JP3349418B2 - Fiber optic cable spacer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in an optical fiber cable spacer for accommodating an optical fiber to form an optical fiber cable.

[0002]

2. Description of the Related Art Optical fibers are housed in optical fiber cable spacers provided with spiral or wavy grooves in the longitudinal direction in order to prevent damage due to various external forces such as stress applied during installation. That is being done. Conventionally, as a method for manufacturing this type of spacer, a resin portion formed by extruding and foaming a foamable thermoplastic resin around a strength member such as a steel wire or fiber-reinforced plastic is formed, and the resin portion is formed. There is known a method of forming a groove for accommodating an optical fiber by a rotary extrusion die (Japanese Patent Laid-Open No. Hei.
183609). Further, as shown in FIG.
2, a spacer 11 having a foam layer 13 and an unfoamed outermost layer 14 in which an optical fiber receiving groove 17 is formed.
Has been proposed (JP-A-8-234066).

[0003]

In recent years, with the desire to increase the number of optical fibers constituting an optical fiber cable, a spacer capable of accommodating more optical fibers has been desired. Therefore, in order to meet the demand, the diameter of the spacer is increased and the dimension of the groove is increased. However, in the former spacer in which a foam layer is formed around the strength member, if the groove size is increased, the spacer is deformed when a lateral pressure is applied, thereby increasing the transmission loss of the optical fiber or causing the drum to have a loss. During the winding and storage, the surface of the spacer sometimes cracked. Further, when the depth of the groove is increased to increase the groove size, the thickness of the outermost layer in which the groove is formed becomes large, and in the case of the latter spacer, the thickness of the foam layer becomes relatively small. As a result, effects such as improvement in flexibility and weight reduction due to the formation of the foam layer are reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides an optical fiber cable spacer having improved flexibility and strength against side pressure regardless of the groove size of the optical fiber cable spacer. The purpose is to:

[0005]

That is, a first aspect of the present invention is an optical fiber cable spacer having a resin portion in which an optical fiber receiving groove is formed around a tensile strength member, wherein the resin portion is at least. The outermost part is the optical fiber
It has a thickness greater than the depth of the groove, and the outermost
10 to 70% of foaming rate, bubble diameter is 10~400μm
And a spacer for an optical fiber cable, which is a thermoplastic resin foam. The invention according to claim 2 provides the optical fiber cable spacer according to claim 1, wherein the resin portion is a thermoplastic resin foam. The invention according to claim 3 provides the optical fiber cable spacer according to claim 1, wherein the resin portion has an intermediate layer having a foaming ratio of less than 10% and a bubble diameter of less than 400 µm. The invention according to claim 4 provides the optical fiber cable spacer according to claim 3, wherein the intermediate layer is an adhesive resin. The invention according to claim 5 provides the spacer for an optical fiber cable according to any one of claims 1 to 4, wherein the resin portion has an innermost part made of a thermoplastic resin foam. In the invention according to claim 6, the innermost part of the resin portion has a foaming rate of 10 to 70% and a bubble diameter of 10 to 400.
The optical fiber cable spacer according to any one of claims 1 to 5, wherein the spacer is μm. The invention of claim 7 is
The optical fiber cable spacer according to any one of claims 1 to 4, wherein the innermost part of the resin portion is a solid thermoplastic resin body. The invention according to claim 8 provides the optical fiber cable spacer according to any one of claims 1 to 7, wherein the optical fiber housing groove is provided at the outermost part.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The resin portion provided around the tensile strength member and having an optical fiber housing groove may be composed of one layer or a plurality of layers.
It is necessary to be a thermoplastic resin foam having a thickness equal to or greater than the depth of the optical fiber accommodating groove, a foaming ratio of 10 to 70%, and a bubble diameter of 10 to 400 μm. By adjusting the foaming ratio and the bubble diameter of the foam of the resin portion to the above ranges, even if the size of the accommodation groove of the optical fiber is increased, the spacer for the optical fiber cable has good flexibility and strength against lateral pressure. Becomes

[0007] When the foaming ratio is less than 10%, the flexibility of the spacer becomes insufficient. When the foaming ratio exceeds 70%, the spacer does not have sufficient strength and is deformed when subjected to an external force. This causes problems such as an increase in the transmission loss of the optical fiber housed in the groove and the occurrence of the groove falling down.

