JP2003029105A - Spacer for optical cable and the optical cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spacer for an optical cable which can fully decrease the residual strain in fibers in bending the cable, even when tape-type optical fibers are housed. SOLUTION: The spacer 1 for an optical cable has a plurality of slots 3 for housing optical fibers on the outer peripheral face and is housed in a cable. The slots 3 are SZ grooves and are formed, in such a manner that the transiting part C between the inversion part of the SZ pattern and the inversion part of the ZS pattern produces a trace periodically changing on the surface of the spacer 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable spacer which is housed inside an optical cable and holds an optical fiber core while protecting the optical fiber, and an optical cable using the optical cable spacer.

[0002]

2. Description of the Related Art As shown in FIG. 11, as a spacer 1 for an optical cable, a slot for accommodating an optical fiber is provided to prevent an abnormal tension from being applied to the optical fiber 2 and to improve workability at the time of branching after intermediate. A spacer 1 in which a groove 3 is meandered (as an SZ groove) is used. Regarding the optical cable 0 having such an SZ groove, Japanese Patent Laid-Open No. 63-301911 (Japanese Patent Publication No.7-13687), Japanese Patent No. 2521526, 1997
It is described in the IEICE Communications Society Conference Proceedings B-10-3, etc.

In the optical cable 0 shown in FIG. 11, the tape-shaped optical fiber 2 is housed in the slot 3. However, there are some which house a single-core optical fiber, and the above-mentioned JP-A-63-301911 ( Japanese Examined Patent Publication (Kokoku) No. 7-13687) describes a reversal angle of a slot suitable for accommodating a single-core optical fiber. The reversal angle is the central angle corresponding to the formation range of the SZ groove on the plane perpendicular to the central axis of the optical cable (see angle α in FIG. 12). Japanese Patent Laid-Open No. 63-301911 (Japanese Patent Publication No. 7-137687) discloses that when a "single core" optical fiber is housed in an SZ groove, if the reversal angle is 275 °, the residual fiber strain when the cable is bent It is disclosed that can be minimized.

[0004]

[Problems to be Solved by the Invention] However, JP-A-63-301
The case of a "single-core" optical fiber is considered in Japanese Patent No. 911 (Japanese Patent Publication No. 713687), and this is directly applied to an optical cable 0 containing a tape-shaped optical fiber 2 as shown in FIG. However, there are the following problems in applying it. The state of the tape-shaped optical fiber 2 in the SZ groove (slot 3) is schematically shown in FIG. FIG. 12 also shows a developed view of the surface of the spacer 1 at the same time, which is shown so that it can be compared with the state of the SZ groove (slot 3) being inverted. For the sake of clarity, only one slot 3 is shown in the sectional view of the spacer 1 shown in the upper part of FIG. Further, the tape-shaped optical fibers 2 stacked in each slot 3 are shown with black circles and white circles so that the stacked state can be easily understood.

The schematic cross-sectional view shown in the upper part of FIG. 12 relates to a cross-section taken along the alternate long and short dash line on the surface development view therebelow. As can be seen from FIG. 12, the laminated tape-shaped optical fiber 2 in the slot 3 is in fact perfectly aligned with the SZ-shaped meander of the slot 3 due to its inability to deform. It cannot be transformed. Therefore, as shown in the upper part of FIG. 12, the tape-shaped optical fiber 2 in the laminated state is in a state in which it is twisted inside the slot 3. The angle α in FIG. 12 is the reversal angle of the SZ groove (slot 3). FIG. 13 shows the schematic sectional views of the upper portion of FIG.

As described above, since the optical fiber 2 does not meander in a state that the shape of the slot 3 is completely matched, the reversal angle of the optical fiber 2 in the slot 3 varies depending on its position. For example, the reversal angle of the optical fiber 2 (marked with a black circle) located above the slot 3 in the state shown in the upper center of FIG. 13 is β in FIG. 13, and the optical fiber 2 located at the bottom of the slot 3 is shown. The reversal angle (marked with a white circle) is γ in FIG. 13, which does not match α. β <α <γ. Therefore, as described in the above-mentioned Japanese Patent Laid-Open No. 63-301911 (Japanese Patent Publication No.7-13687), even if the inversion angle of the slot 3 is 275 °, the actual inversion angle of the optical fiber 2 is 275. Since the temperature does not reach 0 °, some fibers cannot sufficiently reduce the residual fiber strain when the cable is bent.

