KR20050018625A - Small Diameter High Strength Optical Fiber - Google Patents

Abstract

The coated optical fiber, preferably GGP optical fiber, provides a silica clad core comprising an optical fiber core and a silica cladding on the optical fiber core. A permanent polymer coating is formed on the silica cladding during ultraviolet irradiation of the photocurable composition containing the non-hydrolyzable photoinitiator. The coated optical fiber has a diameter of 120 microns to 160 microns and is at least 85% for dynamic fatigue measurements between 49.2 x 10 ³ kg / cm ² (700 kpsi) and 63.3 x 10 ³ kg / cm ² (900 kpsi). Have a relative frequency distribution.

Description

Small Diameter High Strength Optical Fiber

The present invention relates generally to silica optical fibers, more particularly to thin, permanently coated optical fibers having a small average diameter but comparable in strength to conventional optical fibers.

Modern communication networks have been constructed to supply and share an almost infinite amount of information. Regardless of the current capacity of the communication system, more information and communication services are required. This need could be met using additional signal carriers, ie optical fibers. Each additional carrier adds the space needed to form a connection between the optical fiber and the associated optoelectronic device. This is in opposition to the general trend for the next generation of signal carriers, which occupy less space than current systems.

The method of making optical fibers requires the preparation of a pre-form comprising a higher refractive index wave-inducing device surrounded by a lower refractive index silica cladding. The pre-form is melted by heating in a furnace and raising its temperature, and then the optical fibers are drawn from the molten pre-form. The glass fibers generally comprise one or more polymer coatings applied in line to the outer diameter, or cladding, of the optical fibers, also known as buffer coatings. Coated optical fibers, also known as GGP fibers, include permanent polymers (P-coated) applied over silica cladding prior to the application of additional buffer coatings as described above.

US Pat. Nos. 5,381,504 and US RE 36,146 disclose commonly used commercially available GGP fibers ( G lass), including doped silica cores, silica cladding and permanent polymer coatings or P-coats surrounding the cladding. It describes a glass (G lass), polymer (P olymer)). The dimension of the material layer comprising commercially available GGP fibers produces a cumulative fiber diameter of about 250 microns in which the silica core and the reduced silica cladding contribute 100 microns. Adding P-coating increases the diameter to about 125 microns. After application of two standard buffer coatings (first to provide microbend protection and second to provide wear resistance), the coated optical fibers reached a final diameter of about 250 microns. Other types of fibers called standard fibers do not include a permanent polymer layer; That is, they are non-GGP fibers. Typical non-GGP fibers comprise a silica core and cladding with a combined diameter of 125 microns, with two standard buffer coatings providing a final coated optical fiber diameter of about 250 microns. Internal or primary buffers typically have lower Shore D hardness compared to external or secondary buffers.

U.S. Patent U.S. 5,644,670 describes the formation of bare optical fibers comprising an optical fiber core, cladding and a polymer sheath. Repeated mention indicates that the exposed optical fiber preferably has a diameter of less than 128 microns and the polymer sheath has a Shore hardness of D55 or greater. Restrictions on the diameter of the exposed fiber relate to the need to match optical fiber connectors, which typically have a cross-sectional size of 125 microns. The use of a polymer coating with high shore hardness prevents damage to the cladding of the optical fibers exposed by the crimp connector. Attaching the crimp connector to the distal end of the exposed optical fiber first removes the protective primary and secondary sheaths from a wide bandwidth optical fiber cable wrapped with a jacket that the exposed optical fiber uses as a wave-guided element. Ask to do Similar protected 125 micron wave-inducing device elements are described in European patent application EP0953857 A1. In this case, the optical fiber ribbon includes a plurality of optical fibers arranged in a line. Each optical fiber comprises a core, cladding and an unpeeled thin coating made of 2 micron to 15 micron thick synthetic resin coated around the cladding. The thin, non-peeling coating provides protection for the underlying cladding and glass core during fiber connection to the fiber optic connector or planar lightwave circuit (PLC). The optical fiber ribbon includes a primary coating having a thickness up to twice the diameter of the optical fiber and a secondary coating which may be from 20 microns to 100 microns thick. U.S. 5,644,670 and EP0953857 A1 both describe the effect of the thickness of the polymer sheath or unpeeled sheath on the occurrence of damage to the cladding layer, while the crimp connector is fixed on the ends of the optical fibers from which the primary and secondary sheaths are removed therefrom. To influence. There is no information related to the overall mechanical strength of the exposed optical fibers.

In many optoelectronic devices and optical fiber containing structures, space is limited to accommodate large diameter fibers including primary and secondary coated layers as described above. This has created a need for optical fibers that can withstand finer, preferably bending around small diameters for a range of communication applications. As mentioned, communication applications represent fiber optic networks that require interconnection using standard fiber optic connectors. Standard connectors typically include 125 micron ferrules, in which optical fibers are inserted to align and securely align with another optical fiber or related optical and electronic devices. Standard coated optical fibers typically have a diameter of about 250 microns as described above. Inter-fiber connections can be made with only these fibers after removing the sheath to provide stripped fibers with a diameter small enough to be inserted into standard ferrules. Fiber damage typically occurs during the stripping process to remove the buffer coating from the optical fiber. Such damage could be prevented by the use of strong optical fibers that do not require peeling of the cushioning coating to comfortably fit into connectors with standard 125 micron ferrules. Another advantage would be that the fibers do not show signs of wear or collapse by wear or chemical attack.

P-coatings of GGP fibers typically comprise an epoxy resin that can be cationicly cured, preferably by exposure to the appropriate form of actin based irradiation. Other known cationic curable resins include alicyclic epoxy groups or vinyl ethers in their structure. The production of GGP coated optical fibers requires the application of P-coating immediately after solidification of the stretched silica clad fibers in a furnace. P-coats typically contain iodonium salts as cationic photoinitiators that interact with appropriate radiation to cure the polymer. One or more protective buffer coatings applied on the cured P-coat provide protection and wear resistance while increasing the total diameter of the GGP fiber structure to about 250 microns.

