JP6085788B2 - Light shielding fiber, bundle fiber, light shielding fiber manufacturing method, and bundle fiber manufacturing method - Google Patents

Description

  The present invention relates to a light shielding fiber having a black coating, a method for producing the light shielding fiber, a bundle fiber in which a plurality of optical fibers including the light shielding fiber are bundled, and a method for producing the bundle fiber.

  Conventionally, an optical fiber having a black carbonaceous coating is known (see, for example, Patent Document 1). Since this optical fiber has a black carbonaceous coating film, leakage of light in the optical fiber and entry of light from the outside can be prevented. The carbonaceous coating of this optical fiber is formed by exposing the surface to a gas containing carbon during the drawing process during the production of the optical fiber.

JP 02-267140 A JP 2009-31548 A

  However, the heat-resistant temperature of such a carbonaceous film is about 800 ° C., and if an optical fiber having a carbonaceous film is to be processed such as drawing, it is heated at a high temperature of 800 ° C. or higher (for example, Patent Documents). 2), and there was a problem that the carbonaceous film was destroyed.

  Accordingly, in order to solve the above-described problems, the present invention provides a light-shielding fiber that can shield the light propagation part and the outside and can withstand high-temperature heating by drawing or the like, and a bundle fiber in which a plurality of optical fibers including the light-shielding fiber are bundled An object of the present invention is to provide a method for manufacturing the light shielding fiber and a method for manufacturing the bundle fiber.

  In order to solve the above-mentioned problems, the present invention forms black glass containing bismuth on the clad surface layer of an optical fiber.

  Specifically, the light shielding fiber according to the present invention has a core at the center and a clad having a profile in which the bismuth content decreases from the outer periphery toward the core.

  Quartz-based glass containing bismuth is black, and if it is disposed on the cladding surface layer, the core and the outside can be shielded from light. The heat resistant temperature of the quartz glass is 1800 ° C. For this reason, it is not destroyed even by processing such as drawing of the optical fiber. Therefore, the present invention can provide a light-shielding fiber that can shield the core from the outside and can withstand high-temperature heating by processing such as stretching.

  The light shielding fiber according to the present invention further includes a quartz layer outside the cladding. Bubble generation can be prevented when drawing the base material.

The light shielding fiber can be manufactured by the light shielding fiber manufacturing method according to the present invention. Specifically, the light shielding fiber manufacturing method according to the present invention includes a soot forming step of forming a soot of an optical fiber by a gas phase axial method (VAD),
A presintering step of presintering the soot formed in the soot forming step;
A liquid immersion step of immersing the soot after the preliminary sintering step in a liquid containing bismuth;
A sintering step of heating the soot after the immersion step;
Inserting the soot after the sintering step into a quartz tube and sealing one end of the quartz tube, and inserting the quartz tube in the furnace after the quartz tube insertion step together with the quartz tube from the one end of the quartz tube A drawing step of drawing.

  The bundle fiber according to the present invention is a bundle fiber obtained by bundling a plurality of optical fibers, wherein at least one of the optical fibers is the light shielding fiber, and the diameter of the optical fiber at one end is the other part of the optical fiber. It is smaller than the diameter. Since the light-shielding fiber has heat resistance, it is not broken even by processing such as drawing of the optical fiber when manufacturing the bundle fiber. Therefore, the present invention can provide a bundle fiber in which a plurality of optical fibers including a light shielding fiber are bundled.

The bundle fiber can be manufactured by the bundle fiber manufacturing method according to the present invention. Specifically, the bundle fiber manufacturing method according to the present invention includes a bundling step of bundling a plurality of optical fibers, at least one of which is a light shielding fiber manufactured by the light shielding fiber manufacturing method, and inserting the bundle into one glass tube. ,
After the bundling step, a part of the glass tube is heated, and a stretching step of stretching the glass tube of the heated part and the optical fiber in the glass tube;
After the stretching step, a cutting step of cutting the heated portion of the glass tube;
Repeat in order.

