JP4578828B2 - Stopper shape setting method - Google Patents

Description

  The present invention relates to a technique for fixing an optical fiber.

  Conventionally, there are the following structures for fixing an optical fiber to an optical connector or the like.

  First, there is a first fixing structure in which an end portion of an optical fiber is inserted into a ferrule, and an adhesive is poured between the outer peripheral surface of the coating portion of the optical fiber and the inner peripheral surface of the ferrule for fixing.

  Further, as a second fixing structure, there is a structure in which an optical fiber end portion is inserted into a ferrule and the ferrule is deformed and pressure-fixed (for example, see Patent Document 1).

  Furthermore, as a third fixing structure, there is a structure in which a blade of an optical fiber fixing stopper is engaged with an optical fiber coating portion and fixed (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 9-15451 JP 2002-202433 A

  However, in the first fixing structure, it is necessary to strictly manage the filling degree of the adhesive in order to obtain a sufficient fixing strength.

  Further, in the second fixing structure, it is necessary to strictly control the deformation amount of the ferrule in order to prevent the optical fiber from being deformed due to the pressure applied to the optical fiber itself.

  As described above, in any of the first and second fixing structures, strict manufacturing management is required. However, since such strict manufacturing management is difficult and requires a great amount of labor, it is a cause of cost increase. It was.

  On the other hand, in the third fixing structure, it is only necessary to engage the fixing stopper with the coating portion of the optical fiber, so that the strict manufacturing management as described above is unnecessary.

  However, in this case, it is necessary to set the shape of the fixing stopper so as to prevent damage to the core wires (core and clad) of the optical fiber and to obtain a desired fixing strength.

  However, since the fixing strength of the optical fiber has not been quantitatively grasped in the past, it is necessary to determine whether the stopper is engaged by trial and error while checking whether there is any flaws on the core wire or measuring the fixing strength. There was a lot of effort at the stopper shape setting (design) stage.

  In particular, in recent years, as the diameter of optical fibers has been reduced and the thickness of the covering portion tends to decrease, it is possible to obtain a desired fixing strength while preventing damage to the core of the optical fiber. The delicate setting of the amount of engagement of the stopper became difficult.

  Accordingly, an object of the present invention is to provide a technique capable of easily setting the shape of the stopper in accordance with the required fixing strength of the optical fiber when the optical fiber is fixed using the stopper.

According to a first aspect of the present invention, there is provided at least one pair of engagement pieces arranged in parallel with a spacing dimension smaller than the width dimension of the covering portion of the optical fiber, and the pair of engaging pieces are arranged on both sides of the covering portion. The present invention relates to a stopper shape setting method in which the pair of engaging pieces are engaged with both side portions of the covering portion by being pushed in a direction substantially orthogonal to the axial direction of the optical fiber while being pressed against the portion.

The non-engagement area SA of the stopper of the covering portion in a state where the stopper is engaged with the covering portion is Pt × SA ≧ F (where Pt is a limit per unit sectional area of the covering portion) The shape of the stopper is set so as to satisfy the tensile stress (F, the required fixed tensile strength of the optical fiber).

According to a second aspect of the present invention, there is provided at least one pair of engaging pieces arranged in parallel at a distance smaller than the width of the covering portion of the optical fiber, and the pair of engaging pieces are arranged on both sides of the covering portion. A stopper shape setting method in which the pair of engaging pieces engage with both side portions of the covering portion by being pushed in a direction substantially perpendicular to the axial direction of the optical fiber while being pressed against the portion. The engagement area SB of the stopper when the stopper is engaged with the covering portion is Pp × SB ≧ F (where Pp is the limit compressive stress per unit cross-sectional area of the covering portion, and F is required) The shape of the stopper is set so as to satisfy the fixed tensile strength of the optical fiber.

  In addition, in the case where the stopper includes a plurality of stopper pieces that engage with the covering portion substantially perpendicularly to the length direction at different positions along the length direction of the optical fiber, The shape of the stopper may be set by evaluating the sum of the combined area or the non-engaging area as the engaging area of the stopper or the non-engaging area of the stopper.

According to the first aspect of the present invention, the shape of the stopper is such that the non-engagement area SA of the stopper of the covering portion in a state where the stopper is engaged with the covering portion satisfies Pt × SA ≧ F. By setting, the shape of the stopper can be easily set so that a desired fixing strength F can be obtained.

