JP5640059B2 - Manufacturing method of optical fiber preform to which dummy rod is connected, and manufacturing method of dummy rod - Google Patents

Description

  In the production of an optical fiber preform, the optical fiber preform and the dummy rod, or the ends of the dummy rods are heated and melted, and both of them are welded and connected, whereby the optical fiber preform to which the dummy rod is connected. The present invention relates to a method of manufacturing a material or a dummy bar.

  An optical fiber is manufactured by drawing an optical fiber preform. The optical fiber preform is manufactured by first obtaining a deposit made of silicon dioxide fine particles by the VAD method, the CVD method or the like, and then dehydrating and sintering the deposit to form a transparent glass. . In addition, after the optical fiber preform is manufactured, a drawing process may be performed. If necessary, the optical fiber preform is cut into a plurality of parts for convenience of processing, and the cut optical fiber preform is rotated around the axis. However, after the external deposition step for further deposition, dehydration and sintering may be performed to obtain a larger optical fiber preform.

  In manufacturing the optical fiber, a dummy rod is used for supporting the optical fiber preform. A dummy rod (eg, a quartz glass rod) needs to be connected to the optical fiber preform. For example, in the external attaching step, a dummy bar is connected to both ends of the optical fiber preform, the dummy rod is gripped by a glass lathe with a chuck, and at least one burner is attached while rotating the optical fiber preform. This is done by depositing silicon dioxide while traversing (reciprocating) in the direction of the optical fiber preform (arrow). The dehydration and sintering processes are also performed by connecting dummy bars to both ends of the optical fiber preform. Note that the connection of the dummy bar is not limited to both ends of the optical fiber preform, and the dummy rod may be connected to only one end of the optical fiber preform.

  In some cases, the dummy rod is gripped by a glass lathe with a chuck and the optical fiber preform is processed. Furthermore, after that, the bending of the optical fiber preform is corrected using a glass lathe, the heat drawing process for making the predetermined outer diameter and length, removal of irregularities and scratches on the optical fiber preform surface, impurities, etc. There are cases where processing such as flame polishing is performed. Moreover, the dummy rod which has a length suitable for use may be manufactured by joining the dummy rods too short to use for said use. In order to connect the dummy rod and the optical fiber preform, the end portions of both are heated and melted, then the end portions are butted together and pressed to perform welding.

  At the time of this welding, the periphery of the welded portion may rise and become a ridge shape. When silicon dioxide is deposited while the periphery of the welded portion is in the shape of a bump, the deposition density varies, causing delamination and cracking after dehydration and sintering. For this reason, after welding the end parts, the operator presses the heel against the knob-like part and molds it to smooth the periphery of the welded part, or after welding, presses the heel member around the welded part and welds it. The part is smoothed. (Patent Document 1)

JP-A-6-199533

  However, molding with a hook requires skill and skill, and is a work near a heat source, which is dangerous. Moreover, in the method described in Patent Document 1, it is necessary to introduce a new device in order to smooth the periphery of the welded portion by pressing the eaves member, and to increase the size of the optical fiber preform as described above. Along with this, there has been a problem that a great amount of time is required for the smoothing step.

  In addition, by suppressing the deformation of the contacted end portions by reducing the pressing distance after the dummy rod and the optical fiber preform or the dummy rods are in contact with each other, a bump is generated around the welded portion. Can also be prevented. However, if the pressing distance after contact between the end portions is not sufficient, the adhesion force at the welding end surface is insufficient, the bonding at the welding surface becomes insufficient, and a groove is generated at the welding portion at the time of welding. In later steps, cracks may occur starting from the groove. Therefore, when adopting a method that suppresses the deformation of the contacted end portions by reducing the pressing distance after the dummy rods are in contact with each other, there is no generation of a groove on the welding end surface, and bonding with sufficient strength In order to perform the above, it is necessary to increase the pressing distance while allowing a certain amount of generation of a bump around the welded portion.

  The present invention has been devised in order to solve the above-mentioned problems. When welding a dummy rod and an optical fiber preform or dummy rods, they are brought into contact with each other, pushed together, separated, pushed together, separated. A dummy rod and an optical fiber, or a method for manufacturing a dummy rod, in which the end portion is moved in the axial direction in this order to maintain the strength of the joint surface and suppress the occurrence of lumps around the welded portion. Is.

  The present invention provides a method for manufacturing an optical fiber preform to which a dummy rod is connected, or a method for manufacturing a dummy rod, which is simple and safe, has little manufacturing variation, and suppresses the occurrence of a bump around a welded portion. For the purpose.

The present invention is a method of manufacturing an optical fiber preform to which a dummy rod is connected,
In the step of connecting the dummy rod and the optical fiber preform coaxially by melting the opposite ends,
Melting the opposing ends; and
A first step of relatively abutting the melted ends of the dummy rod and the optical fiber preform, and welding while pressing together,
A second step of relatively pulling away the dummy rod and the optical fiber preform while the melted ends are welded to each other;
A third step of relatively pressing the melted ends of the dummy rod and the optical fiber preform; and the dummy rod and the optical fiber preform again with the melted ends welded together. The present invention relates to a method for manufacturing an optical fiber preform to which a dummy rod is connected, including a fourth step of relatively separating the elements.

  According to the present invention, it is possible to manufacture an optical fiber preform by a process of moving at least one of the dummy rod and / or the optical fiber preform along its central axis. By performing the operation in the moving process consisting of movement, an optical fiber preform to which a dummy rod is connected can be obtained easily and safely with little manufacturing variation.

