Optical fiber and fabrication process and apparatus of same

Abstract

 Disclosed herein are a fabrication process of optical fiber, a fabrication machine of optical fiber and optical fiber fabricated thereby. In the fabrication machine, for smoothly supplying sea part fluid into sea parts between adjacent wings, a plurality of cylinders are connected to the bottom of a spinning head. In accordance with the present invention, the above fluid guided by the cylinders is supplied to the space between the adjacent wings with certainty so that the wings are never fused to spin the optical fiber having the predetermined optical characteristics.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to fabrication process and machine of high performance optical fiber using a melt spinning method, and more particularly to fabrication process and machine for reliably spinning high performance sea island optical fiber composed of at least two kinds of fibers into a predetermined shape.

[0002] Conventionally, a coloring structural body in which color is changed depending on a direction to be seen and which is elegant and high-grade feeling and has a color tone of higher saturation, has been required from users' multi-taste and high rank orientation. This requirement cannot be achieved by only coloring matters such as dyes, pigments and the like but by a structural body colored by reflection, interference, diffraction or scattering of light, or a combination of this coloring function and such coloring matters, and deeply and vividly coloring structural bodies have been energetically researched and developed.

[0003] Many proposals have so far been done, for example, a composite fiber constituted by at least two resins with different optical refractive indices, having pearly luster (Japanese Patent Publication Gazette No. 43-14185, Japanese Patent Laid Open Gazette No. 1-139803); a coloring material having a sandwich construction composed of one molecular orientation anisotropic film and two polarizing films sandwiching the film between (Proceedings of the Textile Machinery Society of Japan, Vol. 42, No.2, p. 55 and No.10, p. 160, 1989); a coloring structural body utilizing the coloring of Morphinae butterfly from South America, which is famous for which the color tone is changed depending on a direction to be seen and has vivid color tone efficiency (Japanese Patent Laid Open Gazette No. 59-228042, Japanese Patent Publication Gazette No. 60-24847, Japanese Patent Publication No. 63-64535); and a structural body emitting an interference color by forming fine slits having a fixed width on fiber surface (Japanese Patent Laid Open Gazette No.62-170510, Japanese Patent Laid Open Gazette No.63-120642).

[0004] However, for these coloring structural bodies, various problems arise for their practical uses, for example, it is difficult to control conditions for attaining a predetermined function, and a spinneret suitable for keeping a composite fiber having a complicated shape cannot be obtained.

[0005] The present applicants have developed coloring optical fiber having a vivid color taste changeable in a direction to be seen and a reflection interference function without a change with the elapse of time (Japanese Patent Laid Open Gazette No. 6-17349). This optical fiber has a cross section of a sea island type, as shown in Fig.1a, and comprises a core 1 extending in a longitudinal direction, 10 pairs of wings 2 connected to, and arranged with slits therebetween on, both the sides of the core 1, the core 1 and the wings 2 constituting an island part 3, and a sea part 4 filling up the periphery of the island parts 3 and the slits between the wings 2. The island part 3 and the sea part 4 of the sea island type optical fiber are made different in their optical refractive indexes and satisfy their optical reflection and interference conditions to provide optical fiber having a vivid color and a color taste changeable in a direction to be seen. Usually, the sea part of the optical fiber is dissolved and only the island part is used as the optical fiber, as shown in Fig.1b.

[0006] In order to manifest the optical function of this optical fiber, it is necessary to ensure the foregoing shape and dimensions. The above described optical fiber is constituted by the wings having a thickness of approximately 0.01 to 0.1 µm, and it is the most essential point in the steps from the polymer dissolution to the fiber preparation to certainly separate the slits between the adjacent wings 2 to maintain the predetermined shape. However, when spinning the molten polymer, the spacing between the adjacent wings 2 is narrow and a mutual contact or fusion is often caused in the wings 2.

