JP2010191085A - Spacer for optical fiber cable and optical fiber cable having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a parameter of groove depth in an optimum design of the thickness of a rib which is a major factor for reducing the outer diameter of an optical fiber cable and to provide an optical fiber cable in which the parameter is taken into consideration. <P>SOLUTION: In the optical fiber cable, the depth of grooves is denoted by h, the thickness of each rib between the groove bottom corners of a plurality of optical fiber ribbon housing grooves is denoted by b, the clearance of the groove depth which gives the allowable deformation quantity of cables is denoted by L, when L is a fixed set value and h is set to be a fixed value not smaller than 1.8 mm and smaller than 4.5 mm, b is given as a function of h by b≥Ah<SP>3</SP>/(L-B), where A and B are constants, respectively, and b is not larger than 0.95 mm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical fiber cable.

  There is a demand for reducing the outer diameter of an optical fiber cable.

  Patent Document 1 proposes to reduce the outer diameter of the optical fiber cable by using a metal laminate tape obtained by laminating a metal and a resin on the outer peripheral surface of the hollow pipe.

  Patent Document 2 proposes that the outer diameter of the optical fiber cable is reduced by stacking two or more core wires made of a plurality of optical fibers in parallel and storing them in the groove of the spacer.

  Patent Document 3 proposes that the outer diameter of the optical fiber cable with respect to the optical fiber core wire is reduced so that the circle C surrounding the cross section of the cable core has a minimum diameter.

JP 2004-317586 A Japanese Patent Application Laid-Open No. 10-123381 JP 2002-341001 A

  As described above, various proposals for reducing the size of the cable core have been made in order to reduce the outer diameter of the optical fiber cable.

  Conventionally, a design philosophy that employs a large rib thickness has been applied when it is assumed that the amount of cable deformation is large because the amount of cable deformation due to lateral pressure load is directly related to the thickness of the rib. .

  According to the experiments by the inventors of the present application, when compared with each slot, a result that the rib is more likely to collapse is obtained when the outer diameter is larger, and a result that the thicker rib is weak against the side pressure is obtained. As a result, the conventional concept of rib thickness = side pressure retention characteristics should be reexamined, and it is necessary to consider the groove depth parameter for optimal design of rib thickness. understood.

  In view of the above, the present invention provides an optical fiber cable in which the groove depth parameter is obtained and the parameter is taken into consideration in the optimum design of the rib thickness, which is the main cause of reducing the outer diameter of the optical fiber cable. The purpose is to do.

  In addition, the present invention provides an optical fiber cable in which the groove depth clearance, which is the allowable deformation amount of the cable, is optimized in consideration of the relationship between the rib thickness and the groove depth in order to reduce the outer diameter of the optical fiber cable. The purpose is to provide.

In the present invention, a plurality of optical fiber ribbon core storage grooves are provided around a circular cable core in the center direction, and the optical fiber ribbons are stored in the respective optical fiber ribbon storage grooves. In the optical fiber cable in which a rib is formed between the bottom ends of the optical fiber tape core housing grooves,
The plurality of optical fiber ribbon core storage grooves include or do not include at least one shallow optical fiber ribbon storage groove, and are formed in the same shape by removing the shallow optical fiber ribbon storage groove. The groove depths are defined by h, the groove depths between the groove bottom corners of the plurality of optical fiber ribbon core storage grooves, and the allowable cable deformation amount of the groove depth. The clearance of the groove depth is set to L, L is set to a fixed value, and h = L + N · t
Where N is the number of optical fiber cores housed in the optical fiber tape core housing grooves of the same groove depth and is a fixed value in the range of 5 to 10, and t is the optical fiber housed in the grooves It is a fixed value in the range of 0.26-0.30 in the thickness mm of the core wire,
When h is set to a fixed value in the range of 1.8 to less than 4.5 mm,
b is for h,
b> or = Ah ³ / (LB)
Here, A and B are set as constants, and are set to values within a range of 0.95 mm or less. An optical fiber cable is provided.

