JP6887201B2 - Optical fiber manufacturing method and optical fiber - Google Patents

Description

The present invention relates to an optical fiber manufacturing method and an optical fiber.

An optical fiber in which a region containing a large number of minute and irregular bubbles (hereinafter, may be referred to as a microbubble region) is formed in a clad portion of the optical fiber so as to surround the core portion is disclosed (Patent Document). See 1-3). Here, the irregular bubble means a bubble having a non-uniform size and an irregular arrangement.

U.S. Pat. No. 8464556 U.S. Pat. No. 792,675 U.S. Pat. No. 7,930,904

However, in Patent Documents 1 to 3, an optical fiber base material in which a microbubble region is formed is manufactured, and an optical fiber is drawn from the optical fiber base material to manufacture an optical fiber. In such a manufacturing method, the characteristics of the microbubble region (ratio of the volume of bubbles and glass in the region, etc.) are almost determined at the time of manufacturing the optical fiber base material, so that the microbubble region in the actually manufactured optical fiber is determined. It may be difficult to control the characteristics of the above to the desired characteristics.

The present invention has been made in view of the above, and an object of the present invention is to provide an optical fiber manufacturing method and an optical fiber in which the characteristics of a microbubble region can be easily controlled.

In order to solve the above-mentioned problems and achieve the object, the method for manufacturing an optical fiber according to one aspect of the present invention includes a core portion made of glass and a clad portion made of glass and formed on the outer periphery of the core portion. A second clad region formed so as to be adjacent to the outer periphery of the core portion and a second clad region formed at a position separated from the core portion and containing minute and irregular bubbles. A method for manufacturing an optical fiber having a clad region, the core rod including a core forming portion to be the core portion and a clad forming portion to be the first clad region formed so as to be adjacent to the outer periphery of the core forming portion. The insertion step of inserting the glass into a hole extended in the longitudinal direction of the glass rod that becomes a part of the clad portion, and the fine particle filling step of filling the gap between the inner surface of the hole of the glass rod and the core rod with the glass fine particles. The gap filled with the glass fine particles is made airtight, and the glass rod, the core rod, and the glass fine particles are heated and melted to draw an optical fiber, and the glass fine particles are drawn by the drawing step. It is characterized by being a second clad region.

In the method for manufacturing an optical fiber according to one aspect of the present invention, the optical fiber includes a plurality of the core portions, and in the insertion step, the glass rod is inserted into each hole of the glass rod having the plurality of the holes. In the fine particle filling step, the glass fine particles are filled in the gap between the inner surface of the hole of the glass rod and each of the core rods.

The method for manufacturing an optical fiber according to one aspect of the present invention includes a core portion made of glass and a clad portion made of glass and formed on the outer periphery of the core portion, and the clad portion is formed from the core portion. A method for manufacturing an optical fiber having microbubble regions formed at separated positions and containing fine and irregular bubbles, which are formed so as to be adjacent to a core forming portion to be the core portion and the outer periphery of the core forming portion. A fine particle filling step of filling the holes of the optical fiber base material, which is provided with a clad forming portion to be the clad portion and has holes extended in the longitudinal direction in the clad forming portion, with glass fine particles, and a plurality of the above. The hole filled with the glass fine particles is made airtight, and the optical fiber base material and the glass fine particles are heated and melted to draw a line of the optical fiber. It is characterized by having a bubble region.

In the method for producing an optical fiber according to one aspect of the present invention, the optical fiber includes a plurality of the core portions, and in the fine particle filling step, the glass is formed in the hole of the optical fiber base material having the plurality of core portions. It is characterized by being filled with fine particles.

The method for manufacturing an optical fiber according to one aspect of the present invention includes a core portion made of glass and a clad portion made of glass and formed on the outer periphery of the core portion, and the clad portion is formed from the core portion. A method for manufacturing an optical fiber having microbubble regions formed at separated positions and containing minute and irregular bubbles, which are formed so as to be adjacent to a core forming portion to be the core portion and the outer periphery of the core forming portion. A plurality of core rods having a clad forming portion that becomes a part of the clad portion are inserted into a hole extended in the longitudinal direction of the glass rod that becomes a part of the clad portion, and the inner surface of the hole of the glass rod is formed. An insertion step of inserting a plurality of support glass rods into the gaps between the plurality of core rods, and a fine particle filling step of filling the gaps between the inner surface of the holes of the glass rods and the plurality of core rods and the plurality of support glass rods with glass fine particles. And the drawing step of drawing the optical fiber by heating and melting the glass rod, the core rod, the support glass rod, and the glass fine particles by making the gap filled with the plurality of glass fine particles airtight. It is characterized in that the glass fine particles are made into the fine bubble region by a drawing step.

The method for producing an optical fiber according to one aspect of the present invention is characterized in that the average particle size of the glass fine particles to be filled is 50 μm or more in the fine particle filling step.

The method for producing an optical fiber according to one aspect of the present invention is characterized in that the glass rod or the optical fiber base material is vibrated while or after the glass fine particles are filled.

The method for manufacturing an optical fiber according to one aspect of the present invention includes a core portion made of glass and a clad portion made of glass and formed on the outer periphery of the core portion, and the clad portion is the outer periphery of the core portion. A method for manufacturing an optical fiber having a first clad region formed so as to be adjacent to each other and a second clad region formed at a position separated from the core portion and containing minute and irregular bubbles. A core rod having a core forming portion to be the core portion and a clad forming portion to be the first clad region formed over the outer periphery of the core forming portion, and a glass porous body formed so as to be adjacent to the outer periphery of the core rod. An insertion step of inserting a glass molded body comprising the above into a hole extended in the longitudinal direction of a glass rod that becomes a part of the clad portion, and the hole into which the glass molded body is inserted are brought into an airtight state. The glass rod and the glass molded body are heated and melted to draw an optical fiber, and the glass porous body is made into the second clad region by the drawing step.

In the method for manufacturing an optical fiber according to one aspect of the present invention, the optical fiber includes a plurality of the core portions, and in the insertion step, the glass molded body is inserted into each hole of a glass rod having the plurality of the holes. It is characterized by doing.

The method for producing an optical fiber according to one aspect of the present invention is characterized in that a dopant that lowers the refractive index of glass is added to the clad forming portion.

In the method for manufacturing an optical fiber according to one aspect of the present invention, a measuring step for measuring the brightness of the drawn optical fiber and the drawing conditions in the drawing step are adjusted based on the measurement results obtained in the measuring step. It is characterized by including an adjustment step.

The method for manufacturing an optical fiber according to one aspect of the present invention includes a measurement step of irradiating the drawn optical fiber with light to measure at least one of the transmitted light and the reflected light, and the measurement obtained in the measurement step. It is characterized by including an adjustment step of adjusting the drawing condition in the drawing step based on the result.

The method for manufacturing an optical fiber according to one aspect of the present invention is characterized in that the adjusting step adjusts the predetermined pressure value.

The optical fiber according to one aspect of the present invention includes a core portion made of glass and a clad portion made of glass and formed on the outer periphery of the core portion, and the clad portion is located at a position separated from the core portion. It is characterized in that it is formed in a shape other than an annular shape surrounding the core portion and has a microbubble region containing minute and irregular bubbles.

According to the present invention, it is possible to realize an optical fiber manufacturing method and an optical fiber in which the characteristics of the microbubble region can be easily controlled.

