CA2312535A1 - Coated optical fiber with increased modulus and thermally enhanced strippability - Google Patents
Coated optical fiber with increased modulus and thermally enhanced strippability Download PDFInfo
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- CA2312535A1 CA2312535A1 CA002312535A CA2312535A CA2312535A1 CA 2312535 A1 CA2312535 A1 CA 2312535A1 CA 002312535 A CA002312535 A CA 002312535A CA 2312535 A CA2312535 A CA 2312535A CA 2312535 A1 CA2312535 A1 CA 2312535A1
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- optical fiber
- fibers
- fiber
- delamination resistance
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 46
- 238000000576 coating method Methods 0.000 claims abstract description 79
- 239000000835 fiber Substances 0.000 claims abstract description 77
- 230000032798 delamination Effects 0.000 claims abstract description 50
- 239000000178 monomer Substances 0.000 claims abstract description 16
- 239000004721 Polyphenylene oxide Substances 0.000 claims abstract description 12
- 229920000570 polyether Polymers 0.000 claims abstract description 12
- 239000011248 coating agent Substances 0.000 claims description 65
- 239000000463 material Substances 0.000 claims description 56
- 239000011159 matrix material Substances 0.000 claims description 12
- NIXOWILDQLNWCW-UHFFFAOYSA-M acrylate group Chemical group C(C=C)(=O)[O-] NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 claims description 11
- 239000011521 glass Substances 0.000 claims description 10
- 229920000728 polyester Polymers 0.000 claims description 6
- UHESRSKEBRADOO-UHFFFAOYSA-N ethyl carbamate;prop-2-enoic acid Chemical compound OC(=O)C=C.CCOC(N)=O UHESRSKEBRADOO-UHFFFAOYSA-N 0.000 claims description 5
- 125000001931 aliphatic group Chemical group 0.000 claims description 4
- 238000011065 in-situ storage Methods 0.000 claims description 4
- 239000004033 plastic Substances 0.000 claims description 3
- 229920003023 plastic Polymers 0.000 claims description 3
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 claims description 2
- 125000003118 aryl group Chemical group 0.000 claims description 2
- 239000012986 chain transfer agent Substances 0.000 claims description 2
- 239000007822 coupling agent Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 239000011253 protective coating Substances 0.000 abstract description 5
- 239000003365 glass fiber Substances 0.000 description 32
- 238000000034 method Methods 0.000 description 14
- 239000000203 mixture Substances 0.000 description 12
- 230000008569 process Effects 0.000 description 10
- HVVWZTWDBSEWIH-UHFFFAOYSA-N [2-(hydroxymethyl)-3-prop-2-enoyloxy-2-(prop-2-enoyloxymethyl)propyl] prop-2-enoate Chemical compound C=CC(=O)OCC(CO)(COC(=O)C=C)COC(=O)C=C HVVWZTWDBSEWIH-UHFFFAOYSA-N 0.000 description 8
- 239000010410 layer Substances 0.000 description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 7
- 238000009472 formulation Methods 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- FIHBHSQYSYVZQE-UHFFFAOYSA-N 6-prop-2-enoyloxyhexyl prop-2-enoate Chemical compound C=CC(=O)OCCCCCCOC(=O)C=C FIHBHSQYSYVZQE-UHFFFAOYSA-N 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 4
- HCLJOFJIQIJXHS-UHFFFAOYSA-N 2-[2-[2-(2-prop-2-enoyloxyethoxy)ethoxy]ethoxy]ethyl prop-2-enoate Chemical compound C=CC(=O)OCCOCCOCCOCCOC(=O)C=C HCLJOFJIQIJXHS-UHFFFAOYSA-N 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
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- 239000011247 coating layer Substances 0.000 description 3
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- ZDQNWDNMNKSMHI-UHFFFAOYSA-N 1-[2-(2-prop-2-enoyloxypropoxy)propoxy]propan-2-yl prop-2-enoate Chemical compound C=CC(=O)OC(C)COC(C)COCC(C)OC(=O)C=C ZDQNWDNMNKSMHI-UHFFFAOYSA-N 0.000 description 2
- FTALTLPZDVFJSS-UHFFFAOYSA-N 2-(2-ethoxyethoxy)ethyl prop-2-enoate Chemical compound CCOCCOCCOC(=O)C=C FTALTLPZDVFJSS-UHFFFAOYSA-N 0.000 description 2
- LEJBBGNFPAFPKQ-UHFFFAOYSA-N 2-(2-prop-2-enoyloxyethoxy)ethyl prop-2-enoate Chemical compound C=CC(=O)OCCOCCOC(=O)C=C LEJBBGNFPAFPKQ-UHFFFAOYSA-N 0.000 description 2
- CTJNIFYNYXUFFE-UHFFFAOYSA-N 6-prop-2-enoyloxyhexyl prop-2-enoate Chemical compound C(C=C)(=O)OCCCCCCOC(C=C)=O.C(C=C)(=O)OCCCCCCOC(C=C)=O CTJNIFYNYXUFFE-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000001723 curing Methods 0.000 description 2
- 239000003085 diluting agent Substances 0.000 description 2
- 239000002355 dual-layer Substances 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- PBOSTUDLECTMNL-UHFFFAOYSA-N lauryl acrylate Chemical compound CCCCCCCCCCCCOC(=O)C=C PBOSTUDLECTMNL-UHFFFAOYSA-N 0.000 description 2
- ZDHCZVWCTKTBRY-UHFFFAOYSA-N omega-Hydroxydodecanoic acid Natural products OCCCCCCCCCCCC(O)=O ZDHCZVWCTKTBRY-UHFFFAOYSA-N 0.000 description 2
- -1 polyethylene Polymers 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- PJAKWOZHTFWTNF-UHFFFAOYSA-N (2-nonylphenyl) prop-2-enoate Chemical class CCCCCCCCCC1=CC=CC=C1OC(=O)C=C PJAKWOZHTFWTNF-UHFFFAOYSA-N 0.000 description 1
- RIWRBSMFKVOJMN-UHFFFAOYSA-N 2-methyl-1-phenylpropan-2-ol Chemical compound CC(C)(O)CC1=CC=CC=C1 RIWRBSMFKVOJMN-UHFFFAOYSA-N 0.000 description 1
- UUEWCQRISZBELL-UHFFFAOYSA-N 3-trimethoxysilylpropane-1-thiol Chemical compound CO[Si](OC)(OC)CCCS UUEWCQRISZBELL-UHFFFAOYSA-N 0.000 description 1
- ORDRGXFSRBRQQG-UHFFFAOYSA-N 6-methylheptyl 2-sulfanylpropanoate Chemical compound CC(C)CCCCCOC(=O)C(C)S ORDRGXFSRBRQQG-UHFFFAOYSA-N 0.000 description 1
- 229920000742 Cotton Polymers 0.000 description 1
- LFOXEOLGJPJZAA-UHFFFAOYSA-N [(2,6-dimethoxybenzoyl)-(2,4,4-trimethylpentyl)phosphoryl]-(2,6-dimethoxyphenyl)methanone Chemical compound COC1=CC=CC(OC)=C1C(=O)P(=O)(CC(C)CC(C)(C)C)C(=O)C1=C(OC)C=CC=C1OC LFOXEOLGJPJZAA-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000002318 adhesion promoter Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000008199 coating composition Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- KAATUXNTWXVJKI-UHFFFAOYSA-N cypermethrin Chemical compound CC1(C)C(C=C(Cl)Cl)C1C(=O)OC(C#N)C1=CC=CC(OC=2C=CC=CC=2)=C1 KAATUXNTWXVJKI-UHFFFAOYSA-N 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 230000005670 electromagnetic radiation Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000007526 fusion splicing Methods 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000012768 molten material Substances 0.000 description 1
- 230000008447 perception Effects 0.000 description 1
- 238000000016 photochemical curing Methods 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 150000003254 radicals Chemical class 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000009897 systematic effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D4/00—Coating compositions, e.g. paints, varnishes or lacquers, based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; Coating compositions, based on monomers of macromolecular compounds of groups C09D183/00 - C09D183/16
- C09D4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09D159/00 - C09D187/00
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
- C03C25/10—Coating
- C03C25/104—Coating to obtain optical fibres
- C03C25/106—Single coatings
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
- C03C25/10—Coating
- C03C25/104—Coating to obtain optical fibres
- C03C25/1065—Multiple coatings
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
- G02B6/4401—Optical cables
- G02B6/4402—Optical cables with one single optical waveguide
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
- G02B6/4401—Optical cables
- G02B6/4429—Means specially adapted for strengthening or protecting the cables
- G02B6/443—Protective covering
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Wood Science & Technology (AREA)
- Surface Treatment Of Glass Fibres Or Filaments (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
Abstract
In accordance with the invention, an optical fiber is provided with a protective coating having enhanced thermal characteristics for easy removal from the optical fiber.