In the present invention, a plurality of optical fiber ribbon core storage grooves are provided around a circular cable core in the center direction, and the optical fiber ribbons are stored in the respective optical fiber ribbon storage grooves. In the optical fiber cable in which a rib is formed between the bottom ends of the optical fiber tape core housing grooves,
The plurality of optical fiber ribbon core storage grooves include or do not include at least one shallow optical fiber ribbon storage groove, and are formed in the same shape by removing the shallow optical fiber ribbon storage groove. The groove depths are defined by h, the groove depths between the groove bottom corners of the plurality of optical fiber ribbon core storage grooves, and the allowable cable deformation amount of the groove depth. The clearance of the groove depth is set to L, L is set to a fixed value, and h = L + N · t
Where N is the number of optical fiber cores housed in the optical fiber tape core housing grooves of the same groove depth and is a fixed value in the range of 5 to 10, and t is the optical fiber housed in the grooves It is a fixed value in the range of 0.26-0.30 in the thickness mm of the core wire,
When h is set to a fixed value in the range of 1.8 to less than 4.0 mm,
b is for h,
b> or = Ah ³ / (LB)
Here, A and B are set as constants, and are set to values within an area of 0.85 mm or less. An optical fiber cable is provided.

In the present invention, a plurality of optical fiber ribbon core storage grooves are provided around a circular cable core in the center direction, and the optical fiber ribbons are stored in the respective optical fiber ribbon storage grooves. In the optical fiber cable in which a rib is formed between the bottom ends of the optical fiber tape core housing grooves,
The plurality of optical fiber ribbon core storage grooves include or do not include at least one shallow optical fiber ribbon storage groove. The same shape and shape are the same except for the shallow optical fiber ribbon storage groove. The groove depths are defined by h, the groove depths between the groove bottom corners of the plurality of optical fiber ribbon core storage grooves, and the allowable cable deformation amount of the groove depth. Let the clearance of the groove depth be L,
h = L + N · t
Where N is the number of optical fiber cores housed in the optical fiber tape core housing grooves of the same groove depth and is a fixed value in the range of 5 to 10, and t is the optical fiber housed in the grooves It is a fixed value in the range of 0.26-0.30 in the thickness mm of the core wire,
h is set to a fixed value in the range of 1.8 to less than 4.5 mm, and b is b> or = Ah ³ / (LB)
And (where B is a constant) when a fixed value within 0.95 mm,
L <or = A · (h ³ / b) + B
An optical fiber cable is provided that is set to a value within the range obtained in (1).

In the present invention, a plurality of optical fiber ribbon core storage grooves are provided around a circular cable core in the center direction, and the optical fiber ribbons are stored in the respective optical fiber ribbon storage grooves. In the optical fiber cable in which a rib is formed between the bottom ends of the optical fiber tape core housing grooves,
The plurality of optical fiber ribbon core storage grooves include or do not include at least one shallow optical fiber ribbon storage groove, and are formed in the same shape by removing the shallow optical fiber ribbon storage groove. The groove depths are defined by h, the groove depths between the groove bottom corners of the plurality of optical fiber ribbon core storage grooves, and the allowable cable deformation amount of the groove depth. Let the clearance of the groove depth be L,
h = L + N · t
Where N is the number of optical fiber cores housed in the optical fiber tape core housing grooves of the same groove depth and is a fixed value in the range of 5 to 10, and t is the optical fiber housed in the grooves It is a fixed value in the range of 0.26-0.30 in the thickness mm of the core wire,
h is set to a fixed value in the range of 1.8 to less than 4.0 mm, and b is b> or = Ah ³ / (LB)
And (where B is a constant) when the fixed value is within 0.85 mm,
L <or = A · (h ³ / b) + B
An optical fiber cable is provided that is set to a value within the range obtained in (1).

According to the present invention, h, which is not employed in the design of the conventional optical fiber cable, is set to a fixed value in the range of 1.8 to 4.5 mm, preferably 1.8 to 4.0 mm. The relationship between b and h, that is, b is 0 on the curve represented by this curve, or on the upper side of the curve, using the relational expression represented by Ah ³ / (LB) for h, and 0 .95 mm, preferably within 0.85 mm. By adopting this value, the outer diameter of the cable can be reduced from 22.0 mm to 25.0 mm. The above example is a case where L is set to a fixed value. On the other hand, when b and h are fixed in the above relationship, an optical fiber in which the value of L is set in the above relationship. The cable can be designed, and the outer diameter of the cable can be reduced as well.

