JPH07159628A - Optical fiber cable - Google Patents

Abstract

PURPOSE:To lessen the degradation in transmission efficiency by making the coefft. of friction between the optical fiber ribbon of the the lowermost layer and the base of a group or the base of a slot equal to or smaller than the coefft. of friction between the respective layers of the optical fiber ribbon. CONSTITUTION:The coefft. muts of friction between the optical fiber ribbon Ta of the the lowermost layer and the base(f) (or the base of the slot) of the group is made equal to or lower than the coefft. mutt of friction between the respective layers (muts<=mutt). As a result, the optical fiber Ta of the lowermost layer slips with the base (f) of the group and the transmission of the dragging force to the optical fiber ribbon Ta of the the lowermost layer is shut off. Then, the generation of the dragging between the respective layers substantially obviated and the residual stresses of the respective layers generated by the dragging are equalized approximately to zero. The similar effect is obtd. even if the coefft. of friction between the optical fiber ribbon Ta of the the lowermost layer and the base (f) of the group and the coefft. of friction between the respective layers are about the same in the case the respective absolute values of the coeffts. of friction of both are small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slot type or groove type optical fiber cable in which a large number of optical fiber tapes are stacked and accommodated in a slot or a groove, and the optical fiber cable is wound up and the feeding operation is repeated. It is possible to effectively prevent the resulting reduction in the transmission efficiency of the optical fiber cable.

[0002]

2. Description of the Related Art A slot-type or groove-type optical fiber cable is known in which a large number of optical fiber tapes are stacked and accommodated in a slot or groove. The structure of the groove type optical fiber cable is shown in FIG. In this case, the optical fiber tapes T are multiply laminated and mounted on the groove 3 of the U-shaped holding member 2, and the U-shaped holding member 2 is arranged in multiple layers on the outer periphery of the tension member 1 and twisted in a spiral shape. The cable C is formed. The cable C is wound up on a winding drum and conveyed, and is unwound to be used for attaching a communication line. However, when this winding up and unwinding is repeated, the transmission efficiency may decrease, and The higher the degree of integration of the fiber tape, the more marked the above-mentioned decrease in transmission efficiency. It is considered that this decrease in transmission efficiency is caused by the residual stress due to tensile and compressive stress remaining in the fiber cores of the laminated optical fiber tapes as the optical fiber cable is bent or extended.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to alleviate the above-mentioned decrease in transmission efficiency.
Therefore, it is an object to reduce the amount of slip between the layers of the optical fiber tape T caused by bending and extending of the cable as much as possible to reduce the residual effect as much as possible.

[0004]

[Means for Solving the Problems] Means for solving the above-mentioned problems are as follows. The optical fiber tape in the lowermost layer among the optical fiber tapes laminated on the groove or slot and the bottom surface or slot of the groove. The coefficient of friction μts with the bottom surface of the
Is equal to or smaller than (μts ≦ μtt).

[0005]

[Operation] When the cable C is bent with a radius of curvature R,
In the radial cross section, the outer half in the radial direction receives a tensile stress and the inner half in the radial direction receives a compressive stress (see FIG. 2), so that the U-shaped holding member 2 spirally twisted has a radius outwardly, i.e. moves in the arrow S ₁ direction, the bottom layer of the optical fiber tape Ta of the optical fiber tape T of the groove 3 in accordance with this movement is an optical fiber tape Ta of the bottom surface f the outermost layer of the groove 3 It is dragged by the U-shaped holding member 2 with a force corresponding to the frictional force. Further, this dragging force drags the second lowest tape Tb via the frictional force between the lowermost optical fiber tape Ta and the second lowest optical fiber tape Tb. In this way, dragging occurs between the optical fiber tapes (Tc ...) In each layer, the residual stress corresponding to the frictional force between the optical fiber tape layers at this time is applied to the optical fiber tapes T in each layer, and the cable is again used. When C is extended, a shift in the opposite direction occurs between the optical fiber tape layers and a residual stress in the opposite direction occurs. However, the friction coefficient μts between the optical fiber tape Ta in the lowermost layer and the bottom surface f of the groove (or the bottom surface of the slot, the same applies hereinafter) is calculated as follows:
Equal to or less than tt (μts ≤ μtt)
Therefore, the lowermost optical fiber tape Ta (see FIG. 3, hereinafter the same in this section) slips with respect to the bottom surface f of the groove, and the transmission of the drag force to the optical fiber tape Ta is interrupted. There is almost no drag between layers. Therefore, the residual stress of each layer caused by the above-mentioned drag is substantially zero. Further, when the absolute value of the friction coefficient between the lowermost optical fiber tape Ta and the bottom surface f of the groove is small, the same effect as above can be obtained even if the friction coefficients of both layers are approximately the same. In addition,
As a concrete means for making the friction coefficient between the lowermost optical fiber tape Ta and the bottom surface f of the groove equal to or smaller than the friction coefficient between the layers, there is a lubricity of fluororesin, polyethylene, silicone resin or the like. Resin fine particles and MoS
₂ , a solid lubricant layer made of lubricating inorganic particles such as WS ₂ , BN, talc, etc. is formed on the bottom surface f of the groove, or these lubricant substances are mixed in the groove or the slot member. The groove coefficient is reduced so that the coefficient of friction between the bottom layer tape Ta is reduced, or the coefficient of friction between the respective layers is equal to or higher than the friction coefficient between the bottom surface f and the bottom layer tape Ta. Alternatively, the resin of the slot and the resin of the coating layer of the optical fiber tape may be selected and used. Furthermore, in order to reduce the absolute value of the friction coefficient of both and to make them equal, the respective tape surfaces may be coated with a lubricating substance that lowers the friction coefficient.

