Method for hot fusion of optical fibers, optical waveguide adapter

Abstract

The application belongs to the technical field of optical communication, and discloses a hot fusion method of an optical fiber and an optical waveguide adapter. The application performs inclined angle cutting on a solid core optical fiber and a hollow core optical fiber respectively, so that the solid core optical fiber has a first inclined cutting angle, the hollow core optical fiber has a second inclined cutting angle, and the first inclined cutting angle is smaller than the second inclined cutting angle. Then, the solid core optical fiber with the first inclined cutting angle is hot fused with the hollow core optical fiber with the second inclined cutting angle. Through the unequal angle optical fiber fusion form, the application realizes the combination of low fusion loss and low return loss. Meanwhile, the application is a non-coating type fusion method, and the operation process is simpler, more convenient for outdoor site construction, and can reduce the requirement for fusion equipment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical communication, and more particularly relates to a hot fusion method of an optical fiber and an optical waveguide adapter. BACKGROUND

[0002] In the practical application of hollow-core anti-resonant optical fibers, it is often necessary to solve the connection problem of single-mode optical fibers and hollow-core anti-resonant optical fibers. In order to realize low fusion loss (mainly insertion loss) and low return loss of the connection of single-mode optical fibers and hollow-core optical fibers, domestic and foreign scholars have done a lot of research and experiments. At present, the more mainstream solution is to heat-expand the core of the single-mode optical fiber or to fuse a section of multimode transition fiber to the single-mode optical fiber to realize the mode field matching with the hollow-core optical fiber, and to coat a layer of anti-reflection film on the end of the heat-expanded single-mode optical fiber or the end of the multimode transition fiber after angle cutting to reduce the return loss. The connection of the single-mode optical fiber and the hollow-core optical fiber after the above processing is coupled and packaged using a micro-processing platform, and the conventional optical fiber hot fusion method is rarely used to realize the optical fiber connection. The reason is that the traditional hot fusion process cannot meet the mode field matching accuracy and has a high requirement on the heat resistance of the coated film layer, and it is difficult to realize the low insertion loss and low return loss connection of the single-mode optical fiber and the hollow-core optical fiber through hot fusion.

[0003] For example, a conventional optical fiber hot fusion method is to fuse a transition fiber to a single-mode optical fiber and cut an angle, and then directly discharge and hot fuse the single-mode optical fiber with a hollow-core optical fiber cut at the same angle. By adjusting the fusion program, a weak fusion without collapse between the transition fiber and the hollow-core optical fiber can be realized. When the cutting angle of the optical fiber is larger (≤8°), the return loss is lower, but the fusion loss is higher, so it is difficult to simultaneously obtain low return loss and fusion loss.

[0004] Similar to the above method, for another example, an angle-cut single-mode optical fiber is directly fused with a hollow-core optical fiber at the same angle. In this method, the larger the angle-cut angle of the single-mode optical fiber, the lower the return loss. However, due to the refraction of the core beam at the angle-cut end face of the optical fiber, a certain angle between the core beam propagation direction and the axial direction of the optical fiber is generated, as shown in Figure 1 This is also the main reason why the fusion of the angle-cut single-mode optical fiber and the hollow-core optical fiber at the same angle has a large fusion loss. This fusion method also cannot simultaneously obtain low return loss and fusion loss.

[0005] Another conventional optical fiber hot fusion method is to cut a single-mode optical fiber in the middle of the taper region after reverse tapering to obtain an expanded-core single-mode optical fiber, and then coat a film on the expanded-core single-mode optical fiber and directly hot fuse the expanded-core single-mode optical fiber with a 0° angle hollow-core optical fiber. However, the above fusion technology has a high requirement on the uniformity and heat resistance of the hot field of the fusion equipment and the uniformity and heat resistance of the coated film, and the fusion process is complex and not convenient for outdoor site construction.

[0006] Considering that the heat fusion of the optical fiber is more convenient, the fusion of the optical fiber using the fusion machine is more suitable for operation in the outdoor field, and the volume of the additional heat shrink tube fixed at the fusion point is smaller than that of the coupler package, so it is easier to realize the wiring in a small space, therefore, the heat fusion technology is used to solve the connection problem of the single-mode optical fiber and the hollow optical fiber, which is a key technology to be solved urgently for popularizing and laying the hollow optical fiber. SUMMARY

[0007] The present application provides a heat fusion method of an optical fiber and an optical waveguide adapter, which solves the problem that the existing heat fusion method of the optical fiber is difficult to realize low return loss and low fusion loss in the connection of the single-mode optical fiber and the hollow optical fiber.