In particular, at elevated temperatures used in stripping, the delamination resistance drops to low levels substantially independent of modulus. This permits fabrication of a protectively coated fiber which has relatively high modulus and delamination resistance at room temperature but, due to its enhanced thermal characteristics, is nonetheless relatively easy to strip at elevated temperatures. Thus, for example, applicants can provide a protectively coated optical fiber or ribbon with a room temperature modulus of at least 90 psi, and a high temperature delamination resistance that is less than 40% of the room-temperature delamination resistance and preferably less than 30%.
Coatings based on a polyether backbone and non-polar monomers are preferred.
In particular, at elevated temperatures used in stripping, the delamination resistance drops to low levels substantially independent of modulus. This permits fabrication of a protectively coated fiber which has relatively high modulus and delamination resistance at room temperature but, due to its enhanced thermal characteristics, is nonetheless relatively easy to strip at elevated temperatures. Thus, for example, applicants can provide a protectively coated optical fiber or ribbon with a room temperature modulus of at least 90 psi, and a high temperature delamination resistance that is less than 40% of the room-temperature delamination resistance and preferably less than 30%.
Coatings based on a polyether backbone and non-polar monomers are preferred.
Description
Aloisio 12-15-20-7-1 COATED OPTICAL FIBER WITH INCREASED MODULUS AND
THERMALLY ENHANCED STRIPPABILITY
Technical Field This invention relates generally to a protective coating for an optical fiber, and more particularly to a coating of increased modulus and enhanced thermal characteristics for easy removal from the optical fiber.
Background Of The Invention In the manufacture of optical fiber, a glass preform rod is suspended vertically and moved into a furnace at a controlled rate. The preform softens in the furnace and a glass 1 o fiber (also referred to as an optical fiber) is drawn freely from the molten end of the preform rod by a capstan located at the base of a draw tower. Because the surface of the glass fiber is susceptible to damage caused by abrasion, it is necessary to coat the fiber immediately after it is drawn but before it comes into contact with any surface. Inasmuch as the application of a coating material must not damage the glass surface, the coating t 5 material is applied in a liquid state. Once applied, the coating material must solidify before the glass fiber reaches the capstan. This is typically accomplished within a brief time interval by photocuring -- a process in which the liquid coating material is converted to a solid upon exposure to electromagnetic radiation, preferably ultraviolet (UV) light.
Because the fibers are thin and flexible, they are readily bent when subjected to 2o mechanical stresses such as those encountered during handling or exposure to varying temperature environments. Such bends in the fiber frequently result in optical loss that is much greater than the intrinsic loss of the fiber itself, and it has been found desirable to protect the glass fiber against such bending. Accordingly, the coating material is required to cushion the glass fiber against bends and two layers of coating materials are typically 25 applied to the drawn optical fiber. An inner (primary) coating, having a relatively low in 2 Aloisio 12-15-20-7-l situ equilibrium modulus, is applied directly to the glass fiber. The in situ modulus of the primary coating is the equilibrium modulus of the coating measured on the fiber. An outer (secondary) coating, having a relatively high modulus, surrounds the primary coating. Together, these coatings protect the inherently high tensile strength of the glass fiber as long as the primary coating remains bonded to the glass.
The interfacial bond between the fiber and the primary coating desirably is strong to prevent bond failure during fiber manufacturing and subsequent handling.
Such failure can result in the formation of a "delamination" area which can adversely affect the optical performance of the fiber. A delaminated area is characterized by a gap at the interface of 1 o the fiber and the primary coating. The gap alters the mechanical properties at the point of delamination and may cause fiber transmission losses. Even if the optical performance is substantially not affected, the delamination can result in negative customer perception and is therefore unacceptable. Thus, the fiber/primary coating bond desirably should be robust.
Delamination resistance at a given temperature is typically determined by supporting the coated fiber under tension on a support member and driving a cylindrical steel member with a known load against the fiber. After impact, the fiber is observed for delamination, and the test is repeated at another position on the fiber. The load for which 50% of the impacted areas delaminate is referred to as the delamination resistance ("DR50") of the coated fiber. Further details concerning the measurement of delamination resistance are set forth in United States Patent No. 5,908,484 issued to R.L.
Decker et al. on June 1, 1999 and entitled "Method of Making A Coated Optical Fiber Comprising Measuring The Delamination Resistance of the Coating", which is incorporated herein by reference.
In what appears to be a requirement contradictory to delamination resistance, it is ' also desirable to be able to easily strip the primary coating from the glass fiber --particularly when a number of fibers are bonded together in an array such as shown in Aloisio 12-15-20-7-1 United States Patent 4,900,126. Such an array is frequently referred to as a "ribbon."
Indeed, if the coating materials cannot be cleanly and easily stripped, then splicing and interconnecting operations will be seriously hampered.
It is generally believed that the delamination resistance of a coated fiber (and its resistance to stripping) are proportional to the in situ modulus of the primary coating (hereinafter "modulus"). As a consequence, the choice of modulus level has not been to ' provide maximum protection to the fiber but rather has been constrained to the relatively lower levels associated with easy stripping.
Summary Of The Invention I o In accordance with the invention, an optical fiber is provided with a protective coating having enhanced thermal characteristics for easy removal from the optical fiber.
In particular, at elevated temperatures used in stripping, the delamination resistance drops to low levels substantially independent of modulus. This permits fabrication of a protectively coated fiber which has relatively high modulus and delamination resistance at room temperature but, due to its enhanced thermal characteristics, is nonetheless relatively easy to strip at elevated temperatures. Thus, for example, applicants can provide a protectively coated optical fiber or ribbon with a room temperature modulus of at least 90 psi, and a high temperature delamination resistance that is less than 40% of the room-temperature delamination resistance and preferably less than 30%.
Coatings based on a polyether backbone and non-polar monomers are preferred.
Brief Description Of The Drawings The invention and its mode of operation will be more clearly understood from the following detailed description when read with the appended drawing in which:
FIG. 1 is an end view, in cross section, of an optical fiber that includes a coating system in accordance with the present invention;
Aloisio 12-15-20-7-1 FIG. 2 is a perspective view of an optical fiber ribbon showing a group of coated glass fibers bonded together with a matrix material;
FIG. 3A-3C illustrate the use of a ribbon-stripping tool showing three progressive stages in the removal of matrix and coating materials from a group of glass fibers;
FIG. 4A-4C illustrate various outcomes of the ribbon-stripping procedure;
FIG. 5 discloses a cable having a number of optical fiber ribbons.
Detailed Description This description is divided into three parts: Part I describes the experimental results leading to the invention; Part II describes typical fiber products to which the l0 invention is applied; and Part III describes specific examples of coated fibers in accordance with the invention.
I. The Experimental Basis For the Invention Applicants have investigated the mechanics of fiber stripping using a delaminator similar to the aforementioned Decker et al. patent. The delaminator presses a weighted 6 mm diameter steel rod against a coated fiber, and the operator observes through a microscope the formation of voids between the glass fiber and the primary coating in response to the applied force. The applied weight at which void formation is seen in half the samples is the delamination resistance ("DR50") of the coated fiber. The Decker et al. apparatus was modified by adding a heater and a video camera so that applicants could observe real-time delamination mechanics at elevated temperature.
Using this apparatus, applicants studied how the delamination resistance (DR) changes as the modulus is changed. It was previously believed that at room temperature ' the DR always increases monotonically and approximately linearly as the modulus increases. But contrary to this conventional belief, they discovered a series of coatings Aloisio 12-15-20-7-1 wherein the DR goes down with increasing modulus, goes through a minimum at about 90 psi and then goes up. They further found different behavior for this series at elevated temperatures. There the DR goes down as the modulus increases and eventually tapers off to a low level value. At all points, the high-temperature DR versus modulus curve 5 lies below the room-temperature curve.
In view of these thermal characteristics, applicants recognized that at values of the ' modulus that lie above the minimum in the room-temperature curve, a coated fiber will exhibit a disproportionate reduction in delamination resistance when heated to elevated temperature, e.g. 140° C. Thus one can use coatings having high values of room _ to temperature modulus and delamination resistance that have heretofor been avoided s because presumed difficulty in stripping. The disproportionate reduction in delamination resistance at elevated temperatures avoids this difficulty. The modulus of the primary coating should be kept below about 500 psi in order to avoid excessive microbending losses.
