JP5429102B2 - Protection structure for loose tube type optical cable - Google Patents

Description

  The present invention relates to a protective structure for an optical fiber cable mounted on a substrate such as an optical communication device, an optical switching device, or an optical information processing device.

A conventional technique for mounting a loose tube type optical cable wired to an optical communication device, an optical switching device, an optical information processing device, etc. on a substrate mounted on the wiring device will be described with reference to FIGS. To do.
FIG. 8 is a schematic view of the loose tube type optical cable mounted on the substrate 1, and FIG. 9 is an enlarged view of a main part A of FIG.
In FIG. 8, the optical component 2 is mounted on the substrate 1, and a loose tube type optical cable including the optical fiber 6 and the loose tube 4 protecting the optical fiber 6 is connected to the optical component 2 and mounted on the substrate 1. Has been. The loose tube type optical cable is locked to the substrate 1 by a clamp 3.

  Further, as a conventional technique, a circular inner wall is protruded, and concentric intermediate partition walls are formed outside the circular inner wall with two wide through openings at 180 ° symmetrical positions. On the outside of the intermediate partition wall, an outer peripheral partition wall having approximately 1/4 of the concentric circle outwardly extended in a spiral shape is projected, a line opening is formed between both ends, and the circular inner wall and the intermediate partition A substantially double-circular inner periphery storage portion and outer periphery storage portion are formed between the walls and between the intermediate partition wall and the outer periphery partition wall, and the optical fiber cord is wound in a substantially circular shape between the inner periphery storage portion and the outer periphery storage portion. There is an optical fiber cable distribution board that is housed in (see, for example, Patent Document 1).

JP-A-4-291207 (page 3-4, FIG. 1)

  If the optical fiber 6 is bent when wiring the loose tube type optical cable to the apparatus, the optical fiber 6 is broken or the electrical characteristics are deteriorated. Therefore, it is necessary to secure the minimum bending radius of the optical fiber 6.

However, if the storage area of the loose tube type optical cable is to be reduced in size, the boundary between the exposed portion of the optical fiber 6 and the loose tube 4 is applied to the bent portion of the loose tube type optical cable when the loose tube type optical cable is mounted on the substrate. However, when the optical fiber 6 is bent, a return force is applied to the optical fiber 6 and the loose tube 4 in the direction opposite to the bending direction.
Further, since the loose tube 4 is harder than the optical fiber 6 and has a strong return force, conventionally, the strong return force of the loose tube 4 is applied to the optical fiber 6 as shown in FIG. There is a problem that the optical fiber 6 is bent at the boundary with the loose tube 4.

  In Patent Document 1, the partition wall for guiding the optical fiber cable is provided on the wiring board so that the optical fiber cable is not bent. However, since the wiring board itself is large, the entire apparatus becomes large. There was a point.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a protection structure for a loose tube type optical cable that can reduce the optical cable storage area while ensuring the minimum bending radius of the optical fiber. It is what.

The loose tube type optical cable protection structure according to the present invention includes a loose tube type optical cable having an optical fiber and a loose tube that protects the optical fiber, and a substrate on which the loose tube type optical cable is mounted. And a protective tube is provided so as to cover the boundary between the optical fiber and the loose tube, and the inner side of the inner wall of the protective tube has a bending radius based on a minimum radius R satisfying the following formula: The outer side of the inner wall has a first contact that contacts the optical fiber with the minimum allowable radius of the optical fiber .

In the protective structure of the loose tube type optical cable according to the present invention, a protective tube is provided so as to cover the boundary between the optical fiber and the loose tube, and the inner wall of the protective tube has a bending radius based on the minimum radius R satisfying the following equation: Alternatively, since the outer wall of the protective tube has the first contact point that contacts the optical fiber at the minimum allowable radius of the optical fiber , the optical cable housing area can be reduced in size while ensuring the minimum bending radius of the optical fiber. There is an effect that can.

