JP2004240014A - Method of branching coated optical fiber tape, tool for branching the coated optical fiber tape and coated optical fiber tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a branching method which is used to easily and safely branch a coated optical fiber tape, a branching tool for the tape and the coated optical fiber tape. <P>SOLUTION: When a plurality of optical fibers 11 are to be branched from an coated optical fiber tape 10 in which the plurality of optical fibers 11 are integrated into a single body by a jacket 12, wires 23 are pressed onto the coated optical fiber tape 10 or the wires 23 are relatively moved along the longitudinal direction of the coated optical fiber tape 10 so as to branch the optical fibers 11 by applying a cut to the jacket 12 or peeling off the jacket. For example, both sides of the arrangement surface of the fibers 11 are interposed between and pressed by the wires 23 and or the wires 23 are pressed to the coated optical fiber tape 10 from one side while the other arrangement side surface is fixed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for branching an optical fiber ribbon, a tool for branching an optical fiber ribbon, and an optical fiber ribbon.
[0002]
[Prior art]
As a conventional branching method of an optical fiber ribbon, there is a method in which an optical fiber is collectively cut by a shearing force to cut an outer jacket, and the optical fiber is branched (for example, see Patent Document 1).
Further, in the branching tool 100 as shown in FIG. 8, the upper blade 101 having the convex blade portion 101a and the lower blade 102 having the concave blade portion 102a into which the convex blade portion 101a fits. By operation, the optical fiber ribbon 103 positioned between the upper blade 101 and the lower blade 102 may be branched into a desired number, for example, one, two, or one.
Further, there is also a type in which a cutting blade is cut into an outer cover, and the outer cover is removed by relatively moving the optical fiber ribbon with the cutting blade and a holding member sandwiching the optical fiber ribbon (for example, See Patent Document 2.).
[0003]
[Patent Document 1]
JP-A-8-75929 (page 3, FIG. 1)
[Patent Document 2]
JP-A-8-114713 (pages 3, 4 and FIG. 1)
[0004]
[Problems to be solved by the invention]
However, in the techniques disclosed in Patent Documents 1 and 2 described above, the relative position between the blade and the optical fiber ribbon 103 is shifted, or the pitch of the optical fibers 104 included in the optical fiber ribbon 103 is reduced. In the case where the optical fiber 104 is misaligned, the blade may damage the optical fiber 104 and the strength of the optical fiber may be reduced.
Further, if at least one of the optical fibers 104 of the optical fiber ribbon 103 transmits a signal, the live line is momentarily disconnected at the time of branching. Cannot branch.
[0005]
An object of the present invention is to provide a method for branching an optical fiber ribbon, a tool for branching an optical fiber ribbon, and an optical fiber ribbon that can easily and safely branch an optical fiber.
[0006]
[Means for Solving the Problems]
In order to achieve the above-described object, a method for branching an optical fiber ribbon according to the present invention is directed to an optical fiber ribbon for branching an optical fiber from an optical fiber ribbon in which a plurality of optical fibers are integrated by a jacket. A method of branching a wire, in which a flexible member is pressed against an optical fiber ribbon, and the sheath of the optical fiber ribbon is scratched or peeled off, and the optical fiber ribbon is attached to the optical fiber. It is characterized by branching.
[0007]
In the branching method of the optical fiber ribbon thus configured, the flexible member is pressed against the optical fiber ribbon, and the outer sheath of the optical fiber ribbon is damaged or peeled off. The optical fiber can be easily branched.
[0008]
In addition, the method of branching an optical fiber ribbon according to the present invention is such that the flexible member is moved relatively to the optical fiber ribbon, so that the optical fiber ribbon is branched into optical fibers. Good.
[0009]
In the method of branching an optical fiber ribbon according to the present invention, the flexible member may be pressed against the optical fiber ribbon from both sides of the arrangement surface of the optical fibers.
[0010]
Further, in the method of branching an optical fiber ribbon according to the present invention, the flexible member is pressed against the optical fiber ribbon from one side of the arrangement surface of the optical fiber, and the other arrangement side surface is fixed. Good.
[0011]
In the branching method of the optical fiber ribbon configured as described above, it is possible to easily branch the optical fiber while suppressing the bending of the optical fiber and suppressing the increase in the transmission loss.
[0012]
Further, in the method of branching an optical fiber ribbon according to the present invention, the sheath of the optical fiber ribbon may be impregnated with an organic solvent to branch the optical fiber ribbon into optical fibers.