[0007] In order to solve this drawback the present applicants have developed a spinneret for use in fabricating optical fiber, as shown in Figs.2 and 3 (Japanese Patent Application No. 7-28519 and Japanese Patent Application No. 7-28521). Fig.2 is a perspective view, partly in section, seen from the lower side, of a spinneret for fabricating optical fiber, omitting a lower funnel-shaped nozzle portion, Fig.3a is a longitudinal cross section of the spinneret shown in Fig.2, including the lower nozzle portion, and Fig.3b is a cross section along a line C - C of Fig.3a.

[0008] In Figs.2 and 3, the spinneret 5 includes a ring-shaped spinning head 8 having polymer inlets 6 and 7 for the island and sea parts 3 and 4, a bottom 9, and a concavo-convex-shaped partition wall 10 for a flow path control of the island part 3, mounted on the bottom 9, so as to surround the space corresponding to the island part 3 in its upper half, The spinneret 5 also includes a spinning seat 12 having a funnel-shaped spinning nozzle 11 in its center under the spinning head 8 in its lower half.

[0009] In Fig. 3, as shown by arrows, a polymer for the island part 3 is introduced from the polymer inlet 6 into the inside of the partition wall 10 and another polymer for the sea part 4 from the polymer inlet 7 into the peripheral space of the partition wall 10, resulting in forming the shapes corresponding to the island part 3 and the sea part 4 of the optical fiber, as shown in Fig.1a, in conformity to the internal and external shapes of the partition wall 10. The two polymers contact their conforming surfaces to each other to integrate, while moving down in the spinning nozzle 11, to spin into a sea island type optical fiber, as shown in Fig.1a.

[0010] In this spinning method, when the sea part polymer is introduced from the polymer inlet 7 into the space or slits 13 of the adjacent external projection wings of the partition wall 10 shown in Fig.2, the sea part polymer enters the slits sufficiently between the adjacent wings 2 and the spinning is carried out as it is. As a result, the adjacent wings 2 are spun into the predetermined shape without a welding to produce optical fiber having the foregoing desired characteristics.

[0011] However, this optical fiber is of a very fine size, and the slits between the adjacent wings 2 are finer. When, for example, a wavelength 0.47 µm (a peak wavelength in a reflection Spectrum) which emits blue is obtained, the thickness of the wing plate is made to be 0.08 µm (in case that the optical refraction index (n) of composition material is 1.56) and the space between the adjacent wing plates is made to be about 0.12 µm (in case that the optical refraction index (n) of composition material which is air is 1.0) so that at least eight wing plates are required for generating sufficient optical reflection and interference as mentioned in detail later. In order to precisely obtain such a fine dimension, it is required that the sea part polymer supplied from polymer inlet 7 of Fig.3 penetrates into the space between the wings for the island part polymer to partition every wing to maintain the precise dimension. In order to realize this, the height of the partition wall partitioning the wing from the adjacent wing is made to be high to make a longitudinal dimension into which the island part polymer sufficiently penetrates. However, if the dimension of the island part flow path constituting the wing is made small, the width of the wing and the space between the wings are made narrow so that even with such a high precision processing technique as a laser beam machining and an electric discharge machining, it is difficult to make a high partition wall with currently employed machining techniques. Accordingly, the height must be small.

[0012] In the optical fiber spun in this manner, the adjacent wings 2 tend to contact to each other or to be fusible, and the optical fiber often fails to have the required optical characteristics. This is a main cause to prevent from its practical use.

SUMMARY OF THE INVENTION

[0013] It is therefore an object of the present invention to provide a fabrication process of optical fiber in view of the problems of the prior art, which is capable of preventing a mutual contact or fusion of adjacent wings of sea island optical fiber themselves, that has likely occurred due to the difficulty of precisely realizing a sufficiently high partition wall even with the precision machining for obtaining the above fine dimension, to fabricate optical fiber having the desired optical characteristics.

[0014] Another object of the invention is to provide optical fiber manufactured by means of the above fabrication process.

[0015] A further object of the invention is to provide a fabrication machine of optical fiber employable in the above fabrication process.

