wave plate rotates the p-light 135° clockwise and the s-light 45° counterclockwise. A quarter-wave plate converts the change in the rotation angle of a Faraday rotator crystal into a phase delay change in polarized light. The Faraday rotator crystal applies magnetic fields in different directions to rotate the main optical path 45° clockwise or counterclockwise, simultaneously generating two weak optical paths. The full-wave plate reduces the phase delay change in polarized light and eliminates the angular dispersion of the Faraday rotator crystal. A second polarization beam splitter combines the two main optical paths and the two weak optical paths. When the optical channel is switched, both the strong light and the weak light are coupled into different channels. In the present application, the sum of the energies at the two output ends remains stable before and after the switching is completed. The quarter-wave plate and the full-wave plate solve the problem of optical crosstalk in optical transmission systems.

Description

Technical Field

[0001] The present invention relates to the field of optical elements, and in particular to a magneto-optical switch for lossless switching. Background Art

[0002] In the field of fiber-optic communications, optical switches, as a key passive component, are widely used to selectively switch optical signals within fiber-optic communication networks. Magneto-optical switches utilize the Faraday magneto-optical effect, primarily by altering the direction of an applied magnetic field to change the Faraday rotation angle within a magneto-optical crystal, thereby switching the optical path. Compared to traditional optical switches, magneto-optical switches offer advantages such as fast switching speed, no moving parts, and high stability, and are garnering increasing attention and research.

[0003] Currently, common magneto-optical switches do not adhere to energy conservation during switching. This means the sum of the energies of the connected and closed optical paths cannot maintain a stable value. The energy loss caused by switching severely impacts the stability of optical transmission systems. Lossless magneto-optical switches achieve low energy loss during switching, significantly improving the stability of optical transmission systems. However, existing lossless magneto-optical switches suffer from poor directionality, which can lead to optical signal crosstalk and hinder the selective switching of optical signals in optical transmission systems. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide a magneto-optical switch with good directionality and lossless switching.

[0005] In order to overcome the deficiencies of the prior art, a second object of the present invention is to provide a method for adjusting the wave plate angle of a magneto-optical switch with good directivity and lossless switching.

[0006] One of the purposes of the present invention is achieved by the following technical solution:

[0007] A lossless switching magneto-optical switch comprises an input end, a first output end, a second output end, and a first polarization beam splitter prism, a first half-wave plate, a quarter-wave plate, a Faraday rotator crystal, a full-wave plate, and a second polarization beam splitter prism arranged in sequence, wherein the input end is located on the side of the first polarization beam splitter prism away from the first half-wave plate, the first output end and the second output end are located on the side of the second polarization beam splitter prism away from the full-wave plate, the first polarization beam splitter prism and the second polarization beam splitter prism each comprise two crystals, the junction of the two crystals being coated, the first polarization beam splitter prism decomposes the parallel light input from the input end into two sub-beams p-light and s-light with orthogonal polarization directions, the p-light and the s-light forming two main optical paths, and the first half-wave plate is capable of polarizing the p-light. The polarization direction of the P light is rotated 135° clockwise along the optical transmission direction, and the polarization direction of the S light is rotated 45° counterclockwise along the optical transmission direction. The quarter-wave plate can convert the change in the rotation angle of the Faraday rotator crystal into a phase delay change of the polarized light. The Faraday rotator crystal applies magnetic fields in different directions to rotate the main optical path by 45° clockwise or 45° counterclockwise, while the polarization direction of a very weak light beam is not rotated to produce two weak optical paths. The full-wave plate can reduce the phase delay change of the polarized light, thereby eliminating the angular dispersion of the Faraday rotator crystal. The second polarization beam splitter converges the P light and the S light of the two main optical paths to the first output end or the second output end, and converges the P light and the S light of the two weak optical paths to the other second output end or the first output end.

[0008] Furthermore, the angle between the optical axis of the quarter wave plate and the optical axis of the first polarization beam splitter prism is -45°.

[0009] Furthermore, the angle between the optical axis direction of the full-wave plate and the optical axis direction of the first polarization beam splitter prism is -0.4°.

[0010] Furthermore, the two crystals of the first polarization beam splitter are respectively a parallelogram crystal and a triangular crystal, and the mating surfaces of the parallelogram crystal and the triangular crystal are coated with a film, and the film reflects S light.

[0011] Furthermore, the two crystals of the second polarization beam splitter are respectively two parallelogram crystals, and the bonding surfaces of the two parallelogram crystals are coated with a film, and the film reflects s ​​light and transmits p light.

[0012] Furthermore, the lossless switching magneto-optical switch also includes a second half-wave plate and a third half-wave plate, the second half-wave plate is located between the first polarization beam splitter prism and the first half-wave plate, the second half-wave plate is located on the p-light channel emitted from the first polarization beam splitter prism, the third half-wave plate is located between the Faraday rotator crystal and the second polarization beam splitter prism, and the third half-wave plate is located on the s-light channel emitted from the first polarization beam splitter prism.

[0013] Furthermore, the position of the second half-wave plate corresponds to the triangular crystal of the first polarization beam splitter prism, and the position of the third half-wave plate corresponds to the parallelogram crystal of the first polarization beam splitter prism.

[0014] Furthermore, the lossless switching magneto-optical switch further includes a first single-fiber collimator, which is located at the input end and collimates the divergent light beam output by the optical fiber into a parallel light beam.

[0015] Furthermore, the lossless switching magneto-optical switch further includes a second single-fiber collimator and a third single-fiber collimator, and the second single-fiber collimator and the third single-fiber collimator are respectively located at the first output end and the second output end.