Subsequent substrates relate to other cationic photoinitiators, most of which have been used in applications independent of the production of coated optical fibers. US 5,340,898, US 5,468,902, US 5,550,265 and US 5,668,192 describe various iodonium borate and organometallic borate salts as photoinitiators. However, the patent does not mention borate anions containing photoinitiators as curing agents for polymeric materials applied to optical fibers. US Pat. No. 6,011,180 discloses organoboron photoinitiators suitable for photopolymerization of monomer compositions having acid group functionality. The photoinitiator has the formula G ⁺ (R) ₄ B ^-, and represented by, where the G ⁺ include an onium cation, especially a sulfonium cation or iodonium cation, and, (R) ₄ represents a substituted alkyl and aryl.

Several references describe photoinitiators comprising "polyborate" anions, see for example EP 775706, U.S. 5,807,905 and WO 9852952. European patent EP 834492 describes polyiodonium cation-containing photoinitiators but does not mention the application of such materials to optical fiber coating.

U.S. Patent U.S. 4,655,545 discloses glass fibers for a fiber optical transmission network. This reference describes optical fiber extrusion coated with fluorine containing resins. Fluorine containing resin coatings are known to cause a reduction in the mechanical strength of optical fibers as compared to similar optical fibers coated using resins that do not contain fluorine. The document describes the decrease in mechanical strength due to the production of fluorine gas or hydrogen fluoride during melt extrusion. According to this document, these acid gases pass through the first baked layer to reach the glass surface, weakening the glass fiber by corrosion of the glass or interference of chemical bonds between the baked extruded coating and the glass surface. U.S. Patent U.S. 5,181,269 presents the opposite finding by suggesting optical fiber strength improvements using acidic cationic photocured coatings containing hydrolyzable components such as, for example, hexafluorobisate and hexafluorophosphate anions. Although the materials and coating methods are included, the patent (U.S. 5,181,269) does not provide supporting data regarding optical fiber strength.

US Pat. No. 5,554,664 describes energy activated salts with fluorocarbon anions. This reference describes the advantages of catalysts with non-hydrolyzable anions for related coatings used in adhesives and electronics applications. Hydrolyzable anions, exemplified by hexafluorophosphate (PF ₆ ⁻ ) and hexafluoroantimonate (SbF ₆ ⁻ ) ions, react in the presence of moisture to produce corrosive hydrofluoric acid. This document describes onium salts containing methide and imide anions in other respects and provides examples of borate anion initiators.

The mechanical properties and lifespan of the coated optical fibers can be adversely affected by the inappropriate choice of photoinitiators for curing the polymer fiber coating. The above description of fluorinated photoinitiators describes the formation of hydrofluoric acid in the presence of moisture. In the presence of corrosive materials such as hydrofluoric acid, some GGP fibers show a decrease in fiber strength when placed in a high temperature / high humidity environment, as shown in the kinetic fatigue test. Unfortunately, high temperature and high humidity conditions are relatively common during the operation of vehicles, including submarines and related warships, spacecraft, aircraft and other applications that currently use or have the potential to use optical fibers and related equipment. In this case it is important to avoid corrosive substances.

In view of increasing the amount of information transmitted through a communication network using signal carriers with greater strength retention, small diameter coated optical fibers that retain their strength even after exposure to high temperatures and high humidity are Required. Small diameter coated optical fibers offer the possibility to fabricate fiber optic devices containing more signal carrier connections than current devices using fibers coated up to 250 microns in diameter.

Summary of the Invention

The present invention satisfies the need for small diameter, mechanically strong coated optical fibers utilizing silica-clads, wherein silica fibers are coated with a permanent polymer layer to reach a total diameter of 120 microns to 160 microns. Preferred embodiments of the coated optical fibers incorporate a silica clad silica core drawn to a diameter of 80 to 85 microns prior to in-tower application of at least one permanent coating that contributes to a finished optical fiber diameter of about 125 microns. Have The coated optical fiber obtained exhibits resistance to stress corrosion and surprisingly high strength as measured by standard test method FOTP-28 (kinetic fatigue). The cleavable optical fibers processed according to the present invention are easily connected without stripping with a number of standard fiber optical connectors to provide a connection in which the optical fibers are highly resistant to flexural stress. This provides a useful advantage by reducing the time required to connect the optical fiber to the appropriate connector. No stripping step also increases the reliability of the optical fiber since there is no need to expose the bare glass of the fiber for the connection. Further reliability of the coated optical fibers according to the present invention arises from polymerizing permanent polymer coatings of GGP fibers with photoinitiators that do not produce potentially corrosive byproducts. In the absence of corrosive byproducts, the coated optical fibers retain their strength even when used in applications involving exposure to high temperature and high humidity conditions.

More particularly the present invention provides GGP optical fibers that provide a silica clad core, including coated optical fibers, preferably optical fiber cores, and silica cladding on the optical fiber cores. Permanent polymer coatings are applied to silica cladding during exposure to actin-based irradiation of photocurable compositions containing non-hydrolyzable photoinitiators. The coated optical fibers have a diameter of 120 microns to 150 microns, and at least 85% for kinetic fatigue measurements between 49.2 x 10 ³ kg / cm ² (700 kpsi) and 63.3 x 10 ³ kg / cm ² (900 kpsi). Have a relative frequency distribution. The coated optical fibers according to the invention are non-inserted or otherwise not supported by materials such as primary or secondary buffers, associated coatings, encapsulants and the like.

Justice

The use of terms such as "peel" or "peel off" or "peel off" means removing the coating from the coated optical fiber. Peeling can be performed mechanically using tools similar to wire strippers or chemically by dissolving the protective coating using aggressive liquid compositions such as concentrated sulfuric acid.

The term "optical fiber core" means the central cylinder of a fiber. The signal travels downward in the fiber and is mostly compressed at the core due to the overall internal reflection.

The term "buffer" or "buffer coating" means one or more outer coatings applied to the optical fibers during the manufacturing process after stretching from the molten pre-form to the optical fibers. Typically, the formation of an optical fiber connection requires removal of the buffer before inserting the optical fiber ends into the connector.

As used herein, the term "cladding" refers to a layer of material that is typically silica around the optical fiber core. Preferably the cladding has a lower refractive index than the core to substantially limit the optical signal to the core.