Thus applicants have discovered coated fibers in which the primary coating has a modulus that lies above a first threshold. At room temperature, the fiber has a delamination resistance that lies above a second threshold. And at elevated temperature the delamination resistance drops below a third threshold significantly below the second.
Reductions of 61 % to 86% have been observed.
2o II. Typical Fiber Structures To Which the Invention Applies FIG. 1 shows an end view, in cross section, of a coated optical fiber 10 comprising a glass fiber 12 surrounded by a protective coating system comprising layers 14, 15. It is well known to draw glassy optical fiber from a specially prepared, cylindrical preform which has been locally and symmetrically heated to a temperature of about 2000°C. As the preform is fed into and through a furnace, glass fiber 12 is drawn from the molten material. A protective coating system is applied to the glass fiber 12 Aloisio 12-15-20-7-t after it has been drawn from the preform that preferably comprises two layers of radiation-cured polymeric materials. An inner layer 14 contacts the glass fiber 12 at a glass-coating interface 13 and is referred to as a primary coating material.
An outer layer 15, which is referred to as a secondary coating material, surrounds the inner layer. One method of applying dual layers of coating materials to a moving glass fiber is disclosed in US Patent 4,474,830 which issued on Oct. 2, 1984 to C. R. Taylor. Another method for applying dual layers of coating materials onto glass fiber is disclosed in US
Patent 4,851,165, which issued on July 25, 1989 to J. A. Rennell and C. R. Taylor. By way of illustration, the typical diameter of glass fiber 12 is about 125 micrometers, while the 1 o diameter of its core 11 is generally less than 10 micrometers for single mode fibers.
(Core 11 is the region where light is substantially confined during its propagation along the glass fiber's longitudinal axis by the refractive index profile of the glass fiber.) And finally, each layer of coating material has a thickness of about 30 micrometers so that the overall diameter of coated fiber 10 is approximately 250 micrometers.
t 5 Coating Materials Coating materials not only protect the glass fiber from abrasion and cushion it against microbending loss, but they also help preserve its tensile strength.
However, in order to preserve tensile strength, the primary coating material must stay bonded to the glass -- at least until it is stripped off, and then it is desirable that it be fully removable 2o without leaving a residue on the glass. More specifically, the interface between the primary coating material and the glass fiber must be characterized by suitable strength to prevent delamination and must be such that the coating system can be easily stripped from the optical fiber without tenacious residues being left on the fiber surface. On the other hand, the surface of the secondary coating material must be such that tacking does 25 not occur between adjacent convolutions of the fiber, resulting in a jerky payoff from a process spool.
Aloisio.12-15-20-7- t Coating materials typically comprise urethane-acrylate liquids whose molecules become crosslinked when exposed to ultraviolet light. Various additives are also present that enhance one or more properties of the coating. For example, photoinitiators are added to accelerate the curing process which is important because coated optical fiber is wrapped around spools for storage as soon as it is cured, and manufacturing speed is critical to profitability. Curing is the conversion of the liquid coating material into a solid. In the present system this process is known as free-radical cure wherein, upon absorption of light, the photoinitiator components cleave to form free radical pairs, which diffuse away from each other and react with acrylate-terminated components to initiate a 1 o chain polymerization process. In addition to photoinitiators, coating materials further include diluents, antioxidants, adhesion promoters and, in some cases, additives to improve strippability. However, before addressing strippability, it is important to first discuss the composition of the primary coating material which makes contact with the glass surface, and whose properties are the subject of the present invention.
t 5 Referring now to FIG. 2, there is shown a perspective view of an optical fiber ribbon 20 showing a group of coated glass fibers 10-10 that are held together with an ultraviolet (UV)-curable matrix bonding material 21. The group of optical fibers are disposed in a coplanar parallel array, and while only four fibers are shown, such arrays typically comprise eight or more individual fibers. The equilibrium modulus of the 2o matrix material has a value less than that of the outer coating layer of the fiber but greater than the equilibrium modulus of the inner coating layer. The matrix material 21 fills the interstices, bonds together the optical fibers, and extends to the outside boundary of the ribbon. Known UV-curable matrix materials 21 comprise a resin, a diluent and a photoinitiator. More detailed information regarding bonded arrays of optical fibers is 25 available in the aforementioned US Patent 4,900,126.
Ribbon Stripping Aloisio 12-l5-20-7-I
Reference is made to FIG. 3A-3C, which illustrates use of a ribbon-stripping tool such as used by splicing technicians for mass fusion splicing. FIG. 3A shows the principal elements of the ribbon stripping tool and associated apparatus.
Ribbon 20 is placed within fiber holder 30 to facilitate handling of the fiber during the stripping process. The stripping tool comprises a holder grip 40 and a main body 50 that are used for removing the various layers that surround a bonded fiber array. Lid 53 is closed during the stripping operation and includes an inner surface 54 which cooperates with a heated platen 51 to frictionally hold the outside jacket material surrounding the glass fibers within ribbon 20.
to Referring first to FIG. 3A, fiber holder 30 is shown in its closed position around ribbon 20 which is about to be inserted into the ribbon-stripping tool. The portion of ribbon 20 which is to have its coating layers removed extends beyond the forward end of the fiber holder so that it can be captured between platen 51 and the inside surface 54 of lid 53 when the lid is closed onto the main body 50. Upon closure, opposing blades 55, 56 are positioned to cut partially into opposite sides of ribbon 20 so that a well-defined break in the coating material can be made. The particular tool used is electrically heated from an AC power source, which is converted to 12 volts DC for use by a heater element within the main body 50. Holder grip 40 is adapted to capture fiber holder 30 therein when its lid 43 is closed.
2o FIG. 3B illustrates the movement of holder grip 40 away from the main body of the ribbon-stripping tool. Guide rails 45-45 allow the holder grip to slide into engagement with the main body in a controlled manner. A heater (not shown) within the main body raises the temperature of platen 51 to a predetermined level which weakens/breaks the adhesive bond at the interface 13 between primary coating 14 and glass fiber 12 (see FIG. 1 or 2) of the various coated fibers. Illustratively, a temperature of 100-200°C for about 10 seconds provides acceptable results. Once the bond is weakened/broken the rest of the operation involves sliding the primary coating along the Aloisio 12-15-20-7-1 glass fiber surface. The ability of the primary coating to slide will depend on it sliding friction with the glass fiber. This action will determine how easily the composite (matrix 21 and coatings 14, 15) can be removed and the amount of residue that remains on the bare glass fibers.
Finally, FIG. 3C shows end results of the ribbon stripping process in which glass fibers 12-12 protrude from ribbon 20 which is still held within the fiber holder 30. And ' matrix material 21, which has just been stripped away, remains on the heated platen 51 of the main body 50. Having stripped the matrix and coating materials away from the glass fibers 12-12, FIG. 4A-4C are used for illustrating the various possible results of the 1 o stripping process and for discussing their acceptability. For example, FIG. 4A shows an ideal condition wherein the matrix 21 and coating materials 14, 15 are fully removed from the glass fibers 12-12. Such results are frequently possible with the present invention although the presence of some residues 16-16, as shown in FIG. 4B, is less desirable but acceptable provided they can be removed by gentle wiping with an alcohol-moistened cotton swab. However, FIG. 4C illustrates an unacceptable condition in which the coating materials have clung to the glass fibers so tenaciously that either breakage occurs or large patches remain that cannot be easily removed.
Bonded arrays of optical fibers, as discussed above, are commercially available.
Each ribbon comprises twelve fibers, and as many as twelve ribbons are stacked together 2o for high density. The ribbon stack is surrounded by a core tube that may also contain a filler that prevents the incursion of water in outside plant applications.
FIG. 5 provides greater detail regarding the construction of a practical cable according to the present invention. Optical cable 60 includes ribbons 20 as discussed above. These ribbons are disposed within a tubular member 61, which is made from a dielectric material such as polyvinyl chloride or polyethylene, for example. Surrounding tubular member 61 is a , water -absorbing tape 63, a corrugated metallic shield 64, and plastic jacket 66. A ripcord 62 made of I~evlar~ plastic, facilitates sheath removal, and jacket 66 of polyethylene Aloisio 12-15-20-7-1 material, for example, encloses strength members 65-65. Strength members are used to eliminate or reduce stresses that might otherwise be applied to the optical fibers during handling or normal service, and may be included within the cable 60 in any number of known ways. Typically, a filling material is disposed within the tubular member 61 that 5 serves to cushion the fibers contained therein, thereby protecting against microbending loss. Greater detail regarding the construction of cable 60 and suitable filling materials are disclosed in US Patent 4,844,575, which is hereby incorporated by reference.
