JP4420344B2 - Optical fiber preform manufacturing equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for producing an optical fiber preform in which one can accurately know the weight, the volume and the density of deposited soot at any time in the production process, and can take measures against the inferior deposition state or the like by knowing the state or the like at early time of the process progress. <P>SOLUTION: The method and the apparatus for producing an optical fiber preform, which is an outside vapor phase deposition method and which is characterized in that one can know the weight of the deposited soot for optional number of layers of soot deposited on the optical fiber preform 1 during the optional number of one-way strokes of the traverse of the burner 5, by the change amount of measured value of the weight detector 6 at starting point and ending point of elapsed time during the optional number of one-way strokes, in that one can calculate the volume of the deposited soot using the moved distance of the optical fiber preform 1 in the direction to get apart from the burner 5 during the elapsed time, and in that one can calculate the density of the deposited soot for the optional number of layers from the weight value and the volume value of the deposited soot. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

The present invention an optical fiber preform manufactured by ZoSo location, and more particularly, attention to the movement of direction perpendicular to the axis of the central member under control conditions to keep the distance between the burner and the preform surface constant and, manufactured ZoSo location of the center precise measurement of the movement amount of the application of low frequency counter member, and the optical fiber preform handling precise measurement of deposition soot total weight by using this for as soot deposition growth It is about.

  FIG. 1 is a simplified plan view for explaining an external manufacturing method of an optical fiber preform. In short, this manufacturing method is a shaft-shaped central member having relatively high refractive index (both ends thereof). 1A, 1B) is held horizontally and rotated, while a burner of a raw material gas having a lower refractive index is blown around it by the burner while traversing the burner in the longitudinal direction of the central member. Soot is attached.

  In such a method of manufacturing an optical fiber preform, in a state where various conditions relating to the temperature and flow rate of the burner flame for blowing the raw material gas used are basically constant, both ends 1A and 1B of the central member are connected to the optical fiber. The process of synchronous rotation with a predetermined number of times determined by the surface temperature of the base material, and the control of the distance between the burner and the surface of the optical fiber base material to maintain a constant result. The step of moving and adjusting in a direction perpendicular to the axis so as to move away from the burner, and the step of measuring the weight of the soot deposition amount after the completion of the manufacturing process are important.

  Regarding the former, the process technology for synchronously rotating the both ends 1A, 1B of the central member at a predetermined number of times determined by the surface temperature of the optical fiber preform, the inventor of the present invention has already been researched by Japanese Patent Application Laid-Open No. 2004-155634. One end is disclosed, and in the present invention, a technique relating to the latter process is mainly described.

The soot weight deposited and deposited by the external method is conventionally set under the bearings 2A and 2B for supporting the both end portions 1A and 1B of the center member, respectively, and is a weight such as a load cell shown by a broken line in FIG. It was common to measure by the difference between the indicated weight of the detector 6 before the start of manufacture and that after completion.
JP 2003-020245 A

  When the conventional method for measuring the weight of the deposited soot is used, the total weight of the deposited soot can be known after completion of the manufacturing process, but the volume of the soot deposited layer portion cannot be known. Therefore, there was a drawback that the density of soot could not be known. For this reason, the soot density distribution in the deposited layer is most preferably relatively high toward the center for the next sintering process, but knowing the density value during the process. In other words, the manufacturing process cannot be ideally managed as described above.

The present invention has been made to solve the above-mentioned problems, and it is necessary to use a burner that traverses the vicinity while rotating both ends of the center member of the optical fiber preform rotatably supported by bearings. In an external manufacturing apparatus for an optical fiber preform, in which an optical fiber preform is manufactured by spraying a combustion flame of a source gas and depositing the soot of the source gas on the outer peripheral portion of the central member, the both ends are driven to rotate. The first motor and the second motor are synchronously rotated at a predetermined number of revolutions, and the both end portions are integrated so that the distance between the outer peripheral surface of the optical fiber preform and the burner is kept constant. perpendicular to the axis of the central member away from the burner also moved adjusted in a direction approaching to this, on the frame at both ends bearings supporting the one of the central member The feed screw shaft, which is held and fixed, engages with this frame and has a known advance amount of one rotation, and rotates the feed screw shaft to move the frame away from the burner perpendicular to the axis of the central member. The amount of rotation of the feed screw shaft is measured by counting the number of pulses output from a pulse transmitter provided thereon with a low-frequency counter .

