Isolator based on birefringent crystal plain film

Abstract

The utility model relates to an isolator based on a birefringent crystal plain film. The isolator comprises an inlet end optical fiber assembly and an outlet end optical fiber assembly which are coupled with each other. The inlet end optical fiber assembly comprises an inlet end optical fiber head, a first birefringent crystal plain film, a wave plate and a first lens which are sequentially arranged along the direction of an optical path; the output end optical fiber assembly comprises a second lens, a magneto-optical crystal, a second birefringent crystal plain film and an output end optical fiber head which are sequentially arranged along the optical path direction; and a magnetic element is arranged outside the magneto-optical crystal. A wedge-shaped structure is replaced by the birefringent crystal plain film, and the lens is combined for direct coupling, so that the number of discrete components is reduced. Through the compact layout of the plain films, the integration level is improved, and beam splitting offset caused by a wedge angle is avoided. The use of the birefringent crystal plain film significantly reduces the length of an optical path, and the method can select a plain film, a wave plate and a magneto-optical crystal with smaller areas to realize an isolation function, thereby saving the cost.

Description

Technical Field

[0001] This utility model relates to the field of optical isolation devices in optical fiber communication and laser systems, and in particular to an isolator based on a birefringent crystal flat plate. Background Technology

[0002] Traditional optical isolators often employ a combination of optically active crystals and birefringent crystal wedges, requiring the separate production of the isolator core, which results in large size and low coupling efficiency. Two-stage isolators rely on complex fiber couplers, leading to low overall integration. Furthermore, heat dissipation issues in high-power scenarios also limit device stability. Utility Model Content

[0003] To address the aforementioned problems in the prior art, this invention provides an isolator based on a birefringent crystal flat plate.

[0004] To achieve the above objectives, the main technical solutions adopted by this utility model include:

[0005] An isolator based on a birefringent crystal flat plate includes an input fiber assembly and an output fiber assembly coupled to each other; the input fiber assembly includes an input fiber head, a first birefringent crystal flat plate, a waveplate, and a first lens arranged sequentially along the optical path direction; the output fiber assembly includes a second lens, a magneto-optical crystal, a second birefringent crystal flat plate, and an output fiber head arranged sequentially along the optical path direction; the magneto-optical crystal is provided with a magnetic element.

[0006] In some embodiments of this utility model, the first birefringent crystal plate is fixed at one end of the inlet fiber optic head opposite the first lens; the waveplate is fixed on the first birefringent crystal plate; and the inlet fiber optic head and the first lens are fixedly disposed inside the first glass tube.

[0007] In some embodiments of this utility model, the second birefringent crystal plate is fixedly disposed at one end of the output fiber head opposite the second lens; the magneto-optical crystal is fixedly disposed on the second birefringent crystal plate; and the second lens and the output fiber head are fixedly disposed inside the second glass tube.

[0008] An isolator based on a birefringent crystal flat plate is characterized in that it includes an input fiber assembly and an output fiber assembly coupled to each other; the input fiber assembly includes an input fiber head, a first birefringent crystal flat plate, a waveplate, a magneto-optical crystal, and a first lens arranged sequentially along the optical path direction; the output fiber assembly includes a second lens, a second birefringent crystal flat plate, and an output fiber head arranged sequentially along the optical path direction; and the magneto-optical crystal is provided with a magnetic element.

[0009] In some embodiments of this utility model, the first birefringent crystal plate is fixed on one end of the inlet fiber optic head opposite the first lens; the waveplate is fixed on the first birefringent crystal plate; the magneto-optical crystal is fixed on the waveplate; and the inlet fiber optic head and the first lens are fixedly disposed inside the first glass tube.

[0010] In some embodiments of this invention, the second birefringent crystal plate is fixedly disposed at one end of the output fiber head opposite the second lens; the second lens and the output fiber head are fixedly disposed inside the second glass tube.

[0011] In some embodiments of this utility model, the first glass tube and the second glass tube are coaxially arranged and fixedly disposed inside the third glass tube.

[0012] In some embodiments of this invention, the magnetic element is a magnetic ring, which is sleeved on the outside of the second glass tube.

