CA2021927A1 - Polymer clad optical fiber - Google Patents
Polymer clad optical fiberInfo
- Publication number
- CA2021927A1 CA2021927A1 CA 2021927 CA2021927A CA2021927A1 CA 2021927 A1 CA2021927 A1 CA 2021927A1 CA 2021927 CA2021927 CA 2021927 CA 2021927 A CA2021927 A CA 2021927A CA 2021927 A1 CA2021927 A1 CA 2021927A1
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- Canada
- Prior art keywords
- optical fiber
- polymethylsiloxane
- ladder type
- polymer
- polysiloxane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
ABSTRACT
The present invention is directed to a polymer clad optical fiber comprising a core made of quartz glass or optical glass, a cladding made of a cured material of a polymer composition comprising a ladder type polymethylsiloxane, a linear polymethylsiloxane having hydroxyl groups and optionally a solvent. The fiber may optionally have a protecting layer made of a polymer material comprising a ladder type polysiloxane having phenyl side groups. The fiber of the invention has low light transmission loss and good mechanical strength.
The present invention is directed to a polymer clad optical fiber comprising a core made of quartz glass or optical glass, a cladding made of a cured material of a polymer composition comprising a ladder type polymethylsiloxane, a linear polymethylsiloxane having hydroxyl groups and optionally a solvent. The fiber may optionally have a protecting layer made of a polymer material comprising a ladder type polysiloxane having phenyl side groups. The fiber of the invention has low light transmission loss and good mechanical strength.
Description
POLYMER CLAD OPTICAL FIBER
The present invention relates to a polymer clad optical fiber comprising a core made of quartz glass or optical glass and a cladding made of a polymer. More particularly, the present invention relates to a polymer clad optical fiber comprising a cladding made of a ladder type polymethylsiloxane.
A silicone resin (cf. Japanese Patent Publication No.
2321/1981), a fluoroalkyl methacrylate polymer (cf. Japanese Patent Kokai Publication No. 12146/1983), a copolymer of vinylidene fluoride and tetrafluoroethylene (cf. Japanese Patent Publication No. 41966/1981), polyetheresteramide (cf.Japanese Patent Kokai Publication No. 60402/1981~, and a W light-curable fluorinated acrylate composition (cf. U.S.
Patent No. 4,211,209) are used as the cladding polymer of conventional polymer clad optical fibers (hereinafter referred to as "PCF").
These cladding polymers cannot satisfy high level requirements for polymer clad optical fibers, e.g. decrease of light transmission loss, easy fitting of a caulking type connector to the optical fiber, stability of temperature characteristics of light transmission loss and the like.
For example, since the silicone rèsin has poor mechanical characteristics, in particular mechanical strength, the light transmission loss of a PCF comprising the silicone resin as the cladding polymer is increased when a caulking type connector is used.
Although the fluoroalkyl methacrylate polymer is highly transparent, its adhesivity to the core glass is insufficient.
Since the copolymer of vinylidene fluoride and tetrafluoroethylene and the polyetheresteramide have large scattering and absorption characteristics, they have inferior light transmission, and the light transmission loss of the optical fiber cannot be decreased.
Since the W light curable fluorinated acrylate composition is cured with W light irradiation after it is applied on the core glass, it is difficult to control the degree of curing, and residual stress caused by shrinkage of the polymer during curing increases the transmission loss of the optical fiber. In addition, adjustment of the outer diameter of the optical fiber is difficult.
As a cladding material which satisfies the above described requirements, a ladder type polysiloxane (organosilsesquioxane) is proposed (cf. U.S. Patent No.
4,835,057)-However, a cured material of the ladder type polysiloxane has very small elongation. When it is coated on the glass core as the cladding material, its surface may crack because lo of the presence of bending strain, strain generated by a difference in coefficients of thermal expansion between the core glass and the ladder type polysiloxane, or strain due to shrinkage of the ladder type polysiloxane during curing.
Since the ladder type polysiloxane is in general dissolved or ; 15 dispersed in a solvent, coated on the core glass and then cured by heating simultaneously with evaporation of the solvent, bubbles generated from the solvent may be trapped in the cured polysiloxane and increase the light transmission loss.
In addition, the ladder type polymethylsiloxane is degraded since the side methyl groups are cleaved and dissociated by oxidation in a high temperature atmosphere.
- The above drawbacks of the ladder type polysiloxane are not overcome by the invention disclosed in U.S. Patent No.
4,385,057.
One object of the present invention is to provide a polymer clad optical fiber which has low light transmission loss and increased mechanical strength.
Another object of the present invention is to provide a polymer clad optical fiber which comprises a cladding comprising a ladder type polysiloxane and has little or no surface cracking, devitrification or deterioration of characteristics.