  The first to fourth steps are preferably performed in a state in which the dummy bar and the optical fiber preform are attached to a lathe that is automatically numerically controlled.

  An optical fiber preform to which a dummy rod is connected can be obtained easily and safely by remote operation by an automated operation using a numerically controlled automated lathe without requiring a skilled technician.

  In the pressing of the first step, Da is the maximum outer diameter of the portion protruding in the radial direction by welding in the dummy rod or optical fiber preform at the end of the first step, and the dummy rod or optical fiber preform. It is preferable that the ratio of Da to D0 (Da / D0) does not exceed 110%, where D0 is the smaller diameter of the material (or the diameter if both are the same).

  The corners at the ends of the dummy rod and the optical fiber preform are rounded by the surface tension when melted by the flame (see FIG. 1B). This is called scraping of the corners of the end. The recess (see the center part of FIG. 1C) that occurs in the welded part at the time of connection due to scraping of the corners of the end part is within a range where the above ratio (Da / D0) does not exceed 110%. A sufficient recovery can be achieved by increasing the contact area between the dummy rod and the optical fiber preform by pressing the dummy rod and the optical fiber preform.

  Also, if the above ratio (Da / D0) is pressed until it exceeds 110%, the bumps formed at the joint portion become too large, and the dummy rod and the optical fiber preform are relatively moved in the second step later. Even if pulled apart, the shape of the knob may not disappear.

  In the second step, the distance at which the dummy rod and the optical fiber preform are relatively separated from each other (hereinafter sometimes referred to as L2) is the contact between the melted ends in the first step. Then, it is preferably longer than a relative pressing (approaching) distance (hereinafter referred to as L1) between the dummy rod and the optical fiber preform until the first step is completed. .

  It is possible to increase the force acting cumulatively on the contact surfaces of the two, thereby further ensuring the welding on the contact surfaces.

  In the third step, the outer diameter of the portion raised in the radial direction by pressing is Dc, and the diameter of the dummy rod or the diameter of the optical fiber preform, whichever is smaller (or if both are the same) When the diameter is D0, it is preferable that the ratio (Dc / D0) of Dc to D0 does not exceed 110%.

  This is in order to make the welding on the contact surface more reliable, and when the above ratio (Dc / D0) is pressed until it exceeds 110%, the lumps formed at the joint portion become too large, and the later fourth In the process, even if the dummy rod and the optical fiber preform are relatively separated from each other, the shape of the knob may not disappear.

  In the fourth step, the distance at which the dummy rod and the optical fiber preform are relatively separated (hereinafter sometimes referred to as L4) is the first step, and the melted ends start to contact each other. After that, it is preferable that the distance is approximately the same as the relative pressing (approaching) distance (L1) between the dummy rod and the optical fiber preform until the first step is completed.

  This is for more reliably suppressing the occurrence of the bump-like portion around the welded portion. Here, the same degree refers to a range in which the difference between the lengths of L1 and L4 is within ± 10% with the length of L1 as a reference of 100%.

Further, the present invention is a method for manufacturing a dummy bar,
In the process of connecting the two dummy rods coaxially by melting the opposing ends,
Melting opposite ends, and
A first step of relatively abutting the melted ends of the dummy rods and welding while pressing together;
A second step of relatively pulling away the dummy bar while keeping the melted ends welded;
A third step of relatively pressing the melted end portions of the dummy rods together, and a fourth step of relatively pulling the dummy rods again with the melted end portions welded. The present invention relates to a method for manufacturing a dummy bar.

  In the first to fourth steps, a dummy step can be manufactured by a step of moving at least one of the two dummy rods along its central axis, and the moving step comprises a simple movement. By performing the work, a dummy bar with little manufacturing variation can be obtained simply and safely.

  The first to fourth steps are preferably performed in a state where the two dummy bars are attached to a lathe that is automatically numerically controlled.

  A dummy rod can be obtained easily and safely by remote operation by an automated operation using a numerically controlled automated lathe without requiring a skilled technician.

  At the end of the first step, the pressing of the first step is Da, where Da is the maximum outer diameter of the portion of the two dummy rods raised in the radial direction by welding, and the diameter of the two dummy rods. When the smaller one (or the diameter when both are the same) is D0, it is preferable that the ratio of Da to D0 (Da / D0) does not exceed 110%.

  When the corner of the end of the dummy bar is melted by the flame and becomes round due to surface tension, the corner is scraped (see FIG. 1B). The recess (see the center part of FIG. 1C) that occurs in the welded part at the time of connection due to scraping of the corners of the end part is within a range where the above ratio (Da / D0) does not exceed 110%. It is possible to sufficiently recover by increasing the contact area between the dummy bars by pressing the dummy bars together.

  In addition, if the above ratio (Da / D0) is pressed until it exceeds 110%, the bumps generated at the joint portion become too large, and even when the dummy bars are relatively separated in the second step, The shape of the knob may not disappear.

  In the second step, the distance at which the two dummy bars are relatively separated (hereinafter sometimes referred to as L2) is the first step after the melted ends start to contact each other. It is preferable that it is longer than the relative pressing (approaching) distance between the two dummy rods (hereinafter sometimes referred to as L1) until the first step is completed.

  This is because the force acting cumulatively on both contact surfaces is made larger, and welding on the contact surfaces is made more reliable.

