Source: http://www.google.com/patents/US20100135625?dq=5,838,906
Timestamp: 2016-09-28 18:50:28
Document Index: 629203271

Matched Legal Cases: ['Application No. 61', 'Application No. 61', 'Application No. 61', 'Application No. 61', 'Application No. 61', 'Application No. 61', 'Application No. 61', 'Application No. 61', 'Application No. 61', 'Application No. 61']

Patent US20100135625 - Reduced-Diameter Ribbon Cables with High-Performance Optical Fiber - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsDisclosed is an improved optical fiber that employs a novel coating system. When combined with a bend-insensitive glass fiber, the novel coating system according to the present invention yields an optical fiber having exceptionally low losses. The coating system features (i) a softer primary coating...http://www.google.com/patents/US20100135625?utm_source=gb-gplus-sharePatent US20100135625 - Reduced-Diameter Ribbon Cables with High-Performance Optical FiberAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS20100135625 A1Publication typeApplicationApplication numberUS 12/615,698Publication dateJun 3, 2010Filing dateNov 10, 2009Priority dateNov 9, 2007Also published asUS8041168Publication number12615698, 615698, US 2010/0135625 A1, US 2010/135625 A1, US 20100135625 A1, US 20100135625A1, US 2010135625 A1, US 2010135625A1, US-A1-20100135625, US-A1-2010135625, US2010/0135625A1, US2010/135625A1, US20100135625 A1, US20100135625A1, US2010135625 A1, US2010135625A1InventorsBob J. OvertonOriginal AssigneeDraka Comteq, B.V.Export CitationBiBTeX, EndNote, RefManPatent Citations (99), Referenced by (78), Classifications (14), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetReduced-Diameter Ribbon Cables with High-Performance Optical Fiber
US 20100135625 A1Abstract
one or more optical-fiber ribbons, each of said optical-fiber ribbons comprising a plurality of optical fibers, wherein at least one of said optical-fiber ribbons includes at least one optical fiber comprising a glass fiber and a low-modulus primary coating surrounding said glass fiber, said low-modulus primary coating possessing (i) an in situ modulus of less than about 0.65 MPa and (ii) a glass transition temperature of less than about −50� C.; and a tube surrounding said optical-fiber ribbons; wherein the buffer tube has a buffer-tube filling coefficient of at least about 0.3. 2. A buffer tube according to claim 1, wherein at least one of said optical fibers is a single-mode optical fiber.
6. A buffer tube according to claim 1, wherein said low-modulus primary coating possesses a glass transition temperature of less than about −55� C.
said optical-fiber ribbons are arranged in a rectangular ribbon stack; and the buffer tube has a buffer-tube filling coefficient of between about 0.32 and 0.38. 8. A buffer tube according to claim 1, wherein:
said optical-fiber ribbons are arranged in a rectangular ribbon stack; and the buffer tube has a buffer-tube filling coefficient of at least 0.35. 9. A buffer tube according to claim 1, wherein:
said optical-fiber ribbons are arranged in a ribbon stack; and the buffer tube has an optimal minimum clearance of less than about 0.32 millimeter. 10. A buffer tube according to claim 9, wherein the buffer tube has an optimal minimum clearance of between about 0.1 millimeter and 0.2 millimeter.
a cable jacket; and one or more buffer tubes positioned within said cable jacket, wherein one or more of said buffer tubes enclose one or more optical-fiber ribbons, each of said optical-fiber ribbons comprising a plurality of optical fibers; wherein at least one of said optical-fiber ribbons includes at least one optical fiber comprising a glass fiber and a primary coating surrounding said glass fiber, said primary coating possessing (i) an in situ modulus of less than about 0.65 MPa and (ii) a glass transition temperature of less than about −50� C.; wherein one or more of said buffer tubes possess a buffer-tube filling coefficient of at least about 0.3. 13. An optical-fiber ribbon cable according to claim 12, wherein the optical-fiber ribbon cable has a cumulative buffer-tube filling coefficient of at least about 0.35.
one or more said buffer tubes comprise optical-fiber ribbons arranged as a ribbon stack; and for each said buffer tube comprising optical-fiber ribbons arranged as a ribbon stack, said buffer tube has an optimal minimum clearance of less than about 0.25 millimeter. 17. An optical-fiber ribbon cable according to claim 12, wherein:
one or more said buffer tubes comprise optical-fiber ribbons arranged as a ribbon stack; and for each said buffer tube comprising optical-fiber ribbons arranged as a ribbon stack, said buffer tube has an optimal minimum clearance of between about 0.15 millimeter and 0.3 millimeter. 18. An optical-fiber ribbon cable according to claim 12, wherein:
one or more said buffer tubes comprise optical-fiber ribbons arranged as a ribbon stack; and for each said buffer tube comprising optical-fiber ribbons arranged as a ribbon stack, said buffer tube has an optimal minimum clearance of about 0 millimeter. 19. An optical-fiber cable according to claim 12, wherein at least one of said optical fibers meets the ITU-T G.657.A standard and/or the ITU-T G.657.B standard.
20. An optical-fiber cable according to claim 12, wherein said primary coating possesses an in situ modulus of less than about 0.5 MPa. Description
[0002] This application further claims the benefit of U.S. Provisional Application No. 61/112,965 for Reduced-Diameter Ribbon Cables with High-Performance Optical Fiber (filed Nov. 10, 2008), U.S. Provisional Application No. 61/177,996 for a Reduced-Diameter Optical Fiber (filed May 13, 2009) and U.S. Provisional Application No. 61/248,319 for a Reduced-Diameter Optical Fiber (filed Oct. 2, 2009).
[0004] The present invention embraces optical fibers possessing an improved coating system that reduces stress-induced microbending. The present invention further embraces the use of such optical fibers in ribbon cables having relatively high filling coefficients and fiber counts, and thus reduced cable dimensions.
[0009] In this regard, U.S. Pat. No. 7,272,289 (Bickham et al.), which is hereby incorporated by reference in its entirety, proposes an optical fiber having low macrobend and microbend losses. U.S. Pat. No. 7,272,289 broadly discloses an optical fiber possessing (i) a primary coating having a Young's modulus of less than 1.0 MPa and a glass transition temperature of less than �25� C. and (ii) a secondary coating having a Young's modulus of greater than 1,200 MPa.
[0021] It is yet another object to provide an optical fiber that synergistically combines a bend-insensitive glass fiber (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�) with the coating according to the present invention (e.g., Draka Comteq's ColorLockXS brand coating system).
[0042] FIG. 13 schematically depicts a cross-sectional view of an optical-fiber ribbon cable employing bend-insensitive optical fibers according to the present invention.
[0043] In one aspect, the present invention embraces optical fibers possessing an improved coating system that reduces stress-induced microbending, even in exceptionally cold environments required for FTTx deployments. The coating system according to the present invention includes a primary coating that combines low in situ modulus (e.g., less than about 0.5 MPa as measured on the fiber) and low glass transition temperature (Tg) (e.g., less than about −50� C.) to reduce stresses caused by external force and temperature. In addition, the coating system can be processed at high production speeds (e.g., 15-20 msec or more).
[0044] The present invention achieves a microbend-resistant optical fiber, particularly a single-mode optical fiber, by employing as its primary coating a UV-curable, urethane acrylate composition. In this regard, the primary coating includes between about 40 and 80 weight percent of polyether-urethane acrylate oligomer as well as photoinitiator, such as LUCERIN TPO, which is commercially available from BASF. In addition, the primary coating includes one or more oligomers and one or more monomer diluents (e.g., isobornyl acrylate), which may be included, for instance, to reduce viscosity and thereby promote processing. A suitable composition for the primary coating according to the present invention is a UV-curable urethane acrylate product provided by DSM Desotech (Elgin, Ill.) under the trade name DeSolite� DP 1011.
