JP3096695B2 - Manufacturing method of optical waveguide base material - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide and an optical waveguide.
Regarding the production method of the base material (preform) and their products,
In particular, the footprint of preforms manufactured by vapor deposition
The present invention relates to the formation of a silicon nitride-impregnated cladding. [0002] The most commonly used optical waveguides at present
Is made of porous glassy particles called soot.
Decomposition of the glass components in the flame to form the base metal
It is based. The “soot” base material cannot be sintered at high temperatures.
And can be changed to a glassy state. This is called "Prefor
" A predetermined combination of core and clad
Reform) is tensioned under high temperature and
It is drawn to the final diameter. As the use of optical waveguides increases, communications
The technical demands on the system have also increased. Current status
Signal transmission loss of 0.4 dB per km
Properties such as loss, low dispersion, and accurate cutoff wavelength
Required. These factors are extremely low in impurities.
In addition to the fact that the structure is uniform and free of fine bubbles, the core part
Index defined by the shape and material of the cladding and cladding
The distribution must be reliable and controlled as expected
Means that More naturally used
Since the economics of the manufacturing method are also important, the basic cost and yield are satisfactory
Must be at the level to be. [0004] Given these factors, the traditionally used
Is not satisfactory from one or more perspectives.
No. The method widely used in the early days was the so-called “internal method (in
Partial vapor deposition), which is an improved chemical deposition method.
In this method, the core soot material is special
Is deposited inside the silica tube prepared in
After vitrification, close the inside before or during drawing
To be solidified. Prepare hollow silica tube
Is expensive and the dimensions of the base material produced by this method
Is also restricted. Others now widely used instead
There is an external method (external vapor deposition method), and this method is
This is a radial deposition method. External method deposits on mandrel
And the next mandrel removal before sintering. this
The operation is subtle and the length of the base material is limited. 1977
Around 1978, with vapor phase shaft for continuous soot deposition and base metal production
Method (VAD method) was invented. This method is Academic
Press Inc. Published (Tingye Li, 1985)
This "Optical Fiber Communication"
Shin) ”Vol. 1, “Fiber Fabricati
on (optical fiber manufacturing method) "
Soot material towards the center vertical axis rotating target
As the material is deposited in a solid cylinder
Providing relative axial movement between the flow and the target
Is the feature. Among them in VAD method (gas phase shaft method)
Real cylinders are capable of continuous sintering and, if necessary,
To form a spring rod, or a radius
The soot material flow impinges in the
Heads can be deposited simultaneously. This manufacturing method
Are theoretically advantageous, but there are many benefits
Inhibited by practical factors of number or technical limitations. Axial direction
Upward soot material flow to prevent side deposits
Must be directed from the side, and this
Exact burner control using exhaust of a specific shape
Must be done. And at the same time, radial deposition
When used, the radial growth rate is referred to as the axial growth rate.
Difficult to synchronize, axial direction if the room is unstable
The growth rates are also not uniform. Also, both burners are in the same room
Mixing of both soot material streams is unavoidable,
And a diffusion boundary layer exists between the first and second portions. When the VAD method is actually performed,
There are basic restrictions. References and US Pat. No. 4,2
As described in US Pat.
The material flow should be coaxial (= 0 °) and vertical
It was that. The next researcher is the cylinder to be deposited
Is rotated about a vertical axis, but the spray angle is about 40
Degrees, the maximum absolute angle for growth should be 60 degrees
(US Pat. No. 4,367,085).
issue). To further control deposition, the flow of soot material
It must be laminar with Reynolds number less than about 100
Was considered. According to published data, glass particles
Deposition rate drops at Reynolds number of about 30-50 or more, and about 8
If it is greater than 0, it will decrease considerably. These operational constraints
Increases the deposition rate and reduces costs
Is impossible. In order to provide an additional cladding portion,
Axial and radial synchronization of core and cladding
If the deposition method is used at the same time as the outer sleeve,
And other obstacles in terms of performance come up. Core radius (a)
The ratio of cladding thickness (t) to working and economical aspects
More important to you. The loss can be reduced by increasing the ratio t / a.
Can be reduced, but the formation of the initial layer is the most costly,
Excessive costs for forming the core and cladding
This cannot be adopted. In addition, during the manufacturing process
When OH ions are introduced, this becomes moisture, which becomes light
Is directly proportional to the absorption of
It is necessary to limit the hydroxyl ion content. So
Nevertheless, most productions using the VAD method
Set the limit value of the t / a ratio of the core and cladding to 7
And then apply this method to a low hydroxyl ion sleeve tube.
