Patent Description:
A newly designed optical fiber ribbon cable has been introduced, in which the individual optical fibers within the ribbon have a core-to-core spacing of <NUM>, compared with earlier ribbon designs having a core-to-core spacing of <NUM>. The new design increases the cable density and improves the cable capacity to meet the fast-growing construction demands of data centers and Web <NUM>-type networks.

In a common application, <NUM>-spaced, <NUM>-fiber ribbons are mass fusion-spliced by craft personnel in the field. There are times when a <NUM> ribbon must be spliced to a <NUM> ribbon. There are currently no mass fusion splicers capable of a making a splice between a <NUM> ribbon and to a <NUM> ribbon.

<CIT> discloses an apparatus for recoating uncoated and spliced end portions of optical fibers, which comprises two mold blocks, each of which includes a groove. The mold blocks are arrangable in a closed state, wherein the grooves cooperate to form a mold cavity for the fiber end portions, and in an open state, wherein the fiber end portions are insertable into the grooves. The apparatus further includes an injection system for injecting a recoating material into the mold cavity, and a UV curing system for irradiating the recoating material with UV light, thus curing the recoating material. At least one mold block is made of a plastic material comprising a fluoroplastic, e.g. PCTFE, the plastic material being at least partly transparent to UV light to enable the curing system to irradiate the UV curable recoating material with UV light through this mold block.

<CIT> discloses a photopolymerization molding apparatus having a light irradiator for photopolymerization (e.g. a halogen lamp), a photopolymerizable resin molding frame comprising a movable frame member and a fixed frame member, adjacent to which is a photopolymerizable resin feed device. The irradiator is disposed at a predetermined position where it can apply light to a photopolymerizable resin material in the frame through the light-transmitting portion of the frame.

<CIT> relates to an optical fiber recoating device provided for filling a recoating resin into molds, wherein semicircular mold grooves in molds into which the recoating resin is filled are longer than a bare fiber portion of an optical fiber, and an outer diameter of mold groove is larger than the outer diameter of semicircular sheath engaging grooves that engage a sheath of the optical fiber. As a result, a cylindrically shaped extending portion which extends to the sheath is formed to each end of the recoated sheath, so that joining strength of the recoated sheath is improved.

<CIT> relates to a recoating method for optical fiber, and in particular to prevent incorporation of bubbles into the recoating resin. In a recoating method for optical fiber, a bare fiber portion of an optical fiber is recoated by guiding recoating resin into mold forms, and the injection speed of the recoating resin injected into the mold forms is such that bubbles are not trapped due to the resin injection.

The invention provides a method according to claim <NUM>. Further developments of the invention are defined in the dependent claims. Any embodiments and examples of the description not falling within the scope of the claims do not form part of the invention and are provided for illustrative purposes only.

Further aspects of the invention are described below.

Aspects of the present invention are directed to systems and techniques to facilitate the splicing of a <NUM>-spaced fiber ribbon to a <NUM>-spaced fiber ribbon. It will be appreciated from the following discussion that aspects of the invention can be adapted for use in other contexts, including for example ribbons having different numbers of fibers, different configurations, and different core-to-core spacings.

<FIG> shows a top view of an exemplary <NUM> fiber ribbon <NUM> according to the prior art, and <FIG> shows a cross section of the <NUM> fiber ribbon <NUM> through the plane 1B-1B. <FIG> shows a top view of an exemplary <NUM> fiber ribbon <NUM> according to the prior art, and <FIG> shows a cross section of the <NUM> fiber ribbon <NUM> through the plane 2B-2B.

As discussed above, the splicing of a <NUM> fiber ribbon to a <NUM> fiber ribbon is problematic because of the mismatch between the respective core-to-core spacings of the individual fibers packaged into each ribbon.

