KR100956486B1 - Furnace for drawing down optical fiber preform into optical fiber by configuration factor - Google Patents

Abstract

The present invention relates to an optical fiber edge line using a shape coefficient, and an optical fiber edge line including an annular heating element having an inner diameter D and a length l according to the present invention, wherein the configuration factor (F) satisfies the following equation: _{Heater- base material} ) characterized in that the inner diameter (D) and the length (l) of the heating element is designed so that 0.4 ~ 0.6.

[Equation]

Where R = D / d, L = l / d, A = L ² + R ^2-1 , B = L ² -R ² + 1,

d: represents the diameter of the base material.)

According to the present invention, the heat distribution is uniformly transmitted to the outer circumferential surface of the optical fiber base material when the optical fiber is edged, thereby reducing the specific ration of the optical fiber. In addition, the optical fiber drawn in accordance with the present invention can be used suitably for ultra-high speed and long-distance optical communication by reducing the polarization mode dispersion (Polarization Mode Dispersion).

Edge line, heating element, shape factor, heat radiant energy, optical fiber base material

Description

FURNACE FOR DRAWING DOWN OPTICAL FIBER PREFORM INTO OPTICAL FIBER BY CONFIGURATION FACTOR}

The present invention relates to an optical fiber cutting line, and more particularly, to a cutting line for uniformly transmitting the heat radiation energy generated in the cutting line to the outer peripheral surface of the optical fiber base material.

In general, a method of manufacturing an optical fiber is divided into a process of forming an optical fiber preform and a process of drawing an optical fiber from the optical fiber base material.

The method of manufacturing the optical fiber base material may include a modified chemical vapor deposition ("MCVD"), a vapor phase deposition ("VAD"), and an external vapor deposition ("outer"). OVD ") method.

The MCVD method injects a raw gas such as SiCl ₄ or GeCl ₄ into the rotating quartz tube together with oxygen gas, and repeatedly heats the outer wall of the quartz tube several times using a moving heat source such as an oxygen-hydrogen burner. The soot is repeatedly deposited on the inner wall in layers. After the deposition is completed, the quartz tube outer wall is reciprocally heated several times above the deposition temperature. Accordingly, the quartz tube on which the soot is deposited collapses while the inner and outer diameters decrease due to the pressure difference between the inner and outer walls and the surface tension, thereby forming an optical fiber base rod capable of cutting the optical fiber.

The VAD method, the injected into a quartz rod lower rotating SiCl _4, GeCl _4-dispersion water of a raw material gas such as rise-to the lower quartz of the soot (soot) particles rods to cause the flame hydrolysis by heating with hydrogen burner Deposit. In addition, as the quartz rod is raised in the axial direction, soot particles are grown at the bottom of the quartz rod to form a porous optical fiber base material. The porous base material is sintered and vitrified to become an optical fiber base material capable of cutting the optical fiber.

In the OVD method, a raw material gas such as SiCl ₄ or GeCl ₄ sprayed on a rotating quartz rod outer wall is repeatedly heated several times using a moving heat source such as an oxygen-hydrogen burner to induce a flame hydrolysis reaction. Evaporation of the soot (soot) is repeatedly performed in units of layers to form a deposition layer. The quartz rod is removed from the deposition layer, and the outer wall of the deposition layer is reciprocally heated several times through a moving heat source to form an edgeable optical fiber base material.

When the optical fiber base material is manufactured by the above-described method or the like, the optical fiber base material is put into a cutting process, heated and melted above a predetermined temperature, and drawn into an optical fiber having a diameter of several hundred micrometers. However, the specific ratio of the base fiber of the optical fiber and the ratio of the finished optical fiber may be different. The main cause of such a change in specific ratio is that heat radiation energy is not uniformly transmitted to the outer circumferential surface of the optical fiber base material when the optical fiber base material introduced to the edge line is heated.

1 is a diagram measuring the heating element temperature of the cutting line in the circumferential direction.

Referring to FIG. 1, the temperature distribution of an ideal edge line is uniformly expressed as shown in FIG. 1A, but the temperature distribution of the actually measured edge line shows a non-uniform distribution as shown in FIG. 1B. When the optical fiber base material is heated using a cutting line having a temperature distribution as shown in FIG. 1 (b), the heat distribution of the outer circumferential surface of the optical fiber base material is not uniformly formed, and thus the viscosity varies in the circumferential direction. As a result, the optical fiber having an elliptical cross section is edged, and the specific ratio of the optical fiber is increased.