[0016] The second object of the present invention is achieved by adopting the following technical solution:

[0017] A method for adjusting the wave plate angle of a magneto-optical switch based on any one of the above lossless switching methods, characterized by comprising the following steps:

[0018] The Jones matrix expression of the first half-wave plate is:

[0019]

[0020] Wherein, θ1 is the angle between the optical axis of the first half-wave plate and the optical axis of the first polarization beam splitter prism, i represents an imaginary number, δ1 is the phase delay of the first half-wave plate, and θ1 and δ1 are known values ​​according to the specific structure of the lossless magneto-optical switch;

[0021] The Jones matrix expression of the 1 / 4 wave plate is:

[0022]

[0023] Wherein, θ2 is the angle between the optical axis of the quarter wave plate and the optical axis of the first polarization beam splitter prism, i represents an imaginary number, δ2 is the phase delay of the quarter wave plate, θ2 is the angle to be solved, and δ2 is a known value;

[0024] The Jones matrix expression of the Faraday-rotating crystal is:

[0025]

[0026] Where θ3 is the rotation angle of the polarization direction of the sub-beam after passing through the Faraday rotator crystal,

[0027] θ3=45+k0(λ-λc)+k1(T-Tc) (4)

[0028] Wherein k0 is the wavelength correlation coefficient of the Faraday rotator crystal, λ is the wavelength of the incident light in vacuum, λc is the central wavelength of the magneto-optical switch, k1 is the temperature correlation coefficient of the Faraday rotator crystal, T is the temperature when the magneto-optical switch is operating, and Tc is the room temperature of 23°C;

[0029] The Jones matrix expression of the full-wave plate is:

[0030]

[0031] Wherein θ4 is the angle between the optical axis of the full-wave plate and the optical axis of the first polarization beam splitter prism, i represents an imaginary number, δ4 is the phase delay of the full-wave plate, θ4 is the angle to be solved, and δ4 is a known value;

[0032] When the optical path from the input end to the first output end is working, the directionality of the lossless magneto-optical switch is from the input end to the second output end.

[0033] The Jones matrix expression of p-polarized light in the forward direction is:

[0034]

[0035] The Jones matrix expression for s-polarized light forward transmission is:

[0036]

[0037] When the optical path from the input end to the second output end is working, the directionality of the lossless magneto-optical switch is from the input end to the first output end.

[0038] The Jones matrix expression of p-polarized light in the forward direction is:

[0039]

[0040] The Jones matrix expression for s-polarized light forward transmission is:

[0041]

[0042] Since Mp1 and Ms1 are positively correlated, and Mp2 and Ms2 are positively correlated, when Mp1 is at its maximum value, Ms1 is also at its maximum value; when Mp2 is at its maximum value, Ms2 is also at its maximum value; therefore, when either Mp1 or Ms1 is at its maximum value and either Mp2 or Ms2 is at its maximum value, the corresponding value of θ2 is the angle between the optical axis direction of the 1 / 4 wave plate and the optical axis direction of the first polarization beam splitter prism; the corresponding value of θ4 is the angle between the optical axis direction of the full-wave plate and the optical axis direction of the first polarization beam splitter prism.

[0043] Compared with the prior art, the lossless switching magneto-optical switch of the present invention includes a first polarization beam splitter prism, a first half-wave plate, a quarter-wave plate, a Faraday rotator crystal, a full-wave plate and a second polarization beam splitter prism arranged in sequence, the input end is located on the side of the first polarization beam splitter prism away from the first half-wave plate, the first output end and the second output end are located on the side of the second polarization beam splitter prism away from the full-wave plate, the first polarization beam splitter prism and the second polarization beam splitter prism each include two crystals, the two crystals are coated at the junction, the first polarization beam splitter prism decomposes the parallel light input at the input end into two sub-beams p light and s light with orthogonal polarization directions, the p light and s light are the two main light paths, the first half-wave plate can The polarization direction of the p light rotates 135° clockwise along the direction of optical transmission, and the polarization direction of the s light rotates 45° counterclockwise along the direction of optical transmission. The 1 / 4 wave plate can convert the change in the rotation angle of the Faraday rotator crystal into a phase delay change of the polarized light. The Faraday rotator crystal rotates the main light path 45° clockwise or 45° counterclockwise by applying magnetic fields in different directions. At the same time, the polarization direction of the very weak light beam does not rotate to produce two weak light paths. The full-wave plate can reduce the phase delay change of the polarized light, thereby eliminating the angular dispersion of the Faraday rotator crystal; the second polarization beam splitter converges the p light and s light of the two main light paths to the first output end or the second output end And the p light and s light of the two weak light paths are converged to another second output end or the first output end. By adopting multiple wave plate components, it is ensured that all light beams (main sub-beams and weak sub-beams) can be accurately converged to the output end after passing through the second polarization beam splitter prism. When the light channel is switched, it is essentially the intensities of the strong light and weak light paths are exchanged, and the strong light and weak light are coupled into different channels. When the switch is switched, it actually takes a certain response time to complete the switching. During the time from the start of the switching to the completion of the switching, the energy of the weak light will increase when the energy between the strong light and the weak light is converted. However, the magneto-optical switch in the prior art does not couple the weak light. Channel, resulting in instability in the system, which will not stabilize until all switching is completed. In the present application, the sum of the energies at the first output end and the second output end and the sum of the energies at the first output end and the second output end after switching are always in a stable state, which brings stability to network transmission; the 1 / 4 wave plate can convert the change in the rotation angle of the Faraday rotator crystal into a phase delay change of polarized light, and the full-wave plate can reduce the phase delay change of polarized light, thereby eliminating the angular dispersion of the Faraday rotator crystal. Therefore, the use of 1 / 4 wave plate and full-wave plate compensation can effectively solve the optical crosstalk problem generated by the lossless magneto-optical switch in the optical transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A perspective view of a magneto-optical switch for lossless switching according to a first embodiment of the present invention;

[0045] Figure 2This is a light path diagram from the input end to the first output end during operation in the first embodiment;

[0046] Figure 3 This is a light path diagram from the input end to the second output end in operation in the first embodiment;

[0047] Figure 4 This is a graph showing the relationship between wavelength and directivity before and after compensation from the input end to the second output end at room temperature when the input end to the first output end is working in the first embodiment;

[0048] Figure 5 This is a graph showing the relationship between wavelength and directivity before and after compensation from the input end to the first output end at room temperature when the input end to the second output end is working in the first embodiment;

[0049] Figure 6 A perspective view of a magneto-optical switch with lossless switching according to a second embodiment of the present invention;

[0050] Figure 7 This is a light path diagram from the input end to the first output end in operation in the second embodiment;

[0051] Figure 8 This is a light path diagram from the input end to the second output end during operation in the second embodiment;

[0052] Figure 9 Graph showing the relationship between wavelength and directivity before and after compensation from the input end to the second output end at room temperature when the input end to the first output end is working in the second embodiment;

[0053] Figure 10 This is a relationship diagram between wavelength and directivity before and after compensation from the input end to the first output end at room temperature when the input end to the second output end is working in the second embodiment.