[0016] In accordance with one aspect of the present invention, there is provided a fabrication process of optical fiber, comprising supplying sea part fluid and island part polymer to a plurality of sea part-forming cylinders and island polymer flow paths, respectively, of a spinning head including, at the bottom thereof, the cylinders each having upper and lower openings at a uniform space so as to obtain a ratio of an internal dimension thickness or an inner diameter of the cylinder to space between the adjacent cylinders in a range of 30:1 to 1:30, and the island part polymer flow paths around the cylinders; and conducting the spinning by means of a funnel-shaped spinning nozzle of a spinning seat positioned below the cylinders.

[0017] In the process in accordance with the present invention, the sea part fluid which fills in the adjacent wings of the sea parts with itself or separates the said wings reaches to the spinning nozzle guided by the cylinders without passing through other paths. Accordingly, the sea part fluid is supplied with certainty to the predetermined position or to the space between the adjacent wings so as to fill the space with itself or to present in the space during the spinning process.

[0018] If the sea part fluid is a polymer as in the case of a conventional machine, a ratio between the polymers passing through the both paths makes a difference of the amounts of the polymers filling the space between the wings to exert bad influences on the optical characteristics of the optical fiber obtained. Differently from this machine, since all the sea part polymer supplied is guided with certainty by the cylinders and employed for the sea part formation, the supply paths can be determined without any trouble so as to provide the optical fiber excellent in its optical characteristics without the fusion between the adjacent wings.

[0019] When gas is employed as the sea part fluid, the adjacent wings are never in contact with each other during the spinning process because the gas which is guided by the cylinders is supplied into the space between the adjacent wings, so that the optical fiber having the hollow sea parts of the predetermined shape without the fusion of the adjacent wings can be provided. In accordance with the present process, the number of steps is largely decreased and the optical fiber can be advantageously fabricated less costly compared with the conventional process in which the above-mentioned two kinds of polymers are employed to fabricate the optical fiber of which the sea parts are filled with the polymers followed by the dissolution of the sea parts.

[0020] In order to obtain the optical fiber of the predetermined characteristics, the sea parts are required to present in the form of layers or the sea parts which ordinarily have the rectangular shape are required to position in parallel. When the cross sections of the sea part-forming cylinders are made rectangular or oval, the optical fiber having the sea parts of a rectangular or oval section can be obtained. The comparable optical characteristics may be manifested even if the shape of the sea parts is an ellipse.

[0021] Although the final shape of the sea parts of the optical fiber must be rectangular or the like, the cross section of the sea part-forming cylinders may be made circular and the obtained sea parts of the circular section may be deformed to the oval sea parts by means of compressing.

[0022] The optical fiber in accordance with the present invention may be fabricated through one of the several processes previously described, and the said optical fiber possesses the excellent optical characteristics as mentioned.

[0023] Further, the fabrication machine in accordance with the present invention can also provide the optical fiber of the excellent optical characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and other objects, features and advantages of the present invention will more fully appear from the following description of the preferred embodiments with reference to the accompanying drawings, in which:

Fig. 1a is a cross section of one example of optical fiber having a sea island type cross section, which can be produced by a machine according to the present invention and by a conventional technique, Fig.1b is a cross section of an optical fiber having only an island part, prepared from the optical fiber shown in Fig.1a.

Fig. 2 is a perspective view, partly in section, seen from a lower side, of a conventional spinneret for fabricating optical fiber, omitting a lower funnel-shaped nozzle portion, which is proposed to solve a problem of the prior art;

Fig.3a is a longitudinal cross section of a spinning machine with nozzle and Fig.3b is a cross section taken along the line C -C of Fig.3a;

Fig. 4 is a schematic view illustrating a cross section of optical fiber obtainable by a machine of the present invention;

Fig. 5 is a cross sectional view illustrating a manufacturing machine of optical fiber in accordance with the present invention;