III. Illustrative Embodiments In illustrative embodiments of the invention the primary coating comprises an to oligomer based on a polyether backbone. The polyether backbone is advantageously end-capped with acrylate groups via urethane linkages.
EXAMPLES
The following examples present commercial fibers used as controls and a series of coated fibers exhibiting the advantageous characteristics of the invention.
Example 1. A commercial fiber (we shall call it "control") having a modulus of about 75 psi sometimes displays delaminations after routine handling. The resistance to delamination determined with the method described in this application is DR50 = 218g.
The stripping performance of this fiber is acceptable but not very good.
Coating residues remain on the fiber after stripping, and it is necessary to wipe them off, with the potential of damaging the fiber. The stripping behavior at high temperature has been observed under the microscope, and it can be seen that as the fiber is stripped, the coating seems to delaminate and heal immediately. The coating does not tube-off easily, and sometimes the fiber buckles. The delamination resistance measured at 140°C is DR50 = 171 g.
Example 2. A commercial fiber from a different supplier having a modulus of about 105 psi also shows occasional delaminations after routine handling. Different lots of this 11 Aloisio 12-15-20-7-1 fiber show DR50 values ranging from 200 to 270 g. This fiber strips very well.
The process is easy and no residues are left behind. Microscopic examination of the stripping process at high temperature reveals that the coating separates from the glass as soon as the fiber is clamped down in the stripping tool, and as stripping takes place delaminations can be seen propagating through the fibers. The delamination resistance measured at 140°C is DR50 = 139 g.
These two experiments reveal that there is both a qualitative and quantitative correlation between strippability and delamination resistance at high temperature. The fiber that strips easily (Example 2) has a relatively low delamination resistance at high temperature to (DR50 = 139g), and the microscopic observations demonstrate that delamination is associated with a clean stripping process. The fiber that does not strip so easily (Example 1 ) has a higher resistance to delamination at high temperature (DR50 = 171 g).
Example 3. Several UV-curable primary coating formulations based on either a polyester or a polyether urethane acrylate oligomer were prepared by blending the oligomer with acrylate monomers, photoinitator, and some additives as shown in the table below. The components of the formulations were varied in a systematic way to provide coatings with different elastic moduli and with different degrees of covalent coupling to the glass fiber.
In addition, the monomers employed with the polyester oligomer were relatively polar, while the monomers used with the polyether oligomer were relatively non-polar.
The 2o blends were prepared simply by weighing the appropriate amount of ingredients and mixing them with a mechanical stirrer. The blends were then filtered through 1.2 micrometer filters. The viscosity of each of these formulations was between 6,000 and 7,000 cP at 23°C.
The materials used and the resulting compositions are set forth below:
MATERIALS USED:
12 Aloisio .12-15-20-7-1 IOMP Isooctyl mercaptopropionate (Hampshire Chemical Corp., Lexington, MA) MPTMS Mercaptopropyl trimethoxysilane (United Chemical Technologies) CN934 CN934 oligomer from Sartomer (POLYETHER) CN966R60 CN966R60 oligomer from Sartomer (POLYESTER) HDDA 1,6- Hexanediol diacrylate (Sartomer SR 238) LA Lauryl acrylate (Sartomer SR 335) ENPA Ethoxylated nonyl phenol acrylate (SARTOMER
SR 504) DEGDA Diethyleneglycol diacrylate (Sartomer SR 230) to EEEA 2-(2-ethoxyethoxy) ethyl acrylate (Sartomer SR 256) PETA Pentaerythritol triacrylate (Sartomer SR 444) TEGDA Tetraethyleneglycol diacrylate (Sartomer SR 268) TPGDA Tripropylene glycol diacrylate (Sartomer SR 306) I-1700 Irgacure 1700 photoinitatior (Ciba Specialty Chemicals) t 5 COMPOSITIONS:
Material Wt. Fraction CN966R60 79.33 PETA 7.05 2o EEEA 6.81 TEGDA 2.89 IOMP 1.96 I-1700 1.96 13 Aloisio 12-15-20-7-1 Material wt. fraction CN966R60 79.33 PETA 7.05 DEGDA 5.00 TEGDA 2.89 MPTMS 1.96 I-1700 1.96 EEEA 1.81 to HP-411-NLY
Material wt. fraction LA S
~ 5 IOMP 2 2o Material wt. fraction Material wt. fraction 14 Aloisio 12-15-20-7-I
Material wt. fraction t o ENPA 21 Material wt. fraction CN966R60 79.33 PETA 7.05 2o EEEA 6.81 TEGDA 2.89 MPTMS 1.96 I-1700 1.96 Material wt. fraction r CN966R60 79.33 PETA 7.05 IS Aloisio 12-15-20-7-1 DEGDA 5.00 TEGDA 2.89 IOMP 1.96 I-1700 1.96 EEEA 1.81 Material wt. fraction t o ENPA 21 LA 2.5 HDDA 2.5 Material wt. fraction CN966R60 79.33 PETA 7.05 EEEA 4.31 TEGDA 2.89 DEGDA 2.5 IOMP 0.98 MPTMS 0.98 I-1700 1.96 16 Aloisio 12-15-20-7-1 Example 4. Two secondary UV-curable formulations were were designed to provide two different glass transition temperatures. The formulations were prepared simply by weighing the appropriate amount of ingredients and mixing them with a mechanical s stirrer. The blends were then filtered through 1.2 micrometer filters. The viscosity of each of these formulations was between 6,000 and 7,000 cP at 23°C.
MATERIALS:
HDDA 1,6- Hexanediol diacrylate (Sartomer SR 238) CN983B88 CN983 B88 Sartomer Oligomer to CN970A60 CN970A60 Sartomer Oligomer TPGDA Tripropylene glycol diacrylate (Sartomer SR 306) D-1173 Darocur 1173 (Ciba Specialty Chemicals) COMPOSITIONS:
HS-L
15 Material wt. fraction CN970A60 80.58 TPGDA 16.50 D-1173 2.91 2o HS-H
Material wt. fraction CN983 B88 83.5 HDDA 13.59 D-1173 2.91 25 Example 5. Glass optical fibers were drawn and coated using several primary/secondary coating combinations. The fibers were drawn in a standard production draw tower 1~ Aloisio 12-15-20-7-1 facility. The two coatings were applied onto the fiber using a dual-coating die, and both coatings were cured simultaneously with high intensity UV lamps. The delamination resistance of these fibers at room temperature and at 140°C was measured. These results, along with the measured in-situ modulus (IM) and pull-out force (PO) are shown in the table below.
Primary/SecondaryDelam at Delam at 140C IM (psi) PO
22C (lbs) ' HP 600-NHY/HS-H 656 92 169 2.3 HP 600-NHY/HS-L 470 98 175 2.66 HP 411-NLY/HS-L 428 128 137 2.21 HP 512-NHN/HS-L 433 106 147 2.37 HP 1300-NMM/HS-L495 125 2.27 CONTROL 218 168 75 2.31 HP 900-PHN/HS-L 203 67 161 1.71 HP 900-PHN/HS-H 196 68 137 0.52 HP 210-PHY/HS-H 207 59 224 2.14 HP 210-PHY/HS-L 172 67 217 1.99 HP 800-PLY/HSL 189 66 175 1.52 HP 1400-PMM/HS-L216 157 1.78 HP 107-PLN/HS-L 203 112 1.41 These results show that an important factor affecting resistance to delamination is the chemical nature of the coating. In addition, we have found that fibers with primary coatings based on a polyether backbone and non-polar monomers (the first five fibers in t o the above table) have outstanding behavior in two respects:
Ig Aloisio 12-15-20-7-I
a. Their resistance to delamination at room temperature is much higher than that of the control, which implies they are very robust b. Their resistance to delamination at high temperature is much lower than that of the control, which correlates with good strippability.
The last seven fibers in the above table are based on primary coatings with a , polyester backbone and polar monomers. The room temperature delamination resistance of these fibers is similar to that of the control, but their delamination resistance at elevated temperatures is much lower than that of the control. Therefore these fibers should have adequate (though not outstanding) robustness, but excellent stripping t o behavior.
These trials demonstrate two useful series of coated fibers. The primary coatings comprise either a difunctional polyether urethane acrylate oligomer or a difunctional polyester urethane acrylate oligomer, in an amount between 40% and 85% by weight, and a photoindicator in an amount between 0.1 % and 10% by weight. In addition the coatings comprise one or more of the following: 1 ) a monofunctional acrylate monomer with at least one aromatic moiety (typically less than 40% by weight), 2) a monofunctional aliphatic acrylate monomer (typically less than 10% by weight), or 3) a difunctional aliphatic acrylate monomer (typically less than 10% by weight).
