JP4619424B2 - Fiber optic cable - Google Patents

Description

  The present invention relates to an optical fiber cable which is a component of information wiring using an optical fiber outdoors and indoors.

  Currently, with the increase in broadband services, the number of FTTH subscribers using optical fibers is rapidly increasing. As a result, in the infrastructure such as a pipeline for laying the optical fiber cable, a space for additionally laying the optical fiber cable is becoming insufficient. For this reason, it is very effective to further reduce the diameter and density of the optical fiber cable in order to effectively use the infrastructure.

  As an optical fiber cable having a small diameter and a high density, for example, in Patent Document 1, a plurality of optical fibers in which an increase in optical loss due to bending is reduced and a plurality of single-core coated optical fibers in which the outer periphery of the optical fiber is coated are assembled. A multi-fiber optical fiber cable having a very small diameter and high density has been proposed by using a structure in which the outer periphery of the bundle is coated. However, since the optical fiber cable described in Patent Document 1 uses a single-core coated optical fiber, when constructing an optical fiber transmission line, it is necessary to connect the optical fiber cables to each other. There was a problem of poor connection efficiency.

  On the other hand, optical fiber tape cores coated with a plurality of single-core coated optical fibers arranged in parallel are optical fiber units that can be connected together with a fusion splicer, etc., and are often used for conventional optical fiber cables. It has been. However, the conventional optical fiber ribbon has a bending anisotropy that it is difficult to bend in the width direction due to its shape. Since loss occurs, it is necessary to use a manufacturing method and a cable structure that can suppress this.

  Thus, optical fiber cables using optical fiber ribbons having a new structure have been proposed so far.

  In each of the optical fiber cables described in Patent Documents 2 to 5, an optical fiber tape core wire in which a plurality of single-core coated optical fibers are intermittently bonded in the longitudinal direction is used. Improvement of single-fiber separation performance for separating only a desired optical fiber from the optical fiber ribbon at the time of post-branching is attempted.

  Each of the optical fiber cables of Patent Documents 2 and 3 is an optical fiber tape core in which resin portions for adhering the entire width direction of a plurality of single-core coated optical fibers arranged in parallel are intermittently arranged in the longitudinal direction. And is housed in the cable in a stacked state.

  The optical fiber cable of Patent Document 4 is an optical fiber tape core in which a conventional optical fiber ribbon is intermittently divided in the manufacturing process, and the divided portion is shifted in the width direction along the longitudinal direction of the optical fiber tape. It uses wires and is housed in the cable in a stacked state. In addition, it is possible to reduce the distortion of the optical fiber against the bending in the width direction that the optical fiber tape core wire undergoes during manufacture by arranging the dividing portion in, for example, the twist reversal portion of the SZ twisted slot type optical fiber cable. Has been.

  In the optical fiber cable, the resin part is a resin in which only two adjacent cores of the single-core coated optical fiber are bonded to each other, and the length of the resin part is shorter than the length of the unbonded part and is adjacent in the width direction. The part uses an optical fiber tape core wire characterized in that it is spaced apart, and some are folded and accommodated in a cable. Since such an optical fiber ribbon has a small bending anisotropy and can be easily folded into a cylindrical shape, it may be possible to manufacture a small-diameter and high-density optical fiber cable in the same manner as a bundle of single-core coated optical fibers. Are known.

JP 2007-41568 A JP-A-5-281444 Japanese Patent Laid-Open No. 8-334662 JP 2005-62427 A JP 2003-315639 A S. T.A. Kreger et. al. , International Conference on Optical Fiber Sensors (OFS-18), paper ThE42, 2006. Journal of the Japan Society of Mechanical Engineers, September 2004, Vol. 107 No. 1030 Special Feature Ultra High Capacity Optical Fiber Communication Technology Internet search [May 7, 2008 search] http: // www. optimize. jp / faq / index. html

  By the way, since an optical fiber cable is laid on a bent pipe or the like and used for a long time, it can maintain a stable optical loss characteristic against an external force applied to the cable, Even in the radius, it is necessary to ensure sufficient long-term reliability so that a large strain is not applied to the optical fiber.