[0006]

[Examples] Next, examples of the present invention will be described.

Example 1 Five optical fiber tapes of eight cores (tape width 2, 2 mm) coated with an ultraviolet curable resin were laminated on a U-shaped holding member made of polybutylene terephthalate having a groove width 2, 6 mm and mounted. Then, the conventional cable having the structure shown in Fig. 1 is constructed by setting the friction coefficient between the respective tape layers relatively high, and at the same time, it is wound on a drum and its transmission loss is measured, and then it is extended. Then, the transmission loss was measured, and then the transmission loss was measured while being wound on a winding drum having a diameter of 1 m. The result is shown in Figure 4.
As shown in. In this case, friction coefficient μt between layers
t is 0.36, and the friction coefficient μts between the lowermost optical fiber tape and the groove bottom surface is 0.32.

Example 2 Using the same optical fiber tape, as in the above, five pieces were laminated and mounted on a U-shaped holding member made of polybutylene terephthalate, and talc powder was applied to the surface of the optical fiber tape. A similar cable was constructed by lowering the absolute value of the friction coefficient between layers and the friction coefficient between the bottommost optical fiber tape and the bottom surface of the groove, and the same transmission loss as above was measured. The result is as shown in FIG. In this case, the friction coefficient μtt between the layers is 0.31, and the friction coefficient μts between the lowermost optical fiber tape and the groove bottom surface is 0.31.

Comparative Example: Using the same optical fiber tape,
A conventional cable having the structure shown in FIG. 1 was constructed by stacking and mounting five U-shaped holding members made of polycarbonate in the same manner as above, and the same transmission loss as above was measured.
The result is as shown in FIG. In this case, the coefficient of friction μtt between the layers is 0.36, and the coefficient of friction μts 0.42 between the lowermost optical fiber tape and the bottom surface of the groove.

[0010]

[Effect] From the above test results, the friction coefficient μ between layers
When tt is smaller than the friction coefficient μts between the lowermost optical fiber tape and the bottom surface of the groove, the transmission loss when the wire is drawn is significantly higher than the transmission loss when the cable is formed and wound at the same time. , The transmission loss when rewinding after drawing the wire reaches more than twice as much as the transmission loss when rewinding at the same time as forming the cable, but the friction coefficient μ between layers
When tt is equal to or larger than the friction coefficient μts between the lowermost optical fiber tape and the bottom surface of the groove, the wire was then extended as compared with the transmission loss when it was wound at the same time as the cable was formed. It is proved that the transmission loss at the time and the transmission loss at the time of rewinding after the wire drawing are almost unchanged.

[Brief description of drawings]

FIG. 1 is a perspective view of an example of a conventional optical communication cable.

FIG. 2 is a front view of the cable of FIG. 1 in a bent state.

FIG. 3 is a cross-sectional view of a U-shaped holding member on which an optical fiber tape is mounted.

FIG. 4 is a graph showing transmission loss measurement results for the optical communication cable according to the first embodiment of the present invention.

FIG. 5 is a graph showing transmission loss measurement results for an optical communication cable according to a second embodiment of the present invention.

FIG. 6 is a graph showing transmission loss measurement results for a communication cable of a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tension member 2 ... U-shaped holding member 3 ... Groove T ... Optical fiber tape Ta ... Bottom optical fiber tape Tb ... Second optical fiber tape Tc from the bottom・ ・ ・ Optical fiber tape of the third or more layers from the bottom f ・ ・ ・ Bottom of U-shaped holding member C ・ ・ ・ Cable

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Suehiro Miyamoto 1440 Rokuzaki, Sakura City, Chiba Fujikura Co., Ltd. Sakura Factory (72) Inventor Shigeru Tomita 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Date Inside Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A slot-type or groove-type optical fiber cable in which a large number of optical fiber tapes are stacked and accommodated in a slot or a groove, and the most optical fiber tape among the optical fiber tapes arranged in the groove or the slot. An optical fiber cable in which the friction coefficient μts between the lower layer tape and the bottom surface of the groove or the bottom surface of the slot is equal to or smaller than the friction coefficient μtt between the optical fiber tape layers (μts ≦ μtt).