JPS6241737A - Production of optical fiber preform - Google Patents

Abstract

PURPOSE:To produce an optical fiber preform having desired refractive index distribution, stably, by radiating white X-ray to the core part and the circumferential part of a growing optical fiber preform under rotation, separating the transmitted ray into plural monochromatic X-rays, and controlling the preform- producing system according to the result of the spectrometry. CONSTITUTION:The white X-ray radiated from the X-ray source 5 is separated into X1 and X2 with the collimator 6 and radiated to the core part and the circumferential part of the growing optical fiber preform 4 under rotation. The white X-rays X1 and X2 transmitted through the core part and the circumferential part of the optical fiber preform 4 are passed through the collimators 9, 10, separated into monochromatic X-rays having specific energy levels E1, E2 by single crystals 11, 12, 13 and 14 and introduced into each X-ray detection system 7, 8. The energy E1, E2 of the incident X-rays are measured by the detection systems and the signal is inputted to a computer 15. The computer 15 analyzes the composition of the growing preform based on the inputted signal and controls the preform-production system to the optimum state according to the result of analysis. An optical fiber preform 4 having desired refractive index can be produced stably by this process.

Description

[Detailed description of the invention] r Industrial application field 1 The present invention relates to a method of manufacturing optical fiber material.

``Prior art 1 When non-destructively measuring the composition concentration, composition distribution, etc. of an opaque object by irradiating it with radiation, γ-rays such as isotopes (Ga, Ir, Co), or X-rays are used as the radiation source.
The object to be measured is irradiated with radiation emitted from a radiation irradiation system, and the intensity of the transmitted radiation is measured and analyzed by a detection system.These technologies are also being applied in the field of manufacturing optical fiber AT materials. It is being considered to do so.

By the way, in the case of non-destructive measurement methods using isotopes, it is said that it is difficult to industrialize the isotopes because it is difficult to obtain them manually, their strength is weak or strong, and their half-life is short. Methods using X-rays are popular.

There are two types of X-rays: white X-rays and monochromatic X-rays. For example, when the object to be measured consists of two elements, white X-rays or monochromatic A beam is irradiated onto the object to be measured, and the intensity of the transmitted beam at a specific wavelength or energy on the duplex is determined by the detection system, and then calculated using calculation methods such as the multilayer splitting method and the Aber transformation method based on the measurement data. , the composition distribution of the object to be measured is determined.

At this time, the energy of the xy;

"Problems to be Solved by the Invention" In the optical fiber preform (porous preform) being manufactured using a desired 11 material manufacturing system, for example, the VAD method, the set Ik, concentration, composition distribution, etc. of the It material. When measuring with two consecutive non-destructive measurement stages and controlling the above base material manufacturing system online based on the measurement results, the seven non-destructive measurement stages are scanned along the optical fiber base material, or the non-destructive measurement stage is One of two methods is used: holding the 7 stages of destructive measurement in place and scanning the 1"J material manufacturing system, but in the former case, the X-ray source becomes unstable and the alignment of the measurement optical system becomes difficult. In the latter case, the stability of the base material manufacturing system is hindered.

Incidentally, the invention of JP-A-58-18033!3, which scans the X-ray source side with respect to the optical fiber AT material, can be said to be an unrealistic method due to the former reason.

In view of the problems described in I-, the present invention is based on the following: [1] Material manufacturing system, non-destructive measurement R The M1 concentration, composition 71, etc. of the optical fiber base material can be measured without scanning the step cap, and the measurement results are Based on l
The purpose of this invention is to provide a method for producing 4H material.

F step 1 to solve the problem f When manufacturing an optical fiber preform through a preform production system, the present invention provides an X-ray irradiation system and an X-ray detection system that sandwich the optical fiber preform. is placed, and the optical fiber preform in a rotating state during manufacture is irradiated with white X-rays from the X-ray irradiation system toward its center and outer periphery through the tanzai manufacturing system. After the transmitted rays transmitted through the predetermined portion -F of the optical fiber base material are separated into two or more types of medium colors xvj, these medium color X-rays are detected by the X-ray detection system described in 1-1. The present invention is characterized in that the base material manufacturing system is controlled based on the detection results.

Effect 1 In the method of the present invention, for example, when manufacturing an optical fiber fij material (porous base material) through a base material manufacturing system using the VAD method, one glass raw material (SiC
14), 1-B raw material gas (e.g. GeC:Ia),
Oxygen (02), hydrogen (H2), inert gas (Ar), etc. are supplied to keep the /Hena in a combustion state, and the glass particles generated thereby are pulled up into a target /1. A rod-shaped optical fiber Rj material is produced by depositing and growing the material at the end of the fiber.

When manufacturing the optical fiber base material (porous base material) in this way, white X-rays are irradiated from the X-ray irradiation system to the center and outer periphery of the optical fiber base material, and the transmitted rays transmitted through the center and outer periphery. is divided into two or more types of monochromatic X-rays, and each of the ? The energy intensity of U color X-rays is measured by an X-ray detection system.

In this case, a medium crystal is used for spectroscopy, and this crystal spectrally spectra specifies a specific energy according to the incident angle of the transmitted light according to the following formula.

n@he/E=2d 5jnO where n-1, h blank constant, C: speed of light, E: energy, d: lattice constant, 0: angle of incidence.