  However, in order to provide an optical fiber cable with high connection efficiency and a small diameter and high density, there are problems as follows using the conventional technology, and the stable condition that is a requirement of the optical fiber cable is as follows. There is a problem that both optical loss characteristics and long-term reliability cannot be secured.

  Specifically, the optical fiber cables described in Patent Documents 2 to 4 are accommodated in the cable core portion in a form in which a plurality of optical fiber tape core wires bonded intermittently are stacked. When a plurality of optical fiber ribbons are housed in a stacked state, a large gap is formed in the cable. Therefore, in order to increase the mounting density of the cable core, it is overwhelming to use a bundle of single-core coated optical fibers. Is advantageous. For this reason, the optical fiber cables described in Patent Documents 2 to 4 are not suitable for small-diameter and high-density optical fiber cables.

  Furthermore, when the fiber cores are forcibly housed in the cable core portion in a laminated state, the optical fiber cables described in Patent Documents 2 to 4 are bonded to the whole or three or more optical fiber tape cores in the width direction. The resin portion is present, and the resin portion has a large bending anisotropy, which is insufficient because a large optical loss or distortion occurs locally during cable manufacturing or cable bending.

  The optical fiber cable shown at the end of the background art has been devised to reduce the bending anisotropy of the optical fiber ribbon described above, and can be accommodated at the same mounting density as when a bundle of single-core coated optical fibers is used. Therefore, the mounting density of the cable core part can be increased as much as possible. However, when mounted at high density, optical loss increases due to random bending applied to the optical fiber during manufacturing of the optical fiber cable, and optical loss increases due to bending of the optical fiber in the cable due to bending applied to the cable and side pressure. Occurs, and stable light loss characteristics cannot be maintained. Furthermore, the strain applied when the cable is bent has a problem in that long-term reliability cannot be secured because strain exceeding the allowable value is applied to the optical fiber depending on the bonding state of the single-core coated optical fiber in the optical fiber ribbon used for the cable. is there.

  The present invention has been made in view of the above circumstances, and has a good optical fiber connection efficiency, prevents an increase in optical loss generated in the optical fiber, provides a stable optical loss characteristic, and reduces distortion applied to the optical fiber. The objective is to provide a small-diameter and high-density optical fiber cable with sufficient long-term reliability.

  In order to achieve the above object, the present invention provides an optical fiber cable including an optical fiber ribbon comprising three or more single-core coated optical fibers coated on the outer periphery of the optical fiber, The fiber has a bending loss characteristic in which an increase in optical loss when bent at a radius of 13 mm at a wavelength of 1.55 μm is 0.2 dB / 10 turn or less. Resin portions for bonding single-core coated optical fibers to each other two-dimensionally in the longitudinal direction and the width direction are arranged at a plurality of positions, and the length of the resin portion applied between the same adjacent two-core single-core coated optical fibers Is shorter than the length of the non-resin portion where the two adjacent single-core coated optical fibers are not bonded to each other, and the resin portions adjacent to each other in the width direction of the optical fiber ribbon are the optical fiber tapes. A cable core portion that is arranged apart from each other in the longitudinal direction of the wire, and that the optical fiber cable accommodates a unit in which a plurality of single-core coated optical fibers constituting the optical fiber ribbon are assembled together And a ratio of a cross-sectional area occupied by the plurality of single-core coated optical fibers to a cross-sectional area of the cable core portion is 0.3 or more. Is.

  The optical fiber cable of the present invention maintains a stable optical loss characteristic with respect to external force applied during use at a mounting density of the cable core portion that is almost equivalent to that of an optical fiber cable using a single-core coated optical fiber, The distortion applied to the optical fiber with respect to cable bending is small, and sufficient long-term reliability can be ensured. Moreover, since the optical fiber cable of the present invention can be collectively connected using the optical fiber ribbon, there is an effect that the connection efficiency is high. In addition, the desired optical fiber can be easily distinguished and taken out, and the single-core separation at the time of intermediate post-branching is also excellent.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the figure, the same portions are described with the same reference numerals.

