JPH11194071A - Coated optical fiber and method of measuring its friction coefficient - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily and precisely measuring the friction coefficient of coated optical fibers. SOLUTION: The face of a moving substrate 20b where the coated optical fibers, 10b are adhered and fixed is made to face the face of a fixed substrate 20a where the coated optical fiber 10a is adhered and fixed and the coated optical fiber 10a and 10b are arranged perpendicularly to each other. In the method of measuring the friction coefficient of a coated optical fiber, an adjusting weight 30 is placed on the moving substrate 20b, the moving substrate 20b is pulled in a direction shown by A at constant speed by a load cell and modulus, namely, friction force required for it is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method for easily and accurately measuring a coefficient of friction of an optical fiber core, and an optical fiber core having excellent winding characteristics on a bobbin.

[0002]

2. Description of the Related Art The coefficient of friction of a resin coating layer of an optical fiber cable is an important factor affecting the productivity and quality of an optical cable. That is, if the coefficient of friction of the resin coating layer of the optical fiber core is high, for example, the frictional force generated between the optical fiber core, between the optical fiber core and the bobbin, between the optical fiber core and the cable constituent material, etc. For example, increase in light loss due to generation of lateral pressure, poor winding and unwinding of the bobbin, and in extreme cases, damage to the resin coating of the optical fiber core leads to reduced productivity and defective products. It causes the occurrence.

However, the coefficient of friction of an optical fiber core wire is a complicated phenomenon that is affected by many factors such as surface irregularities, surface hardness, and adhesiveness, and it is not easy to accurately grasp the friction coefficient. Many techniques have been proposed (JP-A-5-203847, JP-A-1-17775).
No. 06, JP-A-8-179172, JP-A-6-179172
However, many problems such as damage to the resin coating of the optical fiber, increase in optical loss due to micro-bending in a state where the optical fiber cores are gathered, winding on a bobbin, trouble in feeding out, etc. are still unsolved. It is in the state of.

[0004] In particular, in the case of an optical fiber colored core, the friction coefficient generally becomes large because the size of the colorant particles is about 1 μm in addition to the adhesiveness of the coating resin, and the influence thereof is large.

[0005] The friction coefficient is a value obtained by dividing a friction force, which is a resistance force generated in a tangential direction of a friction surface, by a contact force, which is a force acting in a direction to compress the friction surface. It is represented by Coefficient of friction = frictional force / contact force The frictional coefficient includes a static frictional coefficient for a frictional force when the opposing frictional surface is stationary and a dynamic frictional coefficient for a frictional force when the opposing friction surface is moving. The values of the obtained friction coefficients differ greatly.

For a general method of measuring the coefficient of friction, see J.
There is a method of measuring using a sheet formed of the same material as the material to be measured according to IS standard K7125.

[0007]

However, when the resin material of the coating layer of the optical fiber core is measured by the method of the above-mentioned JIS standard, the result of the measurement is extremely large.
In particular, in the case of a colored optical fiber, it is difficult to obtain a reliable coefficient of friction due to the adhesive force of the test piece sheet.

It is a main object of the present invention to propose a measuring method capable of easily and accurately measuring the coefficient of friction of an optical fiber core.

[0009]

SUMMARY OF THE INVENTION In order to overcome the above-mentioned problems, the present invention provides an optical fiber core bonded and fixed to a plane of a fixed substrate and a movable substrate, and placing the movable substrate on the fixed substrate. A method for measuring a friction coefficient of an optical fiber core, wherein the optical fiber cores are brought into contact with each other and a frictional force generated when the movable substrate is moved is measured.

Specifically, for example, the number of optical fiber cores fixed on the planes of the fixed substrate and the movable substrate is 2 respectively.
Book and parallel, the contact between the optical fibers is in a direction orthogonal to each other, and a value obtained by dividing the frictional force by the load applied to the optical fibers is defined as a friction coefficient. This is a method for measuring the coefficient of friction of an optical fiber core.

