Hollow-core optical fiber and single-mode optical fiber coupling structure and coupling method thereof

Abstract

The invention relates to the technical field of optical communication, in particular to a hollow-core optical fiber and single-mode optical fiber coupling structure and a coupling method thereof.On one hand, a light converging part is arranged through corrosion, then the light converging part is inserted into a coupling pipe, operation is easy, accuracy is high, insertion core corrosion can be conducted in batches, production is facilitated, and through non-insertion type coupling, the coupling efficiency is improved; the coupling structure can be suitable for hollow-core optical fibers with various fiber core sizes, has lower connection loss and higher coupling efficiency, has higher flexibility and compatibility in the aspect of connection between the hollow-core optical fibers and other optical fibers, and is not easily influenced by external interference and environment; and on the other hand, by controlling the distance between the light converging part on the optical fiber coupling section and the joint of the coupling tube and the hollow-core optical fiber, the situation that reflected light enters the hollow-core optical fiber can be reduced, echo reflection is reduced, and therefore the transmission effect of optical signals is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a coupling structure of a hollow core optical fiber and a single mode optical fiber and a coupling method thereof. Background Art

[0002] Hollow-core fiber is a specially designed optical fiber with an air core. It has advantages such as low latency, low dispersion, low nonlinearity, high damage threshold, low thermal sensitivity, and radiation resistance, which can achieve more efficient and stable optical communication and transmission systems. In order to promote the application of hollow-core fiber, it is urgent to solve the coupling problem between hollow-core fiber and single-mode fiber.

[0003] In the coupling technology of hollow-core optical fiber and single-mode optical fiber, the coupling structure will affect the transmission efficiency of optical signals. The coupling methods currently proposed include fusion splicing, insertion coupling, angle-splitting fusion splicing, and gluing. The mode field diameter mismatch and large echo reflection in the existing coupling scheme cause the reflected light to enter the hollow-core optical fiber, affecting the transmission effect of the optical signal. At the same time, the existing scheme also has the problem of low coupling efficiency.

[0004] In view of this, overcoming the defects of the prior art is an urgent problem to be solved in the field of this technology. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to improve the transmission effect and coupling efficiency of optical signals during the coupling process of hollow core optical fiber and single mode optical fiber.

[0006] The present invention adopts the following technical solution:

[0007] In a first aspect, a coupling structure of a hollow-core optical fiber 4 and a single-mode optical fiber 3 is provided, comprising a coupling tube 1 and an optical fiber coupling segment 2, wherein the optical fiber coupling segment 2 is arranged in the coupling tube 1; one end of the coupling tube 1 is coupled to the single-mode optical fiber 3, and the other end of the coupling tube 1 is coupled to the hollow-core optical fiber 4;

[0008] A light collecting portion 20 is provided at one end of the optical fiber coupling section 2, and the other end of the optical fiber coupling section 2 is connected to the single-mode optical fiber 3. The light collecting portion 20 is coupled to the core of the hollow-core optical fiber 4 and is spaced from the end face of the hollow-core optical fiber 4 by a preset distance;

[0009] By adjusting the preset distance between the light collecting portion 20 and the hollow-core optical fiber 4 , the reflected light entering the hollow-core optical fiber 4 can be reduced.

[0010] Preferably, the light collecting portion 20 is spherical or ellipsoidal in shape.

[0011] Preferably, when the light collecting portion 20 is in an ellipsoidal shape, the major axis of the light collecting portion 20 is perpendicular to the center line of the core of the hollow-core optical fiber 4 .

[0012] Preferably, the optical fiber coupling section 2 further includes a tapered waist 21, one end of the tapered waist 21 is connected to the single-mode optical fiber 3, and the other end of the tapered waist 21 is connected to the light converging portion 20;

[0013] An adhesive is provided between the tapered waist 21 and the inner tube wall of the coupling tube 1 to fix the optical fiber coupling section 2 and the coupling tube 1 .

[0014] Preferably, the numerical aperture of the single-mode optical fiber 3 is 0.12-0.17; the numerical aperture of the hollow-core optical fiber 4 is 0.03-0.22.

[0015] Preferably, the diameter of the core of the hollow-core optical fiber 4 is 20 μm to 200 μm.