Combined. High cost limits growth rate and size
Soot piles and specially prepared soot
Included in both Reeve embedded. Remove these constraints
It is particularly desired that In order to obtain particularly high quality, US Pat.
No. 4,378,985.
It is also known to use a "hybrid method".
In this manufacturing method, the outer cladding is formed by adding a soot layer.
It is formed by addition. This method involves axial and radial
There is a problem with the above synchronization during deposition. [0008] Therefore, the optical waveguide
In technology, product and performance advancements are constant
However, subtle and complex interrelationships have
Hinders goodness. In addition to the above, the nature of signal transmission is
It is substantially affected by the shape of the fold distribution. Bandwidth power
Single-mode transmission widely used because of its large size
For transmission, it is necessary to precisely control the t / a ratio,
Interface has predictable "quasi-step" characteristics
Should give. VAD with simultaneous soot deposition
The law cannot inherently provide the above properties, and therefore
There may be large fluctuations in the cutoff wavelength and degradation in dispersion characteristics.
To control the hydroxyl content in the fiber,
Hydroxide ion contamination in the tubing operation has a large t / a ratio.
Requires use. Therefore, the manufacturing method is expensive, and
The properties of the fiber obtained as a result of
Becomes [0009] A soot material described above.
To form soot for preform by depositing material
In the core, larger than the pure silica cladding
It is possible to have a refractive index. However,
In fact, the refractive index of the cladding is
Fluoride the clad during sintering to reduce the
You. Specifically, the soot material is deposited to form a cylindrical core.
For forming a preform soot consisting of cladding
In the method, a cylindrical silica core is
Fluoride that sinters before deposition and has a lower refractive index than the core
Contains fluorine to form silica-impregnated silica cladding
Sinter the silica cladding in an atmosphere. According to the present invention, the core of silica is
Deposited by a large technology with a fast generation angle, then dried
And sintered. Silica cladding deposited to a specified thickness
However, solidification or vitrification takes place in the presence of a fluorinating agent.
The fluorinating agent diffuses only in the cladding and is refracted.
The rate is reduced by a predetermined amount. By this method, 1.5
Low transmission loss of 0.2 dB / km at 5 micron wavelength
Fluorosilicate fibers were produced. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for producing a preform which is a starting point of the present invention
The method is described below. As shown in FIG. 1, the device according to the invention
Most of the work parts are mounted in a large enclosure deposition chamber 10.
It is. The first whisk 12 comprises a silica compound (in this case S
i Cl _Four )).
The stand 12 may be inside or outside the room 10. Silica glass
The precursor gas phase may be a carrier gas, especially oxygen or any other suitable gas.
The material under pressure into the first whisk 12
It is ejected from the first whisk 12. Also in this case
Physically, the germanium compound GeCl _Four Is a purification precursor
Second whisk 14 containing a doping substance (additive substance)
Is included. The dope precursor vapor is also O _Two By carrier
And is ejected from the second whisk 14. O _Two In the carrier tube
The valve 15 is operated by operating the valve 15 when necessary.
Can be shut off. Shapes components in a gas-phase flow
The resulting entrained glass is mixed and, in this example, deposited
First burner 16 held in a substantially fixed position with respect to the area
And is dissociated as is known. First burner 16
Generates a laminar soot material stream 17 and the soot material
Stream 17 is directed upward at a tilt angle of 65 ° to the horizontal axis of rotation.
Be killed. The thin beam from laser 18 is mirror 19
Is deflected to the photodetector 20. The rays of mirror 19 will be described later.
Make an angle that intersects the geometric center axis of the deposited material
ing. However, the soot material flow 17 is
Not centered, as described in more detail below.
In both the horizontal and horizontal directions, it is shifted from the geometric center. Ray Bee
Horizontal or vertical so that the
Can be arranged to cross the center axis at an angle to the direction
In the diagram, tilt from the vertical position for clarity
Only the place shown. In the soot material flow 17
The chemical composition has a flow rate of 40 ft / sec, while the other gases
The flow rate is about 25 ft / sec. Right above the target area
A certain exhaust port 22 is a valve in the exhaust path leading to the fan 25.