The coatings can also advantageously include a trifunctional acrylate monomer (typically less than 10% by weight), an alkoxysilane coupling agent (0-5%) and a mercapton chain transfer agent (0-S%).
It is to be understood that the above-described embodiments are illustrative of only a few of the many possible specific embodiments which can represent applications of the principles of the invention. Numerous and varied other arrangements can be readily devised by those skilled in the art without departing from the spirit and scope of the invention.
THERMALLY ENHANCED STRIPPABILITY
Technical Field This invention relates generally to a protective coating for an optical fiber, and more particularly to a coating of increased modulus and enhanced thermal characteristics for easy removal from the optical fiber.
Background Of The Invention In the manufacture of optical fiber, a glass preform rod is suspended vertically and moved into a furnace at a controlled rate. The preform softens in the furnace and a glass 1 o fiber (also referred to as an optical fiber) is drawn freely from the molten end of the preform rod by a capstan located at the base of a draw tower. Because the surface of the glass fiber is susceptible to damage caused by abrasion, it is necessary to coat the fiber immediately after it is drawn but before it comes into contact with any surface. Inasmuch as the application of a coating material must not damage the glass surface, the coating t 5 material is applied in a liquid state. Once applied, the coating material must solidify before the glass fiber reaches the capstan. This is typically accomplished within a brief time interval by photocuring -- a process in which the liquid coating material is converted to a solid upon exposure to electromagnetic radiation, preferably ultraviolet (UV) light.
Because the fibers are thin and flexible, they are readily bent when subjected to 2o mechanical stresses such as those encountered during handling or exposure to varying temperature environments. Such bends in the fiber frequently result in optical loss that is much greater than the intrinsic loss of the fiber itself, and it has been found desirable to protect the glass fiber against such bending. Accordingly, the coating material is required to cushion the glass fiber against bends and two layers of coating materials are typically 25 applied to the drawn optical fiber. An inner (primary) coating, having a relatively low in 2 Aloisio 12-15-20-7-l situ equilibrium modulus, is applied directly to the glass fiber. The in situ modulus of the primary coating is the equilibrium modulus of the coating measured on the fiber. An outer (secondary) coating, having a relatively high modulus, surrounds the primary coating. Together, these coatings protect the inherently high tensile strength of the glass fiber as long as the primary coating remains bonded to the glass.
The interfacial bond between the fiber and the primary coating desirably is strong to prevent bond failure during fiber manufacturing and subsequent handling.
Such failure can result in the formation of a "delamination" area which can adversely affect the optical performance of the fiber. A delaminated area is characterized by a gap at the interface of 1 o the fiber and the primary coating. The gap alters the mechanical properties at the point of delamination and may cause fiber transmission losses. Even if the optical performance is substantially not affected, the delamination can result in negative customer perception and is therefore unacceptable. Thus, the fiber/primary coating bond desirably should be robust.
Delamination resistance at a given temperature is typically determined by supporting the coated fiber under tension on a support member and driving a cylindrical steel member with a known load against the fiber. After impact, the fiber is observed for delamination, and the test is repeated at another position on the fiber. The load for which 50% of the impacted areas delaminate is referred to as the delamination resistance ("DR50") of the coated fiber. Further details concerning the measurement of delamination resistance are set forth in United States Patent No. 5,908,484 issued to R.L.
Decker et al. on June 1, 1999 and entitled "Method of Making A Coated Optical Fiber Comprising Measuring The Delamination Resistance of the Coating", which is incorporated herein by reference.
In what appears to be a requirement contradictory to delamination resistance, it is ' also desirable to be able to easily strip the primary coating from the glass fiber --particularly when a number of fibers are bonded together in an array such as shown in Aloisio 12-15-20-7-1 United States Patent 4,900,126. Such an array is frequently referred to as a "ribbon."
Indeed, if the coating materials cannot be cleanly and easily stripped, then splicing and interconnecting operations will be seriously hampered.
It is generally believed that the delamination resistance of a coated fiber (and its resistance to stripping) are proportional to the in situ modulus of the primary coating (hereinafter "modulus"). As a consequence, the choice of modulus level has not been to ' provide maximum protection to the fiber but rather has been constrained to the relatively lower levels associated with easy stripping.
Summary Of The Invention I o In accordance with the invention, an optical fiber is provided with a protective coating having enhanced thermal characteristics for easy removal from the optical fiber.
In particular, at elevated temperatures used in stripping, the delamination resistance drops to low levels substantially independent of modulus. This permits fabrication of a protectively coated fiber which has relatively high modulus and delamination resistance at room temperature but, due to its enhanced thermal characteristics, is nonetheless relatively easy to strip at elevated temperatures. Thus, for example, applicants can provide a protectively coated optical fiber or ribbon with a room temperature modulus of at least 90 psi, and a high temperature delamination resistance that is less than 40% of the room-temperature delamination resistance and preferably less than 30%.
Coatings based on a polyether backbone and non-polar monomers are preferred.
Brief Description Of The Drawings The invention and its mode of operation will be more clearly understood from the following detailed description when read with the appended drawing in which:
FIG. 1 is an end view, in cross section, of an optical fiber that includes a coating system in accordance with the present invention;
Aloisio 12-15-20-7-1 FIG. 2 is a perspective view of an optical fiber ribbon showing a group of coated glass fibers bonded together with a matrix material;
FIG. 3A-3C illustrate the use of a ribbon-stripping tool showing three progressive stages in the removal of matrix and coating materials from a group of glass fibers;
FIG. 4A-4C illustrate various outcomes of the ribbon-stripping procedure;
FIG. 5 discloses a cable having a number of optical fiber ribbons.
Detailed Description This description is divided into three parts: Part I describes the experimental results leading to the invention; Part II describes typical fiber products to which the l0 invention is applied; and Part III describes specific examples of coated fibers in accordance with the invention.
I. The Experimental Basis For the Invention Applicants have investigated the mechanics of fiber stripping using a delaminator similar to the aforementioned Decker et al. patent. The delaminator presses a weighted 6 mm diameter steel rod against a coated fiber, and the operator observes through a microscope the formation of voids between the glass fiber and the primary coating in response to the applied force. The applied weight at which void formation is seen in half the samples is the delamination resistance ("DR50") of the coated fiber. The Decker et al. apparatus was modified by adding a heater and a video camera so that applicants could observe real-time delamination mechanics at elevated temperature.
Using this apparatus, applicants studied how the delamination resistance (DR) changes as the modulus is changed. It was previously believed that at room temperature ' the DR always increases monotonically and approximately linearly as the modulus increases. But contrary to this conventional belief, they discovered a series of coatings Aloisio 12-15-20-7-1 wherein the DR goes down with increasing modulus, goes through a minimum at about 90 psi and then goes up. They further found different behavior for this series at elevated temperatures. There the DR goes down as the modulus increases and eventually tapers off to a low level value. At all points, the high-temperature DR versus modulus curve 5 lies below the room-temperature curve.
In view of these thermal characteristics, applicants recognized that at values of the ' modulus that lie above the minimum in the room-temperature curve, a coated fiber will exhibit a disproportionate reduction in delamination resistance when heated to elevated temperature, e.g. 140° C. Thus one can use coatings having high values of room _ to temperature modulus and delamination resistance that have heretofor been avoided s because presumed difficulty in stripping. The disproportionate reduction in delamination resistance at elevated temperatures avoids this difficulty. The modulus of the primary coating should be kept below about 500 psi in order to avoid excessive microbending losses.
Thus applicants have discovered coated fibers in which the primary coating has a modulus that lies above a first threshold. At room temperature, the fiber has a delamination resistance that lies above a second threshold. And at elevated temperature the delamination resistance drops below a third threshold significantly below the second.
Reductions of 61 % to 86% have been observed.
2o II. Typical Fiber Structures To Which the Invention Applies FIG. 1 shows an end view, in cross section, of a coated optical fiber 10 comprising a glass fiber 12 surrounded by a protective coating system comprising layers 14, 15. It is well known to draw glassy optical fiber from a specially prepared, cylindrical preform which has been locally and symmetrically heated to a temperature of about 2000°C. As the preform is fed into and through a furnace, glass fiber 12 is drawn from the molten material. A protective coating system is applied to the glass fiber 12 Aloisio 12-15-20-7-t after it has been drawn from the preform that preferably comprises two layers of radiation-cured polymeric materials. An inner layer 14 contacts the glass fiber 12 at a glass-coating interface 13 and is referred to as a primary coating material.