  In the third step, the outer diameter of the portion raised in the radial direction by the pressing is Dc, and the smaller one of the two dummy rods (or the diameter if both are the same) is used. When D0 is set, the ratio is preferably set so that the ratio of Dc to D0 (Dc / D0) does not exceed 110%.

  If the above ratio (Dc / D0) is in a range not exceeding 110%, the depressions that occur in the welded part due to scraping of the corners of the end of the dummy rod caused by heating are pressed together. A sufficient recovery can be achieved by increasing the contact area between the dummy bars. Moreover, if it pushes together until said ratio (Dc / D0) exceeds 110%, the lump formed in the circumference | surroundings of a welding part will become large too much, and in the 4th process of the following, it pulls apart dummy rods relatively. However, the shape of the knob may not disappear.

  In the fourth step, the distance (L4) at which the two dummy bars are relatively separated from each other is such that the first step ends after the melted ends start contacting in the first step. It is preferable that the distance is approximately the same as the relative pressing (approaching) distance (L1) of the two dummy bars.

  This is for more reliably suppressing the occurrence of the bump-like portion around the welded portion. Here, the same degree means a range in which the difference between the two (L1 and L4) is within ± 10% with the length of L1 as a reference of 100%.

  According to the manufacturing method of the optical fiber preform to which the dummy rod according to the present invention is connected, or the manufacturing method of the dummy rod, the occurrence of lumps around the welded portion is suppressed easily and safely with less manufacturing variation. An optical fiber preform or a dummy rod can be manufactured.

It is a side view which shows the manufacturing method of the optical fiber preform | base_material to which the dummy rod of this invention was connected. In the manufacturing method of the optical fiber preform to which the dummy rod according to the present invention is connected, it is a diagram showing the distance between the ends of the optical fiber preform and the dummy rod separated from each other in time series. It is a side view which shows a mode that the welding operation process of an optical fiber preform | base_material and a dummy stick is performed using the lathe automatically controlled numerically, controlling the amount of pushing movement. It is a figure which shows a mode that an external attachment process is further performed after the manufacturing method of the optical fiber preform | base_material to which the dummy rod of this invention was connected. It is a figure which shows the aspect which becomes impossible to extend, making the shape of the side view of the extended part of the welding part of a dummy rod and an optical fiber preform | base_material into a taper shape.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1A is a side view showing a state in which the end portions of the optical fiber preform 10 and the dummy rod 11 face each other.

  Here, the optical fiber preform refers to, for example, a quartz glass body obtained by dehydrating and sintering a silicon dioxide deposit obtained by flame hydrolysis reaction of silicon tetrachloride. In a broad sense, the silicon dioxide deposit before dehydration and sintering is sometimes referred to as an optical fiber preform, but here refers to a quartz glass body obtained by dehydration and sintering. Quartz glass may contain an additive (dopant) such as germanium or fluorine. The distribution of the additive (dopant) may have a distribution corresponding to the cross-sectional structure of the optical fiber such as the core and the clad. The optical fiber preform may be stretched after the above dehydration and sintering processes, or after stretching and further after deposition, so-called external process, followed by dehydration and sintering processes. It may be a thing. Thereafter, the optical fiber preform may be further subjected to a drawing and / or external attachment process. The optical fiber preform becomes an optical fiber bare wire by drawing in a later spinning process, and then becomes an optical fiber strand by being coated with a resin.

  The optical fiber preform is composed of a portion that becomes a core through which light is guided after drawing in the spinning process and a portion that becomes a clad that protects the core after drawing in the spinning process and has a slightly lower refractive index than the core. Also good.

  The dummy rod is a member that is used by being coaxially connected to the optical fiber preform in order to fix the optical fiber preform to the apparatus by a chuck or the like. The optical fiber preform is installed in the apparatus via a chuck or the like by a dummy rod connected to one end or both ends thereof.

  Usually, the dummy bar is made of a quartz glass body. The dummy rod may also be obtained, for example, by dehydrating and sintering a silicon dioxide deposit obtained by a flame hydrolysis reaction of silicon tetrachloride, or by melting natural quartz.

  The dummy rod is not usually drawn, and after the connected optical fiber preform is drawn, it is repaired and processed as necessary, and used repeatedly. Thus, by using the optical fiber preform connected to the dummy rod, the optical fiber preform can be used for drawing without waste and a longer optical fiber can be obtained.

  First, the dummy rod is melted by heat at the opposite ends of the optical fiber preform. As shown in FIG. 1 (a), the optical fiber preform 10 and the dummy rod 11 are held by a rotating device (not shown) and rotated around the axis, while the dummy rods are rotated by the oxyhydrogen flame from the burner 13, and The end face of the optical fiber preform is heated. The burner 13 may traverse (reciprocate) the vicinity of the heated portion of the dummy rod and the optical fiber preform as necessary. In this way, both ends are melted and softened. In addition, the temperature of the flame by the burner 13 is preferably 2,000 to 3,000 ° C., and the surface temperature of the optical fiber preform and the dummy rod at that time is preferably about 1,500 to 2,000 ° C. . In the above-mentioned heating power, it takes about 3 to 10 minutes to melt the ends. In addition, it is preferable that the heating of the end face of the dummy rod and / or the optical fiber preform by the oxyhydrogen flame from the burner 13 is continuously performed also in the first to fourth steps described later.

  The corners at the ends of the dummy rod and the optical fiber preform are rounded by the surface tension when melted by the flame (see FIG. 1B). This is sometimes referred to as scraping at the corners of the ends.