Approximately 300 ft / min, preset by the turf valve 24
Gas and non-colliding particles at a gas flow rate of
You. The end burner 26 adjacent to the first burner 16 is
Make sure that the temperature at the deposition point reaches a certain height before the product starts.
To assist. Valve 28 controls the use of first burner 16
Can be opened and closed. In the deposition chamber 10, a chuck is made along a reference axis.
The silica seed rod 34 having a relatively short length
Provided. The chuck 36 and the seed rod 34 move linearly and laterally.
The rotary drive 38 provided on the mechanism 40 provides the core position.
Is rotated at a predetermined speed of 10 rotations / minute with respect to the position. Core bank
Position control for receiving signals from the photodetector 20 in the product mode
The controller 42 moves the lateral movement mechanism 40 in one direction at a predetermined speed.
It is possible. By bypassing the position controller 42
The horizontal moving mechanism 40 over a predetermined predetermined horizontal moving length.
It is possible to perform a reciprocating motion at a constant speed. Core bank
In the product mode, the seed rod 34 initially moves over a short distance.
Reciprocating movement, and then while controlling the position,
It is moved in the direction. The lateral movement mechanism 40 also has a
In this case, a round trip of approximately 40cm is required for deposition.
Movement is possible. In the deposition chamber 10, a seed rod 34 is set along a reference axis.
Apart from the second, separately for the deposition of the cladding
A burner 50 is used. When valve 52 is opened,
The particle-forming compound that is pure silica is _Two Depends on carrier gas
From the first whisk 12 to the second burner 50
You. Second soot material flow directed at right angles to the horizontal reference axis
55 is generated later. Core or starting part for optical waveguide preform
Rod formation starts almost entirely from conventional VAD technology.
ing. First, the deposition chamber 10 is cleaned, and the seed rod 34 is
And is centered on the rotation axis. No.
One burner 16 determines the tip of the deposited material during position control.
It is positioned in relation to the laser beam to be determined. Next
The first burner 16 is ignited, the exhaust speed is maintained,
After the stabilization, the seed rod 34 is rotated about 20 times by the drive unit 38.
First soot material spun at / min and containing core particles
It is advanced into the path of stream 17. Soot material flow 17 is a seed rod
Collision with a large angle of incidence at and near the tip of 34
The seed rod 34 is vibrated back and forth at a speed of about 45 cm / hr.
It is. Start bulbous about 2 cm long on free end of seed rod 34
The tip 60 grows. Once enough material has been deposited,
The bulbous tip 60 is a suitable base for the growth of the core 62
That is, an anchor is formed. The core part of the suit is
In particular, it may be a soot core. The axial growth of the soot core 62 is controlled by the position control.
The controller 42 first gives a constant withdrawal speed of 12 cm / hr.
And started with First soot material flow 17 is bulbous
Injected at the end of the start tip 60 and at the beginning of the core 62
To form a part. The chemical composition of the soot material stream is 40
Other gases have a flow rate of 25 ft / sec.
The flow of the soot material stream 17 is laminar, and the Reynolds
The number is about 1000 and the deposition rate is about 0.14 gr / min
It is. An upward high flow rate is accompanied by some excess injection.
However, the gas bypassing the core 62 rises in high-temperature gas.
It is discharged from the outlet 22 with the help of natural convection tendency.
When the deposition of the core part 62 is started, a drawer of 12 cm / hr is drawn.
The speed is slightly faster than the growth rate of the core part 62, but the bulb starts
Growth on tip 60 is balanced. Next, the position controller 42
Is switched to the servo mode, and the laser beam is
2 intersects the geometric center of the free end. Material is deposited
When holding the free end of the core portion 62 at a fixed position
By pulling out the core part 62, the position controller 42
Responds to a signal from output unit 20. Mother about 2.5cm in diameter
In order to form the material, this results in a 6-8 cm / hr non-
A steady withdrawal speed is formed. The core portion 62 continues to grow and is 20 cm (normally
Is in the range of 20 to 30 cm).
The core portion 62 is pulled out by the mechanism 40. This discontinuous work
The industry does not mix particles and gases with each other,
Process without synchronizing the process, so a better overall system
Control becomes possible. When the core portion 62 having a predetermined length is formed,
The first burner 16 is extinguished and the second burner 50 is ignited.
Is stabilized. Next, the lateral moving mechanism 40 is connected to the second burner.