Further, according to the second aspect, by setting the shape of the stopper so that the engagement area SB in the state where the stopper is engaged with the covering portion satisfies Pp × SB ≧ F, a desired fixing strength can be obtained. The shape of the stopper can be easily set so that it can be obtained.

  Further, when the stopper includes a plurality of stopper pieces, the sum of the engagement area or the non-engagement area in each stopper piece is evaluated as the engagement area of the stopper or the non-engagement area of the stopper, By setting the shape of the stopper, it is possible to easily set the shape of the stopper so that a desired fixing strength can be obtained even when there are a plurality of stopper pieces.

  A stopper shape setting method and an optical fiber fixing portion structure according to embodiments of the present invention will be described below.

  First, the application object of this fixed part structure is demonstrated. FIG. 1 is an explanatory view showing a state in which an optical fiber is fixed to an optical connector.

  The optical fiber 10 is configured such that the outer periphery of a fiber core wire 12 including a core and a clad is covered with a coating portion 14 such as a resin. For example, a plastic optical fiber is used as the optical fiber 10.

  When the optical fiber 10 is fixed to the optical connector 20, the coating 14 at the tip is removed in advance, and the fiber core wire 12 is exposed to a predetermined length.

  The optical connector 20 is formed of resin or the like. A ferrule portion 24 is formed at one end of the housing main body portion 22 and an outer tube portion 26 is formed so as to surround the ferrule portion 24. Become. The ferrule portion 24 is formed in a thin cylindrical shape, and a fine fiber-like fiber accommodation hole portion 24h is formed in the inside along the axial direction. In addition, a sheath receiving hole 22h having a larger diameter than the fiber receiving hole 24h is formed in the housing main body 22. The fiber accommodation hole 24h and the coating part accommodation hole 22h communicate in a straight line.

  A stopper mounting hole 28 is formed on one side of the housing body 22.

  When the optical fiber 10 is fixed to the optical connector 20, first, the optical fiber 10 is inserted into the covering portion receiving hole portion 22h and the fiber receiving hole portion 24h, and the fiber core wire at the end of the optical fiber 10 is inserted. The 12 exposed portions are accommodated in the fiber accommodating hole 24h, and the portion of the covering portion 14 in front thereof is accommodated in the covering portion accommodating hole 22h. When the stopper 30 is pushed into the stopper mounting hole 28 in this state, the stopper 30 is engaged with the covering portion 14 and the optical fiber 10 is positioned and fixed.

  The aspect in which the stopper 30 and the stopper 30 engage with the covering portion 14 will be described more specifically.

  2 is a perspective view showing the stopper, FIG. 3 is a view showing an initial state where the stopper starts to engage with the covering portion, and FIG. 4 is a view showing a state where the stopper is engaged with the covering portion.

  The stopper 30 is formed, for example, by appropriately bending and punching a metal plate having a predetermined thickness, or by resin molding, and a pair of engagement pieces 32 are connected and supported via a base 31. It has a substantially inverted U-shaped plate shape.

  The pair of engagement pieces 32 are formed in a substantially rectangular plate shape, and a predetermined interval dimension is provided between them. This interval dimension is set within a range smaller than the diameter dimension (width dimension) of the covering portion 14 and larger than the diameter dimension (width dimension) of the fiber core wire 12. A more preferable setting within this range will be described in detail later.

  Further, the distal end portions of the pair of engaging pieces 32 are formed on the distal end surface 32b substantially orthogonal to the distal end direction. The pair of engagement pieces 32 includes a blade portion 32c on each distal end side. Each blade portion 32c is configured by the front end surface 32b of the pair of engagement pieces 32 and the opposed inner side surface 32a of the pair of engagement pieces 32 intersecting, and has a blade edge extending along the axial direction of the optical fiber 10. ing. In the present embodiment, the opposed inner side surface 32a and the front end surface 32b intersect at a substantially right angle, but may intersect at an acute angle or the like. Further, the length of the blade edge of the blade portion 32c (the thickness of the engagement piece 32) may be shorter than 1 mm or less. In short, the blade part 32c should just be formed in the magnitude | size and shape which can scrape off the coating | coated part 14. FIG.

  Then, the blade portion 32c is pressed against both sides of the covering portion 14 so that the covering portion 14 of the optical fiber 10 is relatively pushed from the opening side between the pair of engaging pieces 32 of the stopper 30 (FIG. 3). After that, the stopper 30 is further pushed in a direction substantially perpendicular to the axial direction of the optical fiber 10. Then, the blade part 32c scrapes off both sides of the covering part 14 in a flat shape without pushing the covering part 14 toward the fiber core wire 12. And the opposing inner side surface 32a part of a pair of engagement piece 32 enters the said scraping part among the coating | coated parts 14, and it becomes a structure which a pair of engagement piece 32 engages with the coating | coated part 14. FIG.

