JP4795269B2 - Fiber optic cable - Google Patents

Description

  The present invention relates to an optical fiber cable having an optical fiber ribbon inside, and more particularly to an optical fiber cable used for aerial use.

  Conventionally, for example, an optical fiber having a coating made of an ultraviolet curable resin or a thermosetting resin on the outer periphery of a glass optical fiber, a so-called optical fiber core wire, a tension member, and a support wire integrally provided with a sheath Various fiber cables are manufactured and used.

By the way, when these optical fiber cables are installed over the air, characteristic deterioration of unknown cause may occur over time. In recent years, it has become clear that this cause is due to the spawning behavior of the cicada, especially the komazemi, on the optical fiber cable that occurs in the summer.
Specifically, the cause is that an optical fiber cable laying in an imaginary mist is mistaken for a trunk or branch of a tree, and a spawning tube is inserted into the sheath to lay eggs inside.

  When the egg-laying tube is inserted into the sheath in this manner, moisture such as rainwater easily enters the inside of the cable from the opened hole. When moisture enters the cable in this way, the risk of causing an increase in transmission loss in the optical fiber due to the moisture increases rapidly.

Therefore, for example, as described in Patent Document 1, an optical fiber cable in which a protective tape is disposed on the inside or the outer surface of the sheath so as to cover at least a part of the optical fiber ribbon coated with the sheath. Has been proposed.
If such a fiber optic cable is used, even if the bearfish pierces the laying tube into the thin part of the sheath, the tip of the laying tube is blocked by the protective tape and does not reach the internal optical fiber, and the above-mentioned danger, that is, The risk of an increase in transmission loss of the optical fiber can be reduced.

JP 2006-195109 A

  This protective tape has a thin cross-section that is substantially rectangular or elliptical, and generally has a property of being easily warped in an arc. Therefore, some of the manufactured protective tapes have an arc-shaped shape, but the frequency is manufactured. However, it has not been understood how the warpage affects the characteristics of the optical fiber cable.

  In view of the above problems, an object of the present invention is to provide an optical fiber cable that does not have a problem in characteristics while maintaining a protective effect against a black spot even when a protective tape whose cross-sectional shape is curved in an arc shape is used.

  In order to achieve the above object, an optical fiber cable according to claim 1 of the present invention comprises a plurality of optical fiber strands arranged in parallel in a planar shape, and an optical fiber tape core wire obtained by collectively coating the optical fiber tape; A sheath applied to the fiber ribbon, a pair of tension members disposed in parallel with the optical fiber ribbon on both sides of the optical fiber ribbon, and the sheath in the sheath In the optical fiber cable having a pair of protective tapes disposed on both sides of the optical fiber ribbon, the protective tape has an arc shape in cross section, and the optical fiber ribbon and It is arranged so that the center of the arc is located on the opposite side.

  According to the present invention configured as described above, it is possible to provide an optical fiber cable having no problem in characteristics while maintaining the protection effect against the blackberry even when the protective tape whose cross-sectional shape is curved in an arc shape is used.

FIG. 1 is a cross-sectional view showing an embodiment of the optical fiber cable of the present invention. The optical fiber ribbon 2 includes, for example, a plurality of optical fiber strands 1 in which a general optical fiber made of quartz glass having an outer diameter of 125 μm is coated with a resin such as an ultraviolet curable resin or a thermosetting resin. It is what you have.
In the embodiment shown in FIG. 1, for example, four optical fiber strands 1 are arranged in parallel in a planar shape, and a collective coating made of an ultraviolet curable resin or the like is applied thereto, the width is 1.1 mm, and the thickness is 0. .32 mm optical fiber ribbon 2 is used.

  In the optical fiber cable shown in FIG. 1, two optical fiber ribbons 2 described above are prepared, and their end portions are aligned and laminated. The optical fiber tape cores 2 and 2 are sandwiched between the two optical fiber tape cores 2 in the thickness direction so as to sandwich the optical fiber tape cores 2 in parallel with the optical fiber tape core 2. Two protective tapes 5 and 5 made of polyamide resin or polyester resin tape are disposed so as to cover the entire width direction of the fiber ribbons 2 and 2. Further, the protective tapes 5 and 5 are positioned so that the cross-section of the protective tapes 5 and 5 is curved in an arc shape, and the warp is opposite to the optical fiber ribbons 2 and 2. In other words, the center of the curved arc is positioned so as to be located on the opposite side of the optical fiber ribbon 2.