Fig. 6 is a vertical cross sectional view taken along the line A - A shown in Fig.5;

Fig. 7 is a vertical cross sectional view taken along the line B - B shown in Fig.5;

Fig. 8 is a vertical cross sectional view taken along the line C - C shown in Fig.5;

Fig.9 is a partially broken perspective view of the machine of Fig.5;

Fig.10 is a cross sectional view showing another example of a fabrication machine of optical fiber in accordance with the present invention;

Fig.11 is a vertical cross sectional view taken along the line B - B shown in Fig.10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present invention will now be described in detail with reference to its preferred embodiments in connection with the accompanying drawings.

[0026] In the fabrication process of optical fiber of the present invention, the optical fiber as shown in Fig.4 can be obtained when cylinders having a rectangular or oval section are employed as sea part-forming cylinders. The optical fiber of Fig.1b can be obtained when the sea parts of the optical fiber are dissolved by means of a solvent. In the optical fiber of Fig.4, 20 rectangular parts are formed in total, and this part is referred to at a sea part 14 and a portion of the island parts 15 positioned between the adjacent sea parts 14 is especially referred to as a wing 16 in the present specification in conformity with Fig.1a and b. The optical fiber strongly exhibits its optical functions when a ratio of the thickness of the sea part 14 to the thickness of the wing 16 ranges from 30 : 1 to 1: 30. This may be described more in detail employing the reflection and interference conditions. The optical functions are strongly exhibited when a ratio of the optical thickness of the sea part and that of the wing is in a range between 1 : 5 and 5 : 1, and the optical functions become maximum when the ratio is 1 :1 (so-called quater wavelength). "Optical thickness" herein is defined as "geometrical thickness (ordinarily referred to simply as 'thickness' x optical refraction index".

[0027] The sea parts 14 may be left as they are in the optical fiber of Fig.4. Ordinarily, as shown in Fig.4, the target optical fiber can be obtained by dissolving the sea parts 14 with a solvent to leave only the island parts and to make the sea parts to air layers.

[0028] Generally, the refraction indexes of the island part material and of the sea part material are required to be different for generating color, the ratio of the both refractions is preferably not less than 1 : 1.1 if desired. The optical refraction indexes of the polymers constituting the fiber may be difficult to be largely different.

[0029] When, however, one is made to be polymer material (for example, PET (polyethylene terephthalate) and the other to be an air layer, the ratio of the both optical refraction indexes is 1.56 : 1 which is a very large value to be secured so that a high refraction index can be obtained even if the number of the wings are small. Because of the obtainment of the so-called remarkably vivid coloring and the like, the employment of the gas in one part is important.

[0030] In the present invention, the sea part gas can be supplied in place of the conventional sea part polymer to the sea part-forming cylinders and the island polymer can be supplied to the periphery of the cylinders so as to conduct the spinning for obtaining the optical fiber shown with solid lines in Fig.4. Accordingly, in the present invention, the sea part fluid, that is, the sea part polymer or the sea part gas is supplied to the sea part-forming cylinders.

[0031] Even if it is attempted that the island part is formed by the polymer and the sea part is formed as an air layer or another gas layer employing the machine shown in Figs.2 and 3, the polymer and the gas are joined at the stage of entering into the inlet to become composite fiber so that the island parts having the target wings 16 cannot be completely constituted.

[0032] If, conversely, the island part is formed as the air layer and the sea part is formed by the polymer, the gas changes its original shape by the time of the spinning from the spinning nozzle by means of a surrounding pressure (discharge pressure of polymer) and the target shape cannot be exhibited because the structure of the wings is connected as a whole so that the inlet flow path constituting the air layer runs from the inlet to the discharge aperture.