As shown in <FIG>, each fiber ribbon <NUM>, <NUM> comprises a 1x12 array of individual optical fibers <NUM>, <NUM> each of which having a respective coating <NUM>, <NUM>. In the ribbon <NUM> shown in <FIG>, the individual optical fibers have a core-to-core spacing <NUM> of <NUM>. In the ribbon <NUM> shown in <FIG>, the individual optical fibers have a core-to-core spacing <NUM> of <NUM>. Each array of coated fibers is depicted as being packaged inside of an outer jacket <NUM>, <NUM> (i.e., in an encapsulated ribbon design). It is noted that the invention may be practiced in other contexts including, for example, splicing together fiber ribbons employing an edge-bonded design.

As mentioned above, the spacing mismatch means that a mass fusion splicer according to the prior art cannot be used to splice the two ribbons together. Aspects of the present invention are directed to structures and techniques for modifying the core-to-core spacing of the fibers in a first ribbon to match the core-to-core spacing of the fibers in a second ribbon.

<FIG> shows a top view of a <NUM> fiber ribbon <NUM> that has been modified in accordance with an exemplary practice of a technique according to the present invention for splicing the <NUM> fiber ribbon <NUM> to a second fiber ribbon having a core-to-core spacing of <NUM>. <FIG> shows a cross section of the modified fiber ribbon <NUM> through the plane <NUM>-<NUM>.

As described in detail below, a system is provided for use in the field, or in other contexts, that forms at least one molded strip <NUM> around the individual stripped fibers <NUM> at the end of the <NUM> ribbon to form a new ribbon segment <NUM> having a core-to-core spacing <NUM> of <NUM>, thereby allowing a standard mass fusion splicer to be used.

<FIG> shows an isometric view of an exemplary <NUM>-fiber mold used according to an aspect of the invention. The mold comprises a lower portion and a higher portion that are fabricated from a UV-transparent material, such as quartz. <FIG> shows a wireframe isometric view of the assembled mold, in which the lower portion and upper portion are fitted together at a split line.

The lower and upper mold portions are each provided with a respective set of semicircular grooves and a rectangular central cavity. When the lower and upper lower portions of the mold are fitted together, the five respective pairs of semicircular grooves form five circular channels that extend from a proximal end of the assembled mold to a distal end. Grooves and be formed using a wire-cut technique.

It is noted that alternative practices of the invention may employ grooves having shapes different from the semicircular shape depicted in <FIG>, resulting in an assembled mold in which the individual fiber channels have non-circular shapes. For example, V-shaped or rectangular grooves can be employed, resulting in channels shaped as a square, or the like, that is suitable for holding each of the individual ribbon fibers.

Returning to <FIG>, the circular channels are dimensioned to fit closely around a corresponding set of bare optical fibers having an outer diameter of <NUM>. The lower and upper rectangular cavities form a central rectangular chamber having a width and a height slightly larger than the matrix of fibers to be ribbonized, and a length of approximately <NUM> inch. The circular channels and the central chamber are positioned with respect to each other, such that fibers threaded through the circular channels pass through the central chamber without touching its walls.

In an exemplary practice of the invention, after the lower and upper portions of the mold are assembled together, an end of a <NUM>-fiber <NUM> ribbon is separated and stripped to produce five individual, bare fibers. The bare fibers are threaded through respective mold channels. A UV-curable resin (i.e., epoxy) is injected into the chamber, and the resin is then cured by a UV light that passes through the UV-transparent mold material. After the epoxy is cured the mold is opened, and the ribbonized fiber removed.

<FIG> shows an isometric view of the newly formed ribbon segment, wherein a strip has been molded around the matrix of individual fibers, resulting in a core-to-core spacing of <NUM>.

<FIG> shows a schematic diagram of a system incorporating a mold of the type illustrated in <FIG>. During the molding process, the mold's lower and upper portions, are held together by a suitable holder structure, which includes an upper window.

System further includes a pusher for injecting a UV-curable resin (e.g., epoxy), or other suitable flowable material from a reservoir into the central chamber. Mold further includes side vents to allow air to escape from the chamber, as resin is injected into the central chamber. As mentioned above, mold is fabricated from a material that is transparent to the curing light. Mold further includes a split line that is configured to allow the lower and upper portions of the mold to be separated to release the completed ribbon.

