Optical connector plug

Abstract

An optical connector plug 1 has a plug frame 3 and a ferrule 4 inserted into the plug frame 3. On an outer peripheral surface of a flange part 43 of the ferrule 4, first and second flange part-side flat surfaces 431a, 431b disposed to face third and fourth sides 3c, 3d, and first and second grooves 432a, 432b recessed toward a central axis J are formed. On an inner peripheral surface 34 of the plug frame 3, first and second plug frame-side flat surfaces 341a, 341b disposed to face the first and second flange part-side flat surfaces 431a, 431b, and first and second projections 342a, 342b projecting toward the central axis J and inserted into the first and second grooves 432a, 432b are formed.

Description

Optical Connector Plug CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority based on Japanese Patent Application No. 2024-103672 (titled "Optical Connector Plug"), filed on June 27, 2024, the contents of which are incorporated herein by reference in their entirety.

[0002] The present invention relates to an optical connector plug.

[0003] For example, Patent Document 1 discloses an optical connector plug for holding a multi-fiber having multiple cores. An SC connector 9 incorporating this optical connector plug may include, for example, a ferrule 92 for holding an optical fiber 91 and a plug frame 93 for accommodating the ferrule 92, as shown in FIG. 1 . Note that FIG. 1 does not illustrate a "tab" included in the SC connector (the same applies to FIG. 2 , which will be described later). A pair of protrusions 931 a, 931 b are disposed opposite each other on the inner circumferential surface of the plug frame 93, and a pair of grooves 921 a, 921 b are formed on the outer circumferential surface of a flange portion 920 of the ferrule 92, into which the protrusions 931 a, 931 b fit. By engaging the protrusions 931 a, 931 b with the grooves 921 a, 921 b, rotation of the ferrule 92 relative to the plug frame 93 is restricted.

[0004] 1 , when the protrusions 931a and 931b are formed on the portions Qa and Qb located at 0° and 180° angles of the plug frame 93, the thickness of the portions Qa and Qb is increased by the protrusions 931a and 931b, making it less likely that the strength of the plug frame 93 will be insufficient. In contrast, for example, when the protrusions 931a and 931b are formed on the portions located at 45° rotated from the position shown in FIG. 1 , i.e., at 45° and 225° angles of the plug frame 93, as shown in FIG. 2 , the thickness of the portions Qa and Qb becomes thinner, causing the strength of the plug frame 93 to be insufficient. This reduces the reliability of the SC connector 9.

[0005] Patent No. 7047221 Public Relations

[0006] SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the prior art, and an object of the present invention is to provide an optical connector plug that has sufficient strength and high reliability.

[0007] Such an object can be achieved by the present invention as defined by the following (1).

[0008] (1) A plug frame having a cylindrical plug frame and a ferrule inserted into the plug frame, wherein the ferrule has a base portion for holding an optical fiber and a flange portion protruding to an outer circumferential side of the base portion, wherein, in a plan view from a direction along a central axis of the ferrule, axes that intersect with the central axis and are orthogonal to each other are defined as an X-axis and a Y-axis, and further, a direction along the X-axis is defined as an X-axis direction, and a direction along the Y-axis is defined as a Y-axis direction, the plug frame, in a cross section that is orthogonal to the central axis and overlaps with the flange portion, has: a first side and a second side that are aligned in the Y-axis direction and both extend in the X-axis direction, and a third side and a fourth side that are aligned in the X-axis direction and both extend in the Y-axis direction, and the plug frame has an outer peripheral surface whose width in the X-axis direction, which is a distance between the third side and the fourth side, is shorter than the width in the Y-axis direction, which is a distance between the first side and the second side; and a circular inner peripheral surface that surrounds the flange portion and has an inner diameter greater than an outer diameter of the flange portion. an outer peripheral surface of the flange portion formed with a first flange portion-side flat surface arranged opposite the third side, a second flange portion-side flat surface arranged opposite the fourth side, a first groove recessed toward the central axis, and a second groove facing the first groove across the central axis and recessed toward the central axis; and an inner peripheral surface of the plug frame formed with a first plug frame-side flat surface arranged opposite the first flange portion-side flat surface, a second plug frame-side flat surface arranged opposite the second flange portion-side flat surface, a first protrusion protruding toward the central axis and inserted into the first groove, and a second protrusion protruding toward the central axis and inserted into the second groove.

[0009] In the optical connector plug of the present invention, the inner peripheral surface of the plug frame is formed with a first plug frame-side flat surface facing the first flange-side flat surface and a second plug frame-side flat surface facing the second flange-side flat surface. This makes it easier to ensure the thickness between the third side and the first plug frame-side flat surface and the thickness between the fourth side and the second plug frame-side flat surface. Therefore, the optical connector plug of the present invention has sufficient strength and can exhibit high reliability.

[0010] Furthermore, in the optical connector plug of the present invention, the engagement of the first and second grooves with the first and second protrusions restricts rotation of the ferrule about the central axis relative to the plug frame, making the optical connector plug of the present invention particularly suitable for holding optical fibers that have directionality about the central axis, such as multi-core fibers.

