JPS60107552A - Analysis for composition of base material for optical fiber - Google Patents

Abstract

PURPOSE:To analyze non-destructively a base material for an optical fiber with good accuracy whether said material is transparent or opaque by combining adequate ray sources to constitute a composite ray source and irradiating the radiation from said ray source to the base material. CONSTITUTION:A composite ray source 4 consists of a combination of a ray source consisting of Gd<153> and other ray source (Cs<137>, Ir<192>, Ba<133>, etc.). The radiation I from the source 4 is irradiated to a base material 1 for an optical fiber and the transmitted ray J thereof enters a detecting element 6 of a radiation detector 3 via collimators 8c, 8d. The detection signal is related with the compsn. in the material 1, i.e., concn. of Ge via an amplifier 9 and a pulse height analyzer 10 and is recorded in a recorder 11. A radiation detector 2 and a transmitted ray detector 3 are scanned as shown in the figure when viewed from the section of the base material and if the Ge distribution in the base material 1 is assumed to be the distribution shown in the figure, the Ge distribution is obtd. with good accuracy by the above-mentioned analysis.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for analyzing the composition of an optical fiber matrix by non-destructive means.

Composition analysis of optical fiber base materials is said to be useful for feedback control during manufacturing, and for research and development to obtain optical fibers with good characteristics.
As one method, a non-destructive second digit method is adopted.

Composition distribution at any location in the longitudinal direction of the optical fiber base material (
As a means of non-destructively measuring the refraction weight distribution), there are two methods: irradiating the base material with a laser beam and analyzing the scattering pattern of the emitted light; Methods for analyzing interference fringes are known, but these optical methods are only effective when the base material is transparent. In the case of a porous glass optical fiber base material, that is, an opaque base material, this cannot be measured.

On the other hand, as a non-destructive measurement method for opaque base materials, there have been attempts to irradiate the base material with monochromatic X-rays and estimate the distribution of the negative component (e.g. Ge) from the relationship with other components (e.g. 5iO2). In this method, the base material component is mainly quartz (SIO2
) and Ge, two or more types of energy components are required. For example, when the mass absorption coefficients of S i 02 and Ge for the two types of energy components do not have an appropriate relationship, high It is said that it is not possible to analyze the accuracy.

Particularly in view of the fact that current general X-ray generators can only generate energy of 100 KeV or less, energy components suitable for satisfying the above-mentioned high-precision analysis cannot be obtained.

In addition, it is known that gamma rays can be used, but there have been no specific reports regarding this in the analysis of optical fiber base materials.

The object of the present invention is to configure a composite radiation source by combining appropriate radiation sources, and to irradiate radiation from the composite radiation source to an optical fiber matrix, which can be used not only for a transparent matrix but also for
The purpose of the present invention is to provide a method that allows non-destructive and accurate analysis of even opaque base materials.

The method of the present invention consists of configuring a composite radiation source by combining a radiation source made of Cd168 with another radiation source, irradiating radiation from the composite radiation source onto an optical fiber base material, and measuring and analyzing the transmitted dose. The present invention is characterized by analyzing the composition distribution of the optical fiber base material.

Examples of the method of the present invention will be described below with reference to the drawings.

FIG. 1 shows one means for carrying out the method of the invention.

In the figure, 1 is an optical fiber base material, 2 is a radiation generator for irradiating the base material 1 with radiation such as X-rays and γ-rays, and 3 is a radiation generator for detecting the radiation transmitted through the base material 1. It is a transmitted radiation detector.

The radiation generator 2 is constructed by housing a compound radiation source 4 in a storage box 5, and the compound radiation source 4 is
7. Sources consisting of q3 and other sources (CS 187.1
r 192, B a 13a, etc.), and the storage box 5 having an irradiation opening is made of a radiation shielding material such as iron or lead.

On the other hand, the transmitted radiation detector 3 is composed of a conventional detection element 6 and a storage box 7 made of a radiation shielding material, and the detection element 6 is housed in a storage box γ having a receiving opening.

The radiation generator 2 and the transmitted radiation detector 3 are arranged to face each other, and the optical fiber preform 1 is interposed between them. ,
Collimators 8a, 8b, 8c, and 8d are arranged between the optical fiber base material 1 and the transmitted radiation detector 3, respectively. An amplifier 9 that electrically amplifies the output, and a pulse height analyzer such as a multi-channel type that selects signals from the amplifier 9 to select only those with specific energy from among each transmitted line. 1Q and the recorder 11 are sequentially connected.