[0054] In the figure: 101, first single-fiber collimator; 102, first polarization beam splitter prism; 103, first half-wave plate; 104, 1 / 4 wave plate; 105, Faraday rotator crystal; 106, full-wave plate; 107, second polarization beam splitter prism; 108, second single-fiber collimator; 109, third single-fiber collimator; 110, second half-wave plate; 111, third half-wave plate. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be another intermediate component through which it is fixed. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0058] First embodiment

[0059] See also Figures 1 to 5 , which is the first embodiment of the present application, a lossless switching magneto-optical switch includes a first single-fiber collimator 101, a first polarization beam splitter prism 102, a first half-wave plate 103, a quarter-wave plate 104, a Faraday rotator crystal 105, a full-wave plate 106, a second polarization beam splitter prism 107, a second single-fiber collimator 108, and a third single-fiber collimator 109, which are arranged in sequence.

[0060] The first single-fiber collimator 101 is used to collimate the incident light at the input end into a parallel light beam. The first single-fiber collimator 101 is located at the input end P1.

[0061] The first polarization beam splitter prism 102 includes two crystals, and the two crystals are coated at the bonding surface. Specifically, the two crystals of the first polarization beam splitter prism 102 are respectively a parallelogram crystal and a triangular crystal, and the parallelogram crystal and the triangular crystal are coated at the bonding surface, and the film reflects the s-light. The first polarization beam splitter prism 102 decomposes the parallel light input at the input end into two sub-beams of p-light and s-light with orthogonal polarization directions. At this time, the p-light and the s-light are the two main light paths. After being coated, the p-light can be directly transmitted and transmitted along the lower light path. The s-light is first reflected at the coating, and then undergoes total internal reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the upper light path.

[0062] The first half-wave plate 103 rotates the polarization direction of the p-light by 135° clockwise along the optical transmission direction, and rotates the polarization direction of the s-light by 45° counterclockwise along the optical transmission direction.

[0063] The Jones matrix expression of the first half-wave plate 103 is:

[0064]

[0065] Wherein, θ1 is the angle between the optical axis direction of the first half-wave plate 103 and the optical axis direction of the first polarization beam splitter prism 102, i represents an imaginary number, δ1 is the phase delay of the first half-wave plate 103, and θ1 and δ1 are known values ​​according to the specific structure of the lossless magneto-optical switch;

[0066] The quarter wave plate 104 can convert the change in the rotation angle of the Faraday rotator crystal 105 into a change in the phase delay of the polarized light.

[0067] The Jones matrix expression of the quarter wave plate 104 is:

[0068]

[0069] Wherein, θ2 is the angle between the optical axis of the quarter wave plate 104 and the optical axis of the first polarization beam splitter prism 102, i represents an imaginary number, δ2 is the phase delay of the quarter wave plate 104, θ2 is the angle to be solved, and δ2 is a known value;

[0070] Faraday rotator crystal 105 controls the operation of different channels of the magneto-optical switch by altering the direction of the magnetic field by applying different polarities to the applied voltage. This rotates the polarization of the two sub-beams in the main optical path. Due to the extinction ratio between the Faraday and wave plates, not all sub-beams are aligned in the ideal polarization state. Some very weak beams remain polarized, forming two weak optical paths.

[0071] The Jones matrix expression of the Faraday optically rotating crystal 105 is:

[0072]

[0073] Where θ3 is the rotation angle of the polarization direction of the sub-beam after passing through the Faraday rotator crystal 105,

[0074] θ3=45+k0(λ-λc)+k1(T-Tc) (4)

[0075] Wherein k0 is the wavelength-dependent coefficient of the Faraday rotator crystal 105, λ is the wavelength of the incident light in vacuum, λc is the central wavelength of the magneto-optical switch, k1 is the temperature-dependent coefficient of the Faraday rotator crystal 105, T is the temperature at which the magneto-optical switch operates, and Tc is the room temperature of 23°C;

[0076] The full-wave plate 106 can reduce the phase delay variation of polarized light, thereby eliminating the angular dispersion of the Faraday rotator crystal 105. The Jones matrix expression of the full-wave plate 106 is:

[0077]

[0078] Wherein θ4 is the angle between the optical axis direction of the full-wave plate 106 and the optical axis direction of the first polarization beam splitter prism 102, i represents an imaginary number, δ4 is the phase delay of the full-wave plate 106, θ4 is the angle to be solved, and δ4 is a known value.

[0079] The second polarization beam splitter prism 107 is used to combine light and comprises two crystals with a film coated at the joining surface of the two crystals. Specifically, the second polarization beam splitter prism 107 comprises two parallelogram crystals with a film coated at the joining surface of the two parallelogram crystals to reflect the S light.

[0080] The second single fiber collimator 108 is located at the first output end P2, and the third single fiber collimator 109 is located at the first output end P3.

[0081] Please continue reading Figure 2 When the magneto-optical switch is in the optical path from input terminal P1 to first output terminal P2, the working principle is as follows:

[0082] The divergent light beam output from the optical fiber (input end P1) is first collimated into a parallel beam by the first single-fiber collimator 101. After passing through the first polarization beam splitter prism 102, the parallel beam is decomposed into two sub-beams, p-light and s-light, with orthogonal polarization directions. The p-light is directly transmitted after being coated and transmitted along the lower optical path. The s-light is first reflected by the coating, then undergoes total internal reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the upper optical path. When passing through the first half-wave plate 103, the polarization direction of the p-light is rotated 135° clockwise along the optical transmission direction, and the polarization direction of the s-light is rotated 45° counterclockwise along the optical transmission direction. The quarter-wave plate 104 can convert the change in the rotation angle of the Faraday rotator crystal 105 into a change in the phase delay of the polarized light. After passing through Faraday rotator crystal 105, the polarization directions of the two sub-beams rotate 45° clockwise along the optical path. At this point, the p-light exiting the first polarization splitter prism 102 remains p-light, and the s-light remains s-light. This portion of the optical path is considered the main optical path. Due to the extinction ratio between the Faraday and wave plates, not 100% of the sub-beams are concentrated in the ideal polarization state. Some very weak beams remain polarized without any rotation. This portion of the optical path is considered the weak optical path, where the p-light exiting the first polarization splitter prism 102 is converted to s-light and vice versa. The full-wave plate 106 reduces the phase delay variation of the polarized light, thereby eliminating the angular dispersion caused by the Faraday rotator crystal 105.

