JP2008216785A - Optical cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical cable whose winding part for changing its extra length is compactly accommodated to protect itself from external force or birds and which is facilitated in terms of installation work, extra length adjustment and transportation. <P>SOLUTION: The optical cables 11 and 11' are provided with main body parts 12 and 12' formed by coating optical fiber cores with jackets. In this case, the parts of the cables are formed with winding parts 17 which comprise a plurality of winding turns whose winding diameters are larger than the permissible winding diameters of the optical fibers, and the winding parts are covered with cylindrical covering bodies 19. Spiral grooves, which hold the winding turns of the winding parts 17, can be formed in the inner surface of the cylindrical covering bodies 19. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical cable used for pulling down from a trunk optical cable to a subscriber's house or the like through a closure.

  With the recent expansion of broadband services such as video distribution, IP telephony, and data communications, the number of subscribers to home-use data communications services (FTTH: Fiber To The Home) using optical fibers is increasing. In this FTTH, for example, an optical cable called a drop optical cable, which is pulled down from an imaginary trunk optical cable to a subscriber's house or the like through a closure, is often used. For example, as shown in FIG. 7, an optical fiber is dropped into a subscriber's house by branching a trunk optical cable laid on a utility pole in a city by a connection box usually called a closure. The drop is connected to the optical cable

  In general, a drop optical cable used for pulling down an optical fiber is formed with a small number of cores, one to several optical fibers in the cable. FIG. 8 is a diagram showing an example of a general drop optical cable. FIG. 8A shows a structure in which a cable main body portion 2 having a rectangular cross section and a circular suspension wire portion 3 are connected and integrated by a neck portion 4. . FIG. 8B shows a structure in which the circular cable body portion 2 ′ having a circular cross section is similarly connected and integrated with the circular suspension wire portion 3 at the neck portion 4.

  In the cable main body 2 in FIG. 8A, tension members 6 are arranged on both sides of the optical fiber core wire 5, and these are formed into a main body jacket 7 having a rectangular cross section (for example, the long side 3 mm, the short side 2 mm). Degree). The optical fiber core 5 is a glass fiber having a standard outer diameter of 125 μm coated with a protective coating having an outer diameter of about 250 μm. The tension member 6 is made of a non-metallic wire material in which a steel wire or high-strength fiber is hardened with a matrix resin. Further, a V-shaped notch 8 is provided on the side surface of the cable main body 2, and the inner optical fiber 5 is taken out by tearing the main body sheath 7 at this notch portion, so that branch connection and terminal formation are easy. It can be done.

The cable main body 2 ′ in FIG. 8B has a high-strength fiber 6 ′ such as an aramid fiber arranged around the optical fiber core 5, and these are formed into a main body jacket 7 ′ having a circular cross section (for example, And an outer diameter of about 2 mm). The high-strength fiber 6 'has a function as a buffer for the optical fiber and a tension member.
The suspension wire portion 3 is formed, for example, by covering the outer periphery of a support wire 9 made of a steel wire of about 1.2 mmφ with a suspension wire jacket 10. The main body jackets 7 and 7 'and the suspension jacket 10 are made of the same resin material such as polyethylene, and both are connected together via a narrow neck 4 and are formed together by extrusion molding. .

  Moreover, the indoor optical cable used for indoor wiring can be used in the shape of the cable main body portions 2 and 2 ′ from which the hanging portion 3 of the optical cable is removed. This indoor optical cable is used in an apartment house such as a building for branching an optical fiber from a trunk optical cable drawn into the building and optically wiring it to each house.

  In response to the increasing demand for laying optical cables, it is desired to speed up the laying work using drop optical cables and indoor optical cables. In the case of a pull-down work from an imaginary trunk optical cable, it is often performed in a poor working environment such as on a power pole or a bucket car, and the cable is cut to a predetermined length and the optical fiber core wire is connected from within the cable. The operations such as taking out, fusion splicing between optical fibers and reinforcing processing are not easy and take time. For this reason, there is a method of reducing work at the site by attaching optical connectors in advance to both ends of the optical cable cut to a predetermined length.

