JPH1081529A - Processing for optical fiber preform and processing apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both an improved processing method for joining an optical fiber preform (glass rod) by melting and bonding by a vertical type glass lathe and an apparatus therefor. SOLUTION: This method for processing an optical fiber preform comprises making one end of a glass rod for optical fiber having the other end gripped by one chuck of a vertical type glass lathe and one end of a dummy rod similarly having the other end gripped by the other chuck of the vertical type glass lathe face each other mutually at a proper interval, bringing both the ends face to face while heating for a fixed time and bonding the glass rod to the dummy rod. In this case, pressing pressure between the face at the end of the glass rod for optical fiber and the face at the end of the dummy rod is monitored and joining by melting and bonding are carried out while controlling the chuck operation so as to make a molten state optimum for the joining by melting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for processing an optical fiber preform, and more particularly to a method of welding and connecting a dummy rod such as a glass rod to an optical fiber preform using a vertical glass lathe. The improvement of glass lathes.

[0002]

2. Description of the Related Art A transparent glass preform (preform) for an optical fiber comprising a glass portion corresponding to a core and a clad.
Usually, before drawing into an optical fiber in a drawing furnace, the fiber is stretched and reduced in diameter so as to have an optimal size for drawing, and is used as a drawing base material. Also, a glass rod such as a dummy rod is provided at one end of the drawing base material so that the drawing base material can be gripped by the fitting portion at the lower end of the support member of the drawing machine suspension mechanism for disposing the drawing base material in the drawing furnace. Weld and connect. In this case, when welding and connecting with a dummy bar using a conventional horizontal glass lathe, there is a risk that the glass rod for optical fiber will bend under its own weight, or that the rod will break from the part gripped by the chuck because it is heavy. There is.

[0003] Generally, prior to welding, an operation of aligning (centering) the center axis of the rod with the center axis of the lathe is performed. For example, in Japanese Patent Application Laid-Open No. 7-25636, one end of an optical fiber preform and one end of a dummy rod are gripped by a chuck of a horizontal glass lathe as shown in FIG. As a method of centering at the time of welding, the centering detection and pressing lever member supported by the support member is pressed against at least one outer periphery in the vicinity of the butt portion, and the load at the time of pressing is detected by the load sensor, and It has been proposed to center the rod at the butted portion so that the supporting member to be loaded has an appropriate load.
In other words, in the state where the core is not protruded, the load sensor moves up and down due to whirling at the free end, and detects the load applied to the pressing lever member, but when the pressing lever member is pressed, the rod core comes out and the sensor comes to the sensor. No load is applied.

[0004]

In order to reduce the cost of the optical fiber and increase the production volume, the size of the base material (preform) has been increased. The glass rod for use is also large and long. As described above, it is difficult to handle with a horizontal glass lathe, so welding and connecting work are performed with a vertical glass lathe, but the finished state of the welded part often varies, and bubbles are mixed from the connected part and There was a problem of breaking. The present invention is intended to solve such a problem and to provide an optical fiber preform processing method and apparatus capable of realizing further improved welding and connection using a vertical glass lathe.

[0005]

Means for Solving the Problems As means for solving the above problems, the present invention provides (1) one end of an optical fiber glass rod gripped by one chuck of a vertical glass lathe; The other end of the dummy bar gripped by the other chuck of the vertical glass lathe is opposed to each other at an appropriate interval, and butt-welded while heating for a certain time,
In the processing method of the optical fiber preform to be connected, the pressing operation between the other end face of the glass rod for the optical fiber and the other end face of the dummy rod is monitored, and the chuck operation is controlled so that the melted state is optimal for welding. (2) The monitoring of the pressing pressure is performed by a load monitoring device attached to one of the chucks of the glass lathe. (1) The method for processing an optical fiber preform described in (1), (3) the monitoring of the pressing pressure is performed by a device for monitoring the motor torque of the glass lathe during traverse, which is attached to one chuck of the glass lathe. The method for processing an optical fiber preform according to the above (1), and (4)
The method for processing an optical fiber preform according to (1), wherein the monitoring of the pressing pressure is performed by a handle operation function attached to one or both chucks of the glass lathe. Also, the present invention provides (5) an optical fiber preform processing apparatus that has upper and lower chucks capable of rotating and moving up and down, and coaxially welds and connects glass rods respectively held to the upper and lower chucks.
(6) the detection device, comprising: a detection mechanism for detecting a pressing pressure on the end faces of the glass rods facing each other; and a mechanism for controlling the operation of the upper or lower chuck based on the detection value. The processing device according to (5), wherein the mechanism is a load measuring device attached to one chuck or a motor torque measuring device attached to one or both chucks, and (7)
It has upper and lower chucks that can rotate and move up and down,
In the optical fiber preform processing apparatus for coaxially welding and connecting the glass rods respectively held by the upper and lower chucks, a mechanism for visually observing the welded state on the mutually facing end faces of the glass rod, and The above-mentioned processing apparatus is provided with a handle mechanism having a handle mechanism for manually controlling the operation of the upper or lower chuck while checking the welding state.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have studied the problems of a conventional vertical glass lathe in depth, and as a result, when welding and connecting, the operator has confirmed the amount of indentation corresponding to the molten state of the glass at the connection portion. It has been found that, because of the inability to do so, the finish of the welded portion often varies by the operator, and when the amount of heat is insufficient, air bubbles and the like are mixed and the joint is broken. Based on these new findings, in the present invention, if the pressing pressure at the end face corresponding to the pushing amount is monitored,
That the molten state and the pushed state at the butted portion of the optical fiber glass rod and the dummy rod can be confirmed,
Further, the pushing amount, that is, the pushing amount so that this value becomes a predetermined value, that is,
By controlling the chuck speed, a uniform and high quality connection is realized.