According to the present invention, there is provided a polymer clad optical fiber which comprises a core made of glass selected from the group consisting of quartz glass and optical glass and a cladding made of a cured material of a polymer composition comprising a ladder type polymethylsiloxane, a linear polymethylsiloxane having hydroxyl groups and optionally a solvent.
Further, the polymer clad optical fiber may comprise a protecting layer made of a polymer material comprising a ladder type polysiloxane having phenyl side groups.
A typical ladder type polymethylsiloxane is a polysiloxane of the formula:
H0 - - Si O - H
0 (I) H0 - - Si O - H
CH3 n ; 15 The ladder type polymethylsiloxane preferably has a number average molecular weight of 5,000 to 100,000.
Since the ladder type polymethylsiloxane used in the present invention has a refractive index of 1.40 to 1.42, it is suitable as a cladding material of an optical fiber comprising a core made of quartz glass or optical glass which has a refractive index of about 1.45.
The invention is described in more detail below with reference to the accompanying drawing in which the single Figure is a ternary composition diagram showing compositions including those suitable for the present invention.
- The ladder type polymethylsiloxane used in the present invention i5 a known polymer and may be prepared, for example, by the method disclosed in Japanese Patent Kokai Publication No. 88099/1978.
A typical linear polymethylsiloxane having hydroxyl groups is a polysiloxane comprising repeating units of the formula:
, .
. .
`:A
Sl - 0 ~ (II) CH3 n in which the hydroxyl groups may be attached to the chain end(s) or the side group(s).
The linear polymethylsiloxane having hydroxyl groups preferably has a number average molecular weight of about 500 to about 100,000, more preferably 1,000 to 20,000.
The linear polymethylsiloxane has a refractive index of 1.40 to 1.44 and the cured material of the mixture of the linear polymethylsiloxane and the ladder type polymethylsiloxane has a refractive index of 1.41 to 1.43.
Therefore, such a cured material is suitable as the cladding material for an optical fiber comprising a core made of quartz glass or optical glass which has a refractive index of about 1.45.
The weight ratio of the ladder type polymethylsiloxane to the linear polymethylsiloxane is in general from 99:1 to 1:99, preferably from 95:5 to 5:95, more preferably 80:20 to 20:80.
By adjusting the ratio of the two polymethylsiloxanes, the properties of the cladding, e.g. hardness and heat resistance, can be controlled. That is, when the content of the ladder type polymethylsiloxane is increased, the cured material has increased hardness and better heat resistance. When the content of the linear polymethylsiloxane is increased, the cured material has better elongation and flexibility.
As the solvent which may be used together with the polymethylsiloxanes, any solvent that has good compatibility with the polymethylsiloxanes can be used provided that the solvent does not remain in the cured material after thermal curing of the polysiloxanes. Therefore, the solvent preferably has a low boiling point. However, when the solvent has too low a boiling point, it may form bubbles in the cured material of the polysiloxanes. Preferably, the solvent has a 3~ boiling point of 70 to 200c.
Specific examples of the solvent are alcohols te.g.
-.~
. .
ethanol, n-propanol, isopropanol and n-butanol), ketones (e.g.
methyl ethyl ketone and diethyl ketone), esters (e.g. ethyl acetate and n-butyl acetate~, aromatic hydrocarbons (e.g.
toluene and xylene), and the like.
When the solvent is used, the component composition of the polysiloxane composition is preferably that as indicated by the hatched area in the ternary composition diagram of the appended Figure in which the values are "~ by weight". When the amount of the latter type polymethylsiloxane is too large, the cured material has poor elongation and the cladding tends to be easily cracked. When the amount of the lader type polymethylsiloxane is too small, the cured material is too soft so that the optical fiber is not suited to fit a caulking type connector. When the amount of the solvent is too large, the viscosity of the composition is too small.
The polysiloxane composition may contain other siloxanes, e.g. diorganopolysiloxane and alkoxyorganosilane, in such amount that the functions of the ladder type polymethylsiloxane are not adversely affected.
Further, the polysiloxane composition may contain a catalyst which catalyzes condensation and curing reactions, e.g. platinum base catalysts, Lewis acids, Lewis bases, zinc naphthenate, lead naphthenate and tetramethylammonium hydroxide.
In the present invention, the core glass fiber can be the same as that used in the conventional PCF. That is, the core glass fiber can be prepared by drawing high purity quartz glass or optical glass. The diameter of the core glass fiber is not critical and is preferably from 0.05 to 0.5mm.
For example, after drawing the quartz or optical glass, the polysiloxane composition may be applied on the core glass fiber with a die and cured in a curing furnace to ~orm a cladding layer. The curing conditions are selected according to the types and ratios of the polysiloxanes, the amount of the solvent and the like. For example, the polysiloxane composition is cured in an IR heating furnace of 1 to 3 meters in length at a curing temperature of 200 to 300C.