[0013] In some embodiments of this utility model, the magnetic element is a magnetic ring, which is sleeved on the outside of the first glass tube.

[0014] In some embodiments of this invention, the waveplate is a quarter waveplate.

[0015] The beneficial effects of this invention are as follows: It replaces the wedge structure with a birefringent crystal flat plate, and combines it with direct coupling via a lens, reducing the number of discrete components. For example, the first birefringent crystal flat plate in the input assembly is integrated with the waveplate and lens, while the second birefringent crystal flat plate in the output assembly is directly connected to the magneto-optical crystal, simplifying the optical path and reducing the overall size. Furthermore, traditional two-stage isolators require multiple complex components connected in series, demanding extremely high assembly precision, while the new structure improves integration through the compact layout of the flat plates. Traditional wedge-shaped birefringent crystals, due to the increased wedge angle, lead to a wider beam spacing between the o-ray and e-ray, reducing collimation and increasing insertion loss. The new flat plate design avoids beam offset caused by the wedge angle. Through precise collimation by lenses (such as self-focusing lenses) and polarization rotation compensation by the waveplate, the forward-propagating beam is more efficiently combined and coupled to the output fiber, reducing energy loss. The use of birefringent crystal flat plates significantly reduces the optical path length, allowing for isolation functions to be achieved with smaller-area flat plates, waveplates, and magneto-optical crystals, saving costs.

[0016] This invention incorporates magnetic elements outside a magneto-optical crystal and forms a ring-shaped heat dissipation structure via a glass tube, utilizing an adhesive structure to create an efficient heat dissipation path. For example, the combination of the magnetic ring and the glass tube can quickly dissipate the heat generated by the magneto-optical crystal, preventing temperature accumulation from affecting the Faraday rotation accuracy, thereby enhancing the stability of the device in high-power scenarios.

[0017] The combination of a birefringent crystal planar sheet and the non-reciprocity of a magneto-optical crystal ensures low-loss transmission of forward light and effective isolation of reverse light. Furthermore, the polarization rotation properties of the magneto-optical crystal cause the reverse light to deflect at an angle as it passes through the birefringent crystal planar sheet, preventing it from coupling back into the input fiber, thus achieving high isolation. For wider bandwidth requirements, the low coefficient of thermal expansion of the planar sheet material (such as YVO4) reduces the impact of temperature variations on performance, broadening the operating wavelength range.

[0018] Traditional wedge-type isolators require precision machining of wedge-shaped crystals (wedge angle tolerance ±15%), while flat-plate structures are easier to machine and have easier dimensional tolerance control (e.g., YVO4 flat-plate tolerance ±0.05mm). Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of this utility model;

[0021] Figure 2 This is a schematic diagram of another embodiment of the structure of this utility model;

[0022] Explanation of reference numerals in the attached figures:

[0023] 100. Inlet fiber optic assembly; 110. Inlet fiber optic tip; 120. First birefringent crystal plate; 130. Waveplate; 140. First lens; 150. First glass tube; 160. Third glass tube; 200. Outlet fiber optic assembly; 210. Second lens; 220. Magneto-optic crystal; 230. Second birefringent crystal plate; 240. Outlet fiber optic tip; 250. Magnetic element; 260. Second glass tube. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model. Therefore, the following detailed description of the embodiments of this utility model provided in the accompanying drawings is not intended to limit the scope of the claimed utility model, but merely represents selected embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0025] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0027] Example:

[0028] like Figure 1 As shown, the input fiber assembly 100 includes an input fiber head 110, a first birefringent crystal plate 120, a waveplate 130, and a first lens 140 arranged sequentially along the optical path. The input fiber head 110 converts fiber light into collimated light, the birefringent crystal plate achieves optical path separation through polarization beam splitting, the waveplate 130 adjusts the polarization state, and the first lens 140 completes the beam shaping.

[0029] The output fiber optic assembly 200 includes a second lens 210, a magneto-optical crystal 220 and a magnetic element 250, a second birefringent crystal plate 230, and an output fiber optic connector 240 arranged along the optical path. The second lens 210 focuses the light beam, the magneto-optical crystal 220 rotates the polarization plane under the action of a magnetic field, the magnetic element 250 provides a constant magnetic field, the birefringent crystal plate synthesizes polarized light, and the output fiber optic connector 240 couples the light to the optical fiber.

