Patent Application
20240288645
The present disclosure generally relates to optical fiber cables and in particular to optical fiber cables having a high density of optical fibers and minimized free space.
In general, an optical fiber cable needs to carry more optical fibers in order to transmit more optical data, and in order to carry more optical fibers, the size of the optical fiber cable needs to be increased. The increased size is at least partially the result of free space considerations to avoid macro- and micro-bending attenuation losses. For existing installations, size limitations and duct congestion limit the size of optical fiber cables that can be used without the requirement for significant retrofitting. Thus, it may be desirable to provide optical fiber cables having a higher fiber density (i.e., more fibers per cross-sectional area of the cable) without increasing the cable diameter such that the high fiber density cables can be used in existing ducts.
In one aspect, embodiments of the present disclosure relate to an optical fiber cable. The optical fiber cable includes a cable jacket having an inner surface and an outer surface. The inner surface defines a central cable bore, and the outer surface defines an outermost surface of the optical fiber cable. The cable outer diameter is 11 mm or less. The optical fiber cable also includes a cable core disposed in the central cable bore. The cable core has a cross-sectional area and a plurality of optical fibers provided in the core, each of the plurality of optical fibers having an outer diameter of less than or equal to 210 microns, preferably less than or equal to 200 microns. The plurality of optical fibers fill at least 40% of the cross-sectional area of the cable core, and the cable comprises at least 48 optical fibers and a fiber density based on cable outer cross-sectional area that is at least 7.5 fibers/mm2. The plurality of optical fibers has a mode field diameter at 1310 nm of between 8.2 microns and 9.5 microns, a cable cutoff less than 1260 nm, a zero-dispersion wavelength between 1300 nm and 1324 nm. The plurality of optical fibers exhibit an attenuation increase of less than 0.15 dB/km at 1550 nm at −10° C., preferably an attenuation increase of less than 0.15 dB/km at 1550 nm at −30° C. as measured by IEC 60794-5-10:2014.
In another aspect, embodiments of the present disclosure relate to a lumen. The lumen includes a plurality of optical fibers in which each of the plurality of optical fibers has an outer diameter of 210 microns or less, preferably 200 microns or less. The lumen further includes a membrane surrounding the plurality of optical fibers. The membrane may be made of any suitable material, including a polypropylene, a polyester, a polyethylene, a polyamide, a polyvinyl chloride (PVC), or a polytetrafluoroethylene material, and may include small quantities of other materials or fillers that provide different properties to the material of the membrane, such other materials including material that provides for easy access by tearing of the membrane (e.g., tearing by hand), coloring, UV/light blocking (e.g., carbon black), or fire resistance/flame retardancy. A thickness of the membrane is 50 microns or less, and a free space within the membrane is 60% or less.
In a further aspect, embodiments of the present disclosure relate to an optical fiber cable. The optical fiber cable includes a cable jacket having an inner surface and an outer surface. The inner surface defines a central cable bore, and the outer surface defines an outermost surface of the optical fiber cable. The optical fiber cable also includes a cable core disposed within the central bore of the cable jacket. The cable core includes a plurality of optical fibers. The cable core includes a plurality of elements that may be SZ-stranded, unidirectionally stranded, or not stranded at all. In the case of a cable having no strength elements, the cable core is able to withstand a tensile load greater than a weight of one kilometer of the optical fiber cable, and the plurality of optical fibers comprise a cumulative tensile rigidity of at least 75% of the optical fiber cable at 0.1% core strain.
In still another aspect, embodiments of the present disclosure relate to an optical fiber cable. The optical fiber cable includes a cable jacket having an inner surface and an outer surface. The inner surface defines a central cable bore, and the outer surface defines an outermost surface of the optical fiber cable. The optical fiber cable also includes a cable core disposed within the central bore of the cable jacket. The cable core includes two or more lumens. Each lumen includes a plurality of optical fibers in which each of the plurality of optical fibers has an outer diameter of 210 microns or less, preferably 200 microns or less. Each lumen also includes a membrane surrounding the plurality of optical fibers in which the membrane has a thickness of 50 microns or less. In the case of a cable without any strength elements, the plurality of optical fibers have a cumulative tensile rigidity that is at least 75% of a tensile rigidity of the optical fiber cable.