<FIG> shows a ribbonizing system provided according to a further aspect of the invention. The structural framework for system comprises a chassis having an enclosure therein. A molding subassembly is mounted to the top of the chassis. An ultraviolet light unit is mounted into the chassis enclosure, and is operated by switch.

The molding subassembly comprises a base and a lid that is hingeably attached on top of the base. The lid is configured to swing between a closed position, shown in <FIG>, and an open position, shown in <FIG>. As shown in <FIG>, an epoxy reservoir and pump are mounted to the upper surface of the lid.

The molding subassembly further comprises a two-piece mold having a lower portion mounted to the molding subassembly base and an upper portion mounted to the molding subassembly lid.

<FIG> shows an isometric view of the lower and upper mold portions in an open, unassembled configuration. <FIG> shows a wireframe isometric view of the lower and upper mold portions in a closed configuration.

As shown in <FIG>, the lower and upper portions of the mold include semicircular grooves and respective sets of three rectangular cavities that fit together to form a plurality of circular channels for receiving a corresponding plurality of optical fibers, and three rectangular chambers for forming three ribbon strips around optical fibers contained in the circular channels. It is noted that the number of rectangular cavities can be greater than or less than the three cavities shown in <FIG>.

The upper portion of the mold is provided with an input port for receiving epoxy resin from the reservoir (<FIG>), and three input channels for feeding epoxy into respective chambers. The upper portion of the mold further includes air vents for allowing air to escape from the chambers as they are filled with injected epoxy.

<FIG> shows an exemplary <NUM> ribbon that has been ribbonized using the system shown in <FIG> in order to allow the <NUM> ribbon to be spliced to an exemplary <NUM> ribbon. In the depicted practice of the invention, three strips are molded around bare individual fibers to form the ribbonized segment.

<FIG> shows an isometric view of ultraviolet light unit, mounted into the chassis enclosure. The ultraviolet light unit comprises a housing, UV lighting element, a capacitor, and timer circuitry.

<FIG> shows a flowchart of a method <NUM> according to a further aspect of the invention.

Claim 1:
A method (<NUM>) for forming, at an end of an existing multifiber ribbon cable having an initial first core-to-core spacing, a multifiber ribbon cable segment having an enlarged second core-to-core spacing, comprising:
(a) providing a system comprising:
a chassis;
an enclosure within the chassis;
a mold mounted on top of the chassis,
a reservoir and pumping system mounted on top of the mold for holding a flowable, light-curable material and injecting the light-curable material into the mold; and
a curing light source mounted into the enclosure;
wherein the mold is formed from a material that is transparent to the curing light and is positioned such that light-curable material injected into the mold is exposed to light from the curing light source;
wherein the mold comprises a base and a lid that, when in a closed configuration, define an internal cavity comprising a plurality of individual fiber channels corresponding to individual fibers of the existing multifiber ribbon cable with the initial first core-to-core spacing, wherein the plurality of individual fiber channels has a spacing equal to that of the second enlarged core-to-core spacing, wherein each individual fiber channel passes through the internal cavity, wherein each individual fiber channel extends between a respective entrance at a first end of the mold to a respective exit at a second end of the mold;
wherein the assembled mold further includes an injection system for receiving the light-curable, flowable material from the reservoir and pumping system and feeding it into the internal cavity, and at least one vent for allowing air to escape from the internal cavity as the light-curable, flowable material is fed into the internal cavity;
(b) placing the mold into a closed configuration;
(c) stripping (<NUM>) an end portion of the existing multifiber ribbon cable to bare glass, separating the end portion of the existing multifiber ribbon cable into individual fibers, and cleaning them;
(d) threading (<NUM>) the individual fibers through respective channels in the mold;
(e) injecting (<NUM>) the curable material into the chamber;
(f) using (<NUM>) the curing light to cure the flowable material; and
(g) opening (<NUM>) the mold and remove the ribbonized fiber.