  Next, in the first step, as shown in FIGS. 1C and 1D, the melted end portions of the dummy rod 11 and the optical fiber preform 10 are relatively abutted against each other and pushed. Weld while matching.

  Welding is performed by pressing the melted dummy rod and the end face of the optical fiber preform. The pressing distance in the first step is set to such a distance that the diameter of either the dummy rod or the optical fiber preform is increased by at least 1% due to the protrusion of the joint portion. The pressing distance in the first step is the above-described dummy rod and the optical fiber mother from the start of contact between the melted ends in the first step until the end of the first step. Since it is synonymous with the relative approach distance of the material, it is also referred to as L1. The pressing distance (L1) in the first step is the same as that in the first step after the optical fiber preform 10 and the dummy rod 11 contact each other until the pressing is stopped. And the distance between the end portions of the dummy bar 11 that are separated from each other is relatively close.

  In the first step, the upper limit of the pressing distance (L1) is that the diameter (Da) of the raised welded portion at the joint portion is the smaller one of the diameter of the dummy rod and the diameter of the optical fiber preform (both Are the same), the ratio (Da / D0) to the diameter (D0) should not exceed 110%. This is because when the ratio (Da / D0) exceeds 110%, the bumps become too large, and when the dummy rod and the optical fiber preform are relatively separated in the second step, the bumps This is because the extension S occurs at both end portions of the aneurysm while maintaining the form (see FIG. 5). That is, in the subsequent second step, it becomes impossible to stretch the shape of the stretched portion of the welded portion of the dummy rod and the optical fiber preform while making the shape of the side view tapered (see FIG. 1E). Sometimes.

  Next, in the second step, the dummy rod 11 and the optical fiber preform 10 are relatively separated in the direction opposite to the pressing in the first step while the molten ends are welded to each other (FIG. 1). (E)). By relatively separating the two, the end of the welded portion of the dummy rod and the optical fiber preform in the softened state is stretched, so that the central portion of the welded portion of the dummy rod and the optical fiber preform is thinned by the surface tension. Thus, the side view is tapered. By enlarging and making the shape of the welded portion in a side view a larger tension acts in the pulling direction on the welding surface of the dummy rod and the optical fiber preform, and the welding of both is ensured. . Therefore, it is possible to suppress the generation of grooves that occur at the weld boundary at the time of pressing in the subsequent third step, and further, by making the cross section of the weld part tapered in a side view, the volume of the glass to be heated and melted by the burner is reduced. It is possible to reduce, and at the time of re-pressing in the third step, it is possible to suppress an increase in the size of a bump caused by the melted portion at the joint portion.

Moreover, the separation distance (refer FIG.1 (e)) in a 2nd process shall be more than the relative pressing distance (L1) of a 1st process at least.
The separation distance in the second step is synonymous with the distance (L2) in which the dummy rod 11 and the optical fiber preform 10 are relatively separated in the second step described above, and is also referred to as L2 below.
The upper limit of the separation distance is not particularly specified, but if the separation distance is too long, the end of the tapered portion in the side view moves away from the heat source (for example, one burner) in the vicinity of the welded portion, and cooling is performed. Therefore, it is necessary to reheat later, which is not economical. The separation distance (L2) in the second step is defined as a distance in which the ends of the optical fiber preform 10 and the dummy rod 11 that are separated from each other are relatively separated in the second step. .

  In the third step of pressing the melted ends of the dummy rod and the optical fiber preform relative to each other again, as in the first step, the diameter of the welded portion when the pressing is completed. Dc is pressed so that the ratio (Dc / D0) to the smaller one of the diameter of the dummy rod or the diameter of the optical fiber preform (the diameter when both are the same) (D0) does not exceed 110%. Thereby, the contact area of the welded portion of the end of the dummy rod and the optical fiber preform is sufficiently wide, and for a wide contact area of the welded portion, over a long period of time, by applying a large pressing force, A larger and stronger connection is possible.

  In the third step, the relative approach distance between the dummy rod and the optical fiber preform from the start of contact between the melted ends to the end of the third step is the third step. (Hereinafter also referred to as L3) (see FIG. 1 (f)). Note that the pressing distance (L3) in the third step is defined as a distance in which the ends of the optical fiber preform 10 and the dummy rod 11 that are separated from each other relatively approach in the third step. The

  In the fourth step in which the dummy rod 11 and the optical fiber preform 10 are relatively separated again in the opposite direction while the ends are welded to each other, the separation distance in the fourth step is the same as that in the first step. The same distance as the alignment distance (L1). Thereby, the lump formed in the third step can be made sufficiently small, and the periphery of the welding surface can be made smooth. The separation distance in the fourth step is also referred to as L4 because it is synonymous with the distance in which the dummy rod and the optical fiber preform are relatively separated in the fourth step described above. The separation distance (L4) in the fourth step is defined as the distance at which the ends of the optical fiber preform 10 and the dummy rod 11 that are separated from each other are relatively separated in the fourth step. .

  FIG. 4 is a diagram showing a time series of distances between ends of the optical fiber preform 10 and the dummy rod 11 that are separated from each other in the optical fiber preform manufacturing method to which the dummy rod according to the present invention is connected. It is shown in 2.