The optical fiber matrix 1 to be measured in the method of the present invention is quartz-based, specifically 5in2-Ge02-based, or aluminum to which P2O3, B2O2, etc. are added.

In addition, there are various types of base materials such as porous glass (opaque) made by the VAD method and OvD method, and transparent glass made by the MCVD method. Various types of base materials 1 are to be measured, such as those consisting of a core layer, a cladding layer, and a support layer or jacket layer.

When using the method of the present invention, the composition of the optical fiber base material 1 can be analyzed in synchronization with the manufacturing process thereof, and
The composition of the base material can also be analyzed after it is produced.

Generally, SiO□ is an essential component in the silica-based optical fiber base material 1, and GeO2 is an important component that determines the refractive index characteristics.Measurement and analysis of the Ge concentration in the base material 1 reveals that the refractive index The rate characteristics become clear.

Furthermore, the above analysis results can be used for feedback control during base material manufacturing, determining the quality of the base material, and materials for base material research and development.

Therefore, in the specific example of the method of the present invention described below, the optical fiber preform 1 is based on 5IO2-GeO2 (usually 5i02
A case will be explained in which the amount of Ge is less than or equal to the lo number coefficient.

In FIG. 1, when the radiation radiation emitted from the composite radiation source 4 of the radiation generator 2 is irradiated onto the optical fiber preform 1 via the collimators 8a and 8b, the radiation ■ is emitted from the preform 1tl.
- The transmitted ray J enters the detection element 6 of the transmitted ray detector 3 via the collimators 8c and 8d.

In other words, the radiation (2) is waved according to the mass absorption coefficient of the substance and distance relative to its energy, and enters the detection element (6) as a transmission line J.

The detection element 6 that receives this transmission line J analyzes the composition, that is, the Ge concentration, in the base material 1 via the amplifier 9 and the pulse height analyzer 1o, and records this on the recorder 11.

At this time, the radiation generator 2 and the transmitted radiation detector 3 are scanned as shown in Figure 2 when viewed from the cross section of the base material, so assuming that the Ge distribution in the optical fiber base material 1 is as shown in Figure 3. According to the above analysis, the F)Ge distribution can be seen with good accuracy as shown in FIG.

When the optical fiber base material 1 has the Ge distribution as shown in FIG. 3, the intensity of the transmission line J is expressed as a ratio of the intensity of the radiation (2) to K as shown in the following table.

Next, the effectiveness of the method of the present invention will be described by generalizing the object to be measured.

The component of the measurement object is j (j = 1 to m), the amount of the component is Xj,
The i-th (1-1 to m) photon energy is E l , and the mass attenuation absorption coefficient of the J@th component with respect to that El is μl
J/pH If the intensity of the above Ei incident on the measurement object is 11, and the intensity of the above E1 waveformed and output from the measurement object is Ji, then
The following formula is determined from the principle of radiation waves.

Here, in order to simplify equation (1), h 1=in (I
i/I j ), alg-μ]J/ρ1, the following equation is obtained.

In other words, it becomes a component of the determinant of equation (2) above.

This converts the respective corresponding matrices into H and A.

Letting it be X, it can be expressed as follows.

H=AX...-(4) X is an unknown quantity, A is a known quantity, and H is a quantity obtained by measurement.

The above equation (1) or equation (4) can be solved for Xj.

However, when m=n, it can be solved as a mathematical formula using linear simultaneous equations with n elements, but the measured values in this case include so-called measurement errors, and the solution becomes unstable due to this influence.

m) If n is the measured value of hl, a stable solution can be obtained by deriving Xj using the squared method.

Here, as long as the difference including the solution of fX (j -1, . . . , n) is not necessarily -0.

Therefore, the formula +51 below can be minimized as follows.

However, A' is the transposed matrix of A.

Note that equation (6) can be uniquely solved even if m > n, indicating that the quantity of each component Xj (j-1, ..., n) can be calculated by the method of least squares. .

Now, if the number of base material components is 2 as in the example, then j=
12, A' A, A' H Haggino (71 + 81
It becomes like the expression.

According to the above equation (8), the above equation (6) becomes the following equation.

Subtracting Xl and X2 from each of these equations yields the following equation.

By the way, regarding equation (7) mentioned above, there is no solution if the absorption coefficients of component L1 and component t2 are in a proportional relationship as shown in Figure 4, and even if they are close to proportionality, the solution will be unstable. I understand.

That is, if K is a constant, then the circle (lH31, υ, there is no solution.