[0083] After passing through the second polarization beam splitter prism 107, the connection between the two parallelogram crystals is coated. The p-ray can be directly transmitted through the film, while the s-ray is reflected after passing through the film. In the main optical path, the p-ray first passes through the lower parallelogram crystal, undergoing total internal reflection at the interface between the parallelogram crystal and the external air. It then transmits through the thin film connecting the two parallelogram crystals. It then passes through the upper parallelogram crystal, undergoing total internal reflection at the interface between the parallelogram crystal and the external air, and finally transmits to the second single-fiber collimator 108 (i.e., the first output port P2). The s-ray first reflects from the thin film connecting the two parallelogram crystals, then passes through the upper parallelogram crystal, undergoing total internal reflection at the interface between the parallelogram crystal and the external air, and finally transmits to the second single-fiber collimator 108 (i.e., the first output port P2). In the weak light path, the p-light is directly transmitted through the thin film connecting the two parallelogram crystals and transmitted to the third single-fiber collimator 109 (i.e., the second output end P3); the s-light first passes through the parallelogram crystal below, undergoes total internal reflection at the interface between the parallelogram crystal and the external air, and then is reflected at the thin film connecting the two parallelogram crystals and transmitted to the third single-fiber collimator 109 (i.e., the second output end P3).

[0084] When the optical path from the input end to the first output end is working, the directionality of the lossless magneto-optical switch is from the input end to the second output end.

[0085] The Jones matrix expression of p-polarized light in the forward direction is:

[0086]

[0087] The Jones matrix expression for s-polarized light forward transmission is:

[0088]

[0089] By setting the angle θ2 between the optical axis direction of the 1 / 4 wave plate 104 and the optical axis direction of the first polarization beam splitter prism 102, and the angle θ4 between the optical axis direction of the full wave plate 106 and the optical axis direction of the first polarization beam splitter prism 102, the directional bandwidth of the lossless magneto-optical switch can be increased, and the directionality can also be improved.

[0090] Since Mp1 is positively correlated with Ms1, when Mp1 is maximum, Ms1 is also maximum. Therefore, the values ​​of θ2 and θ4 can be determined in reverse by maximizing Mp1 or Ms1.

[0091] If the central wavelength of the lossless magneto-optical switch is 1550nm, the angle θ2 between the optical axis direction of the zero-order 1 / 4 wave plate 104 made of quartz material and the optical axis direction of the first polarization beam splitter prism 102 is selected to be -45°, and the angle θ4 between the optical axis direction of the full-wave plate 106 and the optical axis direction of the first polarization beam splitter prism 102 is selected to be -0.4°. The lossless magneto-optical switch can obtain the optimal directional bandwidth and can improve the directionality.

[0092] like Figure 4 As shown, when the operating wavelength of the lossless magneto-optical switch is 1520nm-1580nm, the directivity curves of P1->P3 vary with wavelength without adding the quarter wave plate 104 and the full wave plate 106 and with adding the quarter wave plate 104 and the full wave plate 106. Figure 4 It shows that the directivity of the lossless magneto-optical switch in the prior art is poor at the edge of the band. After compensation by the 1 / 4 wave plate 104 and the full wave plate 106, the directivity and bandwidth of the lossless magneto-optical switch are significantly improved. Therefore, using the 1 / 4 wave plate 104 and the full wave plate 106 for compensation can effectively solve the optical crosstalk problem generated by the lossless magneto-optical switch in the optical transmission system.

[0093] Please continue reading Figure 3 When the magneto-optical switch is in the input end P1->second output end P3 optical path channel (main optical path): observed in the light transmission direction, when P1 to P3 are connected, the working principle is as follows:

[0094] The divergent light beam output from the optical fiber (input end P1) is first collimated into a parallel beam by the first single-fiber collimator 101. After passing through the first polarization beam splitter prism 102, the parallel beam is decomposed into two sub-beams, p-light and s-light, with orthogonal polarization directions. The p-light is directly transmitted after being coated and transmitted along the lower optical path. The s-light is first reflected by the coating, then undergoes total internal reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the upper optical path. When passing through the first half-wave plate 103, the polarization direction of the p-light is rotated 135° clockwise along the optical transmission direction, and the polarization direction of the s-light is rotated 45° counterclockwise along the optical transmission direction. The quarter-wave plate 104 can convert the change in the rotation angle of the Faraday rotator crystal 105 into a change in the phase delay of the polarized light. After passing through Faraday rotator crystal 105, the polarization directions of the two sub-beams rotate 45° counterclockwise along the optical path. At this point, the light exiting the first polarization splitter prism 102 changes to s-light, and the s-light changes to p-light. This portion of the optical path is considered the main optical path. Due to the extinction ratio between the Faraday and wave plates, not 100% of the sub-beams are concentrated in the ideal polarization state. Some very weak beams remain polarized without rotation. These beams, i.e., the p-light and the s-light, exiting the first polarization splitter prism 102, remain p-light and s-light, respectively. This portion of the optical path is considered the weak optical path. The full-wave plate 106 reduces the phase delay variation of the polarized light, thereby eliminating the angular dispersion of the Faraday rotator crystal 105.

[0095] After passing through the second polarization beam splitter prism 107, the junction of the two parallelogram crystals is coated. This allows the p-ray to pass directly through the film, while the s-ray is reflected. In the main optical path, the p-ray is directly transmitted through the film connecting the two parallelogram crystals and transmitted to the third single-fiber collimator 109 (i.e., the second output port P3). The s-ray first passes through the lower parallelogram crystal, undergoes total internal reflection at the interface between the parallelogram crystal and the external air, and then reflects from the film connecting the two parallelogram crystals, transmitting to the third single-fiber collimator 109 (i.e., the second output port P3). In the weak light path, the p-light first passes through the parallelogram crystal below, undergoes total reflection at the interface between the parallelogram crystal and the external air, then transmits through the thin film connecting the two parallelogram crystals, then passes through the parallelogram crystal above, undergoes total reflection at the interface between the parallelogram crystal and the external air, and finally is transmitted to the second single-fiber collimator 108 (i.e., the first output end P2); the s-light first reflects at the thin film connecting the two parallelogram crystals, then passes through the parallelogram crystal above, undergoes total reflection at the interface between the parallelogram crystal and the external air, and finally is transmitted to the second single-fiber collimator 108 (i.e., the first output end P2).