  Moreover, if the invention of the present application is used, the optical fiber preform 10 and the dummy rod 11 are welded by using a lathe 16 which can be controlled by the control device 14 as shown in FIG. It becomes possible to automate the operation of manufacturing the optical fiber preform to which the dummy rod is connected. Since the welding of the optical fiber preform and the dummy rod can be performed only by moving in the axial direction, the configuration of only the outer diameter measuring instrument (not shown) and the control device 14 for controlling the movement amount can be used. Since the welding operation can be automated, it is not necessary to use a complicated apparatus for bringing the welding part into contact with the grinding member for smoothing, which is advantageous in terms of cost and safety.

  Thereafter, an external attaching process may be performed on the optical fiber preform to which the dummy rod is connected. Specifically, in the external attaching process, for example, as shown in FIG. 4, dummy rods 11 are connected to both ends of the optical fiber preform 10, and the dummy rods 11 are held on a glass lathe by a chuck 12, While rotating the fiber preform 10 and traversing (reciprocating) at least one deposition burner 15 in the direction of the central axis (arrow) of the optical fiber preform 10, the outer periphery of the optical fiber preform 10 is oxidized. This is done by depositing silicon.

The dehydration and sintering processes are also performed with the dummy rods 11 connected to both ends of the optical fiber preform 10, but the dummy rods 11 may be connected to only one end of the optical fiber preform 10.
In some cases, the dummy rod 11 is held on a glass lathe by a chuck and the optical fiber preform 10 is processed.

  Further, after that, the bending of the optical fiber preform 10 is corrected using a glass lathe, the heat stretching process to a predetermined outer diameter or length, the surface irregularities, scratches, impurities, etc. of the optical fiber preform 10 are removed. In some cases, a process such as a flame polishing process is performed.

"Dummy rod manufacturing method"
The manufacturing method of the dummy rod of the present invention is performed in the same manner as the manufacturing method of the optical fiber preform to which the above-described dummy rod of the present invention is connected. That is, the manufacturing method of the dummy rod of the present invention connects two dummy bars by using the same method as the manufacturing method of the optical fiber preform to which the dummy rod of the present invention is connected. The present invention relates to a method of manufacturing a dummy bar.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

"Example 1"
A dummy rod 11 having the same diameter as the optical fiber preform 10 having a diameter of 45 mm was connected by the method shown in FIG. 1 to produce an optical fiber preform to which the dummy rod was connected.

  The opposite ends of the optical fiber preform 10 and the dummy rod 11 were heated by an oxyhydrogen burner 13 having a hydrogen amount of 300 L / min for 6 minutes while being rotated about the axis, and sufficiently melted (see FIG. 1 (b)). The corner portion of the end portion was in a state of being rounded by surface tension by melting by a flame, that is, a state in which the corner portion of the end portion was scraped.

  Next, as the first step, the melted end portions were brought into contact with each other (see FIG. 1C), and pressed against each other until the outer diameter Da of the welded portion reached 48 mm. The outer diameter value was measured by using an infrared laser as an outer shape measuring instrument. The pressing distance (L1) at this time was 2 mm (see FIG. 1 (d)).

  Thereafter, as a second step, the dummy rod 11 having the same diameter as the optical fiber preform 10 was separated while the ends were welded. The joints at both ends were stretched so that the side view was tapered. The two portions were relatively separated from each other until the outer diameter Db of the welded portion between the ends, which is the thinnest portion of the tapered portion in side view, was 2 mm (see FIG. 1E).

  In the third step, the two were pressed together by the same distance as the amount separated in the second step (see FIG. 1 (f)).

  Next, as a fourth step, the dummy rod 11 having the same diameter as the optical fiber preform 10 is relatively separated by the same distance as the pressing distance 2 mm in the first step while the ends are welded to each other. Thus (see FIG. 1G), an optical fiber preform to which a dummy rod was connected was manufactured. By the same method as the above connection method, a dummy rod having the same diameter was connected to the other end of the optical fiber preform, and an optical fiber preform having the same diameter dummy rod connected to both ends was manufactured.

  Although both ends of the optical fiber preform to which the dummy rods of the same diameter were connected were gripped by a lathe chuck and tension was applied with a load of 100 kg, no cracks or cracks occurred at the connection part. Silicon dioxide was deposited by performing an external process while holding the portions of the dummy rods connected to both ends of the optical fiber preform connected to the dummy rods with a chuck (see FIG. 4). Thereafter, dehydration and sintering were performed to obtain a vitrified optical fiber preform.

  Ten vitrified optical fiber preforms were obtained using an optical fiber preform to which dummy rods obtained by the same connection processing were connected. In these manufactured vitrified optical fiber preforms, peeling / cracking of the joint surface between the optical fiber preform and the dummy rod did not occur during the external attachment process, dehydration and sintering processes.

"Example 2"
A dummy rod 11 having the same diameter as the optical fiber preform 10 having a diameter of 50 mm was connected by the method shown in FIG. 1 to produce an optical fiber preform to which the dummy rod was connected.

  The opposite ends of the optical fiber preform 10 and the dummy rod 11 were heated by an oxyhydrogen burner 13 having a hydrogen amount of 300 L / min for 6 minutes while being rotated about the axis, and sufficiently melted (see FIG. 1 (b)). The corner portion of the end portion was in a state of being rounded by surface tension by melting by a flame, that is, a state in which the corner portion of the end portion was scraped.

  Next, as the first step, the melted ends were brought into contact with each other (see FIG. 1C), and pressed against each other until the outer diameter Da of the welded portion reached 54 mm. The outer diameter value was measured by using an infrared laser as an outer shape measuring instrument. The pressing distance (L1) at this time was 2.5 mm (see FIG. 1 (d)).