[0016] In a second aspect, a coupling method of a hollow core optical fiber 4 and a single mode optical fiber 3 is provided, wherein the coupling method is applicable to the coupling structure of the hollow core optical fiber 4 and the single mode optical fiber 3 as described in the first aspect, and comprises:

[0017] Processing one end of the optical fiber coupling section 2 to obtain the light collecting portion 20;

[0018] The optical fiber coupling section 2 is arranged in the coupling tube 1, so that the light collecting portion 20 is spaced a preset distance from one end of the coupling tube 1, and the optical fiber coupling section 2 is fixed to the coupling tube 1;

[0019] One end of the coupling tube 1 is connected to the hollow-core optical fiber 4 , and the other end of the optical fiber coupling section 2 is connected to the single-mode optical fiber 3 , so as to couple the hollow-core optical fiber 4 with the single-mode optical fiber 3 .

[0020] Preferably, the step of processing one end of the optical fiber coupling section 2 to obtain the light collecting portion 20 comprises:

[0021] Stripping off the coating layer at one end of the optical fiber coupling section 2, and performing immersion corrosion on the position of the optical fiber coupling section 2 where the coating layer is stripped off;

[0022] The end of the optical fiber coupling section 2 that has been immersion-corroded is heated, and the optical fiber coupling section 2 is clamped and moved toward the heat source while being rotated, so that the end of the optical fiber coupling section 2 close to the heat source forms the light collecting portion 20 under the action of surface tension.

[0023] Preferably, the step of arranging the optical fiber coupling section 2 in the coupling tube 1 so that the light collecting portion 20 is spaced a preset distance from one end of the coupling tube 1 and fixing the optical fiber coupling section 2 to the coupling tube 1 comprises:

[0024] Inserting the light collecting portion 20 on the optical fiber coupling section 2 into the coupling tube 1, and adjusting the preset distance by adjusting the insertion depth of the light collecting portion 20;

[0025] When the light collecting portion 20 and one end of the coupling tube 1 reach a preset distance, adhesive is injected into the gap between the optical fiber coupling section 2 and the inner wall of the coupling tube 1 to fix the optical fiber coupling section 2 and the coupling tube 1 .

[0026] Preferably, the step of connecting one end of the coupling tube 1 to the hollow-core optical fiber 4 and connecting the other end of the optical fiber coupling section 2 to the single-mode optical fiber 3 to couple the hollow-core optical fiber 4 to the single-mode optical fiber 3 includes:

[0027] The coupling portion between the coupling tube 1 and the hollow-core optical fiber 4 is heated to connect one end of the coupling tube 1 to the hollow-core optical fiber 4;

[0028] The coupling point between the other end of the optical fiber coupling section 2 and the single-mode optical fiber 3 is heated to connect the other end of the optical fiber coupling section 2 to the single-mode optical fiber 3 .

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] On the one hand, the present invention sets a light collecting portion 20 at one end of the optical fiber coupling section 2, and then inserts the light collecting portion 20 into the coupling tube 1. The operation is simple and accurate, and can be carried out in batches, which is conducive to production. Through non-insertion coupling, the coupling structure can be applicable to hollow-core optical fibers 4 with various core sizes, has lower connection loss and higher coupling efficiency, has greater flexibility and compatibility in connecting the hollow-core optical fiber 4 with other optical fibers, and is not easily affected by external interference and environmental influences. On the other hand, the present invention controls the distance between the light collecting portion 20 on the optical fiber coupling section 2 and the connection between the coupling tube 1 and the hollow-core optical fiber 4, thereby reducing the reflected light entering the hollow-core optical fiber 4 and reducing the echo reflection, thereby improving the transmission effect of the optical signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a coupling schematic diagram of a coupling structure of a hollow core optical fiber and a single-mode optical fiber provided by an embodiment of the present invention;

[0033] Figure 2It is a structural schematic diagram of a fiber coupling section of a coupling structure of a hollow core optical fiber and a single-mode optical fiber provided by an embodiment of the present invention;

[0034] Figure 3 It is a schematic flow chart of a method for coupling a hollow core optical fiber with a single-mode optical fiber provided in an embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of an initial structure of an optical fiber coupling section provided by an embodiment of the present invention;

[0036] Figure 5 is a schematic diagram of the structure of an optical fiber coupling section after acid immersion provided by an embodiment of the present invention;

[0037] Figure 6 is a schematic diagram of generating a light converging portion provided by an embodiment of the present invention;

[0038] Figure 7 It is a structural schematic diagram of inserting an optical fiber coupling section into a coupling tube provided by an embodiment of the present invention;

[0039] Figure 8 is a schematic diagram of inserting an optical fiber coupling section into a coupling tube according to an embodiment of the present invention;

[0040] Fig. 9 It is a structural schematic diagram of coupling a coupling structure with a hollow core optical fiber and a single-mode optical fiber respectively provided by an embodiment of the present invention.

