JP2000275482A - Coated optical fiber and optical fiber unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a coated optical fiber or an optical fiber unit of a tight structure to have good transfer characteristic even when an optical fiber with a increased effective core cross section (Aeff) is used by restraining formation of microbends in the optical fiber. SOLUTION: This optical fiber unit comprises a plurality of coated optical fibers 2 twisted around a central tensioning member 1, each of the coated optical fibers 2 comprising an optical fiber having an Aeff of 70 μm2 or more and a primary covering layer formed on the circumference of each optical fiber, the primary covering layer having a Young's modulus of 0.15 kg/mm2 or less at room temperature and a glass transition point of 0 deg.C of below. An integrating material 3 with a Young's modulus of 0.5 kg/mm2 or less at room temperature and a glass transition point of -20 deg.C of below integrally covers the circumference of the plurality of the coated optical fibers 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber unit and an optical fiber which are suitably used for constructing a submarine optical fiber cable.

[0002]

2. Description of the Related Art FIG. 1 is a sectional view showing an example of an optical fiber unit used for a submarine optical fiber cable.
In the optical fiber unit of this example, eight optical fiber strands 2 are twisted around the center tension member 1, the integrated material 3 is collectively covered around these, and an overcoat layer 4 is further surrounded therearound. Is covered.
In this optical fiber unit, the optical fiber 2 is tightly gathered around the central tension member 1 by the integrated material 3, and such a structure is referred to as a tight structure in this specification. Further, the optical fiber 2 has a primary coating layer made of UV resin formed on the circumference of the optical fiber, and conventionally has excellent uniform bending characteristics and microbend characteristics for a submarine optical fiber cable. Things were used.

[0003]

However, recently, in order to meet the demand for large-capacity transmission, an optical fiber having an enlarged effective core area (hereinafter sometimes referred to as Aeff) has been used. However, an optical fiber configured to have a large Aeff has the following problem because the microbend sensitivity is increased. That is, the transmission loss of an optical fiber having an increased Aeff is likely to increase even with a small microbend, and the resin forming the primary coating layer of the optical fiber 2 is hardened when the optical fiber cable is exposed to a low temperature. Also, there is a problem that the transmission loss tends to increase. In an optical fiber unit having a tight structure, the optical fiber 2 is greatly affected by the mechanical characteristics of the integrated material 3. Unless mechanical properties are taken into account, there is also a problem that transmission loss is likely to increase even with small microbends due to changes in water pressure or temperature.

The present invention has been made in view of the above circumstances, and in an optical fiber unit or an optical fiber unit having a tight structure, the occurrence of microbends in an optical fiber is suppressed, and the effective core area (Aeff) is reduced. An object is to obtain good transmission characteristics even when an enlarged optical fiber is applied.

[0005]

Means for Solving the Problems To solve the above problems, an optical fiber of the present invention comprises:
A primary coating layer having a Young's modulus at room temperature of 0.15 kg / mm ² or less and a glass transition temperature of 0 ° C. or less is formed. The optical fiber has an effective core area of 70 μm ²
A structure configured as described above can be preferably used. In the optical fiber unit of the present invention, a plurality of optical fiber wires each having a primary coating layer formed on the circumference of the optical fiber are twisted around the center tension member, and the Young's modulus at room temperature is zero around these. .5kg / mm ² in the following,
It is one in which an integrated material having a glass transition temperature of −20 ° C. or lower is collectively coated. As the optical fiber, a fiber configured to have an effective core area of 70 μm ² or more can be preferably used. It is particularly preferable that a primary coating layer having a Young's modulus at room temperature of 0.15 kg / mm ² or less and a glass transition temperature of 0 ° C. or less is provided on the circumference of an optical fiber having an effective core area of 70 μm ² or more. A plurality of formed optical fibers are twisted around the center tension member, and the Young's modulus at room temperature is 0.5 kg /
This is an optical fiber unit obtained by collectively coating an integrated material having a glass transition temperature of −20 ° C. or less with mm ² or less.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
Although the optical fiber of the present invention has a primary coating layer made of a UV resin formed on the circumference of the optical fiber, a coating layer made of nylon or the like may be further provided if necessary. As the optical fiber, various existing optical fibers can be used. However, in the present invention, since the primary coating layer has a configuration described later, the effective core area (Aeff) is 7 mm.
A material configured to have a thickness of 0 μm ² or more can be used. The use of an optical fiber configured to increase Aeff in this manner can cope with large-capacity transmission, so that a preferable optical fiber for forming a submarine optical fiber cable can be obtained.