FIG. 1A is a diagram showing a cross section of an optical fiber cable, FIG. 1A is a diagram showing a cross section of an example provided with one shallow storage groove, and FIG. 1B is a diagram showing a cross section of an example in which all are formed with deep storage grooves. The figure which shows the definition of each part of a storage groove. The figure which shows another example about the definition of the groove depth h. The figure which shows the structure of the calculation assistance apparatus of a cable outer diameter. The figure which shows the condition of a deformation | transformation of the cable core by having added the side pressure load. The figure which shows an experimental result. The figure which shows the rib thickness about the same optical fiber cable, and the deformation amount per unit load. Diagram showing the relationship between the optical fiber deformation amount and h ³ / b. The figure which shows the relationship with the allowable minimum rib thickness with a groove depth. The figure which shows the cross section of the modification of Fig.1 (a). The figure which shows the cross section of the modification of Fig.1 (a). The figure which shows the cross section of the modification of FIG.1 (b). The figure which shows the cross section of the modification of FIG.1 (b). The figure which shows the modification of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross section of a spacer type optical fiber cable 100.
In FIG. 1, an optical fiber cable 100 has a tension member 2 disposed at the center of a circular spacer 1 serving as a cable core, and an optical fiber tape core wire storage groove 3 (hereinafter referred to as “storage”) toward the center of a rib 10. (Referred to as “grooves”) are provided at equal intervals, the optical fiber ribbons 4 are housed in the respective housing grooves 3, a presser winding 5 is wound around the cable core, and a sheath that is an outer skin (outer jacket) is formed on the outside 6 is provided. FIG. 1 shows an example in which 13 storage grooves are formed.

  In FIG. 1 (a), of the 13 storage grooves 3, 12 storage grooves 3A are the storage grooves of the same shape and the same groove depth, and only one is the shallow storage groove 3B. In this shallow storage groove 3B, a smaller number of optical fiber cores 4B than the number of optical fiber cores 4A stored in the 12 deep storage grooves 3A are stored. Such an optical fiber cable is usually called a 12.5 groove because it has a shallow groove housing groove. FIG. 1B shows an example in which the storage grooves of 13 deep grooves are formed with the same groove depth.

  The embodiment shown in FIG. 1A includes an optical fiber in which one shallow storage groove 3B is included and a plurality of other storage grooves are formed with the same shape and the same groove depth except for the shallow storage groove. It does not include the cable and the shallow storage groove 3B, but includes an optical fiber in which a plurality of storage grooves are formed with the same shape and the same groove depth. In either case, the rib interval between the rib bottoms has the same length b as will be described later. Therefore, as a whole, a plurality of storage grooves 3 are provided at equal intervals around the circular table core in the central direction. In the following, the example shown in FIG. 1A will be described, but the present invention is not limited to this example or the example shown in FIG.

  FIG. 2 shows an A portion enlargement (FIG. 2B) and an B portion enlargement (FIG. 2C) of the optical fiber cable 100 shown in FIG. 1 (FIG. 2A). In FIG. 2B, the groove depth of the storage groove 3A is indicated by h, and the clearance of the groove depth represented by the cable allowable deformation amount of the groove depth is indicated by L and stored in the storage groove 4A. The number of optical fiber tapes is indicated by N, and the interval between the bottom corners of the storage groove, that is, the minimum interval of the ribs 10 is indicated by b. As shown in FIG. 2B, when a shallow storage groove is provided between the deep storage grooves, the shortest width from the bottom corner of the shallow groove to the adjacent deep groove is indicated by the rib thickness b.

  In the example shown in FIG. 2B, the rib 10 is thinnest at the groove bottom. As shown in FIG. 3, the thinnest portion of the rib 10 may be in the middle of the height of the rib 10. In such a case, the groove depth h in this embodiment is the height from the position of the thinnest part to the groove top. Thus, h is not the height H from the groove bottom to the groove top.

  In the present embodiment, the groove depth h indicates the groove depth of the storage groove of the deep groove in the above-described example occupying most or all of the plurality of optical fiber core wires, and the clearance L is the clearance for these grooves. In the above-described example, the rib thickness indicates the interval between the bottom corners of the deep storage groove and the shortest width from the groove bottom corner of the shallow groove to the adjacent storage groove.