  FIG. 1 is a cross-sectional view showing an optical fiber cable according to an embodiment of the present invention. In FIG. 1, 11 is a single-core coated optical fiber, 12 is an identification thread, 13 is a protective tape, 14 is a polyethylene jacket, 15 is a strength member, 16 is a protrusion, and 17 is a tear string.

  As shown in FIG. 1, a unit configured by winding an identification yarn 12 around the outer periphery of an optical fiber bundle in which a plurality of, for example, 20 single-core coated optical fibers 11 having a diameter of 0.25 mm are densely assembled. In addition, a plurality of the units, for example, 10 are twisted in one direction and densely assembled on the outer periphery, and a pressing roll layer composed of a plurality of thin protective tapes 13 is provided on the outer periphery. A very high-density 200-fiber optical fiber cable is formed by applying the cover 14. The unit is configured by using an optical fiber tape core composed of three or more single-core coated optical fibers in which the outer periphery of the optical fiber is coated. That is, the multi-core optical fiber cable is configured to include a cable core portion that accommodates a plurality of twisted units, and a jacket on the outer periphery of the cable core portion.

  In addition, the optical fiber cable of FIG. 1 has the protrusions 16 embedded in the jacket 14 so that the two strength members 15 are positioned symmetrically with respect to the center of the optical fiber cable. In addition, the thickness of the outer cover 14 of the protrusion 16 is thicker than the thickness of the outer cover 14 other than the protrusion 16. In this embodiment, the strength member 15 is made of, for example, a steel wire having a diameter of 0.95 mm. A tear string 17 is provided at a position symmetrical to each other with respect to the center of the optical fiber cable at an intermediate portion between the strength members 15 in the jacket 14. The tear string 17 is provided for tearing the outer sheath 14 and taking out the single-core coated optical fiber 11.

The outer diameter of the optical fiber cable according to the embodiment of the present invention is such that the major axis measured at the projection 16 is 11.7 mm, for example, and the minor axis D measured at a portion other than the projection 16 is, for example, D = The thickness of the outer cover 14 excluding the protrusion 16 is 1.9 mm, for example. The cross-sectional area Acore of the portion in which the optical fiber 11 is accommodated, that is, the cable core portion is 27.3 mm ² , for example, and the cross-sectional area Afiber occupied by 200 single-core coated optical fibers 11 is calculated from the following relationship: And
Afiber = n × (d / 2) ² × π (3)
It becomes.

Here, n is the number of optical fibers 11 in the optical fiber cable (= 200), d is the standard outer diameter (= 0.25 mm) of the single-core coated optical fiber 11, and π is the circular ratio. Therefore, the cross-sectional area Afiber occupied by a plurality of single-core coated optical fibers 11 in this embodiment is 9.82 mm ² . The ratio of the cross-sectional area Afiber occupied by a plurality of single-core coated optical fibers 11 to the cross-sectional area Acore of the cable core portion is Afiber / Acore≈0.36.
Moreover, as a result of actually manufacturing optical fiber cables having different numbers of cores in the same structure, Afiber / Acore was about 0.3 to about 0.55 in a 100-1000 optical fiber cable. Therefore, this embodiment is characterized in that the ratio of the cross-sectional area occupied by the plurality of single-core coated optical fibers to the cross-sectional area of the cable core portion is 0.3 or more.

  In addition, in the conventional optical fiber cable in which the cable core portion is formed by using the currently used slot (for example, a polyethylene rod having a spiral groove for accommodating the optical fiber unit on the surface), for example, the same In the 200-core optical fiber cable, Afiber / Acore is about 0.1, and the optical fiber cable according to the embodiment of the present invention is three times or more, which is greatly different from the conventional optical fiber cable, and has a very high density. It can be seen that

  The cross-sectional shape of the optical fiber cable according to the embodiment of the present invention is not necessarily provided with the protrusion 16 in the outer jacket 14, and may be circular. Further, the number n of the optical fibers 11 in the optical fiber cable is usually about several 10 to 1000. Further, the standard outer diameter d of the single-core coated optical fiber 11 is not limited to 0.25 mm, and may be other outer diameters such as 0.5 mm and 0.9 mm that are currently used.

