JP5889108B2 - Optical fiber cable and optical fiber cable manufacturing method - Google Patents

Description

  The present invention relates to an optical fiber cable in which an optical fiber core wire is accommodated in a protective tube, and a method for manufacturing the optical fiber cable.

  Conventionally, an optical fiber cable in which an optical fiber core wire is inserted into a protective tube is used. Such an optical fiber cable is used after being laid. For example, the intermediate portion of the optical fiber cable is removed, the internal optical fiber core wire is taken out, and connected to another optical fiber cable or the like.

  In such a branching operation, it is necessary to take out an optical fiber core having a predetermined length from the installed optical fiber cable. This is because, for example, it is confirmed that the optical fiber core taken out is not in use, and the tips of the other optical fiber core wires are installed in a fusion machine or the like to perform connection work. . Therefore, when the coating of a predetermined length is removed, it is desirable that the optical fiber core wire has a surplus length necessary for work.

  As such an optical fiber cable having a surplus length, there is one in which an optical fiber core wire is provided in a sheath, and the optical fiber core wire is intermittently formed in a coil shape in the longitudinal direction (Patent Document 1). ).

Japanese Unexamined Patent Publication No. 63-201609

  However, in the optical fiber cable described in Patent Document 1, it is necessary to form the optical fiber core wire into a coil form in advance. For this reason, it is inferior to manufacturability. It is also difficult to make the optical fiber core as a coil as designed. Moreover, since the optical fiber core wire having the coil portion is inserted into the covering portion, the coil diameter is formed smaller than the inner diameter of the covering portion. However, when the curvature of the optical fiber core wire is increased, the optical transmission loss may increase.

  Further, since the optical fiber core wire can freely move inside the covering portion, the coil portion does not necessarily remain in a predetermined position. Therefore, depending on the part, the coil part may already extend inside the covering part at the time of laying. Therefore, it is difficult to reliably obtain the extra length at any part.

  The present invention has been made in view of such a problem. An optical fiber cable or the like that can stably form an extra length of an optical fiber core at an arbitrary portion of the optical fiber cable and is excellent in manufacturability. The purpose is to provide.

In order to achieve the above-mentioned object, the first invention comprises a hollow protective tube made of resin, and an optical fiber core inserted into the protective tube, and the optical fiber core is An optical fiber cable that is spirally arranged inside the protective tube and contacts the inner surface of the protective tube over substantially the entire length, wherein an inner diameter (substantially fiber helical diameter) when the protective tube is removed is d, and the optical fiber P is the helical pitch of the core wire, and Ls is the linear distance projected S and T on the same cross section of both ends S and T of the exposed optical fiber core at the removal portion of the protection tube, and the protection tube is removed. Lf is the length of the optical fiber core in the measured range, H is the maximum height from the extraction position when the optical fiber core is extracted in the range where the protective tube is removed, T is the sheath thickness, The top connecting S and T The distance from the distance midpoint to cover the inner surface Hi, when the Ef taken out height of the optical fiber, when removed the length of the protective tube is L,
Lf = (L / p) × (p ² + (πd) ² ) ^1/2
Ls = (L ² + (d / 2) ² × (1-cos (2πL / p)) ² + (d / 2) ² × sin ² (2πL / p)) ^1/2
If n ≦ L / p <n + 1/2 (where n = 0, 1, 2,...),
Hi = (d / 2) × (1-cos (π × ((L / p) −n)),
When n + 1/2 ≦ L / p <n + 1 (where n = 0, 1, 2,...), Hi = (d / 2) × (1−cos (π × (n + 1− (L / p ))))
And
Ef = ((Lf / 2) ² − (Ls / 2) ² ) ^1/2 Spiral pitch that is 10 mm or more when the extraction height Ef of the optical fiber represented by −T−Hi is L = 500 mm p is an optical fiber cable.

  A groove for preventing a shift of the optical fiber core wire may be formed on the inner surface of the protective tube.

  The optical fiber core may be a tape core.

The protective tube is a multi-layer structure over the entire length, the resin constituting the inner surface of the protective tube, Ri resin der lower softening point than the resin constituting the outer surface of the protective tube, the protective tube The inner layer may have flexibility and tackiness compared to the outer layer .

  A tearing base portion for tearing the protective tube may be formed on the outer peripheral surface of the protective tube.

  According to the first invention, the optical fiber core wire is spirally arranged inside the protective tube. For this reason, the length of an internal optical fiber core line becomes long with respect to the length of the longitudinal direction of a protective tube. Therefore, when taking out the optical fiber core wire from the protective tube, it is possible to secure an extra length necessary for the work.