  Thereafter, as a second step, the dummy rod 11 having the same diameter as the optical fiber preform 10 was separated while the ends were welded. The joints at both ends were stretched so that the side view was tapered. The two portions were relatively separated from each other until the outer diameter Db of the welded portion between the ends, which is the thinnest portion of the tapered portion in side view, was 2 mm (see FIG. 1E).

  As a third step, the two were pressed against each other until the outer diameter Dc of the welded portion increased by 4 mm from the initial diameter, that is, until the outer diameter Dc reached 54 mm (see FIG. 1 (f)).

  Next, as a fourth step, the dummy rod 11 having the same diameter as that of the optical fiber preform 10 is relative to the pressing distance of 2.5 mm in the first step while the ends are welded to each other. (See FIG. 1 (g)), the optical fiber preform 10 to which the dummy rods were connected was manufactured. A dummy rod having the same diameter was connected to the other end of the optical fiber preform by the same method as the above processing, and an optical fiber preform having the same diameter dummy rod connected to both ends was manufactured.

  Although both ends of the optical fiber preform to which the dummy rods of the same diameter were connected were gripped by a lathe chuck and tension was applied with a load of 100 kg, no cracks or cracks occurred at the connection part. Silicon dioxide was deposited by performing an external process while holding the portions of the dummy rods connected to both ends of the optical fiber preform connected to the dummy rods with a chuck (see FIG. 4). Thereafter, dehydration and sintering were performed to obtain a vitrified optical fiber preform.

  Ten vitrified optical fiber preforms were obtained using an optical fiber preform to which dummy rods obtained by the same connection processing were connected. In these manufactured vitrified optical fiber preforms, peeling / cracking of the joint surface between the optical fiber preform and the dummy rod did not occur during the external attachment process, dehydration and sintering processes.

"Example 3"
A dummy bar 11 having a diameter of 45 mm and a dummy bar 11 having the same diameter were connected in the same manner as in Example 1 to produce one dummy bar. For the sake of convenience, description will be made based on the drawings for explaining a method of manufacturing an optical fiber preform to which a dummy rod is connected.

  The opposing end portions of the two dummy rods 11 were heated for 6 minutes with an oxyhydrogen burner 13 having a hydrogen amount of 300 L / min while rotating both of them around the axis, and sufficiently melted (FIG. 1 (b )reference). The corner portion of the end portion was in a state of being rounded by surface tension by melting by a flame, that is, a state in which the corner portion of the end portion was scraped.

  Next, as the first step, the melted end portions were brought into contact with each other (see FIG. 1C), and pressed against each other until the outer diameter Da of the welded portion reached 48 mm. The pressing distance (L1) at this time was 2.0 mm (see FIG. 1 (d)).

  Thereafter, as a second step, the dummy rods 11 having the same diameter were separated from each other while the ends were welded. The extended portions, which are tapered when viewed from the side, are relatively separated from each other until the outer diameter Db of the welded portion becomes 2.0 mm (see FIG. 1E).

  In the third step, both were pressed together by the same distance as the amount separated in the second step (see FIG. 1 (f)).

  Next, as a fourth step, the dummy bars are relatively separated by the same distance as the pressing distance (L1 = 2.0 mm) in the first step while the ends are welded to each other (see FIG. 1 (g)), one dummy bar was manufactured. One dummy rod manufactured in this way is connected to both ends of the optical fiber preform having the same diameter as the dummy rod by the method of Example 1, and the optical fiber preform having the same diameter dummy rod connected to both ends. Manufactured.

  Although both ends of the optical fiber preform to which the dummy rods of the same diameter were connected were gripped by a lathe chuck and tension was applied with a load of 100 kg, no cracks or cracks occurred at the connection part. Silicon dioxide was deposited by performing an external process while holding the portions of the dummy rods connected to both ends of the optical fiber preform connected to the dummy rods with a chuck (see FIG. 4). Thereafter, dehydration and sintering were performed to obtain a vitrified optical fiber preform.

  Ten vitrified optical fiber preforms were obtained from the optical fiber preforms connected to the dummy rods obtained by the same connection process. In these manufactured vitrified optical fiber preforms, peeling / cracking of the joint surfaces of the dummy rods did not occur during the external attachment process and the dehydration and sintering processes.

Example 4
A dummy bar 11 having the same diameter as the dummy bar 11 having a diameter of 50 mm was connected by the method shown in FIG. 1 to produce one dummy bar. For the sake of convenience, description will be made based on the drawings for explaining a method of manufacturing an optical fiber preform to which a dummy rod is connected.

  The opposing end portions of the two dummy rods 11 were heated for 6 minutes with an oxyhydrogen burner 13 having a hydrogen amount of 300 L / min while rotating both of them around the axis, and sufficiently melted (FIG. 1 (b )reference). The corner portion of the end portion was in a state of being rounded by surface tension by melting by a flame, that is, a state in which the corner portion of the end portion was scraped.

  Next, as the first step, the melted ends were brought into contact with each other (see FIG. 1C), and pressed against each other until the outer diameter Da of the welded portion reached 54 mm. The pressing distance (L1) at this time was 2.5 mm (see FIG. 1 (d)).

  Thereafter, as a second step, the outer diameter Db of the welded portion of the extension portion in which the side portions of both end portions are tapered while the dummy rods 11 having the same diameter are welded to each other while the ends are welded to each other. They were relatively separated until reaching 2.0 mm (see FIG. 1 (e)).