In this case, optical connectors are attached to both ends of the optical cable in advance to improve the efficiency of connection work, and a curl portion is provided in the optical cable to make the extra length variable so as to absorb an error in the installation length (for example, Non-Patent Document 1). reference). In addition, there is a method for simplifying the installation work by curling the entire length of the optical cable, winding it around an existing suspension line, and laying it by pulling in the longitudinal direction (see, for example, Patent Document 1).
JP-A-2005-292205 Kunihiro Toge, and two others, “Optical cable technology that enables effective use of circuit board maintenance”, NTT Technical Journal, Telecommunications Association, December 2006, p. 64-65

However, the optical cable disclosed in Non-Patent Document 1 is intended for laying in underground pipes including manholes, but there is a specific disclosure about the protection and storage of the curled portion for varying the extra length. Not done.
In addition, the optical cable disclosed in Patent Document 1 is an optical cable that does not have a hanging line portion and can be pulled down from an aerial space. Installed. Since this optical cable is curled over its entire length, there are still problems in handling such as winding around a pre-installed suspension line and stretching and bending of the curled portion during transportation. It was.

  In addition, if an optical cable with a curl is exposed and supported on an aerial suspension line, etc., there is a risk of adhesion of ice and snow, bending or cutting due to external pressure, and friction due to vibration or vibration caused by wind pressure may cause injury. There is a fear. Furthermore, there are cases where crows and other birds curl the winding loop as if it is a material for nesting and pulling or playing, and bugs such as insects forming a nest in the winding part. is there.

  The present invention has been made in view of the above-described circumstances, and can accommodate a winding portion for variable extra length in a compact manner and protect it from external forces, birds, etc. An object is to provide an optical cable that can be easily processed.

  An optical cable according to the present invention is an optical cable having a main body part in which an optical fiber core wire is covered with a jacket, and a part of the cable is wound from a plurality of winding turns wound with a diameter greater than an allowable bending diameter of the optical fiber. The winding part is covered with a cylindrical covering body. In addition, you may make it form the helical groove | channel which hold | maintains the winding turn of a winding part in the inner surface of the said cylindrical cover.

The winding portion can be formed by curling. The curled winding portion has its winding direction reversed at at least one intermediate position, or the winding portion does not twist when wound in the longitudinal direction. Are twisted in the opposite direction in advance and curled to reduce twisting caused by stretching of the wound portion.
In addition, a suspended wire is inserted into the winding portion, or the suspended wire is inserted through a guide pipe disposed in the wound portion, and the winding turn is extended so as to be wound around the suspended wire. Moreover, the shielding body which prevents a foreign material approaching in the both ends of the cover body is provided, and the winding part prevents these foreign materials from entering. Furthermore, an optical connector is attached to at least one of the cable ends to shorten the work time.

  According to the present invention, the winding portion for the extra length that absorbs an error in the installation length of the optical cable is protected from damage due to external force by the cover, and also the winding portion is not scattered, and the winding portion is transported during transportation. Can be prevented from stretching or bending. In addition, after laying the optical cable, it is possible to prevent snow from accumulating in the winding portion and intrusion of birds, insects, etc., and to minimize damage.

  Embodiments of the present invention will be described with reference to the drawings. 1 (A) and 1 (B) are diagrams for explaining a cable drawing configuration using an optical cable according to the present invention, and FIGS. 1 (C) and 1 (D) are configuration examples of an optical cable used in the present invention. FIG. In the figure, 11 and 11 'are optical cables, 12 and 12' are main body parts, 13 is a hanging line part, 14 is a neck part, 15 is a connected and integrated part, 16 is a separated part, 17 is a wound part, and 18 is light. A connector 19 indicates a cover.

