JP2005141143A - Tape type coated optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tape type coated optical fiber which solves problems that the conventional tape type coated optical fiber cannot satisfy PMD (polarization mode dispersion) characteristics because a plurality of coated optical fibers arranged into a tape are not disposed at appropriate intervals and because an overall coating layer covering the fibers is not controlled to proper thickness, which shows satisfied PMD characteristics, and which is small in size and excellent in mechanical strength. <P>SOLUTION: In the tape type coated optical fiber, the interval S μm between the coated optical fiber in both ends in the width direction and the adjacent optical fibers in the inner side of the fibers in the both ends in the width direction, the interval C μm of coated optical fibers adjacent to each other excluding the coated optical fiber on the both ends, and thickness t μm of the overall coating layer satisfy the relation expressed by 0<t≤7 or 25<t≤80, and 10≤(1.8×t-29)<S<(2.9×t+141)<200 and 10≤(1.8×t-29)<C<(2.9×t+141)<200. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tape-type optical fiber used as an optical communication line, and in particular, to reduce Polarization Mode Dispersion (PMD), which is one of the factors that determine the upper limit of communication speed. Is intended.

With the rapid increase in communication volume due to the increase in the number of Internet users in recent years, it is required to increase the speed in optical fiber communication. For example, when performing high-speed optical fiber communication of 40 GBPS or higher, it is necessary to consider so-called polarization dispersion, which is a polarization mode that has not been a problem at the conventional communication speed.
Polarization mode dispersion is caused by a change in the refractive index distribution due to non-uniform stress generated inside the optical fiber due to stress applied to the optical transmission line or changes in humidity.

  In a tape-type optical fiber, when the optical fiber core is collectively coated into a tape, a large amount of non-uniform stress is applied to the polarization due to curing shrinkage of the batch coating material, resulting in polarization. The mode dispersion value increases.

  Currently, development of an apparatus that compensates for polarization mode dispersion is underway, but no attempt has been made to reduce the polarization mode dispersion produced by the optical fiber core itself.

  That is, as shown in FIG. 15, a conventionally proposed tape-type optical fiber has a plurality of optical fibers 4 arranged so that their side surfaces are in contact with each other (K = 0), and various types of optical fiber cores are provided on the optical fiber. In most cases, the collective coating layer 5 is formed with a thickness t. (For example, Patent Documents 1 to 3)

  Further, as another conventional tape-type optical fiber core, as shown in FIG. 16, the side surfaces of a plurality of optical fiber core wires 4 are separated from each other by a predetermined distance K, and a predetermined thickness t is formed thereon. Those having a collective coating layer have been proposed. (For example, Patent Documents 4 to 7)

Among these, in the invention of Patent Document 4, the thickness t of the collective coating layer is zero, and the distance K between the optical fiber cores is 50 μm or 100 μm.
In addition, the inventions of Patent Documents 5 to 6 are such that the distance K between the optical fiber cores is set to 200 μm or more.
In the invention of Patent Document 7, the distance K between the optical fiber cores is 50 μm, and the thickness t of the collective coating layer is 25 μm.

JP 11-31726 A Japanese Patent Application Laid-Open No. 2000-241685 JP 2002-341001 A Japanese Patent Laid-Open No. 5-80238 JP 2001-208944 A JP 2002-250850 A JP-A-4-268522

  However, in the inventions described in Patent Documents 1 to 3, since the side surfaces of the optical fiber cores are in close contact with each other, when the collective coating layer is cured after extrusion coating the collective coating layer, the optical fiber core wires of each other Both of them are subjected to compressive stress by the collective coating layer, and the PMD characteristics are deteriorated.

  In the invention described in Patent Document 4, since the thickness t of the collective coating layer is zero and the collective coating layer exists only on the side surface of the optical fiber core, the collective coating layer is the outer periphery of the optical fiber core. In other words, the PMD characteristics are deteriorated.

  Further, since the inventions of Patent Documents 5 and 6 have a structure in which the distance between the optical fiber cores is greatly separated as 200 μm, the tape-type optical fiber cores are bulky, and a plurality of these optical fibers are assembled into an optical cable. At times, optical cables cannot be made small.