  The clearance L is represented by L = h−N · t (or h = L + N · t). Here, in this embodiment, N represents the number of optical fiber ribbons 4 accommodated in the accommodation grooves having a deep groove depth, and t represents the thickness of the optical fiber ribbon 4.

  Further, in this embodiment, N is set to a number in the range of 5 to 10, and t is set to a numerical value in the range of 0.26 to 0.30.

  The allowable deformation amount of the cable is defined as an amount that is allowed by the clearance of the groove depth when the side pressure is applied to the optical cable 1.

FIG. 4 is a block diagram of the cable outer diameter calculation support device 200.
In FIG. 4, the cable outer diameter calculation support device 200 includes an arithmetic device 11 and a storage device (storage device) 12, and the arithmetic device 11 includes an input means 13, an arithmetic means 14, and an output means 15.

  The input means 13 can input the material (resin) constituting the cable core (spacer 1) and the allowable cable deformation amount 0 or the groove depth h and the rib thickness b.

３）ｂまたはＬの範囲
ＡおよびＢは材料（樹脂）ごとに定まる定数であり、ケーブル外径の計算支援装置２００はリブの厚さｂあるいは／および溝深さのクリアランスＬの計算支援装置である。 The computing means 14 comprises means 21 for selecting a calculation formula formed for each sample constituting the cable core and a computation processing means 22, and the computation processing means 22 is a computation process based on the following formula obtained as described later. It can be performed.

3) Range of b or L A and B are constants determined for each material (resin), and the cable outer diameter calculation support device 200 is a calculation support device for the rib thickness b and / or the groove depth clearance L. is there.

Hereinafter, the technical meaning of these formulas will be described.
The inventors investigated the mechanical characteristics by taking 12.5 grooves as an example. Mechanical properties were examined for the optical fiber configuration shown in FIG. 5 (a) by applying lateral pressure as shown in FIG. 5 (b). FIG. 5 (a) shows the groove depth h and the rib thickness b, and FIG. 5 (b) shows the state of deformation of the cable core due to the application of a lateral pressure load.

  As shown in FIG. 5B, when a side pressure load is applied to the cable sheathed on the cable core from above and below, the cable core is deformed. The amount of deformation occurs vertically. Accordingly, the total deformation amount is twice the deformation amount on one side. Since the side pressure load is applied until the presser winding 5 comes into contact with the upper end surface of the optical fiber cable core wire 4, the deformation amount on one side is substantially equal to the groove depth clearance L. Accordingly, here, the groove depth clearance L indicates the allowable deformation amount of the cable. The allowable cable deformation amount can be set within the clearance L of the groove depth, but it is not allowed to increase it beyond L theoretically because the loss of light transmission starts to react. It can be set as the clearance L of the groove depth represented by the deformation amount.

  Four types of optical fiber cables in which the spacer 1 is formed of a high-density thermoplastic resin were selected in order to examine the deformation amount with respect to the side pressure load.

  FIG. 6 shows the experimental results. No. 1-No. Reference numeral 4 denotes four selected optical fiber cables. FIG. 6 shows the lateral pressure load N [N / 100 mm] on the X axis and the cable deformation (mm) on the Y axis. The outer diameter of each spacer is shown in FIG. Since the cable outer diameter is covered with a tape or a sheath, the relationship between the cable outer diameter and the spacer outer diameter is 1: 1. Each line is marked with a circle. The point marked with ○ is the point where the deformation reaches the clearance L and the loss starts to react theoretically. According to FIG. 6, it is shown that the rib is more likely to fall as the amount of cable deformation is larger, and the rib is less likely to fall as the cable is smaller.

  In the relationship between the lateral pressure load and the amount of deformation of the cable shown in FIG. 6, it is shown that the rib is more likely to fall when the outer diameter is larger than in each slot.

  FIG. 7 shows the rib thickness and the deformation amount per unit load for the same optical fiber cable. The X axis indicates the rib thickness b, and the Y axis indicates the amount of cable deformation.

