CN118192013A - Conversion core piece, double-lens mode field conversion device and manufacturing method thereof - Google Patents

Abstract

The invention discloses a conversion core piece, a double-lens mode field conversion device and a manufacturing method thereof, wherein the conversion core piece comprises a solid optical fiber component, a hollow optical fiber component and a calibration sleeve, the solid optical fiber component comprises a solid end lens and a solid single-mode optical fiber with a first mode field diameter, the solid end lens is positioned at the tail end part of the solid optical fiber component, the hollow optical fiber component comprises a hollow end lens and a hollow optical fiber with a second mode field diameter, the calibration sleeve is axially provided with a hollow cavity I, the solid optical fiber component and the hollow optical fiber component extend into the calibration sleeve from two ports of the cavity I respectively, and the solid end lens and the hollow end lens are oppositely arranged. The device realizes the conversion of different mode field diameters between the single-mode fiber and the hollow fiber through the two lenses, thereby realizing the reliable and stable connection between the single-mode fiber and the hollow fiber.

Description

Conversion core piece, double-lens mode field conversion device and manufacturing method thereof

Technical Field

The invention belongs to the technical field of optical signal transmission, and particularly relates to a conversion core piece, a double-lens mode field conversion device and a manufacturing method thereof.

Background

The hollow anti-resonance optical fiber (hereinafter simply referred to as hollow optical fiber) realizes hollow light guide through an anti-resonance reflection optical waveguide mechanism, has the advantages of low delay, low dispersion, low nonlinearity, high damage threshold, broadband light guide, low thermal sensitivity, radiation resistance and the like, has application prospect in the fields of optical communication, high-power laser transmission, ultrafast optics, nonlinear optics, optical fiber sensing and the like, and is very suitable for severe environments such as aerospace radiation and the like.

In order to improve the compatibility between the hollow optical fiber and the traditional optical fiber device system or between the optical fiber and the optical waveguide, the realization of the connection with low insertion loss, high return loss and high stability among different optical fibers is a core problem to be solved. However, there are often large differences in structure and mode field between the two, and it is difficult to achieve efficient and reliable coupling. The optical fiber mode field conversion device can change the mode field characteristic of transmitted light, thereby breaking through the coupling bottleneck of hollow optical fiber and traditional single mode optical fiber, realizing the high-efficiency integration of optical fiber photon devices and bringing more possibility for the development and application of the optical fiber photon devices. The optical fiber mode field conversion device is required to be developed in order to meet the large-scale application requirements of future hollow optical fibers in the fields of high-speed high-capacity optical communication, high-power laser transmission, optical fiber sensing, special scene optical transmission and the like.

The development of a hollow fiber mode field diameter conversion device realizes the high-efficiency connection between a hollow fiber and a traditional solid single-mode fiber widely used in the existing optical transmission system, and mainly has the technical bottleneck problems of the following three aspects. In the first aspect, the mode field diameter of the conventional solid-core single-mode fiber is about 9.2 μm at the transmission wavelength of 1310nm, and the mode field diameter of the hollow-core fiber is generally 20-40 μm, so that the mode field sizes of the conventional solid-core single-mode fiber and the hollow-core single-mode fiber are seriously mismatched, which can result in high coupling loss. In addition, mode field mismatch at the coupling interface of the two can excite higher order modes in the hollow fiber, affecting the quality of the transmitted beam. Matching the mode field characteristics of two fibers is therefore one of the key technical bottlenecks that need to be resolved. In the second aspect, the air-glass interface existing at the optical fiber coupling interface also generates stronger fresnel reflection, so as to increase the insertion loss and bring back reflection, so that the improvement of return loss is a second technical bottleneck problem to be solved. In the third aspect, for hollow-core optical fibers with microstructures inside, since the optical fibers themselves rely on the microstructures inside to achieve low-loss optical transmission, ensuring the integrity of the microstructures inside the optical fibers during coupling is also a key technical bottleneck problem to be solved.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provide a conversion core piece, a double-lens mode field conversion device and a manufacturing method thereof.

To achieve the above object, one of the objects of the present invention is to provide a conversion core member including a solid optical fiber member including a solid end lens and a solid single-mode optical fiber having a first mode field diameter, the solid end lens being located at a distal end portion of the solid optical fiber member, a hollow optical fiber member including a hollow end lens and a hollow optical fiber having a second mode field diameter, and a calibration sleeve; the calibration sleeve is provided with a hollow cavity I along the axial direction of the calibration sleeve, the solid optical fiber component and the hollow optical fiber component respectively extend into the calibration sleeve from two ports of the cavity I of the calibration sleeve, and the solid end lens and the hollow end lens are oppositely arranged.

As a preferred scheme, the solid optical fiber component further comprises a solid end sleeve, the solid end sleeve is provided with a cavity II with two open ends along the axial direction of the solid end sleeve, the solid single-mode optical fiber stretches into the cavity II from one port of the cavity II of the solid end sleeve, and the solid end lens is arranged at the other port of the cavity II of the solid end sleeve and stretches out; the hollow fiber component further comprises a hollow end sleeve, the hollow end sleeve is provided with a cavity III with two open ends along the axial direction of the hollow end sleeve, the hollow fiber extends in from one port of the cavity III of the hollow end sleeve, and the hollow end lens is arranged at the other port of the cavity III of the hollow end sleeve and extends outwards.

As a preferred scheme, the solid end lens and the hollow end lens adopt C lenses, the C lenses are provided with two ends, one end of each C lens is a convex spherical surface, the other end of each C lens is a plane, the solid end lens comprises a first spherical surface end and a first plane end, the first spherical surface end is arranged towards a solid single-mode optical fiber, the hollow end lens comprises a second spherical surface end and a second plane end, the second spherical surface end is arranged towards the hollow optical fiber, and the first plane end and the second plane end are correspondingly arranged.