The low-frequency counter is a two-phase A and B type whose phases are shifted by 90 degrees from each other, and one of the phases is accompanied by the rotation of the feed screw shaft when the optical fiber preform moves away from the burner. Assign the other phase to the counting of pulses emitted and the other phase to the counting of pulses emitted with the same rotation of the feed screw shaft, and the algebraic sum addition of the A and B phase pulses is opposite By executing at the pulse falling point of the phase, an error in counting the number of pulses is avoided .

According to the present invention, while the both ends of the central member of the optical fiber preform are rotatably supported by the bearings, the required source gas combustion flame is blown from the burner traversing the vicinity, In an optical fiber preform external manufacturing apparatus for producing an optical fiber preform by depositing the soot of the raw material gas on the outer periphery, the first motor and the second motor that respectively rotate and drive the both ends are set to a predetermined number of rotations. And the both ends are integrally moved away from the burner perpendicular to the axis of the central member so that the distance between the outer peripheral surface of the optical fiber preform and the burner is kept constant. The bearing that supports both ends of the central member is supported and fixed on one frame, and the amount of advancement of one rotation is already fixed to this frame. The feed screw shaft is engaged, and by rotating the feed screw shaft, the frame is moved perpendicularly to the axis of the central member, away from the burner, and adjusted and moved in a direction approaching the burner. Since the amount of rotation of the lead screw shaft is measured by counting the number of pulses output from a pulse transmitter provided on the lead screw shaft with a low frequency counter, the amount of deposited soot deposition can be measured at any time during the manufacturing process. In addition, it is possible to measure the amount of soot for any number of layers corresponding to any number of steps of traversing the burner, and to calculate the soot density at that time at the same time. Detection can be avoided at any time, and this has the effect of efficiently producing a high-quality optical fiber preform.

The low-frequency counter is a two-phase A and B type whose phases are shifted by 90 degrees from each other, and one of the phases is accompanied by the rotation of the feed screw shaft when the optical fiber preform moves away from the burner. Assign the other phase to the counting of pulses emitted and the other phase to the counting of pulses emitted with the same rotation of the feed screw shaft, and the algebraic sum addition of the A and B phase pulses is opposite By avoiding pulse number counting errors by running at the phase pulse falling point, the volume of soot deposition can be accurately measured, so the soot weight and density can be determined at any point during the manufacturing process. There is an effect that it can be calculated accurately, and this is fed back to the control device, so that it is possible to produce a high-quality optical fiber preform.

  An example of the inventive device will be described with reference to FIG. The diameter of the optical fiber preform 1 to be manufactured is successively increased by a soot that adheres and accumulates on the outer periphery of the central member having both ends 1A and 1B. The soot is deposited and deposited by spraying a combustion flame of a raw material gas of a predetermined composition by a burner 5 that reciprocates and traverses from one end 1A to the other end 1B of the central member.

  The surface temperature of the optical fiber preform 1 during manufacture is measured by the surface thermometer 4, and the optimum traverse speed of the burner 5 is determined according to this temperature. In addition, it is important that the distance B between the surface of the optical fiber preform 1 and the burner 5 is measured and controlled by the laser displacement meter 3 and is always kept at a suitable value. Therefore, during the manufacturing process, the optical fiber preform 1 always has an optical fiber of the thickness of one soot layer deposited so far when the burner 5 travels one way from one end 1A to the other end 1B, that is, when one stroke moves. It is necessary to move away from the burner 5 in a direction perpendicular to the axis of the base material 1.

  Actually, the optical fiber preform 1 is not always attached with soot having the same thickness over the entire length in each one-way stroke of the traverse of the burner 5, so that an uneven portion is generated on the surface as the process proceeds. When the laser displacement meter 3 captures the recess, the optical fiber preform 1 may be moved in the direction approaching the burner 5 according to the above control conditions.

  The movement adjustment of the entire optical fiber preform 1 in the direction perpendicular to the axis of the optical fiber preform 1 and coincident with the combustion gas injection direction by the burner 5 is mechanically performed on the frame 10 that supports and fixes both end portions 1A and 1B of the central member. Advancing amount of one rotation (for example, if it is a double screw, this is twice the pitch) A known feed screw shaft 7 is engaged, and this feed screw shaft 7 is attached with a driver such as a servo motor or a stepping motor. This is performed by forward / reverse rotation driving by an appropriate drive motor 9. Normally, the optical fiber preform 1 is configured to move in a direction away from the burner 5 when the drive motor 9 rotates forward.

