A coupling system for sapphire fiber to quartz fiber

Abstract

The present invention discloses a coupling system from a sapphire optical fiber to a quartz optical fiber. The system includes a collimating lens, a self-focusing lens, and an optical fiber connector that are sequentially arranged behind the sapphire optical fiber, and the optical fiber connector is used to connect the quartz optical fiber. The present invention uses a collimating lens and a self-focusing lens that are sequentially arranged behind the sapphire optical fiber to form a double-coupling lens. This double-coupling lens system has the function of reducing the beam waist and divergence angle of light, and can enable light rays at different angles emitted from the sapphire optical fiber to be coupled by the double-coupling lens, enter the quartz optical fiber through the optical fiber connector, and converge at the core axis, thereby realizing the coupling from the sapphire optical fiber to the quartz optical fiber, and can greatly improve the coupling efficiency of the sapphire optical fiber input into the single-mode optical fiber.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber coupling, and more particularly to a coupling system for sapphire optical fiber to quartz optical fiber. Background Art

[0002] Sensing in high-temperature environments is of great significance in many engineering fields involving harsh environments, such as aerospace, metallurgy, and fossil fuel production. Due to the small size of optical fiber sensors, immunity to electromagnetic interference, multiplexing, and distributed sensing capabilities, there has been a trend in recent years to replace traditional electronic sensors with optical fiber sensors for high-temperature measurements. Since the optical and mechanical properties of commonly used quartz optical fibers will significantly deteriorate when the temperature is higher than 1000°C, single-crystal sapphire optical fibers with excellent optical transparency, thermal stability, chemical stability, mechanical stability, and high melting temperature (2040°C) have become strong candidates for sensing applications in high-temperature environments. However, because the process conditions for crystal growth determine the limited length of sapphire single-crystal optical fibers and long-distance signal transmission cannot be achieved, the sapphire optical fiber sensing technology is difficult to be widely promoted in the field of optical fiber sensing. Therefore, coupling sapphire optical fibers into quartz optical fibers is an effective solution to achieve long-distance transmission of sapphire optical fiber sensing signals. Therefore, optical fiber coupling technology is a key technology in sapphire optical fiber sensing, which reduces the influence of signals during optical fiber transmission in the process of optical fiber signal transmission.

[0003] In optical fiber coupling technology, improving the coupling efficiency of two optical signals is a hot issue. The coupling efficiency of light has an important impact on signal transmission on the optical fiber link. To address the problems of sapphire optical fiber signal transmission and control in high-temperature and high-pressure environments, sapphire optical fibers and quartz optical fibers need to be coupled to achieve signal demodulation.

[0004] Normally, due to the large difference in refractive indices between sapphire optical fibers and quartz optical fibers, direct splicing will result in large Fresnel reflection losses, and the numerical apertures (NAs) of the two are quite different. Therefore, the optical energy conversion efficiency from sapphire optical fiber to quartz optical fiber is extremely low. For a sapphire with an NA of 0.45 and a single-mode optical fiber with an NA of 0.1, the coupling efficiency from sapphire optical fiber to single-mode optical fiber is almost zero. Summary of the Invention

[0005] To overcome the problems existing in the related art, the present invention provides a coupling system for sapphire optical fiber to quartz optical fiber to solve the defects in the related art.

[0006] According to a first aspect of the present invention, there is provided a coupling system for sapphire optical fiber to quartz optical fiber, the system comprising a collimating lens, a self-focusing lens, and an optical fiber connector sequentially arranged behind the sapphire optical fiber, and the optical fiber connector is used for connecting the quartz optical fiber.

[0007] Preferably, the collimating lens is a doublet lens.

[0008] Preferably, the doublet lens includes a first aspheric shaping lens and a second aspheric shaping lens.

[0009] Preferably, the first aspheric shaping lens has a diameter of 0.995 - 1.005 mm and is made of N-SF66; the first surface of the first aspheric shaping lens in the light propagation direction is a convex surface with a curvature radius of 2.784030239663861E+000 - 2.788030239663861E+000 mm, and the second surface is a plane with an infinite curvature radius; the distance from the sapphire optical fiber to the vertex of the first surface of the first aspheric shaping lens is 0.495 - 0.505 mm.