(μ/ρ)t2=K(μ/ρ)1+...En ai2
=ni*ai1@@I+@@Q31A'AI=ni2(
Σai, 2)2 K2(Σail?)2=0*
(131) As is clear from the above explanation, there must be an appropriate relationship between the photon energy and the mass absorption coefficient of the component of the substance to be measured.

Like the optical fiber base material mentioned above, the components are 8102 and G.
When e, the mass absorption coefficients of these components with respect to photon energy are examined in detail as shown in FIG.

As is clear from Fig. 5, the absorption characteristics change greatly after the above energy of 100 KeV,
In the range smaller than V, (μ/ρ) Ge/(μ/ρ
) St is about 8 to 11, and the mass absorption coefficients of both can be considered to be in a roughly proportional relationship.

In other words, it is not appropriate to use an energy within this range because the solution will become unstable, and the energy 10 described in the conventional example is not suitable.
This applies to X-rays below 0 KeV.

In Figure 5, the ratio of the mass absorption coefficients of each component at 2.00 KeV or higher, for example (μ/ρ)Ge/(μ/
ρ)81 is smaller than 24, so 100Ke
It can be seen that the range is significantly different from V2 or less, and there is no proportional relationship between the range of 100 KeV or less and the range of 200 KeV or more.

When the components are SiO□ and Ge as in the optical fiber base material 1, the two types of radiation energies are one of approximately 100 KeV or less and the other of approximately 200 KeV.
Must be within the above range.

Among the other radiation sources used in the present invention, B a 1
As is clear from FIGS. 6 and 7, 3B and i r 192 have energy components in both of the above ranges,
For Ba138, it is 31.0KeV' and 80.8KeV.

356, OK e V, ■r x9x, is 6
6.8 KeV, 316.5 KeV, 467.9 Ke
V is at a superior level.

Each of these energies shown in Figure 5 is 100K.
It is distributed around eV, B a 188, I r
It is confirmed that +Q2 is an effective radiation source for analyzing the optical fiber matrix 1 containing 5i02, Ge, etc. as components.

On the other hand, the radiation source Gd 138 specified in the present invention and another radiation source C813ff are shown in FIG.
It has a principal energy component only on one side of eV,
Q d16B is around 100KeV, C5187 is 662
Each has a main energy component in KeV, but as mentioned above, if G d1fi3 is a specific radiation source, C81
8VXB a1'+ , (rIJ2, etc. are used as other radiation sources, and a composite radiation source 4 consisting of a combination of these radiation sources)
In this case, it can be said that it is effective for the analysis of the self-evident threaded optical fiber preform 1.

As explained above, when using the method of the present invention, not only transparent optical fiber base materials but also opaque optical fiber base materials such as those made of porous glass can be accurately measured and analyzed. It will greatly contribute to such areas as feed bank control, determination of the quality of base materials, and materials for base material research and development.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing one embodiment of the method of the present invention, Fig. 2 is an explanatory diagram showing the situation of radiation investigation in the same as above. Explanatory diagram,
Figures 4 and 5 are explanatory diagrams showing the relationship between photon energy and mass absorption coefficient, and Figures 6 and 7 are B als
s, ■r192 is an explanatory diagram of the photon energy spectrum of r192. 1, ... Optical fiber base material 4 ... Composite radiation source 6 ... Detection element ■ ... Radiation J ... Transmission line 117 Flash lf+ - Temporary number Figure 3. Fig. 4 bm Light amount principal energy (Ke71 Fig. 5 Photon energy [Ke7] 1J7 Fig. 1) Procedural amendment 1 Indication of the case Patent application 1982-2147452 Title of the invention Optical fiber matrix Compositional analysis method 3 Relationship with the case of the person making the amendment Patent applicant Furukawa Electric Co., Ltd. 4 Represented by Mr. Kotari Building, 1-8-8 Yurakucho, Chiyoda-ku, Tokyo 1982
February 28th 6 Full text of the specification to be amended 7 Details of the amendment Typewritten specification as shown in the attached sheet (no change in content)
I will capture it.

Claims (1)

[Claims] (A composite radiation source is constructed by combining a radiation source consisting of 1,Q d15f with another radiation source, and radiation from the composite radiation source is irradiated onto an optical fiber base material, and its transmission is A method for analyzing the composition of an optical fiber base material, which analyzes the composition distribution of the optical fiber base material by measuring and analyzing the radiation dose. (2) Other radiation sources are CS, 18B, A192, B a
+sa. The method for analyzing the composition of an optical fiber base material according to claim 1.