Conversion core, double-lens mode field conversion device and connector

Abstract

The invention discloses a conversion core piece, a double-lens mode field conversion device and a connector, the conversion core piece comprises a solid core optical fiber part, a hollow core optical fiber part and a calibration sleeve, the solid core optical fiber part comprises a solid core end lens and a solid core single-mode optical fiber with a first mode field diameter, the solid core end lens is located at the tail end part of the solid core optical fiber part, and the hollow core optical fiber part is located at the tail end part of the solid core optical fiber part. The solid-core optical fiber component comprises a solid-core end lens and a solid-core optical fiber with a first mode field diameter, the hollow-core optical fiber component comprises a hollow-core end lens and a hollow-core optical fiber with a second mode field diameter, the calibration sleeve is provided with a hollow cavity I along the axial direction, the solid-core optical fiber component and the hollow-core optical fiber component respectively extend into the calibration sleeve from two ports of the cavity I, and the solid-core end lens and the hollow-core end lens are oppositely arranged. According to the device, conversion of different mode field diameters between the single-mode optical fiber and the hollow-core optical fiber is realized through the two lenses, so that reliable and stable connection between the single-mode optical fiber and the hollow-core optical fiber is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical signal transmission, and particularly relates to a conversion core component, a dual-lens mode field conversion device, and a connector. Background Art

[0002] Hollow anti-resonant fiber (hereinafter simply referred to as hollow fiber) realizes hollow light guiding through the anti-resonant reflection optical waveguide mechanism, and has advantages such as low delay, low dispersion, low non-linearity, high damage threshold, broadband light guiding, low thermal sensitivity, radiation resistance, etc. Therefore, it has great application prospects in the fields of optical communication, high-power laser transmission, ultrafast optics, non-linear optics, fiber sensing, etc., and is very suitable for harsh environments such as space radiation.

[0003] To improve the compatibility between hollow fiber and traditional fiber device systems, or between fiber and optical waveguide, and to achieve low insertion loss, high return loss, and high stability connection between different fibers is the core problem to be solved. However, there are often large structural and mode field differences between them, making it difficult to achieve efficient and reliable coupling. The fiber mode field conversion device can change the mode field characteristics of the transmitted light, thereby breaking through the coupling bottleneck between hollow fiber and traditional single-mode fiber, realizing the efficient integration of fiber optic devices, and bringing more possibilities for its development and application. Facing the upcoming large-scale application demands of hollow fiber in the fields of high-speed large-capacity optical communication, high-power laser transmission, fiber sensing, and special-scene optical transmission in the future, it is necessary to develop fiber mode field conversion devices.

[0004] There are mainly the following three technical bottleneck problems in developing a hollow fiber mode field diameter conversion device to achieve efficient connection between hollow fiber and traditional solid-core single-mode fiber widely used in existing optical transmission systems. First, the mode field diameter of traditional solid-core single-mode fiber is about 9.2μm when the transmission wavelength is 1310nm, while the mode field diameter of hollow fiber is generally 20 - 40μm. The mode field sizes of the two are seriously mismatched, resulting in high coupling loss. For example, for a hollow fiber with a mode field diameter of 20μm, the coupling loss with single-mode fiber is not less than 1.9dB; for a hollow fiber with a mode field diameter of 40μm, the coupling loss will be at least as high as 6.6dB. In addition, the mode field mismatch at the coupling interface of the two may also excite higher-order modes in the hollow fiber, affecting the quality of the transmitted light beam. Therefore, matching the mode field characteristics of the two fibers is one of the key technical bottleneck problems to be solved. Second, the air-glass interface existing at the fiber coupling interface will also generate strong Fresnel reflection, thereby increasing the insertion loss and bringing back reflection. Therefore, improving the return loss is the second technical bottleneck problem to be solved. Third, for hollow fiber with internal microstructures, since the fiber itself relies on the internal microstructures to achieve low-loss light transmission, ensuring the integrity of the internal microstructures of the fiber during coupling is also a key technical bottleneck problem to be solved. Summary of the Invention

[0005] The object of the present invention is to solve the problems existing in the above-mentioned prior art, and to provide a conversion core component, a dual-lens mode field conversion device and a connector. The device realizes the conversion of different mode field diameters between a single-mode fiber and a hollow-core fiber through two lenses, so as to realize a reliable and stable connection between the single-mode fiber and the hollow-core fiber.

[0006] To achieve the above object, one of the objects of the present invention is to provide a conversion core component, which includes a first optical fiber component, a second optical fiber component and a calibration sleeve. The first optical fiber component includes a first lens and a first optical fiber having a first mode field diameter. The first lens is located at the end of the first optical fiber component. The second optical fiber component includes a second lens and a second optical fiber having a second mode field diameter. The second lens is located at the end of the second optical fiber component. The calibration sleeve has a hollow cavity Ⅰ along its axis. The first optical fiber component and the second optical fiber component respectively extend into the two ports of the calibration sleeve cavity Ⅰ, and the first lens and the second lens are arranged opposite to each other.

[0007] As a preferred solution, the first optical fiber component further includes a first sleeve, which has a cavity Ⅱ with two open ends along its axis. The first optical fiber extends into one port of the cavity Ⅱ of the first sleeve, and the first lens is arranged at the other port of the cavity Ⅱ of the first sleeve and extends outwards.

[0008] The second optical fiber component further includes a second sleeve, which has a cavity Ⅲ with two open ends along its axis. The second optical fiber extends into one port of the cavity Ⅲ of the second sleeve, and the second lens is arranged at the other port of the cavity Ⅲ of the second sleeve and extends outwards.

[0009] As a preferred solution, the first lens and the second lens are C lenses. The C lens has two ends, one of which is a convex spherical surface and the other is a plane. The first lens includes a first spherical end and a first plane end. The first spherical end faces the first optical fiber. The second lens includes a second spherical end and a second plane end. The second spherical end faces the hollow optical fiber. The first plane end and the second plane end are arranged corresponding to each other.

[0010] As a preferred solution, the first plane end of the first lens extends out of the first sleeve, and the first plane end is an inclined cut surface, and the first plane end is not perpendicular to the axis of the first lens.

[0011] The second plane end of the second lens extends out of the second sleeve, and the second plane end is an inclined cut surface, and the second plane end is not perpendicular to the axis of the second lens.

[0012] The first plane end and the second plane end are opposite and parallel to each other.

[0013] As a preferred solution, the first end of the first optical fiber is a bare fiber segment, and this bare fiber segment of the first optical fiber is arranged in the hollow lumen of the first ferrule to form a first ferrule assembly. The first ferrule assembly is inserted into and fixed in the first sleeve from one end of the first sleeve; the first end of the second optical fiber is a bare fiber segment, and this bare fiber segment of the second optical fiber is arranged in the hollow lumen of the second ferrule to form a second ferrule assembly. The second ferrule assembly is inserted into and fixed in the second sleeve from one end of the second sleeve.

[0014] As a preferred solution, an inclined cut surface is formed at one end of the first ferrule assembly facing the first lens, and the inclined cut surface of the first ferrule assembly is not perpendicular to the axis of the first ferrule assembly.

[0015] As a preferred solution, antireflection films are coated on both the inclined cut surface of the first ferrule assembly and the first spherical end of the first lens.

[0016] As a preferred solution, the first lens and the second lens are C lenses. The C lens has two ends, one end is a convex spherical surface, and the other end is a plane. The first lens includes a first spherical end and a first plane end. The first plane end faces the first optical fiber. The second lens includes a second spherical end and a second plane end. The second plane end faces the second optical fiber. The first spherical end and the second spherical end are arranged corresponding to each other.

[0017] As a preferred solution, the first plane end of the first lens extends into the first sleeve from one end of the first sleeve. The first spherical end of the first lens protrudes outward from the first sleeve, and the first plane end is an inclined cut surface, and the first plane end is not perpendicular to the axis of the first lens;

[0018] The second plane end of the second lens extends into the second sleeve from one end of the second sleeve. The second spherical end of the second lens protrudes outward from the second sleeve, and the second plane end is an inclined cut surface, and the second plane end is not perpendicular to the axis of the second lens.

[0019] As a preferred solution, a connector ferrule is further included. The bare fiber segment at the head end of the first optical fiber is arranged in the hollow lumen of the connector ferrule. The bare fiber segment at the tail end of the first optical fiber is arranged in the hollow lumen of the first ferrule to form a first ferrule assembly. The tail end of the first ferrule is inserted into and fixed in the first sleeve from one end of the first sleeve; the first end of the second optical fiber is a bare fiber segment, and this bare fiber segment of the second optical fiber is arranged in the hollow lumen of the second ferrule to form a second ferrule assembly. The second ferrule assembly is inserted into and fixed in the second sleeve from one end of the second sleeve.