[0011] FIG. 1 is a cross-sectional view showing an example of an SC connector to which conventional technology is applied. FIG. 2 is a cross-sectional view showing an example of an SC connector to which conventional technology is applied. FIG. 3 is a perspective view showing an optical connector plug according to a first embodiment. FIG. 4 is a cross-sectional view of an optical fiber held by the optical connector plug. FIG. 5 is an exploded perspective view of the optical connector plug. FIG. 6 is a cross-sectional view taken along the central axis of the optical connector plug. FIG. 7 is a perspective view of a ferrule provided in the optical connector plug. FIG. 8 is a cross-sectional view taken along line A-A in FIG. 6. FIG. 9 is a cross-sectional view taken along line B-B in FIG. 6. FIG. 10 is a cross-sectional view showing the shapes of the first and second protrusions. FIG. 11 is a cross-sectional view showing a conventional configuration. FIG. 12 is a cross-sectional view showing a modified example in which the positions of the first and second protrusions are different. FIG. 13 is a cross-sectional view showing the free movement of the ferrule relative to the plug frame. FIG. 14 is a cross-sectional view showing a modified example of the first and second protrusions. FIG. 15 is a cross-sectional view showing a modified example of the first and second protrusions. FIG. 16 is a cross-sectional view showing a modified example of the first and second protrusions. FIG. 17 is a cross-sectional view showing two optical connector plugs connected by an optical connector adapter. FIG. 18 is a cross-sectional view showing an optical connector plug according to the second embodiment.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical connector plug of the present invention will now be described in detail with reference to preferred embodiments shown in the accompanying drawings.

[0013] <First Embodiment> Fig. 3 is a perspective view showing an optical connector plug according to the first embodiment. Fig. 4 is a cross-sectional view of an optical fiber held by the optical connector plug. Fig. 5 is an exploded perspective view of the optical connector plug. Fig. 6 is a cross-sectional view taken along the central axis of the optical connector plug. Fig. 7 is a perspective view of a ferrule included in the optical connector plug. Fig. 8 is a cross-sectional view taken along line A-A in Fig. 6. Fig. 9 is a cross-sectional view taken along line B-B in Fig. 6. Fig. 10 is a cross-sectional view showing the shapes of the first and second protrusions. Fig. 11 is a cross-sectional view showing a conventional configuration. Fig. 12 is a cross-sectional view showing a modified example in which the positions of the first and second protrusions are different. Fig. 13 is a cross-sectional view showing the free movement of the ferrule relative to the plug frame. Figs. 14 to 16 are cross-sectional views showing modified examples of the first and second protrusions, respectively. Fig. 17 is a cross-sectional view showing two optical connector plugs connected by an optical connector adapter.

[0014] 3 is a connector for holding an optical fiber 8, and is an F04 type optical fiber connector, a so-called "SC connector," specified in JIS C 5973. However, the optical connector plug 1 is not particularly limited, and may be configured in accordance with standards other than the SC connector, such as an SC2 connector, an LC connector, an FC connector, or an ST connector, or may have a non-standard configuration.

[0015] The optical fiber 8 held in the optical connector plug 1 is not particularly limited, but for example, as shown in FIG. 4 , a so-called "multi-core fiber" in which multiple cores 82 are covered with a cladding 81 can be suitably used. This is because, as will be described later, the optical connector plug 1 can restrict the rotation of the optical fiber 8. In FIG. 4 , four cores 82 are arranged on the same circumference centered on the central axis of the cladding 81 at equal intervals, i.e., 90° intervals. However, the number of cores 82 is not particularly limited and may be, for example, two, three, or five or more. Furthermore, the optical fiber 8 is not limited to a multi-core fiber, and may be a so-called "single-core fiber" in which one core 82 is covered with a cladding 81, and the single-core fiber may be a polarization-maintaining fiber.

[0016] As shown in FIGS. 5 and 6, the optical connector plug 1 mainly includes a tab 21, a plug frame 3, a ferrule 4, a spring 22, a stop ring 23, and a boot 24.

[0017] Of these, the plug frame 3 is inserted into the cylindrical knob 21 from the base end side. The knob 21 is slidable relative to the plug frame 3 in a direction along the central axis J of the ferrule 4. The ferrule 4 holds the tip end (one end) of the optical fiber 8 and is inserted into the cylindrical plug frame 3. The tip end of the ferrule 4 protrudes from the tip end surface of the plug frame 3. The stop ring 23 is cylindrical and inserted into the plug frame 3 from the base end side, and is located immediately proximal to the ferrule 4. The spring 22 is positioned in a contracted state between the ferrule 4 and the stop ring 23 and urges the ferrule 4 toward the tip end side. The boot 24 is flexible and covers necessary areas of the optical connector plug 1.

[0018] The overall configuration of the optical connector plug 1 has been briefly described above. However, the configuration of the optical connector plug 1 is not particularly limited as long as it meets the SC connector standard. Among the above-mentioned components, the optical connector plug 1 is particularly characterized by the plug frame 3 and the ferrule 4. Therefore, the plug frame 3 and the ferrule 4 will be described in detail below.

[0019] First, a description will be given of the ferrule 4. As shown in Figures 6 and 7, the ferrule 4 has a base 40 equipped with a capillary 41 and a pipe 42, and a flange 43 that protrudes from the outer circumferential surface of the base 40 and has a larger diameter than the base 40.

[0020] The capillary 41 has a cylindrical shape extending along the central axis J and constitutes the tip of the ferrule 4 (base 40). The capillary 41 also has a linear hole 411 formed along the central axis J that penetrates both end faces. The end of the optical fiber 8 is inserted into the hole 411, and the capillary 41 and the optical fiber 8 are adhesively fixed together. The capillary 41 is made of zirconia and has high strength. However, the constituent material and shape of the capillary 41 are not particularly limited as long as they comply with the SC connector standard.

[0021] The pipe 42 has a cylindrical shape extending along the central axis J and constitutes the base end of the ferrule 4 (base portion 40). The pipe 42 also has a base end 421 and a tip end 422 whose inner and outer diameters are both larger than those of the base end 421. Therefore, a stepped surface 423 facing the tip side is formed at the boundary between the base end 421 and the tip end 422 on the inner circumferential surface of the pipe 42. The pipe 42 also has a ring-shaped (annular) positioning protrusion 424 protruding from the outer circumferential surface of the tip end 422. The positioning protrusion 424 functions as a positioning portion for positioning the flange portion 43 relative to the pipe 42.

