LASER-ENABLED MULTI-LAYER INK ADHESION ONTO OPTICAL FIBERS

A method of marking an optical fiber that includes directing a laser beam onto a first colored layer of an optical fiber. The optical fiber includes a core and a cladding surrounding the core, the first colored layer surrounds the cladding, and the laser beam modifies the first colored layer to form one or more laser-modified regions along an outer surface of the first colored layer.

BACKGROUND

Field

The present specification generally related to apparatuses and methods for laser-enabled adhesion of ink over an existing color layer of optical fibers to increase the number of color-coded identifications of individual optical fibers in groups of optical fibers, such as in a cable assembly or devices with multiple fiber inputs and outputs.

Technical Background

Optical communications rely on cable assemblies that include multiple optical fibers to maximize data transmission rates. Construction of optical fiber networks frequently requires splicing and joining of individual optical fibers in different cable assemblies. When joining optical fibers after splicing, it is necessary to map optical fiber connections in different cable assemblies to enable tracking of the optical signal. Mapping of optical fiber connections is accomplished by applying distinct indicia, such as identifying marks, to the individual optical fibers and matching the indicia when joining optical fibers from different cable assemblies.

Conventionally, optical fibers in a cable assembly are limited to 12 colors for use as identifying marks. The limited number of colors creates design hurdles for increasing data throughput by increasing the number of fibers in a cable assembly. Current attempts to increase the number of identifying marks focus on combinations of two or more of the 12 colors. In a typical process, the optical fiber includes a color layer that extends along the length of the fiber and one or more additional marks are applied underneath the color layer at selected locations along the optical fiber (typically near the ends to simplify joining). If the color layer is sufficiently translucent (e.g. by controlling its thickness), the underlying additional marks are visible and the combination of underlying marks and color layer functions to identify the fiber and the number of unique identifying indicia is increased. These methods, however, are costly and result in attribute degradation (e.g. delamination of the color layer).

Optical fiber and optical cable lengths are typically on the 10's to 100's of kilometers and both the optical waveguiding properties and the integrity of optical fibers and optical cables are dependent on the integrity of each component. Thus, the color marking process for optical fiber identification must be robust and indelible. One current color marking process includes applying a coded black tracer on top of a secondary coating and overcoating with a semi-transparent color ink layer through which the coded black tracer is visible. However, this process has drawbacks. Some colors for the color ink layer do not have the transparency required for visibility of the black ink tracers. Some colors for the color ink layer change the perceived color of the secondary colored layer. Moreover, current solutions cause large performance penalties for optical signal transmission through the optical fiber.

Accordingly, a need exists for methods and systems to increase the number of color identifiers that can be applied to an optical fiber without compromising optical performance.

SUMMARY

According to a first aspect of the present disclosure, a method of marking an optical fiber includes directing a laser beam onto a first colored layer of an optical fiber, wherein: the optical fiber includes a core and a cladding surrounding the core, the first colored layer surrounds the cladding, and the laser beam modifies the first colored layer to form one or more laser-modified regions along an outer surface of the first colored layer.

A second aspect of the present disclosure includes the method of the first aspect, wherein the one or more laser-modified regions of the outer surface include a plurality of microcracks extending into the first colored layer, a plurality of protrusions extending from the first colored layer, or combinations thereof.

A third aspect of the present disclosure includes the method of the first aspect or the second aspect, wherein the one or more laser-modified regions comprise a thickness of from 0.2 μm to 3 μm.

A fourth aspect of the present disclosure includes the method of any of the previous aspects, wherein the one or more laser-modified regions comprise a thickness less than a thickness of the first colored layer.

A fifth aspect of the present disclosure includes the method of any of the previous aspects, wherein the one or more laser-modified regions comprise a plurality of laser-modified regions intermittently spaced along a length of the optical fiber.

A sixth aspect of the present disclosure includes the method of any of the previous aspects, wherein the one or more laser-modified regions comprise a single continuous laser-modified region extending along a length of the optical fiber.

A seventh aspect of the present disclosure includes the method of any of the previous aspects, further comprising translating the optical fiber along a fiber pathway while directing the laser beam onto the first colored layer of the optical fiber.

An eighth aspect of the present disclosure includes the method of the seventh aspect, wherein the fiber pathway is disposed along an optical fiber draw tower.

A ninth aspect of the present disclosure includes the method of the eighth aspect, wherein the optical fiber draw tower comprises a draw furnace, a fiber coating unit, a drying unit, a curing unit, an optical system for producing the laser beam, and a fiber collection unit, wherein the fiber pathway extends from the draw furnace to the fiber collection unit.

A tenth aspect of the present disclosure includes the method of the seventh aspect, wherein the fiber pathway is disposed along a spool-to-spool system.

An eleventh aspect of the present disclosure includes the method of the tenth aspect, wherein the spool-to-spool system comprises a first fiber spool, an optical system for producing the laser beam, and a second fiber spool, wherein the fiber pathway extends from the first fiber spool to the second fiber spool.

A twelfth aspect of the present disclosure includes the method of any of the previous aspects, wherein the laser beam is output by a beam source of an optical system and directed to the first colored layer along a laser pathway, the optical system comprising a first cylindrical lens and a second cylindrical lens positioned along the laser pathway between the beam source and the first colored layer, and the first cylindrical lens is rotated 90° about the laser pathway with respect to the second cylindrical lens.

A thirteenth aspect of the present disclosure includes the method of the twelfth aspect, wherein the laser beam is directed onto a first portion of a circumference of the first colored layer, the first portion extending around less than an entirety of the circumference, the one or more laser-modified regions formed on the first portion.

A fourteenth aspect of the present disclosure includes the method of the thirteenth aspect, further including directing a second laser beam onto a second portion of the circumference of the first colored layer, the second laser beam output by a second beam source of a second optical system and directed to the second portion along a second laser pathway, the second portion extending around less than the entirety of the circumference, the second laser beam forming one or more additional laser-modified regions on the second portion.

A fifteenth aspect of the present disclosure includes the method of the fourteenth aspect, wherein the first portion and the second portion combine to include the entirety of the circumference of the first colored layer.

A sixteenth aspect of the present disclosure includes the method of the fourteenth aspect, wherein the second optical system includes a third cylindrical lens and a fourth cylindrical lens positioned along the second laser pathway between the second beam source and the first colored layer and the third cylindrical lens is rotated 90° about the second laser pathway with respect to the fourth cylindrical lens.

A seventeenth aspect of the present disclosure includes the method of any of the previous aspects, wherein the laser beam is output by a beam source of an optical system along a laser pathway, the optical system comprising an aspheric optical element positioned along a first segment of the laser pathway between the beam source and a mirror, wherein the mirror optically couples the first segment of the laser pathway with a second segment of the laser pathway, the first segment of the laser pathway is orthogonal with the second segment of the laser pathway, the second segment of the laser pathway is collinear with a fiber pathway along which the optical fiber is positioned, and the fiber pathway extends through a hole in the mirror.

An eighteenth aspect of the present disclosure includes the method of the seventeenth aspect, further including a first lens positioned along the first segment of the laser pathway between the aspheric optical element and the mirror and a second lens positioned along the second segment of the laser pathway downstream the mirror, wherein the fiber pathway extends through a hole in the second lens.

A nineteenth aspect of the present disclosure includes the method of any of the previous aspects, wherein the laser beam is output by a beam source of an optical system, the optical system including an off-axis parabolic mirror optically coupled to the beam source and optically coupling a first segment of a laser pathway with a second segment of the laser pathway, wherein the first segment of the laser pathway is orthogonal with the second segment of the laser pathway, the second segment of the laser pathway is collinear with a fiber pathway along which the optical fiber is positioned, and the fiber pathway extends through a hole in the off-axis parabolic mirror.

A twentieth aspect of the present disclosure includes the method of any of the previous aspects, wherein the laser beam is output by a beam source of an optical system along a laser pathway, the optical system including a first aspheric optical element and a second aspheric optical element positioned along a first segment of the laser pathway between the beam source and a mirror, wherein the mirror optically couples the first segment of the laser pathway with a second segment of the laser pathway, a focusing mirror is positioned along the second segment of the laser pathway downstream the mirror, the first segment of the laser pathway is orthogonal with the second segment of the laser pathway, the second segment of the laser pathway is collinear with a fiber pathway along which the optical fiber is positioned, and the fiber pathway extends through a hole in the mirror and a hole in the focusing mirror.