[0020] As a preferred solution, the first optical fiber is a solid-core single-mode optical fiber, and the second optical fiber is a hollow-core optical fiber.

[0021] The second object of the present invention is to provide a dual-lens mode field conversion device, including a conversion core component as described in any one of the above items.

[0022] As a preferred solution, it further includes a housing, which is arranged outside the conversion core component and includes a first housing body and a second housing body. The docking ends of the first housing body and the second housing body are fixedly connected. A first fixing sleeve fixes the first optical fiber at the end of the first housing body, and a second fixing sleeve fixes the second optical fiber at the end of the second housing body.

[0023] As a preferred solution, it further includes a flange. An adjustable gap is formed between one end of the flange and the end of the first sleeve. The adjustable gap is used to accommodate the bonding layer. The flange has an inner lumen along the central axis, and one end of the flange is correspondingly connected to the end of the first sleeve.

[0024] As a preferred solution, the inner lumen of the flange includes a cavity Ⅳ and a cavity Ⅴ that are interconnected. The cavity Ⅳ and the cavity Ⅴ are coaxially arranged. The cross-sectional diameter of the cavity Ⅳ is larger than the cross-sectional diameter of the cavity Ⅴ. Both ends of the first pin assembly are located in the cavity Ⅳ and the first sleeve respectively and are fixed. The cavity Ⅴ is used to pass through the first optical fiber.

[0025] As a preferred solution, on the outer cylindrical surface near the first end of the flange, there is an annular protrusion. The head part of the annular protrusion near the first end side of the flange is inserted into the cavity Ⅰ of the calibration sleeve, and the annular protrusion abuts against one end of the calibration sleeve. On the outer wall of the flange near its second end, there is a groove for installing a retaining ring. The first end of the flange cooperates with the retaining platform in the lumen of the first housing body through the annular protrusion to define the position of the flange relative to the first housing body in the first direction. The second end of the flange cooperates with the end of the first housing body and the retaining ring to define the position of the flange relative to the first housing body in the second direction, where the first direction and the second direction are opposite directions.

[0026] The third object of the present invention is to provide a connector, including a conversion core component as described in any one of the above items.

[0027] As a preferred solution, it further includes a housing and a flange. The housing is arranged outside the conversion core component. The housing includes a first housing body and a second housing body. The docking ends of the first housing body and the second housing body are fixedly connected. A retaining platform Ⅰ is formed on the inner wall of the lumen of the first housing body, and a retaining platform Ⅱ that cooperates with the retaining platform Ⅰ is formed on the end face of the flange.

[0028] As a preferred solution, the flange has an inner lumen along the central axis, and one end of the flange is correspondingly connected to the end of the first sleeve; the inner lumen of the flange includes a cavity Ⅳ and a cavity Ⅴ that communicate with each other, the cavity Ⅳ and the cavity Ⅴ are coaxially arranged, the head end of the first pin is located in the cavity Ⅳ, and the tail end of the first pin is located in the first sleeve and fixed, and the cavity Ⅴ is used to accommodate the tail end of the fixed connector pin.

[0029] As a preferred solution, it further includes an elastic member, the elastic member is arranged in the accommodating cavity of the housing, the first end of the elastic member can abut against the circumferential step of the flange, and the second end of the elastic member abuts against the stop platform in the second housing body.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] First, by improving the structure, the present invention is designed according to the characteristics of hollow optical fibers and the requirements of low insertion loss and high return loss. Two different C-lenses are used to realize the conversion of different mode field diameters between optical fibers, so as to realize a reliable and stable connection between optical fibers with different mode field diameters. In this solution, the first lens and the first optical fiber are combined into a first optical fiber component through the first sleeve, and the second lens and the second optical fiber are combined into a second optical fiber component through the second sleeve. During the installation and adjustment process, the first optical fiber component and the second optical fiber component are introduced into the calibration sleeve, so as to realize the alignment between the first optical fiber component and the second optical fiber component. In this way, through the lenses respectively arranged on the first optical fiber component and the second optical fiber component, the conversion of different mode field diameters between the first optical fiber and the second optical fiber can be realized, so as to realize a reliable and stable connection between the first optical fiber and the second optical fiber. Oblique cut surfaces that form a certain angle with their respective axial directions are formed on the flat end surfaces where the two lenses are oppositely arranged, and an anti-reflection film is plated on the oblique cut surfaces to reduce the influence of the Fresnel effect. The purpose of such a design is to improve the return loss through the above means.

[0032] Second, this solution also provides a connector. By integrating the conversion core component inside the connector housing, the connector has the function of mode field diameter conversion and efficient connection of optical fibers between different mode field diameters. For the coupling method of hollow optical fibers and solid-core single-mode optical fibers, this solution not only realizes the efficient connection between hollow optical fibers and traditional solid-core single-mode optical fibers widely used in existing optical transmission systems, but also helps to meet the large-scale application requirements of hollow optical fibers in the fields of high-speed large-capacity optical communication, high-power laser transmission, fiber sensing, and optical transmission in special scenarios. Description of the Drawings

[0033] To more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0034] Figure 1 This is the external structure diagram of the dual-lens mode field conversion device of the present invention;

[0035] Figure 2 This is the cross-sectional view of the dual-lens mode field conversion device of the present invention;

[0036] Figure 3 This is the cross-sectional view of Embodiment 1 of the conversion core component of the present invention;

[0037] Figure 4 This is the structure diagram of the solid-core end lens component of the present invention;

[0038] Figure 5 This is the structure diagram of the solid-core pin component of the present invention;

[0039] Figure 6 This is the structure diagram of the solid-core optical fiber component of the present invention;

[0040] Figure 7 This is the structure diagram of an implementation manner of the flange in the present invention;

[0041] Figure 8 This is the docking schematic diagram of the flange and the calibration sleeve in the present invention;

[0042] Figure 9 This is the connection schematic diagram of the annular protrusion and the groove part of the flange in the present invention;

[0043] Figure 10 This is the structure diagram of the hollow-core end lens component of the present invention;

[0044] Figure 11 This is the structure diagram of the hollow-core pin component of the present invention;

[0045] Figure 12 This is the structure diagram of the hollow-core optical fiber component of the present invention;

[0046] Figure 13 This is the structure diagram in the specific embodiment of the present invention;

[0047] Figure 14 This is the simulation diagram in the specific embodiment of the present invention: solid-core single-mode fiber I - hollow-core optical fiber;

[0048] Figure 15 This is the simulation diagram in the specific embodiment of the present invention: hollow-core optical fiber - solid-core single-mode fiber II;

[0049] Figure 16 It is a cross-sectional view of Embodiment 2 of the conversion core component of the present invention;

[0050] Figure 17 It is an external structure diagram of the connector in the present invention;

[0051] Figure 18 It is a cross-sectional view of the connector housing in the present invention;

[0052] Figure 19 It is a cross-sectional view of the connector in the present invention;

[0053] Figure 20 It is a cross-sectional view of the flange in Embodiment 2 of the present invention;

[0054] Figure 21 It is a perspective view of the flange in Embodiment 2 of the present invention;

[0055] Figure 22 It is a structure diagram of the connector pin in Embodiment 2 of the present invention;

[0056] Markings in the figure: 1. solid core optical fiber component, 11. solid core single-mode optical fiber, 111. solid core single-mode optical fiber I, 112. solid core single-mode optical fiber II, 113. solid core bare optical fiber segment, 114. solid core optical fiber outer sheath layer, 115. solid core optical fiber coating layer, 116. solid core optical fiber reinforcement element, 117. solid core optical fiber inner protective layer, 12. solid core end lens, 121. solid core end lens I, 122. solid core end lens II, 1201. first ball face end, 1202, first plane end, 13, solid end sleeve, 131, cavity II, 14, solid end pin, 141, chamfered surface, 15, flange, 151, annular protrusion, 152, groove, 153, inner tube cavity, 154, cavity IV, 155, cavity V, 156, column head part, 157, outer circumferential step, 158, stop platform II, 16, adjustable gap, 17, connector pin, 171, core cavity, 172, bonding cavity, 173, chamfer, 2, hollow core fiber component, 21, hollow core fiber, 211, hollow core fiber bare fiber segment, 212, hollow core fiber outer sheath layer, 213, hollow core fiber coating layer, 214, hollow core fiber strengthening element, 22, hollow core end lens, 221, hollow core end lens I, 222, hollow core end lens II, 2201, second spherical end, 2202, second plane end, 23, hollow core end sleeve, 231, cavity III, 24 , hollow end pin, 3, calibration sleeve, 31, cavity I, 4, solid end outer shell, 41, stopper I, 5, hollow end outer shell, 51, stopper III, 52, inner sleeve, 6, solid end fixing sleeve, 7, hollow end fixing sleeve, 8, retaining ring, 9, conversion core, 10, elastic member, 100, solid pin assembly, 200, hollow pin assembly, 300, accommodating cavity, A, bonding point, B, crimping or bonding point, D, center axis. DETAILED DESCRIPTION

[0057] The present invention is described in detail below by means of exemplary embodiments. However, it should be understood that, without further description, elements, structures and features in one embodiment may also be beneficially combined in other embodiments.

