JPH02208234A - Production of optical fiber preform - Google Patents

Abstract

PURPOSE:To obtain high-strength fiber without reducing transmission loss characteristics by previously synthesizing a transparent glass rod as a starting material into a specific size and depositing fine particles of SiO2 glass containing Zr or Ti on the periphery of rod. CONSTITUTION:A transparent glass rod 10 having formed 80-120mum diameter thereof by pervious synthesis in the case of making optical fiber is prepared and is used as a starting material. Fine particles 20 of SiO2 glass containing Zr or Ti are piled on the periphery of the glass rod 10 to give a rod having a porous glass layer. Then the porous glass layer is made into transparent glass.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to an SiO□ film containing Zr or Ti in the outermost layer.
This invention relates to a method for manufacturing an optical fiber preform having a glass layer, and provides an optical fiber that is excellent in weather resistance and long-term reliability.

(Prior Art) As a method for manufacturing an optical fiber preform having an SiO□ glass layer containing Zr or Ti as the outermost layer, the following method is conventionally known. Figure 1 shows an example.
By using one core burner 1 and two side burners 2.3, a core clad type porous glass body having glass containing Zr or Ti in the outermost layer is formed, and this is made into transparent glass. be. Another method is to directly obtain glass containing Zr or T1 around a core-clad transparent glass rod by vitrification.

(Problem to be Solved by the Invention) However, in the former method, all the glass layers are obtained from glass particles, so there is a risk that Zr and Ti may be mixed into the core glass and cause an increase in optical fiber loss. was there. Furthermore, if a defect such as a refractive index distribution occurs in the core portion, the glass portion using expensive Zr and Ti must also be discarded at the same time, which may not be worth the cost.

In addition, since the latter method is a method of directly vitrifying the glass part using Zr or Ti, the deposition speed is extremely slow, which hinders cost reduction, or bubbles are likely to occur after transparent vitrification. There were problems such as a decrease in strength.

(Means for Solving the Problems) This invention eliminates the above-mentioned drawbacks, and is characterized by the fact that when it is made into an optical fiber, its diameter is
A transparent glass rod having a thickness of up to 120 μm formed in advance by synthesis is prepared, and SiO□ glass fine particles containing Zr or Ti are deposited around this rod to form a rod having a porous glass layer. The purpose is to make the layer transparent and vitrified.

(Function) Since the transparent glass rod serving as the starting member is synthesized in advance to a diameter of 80 to 120 μm when it is made into an optical fiber, the surface compressive stress in the case of a diameter of 80 μm or less is dispersed over a wide area. Problems such as reduction in compression per unit area, difficulty in controlling external magnification when the diameter is 120 μm or more, and the problem that the reinforcing layer is thin and scratches can reach the central glass rod beyond that layer. Not only can it be prevented, but also a layer of glass fine particles containing Zr or Ti is deposited on the transparent glass rod.
Not only can the manufacturing speed be increased, but since no Zr or Ti is mixed into the optical fiber, an increase in loss in the resulting optical fiber can be prevented.

(Example 1) A transparent glass rod with a core/clad diameter ratio of about 11 times, a diameter of 50 mm, a length of 300 mm, and Δ=0.3% was prepared by the VAD method. At this stage, the refractive index profile of the transparent glass rods was calculated and only rods determined to be of good quality were used. This transparent glass rod 25
The starting base material 10 was prepared by stretching the material to a length of 500 mm and cutting it into a length of 500 mm. A concentric quadruple pipe burner extraction was used around the base material 10 having an angle of 2°.

Gas supply amount center of concentric quadruple tube burner 5iC14800cc/min ZrCL 200 cc/min 2nd layer H216ρ/min 3rd layer Ar 1000 cc/min 4th layer 0232I2/min Burner traverse speed 20 mm 7 minute lot rotation Speed 25 rpm Thus obtained SiO□-
A rod with a 2rO□ glass fine particle layer was heated at 1500°C.
It was housed in a He atmosphere furnace maintained at 30 mm in diameter.
It was a transparent glass rod inside. This rod was drawn into a fiber with a diameter of 125 μm, and an ultraviolet curable resin was coated on the fiber to a thickness of 400 μm. When the obtained fiber was subjected to a short length strength test and a static fatigue test, the average breaking strength of the former was 7.2 kg, and the n value of the latter was 35.
The conventional model has an average breaking strength of 6.7 kg, and the latter has an n value of 27.
However, it was excellent.

In addition, by law, 51y2Z is required for external mounting on a base material of good quality.
Since the rL glass layer is formed, the only defects are due to failures in external attachment, and if it is also due to soot cracking, the starting base material can be used again, and 10 starting base materials can be used. We were able to convert nine of them into fiber. This result is a significant improvement compared to the conventional method, which requires five. Furthermore, since the ZrO□ layer is formed after the core part is made of high-purity glass in advance, there is no diffusion of Zr into the core part, and the wavelength 1.
The loss at 55 μm was as low as 0.21 dB/km, which was comparable to that of a normal fiber.

(Example 2) For numbing, the starting base material was flame polished by flowing H2 at 100β/min and 0□ at 50°C/min. The second bar≠drawing is H2 at 16℃/min, 0□ at 32! /min, 400 SiC14
Cc/min, flow 100cc/min of ZrCl4 to Si○z
-ZrOz glass fine particle layer 20 was formed to have a thickness of 1.5 mm. The third burner 16 has H2 at 200 A/min;
The SiO□-ZrO2 glass fine particle layer was made into transparent glass by flowing 02 at 100β/minute. 22 is a transparent glass layer.

When the thus obtained iron was made into a fiber and its breaking strength and loss were measured, the results were almost the same as in Example 1.

(Effects of the Invention) In obtaining a high-strength fiber having a glass layer containing Zr or Ti as the outermost layer as described above, the present invention provides the following advantages:
A base material made of high-purity glass was prepared in advance up to the part that affected the transmission loss characteristics of the optical fiber, and a glass layer containing Zr or Ti was formed on it.
A high-strength fiber can be obtained without reducing the transmission loss characteristics of the optical fiber. Furthermore, if the glass layer containing Zr or Ti is formed using a formation method called soot transparent vitrification, even if soot cracking occurs, the starting base material can be used again, so production efficiency can be improved.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams showing a method for manufacturing an optical fiber preform according to the present invention, and FIG. 3 is a schematic diagram showing a method for manufacturing an optical fiber preform according to a conventional method. 10; Starting base material

Claims (1)

[Claims] When used as an optical fiber, its diameter is 80 to 120μ
Prepare a transparent glass rod in which up to m is formed in advance by synthesis, deposit SiO_2 glass particles containing Zr or Ti around this rod to form a rod having a porous glass layer, and then add the porous glass layer to the rod. 1. A method for producing an optical fiber base material, which comprises converting it into transparent glass.