A twenty-first aspect of the present disclosure includes the method of any of the previous aspects, further including applying an ink to the one or more laser-modified regions of the outer surface of the first colored layer to form a second colored layer directly adhered to the one or more laser-modified regions of the first colored layer.

A twenty-second aspect of the present disclosure includes the method of the twenty-first aspect, wherein the ink is applied by a rotogravure ink station.

A twenty-third aspect of the present disclosure includes the method of the twenty-first aspect, wherein the ink is applied by a jetting ink station.

A twenty-fourth aspect of the present disclosure includes the method of any of the twenty-first aspect through the twenty-third aspect, wherein the ink is a silicone based ink.

A twenty-fifth aspect of the present disclosure includes the method of any of the twenty-first aspect through the twenty-fourth aspect, wherein the first colored layer is a different color than the second colored layer.

A twenty-sixth aspect of the present disclosure includes the method of any of the previous aspects, wherein the laser beam comprises a pulsed laser beam.

A twenty-seventh aspect of the present disclosure includes the method of any of the previous aspects, wherein the laser beam comprises a continuous wave laser beam.

A twenty-eighth aspect of the present disclosure includes the method of any of the previous aspects, wherein the one or more laser-modified regions extend around at least 50% of a circumference of the outer surface of the first colored layer.

A twenty-ninth aspect of the present disclosure includes the method of any of the previous aspects, wherein the one or more laser-modified regions extend around at least 75% of a circumference of the outer surface of the first colored layer.

A thirtieth aspect of the present disclosure includes the method of any of the previous aspects, wherein the one or more laser-modified regions extend around at least 90% of a circumference of the outer surface of the first colored layer.

A thirty-first aspect of the present disclosure includes the method of any of the previous aspects, wherein the outer surface of the first colored layer comprises a portion not modified by the laser beam adjacent to the one or more laser-modified regions, the portion and the one or more laser-modified regions differing in a reflection or a scattering of visible light to provide an optical contrast of the portion relative to the one or more laser-modified regions.

A thirty-second aspect of the present disclosure includes the method of any of the previous aspects, wherein the outer surface of the first colored layer comprises a portion not modified by the laser beam adjacent to the one or more laser-modified regions, the one or more laser-modified regions having a higher root-mean-square roughness than the portion.

A thirty-third aspect of the present disclosure includes the method of any of the previous aspects, wherein the optical fiber comprises a buffer layer between the first colored layer and the cladding, the first colored layer surrounding the buffer layer and the buffer layer surrounding the cladding and wherein the buffer layer is not modified by the laser beam.

A thirty-fourth aspect of the present disclosure includes the method of the thirty-third, wherein the buffer layer is not ablated by the laser beam.

A thirty-fifth aspect of the present disclosure includes the method of any of the previous aspects, wherein the laser beam modifies the first colored layer by ablating the first colored layer.

According to thirty-sixth aspect of the present disclosure a method of marking a fiber bundle support includes directing a laser beam onto a first colored layer of a fiber bundle support, wherein the fiber bundle support is configured to house a plurality of optical fibers within an opening of the fiber bundle support and the laser beam modifies the first colored layer to form one or more laser-modified regions along an outer surface of the first colored layer.

A thirty-seventh aspect of the present disclosure includes the method of the thirty-sixth aspect, wherein the fiber bundle support comprises a cable jacket, the cable jacket comprising the first colored layer.

A thirty-eighth aspect of the present disclosure includes the method of the thirty-seventh aspect, wherein the cable jacket comprises an inner cable jacket configured to house a bundle of optical fibers, the first colored layer surrounding the inner cable jacket.

A thirty-ninth aspect of the present disclosure includes the method of the thirty-seventh aspect, wherein the cable jacket comprises an outer cable jacket configured to house a plurality of inner cable jackets each of the inner cable jackets configured to house a bundle of optical fibers, the outer cable jacket comprising the first colored layer.

A fortieth aspect of the present disclosure includes the method of the thirty-sixth aspect, wherein the fiber bundle support comprises a ribbon jacket.

A forty-first aspect of the present disclosure includes the method of any of the thirty-sixth through fortieth aspects, wherein the one or more laser-modified regions of the outer surface comprise a plurality of microcracks extending into the first colored layer, a plurality of protrusions extending from the first colored layer, or combinations thereof.

A forty-second aspect of the present disclosure includes the method of any of the thirty-sixth through forty-first aspects, wherein the one or more laser-modified regions comprise a thickness of from 0.2 μm to 3 μm.

A forty-third aspect of the present disclosure includes the method of any of the thirty-sixth through forty-second aspects, further including translating the fiber bundle support along a fiber bundle support pathway while directing the laser beam onto the first colored layer of the fiber bundle support.

A forty-fourth aspect of the present disclosure includes the method of the forty-third aspect, wherein the fiber bundle support pathway is disposed along a spool-to-spool system, wherein the spool-to-spool system comprises a first fiber spool, an optical system for producing the laser beam, and a second fiber spool, wherein the fiber bundle support pathway extends from the first fiber spool to the second fiber spool.

A forty-fifth aspect of the present disclosure includes the method of any of the thirty-sixth through forty-fourth aspects, wherein the laser beam is output by a beam source of an optical system and directed to the first colored layer along a laser pathway, the optical system comprising a first cylindrical lens and a second cylindrical lens positioned along the laser pathway between the beam source and the first colored layer and the first cylindrical lens is rotated 90° about the laser pathway with respect to the second cylindrical lens.

A forty-sixth aspect of the present disclosure includes the method of any of the thirty-sixth through forty-fifth aspects, wherein the laser beam is output by a beam source of an optical system along a laser pathway, the optical system comprising an aspheric optical element positioned along a first segment of the laser pathway between the beam source and a mirror, wherein the mirror optically couples the first segment of the laser pathway with a second segment of the laser pathway, the first segment of the laser pathway is orthogonal with the second segment of the laser pathway, the second segment of the laser pathway is collinear with a fiber bundle support pathway along which the fiber bundle support is positioned, and the fiber bundle support pathway extends through a hole in the mirror.

A forty-seventh aspect of the present disclosure includes the method of the forty-sixth aspect, further including a first lens positioned along the first segment of the laser pathway between the aspheric optical element and the mirror and a second lens positioned along the second segment of the laser pathway downstream the mirror, wherein the fiber bundle support pathway extends through a hole in the second lens.

A forty-eighth aspect of the present disclosure includes the method of any of the thirty-sixth through forty-seventh aspects, wherein the laser beam is output by a beam source of an optical system along a laser pathway, the optical system comprising an off-axis parabolic mirror optically coupled to the beam source and optically coupling a first segment of the laser pathway with a second segment of the laser pathway, wherein the first segment of the laser pathway is orthogonal with the second segment of the laser pathway, the second segment of the laser pathway is collinear with a fiber bundle support pathway along which the fiber bundle support is positioned, and the fiber bundle support pathway extends through a hole in the off-axis parabolic mirror.

A forty-ninth aspect of the present disclosure includes the method of any of the thirty-sixth through forty-eighth aspects, further including applying an ink to the one or more laser-modified regions of the outer surface of the first colored layer to form a second colored layer directly adhered to the one or more laser-modified regions of the first colored layer.

A fiftieth aspect of the present disclosure includes the method of any of the thirty-sixth through forty-ninth aspects, wherein the laser beam is output by a beam source of an optical system along a laser pathway, the optical system includes a first aspheric optical element and a second aspheric optical element positioned along a first segment of the laser pathway between the beam source and a mirror, wherein the mirror optically couples the first segment of the laser pathway with a second segment of the laser pathway, a focusing mirror is positioned along the second segment of the laser pathway downstream the mirror, the first segment of the laser pathway is orthogonal with the second segment of the laser pathway, the second segment of the laser pathway is collinear with a fiber bundle support pathway along which the fiber bundle support is positioned; and the fiber bundle support pathway extends through a hole in the mirror and a hole in the focusing mirror.

According to a fifty-first aspect of the present disclosure an optical fiber includes a core, a cladding surrounding the core, and a first colored layer surrounding the cladding, wherein the first colored layer comprises an outer surface, the outer surface corresponding to an outermost surface of the optical fiber, the outer surface comprising a first portion with a first root-mean-square roughness and a second portion with a second root-mean-square roughness less than the first root-mean-square roughness.