[0058] It should be noted that, unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by persons with ordinary skills in the field to which the invention belongs. The words "one", "an" or "the" and the like used in the patent application specification and claims of the present invention do not express quantitative limitations, but indicate the existence of at least one. Words such as "include" or "comprise" indicate that the elements or objects appearing before "include" or "comprises" include the elements or objects listed after "include" or "comprises" and their equivalents, but do not exclude other elements or objects with the same function.

[0059] In an embodiment of the present solution, the coupling of a solid-core single-mode fiber and a hollow-core fiber is taken as an example for illustration. It should be noted that the first fiber of the present solution is not limited to a solid-core single-mode fiber, and the second fiber is not limited to a hollow-core fiber. The coupling of the first fiber and the second fiber with different mode field diameters can all be applied to the present solution.

[0060] Embodiment 1

[0061] As Figure 1-12 shown, a typical embodiment of the present invention provides a conversion core component, including a calibration sleeve 3. The calibration sleeve 3 is of a cylindrical structure, and the calibration sleeve 3 has a cavity Ⅰ 31 that penetrates axially at both ends. The first fiber component and the second fiber component respectively extend relatively into the calibration sleeve 3 from the openings at both ends of the cavity Ⅰ 31. The first fiber component is a solid-core fiber component 1, and the second fiber component is a hollow-core fiber component 2. Among them, the first fiber component includes a first fiber and a first lens. The first fiber is a solid-core single-mode fiber 11, and the first lens is a solid-core end lens 12. The solid-core single-mode fiber 11 has a first mode field diameter. The second fiber component includes a second fiber and a second lens. The second fiber is a hollow-core fiber 21. The second lens is a hollow-core end lens 22. The hollow-core fiber 21 has a second mode field diameter. The solid-core fiber component 1 and the hollow-core fiber component 2 respectively extend into the calibration sleeve 3 from the two ports of the cavity. The solid-core end lens 12 and the hollow-core end lens 22 are arranged opposite to each other. By using two lenses to achieve the conversion of different mode field diameters between the solid-core single-mode fiber 11 and the hollow-core fiber 21, a reliable and stable connection between the solid-core single-mode fiber 11 and the hollow-core fiber 21 is realized.

[0062] In the present solution, the mode field matching of the two fibers is realized through a double-lens structure. Among them, the solid-core end lens 12 close to the solid-core single-mode fiber 11 with a small mode field is used to expand and collimate the light emitted by the solid-core single-mode fiber 11 with a small mode field, and the hollow-core end lens 22 close to the hollow-core fiber 21 with a large mode field is used to focus the collimated light to a spot mode field size close to that of the hollow-core fiber 21 with a large mode field. Or, in the present solution, the hollow-core end lens 22 close to the hollow-core fiber 21 with a large mode field is used to expand and collimate the light emitted by the hollow-core fiber 21 with a large mode field, and the solid-core end lens 12 close to the solid-core single-mode fiber 11 with a small mode field is used to focus the collimated light to a spot mode field size close to that of the solid-core single-mode fiber 21 with a small mode field.

[0063] In this solution, in order to facilitate the reinforcement of the end of the optical fiber and facilitate a series of subsequent debugging processes, the ends of the solid-core single-mode optical fiber 11 and the hollow-core optical fiber 21 are respectively provided with ferrule structures. The specific implementation is as follows: By removing the solid-core optical fiber coating layer 115 outside the optical fiber cladding at the first end of the solid-core single-mode optical fiber 11, the solid-core bare fiber section 113 of the solid-core single-mode optical fiber 11 after removing the solid-core optical fiber coating layer 115 includes a core and a cladding. The solid-core bare fiber section 113 is arranged in the hollow tube cavity of the solid-core end ferrule 14 to form a first ferrule assembly, which is also the solid-core ferrule assembly 100. The axis of the solid-core ferrule assembly 100 refers to its central axis D in the axial direction. An inclined section 141 that is not perpendicular to the central axis D of the solid-core ferrule assembly 100 is formed at the end of the solid-core ferrule assembly 100. The purpose of such a design is to improve the return loss. By removing the hollow-core optical fiber coating layer 213 outside the optical fiber cladding at the first end of the hollow-core optical fiber 21, the hollow-core bare fiber section 211 after removing the hollow-core optical fiber coating layer 213 is arranged in the capillary hollow tube cavity of the hollow-core end ferrule 24 to form a second ferrule assembly, which is also the hollow-core ferrule assembly 200.

[0064] In the present invention, in order to further realize the connection between the optical fiber and the lens and facilitate a series of debugging in the subsequent process, the first optical fiber component 1 is further provided with a first sleeve, which is also the solid-core end sleeve 13. The solid-core end sleeve 13 is a hollow cylindrical structure with a cavity II 131 that penetrates through both ends. The solid-core ferrule assembly 100 extends into the first end of the cavity of the solid-core end sleeve 13, and the solid-core end lens 12 is arranged at the second end of the cavity of the solid-core end sleeve 13. The solid-core ferrule assembly 100 is placed near the focal plane position of the solid-core end lens 12, and the axial distance between the solid-core ferrule component 100 and the solid-core end lens 13 is finely adjusted near the focal plane position. When the output light of the solid-core end lens 13 is collimated, the positions of the solid-core ferrule component 100 and the solid-core end lens 12 in the solid-core end sleeve 13 are fixed by glue, and the size of the collimated light spot at this time is recorded to obtain the solid-core optical fiber component 1. On the other hand, the hollow-core optical fiber component 2 is further provided with a second sleeve, which is also the hollow-core end sleeve 23. The hollow-core end sleeve 23 is a cylindrical structure with a cavity III 231 that penetrates along the axis. The hollow-core ferrule component 200 extends into the first end of the cavity of the hollow-core end sleeve 23, and the hollow-core end lens 22 is arranged at the second end of the cavity of the hollow-core end sleeve 23. According to the theoretical design value, the axial distance between the hollow-core ferrule assembly 200 and the hollow-core end lens 22 is adjusted. By adjusting the axial distance between the hollow-core ferrule assembly 200 and the hollow-core end lens 22 and the lateral offset distance in the hollow-core end sleeve 23, the position of the hollow-core ferrule assembly 200 when the output collimated light spot is closest to the collimated light spot on the solid-core side is found, which is the best coupling state. The hollow-core ferrule component 200 and the hollow-core end lens 22 are fixed to obtain the hollow-core optical fiber component 2.

[0065] In a preferred embodiment of the present solution, the solid-core end lens 12 is a C lens. The two ends of the C lens are a spherical surface and a plane respectively. The solid-core end lens 12 includes a first spherical end 1201 and a first plane end 1202. The first spherical end 1201 faces the solid-core single-mode optical fiber 11. The first plane end 1202 of the solid-core end lens 12 extends out of the solid-core end sleeve 13, and the first plane end 1202 is an inclined section. The first plane end 1202 is not perpendicular to the axial direction of the solid-core end lens 12. The hollow-core end lens 22 is a C lens. The hollow-core end lens 22 includes a second spherical end 2201 and a second plane end 2202. The second spherical end 2202 faces the hollow optical fiber 21. The first plane end 1202 and the second plane end 2202 are arranged correspondingly. The radius of curvature of the first spherical end 1201 is smaller than that of the second spherical end 2201. The second plane end 2202 of the hollow-core end lens 22 extends out of the hollow-core end sleeve 23, and the second plane end 2202 is an inclined section. The second plane end 2202 is not perpendicular to the axial direction of the hollow-core end lens 22. The first plane end 1202 and the second plane end 2202 are opposite and parallel to each other. In the present solution, the first plane end 1202 and the second plane end 2202 are both inclined sections, and the main function is to eliminate the Fresnel effect existing there. The ultimate goal is to improve the return loss. Specifically, according to different return loss standards, the present solution can process inclined sections with different angles and coat anti-reflection films at the same time, so that the transmittance is higher than 99.9%.