  As described above, the pushing portion of the stopper 30 causes the blade portion 32c to scrape the covering portion 14, and the opposing inner side surface 32a portion enters the scraping portion, whereby the engaging piece 32 engages the covering portion 14. In this case, there is an advantage that the optical force can be reduced by avoiding the compressive force acting on the fiber core wire 12.

  However, the engaging piece 32 may be formed in a knife blade shape, and the knife blade-shaped engaging piece 32 may be engaged with the covering portion 14 so as to cut into the covering portion 14.

  A method of setting the shape of the stopper 30 that engages with the coating portion 14 of the optical fiber 10 as described above will be described.

  In this stopper shape setting method, in a state where the stopper 30 is engaged with the covering portion 14, the non-engagement area of the stopper 30 in the covering portion 14 and the tensile strength of the covering portion 14, the stopper 30 and the covering portion 14. The shape of the stopper 30 is set on the basis of the engagement area and the compressive strength of the covering portion 14.

  This will be described more specifically with reference to FIG. 5, in the plane including the cross section of the optical fiber 10, the center axis of the optical fiber 10 is the center O, the pushing direction of the stopper 30 (the extending direction of the opposed inner side surface 32a of the engaging piece 32) is the Y axis, An XY coordinate system having orthogonal X axes is set. Further, in the cross section, a region (engagement region) where the engagement piece 32 of the stopper 30 is engaged with the covering portion 14 is a net pattern, and a region (not non-engaged) of the covering portion 14 where the stopper 30 is not engaged. (Engagement region) is indicated by a hatched pattern.

The radius of the covering portion 14 is R, the radius of the fiber core wire 12 is r, the distance between the pair of engagement pieces 32 is 2L, the area of the non-engagement region (non-engagement area) is SA, The area (engagement area) is SB. Furthermore, the tensile strength of the covering portion 14 is Pt, and the compressive strength of the covering portion 14 is Pp. These tensile strengths Pt are the limit tensile stresses per unit cross-sectional area, and the compressive strengths Pp are the limit compressive stresses per unit cross-sectional area, which are determined by the material characteristics of the covering portion 14 respectively.

  A method for setting the shape of the stopper 30 when the required tensile strength of the optical fiber 10 is F will be described.

In this case , when the optical fiber 10 is pulled, a compressive force is applied to the engaging region portion of the stopper 30 in the covering portion 14, and a tensile force is applied to the non-engaging region portion of the stopper 30. Therefore, it is necessary that the engaging region portion of the stopper 30 has a compressive strength equal to or higher than the above strength F, and the non-engaging region portion of the stopper 30 needs to have a tensile strength equal to or higher than the above strength F. It is believed that there is.

  First, considering the tensile strength in the non-engagement region portion of the stopper 30, the tensile strength can be considered as a value obtained by multiplying the non-engagement area SA by the tensile strength Pt of the covering portion 14.

  Then, if the tensile strength required here is T (= F), the shape of the stopper 30 may be set so as to satisfy the following formula (1).

Pt × SA ≧ T (1)
Here, the non-engagement area SA is represented by R, r, and L as follows.

That is, in FIG. 5, the area of the sector OAR is π · R ² × θ / 2π = R ² · θ / 2. Here, θ (rad) is the angle AOR, and θ = cos ⁻¹ (L / R).

Therefore, the area of the sector OAR ^{becomes, (R 2/2) ×} cos -1 (L / R).

The area of the triangle AOL is (L / 2) × (R ² −L ² ) ^1/2 .

  Then, the area of the triangle AOL is subtracted from the area of the sector OAR and multiplied by 4 to obtain an engagement area SB, which is expressed by the following formula (2).

SB = 2R ² · cos ⁻¹ (L / R) −2L · (R ² −L ² ) ^1/2 (2)
Further, the non-engagement area SA is an area obtained by subtracting the SB from the cross-sectional area of the covering portion 14, and is represented by the following formula (3).

SA = πR ² −πr ² −SB (3)
Based on the above formulas (1), (2), and (3), the required tensile strength T, the radius R of the coating 14, the radius r of the fiber core wire 12, and the tensile strength Pt of the coating 14 are obtained. Accordingly, the range of the distance dimension 2L between the pair of engagement pieces 32 can be determined.