FIG. 1 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the first embodiment. FIG. 2 is a schematic view illustrating the manufacturing method according to the first embodiment. FIG. 3 is a schematic view illustrating a process of filling fine glass particles. FIG. 4 is a schematic diagram illustrating a drawing process. FIG. 5 is a schematic view illustrating the manufacturing method according to the second embodiment. FIG. 6 is a schematic view illustrating an insertion process. FIG. 7 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the third embodiment. FIG. 8 is a schematic view illustrating the manufacturing method according to the third embodiment. FIG. 9 is a schematic view illustrating the insertion process. FIG. 10 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the fourth embodiment. FIG. 11 is a schematic view illustrating the manufacturing method according to the fourth embodiment. FIG. 12 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the fifth embodiment. FIG. 13 is a schematic view illustrating the manufacturing method according to the fifth embodiment. FIG. 14 is a schematic cross-sectional view of an optical fiber manufactured by applying the manufacturing method according to the fifth embodiment. FIG. 15 is a schematic diagram illustrating the eccentricity. FIG. 16 is a diagram showing the relationship between the average particle size of the glass fine particles and the eccentricity. FIG. 17 is a diagram showing the relationship between the average particle size of the glass fine particles and the eccentricity when vibrated. FIG. 18 is a schematic view illustrating the manufacturing method according to the sixth embodiment. FIG. 19 is a diagram showing the relationship between the line drawing length and the thickness of the microbubble region. FIG. 20 is a schematic view illustrating the manufacturing method according to the seventh embodiment. FIG. 21 is a diagram showing the relationship between the line drawing length and the thickness of the microbubble region. FIG. 22 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the eighth embodiment. FIG. 23 is a schematic view illustrating the manufacturing method according to the eighth embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. Further, in each drawing, the same or corresponding elements are appropriately designated by the same reference numerals.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the first embodiment. The optical fiber 10 is an optical fiber made of quartz glass, and includes a core portion 1 and a clad portion 2 formed on the outer periphery of the core portion 1. The outer circumference of the clad portion 2 is covered with a coating (not shown). The coating used is that normally used for optical fibers.

The clad portion 2 has a first clad layer 2a, which is a first clad region formed so as to be adjacent over the outer circumference of the core portion 1, and a second clad region formed so as to be adjacent over the outer circumference of the first clad layer 2a. The second clad layer 2b and the third clad layer 2c formed so as to be adjacent to each other over the outer periphery of the second clad layer 2b are provided. The second clad layer 2b is a microbubble region formed at a position separated from the core portion 1 and containing minute and irregular bubbles. The second clad layer 2b is a region having a low refractive index because it contains minute and irregular bubbles.

The core portion 1 is made of quartz glass to _{which GeO 2,} which is a dopant for increasing the refractive index, is added. The clad portion 2 is made of pure quartz glass to which a dopant for adjusting the refractive index is not added.

Next, the manufacturing method according to the first embodiment will be described with reference to FIGS. 2 to 4. The manufacturing method according to the first embodiment includes an insertion step, a fine particle filling step, and a drawing step.

In the insertion step, the core rod is inserted into the hole of the glass rod. As shown in FIG. 2A, the glass rod 3 is a pipe-shaped rod having a hole 3a extending in the longitudinal direction. The glass rod 3 of the present embodiment is made of, for example, a synthetic quartz pipe having an outer diameter of 125 mm and an inner diameter of 30 mm to which a dopant for adjusting the refractive index is not added. The lower end 3b of the glass rod 3 is sealed, and the lower end 3aa of the hole 3a is conical. A support pipe 4 made of quartz glass is connected to the upper end of the glass rod 3. The glass rod 3 becomes a third clad layer 2c which is a part of the clad portion 2 of the optical fiber 10.

As shown in FIG. 2A, the core rod 5 includes an upper end portion 5a and a core rod main body 5b. The upper end portion 5a is connected to the upper end of the core rod main body 5b. As shown in the arrow A in FIG. 2B, the upper end portion 5a has a shape in which three notches 5aa are formed on the side surface of the cylindrical quartz glass member. The maximum diameter of the upper end portion 5a is slightly smaller than the inner diameter of the hole 3a of the glass rod 3, and is 29.9 mm in the present embodiment.

As shown in FIG. 2C, the core rod main body 5b includes a core forming portion 5ba that becomes the core portion 1 of the optical fiber 10 and a clad forming portion 5bb formed so as to be adjacent to each other over the outer periphery of the core forming portion 5ba. The core forming portion 5ba becomes the core portion 1 of the optical fiber 10, and the clad forming portion 5bb becomes the first clad layer 2a. The core forming portion 5ba is _{made of quartz glass to which GeO 2} is added, and the clad forming portion 5bb is made of pure quartz glass. The difference in the specific refractive index of the core forming portion 5ba with respect to the clad forming portion 5bb is, for example, 0.23 to 3.5%. Further, the outer diameter of the clad forming portion 5bb (that is, the diameter of the core rod main body 5b) is 2.5 times the diameter of the core forming portion 5ba in the present embodiment. The core rod body 5b is manufactured by, for example, the VAD method, the OVD method, the MCVD method, or the like.

Further, the lower end portion 5c of the core rod main body 5b is processed into a hemispherical shape, and a groove 5ca is formed as shown in FIG. 2D.

When the core rod 5 is inserted into the hole 3a of the glass rod 3 as shown in FIG. 2A, the lower end portion 5c of the core rod body 5b comes into contact with the conical hole of the lower end portion 3aa of the hole 3a of the glass rod 3, and the core rod 5 It will be located approximately in the center of the hole 3a.

Subsequently, the fine particle filling step is performed. In the fine particle filling step, as shown in FIG. 3, a plurality of glasses are formed in the gap between the inner surface of the hole of the glass rod 3 and the core rod body 5b of the core rod 5 via the support pipe 4 and the notch 5aa of the upper end portion 5a of the core rod 5. Fill with fine particles 6. As a result, the gap is filled with the glass fine particles 6. The glass fine particles 6 are filled to the tip of the lower end 3aa of the hole 3a through the groove 5ca of the lower end 5c of the core rod body 5b. The glass fine particles 6 have an average particle diameter of 200 μm in the present embodiment, and are made of synthetic quartz glass to which a dopant for adjusting the refractive index is not added.

Next, the line drawing process is performed. In the drawing step, as shown in FIG. 4, the support pipe 4 is first covered with the lid 100, and the inside of the support pipe 4 and the gap filled with the glass fine particles 6 are made airtight. A gas introduction pipe 101 and a gas exhaust pipe 102 leading to the inside of the support pipe 4 and the gap which are in an airtight state are connected to the lid 100. The vacuum pump 103 and the gas exhaust pipe 104 are sequentially connected to the gas exhaust pipe 102. Argon (Ar) gas is supplied from the gas introduction pipe 101 into the support pipe 4 and the gap. Further, the lid 100 is provided with a pressure gauge 105 for measuring the pressure in the gap in the airtight state. The pressure gauge 105 transmits the measurement result data of the measured pressure value to the control unit C. The control unit C is configured to control the vacuum pump 103 based on the data of the measurement result of the pressure value, and to control the pressure in the support pipe 4 and the gap to a predetermined pressure value.

