JPS5812215B2 - Highly 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 smaller refractive index than the core, and 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 to confine it within the core and transmit it to the other end of the fiber.

By the way, conventionally, multi-component glass fibers for optical communication, such as Na2020%, Ca09% and SiO27
Na20 is added to the core glass consisting of 1% (both by weight).
A glass coating consisting of 22% Ca, 3.5% Ca, and 274.5% Sin (all by weight) is used.

However, since this glass fiber has a high alkali content, it is easy to reduce the loss, but on the other hand, the alkali component is easily eluted to the outside, resulting in poor weather resistance.

On the other hand, the double Lunovo method is mainly adopted as a method for manufacturing step-type multi-component glass fibers for optical communications.

In this method, molten core glass and coating glass are simultaneously allowed to flow down naturally from orifices at the ends of the inner and outer tubes arranged in concentric circles, respectively, and drawn to produce a multi-component glass fiber for optical communications. It is.

In this case, it is necessary to raise the drawing temperature, that is, the spinning temperature of the core glass and coating glass, to keep the viscosity low (usually the viscosity is 106 to 103 poise), and to facilitate the natural flow of each glass from the orifice. be.

By the way, when manufacturing a multicomponent glass fiber for optical communication using the double crucible method using various multicomponent glasses as conventional core materials and coating materials, the multicomponent glass should be adjusted to have a viscosity within the above-mentioned range. When the drawing temperature is increased,
During the drawing process, crystals tend to form in some parts of the glass, and this crystallization increases the optical transmission loss and tensile strength of the glass fiber obtained. There were drawbacks that led to a decline.

In view of this, the inventors of the present invention have conducted extensive research in order to eliminate the above-mentioned drawbacks, and as a result, they have developed Si02, A as a core material.
l203, alkali metal oxide, Cab, MgO, B2
A multi-component glass consisting of 03 and zrO2 with defined component values was used, while Si was used as a coating material.
O2, Al203, alkali metal oxides CaO, MgO
By using a multi-component glass consisting of the following components: and B2031ZnOtZr02, TiO, and with defined values of these components, the multi-component glass for coating has (1) chemical resistance properties such as water resistance, acid resistance, and alkali resistance. (2) The multi-component glass for the core and the multi-component glass for the coating are
No devitrification during the drawing process, and at the same time, the fiber has excellent dimensional stability.

(3) The multi-component glass for the core should have low loss.

Glass composition with low scattering loss and easy melting (low melting temperature).

If the melting temperature is high, the crucible used and the atmosphere
This is because the loss increases due to the inclusion of substances with high absorption loss, such as iron and copper, and the occurrence of scattering defects.

(Low loss) (4) The difference in expansion coefficient (△α) between the multi-component glass for the core and the multi-component glass for the coating is 3 x 10-6 cm/cm℃ (a
tO~300℃) or less.

A large difference in expansion coefficients increases stress in the fiber and reduces reliability.

(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 (nl-n2/n1) is 0.003
We have found a multi-component glass fiber with high weather resistance and low loss that has various excellent properties such as the above.

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: (1) SiO2 40-80% (of which Ge
02), AI.

0320.5-7%, alkali metal oxide 10-23, CaO2-12%, MgO2-5%, B2030-
(B) SiO260-80% by weight) AI203
0.5-10%, alkali metal oxide 9-17%, ? a
A multi-component glass for coating consisting of 00 to 5%, MgOO to 4, B2030 to 10%, and 7% or less (not including 0) of at least one of ZnO, ZrO2, TiO2; It is.

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

IA) SiO SiO2 is a glass-forming oxide whose content is
If the content is less than 40 wt%, water resistance is low, while if the content exceeds 80 wt%, a uniform glass cannot be obtained, which is not preferable.

However, this Si02 component can be replaced with GeO2 within a range of 30 parts (Si02 has a minimum of 10 parts) to lower the melting temperature.

2A) Al203 A103 contributes to improving the water resistance of glass.

If the content of Al203 is less than 0.5 wt%, no improvement in water resistance can be expected; on the other hand, if the content is less than 7 wt%
Exceeding this is not preferable as it tends to cause devitrification.

3A) Alkali metal oxides Alkali metal oxides are mainly Na20, K20, Li
20 and acts as a network modifying oxide.

When the content of alkali metal oxide is less than 10wt,
It becomes easy to devitrify, and on the other hand, if it exceeds 23 wt%, water resistance decreases.

However, the constituent components in alkali metal oxides (Na20, K
The blending ratio of Li20 and Li20) is adjusted as appropriate depending on the required change in the physical properties of the core.

Specifically, to reduce the viscosity, the ratio of K20 is lowered, to increase the expansion coefficient, the ratio of Li20 is increased, and further, to increase the refractive index, the ratio of Li20 is increased.