[0048] Exemplary single-mode glass fibers for use in the present invention are commercially available from Draka Comteq (Claremont, N.C.) under the trade name BendBright�, which is compliant with the ITU-T G.652.D requirements, and the trade name BendBrightXS�, which is compliant with the ITU-T G.657.A/B and ITU-T G.652.D requirements.
[0049] In particular and as set forth herein, it has been unexpectedly discovered that the pairing of a bend-insensitive glass fiber (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�) and a primary coating having very low modulus (e.g., DSM Desotech's UV-curable urethane acrylate product provided under the trade name DeSolite� DP 1011) achieves optical fibers having exceptionally low losses (e.g., reductions in microbend sensitivity of at least 10� (e.g., 40� to 100� or more) as compared with a single-mode fiber employing a conventional coating system). Draka Comteq's bend-resistant, single-mode glass fiber available under the trade name BendBrightXS� employs a trench-assisted design that reduces microbending losses.
[0051] The IEC fixed-diameter sandpaper drum test (i.e., IEC TR62221, Method B) provides a microbending stress situation that affects single-mode fibers even at room temperature. The sandpaper, of course, provides a rough surface that subjects the optical fiber to thousands, if not millions, of stress points. With respect to the test data presented in FIG. 1, a 300-mm diameter fiber spool was wrapped with adhesive-backed, 40-micron grade sandpaper (i.e., approximately equivalent to 300-grit sandpaper) to create a rough surface. Then, 400-meter fiber samples were wound at about 2,940 mN (i.e., a tension of 300 gf on a 300-mm diameter cylinder), and spectral attenuation was measured at 23� C.
[0055] As disclosed herein, the optical fiber according to the present invention includes a primary coating possessing lower modulus and lower glass transition temperature than possessed by conventional single-mode fiber primary coatings. Even so, the improved primary coating formulation nonetheless facilitates commercial production of the present optical fiber at excellent processing speeds (e.g., 1,000 m/min or more). In this regard, the primary coating employed in the optical fibers of the present invention possesses fast curing rates—reaching 50 percent of full cure at a UV dose of about 0.3 J/cm2, 80 percent of full cure at a UV dose of about 0.5 J/cm2, and 90 percent of full cure at a UV dose of about 1.0 J/cm2 as measured on a standard 75-micron film at 20� C. and atmospheric pressure (i.e., 760 ton) (i.e., standard temperature and pressure—STP).
[0061] The temperature dependence of the modulus is an important consideration to ensure that the primary coating provides enhanced microbending protection in FTTx applications. A primary coating having low modulus only at room temperature would be inadequate because deployment in the field will expose the optical fiber to microbend-inducing stresses at extreme environmental temperatures (e.g., −40� C. and below). Therefore, a suitable primary coating according to the present invention possesses an exceptionally low glass transition temperature so that the primary coating remains soft and protective in extremely cold environmental conditions.
[0062] FIGS. 3 and 4, respectively, depict dynamic mechanical properties of a typical commercial primary coating (i.e., the conventional primary coating) and an exemplary primary coating used in making the optical fibers according to the present invention. The conventional primary coating was a UV-curable urethane acrylate provided by DSM Desotech (Elgin, Ill.) under the trade name DeSolite� DP 1007. The exemplary primary coating according to the present invention (i.e., employed to form optical fibers of the present invention) was a UV-curable urethane acrylate provided by DSM Desotech (Elgin, Ill.) under the trade name DeSolite� DP 1011.
[0065] The glass transition temperature of the conventional primary coating is estimated by the peak in tan δ to be approximately −30� C. Thus, the conventional primary coating (and similar formulations) will behave like a glassy polymer at extremely low temperatures (e.g., less than −40� C., particularly less than −50� C.). (Although stress induced by strain is time dependent at low temperatures, estimated glass transition temperature is a useful comparative property.)
[0068] The glass transition temperature of the exemplary primary coating according to the present invention is estimated by the peak in tan δ at less than about −50� C. (e.g., about −60� C.). This is at least about 20� C. below the glass transition temperature of the comparative, conventional primary coating. Accordingly, primary coatings according to the present invention provide much more rapid stress relaxation during temperature excursions.
[0069] As set forth in Examples 2 and 3 (below), two different methods were used to evaluate the respective microbend sensitivities of glass fibers coated with (i) a typical commercial primary coating (i.e., the conventional primary coating) and (ii) an exemplary primary coating according to the present invention. As with Example 1 (above), the conventional primary coating was a UV-curable urethane acrylate provided by DSM Desotech (Elgin, Ill.) under the trade name DeSolite� DP 1007, and the exemplary primary coating according to the present invention (i.e., employed to form optical fibers of the present invention) was a UV-curable urethane acrylate provided by DSM Desotech (Elgin, Ill.) under the trade name DeSolite� DP 1011.
[0072] Those having ordinary skill in the art will appreciate that, at room temperature, such fiber crossovers can sometimes cause added loss (i.e., if the optical fiber is very sensitive) but that typically little or no added loss is observed. Consequently, the drum (with wound fiber) was temperature cycled twice from about room temperature through (i) −40� C., (ii) −60� C., (iii)+70� C., and (iv)+23� C. (i.e., near room temperature) while making loss measurements at 1550 nanometers. In both temperature cycles, fiber attenuation was measured after one hour at each test temperature.
[0073] FIG. 5 depicts exemplary results for single-mode glass fibers coated with, respectively, a conventional primary coating (i.e., DeSolite� DP 1007) and an exemplary primary coating according to the present invention (i.e., DeSolite� DP 1011). The respective fiber specimens were chosen to match the coating geometry, mode field diameter, and cutoff wavelength. Accordingly, the respective optical fibers employed different formulations of colored secondary coatings.
[0074] In summary, the conventional primary coating and the exemplary primary coating according to the present invention each provided good protection against microbending stresses at 23� C. Moreover, at −40� C., the optical fiber having the conventional primary coating demonstrated only a small added loss. (It would appear that at −40� C., the conventional primary coating provided adequate protection against microbending by stress relaxing in a reasonable timeframe, even though this was near its glass transition temperature.) By way of comparison, the optical fiber according to the present invention demonstrated essentially no added loss at −40� C. (i.e., better performance).
[0075] At −60� C., however, the optical fiber having the conventional primary coating demonstrated significant added loss. (This temperature extreme was well below the glass transition temperature of the conventional primary coating.) By way of comparison, the optical fiber according to the present invention demonstrated essentially no added loss at −60� C., which is close to the glass transition temperature of this embodiment of the primary coating according to the present invention.
[0079] Using matched fiber samples (as with the basket weave/temperature cycling test of Example 2) fiber attenuation was measured after winding at room temperature (i.e., 23� C.) for each test condition. Then, the drum (with 400 meters of wound fiber) was temperature cycled from about room temperature through (i) −40� C., (ii) −60� C., and (iii)+23� C. (i.e., near room temperature) while making loss measurements at 1550 nanometers using an optical time domain reflectometer (OTDR).
[0080] The several samples of each kind of optical fiber were initially measured at 23� C. on the original spools (i.e., before winding on the roughened drum surface to establish baseline spectral attenuation) then were subjected to the foregoing rigorous testing conditions for one hour at each temperature. Fiber attenuation was measured after one hour (as in Example 2) at each test temperature.