Then, first, the inside of the support pipe 4 and the inside of the gap are replaced with argon gas, and the pressure inside the support pipe 4 and the gap is set to a predetermined argon gas pressure (absolute pressure in the support pipe 4 when the vacuum is 0 atm) 0. While controlling to 9.9 to 0.98 atm, the lower end of the glass rod 3 is heated to, for example, 2200 ° C. by the heater 106a of the optical fiber drawing furnace 106, and the glass rod 3, the core rod 5 and the glass fine particles 6 are heated and melted to obtain light. The fiber F is drawn. As a result, in the region filled with the glass fine particles 6, the gap between the glass fine particles 6 becomes a closed space, and minute and irregular bubbles are formed. As a result, the glass fine particles 6 become the second clad layer 2b which is a micro bubble region. After that, the outer circumference of the drawn optical fiber F is coated, and the optical fiber 10 shown in FIG. 1 is manufactured. It is possible to control the amount of bubbles by controlling the gas pressure within the range where the pipe does not swell near the melting of the glass particles and the airtightness inside the pipe can be maintained. It was difficult to generate a region, and it was difficult to secure the airtightness of the pipe when the pressure on the atmosphere (the pressure inside the pipe when the atmospheric pressure was 0) was +1.0 atm or more.

According to the manufacturing method of the first embodiment, the optical fiber 10 is drawn while controlling the pressure of the gap filled with the glass fine particles 6 to a predetermined pressure value in the drawing step, so that the characteristics of the second clad layer 2b can be easily obtained. Can be controlled. As the predetermined pressure value, a value set according to the required characteristics (for example, refractive index) of the second clad layer 2b by a preliminary experiment or the like can be used.

(Modified Example of Embodiment 1)
In the first embodiment, the inside of the support pipe 4 and the inside of the gap are replaced with argon gas, and the line is drawn while controlling the pressure inside the support pipe 4 and the inside of the gap to the argon gas pressure of 0.9 to 0.98 atm. On the other hand, in the modified example of the first embodiment, the inside of the support pipe 4 and the inside of the gap are replaced with a mixed gas of 90% oxygen gas and 10% helium gas, and the pressure inside the support pipe 4 and the inside of the gap is 1.0 atm. pressure (altitude, depending on the weather 10 mm H 2 _O condition approximately + than ambient) perform drawing while controlling so as to. That is, in the first embodiment, the pressure inside the pipe is drawn as a negative pressure with respect to the atmosphere, but in the modified example, the pressure inside the pipe is slightly positive, but the line is drawn under the condition that it is almost equal to the atmosphere. It was.

The optical fiber 10 can be drawn by easily controlling the characteristics of the second clad layer 2b also by the manufacturing method of the modified example of the first embodiment. Further, when the present inventors carried out the manufacturing method of the modified example of the first embodiment and pulled up the glass rod after drawing and observed it, almost no deformation was observed in the support pipe near the connection portion with the glass rod. It was confirmed that it is possible to increase the reusable support pipe length.

(Embodiment 2)
Next, the manufacturing method according to the second embodiment will be described. The manufacturing method according to the second embodiment is a method capable of manufacturing the optical fiber 10 shown in FIG. 1 in the same manner as the manufacturing method according to the first embodiment, and includes an insertion step and a drawing step.

In the insertion step, a core rod having a core forming portion to be a core portion and a clad forming portion formed so as to be adjacent to the outer periphery of the core forming portion, and a glass porous body formed over the outer periphery of the core rod are provided. The glass molded body is inserted into a hole extending in the longitudinal direction of the glass rod.

First, a method for manufacturing a glass molded body will be described. Here, the core rod body 5b shown in FIG. 2 is used as the core rod. Then, spherical silica particles (average particle diameter 10 μm), binder (polyvinyl alcohol (PVA)), and plasticizer (glycerin) prepared by the vapor phase synthesis method are prepared, and these are mixed to prepare a silica particle slurry. Subsequently, the produced silica particle slurry is spray-dried with a spray dryer to form granulated particles having a diameter of 100 μm. Subsequently, the core rod main body 5b is filled in the center of the rubber molding die, the granulated particles are filled in the periphery thereof, and pressure molding is performed using a hydrostatic pressure molding device to prepare a pressure molded body. Subsequently, the outer surface of the produced pressure-molded body is cut with a lathe to make the outer diameter uniform.

Subsequently, as shown in FIG. 5, a pressure-molded body including the core rod body 5b is set in the furnace 107. The furnace 107 includes a furnace body 107a, a heater 107b, a gas introduction pipe 107c, a gas discharge pipe 107d, and a support tool 107e. A glass molded body 8 is set on a support 107e in the furnace body 107a, and a mixed gas of 20% oxygen and 80% nitrogen as a processing gas is discharged from the gas discharge pipe 107d while discharging the gas in the furnace body 107a from the gas introduction pipe 107c. Is introduced, the pressure molded body is heated to 500 ° C. by the heater 107b and held in an oxygen atmosphere for 5 hours to decompose the binder and the plasticizer. After that, a mixed gas of 10% chlorine and 90% nitrogen as a processing gas was introduced from the gas introduction pipe 107c while discharging the gas in the furnace body 107a from the gas discharge pipe 107d, and the temperature of the glass molded body 8 was raised to 1000 ° C. The pressure-formed body is refined by creating a chlorine atmosphere, and the surface of the pressure-formed body is hardened. As a result, the glass molded body 8 including the glass porous body 8a formed over the outer periphery of the core rod main body 5b is manufactured. The diameter of the glass molded body 8 is slightly smaller than that of the pressure molded body.

Then, the insertion process is performed. That is, as shown in FIG. 6, the glass molded body 8 is inserted into the hole 3a of the glass rod 3 to which the support pipe 4 is connected to the upper portion.

Subsequently, the drawing step is performed in the same manner as the drawing step of the first embodiment. That is, the support pipe 4 is covered with the lid 100, and the inside of the support pipe 4 and the hole 3a into which the glass molded body 8 is inserted are made airtight.

Then, first, the inside of the support pipe 4 and the hole 3a are replaced with argon gas, and the pressure inside the support pipe 4 and the hole 3a is controlled to a predetermined pressure value (for example, argon gas pressure 0.7 to 0.9 atm). The lower end of the glass rod 3 is heated to, for example, 2200 ° C. by the heater 106a of the optical fiber drawing furnace 106, and the glass rod 3 and the glass molded body 8 are heated and melted to draw the optical fiber F. As a result, minute and irregular bubbles are formed in the glass porous body 8a. As a result, the glass porous body 8a becomes the second clad layer 2b which is a microbubble region, and the optical fiber 10 shown in FIG. 1 is manufactured by being coated.

According to the manufacturing method of the second embodiment, the optical fiber 10 is drawn while controlling the pressure in the hole 3a into which the glass molded body 8 is inserted in the drawing step to a predetermined pressure value. The characteristics of the two-clad layer 2b can be easily controlled.

(Modified Example of Embodiment 2)
In the second embodiment, silica granulated particles are pressure-molded around the core rod body 5b and heat-purified to produce a glass molded body 8. Then, the inside of the support pipe 4 and the inside of the hole 3a are replaced with argon gas, and the line is drawn while controlling the pressure in the support pipe 4 and the inside of the hole 3a to the argon gas pressure of 0.7 to 0.9 atm. On the other hand, in the modified example of the second embodiment, the vapor phase synthetic silica particles are deposited on the outer periphery of the core rod 5 used in the first embodiment to form a porous body, and the furnace 107 is used at 1200 ° C. The porous body is dehydrated and purified in the chlorine / nitrogen mixed atmosphere of the above to produce the glass molded body 8. Further, the inside of the support pipe 4 and the holes 3a was replaced with argon gas, support pipes 4 within and pressure pressure 1.0atm in hole 3a (altitude, depending on the weather, but roughly + 10 mm H ₂ O above ambient conditions) Draw a line while controlling so that it becomes. That is, in the first embodiment, the pressure inside the pipe was drawn as a negative pressure with respect to the atmosphere, but in the modified example, the pressure inside the pipe was drawn with a slightly positive pressure with respect to the atmosphere.