  In the above description, ten units are twisted in one direction. However, the present invention is not limited to this, and for example, SZ twisting having a twisted portion in the opposite direction may be performed in the middle.

  In the embodiment of the present invention, the outer diameter of the optical fiber cable (or the shorter diameter when the cross-sectional shape is not circular) is D, and the optical fiber cable is bent at a bending radius of 10D. The maximum strain applied in the direction is 0.2% or less.

  2 is a schematic perspective view showing an optical fiber ribbon according to an embodiment of the present invention, and FIG. 3 is a schematic perspective view showing a folded state of the optical fiber ribbon according to an embodiment of the present invention. 2 and 3, 18 is a resin part, and 19 is a non-resin part.

  As shown in FIG. 2, the optical fiber tape constituting the optical fiber cable has three or more, for example, four single-core coated optical fibers 11 and two adjacent single-core coated optical fibers 11. A plurality of resin portions 18 to be bonded are provided, and the resin portions 18 are two-dimensionally arranged in a longitudinal direction and a width direction. By adhering only the two single-core coated optical fibers 11 adjacent to each other, the entire optical fiber tape core in the width direction of Patent Documents 2 to 4 or a structure of adhering three single-core coated optical fibers is used. Bending anisotropy is reduced.

  For the resin portion 18, an ultraviolet curable resin, a thermoplastic resin, or a thermosetting resin that bonds the single-core coated optical fibers 11 to each other can be used. Moreover, in order to provide the discriminability of the optical fiber ribbon, the resin portion 18 may be colored.

  Also, the optical fiber tape core shown in FIG. 2 has the length B of the resin portion 18 provided between the same adjacent two-core single-coated optical fibers 11 and the same two adjacent single-core fibers. It is characterized by being shorter than the length AB of the non-resin portion 19 where the coated optical fibers 11 are not bonded. In this embodiment, the interval A between the resin portions 18 arranged in the longitudinal direction of the single-core coated optical fiber 11 is about 200 mm, and the length B of the resin portion is about 80 mm. That is, in this embodiment, the ratio of the length of the resin part 18 to the interval between the resin parts 18 arranged in the longitudinal direction of the single-core coated optical fiber 11 is 0.4 or less, and the length of the resin part 18 Is 80 mm or less. Further, a material having a Young's modulus smaller than that used for the outermost coating layer of the single-core coated optical fiber 11 is used as the material of the resin portion 18.

  The resin portions 18 adjacent to each other in the width direction of the optical fiber ribbon are arranged apart from each other in the longitudinal direction of the optical fiber ribbon.

  As shown in FIG. 2, the resin portion 18 is arranged to have a portion where the resin portion 18 does not exist at all in the width direction of the optical fiber ribbon. This is because the adjacent resin portions 18 do not affect each other so that the optical fiber tape core wire can be easily folded as shown in FIG. This is because it is easy to increase the ratio of the occupied area, that is, Afiber / Acore. Further, it is desirable that the length C of the portion where the resin portion 18 does not exist at all in the width direction of the optical fiber ribbon is 50 mm or less. Since it is unknown where to cut when using the optical fiber cable, a portion where the resin portion 18 does not exist at all in the width direction of the optical fiber ribbon is disposed at the tip of the optical fiber ribbon However, it can be said that it is a situation in which it is difficult to align the plurality of single-core coated optical fibers 11 in a plane when connecting the optical fiber ribbons. For this reason, from the viewpoint of ensuring a certain connection efficiency, the resin portion 18 is completely present in the width direction of the optical fiber ribbon from the length (about 50 mm) of the optical fiber holder used in general optical fiber fusion splicing. It is necessary to make the length of the portion not to be short and at least one resin portion 18 to exist.

  In the present embodiment, the optical fiber tape core wire composed of the four-core single-core coated optical fiber 11 and the resin portion 18 that bonds the single-core coated optical fibers 11 to each other has been described. The optical fiber ribbon may be composed of another number of cores, for example, an eight-core single-core coated optical fiber and a resin portion.