[0081] FIG. 6, a line chart, and FIG. 7, a box plot, depict exemplary results under these more rigorous testing conditions for single-mode optical fibers that include a conventional primary coating (i.e., DeSolite� DP 1007 UV-curable urethane acrylate) and for single-mode optical fibers that include an exemplary primary coating according to the present invention (i.e., DeSolite� DP 1011 UV-curable urethane acrylate).
[0083] Likewise, FIG. 7 shows that, as compared with conventional optical fibers, exemplary optical fibers according to the present invention possess substantially reduced microbend sensitivity at a higher winding tension (i.e., 150 gf on a 300-mm diameter quartz cylinder). FIG. 7 thus illustrates that the exemplary primary coating according to the present invention (i.e., DeSolite� DP 1011 UV-curable urethane acrylate) promotes both significantly reduced and significantly more uniform microbending performance.
[0085] It has been further found that pairing a bend-insensitive glass fiber (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�) and a primary coating having very low modulus (e.g., DSM Desotech's UV-curable urethane acrylate product provided under the trade name DeSolite� DP 1011) achieves optical fibers having exceptionally low losses. Additional testing was performed, therefore, to demonstrate the dramatic and unexpected reductions in microbend sensitivity provided in accordance with the present invention.
[0086] The respective microbend sensitivities were measured for exemplary optical fibers, including (i) a conventional single-mode glass fiber with a conventional commercial coating, (ii) a bend-insensitive glass fiber with a conventional commercial coating, and (iii) a bend-insensitive glass fiber (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�) with the coating according to the present invention (e.g., Draka Comteq's ColorLockXS brand coating system).
[0087] FIG. 8 demonstrates that the optical fiber according to the present invention, namely including a bend-insensitive glass fiber (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�) and a primary coating having very low modulus (e.g., DSM Desotech's UV-curable urethane acrylate product provided under the trade name DeSolite� DP 1011), provides exceptionally low attenuation losses as compared with other optical fibers. Moreover, this bend-resistant optical fiber exhibits small wavelength dependence within the transmission window between 1400 nanometers and 1700 nanometers, and is essentially unaffected by the microbend-inducing test conditions across the test spectrum.
[0089] Like the curves presented in FIG. 1, the curves depicted in FIG. 8 represent, at 23� C., the difference between the initial spectral curve and the curve when the fiber is on the sandpaper drum of fixed diameter, thereby providing the added loss due to microbending stresses (i.e., delta-attenuation across the spectral range).
[0090] The respective microbend sensitivities were measured under rigorous test conditions for exemplary optical fibers, including (i) a conventional single-mode glass fiber with a conventional commercial coating and (ii) a bend-insensitive glass fiber (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�) with the coating according to the present invention (e.g., Draka Comteq's ColorLockXS brand coating system).
[0091] FIG. 9 demonstrates that, even under extremely harsh conditions, the optical fiber according to the present invention, namely including a bend-insensitive glass fiber (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�) and a primary coating having very low modulus (e.g., DSM Desotech's UV-curable urethane acrylate product provided under the trade name DeSolite� DP 1011), provides surprisingly low attenuation losses as compared with other optical fibers.
[0093] FIG. 9 presents exemplary temperature-cycle data for three specimens of standard single-mode fiber (i.e., a conventional single-mode glass fiber with a conventional commercial coating) and three specimens of optical fiber according to the present invention (i.e., a bend-insensitive glass fiber with improved coating according to the present invention). As noted, 440 meters of optical fiber is wound onto the aforementioned sandpaper-covered, fixed-diameter drum. One hour after winding, fiber attenuation was measured at room temperature (i.e., 23� C.) using an optical time domain reflectometer (OTDR). Then, the drum (with 440 meters of wound fiber) was temperature cycled from about room temperature through (i) −40� C. and (ii) −60� C. in a temperature-controlled chamber. Fiber attenuation at 1550 nanometers was measured by an OTDR after one hour of equilibration at both −40� C. and −60� C.
[0095] Table 1 (below) presents the microbending-sensitivity metric obtained from the attenuation data (at a wavelength of 1550 nanometers) depicted in FIG. 9 (i.e., employing 180-grit sandpaper). Table 1 shows that, as compared with a conventional standard single-mode fiber, the optical fiber according to the present invention provides microbending sensitivity that is about 2�-10� lower at 23� C. and about 2�-5� lower at −40� C.:
[0096] The respective microbend sensitivities were further measured for exemplary optical fibers, including (i) a conventional single-mode glass fiber with a conventional commercial coating and (ii) a bend-insensitive glass fiber (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�) with the coating according to the present invention (e.g., Draka Comteq's ColorLockXS brand coating system).
[0098] As in Example 3, using matched fiber samples, fiber attenuation was measured after winding at room temperature (i.e., 23� C.). Then, the drum (with about 400 meters of wound fiber) was temperature cycled from about room temperature through (i) −40� C., (ii) −60� C., and (iii)+23� C. (i.e., near room temperature) while making loss measurements at 1550 nanometers using an optical time domain reflectometer (OTDR).
[0099] Three (3) samples of each kind of optical fiber were initially measured at 23� C. on the original spools (i.e., before winding on the roughened drum surface to establish baseline spectral attenuation) and then were subjected to the foregoing rigorous testing conditions for one hour at each temperature. Fiber attenuation was measured after one hour at each temperature.
[0100] FIG. 10 depicts exemplary results for single-mode optical fibers that include a conventional primary coating (i.e., DeSolite� DP 1007 UV-curable urethane acrylate) and for bend-insensitive glass fibers (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�) that include a primary coating having very low modulus (i.e., DSM Desotech's UV-curable urethane acrylate product provided under the trade name DeSolite� DP 1011).
[0101] FIG. 10 demonstrates that the optical fiber according to the present invention, namely Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS� with a primary coating having very low modulus (e.g., DSM Desotech's UV-curable urethane acrylate product provided under the trade name DeSolite� DP 1011), provides exceptionally low attenuation losses as compared with standard single-mode optical fibers (SSMF).
[0102] In addition, FIGS. 11 and 12 depict attenuation and microbend sensitivity, respectively, at a wavelength of 1550 nanometers as a function of MAC number (i.e., mode field diameter divided by cutoff wavelength) for various exemplary optical fibers in accordance with the standard IEC fixed-diameter sandpaper drum test (i.e., IEC TR62221, Method B). The respective attenuation data depicted in FIG. 11 (added loss) and FIG. 12 (microbend sensitivity) were obtained at 23� C. under the test conditions previously described with respect to FIG. 1 (i.e., 400-meter fiber samples were wound at about 2,940 mN (i.e., a tension of 300 gf) on a 300-mm diameter fiber spool wrapped with adhesive-backed, 40-micron grade sandpaper).
[0103] FIG. 11 shows that Draka Comteq's bend-resistant, single-mode glass fiber available under the trade name BendBrightXS� in combination with Draka Comteq's ColorLockXS brand coating system provides outstanding performance with respect to added loss.
[0104] FIG. 12 shows that Draka Comteq's bend-resistant, single-mode glass fiber available under the trade name BendBrightXS� in combination with Draka Comteq's ColorLockXS brand coating system provides superior microbend sensitivity (i.e., microbend sensitivity of 0.01 to 0.03 (dB/km)/(gf/mm)).
[0108] Employing Draka Comteq's bend-resistant, single-mode glass fiber available under the trade name BendBrightXS� (or the trade name BendBright-Elite™) with the present dual-coating system, which includes a low-modulus primary coating, has been found to reduce microbending sensitivity by between about one to two orders of magnitude relative to standard single-mode fiber (SSMF) at the key transmission frequencies of 1550 nanometers and 1625 nanometers. As noted, such optical fiber not only provides outstanding resistance to microbending and macrobending, but also complies with the ITU-T G.657.A/B and ITU-T G.652.D requirements.