The terms "polymeric coating" or "P-coating" or "protective coating" and the like refer to a coating that is strongly attached to silica, for example an optical fiber cladding, which is not easily removed. The coating presents a barrier against water vapor, dust, and other materials that mechanically or chemically attack glass optical fibers. The polymer coating also forms a strong bond with the adhesive used to secure the optical fibers to the optical fiber connectors. The expression of the polymer coating as "permanent polymer coating" relates to the fact that the optical fiber connection can be carried out without removing the P-coat. The polymer coating material preferably comprises cationic cured, non-ester containing epoxys and polyols using a diaryl iodonium methoxide initiator. Suitable compositions include mono- and multi-functional epoxys and polyols as diluents.

The term "GGP fiber" is a doped silica when viewed in cross-section (G lass) a core of silica (G lass) cladding and the at least one permanent protective polymer coating; means an optical fiber structure comprising a (P-coated). The GGP fibers according to the present invention preferably have a cross-sectional diameter of 120 microns to 160 microns, most preferably 125 microns, while maintaining a tensile strength comparable to the GGP optical fiber structure close to twice its diameter.

The terms "non-inserted" or "unsupported" and other substantially similar terms are used herein to refer to any further substances such as primary or secondary coatings, buffers, potting resins or compositions in related encapsulated forms. It means a coated optical fiber that does not require protection. Ribbon cables represent a form of fiber optic splice structure that typically contains optical fibers surrounded by a polymer encapsulant that supports and prevents damage to the encapsulated fibers.

"Kinematic fatigue" is a technique that is a tensile test up to rupture that substantially measures the stress required to rupture the optical fiber. Kinetic fatigue measurements according to the present invention use a modified EIA / TIA-455-28B standard test method that includes a strain rate of 9% per minute and a gauge length of 4 meters under ambient conditions. The test is otherwise a fiber optic test method (FOTP) entitled "Measurement of Kinetic Tensile Strength of Optical Fibers" (ie EIA / TIA-455-28B-EIA = Electronic Industries Association and TIA = Telecommunications Industry Association). It is also called 28.

The use of terms such as "consistent performance" or "consistent strength" refers to the properties of the optical fibers according to the invention when subjected to kinetic fatigue tests. Consistent performance requires that for optical fibers given the relative frequency distribution of the test results,> 85% of the plural test samples reach their burst point under tensile stress within a narrow range of values. Preferably, for the dynamic fatigue test, the coated optical fiber is 49.2 x 10 ³ kg in the range of 3.5 x 10 ³ kg / cm ² (50 kpsi) to 7.0 x 10 ³ kg / cm ² (100 kpsi). / cm ² (700 kpsi). Relative frequency distributions above 90% are preferred. Dynamic fatigue values above 95% represent the highest levels of consistent performance.

The term "coated optical fiber diameter" or related term refers to the maximum diameter distance of the outer surface of the outermost sheath around the optical fiber. The diameter may vary slightly depending on the coating precision of the coating in terms of thickness control and relative concentration to the optical fiber core.

As used herein, the term "diaryliodonium metaide" refers to a photoinitiator belonging to the class of materials commonly known as onium salts. Preferred diaryliodonium metades are bis (dodecylphenyl) iodonium tris (trifluoromethylsulfonyl) methides.

Detailed description of the preferred embodiment

The foregoing description shows that consideration has been given to the formation of optical fibers, including cores, claddings, and polymeric coatings, to maintain the diameter of the optical fiber structure at about 125 microns. This diameter was important for easy insertion of optical fiber ends to fit within 125 micron connectors such as crimp connectors. The durable polymer coating resisted penetration by the splice structure and prevented damage due to scratching, cracking, and the like of the cladding. There has been concern for protection against side pressures during the application of the connector, but no consideration has been given to the general strength properties of the optical fibers.

The present invention provides coated glass fibers as fine filaments having an outer diameter of less than 160 microns, preferably less than 130 microns, while maintaining strength properties comparable to coated optical fibers that are twice the diameter. Under the force of flexural stress, the coated optical fiber according to the present invention withstands 6 mm (0.25 inch) radius of curvature. Other beneficial properties include abrasion resistance, and insertion and attachment without peeling off to remain in the optical fiber connector. Although there is no external buffer coating to peel off, secure attachment of the fiber to the connector typically requires an adhesive.

Typical commercial GGP fiber structures have a silica core and a reduced silica cladding forming a structure of 100 micron diameter. Permanent polymer coating or P-coating of 12.5 microns thick, and two standard buffer coatings, each about 31.0 microns thick, give the GGP fiber a final diameter of about 250 microns. The first buffer coating provides microflex protection and the second buffer coating provides wear resistance. Suitable coating compositions include acrylated urethane polymers available from DSM Desotech, Elgin, IL.

The coated optical fiber structure according to the invention preferably exhibits varying strength properties in relation to the cross-sectional structure of the optical fiber having a total outer diameter of less than 160 microns. A distinguishing feature of the present invention lies in the production of optical fibers having consistent strength properties in the absence of protection of primary and secondary coatings, or buffers. Primary and secondary coatings, such as, for example, US Pat. No. 5,644,670 and EP 0953857 A1, are conventional in the art and are believed to be indispensable in appearance. Consistent strength performance was not immediately apparent but required careful statistical analysis of kinetic fatigue measurements involving numerous test samples. The analysis indicated that coated silica clad fibers using a photocurable coating polymerized with a cationic photoinitiator, preferably a diaryl iodonium salt, were preferred. Comparison of the statistical results also showed that the coated optical fibers according to the present invention changed in strength properties depending on the anion of the diaryl iodonium salt. Optical fibers coated with a coating composition containing a non-hydrolyzable, diaryl iodonium amide photoinitiator are generally higher than similar optical fibers using coating compositions containing hydrolyzable anions such as hexafluoroantimonate anions. Consistent strength performance was shown (see Table 3 and Table 4). In contrast to known optical fibers, including primary or secondary buffers, or associated coatings, the optical fibers of the present invention can maintain a consistent strength that is at least equivalent to that of known optical fibers protected with coatings up to a diameter of 250 microns or more. It can be thought of as "non-inserted" or "unsupported" having a diameter of from micron to 160 micron. Comparative Examples C1A to C1E (Table 1) provide coated GGP optical fibers comprising a silica clad optical fiber core with a single permanent polymer coating (P-coating) applied to its surface. The silica clad optical fiber core has a diameter of 100 microns and the coating has a thickness of 12.5 microns to produce coated optical fibers having an outer diameter of 125 microns. Comparative Example C1A to C1D, the coating is bis (dodecylphenyl) iodonium hexafluoro-antimonate (SbF6 ^-) of 5 wt% of an epoxy action of a photoinitiator solution and 95% by weight property, photo-curing resin. The curable resin includes 90% by weight of EPON 828 (bisphenol diglycidyl ether resin available from Shell Chemical Co., Houston, TX) and 10% by weight of TONE 0301 (union carbide, available from Danbury CT. Caprolactone triol based polymer). The photoinitiator solution contained 38.5 wt% (40 parts) iodonium hexafluoroantimonate, 57.7 wt% (60 parts) decyl alcohol and 3.8 wt% (4 parts) isopropyl thioxanthone. Measurements using the kinetic fatigue test (FOTP-28) of the coated fibers were carried out at 52.7 x 10 ³ kg / cm ² (750 kpsi) with sufficient fibers bursting at 14.1 x 10 ³ kg / cm ² (200 kpsi). It showed maximum strength and indicated that this type of coated fiber had consistent strength properties.