[0096] When the optical path from the input end to the second output end is working, the directionality of the lossless magneto-optical switch is from the input end to the first output end.

[0097] The Jones matrix expression of p-polarized light in the forward direction is:

[0098]

[0099] The Jones matrix expression for s-polarized light forward transmission is:

[0100]

[0101] By setting the angle θ2 between the optical axis direction of the 1 / 4 wave plate 104 and the optical axis direction of the first polarization beam splitter prism 102, and the angle θ4 between the optical axis direction of the full wave plate 106 and the optical axis direction of the first polarization beam splitter prism 102, the directional bandwidth of the lossless magneto-optical switch can be increased, and the directionality can also be improved.

[0102] Since Mp2 is positively correlated with Ms2, when Mp2 is maximum, Ms2 is also maximum. Therefore, the values ​​of θ2 and θ4 can be determined in reverse by maximizing Mp2 or Ms2.

[0103] If the central wavelength of the lossless magneto-optical switch is 1550nm, the angle θ2 between the optical axis direction of the zero-order 1 / 4 wave plate 104 made of quartz material and the optical axis direction of the first polarization beam splitter prism 102 is selected to be -45°, and the angle θ4 between the optical axis direction of the full-wave plate 106 and the optical axis direction of the first polarization beam splitter prism 102 is selected to be -0.4°. The lossless magneto-optical switch can obtain the optimal directional bandwidth and can improve the directionality.

[0104] like Figure 5 As shown, when the operating wavelength of the lossless magneto-optical switch is 1520nm-1580nm, the directivity of P1->P2 varies with wavelength without adding the quarter wave plate 104 and the full wave plate 106 and with adding the quarter wave plate 104 and the full wave plate 106. Figure 5 It shows that the directivity of the lossless magneto-optical switch in the prior art is poor at the edge of the band. After compensation by the 1 / 4 wave plate 104 and the full wave plate 106, the directivity and bandwidth of the lossless magneto-optical switch are significantly improved. Therefore, using the 1 / 4 wave plate 104 and the full wave plate 106 for compensation can effectively solve the optical crosstalk problem generated by the lossless magneto-optical switch in the optical transmission system.

[0105] Second embodiment

[0106] Please continue reading Figures 6 to 10, which is the second embodiment of the present application, a lossless switching magneto-optical switch includes a first single-fiber collimator 101, a first polarization beam splitter prism 102, a second half-wave plate 110, a first half-wave plate 103, a quarter-wave plate 104, a Faraday rotator crystal 105, a full-wave plate 106, a third half-wave plate 111, a second polarization beam splitter prism 107, a second single-fiber collimator 108 and a third single-fiber collimator 109, which are arranged in sequence.

[0107] The first single-fiber collimator 101 is used to collimate the incident light at the input end into a parallel light beam. The first single-fiber collimator 101 is located at the input end P1.

[0108] The first polarization beam splitter prism 102 includes two crystals, and the two crystals are coated at the bonding surface. Specifically, the two crystals of the first polarization beam splitter prism 102 are respectively a parallelogram crystal and a triangular crystal, and the parallelogram crystal and the triangular crystal are coated at the bonding surface, and the film reflects the s-light. The first polarization beam splitter prism 102 decomposes the parallel light input at the input end into two sub-beams of p-light and s-light with orthogonal polarization directions. At this time, the p-light and the s-light are the two main light paths. After being coated, the p-light can be directly transmitted and transmitted along the lower light path. The s-light is first reflected at the coating, and then undergoes total internal reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the upper light path.

[0109] The second half-wave plate 110 is located corresponding to the triangular crystal of the first polarization beam splitter prism 102 . The second half-wave plate 110 rotates the polarization direction of the p-light 90° counterclockwise along the optical transmission direction, and the p-light is converted into s-light.

[0110] The Jones matrix expression of the second half-wave plate 110 is:

[0111]

[0112] Wherein, θ5 is the angle between the optical axis direction of the second half-wave plate 110 and the optical axis direction of the first polarization beam splitter prism 102, i represents an imaginary number, δ5 is the phase delay of the second half-wave plate 110, and θ5 and δ5 are known values ​​according to the specific structure of the lossless switching magneto-optical switch;

[0113] The first half-wave plate 103 rotates the polarization direction of the s-light by 45° counterclockwise along the optical transmission direction.

[0114] Faraday rotator crystal 105 controls the operation of different channels of the magneto-optical switch by altering the direction of the magnetic field by applying different polarities to the applied voltage. This rotates the polarization of the two sub-beams in the main optical path. Due to the extinction ratio between the Faraday and wave plates, not all sub-beams are aligned in the ideal polarization state. Some very weak beams remain polarized, forming two weak optical paths.

[0115] The position of the third half-wave plate 111 corresponds to the quadrilateral crystal of the first polarization beam splitter prism 102. The third half-wave plate 111 rotates the s-light in the main light path 90° counterclockwise along the direction of light path propagation, and rotates the p-light in the weak light path 90° clockwise along the direction of light path propagation. At this time, the s-light in the upper main light path is converted into p-light, and the p-light in the weak light path is converted into s-light.

[0116] The Jones matrix expression of the third half-wave plate 111 is:

[0117]

[0118] Wherein, θ6 is the angle between the optical axis direction of the third half-wave plate 111 and the optical axis direction of the first polarization beam splitter prism 102, i represents an imaginary number, δ6 is the phase delay of the third half-wave plate 111, and θ6 and δ6 are known values ​​according to the specific structure of the lossless magneto-optical switch;

[0119] The second polarization beam splitter prism 107 is used to combine light and comprises two crystals with a film coated at the joining surface of the two crystals. Specifically, the second polarization beam splitter prism 107 comprises two parallelogram crystals with a film coated at the joining surface of the two parallelogram crystals to reflect the S light.

[0120] The second single fiber collimator 108 is located at the first output end P2, and the third single fiber collimator 109 is located at the first output end P3.