An outer layer 15, which is referred to as a secondary coating material, surrounds the inner layer. One method of applying dual layers of coating materials to a moving glass fiber is disclosed in US Patent 4,474,830 which issued on Oct. 2, 1984 to C. R. Taylor. Another method for applying dual layers of coating materials onto glass fiber is disclosed in US
Patent 4,851,165, which issued on July 25, 1989 to J. A. Rennell and C. R. Taylor. By way of illustration, the typical diameter of glass fiber 12 is about 125 micrometers, while the 1 o diameter of its core 11 is generally less than 10 micrometers for single mode fibers.
(Core 11 is the region where light is substantially confined during its propagation along the glass fiber's longitudinal axis by the refractive index profile of the glass fiber.) And finally, each layer of coating material has a thickness of about 30 micrometers so that the overall diameter of coated fiber 10 is approximately 250 micrometers.
t 5 Coating Materials Coating materials not only protect the glass fiber from abrasion and cushion it against microbending loss, but they also help preserve its tensile strength.
However, in order to preserve tensile strength, the primary coating material must stay bonded to the glass -- at least until it is stripped off, and then it is desirable that it be fully removable 2o without leaving a residue on the glass. More specifically, the interface between the primary coating material and the glass fiber must be characterized by suitable strength to prevent delamination and must be such that the coating system can be easily stripped from the optical fiber without tenacious residues being left on the fiber surface. On the other hand, the surface of the secondary coating material must be such that tacking does 25 not occur between adjacent convolutions of the fiber, resulting in a jerky payoff from a process spool.
Aloisio.12-15-20-7- t Coating materials typically comprise urethane-acrylate liquids whose molecules become crosslinked when exposed to ultraviolet light. Various additives are also present that enhance one or more properties of the coating. For example, photoinitiators are added to accelerate the curing process which is important because coated optical fiber is wrapped around spools for storage as soon as it is cured, and manufacturing speed is critical to profitability. Curing is the conversion of the liquid coating material into a solid. In the present system this process is known as free-radical cure wherein, upon absorption of light, the photoinitiator components cleave to form free radical pairs, which diffuse away from each other and react with acrylate-terminated components to initiate a 1 o chain polymerization process. In addition to photoinitiators, coating materials further include diluents, antioxidants, adhesion promoters and, in some cases, additives to improve strippability. However, before addressing strippability, it is important to first discuss the composition of the primary coating material which makes contact with the glass surface, and whose properties are the subject of the present invention.
t 5 Referring now to FIG. 2, there is shown a perspective view of an optical fiber ribbon 20 showing a group of coated glass fibers 10-10 that are held together with an ultraviolet (UV)-curable matrix bonding material 21. The group of optical fibers are disposed in a coplanar parallel array, and while only four fibers are shown, such arrays typically comprise eight or more individual fibers. The equilibrium modulus of the 2o matrix material has a value less than that of the outer coating layer of the fiber but greater than the equilibrium modulus of the inner coating layer. The matrix material 21 fills the interstices, bonds together the optical fibers, and extends to the outside boundary of the ribbon. Known UV-curable matrix materials 21 comprise a resin, a diluent and a photoinitiator. More detailed information regarding bonded arrays of optical fibers is 25 available in the aforementioned US Patent 4,900,126.
Ribbon Stripping Aloisio 12-l5-20-7-I
Reference is made to FIG. 3A-3C, which illustrates use of a ribbon-stripping tool such as used by splicing technicians for mass fusion splicing. FIG. 3A shows the principal elements of the ribbon stripping tool and associated apparatus.
Ribbon 20 is placed within fiber holder 30 to facilitate handling of the fiber during the stripping process. The stripping tool comprises a holder grip 40 and a main body 50 that are used for removing the various layers that surround a bonded fiber array. Lid 53 is closed during the stripping operation and includes an inner surface 54 which cooperates with a heated platen 51 to frictionally hold the outside jacket material surrounding the glass fibers within ribbon 20.
to Referring first to FIG. 3A, fiber holder 30 is shown in its closed position around ribbon 20 which is about to be inserted into the ribbon-stripping tool. The portion of ribbon 20 which is to have its coating layers removed extends beyond the forward end of the fiber holder so that it can be captured between platen 51 and the inside surface 54 of lid 53 when the lid is closed onto the main body 50. Upon closure, opposing blades 55, 56 are positioned to cut partially into opposite sides of ribbon 20 so that a well-defined break in the coating material can be made. The particular tool used is electrically heated from an AC power source, which is converted to 12 volts DC for use by a heater element within the main body 50. Holder grip 40 is adapted to capture fiber holder 30 therein when its lid 43 is closed.
2o FIG. 3B illustrates the movement of holder grip 40 away from the main body of the ribbon-stripping tool. Guide rails 45-45 allow the holder grip to slide into engagement with the main body in a controlled manner. A heater (not shown) within the main body raises the temperature of platen 51 to a predetermined level which weakens/breaks the adhesive bond at the interface 13 between primary coating 14 and glass fiber 12 (see FIG. 1 or 2) of the various coated fibers. Illustratively, a temperature of 100-200°C for about 10 seconds provides acceptable results. Once the bond is weakened/broken the rest of the operation involves sliding the primary coating along the Aloisio 12-15-20-7-1 glass fiber surface. The ability of the primary coating to slide will depend on it sliding friction with the glass fiber. This action will determine how easily the composite (matrix 21 and coatings 14, 15) can be removed and the amount of residue that remains on the bare glass fibers.
Finally, FIG. 3C shows end results of the ribbon stripping process in which glass fibers 12-12 protrude from ribbon 20 which is still held within the fiber holder 30. And ' matrix material 21, which has just been stripped away, remains on the heated platen 51 of the main body 50. Having stripped the matrix and coating materials away from the glass fibers 12-12, FIG. 4A-4C are used for illustrating the various possible results of the 1 o stripping process and for discussing their acceptability. For example, FIG. 4A shows an ideal condition wherein the matrix 21 and coating materials 14, 15 are fully removed from the glass fibers 12-12. Such results are frequently possible with the present invention although the presence of some residues 16-16, as shown in FIG. 4B, is less desirable but acceptable provided they can be removed by gentle wiping with an alcohol-moistened cotton swab. However, FIG. 4C illustrates an unacceptable condition in which the coating materials have clung to the glass fibers so tenaciously that either breakage occurs or large patches remain that cannot be easily removed.
Bonded arrays of optical fibers, as discussed above, are commercially available.
Each ribbon comprises twelve fibers, and as many as twelve ribbons are stacked together 2o for high density. The ribbon stack is surrounded by a core tube that may also contain a filler that prevents the incursion of water in outside plant applications.
FIG. 5 provides greater detail regarding the construction of a practical cable according to the present invention. Optical cable 60 includes ribbons 20 as discussed above. These ribbons are disposed within a tubular member 61, which is made from a dielectric material such as polyvinyl chloride or polyethylene, for example. Surrounding tubular member 61 is a , water -absorbing tape 63, a corrugated metallic shield 64, and plastic jacket 66. A ripcord 62 made of I~evlar~ plastic, facilitates sheath removal, and jacket 66 of polyethylene Aloisio 12-15-20-7-1 material, for example, encloses strength members 65-65. Strength members are used to eliminate or reduce stresses that might otherwise be applied to the optical fibers during handling or normal service, and may be included within the cable 60 in any number of known ways. Typically, a filling material is disposed within the tubular member 61 that 5 serves to cushion the fibers contained therein, thereby protecting against microbending loss. Greater detail regarding the construction of cable 60 and suitable filling materials are disclosed in US Patent 4,844,575, which is hereby incorporated by reference.
III. Illustrative Embodiments In illustrative embodiments of the invention the primary coating comprises an to oligomer based on a polyether backbone. The polyether backbone is advantageously end-capped with acrylate groups via urethane linkages.
EXAMPLES
The following examples present commercial fibers used as controls and a series of coated fibers exhibiting the advantageous characteristics of the invention.
Example 1. A commercial fiber (we shall call it "control") having a modulus of about 75 psi sometimes displays delaminations after routine handling. The resistance to delamination determined with the method described in this application is DR50 = 218g.
The stripping performance of this fiber is acceptable but not very good.
Coating residues remain on the fiber after stripping, and it is necessary to wipe them off, with the potential of damaging the fiber. The stripping behavior at high temperature has been observed under the microscope, and it can be seen that as the fiber is stripped, the coating seems to delaminate and heal immediately. The coating does not tube-off easily, and sometimes the fiber buckles. The delamination resistance measured at 140°C is DR50 = 171 g.