On the other hand, Japanese Laid-Open Patent Publication No. 2002-249334 improves the refractive index difference between the clad and the core by maintaining the length ratio of the outer diameter (D) of the optical fiber base material and the furnace body (L) surrounding the heater to L / D ≥ 8 It describes.

In addition, Japanese Laid-Open Patent Publication No. 2004-224587 maintains the length L of the heater and the inner diameter E of the heater according to the following equation according to the diameter D of the base material, thereby reducing the specific ratio of the optical fiber. It describes.

L (mm) ≥ 5D (mm)-50mm

L (mm) ≥ 5E (mm)-50mm

However, the above two methods only describe the length of the heater (or the length of the furnace) with respect to the radius of the base material, and do not consider the heat distribution of the outer peripheral surface of the optical fiber base material introduced into the heater. That is, when the length of the heater (or furnace) is changed, non-uniform temperature distribution may occur in the circumferential direction of the heater as shown in FIG. And the optical fiber base material received the heat radiation energy from the heater to form a non-uniform heat distribution on the outer peripheral surface, thereby increasing the specific ratio of the drawn optical fiber.

The present invention has been proposed to solve the above problems, and an object of the present invention is to provide an optical fiber edge line which uniformly transmits thermal radiation energy to an outer circumferential surface of an optical fiber base material to reduce specific ratio of the final optical fiber.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

According to the present invention for achieving the above object, the optical fiber edge line including the annular heating element having an inner diameter D and the length l, the configuration factor (F _{heating element- base material} ) satisfying the following equation is 0.4 ~ It is characterized in that the inner diameter (D) and the length (l) of the heating element is designed to be 0.6.

[Equation]

Where R = D / d, L = l / d, A = L ² + R ^2-1 , B = L ² -R ² + 1,

d: represents the diameter of the base material.)

According to the present invention, the heat distribution of the outer circumferential surface of the optical fiber base material is made uniform so as to reduce the specific phenomena of the increase in the specific ratio of the optical fiber generated in the cutting process.

In addition, the optical fiber drawn in accordance with the present invention is useful for ultra-high speed optical communication by reducing the polarization mode dispersion (Polarization Mode Dispersion).

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which: There will be. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a view showing a schematic configuration of an optical fiber cutting apparatus according to an embodiment of the present invention.

As shown in FIG. 2, the optical fiber cutting process apparatus for cutting the optical fiber 40 in the optical fiber base material 20 includes a support part 10, a cutting line 30, a coating part 50, a hardening part 60, and a turn. A pulley 70, a turn pulley, and a winder 80.

The support unit 10 supports the optical fiber base material 20, and the edge line 30 heats and melts the optical fiber base material 20 to a predetermined temperature or more to edge the optical fiber 40 of several hundred micrometers. .

The coating part 50 coats the surface of the drawn optical fiber 40 with a liquid coating material, and the curing part 60 cures the coating material. The turn poly 70 changes the movement path of the cured optical fiber 40 in the direction of the winding machine 80, and the winding machine 80 winds up the optical fiber 40 to organize it.

Figure 3 shows a cross-sectional view of the edge line, according to a preferred embodiment of the present invention.

As shown in FIG. 3, the edge line 30 according to an embodiment of the present invention includes a heating element 31 for generating thermal radiation energy for heating and melting the optical fiber base material 20, from the heating element 31. It is arranged spaced apart a predetermined distance, the heat insulating material 32 to block the heat from the heat generating element 31, the case 33 to surround the heat insulating material 32 to protect the heat generating element 31 and the heat insulating material 32 from external impact. It includes.

On the other hand, in order to uniformly transfer the thermal radiation energy to the outer peripheral surface of the optical fiber base material 20, the inner diameter (D) and the length (l) of the heating element 31 is adjusted according to the diameter of the optical fiber base material 20.

The following equation (2) is a shape factor _- a formula for calculating the (configuration factor, F _{the heating element base material),} the shape coefficient (F _{heating-base material)} is a heat radiation of the heating element (31) optical fiber preform 20 and the heating element It means a ratio passing directly through the space (D-d) between the (31), and directly transmitted to the outer peripheral surface of the optical fiber base material (20).

