Optical fiber fixing member and optical connector using the same

Abstract

To provide an optical fiber connector that suppresses a load generated in optical fiber even when the optical connector becomes high temperature.SOLUTION: An optical connector is constituted by using an optical fiber fixing member having an enclosure part into which optical fiber is inserted and that covers an outer peripheral surface of the optical fiber, and a loading part on which the optical fiber is loaded so as not to cover a half circumference or more of the outer peripheral surface of the optical fiber. Fixing of the optical fiber is performed using a fixing agent on the loading part, and no fixing agent is present in the enclosure part.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an optical connector to be provided in an optical fiber that transmits high-energy light such as laser light, and more particularly to components that constitute the optical connector. [Background technology]

[0002] 2. Description of the Related Art Optical fiber cables that transmit high-energy light are used to transmit laser light output from a laser light source to a target location in the field of laser processing, such as laser cutting and laser welding.

[0003] Optical connectors provided on optical fiber cables used in such fields are required to be free from burnout caused by laser light leaking from the optical fiber, and one example is the optical connector described in Patent Document 1.

[0004] In the optical connector of Patent Document 1, the optical fiber is bonded to the ferrule with a low refractive index adhesive that has a refractive index lower than that of the optical fiber, thereby preventing laser light from being emitted from the outer surface of the optical fiber and preventing burning and damage to the components that make up the optical fiber connector.

[0005] However, because high-energy laser light is transmitted, the optical fiber and optical connector reach high temperatures, causing thermal expansion of the optical fiber, the components of the optical connector, and the adhesive. At this time, a load is placed on the optical fiber due to thermal expansion at the adhesive-fixed portion of the optical fiber, which increases distortion in the optical fiber and can cause damage to the optical fiber itself, or can cause burning due to increased leakage of laser light.

[0006] Prior art techniques for suppressing temperature rise in optical fibers and optical connectors include cooling using coolant, as in Patent Document 2, but these techniques pose problems such as the increase in size of the optical connector and the complexity of its structure. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 9-61669 [Patent Document 2] Special publication 2000-514930 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide an optical connector that suppresses the load generated in the optical fiber even at high temperatures, without complicating the structure of the optical connector. [Means for solving the problem]

[0009] As a result of careful consideration of the structure of optical connectors, the inventors have devised a structure for the optical fiber fixing member that directly contacts the optical fiber within the optical connector and fixes the optical fiber, thereby achieving an optical connector that suppresses the load on the optical fiber and also contributes to suppressing temperature rise.

[0010] The optical fiber fixing member of the present invention is characterized by having an enclosing portion through which the optical fiber is inserted and which covers the outer surface of the optical fiber, and a loading portion on which the optical fiber is loaded so as not to cover more than half of the outer surface of the optical fiber. [Effects of the Invention]

[0011] The optical fiber fixing component of the present invention is expected to have the excellent effect of alleviating stresses generated in the optical fiber even at high temperatures, thereby suppressing adverse effects on the optical fiber. [Brief explanation of the drawings]

[0012] [Figure 1] This is the basic structure of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the thermal expansion of a fixing agent. [Figure 3] This is a preferred embodiment of the present invention. [Figure 4] This is an example of a specific structure of the present invention. [Figure 5] 1 is a view showing an optical connector according to the present invention in the process of being assembled; [Figure 6] 1 is an optical connector using the present invention. [Figure 7] These are the results of the heating test. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will now be described with reference to FIG.

[0014] As shown in Fig. 1, the optical fiber fixing member 1 of the present invention has an enclosing part 10 through which an optical fiber 100 is inserted and which covers the outer peripheral surface of the optical fiber 100, and a loading part 20 on which the optical fiber 100 is loaded. Fig. 1(a) is a radial cross-sectional view when Fig. 1(b) is viewed from the left side, and Fig. 1(c) is a radial cross-sectional view when Fig. 1(b) is viewed from the right side.

[0015] The outer shape of the enclosure 10 is not particularly limited as long as it has a through hole 13 for inserting the optical fiber 100, but it may be formed into a cylindrical shape that is typically used in components that make up various optical connectors.

[0016] Usually, the through-hole 13 is formed in the center of the surrounding portion 10 in a radial cross section.