[0109] In particular, Draka Comteq's bend-resistant, single-mode glass fiber available under the trade name BendBrightXS� (e.g., enhanced with Draka Comteq's ColorLockXS brand coating system) provides resistance to macrobending required for sustained bends having a radius as low as five (5) millimeters with an estimated failure probability of less than two (2) breaks per million full-circle bends (i.e., 360�) over 30 years in a properly protected environment. These bend-resistant optical fibers facilitate the rapid deployment of small, flexible cables for the delivery of fiber to the premises/business/home (i.e., FTTx) by virtue of the optical fiber's ability to sustain a loss-free transmission through small-radius bends. Cables employing such bend-resistant optical fibers may be routed around sharp bends, stapled to building frame, coiled, and otherwise employed in demanding environments while retaining clear and strong signal transmission.
[0111] Those having ordinary skill in the art will recognize that an optical fiber with a primary coating (and an optional secondary coating and/or ink layer) typically has an outer diameter of between about 235 microns and about 265 microns (μm). The component glass fiber itself (i.e., the glass core and surrounding cladding layers) typically has a diameter of about 125 microns, such that the total coating thickness is typically between about 55 microns and 70 microns.
[0116] In accordance with the foregoing, a particular reduced-diameter, optical-fiber embodiment having exceptionally low losses employs Draka Comteq's 125-micron single-mode glass fiber available under the trade name BendBrightXS� with a 155-micron-diameter, low-modulus primary coating layer (e.g., Draka Comteq's ColorLockXS brand coating system) and a secondary coating (e.g., a nominal 200-micron-diameter secondary coating). As noted, BendBrightXS� bend-insensitive optical fiber complies with the ITU-T G.657.A/B and ITU-T G.652.D requirements. In this optical-fiber embodiment, the maximum tolerance with respect to the primary-coating thickness is +/−5 microns (i.e., a primary-coating outer diameter of between 150 microns and 160 microns), more typically about +/−2.5 microns (i.e., a primary-coating outer diameter of between about 152.5 microns and 157.5 microns).
[0117] Another particular reduced-diameter, optical-fiber embodiment having exceptionally low losses employs Draka Comteq's 125-micron single-mode glass fiber available under the trade name BendBright-Elite™ with a 155-micron-diameter, low-modulus primary coating layer (e.g., Draka Comteq's ColorLockXS brand coating system) and a secondary coating (e.g., a nominal 200-micron-diameter secondary coating). Like BendBrightXS� bend-insensitive optical fiber, BendBright-Elite™ bend-insensitive optical fiber complies with the ITU-T G.657.A/B and ITU-T G.652.D requirements. In this optical-fiber embodiment, the maximum tolerance with respect to the primary-coating thickness is +/−5 microns (i.e., a primary-coating outer diameter of between 150 microns and 160 microns), more typically about +/−2.5 microns (i.e., a primary-coating outer diameter of between about 152.5 microns and 157.5 microns).
[0118] The synergistic combination of (i) Draka Comteq's BendBrightXS� bend-insensitive single-mode glass fiber (or Draka Comteq's BendBright-Elite™ bend-insensitive glass fiber) and (ii) Draka Comteq's ColorLockXS brand coating system promotes significant reductions in optical-fiber diameter.
[0119] By way of example, Draka Comteq's 125-micron BendBrightXS� bend-insensitive single-mode glass fiber in combination with a 155-micron-diameter, low-modulus primary coating layer (e.g., Draka Comteq's ColorLockXS brand coating system) and a 200-micron-diameter secondary coating layer provides (i) comparable microbending performance to that of a 125-micron, standard single-mode glass fiber coated with a 185-micron-diameter, low-modulus primary coating layer (e.g., Draka Comteq's ColorLockXS brand coating system) and a 242-micron-diameter secondary coating layer and (ii) significantly better microbending performance than that of a standard single-mode optical fiber (SSMF) that employs conventional primary and secondary coatings (i.e., at an outer diameter of about 235-265 microns).
[0120] As noted previously, one suitable composition for the primary coating is a UV-curable urethane acrylate product provided by DSM Desotech (Elgin, Ill.) under the trade name DeSolite� DP 1011. It is believed that this UV-curable urethane acrylate product includes about 1.0 percent of adhesion promoter. Other suitable compositions for the primary coating include alternative UV-curable urethane acrylate products provided by DSM Desotech under various trade names, including DeSolite� DP 1014, DeSolite� DP 1014XS, and DeSolite� DP 1016. It is believed that these alternative compositions possess essentially the same low-modulus and glass-transition properties as those possessed by the aforementioned DeSolite� DP 1011 UV-curable urethane acrylate product, albeit with some compositional variation (e.g., adhesion promoter concentration increased to 1.25 percent). As will be appreciated by those having ordinary skill in the art, compositional variations may provide particular primary-coating properties that are desirable for particular applications. It appears that the DeSolite� DP 1014XS UV-curable urethane acrylate product, for instance, exhibits favorable processing characteristics and provides improved delamination resistance.
[0121] Those having ordinary skill in the art will appreciate that each of these exemplary UV-curable urethane acrylate products (i.e., DeSolite� DP 1011, DeSolite� DP 1014, DeSolite� DP 1014XS, and DeSolite� DP 1016) provides better microbending performance than do conventional primary coatings, such as other UV-curable urethane acrylate products provided by DSM Desotech under the respective trade names DeSolite� DP 1004 and DeSolite� DP 1007.
[0122] The respective microbend sensitivities were further measured for exemplary optical fibers, including (i) an enhanced single-mode glass fiber (ESMF) with a low-modulus coating, (ii) various bend-insensitive glass fibers (e.g., Draka Comteq's single-mode glass fibers available under the trade names BendBrightXS�) with conventional primary coatings, and (iii) various bend-insensitive glass fibers and macrobend-resistant glass fibers (e.g., Draka Comteq's single-mode glass fibers available under the trade names BendBrightXS� and BendBright�) with low-modulus primary coatings.
[0124] Two hours after winding, fiber attenuation was measured at room temperature (i.e., 23� C.) using an optical time domain reflectometer (OTDR). Then, the drum (with 440 meters of wound fiber) was temperature cycled in a temperature-controlled chamber from about room temperature through (i) −40� C. and (ii) −60� C. Fiber attenuation was measured by an optical time domain reflectometer (OTDR) after two hours of equilibration at both −40� C. and −60� C.
[0126] Table 2 (above) shows that Draka Comteq's 125-micron BendBrightXS� bend-insensitive single-mode glass fiber facilitates a reduction in total optical-fiber diameter by permitting use of thinner primary and/or secondary coatings. In this regard, a 200-micron optical fiber using Draka Comteq's BendBrightXS� bend-insensitive single-mode glass fiber and relatively thin primary and secondary coatings provides microbending performance that approaches that of a 242-micron optical fiber having an enhanced standard single-mode fiber (ESMF) and thicker layers of comparable low-modulus primary and secondary coatings.
[0130] Moreover, Tables 2 and 3 (above) indicate that, all things being equal, Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS�, which employ a trench-assisted design, provide better microbending performance than do single-mode fibers that do not employ trench-assisted and/or void-assisted design (e.g., Draka Comteq's single-mode glass fibers available under the trade name BendBright�). This is somewhat unexpected—trench-assisted and other bend-insensitive glass designs are generally understood to have more pronounced effects upon macrobending rather than microbending.