[0041] In all the drawings, the same reference numerals denote the same structure, including: coupling tube 1, optical fiber coupling section 2, light converging portion 20, tapered waist 21, single-mode optical fiber 3, hollow-core optical fiber 4, and ceramic core 5. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] Unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as open inclusion, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "examples", "specific examples" or "some examples" and the like are intended to indicate that specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner, that is, although they may be carried in the embodiments or examples of the above terms due to reasons such as the order and position of appearance, it is not limited to that they can be carried in combination by one embodiment or example.

[0044] In the description of the present invention, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, the meaning of "multiple" is two or more. In addition, for example, the same type of nouns may be described as two independent individuals by adding "A" and "B" at the end. In this case, the corresponding features defined as "A" and "B" are only used to distinguish the same type of individuals for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features.

[0045] When describing some embodiments, the expressions "coupling", "coupling" and "connection" and their derivatives may be used. For example, when describing some embodiments, the term "connection" may be used to indicate that two or more components are in direct physical or electrical contact with each other. For another example, when describing some embodiments, the term "coupling" may be used to indicate that two or more components are in direct physical or electrical contact. However, the terms "connection" or "coupling" may also refer to two or more components that are not in direct contact with each other, but still cooperate or interact with each other, such as "optical path coupling", "wireless connection", etc. The embodiments disclosed herein are not necessarily limited to the contents of the present invention.

[0046] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] Embodiment 1:

[0048] In order to solve the problem of low coupling efficiency in the existing hollow core fiber and single mode fiber coupling method and low transmission effect of optical signals after coupling, embodiment 1 of the present invention provides a coupling structure of hollow core fiber and single mode fiber, such as Figure 1 As shown, it includes a coupling tube 1 and an optical fiber coupling section 2, and the optical fiber coupling section 2 is arranged in the coupling tube 1; one end of the coupling tube 1 is coupled to the single-mode optical fiber 3, and the other end of the coupling tube 1 is coupled to the hollow-core optical fiber 4; one end of the optical fiber coupling section 2 is provided with a light collecting portion 20, and the other end of the optical fiber coupling section 2 is connected to the single-mode optical fiber 3, and the light collecting portion 20 is coupled to the core of the hollow-core optical fiber 4. The coupling here means that the optical signal can be transmitted between the light collecting portion 20 and the hollow-core optical fiber 4, and the light collecting portion 20 is spaced from the end face of the hollow-core optical fiber 4 by a preset distance; by adjusting the preset distance between the light collecting portion 20 and the hollow-core optical fiber 4, the reflected light entering the hollow-core optical fiber 4 can be reduced.

[0049] The coupling tube 1 is mainly used to protect the optical fiber coupling section 2, and the coupling tube 1 can be a quartz glass tube. The optical fiber coupling section 2 is arranged in the inner tube of the coupling tube 1. In one embodiment, for the transmission effect of the optical signal, the light collecting part 20 needs to be arranged at the center of the inner tube of the coupling tube 1, and the upper and lower sides of the light collecting part 20 need to avoid contact with the inner tube wall of the coupling tube 1, so that it is in a suspended state.

[0050] In one embodiment, there are two ways to implement the optical fiber coupling section 2: the first is that the optical fiber coupling section 2 can be a small section of independent single-mode optical fiber, one end of the single-mode optical fiber is processed to obtain the light-collecting portion 20, and then the single-mode optical fiber is reconnected with the single-mode optical fiber 3 to be coupled, and one end of the optical fiber coupling section 2 is processed to form the light-collecting portion 20. In this way, a small section of single-mode optical fiber is retained outside the coupling tube 1 at the tail end of the optical fiber coupling section 2 as a part for fusion-splicing the single-mode optical fiber, or made into a jumper connector for connecting the single-mode optical fiber; the second is that the optical fiber coupling section 2 can be a part of the single-mode optical fiber 3 to be coupled, and one end of the single-mode optical fiber 3 is directly processed to form the light-collecting portion 20. The second way can save the process of connecting the optical fiber coupling section 2 with the single-mode optical fiber 3 to be coupled, but the practicality of the second way is not as good as the first way. Taking into account the practicality of the product, the first method is generally used to manufacture the optical fiber coupling segment 2. Not only can the entire coupling structure including the coupling tube 1 and the optical fiber coupling segment 2 be directly mass-produced and put into actual application scenarios, but also when the length of the single-mode optical fiber 3 is too long, it can avoid pulling or bending the single-mode optical fiber 3 during the production process of the light gathering part 20, thereby achieving higher coupling efficiency and better coupling effect.