R = D / d, L = l / d, A = L ² + R ^2-1 , B = L ² -R ² + 1

D: heating element inner diameter d: diameter of optical fiber base material

l: heating element length

(Reference: Thermal radiation Heat Transfer 3 ^rd ed., Published by Hemisphere Publishing Corporation, 1034p)

The shape coefficient (F _{heating element- base material} ) is represented by 0 ~ 1, the larger the shape coefficient (F _{heating element- base} material), the narrower the space (D-d) between the heating element 31 and the optical fiber base material 20 (that is, In this case, the optical fiber base material 20 and the heating element 31 are closer to each other, which means that the loss of thermal radiation energy transmitted from the heating element 31 to the outer circumferential surface of the optical fiber base material 20 is small. On the other hand, as the shape coefficient (F _{heating element- base material} ) is smaller, the space (D-d) between the heating element 31 and the base material becomes wider, which is transmitted from the heating element 31 to the outer circumferential surface of the optical fiber base material 20. The loss of thermal radiation becomes large.

As shown in FIG. 1, in a general edge line, the heat distribution in the circumferential direction θ of the heating element 31 is nonuniform. Therefore, when the shape coefficient (F _{heating element- base material} ) is too large (ie, close to 1), the thermal radiation energy of the nonuniform heating element 31 is transmitted to the outer peripheral surface of the optical fiber base material 20 as it is, the optical fiber base material 20 The heat distribution of is uneven.

Therefore, by appropriately adjusting the shape coefficient (F _{heating element- base material} ), it is possible to uniformly transmit the thermal radiation energy of the nonuniform heating element 31 to the outer peripheral surface of the optical fiber base material 20. That is, even if the thermal radiation energy is unevenly emitted from the heating element 31, the shape coefficient (F _{heating element-the base material} ) can be adjusted to make the thermal radiation energy absorbed by the outer circumferential surface of the optical fiber base material 20 uniform. The shape coefficient F _{heating element- base} material can be adjusted by adjusting the length l and the inner diameter D of the heating element 31 according to the diameter d of the optical fiber base material 20 based on Equation 2.

Table 1 changes the heat distribution of the outer peripheral surface of the optical fiber base material 20 by adjusting the shape coefficient (F _{heating element- base material} ) based on Equation 2 during the cutting process, and thus the clad specific ratio (%) of the optical fiber 40 drawn. ) Is measured.

 number  Fiber Optic Base Material Diameter (mm)  Heating element diameter (mm)  Heating element length (mm) F _{heating element- base material}  Clad specific ratio (%) One 50 100 104 0.34 0.26 2 60 100 104 0.44 0.15 3 70 100 104 0.55 0.08 4 80 100 104 0.68 0.26 5 90 100 104 0.83 0.37 6 90 145 150 0.46 0.19 7 100 145 150 0.54 0.09 8 110 145 150 0.62 0.25 9 120 145 150 0.72 0.27 10 130 145 150 0.82 0.40

Referring to Table 1, when the shape coefficient (F _{heating element-the base material} ) exceeds 0.6, the clad specific ratio of the drawn optical fiber is 0.25% or more.

When the shape coefficient (F _{heating element- base material} ) is less than 0.4, the clad specific ratio of the optical fiber is 0.25% or more. The reason is that the space D-d of the heating element 31 and the optical fiber base material 20 is widened so that the flow of thermal radiation energy passing through the space D-d becomes irregular, and thus the thermal radiation energy. This is because the non-uniform heat distribution appears on the outer circumferential surface of the optical fiber base material 20 received.

Therefore, the length l and the inner diameter D of the heating element 31 of the cutting line 30 are preferably designed such that the shape factor F _{heating element-the base material} satisfies 0.4 to 0.6.

Through the above-described embodiment, it is possible to reduce the specific ration increase of the optical fiber generated in the cutting process. In addition, the optical fiber manufactured according to the present invention can be used suitably for ultra-high speed and long-distance optical communication because the specific ratio is improved and the polarization mode dispersion is reduced.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

The following drawings, which are attached to this specification, illustrate exemplary embodiments of the present invention, and together with the detailed description of the present invention, serve to further understand the technical spirit of the present invention. It should not be construed as limited to.

1 is a diagram measuring the heating element temperature of the cutting line in the circumferential direction.

2 is a view showing a schematic configuration of an optical fiber cutting apparatus according to an embodiment of the present invention.

Figure 3 shows a cross-sectional view of the edge line, according to a preferred embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: support portion 20: optical fiber base material

30: cutting line 31: heating element

32: insulation 33: case

40: optical fiber 50: coating

60: hardening part 70: turn pulley

80: winder

Claims (1)

An optical fiber edge line comprising an annular heating element having an inner diameter D and a length l, An inner diameter (D) and a length (l) of the heating element are designed such that a configuration factor (F _{heating element-base material} ) satisfying the following equation is 0.4 to 0.6. [Equation]

Where R = D / d, L = l / d, A = L ² + R ^2-1 , B = L ² -R ² + 1, d: represents the diameter of the base material.)

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