JPS5915100B2 - Glass fiber for optical communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a step-type glass fiber for optical communication comprising a core glass and a coated glass.

Generally, this type of glass fiber for optical communication has a core provided with a coating 15 having a slightly smaller refractive index than the core, and optical information incident into the core from one end of the glass fiber is transmitted to the core. The idea is to transmit it to the other end while causing total reflection at the interface with the coating. By the way, various glasses have been studied as core materials and coating materials for this type of glass fiber.

For example, in the laboratory, (1) multi-component glass consisting of SiO2, Na2O and CaO, (2) SiO2
, a multicomponent glass consisting of Na2O and B2O3, (
3) Multi-component glass consisting of SiO2, Na2O and PbO, (4) SiO2, Na2O and TiO
A multi-component glass consisting of two components is used as a core glass or a covering glass by appropriately changing the composition ratio of each multi-component glass. However, the 30-core glass and coated glass made of the multi-component glass described in (1) to (4) above have the following drawbacks. That is, since the core glass and the covering glass made of the multi-component glass described in (1) above have poor water resistance, the atmosphere in which the glass fibers formed from these can be used is restricted. Furthermore, since the core 35 glass and the covering glass made of the multi-component glass described in (2) have high evaporation during the melting process, glass fibers with low scattering loss cannot be obtained. Furthermore, a core glass made of the multi-component glass of (3) above. Since the coated glass contains PbO, glass fibers with low scattering loss cannot be obtained.

Furthermore, since the core glass and the covering glass made of the multi-component glass described in (4) above absorb light due to the inclusion of Ti3+, a glass fiber with low light absorption loss cannot be obtained. On the other hand, the double crucible method is mainly adopted as a method for producing step-type glass fibers for optical communication.

In this method, molten core glass and coating glass are allowed to flow down simultaneously from orifices at the ends of the inner tube and the outer tube arranged concentrically, respectively, and drawn to produce glass fibers for optical communications. However, this method benefits from working temperature,
In other words, it is necessary to raise the melting temperature of the core glass and the coating glass to keep the viscosity low (usually the viscosity is 10 6 to 10 3 poise), and to facilitate the natural flow of each glass from the orifice. However, when manufacturing optical communication glass fiber using the double crucible method using various multi-component glasses as conventional core materials and coating materials, the drawing operation temperature is When the temperature is increased, the glass liquidus temperature (glass crystallization temperature) specific to the multicomponent glass is low and becomes close to the drawing temperature. For this reason, during the drawing operation, crystals tend to form in a part of the glass, and this crystallization has the disadvantage of increasing optical transmission loss and decreasing tensile strength of the glass fiber obtained.
In view of this, the inventors of the present invention have conducted extensive research to eliminate the above drawbacks, and have found that SiO2, Ae and SiO2 can be used as core materials.
2O3, alkali metal oxides, CaO, SrO and BaO
A multi-component glass consisting of a composite of components with limited values of these components is used, while SiO is used as a coating material.
2. By using a multi-component glass consisting of Ae2O3, alkali metal oxides and CaO, and with limited values of these components, 1. Good chemical resistance such as water resistance, acid resistance and alkali resistance. The liquidus temperature of the two glasses is sufficiently higher than the wire drawing temperature, devitrification does not occur during the drawing operation, and the difference in expansion coefficient (Δα) between the three-core multi-component glass and the coating multi-component glass is small. , and the viscosity properties of both multi-component glasses are similar at the drawing temperature (600 to 1000°C), so the fiber drawn by the crucible method has excellent dimensional stability, and the refractive index of the four cores is 1.5300-1.57001 The refractive index of the coating is 1.4
We have found a glass fiber for optical communications that has various excellent properties, such as having a molecular weight within the range of 800 to 1.5250.

Furthermore, it has been discovered that by adding a predetermined amount of MgO to each of the above-mentioned multi-component glass compositions, it is possible to obtain glass fibers for optical communications that have not only the above-mentioned various excellent properties but also excellent weathering resistance. Ta. The present invention will be explained in detail below. The glass fiber for optical communication of the present invention has (4) weight ratio of SlO255 to 65 (Ff), Ae
2O3l~5%, alkali metal oxide 14~21%, C
A multi-component glass for the core consisting of ~7% aOl and 11~20% of a total amount containing both SrO and BaO, and (B) a weight ratio of SlO27O~76, Al2O3l~50
! ), alkali metal oxides mainly composed of Na2O 17~
23% and a coating multicomponent glass consisting of ~5(?l) CaOl.

Next, the reason for limiting the values of each component of the multi-component glass for the core will be described.

1A) SlO2 SiO2 is essential for providing transparency to the core. If the content of SiO2 is less than 55% by weight, the acid resistance will decrease, while if the content exceeds 65% by weight, the refractive index will decrease. This is because it becomes too low, and the preferable range is 56 to 6.
It is 3% by weight.

2A) Ae2O3 A'203 has the effect of improving the water resistance of the core.