The present invention also relates to a method of measuring a coefficient of friction according to the present invention, wherein the coefficient of friction is 0.10 to 0.15, and an increase in light loss due to micro bending when wound on a bobbin occurs. An optical fiber core wire characterized in that there is no winding and no collapse occurs.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a method for measuring the friction coefficient of an optical fiber according to the present invention. FIG. 1A is a plan view, and FIG. 1B is a side view. FIG. 2 is a cross-sectional view of the optical fiber. Hereinafter, an embodiment of the present invention will be described with reference to FIGS. Note that the same parts are assigned the same numbers, and duplicate descriptions are omitted.

First, four identical test pieces are prepared for an optical fiber core to be measured. The two optical fiber cores 10a are adhered and fixed in parallel with the two optical fiber cores 10a stretched linearly on the plane of the fixed substrate 20a. Also, the remaining two optical fiber cores 10b are bonded and fixed in parallel to the plane of the moving substrate 20b in a straight line. The optical fibers 10a and 10b may be singular or plural.

The optical fiber core 10a is also attached to the plane of the fixed substrate 20a on which the optical fiber core 10a is bonded and fixed.
The optical fibers 10a and 10b are placed in a direction orthogonal to each other with the planes of the movable substrate 20b on the side where b is bonded and fixed facing each other. Further, the adjustment load 30 is placed on the moving substrate 20b.
And the load is adjusted so that the entire load becomes a predetermined value. Then, the moving substrate 20b is moved by the load cell in the direction shown in FIG. 1A, that is, the direction of the optical fiber core 10a, in other words, the optical fiber core. It is pulled at a constant speed in a direction perpendicular to the line 10b, and the tensile stress required for this, that is, the frictional force is measured.

The weight of the adjustment load 30 is a value obtained by dividing the total weight of the adjustment load 30 and the movable base 20b by the total number of the bonded and fixed optical fiber cores 10a and 10b.
Since the range of g / piece, particularly the range of 4 g / piece to 15 g / piece, is suitable, the range is selected in consideration of the weight of the movable base 20b. The pulling speed of the load cell is 1
Since the value of the obtained friction coefficient varies at 0 mm / sec or more, a range below this value is preferable.

A value obtained by dividing the obtained frictional force by the adjustment load 30 and the total weight of the movable substrate 20b, that is, the contact force is defined as a friction coefficient. According to this measurement method, since the optical fiber cores 10a and 10b to be measured have a columnar shape, they come into contact with each other in a state close to a point, and the adhesion of the resin coating layer of the optical fiber core is performed. The difficulty of measurement due to the force can be eliminated, the variation in the coefficient of friction is extremely small, and a highly reproducible result can be obtained under the same conditions. Therefore, the method for measuring a friction coefficient according to the present invention can be a powerful means for clarifying various problems caused by the friction coefficient of the optical fiber core.

The method of measuring a friction coefficient according to the present invention can measure both a dynamic friction coefficient and a static friction coefficient. When measuring the static friction coefficient, the maximum friction force obtained when the moving base 20b starts moving is adopted as the static friction force. When measuring the dynamic friction coefficient, the maximum friction force is exceeded after the movement starts and the minimum friction force is obtained. The frictional force after the frictional force is obtained is adopted as the dynamic frictional force, and is obtained by dividing the adhesive force, which is the total load, respectively. In the present application, unless otherwise specified, the coefficient of friction indicates a dynamic friction coefficient.

When one optical fiber is bonded and fixed to the fixed substrate 20a and the movable substrate 20b, respectively,
It is necessary to prevent the optical fibers from coming into contact only with each other and to prevent the fixed substrate 20a and the movable substrate 20b from coming into contact with each other on the planes. Therefore, a mechanism for appropriately supporting the movable substrate 20b is required.

Adhering to fixed substrate 20a and moving substrate 20b,
When the number of optical fiber cores to be fixed is two or more, an average friction coefficient of the plurality of optical fiber cores is obtained. Therefore, the number of optical fiber cores in this case must be appropriately selected according to the purpose of using the obtained friction coefficient. In this embodiment, the same test piece is used for each of the optical fibers to be bonded and fixed to the fixed substrate 20a and the moving substrate 20b. However, the present invention is not limited to this. Alternatively, different test pieces can be bonded and fixed to the fixed substrate 20a and the movable substrate 20b to measure the friction coefficient.

