JPS5953225B2 - Weather-resistant multi-component glass fiber for optical communications - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a step-type multicomponent glass fiber for optical communications, which comprises a core glass and a coated glass.

Generally, this type of glass fiber has a coating layer around the core that has a refractive index smaller than that of the core.The optical information incident on the core from one end of the fiber is transferred to the interface between the core and the coating. The idea is to use total internal reflection of the signal to confine it within the core and transmit it to the other end of the fiber.

By the way, conventional multi-component glass fibers for optical communication include Na, 020%, Ca09% and SiO2.
.

Na2 is added to the core glass consisting of 71% (both by weight)
O22%, CaO3.5% and SiO274.5% (
A type of glass coated with glass consisting of (both weight ratios) is used.

However, since this glass fiber has a high alkali content, it is easy to reduce loss, but on the other hand, the alkali component tends to be eluted to the outside, so it has a disadvantage of poor weather resistance. on the other hand,
The double crucible method is mainly adopted as a method for producing step-type multi-component glass fibers for optical communication.

In this method, molten core glass and coating glass are simultaneously allowed to naturally flow down from orifices at the ends of the inner and outer tubes arranged in a circular shape, respectively, and drawn to produce a multi-component glass fiber for optical communications. be. During this drawing process, if crystals form in a part of the glass (devitrification), this has the disadvantage of increasing optical transmission loss and decreasing tensile strength of the glass fiber, so it is essential that devitrification does not occur.
For these reasons, the inventors of the present invention have conducted extensive research to eliminate the above drawbacks, and have found that the core material is made of SiO2, alkali metal oxide, CaO, ZnO, and BaO.
And using multi-component glass with specified component values,
On the other hand, SiO is used as a coating material.

, A1. O. , alkali metal oxide, CaO, MgO,
By using a multi-component glass consisting of B2O3, ZnO, Zro3, and TiO2, and with defined values of these components, (1) the multi-component glass for coating has water resistance, acid resistance, alkali resistance, etc. It has good chemical resistance, low alkali elution, and excellent weather resistance.

(High weather resistance) 5 (
2) The multi-component glass for the core and the multi-component glass for the coating should not devitrify during the drawing process, and at the same time, the dimensional stability of the fiber should be excellent. (3) The multi-component glass for the core should have low loss.

In other words, the glass composition has low scattering loss and is easy to melt (low melting temperature 1t). This is because if the melting temperature is high, the loss increases due to the contamination of substances with high absorption loss, such as iron and copper, from the crucible used and the atmosphere, as well as the occurrence of scattering defects. (low loss)
(4) The expansion coefficient of the multi-component glass for the core is larger than the expansion coefficient of the multi-component glass for the coating, and the difference (Δα) is 3X10-6Cn1/Cml.
℃ (AtO ~ 300℃) or less. If the difference in expansion coefficients is large, the stress in the fiber will be high and reliability will decrease.
．． decreases. (5) When the refractive index of the core is n1 and the refractive index of the coating is N2, the relative refractive index difference Δn(n1-N2/n1
) has been found to be 0.002 or more, and a multi-component glass fiber with high weather resistance and low loss that has various excellent properties.

The present invention will be explained in detail below.

The multi-component glass fiber for optical communication of the present invention includes (4)
Weight ratio: 335-65% of SlO (up to 30% of this may be replaced with GeO2), 10-23% of alkali metal oxide, 2-12% of CaO, 5-20% of ZnO,
A multi-component glass for the core consisting of 5% to 5% BaO (however, the total amount of CaO.BaO.ZnO is 15% to slightly less than 2%);
B) SK) 260-80% by weight, Al, O, O.
5-10,%, alkali metal oxides 9-17%, CaO
O~5%, at least one selected from ZnOlzrO2, TiO, 0~7%, MgOO~4% and B
Coated multi-component glass fiber consisting of more than 2O3lO up to 15%.

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

(1A) SiO2 SiO2 is a glass-forming oxide whose content is
If the content is less than 35 wt%, the water resistance will be low, while if the content exceeds 65 wt%, the desired refractive index conditions cannot be satisfied, which is not preferable.

In addition, this SiO2 component lowers the melting temperature of glass,
It may be replaced with GeO2 up to 30 wt% (SiO
2 is a minimum of 5%). 2A) Alkali metal oxides Alkali metal oxides are mainly Na2O, K2O, Li
It consists of 2O and acts as a network modifying oxide.

If the alkali metal oxide content is less than 10.0 wt%, devitrification tends to occur, while if it exceeds 23 wt%, water resistance decreases.

In addition, constituent components in alkali metal oxides (Na2O, K2
The blending ratio of O, Li2O) is adjusted as appropriate depending on the required change in the physical properties of the core. Specifically, to reduce the viscosity, the ratio of K2O is lowered, to increase the expansion coefficient, the ratio of Li2O is increased, and further, to increase the refractive index, the ratio of Li2O is increased. 73A) CaO and B
aO,! -The blending ratio of CaO in the ZnO mixture is 2wt.
If it is less than 12wt%, devitrification tends to occur, and if it exceeds 12wt%, it is difficult to obtain a uniform glass.
Select approximately t%.