A fifty-second aspect of the present disclosure includes the method of the fifty-first aspect, further including one or more buffer layers surrounding the cladding and disposed between the cladding and the first colored layer.

A fifty-third aspect of the present disclosure includes the method of the fifty-first aspect or the fifty-second aspect, wherein the first portion of the outer surface include a plurality of microcracks extending into the first colored layer, a plurality of protrusions extending from the first colored layer, or a combination thereof.

A fifty-fourth aspect of the present disclosure includes the method of any of the fifty-first through fifty-third aspects, wherein the first portion comprises a thickness of from 0.2 μm to 3 μm.

A fifty-fifth aspect of the present disclosure includes the method of any of the fifty-first through fifty-fourth aspects, further including a second colored layer disposed on and in direct contact with the first portion.

A fifty-sixth aspect of the present disclosure includes the method of the fifty-fifth aspect, wherein the first colored layer is a different color than the second colored layer.

A fifty-seventh aspect of the present disclosure includes the method of the fifty-fifth aspect, wherein the first colored layer and the second colored layer each comprise a silicone based ink material.

A fifty-eighth aspect of the present disclosure includes the method of any of the fifty-first through fifty-seventh aspects, wherein the first portion of the outer surface and the second portion of the outer surface differ in optical reflectivity or scattering of visible light.

A fifty-ninth aspect of the present disclosure includes the method of any of the fifty-first through fifty-eighth aspects, wherein the first root-mean-square roughness is in a range of from 50 nm to 500 nm.

A sixtieth aspect of the present disclosure includes the method of the fifty-ninth aspect, wherein the second root-mean-square roughness is in a range of from 20 nm to 40 nm.

A sixty-first aspect of the present disclosure includes the method of any of the fifty-first through sixtieth aspects, wherein the first portion is a laser-modified region of the outer surface.

Additional features and advantages of the processes and systems described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of methods and systems for processing optical fibers and fiber bundle supports, such as cable jackets, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. More specifically, the methods and systems described herein relate to laser-based systems and processes that enable the application and adhesion of a second colored layer directly over a first colored layer of an optical fiber or an optical fiber support to enable an increase in the number of color-coded identifications of individual optical fibers in a group of optical fibers, such as in bundles of optical fibers in a cable assembly. The embodiments described herein may be used to directly apply distinctive color markings (i.e., the second colored layer) onto an existing colored ink layer (i.e., the first colored layer) to uniquely identify and to make optical fibers and fiber bundle supports distinguishable to an in-field installation technician/engineer.

For example, in methods described herein, a laser beam may be directed onto the first colored layer of the optical fiber or the fiber bundle support to modify the first colored layer and form one or more laser-modified regions. The laser-modified regions may comprise microcracks, protrusions, or both, which enables ink or other coloring agent to be directly adhered to the first colored layer to form the second colored layer. The laser-modified regions are preferably shallow, having a thickness of about 10 μm or less in some embodiments. Thus, when formed in the first colored layer of an optical fiber, the laser-modified regions do not degrade the mechanical integrity of the optical fiber or the waveguiding properties and performance of the optical fiber. Moreover, the processes described herein provide a low-cost solution with good tolerance to positional accuracy of optical fibers and/or fiber bundle supports during the process. Various embodiments of methods and systems for processing optical fibers and fiber bundle supports to increase the number of color-coded identifications of individual optical fibers and bundles of optical fibers in a cable assembly will be described herein with specific reference to the appended drawings.

Referring now toFIGS.1and2, processing systems configured to process an optical fiber20are schematically depicted.FIG.1depicts a processing system comprising an optical fiber draw tower101configured to draw the optical fiber20from an optical fiber preform10.FIG.2depicts a processing system comprising a spool-to-spool system102configured to modify the optical fiber20in an offline process after the optical fiber20has been drawn. Both the optical fiber draw tower101and the spool-to-spool system102comprise an optical system120and an ink station150. As described in detail herein, the optical system120is configured to modify, for example to ablate, a first colored layer32(FIGS.3A-4) of the optical fiber20to form one or more laser-modified regions34on an outer surface35of the first colored layer32and the ink station150is configured to apply an ink152(FIGS.9A-9C) to the one more laser-modified regions34to form the second colored layer36(FIG.4) directly adhered to the one or more laser-modified regions34of the first colored layer32.

Referring now toFIG.1, the optical fiber draw tower101comprises a draw furnace110, a coating station112, a drying station114, a first curing station116, a second curing station118and a fiber collection unit190. The optical fiber draw tower101further comprises the optical system120and the ink station150. As depicted inFIG.1, a fiber pathway15extends from the draw furnace110to the fiber collection unit190and is the pathway along which an optical fiber20travels during production. As depicted inFIG.1, an optical fiber preform10is placed in the draw furnace110. The optical fiber preform10may be constructed of any glass or material suitable for the manufacture of optical fibers20(e.g. silica, doped silica, or combinations thereof). In operation, the draw furnace110may heat the optical fiber preform10such that the optical fiber20may be drawn from the optical fiber preform10. The draw furnace110may be oriented along the fiber pathway15, which may be a vertical pathway, such that the optical fiber20drawn from the optical fiber preform10exits the draw furnace110in a downward direction. By orienting the draw furnace110in a vertical direction, the optical fiber20may be drawn from the optical fiber preform10by the weight of the optical fiber preform10as the optical fiber preform10softens due to the temperature of the draw furnace110and, in some embodiments, by tension applied to the optical fiber20, and thereby applied to the optical fiber preform10, by the fiber collection unit190.

After the optical fiber20exits the draw furnace110, the optical fiber20traverses the coating station112, which applies a first colored layer32to the optical fiber20, and in some embodiments, applies one or more buffer layers, such as a first buffer layer26and a second buffer layer28. First buffer layer26and second buffer layer28are also known in the art as primary and secondary coatings, respectively. For example, in embodiments comprising buffer layers, the coating station112may first apply the first buffer layer26onto the cladding24, next apply the second buffer layer28onto the first buffer layer26, and next apply the first colored layer32directly onto the second buffer layer28. While a single coating station112is depicted inFIG.1, it should be understood that embodiments comprising multiple coating stations are contemplated, for example, coating stations for applying each of the first buffer layer26, the second buffer layer28, and the first colored layer32, respectively.

As shown inFIG.1, the optical fiber20next traverses an optional drying station114and the first curing station116. In some embodiments, the drying station114is an oven that applies heat to the first colored layer32and any other layers applied by the coating station112to dry these layers. In addition, the first curing station116ensures that the first buffer layer26, the second buffer layer28, and/or the first colored layer32are cured before the optical fiber20reaches the optical system120. AlthoughFIG.1depicts the first curing station116as a single process unit following the coating station112, it is understood that in other embodiments, multiple curing stations may be present along fiber pathway15before the optical fiber20enters the optical system120. For example, first buffer layer26may be applied by a coating station and cured before applying (or curing) second buffer layer28. Second buffer layer28may be applied and cured before applying (or curing) first colored layer32. First buffer layer26and second buffer layer28may be applied and cured simultaneously before applying (or curing) first colored layer32. In each embodiment, the first colored layer32is cured upon entry to optical system120in which a laser beam180is directed onto the first colored layer32. The first curing station116may be an ultraviolet (UV) curing station that includes UV light emitting diodes (LEDs) to cure the first colored layer32. Alternatively, the first curing station116may include Hg lamps for UV curing or a heater for thermal curing.

Next, the optical fiber20traverses the optical system120where the laser beam180is directed onto the optical fiber20to form the one or more laser-modified regions34in the first colored layer32. After formation of the one or more laser-modified regions34, the optical fiber20traverses the ink station150where the second colored layer36is directly applied to the one or more laser-modified regions34. Both the optical system120and laser formation of the one or more laser-modified regions34are described in more detail below with respect toFIGS.3A-8. Furthermore, both the ink station150and the application of ink152to form the second colored layer36directly onto the one or more laser-modified regions34are described in more detail below with respect toFIGS.9A-9C. After application of ink to form the second colored layer36, the optical fiber20may traverse the optional second curing station118, which cures the ink of the second colored layer36. Like the first curing station116, the second curing station118may be an ultraviolet (UV) curing station that includes UV light emitting diodes (LEDs) to cure the second colored layer36. Alternatively, the second curing station118may include Hg lamps for UV curing or a heater for thermal curing.