The core portion 62 is reciprocated over the entire length while facing the
Actuated to move. The core part 62 is a rotary drive
38 at a speed of 20 revolutions / minute and the second bar
The corner 50 is approximately 17.5 cm from the rotation axis of the core 62.
It is kept at a fixed distance. Next, move the horizontal moving mechanism 40 to about 250 cm.
/ Hr, the core part 62 moves to the second
Horizontal axis relative to cladding soot material flow 55
Are moved back and forth along. Deposition of pure silica soot particles
Is the flame-hydrolysis of the gas phase entrained by the carrier gas from the first frother 12.
Performed at an average speed of about 2.5 gr / min obtained by decomposition
It is. A thin contact layer about 5 mm thick is deposited on the core 62.
Gas / oxygen flow rate for the first 15 minutes working time until
By gradually increasing the surface area of the core 62.
The deposition temperature is gradually raised to standard operating levels.
As a result, the temperature can be lowered.
Removal of germanium is avoided, but even at lower temperatures
The initially deposited cladding particles are deposited on the surface of the core soot.
Strongly bond. The diameter of the core 62 is kept exactly constant
Unless the surface is wavy in the longitudinal direction,
Also, the change of the surface of the core portion 62 is completely matched.
The core 62 and the completely formed outer
The boundary layer between the contact portion 64 and the contact portion 64 has almost constant characteristics and extremely
Properties of very thin transition layers with low moisture content
This factor depends on the refractive index distribution of the final optical waveguide and water.
Significantly important for the acid ion content. The deposition of the cladding 65 is about 10.5 cm.
Once the final diameter has been obtained, in this example the cladding thickness (t
) To the core radius (a) until the ratio becomes 2: 1.
Continued. This soot base material is 35cm long and about 550gr
With no discontinuity inside. Cladding
When a part is added, the surface velocity increases, but the increase
Velocity decreases with increasing radius. Almost constant density
To maintain, generally over time, corresponding to the surface speed
Burner temperature is increased. According to the manufacturing process shown in FIG.
First dry in a hydrophilic (here chlorine) atmosphere at 1150 ° C
Dried, then about 3.8 cm in diameter in a chlorine atmosphere at 1450 ° C
Of the transparent glass rod base material. Next, the glass rod base material is heated to about 2000 ° C.
Draw a starting rod with a diameter of about 9mm in an anhydrous furnace atmosphere
Is done. These vitreous rods were dried and sintered
It is 1/10 or more of the product diameter. Departure rod is about full length
Form a 150 cm usable rod, usually 4 mm
Divided into 0-50cm lengths. The rod has a refractive index distribution,
Inspected for clad to core diameter ratio and glass quality
It is. Ends of these individual rods with appropriate properties
Are fitted with handles, and their exteriors are cleaned.
When the t / a ratio is about 2 or more, the base material is reciprocated in an oxygen flame.
Kinetic and rotational movements and flame polished,
A clean surface for providing a cladding is provided. t / a
When the ratio is about 1, it is cleaned by dry etching. In the second cladding step, the first glass
The raw material rod rotates again in front of the second burner 50
Reciprocating motion is performed, and 11
Another cladding of cm thickness is formed. To an appropriate diameter
Once shaped, the redeposited rods are then dried as before
And sintered to form a final fiber preform with a diameter of about 5.5 cm.
Is done. Most manufacturers wire their own optical waveguides
Because they prefer to draw, such matrices are
Business products. Preform rod to form optical waveguide
Is the final file for 1300 nm wavelength work as usual.
It is drawn to a diameter of 125 μm. Silica-germaniu
These optical waveguides have a core and a silica cladding.
The fiber has a t / a ratio of about 13 and a transmission loss of 1.0 dB /
km (typically 0.4 dB / km), and 1285
3.5 ps / nm dispersion at wavelengths in the range of 1330 nm
A single mode fiber less than -km. Flow of soot material at high speed and large angle of incidence
With high growth rate, uniform soot deposition, and control
In order to get the diameter you have to consider several complex factors
No. Referring now to FIG. 3 and FIG.
The imaginary core portion 62 has a slightly convex end and is substantially constant.
It is preferable to have a diameter D of Front end of core part 62
The geometric center of the surface is used to measure the growth of the core 62.
The target point of the laser beam used. This is
A nodal point, essentially a symmetry point should be tracked
However, in the core deposition according to the present invention, the chemical component
The center of this is geometric along the reference axis, as can be seen in FIG.
