JP2005017966A - Optical fiber ribbon and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a optical fiber ribbon which suppresses PMD to a small value as the optical fiber ribbon whose PMD value tends to increase, and to provide its manufacturing method. <P>SOLUTION: In the optical fiber ribbon 3 constituted by arranging a plurality of optical fibers 1 side by side in a plane in parallel and coating them together at a time, the plurality of the optical fibers are twisted alternately counterclockwise and clockwise along the length to realize low PMD at low cost. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical fiber ribbon and a manufacturing method thereof in which a plurality of optical fibers are arranged in parallel and integrated, and particularly to a technique for improving the polarization mode dispersion characteristics of an optical fiber.
[0002]
[Prior art]
2. Description of the Related Art An optical fiber tape core (hereinafter also referred to as a tape core) in which a plurality of optical fibers are arranged in parallel in a single plane and collectively covered with a resin coating (hereinafter also referred to as a tape core) is widely used as a basic component of an optical fiber cable. . In recent years, in high-speed optical communication, polarization mode dispersion (PMD for short) of optical fibers has been regarded as important. Although the PMD is preferably as small as possible, there is a general and inevitable tendency that the PMD tends to be large and a small one is difficult to obtain in a tape core and a cable using the same.
[0003]
The internal structure of the cross section of the optical fiber is ideally a concentric structure, but any asymmetry such as deviation from the true circle or eccentricity of these circles is the directionality inherent in the cross section of the optical fiber. Since the directionality inside the optical fiber is due to manufacturing, it tends to be continuous in the longitudinal direction of the optical fiber without being limited to one cross section. When light propagates in an optical fiber having such directionality, dispersion occurs because there is a difference in propagation speed between the X polarization mode and the Y polarization mode, which are propagation modes. This is PMD.
[0004]
On the other hand, when the tape core is configured, a cross section of the tape core has a geometrical direction of thickness direction and width direction, which is a mechanical direction that determines the direction in which the tape core is susceptible to external force. Form sex. When the directionality of the tape core wire promotes the directionality inside the optical fiber, a large PMD is generated. In other words, when the direction inside the optical fiber and the direction of the tape core keep a certain relationship in the longitudinal direction, PMD becomes a very large value. This is exactly the case with the cables used, so PMD tends to be large.
[0005]
Therefore, if a plurality of optical fibers are individually twisted to form a tape core, the direction inside the optical fiber and the direction of the tape core are avoided from being maintained in the longitudinal direction in a fixed relationship. PMD can be reduced. Conventionally, based on this idea, an invention has been made in which a plurality of optical fibers are twisted to form a tape core wire (see Patent Document 1). Here, an invention is disclosed in which the amount of twist of each optical fiber is changed depending on the position in the tape core in order to avoid the entire tape core from being twisted by twisting the optical fiber.
[0006]
In the invention disclosed in Patent Document 1, the twist direction and the twist amount of one optical fiber are constant over the entire length, but the twist direction and the twist amount are changed for each optical fiber to twist the entire tape core. It is to balance mechanically so that it does not. Therefore, it is necessary to control each optical fiber so as to accurately realize the twist direction and the twist amount, and the implementation is somewhat complicated. In addition, since the twisting direction of a single optical fiber is constant, it is necessary to continue the two independent rotations of the rotation for feeding and the rotation for giving twisting to the feeding bobbin of the optical fiber. However, there is a problem that the equipment becomes large and the manufacturing cost increases.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 08-043694
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber ribbon that suppresses PMD to a small value and a method for manufacturing the same in an optical fiber ribbon that tends to increase the value of PMD. It is easy to implement and allows low costs to be realized.