[0066] Since the Fresnel reflection occurs when light is incident on the interface of two media with different refractive indices, the present solution suppresses the Fresnel reflection by coating anti-reflection films on the end face of the small-mode-field solid-core single-mode optical fiber 11 and the end face of the solid-core end lens 12. The principle of designing the anti-reflection film is that the two reflected light beams on the upper and lower surfaces of the film undergo destructive interference. Therefore, the optical path difference between the two reflected lights should be an odd multiple of half a wavelength, and the optical thickness of the film layer [the product of the actual thickness and the refractive index of the material] must be an odd multiple of a quarter wavelength. The Fresnel reflection occurs at each material interface. Each time the reflected light reaches another interface, a part of it will experience additional Fresnel reflection.

[0067] In this solution, a flange 15 and a retaining ring 8 are also included. The flange 15 and the retaining ring 8 are used to realize the fixed connection between the housing and the conversion core component 9. The specific method is as follows: The main structure of the flange 15 is a hollow cylindrical structure. An annular protrusion 151 and a groove 152 are respectively arranged at positions near both ends of the flange 15. One end of the flange 15 with the annular protrusion 151 is connected to the solid core end sleeve 13, and the central axis of the flange 15 is parallel or coincident with the central axis of the solid core end sleeve 13. The flange 15 has an inner lumen 153 along the central axis. One end of the flange 15 is bonded to the end of the solid core end sleeve 13. Specifically, an adjustable gap 16 is formed between the flange 15 and the solid core end sleeve 13. The adjustable gap 16 is used to accommodate the bonding layer, so as to realize the distance adjustment during the installation of the two components after the bonding layer solidifies. By setting the adjustable gap 16, the purpose is to realize the adjustment of the axial distance between the solid core pin assembly 100 and the solid core end lens 12. A stud portion 156 is formed between the annular protrusions 151 near the end of the flange 15. Through the stud portion 156, a part of the end of the flange 15 is inserted into the cavity of the calibration sleeve 3. During installation, it is necessary to pre-fix the flange 15 and the solid core pin component 100 together with an adhesive, then connect them to the solid core end sleeve 13 to form a solid core optical fiber component 1, and then insert the whole solid core optical fiber component 1 into the calibration sleeve 3. At this time, after the annular protrusion 151 abuts against one end of the calibration sleeve 3, the retaining ring 8 is buckled into the groove 152 at the other end of the flange 15. In this way, the axial limit of the solid core optical fiber component 1 and the solid core end housing 4 is realized through both sides of the annular protrusion 151 and the groove 152. The first end of the flange 15 is in a blocking and limiting fit with the retaining platform 41 in the lumen of the solid core end housing 4 through the annular protrusion 151, which limits the position of the flange 15 relative to the solid core end housing 4 in the first direction. The second end of the flange 15 is in a blocking and limiting fit with the retaining ring 8 through the groove 152, which limits the position of the flange 15 relative to the solid core end housing 4 in the second direction. The first direction and the second direction are opposite directions.

[0068] In this solution, the inner lumen 153 of the flange 15 includes a cavity Ⅳ154 and a cavity Ⅴ155 that are connected to each other and coaxially arranged. The cross-sectional diameter of the cavity Ⅳ154 is larger than the cross-sectional diameter of the cavity Ⅴ155. The cavity Ⅳ154 is used to accommodate and bond and fix one end of the solid core pin assembly 100, and the cavity Ⅴ155 is used to pass through the solid core single-mode optical fiber 11.

[0069] In this solution, the solid-core single-mode optical fiber 11 sequentially includes a solid-core optical fiber outer sheath layer 114, a solid-core optical fiber strengthening element 116, a solid-core optical fiber inner protection layer 117, a solid-core optical fiber coating layer 115, and a solid-core optical fiber bare fiber section 113 from outside to inside. The solid-core optical fiber bare fiber section 113 includes a cladding and a core part. The hollow-core optical fiber 21 sequentially includes a hollow-core optical fiber outer sheath layer 212, a hollow-core optical fiber strengthening element 214, a hollow-core optical fiber coating layer 213, and a hollow-core optical fiber bare fiber section 211 from outside to inside.

[0070] Embodiment 2

[0071] As Figure 16-22 shown, a typical embodiment of the present invention provides a conversion core component, including a calibration sleeve 3. The calibration sleeve 3 has a cylindrical structure, and the calibration sleeve 3 has a cavity Ⅰ31 that penetrates both ends along the axial direction. The first optical fiber component and the second optical fiber component respectively extend relatively into the calibration sleeve 3 from the two open ends of the cavity Ⅰ31. The first optical fiber component is a solid-core optical fiber component 1, and the second optical fiber component is a hollow-core optical fiber component 2. The first optical fiber component includes a first optical fiber and a first lens. The first optical fiber 11 is a solid-core single-mode optical fiber 11, and the first lens is a solid-core end lens 12. The solid-core single-mode optical fiber 11 has a first mode field diameter. The second optical fiber component 2 includes a second optical fiber and a second lens. The second optical fiber is a hollow-core optical fiber 21, and the second lens is a hollow-core end lens 22. The hollow-core optical fiber 21 has a second mode field diameter. The solid-core optical fiber component 1 and the hollow-core optical fiber component 2 respectively extend into the calibration sleeve 3 from the two ports of the cavity. The solid-core end lens 12 and the hollow-core end lens 22 are arranged oppositely. By using two lenses to realize the conversion of different mode field diameters between the solid-core single-mode optical fiber 11 and the hollow-core optical fiber 21, a reliable and stable connection between the solid-core single-mode optical fiber 11 and the hollow-core optical fiber 21 can be realized.

[0072] In this solution, the mode field matching of the two optical fibers is realized through a double-lens structure. The solid-core end lens 12 close to the solid-core single-mode optical fiber 11 with a small mode field is used to expand and collimate the light emitted by the solid-core single-mode optical fiber 11 with a small mode field. The hollow-core end lens 22 close to the hollow-core optical fiber 21 with a large mode field is used to focus the collimated light to a spot mode field size close to that of the hollow-core optical fiber 21 with a large mode field. Or, in this solution, the hollow-core end lens 22 close to the hollow-core optical fiber 21 with a large mode field is used to expand and collimate the light emitted by the hollow-core optical fiber 21 with a large mode field. The solid-core end lens 12 close to the solid-core single-mode optical fiber 11 with a small mode field is used to focus the collimated light to a spot mode field size close to that of the solid-core single-mode optical fiber 21 with a small mode field.

[0073] In this solution, in order to facilitate the reinforcement of the end of the optical fiber and facilitate a series of subsequent debugging processes, the ends of the solid-core single-mode optical fiber 11 and the hollow-core optical fiber 21 are respectively provided with ferrule structures. The specific implementation method is as follows: The outer cladding of the whole solid-core single-mode optical fiber 11 is removed to obtain a solid-core bare optical fiber. The tail end of the solid-core bare optical fiber is arranged in the hollow tube cavity of the solid-core end ferrule 14. The head end of the solid-core single-mode optical fiber 11 is inserted into the ferrule cavity 171 of the connector ferrule 17, thereby forming a first ferrule assembly. The first ferrule assembly is the solid-core ferrule assembly 100. The axis of the solid-core ferrule assembly 100 refers to its central axis along the axial direction. An inclined plane 141 that is not perpendicular to the central axis of the solid-core ferrule assembly 100 is formed at the end of the tail end of the solid-core ferrule assembly 100. The purpose of such a design is to improve the return loss. By removing the hollow-core optical fiber coating layer 213 outside the optical fiber cladding at the first end of the hollow-core optical fiber 21, the hollow-core bare optical fiber section after removing the hollow-core optical fiber coating layer 213 is arranged in the capillary hollow tube cavity of the hollow-core end ferrule 24, forming a second ferrule assembly. The second ferrule assembly is the hollow-core ferrule assembly 200.