Example 2. A commercial fiber from a different supplier having a modulus of about 105 psi also shows occasional delaminations after routine handling. Different lots of this 11 Aloisio 12-15-20-7-1 fiber show DR50 values ranging from 200 to 270 g. This fiber strips very well.
The process is easy and no residues are left behind. Microscopic examination of the stripping process at high temperature reveals that the coating separates from the glass as soon as the fiber is clamped down in the stripping tool, and as stripping takes place delaminations can be seen propagating through the fibers. The delamination resistance measured at 140°C is DR50 = 139 g.
These two experiments reveal that there is both a qualitative and quantitative correlation between strippability and delamination resistance at high temperature. The fiber that strips easily (Example 2) has a relatively low delamination resistance at high temperature to (DR50 = 139g), and the microscopic observations demonstrate that delamination is associated with a clean stripping process. The fiber that does not strip so easily (Example 1 ) has a higher resistance to delamination at high temperature (DR50 = 171 g).
Example 3. Several UV-curable primary coating formulations based on either a polyester or a polyether urethane acrylate oligomer were prepared by blending the oligomer with acrylate monomers, photoinitator, and some additives as shown in the table below. The components of the formulations were varied in a systematic way to provide coatings with different elastic moduli and with different degrees of covalent coupling to the glass fiber.
In addition, the monomers employed with the polyester oligomer were relatively polar, while the monomers used with the polyether oligomer were relatively non-polar.
The 2o blends were prepared simply by weighing the appropriate amount of ingredients and mixing them with a mechanical stirrer. The blends were then filtered through 1.2 micrometer filters. The viscosity of each of these formulations was between 6,000 and 7,000 cP at 23°C.
The materials used and the resulting compositions are set forth below:
MATERIALS USED:
12 Aloisio .12-15-20-7-1 IOMP Isooctyl mercaptopropionate (Hampshire Chemical Corp., Lexington, MA) MPTMS Mercaptopropyl trimethoxysilane (United Chemical Technologies) CN934 CN934 oligomer from Sartomer (POLYETHER) CN966R60 CN966R60 oligomer from Sartomer (POLYESTER) HDDA 1,6- Hexanediol diacrylate (Sartomer SR 238) LA Lauryl acrylate (Sartomer SR 335) ENPA Ethoxylated nonyl phenol acrylate (SARTOMER
SR 504) DEGDA Diethyleneglycol diacrylate (Sartomer SR 230) to EEEA 2-(2-ethoxyethoxy) ethyl acrylate (Sartomer SR 256) PETA Pentaerythritol triacrylate (Sartomer SR 444) TEGDA Tetraethyleneglycol diacrylate (Sartomer SR 268) TPGDA Tripropylene glycol diacrylate (Sartomer SR 306) I-1700 Irgacure 1700 photoinitatior (Ciba Specialty Chemicals) t 5 COMPOSITIONS:
Material Wt. Fraction CN966R60 79.33 PETA 7.05 2o EEEA 6.81 TEGDA 2.89 IOMP 1.96 I-1700 1.96 13 Aloisio 12-15-20-7-1 Material wt. fraction CN966R60 79.33 PETA 7.05 DEGDA 5.00 TEGDA 2.89 MPTMS 1.96 I-1700 1.96 EEEA 1.81 to HP-411-NLY
Material wt. fraction LA S
~ 5 IOMP 2 2o Material wt. fraction Material wt. fraction 14 Aloisio 12-15-20-7-I
Material wt. fraction t o ENPA 21 Material wt. fraction CN966R60 79.33 PETA 7.05 2o EEEA 6.81 TEGDA 2.89 MPTMS 1.96 I-1700 1.96 Material wt. fraction r CN966R60 79.33 PETA 7.05 IS Aloisio 12-15-20-7-1 DEGDA 5.00 TEGDA 2.89 IOMP 1.96 I-1700 1.96 EEEA 1.81 Material wt. fraction t o ENPA 21 LA 2.5 HDDA 2.5 Material wt. fraction CN966R60 79.33 PETA 7.05 EEEA 4.31 TEGDA 2.89 DEGDA 2.5 IOMP 0.98 MPTMS 0.98 I-1700 1.96 16 Aloisio 12-15-20-7-1 Example 4. Two secondary UV-curable formulations were were designed to provide two different glass transition temperatures. The formulations were prepared simply by weighing the appropriate amount of ingredients and mixing them with a mechanical s stirrer. The blends were then filtered through 1.2 micrometer filters. The viscosity of each of these formulations was between 6,000 and 7,000 cP at 23°C.
MATERIALS:
HDDA 1,6- Hexanediol diacrylate (Sartomer SR 238) CN983B88 CN983 B88 Sartomer Oligomer to CN970A60 CN970A60 Sartomer Oligomer TPGDA Tripropylene glycol diacrylate (Sartomer SR 306) D-1173 Darocur 1173 (Ciba Specialty Chemicals) COMPOSITIONS:
HS-L
15 Material wt. fraction CN970A60 80.58 TPGDA 16.50 D-1173 2.91 2o HS-H
Material wt. fraction CN983 B88 83.5 HDDA 13.59 D-1173 2.91 25 Example 5. Glass optical fibers were drawn and coated using several primary/secondary coating combinations. The fibers were drawn in a standard production draw tower 1~ Aloisio 12-15-20-7-1 facility. The two coatings were applied onto the fiber using a dual-coating die, and both coatings were cured simultaneously with high intensity UV lamps. The delamination resistance of these fibers at room temperature and at 140°C was measured. These results, along with the measured in-situ modulus (IM) and pull-out force (PO) are shown in the table below.
Primary/SecondaryDelam at Delam at 140C IM (psi) PO
22C (lbs) ' HP 600-NHY/HS-H 656 92 169 2.3 HP 600-NHY/HS-L 470 98 175 2.66 HP 411-NLY/HS-L 428 128 137 2.21 HP 512-NHN/HS-L 433 106 147 2.37 HP 1300-NMM/HS-L495 125 2.27 CONTROL 218 168 75 2.31 HP 900-PHN/HS-L 203 67 161 1.71 HP 900-PHN/HS-H 196 68 137 0.52 HP 210-PHY/HS-H 207 59 224 2.14 HP 210-PHY/HS-L 172 67 217 1.99 HP 800-PLY/HSL 189 66 175 1.52 HP 1400-PMM/HS-L216 157 1.78 HP 107-PLN/HS-L 203 112 1.41 These results show that an important factor affecting resistance to delamination is the chemical nature of the coating. In addition, we have found that fibers with primary coatings based on a polyether backbone and non-polar monomers (the first five fibers in t o the above table) have outstanding behavior in two respects:
Ig Aloisio 12-15-20-7-I
a. Their resistance to delamination at room temperature is much higher than that of the control, which implies they are very robust b. Their resistance to delamination at high temperature is much lower than that of the control, which correlates with good strippability.
The last seven fibers in the above table are based on primary coatings with a , polyester backbone and polar monomers. The room temperature delamination resistance of these fibers is similar to that of the control, but their delamination resistance at elevated temperatures is much lower than that of the control. Therefore these fibers should have adequate (though not outstanding) robustness, but excellent stripping t o behavior.
These trials demonstrate two useful series of coated fibers. The primary coatings comprise either a difunctional polyether urethane acrylate oligomer or a difunctional polyester urethane acrylate oligomer, in an amount between 40% and 85% by weight, and a photoindicator in an amount between 0.1 % and 10% by weight. In addition the coatings comprise one or more of the following: 1 ) a monofunctional acrylate monomer with at least one aromatic moiety (typically less than 40% by weight), 2) a monofunctional aliphatic acrylate monomer (typically less than 10% by weight), or 3) a difunctional aliphatic acrylate monomer (typically less than 10% by weight).
The coatings can also advantageously include a trifunctional acrylate monomer (typically less than 10% by weight), an alkoxysilane coupling agent (0-5%) and a mercapton chain transfer agent (0-S%).
It is to be understood that the above-described embodiments are illustrative of only a few of the many possible specific embodiments which can represent applications of the principles of the invention. Numerous and varied other arrangements can be readily devised by those skilled in the art without departing from the spirit and scope of the invention.
Claims (16)
1. An optical fiber coated with a radiation-cured primary coating of polymeric material, the optical fiber comprising an elongated strand of glass that is adapted to guide lightwaves along its length, the primary coating of polymeric material being CHARACTERIZED BY
an in situ modulus that resides within the range: 90 to 500 psi at 20°
C;
a first delamination resistance at 20° C; and a second delamination resistance at a temperature in the range 100-200°C which is less than 40% of the first delamination resistance.
an in situ modulus that resides within the range: 90 to 500 psi at 20°
C;
a first delamination resistance at 20° C; and a second delamination resistance at a temperature in the range 100-200°C which is less than 40% of the first delamination resistance.
