JP4651585B2 - Optical fiber cord - Google Patents

Description

  The present invention relates to a flexible optical fiber cord used indoors and the like, and more particularly, to a measure for improving bending resistance.

  In general, as shown in an enlarged view in FIG. 7, the optical fiber cord includes an optical fiber core wire 200, a tensile body 300 disposed along the optical fiber core wire 200, and the optical fiber core wire 200 and the tensile body. 300, and is used for connection of an optical fiber cable in a station (see Patent Document 1).

  In the conventional case, the tensile body 300 having a tensile elongation characteristic Lt in the elastic region of about Lt = 0.011% / N (≈0.8% / 70N) is used. As shown in the following Table 1, when the cord diameter φ is 2 mm to 3 mm, the thickness T ([outer diameter−inner diameter] / 2) is 0.3 mm ≦ T ≦ 0.7 mm. It is. The sheath 400 is molded by being extruded from the die together with the optical fiber core wire 200 and the strength member 300 in a state of being formed in a predetermined cross-sectional shape.

Further, an appropriate tensile elongation characteristic L of the optical fiber cord 100 (elongation rate when a tension of 70 N is applied) is generally 0.5% / 70 N or less (L ≦ 0.5% / 70 N). Yes.
Japanese Patent Laid-Open No. 10-10380 (page 3, FIG. 1)

  By the way, as illustrated in FIG. 1, for example, when the optical fiber cord 100 is used for connection between the information outlet 51 and the ONU 52 in a room of a general household, It is necessary to make it possible to maintain the transmission characteristics and the like without breaking the fiber core wire 200. For this purpose, the thickness T of the sheath 400 needs to be increased (for example, T ≧ 1.1 mm).

  However, as the sheath thickness T increases, the sheath 400 contracts more due to material distortion during extrusion molding. For this reason, the tensile body 300 has a surplus length (the actual tensile elongation is higher than the original tensile elongation characteristics). As a result, the tensile elongation characteristic L of the optical fiber cord 100 exceeds 0.5% / 70N (L> 0.5% / 70N). .

  The present invention has been made in view of these points, and its main object is to increase the sheath thickness and bend resistance in an optical fiber cord including an optical fiber core, a tensile body, and a sheath. In order to improve the property, the shrinkage of the sheath after molding becomes large and the tensile body is accommodated in the extra length state so that the tensile elongation characteristic does not exceed 0.5% / 70N. Another object of the present invention is to provide a flexible optical fiber cord that can be used with peace of mind even in a room of a general household.

  In order to achieve the above object, in the present invention, the tensile elongation characteristic of the tensile strength body is lowered by the amount that the sheath thickness is increased and the sheath contraction is increased, thereby suppressing the tensile elongation characteristic of the optical fiber cord. I did it.

Specifically, the present invention includes an optical fiber core, a tensile body disposed along the optical fiber core, and a sheath that covers the optical fiber core and the tensile body, and has a tension of 70 N. An optical fiber cord having an elongation rate of 0.5% or less when applied is assumed.

The thickness T of the sheath is a 1.1 mm ≦ T ≦ 1.5 mm, shrinkage after extrusion of the sheath, it der less 3.1%, than the shrinkage ratio of the strength member It is assumed that the tensile elongation characteristic Lt of the strength member is 0.007% / N or less (Lt ≦ 0.007% / N). Here, the tensile elongation characteristic Lt of the tensile body is a tensile elongation coefficient [unit:% / N] in the elastic region of the tensile body.

In the above configuration, when the strength member is a strength fiber, the fineness F can be 3585 dtex or more (F ≧ 3585 dtex). On the other hand, if the fineness F is too large, as an example, there is a problem that it becomes difficult to pass through the fiber for forming the sheath together with the optical fiber core wire. Therefore, the fineness F is set to 6354 dtex or less (F ≦ 6354 dtex). Can be suppressed. Tensile elongation properties Lt of tensile strength fiber at this time is Lt = 0.002% / N.

In the present invention, the thickness of the sheath is obtained as an optical fiber cord comprising an optical fiber core, a tensile body disposed along the optical fiber core, and a sheath covering the optical fiber core and the tensile body. T is 1.1 mm ≦ T ≦ 1.5 mm, extrusion after shrinkage of the sheath, I der less 3.1%, it is larger than the shrinkage ratio of the strength member, the strength member Since the tensile elongation characteristics of the steel sheet were set to 0.007% / N or less, when the sheath thickness was increased to improve the bending resistance, the shrinkage of the sheath after molding was increased, and the tensile strength body was excessive. To provide a flexible optical fiber cord that can suppress the tensile elongation property to 0.5% / 70 N or less despite being accommodated in a long state, and can be used with peace of mind even in a general household room. Can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an enlarged cross-sectional view schematically showing the overall configuration of an optical fiber cord according to an embodiment of the present invention. As shown in FIG. 1, the optical fiber cord 10 is an information outlet on the network side in a room. (Information wall socket) 51 and a terminal-side ONU (Optical Network Unit) 52 are used for connection. The information outlet 51 is connected to the aerial cable 56 through the indoor cable 53, the outdoor cabinet 54, and the drop cable 55 in this order.