[0008] Here, the foaming ratio means a value obtained as follows. ρ ': density of resin before foaming ρ: density of foam

If the outermost foam contains a large number of air bubbles having a size of less than 10 μm, the flexibility required as a spacer cannot be obtained. Further, when the bubble diameter exceeds 400 μm, when the spacer receives an external force, a bubble portion having a bubble diameter larger than 400 μm may be deformed, and the transmission loss of the optical fiber housed in the groove may increase. Further, the spacer is wound around the drum and stored. If the bubble diameter is too large, the winding stress concentrates on a portion having a large bubble diameter, which may cause an abnormality such as a crack on the surface.

Although the bubble shape is not always spherical, for example, in the case of a flat shape, the maximum major axis is defined as the bubble diameter of the bubble. Actually, the bubble diameter is determined by slicing or polishing the bubbles appearing in the cross section of the spacer. As will be described later, in the case of a spacer manufactured by extruding the foamable resin onto the tensile strength member at the same time as foaming, the bubbles are formed such that the longitudinal direction of the spacer is substantially parallel to the longitudinal direction of the bubbles. Therefore, it is preferable to measure the bubble diameter of the bubbles that appear by cutting in the horizontal direction with respect to the longitudinal direction of the spacer.

In the present invention, it is necessary that both the outermost foaming ratio and the bubble diameter of the resin portion are within the above-mentioned ranges, and if any one of them is out of the above-mentioned range, a good spacer cannot be obtained. .

The thermoplastic resin foam constituting the outermost part of the resin portion is, for example, a polyolefin resin such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, or polypropylene alone. Alternatively, it is formed by foaming a mixture appropriately mixed as required. Among them, a high-density polyethylene foam is preferably used in consideration of workability, strength, price, and use record.

As a method for foaming the thermoplastic resin, a physical foaming method in which a gas which does not react with the resin such as nitrogen, carbon dioxide, argon, methane, propane or fluorocarbon is injected from the middle of the extrusion cylinder and extruded and foamed, or There is a chemical foaming method of extruding and foaming using a compound in which a chemical foaming agent is blended with the thermoplastic resin, and any of them may be used. Chemical foaming agents used for chemical foaming, when heated above its decomposition temperature, nitrogen,
Compounds that generate gas such as carbon dioxide, and examples thereof include dinitrosopentamethylenetetramine, azodicarbonamide and metal salts thereof, 4,4-oxybis (benzenesulfonylhydrazine), and toluenesulfonylhydrazide. These foaming agents may be used alone or in combination of two or more. Also,
The decomposition temperature can be appropriately adjusted by a foaming aid such as urea, a urea-based compound, zinc white, and zinc stearate.

The amount of the foaming agent is appropriately adjusted in accordance with the desired foaming rate, cell diameter, molding method, and type of the foaming agent. It is appropriate to adjust in the range of 0.1 to 2 parts by weight with respect to parts by weight.

The above-mentioned thermoplastic resin may contain an organic pigment, in order to prevent deterioration of the product during and after the production process.
An inorganic pigment such as carbon black, an antioxidant, an ultraviolet absorber and the like may be appropriately added. Also, if necessary,
A flame retardant such as magnesium hydroxide, aluminum hydroxide, silicone, red phosphorus, or a flame retardant auxiliary may be appropriately added.

Next, a method for manufacturing the optical fiber cable spacer of the present invention will be described. As the strength member, a metal wire such as a steel wire, which is usually used as a strength member of the spacer, or a single wire or a stranded wire of a linear material such as a fiber-reinforced plastic wire can be used. The resin portion provided on the outer periphery of the strength member can be provided by extruding and coating the thermoplastic resin melt-kneaded in the extruder on the periphery of the strength member, and after the obtained elongated body is cured, A spacer is formed on the outer peripheral surface by providing a groove for accommodating the optical fiber. In addition, the outermost part of the resin part is always made of a foamable thermoplastic resin, and the type of the foaming agent, the amount of the foaming agent, the extrusion temperature, and the like are set so that the foaming rate after extrusion foam coating and the cell diameter are within a predetermined range. adjust.
The optical fiber housing groove is formed by cutting the outer peripheral surface with a cutter (a groove milling cutter, an end mill cutter, or the like). At this time, by rotating or reciprocating the cutter about the elongated foam, the groove can be formed in a spiral shape or in a wave shape inverted at a suitable period. Further, the cutting for forming the groove is performed in several steps, and if the cutting is gradually performed with finer precision, a spacer having high efficiency and excellent dimensional stability can be obtained.