The present invention provides an optical cable spacer capable of sufficiently reducing the residual fiber strain when the cable is bent, even if the tape-shaped optical fiber is accommodated, and an optical cable using the same. To aim.

[0008]

According to a first aspect of the present invention, there is provided an optical cable spacer having a plurality of optical fiber storage slots on an outer peripheral surface thereof, the optical fiber spacer being accommodated in an optical cable. The slot is formed so that the position of the transition portion between the SZ inversion portion and the ZS inversion portion of the slot in the spacer circumferential direction draws a locus that periodically changes on the spacer surface.

According to a second aspect of the present invention, in the first aspect of the invention, the locus of the transition portion that changes periodically draws a locus that changes spirally with respect to the central axis of the spacer. I am trying.

According to a third aspect of the present invention, in the invention according to the first aspect, the locus of the transitional portion that changes periodically is divided into a portion that rotates to the right and a portion that rotates to the left with respect to the central axis of the spacer. The feature is to draw the loci that appear alternately.

The invention according to claim 4 is characterized in that, in the invention according to claim 3, the locus of the transition portion is represented by the following formula (i) on the developed plane of the outer surface of the spacer. _{y = aφ 0/2 × [} ± (2n + 1-4 × z / P 0)] + aφ 1/2 × sin [2π (z + z 1) / P 1] ... (i) y: along section circumference of the spacer Coordinates z: Coordinates along the central axis of the spacer z ₁ : Arbitrary constant φ ₀ : Inversion angle of trajectory (long period inversion angle) φ ₁ : Inversion angle of slot with respect to trajectory (short period inversion angle) P ₀ : Long period Inversion angle period P ₁ : Short period Inversion angle period (however, P ₁ <P ₀ ) a: Slot core radius n: z / (P _0/2 ) integer part The composite is + when n is an even number and − when n is an odd number.

The invention described in claim 5 is characterized in that, in the invention described in claim 4, the following condition (ii) is satisfied. φ ₀ = 360 ° × m (m is a natural number), 230 ° ≦ φ ₁ ≦ 330 ° (ii)

The invention according to claim 6 is characterized in that, in the invention according to claim 3, the locus of the transition portion is represented by the following formula (iii) on the developed plane of the outer surface of the spacer. _{y = aφ 0/2 × sin} (2πz / P 0) + aφ 1/2 × sin [2π (z + z 1) / P 1] ... (iii) y: coordinate along section circumference of the spacer z: center of the spacer Coordinates along the axis z ₁ : arbitrary constant φ ₀ : reversal angle of trajectory (long period reversal angle) φ ₁ : reversal angle of slot with respect to trajectory (short period reversal angle) P ₀ : period of long period reversal angle P ₁ : Period of short period reversal angle (however, P ₁ <P ₀ ) a: Slot core radius

The invention described in claim 7 is characterized in that, in the invention described in claim 6, the following condition (iv) is satisfied. φ ₀ = 275 ° + 360 ° × (m−1) (m is a natural number), 230 ° ≦ φ ₁ ≦ 330 ° ... (iv)

The invention described in claim 8 uses the optical cable spacer according to any one of claims 1 to 7, and a plurality of tape-shaped optical fibers are housed in each slot of the spacer. It is characterized by that.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION When the cable is bent, S
The strain ε remaining in the optical fiber housed in the Z groove is roughly expressed by the following equation (v). This is disclosed in the above-mentioned Japanese Patent Laid-Open No. 63-301911 (Japanese Patent Publication No. 7-137687).

[Equation 1]

For each character in formula (v), the following values are represented as shown in FIG. Furthermore, each integral represents an integral over one period of the slot. z: Coordinate system u, v along the central axis of the cable: Cartesian coordinate system u '(z), v' (z): u, v orthogonal to the z axis R: Cable Bending radius of the central axis a: Layer radius (distance from the center of the cable to the corresponding optical fiber) P ₁ : Length of one cycle of the SZ groove along the z axis

Here, Japanese Patent Laid-Open No. 63-301911 (Japanese Patent Publication No. 7-136)
Japanese Patent No. 87) considers a "single-core" optical fiber and discusses the case of an SZ groove that draws a simple sine curve on the surface of the spacer. In the case of such an SZ groove, u and v in the equation (v) are obtained by the following equation (vi). However, φ is the reversal angle of this SZ groove.

