JPS6136134A - Method and apparatus for producing preform for stress-imparted polarization-keeping optical fiber - Google Patents

Abstract

PURPOSE:To obtain the titled preform easily and continuously, by intermittently controlling the deposition of glass soot for stress-imparting part and the deposition of glass soot for clad, thereby alternately forming the preform for stress- imparting part and the preform for clad. CONSTITUTION:A preform 30 for core is formed at one end of a rotating supporting rod by VAD process, and a preform 32 for an intermediate layer is formed to the circumference of the core preform. Thereafter, the glass soot for the stress-imparting part and the glass soot for the clad are deposited on the preform 32 for the intermediate layer using the torch 26 for the stress-imparting part and the torch 28 for the clad. Both torches are placed on the same plane perpendicular to the axis of the supporting rod making a definite angle (e.g. 90 deg.) to the axis of the supporting rod. The deposition of the soot is paused intermittently during the one revolution of the supporting rod in a manner to deposit the glass soot having the same composition to the parts symmetrical around the supporting rod. The preforms 36A, 36B for the stress-imparting part and the preforms 38A, 38B for the clad are formed alternately.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method and apparatus for producing a preform for a stress-applied polarization-maintaining optical fiber with good polarization-maintaining properties used for coherent optical transmission or optical measurement. It is related to.

2. Description of the Related Art A stressed type polarization maintaining optical fiber with good polarization maintaining property includes a core, a cladding surrounding the core, and a thermal expansion coefficient that is different from that of the cladding. The structure includes at least a stress applying section having a stress applying section. Conventionally, such stress-applied polarization-maintaining optical fibers have been manufactured using a method (RoD, Birc
h etal,, Blectron, I,ett,
, Vol, 1B, No. 24. PP, 1036-
1038, 1982>, or the rod-in-tube method as shown in FIG.
The holes shown in the figure are made by the jacket method (Y, 5asaki et al., former ectron,
Lett.

Vow, 19. No, 19. PP, 792-794
．． 1983> etc.

For example, in the case of the rod-in-tube method as shown in FIG. A pair of stress-applying glass base materials 4 sandwiched therebetween
is placed, and a dummy glass rod 5 is inserted into the remaining gap, which is then heated, melted, and drawn.

In addition, when the hole is formed by the jacket method as shown in FIG. 8, a pair of stress-applying glass base materials are inserted into the jacket base material 6 in which the core 2 is formed in the center so as to sandwich the core 2 therebetween. It is produced by forming holes 7 and inserting stress-applying glass base materials 4 into the insertion holes 7, heating and melting and drawing.

Problems to be Solved by the Invention Among the conventional manufacturing methods mentioned above, the MCVD method, the rod-in-tube method, and the hole-opening jacket method are not continuous manufacturing methods, and it is difficult to manufacture long fibers. There was a drawback. In addition, the rod-in-tube method or hole-making jacket method involves processes such as polishing the stress-applying base material and drilling high-precision holes to improve dimensional accuracy, making the manufacturing process complicated and expensive. It had the disadvantage of being long.

Therefore, the present invention aims to eliminate these drawbacks and provide a relatively simple method and apparatus for producing a long stress-applied polarization-maintaining optical fiber.

According to the present invention, a porous glass base material for the core is formed at one end of the rotating support rod, and an intermediate layer is formed on the circumferential surface of the porous glass base material for the core. A porous glass base material for the intermediate layer is formed by depositing glass fine particles for the intermediate layer, and then, on the circumferential surface of the intermediate porous glass base material, on the same plane intersecting the axis of the support rod, with respect to the axis. The glass particles for the stress applying portion and the glass particles for the cladding are deposited from directions at angles to each other, and the glass particles for the stress applying portion and the glass particles for the cladding are deposited while the support rod makes one rotation. The porous stress-applying member is intermittently paused on the peripheral surface of the porous glass base material for the intermediate layer so that glass fine particles of the same composition are deposited at axially symmetrical positions about the support rod. Provided is a method for producing a preform for a stress-applied polarization-maintaining optical fiber, which comprises alternately forming a porous glass preform for cladding and a porous glass preform for cladding.

