News Column

Patent Issued for Multiple Channel Optical Fiber Furcation Tube and Cable Assembly Using Same

September 10, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventor Nave, Samuel D. (Newton, NC), filed on March 24, 2011, was published online on August 26, 2014.

The assignee for this patent, patent number 8818156, is Corning Cable Systems LLC (Hickory, NC).

Reporters obtained the following quote from the background information supplied by the inventors: "Optical fibers are widely used in a variety of applications, most notably in telecommunications, where optical fibers revolutionized the industry. Optical fibers are typically carried in fiber optic cables which range from one to as many as hundreds of optical fibers per cable. Normally, the fiber optic cable contains optical fiber strands in buffer tubes, either loose or in ribbon form. If a cable is to be joined to another cable or hardware in the field by connectors, it is common to attach the connectors to the cable at the factory before the cable is shipped to the installation site. This process is called 'connectorization.'

"Fiber optic cable connectorization can be a very labor intensive process because the fiber optic connector is usually attached to each optical fiber in the fiber optic cable manually, one at a time. The manual process involves breaking out or 'furcating' the optical fiber strands housed in the buffer tube or tubes inside the fiber optic cable using a buffer tube fanout insert assembly. For example, U.S. Pat. No. 5,231,688 discloses a furcation kit used to furcate the individual fibers from a cable for connectorization. After furcation, a connector is installed that requires precise techniques to insure quality.

"Optical cables comprising 12-strand groups have typically been used for connectivity in data centers. The optical fiber strands of a particular 12-strand group can be furcated using a single-channel furcation tube and thereby routed to a 12 fiber connector where the individual optical fibers are terminated in the connector. Typically, the connector is configured to receive the furcation tube and is coupled thereto. With the migration from 10 GbE systems to 40 GbE and 100 GbE systems there will be a need to transition to 24 fiber connectors for data transmission over parallel optics. Since standardized color coding provides for only 12 colors (without resorting to stripes, bands or additional indicia), using a conventional single-cavity furcation tube to accommodate 24 optical fiber strands will require 12 of the 24 strands to be separately marked so they can be sorted at the connector end. Moreover, using two single-cavity furcation tubes and feeding them into the back of the 24 fiber connector would be bulky and cumbersome, and is not a commercially attractive option. Thus, there is a need for a furcation tube sized to fit properly into the back of a conventional 24-strand connector that avoids the disadvantages of one or two single-cavity furcation tubes."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventor's summary information for this patent: "Furcation tubes are useful for the fanout of optical fiber strands from an optical fiber cable, allowing, among other things, for the connectorization of a cable length prior to shipping from the factory or warehouse to an end user. Prior art furcation tubes have been single channel tubes. Where an optical fiber cable contains optical fiber strands utilizing only 12 standard colors for coding, difficulties can arise when attempting to connectorize the cable with an optical fiber connector that accepts more than 12 colors. Whereas individual 12-strand color groups can be segregated within the cable via individual buffer tubes (e.g. one buffer tube for each group of twelve strands), if, for example, 24 optical fiber strands must be used with a single connector, the 24 strands utilizing 12 colors must be co-mingled within the same conventional single channel furcation tube to transition to the connector. This requires additional demarcation of the optical fiber strands to prevent confusion, or the use of several furcation tubes, one tube for each 12-strand group. Both approaches can be awkward. For example, the several single channel furcation tubes may not fit within the back side of the optical fiber connector.

"To overcome these difficulties, a furcation tube comprising multiple channels for loosely receiving a plurality of optical fiber strands is disclosed. By loosely receive what is meant is that the optical fiber strands contained within each channel of the furcation tube are free to move within that channel. Additionally, the furcation tube includes one or more additional channels that hold strength members for relieving strain on the optical fiber strands when the strands are connectorized. The strength members may comprise, for example, a polymeric yarn like aramid.

"In accordance with one embodiment, a furcation tube for connectorizing an optical fiber cable is described, the furcation tube comprising a first end and a second end, and further comprising a partition member, a protective jacket disposed about the partition member, and wherein the partition member defines a plurality of longitudinal fiber channels extending from the first end to the second end of the furcation tube, each of the fiber channels sized to loosely receive at least twelve optical fiber strands having an individual outside diameter of at least about 235 .mu.m each, and wherein the partition member further defines a plurality of longitudinal strength member channels extending from the first end to the second end, each strength member channel including one or more strength members disposed loosely therein. The furcation tube is sized to accommodate at least two optical fiber channels having a cross sectional area that is at least 1 mm.sup.2 each. For example, the furcation tube may have an outside diameter in the range between about 2.8 mm and 5.6 mm, preferably in the range between about 2.8 mm and 3.3 mm.

"The strength members preferably comprise a polymeric yarn. In some embodiments the partition member comprises web portions, wherein an intersection between adjacent web portions forms a radius. The web portions may be, for example, substantially planar walls or fins. The partition member may comprise two V-shaped web portions connected to and separated by a central web portion. In some embodiments an angle between substantially planar web portions bounding a strength member channel is in a range between about 60 degrees and about 90 degrees. Preferably a cross sectional shape of the furcation tube is substantially circular.

"In another embodiment a connectorized optical fiber cable assembly is disclosed comprising an optical fiber cable comprising a plurality of optical fiber strands, a furcation tube having a first end and a second end, the furcation tube comprising a partition member and the first end being coupled to a free end of the optical fiber cable and. The partition member forms a plurality of longitudinal fiber channels extending from the first end of the furcation tube to the second end of the furcation tube, each of the fiber channels loosely containing at least twelve optical fiber strands from the optical fiber cable, the optical fiber strands having an individual outside diameter of at least 235 .mu.m each, and wherein the partition member further forms at least one longitudinal strength member channel extending from the first end of the furcation tube to the second end of the furcation tube. The at least one strength member channel includes one or more strength members disposed loosely therein. The one or more strength members may comprise, for example, a polymeric yarn. The partition member can include substantially planar web portions. An intersection between adjacent web portions can be manufactured to form a radius. The partition member may comprise two V-shaped web portions connected to and separated by a central web portion. An angle between substantially planar web portions bounding a strength member channel is preferably in a range between about 60 degrees and about 90 degrees.

"A cross sectional area of each fiber channel is at least 1 mm.sup.2.

"An optical fiber connector is coupled to the second end of the furcation tube. In some embodiments a protective jacket is disposed about the partition member. Preferably, a cross sectional shape of the furcation tube is substantially circular. An outside diameter of the furcation tube can be in the range between about 2.8 mm and 5.6 mm, preferably between about 2.8 and 3.3 mm.

"In certain embodiments the furcation tube is un-jacketed, and the plurality of fiber channels are enclosed within the partition member along a length of the partition member. That is, each fiber channel is embedded within the partition member and is open only at the furcation tube ends. The partition member may further include a plurality of strength member channels, each strength member channel being enclosed within the partition member along a length of the partition member.

"Additional features and advantages of the invention are 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 invention as described herein. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. It is to be understood that the various features of the invention disclosed in this specification and in the drawings can be used in any and all combinations."

For more information, see this patent: Nave, Samuel D.. Multiple Channel Optical Fiber Furcation Tube and Cable Assembly Using Same. U.S. Patent Number 8818156, filed March 24, 2011, and published online on August 26, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8818156.PN.&OS=PN/8818156RS=PN/8818156

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Source: Journal of Engineering


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