[0131] The respective microbend sensitivities were further measured in accordance with the IEC fixed-diameter sandpaper drum test (i.e., IEC TR62221, Method B) for exemplary optical fibers, including (i) enhanced single-mode glass fibers (ESMF) with Draka Comteq's ColorLock brand coating system and (ii) Draka Comteq's single-mode glass fibers available under the trade name BendBrightXS� with Draka Comteq's improved ColorLockXS brand coating system.
[0132] As with Example 7 (above), the testing procedure for Example 8 was likewise an adaptation of IEC TR62221, Method B (i.e., the “Reduced-Diameter Optical-Fiber Microbend Sensitivity Test”). For this modified IEC fixed-diameter sandpaper drum test, a 300-millimeter diameter quartz cylinder was wrapped with adhesive-backed, 320-grit sandpaper (i.e., approximately equivalent to 36-micron-grade sandpaper) to create a rough surface. Then, each 440-meter fiber sample was wound in a single layer at about 1,470 mN (i.e., a controlled tension of 150 gf on the 300-millimeter diameter quartz drum using a Delachaux optical fiber winding apparatus). Two hours after winding, fiber attenuation was measured at room temperature (i.e., 23� C.) using an optical time domain reflectometer (OTDR).
[0134] Table 4 (above) shows that, Draka Comteq's 125-micron BendBrightXS� bend-insensitive single-mode glass fiber in combination with (i) a low-modulus primary coating having an outer diameter of between about 150 microns and 160 microns and (ii) a secondary coating having an outer diameter of between about 195 microns and 200 microns provides significantly better microbending performance compared with that of conventional 125-micron enhanced single-mode glass fiber (ESMF) in combination with a 190-micron-diameter, conventional primary coating and a 242-micron-diameter, conventional secondary coating.
[0135] Stated otherwise, a nominal 200-micron optical fiber formed from Draka Comteq's 125-micron BendBrightXS� bend-insensitive single-mode glass fiber and Draka Comteq's ColorLockXS brand coating system provides superior microbending performance to that of a 242-micron, enhanced single-mode optical fiber (ESMF) that employs conventional primary and secondary coatings.
[0136] Moreover, a nominal 200-micron optical fiber formed from Draka Comteq's 125-micron BendBrightXS� bend-insensitive single-mode glass fiber and Draka Comteq's ColorLockXS brand coating system provides similar microbending performance to that of a 242-micron, enhanced single-mode optical fiber (ESMF) that employs a comparable low-modulus primary coating and a comparable secondary coating. By way of example, the 200-micron optical fibers designated Examples A-E in Table 4 (above) provide comparable microbending performance to that of the 242-micron optical fiber designated Example H in Table 2 (above), which, as noted, is a 242-micron optical fiber having an enhanced standard single-mode fiber (ESMF) and thicker layers of comparable low-modulus primary and secondary coatings.
[0137] As noted, whereas single-mode glass fibers that are commercially available from Draka Comteq under the trade name BendBright� are compliant with the ITU-T G.652.D requirements, single-mode glass fibers that are commercially available from Draka Comteq under the trade names BendBrightXS� and BendBright-Elite™ are compliant with the ITU-T G.652.D requirements and the ITU-T G.657.A/B requirements. The respective ITU-T G.652 recommendations and the respective ITU-T G.657 recommendations are hereby incorporated by reference in their entirety.
[0138] In this regard, this application incorporates by reference product specifications for the following Draka Comteq single-mode optical fibers: (i) Enhanced Single Mode Fiber (ESMF); (ii) BendBright� single-mode optical fiber; (iii) BendBrightXS� single-mode optical fiber; and (iv) BendBright-Elite™ single-mode optical fiber. This technical information is provided as Appendices 1-4, respectively, in priority U.S. Provisional Application No. 61/248,319 for a Reduced-Diameter Optical Fiber (filed Oct. 2, 2009), which, as noted, is incorporated by reference in its entirety.
[0143] That said, it has been preliminarily observed that, with respect to reduced-diameter optical fibers having low-modulus primary coatings, bend-insensitive glass fibers having full-solid designs (e.g., 125-micron BendBrightXS� bend-insensitive single-mode glass fiber) seem to provide better microbending performance than do bend-insensitive glass fibers having hole-assisted designs.
[0144] Furthermore, it has been preliminarily observed that, with respect to reduced-diameter optical fibers, bend-insensitive glass fibers having full-solid designs (e.g., 125-micron BendBrightXS� bend-insensitive single-mode glass fiber) also seem to provide better mechanical performance than do bend-insensitive glass fibers having void-assisted designs (e.g., holey fibers). Those having ordinary skill in the art will appreciate that mechanical robustness is an important consideration when employing a bend-insensitive glass fiber within a nominal 200-micron optical fiber.
[0145] In this regard, 200-micron optical fibers that are formed from (i) Draka Comteq's 125-micron BendBrightXS� bend-insensitive single-mode glass fiber, which has a full-solid glass design, and (ii) Draka Comteq's ColorLockXS brand coating system demonstrate comparable mechanical reliability to that of a standard 242-micron optical fiber (e.g., a SSMF).
[0146] The 200-micron optical fibers that are formed from Draka Comteq's 125-micron BendBrightXS� bend-insensitive single-mode glass fiber and Draka Comteq's ColorLockXS brand coating system were tested for tensile strength and dynamic fatigue in accordance with the FOTP-28 standard, which is hereby incorporated by reference in its entirety. Representative mechanical reliability for these 200-micron optical fibers, which possessed differently colored secondary coatings, is provided (below) in Table 5.
[0157] Accordingly, the optical fiber (e.g., bend-insensitive optical fiber) as herein disclosed may be included in optical-fiber ribbon cables having relatively high filling coefficients and fiber counts, and thus reduced cable dimensions.
[0158] Those having ordinary skill in the art will know that to reduce optical attenuation in optical-fiber ribbon cables, optical-fiber ribbons have typically been placed inside buffer tubes.
[0159] Such buffer tubes are typically reinforced and protected by additional layers of plastic, metal, and/or fiberglass. In such designs, the optical-fiber ribbons are allowed to “float” in an unstressed state inside the buffer tube as the tube itself and/or the surrounding cable components expand and contract (e.g., during installation and use).
[0160] The dimensions of the hollow space (i.e., cavity) inside the buffer tube and of all of the surrounding cable components are typically selected to prohibit the application of undue mechanical forces on the optical-fiber ribbon. The boundaries of optical-fiber ribbon-cable design have been limited by how much stress (e.g., tensile stress) can be applied to an optical fiber (both short term and long term) and by how much attenuation the optical fiber experiences as a result of microbending and macrobending during cable expansion and contraction (e.g., thermal contraction and/or post-extrusion shrinkage). In other words, the density of optical fibers within buffer tube cables has been limited by a need for a clearance (e.g., empty space) between optical-fiber ribbons and the interior surface of the buffer tubes. Ribbon-stack clearances in conventional buffer tubes range between about 0.35 millimeter and 2.8 millimeters. Accordingly, such buffer tubes typically have a filling coefficient of less than about 0.26.
[0161] Buffer tubes may also employ additional elements such as water-swellable tapes or compressible elements for blocking the longitudinal flow of water or to couple the ribbon or ribbon stack to the buffer tube. Such elements may also help to reduce the risk of microbending and macrobending. Despite the need to limit the risk of attenuation, it is desirable to design cables and buffer tubes with high optical-fiber density to reduce cable diameter and cost.
[0162] As a result of cost and performance trade-offs, the fiber-optic-cable industry has effectively standardized most cable designs and dimensions. This standardization is possible because most manufacturers use optical fibers with similar bend sensitivities.