[0008] The present application provides a heat fusion method of an optical fiber, comprising the following steps:

[0009] The real core optical fiber and the hollow optical fiber are respectively subjected to bevel cutting, so that the real core optical fiber has a first bevel cutting angle, and the hollow optical fiber has a second bevel cutting angle, and the first bevel cutting angle is smaller than the second bevel cutting angle.

[0010] The real core optical fiber with the first bevel cutting angle is heat fused with the hollow optical fiber with the second bevel cutting angle.

[0011] Preferably, the real core optical fiber is a single-mode optical fiber, and the mode field diameter of the hollow optical fiber is larger than that of the single-mode optical fiber.

[0012] Preferably, the real core optical fiber is one of a heat-expanded core single-mode optical fiber, a reverse taper single-mode optical fiber and a single-mode optical fiber fusion transition optical fiber; when the real core optical fiber is a single-mode optical fiber fusion transition optical fiber, the end side of the transition optical fiber is heat fused with the hollow optical fiber.

[0013] Preferably, the transition optical fiber is a graded-index optical fiber.

[0014] Preferably, the heat fusion is performed in a two-step fusion mode.

[0015] Preferably, the discharge parameters in the primary fusion include a first time, a first power and a first optical fiber overlap amount, the first time is 1-3s, the first power is 1900-3000bit, and the first optical fiber overlap amount is 10-20μm; the discharge parameters in the secondary fusion include a second time, a second power and a second optical fiber overlap amount, the second time is 3-6s, the second power is 1300-1800bit, and the second optical fiber overlap amount is 1-5μm.

[0016] Preferably, the first bevel cutting angle is determined according to the requirement of return loss, and the range of the first bevel cutting angle is 1° to 6°.

[0017] Preferably, after the solid core fiber and the cladding of the hollow core fiber are aligned, before the discharge fusion, further comprising: in the direction of the bevel angle, displacement correction is performed to make the core beam propagation direction of the beveled solid core fiber coincide with the optical axis direction of the beveled hollow core fiber.

[0018] Preferably, in order to obtain the lowest fusion loss, the optimal bevel angle and the optimal displacement correction amount of the hollow core fiber are determined; the optimal bevel angle is taken as the second bevel angle, and displacement correction is performed in the direction of the bevel angle according to the optimal displacement correction amount.

[0019] In another aspect, the present application provides an optical waveguide adapter, comprising a solid core fiber and a hollow core fiber, and the solid core fiber and the hollow core fiber are fused by the above-mentioned optical fiber hot fusion method.

[0020] One or more technical solutions provided in the present application have at least the following technical effects or advantages:

[0021] (1) In the present application, the solid core fiber and the hollow core fiber are respectively cut at an angle, so that the solid core fiber has a first bevel angle and the hollow core fiber has a second bevel angle, and the first bevel angle is smaller than the second bevel angle; then the solid core fiber with the first bevel angle and the hollow core fiber with the second bevel angle are hot fused. The solid core fiber can be a single-mode fiber, a hot expanded core single-mode fiber, a reverse draw-taper single-mode fiber or a single-mode fiber fusion transition fiber. For the connection problem of the single-mode fiber and the hollow core fiber, the present application makes the bevel angle of the hollow core fiber larger than the bevel angle of the single-mode fiber, which is different from the same angle fusion scheme adopted by the conventional optical fiber hot fusion method. When the fiber fusion occurs between fibers of different angles, the two fibers will be bent to a certain extent near the fusion point, and because the bending strengths of the single-mode fiber and the hollow core fiber used are different, after the fusion of the two fibers of different angles, only the beveled single-mode fiber will be bent to a large extent, forming a non-axially parallel beveled fiber fusion form. This fusion form can make the core beam propagation direction of the beveled single-mode fiber re-parallel to the optical axis direction of the hollow core fiber, thereby eliminating the additional fusion loss caused by the refraction of the core beam at the end face of the beveled single-mode fiber. Moreover, due to the hollow structure of the hollow core fiber, the bevel angle of the core position of the beveled single-mode fiber will not change greatly due to the fusion, so the return loss at the fusion point can also be guaranteed. Therefore, the present application can realize low return loss and low fusion loss for the connection of the single-mode fiber and the hollow core fiber. That is, the present application realizes the combination of low fusion loss and low return loss through the fusion of fibers of different angles (i.e. non-axially parallel fusion). At the same time, the present application is also a non-coating type fusion method, compared with some existing fusion methods which need to be coated, the operation process of the present application is simpler, more convenient for outdoor site construction, and can also reduce the requirements for fusion equipment.