[0010] Preferably, the second aspheric shaping lens has a diameter of 0.995 - 1.005 mm and is made of N-LASF41; the first surface of the second aspheric shaping lens in the light propagation direction is a plane with a curvature radius of 5.573723449348422E-001 - 5.577723449348422E-001 mm, and the second surface is a convex surface with a curvature radius of -1.508642787945786E+000 - -1.512642787945786E+000 mm; the distance from the vertex of the second surface of the second aspheric shaping lens to the vertex of the first surface of the self-focusing lens is 0.995 - 1.005 mm.

[0011] Preferably, the self-focusing lens has a diameter of 0.995 - 1.005 mm and is made of SLW-1.8; the first surface of the self-focusing lens in the light propagation direction is a plane with an infinite curvature radius where the refractive index varies radially, and the second surface is a plane with an infinite curvature radius; the distance from the vertex of the second surface of the self-focusing lens to the end face of the fiber optic connector is 2.895 - 2.905 mm.

[0012] Preferably, the fiber optic connector is an FC / APC connector.

[0013] Preferably, the quartz optical fiber is a single-mode fiber or a multi-mode fiber.

[0014] Preferably, the quartz optical fiber is a single-mode fiber with a mode field diameter of 20 μm and a numerical aperture of 0.13.

[0015] Preferably, the system further includes a metal protective shell.

[0016] The present invention discloses a coupling system from sapphire optical fiber to quartz optical fiber, which uses a collimating lens and a self-focusing lens arranged behind the sapphire optical fiber to form a double-coupling lens. This double-coupling lens system has the function of reducing the beam waist and divergence angle of light, enabling light rays emitted from the sapphire optical fiber at different angles to be coupled by the double-coupling lens, enter the quartz optical fiber through an optical fiber connector, and converge at the core axis, thereby realizing the coupling from the sapphire optical fiber to the quartz optical fiber. Moreover, from the simulation results obtained by modeling and optimizing the coupling system proposed in the present invention through ZEMAX software, it can be seen that the coupling system proposed in the present invention can greatly improve the coupling efficiency of the sapphire optical fiber input into the single-mode optical fiber.

[0017] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present invention. Brief Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of a coupling system from sapphire optical fiber to quartz optical fiber shown according to an embodiment of the present invention.

[0019] Figure 2 is a schematic diagram of the optical path of a coupling system model shown according to an embodiment of the present invention.

[0020] Figure 3 is a schematic diagram of the radial variation of the refractive index of a self-focusing lens shown according to an embodiment of the present invention.

[0021] Figure 4 is a schematic diagram of the coupling efficiency of a single-mode optical fiber and a multi-mode optical fiber at different temperatures shown according to an embodiment of the present invention.

[0022] Figure 5 is a schematic diagram of the mismatch between a collimating lens and a self-focusing lens shown according to an embodiment of the present invention.

[0023] Figure 6 is a spot diagram of the image quality evaluation of the coupling system model described in the present invention in ZEMAX software shown according to an embodiment of the present invention.

[0024] Figure 7 is a geometric diagram of the image quality evaluation of the coupling system model described in the present invention in ZEMAX software shown according to an embodiment of the present invention.

[0025] Wherein, 1 - collimating lens; 2 - self-focusing lens; 3 - optical fiber connector; 4 - quartz optical fiber; 5 - metal protective shell. Detailed Embodiments

[0026] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0027] The terms used in the present invention are for the purpose of describing particular embodiments only and are not intended to limit the present invention. The singular forms "a", "the", and "said" used in the present invention and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0028] It should be understood that although the terms first, second, third, etc. may be used in the present invention to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining".

[0029] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The present invention aims to provide an intelligent Q&A system for site soil pollution to solve the problems of scattered information, high professional knowledge requirements, and low query efficiency in the prior art. The system uses artificial intelligence technology to provide accurate, timely, and comprehensive information related to site soil pollution through intelligent Q&A.