Comparative Example C1E was prepared using a P-coat comprising 5% by weight bis (dodecylphenyl) iodonium metaide photoinitiator solution and 95% by weight epoxy functional photocurable resin. The photocurable resin in this case contained 60% by weight of EPON 828 (Shell Chemical Co., Houston, TX) and 40% by weight of GP 554 (Genesee Polymers Inc., Flint MI). The photoinitiator solution contained 38.5 wt% (40 parts) bis (dodecylphenyl) iodonium amide, 57.7 wt% (60 parts) decyl alcohol and 3.8 wt% (4 parts) isopropyl thioxanthone. . Measurement of the coated fibers of Comparative Example C1E using the kinetic fatigue test (FOTP-28) showed a maximum strength of 52.7 x 10 ³ kg / cm ² (750 kpsi). Sufficient fibers were ruptured at 16.2 x 10 ³ kg / cm ² (230 kpsi), showing consistent strength characteristics. A slight improvement was observed at the lower end of the measured range when compared to Comparative Examples C1A to C1D.

Applying a 17.5 micron thick urethane-acrylate buffer layer on P-coated with a thickness similar to Comparative Examples C1A to C1E increases the strength of the coated fibers and lowers the lower limit of dynamic fatigue to about 28.1 x 10 ³ kg / cm ^2. Raise to (400 kpsi). The outer diameter of the coated optical fiber reaches 160 microns (Examples 1A-1C), which is towards the upper limit of the preferred GGP coated optical fiber according to the present invention.

The coated 160 micron optical fibers of Examples 1A and 1B included P-coated polymers photocured using bis (dodecylphenyl) iodonium hexafluoroantimonate photoinitiator. The photocurable resin is 75% by weight of EPON 828 (bisphenol diglycidyl ether resin available from Shell Chemical Co., Houston, TX) and 25% by weight of GP 554 (highly available from Genesee Polymers Inc., Flint MI). Silicone with a level of epoxy functionality). The photoinitiator solution contained 38.5 wt% (40 parts) iodonium hexafluoroantimonate, 57.7 wt% (60 parts) decyl alcohol and 3.8 wt% (4 parts) isopropyl thioxanthone.

The replacement of the hexafluoroantimonate photoinitiator with dodecylphenyl iodonium amide photoinitiator (Example 1C) in Examples 1A and 1B provided a significant improvement in the consistency of the kinetic fatigue measurement. This improvement due to the selection of bis (dodecylphenyl) iodonium methide photoinitiator allowed the development of coated optical fibers having a diameter of about 130 microns (see Examples 2A-2D). In this case, the coated fiber comprises 80 micron silica clad optical fiber coated with about 12.5 micron thick P-coated and also about 12.5 micron thick urethane-acrylate buffer. Compared to the thicker 160 micron coated optical fibers, the coated optical fibers of Examples 2A-2D often rupture above 42.2 x 10 ³ kg / cm ² (600 kpsi) but are 56.2 x 10 ³ kg / cm ² (800 kpsi) and consistently withstand the higher maximum stress. This is phenomenal considering that the 160 micron fiber comprises a thicker buffer layer than the 100 micron silica clad fiber, and the coated optical fiber having a diameter of about 130 microns.

Advances towards desirable coated optical fibers have been made by continuing to use the double coated structure but by reducing the outer diameter to 125 microns. Suitable coated optical fibers were 125 microns in the double coated fibers, including 80 micron diameter silica clad optical fibers coated with 11 micron thick P-coated followed by a 11.5 micron layer of commercially available urethane-acrylate. Gives the outer diameter. The coated optical fibers obtained (see Example 3) rupture rarely at 45.7 x 10 ³ kg / cm ² (650 kpsi) but consistently undergo a dynamic fatigue test up to 51.3 x 10 ³ kg / cm ² (730 kpsi). Endured The range of dynamic fatigue, from 45.7 x 10 ³ kg / cm ² (650 kpsi) to 51.3 x 10 ³ kg / cm ² (730 kpsi), is its upper limit (ie 51.3 x 10 ³ kg / cm ² (730 kpsi)). Although this has already been exceeded, it is narrower than in the case of the coated optical fiber structure described above.

Preferred coated optical fibers having an outer diameter of 125 microns include silica clad fibers having 80 micron diameter coated with permanent polymer coating or P-coating only. The thickness of the P-coat is about 22.5 microns to provide a coated optical fiber having an outer diameter of 125 microns. Preferred polymer coated compositions for single coated fibers include commercially available acrylated urethane compositions cured with free radical photoinitiators (Example 4). Suitable protective coatings are available from DSM Desotech, Elgin, IL, in particular as compositions identified as DSM 3471-2-136 comprising photoinitiators. Otherwise, a cationic photocurable P-coating containing, for example, an epoxy functional monomer crosslinkable with a diaryl iodonium amide photoinitiator can be used (Example 5). The results of the kinetic fatigue test suggest improved strength properties of 125 micron optical fibers coated with cured epoxide resin when compared to urethane acrylate resins of the same thickness. Regardless of the relative results, both coated optical fibers exceed a generally satisfactory kinetic fatigue value of 49.2 × 10 ³ kg / cm ² (700 kpsi).

