Nondestructive switching magneto-optical switch and wave plate included angle adjusting method

Abstract

The invention discloses a lossless switching magneto-optical switch and a wave plate included angle adjusting method, and belongs to the field of optics, a first polarization splitting prism decomposes parallel light into p light and s light, a first half-wave plate rotates the p light clockwise by 135 degrees and rotates the s light anticlockwise by 45 degrees, and a second half-wave plate rotates the p light clockwise by 135 degrees and rotates the s light anticlockwise by 45 degrees; the 1 / 4 wave plate converts the change of the rotation angle of the Faraday optical rotation crystal into the phase delay change of polarized light, the Faraday optical rotation crystal enables light of a main light path to rotate by 45 degrees clockwise or anticlockwise by applying magnetic fields in different directions, two weak light paths are generated at the same time, and the full wave plate reduces the phase delay change of the polarized light and eliminates angular dispersion of the Faraday optical rotation crystal. The second polarization splitting prism combines the light of the two main light paths and combines the light of the two weak light paths, when the light channels are switched, the strong light and the weak light are coupled into different channels, the sum of the energy of the two output ends is always in a stable state before and after switching is completed, and the switching efficiency is improved. The 1 / 4 wave plate and the full wave plate solve the problem of optical crosstalk in an optical transmission system.

Description

Technical Field

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

[0002] In the field of fiber-optic communication, optical switches, as an important component of passive devices, are widely used in fiber-optic communication networks to selectively switch optical signals. Magneto-optical switches are optical switches that use the Faraday magneto-optical effect. They mainly change the direction of the Faraday rotation angle in the magneto-optical crystal by changing the direction of the external magnetic field, thereby achieving the purpose of switching the optical path. Compared with traditional optical switches, magneto-optical switches have the advantages of fast switching speed, no moving parts, and high stability, and have received more and more attention and research.

[0003] At present, common magneto-optical switches do not satisfy the energy conservation law during the switching process, that is, the sum of the energy of the connected optical path and the closed optical path cannot maintain a stable value, and the energy loss caused by the switch seriously affects the stability of the optical transmission system. The lossless magneto-optical switch realizes the function of low energy loss during the switch switching process, greatly improving the stability of the optical transmission system, but the existing lossless magneto-optical switch has the problem of poor directionality, which will cause the problem of optical signal crosstalk, which is not conducive to the optical transmission system to selectively switch the optical signal. 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 directivity and lossless switching.

[0005] In order to overcome the shortcomings of the prior art, a second object of the present invention is to provide a method for adjusting the angle of a magneto-optical switch wave plate 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 a 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 a 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 joint, 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 polarize the p light. The polarization direction of the S light rotates 135° clockwise along the transmission direction of the optical path, and the polarization direction of the S light rotates 45° counterclockwise along the transmission direction of the optical path. The 1 / 4 wave plate can convert the change of 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 light path by 45° clockwise or 45° counterclockwise. 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 the S light of the two main light paths to the first output end or the second output end, and converges the P light and the S light of the two weak light paths to the other second output end or the first output end.

[0008] Furthermore, the angle between the optical axis direction of the quarter wave plate and the optical axis direction 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 prism 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 prism are respectively two parallelogram crystals, and the mating surfaces of the two parallelogram crystals are coated with a film, and the film reflects the s light and transmits the 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] Further, 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 also 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 also 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 in that it comprises 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 direction of the first half-wave plate and the optical axis direction 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 magneto-optical switch for lossless switching;

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

[0022]

[0023] Wherein, 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, i represents an imaginary number, δ2 is the phase delay of the 1 / 4 wave plate, θ2 is the angle to be solved, and δ2 is a known value;

[0024] The Jones matrix expression of the Faraday optically active 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 of the magneto-optical switch when it is working, 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 direction of the full-wave plate and the optical axis direction 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 of 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 of 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 the maximum value, Ms1 is also the maximum value; when Mp2 is the maximum value, Ms2 is also the maximum value; therefore, when any one of Mp1 and Ms1 is the maximum value and any one of Mp2 and Ms2 is the 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 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 splitter prism.