If the content of Al2O3 is less than 1% by weight, no improvement in water resistance can be expected, while if the content exceeds 5% by weight, devitrification tends to occur, and the preferable range is 1 to 4% by weight. It is. 3A) Alkali metal oxide This alkali metal oxide contains 8 to 30% by weight of Li2O, with the balance consisting of Na2O and K2O, and has the effect of improving workability.

If the content of the alkali metal oxide is less than 14% by weight, high-temperature viscosity will be strong and wire drawing will be difficult, while if the content exceeds 21% by weight, the water resistance will decrease, and preferably 15% by weight. -20% by weight. 4A)
CaO CaO has the effect of improving water resistance and increasing refractive index.

If the content of CaO is less than 1% by weight, the desired effect cannot be sufficiently achieved, while if the content exceeds 7% by weight, devitrification tends to occur, and preferably 2 to 5% by weight. range. 5A) Combined product containing both SrO and BaO This combined product contains 5 to 85% by weight of SrO and 95 to 15% by weight of BaO.
If the content of the combined substance, which has the effect of increasing the refractive index and preventing devitrification, is less than 11% by weight, the desired effect cannot be sufficiently achieved;
This is because if the amount exceeds 1 part by weight, striae are likely to occur in the core, and the preferred range is 12 to 18% by weight.

Note that if the blending ratio of one SrO in the composite is less than 5% by weight, devitrification tends to occur, and if the ratio exceeds 85% by weight, striae tend to occur. In addition, the reason for limiting the values of each component of the multi-component glass for coating will be described.
1B) SlO2 SlO2 is essential to impart transparency to the coating.

If the content of SiO2 is less than 70% by weight, acid resistance will decrease, while if the content exceeds 76% by weight, the refractive index will become too low, preferably 72 to 76% by weight.
is within the range of 2B) A'203 Ae203 has the effect of improving the water resistance of the coating.

If the content of A'203 is less than 1% by weight, no improvement in water resistance can be expected, while if the content exceeds 5% by weight, devitrification tends to occur, and preferably 1 to 4% by weight. %
is within the range of 3B) Alkali metal oxide mainly composed of Na2O This alkali metal oxide contains 55% by weight or more of Na2O, with the balance being Ll2O and K2O, and has the effect of improving workability.

If the content of the alkali metal oxide is less than 17% by weight, the high temperature viscosity will be high, making it difficult to draw the wire, while if the content exceeds 23% by weight, the water resistance will decrease. It is in the range of 22% by weight. 4B)
CaO CaO has the effect of improving water resistance and increasing refractive index.

If the content of CaO is less than 1% by weight, the desired effect cannot be sufficiently achieved, while if the content exceeds 5% by weight, devitrification tends to occur, and preferably 2 to 4.5% by weight. %
is within the range of Further, the glass fiber for optical communication of the second invention of the present application has (A) weight ratio of 55% to 65% of SlO2, M
2O3l~5%, alkali metal oxide 14~2101)
, CaOl~70t) and a composite containing both SrO and BaO, 11~200f), a multicomponent glass composition for a core, which is made by adding 5 parts by weight or less of MgO to 100 parts by weight of a multicomponent glass composition. and (B) in weight ratio, SlO
Multi-component glass composition 100 consisting of 27O~76%, A'2031~5%, an alkali metal oxide mainly composed of Na2O, 17~23(:Ff) and CaOl~5%
It is formed from a multi-component coating glass in which 4 parts by weight or less of MgO is added to each part by weight.

By using the multi-component glass for the core and the multi-component glass for the coating in which MgO is added to each multi-component glass composition as described above, the weathering resistance of the obtained glass fiber for optical communication can be significantly improved. The reason for limiting the amount of MgO added to the multi-component glass composition for the core is that if the amount of MgO added exceeds 5 parts by weight, the core tends to devitrify. The amount ranges from 1 to 4.5 parts by weight per 100 parts by weight.

In addition, Mg for the multi-component glass composition for coating
The reason for limiting the amount of O added is that if the amount of MgO added exceeds 4 parts by weight, the coating tends to devitrify, and the preferable amount added is 0.00 parts by weight per 100 parts by weight of the glass composition.
It is 5 to 3 parts by weight. In this case, the glass fiber for optical communication may be formed using either one of the multi-component glass for the core and the multi-component glass for the coating to which MgO is added. In addition, in the present invention, if necessary, B2O3 and/or ZrO2 may be added alone or in the multi-component glass composition for the core and the multi-component glass composition for the coating.
It may be added in combination with gO 〇゛ In this way, by using the multi-component glass for the core and the multi-component glass for the coating in which B2O3 is added to each multi-component glass composition,
The tendency of the obtained optical communication glass fiber to devitrify can be significantly improved.