[0013]
In the branching method of the optical fiber ribbon thus configured, the sheath can be easily branched since it is swelled and softened by an organic solvent such as alcohol.
[0014]
In the method of branching an optical fiber ribbon according to the present invention, the optical fiber ribbon may be branched into optical fibers by holding an organic solvent in a flexible member.
[0015]
In the method of branching an optical fiber ribbon according to the present invention, it is preferable that the amount of transmission loss fluctuation of the optical signal at the time of branching is 0.5 dB or less.
[0016]
In the branching method of the optical fiber ribbon configured as described above, the optical fiber ribbon including the live line can be branched without instantaneously interrupting the live line.
[0017]
Further, in the method of branching an optical fiber ribbon according to the present invention, it is preferable that the flexible member has a Young's modulus of 100 MPa or more and 2000 MPa or less.
[0018]
In the method for branching an optical fiber ribbon according to the present invention, the flexible member may be a plurality of wires.
[0019]
In the branching method of the optical fiber ribbon thus configured, since the flexible member is composed of a plurality of wires, the outer diameter of the optical fiber ribbon when pressed against the optical fiber ribbon is reduced. It can change freely along the shape. For example, the optical fiber tape can penetrate into the concave portions between the optical fibers constituting the optical fiber ribbon, and the optical fibers can be easily separated.
[0020]
In the method of branching an optical fiber ribbon according to the present invention, the tip of the wire may have a corner.
[0021]
In the optical fiber tape core branching method configured as described above, since the tip of the wire is angled, it is easily damaged or peeled when the tip of the wire comes into contact with the jacket of the optical fiber tape. The optical fiber can be efficiently branched.
[0022]
In the method of branching an optical fiber ribbon according to the present invention, it is preferable that the outer circumference of the wire be 0.1 mm to 1.5 mm.
[0023]
In the method for branching an optical fiber ribbon according to the present invention, the length of the wire is preferably 0.1 mm to 10 mm.
[0024]
Further, in the method of branching an optical fiber ribbon according to the present invention, the optical fiber ribbon whose thickness of the jacket is 20 μm or less may be branched into optical fibers.
[0025]
In the branching method of the optical fiber ribbon configured as described above, the branching of the optical fiber can be effectively performed when the thickness of the jacket is 20 μm or less.
[0026]
In addition, the method of branching an optical fiber ribbon according to the present invention includes the steps of: placing the optical fiber ribbon on a flat plate or an arc plate; pressing the optical fiber ribbon; May be branched into the optical fiber.
[0027]
In addition, the branching tool for an optical fiber ribbon according to the present invention includes a first contact portion that abuts one side surface of the optical fiber ribbon, and a second abutment portion that abuts the other side surface of the optical fiber ribbon. And a contact portion, wherein at least one of the first contact portion and the second contact portion has a flexible member.
[0028]
The optical fiber ribbon according to the present invention is an optical fiber ribbon in which a plurality of optical fibers are collectively coated in a jacket having a thickness of 20 μm or less, and the flexible member is pressed against the core. The optical fiber is branched into the optical fiber by relatively moving in the length direction of the optical fiber ribbon, and the transmission loss fluctuation amount of the optical signal at the time of branching is 0.5 dB or less.
[0029]
In addition, the optical fiber ribbon according to the present invention preferably has an MFD of 10.0 μm or less when signal light having a wavelength of 1550 nm is transmitted.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a method for branching an optical fiber ribbon, a tool for branching an optical fiber ribbon, and an optical fiber ribbon according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view of a branching tool of an optical fiber ribbon for executing a method of branching an optical fiber ribbon according to the present invention, and FIG. 2 (A) is a sectional view of the optical fiber ribbon according to the present invention. FIG. 2B is a perspective view.
[0031]
As shown in FIGS. 2A and 2B, an optical fiber ribbon 10 according to the present invention is arranged in parallel by bringing a plurality of (here, for example, four) optical fibers (colored cores) 11 into contact. , And the outside thereof is integrated by a jacket 12 over the entire length of the optical fiber ribbon 10. As the jacket 12, for example, an ultraviolet curable resin, a thermoplastic resin, a thermosetting resin, or the like can be used. The optical fiber 11 has a protective coating 14 and a colored layer 15 provided outside a glass fiber 13 composed of a core 13a and a clad 13b. Alternatively, it may have only the protective coating 14.