[0043] Compared with the prior art, the lossless switching magneto-optical switch of the present invention 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 both comprise two crystals, the two crystals are coated at the joint, 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 the s light are two main light paths, the first half-wave plate can The polarization direction of the p light rotates 135° clockwise along the transmission direction of the optical path, and the polarization direction of the s light rotates 45° counterclockwise along the transmission direction of the optical path. 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 applies magnetic fields in different directions to rotate the main light path 45° clockwise or 45° counterclockwise. 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 the 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 optical channel is switched, it is essentially the intensities of the strong light and the weak light paths are exchanged, and the strong light and the 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 when the switching starts but the switching is not completed, when the energy between the strong light and the weak light is converted, the energy of the weak light will increase. However, since the magneto-optical switch in the prior art does not couple the weak light Channel, resulting in instability in the system, until all switching is completed, the system will not stabilize, while 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 the switching is completed are always in a stable state, which brings stability to the network transmission; the 1 / 4 wave plate can convert the change of the rotation angle of the Faraday rotator crystal into the phase delay change of the polarized light, and the full-wave plate can reduce the phase delay change of the 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 three-dimensional diagram 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 in operation in the first embodiment;

[0046] Figure 3 It 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 the wavelength and directivity of the input end to the second output end before and after compensation at room temperature when the input end to the first output end is working in the first embodiment;

[0048] Figure 5 A graph showing the relationship between the wavelength and the 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 in the first embodiment works;

[0049] Figure 6 A three-dimensional diagram of a magneto-optical switch for 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 It is a light path diagram from the input end to the second output end in operation in the second embodiment;

[0052] Fig. 9 A graph showing the relationship between the wavelength and the 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 in the second embodiment works;

[0053] Fig.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 works in the second embodiment.

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

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of 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 those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related 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 joint. 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 joint 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 p-light and s-light with orthogonal polarization directions. At this time, the p-light and the s-light are two main light paths. The p-light can be directly transmitted after being coated and transmitted along the optical path below. The s-light is first reflected at the coating, and then undergoes total reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the optical path above.

[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 magneto-optical switch for lossless switching;

[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 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 direction of the 1 / 4 wave plate 104 and the optical axis direction of the first polarization beam splitter prism 102, i represents an imaginary number, δ2 is the phase delay of the 1 / 4 wave plate 104, θ2 is the angle to be solved, and δ2 is a known value;

[0070] The Faraday rotator crystal 105 controls the operation of different channels of the magneto-optical switch by changing the direction of the magnetic field by connecting different positive and negative poles of the voltage. The Faraday rotator crystal 105 rotates the polarization directions of the two sub-beams of the main optical path. Due to the relationship between the extinction ratio of the Faraday and the wave plate, not 100% of the sub-beams are concentrated in the ideal polarization state, and the polarization directions of some very weak beams are not rotated, 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 correlation 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 correlation coefficient of the Faraday rotator crystal 105, T is the temperature of the magneto-optical switch when it is working, and Tc is the room temperature of 23°C;

[0076] The full-wave plate 106 can reduce the phase delay change of the 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 for combining light, and includes two crystals, and the joint of the two crystals is coated. Specifically, the second polarization beam splitter prism 107 includes two parallelogram crystals, and the joint surface of the two parallelogram crystals is coated with a film, and the film reflects 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 input end P1->first output end P2 optical path channel: observed in the light transmission direction, when P1 to P2 is connected, the working principle is as follows:

[0082] The divergent light beam outputted from the optical fiber (input end P1) is first collimated into a parallel light beam by the first single-fiber collimator 101; after the parallel light beam passes through the first polarization beam splitter prism 102, the parallel light beam is decomposed into two sub-beams p light and s light with orthogonal polarization directions. The p light can be directly transmitted after being coated and transmitted along the optical path below. The s light is first reflected at the coating, and then undergoes total reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the optical path above; when passing through the first half-wave plate 103, the polarization direction of the p light rotates 135° clockwise along the optical path transmission direction, and the polarization direction of the s light rotates 45° counterclockwise along the optical path transmission direction. The 1 / 4 wave plate 104 can convert the change in the rotation angle of the Faraday rotator crystal 105 into a phase delay change 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 transmission direction of the optical path. At this time, the p-light emitted at the first polarization beam splitter prism 102 is still p-light, and the s-light is still s-light. This part of the optical path belongs to the main optical path. Due to the relationship between the extinction ratio of Faraday and the wave plate, not 100% of the sub-beams are concentrated in the ideal polarization state. There are also some very weak beams whose polarization directions are not rotated. This part of the beam is the p-light emitted at the first polarization beam splitter prism 102 changed to s-light, and the s-light changed to p-light. This part 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.

[0083] After passing through the second polarization beam splitter prism 107, the connection between the two parallelogram crystals is subjected to coating treatment, and the p-light can be directly transmitted after passing through the film, and the s-light will be reflected after passing through the film. In the main optical path, the p-light first passes through the lower parallelogram crystal, and a total reflection phenomenon occurs at the interface between the parallelogram crystal and the external air, and then transmits through the thin film connected by the two parallelogram crystals, and then passes through the upper parallelogram crystal, and a total reflection phenomenon occurs 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 end P2); the s-light first reflects at the thin film connected by the two parallelogram crystals, and then passes through the upper parallelogram crystal, and a total reflection phenomenon occurs 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 end P2). In the weak light path, the p light is directly transmitted through the thin film connected by the two parallelogram crystals, and is 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 reflection at the interface between the parallelogram crystal and the external air, and is then reflected at the thin film connected by the two parallelogram crystals, and is 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 of 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 -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 -0.4°, the lossless magneto-optical switch can obtain the best directional bandwidth and can improve the directionality.

[0092] like Figure 4 As shown, when the working wavelength of the lossless magneto-optical switch is 1520nm-1580nm, the directivity of P1->P3 changes with the wavelength without adding the 1 / 4 wave plate 104 and the full wave plate 106 and with adding the 1 / 4 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 working (main optical path): observed in the direction of light transmission, when P1 to P3 are connected, the working principle is as follows:

[0094] The divergent light beam outputted from the optical fiber (input end P1) is first collimated into a parallel light beam by the first single-fiber collimator 101; after the parallel light beam passes through the first polarization beam splitter prism 102, the parallel light beam is decomposed into two sub-beams p light and s light with orthogonal polarization directions. The p light can be directly transmitted after being coated and transmitted along the optical path below. The s light is first reflected at the coating, and then undergoes total reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the optical path above; when passing through the first half-wave plate 103, the polarization direction of the p light rotates 135° clockwise along the optical path transmission direction, and the polarization direction of the s light rotates 45° counterclockwise along the optical path transmission direction. The 1 / 4 wave plate 104 can convert the change in the rotation angle of the Faraday rotator crystal 105 into a phase delay change 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 transmission direction of the optical path. At this time, the light emitted at the first polarization beam splitter prism 102 changes to s light, and the s light changes to p light. This part of the optical path belongs to the main optical path. Due to the relationship between the extinction ratio of Faraday and the wave plate, not 100% of the sub-beams are concentrated in the ideal polarization state. There are also some very weak beams whose polarization directions are not rotated. This part of the beam is the p light emitted at the first polarization beam splitter prism 102, and the s light is still the s light. This part 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.

[0095] After passing through the second polarization beam splitter prism 107, the connection between the two parallelogram crystals is subjected to a coating treatment, and the p-light can be directly transmitted after passing through the film, and the s-light will be reflected after passing through the film. In the main optical path, the p-light is directly transmitted through the film connected by the two parallelogram crystals, and is 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, and is totally reflected at the interface between the parallelogram crystal and the external air, and then is reflected at the film connected by the two parallelogram crystals, and is transmitted to the third single-fiber collimator 109 (i.e., the second output end P3). In the weak light path, the p light first passes through the parallelogram crystal below, and is totally reflected at the interface between the parallelogram crystal and the external air, then is transmitted through the thin film connecting the two parallelogram crystals, then passes through the parallelogram crystal above, and is totally reflected 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 is reflected at the thin film connecting the two parallelogram crystals, then passes through the parallelogram crystal above, and is totally reflected 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 of 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 -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 -0.4°, the lossless magneto-optical switch can obtain the best directional bandwidth and can improve the directionality.