[0031] As Figure 1 shown, Figure 1 is a schematic structural diagram of a coupling system from a sapphire optical fiber to a quartz optical fiber according to an embodiment of the present invention. The system includes a collimating lens 1, a self-focusing lens 2, and an optical fiber connector 3 sequentially disposed behind the sapphire optical fiber. Among them, the optical fiber connector 3 is used to connect the quartz optical fiber 4. Among them, the signal light transmitted through the sapphire optical fiber reaches the quartz optical fiber 4 after passing through the collimating lens 1, the self-focusing lens 2, and the optical fiber connector 3 in sequence.

[0032] In this coupling system, the present invention uses a collimation lens 1 and a self-focusing lens 2 disposed behind the sapphire optical fiber to form a double-coupling lens. This double-coupling lens system has the function of reducing the beam waist and divergence angle of light, enabling light rays emitted from the sapphire optical fiber at different angles to be coupled by the double-coupling lens and enter the quartz optical fiber 4 through the fiber optic connector 3 and converge at the core axis, thereby achieving the coupling from the sapphire optical fiber to the quartz optical fiber. As Figure 2 shown, Figure 2 FIG. Figure 2 is a schematic optical path diagram of a coupling system model shown according to an embodiment of the present invention, which can reflect the optical path of the light emitted from the sapphire optical fiber passing through the double-coupling system composed of the collimation lens 1 and the self-focusing lens 2 and then entering the quartz optical fiber 4 in the coupling system proposed by the present invention.

[0033] In the present invention, the collimation lens refers to an instrument that can turn the light rays from each point in the aperture stop into a parallel collimated light beam. Specifically, the collimation lens 1 used in the coupling system of the present invention can be any lens or instrument that can turn the light rays from the sapphire optical fiber into a parallel collimated light beam.

[0034] Specifically, in some embodiments, the collimation lens 1 used in the present invention can be a doublet lens. A doublet lens is a lens obtained by gluing two lenses together, which has a short focal length, a large magnification, and good imaging quality.

[0035] Specifically, the doublet lens serving as the collimation lens 1 can include a first aspherical shaping mirror and a second aspherical shaping mirror. Among them, the first aspherical shaping mirror is used to receive the light rays from the sapphire optical fiber, while the second aspherical shaping mirror emits the collimated light beam obtained by shaping the doublet lens into the self-focusing lens 2.

[0036] Specifically, in other embodiments, the collimation lens 1 used in the coupling system of the present invention can also be other collimation lenses other than the doublet lens, or doublet lenses of other configurations, as long as it can achieve shaping the light rays of the sapphire optical fiber into parallel collimated light rays, and it can be specifically set according to the requirements of the actual application environment, and the present invention does not limit this.

[0037] In the present invention, the self-focusing lens refers to a special graded-index cylindrical optical lens for collimation and focusing, and can also be called a Grin-lens. Compared with ordinary spherical and aspherical lenses, the refractive index of the Grin-lens gradually changes along the optical axis, and the optical paths of all light beams are the same, which can correct the spherical aberration and chromatic aberration of the optical system. The end face of the Grin-lens is a plane, enabling the correction of its spherical aberration and chromatic aberration. In the coupling system described in the present invention, the optical fiber propagates along a smooth curve in the self-focusing lens 2 and finally converges at a point, and is finally directly glued to the end face of the quartz optical fiber 4, featuring a simple structure and easy operation. Specifically, in some embodiments, the axial refractive index of the designed self-focusing lens 2 can be as Figure 3 shown. According to the requirements of the actual application environment, in other embodiments, the radial variation law of the refractive index of the self-focusing lens 2 can also be designed in other forms, and the present invention places no restrictions thereon.

[0038] Specifically, if the coupling system from the sapphire optical fiber to the quartz optical fiber is to operate in a high-temperature environment, there are great challenges to the thermal stability of the coupling system, especially the influence of the thermal expansion coefficient of the lens material and the change of the refractive index at high temperature on the coupling efficiency of the system.

[0039] Specifically, lens materials N-SF66 and N-LASF41 with excellent optical transparency, thermal stability, chemical stability, mechanical stability, and high melting temperature can be selected to prepare the collimating lens 1 and the self-focusing lens 2.

