JP2592940Y2 - Optical fiber preform transparentizer - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing fine glass particles by a flame hydrolysis reaction, depositing soot on the surface of a seed rod, and then dehydrating and clearing the soot. It keeps the condition and prevents the contamination of impurities
Uniform temperature distribution in the radial direction of the furnace core tube
The present invention relates to a device for making an optical fiber preform transparent which can be uniformly heated without being rotated .

[0002]

2. Description of the Related Art Generally, in an optical fiber, light propagates through the core while undergoing total reflection at the interface between the core and the clad of the optical fiber. The manner of propagation varies depending on the refractive index distribution of the core. When the core diameter of the step index type or the graded index type is several tens μm or more, the light path differs depending on the incident angle of light, and a large number of optical paths are generated. When the outer diameter of the core is about 5 to 15 μm, light travels straight through the core without being reflected on the boundary surface between the core and the clad, and the optical path becomes one. Such an optical fiber is a single mode optical fiber.

In such an optical fiber, it is ideal that the intensity of the incident light is emitted without attenuating. However, various kinds of light are propagated while propagating through the core of the optical fiber. This causes transmission loss. The degree to which the light intensity becomes weaker while propagating through the optical fiber is the transmission loss of the optical fiber. The transmission loss of an optical fiber is mainly caused by absorption due to electron transition in the ultraviolet region, absorption due to molecular vibration in the infrared region, Rayleigh scattering inversely proportional to the fourth power of wavelength, and absorption due to impurities, particularly water (hydroxyl ions / OH groups). And has a wavelength dependency as a sum of these.

[0004] In an optical fiber, the larger the transmission band, the larger the information transmission capacity. That is, the wider the transmission band, the more signals can be sent at once. This transmission band is represented by a value where a signal having a constant amplitude having a band from DC to high frequency is input to one end of an optical fiber having a length of 1 km and the amplitude of a received signal at an output end is reduced by 6 dB. is there.

In the production of such an optical fiber preform, roughly, a first step (soot synthesis) of depositing and forming glass fine particles (soot) of SiO ₂ and GeO ₂ which are constituent materials of the preform in a column shape. Step) and a second step (dehydration / clearing step) of dehydrating / clarifying the soot to obtain a high-purity glass body. That is, in the first step (soot synthesis step), SiCl ₄ as a glass material and GeCl ₄ as a dope material are supplied to a torch disposed in a reaction chamber, and a glass seed rod as a target is supplied from the torch. A flame containing glass fine particles is sprayed toward the substrate, and a soot of the glass fine particles is attached to and deposited on the tip of a glass seed rod to form a porous optical fiber preform.

Conventionally, as shown in FIG. 4, a manufacturing apparatus for the second step (dehydration / clearing step) mainly includes a quartz furnace core tube, a heating furnace,
It is composed of a base material elevating / rotating device. The porous glass body (soot) 3 produced in the first step is held in a quartz furnace core tube 1 and heated to a high temperature by a heater 2.
At the same time, gases having a dehydrating action and a dopant volatilizing action such as He, Cl ₂ and O ₂ are introduced into the quartz furnace core tube 1. In this high-temperature gas atmosphere, the soot 3 is dehydrated and made transparent while moving up and down as shown by the arrow B shown in FIG. 4 while rotating as shown by the arrow A shown in FIG.

He, introduced into the quartz furnace core tube 1,
Gases such as Cl ₂ and O ₂ and impurities in the base material pass through the exhaust gas insertion port 4 and are sent from the exhaust port 6 to the exhaust gas processing device (not shown) through the exhaust chamber 5.

[0008]

However, in the conventional optical fiber preform clearing apparatus, the soot 3 is rotated by rotating the glass seed rod during dehydration and clearing, and the glass seed is rotated. Since the rod is moved up and down, the glass seed rod insertion port 7 formed in the exhaust chamber 5 cannot be completely sealed and there is a gap, so a large amount of He gas is used as the atmosphere gas. However, impurities may flow from the outside into the furnace core tube 1 through this gap, or the furnace core tube 1
There is a problem that gas flows out from the inside to the outside.