[0051] The light collecting portion 20 is used to collect the optical signal transmitted from the single-mode optical fiber 3 and effectively couple the optical signal to the hollow-core optical fiber 4, or to collect the optical signal transmitted from the hollow-core optical fiber 4 and effectively couple the optical signal to the single-mode optical fiber 3. In one embodiment, the shape of the light collecting portion 20 is spherical or ellipsoidal. When the shape of the light collecting portion 20 is ellipsoidal, the long axis of the light collecting portion 20 is perpendicular to the center line of the core of the hollow-core optical fiber 4. In one embodiment, the diameter of the core of the hollow-core optical fiber 4 is 20μm to 200μm.

[0052] When the light converging portion 20 is ellipsoidal, its long axis is perpendicular to the centerline of the air core optical fiber, which helps to further reduce reflection because the ellipsoidal structure can better adapt to the core shapes of two different optical fibers, thereby reducing light reflection caused by geometric mismatch.

[0053] In one embodiment, Figure 2 As shown, after simulation experiments, when the light-collecting portion 20 is ellipsoidal, and the numerical aperture of the single-mode optical fiber 3 is 0.12, and the numerical aperture of the hollow-core optical fiber 4 is 0.17, the short axis length of the light-collecting portion 20 is 163.87 μm, the long axis length is 211.55 μm, and the long axis is perpendicular to the center line of the fiber core. At this time, the light-collecting effect is better, and the optimal value of the preset distance selected according to the simulation experiment is 921.92 μm, which can improve the light-collecting effect while reducing reflection. In practical applications, selecting a suitable shape and size of the light-collecting portion 20 requires consideration of many factors, including the physical properties of the optical fiber, coupling efficiency, transmission requirements of the optical signal, and limitations of the manufacturing process. Usually, these parameters need to be determined through experimental optimization, or computer simulation is used to predict the optimal design parameters, which will not be described in detail in this embodiment.

[0054] In one embodiment, the preset distance can be determined by the vertical distance from the center of the light collecting portion 20 to the end face of the hollow core optical fiber 4; the preset distance can also be determined by the vertical distance from the leftmost point of the light collecting portion 20 to the end face of the hollow core optical fiber 4, that is, Figure 1 As shown, the preset distance d refers to the distance between the leftmost point of the light collecting part 20 and the end face of the hollow-core optical fiber 4, which is equivalent to the distance between the light collecting part 20 and the connection point between the coupling tube 1 and the hollow-core optical fiber 4. When light is emitted from the hollow-core optical fiber 4 into the light collecting part 20, part of the light will directly enter the single-mode optical fiber 3, while the other part of the light will return to the hollow-core optical fiber 4 due to reflection. If the distance between the light collecting part 20 and the end face of the hollow-core optical fiber 4 is too close, more reflected light will enter the hollow-core optical fiber 4. On the contrary, if the distance is too far, the coupling efficiency will decrease because the light directly entering the single-mode optical fiber 3 is reduced. Among them, the size of the preset distance needs to take into account the shape of the light collecting part and the numerical aperture of the hollow-core optical fiber and the single-mode optical fiber.

[0055] In one embodiment, after the optical fiber coupling segment 2 is inserted into the coupling tube 1, in order to fix the optical fiber coupling segment 2 and the coupling tube 1, as shown in FIG. Figure 1 and Figure 2 As shown, the optical fiber coupling section 2 also includes a tapered waist 21, one end of the tapered waist 21 is connected to the single-mode optical fiber 3, and the other end of the tapered waist 21 is connected to the light collecting portion 20; an adhesive is provided between the tapered waist 21 and the inner tube wall of the coupling tube 1 to fix the optical fiber coupling section 2 and the coupling tube 1.

