# US 10,261,278 B1 · Optical fiber cable with dual layer buffer tube for microduct application > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,261,278 B1 - Document ID: US10261278B1 - Status: Granted - Kind: B1 - Application number: 16/158,484 - Filed: 2018-10-12 - Published: 2019-04-18 - Granted: 2019-04-16 - Earliest claimed: 2018-10-12 - Assignees: Sterlite Technologies Limited - Applicants: Sterlite Technologies Limited - Inventors: Venkatesh Murthy; Kishore Sahoo; Atul Mishra; Kavya Chintada - Web page: https://patentgrep.com/patent/US10261278B1 ## CPC - G02B 6/4434: {Central member to take up tensile loads} - G02B 6/4413: {Helical structure} - G02B 6/4415: {Cables for special applications (G02B6/4429, G02B6/4439, G02B6/4479 take precedence)} - G02B 6/4431: {with provision in the protective covering, e.g. weak line, for gaining access to one or more fibres, e.g. for branching or tapping (break-out terminations G02B6/4471)} - G02B 6/4438: {for facilitating insertion by fluid drag in ducts or capillaries} - G02B 6/44384: {the means comprising water blocking or hydrophobic materials (G02B6/4439, G02B6/4479 take precedence)} - G02B 6/4482: {Code or colour marking} - G02B 6/52: using fluid, e.g. air - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract The present disclosure provides an optical fiber cable. The optical fiber cable includes a central strength member. The central strength member lies substantially along a longitudinal axis of the optical fiber cable. In addition, the optical fiber cable includes a first layer. The first layer includes a plurality of water swellable yarns. Further, the optical fiber cable includes a plurality buffer tubes. Each of the plurality of buffer tubes includes a plurality of optical fiber. Moreover, the optical fiber cable includes a second layer of a pair of binder yarns. Further, the optical fiber cable includes a third layer. The third layer is formed of a plurality of water swellable yarns. The optical fiber cable includes a fourth layer. The fourth layer is a sheath layer. ## Claims ### Claim 1 An optical fiber cable comprising: a central strength member lying substantially along a longitudinal axis of the optical fiber cable, wherein the central strength member is formed of fiber reinforced plastic, wherein the central strength member has a diameter of about 3.0 mm; a first layer wrapped helically around the central strength member, wherein the first layer is formed of a plurality of water swellable yarns; a plurality of buffer tubes stranded helically around the first layer, wherein each of the plurality of buffer tubes encloses a plurality of optical fibers, wherein each of the plurality of buffer tubes is formed of a combination of two sub layers having different material, wherein each of the plurality of buffer tubes has a first sub layer and a second sub layer; wherein the first sub layer is formed of polycarbonate, wherein the second sub layer is formed of polybutylene terephthalate; a second layer, wherein the second layer cross helically surrounds a core of the optical fiber cable, wherein the second layer is formed of a pair of binder yarns, wherein the pair of binder yarn comprising: a first binder yarn, wherein the first binder yarn is wrapped helically in clockwise direction; and a second binder yarn, wherein the second binder yarn is wrapped helically in anti-clockwise direction; a third layer, wherein the third layer is wrapped helically around the core of the optical fiber cable, wherein the third layer is formed of a plurality of water swellable yarns; and a fourth layer surrounding the third layer, wherein the fourth layer is formed of high density polyethylene, wherein the optical fiber cable has a diameter of about 7.7 mm±0.2 mm. ### Claim 2 (depends on 1) The optical fiber cable as recited in claim 1, wherein each of the plurality of buffer tubes has a first diameter of about 1.55 mm±0.05 mm, wherein each of the plurality of buffer tubes has a second diameter of about 1.85 mm±0.05 mm. ### Claim 3 (depends on 1) The optical fiber cable as recited in claim 1, wherein the first sub layer has a thickness of about 75 microns±10 microns, wherein the first sub layer has a density of about 1.2 gm/cm3. ### Claim 4 (depends on 1) The optical fiber cable as recited in claim 1, wherein the second sub layer has a thickness of about 75 microns±10 microns, wherein the second sub layer has a density of about 1.31 gm/cm3. ### Claim 5 (depends on 1) The optical fiber cable as recited in claim 1, wherein the plurality of buffer tubes is eight, wherein the plurality of optical fibers in each of the plurality of buffer tubes is twenty four, wherein each of the plurality of optical fibers has a diameter of about 250 microns. ### Claim 6 (depends on 1) The optical fiber cable as recited in claim 1, wherein the fourth layer has a thickness in a range of about 0.4 mm to 0.6 mm, wherein the fourth layer has a density in a range of about 0.90 gm/cm3 to 0.96 gm/cm3. ### Claim 7 (depends on 1) The optical fiber cable as recited in claim 1, wherein the central strength member is a solid pultrusion type fiber reinforced plastic, wherein the central strength member is coated with a polyethylene layer, wherein the central strength member is coated to accommodate plurality of buffer tubes. ### Claim 8 (depends on 1) The optical fiber cable as recited in claim 1, wherein the first binder yarn is aramid binder yarn, wherein the second binder yarn is aramid binder yarn. ### Claim 9 (depends on 1) The optical fiber cable as recited in claim 1, further comprising a plurality of ripcords, wherein the plurality of ripcords are positioned below the fourth layer. ### Claim 10 (depends on 1) The optical fiber cable as recited in claim 1, wherein the optical fiber cable is blown into a duct, wherein the duct is having an inner diameter of about 10 mm and outer diameter of about 14 mm, wherein the optical fiber cable has a fill factor in a range of about 54% to 64% in the duct. ### Claim 11 (depends on 1) The optical fiber cable as recited in claim 1, wherein each of the plurality of buffer tubes has a packing factor in a range of about 75% to 92%, wherein the packing factor is defined as ratio of equivalent cross sectional area of fiber bunch to inner cross sectional