Two-stage optical isolator sharing magnet
By combining a shared magnet design with optical path foldback components, the problems of high cost, large size, and complex assembly caused by two sets of magnets in optical isolators are solved, achieving miniaturization and improved performance stability of optical isolators.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ADVANCED FIBER RESOURCES (ZHUHAI) LTD
- Filing Date
- 2026-01-30
- Publication Date
- 2026-05-12
AI Technical Summary
The existing optical isolators have two independent permanent magnet components, which result in high cost, large size, increased weight and complicated assembly, and there is a risk of mutual magnetic field interference, which affects performance stability.
By adopting a shared magnet design, a single set of magnets provides the same magnetic field space for two Faraday rotator crystals. Combined with the optical path folding component, this achieves compact optical path reversal, eliminating the need for a separate magnet assembly and simplifying the assembly process.
Significantly reduce cost and size, achieve miniaturization and lightweighting of devices, improve production efficiency and performance stability, and avoid performance fluctuations caused by magnetic field coupling.
Smart Images
Figure CN122018186A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of passive optical device technology, and specifically to a two-stage optical isolator with a shared magnet. Background Technology
[0002] Optical isolators are key passive components in optical communication, laser processing, and precision optical systems. Their core function is to allow unidirectional transmission of optical signals, thereby effectively isolating the light source from interference and damage caused by reflected light. To achieve higher isolation levels, the industry commonly adopts a scheme of cascading two-stage optical isolation units.
[0003] In existing technologies, each isolator core requires an independent permanent magnet assembly to generate the axial magnetic field needed for Faraday optical rotation crystals. While this traditional two-magnet architecture achieves the desired function, it also introduces significant drawbacks.
[0004] First, the two sets of high-performance permanent magnets directly increase material costs. Second, the magnets and their supporting structures increase the overall size and weight of the device. Third, the two sets of magnets in the limited packaging space not only pose a risk of mutual magnetic field interference, affecting performance stability, but also bring great complexity to assembly and debugging. It is necessary to accurately ensure the consistency of the spatial relative position, magnetic field direction and magnetic field strength of the two sets of magnets, which has stringent process requirements and low production efficiency.
[0005] Therefore, it is necessary to design a two-stage optical isolator that can overcome the inherent defects of the multi-magnet architecture while ensuring high performance. Summary of the Invention
[0006] The purpose of this invention is to provide a two-stage optical isolator with a shared magnet.
[0007] To achieve the objective of this invention, a two-stage optical isolator with a shared magnet is provided, comprising a set of magnets, a first optical isolator core, a second optical isolator core, and an optical path folding component. A magnetic field space is formed inside the magnet. The first optical isolator core includes a first polarization beamsplitter, a first half-wave plate, a first Faraday rotator crystal, and a second polarization beamsplitter arranged sequentially along a first forward optical path. The second optical isolator core includes a third polarization beamsplitter, a second half-wave plate, a second Faraday rotator crystal, and a fourth polarization beamsplitter arranged sequentially along a second forward optical path. The first and second forward optical paths are arranged parallel to each other in the same direction. Both the first and second Faraday rotator crystals are disposed within the magnetic field space of the same magnet. The input end of the optical path folding component receives the combined beam output from the second polarization beamsplitter, and the output end of the optical path folding component outputs the combined beam to the third polarization beamsplitter.
[0008] A further embodiment is that the optical path folding component includes a first reflecting prism and a second reflecting prism. The first reflecting prism is arranged after the second polarization beam splitter based on the first forward optical path, and the second reflecting prism is arranged before the third polarization beam splitter based on the second forward optical path. The first reflecting prism is used to receive the combined beam output from the second polarization beam splitter, the first reflecting prism is used to output the combined beam to the second reflecting prism, and the second reflecting prism is used to output the combined beam to the third polarization beam splitter.
[0009] A further proposed solution is that both the first and second reflecting prisms are right-angle reflecting prisms. The first reflecting prism includes a first reflecting surface and a second reflecting surface that are perpendicular to each other, and the second reflecting prism includes a third reflecting surface and a fourth reflecting surface that are perpendicular to each other. The first reflecting surface is opposite to the second polarizing beam splitter, the second reflecting surface is opposite to the third reflecting surface, and the fourth reflecting surface is opposite to the third polarizing beam splitter.