As a method of forming the groove, there is also a method of forming the groove by extruding a molten resin from a rotating die attached to an extruder. In this case, a spiral groove can be formed by rotating the rotary die. In addition, in the semi-crystallized state before the extruded spacer is cooled and solidified, when a die having the same shape as the rotating die attached to the extruder is passed through and forcibly adjusted, the dimensional stability of the spacer is improved, Surface irregularities can be reduced. Further, there is an advantage that the groove hardly falls due to the compensation.

In the optical fiber cable spacer according to the present invention, the outermost part of the resin portion provided around the strength member may be a thermoplastic foam having the specific foaming ratio and cell diameter as described above. Various configurations other than the outermost portion of the resin portion are conceivable. For example, in the spacer 1 shown in FIG. 1, the resin portion 6 provided around the strength member 2 is entirely made of a thermoplastic resin foam. Reference numeral 7 denotes a groove provided on the outer periphery of the resin portion 6. In this case, except for the outermost part 3 of the resin part 6, it is not particularly necessary to limit the foaming rate and the cell diameter,
If the foaming ratio and the cell diameter are too large, the strength as a spacer is inferior. Therefore, the foaming ratio and the cell diameter are substantially the same as those of the outermost foam.

The spacer 21 shown in FIG.
, A resin portion 26 is provided.
Is the innermost 24 made of a solid thermoplastic resin and a foaming rate of 10
The outermost portion 23 is made of a thermoplastic resin foam having a cell size of about 70% and a cell diameter of 10 to 400 μm. The groove 27 is formed in the foam part which is the outermost part 23. As the thermoplastic resin of the solid thermoplastic resin body constituting the innermost part, the same resin as the foam can be used.

The spacer 31 shown in FIG.
A resin portion 36 is provided around the
Is composed of an innermost part 34, an intermediate layer 35 and an outermost part 33. The innermost part 34 and the outermost part 33 have a foaming ratio of 10 to 7
0%, formed of a thermoplastic resin foam having a cell diameter of 10 to 400 μm, the intermediate layer 35 has a foaming rate of less than 10%,
It is formed of a thermoplastic resin body having a bubble diameter of 400 μm or less. The groove 37 for accommodating the optical fiber is formed in the outermost part 33.

The spacer 41 shown in FIG.
A resin part 46 is provided around the
Is composed of an innermost part 44, an intermediate layer 45 and an outermost part 43. The innermost part 44 and the outermost part 43 have a foaming ratio of 10 to 7
0%, formed of a thermoplastic resin foam having a cell diameter of 10 to 400 μm, the intermediate layer 45 has a foaming rate of less than 10%,
It is formed of a thermoplastic resin body having a bubble diameter of 400 μm or less. The groove 47 for accommodating the optical fiber is formed so that the groove bottom reaches the intermediate layer 45.

When the spacer receives an external force, the external force concentrates on the ribs 38 and 48 shown in FIGS. If the external force increases, separation between the layers may occur or the grooves may fall, and the grooves 37 and 47 may be formed due to the separation or the fall of the grooves.
Collapsed leads to an increase in transmission loss of the optical fiber housed in the groove.

Therefore, as shown in FIG. 3 and FIG.
When 45 is provided, the foaming ratio of the intermediate layer is less than 10%,
When formed from a thermoplastic resin body having a bubble diameter of 400 μm or less, the strength against lateral pressure is improved, and delamination, groove collapse, and the like are less likely to occur. Further, since the strength against the lateral pressure is improved, it is possible to increase the size of the spacer accommodating groove and reduce the rib portion, which contributes to increasing the number of optical fibers accommodated in the optical fiber groove. Also,
As shown in FIG. 4, when the groove is provided in the portion formed of the outermost foam as shown in FIG. 3, the outermost surface of the intermediate layer is located 0.2 mm or more inward from the groove bottom. When the groove is formed such that the groove bottom reaches the intermediate layer, the outermost surface of the intermediate layer is located at least 0.2 mm outside the groove bottom, and the thickness of each layer is 0.5 to 1 mm. .5m
When m, the strength against lateral pressure is improved, and delamination, groove collapse, and the like are less likely to occur. Further, since the strength against the lateral pressure is improved, it is possible to increase the size of the spacer accommodating groove and reduce the rib portion, which contributes to increasing the number of optical fibers accommodated in the optical fiber groove.