Referring still toFIG.1, after formation and processing, the optical fiber20may be wound onto a fiber storage spool192with a fiber collection unit190. The fiber collection unit190utilizes drawing mechanisms and tensioning pulleys, such as a capstan194and a screen-testing pulley193, to facilitate winding the optical fiber20onto the fiber storage spool192. The capstan194may provide the necessary tension to the optical fiber20as the optical fiber20is drawn along the fiber pathway15and the screen-testing pulley193moves into and out of contact with the optical fiber20for tension testing/quality control. Accordingly, the fiber collection unit190may directly contact the optical fiber20in order to both wind the optical fiber20onto fiber storage spool192as well as to provide the desired tension on the optical fiber20as it is drawn through the draw furnace110, the coating station112, the drying station114, the first curing station116, the optical system120, the ink station150, and the second curing station118.

Referring now toFIG.2, the spool-to-spool system102comprises a first fiber spool195and a second fiber spool196positioned such that the fiber pathway15extends from the first fiber spool195to the second fiber spool196. Similar to the optical fiber draw tower101, the spool-to-spool system102includes the optical system120and the ink station150, each positioned along the fiber pathway15where the optical system120is positioned between the first fiber spool195and the ink station150. While not depicted, the spool-to-spool system102may further comprise a curing station, similar to the second curing station118ofFIG.1, that is configured to cure the ink applied by the ink station150, which forms the second colored layer36. The spool-to-spool system102facilitates the formation of laser-modified regions34on the first colored layer32of the optical fiber20and the application of the second colored layer36directly onto the first colored layer32during a process that is separate from the initial manufacture of the optical fiber20(e.g., the initial drawing process that forms the optical fiber20from the optical fiber preform10as shown inFIG.1). In other embodiments, first buffer layer26and second buffer layer28are formed in the initial manufacture of the optical fiber20and first colored layer32is subsequently applied in a separate offline process that includes, for example, a spool-to-spool system that includes a coating station and a curing station. The optical fiber20so formed may then be introduced into the spool-to-spool system shown inFIG.2for laser modification and formation of the second colored layer36. Alternatively, the spool-to-spool system102may include a coating station and a curing station positioned between first fiber spool195and optical system120so that application and curing of first colored layer32laser modification, and formation of second colored layer36occur in a single spool-to-spool process. The optical fiber draw tower101and the spool-to-spool system102are two example processing systems that facilitate the formation of laser-modified regions34on the first colored layer32of the optical fiber20and the application of the second colored layer36directly onto the first colored layer32. However, it should be understood that the methods described herein may be applied to any processing system that includes the optical system120and the ink station150.

Referring now toFIGS.3A and3B, the optical fiber20is depicted undergoing laser processing by the optical system120to form the one or more laser-modified regions34in the first colored layer32. In particular,FIG.3Ais a schematic lengthwise cross section of the optical fiber20undergoing laser processing andFIG.3Bis a schematic radial cross section of the optical fiber20undergoing laser processing. The optical fiber20comprise a core22and a cladding24surrounding the core22. The core22and the cladding24each comprises a glass material and the core22comprises a higher refractive index than the cladding24. The first colored layer32surrounds the cladding24. In some embodiments, as depicted inFIGS.3A and3B, the optical fiber20further comprises one or more buffer layers disposed between the cladding24and the first colored layer32, such as the first buffer layer26and the second buffer layer28. The first buffer layer26and the second buffer layer28may comprise a polymer material, such as acrylate, epoxy, or the like.FIGS.3A and3Bdepict the laser beam180output by the beam source122of the optical system120directed onto the first colored layer32of the optical fiber20such that the laser beam180modifies the first colored layer32to form the one or more laser-modified regions34along an outer surface35of the first colored layer32.

Referring now toFIGS.3C and3D, a portion of the optical fiber20ofFIGS.3A and3Bis shown that depicts embodiments of the laser-modified region34formed in the first colored layer32in more detail. The laser-modified regions34include modification features38formed by modifying the first colored layer32with a laser beam. The modification features38correspond to deviations in the smoothness or texture of outer surface35relative to the unmodified portions of outer surface35. Examples of modification features38include microcracks, protrusions, depressions, undulations, and combinations thereof. The modification features38increase the roughness and/or surface area of the portion of the outer surface35modified by the laser to form laser-modified regions34. While not wishing to be bound by theory, it is believed that the increased roughness and/or surface area of laser-modified regions34increase adhesion of second colored layer36to first colored layer32. The laser-modified regions34include a plurality of modification features38, which may or may not be equal in physical dimensions and which may or may not be positioned equally spaced within laser-modified regions34. For purposes of the present disclosure, the term “roughness” means root-mean-square roughness. In some embodiments, the roughness of the laser-modified regions34may be in a range of from 25 nm to 500 nm, for example 25 nm, 35 nm, 50 nm, 70 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 750 nm, 1.0 μm, 2.0 μm, 3.0 μm, up to the full thickness of the first colored layer32, or any range having any two of those values as endpoints. Portions of the first colored layer32that are not laser modified have a lower roughness than the laser-modified regions34. For example, portions of the first colored layer32that are not laser modified have a roughness in a range of from 20 nm to 40 nm, for example 25 nm, 30 nm, 35 nm, or any range having any two of those values as endpoints.

For example,FIG.3Cshows an embodiment of the laser-modified region34with modification features38comprising a plurality of microcracks extending into the first colored layer32andFIG.3Dshows an embodiment of the laser-modified region34with modification features38comprising a plurality of protrusions extending from the first colored layer32. It should be understood that, the modification features38of the one or more laser-modified regions34may comprise a plurality of microcracks extending into the first colored layer32, a plurality of protrusions extending from the first colored layer32, or combinations thereof. Although depicted as equally spaced inFIGS.3C and3D, it is understood that the spacing between adjacent ones of the modification features38or the thickness of the features within laser-modified regions34may be the same or different. The modification features38within laser-modified regions34may be periodically arranged or randomly arranged.

As depicted inFIGS.3C and3D, the one or more laser-modified regions34comprise a thickness T of 10 μm or less. For example, the thickness T of the one or more laser-modified regions34, or of the one or more modification features38formed therein, may comprise a range of from 0.2 μm to 10 μm or a range of from 0.5 μm to 10 μm, such as from 0.2 μm to 8 μm, or from 0.2 μm to 5 μm, or from 0.2 μm to 3 μm, or from 0.5 μm to 8 μm, or from 0.5 μm to 5 μm, or from 0.5 μm to 3 μm, or from 1 μm to 8 μm, or from 1 μm to 5 μm, or from 1 μm to 3 μm, for example, the thickness T may be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or any range having any of these two values as endpoints. Furthermore, the first colored layer32may comprise a thickness of in a range of from 1 μm to 20 μm, such as 2 μm to 10 μm. The thickness T of the one or more laser-modified regions34may be less than the thickness of the first colored layer32. For example, the thickness T of the one or more laser-modified regions34may be less than 90% of the thickness of the first colored layer32, for example, less than 80%, less than 70%, less than 50%, less than 30%, or a range having any of these values as endpoints. Moreover, after application of the second colored layer36onto the laser-modified regions34, the outer diameter of the second colored layer36may be within 20% of the outer diameter of the first colored layer32prior to forming the laser-modified regions34, such as within 15%, within 10%, within 5%, or within a percentage range having any two of these values as endpoints.

In some embodiments, the one or more laser-modified regions34are intermittently spaced along a length of the optical fiber20and in other embodiments the one or more laser-modified regions comprise a single, continuous laser-modified region34extending along the length of the optical fiber20. In some embodiments, the one or more laser-modified regions34extend around an entire circumference of outer surface35and in other embodiments the one or more laser-modified regions34extend around a portion of an entire circumference of outer surface35. The one or more laser-modified regions34, for example, may extend around greater than 5%, or greater than 10%, or greater than 25%, or greater than 50%, or greater than 75%, or greater than 90%, or between 5% and 100%, or between 25% and 100%, or between 50% and 100%, or between 10% and 90%, or between 20% and 80% of the entire circumference of the outer surface35. Moreover, the one or more laser-modified regions34may extend around the circumference of the outer surface35is an intermittent manner, such that the coverage of the one or more laser-modified regions34is not continuous. This facilitates adherence of the second colored layer36to the outer surface35in an intermittent manner, such as a striped manner.