[0010] A further approach is to include an input collimator in the dual-stage optical isolator, which is positioned before the first polarization beamsplitter based on the first forward optical path.
[0011] A further proposed approach is to arrange the first Faraday optical rotator crystal and the second Faraday optical rotator crystal side by side, with the magnetic flux passing through the first Faraday optical rotator crystal being the same as that passing through the second Faraday optical rotator crystal.
[0012] A further proposed solution is to arrange the magnets in a ring.
[0013] A further proposed solution is that the magnet comprises a first magnet and a second magnet, with a magnetic field space formed between the first magnet and the second magnet.
[0014] The beneficial effects of this invention are that, compared with the traditional technical solution of two sets of magnets in the prior art, the bi-stage optical isolator with a shared magnet provided by this invention can significantly reduce cost and volume. By sharing the uniform magnetic field space provided by the same set of magnets between the first and second Faraday rotator crystals, a set of magnet components is directly eliminated. This not only significantly reduces the cost of expensive magnetic materials, but also, due to the reduction of the space occupied by a set of magnets and their mounting structure, the overall volume and weight of the device, especially the axial length, are greatly reduced, realizing the miniaturization and lightweighting of the device.
[0015] In addition, it simplifies the assembly process and improves production efficiency. Only a single set of magnets needs to be installed, aligned and fixed at once, which completely eliminates the complicated process of calibrating two sets of magnets separately and ensuring that their magnetic fields do not interfere with each other in the traditional solution. This reduces the requirements for assembly accuracy and thus improves production efficiency and product yield.
[0016] Furthermore, the two Faraday crystals are placed in the same magnetic field environment generated by the same magnetic source, ensuring that the magnetic flux, magnetic field direction, and temperature field they experience are highly consistent. This allows the optical rotation characteristics of the two stages (such as the rotation angle and its temperature drift) to achieve optimal matching, guaranteeing excellent and stable overall performance of the two-stage isolator from a physical perspective.
[0017] Furthermore, the single-magnet design eliminates the potential magnetic field coupling or mutual weakening effects between two independent magnets from the source, avoiding the risk of performance fluctuations or degradation caused by this, and greatly improving the reliability and environmental adaptability of the device during long-term operation.
[0018] Furthermore, by employing optical path folding components such as reflective prism groups to connect the front and rear isolator cores, a compact optical path reversal is achieved, allowing the two optical isolator cores to be arranged in parallel in the same direction and naturally placed together within the effective magnetic field space of the magnet. The design achieves functional integration while maintaining low optical path loss and good collimation. Attached Figure Description
[0019] Figure 1 This is an overall optical path diagram of an embodiment of the two-stage optical isolator of the present invention.
[0020] Figure 2 This is the forward optical path diagram of the first isolator core in an embodiment of the dual-stage optical isolator of the present invention.
[0021] Figure 3 This is the forward optical path diagram of the second isolator core in an embodiment of the dual-stage optical isolator of the present invention.
[0022] Figure 4 This is the reverse optical path diagram of the second isolator core in the embodiment of the dual-stage optical isolator of the present invention.
[0023] Figure 5 This is a reverse optical path diagram of the first isolator core in an embodiment of the dual-stage optical isolator of the present invention.
[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments. Detailed Implementation
[0025] Reference Figures 1 to 5 The dual-stage optical isolator includes a set of magnets 600, a first optical isolator core 500, a second optical isolator core 501, an input collimator 700, and an optical path folding component. The magnets 600 are arranged in a ring, and a magnetic field space is formed inside the magnets 600.
[0026] The first optical isolator core 500 includes a first polarization beam splitter 100, a first half-wave plate 200, a first Faraday rotator crystal 300, and a second polarization beam splitter 101 arranged sequentially along the first forward optical path L1. The second optical isolator core 501 includes a third polarization beamsplitter 102, a second half-wave plate 201, a second Faraday rotator crystal 301, and a fourth polarization beamsplitter 103 arranged sequentially along the second forward optical path L2. The first optical isolator core 500 and the second optical isolator core 501 are arranged side by side. The first Faraday rotator crystal 300 and the second Faraday rotator crystal 301 are arranged side by side along the side-by-side direction. The first forward optical path L1 and the second forward optical path L2 are arranged in the same direction and parallel to each other, with the side-by-side direction perpendicular to the first forward optical path L1. The first Faraday rotator crystal 300 and the second Faraday rotator crystal 301 are both set in the magnetic field space of the same magnet 600. The first Faraday rotator crystal 300 and the second Faraday rotator crystal 301 are arranged side by side, and the magnetic flux passing through the first Faraday rotator crystal 300 is the same as the magnetic flux passing through the second Faraday rotator crystal 301.