In the present invention, since the pressing pressure when the end faces of the optical fiber glass rod and the dummy rod come into contact with each other is monitored, the optimum welding state can be monitored, and the variation in the connection state can be reduced. In addition, breakage from the connection portion can be reduced. In the present invention, the “pressing pressure” refers to a force per unit area applied to a rod when butting and welding are performed. Since the present invention uses a vertical glass lathe, it goes without saying that there is an advantage that bending of the rod due to its own weight does not occur.

In the present invention, as a specific means for monitoring the pressing pressure, a monitoring device having a load sensor is attached to an upper or lower chuck of a vertical glass lathe, or a device for monitoring a motor torque value of the upper or lower chuck is attached. Or a method in which a handle is attached to the upper or lower chuck to directly observe the welding state and operate the chuck.

FIG. 2 illustrates one specific example of the above, in which a load detecting sensor is incorporated in an upper chuck mounting portion. As the load detection sensor used in the present invention,
For example, a load cell may be used, and the relationship between the connection state and the optimum load value may be obtained by an experiment, and monitored using this value. The load optimum value is not particularly limited because it is related to the physical properties and size of the glass, but for example, 5 to 100 g.
/ Cm ^{2. If the} load is too small, the adhesion of the glass becomes insufficient, and if the load is too large, the core is displaced from the center axis.

In the above case, the upper or lower chuck is automatically moved up and down. However, when the upper and lower chucks are welded by lowering the upper chuck, for example, when the upper chuck is lowered, the free glass is pressed against the softened glass. As the state changes to a pressed state (a state in which the glass cannot be pressed even if pressed further), the force applied to the motor that moves up and down increases. By converting the force applied to the motor into a numerical value, a correspondence with the optimum pressing pressure is achieved. In this case as well, the optimum torque range is determined by experiment according to the glass material, size, etc., and monitoring is performed based on this value.

FIG. 3 shows one specific example of the above. In the handle operation, a reducer is loaded on the chuck traverse mechanism, and the chuck is moved up and down by manual operation (handle). In this case, the welded state is confirmed by visually observing the welded portion, and the optimum welded state is determined.

[0012]

【Example】

Example 1 An optical fiber glass rod having an outer diameter of 40 mmφ and a length of 1200 mm and comprising a core / cladding, and a quartz dummy rod having an outer diameter of 40 mmφ and a length of 600 mm were prepared. While holding one end of the dummy rod on the upper chuck of the vertical glass lathe, holding one end of the glass rod for optical fiber with the lower chuck on the opposite side, make each free end face each other at appropriate intervals, for a certain time, The chuck of the lathe is moved while being heated by the oxyhydrogen burner for heating, and the free ends are welded to each other. At this time, each free end is heated uniformly by rotating each chuck. The upper chuck has a built-in load sensor (load cell) for monitoring the load at the time of pressing.

If the core of the optical fiber glass rod is not protruded, an operation of setting the core of the rod is performed before welding. In this operation, the bent portion of the rod is heated and softened with an oxyhydrogen burner, and an L-shaped glass rod is centered on the upper portion along the rod.

When the free ends of the glass rod for optical fiber and the dummy rod are sufficiently heated and the melted state is optimal for welding, the upper chuck or the lower chuck is moved to move the free end of the glass rod for optical fiber. Press the end against the free end of the dummy bar. The pressing pressure at this time can be detected by a load sensor built in the upper chuck shown in FIG. This pressing is performed in a state where the pressing pressure has reached a set value to a certain degree (a value at which a good welding result was obtained by a previous welding experiment). With this load monitor, the operator can grasp the optimum welding state.