In some embodiments, the laser beam180modifies the first colored layer32by ablation, which is the removal and/or modification of a material by laser interaction. Ablation occurs due to energy transfer from the laser beam180to the material of the first colored layer32. In the embodiments described herein, the laser beam180ablates by non-linear absorption, which is often referred to as multi-photon absorption (MPA), linear absorption, or a combination of non-linear and linear absorption. Ablation changes the texture and the topography of the laser-modified regions34, which include peaks and valleys due to spatially inhomogeneous material removal induced by the laser beam180, cracks that penetrate at or below the outer surface35, and melted and redeposited material. Without intending to be limited by theory, adhesion of the ink152(FIGS.9A-9C) to the one or more laser-modified regions34is due to the change in the texture and the topography of the laser-modified regions34, because the ink152permeates and interlocks with the modified surface of the laser-modified regions34. For example, topography changes creates roughness in the laser-modified regions34that increases the contact area between the ink152and the laser-modified regions34facilitating mechanical interlocking therebetween. In addition, the ink152may flow into the cracks and crevasses of the laser-modified regions34to retain and hold the color of the ink152and help increase ink adhesion. Moreover, melted and redeposited material in the laser-modified regions34form protrusions that allow interlocking or entanglement with the ink152after it dries and forms the second colored layer36—analogous to a “velcro-type” adhesion. Adhesion strength depends on both the characteristics of the laser-modified regions34and characteristics of the ink152, such as ink layer thickness and viscosity.

Without intending to be limited by theory, laser modification on the outer surface35of the first colored layer32depends on the pulse duration, wavelength, repetition rate, concentration, and shape of the laser beam180. For example, reducing the beam waist size of the laser beam180at the outer surface35increases its energy fluence and intensity, therefor increasing the ablation rate and ablated volume in the first colored layer32. In the embodiments described herein, the energy fluence and intensity of the laser beam180impinging the first colored layer32is such that the first colored layer32is modified enough to promote ink adhesion without damaging or modifying the optical and mechanical properties of the optical fiber20. In one embodiment, the attenuation of an optical signal in the optical fiber (as measured in units of dB/km e.g. at a wavelength of 1310 nm or 1550 nm) is the same before and after exposure of the first colored layer32to the laser beam180. Furthermore, the first buffer layer26and the second buffer layer28are not laser modified by the laser beam180, even in portions of the first buffer layer26and the second buffer layer28directly below the laser-modified regions34of the first colored layer32.

While ablation is primarily discussed herein, other forms of laser modification are contemplated, such as severing of the first colored layer32, modification of the surface chemistry of the first colored layer32, such as modification of the surface tension of the first colored layer32or modification of the energy state of the molecules of the first colored layer32, or densification of the first colored layer32. Moreover, in embodiments in which the surface chemistry of the first colored layer32is modified, the laser-modified regions34comprise minimal to no thickness (i.e., the thickness T of the laser-modified regions would be at or near zero), minimizing the thickness of the second colored layer36needed to adhere to the first colored layer32. Alternatively, in other embodiments, the second colored layer36may be applied to the first colored layer32before laser forming the laser-modified regions34on the outer surface35of the first colored layer32. In this embodiment, the laser beam180traverses the second colored layer36and impinges the outer surface35of the first colored layer32, depositing enough laser energy to generate a phase change on the first colored layer32(such as melting) or a viscosity change on the first colored layer32, such that the ink of the second colored layer36can diffuse into or combine with the first colored layer32. In this alternative embodiment, the ink station150may be placed upstream the optical system120along the fiber pathway15in the various processing systems described herein such that the ink of the second colored layer36is applied before laser processing.

Referring now toFIG.4, the optical fiber20is depicted after both laser processing and ink application in an embodiment such that the optical fiber20comprises the first colored layer32having one or more laser-modified regions34and the second colored layer36surrounding the first colored layer32. The second colored layer36is directly adhered to the one or more laser-modified regions34of the first colored layer32. The first colored layer32and the second colored layer36each comprise a different color to provide unique visual identification for use in a cabling assembly. The one or more laser-modified regions34are a surface onto which the ink152that forms second colored layer36can adhere. Without the one or more laser-modified regions34, the ink152will disperse and agglomerate without any adherence on the first colored layer32, allowing the ink152to be easily wiped off. However, the processes described herein promote adhesion of inks152and existing paint composition that are standards in the optical fiber industry, such as silicone based inks including NEO 8 and NEO 9. Furthermore, the texture or surface area associated with the one or more laser-modified regions34may lead to differences in the reflection or scattering of visible light to provide an optical contrast relative to the unmodified portion of outer surface35. Such optical contrast within or along the first colored layer32may in and of itself provide a unique visual identification, independent of and/or without application of the ink152, that forms the second colored layer36.

Referring now toFIGS.5A-8, example embodiments of the optical system120for producing a laser beam180are schematically depicted.FIGS.5A-5Cdepict an optical system120A,120A′ that comprises the beam source122and a cylindrical lens pair124,124′.FIG.6depicts an optical system120B that comprises the beam source122and a first aspheric optical element130.FIGS.7A-7Cdepict an optical system120C that comprises the beam source122and an off-axis parabolic mirror140.FIG.8depicts an optical system120D that comprises the beam source122, the first aspheric optical element130, a second aspheric optical element131, and a focusing mirror138. Some or all of the lenses, the mirrors, and the beam source122of the optical system120ofFIGS.5A-8may be mounted on movable stages, such as galvo-scanners, linear translation stages, electro-optical devices, acousto-optical devices, or the like, to help align the optical components and steer the laser beam180. In some embodiments, one or more sensors may be used to track the lateral position of the optical fiber20along the fiber pathway15and use the movable stages to maintain the focus of the laser beam180on the optical fiber20. This may account for the natural fiber motion that occurs in the optical fiber draw tower101and the spool-to-spool system102.

Each of the optical assemblies comprise the beam source122that outputs the laser beam180, which may comprise a Gaussian laser beam. The beam source122may comprise, a gas laser, a solid state laser, a fiber laser, a semiconductor diode laser, or the like. The beam source122may have adjustable power up to 5 kW and adjustable repetition rate from a single shot up to 10 MHz. In some embodiments, the beam source122may output a laser beam180comprising a wavelength of, for example, 10600 nm, 9300 nm, 1064 nm, 1030 nm, 532 nm, 530 nm, 355 nm, 343 nm, or 266 nm, or 215 nm.

In some embodiments, the laser beam180emitted by the beam source122is pulsed and comprises short light pulses (e.g., in the range from femtoseconds to microseconds) or pulse bursts having a closely spaced series of sub-pulses. Pulsed versions of the laser beam180may comprise a pulse duration ranging from a few nanoseconds to tens of microseconds. Moreover, the beam source122may simultaneously generate multiple pulsed beams having different phases. In some embodiments, the laser beam180emitted by the beam source122is a continuous wave laser beam. Without intending to be limited by theory, embodiments comprising a continuous wave laser beam are emitted with more laser energy than the pulsed laser beams because the energy is temporally spread over a much longer period than the sharp intensity provided by a pulsed laser beam.

Without intending to be limited by theory, the energy transfer to the first colored layer32depends on how much of the energy of the laser beam180is absorbed by the first colored layer32and, in some embodiments, the second buffer layer28, in the linear absorption regime and non-linear absorption regime. In the linear absorption regime, the amount of laser energy that is transferred to the first colored layer32to modify the first colored layer32(i.e., to form the one or more laser-modified regions34) is dependent on the absorption curve of the material of the first colored layer32and, in some embodiments, the absorption curve of the adjacent buffer layer (e.g., the second buffer layer28) relative to the wavelength of the laser beam180. Since the ink colors used in first colored layer32are in the visible range of the electromagnetic spectrum, it may be useful to use wavelengths in the visible range, such as a 532 nm laser, to increase linear absorption. High levels of linear absorption are also achievable at ultraviolet wavelengths, such as 355 nm, and infrared wavelengths such as wavelengths in a range of from 9 μm to 10 μm.