  Next, considering the compressive strength in the engaging region portion of the stopper 30, the compressive strength can be considered as a value obtained by multiplying the engaging region SB by the compressive strength Pp of the covering portion 14.

  Then, if the required compression strength is P (= F), the shape of the stopper 30 may be set so as to satisfy the following formula (4).

Pp × SB ≧ P (4)
From the above, based on the above formulas (2) and (4), depending on the required compressive strength P, the radius R of the covering portion 14, the radius r of the fiber core wire 12, and the compressive strength Pp of the covering portion 14. The range of the distance dimension 2L between the pair of engaging pieces 32 can be determined.

  Then, by setting the shape of the stopper 30 so as to satisfy both of the above formulas (1) and (4), the desired strength T (= F) for both the tensile strength and the compressive strength at the engaging portion of the stopper 30. ), P (= F) or more.

  In order to prevent the stopper 30 from damaging the fiber core wire 12, the distance 2L between the pair of engagement pieces 32 needs to be larger than the diameter 2 r of the fiber core wire 12.

  According to the shape setting method of the stopper 30 configured as described above and the fixing portion structure of the optical fiber 10, the engagement area SB between the stopper 30 and the covering portion 14, the tensile strength Pt of the covering portion 14, and the non-engagement. The shape of the stopper 30 can be easily set so that a desired fixed tensile strength F can be obtained by quantitatively estimating the tensile strength and the compressive strength based on the area SA and the compressive strength Pp.

  Specifically, the non-engagement area SA of the stopper 30 satisfies Pt × SA ≧ T, or the engagement area SB with the stopper engaged with the covering portion is Pp × SB ≧ By setting the shape of the stopper 30 to satisfy P, the shape of the stopper 30 can be easily set so that a desired fixed tensile strength F can be obtained.

  In the above embodiment, the case where the stopper 30 fixes the optical fiber 10 at one place has been described. However, as shown in FIG. 6, the stopper 30B includes two stopper pieces 31B (each stopper piece 31B is the stopper 30). 7, or when the stopper 30 </ b> C includes three stopper pieces 31 </ b> C (each stopper piece 31 </ b> B has the same configuration as the stopper 30) as shown in FIG. 7.

  As described above, when the stoppers 30B and 30C are provided with a plurality of stopper pieces 31B and 31C that engage the covering portion 14 substantially perpendicularly to the length direction at different positions along the length direction of the optical fiber 10. The sum of the engagement areas where the stopper pieces 31B, 31C are engaged with the covering portion 14 at each position or the sum of the non-engagement areas is defined as the engagement area SB as the entirety of the stoppers 30B, 30C or the entire stopper. The shape of the stopper 30 may be set by evaluating the non-engagement area SA and applying to the above formulas (1) to (4).

  Even in this case, it is possible to easily set the shapes of the stoppers 30B and 30C so that a desired fixed tensile strength F can be obtained in the same manner as described above.

<Example>
As Example 1, consider the following example.

First, as the covering portion 14, polypropylene (PP) was used. The tensile strength of this polypropylene, 5kgf · mm ^-2 (about 49.03N · mm ^-2), compressive strength, 6kgf · mm ^-2 (about 58.84N · mm ^-2), is.

  Further, it is assumed that the diameter 2R of the covering portion 14 of the optical fiber 10 is 2.5 mm, and the diameter 2r of the fiber core wire 12 is 1 mm.

  Here, it is assumed that 9 kgf (about 88.26 N) or more is required as the fixed tensile strength F of the optical fiber 10 by the stopper 30.

In this case, if the distance 2L between the pair of engagement pieces 32 is 1.2 mm, the non-engagement area SA is 1.84 mm ² from the above formulas (2) and (3). ), The tensile strength due to the non-engaging portion is about 9 kgf (about 88.26 N), which is substantially the same as the desired fixed tensile strength F.

On the other hand, the engagement area SB is 2.02 mm ² from the above formula (2), and from the above formula (1), the compression strength is about 12 kgf (about 117.68 N), and the desired fixed tensile strength F Is over.

  From the above, it can be seen that a fixed tensile strength equal to or higher than the desired fixed tensile strength F can be obtained when the distance 2L between the pair of engagement pieces 32 is 1.2 mm under the above conditions.

  Next, as Example 2, consider a case where the optical fiber 10 is fixed by a plurality of stopper pieces 31B (or 31C).

  First, as the covering portion 14, the same polypropylene (PP) as described above was used.