Therefore, by measuring the energy intensity of each monochromatic X-ray using the detection system 1-, the distribution situation of Ge07 in the ``[9 terms, for example, SiO;

Note that the optical fiber base material is irradiated with X-rays only at the center of the ITL material and the outer periphery of the base material, but since the optical fiber 11 material is in a rotating state at this time, the X-rays irradiated onto the center of the base material Regarding the X-rays, it is equivalent to when X-rays are irradiated from the entire circumference to the center of the optical fiber, and the XLA irradiated to the outer circumference of the C7 material is also irradiated to the entire outer circumference of the base material. Become.

1- As mentioned above, the optical fiber Hi material is manufactured, and its composition is measured by the non-destructive measurement F-stage. Distance between manufacturing burner and base material, combustion residue -41-1
Optical fiber LjI material that controls raw material gas supply amount, etc. and satisfies manufacturing targets! Build A.

Embodiment j An embodiment of the tree civilization method will be described below with reference to the drawings.

In the uninvented method shown in FIGS. 1 and 2, the known VAD
As a system for producing the muI material in which the method is to be carried out, a burner 2 having a multi-tube structure connected to a gas supply system 1, a target lift 3, etc. are set in a reaction vessel (not shown).

When producing the rod-shaped optical fiber preform (porous preform) 4 through the above preform production system, as is well known, the burner 2 is
Cla, GeCl4.07. The burner 2 is maintained in a combustion state by supplying H2, Ar, etc., and the glass particles thus generated are deposited and grown on the lower end of the target 3, which is pulled in the rotating state.

Note: The X-ray irradiation system 5 for irradiating white X-rays onto the optical fiber base material 4 during manufacturing is equipped with a white X-ray source. It is arranged on the left side of the optical fiber preform 4 with a collimator 6 interposed therebetween.

The white X-rays emitted from this X-ray irradiation system 5 are separated into Xl and X2 by a collimator 6, and Xl is irradiated to the center of the optical fiber base material 4, and x2 is irradiated to the outer peripheral part of the optical fiber base material 4. Ru.

The above white X-ray X1. The X-ray detection system 7.8 that detects the transmitted radiation of X2 is composed of a scintillation tube, etc., and is placed on the right side of the optical fiber base material 4. Between.

A collimator 9.10 and a single crystal 11.12.13.14 are interposed.

In the above, the transmitted rays transmitted through the center and outer periphery of the optical fiber preform 4 pass through collimators 9 and 10, respectively, and
n crystal ll, 12.13.14wosuke1. Te specific energy E1. After being separated into monochromatic X-rays of E2, each X-ray detection system 7
．． 8.

The X-ray detection system 7.8 into which the medium-color X-rays are thus incident measures the intensities of energies E1 and E2 7, and the measurement signals are input to the electronic computer 15.

The electronic computer 15 analyzes the composition of the material being manufactured based on the above-mentioned determination signal, and appropriately controls the L;I material manufacturing system based on the analysis result.

FIG. 3 shows the refractive index distribution of a single mode optical fiber preform being manufactured by the method of the present invention.

Of course, the method of the present invention is also effective in manufacturing an optical fiber preform having a Gl-type refraction (one distribution).

In addition, in the above-mentioned example, composition analysis was explained when manufacturing an optical fiber base material by the VAD method.1 For example, when manufacturing an optical fiber R1 material by the known MCVD method, the composition analysis is performed in the same manner as above. , the base material manufacturing system can be controlled.

Effect of N'9 Light J As explained below, when using the method of the present invention, the base material!
The composition C degree, composition 1rj, etc. of the optical fiber base material can be measured without scanning the A system, non-destructive measurement device, etc., and the base material manufacturing system can be controlled based on the measurement results, so the desired refractive index can be determined. It is possible to stably manufacture a distributed optical fiber preform.

[Brief explanation of drawings]

FIG. 1 is a front view schematically showing an embodiment of the method of the present invention [4,:
Figure B2 is a fim diagram of the same as above, and Figure 3 is a refractive index distribution diagram of the SN type optical fiber preform. III...B, S2...Meeting...Gas supply system 3...0, Target 4...Optical fiber 11 material 5...X Line irradiation system 811111111$l111 Collimator 7.8...
...X-ray detection system 9.10--Collimator 11-14--Dispute e Single crystal 15...-Electronic computer E1-E2φ...-Energy of monochromatic X-rays X1-X hmm·
・φ・・White X-ray

Claims (1)

[Claims] When manufacturing an optical fiber base material through the base material manufacturing system, an X-ray irradiation system and an X-ray detection system are arranged to sandwich the optical fiber base material, and the optical fiber base material is manufactured through the base material manufacturing system. The optical fiber base material in a rotating state is irradiated with white X-rays from the X-ray irradiation system toward its center and outer periphery, and the transmitted light transmitted through the predetermined portion of the optical fiber base material is For an optical fiber, the method comprises: separating a ray into two or more types of monochromatic X-rays, detecting these monochromatic X-rays with the X-ray detection system, and controlling the base material manufacturing system based on the detection results. Method for manufacturing porous base material.