The bundle fiber can also be manufactured by the bundle fiber manufacturing method according to the present invention. Specifically, in the bundle fiber manufacturing method according to the present invention, after inserting a plurality of optical fibers, at least one of which is a light shielding fiber manufactured by the light shielding fiber manufacturing method, into a glass tube, A ring forming step in which one end and the other end are connected to form a ring;
After the ring formation step, an alignment step of arranging connection points between one end and the other end of all the optical fibers in the glass tube,
After the alignment step, a part of the glass tube is heated, and a drawing step of drawing the glass tube of the heated portion and the optical fiber in the glass tube;
After the stretching step, a cutting step of cutting the heated portion of the glass tube;
Repeat in order.

  The optical fiber bundle is cut together with the glass tube in the cutting step. For this reason, the position coordinate of each optical fiber corresponds in both cut surfaces. For this reason, when an image is transferred with this bundle fiber, image distortion can be prevented.

  The present invention relates to a light shielding fiber that can shield a light propagation part and the outside and can withstand high temperature heating by processing such as stretching, a bundle fiber in which a plurality of optical fibers including the light shielding fiber are bundled, a method for manufacturing the light shielding fiber, and A method for manufacturing the bundle fiber can be provided.

It is a figure explaining the cross section of the preform | base_material for manufacturing the light shielding fiber which concerns on this invention. It is a figure explaining the cross section of the preform | base_material for manufacturing the light shielding fiber which concerns on this invention. It is a figure explaining the cross section of the light shielding fiber which concerns on this invention. It is a figure explaining the light-shielding fiber manufacturing method which concerns on this invention. It is a figure explaining the light-shielding fiber manufacturing method which concerns on this invention. It is a figure explaining the light-shielding fiber manufacturing method which concerns on this invention. It is a figure explaining the light-shielding fiber manufacturing method which concerns on this invention. It is a figure explaining the light-shielding fiber manufacturing method which concerns on this invention. It is a figure explaining the light-shielding fiber manufacturing method which concerns on this invention. It is a figure explaining the bundle fiber which concerns on this invention. It is a figure explaining the bundle fiber manufacturing method concerning the present invention. It is a figure explaining the bundle fiber manufacturing method concerning the present invention. It is a figure explaining the bundle fiber manufacturing method concerning the present invention. It is a figure explaining the bundle fiber manufacturing method concerning the present invention. It is a figure explaining the bundle fiber manufacturing method concerning the present invention. It is a figure explaining the bundle fiber manufacturing method concerning the present invention. It is a figure explaining the bundle fiber manufacturing method concerning the present invention. It is a figure explaining the bundle fiber manufacturing method concerning the present invention. It is a figure explaining the bundle fiber manufacturing method concerning the present invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 3A is a cross-sectional view of the light shielding fiber 18 of the present embodiment. The light shielding fiber 18 includes a core 31 at the center and a clad 32 having a profile in which the bismuth content decreases from the outer periphery toward the core 31. In FIG. 3A, a region containing bismuth in the cladding 32 is indicated by a bismuth-containing region 33. The light shielding fiber 18 further includes a quartz layer 34 outside the cladding 32.

  For example, the diameter of the core 31 is 50 μm, the diameter including the core 31 and the clad 32 is 125 μm, and the thickness of the quartz layer 34 is 10 ± 1 μm. Moreover, the thickness of the bismuth containing area | region 33 is 15-30 micrometers. The bismuth-containing region 33 is black in the visible light region, and has a light shielding function and can prevent crosstalk with an adjacent optical fiber if communication is performed using visible light.

  FIGS. 3B and 3C are diagrams for explaining the bismuth concentration profile of the bismuth-containing region 33. FIG. The horizontal axis represents the position of the light shielding fiber 18 in the diameter direction, and the vertical axis represents the concentration of bismuth. The bismuth-containing region 33 is a profile in which the bismuth content decreases from the outer periphery toward the core 31 as shown in FIG. Moreover, the bismuth containing area | region 33 may be the profile which bismuth contains only to the predetermined range of the direction of the core 31 from an outer periphery like FIG.3 (c).