[0074] In the present invention, in order to further realize the connection between the optical fiber and the lens and facilitate a series of debugging in the subsequent process, the solid-core optical fiber component 1 is further provided with a first sleeve, that is, the solid-core end sleeve 13. The solid-core end sleeve 13 is a hollow cylindrical structure with a cavity II 131 that penetrates through both ends. The head end of the solid-core ferrule assembly 100 extends into the cavity of the solid-core end sleeve 13 (the end facing the connector ferrule 17 is the head end). The solid-core end lens 12 is arranged at the tail end of the cavity of the solid-core end sleeve 13, obtaining the solid-core optical fiber component 1. On the other hand, the hollow-core optical fiber component 2 is further provided with a second sleeve, that is, the hollow-core end sleeve 23. The hollow-core end sleeve 23 is a cylindrical structure with a cavity III 231 that penetrates along the axis. The hollow-core ferrule component 200 extends into the tail end of the cavity of the hollow-core end sleeve 23. The hollow-core end lens 22 is arranged at the head end of the cavity of the hollow-core end sleeve 23. According to the theoretical design value, the axial distance between the hollow-core ferrule assembly 200 and the hollow-core end lens 22 is adjusted. By adjusting the axial distance between the hollow-core ferrule assembly 200 and the hollow-core end lens 22 and the lateral offset distance in the hollow-core end sleeve 23, the position of the hollow-core ferrule assembly 200 when the output collimated light spot is closest to the solid-core side collimated light spot is found, which is the best coupling state.

[0075] Such as Figure 19As shown in the figure, in another preferred embodiment of the present solution, the solid-core end lens 12 is a C lens. The two ends of the C lens are a spherical surface and a plane respectively. The solid-core end lens 12 includes a first spherical surface end 1201 and a first plane end 1202. The first plane end 1202 faces the solid-core single-mode optical fiber 11. The first spherical surface end 1201 of the solid-core end lens 12 protrudes outward from the solid-core end sleeve 13, and the first plane end 1202 is an inclined cut surface, and the first plane end 1202 is not perpendicular to the axial direction of the solid-core end lens 12; the hollow-core end lens 22 is a C lens. The hollow-core end lens 22 includes a second spherical surface end 2201 and a second plane end 2202. The second plane end 2202 faces the hollow optical fiber 21. The first spherical surface end 1201 and the second spherical surface end 2201 are arranged corresponding to each other. The second spherical surface end 2201 of the hollow-core end lens 22 protrudes outward from the hollow-core end sleeve 23, and the second plane end 2202 is an inclined cut surface, and the second plane end 2202 is not perpendicular to the axial direction of the hollow-core end lens 22; in this solution, the first plane end 1202 and the second plane end 2202 are both arranged as inclined cut surfaces. The first plane end 1202 is parallel to the inclined cut surface 141 at the tail end of the solid-core end pin 14. The main function is to eliminate the Fresnel effect existing at this place. The ultimate goal is to improve the return loss. Specifically, according to different return loss standards, this solution can process inclined surfaces with different inclination angles and simultaneously coat an antireflection film to improve the transmittance. It should be noted that in this embodiment, it is also possible to arrange the first plane end 1202 and the second plane end 2202 corresponding to each other and the first spherical surface end 1201 and the second spherical surface end 2201 facing away from each other as in Embodiment 1.

[0076] As Figure 16 , 19As shown in FIGS. 20 and 21, this solution further includes a flange 15. The main structure of the flange 15 is a hollow cylindrical structure. The central axis of the flange 15 is parallel to or coincides with the central axis of the solid end sleeve 13. The flange 15 has an inner lumen 153 along the central axis, and one end of the flange 15 is bonded to the end of the solid end sleeve 13. Specifically, an adjustable gap 16 is formed between the flange 15 and the solid end sleeve 13. The adjustable gap 16 is used to accommodate the bonding layer, so as to realize the spacing adjustment during the installation of the two components after the bonding layer solidifies. By setting the adjustable gap 16, the purpose is to realize the adjustment of the axial spacing between the solid pin assembly 100 and the solid end lens 12. An outer circumferential step 157 is formed on the outer cylindrical surface of the flange 15. The outer circumferential step 157 divides the flange 15 into a large-diameter end and a small-diameter end. The small-diameter end of the flange 15 is inserted into the inner head end of the cavity I 31 of the calibration sleeve 3. In this solution, the inner lumen 153 of the flange 15 includes a cavity IV 154 and a cavity V 155 that are interconnected and coaxially arranged. The cavity IV 154 is used to accommodate and bond and fix the head end of the solid end pin 14, and the cavity V 155 is used to accommodate the tail end of the fixed connector pin 17. More specifically, the cross-sectional diameter of the cavity V 155 is different from the cross-sectional diameter of the cavity IV 154. For example, the cross-sectional diameter of the cavity V 155 is larger than the cross-sectional diameter of the cavity IV 154, so as to form a step therebetween. The connector pin 17 can adopt the following structure, or can also adopt the pin structures of other existing technologies. For example, in one of the embodiments of this solution, the adopted connector pin 17 includes a ferrule cavity 171 formed along the central axis for passing through the solid bare optical fiber section. A tapered bonding cavity 172 for filling the bonding colloid is provided at the tail end of the ferrule cavity 171, so as to more firmly fix the solid bare optical fiber section by filling the colloid in the bonding cavity 172. A frustum-shaped chamfer 173 is formed at the plug end of the connector pin 17.

[0077] The assembly process of the conversion core component 9 is as follows: Step 1: Strip the outer protective layer of the solid-core single-mode optical fiber 11 to obtain a solid-core bare optical fiber. Insert the first end of the solid-core bare optical fiber into the solid-core end ferrule 14 and perform grinding processing on the end face according to requirements. For example, process the end face of the solid-core end ferrule 14 into an inclined cut surface 141. Step 2: Connect and combine the connector socket 17 and the flange 15 to form a connector ferrule component. Step 3: Insert the second end of the solid-core bare optical fiber completed in Step 1 into the connector ferrule component obtained in Step 2 to obtain a solid-core ferrule component 100. Specifically, insert the head end of the solid-core single-mode optical fiber 11 from the tail end of the connector ferrule component and into the ferrule cavity 171 of the connector ferrule 17. Before insertion, inject an adhesive into the middle section of the inner tube cavity 153 of the flange 15 to achieve fixed connection. Step 4: Insert and fix the solid-core end lens 12 inside the solid-core end sleeve 13 to form a solid-core end lens component. Step 5: Connect the head end of the solid-core end lens component obtained in Step 4 to the tail end of the solid-core ferrule component 100 obtained in Step 3 to obtain a solid-core optical fiber component 1. Specifically, the solid-core end ferrule 14 extends into the cavity II 131 of the solid-core end sleeve 13. Step 6: Strip the outer protective layer from the head end of the hollow-core optical fiber 21 to obtain a hollow-core bare optical fiber section. Insert this hollow-core bare optical fiber section into the hollow-core end ferrule 24 to obtain a hollow-core ferrule component 200. Step 7: Connect the hollow-core end lens 22 to the head end of the hollow-core end sleeve 23 to obtain a hollow-core end lens component. Step 8: Assemble the hollow-core ferrule component 200 obtained in Step 6 and the hollow-core end lens component obtained in Step 7 together, but do not fix them temporarily to obtain a hollow-core optical fiber component 2. Specifically, the head end of the hollow-core end ferrule 24 extends into the cavity of the hollow-core end sleeve 23, but they are not adhesively fixed to facilitate the position adjustment of the hollow-core ferrule component 200. Step 9: Fix the solid-core optical fiber component 1 obtained in Step 5 and the hollow-core optical fiber component 2 obtained in Step 8 in two toolings of the adjustment frame respectively. By adjusting the relative positions of the solid-core optical fiber component 1 and the hollow-core optical fiber component 2, and simultaneously adjusting the position of the hollow-core end ferrule 24 inside the hollow-core end sleeve 23, the overall loss is optimized. Step 10: Fix the hollow-core end ferrule 24 inside the hollow-core end sleeve 23 at the optimal loss point. Step 11: Then move the relative positions of the solid-core optical fiber component 1 and the hollow-core optical fiber component 2 and fix the solid-core optical fiber component 1 and the hollow-core optical fiber component 2 at the best coupling position inside the calibration sleeve 3.