[0027] The input end of the optical path folding component is used to receive the combined beam output from the second polarization beam splitter 101, and the output end of the optical path folding component is used to output the combined beam to the third polarization beam splitter 102. Specifically, the optical path folding component includes a first reflecting prism 400 and a second reflecting prism 401. The first reflecting prism 400 is arranged after the second polarization beam splitter 101 based on the first forward optical path L1, and the second reflecting prism 401 is arranged before the third polarization beam splitter 102 based on the second forward optical path L2.
[0028] Both the first reflecting prism 400 and the second reflecting prism 401 are right-angle reflecting prisms. The first reflecting prism 400 includes a first reflecting surface and a second reflecting surface that are perpendicular to each other. The second reflecting prism 401 includes a third reflecting surface and a fourth reflecting surface that are perpendicular to each other. The first reflecting surface is opposite to the second polarizing beam splitter 101, the second reflecting surface is opposite to the third reflecting surface, and the fourth reflecting surface is opposite to the third polarizing beam splitter 102. The first reflecting prism 400 is used to receive the combined beam output from the second polarizing beam splitter 101, and the first reflecting prism 400 is used to output the combined beam to the second reflecting prism 401. The second reflecting prism 401 is used to output the combined beam to the third polarizing beam splitter 102.
[0029] The input collimator 700 is arranged in front of the first polarization beam splitter 100 based on the first forward optical path L1. Light is input from the input collimator 700 into the first polarization beam splitter 100 of the first optical isolator core 500. The first polarization beam splitter 100, the second polarization beam splitter 101, the third polarization beam splitter 102 and the fourth polarization beam splitter 103 are respectively coated with polarization beam splitting films on their respective inclined surfaces. The polarization beam splitting films transmit P light and reflect S light, respectively.
[0030] Forward light first enters the first polarizing beam splitter 100, such as... Figure 2 As shown, after entering the first polarization beam splitter 100, the light is split into two parallel sub-beams. The sub-beams are transmitted and then first enter the first half-wave plate 200 to achieve a 45° polarization rotation. Then they enter the first Faraday rotator crystal 300. Under the action of the magnetic field, the light of the target wavelength can achieve a 45° polarization rotation after passing through the first Faraday rotator crystal 300. Finally, the two beams are combined into one beam by the second polarization beam splitter 101 for output.
[0031] After being output from the first optical isolator core 500, the light passes through the first reflecting prism 400 and the second reflecting prism 401 before entering the second optical isolator core 501.
[0032] Similar to the operation of the first optical isolator core 500, light propagating in the second optical isolator core 501 first enters the third polarization beam splitter 102, such as... Figure 3 As shown, after entering the third polarization beam splitter 102, the light is split into two parallel sub-beams. The sub-beams are transmitted and then first enter the second half-wave plate 201, achieving a 45° polarization rotation. Then they enter the second Faraday rotator crystal 301. Under the action of the magnetic field, the light of the target wavelength can achieve a 45° polarization rotation after passing through the second Faraday rotator crystal 301. Finally, the two beams are combined into one output beam by the fourth polarization beam splitter 103.
[0033] Reverse light, due to its non-reciprocal rotation property, cannot return to the source. The specific reverse isolation process is as follows: Figure 4 As shown, when the returned light returns along the original path from the output of the second optical isolator core 501, due to the non-reciprocal 45° polarization rotation provided by the second Faraday rotator crystal 301, the returned light cannot return to the output of the first optical isolator core 500 at the input of the third polarization beamsplitter 102. However, in reality, due to the PER limit of the polarization beamsplitter, the rotation angle error of the Faraday rotator crystal, and the magnetic field temperature drift, approximately 0.1% of the returned light power will still return to the output of the first optical isolator core 500 from the input of the third polarization beamsplitter 102 and the optical path folding section, and then be input back into the first optical isolator core 500 from that output.
[0034] like Figure 5 As shown, similar to the first-stage isolation process, when the return light returns from the output of the first optical isolator core 500, due to the non-reciprocal 45° polarization rotation provided by the first Faraday rotator crystal 300, the return light cannot return to the input collimator 700 at the input of the first polarization beam splitter 100, thereby achieving two-stage optical isolation.