4-9 is a figure explaining the light-shielding fiber manufacturing method which manufactures the light-shielding fiber 18. FIG. The light-shielding fiber manufacturing method includes a soot forming step (FIG. 4) for forming a soot 11 of an optical fiber by a gas phase axial method (VAD),
A presintering step (FIG. 5) for presintering the soot 11 formed in the soot forming step;
A liquid immersion process (FIG. 6) in which the soot 24 after the preliminary sintering process is immersed in a liquid 25 containing bismuth;
A sintering step (FIG. 7) for heating the soot 24 after the liquid immersion step;
A quartz tube insertion step (FIG. 8) for inserting the soot 14 after the sintering step into the quartz tube 26 and sealing one end of the quartz tube 16;
A drawing process (FIG. 9) for drawing the soot 14 after the quartz tube insertion process in the furnace from one end of the quartz tube 26 together with the quartz tube 26;
including.

Hereinafter, the method for manufacturing the light shielding fiber will be described in detail.
(1) Soot formation process (FIG. 4)
Addition of additives such as germanium chloride, phosphorus chloride, boron chloride, titanium chloride, aluminum chloride, etc., capable of controlling the refractive index, to the main raw material silicon chloride, transport to the burner 21 and pass through the oxyhydrogen flame 20 A rod-like soot 11 containing silicon oxide and an oxide of its additive is produced by a decomposition method. This process is also referred to as a gas phase axis (VAD) method. FIG. 1 is a diagram for explaining a cross section of the soot 11. The soot 11 has a soot 12 with a high refractive index at the center and a soot 13 with a low refractive index on the outside. The refractive index profile of the soot 12 is a flat shape in the diameter direction or a shape having a high central portion and a low peripheral portion. Alternatively, the soot 11 may be produced by a method similar to the OVD method in which soot is deposited on the outer periphery of the silica-based optical fiber preform.

(2) OH group removal step In order to remove OH groups from the soot 11, the soot 11 is placed in chlorine gas and He gas, and heated at a temperature of 900 ° C or higher for 50 hours or more.

(3) Temporary sintering process (Fig. 5)
In order to take in the soot 11 an additive for preventing the soot from collapsing in the liquid immersion process of the next process, the soot 11 is a high-purity inert gas (He, He, within a temperature range of 1400 to 1550 ° C. Ar, N2, etc.) 23 is sent at a feed rate of 4 mm / min or less in the atmosphere to prepare the pre-sintered soot 24.

(4) Immersion process (Figure 6)
The pre-sintered soot 24 is immersed in a solution 25 containing a light shielding additive. The solution 25 is a liquid in which bismuth oxide and aluminum oxide are dissolved in acetate. In order to synthesize the light shielding glass in the subsequent sintering step, the weight ratio of bismuth oxide to aluminum oxide is preferably in the range of 1: 1 to 3: 1. The pre-sintered soot 24 is immersed in the solution at a feed rate of 0.5 to 2 mm / min. When all the immersion is completed, the pre-sintered soot 24 containing bismuth is taken out from the solution 25 immediately.

(5) Sintering process (Fig. 7)
The pre-sintered soot 24 taken out after immersion is dried and then vitrified in a sintering process. In the sintering step, when the temperature of the electric furnace 22 is in the range of 1650 to 1800 ° C. and the soot diameter is 45 mm or less, the pre-sintered soot 24 is transported from the upper part of the electric furnace at a feed rate of 2 mm / min or less. The preliminary sintering soot 24 becomes the black glass rod 14 by the sintering process. The black glass rod 14 becomes a light shielding optical fiber preform. The cross-sectional shape of the black glass rod 14 is shown in FIG. The black glass rod 14 has a glass portion 16 having a high refractive index as a core and a glass portion 17 having a low refractive index as a cladding. The glass portion 17 has a black portion 15 containing bismuth on the outer peripheral side.

(6) Quartz tube insertion process (Figure 8)
The black glass rod 14 formed in the sintering process becomes a quartz-based light-shielding optical fiber preform whose surface is black and whose inside is transparent. Next, a light shielding optical fiber is manufactured by a drawing process in which the base material is processed into an optical fiber. The drawing process is a process for producing an optical fiber by drawing with an electric furnace for producing a silica-based optical fiber. However, a large amount of bismuth oxide is distributed on the surface of the base material. For this reason, if the drawing process is performed immediately after the sintering process, bubbles are generated from the surface of the base material, and optical loss as an optical fiber increases. In order to prevent this, a quartz tube insertion process is performed after the sintering process. In the quartz tube insertion step, the base material (black glass rod 14) is inserted into the quartz tube 26 and sealed at one end.