[0009]
[Means for Solving the Problems]
The present invention relates to an optical fiber tape core wire in which a plurality of optical fibers are arranged in parallel in a single plane and are integrally coated with a resin, and each of all or a part of the plurality of optical fibers includes The optical fiber tape core wire is characterized in that a twist is given in the longitudinal direction, and the twist direction changes in the longitudinal direction, and a plurality of optical fibers are arranged in parallel in a single plane and covered with a lump of resin. In the method of manufacturing an optical fiber ribbon that is integrated with each other, all or a part of the plurality of optical fibers are collectively covered with a resin coating while being twisted so as to be alternately reversed left and right in the longitudinal direction. An optical fiber ribbon manufacturing method characterized in that:
[0010]
In order to give a twist (called SZ twist) that is alternately reversed left and right in the longitudinal direction of the optical fiber, the optical bobbin of the optical fiber is rotated in the forward and reverse directions in the direction of applying the SZ twist simultaneously with the rotation for feeding. However, it is possible to use a simpler method. In a simple method, it is not necessary to rotate the optical fiber feeding bobbin for twisting the optical fiber. Manufacturing becomes possible. This is because the SZ twisting can be applied by a simple method after the optical fiber exits the feeding bobbin.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An example of the optical fiber ribbon of the present invention is shown in FIG. The figure shows a 4-core tape core, 1 is an optical fiber, 2 is a tape resin, 3 is a tape core, and a state in which the optical fiber 1 is twisted is shown by a thin line. Actually, although this thin line is not visible, it can be considered that the directionality inside the optical fiber rotates along this line. The tape resin 2 that collectively coats the four optical fibers is indicated by a dotted line. SZ twisting does not have to be in phase with four optical fibers, and each optical fiber may be twisted independently as shown in the figure. The pitch of inversion need not be the same.
[0012]
In the cross section of the optical fiber, if the internal directionality is indicated by an arrow and the tip of the arrow points to a thin line in the figure, the cross section of the tape core wire 3 at points a, b, and c in FIG. 2 (a), (b), (c). As shown in FIG. 2, the tape core wire is susceptible to external pressure from the upper and lower surfaces (up and down arrows in the figure), and the optical fiber 1 is also susceptible to distortion in that direction, but the arrow indicating the directionality inside the optical fiber. Since it changes variously with respect to the direction of distortion, the PMD is not promoted to a large value by using the tape core wire.
[0013]
In the present invention, the individual optical fibers constituting the tape core are twisted by SZ, so that the twisting torque is canceled for each optical fiber, and the torque for twisting the entire tape core does not remain. Also, since no special means such as aligning the twisting phases with four optical fibers or making the reversal pitch the same is used, the individual optical fibers are aligned by chance at the position where the twisting occurs. First of all, the whole core wire is not twisted locally. Therefore, according to the present invention, in order to suppress twisting as a tape core wire, a complicated operation such as controlling the twisting amount of each optical fiber as in the invention disclosed in Patent Document 1 is not necessary.
[0014]
In order for the tape core of the present invention to exhibit the effect of reducing PMD, it is desirable that the amount of twist in the SZ twist is at least 180 degrees. That is, it is desirable to twist 180 degrees or more to the right and then twist 180 degrees or more to the left. More preferably, the amount of twist is 360 degrees or more. Conversely, if the twist amount is as small as several tens of degrees, the PMD reduction effect is reduced. These are apparent from the description of FIGS. 1 and 2 described above.
[0015]
In the SZ twisting, the period in which the twisting direction is alternately reversed left and right is not necessarily constant. That is, the period in which the twisting direction is reversed for any one of the plurality of optical fibers is not necessarily constant in the length direction. Even if the inversion period changes, if the sufficient amount of twist is given, a sufficient PMD reduction effect can be obtained.
[0016]
In a more special case, a tape core including an optical fiber that does not require PMD reduction is assumed. For example, in an 8-fiber ribbon, 6 fibers are used for high-speed communication and require PMD reduction, but the other 2 fibers may be used for purposes that do not require PMD reduction. At this time, it is not necessary to twist the two cores that do not require PMD reduction.