  With respect to the rib thickness and the amount of cable deformation per unit load shown in FIG. 7, one straight line can be drawn as shown in the figure, and according to this, the result that the thicker rib is weak against the side pressure was obtained. This result shows that the conventional concept of rib thickness = side pressure characteristic should be reexamined, and that the groove depth parameter must also be taken into account for optimum rib thickness design. That is, in FIG. 6, the side pressure load at which the loss of each slot starts to increase is indicated by a circle in the figure, but the deformation amount at which the loss starts to increase theoretically becomes the groove clearance L × 2. Therefore, in order to obtain a good lateral pressure specification, it is required to investigate the relationship between increasing the clearance L or optimizing the rib thickness and the groove depth that are difficult to collapse. Here, the relationship between the rib thickness and the groove depth parameter will be investigated using the clearance L as a predetermined amount.

FIG. 8 shows the relationship between the amount of deformation of the optical fiber and h ³ / b. H ³ / b is shown on the X axis, the amount of deformation of the optical cable is taken on the Y axis, and plots are made for four types of optical fiber cables, and one straight line can be drawn through the vicinity of these plots. According to this, it was found that the amount of deformation of the optical cable is proportional to h ³ / b. According to this result, the amount of deformation of the optical cable is proportional to the equation of rib thickness and groove depth shown in FIG. When the amount of deformation is indicated by y, the straight line shown in FIG.
y = A′X + B ′ (1)
It is represented by A ′ and B ′ are constants.

  In calculating the amount of deformation, the groove depth h is effective to the third power, so that the rib thickness b has less influence on the lateral pressure strength of the cable than the influence of the groove depth. From this, it can be seen that the rib thickness b can be designed to be smaller than the conventional idea by setting the groove depth h small. The minimum rib thickness b can be calculated from these relationships.

（１）式を変形すると

となる。 According to the analysis, when the optical fiber deformation amount y is designed to match the clearance L of the groove depth, the equation (1) becomes as follows.

When formula (1) is transformed

It becomes.

  There is a required groove depth clearance L depending on the fiber type. Therefore, if the groove depth clearance L is set, the minimum rib thickness is calculated.

FIG. 9 shows the relationship between the groove depth h and the allowable minimum rib thickness b. The X axis indicates the groove depth h, and the Y axis indicates the minimum rib thickness b. According to this diagram, at the groove depth of the four types of optical fiber cables, the value above the above line is taken (located on the curve in FIG. 9), so that the minimum rib thickness b is sufficient. Satisfied. In these cases, by bringing the rib thickness closer to the curve in FIG.
Further reduction in the outer diameter of the cable is achieved.

As the groove depth h from FIG. 9, it is further shortened from 4.5mm minimum by setting the thickness b of the ribs in relation to the h ³ was remarkably small ribs thickness b, pulls the optical fiber It turns out that it can set as a preferable range which can make the outer diameter of a cable small.

  According to experiments by the inventors, it was found that an epoch-making effect can be obtained from the above-mentioned curve characteristics in a groove depth range of 1.8 to 4.5 mm or less (less than 4.5 mm). This proves that it is effective in reducing the outer shape of the cable.

In FIG. 9, h = L + N · t, where N is a fixed value in the range of 5 to 10 in terms of the number of optical fiber cores housed in the optical fiber tape core housing grooves having the same groove depth, Alternatively, in an optical fiber cable having a fixed value in the range of 0.26 to 0.30 in the thickness of the optical fiber core wire accommodated in the groove, a range that is epoch-making for reducing the outer shape of the cable. Is represented by region P. This region P has a groove depth h, a rib thickness b between the groove bottom spaces of the plurality of optical fiber ribbon core housing grooves, and a groove depth clearance expressed by the groove depth cable allowable deformation amount. L
When L is set to a fixed value and h is set to a fixed value in the range of 1.8 to 4.5 mm, preferably 1.8 to less than 4.0 mm,
b is for h,
b> or = Ah ³ / (LB)
Here, A and B are constant areas, which are set to 0.95 mm, preferably within 0.85 mm.
Therefore, b is set with a value in this P region.
And preferably
b = Ah ³ / (LB)
It is better to set it near the line.