[0121] Please continue reading Figure 7 When the magneto-optical switch is in the optical path from input terminal P1 to first output terminal P2, the working principle is as follows:

[0122] The divergent light beam output from the optical fiber (input end P1) is first collimated into a parallel beam by the first single-fiber collimator 101. After passing through the first polarization beam splitter prism 102, the parallel beam is split into two sub-beams, p-light and s-light, with orthogonal polarization directions. The p-light is directly transmitted after being coated and transmitted along the lower optical path. The s-light is first reflected by the coating, then undergoes total internal reflection at the interface between the parallelogram crystal and the external air, transmitting along the upper optical path. The second half-wave plate 110 is located in the lower optical path. Since the s-light does not pass through the second half-wave plate 110, it continues to propagate in the air medium. After passing through the second half-wave plate 110, the polarization direction of the p-light beam rotates 90° counterclockwise along the optical path, converting it to s-light. Both sub-beams on the two optical paths are s-light. After passing through the first half-wave plate 103, the polarization directions of the two sub-beams rotate 45° counterclockwise along the optical path. The quarter-wave plate 104 converts the change in the rotation angle of the Faraday rotator crystal 105 into a change in the phase delay of the polarized light. After passing through the Faraday rotator crystal 105, the polarization directions of the two sub-beams rotate 45° counterclockwise along the optical path, converting them from s-light to p-light. This portion of the optical path belongs to the main optical path. Due to the extinction ratio between the Faraday and wave plates, not 100% of the sub-beams are concentrated in the ideal polarization state. Some very weak beams remain s-light, with their polarization directions not rotated. The full-wave plate 106 reduces the phase delay change of the polarized light, thereby eliminating the angular dispersion of the Faraday rotator crystal 105. In the upper optical path of the third half-wave plate 111, the p-light in the lower direction does not pass through the third half-wave plate 111 and continues to propagate through the air. The p-light in the upper main optical path rotates 90° clockwise along the optical path propagation direction, while the s-light in the weak optical path rotates 90° counterclockwise along the optical path propagation direction. At this time, the p-light in the upper main optical path is converted to s-light, and the s-light in the weak optical path is converted to p-light.

[0123] After passing through the second polarization beam splitter prism 107, the connection between the two parallelogram crystals is coated. The p-ray can be directly transmitted through the film, while the s-ray is reflected after passing through the film. In the main optical path, the p-ray first passes through the lower parallelogram crystal, undergoing total internal reflection at the interface between the parallelogram crystal and the external air. It then transmits through the thin film connecting the two parallelogram crystals. It then passes through the upper parallelogram crystal, undergoing total internal reflection at the interface between the parallelogram crystal and the external air, and finally transmits to the second single-fiber collimator 108 (i.e., the first output port P2). The s-ray first reflects from the thin film connecting the two parallelogram crystals, then passes through the upper parallelogram crystal, undergoing total internal reflection at the interface between the parallelogram crystal and the external air, and finally transmits to the second single-fiber collimator 108 (i.e., the first output port P2). In the weak light path, the p-light is directly transmitted through the thin film connecting the two parallelogram crystals and transmitted to the third single-fiber collimator 109 (i.e., the second output end P3); the s-light first passes through the parallelogram crystal below, undergoes total internal reflection at the interface between the parallelogram crystal and the external air, and then is reflected at the thin film connecting the two parallelogram crystals and transmitted to the third single-fiber collimator 109 (i.e., the second output end P3).

[0124] When the optical path from the input end to the first output end is working, the directionality of the lossless magneto-optical switch is from the input end to the second output end.

[0125] The Jones matrix expression of p-polarized light in the forward direction is:

[0126]

[0127] The Jones matrix expression for s-polarized light forward transmission is:

[0128]

[0129] By setting the angle θ2 between the optical axis direction of the 1 / 4 wave plate 104 and the optical axis direction of the first polarization beam splitter prism 102, and the angle θ4 between the optical axis direction of the full wave plate 106 and the optical axis direction of the first polarization beam splitter prism 102, the directional bandwidth of the lossless magneto-optical switch can be increased, and the directionality can also be improved.

[0130] Since Mp1 is positively correlated with Ms1, when Mp1 is maximum, Ms1 is also maximum. Therefore, the values ​​of θ2 and θ4 can be determined in reverse by maximizing Mp1 or Ms1.

[0131] If the central wavelength of the lossless magneto-optical switch is 1550nm, the angle θ2 between the optical axis direction of the zero-order 1 / 4 wave plate 104 made of quartz material and the optical axis direction of the first polarization beam splitter prism 102 is selected to be -45°, and the angle θ4 between the optical axis direction of the full-wave plate 106 and the optical axis direction of the first polarization beam splitter prism 102 is selected to be -0.4°. The lossless magneto-optical switch can obtain the optimal directional bandwidth and can improve the directionality.

[0132] like Figure 9 As shown, when the operating wavelength of the lossless magneto-optical switch is 1520nm-1580nm, the directivity curves of P1->P3 vary with wavelength without adding the quarter wave plate 104 and the full wave plate 106 and with adding the quarter wave plate 104 and the full wave plate 106. Figure 9 It shows that the directivity of the lossless magneto-optical switch in the prior art is poor at the edge of the band. After compensation by the 1 / 4 wave plate 104 and the full wave plate 106, the directivity and bandwidth of the lossless magneto-optical switch are significantly improved. Therefore, using the 1 / 4 wave plate 104 and the full wave plate 106 for compensation can effectively solve the optical crosstalk problem generated by the lossless magneto-optical switch in the optical transmission system.