.~, The thickness of the cladding is not critical as long as the optical fiber thus produced exhibits sufficient performance qualities. Preferably, the thickness of the cladding is from 10 to 30~m.
The optical fiber of the present invention may have a protective layer around the cladding. The protective layer material may be a thermoplastic polymer, e.g. polyethylene, polyamide, chlorinated polyethylene, polycarbonate, ethylene-tetrafluoroethylene (ETFE) copolymer and a perfluoroalkylvinylether (PFA).
In a preferred embodiment, the protective layer comprises a ladder type polysiloxane having phenyl side groups. Since the ladder type polysiloxane having the phenyl side groups has good heat resistance and blocks oxygen contact with the cladding layer, it can present the degradation of the ladder type polymethyl siloxane in the cladding, e.g. oxidation of the latter type polymethylsiloxane or cleavage of the methyl groups, and liberation of the uncured materials or decomposed materials in the cladding layer. Therefore, the deterioration of the characteristics of the optical fiber due to the above degradation, or weight loss due to liberation of the materials can be prevented.
A typical ladder type polysiloxane having the phenyl side groups is a polysiloxane of the formula:
HO - Si - O - H
O (III) HO Si - O - H
R4 n wherein R3 and R4 independently represent a methyl group or a phenyl group, provided that at least one of them is a phenyl group.
The ladder type polysiloxane (III) preferably has a 35number average molecular weight of 5,000 to 100,000.
The ladder type polysiloxane for the protective layer may .~ ' ' ., be dissolved in a solvent to adjust the viscosity and then the solution is applied to the polymer clad optical fiber.
The thickness of the protective layer is not critical.
Preferably, it is from 5 to 50~m, preferably from 10 to 40~m.
; 5 The present invention will be illustrated by the following Examples.
A flake-form ladder type polymethylsiloxane having a refractive index of 1.42 and a number average molecular weight of 6,000 was dissolved in an oily linear dimethylsiloxane which had a refractive index of 1.41, a viscosity of 300 cps and a number average molecular weight of 10,000 and contained the -ROH (alcohol) groups wherein R is a Cl-C3 alkyl group at both chain ends in a weight ratio of 1:1 to prepare a polysiloxane composition having a refractive index of 1.415 and a viscosity of 100,000 cps.
From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with the above polysiloxane composition through a die.
Then, the coated glass fiber was passed through a baking oven at about 200C to thermally cure the polysiloxanes to produce polymer clad optical fiher having an outer diameter of 230~m.
Light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 810nm. It was 7.5 dB/km.
The light transmission loss did not increase when the optical fiber was fitted with the caulking type connector, and the fitting strength of the optical fiber to the connector was 1.5kg.
The adhesion of the cladding to the core glass fiber was ; good, and the optical fiber could be used at 200C.
`~ No bubbles appeared in the cladding layer.
Comparative Example 1 From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with a thermally curable silicone resin of linear polymethylsiloxane having a refractive index of 1.41 and a viscosity of 1,000 cps through a die. Then, the coated glass fiber was passed through a baking oven at about 500C to thermally cure the polysiloxane to produce a polymer clad optical fiber having an outer diameter of 230~m.
Light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 810nm. It was 5.6 dB/km.
When the optical fibers were connected to the caulking type connectors, the transmission loss increased by about 2 dB/km per connector. When the caulking strength was decreased to reduce the transmission loss, the fitting strength of the optical fiber to the connector was decreased to less than O.lkg, and the connected optical fibers could not be practically used.
A flake-form ladder type polymethylsiloxane having a refractive index of 1.42 and a number average molecular weight of 6,000 was dissolved in an oily linear dimethylsiloxane which had a refractive index of 1.41, a viscosity of 300 cps and a number average molecular weight of 10,000 and contained the -ROH groups at a part of the chain ends (the OH content of 2.1%) and n-butanol in a weight ratio of 9:1:2 to prepare a polysiloxane composition having a refractive index of 1.42 and a viscosity of 6,000 cps.
From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with the above polysiloxane composition through a die.
Then, the coated glass fiber was passed through a baking oven at about 250C to thermally cure the polysiloxanes to produce ; 30 a polymer clad optical fiber having an outer diameter of 230~m.
Light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 850nm. It was 7.5 dB/km.
The cladding layer showed no cracking.
The light transmission loss did not increase when the optical fiber was fitted with the caulking type connector, and ~`'~
.. , .. ~
the fitting strength of the optical fiber to the connector was 1.5kg.
The tensile strength was measured at a distance of 300mm at a pulling rate of 100mm/min. It was 14 to 15kg.