(7) Drawing process (Figure 9)
The base material after the quartz tube insertion step is inserted into a drawing furnace from the side where the quartz tube 26 is sealed. By drawing the black glass rod 14 together with the quartz tube 26, generation of bubbles on the surface can be prevented. The optimum drawing temperature is 1900-2000 ° C. The light shielding fiber 18 obtained in the temperature drawing step has a cross section as shown in FIG.

(Embodiment 2)
FIG. 10 is a diagram illustrating the bundle fiber 50 of the present embodiment. The bundle fiber 50 is a bundle fiber in which a plurality of optical fibers 38 are bundled, and at least one optical fiber is the light shielding fiber 18 of the first embodiment, and the diameter of the optical fiber 38 at one end is the optical fiber of the other part. It is smaller than the diameter of 38. The bundle fiber 50 has a funnel-shaped glass tube 54 disposed at one end thereof, and a portion other than the glass tube 54 is covered with an outer coating 55.

  FIG. 10 also shows a cross-sectional view taken along line A-A ′ near one end and a cross-sectional view taken along line B-B ′, which is another part. As shown in this sectional view, the diameter of the optical fiber 38 at one end is smaller than the diameter of the optical fiber 38 at the other part. In FIG. 10, four fibers near the center of the bundle fiber are the light shielding fibers 18, but only one light shielding fiber 18 or all of the light shielding fibers 18 may be used. The light shielding fiber 18 can reduce crosstalk with other optical fibers 38 and the light shielding fiber 18.

FIGS. 11-13 is a figure explaining the bundle fiber manufacturing method (short fiber) which manufactures the bundle fiber 50. FIG. This bundle fiber manufacturing method bundles a plurality of optical fibers 38 including at least one light-shielding fiber 18 manufactured by the light-shielding fiber manufacturing method described in the first embodiment and inserts them into one glass tube 41 (FIG. 11) and
After the bundling step, a part of the glass tube 41 is heated, and a drawing step (FIG. 12) for drawing the glass tube 41 of the heated part and the optical fiber 38 in the glass tube 41;
After the stretching step, a cutting step (FIG. 13) for cutting the heated portion of the glass tube 41;
Repeat in order.

Hereinafter, the bundle fiber manufacturing method (short fiber) will be described in detail.
(1) Bundling process (Fig. 11)
A plurality of optical fibers 38 including at least one light shielding fiber 18 are bundled and inserted into the glass tube 41. For example, the glass tube 41 is quartz. If a glass tube with a slit having an axial slit is used, it is not necessary to move the glass tube to a desired location after inserting the optical fiber, and the manufacturing becomes easy.
(2) Stretching process (Fig. 12)
The vicinity of the center of the glass tube 41 is heated by the heating means 42, and when the glass tube 42 and the optical fiber 38 are softened, the glass tube 42 and the optical fiber 38 are stretched together so as to separate both ends of the glass tube 41. The heating means 42 is, for example, a burner or an electric furnace.
(3) Cutting process (FIG. 13)
After the stretching step, the glass tube 41 and the optical fiber 38 are cooled and cut at a heated portion, that is, a portion (CC ′ line) that has been stretched and has a reduced diameter.
(4) Outer coating forming step A protective outer coating 55 is placed on the bundle fiber manufactured in the cutting step. The outer coating 55 is, for example, a heat shrinkable tube.

  The light shielding fiber 18 manufactured in the first embodiment has heat resistance. For this reason, the bundle fiber 50 can be manufactured by the bundle fiber manufacturing method which employs the light shielding fiber 18 and is heated by the burner 42 as described in the present embodiment.