[0032]
As shown in FIG. 2A, in the optical fiber ribbon 10, the ultraviolet curable resin as the jacket 12 applied to the outside of the four optical fibers 11 arranged in parallel is disposed between the adjacent optical fibers 11. Is applied so as not to exceed the common tangent 17 of the adjacent optical fiber 11. Further, the outer cover 12 in the concave portion 16 is formed so as to have a continuous shape with a smooth curve.
[0033]
Assuming that the outer diameter of the optical fiber 11 is D, the thickness of the jacket 12 is t, and the thickness of the optical fiber ribbon 10 in the concave portion 16 is G, it is desirable that G be D-50 μm or less. Here, when the outer diameter D of the optical fiber 11 is 250 μm, the thickness G of the optical fiber ribbon 10 in the concave portion 16 is 200 μm or less. This is because when the thickness G of the optical fiber ribbon 10 is increased, the rigidity is increased, so that the jacket 12 is less likely to be broken and the branchability is reduced.
[0034]
It is desirable that the thickness t of the jacket 12 be 20 μm or less. Also, if the transmission loss fluctuation of the optical signal when the optical fiber 11 is branched is larger than 0.5 dB, communication may be interrupted, so that hot-line branching is not possible. For this reason, it is desirable that the transmission loss fluctuation be 0.5 dB or less. The measurement of the transmission loss fluctuation at the time of branching of the optical fiber 11 is performed, for example, by connecting one end face of the optical fiber ribbon 10 to a light source and connecting the other end face to a light receiver. Then, a light having a wavelength of 1.55 μm is incident on the optical fiber 11 from the light source, and the power (for example, a waveform converted into a voltage) received by the light receiver is monitored. Can be measured by decay.
[0035]
Further, the branching property and integration of the optical fiber ribbon 10 are related to the physical properties of the resin forming the jacket 12. For example, when a resin having a large Young's modulus is used for the jacket 12, even if the thickness G of the optical fiber ribbon 10 in the recess 16 is small, the binding force for integrating the optical fiber ribbon 10 is sufficient. Conversely, when the Young's modulus is large, it is necessary to reduce the thickness G of the optical fiber ribbon 10 from the viewpoint of the branchability of the optical fiber 11. The measurement of the Young's modulus was performed by first preparing a sheet using a resin forming the jacket 12, and using a test piece molded into an IS No. 2 dumbbell in accordance with JIS K7113, using a test piece molded into an IS No. 2 dumbbell, using a tensile distance of 25 mm, and pulling a tensile strength. The film was pulled at a speed of 1 mm / min, and the Young's modulus was calculated.
[0036]
Next, as shown in FIG. 1, the branching tool 20 of the optical fiber ribbon is used as an upper base as a first contact portion that abuts on the upper surface 12U of the jacket 12 which is one side surface of the optical fiber ribbon 10. 21 and a lower base 22 as a second contact portion that contacts the lower surface 12L of the jacket 12, which is the other side surface of the optical fiber ribbon 10. At least one of the upper base 21 and the lower base 22 (both in FIG. 1B) is provided with a large number of wires 23 as flexible members, and the tips of the wires 23 are located on substantially the same plane. It is arranged as follows.
[0037]
In addition, a plate-shaped member other than the wire 23 can be considered as the flexible member. Examples of the material of the wire 23 include chemical members such as nylon, PP, vinyl chloride, ester, and conex, and animal members such as horse hair, pig hair, white goat wool, and bera wool. However, those made of metal are not suitable because they may damage the optical fiber 11. In addition, nylon can be mentioned as the most suitable material at present.
[0038]
As the dimensions of the wire 23, those having an outer periphery of 0.1 mm to 1.5 mm are suitable. If the outer circumference exceeds 1.5 mm, it is too thick and it is difficult to make a scratch between the optical fibers. If the outer circumference is shorter than 0.1 mm, the wire tends to be too thin and the stiffness of the wire tends to be weak, and it is difficult to damage the jacket. The length of the wire is preferably 0.1 mm to 10 mm. If the length exceeds 10 mm, the stiffness of the wire tends to be weak. If the length is less than 0.1 mm, the flexibility of the wire is lost and the outer cover is not easily damaged. Most preferably, the diameter is 0.20 to 0.30 mm and the hair length is 2 to 6 mm.
Further, when the wires 23 are attached to the upper base 21 and the lower base 22, if the arrangement of the wires 23 is dense, the outer cover can be efficiently scratched or the outer cover can be peeled off, so that branching is easy.