[0022] The inner diameter of the tip portion 422 is slightly smaller than the outer diameter of the capillary 41, and the base end of the capillary 41 is press-fitted into the tip portion 422. This allows the capillary 41 and the pipe 42 to be easily fixed together. Furthermore, when press-fitting the capillary 41, the base end face of the capillary 41 is abutted against the step face 423, thereby allowing the insertion amount (insertion depth) of the capillary 41 into the pipe 42 to be easily controlled. However, the method for fixing the capillary 41 and the pipe 42 is not particularly limited, and they may be fixed together using an adhesive, for example. Furthermore, a gap may be provided between the base end face of the capillary 41 and the step face 423, and the insertion depth may be adjusted using a jig or the like.

[0023] The pipe 42 is made of stainless steel and has high strength, but the material and shape of the pipe 42 are not particularly limited as long as they comply with the SC connector standard.

[0024] The flange portion 43 has a short annular shape extending along the central axis J. The inner diameter of the flange portion 43 is slightly smaller than the outer diameter of the tip end 422 of the pipe 42, and the flange portion 43 is press-fitted into the tip end 422 of the pipe 42. This allows the pipe 42 and the flange portion 43 to be easily fixed together. When press-fitting the flange portion 43, the flange portion 43 can be abutted against a positioning protrusion 424 formed on the pipe 42, thereby easily controlling the position of the flange portion 43 relative to the pipe 42. However, the method for fixing the pipe 42 and the flange portion 43 is not particularly limited, and they may be fixed together using an adhesive, for example.

[0025] As shown in FIG. 7 , the flange portion 43 has a first flange-side flat surface 431a and a second flange-side flat surface 431b formed by cutting a portion of the circular outer circumferential surface flat. The first and second flange-side flat surfaces 431a and 431b have the same shape and are arranged opposite each other across the central axis J. That is, the first and second flange-side flat surfaces 431a and 431b are formed symmetrically with respect to the central axis J. The flange portion 43 also has a first groove 432a and a second groove 432b formed on the outer circumferential surface. The first and second grooves 432a and 432b have the same shape and are both rectangular grooves recessed toward the central axis J. The first and second grooves 432a and 432b are arranged opposite each other across the central axis J. That is, the first and second grooves 432a and 432b are formed symmetrically with respect to the central axis J.

[0026] As shown in FIG. 8 , in a plan view from the direction along the central axis J, two axes that intersect the central axis J and are perpendicular to each other are defined as the X-axis and the Y-axis. Furthermore, when the positive side (the side indicated by the arrow) of the X-axis is defined as 0°, the positive side (the side indicated by the arrow) of the Y-axis is defined as 90°, the negative side (the side opposite the arrow) of the X-axis is defined as 180°, and the negative side (the side opposite the arrow) of the Y-axis is defined as 270°, the first flange-side flat surface 431a is formed at the 0° position of the flange portion 43, and the second flange-side flat surface 431b is formed at the 180° position of the flange portion 43. In other words, the first and second flange-side flat surfaces 431a, 431b are arranged side by side in the X-axis direction. Furthermore, the first groove 432a is formed at the 45° position of the flange portion 43, and the second groove 432b is formed at the 225° position of the flange portion 43.

[0027] The flange portion 43 as described above is made of stainless steel and has high strength, but the material of which the flange portion 43 is made is not particularly limited.

[0028] The ferrule 4 has been described above. However, the ferrule 4 is not limited to the above-described configuration as long as it complies with the SC connector standard. For example, in the above-described configuration, the capillary 41, the pipe 42, and the flange portion 43 are each formed separately and then combined to form the ferrule 4. However, this is not limited to this configuration, and two or more members arbitrarily selected from the capillary 41, the pipe 42, and the flange portion 43 may be integrally formed. Specifically, the capillary 41 and the pipe 42 may be integrally formed and the flange portion 43 may be fixed thereto, or the pipe 42 and the flange portion 43 may be integrally formed and the capillary 41 may be fixed thereto, or the capillary 41, the pipe 42, and the flange portion 43 may be integrally formed.

[0029] Next, a description will be given of the plug frame 3. The plug frame 3 is made of various resin materials such as PBT (polybutylene terephthalate) and is formed by injection molding. However, the constituent material and forming method of the plug frame 3 are not particularly limited.

[0030] 5 , the plug frame 3 is cylindrical with a rectangular outer peripheral surface and a circular inner peripheral surface, and the ferrule 4 is inserted into the plug frame 3. When the ferrule 4 is inserted into the plug frame 3, the tip of the ferrule 4 protrudes from the plug frame 3 and is exposed to the outside of the plug frame 3.

[0031] 6 , a wall portion 31 is formed on the inner peripheral surface of the plug frame 3, located closer to the tip end than the flange portion 43, and an insertion hole for inserting the capillary 41 of the ferrule 4 is formed in the wall portion 31. The inner diameter of the insertion hole is larger than the outer diameter of the capillary 41 and smaller than the outer diameter of the flange portion 43. Therefore, the flange portion 43 abuts against the wall portion 31, preventing the ferrule 4 from moving further toward the tip end of the plug frame 3.