[0017] The loading section 20 is formed so as not to cover more than half of the outer circumferential surface of the optical fiber 100, and may be formed in a semicircular groove or a flat surface, which will be described later.

[0018] The surrounding portion 10 covers the outer peripheral surface of the optical fiber 100, thereby restricting radial movement of the optical fiber 100 on the optical fiber fixing member 1 and enabling the optical fiber 100 to be fixed near the central axis of the optical fiber fixing member 1.

[0019] In the loading section 20, the amount of the outer surface of the optical fiber 100 covered by the optical fiber fixing member 1 is smaller than in the enclosing section 10, so if any undesirable effect on the optical fiber 100 occurs due to being covered by the optical fiber fixing member 1, the effect can be suppressed.

[0020] From the viewpoint of reducing the influence of the optical fiber fixing member 1 on the optical fiber 100, it is preferable to form the loading section 20 in a planar shape. The optical fiber 100 loaded on the planar loading section 20 comes into contact with the loading section 20 in a state close to line contact, so that the contact area between the optical fiber fixing member 1 and the optical fiber 100 is reduced, which contributes to suppressing the influence of the optical fiber fixing member 1 on the optical fiber 100.

[0021] When fixing the optical fiber 100 to the optical fiber fixing member 1, a fixing agent 30 such as an adhesive may be used, but when fixing the optical fiber 100 using the fixing agent 30, it is preferable to fix it on the loading section 20.

[0022] When the optical fiber 100 is fixed using the fixing agent 30, the optical fiber 100 is often fixed in a state in which the outer peripheral surface of the optical fiber 100 is covered with the fixing agent 30 in order to obtain sufficient fixing strength.

[0023] In the portion where the outer surface of the optical fiber 100 is covered with the fixing agent 30, stress is generated in the optical fiber 100 due to thermal expansion of the fixing agent 30 at high temperatures, which may adversely affect optical transmission or cause damage to the optical fiber 100.

[0024] By fixing the optical fiber 100 using the loading section 20, which is configured so as not to cover more than half of the outer surface of the optical fiber 100, there is created room for the fixing agent 30 to thermally expand radially outward of the optical fiber 100, as shown in Figure 2, which reduces stress on the optical fiber 100 and suppresses adverse effects occurring to the optical fiber 100.

[0025] On the other hand, it is preferable that the fixing agent 30 is not present in the surrounding portion 10. Because the surrounding portion 10 covers the entire outer peripheral surface of the optical fiber 100, if the fixing agent 30 is present, there is little room for the fixing agent 30 to thermally expand radially outward of the optical fiber 100, and stress on the optical fiber 100 tends to increase.

[0026] The absence of fixing agent 30 in the enclosing portion 10 creates play between the outer surface of the optical fiber 100 and the inner surface of the enclosing portion 10, thereby alleviating the stress on the optical fiber 100 that occurs due to thermal expansion of the optical fiber 100 and the enclosing portion 10.

[0027] In addition, it is preferable to form a recess 21 near the boundary between the surrounding portion 10 and the loading portion 20 as shown in FIG.

[0028] When the optical fiber 100 is fixed to the loading section 20 via the fixing agent 30, there is a possibility that the fixing agent 30 will penetrate into the small gap between the optical fiber 100 and the loading section 20 due to capillary action, and the fixing agent 30 will infiltrate into the surrounding section 10.

[0029] By forming a recess 21 near the boundary between the enclosing section 10 and the loading section 20, the fixing agent 30 can escape into the recess 21 before reaching the enclosing section 10, thereby preventing the fixing agent 30 from unintentionally penetrating into the enclosing section 10.

[0030] 3 shows the case where the recess 21 is provided in front of the surrounding part 10, the location of the recess 21 is not limited to this position, and it may be formed in a position that can prevent the fixing agent 30 from penetrating into the surrounding part 10. Specific shapes of the recess 21 include a rectangular groove perpendicular to the length direction of the optical fiber fixing member 1, a round hole provided in the loading part 20, and the like.

[0031] The optical fiber fixing member 1 of the present invention is a member intended to hold an optical fiber 100 inside an optical connector as a component of the optical connector, and is preferably designed to be used as a component of the optical connector.