[0020]

FIG. 1 shows a method for measuring the coefficient of friction of an optical fiber according to the present embodiment. The measurement target is an optical fiber colored cord having a generally large friction coefficient, and the cross-sectional structure is shown in FIG. In order to obtain various colored optical fibers having different friction coefficients, the composition of the coating resin of the colored layer 4 and the ultraviolet rays thereof were employed for the purpose of making the surface state of the colored layer 4 which is the outermost layer thereof variously different. Table 1 shows the oxygen concentration during curing. Measurement values and measurement accuracy of friction coefficient of these various colored optical fibers, sheet-like test pieces of the same material, JI
Table 2 shows the measurement accuracy when measured by the measuring method according to the S standard, the frequency of occurrence of micro-bending when these colored optical fibers are wound around a bobbin, and the results of tests for the presence or absence of winding collapse.

(Purpose) Hereinafter, a method for measuring the coefficient of friction of the optical fiber according to the present invention will be described with reference to FIGS. 1 and 2 and Tables 1 and 2. Applying the method for measuring the coefficient of friction of the present invention to a problem occurring in the optical fiber core wound on the bobbin,
Clarify its effectiveness. In addition, the range of the coefficient of friction of the optical fiber cable suitable for this problem is clarified.

(Structure of the resin coating layer of the colored optical fiber) The colored optical fibers 10a and 10b to be measured
Is a single-mode optical fiber having a cross-sectional structure as shown in FIG. First, an ultraviolet curable urethane acrylate resin having a Young's modulus of 1 MPa is coated on the bare optical fiber 1 having an outer diameter of 125 μm to form a primary coating layer 2 having an outer diameter of about 195 μm. Furthermore, the Young's modulus is 0.8G
An ultraviolet curable urethane acrylate resin of Pa is coated to form a secondary coating layer 3 having an outer diameter of about 240 μm, thereby obtaining an optical fiber. It is considered that the thickness and hardness of each of these coating layers change the value of the friction coefficient by affecting the contact area at the time of contact between the optical fibers.

On this optical fiber, a fixed amount of 1 μm
An ultraviolet curable ink containing a colorant having a particle size of 3 is coated to form a colored layer 4 to produce a colored optical fiber.

As shown in Table 1, the resin composition of the coloring layer 4 has a relatively high molecular weight compared to a urethane acrylate ultraviolet curable resin ink containing 10% by weight of a coloring agent having a particle diameter of 1 μm. Adjusting each amount of smoothing agent made of silicone resin with high tension, lubricating material made of silicone resin with small compatibility with ink base resin, and Teflon fine powder of about 1μm particle size to give lubricity Then, the degree of curing of the colored layer 4 was adjusted by adjusting the oxygen concentration at the time of ultraviolet curing, thereby producing seven types of colored optical fibers having different friction coefficients.

In this case, as the smoothing agent, silicon oil having a low surface tension, made of silicone resin, oozes out into recesses on the surface of the outermost layer 4 to form a liquid surface, thereby smoothing the surface and lowering the friction coefficient. Has functions. The lubricant is
Silicon oil having excellent lubricity and relatively low surface tension made of silicone resin oozes out on the surface of the outermost layer 4 to form a film surface, thereby having a function of reducing the friction coefficient. Further, since the Teflon particles have a low coefficient of friction of Teflon itself, a part thereof protrudes from the surface of the outermost layer 4 to constitute a part of the surface, thereby having a function of reducing the coefficient of friction.

[0026]

[Table 1]

The colored layer 4 was adjusted under the conditions for adjusting the coefficient of friction shown in Table 1.
The seven types of optical fiber colored cores formed with
Manufactured from 00km to 300km, 25 per bobbin
It was wound with a set tension of 80 gf on a plurality of bobbins having a body diameter of 28 cm, which could be wound for a length of km.

(Measurement method) First, the 7
The same measurement is repeated 10 times for each type of colored optical fiber, and the same four test pieces are used for each measurement. First, for one measurement, two of the four test pieces made of the same optical fiber colored core are bonded and fixed in parallel to the plane of the fixed substrate 20a. The remaining two test pieces are also adhered and fixed in parallel on the plane of the moving substrate 20b.