  At this time, the optical fiber core wire is in contact with the inner surface of the protective tube over substantially the entire length. Further, since the optical fiber core wire is longer than the length in the longitudinal direction of the protective tube, the optical fiber core wire tends to spread inside the protective tube. That is, the optical fiber core wire is pressed against the inner surface of the protective tube. Therefore, the optical fiber core wire is less likely to shift with respect to the inner surface of the protective tube.

  In particular, since the groove is formed on the inner surface of the protective tube, the optical fiber core wire can be prevented from being displaced on the inner surface of the protective tube so as to be caught in the groove.

  If a tape core is used as the optical fiber core, a more rigid optical fiber core can be applied. As described above, the optical fiber core wire is pressed against the inner surface of the protective tube. However, the higher the rigidity of the optical fiber core wire, the more reliably the optical fiber core wire can be pressed against the protective tube. For this reason, by using the tape core wire, the optical fiber core wire can be more reliably pressed against the inner surface of the protective tube, and the shift of the optical fiber core wire on the inner surface of the protective tube can be prevented.

  In addition, the protective tube has a two-layer structure, and the resin on the inner surface is made of a resin having a low softening point, so that when the optical fiber core wire is pressed against the inner surface of the protective tube immediately after being extruded, Deforms easily. Therefore, the optical fiber core wire partially digs into the inner surface of the protective tube, thereby increasing the contact area between the optical fiber core wire and the inner surface of the protective tube. For this reason, the optical fiber core wire can be embedded in the inner surface of the protective tube, and the optical fiber core wire can be prevented from being displaced from the inner surface of the protective tube. For this reason, the optical fiber core wire can be more securely fixed to the inner surface of the protective tube. Therefore, the shift | offset | difference in the protective tube inner surface of an optical fiber core wire can be prevented.

2nd invention is the manufacturing method of the optical fiber cable concerning 1st invention, Comprising: The process of extruding hollow resin and forming a protective tube, The process of sending an optical fiber core wire into the inside of the said protective tube And the optical fiber core when the optical fiber core wire is spirally arranged and brought into contact with the inner surface of the protective tube with respect to the helical pitch length with respect to the longitudinal direction of the optical fiber cable protective tube. While calculating the ratio of the lengths of the wires and twisting the optical fiber one turn, the feed direction of the optical fiber is used as the rotation axis at a feed rate higher than the ratio of the pushing length of the protective tube. seen twisting while feeding write, the optical fiber, is helically disposed within said protective tube, a method for manufacturing an optical fiber cable comprising contacting an inner surface of the protective tube over substantially the entire length.

  According to the second aspect of the invention, the optical fiber core wire can be spirally arranged on the inner surface of the protective tube, and the optical fiber core wire can be brought into contact with the inner surface of the protective tube over substantially the entire length.

  ADVANTAGE OF THE INVENTION According to this invention, the optical fiber cable etc. which are excellent in manufacturability while being able to form the extra length part of an optical fiber core wire stably in the arbitrary site | parts of an optical fiber cable can be provided.

(A) is a perspective perspective view which shows the optical fiber cable 1, (b) is longitudinal direction sectional drawing. (A) is sectional drawing of the optical fiber cable 1, (b) is the A section enlarged view of (a). The figure which shows the branch work process of the optical fiber cable. 1 is a conceptual cross-sectional view of an optical fiber cable 1. FIG. (A) is a perspective perspective view which shows the optical fiber cable 20, (b) is longitudinal direction sectional drawing. (A) is sectional drawing of the optical fiber cable 20, (b) is the C section enlarged view of (a). (A) is sectional drawing of the optical fiber cable 1a, (b) is sectional drawing of the optical fiber cable 20a. 1 is a cross-sectional view of an optical fiber cable 30. FIG. (A) is sectional drawing of the optical fiber cable 20b, (b) is sectional drawing of the optical fiber cable 20c.

  Hereinafter, an optical fiber cable 1 according to an embodiment of the present invention will be described. FIG. 1A is a perspective perspective view showing the optical fiber cable 1, and FIG. 1B is a longitudinal sectional view of the optical fiber cable 1. The optical fiber cable 1 mainly includes a protective tube 3 that is a covering portion, an optical fiber core wire 5 and the like.

  The protective tube 3 is a hollow tubular body, and is made of a resin such as polyethylene, for example. The protective tube 3 has flexibility. An optical fiber core wire 5 is provided inside the protective tube 3. The optical fiber core wire 5 is disposed in a spiral shape over substantially the entire length inside the protective tube 3.