In a conventional optical fiber preform clearing apparatus, the preform is moved up and down in the apparatus, and the stroke (400 to 1000 mm) at that time corresponds to the furnace core tube 1 and the furnace body. However, there is a problem that the size is increased.

The present invention has been made in view of such problems of the prior art, and is an optical fiber motherboard capable of performing a dewatering / clearing treatment of a porous base material in a completely sealed state. It is an object of the present invention to provide an apparatus for making a material transparent.

[0011]

In order to achieve the above object, an apparatus for transparentizing an optical fiber preform according to claim 1 of the present invention has a lower end sealed and an exhaust port or gas inlet at each end. a furnace core tube but which gills <br/> Bei, detachably to the upper portion of the furnace core tube
A lid for sealing the placed on the furnace core tube, and seed rod with attachable detachable supporting <br/> lifting jig depositing the soot adhered to the lid, the periphery of the furnace core tube Surrounding the furnace core tube in the longitudinal direction.
Having a predetermined width, in the furnace core tube longitudinal direction and circumferential direction
The relative position with respect to the suite is fixed, and
A heating means provided a plurality of stages in the direction, sedimentary the tip of the seed rod
The temperature at the lower end of the stacked soot will be
Heating the heating means to reach a predetermined peak temperature
After that, the temperature peaks gradually as the predetermined time elapses.
The heating means is controlled so that
And a control device for controlling the operation.

[0012] In order to achieve the above object, a second aspect of the present invention is provided.
The apparatus for clarifying an optical fiber preform according to claim 1, wherein
Blocks thermal interference with other adjacent heating means in the longitudinal position
It is configured by providing a shielding plate. Achieve the above purpose
To achieve this, the optical fiber preform according to claim 3 of the present application is required to be transparent.
The lightening device includes a heating device having a plurality of heating means arranged around the furnace tube.
For a divided ring-shaped heating element that can be attached to surround
Therefore, each of the divided ring-shaped heating elements is configured to be capable of independently controlling the temperature.
You .

[0013]

According to the optical fiber preform clearing apparatus of the present invention, in the soot synthesizing step (first step), a flame containing fine glass particles is radiated from a torch and the soot is deposited on a glass seed rod. Dewater the fiber preform in the second step
When clarifying, cover the upper end of the furnace core tube with a lid and seal it,
Bottom heating means in a plurality of stages hit the heating the furnace core tube
The process is performed such that the peak temperature moves at a predetermined speed from the heating means in the stage toward the heating means in the upper part . Therefore, the soot itself can be raised or rotated without raising or lowering or rotating the optical fiber preform on which the soot is deposited.
To achieve the same effect as
Can be heated . The optical fiber mother according to claim 2.
According to the material clarifying device, it is adjacent to the longitudinal position of the heating means.
Provide a shielding plate to block thermal interference with other heating means
Prevents impact from adjacent heating means
And the peak temperature can be accurately controlled. Claim
According to the transparent device of an optical fiber preform according to claim 3, constituted by a heating element shaped ring that will be provided by being divided into a plurality of stages attached to the heating means so as to surround a furnace core tube, the divided since the a ring-shaped heating element are also available temperature controlled independently, without causing non-uniformity of the temperature distribution in the radial direction of the furnace core tube, it is possible to heat the soot evenly scratch.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical fiber preform transparentizing apparatus according to the present invention will be described below. 1 to 3 show an embodiment of the optical fiber preform transparentizing device according to the present invention.

In FIG. 1, reference numeral 20 denotes a lid, which is formed of a quartz plate. The lid 20 is detachably mounted on the upper end of the furnace core tube 1 so as to seal the furnace core tube 1. The method of sealing the furnace core tube 1 with the lid 20 can be easily realized by providing packing or the like at the boundary between the lid 20 and the furnace core tube 1. Reference numeral 21 denotes a support jig provided on the lower surface of the lid 20 so as to suspend a glass seed rod on which the soot 3 is deposited. That is, the glass seed rod can be hung on the support jig 21 by inserting the pin 22 through the support jig 21 and the glass seed rod. The support jig 21 may be formed separately from the lid 20, or may be formed integrally with the lid 20.