The adhesion of the cladding to the core glass fiber was good, and the optical fiber could be used at 200c.
comparative Example 2 The same flake-form ladder type polymethylsiloxane as used in Example 2 was dissolved in n-butanol in a weight ratio of 75:25 to prepare a polysiloxane composition having a viscosity of 3,000 cps.
From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with the above polysiloxane composition with a die.
Then, the coated glass fiber was passed through a baking oven at about 250C to thermally cure the polysiloxane to produce a polymer clad optical fiber having an outer diameter of 230~m.
The light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 850nm. It was 200 dB/km.
Observation of the cladding layer with a microscope found that cracks were partly formed.
The tensile strength was from 3 to 15kg.
; 25 A flake-form ladder type polymethylsiloxane having a refractive index of 1.42 and a number average molecular weight of 6,000 was dissolved in an oily linear dimethylsiloxane which had a refractive index of 1.44, a viscosity of 200 cps and a number average molecular weight of 10,000 and contained the -ROH groups at both chain ends and ethyl acetate in a weight ratio of 8:2:2. Lead naphthenate was added to the solution in an amount of 1% by weight based on the weight of the ladder type polymethylsiloxane to prepare a polysiloxane composition having a refractive index of 1.42 and a viscosity f 5,000 cps.
With this polysiloxane composition, a polymer clad optical fiber was produced in the same manner as in Example 2.
The properties of the produced optical fiber were substantially the same as those of Example 2.
A flake-form ladder type polymethylsiloxane having a refractive index of 1.42 and a number average molecular weight of 6,000 was dissolved in an oily linear dimethylsiloxane which had a refractive index of 1.43, a viscosity of 300 cps and a number average molecular weight of 10,000 and contained the -ROH groups at a part of the chain ends (the OH content of 2.1%) and n-butanol in a weight ration of 9:1:2 to prepare a polysiloxane composition for cladding having a refractive index of 1.42 and a viscosity of 6,000 cps.
A flake-form ladder type polyphenylsiloxane of the formula (III) in which both R3 and R4 are phenyl having a refractive index of 1.56 and a number average molecular weight of 6,000 was dissolved in n-butanol in a weight ratio of 75:25 to prepare a coating composition having a viscosity of 2,000 cps.
From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with the above polysiloxane composition through a die.
Then, the coated glass fiber was passed through a baking oven at about 250C to thermally cure the polysiloxanes to produce a polymer clad optical fiber having an outer diameter of 230~m.
Thereafter, the coating composition was coated around the cladding layer through a die and thermally cured by passing the coated polymer clad optical fiber through a baking oven at about 250C to obtain a coated optical fiber consisting of a core glass fiber, a cladding layer and a protective layer having an outer diameter of 250~m.
THe light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 850nm. It was 7.5 dB/km.
No cracking was observed.
The light transmission loss did not increase when the optical fiber was fitted with the caulking type connector, and ',. ~,, the fitting strength of the optical fiber to the connector was 1.5kg.
The tensile strength was measured at a standard distance of 300mm at a pulling rate of lOOmm/min. It was 14 to 15kg.
When the optical fiber was left standing at 250C for 3 days, no cracking was observed and no increase in the transmission loss was measured.
A flake-form ladder type polysiloxane containing phenyl groups and methyl groups in a molar ratio of 1:2 and having a refractive index of 1.50 and a number average molecular weight of 6,000 was dissolved in butanol in a weight ratio of 75:25 to prepare a coating composition having a viscosity of 2,000.
Around the same optical fiber comprising the polysiloxane cladding as that in Example 4, the above coating composition was coated and cured by passing the coated fiber through the baking oven at about 250C to obtain a polymer clad optical fiber having an outer diameter of 250~m.
The light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 850nm. It was 7.5 dB/km.
- No cracking was observed on the coating surface.
The light transmission loss did not increase when the optical fiber was fitted with the caulking type connector, and the fitting strength of the optical fiber to the connector was ' 1.5kg.
The tensile strength was measured at a standard distance of 300mm at a pulling rate of lOOmm/min. It was 14 to 15kg.
When the optical fiber was left standing at 250C for 3 days, no cracking was observed and no increase in the - transmission loss was measured.
,~.
The present invention relates to a polymer clad optical fiber comprising a core made of quartz glass or optical glass and a cladding made of a polymer. More particularly, the present invention relates to a polymer clad optical fiber comprising a cladding made of a ladder type polymethylsiloxane.
A silicone resin (cf. Japanese Patent Publication No.
2321/1981), a fluoroalkyl methacrylate polymer (cf. Japanese Patent Kokai Publication No. 12146/1983), a copolymer of vinylidene fluoride and tetrafluoroethylene (cf. Japanese Patent Publication No. 41966/1981), polyetheresteramide (cf.Japanese Patent Kokai Publication No. 60402/1981~, and a W light-curable fluorinated acrylate composition (cf. U.S.