14-19 is a figure explaining the bundle fiber manufacturing method which manufactures the bundle fiber 50. FIG. In this bundle fiber manufacturing method, at least one optical fiber 38 that is the light shielding fiber 18 manufactured by the light shielding fiber manufacturing method described in the first embodiment is inserted into the glass tube 41, and then each of the optical fibers 38. A ring forming step (FIG. 14) for connecting one end and the other to form a ring;
After the ring formation step, an alignment step (FIG. 15) in which the connection points between one end and the other end of all the optical fibers 38 are arranged in the glass tube 41;
After the alignment step, a part of the glass tube 41 is heated, and a drawing step (FIG. 16) for drawing the glass tube 41 in the heated portion and the optical fiber 38 in the glass tube;
After the stretching step, a cutting step (FIGS. 17 and 18) for cutting the heated portion of the glass tube 41;
Repeat in order.

Hereinafter, the bundle fiber manufacturing method (long fiber) will be described in detail.
(1) Ring formation process (FIG. 14)
After the light shielding fiber 18 or a normal optical fiber is passed through the glass tube 41, the tips of the fibers are fused and connected to each other to form a ring shape.
(2) Positioning process (FIG. 15)
Similarly, prepare many optical fiber rings and bundle them. If a glass tube with a slit having a slit in the axial direction is used, an optical fiber that is already in the shape of a ring can be inserted at a desired position, and manufacturing becomes easy.
(3) Stretching process (Fig. 16)
The center portion of the glass tube 41 is heated and stretched by a burner 42.
(4) Cutting process (FIGS. 17 and 18)
Cut at the portion (CC ′ line) where the diameter has been narrowed by stretching.

  According to this method, the long bundle fiber 50A shown in FIG. 19 can be formed, and the position of the fiber of the optical fiber 38 is the same at the observation position on the side opposite to the image capturing position. Absent. Further, when the light shielding fiber 18 described in the first embodiment is used as an optical fiber, since the black portion 15 is at the boundary of the optical fiber, a long bundle fiber capable of transmitting a clear image without interference between the light shielding fibers 18. Can provide.

11: Soot 12: Soot with high refractive index 13: Soot with low refractive index 14: Black glass rod 15: Black portion 16: Glass portion with high refractive index 17: Glass portion with low refractive index 18: Light shielding fiber 20: Oxyhydrogen Flame 21: Burner 22: Electric furnace 23: Inert gas 24: Temporary sintering soot 25: Solution 26: Quartz tube 31: Core 32: Clad 33: Bismuth-containing region 34: Quartz layer 38: Optical fiber 41: Glass tube 42 : Heating means 50: Bundle fiber (short fiber)
50A: Bundle fiber (long fiber)
54: Glass tube 55: Outer coating

Claims (3)

A soot forming process for forming an optical fiber soot;
A presintering step of presintering the soot formed in the soot forming step;
A liquid immersion step of immersing the soot after the preliminary sintering step in a liquid containing bismuth oxide ;
A sintering step of heating the soot after the immersion step;
Inserting the soot after the sintering step into a quartz tube, sealing the quartz tube, and sealing one end of the quartz tube;
A drawing step of drawing the soot after the quartz tube insertion step in the furnace together with the quartz tube from the one end of the quartz tube;
A method for manufacturing a light-shielding fiber. A bundling step of bundling a plurality of optical fibers, at least one of which is a light shielding fiber manufactured by the method of manufacturing a light shielding fiber according to claim 1 , and inserting the optical fiber into one glass tube;
After the bundling step, a part of the glass tube is heated, and a stretching step of stretching the glass tube of the heated part and the optical fiber in the glass tube;
After the stretching step, a cutting step of cutting the heated portion of the glass tube;
The bundle optical fiber manufacturing method which performs these in order. After inserting a plurality of optical fibers, at least one of which is a light shielding fiber manufactured by the method of manufacturing a light shielding fiber according to claim 1, into one glass tube, one end and the other end of each of the optical fibers are connected to form a ring. A ring forming step;
After the ring formation step, an alignment step of arranging connection points between one end and the other end of all the optical fibers in the glass tube,
After the alignment step, a part of the glass tube is heated, and a drawing step of drawing the glass tube of the heated portion and the optical fiber in the glass tube;
After the stretching step, a cutting step of cutting the heated portion of the glass tube;
The bundle optical fiber manufacturing method which performs these in order.

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