[0033] To the contrary, in the machine of the present invention, since the sea part fluid corresponding to the sea part polymer filling in the space between the wings 2 of the optical fiber of Fig.1 guided by the cylinders equipped on and connected with the spinning head, the whole amount of the sea part fluid supplied reaches to the spinning inlet with certainty. Since, in other words, the sea part fluid reaches to the spinning inlet through a single path, the optical fiber having the desired optical characteristics in which the space between the adjacent wings is always filled with the sea part fluid or the adjacent wings are always separated by the sea part fluid, different from the machine of Figs.2 and 3, can be fabricated.

[0034] The cross section of the cylinder is not restricted to rectangular or oval. In order to obtain optical fiber having a cross section other than that of Fig.4, the cylinder may have a portion such as an ellipse cross section suitably overlapping with the shape of the optical fiber, especially the shape of the sea part.

[0035] In order to obtain specific optical fiber, the adjacent sea parts are desirably shaped as parallel rectangular forms or parallel oval forms. If the cross section of the cylinder is circular, the desired optical characteristics cannot be obtained. However, if the optical fiber having the circular section is compressed in the direction perpendicular to the cross section, the circle is deformed to an oval to provide optical fiber having the excellent optical characteristics. In this case, the island parts are required to exist in the whole periphery of the sea parts so that it is not applicable to the conventional optical fiber shown in Fig.4.

[0036] The cross section of the sea part-forming cylinder is not required to have a same diameter along the flow of the sea part fluid, and the section may be diminished in size, for example, in the shape of taper.

[0037] The material of the cylinder is not especially restricted, and the cylinder may be constituted by material having the resistance to the sea part fluid and the island part polymer and exerting no bad influence to the polymer and the fluid.

[0038] As to the sea part polymer and the island part polymer to be used in the optical fibers spun by the present machine, it is sufficient that their optical characteristics, particularly, optical refractive indexes are different. For example, polyolefins such as polyethylene, polypropylene and the like, polyesters such as polyethylene terephthalate, polytetramethylene terephthalate and the like, polystyrene, polycarbonate, polyfluoroethylene, polyacetals, poly-phenylene sulfide, polymethyl methacrylate and the like can be used, and copolymers of these compounds can be also used. As the sea part gas, any gas which does not react with the island part polymer and does not corrode the cylinder, for example, nitrogen gas may be employed.

[0039] One example of the fabrication machine of optical fiber in accordance with the present invention will be described in detail referring to the annexed drawings, and it is readily understood that the present invention is not restricted to the specific embodiments.

[0040] Fig. 5 to Fig. 9 show a first embodiment of a fabrication machine of optical fiber according to the present invention. Fig.5 is its vertical cross sectional view; Fig.6 is a vertical cross sectional view taken along the line A - A shown in Fig.5; Fig.7 is a vertical cross sectional view taken along the line B - B shown in Fig.5; Fig.8 is a vertical cross sectional view taken along the line C - C shown in Fig.5; and Fig.9 is a partially broken perspective view.

[0041] In Figs. 5 to 9, the fabrication machine 21 of optical fiber comprises a spinning head 24 having a sea part fluid inlet 22 of a relatively large diameter in its center and a plurality of island part polymer inlets 23 in its peripheral part; and 30 pieces in total of sea part-forming cylinders 26 having upper and lower openings corresponding to the sea parts 14 of Fig.4 and downwardly mounted on a bottom plate 25 of the spinning head 24. Below the head 24 and the cylinders 25, is mounted a spinning seat 28 having a funnel-shaped spinning nozzle 27 in its center corresponding to a position below the cylinders 26.

[0042] When a sea part polymer and an island part polymer are supplied through the sea part fluid inlet 22 and the island part polymer inlets 23, respectively, of the fabrication machine of optical fiber thus constituted, the sea part polymer penetrates into the sea part-forming cylinders 26 from the bottom 25 of the head 24 while the island part polymer penetrates into a space formed by the bottom 25 of the head 24 and the upper plate of the seat 28 from the outlet of the island part polymer inlet 23 so that the two polymers fill the space between the adjacent cylinders 26 and the space around it.