  Further, for example, the length and the arrangement interval of the resin portions arranged between the first and second fibers of the four-core single-core coated optical fibers arranged in parallel are, for example, resins arranged between the second and third fibers. It may be different from the length of the part and the arrangement interval. In this case, it is necessary to set the arrangement interval so that the resin portions are not adjacent to each other in the width direction of the optical fiber ribbon.

  Moreover, in this embodiment, the photonic crystal fiber which has a void | hole in the cladding part of the said optical fiber can be used as said optical fiber.

  Next, the optical loss characteristic of the optical fiber cable according to the embodiment of the present invention will be described in detail below.

  FIG. 4 is a characteristic diagram showing the results of measuring the relationship between the increase in optical loss at the time of manufacturing the optical fiber cable according to the embodiment of the present invention and the bending loss characteristic of the optical fiber used. The bending loss characteristic of the optical fiber is represented by a minimum allowable bending radius (a bending radius that becomes 0.2 dB / 10 turn at a wavelength of 1.55 μm), and is experimentally obtained from a bending test of the optical fiber. Several types of optical fibers having various minimum allowable bending radii were mounted on the optical fiber cable according to the present embodiment.

  As can be seen from FIG. 4, when the minimum allowable bending radius of the optical fiber is increased, that is, when the loss tolerance to bending of the optical fiber is decreased, the optical loss is rapidly increased during manufacturing. This is due to random bending applied to the optical fiber when the optical fiber cable is manufactured. Further, it can be seen that by using an optical fiber having a minimum allowable bending radius of about 13 mm or less, an increase in optical loss at the time of manufacturing the optical fiber cable according to the present embodiment can be suppressed, and other optical fibers cannot be suppressed.

  FIG. 5 is a characteristic diagram showing measurement results obtained by performing a temperature cycle test in the temperature range of −30 ° C. to 70 ° C. for the optical fiber cable according to the embodiment of the present invention. As can be seen from FIG. 5, as the minimum allowable bending radius of the optical fiber increases as in FIG. 4, the optical loss increases rapidly. This is because bending and lateral pressure are applied to the optical fiber in the cable because the cable expands and contracts as the temperature changes. Further, it can be seen that by using an optical fiber having a minimum allowable bending radius of about 13 mm or less, stable optical loss characteristics can be maintained, and other optical fibers cannot be maintained.

  4 and 5, it is understood that an optical fiber having a minimum allowable bending radius of 13 mm or less may be used as a condition for suppressing an increase in optical loss due to temperature change when manufacturing the optical fiber cable according to the present embodiment. . In addition, if the optical loss increase for bending, lateral pressure, tension, ironing, and twisting tests, which are general mechanical tests assuming external force applied to the optical fiber cable, also satisfies the above minimum allowable bending radius conditions, It has been experimentally confirmed that stable optical loss characteristics can be maintained.

  In addition, since the optical fiber cable which concerns on this invention uses the optical fiber tape core wire bonded intermittently, the optical fiber cable which uses the single core coating | coated optical fiber as described in patent document 1, Since the ease of movement of the optical fiber in the cable, that is, in the restraint state, is greatly different, the above-described conditions for the minimum allowable bending radius of the optical fiber apply only to the optical fiber cable according to the present invention. It is.

  Optical fiber having a bending loss characteristic with a minimum allowable bending radius of about 13 mm or less, for example, an optical fiber having a bending loss characteristic with an increase in light loss of 0.2 dB / 10 turn or less when bent at a radius of 13 mm at a wavelength of 1.55 μm As a result, the amount of germanium added to the optical fiber core is increased, or the refractive index of the cladding is lowered by adding fluorine, for example, from the optical fiber core, so that light can be easily confined even in a bent state. An optical fiber for guiding light has been proposed. In addition, a photonic crystal fiber has also been proposed that has a hole in the cladding of the optical fiber so that light can be easily confined in the optical fiber core even in a bent state, and light can be guided.

  Next, the strain characteristics when the optical fiber cable according to the embodiment of the present invention is bent will be described in detail below.