4A) CaO CaO contributes to improving water resistance and increasing refractive index.

This is because if the CaO content is less than 2 wt, the desired effect cannot be sufficiently achieved, whereas if the content exceeds 12 wt, devitrification tends to occur.

5A) MgO MgO contributes to improving weathering resistance.

If MgO exceeds 5 wt%, devitrification tends to occur, which is not preferable.

? A) B203 B203 has the effect of preventing devitrification and the effect of adjusting high temperature viscosity.

If it exceeds 1 swt%, high temperature viscosity decreases and wire drawing becomes difficult.

7A) ZrO zrO2 improves water resistance and alkali resistance.

It also improves the tendency to devitrify.

If the content of Zr02 is less than 1 wt%, the intended purpose cannot be sufficiently achieved, while if the content exceeds 12 wt%, striae increase and a uniform glass cannot be obtained.

The reasons for limiting each component of the multi-component glass for coating will now 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? On the other hand, if it exceeds 80% by weight, the high temperature viscosity increases and the difference in viscosity with the core glass increases, which is not preferable.

2B) Al03 Al203 has the effect of improving water resistance.

This is because if the content of Al203 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 Na20, K20, Li20
It acts as a network-modifying oxide.

If the content of the alkali metal oxide is less than 9% by weight, devitrification tends to occur, and if it exceeds 17% by weight, the water resistance decreases and a coating that satisfies the desired requirements cannot be obtained.

4B) CaO CaO has the effect of improving water resistance, but if it exceeds 5% by weight, it tends to devitrify, which is not preferable.

5B) MgO MgO contributes to improving weathering resistance.

If MgO exceeds 4 weight coefficients, devitrification occurs, which is not preferable.

6B) B203 B203 contributes to improving water resistance and increasing refractive index.

If B203 exceeds 10% 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.

7B) ZnO, Zr02, TiO2 Addition of these components contributes to improving water resistance.

However, the lever component may be a single type or a mixture of two or more types, but if the composition ratio exceeds 7%, striae are likely to form, so it is necessary to always keep the upper limit at 7%.

Next, examples of the present invention will be described.

As shown in Tables 1 to 4 below, multi-component glass for the core and multi-component glass for the coating, each having a different composition ratio, are drawn at a temperature of 800 to 1100°C by the double crucible method to obtain 1.
A type of multi-component glass fiber for optical communication (core diameter 80μ
, a coating diameter of 150μ) was obtained.

Therefore, the refractive index n, thermal expansion coefficient α, water resistance, weathering resistance, temperature at IQ 4, 105, 106 poise, and devitrification tendency of the core and coating of each multicomponent glass fiber for optical communications obtained. Check it out.

The results are also listed in Tables 1 to 4. In addition, water resistance, weathering resistance, and devitrification tendency were determined by the following tests.

■) Water resistance: Powder sample that passes a JIS standard sieve with a mesh size of 0.5 mm, but does not pass the same standard sieve with a mesh size of 0.3 mm.5.
After soaking 01 in 100ml of distilled water and heating it in a boiling water bath for 1 hour, titrate the solution with 0.01N-MCI solution, and determine the superiority or inferiority of water resistance based on the titrated amount (ml). .

2) @Weathering; Haze that forms on the glass surface
Observe and select ASK-16 which is less likely to cause haze than SK-16.
A product with the same level of haze as ABSK-16 is rated as B.

3) Tendency to devitrify; heating at 800°C for 15 hours and 110°C
Those that do not precipitate crystals after heating at 0°C for 15 hours are evaluated as: (a) Those that deposit crystals on the surface; (b) Those that deposit crystals on the surface and inside are evaluated as C.

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

In addition, the glass with the above composition can be manufactured by a method other than the double crucible method,
For example, fibers with high weather resistance and low loss can be obtained by spinning using the rod-in-tube method.

As detailed above, the present invention has low loss, good chemical resistance such as water resistance and weathering resistance, particularly low alkali elution from the coating layer, excellent weather resistance, and excellent dimensional stability. Moreover, it is possible to provide a multi-component glass fiber for optical communications which can prevent the tendency of devitrification during drawing operations and has significantly improved performance, service life and loss.

Claims (1)

[Claims] 1 (4) St0240 to 80% by weight (up to 30% of this may be replaced with Ge02), Al203
0.5-7%, alkali metal oxides 10-23%, Ca
O2~12%, ZrO21~12%, B2030~15
% and MgOO~5% of the core multi-component glass; and (i) SiO in weight ratio. 60-80%, Al2030.5-1. 0%, alkali metal oxides 9-17%, CaOO-5%
At least one selected from ZnO, Zr02, Ti02, 7% or less (however, 0 is not included), Mg00-4
% and B2030 to 10% for coating.