Patent No. 4,211,209) are used as the cladding polymer of conventional polymer clad optical fibers (hereinafter referred to as "PCF").
These cladding polymers cannot satisfy high level requirements for polymer clad optical fibers, e.g. decrease of light transmission loss, easy fitting of a caulking type connector to the optical fiber, stability of temperature characteristics of light transmission loss and the like.
For example, since the silicone rèsin has poor mechanical characteristics, in particular mechanical strength, the light transmission loss of a PCF comprising the silicone resin as the cladding polymer is increased when a caulking type connector is used.
Although the fluoroalkyl methacrylate polymer is highly transparent, its adhesivity to the core glass is insufficient.
Since the copolymer of vinylidene fluoride and tetrafluoroethylene and the polyetheresteramide have large scattering and absorption characteristics, they have inferior light transmission, and the light transmission loss of the optical fiber cannot be decreased.
Since the W light curable fluorinated acrylate composition is cured with W light irradiation after it is applied on the core glass, it is difficult to control the degree of curing, and residual stress caused by shrinkage of the polymer during curing increases the transmission loss of the optical fiber. In addition, adjustment of the outer diameter of the optical fiber is difficult.
As a cladding material which satisfies the above described requirements, a ladder type polysiloxane (organosilsesquioxane) is proposed (cf. U.S. Patent No.
4,835,057)-However, a cured material of the ladder type polysiloxane has very small elongation. When it is coated on the glass core as the cladding material, its surface may crack because lo of the presence of bending strain, strain generated by a difference in coefficients of thermal expansion between the core glass and the ladder type polysiloxane, or strain due to shrinkage of the ladder type polysiloxane during curing.
Since the ladder type polysiloxane is in general dissolved or ; 15 dispersed in a solvent, coated on the core glass and then cured by heating simultaneously with evaporation of the solvent, bubbles generated from the solvent may be trapped in the cured polysiloxane and increase the light transmission loss.
In addition, the ladder type polymethylsiloxane is degraded since the side methyl groups are cleaved and dissociated by oxidation in a high temperature atmosphere.
- The above drawbacks of the ladder type polysiloxane are not overcome by the invention disclosed in U.S. Patent No.
4,385,057.
One object of the present invention is to provide a polymer clad optical fiber which has low light transmission loss and increased mechanical strength.
Another object of the present invention is to provide a polymer clad optical fiber which comprises a cladding comprising a ladder type polysiloxane and has little or no surface cracking, devitrification or deterioration of characteristics.
According to the present invention, there is provided a polymer clad optical fiber which comprises a core made of glass selected from the group consisting of quartz glass and optical glass and a cladding made of a cured material of a polymer composition comprising a ladder type polymethylsiloxane, a linear polymethylsiloxane having hydroxyl groups and optionally a solvent.
Further, the polymer clad optical fiber may comprise a protecting layer made of a polymer material comprising a ladder type polysiloxane having phenyl side groups.
A typical ladder type polymethylsiloxane is a polysiloxane of the formula:
H0 - - Si O - H
0 (I) H0 - - Si O - H
CH3 n ; 15 The ladder type polymethylsiloxane preferably has a number average molecular weight of 5,000 to 100,000.
Since the ladder type polymethylsiloxane used in the present invention has a refractive index of 1.40 to 1.42, it is suitable as a cladding material of an optical fiber comprising a core made of quartz glass or optical glass which has a refractive index of about 1.45.
The invention is described in more detail below with reference to the accompanying drawing in which the single Figure is a ternary composition diagram showing compositions including those suitable for the present invention.
- The ladder type polymethylsiloxane used in the present invention i5 a known polymer and may be prepared, for example, by the method disclosed in Japanese Patent Kokai Publication No. 88099/1978.
A typical linear polymethylsiloxane having hydroxyl groups is a polysiloxane comprising repeating units of the formula:
, .
. .
`:A
Sl - 0 ~ (II) CH3 n in which the hydroxyl groups may be attached to the chain end(s) or the side group(s).
The linear polymethylsiloxane having hydroxyl groups preferably has a number average molecular weight of about 500 to about 100,000, more preferably 1,000 to 20,000.
The linear polymethylsiloxane has a refractive index of 1.40 to 1.44 and the cured material of the mixture of the linear polymethylsiloxane and the ladder type polymethylsiloxane has a refractive index of 1.41 to 1.43.
Therefore, such a cured material is suitable as the cladding material for an optical fiber comprising a core made of quartz glass or optical glass which has a refractive index of about 1.45.
The weight ratio of the ladder type polymethylsiloxane to the linear polymethylsiloxane is in general from 99:1 to 1:99, preferably from 95:5 to 5:95, more preferably 80:20 to 20:80.