  FIG. 6A is a characteristic diagram showing an example of a result of measuring a distribution of strain applied in the longitudinal direction of the optical fiber when the optical fiber cable according to the embodiment of the present invention is bent. For comparison, FIG. 6B and FIG. 6C show the results of measuring and measuring optical fiber cables having the same outer diameter and cable core portion and different subunit structures.

  FIG. 6b is a characteristic diagram showing a measurement result of a strain distribution applied in the longitudinal direction of the optical fiber in the cable when the single-core optical fiber cable according to the comparative example of the present invention is bent, and FIG. 6c is according to the comparative example of the present invention. It is a characteristic view which shows the measurement result of the distortion distribution added to the optical fiber longitudinal direction in a cable when a tape core optical fiber cable is bent.

  That is, FIG. 6B shows an optical fiber cable having a structure in which there is no resin part for bonding single-core coated optical fibers and a unit in which 20 single-core coated optical fibers are assembled in a straight line (hereinafter referred to as single-core optical fiber cable). FIG. 6c shows a structure using a unit in which five conventional optical fiber ribbons, which are continuously coated in the longitudinal direction with four single-core coated optical fibers, are gathered in a straight line. The result in an optical fiber cable (hereinafter referred to as a tape core optical fiber cable) is shown. Note that the number of cores is 200. The cable bending radius is 100 mm.

  From FIG. 6a, it can be seen that in the longitudinal direction of the optical fiber in the optical fiber cable according to the present embodiment, the strain periodically changes greatly at the same interval as the interval at which the resin portions are intermittently arranged. That is, it can be seen that a large strain due to cable bending occurs in the resin portion.

  From FIG. 6b, it can be seen that the strain applied in the longitudinal direction of the optical fiber in the single-core optical fiber cable only changes gently with a large period, and the strain variation is small.

  From FIG. 6c, it can be seen that the strain periodically changes greatly in the longitudinal direction of the optical fiber in the tape optical fiber cable as in FIG. 6a. Compared to FIG. 6a, it can be seen that the period of strain change is long. This is because it corresponds to the twist pitch of the units in the optical fiber cable.

  As described above, in order to measure the strain applied in the longitudinal direction of the optical fiber with high distance resolution, for example, the optical frequency domain interferometer (Optical Frequency domain interferometry) method shown in Non-Patent Document 1 is effective. The measurement distance resolution is about 20 mm or less.

  FIG. 7 shows the measurement results of the relationship between the maximum value of strain applied to the longitudinal direction of the optical fiber in the cable and the bending radius of the cable when the optical fiber cable, the single-core optical fiber cable, and the tape optical fiber cable according to the embodiment of the present invention are bent. FIG.

  That is, FIG. 7 shows the result of measuring the maximum value of strain applied in the longitudinal direction of the optical fiber by changing the bending radius of the optical fiber cable according to the present embodiment. For comparison, the results for the above-described single-core optical fiber cable and tape-core optical fiber cable are also shown.

  As can be seen from FIG. 7, the strain increases as the cable bending radius decreases.

  Further, it can be seen that the optical fiber cable according to the present embodiment has a strain characteristic substantially between the two, unlike the strain characteristics of the tape core optical fiber cable and the single core optical fiber cable.

  In general, optical fiber cables with low mounting density in the cable core and weak optical fiber tape core wire restraint in the cable are considered to have a small difference in strain characteristics due to cable bending because the optical fiber can easily move within the cable. However, since the optical fiber cable according to the present embodiment has a very high cable core portion, that is, Afiber / Acore is 0.3 or more, as described in FIGS. The characteristic is greatly different from the characteristic of the optical fiber cable having the other subunit structure.

  By the way, when strain is applied in the longitudinal direction of the optical fiber, the breaking strength of the optical fiber decreases.

  The strain allowed for the optical fiber in the optical fiber cable is calculated by the proof strain amount and the fatigue coefficient n. The strain allowed for a silica-based optical fiber used in a normal environment with an n value of about 20 is required to be about 1/3 or less of the proof strain in order to ensure long-term reliability over 20 years. (For example, refer nonpatent literature 2). In general, the proof strain of currently produced optical fiber is, for example, 1.0%, so that the allowable strain for the optical fiber is about 0.3%. In addition, residual strain, etc. remaining at the time of optical fiber cable manufacture and after laying is also superimposed on the strain generated by cable bending (about 0.1%). The strain needs to be about 0.2% or less.