It is the schematic which mounted the loose tube type optical cable of this invention on the board | substrate 1. FIG. FIG. 3 is an enlarged view of a main part A of FIG. 1 according to the first and second embodiments. 3 is a diagram illustrating a positional relationship between a loose tube type optical cable and a protective tube 5 according to Embodiment 1. FIG. It is the enlarged view to which the front-end | tip part vicinity of the loose tube 4 of FIG. 3 was expanded. FIG. 10 is a diagram illustrating a position of a clamp 3 that guides an optical fiber 6 exposed from a protective tube 5 according to the second embodiment. FIG. 10 is an enlarged view of a main part A of FIG. 1 according to the third embodiment. FIG. 10 is a diagram illustrating a position of a clamp 3 for guiding an optical fiber 6 exposed from a protective tube 5 according to a third embodiment. It is the schematic which mounted the conventional loose tube type optical cable on the board | substrate 1. FIG. It is an enlarged view of the principal part A of FIG.

Embodiment 1 FIG.
FIG. 1 is a view of a loose tube type optical cable according to the present invention mounted on a substrate 1. In the figure, an optical component 2 is mounted on a substrate 1, and a loose tube type optical cable comprising an optical fiber 6 and a loose tube 4 protecting the optical fiber 6 is connected to the optical component 2 and mounted on the substrate 1. Yes. The boundary between the loose tube 4 and the optical fiber 6 is covered with a thermoplastic protective tube 5 having a desired bending radius, and the loose tube type optical cable is locked to the substrate 1 with a clamp 3.

FIG. 2 is an enlarged view of a main part A of FIG. 1 according to the first and second embodiments.
When the loose tube 4 is passed through the protective tube 5, the friction between the distal end of the loose tube 4 and the protective tube 5, which becomes the boundary with the optical fiber 6, and the return force that the loose tube 4 naturally becomes straight, The vicinity of the tip of the loose tube 4 does not follow the inside of the inner wall of the protective tube 5.
In the figure, the vicinity of the tip of the loose tube 4 is in contact with the inner wall of the protective tube 5 at the contact A and is in contact with the outer wall of the protective tube 5 at the contact B. Further, the outer wall outer side of the optical fiber 6 is in contact with the inner wall outer side of the protective tube 5 at the contact point G 2, and the optical fiber 6 is bent along the protective tube 5 from the contact point G 2 to the end surface N of the protective tube 5.

FIG. 3 is a diagram showing a positional relationship between the loose tube type optical cable and the protective tube 5 according to the first embodiment. The loose tube type optical cable is obtained by passing an optical fiber 6 having an outer diameter d1 through a loose tube 4 having an inner diameter d2 and an outer diameter d3. The loose tube 4 is cut in the middle of the optical fiber 6. In the figure, a loose tube type optical cable is passed through a protective tube 5 having an inner diameter d4 (d4> d3) larger than the outer diameter d3 of the loose tube 4.
FIG. 4 is an enlarged view in which the vicinity of the distal end portion of the loose tube 4 of FIG. 3 is enlarged.

In the optical fiber 6, due to a return force that tends to be straight, the outside of the optical fiber 6 is outside the inner wall of the loose tube 4 (contact point J), and the inside of the optical fiber 6 is inside the inner wall of the tip of the loose tube 4 (contact point I). ) And the outer wall outer side of the optical fiber 6 tends to be arcuate in contact with three points on the outer wall inner side (contact point G2) of the protective tube 5.
In FIG. 3, the radius of the center line of the optical fiber 6 that draws arcs in contact with the loose tube 4 and the protective tube 5 at the contacts J, I, and G2, respectively, is the minimum allowable radius R2 as the minimum bending radius of the optical fiber 6 to be secured. .

  Next, the minimum radius R inside the inner wall of the protective tube 5 is derived for reducing the size of the optical cable storage area while ensuring the minimum allowable radius R2 of the optical fiber 6.

  The center of the minimum radius R inside the inner wall of the protective tube 5 is the origin (0, 0), the outer diameter d1 of the optical fiber 6, the inner diameter of the loose tube 4 is d2, the outer diameter is d3, and the inner diameter of the protective tube 5 is d4. The coordinates of the contact A at which the straight loose tube 4 is in contact with the inner wall of the protective tube 5 is (−R, 0). The center of the minimum allowable radius R2 of the optical fiber 6 is defined as (α, β).