When an adhesive resin is used as the thermoplastic resin for the intermediate layer, it is difficult for the interlayer to peel off even when subjected to an external force. Examples of the adhesive resin include ethylene-vinyl acetate copolymer, polyolefin-based resin such as ethylene-ethyl acrylate copolymer, polyamide-based resin, polyester-based resin, polyurethane-based resin, and the like. They can be used in combination.

[0025]

The present invention will be described below in detail with reference to examples. [Example 1 (No. 1)] A high density polyethylene (density 0.95 g / cm ³ ,
Flexural modulus 90 kg / mm ² , melt flow rate 0.
12 g / 10 min) To 100 parts by weight, 0.2 parts by weight of azodicarbonamide was mixed and kneaded to form a molten resin of 20 parts.
Extrusion foam coating was performed at 0 ° C to obtain a foamed elongated body having an outer diameter of 14.0 mm. After cooling and solidifying the obtained foamed long body, width 2.
Using a cutting blade set so that five spiral grooves that are inverted at a constant period of 6 mm and a depth of 4.1 mm are formed,
The foamed long body was roughly cut, and then passed through a cutting die having a waveform of 2.7 mm in width and 4.2 mm in depth, and was 2.7 mm in width, 4.2 mm in depth and 1.5 μm in surface roughness (center line). (Average roughness value) The finished groove was formed below, and a spacer (No. 1) having a structure as shown in FIG. 1 was produced. The foam ratio of the foam part of the spacer (No. 1) was 25%, and the bubble diameter was 10 to 50 μm. The bubble diameter is shown in FIG.
As shown in (a), arbitrarily, 20 air bubbles are selected from among the air bubbles appearing on the aa ′ cut surface cut horizontally in the longitudinal direction of the spacer, and the air bubbles are polished and the air bubble diameter (for example, FIG. In 5 (b), b out of aa 'to cc'
−b ′ is defined as the bubble diameter), and the minimum bubble diameter and the maximum bubble diameter are described.

Example 1 (Nos. 2 to 8), Comparative Example 1
(Nos. 1 to 9)] Example 1 (No. 2) was carried out in the same manner by varying the amount of azodicarbonamide and the extrusion temperature.
To 8) and Comparative Example 1 (Nos. 1 to 9) were produced. Tables 1 and 2 show the foaming ratio and cell diameter of the foam portion (resin portion) of the obtained spacer.

[0027]

[Table 1]

[0028]

[Table 2]

[Conventional example] A high-density polyethylene (density 0.95 g / cm ³ , flexural modulus 90 kg / mm ² , melt flow rate 0.1) was wrapped around a single steel wire having an outer diameter of 1.4 mm.
2 g / 10 min) 100 parts by weight of azodicarbonamide and 0.4 part by weight of a kneaded resin were mixed and mixed.
The foam layer was formed by extrusion foam coating at 00 ° C. so that the outer diameter became 5.0 mm. On the foam layer, high-density polyethylene (density 0.95 g / cm ³ , flexural modulus 90 kg)
/ Mm ² , melt flow rate 0.12 g / 10 mi
n) was extruded using a rotary die to a final outer diameter of 14.0 mm, and grooves having the same size were formed in the same manner as in Example 1 to form a groove on the foam layer as shown in FIG. A conventional spacer having an unfoamed outermost layer was made. The foam ratio of the foam layer of the obtained spacer was 45 to 55%, and the bubble diameter was 300 to 350 μm.

With respect to the obtained spacers of Example 1 (Nos. 1 to 8) and Comparative Example 1 (Nos. 1 to 9), the following tests (1) to (3) were performed to evaluate the characteristics. . The results are shown in Tables 1 and 2.