[0078] Example 3

[0079] Another embodiment of the present invention further provides a dual-lens mode field conversion device, which includes the conversion core member 9 in the above-mentioned Embodiment 1 and a housing arranged outside the conversion core member 9. The housing is used to protect the conversion core member from external contamination and provide a certain mechanical strength protection for the internal connection structure to avoid mechanical damage to the internal conversion core member 9. The housing includes a first housing body and a second housing body connected by threads. The first housing body is a solid-core end housing body 4, and the second housing body is a hollow-core end housing body 5; as Figure 2 shown in, wherein the solid-core end fixing sleeve 6 (the solid-core end fixing sleeve 6 is the first fixing sleeve) fixes the solid-core optical fiber outer sheath layer 114 of the solid-core single-mode optical fiber 11 to the end of the solid-core end housing body 4 by means of crimping or bonding. The hollow-core end fixing sleeve 7 (the hollow-core end fixing sleeve 7 is the second fixing sleeve) fixes the hollow-core optical fiber outer sheath layer 212 of the hollow-core optical fiber 21 to the end of the hollow-core end housing body 5 by means of crimping or bonding.

[0080] In a typical embodiment of the present invention, both the solid-core end fixing sleeve 6 and the hollow-core end fixing sleeve 7 are of an annular sleeve structure, including a large-diameter end and a small-diameter end. The large-diameter end of the solid-core end fixing sleeve 6 is connected to the crimping joint at the end of the solid-core end housing body 4, and the small-diameter end of the solid-core end fixing sleeve 6 is in contact with the solid-core optical fiber outer sheath layer 114. The large-diameter end of the hollow-core end fixing sleeve 7 is connected to the crimping joint at the end of the hollow-core end housing body 5, and the small-diameter end of the hollow-core end fixing sleeve 7 is in contact with the hollow-core optical fiber outer sheath layer 212. It should be noted that the solid-core end fixing sleeve 6 and the hollow-core end fixing sleeve 7 can adopt the crimping method. Specifically, the solid-core end fixing sleeve 6 and the hollow-core end fixing sleeve 7 are made of elastic materials. Through the contraction force of the elastic materials, the optical fibers at both ends are tightly crimped on the solid-core end fixing sleeve 6 and the hollow-core end fixing sleeve 7 respectively. They can also adopt the bonding method. Specifically, the outer surfaces of the optical fibers at both ends are bonded to the small-diameter end of the fixing sleeve through glue, and the crimping joints of the solid-core end housing body 4 and the hollow-core end housing body 5 are bonded to the large-diameter end of the fixing sleeve through glue.

[0081] In this embodiment, in order to achieve a better fixing effect, at least one annular groove is provided on the outer cylindrical surface of the crimping joints of the solid-core end housing body 4 and the hollow-core end housing body 5. Preferably, two annular grooves are arranged along the axial direction of the crimping joint in this solution. Designed in this way, when the solid-core end fixing sleeve 6 and the hollow-core end fixing sleeve 7 adopt the shrinkage crimping method, the fixing sleeve will be fastened at the position of the annular groove after deformation and tightening. The annular groove can increase the relative friction between the fixing sleeve and the crimping joint, playing a role in strengthening the connection strength and improving the sealing effect at the connection. If the solid-core end fixing sleeve 6 and the hollow-core end fixing sleeve 7 are fixed by gluing, the annular groove is used to accommodate the glue, thereby playing a role in increasing the bonding firmness and improving the sealing effect at the connection.

[0082] In this embodiment, since the solid core optical fiber component 1, the calibration sleeve 3 and the hollow core optical fiber component 2 are fixed by bonding, and the solid core end outer shell 4 and the hollow core end outer shell 5 are connected by threaded fixation, the connection and cooperation between the retaining ring 8 and the flange 15 can achieve the fixation of the relative position of the entire outer shell and the internal conversion core 9 in the axial direction.

[0083] Example 4

[0084] Reference Figure 17-19 Another embodiment of the present invention also provides a dual-lens mode field conversion connector, which is described by taking an LC connector as an example. The LC connector includes the conversion core 9 in the above-mentioned embodiment 2 and a shell arranged outside the conversion core 9. The head end of the conversion core 9 (the end of the connector pin 17) passes through the accommodating cavity 300 of the shell and is exposed from the head end of the shell. The hollow optical fiber at the tail end of the conversion core 9 passes out from the tail end of the shell.

[0085] The housing includes a first housing body and a second housing body connected by snap-fitting, the first housing body is a solid end housing body 4, and the second housing body is a hollow end housing body 5. An elastic member 10 is also provided in the housing. Specifically, the elastic member 10 is a spring. The spring and the hollow end housing body 5 are inserted outside the conversion core 9, and then the head end of the conversion core 9 is passed through the solid end housing body 4, and then the connecting ends of the solid end housing body 4 and the hollow end housing body 5 are relatively close to achieve the connector snap-fit connection. One of the connection methods of the housing is as follows, that is, a clamping block 53 is provided on the outer side wall of the hollow end housing body 5, and a clamping hole 42 or a clamping groove is provided on the side wall of the solid end housing body 4. When the two parts of the housing are docked in place, the clamping block 53 enters the clamping hole 42 or the clamping groove to achieve the fixation of the two. It should be noted that the solid end outer shell 4 and the hollow end outer shell 5 can also be fixedly connected in other ways, for example, a clamping hole is provided on the side wall of the hollow end outer shell 5, and a clamping block that cooperates with the clamping hole is provided on the outer side wall of the solid end outer shell 4. Moreover, the connection between the two is not limited to the above-mentioned clamping connection method.

[0086] In this embodiment, the head end of the elastic member 10 can abut against the outer circumferential step 157 of the flange 15, and the tail end of the elastic member 10 can abut against the stop platform III 51 in the hollow end outer shell 5, and the elastic member 10 can provide a preload force in the head direction for the conversion core member 9 (such as Figure 19 D direction as shown), the stop platform III 51 is formed by pre-setting an inner sleeve 52 inside the accommodating cavity of the hollow end outer shell 5, that is, the stop platform III 51 is the end of the inner sleeve 52. It should be pointed out that the stop platform III 51 can also be set in other structural forms.

[0087] In this solution, a stop platform I 41 is arranged in the inner cavity of the solid core end housing 4, and a stop platform II 158 is arranged at the head end of the flange 15. The stop platform I 41 and the stop platform II 158 cooperate to form a stop limit for the movement of the conversion core component 9 towards the head end direction, so that the head end of the conversion core component 9 is blocked by the stop platform I 41, and the tail end of the flange 15 is subjected to a pre-tightening force towards the head end provided by the elastic component 10, so that the whole conversion core component 9 is abutted against the inner side wall of the accommodation cavity 300 of the housing towards the head end direction. After the conversion core component 9 is pressed, it can compress the elastic component 10 and thus move towards the tail end direction as a whole.

[0088] Embodiment 5

[0089] Based on the structure of the mode field conversion component in Embodiment 3, the present invention further provides a manufacturing method of a double-lens mode field conversion component, and the specific steps are as follows:

[0090] Step 1: Assemble the solid core end lens 12 and the solid core end sleeve 13 to form a solid core end lens component, assemble the solid core single-mode optical fiber 11 and the solid core end pin 14 to form a solid core pin component 100, insert the solid core pin component 100 into the cavity II 131 of the solid core end sleeve 13 from one end opposite to the solid core end lens 12, and perform debugging to obtain a solid core optical fiber component 1.

[0091] In this solution, the solid core pin assembly 100 is manufactured by the following steps: remove the coating layer from the end of the solid core single-mode optical fiber 11 to form a solid core optical fiber bare fiber section 113, insert the solid core optical fiber bare fiber section 113 without the coating layer into the hollow tube cavity of the solid core end pin 14 from the first end and bond and fix it, and insert the first end of the solid core end pin 14 into the cavity IV 154 of the flange 15 and bond and fix it.

[0092] The debugging process of this step is as follows: The light source is injected from one end of the solid core single-mode optical fiber 11, and after being coupled by the solid core end lens 12, it is transmitted to the beam quality analysis equipment for on-line monitoring. The specific process is as follows: Place the end face of the solid core pin assembly 100 at the focal plane position of the solid core end lens 12, finely adjust the axial distance between the solid core pin assembly 100 and the solid core end lens 12 nearby. When the output light is collimated, fix the positions of the solid core pin assembly 100 and the solid core end lens 12 in the solid core end sleeve 13, and record the size of the collimated light spot at this time.