[Equation 2]

By substituting the equation (vi) into the equation (v) and obtaining the relationship between the inversion angle φ and the residual strain ε, the graph shown in FIG. 2 is obtained. As can be seen from the graph of FIG. 2, in the case of the SZ groove that draws a simple sine curve on the surface of the spacer (see FIG. 12), the maximum strain ε occurs when φ = 275 °.
Becomes smaller. This has already been explained. However, as shown in FIG. 13, different reversal angles (α in FIG. 13,
(See β and γ), it becomes difficult to set the residual strain ε to 0 for all the optical fibers 2. The present invention solves such a problem.

Embodiments of the optical cable spacer and the optical cable of the present invention will be described below with reference to the drawings. The basic configuration of the optical cable described below is shown in FIG.
It is the same as the optical cable 0 shown in FIG. Only the trajectory of the slot 3 formed in the spacer 1 is different for each embodiment. Therefore, the following description of each embodiment will be given focusing on the locus of the slot 3. First, the first embodiment will be described.

A developed view of the outer surface of the spacer of the first embodiment is shown in FIG. In the development view of FIG. 3, for easy understanding, only one locus of the plurality of slots 3 formed is shown. The loci of the other slots 3 are formed parallel to the illustrated slots 3 and all the slots 3 are equidistant. Further, in the developed view of FIG. 3, the slot 3 is shown as a single line for the sake of clarity. In the development view of No. 3, spacer 1
The z-axis is set in the central axis direction of the (cable 0), and the y-axis is set in the direction perpendicular to this.

In the present embodiment, the locus of the slot 3 is such that a locus that vibrates in an SZ shape is superimposed on a locus that changes spirally with respect to the central axis (z axis) of the spacer 1. There is. The spiral locus on which the SZ-shaped vibration is superposed is the SZ inversion part of the slot 3 and the ZS inversion part.
It is a locus connecting the transitional part with the inversion part. The locus of this transition portion is a locus that periodically changes on the surface of the spacer 1. The SZ reversal portion refers to a portion (A portion in FIG. 3) where the locus of the slot 3 on the development plane changes from the S-shape to the Z-shape. On the contrary, the ZS reversal portion means a portion (B portion in FIG. 3) where the locus of the slot 3 on the development plane changes from the Z-shape to the S-shape. The transition section refers to a section (C section in FIG. 3) located between the SZ inversion section and the ZS inversion section described above.

That is, the slot 3 draws a wavy (sine curve in this case) locus so as to be superimposed on the line connecting the transition portions C. Further, in the present embodiment, the line connecting the transition portions C draws a spiral locus (which appears as parallel straight lines on the development plane). The locus of the transition portion C changes periodically as described above, and this will be referred to as "long-period component (dotted line in FIG. 3)" for the sake of description. The slot 3 changes with a further period on this long period component, and this will be referred to as a "short period component" for the sake of explanation. The inversion angle of this short period component is φ ₁ . Further, one cycle of the long cycle component is P ₀ and one cycle of the short cycle component is P ₁ . For example, in this embodiment, φ ₁ = 275 °, P ₀ = 2
000 mm and P ₁ = 500 mm.

In the case of FIG. 3, the long-period component and the short-period component are
It is represented by the following equation (vii) on the yz coordinate axes on the development view. Further, by combining the following expression (vii) into one, the slot 3 is expressed as the following expression (viii) on the yz coordinate axes on the development view.

[Equation 3]

[Equation 4]

Further, considering the coordinate system shown in FIG. 1, the slot 3 of this embodiment is expressed by the following equation (ix).

[Equation 5]

By substituting the equation (ix) into the above equation (v) and obtaining the relationship between the inversion angle φ ₁ and the residual strain ε, FIG.
It looks like the graph shown in. As can be seen from FIG. 4, in the case of the present embodiment, the residual strain ε can be set to almost 0 regardless of the inversion angle φ ₁ of the short period component. However, if the reversal angle φ ₁ is too small, it will be difficult to take out the optical fiber 2 at the time of branching work after intermediate,
The meaning of using the slot 3 as an SZ groove is lost. However, as described above, in the case of this embodiment, the residual strain ε
From this point of view, the reversal angle φ ₁ may be any number.