  In addition, the invention described in Patent Document 7 is relatively appropriate with the interval between the optical fiber cores being 50 μm and the thickness t of the collective coating layer being 25 μm, but one more step, the thickness of the collective coating layer is large, There was a drawback that the PMD value was high and the PMD value was different between the optical fiber cores.

The present invention has been made in view of the above points, and four or more optical fiber cores are arranged in parallel on the plane with the side surfaces facing each other and spaced apart from each other. In a tape-type optical fiber having a coating layer formed on the outer periphery in a tape shape, the optical fiber cores located at both ends in the width direction are adjacent to the inside in the width direction of the optical fiber cores located at both ends. When the distance between the optical fiber cores is S μm, the distance between the optical fiber cores other than the optical fiber cores located at both ends is C μm, and the thickness of the collective coating layer is t μm,
0 <t <= 7 or 25 <t <= 80
10 ≦ (1.8 × t−29) <S <(2.9 × t + 141) <200
10 ≦ (1.8 × t-29) <C <(2.9 × t + 141) <200
It is characterized by being.

  Another aspect of the present invention is the above-described present invention, wherein (1.9 × t−7) μm ≦ C ≦ (2.5 × t + 100) μm (1.9 × t−7) μm ≦ S ≦ (2.5 × t + 100) μm It is characterized by being.

  Still another aspect of the present invention is characterized in that, in the present invention, C = 2 × t + 32 μm and S = 2 × t + 32 μm.

  As described above, the present invention can provide a tape-type optical fiber having excellent PMD characteristics, a small size, and excellent mechanical strength.

  Prior to reaching the present invention, the present inventor conducted the following experiment to determine how the polarization mode dispersion value in a tape-type optical fiber changes depending on the thickness of the cover material and the distance between the optical fiber cores. .

  FIG. 1 shows a tape type four-core optical fiber core wire used in the experiment. 1 is a bare optical fiber made of quartz, 2 is a primary layer made of plastic resin coated thereon, and 3 is a primary layer 2. The optical fiber core wire 4 is formed by these layers. Reference numeral 5 denotes a batch coating layer of a thermoplastic resin that is commonly coated on four optical fiber cores that are arranged in a row at predetermined intervals with the side surfaces of the optical fiber cores facing each other.

  The bare optical fiber 1 has a diameter of 125 μm. Although the bare optical fiber 1 is not shown in the figure, it is composed of a core layer having a predetermined refractive index disposed in the axial center portion and a clat layer having a smaller refractive index around the core layer. The primary layer 2 has a diameter of 205 μm, and the secondary layer 3 has a diameter of 256 μm. In addition, the Young's modulus of the primary layer 2 is configured to be smaller than the Young's modulus of the secondary layer 3, and the bare optical fiber 1 is protected from external force. This optical fiber core 4 is a general one as a non-zero optical fiber (non zero dispersion shift fiber) core.

  The four optical fiber cores 4 are optical fiber cores positioned at both ends in the width direction (hereinafter referred to as “side optical fiber cores”) and optical fiber cores adjacent to the inner side in the width direction of the side optical fiber cores. And S (μm) (see S dimension in FIG. 1, hereinafter referred to as “side optical fiber spacing”), optical fiber cores other than the optical fiber cores positioned at both ends (hereinafter referred to as “center optical fiber core wires”) Is defined as C (μm) (see C dimension in FIG. 1, hereinafter referred to as “center optical fiber interval”), and the thickness of the collective coating layer is t μm. Experiments were performed by varying the thickness t of the collective coating layer (hereinafter referred to as “ribbon thickness”) t. For the measurement, an optical polarization analyzer (Agilent 8509B) was used, and polarization mode dispersion was measured by the Jones matrix method.