Furthermore, according to the present invention, a reaction container, an exhaust gas treatment device coupled to the reaction container, a support rod that moves up and down within the reaction container, a drive device that rotates and pulls up the support rod, and the support rod a torch for synthesizing a porous base material for a core, which is oriented along an axis through which the central axis of the support rod passes; a torch for synthesizing a porous glass base material for a stress-applying member, and a torch for synthesizing a porous glass base material for a stress applying member, which is oriented toward an axis through which the central axis of the support rod passes above the torch for synthesizing an intermediate layer porous glass base material; It is equipped with a torch for synthesizing porous glass base material for cladding.
The torch for synthesizing the porous glass base material for the stress-applying member and the torch for synthesizing the porous glass base material for the cladding are arranged at an angle with respect to the axis on the same plane that intersects the axis through which the central axis of the support rod passes. Further, the amount of raw material supplied to the torch for synthesizing the porous glass base material for the stress applying member and the torch for synthesizing the porous glass base material for the cladding is controlled by the rotation of the support rod. Provided is an apparatus for producing a preform for a stress-applied polarization-maintaining optical fiber, which is characterized in that it is provided with a control that performs control in accordance with the angle.

In the method and apparatus for producing a preform for a stress-applying polarization-maintaining optical fiber according to the present invention as described above, a porous glass preform for a stress-applying member on the circumferential surface of a porous glass preform for an intermediate layer; The porous glass preforms for cladding are formed so that they are alternately located in the circumferential direction but are continuous in the axial direction. Therefore, by heating the base material to make it transparent, jacketing it with a quartz glass tube and drawing it as necessary, stress applying members are provided to extend in the axial direction on opposite sides of the core. polarization-maintaining optical fiber can be produced. Furthermore, there is no need for high-precision polishing or hole-drilling, and the base material is manufactured using a shaft-mounted method, so long stress-applied polarization-maintaining optical fibers can be manufactured relatively easily. .

EXAMPLES Hereinafter, examples of the method and apparatus for producing a preform for a stress-applied polarization-maintaining optical fiber according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an embodiment showing a schematic configuration of an apparatus for producing a preform for a stress-applied polarization-maintaining optical fiber according to the present invention, which implements a method for producing a preform for a pre-stress-applied polarization-maintaining optical fiber according to the present invention. It is.

The illustrated apparatus has a reaction vessel 10;
A support rod 12 hangs down from the top of the support rod 12, and the top of the support rod 12 is connected to a drive device 14 so that it can be rotated in the direction of arrow 16 and pulled up in the direction of arrow 1B.

Furthermore, an exhaust gas treatment device 20 is connected to the reaction vessel 10 for removing surplus reaction gas, glass particles, etc. in the reaction vessel 10.

A torch 22 for synthesizing the porous glass preform for the core is arranged at the lower part of the reaction vessel 10, facing the axis along which the central axis of the support rod 12 passes. Above the core porous base material synthesis torch 22, an intermediate layer porous glass base material synthesis torch 24 is arranged, similarly facing the axis through which the central axis of the support rod 12 passes.

Further above the intermediate layer porous glass base material synthesis torch 26 is a stress-applying member porous glass base material synthesis torch 26 oriented toward the axis through which the central axis of the support rod 12 passes.
and a torch 28 for synthesizing a porous glass base material for cladding. The torch 26 for synthesizing the porous glass base material for the stress applying member and the torch 28 for synthesizing the porous glass base material for the cladding are located in a plane substantially perpendicular to the axis through which the central axis of the support rod 12 passes. , as shown in FIG. 2, is arranged at an angle, for example, 90 degrees, with respect to the axis through which the central axis of the support rod 12 passes.