The surface of the movable substrate 20b on the side where the optical fiber colored core 10b is bonded and fixed similarly faces the surface of the fixed substrate 20a on the side where the optical fiber colored core 10a is bonded and fixed. The core wires 10a and 10b are placed in a direction orthogonal to each other. Further, the adjustment load 30 is placed on the moving substrate 20b to make the total weight 4 gf, and the moving substrate 20b is pulled by the load cell at a speed of 5 mm / sec in the direction shown in FIG. The average tensile stress, i.e., the frictional force, is measured over a distance of 70 mm from the position of the minimum after passing the first maximum position corresponding to the force.

A value obtained by dividing the obtained frictional force by the adjustment load 30 and the total weight of the movable substrate 20b, that is, the contact force 4 gf is defined as a friction coefficient.

As shown in Table 2, the measurement results of the coefficient of friction of each of the colored optical fibers were 0.05 to 0.5.
22. In addition, in order to clarify the variation indicating the reliability of the measurement, the ratio of the standard deviation to the average was determined for ten measurement values obtained by repeating the same test ten times. For comparison, a sheet-like test piece made of the same resin coating material as the colored layer 4 was prepared for the case of the colored optical fiber core, and the friction coefficient was measured according to the JIS standard. Similarly, the ratio of the standard deviation to the average value was determined for the measured values.

As can be seen from Table 2, the percentage value of the standard deviation with respect to the average value according to the present embodiment is less than one digit,
Compared with the value obtained by the measurement according to the JIS standard, it can be said that the measurement method of the present invention is extremely suitable for measuring the friction coefficient of an optical fiber. The above results are for the case where the total load of the movable substrate 20b and the adjustment load 30, that is, the contact force is 4 gf. Similar results were obtained for 15 gf.

[0033]

[Table 2]

(Application to Problems Produced by Colored Optical Fiber Wound on Bobbin) (Applicable object) The optical characteristics of the optical fiber manufactured or processed during the manufacturing process of the optical cable are wound around the bobbin for convenience of handling the optical fiber. It is measured in the state where it was. Therefore, the optical characteristics of the optical fiber measured while being wound on the bobbin and the optical characteristics of the optical fiber with the optical cable laid must be identical. If they do not match, unwind the optical fiber from the bobbin each time the optical characteristics of the optical fiber are measured, and in extreme cases, measure the optical fiber in a state where it is stretched linearly for tens of kilometers as in the installed state, or close to it This is because the measurement of optical characteristics becomes extremely complicated and inefficient.

However, regarding the optical fiber colored core,
In addition to the adhesive strength of the coating layer, the coloring layer constituting the outermost layer contains a coloring agent having a particle size of about 1 μm, so that the friction coefficient generally increases. The optical fiber colored core having a large coefficient of friction causes expansion and contraction due to slight tension fluctuation caused by vibration of a guide roller when wound on a bobbin, but if the coefficient of friction is large, no slip occurs between the optical fiber colored cores. Therefore, the tension fluctuation caused by the expansion and contraction is not eliminated, and the bobbin is stacked in a stored state.

For this reason, there is a portion where the portion wound with high tension overlaps the portion wound with low tension.
At the position where such colored optical fibers intersect, the colored optical fiber wound with a weak tension bends smaller than the diameter of the optical fiber, causing so-called micro-bending, which causes an increase in light loss. Becomes In this case, the light loss inherent in the state of being wound on the bobbin occurs and does not match the light loss measured in the laid state. Therefore, the occurrence of micro-bending in the state of being wound on the bobbin must be eliminated.

(Relationship between Coefficient of Friction of Colored Optical Fiber and Microbending Caused by Winding) For each of the seven types of colored optical fibers having different friction coefficients,
In the state of being wound up on the bobbin, the frequency of occurrence of light loss due to micro-bending caused by friction per 100 km was measured. The results are shown in Table 2 in the column of occurrence frequency of increase in optical loss due to microbending.