[0022] (2) The present application adopts two-step fusion welding method for hot fusion welding, the primary fusion welding is short-time high-power discharge plus larger optical fiber overlap, the secondary fusion welding is long-time small-power discharge plus smaller optical fiber overlap, the two-step fusion welding method is used for fusing the bevel angle hollow core optical fiber and the bevel angle single-mode optical fiber, the obtained fusion strength is higher, and the fusion additional loss is lower.

[0023] (3) The present application can obtain lower fusion loss by scanning and optimizing the bevel angle of the hollow core optical fiber.

[0024] (4) After the cladding of the solid core optical fiber and the hollow core optical fiber is aligned, the displacement correction in the bevel direction is further optimized before the discharge fusion welding, so that the core beam propagation direction of the bevel angle solid core optical fiber is coincided with the optical axis direction of the bevel angle hollow core optical fiber, and the effect of further reducing the fusion loss is achieved. The scanning and optimization of the bevel angle of the hollow core optical fiber and the displacement correction amount before the fusion discharge can make the fusion loss of the non-axial parallel fusion optimal. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of the bevel angle optical fiber beam propagation direction.

[0026] Figure 2 It is a schematic diagram of the effect of the unequal angle optical fiber fusion realized by the optical fiber hot fusion welding method provided by the embodiment 1 of the present application.

[0027] Figure 3 It is a flow chart of the scanning and optimization of the bevel angle and displacement correction amount parameters of the hollow core optical fiber in the optical fiber hot fusion welding method provided by the embodiment 1 of the present application. DETAILED DESCRIPTION

[0028] In order to better understand the above technical solutions, the above technical solutions will be described in detail in combination with the drawings of the specification and the specific embodiments.

[0029] Embodiment 1:

[0030] The embodiment 1 provides an optical fiber hot fusion welding method, which comprises the following steps:

[0031] Step 1, the solid core optical fiber and the hollow core optical fiber are respectively bevel cut, so that the solid core optical fiber has a first bevel angle, and the hollow core optical fiber has a second bevel angle, and the first bevel angle is smaller than the second bevel angle.

[0032] The solid core fiber can be a single-mode fiber, and a mode field diameter of the hollow core fiber is greater than a mode field diameter of the single-mode fiber. The solid core fiber can also be one of a hot expanded core single-mode fiber, a reverse tapered single-mode fiber, and a single-mode fiber fusion transition fiber. When the solid core fiber is the single-mode fiber fusion transition fiber, a side of the transition fiber where the transition fiber is located is heat fused with the hollow core fiber, and the transition fiber can be a graded index fiber. Compared with a scheme of directly heat fusing the single-mode fiber and the hollow core fiber, heat fusing the single-mode fiber after pretreatment (for example, the single-mode fiber fusion transition fiber) and then heat fusing the single-mode fiber with the hollow core fiber can achieve lower fusion loss.

[0033] Specifically, the first beveling angle can be determined according to a requirement for return loss, and the first beveling angle ranges from 1° to 6°.

[0034] Step 2: heat fusing the solid core fiber with the first beveling angle with the hollow core fiber with the second beveling angle.

[0035] Specifically, the application adopts a two-step fusion manner to perform heat fusion. The first fusion is short-time high-power discharge plus large fiber overlap, and the second fusion is long-time small-power discharge plus small fiber overlap. In the two-step fusion, the fibers are all in the electrode center discharge. The two-step fusion method is used to fuse the beveling angle hollow core fiber with the beveling angle single-mode fiber, so that higher fusion strength and lower fusion additional loss are obtained.

[0036] The discharge parameter setting of the first discharge in the fusion can be the maximum discharge amount of the fusion of the solid core fiber with the same beveling angle and the hollow core fiber without additional loss caused by the collapse of the internal structure of the hollow core fiber.

[0037] The second discharge in the fusion and the increase of the fiber overlap are used to enhance the fusion strength of the beveling angle fiber. The discharge parameter setting can slightly increase the additional loss caused by the collapse of the internal structure of the hollow core fiber after the second discharge (for example, the increase of the additional loss can meet the condition of being less than 0.05 dB), and the fused fiber fusion point can be taken out and protected by external heat shrinkage.

[0038] For example, the fusion machine can be Fujikura fusion machine. The discharge parameters in the first fusion include a first time, a first power, and a first fiber overlap. The first time is 1-3 s, the first power is 1900-3000 bit, and the first fiber overlap is 10-20 μm. The discharge parameters in the second fusion include a second time, a second power, and a second fiber overlap. The second time is 3-6 s, the second power is 1300-1800 bit, and the second fiber overlap is 1-5 μm.