  As shown in FIG. 1C, the optical cable 11 used in the present invention does not have, for example, an optical cable having a rectangular cable cross section similar to that described in FIG. It is an optical cable. Although detailed description of the optical cable 11 is omitted, the main body 12 of the cable has tension members disposed on both sides of one or more optical fiber cores, and these are formed into a main body jacket (for example, a long side) having a rectangular cross section. 3 mm, about 2 mm on the short side). The optical fiber core is obtained by coating a glass fiber having a standard outer diameter of 125 μm with a protective coating having an outer diameter of about 250 μm. The tension member is formed of a non-metallic wire material in which a steel wire or high-strength fiber is hardened with a matrix resin. Further, the side surface of the main body 12 of the cable may be provided with a V-shaped notch for tearing, but may have a shape not having a notch.

  Further, as another optical cable 11 ′ used in the present invention, as shown in FIG. 1D, an optical cable having a circular cable cross section similar to that described in FIG. 8B. Although a detailed description of the optical cable 11 ′ is omitted, the main body 12 ′ of the cable is provided with a high-strength fiber such as an aramid fiber around the optical fiber core wire, and the main body 12 For example, the outer diameter is about 2 mm). The high-strength fiber has a function as a buffer and tension member for the optical fiber core wire.

  The suspension line portion 13 of the optical cables 11 and 11 ′ is formed, for example, by covering the outer periphery of a steel wire or the like of about 1.2 mmφ with a suspension line jacket. The outer cover of the main body parts 12 and 12 ′ and the outer cover of the hanging line part 13 are collectively formed by extrusion molding using the same resin material such as polyethylene, and the main body parts 12 and 12 ′ and the hanging line part 13 are thin. They are connected and integrated through a width neck 14. Therefore, although the main body parts 12 and 12 'and the hanging line part 13 are connected and integrated, the neck part 14 can be easily separated by cutting by hand as necessary.

  As shown in FIG. 1A, the optical cable according to the present invention is used as, for example, a drop optical cable that draws an optical fiber from a trunk optical cable C installed on a utility pole P to a house H or the like. The optical fiber from the trunk optical cable C is branched by the closure K, and the optical cables 11 and 11 'are optically connected to the branched optical fiber. The optical cables 11 and 11 ′ are composed of a part 15 in which the main body parts 12 and 12 ′ and the hanging line part 13 are connected and integrated, and a part 16 in which the main body parts 12 and 12 ′ and the hanging line part 13 are separated. A cylindrical winding portion 17 for extra length is formed on the main body portions 12 and 12 ′ of the separated portion 16 so as to be wound on the separated hanging portion 13. The wound portion 17 is surrounded and protected by a cover body 19 described later.

  The hanging portion 13 is attached along the laying path of the optical cable by attaching the fixture R using the existing trunk optical cable C and other structures. When the spiral hanger S is installed in the existing trunk optical cable C, the optical cables 11, 11 'may be installed using this. The optical cables 11, 11 'are cut in advance to a predetermined length, and it is desirable to shorten the installation work by attaching an optical connector 18 to at least one end of the optical cables. The optical connector 18 can be attached at the work site, but may be prepared in a state of being attached in advance.

  The winding portion 17 and the covering body 19 surrounding the winding portion 17 are laid so as to be close to the cable termination side of the house side H in FIG. 1 (A). However, as shown in FIG. It can also be laid close to the side. This is due to the difference in which of the portion 15 where the main body portions 12, 12 ′ are connected and integrated and the portion 16 where the main body portions 12, 12 ′ are separated is connected to the closure K side. Considering the situation, etc., it is determined by the selection of the starting point when laying. Moreover, the position of the winding part 17 and the covering body 19 which covers this can also be changed by extending | stretching of the optical cable from the winding part 17 from which direction of right and left, or both.

  FIG. 2 is a diagram for explaining an example of an optical cable according to the present invention. The optical cable shown in the figure shows an example in which the hanging portion 13 described with reference to FIGS. 1C and 1D is not provided, but the main portion 12 in the portion 16 in which the main portions 12 and 12 ′ are separated from the hanging portion 13. , 12 ′ only. In this optical cable shown in FIG. 2A, a part or the whole of the main body part 12, 12 ′ is wound in a cylindrical shape to form a wound part 17, and the wound part 17 is accommodated in a covering body 19. Alternatively, the winding portion 17 is surrounded by the cover body 19 so that the winding state of the winding portion 17 is maintained.

