JP2001042180A - Optical fiber unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber unit having excellent a side pressure characteristic and transmission characteristic. SOLUTION: This unit 5 is constituted by twisting and assembling a plurality of optical fibers 2, 2,... around a tension member 1, then successively forming an integrating layer 3 and a shell layer 4 on the assembly. The shell layer 4 is formed of a resin of >=100 kg/mm2 in Young's modulus and <=100 deg.C in glass transition temperature.

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 used for an optical submarine cable or the like, and adjusts the Young's modulus and glass transition temperature (hereinafter abbreviated as Tg) of a resin used for a shell layer of the optical fiber unit. Thereby, the side pressure characteristics and the transmission characteristics of the optical fiber unit are improved.

[0002]

2. Description of the Related Art An optical fiber unit is formed by twisting and assembling a plurality of optical fiber wires around a strength member made of a copper-plated steel wire or the like, and then made of an ultraviolet curable resin or the like on the assembly. The optical fiber is integrated with the tensile strength member by providing an integrated layer, and a shell layer made of an ultraviolet curable resin or the like is provided on the integrated layer. The optical fiber unit having such a structure is particularly suitably used as an optical submarine cable.

[0003]

By the way, in such an optical fiber unit for an optical submarine cable, due to the special laying environment, the optical fiber is not affected by the side pressure received when the optical fiber cable is extended or the water pressure received in the deep sea. There is a problem that transmission loss increases. Further, there is a problem that the transmission loss of the optical fiber increases due to the stress generated by the shrinkage of the integrated layer and the shell layer due to a temperature change at the time of forming (unitizing) or laying these optical fiber units. is there.

[0004] From such a problem, an optical fiber unit used for an optical submarine optical fiber cable is required to have excellent lateral pressure characteristics and transmission characteristics. The lateral pressure characteristics and the transmission characteristics of the optical fiber unit are closely related to the mechanical characteristics of the resin used for the shell layer of the optical fiber unit. In particular, when the effective core area (Aeff) of the optical fiber used in the optical fiber unit is large,
Since the microvent sensitivity of the optical fiber is increased, the lateral pressure characteristics and the transmission characteristics of the optical fiber unit are easily affected by the mechanical characteristics of the resin used for the shell layer of the optical fiber unit. For this reason, it is necessary to consider the mechanical properties of the resin used for the shell layer.

[0005] The present invention has been made in view of the above circumstances, and has as its object to obtain an optical fiber unit having excellent lateral pressure characteristics and transmission characteristics.

[0006]

According to the present invention, a plurality of optical fiber strands are twisted and assembled around a tensile strength member, and an integrated layer and a shell layer are sequentially formed on the aggregate. In the optical fiber unit, the shell means is made of a resin having a Young's modulus of 100 kg / mm ² or more and a glass transition temperature of 100 ° C. or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 shows an example of the optical fiber unit of the present invention. The optical fiber unit 5 of this example is formed by twisting and gathering a plurality of optical fiber wires 2, 2,... Around a strength member 1 made of a copper-plated steel wire, and then, on this assembly, an ultraviolet curable resin is used. The integrated layer 3 is provided, and a shell layer 4 made of a resin is further provided on the periphery of the integrated layer 3.

The shell layer 4 has a Young's modulus of 100 kg.
/ Mm ² or more and Tg of 100 ° C. or less. When the Young's modulus of the resin is less than 100 kg / mm ² , the lateral pressure resistance of the shell layer 4 is reduced, and a stress is applied to the optical fiber unit 5 by a lateral pressure applied when the optical fiber unit 5 is laid or a water pressure received in the deep sea. This increases the transmission loss of the optical fibers 2, 2,..., Which is not preferable.