Preferred optical fibers according to the present invention include GGP fibers having an outer diameter of 120 microns to 160 microns. These coated optical fibers overcome the problem of drop in strength, consistently maintaining kinetic fatigue performance comparable to GGP fibers including double buffers that raise the coated fiber diameter to 250 microns. The use of P-coated compositions comprising preferred non-hydrolyzable photoinitiators such as diaryl iodonium amide eliminates the problem of hydrolysis even in the presence of fluorine-containing moieties.

By way of non-example of the hydrolyzable photoinitiator _{C (SO 2 CF 3) 3} -, B (C 6 F 5) 4 - , and _{N (SO 2 CF 3) 2} - the iodonium salt is also diaryliodonium containing selected anions from Can be mentioned. Although it contains fluorinated ions, a preferred class of anions of cationic photoinitiators according to the present invention include fluorinated tris alkyl- or arylsulfonyl amides and the corresponding bis alkyl- or arylsulfonyl imides. The following formulas (I) and (II) provide general formulas representing “methide” and “imide” anions, respectively.

_{(R f SO 2) 3 C} -

_{(R f SO 2) 2 N} -

Each R _f is independently selected from the group consisting of highly fluorinated or perfluorinated alkyl or fluorinated aryl groups. The metade and the imide may be cyclic by the combination of any two R _f groups to form a bridge. Typically, the R _f alkyl chain contains 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms. The R _f alkyl chain may be branched or cyclic, but is preferably straight chain. Heteroatoms or groups such as divalent oxygen, trivalent nitrogen or hexavalent sulfur may interfere with the skeletal chain. When R _f is a cyclic structure or contains a cyclic structure, the structure preferably has 5 or 6 ring atoms comprising 1 or 2 heteroatoms. The alkyl group R also has no ethylenic or other carbon-carbon unsaturations, for example it is a saturated aliphatic, cycloaliphatic or heterocyclic group. By “highly fluorinated” it is meant that the degree of fluorination on the chain is sufficient to provide a chain having properties similar to the perfluorinated chain. More particularly, highly fluorinated alkyl groups will have more than half of the total number of hydrogen atoms on the chain replaced by fluorine atoms. Although hydrogen atoms may remain on the chain, it is preferred that all hydrogen atoms be replaced with fluorine to form perfluoroalkyl groups. The bromine or chlorine atom may be substituted for any hydrogen atom not substituted with fluorine. More preferably, at least two of the three hydrogens on the alkyl group are replaced with fluorine, even more preferably at least three of the four hydrogen atoms are replaced with fluorine, and all hydrogen atoms are substituted with fluorine to make the perfluorinated alkyl group Most preferably.

The fluorinated aryl groups of formula (I) or (II) may contain 6 to 22 ring carbon atoms, preferably 6 ring carbon atoms, wherein at least one, preferably at least of each aryl group Two ring carbon atoms are substituted with a fluorine atom or a highly fluorinated or perfluorinated alkyl group such as for example CF ₃ as defined above.

(C ₂ F ₅ SO ₂₎ As a specific example of a useful anion in the practice of the invention ^{_{2 N -, (C 4 F}} 9 SO 2) 2 N -, (C 8 F 17 SO 2) 3 C -, (CF 3 ^{_{SO 2) 3 C -, (}} CF 3 SO 2) 2 N -, (C 4 F 9 SO 2) 3 C - , and the like. More preferred anions are those represented by formula (I) wherein R is a perfluoroalkyl group having 1 to 4 carbon atoms, especially tris (trifluoromethylsulfonyl) methide anion. Anions of this kind and methods for their preparation are described in US 4,505,997, US 5,021,308, US 4,387,222, US 5,072,040, US 5,162,177 and US 5,273,840 and Turowsky and Seppelt, Inorg. Chem., 27, 2135-2137 (1988). Turowsky and Seppelt is from CF ₃ SO ₂ F, and _{CH 3 MgCl (CF 3 SO 2} ) 3 C - anions to, CF ₃ SO ₂ F 20% yield, CH based on the ₃ MgCl directly synthesized in 19% yield with respect Describe what you do. US 5,554,664 describes an improved method of synthesizing iodonium metaides.

Salts of the foregoing anions, commonly known as onium salts, may include sulfonium and iodonium cations. These salts may be activated by actinic radiation or heat or may require two stages of activation with actinic radiation followed by heating. Suitable salts include those that generate reactive species for the polymerization of the P-coated composition when exposed to sufficient energy with a wavelength between 200 nm and 800 nm. Initiation can occur during exposure to energy from various sources, including heat, accelerated particle beams (electron beams), or electromagnetic radiation sources.

Experiment

The following section provides a description of a general method for the production of coated optical fibers according to the present invention.

Fiber Drawing Process

Nokia-Maillefer fiber stretching tower (Vantaa, Finland) was used as the optical stretching tower for the coated optical fibers according to the invention. The fiber drawing process used a down feed system to control the feed rate into an optical pre-formed 15KW Lepel Zirconia induction furnace (Lepel Corp., Maspeth, NY). Suitable pre-forms include those produced by modified chemical vapor deposition (MCVD). In order to stretch the optical fibers to the required dimensions, the temperature was raised between 2200 ° C. and 2250 ° C. by heating the pre-form in the furnace. A laser telemetry meter (LaserMike ^™ ) located underneath the heat source was used to measure the stretched fiber diameter while monitoring the position of the fiber in the tower.

The newly formed fibers were passed through a primary coating station to apply a permanent protective coating. The sheath station is a sheath die assembly, Fusion Systems R Corp. It included a microwave UV curing system, a concentrator monitor and another laser telemetry system. The cladding die assembly included a sorting die and a back pressure die in a receiving frame placed on an adjustable stage with x-y translation for pitch and tilt control and cladding concentration. The protective coating material was fed from the pressure vessel for application to the optical fiber into the coating die assembly, then the coating was cured and the fiber dimensions measured in the primary coating station were measured. Preferably the UV source is a Fusion Systems UV lamp with an H + bulb that emits actin-based radiation in the wavelength range of 254 nm to 365 nm. The exposure time for UV irradiation depends on the stretching speed of the optical fiber and is typically less than 1 second.