  The cover 19 has, for example, a shape having a funnel-like opening 9b at both ends of a cylindrical (circular or rectangular) storage portion 19a, and can be formed of a soft or hard resin. As the structure of the cover body 19, for example, a half-divided structure for storing the winding portion 17 and a seam portion that is fastened with an adhesive or a band after the winding portion 17 is stored can be used. Further, it is divided into three parts, a central cylindrical storage portion 19a and an end portion having an opening 19b. After the winding portion 17 is stored in the storage portion 19a, the end portions are bonded, screwed, taped, etc. from both sides. It can also be set as the form which integrates by. The material of the cover is the same as the sheath material of an optical cable such as polyethylene or polypropylene, or an elastic member such as rubber. If a soft material is used, it will be easy to bend, and it will be easy to wind up on a drum with the cable part which is not wound.

  By enclosing the winding portion 17 with the cover 19 having the cylindrical storage portion 19a as described above, it is possible to maintain the winding state of the winding portion 17 without performing curl processing described later. . If the winding portion 17 for extra length can be formed without performing curl processing, when the winding portion is extended, the free end can be freed so that it can be laid without causing twisting, resulting in transmission loss. It is easy to suppress the increase in

Further, as shown in FIG. 2 (B), a spiral groove 19d may be provided on the inner surface of the cylindrical storage portion 19a of the cover 19. The spiral grooves 19d can be housed in an aligned state so that the winding turns of the wound portions 17 to be housed are switched and no crossing occurs.
In particular, when a steel wire is used as a tension member of an optical cable, it acts so as to increase the winding diameter elastically with a large rigidity. Therefore, keep the winding shape in contact with the inner surface of the cover 19. Stored. Therefore, by providing the spiral groove 19 c on the inner surface of the cover body 19, the winding turns are automatically aligned by the groove 19 c, and the storage performance of the winding portion 17 can be improved.

  The cylindrical winding portion 17 is wound with a diameter D equal to or larger than the allowable bending diameter of the optical cable. It is desirable that the bending diameter D at this time be suppressed to a transmission loss or less that causes a practical problem in the state where the winding portion 17 is extended. For example, it is preferable to use an optical fiber having a bending loss of 0.5 dB / 10 turns or less at a bending diameter of 30 mm at a wavelength of 1.55 μm. Furthermore, it is preferable to use an optical fiber having a small allowable bending diameter such that a bending loss at a bending diameter of 15 mm at a wavelength of 1.55 μm is 0.5 dB / 10 turns or less.

  For example, an optical fiber having a mode field diameter (MFD) of 9.0 μm or less as defined by Petermann-I at a wavelength of 1.3 μm is used as the optical fiber of the optical cable that satisfies the above conditions. It is preferable. Furthermore, by setting the mode field diameter at a wavelength of 1.55 μm to 8.0 μm, it becomes possible to suppress the microbend and bending loss due to the side pressure and reduce the allowable bending diameter.

From the above points, the bending diameter D of the optical cables 11, 11 ′ is set to about 30 mm, for example. In this case, the length L of the winding portion 17 on the cylinder can be set to about 1 m (about 300 turns), for example, so that an extra length of about 20 m can be obtained.
Here, returning to FIG. 1, the laying distance of the optical cables 11, 11 ′ by dropping from the imaginary trunk optical cable C to the house H is, for example, about 45 to 50 m. In this case, the portion 15 where the main body portions 12, 12 ′ and the hanging wire portion 13 are connected and integrated is about 40 m, and the portion 16 where the main body portions 12, 12 ′ and the hanging wire portion 13 are separated is about 10 m. It is wound in a cylindrical shape to make the extra length. In addition, it is preferable to attach the optical connector 18 to both ends of the main body portions 12 and 12 ′.