  As a third step, both were pressed together until the outer diameter Dc of the welded portion increased by 4 mm from the initial diameter, that is, until the outer diameter Dc reached 54 mm (see FIG. 1 (f)). Next, as a fourth step, two dummy rods 11 having the same diameter are relative to each other by the same distance as the pressing distance (L1 = 2.5 mm) in the first step while the ends are welded to each other. By pulling them apart (see FIG. 1 (g)), a single dummy bar was manufactured. One dummy rod manufactured in this way is connected to both ends of an optical fiber preform having the same diameter as the dummy rod by the method of Example 1, and an optical fiber preform in which dummy rods having the same diameter are connected to both ends. Manufactured. Although both ends of the optical fiber preform to which the dummy rods of the same diameter were connected were gripped by a lathe chuck and tension was applied with a load of 100 kg, no cracks or cracks occurred at the connection part.

Silicon dioxide was deposited by performing an external process while holding the portions of the dummy rods connected to both ends of the optical fiber preform connected to the dummy rods with a chuck (see FIG. 4). Thereafter, dehydration and sintering were performed to obtain a vitrified optical fiber preform.
Ten vitrified optical fiber preforms were obtained from the optical fiber preforms connected to the dummy rods obtained by the same connection process. In these manufactured vitrified optical fiber preforms, peeling / cracking of the joint surfaces of the dummy rods did not occur during the external attachment process and the dehydration and sintering processes.

"Comparative Example 1"
A dummy rod 11 having the same diameter as the optical fiber preform 10 having a diameter of 45 mm was connected by the following method to manufacture an optical fiber preform to which the dummy rod was connected.

  The opposite ends of the optical fiber preform 10 and the dummy rod 11 were heated for 6 minutes with an oxyhydrogen burner 13 having a hydrogen amount of 300 L / min while being rotated about the axis, and sufficiently melted. The corner portion of the end portion was in a state of being rounded by surface tension by melting by a flame, that is, a state in which the corner portion of the end portion was scraped.

  Next, both ends were brought into contact with each other and pressed against each other until the outer diameter Da of the welded portion reached 48 mm (L1 = 2.0 mm).

  A dummy rod having the same diameter was connected to the other end of the optical fiber preform by the same method as the above connection processing, and an optical fiber preform 10 having the same diameter dummy rod 11 connected to both ends was manufactured. .

  Ten similar connection processes were performed, and both ends of the optical fiber preform to which the dummy rods of the same diameter were connected were gripped by a lathe chuck and tension was applied with a load of 100 kg. 10 and the dummy rod 11 were cracked from the groove on the end face of the welded portion, and the joint surface between the two was broken.

"Comparative Example 2"
A dummy rod 11 having the same diameter as the optical fiber preform 10 having a diameter of 50 mm was connected by the following method to produce an optical fiber preform to which the dummy rod was connected.

  The opposite ends of the optical fiber preform 10 and the dummy rod 11 were heated for 6 minutes with an oxyhydrogen burner 13 having a hydrogen amount of 300 L / min while being rotated about the axis, and sufficiently melted. The corner portion of the end portion was in a state of being rounded by surface tension by melting by a flame, that is, a state in which the corner portion of the end portion was scraped.

  Next, both ends were brought into contact with each other and pressed against each other until the outer diameter Da of the welded portion became 54 mm (L1 = 2.5 mm), thereby joining the two.

  A dummy rod having the same diameter was connected to the other end of the optical fiber preform by the same method as the above connection processing, and an optical fiber preform 10 having the same diameter dummy rod 11 connected to both ends was manufactured. .

  Ten similar connection processes were performed, and both ends of the optical fiber preform to which the dummy rods of the same diameter were connected were gripped by a lathe chuck and tension was applied with a load of 100 kg. 10 and the dummy rod 11 were cracked from the groove on the end face of the welded portion, and the joint surface between the two was broken.

“Comparative Example 3”
A dummy rod 11 having the same diameter as the optical fiber preform 10 having a diameter of 45 mm was connected by the following method to manufacture an optical fiber preform to which the dummy rod was connected.

  The opposite ends of the optical fiber preform 10 and the dummy rod 11 were heated for 6 minutes with an oxyhydrogen burner 13 having a hydrogen amount of 300 L / min while being rotated about the axis, and sufficiently melted. The corner portion of the end portion was in a state of being rounded by surface tension by melting by a flame, that is, a state in which the corner portion of the end portion was scraped.

  Next, the melted both ends were brought into contact with each other and pressed against each other until the outer diameter Da of the welded portion reached 50 mm (L1 = 3.5 mm), thereby joining the two.

  Thereafter, the optical fiber preform 10 and the dummy rod 11 were relatively separated from each other, and an attempt was made to extend the outer diameter Db of the welded portion that was tapered in side view to 2 mm. Since the lumps formed on the surface were too large, even if they were pulled apart, elongation (S) due to melting occurred only at both ends of the lumps, and the lumps could not be eliminated (see FIG. 5). As a result, the optical fiber preform 10 was obtained in which the welded portion could not be tapered as viewed from the side, and the periphery of the welded portion was raised and the dummy rods 11 were connected.

“Comparative Example 4”
A dummy rod 11 having the same diameter as the optical fiber preform 10 having a diameter of 50 mm was connected by the following method to produce an optical fiber preform to which the dummy rod was connected.