The optical fiber 10 can be drawn by easily controlling the characteristics of the second clad layer 2b also by the manufacturing method of the modified example of the second embodiment. Further, when the present inventors carried out the manufacturing method of the modified example of the second embodiment and pulled up the glass rod after drawing and observed it, almost no deformation was observed in the support pipe near the connection portion with the glass rod. It was confirmed that it is possible to increase the reusable support pipe length.

It is preferable that the atmosphere in the support pipe 4 and the hole 3a is appropriately selected depending on the degree to which bubbles are contained in the required microbubble region, the particle size of the glass fine particles in the porous body, and the like. When the desired atmospheric gas pressure in the pipe is lower than the atmospheric pressure, the atmospheric gas in the pipe is divided into a gas that diffuses quickly into the glass (helium, hydrogen, deuterium, etc.) and a gas that diffuses slowly (oxygen, nitrogen, etc.). By combining with (argon, etc.), it is possible to draw a line in the atmosphere in the support pipe 4 and the hole 3a in a state close to atmospheric pressure.

(Embodiment 3)
FIG. 7 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the third embodiment. The optical fiber 10A is made of quartz glass, and includes a plurality of core portions 1 (four arranged in a square lattice in the present embodiment) and a clad portion 2A formed on the outer periphery of the plurality of core portions 1. It is a so-called multi-core fiber. The outer circumference of the clad portion 2A is covered with a coating (not shown). The coating used is that normally used for optical fibers.

The clad portion 2A is a first clad layer 2Aa which is a first clad region formed so as to be adjacent over the outer periphery of each core portion 1, and a second clad layer 2Aa formed so as to be adjacent over the outer periphery of each first clad layer 2Aa. A second clad layer 2Ab, which is a clad region, and a third clad layer 2Ac formed so as to be adjacent to each other over the outer periphery of each second clad layer 2b are provided. Each second clad layer 2Ab is a microbubble region formed at a position separated from each core portion 1. The second clad layer 2Ab is a region having a low refractive index because it contains minute and irregular bubbles.

The core portion 1 is made of quartz glass to which _{Geo 2 is added.} The clad portion 2A is made of pure quartz glass.

Next, the manufacturing method according to the third embodiment will be described with reference to FIGS. 8 and 9. The manufacturing method according to the third embodiment includes an insertion step, a fine particle filling step, and a drawing step.

To perform the insertion process, first prepare a glass rod. As shown in FIGS. 8A and 8B, the glass rod 3A is a pipe-shaped rod having holes 3Aa extending in the longitudinal direction, and has a refractive index of, for example, an outer diameter of 125 mm and an inner diameter of 30 mm of each hole 3Aa. It is made from synthetic quartz pipe without the addition of conditioning dopants. As shown in the arrow C view in FIG. 8B, there are a plurality of holes 3Aa (four holes arranged in a square grid in this embodiment). The lower end 3Ab of the glass rod 3A is sealed, and the lower end 3Aa of each hole 3Aa is conical hole processed. A support pipe 4A made of quartz glass is connected to the upper end of the glass rod 3A. The glass rod 3A becomes a third clad layer 2Ac which is a part of the clad portion 2A of the optical fiber 10A.

Then, in the insertion step, as shown in FIG. 9, four core rods 5 used in the first embodiment are prepared, and each core rod 5 is inserted into each hole 3Aa of the glass rod 3A. Subsequently, as shown in FIG. 9, a fine particle filling step of filling the gap between the inner surface of each hole 3Aa of the glass rod 3A and the core rod main body 5b of each core rod 5 with a plurality of glass fine particles 6 is performed in the same manner as in the first embodiment. .. As a result, each gap is filled with the glass fine particles 6.

Subsequently, the drawing step is performed in the same manner as in the first embodiment, but each gap filled with the glass fine particles 6 is made airtight, and the pressure in each gap is set to a predetermined pressure value (argon gas pressure 0.9 to 0. Draw a line while controlling it to 98 atm). As a result, the glass fine particles 6 become each second clad layer 2Ab which is a microbubble region, and the optical fiber 10A shown in FIG. 7 is manufactured by coating.

According to the manufacturing method of the third embodiment, the optical fiber 10A is drawn while controlling the pressure of each gap filled with the glass fine particles 6 to a predetermined pressure value in the drawing step. Easy to control. Further, the optical fiber 10A, which is a multi-core fiber having a microbubble region, can be easily manufactured.

In the optical fiber 10A shown in FIG. 7, the glass molded body 8 is inserted into each hole 3Aa of the glass rod 3A to bring the pressure in each hole 3Aa to a predetermined pressure value as in the manufacturing method according to the second embodiment. It can also be manufactured by drawing a line while controlling it.

(Embodiment 4)
FIG. 10 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the fourth embodiment. The optical fiber 10B is an optical fiber made of quartz glass, and includes a core portion 1B and a clad portion 2B formed on the outer periphery of the core portion 1B. The outer circumference of the clad portion 2B is covered with a coating (not shown). The coating used is that normally used for optical fibers.

The clad portion 2B has a plurality of microbubble regions 2Ba (six in the present embodiment) formed at positions separated from the core portion 1B. The microbubble region 2Ba of No. 6 has a substantially circular cross section and is arranged so as to surround the core portion 1B, and is a region having a low refractive index due to the inclusion of minute and irregular bubbles. As described above, the microbubble region 2Ba is formed in a shape other than the annular shape surrounding the core portion 1B.

The core portion 1B is made of quartz glass to which _{GeO 2 is added.} The clad portion 2B is made of pure quartz glass.

Next, the manufacturing method according to the fourth embodiment will be described. The manufacturing method according to the fourth embodiment includes a fine particle filling step and a drawing step.

In the fine particle filling step, a core forming portion to be the core portion 1B and a clad forming portion to be the clad portion 2B formed so as to be adjacent to each other over the outer periphery of the core forming portion are provided, and a hole extending in the longitudinal direction is provided in the clad forming portion. A plurality of glass fine particles are filled in the holes of the optical fiber base material in which the above is formed.

First, a method for manufacturing an optical fiber base material will be described. When manufacturing the optical fiber base material 3B shown in FIG. 11, first, for example, a known method such as a VAD method or an OVD method is combined to obtain an optical fiber base material having a core forming portion 3Ba and a clad forming portion 3Bb. To manufacture. Next, holes 3Bc are formed in the clad forming portion 3Bb of the optical fiber base material by a drill so as to surround the core forming portion 3Ba, and the inner surface of each hole 3Bc is etched. The difference in the specific refractive index of the core forming portion 3Ba with respect to the clad forming portion 3Bb is, for example, 0.23 to 3.5%. The outer diameter of the optical fiber base material 3B is, for example, 125 mm.