  FIG. 3 is a diagram illustrating an example in which the cylindrical winding portion 17 is formed by curl processing. Although the winding part 17 can hold the winding state using the cover or the binding string according to the present invention, the winding turns may intersect if the winding is performed simply. It is difficult to keep the cylinder aligned until it is stored in the cover. Therefore, as shown in FIG. 3A, the main body parts 12 and 12 ′ without winding rods from which the hanging line parts 13 are separated are aligned and wound with a predetermined diameter using a cylindrical winding jig 20.

Next, as shown in FIG. 3 (B), the entire main body 12, 12 ′ including the outer cover is curled by heating with the heating device 21, and the winding turn of the winding part 17 is cylindrical. Arrange to align, keep the winding state. The curled cylindrical winding portion 17 can be expanded and contracted like a coil spring along the longitudinal direction of the hanging portion 13. As the heating means 21a, various methods such as heater heating and infrared heating can be used.
In addition, in the optical cable 11 as shown in FIG. 1C, when a steel wire is used for the tension member of the main body 12, the tension member is not curled by heating to the extent that the resin is curled. It is difficult to hold. For this reason, the optical cable 11 is, for example, a cable formed of a nonmetallic tension member using FRP in which high-strength fibers are hardened with a matrix resin.

  FIG. 4 is a diagram showing another embodiment of the winding portion. The winding portion 17 is usually wound in a spiral shape in which the winding direction is one direction, the outer surface of the winding turn is located outside the entire winding length, and the inner surface is the entire winding length. It is located inside. For this reason, if the wound portion 17 is stretched in the longitudinal direction with both ends fixed, the main body portions 12 and 12 ′ are twisted, which may increase the transmission loss of the internal optical fiber. Therefore, by providing at least one reversing portion 22 that reverses the winding direction in the middle of the winding portion 17, this twist can be reduced and an increase in transmission loss can be reduced. When a plurality of reversing parts 22 are provided, they are provided at odd places.

  Further, instead of providing the reversing portion 22 in the winding portion 17, when the main body portions 12 and 12 ′ are wound and curled, when the winding portion 17 is stretched, the main body portions 12 and 12 ′ are twisted. In order not to occur, winding may be performed in advance, and curling may be performed thereafter. In addition, since the optical fiber core wire in the main body is integrated with the main body jacket, when the winding portion 17 is extended and installed, an increase in transmission loss due to twisting can be reduced.

  The winding portion 17 is formed in a cylindrical shape after the winding shape is maintained by the curling process described above, or by surrounding the winding turn wound without being curled by the covering body 19 so as not to be separated. Aligned and held. Moreover, the suspended portion 13 of the separated portion 16 can be inserted into the wound portion 17 so as to be wound and held on the suspended portion 13 as shown in FIG. In addition, you may make it make the hanging line part 13 into the form which is not penetrated in the winding part 17 according to the condition of a work site.

  After the winding portion 17 is processed as described above, the optical cables 11 and 11 ′ are separated by winding and binding the connected and integrated portion 15 with a predetermined diameter and extending from the winding portion 17. The hanging part 13 is wound up and bound separately. By packing and storing in this state, it is possible to eliminate handling problems such as the winding portion 17 housed or enclosed in the cover body 19 being stretched or bent during transportation. In the case of an optical cable that has only a main body portion and does not originally have a hanging portion, a linear portion other than the winding portion 17 is wound and bound with a predetermined diameter, and the winding portion 17 surrounded by a cover Pack and store together.

FIG. 5 (A) is a diagram showing a form in which the hanging portion 13 is inserted into the winding portion 19 and the winding turn of the winding portion is extended and supported on the hanging portion. The hanging line portion 13 may be a hanging line of a portion 16 separated from the main body portions 12 and 12 ′ of FIG. 1A, or may be a separately prepared hanging line.
In addition, since the winding part 17 consisting of a plurality of winding turns is aligned and held in a cylindrical shape by the cover body 19, the suspension wire portion 13 is wound by using the openings 19 b at both ends of the cover body 19 as guides. It can be easily inserted into the portion 17.

