JP2001089160A - Method for forming glass layer, method for producing optical fiber preform, method for producing optical fiber, and metal chemical vapor deposition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an optical fiber preform and optical fiber having a core and/or clad section little changing in composition or shape in the longitudinal (axial) direction. SOLUTION: This method is for forming a glass layer over the inner peripheral area of a hollow tube, comprising steps of (1) reacting the gaseous stock for the glass layer, ejected into the hollow tube from a gaseous stock ejecting port moving in the longitudinal direction of the hollow tube, with oxygen to continuously deposit the resultant glass layer precursor over the inner peripheral area of the hollow tube in the longitudinal direction, and (2) heating the glass layer precursor to form the glass layer. The method of another invention for forming a glass layer over the inner peripheral area of a hollow tube, comprising a step of reacting the gaseous stock for the glass layer, ejected into the hollow tube from a gaseous stock ejecting port moving in the longitudinal direction of the hollow tube, with oxygen to continuously deposit the glass layer over the inner peripheral area of the hollow tube in the longitudinal direction. The method and device of still other invention are for producing a optical fiber preform and optical fiber using one of the above methods.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a glass layer on the inner peripheral surface of a hollow tube by an MCVD method (internal chemical vapor deposition), a method for manufacturing a glass (optical) fiber preform, and a manufacturing apparatus. In particular, the present invention belongs to a technical field related to a method of manufacturing an optical fiber to which a light emitting substance is added for laser oscillation and an optical amplifier.

[0002]

2. Description of the Related Art In recent years, in the field of optical communication technology, a quartz optical fiber having extremely low loss has been used as an optical fiber for transmission. It is also known that by adding a rare earth element such as Pr, Yb, Nd, or Er as a light emitting substance to an optical fiber, an oscillator and an amplifier with extremely high efficiency can be manufactured. In order for light incident into the fiber to propagate through the core layer while causing total reflection, a core layer with a high refractive index is provided at the center, and a cladding layer with a lower refractive index than the core layer is provided around the core. Optical fiber preforms have been manufactured. In a silica-based optical fiber, the main component of each layer is silica glass (SiO ₂ ), but in the core layer, germanium (Ge) is added to increase the refractive index, and in the cladding layer, the refractive index is decreased. Fluorine (F), boron (B) and the like are added, and phosphorus (P) is added for the purpose of lowering the vitrification temperature during production. In a quartz-based optical fiber for ordinary optical communication, an optical fiber doped with Ge that can relatively increase the refractive index of the core layer is used only for the purpose of totally reflecting the propagation light in the core layer. However, for the purpose of adding new functions such as for fiber lasers or optical amplifiers, P and P
Fibers to which rare earth elements such as r, Yb, Nd, and Er are added are used.

[0003] As a method for producing a quartz optical fiber preform, there are internal chemical vapor deposition (MCVD), external vapor deposition (OVD), axial vapor deposition (VAD) and the like. MCVD is widely used in terms of the ease of controlling the composition of deposited compounds by adjusting the gas flow rate into the quartz tube in the time domain, and the ease of controlling the deposition by controlling the tube surface temperature using an oxyhydrogen burner. I have. Where MC
An outline of a method for producing a fiber preform by the VD method will be described. FIG. 1 shows an overall schematic view of the MCVD apparatus. The MCVD apparatus includes a glass raw material supply unit 1 and a glass lathe 2 equipped with a quartz tube 5. Each container filled with a liquid chloride raw material ₃ such as SiCl ₄ , GeCl ₄ , POCl ₃ is installed in a glass raw material supply portion, and the liquid raw material is vaporized by supplying oxygen gas into the container and bubbling the liquid. Phase is obtained to obtain a raw material gas for the process. These source gases are supplied together with a carrier gas such as oxygen gas into a quartz tube mounted on a glass lathe. The glass lathe is provided with a heating reaction source 4 such as an oxyhydrogen burner, and has a structure in which a mounted quartz tube 5 is caused to react from the outside while rotating in the axial direction. In the quartz tube, the supplied respective chlorine source gases and the oxygen gas undergo a reaction represented by, for example, the formula 1) to form oxide fine particles.

[0004]

Embedded image SiCl ₄ + O ₂ → SiO ₂ + 2Cl ₂ 1)

[0005] The generated oxide fine particles are deposited as a porous soot in a quartz tube. By treating the deposited soot at a higher temperature, a sintered and transparent glass body can be obtained. After these glass compositions are formed in the quartz tube, the tube is heated at a high temperature near the softening temperature of the quartz tube, whereby the hollow quartz tube is solidified and a rod-shaped fiber preform can be manufactured. The advantages of the MCVD method can be summarized in the following three points. (1) Since the preform manufacturing process can be performed in a state close to a closed system, the absorption loss due to impurity contamination can be reduced to a negligible level. (2) Since glass is synthesized in a thin layer, air bubbles are less taken up and scattering loss can be reduced. (3) The refractive index distribution can be easily formed in the radial direction of the preform.

[0006]

However, many problems remain from a practical point of view. Among them, the following three points are important: (1) the glass composition in the longitudinal direction is not constant; (2) the amount of deposition is limited; and (3) the amount of addition of a luminescent substance or the like is limited. As a general method of adding a rare earth element as a light emitting substance to the core and / or cladding layer in the conventional MCVD method, a method of immersing a rare earth compound solution and a method of vaporizing the rare earth compound are known. Have been.

[0007] The first problem is that in the MCVD method, while a glass material in a gaseous state is introduced from one end of a quartz tube and discharged from the other end, a part of the material reacts with the oxygen and deposits. This is due to the fact that the component ratio and the amount of the raw material gas flow change between upstream and downstream. Therefore, the glass composition and the deposition amount vary in the longitudinal direction of the preform, and the shape and refractive index of the core and / or cladding of the drawn fiber fluctuate. Furthermore, for the same reason, the distribution of the concentration of the added luminescent substance in the longitudinal direction occurs. In extreme cases, due to fiber shape and refractive index fluctuation,
In some cases, the light propagation structure changes and causes loss.
In addition, since the concentration of the luminescent material differs in the longitudinal direction, the oscillation and amplification characteristics differ depending on the location of the fiber, and there is also a problem that stable characteristics cannot be obtained.

The second problem is particularly important when producing a multimode fiber. When producing a preform for a multimode fiber by the MCVD method, it is necessary to deposit a large amount of a core glass component in order to increase the core diameter. In the conventional method, since the soot that can be deposited by one sweep is thin, it was necessary to increase the number of depositions by sweeping the heating source (for example, about six times) and increase the thickness of the core glass layer. However, the problem here is that the glass layer often peels off during repeated deposition, and the core-cladding structure to be formed is destroyed, resulting in increased losses. Is to occur.