[0163] Existing fiber optic ribbon cables provide adequate performance, but there remains a desire to produce fiber optic ribbon cables with smaller diameters that provide improved handling and that can function well in harsh environments. In addition, smaller fiber optic ribbon cables use less material and, as such, can be produced at a reduced cost.
[0164] The bend-insensitive optical fibers according to the present invention facilitate the manufacture of optical-fiber ribbon cables and buffer tubes that possess high fiber densities and that are capable of withstanding harsh environments. In general, it is desirable to increase the density of transmission elements (e.g., optical-fiber ribbons) in buffer tubes or cables while maintaining acceptable attenuation during installation and use (e.g., during mid-span storage).
[0165] Multiple optical fibers as disclosed herein may be sandwiched, encapsulated, and/or edge bonded to form an optical-fiber ribbon. In general, optical-fiber ribbons can be divisible into subunits (e.g., a twelve-fiber ribbon that is splittable into six-fiber subunits).
[0166] Moreover, a plurality of such optical-fiber ribbons may be aggregated to form a ribbon stack, which can have various sizes and shapes. For example, it is possible to form a rectangular ribbon stack. Alternatively, a non-rectangular ribbon stack in which the uppermost and lowermost optical-fiber ribbons have fewer optical fibers than those toward the center of the stack may be employed. Such ribbon stacks may utilize, for example, 12-fiber, 24-fiber, and/or 36-fiber ribbons. This construction may be useful to increase the density of optical-fiber elements (e.g., optical fibers) within the buffer tube and/or cable.
[0167] In this regard, various ribbon stack configurations are disclosed in the following patents, each of which is hereby incorporated by reference: U.S. Pat. No. 6,778,745 for an Optical Fiber Cable Apparatus Having Encased Ribbon Stack; U.S. Pat. No. 6,744,955 for a Buffer Tube Having a High Fiber Count Ribbon Stack Packaging Configuration and Corner Stack; U.S. Pat. No. 6,621,966 for a Fiber Optic Cable with Profiled Group of Optical Fibers; U.S. Pat. No. 6,519,399 for a Fiber Optic Cable with Profiled Group of Optical Fibers; U.S. Pat. No. 6,487,348 for a Variable Fiber Count Optical Fiber Cable Core; U.S. Pat. No. 6,192,178 for a Fiber Optic Cable with Profiled Group of Optical Fibers; U.S. Pat. No. 5,878,180 for an Optical Fiber Cable with Stacks of Optical Fiber Ribbons; U.S. Pat. No. 5,293,443 for a Cable Utilizing Multiple Light Waveguide Stacks; and U.S. Pat. No. 5,249,249 for a Cable Utilizing Multiple Light Waveguide Stacks.
[0168] An optical-fiber ribbon or ribbon stack defines a maximum cross-sectional width. As used herein, the term “maximum cross-sectional width” is meant to characterize the largest cross-sectional dimension of an optical-fiber element (e.g., an optical-fiber ribbon or ribbon stack).
[0169] For example, the maximum cross-sectional width of a rectangular optical-fiber ribbon stack is defined by its diagonal. More specifically, a ribbon stack containing 144 optical fibers may be arranged as a rectangular stack of twelve (12) 12-fiber ribbons. Assuming the optical fibers have an outer diameter of about 242 microns, each 12-fiber ribbon may be about 0.3 millimeter thick and about 3.0 millimeters wide, and thus the ribbon stack would be about 3.6 millimeters thick and about 3.0 millimeters wide. The rectangular stack's diagonal, and thus its maximum cross-sectional width, is equal to: (3.62+3.02)1/2=4.68 millimeters.
[0170] In an alternative embodiment reduced-diameter optical fibers may be employed. In this regard, assuming the optical fibers have an outer diameter of about 200 microns, each 12-fiber ribbon may be about 0.26 millimeter thick and about 2.6 millimeters wide. Therefore, the ribbon stack would be about 3.12 millimeters thick and about 2.6 millimeters wide. The rectangular stack's diagonal, and thus its maximum cross-sectional width, is equal to: (3.122+2.62)1/2=4.06 millimeters.
[0171] In a typical embodiment, a buffer tube may loosely enclose one or more optical-fiber ribbons (e.g., a ribbon stack) formed from several bend-insensitive fibers of the present invention to thereby achieve a ribbon tube. A single buffer tube enclosing a ribbon stack (i.e., a ribbon tube) may be centrally positioned within a cable sheath to form a central ribbon-tube cable. In this regard, FIG. 13 depicts an exemplary central ribbon-tube cable 20. The central ribbon-tube cable 20 includes a buffer tube 21, enclosing a 12�12 ribbon stack 22. A cable jacket 23 surrounds the buffer tube 21.
[0172] In an alternative embodiment, two or more ribbon tubes may be enclosed (e.g., stranded or unstranded) within an outer protective sheath to form a ribbon cable. For example, six buffer tubes, each containing a 12�12 ribbon stack, may be stranded about a central strength member and enclosed by a cable jacket.
[0173] The ribbon cables in accordance with the present invention may include one or more radial strength members (e.g., formed from glass-reinforced plastic (GRP)), which may be embedded in the cable jacket. The radial strength members may be positioned within the cable to as to give the cable a preferential bend.
[0174] Optical-fiber ribbons (e.g., a ribbon stack) formed from several bend-insensitive fibers of the present invention may be variously positioned within buffer tubes. For example, such bend-insensitive optical-fiber ribbons can be deployed in optical-fiber buffer tubes and cables as disclosed in commonly assigned U.S. Pat. No. 7,515,795 for a Water-Swellable Tape, Adhesive-Backed for Coupling When Used Inside a Buffer Tube (Overton et al.); commonly assigned U.S. Pat. No. 7,599,589 for a Gel-Free Buffer Tube with Adhesively Coupled Optical Element (Overton et al.); commonly assigned U.S. Patent Application Publication No. 2009/0003781 and its related U.S. patent application Ser. No. 12/146,526 for an Optical Fiber Cable Having a Deformable Coupling Element (Parris et al.); commonly assigned U.S. Patent Application Publication No. 2009/0003779 and its related U.S. patent application Ser. No. 12/146,535 for an Optical Fiber Cable Having Raised Coupling Supports (Parris), and commonly assigned U.S. Patent Application Publication No. 2009/0003785 and its related U.S. patent application Ser. No. 12/146,588 for a Coupling Composition for Optical Fiber Cables (Parris et al.), each of which is hereby incorporated by reference in its entirety.
[0175] The present optical-fiber ribbons may be deployed in buffer tubes having water-swellable elements. The buffer tubes may include filling greases or lubricants (e.g., thixotropic filling greases). The present invention also embraces dry cable structures (i.e., grease-free buffer tubes).
[0176] The present optical-fiber ribbons may be deployed within buffer-tube structures having annular free space, that is to say that there is free space between the optical-fiber element (e.g., a ribbon stack) and its surrounding structure (e.g., the inner surface of a buffer tube or the surface of a water-swellable tape or coupling element(s) positioned between the buffer tube and the ribbon stack).
[0177] Moreover, as used herein in this context, the term “annular free space” is intended to characterize unfilled space that can exist between the optical-fiber element and its surrounding structure around the entire perimeter of the optical-fiber element, regardless of the respective shapes of the optical-fiber cable and its components (e.g., a rectangular ribbon stack within a round buffer tube). In this regard, the term “annular free space” as used herein is not limited to the regular gap between two concentric tubes (or casings) having circular cross-sections (i.e., a perfect annulus).