Further, the region P has a groove depth represented by h, a groove depth represented by h, a rib thickness between the groove bottom spaces of the plurality of optical fiber ribbon core housing grooves, and a groove allowable cable deformation amount. The clearance is set to L, and h is set to a fixed value in the range of 1.8 to 4.5 mm, desirably 1.8 mm to less than 4.0 mm, and b is b> or = Ah ³ / (LB)
And (where A and B are constants) 0.95 mm, preferably set to a fixed value within an area that is within 0.85 mm,
L <or = A · (h ³ / b) + B
This area is set to the value obtained in step (b). Therefore, L is set by a value in this P area. And it is good to set to the neighborhood on this desirable expression. The set value to be adopted may be determined by the calculation means shown in FIG. 4 according to a predetermined rule.

In the above formula, A = 0.0265, B = 0.7215 is adopted in one high-density thermoplastic material. These values are for other high density thermoplastic materials, medium density thermoplastic materials,
The low-density thermoplastic material may be set based on experiments.

  Incidentally, the values on the line shown in FIG. 9 indicate that when the groove depth is 1.8 mm, the rib thickness is 0.6 mm, and when the groove depth is 3.0 mm, the rib thickness is 0.7 mm and the groove depth. When the thickness is 3.5 mm, the rib thickness is 0.73 mm, when the groove depth is 4.0 mm, the rib thickness is 0.86 mm, and when the groove depth is 4.5 mm, the rib thickness is 0.95 mm, preferably When the thickness is 4.0 mm, the rib thickness takes a value around 0.85 mm. The rib thickness is desirably set in the vicinity of the line shown in FIG. When the groove depth and the rib thickness are set, the clearance value is set similarly. These values are sufficiently smaller than the conventional example.

  10 to 14 show modifications of the embodiment shown in FIG. 1, and the present invention can be applied to these modifications. FIG. 10 shows a modification of the embodiment shown in FIG. In the example shown in FIG. 1A, only one of the storage grooves (the storage groove 3B) is a shallow storage groove. On the other hand, in the example shown in FIG. 10, the spacers 1 having the same number of shallow storage grooves 3 </ b> B and deep storage grooves are shown. In this example, the total number of storage grooves is 10 including the shallow storage grooves 3B and the deep storage grooves 3A, but other total numbers may be used. Therefore, in this example, the shallow storage groove 3B and the deep storage groove 3A have a structural feature that constitutes each pair (total of 5 pairs).

  FIG. 11 is similar to the example shown in FIG. 10 and shows an example in which a total of 10 pairs are configured.

  FIG. 12 shows a modification of the embodiment shown in FIG. In the example shown in FIG. 1 (b), 13 deep storage grooves 3 are formed. However, in the example shown in FIG. 12, only 12 deep storage grooves 3 are formed. Other numbers may be used. FIG. 13 also shows a modification of FIG. 1 (b), which is formed by only 25 deep storage grooves 3.

  FIG. 14 shows a modification of the embodiment shown in FIG. 10, that is, a further modification of FIG. In the example shown in FIG. 10, the groove width of each storage groove is the same as shown in FIG. 1A, but in the example of FIG. 14, the deep storage groove 4A has a shallow groove width. The groove 4B is formed to be larger than the groove width.

  DESCRIPTION OF SYMBOLS 1 ... Spacer, 2 ... Tension member, 3 ... Optical fiber tape core wire storage groove (storage groove), 3A ... Deep groove storage groove, 3B ... Shallow groove storage groove, 4 ... Optical fiber tape core wire, 4A ... Deep groove Optical fiber tape cores housed in the housing grooves, 4B. Optical fiber tape core wires housed in the shallow groove housing grooves, 10 ... ribs, 100 ... optical fiber cables.

Claims (4)