If desired, a buffer is applied to the coated fiber at a secondary coating station to provide a double coated optical fiber having a second permanent coating. This type of double sheathing requires the use of an additional sized die supplied with material from a separate pressurized container. The coating was cured as described above and the coated fiber outer diameter was measured. The coated optical fibers were collected using a cylindrical winding device of conventional type.

Dynamic Fatigue Testing Method

The kinematic fatigue of the coated optical fibers according to the invention was measured using a modified EIA / TIA-455-28B using a strain rate of 9% per minute and a gauge length of 4 meters under ambient conditions. Another way of expressing this test method is the phrase “Measurement of the Dynamic Tensile Strength of Optical Fibers” of the Fiber Optics Test Method (“FOTP”) 28, ie EIA / TIA-455-28B (which is EIA- Revision of 455-28A, EIA stands for Electronic Industires Association, and TIA stands for Telecommunications Industry Association).

matter

5% by weight of polymer coating A is bis (dodecyl phenyl) iodonium antimonate as iodonium hexafluoro (SbF ₆ ^-) a photoinitiator solution, and 90% by weight of EPON 828 (bisphenol A commercially available from Shell Chemical Co., Houston, TX Diglycidyl ether resin) and 10% by weight of TONE 0301 (Union Carbide, a caprolactone triol based polymer having hydroxyl functionality commercially available from Danbury CT). The photoinitiator contains 38.5 wt% (40 parts) of iodonium hexafluoroantimonate, 57.7 wt% (60 parts) of dodecyl alcohol and 3.8 wt% (4 parts) of isopropyl thioxanthone.

Polymer coating B comprises 5% by weight of bis (dodecylphenyl) iodonium methide photoinitiator solution, and 60% by weight of EPON 828 (bisphenol diglycidyl ether resin available from Shell Chemical Co., Houston, TX) and 95 weight percent resin containing 40 weight percent GP 554 (silicones with high levels of epoxy functionality commercially available from Genesee Polymers Inc., Flint MI). The photoinitiator solution contains 38.5 wt% (40 parts) of bis (dodecylphenyl) iodonium methoxide, 57.7 wt% (60 parts) of decyl alcohol and 3.8 wt% (4 parts) of isopropyl thioxanthone do.

Polymer coating C comprises 5% by weight of bis (dodecylphenyl) iodonium amide photoinitiator solution, and 80% by weight of EPON 830 (bisphenol diglycidyl ether resin available from Shell Chemical Co., Houston, TX) and 95 weight percent resin containing 20 weight percent TERATHANE 2000 (polytetrahydrofuran diol sold from Sigma-Aldrich, Milwaukee, WI). The photoinitiator solution contains 38.5 wt% (40 parts) of bis (dodecylphenyl) iodonium methoxide, 57.7 wt% (60 parts) of decyl alcohol and 3.8 wt% (4 parts) of isopropyl thioxanthone do.

Polymer coating D is 5% by weight of bis (dodecylphenyl) iodonium methide photoinitiator solution, and 40% by weight of EPON 830 (bisphenol diglycidyl ether resin available from Shell Chemical Co., Houston, TX) and 30% by weight of 2,2'-oxybis (6-oxabicyclo (3.1.0] hexane) (available from Sigma-Aldrich, Milwaukee WI) and 30% by weight of Terathane 2900 (Sigma-Aldrich, Milwaukee, WI 95 wt% of a resin containing commercially available polytetrahydrofuran diol). The photoinitiator solution contains 38.5 wt% (40 parts) of bis (dodecylphenyl) iodonium methoxide, 57.7 wt% (60 parts) of decyl alcohol and 3.8 wt% (4 parts) of isopropyl thioxanthone do.

Polymer coating E is in Fig iodonium hexafluoro 5% of bis (dodecylphenyl) weight iodo antimonate (SbF ₆ ^-) bisphenol available from photo-initiator solution, and EPON 828 (Shell Chemical Co., Houston , TX 75% by weight Diglycidyl ether resin) and 95% by weight of a resin containing 25% by weight of GP 554 (Genesee Polymers Inc., silicone with high levels of epoxy functionality available from Flint MI). The photoinitiator solution comprises 38.5 wt% (40 parts) of bis (dodecylphenyl) iodonium hexafluoroantimonate (SbF ₆ ⁻ ), 57.7 wt% (60 parts) of decyl alcohol and 3.8 wt% (4 parts) Isopropyl thioxanthone.

Polymer coating F is 5% by weight bis (dodecylphenyl) iodonium methide photoinitiator solution, and 75% by weight EPON 828 (bisphenol diglycidyl ether resin available from Shell Chemical Co., Houston, TX) and 95 weight percent resin containing 25 weight percent GP 554 (Genesee Polymers Inc., silicone with high levels of epoxy functionality available from Flint MI). The photoinitiator solution contains 38.5 wt% (40 parts) of bis (dodecylphenyl) iodonium methoxide, 57.7 wt% (60 parts) of decyl alcohol and 3.8 wt% (4 parts) of isopropyl thioxanthone do.

Polymer coating G is an acrylated urethane coating identified as DSM 3471-2-136 (obtained from DSM Desotech, Elgin, IL).

Polymer coating H is an acrylated urethane coating identified as DSM 3471-2-137 (available from DSM Desotech, Elgin, IL).

Table 1 provides a comparative example of coated optical fibers prepared using a method similar to that used for the optical fibers of the examples according to the invention shown in Table 2. Both tables contain information indicating the diameter of the silica clad optical fiber, the thickness of the coating applied thereto, and the total diameter of the coated optical fiber.

Comparative Example C1A-C1E

Comparative Examples C1A-C1E represent coated optical fibers made using separate runs of materials under substantially the same stretching tower conditions. The polymer (P-coated) coating used in Comparative Examples C1A-C1D was an epoxy resin cured using a cationic photoinitiator with hexafluoroantimonate anion. Comparative Example C1E used a cationic photoinitiator with metaide anion. Table 3 shows that the strength of the optical fibers of Comparative Examples C1A-C1D can only be changed with a small percentage of samples exceeding 49.2 x 10 ³ kg / cm ² (700 kpsi). The use of different photoinitiators of Example C1E improves the percentage of fibers bursting above 49.2 x 10 ³ kg / cm ² (700 kpsi) without satisfying consistent strength requirements.

