JPH02180735A - Hermetically coating device for optical fiber - Google Patents

Abstract

PURPOSE:To provide a hermetic coating device of the optical fiber, capable of coating a hermetic film outstanding in its quality, by dividing a reaction pipe for the coating into plaral chambers along the fiber transferring direction and by constituting each chamber so as to be able to control the atmospheric gaseous conditions respectively and independently. CONSTITUTION:When spun fiber is passed through the chambers 3A-3C of a reaction pipe 3 is which hermetic coating is performed, the temp. of the gaseous atmosphere, gas concn. and the flow rate of gas in the respective chambers are optimally controlled in coincidence with the temp. of fiber passed through the respective chambers 3A-3C. Thereby a thick film good in quality can be formed. In the hermetically coating device for optical fiber, the proper gaseous atmospheric conditions can be set in the transfer direction of fiber on which a hermetic coating layer is formed. Therefore the thick film good in quality can be formed and in this case, quality of the film is shown by product of film quality X film thickness because film quality is made nearly uniform.

Description

Detailed Description of the Invention <Industrial Utilization Public Funds> The present invention provides optical fibers with heteronuclear chemical attachment (HNTD).
), chemical vapor deposition (including CVDi and low-pressure thermal CVD), etc., and relates to a hermetic coating device for optical fibers that applies methic coatings to metals and inorganic materials.

BACKGROUND OF THE INVENTION Optical fibers are very sensitive to water vapor and many harmful environments, and organic material coatings cannot prevent the diffusion of water vapor or hydroxyl ions. Therefore, in order to maintain the strength of the optical fiber, it is necessary to apply a hermetic coating made of metal or inorganic material.

In order to apply such a hermetic coating to a fiber, for example, as disclosed in Japanese Patent Publication No. 61-32270, an HNTD or CVD reactor is installed between a drawing furnace and an l1tjll coating device to continuously coat the fiber. There is a need to. That is, as shown in FIG. 4, a reaction furnace 4 consisting of a heater 2 and a reaction tube 3 heated by the Tanabata 2 is provided directly below the drawing furnace 1. The treated fiber 5 is sent through reaction v:3 to a resin coating device 6 for coating with resin, and is coated with resin via a resin curing device (not shown). here,
A gas supply port 3a and a gas exhaust port 3b are formed in the reaction tube 3, and source gas and diluent gas are supplied from the gas supply port 3a through valves 7a and ?, respectively. b and flowmeters 8a, 8b, while exhaust gas is exhausted from the gas exhaust port 3b via valve 7C and flowmeter 80, and valves 7m, 7b.

7c to maintain the gas atmosphere inside the reaction tube 3 in an appropriate state.

Further, US Pat. No. 4,735,856 discloses an apparatus for forming multiple layers of hermetic coating by arranging a plurality (7) CVD furnaces in series or by elongating the reaction tube as described above and providing multiple gas supply ports. ing.

<Problems to be Solved by the Invention> In the conventional hermetic coating device described above, the gas atmosphere in the reaction tube forming one coating layer is controlled to be almost uniform across the drawing direction. Since the substrate temperature, that is, the fiber temperature, which is a parameter, decreases exponentially from the spinning point of the drawing furnace, there is a problem in that the coating conditions near the inlet and the outlet of the reaction tube are greatly different. In other words, even if a dense coating is formed near the inlet, a similar film will not be formed near the exit because the fiber temperature is low, and the optimal gas atmosphere range is very narrow, so the overall fiber temperature in the reaction tube may vary. It is not possible to set a combined gas atmosphere. Furthermore, there is also the problem that some of the fine particles resulting from thermal decomposition of the raw material gas on the upstream side do not adhere to the fiber immediately, but grow during the process of flowing downstream, become large particles, and adhere to the fiber, reducing film quality. be.

On the other hand, when trying to form a two-layer hermetic coating,
Another problem is that the fiber temperature in the second layer reaction tube is too low to provide a good secondary coating.