[0039] Further, after the alignment of the solid core fiber and the cladding of the hollow core fiber, before the discharge fusion, it can also include: in the direction of the bevel angle, the displacement correction is made so that the core beam propagation direction of the bevel angle solid core fiber coincides with the optical axis direction of the bevel angle hollow core fiber. That is, before the initial fusion discharge, the motor motor preset axial offset correction value can also be controlled. This operation can make the core beam propagation direction of the bevel angle solid core fiber coincide with the optical axis direction of the bevel angle hollow core fiber, so as to further reduce the fusion loss.

[0040] Specifically, in order to obtain the lowest fusion loss, the optimal bevel angle of the hollow core fiber and the optimal displacement correction amount are determined; the optimal bevel angle is taken as the second bevel angle, and the displacement correction is made in the direction of the bevel angle according to the optimal displacement correction amount. The present application combines the scanning optimization of the bevel angle of the hollow core fiber and the displacement correction amount before fusion discharge, so that the fusion loss of the non-axial parallel fusion can be optimized.

[0041] The present application will be further described below by taking the bevel angle fusion of a single mode fiber with a cladding diameter of 125 μm and a hollow core fiber with a cladding diameter of 230-250 μm as an example.

[0042] First, the cutting knife with a rotation angle function is used to cut the hollow core fiber and the single mode fiber at a bevel angle respectively, and the bevel angle of the hollow core fiber is greater than that of the single mode fiber, and then the two bevel angle fibers are fused by using the above fusion method.

[0043] When the fiber fusion occurs between fibers of different angles, the two side fibers will be bent to a certain extent near the fusion point, and because the bending strengths of the single mode fiber and the hollow core fiber used are different, after the fusion of the two kinds of unequal angle fibers, only the bevel angle single mode fiber is bent to a large extent, that is, a kind of non-axial parallel bevel angle fiber fusion form, as shown in the figure. Figure 2 This fusion form can make the core beam propagation direction of the bevel angle single mode fiber re-parallel with the optical axis direction of the hollow core fiber, so as to eliminate the additional fusion loss caused by the refraction of the core beam at the end face of the bevel angle single mode fiber, and because of the hollow structure of the hollow core fiber, the bevel angle of the core position of the bevel angle single mode fiber will not change greatly due to the fusion, so the return loss at the fusion point can also be guaranteed.

[0044] When the bevel angle hollow core fiber and the bevel angle single mode fiber of unequal angles are fused, although the bevel angle single mode fiber beam will be parallel to the axial direction, a certain axial misalignment will also occur, that is, the propagation direction of the fused beam does not coincide with the axial direction of the hollow core fiber, as shown in the figure. Figure 2As shown. So after the alignment of the two inclined angle fiber cladding, before the electrode discharge, the X or Y motor can be controlled to increase a small displacement correction in the inclined angle direction to ensure the coincidence of the inclined angle single mode fiber beam and the axial direction of the inclined angle hollow core fiber, and to realize the lowest fusion loss with the inclined angle hollow core fiber.

[0045] The flow chart for determining the lowest fusion loss of the inclined angle hollow core fiber and the inclined angle single mode fiber is shown in Figure 3 As shown, the inclined angle of the single mode fiber is usually determined according to the application needs. Taking the inclined angle of the single mode fiber as 4 degrees as an example, the initial inclined angle of the hollow core fiber is set as 5 degrees (i.e. A=5 in Figure 3 ), and the initial value of the fusion loss c is set as a larger value (for ensuring the normal operation of the scanning optimization process), for example, c=10. By gradually changing the value of the displacement correction B, for example, increasing 1 μm each time (i.e. B=B+1 in Figure 3 ), and comparing the fusion losses (including comparing the fusion loss a and the fusion loss b in Figure 3 ), the optimal displacement correction and the lowest fusion loss under the condition of the inclined angle can be obtained. Then, the inclined angle of the hollow core fiber is gradually increased, for example, increasing 0.5 degrees each time (i.e. A=A+0.5 in Figure 3 ), and the displacement correction is optimized again to obtain another group of the lowest fusion loss and compare with the previous group of fusion loss. If it is lower than the previous group of fusion loss, the inclined angle of the hollow core fiber is continuously increased, and the program is cycled until the lowest fusion loss is obtained.

[0046] After the first step of discharge fusion, a second fusion operation is added. The discharge adopts the form of long time and small power discharge, and the step of the Z-axis motor is set to further increase the fiber overlap and reinforce the fiber fusion point.

