JP3245244B2 - Optical fiber holding structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber holding structure.

[0002]

2. Description of the Related Art Conventionally, when connecting an optical fiber cable having a spacer having a groove into which an optical fiber is fitted to each other in a connection box, a tension member passing through the axis of the spacer is fixed in the connection box. In addition, the optical fiber is separated from the groove of the spacer in the connection box and connected to the other optical fiber with an extra length, and the extra length is stored in a loop shape in the extra length storage case. In the portion where the optical fiber is separated from the spacer, the optical fiber is freely movable in the longitudinal direction with respect to the groove of the spacer.

[0003]

However, when the optical fiber cables are connected as described above, the difference in the linear expansion coefficient between the optical fiber and the entire optical fiber cable, the residual elongation strain of the optical fiber, and the construction Due to factors such as elongation strain due to residual laying tension and vibrations, the optical fiber is pulled largely into the cable, the excess length stored in the loop decreases, the optical fiber bends abnormally, and the light is transmitted. There was a problem that loss increased.

[0004] In particular, when there is an extra length storage case, a tension member clamp, or the like that obstructs the smooth movement of the optical fiber, the optical fiber is locally bent at that portion, and the transmission loss is remarkably increased. .

Further, when the optical fiber freely moves in the longitudinal direction, the optical fiber may slide on the spacer or the like and damage the optical fiber.

Accordingly, the present invention has been made to solve the above problems and to provide an optical fiber holding structure capable of preventing an increase in transmission loss of the optical fiber and preventing the optical fiber from being damaged. Aim.

[0007]

SUMMARY OF THE INVENTION An optical fiber holding structure according to the present invention is made of plastic or rubber which is externally fitted to a plurality of optical fibers which are being separated from a plurality of grooves of a spacer in a connection box. A short tube, and a tape body that holds the short tube by being wound together with the spacer in a holding shape with a plurality of the short tubes arranged in a star shape,
It is provided with.

[0008]

The short tube is fixed in a star shape with the spacer at the center with the tape, so that the optical fiber can be held with a suitable frictional resistance so as not to move freely in the longitudinal direction.

Therefore, the optical fiber is caused by the difference in linear expansion coefficient between the optical fiber and the entire optical fiber cable, the residual elongation strain of the optical fiber, the elongation strain due to the residual laying tension during construction, or vibration. It is possible to prevent the cable from being pulled into the cable and leave a sufficient extra length at the connection portion.

Further, since the optical fiber is hard to move in the longitudinal direction, the optical fiber is not damaged.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing embodiments.

In FIG. 1, 1 is an optical fiber cable,
Connection boxes 3 and 3 are end plates provided at both ends of the connection box 1, and 4 is fitted on the outer periphery of the end plates 3 and 3. It is a cylindrical sleeve.

As shown in FIG. 2, the connection box 1 has an internal frame 6 for fixing the ends of the optical fiber cables 2 and 2 and holding a connection portion therein. In FIG. 2, the sleeve 4 is omitted.

The inner frame 6 has an extra length storage case 11 for accommodating an extra length portion including a connection portion of the optical fiber cables 2 and 2 to be described later. Tension member fixing part 12,
12 and has.

As shown in FIG. 3, the optical fiber cable 2 has a tension member 7 at an axial center and a spacer 9 covering the tension member 7 and having a longitudinal groove 10 on the outer peripheral surface.
And the optical fibers 5 housed in the grooves 10 of the spacer 9.
And a jacket 8 that covers the spacer 9.

The tension member 7 is made of a twisted steel wire such as a galvanized steel twisted wire. The spacer 9 is made of a resin such as polyethylene.

A plurality of optical fibers 5 (four in the illustrated example)
In the form of a tape having an optical fiber core. And
A plurality of optical fibers 5 are accommodated in the groove 10 of the spacer 9.

(Return to FIG. 2) Optical fiber cable 2
At the connecting end, the jacket 8 is cut off over a predetermined length.

The tension member 7 is fixed to the tension member fixing portions 12, 12.

As shown in FIG. 4, the optical fibers 5 are connected to each other by a connecting portion 13 with an extra length, and the connecting portion 13 and the extra length connected thereto are stored in the storage case 11 in a loop shape. At the same time, they are stacked up and down via a thin plate-like cushion member 14 and the like.

Thus, the optical fiber holding structures A according to the present invention are provided at portions where the spacers 9 are exposed for connection as shown in FIG.

As shown in FIG. 5, the optical fiber holding structure A includes a short tube 15 which is fitted to the optical fiber 5 which is being separated from the groove 10 of the spacer 9, and a short tube 15 which is And a tape body 16 such as an insulating insulating tape which is wound around the spacer 9 and held.

Reference numerals 17 denote holding metal fittings provided at both ends of the inner frame 6 for fixing the jacket 8 of the optical fiber cable 2.