[0040] Specifically, in some embodiments, when the collimating lens 1 is a doublet lens including a first aspherical shaping mirror and a second aspherical shaping mirror, the aperture of its first aspherical shaping mirror can be 0.995 - 1.005 mm, and the material can be N-SF66; and the first surface of the first aspherical shaping mirror in the light propagation direction can be a convex surface with a radius of curvature of 2.784030239663861E+000 - 2.788030239663861E+000 mm, and the second surface can be a plane with an infinite radius of curvature; and the distance from the sapphire optical fiber to the vertex of the first surface of the first aspherical shaping mirror can be 0.495 - 0.505 mm.

[0041] For example, in some embodiments, the first aspherical shaping lens may have a diameter of 0.995 mm, be made of N-SF66, and the first surface of the first aspherical shaping lens in the light propagation direction is a convex surface with a radius of curvature of 2.784030239663861E+000 mm, and the second surface is a plane with an infinite radius of curvature. The distance from the sapphire optical fiber to the vertex of the first surface of the first aspherical shaping lens is 0.495 mm. In some embodiments, the first aspherical shaping lens may also have a diameter of 1.005 mm, be made of N-SF66, and the first surface of the first aspherical shaping lens in the light propagation direction is a convex surface with a radius of curvature of 2.788030239663861E+000 mm, and the second surface is a plane with an infinite radius of curvature. The distance from the sapphire optical fiber to the vertex of the first surface of the first aspherical shaping lens is 0.505 mm. In some embodiments, the first aspherical shaping lens may also have a diameter of 1 mm, be made of N-SF66, and the first surface of the first aspherical shaping lens in the light propagation direction is a convex surface with a radius of curvature of 2.786030239663861E+000 mm, and the second surface is a plane with an infinite radius of curvature. The distance from the sapphire optical fiber to the vertex of the first surface of the first aspherical shaping lens is 0.5 mm. Specifically, in other embodiments, the first aspherical shaping lens may also have other aperture specifications, its first surface may also be a convex surface with a radius of curvature of other values, and the distance between the vertex of its first surface and the sapphire optical fiber may also be set to other values, which can be designed according to actual needs, and the present invention does not limit this.

[0042] Specifically, the aperture of the second aspherical shaping lens in the doublet lens may be 0.995 - 1.005 mm, and the material may be N-LASF41; the first surface of the second aspherical shaping lens in the light propagation direction may be a plane with a radius of curvature of 5.573723449348422E-001 - 5.577723449348422E-001 mm, and the second surface may be a convex surface with a radius of curvature of -1.508642787945786E+000 - -1.512642787945786E+000 mm; the distance from the vertex of the second surface of the second aspherical shaping lens to the vertex of the first surface of the self-focusing lens 2 may be 0.995 - 1.005 mm.

[0043] For example, in some embodiments, the second aspherical shaping mirror may have a diameter of 0.995 mm, be made of N-LASF41, and the first surface of the second aspherical shaping mirror in the light propagation direction is a plane with a curvature radius of 5.573723449348422E-001 mm, the second surface is a convex surface with a curvature radius of -1.508642787945786E+000 mm, and the distance from the vertex of the second surface of the second aspherical shaping mirror to the vertex of the first surface of the self-focusing lens 2 is 0.995 mm. In some embodiments, the second aspherical shaping mirror may also have a diameter of 1.005 mm, be made of N-LASF41, and the first surface of the second aspherical shaping mirror in the light propagation direction is a plane with a curvature radius of 5.577723449348422E-001 mm, the second surface is a convex surface with a curvature radius of -1.512642787945786E+000 mm, and the distance from the vertex of the second surface of the second aspherical shaping mirror to the vertex of the first surface of the self-focusing lens 2 is 1.005 mm. In some embodiments, the second aspherical shaping mirror may also have a diameter of 1 mm, be made of N-LASF41, and the first surface of the second aspherical shaping mirror in the light propagation direction is a plane with a curvature radius of 5.575723449348422E-001 mm, the second surface is a convex surface with a curvature radius of -1.510642787945786E+000 mm, and the distance from the vertex of the second surface of the second aspherical shaping mirror to the vertex of the first surface of the self-focusing lens 2 is 1 mm. Specifically, in other embodiments, the second aspherical shaping mirror may also have other aperture specifications, its first surface may also be a convex surface with a curvature radius of other values, and the distance between the vertex of its second surface and the vertex of the first surface of the self-focusing lens 2 may also be set to other values, which can be specifically designed according to actual needs, and the present invention does not limit this.