  The optical fiber core wire 5 is in contact with the inner surface of the protective tube 3 over substantially the entire length. It should be noted that contact over substantially the entire length is sufficient if most of the optical fiber core wire 5 is in contact with the inner surface of the protective tube 3, and partly due to variations in the helical pitch of the optical fiber core wire 5. Includes a case where a part of the protective tube 3 is separated from the inner surface of the protective tube 3.

  Next, a method for manufacturing the optical fiber cable 1 will be described. The protective tube 3 is extruded, for example. The tip of the optical fiber core wire 5 disposed inside is fixed near the tip of the protective tube 3. In this state, the optical fiber core wire 5 is continuously introduced into the inside of the protective tube 3 to be pushed out. At this time, the optical fiber core wire 5 is fed into the protective tube 3 in the same direction as the direction in which the protective tube 3 is pushed out at a speed faster than the pushing speed of the protective tube 3.

  Further, the optical fiber core wire 5 is fed into the protective tube 3 while rotating at a predetermined speed with the feeding direction of the optical fiber core wire 5 (the pushing direction of the protective tube 3) as a rotation axis. By doing in this way, the optical fiber core wire 5 is sent in the inside of the protective tube 3, being formed in a spiral.

  Here, the optical fiber core wire 5 itself has a certain degree of rigidity. That is, the optical fiber core wire 5 is protected at a speed higher than a predetermined speed than the pushing speed of the protective tube while twisting the optical fiber core wire 5 with the front end of the optical fiber core wire 5 fixed to the distal end portion of the protective tube 3. By feeding into the inside of the tube 3, the optical fiber core wire 5 spirals inside the protective tube 3 and tries to spread outward.

  By doing in this way, the optical fiber cable 1 can be manufactured, pressing the optical fiber core wire 5 formed in the spiral shape on the inner surface of the protective tube 3. In order to surely press the optical fiber core wire 5 against the inner surface of the protective tube 3, the optical fiber core wire 5 is spiraled with respect to the helical pitch length in the longitudinal direction of the optical fiber cable 1 (protective tube 3). The ratio of the length of the optical fiber core wire 5 when it is shaped and placed in contact with the inner surface of the protective tube 3 is calculated, and the twisted length of the optical fiber core wire is twisted by one turn, In addition, the optical fiber core wire 5 may be fed into the protective tube 3 at a feed rate higher than the ratio.

  2A is a cross-sectional view of the optical fiber cable 1, and FIG. 2B is an enlarged view of a portion A in FIG. 2A. As described above, the optical fiber core wire 5 is disposed so as to be pressed against the inner surface of the protective tube 3. Here, when the optical fiber core wire 5 is fed into the inside while extruding the protective tube 3, the temperature of the protective tube 3 is determined from the molding temperature when the optical fiber core wire 5 contacts the inner surface of the protective tube 3. It has not fallen yet and is in a high temperature state.

  Thus, while the temperature of the protective tube 3 is high, the protective tube 3 is softened. Therefore, as shown in FIG. 2B, when the optical fiber core wire 5 is pressed against the inner surface of the protective tube 3 (in the direction of arrow B in the figure), the inner surface of the protective tube 3 depends on the rigidity of the optical fiber core wire 5. In this state, the optical fiber core wire 5 is slightly embedded. That is, the groove 7 is slightly formed on the inner surface of the protective tube 3, and the optical fiber core wire 5 is disposed so as to fit into the groove 7.

  Since the optical fiber core wire 5 and the protective tube 3 are not firmly joined by fusion or the like, when the protective tube 3 is sufficiently cooled and hardened, the optical fiber core wire 5 is easily formed into the groove 7. Can come off. Therefore, when the optical fiber cable 1 is handled, a part of the optical fiber core wire 5 can be out of the groove 7.

  However, in the present invention, if the groove 7 is partially formed on the inner surface of the protective tube 3 and a part of the longitudinal direction of the optical fiber core wire 5 is fitted in the groove 7, the spiral optical fiber core wire 5 is formed. However, it is possible to prevent free movement within the protective tube 3. Therefore, the shift of the optical fiber core wire 5 can be prevented.

  Next, a branching operation method using the optical fiber cable 1 will be described. FIG. 3 is a diagram illustrating a process of taking out the optical fiber core wire 5 inside the optical fiber cable 1. First, as shown in FIG. 3A, the protective tube 3 of the optical fiber cable 1 is cut to a predetermined length. For example, the protective tube 3 in the range of about 500 mm is cut in the length direction of the optical fiber cable 1. For cutting, a cutter, a nipper, or a special jig may be used as necessary.