[0133] Please continue reading Figure 8 When the magneto-optical switch is in the input end P1->second output end P3 optical path channel (main optical path): observed in the light transmission direction, when P1 to P3 are connected, the working principle is as follows:

[0134] The divergent light beam output from the optical fiber (input end P1) is first collimated into a parallel beam by the first single-fiber collimator 101. After passing through the first polarization beam splitter prism 102, the parallel beam is split into two sub-beams, p-light and s-light, with orthogonal polarization directions. The p-light is directly transmitted after being coated and transmitted along the lower optical path. The s-light is first reflected by the coating, then undergoes total internal reflection at the interface between the parallelogram crystal and the external air, transmitting along the upper optical path. The second half-wave plate 110 is located in the lower optical path. Since the s-light does not pass through the second half-wave plate 110, it continues to propagate in the air medium. After passing through the second half-wave plate 110, the polarization direction of the p-light beam rotates 90° counterclockwise along the optical path, converting it to s-light. Both sub-beams on the two optical paths are s-light. After passing through the first half-wave plate 103, the polarization directions of the two sub-beams rotate 45° counterclockwise along the optical path. The quarter-wave plate 104 converts the change in the rotation angle of the Faraday rotator crystal 105 into a change in the phase delay of the polarized light. After passing through the Faraday rotator crystal 105, the polarization directions of the two sub-beams rotate 45° clockwise along the optical path, remaining s-light. This portion of the optical path belongs to the main optical path. Due to the extinction ratio between the Faraday rotator crystal and the wave plate, not all sub-beams are concentrated in the ideal polarization state. Some very weak beams remain polarized without rotation, converting from s-light to p-light. This portion of the optical path belongs to the weak optical path. The full-wave plate 106 reduces the phase delay change of the polarized light, thereby eliminating the angular dispersion of the Faraday rotator crystal 105. In the upper optical path with the third half-wave plate 111, the s-light in the lower direction does not pass through the third half-wave plate 111 and continues to propagate through the air. The s-light in the upper main optical path rotates 90° counterclockwise along the optical path propagation direction, while the p-light in the weak optical path rotates 90° clockwise along the optical path propagation direction. At this point, the s-light in the upper main optical path is converted to p-light, and the p-light in the weak optical path is converted to s-light.

[0135] After passing through the second polarization beam splitter prism 107, the junction of the two parallelogram crystals is coated. This allows the p-ray to pass directly through the film, while the s-ray is reflected. In the main optical path, the p-ray is directly transmitted through the film connecting the two parallelogram crystals and transmitted to the third single-fiber collimator 109 (i.e., the second output port P3). The s-ray first passes through the lower parallelogram crystal, undergoes total internal reflection at the interface between the parallelogram crystal and the external air, and then reflects from the film connecting the two parallelogram crystals, transmitting to the third single-fiber collimator 109 (i.e., the second output port P3). In the weak light path, the p-light first passes through the parallelogram crystal below, undergoes total reflection at the interface between the parallelogram crystal and the external air, then transmits through the thin film connecting the two parallelogram crystals, then passes through the parallelogram crystal above, undergoes total reflection at the interface between the parallelogram crystal and the external air, and finally is transmitted to the second single-fiber collimator 108 (i.e., the first output end P2); the s-light first reflects at the thin film connecting the two parallelogram crystals, then passes through the parallelogram crystal above, undergoes total reflection at the interface between the parallelogram crystal and the external air, and finally is transmitted to the second single-fiber collimator 108 (i.e., the first output end P2).

[0136] When the optical path from the input end to the second output end is working, the directionality of the lossless magneto-optical switch is from the input end to the first output end.

[0137] The Jones matrix expression of p-polarized light in the forward direction is:

[0138]

[0139] The Jones matrix expression for s-polarized light forward transmission is:

[0140]

[0141] By setting the angle θ2 between the optical axis direction of the 1 / 4 wave plate 104 and the optical axis direction of the first polarization beam splitter prism 102, and the angle θ4 between the optical axis direction of the full wave plate 106 and the optical axis direction of the first polarization beam splitter prism 102, the directional bandwidth of the lossless magneto-optical switch can be increased, and the directionality can also be improved.

[0142] Since Mp4 is positively correlated with Ms4, when Mp4 is maximum, Ms4 is also maximum. Therefore, the values ​​of θ2 and θ4 can be determined in reverse by maximizing Mp4 or Ms4.

[0143] If the central wavelength of the lossless magneto-optical switch is 1550nm, the angle θ2 between the optical axis direction of the zero-order 1 / 4 wave plate 104 made of quartz material and the optical axis direction of the first polarization beam splitter prism 102 is selected to be -45°, and the angle θ4 between the optical axis direction of the full-wave plate 106 and the optical axis direction of the first polarization beam splitter prism 102 is selected to be -0.4°. The lossless magneto-optical switch can obtain the optimal directional bandwidth and can improve the directionality.

[0144] like Figure 10 As shown, when the operating wavelength of the lossless magneto-optical switch is 1520nm-1580nm, the directivity of P1->P2 varies with wavelength without adding the quarter wave plate 104 and the full wave plate 106 and with adding the quarter wave plate 104 and the full wave plate 106. Figure 10 It shows that the directivity of the lossless magneto-optical switch in the prior art is poor at the edge of the band. After compensation by the 1 / 4 wave plate 104 and the full wave plate 106, the directivity and bandwidth of the lossless magneto-optical switch are significantly improved. Therefore, using the 1 / 4 wave plate 104 and the full wave plate 106 for compensation can effectively solve the optical crosstalk problem generated by the lossless magneto-optical switch in the optical transmission system.

[0145] As can be seen from the above principle, when the optical channel is switched, it is essentially the exchange of the intensity of the strong light and weak light paths. After deducting the material absorption, material reflectivity loss and coupling loss between parts, theoretically the sum of the energy of the two is equal to the input light energy. This solution couples both strong light and weak light into different channels (the magneto-optical switches currently on the market only couple strong light channels, not weak light channels). When the switch is switched, it actually takes a certain response time to complete the switch. During the time when the switch starts but is not completed, the energy of the weak light increases when the energy is converted between the strong light and the weak light. However, since the conventional magneto-optical switch does not couple the weak light channel, instability occurs in the system, and it will not stabilize until all switches are completed). In this invention, the sum of the energy at the P2+P3 channel and the sum of the energy of the P2+P3 channel after the switch is completed are always in a stable state, which brings stability to the network transmission.

[0146] The dispersion of the Faraday rotator crystal 105 is compensated by using a quarter-wave plate 104 and a full-wave plate 106, remedying the poor directivity of existing lossless magneto-optical switches and achieving high directivity within the wavelength range of 1520-1580 nm. This design not only significantly reduces the energy loss during the switching process but also avoids the optical crosstalk problem associated with lossless magneto-optical switches, providing high stability and selectivity for optical transmission systems.

[0147] The above embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patented invention. It should be noted that those skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention. These variations and improvements are equivalent modifications and improvements to the above embodiments based on the essential technology of the present invention and fall within the scope of protection of the present invention.