As a preferable scheme, the first plane end of the solid end lens extends out of the solid end sleeve, the first plane end is a chamfer, and the first plane end is not perpendicular to the axis of the solid end lens; the second plane end of the hollow end lens extends out of the hollow end sleeve, the second plane end is a chamfer surface, and the second plane end is not perpendicular to the axis of the hollow end lens; the first plane end is opposite to the second plane end and is arranged in parallel.

As a preferred scheme, the first end of the solid single-mode optical fiber is a solid bare optical fiber section without a coating layer, the solid bare optical fiber section of the solid single-mode optical fiber is arranged in a hollow pipe cavity of a solid end contact pin to form a solid contact pin assembly, and the solid contact pin assembly is inserted into and fixed in a solid end sleeve from one end of the solid end sleeve; the first end of the hollow optical fiber is a hollow bare optical fiber section without a coating layer, the hollow bare optical fiber section is arranged in a hollow pipe cavity of a hollow end contact pin to form a hollow contact pin assembly, and the hollow contact pin assembly is inserted into and fixed in a hollow end sleeve by one end of the hollow end sleeve.

As a preferable scheme, one end of the solid pin component, which faces the solid end lens, is provided with a chamfer, and the chamfer of the solid pin component is not perpendicular to the axis of the solid pin component.

As a preferable scheme, the chamfer surface of the solid contact pin assembly and the first spherical end of the solid end lens are plated with anti-reflection films.

It is a second object of the present invention to provide a dual-lens mode field switching device comprising a switching core member as described in any of the above.

As the preferred scheme, still include the shell, the shell sets up outside the conversion core piece, including hollow end shell body and solid end shell body, the butt joint end of solid end shell body and hollow end shell body is fixed to link to each other, and solid end fixed cover is fixed solid single mode fiber at the tip of solid end shell body, and hollow end fixed cover is fixed hollow fiber at the tip of hollow end shell body.

As the preferable scheme, still include the ring flange, form adjustable clearance between ring flange's one end and the sheathed tube tip of solid end, adjustable clearance is used for holding the tie coat, and the ring flange has inner tube along central axial, and the one end of ring flange corresponds with the sheathed tube tip of solid end and be connected.

As a preferred scheme, the inner cavity of the flange plate comprises a cavity IV and a cavity V which are communicated with each other, the cavity IV and the cavity V are coaxially arranged, the cross section diameter of the cavity IV is larger than that of the cavity V, two ends of the solid-core contact pin assembly are respectively positioned in the cavity IV and the solid-core end sleeve and fixed, and the cavity V is used for penetrating a solid-core single-mode fiber.

As a preferable scheme, an annular bulge is arranged on an outer cylindrical surface close to the first end of the flange, a column head part of the annular bulge close to the first end side of the flange is inserted into a cavity I of the calibration sleeve, and the annular bulge is abutted with one end of the calibration sleeve; the flange is provided with a groove for installing a retainer ring on the outer wall of the flange, which is close to the second end of the flange, the first end of the flange is matched with a baffle table in the pipe cavity of the solid end outer shell through an annular bulge, the position of the flange along the first direction relative to the solid end outer shell is limited, the second end of the flange is matched with the retainer ring through the end of the solid end outer shell, the position of the flange along the second direction relative to the solid end outer shell is limited, and the first direction and the second direction are opposite.

The third object of the present invention is to provide a method for manufacturing a dual-lens mode field conversion device, comprising the following steps:

Assembling a solid end lens and a solid end sleeve to form a solid end lens component, assembling a solid single-mode optical fiber and a solid end contact pin to form a solid contact pin component, and extending the solid contact pin component into a cavity II of the solid end sleeve from one end opposite to the solid end lens to obtain a solid optical fiber component;

Assembling a hollow end lens and a hollow end sleeve to form a hollow end lens component, assembling a hollow optical fiber and a hollow end contact pin to form a hollow contact pin component, and extending the hollow contact pin component into a cavity III of the hollow end sleeve from one end of the opposite hollow end lens to obtain a hollow optical fiber component;

inserting the solid optical fiber component and the hollow optical fiber component into the calibration sleeve from two ends of the calibration sleeve respectively and fixing the two ends of the calibration sleeve so as to obtain a conversion core piece;

Arranging the solid end of the conversion core piece in the solid end shell, penetrating the hollow end of the conversion core piece into the hollow end shell, and connecting the solid end shell with the opposite end of the hollow end shell;

and fourthly, fixing the solid fiber outer sheath layer of the solid single-mode fiber on the solid end outer shell through a solid end fixing sleeve, and fixing the hollow fiber outer sheath layer of the hollow fiber on the hollow end outer shell through a hollow end fixing sleeve.

In the first step, the method for manufacturing the solid pin assembly includes the following steps: after the coating layer is removed from the tail end of the solid single-mode fiber, the solid single-mode fiber end with the coating layer removed is inserted into the hollow cavity from the first end of the solid end contact pin and fixed, and the first end of the solid end contact pin is inserted into the inner cavity of the flange plate and fixed.

In the fourth step, after the solid end outer shell and the hollow end outer shell are connected together, the retainer ring is arranged in the groove of the flange plate, so that the outer shell is limited along the axial direction relative to the conversion core piece.