  FIG. 5B is a diagram illustrating an example in which the guide pipe 22 is inserted in advance so that the hanging line can be easily inserted into the winding portion 17. The guide pipe 22 only needs to be long enough to pass between the openings 19 b at both ends of the cover 19. The suspension wire portion 13 made of steel wire can be smoothly inserted into the winding portion 17 without being caught by using the guide pipe 22 as a guide. The guide pipe 22 may remain in the winding portion 17 after the hanging wire portion 13 is inserted into the winding portion 17, but may be removed.

  6A and 6B are diagrams illustrating an example in which the openings at both ends of the cover body 19 are closed. FIG. 6A illustrates an example having no hanging line portion, and FIG. 6B illustrates an example in which the hanging line portion is inserted. Show. When laying the main body portions 12 and 12 ′ of the optical cable, openings 19 b serving as lead-out ports for drawing a winding turn from the inside of the covering body 19 surrounding the winding portion 17 are formed at both ends of the covering body 19. The opening 19b is preferably formed with a large opening for easily pulling out the inner winding turn. However, if the opening 19b is large, rain and snow can easily enter the interior, and insects and birds can enter the nest. There are things to make.

  On the other hand, in the present invention, after the winding turn of the winding portion 17 surrounded by the cover body 19 is extended from the opening 19b and installed, the remaining winding turn is used as an extra length of the installation cable. It is preferably housed in 19 and the openings 19 b at both ends are closed by the shield 23. Moreover, you may make it the shielding body 23 have a function as a clamp which prevents that the winding turn of the winding part 17 is pulled out after optical cable installation.

It is a figure explaining the outline of the embodiment of the present invention. It is a figure explaining an example of the optical cable by this invention. It is a figure explaining the curling process of the cylindrical winding part in this invention. It is a figure which shows the example which provided the inversion part in the winding part in this invention. It is a figure which shows the example which inserted the hanging line in the winding part in this invention. It is a figure which shows the example which obstruct | occludes opening of the cover body both ends in this invention. It is a figure explaining the pulling-down method of the conventional optical cable. It is a figure explaining the structural example of the conventional drop optical cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 11 '... Optical cable, 12, 12' ... Main-body part, 13 ... Hanging part, 14 ... Neck part, 15 ... Connection integrated part, 16 ... Separation part, 17 ... Winding part, 18 ... Optical connector, 19 ... Cover Body, 19a ... housing part, 19b ... opening, 19c ... groove, 20 ... winding jig, 21 ... heating device, 21a ... heating means, 22 ... reversing part, 23 ... shield.

Claims (9)

  An optical cable having a main body with an optical fiber core covered with a jacket, wherein a part of the cable is formed of a winding portion composed of a plurality of winding turns wound at a diameter greater than the allowable bending diameter of the optical fiber. An optical cable characterized in that the wound portion is surrounded by a cylindrical cover.   The optical cable according to claim 1, wherein a spiral groove that holds the winding turn is formed on an inner surface of the cylindrical cover.   The optical cable according to claim 1, wherein the wound portion is formed by curling.   The optical cable according to claim 3, wherein the winding direction of the curled winding portion is reversed at at least one intermediate position.   The optical cable according to claim 3, wherein the winding portion is previously curled by being twisted in a reverse direction so that the winding is not twisted when it is stretched in the longitudinal direction.   The optical cable according to any one of claims 1 to 5, wherein a suspended wire is inserted through the winding portion.   The optical cable according to any one of claims 1 to 5, wherein a guide pipe for inserting a suspension wire is disposed in the winding portion.   The optical cable according to any one of claims 1 to 7, wherein a shield for preventing foreign matter from entering is provided at both ends of the cover.   The optical cable according to claim 1, wherein an optical connector is attached to at least one of the cable ends.

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