If the Tg of the resin is higher than 100 ° C., the modulus of elasticity of the shell layer 4 changes due to a temperature change when the optical fiber unit 5 is laid or unitized. 4 are deformed, stress is applied to the optical fiber strands 2, 2,..., And the transmission characteristics of the optical fiber strands 2, 2,. In particular, at high temperatures, the elastic modulus of the shell layer 4 increases, so that the stress applied to the optical fiber strands 2, 2,... Increases, and the transmission loss of the optical fiber strands 2, 2,. If the above Tg is 100 ° C. or less, the change in the elastic modulus of the shell layer 4 due to a temperature change when the optical fiber unit 5 is laid or unitized becomes small, and the stress applied to the optical fiber strands 2, 2,. .., The transmission characteristics of the optical fibers 2, 2,... Do not deteriorate. In particular, at high temperatures, the elastic modulus of the shell layer 4 decreases, and the stress applied to the optical fibers 2, 2,... In the optical fiber unit 5 also decreases, so that the transmission loss of the optical fibers 2, 2,. Can be minimized. Therefore, the transmission characteristics of the optical fiber unit 5 do not deteriorate.

The Tg of the resin used for the shell layer 4 is
Is known to have a close relationship with the pull-out force of the tensile strength member 1 of the optical fiber unit 5, and when the resin having the Tg in the above range is used for the shell layer 4, the temporal stability of the pull-out force is obtained. Can be obtained. The pull-out force of the tensile strength member 1 indicates an adhesive force between the tensile strength member 1 and the optical fiber wires 2, 2,. If the adhesive strength between the two is weak, the function of the tensile strength member 1 in the optical fiber unit 5 is not sufficiently exhibited.
Has a weak structure that is susceptible to external tensile forces. Conversely, if the adhesive force is strong, the function of the tensile strength member 1 is sufficiently exhibited, and the optical fiber unit 5 has a structure that is strong against an external tensile force. It is important to stabilize the adhesive force between the tensile strength member 1 and the optical fibers 2, 2,... With time to maintain the tensile strength of the optical fiber unit 5. Specifically, an ultraviolet curable resin is used as the resin used for the shell layer 4.

The tensile member 1 used in the present invention includes:
A plurality of steel wires plated with copper and twisted and assembled, and the surface of the aggregate is subjected to a heat treatment to form a copper oxide film is preferably used. As the optical fibers 2, 2,..., Single-mode optical fibers having an outer diameter of about 250 μm or 400 μm are mainly used. As the integrated layer 3, an ultraviolet curable resin is preferably used. Its thickness is about 0.26 to 1.00 mm, and its Young's modulus is 0.1 to 10.0 kg / mm ² .

As described above, the shell layer 4 of the optical fiber unit 5 has a Young's modulus of 100 kg / mm ² or more and T
By using a resin having a g of 100 ° C. or less, the lateral pressure characteristics of the optical fiber unit 5 can be improved.
Further, transmission loss of the optical fiber due to a temperature change when the optical fiber unit 5 is unitized or laid can be minimized. Since the pull-out force of the tensile strength member 1 of the optical fiber unit 5, in other words, the adhesive strength between the tensile strength member 1 and the optical fiber wires 2, 2... Can be kept good, the tensile strength of the optical fiber unit 5 can be reduced. It can be kept stable over time.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. An optical fiber unit having the structure shown in FIG. 1 was manufactured.
First, a copper-plated steel wire coated with a copper oxide film is used as the strength member 1, and eight optical fiber wires 2, 2,... Having an outer diameter of 250 μm are twisted and assembled on the strength member 1, and the assembly is performed. An ultraviolet ray resin having a Young's modulus of 0.5 kg / mm ² is applied on the body and cured to form an integrated layer 3.
Further, a resin adjusted to the Young's modulus and Tg shown in Table 1 below is applied onto the integrated layer 3 and cured to form a shell layer 4, thereby forming a shell layer 4 according to Example 1, Comparative Examples 1 to 3. Was obtained. A side pressure test was performed on each of the optical fiber units thus obtained,
The side pressure loss (side pressure loss) of the optical fiber unit and the flatness during the side pressure test were measured. In addition, the transmission loss of the optical fiber unit due to the temperature change was measured. Further, the stability over time of the tensile strength member was evaluated. The results are shown in Table 1 below.