In yet another aspect, embodiments of the present disclosure relate to an optical fiber cable. The optical fiber cable includes a cable jacket having an inner surface and an outer surface. The inner surface defines a central cable bore, and the outer surface defines an outermost surface of the optical fiber cable. The optical fiber cable also includes a plurality of optical fibers disposed within the central cable core. A plurality of optical fibers may be encased in a membrane material to form a lumen, and a plurality of lumens may be provided in the cable core to form a lumen bundle. The cable may include strength elements that may be embedded in the cable jacket or provided between the lumen bundle and the cable jacket. In accordance with yet other aspects, an armor layer, such as a two-piece armor layer, may be provided to surrounded the lumen bundle between the lumen bundle and the cable jacket. In addition, a protective layer of foamed material or another suitable material may be provided between the lumen bundle and the armor or cable jacket to provide additional protection to the optical fibers in the lumens.
In still yet another aspect, embodiments of the present disclosure relate to an optical fiber cable. The optical fiber cable includes a cable jacket having an inner surface and an outer surface in which the inner surface defines a central cable bore and in which the outer surface defines an outermost surface of the optical fiber cable. The optical fiber cable also includes from 48 to 864 optical fibers disposed within the central cable bore. The outer surface of the cable jacket defines a cable diameter of at least 2 mm and up to 11 mm. The optical fiber cable may have a fiber density of at least 7.5 optical fibers per mm2 based on a cross-sectional area of the optical fiber cable as measured from the outer surface of the cable jacket. In accordance with some aspects of the present disclosure, the optical fiber cable does not include a strength member. In accordance with yet other aspects of the present disclosure, the optical fiber cable may include one or more strength members.
In still a further aspect, embodiments of the present disclosure relate to an optical fiber cable. The optical fiber cable includes a cable jacket having an inner surface and an outer surface in which the inner surface defines a central cable bore extending along a longitudinal axis of the optical fiber cable and in which the outer surface defines an outermost surface of the optical fiber cable. The optical fiber cable also includes a plurality of lumens disposed within the central cable bore. Each lumen of the plurality of lumens includes at least two optical fibers surrounded by a membrane. The membrane of each lumen has a thickness of 50 microns or less. The membrane is reconfigurable between a plurality of shapes, and the plurality of shapes is defined by a perimeter of the membrane as viewed from a cross-section of the lumen taken perpendicular to the longitudinal axis. The plurality of lumens is arranged in at least a first layer and a second layer within the central cable bore. The second layer is in contact and surrounds the first layer, and a shape of at least one lumen in the first layer is different from a shape of at least one lumen in the second layer.
In accordance with yet other aspects of the present disclosure, the membrane may be drawn down tight onto the plurality of optical fibers such that the membrane is more static in shape to maintain the smallest cross-sectional area of the plurality of fibers. Each lumen in this configuration maintains a similar shape to each other lumen in the core regardless of the position or layer of the lumen in the core.
Additional features and advantages will be 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 embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description serve to explain principles and operation of the various embodiments.
Embodiments of the present disclosure relate to a high-density optical fiber cable. In one or more embodiments, the optical fibers are provided in reconfigurable lumens having a thin membrane so that the lumens can be tightly packed within the cable core. As will be discussed more fully below, some embodiments of the optical fiber cable are configured to eliminate strength members, such as glass-reinforced plastic rods, metal wires, and tensile strands, by eliminating free space around the optical fibers so that the optical fibers together act as the strength member of the optical fiber cable. In such embodiments without strength members, the optical fibers may account for 75% or more of the tensile rigidity of the optical fiber cable. Advantageously, an optical fiber cable having these characteristics combines a high fiber density with a small diameter and the requisite properties for jetting the cable through ducts. In a particular example disclosed herein, the optical fiber cable includes 288 optical fibers in a cable jacket having an outer diameter small enough to jet at least 1500 m in an 8 mm duct. Examples of other high fiber density optical fiber cables include from 48 to 864 optical fibers that do and do not include strength elements are also provided herein.
