JPH11174286A - Optical fiber cord - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber cord of a narrow diameter for satisfying all of connector fixability, flexural rigidity and low temperature characteristics. SOLUTION: This optical fiber cord is constituted by an optical fiber core wire 1 at a center, a tension fiber 2 on the periphery and a jacket 3 on the outer side with the outer diameter being less than 1.2 mm. In the optical fiber cord, the flexural rigidity of more than 2.4 kg.mm<2> similar to the conventional optical cord of a large diameter is secured and the flexural rigidity is made to be less than 7 kg.mm<2> so as to provide required flexibility. At this time, a material whose the Young's modulus is more than 50 kg/mm<2> and less than 150 kg/mm<2> is used as the jacket 3 and the packing ratio of the tension fiber 2 occupying a space between the optical fiber core wire 1 and the jacket 3 is made to be more than 30%. Thus, the optical fiber cord having the required flexural rigidity, being less in a transmission loss at the time of a low temperature and excellent in connector fixability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-rigidity and small-diameter optical fiber cord used for optical wiring in a telephone office, for example.

[0002]

2. Description of the Related Art With the change of subscribers, it is required to increase the wiring configuration in a station. In view of this, the development of an optical fiber cord having an outer diameter of 2 mmφ (hereinafter abbreviated as a large diameter optical cord) which has been used so far has been developed to reduce the outer diameter to 1.2 mmφ or less, which is about half.

Generally, in an optical fiber cord, it is necessary to wrap the optical fiber core with a tensile strength fiber for satisfying the tensile strength characteristics. When realizing a small-diameter optical fiber cord using, for example, vinyl chloride (PVC) as a jacket material, the proceedings of the 1996 IEICE General Conference,
Nakanishi et al., B-1088 "Small-diameter intra-station optical code", p. 5
20, it is preferable that the space factor (hereinafter, referred to as a filling factor) occupied by the tensile strength fibers in the space between the jacket and the optical fiber core be 60% or less from the viewpoint of the connector attachability to the terminal. It has been reported.

[0004]

The characteristics required for a small-diameter optical fiber cord include, in addition to the above-mentioned connector mountability, important factors such as bending rigidity and optical transmission loss characteristics at low temperatures (hereinafter referred to as low-temperature characteristics). Characteristics). Even in the case of a small-diameter optical fiber cord, it is desirable to have bending rigidity equal to or higher than that of a conventional large-diameter optical cord and to have appropriate flexibility in consideration of handleability at the time of wiring. In order to keep the bending stiffness equivalent to that of the conventional large-diameter optical cord while reducing the diameter of the optical fiber cord, the conventional sheath material PVC is used.
It is necessary to select a material having an appropriate high Young's modulus instead of a material having a low Young's modulus such as (Young's modulus 6 to 20 kg / mm ² ).

On the other hand, in order to improve the low-temperature characteristics, it is necessary to prevent the optical fiber from bending at low temperatures. As described above, if the filling rate of the tensile strength fiber is reduced in order to improve the connector mounting property, the clearance in which the optical fiber core wire can meander becomes large. Therefore, when the plastic jacket shrinks at a low temperature, bending occurs in the optical fiber core wire, and as a result, there is a problem that the low-temperature characteristics deteriorate. It is generally known that the lower the Young's modulus of the jacket material, the smaller the low-temperature shrinkage force, so that the low-temperature characteristics are improved. However, as described above, there is also a problem that merely reducing the Young's modulus of the jacket leads to a decrease in bending rigidity.

The present invention has been made in view of the above circumstances, and has as its object to provide a small-diameter optical fiber cord that satisfies all of the connector mounting properties, bending rigidity, and low-temperature characteristics.

[0007]

According to the first aspect of the present invention, an optical fiber core is provided at the center, a tensile fiber is provided around the optical fiber, and a jacket is provided on the outside thereof. The bending rigidity is 2.4 kg · mm ^2.
In an optical fiber cord having an outer diameter of 7 kg · mm ² or less and an outer diameter of 1.2 mm or less, the Young's modulus of the jacket is 50 kg / mm.
mm ^{2 to} 150 kg / mm ² , and the filling ratio of the tensile strength fiber in the space between the optical fiber core and the jacket is 30% or more.

