JPS5935035A - Preparation of rediation resistant optical fiber - Google Patents

Abstract

PURPOSE:To obtain an optical fiber, having improved radiation resistance characteristics, and suitable for use in environment of radiation, by heating a soot containing OH groups added to a core part in an atmosphere of oxygen, and spinning the resultant vitrified soot. CONSTITUTION:Oxygen gas is made to flow in a furnace core tube 2 in an electric furnace 1 provided around the core tube 2. A soot 3 having OH groups added to a core part is introduced into the furnace core tube 2 while rotated and vitrified under heating. Thus, the silicon atoms unlinked to oxygen are linked to the diffused oxygen as shown in the formula, and the diffusion path is formed due to the high self-diffusion coefficient of the OH groups added to the soot 3. Thus, the apparent self-diffusion coefficient of the oxygen passing through the path is increased to cause the reaction in the whole soot 3, eliminate the structural defects and improve the radiation resistance. The resultant vitrified preform is then drawn to give the aimed titled optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a radiation-resistant optical fiber used in a radiation environment F.

To improve the radiation resistance properties of optical fibers, O is added to the core.
It has already been proposed to add a II group or to optimize the spinning conditions.

However, by adding 0.1 groups or optimizing the spinning conditions, 1
111 The improvement of the radiation properties was insufficient. In view of the above problems, the present invention aims to improve the radiation resistance properties by vitrifying the OT (group-doped soot) in an oxygen atmosphere. This will be explained with reference to the embodiments shown in the drawings. It has already been stated that adding OII groups to the core of an optical fiber improves radiation resistance.

Separately, it has been found that the radiation resistance can be improved by vitrifying nudes to which no OH groups are added in an oxygen atmosphere.However, this alone was still insufficient.

As a result of extensive research, we found that when a soot containing 0)-1 radical is vitrified in an oxygen atmosphere, the radiation resistance properties are further improved due to the synergistic effect of the two, as shown in Figure 1. Got it? Figure (a) shows the increase in loss after 1 hour has elapsed after 5 Mrad γ-ray irradiation, and Figure (1)) shows the increase in 5 Mrad gamma rays.
In both figures (a) and (b), the vertical IQb indicates the transmission loss α (dB/Km). The * mark indicates that the optical fiber with only CHI base dosing is also OH.
1 shows a redundant fiber in which OII group-doped Su1- is vitrified in an oxygen atmosphere.

The optical fiber on the A line carries 1 ppm O12 group, and the optical fiber on the cut B line carries 10 ppm 01 group.
Contains 1 unit.

Here, regarding the specific manufacturing method of such optical fiber, 4
To explain with reference to the apparatus shown in Fig. 42, 02 gas is passed through a core tube (2) with an electric furnace (1) arranged on the outer periphery, and soot (3) with 011 groups added to the core.
is charged into the core tube (2) while rotating.

The charged soot (3) is heated and vitrified, but during vitrification, the unbonded oxygen atoms of silicon and the diffused oxygen bond as shown in the following reaction formula (shown below), resulting in structural defects. disappears.

The fewer structural defects there are, the better the radiation resistance characteristics will be.

However, if the 02 gas is simply allowed to flow, the self-diffusion coefficient of oxygen is small, so the above reaction occurs only in a portion of the soot (3).

However, when an OH group is added to soot (3), OH
Since the self-diffusion coefficient of the group is large, a diffusion path is created, and the apparent self-diffusion coefficient of oxygen passing through this path becomes large.

Therefore, the above reaction occurs throughout the soot, and the effect of oxygen becomes significant.

Therefore, the effect of culm oxygen with a high concentration of O12 groups is large, but if the concentration exceeds ]OOOOppm, the strength of the optical fiber will deteriorate slightly, so 10000 ppln
is the upper limit.

Note that similar effects can also be obtained by producing soot using oxygen plasma.

At this time, doping with OH groups is also performed at the same time.

Similarly, Noriform is also produced using oxygen plasma and ζ is also good.

By drawing the vitrified preform in this manner, a radiation-resistant optical fiber can be obtained.

As described above, the odorstone of the present invention is produced by vitrifying the soot to which diOH groups have been added in the core portion by heating it in an oxygen atmosphere and then spinning it, thereby significantly improving the radiation resistance properties of the optical fiber. It's my turn.

[Brief explanation of drawings]

ff11 Figures (a) and (b) are graphs showing a comparison of radiation characteristics between the conventional example and the optical fiber obtained by the present invention,
FIG. 2 is a schematic illustration of the method according to the invention. (Patent attorney Makoto Tsukifuji, 3-rate suite patent applicant representative)

Claims (1)

[Claims] (1) A method for producing a radiation-resistant optical fiber, which comprises vitrifying soot in which the 014 group is added to the core portion by heating in an oxygen atmosphere, and then spinning the vitrified soot. F2+ 011 group is contained in 1 to 10,000 ppm +1 of Claim W1 Claim 1
1. Method for manufacturing radiation optical fiber.