A plurality of optical fiber ribbon fibers are provided around the circular cable core in the center direction, and the optical fiber ribbons are accommodated in the respective optical fiber ribbon storage grooves. In the optical fiber cable in which a rib is formed between the groove bottom ends of the tape core wire storage groove,
The plurality of optical fiber ribbon core storage grooves include or do not include at least one shallow optical fiber ribbon storage groove, and are formed in the same shape by removing the shallow optical fiber ribbon storage groove. The groove depths are defined by h, the groove depths between the groove bottom corners of the plurality of optical fiber ribbon core storage grooves, and the allowable cable deformation amount of the groove depth. The clearance of the groove depth is set to L, L is set to a fixed value, and h = L + N · t
Where N is the number of optical fiber cores housed in the optical fiber tape core housing grooves of the same groove depth and is a fixed value in the range of 5 to 10, and t is the optical fiber housed in the grooves It is a fixed value in the range of 0.26-0.30 in the thickness mm of the core wire,
When h is set to a fixed value in the range of 1.8 to less than 4.5 mm,
b is for h,
b> or = Ah ³ / (LB)
Here, A and B are constants, and are set to values within an area of 0.95 mm or less. A plurality of optical fiber ribbon fibers are provided around the circular cable core in the center direction, and the optical fiber ribbons are accommodated in the respective optical fiber ribbon storage grooves. In the optical fiber cable in which a rib is formed between the groove bottom ends of the tape core wire storage groove,
The plurality of optical fiber ribbon core storage grooves include or do not include at least one shallow optical fiber ribbon storage groove, and are formed in the same shape by removing the shallow optical fiber ribbon storage groove. The groove depths are defined by h, the groove depths between the groove bottom corners of the plurality of optical fiber ribbon core storage grooves, and the allowable cable deformation amount of the groove depth. The clearance of the groove depth is set to L, L is set to a fixed value, and h = L + N · t
Where N is the number of optical fiber cores housed in the optical fiber tape core housing grooves of the same groove depth and is a fixed value in the range of 5 to 10, and t is the optical fiber housed in the grooves It is a fixed value in the range of 0.26-0.30 in the thickness mm of the core wire,
When h is set to a fixed value in the range of 1.8 to less than 4.0 mm,
b is for h,
b> or = Ah ³ / (LB)
Here, A and B are constants and are set to values within an area of 0.85 mm or less. A plurality of optical fiber ribbon fibers are provided around the circular cable core in the center direction, and the optical fiber ribbons are accommodated in the respective optical fiber ribbon storage grooves. In the optical fiber cable in which a rib is formed between the groove bottom ends of the tape core wire storage groove,
The plurality of optical fiber ribbon core storage grooves include or do not include at least one shallow optical fiber ribbon storage groove, and are formed in the same shape by removing the shallow optical fiber ribbon storage groove. The groove depths are defined by h, the groove depths between the groove bottom corners of the plurality of optical fiber ribbon core storage grooves, and the allowable cable deformation amount of the groove depth. Let the clearance of the groove depth be L,
h = L + N · t
Where N is the number of optical fiber cores housed in the optical fiber tape core housing grooves of the same groove depth and is a fixed value in the range of 5 to 10, and t is the optical fiber housed in the grooves It is a fixed value in the range of 0.26-0.30 in the thickness mm of the core wire,
h is set to a fixed value in the range of 1.8 to less than 4.5 mm, and b is b> or = Ah ³ / (LB)
And (where B is a constant) when a fixed value within 0.95 mm,
L <or = A · (h ³ / b) + B
An optical fiber cable characterized by being set to a value within the range required by A plurality of optical fiber ribbon fibers are provided around the circular cable core in the center direction, and the optical fiber ribbons are accommodated in the respective optical fiber ribbon storage grooves. In the optical fiber cable in which a rib is formed between the groove bottom ends of the tape core wire storage groove,
The plurality of optical fiber ribbon core storage grooves include or do not include at least one shallow optical fiber ribbon storage groove, and are formed in the same shape by removing the shallow optical fiber ribbon storage groove. The groove depths are defined by h, the groove depths between the groove bottom corners of the plurality of optical fiber ribbon core storage grooves, and the allowable cable deformation amount of the groove depth. Let the clearance of the groove depth be L,
h = L + N · t
Where N is the number of optical fiber cores housed in the optical fiber tape core housing grooves of the same groove depth and is a fixed value in the range of 5 to 10, and t is the optical fiber housed in the grooves It is a fixed value in the range of 0.26-0.30 in the thickness mm of the core wire,
h is set to a fixed value in the range of 1.8 to less than 4.0 mm, and b is b> or = Ah ³ / (LB)
And (where B is a constant) when the fixed value is within 0.85 mm,
L <or = A · (h ³ / b) + B
An optical fiber cable characterized by being set to a value within the range required by

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