The primary coating layer of the optical fiber is made of a UV resin having a glass transition temperature (Tg) of 0 ° C. or less, and has a Young's modulus at room temperature of 0.15 kg / mm ² or less. . Here, in this specification, normal temperature is a temperature range of 23 ± 2 ° C. Under the use environment of the submarine optical fiber cable, the temperature zone to which the optical fiber is exposed is usually 0 ° C.
taller than. The Tg of the UV resin constituting the primary coating layer is set to 0 ° C.
When the temperature is higher than 0 ° C. when the optical fiber is exposed to a low temperature, the primary coating layer is prevented from becoming hard. As a result, the occurrence of microbending in the optical fiber in a temperature range higher than 0 ° C. is suppressed, so that the optical fiber can be preferably used as an optical fiber for a submarine optical fiber cable, and good transmission characteristics are obtained. Further, if the Young's modulus of the primary coating layer of the optical fiber at room temperature is large, external stress is easily transmitted to the optical fiber, particularly in the case of a tight type structure, and microbends are easily generated, so that the Young's modulus is 0.15 kg / mm ² or less is preferable. If the Young's modulus is too small, the coating may be crushed and broken at the time of unitization. Therefore, the lower limit of the Young's modulus of the primary coating layer is preferably set to about 0.03 kg / mm ² . As a UV resin material constituting the primary coating layer of the optical fiber 2,
For example, a urethane acrylate resin is preferably used.

The optical fiber unit according to the present invention has a tight structure, for example, the structure shown in FIG. Optical fiber 2 constituting the optical fiber unit
Can be changed as appropriate. As the center tension member 1, a known member such as a steel wire can be used. As the optical fiber 2, various existing optical fiber can be used. Preferably, the Aeff of the optical fiber is 70 μm ² or more, particularly preferably 75 μm.
^Two or more optical fibers are used, and the optical fiber of the present invention in which the primary coating layer is defined as described above is preferably used.

The integrated material 3 is formed by using a UV resin having a glass transition temperature (Tg) of -20 ° C. or less, and having a Young's modulus at room temperature of 0.5 kg / mm ² or less. In the use environment of the submarine optical fiber cable, the temperature zone to which the integrated material 3 constituting the optical fiber unit is exposed is usually −2.
Higher than 0 ° C. By setting the Tg of the UV resin constituting the integrated material 3 to -20 ° C or lower, the integrated material 3 is exposed to a temperature range higher than -20 ° C even in a low temperature environment. 3 is obtained, and the occurrence of microbending in the optical fiber 2 is suppressed. Therefore, it can be preferably used as an optical fiber unit for a submarine optical fiber cable, and good transmission characteristics can be obtained. When the Young's modulus of the integrated material 3 at room temperature is large, external stress is easily transmitted to the optical fiber, and therefore the Young's modulus is preferably 0.5 kg / mm ² or less. As the UV resin material constituting the integrated material 3, for example, a urethane acrylate resin, an epoxy acrylate resin, or the like can be preferably used. The overcoat layer 4 formed on the periphery of the integrated material 3 is preferably formed using a resin such as a urethane acrylate resin or an epoxy acrylate resin.

In order to manufacture the optical fiber unit of the present invention, a plurality of optical fiber wires 2 are twisted around the center tension member 1 and the integrated material 3 is wound around these around, preferably by a pressure coating method. The coating may be performed collectively, and the surroundings may be further coated with the overcoat layer 4, preferably by a pressure coating method. Then, a seafloor optical fiber cable is formed by providing a tensile member, a waterproof layer, a sheath, and the like around the optical fiber unit.

In the present invention, a resin having a Tg of 0 ° C. or less is used as a material of the primary coating layer of the optical fiber and the Young's modulus of the primary coating layer at room temperature is 0.15 k.
g / mm ² or less to prevent the transmission of external stress to the optical fiber and to prevent the primary coating layer from becoming hard when the optical fiber unit is exposed to a low temperature (0 ° C. or more). Thus, the occurrence of microbends in the optical fiber can be suppressed. Therefore, Aeff
Good transmission characteristics can be obtained even when an optical fiber with an enlarged size is applied. The optical fiber having such a configuration is suitable for forming a submarine optical fiber cable, but the temperature range to which the optical fiber is exposed is 0 ° C. to + 50 ° C.
It can be used for various types of optical cables, optical fiber units, optical fiber cords, etc. as long as it is used in an environment of a certain degree, and can realize large capacity transmission using an optical fiber with an increased Aeff. .

