JPS5929534B2 - 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 coating around the core with a smaller refractive index.
Optical information incident on the core from one end of the fiber is confined within the core by utilizing total reflection at the interface between the core and the coating, and transmitted to the other end. By the way, various glasses are being considered as core materials and coating materials for this type of glass fiber.

For example, in the laboratory (1) SiO2, Na2O, Ca
Multi-component glass consisting of O, (2) SiO2, N
Multicomponent glass consisting of a2O and B2O3, (3)
Multi-component glass consisting of SiO2, Na2O and PbO (4) Multi-component glass consisting of SiO2, Na2O and TiO2 is used as the core glass and coating glass by appropriately changing the composition ratio of each multi-component glass. , forming glass fibers for optical communications. but,
The core glasses and covering glasses made of the multi-component glasses (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. Further, since the core glass and the covering glass made of the multi-component glass described in (2) above undergo high evaporation during the melting process, glass fibers with low scattering loss cannot be obtained. Furthermore, since the core glass and the covering glass made of the multicomponent glass described in (3) above contain 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 used to manufacture step-type glass fibers for optical communications. 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. In this case, the drawing temperature, that is, the melting temperature of the core glass and coating glass, is raised to keep the viscosity low (usually the viscosity is 106
~103 Boise), it is necessary 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 multi-component glass is low, so that it approaches the drawing temperature. For this reason, crystals tend to form in a part of the glass during the drawing operation, and this crystallization has the drawback of increasing optical transmission loss and decreasing tensile strength of the glass fiber obtained. For this reason, the inventor of the present invention has conducted extensive research in order to eliminate the above drawbacks, and as a result,
A multi-component glass consisting of SlO2, Al2O3, alkali metal oxide, CaO and ZrO2 with limited values of these components is used as the core material, while SiO2, Al2O3, alkali metal oxide and CaO are used as the coating material. By using a multi-component glass consisting of the following components and with limited values of these components, 1) it has good chemical resistance such as water resistance, acid resistance, and alkali resistance, and 2)
The respective glass liquidus temperatures of the core material and the coating material are sufficiently higher than the drawing temperature to prevent devitrification during the drawing process, and the viscosity of both materials is similar at the drawing process temperature (600 to 1000°C) to ensure that the viscosity is similar during the drawing process. It has excellent dimensional stability, and the difference in expansion coefficient between the 3-core material and the coating material (CΔα) is small (Δα
10-6), and the refractive index of the four cores is 1.5300 to 1.
．． The refractive index of 58001 coating is 1.4800 to 1.525
We have discovered a glass fiber for optical communications that has various excellent properties such as being within the range of 0.

Furthermore, we have discovered that by further adding a predetermined amount of MgO to the multi-component glass composition described above, it is possible to obtain a glass fiber for optical communications that has excellent weathering resistance in addition to the various properties described above. Ta.

The present invention will be explained in detail below. The glass fiber for optical communication of the present invention has (A) weight ratio of 59% to 70% of SlO2, Al2O3
l~5%, alkali metal oxides 17~23%, CaO5
A multicomponent glass for a core prepared by adding 0 to 4 parts by weight of B2O3 to 100 parts by weight of a multicomponent glass composition consisting of ~12% and ~6% ZrO2 and (B) a weight ratio of Sl
Coating made by adding 0 to 3 parts by weight of B2O3 to 100 parts by weight of a multi-component glass composition consisting of ~78% O27O, ~5% Al2O3, 17-23% alkali metal oxide and ~5% CaOl. It is formed from multi-component glass.

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 component that forms the skeleton of the core glass.
When the content of O2 is less than 59% by weight, acid resistance decreases,
On the other hand, if the content exceeds 70% by weight, the refractive index becomes too low, and the preferred range is 61 to 68% by weight.

(2A) Al2O3 Al2O3 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.The preferable range is 1 to 1% by weight.
It is 4% by weight. (3A) Alkali metal oxide The alkali metal oxide is Na2O, . Li2O or K2
It is composed of O and contributes to improving the wire drawing workability.

If the alkali metal oxide content is less than 17% by weight, high temperature viscosity increases and wire drawing becomes difficult, while if the content exceeds 23% by weight, water resistance decreases, and the preferred range is 17% by weight. ~22% by weight.

(4A) CaO CaO has the effect of improving water resistance and increasing refractive index.