[0056] The tapered waist 21 is formed during the manufacturing process of the light-collecting portion 20, and the diameter of the tapered waist 21 can be controlled to be 45 μm. The tapered waist 21 provides a gradually changing area between the single-mode optical fiber 3 and the light-collecting portion 20, so that the diameter of the light beam is reduced in the process of light entering the hollow-core optical fiber 4 from the single-mode optical fiber 3, thereby reducing energy loss and reflection.

[0057] The adhesive is provided between the tapered waist 21 and the inner tube wall of the coupling tube 1 to fix the optical fiber coupling section 2 and the coupling tube 1 together to ensure that they maintain a stable position during the coupling process. The adhesive can also provide additional protection to prevent the optical fiber from being damaged during operation or transportation. In one embodiment, commonly used adhesives include epoxy resin, silicone or other optical grade adhesives, which usually have good transparency and bonding properties to better fix the optical fiber coupling section 2 and the coupling tube 1.

[0058] In order to enable the coupling structure proposed in this embodiment to better couple the hollow-core optical fiber 4 and the single-mode optical fiber 3, the numerical apertures of the single-mode optical fiber 3 and the hollow-core optical fiber 4 can be limited in this embodiment. In one embodiment, the numerical aperture of the single-mode optical fiber 3 is 0.12 to 0.17; the numerical aperture of the hollow-core optical fiber 4 is 0.03 to 0.22, wherein the numerical aperture is a dimensionless number used to measure the angular range of light that can be collected by the system. That is, the numerical aperture of the single-mode optical fiber 3 can be 0.12, 0.17, or any value between 0.12 and 0.17, and the numerical aperture of the hollow-core optical fiber 4 can be 0.03, 0.22, or any value between 0.03 and 0.22. Specifically, after selecting the corresponding numerical apertures of the single-mode optical fiber 3 and the hollow-core optical fiber 4, according to the simulation experiment, the shape of the light-gathering portion 20 and the distance between the light-gathering portion 20 and the core end face of the hollow-core optical fiber 4 can be obtained. The specific method includes setting the corresponding numerical apertures of the single-mode optical fiber 3 and the hollow-core optical fiber 4, and then performing a simulation experiment to obtain the final required data for the purpose of optimizing the transmission effect of the optical signal. A more specific acquisition method is not specifically described in this embodiment. The numerical aperture size of the optical fiber is related to the core refractive index and the core-cladding relative refractive index difference. From a physical point of view, the numerical aperture of the optical fiber represents the ability of the optical fiber to receive incident light. The larger the numerical aperture, the stronger the ability of the optical fiber to receive light. From the perspective of increasing the optical power entering the optical fiber, the larger the numerical aperture, the better, because a larger numerical aperture of the optical fiber is beneficial to the docking of the optical fiber. However, when the numerical aperture is too large, the mode distortion of the optical fiber increases, which will affect the bandwidth of the optical fiber. Usually, in order to most efficiently transmit optical signals from one optical fiber to another, optical fibers with the same or similar numerical apertures should be used to transmit optical signals.

[0059] To summarize, on the one hand, in this embodiment, a light collecting portion 20 is arranged at one end of the optical fiber coupling segment 2, and then the light collecting portion 20 is inserted into the coupling tube 1. The operation is simple and accurate, and it can be carried out in batches, which is conducive to production. Through non-insertion coupling, the coupling structure can be applicable to hollow-core optical fibers 4 of various core sizes, and has lower connection loss and higher coupling efficiency. It has greater flexibility and compatibility in connecting the hollow-core optical fiber 4 with other optical fibers, and is not easily affected by external interference and environmental influences. On the other hand, in this embodiment, by controlling the distance between the light collecting portion 20 on the optical fiber coupling segment 2 and the connection between the coupling tube 1 and the hollow-core optical fiber 4, the reflected light entering the hollow-core optical fiber 4 can be reduced, and the echo reflection can be reduced, thereby improving the transmission effect of the optical signal.

[0060] Embodiment 2:

[0061] In Example 1, a coupling structure of a hollow core optical fiber and a single-mode optical fiber is proposed. In order to further illustrate the present invention, a coupling method of a hollow core optical fiber and a single-mode optical fiber is proposed in this embodiment. In one embodiment, the optical fiber coupling section 2 is a small section of an independent single-mode optical fiber as an example for explanation. Figure 3 As shown, the coupling method includes:

[0062] Step 101 : processing one end of the optical fiber coupling section 2 to obtain the light collecting portion 20 .