[0030] In one embodiment, the first birefringent crystal plate 120 is a yttrium vanadate (YVO4) plate, which splits light into O light and E light; in another embodiment, the first birefringent crystal plate 120 is a lithium niobate (LiNbO3) or strontium titanate (SrTiO3) or potassium lithium niobate (KTN).

[0031] In one embodiment, waveplate 130 is a quarter waveplate 130.

[0032] In one embodiment, the first lens 140 is a self-focusing lens (GRIN lens) with a pitch of 2.1 and a numerical aperture matched fiber.

[0033] In one embodiment, the second lens 210 is a self-focusing lens with a pitch of 2.1.

[0034] In one embodiment, the magneto-optical crystal 220 is a Faraday rotator with a rotation angle of 45°. In another embodiment, the magneto-optical crystal 220 is replaced with a rare-earth iron garnet (YIG) crystal to reduce temperature dependence.

[0035] In one embodiment, the second birefringent crystal plate 230 is a lithium niobate (LiNbO3) plate, with its optical axis forming a 45° angle with the axis of the magneto-optical crystal 220. In another embodiment, the second birefringent crystal plate 230 is made of yttrium vanadate (YVO4), strontium titanate (SrTiO3), or potassium lithium niobate (KTN).

[0036] In one embodiment, the output fiber optic head 240 is directly coupled to the second lens 210.

[0037] In one embodiment, the first glass tube 150 is encapsulated in epoxy resin with the incoming fiber optic head 110, the first birefringent crystal flat plate 120, the waveplate 130, and the first lens 140 as a single unit, with a tube diameter of 6 mm.

[0038] In one embodiment, the second glass tube 260 encapsulates the second lens 210, the second birefringent crystal flat plate 230, the magneto-optical crystal 220, and the output fiber optic head 240 with epoxy resin, and the tube diameter is 6mm.

[0039] In one embodiment, the third glass tube 160 coaxially fixes the first and second glass tubes 260.

[0040] In one embodiment, the magnetic element 250 is a neodymium iron boron magnetic ring sleeved outside the second glass tube 260, with a magnetic flux density ≥1.5T;

[0041] In one embodiment, the first birefringent crystal plate 120 is fixed to one end of the input fiber optic head 110 opposite to the first lens 140; the waveplate 130 is fixed on the first birefringent crystal plate 120; the input fiber optic head 110 and the first lens 140 are fixedly disposed within the first glass tube 150. By integrating the first birefringent crystal plate 120, the waveplate 130, and the input fiber optic head 110 within the first glass tube 150 and fixing them by fusion or gluing, a tight connection between the components is achieved. This fixing method ensures the relative positional stability of each component in the optical path, avoids optical path offset caused by mechanical vibration or temperature changes, thereby reducing signal crosstalk and improving switching speed. This configuration allows light rays, after exiting the input fiber optic head 110, to sequentially pass through the first birefringent crystal plate 120 and the waveplate 130. During this process, the distances and angles between the optical elements are precisely controlled, ensuring that the light undergoes refraction and polarization as designed, optimizing optical path transmission and improving signal processing and transmission quality. Integrating all components within the first glass tube 150 forms a compact module, facilitating the integrated design and manufacturing of the entire isolator. During production, the input fiber optic assembly 100 can be assembled and tested as a whole before connecting and integrating with other parts, improving production efficiency, reducing costs, and facilitating quality inspection and maintenance of the entire isolator. A ring-shaped heat dissipation structure is formed using the glass tube, and an efficient heat dissipation path is created using bonding structures. For example, the combination of a magnetic ring and a glass tube can quickly dissipate the heat generated by the magneto-optical crystal 220, preventing temperature accumulation from affecting Faraday rotation accuracy and thus enhancing the stability of the device in high-power scenarios.