The third problem is related to the second problem. In the case of adding a luminescent substance or the like, the amount that can be added at one time is limited in the same situation as the second problem in the gas phase addition.
In addition, in the case of adding in a liquid phase, since a liquid containing a luminescent substance is immersed in the deposited glass layer and taken in, if the glass deposition amount is small, the addition amount of the luminescent substance or the like is limited. As a result, it was difficult to add a high concentration of a luminescent substance or the like. As described above, in the conventional MCVD method, it was difficult to produce a preform having no change in composition and shape in the longitudinal direction, a large core diameter, and a high concentration of a luminescent substance.

Accordingly, an object of the present invention is to provide a method of forming a glass layer having a composition and a shape that are extremely small in the longitudinal direction (axial direction) of the inner peripheral surface of a hollow tube, and an optical fiber motherboard using the method. An object of the present invention is to provide a method for manufacturing a material, and a method for manufacturing an optical fiber from a preform obtained by the manufacturing method. In addition, an object of the present invention is to provide an apparatus for forming a glass layer on the inner peripheral surface of a hollow tube, in which the composition and the shape of the glass layer vary little along the longitudinal direction (axial direction).

[0011]

SUMMARY OF THE INVENTION The present invention is a method for forming a glass layer on the inner peripheral surface of a hollow tube, wherein the raw material gas for the glass layer is supplied from a raw material gas outlet moving in the axial direction of the hollow tube. Spouting into the hollow tube, reacting the spouted raw material gas with oxygen to continuously deposit a glass layer precursor on the inner surface of the hollow tube along the axial direction of the hollow tube, and the glass layer precursor To form a glass layer by heating (hereinafter referred to as a first glass layer forming method). Further, the present invention is a method of forming a glass layer on the inner peripheral surface of the hollow tube, from a raw material gas jet port moving in the axial direction of the hollow tube, to eject a raw material gas of the glass layer into the hollow tube, The present invention relates to a method including a step of reacting ejected raw material gas with oxygen to continuously deposit a glass layer on the inner peripheral surface of the hollow tube along the axial direction of the hollow tube (hereinafter, referred to as a second glass layer forming method). .

Further, the present invention provides a method of manufacturing an optical fiber preform having a core glass and a cladding glass, wherein the glass layer made of the cladding glass is hollowed out by the method of forming the first or second glass layer of the present invention. Formed on the inner peripheral surface of the tube, and then the first or second glass layer forming method of the present invention is used to form a glass layer made of glass for core on a glass layer made of glass for cladding, or a glass for cladding. A glass layer made of glass for a core is formed on the inner peripheral surface of a hollow tube having a glass layer made of the first or second glass layer forming method of the present invention, and then the hollow tube is solidified to form the base material. A method characterized by obtaining
In addition, the present invention provides a method for producing an optical fiber preform for a hollow core fiber, wherein a glass layer made of glass for cladding is formed on the inner peripheral surface of a hollow tube by the method for forming a first or second glass layer of the present invention. And thereby obtaining a hollow base material. Furthermore, the present invention
The present invention relates to a method of producing an optical fiber by preparing an optical fiber preform by the method of the present invention, and heating and drawing the preform.

[0013] The present invention also provides a chemical vapor deposition apparatus for forming a deposit on the inner peripheral surface of a hollow tube, wherein a holding portion for holding the hollow tube and a hollow tube for holding the hollow tube are provided. A rotating part for rotating around the axis of the tube, a raw material gas which can be inserted into the held hollow tube, and which has a raw material gas outlet at its tip for supplying the raw material gas of the deposit to the inside of the hollow tube A supply tube, wherein the raw material gas ejection port is movable relative to the hollow tube in an axial direction of the hollow tube while being inserted into the hollow tube; The present invention relates to an apparatus having an exhaust unit for exhausting the inside of a tube, and a heating means movable relatively to the held hollow tube and locally heating the hollow tube from the outside.

In the method of the present invention, in the MCVD method, the source gas is jetted from the source gas jet at the tip of the movable source feed tube, and the distance between the source gas jet and the reaction deposition section is always kept constant. By keeping it, the deposition conditions are made uniform in the axial direction of the hollow tube, and a uniform porous layer (precursor) or glass layer can be formed. Further, since the raw material gas is directly supplied to the reaction and deposition section, the raw material gas can be heated and reacted immediately after being blown out from the raw material gas outlet, so that there is an advantage that a large number of glass layers can be deposited by one sweep. is there. Hereinafter, the present invention will be described more specifically.

[0015]

FIG. 2 shows an apparatus used in the method of the present invention. This apparatus is a chemical vapor deposition apparatus 10 for forming a deposit on the inner peripheral surface of a hollow tube 5. Apparatus 10
Is a holding unit 11 for holding the hollow tube 5 at both ends, a rotating unit 12 for rotating the held hollow tube 5 around the axis of the hollow tube 5, and inserted into the held hollow tube 5. It has a source gas supply tube 6 having a source gas outlet 8 for supplying a source gas of sediment to the inside of the hollow tube 5 at the tip thereof. The raw material gas ejection port 8 is movable relative to the hollow tube in the axial direction of the hollow tube while being inserted into the hollow tube 5. Furthermore, the device 10 is capable of moving relative to the held hollow tube 5 with an exhaust unit (not shown) for exhausting the inside of the hollow tube 5, so that the hollow tube can be locally moved from the outside. And a heating means 4 for heating. The hollow tube 5 can be, for example, a quartz tube, and the heating means 4 can be an oxyhydrogen burner.

As described above, a preform manufacturing system for carrying out the present invention includes a glass lathe for supporting and rotating both ends of a quartz glass tube, a raw material gas supply system for mixing a desired glass raw material composition, and quartz glass. It is implemented in an apparatus having a moving heating source for externally heating the tube. However, these are nothing but the basic configuration of a conventional MCVD apparatus. In addition, a glass lathe and a heating burner can be used as they are in a conventional MCVD apparatus. In order to solve the above-mentioned problem by the present invention, it is only necessary to provide a function of controlling the movement and the moving speed of the raw material gas supply tube. Here, the source gas supply tube includes at least one movable tube, but a plurality of source gas supply tubes can be used according to the purpose. For example, a carrier gas such as an oxygen gas or a He gas may be supplied from the movable tube together with the raw material gas, or a part thereof may be supplied from another tube as an atmosphere control gas. In this case, the atmosphere control gas supply tube may be fixed.

Further, as will be described later, for example, a movable tube can also be used when a luminescent substance is added by a spray method (JP-A-5-330842). This liquid phase addition movable tube may be the same as the raw material gas supply tube, but there is a possibility that the liquid remaining on the tube may be sprayed. It is preferable to use. The plurality of tubes may be arranged in parallel with each other as shown in FIG. 2, or may be a multi-tube as shown in FIG. Material supply tube material is MCVD
What does not cause thermal deformation or chemical change during the process is required. This is because if the shape of the ejection port changes due to thermal deformation, it becomes difficult to control the flow rate of the gas or the liquid containing the luminescent substance. or,
Bending the tube creates a risk of contact with the sediment, creating foreign material and, in severe cases, destroying the fiber structure.
Further, if the material of the tube is eroded due to a chemical change, foreign particles fall on the sediment due to deterioration of durability, causing a significant change in composition. In the apparatus of the present invention,
It is desirable to introduce a computer for CPU control of the above components and to eliminate human error, and to achieve automation.