[0093] Step 2: Assemble the hollow core end lens 22 and the hollow core end sleeve 23 to form a hollow core end lens component, assemble the hollow core optical fiber 21 and the hollow core end pin 24 to form a hollow core pin component 200, insert the hollow core pin component 200 into the cavity of the hollow core end sleeve 23 from one end opposite to the hollow core end lens 22, and perform debugging to obtain a hollow core optical fiber component 2;

[0094] In this step, the debugging process is as follows: First, the hollow-core optical fiber 2 is connected to a light source. After being coupled by the hollow-core end lens 22, it is connected to a beam quality analysis device for on-line monitoring. The specific process is as follows: Adjust the axial distance between the end face of the hollow-core pin assembly 200 and the hollow-core end lens 22 according to the theoretical design value. By adjusting the axial distance between the hollow-core pin assembly 200 and the hollow-core end lens 22, as well as the lateral offset distance in the hollow-core end sleeve 23, find the position of the hollow-core pin assembly 200 when the output collimated light spot and the collimated light spot on the other side are closest, which is the optimal coupling state. Fix the positions of the hollow-core pin component 200 and the hollow-core end lens 22.

[0095] In this solution, in order to protect the internal microstructure of the hollow-core optical fiber 21, for the internal microstructure of the hollow-core optical fiber 21, light can be confined in the hollow-core optical fiber 21 and transmitted with low loss. Therefore, its internal microstructure cannot be damaged, and glue cannot be inhaled to affect light transmission. The fixing method of the traditional solid-core single-mode optical fiber 11 and the solid-core end pin 14 is different from that of the solid-core pin assembly as follows:

[0096] The traditional method is that the bare fiber section 113 of the solid-core optical fiber penetrates into the solid-core end pin 14. It is necessary to first inject glue to fix the solid-core single-mode optical fiber 11 and grind the end face of the solid-core pin assembly 100. However, these processes in the traditional method are likely to damage the end face structure of the hollow-core optical fiber 21 and easily inhale glue into the capillary inside the hollow-core optical fiber 21.

[0097] In this solution, during actual operation, first remove a part of the coating 213 of the hollow-core optical fiber near the end face of the hollow-core optical fiber 21 to form a bare fiber section 211 of the hollow-core optical fiber. Then, insert the bare fiber section 211 of the hollow-core optical fiber into the central cavity of the hollow-core end pin 24 to form a hollow-core pin assembly 200. Use an optical fiber cutter to cut the end face of the bare fiber section 211 of the hollow-core optical fiber. Then pull the hollow-core optical fiber 21 back into the cavity of the hollow-core end pin 24, and make the end face of the end of the bare fiber section 211 of the hollow-core optical fiber slightly recessed inside the end face of the hollow-core end pin 24, and carefully fix the end of the hollow-core optical fiber 21 in the cavity of the hollow-core end pin 24 with glue. The purpose of such a design can effectively avoid damaging the end face of the hollow-core optical fiber 21 and at the same time avoid inhaling glue into the capillary inside the hollow-core optical fiber 21.

[0098] Step 3: Insert the solid-core optical fiber component 1 obtained in Step 1 and the hollow-core optical fiber component 2 obtained in Step 2 into the inside of the calibration sleeve 3 from both ends respectively, and fix the solid-core optical fiber component 1 and the hollow-core optical fiber component 2 inside the calibration sleeve 3 after debugging to obtain a conversion core component 9;

[0099] In this solution, a calibration sleeve 3 is used to debug and fix the positions of the solid-core optical fiber component 1 and the hollow-core optical fiber component 2 to form an integral whole. Note that the two opposite inclined planes of the two lenses slightly protrude from the end faces of the two sleeves. Such a design is beneficial for aligning the inclination angles of the two inclined planes during debugging, thereby reducing the additional loss caused by misalignment in the inclined plane direction.

[0100] Step 4: Place the solid-core end of the conversion core component 9 inside the solid-core end housing 4, insert the hollow-core end of the conversion core component 9 into the hollow-core end housing 5, and then screw the threaded ends of the solid-core end housing 4 and the hollow-core end housing 5 together.

[0101] In this solution, after screwing the threaded ends of the solid-core end housing 4 and the hollow-core end housing 5 together, the housing is axially limited relative to the conversion core component 9 by setting the retaining ring 8 in the groove 152 of the flange 15.

[0102] Step 5: Fix the solid-core optical fiber outer sheath layer 114 of the solid-core single-mode optical fiber 1 to the solid-core end housing 4 through the solid-core end fixing sleeve 6, and fix the hollow-core optical fiber outer sheath layer 212 of the hollow-core optical fiber 2 to the hollow-core end housing 5 through the hollow-core end fixing sleeve 7.

[0103] Specifically, the solid-core optical fiber outer sheath layer 114 of the solid-core single-mode optical fiber 11 is fixed between the solid-core end fixing sleeve 6 and the solid-core end housing 4, and the hollow-core optical fiber outer sheath layer 212 of the hollow-core optical fiber 21 is fixed between the hollow-core end fixing sleeve 7 and the hollow-core end housing 5.

[0104] In this solution, the manufacturing process of the conversion device is optimized. By combining with the specific structure of the above double-lens mode field conversion device, each step of the manufacturing process is refined. First, the solid-core end sleeve 13 and the solid-core end lens 12 form a solid-core end lens component, and the solid-core single-mode optical fiber 11 and the solid-core end pin 14 form a solid-core pin assembly. Then, the solid-core end lens component and the solid-core pin assembly 100 are debugged and installed to form the solid-core optical fiber component 1; the hollow-core end sleeve 23 and the hollow-core end lens 22 form a hollow-core end lens component, and the hollow-core optical fiber 21 and the hollow-core end pin 14 form a hollow-core pin assembly 200. Then, the hollow-core end lens component and the hollow-core pin assembly 200 are debugged and installed to form the hollow-core optical fiber component 2. In this way, during the final adjustment, only the axial distance and radial offset value of the hollow-core optical fiber component 2 and the solid-core optical fiber component 1 in the calibration sleeve need to be debugged. The above step-by-step adjustment method reduces the debugging and installation difficulty during the manufacturing process to a certain extent and improves the optical fiber coupling effect.

[0105] The following is an illustration with specific embodiments:

[0106] The following is a specific embodiment of the designed double-lens structure (refer to the schematic Figure 13-15), a solid-core single-mode optical fiber Ⅰ 111 - hollow-core optical fiber 21 - solid-core single-mode optical fiber Ⅱ 112 optical transmission link with low insertion loss and high return loss can be achieved. In the figure, the mode field diameters of the solid-core single-mode optical fibers Ⅰ and Ⅱ 111 and 112 and the hollow-core optical fiber 21 are 9.2μm and 20μm (@1310nm), respectively. This solution includes two optical paths, in which the double-lens mode field conversion components with the above structure are used for both the solid-core single-mode optical fiber Ⅰ 111 - hollow-core optical fiber 21 and the hollow-core optical fiber 22 - solid-core single-mode optical fiber Ⅱ 112. The data of the double-lens coupling system designed in this embodiment are shown in the following table. The basic parameters of the solid-core end lenses Ⅰ and Ⅱ 121 and 122 are: material N-SF11, curvature radius 1.15mm, length 2.35mm; the basic parameters of the hollow-core end lenses Ⅰ and Ⅱ 221 and 222 are: material N-SF11, curvature radius 2.52mm, length 2.5mm. The transmittance of the anti-reflection film at the beveled surface in this embodiment is higher than 99.9%. As shown in Table 1, the distance from the solid-core single-mode optical fiber Ⅰ 111 to the solid-core end lens Ⅰ 121 is L1; the distance from the solid-core end lens Ⅰ 121 to the hollow-core end lens Ⅰ 221 is L2; the distance from the hollow-core end lens Ⅰ 221 to the first end of the hollow-core optical fiber 21 is L3, and the distance between the second end of the hollow-core optical fiber 21 and the hollow-core end lens Ⅱ 222 is L4; the distance between the hollow-core end lens Ⅱ 222 and the solid-core end lens Ⅱ 122 is L5, and the distance between the solid-core end lens Ⅱ 122 and the solid-core single-mode optical fiber Ⅱ 112 is L6.

[0107] Table 1 Axial distance data table between components

[0108]

[0109] Table 2 Lateral offset data table between components

[0110]

[0111] The lateral offset values of each component in Table 2 above are obtained with the position of the solid-core single-mode optical fiber 11 as the origin.

[0112] The above theoretical simulation shows that when the end face of the single-mode optical fiber is beveled, the coupling loss from the single-mode optical fiber to the hollow-core optical fiber is ≤0.3dB, the coupling loss from the hollow-core optical fiber to the single-mode optical fiber is ≤0.3dB, and the return loss exceeds 45dB.