In the optical fiber unit of the present invention, the Young's modulus at room temperature of the integrated member 3 disposed around the optical fiber ² is reduced to 0.5 kg / mm ² or less, and Tg is -20 ° C. By using the following resin,
In a wide temperature range of −20 ° C. to + 50 ° C., transmission of external stress such as water pressure to the optical fiber 2 is suppressed, and the integrated material is prevented from being hardened at a low temperature. Bending can be suppressed. Therefore, good transmission characteristics can be obtained even when an optical fiber having an increased Aeff is applied. In particular, it is preferable to use the optical fiber of the present invention in which Aeff is used in the optical fiber unit of the present invention and the primary coating layer formed on the periphery thereof is defined as described above, An optical fiber unit suitable for constructing a submarine optical fiber cable using an optical fiber with an increased Aeff is obtained. In addition, the optical fiber unit of the present invention is not limited to submarine optical fiber cables, and various optical cables and the like can be used as long as the optical fiber unit is used in an environment where the temperature range to which the optical fiber unit is exposed is about -20 ° C to + 50 ° C. It is possible to realize large-capacity transmission using an optical fiber with an increased Aeff.

[0013]

EXAMPLES Hereinafter, the effects of the present invention will be clarified by showing specific examples. (Examples 1 and 2 and Comparative Examples 1 to 3) First, the following Examples 1 and 2 and Comparative Examples 1 to 3 were performed in order to clarify the effect of the primary coating layer of the optical fiber. The value of Aeff of the optical fiber in the optical fiber 2 used, the Young's modulus of the primary coating layer at room temperature, and Tg were changed as shown in Table 1 below to produce an optical fiber unit having the structure shown in FIG. That is, the center tension member 1 has an outer diameter of 0.1 mm.
A 75 mm steel wire is used, eight optical fiber wires 2 having an outer diameter of 400 μm are twisted around the steel wire, and then a urethane acrylate resin is coated as an integral material 3 around these wires and cured by irradiating ultraviolet rays. I let it. Further, a urethane-based acrylate resin was coated as an overcoat layer 4 and cured by irradiating ultraviolet rays to obtain an optical fiber unit. The water pressure loss of the obtained optical fiber unit was measured. The measurement was performed before and after applying water pressure up to 100 kg / cm ^2.
The measurement was performed by monitoring the transmission loss fluctuation of 5 μm. The results are shown in Table 1 below. In an optical fiber unit used for a submarine optical fiber cable, the value of the water pressure loss is required to be +10 mdB / km or less. -20 ° C of the obtained optical fiber unit
The loss was measured. The measurement was performed based on the transmission loss at an ambient temperature of + 15 ° C., and a method of obtaining a 1.55 μm transmission loss variation when the ambient temperature was lowered to −20 ° C. The results are shown in Table 1 below. In an optical fiber unit used for a submarine optical fiber cable, the value of the -20 ° C loss is required to be smaller than ± 10 mdB / km.

[0014]

[Table 1]

From the results shown in Table 1, in Examples 1 and 2 in which the Young's modulus and Tg of the primary coating layer of the optical fiber are within the range of the present invention, an optical fiber having a large Aeff of 78 μm ² or more was used. Also, the water pressure loss and the −20 ° C. loss are suppressed to be small. On the other hand, in Comparative Examples 1 and 2 where the Tg of the primary coating layer is high, there is no problem when the Aeff of the optical fiber is as small as 55 μm ² ,
It can be seen that when f is increased to 75 μm ² , the loss at −20 ° C. greatly deteriorates. Also, it can be seen that in Comparative Example 3 in which the Young's modulus of the primary coating layer is large, the water pressure loss has deteriorated.