From Table 2, it can be seen that the value of the coefficient of friction obtained by the measuring method of the present invention and the frequency of occurrence of an increase in light loss caused by microbending correspond very well, and that the value obtained by the measuring method of the present invention was obtained. When the friction coefficient is 0.15 or less, the frequency of occurrence of light loss increases is 1/100 km or less, and when the friction coefficient exceeds this, the number of occurrences of frequency increases rapidly. .

On the other hand, if the coefficient of friction is too small, microbending does not occur in the state of being wound on the bobbin, but the colored optical fibers become slippery. When lateral vibration is applied to the optical fiber core wound around the bobbin during handling during transportation or the like, winding collapse occurs.

With respect to each of the above seven types of colored optical fibers, a vibration test was conducted in which the vibration applied in the transportation step was simulated, and vibration was applied in the lateral direction while being wound on the bobbin. As a result, as shown in Table 2 in the column of presence / absence of collapse, it was found that the collapse was significant when the friction coefficient of the colored optical fiber was 0.05 or less.

The above facts indicate that the coefficient of friction obtained by the method of measuring a coefficient of friction of the present invention is not limited to the reliability of the measured values of the optical characteristics of the optical fiber core measured in the state of the bobbin and the reliability of the optical fiber core. This shows that this is an effective means for judging the winding and feeding characteristics.

The measurement of the frequency of occurrence of an increase in light loss due to microbending that occurs when the colored optical fiber is wound around a bobbin is based on the so-called OTDR method (backscattering loss measuring method). That is, a light pulse is incident from the end of the optical fiber wound on the bobbin, and the backscattered light reflected from each point in the longitudinal direction of the optical fiber is observed on the time axis as shown in FIG. This is a method for detecting a place where micro-bending occurs from a curve.

That is, when there are optical abnormalities in the longitudinal direction of the optical fiber, an increase in light loss due to various causes based on these abnormalities occurs in these places in the optical fiber in addition to Rayleigh scattering. Therefore, a place where the loss such as the position A increases stepwise in the attenuation curve of FIG. 3, that is, a so-called OTDR step occurs. In the present embodiment, among the OTDR steps due to these various causes, those having a difference of 0.02 dB or more in the loss average value between the front and rear 100 m sections were determined to be caused by micro-bending.

[0044]

By using the method for measuring the coefficient of friction of an optical fiber core according to the present invention, the coefficient of friction of an optical fiber core can be accurately and easily measured.

The coefficient of friction obtained by the method for measuring the coefficient of friction of an optical fiber core according to the present invention can be used to determine the reliability of the measured values of the optical characteristics of the optical fiber core measured in the state of the bobbin and the bobbin of the optical fiber core. It is an effective means for judging the winding and unwinding characteristics. In addition, by using the friction coefficient measuring method of the present invention, it is easy to solve various problems in the production process caused by the friction coefficient of the optical fiber.

[Brief description of the drawings]

FIG. 1A is a plan view showing a method for measuring the friction coefficient of a colored optical fiber core according to the present invention, and FIG. 1B is a side view.

FIG. 2 is a cross-sectional view showing a structure of a colored optical fiber.

FIG. 3 is a diagram showing an OTDR step on an attenuation curve by the OTDR method.

[Explanation of symbols]

 10a, 10b: Optical fiber core wire 20a: Moving board 20b: Fixed board 30: Adjusting load

Claims (3)

[Claims] 1. An optical fiber core wire is fixed linearly on each plane of a fixed substrate and a movable substrate, the movable substrate is placed on the fixed substrate, and the optical fiber core wires are brought into contact with each other. And measuring a frictional force generated when the movable substrate is moved in a state where the movable substrate is moved. 2. The number of optical fiber cores fixed to the plane of the fixed substrate and the movable substrate is two and parallel, respectively, and the contact between the optical fiber cores is a direction orthogonal to each other; The method for measuring a friction coefficient of an optical fiber core according to claim 1, wherein a value obtained by dividing the frictional force by a load applied to the optical fiber core is used as a friction coefficient. 3. An optical fiber core having a coefficient of friction of 0.10 to 0.15 measured by the method of measuring a coefficient of friction according to claim 2.