According to a second aspect of the present invention, an optical fiber core is provided at the center, a tensile fiber is provided around the optical fiber, and a jacket is provided on the outside thereof. The bending rigidity is 2.4 kg · mm ² or more and 7 kg · mm ^2.
Hereinafter, in an optical fiber cord having an outer diameter of 1.2 mm or less, the outer diameter of the optical fiber core wire is 0.25 mm or less and the Young's modulus of the jacket is 90 kg / mm ² or more and 150 kg.
/ Mm ² or less, or the outer diameter of the optical fiber is 0.4 mm or less and the Young's modulus of the jacket is 130 kg /
mm ² or more and 150 kg / mm ² or less, and the filling ratio of the tensile strength fiber in the space between the optical fiber core wire and the jacket is 55% or less.

According to a third aspect of the present invention, an optical fiber core wire is provided at the center, a tensile strength fiber is provided around the optical fiber core, and a jacket is provided on the outside thereof. The bending rigidity is 2.4 kg · mm ² or more and 7 kg · mm ^2.
Hereinafter, in an optical fiber cord having an outer diameter of 1.2 mm or less, the outer diameter of the optical fiber cord is 0.25 mm or less, and the Young's modulus of the jacket is 50 kg / mm ² or more and 90 kg /.
mm ² or less, or the outer diameter of the optical fiber core is 0.
25 mm or more and 0.4 mm or less, and the Young's modulus of the jacket is 50 kg / mm ² or more and 130 kg / mm ² or less;
The filling ratio of the tensile strength fiber in the space between the optical fiber core wire and the jacket is 65% or less.

According to a fourth aspect of the present invention, an optical fiber core is provided at the center, a tensile strength fiber is provided around the optical fiber, and a jacket is provided on the outside thereof. The flexural rigidity is 2.4 kg · mm ² or more and 7 kg · mm ^2.
Hereinafter, in an optical fiber cord having an outer diameter of 1.2 mm or less, the outer diameter of the optical fiber cord is 0.5 mm or more and the Young's modulus of the jacket is 50 kg / mm ² or more and 150 kg /.
mm ² or less, or the outer diameter of the optical fiber core is 0.
4 mm or more and the Young's modulus of the jacket is 50 kg / mm ²
90 kg / mm ² or less, or the outer diameter of the optical fiber core is 0.25 mm or more and the Young's modulus of the jacket is 50 kg / mm ² , and the space between the optical fiber core and the jacket 60% of the filling rate of the tensile strength fiber
The above is the feature.

According to a fifth aspect of the present invention, in the optical fiber cord according to any one of the first to fourth aspects,
The material of the jacket is one of an ultraviolet curable resin, nylon, and polybutylene terephthalate (PBT).

[0012]

FIG. 1 is a sectional view showing an embodiment of an optical fiber cord according to the present invention. In the figure, 1 is an optical fiber core, 2 is a tensile fiber, and 3 is a jacket. The optical fiber cord of the present invention is a small-diameter optical fiber cord having an outer diameter D of 1.2 mm or less. An optical fiber core 1 is provided at the center, and a tensile strength fiber 2 is arranged around the optical fiber. Further, a jacket 3 is provided on the outside thereof. Optical fiber cable 1
As compared with the conventional large-diameter optical cord having a diameter of about 0.9 mm, a thin cord having a diameter of about 0.6 mm or less is used. As the jacket 3, for example, a plastic material having a predetermined Young's modulus as described later can be used. The tensile strength fiber 2 is arranged between the optical fiber core 1 and the jacket 3 at a predetermined filling rate as described later. As the tensile strength fiber 2, specifically, an aromatic polyamide-based synthetic fiber (aramid fiber), for example, Kevlar (registered trademark)
Alternatively, polyparaphenylin-benzobis-oxazole (PBO) or the like can be used.