(1) Flexibility test An optical fiber cable spacer was cut into a length of 600 mm, one end was fixed at 100 mm, and the other end was fixed at 500 mm so as to protrude into the air. Next, a load of 2.5 kg was applied to the tip of one end protruding into the air, and the flexibility was examined.
The tip of the spacer protruding into the air is 300m within 30 seconds
Those that flexed by m or more were rated as ○, and those that flexed less than 300 mm were rated as x. (2) Lateral pressure test Ten pieces of 8-core tape-shaped optical fiber core wires having a width of 2.1 mm and a thickness of 0.3 mm were accommodated in all five grooves of the optical fiber cable spacer having a length of 5 m, and the thickness was 125 μm. PET
One sheet of the tape was wound around the outer periphery of the spacer so that the PET tape did not overlap. This 8-fiber tape-shaped optical fiber core mounting spacer was sandwiched between two flat plates of 50 mm square and 5 mm thick so that the flat plates were parallel to each other and fixed to a compression tester. Load 500kg between flat plates 1.0mm
/ Min, and the increase in transmission loss of the eight-core tape-shaped optical fiber core housed in the spacer was measured in a wavelength band of 1.55 μm. When the increase in the transmission loss was 0.1 dB / km or less, the result was indicated by ○, and when the increase in the transmission loss exceeded 0.1 dB / km, the result was indicated by ×. (3) Constant strain environmental stress crack test A 5 m long optical fiber cable spacer was
A sample was wound around a 5 mm mandrel for 5 turns. After immersing this sample in a 10% aqueous solution of alkyl allyl polyoxyethylene at 50 ± 2 ° C. for 100 hours, the surface of the spacer was observed with a magnifying glass. When the surface of the spacer had no abnormalities such as cracks and cracks, it was evaluated as ○, and when the surface of the spacer had abnormalities such as cracks and cracks, it was evaluated as x.

As shown in Table 1, Example 1 (No.
The spacer of 8) has excellent flexibility and strength against side pressure since the resin portion is made of a foam having a foaming ratio of 10 to 70% and a bubble diameter of 10 to 400 μm, and is in a state wound around a mandrel. And can be stably stored for a long time. In contrast, Comparative Example 1 (N
o. Since the spacer of 1) is made of a solid resin body in which the resin portion is not foamed, it has poor flexibility. Comparative Example 1
The spacers of Nos. 2, 3, 8, and 9 have a resin part made of a foam, and the bubble diameter is in the range of 10 to 400 μm, but the foaming rate is too small or too large. The flexibility or the strength against lateral pressure is poor. In the spacers of Comparative Examples (Nos. 4 to 7), although the foam constituting the outermost part has an appropriate foaming ratio, the bubble diameter is too small or too large. It is inferior. The same tests as in Examples 1 and 2 were performed for the conventional spacers in which a foam and a solid resin body were provided in this order on a tensile strength member. It was inferior in flexibility.

[Example 2 (No. 9)] Outer diameter 1.4 mm
Around a single steel wire of high density polyethylene (density 0.95
g / cm ³ , a flexural modulus of elasticity of 90 kg / mm ² , and a melt flow rate of 0.12 g / 10 min) by extrusion coating so as to have an outer diameter of 5.0 mm, and simultaneously high-density polyethylene (density 0.95 g / cm 3). ³ , Flexural modulus 90 kg /
mm ² , melt flow rate 0.12 g / 10 min)
0.16 azodicarbonamide to 100 parts by weight
The molten resin blended and kneaded by weight was extruded and foamed at 195 ° C. to obtain a long body having an outer diameter of 14.0 mm. After the obtained elongated body was cooled and solidified, the width was 2.7 in the same manner as in Example 1.
mm, a depth of 4.2 mm, and a surface roughness of 1.5 μm (center line average roughness value). Example 2 having an innermost part made of a body and an outermost part made of a foam
(No. 9) spacer was produced. The foam ratio (outermost) of the foam part was 17%, and the cell diameter was 10 to 50 μm.

Example 2 (Nos. 10 to 12) In the same manner, by adjusting the amount of azodicarbonamide and the extrusion temperature, the foaming rate and cell diameter of the foam constituting the outermost part were variously adjusted. Example 2 (No. 10 to No. 10)
12) A spacer was prepared. Table 3 shows the foaming ratio and cell diameter of the foam part (outermost part) of the obtained spacer.

[0035]

[Table 3]

With respect to the obtained spacers of Example 2 (Nos. 9 to 12), tests (1) to (3) were performed in the same manner as in Example 1, and the characteristics were evaluated. Table 3 shows the results.