The protective tapes 5 and 5 used in this example have a width of 1.6 mm, a thickness of 0.2 mm, and a warp amount of 30 μm. As shown in FIG. 2, the amount of warping is defined by the difference (ab) between the maximum height a in the vertical direction and the thickness b of the protective tape 5 when the protective tape 5 is placed on a horizontal plane.
The allowable range of the amount of warp varies depending on the structure and dimensions of the optical fiber cable to be manufactured, but is preferably 40 μm or less in the optical fiber cable of this embodiment.

In this way, the two optical fiber tape cores 2 are laminated, and the resin protective tapes 5 and 5 that warp on the opposite side to the optical fiber tape core 2 are sandwiched from both sides in the thickness direction. These were provided with a sheath 3 made of, for example, non-halogen flame retardant polyethylene.
The width of the protective tape 5 is large enough to cover the entire width direction of the optical fiber ribbon 2 (vertical direction in FIG. 1). Specifically, the optical fiber ribbon 2 having a width of 1.1 mm is covered from both sides in an arc shape. To cover the entire width direction of the optical fiber ribbon 2 having a width of 1.1 mm used in this embodiment, the length on the long diameter side becomes 1.3 to 1.7 mm in an arcuate state. Such a protective tape 5 is preferably used.

  As a result, from the thickness direction of the optical fiber ribbons 2 and 2 (left and right in FIG. 1), the protective tapes 5 and 5 prevent further invasion of the egg-laying tube even if the bearfish inserts the egg-laying tube into the sheath 3. It is blocked so that the optical fiber is not damaged.

In FIG. 1, reference numerals 6 and 6 denote directions orthogonal to the direction in which the protective tapes 5 and 5 are arranged, that is, both sides in the width direction of the optical fiber ribbon 2 (up and down in FIG. 1). Further, for example, a reinforcing fiber is positioned so as to be substantially equidistant from the optical fiber ribbon 2 and whose center is substantially flush with the contact surface between the two optical fiber ribbons 2. A tension member having an outer diameter of 0.5 mm made of FRP (fiber reinforced plastic) using aramid fibers.
The tension members 6 and 6 are used to protect an optical fiber having inferior mechanical strength when it receives an external force in its longitudinal direction.

  Further, reference numerals 7 and 7 are notches provided as necessary on opposite surfaces of the sheath 3. If this notch 7 is provided, the sheath 3 can be easily torn when laying the cable, and the inner optical fiber ribbon 2 can be easily taken out, which is convenient.

Reference numeral 8 is a support wire made of FRP, galvanized steel wire, or the like provided as necessary. The center of the support wire 8 is positioned so as to be substantially on the same plane as the centers of the tension members 6 and 6. Yes. Such an optical fiber cable is a so-called self-supporting optical fiber cable. Incidentally, an optical fiber cable without the support line 8 can be used in a cable that is laid for a very short distance.
As an example of the dimensions of the optical fiber cable thus obtained, the long side dimension (excluding the support line portion) is 3.7 mm, and the short side dimension is 2.0 mm.

In order to confirm the long-term reliability of the optical fiber cable of the present invention shown in FIG. 1, a water running evaluation test as shown in FIG. 3 was performed.
As shown in FIG. 3, a hose 21 was connected to one end of an optical fiber cable 20 having a length of 40 m so as to stand upright, and artificial salt water 22 was put into the hose 21 so that the head length was 1 m. After 240 hours had passed in this state, the length of penetration of the artificial salt water from the end of the optical fiber cable 20 added with artificial salt water into the cable was examined.
As a comparison object, as shown in FIG. 5, the protective tape 5 was warped toward the optical fiber ribbon 2 side. The number of samples of each optical fiber cable is n = 5.