The bending rigidity is represented by a product EI of Young's modulus E and second moment of area I. Second moment I (cylindrical) and an outer diameter D ₁ of the cylindrical material of the outer diameter D, the geometrical moment of inertia I (cylinder) of the cylindrical material having an inner diameter D _2, respectively, I (cylinder) = πD ^4/64, I (cylinder) = represented by ^{_{π (D 1 4 -D 2 4}} ) / 64 ··· (1). Therefore, each bending rigidity is given by the following equation. EI ^{(cylinder) = πED 4/64, EI} ( ^{_{cylinder) = πE (D 1 4 -D}} 2 4) / 64 ··· (2)

FIG. 2 is a graph showing an example of the relationship between the Young's modulus E of the jacket material and the bending stiffness of the small-diameter optical fiber cord. As an example, in the optical fiber cord having the structure shown in FIG. 1, the outer diameter is 1.0 mmφ, and the inner diameter of the jacket is 152 mm.
Calculated as the value at which the filling rate of 0 denier tensile fiber becomes 100% (0.46 mm when the optical fiber core is 0.25 mmφ and 0.63 mm when the optical fiber core is 0.6 mmφ). did. Then, each figure 2
The relationship between the Young's modulus E of the outer skin and the bending rigidity as shown in FIG. In FIG. 2, the solid line graph shows the case where the optical fiber core is 0.25 mmφ, and the broken line graph shows the case where the optical fiber core is 0.6 mmφ.

Here, as an example of a conventional large-diameter optical cord, an outer diameter is 2.0 mm, an optical fiber core is 0.9 mmφ, and
In the case where 5500 denier fiber is used as the tensile fiber and vinyl chloride (PVC) is applied as a jacket with a thickness of 0.25 mm, the bending rigidity is EI = 2.4 kg · mm from the equation (2).
^{Was 2} . Generally, an optical fiber cord is designed to have a bending rigidity of 7 kg · mm ² or less in order to maintain flexibility.

In view of the above, the bending rigidity (2.4 k) of the conventional large diameter optical cord in a small diameter optical fiber cord is obtained.
g · mm ² ) or more, it is necessary to satisfy Young's modulus of the jacket E ≧ about 50 kg / mm ² from FIG. Also,
In order to keep the flexural rigidity at 7 kg · mm ² or less in order to maintain the flexibility, the Young's modulus of the jacket E ≦ about 15 from FIG.
It is understood that it is necessary to set the pressure to 0 kg / mm ² .

FIG. 3 is a graph showing an example of the relationship between the filling factor of the tensile fiber and the bending rigidity. Here, the outer diameter is 1 mm
UV curable resin (Young's modulus after curing E = 50 kg / mm ² ) as the outer material of the optical fiber cord having a small diameter of φ,
Nylon (E = 90 kg / mm ² ) and PBT (E =
130 kg / mm ² ), and 1520
Using denier, optical fiber core diameter is 0.25m
mφ was used. In FIG. 3, crosses indicate actual measured values when an ultraviolet-curable resin is used as the jacket material, circles indicate actual measured values when nylon is used as the jacket material, and ● indicates PBT as the jacket material. The measured values when used are shown. FIG. 3 also shows a theoretical curve when each of the jacket materials is used.

When the filling rate of the tensile fiber increases, the coating inner diameter becomes smaller when the outer diameter of the optical fiber cord is equal, so that the coating thickness becomes larger. Accordingly, there is a positive correlation between the filling factor of the tensile strength fibers and the bending stiffness, and a graph as shown in FIG. 3 is obtained. From FIG. 3, it can be seen that, in order to achieve a bending rigidity higher than that of the conventional large-diameter optical cord (2.4 kg · mm ² ), the filling rate of the tensile fiber is set to 30% or more when the jacket is made of an ultraviolet curable resin. It can be seen that it is necessary to make it 25% or more in the case of a nylon jacket and 20% or more in the case of a PBT jacket. 0.4mmφ, 0.6mmφ
It was confirmed even when the optical fiber core was used. In addition, in these jacket materials, the bending stiffness is 7 kg · mm ² or less regardless of the filling ratio of the tensile strength fiber,
Flexibility is maintained.