As shown in Table 3, Example 2 (No. 9 to
The spacer of 12) is formed of a foam having an outermost portion of a foaming rate of 10 to 70% and a bubble diameter of 10 to 400 μm, so that it has excellent flexibility and strength against lateral pressure, and has a long term when wound around a mandrel. And can be stored stably.

[Example 3 (No. 13)] Outer diameter 1.4 m
m high density polyethylene (density 0.9)
5 g / cm ³ , flexural modulus 90 kg / mm ² , melt flow rate 0.12 g / 10 min) 100 parts by weight
A molten resin obtained by mixing and kneading 0.2 parts by weight of azodicarbonamide was extrusion-foamed and coated at 200 ° C., and an adhesive resin (density: 0.95 g / cm ³ , melt flow rate: 0.2 g / 10 min) was placed thereon. Extrusion coating at 180 ° C., and high-density polyethylene (density 0.95 g / cm ³ , flexural modulus 90 kg / mm ² , melt flow rate 0.12 g / 10
min) 100 parts by weight of azodicarbonamide was mixed with 0.2 part by weight of a kneaded resin, followed by extrusion foam coating at 200 ° C. After the obtained elongated body is cooled and solidified, it is inverted at a constant period of 2.7 mm in width, 4.2 mm in depth, and 1.5 μm in surface roughness (center line average roughness value) in the same manner as in Example 1. Example 3 (No. 3) having five spiral grooves and having the innermost, central, and outermost layers as shown in FIG.
13) A spacer was produced. The thickness of each part was adjusted so that the innermost part was 1.3 mm, the intermediate layer was 0.5 mm, and the outermost part was 4.5 mm. Table 4 shows the innermost portion, the intermediate layer, and the outermost foaming ratio and bubble diameter of the obtained spacer.

[Example 3 (Nos. 14 to 22)] [Comparative Example 2 (Nos. 10 to 20)] In the same manner as described above, the amount of the azodicarbonamide and the extrusion temperature were adjusted to obtain a foam part. Example 3 (Nos. 14 to 22) and Comparative Example 2 (N
o. 10-20) were prepared. Table 4 shows the foaming ratio and cell diameter of the foamed portion (outermost portion) of the obtained spacer.
It is shown in FIG.

[0040]

[Table 4]

[0041]

[Table 5]

Example 3 (Nos. 14 to 22), Comparative Example 2
For the spacers (Nos. 10 to 20), the above tests (1) to (3) were performed, and their characteristics were evaluated. In addition, (2) the side pressure test was performed by changing the conditions as follows. All five grooves of a 5 m long optical fiber cable spacer accommodate ten pieces of 8-core tape-shaped optical fiber core wires having a width of 2.1 mm and a thickness of 0.3 mm, and a P having a thickness of 125 μm.
One sheet of the ET tape was wound around the outer periphery of the spacer so that the PET tape did not overlap. This 8-fiber tape-shaped optical fiber core mounting spacer was sandwiched between two flat plates of 50 mm square and 5 mm thick so that the flat plates were parallel to each other and fixed to a compression tester. Apply a 750 kg load between the flat plates to 1.0
mm / min, and increase the transmission loss of the 8-core optical fiber ribbon housed in the spacer by 1.55 μm.
The band was measured. When the increase in the transmission loss was 0.1 dB / km or less, the result was indicated by ○, and when the increase in the transmission loss exceeded 0.1 dB / km, the result was indicated by ×.

As shown in Table 4, Example 3 (No. 13)
22), the outermost part of the resin portion has a foaming ratio of 10 to 10.
Since it is composed of a foam having 70% and a cell diameter of 10 to 400 μm, it has excellent flexibility and strength against lateral pressure, and can be stably stored for a long time in a state wound around a mandrel. On the other hand,
The spacers of Comparative Example 2 (Nos. 10 to 14) are inferior in flexibility because the outermost portion is not foamed. Comparative Example 2 (N
o. As shown in 15 to 20), even if the outermost part is a foam, if the foaming rate and the cell diameter do not satisfy the predetermined ranges at the same time, the flexibility or the strength against the lateral pressure becomes poor, or the mandrel becomes inferior. In other words, it became a spacer that was not suitable for stable storage over a long period of time while being wound.