  In general, referring to a point that is 10 times the outer diameter D of the optical fiber cable as a guide for the fixed bending radius of the cable actually used (see, for example, Non-Patent Document 3), in this embodiment, the cable bending Radius 10D (in the case of the optical fiber cable according to the present embodiment, D is the short diameter of the cable) = about 100 mm, it is 0.2% or less, which indicates that long-term reliability can be ensured. On the other hand, in the case of the tape core optical fiber cable, it is about 0.3% when the bending radius is about 100 mm, and it is understood that long-term reliability cannot be ensured. The reason for this is that it is difficult to control the direction of the optical fiber ribbon when it is accommodated in the optical fiber cable at a high density, and it is large when the optical fiber tape is bent in the width direction. This is because distortion was generated. For this reason, it can be seen that the tape core optical fiber cable is not suitable for an optical fiber cable having an extremely small diameter and high density as in the present invention. In other words, the optical fiber cables described in Patent Documents 2 to 4 that are accommodated in a state where the optical fiber ribbons are laminated are not suitable for the present invention.

  Next, a method for reducing strain generated in the longitudinal direction of the optical fiber when the optical fiber cable according to the present embodiment is bent will be described in detail.

  When the optical fiber cable according to the present embodiment is used with a smaller bending radius of 10 D or less, as a first method for satisfying the strain allowed for the cable bending, in the longitudinal direction of the single-core coated optical fiber, It is effective to lengthen the interval between the arranged resin parts and to make the length of the resin parts smaller than 80 mm so as to reduce the constraint imposed on the single-core coated optical fiber in the optical fiber ribbon. That is, it is effective to reduce the ratio of the length of the resin portion to the interval between the resin portions arranged in the longitudinal direction of the single-core coated optical fiber (0.4 in this embodiment). This means that when the ratio is infinitely small, it means a bundle of single-core coated optical fibers, and conversely, when the ratio is large and approaches 1 as much as possible, it means an optical fiber ribbon. I can imagine it easily.

  In addition, the 1st method for reducing the said distortion also has the effect of improving the workability | operativity at the time of the isolation | separation operation | work which isolate | separates a desired optical fiber from an optical fiber tape core wire, and connects with another optical fiber. Play. Since the optical fiber cable according to the present embodiment uses an optical fiber in which an increase in optical loss with respect to bending is reduced as compared with a normal optical fiber, an increase in optical loss of an optical fiber ribbon during single fiber separation work is suppressed. It is possible to work on live lines.

  Further, as a second method for reducing the strain, it is effective to use a resin having a low Young's modulus, that is, an elongation, as the resin used for the resin portion. Specifically, a material having a lower Young's modulus after curing than a cured Young's modulus (about 250 to 1500 MPa, for example, see Patent Document 6) of an outermost coating resin of a single-core coated optical fiber, for example, a conventional single-core coating By using the resin used for the primary coating layer of the optical fiber (Young's modulus after curing is about 5 to 100 MPa or less, for example, see Patent Document 6), the strain generated in the longitudinal direction of the optical fiber when the optical fiber cable is bent is alleviated. Is possible.

  The second method for reducing the strain can also be separated without applying a large external force to the single-core coated optical fiber during the single-core separation operation. There is also an effect of suppressing an increase in loss.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