[0032] 8 shows a cross section taken along line A-A in Fig. 6, that is, a cross section on the X-Y plane located immediately behind the mechanical reference plane F0 of the optical connector plug 1 and intersecting with the flange portion 43. In this cross section (hereinafter also referred to as "cross section F"), the outer peripheral surface of the plug frame 3 is located on the positive side in the Y-axis direction, and is a substantially rectangular shape with two adjacent corners in the X-axis direction chamfered by C-chamfers. Specifically, in cross section F, the outer peripheral surface of the plug frame 3 has a first side 3a and a second side 3b aligned in the Y-axis direction and both extending in the X-axis direction, a third side 3c and a fourth side 3d aligned in the X-axis direction and both extending in the Y-axis direction, a fifth side 3e connecting adjacent ends of the first side 3a and the third side 3c and inclined at approximately 45° with respect to the first and third sides 3a and 3c, and a sixth side 3f connecting adjacent ends of the first side 3a and the fourth side 3d and inclined at approximately 45° with respect to the first and fourth sides 3a and 3d. Furthermore, the width Wx of the plug frame 3 in the X-axis direction in cross section F (the distance between the third side 3c and the fourth side 3d) is smaller than the width Wy in the Y-axis direction (the distance between the first side 3a and the second side 3b). In other words, Wx<Wy, and the plug frame 3 in cross section F has a flattened shape in the X-axis direction.

[0033] 9 shows a cross-sectional view taken along line B-B in FIG. 6. As shown in the figure, the plug frame 3 has an outer shape similar to that of cross section F, even at the tip portion 30 located distally of the mechanical reference plane F0. That is, the outer peripheral surface of the tip portion 30 has a first side 30a and a second side 30b aligned in the Y-axis direction and both extending in the X-axis direction, a third side 30c and a fourth side 30d aligned in the X-axis direction and both extending in the Y-axis direction, a fifth side 30e connecting adjacent ends of the first side 30a and the third side 30c and inclined at approximately 45 degrees with respect to the first and third sides 30a and 30c, and a sixth side 30f connecting adjacent ends of the first side 30a and the fourth side 30d and inclined at approximately 45 degrees with respect to the first and fourth sides 30a and 30d. Furthermore, the width Wx1 of the tip 30 in the X-axis direction (the distance between the third side 30c and the fourth side 30d) is slightly smaller than the width Wy1 in the Y-axis direction (the distance between the first side 30a and the second side 30b). In other words, Wx1<Wy1, and the tip 30 has a flattened shape in the X-axis direction.

[0034] The widths Wx1 and Wy1 are defined in JIS C 5973 as follows: Wx1 = 5.59 mm (within a margin of error of -0.1 mm or less), and Wy1 = 5.99 mm (within a margin of error of -0.1 mm or less). In this embodiment, the first side 3a and the first side 30a are formed by a continuous surface, and the second side 3b and the second side 30b are formed by a continuous surface. Therefore, the width Wy of the plug frame 3 at the cross section F is equal to the width Wy1 at the front end portion 30. That is, Wy = Wy1. In contrast, the third side 3c is located closer to the central axis J than the third side 30c, and the fourth side 3d is located closer to the central axis J than the fourth side 30d. Therefore, the width Wx of the plug frame 3 at the cross section F is smaller than the width Wx1 at the front end portion 30. That is, Wx < Wx1. Therefore, the outer shape of the plug frame 3 at the cross section F is flattened further in the X-axis direction than the outer shape of the plug frame 3 at the front end portion 30. The width Wx is defined in JIS C 5964-4 as 4.9 mm to 5.3 mm.

[0035] 8 , the inner circumferential surface 34 of the plug frame 3 is circular in cross section F. The inner diameter of the inner circumferential surface 34 is slightly larger than the outer diameter of the flange portion 43, and a gap G1 is formed between the outer circumferential surface of the flange portion 43 and the inner circumferential surface 34. The thickness of the gap G1 (the difference between the outer diameter of the flange portion 43 and the inner diameter of the inner circumferential surface 34) is not particularly limited, but is preferably 0.05 mm to 0.3 mm, and more preferably 0.1 mm to 0.2 mm, for example. By setting the thickness within this range, the ferrule 4 can be allowed to move freely with respect to the plug frame 3, as will be described later.

[0036] Similarly to the flange portion 43, the inner circumferential surface 34 has a first plug frame-side flat surface 341a and a second plug frame-side flat surface 341b, each of which is formed by cutting a portion flat. The first and second plug frame-side flat surfaces 341a, 341b have the same shape (size) and are disposed opposite each other across the central axis J. That is, the first and second plug frame-side flat surfaces 341a, 341b are formed symmetrically with respect to the central axis J. The plug frame 3 also has a first protrusion 342a and a second protrusion 342b that protrude from the inner circumferential surface 34 toward the central axis J. The first and second protrusions 342a, 342b are disposed opposite each other across the central axis J. That is, the first and second protrusions 342a, 342b are formed symmetrically with respect to the central axis J. The first and second protrusions 342a, 342b have the same shape and are rectangular protrusions that protrude toward the central axis J, as shown in FIG. 10 .

[0037] The first plug frame-side flat surface 341a is formed at a 0° position on the plug frame 3 and is disposed opposite the first flange-side flat surface 431a of the flange portion 43 across a gap G1. On the other hand, the second plug frame-side flat surface 341b is formed at a 180° position on the plug frame 3 and is disposed opposite the second flange-side flat surface 431b of the flange portion 43 across a gap G1.