  The opposite ends of the optical fiber preform 10 and the dummy rod 11 were heated for 6 minutes with an oxyhydrogen burner 13 having a hydrogen amount of 300 L / min while being rotated about the axis, and sufficiently melted.

  Next, the melted both ends were brought into contact with each other and pressed against each other until the outer diameter Da of the welded portion reached 57 mm (L1 = 4.3 mm), thereby joining the two.

  After that, the optical fiber preform 10 and the dummy rod 11 were relatively separated from each other, and an attempt was made to stretch the outer diameter Db of the welded portion that was tapered in side view to 2 mm. Since the aneurysm formed in the part was too large, even if both were separated, the expansion due to melting occurred only at both ends of the aneurysm, and the aneurysm could not be eliminated (see FIG. 5). As a result, the optical fiber preform 10 was obtained in which the welded portion could not be tapered as viewed from the side, and the periphery of the welded portion was raised and the dummy rods 11 were connected.

DESCRIPTION OF SYMBOLS 10 Optical fiber base material 11 Dummy rod 12 Chuck 13 Oxyhydrogen burner 14 Control apparatus 15 Deposition burner 16 Lathe

Claims (10)

A method of manufacturing an optical fiber preform to which a dummy rod is connected,
In the step of connecting the dummy rod and the optical fiber preform coaxially by melting the opposite ends,
Melting the opposing ends; and
A first step of relatively abutting the melted ends of the dummy rod and the optical fiber preform, and welding while pressing together,
A second step of relatively pulling away the dummy rod and the optical fiber preform while the melted ends are welded to each other;
A third step of relatively pressing the melted ends of the dummy rod and the optical fiber preform, and the previous dummy rod and the optical fiber preform again with the melted ends welded together. A method of manufacturing an optical fiber preform to which a dummy rod is connected, including a fourth step of relatively separating the steps ,
At the end of the first step, the pressing in the first step is Da, where Da is the maximum outer diameter of the portion of the dummy rod or optical fiber preform that is raised in the radial direction by welding. When the smaller diameter of the fiber preform or the same diameter when both are the same is D0, the ratio of Da to D0 (Da / D0) should not exceed 110%. A method of manufacturing an optical fiber preform to which a dummy rod is connected.   2. The method according to claim 1, wherein the first to fourth steps are performed in a state in which the dummy bar and the optical fiber preform are attached to a lathe that is automatically numerically controlled. A method of manufacturing an optical fiber preform to which a dummy bar is connected. In the second step, the distance (L2) at which the dummy rod and the optical fiber preform are relatively separated from each other is the first step after the melted ends in the first step start to contact each other. The optical fiber to which the dummy bar is connected according to claim 1 or 2 , characterized in that it is longer than a relative pressing distance (L1) between the dummy bar and the optical fiber preform until the end of the process. A manufacturing method of a base material. The pressing in the third step is such that the outer diameter of the portion raised in the radial direction by pressing is Dc, and the smaller diameter of the dummy rod or the optical fiber preform, or the diameter when both are the same when to the D0, optical fiber dummy rods are connected according to any one of claims 1 to 3 ratio D0 of Dc (Dc / D0) is characterized by performing so as not to exceed 110% A manufacturing method of a base material. The distance (L4) in which the dummy rod and the optical fiber preform are relatively separated in the fourth step is the first step after the melted ends in the first step start to contact each other. The dummy bar according to any one of claims 1 to 4 , wherein the dummy bar is approximately equal to a relative pressing distance (L1) between the dummy bar and the optical fiber preform until the end of the process. A method of manufacturing an optical fiber preform to which is connected. A method of manufacturing a dummy bar,
In the process of connecting the two dummy rods coaxially by melting the opposing ends,
Melting the opposing ends; and
A first step of relatively abutting the melted ends of the dummy rods and welding while pressing together;
A second step of relatively pulling away the dummy bar while keeping the melted ends welded;
A third step of relatively pressing the melted end portions of the dummy rods together, and a fourth step of relatively pulling the dummy rods again with the melted end portions welded. A method of manufacturing a dummy bar ,
At the end of the first step, the pressing in the first step is Da, where Da is the maximum outer diameter of the portion raised in the radial direction by welding in the two dummy rods. The dummy rod is characterized in that the ratio of Da to D0 (Da / D0) does not exceed 110% when the smaller diameter or the diameter when both are the same is D0. Production method. The method for manufacturing a dummy bar according to claim 6 , wherein the first to fourth steps are performed in a state where the two dummy bars are attached to a lathe that is automatically numerically controlled. . In the second step, the distance (L2) between which the two dummy bars are relatively separated from each other is such that the first step ends after the melted ends in the first step start to contact each other. The method for manufacturing a dummy bar according to claim 6 or 7 , characterized in that it is longer than a relative pressing distance (L1) between the two dummy bars. In the pressing in the third step, the outer diameter of the portion raised in the radial direction by pressing is Dc, and the smaller one of the diameters of the two dummy rods or the diameter when both are the same is D0. when the method of the dummy bar according to any one of claims 6 to 8 ratio D0 of Dc (Dc / D0) is characterized by performing so as not to exceed 110%. In the fourth step, the distance (L4) between which the two dummy bars are relatively separated from each other is such that the melted ends in the first step start contact with each other, and then the first step is completed. The method for manufacturing a dummy bar according to any one of claims 6 to 9 , wherein the manufacturing method is substantially the same as a relative pressing distance (L1) between the two dummy bars.

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