Referring now toFIGS.5A-5C, the optical system120A will be described in more detail.FIG.5Ais a schematic side view of the optical system120A andFIG.5Bis a schematic top view of the optical system120A, whileFIG.5Cdepicts a laser beam focus182formed using the optical system120A. The optical system120A comprises the cylindrical lens pair124, which includes a first cylindrical lens125and a second cylindrical lens126positioned between and optically coupled to the beam source122and the fiber pathway15. In other words, the second cylindrical lens126is downstream the first cylindrical lens125along a laser pathway181and the second cylindrical lens126is upstream the fiber pathway15, which intersects the laser pathway181such that the laser beam180may be directed onto the optical fiber20when the optical fiber20is traversing the fiber pathway15. As used herein, “upstream” and “downstream” refer to the relative position of two locations or components along a laser pathway with respect to a beam source. For example, a first component is upstream from a second component if the first component is closer to the beam source122along the laser pathway181traversed by the laser beam180than the second component.

In operation, a cylindrical lens, such as the first and second cylindrical lenses125,126, widens the laser beam focus182of the laser beam180. Without intending to be limited by theory, a single cylindrical lens focuses the laser beam180in one direction orthogonal to the laser pathway181, that is, orthogonal to the beam propagation direction (e.g., a first orthogonal direction) without affecting the beam in another direction orthogonal to the laser pathway181(e.g., a second orthogonal direction, which is also orthogonal to the first orthogonal direction). However, for many lasers, modification by a single cylindrical lens would not form an energy density at the laser beam focus182large enough to modify (e.g., ablate) the first colored layer32of the optical fiber20. Thus, in the optical system120A, the first cylindrical lens125is rotated 90° about a laser pathway181with respect to the second cylindrical lens126to further widen the laser beam focus182. Indeed, as shown inFIG.5C, the cylindrical lens pair124produces a laser beam focus182comprising a short axis SAorthogonal a long axis LA, where the long axis LAis longer than the short axis SA, such as 10 or more times longer than the short axis SA. For example, the long axis LAmay be 5 or more times longer than the short axis SA. This increases the energy density of the laser beam focus182along the short axis SAand thus, by orienting the short axis SAalong the fiber pathway15, this increased energy density is directed onto the outer surface35of the optical fiber20. Moreover, by orienting the long axis LAorthogonal to fiber pathway15, it is possible to modify half the circumference of the outer surface35of the optical fiber (i.e., modify a “hemisphere” of the outer surface35of the optical fiber20) in a single laser impingement, while providing tolerance for some lateral motion of the optical fiber20as the optical fiber traverses the fiber pathway15. Moreover, due to lensing effects caused by the first colored and/or buffer layers of the optical fiber20, the laser beam focus182may modify more than one half of the circumference of the optical fiber20, extending the laser-modified regions34further around the circumference of the optical fiber20. Indeed, the geometric shape of the optical fiber20, it acts as a lens and refocuses light absorbed by the first colored layer32upon initial impingement and ablation.

In some embodiments, as depicted inFIGS.5A and5B, the optical system120A is a first optical system120A and the optical system120further comprises a second optical system120A′. In this embodiment, the beam source122is a first beam source122, the laser beam180output by the first beam source122is a first laser beam180, and the cylindrical lens pair124is a first cylindrical lens pair124. Furthermore, the second optical system120A′ comprises a second beam source122′ configured to output a second laser beam180′ and a second cylindrical lens pair124′ comprising a first cylindrical lens125′ and a second cylindrical lens126′. The first cylindrical lens125′ is rotated 90° about a second laser pathway181′ with respect to the second cylindrical lens126′. In operation, the first laser beam180is directed onto a first hemisphere41(FIG.4) of the first colored layer32and the second laser beam180′ is directed onto a second hemisphere42(FIG.4) of the first colored layer32, such that the second laser beam180′, for example, the second laser beam focus182′ modifies the first colored layer32to form laser-modified regions34on the second hemisphere42of the first colored layer32. As shown in more detail inFIG.4, the first hemisphere41of the first colored layer32is opposite the second hemisphere42of the first colored layer32and the first hemisphere41is depicted as separated from the second hemisphere42by a radial centerline40. Thus, using the first laser beam180and the second laser beam180′, the one or more laser-modified regions34may be formed around the entire circumference of the first colored layer32. Moreover, whileFIGS.5A and5Bdescribe laser modification of the first colored layer32using two laser beams180,180′, it should be understood that laser modification of the first colored layer32may be performed by more than two laser beams, which may each impinge the first colored layer32simultaneously.

Referring now toFIG.6, the optical system120B comprises a first aspheric optical element130, such as an axicon lens positioned along a first segment183of the laser pathway181between the beam source122and a mirror136, such as a folding mirror. The mirror136optically couples the first segment183of the laser pathway181with a second segment185of the laser pathway181. In some embodiments, the first segment183of the laser pathway181is orthogonal to the second segment185of the laser pathway181. Furthermore, the second segment185of the laser pathway181is collinear with the fiber pathway15. Indeed, the fiber pathway15extends through a hole137in the mirror136such that the optical fiber20may travel along the second segment185of the laser pathway181and pass through the hole137. As described in more detail below, this allows the laser beam180to impinge the entire circumference of the optical fiber20.

Referring still toFIG.6, the optical system120B further comprises a first lens132positioned along the first segment183of the laser pathway181between the first aspheric optical element130and the mirror136and a second lens134positioned along the second segment185of the laser pathway181, downstream the mirror136. As the second lens134is positioned within the second segment185of the laser pathway181, which is collinear with the fiber pathway15, the second lens134comprises a hole135aligned with both the second segment185of the laser pathway181and the fiber pathway15, such that the optical fiber20may extend through the hole135in the second lens134. In operation, the first lens132collimates the laser beam180between the first lens132and the second lens134and the second lens134may focus the laser beam180, for example, onto the optical fiber20. In some embodiments, the first lens132and the second lens134each comprise plano-convex lenses. When the first lens132and the second lens134each comprise plano-convex lenses, the curvature of the first lens132and the second lens134may each be oriented toward the mirror136. In other embodiments, the first lens132may comprise other collimating lenses and the second lens134may comprise a meniscus lens, an asphere, or another higher-order corrected focusing lens. Moreover, it should be understood that some embodiments may not include the first lens132and the second lens134and instead, the first aspheric optical element130may focus the laser beam180off the mirror136and thereafter directly onto the optical fiber20.

In some embodiments, the first aspheric optical element130comprises a conical wavefront producing optical element, such as an axicon lens, which may be a negative refractive axicon lens (e.g., negative axicon), a positive refractive axicon lens, a reflective axicon lens, a diffractive axicon lens, a phase axicon, or the like. In operation, propagating the laser beam180, e.g., an incoming Gaussian beam, through the first aspheric optical element130may alter, for example, phase alter, the laser beam180such that the portion of the laser beam180propagating downstream the first aspheric optical element130is a quasi-non-diffracting beam of the Bessel type. A detailed description of the formation of quasi-non-diffracting beams of the Bessel type and determining their length, is provided in U.S. Pat. No. 10,730,783, which is incorporated by reference in its entirety. In the unfocused space, the quasi-non diffracting beam has an annular shape (e.g., a ring shape). A tight focus in the transverse direction (e.g., a laser beam focus184) is attainable and it extends over a longer region along the laser pathway181(i.e., the beam axis) and along the outer surface35of first colored layer32than a focused Gaussian beam, such as the laser beam focus182,182′.

In operation, the light annulus can be focused with a lens and therefore it is possible to make the light converge from all directions with equal intensity. As shown inFIG.6, the first aspheric optical element130generates a diverging annulus of light that is quasi-non-diffracting of the Bessel type. The first lens132collimates the annulus, the mirror136directs the collimated annulus along the second segment185of the laser pathway181, collinear with the fiber pathway15, and the second lens134re-images (e.g., focuses) the quasi-non-diffracting Bessel type onto the fiber pathway15. Thus, the optical fiber20may be impinged by the laser beam180along its entire circumference in a single impingement. However, due to the nature of the quasi-non-diffracting Bessel type beam, a more powerful laser might be needed when compared to the optical system120A ofFIGS.5A-5Csince the energy is distributed over a larger volume compared to a Gaussian beam, as shown inFIGS.7B and7C, described below.