Embodiment 4 (No. 23) Embodiment 3 (N
o. Example 3 (No. 14) having the innermost, central and outermost layers as shown in FIG.
Was manufactured. The thickness of each part was adjusted so as to be 1.3 mm at the innermost part, 1.1 mm at the intermediate layer, and 3.9 mm at the outermost part. The groove bottom for accommodating the optical fiber is formed 0.2 mm inward from the outermost surface of the intermediate layer. Table 6 shows the innermost, intermediate, and outermost foaming ratios and cell diameters of the obtained spacers.

[0045]

[Table 6]

With respect to the spacer of Example 4 (No. 23), the same tests (1) to (3) as in Example 3 were carried out. However, the spacer was excellent in both flexibility and lateral pressure, and also had a mandrel. And could be stably stored for a long time in a state of being wound around.

[0047]

The spacer for an optical fiber cable of the present invention has superior flexibility as compared with a conventional optical fiber cable spacer having an optical fiber housing groove of the same size,
In addition, the strength against lateral pressure is improved.
Furthermore, it can be wound around a drum and stably stored for a long period of time, so that it is excellent in handling and operability in laying work can be improved. This effect increases as the outer diameter of the spacer increases as the number of optical fibers constituting the optical fiber cable increases.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining an optical fiber cable spacer of the present invention.

FIG. 2 is a schematic cross-sectional view for explaining an optical fiber cable spacer of the present invention.

FIG. 3 is a schematic sectional view for explaining an optical fiber cable spacer of the present invention.

FIG. 4 is a schematic sectional view for explaining an optical fiber cable spacer of the present invention.

FIG. 5 is an explanatory diagram for explaining measurement of a bubble diameter.

FIG. 6 is a schematic cross-sectional view for explaining a conventional optical fiber cable spacer.

[Explanation of symbols]

 1, 21, 31, 41 Optical fiber cable spacer 2, 22, 32, 42 Strength member 3, 23, 33, 43 Outermost 24, 34, 44 Innermost 35, 45 Intermediate layer 6, 26, 36, 46 Resin Part 7, 27, 37, 47 Optical fiber receiving groove 38, 48 Rib part 11 Conventional optical fiber cable spacer 12 Strength member 13 Foam layer 14 Outermost layer 17 Optical fiber receiving groove

──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Masanori Hattori 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Nobuo Ishii 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Ichiro Kobayashi 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Hideyuki Iwata 3-192-2 Nishishinjuku, Shinjuku-ku, Tokyo Date Inside the Telegraph and Telephone Co., Ltd. (72) Takaro Ikeda 2-5-18, Senyucho, Zentsuji-shi, Kagawa Prefecture Inside Sanwa Industry Co., Ltd. (56) References JP-A-8-234066 (JP, A) JP-A Heihei 8-146263 (JP, A) JP-A-1-183609 (JP, A) JP-A-60-100711 (JP, U) JP-A-5-11112 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , D B name) G02B 6/44

Claims (8)

(57) [Claims] An optical fiber cable spacer having a resin portion having an optical fiber housing groove formed around a strength member, wherein at least the outermost portion of the resin portion has the optical fiber.
Thickness greater than the depth of the fiber accommodation groove
The outside has a foaming rate of 10 to 70% and a cell diameter of 10 to 400.
Spacer for optical fiber cable made of thermoplastic resin foam of μm. 2. The resin part is a thermoplastic resin foam,
The spacer for an optical fiber cable according to claim 1. 3. The optical fiber cable spacer according to claim 1, wherein said resin portion has an intermediate layer having a foaming rate of less than 10% and a bubble diameter of 400 μm or less. 4. The intermediate layer is made of an adhesive resin.
3. The spacer for an optical fiber cable according to claim 1. 5. The spacer for an optical fiber cable according to claim 1, wherein said resin portion has an innermost portion made of a thermoplastic resin foam. 6. An innermost part of said resin portion has a foaming ratio of 10 to 7
0% and a bubble diameter of 10 to 400 μm.
The spacer for an optical fiber cable according to any one of the above. 7. The optical fiber cable spacer according to claim 1, wherein said resin portion has an innermost part of a solid thermoplastic resin body. 8. An optical fiber cable spacer according to claim 1, wherein said optical fiber receiving groove is provided at said outermost portion.