Furthermore, a torch for synthesizing a porous glass base material for a stress applying member 2
6 and the porous glass base material synthesis torch 28 for cladding, the conduit means extending to the raw material supply port is provided with solenoid valves ■1 and ■2, respectively.
The opening/closing is controlled by the control device 40.

The stressed cylindrical polarization-maintaining optical fiber preform manufacturing apparatus configured as described above operates as follows.

For example, with the support rod 12 at the lowest position, the drive device 1
4 to rotate at a rotation speed of 5 rpm. Oxygen gas was supplied at 511/min and hydrogen gas was supplied at 4/min to the core porous base material synthesis torch 22 facing the lower end of the support rod 12.
5iC1 gas is supplied at a rate of 11 /min and transported with argon gas at 100cc /+nin.
Then, GeCl is supplied at a rate of 10 cc/min.

As a result, an H2-02 flame is formed on the front surface of the torch 22 for synthesizing the porous base material for the core, and within that flame, 5iCI4, G
eCl4 undergoes a flame hydrolysis reaction, 5102 glass fine particles (SI02 G[+02) containing G e O2 are deposited on the lower end of the support rod 12, and the porous glass base material 30 for the core is deposited on the lower end of the support rod 12. It is formed.

The support rod 12 is rotated at a rotation speed of 5 rpm by a drive device 14.
The core porous glass base material 30 is rotated at m.
The growth end face of the base material is always kept constant by pulling it upward according to the growth rate of the base material.

On the core porous glass base material 30 synthesized in this way, oxygen gas is 5 II /min and hydrogen gas is 41! 200 cc/min of raw material gas 5iC1, which was supplied at a rate of 200 cc/min and transported with argon gas.
The intermediate layer porous glass base material synthesis torch 24 supplied at a rate of
2 glass particles are generated and deposited on the core porous base material 30 to form the intermediate layer porous glass base material 32.

The intermediate layer porous glass base material 32 formed on the core porous glass base material 30 is exposed to 50%
4! /min, hydrogen gas was supplied at a rate of 411 /min, and 5IC was transported with argon gas.
A torch 26 for synthesizing a porous glass base material for a stress applying member, to which I4 gas is supplied at a rate of 200 cc/min and BBra gas is supplied at a rate of 100 cc/min, forms an H2-0□ flame on the front surface of the torch 26. and 5ic in the flame
k,, 5iO2 for the stress applying part by reacting BBr+ gas
-820, synthesize and deposit glass particles.

Similarly, oxygen gas was supplied at a rate of 5 j2 /min, hydrogen gas was supplied at a rate of 4127 m1n, and SIC]4 gas transported with argon gas was supplied at a rate of 200 cc/min.
The torch 28 for synthesizing the porous glass base material for cladding, which is supplied at a rate of 1n, has, on the front side of the torch 28,
8202 flame is formed, SiC] and gas are reacted within the flame, and SiO2 glass fine particles for cladding are synthesized and deposited.

As a result, a base material 34 made of porous glass for stress applying member and porous glass for cladding is formed on intermediate layer porous glass base material 32 .

As described above, the torch 26 for synthesizing the porous glass base material for the stress applying member and the torch 28 for synthesizing the porous glass base material for the cladding are in the same horizontal plane and are at an angle of, for example, 90 degrees as shown in FIG. It is set up to have. When arranged in this way, 5ICI4 and BBr3 are supplied to the torch 26 for synthesizing the porous glass base material for the stress applying member, and the torch 2 for synthesizing the porous glass base material for the cladding.
The supply of S] CI4 in 8 is repeated on and off at time 2 of the time T required for one rotation of the support rod 5 by controlling the opening and closing of the solenoid valves 1 and 2 by the control device 40. controlled. That is, when the support rod 12 is rotating at 5 rpm as described above, T is 12
seconds, the control device 40 controls the solenoid valves ■1 and ■2 to 3 seconds.
By switching from open to close or from open to open every second, the supply of the material is controlled to cycle on and off at 3 second intervals.