[0113] The above solid-core single-mode optical fiber 1 is directly connected to the hollow-core optical fiber 2 by using the conventional fusion splicing method of the existing technology. The difference is that the fiber structure of the fusion splicing method does not include the double-lens mode field conversion device of this solution. The mode field diameter of the solid-core single-mode optical fiber 1 is 9.2μm; the mode field diameter of the hollow-core optical fiber 2 is 20μm (@1310nm). The coupling loss of the fiber structure after the direct fusion splicing method is higher than 2.4dB, and the return loss is about 15dB.

[0114] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to form equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A conversion core component, characterized in that: It includes a first optical fiber component, a second optical fiber component and a calibration sleeve. The first optical fiber component includes a first lens and a first optical fiber having a first mode field diameter. The first lens is located at the end of the first optical fiber component. The second optical fiber component includes a second lens and a second optical fiber having a second mode field diameter. The second lens is located at the end of the second optical fiber component. The calibration sleeve has a hollow cavity Ⅰ along its axial direction. The first optical fiber component and the second optical fiber component extend into the calibration sleeve cavity Ⅰ from both ends respectively, and the first lens and the second lens are arranged opposite to each other.

2. The conversion core component according to claim 1, wherein: The first optical fiber component further includes a first sleeve. The first sleeve has a cavity Ⅱ with openings at both ends along its axial direction. The first optical fiber extends into the cavity Ⅱ of the first sleeve from one end, and the first lens is arranged at the other end of the cavity Ⅱ of the first sleeve and extends outwards. The second optical fiber component further includes a second sleeve. The second sleeve has a cavity Ⅲ with openings at both ends along its axial direction. The second optical fiber extends into the cavity Ⅲ of the second sleeve from one end, and the second lens is arranged at the other end of the cavity Ⅲ of the second sleeve and extends outwards.

3. The conversion core component according to claim 1 or 2, characterized in that: The first lens and the second lens adopt C lenses. The C lens has two ends, one of which is a convex spherical surface and the other is a plane. The first lens includes a first spherical end and a first plane end. The first spherical end faces the first optical fiber. The second lens includes a second spherical end and a second plane end. The second spherical end faces the second optical fiber. The first plane end and the second plane end are arranged corresponding to each other.

4. A conversion core component according to claim 3, characterized in that: The first plane end of the first lens extends out of the first sleeve, and the first plane end is an inclined cut surface, and the first plane end is not perpendicular to the axis of the first lens. The second plane end of the second lens extends out of the second sleeve, and the second plane end is an inclined cut surface, and the second plane end is not perpendicular to the axis of the second lens. The first plane end and the second plane end are opposite and parallel to each other.

5. The conversion core component according to claim 2, wherein: The first end of the first optical fiber is a bare optical fiber section. The bare optical fiber section of the first optical fiber is arranged in the hollow tube cavity of the first ferrule to form a first ferrule assembly. The first ferrule assembly is inserted into and fixed in the first sleeve from one end of the first sleeve. The first end of the second optical fiber is a bare optical fiber section. The bare optical fiber section of the second optical fiber is arranged in the hollow tube cavity of the second ferrule to form a second ferrule assembly. The second ferrule assembly is inserted into and fixed in the second sleeve from one end of the second sleeve.

6. A conversion core component according to any one of claims 5, characterized in that: The first ferrule assembly forms an inclined cut surface at the end facing the first lens, and the inclined cut surface of the first ferrule assembly is not perpendicular to the axis of the first ferrule assembly.

7. The conversion core component according to claim 6, characterized in that: Anti-reflection films are coated on both the inclined cut surface of the first ferrule assembly and the first spherical end of the first lens.

8. A conversion core component according to claim 1 or 2, characterized in that: The first lens and the second lens are C lenses. The C lens has two ends, one of which is a convex spherical surface and the other is a plane. The first lens includes a first spherical end and a first plane end. The first plane end faces the first optical fiber. The second lens includes a second spherical end and a second plane end. The second plane end faces the second optical fiber. The first spherical end and the second spherical end are correspondingly arranged.

9. The conversion core component according to claim 8, characterized in that: The first plane end of the first lens extends into one end of the first sleeve. The first spherical end of the first lens protrudes outward from the inside of the first sleeve. The first plane end is an inclined cut surface and is not perpendicular to the axis of the first lens. The second plane end of the second lens extends into one end of the second sleeve. The second spherical end of the second lens protrudes outward from the inside of the second sleeve. The second plane end is an inclined cut surface and is not perpendicular to the axis of the second lens.

10. A conversion core component according to claim 9, characterized in that: It further includes a connector pin. The bare optical fiber section at the head end of the first optical fiber is arranged in the hollow lumen of the connector pin. The bare optical fiber section at the tail end of the first optical fiber is arranged in the hollow lumen of the first pin to form a first pin assembly. The tail end of the first pin is inserted into and fixed in the first sleeve from one end of the first sleeve. The first end of the second optical fiber is a bare optical fiber section. The bare optical fiber section of the second optical fiber is arranged in the hollow lumen of the second pin to form a second pin assembly. The second pin assembly is inserted into and fixed in the second sleeve from one end of the second sleeve.

11. A conversion core component according to claim 1, characterized in that: The first optical fiber is a solid-core single-mode optical fiber, and the second optical fiber is a hollow-core optical fiber.

12. A dual-lens mode field conversion device, characterized in that: It includes a conversion core component according to any one of claims 1-7.

13. A dual-lens mode field conversion device according to claim 12, characterized in that: It further includes a housing. The housing is arranged outside the conversion core component and includes a first housing body and a second housing body. The docking ends of the first housing body and the second housing body are fixedly connected. The first fixing sleeve fixes the first optical fiber at the end of the first housing body, and the second fixing sleeve fixes the second optical fiber at the end of the second housing body.

14. A dual-lens mode field conversion device according to claim 13, characterized in that: It further includes a flange. An adjustable gap is formed between one end of the flange and the end of the first sleeve. The adjustable gap is used to accommodate the bonding layer. The flange has a lumen along the central axis, and one end of the flange is correspondingly connected to the end of the first sleeve.

15. A dual-lens mode field conversion device according to claim 14, characterized in that: The lumen of the flange includes a cavity Ⅳ and a cavity Ⅴ that are in communication with each other. The cavity Ⅳ and the cavity Ⅴ are coaxially arranged. The cross-sectional diameter of the cavity Ⅳ is larger than the cross-sectional diameter of the cavity Ⅴ. Both ends of the first pin assembly are respectively located in the cavity Ⅳ and the first sleeve and are fixed. The cavity Ⅴ is used for passing through the first optical fiber.

16. A dual-lens mode field conversion device according to claim 14, characterized in that: On the outer cylindrical surface near the first end of the flange, there is an annular protrusion. The head part of the annular protrusion near the first end side of the flange is inserted into the cavity Ⅰ of the calibration sleeve, and the annular protrusion abuts against one end of the calibration sleeve. On the outer wall of the flange near its second end, there is a groove for installing a retaining ring. The first end of the flange cooperates with the retaining platform in the lumen of the first housing body through the annular protrusion to limit the position of the flange relative to the first housing body in the first direction. The second end of the flange cooperates with the end of the first housing body and the retaining ring to limit the position of the flange relative to the first housing body in the second direction, where the first direction and the second direction are opposite directions.

17. A connector, characterized in that: Including the conversion core component according to any one of claims 1-11.

18. The connector according to claim 17, characterized in that: It further includes a housing and a flange. The housing is arranged outside the conversion core component. The housing includes a first housing body and a second housing body. The docking ends of the first housing body and the second housing body are fixedly connected. A stop platform I is formed on the inner wall of the cavity of the first housing body, and a stop platform II that cooperates with the stop platform I is formed on the end face of the flange.

19. The connector according to claim 18, wherein: The flange has an inner lumen along the central axis, and one end of the flange is correspondingly connected to the end of the first sleeve. The inner lumen of the flange includes a cavity IV and a cavity V that communicate with each other. The cavity IV and the cavity V are coaxially arranged. The head end of the first pin is located in the cavity IV, and the tail end of the first pin is located in the first sleeve and fixed. The cavity V is used to accommodate the tail end of the fixed connector pin.

20. The connector according to claim 18 or 19, characterized in that: It further includes an elastic member. The elastic member is arranged in the accommodation cavity of the housing. The first end of the elastic member can abut against the circumferential step on the outer periphery of the flange, and the second end of the elastic member abuts against the stop platform in the second housing body.

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