[0042] In one embodiment, the second birefringent crystal plate 230 is fixedly disposed at one end of the output fiber optic head opposite the second lens 210; the magneto-optical crystal 220 is fixedly disposed on the second birefringent crystal plate 230; the second lens 210 and the output fiber optic head 240 are fixedly disposed inside the second glass tube 260; this allows light emitted from the second lens 210 to precisely pass through the magneto-optical crystal 220 and the second birefringent crystal plate 230 sequentially. This facilitates precise modulation and processing of the optical signal, ensuring that the optical signal changes its polarization state and other characteristics according to design requirements, thereby achieving good optical isolation and improving the performance of the isolator. Fixing the second lens 210 and the output fiber optic head 240 inside the second glass tube 260, together with the internal second birefringent crystal plate 230 and magneto-optical crystal 220, forms a stable overall structure. This ensures that the relative positions of the various components in the output fiber optic assembly 200 remain precisely fixed, effectively resisting the influence of external forces such as vibration and impact in practical applications, avoiding optical path deviation due to component displacement, and ensuring the long-term stable operation of the optical isolator. The second glass tube 260 provides physical protection for the internal optical components, preventing the ingress of external contaminants such as dust and moisture, thus avoiding damage to the surface of the optical components or affecting their optical performance. Simultaneously, the material of the glass tube also helps reduce the impact of factors such as ambient temperature changes on the internal components, further improving the stability and reliability of the output fiber optic assembly 200. This modular design allows the output fiber optic assembly 200 to be manufactured and assembled as an independent unit. During manufacturing, each component can be precisely installed and debugged within the second glass tube 260 to form a complete assembly before integration with other parts. This greatly simplifies the entire isolator assembly process, improves production efficiency, and reduces production costs.

[0043] In one embodiment, the first glass tube 150 and the second glass tube 260 are coaxially arranged and fixedly disposed within the third glass tube 160. The coaxial arrangement of the first glass tube 150 and the second glass tube 260 ensures strict alignment of the optical paths of the input fiber optic assembly 100 and the output fiber optic assembly 200. This allows for accurate transmission of optical signals between the two components, reducing signal loss and scattering caused by optical path deviations, and ensuring the high performance of the optical isolator. Fixing both components within the third glass tube 160 further enhances the stability of the overall structure, preventing changes in the relative positions of the two glass tubes due to external forces or other factors during use, thereby continuously ensuring the accuracy of the optical path and guaranteeing stable optical signal transmission.

[0044] In this invention, a birefringent crystal flat plate replaces the traditional crystal. By optimizing the crystal size, the coupling with the fiber optic head is simplified, and the overall volume is reduced. Furthermore, by optimizing the internal structure of the isolator and using a birefringent crystal flat plate, the maximum optical power of the isolator can be further increased. Simultaneously, it can completely replace traditional devices in terms of structure and performance. This not only improves product performance but also simplifies the user's application process.

[0045] The magneto-optical element and heat dissipation structure work together, with a magnetic ring surrounding the magneto-optical crystal 220 and a ring-shaped glass tube for heat dissipation, to avoid performance degradation caused by temperature rise in high-power scenarios.

[0046] The lens pair design incorporates lenses at both the inlet and outlet ends to balance beam collimation and focusing, thereby improving optical path stability. Spherical lenses and focusing fiber lenses are typically used. Spherical lenses utilize their focusing and diffusion properties to effectively guide the input beam in a specific direction, maintaining beam integrity. Focusing fiber lenses are used to focus the beam into parallel light, ensuring beam stability and transmission quality.

[0047] like Figure 2 As shown, an isolator based on a birefringent crystal flat plate includes an input fiber assembly 100 and an output fiber assembly 200 coupled to each other. The input fiber assembly 100 includes an input fiber head 110, a first birefringent crystal flat plate 120, a waveplate 130, a magneto-optical crystal 220, and a first lens 140 arranged sequentially along the optical path direction. The output fiber assembly 200 includes a second lens 210, a second birefringent crystal flat plate 230, and an output fiber head 240 arranged sequentially along the optical path direction. The magneto-optical crystal 220 is externally provided with a magnetic element 250.

[0048] In one embodiment, the first birefringent crystal plate 120 is fixed at one end of the input fiber head 110 opposite to the first lens 140; the waveplate 130 is fixed on the first birefringent crystal plate 120; the magneto-optical crystal 220 is fixed on the waveplate 130; and the input fiber head 110 and the first lens 140 are fixedly disposed inside the first glass tube 150.