[0043] The both polymers supplied to the inside and outside of the cylinders 26 are integrated at a position below the cylinders, and the integrated polymer is spun while it descends along the funnel-shaped spinning nozzle 27 to be taken out as optical fiber.

[0044] Since the sea part polymer reaches to the inlet of the spinning nozzle 27 with certainty by means of the cylinders 26 and then is spun, the adjacent wings 16 of the island parts 14 are surely separated and the adjacent wings 16 are never fused with each other as shown Fig.4 so that the optical fiber thus spun possesses the predetermined optical characteristics and the optical characteristics of the obtained optical fiber are never deteriorated.

[0045] When sea part gas and the island part polymer are supplied to the sea part fluid inlet 22 and the island part polymer inlets 23, respectively, the sea part gas penetrates into the sea part-forming cylinders 26 from the bottom 25 of the head 24 while the island part polymer penetrates into a space formed by the bottom 25 of the head 24 and the upper plate of the seat 28 from the outlet of the island part polymer inlet 23.

[0046] Then, since, during the spinning of the island polymer descending along the spinning nozzle 27, the gas is always present between the adjacent wings 16 so as to prevent the contact of the both wings 16, the optical fiber having the hollow sea parts 14 as shown in Fig. 4 may be obtained.

Examples

[0047] Although Examples of fabricating optical fiber employing the machine of the present invention will be described, these Examples are not to be construed to restrict the present invention.

Example 1

[0048] Optical fiber was fabricated employing the spinning machine shown in Figs.5 to 9. Cylinders made of stainless steel shown in Fig.8 possessed dimensions of a = 0.3 mm, b = 0.6 mm, their respective thicknesses of 0.05 mm, and a straight length of the whole inlet flow path of 8 mm, and the cylinders were projected at a height of 6 mm toward the flow-out side from the spinning nozzle. The number of the cylinders was 30 pieces in total and the respective 15 pieces were aligned in parallel in two lines and a pitch between the parallel portions was made to be 0.6 mm. In accordance with this arrangement, a dimension ratio between a width of the openings of the cylinders constituting the sea parts and the space between a cylinder and the adjacent cylinder which were aligned in parallel and constituted the island parts as 1 : 1.5.

[0049] On the other hand, the dimensions of the inlet of the funnel-shaped spinning nozzle 27 shown in Fig.7 were such that i = 1.6 mm, j = 9.9 mm, q = 0.2 mm, r = 0.9mm and the length of the straight portion was 5 mm, and the discharge opening of the funnel-shaped spinning nozzle 27 possessed the dimensions of 0.2 mm x 0.2 mm and a straight length of 0.5 mm. The specification of an extrusion machine for spinning employed in this Example was as shown in Table 1.

[0050] Polyethylene terephthalate (PET) and polystyrene (PS) were employed as an island part polymer and a sea part polymer, respectively, and the spinning was conducted under the conditions of a spinning temperature of 270 to 290 degree Cels. , the rotation number of a gear pump for the sea part polymer of 14 rpm, and that for the island part polymer being in a range of 1.5 to 3 rpm, and a roll-up speed of 5000/min.

[0051] As a result, the outer dimensions of the spun fiber were such that the thickness thereof in the direction of 15 aligned lines of the sea part layers was 3.3 µm, the thickness of the wing was 0.08 µm, and the space between the wing and the adjacent wing

Table 1

(Specification of Composite Spinning Machine)
Items			1st Extruder	2nd Extruder
			(B Block)	(A Block)
Molten (Extrusion) Part	Screw Diameter (mm)		φ 25	φ 25
	Screw Revolution (rpm)		8-80	5-50
	Max. Use Temp. (°C)		350	400
	Number of Heater Zones		3 zones	4 zones
	Gear Pump	Revolution (rpm)	14-40	3-30
		Capaci (cc/REV)	0.3	0.6
	Extruder-Gear Pump Control		Manual	Feedback
Head Part	Relief Valve of Molten Polymer		Provided

was 0.12 µm, and the optical fiber having the target optical functions could be obtained.