By adjusting the ratio of the two polymethylsiloxanes, the properties of the cladding, e.g. hardness and heat resistance, can be controlled. That is, when the content of the ladder type polymethylsiloxane is increased, the cured material has increased hardness and better heat resistance. When the content of the linear polymethylsiloxane is increased, the cured material has better elongation and flexibility.
As the solvent which may be used together with the polymethylsiloxanes, any solvent that has good compatibility with the polymethylsiloxanes can be used provided that the solvent does not remain in the cured material after thermal curing of the polysiloxanes. Therefore, the solvent preferably has a low boiling point. However, when the solvent has too low a boiling point, it may form bubbles in the cured material of the polysiloxanes. Preferably, the solvent has a 3~ boiling point of 70 to 200c.
Specific examples of the solvent are alcohols te.g.
-.~
. .
ethanol, n-propanol, isopropanol and n-butanol), ketones (e.g.
methyl ethyl ketone and diethyl ketone), esters (e.g. ethyl acetate and n-butyl acetate~, aromatic hydrocarbons (e.g.
toluene and xylene), and the like.
When the solvent is used, the component composition of the polysiloxane composition is preferably that as indicated by the hatched area in the ternary composition diagram of the appended Figure in which the values are "~ by weight". When the amount of the latter type polymethylsiloxane is too large, the cured material has poor elongation and the cladding tends to be easily cracked. When the amount of the lader type polymethylsiloxane is too small, the cured material is too soft so that the optical fiber is not suited to fit a caulking type connector. When the amount of the solvent is too large, the viscosity of the composition is too small.
The polysiloxane composition may contain other siloxanes, e.g. diorganopolysiloxane and alkoxyorganosilane, in such amount that the functions of the ladder type polymethylsiloxane are not adversely affected.
Further, the polysiloxane composition may contain a catalyst which catalyzes condensation and curing reactions, e.g. platinum base catalysts, Lewis acids, Lewis bases, zinc naphthenate, lead naphthenate and tetramethylammonium hydroxide.
In the present invention, the core glass fiber can be the same as that used in the conventional PCF. That is, the core glass fiber can be prepared by drawing high purity quartz glass or optical glass. The diameter of the core glass fiber is not critical and is preferably from 0.05 to 0.5mm.
For example, after drawing the quartz or optical glass, the polysiloxane composition may be applied on the core glass fiber with a die and cured in a curing furnace to ~orm a cladding layer. The curing conditions are selected according to the types and ratios of the polysiloxanes, the amount of the solvent and the like. For example, the polysiloxane composition is cured in an IR heating furnace of 1 to 3 meters in length at a curing temperature of 200 to 300C.
.~, The thickness of the cladding is not critical as long as the optical fiber thus produced exhibits sufficient performance qualities. Preferably, the thickness of the cladding is from 10 to 30~m.
The optical fiber of the present invention may have a protective layer around the cladding. The protective layer material may be a thermoplastic polymer, e.g. polyethylene, polyamide, chlorinated polyethylene, polycarbonate, ethylene-tetrafluoroethylene (ETFE) copolymer and a perfluoroalkylvinylether (PFA).
In a preferred embodiment, the protective layer comprises a ladder type polysiloxane having phenyl side groups. Since the ladder type polysiloxane having the phenyl side groups has good heat resistance and blocks oxygen contact with the cladding layer, it can present the degradation of the ladder type polymethyl siloxane in the cladding, e.g. oxidation of the latter type polymethylsiloxane or cleavage of the methyl groups, and liberation of the uncured materials or decomposed materials in the cladding layer. Therefore, the deterioration of the characteristics of the optical fiber due to the above degradation, or weight loss due to liberation of the materials can be prevented.
A typical ladder type polysiloxane having the phenyl side groups is a polysiloxane of the formula:
HO - Si - O - H
O (III) HO Si - O - H
R4 n wherein R3 and R4 independently represent a methyl group or a phenyl group, provided that at least one of them is a phenyl group.
The ladder type polysiloxane (III) preferably has a 35number average molecular weight of 5,000 to 100,000.
The ladder type polysiloxane for the protective layer may .~ ' ' ., be dissolved in a solvent to adjust the viscosity and then the solution is applied to the polymer clad optical fiber.
The thickness of the protective layer is not critical.
Preferably, it is from 5 to 50~m, preferably from 10 to 40~m.
; 5 The present invention will be illustrated by the following Examples.
A flake-form ladder type polymethylsiloxane having a refractive index of 1.42 and a number average molecular weight of 6,000 was dissolved in an oily linear dimethylsiloxane which had a refractive index of 1.41, a viscosity of 300 cps and a number average molecular weight of 10,000 and contained the -ROH (alcohol) groups wherein R is a Cl-C3 alkyl group at both chain ends in a weight ratio of 1:1 to prepare a polysiloxane composition having a refractive index of 1.415 and a viscosity of 100,000 cps.