Compared with the prior art, the invention has at least the following beneficial effects:

Firstly, the invention designs the hollow fiber according to the characteristics of the hollow fiber and the requirements of low insertion loss and high return loss by improving the structure. Two different C lenses are adopted to realize the conversion of different mode field diameters between the single-mode fiber and the hollow fiber, thereby realizing the reliable and stable connection between the single-mode fiber and the hollow fiber. In this scheme, solid terminal lens and solid single mode fiber pass through solid terminal sleeve group combination solid fiber component, and hollow terminal lens and hollow optic fibre pass through hollow terminal sleeve group and become hollow fiber component, in the installation adjustment process, through introducing hollow fiber component and solid fiber component into the calibration sleeve to be used for the alignment between solid hollow fiber component and the solid fiber component. The lenses respectively arranged on the solid optical fiber component and the hollow optical fiber component can realize the conversion of different mode field diameters between the single-mode optical fiber and the hollow optical fiber, thereby realizing the reliable and stable connection between the single-mode optical fiber and the hollow optical fiber. The two lenses are arranged oppositely, the flat end surfaces of the two lenses are provided with inclined surfaces forming a certain included angle with the respective axial directions, and the inclined surfaces are plated with anti-reflection films at the same time so as to reduce the influence of Fresnel effect.

Secondly, the scheme optimizes the manufacturing process of the conversion device, and by combining the specific structure of the double-lens mode field conversion device, each step procedure of the manufacturing process is thinned, a solid end sleeve and a solid end lens form a solid end lens component, a solid single-mode fiber and a solid contact pin form a solid contact pin component, and then the solid end lens component and the solid contact pin component form a solid fiber component through debugging and installation; the hollow end sleeve and the hollow end lens form a hollow end lens component, the hollow optical fiber and the hollow contact pin form a hollow contact pin assembly, and then the hollow end lens component and the hollow contact pin assembly are assembled to form a hollow optical fiber component through debugging, so that when final adjustment is performed, only the axial distance and the radial offset value of the hollow optical fiber component and the solid optical fiber component in the calibration sleeve are required to be debugged, the debugging and installation difficulty in the manufacturing process is reduced to a certain extent by the stepped adjustment mode, and the optical fiber coupling effect is improved.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained from these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a diagram showing the external appearance of a dual-lens mode field switching device according to the present invention;

FIG. 2 is a cross-sectional view of a dual-lens mode field switching device of the present invention;

FIG. 3 is a cross-sectional view of a conversion core of the present invention;

FIG. 4 is a block diagram of a solid end lens member of the invention;

FIG. 5 is a block diagram of a solid pin component of the present invention;

FIG. 6 is a block diagram of a solid core optical fiber component of the present invention;

FIG. 7 is a block diagram of one embodiment of a flange in accordance with the present invention;

FIG. 8 is a schematic view of the interface between the flange and the alignment sleeve according to the present invention;

FIG. 9 is a schematic view of the connection of annular raised and recessed portions of the flange of the present invention;

FIG. 10 is a block diagram of a hollow end lens member of the invention;

FIG. 11 is a block diagram of a hollow pin member of the present invention;

FIG. 12 is a block diagram of a hollow core optical fiber component of the present invention;

FIG. 13 is a block diagram of an embodiment of the present invention;

fig. 14 is a simulation diagram in an embodiment of the present invention: solid single-mode optical fiber I-hollow fiber;

fig. 15 is a simulation diagram in an embodiment of the present invention: hollow fiber-solid single mode fiber II;

The marks in the figure: 1. solid fiber component, 11, solid single mode fiber, 111, solid single mode fiber I, 112, solid single mode fiber II, 113, solid bare fiber segment, 114, solid fiber outer jacket layer, 115, solid fiber coating layer, 116, solid fiber reinforcing element, 117, solid fiber inner jacket layer, 12, solid end lens, 121, solid end lens I, 122, solid end lens II, 1201, first spherical end, 1202, first planar end, 13, solid end sleeve, 131, cavity II, 14, solid end pin, 141, chamfer, 15, flange, 151, annular protrusion, 152, groove, 153, inner lumen, 154, cavity IV, 155, cavity V, 156, post head portion, 16, adjustable gap, 2, hollow fiber component, 21, hollow fiber, 211, hollow fiber bare fiber section, 212, hollow fiber outer jacket layer, 213, hollow fiber coating layer, 214, hollow fiber reinforcing element, 22, hollow end lens, 221, hollow end lens i, 222, hollow end lens ii, 2201, second spherical end, 2202, second planar end, 23, hollow end sleeve, 231, cavity iii, 24, hollow end pin, 3, alignment sleeve, 31, cavity i, 4, solid end outer shell, 41, baffle, 5, hollow end outer shell, 6, solid end fixing sleeve, 7, hollow end fixing sleeve, 8, retainer ring, 9, conversion core, 100, solid pin assembly, 200, hollow pin assembly, a, bond, B, crimp or bond, D, central axis.

Detailed Description

The invention is described in detail below by way of exemplary embodiments. It is to be understood that elements, structures and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

It should be noted that: unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. As used in the specification and claims of this application, the terms "a," "an," and "the" and similar referents are not to be construed to limit the scope of at least one. The word "comprising" or "comprises", and the like, indicates that elements or items listed thereafter or equivalents thereof may be substituted for elements or items thereof in addition to those listed thereafter or equivalents thereof without departing from the scope of the word "comprising" or "comprising".

As shown in the drawing, an exemplary embodiment of the present invention provides a conversion core member, which includes a calibration sleeve 3, the calibration sleeve 3 has a cylindrical structure, and the calibration sleeve 3 has a cavity i 31 with two ends penetrating in an axial direction, and the solid fiber member 1 and the hollow fiber member 2 are respectively extended relatively from two openings of the cavity i 31 of the calibration sleeve 3, wherein the solid fiber member 1 includes a solid single-mode fiber 11 and a solid end lens 12, the solid single-mode fiber 11 has a first mode field diameter, the hollow fiber member 2 includes a hollow fiber 21 and a hollow end lens 22, the hollow fiber 21 has a second mode field diameter, the solid fiber member 1 and the hollow fiber member 2 are respectively extended from two openings of the cavity of the calibration sleeve 3, and the solid end lens 12 and the hollow end lens 22 are oppositely disposed, so that conversion of different mode field diameters between the solid single-mode fiber 11 and the hollow fiber 21 is achieved by using two lenses, thereby achieving reliable and stable connection between the solid single-mode fiber 11 and the hollow fiber 21.