[0014]

[Table 1]

The lateral pressure test will be described with reference to FIG.
Reference numeral 10 in the drawing indicates an optical fiber unit. The outer diameter of the optical fiber unit 10 is measured in advance (this is referred to as a
And). Next, as shown in FIG. 2, the optical fiber unit 10 is placed over two 300 mm long flat plates 11 and 12.
Between upper and lower sides, 300kg / 60c from above
applying a load of m ^2. And the optical fiber unit 1
0 for 1 hour with a load applied, and then measure the outer diameter of the optical fiber unit 10 in the vertical direction (this is referred to as b
And). Using the measured values a and b thus obtained, the flattening ratio was determined by the following equation (1). Those having an aspect ratio of 15% or less were determined to have good body side pressure. Flattening rate (%) = (ab) / a × 100 (1)

Further, the transmission loss before and after the application of the lateral pressure of each optical fiber unit was measured, and the difference between these values (lateral pressure loss) was determined. The side pressure loss of +3 mdB / km or less was determined to be good with little transmission loss.

Further, the transmission loss of the optical fiber unit due to the temperature change is obtained by changing the temperature from 15 ° C. to 50 ° C.
The transmission loss of the optical fiber unit at 15 ° C. and 50
The transmission loss at a temperature of ° C was measured, and the difference between them (50 ° C loss) was determined. And these values are 10mdB / km
The following were evaluated as good with little transmission loss.

Further, the tensile strength member pulling force (TM pulling force) of each optical fiber unit was measured with time, and those whose values did not change with time were evaluated as having stability. Those whose values decreased with time were evaluated as having poor stability, and
○, × are shown in Table 1.

From the test results of Example 1 and Comparative Examples 1 to 3, in Example 1, the flatness at the time of the lateral pressure test was 1
It can be seen that the lateral pressure is suppressed to 5% or less, and there is no lateral pressure loss, and good lateral pressure characteristics are obtained. Further, the transmission loss due to the temperature change is also kept low, and it can be seen that good transmission loss is obtained. Further, it can be seen that the pull-out force of the tensile strength member maintains stability over time. On the other hand, in Comparative Examples 1 to 3, the flatness at the time of the lateral pressure test, the lateral pressure loss, the transmission loss at the time of temperature change,
It can be seen that there is a problem in any of the temporal stability of the tensile strength body pulling force.

[0020]

As described above, the optical fiber unit of the present invention comprises a plurality of optical fiber strands twisted and assembled around a strength member, and then an integrated layer and a shell are formed on the aggregate. An optical fiber unit in which layers are sequentially formed, wherein the shell layer has a Young's modulus of 100 kg / mm.
² or more, and so is characterized in that comprising a glass transition temperature of 100 ° C. or less is a resin, it is possible to have a lateral pressure characteristics that can sufficiently withstand the pressure applied at the time unit of the optical fiber unit or laying. Further, the optical fiber unit of the present invention can have excellent transmission characteristics capable of minimizing the transmission loss of the optical fiber even when a temperature change occurs during unitization or installation. . Further, the optical fiber unit of the present invention can maintain the pull-out force of the tensile strength member, in other words, the adhesive force between the tensile strength member and the optical fiber strand, so that the tensile strength of the optical fiber unit is stable over time. Can be kept.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a lateral pressure test method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tensile body, 2 ... Optical fiber, 3 ...
Integrated layer 4 ・ ・ ・ Shell layer, 5 ・ ・ ・ Optical fiber unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Shimichi 1440, Mukurosaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Office (72) Inventor Keiji Ohashi 1440, Musaki, Sakura City, Chiba Prefecture Fujikura Sakura Office F term (reference) 2H001 BB01 DD04 DD11 KK06 KK17 KK22 PP01

Claims (1)

[Claims] 1. An optical fiber unit comprising a plurality of optical fiber strands twisted and assembled around a strength member, and an integrated layer and a shell layer are sequentially formed on the aggregate. An optical fiber unit, wherein the shell layer is made of a resin having a Young's modulus of 100 kg / mm ² or more and a glass transition temperature of 100 ° C. or less.