[0038] As mentioned above, since the outer shape of the plug frame 3 in cross section F is flattened in the X-axis direction, forming a circular inner peripheral surface 34 would result in a thinner wall thickness at the 0° and 180° positions of the plug frame 3, resulting in problems such as a reduction in the mechanical strength of the plug frame 3. To address this problem, as in the optical connector plug 1, by forming first and second plug frame-side flat surfaces 341a and 341b at the 0° and 180° positions of the plug frame 3, the wall thickness D1 of the plug frame 3 at these positions can be made thicker than the wall thickness D2 of the plug frame 3 without the first and second plug frame-side flat surfaces 341a and 341b, as shown in FIG. 11 . This increases the mechanical strength of the plug frame 3, resulting in a highly reliable optical connector plug 1. Furthermore, if the wall thickness D2 is too thin, injection molding can easily become unstable, potentially reducing the yield of the plug frame 3. However, in this embodiment, the wall thickness required during injection molding can be sufficiently secured, allowing the plug frame 3 to be stably formed by injection molding.

[0039] The thickness D1 is not particularly limited, but is preferably 0.2 mm or more, and more preferably 0.25 mm or more, for example. This makes the above-mentioned effects more pronounced.

[0040] When the optical connector plug 1 is applied to an SC connector as in this embodiment, the thickness D1 is preferably, for example, 0.2 mm to 0.6 mm, and more preferably 0.25 mm to 0.45 mm. By setting the thickness D1 to the above-mentioned lower limit, the mechanical strength of the plug frame 3 can be sufficiently increased, and the plug frame 3 can be formed sufficiently stably by injection molding. On the other hand, by setting the thickness D1 to the above-mentioned upper limit, it is possible to effectively prevent the first and second flange-side flat surfaces 431a, 431b formed on the flange 43 from becoming too large, thereby reducing the area in which the first and second grooves 432a, 432b can be formed, or the mechanical strength of the flange 43 from being excessively reduced.

[0041] In this regard, as shown in FIG. 8 , the central angle θ2 of the sector defined by both ends of the first flange-side flat surface 431a and the central axis J is preferably 60° or less (0°±30° or less). Similarly, the central angle θ2 of the sector defined by both ends of the second flange-side flat surface 431b and the central axis J is preferably 60° or less (0°±30° or less). This allows the first and second flange-side flat surfaces 431a, 431b to have an appropriate size, ensuring a sufficiently large area in which the first and second grooves 432a, 432b can be formed. This increases the degree of freedom in forming the first and second grooves 432a, 432b. In particular, as in this embodiment, the first and second grooves 432a, 432b can be formed at positions of 45° and 225°. Furthermore, the mechanical strength of the flange portion 43 can be sufficiently ensured. Furthermore, JIS C 5965-3-1 stipulates that the outer diameter of the capillary 41 must be between 2.4985 mm and 2.4995 mm. Therefore, by setting the upper limit value as described above, the use of a capillary 41 with an outer diameter of 2.4995 mm, which is the specified maximum value, is not hindered, resulting in an optical connector plug 1 with a high degree of design freedom.

[0042] Furthermore, the first protrusion 342a is fitted into the first groove 432a of the flange portion 43, and the second protrusion 342b is fitted into the second groove 432b of the flange portion 43. In this manner, the first and second grooves 432a, 432b of the flange portion 43 engage with the first and second protrusions 342a, 342b of the plug frame 3, thereby restricting rotation of the ferrule 4 (the optical fiber 8 held in the ferrule 4) about the central axis J relative to the plug frame 3. As described above, the optical fiber 8 is a multi-core fiber and has directionality about the central axis J. Therefore, by restricting rotation of the ferrule 4 relative to the plug frame 3, when two optical connector plugs 1 (1A, 1B) are connected by the optical fiber adapter 7, as will be described later, the optical fibers 8 can be reliably connected to each other.

[0043] The first protrusion 342a is formed at a 45° position on the plug frame 3, and the second protrusion 342b is formed at a 225° position on the plug frame 3. In other words, the inclination θ1 of the direction V in which the first and second protrusions 342a, 342b are aligned with respect to the X-axis is 45°. Note that the term "45°" refers not only to cases where the angle is identical to 45°, but also to cases where the angle is deviated to a degree that can be considered equivalent to 45° in terms of common technical knowledge (for example, approximately ±1°).

[0044] However, the inclination θ1 is not particularly limited as long as it does not impede the formation of the first and second plug frame-side flat surfaces 341a, 341b, i.e., as long as it is not 0°. However, the inclination θ1 is preferably 30° to 150°. By setting the inclination θ1 in this range, sufficient space can be secured to form the first and second plug frame-side flat surfaces 341a, 341b at the portions of the plug frame 3 located at 0° and 180°. Therefore, the first and second plug frame-side flat surfaces 341a, 341b can be formed to the required size, and the wall thickness D1 can be sufficiently secured. Among the inclination θ1 ranges from 30° to 150°, setting the inclination θ1 to 45° as in this embodiment provides the advantage that, as will be described later, when two optical connector plugs 1 (1A, 1B) are connected by an optical fiber adapter 7, the directions V of the optical connector plugs 1A, 1B are perpendicular to each other. Note that, as shown in FIG. 12, even if the inclination θ1 is 135°, the same effect as this embodiment can be achieved.

[0045] In particular, in this embodiment, as shown in FIG. 8 , the width W1 of the first and second grooves 432a, 432b and the width W2 of the first and second protrusions 342a, 342b are substantially equal, and both outer side surfaces of the first protrusion 342a abut (surface-contact) against both inner side surfaces of the first groove 432a, and both outer side surfaces of the second protrusion 342b abut (surface-contact) against both inner side surfaces of the second groove 432b. This more effectively restricts rotation of the ferrule 4 relative to the plug frame 3. However, this is not limited thereto, and the width W1 may be slightly greater than the width W2, allowing the ferrule 4 to rotate slightly about the central axis J relative to the plug frame 3. In this case, the amount of rotation of the ferrule 4 relative to the plug frame 3 is preferably limited to ±1° or less, more preferably ±0.5° or less, relative to the reference position.