  After the optical fiber 6 comes into contact with the protective tube 5 at the contact point G2, the optical fiber 6 naturally bends along the inner wall of the protective tube 5 due to the return force. The circle E is a circle drawn by the inner wall of the optical fiber 6 at that time. Yes, the following equation (1) holds from the equation of the circle.

  The circle F is a circle drawn on the inner side of the outer wall of the optical fiber 6 when the optical fiber 6 is bent at the minimum allowable radius R2, and the following equation (2) is established from the equation of the circle.

  The circle E is inscribed in the circle F, and the inner contact point G is disposed on an extension line connecting the circle E and the center of the circle F. When the coordinates of the inner contact G are (kα, kβ) and are substituted for (X, Y) in the equations (1) and (2), the following equations (3) and (4) are established.

  From the above equations (3) and (4), the following equations (5) and (6) are derived, respectively.

  From the above equations (5) and (6), the following equation (7) is derived.

Next, the circle F passes through the intersection H of the line connecting the contact J and the center point (α, β) of the minimum allowable radius R2 of the optical fiber 6 and the contact I.
The coordinates of the point H are (− (R + (d3−d2) / 2 + d2−d1), β).
Since the Y coordinate of the point I is the same as the Y coordinate of the point B, and the point B is on the circle C drawn by the outside of the inner wall of the protective tube 5, the following equation (8) is established from the circle equation of the circle C.

上記式（８）と点ＢのＸ座標がＸ＝−（Ｒ＋ｄ３）であることから、点Ｂの座標は、次のようになる。

Since the X coordinate of the above equation (8) and the point B is X = − (R + d3), the coordinate of the point B is as follows.

  Therefore, the coordinates of the point I are as follows.

  Since the point H is on the circle F, substituting the coordinates of the point H into (X, Y) in the equation (2) gives the following equation (9).

この式（９）から次式（１０）が導き出される。

From this equation (9), the following equation (10) is derived.

αは点ＨのＸ座標より大きいことからαの範囲が（−（Ｒ＋（ｄ３−ｄ２）／２＋ｄ２−ｄ１）＜α＜０）となって次式（１１）が導き出される。

Since α is larger than the X coordinate of the point H, the range of α is (− (R + (d3−d2) / 2 + d2−d1) <α <0), and the following equation (11) is derived.

  From the above equations (7) and (11), the following equation (12) is derived.

点Ｉは円Ｆ上にあるので、点Ｉの座標、式（１１）のα及び式（１２）のβを、式（２）にそれぞれ代入すると、次式（１３）が導き出される。

Since the point I is on the circle F, the following equation (13) is derived by substituting the coordinates of the point I, α in equation (11), and β in equation (12) into equation (2), respectively.

  From the above formula (13), the minimum allowable radius R2 of the optical fiber 6, the outer diameter d1 of the optical fiber 6, the inner diameter d2 of the loose tube 4, the outer diameter d3 of the loose tube 4, and the inner diameter d4 of the protective tube 5, the minimum radius of the protective tube 5 R can be derived.

  The protective tube 5 having such a length that the minimum radius inside the inner wall derived in this way exceeds R, the inner diameter d4, and the contact point G2 between the outer wall of the optical fiber 6 is passed through the boundary between the loose tube 4 and the optical fiber 6. Thus, the optical fiber 6 can be guided to a desired bending radius while ensuring the minimum allowable radius R2 of the optical fiber 6, and the optical cable storage area can be reduced in size.

In the first embodiment, the clamp 3 that guides the optical fiber 6 is installed on the circle C drawn by the outer side of the inner wall of the protective tube 5 after the optical fiber 6 exits from the end face of the protective tube 5.
By doing in this way, the optical fiber 6 which came out from the end surface of the protection tube 5 can be guided, without the optical fiber 6 leaving | separating from the contact G2.

Embodiment 2. FIG.
FIG. 5 is a diagram illustrating the position of the clamp 3 for guiding the optical fiber 6 exposed from the protective tube 5 according to the second embodiment. The portion of the optical fiber 6 beyond the contact point G2 is along the outside of the inner wall of the protective tube 5 due to the return force that the fiber 3 tries to straighten. If the end face N of the optical fiber 6 and the protective tube 5 is a contact point G3, and a circle having the same radius R2 as the minimum allowable radius of the optical fiber 6 is a circle F3, the clamp 3 is on the circle F3 or from the outside of the circle F3. It is installed between the inside of a circle C that draws the minimum radius R.