In the first method for forming a glass layer according to the present invention, a raw material gas for a glass layer is injected into the hollow tube 5 from a raw material gas outlet 8 moving in the axial direction of the hollow tube 5. The ejected raw material gas is reacted with oxygen supplied as a carrier gas to deposit a glass layer precursor continuously on the inner peripheral surface of the hollow tube along the axial direction of the hollow tube. The raw material gas is supplied to the vicinity of the deposition position of the glass layer precursor by discharging the raw material gas of the glass layer into the hollow tube 5 from the raw material gas outlet 8 moving in the axial direction of the hollow tube 5. It is possible to increase the deposition amount of the glass layer precursor per deposition step and to control the deposition amount. Further, it is preferable that the moving speed of the source gas jet and the amount of the source gas jetted from the source gas jet be adjusted so that the deposition amount of the glass layer precursor is uniform in the axial direction of the hollow tube. For the purpose of adjusting the deposition amount of the glass layer precursor to be uniform in the axial direction of the hollow tube, for example, moving the raw material gas outlet at a constant speed and quantitatively discharging the raw material gas Can be. The amount of the source gas ejected into the hollow tube and the moving speed of the source gas outlet can be appropriately determined in consideration of the composition of the source gas, heating conditions for deposition, and the like.

The hollow tube near the source gas outlet is heated at a temperature sufficient to allow the source gas to react with oxygen and be converted into a glass layer precursor. The temperature sufficient for the source gas to react with oxygen and be converted to a glass layer precursor is, for example, 1000
In the range of ~ 2000 ° C. The heating of the hollow tube can be locally performed from outside the hollow tube using the heating means 4 as shown in FIG. The deposition amount of the glass layer precursor varies depending on the supply amount of the raw material gas and the heating conditions at the deposition position. Therefore, in the above case, depositing the glass layer precursor while maintaining a constant distance between the heating position (deposition position) of the hollow tube and the raw material gas outlet, the deposition conditions of the glass layer precursor are fixed. From the viewpoint of keeping the composition and amount of the glass layer constant.

The deposition of the glass layer precursor may be performed two or more times, if desired, to laminate the glass layer precursor.
The number of repetitions of deposition of the glass layer precursor can be appropriately determined according to the thickness of the formed glass layer. Incidentally, the thickness obtained by one deposition by the method of the present invention is, for example, 0.1 to 1.
It is about 0 mm. After laminating the glass layer precursor, the glass layer precursor lamination is heated to form a glass layer. The heating of the glass layer precursor for forming the glass layer varies depending on the composition of the glass, but is suitably performed, for example, at a temperature in the range of 1400 to 2200 ° C. The heating of the hollow tube performed for heating the glass layer precursor is performed locally from outside the hollow tube using the heating means 4 as shown in FIG. It can be carried out.

Further, in the second method for forming a glass layer according to the present invention, the raw material gas injection port 8 moving in the axial direction of the hollow tube is used to
The raw material gas for the glass layer is jetted into the hollow tube 5,
The ejected raw material gas is reacted with oxygen supplied as a carrier gas to continuously deposit a glass layer on the inner peripheral surface of the hollow tube along the axial direction of the hollow tube. By injecting the raw material gas of the glass layer into the hollow tube 5 from the raw material gas outlet 8 moving in the axial direction of the hollow tube 5, the raw material gas can be supplied near the deposition position of the glass layer, It is easy to increase the amount of glass layer deposited per deposition step and to control the amount of deposition. Further, the moving speed of the source gas jet and the amount of the source gas jetted from the source gas jet are
It is preferable that the deposition amount of the glass layer is adjusted to be uniform in the axial direction of the hollow tube. For the purpose of adjusting the deposition amount of the glass layer to be uniform in the axial direction of the hollow tube, for example, the movement of the raw material gas outlet can be performed at a constant speed, and the raw material gas can be discharged quantitatively. . The amount of the source gas ejected into the hollow tube and the moving speed of the source gas outlet can be appropriately determined in consideration of the composition of the source gas, heating conditions for deposition, and the like.

The heating of the hollow tube can be locally performed from outside the hollow tube using the heating means 4 as shown in FIG. In this case, depositing the glass layer precursor while keeping the distance between the heating position of the hollow tube and the raw material gas outlet constant, making the deposition conditions of the glass layer constant,
It is preferable from the viewpoint of keeping the composition and amount of the glass layer constant.

The glass layer may be deposited two or more times, if desired, to laminate the glass layers. The number of repetitions of the deposition of the glass layer can be appropriately determined according to the thickness of the formed glass layer. The heating for forming the glass layer varies depending on the composition of the glass. For example, it is appropriate to perform the heating at a temperature in the range of 1400 to 2200 ° C.

The above method will be further described with reference to FIG. A hollow tube (quartz tube) is mounted on a glass lathe, and SiCl ₄ , S
A raw material gas such as iF ₄ or POCl ₃ is supplied into a quartz tube from a glass raw material supply device 1 together with a carrier gas such as oxygen gas, and heated with an oxyhydrogen burner 4 from the outside of the quartz tube to react with oxygen. , Depositing a glass layer precursor or glass layer. At this time, it is preferable that the raw material gas supply tube 6 be moved together with the burner 4 so that the injection port is always at a certain distance from the place where the deposition reaction is most active. The carrier gas such as oxygen gas is supplied to the movable tube 6 together with the raw material gas.
However, as shown in FIG. 2, part of the atmosphere control gas is used as the atmosphere control gas.
It may be supplied from. In this case, the atmosphere control gas supply pipe 7 is not necessarily movable, and may be fixed to one end (upstream side) of the quartz pipe.

In the first method for forming a glass layer according to the present invention,
After forming the glass layer precursor and before forming the glass layer, a luminescent substance or a precursor thereof is added to the glass layer precursor, and then the obtained luminescent substance-containing glass layer precursor is heated, whereby the luminescent substance is obtained. Can be formed.
Alternatively, a glass layer containing a luminescent substance can also be formed by using a gas containing a luminescent substance or a precursor thereof as the source gas. In the second method for forming a glass layer of the present invention, a glass layer containing a light-emitting substance can be formed by using a gas containing a light-emitting substance or a precursor thereof as the source gas. The luminescent substance and its precursor can be appropriately selected from known substances.

The addition of a luminescent substance to the above-mentioned glass layer precursor is described, for example, in JP-A-5-330842 and JP-A-9-309.
In addition to the solution immersion method described in JP-A-2866, the method described in Japanese Patent Application No. 10-371754 can also be used. When the method described in Japanese Patent Application No. 10-371754 is used, a luminescent substance or a medium containing a luminescent substance is sprayed on the glass layer precursor layer. The spraying of the luminescent substance or the medium containing the luminescent substance can be performed by inserting the luminescent substance into the hollow tube and performing the spraying from the vicinity of the tip of the nozzle which moves relatively to the hollow tube. By spraying the luminescent substance or the medium containing the luminescent substance from the nozzle tip in this manner, the luminescent substance can be added uniformly.
In particular, it is preferable to spray the luminescent substance or the medium containing the luminescent substance so that the content of the luminescent substance in the axial direction of the hollow tube becomes uniform. From that perspective,
It is preferable that the moving speed of the tip of the nozzle is constant, and that the luminescent substance or the medium containing the luminescent substance is sprayed from the tip of the nozzle quantitatively.