  Further, it is assumed that the diameter 2R of the covering portion 14 of the optical fiber 10 is 2.2 mm and the diameter 2r of the fiber core wire 12 is 1 mm.

  Here, the fixed tensile strength F of the optical fiber 10 by the stopper 30 is assumed to be 10 kgf (about 98.07 N) or more.

In this case, if the distance 2L between the pair of engagement pieces 32 is 1.6 mm, the engagement area in the single stopper piece 31B (or 31C) is 0.62 mm ² from the above formula (1), Thus, the compressive strength by the engaging portion of the single stopper piece 31B (or 31C) is approximately 3.72 kgf (about 36.48 N).

  Therefore, the single stopper piece 31B (or 31C) cannot obtain a strength satisfying the fixed tensile strength F.

  Even when there are two stopper pieces 31B (or 31C), the compressive strength is 7.44 kgf (about 72.96 N), which is twice the compressive strength, and still has the desired fixed tensile strength. A strength satisfying the strength F cannot be obtained.

  When there are three stopper pieces 31B (or 31C), the compression strength is 11.16 kgf (about 109.44 N), which is three times the compression strength, and exceeds the fixed tensile strength F. Compressive strength can be obtained.

  Therefore, from the viewpoint of compressive strength, for example, as shown in FIG. 7, it can be seen that at least three stopper pieces 31C are required.

Further, the non-engagement area is 2.4 mm ² from the above formulas (2) and (3), and from the formula (4), the tensile strength by the non-engagement portion is about 12 kgf (about 117.68 N). A tensile strength exceeding the desired fixed tensile strength F can be obtained. For example, as shown in FIG. 7, when the three stopper pieces 31C are provided, a tensile strength of 36 kgf (about 353.04 N) or more can be obtained.

  For this reason, it is sufficient to provide a single stopper piece 31B, 31C in terms of tensile strength.

  From the viewpoint of both compressive strength and tensile strength, it can be seen that at least three stopper pieces are required, and a stopper 30C as shown in FIG. 7 is appropriate.

It is a figure which shows the state which fixed the optical fiber to the optical connector. It is a perspective view which shows a stopper. It is a figure which shows the initial state which a stopper begins to engage with a coating | coated part. It is a figure which shows the state which the stopper engaged with the coating | coated part. It is a figure which shows the cross section of the optical fiber in XY coordinate system. It is a perspective view which shows the modification of a stopper. It is a perspective view which shows the other modification of a stopper.

Explanation of symbols

10 Optical fiber 14 Covering portion 30, 30B, 30C Stopper 31B, 31C Stopper piece 32 Engagement piece SA Non-engagement area SB Engagement area

Claims (3)

The optical fiber includes at least one pair of engagement pieces arranged in parallel with a spacing dimension smaller than the width dimension of the covering portion of the optical fiber, and presses the pair of engaging pieces against both side portions of the covering portion. A shape setting method of a stopper in which the pair of engaging pieces engage with both side portions of the covering portion by pushing in a direction substantially perpendicular to the axial direction of the covering portion,
The non-engaging area SA of the stopper in the covering portion in a state where the stopper is engaged with the covering portion,
Pt × SA ≧ F
(Where Pt is the limit tensile stress per unit cross-sectional area of the coating, and F is the required fixed tensile strength of the optical fiber)
A stopper shape setting method for setting the shape of the stopper so as to satisfy. The optical fiber includes at least one pair of engagement pieces arranged in parallel with a spacing dimension smaller than the width dimension of the covering portion of the optical fiber, and presses the pair of engaging pieces against both side portions of the covering portion. A shape setting method of a stopper in which the pair of engaging pieces engage with both side portions of the covering portion by pushing in a direction substantially perpendicular to the axial direction of the covering portion,
An engagement area SB of the stopper in a state where the stopper is engaged with the covering portion,
Pp × SB ≧ F
(Where, Pp is the critical compressive stress per unit cross-sectional area of the coating, and F is the required fixed tensile strength of the optical fiber)
A stopper shape setting method for setting the stopper shape so as to satisfy. A stopper shape setting method according to claim 1 or claim 2,
The stopper includes a plurality of stopper pieces that engage the cover portion substantially perpendicularly to the length direction at different positions along the length direction of the optical fiber,
A stopper shape setting method for setting a shape of the stopper by evaluating a sum of engagement areas or non-engagement areas of the stopper pieces as an engagement area of the stopper or a non-engagement area of the stopper.

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