  By doing in this way, the optical fiber 6 which came out from the end surface N of the protection tube 5 can be guided, without the optical fiber 6 leaving | separating from the contact G2. Moreover, since the clamp 3 is provided inside the circle C that draws the minimum radius R of the protective tube 5, the optical cable storage area can be further reduced in size.

Embodiment 3 FIG.
FIG. 6 is an enlarged view of a main part A of FIG. 1 according to the third embodiment.
In the figure, the optical fiber 6 is in contact with the protective tube 5 at the contact point G2, and the end surface N of the protective tube 5 is intended to further reduce the size of the optical cable storage area by bending the outer wall outer side of the optical fiber 6 to the inner side of the inner wall of the protective tube 5. It is a thing.

FIG. 7 is a diagram illustrating the position of the clamp 3 for guiding the optical fiber 6 exposed from the protective tube 5 according to the third embodiment.
If there is a tolerance in the outer diameter d3 of the loose tube 4 and the tolerance is determined by the specifications of the loose tube type optical cable, the position where the loose tube 4 is supported by the protective tube 5 is the outer diameter d3 of the loose tube 4. Varies with size.
In Embodiment 3, the contacts between the loose tube 4 and the protective tube 5 when the outer diameter d3 of the loose tube 4 is the largest are A and B, and the contact between the optical fiber 6 and the protective tube 5 at that time is G2. When the outer diameter d3 of the loose tube 4 is the smallest, the contacts between the loose tube 4 and the protective tube 5 are A ′ and B ′, and the contact between the optical fiber 6 and the protective tube 5 at that time is G2 ′.
In order to ensure the minimum allowable radius R2 of the optical fiber 6, it is necessary that not only the contacts B and G2 but also the contacts B ′ and G2 ′ can exist outside the inner wall of the protective tube 5. When the contact point between the optical fiber 6 and the protective tube 5 is G2 ′ and the circle R2 having the same radius as the minimum allowable radius of the optical fiber 6 is a circle F2 ′, the clamp 3 is on the circle F2 ′ or outside the circle F2 ′. To the inside of a circle C that describes the minimum radius R of the protective tube 5.

  By doing in this way, the optical fiber 6 which came out from the end surface of the protection tube 5 can be guided, without the optical fiber 6 leaving | separating from the contact G2 or G2 '. Moreover, since the clamp 3 is provided inside the circle C that draws the minimum radius R of the protective tube 5, the optical cable storage area can be further reduced in size.

  In the first to third embodiments, the clamp 3 is used to guide the optical fiber 6. However, any clamp may be used as long as positioning is performed after the optical fiber 6 is exposed.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Optical component 3 Clamp 4 Loose tube 5 Protection tube 6 Optical fiber

Claims (4)

A loose tube type optical cable having an optical fiber and a loose tube protecting the optical fiber;
A protective structure for a loose tube type optical cable comprising a substrate on which the loose tube type optical cable is mounted,
A protection tube is provided to cover the boundary between the optical fiber and the loose tube, and the inner wall of the protection tube has a bending radius based on a minimum radius R satisfying the following formula. Construction.

2. The protective structure of a loose tube type optical cable according to claim 1, wherein the outer side of the inner wall of the protective tube has a first contact point in contact with the optical fiber at a minimum allowable radius of the optical fiber. A guide portion for locking the exposed portion of the optical fiber;
The guide portion is provided between the outside of the inner wall of the end face of the protective tube and the minimum allowable radius of the optical fiber passing through the contact point between the optical fiber and the inside of the minimum radius inside the protective tube inner wall. The protective structure of the loose tube type optical cable according to claim 2. A guide portion for locking the exposed portion of the optical fiber;
The loose tube type according to claim 2, wherein the guide portion is provided between a minimum allowable radius of the optical fiber passing through the first contact and an inner side of the minimum radius inside the protective tube inner wall. Optical cable protection structure.

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