When a luminescent substance such as a rare earth element is added in a liquid phase as described above, a solution prepared in advance, such as an alcohol containing a rare earth element, is poured into a tube, and the solution is immersed in a porous glass layer precursor. Then, it is appropriate to dry the inside of the tube while flowing chlorine gas or the like, evaporate the solvent, and add a luminescent substance such as a rare earth element. Furthermore, by heating and sintering the obtained glass layer precursor containing a luminescent substance at a high temperature, a transparent glass body layer can be obtained.

As described above, as a method for adding a luminescent substance for laser oscillation or light amplification, for example, as a method for adding a solution, a spray method described in JP-A-5-330842,
9-142866 and the like. In each case, after forming a porous layer on the inner wall of the quartz tube, a solution such as alcohol containing a rare earth element prepared in advance is poured into the tube and immersed in the solution.
This is a method in which the inside of the tube is dried while flowing a chlorine gas or the like to evaporate the solvent and a rare earth element is added to the porous layer.
On the other hand, as a method of gas phase addition, Journal of American
It is introduced in Ceramic Society Vol. 73, No. 12 (1990) p. 3537-3556 or JP-A-9-25135. A typical method is to separate the usual preform forming part in a quartz tube,
A portion filled with a powder containing a rare earth element is formed, and the powder portion is heated from the outside of the tube at a high temperature to generate a vaporized rare earth gas and supply the gas to a preform forming portion together with a carrier gas such as oxygen. . As a result, rare earth elements are deposited on the fiber preform portion, and a rare earth added core is obtained.

When a gas containing a luminescent substance or a precursor thereof is used as the raw material gas, the raw material gas of the core glass such as SiCl ₄ , GeCl ₄ , or the luminescent substance is added to the surface of the cladding layer while moving the tube 6 in the same manner. A glass layer precursor or a glass layer containing a light-emitting substance can be formed by supplying the mixture into a quartz tube together with a carrier gas such as described above. As described above, the glass layer precursor containing the luminescent substance can be heated and sintered at a high temperature to form a transparent glass body layer. Finally, the quartz tube is solidified to produce a fiber preform. As described above, in the production of an optical fiber for oscillation and amplification,
In depositing the core and / or cladding layer, a component containing a luminescent substance may be added to the raw material gas, or may be added by dipping in a liquid layer. For example, it may be added by a spray method as disclosed in the above-mentioned JP-A-5-330842.

By using the glass layer forming method of the present invention, an optical fiber preform having a core glass and a cladding glass can be manufactured. For example, a glass layer made of glass for cladding is formed on the inner peripheral surface of a hollow tube by the method of forming the first or second glass layer of the present invention, and then the core is formed by the method of forming the first or second glass layer of the present invention. An optical fiber preform can be obtained by forming a glass layer made of glass for use on a glass layer made of glass for cladding and then solidifying the hollow tube. Alternatively, a glass layer made of glass for core is formed on the inner peripheral surface of a hollow tube having a glass layer made of glass for clad formed by a known method or the like by the method for forming the first or second glass layer of the present invention, and thereafter, The optical fiber preform can also be obtained by solidifying the hollow tube.

Further, by using the method for forming a glass layer of the present invention, an optical fiber preform for a hollow core fiber can be produced. For example, a hollow optical fiber preform can be manufactured by forming a glass layer made of glass for cladding on the inner peripheral surface of a hollow tube by the first or second method for forming a glass layer of the present invention.

In the method of the present invention, by ejecting the gas from the movable raw material supply tube, the raw material gas always reacts under the same conditions as compared with the conventional method, so that the porous core and the clad layer can be uniformly deposited. The raw material gas is thermally reacted and deposited immediately after it is ejected from the supply pipe, so that the deviation from the desired composition, addition amount and deposition amount is eliminated and stabilized. Since the raw material consumption by the reaction is eliminated, the raw material gas used can be minimized and an excessive component addition layer is not formed, and the raw material gas is thermally reacted immediately after being ejected, so that it is deposited efficiently and in large quantities. have.

According to the present invention, an optical fiber preform is manufactured by using an MC.
This is a method of manufacturing by the VD method. In the present invention, the optical fiber
The composition of the core and clad glass of the bar was known before.
There is no particular limitation. For example, SiO_Two-GeO_Two, S
iO_Two-GeO_Two-Al_TwoO_Three, SiO_Two-GeO_Two-Al _TwoO_Three-MgO, etc. glass
Can be mentioned. The present invention is produced by the method of the present invention.
The manufactured optical fiber preform is heated, drawn, and
And a method for producing iva. Optical fiber preform
Heating and drawing can be performed according to a conventional method. Book
The optical fiber obtained by the manufacturing method of the invention has a core and
And the cladding glass composition is uniform in the axial direction
When a light-emitting substance is contained, the content of the light-emitting substance is also
It is uniform and the content of the luminescent substance is higher than before.
You can also.

[0034]

The present invention will be described in more detail with reference to the following examples. Tables 1 and 2 show the operating conditions of each example, and Table 3 shows the characteristics of the obtained fiber.

Example 1 A quartz tube having an outer diameter of 25 mm, an inner diameter of 21 mm, and a length of 1 m was used as a start tube, and both ends were supported and rotated on a glass lathe of an MCVD apparatus. The following steps were performed to prepare a preform. Supply 20 sccm of C ₂ F ₆ gas into the start quartz tube, and use an oxyhydrogen burner to
The inside of the quartz tube was cleaned by heating at 00 ° C. 1) In the starting quartz tube, SiCl ₄ (400 sccm), SiF ₄ , which is a material gas for the cladding layer, together with oxygen gas O ₂ (1000 sccm) via a material gas supply quartz tube that can move in the axial direction.
(400 sccm) gas was supplied. 2) The outer wall of the starting quartz tube was heated to about 1600 ° C. with an oxyhydrogen flame, whereby the glass raw material in the starting quartz tube was deposited on the inner wall as glass particles by a thermal oxidation reaction. 3) While keeping the distance between the oxyhydrogen flame and the spout of the raw material gas supply quartz tube always at 20 cm, the two were repeatedly swept five times in the axial direction to deposit a clad glass layer in a multilayer shape in the start tube. 4) SiCl ₄ (200 sccm), GeCl ₄
(200sccm), Cl ₂ (70sccm), He (1500sccm), O ₂ (400scc
m) The gas was flowed into the quartz tube, and the oxyhydrogen flame and the quartz tube for supplying the raw material gas were swept once as in 4) to deposit a core glass at about 1800 ° C. 5) Flow O ₂ (400sccm) gas, sweep the quartz tube for supplying the oxyhydrogen flame and the raw material gas four times in the same manner as in 4), and solidify the quartz tube while heating it at a high temperature of about 2000 ° C to perform a preform. A rod was made. 6) The measurement results of the characteristics of the single mode fiber produced from the preform obtained by the above steps are shown.
See Figure 3. It was confirmed that the characteristics of the obtained fiber did not vary depending on the fiber position, and that the core and the cladding layer were formed uniformly and uniformly in the axial direction at the preform stage. 7) On the other hand, in the sweeping of the above steps 4) to 7), the raw material gas supply quartz tube fixed to one end of the start tube, and the raw material gas was flowed and deposited and sintered, as shown in Table 3. It was recognized that the propagation characteristics and the core diameter changed little by little from the first half to the second half of the fiber drawing. Especially, the fiber at the rear did not meet the specifications.