[0063] The light converging portion 20 is designed to optimize the coupling of optical signals and usually has a specific shape and size, so as to minimize the reflection and loss of light between the two optical fibers.

[0064] In one embodiment, the optical fiber coupling section 2 has two implementation methods: the first is that the optical fiber coupling section 2 can be a section of independent single-mode optical fiber, one end of the single-mode optical fiber is processed to obtain the light-collecting portion 20, and then the single-mode optical fiber is reconnected with the single-mode optical fiber 3 to be coupled; the second is that the light-collecting portion 20 on the optical fiber coupling section 2 can also be directly processed from one end of the single-mode optical fiber 3 to be coupled, which saves the process of connecting the optical fiber coupling section 2 with the single-mode optical fiber 3 to be coupled, but it is easy to be inconvenient to operate during the production process of the light-collecting portion 20 and it is easy to damage the single-mode optical fiber 3. This embodiment takes the first method as an example.

[0065] In one embodiment, Figure 4 , Figure 5 and Figure 6 As shown, the step 101 includes: stripping the coating layer at one end of the optical fiber coupling segment 2, and immersion etching the position of the optical fiber coupling segment 2 after the coating layer is stripped; heating the end of the optical fiber coupling segment 2 after the immersion etching, and clamping the optical fiber coupling segment 2 close to the heat source and rotating it at the same time, so that the end of the optical fiber coupling segment 2 close to the heat source forms the light collecting portion 20 under the action of surface tension.

[0066] The rotation operation can be either clockwise or counterclockwise.

[0067] The optical fiber coupling section 2 is a section of single-mode optical fiber, including a coating, a cladding and a core. The coating at one end is stripped. The coating is usually used to protect the optical fiber, but during the coupling process, the core of the optical fiber needs to be exposed to facilitate the transmission of optical signals. The coating can be stripped by mechanical stripping, chemical corrosion or other methods. After stripping the coating, the diameter of the area after the coating is stripped can be reduced by the step of immersion corrosion to ensure that the shape and size of the light collecting part 20 meet the design requirements. In one embodiment, the immersion corrosion can be performed by hydrofluoric acid. By heating, the material of the optical fiber coupling section 2 will soften, so that it will flow and shape under the action of surface tension to ensure the shape and quality of the light collecting part 20. While heating, the optical fiber coupling section 2 needs to be clamped and moved closer to the heat source, and rotated at the same time. This operation can help form a smooth and symmetrical light collecting part 20. The role of rotation is to make the material of the optical fiber coupling section 2 evenly distributed when flowing, thereby forming the light collecting part 20, which can be used to improve the coupling efficiency. The size of the light collecting part 20 is controlled by controlling the heating, depending on the actual situation, and will not be explained in detail in this embodiment.

[0068] Step 102 : placing the optical fiber coupling section 2 in the coupling tube 1 , so that the light collecting portion 20 is spaced a preset distance from one end of the coupling tube 1 , and fixing the optical fiber coupling section 2 to the coupling tube 1 .

[0069] In one embodiment, Figure 7 and Figure 8 As shown, the step 102 specifically includes: inserting the light collecting portion 20 on the optical fiber coupling segment 2 into the coupling tube 1, and adjusting the preset distance by adjusting the insertion depth of the light collecting portion 20; when the light collecting portion 20 and one end of the coupling tube 1 reach the preset distance, injecting adhesive into the gap between the optical fiber coupling segment 2 and the inner wall of the coupling tube 1 to fix the optical fiber coupling segment 2 to the coupling tube 1.

[0070] like Figure 7 As shown, a ceramic core 5 is further provided outside the single-mode optical fiber 3 and the coupling tube 1 to further protect the single-mode optical fiber 3 and the coupling tube 1. The light collecting portion 20 maintains a preset distance from one end of the coupling tube 1, and this distance is usually optimized and calculated to ensure that the optical signal can be optimally transmitted during the coupling process. The optical fiber coupling section 2 and the coupling tube 1 are fixed by adhesive or other fixing methods to keep their positions stable.