From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with the above polysiloxane composition through a die.
Then, the coated glass fiber was passed through a baking oven at about 200C to thermally cure the polysiloxanes to produce polymer clad optical fiher having an outer diameter of 230~m.
Light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 810nm. It was 7.5 dB/km.
The light transmission loss did not increase when the optical fiber was fitted with the caulking type connector, and the fitting strength of the optical fiber to the connector was 1.5kg.
The adhesion of the cladding to the core glass fiber was ; good, and the optical fiber could be used at 200C.
`~ No bubbles appeared in the cladding layer.
Comparative Example 1 From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with a thermally curable silicone resin of linear polymethylsiloxane having a refractive index of 1.41 and a viscosity of 1,000 cps through a die. Then, the coated glass fiber was passed through a baking oven at about 500C to thermally cure the polysiloxane to produce a polymer clad optical fiber having an outer diameter of 230~m.
Light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 810nm. It was 5.6 dB/km.
When the optical fibers were connected to the caulking type connectors, the transmission loss increased by about 2 dB/km per connector. When the caulking strength was decreased to reduce the transmission loss, the fitting strength of the optical fiber to the connector was decreased to less than O.lkg, and the connected optical fibers could not be practically used.
A flake-form ladder type polymethylsiloxane having a refractive index of 1.42 and a number average molecular weight of 6,000 was dissolved in an oily linear dimethylsiloxane which had a refractive index of 1.41, a viscosity of 300 cps and a number average molecular weight of 10,000 and contained the -ROH groups at a part of the chain ends (the OH content of 2.1%) and n-butanol in a weight ratio of 9:1:2 to prepare a polysiloxane composition having a refractive index of 1.42 and a viscosity of 6,000 cps.
From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with the above polysiloxane composition through a die.
Then, the coated glass fiber was passed through a baking oven at about 250C to thermally cure the polysiloxanes to produce ; 30 a polymer clad optical fiber having an outer diameter of 230~m.
Light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 850nm. It was 7.5 dB/km.
The cladding layer showed no cracking.
The light transmission loss did not increase when the optical fiber was fitted with the caulking type connector, and ~`'~
.. , .. ~
the fitting strength of the optical fiber to the connector was 1.5kg.
The tensile strength was measured at a distance of 300mm at a pulling rate of 100mm/min. It was 14 to 15kg.
The adhesion of the cladding to the core glass fiber was good, and the optical fiber could be used at 200c.
comparative Example 2 The same flake-form ladder type polymethylsiloxane as used in Example 2 was dissolved in n-butanol in a weight ratio of 75:25 to prepare a polysiloxane composition having a viscosity of 3,000 cps.
From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with the above polysiloxane composition with a die.
Then, the coated glass fiber was passed through a baking oven at about 250C to thermally cure the polysiloxane to produce a polymer clad optical fiber having an outer diameter of 230~m.
The light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 850nm. It was 200 dB/km.
Observation of the cladding layer with a microscope found that cracks were partly formed.
The tensile strength was from 3 to 15kg.
; 25 A flake-form ladder type polymethylsiloxane having a refractive index of 1.42 and a number average molecular weight of 6,000 was dissolved in an oily linear dimethylsiloxane which had a refractive index of 1.44, a viscosity of 200 cps and a number average molecular weight of 10,000 and contained the -ROH groups at both chain ends and ethyl acetate in a weight ratio of 8:2:2. Lead naphthenate was added to the solution in an amount of 1% by weight based on the weight of the ladder type polymethylsiloxane to prepare a polysiloxane composition having a refractive index of 1.42 and a viscosity f 5,000 cps.
With this polysiloxane composition, a polymer clad optical fiber was produced in the same manner as in Example 2.
The properties of the produced optical fiber were substantially the same as those of Example 2.
A flake-form ladder type polymethylsiloxane having a refractive index of 1.42 and a number average molecular weight of 6,000 was dissolved in an oily linear dimethylsiloxane which had a refractive index of 1.43, a viscosity of 300 cps and a number average molecular weight of 10,000 and contained the -ROH groups at a part of the chain ends (the OH content of 2.1%) and n-butanol in a weight ration of 9:1:2 to prepare a polysiloxane composition for cladding having a refractive index of 1.42 and a viscosity of 6,000 cps.
A flake-form ladder type polyphenylsiloxane of the formula (III) in which both R3 and R4 are phenyl having a refractive index of 1.56 and a number average molecular weight of 6,000 was dissolved in n-butanol in a weight ratio of 75:25 to prepare a coating composition having a viscosity of 2,000 cps.
From a bar of anhydrous synthetic quartz, a core glass fiber having a diameter of 200~m was drawn and simultaneously coated with the above polysiloxane composition through a die.