area of a buffer tube of the plurality of buffer tubes, wherein the equivalent cross sectional area is area formed by equivalent diameter of fiber bunch which is calculated by formula, 1.155*Square root of number fibers per tube*Diameter of the fiber. ### Claim 12 An optical fiber cable comprising: a central strength member lying substantially along a longitudinal axis of the optical fiber cable, wherein the central strength member is formed of fiber reinforced plastic, wherein the central strength member has a diameter of about 3.0 mm; a first layer wrapped helically around the central strength member, wherein the first layer is formed of a plurality of water swellable yarns; a plurality of buffer tubes stranded helically around the first layer, wherein each of the plurality of buffer tubes encloses a plurality of optical fibers, wherein each of the plurality of buffer tubes has a first diameter of about 1.55 mm±0.05 mm, wherein each of the plurality of buffer tubes has a second diameter of about 1.85 mm±0.05 mm, wherein each of the plurality of buffer tubes is formed of a combination of two sub layers having different material, wherein each of the plurality of buffer tubes has a first sub layer and a second sub layer; wherein the first sub layer is formed of polycarbonate, wherein the second sub layer is formed of polybutylene terephthalate; a second layer, wherein the second layer cross helically surrounds a core of the optical fiber cable, wherein the second layer is formed of a pair of binder yarns, wherein the pair of binder yarns comprising: a first binder yarn, wherein the first binder yarn is wrapped helically in clockwise direction; and a second binder yarn, wherein the second binder yarn is wrapped helically in anti-clockwise direction; a third layer wrapped helically around the core of the optical fiber cable, wherein the third layer is formed of a plurality of water swellable yarns; and a fourth layer surrounding the third layer, wherein the fourth layer is formed of high density polyethylene, wherein the fourth layer has a thickness in a range of about 0.4 mm to 0.6 mm, wherein the fourth layer has a density in a range of about 0.90 gm/cm3 to 0.96 gm/cm3, wherein the optical fiber cable has a diameter of about 7.7 mm±0.2 mm. ### Claim 13 (depends on 12) The optical fiber cable as recited in claim 12, wherein the first sub layer has a thickness of about 75 microns±10 microns, wherein the first sub layer has a density of about 1.2 gm/cm3. ### Claim 14 (depends on 12) The optical fiber cable as recited in claim 12, wherein the second sub layer has a thickness of about 75 microns±10 microns, wherein the second sub layer has a density of about 1.31 gm/cm3. ### Claim 15 (depends on 12) The optical fiber cable as recited in claim 12, wherein the plurality of buffer tubes is eight, wherein the plurality of optical fibers in each of the plurality of buffer tubes is twenty four, wherein each of the plurality of optical fibers has a diameter of about 250 microns. ### Claim 16 (depends on 12) The optical fiber cable as recited in claim 12, wherein the central strength member is a solid pultrusion type fiber reinforced plastic, wherein the central strength member is coated with a polyethylene layer, wherein the central strength member is coated to accommodate the plurality of buffer tubes. ### Claim 17 (depends on 12) The optical fiber cable as recited in claim 12, wherein the first binder yarn is aramid binder yarn, wherein the second binder yarn is aramid binder yarn. ### Claim 18 (depends on 12) The optical fiber cable as recited in claim 12, further comprises a plurality of ripcords, wherein the plurality of ripcords is positioned below the fourth layer and along with the third layer in a linear manner. ### Claim 19 An optical fiber cable comprising: a central strength member lying substantially along a longitudinal axis of the optical fiber cable, wherein the central strength member is formed of fiber reinforced plastic, wherein the central strength member has a diameter of about 3.0 mm; a first layer wrapped helically around the central strength member, wherein the first layer is formed of a plurality of water swellable yarns; a plurality of buffer tubes stranded helically around the first layer, wherein each of the plurality of buffer tubes has a first diameter of about 1.55 mm±0.05 mm, wherein each of the plurality of buffer tubes has a second diameter of about 1.85 mm±0.05 mm, wherein each of the plurality of buffer tubes is formed of a combination of two sub layers having different material, wherein each of the plurality of buffer tubes has a first sub layer and a second sub layer; wherein the first sub layer is formed of polycarbonate, wherein the first sub layer has a thickness of about 75 microns±10 microns, wherein the first sub layer has a density of about 1.2 gm/cm3, wherein the second sub layer is formed of polybutylene terephthalate, wherein the second sub layer has a thickness of about 75 microns±10 microns, wherein the second sub layer has a density of about 1.31 gm/cm3, wherein each of the plurality of buffer tubes encloses a plurality of optical fibers, wherein the plurality of buffer tubes is eight, wherein the plurality of optical fibers in each of the plurality of buffer tubes is twenty four, wherein each of the plurality of optical fibers has a diameter of about 250 microns; a second layer, wherein the second layer cross helically surrounds a core of the optical fiber cable, wherein the second layer is formed of a pair of binder yarns, wherein the pair of binder yarn comprising: a first binder yarn, wherein the first binder yarn is wrapped helically in clockwise direction; and a second binder yarn, wherein the second binder yarn is wrapped helically in anti-clockwise direction; a third layer wrapped helically around the core of the optical fiber cable, wherein the third layer is formed of a plurality of water swellable yarns; and a fourth layer surrounding the third layer, wherein the fourth layer is formed of high density polyethylene, wherein the fourth layer has a thickness in a range of about 0.4 mm to 0.6 mm, wherein the fourth layer has a density in a range of about 0.90 gm/cm3 to 0.96 gm/cm3, wherein the optical fiber cable has a diameter of about 7.7 mm±0.2 mm.