With such intermittent control, as can be seen from FIG. A porous glass base material part 36A and a porous glass base material part 38A for cladding are formed. During the next 'AT downtime, no glass synthesis material is supplied to the torches 26 and 28, and only the glass preform rotates. As a result, during the next raw material supply time y4T, the stress applying member is placed at a position axially symmetrical to the stress applying member porous glass base material part 36A and the cladding porous glass base material part 3BA that have already been deposited. A porous glass base material part 36B for use as a cladding material and a porous glass base material part 38B for a cladding are formed. During the raw material supply time that is further after the y4T rest time, the stress applying member porous glass base material part 36A and the cladding porous glass base material part 38A are formed again.

In this way, as the raw material gas is periodically interrupted in the torch 26 for forming the porous glass base material for the stress applying member and the torch 28 for synthesizing the porous glass base material for the cladding, as described above, the stress applying part While the 5in2-B203 areas for cladding and the 8102 area for cladding exist alternately at 90° angles, the respective base material portions are formed to be continuous in the axial direction.

b The porous base material thus obtained is dehydrated and made transparent in an electric furnace provided above the reaction vessel or elsewhere. The transparent glass base material is jacketed with a quartz glass tube with an appropriate inner and outer diameter according to the wavelength of single mode operation (cutoff wavelength λC), and by drawing a wire, a stress-applied polarization-maintaining light beam is produced. Fabricate the fiber.

By the above manufacturing method, the core diameter was 4 mm and the intermediate layer diameter was 3 m.
m, cladding (stress applying part) diameter 25 mm, refractive index difference between core and intermediate layer 0.3%, 6e02 molar concentration in core 3 m
o1%, B203 molar concentration of stress applying part 10mol1%
A glass base material was prepared. This was stretched to a cladding diameter of 12.5mm (core diameter 2mm), and an inner diameter of 1mm.
A quartz tube with a diameter of 2.7 mm and an outer diameter of 40 mm was jacketed and drawn to form a fiber. The fiber outer diameter was 200 μm, the core diameter was 10 μm, and the cutoff wavelength λc was 1.5 μm. The mode birefringence B of this fiber is approximately 1.0×10-4
, and the crosstalk in a short distance (3 m) is 140 d days,
For a 7-fiber length of 100 m, it was -30 dB.

Due to variations in stress-applying parts in the length direction, crosstalk in conventional hole-drilled fibers was worse than that in fibers produced by the method, but this is not an essential problem, and by optimizing the fabrication conditions, crosstalk can be improved more than before. The fact that crosstalk can be reduced and a long stress-applied polarization-maintaining optical fiber can be manufactured by the present invention is extremely significant.

In this embodiment, the rotational speed of the support rod was 5 rpm, and the intermittent interval of the raw material gas flow rate of the torches 10 and 11 was set to 3 seconds, but the rotational speed and the intermittent interval are not limited thereto.

That is, a torch 26 for synthesizing a porous glass base material for a stress applying member and a torch 28 for synthesizing a porous glass base material for a cladding.
The angle between the two torches does not need to be 90 degrees as long as the glass particles from both torches can be deposited so that they do not overlap in the cross section of the porous base material.

For example, as shown in FIG. 4, the stress applying member porous glass base material synthesis torch 26 and the cladding porous glass base material synthesis torch 2B are arranged at an angle of 120 degrees.

For example, if the base material is rotating in the direction of the arrow, material is supplied to both torches during the first T/6 period, and then during the second
During the period T/6, only the torch 26 for synthesizing the porous glass base material for the stress-applying member is stopped, material is continued to be supplied to the torch 28 for synthesizing the porous glass base material for the cladding, and the third The supply of material to both torches is stopped for a period of T/6. After that, return to the first T/6 period again,
Feed material to both torches.

A cross section of the base material thus formed is shown in FIG.