2. The optical fiber of claim 1 wherein the first delamination resistance is greater than 180 grams.
3. The optical fiber of claim 1 wherein the first delamination resistance is greater than 400 grams.
4. The optical fiber of claim 1 wherein the second delamination resistance is less than 130 grams.
5. The optical fiber of claim 1 wherein the second delamination resistance is less than 30% of the first.
6. The optical fiber of claim 1 wherein the primary coating material comprises a polyether oligomer, one or more monomers, and a photoinitiator.
7. The optical fiber of claim 1 wherein the primary coating material comprises an oligomer based on a polyether backbone that is end-capped with acrylate groups via urethane linkages.
20~
20~
8. The optical fiber of claim 1 further including a secondary layer of coating material that surrounds the primary layer of coating material, the secondary layer having a substantially higher equilibrium modulus than the primary coating material.
9. The optical fiber of claim 1 wherein a plurality of said fibers are disposed in a longitudinal array with longitudinal axes thereof being substantially parallel to one another, said fibers being surrounded by a matrix bonding material that fills interstices between adjacent optical fibers and extends to a periphery that envelops the array.
10. The bonded array of claim 9 wherein said bonded array is substantially flat.
11. The optical fiber of claim 1 wherein a plurality of the fibers are disposed in a core tube that extends along a longitudinal axis of a cable, the cable including: (i) a plastic jacket that encloses the core tube, and (ii) strength members having tensile stiffness for receiving loads applied to the cable.
12. The optical fiber of claim 11 wherein said fibers are positioned in a longitudinal array with longitudinal axes thereof being substantially parallel to one another, said fibers being surrounded by a matrix bonding material that fills interstices between adjacent optical fibers and extends to a periphery that envelops the array.
13. The optical fiber of claim 1 wherein the primary coating comprises:
a difunctional polyester or polyether urethane acrylate oligomer in an amount between 40% and 85% by weight;
a photoinitiator in an amount between 0.1% and 10% by weight; and one or more of the following: 1) a monofunctional acrylate monomer with at least one aromatic moiety, 2) a monofunctional aliphatic acrylate monomer, or 3) a difunctional aliphatic acrylate monomer.
a difunctional polyester or polyether urethane acrylate oligomer in an amount between 40% and 85% by weight;
a photoinitiator in an amount between 0.1% and 10% by weight; and one or more of the following: 1) a monofunctional acrylate monomer with at least one aromatic moiety, 2) a monofunctional aliphatic acrylate monomer, or 3) a difunctional aliphatic acrylate monomer.
14. The optical fiber of claim 13 further comprising a trifunctional acrylate monomer.
15. The optical fiber of claim 13 further comprising an alkoxysilane coupling agent.
16. The optical fiber of claim 13 further comprising a mercapton chain transfer agent.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US34261199A | 1999-06-29 | 1999-06-29 | |
US09/342,611 | 1999-06-29 |
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CA2312535A1 true CA2312535A1 (en) | 2000-12-29 |
Family
ID=23342546
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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CA002312535A Abandoned CA2312535A1 (en) | 1999-06-29 | 2000-06-27 | Coated optical fiber with increased modulus and thermally enhanced strippability |
Country Status (6)
Country | Link |
---|---|
US (1) | US6243523B1 (en) |
EP (1) | EP1065181A2 (en) |
JP (1) | JP2001056423A (en) |
CN (1) | CN1298647C (en) |
AU (1) | AU4252100A (en) |
CA (1) | CA2312535A1 (en) |
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AU4969697A (en) * | 1996-11-08 | 1998-06-03 | Dsm N.V. | Radiation-curable optical glass fiber coating compositions, coated optical glass fibers, and optical glass fiber assemblies |
US6428204B1 (en) * | 1999-06-29 | 2002-08-06 | Fitel Usa Corp. | Method of making a coated optical fiber comprising measuring the delamination resistance of the coating at two different temperatures |
US6453104B1 (en) * | 1999-12-28 | 2002-09-17 | Mitsubishi Rayon Co., Ltd. | Optical fiber cable and optical fiber cable with plug |
US6852169B2 (en) | 2001-05-16 | 2005-02-08 | Nordson Corporation | Apparatus and methods for processing optical fibers with a plasma |
US7211368B2 (en) * | 2003-01-07 | 2007-05-01 | 3 Birds, Inc. | Stereolithography resins and methods |
US7207732B2 (en) * | 2003-06-04 | 2007-04-24 | Corning Incorporated | Coated optical fiber and curable compositions suitable for coating optical fiber |
US6862392B2 (en) | 2003-06-04 | 2005-03-01 | Corning Incorporated | Coated optical fiber and curable compositions suitable for coating optical fiber |
US7050688B2 (en) * | 2003-07-18 | 2006-05-23 | Corning Cable Systems Llc | Fiber optic articles, assemblies, and cables having optical waveguides |
US7715675B2 (en) * | 2003-07-18 | 2010-05-11 | Corning Incorporated | Optical fiber coating system and coated optical fiber |
US20050034443A1 (en) * | 2003-08-14 | 2005-02-17 | Cook Thomas Christopher | Optical fibers twinning apparatus and process |
JP2008090040A (en) * | 2006-10-03 | 2008-04-17 | Furukawa Electric Co Ltd:The | Coated optical fiber ribbon |
KR101740536B1 (en) * | 2011-01-12 | 2017-05-26 | 동우 화인켐 주식회사 | Adhesive composition for optical use |
JP5852045B2 (en) | 2013-05-07 | 2016-02-03 | 株式会社フジクラ | Optical fiber ribbon and optical fiber cable |
KR102430818B1 (en) * | 2015-10-02 | 2022-08-11 | 삼성디스플레이 주식회사 | Composition for preparing hybrid resin, hybrid resin and hybrid resin film prepared therefrom |
US9921380B2 (en) * | 2016-03-22 | 2018-03-20 | Ofs Fitel, Llc | Composite cable |
CN107285647B (en) * | 2016-04-01 | 2020-08-28 | 中国兵器装备研究院 | Optical fiber surface processing device |
US20180127593A1 (en) | 2016-11-08 | 2018-05-10 | Corning Incorporated | Fiber coatings with low modulus and high critical stress |
US10451795B2 (en) * | 2017-11-16 | 2019-10-22 | Ofs Fitel, Llc | Optical fiber for applications requiring high system optical signal-to-noise ratio performance and low degradation from nonlinear impairments |
CN112930362B (en) * | 2018-11-09 | 2023-06-13 | 住友电气工业株式会社 | Optical fiber |
US20200224037A1 (en) | 2019-01-16 | 2020-07-16 | Corning Incorporated | Secondary coatings for optical fibers |
NL2022651B1 (en) | 2019-01-16 | 2020-08-14 | Corning Inc | Secondary coatings for optical fibers |
JPWO2022264873A1 (en) * | 2021-06-14 | 2022-12-22 |
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CN85101537B (en) * | 1985-04-01 | 1988-07-13 | 菲利浦斯光灯制造公司 | Method and equipment for manufacturing optical fibres with protective coating |
EP0854022A1 (en) * | 1997-01-15 | 1998-07-22 | Lucent Technologies Inc. | Two stage curing for optical fiber |
WO1998033081A1 (en) * | 1997-01-24 | 1998-07-30 | Borden Chemical, Inc. | Coated optical fibers having strippable primary coatings and processes for making and using same |
US5908484A (en) * | 1998-10-16 | 1999-06-01 | Lucent Technologies Inc. | Method of making a coated optical fiber comprising measuring the delamination resistance of the coating |
-
1999
- 1999-11-19 US US09/443,739 patent/US6243523B1/en not_active Expired - Lifetime
-
2000
- 2000-06-19 AU AU42521/00A patent/AU4252100A/en not_active Abandoned
- 2000-06-20 EP EP00305197A patent/EP1065181A2/en not_active Withdrawn
- 2000-06-27 CA CA002312535A patent/CA2312535A1/en not_active Abandoned
- 2000-06-28 CN CNB001193309A patent/CN1298647C/en not_active Expired - Fee Related
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CN1279217A (en) | 2001-01-10 |
EP1065181A2 (en) | 2001-01-03 |
US6243523B1 (en) | 2001-06-05 |
AU4252100A (en) | 2001-01-04 |
JP2001056423A (en) | 2001-02-27 |
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