As described above, by making the long-period component cyclically change, in particular, by making the long-period component spiral, in the present embodiment, the plurality of optical fibers 2 in the slot 3 are formed. Even if it is not possible to make all the inversion angles of the actual short-period components of the same, the difference can be offset by the long-period components. As a result, the residual strain ε can be made almost zero as described above.
Although the reversal angle φ ₁ of the short-period component can take any value, the movement of the optical fiber 2 from the inside (compression side) to the outside (tensile side) of the bending of the cable is ideal over a long distance. Assuming a case where it does not occur in the value of 275 ° (230 ° to 330 °: ± 0.2% in the graph of FIG. 2)
It is preferable to set it as a range of degree).

Next, FIG. 5 shows an outer surface development view of the spacer of the second embodiment. It should be noted that, as in the expanded view of FIG.
In the development view of, only one locus of the plurality of slots 3 formed is shown. The loci of the other slots 3 are formed parallel to the illustrated slots 3 and all the slots 3 are equidistant. Further, in the development view of FIG. 5, the slot 3 is shown as a single line for the sake of clarity. How to set the y-axis and z-axis,
This is similar to the case of FIG.

In the present embodiment, the locus of the slot 3 oscillates in an SZ shape on the locus in which the right rotating portion and the left rotating portion alternately appear with respect to the central axis (z axis) of the spacer 1. The loci are superimposed.
In particular, in the present embodiment, the locus on which the SZ-shaped vibration is superposed is a locus in which spirals of right rotation and left rotation are alternately continuous. The locus in which the right-handed and left-handed spirals are alternately continuous is a locus connecting the transitional portions between the SZ inversion portion and the ZS inversion portion of the slot 3. The locus of this transition portion is a locus that periodically changes on the surface of the spacer 1. The definitions of the SZ inversion unit, ZS inversion unit, and transition unit are the same as in the case of FIG.

That is, the slot 3 draws a wavy (here, sine curve) locus so as to be superimposed on the line connecting the transition portions (dotted line in FIG. 5). Further, in the present embodiment, the locus in which the line connecting the transitional portions alternates between the clockwise rotating portion and the counterclockwise rotating portion is drawn. This trajectory is
A locus in which a left-handed spiral locus and a right-handed spiral locus are alternately continuous (represented as a polygonal line on the developed plane) is drawn. As described above, the locus of this transition portion changes periodically (long period component), and the slot 3 changes with a further period on the long period component (short period component). The inversion angle of this long period component is φ ₀ , and the inversion angle of the short period component is φ ₁ . Further, one cycle of the long cycle component is P ₀ and one cycle of the short cycle component is P ₁ .
For example, in the present embodiment, φ ₀ = 360 °, φ ₁ = 275
, P ₀ = 4000 mm and P ₁ = 500 mm.

In the case of FIG. 5, the long period component and the short period component are
It is represented by the following equation (x) on the yz coordinate axes on the development view. Further, by combining the following expression (x) into one, the slot 3 is expressed by the following expression (xi) on the yz coordinate axes on the development view. Incidentally, n is an integer part of _{z / (P 0/2)} , the long-period component of the formula (x), and the formula (x
The compound (±) in the first term parenthesis in i) is + when n is an even number and − when n is an odd number.

[Equation 6]

[Equation 7]

Further, considering the coordinate system shown in FIG. 1, the slot 3 of this embodiment is expressed by the following equation (xii).

[Equation 8]

By substituting the equation (xii) into the above-mentioned equation (v), the relationship between the inversion angles φ ₀ and φ ₁ and the residual strain ε is obtained.
The graphs shown in FIGS. 6 and 7 are obtained [P ₀ = 4
000 mm, P ₁ = 500 mm, R = 500 mm, integration range 0 ≦ z ≦ 4000 (mm)]. FIG. 6 shows the relationship between the inversion angle φ ₀ of the long period component and the residual strain ε when the inversion angle φ ₁ of the short period component is 180 °, 275 °, and 360 °. As can be seen from FIG. 6, in the case of the present embodiment, when the inversion angle φ ₁ of the short-period component is 275 °, the residual strain ε is low and is hardly affected by the inversion angle φ ₀ of the long-period component. I understand. If the reversal angle φ ₀ on the long cycle side is m times 360 ° (m is a natural number),
Residual strain ε regardless of the inversion angle φ ₁ of the short-period component
It can be seen that can be zero.