  As shown in an enlarged view in FIG. 2, the optical fiber cord 10 includes an optical fiber core 20, and a tensile fiber 30 (for example, an aramid fiber) as a tensile body disposed along the optical fiber core 20. The sheath 40 (for example, a thermoplastic elastomer) that covers the optical fiber core wire 20 and the tensile strength fiber 30 is formed. The optical fiber core wire 20 is formed by applying a secondary coating to an optical fiber strand obtained by primary coating of an optical fiber. The tensile strength fiber 30 extends over the entire circumference of the optical fiber core wire 20. It is arranged to cover.

  In this embodiment, the shrinkage rate Es of the sheath 40 is 3.1% or less (Es ≦ 3.1%), and the tensile elongation Lt in the elastic region of the tensile strength fiber 30 is 0.007% / N. Hereinafter (Lt ≦ 0.007% / N).

  Specifically, the outer diameter Do of the sheath 40 (diameter φ of the optical fiber cord 10) is 4.0 mm ≦ Do ≦ 5.0 mm, and the thickness T (radial dimension) of the sheath 40 is 1.1 mm. ≦ T ≦ 1.5 mm. For example, as shown in Table 2 below, when the outer diameter Do of the sheath 40 is Do = 4.0 mm and the sheath thickness T is T = 1.1 mm, the inner diameter Di (optical The outer diameter of the fiber core wire 20 and the tensile strength fiber 30) is Di = 1.8 mm. When the outer diameter Do of the sheath 40 is Do = 5.0 mm and the sheath thickness T is T = 1.5 mm, the inner diameter Di of the sheath 40 is Di = 2.0 mm.

  Here, the balance between the shrinkage of the sheath 40 and the shrinkage of the tensile strength fiber 30 after molding will be described.

  In general, the optical fiber cord 10 is manufactured by passing the optical fiber core wire 20 through a die of an extrusion molding apparatus while attaching the tensile strength fiber 30 and extruding the sheath 40 so that it is covered with the sheath 40. . When the tensile strength fiber 30 and the sheath 40 contract after extrusion, the tensile elongation characteristic L of the optical fiber cord 10 changes due to the balance between the two.

  That is, when the shrinkage rate Es of the sheath 40 and the shrinkage rate Et of the tensile strength fiber 30 are Es> Et as shown in FIG. 3A, they are exaggerated in FIG. Moreover, since the tensile strength fiber 30 is accommodated in a state having an excess length, the sheath 40 is easily stretched, and as a result, the optical fiber core wire 20 is likely to be drawn (open arrow). On the other hand, as shown in FIG. 4 (a), when Es <Et, as shown in FIG. 4 (b), the tensile strength fiber 30 is accommodated in a tensioned state and is easily loaded with tension. The sheath 40 is difficult to extend, and as a result, the optical fiber core wire 20 is likely to protrude (open arrow).

  In the case of the conventional optical fiber cord, since the sheath thickness T is relatively small (0.3 mm ≦ T ≦ 0.7 mm), the sheath hardly contracts, and thus the tensile elongation characteristic L of the optical fiber cord. It is sufficient to consider that only the tensile strength fiber is the determining factor. As for the tensile elongation characteristic L of the optical fiber cord itself, the tensile fiber having an appropriate elasticity loosens in the sheath so that an excessive tension is not applied to the optical fiber core wire when the optical fiber cord is pulled. It is sufficient as a product if it is housed without any problem and has the structure shown in the figure and the dimensions shown in the following table.

  However, if the sheath thickness Ts is increased (for example, 1.1 mm ≦ T ≦ 1.5 mm) to prevent breakage of the optical fiber core wire due to extreme bending, the contraction of the sheath cannot be ignored. In other words, the balance between the shrinkage of the sheath and the elongation of the tensile strength fiber is important, and the elongation of the tensile strength fiber when the optical fiber cord is pulled becomes larger due to the shrinkage of the sheath. That is, the elongation characteristic L exceeds 0.5% / 70N (L> 0.5% / 70N).

  Next, three types of tensile strength fibers 30 having different tensile elongation characteristics were used, and the relationship between the shrinkage rate Es of the sheath 40 and the tensile elongation L of the optical fiber cord 10 was examined. Specifically, the tensile elongation characteristics Lt of the tensile strength fiber 30 were Lt = 0.010% / N, Lt = 0.007% / N, and Lt = 0.004% / N. The results are also shown in FIG.

  As can be seen from FIG. 5, the tensile elongation characteristic L of the optical fiber cord 10 increases as the shrinkage rate Es of the sheath 40 increases, and the increase rate of the tensile elongation characteristic L is the tensile elongation characteristic of the tensile strength fiber 30. Lt = 0.007% / N than Lt = 0.004% / N, and Lt = 0.010% than Lt = 0.007% / N. In the case of% / N, each is higher.