[0178] The term “optimal minimum clearance” refers to the minimum distance between the optical-fiber element and its surrounding structure (e.g., the surrounding buffer tube or surrounding water-swellable tape) when the optical-fiber element is optimally positioned to maximize clearance. Those having ordinary skill in the art will appreciate that clearance is typically maximized when the optical-fiber element is centrally positioned within its surrounding structure. By way of illustration, the optimal minimum clearance for a rectangular ribbon stack is the distance between a corner optical fiber and its closest adjacent surrounding structure when the rectangular ribbon stack is centrally positioned (e.g., within the surrounding buffer tube).
[0179] When the closest adjacent surrounding structure to the centrally positioned optical-fiber element is the inner surface of the buffer tube, the optimal minimum clearance is equal to one-half of the difference between the buffer tube's inner diameter and the optical-fiber element's maximum cross-sectional width. Because of the improved bend insensitivity of the present bend-insensitive optical fibers, optical-fiber cables and buffer tubes containing the present optical fibers may have a relatively high optical-fiber density resulting from a relatively small clearance.
[0180] In particular, the buffer tube may have an optimal minimum clearance of less than about 0.32 millimeter, such as between about 0.15 millimeter and 0.3 millimeter. Typically, the present buffer tubes have an optimal minimum clearance of less than about 0.25 millimeter (e.g., between about 0.10 millimeter and 0.20 millimeter), more typically less than about 0.15 millimeter (e.g., between about 0.05 millimeter and 0.10 millimeter). Indeed, a zero-clearance buffer-tube configuration (i.e., about 0 millimeter) is within the scope of the present invention.
[0181] As noted, the present optical-fiber ribbons may be deployed within buffer-tube structures or cable cavities (i.e., cables not having buffer tubes such as a drop cable) having one or more compressible coupling elements and/or compressible water-swellable tapes, which may also serve to alleviate microbending and macrobending. Exemplary compressible coupling elements are disclosed in commonly assigned U.S. Patent Application Publication No. 2009/0003781 (Parris et al.).
[0182] Within such buffer tubes or cable cavities, the optical-fiber element may be in contact with one or more compressible coupling elements and/or water-swellable tapes so that there is no annular free space within the buffer tubes or cable cavities. For example, one or more compressible coupling elements may compressibly squeeze the optical-fiber element (e.g., at the corners of the ribbon stack). The compressible coupling elements and/or compressible water-swellable tapes used within such buffer tubes or cable cavities need not be as thick or as compressible as the compressible coupling elements and/or water-swellable tapes found in conventional buffer tubes or cable cavities. Consequently, the pertinent cable and buffer-tube diameters may be smaller than those of conventional ribbon cables without promoting undue microbending or macrobending.
[0183] As noted, the present buffer tubes may have relatively high optical-fiber densities and thus high filling coefficients.
[0184] As used herein, the term “buffer-tube filling coefficient” refers to the ratio of the total cross-sectional area of the optical fibers within a buffer tube versus the inner cross-sectional area of that buffer tube (i.e., defined by the inner boundary of the buffer tube). By way of clarification, the term “buffer-tube filling coefficient” excludes ribbon matrix materials (e.g., subunit and common ribbon matrices).
[0185] Additionally, as used herein, the term “cumulative buffer-tube filling coefficient” refers to the ratio of the total cross-sectional area of the optical fibers enclosed within buffer tubes versus the sum of the inner cross-sectional areas of the buffer tubes containing those optical fibers.
[0186] In this regard, the present buffer tubes typically possess a buffer-tube filling coefficient of at least about 0.3 (e.g., between about 0.32 and 0.38), more typically at least about 0.35, such as about 0.4 or more.
[0187] Moreover, as used herein, the term “ribbon-stack filling coefficient” refers to the ratio of the total cross-sectional area of a ribbon stack enclosed within a buffer tube versus the inner cross-sectional area of the buffer tube. In this regard, the term “ribbon-stack filling coefficient” specifically includes ribbon matrix materials (e.g., subunit and common ribbon matrices). Assuming a rectangular ribbon stack, the present buffer tubes typically have a ribbon-stack filling coefficient of at least about 0.35, more typically at least about 0.4 (e.g., between about 0.45 and 0.65). That said, even higher ribbon-stack filling coefficients might be achieved by employing non-rectangular ribbon stacks.
[0188] In an exemplary embodiment, a 12�12 ribbon stack having a width of about 3 millimeters and a thickness of about 3.6 millimeters may be placed in a buffer tube having an inner diameter of about 5 millimeters. The buffer tube may be filled with a thixotropic composition. In this embodiment, the optimal minimum clearance would be about 0.16 millimeters and the buffer-tube filling coefficient would be about 0.34. Furthermore, the ribbon-stack filling coefficient would be about 0.55.
[0189] Buffer tubes in accordance with the present invention typically have a thickness of between about 0.5 millimeter and 1.0 millimeter. Accordingly and by way of example, a buffer tube having an inner diameter of about 5 millimeters may have a outer diameter of between about 6 millimeters and 7 millimeters.
[0190] In an alternative embodiment, a 12�12 ribbon stack having a width of about 3 millimeters and a thickness of about 3.6 millimeters may be placed in a buffer tube having an inner diameter of about 5.2 millimeters. A layer of water-swellable tape having a thickness of about 0.2 millimeters may be placed in the interior of the buffer tube. In this alternative embodiment, the optimal minimum clearance would be about 0.06 millimeters and the buffer tube filling coefficient would be about 0.31. Furthermore, the ribbon-stack filling coefficient would be about 0.51.
[0191] Smaller cable structures, as described previously, have many benefits, including less material usage, which not only can reduce manufacturing costs but also can make such cables more suitable for deployments in tight enclosures. As compared with previous cables, these smaller cable structures typically weigh less and are easier to handle.