Claims

1. A magneto-optical switch for lossless switching, comprising an input terminal, a first output terminal, and a second output terminal, characterized in that: The lossless switching magneto-optical switch further comprises a first polarization beam splitter prism, a first half-wave plate, a quarter-wave plate, a Faraday rotator crystal, a full-wave plate and a second polarization beam splitter prism which are arranged in sequence. The input end is located on the side of the first polarization beam splitter prism away from the first half-wave plate, the first output end and the second output end are located on the side of the second polarization beam splitter prism away from the full-wave plate, the first polarization beam splitter prism and the second polarization beam splitter prism each comprise two crystals, the two crystals are coated at the junction, the first polarization beam splitter prism decomposes the parallel light input from the input end into two sub-beams p light and s light with orthogonal polarization directions, the p light and the s light are two main optical paths, and the first half-wave plate can adjust the polarization direction of the p light in the clockwise direction along the optical path transmission direction. The Faraday rotator crystal rotates the main optical path by 135°, and the polarization direction of the S light rotates counterclockwise by 45° along the optical path propagation direction. The quarter-wave plate can convert the change in the rotation angle of the Faraday rotator crystal into a phase delay change of the polarized light. The Faraday rotator crystal applies magnetic fields in different directions to rotate the main optical path by 45° clockwise or 45° counterclockwise, while the polarization direction of a very weak light beam does not rotate, resulting in two weak optical paths. The full-wave plate can reduce the phase delay change of the polarized light, thereby eliminating the angular dispersion of the Faraday rotator crystal. The second polarization beam splitter converges the P light and S light of the two main optical paths to one of the first output end and the second output end, and converges the P light and S light of the two weak optical paths to the other of the second output end and the first output end.

2. The magneto-optical switch for lossless switching according to claim 1, characterized in that: The angle between the optical axis of the quarter wave plate and the optical axis of the first polarization beam splitter prism is -45°.

3. The magneto-optical switch for lossless switching according to claim 1, characterized in that: The angle between the optical axis direction of the full-wave plate and the optical axis direction of the first polarization beam splitter prism is -0.4°.

4. The magneto-optical switch for lossless switching according to claim 1, wherein: The two crystals of the first polarization beam splitter are respectively a parallelogram crystal and a triangular crystal, and the mating surfaces of the parallelogram crystal and the triangular crystal are coated to reflect the s light and transmit the p light.

5. The magneto-optical switch for lossless switching according to claim 4, characterized in that: The two crystals of the second polarization beam splitter are two parallelogram crystals, and the bonding surfaces of the two parallelogram crystals are coated to reflect the S light.

6. The magneto-optical switch for lossless switching according to claim 5, characterized in that: The lossless magneto-optical switch also includes a second half-wave plate and a third half-wave plate, wherein the second half-wave plate is located between the first polarization beam splitter prism and the first half-wave plate, and the second half-wave plate is located on the p-light channel emitted from the first polarization beam splitter prism; the third half-wave plate is located between the Faraday rotator crystal and the second polarization beam splitter prism, and the third half-wave plate is located on the s-light channel emitted from the first polarization beam splitter prism.

7. The magneto-optical switch for lossless switching according to claim 6, characterized in that: The position of the second half-wave plate corresponds to the triangular crystal of the first polarization beam splitter prism, and the position of the third half-wave plate corresponds to the parallelogram crystal of the first polarization beam splitter prism.

8. The magneto-optical switch for lossless switching according to claim 1, characterized in that: The lossless switching magneto-optical switch further includes a first single-fiber collimator, which is located at the input end and collimates the divergent light beam output by the optical fiber into a parallel light beam.

9. The magneto-optical switch for lossless switching according to claim 8, characterized in that: The lossless switching magneto-optical switch further includes a second single-fiber collimator and a third single-fiber collimator, and the second single-fiber collimator and the third single-fiber collimator are respectively located at the first output end and the second output end.

10. A method for adjusting the wave plate angle of a magneto-optical switch for lossless switching according to any one of claims 1 to 9, characterized in that: The following steps are involved: The Jones matrix expression of the first half-wave plate is: （1） in, is the angle between the optical axis of the first half-wave plate and the optical axis of the first polarization beam splitter prism, represents an imaginary number, is the phase retardation of the first half-wave plate, as well as The specific structure of the magneto-optical switch according to lossless switching is a known value; The Jones matrix expression of the 1 / 4 wave plate is: （2） in, is the angle between the optical axis of the quarter wave plate and the optical axis of the first polarization beam splitter prism, represents an imaginary number, is the phase retardation of the quarter-wave plate, is the angle to be solved, is a known value; The Jones matrix expression of the Faraday-rotating crystal is: （3） in is the rotation angle of the polarization direction of the sub-beam after passing through the Faraday rotator crystal, （4） in is the wavelength-dependent coefficient of the Faraday rotatory crystal, is the wavelength of the incident light in vacuum, is the central wavelength of the magneto-optical switch, is the temperature dependence coefficient of the Faraday rotatory crystal, is the working temperature of the magneto-optical switch, Normal temperature is 23℃; The Jones matrix expression of the full-wave plate is: （5） in is the angle between the optical axis of the full-wave plate and the optical axis of the first polarization beam splitter prism, represents an imaginary number, is the phase delay of the full-wave plate, θ4 is the angle to be solved, is a known value; When the optical path from the input end to the first output end is working, the directionality of the lossless magneto-optical switch is from the input end to the second output end. The Jones matrix expression of p-polarized light in the forward direction is: （6） The Jones matrix expression for s-polarized light forward transmission is: （7） When the optical path from the input end to the second output end is working, the directionality of the lossless magneto-optical switch is from the input end to the first output end. The Jones matrix expression of p-polarized light in the forward direction is: （8） The Jones matrix expression for s-polarized light forward transmission is: （9） because and Positive correlation, and Positive correlation, when When it is the maximum value, It is also the maximum value; When it is the maximum value, is also the maximum value; therefore, when and When any one of and When any one of is the maximum value, the corresponding The value of is the angle between the optical axis direction of the 1 / 4 wave plate and the optical axis direction of the first polarization beam splitter prism; The value of is the angle between the optical axis direction of the full-wave plate and the optical axis direction of the first polarization beam splitter prism.

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