FIG. 4 is a graph showing an example of the relationship between the filling factor of the tensile fiber and the transmission loss. As described above, the sheath of the optical fiber tends to buckle in the longitudinal direction due to the shrinkage of the jacket at a low temperature. At this time, by setting the filling factor of the tensile strength fibers to at least 30% or more, the clearance at which the optical fiber core wire can buckle can be reduced, and bending loss can be prevented. Here, we measured the increase in transmission loss at -10 ° C when the filling rate of tensile fiber was changed for an optical fiber cord using five types of jacket materials and an optical fiber core wire of 0.25 mmφ. did.
The increase in the transmission loss was based on the transmission loss at + 20 ° C., and the wavelength was 1.55 μm. 3 for the jacket material
Five types of UV curable resins, PBT, and nylon were used. In FIG. 4, 印 indicates an ultraviolet curable resin a (Young's modulus after curing E = 180 kg / mm ² ), X indicates an ultraviolet curable resin b (Young's modulus E after curing = 150 kg / mm ² ), and □ indicates PBT. ^{(E = 130kg / mm 2)} , ■ mark nylon ^{(E = 90kg / mm 2)} , △ mark ultraviolet curable resin c
(Young's modulus E after curing = 50 kg / mm ² ).

Assuming that the allowable amount of increase in transmission loss at -10 ° C. is 0.03 dB / km, within the range of Young's modulus E ≦ 150 kg / mm ² obtained in FIG. It can be seen that if the ratio is 30% or more, the increase in transmission loss can be suppressed within an allowable range. As a result, the cured Young's modulus E ≦ 150 kg / m
Even if any material of UV curable resin b, c, nylon, or PBT of m ² is used as the jacket, if the filling rate of the tensile fiber is 30% or more, the increase in the transmission loss at low temperature is within the allowable range. Can be suppressed. A similar result is 0.4
It was also confirmed with an optical fiber cord using an optical fiber cord of mmφ and 0.6 mmφ.

FIG. 5 is an explanatory diagram showing an example of the relationship between the filling factor of the tensile strength fibers and the connector mounting properties. In FIG. 5, an ultraviolet curable resin (Young's modulus after curing E = 50 k)
g / mm ² ), nylon (E = 90 kg / mm ² ), and PBT (E = 130 kg / mm ² ) using 0.25 mmφ, 0.4 mmφ, and 0.5 mmφ optical fiber cores, respectively. Then, the connector attachability to each optical fiber cord having a different tensile fiber filling rate was examined. In FIG. 5, the attachability of the connector to each optical fiber cord was evaluated in three stages, and the results were shown as ○ = no problem, Δ = somewhat difficult, × = difficult.

When the diameter of the optical fiber was 0.5 mmφ, the connector could be mounted without any problem regardless of the filling rate of the tensile strength fiber. However, when the diameters of the optical fiber cores are 0.25 mmφ and 0.4 mmφ, especially in the case of jacket materials such as nylon and PBT having a large Young's modulus, it is difficult to attach the connector unless the filling ratio of the tensile fiber is low. It turned out to be. From FIG. 5, it was confirmed that the attachment property was good in any case when the filling rate of the tensile strength fiber was 55% or less.

The outer diameter of the optical fiber is 0.25 m.
m or less and the Young's modulus of the jacket is 50 kg / mm ² or more and 90
kg / mm ² or less, or when the outer diameter of the optical fiber is 0.25 mm or more and 0.4 mm or less, and the Young's modulus of the jacket is 50 kg / mm ² or more and 130 kg / mm ² or less, When the filling rate of the tensile strength fibers in the space between the sheaths was 65% or less, it was confirmed that the mountability was good.

FIG. 6 is an explanatory diagram showing the relationship between the Young's modulus of the jacket and the filling rate of tensile strength fibers in the optical fiber cord of the present invention. As described above, the Young's modulus E of the jacket from FIG.
It was found that 50 ≦ E ≦ 150 (kg / mm ² ) was preferable. Also, from FIGS. 3 and 4, it was found that the filling rate of the tensile strength fibers was preferably 30% or more. further,
From FIG. 5, it was found that the filling rate of the tensile strength fibers was preferably 55% or less. Summarizing these, as shown by hatching in FIG. 6, the Young's modulus E of the jacket is 50 ≦ E
≦ 150 (kg / mm ² ) and filling rate of tensile fiber is 3
In the range of 0% or more and 55% or less, it is possible to provide a good optical fiber cord in all aspects of bending rigidity, low-temperature characteristics, and connector mountability.