As can be seen from FIG. 5, the stress applying member porous glass base material part 36 extends over a range of 60 degrees, while the cladding porous glass base material part 38 spreads over a range of 120 degrees.

Furthermore, as shown in FIG. 6, the torch 26 for synthesizing the porous glass base material for the stress applying member and the torch 28 for synthesizing the porous glass base material for the cladding may be arranged at an angle of 60 degrees. Again, assuming that the base metal is rotating in the direction of the arrow, material is supplied to both torches during the first T/6 period, and during the second T/6 period, the stress Only the torch 26 for synthesizing the porous glass base material for the imparting member is stopped, material is continued to be supplied to the torch 28 for synthesizing the porous glass base material for the cladding, and both torches are further supplied during the third period of T/6. Suspension of supply of materials to. Thereafter, the process returns to the initial T/6 period and supplies material to both torches.

The base material thus formed also has a cross section similar to that shown in FIG. That is, the stress applying member porous glass base material part 36 spreads over a range of 60 degrees, while the porous glass base material part 38 for cladding spreads over a range of 120 degrees.

As is clear from the above, the positional relationship between the stress applying member porous glass base material synthesis torch 26 and the cladding porous glass base material synthesis torch 28 is not limited to 90 degrees,
By changing the control timing of raw material supply suspension,
It is possible to compensate for the difference in angle between the two.

The timing of supplying raw materials to the torch 26 for synthesizing the porous glass base material for the stress applying member and the torch 28 for synthesizing the porous glass base material for the cladding is determined according to the rotational speed of the support rod 12 and the angle of both torches. be done.

Furthermore, the amount of raw material supplied to each torch is not limited to the above example, and the raw material to be supplied is not limited to the above example, but can be selected according to the composition of the optical fiber to be manufactured. Ru.

For example, the compositions of the glass for the core, the glass for the intermediate layer, and the glass for the stress applying part are 5102 GeOx, 5102-
Not limited to 8203, 5102- as core glass
P2. o5, 5I02 as intermediate layer and stress applying part
G302B 203 or S 102 P 20
By using s B 203, it is possible to provide a larger birefringence and improve polarization maintaining performance.

Further, by using 5102 as the core glass and SiO□-GeO3-F as the intermediate layer and the stress-applying portion, the effect of fluorine is that it is resistant to radiation, making it suitable for use in outer space.

As described in detail of the invention, the method and apparatus for producing a stress-applied polarization-maintaining optical fiber according to the present invention can relatively easily produce a stress-applied polarization-maintaining optical fiber without requiring high-precision processing. can be manufactured continuously, improving properties and making it more economical. Also, it is possible to achieve longer lengths, which is an original feature of the ΔD method.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a stress-applying type polarization-maintaining optical fiber preform manufacturing apparatus according to the present invention, and FIG. 2 is a stress-applying type polarization-maintaining optical fiber preform manufacturing apparatus shown in FIG. A diagram showing the positional relationship between a torch for synthesizing a porous glass base material for a stress-applying member and a torch for synthesizing a porous glass base material for a cladding. A cross-sectional view of the base material made by the base material manufacturing device, FIG. 4 shows a torch for synthesizing the porous glass base material for the stress-applying member and a porous material for the cladding used in the base material manufacturing device for the stress-applying polarization-maintaining optical fiber. FIG. 5 is a diagram showing a modification of the positional relationship with the torch for synthesizing the glass base material, and FIG. FIG. 6 is a cross-sectional view of a base material produced by a stress-applying type polarization-maintaining optical fiber base material manufacturing apparatus in which a torch is arranged; FIG. Figure 7 shows another modification of the positional relationship between the torch for synthesizing the porous glass base material for cladding and the torch for synthesizing the porous glass base material for cladding. FIG. 8 is a schematic diagram illustrating a conventional method for manufacturing an optical fiber. FIG. [Main reference numbers] 1 jacket quartz tube, 2 core, 3 glass base material for core, 4 glass base material for stress application, 5 dummy glass rod, 6 salmon/soto base material, 7 insertion hole for stress application glass, 10 Reaction container, 12 Support rod, 14 Drive device, 20 Exhaust gas treatment device, 22 Torch for synthesizing porous glass base material for core, 24
Torch for synthesizing porous glass base material for intermediate layer, 26 Torch for synthesizing porous glass base material for stress applying member, 28 Torch for synthesizing porous glass base material for cladding, 4
0 control device