[0104] like Figure 5 As shown, when the working wavelength of the lossless magneto-optical switch is 1520nm-1580nm, the directivity of P1->P2 changes with the 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 joint. 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 joint 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 p-light and s-light with orthogonal polarization directions. At this time, the p-light and the s-light are two main light paths. The p-light can be directly transmitted after being coated and transmitted along the optical path below. The s-light is first reflected at the coating, and then undergoes total reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the optical path above.

[0109] The position of the second half-wave plate 110 corresponds 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 by 90° counterclockwise along the transmission direction of the optical path, and the p-light is converted into the 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 magneto-optical switch for lossless switching;

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

[0114] The Faraday rotator crystal 105 controls the operation of different channels of the magneto-optical switch by changing the direction of the magnetic field by connecting different positive and negative poles of the voltage. The Faraday rotator crystal 105 rotates the polarization directions of the two sub-beams of the main optical path. Due to the relationship between the extinction ratio of the Faraday and the wave plate, not 100% of the sub-beams are concentrated in the ideal polarization state, and the polarization directions of some very weak beams are not rotated, forming two weak optical paths.

[0115] The position of the third half-wave plate 111 corresponds to the quadrilateral crystal of the first polarization splitter prism 102. The third half-wave plate 111 rotates the s-light of the main light path 90° counterclockwise along the propagation direction of the light path, and rotates the p-light of the weak light path 90° clockwise along the propagation direction of the light path. 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 magneto-optical switch for lossless switching;

[0119] The second polarization beam splitter prism 107 is used for combining light, and includes two crystals, and the joint of the two crystals is coated. Specifically, the second polarization beam splitter prism 107 includes two parallelogram crystals, and the joint surface of the two parallelogram crystals is coated with a film, and the film reflects 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 input end P1->first output end P2 optical path channel: observed in the light transmission direction, when P1 to P2 is connected, the working principle is as follows:

[0122] The divergent light beam outputted from the optical fiber (input end P1) is first collimated into a parallel light beam by the first single-fiber collimator 101; after the parallel light beam passes through the first polarization beam splitter prism 102, the parallel light beam is decomposed into two sub-beams p light and s light with orthogonal polarization directions. The p light can be directly transmitted after being coated and transmitted along the optical path below. The s light is first reflected at the coating, and then undergoes total reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the optical path above; the second half-wave plate 110 is in the optical path below, and since the s light does not pass through the second half-wave plate 110, it continues to propagate in the air medium. After the p-light passes through the second half-wave plate 110, the polarization direction rotates 90° counterclockwise along the transmission direction of the optical path. At this time, the p-light is converted into s-light, and the sub-beams on the two optical paths are all s-light; after passing through the first half-wave plate 103, the polarization directions of the two sub-beams rotate 45° counterclockwise along the transmission direction of the optical path; the 1 / 4 wave plate 104 can convert the change in the rotation angle of the Faraday rotator crystal 105 into a phase delay change of polarized light. After passing through the Faraday rotator crystal 105, the polarization directions of the two sub-beams rotate 45° counterclockwise along the transmission direction of the optical path. At this time, the two sub-beams change from s-light to p-light, and this part of the optical path belongs to the main optical path. Due to the relationship between the extinction ratio of Faraday and the wave plate, not 100% of the sub-beams are concentrated in the ideal polarization state, and there are some very weak beams whose polarization directions do not rotate. This part of the beam is still s-light, and this part 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. The third half-wave plate 111 is in the upper optical path. Since the p light at the lower side does not pass through the third half-wave plate 111, it continues to propagate along the air medium. The p light at the upper main optical path rotates 90° clockwise along the optical path propagation direction, and the s light at the weak optical path rotates 90° counterclockwise along the optical path propagation direction. At this time, the p light at the upper main optical path is converted into s light, and the s light at the weak optical path is converted into p light;