[0044] Specifically, the aperture of the self-focusing lens 2 may be 0.995 to 1.005 mm, and the material may be SLW-1.8; the first surface of the self-focusing lens 2 in the light propagation direction may be a plane with an infinite curvature radius where the refractive index changes along the radius, and the second surface may be a plane with an infinite curvature radius; the distance from the vertex of the second surface of the self-focusing lens 2 to the end face of the fiber optic connector 3 may be 2.895 to 2.905 mm.

[0045] For example, in some embodiments, the self-focusing lens 2 may have an aperture of 0.995 mm, be made of SLW-1.8, and the first surface of the self-focusing lens 2 in the light propagation direction be a plane with an infinite radius of curvature where the refractive index varies radially, the second surface be a plane with an infinite radius of curvature, and the distance from the vertex of the second surface of the self-focusing lens 2 to the end face of the fiber optic connector 3 be 2.895 mm. In some embodiments, the self-focusing lens 2 may have an aperture of 1.005 mm, be made of SLW-1.8, and the first surface of the self-focusing lens 2 in the light propagation direction be a plane with an infinite radius of curvature where the refractive index varies radially, the second surface be a plane with an infinite radius of curvature, and the distance from the vertex of the second surface of the self-focusing lens 2 to the end face of the fiber optic connector 3 be 2.905 mm. In some embodiments, the self-focusing lens 2 may have an aperture of 1 mm, be made of SLW-1.8, and the first surface of the self-focusing lens 2 in the light propagation direction be a plane with an infinite radius of curvature where the refractive index varies radially, the second surface be a plane with an infinite radius of curvature, and the distance from the vertex of the second surface of the self-focusing lens 2 to the end face of the fiber optic connector 3 be 2.9 mm. Specifically, in other embodiments, the self-focusing lens 2 may also have other aperture specifications, and the distance between the vertex of its second surface and the end face of the fiber optic connector 3 may also be set to other values, which can be designed according to actual needs, and the present invention does not limit this.

[0046] Specifically, it should be understood that the above parameters are only the specific parameters of an embodiment of the coupling system proposed by the present invention to achieve a better coupling effect. In the coupling systems implemented in other embodiments, the apertures, surface radii of curvature, and distances of the collimating lens 1 and the self-focusing lens 2 can also be designed as other values according to actual needs. The collimating lens 1 and the self-focusing lens 2 can also use lens materials with other physical properties according to actual needs, and the present invention does not limit this.

[0047] In the coupling system of the present invention, the optical fiber connector 3 used refers to any connecting device for accessing the quartz optical fiber 4 into the coupling system. According to actual usage requirements, the interface shape of the optical fiber connector 3 used in the present invention can be any one of the interface shapes such as FC (Ferrule Connector), SC (Square Connector), LC (Lucent Connector), ST (Straight Tip), etc., and the end face shape of the optical fiber connector 3 can be any one of the end face shapes such as PC (Physical Contact), SPC (Super Physical Contact), UPC (Ultra Physical Contact), APC (Angled Physical Contact), etc. The present invention does not limit this. For example, specifically, in some embodiments, the optical fiber connector 3 used in the coupling system proposed by the present invention can be an FC / APC connector.

[0048] Specifically, the quartz optical fiber 4 used in the coupling system proposed by the present invention can be a single-mode fiber (Single Mode Fiber, SMF) or a multi-mode fiber (Multi Mode Fibre, MMF) to meet different usage requirements. For example, specifically, the quartz optical fiber 4 used in the coupling system proposed by the present invention can be a single-mode fiber with a mode field diameter (Mode Field Diameter, MDF) of 20 μm and a numerical aperture of 0.13. Specifically, in other embodiments, the quartz optical fiber 4 used in the coupling system of the present invention can also be a single-mode fiber or a multi-mode fiber with other mode field diameters and numerical apertures. The present invention does not limit this.