[0046] Furthermore, the insertion distance of the first and second protrusions 342a, 342b into the first and second grooves 432a, 432b is shorter than the depth of the first and second grooves 432a, 432b. Therefore, a gap G2 is formed between the bottom surfaces of the first and second grooves 432a, 432b and the top surfaces of the first and second protrusions 342a, 342b. The thickness of the gap G2 is not particularly limited, but is preferably approximately the same as the gap G1, for example.

[0047] In the optical connector plug 1 configured as described above, the gaps G1 and G2 formed between the plug frame 3 and the flange portion 43 allow the ferrule 4 to move freely relative to the plug frame 3 in several directions other than around the central axis J. Specifically, as shown in FIG. 13 , when the axis along the direction V in which the first and second protrusions 342a and 342b are aligned is defined as the first axis J1 in the cross section F and the axis perpendicular to the first axis J1 is defined as the second axis J2, the ferrule 4 is allowed to perform a translational movement M1 along the first axis J1 and a second rotational movement M3 around the second axis J2. Furthermore, in this embodiment, the first and second protrusions 342a and 342b elastically deform, allowing the first rotational movement M2 around the first axis J1.

[0048] However, the present invention is not limited to this, and the first and second protrusions 342 a, 342 b may not substantially deform elastically and the first rotational movement M2 about the first axis J1 may not be permitted. Alternatively, for example, as shown in Fig. 14, the first and second protrusions 342 a, 342 b may be cylindrical and both outer surfaces of the first protrusion 342 a may be in line contact with both inner surfaces of the first groove 432 a, or as shown in Fig. 15, the first and second protrusions 342 a, 342 b may be rectangular prisms and corners of the first protrusion 342 a may be in line contact with both inner surfaces of the first groove 432 a, thereby permitting the first rotational movement M2 about the first axis J1 without elastically deforming the first and second protrusions 342 a, 342 b. Also, as shown in FIG. 16 , as described above, by making the width W1 slightly larger than the width W2 and configuring the ferrule 4 to be able to rotate slightly (within ±1° of the reference position as described above) around the central axis J relative to the plug frame 3, the first rotational movement M2 around the first axis J1 may be permitted without elastically deforming the first and second protrusions 342 a, 342 b.

[0049] As shown in FIG. 13 , the insertion length L of the first and second protrusions 342a, 342b relative to the first and second grooves 432a, 432b is not particularly limited. However, when the optical connector plug 1 is applied to an SC connector as in this embodiment, it is preferably 0.3 mm to 0.8 mm, and more preferably 0.4 mm to 0.8 mm. Setting the lower limit as described above ensures a sufficient insertion length, thereby more reliably restricting rotation of the ferrule 4 relative to the plug frame 3. On the other hand, setting the upper limit as described above prevents the first and second grooves 432a, 432b from becoming too deep, effectively eliminating various disadvantages such as a reduction in the mechanical strength of the flange portion 43 or the need to reduce the diameter of the capillary 41. As mentioned above, JIS C 5965-3-1 stipulates that the outer diameter of the capillary 41 must be 2.4985 mm to 2.4995 mm. Therefore, by setting the upper limit as described above, the use of a capillary 41 having an outer diameter of 2.4995 mm, which is the specified maximum value, is not hindered, and the optical connector plug 1 has a high degree of freedom in design.

[0050] The above describes the configuration of the optical connector plug 1. Next, we will explain a method for connecting two optical connector plugs 1. For ease of explanation, one optical connector plug 1 will also be referred to as optical connector plug 1A, and the other optical connector plug 1 will also be referred to as optical connector plug 1B.

[0051] 17 , the optical connector plugs 1A, 1B are mechanically and optically connected by the optical fiber adapter 7. When the optical connector plugs 1A, 1B are connected by the optical fiber adapter 7 (hereinafter, this state will also be referred to as the "optical connector plug connection structure 10"), the tip faces of the ferrules 4 butt against each other within the alignment member 71 provided in the optical fiber adapter 7, and the optical fibers 8 held in the optical connector plugs 1A, 1B are optically connected to each other. As described above, in the optical connector plug 1, rotation of the ferrules 4 about the central axis J relative to the plug frame 3 is restricted, so that the optical fibers 8 held in the optical connector plugs 1A, 1B can be easily connected to each other.

[0052] Furthermore, when an external force is applied to the optical connector plugs 1A, 1B, the ferrules 4 move freely relative to the plug frame 3 (through a translational movement M1, a first rotational movement M2, and a second rotational movement M3), thereby effectively absorbing the external force and maintaining contact between the tip faces of the ferrules 4. In particular, according to the optical connector plug 1 of this embodiment, the first axes J1 of the optical connector plugs 1A, 1B are orthogonal to each other, and the second axes J2 of the optical connector plugs 1A, 1B are orthogonal to each other. Therefore, for example, the first rotational movement M2 of the optical connector plug 1B occurs in response to the translational movement M1 and the second rotational movement M3 of the optical connector plug 1A, and the second rotational movement M3 and the translational movement M1 of the optical connector plug 1B occur in response to the first rotational movement M2 of the optical connector plug 1A. As a result, the external force can be more effectively absorbing, and contact between the tip faces of the ferrules 4 can be maintained.