In particular, the smallest slope of the graph when φ ₀ is around 360 ° × m is φ ₀ = 360 ° (m = 1)
And φ ₁ = 275 °. This is
This means that even if the reversal angles φ ₀ and φ ₁ slightly change, the residual strain ε does not change significantly, and a large manufacturing tolerance can be taken, which is advantageous in improving the yield.
However, as described in the case of FIG. 3, if the reversal angle φ ₁ of the short-period component is too small, it becomes difficult to take out the optical fiber 2 at the time of post-intermediate branching work.

FIG. 7 shows that the inversion angle φ ₀ of the long period component is 3
The relationship between the inversion angle φ ₁ of the short-period component and the residual strain ε when 60 ° is shown. As you can see from Figure 7,
It can be seen that if the inversion angle φ ₀ of the long-period component is 360 °, the residual strain ε can be set to 0 regardless of the inversion angle φ ₁ of the short-period component. That is, even if the actual reversal angles of all the optical fibers 2 in the slots 3 are not the same, the residual strain ε of all the optical fibers 2 can be made almost zero.

As described above, the long-period component is periodically changed, and in particular, in the present embodiment, the left-hand spiral spiral locus and the right-hand spiral spiral trace are alternately continuous. By doing so, even if the inversion angles of the actual short period components of the plurality of optical fibers 2 in the slot 3 cannot all be made the same, this difference can be canceled by the long period component. . As a result, the residual strain ε is small as described above, and is almost 0 depending on the conditions.
Can be The inversion angle φ of the short-period component
_{Although 1} can take any value, the optical fiber 2 from the inside (compression side) to the outside (tensile side) of the cable bend
Assuming that the movement of does not occur ideally over a long distance, values near 275 ° (230 ° to 330 °:
It is preferable to set it in the range of about ± 0.2% in the graph of FIG.

The above formula (i) and formula (xi) are substantially the same. However, regarding the formula (i), z
The value of ₁ is introduced so that the phase shift of the short period component with respect to the long period component can be expressed. In other words, the case where z ₁ = 0 in the formula (i) is the formula (xi).

Next, FIG. 8 shows an outer surface development view of the spacer of the third embodiment. Similar to the developed views of FIGS. 3 and 5, the developed view of FIG. 8 shows only one locus of the plurality of slots 3 formed. The loci of the other slots 3 are formed parallel to the illustrated slots 3 and all the slots 3 are equidistant. Also,
In the exploded view of FIG. 8, the slot 3 is shown as a single line for clarity. The method of setting the y-axis and the z-axis is the same as in the case of FIGS.

In the present embodiment, the locus of the slot 3 is also alternated between the portion that rotates to the right and the portion that rotates to the left with respect to the central axis (z axis) of the spacer 1, as in the second embodiment described above. A locus that vibrates in an SZ shape is superimposed on the locus that appears. However, in the present embodiment, the locus on which the SZ-shaped vibration is superimposed is not a simple spiral shape but a locus that draws a sine curve on the development plane. The locus that draws a sine curve on the development plane that is the superimposing source is a locus that connects the transitional portion between the SZ inversion portion and the ZS inversion portion of the slot 3. The locus of this transition portion is a locus that periodically changes on the surface of the spacer 1. The definitions of the SZ inversion unit, the ZS inversion unit, and the transition unit are the same as those in FIGS. 3 and 5.

That is, the slot 3 is a line connecting the transition parts (see FIG.
Wavy around here (dotted line in 5)
The path of (b) is drawn. And in this embodiment,
The part connecting the line part turns right and the part turns left
It depicts the paths that appear to each other. This trajectory is
It appears as a sine wave curve on the surface. This move
The locus of the line part changes periodically as described above (long
(Periodic component), slot 3 has a further period on the long period component.
It has been changing (short period component). Of this long period component
Inversion angle is φ₀And the inversion angle of the short period component is φ₁Is.
In addition, one cycle of the long cycle component is P₀， One cycle of short cycle component
Is P₁Is. For example, in this embodiment, φ ₀= 360
°, φ₁= 275 °, P₀= 4000 mm, P₁= 500
It is set to mm.

In the case of FIG. 8, the long period component and the short period component are
It is represented by the following equation (xiii) on the yz coordinate axes on the development view. Further, by combining the following expression (xiii) into one, the slot 3 is expressed by the following expression (xiv) on the yz coordinate axes on the development view.

[Equation 9]

[Equation 10]

Further, considering the coordinate system shown in FIG. 1, the slot 3 of this embodiment is represented by the following equation (xv).