In view of these circumstances, an object of the present invention is to provide an optical fiber hermetic coating device that can apply a hermetic coating with good film quality.

Means for Solving the Problems〉 The hermetic coating device for optical fiber according to the present invention that achieves the above-mentioned object has a reaction tube through which a fiber spun in a drawing furnace passes. In an optical fiber hermetic coating device that forms a hermetic coating made of a metal or an inorganic material in a deposition reaction furnace, a portion forming one coating of the reaction tube is divided into a plurality of chambers along the direction of movement of the fiber, and each chamber is The gas atmosphere conditions of the two can be controlled independently.

Function: When the spun fiber passes through multiple chambers where one hermetic coating is applied to the reaction tube, the temperature, gas concentration, and gas flow rate of the gas atmosphere in each section are optimized to match the temperature of the fiber passing through each chamber. A thick film with good film quality is formed.

The temperature of the fiber leaving the drawing furnace is approximately expressed by the following equation.

hz T, = T0+ (T, To) e "dVFTl: Fiber temperature, To: Outside temperature.

T6: Fiber temperature immediately after spinning.

h: heat transfer coefficient, ρ: fiber density, C: fiber specific heat.

d: fiber diameter, z: distance from the spinning point.

■F: s speed Therefore, the fiber temperature Tl is the distance Z from the spinning point
decreases exponentially as .

Here, for the sake of simplicity, the outside air temperature is assumed to be about 20°C, and the actual gas temperature in the furnace and the effects of exothermic and endothermic gas reactions due to CVD are ignored. For example, cl = 125 μm, V
In the case of F=150 m/+in, a fiber at 1600° C. at the furnace entrance will be rapidly cooled to 1380° C. below 10 gloss, 1030° C. below 30 cm, and 770° C. below 50 cm.

FIG. 3 shows how the fiber is cooled. In the figure, TI is the fiber temperature, and T2 is the optimum gas atmosphere temperature for the fiber temperature. Further, the eighted portions above and below the TQ are within the temperature range in which a viable film can be produced in an optimal state; if the temperature is higher than that range, dust will be generated, and if it is too low, there will be no reaction and no film will be formed. In addition,
Here, the gas concentration and gas flow rate are assumed to be constant.

Therefore, by adjusting the temperature of the gas atmosphere in multiple rooms so that it falls within the optimal range, and by adjusting the gas concentration and flow rate so that it falls within the optimal temperature range, it is possible to A film with good film quality is formed over the period of time.

Example of implementation Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 schematically shows an optical fiber hermetic coating apparatus according to a preferred embodiment of the present invention. In addition,
Parts that are the same as those in the prior art are given the same reference numerals and redundant explanations will be omitted.

As shown in the figure, the reaction tube 3 of the reaction furnace 4 provided directly below the drawing furnace 1 is divided into three chambers 3A to 30 along the moving direction of the fiber by a shutter 9. Independent heaters 2A to 2C are provided so that the gas temperature within 3C can be independently controlled. Further, each of the rooms 3A to 3C is independently provided with a gas supply port 3a and a gas exhaust port 3b, and each gas supply port 3a and gas exhaust port 3b has the concentration and flow rate of the source gas in each room 3A. Valves 78 to 7C and flowmeters 8a to 8C are provided independently so that the flow can be adjusted every 3C. As shown in Part B, the gas atmosphere conditions in each of the rooms 3A to 3C, that is, the gas temperature, gas flow rate and concentration, can be set independently.

In addition, the diameter of the fiber passage hole of the shutter is made sufficiently small, about 4 gates φ, to balance the amount of gas supplied and exhausted into each room 3A to 3C, and to prevent the mixture of gas and the atmosphere between each room 3A to 30. This prevents contamination. Also, each room has 3
Gas temperatures in A to 3C are each measured by inserted thermocouples.