[0053] The above has described the optical connector plug 1. As described above, such an optical connector plug 1 has a cylindrical plug frame 3 and a ferrule 4 inserted into the plug frame 3. The ferrule 4 also has a base 40 that holds an optical fiber 8 and a flange 43 that protrudes outward from the base 40. Furthermore, when viewed in a plan view from a direction along the central axis J of the ferrule 4, axes that intersect with the central axis J and are perpendicular to each other are defined as the X-axis and Y-axis, and further, when the direction along the X-axis direction is defined as the X-axis direction and the direction along the Y-axis is defined as the Y-axis direction, the plug frame 3 has, in a cross section F that is perpendicular to the central axis J and overlaps with the flange portion 43, a first side 3 a and a second side 3 b that are aligned in the Y-axis direction and both extend in the X-axis direction, and a third side 3 c and a fourth side 3 d that are aligned in the X-axis direction and both extend in the Y-axis direction, and has an outer peripheral surface whose width Wx in the X-axis direction, which is the distance between the third side 3 c and the fourth side 3 d, is shorter than the width Wy in the Y-axis direction, which is the distance between the first side 3 a and the second side 3 b, and a circular inner peripheral surface 34 that surrounds the flange portion 43 and has an inner diameter larger than the outer diameter of the flange portion 43. The outer peripheral surface of the flange portion 43 is formed with a first flange portion-side flat surface 431a disposed opposite the third side 3c, a second flange portion-side flat surface 431b disposed opposite the fourth side 3d, a first groove 432a recessed toward the central axis J, and a second groove 432b opposed to the first groove 432a across the central axis J and recessed toward the central axis J. The inner peripheral surface 34 of the plug frame 3 is formed with a first plug frame-side flat surface 341a disposed opposite the first flange portion-side flat surface 431a, a second plug frame-side flat surface 341b disposed opposite the second flange portion-side flat surface 431b, a first protrusion 342a protruding toward the central axis J and inserted into the first groove 432a, and a second protrusion 342b protruding toward the central axis J and inserted into the second groove 432b. With this configuration, the thickness D1 of the plug frame 3 can be made thicker than the thickness D2 when the first and second plug frame-side flat surfaces 341 a, 341 b are not present, thereby increasing the mechanical strength of the plug frame 3 and providing the optical connector plug 1 with high reliability.Furthermore, when the plug frame 3 is formed by injection molding, if the thickness D2 is too thin, the injection molding is likely to become unstable, which may result in a decrease in the production yield of the plug frame 3. However, in the present embodiment, the necessary thickness can be sufficiently ensured during injection molding, and the plug frame 3 can be stably formed by injection molding.

[0054] As described above, both side surfaces of the first protrusion 342a abut against both side surfaces of the first groove 432a, and both side surfaces of the second protrusion 342b abut against both side surfaces of the second groove 432b in the cross section F. With this configuration, rotation of the ferrule 4 about the central axis J relative to the plug frame 3 can be more effectively restricted.

[0055] As described above, when the axis along the direction V in which the first protrusions 342a and the second protrusions 342b are aligned in the cross section F is defined as the first axis J1 and the axis perpendicular to the first axis J1 is defined as the second axis J2, at least one of a translational movement M1 of the ferrule 4 along the first axis J1, a first rotational movement M2 about the first axis J1, and a second rotational movement M3 about the second axis J2 is allowed relative to the plug frame 3. With this configuration, when two optical connector plugs 1 (1A, 1B) are connected using the optical fiber adapter 7, contact between the tip surfaces of the ferrules 4 can be effectively maintained.

[0056] As described above, the optical connector plug 1 has a gap G1 (first gap) formed between the outer peripheral surface of the flange portion 43 and the inner peripheral surface 34 of the plug frame 3, and gaps G2 (second gaps) formed between the bottom surface of the first groove 432a and the top surface of the first protrusion 342a and between the bottom surface of the second groove 432b and the top surface of the second protrusion 342b. This simple configuration allows the ferrule 4 to move freely relative to the plug frame 3.

[0057] As described above, the direction V in which the first protrusions 342a and the second protrusions 342b are aligned is inclined at an angle ranging from 30° to 150° with respect to the X-axis. With this configuration, sufficient space can be secured in the flange portion 43 for forming the first and second flange portion-side flat surfaces 431a, 431b, and sufficient space can be secured in the plug frame 3 for forming the first and second plug frame-side flat surfaces 341a, 341b.

[0058] As described above, the direction V in which the first protrusions 342a and the second protrusions 342b are aligned is inclined at 45° with respect to the X-axis. With this configuration, when two optical connector plugs 1 (1A, 1B) are connected using the optical fiber adapter 7, the directions V of the two optical connector plugs 1 are perpendicular to each other. This makes it possible to effectively maintain contact between the tip faces of the ferrules 4.

[0059] Second Embodiment FIG. 18 is a cross-sectional view showing an optical connector plug according to a second embodiment.

[0060] The optical connector plug 1 of this embodiment is similar to the optical connector plug 1 of the first embodiment described above, except that the positions of the first and second grooves 432a, 432b formed in the flange portion 43 and the first and second protrusions 342a, 342b formed in the plug frame 3 are different. Therefore, in the following description, the differences between this embodiment and the first embodiment will be mainly described, and a description of similar points will be omitted. Furthermore, in the drawings of this embodiment, the same reference numerals are used to designate the same components as those in the previously described embodiment.

[0061] 18, in the optical connector plug 1 of this embodiment, the inclination θ1 of the direction V in which the first and second protrusions 342a, 342b are aligned relative to the X-axis at cross section F is 90°. In other words, the first and second protrusions 342a, 342b are arranged along the Y-axis direction. Note that the term "90°" refers not only to cases where the angle is exactly 90°, but also to cases where the angle is deviated to a degree that can be considered equivalent to 90° in terms of common technical knowledge (for example, approximately ±1°).