Reference numeral 23 denotes a gas inlet, which is provided below the furnace core tube 1. The gas inlet 23 is an inlet for introducing a gas such as He, Cl ₂ , O ₂ , which has a dehydrating function and a dopant volatilizing function used when the soot 3 is dehydrated and made transparent. An exhaust port 24 is provided above the furnace core tube 1. The exhaust port 24 is for exhausting gases such as He, Cl ₂ , and O ₂ introduced into the furnace core tube 1 and impurities in the base material.

Reference numeral 30 denotes a heating means, which is constituted by a heater for heating. As shown in FIG. 2, the heating means 30 is formed of a ring-shaped resistance type or induction heating type heater for heating the inside of the furnace core tube 1 and has a plurality of stages in the longitudinal direction of the furnace core tube 1 (this embodiment). In the example, four stages are provided.

Reference numeral 31 denotes a heat shield plate, which is formed of a ring-shaped plate material, and is provided between each of the heating means 30 provided in a plurality of stages (four in this embodiment). As shown in FIG. 2, the heat shielding plate 31
It has a shape larger than 0. The heat shield plate 31 is preferably made of a material having a high heat insulating effect. The heat shield plate 31 is for preventing the heating means 30 from thermally affecting each other.

Reference numeral 32 denotes a temperature sensor, which is attached to a plurality of appropriate locations inside the furnace body constituting the furnace core tube 1 and measures the temperature inside the furnace body. The temperature sensor 32 is constituted by, for example, a thermocouple. The number of the temperature sensors 32 is equal to or greater than the number of the heating units 30. The method of mounting the heating means 30 is such that the heating means 30 is sequentially mounted above and below the heating means 30 so as to be disposed above and below the entire heating means 30.

Reference numeral 40 denotes a control unit to which the heating means 30 and the temperature sensor 30 are connected. And this control device 4
Numeral 0 controls the power supply to the heating means 30 and inputs the measured temperature from the temperature sensor 30 to control the heating means 30 based on the temperature measured by the temperature sensor 30. It has the function of controlling the internal temperature to a predetermined pattern temperature. As shown in FIG. 3, the temperature control by the control device 40 first controls the heating means 30 so that the temperature at the lower end of the soot 3 deposited on the tip of the glass seed rod has a peak. The peak gradually rises over a predetermined time (t
= 0 → t = 60 → t = 120) The heating control of the heating means 30 is performed so as to move.

Each heating means 3 provided around the furnace core tube 1
0 is a furnace core tube 1 as shown in FIG.
It is controlled to form an internal temperature distribution. This temperature distribution has, for example, a mountain shape having a peak at the soaking 3 clearing temperature of about 1450 ° C., and this peak portion changes with time (t = 0 → t = 60 → t = 120). It moves upward with respect to the core tube 1. The moving speed of the temperature peak is set, for example, in the range of 1 to 10 mm / min. When the position of the temperature peak finishes passing through the entire length of the soot 3, the transparency process is completed.

Therefore, according to the present embodiment, since the soot 3 as the porous preform can be subjected to the dehydration / clearing treatment in a completely sealed state, a high-quality optical fiber free from impurities is mixed. A base material can be obtained. Further, according to the present embodiment, since the soot 3 is subjected to the dehydration and transparency treatment in a completely sealed state, it is possible to prevent leakage of harmful gases such as Cl ₂ and SF ₆ around the manufacturing apparatus. Furthermore, according to this embodiment, since the soot 3 is dehydrated and clarified in a completely sealed state, the amount of gas used for clarification such as He, Cl ₂ , and SF ₆ can be reduced. Thus, costs can be reduced. Further, according to this embodiment, since the position of the temperature peak passes over the soot 3, the same effect as raising the soot 3 itself without raising the soot 3 itself can be obtained. Furthermore, according to the present embodiment, since the heating means 30 is constituted by a ring-shaped resistance type or induction heating type heater, the soot 3 can be formed without causing non-uniformity in the temperature distribution of the furnace core tube 1 in the radial direction. Need not be rotated as in the prior art. As described above, according to the present embodiment, since the lifting / lowering / rotating device that was conventionally required is unnecessary,
The manufacturing apparatus is inexpensive, and the cost required for maintenance can be reduced. In the soot 3 dehydrating step, the purpose of the soot 3 is to be dehydrated. Therefore, it is sufficient to form a uniform temperature distribution over the entire length of the soot 3 without requiring the above-described temperature distribution control.