Referring now toFIGS.7A-7C, the optical system120C comprises an off-axis parabolic mirror140optically coupled to the beam source122and optically coupling the first segment183of the laser pathway181with the second segment185of the laser pathway181. Similar to the optical system120B, the second segment185of the laser pathway181is collinear with the fiber pathway15. Furthermore, the first segment183of the laser pathway181is orthogonal with the second segment185of the laser pathway181. Similar to the mirror136of the optical system120B, the off-axis parabolic mirror140comprises a hole141aligned with the fiber pathway15such that the fiber pathway15extends through the hole141and the optical fiber20may be translated through the hole141. In operation, the off-axis parabolic mirror140focuses the laser beam180in a direction perpendicular to the direction in which the laser beam180impinges the off-axis parabolic mirror140. Similar to the optical system120B, the optical system120C directs the laser beam180onto the entire whole circumference of the optical fiber20.

The laser beam focus186formed using the off-axis parabolic mirror140may comprise a Gaussian laser beam focus186A, as shown inFIG.7B, which resembles the focus formed using a traditional spherical lens (similar to the second laser beam focus182′ ofFIGS.5A-5C). However, in some embodiments, the first aspheric optical element130ofFIG.6may be positioned between the beam source122and the off-axis parabolic mirror140such that the laser beam focus formed using the off-axis parabolic mirror140comprises a Bessel laser beam focus186B (similar to the laser beam focus184ofFIG.6).FIG.7Bschematically depicts the length of interaction LiAbetween the Gaussian laser beam focus186A and the optical fiber20, which is the length along the optical fiber20in which the Gaussian laser beam focus186A induces linear and/or non-linear absorption in the first colored layer32.FIG.7Cschematically depicts the length of interaction LiBbetween the Bessel laser beam focus186B and the optical fiber20, which is the length along the optical fiber20in which the Bessel laser beam focus186B induces linear and/or non-linear absorption in the first colored layer32. Due to the nature of the quasi-non-diffracting Bessel type beam that forms Bessel laser beam focus186B, the length of interaction LiBof the Bessel laser beam focus186B is longer than the length of LiAof the Gaussian laser beam focus186A, thus, a more powerful laser may be needed when compared to the optical system120A ofFIGS.5A-5Csince the energy is distributed over a larger volume compared to a Gaussian beam.

Referring now toFIG.8, the optical system120D comprises the first aspheric optical element130and a second aspheric optical element131positioned along the first segment183of the laser pathway181between the beam source122and the mirror136, which optically couples the first segment183of the laser pathway181with the second segment185of the laser pathway181. The optical system120D further comprises a focusing mirror138positioned along the second segment185of the laser pathway181downstream the mirror136. Similar to the optical system120B (FIG.6), the first segment183of the laser pathway181is orthogonal to the second segment185of the laser pathway181. Furthermore, the second segment185of the laser pathway181is collinear with the fiber pathway15. The fiber pathway15extends through the hole137in the mirror136and a hole139in the focusing mirror138such that the optical fiber20may travel along the second segment185of the laser pathway181and pass through the hole137and the hole139. The hole139is collinear with the fiber pathway15and is aligned with the second segment185of the laser pathway181, the fiber pathway15, and the hole137of the mirror136. As described in more detail below, this allows the laser beam180to impinge the entire circumference of the optical fiber20.

Similar to the first aspheric optical element130, the second aspheric optical element131comprises a conical wavefront producing optical element, such as an axicon lens, which may be a negative refractive axicon lens (e.g., negative axicon), a positive refractive axicon lens, a reflective axicon lens, a diffractive axicon lens, a phase axicon, diffractive optical element, or the like. In operation, propagating the laser beam180, e.g., an incoming Gaussian beam, through the first aspheric optical element130may alter, for example, phase alter, the laser beam180such that the portion of the laser beam180propagating downstream the first aspheric optical element130is a quasi-non-diffracting beam of the Bessel type. Moreover, the second aspheric optical element131may be oriented such that its conical end faces the conical end of the first aspheric optical element130and thus the second aspheric optical element131collimates the quasi-non-diffracting beam. For example, the first aspheric optical element130may comprise a concave axicon and the second aspheric optical element131may comprise a convex axicon. Furthermore, the first aspheric optical element130and the second aspheric optical element131may be replaced by a single monolithic optical element with a concave conical surface at an upstream surface (e.g., input surface), which replaces the first aspheric optical element130, and a convent conical surface at a downstream surface (e.g., output surface), which replaces the second aspheric optical element131. In the unfocused space, the quasi-non diffracting beam has an annular shape (e.g., a ring shape). A tight focus in the transverse direction (e.g., a laser beam focus188) is attainable and it extends over a longer region along the laser pathway181(i.e., the beam axis) and along the outer surface35of first colored layer32than a focused Gaussian beam, such as the laser beam focus182,182′ (FIG.5C).

In operation, the light annulus can be focused with the focusing mirror138and therefore it is possible to make the light converge from all directions with equal intensity. As shown inFIG.8, the first aspheric optical element130generates a diverging annulus of light that is quasi-non-diffracting of the Bessel type. The second aspheric optical element131collimates the annulus, the mirror136directs the collimated annulus along the second segment185of the laser pathway181, collinear with the fiber pathway15, and the focusing mirror138redirects and re-images (e.g., focuses) the quasi-non-diffracting Bessel type onto the fiber pathway15. Indeed, the focusing mirror138redirects the laser beam180such that the laser beam focus188forms between the mirror136and the focusing mirror138and the optical fiber20may be impinged by the laser beam180along its entire circumference in a single impingement. However, due to the nature of the quasi-non-diffracting Bessel type beam, a more powerful laser might be needed when compared to the optical system120A ofFIGS.5A-5Csince the energy is distributed over a larger volume compared to a Gaussian beam.

Referring again toFIGS.5A-8, in any of the embodiments described herein, the laser beam180may comprise a pulsed laser beam comprising single pulses or pulse bursts having 2 sub-pulses per pulse burst or more. In some embodiments, the pulsed laser beam comprises a pulse burst having from 2 sub-pulses to 30 sub-pulses, such as from 2 sub-pulses to 25 sub-pulses, from 2 sub-pulses to 20 sub-pulses, from 2 sub-pulses to 25 sub-pulses, from 2 sub-pulses to 12 sub-pulses, from 2 sub-pulses to 10 sub-pulses, from 2 sub-pulses to 8 sub-pulses, from 2 sub-pulses to 5 sub-pulses or any range having any two of these values as endpoints. A pulse burst is a short and fast grouping of sub-pulses (i.e., a tight cluster of sub-pulses, such as sub-pulses that are emitted by the beam source122and interact with the material (i.e. MPA in the material of the optical fiber20, particularly the first colored layer32and the second buffer layer28). While not intending to be limited by theory, if the laser beam180is directed onto the optical fiber20as a pulse burst and a time between temporally adjacent sub-pulses is equal to or less than the rate of thermal diffusion in the first colored layer32, then the temperature rise in the first colored layer32from subsequent sub-pulses is additive. This additive temperature rise may increase the multi-photon absorption imparted by the laser beam180and reduce unwanted nonlinear effects.

Furthermore, each pulse burst may comprise a burst duration (i.e., a time between the start of first sub-pulse in the pulse burst and the end of the final sub-pulse in pulse burst) of from 10 ps to 500 ns, such as from 3 ns to 50 ns. In addition, each pulse burst may have a sub-pulse separation between temporally adjacent sub-pulses of from 1 ps to 50 ns, such as from 10 ns to 30 ns. Moreover, each pulse burst may comprise a repetition rate of from 100 kHz to 1500 kHz, such as 200 kHz, 300 kHz, 400 kHz, 500 kHz, 600 kHz, 700 kHz, 800 kHz, 900 kHz, 1000 kHz, 1100 kHz, 1200 kHz, 1300 kHz, 1400 kHz or any range having any two of these value as endpoints. Without intending to be limited by theory, by increasing the burst duration, while still retaining a time between temporally adjacent sub-pulses low enough to generate multi-photon absorption and a fast temperature rise in the first colored layer32, more power can be delivered to the first colored layer32while minimizing or even avoiding unwanted nonlinear effects. The repetition rate of the laser beam180may correspond to the translation speed of the optical fiber20along the fiber pathway15, such that pulse overlap during laser processing results in homogenous treatment of the outer surface35of the first colored layer32. The translation speed of the optical fiber20may be from 1 m/s to 100 m/s, or from 2 m/s to 80 m/s, or from 5 m/s to 60 m/s, or from 10 m/s to 50 m/s. If the pulses or sub-pulses of the laser beam180impinge the outer surface35with too little overlap, there may be less ablation and less surface modification, such that ink adhesion onto the resultant laser-modified regions34is weak. Alternatively, if the pulses or sub-pulses impinge the outer surface35with too much overlap, too much damage and more heat accumulation may occur leading to unwanted melting and damage to the optical and mechanical properties of the optical fiber20.

