JPS602253B2 - Optical transmission line manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission line manufacturing apparatus, particularly an optical transmission line manufacturing apparatus in which a preform rod is remelted, a U-shaped tubular conduit is interposed, and molten glass is transferred to a paper yarn crucible. Regarding the crucible used.

Optical fabrics for transmitting information by light must especially minimize transmission loss of optical energy as much as possible.

As a method for manufacturing low-loss optical fibers, a glass-forming oxide, which is the core of the optical fiber, is coated on the inner wall of the tube as a thin glass film through a gas-phase chemical reaction inside a quartz tube, and the quartz tube is stretched to form the final fiber. A method for making optical fibers is well known. However, this method is essentially not suitable for continuous spinning of the longest optical fibers because the length of the quartz tube is limited. As a method for continuous spinning of optical fibers, a method is well known in which raw glass is melted in a crucible, and the glass is drawn out from the crucible and made into yarn.

This crucible is particularly of a double crucible structure made of quartz glass and arranged concentrically. Each of these double crucibles is funnel-shaped, and raw glass for the core and cladding is supplied to each crucible from the opening on the top surface.
The feed double crucible is heated, and when the raw glass in the crucible melts and reaches the temperature of paper yarn, the molten glass is drawn out from the pores at the bottom of the crucible and spun. However, especially when phosphoric acid-based raw material glass is used, spinning immediately after the temperature reaches the paper yarn temperature will cause devitrification in the glass due to crystallization, resulting in a significant deterioration in the light transmission properties of the completed optical fiber.
In order to prevent such devitrification of molten glass, it is necessary to maintain the raw material glass in a high-temperature molten state for a certain period of time, and then lower the raw material glass to a set yarn grade temperature and form it into paper yarn. However, with conventional funnel-shaped crucibles, it is inconvenient to set the furnace heating temperature in two stages: the temperature during glass devitrification prevention treatment and the grade thread temperature, and the disadvantage is that it is difficult to seal the grade thread crucible. there were. The present invention has been made to solve the above-mentioned drawbacks, and the preform rod is placed in a melting crucible in advance and remelted in a heating furnace, and the melting crucible and spinning crucible are connected in order to prevent glass crystallization. The object of the present invention is to provide a new optical transmission line manufacturing apparatus that can remelt for a certain period of time by interposing a U-shaped tubular conduit between the two.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical transmission line manufacturing apparatus according to the present invention will be described in detail below with reference to the drawings.

The drawing is a sectional view showing one embodiment of the present invention, in which a core preform rod 1 and a cladding preform rod 2 are inserted into respective melting tubular glass crucibles 3 and 4 and melted in a melting heating furnace 7. However, in order to prevent devitrification after melting the preform rods 1 and 2, U-shaped tubular conduits 5 and 6 are provided between the melting crucibles 3 and 4 and the grade crucible 8.
The glasses 1' and 2' melted through the glass are kept at a predetermined high temperature for a certain period of time, and then sent to a paper thread crucible 8 to be made into paper threads. In this case, the melting crucibles 3 and 4 and the U-shaped tubular conduits 5 and 6 are installed in the same melting and heating furnace 7, and the temperature of the heating furnace 7 is higher than that of the grade yarn heating furnace 9 that heats the paper yarn crucible 8. The high temperature also prevents devitrification of the glass during paper thread. Further, in order to prevent contamination of impurities, the melting crucibles 3 and 4 to the double crucible 8 have a nearly hermetic structure, and a gas venting capillary 10 is provided in the paper thread crucible 8 to remove air bubbles. By the way, according to the inventors' experiments, for example, 3 of P205, G02, and Ga203
In the case of a glass preform rod consisting of the following components, the paper thread temperature is approximately 1100°C, and the temperature of the melting furnace 7 is 130°C.
The degree was optimal. Further, the heating and holding time of the molten glasses 1' and 2' is preferably about 1 hour. The heating holding time can be adjusted by adjusting the inner diameters and head heights of the melting crucibles 3 and 4 and the U-shaped tubular conduits 5 and 6. When spinning an optical fiber with a core diameter of ◇ of 100 degrees at a rate of 20 skins/mjn, H=
If it was set to the 78 side, the melting retention time was about 1 hour. Further, the adjustment of the core diameter and the outer diameter of the optical fiber is determined by the paper thread diameter of the paper thread crucible 8 and the paper thread speed. As explained above, the optical transmission line manufacturing apparatus according to the present invention can continuously perform heating and spinning to prevent devitrification of molten glass, and has a nearly hermetic structure. By doing this, contamination of impurities can be prevented, and by adjusting the glass melting surface, the pressure applied to the paper yarn end of the paper yarn crucible 8 becomes almost constant, so that optical fibers of high quality and uniform dimensions can be continuously manufactured. becomes possible.

[Brief explanation of drawings]

The drawing is a sectional view showing an embodiment of an optical transmission line manufacturing apparatus according to the present invention. 1: Core preform rod, 2: Clad preform rod, 3, 4: Melting crucible, 5, 6: U-shaped tubular conduit, 7: Melting heating furnace, 8: Wire thread crucible, 9: Heating for thread removal Furnace, 10:. Air venting tube, H: Head of U-shaped tubular conduit.

Claims (1)

[Scope of Claims] 1 A heating furnace is equipped with a spinning crucible having a guide hole at the lower part, and a glass material melting crucible connected to the upper part of the spinning crucible, and the spinning crucible and the melting crucible An optical transmission line manufacturing device characterized by having a U-shaped tubular conduit connecting crucibles. 2. The optical transmission line according to claim 1, wherein the glass material melting crucible is maintained at the liquidus temperature of glass, and the spinning crucible is maintained at a spinning temperature below the liquidus temperature. Manufacturing equipment.