Example 2

[0052] The spinning machine shown in Figs. 10 and 11 was employed. Fig.10 is its vertical cross section, and Fig.11 is a horizontal cross section taken along the line B - B shown in Fig. 10.

[0053] The spinning machine is similar to that shown in Fig.5, and differs from the latter only in that the periphery of the cylinders 26 is not in contact with the upper periphery of the spinning nozzle 27 to make a space. The description of the other members is omitted by putting the same numerals as those in Fig.5.

[0054] The shape of the openings of the cylinders was the same as those of Example 1, and the inlet dimensions of the funnel-shaped spinning nozzle 27 were such that k = 2.6 mm, l = 9.9 mm, m = 0,2 mm, n = 3 mm as shown in Fig.11, and those of the other members were same as those of Example 1.

[0055] When the spinning was conducted under the same conditions as those of Example 1 except that air was supplied in place of the sea part polymer, the outer dimensions of the spun fiber were such that the thickness thereof in the direction of 15 aligned lines of the air layers was 4.0 mm, the thickness of the wing was 0.08 µm, and the fiber having the two lines in which the air layers as the space between the wings were stretched at an interval of 0.12 µm was obtained, and this fiber excellently exhibited the optical functions.

[0056] Although the present invention has been described in its preferred embodiments with reference to the accompanying drawings, it ireadily understood that the present invention is not restricted to the preferred embodiments and that various changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. A fabrication process of optical fiber, comprising:

supplying sea part fluid and island part polymer to a plurality of sea part-forming cylinders and island polymer flow paths, respectively, of a spinning head including, at the bottom thereof, the cylinders each having upper and lower openings at a uniform space so as to obtain a ratio of an internal dimension thickness or an inner diameter of the cylinder to space between the adjacent cylinders in a range of 30:1 to 1:30, and the island part polymer flow paths around the cylinders; and

conducting the spinning by means of a funnel-shaped spinning nozzle of a spinning seat positioned below the cylinders.

2. A fabrication process of claim 1, wherein the sea part fluid is gas.

3. A fabrication process of claim 1, wherein the sea part-forming cylinders have a rectangular or oval section for obtaining optical fiber having rectangular or oval sea parts.

4. A fabrication process of claim 1, wherein the sca part-forming cylinders have a circular section for obtaining optical fiber having oval sea parts by compressing the obtained sea parts having a circular section.

5. Optical fiber fabricated through a process comprising:

supplying sea part fluid and island part polymer to a plurality of sea part-forming cylinders and island polymer flow paths, respectively, of a spinning head including, at the bottom thereof, the cylinders each having upper and lower openings at a uniform space so as to obtain a ratio of an internal dimension thickness or an inner diameter of the cylinder to space between the adjacent cylinders in a range of 30:1 to 1:30, and the island part polymer flow paths around the cylinders; and

conducting the spinning by means of a funnel-shaped spinning nozzle of a spinning seat positioned below the cylinders.

6. Optical fiber of claim 5, wherein the sea part fluid is gas.

7. Optical fiber of claim 5, wherein the sea part-forming cylinders have a rectangular or oval section for obtaining optical fiber having rectangular or oval sea parts.

8. Optical fiber of claim 5, wherein the sea part-forming cylinders have a circular section for obtaining optical fiber having oval sea parts by compressing the obtained sea parts having a circular section.

9. A fabrication machine of optical fiber, comprising;

a spinning head including, at the bottom thereof, cylinders each having upper and lower openings at a uniform space so as to obtain a ratio of an internal dimension thickness or an inner diameter of the cylinder to space between the adjacent cylinders in a range of 30:1 to 1:30, a sea part fluid inlet for supplying sea part fluid into the cylinders and an island part polymer inlet for supplying island part polymer into spaces between the cylinders and those around the cylinders; and

a spinning seat which is positioned below the cylinders and possesses a funnel-shaped spinning nozzle for spinning at least the island part polymer.

Drawing