[0192] This application further incorporates entirely by reference the following commonly assigned patents, patent application publications, and patent applications: U.S. Pat. No. 5,574,816 for Polypropylene-Polyethylene Copolymer Buffer Tubes for Optical Fiber Cables and Method for Making the Same; U.S. Pat. No. 5,717,805 for Stress Concentrations in an Optical Fiber Ribbon to Facilitate Separation of Ribbon Matrix Material; U.S. Pat. No. 5,761,362 for Polypropylene-Polyethylene Copolymer Buffer Tubes for Optical Fiber Cables and Method for Making the Same; U.S. Pat. No. 5,911,023 for Polyolefin Materials Suitable for Optical Fiber Cable Components; U.S. Pat. No. 5,982,968 for Stress Concentrations in an Optical Fiber Ribbon to Facilitate Separation of Ribbon Matrix Material; U.S. Pat. No. 6,035,087 for an Optical Unit for Fiber Optic Cables; U.S. Pat. No. 6,066,397 for Polypropylene Filler Rods for Optical Fiber Communications Cables; U.S. Pat. No. 6,175,677 for an Optical Fiber Multi-Ribbon and Method for Making the Same; U.S. Pat. No. 6,085,009 for Water Blocking Gels Compatible with Polyolefin Optical Fiber Cable Buffer Tubes and Cables Made Therewith; U.S. Pat. No. 6,215,931 for Flexible Thermoplastic Polyolefin Elastomers for Buffering Transmission Elements in a Telecommunications Cable; U.S. Pat. No. 6,134,363 for a Method for Accessing Optical Fibers in the Midspan Region of an Optical Fiber Cable; U.S. Pat. No. 6,381,390 for a Color-Coded Optical Fiber Ribbon and Die for Making the Same; U.S. Pat. No. 6,181,857 for a Method for Accessing Optical Fibers Contained in a Sheath; U.S. Pat. No. 6,314,224 for a Thick-Walled Cable Jacket with Non-Circular Cavity Cross Section; U.S. Pat. No. 6,334,016 for an Optical Fiber Ribbon Matrix Material Having Optimal Handling Characteristics; U.S. Pat. No. 6,321,012 for an Optical Fiber Having Water Swellable Material for Identifying Grouping of Fiber Groups; U.S. Pat. No. 6,321,014 for a Method for Manufacturing Optical Fiber Ribbon; U.S. Pat. No. 6,210,802 for Polypropylene Filler Rods for Optical Fiber Communications Cables; U.S. Pat. No. 6,493,491 for an Optical Drop Cable for Aerial Installation; U.S. Pat. No. 7,346,244 for a Coated Central Strength Member for Fiber Optic Cables with Reduced Shrinkage; U.S. Pat. No. 6,658,184 for a Protective Skin for Optical Fibers; U.S. Pat. No. 6,603,908 for a Buffer Tube that Results in Easy Access to and Low Attenuation of Fibers Disposed Within Buffer Tube; U.S. Pat. No. 7,045,010 for an Applicator for High-Speed Gel Buffering of Flextube Optical Fiber Bundles; U.S. Pat. No. 6,749,446 for an Optical Fiber Cable with Cushion Members Protecting Optical Fiber Ribbon Stack; U.S. Pat. No. 6,922,515 for a Method and Apparatus to Reduce Variation of Excess Fiber Length in Buffer Tubes of Fiber Optic Cables; U.S. Pat. No. 6,618,538 for a Method and Apparatus to Reduce Variation of Excess Fiber Length in Buffer Tubes of Fiber Optic Cables; U.S. Pat. No. 7,322,122 for a Method and Apparatus for Curing a Fiber Having at Least Two Fiber Coating Curing Stages; U.S. Pat. No. 6,912,347 for an Optimized Fiber Optic Cable Suitable for Microduct Blown Installation; U.S. Pat. No. 6,941,049 for a Fiber Optic Cable Having No Rigid Strength Members and a Reduced Coefficient of Thermal Expansion; U.S. Pat. No. 7,162,128 for Use of Buffer Tube Coupling Coil to Prevent Fiber Retraction; U.S. Pat. No. 7,515,795 for a Water-Swellable Tape, Adhesive-Backed for Coupling When Used Inside a Buffer Tube (Overton et al.); U.S. Patent Application Publication No. 2008/0292262 for a Grease-Free Buffer Optical Fiber Buffer Tube Construction Utilizing a Water-Swellable, Texturized Yarn (Overton et al.); European Patent Application Publication No. 1,921,478 A1, for a Telecommunication Optical Fiber Cable (Tatat et al.); U.S. Pat. No. 7,570,852 for an Optical Fiber Cable Suited for Blown Installation or Pushing Installation in Microducts of Small Diameter (Nothofer et al.); U.S. Patent Application Publication No. US 2008/0037942 A1 for an Optical Fiber Telecommunications Cable (Tatat); U.S. Pat. No. 7,599,589 for a Gel-Free Buffer Tube with Adhesively Coupled Optical Element (Overton et al.); U.S. Pat. No. 7,567,739 for a Fiber Optic Cable Having a Water-Swellable Element (Overton); U.S. Patent Application Publication No. US2009/0041414 A1 for a Method for Accessing Optical Fibers within a Telecommunication Cable (Lavenne et al.); U.S. Patent Application Publication No. US2009/0003781 A1 for an Optical Fiber Cable Having a Deformable Coupling Element (Parris et al.); U.S. Patent Application Publication No. US2009/0003779 A1 for an Optical Fiber Cable Having Raised Coupling Supports (Parris); U.S. Patent Application Publication No. US2009/0003785 A1 for a Coupling Composition for Optical Fiber Cables (Parris et al.); U.S. Patent Application Publication No. US2009/0214167 A1 for a Buffer Tube with Hollow Channels, (Lookadoo et al.); U.S. patent application Ser. No. 12/466,965 for an Optical Fiber Telecommunication Cable, filed May 15, 2009, (Tatat); U.S. patent application Ser. No. 12/506,533 for a Buffer Tube with Adhesively Coupled Optical Fibers and/or Water-Swellable Element, filed Jul. 21, 2009, (Overton et al.); U.S. patent application Ser. No. 12/557,055 for an Optical Fiber Cable Assembly, filed Sep. 10, 2009, (Barker et al.); U.S. patent application Ser. No. 12/557,086 for a High-Fiber-Density Optical Fiber Cable, filed Sep. 10, 2009, (Lovie et al.); U.S. patent application Ser. No. 12/558,390 for a Buffer Tubes for Mid-Span Storage, filed Sep. 11, 2009, (Barker); U.S. patent application Ser. No. 12/614,692 for Single-Fiber Drop Cables for MDU Deployments, filed on Nov. 9, 2009, (Overton); U.S. patent application Ser. No. 12/614,754 for Optical-Fiber Loose Tube Cables, filed on Nov. 9, 2009, (Overton); U.S. patent application Ser. No. 12/615,003 for a Reduced-Size Flat Drop Cable, filed on Nov. 9, 2009, (Overton et al.); U.S. patent application Ser. No. 12/615,106 for ADSS Cables with High-Performance Optical Fiber, filed on Nov. 9, 2009, (Overton); U.S. patent application Ser. No. 12/______ for a Reduced-Diameter, Easy-Access Loose Tube Cable, filed on Nov. 10, 2009, (Overton); U.S. Patent Application No. 61/112,845 for Single-Fiber Drop Cables for MDU Deployments, filed Nov. 10, 2008, (Overton); U.S. Patent Application No. 61/112,863 for Bend-Insensitive-Fiber Loose Tube Cables, filed Nov. 10, 2008, (Overton); U.S. Patent Application No. 61/112,912 for a Reduced-Size Flat Drop Cable with Bend-Insensitive Fiber, filed Nov. 10, 2008, (Overton); U.S. Patent Application No. 61/112,926 for ADSS Cables with Bend-Insensitive Fiber, filed Nov. 10, 2008, (Overton); U.S. Patent Application No. 61/112,965 for Reduced-Diameter Ribbon Cables with High-Performance Optical Fiber, filed Nov. 10, 2008, (Overton); U.S. Patent Application No. 61/113,067 for a Reduced-Diameter, Easy-Access Loose Tube Cable, filed Nov. 10, 2008, (Overton).
[0193] In the specification and/or figures, typical embodiments of the invention have been disclosed. The present invention is not limited to such exemplary embodiments. The figures are schematic representations and so are not necessarily drawn to scale. Unless otherwise noted, specific terms have been used in a generic and descriptive sense and not for purposes of limitation.
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20, 2014Corning Cable Systems LlcFiber optic ribbon cable* Cited by examinerClassifications U.S. Classification385/114International ClassificationG02B6/44Cooperative ClassificationG02B6/4482, G02B6/4494, G02B6/4429, G02B1/048, G02B6/02395, C03C25/106, G02B6/4411European ClassificationG02B6/44C5A, G02B6/44C7, G02B1/04D4, G02B6/02, C03C25/10P2D2Legal EventsDateCodeEventDescriptionApr 21, 2010ASAssignmentOwner name: DRAKA COMTEQ B.V.,NETHERLANDSFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:OVERTON, BOB J.;REEL/FRAME:024267/0227Effective date: 20100412Owner name: DRAKA COMTEQ B.V., NETHERLANDSFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:OVERTON, BOB J.;REEL/FRAME:024267/0227Effective date: 20100412Apr 20, 2015FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services