If the composition ratio of ZnO is less than 5 wt%, devitrification is likely to occur;
If it exceeds 0 Wt%, it tends to be difficult to obtain a uniform glass, so it is selected within the above range.

Moreover, if the composition ratio of BaO is less than 5 Wt%, it will be difficult to satisfy the desired refractive index requirement, and if it exceeds 35 Wt%, devitrification will easily occur, so the above range is selected.

However, these CaO. ZnO and BaO are components that particularly contribute to increasing the refractive index, and if the total amount is less than 15 Wt%, the desired refractive index requirement cannot be met.
If it exceeds 50 wt%, devitrification tends to occur.

A desirable range is 30-48 wt%. (4A) In addition, it is preferable to replace part of CaO with MgO and replace part of BaO with SrO because they do not change the properties and improve the meltability.

In addition, the reason for limiting each component of the multi-component glass for coating will be described.

(1B) SiO2 SiO2 forms the skeleton of the coating, and if its content is less than 60% by weight, water resistance will decrease, while if it exceeds 80% by weight, high temperature viscosity will increase and the viscosity difference with the core glass will increase. is undesirable because it increases

(2B) Al2O3 Al2O3 has the effect of improving water resistance and devitrification tendency.

This is because if the content of Al2O3 is less than 0.5% by weight, the desired effect cannot be sufficiently achieved, whereas if it exceeds 10% by weight, devitrification tends to occur. (3B) Alkali metal oxides Alkali metal oxides are mainly Na2O, K2O, Li2O
It acts as a network-modifying oxide.

When the alkali metal oxide content is less than 9% by weight, devitrification tends to occur, and when it exceeds 17% by weight, water resistance decreases and a coating that meets the desired requirements cannot be obtained. (4B) CaO CaO has the effect of improving water resistance.

If the CaO content exceeds 5% by weight, devitrification tends to occur, which is not preferable. (5B) MgO MgO contributes to improving weathering resistance.

If MgO exceeds 4% by weight, devitrification occurs, so it is preferable.
do not have. (6B) B2O3 B2O3 contributes to improving water resistance and increasing refractive index.

Therefore, the composition ratio of this B2O3 component exceeds 10 and 15
If the amount is selected within a range of 15% by weight, the refractive index of the coated glass becomes too high and the desired refractive index difference cannot be obtained, which is not preferable. Moreover, if it is less than 10% by weight, the high temperature viscosity cannot be sufficiently lowered, and there is a tendency that it is difficult to form a fiber. (7B) ZnO. ZrO2, TiO2 Addition of these components is effective in improving water resistance.

However, the lever component may be one type or a mixture of two or more types, but the composition ratio thereof should always be selected to be within 7 wt%, and addition of 7% or more will cause striae. Next, examples of the present invention will be described.

As shown in the table below, three types of multi-component glass for optical communication were obtained by drawing multi-component glasses for cores and multi-component glasses for coating, each having different composition ratios, at a temperature of 800 to 1000°C using the double crucible method. glass fiber (core diameter 80μ, coating diameter 1
50μ) was obtained.

Thus, the refractive index (n) and thermal expansion coefficient (α
), water resistance, weathering resistance, temperatures at 104, 105, and 106 poise, and devitrification tendency were investigated.

The results are also listed in the same table. In addition, water resistance, weathering resistance,
The devitrification tendency was determined by the following test.

(1) Water resistance: 0.5 mm opening (7) 5.0 g of a powder sample that passes a JIS standard sieve but does not pass the same standard sieve with a 0.3 mm opening is immersed in 100 ml of distilled water and placed in a boiling bath. After heating for 1 hour, the solution is titrated with a 0.01N-HCl solution, and the titrated amount (ml) is used to determine the superiority or inferiority of water resistance.

(2) Weathering resistance: Haze that forms on the glass surface
), and choose one with less haze than SK-16, and one with the same level of haze as ASK-16.
B
I evaluate it as.

(3) Tendency to devitrify; heating at 800°C for 15 hours and 11
No crystals precipitate when heated at 00℃ for 15 hours.
A that precipitates crystals on the surface.
b Those that precipitate crystals on the surface and inside
Rated C.

Thus, the multi-component glass fiber according to the present invention had a transmission loss of 20 dB/m or less when measured at a wavelength of 850 mμ, and was a low-loss fiber.

Claims (1)

[Claims] 1 (A) Weight ratio of SiO_235 to 65% (within 30% may be replaced with GeO_2), alkali metal oxide 10 to 23%, CaO2 to 12%, ZnO
5-20%, BaO5-35% (however, CaO, BaO
, (total amount of ZnO 15 to 50%), and (B) SiO_260 to 80% by weight,
Al_2O_30.5-10%, alkali metal oxide 9
~17%, CaO0~5%, ZnO, ZrO_2, Ti
At least one species selected from O_2 0-7%, M
A highly weather resistant multi-component glass fiber for optical communications formed from 0 to 4% gO and a multi-component coating glass comprising more than 15% B_2O_310.