JPH04182608A - Optical cable - Google Patents

Abstract

PURPOSE:To prevent an optical fiber tape from being bent or distorted by making the width of the inside groove and the height of the groove side wall of a unislot tube larger than the length of diagonal of a housing body of an optical fiber tape. CONSTITUTION:The width (a) of the inside groove and the height (b) of the groove side wall of the unislot tube 111 are made larger than the length (c) of the diagonal of housing body 113A for the optical fiber tape which is housed and laminated in a groove 112. By such relation, even in the case of bending stress acts on the tube 11 from the outside at the time of manufacturing, carrying or laying a cable, the optical fiber tape 113 inside is not bent or distorted, and can be freely moved without receiving any restriction in the groove 112. Thus, wrinkles or a fold is prevented from being generated.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an optical cable in which a plurality of optical fibers are housed in a long flexible uni-slot tube having a single groove in the longitudinal direction, and a plurality of uni-slot tubes are twisted together.

[Conventional technology]

In recent years, in the technical field of optical cables, the density of optical fibers has been increased, and an optical cable as shown in FIG. 6, for example, has been proposed. This cable consists of a plurality of slot rods 1 each having a plurality of optical fiber tapes 3 housed in a plurality of grooves 2 formed in the longitudinal direction of the outer periphery, which are twisted around the outer periphery of a central tension member 4; Presser tape 5 on top
After applying this, the sheath 6 of the outer bag is covered. According to this cable, the number of optical fibers can be increased to about 1000.

[Problem to be solved by the invention]

However, in the case of the above cable, it cannot be said that the optical fiber density relative to the cable diameter is necessarily high, and when the number of optical fibers is increased to 3,000 to 4,000 or more, there are problems such as the cable diameter becoming too large. . Therefore, the present applicant developed a long flexible uni-slot having a single square groove 12, for example as shown in FIG.
A single groove) tube 11 is proposed, a plurality of optical fibers, such as an optical fiber tape 13, are housed in this uni-slot tube 11, and the plurality of uni-slot tubes 11 are connected to a central tension member as shown in FIG. One method has been proposed in which a cable core is created by twisting the fibers around the outer circumference of 14 fibers, and then a holding tape or sheath is applied to obtain an optical cable. According to this optical cable, the central tension member 14
Since one or more slot tube layers are twisted at high density around the fiber, the number of optical fibers is 30.
Although it is possible to easily achieve a number of 00 to 4000 or more, we have found the following points that should be improved. In other words, when bending stress is applied from the outside to such a uni-slot tube 11 during cable manufacturing, transportation, or installation, the optical fiber tape 13 housed inside also tends to move appropriately within the groove. However, at this time, as shown in FIG. <c), the free movement of the optical fiber tape 13 is restricted, but when the free movement of the optical fiber tape 13 is restricted in this way, the bending strain on the optical fiber tape 13 increases, and the optical fiber tape 13 Problems such as wrinkles, creases, and even damage occurred. In addition, the optical fiber tape 1 that rubs against the inner wall of the groove, etc.
There was also a problem that the edges (ends) of No. 3 were prone to curling and other curls. The present invention has been made in view of these circumstances.

[Means to solve the problem]

The present invention is characterized by an optical cable in which a plurality of flexible uni-slot tubes in which one or more optical fiber tapes are housed in a single groove are twisted around the outer periphery of a central tension member. , in the optical cable, the inner groove width and the groove side wall height of each of the uni-slot tubes are larger than the diagonal length of the optical fiber tape storage body.

[Effect]

As described above, in the present invention, since the inner groove width and groove side wall height of each uni-slot tube are larger than the diagonal length of the optical fiber tape storage body, movement of the optical fiber tape within the uni-slot tube groove is prevented. can be freely formed, bending distortion is released, and there is no occurrence of bending at the edges, resulting in excellent transmission characteristics.