It's out of my mind, and it's also displaced horizontally, as can be seen in FIG.
ing. The excess injection from soot material stream 17
I'm not sure, but the target area and past it
Later flow patterns are important. Past direct collision area
Along the upward path of the subsequent soot, the flow
Before being sucked in the direction, the flow is a certain distance
Flows along the convex end face of the. This flow is also
Some diffusion in the collision area. Heap soot
Along this arc adjacent to the material flow,
This is performed further downstream where the temperature is lower. The center of the soot material flow 17 is the core 6
Distance d on the reference axis from the front edge surface and the geometric center of
Only at a point inward away. This is illustrated in FIGS.
As can be seen from Figure 4, the true center of soot material flow is the base
Means below the quasi-axis. Soot material flow 1
7 and a drop into the flow of soot material through the geometric center
The distance from the straight line is 4.875 "(12.4 cm).
Along the quasi-axis, the geometric center on the core surface and the soot material
The distance d between the center line of the flow 17 and the intersection with the reference axis is
1/8 "(0.313 cm) for optimum growth rate
I understand. The center of the soot material flow 17 is at the same corner
When oriented to the geometric center while preserving degrees, the shape is almost
Even if they are similar, the growth rate is equal to nothing. If the angles are the same
If the distance d is too large while holding, the core is soft
Has outer layer, cracks and poor refractive index distribution
I do. The shape of the free end of the core portion 62 is as shown in FIG.
Between the flow center of the soot material and a line parallel to the axis of rotation.
It is slightly convex for the optimum included angle, in this case 65 °.
If the angle is less than the optimal value, the shape of the tip is indicated by a dotted line.
It becomes concave like this, and the growth rate drops sharply. If the angle
Is larger than the optimal value, the edge of the core portion 62 is indicated by a one-dot chain line.
Flat as shown, diameter and growth rate are substantially reduced
I do. As can be seen particularly from FIG.
The density distribution and the refractive index distribution of the core 62
Horizontal displacement of the center of soot material flow 17 with respect to the center
It is further controlled by (t). In this example and conditions
On the other hand, the distance (t) is preferably 0.5 cm or less and 0.35 cm.
(0.138 ") seems optimal, as can be seen in FIG.
Thus, when t is optimal, the refractive index distribution is at the edge of the core.
Has a sharp side, almost constant value across the core section
Having. If the value of t = 0, the value of the refractive index is
From the center of the part to both sides (dotted line), while if t is
If it is larger than the appropriate value (dotted line), the refractive index distribution is
It shows a high value near. When the deviation is substantially large,
These conditions are unacceptable. The flow interval of the soot material, the chemical components and
If the gas flow for other gases is
If servo control is used for the feed rate, the method
At a rate of about 0.14 gr / min, an almost constant growth rate can be obtained.
The Reynolds number is about 1000, but in any case
Qualitatively greater than 80, the flow in the soot stream is laminar.
The soot / soo between the core and clad
High quality so that the body is formed with a boundary layer
The quality core and the starting rod are formed simultaneously. This product
The process is substantially costly and requires high quality silica-based
Body or sleeve tubes must be used.
Have substantial economic advantages over prior art
You. Manufacturing method according to the present invention and waveguide obtained thereby
The path also has substantial benefits with respect to the optical properties of the resulting waveguide.
give. The refractive index distribution shown in FIG. 6 has excellent optical characteristics.
It helps to understand that it is sexual. High refraction at the core
The index and the low refractive index of the cladding are comparative values,
Not adjusted. The saw-like trajectory is read in 20 micron increments
Due to the instability of the instrument at High level and
The nature of the transition line to and from the low level is
To obtain the “quasi-step” distribution required for
In this type of manufacturing, infinite gradient (ie vertical)
It is inherently impossible to get However, from FIG.
As you can see, the slope of the transition line is steep and the bottom and top
There is almost no disturbance in any of them. Made from the deposition method
Since there is some dimensional change in the rising core, the slope of the transition line
The arrangement is not exactly vertical. To control the refractive index distribution during core deposition
Temperature control is important. The effect of temperature on distribution
As shown in FIG. If the temperature is lower than the optimal temperature, the distribution
(Dotted curve) is the side slope that makes a large angle to the vertical line
And the peak refractive index is only near the center of the core.
You. If the temperature is above a certain level, the intermediate core
Part has a lower refractive index, but the outer core has a large refractive index
With a side gradient that is reasonably vertical. But
From the results of this temperature dependence, the constant bending through the core
Use a lower temperature than required for the folding rate.