  2 and 3 show the deviation of the tape type four-core optical fiber produced by changing the center optical fiber core spacing C and the side optical fiber core spacing S when the thickness t of the collective covering material is 32 μm. The results of how the wave mode dispersion distribution changes are shown. FIG. 2 shows the characteristics of the center optical fiber and FIG. 3 shows the characteristics of the side optical fiber. From this, it is understood that the polarization mode dispersion value is larger in the center optical fiber core wire than in the side optical fiber core wire at all intervals. Therefore, in the tape type optical fiber, the polarization mode dispersion value of the entire tape type optical fiber can be reduced by adopting a structure that lowers the polarization mode dispersion of the center optical fiber. it can.

  4 to 8 show the polarization mode dispersion distributions of the center optical fiber core when the thickness t of the collective covering material of the tape optical fiber core is changed to 16 μm, 32 μm, 48 μm, 64 μm, and 80 μm, respectively. . The most depressed portion in this distribution is the portion where the polarization mode dispersion is minimum. The PMD distribution decreases as the thickness t of the collective covering material increases. It can also be seen that the minimum value of PMD shifts from the right side (part with a narrow interval) to the left side (part with a wide interval) on the graph as the collective coating layer becomes thicker.

FIG. 9 shows an approximate curve in which the minimum value of PMD is extracted based on the ribbon thickness t obtained from the polarization mode dispersion distribution of the optical fiber (approximate curve: PMD minimum value = 4.82 × 10 ⁻¹ −1.65 ×). 10 ⁻² × t + 3.06 × 10 ⁻⁴ × t ² −2.94 × 10 ⁻⁶ × t ³ + 1.13 × 10 ⁻⁸ × t ⁴ ). From this equation, the PMD value that varies depending on the ribbon thickness can be estimated.

  FIG. 10 is a characteristic diagram of the minimum PMD value with respect to the ribbon thickness t. At this time, the minimum PMD values were all when the center optical fiber core interval C and the side optical fiber core interval S were equal (C = S). From this figure, it was found that the optimum interval at which PMD is minimized is proportional to the ribbon thickness.

  FIG. 11 shows the polarization mode characteristics when the side interval S changes with respect to the center optical fiber core interval C where the PMD value obtained from each characteristic of FIGS. The characteristics shown in FIG. 11 indicate that the PMD value changes gently when the side optical fiber spacing S changes in the vicinity where the PMD value is minimized.

  From this, it is understood that the same PMD value can be obtained at a narrower interval without taking the optical fiber core wire interval that minimizes the PMD value. That is, it is possible to achieve both a reduction in PMD value and a reduction in the size of the tape-type optical fiber.

  When this is seen in terms of specific numerical values, the ranges of the optical fiber core distances in which the minimum value is increased by 5 or 10% from the PMD distribution shown in FIG. 9 are shown in FIGS.

  At this time, the distance between the optical fiber cores that can be taken by the tape-type optical fiber in the region from the upper limit to the lower limit of each figure depending on the ribbon thickness is C and S below.

Fig. 12 Optical fiber core interval Upper limit Approximate straight line: C = S = 2.5 × t + 100
Lower limit approximate straight line: C = S = 1.9 × t-7

Fig. 13 Optical fiber core interval Upper limit Approximate straight line: C = S = 2.9 × t + 141
Lower limit approximate straight line: C = S = 1.8 × t-22

  From the above results, the range of the structure in which the PMD value generated by the curing shrinkage of the batch coating layer of the tape type optical fiber core wire is made clear is clarified.

  From this result, the present invention is in the range of 10% from the optimum PMD value, but even in such a range of 10%, the optical fiber core interval is 200 μm or more, and the ribbon thickness t is 20 μm or more. If the distance between the optical fiber cores is 10 μm or less or the ribbon thickness t is 10 μm or less, the mechanical strength of the tape-type optical fiber is weak. Therefore, it is the range where the downward sloping line shown in FIG.

Moreover, other this invention is the range within 5% from the optimal PMD value within the said range. In FIG. 14, this range is indicated by a diagonal line with a lower left corner. Thereby, it is possible to provide a tape-type optical fiber having a low PMD value.
Yet another aspect of the present invention is characterized in that, in the above range, C = 2 × t + 32 μm and S = 2 × t + 32 μm. As a result, it is possible to provide a tape-type optical fiber core that further secures a low PMD value.