[0017]
Next, the manufacturing method of the optical fiber tape core wire of this invention is demonstrated. As described above, in order to apply SZ twist to the optical fiber, it is not necessary to rotate the feeding bobbin of the optical fiber to twist the fiber. As one simple method for providing SZ twisting, there is a method using a guide roller having a groove section of a U-shaped or V-shaped groove. If the optical fiber is run by contacting the optical fiber at a position off the center of the groove bottom of such a roller, the optical fiber runs up and down while rolling the wall surface of the groove of the guide roller. Repeat on your own.
[0018]
This situation will be described with reference to FIG. FIG. 3A shows a state in which the optical fiber 1 is in contact with the guide roller 4 and is traveling in the direction of the arrow in the figure. The guide roller 4 has a U-shaped or V-shaped groove cross section, and the optical fiber passing through the guide roller is in contact with the groove bottom of the groove and travels normally. Show. In the present invention, the optical fiber is brought into contact with a position deviated from the center of the groove bottom of the guide roller, and the optical fiber is twisted by running a line shifted from the one-dot chain line (shifted from the center). is there.
[0019]
A mechanism for twisting the optical fiber will be described with reference to FIG. FIG. 3B is a sectional view of FIG. 3A and shows the relationship between the optical fiber 1 and the groove of the guide roller 4. First, if the optical fiber is set so as to contact the point N off the center of the groove of the guide roller, the L point (near the groove bottom) where the optical fiber can reduce the tension soon after running. Run. However, when moving from point N to point L, the optical fiber twists clockwise in the figure. In order to release this twist, the optical fiber moves back to the point N. At this time, the optical fiber climbs up to the point U by a spring and receives a twist in the counterclockwise direction. In order to release this twisting, it goes to the point L again, and this is repeated up and down between the points U and L. Conditions for repeating such vibration are not special but rather general, in other words, the optical fiber repeats SZ twisting itself. The twisting amount can be 360 degrees or more and several rotations per direction depending on conditions.
[0020]
In order to manufacture a tape core wire with the above guide roller, such guide rollers are prepared for the number of optical fiber cores, and each optical fiber is moved while shifting the center of the corresponding guide roller. Then, it is led to a batch resin coating apparatus, and immediately after the optical fibers are concentrated in parallel, the batch resin coating is performed. As a result, the individual optical fibers are accommodated in the tape core in the SZ twisted state.
[0021]
As another simple method for providing SZ twisting, a guide roller having a groove having a U-shaped or V-shaped cross section is used so that the rotation direction of the roller and the traveling direction of the optical fiber form an acute angle. Then, there is a method of running an optical fiber in contact with a guide roller. In this case, the optical fiber travels while being twisted by the guide roller, but when the twist reaches a certain limit, the reverse rotation is instantaneously attempted to release the strain energy of the twist. Repeat SZ twisting by itself.
[0022]
This situation will be described with reference to FIG. FIG. 4 is a plan view of the optical fiber traveling in the direction of the arrow as viewed from above, and shows the relationship between the optical fiber 1 and the groove of the guide roller 4. If the traveling direction of the optical fiber makes an acute angle with the rotation direction of the guide roller as shown in the figure, the optical fiber is continuously twisted by receiving a twisting torque from the guide roller during traveling. When the twist is accumulated, the reverse rotation is performed to release the twist, and the forward rotation and the reverse rotation are repeated. This condition that the direction of rotation vibrates is not special but rather general. In this case as well, the optical fiber repeats SZ twisting itself. Also in this case, the twist amount can be 360 degrees or more and several rotations per direction depending on the conditions.
[0023]
In order to manufacture a tape core wire using this guide roller, prepare guide rollers for the number of optical fiber cores in exactly the same manner as described above, and run each optical fiber on the corresponding guide roller. It leads to a batch resin coating device, and collects optical fibers in parallel and simultaneously coats the resin. As a result, the individual optical fibers are accommodated in the tape core in a state where the SZ is twisted.