Claims (5)

[Claims] (1) A porous glass base material for the core is formed at one end of the rotating support rod, and glass fine particles for the intermediate layer are deposited on the circumferential surface of the porous glass base material for the core to form the porous glass for the intermediate layer. A base material is formed, and then a stress-applying portion is applied onto the peripheral surface of the porous glass base material for the intermediate layer from directions mutually angular to the axis on the same plane intersecting the axis of the support rod. The glass particles for the stress-applying portion and the glass particles for the cladding are deposited, and the deposition of the glass particles for the stress applying portion and the glass particles for the cladding is intermittently paused during one rotation of the support rod, and the support rod is rotated. A porous glass base material for the stress applying member and a porous glass base material for the cladding are placed on the peripheral surface of the porous glass base material for the intermediate layer so that glass fine particles having the same composition are deposited at axially symmetrical positions around the center. 1. A method for producing a preform for a stress-applied polarization-maintaining optical fiber, characterized by forming material parts alternately. (2) The porous base material for the core is SiO_2-GeO_2,
It is formed from SiO_2-P_2O_5 or SiO_2, and the intermediate layer is formed from SiO_2, SiO_2-GeO_2-
F, SiO_2-GeO_2-B_2O_3, SiO_
2-P_2O_5-B_2O_3, and the stress applying part is formed from SiO_2-B_2O_3, SiO_2-P_2
O_5-B_2O_3, SiO_2-GeO_3-B_
2O_3, SiO_2-GeO_2-F, and the cladding is formed from SiO_2. (3) A reaction vessel, an exhaust gas treatment device coupled to the reaction vessel, a support rod that moves up and down within the reaction vessel, a drive device that rotates and pulls up the support rod, and a central axis of the support rod passing through. A torch for synthesizing a porous base material for a core oriented toward an axis, and an intermediate layer porous glass base material synthesis oriented toward an axis through which the central axis of the support rod passes above the torch for synthesizing a porous base material for a core. a torch for synthesizing a porous glass base material for a stress applying member, and a porous glass for cladding, which is oriented toward an axis through which the central axis of the support rod passes above the torch for synthesizing an intermediate layer porous glass base material. The torch for synthesizing the porous glass base material for the stress applying member and the torch for synthesizing the porous glass base material for the cladding intersect the axis through which the central axis of the support rod passes. are arranged at angles to each other with respect to the axis on the same plane, and further connected to the stress applying member porous glass base material synthesis torch and the cladding porous glass base material synthesis torch. 1. An apparatus for producing a preform for a stress-applied polarization-maintaining optical fiber, characterized in that a control device is provided for controlling the supply amount of the raw material in accordance with the rotation angle of the support rod. (4) The torch for synthesizing the porous glass base material for the stress applying member and the torch for synthesizing the porous glass base material for the cladding are arranged on the same plane substantially perpendicular to the axis through which the central axis of the support rod passes. 4. A method for producing a preform for a stress-applied polarization-maintaining optical fiber according to claim 3. (5) The torch for synthesizing the porous glass base material for the stress applying member and the torch for synthesizing the porous glass base material for the cladding are arranged at an angle of 90 degrees, and the control device is configured to control the support rod. Supplying raw materials to both the torch for synthesizing the porous glass base material for the stress applying member and the torch for synthesizing the porous glass base material for the cladding every 1/4 period for the time T for one rotation of the 5. A method for producing a preform for a stress-applied polarization-maintaining optical fiber according to claim 3 or 4, further comprising a pause.