The mode field matching of the two optical fibers is realized through the double-lens structure, wherein the solid end lens 12 close to the small-mode field solid single-mode optical fiber 11 is used for expanding and collimating light emitted by the small-mode field solid single-mode optical fiber 11, and the hollow end lens 22 close to the large-mode field hollow-core optical fiber 21 is used for focusing the collimated light to the spot mode field size close to the large-mode field hollow-core optical fiber 21. Or in this embodiment, the hollow end lens 22 near the large-mode-field hollow-core optical fiber 21 is used to expand and collimate the light emitted by the large-mode-field hollow-core optical fiber 21, and the solid end lens 12 near the small-mode-field solid-core single-mode optical fiber 11 is used to focus the collimated light to a spot mode field size close to that of the small-mode-field solid-core single-mode optical fiber 21.

In this scheme, in order to be convenient for consolidate the terminal of optic fibre and make things convenient for a series of debugging processes of follow-up, be provided with the contact pin structure respectively with the terminal of solid single mode fiber 11 and hollow optic fibre 21, concrete implementation is as follows: the solid core single mode fiber 11 with the first end of the solid core single mode fiber 11 removed and the solid core bare fiber segment 113 of the solid core single mode fiber 11 with the solid core single mode fiber coating 115 removed comprises a fiber core and a cladding, the solid core bare fiber segment 113 is arranged in a hollow pipe cavity of the solid core end pin 14 to form the solid core pin assembly 100, an axis of the solid core pin assembly 100 refers to a central axis D of the solid core pin assembly along an axial direction, and an inclined plane 141 which is not perpendicular to the central axis D of the solid core pin assembly 100 is formed at an end of the solid core pin assembly 100. The hollow core pin assembly 200 is formed by removing the hollow core fiber coating layer 213 outside the fiber cladding from the first end of the hollow core optical fiber 21, and disposing the hollow core bare fiber segment 211 from which the hollow core fiber coating layer 213 is removed in the capillary hollow cavity of the hollow core end pin 24.

In order to further realize connection between the optical fiber and the lens and facilitate a series of debugging in a subsequent process, the solid optical fiber component 1 is further provided with a solid end sleeve 13, wherein the solid end sleeve 13 is of a hollow cylindrical structure and is provided with a cavity I31 with two through ends, wherein a solid pin component 100 extends into a first end of a cavity of the solid end sleeve 13, the solid end lens 12 is arranged at a second end of the cavity of the solid end sleeve 13, the solid pin component 100 is arranged near a focal plane position of the solid end lens 13, the axial distance between the solid pin component 100 and the solid end lens 13 is finely adjusted near the focal plane position, when output light of the solid end lens 13 is collimated, the positions of the solid pin component 100 and the solid end lens 12 in the solid end sleeve 13 are fixed through viscose, and the collimated light spot size at the moment is recorded, so that the solid optical fiber component 1 is obtained. On the other hand, the hollow fiber component 2 is further provided with a hollow end sleeve 23, wherein the hollow end sleeve 23 has a cylindrical structure, a through cavity iii 231 is formed along the axis, the hollow pin component 200 extends into the first end of the cavity of the hollow end sleeve 23, the hollow end lens 22 is arranged at the second end of the cavity of the hollow end sleeve 23, the axial distance between the hollow pin component 200 and the hollow end lens 22 is adjusted according to the theoretical design value, and the position of the hollow pin component 200 when the output collimation light spot is closest to the solid side collimation light spot is found by adjusting the axial distance between the hollow pin component 200 and the hollow end lens 22 and the lateral offset distance in the hollow end sleeve 23, so that the coupling optimal state is obtained. The hollow fiber end pin member 200 and the hollow end lens 22 are fixed, thereby obtaining the hollow fiber member 2.

In a preferred embodiment of the present disclosure, the solid end lens 12 is a C lens, two ends of the C lens are a spherical surface and a planar surface, the solid end lens 12 includes a first spherical end 1201 and a first planar end 1202, the first spherical end 1201 is disposed towards the solid single-mode optical fiber 11, the first planar end 1202 of the solid end lens 12 extends out of the solid end sleeve 13, and the first planar end 1202 is a chamfer, and an angle between the first planar end 1202 and the axial direction of the solid end lens 12 is 8 °; the hollow end lens 22 adopts a C lens, the hollow end lens 22 includes a second spherical end 2201 and a second planar end 2202, the second spherical end 2202 is disposed towards the hollow optical fiber 21, the first planar end 1202 and the second planar end 2202 are disposed correspondingly, and a radius of curvature of the first spherical end 1201 is smaller than a radius of curvature of the second spherical end 2201. The second plane end 2202 of the hollow end lens 22 extends outwards from the hollow end sleeve 23, the second plane end 2202 is a chamfer, and an included angle of 8 degrees is formed between the second plane end 2202 and the axial direction of the hollow end lens 22; the first planar end 1202 is opposite and parallel to the second planar end 2202. In this scheme, first plane end 1202 and second plane end 2202 are the setting of the chamfer of 8 contained angles, and main effect lies in: the fresnel effect present there is eliminated, the final objective being to boost the return loss. Specifically, according to different return loss standards, the scheme can process inclined planes with different inclination angles of 1-14 degrees, and simultaneously plating an anti-reflection film, so that the transmittance is higher than 99.9%.

Since fresnel reflection occurs when light is incident on the interface between two media with different refractive indexes, the fresnel reflection is suppressed by plating anti-reflection films on the end faces of the small-mode field solid-core single-mode fiber 11 and the solid-core end lens 12. The principle of designing the anti-reflection film is that the two reflected light beams on the upper surface and the lower surface of the film are subjected to destructive interference. Therefore, the optical path difference of the two reflected lights should be an odd multiple of half wavelength, the optical thickness of the film layer [ the product of the actual thickness and the refractive index of the material ] should be an odd multiple of a quarter wavelength, the fresnel reflection occurs at each material interface, and each time the reflected light reaches the other interface, a part of the reflected light undergoes additional fresnel reflection.