[0047] The thermal fusion method of the fiber provided in embodiment 1 can realize lower fusion loss under the premise of ensuring low return loss of the fusion point.

[0048] Embodiment 2:

[0049] Embodiment 2 provides an optical waveguide adapter, which comprises a solid core fiber and a hollow core fiber, and the solid core fiber and the hollow core fiber are fused by the thermal fusion method of the fiber as described in embodiment 1.

[0050] For example:

[0051] (1) Thermal fusion of a single mode fiber and a hollow core fiber;

[0052] (2) Thermal fusion of a thermal expansion core single mode fiber and a hollow core fiber;

[0053] (3) Thermal fusion of a reverse taper single mode fiber and a hollow core fiber;

[0054] (4) After the single-mode optical fiber is fused to the transition optical fiber, the end side of the transition optical fiber is heat fused to the hollow-core optical fiber.

[0055] Since the solid-core optical fiber and the hollow-core optical fiber in the optical waveguide adapter provided by the embodiment 2 are fused by the heat fusion method of the optical fiber as described in the embodiment 1, the embodiment 2 can be understood by referring to the description of the embodiment 1, and the description is not repeated here.

[0056] In summary, the present application provides a heat fusion technology of a non-axial parallel hollow-core optical fiber and a solid-core optical fiber, which can simultaneously obtain a lower return loss and a fusion loss. Meanwhile, the present application is also a non-coating type inclined angle hollow-core optical fiber and inclined angle solid-core optical fiber fusion technology, which not only simplifies the fusion process, but also can obtain a lower return loss.

[0057] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A method for thermally welding optical fibers, characterized in that: The following steps are involved: Performing bevel cutting on the solid core optical fiber and the hollow core optical fiber respectively, so that the solid core optical fiber has a first bevel cutting angle and the hollow core optical fiber has a second bevel cutting angle, wherein the first bevel cutting angle is smaller than the second bevel cutting angle; A solid core optical fiber having a first bevel angle and a hollow core optical fiber having a second bevel angle are thermally fused.

2. The optical fiber thermal fusion splicing method according to claim 1, wherein: The solid core optical fiber is a single-mode optical fiber, and the mode field diameter of the hollow core optical fiber is larger than the mode field diameter of the single-mode optical fiber.

3. The optical fiber thermal fusion splicing method according to claim 1, wherein: The solid core optical fiber is one of a thermally expanded core single-mode optical fiber, a reverse tapered single-mode optical fiber, and a single-mode optical fiber fusion-splicing transition optical fiber; when the solid core optical fiber is a single-mode optical fiber fusion-splicing transition optical fiber, the end side where the transition optical fiber is located is thermally fused with the hollow core optical fiber.

4. The optical fiber thermal fusion splicing method according to claim 3, wherein: The transition optical fiber is a graded-refractive-index optical fiber.

5. The optical fiber thermal fusion splicing method according to claim 1, wherein: Thermal welding is performed using a two-step welding method.

6. The optical fiber thermal fusion splicing method according to claim 5, characterized in that: The discharge parameters during the initial fusion splicing include the first time, the first power, and the first fiber overlap. The first time is 1-3s, the first power is 1900-3000bit, and the first fiber overlap is 10-20μm. The discharge parameters during the secondary fusion splicing include the second time, the second power, and the second fiber overlap. The second time is 3-6s, the second power is 1300-1800bit, and the second fiber overlap is 1-5μm.

7. The optical fiber thermal fusion splicing method according to claim 1, wherein: The first bevel angle is determined according to the requirement on return loss, and the range of the first bevel angle is 1° to 6°.

8. The optical fiber thermal fusion splicing method according to claim 1, wherein: After aligning the claddings of the solid core optical fiber and the hollow core optical fiber and before discharge welding, the method further includes: performing displacement correction in the oblique angle direction so that the core beam propagation direction of the oblique solid core optical fiber coincides with the optical axis direction of the oblique hollow core optical fiber.

9. The optical fiber thermal fusion splicing method according to claim 8, characterized in that: With the goal of obtaining the lowest fusion loss, the optimal bevel angle and optimal displacement correction amount of the hollow-core optical fiber are determined; the optimal bevel angle is used as the second bevel angle, and displacement correction is performed in the bevel direction according to the optimal displacement correction amount.

10. An optical waveguide adapter comprising a solid core optical fiber and a hollow core optical fiber, characterized in that: The solid core optical fiber and the hollow core optical fiber are fusion-spliced ​​using the optical fiber thermal fusion splicing method according to any one of claims 1 to 9.

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