[0032] As an embodiment intended for use as a component of an optical connector, there is an embodiment shown in FIG. 3 in which engaging means 40 capable of engaging and fixing other members is formed on the outer peripheral surface of the enclosure 10.

[0033] Other members that can be engaged and fixed to the optical fiber fixing member 1 include a housing member that forms the outer shell of the optical connector, and a sleeve member that fixes a protective tube for the optical fiber 100 when constructing an optical fiber cable.

[0034] The engaging means 40 is preferably one that can engage and fix the optical fiber fixing member 1 and another member so that a gap is formed between them.

[0035] The present invention is intended to be used in an environment where the optical fiber 100 becomes hot, such as for laser light transmission applications. In such an environment, other components engaged and fixed to the optical fiber fixing member 1 also become hot, and it is expected that this heat will be transmitted to the optical fiber fixing member 1 and the optical fiber 100.

[0036] When laser light is being transmitted through the optical fiber 100, the optical fiber 100 and the optical fiber fixing member 1 are already at high temperatures, so it is preferable to suppress heat transfer from surrounding members as much as possible. In particular, parts located closer to the tip of the optical fiber 100 than the optical fiber fixing member 1, such as the ferrule fixing member 230 and the housing member 250 used in the examples described below, are particularly likely to become hot because they absorb laser light leaking from the exposed cladding portion and laser light not coupled to the optical fiber 100. By suppressing heat transfer from these members, the effects of high temperatures on the optical fiber fixing member 1 can be effectively suppressed.

[0037] By adopting an engagement means 40 that forms a gap between the optical fiber fixing member 1 and another member, the gap acts as a heat insulating layer, and heat transfer from other members to the optical fiber fixing member 1, particularly from members existing between the optical fiber fixing member 1 and the tip of the optical fiber 100, can be suppressed.

[0038] A specific example of the engaging means 40 is a screwing means. When using a screwing means, it is sufficient to form a male thread on the outer peripheral surface of the enclosure portion 10 and a female thread on the other member, which is easy to form and also has excellent heat insulating properties because multiple minute gaps are formed in the screwing portion.

[0039] The screwing means is a preferred engagement means 40 in that when assembling an optical connector using the optical fiber fixing member 1 of the present invention, it is possible to align the optical fiber 100 within the optical connector by adjusting the screwing, and it is also possible to prevent the position from shifting unexpectedly after alignment.

[0040] Although FIG. 3 shows a case where the engaging means 40 (screw means) is provided only around the periphery of the surrounding portion 10, the engaging means 40 may be provided over the entire length of the optical fiber fixing member 1.

[0041] 4, the optical fiber fixing member 1 of the present invention may have, as the surrounding portion 10, a first surrounding portion 11 formed on one end side of the loading portion 20 and a second surrounding portion 12 formed on the other end side of the loading portion 20. By covering the outer peripheral surface of the optical fiber 100 at two points, the first surrounding portion 11 and the second surrounding portion 12, the optical fiber 100 can be more stably fixed near the central axis of the optical fiber fixing member 1.

[0042] When forming the first surrounding portion 11 and the second surrounding portion 12, the inner diameters of the first surrounding portion 11 and the second surrounding portion 12 may be different. For example, the inner diameter of the first surrounding portion 11 may be set to a dimension corresponding to the outer diameter of the cladding of the optical fiber 100, and the inner diameter of the second surrounding portion 12 may be set to a dimension corresponding to the outer diameter of the protective coating layer of the optical fiber 100, so that the first surrounding portion 11 covers the exposed cladding portion of the optical fiber 100, and the second surrounding portion 12 covers the outer periphery of the protective coating layer. Furthermore, even when both the first enclosure 11 and the second enclosure 12 cover the outer periphery of the protective coating layer of the optical fiber 100, the enclosure covering the tip side of the optical fiber 100 has a dimension equivalent to the outer diameter of the protective coating layer, and the enclosure covering the side of the optical fiber 100 toward the other end has a dimension that allows for a sufficient gap to be formed relative to the outer diameter of the protective coating layer, so that the optical fiber 100 is held near the central axis of the optical fiber fixing member 1 on the tip side, while the gap is expected to alleviate the load generated when the optical fiber 100 is bent on the other end side.