Subsequently, the support pipe is connected to the optical fiber base material 3B. Subsequently, a fine particle filling step of filling each hole 3Bc with glass fine particles having an average particle diameter of 100 μm is performed, and each hole 3Bc is filled with glass fine particles.

Subsequently, the drawing step is performed in the same manner as in the first embodiment, but each hole 3Bc filled with glass fine particles is made airtight, and the pressure in each hole 3Bc is set to a predetermined pressure value (argon gas pressure 1.0 to 1). Draw a line while controlling it to .5 atm). As a result, the glass fine particles become each microbubble region 2Ba, and the optical fiber 10B shown in FIG. 10 is manufactured by coating. The optical fiber 10B has, for example, an outer diameter of 125 μm.

According to the manufacturing method of the fourth embodiment, the optical fiber 10B is drawn while controlling the pressure in each hole filled with the glass fine particles to a predetermined pressure value in the drawing step, so that the characteristics of each microbubble region 2Ba can be easily obtained. Can be controlled. Further, according to the manufacturing method of the fourth embodiment, since the position where the hole is formed by the drill in the optical fiber base material 3B can be arbitrarily determined, the optical fiber 10B in which the microbubble region 2Ba is formed at an arbitrary position can be easily determined. Can be manufactured. Therefore, the microbubble region 2Ba can be formed in a shape other than the annular shape. Further, by making the shape of the hole not circular but any other shape, the microbubble region 2Ba can be made into an arbitrary shape. As a method of making the shape of the hole an arbitrary shape, for example, an optical fiber base material is formed by combining a plurality of glass members so that a hole having an arbitrary shape is formed between the combined glass members. There is a way.

(Embodiment 5)
FIG. 12 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the fifth embodiment. The optical fiber 10C is an optical fiber made of quartz glass, and includes four core portions 1C arranged in a square lattice and a clad portion 2C formed on the outer periphery of the core portion 1C. The outer circumference of the clad portion 2C is covered with a coating (not shown). The coating used is that normally used for optical fibers.

The clad portion 2C has four microbubble regions 2Ca formed at positions separated from each core portion 1C. The microbubble region 2Ca is arranged in the middle of the two core portions 1C, respectively, and contains minute and irregular bubbles to form a region having a low refractive index. The microbubble region 2Ca has a function of suppressing light crosstalk between the two core portions 1C.

The core portion 1C is made of quartz glass to which _{GeO 2 is added.} The clad portion 2C is made of pure quartz glass.

Next, the manufacturing method according to the fifth embodiment will be described. The manufacturing method according to the fifth embodiment includes a fine particle filling step and a drawing step.

In the fine particle filling step, a core forming portion to be the core portion 1C and a clad forming portion to be the clad portion 2C formed so as to be adjacent to each other over the outer periphery of the core forming portion are provided, and a hole extending in the longitudinal direction is provided in the clad forming portion. The holes of the optical fiber base material in which the above is formed are filled with fine glass particles.

First, a method for manufacturing an optical fiber base material will be described. When manufacturing the optical fiber base material 3C shown in FIG. 13, for example, a known method such as a VAD method or an OVD method is combined to obtain an optical fiber base material having a core forming portion 3Ca and a clad forming portion 3Cb. To manufacture. Next, holes 3Cc are formed in the clad forming portion 3Cb of the optical fiber base material 3C, and the inner surface of each hole 3Cc is etched. The difference in the specific refractive index of the core forming portion 3Ca with respect to the clad forming portion 3Cb is, for example, 0.23 to 3.5%. The outer diameter of the optical fiber base material 3C is, for example, 125 mm.

After that, the support pipe is connected to the upper part of the optical fiber base material 3C. Then, a fine particle filling step of filling each hole 3Cc with glass fine particles having an average particle diameter of 100 μm is performed, and each hole 3Cc is filled with glass fine particles.

Subsequently, the drawing step is performed in the same manner as in the first embodiment, but each hole 3Cc filled with glass fine particles is made airtight, and the pressure in each hole is set to a predetermined pressure value (argon gas pressure 1.0 to 1.5 atm). ) To draw a line. As a result, the glass fine particles become each microbubble region 2Ca and are coated to produce the optical fiber 10C shown in FIG. The optical fiber 10C has, for example, an outer diameter of 125 μm.

According to the manufacturing method of the fifth embodiment, the optical fiber 10C is drawn while controlling the pressure in each hole filled with the glass fine particles to a predetermined pressure value in the drawing step, so that the characteristics of each microbubble region 2Ca can be easily obtained. Can be controlled. Further, according to the manufacturing method of the fifth embodiment, since the position where the hole is formed by the drill can be arbitrarily determined, the multi-core fiber in which the microbubble region 2Ca is formed at the arbitrary position can be easily manufactured. Therefore, each microbubble region 2Ca can be formed into a shape other than the annular shape. Further, by making the shape of the hole not circular but any other shape, the microbubble region 2Ca can be made into an arbitrary shape.

By applying the manufacturing method of the fifth embodiment, it is possible to manufacture a multi-core fiber having a microbubble region as a marker for identifying the core portion.

FIG. 14 is a schematic cross-sectional view of an optical fiber manufactured by applying the manufacturing method according to the fifth embodiment. The optical fiber 10D is an optical fiber made of quartz glass, and includes four core portions 1D arranged in a square lattice and a clad portion 2D formed on the outer periphery of the core portion 1D.

The clad portion 2D has one microbubble region 2Da formed at a position separated from each core portion 1D. The microbubble region 2Da is a region having a low refractive index because it contains minute and irregular bubbles. Therefore, the microbubble region 2Da can be used as four core portion 1D identification markers because the microbubble region 2Da can be seen with a brightness different from that of the other regions of the clad portion 2D in the cross section obtained by cutting the optical fiber 10D.

(Experiment on average particle size of glass fine particles)
Next, the experimental results regarding the average particle size of the glass fine particles used in the production methods according to the first, third to fifth embodiments will be described. In this experiment, in the production method of Embodiment 1, glass fine particles made of synthetic quartz glass having average particle diameters of 30 μm, 50 μm, 70 μm, 100, 150 μm, and 300 μm, respectively, are used as the glass fine particles, and the light having the configuration shown in FIG. 1 is used. Manufactured fiber.

Subsequently, the eccentricity of the first clad layer with respect to the second clad layer in the manufactured optical fiber was measured. FIG. 15 is a schematic diagram illustrating the eccentricity. In FIG. 15, the point O1 is the central axis of the core portion 1 formed from the core rod 5 and the first clad layer 2a. The point O2 is the central axis of the second clad layer 2b, which is a microbubble region formed from the glass fine particles 6. Assuming that the distance between the point O1 and the point O2 is d, the eccentricity is represented by d / (the average thickness of the second clad layer 2b in the circumferential direction). Here, the larger the eccentricity, the more uneven the thickness of the second clad layer 2b.

FIG. 16 is a diagram showing the relationship between the average particle size of the glass fine particles and the eccentricity. As shown in FIG. 16, the eccentricity was about 15% when the average particle size of the glass fine particles was 30 μm. On the other hand, it was confirmed that when the average particle size of the glass fine particles was 50 μm or more, the eccentricity was 6% or less, and the thickness of the second clad layer 2b became more uniform. Therefore, the average particle size of the glass fine particles is preferably 50 μm or more.

