Depressed cladding optical fiber cable
First Claim
1. An optical fiber cable, which comprises:
- a plurality of optical fibers which are assembled together without intended stranding to form a unit which extends in a direction substantially along a longitudinal axis of the cable, each of said optical fibers including a core, an outer cladding, and an inner cladding having an index of refraction which is less than that of the outer cladding and being characterized by a difference between the indices of refraction of said core and of said inner cladding which is sufficiently high to cause said each optical fiber to be substantially insensitive to microbending with the ratio of the inner cladding diameter to the core diameter, which ratio is sufficiently large to avoid affecting the dispersive properties of the optical fiber, and the ratio of the difference in the indices of refraction of the inner and the outer claddings to the difference in the indices of refraction between the core and the inner cladding being such that each said optical fiber is capable of operation in a single mode fashion at a predetermined wavelength;
a binder which is wrapped about said plurality of optical fibers;
a tube which is made of a plastic material and which encloses the plurality of optical fibers with the ratio of the cross-sectional area of the plurality of optical fibers to the cross-sectional area within the tube not exceeding a predetermined value, said tube being substantially parallel to the longitudinal axis of the cable;
a strength member system; and
a jacket which is made of a plastic material and which encloses said tube.
6 Assignments
0 Petitions
Accused Products
Abstract
An optical fiber cable (20) includes a core (21) comprising plurality of units (22--22). Each unit is formed by a plurality of optical fibers (24--24) which are assembled together without intended stranding. Each of the optical fibers includes a core, and inner and outer claddings with the inner cladding characterized by an index of refraction depressed from that of the outer cladding. The ratio of the inner cladding diameter to the core diameter and the ratio of the difference in the indices of refraction of the inner and outer claddings to the difference in indices of refraction between the core and the inner cladding are such that each optical fiber is capable of operation in a single mode fashion at a predetermined wavelength. Also, the difference between the indices of refraction of the core and the inner cladding is sufficiently high to cause each fiber to be substantially insensitive to microbending. The plurality of units are enclosed in a common tube (34) which provides a predetermined packing density. In one embodiment, a waterblocking material (46) is disposed within the tube to fill the interstices between the optical fibers and between the units. The waterblocking material is such that its critical yield stress does not exceed about 70 Pa at 20° C. and such that it has a shear modulus of less than about 13 KPa at 20° C. The common tube is enclosed with a sheath system. This arrangement is such that the optical performance of the cable is not degraded at temperatures as low as -40° F.
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Citations
16 Claims
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1. An optical fiber cable, which comprises:
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a plurality of optical fibers which are assembled together without intended stranding to form a unit which extends in a direction substantially along a longitudinal axis of the cable, each of said optical fibers including a core, an outer cladding, and an inner cladding having an index of refraction which is less than that of the outer cladding and being characterized by a difference between the indices of refraction of said core and of said inner cladding which is sufficiently high to cause said each optical fiber to be substantially insensitive to microbending with the ratio of the inner cladding diameter to the core diameter, which ratio is sufficiently large to avoid affecting the dispersive properties of the optical fiber, and the ratio of the difference in the indices of refraction of the inner and the outer claddings to the difference in the indices of refraction between the core and the inner cladding being such that each said optical fiber is capable of operation in a single mode fashion at a predetermined wavelength; a binder which is wrapped about said plurality of optical fibers; a tube which is made of a plastic material and which encloses the plurality of optical fibers with the ratio of the cross-sectional area of the plurality of optical fibers to the cross-sectional area within the tube not exceeding a predetermined value, said tube being substantially parallel to the longitudinal axis of the cable; a strength member system; and a jacket which is made of a plastic material and which encloses said tube. - View Dependent Claims (2, 3, 4, 5)
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6. An optical fiber cable, which comprises:
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a plurality of units, each of the units comprising a plurality of optical fibers which are assembled together without intended stranding to form a unit which extends along the cable and a binder wrapped about the unit, each of said optical fibers including a core, an outer cladding and an inner cladding having an index of refraction which is less than that of said outer cladding and being characterized by a difference between the indices of refraction of said core and of said inner cladding which is sufficiently high to cause each fiber to be substantially insensitive to microbending with the ratio of the cladding diameter to the core diameter, which ratio is sufficiently large to avoid affecting dispersive properties of the optical fiber, and the ratio of the difference in the indices of refraction of the inner and outer claddings to the overall difference in indices of refraction between the core and the inner cladding being such that each said optical fiber is capable of operation in a single mode fashion at a predetermined wavelength; a tube which is made of a plastic material and which encloses the plurality of units with the ratio of the cross-sectional area of the plurality of optical fibers to the cross-sectional area within the tube not exceeding a predetermined value, said tube being substantially parallel to the longitudinal axis of the cable; a waterblocking material which is disposed within the tube and which fills substantially the interstices between the optical fibers of the units within the tube and between the units and the tube, the waterblocking material having a critical yield stress and a shear modulus which allow movement of the units within the tube when the waterblocking material is subjected to a predetermined stress; a strength member system; and a jacket which encloses said tube and which is made of a plastic material. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An optical fiber cable, which comprises:
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a plurality of optical fibers which extend in a direction substantially along a longitudinal axis of the cable, each of said optical fibers including a core, an outer cladding, and an inner cladding having an index of refraction which is less than that of the outer cladding and being characterized by a difference between the indices of refraction of said core and of said inner cladding which is sufficiently high to cause said each optical fiber to be substantially insensitive to microbending with the ratio of the inner cladding diameter to the core diameter, which ratio is sufficiently large to avoid affecting the dispersive properties of the optical fiber, and the ratio of the difference in the indices of refraction between the core and claddings to the difference in the indices of refraction between the core and the inner cladding being such that each said optical fiber is capable of operation in a single mode fashion at a predetermined wavelength; a tube which is made of a plastic material and which encloses the plurality of optical fibers with the ratio of the cross-sectional area of the plurality of optical fibers to the cross-sectional area within the tube not exceeding a predetermined value, said tube being substantially parallel to the longitudinal axis of the cable; a strength member system; and a jacket which is made of a plastic material and which encloses said tube.
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Specification