Another embodiment of the present invention further provides a dual-lens mode field conversion device, which includes the conversion core 9 in the above embodiment and a housing disposed outside the conversion core 9, where the housing is used to protect the conversion core from external contamination, and provide a certain mechanical strength protection for the internal connection structure, so as to avoid mechanical damage to the internal conversion core 9. The outer housing comprises a solid end outer housing 4 and a hollow end outer housing 5 which are in threaded connection, as shown in fig. 2, wherein a solid end fixing sleeve 6 fixes a solid optical fiber outer sheath layer 114 of a solid single-mode optical fiber 11 at the end of the solid end outer housing 4 in a crimping or bonding mode, and a hollow end fixing sleeve 7 fixes a hollow optical fiber outer sheath layer 212 of a hollow optical fiber 21 at the end of the hollow end outer housing 5 in a crimping or bonding mode.

In an exemplary embodiment of the present invention, the solid end fixing sleeve 6 and the hollow end fixing sleeve 7 are in an annular sleeve structure, and include a large diameter end and a small diameter end, where the large diameter end of the solid end fixing sleeve 6 is connected to the crimp joint at the end of the solid end housing 4, the small diameter end of the solid end fixing sleeve 6 is connected to the solid fiber outer jacket 114, the large diameter end of the hollow end fixing sleeve 7 is connected to the crimp joint at the end of the hollow end housing 5, the small diameter end of the hollow end fixing sleeve 7 is connected to the hollow fiber outer jacket 212, and it should be noted that the solid end fixing sleeve 6 and the hollow end fixing sleeve 7 may be made of an elastic material, and the optical fibers at both ends are fastened and crimped to the solid end fixing sleeve 6 and the hollow end fixing sleeve 7 by the shrinkage force of the elastic material, or may be made of an adhesive, specifically, by bonding the outer skins of the optical fibers at both ends to the outer jacket 212, and bonding the solid end fixing sleeve 6 and the hollow end housing 5 to the large diameter end fixing sleeve 4 by the large diameter end of the solid end housing 4.

In this embodiment, in order to realize better fixed effect, all be provided with at least one annular groove on the crimping head outer cylinder of solid end shell body 4 and hollow end shell body 5, preferably, the annular groove of this scheme sets up to two along the axial of crimping head, so design, the mode that adopts shrink crimping when solid end fixed cover 6 and hollow end fixed cover 7, then can fasten the position at annular groove after fixed cover deformation tightens up, the annular groove can increase the relative frictional force of fixed cover and crimping head, play the effect of strengthening joint strength and promotion junction sealing effect, if solid end fixed cover 6 and hollow end fixed cover 7 adopt the sticky mode to fix, then annular groove is used for holding glue, thereby play the effect of increase bonding firmness and promotion junction sealing effect.

In this scheme, still include ring flange 15 and retaining ring 8, be used for realizing the fixed connection of shell and conversion core 9 through ring flange 15 and retaining ring 8, the concrete mode is as follows: the main structure of the flange 15 is a hollow cylinder structure, and annular protrusions 151 and grooves 152 are respectively arranged at positions, close to two end parts, of the flange 15, wherein one end of the flange 15 provided with the annular protrusions 151 is connected with the solid end sleeve 13, the central axis of the flange 15 is parallel or coincident with the central axis of the solid end sleeve 13, the flange 15 is provided with an inner tube 153 along the central axial direction, and one end of the flange 15 is bonded with the end part 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 for accommodating the adhesive layer, thereby realizing the interval adjustment in the installation process of the two components after the adhesive layer is solidified, by setting the adjustable gap 16, the purpose is for adjusting the axial interval between the solid core ferrule assembly 100 and the solid end lens 12, a column head portion 156 is formed between the annular protrusion 151 of the flange 15 and the adjacent end portion, a part of the end portion of the flange 15 is inserted into the cavity of the calibration sleeve 3 through the column head portion 156, during installation, the flange 15 and the solid ferrule assembly 100 are required to be fixed together through an adhesive in advance, the solid fiber assembly 1 is formed by being connected with the solid end sleeve 13, then the solid fiber assembly 1 is integrally inserted into the calibration sleeve 3, at this time, after the annular protrusion 151 is in abutting contact with one end of the calibration sleeve 3, the retainer ring 8 is buckled in a groove 152 of the other end of the flange 15, the solid fiber assembly 1 and the solid end housing 4 are limited by the annular protrusion 151 and the two sides of the groove 152, and the first end of the flange 15 and the solid end housing 4 are limited by the first end of the flange 15 and the solid end housing 4 and the second end housing 4 are blocked by the first end of the annular protrusion and the second end housing 4 and the second end of the second end housing 4, and the first end of the second end 15 and the second end of the second end housing 4 are opposite to the first end and the second end of the second end 4 and the opposite to the first end and the second end and the end of the end 15 and the second end 4 and the end opposite the position.

In this solution, the inner cavity 153 of the flange 15 includes a cavity iv 154 and a cavity v 155 that are mutually communicated and coaxially disposed, where the cross-sectional diameter of the cavity iv 154 is greater than the cross-sectional diameter of the cavity v 155, the cavity iv 154 is used to accommodate one end of the solid core pin assembly 100 and is fixed by bonding, and the cavity v 155 is used to pierce the solid core single mode fiber 11.

In this embodiment, the solid single-mode optical fiber 11 sequentially includes, from outside to inside, a solid fiber outer sheath layer 114, a solid fiber reinforcing element 116, a solid fiber inner protection layer 117, a solid fiber coating layer 115, and a solid fiber bare fiber segment 113, where the solid fiber bare fiber segment 113 includes a cladding layer and a fiber core portion. The hollow fiber 21 includes, in order from outside to inside, a hollow fiber outer sheath layer 212, a hollow fiber reinforcing member 214, a hollow fiber coating layer 213, and a hollow fiber bare fiber section 211.