[0123] After passing through the second polarization beam splitter prism 107, the connection between the two parallelogram crystals is subjected to coating treatment, and the p-light can be directly transmitted after passing through the film, and the s-light will be reflected after passing through the film. In the main optical path, the p-light first passes through the lower parallelogram crystal, and a total reflection phenomenon occurs at the interface between the parallelogram crystal and the external air, and then transmits through the thin film connected by the two parallelogram crystals, and then passes through the upper parallelogram crystal, and a total reflection phenomenon occurs 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 end P2); the s-light first reflects at the thin film connected by the two parallelogram crystals, and then passes through the upper parallelogram crystal, and a total reflection phenomenon occurs 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 end P2). In the weak light path, the p light is directly transmitted through the thin film connected by the two parallelogram crystals, and is 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 reflection at the interface between the parallelogram crystal and the external air, and is then reflected at the thin film connected by the two parallelogram crystals, and is 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 of 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 -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 -0.4°, the lossless magneto-optical switch can obtain the best directional bandwidth and can improve the directionality.

[0132] like Fig. 9 As shown, when the working wavelength of the lossless magneto-optical switch is 1520nm-1580nm, the directivity of P1->P3 changes with the wavelength without adding the 1 / 4 wave plate 104 and the full wave plate 106 and with adding the 1 / 4 wave plate 104 and the full wave plate 106. Fig. 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 working (main optical path): observed in the direction of light transmission, when P1 to P3 are connected, the working principle is as follows:

[0134] The divergent light beam outputted from the optical fiber (input end P1) is first collimated into a parallel light beam by the first single-fiber collimator 101; after the parallel light beam passes through the first polarization beam splitter prism 102, the parallel light beam is decomposed into two sub-beams p light and s light with orthogonal polarization directions. The p light can be directly transmitted after being coated and transmitted along the optical path below. The s light is first reflected at the coating, and then undergoes total reflection at the interface between the parallelogram crystal and the external air, and is transmitted along the optical path above; the second half-wave plate 110 is in the optical path below, and since the s light does not pass through the second half-wave plate 110, it continues to propagate in the air medium. After the p-light passes through the second half-wave plate 110, the polarization direction rotates 90° counterclockwise along the transmission direction of the optical path. At this time, the p-light is converted into s-light, and the sub-beams on the two optical paths are all s-light; after passing through the first half-wave plate 103, the polarization directions of the two sub-beams rotate 45° counterclockwise along the propagation direction of the optical path; the 1 / 4 wave plate 104 can convert the change in the rotation angle of the Faraday rotator crystal 105 into a phase delay change 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 transmission direction of the optical path. At this time, the two sub-beams are still s-light, and this part of the optical path belongs to the main optical path. Due to the relationship between the extinction ratio of Faraday and the wave plate, not 100% of the sub-beams are concentrated in the ideal polarization state, and there are some very weak beams whose polarization directions are not rotated. This part of the beam is changed from s-light to p-light, and this part 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. The third half-wave plate 111 is in the upper optical path. Since the s-light at the bottom does not pass through the third half-wave plate 111, it continues to propagate along the air medium. The s-light at the upper main optical path rotates 90° counterclockwise along the optical path propagation direction, and the p-light at the weak optical path rotates 90° clockwise along the optical path propagation direction. At this time, the s-light at the upper main optical path is converted into p-light, and the p-light at the weak optical path is converted into s-light;