The following detailed description represents embodiments that are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanied drawings are included to provide a further understanding of the claims and constitute a part of the specification. The drawings illustrate various embodiments, and together with the descriptions serve to explain the principles and operations of these embodiments as claimed.
with A being the cross-sectional area of the optical fiber cable 10. The optical fiber cable 10 had a weight of 28 kg/km. The fiber density in the optical fiber cable 10 is 11.2 fibers per mm2 (based on cable cross-sectional area A) and the fiber free space of loose fibers inside the cable core is 25%. The cable is rated for 1000 N at 0.4% fiber strain (or 3.6× cable weight).
In one or more embodiments, the optical fibers 20 of the optical fiber cable 10 are stranded as shown in
Thus, in one or more embodiments, the optical fiber cable 10 may consist essentially of the cable jacket 12 surrounding a plurality of first groups 21 of optical fibers 20, that may or may not be arranged into larger second groups 23. Other components that do not affect the basic and novel characteristics of the optical fiber cable 10 that may be included are, for example, a binder film 32 provided between the plurality of first groups 21 or second groups 23 and the cable jacket 12, water blocking material (e.g., tapes and powders, including powders made of super absorbent polymers (SAP)), lubricants, friction-enhancing materials, and access features (e.g., ripcords or preferential tear features, such as a strip of dissimilar polymer in the cable jacket 12). In one or more embodiments, armor layers and strength elements are excluded from the construction of the optical fiber cable 10, while in other embodiments, such as shown in
In order to provide a level of organization of the optical fibers 20 within the optical fiber cable 10, the optical fibers 20 may include an outer coating layer. Optical fibers 20 within first groups 21 or second groups 23 may include optical fibers 20 having the following sequence of twelve color coatings: blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, and aqua. That is, within one first group 21, there will be only one optical fiber 20 having a blue color coating, only one optical fiber 20 having an orange color coating, one optical fiber 20 having a green color coating, etc. For first groups 21 having more than twelve optical fibers 20, the color sequence can be repeated but the color coating may further include a stripe along the length of the optical fiber 20. For all of the color coatings except for black, the stripe may be a black stripe, and for the black color coating, the stripe may be, e.g., a white, yellow, or gray. Thus, despite the large number of loose optical fibers within the optical fiber cable 10, the coloring of the outer layer of the optical fibers 20 along with the grouping and/or stranding of the optical fibers 20 into groups 21, 23 allows for differentiation of the optical fibers 20. Further, the groups 21, 23 of the optical fibers 20 can be differentiated from other groups 21, 23 of optical fibers 20 by providing colored banding, tape, or wrap. For example, each first group 21 may include a periodically spaced band, tape, or wrap along the length of the stranded optical fibers 20. In this way, a particular first group 21 may be identified by the particular striped or unstriped blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, or aqua band along its length. While one common color-coding scheme for twelve optical fibers was discussed for the purposes of illustration, other color-coding schemes used for fewer or greater than twelve optical fibers may also be used without departing from the scope of the present disclosure.
In one or more embodiments, the optical fibers 20 are arranged in groups and enclosed within a thin membrane 22 to form a lumen 24.
In one or more embodiments, the thickness of the membrane 22 is 50 microns or less, 40 microns or less, or 30 microns or less, in particular between 10 microns and 50 microns. In one or more embodiments, the membrane 22 groups from two to ninety-six in particular from eight to thirty-six, and particularly from twelve to twenty-four, optical fibers 20 into a lumen 24. As discussed above, the optical fibers 20 within the lumen 24 may be provided in a color-coded sequence of striped or unstriped coatings of blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, and aqua, or other indicia stripes, ring marking, tally marks, or combinations of such fiber identification schema.
As shown in
In one or more embodiments, the grouping of the optical fibers 20 by the membrane 22 into lumens 24 allows for the optical fiber cable 10 to be constructed without any conventional strength members. In other embodiments, conventional strength members 40 may be provided (see, e.g.,
In one or more embodiments, an outer surface of the lumen 24 is frictionally coupled to the cable jacket 12. This frictional coupling helps to limit buckling of the optical fibers 20 within the optical fiber cable 10. In one or more embodiments, the frictional coupling between the lumens 24 and cable jacket 12 can be enhanced by pulling the cable jacket 12 around the lumens 24 during extrusion, which increases the normal force of the cable jacket 12 on the lumens 24, thereby increasing the friction between them. Alternatively or additionally, the frictional coupling between the lumens 24 and the cable jacket 12 can be enhanced by providing grease, gel, or a pressure sensitive adhesive at the interface between the lumens 24 and the cable jacket 12. In one or more embodiments, such friction enhancing materials can also be provided between the lumens 24 in the cable core 30.