[Equation 11]

By substituting the equation (xv) into the above equation (v), the relationship between the inversion angles φ ₀ and φ ₁ and the residual strain ε is obtained.
The graphs shown in FIGS. 9 and 10 are obtained [P ₀ =
4000 mm, P ₁ = 500 mm, R = 500 mm, integration range 0 ≦ z ≦ 4000 (mm)]. FIG. 9 shows the relationship between the inversion angle φ ₀ of the long period component and the residual strain ε when the inversion angle φ ₁ of the short period component is 180 °, 275 °, and 360 °. As can be seen from FIG. 9, in the case of the present embodiment, when the inversion angle φ ₁ of the short period component is 275 °, the residual strain ε is almost 0 without being substantially affected by the inversion angle φ ₀ of the long period component. I understand that I can do it. In addition, the reversal angle φ ₀ on the long cycle side is 275 ° + 360 ° × (m-1)
It can be seen that if (m is a natural number), the residual strain ε can be set to 0 regardless of the inversion angle φ ₁ of the short period component.

Therefore, φ ₀ = 275 ° + 360 ° × (m
−1) and φ ₁ = 275 °, the reversal angle φ ₀ ,
This means that the residual strain ε can be made almost zero even if φ ₁ is slightly changed, and a large manufacturing tolerance can be taken, which is advantageous in improving the yield. However, if the reversal angle φ ₁ of the short period component is too small, it becomes difficult to take out the optical fiber 2 at the time of post-intermediate branching work, as described with reference to FIGS. 3 and 5.

Contrary to the case of FIG. 9, FIG. 10 shows the reversal angles φ ₀ of the long period components of 180 °, 275 °, 360 °, 6
The relationship between the inversion angle φ ₁ of the short-period component and the residual strain ε is shown for the case of 35 ° (635 ° = 275 ° + 360 °). As can be seen from FIG. 7, if the inversion angle φ ₀ of the long-period component is 275 ° + 360 ° × (m−1), the residual strain ε is 0 regardless of the inversion angle φ ₁ of the short-period component. I see you can do it. However, when the inversion angle φ ₀ of the long-period component is not 275 ° + 360 ° × (m−1), the residual strain ε is determined only when φ ₁ = 275 ° + 360 ° × (l−1) (l is a natural number). It can be seen that it can be 0. That is, φ ₀ = 275 ° + 360 ° × (m−
1) or 275 ° + 360 ° × (l-1), the residual strains ε of all the optical fibers 2 in the slots 3 are not the same even if the actual inversion angles are not the same. It can be almost zero.

As described above, by making the long-period component cyclically change, in particular, in the present embodiment, the long-period component is formed into a locus that draws a sine curve on the developed plan view, so that the slot 3 can be obtained. Even if the inversion angles of the actual short-period components of the plurality of optical fibers 2 cannot all be made the same, this difference can be canceled by the long-period components. As a result, the residual strain ε can be made small as described above, and can be made almost zero depending on the conditions. Although the reversal angle φ ₁ of the short-period component can take any value, the movement of the optical fiber 2 from the inside (compression side) to the outside (tensile side) of the bending of the cable is ideal over a long distance. Assuming a case where it does not occur in the value of 275 ° (230 ° to 330 °: ± 0.2% in the graph of FIG. 2)
It is preferable to set it as a range of degree).

The above equation (iii) and equation (xi)
v) is substantially the same. However, with regard to the formula (iii), the value of z ₁ is introduced so that the phase shift of the short period component with respect to the long period component can be expressed.
In other words, the case where z ₁ = 0 in the formula (iii) is the formula (xiv).

[0048]

In the optical cable spacer (optical cable) of the present invention, the transition portion between the SZ inversion portion and the ZS inversion portion of the slot formed as the SZ groove has a locus that periodically changes on the spacer surface. As illustrated, the slots are formed, that is, the slots are formed so as to draw a locus in which the long-period component described above periodically changes along the central axis of the spacer. Therefore, according to the present invention, even if the actual inversion angles of the plurality of tape-shaped optical fibers in the slot cannot all be the same, this difference can be canceled by the long-period component described above, The residual strain ε can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing respective values used for calculation of residual strain in an optical cable.

FIG. 2 is a graph showing the relationship between inversion angle and residual strain.