In this embodiment, since the solid optical fiber component 1, the calibration sleeve 3 and the hollow optical fiber component 2 are fixed by bonding, and the solid end outer housing 4 and the hollow end outer housing 5 are fixedly connected by threads, the connection cooperation of the retainer ring 8 and the flange 15 can realize the fixation of the relative positions of the whole outer housing and the internal conversion core 9 in the axial direction.

The invention also provides another embodiment, a manufacturing method of the double-lens mode field conversion part, which comprises the following specific steps:

Step one, assembling the solid end lens 12 and the solid end sleeve 13 to form a solid end lens component, assembling the solid single-mode optical fiber 11 and the solid end pin 14 to form a solid pin component 100, extending the solid pin component 100 from one end opposite to the solid end lens 12 into a cavity ii 131 of the solid end sleeve 13, and performing debugging to obtain the solid optical fiber component 1.

In this embodiment, the solid pin assembly 100 is manufactured by removing a coating layer from a terminal end of a solid single-mode fiber 11 to form a solid fiber bare fiber segment 113, inserting the solid fiber bare fiber segment 113 with the coating layer removed into a hollow pipe cavity from a first end of a solid pin 14 and bonding and fixing the hollow pipe cavity, and inserting the first end of the solid pin 14 into a cavity iv 154 of a flange 15 and bonding and fixing the hollow pipe cavity.

The debugging process of the step is as follows: the light source is injected from one end of the solid single-mode fiber 11, coupled through the solid end lens 12 and transmitted to the beam quality analysis equipment for on-line monitoring. The specific process is as follows: the end face of the solid pin assembly 100 is placed at the focal plane position of the solid end lens 12, the axial distance between the solid pin assembly 100 and the solid end lens 12 is finely adjusted nearby, when output light is collimated, the positions of the solid pin assembly 100 and the solid end lens 12 in the solid end sleeve 13 are fixed, and the size of the collimated light spot at the moment is recorded.

Step two, assembling the hollow end lens 22 and the hollow end sleeve 23 to form a hollow end lens component, assembling the hollow optical fiber 21 and the hollow end pin 24 to form a hollow pin component 200, extending the hollow pin component 200 into the cavity of the hollow end sleeve 23 from one end opposite to the hollow end lens 22, and debugging to obtain the hollow optical fiber component 2;

In the step, the debugging process is as follows: the hollow optical fiber 2 is connected to a light source, coupled through a hollow end lens 22 and connected to beam quality analysis equipment for on-line monitoring. The specific process is as follows: the axial distance between the end face of the hollow pin assembly 200 and the hollow end lens 22 is adjusted according to the theoretical design value, and the position of the hollow pin assembly 200 when the output collimation light spot is closest to the collimation light spot on the other side is found out by adjusting the axial distance between the hollow pin assembly 200 and the hollow end lens 22 and the lateral offset (radial offset) distance of the hollow pin assembly 200 and the hollow end lens 22 in the hollow end sleeve 23, namely the coupling optimal state. The positions of the hollow pin member 200 and the hollow end lens 22 are fixed.

In this solution, in order to protect the internal microstructure of the hollow fiber 21, the microstructure in the hollow fiber 21 makes light capable of being transmitted in the hollow fiber 21 with low loss, so that the internal microstructure cannot be damaged, and the light transmission cannot be affected by the suction of glue. The conventional solid single-mode optical fiber 11 and the solid terminal pin 14 are fixed in the following manner, which is different from the solid terminal pin assembly:

Conventionally, the solid-core optical fiber bare fiber segment 113 penetrates into the solid-core end pin 14, and the solid-core single-mode optical fiber 11 needs to be fixed by glue injection and the end face of the solid-core pin assembly 100 needs to be ground. However, these processes in the conventional manner tend to damage the end face structure of the hollow fiber 21 and tend to cause the glue to be sucked into the capillary inside the hollow fiber 21.

In this scheme, during actual operation, firstly, the hollow fiber coating 213 near the end face of the hollow fiber 21 is partially removed to form a hollow fiber bare fiber segment 211, then the hollow fiber bare fiber segment 211 is inserted into the central cavity of the hollow end pin 24 to form the hollow pin assembly 200, and the end face of the hollow fiber bare fiber segment 211 is cut by using the optical fiber cutting knife. The hollow optical fiber 21 is pulled back into the cavity of the hollow end pin 24, the end face of the bare optical fiber segment 211 of the hollow optical fiber is slightly trapped inside the end face of the hollow end pin 24, and the end of the hollow optical fiber 21 is carefully fixed in the cavity of the hollow end pin 24 by glue. The purpose of this design can effectively avoid causing the destruction to the terminal surface of hollow optic fibre 21, has avoided glue to inhale in the capillary of hollow optic fibre 21 inside simultaneously.

Step three, inserting the solid optical fiber component 1 obtained in the step one and the hollow optical fiber component 2 obtained in the step two into the calibration sleeve 3 from two ends of the calibration sleeve 3 respectively, and fixing the solid optical fiber component 1 and the hollow optical fiber component 2 in the calibration sleeve 3 respectively after debugging to obtain a conversion core 9;

In this solution, the positions of the solid fiber part 1 and the hollow fiber part 2 are adjusted and fixed by using the calibration sleeve 3, so that the solid fiber part and the hollow fiber part form a whole. Note that the two opposite chamfer faces of the two lenses slightly protrude from the two sleeve end faces, so designed: the method is beneficial to the alignment of the inclination angles of the two inclined planes during debugging, thereby reducing the extra loss caused by the misalignment of the direction of the inclined planes.