Example 2 A quartz tube having an outer diameter of 25 mm, an inner diameter of 21 mm and a length of 1 m was used as a start tube, and both ends were supported and rotated on a glass lathe of an MCVD apparatus. Next, two quartz tubes for gas supply were set in parallel and set, and one of them could be moved in the axial direction, and a preform was manufactured in the following steps. A preform was prepared by the following steps. 1) 20 sccm of C ₂ F ₆ gas was supplied into the starting quartz tube, and heated at about 1500 ° C. with an oxyhydrogen burner to etch and clean the inside of the quartz tube. 2) Of the quartz tubes for gas supply, the one that can move in the axial direction is a quartz tube for supplying source gas, through which oxygen gas O ₂ (5
00sccm) and SiCl ₄ (4
00 sccm) and SiF ₄ (400 sccm) gas were supplied into the starting quartz tube. Oxygen gas O ₂ (300 sccm) and He (100 sc) were passed through another quartz tube with the ejection port fixed upstream of the start quartz tube.
0 sccm) was supplied as an atmosphere control gas. 3) The outer wall of the starting quartz tube was heated to about 1600 ° C. with an oxyhydrogen flame, so that the glass material in the starting quartz tube was deposited on the inner wall as glass particles by a thermal oxidation reaction. 4) While keeping the distance between the oxyhydrogen flame and the jet port of the quartz tube for supplying the raw material gas always 20 cm, the two were repeatedly swept five times in the axial direction to deposit a multilayer clad glass layer in the start tube. 5) SiCl ₄ (200 sccm), GeCl ₄ (100 sccm), O ₂ (400 sccm) in the start quartz tube via a quartz tube for supplying a raw material gas.
The gas was flowed into the quartz tube, and the quartz tube for supplying the oxyhydrogen flame and the raw material gas was swept once as in 4) to deposit a porous core layer at about 1300 ° C. 6) A liquid was prepared by dissolving 0.015 mol of erbium chloride (ErCl ₃ .6H ₂ O) and 0.5 mol of aluminum chloride (AlCl ₃ ) in 1 L of ethanol. 7) The solution is supplied at a spray rate of 2 (cc) / min through a quartz tube for supplying a raw material gas into the quartz tube having the porous core layer formed in 5) above, and the inside of the quartz tube is 1 (min). After reciprocating the spray nozzle between them, the supply of the liquid was stopped. 8) Burner heating was repeated at about 1000 ° C. while supplying Cl ₂ (70 sccm) gas into the starting quartz tube to dry the inside of the tube. 9) O ₂ (70sccm) and He (1500sccm) gas are supplied from the atmosphere gas supply quartz tube into the start quartz tube to generate an oxyhydrogen flame.
The core layer was sintered into a transparent glass body at about 1800 ° C. with four sweeps. 10) O ₂ (400 sccm) gas was flowed, the oxyhydrogen flame was swept four times, and the quartz tube was solidified while heating at a high temperature of about 2000 ° C. to produce a preform rod.

Table 3 shows the measurement results of the characteristics of the single-mode fiber for amplification manufactured from the preform obtained by the above steps. It was confirmed that the characteristics of the obtained fiber did not vary depending on the fiber position, and that the core and the cladding layer were formed uniformly and uniformly in the axial direction at the preform stage. Table 3 shows the measurement results of the Er concentration distribution. It was confirmed that Er ions were uniformly added in the core regardless of the location of the fiber. The reason why the Er concentration slightly spreads at the clad / core layer interface is that ions diffuse into the formed clad. In addition, the amplifier manufactured using this fiber had a constant amplification characteristic irrespective of the location of the fiber used, and all satisfied the specifications. On the other hand, in the sweeping of the above process, the raw material gas was supplied and deposited and sintered while the raw material gas supply quartz tube was fixed to one end of the start tube, and as shown in Table 3, the first half to the second half of the fiber drawing was performed. It was recognized that the propagation characteristics and the core diameter gradually changed as the process reached. Also, as shown in Table 3, it was confirmed that the Er concentration in the core layer depends on the location of the fiber, and the more ions were added toward the rear part of the drawing, that is, toward the gas upstream side during preform fabrication. Was.
The amplification characteristics of the manufactured amplifiers were slightly different depending on the fibers used, and in particular, those using the rear fiber did not satisfy the specifications.

Example 3 A quartz tube having an outer diameter of 25 mm, an inner diameter of 21 mm and a length of 1 m was used as a start tube, and both ends were supported and rotated on a glass lathe of an MCVD apparatus. Next, of the quartz tubes for gas supply composed of double tubes, the inner tube was set so as to be movable in the axial direction, and a preform was manufactured in the following steps. 1) 20 sccm of C ₂ F ₆ gas was supplied into the starting quartz tube and heated at about 1500 ° C. with an oxyhydrogen burner to etch and clean the inside of the quartz tube. 2) In the start quartz tube, oxygen gas O ₂ (500 sccm) and SiCl ₄ (400 sccm), which is a material gas of the cladding layer, are passed through an inner tube that can move in the axial direction among the quartz tubes for gas supply.
SiF ₄ (400 sccm) gas was supplied. In addition, oxygen gas is used as an atmosphere adjusting gas from the outer tube fixed to one end of the start quartz tube.
O ₂ (100 sccm) and He (1000 sccm) were supplied. 3) The outer wall of the starting quartz tube was heated to about 1600 ° C. with an oxyhydrogen flame, so that the glass material in the starting quartz tube was deposited on the inner wall as glass particles by a thermal oxidation reaction. 4) The cladding glass layer was deposited in a multilayered shape in the start tube by repeatedly sweeping the oxyhydrogen flame and the jet tube of the inner tube of the gas supply quartz tube once every time in the axial direction while always keeping the interval of 20 cm. 5) In the start quartz tube, SiCl ₄ (200sccm), GeCl ₄
(500 sccm) and O ₂ (250 sccm) gas from the inner tube of O ₂ (10
0 sccm) gas was supplied from the outer tube. 6) The inner tube of the oxyhydrogen flame and the quartz tube for gas supply is 6
With a single sweep, a porous core layer was deposited at about 1300 ° C. 7) neodymium chloride _{(NdCl 3 · 6H 2 O)} : 0.015mol, aluminum chloride (AlCl _3): obtained by compounding a liquid obtained by dissolving 0.5mol ethanol 1L. 8) The above solution is supplied at a spraying rate of 7 (cc) / min through the raw material gas supply quartz tube into the quartz tube having the porous core layer formed in the above 6), and the inside of the quartz tube is maintained for 1 (min). After the reciprocating of the spray nozzle at, the supply of the liquid was stopped. 9) Burner heating was repeated at about 1000 ° C. while supplying Cl ₂ (70 sccm) gas into the start quartz tube to dry the inside of the tube. 10) O ₂ (70 sccm) and He (1500 sccm) gas are supplied from the outer tube as an atmosphere control gas into the quartz tube, and an oxyhydrogen flame is applied to the quartz tube.
The core layer was sintered into a transparent glass body at about 1800 ° C. by sweeping twice. 11) Flow O ₂ (400sccm) gas from the outer tube,
The quartz tube was solidified while being swept twice and heated at a high temperature of about 2000 ° C. to produce a preform rod.