In one or more embodiments, the lumens 24 are grouped together into multi-lumens 26 as shown in
In one or more embodiments, the cable core 30 may be further wrapped with a binder film 32. In one or more embodiments, the multi-lumens 26 are stranded (e.g., SZ, S, or Z stranded) within the cable core 30, and the binder film 32 may be used to hold the multi-lumens 26 in the stranded configuration. Thus, in one or more embodiments, the optical fiber cable 10 may consist essentially of the cable jacket 12 surrounding a plurality of lumens 24 grouped by membranes 28 into one or more multi-lumens 26. Other components that do not affect the basic and novel characteristics of the optical fiber cable 10 that may be included are, for example, the binder film 32 provided between the plurality of lumens 24 and the cable jacket 12, water blocking material (e.g., tapes and powders), lubricants, friction enhancing materials, and access features (e.g., ripcords or preferential tear features, such as a strip of dissimilar polymer in the cable jacket 12). In one or more embodiments, the multi-lumens 28 are frictionally coupled to the cable jacket 12 as described above.
In one or more embodiments, the membrane 28 includes from two to twenty-four, in particular from four to twelve lumens 24 to form multi-lumen 26. In one or more embodiments, the cable core 30 includes from two to ten, in particular from three to eight multi-lumens 26.
In one or more embodiments, the binder film 32 is a thin film jacket having a thickness between 40 microns and 150 microns, preferably less than 100 microns. A binder film 32 in this thickness range reduces the thermal load of the binder film 32 on the lumens 24 (or multi-lumens 26) during extrusion. That is, a thick binder layer could hold enough heat after extrusion to remelt the thin membranes 22, 28 of the lumens 24 and/or the multi-lumens 26 causing the lumens 24 or multi-lumens 26 to stick to the binder film 32 such that they become inseparable or difficult to separate. In accordance with yet other embodiments, the binder film 32 may be comprised of a material dissimilar to the material of the membranes 22, 28 of the lumens 24 or multi-lumens 26 such that when both materials reach their respective melting points, there is no bonding or limited bonding of either material to the other so that they remain easily separable.
In one or more embodiments, the cable jacket 12 has a thickness of between 0.5 mm and 1 mm. In particular embodiments, the cable jacket 12 has a thickness that is greater than 8% of the outer diameter of the optical fiber cable 10, such as between 8% and 10% of the outer diameter.
In one or more embodiments, the membranes 22, 28 are made from a polypropylene, a polyester, a polyethylene, a polyamide, a polyvinyl chloride (PVC), or a polytetrafluoroethylene material, amongst other possibilities, and may include small quantities of other materials or fillers that provide different properties to the material of the membrane, uch other materials including material that provides for easy access by tearing of the membrane (e.g., tearing by hand), coloring, UV/light blocking (e.g., carbon black), or fire resistance/flame retardancy Further, in embodiments, one or both of the membranes 22, 28 are substantially continuous around the optical fibers 20. In one or more embodiments, one or both of the membranes 22, 28 are discontinuous around the optical fibers 20. For example, one or both of the membranes 22, 28 may be a mesh material, may include cutouts, or may be in the form of a plurality of strips wrapped around the optical fibers 20.
In one or more embodiments, the cable jacket 12 is made from a polyethylene material (such as high density polyethylene (HDPE)), a nylon or polyamide, a low-smoke zero halogen (LSZH) polymer, a filled polyethylene, a flame retardant (FR) polymer, or a urethane polymer, amongst other possibilities.
In one or more embodiments, the binder film 32 is made from, e.g., linear low density polyethylene (LLDPE).