  In the above-described embodiment of the present invention, only the optical fiber core wire of a specific diameter and the tape type optical fiber core wire in the case where this optical fiber core wire is four cores have been described. The present invention can be applied to a tape-type optical fiber core in which an optical fiber core having a shape and many other optical fiber cores are assembled.

The end view of the tape type optical fiber core wire used in inventing the present invention. The characteristic view which shows the relationship between the center optical fiber core wire | interval when ribbon thickness t is 32 micrometers, the side optical fiber core wire | interval, and PMD of a center optical fiber core wire. The characteristic view which shows the relationship between the center optical fiber core wire | line space | interval when ribbon thickness t is 32 micrometers, the side optical fiber core wire space | interval, and PMD of a side optical fiber core wire. The characteristic view which shows the relationship between the center optical fiber core wire | line space | interval in case ribbon thickness t is 16 micrometers, the side optical fiber core wire space | interval, and PMD of a center optical fiber core wire. The characteristic view which shows the relationship between the center optical fiber core wire | interval when ribbon thickness t is 32 micrometers, the side optical fiber core wire | interval, and PMD of a center optical fiber core wire. The characteristic view which shows the relationship between the center optical fiber core wire | line space | interval in case ribbon thickness t is 48 micrometers, the side optical fiber core wire space | interval, and PMD of a center optical fiber core wire. The characteristic view which shows the relationship between the center optical fiber core wire | line space | interval in case ribbon thickness t is 64 micrometers, the side optical fiber core wire space | interval, and PMD of a center optical fiber core wire. The characteristic view which shows the relationship between the center optical fiber core wire | line space | interval in case ribbon thickness t is 80 micrometers, the side optical fiber core wire space | interval, and PMD of a center optical fiber core wire. The characteristic view which shows the relationship between minimum PMD of the characteristic shown by FIGS. 4-8, and ribbon thickness t. The characteristic view which shows the optical fiber core wire space | interval which shows the minimum PMD value with respect to ribbon thickness t. FIG. 9 is a polarization mode characteristic diagram when the side optical fiber core spacing S changes with respect to the center optical fiber core spacing C at which the PMD value obtained from each characteristic of FIGS. The characteristic view which shows the range of the range of the optical fiber core wire distance with respect to ribbon thickness t which shows the range of +/- 10% from the best PMD value. The characteristic view which shows the range of the range of the optical fiber core wire space | interval with respect to ribbon thickness t which shows the range of +/- 5% from the best PMD value. The dispersion | distribution characteristic figure with respect to the wavelength of the dispersion compensation optical fiber used by this invention. The end view which shows an example of the past. The end view which shows another example of the past.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bare optical fiber 2 Primary layer 3 Secondary layer 4 Optical fiber core wire 5 Collective coating layer

Claims (3)

Four or more optical fiber cores are arranged with their side surfaces facing each other and arranged in parallel on the plane at intervals, and a coating layer is formed in a tape shape on the outer periphery of these optical fiber core wires In the tape type optical fiber, the distance between the optical fiber cores located at both ends in the width direction and the optical fiber core wires adjacent to the inner side in the width direction of the optical fiber core wires located at both ends is S μm, When the spacing between adjacent optical fiber cores other than the optical fiber cores positioned at C is C μm, and the thickness of the collective coating layer is t μm,
0 <t <= 7 or 25 <t <= 80
10 ≦ (1.8 × t−29) <S <(2.9 × t + 141) <200
10 ≦ (1.8 × t-29) <C <(2.9 × t + 141) <200
A tape-type optical fiber, characterized by being. (1.9 × t-7) μm ≦ C ≦ (2.5 × t + 100) μm
(1.9 × t-7) μm ≦ S ≦ (2.5 × t + 100) μm
The tape-type optical fiber according to claim 1, wherein C = 2 × t + 32μm
S = 2 × t + 32μm
The tape-type optical fiber according to claim 1, wherein

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