[0043] When forming the first surrounding portion 11 and the second surrounding portion 12, it is also preferable that the fixing agent 30 is not present in each surrounding portion. In order to prevent the fixing agent 30 from penetrating into each surrounding portion, it is preferable to provide a first recess 211 corresponding to the first surrounding portion 11 and a second recess 212 corresponding to the second surrounding portion 12. When providing the engaging means 40, it may be provided in both the first surrounding portion 11 and the second surrounding portion 12, or only one of them, as necessary.

[0044] As described above, the optical fiber fixing member 1 of the present invention can be preferably used when laser light is input into the optical fiber 100 and the optical fiber 100 and its surroundings become hot, and can be suitably used as one of the components that make up the optical connector provided at the end of an optical fiber cable for transmitting laser light. [Example]

[0045] As an embodiment of the present invention, an optical connector 200 using the optical fiber fixing member 1 of the present invention will be produced below.

[0046] [Example 1] In Example 1, an optical connector 200 is constructed using an optical fiber 100 having a core diameter of 105 μm, a cladding diameter of 125 μm, and an outer diameter of the protective coating layer of 250 μm, fixed to the optical fiber fixing member 1 of the present invention.

[0047] The optical fiber fixing member 1 shown in Fig. 4 was created. Specifically, a semicircular section of 15 mm in length and 2.1 mm in depth was removed from the center of a stainless steel cylindrical member having a length of 25 mm and an outer diameter of 4 mm, forming a flat section that would become the loading section 20. A through-hole 13 was provided in the center of the radial cross section of the cylindrical section remaining at both ends, forming the first surrounding section 11 and the second surrounding section 12.

[0048] The inner diameter of the through-hole 13 was set to 0.5 mm in the first enclosure portion 11 and 1 mm in the second enclosure portion 12.

[0049] At both ends of the loading section 20 (in front of the first surrounding section 11 and the second surrounding section 12), drill holes with a diameter of 2 mm and a maximum depth of 1 mm were provided to form a first recess 211 and a second recess 212.

[0050] The protective coating layer was removed over 45 mm of the tip of the optical fiber 100 to expose the clad, and the exposed clad portion of the optical fiber 100 was inserted from the second enclosure portion 12 side of the optical fiber fixing member 1, causing the exposed clad portion to protrude from the first enclosure portion 11.

[0051] With the tip of the protective coating layer located at the base end of the exposed cladding portion slightly protruding from the first enclosure portion 11, an epoxy-based heat-resistant adhesive was applied as a fixing agent 30 to the protective coating layer of the optical fiber 100 placed on the loading portion 20, and the adhesive was heated and hardened to fix the optical fiber 100 to the loading portion 20 of the optical fiber fixing member 1.

[0052] The fixing agent 30 was applied over a range of approximately 10 mm along the length of the optical fiber 100 located between the recesses 211 and 212. At that time, some of the fixing agent 30 reached the recesses 211 and 212 and accumulated therein, but did not penetrate into the first enclosure portion 11 or the second enclosure portion 12.

[0053] Next, in order to configure the optical connector 200, the optical fiber fixing member 1 and members to be provided around the optical fiber 100 are prepared.

[0054] The ferrule 220 is press-fitted onto the tip of the ferrule fixing member 230, and the outer periphery of the ferrule fixing member 230 is covered with a fixing nut 240 for fixing the optical connector 200 to a predetermined receptacle.

[0055] The optical fiber fixing member 1 was passed through the housing member 250, and the second surrounding portion 12 was temporarily fixed to the inner peripheral surface of the rear end of the housing member 250 so that the first surrounding portion 11 protruded from the front end of the housing member 250.

[0056] While inserting the exposed cladding portion of the optical fiber 100 into the ferrule 220, the rear end of the ferrule fixing member 230 is fitted and fixed to the front end of the housing member 250. After the fitting and fixing are completed, the temporary fixing of the second surrounding portion 12 to the inner peripheral surface of the rear end of the housing member 250 is released, and the front end of the optical fiber 100 is allowed to protrude a predetermined amount from the front end of the ferrule 220, and then temporary fixing is performed again, resulting in the state shown in FIG.