And fourthly, arranging the solid end of the conversion core piece 9 in the solid end outer shell 4, penetrating the hollow end of the conversion core piece 9 into the hollow end outer shell 5, and screwing the threaded ends of the solid end outer shell 4 and the hollow end outer shell 5 together.

In this scheme, after the screw thread end of solid end shell body 4 and hollow end shell body 5 are screwed together, through setting up retaining ring 8 in the recess 152 of ring flange 15 to carry out spacingly with the shell relative conversion core piece 9 along axial direction.

Step five, the solid fiber outer sheath layer 114 of the solid single-mode fiber 1 is fixed on the solid end outer shell 4 through the solid end fixing sleeve 6, and the hollow fiber outer sheath layer 212 of the hollow fiber 2 is fixed on the hollow end outer shell 5 through the hollow end fixing sleeve 7.

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

The following description is made with reference to specific embodiments:

Fig. 13-15 show a specific embodiment of a two-lens structure designed to realize a low insertion loss, high return loss optical transmission link from the solid single-mode optical fiber i 111 to the hollow core optical fiber 21 to the solid single-mode optical fiber ii 112. The mode field diameters of the solid core single mode fibers I, II 111, 112 and the hollow core fiber 21 are 9.2 μm and 20 μm (at 1310nm transmission wavelength), respectively. The scheme includes two sections of light paths, wherein the solid single-mode optical fiber I111-hollow optical fiber 21 and the hollow optical fiber 21-solid single-mode optical fiber II 112 both adopt the double-lens mode field conversion piece with the structure, the data of the double-lens coupling system designed in the embodiment are shown in the following table, and the basic parameters of the solid end lenses I, II 121 and 122 are as follows: material N-SF11, radius of curvature 1.15mm, length 2.35mm; the basic parameters of the hollow end lenses I, II 221 and 222 are as follows: the transmittance of the material N-SF11, the curvature radius is 2.52mm, the length is 2.5mm, and the antireflection film at the chamfer in the embodiment is higher than 99.9%. As shown in table 1, the distance from the solid single-mode optical fiber i 111 to the solid end lens i 121 is L1; the distance from the solid end lens I121 to the hollow end lens I221 is L2; the distance from the hollow end lens I221 to the first end of the hollow optical fiber 21 is L3, and the distance from the second end of the hollow optical fiber 21 to the hollow end lens II 222 is L4; the distance between the hollow end lens II 222 and the solid end lens II 122 is L5, and the distance between the solid end lens II 122 and the solid single-mode optical fiber II 112 is L6.

TABLE 1 axial distance data sheet between elements

TABLE 2 lateral offset data table between elements

The lateral offset distance values (radial offset distance values) of the respective elements in table 2 are obtained with the position of the solid single-mode optical fiber 11 as the origin.

The theoretical simulation shows that in the embodiment, the inclined surfaces of the solid end lens I, the hollow end lens II and the solid end lens II all adopt an included angle of 8 degrees with the axial direction of each lens after the end face of the single-mode optical fiber is processed by inclined surface treatment,

In the scheme, the coupling loss from the solid single-mode fiber I111 to the hollow fiber 21 is less than or equal to 0.3dB, the coupling loss from the hollow fiber 21 to the solid single-mode fiber II 112 is less than or equal to 0.3dB, and the return loss is more than 45dB.

The solid single-mode optical fiber 1 is directly connected with the hollow optical fiber 2 by adopting a conventional welding mode in the prior art, and the difference is that: the optical fiber structure of the fusion mode does not comprise the double-lens mode field conversion device of the scheme, and the mode field diameter of the solid single-mode optical fiber 1 is 9.2 mu m (at 1310nm transmission wavelength); the mode field diameter of the hollow core fiber 2 is 20 μm (@ 1310nm transmission wavelength). The coupling loss of the optical fiber structure after the direct welding mode is higher than 2.4dB, and the return loss is about 15dB.

The present invention is not limited to the above-mentioned embodiments, but is intended to be limited to the following embodiments, and any modifications, equivalent changes and variations in the above-mentioned embodiments can be made by those skilled in the art without departing from the scope of the present invention.

Claims (15)

1. A conversion core, characterized by: the optical fiber comprises a solid optical fiber component, a hollow optical fiber component and a calibration sleeve, wherein the solid optical fiber component comprises a solid end lens and a solid single-mode optical fiber with a first mode field diameter, the solid end lens is positioned at the tail end part of the solid optical fiber component, the hollow optical fiber component comprises a hollow end lens and a hollow optical fiber with a second mode field diameter, and the hollow end lens is positioned at the tail end part of the hollow optical fiber component; the calibration sleeve is provided with a hollow cavity I along the axial direction of the calibration sleeve, the solid optical fiber component and the hollow optical fiber component respectively extend into the calibration sleeve from two ports of the cavity I of the calibration sleeve, and the solid end lens and the hollow end lens are oppositely arranged.

2. The conversion core according to claim 1, characterized in that: the solid fiber component further comprises a solid end sleeve, the solid end sleeve is provided with a cavity II with two open ends along the axial direction of the solid end sleeve, the solid single-mode fiber stretches into the cavity II from one port of the solid end sleeve, and the solid end lens is arranged at the other port of the cavity II of the solid end sleeve and stretches out;

The hollow fiber component further comprises a hollow end sleeve, the hollow end sleeve is provided with a cavity III with two open ends along the axial direction of the hollow end sleeve, the hollow fiber extends in from one port of the cavity III of the hollow end sleeve, and the hollow end lens is arranged at the other port of the cavity III of the hollow end sleeve and extends outwards.