[0023]

The present invention is configured as described above, and has the following effects.

[0024] In the transparent device of an optical fiber preform according to claim 1, a furnace core tube outlet or the gas inlet port at each end lower end sealed is gills Bei, the muffle Top edge of
To a lid for removably sealing the placed on the furnace core tube detachably, and removably attachable support jig seed rod depositing the soot adhered to the lid, the periphery of the furnace core tube Enclosure core
A predetermined width in the longitudinal direction of the tube, and
Relative to the suite in the direction is fixed,
A heating means provided a plurality of stages in the furnace core tube longitudinal direction, said seed
The temperature at the lower end of the soot deposited on the tip of the rod is transparent.
The heating is performed so as to reach a predetermined peak temperature at the start of lightening.
Heat the means and then gradually over time
So that the temperature peak moves to the upper part of the soot.
And a control device for controlling the heating of the stage.
The soot-deposited optical fiber preform
The suit itself can be raised or rotated without rolling.
Can have the same effect as
It can be heated uniformly.

In the apparatus for transparentizing an optical fiber preform according to a second aspect, the heating means is adjacent to the longitudinal position.
A shielding plate is provided to block thermal interference with other heating means.
Is not affected by adjacent heating means.
Can be prevented and the peak temperature can be accurately controlled.

In the apparatus for transparentizing an optical fiber preform according to a third aspect, the heating means is provided so as to surround the core tube.
Ri attached is constituted by a ring-shaped heating element that will be provided by being divided into a plurality of stages, for each segmented annular heating element it is also available temperature controlled independently,
Without causing the nonuniformity of the temperature distribution in the radial direction of the furnace core tube, it is possible to heat the soot evenly scratch.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of an optical fiber preform transparentizing apparatus according to the present invention.

FIG. 2 is a sectional view of the furnace core tube shown in FIG.

FIG. 3 is a view showing a moving state of a temperature peak position in the furnace core tube shown in FIG. 1;

FIG. 4 is a schematic view showing a conventional optical fiber preform transparentizing apparatus.

[Explanation of symbols]

1 …………………………………………………
………………………………………………………………………
…… Suit 20 …………………………………………………
……………………………………………………………………………
………………………………………………………………………………
…… Gas inlet 24 ……………………………………………
……… Exhaust port 30 …………………………………………………
…………………………………………………………………………
…… heat shield plate 32 ………………………………………………
…………………………………………………………………………………
………Control device

Claims (3)

(57) [Scope of request for utility model registration] And 1. A lower end furnace core tube outlet or the gas inlet port was gills Bei at each end is sealed, the furnace core tube is freely mounted detachably on the upper end of the furnace core tube A lid to be sealed, a support jig that can be detachably attached to a seed rod fixed to the lid and having soot deposited thereon, and a predetermined width surrounding the furnace core tube and having a predetermined width in the longitudinal direction of the furnace core tube.
The sweep in the longitudinal direction and the circumferential direction of the furnace core tube.
Position relative to the furnace core tube,
The heating means provided and the temperature at the lower end of the soot deposited on the tip of the seed rod
Before reaching the specified peak temperature at the beginning of the clarification.
Heating the heating means, and thereafter, according to the elapse of a predetermined time
So that the temperature peak gradually moves to the upper part of the soot
An optical fiber preform transparentizing device , comprising: a control device for controlling heating of a heating means . 2. A heating device, comprising :
Provided with a shielding plate for blocking thermal interference with heating means
The optical fiber preform transparentizing device according to claim 1, wherein: Wherein the heating means of the plurality of stages, the furnace core tube is mounted so as to surround the periphery consists divided ring-like heating elements, each divided ring-shaped heating element temperature control independently The optical fiber preform transparentizing device according to claim 1 or 2, wherein the device is configured to be capable of being configured .