[0071] The processed light collecting part 20 is inserted into the coupling tube 1. During insertion, it is necessary to ensure that the position of the light collecting part 20 is correct so as to maintain a preset distance with one end of the coupling tube 1. In order to achieve the ideal preset distance, the insertion depth of the light collecting part 20 needs to be adjusted. This is usually achieved by moving the optical fiber coupling section 2 or the coupling tube 1. Once the light collecting part 20 reaches the preset distance with one end of the coupling tube 1, the adhesive is injected into the gap between the optical fiber coupling section 2 and the inner wall of the coupling tube 1. The function of the adhesive is to fix the optical fiber coupling section 2 to prevent it from moving during use and provide additional protection. Commonly used adhesives include epoxy resin, silicone or other suitable optical fiber coupling materials. After the adhesive is cured, the optical fiber coupling section 2 is firmly fixed to the coupling tube 1 to form a stable coupling structure. In this way, the installation and fixation of the optical fiber coupling section 2 is completed, so that it is ready for the transmission of optical signals.

[0072] Step 103 : Connect one end of the coupling tube 1 to the hollow-core optical fiber 4 , and connect the other end of the optical fiber coupling section 2 to the single-mode optical fiber 3 , so as to couple the hollow-core optical fiber 4 to the single-mode optical fiber 3 .

[0073] In this step, if Fig. 9 As shown, the coupling portion (i.e., region a) between the coupling tube 1 and the hollow-core optical fiber 4 is heated to connect one end of the coupling tube 1 to the hollow-core optical fiber 4; the coupling portion (i.e., region b) between the other end of the optical fiber coupling segment 2 and the single-mode optical fiber 3 is heated to connect the other end of the optical fiber coupling segment 2 to the single-mode optical fiber 3. In one embodiment, in order to connect the other end of the optical fiber coupling segment 2 to the single-mode optical fiber 3 to be coupled, a small section of single-mode optical fiber is reserved at the tail end (i.e., region b) of the optical fiber coupling segment 2 outside the coupling tube 1 as a part for fusion splicing the single-mode optical fiber 3, or is made into a jumper connector for connecting the single-mode optical fiber 3.

[0074] One end of the coupling tube 1 is connected to the hollow-core optical fiber 4 by heating. When connecting, it is necessary to ensure that the core of the hollow-core optical fiber 4 is aligned with the light collecting portion 20 so that the optical signal can smoothly enter the hollow-core optical fiber 4 from the single-mode optical fiber 3. Heating can be achieved by laser or other heating sources. The purpose is to soften the material of the coupling tube 1 so that it can be integrated with the end face of the hollow-core optical fiber 4 to form a solid connection. This hot-melt connection method can ensure the sealing of the connection and the stability of the optical signal transmission. Next, the coupling point between the other end of the optical fiber coupling section 2 and the single-mode optical fiber 3 also needs to be heated.

[0075] During the heating process, the heating temperature and time need to be controlled to ensure the quality and reliability of the connection. Too high a temperature may damage the optical fiber, while too low a temperature may result in a loose connection. At the same time, a stable heating point needs to be maintained to avoid displacement or damage to the optical fiber. After the heating connection is completed, it is necessary to wait for the connection to cool and solidify. Finally, the optical performance of the connection can be tested to ensure that the coupling loss is within an acceptable range so that the optical signal can be transmitted efficiently.

[0076] In one embodiment, when the optical fiber coupling segment 2 is directly made of one end of the single-mode optical fiber to be coupled, the steps can refer to the aforementioned steps. The main difference is that the process of coupling the single-mode optical fiber 3 to be coupled with the optical fiber coupling segment 2 can be omitted, which will not be repeated in this embodiment.

[0077] For the specific structure of the coupling structure between the hollow core optical fiber and the single mode optical fiber, please refer to Example 1, which will not be repeated in this embodiment.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A coupling structure of a hollow core optical fiber and a single mode optical fiber, characterized in that: It comprises a coupling tube (1) and an optical fiber coupling section (2), wherein the optical fiber coupling section (2) is arranged in the coupling tube (1); one end of the coupling tube (1) is coupled to a single-mode optical fiber (3), and the other end of the coupling tube (1) is coupled to a hollow-core optical fiber (4); A light collecting portion (20) is provided at one end of the optical fiber coupling section (2), the other end of the optical fiber coupling section (2) is connected to the single-mode optical fiber (3), the light collecting portion (20) is coupled to the core of the hollow-core optical fiber (4), and is spaced from the end face of the hollow-core optical fiber (4) by a preset distance; By adjusting the preset distance between the light collecting portion (20) and the hollow-core optical fiber (4), the reflected light entering the hollow-core optical fiber (4) is reduced.