As a result, in the case of the optical fiber cables in which the protective tape 5 shown in FIG. 5 is warped toward the optical fiber ribbon 2 toward the inner side of the arc, all five cables are subjected to moisture over the entire length of 40 m after 240 hours. Was invading.
On the other hand, in the optical fiber cable of the present invention shown in FIG. 1, the moisture penetration length was 5 m or less in all five. This is the same result as using a protective tape without warping.

By the way, if the optical fiber cable is exposed for a long time in an aerial state, moisture such as rainwater may enter the optical fiber cable from the end of the cable. In this way, moisture enters the optical fiber cable from the end of the cable, and there is a gap 10 between the protective tape 5 and the optical fiber ribbon 2 as shown in FIG. In this case, moisture runs in the longitudinal direction of the cable through this gap 10 (generally called water running). As a result, this moisture gradually enters the inner optical fiber from the surface of the optical fiber ribbon 2 and can cause an increase in transmission loss in the optical fiber.
Even in the optical fiber cable shown in FIG. 5, it is presumed that an increase in transmission loss is caused in the optical fiber 1 over time due to such a cause.

As described above, in order to more reliably reduce the risk of moisture running in the cable over a long period of time even when the protective tape 5 having warpage is used, the protective tape 5 is used as the optical fiber of the present invention shown in FIG. Like a cable, it is necessary to arrange so that the center position of the arc of the protective tape 5 opposite to the optical fiber ribbon 2, that is, the arc of the cross-sectional shape is opposite to the optical fiber ribbon 2. I understand.
Incidentally, in the optical fiber cable shown in FIG. 5, it is difficult for the resin constituting the sheath 3 to wrap around the back side of the protective tape 5, that is, the optical fiber ribbon 2 side. It is considered that the air gap 10 is easily formed between the two, and as a result, moisture that has entered from the outside through the air gap 10 runs in the longitudinal direction of the cable, causing an increase in transmission loss of the optical fiber for a long time.

FIG. 4 is a cross-sectional view showing another embodiment of the optical fiber cable of the present invention. The only difference from the optical fiber cable shown in FIG. 1 is that only one optical fiber ribbon 2 is arranged in the sheath 3.
As described above, the number of the optical fiber ribbons 2 is appropriately determined depending on the necessary communication amount.
By the way, in the optical fiber cable of the present invention shown in FIG. 1 and FIG. 4, the central portion of the protective tape 5 is in contact with the surface of the optical fiber ribbon 2, but they are separated from each other. Of course, even if it has a structure in which a resin wraps around between the fiber ribbon 2, it is within the scope of the optical fiber cable of the present invention.

  As described above, according to the present invention, it is possible to provide an optical fiber cable that does not have a problem in characteristics while maintaining a protective effect against blackberry even when a protective tape whose cross-sectional shape is curved in an arc shape is used. .

It is a cross-sectional view which shows one Example of the optical fiber cable of this invention. It is sectional drawing which shows the definition of the curvature amount of a protective tape. It is the schematic which shows the method of the water running evaluation test in an optical fiber cable. It is a cross-sectional view which shows another Example of the optical fiber cable of this invention. It is a cross-sectional view which shows an example of the optical fiber cable of a comparative example.

Explanation of symbols

1 Optical Fiber 2 Optical Fiber Tape Core 3 Sheath 5 Protective Tape 6 Tension Member 7 Notch 8 Support Line 20 Optical Fiber Cable 21 Hose

Claims (1)

An optical fiber ribbon formed by arranging a plurality of optical fiber strands in parallel in a planar shape and applying a collective coating thereto,
A sheath applied to the optical fiber ribbon;
A pair of tension members disposed in parallel to the optical fiber tape core on both sides of the optical fiber tape core in the sheath;
In the optical fiber cable having a pair of protective tapes disposed in parallel to the optical fiber ribbon on both sides of the optical fiber ribbon in the sheath,
The protective tape has an arc shape in cross section, and is arranged so that the center of the arc is located on the side opposite to the optical fiber ribbon.

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