3. A conversion core according to claim 1 or 2, characterized in that: the solid end lens and the hollow end lens adopt C lenses, the C lenses are provided with two ends, one end of each C lens is a convex spherical surface, the other end of each C lens is a plane, the solid end lens comprises a first spherical surface end and a first plane end, the first spherical surface end is arranged towards a solid single-mode optical fiber, the hollow end lens comprises a second spherical surface end and a second plane end, the second spherical surface end is arranged towards the hollow optical fiber, and the first plane end and the second plane end are correspondingly arranged.

4. A conversion core according to claim 3, characterized in that:

the first plane end of the solid end lens extends out of the solid end sleeve, the first plane end is a chamfer surface, and the first plane end is not perpendicular to the axis of the solid end lens;

the second plane end of the hollow end lens extends out of the hollow end sleeve, the second plane end is a chamfer surface, and the second plane end is not perpendicular to the axis of the hollow end lens;

The first plane end is opposite to the second plane end and is arranged in parallel.

5. A conversion core according to claim 2, characterized in that: the first end of the solid single-mode optical fiber is a solid bare optical fiber section without a coating layer, the solid bare optical fiber section of the solid single-mode optical fiber is arranged in a hollow pipe cavity of a solid end contact pin to form a solid contact pin assembly, and the solid contact pin assembly is inserted into and fixed in a solid end sleeve from one end of the solid end sleeve; the first end of the hollow optical fiber is a hollow bare optical fiber section without a coating layer, the hollow bare optical fiber section is arranged in a hollow pipe cavity of a hollow end contact pin to form a hollow contact pin assembly, and the hollow contact pin assembly is inserted into and fixed in a hollow end sleeve by one end of the hollow end sleeve.

6. A conversion core according to any one of claims 5, characterized in that: the solid contact pin assembly is provided with a chamfer surface at one end facing the solid end lens, and the chamfer surface of the solid contact pin assembly is not perpendicular to the axis of the solid contact pin assembly.

7. A conversion core according to claim 6, characterized in that: the chamfer of the solid pin assembly and the first spherical end of the solid end lens are plated with anti-reflection films.

8. A dual-lens mode field switching device, characterized by: a conversion core comprising the conversion core of any of claims 1-7.

9. The dual-lens mode field-switching device of claim 8, wherein: still include the shell, the shell sets up outside the conversion core piece, including hollow end shell body and solid end shell body, the butt joint end of solid end shell body and hollow end shell body is fixed to link to each other, and solid end fixed cover is fixed solid single mode fiber at the tip of solid end shell body, and hollow end fixed cover is fixed hollow fiber at the tip of hollow end shell body.

10. The dual-lens mode field-switching device of claim 9, wherein: the flange plate is provided with an inner tube cavity along the central axis, and one end of the flange plate is correspondingly connected with the end part of the solid end sleeve.

11. A conversion core according to claim 10, characterized in that: the inner tube cavity of ring flange includes cavity IV and cavity V of intercommunication each other, cavity IV and cavity V coaxial arrangement, cavity IV's cross section diameter is greater than cavity V cross section diameter, and the both ends of real core contact pin subassembly are located respectively cavity IV and real core end sleeve pipe are interior and fixed, cavity V is used for wearing to establish real core single mode fiber.

12. A conversion core according to claim 10, characterized in that: an annular bulge is arranged on the outer cylindrical surface close to the first end of the flange, a column head part of the annular bulge close to the first end side of the flange is inserted into a cavity I of the calibration sleeve, and the annular bulge is abutted with one end of the calibration sleeve; the flange is provided with a groove for installing a retainer ring on the outer wall of the flange, which is close to the second end of the flange, the first end of the flange is matched with a baffle table in the pipe cavity of the solid end outer shell through an annular bulge, the position of the flange along the first direction relative to the solid end outer shell is limited, the second end of the flange is matched with the retainer ring through the end of the solid end outer shell, the position of the flange along the second direction relative to the solid end outer shell is limited, and the first direction and the second direction are opposite.

13. A manufacturing method of a double-lens mode field conversion part is characterized by comprising the following steps of: the method comprises the following steps:

Assembling a solid end lens and a solid end sleeve to form a solid end lens component, assembling a solid single-mode optical fiber and a solid end contact pin to form a solid contact pin component, and extending the solid contact pin component into a cavity II of the solid end sleeve from one end opposite to the solid end lens to obtain a solid optical fiber component;

Assembling a hollow end lens and a hollow end sleeve to form a hollow end lens component, assembling a hollow optical fiber and a hollow end contact pin to form a hollow contact pin component, and extending the hollow contact pin component into a cavity III of the hollow end sleeve from one end of the opposite hollow end lens to obtain a hollow optical fiber component;

inserting the solid optical fiber component and the hollow optical fiber component into the calibration sleeve from two ends of the calibration sleeve respectively and fixing the two ends of the calibration sleeve so as to obtain a conversion core piece;

Arranging the solid end of the conversion core piece in the solid end shell, penetrating the hollow end of the conversion core piece into the hollow end shell, and connecting the solid end shell with the opposite end of the hollow end shell;

and fourthly, fixing the solid fiber outer sheath layer of the solid single-mode fiber on the solid end outer shell through a solid end fixing sleeve, and fixing the hollow fiber outer sheath layer of the hollow fiber on the hollow end outer shell through a hollow end fixing sleeve.

14. The method for manufacturing a dual-lens mode field converter according to claim 13, wherein: in the first step, the method for manufacturing the solid pin assembly comprises the following steps: after the coating layer is removed from the tail end of the solid single-mode fiber, the solid single-mode fiber end with the coating layer removed is inserted into the hollow cavity from the first end of the solid end contact pin and fixed, and the first end of the solid end contact pin is inserted into the inner cavity of the flange plate and fixed.

15. The method for manufacturing a dual-lens mode field converter according to claim 14, wherein: in the fourth step, after the solid end outer shell body and the hollow end outer shell body are connected together, the retainer ring is arranged in the groove of the flange plate, so that the outer shell is limited along the axial direction relative to the conversion core piece.