[0057] Once the tip of the optical fiber 100 has been protruded by a predetermined amount, a polishing jig is attached and the tip of the optical fiber 100 is optically polished.

[0058] After optical polishing is completed, the polishing jig is removed, and the second surrounding portion 12 is released from temporary fixation to the inner peripheral surface of the rear end of the housing member 250. The optical fiber fixing member 1 is moved toward the rear end so that the first surrounding portion 11 is positioned on the inner peripheral surface of the rear end of the housing member 250, and then the tip end of the ferrule 220 and the tip end of the optical fiber 100 are aligned so that they are flush with each other.

[0059] After the alignment is completed, the inner peripheral surface of the rear end of the housing member 250 is permanently fixed to the first enclosure portion 11. For the permanent fixation, an epoxy-based heat-resistant adhesive was used as the fixing agent 30.

[0060] Next, the sleeve member 260 is placed over the outer periphery of the rear end of the housing member 250 and the optical fiber fixing member 1 protruding from the rear end of the ferrule fixing member 230, and the tip end of the sleeve member 260 is fixed to the rear end of the housing member 250.

[0061] The optical fiber protection tube 270 is inserted into the rear end of the sleeve member 260 and fixed, completing the optical connector 200 of the first embodiment shown in FIG.

[0062] [Example 2] In Example 2, the optical fiber fixing member 1 of Example 1 is used, but with M4 male screws formed as engagement means 40 (screw engagement means) on the outer surfaces of the first enclosure portion 11 and the second enclosure portion 12, and an optical connector 200 is constructed in the same manner as in Example 1.

[0063] The configuration and assembly method of the optical connector 200 of the second embodiment are the same as those of the first embodiment, but the provision of screwing means in the optical fiber fixing member 1 results in the following changes.

[0064] The housing member 250 has an M4 female screw formed on the inner peripheral surface of the rear end, which can be screwed into the first surrounding portion 11 and the second surrounding portion 12. This allows the optical fiber fixing member 1 and the housing member 250 to be screwed together and fixed.

[0065] By screwing and fixing the optical fiber fixing member 1 and the housing member 250 together, they are naturally temporarily fixed together, and by adjusting the screwed state, the position of the tip of the optical fiber 100 can be adjusted. Therefore, there is no need to perform and release the temporary fixation each time, which contributes to reducing the number of steps in assembling the optical connector 200.

[0066] In addition, since the screwed state can be easily adjusted finely, the adjustment of the amount of protrusion of the tip of the optical fiber 100 and the alignment work to make the tip of the ferrule 220 and the tip of the optical fiber 100 flush can be performed with high precision, making the assembly work of the optical connector 200 easier.

[0067] [Comparative Example] As a comparative example, an optical connector was prepared in the same manner as in Example 1, except that instead of the optical fiber fixing member 1, a stainless steel pipe with an inner diameter of 0.5 mm, an outer diameter of 4 mm, and a length of 15 mm was used, which was fixed to the protective coating layer of the optical fiber 100 with the same fixing agent 30 as used in the example.

[0068] The optical connectors of the example and comparative examples prepared as described above were subjected to the following tests to evaluate their performance.

[0069] [Laser durability test] Laser light was input into the optical fiber 100, and the effect on the optical connector was confirmed.

[0070] The total length of the optical fiber 100 was set to 5 m, and the other end side of the optical fiber 100 (the side where the optical connector was not provided) was subjected to only optical polishing.

[0071] The other end of the optical fiber 100 is connected to a laser light source, and a 200 W laser beam is input to the optical fiber 100 .

[0072] In Comparative Example 1, burnout of the optical fiber 100 occurred at the portion where the stainless steel pipe was fixed. Because the optical fiber 100 was covered over its entire circumference with the fixing agent 30 and the stainless steel pipe, the heat generated by the transmission of the laser light caused each component to thermally expand, and this stress acted on the optical fiber 100, increasing the distortion of the optical fiber 100 and increasing the amount of light leaking from the optical fiber 100, which is thought to have led to the burnout.

[0073] On the other hand, in Examples 1 and 2, no noticeable adverse effects, such as burning of the optical fiber 100, were observed in the portion where the optical fiber fixing member 1 was fixed. Since the entire circumference of the optical fiber 100 is not covered in the loading section 20 where the fixing agent 30 is provided, and the fixing agent 30 is not present in the first surrounding section 11 and the second surrounding section 12, it is believed that the effects of thermal expansion were suppressed and durability against 200 W laser light transmission was obtained.