[0024]
Although only one guide roller as described above is required for each optical fiber, two guide rollers with different mounting methods for each optical fiber are used, and the guide rollers are alternately turned on one by one. A method of contacting the fiber is also effective. For example, as shown in FIG. 5 (a), two guide rollers A and B with the center line shifted are arranged in tandem so that the guide roller A and the guide roller B are in contact with each other, or in FIG. 5 (b). As shown in the figure, it is also effective to arrange two guide rollers A and B with different inclinations in tandem so that the guide roller A and the guide roller B contact each other alternately. One guide roller may be periodically changed to the state of the guide roller A and the guide roller B in FIG.
[0025]
【Example】
The tape core wire prototyped according to the present invention and its PMD characteristics will be described. The optical fiber had an outer diameter of 250 μm coated with an ultraviolet curable resin, and the optical fiber 4 core was further coated with an ultraviolet curable resin to constitute an optical fiber ribbon having a thickness of 400 μm and a width of 1100 μm. A guide roller shown in FIG. 4 is disposed in the front stage of the collective resin coating apparatus to twist each optical fiber.
[0026]
When PMD was measured with respect to the four-core optical fiber of the prototyped tape core wire, a result of 0.1 to 0.2 ps / √km was obtained. On the other hand, the same type of optical fiber was used to manufacture a conventional tape core without twisting, but the PMD was as large as 0.2 to 0.5 ps / √km, and this gave an SZ twist to the optical fiber. The invention has confirmed that PMD is significantly improved.
[0027]
【The invention's effect】
According to the present invention, by configuring the optical fiber ribbon by applying SZ twist to the optical fiber, the PMD is suppressed to a small value in the conventional optical fiber ribbon that has been apt to increase the value of PMD. can do. In addition, SZ twisting, which is not continuous twisting in one direction, does not cause the entire optical fiber ribbon to be twisted, and the twisting phase is aligned with four optical fibers, or the reverse pitch Since no special means such as the same is used, it is unlikely that the individual optical fibers are twisted and the entire tape core is locally twisted. That is, the present invention does not require a complicated operation such as controlling the twisting amount of each optical fiber as in the invention disclosed in Patent Document 1. Furthermore, the production that provides the SZ twist is easy to implement because the equipment may be simple.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating an optical fiber ribbon of the present invention.
FIG. 2 is a cross-sectional view illustrating an optical fiber ribbon of the present invention.
FIG. 3 is an explanatory view of a method for twisting an optical fiber by a guide roller.
FIG. 4 is an explanatory diagram of another method for twisting an optical fiber by a guide roller.
FIG. 5 is an explanatory diagram of a method for twisting an optical fiber with two guide rollers.
[Explanation of symbols]
1: Optical fiber 2: Tape resin 3: Tape core wire 4: Guide roller

Claims (5)

In an optical fiber ribbon in which a plurality of optical fibers are arranged in parallel in a single plane and are integrally covered with a resin coating, each of all or some of the plurality of optical fibers has a longitudinal direction. An optical fiber ribbon, which is twisted and a twist direction changes in a longitudinal direction. 2. The optical fiber tape according to claim 1, wherein the twist in the longitudinal direction applied to all or a part of the plurality of optical fibers is a twist that is alternately reversed left and right at a constant period. Heartline. In a method of manufacturing an optical fiber ribbon in which a plurality of optical fibers are arranged in parallel in a single plane and collectively covered with a resin coating, each of all or a part of the plurality of optical fibers has a longitudinal length. A method of manufacturing an optical fiber ribbon, characterized in that a resin is coated and integrated while applying twists that are alternately reversed left and right in the direction. The optical fiber is twisted so as to be alternately reversed left and right in the longitudinal direction by running the optical fiber in contact with the groove wall surface shifted from the groove bottom of the guide roller having the groove. Manufacturing method of optical fiber ribbon. The optical fiber is twisted so as to be alternately reversed left and right in the longitudinal direction by running the optical fiber in contact with the guide roller in a direction that forms an acute angle with the rotation direction of the guide roller having the groove. 4. A method for producing an optical fiber ribbon according to item 3.

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