  When the protective tube 3 in a predetermined range is removed, the optical fiber core wire 5 arranged in the protective tube removing portion 9 is exposed as shown in FIG.

  Next, as shown in FIG.3 (c), the extra length required for an operation | work is formed by drawing out the exposed optical fiber core wire 5. As shown in FIG. Therefore, if necessary, the optical fiber core wire 5 can be cut and connected to another fiber or the like. In addition, the optical fiber core wire 5 is cut | disconnected, and the twist in the said exposed part is eliminated. For this reason, it does not affect subsequent operations.

  In addition, the helical pitch of the optical fiber core wire 5 is set as appropriate. FIG. 4 is a schematic cross-sectional view of the optical fiber cable 1.

  For example, when the protective tube 3 is removed, the inner diameter (substantially fiber helical diameter) is d, the helical pitch of the optical fiber core wire 5 is p, and both end portions S of the exposed optical fiber core wire 5 are removed at the removal portion of the protective tube 3. , T (see FIG. 3C. FIG. 4 shows a state where S and T are projected on the same cross section) Ls (not shown), and light in a range where the protective tube 3 is removed The length of the fiber core wire 5 is Lf (not shown), the maximum height from the take-out position when the optical fiber core wire 5 is taken out in the range where the protective tube 3 is removed is H, the sheath thickness is T, and the same cross section The distance from the midpoint of the shortest distance connecting S and T to the inner surface of the coating is Hi, and the take-out height of the optical fiber core wire 5 is Ef.

If the removal length of the protective tube 3 is L,
Lf = (L / p) × (p ² + (πd) ² ) ^1/2
Ls = (L ² + (d / 2) ² × (1-cos (2πL / p)) ² + (d / 2) ² × sin ² (2πL / p)) ^1/2
If n ≦ L / p <n + 1/2 (where n = 0, 1, 2,...), Hi = (d / 2) × (1−cos (π × ((L / p ) -N)),
When n + 1/2 ≦ L / p <n + 1 (where n = 0, 1, 2,...), Hi = (d / 2) × (1−cos (π × (n + 1− (L / p )))).

In this case, Ef = ((Lf / 2) ² − (Ls / 2) ² ) ^1/2 −T−Hi. Usually, L = 500 mm, d = 10 mm, and T = 1.5 mm. The pitch p may be calculated so that Ef calculated as described above is 10 mm or more, preferably 15 mm or more.

  As mentioned above, according to this Embodiment, since the optical fiber core wire 5 is helically arrange | positioned inside the protective tube 3, if the protective tube 3 of a predetermined range is removed, the extra length required for work will be ensured. Can do. At this time, the optical fiber core wire 5 is arranged so as to contact the inner surface of the protective tube 3 over substantially the entire length. For this reason, compared with the case where the optical fiber core wire 5 does not contact the inner surface of the protective tube 3, the bending radius of the optical fiber core wire 5 bent in a spiral shape can be increased. Therefore, optical transmission loss can be reduced.

  Further, since the optical fiber core wire 5 is held in a spiral shape over the entire length, there is no directivity with respect to the bending direction of the optical fiber cable 1. Therefore, even if the optical fiber cable 1 is bent in any direction, it is possible to prevent the optical fiber core wire 5 from being excessively bent.

  Further, since the optical fiber core wire 5 is pressed against the inner surface of the protective tube 3, the optical fiber core wire 5 is protected by the friction between the optical fiber core wire 5 and the inner surface of the protective tube 3. Is prevented from shifting in the longitudinal direction. Further, the groove 7 is formed by pressing the optical fiber core wire 5 against the inner surface of the protective tube 3 during manufacturing. For this reason, the optical fiber core wire 5 is more reliably prevented from being displaced by the unevenness of the inner surface of the protective tube 3.

  It is possible to bond the optical fiber core wire 5 and the protective tube 3 with an adhesive. However, according to the present invention, the optical fiber core wire 5 and the protective tube 3 can be connected to each other without using an adhesive agent. Therefore, the optical fiber core wire 5 can be easily pulled out from the inside of the protective tube 3. Therefore, it is excellent in branch workability.

  Next, a second embodiment will be described. 5A and 5B are diagrams showing the optical fiber cable 20. FIG. 5A is a perspective perspective view showing the optical fiber cable 20, and FIG. 5B is a longitudinal sectional view of the optical fiber cable 20. FIG. In the following description, components having the same functions as those of the optical fiber cable 1 are denoted by the same reference numerals as those in FIG.

