JPS5849499B2 - 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).
22%, Ca03 5% and Si0274.5% (
Both are coated with glass consisting of (weight ratio).

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, so it has a disadvantage of poor weather resistance.

On the other hand, the double Rumbo method is mainly adopted as a method for producing step-type multicomponent 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 concentric circles, 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 Lusovo 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. If the drawing temperature is increased, crystals will easily form in some parts of the glass during the drawing process.
Increase in optical transmission loss of glass fiber obtained by this crystallization, tensile? There was a drawback that it led to a decrease in performance.

For this reason, the present inventor has conducted extensive research to eliminate the above drawbacks, and has used Si02 as a crystal and core material.
G e O2, Al203, alkali metal oxide, Ca
A multi-component glass consisting of b, MgO, B203, SrO, and BaO, with prescribed values for each of these groups, was used, while SiO2, Al203, alkali metal oxide, Cab, MgOB203, and ZnO were used as coating materials. Z
By using a multi-component glass consisting of one or more of R02 and Ti02 and with defined values of these components, (1) it has good chemical resistance 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 have low alkali elution and excellent weather resistance (high weather resistance).
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.

In other words, the glass must have low scattering loss and melt easily (low melting temperature).

If the melting temperature is high, the rusovo used, from 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 (Aα) between the polypropylene glass for the core and the polypropylene glass for the coating is 3X10'c
Must be small, rrL/cfrL・℃ (atO~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 I n ( nl ~ n2/ nl
) has been found to be 0.003 or more.

The present invention will be explained in detail below.

The multi-component glass fiber for optical communication of the present invention includes (4)
In terms of weight ratio, (1) SiO2 25-65%, G e O
20-30%, Al2030.5-7%, alkali metal oxide 10-20%, CaO 1-7%, SrO and Ba
Total amount of O 10-20%, MgOO-5% and B203
A multi-component glass for the core consisting of 0 to 10%, (B) SiO260 to 80%, A1O by weight ratio
30.5-10%, alkali metal oxide 9-17%, C
aOO~5%, one or more of Zn01Zr02, Ti02 and 7% or less (not including 0), Mg0 0~4% and B
A multi-component glass for coating consisting of 2030 to 10%.

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

(IA) SiO2 SiO2 is a component that forms the core skeleton, and if its content is less than 25% by weight, water resistance will decrease, while if its content exceeds 65% by weight, it will not interact with other components. This relationship makes it impossible to obtain a core with a high refractive index.

(2A) Ge02 GeO2 is a component that increases the refractive index and lowers the glass melting temperature, and can be contained within 30% by weight.

(3A) A1203 Al203 contributes to improving the water resistance of the core.

If the content of A1203 is less than 0.5% by weight, no improvement in water resistance can be expected, while if the content exceeds 7% by weight, devitrification tends to occur, which is not preferable.

(4A) Alkali metal oxides Alkali metal oxides are mainly Na20, K20, Li20
It acts as a network-modifying oxide.

If the alkali metal oxide content is less than 10% by weight, devitrification tends to occur, while if it exceeds 20% by weight, water resistance decreases.

In this case, the constituents in the alkali metal oxide (Na20
, K20, Li20) are adjusted as appropriate depending on the required changes in the physical properties of the core.

Specifically, to reduce the viscosity, lower the K20 ratio in the alkali metal oxide, to increase the expansion coefficient, increase the Li20 ratio, and to further increase the refractive index, lower the Li20 ratio. make it higher.

(5A) CaO CaO has the effect of improving water resistance.

If the CaO content is less than 1% by weight, sufficient improvement in water resistance cannot be achieved, while if the content exceeds 7% by weight, devitrification tends to occur, which is undesirable.

(6A) SrO, Ba0 These SrO and BaO have the effect of increasing the refractive index and preventing devitrification.

If the total amount is less than 10% by weight, the desired effect cannot be sufficiently achieved, while if it exceeds 20% by weight, veins will occur in the core, which is not preferable.

(7A) MgO MgO contributes to improving weathering resistance.

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

(8A) B203 B203 contributes to improving water resistance and increasing refractive index.

If B203 exceeds 10% by weight, phase separation occurs in the obtained core, scattering occurs, and loss increases, which is not preferable.

Moreover, the reason for limiting each component of the multi-component glass for coating is as follows.

(1B) SiO2 Si02 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) Al203 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 alkali metal oxide content 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% by weight, 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, making it impossible to obtain an initial refractive index difference, which is not preferable.

(7B) Zn01Zr02, Ti02 Addition of these components is effective in improving water resistance.

However, these components may be used alone or in a mixed system of two or more, but if they are added in an amount of 7% or more, vein embedding is likely to occur, so the amount is selected to be 7% or less (not including 0).

Next, examples of the present invention will be described.

As shown in Tables 1 to 5 below, multi-component glass for the core and multi-component glass for the substrate, which have different compositions, were drawn at a temperature of 850 to 950°C by the double Rumbo method. 13 types of multi-component glass fiber for optical communication (core diameter 80
μ, coating diameter 150 μ) was obtained.

Thus, the refractive index (n) and thermal expansion coefficient α) of the core and coating of each of the obtained multi-component glass fibers for optical communication
, water resistance, weathering resistance, temperatures at 10', 1o5, and 106 poise, and devitrification tendency were investigated.

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.

(1) Water resistance; opening 0. Powder sample 5.1' that passed through a 5 mm JIS standard sieve but did not pass through a 0.3-mesh standard sieve was immersed in 100 ml of distilled water and heated in a boiling water bath for 1 hour. is titrated with a 0.01N HCI solution, and the water resistance is determined based on the titrated amount (ml).

(2) Weathering resistance: Haze that forms on the glass surface
Observe e) and evaluate.

(3) Tendency to devitrify; Heating at SOO℃ for 15 hours and 1
Evaluation is made after heating at 100°C for 15 hours.

However, the multi-component glass fiber according to the present invention has a transmission loss of 20 dB/km when measured at a wavelength of 850 mn.
It was a low loss fiber.

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

As detailed above, according to the present invention, there is low loss, water resistance,
It has good chemical resistance properties such as weathering resistance, has excellent weather resistance with little alkali elution from the coating, and has excellent dimensional stability.Moreover, it can prevent devitrification during wire drawing, and has excellent performance, service life, and It is possible to provide a multi-component glass fiber for optical communication with significantly improved loss.

Claims (1)

[Claims] 1 (7! Weight ratio: SiO2 25-65%, GeO
20-30%, AI2030.5-7%, alkali metal oxide 10-20%, CaOl-7%, SrO, BaO
Total amount of 10-20%, B203, O-10% and M
A multi-component glass for the core consisting of g0 0-5%, (B) SiO260-80%, AI2 by weight ratio
030.5-10%, alkali metal oxide 9-17%,
A multi-component glass for coating consisting of ~5% CaOO, 7% or less of at least one selected from ZnO, ZrO2, and TiO2 (excluding 0), 0-4% Mg0, and 30-10% B2. Highly weather resistant multi-component glass fiber for optical communication