With this, a graded-index fiber can be obtained.
It is possible. This variant further comprises a free end of the core part.
Position of soot material flow with respect to
Their chemical composition will also be different during deposition. Therefore
Typically, the soot material flow impinges closer to the center of the core.
As a matter of fact, the amount of germanium will be large in the representative example. The burner 16 used for core deposition is gas
FIG. 8 shows the relative positions of the flows. Soot material flow 17
Erupts from the center opening 70 and the orifice
The inner ring of the wheel 72 forms an inner shield for the oxygen flow.
You. Middle of orifice 74 for flammable gas and oxygen
The ring forms a slightly converging circular flame. Finally
Oxygen that shields the outside from the outer ring orifice 76
Gushing. This arrangement allows the flow of soot material to be almost constant diameter
Which forms the frame required for dissociation. As can be seen from FIG.
If the product temperature is high, the boundary layer between the clad and core
The bottom level of the transition between the steep
). At the expense of some manufacturing time
However, at temperatures lower than the standard temperature, the boundary layer
If not, add germanium additive (dopan
G) is thought to be removed and the core will shrink
You. One advantage of the manufacturing method described above is that
All soot / soot preforms are manufactured and sintered, optical waveguides
Is to be drawn directly to For this, the core part
Of soot material so that it is formed only to a diameter of about 1 cm
The flow moves close to the core. Then the cladding is about
Deposited up to 14 cm with a given t / a ratio, this composite
The core / cladding structure is then dried and sintered,
It has a diameter of about 7cm, from this to the direct optical waveguide dimensions
Drawing is possible. Further, at various stages of the manufacturing method,
It can be seen that a number of alternatives are available.
Would. Between the flow of the core soot material and the rotation axis of the core
While maintaining the angle of the
Incline the soot material flow to near vertical position,
Can also be oriented in a completely vertical position and requires an outlet
Then change the shape, provide a gap around the core,
The function of sucking the excessive injection is formed. Vitrified
The rod is dry gas etched, high power laser beam
Polished or cleaned in various ways, including flame polishing
You. Now, as shown in FIG.
In the manufacturing method, pure silica core and low refractive index
Low loss (0.2 dB / km) by using head
Is manufactured. In the first phase, we explain about Figure 2
A pure silica soot core was deposited as in the previous example.
You. The matrix is then dried, sintered and placed on top
Up to a constant thickness, the cladding part also made of silica soot
Is deposited. This soot layer is then placed in a hydrophilic atmosphere for one hour.
Dry at 150 ° C. Therefore, solidified or glass
To allow the soot to penetrate the soot at the same time
In other words, to form a fluorosilicate-impregnated cladding
Fluorinated atmosphere (SF ₆ With zone)
A knot is performed. This is followed by another layer of silica soot.
And then dried and sintered to the desired full cladding
Thickness is obtained. As an example of sintering in a fluorinated atmosphere,
Helium and sulfur hexafluoride in a temperature range of 1450 ° C
There is atmosphere. Drying and sintering are performed in a closed furnace.
A gas stream is blown out at a controlled rate into this furnace,
Maintained at a controlled temperature. The oven for drying is 20
Over a period of 1000 minutes
sccm chlorine flow, 7000 sccm helium flow, and 14
Heated with a flow of oxygen of 0 sccm and then kept the same for 30 minutes
Be held. After this, while maintaining the same flow state, the base material
Withdrawal will take place within 10 minutes. In the sintering step, the dry flow of chlorine is as small as 50 sccm.
Helium flow constant at 7000 sccm, hexachloride
Run as 135 sccm of sulfur stream, temperature from 1200 ° C
Started with a 40 minute heating step that rises to 1450 ° C
You. Next, the base material is sintered at 1450 ° C for 180 minutes.