  The optical fiber cable 20 has substantially the same configuration as the optical fiber cable 1, but differs in that an optical fiber core wire 21 is used. The optical fiber core wire 21 is a tape core wire in which a plurality of optical fiber core wires are provided. In order to integrate the optical fiber cores, the optical fibers may be bonded continuously or intermittently. One surface of the optical fiber core 21 comes into contact with the inner surface of the protective tube 3 in a spiral shape over substantially the entire length.

  6A is a cross-sectional view of the optical fiber cable 20, and FIG. 6B is an enlarged view of a portion C in FIG. 6A. Similarly to the optical fiber cable 1, in the optical fiber cable 20, when the optical fiber core wire 21 is pressed against the inner surface of the protection tube 3 (in the direction of arrow D in the figure), the protection tube 3 is caused by the rigidity of the optical fiber core wire 21. The optical fiber core wire 21 is slightly embedded in the inner surface. That is, the groove 7 is slightly formed on the inner surface of the protective tube 3, and the optical fiber core wire 21 is disposed so as to fit into the groove 7.

  In addition, the optical fiber core wire 21 has larger rigidity than the optical fiber core wire 5 which is a single core. Therefore, it can be more strongly pressed against the inner surface of the protective tube 3. For this reason, the optical fiber core wire 21 can be more reliably fixed to the inner surface of the protective tube 3.

  As described above, according to the second embodiment, the same effects as those of the first embodiment can be obtained. Moreover, since the optical fiber core wire 21 has high rigidity, the optical fiber core wire 21 can be more reliably pressed against the inner surface of the protective tube 3 to form the groove 7. Therefore, the shift of the optical fiber core wire 21 inside the protective tube 3 can be prevented. The optical fiber core 21 may have a unit shape in which a plurality of optical fiber cores are bundled instead of the tape core.

  In the above-described embodiment, the example in which the optical fiber cores 5 and 21 are arranged one by one inside the protective tube 3 is shown, but the present invention is not limited to this. For example, as shown to Fig.7 (a), it is good also as the optical fiber cable 1a which has arrange | positioned the some optical fiber core wire 5. FIG. Or it is good also as the optical fiber cable 20a which has arrange | positioned the some optical fiber core wire 21. FIG. Further, the optical fiber core wire 5 and the optical fiber core wire 21 may be mixed. That is, in the present invention, the number and form of the optical fiber cores disposed inside the protective tube 3 are not limited.

  Further, as in the optical fiber cable 30 shown in FIG. 8, the protective tube 3 may have a multilayer structure. In the optical fiber cable 30, the inner layer 33 and the outer layer 35 are formed of different resins.

  Usually, the protective tube 3 is made of polyethylene, but the outer layer 35 can be made of polyethylene, and the inner layer 33 can be made of styrene elastomer, polyester elastomer, polyurethane, or the like. If it is such a material, since it is the extrusion temperature substantially the same as polyethylene, it can also extrude simultaneously. Further, since the resin as described above has flexibility and tackiness as compared with polyethylene, it is easy to maintain the state in which the inner optical fiber core wire 21 is stuck to the inner surface of the protective tube 3.

  The softening temperature of the resin constituting the inner layer 33 is preferably lower than the softening temperature of the resin constituting the outer layer 35.

  For example, the inner optical fiber core 21 (or the optical fiber core 5, the same applies hereinafter) is introduced after the protective tube 3 is extruded and the inner surface of the protective tube 3 is still softened. It is pressed against the inner surface of the protective tube 3. At this time, the groove 7 is formed by the pressing force of the optical fiber core wire 21. Therefore, if the inner surface of the protective tube 3 is softer, the optical fiber core wire 21 can be embedded in the inner surface of the protective tube 3 more reliably. Therefore, by doing in this way, the optical fiber core wire 21 is reliably arrange | positioned in the groove | channel 7 in the inner surface of the obtained optical fiber cable 30, and a shift | offset | difference can be prevented.

  Moreover, as shown to Fig.9 (a), it can also be set as the optical fiber cable 20b which formed the notch 37 which is a tearing base point part in the outer surface. The notch 37 is a notch formed in the outer periphery of the protective tube 3a, and is formed along the longitudinal direction. When the internal optical fiber core 21 is taken out, the protective tube 3a may be cut in the longitudinal direction with the notch 37 as a base point. By tearing in the longitudinal direction of the protective tube 3a, the inner optical fiber core wire can be taken out from the tearing portion. By doing so, for example, even when a tension member is disposed inside the protective tube 3a and it is difficult to cut the entire circumference of the protective tube 3a, it is easy to perform. The optical fiber core 21 inside can be taken out.