  The sheath shrinkage rate Es when the tensile elongation characteristic L of the optical fiber cord 10 is L = 0.5% / 70N is obtained when the tensile elongation characteristic Lt of the tensile strength fiber 30 is Lt = 0.004% / N. Is Es = 8.0%, when Lt = 0.007% / N, Es = 3.1%, and when Lt = 0.010% / N, Es = 1. It was 5%. Therefore, when the tensile elongation characteristic Lt of the tensile strength fiber 30 is Lt = 0.007% / N, if the sheath shrinkage rate Es is at least 3.1% or less (Es ≦ 3.1%), The tensile elongation characteristic L of the optical fiber cord 10 is 0.5% / 70N or less (L <0.5% / 70N). Accordingly, the tensile elongation characteristic Lt of the tensile strength fiber 30 is 0.007% / N or less (Lt <0.007% / N) and the sheath shrinkage rate Es is 3.1% or less (Es ≦ 3.1%). ), The tensile elongation characteristic L of the optical fiber cord 10 can be suppressed to 0.5% / 70N or less (L ≦ 0.5% / 70N). In other words, by using the tensile strength fiber 30 having a tensile elongation characteristic Lt of 0.007% / N or less (Lt ≦ 0.007% / N), the shrinkage rate Es of the sheath 40 is Es = 3.1. It can be seen that the thickness T of the sheath 40 can be increased within a range not exceeding%.

  Further, the tensile elongation characteristic Lt of the tensile strength fiber 30 varies depending on the fineness F when the type of the fiber is constant. That is, as shown in FIG. 6, the tensile elongation characteristic Lt decreases as the fineness F increases, and increases as the fineness F decreases. Specifically, the fineness F when the tensile elongation characteristic Lt is Lt = 0.007% / N [= 0.49% / 70N] is F = 3585 dtex. By the way, when the fineness F is increased, the tensile elongation characteristic Lt is reduced correspondingly, which is preferable for suppressing the tensile elongation characteristic L of the optical fiber cord 10. However, when the fineness F is excessively increased, another problem arises. That is, the manufacturing problem that the optical fiber core wire 20 and the tensile strength fiber 30 are difficult to pass through the sheath-forming die, and the structural problem that the outer diameter of the optical fiber cord 10 is increased. It is. In these respects, the lower limit of the tensile elongation characteristic Lt of the tensile strength fiber 30 is about 0.002% / N [= 0.14% / 70N], that is, the upper limit of the fineness F of the tensile strength fiber 30 is about 6354 dtex. It is preferable that

  Therefore, in the present embodiment, the optical fiber core wire 20, the tensile strength fiber 30 disposed along the optical fiber core wire 20, and the sheath 40 covering the optical fiber core wire 20 and the tensile strength fiber 30 are provided. Since the tensile elongation characteristic Lt of the tensile strength fiber 30 is set to 0.007% / N or less (Lt ≦ 0.007% / N) as the optical fiber cord 10, the tensile elongation characteristic L of the optical fiber cord 10 is determined. Of the sheath 40 within a range where the shrinkage rate Es of the sheath 40 is 3.1% or less (Es ≦ 3.1%) while suppressing the ratio to 0.5% / 70N or less (L ≦ 0.5% / 70N). T can be increased, and the characteristics can be maintained without breaking the optical fiber core wire 20 due to extreme bending. As a result, the optical fiber core wire 20 can be sufficiently used even in a general household room.

FIG. 1 is a schematic view illustrating the use state of the optical fiber cord according to the embodiment of the invention. FIG. 2 is an enlarged cross-sectional view schematically showing the entire configuration of the optical fiber cord. FIG. 3 is a schematic diagram exaggerating the accommodation state (b) of the tensile strength fiber in the sheath when the contraction rate of the sheath is higher than the shrinkage rate of the tensile strength fiber (a). FIG. 4 is a schematic diagram exaggerating the accommodation state (b) of the tensile strength fiber in the sheath when the shrinkage rate of the tensile strength fiber is higher than the shrinkage rate of the sheath (a). FIG. 5 is a characteristic diagram showing the relationship between the shrinkage rate of the sheath and the tensile elongation of the optical fiber cord. FIG. 6 is a characteristic diagram showing the relationship between the tensile elongation of the tensile strength fiber and the fineness of the tensile strength fiber. FIG. 7 is an enlarged cross-sectional view schematically showing the entire configuration of a conventional optical fiber cord.

DESCRIPTION OF SYMBOLS 10 Optical fiber cord 20 Optical fiber core wire 30 Tensile fiber (tensile body)
40 sheath

Claims (3)

An optical fiber core, a tensile body disposed along the optical fiber core, and a sheath formed so as to cover the optical fiber core and the tensile body, and a tension of 70 N was applied. An optical fiber cord having an elongation percentage of 0.5% or less when
The thickness T of the sheath is 1.1 mm ≦ T ≦ 1.5 mm,
Shrinkage after extrusion of the sheath, I der less 3.1%, is larger than the shrinkage ratio of the strength member,
An optical fiber cord, wherein the tensile strength of the tensile body is 0.007% / N or less. The optical fiber cord according to claim 1,
The tensile body is a tensile fiber,
An optical fiber cord, wherein the tensile strength fiber has a fineness of 3585 dtex or more. The optical fiber cord according to claim 2 ,
An optical fiber cord, wherein the fineness of the tensile strength fiber is 6354 dtex or less.

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