[0039]
As the wire 23, one having a Young's modulus of 100 MPa or more and 2000 MPa or less is used, and particularly preferably 200 MPa or more and 1500 MPa or less. Further, it is preferable to provide a corner 24 at the tip of the wire rod 23 as shown in FIG. Alternatively, as shown in FIG. 3B, an acute angle 25 can be provided. Thus, when the distal end of the wire 23 comes into contact with the jacket 12 of the optical fiber ribbon 10, the jacket 12 can be efficiently damaged or scraped.
[0040]
Next, a method of branching an optical fiber ribbon according to the present invention using the above-described branching tool 20 will be described.
As shown in FIGS. 1A and 1B, the optical fiber ribbon 10 is sandwiched between an upper base 21 and a lower base 22 of a branching tool 20, and a wire 23 is brought closer to the jacket 12 of the optical fiber ribbon 10. Go. Further, when the branching tool 20 is pressed against the optical fiber ribbon 10, as shown in FIG. 1C, the wire 23 is bent, and the tip of the bent wire 23 is outside the optical fiber ribbon 10. Begin to scratch the cover 12. By repeatedly pressing the branching tool 20 (FIG. 1C) and releasing the pressing, the scratches on the jacket 12 increase, or the jacket 12 peels off. In a state where the branching tool 20 is pressed, the branching tool 20 is relatively moved in the longitudinal direction of the optical fiber ribbon 10 (the left-right direction in FIG. 1A), and the distal end of the wire 23 is moved to the jacket 12. The optical fiber 11 is branched by scratching or peeling. Either or both of the branching tool 20 and the optical fiber ribbon 10 may be moved. Since the wire 23 is flexible, when the wire 23 is pressed against the jacket 12 of the optical fiber ribbon 10, the wire 23 warps and the corner of the tip of the wire 23 hits the jacket 12. In this state, when the branching tool 20 or the optical fiber ribbon 10 is moved, the wire 23 (flexible member) damages the jacket 12 or peels the jacket 12. In this manner, the jacket 12 of the optical fiber ribbon 10 is broken, and the optical fiber ribbon 10 is branched into individual optical fibers.
If the force for pressing the flexible member 23 against the optical fiber ribbon is adjusted, the transmission loss fluctuation amount of the optical signal at the time of branching becomes 0.5 dB or less, and even if the optical fiber ribbon includes a live wire, The live line can be branched without an instantaneous interruption.
[0041]
Before pressing the branching tool 20 against the optical fiber ribbon 10, an organic solvent such as alcohol may be applied to the jacket 12 (12U, 12L) of the optical fiber ribbon 20. Since the organic solvent softens the resin jacket 12, when the branching tool 20 is pressed against the jacket 12, or when the branching tool 20 and the jacket 12 perform relative movement, the organic solvent is applied to the jacket 12. It can be easily scratched or peeled off.
[0042]
Further, after the wire 23 of the branch tool 20 is immersed in the organic solvent, the branch tool 20 is pressed against the jacket 12 of the optical fiber ribbon 10 or the branch tool 20 and the jacket 12 are relatively moved. Similarly, the jacket 12 can be softened and easily branched.
[0043]
Further, when the optical fiber ribbon is branched, it is preferable to place the optical fiber ribbon on a flat plate or an arc plate so as not to cause excessive bending of the optical fiber ribbon. In particular, it is preferable to use a gripper that can grip the optical fiber ribbon. 4A and 4B show an embodiment of the gripper, wherein FIG. 4A is a front view and FIG. 4B is a side view. The gripper 40 includes a mounting portion 41 for holding the optical fiber ribbon 10 and a grip portion 42. For the mounting portion 41, a flat plate or an arc plate having a radius of curvature of 30 mm or more is used so that the optical fiber ribbon is not excessively bent. The grip may be formed by a simple projection or the like, but when branching the optical fiber ribbon, for example, by hand, the grip 42 is of a ring shape, and a finger is inserted into the ring. It is convenient to hold it. When the optical fiber ribbon is to be branched, the branch tool 20 is held by inserting the index finger of the other hand into the holding portion 41 of the holding tool 40 in one hand. The optical fiber ribbon 10 is placed on the mounting portion 41 of the gripper 40 and pressed with a thumb from above. By grasping and branching the optical fiber ribbon 10, it is possible to suppress the bending of the optical fiber ribbon and prevent an increase in signal light transmission loss.
[0044]
As described above, according to the method for branching the optical fiber ribbon, the branching tool for the optical fiber ribbon, and the optical fiber ribbon, the optical fiber 11 can be easily and safely branched from the optical fiber ribbon 10. it can.