FIG. 3 is a surface development view of a first embodiment of an optical cable spacer (or optical cable) of the present invention.

FIG. 4 is a graph showing the relationship between the inversion angle and the residual strain in the first embodiment.

FIG. 5 is a surface development view of a second embodiment of the optical cable spacer (or optical cable) of the present invention.

FIG. 6 is a graph showing the relationship between the inversion angle of the long-period component and the residual distortion in the second embodiment.

FIG. 7 is a graph showing the relationship between the inversion angle of the short cycle component and the residual distortion in the second embodiment.

FIG. 8 is a surface development view of a third embodiment of the optical cable spacer (or optical cable) of the present invention.

FIG. 9 is a graph showing the relationship between the inversion angle of the long-period component and the residual distortion in the third embodiment.

FIG. 10 is a graph showing the relationship between the inversion angle of the short cycle component and the residual distortion in the third embodiment.

FIG. 11 is a sectional view and a side view of the optical cable.

FIG. 12 is a schematic cross-sectional view and surface development view of a spacer.

FIG. 13 is a schematic sectional view of a spacer.

[Explanation of symbols]

0 ... Optical cable, 1 ... Spacer, 2 ... Optical fiber, 3 ...
slot.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuhiro Akasaka             Sumitomoden 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa             Ki Industry Co., Ltd. Yokohama Works F term (reference) 2H001 BB10 BB11 BB16 PP01

Claims (8)

[Claims] 1. A spacer for an optical cable having a plurality of slots for accommodating an optical fiber on an outer peripheral surface and accommodated in an optical cable, wherein the slot is an SZ groove, and an SZ inversion portion and a ZS inversion portion of the slot are provided. The spacer for an optical cable, wherein the slot is formed so that the position of the transitional portion of the spacer in the circumferential direction of the spacer draws a locus that periodically changes on the spacer surface. 2. The locus of the transition portion, which changes periodically,
The optical cable spacer according to claim 1, wherein a trajectory that changes spirally with respect to the central axis of the spacer is drawn. 3. A locus of the transition section that changes periodically is
The spacer for an optical cable according to claim 1, wherein a locus in which a right-handed portion and a left-handed portion are alternately formed with respect to the central axis of the spacer is drawn. 4. The spacer for an optical cable according to claim 3, wherein the locus of the transition portion is represented by the following formula (i) on the development plane of the outer surface of the spacer. _{y = aφ 0/2 × [} ± (2n + 1-4 × z / P 0)] + aφ 1/2 × sin [2π (z + z 1) / P 1] ... (i) y: along section circumference of the spacer Coordinates z: Coordinates along the central axis of the spacer z ₁ : Arbitrary constant φ ₀ : Inversion angle of the trajectory (long period inversion angle) φ ₁ : Inversion angle of the slot with respect to the trajectory (short period inversion angle) P ₀ : Period P ₁ of the long period reversal angle: period of the short period reversal angle (where P ₁ <P ₀ ) a: integer part of the core radius n: z / (P _0/2 ) of the slot Compounds in parentheses are + when n is an even number and-when n is an odd number. 5. The optical cable spacer according to claim 4, wherein the following condition (ii) is satisfied. φ ₀ = 360 ° × m (m is a natural number), 230 ° ≦ φ ₁ ≦ 330 ° (ii) 6. The optical cable spacer according to claim 3, wherein a locus of the transition portion is represented by the following formula (iii) on a developed plane of the outer surface of the spacer. _{y = aφ 0/2 × sin} (2πz / P 0) + aφ 1/2 × sin [2π (z + z 1) / P 1] ... (iii) y: coordinate along section circumference of the spacer z: center of the spacer Coordinates along the axis z ₁ : arbitrary constant φ ₀ : reversal angle of the trajectory (long period reversal angle) φ ₁ : reversal angle of the slot with respect to the trajectory (short period reversal angle) P ₀ : the long period reversal angle Period P ₁ : the period of the short period inversion angle (where P ₁ <P ₀ ) a: the center radius of the slot 7. The optical cable spacer according to claim 6, wherein the following condition (iv) is satisfied. φ ₀ = 275 ° + 360 ° × (m−1) (m is a natural number), 230 ° ≦ φ ₁ ≦ 330 ° ... (iv) 8. An optical cable using the optical cable spacer according to claim 1, wherein a plurality of tape-shaped optical fibers are housed in each slot of the spacer.