Comparative Example C2

Comparative Example C2 is a coated optical fiber prepared by stretching tower application of a double permanent coating to a silica clad optical fiber. The polymer (P-coated) coating is an epoxy resin cured using a cationic photoinitiator with metaide anion. It was overlaid with an acrylated urethane coating identified as DSM 3471-2-136 (commercially available from DSM Desotech, Elgin, IL) that cures by radical polymerization mechanism. The results of the dynamic fatigue (tension to rupture as in FOTP-28) of several samples of Comparative Example C2 ranged from 49.2 x 10 ³ kg / cm ² (700 kpsi) to 56.2 x 10 ³ kg / cm ² (800 kpsi) It was distributed in the range of (Table 3). The structure of the coated optical fiber of Comparative Example C2 was similar to that of Example 3 of the present invention. Although slightly higher than Example 3, the dynamic fatigue test of Comparative Example C2 showed more variability than Example 3. The results suggest a change in performance due to a change in the coating material used in the comparative example and inventive example 3.

Comparative Example C3

Comparative Example C3 is a coated optical fiber prepared by stretching tower application of a permanent coating to silica clad optical fiber. The polymer (P-coated) coating was an epoxy / polyol resin combination that was cured using a cationic photoinitiator with metaide anion. The dynamic fatigue (tensile to rupture as in FOTP-28) of several samples of Comparative Example C3 ranged from 45.7 x 10 ³ kg / cm ² (650 kpsi) to 52.7 x 10 ³ kg / cm ² (750 kpsi) And most of them were below 49.2 x 10 ³ kg / cm ² (700 kpsi) (Table 3).

Example 1A-1C

Examples 1A-1C represent coated optical fibers having a diameter of about 160 microns, prepared using separate runs of materials under substantially the same stretching tower conditions. The polymer (P-coated) coating used in Examples 1A and 1B was an epoxy resin cured using a cationic photoinitiator with hexafluoroantimonate anion. Iodonium amide photoinitiator was used to cure the polymer coating of Example 1C. In each case, the P-coated was overlaid with an acrylated urethane coating identified as DSM 3471-2-136 (obtained from DSM Desotech, Elgin, IL) that cures with a radical polymerization mechanism. The dynamic fatigue (tensile to rupture as in FOTP-28) of Examples 1A and 1B resulted in a reasonable ratio of 49.2 x 10 ³ kg / cm ² (700 kpsi) to 52.7 x 10 ³ kg / cm ² (750 kpsi). Consistency was shown. Example 1C provided consistent and improved performance close to 56.2 × 10 ³ kg / cm ² (800 kpsi). Example 1C differs from others only in that it uses bis (dodecylphenyl) iodonium methide photoinitiator to cure the P-coat.

Example 2A-2D

Examples 2A-2D represent coated optical fibers having a diameter of about 130 microns, prepared using separate runs of materials under substantially the same stretching tower conditions. The polymer (P-coated) coating was an epoxy resin cured using a cationic photoinitiator with metaide anion. It was overlaid with an acrylated urethane coating that cured with a radical polymerization mechanism. The dynamic fatigue (tensile to rupture as in FOTP-28) of several samples of Examples 2A-2D showed the highest consistency and strength as a result of approaching 56.2 x 10 ³ kg / cm ² (800 kpsi). .

Example 3

Example 3 is coated optical fibers having a diameter of about 125 microns made by stretching tower application of the coating to graded index multimode silica clad optical fibers. The polymer (P-coated) coating was an epoxy resin cured using a cationic photoinitiator with metaide anion. It was overlaid with an acrylated urethane coating identified as DSM 3471-2-136 (obtained from DSM Desotech, Elgin, IL) that cures with radical polymerization mechanisms. Kinetic fatigue (tensile to rupture as in FOTP-28) of several samples of Example 3 resulted in concentration around 49.2 × 10 ³ kg / cm ² (700 kpsi).

Example 4 and Example 5

Examples 4 and 5 show coated optical fibers having a diameter of about 125 microns made by stretching tower application of a single permanent coating to graded index multimode silica clad optical fibers. An acrylated urethane coating, identified as DSM 3471-2-137 (DSM Desotech, Elgin, IL), cured by radical polymerization mechanism, was used as the polymer (P-coated) coating of Example 4. The polymer (P-coated) coating of Example 5 was an epoxy resin cured using an onium photoinitiator with metaide anion. Kinetic fatigue (tensile to rupture as in FOTP-28) of several samples of Example 4 resulted in a concentration around 51.3 × 10 ³ kg / cm ² (730 kpsi). The test of Example 5 showed a stronger coated optical fiber structure with kinetic fatigue values concentrated around 56.2 x 10 ³ kg / cm ² (730 kpsi).

Fiber Optic Structure and Kinetic Fatigue for Comparative Examples C1A-E, C2 and C3 Example Glass diametermicron P-coated (Type) micron Shock Absorbing (Type) Micron Total diameter C1A 100 12.5 (A) - 125 C1B 100 12.5 (A) - 125 C1C 100 12.5 (A) - 125 C1D 100 12.5 (A) - 125 C1E 100 12.5 (B) - 125 C2 80 11.0 (C) 11.5 (G) 125 C3 90 15.5 (D) 121

Fiber Optic Structure and Kinetic Fatigue for Examples 1A-C, 2A-D, 3, 4, and 5 Example Glass diametermicron P-coated (Type) micron Shock Absorbing (Type) Micron Total diameter 1A 100 12.5 (E) 17.5 (G) 160 1B 100 12.5 (E) 17.5 (G) 160 1C 100 12.5 (F) 17.5 (G) 160 2A 80 12.5 (B) 12.5 (G) 130 2B 80 12.5 (B) 12.5 (G) 130 2C 80 12.5 (B) 12.5 (G) 130 2D 80 12.5 (B) 11.5 (H) 128 3 80 11 (B) 11.5 (G) 125 4 80 - 22.5 (H) 125 5 80 22.5 (B) - 125

Table 3 contains the results of the kinetic fatigue test of the coated optical fibers of Comparative Examples C1A-C1E, Comparative Examples C2 and Comparative Examples C3. Table 4 provides the results of Examples 1A-1C, Examples 2A-2D, and Examples 3-5. This information provides a relative frequency distribution for a number of duplicate samples between 10 and 25, depending on the coated optical fiber being tested. Fiber performance at a given level of kinetic fatigue is given as a percentage of the fiber sample passing through that level.