[0074] [Heating test] The optical connectors 200 of Examples 1 and 2, which were confirmed to be capable of transmitting 200 W laser light, were heated, and the temperature change of the optical fiber fixing member 1 was confirmed.

[0075] A thermocouple for measuring temperature was connected to the fixing agent 30 , and the compensation lead wire was routed through an optical fiber protection tube 270 to a location sufficiently distant from the optical connector 200 .

[0076] An industrial dryer was used to apply hot air at 200° C. to the side of the optical connector 200, and the temperature change of the fixing agent 30 over time was observed. The results are shown in FIG.

[0077] In the optical connector 200 of Example 1, the temperature reached approximately 85°C one minute after the start of the experiment, and approximately 105°C two minutes later. Although this temperature is acceptable for an optical connector 200 to be attached to an optical fiber 100 intended for transmitting laser light, it is believed that the optical fiber 100 will be affected by the sudden temperature rise.

[0078] On the other hand, in the optical connector 200 of Example 2, the temperature reached only about 40°C one minute after the start of the experiment and about 55°C two minutes later, and the rate of temperature rise was slower than in Example 1. Therefore, the effect of the temperature rise on the optical fiber 100 was mitigated, and the optical connector 200 can be evaluated as an embodiment that can be particularly preferably used in laser applications where heat is generated. [Industrial Applicability]

[0079] The optical fiber fixing member of the present invention is suitable for use in laser light transmission applications in processing machines and devices that use laser light, such as laser cutting machines and laser welding machines, but its applications are not limited to these, and it can also be used suitably in optical fiber cables that transmit high energy other than laser light, and optical fiber cables used in high-temperature environments. [Explanation of symbols]

[0080] 1 Optical fiber fixing member 10 Encirclement 11 First Encirclement 12 Second Encirclement 13 Through hole 20 Loading section 21 Recess 211 First recess 212 Second recess 30 Fixative 40 Engagement means 100 optical fiber 200 Optical Connector 220 ferrule 230 Ferrule fixing member 240 Fixing nut 250 Housing material 260 Sleeve member 270 Optical fiber protection tube

Claims

1. An optical fiber assembly having an optical fiber fixing member used to fix an optical fiber, the optical fiber assembly including the optical fiber, the optical fiber fixing member, and a fixing agent for fixing the optical fiber to the optical fiber fixing member; the optical fiber fixing member has an enclosing portion through which the optical fiber is inserted and which covers an outer peripheral surface of the optical fiber, and a loading portion on which the optical fiber is loaded so as not to cover more than half of the outer peripheral surface of the optical fiber; the surrounding portion has a first surrounding portion formed on one end side of the loading portion and a second surrounding portion formed on the other end side of the loading portion, the optical fiber is fixed on the loading section using the fixing agent; The optical fiber assembly is characterized in that the fixing agent is not present in the surrounding portion.

2. 2. The optical fiber assembly according to claim 1, wherein the loading portion is formed in a flat shape.

3. 3. The optical fiber assembly according to claim 1, wherein the first surrounding portion and the second surrounding portion have different inner diameters.

4. 4. The optical fiber assembly according to claim 1, wherein a recess is formed near the boundary between the surrounding portion and the loading portion.

5. 5. The optical fiber assembly according to claim 1, wherein an engaging means is formed on the outer peripheral surface of the surrounding portion, which can engage and fix the optical fiber fixing member to another member.

6. 6. The optical fiber assembly of claim 5, wherein said engaging means is a threaded engaging means.

7. An optical fiber assembly as described in claim 6, characterized in that a plurality of tiny gaps are formed in the threaded portion of the threaded means.

8. The optical fiber assembly according to any one of claims 1 to 7, which is used for transmitting laser light.

9. An optical connector using the optical fiber assembly according to any one of claims 1 to 8, the optical connector having the optical fiber assembly, a housing member, and a ferrule, and the first surrounding portion of the optical fiber fixing member is formed so as to be positioned on the inner surface of the rear end of the housing member.

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