The range in which good characteristics shown by hatching in FIG. 6 can be obtained is when the outer diameter of the optical fiber is 0.25.
This is a good range common to the experimental results for mmφ, 0.4 mmφ, and 0.5 mmφ. For example, as shown in FIG. 5, the filling rate of the tensile strength fiber having a good connector mountability changes depending on the outer diameter of the optical fiber. For example, if the outer diameter of the optical fiber is 0.25 mm or less, and if the Young's modulus of the jacket material is 90 kg / mm ² or more, the filling rate of the tensile strength fibers must be 55% or less. Even when the outer diameter of the optical fiber is 0.4 mm and the Young's modulus of the jacket material is 130 kg / mm ² , the filling rate of the tensile strength fibers must be 55% or less.

However, for example, when the outer diameter of the optical fiber is 0.5 mmφ or more, the Young's modulus of the jacket material is 50 kg /
If it is not less than mm ^{2 and not} more than 150 kg / mm ² , the filling rate of the tensile strength fiber may be not less than 60%. In addition, even when the outer diameter of the optical fiber is 0.4 mm or more, a good optical fiber cord can be obtained even when the Young's modulus of the jacket material is 90 kg / mm ² or less, even if the filling rate of the tensile strength fiber is 60 to 65%. Even when the outer diameter of the optical fiber is 0.25 mmφ or more, when the Young's modulus of the jacket material is 50 kg / mm ² , the filling rate of the tensile strength fiber can be 60% or more.

[0027]

As is apparent from the above description, according to the first aspect of the present invention, an optical fiber core is provided at the center, a tensile fiber is provided around the optical fiber, and a sheath is provided on the outer side. In an optical fiber cord having an outer diameter of 2.4 kg / mm ² or more and 7 kg / mm ² or less and an outer diameter of 1.2 mm or less, the Young's modulus of the jacket is 50 kg / mm ² or more and 150 kg / mm ^2.
When the filling rate of the tensile strength fiber occupying the space between the optical fiber core wire and the jacket is 30% or more, the bending rigidity, low-temperature characteristics, and connector mountability of the optical fiber cord alone are ensured. It is possible to be good.

In particular, as in the second aspect of the present invention, the outer diameter of the optical fiber is 0.25 mm or less and the Young's modulus of the jacket is 90 kg / mm ² or more and 150 kg / mm ² or less.
Alternatively, the outer diameter of the optical fiber is 0.4 mm or less and the Young's modulus of the jacket is 130 kg / mm ² or more and 150 kg / m.
m ² or less, and the filling ratio of the tensile strength fiber in the space between the optical fiber core wire and the jacket is 55% or less, so that the connector mountability can be improved. Of course, also in this case, the bending rigidity and low-temperature characteristics are good.

According to a third aspect of the present invention, the outer diameter of the optical fiber core is 0.25 mm or less and the Young's modulus of the jacket is 50 kg / mm ² or more and 90 kg / mm ² or less, or Outer diameter of core wire is 0.25mm or more 0.4
mm or less and the Young's modulus of the jacket is 50 kg / mm ² or more and 1
When it is 30 kg / mm ² or less, and the filling rate of the tensile strength fiber in the space between the optical fiber core wire and the jacket is 65% or less, the connector mounting property can be improved. Of course, also in this case, the bending rigidity and low-temperature characteristics are good.

Further, according to the present invention, the light
The outer diameter of the fiber is 0.5mm or more and the sheath is young
Rate is 50kg / mm^TwoMore than 150kg / mm^TwoBelow,
Or the outer diameter of the optical fiber
Has a Young's modulus of 50 kg / mm ^Two90 kg / mm^TwoLess than
Bottom or outer diameter of optical fiber core wire is 0.25mm or more
And the Young's modulus of the jacket is 50 kg / mm^TwoAnd the optical
Filling of the tensile strength fiber in the space between the sheath and the sheath.
With a filling rate of 60% or more, connector mounting
Can be improved. Of course, also in this case, the song
Good rigidity and low temperature characteristics.

As the material of the jacket, for example, any one of ultraviolet curable resin, nylon, and polybutylene terephthalate (PBT) can be used.