  Moreover, as shown in FIG.9 (b), it can also be set as the optical fiber cable 20c which formed the soft part 39 which is a tearing base point part in the outer surface. The soft part 39 is formed in the outer peripheral part of the protective tube 3b. The soft part 39 is formed of a flexible resin with respect to other parts. Therefore, it can be easily removed. Therefore, when taking out the internal optical fiber core wire 21, the protective tube 3 b can be cut with the soft portion 39 as a base point. By doing in this way, the internal optical fiber core wire 21 can be taken out easily.

  As mentioned above, although embodiment of this invention was described referring an accompanying drawing, the technical scope of this invention is not influenced by embodiment mentioned above. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

1, 1a, 20, 20a, 20b, 20c, 30 ... optical fiber cable 3, 3a, 3b, 31 ... protective tube 5, 21 ... optical fiber core 7 ... groove 9 ... Protective tube removal section 33 ......... inner layer 35 ......... outer layer 37 ......... notch 39 ......... soft part

Claims (6)

A hollow protective tube made of resin;
An optical fiber core inserted through the protective tube;
Comprising
The optical fiber core is an optical fiber cable that is spirally disposed inside the protective tube and contacts the inner surface of the protective tube over substantially the entire length,
The inner diameter (substantially fiber spiral diameter) when the protective tube is removed is d, the helical pitch of the optical fiber core wire is p, and both ends S and T of the optical fiber core wire exposed at the removal portion of the protective tube Ls is a linear distance obtained by projecting S and T on the same cross section, Lf is the length of the optical fiber core in the range where the protective tube is removed, and the optical fiber core is extracted in the range where the protective tube is removed. H is the maximum height from the take-out position, T is the sheath thickness, Hi is the distance from the midpoint of the shortest distance connecting S and T on the same cross section to the inner surface of the coating, and the optical fiber core is taken out When the height is Ef,
When the removal length of the protective tube is L,
Lf = (L / p) × (p ² + (πd) ² ) ^1/2
Ls = (L ² + (d / 2) ² × (1-cos (2πL / p)) ² + (d / 2) ² × sin ² (2πL / p)) ^1/2
If n ≦ L / p <n + 1/2 (where n = 0, 1, 2,...),
Hi = (d / 2) × (1-cos (π × ((L / p) −n)),
When n + 1/2 ≦ L / p <n + 1 (where n = 0, 1, 2,...), Hi = (d / 2) × (1−cos (π × (n + 1− (L / p ))))
And
Ef = ((Lf / 2) ² − (Ls / 2) ² ) ^1/2 Spiral pitch that is 10 mm or more when the extraction height Ef of the optical fiber represented by −T−Hi is L = 500 mm An optical fiber cable characterized by p.   The optical fiber cable according to claim 1, wherein a groove for preventing a shift of the optical fiber core wire is formed on an inner surface of the protective tube.   The optical fiber cable according to claim 1, wherein the optical fiber core is a tape core.   The protective tube has a multilayer structure over its entire length, and the resin constituting the inner surface side of the protective tube is a resin having a lower softening point than the resin constituting the outer surface side of the protective tube, The optical fiber cable according to any one of claims 1 to 3, wherein the inner layer has flexibility and tackiness as compared with the outer layer.   The optical fiber cable according to any one of claims 1 to 4, wherein a tearing base portion for tearing the protective tube is formed on an outer peripheral surface of the protective tube. A method of manufacturing an optical fiber cable according to any one of claims 1 to 5,
A process of forming a protective tube by extruding a hollow resin;
Sending an optical fiber core wire into the protective tube;
Comprising
The ratio of the length of the optical fiber core wire when the optical fiber core wire is spirally arranged in contact with the inner surface of the protective tube with respect to the helical pitch length with respect to the longitudinal direction of the optical fiber cable protection tube And while twisting the optical fiber core by one rotation, the optical fiber core wire is fed while being twisted with the feed direction of the optical fiber core as the rotation axis at a feed speed that is higher than the ratio of the pushing length of the protective tube,
A method of manufacturing an optical fiber cable, wherein the optical fiber core wire is spirally arranged inside the protective tube and is brought into contact with the inner surface of the protective tube over substantially the entire length.

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