It is noteworthy that Comparative Examples C1A-C1D exhibited relatively poor performance, with less than 50% of the sample fibers passing through dynamic fatigue above 49.2 × 10 ³ kg / cm ² (700 kpsi), which is considered a threshold. While not wishing to be bound by theory, it is believed that the use of a hydrolyzable photoinitiator, iodonium hexafluoroantimonate in a P-coated composition introduces a corrosive fluoride species that attacks and weakens the glass of the coated optical fiber. . This is a comparison that provides 72% of the relative frequency distribution of the tested samples with results better than 49.2 x 10 ³ kg / cm ² (700 kpsi) using non-hydrolyzable bis (dodecylphenyl) iodonium methide photoinitiator. Example appears to be possible when compared to C1E. The coated fiber strength improvement is evident from the comparison of Examples 1A and 1B with Example 1C, where only the latter has a P-coated cured using a photoinitiator containing a non-hydrolyzable metaide anion.

The coated optical fibers of Examples 2A-2C, Examples 3, 4 and 5 include narrow diameter silica clad optical fibers of 80 microns in diameter, fibers of the previous examples having diameters up to 100 microns. Given the expectation that smaller diameter fibers will also be more fragile, coated optical fibers comprising an 80 micron silica clad fiber optical core consistently exhibits good retention of mechanical strength properties as measured by dynamic fatigue . For coated optical fibers (GGP) having a diameter of less than 160 microns, the results of the kinetic fatigue test (Table 4) show the consistent strength of the coated fibers according to the present invention. The use of bis (dodecylphenyl) iodonium amide as a preferred photoinitiator for curing P-coated compositions is such that a narrow diameter with strength properties at least comparable to the preceding GGP coated fibers having almost twice the diameter. Produces coated optical fibers (preferably <130 microns).

Relative frequency distribution of kinetic fatigue measurements for comparative examples C1A-E, C2 and C3 Dynamic Fatigue Measurement (kg / cm ² ) Example 38.7 x 10 ³ ~ 42.2 x 10 ³ 42.2 x 10 ³ to 45.7 x 10 ³ 45.7 x 10 ³ to 49.2 x 10 ³ 49.2 x 10 ³ to 52.7 x 10 ³ 52.7 x 10 ³ to 56.2 x 10 ³ More than 56.2 x 10 ³ C1A - - - 18.2% - - C1B - 9.1% - 27.3% 9.1% - C1C 20% 10% 20% 10% - C1D - 5% - 40% - - C1E - - 4% 72% - - C2 4% 40% 56% C3 4% 4% 56% 36%

Relative frequency distribution of kinetic fatigue measurements for Examples 1A-C, 2A-D, 3, 4, and 5 Dynamic Fatigue Measurement (kg / cm ² ) Example 38.7 x 10 ³ ~ 42.2 x 10 ³ 42.2 x 10 ³ to 45.7 x 10 ³ 45.7 x 10 ³ to 49.2 x 10 ³ 49.2 x 10 ³ to 52.7 x 10 ³ 52.7 x 10 ³ to 56.2 x 10 ³ More than 56.2 x 10 ³ 1A 5% - 5% 90% - - 1B - - 5% 90% - - 1C 5% 95% 2A - - - - - 100% 2B - 5% - - 95% - 2C - - - - 100% - 2D - - - - 100% - 3 - 4% - 96% - - 4 - - - 96% - - 5 4% - - - 92% -

Coated GGP optical fibers possess desirable strength properties and at the same time withstand stresses associated with a bending radius of about 6 mm (0.25 inch). The optical fiber according to the present invention meets the requirements of applications that require a short length of fiber that is not substantially affected by microbending. Such applications include the use of smaller interconnects for thinner optical fibers and optical switches, plate-on-fiber connections, optical back-plate connections and optical cross connections.

Unsupported, small diameter, consistent strength GGP optical fibers and their elements are described herein. These and other changes as will be appreciated by those skilled in the art are also within the intended scope of the invention as claimed below. As mentioned above, while detailed embodiments of the present invention are disclosed herein, it should be understood that the disclosed embodiments are merely illustrative of the present invention, which can be embodied in various forms.

Claims (8)

Silica cladding, and a coating applied to the cladding to provide a coated optical fiber having a diameter of 120 microns to 150 microns, For kinetic fatigue measurements a relative frequency distribution of at least 85% between 49.2 x 10 ³ kg / cm ² and 63.3 x 10 ³ kg / cm ² , Coated optical fiber. The coated optical fiber of claim 1, wherein the relative frequency distribution is at least 90%. The coated optical fiber of claim 1, wherein the diameter is from 128 microns to 135 microns, and wherein the relative frequency distribution is at least 95%. The coated optical fiber of claim 1, wherein the coating is a polymer coating. The method of claim 4 wherein in said polymer coating is hexafluoro-antimonate and the general formula _{(R f SO 2) 3 C} - anions and the diaryl selected from the group consisting of methide anion having an iodo a coating composition containing a cation The coated optical fiber formed by curing. Fiber optic core, Silica clad on the optical fiber core to provide a silica clad core and A permanent polymer coating applied to the cladding by exposing the photocurable composition containing the photoinitiator to actin based irradiation, Has a diameter of 120 microns to 150 microns, With a relative frequency distribution of at least 85% for kinetic fatigue measurements between 49.2 x 10 ³ kg / cm ² and 63.3 x 10 ³ kg / cm ² , GGP optical fiber. The GGP optical fiber of claim 6, wherein the permanent polymer coating has a thickness of 10 microns to 25 microns. 7. The aryl iodonium according to claim 6, wherein the photoinitiator has an anion selected from the group consisting of hexafluoroantimonate and a metaide anion having the formula (R _f SO ₂ ) ₃ C ^- and a diaryliodonium cation. GGP optical fiber comprising a salt.