[0049] In one embodiment, the second birefringent crystal plate 230 is fixedly disposed at one end of the output fiber head opposite the second lens 210; the second lens 210 and the output fiber head 240 are fixedly disposed inside the second glass tube 260.

[0050] In one embodiment, the magnetic element 250 is a magnetic ring, which is sleeved on the outside of the first glass tube 150.

[0051] Working principle:

[0052] During forward transmission:

[0053] The optical signal is decomposed into o-ray and e-ray by the first birefringent crystal plate 120;

[0054] Waveplate 130 rotates the polarization planes of the two beams by 45°, and after entering magneto-optical crystal 220, the polarization planes are non-reciprocally rotated by 45°.

[0055] The second birefringent crystal plate 230 combines two beams of light and couples them to the output optical fiber.

[0056] During reverse transmission:

[0057] The reflected light is decomposed into o'e' light by the second birefringent crystal plate 230, with the polarization plane opposite to the positive direction;

[0058] The magneto-optical crystal 220 has a non-reciprocal rotating polarization plane, which prevents o'e' light from passing through the first birefringent crystal plate 120.

[0059] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent modifications made based on the content of this utility model specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. An isolator based on a birefringent crystal flat, characterized in that: The application relates to a fiber-optic coupler, which comprises an input fiber assembly and an output fiber assembly which are coupled to each other; the input fiber assembly comprises an input fiber head, a first birefringent crystal flat, a wave plate and a first lens which are arranged in sequence along an optical path; the output fiber assembly comprises a second lens, a magneto-optical crystal, a second birefringent crystal flat and an output fiber head which are arranged in sequence along the optical path; and the magneto-optical crystal is externally provided with a magnetic element.

2. An isolator based on a birefringent crystal plate according to claim 1, characterized in that: The first birefringent crystal flat is fixed at one end of the input fiber head opposite to the first lens; the wave plate is fixed on the first birefringent crystal flat; and the input fiber head and the first lens are fixedly arranged in a first glass tube.

3. An isolator based on a birefringent crystal plate according to claim 2, characterized in that: The second birefringent crystal flat is fixedly arranged at one end of the output fiber head opposite to the second lens; the magneto-optical crystal is fixedly arranged on the second birefringent crystal flat; and the second lens and the output fiber head are fixedly arranged in a second glass tube.

4. An isolator based on a birefringent crystal plate, characterized in that: The application relates to a fiber-optic coupler, which comprises an input fiber assembly and an output fiber assembly which are coupled to each other; the input fiber assembly comprises an input fiber head, a first birefringent crystal flat, a wave plate and a first lens which are arranged in sequence along an optical path; the output fiber assembly comprises a second lens, a magneto-optical crystal, a second birefringent crystal flat and an output fiber head which are arranged in sequence along the optical path; and the magneto-optical crystal is externally provided with a magnetic element.

5. An isolator based on a birefringent crystal plate according to claim 4, characterized in that: The first birefringent crystal flat is fixed at one end of the input fiber head opposite to the first lens; the wave plate is fixed on the first birefringent crystal flat; the magneto-optical crystal is fixed on the wave plate; and the input fiber head and the first lens are fixedly arranged in a first glass tube.

6. An isolator based on a birefringent crystal plate according to claim 5, characterized in that: The second birefringent crystal flat is fixedly arranged at one end of the output fiber head opposite to the second lens; and the second lens and the output fiber head are fixedly arranged in a second glass tube.

7. An isolator based on a birefringent crystal plate according to claim 3 or 6, characterized in that: The first glass tube and the second glass tube are coaxially arranged and fixedly arranged in a third glass tube.

8. An isolator based on a birefringent crystal plate according to claim 3, characterized in that: The magnetic element is a magnetic ring which is sleeved outside the second glass tube.

9. An isolator based on a birefringent crystal plate according to claim 6, characterized in that: The magnetic element is a magnetic ring which is sleeved outside the first glass tube.

10. An isolator based on birefringent crystal plate according to claim 1 or 4, characterized in that: The wave plate is a 1 / 4 wave plate.

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