Numeral 18 denotes a protective tape wound around the spacer 9 near the inner end face of the gripping metal 17, and this protective tape 18 prevents the optical fibers 5 from coming into contact with the gripping metal 17, The fibers 5 are prevented from being damaged.

The short tubes 15 are fixed a predetermined distance inward from the end surface of the jacket 8 of the optical fiber cable 2 which coincides with the inner end surface of the holding member 17. Thereby, the optical fiber 5
Can be prevented from being curved and separated from the groove portions 10 of the spacer 9 at a steep angle, and an increase in transmission loss can be prevented.

As shown in FIG. 6, a plurality of (four in the illustrated example) optical fibers 5 are inserted into the short tube 15.

The short tube 15 is fitted into the groove 10 of the spacer 9. The outer diameter of the short tube 15 is such that a part of the outer peripheral surface of the short tube 15 projects from the groove 10. Thereby, the short tube 15 can be securely fixed on the outer surface of the spacer 9 by the tape body 16.

The number of the optical fibers 5 to be fitted into the short tube 15 is such that the optical fibers 5 can be held in the short tube 15 with a certain frictional resistance. When, for example, five optical fibers 5 having four optical fibers are fitted into the short tube 15, the force required to pull out the optical fibers 5 is set to 100 g or more. I do.

The short tube 15 (when viewed in cross section)
Are arranged in a star shape around the spacer 9. Thereby, if the tape body 16 is wound at one location in the longitudinal direction, all the short tubes 15 can be fixed in a holding state, which facilitates construction and saves the tape body 16.

The material of the short tube 15 is such that it has a suitable frictional resistance between the short tube 15 and the spacer 9 and is electrically insulative. It is also preferable to use Further, it can be freely formed of other rubber or plastic.

With the above construction, the difference in the coefficient of linear expansion between the optical fibers 5 and the entire optical fiber cable 2, the residual elongation strain of the optical fibers 5, and the elongation distortion due to the residual laying tension during construction. If the optical fibers 5 are drawn into the cable 2 due to vibration or other factors, the optical fibers 5 can be held by the short tubes 15 so as not to be largely drawn into the cable 2.

Therefore, the extra length loop (see FIG. 4) housed in the extra length storage case 11 in the form of a loop does not become small, and the optical fiber 5 does not bend abnormally and increases the transmission loss. Can be prevented. Further, it is possible to prevent the optical fiber 5 from being damaged.

The optical fibers 5 are movable with respect to the short tubes 15 with an appropriate frictional force, and if the force to be drawn into the cable 2 is large, the optical fibers 5 are drawn to some extent. Accordingly, breakage, cutting, etc. of the optical fibers 5 can be prevented.

In the optical fiber cable 2, the tension member 7 may be made of a single steel wire other than the steel stranded wire.

In the example shown in FIG.
Although it is a book, the number may be two, three, or five, or may be a cross-sectional circular shape having one optical fiber core.

In FIG. 3, there are grooves 10 in which the optical fibers 5 are not accommodated, but it is also preferable to use the optical fiber cable 2 in which the optical fibers 5 are accommodated in all the grooves 10. In this case, the short tubes 15 are fitted in all the grooves 10 and fixed by the tape body 16.

[0037]

Since the present invention is configured as described above,
The following effects are obtained.

The optical fibers 5 can be held with an appropriate frictional resistance. Therefore, scratches, breakage, cutting, etc. of the optical fibers 5 can be prevented.

Further, it is possible to prevent the optical fibers 5 from being largely drawn into the optical fiber cable, and it is possible to sufficiently maintain the extra length of the connection portion. Thereby, the sharp bending of the optical fibers 5 can be prevented, and the transmission loss can be prevented from increasing.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a connection box.

FIG. 2 is a side view of a main part of the connection box.

FIG. 3 is a sectional view of a main part of the optical fiber cable.

FIG. 4 is a plan view of a main part of the extra-length storage case.

FIG. 5 is a perspective view showing one embodiment of the present invention.

FIG. 6 is a sectional view of a main part.

[Explanation of symbols]

 1 Connection Box 5 Optical Fiber 9 Spacer 10 Groove 15 Short Tube 16 Tape

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-181506 (JP, A) JP-A-5-27703 (JP, U) JP-A-61-155803 (JP, U) JP-A-62 43315 (JP, U) Japanese Utility Model Showa 57-84505 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/00 G02B 6/24 G02B 6/44

Claims (1)

(57) [Claims] 1. A plastic or rubber short tube which is externally fitted to a plurality of optical fibers being separated from a plurality of grooves of a spacer in a connection box, and a plurality of stars arranged in a star shape. An optical fiber holding structure, comprising: a tape body wound around the short tube with the spacer to hold the short tube in a holding state.