Table 3 shows the measurement results of the characteristics of the multimode fiber produced from the preform obtained by the above steps. It was confirmed that the characteristics of the obtained fiber did not vary depending on the fiber position, and that the core and the cladding layer were formed uniformly and uniformly in the axial direction at the preform stage. Table 3 shows the measurement results of the Nd concentration distribution.
Shown in Uniform Nd in core layer regardless of fiber location
It was confirmed that ions were added. Clad /
The reason why the Nd concentration slightly spreads at the interface of the core layer is that ions are diffused into the formed clad. In addition, the oscillation characteristics of the laser oscillator manufactured using this fiber were constant irrespective of the location of the fiber used, and all satisfied the specifications. On the other hand, in the sweeping of the above process, the raw material gas was supplied and deposited and sintered while the raw material gas supply quartz tube was fixed to one end of the start tube, and as shown in Table 3, the first half to the second half of the fiber drawing was performed. It was recognized that the propagation characteristics and the core diameter gradually changed as the process reached. Also, as shown in Table 3, it was confirmed that the Nd concentration in the core layer was dependent on the location of the fiber, and the Nd ions were added more toward the rear part of the drawing, and thus toward the gas upstream side during the production of the preform. Was.
Further, the oscillation characteristics of the manufactured laser oscillators are slightly different depending on the fibers used, and in particular, those using the rear fiber did not satisfy the specifications.

Example 4 A quartz tube having an outer diameter of 25 mm, an inner diameter of 21 mm, and a length of 1 m was used as a start tube.
Fig. 4
As shown in the figure, about 25 cm before the spout is the luminescent material
Has bulges 8 for filling powders containing Nd chelates
So that the source gas supply pipe 6 can be moved in the axial direction
Then, a preform was prepared in the following steps. 1) In the start quartz tube, C_TwoF₆Supply gas 20sccm, acid
Heat at about 1500 ° C with a hydrogen burner to etch the inside of the quartz tube
Cleaning. 2) In the start quartz tube, through the quartz tube for supplying raw material gas
And oxygen gas O_Two(500sccm) and the raw material of the cladding layer
SiCl as a gas_Four(400sccm), SiF_Four(400sccm), Cl _Two(70s
ccm) and He (1500 sccm) gas. Also, just before the spout
Fill the powder containing Nd chelate into the swollen part (8)
Was. 3) Start the outer wall of the quartz tube to about 1800 ° C with an oxyhydrogen flame.
By heating, quartz tube start stone for raw material gas supply
The powder containing Nd chelate in the British pipe vaporizes and
Deposited on the inner wall as glass particles by thermal oxidation. 4) Adjust the distance between the oxyhydrogen flame and the spout of the quartz tube
Sweep both times 5 times in the axial direction while always keeping at 20cm
Deposit a clad glass layer in a multilayer
Was. 5) O_Two(400 sccm) gas, and the oxyhydrogen flame and
Sweeps the quartz tube for feed gas four times and heats it at about 2000 ° C.
A preform rod was produced while being hollow while heating.

When the preform obtained by the above steps was drawn, a hollow fiber in which the clad was doped with Nd was obtained. As shown in Table 3, the characteristics of this fiber did not vary depending on the fiber position, and it was confirmed that the cladding layer was formed uniformly and uniformly in the axial direction at the preform stage. Table 3 shows the measurement results of the Nd concentration distribution. It was confirmed that Nd ions were uniformly added to the inner 2 μm thick layer of the clad regardless of the fiber location. The hollow portion was 1 μmφ. On the other hand, in the sweeping of the above process, the raw material gas is supplied while the quartz tube for supplying the raw material gas is fixed to one end of the start tube, and the raw material gas is flown.
As shown in Table 3, in the sintered product, it was recognized that the propagation characteristics and the thickness of the Nd-containing portion gradually changed from the first half to the second half of the fiber drawing. Table
As shown in FIG. 3, it was confirmed that the Nd concentration in the clad layer depends on the location of the fiber, and the Nd ions were added more toward the rear part of the drawing, that is, toward the gas upstream side during the production of the preform. The fibers at the front and rear of the drawing did not meet the specifications.

Example 5 A quartz tube having an outer diameter of 25 mm, an inner diameter of 21 mm, and a length of 1 m was used as a start tube, and both ends were supported and rotated on a glass lathe of an MCVD apparatus. Next, out of the three quartz tubes for supplying the raw material, two tubes (one for supplying the source gas and one for supplying Nd) are set so that they can be moved in the axial direction, and the preform is manufactured in the following steps. did. 1) 20 sccm of C ₂ F ₆ gas was supplied into the starting quartz tube and heated at about 1500 ° C. with an oxyhydrogen burner to etch and clean the inside of the quartz tube. 2) Start quartz tube via one movable tube of the gas supply quartz tube, together with the oxygen gas _{O 2 (500sccm), SiCl 4} (400sccm), SiF 4 as a source gas of the cladding layer (400 s
ccm) gas was supplied. An O ₂ (100 sccm) gas was supplied as an atmosphere adjusting gas from a tube fixed to one end of the start quartz tube. 3) The outer wall of the starting quartz tube was heated to about 1300 ° C. with an oxyhydrogen flame to deposit a porous cladding layer. 4) A porous clad layer was deposited in the start tube by repeatedly sweeping the oxyhydrogen flame and the inner tube of the inner tube of the raw material gas supply tube repeatedly once in the axial direction while always keeping the interval of 20 cm. 5) neodymium chloride _{(NdCl 3 · 6H 2 O)} : 0.015mol, aluminum chloride (AlCl _3): obtained by compounding a liquid obtained by dissolving 0.5mol ethanol 1L. 6) Nd is placed in the quartz tube with the porous cladding layer formed in 5) above.
A movable quartz tube for supply was inserted, and the solution was supplied at a spray rate of 7 (cc) / min. After the solution was reciprocated in the quartz tube between 1 (min), the supply of the solution was stopped. 7) While supplying Cl ₂ (70 sccm) gas into the quartz tube, the burner heating was repeated at about 1000 ° C. to dry the inside of the tube. 8) O ₂ (70 sccm) and He (1500 sccm) gas were supplied from the fixed tube into the quartz tube, and the oxy-hydrogen flame was swept four times to sinter the core layer at 1800 ° C. into a transparent glass body. 9) In the start quartz tube, SiCl ₄ (200 sccm), GeCl ₄
(200 sccm) and O ₂ (250 sccm) gas were supplied from a raw material gas supply quartz tube, and O ₂ (100 sccm) gas was supplied from a fixed tube. 10) Inner tube for oxyhydrogen flame and gas supply quartz tube as in 4)
Four sweeps were performed to deposit a porous core layer at about 1300 ° C. 11) In the same manner as in 5), mix the neodymium raw material
The movable quartz tube for supplying Nd was inserted into the quartz tube having the porous core layer formed in 0), and the solution was supplied in the same manner as in 6). 12) While supplying Cl ₂ (70 sccm) gas into the quartz tube, burner heating was repeated at about 1000 ° C. to dry the inside of the tube. 13) O ₂ (70 sccm) and He (1500 sccm) gas were supplied from the fixed tube into the quartz tube, and the oxy-hydrogen flame was swept four times to sinter the core layer at 1800 ° C. into a transparent glass body. 14) Flow O ₂ (400sccm) gas from the fixed tube,
The quartz tube was solidified while being swept twice and heated at a high temperature of about 2000 ° C. to produce a preform rod.