[0135] After passing through the second polarization beam splitter prism 107, the connection between the two parallelogram crystals is subjected to a coating treatment, and the p-light can be directly transmitted after passing through the film, and the s-light will be reflected after passing through the film. In the main optical path, the p-light is directly transmitted through the film connected by the two parallelogram crystals, and is 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, and is totally reflected at the interface between the parallelogram crystal and the external air, and then is reflected at the film connected by the two parallelogram crystals, and is transmitted to the third single-fiber collimator 109 (i.e., the second output end P3). In the weak light path, the p light first passes through the parallelogram crystal below, and is totally reflected at the interface between the parallelogram crystal and the external air, then is transmitted through the thin film connecting the two parallelogram crystals, then passes through the parallelogram crystal above, and is totally reflected 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 is reflected at the thin film connecting the two parallelogram crystals, then passes through the parallelogram crystal above, and is totally reflected 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 of 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 -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 -0.4°, the lossless magneto-optical switch can obtain the best directional bandwidth and can improve the directionality.

[0144] like Fig.10 As shown, when the working wavelength of the lossless magneto-optical switch is 1520nm-1580nm, the directivity of P1->P2 changes with the 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. Fig.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 rotation crystal 105 is compensated by the quarter wave plate 104 and the full wave plate 106, making up for the defect of poor directivity of the existing lossless magneto-optical switch, and realizing the function of high directivity in the wavelength range of 1520-1580nm. This design can not only greatly reduce the energy loss generated by the magneto-optical switch during the switching process, but also avoid the optical crosstalk problem generated by the lossless magneto-optical switch, providing high stability and selectivity for the optical transmission system.

[0147] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which are equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of them belong to the protection scope of the present invention.

Claims

1. A lossless switching magneto-optical switch, comprising an input end, a first output end and a second output end, characterized in that: The lossless switching magneto-optical switch also 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 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 include two crystals, the two crystals are coated at the joint, 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 light paths, and the first half-wave plate can transmit the polarization direction of the p light along the light path The first output terminal and the second output terminal are used to transmit the p-light and s-light of the main optical path in a clockwise direction of 135°, and the polarization direction of the s-light is rotated 45° counterclockwise along the optical path transmission direction. The 1 / 4 wave plate can convert the change of the rotation angle of the Faraday rotator crystal into the phase delay change of the polarized light. The Faraday rotator crystal can rotate the main optical path light by 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 is not rotated to generate 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 the first output terminal or the second output terminal, and converges the p-light and s-light of the two weak optical paths to the other second output terminal or the first output terminal.

2. The magneto-optical switch for lossless switching according to claim 1, characterized in that: The angle between the optical axis direction of the quarter wave plate and the optical axis direction 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, characterized in that: 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 the s light and transmits 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 prism are two parallelogram crystals respectively, and the bonding surfaces of the two parallelogram crystals are coated with a film, and the film reflects the S light.

6. The magneto-optical switch for lossless switching according to claim 5, characterized in that: The lossless switching 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, and 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 comprises 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: Wherein, θ1 is the angle between the optical axis direction of the first half-wave plate and the optical axis direction 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 magneto-optical switch for lossless switching; The Jones matrix expression of the 1 / 4 wave plate is: Wherein, 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, i represents an imaginary number, δ2 is the phase delay of the 1 / 4 wave plate, θ2 is the angle to be solved, and δ2 is a known value; The Jones matrix expression of the Faraday optically active crystal is: Where θ3 is the rotation angle of the polarization direction of the sub-beam after passing through the Faraday rotator crystal, θ3=45+k0(λ-λc)+k1(T-Tc) (4) 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 of the magneto-optical switch when it is working, and Tc is the room temperature of 23°C; The Jones matrix expression of the full-wave plate is: Wherein 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, 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; 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: The Jones matrix expression of s-polarized light forward transmission is: 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: The Jones matrix expression of s-polarized light forward transmission is: Since Mp1 and Ms1 are positively correlated, and Mp2 and Ms2 are positively correlated, when Mp1 is the maximum value, Ms1 is also the maximum value; when Mp2 is the maximum value, Ms2 is also the maximum value; therefore, when either Mp1 or Ms1 is the maximum value and either Mp2 or Ms2 is the 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 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 splitter prism.

Images