Further, the average particle size of the glass fine particles is preferably about 1 mm or less. The reason is that the width of the gap filled with the glass fine particles and the inner diameter of the hole are about several tens of mm, so that the glass fine particles have an average particle diameter of about 1 mm or less, which is a certain amount smaller than this width and inner diameter. This is because the bubbles to be formed can be made minute and irregular by using.

(Experiment on the effect of vibration)
Next, the experimental results of vibration in the manufacturing methods according to the first, third, and fifth embodiments will be described. In this experiment, in the manufacturing method of the first embodiment, after filling the holes of the glass rod with fine glass particles, the glass rod is vibrated by ultrasonic vibration, and then a drawing step is performed. Manufactured fiber. In this experiment as well, glass fine particles made of synthetic quartz glass having average particle diameters of 30 μm, 50 μm, 70 μm, 100 μm, 150 μm, and 300 μm were used as the glass fine particles.

FIG. 17 is a diagram showing the relationship between the average particle size of the glass fine particles and the eccentricity. As shown in FIG. 17, when the vibration was performed, the eccentricity was about 10% when the average particle size of the glass fine particles was 30 μm, which was smaller than that when the vibration was not performed as shown in FIG. Similarly, when the average particle size of the glass fine particles is 50 μm or more, the eccentricity is 3% or less, which is smaller than that when vibration is not performed, and it is confirmed that the thickness of the second clad layer 2b becomes more uniform. Was done. In this experiment, vibration was performed after filling the glass fine particles, but even if the vibration was performed while filling the glass fine particles, the effect of reducing the eccentricity and making the thickness of the second clad layer 2b uniform. There is expected.

(Embodiment 6)
Next, the manufacturing method according to the sixth embodiment will be described. The manufacturing method according to the sixth embodiment adds a measurement step and an adjustment step to the manufacturing method according to the first embodiment.

As shown in FIG. 18, in the manufacturing method according to the sixth embodiment, first, as in the first embodiment, the lower end of the glass rod 3 is heated by the heater 106a of the optical fiber drawing furnace 106 to draw the optical fiber F. ..

In the optical fiber wire drawing furnace 106, the glass rod 3 has a high temperature and emits light. Since the drawn optical fiber F contains fine bubbles, the light emitted by the glass rod 3 is scattered by the fine bubbles when propagating. As a result, the optical fiber F also emits light L1.

In the present embodiment, the measuring instrument 111 is provided below the optical fiber drawing furnace 106 and above the die 110 used for coating the optical fiber F. Then, the measuring instrument 111 receives the light L1 emitted by the optical fiber F and performs a measuring step of measuring the brightness. The measuring instrument 111 transmits the measurement result data to the control unit C (see FIG. 4).

The control unit C performs an adjustment step of adjusting the drawing conditions in the drawing step based on the measurement result. Since the brightness of the optical fiber F indicates the characteristics of the microbubble region contained in the optical fiber F, the drawing condition of the optical fiber F can be adjusted based on the measurement result of the brightness of the microbubble region included in the optical fiber F. The characteristics are stable. In particular, even when a long optical fiber F is drawn, the variation in the characteristics of the microbubble region in the longitudinal direction is small and stable.

As the drawing condition to be adjusted, it is preferable to adjust the pressure value in the support pipe 4 and the gap. However, a method of controlling the microbubble region by providing a residual heat zone using a heater, a heat insulating material, etc. in the lower part of the optical fiber drawing furnace and appropriately controlling the heat history until the optical fiber is completely solidified in this residual heat zone, etc. There is no particular limitation because it can also be mentioned. When adjusting the pressure value, the control unit C controls the vacuum pump 103 based on the measurement result of the pressure value measured by the pressure gauge 105, and controls the pressure in the support pipe 4 and the gap to a predetermined pressure value. At the same time, the Ar gas flow rate and the vacuum pump 103 are controlled to adjust a predetermined pressure value so that the brightness measured by the measuring instrument 111 becomes a constant value.

(Experiments 1 and 2 related to pressure value adjustment)
Next, the results of Experiments 1 and 2 regarding the adjustment of the pressure value will be described. In Experiment 1, an optical fiber having an outer diameter of 125 μm and a length of 250 km having the configuration shown in FIG. 1 was manufactured by the manufacturing method of the first embodiment. Further, in Experiment 2, in the manufacturing method of the sixth embodiment, by adjusting the pressure value, an optical fiber having the configuration shown in FIG. 1 having an outer diameter of 125 μm and a length of 250 km was manufactured. Then, each of the manufactured optical fibers was cut every 50 km in length, and the average value in the circumferential direction of the thickness of the microbubble region (second clad layer) was measured.

FIG. 19 is a diagram showing the relationship between the length of the optical fiber (line drawing length) and the thickness of the microbubble region (average value) in Experiments 1 and 2. The line drawing length of 0 km is the position of the optical fiber at the start of drawing, and the line drawing length of 250 km is the position of the optical fiber at the end of drawing. As shown in FIG. 19, when the pressure adjustment of Experiment 1 shown by the black dot was not performed, the thickness was substantially constant 5 μm from the line drawing length of 0 km to 150 km, but the thickness decreased at 200 km and 250 km in the latter half of the line drawing. It was lower than about 4 μm. The reason why the thickness decreased in Experiment 1 is that the pressure value of the partial pressure of argon gas is controlled to a constant value (0.9 atm), so that the upper end of the optical fiber base material in the latter half of the drawing is gradually reduced from an early stage. It is probable that as a result of the melting of the glass fine particle region proceeding from an early stage due to the temperature rise, the size of the closed cells generated in the gaps of the glass fine particles became smaller and changed to a thin microbubble region (second clad layer).

On the other hand, in the case of the pressure adjustment of Experiment 2 shown by the white circle, the thickness was 5 μm, which was substantially constant from 0 km to 250 km in line drawing length. In Experiment 2, the pressure value of the argon gas partial pressure was adjusted during the drawing, and changed in the range of 0.99 to 1.05 atm.

(Embodiment 7)
Next, the manufacturing method according to the seventh embodiment will be described. The manufacturing method according to the seventh embodiment is the manufacturing method according to the first embodiment in which a measurement step and an adjustment step are added.

As shown in FIG. 20, in the manufacturing method according to the seventh embodiment, first, as in the first embodiment, the lower end of the glass rod 3 is heated by the heater 106a of the optical fiber drawing furnace 106 to draw the optical fiber F. ..

In the present embodiment, the laser light irradiator 112 and the measuring instruments 113 and 114 are provided below the optical fiber drawing furnace 106 and above the die 110 used for coating the optical fiber F. There is. The laser light irradiator 112 is, for example, a He-Ne laser device. Then, the laser light irradiator 112 irradiates the drawn optical fiber F with the laser light L2. The measuring instrument 113 performs a measuring step of measuring the power of the transmitted light L3 transmitted through the optical fiber F among the laser light L2. The measuring instrument 114 performs a measuring step of measuring the power of the reflected light L4 reflected by the optical fiber F in the direction of 45 degrees among the laser light L2. The measuring instruments 113 and 114 transmit the measurement result data to the control unit C (see FIG. 4).

The control unit C performs an adjustment step of adjusting the drawing conditions in the drawing step based on the measurement result. Since the power of the transmitted light L3 and the power of the reflected light L4 show the characteristics of the microbubble region contained in the optical fiber F, the drawing conditions are based on the measurement results of the power of the transmitted light L3 and the power of the reflected light L4. By adjusting the above, the characteristics of the microbubble region contained in the optical fiber F are stabilized. In particular, even when a long optical fiber F is drawn, the variation in the characteristics of the microbubble region in the longitudinal direction is small and stable.