Then, the coated glass fiber was passed through a baking oven at about 250C to thermally cure the polysiloxanes to produce a polymer clad optical fiber having an outer diameter of 230~m.
Thereafter, the coating composition was coated around the cladding layer through a die and thermally cured by passing the coated polymer clad optical fiber through a baking oven at about 250C to obtain a coated optical fiber consisting of a core glass fiber, a cladding layer and a protective layer having an outer diameter of 250~m.
THe light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 850nm. It was 7.5 dB/km.
No cracking was observed.
The light transmission loss did not increase when the optical fiber was fitted with the caulking type connector, and ',. ~,, the fitting strength of the optical fiber to the connector was 1.5kg.
The tensile strength was measured at a standard distance of 300mm at a pulling rate of lOOmm/min. It was 14 to 15kg.
When the optical fiber was left standing at 250C for 3 days, no cracking was observed and no increase in the transmission loss was measured.
A flake-form ladder type polysiloxane containing phenyl groups and methyl groups in a molar ratio of 1:2 and having a refractive index of 1.50 and a number average molecular weight of 6,000 was dissolved in butanol in a weight ratio of 75:25 to prepare a coating composition having a viscosity of 2,000.
Around the same optical fiber comprising the polysiloxane cladding as that in Example 4, the above coating composition was coated and cured by passing the coated fiber through the baking oven at about 250C to obtain a polymer clad optical fiber having an outer diameter of 250~m.
The light transmission loss of the produced optical fiber of lkm in length was measured at a wavelength of 850nm. It was 7.5 dB/km.
- No cracking was observed on the coating surface.
The light transmission loss did not increase when the optical fiber was fitted with the caulking type connector, and the fitting strength of the optical fiber to the connector was ' 1.5kg.
The tensile strength was measured at a standard distance of 300mm at a pulling rate of lOOmm/min. It was 14 to 15kg.
When the optical fiber was left standing at 250C for 3 days, no cracking was observed and no increase in the - transmission loss was measured.
,~.
Claims (10)
1. A polymer clad optical fiber which comprises a core made of glass selected from the group consisting of quartz glass and optical glass, and a cladding made of a cured material of a polymer composition comprising a ladder type polymethylsiloxane and a linear polymethylsiloxane having hydroxyl groups.
2. The polymer clad optical fiber according to Claim 1, wherein said ladder type polymethylsiloxane is a polysiloxane of the formula:
( I )
( I )
3. The polymer clad optical fiber according to Claim 1, wherein said ladder type polymethylsiloxane has a number average molecular weight of 5,000 to 100,000.
4. The polymer clad optical fiber according to Claim 1, wherein said linear polymethylsiloxane having hydroxyl groups is a polysiloxane comprising repeating units of the formula:
(II) in which the hydroxyl groups may be attached to the chain end(s) or the side group(s).
(II) in which the hydroxyl groups may be attached to the chain end(s) or the side group(s).
5. The polymer ciad optical fiber according to Claim 1, wherein said linear polymethylsiloxane having hydroxyl groups has a number average molecular weight of 500 to 100,000.
6. The polymer clad optical fiber according to Claim 1, wherein a weight ratio of the ladder type polymethylsiloxane to the linear polymethylsiloxane is from 99:1 to 1:99.
7. The polymer clad optical fiber according to Claim 1, wherein said polymer composition for the cladding further contains a solvent.
8. The polymer clad optical fiber according to Claim 1, which further comprises a protecting layer made of a polymer material comprising a ladder type polysiloxane having phenyl side groups.
9. The polymer clad optical fiber according to Claim 8, wherein said ladder type polysiloxane having the phenyl side groups is a polysiloxane of the formula:
(III) wherein R3 and R4 independently represent a methyl group or a phenyl group, provided that at least one of them is a phenyl group.
(III) wherein R3 and R4 independently represent a methyl group or a phenyl group, provided that at least one of them is a phenyl group.
10. The polymer clad optical fiber according to Claim 8, wherein said ladder type polysiloxane having the phenyl side groups has a number average molecular weight of 5,000 to 100,000.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP196686/1989 | 1989-07-31 | ||
| JP1196686A JPH0361909A (en) | 1989-07-31 | 1989-07-31 | Polymer clad fiber for light transmission |
| JP1325831A JPH03186807A (en) | 1989-12-18 | 1989-12-18 | Polymer clad fiber for light transmission |
| JP325831/1989 | 1989-12-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2021927A1 true CA2021927A1 (en) | 1991-02-01 |
Family
ID=26509906
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2021927 Abandoned CA2021927A1 (en) | 1989-07-31 | 1990-07-25 | Polymer clad optical fiber |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2021927A1 (en) |
-
1990
- 1990-07-25 CA CA 2021927 patent/CA2021927A1/en not_active Abandoned
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| FZDE | Dead |