If the content of CaO is less than 5% by weight, the desired effect cannot be sufficiently exhibited, while if the content exceeds 12% by weight, devitrification tends to occur, and preferably 5.5 to 8% by weight.
is within the range of (5A) ZrO2 ZrO2 has the effect of improving water resistance, acid resistance, and alkali resistance.

However, the content ratio of ZrO2 and the wire drawing temperature (η
-104 Poise) There is a correlation as shown in the figure, and if the ZrO2 content is too low or too high, the wire drawing temperature will increase and the core will be lost during the wire drawing operation. There is a risk of it being transparent. Accordingly, the content of ZrO2 needs to be within a range where high temperature viscosity is not inhibited, that is, from 1 to 6% by weight. When the content of ZrO2 is less than 1% by weight, the above-mentioned desired effect cannot be sufficiently achieved and devitrification tends to occur during wire drawing work.On the other hand, even when the content exceeds 6% by weight, wire drawing work is difficult. become. (6A
) B2O3 When B2O3 is added to a multi-component glass composition for core,
By adding 4 parts by weight or less to 100 parts by weight of the composition, the viscosity can be lowered at a relatively low temperature and the wire drawing workability can be improved.

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

(1B) SiO2 SiO2 forms the framework of the coating.

If the content of SiO2 is less than 70% by weight, acid resistance decreases,
On the other hand, if the content exceeds 78% by weight, the refractive index becomes too low, and the content is preferably in the range of 72 to 76% by weight. (2B) Al2O3 Al2O3 contributes to improving the water resistance of the coating.

If the content of Al2O3 is less than 1% by weight, no improvement in water resistance can be expected; on the other hand, if the content exceeds 5% by weight,
This is because devitrification tends to occur, and the preferable range is 1 to 4% by weight. (3B) Alkali metal oxide The alkali metal oxide is Na2O. Li2O or K2O
This contributes to improving the wire drawing workability.

If the alkali metal oxide content is less than 17% by weight, high temperature viscosity increases and wire drawing becomes difficult, while if the content exceeds 23% by weight, water resistance decreases.The preferred range is It is 17-22% by weight. (4
B) 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 the preferable range is 2 to 4.5% by weight. %. (5B) B2O3 When B2O3 is added to the multi-component glass composition for the core,
By adding 3 parts by weight or less to 100 parts by weight of the composition, the viscosity can be lowered at relatively low temperatures and the wire drawing workability can be improved.

In addition, the glass fiber for optical communication of the second invention of the present application has a carbon content of 59 to 70% SlO2 and 5% to 5% Al2O3 by weight ratio.
, alkali metal oxides 17-23%, CaO 5-12%
Multi-component glass composition 1 consisting of and ZrO2l~6%
00 parts by weight, 0 to 4 parts by weight of B2O3 and 5 parts by weight of MgO.
A multi-component glass for a core in which not more than parts by weight are added, and (B)
By weight, SlO27O~78%, Al2O3l~5
%, alkali metal oxides 17-23% and CaOl ~5
% to 100 parts by weight of a multicomponent glass composition consisting of
It is formed from a multi-component coating glass to which 0 to 3 parts by weight of O3 and 4 parts by weight or less of MgO are added.

As mentioned above, by using a multi-component glass for the core and a multi-component glass for the coating in which MgO is added to the multi-component glass composition, the weathering resistance of the obtained glass fiber for optical communication is significantly improved. can.

The reason for limiting the amount of MgO added to each of the above multi-component glass compositions is that if the amount of MgO added exceeds 5 parts by weight in the case of a multi-component glass for the core, the core of the formed glass fiber will be lost. Similarly, in the case of a multi-component glass composition for coating, if the amount exceeds 4 parts by weight, the glass fiber coating tends to devitrify. 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. Next, examples of the present invention will be described.

Examples 1 to 4 As shown in Tables 1 and 2 below, multi-component core glasses and multi-component coating glasses with different composition ratios were drawn at a temperature of 790°C by a double crucible method. Te4
Glass fiber for optical communication (core diameter 80μ, outer diameter 150μ)
I got it.

Therefore, the refractive index (n), thermal expansion coefficient (α), softening temperature (Ts), water resistance, acid resistance, alkalinity resistance of the core and coating of each optical communication glass fiber obtained, 103
, 104, 105, 106 poise temperature, devitrification, and transmission loss of these glass fibers (DB/K7!l
), scattering loss (DB/K7l) 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; mesh size 0.5 muf) Powder sample 5-07 that passes a JIS standard sieve but does not pass the same standard sieve with a mesh size of 0.3 muf is immersed in 100 ml of distilled water and placed in a boiling water bath. After heating for 1 hour, this solution is titrated with a 0.01N HCl solution, and the water resistance is determined based on the amount (ml) required for the titration.