Referring now toFIGS.9A-9C, embodiments of the ink station150of the processing system100for applying ink152to the one or more laser-modified regions34of the first colored layer32to form the second colored layer36. As used herein, the term “ink” refers to inks, paints, pigments, dyes, and other coloring agents known in the art.FIG.9Adepicts a jetting ink station150A configured to direct the ink152onto the one or more laser-modified regions34.FIGS.9Band9C depict a flexographic ink station150B configured to apply the ink152onto the one or more laser-modified regions34. It should be understood that whileFIGS.9A-9Cshow some example ink stations150, any known (e.g. rotogravure) or yet to be developed ink station configured to apply ink to an optical fiber may be used.

As shown inFIG.9A, the jetting ink station150A comprises a print head155, a pump154, a piezoelectric oscillator156, a nozzle158, charging electrodes160, deflection electrodes162, and gutter164. In operation, pressurized ink152is supplied to the print head155where it is fed to the nozzle158which has the piezoelectric oscillator156and a discharge hole159. The ink152is discharged while being oscillated by the piezoelectric oscillator156, and it is simultaneously given a negative electrostatic charge by two charging electrodes160. The ink152is formed into an ink column, but when saturated with the negative charge, the ink152becomes particles, and those particles separate from the ink column. The ink particles that discharge from the nozzle158pass between two deflection electrodes162where an electrical field selectively generated by an applied voltage to apply a bending force on the ink particles to change the direction they travel to selectively direct the ink152towards the fiber pathway15for application onto the optical fiber20or direct the ink to the gutter164, where the ink152may be collected for reuse.

As shown inFIG.9B, the flexographic ink station150B comprises a fountain roller153partially positioned in an ink tray151which houses the ink152. The fountain roller153is adjacent an anilox roller170such that ink152may be transferred from the fountain roller153to the anilox roller170. As shown inFIG.9B, a doctor blade172removes a select portion of the ink152from the anilox roller170. A plate cylinder174is adjacent the anilox roller170and comprises a flexo-plate175that contacts the plate cylinder174to transfer the ink152to the flexo-plate175. As shown in more detail inFIG.9C, ink152may be disposed in one or more pockets171of the anilox roller170and when the flexo-plate175contacts the plate cylinder174, some of the ink152is transferred from the pockets171to the flexo-plate175Referring again toFIG.9B, an impression cylinder176is positioned adjacent the plate cylinder174and the fiber pathway15extends between the plate cylinder174and the impression cylinder176such that the optical fiber20passes through the flexo-plate175and the impression cylinder176and the flexo-plate175applies the ink152to the optical fiber20to form the second colored layer36.

Referring now toFIG.10, a spool-to-spool system202configured to process a fiber bundle support62is schematically depicted. As used herein, a “fiber bundle support” refers to a hollow support structure for housing multiple optical fibers, such as one or more bundles of optical fibers. Example fiber bundle supports include cable jackets and ribbon jackets.FIG.11Adepicts a cable assembly60that includes fiber bundle supports in the form of an inner cable jacket64configured to house a bundle of optical fibers20and an outer cable jacket63configured to house a plurality of inner cable jackets64(and thus houses multiple numbers of optical fibers20). As shown inFIG.11A, the cable assembly60may further comprise strength members (e.g., a first strength member65and a second strength member66) and a buffer tube68. The strength members65,66surround the buffer tube68. The plurality of inner cable jackets64may each house bundles of optical fiber20may be surrounded by the buffer tube68.

Similar to the spool-to-spool system102ofFIG.2, the spool-to-spool system202ofFIG.10comprises a first spool295and a second spool296positioned such that a fiber bundle support pathway55extends from the first spool295to the second spool296. The optical system120is positioned along the spool-to-spool system202. The spool-to-spool system202may comprise any of the optical systems described herein and may operate to form one or more laser-modified regions in a first colored layer of the fiber bundle support62using any of the techniques described above. Moreover, the spool-to-spool system202comprises the ink station150, which may comprise any of the ink stations described herein and may operate to apply a second ink layer directly to the one or more laser-modified regions to form the second colored layer onto the one or more laser-modified regions. As shown inFIG.10, the optical system120is positioned along the fiber bundle support pathway55between the first spool295and the ink station150and the ink station150is positioned along the fiber bundle support pathway55between the optical system120and the second spool296.

A schematic cross section of an outer cable jacket63processed by the spool-to-spool system202ofFIG.10is shown inFIG.11B. As noted above, the outer cable jacket63is an example fiber bundle support. The outer cable jacket63comprises a first colored layer72and a second colored layer76. The first colored layer72comprises one or more laser-modified regions74comprising modification feature78formed on an outer surface75of the first colored layer72using the optical system120, and the second colored layer76is directly adhered to one or more laser-modified regions74. The first colored layer72surrounds an opening79within which a bundle of optical fibers20may be housed. The processing system ofFIG.10facilitates the adherence of the second colored layer76directly onto the first colored layer72to increase the number of color-coded identifications of bundles of optical fibers in a cable assembly. Indeed, the individual optical fibers20bundled and housed in a fiber bundle support that is laser marked, such as the outer cable jacket63, may also be laser marked using the embodiments described herein, to provide further visual identifiers.

In view of the foregoing description, it should be understood that the methods and systems for processing optical fibers and fiber bundle supports using laser-based systems and processes enable the application and adhesion of a second colored layer directly over a first colored layer of an optical fiber or an optical fiber support to enable an increase in the number of color-coded identifications of individual optical fibers and bundles of optical fibers in a cable assembly. Using the methods and system of the present disclosure described herein may be used to directly apply distinctive color markings may be applied directly onto an existing colored ink layer to make optical fibers and fiber bundle supports distinguishable to an in-field installation technician.

Examples

FIGS.12A and12Bdepict a glass sample300having a first ink layer302comprising NEO 9 ink that is laser modified in a first region304and is not laser modified in a second region306. The first ink layer302is laser modified in the first region304using a pulsed laser beam having a pulse rate of from 3 ns to 20 ns, a wavelength of 532 nm, adjustable power (up to 40 watts), adjustable repetition rate (single shot to 1500 kHz) with the laser beam being shaped and focused onto the first ink layer302using an f-theta lens having a 100 mm focal length of 100 mm). The laser beam ablates the first region304of the first ink layer302, increasing the roughness of the first region304relative to the second region306.

FIGS.13A and13Bdepict a glass sample400having a first ink layer402comprising NEO 9 ink that is laser modified in modified regions404and is not laser modified in an unmodified region406. The modified regions404include a first set of modified regions404A and a second set of modified regions404B. The second set of modified regions404B are laser modified with a laser beam comprising double the power of the laser beam used to laser modify the first set of modified regions404A.FIGS.13A and13Balso depict a second ink layer408applied to the modified regions404. InFIG.13A, the second ink layer408is applied to the modified regions404but has not yet been wiped. InFIG.13B, the second ink layer408has been wiped. As shown inFIG.13B, the second ink layer408adheres to the modified regions404. Moreover, relative ink adherence between the first set of modified regions404A and the second set of modified regions404B show that increased laser power (and thus increased ablation) forms laser-modified regions that adhere more ink, as the roughness of the second set of modified regions404B is greater than the first set of modified regions404A.

FIGS.14A and14Bshow the visual effects of laser modification on a single colored layer of ink.FIG.14Adepicts a plurality of optical fibers500having a first ink layer502A that has not been laser modified andFIG.14Bdepicts the plurality of optical fibers500after laser modification such that the first ink layer502A now comprises a modified first ink layer502B. As shown inFIGS.14A and14B, the first ink layer502A and the modified first ink layer502B are visually different, which is due to a difference in optical reflectivity and scattering of visible light between the first ink layer502A and the modified first ink layer502B caused by the increased roughness of the modified first ink layer502B.