(Examples 3 and 4 and Comparative Examples 4 to 8) Next, in order to clarify the effect of the integrated member 3 of the optical fiber unit, the following Examples 3 and 4 and Comparative Examples 4 to 8 went. A of the optical fiber in the used optical fiber 2
eff value, Young's modulus of integrated material 3 at room temperature and T
g was changed as shown in Table 2 below to produce an optical fiber unit having the structure shown in FIG. That is, a steel wire having an outer diameter of 0.75 mm is used as the center tension member 1 and an outer diameter of 4 mm is used.
After eight optical fiber strands 2 of 00 μm are twisted around the tension member 1, an integrated material 3 is
Was extrusion coated and cured. Further, the overcoat layer 4 was coated and cured to obtain an optical fiber unit. About the obtained optical fiber unit, the water pressure loss and the -20 ° C loss were measured in the same manner as in Example 1 above. The results are shown in Table 2 below.

[0017]

[Table 2]

From the results shown in Table 2, in Examples 3 and 4 in which the Young's modulus and Tg of the integrated material are within the range of the present invention, even if an optical fiber having Aeff as large as 70 μm ² or more is used, the hydraulic pressure loss and -20 ° C loss is kept small. On the other hand, Comparative Example 4, in which the Tg of the integrated material was high,
In Nos. 5 and 6, although the Young's modulus of the integrated material was small, the loss at -20 ° C was deteriorated. In Comparative Example 7 where the Young's modulus of the integrated material is large, the hydraulic pressure loss is deteriorated. In Comparative Example 8 where the Young's modulus of the integrated material is large and Tg is high,
Both water pressure loss and -20 ° C loss are deteriorated.

[0019]

As described above, according to the present invention, by defining the Young's modulus and Tg of the primary coating layer of the optical fiber at room temperature as described above, even in a low temperature range, the light of a tight structure can be obtained. Even when applied to a fiber unit, the generation of microbends is suppressed, and good transmission characteristics and temperature characteristics can be obtained. In particular, even when an optical fiber having an increased Aeff is applied, good transmission characteristics can be obtained in a temperature range higher than 0 ° C., and large-capacity transmission using an optical fiber having a large Aeff can be realized. Further, the optical fiber unit of the present invention has a tight structure, and by defining the Young's modulus and Tg at room temperature of the integrated material disposed around the optical fiber at −20 ° C. as described above. Since microbends generated in the optical fiber can be reduced in a wide temperature range of up to + 50 ° C., an optical fiber unit having excellent transmission characteristics and temperature characteristics can be obtained. In particular, even when an optical fiber having an increased Aeff is applied, good transmission characteristics are obtained within the above temperature range, and a submarine optical fiber cable using an optical fiber having a large Aeff can be preferably realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an optical fiber unit.

[Explanation of symbols]

1: Central tension member, 2: Optical fiber strand, 3:
Integrated material.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Shimichi, 1440, Mukurosaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Plant (72) Inventor Keiji Ohashi, 1440, Misaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Plant, Inc. F term (reference) 2H001 BB06 DD04 KK17 KK22 2H050 AC76 BB31Q BB33Q BC02

Claims (5)

[Claims] 1. A light comprising a primary coating layer having a Young's modulus at room temperature of 0.15 kg / mm ² or less and a glass transition temperature of 0 ° C. or less formed on the periphery of an optical fiber. Fiber strand. 2. The optical fiber according to claim 1, wherein said optical fiber has an effective core area of 70.
^2. The optical fiber according to claim 1, wherein the length of the optical fiber is not less than ² μm ² . 3. A plurality of optical fiber strands each having a primary coating layer formed on the circumference of an optical fiber, twisted around a central tension member, and a Young's modulus at room temperature is 0.5 kg / mm ² or less, the optical fiber unit, characterized in that the glass transition temperature is collectively covering the integrated material is -20 ° C. or less. 4. An optical fiber having an effective core area of 70.
4. The optical fiber unit according to claim 3, wherein the optical fiber unit has a thickness of not less than μm ² . 5. Young's modulus at room temperature is 0.15 kg / cm on the circumference of an optical fiber having an effective core area of 70 μm ² or more.
mm ² or less, a plurality of the optical fiber obtained by forming the primary coating layer glass transition temperature of 0 ℃ or less, twisted around a central tension member, a Young's modulus at room temperature in these surrounding 0 .5kg / mm ² or less, the optical fiber unit, characterized in that the glass transition temperature is collectively covering the integrated material is -20 ° C. or less.