  The number of rotations of the feed screw shaft 7 can be accurately counted by counting the number of pulses output from a pulse transmitter 8 such as an encoder attached thereto with a low frequency counter 11. If the used pulse transmitter 8 transmits n pulses per revolution of the feed screw shaft 7 and the advance amount of one revolution of the feed screw shaft is a, for example, until a certain point in the manufacturing process. If the forward rotation pulse count number is N1 and the reverse pulse count number is N2, the thickness of the soot layer deposited on the optical fiber preform 1 up to that point (= the radius increase amount of the optical fiber preform) ) Is calculated by the equation a {N1 + (− N2)} / n.

  FIG. 2 shows one embodiment of the present invention. As this embodiment, one practical device for counting by the low-frequency counter 11 is taken up. As this low frequency counter 11, an A and B two-phase type having a phase difference of 90 degrees is used. The A phase is used for counting forward rotation pulses of the drive motor 9 so as to keep the optical fiber preform 1 away from the burner 5. Phase B is also subject to reversal.

  The most important and important thing in handling this type of counter is the exact counting of the number of pulses, especially when the pulses with positive and negative signs are mixed in one process as in the present case.

  The pulse count of the normal counter is as follows. When one cycle of the A-phase pulse wave is divided into four stages every 90 degrees as shown in the figure, in the forward rotation direction, the B-phase rise while the A-phase is ON, In other words, the measurement is performed at the start point of the second stage, and one pulse is counted here. However, in the present invention, the time until the start point of the fourth stage, that is, the end point of the fourth stage is taken for further accuracy. An interlock is applied to stop the progression of the A-phase pulse train that has been counted up to the B-phase falling while leaving a margin of Δt, and the calculation is confirmed at this point. The same applies to the case where the negative reverse pulse count is changed to the positive pulse count.

The pulse counting means of the counter described in the embodiment can be widely applied to general counting for obtaining the algebraic sum of the number of pulses mixed with positive and negative signs.

It is a simplified top view of the manufacturing apparatus of an optical fiber preform. It is explanatory drawing of the pulse count of an Example.

DESCRIPTION OF SYMBOLS 1 Optical fiber preform 1A, 1B Both ends of central member 2A, 2B Bearing 3 Laser displacement meter 4 Surface thermometer 5 Burner 6 Weight detector 7 Feed screw shaft 8 Pulse transmitter 9 Drive motor 10 Frame 11 Low frequency counter

Claims (2)

The required source gas from the burner (5) traversing the vicinity while rotating both ends (1A, 1B) of the central member of the optical fiber preform (1) rotatably supported by bearings (2A, 2B), respectively. In an external manufacturing apparatus for an optical fiber preform that produces an optical fiber preform (1) by depositing soot of the source gas on the outer peripheral portion of the central member,
The first motor (M1) and the second motor (M2) that respectively rotate and drive the both end portions (1A, 1B) are synchronously rotated at a predetermined rotation number, and the both end portions (1A, 1B) are integrally formed. In order to keep the distance between the outer peripheral surface of the optical fiber preform and the burner (5) constant, the distance is perpendicular to the axis of the central member and is moved away from the burner (5) and adjusted so as to approach it. ,
Bearings (2A, 2B) that support both ends (1A, 1B) of the central member are supported and fixed on one frame (10), and a feed screw shaft (known in advance amount of one rotation) is attached to the frame (10). 7) engaged,
By rotating the feed screw shaft (7), the frame (10) is configured to move perpendicularly to the axis of the central member, away from the burner (5), and adjust and move in a direction approaching the burner (5),
It said feed screw shaft (7) an optical fiber preform, characterized that you measured by counting the rotation amount of the pulse generator which is provided to it the number of pulses output from (8) by a low-frequency counter (11) of External manufacturing equipment . The low-frequency counter (11) is an A / B two-phase type whose phase is shifted by 90 degrees from each other, and one phase is sent when the optical fiber preform (1) moves away from the burner (5). The number of pulses emitted as the screw shaft (7) is rotated and the other phase is assigned to the number of pulses generated as the feed screw shaft approaches the same rotation. algebraic sum of the pulse addition are all external apparatus for manufacturing an optical fiber preform according to claim 1, characterized in that to avoid the errors of the number of pulses counted by performing the pulse falling down point opposite phase .

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