For organizational purposes, the lumens 24 according to embodiments of the present disclosure may be color-coded within the optical fiber cable 10. In particular, the cable core 30 may include a sequence of lumens 24 having membranes 22 of the following colors: blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, and aqua. In one or more embodiments, the lumens 24 beyond the first twelve are also colored one of blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, and aqua, but the membrane 22 may also be provided with a ring marking 25 as shown in
In one or more embodiments, each lumen 24 also includes a yarn 35 on the interior of the membrane 22 as shown in
In accordance with other aspects of the present disclosure, other waterblocking technologies may be used in the cable 10. For example, the lumens 24 may be filled with a gel or lubricant for waterblocking. Similarly, a gel or lubricant could be used to coat core components and/or fill the interstitial spaces in the cable core 18. In other aspects of the disclosure, a water blocking tape or yarn may be provided to surround the cable core 18 or provided within the core.
In one or more embodiments, each of the lumens 24 includes a machine readable code 33, such as a barcode or other sequence of markings (including, e.g., printed stripes or dots), as shown in
Advantageously, because of the thinness of the membrane 22, the membrane 22 is essentially amorphous and may allow the lumen 24 to be reconfigurable in shape. An example of a diamond-shaped embodiment is shown in
Table 1 provides a summary of the geometric parameters of the shapes described in
Table 2 provides a summary of the geometric parameters for a cable including a plurality of lumens as described in Table 1 and depicted in
Because the center subunit(s) 24 take on more of the load, in one or more embodiments, the optical fibers 20 of the center lumens 24 may be made with a higher proof stress fiber, such as 200 kpsi proof stress fiber, and in one or more such embodiments, the other lumens could include optical fibers 20 having a proof stress of 100 kpsi. In one or more other embodiments, the proof stress of the optical fibers 20 may be selected so that optical fibers 20 in lumens 24 at the center have a proof stress of 200 kpsi, optical fibers 20 in lumens 24 in an outer row have a proof stress of 100 kpsi, and optical fibers 20 in lumens 24 between the center and outer row have a proof stress of 150 kpsi. These kpsi proof stress ratings are merely exemplary, and in other embodiments, the exact values needed for the strain and cable load specifications desired can be calculated.
For lumens 24 in the outside layer, the shape shown in
In one or more embodiments, the lumens 24 may comprise a stretchable membrane 22. In such embodiments, the membrane 22 may tightly conform to the optical fibers 20 so that reconfiguring the lumen 24 into different shapes requires stretching of the membrane 22. The stretching of the membrane 22 creates a normal force on the optical fibers 20, compacting them together. As mentioned above, the low free space within the lumen 24 in these embodiments creates a composite strength member of the membrane 22 and optical fibers 20. The stretching of the membrane 22 to compact the optical fibers together enhances the composite strength member effect.
Because the membranes 22 of the lumens 24 are reconfigurable and conformable into a variety of shapes, the conventional stranding layer increments can be disregarded in certain circumstances. In particular, a conventional cable generally includes one or three subunits at the center or a central strength member. For a cable with one subunit or a central strength member at the center that is substantially the same size as the subunits, the next layer of subunits will be six subunits followed by another layer of twelve subunits. Each successive layer will add another six subunits. Similarly, for a conventional cable having three subunits at the center, the next layer will have nine subunits, then fifteen subunits, and an additional six subunits for each successive layer. By using conformable membranes 22 having reconfigurable shapes around the optical fibers 20 in the lumens 24, this layer number of lumens 24 can be modified.
Indeed,
In one or more embodiments, the lumens 24 of each layer are stranded (e.g., S, Z or SZ stranded), along the length of the optical fiber cable 10. In one or more such embodiments, the lumens 24 are SZ stranded along the length of the optical fiber cable 10. In addition, SZ stranding of the lumens 24 enables the cable to be bent and coiled for slack storage without having high fiber strain and fiber breaks. In one or more such embodiments that include 2×6 curved parallelogram lumens 24, the column strength of the 2×6 curved parallelogram lumens 24 is able to push itself against the compressive strain on the inside of the bend.
As mentioned above, the optical fibers 20 may be a primary strength element of the optical fiber cable 10. In that regard, the optical fiber cable 10, in particular the cable core 18, does not include any conventional strength elements, such as glass-reinforced plastic rods, steel wire, or aramid or glass tensile yarns, amongst other conventional strength elements. In accordance with other aspects of the present disclosure, strength elements may be used in the optical fiber cable 10, in which case the optical fibers 20 may be one component that contributes to the overall strength profile of the optical fiber cable 10.