At a speed of 0.2 cm / min while maintaining the flow constant
Pass through the hot zone in degrees. Then interrupt the flow, mother
The material is cooled from 1450 ° C to 1000 ° C in 30 minutes
You.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a combination of a simplified perspective view and a block diagram of an apparatus according to the present invention for manufacturing an optical waveguide preform. FIG. 2 is a block diagram of steps in an optical waveguide manufacturing method related to the present invention. 3 is a side view of the soot material flow and the end of the core in the apparatus of FIG. 1, showing the impact angle and how the impact angle changes the deposited material. FIG. 4 is a side view of the soot flow and the core end showing the collision area in more detail. FIG. 5 is a diagram showing a change in refractive index distribution with respect to a deviation (t) of an impact position from an axis. FIG. 6 is a distribution diagram of a true refractive index read from an optical waveguide related to the present invention. FIG. 7 is a diagram showing the influence of controlling the temperature (T) in core portion deposition on the refractive index distribution. FIG. 8 is an enlarged side view showing a burner used for core portion deposition and a shape of a soot material flow. FIG. 9 is a diagram showing a change in the refractive index distribution when the cladding temperature is changed. FIG. 10 is a process block diagram of a method for manufacturing an optical waveguide according to the present invention. DESCRIPTION OF SYMBOLS 10 Deposition chamber 16 Core soot burner 17 Core soot material flow 18 Laser 20 Photodetector 22 Outlet 28 Rotation drive unit 34 Bait member (seed rod) 40 Horizontal movement mechanism 42 Position controller 50 Clad soot burner 55 Clad Soot material flow 60 Bulb-shaped start part 61 Clad part 62 Core part

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C03B 37/00-37/16 C03B 8/04 C03B 20/00

Claims (1)

(57) [Claims] A method for controlling the deposition of soot material during the formation of a core part for an optical waveguide, comprising the steps of forming a limited laminar flow of soot material of fine particles, and forming a linear flow path without interrupting the laminar flow. Guiding along and in a direction substantially perpendicular to the length direction of the core portion and impinging against an end face of the core portion being formed; and Generating a jet flow; rotating the core portion being formed along its length direction ; discharging the excess jet at a lower speed than the laminar flow; Limiting the contact between the core part and the low-temperature flow lance outside the collision region to be performed. 2. A method of depositing soot material in a predetermined axial direction to form a core portion for a large optical waveguide base material, wherein a target region located at a position shifted from the axis is rotated around the axis. Generating a laminar flow including a soot material having a substantially constant cross-sectional area; forming the laminar flow at a predetermined angle with respect to the axis, and guiding the laminar flow onto the target region to impinge the laminar flow. Maintaining a substantially constant distance relationship between the laminar flow and the target area while soot material is deposited; and minimizing secondary soot material deposition outside the target area. Discharging the excessive jet formed by the laminar flow supplied along the linear trajectory passing through the target area. 3. The method of claim 2, wherein the laminar flow of soot material is surrounded by a converging gas flow and forms an angle of about 60 degrees or more with the axis. 4. A method of forming a core portion having a large diameter and a substantially constant diameter, wherein a flow of a layered soot material having a velocity such that the number of Reynolds nozzles exceeds 80 is formed inside a convergent flame flow. Guiding the flow of soot material through a path of a predetermined length to the target area before colliding with the target area; and rotating the core part around a central axis extending along the longitudinal direction. Guiding the flow of the soot material so as to form an obtuse angle with respect to the central axis, and causing a collision at a position near the central axis and deviated from the central axis; and Maintaining the angle, area and length of the soot material flow collision substantially constant during formation. 5. A method of manufacturing a core used for manufacturing an optical waveguide, comprising: setting a soot starting surface rotated around a predetermined axis; and a soot having a substantially constant diameter with respect to the soot starting surface. Guiding the laminar flow of material flow at a flow velocity sufficient to maintain a linear path to the collision area where the collision with the soot starting surface is made; and Discharging the soot material passing through the collision area to prevent excessive deposition after the desired deposition on the core portion; and maintaining the length of the flow path substantially constant while the core portion is formed. And a method of manufacturing a core part. 6. The method according to claim 5, wherein the flow velocity is about 12.2m / sec, and the length of the flow path is about 12.4cm. 7. The laminar flow of the soot material is 6 to the predetermined axis.