[0045]
When the optical fiber ribbon is branched in the longitudinal direction, a part (length of about several mm) of the optical fiber ribbon is branched into optical fibers by the above-described method, and a wire or the like is placed between the branched optical fibers. The tearing member may be inserted, and the tearing member may be moved in the longitudinal direction to split the optical fiber ribbon and branch. The wire for tearing the optical fiber ribbon is preferably stronger than the wire of the branching tool. The diameter of the wire is preferably 0.1 to 0.5 mm, and the length is preferably 10 to 30 mm. As the material, nylon or the like can be used. It is preferable to use a tearing jig in which a wire for tearing the optical fiber ribbon is attached to a rod having a length of about 5 to 20 cm in a brush shape. When the optical fiber ribbon is put in the closure, it is difficult to move the branching tool in the closure because the optical fiber ribbon is congested. In this case, if the tearing jig as described above is used, it becomes easy to branch the optical fiber ribbon into optical fibers over a certain length.
[0046]
The method for branching an optical fiber ribbon, the tool for branching an optical fiber ribbon, and the optical fiber ribbon according to the present invention are not limited to the embodiments described above, and appropriate modifications and improvements can be made. It is.
For example, in the branching tool 20 described above, the case where the wire 23 is brought into contact with the upper and lower surfaces 12U and 12L of the optical fiber ribbon 10 has been described. The tape core 10 may be simply fixed.
Also, a description has been given of a case where four optical fibers 11 are collectively used as the optical fiber ribbon 10, but the number is not important.
[0047]
【Example】
Next, a specific embodiment of the branching tool for the optical fiber ribbon will be described. 5A is a side view of the branching tool, FIG. 5B is a side view of the branching tool in a state where the optical fiber ribbon is branched, and FIG. 6 is a view from the V direction in FIG. FIG. 6 is a plan view and FIG. 6 is a table showing the result of branching. In FIG. 1 to FIG. 3, portions common to the above-described portions are denoted by the same reference numerals, and redundant description will be omitted.
[0048]
As shown in FIGS. 6A and 6B, the branching tool 30 connects the upper base 21 </ b> U and the lower base 22 </ b> L by a whole U-shaped spring member 31, and is in a released state where an operator does not apply force. The upper base 21U and the lower base 22L are held at predetermined intervals. In this state, the tips of the wires 23 provided on the upper base 21U and the lower base 22L do not contact. The spring member 31 is provided with an interval adjusting screw 32. By turning the knob 32a to adjust the amount of protrusion of the gap adjusting screw 32, it is possible to limit the gap between the upper base 21U and the lower base 22L when the operator presses the spring member 31. Has become. In addition, since the upper base 21U and the lower base 22L are respectively attached to the spring member 31 by the screws 33, when the wire 23 is worn out, it can be easily replaced.
[0049]
When branching the optical fiber 11 from the optical fiber ribbon 10, insert the optical fiber ribbon 10 between the upper base 21 </ b> U and the lower base 22 </ b> L. The tape core 10 is pressed against the jacket 12. Then, the spring member 31 is released to release the wire 23 from the optical fiber ribbon 10. Again, the wire 23 is pressed and released. This is repeated several times to split the optical fiber 11. Alternatively, as shown in FIG. 6, the optical fiber ribbon 10 is fixed at a position 5 to 10 cm away from the branching tool 30 with fingers. In this state, the branching tool 30 is slid about 10 cm along the optical fiber ribbon 10 (the direction of the arrow in FIG. 6), and the optical fiber 11 is squeezed by the wire material 23 by squeezing the jacket 12 of the optical fiber ribbon 10. Branch.
[0050]
As shown in FIG. 7, the optical fiber 11 was branched by a branching tool 30 using nylon having an outer diameter of 0.21 mm as a flexible member. The optical fiber ribbon was sandwiched by the branching tool 30 shown in FIG. 5 and then opened repeatedly to branch the optical fiber ribbon into the respective optical fibers. The condition (2) is that the branching tool 30 is moved in the longitudinal direction while the optical fiber tape core is sandwiched by the branching tool 30 to branch the optical fiber tape core into the respective optical fibers.
In each case, the optical fiber 11 could be easily branched within a transmission loss fluctuation of 0.5 dB or less. The measurement was performed at a base voltage of 11.5 to 12 mV and a trigger level of 11.5 mV.
[0051]
【The invention's effect】
As described above, according to the method for branching an optical fiber ribbon according to the present invention, when an optical fiber is branched from an optical fiber ribbon in which a plurality of optical fibers are integrated by a jacket, the optical fiber ribbon can be used. The flexible member is pressed against the optical fiber ribbon, or the flexible member is relatively moved in the longitudinal direction of the optical fiber ribbon to easily damage or peel the outer cover. The optical fiber can be branched.