In general, the various designs of the optical fiber cable 10 described herein are able to eliminate strength elements because the optical fibers 20 within the cable core 30 are coupled together to act as a composite strength element by reducing the amount of free space within the optical fiber cable 10 and within lumens 24 in the optical fiber cable 10.
In one or more embodiments, the optical fiber cable 10 has a cumulative fiber filling coefficient of at least 40%, at least 50%, at least 60%, at least 65%, or at least 70%. In one or more embodiments, the optical fiber cable 10 has a cumulative fiber filling coefficient of up to 80%. As used herein, the term “cumulative fiber filling coefficient” of an optical-fiber cable 10 refers to the ratio of the sum of the cross-sectional areas of all of the optical fibers 20 within the optical-fiber cable 10 versus the inner cross-sectional area of the optical-fiber cable 10 (i.e., defined by the inner surface 14 of the cable jacket 12 or inner surface of binder film 32, if included). The cross-sectional area of each optical fiber 20 is determined based on an outer surface of the optical fiber 20. In one or more embodiments, the optical fiber 20 has an outer color coating layer as described above and discussed more fully below, and the cross-sectional area of the optical fiber 20 is measured from the outer surface as defined by this outer color coating layer. In one or more other embodiments, the optical fiber 20 is a “bare fiber” and does not include an outer color coating layer in which case the cross-sectional area of the optical fiber 20 is measured from the outer surface of the bare fiber.
In one or more embodiments, the optical fiber cable 10 comprises a free space of at most 60%, at most 50%, at most 42.5%, at most 30%, or at most 25%. In one or more embodiments, the free space of the optical fiber cable 10 is at least 20%. As used herein, the free space is the inverse of cumulative fiber filling coefficient (i.e., 100%-cumulative fiber filling coefficient).
In one or more embodiments, the optical fiber cable 10 includes from 48 to 864 optical fibers 20, in particular from 96 to 288 optical fibers 20. In one or more embodiments, the optical fiber cable 10 has a fiber density of at least 7.5 fibers/mm2. The fiber density is measured based on the number of optical fibers 20 per cross-sectional area of the optical fiber cable 10 as measured from the outer surface 16. In one or more embodiments, the fiber density is at least 8 fibers/mm2, at least 8.5 fibers/mm2, at least 9 fibers/mm2, at least 9.5 fibers/mm2, at least 10 fibers/mm2, at least 10.5 fibers/mm2, at least 11 fibers/mm2, at least 11.5 fibers/mm2, or at least 12 fibers/mm2. In one or more embodiments, the fiber density may be up to 17 fibers/mm2. Further, in one or more embodiments, the outer diameter of the optical fiber cable 10 as measured at the outer surface 16 is 11 mm or less, 9 mm or less, 8.5 mm or less, 8 mm or less, 7.5 mm or less, 7 mm or less, 6.75 mm or less, 6.5 mm or less, 6.25 mm or less, 6 mm or less, 5.75 mm or less, 5.5 mm or less, 5.25 mm or less, or 5 mm or less. Further, in one or more embodiments, the outer diameter of the optical fiber cable 10 as measured from the outer surface 16 is at least 2 mm.
The fiber density and diameter of the optical fiber cable 10 will vary depending primarily on the number of optical fibers 20 in the optical fiber cable 10, size of the optical fibers 20 in the optical fiber cable 10, and the free space in the lumens 24.
Curves A-E of
Curves F-J of
Curves K-O of
The fiber density can then be calculated for each cable 10. The high and low for fiber densities for the optical fiber cables 10 of each size and for each fiber diameter are provided in Table 6, below.
In one or more embodiments, the optical fibers 20 (whether organized into groups 21, 23 or lumens 24, 28) take up at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% of the tensile load on the optical fiber cable 10. The amount of tensile load taken up by the optical fibers 20 can be represented by the ratio of tensile rigidity of the optical fibers 20 to the tensile rigidity of the optical fiber cables 10. The tensile rigidity of the optical fibers 20 is the elastic modulus (E) of the optical fibers 20 multiplied by their cumulative cross-sectional area (A) within the optical fiber cable 10. The cumulative cross-sectional area of the optical fibers 20 is the sum of the cross-sectional area of each optical fiber 20 based on the outer diameter of the optical fibers 20. The tensile rigidity of the optical fiber cable 10 is the sum of the products of the elastic moduli (E) of each component of the optical fiber cable 10 multiplied by the component's cross-sectional area (A) or cumulative cross-sectional area (A).