[0035] Of course, the above embodiments are only preferred embodiments of this case. In specific applications, there may be more variations. For example, the magnet may also include a first magnet and a second magnet, which are located on opposite sides. A magnetic field space is then formed between the first magnet and the second magnet. Arranging the first Faraday rotator crystal and the second Faraday rotator crystal in this magnetic field space can also achieve the purpose of this invention.
[0036] Furthermore, the optical path reversal section in this invention is not limited to using two reflecting prisms; it can also be a mirror group or an optical fiber loop. The optical fiber loop includes two collimators and a transmission optical fiber. The transmission optical fiber is connected between the two collimators. One collimator receives the combined light output from the second polarization beam splitter. After the combined light is transmitted through the transmission optical fiber, the other collimator outputs the combined light to the third polarization beam splitter, thereby achieving 180-degree optical path reversal. Of course, other optical elements that achieve the 180-degree optical path reversal function can also achieve the purpose of this invention.
[0037] As can be seen from the above, this case can significantly reduce costs and volume by using a dual-stage optical isolator with shared magnets. By using the uniform magnetic field space provided by the same set of magnets for the first and second Faraday rotator crystals, a set of magnet components is directly eliminated. This not only significantly reduces the cost of expensive magnetic materials, but also greatly reduces the overall size and weight of the device, especially the axial length, due to the reduction of the space occupied by a set of magnets and their mounting structure, thus achieving miniaturization and weight reduction of the device.
Claims
1. A two-stage optical isolator with a shared magnet, characterized in that, It includes a set of magnets, a first optical isolator core, a second optical isolator core, and an optical path folding-back component, wherein a magnetic field space is formed inside the magnet; The first optical isolator core includes a first polarizing beam splitter, a first half-wave plate, a first Faraday rotator crystal, and a second polarizing beam splitter arranged sequentially along the first forward optical path; The second optical isolator core includes a third polarization beam splitter, a second half-wave plate, a second Faraday rotator crystal, and a fourth polarization beam splitter arranged sequentially along the second forward optical path; The first forward optical path and the second forward optical path are arranged in the same direction and parallel to each other; The first Faraday rotator crystal and the second Faraday rotator crystal are both disposed within the magnetic field space of the same magnet; The input end of the optical path folding component is used to receive the combined beam output from the second polarization beam splitter, and the output end of the optical path folding component is used to output the combined beam to the third polarization beam splitter.
2. The dual-stage optical isolator according to claim 1, characterized in that: The optical path folding component includes a first reflecting prism and a second reflecting prism. The first reflecting prism is arranged in the stage after the second polarization beam splitter based on the first forward optical path, and the second reflecting prism is arranged in the stage before the third polarization beam splitter based on the second forward optical path. The first reflecting prism is used to receive the combined light output from the second polarization beam splitter, the first reflecting prism is used to output the combined light to the second reflecting prism, and the second reflecting prism is used to output the combined light to the third polarization beam splitter.
3. The dual-stage optical isolator according to claim 2, characterized in that: Both the first and second reflecting prisms are right-angle reflecting prisms. The first reflecting prism includes a first and a second reflecting surface that are perpendicular to each other. The second reflecting prism includes a third and a fourth reflecting surface that are perpendicular to each other. The first reflecting surface is opposite to the second polarizing beam splitter, the second reflecting surface is opposite to the third reflecting surface, and the fourth reflecting surface is opposite to the third polarizing beam splitter.
4. The dual-stage optical isolator according to claim 1, characterized in that: The dual-stage optical isolator further includes an input collimator arranged in front of the first polarization beam splitter based on the first forward optical path.
5. The dual-stage optical isolator according to claim 1, characterized in that: The first Faraday rotator crystal and the second Faraday rotator crystal are arranged side by side, and the magnetic flux passing through the first Faraday rotator crystal is the same as that passing through the second Faraday rotator crystal.
6. The dual-stage optical isolator according to any one of claims 1 to 5, characterized in that: The magnets are arranged in a ring.
7. The dual-stage optical isolator according to any one of claims 1 to 5, characterized in that: The magnet includes a first magnet and a second magnet, and the magnetic field space is formed between the first magnet and the second magnet.