[0049] In the coupling system of the present invention, the light beam with a divergent intensity distribution emitted by the sapphire optical fiber can become a parallel light beam with a uniform distribution after passing through the collimating lens 1, and its intensity distribution is a Gaussian distribution; therefore, the core mode field distribution reaching the quartz optical fiber 4 after passing through the self-focusing lens 2 and the optical fiber connector 3 is also a Gaussian distribution.

[0050] Considering that the sapphire optical fiber is highly multi-mode and uses an LED light source, it can be considered that the output intensity distribution of the multi-mode fiber is uniform. In addition, the light beam output from the end of the sapphire optical fiber can be regarded as a Gaussian beam described by the Gaussian-Laguerre function. In fact, any laser beam can be represented by a series of Gaussian-Laguerre functions. When the beam enters the multi-mode fiber, the Gaussian-Laguerre beam can be transformed into the fiber mode described by the following equation:

[0051]

[0052]

[0053] wherein is the core radius; is the first kind of Bessel function; is the second kind of modified Bessel function; U / is the transverse phase function; W / is the attenuation quotient. And based on the coupling efficiency of the Gaussian-Laguerre mode, the coupling efficiency of any beam to a multimode fiber can be obtained. Then, the mode conversion is obtained from the overlap integral, and the sum of all guided modes can obtain the coupling efficiency of the coupling system:

[0054]

[0055] Specifically, as Figure 4 shown, Figure 4 is a schematic diagram of the coupling efficiency of a single-mode fiber (SMF) and a multimode fiber (MMF) at different temperatures shown according to an embodiment of the present invention. As can be seen from Figure 4 , for the coupling system implemented according to the present invention, high-efficiency coupling between a sapphire fiber and a single-mode fiber can be achieved in a high-temperature environment, and the theoretical coupling efficiency can reach 62%, and at the same time, high-efficiency coupling between a sapphire fiber and a multimode fiber can also be achieved, and the theoretical coupling efficiency can reach 100%.

[0056] In addition, when the coupling system of the present invention uses a self-focusing lens 2, that is, a lens with a gradient change in the Green refractive index, the mode field radius of the fiber can be increased, and the tolerance ranges of the off-axis deviation and the defocus deviation can be improved, which is convenient for adjusting the position of the fiber. However, due to the angular deviation existing to a certain extent in the gradient refractive index change lens, the tolerance ranges among the off-axis deviation, the defocus deviation, and the angular deviation must be comprehensively considered. As Figure 5 shown, Figure 5 is a schematic diagram of the mismatch between a collimating lens 1 and a self-focusing lens 2 shown according to an embodiment of the present invention, which shows three mismatch situations of possible radial mismatch, axial mismatch, and angular mismatch between the collimating lens 1 and the self-focusing lens 2. These three mismatch situations will cause off-axis deviation, defocus deviation, or angular deviation between the collimating lens 1 and the self-focusing lens 2, thereby affecting the coupling efficiency of the entire coupling system.

[0057] Specifically, when there is a radial mismatch between the collimating lens 1 and the self-focusing lens 2 in the coupling system, the coupling efficiency caused by the radial mismatch can be calculated by the following formula:

[0058]

[0059] Among them, is the coupling efficiency of the coupling system with radial mismatch, is the off-axis deviation between the collimating lens 1 and the self-focusing lens 2, is the beam radius after collimation by the collimating lens 1.

[0060] When there is an axial mismatch between the collimating lens 1 and the self-focusing lens 2 in the coupling system, the coupling efficiency caused by the axial mismatch can be calculated by the following formula:

[0061]

[0062] Among them, is the coupling efficiency of the coupling system with axial mismatch, is the defocus deviation between the collimating lens 1 and the self-focusing lens 2, is the wavelength of light.

[0063] When there is an angular mismatch between the collimating lens 1 and the self-focusing lens 2 in the coupling system, the coupling efficiency caused by the angular mismatch can be calculated by the following formula:

[0064]

[0065] Among them, is the coupling efficiency of the coupling system with angular mismatch, is the angular deviation between the collimating lens 1 and the self-focusing lens 2.