[Example 2] Outer diameter 40 mmφ, length 120
An optical fiber glass rod having a core / cladding of 0 mm and a quartz dummy rod having an outer diameter of 40 mmφ and a length of 600 mmφ were prepared. The upper chuck was provided with a function of monitoring the torque value of the motor loaded when traversing, instead of the load sensor. That is, by monitoring the torque value of the motor corresponding to the pressing pressure, the optimum welding state is grasped when the torque value reaches a certain set value, and the welding and connection of the optical fiber glass rod and the dummy rod are performed. Did the work.

[Embodiment 3] Outer diameter 40 mmφ, length 120
An optical fiber glass rod having a core / cladding of 0 mm and a quartz dummy rod having an outer diameter of 40 mmφ and a length of 600 mmφ were prepared. The upper chuck has a structure that allows the operator to directly observe the welding state by directly operating the handle via an appropriate gear. When the free ends of the optical fiber glass rod and the dummy rod are sufficiently heated and the melted state is optimal for welding, move the upper chuck by operating the handle, and visually check the pushed state while checking the pushed state. Welded and connected the dummy rod.

Comparative Example 1 An outer diameter of 4 was obtained in the same manner as in Examples 1 to 3.
Glass rod for optical fiber consisting of a core / cladding of 0mmφ and length of 1200mm, outer diameter of 40mmφ and length of 6
When the connection of the 00 mm quartz dummy rod was performed without monitoring the pressing pressure, the two rods were connected in a state where the central axes of the rods were extremely displaced as shown in FIG. This comparative example is a case where it is estimated that the pressing pressure was strong. Conversely, when the pressing pressure was estimated to be weak, heat could not be sufficiently applied to the inside of the rod, and microbubbles remained at the connection. As described above, when relying solely on the operator's feeling, it is difficult to obtain a good connection state with good reproducibility, and the variation in the connection state increases, and the ratio of defective rods increases.

[0018]

According to the processing method and the processing apparatus of the present invention, it is possible to confirm the molten state and the pushed state at the butted portion of the optical fiber glass rod and the dummy rod.
Variations in the finished state of the welded portion by the operator can be reduced. In addition, reliable connection becomes possible, and it is possible to prevent air bubbles in the connection portion from being mixed, thereby avoiding breakage of the connection portion.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view schematically showing the present invention.

FIG. 2 is a schematic explanatory view of an embodiment in which a load sensor is attached to an upper chuck to monitor a load in the present invention.

FIG. 3 is a schematic explanatory view of an example of monitoring by attaching a chuck operation handle to an upper chuck in the present invention.

FIG. 4 is a schematic cross-sectional view showing a state where centers of a glass rod for an optical fiber and a dummy rod are shifted and connected in a comparative example according to a conventional method.

FIG. 5 is a schematic explanatory view of an example of welding a glass rod with a conventional horizontal glass lathe.

Claims (7)

[Claims] 1. The other end of an optical fiber glass rod held at one end by one chuck of a vertical glass lathe and the other end of a dummy bar also held at one end by the other chuck of the vertical glass lathe. Are opposed to each other at an appropriate interval, and are butt-welded while being heated for a certain period of time, and are welded together.In the method for processing an optical fiber preform, between the end face of the other end of the glass rod for optical fiber and the other end face of the other end of the dummy rod A method for processing an optical fiber preform, characterized in that the pressing pressure of the optical fiber is monitored, and welding and connection are performed while controlling the chucking operation so that the molten state is optimal for welding. 2. The optical fiber preform processing method according to claim 1, wherein the monitoring of the pressing pressure is performed by a load monitoring device attached to one of the chucks of the glass lathe. 3. The optical system according to claim 1, wherein the monitoring of the pressing pressure is carried out by a device attached to one or both chucks of the glass lathe and for monitoring a motor torque of the glass lathe during traverse. Processing method of fiber preform. 4. The optical fiber preform processing method according to claim 1, wherein the monitoring of the pressing pressure is performed by a handle operation function attached to one of the chucks of the glass lathe. 5. An optical fiber preform processing apparatus comprising an upper and lower chuck capable of rotating and moving up and down, and coaxially welding and connecting the glass rods gripped by the upper and lower chucks, respectively. The processing apparatus according to claim 1, further comprising a detection mechanism for detecting a pressing pressure on the end faces facing each other, and a mechanism for controlling the operation of the upper or lower chuck based on the detected value. 6. The processing apparatus according to claim 5, wherein the detection mechanism is a load measuring device attached to one of the chucks or a motor torque measuring device attached to one or both of the chucks. 7. An apparatus for processing an optical fiber preform, comprising an upper and lower chuck capable of rotating and moving up and down, and coaxially welding and connecting the glass rods respectively held by the upper and lower chucks. A mechanism for visually observing the welding state at the end faces facing each other,
And a handle mechanism for manually controlling the operation of the upper or lower chuck while visually confirming the welding state.