As described above, according to the present invention, the outer diameter 1.2
Even if the diameter is as small as not more than mm, there is an effect that an optical fiber cord having good bending rigidity, low-temperature characteristics, and connector mountability can be provided. In the future, as subscribers become more and more optical, it is very effective to use them for optical wiring cords in telephone offices, for example, in which the diameter must be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an optical fiber cord according to the present invention.

FIG. 2 is a graph showing an example of the relationship between the Young's modulus E of a jacket material and the bending stiffness of an optical fiber cord having a small diameter.

FIG. 3 is a graph showing an example of the relationship between the filling rate of tensile strength fibers and bending stiffness.

FIG. 4 is a graph showing an example of a relationship between a filling factor of a tensile fiber and a transmission loss.

FIG. 5 is an explanatory diagram showing an example of a relationship between a filling factor of tensile strength fibers and connector attachability.

FIG. 6 is an explanatory diagram showing the relationship between the Young's modulus of the jacket and the filling rate of tensile strength fibers in the optical fiber cord of the present invention.

[Explanation of symbols]

 1 ... optical fiber core wire, 2 ... tensile fiber, 3 ... jacket.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazu Takemoto 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Masao Tachikura 3-19 Nishishinjuku, Shinjuku-ku, Tokyo No. 2 Nippon Telegraph and Telephone Corporation

Claims (5)

[Claims] 1. An optical fiber core in the center, a tensile fiber around the core, and a jacket on the outside, and the bending rigidity is 2.4k.
g · mm ² or more and 7 kg · mm ² or less, and in an optical fiber cord having an outer diameter of 1.2 mm or less, the Young's modulus of the jacket is 50 kg / mm ² or more and 150 kg / mm ² or less,
An optical fiber cord, wherein a filling rate of the tensile strength fiber in a space between the optical fiber core wire and the jacket is 30% or more. 2. An optical fiber core wire at the center, a tensile fiber around the optical fiber core, and a jacket on the outside thereof, and a bending rigidity of 2.4 k.
g · mm ² or more 7 kg · mm ² or less, in the following the optical fiber cord outer diameter 1.2 mm, the optical fiber outer diameter of the core wire 0.25mm or less and the envelope of the Young's modulus of 90
kg / mm ² or more 150 kg / mm ² or less, or an outer diameter of 0.4mm or less and the envelope of the Young's modulus of the optical fiber is 130 kg / mm ² or more 150 kg / mm
^An optical fiber cord, wherein the filling ratio of the tensile strength fiber in the space between the optical fiber core wire and the jacket is 55% or less. 3. An optical fiber core wire at the center, a tensile fiber around the optical fiber core, and a jacket on the outside, having a bending rigidity of 2.4 k.
g · mm ² or more 7 kg · mm ² or less, in the following the optical fiber cord outer diameter 1.2 mm, the optical fiber outer diameter of the core wire 0.25mm or less and the envelope of the Young's modulus of 50
kg / mm ² or more 90 kg / mm ² or less, or the optical fiber outer diameter of the core wire 0.25mm or 0.4mm or less and the envelope of the Young's modulus of 50 kg / mm ² or more 13
0 kg / mm ² or less, and the filling rate of the tensile strength fiber in the space between the optical fiber core and the jacket is 65 kg.
% Or less. 4. An optical fiber core in the center, a tensile fiber around the core, and a jacket on the outside, and the bending rigidity is 2.4k.
g · mm ² or more and 7 kg · mm ² or less and an outer diameter of 1.2 mm or less, the outer diameter of the optical fiber core wire is 0.5 mm or more and the Young's modulus of the jacket is 50 k.
g / mm ² or more and 150 kg / mm ² or less, or the outer diameter of the optical fiber cable is 0.4 mm or more and the Young's modulus of the jacket is 50 kg / mm ² or more and 90 kg / mm ² or the optical fiber Outer diameter of core wire is 0.25mm
An optical fiber, wherein the sheath has a Young's modulus of 50 kg / mm ² , and a filling rate of the tensile strength fiber in a space between the optical fiber core and the jacket is 60% or more. code. 5. The optical fiber cord according to claim 1, wherein the material of the jacket is one of an ultraviolet curable resin, nylon, and polybutylene terephthalate (PBT). .