Table 3 shows the measurement results of the characteristics of the fiber produced from the preform obtained by the above steps. The characteristics of the obtained fiber do not fluctuate depending on the fiber position, and are uniform in the axial direction at the preform stage.
It was confirmed that the core and the clad layer were formed uniformly. Table 3 shows the measurement results of the Nd concentration distribution. Uniform Nd in cladding and core layers regardless of fiber location
It was confirmed that ions were added. On the other hand, in the sweeping of the above process, the raw material gas was supplied and deposited and sintered while the raw material gas supply quartz tube was fixed to one end of the start tube, and as shown in Table 3, the first half to the second half of the fiber drawing was performed. It was confirmed that the propagation characteristics, the core diameter, and the thickness of the cladding layer in the Nd-containing portion gradually changed as the temperature reached. Also, as shown in Table 3, the Nd concentration of both the cladding and the core layer depends on the location of the fiber, and the more Nd ions are added to the rear part of the drawing, and therefore to the gas upstream side during the preform fabrication. Was confirmed. In particular, the rear fiber did not meet specifications.

Example 6 A quartz tube having an outer diameter of 25 mm, an inner diameter of 21 mm, and a length of 1 m was used as a start tube, and both ends were supported and rotated on a glass lathe of an MCVD apparatus. Next, three quartz tubes for gas supply were prepared, two of which were set so that they could move in the axial direction, and one of these movable tubes was about 25 cm before the jet port as in Example 4. Was inflated to prepare a preform by the following steps. 1) 20 sccm of C ₂ F ₆ gas was supplied into the starting quartz tube, and heated at about 1500 ° C. with an oxyhydrogen burner to etch and clean the inside of the quartz tube. 2) Oxygen gas O ₂ (500 sc) is supplied into the starting quartz tube via the non-inflated movable tube of the raw material gas supply quartz tube.
cm) together with SiCl ₄ (400 sc
cm) and SiF ₄ (400 sccm) gas. Also, oxygen gas is supplied from the atmosphere adjusting gas supply pipe fixed to one end of the quartz tube.
O ₂ (100 sccm) and He (1500 sccm) were supplied. 3) The outer wall of the starting quartz tube was heated to about 2000 ° C. with an oxyhydrogen flame, whereby the glass material in the starting quartz tube was vitrified on the inner wall by a thermal oxidation reaction. 4) The transparent clad glass layer was sintered in the start tube by repeatedly sweeping the oxyhydrogen flame and the inner tube of the inner tube of the raw material gas supply tube once once in the axial direction while always keeping the interval of 20 cm. 5) Next, Nd is added to the bulging part in another movable quartz tube.
The powder containing the chelate was filled. Also, SiCl ₄ (400 sccm), GeCl ₄ (800 sccm), and O ₂ (250 sccm) which are raw material gases of the core layer.
O ₂ (100sccm) from the movable quartz tube without gas inflation
Gas was supplied from a fixed tube. 6) By heating the outer wall of this start quartz tube to about 1800 ° C with an oxyhydrogen flame, the powder containing Nd chelate in the quartz tube for supplying the source gas is vaporized and deposited on the inner wall as fine glass particles by a thermal oxidation reaction together with the source gas. did. 7) While maintaining the distance between the oxyhydrogen flame and the two orifices of the quartz tube for supplying the movable raw material gas always at 20 cm, the two were repeatedly swept nine times in the axial direction to deposit a multilayer core glass layer in the start tube. . 8) O ₂ (400sccm) gas is flowed from the fixed tube, and oxyhydrogen flame is
The quartz tube was solidified while being swept twice and heated at a high temperature of about 2000 ° C. to produce a preform rod.

Table 3 shows the measurement results of the characteristics of the multimode fiber produced from the preform obtained by the above steps. It was confirmed that the characteristics of the obtained fiber did not vary depending on the fiber position, and that the core and the cladding layer were formed uniformly and uniformly in the axial direction at the preform stage. In addition, the core diameter is 40μ with few operations
The m and Nd concentrations were as large as 20000 ppm.
Table 3 shows the measurement results of the Nd concentration distribution. It was confirmed that Nd ions were uniformly added in the core layer regardless of the location of the fiber. The reason why the Nd concentration slightly spreads at the clad / core layer interface is that ions diffuse into the formed clad. In addition, the oscillation characteristics of the laser oscillator manufactured using this fiber were constant irrespective of the location of the fiber used, and all satisfied the specifications. On the other hand, in the sweeping of the above process, the raw material gas was supplied and deposited and sintered while the raw material gas supply quartz tube was fixed to one end of the start tube, and as shown in Table 3, the first half to the second half of the fiber drawing was performed. It was recognized that the propagation characteristics and the core diameter gradually changed as the process reached. Also, as shown in Table 3, it was confirmed that the Nd concentration in the core layer was dependent on the location of the fiber, and the Nd ions were added more toward the rear part of the drawing, and thus toward the gas upstream side during the production of the preform. Was. In addition, the manufactured laser oscillators have slightly different oscillation characteristics depending on the fibers used, and in particular, those using the front and rear fibers did not meet the specifications.