The total length of the reaction tube 3 is 32 am, and the length of each chamber 3A to 3C is 9 an, IQ, 5 am, 12
．． 5 am, and the fiber temperature range in each part J13A to J13C is set to be about 200°C. That is, if the fiber temperature at the inlet of the reaction tube is 1600°C and 100.0°C at the outlet as described above, then the temperature in the first chamber 3A is 1600 to 1400°C, and in the second chamber 3B it is 1400 to 1200°C. , the temperature in the third room 3C is 1200 to 1000°C.

Using such a hermetic coating device, the gas concentration and gas flow rate in each chamber 3A to 3C are independently adjusted, and the gas temperature in each chamber 3A to 3C is controlled.
By setting the temperature to the maximum temperature range of 2C, a hermetic coating of good film quality can be applied to all rooms 3A to 30.
It was possible to form it over a period of time.

FIG. 2 shows an eight-mesh coating apparatus according to another embodiment. As shown in the figure, in this embodiment, a shutter 9 is provided that divides the reaction tube 30 into six so that the fiber temperature is in units of 100°C to form rooms aOA to 30F. This embodiment is also similar to the above embodiment in that a gas supply port 30a and a gas exhaust port 30b are provided respectively. The lengths of each room 30A to 30F are 4.0 cm, 4.5 am, 5.0 am, 5.5
am, 6.0 am, 6.5 cm.

1. Each gas supply port 30a and gas exhaust port 30b are provided with independent valves 7a to 7C and flow meters 8a to 8C, respectively.
It is also similar to the embodiment described above that the gas concentration and flow rate in each of the rooms 30A to 30F can be adjusted independently by connecting them.

The reaction tube 30 is surrounded by a heat insulating material 20 to form a reaction furnace 40, and the gas atmosphere temperature in each chamber 30A to 30F is controlled by a heater 10 provided outside the furnace.
It can be controlled by. That is, by adjusting the temperature of the gas supplied to each room individually using the heater 10, the gas atmosphere temperature in each room 30A to 30F is maintained at an appropriate level.

<Effects of the Invention> As explained above, according to the optical fiber hermetic coating apparatus according to the present invention, appropriate gas 5J concave conditions can be set over the fiber moving direction forming one coating layer. It is possible to form a thick film with good film quality, and in this case, the film quality is almost uniform, so the quality of the film can be expressed as film quality x film thickness.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram conceptually showing an optical fiber hermetic coating device according to one embodiment of the present invention, FIG. 2 is an explanatory diagram conceptually showing a device according to another embodiment, and FIG.
The figure is a graph showing fiber cooling and the maximum gas atmosphere temperature, and FIG. 4 is an explanatory diagram showing a hermetic coating apparatus according to the prior art. In the drawing, 1 is a drawing furnace, 2 is a heater, 3.30 is a reaction tube, 3A to 3G, 30A to 30F are rooms, 4.40 is a reaction furnace, 5 is a fiber, 6 is a resin coating device, 7a- 7c is a valve, 88 to 8c are flow meters, 9 is a shutter, 10 is a heater, and 20 is a heat insulating material.

Claims (2)

[Claims] (1) In an optical fiber hermetic coating device that forms a hermetic coating made of metal or inorganic material using a heteronuclear chemical deposition or chemical vapor deposition reactor having a reaction tube through which the fiber spun in a drawing furnace passes, A hermetic coating device for optical fibers, characterized in that a portion forming one coating of a reaction tube is divided into a plurality of chambers along the direction of movement of the fiber, and gas atmosphere conditions in each chamber can be independently controlled. (2) The temperature of the gas atmosphere in each room is adjusted using multiple heaters installed inside the furnace or multiple heat sources outside the furnace, and multiple valves are used to control the mixing ratio and flow rate of the gas supplied to each room. 2. The hermetic coating apparatus for optical fibers according to claim 1, wherein the gas atmosphere conditions in each room are controlled by setting the gas atmosphere conditions in each room.