[0066] Among the above three mismatch cases, the angular mismatch has the greatest impact on the coupling efficiency, while the axial mismatch has the smallest impact on the coupling efficiency.

[0067] Specifically, the coupling system proposed by the present invention may further include a metal protective shell 5 to protect the structure of the coupling system and fix the positions of the collimating lens 1 and the self-focusing lens 2.

[0068] Specifically, the present invention also evaluates the imaging quality of the system by using the spot diagram in the sub-menu of ZEMAX software, obtains the RMS (Root Mean Square) radius, Airy radius, and geometric (GEO) radius values at different fields of view, and analyzes and verifies the imaging quality of the coupling system described in the present invention through these values. The imaging quality evaluation results are as Figure 6 and Figure 7 shown, among which, Figure 6This is the spot diagram for evaluating the image quality of the coupling system model described in the present invention in ZEMAX software according to an embodiment. The RMS radii of the three image planes are 10.263 μm, 11.188 μm, and 13.648 μm respectively, while the GEO radii are 22.045 μm, 33.954 μm, and 45.725 μm respectively. And Figure 7 This is the geometric diagram for evaluating the image quality of the coupling system model described in the present invention in ZEMAX software according to an embodiment.

[0069] Aiming at the problems of sapphire fiber signal transmission and control in high-temperature and high-pressure environments, the present invention proposes a double-coupling lens system with a compact and small structure, which is suitable for short-term and long-term fiber coupling. The coupling system proposed by the present invention greatly improves the coupling efficiency of sapphire fiber into single-mode fiber and improves the thermal stability of fiber-coupled transmission, solves the problems of high alignment accuracy requirements, high system chromatic aberration, and low coupling efficiency, and can obtain a coupling system with high thermal stability, high coupling efficiency, low chromatic aberration, and low aberration, such as a coupler that can work stably at 1000 degrees Celsius.

[0070] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly explaining the present invention, rather than limitations on the implementation manners of the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A sapphire fiber to quartz fiber coupling system, characterized in that: The system comprises a collimating lens (1), a self-focusing lens (2) and an optical fiber connector (3) which are arranged in sequence behind a sapphire optical fiber, and the optical fiber connector (3) is used to connect a quartz optical fiber (4); The self-focusing lens (2) has an aperture of 0.995-1.005 mm and is made of SLW-1.8; the first surface of the self-focusing lens (2) in the light propagation direction is a plane with an infinite curvature radius whose refractive index varies along the diameter, and the second surface is a plane with an infinite curvature radius; the distance between the vertex of the second surface of the self-focusing lens (2) and the end face of the optical fiber connector (3) is 2.895-2.905 mm; The collimating lens (1) is a double-cemented lens; the double-cemented lens comprises a first aspheric shaping lens and a second aspheric shaping lens; The aperture of the first aspheric shaping mirror is 0.995-1.005 mm, and the material is N-SF66; the first surface of the first aspheric shaping mirror in the light propagation direction is a convex surface with a curvature radius of 2.784030239663861E+000-2.788030239663861E+000 mm, and the second surface is a plane with an infinite curvature radius; the distance from the sapphire optical fiber to the vertex of the first surface of the first aspheric shaping mirror is 0.495-0.505 mm; The aperture of the second aspheric shaping mirror is 0.995-1.005 mm, and the material is N-LASF41; the first surface of the second aspheric shaping mirror in the direction of light propagation is a plane with a curvature radius of 5.573723449348422E-001-5.577723449348422E-001 mm, and the second surface is a convex surface with a curvature radius of -1.508642787945786E+000-1.512642787945786E+000 mm; the distance from the second surface vertex of the second aspheric shaping mirror to the first surface vertex of the self-focusing lens (2) is 0.995-1.005 mm.

2. The system according to claim 1, characterized in that The optical fiber connector (3) is an FC / APC connector.

3. The system according to claim 1, characterized in that The quartz optical fiber (4) is a single-mode optical fiber or a multi-mode optical fiber.

4. The system according to claim 3, characterized in that The quartz optical fiber (4) is a single-mode optical fiber with a mode field diameter of 20 μm and a numerical aperture of 0.

13.

5. The system according to claim 1, characterized in that The system also includes a metal protective shell (5).

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