[0046]

【table 1】

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

According to the present invention, in the production of a glass (optical) fiber preform, particularly a glass (optical) fiber preform in which a core and / or a clad contains a luminescent substance, fluctuation of the glass composition in the longitudinal direction and emission of light are performed. A glass (optical) fiber preform can be produced without causing a concentration distribution of the substance. So far, fibers obtained by drawing a preform manufactured by the MCVD method have had a location dependence of the composition and the concentration of the luminescent material, and therefore the fiber characteristics and the luminescent characteristics, but according to the present method, Since a fiber having a uniform composition and a uniform structure can be produced from the base material without depending on the place, the fiber characteristics can be stabilized, the yield can be improved, and the reproducibility can be improved, and the productivity can be improved.
In addition, since the fiber structure is uniform, the propagation loss caused by the fluctuation of the structure can be reduced, and the area for searching for a glass composition having a lower loss and a higher luminous efficiency of the laser active substance is expanded. At this time, a conventional source gas used for producing the preform is sufficient. In addition, since this method is achieved by changing only the source gas supply system in the conventional MCVD equipment, the operation can be performed (safely) with inexpensive equipment.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus used in a conventional MCVD method.

FIG. 2 is a schematic diagram of an apparatus used in the method of the present invention.

FIG. 3 is a schematic diagram of an apparatus used in the method of the present invention.

FIG. 4 is a schematic diagram of an apparatus used in the method of the present invention.

Claims (27)

[Claims] 1. A method for forming a glass layer on the inner peripheral surface of a hollow tube, comprising: blowing a raw material gas of a glass layer into the hollow tube from a raw material gas outlet moving in an axial direction of the hollow tube;
Reacting the ejected raw material gas with oxygen to continuously deposit the glass layer precursor on the inner peripheral surface of the hollow tube along the axial direction of the hollow tube, and heating the glass layer precursor to form a glass layer. A method comprising the step of forming. 2. The method according to claim 1, wherein the moving speed of the source gas outlet and the amount of source gas ejected from the source gas outlet are adjusted so that the deposition amount of the glass layer precursor is uniform in the axial direction of the hollow tube. Item 1. The method according to Item 1. 3. The method according to claim 1, wherein the source gas jet port is moved at a constant speed and the source gas is jetted quantitatively. 4. The method according to claim 1, wherein at least the hollow tube near the material gas ejection port is heated at a temperature sufficient to allow the material gas to react with oxygen and be converted into a glass layer precursor. The method described in. 5. The method according to claim 4, wherein the heating of the hollow tube is performed locally from the outside. 6. The method according to claim 5, wherein the glass layer precursor is deposited while maintaining a constant distance between the heating position of the hollow tube and the source gas jet port. 7. The method according to claim 1, wherein the deposition of the glass layer precursor is performed twice or more, and the glass layer is formed after the glass layer precursor is laminated. 8. The method according to claim 1, wherein the heating of the glass layer precursor for forming the glass layer is performed at a temperature in the range of 1400 to 2200 ° C. 9. The method according to claim 8, wherein the heating of the hollow tube is performed locally from the outside. 10. After forming the glass layer precursor and before forming the glass layer, a luminescent substance or a precursor thereof is added to the glass layer precursor, and then the glass layer precursor is heated to form a glass layer containing the luminescent substance. The method according to claim 1, wherein 11. The method according to claim 1, wherein the source gas contains a luminescent substance or a precursor thereof. 12. A method for producing an optical fiber preform having a core glass and a clad glass, according to claim 1.
A glass layer made of glass for cladding is formed on the inner peripheral surface of the hollow tube by the method according to any one of claims 9 to 10, and then the glass layer is formed.
The glass layer made of glass for core is formed on the glass layer made of glass for cladding by the method according to 0 or 11, or the inner surface of a hollow tube having a glass layer made of glass for cladding is formed on the inner peripheral surface. A method of forming a glass layer made of glass for a core by the method described in 1 above, and then solidifying a hollow tube to obtain the base material. 13. A method for producing an optical fiber preform for a hollow core fiber, wherein a glass layer made of glass for cladding is formed on the inner peripheral surface of a hollow tube by the method according to any one of claims 1 to 11. A method comprising obtaining the hollow base material. 14. A method for producing an optical fiber by preparing an optical fiber preform by the method according to claim 12, and heating and drawing the preform. 15. A method for forming a glass layer on the inner peripheral surface of a hollow tube, comprising: starting a raw material gas of a glass layer into the hollow tube from a raw material gas outlet moving in an axial direction of the hollow tube; A method comprising reacting the ejected raw material gas with oxygen to continuously deposit a glass layer on the inner peripheral surface of the hollow tube along the axial direction of the hollow tube. 16. The moving speed of the source gas jet and the amount of source gas jetted from the source gas jet are adjusted so that the deposition amount of the glass layer is uniform in the axial direction of the hollow tube.
5. The method according to 5. 17. The source gas jet port is moved at a constant speed.
16. The method according to claim 15, wherein the source gas is ejected quantitatively.
7. The method according to 6. 18. The method according to claim 15, wherein at least the hollow tube near the material gas outlet is heated at a temperature sufficient to allow the material gas to react with oxygen to form a glass layer. the method of. 19. The method according to claim 18, wherein the heating of the hollow tube is performed locally from the outside. 20. The method according to claim 19, wherein the glass layer is deposited while keeping a constant distance between the heating position of the hollow tube and the source gas outlet. 21. The method according to claim 15, wherein the deposition of the glass layer is performed twice or more to laminate the glass layer. 22. The method according to claim 15, wherein the source gas contains a luminescent substance or a precursor thereof. 23. A method for producing an optical fiber preform having a core glass and a cladding glass according to claim 15.
A glass layer made of glass for cladding is formed on the inner peripheral surface of the hollow tube by the method according to any one of claims 21 to 21, and a glass layer made of glass for core is formed of glass for cladding by the method according to claim 22. A glass layer made of core glass is formed on the inner surface of a hollow tube having a glass layer formed of glass for cladding or a glass layer formed of glass for cladding by the method according to claim 22, and then the hollow tube is solid. A method for producing an optical fiber preform, comprising: 24. A method for producing an optical fiber preform for a hollow core fiber, comprising forming a glass layer made of glass for cladding on the inner peripheral surface of a hollow tube by the method according to any one of claims 15 to 22. A method for producing an optical fiber preform, wherein the preform is obtained. 25. A method for producing an optical fiber by preparing an optical fiber preform by the method according to claim 23, and heating and drawing the preform. 26. A chemical vapor deposition apparatus for forming a deposit on the inner peripheral surface of a hollow tube, comprising: a holding portion for holding the hollow tube; A rotating part for rotating around, a source gas supply tube having a source gas outlet which can be inserted into the inside of the held hollow tube and which supplies the source gas of the deposit to the inside of the hollow tube at its tip. A tube in which the raw material gas ejection port is movable relative to the hollow tube in an axial direction of the hollow tube while being inserted into the hollow tube, An apparatus comprising: an exhaust unit configured to exhaust air; and heating means movable relatively to the held hollow tube and locally heating the hollow tube from outside. 27. The apparatus according to claim 26, wherein relative movement of the heating means and the raw material gas ejection port with respect to the hollow tube can be performed in conjunction with each other.