[0062] In this configuration, the first and second protrusions 342a, 342b are formed at the 90° and 270° positions of the plug frame 3, which are next to the 0° and 180° positions in thickness. Therefore, the first and second protrusions 342a, 342b increase the thickness of the 90° and 270° positions, thereby reinforcing these positions. In other words, in the optical connector plug 1 of this embodiment, the first and second plug frame-side flat surfaces 341a, 341b are formed at the 0° and 180° positions of the plug frame 3, which are most likely to be thin, and the first and second protrusions 342a, 342b are formed at the 90° and 270° positions, which are next to the thinnest positions. This effectively prevents partial thinning of the plug frame 3. Therefore, the mechanical strength of the plug frame 3 can be more effectively increased.

[0063] Furthermore, in the optical connector plug connection structure 10, if the optical connector plug 1A is the optical connector plug of this embodiment and the optical connector plug 1B is the optical connector plug of the prior art, the first axes J1 of the optical connector plugs 1A and 1B are orthogonal to each other, and the second axes J2 of the optical connector plugs 1A and 1B are orthogonal to each other. Therefore, for example, a first rotational motion M2 of the optical connector plug 1B occurs in response to a translational motion M1 or a second rotational motion M3 of the optical connector plug 1A, and a second rotational motion M3 or a translational motion M1 of the optical connector plug 1B occurs in response to the first rotational motion M2 of the optical connector plug 1A. Therefore, the external force can be more effectively resisted, and contact between the tip surfaces of the ferrules 4 can be maintained.

[0064] As described above, in the optical connector plug 1 of this embodiment, the direction V in which the first protrusions 342 a and the second protrusions 342 b are aligned is inclined by 90° with respect to the X axis. With this configuration, the mechanical strength of the plug frame 3 can be more effectively increased.

[0065] The second embodiment can also achieve the same effects as the first embodiment.

[0066] The optical connector plug of the present invention has been described above based on the illustrated embodiment, but the optical connector plug of the present invention is not limited to this, and the configuration of each part can be replaced with any configuration having the same function. Also, any other configuration may be added to the present invention. Furthermore, each embodiment may be combined as appropriate.

[0067] In the optical connector plug of the present invention, the inner peripheral surface of the plug frame is formed with a first plug frame-side flat surface facing the first flange-side flat surface and a second plug frame-side flat surface facing the second flange-side flat surface. This facilitates ensuring a sufficient wall thickness between the third edge and the first plug frame-side flat surface and between the fourth edge and the second plug frame-side flat surface. Therefore, the optical connector plug of the present invention has sufficient strength and can demonstrate high reliability. Furthermore, in the optical connector plug of the present invention, the engagement of the first and second grooves with the first and second protrusions restricts rotation of the ferrule about its central axis relative to the plug frame. Therefore, the optical connector plug of the present invention is particularly suitable for holding optical fibers that have directionality about their central axes, such as multicore fibers. Therefore, the present invention has industrial applicability.

Claims

1. A plug frame having a cylindrical plug frame and a ferrule inserted into the plug frame, wherein the ferrule has a base portion for holding an optical fiber and a flange portion protruding outward from the base, wherein, in a plan view from a direction along the central axis of the ferrule, axes that intersect with the central axis and are perpendicular to each other are defined as the X-axis and Y-axis, and further, the direction along the X-axis is defined as the X-axis direction, and the direction along the Y-axis is defined as the Y-axis direction, the plug frame, in a cross section that is perpendicular to the central axis and overlaps with the flange portion, has: a first side and a second side that are aligned in the Y-axis direction and both extend in the X-axis direction, and a third side and a fourth side that are aligned in the X-axis direction and both extend in the Y-axis direction, and wherein the width in the X-axis direction, which is the distance between the third side and the fourth side, is shorter than the width in the Y-axis direction, which is the distance between the first side and the second side; and a circular inner side that surrounds the flange portion and has an inner diameter greater than the outer diameter of the flange portion. an outer peripheral surface of the flange portion formed with a first flange portion-side flat surface arranged opposite the third side, a second flange portion-side flat surface arranged opposite the fourth side, a first groove recessed toward the central axis, and a second groove facing the first groove across the central axis and recessed toward the central axis; and an inner peripheral surface of the plug frame formed with a first plug frame-side flat surface arranged opposite the first flange portion-side flat surface, a second plug frame-side flat surface arranged opposite the second flange portion-side flat surface, a first protrusion protruding toward the central axis and inserted into the first groove, and a second protrusion protruding toward the central axis and inserted into the second groove.

2. An optical connector plug according to claim 1, wherein, in the cross section, both side surfaces of said first projection abut against both side surfaces of said first groove, and both side surfaces of said second projection abut against both side surfaces of said second groove.

3. An optical connector plug as described in claim 1, wherein, in the cross section, when an axis along the direction in which the first protrusion and the second protrusion are aligned is defined as a first axis and an axis perpendicular to the first axis is defined as a second axis, at least one of a translational movement of the ferrule relative to the plug frame along the first axis, a first rotational movement about the first axis, and a second rotational movement about the second axis is permitted.

4. An optical connector plug as described in claim 3, having a first gap formed between the outer peripheral surface of the flange portion and the inner peripheral surface of the plug frame, and second gaps formed between the bottom surface of the first groove and the top surface of the first protrusion and between the bottom surface of the second groove and the top surface of the second protrusion.

5. An optical connector plug according to claim 1, wherein the direction in which said first projections and said second projections are aligned is tilted in the range of 30° to 150° with respect to said X-axis.

6. An optical connector plug according to claim 5, wherein the direction in which said first projection and said second projection are aligned is inclined at 45° with respect to said X-axis.

7. An optical connector plug according to claim 5, wherein the direction in which said first projection and said second projection are aligned is inclined at 90° with respect to said X-axis.

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