2. The coupling structure of hollow core optical fiber and single mode optical fiber according to claim 1, characterized in that: The light collecting portion (20) is in the shape of a sphere or an ellipsoid.

3. The coupling structure of hollow core optical fiber and single mode optical fiber according to claim 2, characterized in that: When the shape of the light collecting portion (20) is an ellipsoid, the major axis of the light collecting portion (20) is perpendicular to the center line of the core of the hollow-core optical fiber (4).

4. The coupling structure of hollow core optical fiber and single mode optical fiber according to claim 1, characterized in that: The optical fiber coupling section (2) further comprises a tapered waist (21), one end of the tapered waist (21) is connected to the single-mode optical fiber (3), and the other end of the tapered waist (21) is connected to the light collecting portion (20); An adhesive is provided between the tapered waist (21) and the inner tube wall of the coupling tube (1) to fix the optical fiber coupling section (2) and the coupling tube (1).

5. The coupling structure of a hollow core optical fiber and a single mode optical fiber according to any one of claims 1 to 4, characterized in that: The numerical aperture of the single-mode optical fiber (3) is 0.12 to 0.17; the numerical aperture of the hollow-core optical fiber (4) is 0.03 to 0.

22.

6. The coupling structure of a hollow core optical fiber and a single mode optical fiber according to any one of claims 1 to 4, characterized in that: The diameter of the core of the hollow core optical fiber (4) is 20 μm to 200 μm.

7. A method for coupling a hollow core optical fiber to a single mode optical fiber, characterized in that: The coupling method is applicable to the coupling structure of the hollow core optical fiber and the single mode optical fiber according to any one of claims 1 to 6, comprising: Processing one end of the optical fiber coupling section (2) to obtain the light collecting portion (20); The optical fiber coupling section (2) is arranged in the coupling tube (1), so that the light collecting portion (20) is spaced a preset distance from one end of the coupling tube (1), and the optical fiber coupling section (2) is fixed to the coupling tube (1); One end of the coupling tube (1) is connected to the hollow-core optical fiber (4), and the other end of the optical fiber coupling section (2) is connected to the single-mode optical fiber (3), so as to couple the hollow-core optical fiber (4) with the single-mode optical fiber (3).

8. The method for coupling a hollow core optical fiber to a single mode optical fiber according to claim 7, characterized in that: The step of processing one end of the optical fiber coupling section (2) to obtain the light collecting portion (20) comprises: Stripping off the coating layer at one end of the optical fiber coupling section (2), and performing immersion corrosion on the position of the optical fiber coupling section (2) where the coating layer is stripped off; The end of the optical fiber coupling section (2) that has been immersed and corroded is heated, and the optical fiber coupling section (2) is clamped and moved toward a heat source while being rotated, so that the end of the optical fiber coupling section (2) close to the heat source forms the light collecting portion (20) under the action of surface tension.

9. The method for coupling a hollow core optical fiber to a single mode optical fiber according to claim 7, characterized in that: The step of arranging the optical fiber coupling section (2) in the coupling tube (1) so that the light collecting portion (20) is spaced a preset distance from one end of the coupling tube (1), and fixing the optical fiber coupling section (2) and the coupling tube (1) comprises: Inserting the light collecting portion (20) on the optical fiber coupling section (2) into the coupling tube (1), and adjusting the preset distance by adjusting the insertion depth of the light collecting portion (20); When the light collecting portion (20) reaches a preset distance from one end of the coupling tube (1), adhesive is injected into the gap between the optical fiber coupling section (2) and the inner wall of the coupling tube (1) to fix the optical fiber coupling section (2) and the coupling tube (1).

10. The method for coupling a hollow core optical fiber to a single mode optical fiber according to claim 7, characterized in that: The step of connecting one end of the coupling tube (1) to the hollow-core optical fiber (4) and connecting the other end of the optical fiber coupling section (2) to the single-mode optical fiber (3) to couple the hollow-core optical fiber (4) to the single-mode optical fiber (3) comprises: Heating the coupling point between the coupling tube (1) and the hollow-core optical fiber (4) to connect one end of the coupling tube (1) to the hollow-core optical fiber (4); The coupling point between the other end of the optical fiber coupling section (2) and the single-mode optical fiber (3) is heated to connect the other end of the optical fiber coupling section (2) to the single-mode optical fiber (3).

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