The amount of B2O3 added is 100% of each multicomponent glass composition.
It is added in an amount of 10 parts by weight or less, preferably 2 to 8 parts by weight. The reason for this is that if the amount of B2O3 added exceeds 10 parts by weight, the high-temperature viscosity decreases too much, which interferes with the wire drawing operation. In addition, Zr was added to each multicomponent glass composition.
By using O2-added multi-component glass for the core and multi-component glass for the coating, it is possible to improve the devitrification tendency, increase the refractive index, and improve the chemical resistance of the obtained glass fiber for optical communication. It can be measured.

The amount of ZrO2 added is 10 parts by weight or less, preferably 2 to 8 parts by weight, per 100 parts by weight of the multicomponent glass composition for the core. The reason for this is that if the amount of ZrO2 added exceeds 10 parts by weight, striae will occur in the core of the glass fiber and the scattering loss will increase. On the other hand, the amount of ZrO2 added to the multicomponent glass composition for coating is not more than 4 parts by weight, preferably in the range of 1 to 3 parts by weight, based on 100 parts by weight of the composition. The reason for this is that if the amount of ZrO2 added exceeds 4 parts by weight, the refractive index increases and the desired effect cannot be achieved. Next, examples of the present invention will be described. Examples 1 to 4 Four types of core multi-component glass and coating multi-component glass having different composition ratios as shown in Tables 1 and 2 below were heated at a temperature of 790°C by a double crucible method. Four types of optical communication glass fibers are drawn (core diameter 80μ, outer diameter 150μ).
μ) was obtained.

Therefore, the refractive index (n), thermal expansion coefficient ((4), softening temperature (Ts), water resistance, acid resistance, alkali resistance, 1.03,
Temperature of 104, 105, 106 poise, devitrification tendency,
In addition, the transmission loss (DB/-) of these glass fibers was investigated.

The results are also listed in Tables 1 and 2. Note that water resistance, acid resistance, and alkali resistance were determined by the following tests.

1) Water resistance; opening 0.5? Passes the JIS standard sieve of
A powder sample of 5.0y that did not pass a 0.3W10 JIS standard sieve was immersed in 100ml of distilled water, heated in a boiling water bath for 1 hour, and the solution was titrated with a 0.01N-HCe aqueous solution. The water resistance is determined by the amount required (MI7).

2) Acid resistance; 20.2401)
Add a powder sample of 0 to 30 meshes and calculate the weight loss rate (maximum) when heated for 1 hour 〇3) Alkali resistance; 2N-
20 to 30 meshes of powder sample are added to the NaOH aqueous solution and the weight loss rate (7) when heated for 1 hour is determined.

Examples 5 to 7 As shown in Tables 3 and 4 below, four types of multi-component glasses for cores and multi-component glasses for coating were prepared by adding MgO to multi-component glass compositions by double retouching method. 790℃
Three types of optical communication glass fibers (core diameter 80μ, outer diameter 150μ) were obtained by drawing at a temperature of .

Therefore, the refractive index (n), thermal expansion coefficient ((d), softening temperature (Ts), water resistance, acid resistance, alkali resistance, weathering resistance, The temperature becomes 103, 104, 105, 106 poise,
The tendency of devitrification and the transmission loss (DB/
1 cm) was investigated.

The results are also listed in Tables 3 and 4. Example
9 As shown in Table 5 below, a multi-component glass for a core prepared by adding MgO to a multi-component glass composition and a multi-component glass for a coating with no MgO added were heated at a temperature of 790°C by a double crucible method. Drawn glass fiber for optical communication (core diameter 80μ,
An outer diameter of 150μ) was obtained.

The physical properties of the core and coating of the obtained optical communication glass fiber and the transmission loss (DB/-
) was investigated.

The results are also listed in Table 5. As detailed above, the present invention has good chemical resistance such as water resistance, acid resistance, alkali resistance, etc., excellent dimensional stability, does not cause devitrification during wire drawing, and has other properties such as core and coating. Therefore, it is possible to provide a glass fiber for optical communication which has an optimal difference in refractive index and has significantly improved performance and service life.

Claims (1)

[Claims] 1 (A) By weight ratio, SiO_255 to 65%, Al
_2O_31-5%, alkali metal oxide 14-21%
(B
) In terms of weight ratio, there are ▲mathematical formulas, chemical formulas, tables, etc.▼O_
270-76%, Al_2O_31-5%, Na_2O
17-23% of alkali metal oxides mainly consisting of
A multi-component glass for coating consisting of 1 to 5% aO, and a glass fiber for optical communication. 2 (A) Weight ratio: SiO_255-65%, Al
_2O_31-5%, alkali metal oxide 14-21%
, a multicomponent glass composition 100 consisting of 1 to 7% of CaO and 11 to 20% of a total amount containing both CrO and BaO
A multi-component glass for the core made by adding 5 parts by weight or less of MgO to the parts by weight, and (B) a weight ratio of SiO_270 to 7.
6%, Al_2O_31-5%, alkali metal oxides mainly composed of Na_2O 17-23% and CaO1-5
Mg
A multi-component coating glass to which 4 parts by weight or less of O is added; and a glass fiber for optical communication.