【Example】

FIG. 1 shows an embodiment of an optical cable according to the present invention. In this optical cable, 111 is a plurality of uni-slot (single-groove) tubes twisted in two layers around the outer periphery of a central tension member 114, and 113 is a plurality of uni-slot (single-groove) tubes housed and stacked in the square groove 112 of this uni-slot tube 111. A plurality of optical fiber tapes 116 are sheaths coated on the outermost layer via a holding tape or the like. In this optical cable, Unislot tube 1
The size of the groove 112 of 11 and the optical fiber tape storage body 11
The relationship with 3A is set as shown in FIG. In other words, the inner groove width a and the groove side wall height b of the uni-slot tube 111 are stored in the 711112, and the diagonal length C of the stacked optical fiber tape storage body 113A (when storing a plurality of optical fiber tapes 113 The diagonal length of the laminate is larger than the diagonal length of the optical fiber tape 113 itself when stored as a single piece.
a, b>c). Here, to show these relationships more specifically, with respect to the diagonal length C, the upper limit of the inner groove width a is preferably c + 1.5 mm, the lower limit is preferably c + omm, and the upper limit of the groove side wall height b is c+2mm, and the lower limit is preferably about C+0.5mm. Due to this relationship, even if bending stress is applied to the uni-slot tube 111 from the outside during cable manufacturing, transportation, or installation, the internal optical fiber tape 113 will not be constrained in any way within the groove 112. Since there is no bending and can move freely, there is no bending distortion, which prevents wrinkles and creases from occurring. Of course, there is no risk of damage. Furthermore, since there is no undue rubbing or friction with the inner wall of the groove, there is no risk of bending or curling the edge of the optical fiber tape. In addition, in the above embodiment, the uni-slot tube 111 has a two-layer structure, but the present invention is not limited to this, and it is also possible to have one layer or three or more layers. In addition, the number of optical fiber tapes 113 to be stored in the groove of the uni-slot tube 111 is 2.
Although the above case is preferable, it is also applicable to the case of one sheet.

【Effect of the invention】

As is clear from the above description, according to the optical cable of the present invention, the inner groove width and groove side wall height of each uni-slot tube are larger than the diagonal length of the optical fiber tape storage body housed in this groove. Even if bending stress is applied to the Unislot tube from the outside during cable manufacturing, transportation, or installation, the optical fiber tape stored inside the tube will not be subject to any restrictions (and will be able to move freely) within the groove. Therefore, the occurrence of wrinkles or creases in the optical fiber tape itself due to the accumulation of bending strain is prevented, and of course there is no risk of damage, and there is no need to forcefully rub against the inner wall of the groove. As a result, extremely excellent transmission characteristics can be obtained without any bending or the like occurring at the edges of the optical fiber tape.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the optical cable according to the present invention, and FIG. 2 shows the relationship between the groove of the uni-slot tube used in the optical cable of FIG. 1 and the optical fiber tape storage body. 3 is a perspective view showing a Unislot tube, FIG. 4 is a perspective view showing an optical cable core using this Unislot tube, and FIG. 5 is a groove of the Unislot tube and an optical fiber tape. A vertical cross-sectional view showing the relationship with the storage body, and FIG. 6 is a vertical cross-sectional view showing a conventional optical cable. In the figure, 111...unislot tube, 112...
Groove, 113... Optical fiber tape, 113A-... Optical fiber tape storage body, 114...
・Tension member, 116... ・Sheath, Patent applicant Fujikura Electric Cable Co., Ltd. Nippon Telegraph and Telephone Corporation Representative Patent Attorney Shigenori Ishitoya /)−,−”−”−
・-2--7 ゛ON4- Sir-1,;-.・Mitate - Figure 1 Figure 2 a, b) c Figure 3 Figure 4 a, b (C

Claims (1)

[Claims] An optical cable consisting of a plurality of flexible uni-slot tubes in which one or more optical fiber tapes are housed in a single groove and twisted around the outer periphery of a central tension member, the inner groove width and groove of each uni-slot tube being An optical cable characterized in that a side wall height is greater than a diagonal length of the optical fiber tape housing.