The method for manufacturing a core part according to claim 6, wherein the angle is 5 degrees or more. 8. A method of depositing glass-forming particles on a target area to form a core having a substantially constant diameter around a central axis, the method comprising: forming a starting body surfaced with the particles; Rotating the starting body and the material deposited on the starting body about the central axis; and displacing the central axis close to the central axis on the deposited portion so that the number of Reynolds is about Impinging a controlled laminar flow of fine particles having a flow velocity of more than 80 at a predetermined angle remotely to grow the core portion in the axial direction;
A method for forming a core portion, comprising: 9. A method of manufacturing a core portion used as an optical waveguide by a subsequent process of adding a cladding portion, vitrifying and drawing into a fiber shape, comprising the steps of forming a starting body surfaced with a soot material; Rotating the starting body about a central axis orthogonal to the end face; and passing a laminar flow of soot material having a predetermined cross section in a direction toward the starting body along a path having a predetermined distance to the starting body. Guide at a predetermined speed while maintaining laminar flow,
The tip of the laminar flow of the soot material is offset from the central axis and at an oblique angle with respect to the central axis of the starting body on the end face of the starting body in order to perform radial deposition of the core. Causing the core portion and the laminar flow to perform a relative axial operation while maintaining the oblique angle and the collision region where the collision is performed constant, and Forming a core portion in a direction. 10. A method of manufacturing a core portion for an optical waveguide preform, comprising: an inner portion having a first speed set in advance, and a fine particle flow including a surrounding gas flow having a second speed lower than the first speed. Guiding along a straight path toward the target area; and discharging gas and fine particles having a third speed lower than the second speed and passing through the target area along the straight path. A method of manufacturing a core part, comprising: 11. The first speed is approximately 12.2 m / sec, the second speed is approximately 7.6 m / sec, and the third speed is approximately 7.6 m / sec.
The method according to claim 10, wherein the speed is about 1.5 m / sec. 12. The method for manufacturing a soot core according to claim 11, wherein the fine particle flow is a streamlined flow, and the surrounding gas flow converges along the straight path. 13. The method of manufacturing a core part according to claim 12, wherein a direction of the straight path is inclined with respect to a direction in which the core part is formed so that exhaust of a passing gas is assisted by a natural convection tendency. 14． A method for producing a glassy base material for drawing into an optical waveguide, comprising the steps of: (a) depositing a soot material on a rotating target region, and forming a core having a radius a and a length exceeding 20 cm on a predetermined axis. (B) forming a first cladding portion on the core portion having a substantially uniform thickness t such that the ratio t / a is at least 1; (C) sintering the core / cladding structure comprising the core and cladding to produce a first glass rod preform; (d) ) After sintering, depositing an additional cladding on the rotating first glass rod preform until sufficient soot material has been deposited to obtain the desired final t / a ratio; e) To produce a second glass rod preform After sintering the core / clad structure including the additional clad portion, the manufacturing method of the optical waveguide preform, characterized by comprising the steps of drawing to the desired final diameter. 15. What is claimed is: 1. A method for producing an initial soot base material having a core portion and a clad portion made of a soot material for an optical waveguide, comprising: (a) substantially rotating a core portion while rotating a core portion; While maintaining a constant constant, the flow of the high-speed soot material is guided to the target area on the growth surface to grow the core portion, and the angle of the flow of the soot material is increased.
Selecting the growth rate of the core portion and the location of impact on the target area such that the core portion is formed with a diameter a; and (b) sufficient mass for subsequent addition of the cladding portion. In order to economically supply the initial core base material, the flow of the soot material is guided in the radial direction of the core portion in a number of bidirectional passes, and the ratio t / a of the core portion radius a to the clad portion thickness t is set to t Depositing a clad portion on the core portion to a thickness t so as to be at least about 1 to complete the initial soot base material. 16. A method for growing a soot base material having a core portion and a clad portion made of soot material for manufacturing an optical waveguide, comprising: (a) growing a starting body of soot material; and (b) soot material of fine particles. The soot material is deposited on a starting body that is rotated around the axis while maintaining the angle between the flow and the predetermined axis at 60 degrees or more, and this deposition forms a core having a diameter of 2.5 cm. Forming; (c) detecting the position of the tip of the core portion while the deposition continues; and (d) detecting the position of the soot material flow and the end of the core portion while the deposition continues. 1. changing the relative position to form a core having a substantially constant radius; and (e) until a clad of a predetermined thickness is deposited.
Depositing a soot material for a clad portion in a radial direction of the core portion on the core portion at a speed of about 5 g / min. 17． The soot material for the core portion includes a dopant,
Depositing a thin boundary layer of soot material for the cladding during the initial deposition of the cladding to minimize dopant evaporation,
17. The method according to claim 16, wherein cut-off wavelength characteristics at an interface are improved. 18. After depositing the starting body, the formation of the core portion is controlled in a servo mode so that the ratio of the thickness t of the deposited clad portion to the radius a of the core portion is at least 1. The method according to claim 17.