[Brief description of the drawings]
1A is a side view showing an embodiment of a method and a tool for branching an optical fiber ribbon according to the present invention, FIG. 1B is a front view, and FIG. 1C is a flexible member bent. It is a side view which shows a stagnation state.
FIG. 2A is a sectional view of an optical fiber ribbon according to the present invention, and FIG. 2B is an overall perspective view.
FIGS. 3A and 3B are explanatory views of a corner provided at the tip of a wire. FIG.
4A and 4B show one embodiment of a gripper according to the present invention, wherein FIG. 4A is a front view and FIG. 4B is a side view.
FIG. 5A is a side view showing an embodiment of a branching tool for an optical fiber ribbon, and FIG. 5B is a side view showing a state in which branching is being performed.
FIG. 6 is a plan view seen from a direction V in FIG. 5 (B).
FIG. 7 is a table showing branch results.
FIG. 8 is a sectional view showing an example of a conventional branching tool for optical fiber ribbon.
[Explanation of symbols]
Reference Signs List 10 optical fiber ribbon 11 optical fiber 12 jacket 20, 30 branching tool 21 upper base (first contact part)
22 Lower base (second contact part)
23 wires (flexible members)
24, 25 square 40 gripper

Claims (17)

A method for branching an optical fiber ribbon, wherein the optical fiber is branched from an optical fiber ribbon in which a plurality of optical fibers are integrated by a jacket,
Pressing a flexible member against the optical fiber ribbon, damaging the outer sheath of the optical fiber ribbon or peeling the outer sheath, and branching the optical fiber ribbon into the optical fiber. A method for branching an optical fiber ribbon. The optical fiber tape according to claim 1, wherein the flexible member is moved relative to the optical fiber ribbon to split the optical fiber ribbon into the optical fiber. How to branch the cord. 3. The method according to claim 1, wherein the flexible member is pressed against the optical fiber ribbon from both sides of the arrangement surface of the optical fibers. 4. 3. The optical fiber ribbon according to claim 1, wherein the flexible member is pressed against the optical fiber ribbon from one side of the optical fiber array surface, and the other array side is fixed. How to branch the line. The optical fiber tape according to any one of claims 1 to 4, wherein an organic solvent is impregnated into a jacket of the optical fiber tape, and the optical fiber tape is branched into the optical fibers. How to branch the cord. The optical fiber ribbon according to any one of claims 1 to 5, wherein the flexible member holds an organic solvent to branch the optical fiber ribbon into the optical fiber. Branch method. 7. The method for branching an optical fiber ribbon according to claim 1, wherein a transmission loss variation of the optical signal at the time of branching is 0.5 dB or less. The method according to any one of claims 1 to 7, wherein the flexible member has a Young's modulus of 100 MPa or more and 2000 MPa or less. 9. The method according to claim 1, wherein the flexible member comprises a plurality of wires. 10. The method according to claim 9, wherein a tip of the wire has a corner. The method according to claim 9, wherein the outer circumference of the wire is 0.1 mm to 1.5 mm. The method according to claim 9, wherein the length of the wire is 0.1 mm to 10 mm. 13. The method for branching an optical fiber ribbon according to claim 1, wherein the optical fiber ribbon having a thickness of the outer jacket of 20 [mu] m or less is branched into optical fibers. The optical fiber ribbon is placed on a flat plate or an arc plate, the optical fiber ribbon is held down, and the optical fiber ribbon is branched into the optical fibers. 14. The method for branching an optical fiber ribbon according to claim 13. A first contact portion that abuts one side surface of the optical fiber ribbon, and a second contact portion that abuts the other side surface of the optical fiber ribbon, wherein the first contact portion or the first A branching tool for an optical fiber ribbon, wherein at least one of the second contact portions has a flexible member. An optical fiber ribbon in which a plurality of optical fibers are collectively coated with a jacket having a thickness of 20 μm or less,
By pressing a flexible member and relatively moving in the length direction of the optical fiber ribbon, the optical fiber is branched into the optical fiber, and the transmission loss fluctuation amount of the optical signal at the time of branching is 0.5 dB or less. An optical fiber ribbon. 17. The optical fiber ribbon according to claim 16, wherein the MFD when transmitting a signal light having a wavelength of 1550 nm is 10.0 μm or less.

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