It is sectional drawing which shows the optical fiber cable which concerns on embodiment of this invention. It is a schematic perspective view which shows the optical fiber tape cable core which concerns on embodiment of this invention. It is a schematic perspective view which shows the folded state of the optical fiber tape cable core which concerns on embodiment of this invention. It is a characteristic view which shows the result of having measured the relationship between the optical loss increase at the time of optical fiber cable manufacture which concerns on embodiment of this invention, and the bending loss characteristic of the used optical fiber. It is a characteristic view which shows the measurement result which implemented the temperature cycle test in the temperature range of -30 degreeC-70 degreeC with respect to the optical fiber cable which concerns on embodiment of this invention. It is a characteristic view which shows the example of a result of having measured distribution of the distortion added to the optical fiber longitudinal direction when the optical fiber cable which concerns on embodiment of this invention is bent. It is a characteristic view which shows the example of a result of having measured distribution of the distortion added to the optical fiber longitudinal direction when the optical fiber cable which concerns on embodiment of this invention is bent. It is a characteristic view which shows the measurement result of the strain distribution added to the optical fiber longitudinal direction in a cable, when the tape core optical fiber cable which concerns on the comparative example of this invention is bent. FIG. 6 is a characteristic diagram showing a measurement result of a relationship between a maximum strain value applied in the longitudinal direction of the optical fiber in the cable and a bending radius of the cable when the optical fiber cable, the single-core fiber and the ribbon fiber-optic cable according to the embodiment of the present invention are bent. is there.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Single fiber coated optical fiber, 12 ... Identification thread, 13 ... Protective tape, 14 ... Polyethylene jacket, 15 ... Tensile body, 16 ... Protruding part, 17 ... Ripped string, 18 ... Resin part, 19 ... Non-resin part .

Claims (8)

An optical fiber cable provided with an optical fiber tape core composed of three or more single-core coated optical fibers coated on the outer periphery of the optical fiber,
The optical fiber has a bending loss characteristic in which an increase in optical loss when bent at a radius of 13 mm at a wavelength of 1.55 μm is 0.2 dB / 10 turn or less,
The optical fiber ribbon is a resin part that bonds the two adjacent single-core coated optical fibers to each other in a two-dimensional arrangement in the longitudinal direction and the width direction,
The length of the resin portion provided between the same adjacent two-core single-core coated optical fibers is shorter than the length of the non-resin portion where the same adjacent two-core single-core coated optical fibers are not bonded,
The resin parts adjacent to each other in the width direction of the optical fiber ribbon are arranged apart from each other in the longitudinal direction of the optical fiber ribbon,
The optical fiber cable forms a unit formed by winding an identification yarn around an outer periphery of an optical fiber bundle in which a plurality of single-core coated optical fibers constituting the optical fiber tape core are assembled , and further, the plurality of units A cable core portion having a holding winding layer composed of a plurality of protective tapes on the outer periphery gathered together in one direction, and a jacket on the outer periphery of the cable core portion,
A ratio of a cross-sectional area occupied by the plurality of single-core coated optical fibers to a cross-sectional area of the cable core portion is 0.3 or more.   2. The optical fiber cable according to claim 1, wherein a ratio of a length of the resin portion to an interval between the resin portions arranged in a longitudinal direction of the single-core coated optical fiber is 0.4 or less.   The length of the said resin part is 80 mm or less, The optical fiber cable of Claim 1 or 2 characterized by the above-mentioned.   The optical fiber cable according to any one of claims 1 to 3, wherein a material having a Young's modulus smaller than a material used for an outermost coating layer of the single-core coated optical fiber is used as the material of the resin portion.   The optical fiber tape core has a portion where the resin portion does not exist at all in the width direction of the optical fiber tape, and the length of the portion is 50 mm or less. 5. The optical fiber cable according to any one of 4. In the state where the outer diameter of the optical fiber cable (the short diameter when the cross-sectional shape is not circular) is D, and the optical fiber cable is bent at a bending radius of 10D,
The optical fiber cable according to any one of claims 1 to 5, wherein a maximum value of strain applied in a longitudinal direction of the optical fiber is 0.2% or less. The optical fiber cable includes two strength members,
The two strength members are embedded in the jacket so as to be symmetrical to each other with respect to the center of the optical fiber cable, and the thickness of the jacket of the embedded portion is other than that of the embedded portion. The optical fiber cable according to any one of claims 1 to 6, wherein the optical fiber cable is thicker than a thickness of the jacket. The optical fiber cable according to any one of claims 1 to 7, wherein the optical fiber is a photonic crystal fiber having a hole in a clad portion of the optical fiber.

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