As the drawing condition to be adjusted, it is preferable to adjust the pressure value in the support pipe 4 and the gap. However, a method of controlling the microbubble region by providing a residual heat zone using a heater, a heat insulating material, etc. in the lower part of the optical fiber drawing furnace and appropriately controlling the heat history until the optical fiber is completely solidified in this residual heat zone, etc. There is no particular limitation because it is also mentioned. When adjusting the pressure value, the control unit C controls the vacuum pump 103 based on the measurement result of the pressure value measured by the pressure gauge 105, and controls the pressure in the support pipe 4 and the gap to a predetermined pressure value. At the same time, the vacuum pump 103 is controlled to adjust a predetermined pressure value so that the power of the light measured by the measuring instruments 113 and 114 becomes a constant value.

(Experiment on pressure value adjustment 3)
Next, the result of Experiment 3 regarding the adjustment of the pressure value will be described. In Experiment 3, in the manufacturing method of the sixth embodiment, by adjusting the pressure value, an optical fiber having the configuration shown in FIG. 1 having an outer diameter of 125 μm and a length of 250 km was manufactured. Then, each of the manufactured optical fibers was cut every 50 km in length, and the average value in the circumferential direction of the thickness of the microbubble region (second clad layer) was measured.

FIG. 21 is a diagram showing the relationship between the length of the optical fiber (drawing length) and the thickness of the microbubble region (average value) in Experiment 3. The line drawing length of 0 km is the position of the optical fiber at the start of drawing, and the line drawing length of 250 km is the position of the optical fiber at the end of drawing. In the case of Experiment 3, as shown by the black circle, the thickness was 5 μm, which was substantially constant from 0 km to 250 km in line drawing length. In Experiment 3, the pressure value of the argon gas partial pressure was adjusted during the drawing, and changed in the range of 0.99 to 1.05 atm.

In the seventh embodiment, the transmitted light and the reflected light are measured, but at least one of the transmitted light and the reflected light may be measured, and the drawing condition may be adjusted based on the obtained measurement result. ..

(Embodiment 8)
FIG. 22 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the eighth embodiment. The optical fiber 10E is an optical fiber made of quartz glass, and includes a plurality of (four in this embodiment) core portions 1E and a clad portion 2E formed on the outer periphery of the core portion 1E. The outer circumference of the clad portion 2E is covered with a coating (not shown). The coating used is that normally used for optical fibers.

The clad portion 2E has a plurality of microbubble regions 2Ea formed at positions separated from each core portion 1E (24 locations in the present embodiment). The 24 microbubble regions 2Ea are regions having a low refractive index because they contain minute and irregular bubbles. As described above, the microbubble region 2Ea is formed in a shape other than the annular shape surrounding the core portion 1E. The microbubble region 2Ea has a function of suppressing light crosstalk between the two core portions 1E.

The core portion 1E is made of quartz glass to which _{GeO 2 is added.} The clad portion 2E is made of pure quartz glass.

Next, the manufacturing method according to the eighth embodiment will be described. The manufacturing method according to the eighth embodiment includes an insertion step, a fine particle filling step, and a drawing step.

In the insertion step, as shown in FIG. 23, the four core rods 5E are inserted into the holes 3Ea extending in the longitudinal direction of the glass rod 3E, and the gap between the inner surface of the holes 3Ea of the glass rod 3E and the four core rods 5E. A plurality of support glass rods 9a and 9b (three support glass rods 9a and six support glass rods 9b in the present embodiment) are inserted into the support glass rods 9a and 9b.

Each core rod 5E includes a core forming portion 5Ea that becomes the core portion 1E and a clad forming portion 5Eb that becomes a part of the clad portion 2E and is formed so as to be adjacent to each other over the outer circumference of the core forming portion 5Ea. The glass rod 3E is a pipe-shaped rod having a hole 3Ea extending in the longitudinal direction, and becomes a part of the clad portion 2E. A support pipe is connected to the glass rod 3E. The support glass rods 9a and 9b are rods having different diameters from each other, and the support glass rods 9a have the same outer diameter as the core rod 5E. The support glass rods 9a and 9b become a part of the clad portion 2E. The support glass rods 9a and 9b have a function of arranging each core rod 5E at a predetermined position in the hole 3Ea of the glass rod 3E. Therefore, the four core rods 5E, the three support glass rods 9a, and the six support glass rods 9b are densely arranged in the holes 3Ea.

In the fine particle filling step, the glass fine particles 6 are filled in the inner surface of the hole 3Ea of the glass rod 3E and the gap between each core rod 5E and the support glass rods 9a and 9b, and the gap is filled with the glass fine particles 6.

Subsequently, the drawing step is performed in the same manner as in the first embodiment, but each gap filled with the glass fine particles is made airtight, and the pressure in each gap is set to a predetermined pressure value (argon gas pressure 0.85 in this embodiment). The glass rod 3E, the core rod 5E, the support glass rods 9a and 9b, and the glass fine particles 6 are heated and melted while being controlled to ~ 0.98 atm) to draw a line. As a result, the glass fine particles 6 become each microbubble region 2Ea, and the optical fiber 10E shown in FIG. 22 is manufactured by coating. The optical fiber 10E has, for example, an outer diameter of 125 μm.

According to the manufacturing method of the eighth embodiment, the optical fiber 10E is drawn while controlling the pressure in each gap filled with the glass fine particles to a predetermined pressure value in the drawing step, so that the characteristics of each microbubble region 2Ea can be easily obtained. Can be controlled. Further, the manufacturing method of the eighth embodiment can be easily carried out by applying a known stack & draw method. Further, according to the manufacturing method of the eighth embodiment, the outer diameters and arrangements of the core rod 5E and the support glass rods 9a and 9b can be arbitrarily determined, so that the optical fiber 10E in which the microbubble region 2Ea is formed at an arbitrary position can be easily obtained. Can be manufactured in. Therefore, the microbubble region 2Ea can be formed in a shape other than the annular shape. Further, by making the shape of the gap an arbitrary shape, the microbubble region 2Ea can be made an arbitrary shape. As a method of making the shape of the gap an arbitrary shape, for example, when the shapes of the core rod 5E and the support glass rods 9a and 9b are processed by machining or etching and inserted into the hole 3Ea of the glass rod 3E, a predetermined shape is obtained. There is a method of forming a gap shape. Further, it is also effective to use a glass pipe instead of the glass rod 3E to fill the pipe with fine particles.

In the first to third embodiments, the core portion is _{made of quartz glass to which GeO 2} is added, and the first clad layer or the clad portion is made of pure quartz glass, but the core portion is made of pure quartz glass. The first clad layer or the clad portion may be made of quartz glass to which a dopant (for example, fluorine) that lowers the refractive index is added. In this case as well, the difference in the refractive index of the core portion with respect to the first clad layer or the clad portion can be, for example, 0.23 to 3.5%.