(2) Acid resistance; 2
A powder sample of 0 to 30 meshes is added and heated for 1 hour, and the weight loss rate (%) is determined.

(3) Alkali resistance; 20 to 20% in 2N-NaOH aqueous solution
Add 30 mesh powder samples and heat for 1 hour to determine the weight loss rate (%).

Examples 5 to 6 As shown in Table 3 below, two types of multi-component glass for core and multi-component glass for coating were prepared by adding MgO to the multi-component glass composition and heated at 790°C by a double crucible method. Two types of optical communication glass fibers (core diameter 80 μ, outer diameter 1
50μ) was obtained.

Therefore, the refractive index (n), thermal expansion coefficient (α), softening temperature (Ts), water resistance, acid resistance, alkali resistance of the core *7 and coating of each optical communication glass fiber obtained, 103
, 104, 105, 106 poise temperature, weathering resistance, devitrification tendency, and transmission loss (DB
/Kll) and scattering loss (DB/k shoulder) were investigated. The results are also listed in Table 3. Examples 7-8 B2O3 was added to the multi-component glass composition as shown in Table 4 below.
Two types of glass fibers for optical communications (core diameter 80μ, outer diameter 150μ) was obtained.

Therefore, the refractive index (n), thermal expansion coefficient (α), softening temperature (Ts), water resistance, acid resistance, alkali resistance of the core and coating of each optical communication glass fiber obtained, 103, 1
The temperature at which the glass fibers reached 04, 105, and 106 poise, their tendency to devitrify, and the transmission loss (DB/k shoulder) and scattering loss (DB/K7n) of these glass fibers were investigated.

The results are also listed in Table 4. Examples 9-10 MgO and B2 were added to a multi-component glass composition as shown in Table 5 below.
Two types of glass fibers for optical communication (core diameter 80μ
, outer diameter 150μ) was obtained.

Therefore, the refractive index (n), thermal expansion coefficient (α), softening temperature (Ts), water resistance, acid resistance, alkali resistance of each optical communication glass fiber core* (and coating), 103
, 104, 105, 106 poise temperature, weathering resistance, devitrification tendency, and transmission loss (DB
/K, w) and scattering loss (DB/K77) were investigated.

The results are also listed in Table 5. As detailed above, the present invention has good chemical properties such as water resistance, acid resistance, and alkali resistance, excellent dimensional stability, and can prevent devitrification during wire drawing. It is possible to provide a glass fiber for optical communication, which has performance such as an optimal difference in refractive index between the fiber and the coating, and has significantly improved transmission loss, scattering loss, and service life.

[Brief explanation of the drawing]

The figure is a diagram showing the relationship between the content ratio of ZrO2 and the drawing operation temperature (temperature at which 104 poise is obtained) of a core containing this ZrO2.

Claims (1)

[Claims] 1 (A) Weight ratio: SiO_259 to 70%, Al
_2O_31-5%, alkali metal oxide 17-23%
, 0% B_2O_3 was added to 100 parts by weight of a multicomponent glass composition consisting of 5-12% CaO and 21-6% ZrO.
A multi-component glass for a core containing ~4 parts by weight, and (B)
By weight ratio, SiO_270-78%, Al_2O_3
1-5%, alkali metal oxides 17-23% and CaO
A glass fiber for optical communication is formed from 100 parts by weight of a multicomponent glass composition comprising 1 to 5%, and a multicomponent glass for coating made by adding 0 to 3 parts by weight of B_2O_3. 2 (A) Weight ratio: SiO_259-70%, Al
_2O_31-5%, alkali metal oxide 17-23%
, 0% B_2O_3 was added to 100 parts by weight of a multicomponent glass composition consisting of 5-12% CaO and 21-6% ZrO.
~4 parts by weight and a multi-component glass for the core with 5 parts by weight or less of MgO added, and (B) SiO_270 in weight ratio.
0-3 parts by weight of B_2O_3 and 4 parts by weight or less of MgO are added to 100 parts by weight of a multicomponent glass composition consisting of ~78%, Al_2O_31-5%, alkali metal oxides 17-23%, and CaO 1-5%. A multi-component glass for coating made of the same, and a glass fiber for optical communication made of the multi-component glass for coating.