Moreover, the present invention is not limited by the above-described embodiment. The present invention also includes a configuration in which the above-mentioned components are appropriately combined. For example, the measurement steps and adjustment steps of embodiments 6 and 7 can be carried out in combination with any of the above embodiments. Further, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

1, 1B, 1C, 1D, 1E Core part 2, 2A, 2B, 2C, 2D, 2E Clad part 2a, 2Aa 1st clad layer 2b, 2Ab 2nd clad layer 2c, 2Ac 3rd clad layer 2Ba, 2Ca, 2Da , 2Ea Microbubble region 3,3A, 3E Glass rod 3a, 3Aa, 3Bc, 3Cc, 3Ea Hole 3Aa, 3Ab, 5c Lower end 3B, 3C Optical fiber base material 3Ba, 3Ca, 5ba, 5Ea Core forming part 3Bb, 3Cb, 5bb, 5Eb Clad forming part 4, 4A Support pipe 5, 5E Core rod 5a Upper end part 5a Notch 5b Core rod body 5ca Groove 6 Glass fine particle 8 Glass molded body 8a Glass porous body 9a, 9b Support glass rod 10, 10A, 10B, 10C, 10D, 10E, F Optical fiber 100 lid 101, 107c Gas introduction pipe 102, 104, 107d Gas exhaust pipe 103 Vacuum pump 105 Pressure gauge 106 Optical fiber wire drawing furnace 106a, 107b Heater 107 Furnace 107a Furnace 107e Support 110 Dies 111, 113, 114 Measuring instrument 112 Laser light irradiator C Control unit L1 Light L2 Laser light L3 Transmitted light

Claims (14)

The core made of glass and
It is made of glass and has a clad portion formed on the outer periphery of the core portion.
A first clad region formed so that the clad portion is adjacent to the outer periphery of the core portion, and a second clad region formed at a position separated from the core portion and containing minute and irregular bubbles. It is a manufacturing method of an optical fiber that has
A core rod having a core forming portion to be the core portion and a clad forming portion to be the first clad region formed so as to be adjacent to the outer periphery of the core forming portion, and a length of a glass rod forming a part of the clad portion. Insertion process to insert into a hole stretched in the direction,
A fine particle filling step of filling the gap between the inner surface of the hole of the glass rod and the core rod with fine glass particles.
A wire drawing step in which the gap filled with the glass fine particles is made airtight, and the glass rod, the core rod, and the glass fine particles are heated and melted to draw an optical fiber.
A method for producing an optical fiber, which comprises the above, and the glass fine particles are made into the second clad region by the drawing step. The optical fiber includes a plurality of the core portions, and the optical fiber includes a plurality of the core portions.
In the insertion step, the glass rod is inserted into each hole of the glass rod having the plurality of holes, and in the fine particle filling step, the glass fine particles are filled in the gap between the inner surface of the hole of the glass rod and each of the core rods. The method for manufacturing an optical fiber according to claim 1, wherein the optical fiber is manufactured. The core made of glass and
It is made of glass and has a clad portion formed on the outer periphery of the core portion.
A method for manufacturing an optical fiber in which the clad portion is formed at a position separated from the core portion and has a microbubble region containing minute and irregular bubbles.
It is provided with a core forming portion to be the core portion and an integral clad forming portion to be the clad portion formed so as to be adjacent to the outer periphery of the core forming portion, and is extended in the longitudinal direction to a part of the clad forming portion. A fine particle filling step of filling the holes of the optical fiber base material in which a plurality of holes separated from each other are formed with glass fine particles,
A wire drawing step in which the holes filled with the plurality of glass fine particles are made airtight, and the optical fiber base material and the glass fine particles are heated and melted to draw an optical fiber.
A method for producing an optical fiber, which comprises the above, and the glass fine particles are made into the fine bubble region by the drawing step. The optical fiber includes a plurality of the core portions, and the optical fiber includes a plurality of the core portions.
The method for producing an optical fiber according to claim 3, wherein in the fine particle filling step, the glass fine particles are filled in the holes of the optical fiber base material having the plurality of core portions. The core made of glass and
It is made of glass and has a clad portion formed on the outer periphery of the core portion.
A method for manufacturing an optical fiber in which the clad portion is formed at a position separated from the core portion and has a microbubble region containing minute and irregular bubbles.
A glass having a core forming portion to be a core portion and a plurality of core rods having a clad forming portion to be a part of the clad portion formed so as to be adjacent to each other over the outer periphery of the core forming portion to be a part of the clad portion. An insertion step of inserting a plurality of support glass rods into a hole extended in the longitudinal direction of the rod and inserting a plurality of support glass rods into a gap between the inner surface of the hole of the glass rod and the plurality of core rods.
A fine particle filling step of filling the gap between the inner surface of the hole of the glass rod, the plurality of core rods, and the plurality of support glass rods with glass fine particles.
The gaps filled with the plurality of glass fine particles are made airtight, and the glass rod, the core rod, the support glass rod, and the glass fine particles are heated and melted to draw an optical fiber.
A method for producing an optical fiber, which comprises forming the glass fine particles into the fine bubble region by the drawing step. The method for producing an optical fiber according to any one of claims 1 to 5, wherein in the fine particle filling step, the average particle size of the glass fine particles to be filled is 50 μm or more. The method for producing an optical fiber according to any one of claims 1 to 6, wherein the glass rod or the optical fiber base material is vibrated while or after the glass fine particles are filled. The core made of glass and
It is made of glass and has a clad portion formed on the outer periphery of the core portion.
A first clad region formed so that the clad portion is adjacent to the outer periphery of the core portion, and a second clad region formed at a position separated from the core portion and containing minute and irregular bubbles. It is a manufacturing method of an optical fiber that has
A core rod having a core forming portion to be the core portion and a clad forming portion to be the first clad region formed over the outer periphery of the core forming portion, and a glass porous body formed so as to be adjacent to the outer periphery of the core rod. An insertion step of inserting a glass molded body comprising the above into a hole extended in the longitudinal direction of a glass rod that becomes a part of the clad portion.
A wire drawing step in which the hole into which the glass molded body is inserted is made airtight, and the glass rod and the glass molded body are heated and melted to draw an optical fiber.
A method for producing an optical fiber, which comprises the above, and the glass porous body is made into the second clad region by the drawing step. The optical fiber includes a plurality of the core portions, and the optical fiber includes a plurality of the core portions.
The method for manufacturing an optical fiber according to claim 8, wherein in the insertion step, the glass molded body is inserted into each hole of the glass rod having the plurality of holes. The method for producing an optical fiber according to any one of claims 1 to 9, wherein a dopant that lowers the refractive index of glass is added to the clad forming portion. A measurement process for measuring the brightness of the drawn optical fiber and
The production of the optical fiber according to any one of claims 1 to 10, further comprising an adjustment step of adjusting the drawing conditions in the drawing step based on the measurement result obtained in the measuring step. Method. A measurement step of irradiating the drawn optical fiber with light and measuring at least one of the transmitted light and the reflected light.
The production of the optical fiber according to any one of claims 1 to 10, further comprising an adjustment step of adjusting the drawing conditions in the drawing step based on the measurement result obtained in the measuring step. Method. The adjusting step is characterized in that the inside of the support pipe provided at the upper end of the glass rod and the gap between the inner surface of the hole of the glass rod and the core rod are adjusted to a predetermined pressure value . The method for manufacturing an optical fiber according to any one of claims 11 and 12 , wherein any one of 5, 8 and 9 is cited. Four cores arranged in a square grid made of glass,
It is made of glass and includes a clad portion formed adjacent to the outer periphery of the core portion.
The clad portion is formed in a shape other than an annular shape surrounding the core portion between the two core portions at a position separated from the core portion, and has a micro bubble region containing minute and irregular bubbles. An optical fiber characterized by.

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