Tables 7-13 provide example calculations of the tensile load taken up by the optical fibers 20 for optical fiber cables 10 having various amounts of optical fibers 20 within the optical fiber cable 10. The determination of the tensile load taken up by the optical fibers 20 was based on optical fibers 10 having an outer diameter of 196 microns with coating layers having a total thickness of about 35 microns around the core and cladding, a binder film 32 having a thickness of 150 microns, twelve optical fibers 20 per lumen 24, lumens 24 having membranes 22 with a thickness of 20 microns, and a cable jacket 10 having a thickness of 10% of the outer diameter based on
In one or more embodiments, the optical fibers 20 comprise a tensile rigidity of at least 30,000 N, at least 35,000 N, or at least 40,000 N for an optical fiber cable 10 having 48 optical fibers 20 and a tensile rigidity of 50,000 N or less. In one or more embodiments, the optical fibers 20 comprise a tensile rigidity of at least 60,000 N, at least 70,000 N, or at least 80,000 N for an optical fiber cable 10 having 96 optical fibers 20 and a tensile rigidity of 100,000 N or less. In one or more embodiments, the optical fibers 20 comprise a tensile rigidity of at least 120,000 N, at least 140,000 N, or at least 160,000 N for an optical fiber cable 10 having 192 optical fibers 20 and a tensile rigidity of 180,000 N or less. In one or more embodiments, the optical fibers 20 comprise a tensile rigidity of at least 175,000 N, at least 200,000 N, or at least 225,000 N for an optical fiber cable 10 having 288 optical fibers 20 and a tensile rigidity of 300,000 N or less. In one or more embodiments, the optical fibers 20 comprise a tensile rigidity of at least 250,000 N, at least 280,000 N, or at least 310,000 N for an optical fiber cable 10 having 384 optical fibers 20 and a tensile rigidity of 350,000 N or less. In one or more embodiments, the optical fibers 20 comprise a tensile rigidity of at least 300,000 N, at least 350,000 N, or at least 400,000 N for an optical fiber cable 10 having 480 optical fibers 20 and a tensile rigidity of 450,000 N or less. In one or more embodiments, the optical fibers 20 comprise a tensile rigidity of at least 375,000 N, at least 425,000 N, or at least 475,000 N for an optical fiber cable 10 having 576 optical fibers 20 and a tensile rigidity of 550,000 N or less.
In one or more embodiments of cables without strength members, the optical fibers 20 (whether organized into groups 21, 23 or lumens 24, 26) of the optical fiber cable 10 may have the highest elastic modulus of any component in the optical fiber cable 10. In one or more such embodiments, no component in the optical fiber cable 10 besides the optical fibers 20 has a modulus higher than 48 GPa, higher than 40 GPa, higher than 30 GPa, or higher than 25 GPa.
In one or more embodiments, all lumens 24 in the lumen bundle 30 are SZ stranded in unison with a common lay length. The path length for each lumen 24 while in a constant helix can be described by the following equation:
where HL is the helical path length, L is the sample length, and r is the radial location of the lumen 24 with respect to the center of the lumen bundle 30. A Helix Factor can be defined as HL/L. When such a lumen bundle 30 is subject to a tensile load, the SZ stranding may tend to unwind, such unwinding is resisted by the coupling of the lumen bundle 30 outer layer with the layers of material surrounding the lumen bundle 30. In the conservative case where the unwinding is uncontested, the tensile rigidity of the individual optical fibers 20 within the lumen bundle 30 will begin to contribute to the cumulative tensile rigidity of the optical fiber cable 10 as the helical path length HL is consumed by cable strain. When the cable strain reaches the maximum helical path length HL, all optical fibers 20 in the lumen bundle 30 will be contributing to the tensile rigidity of the optical fiber cable 10. In the ideal case where the SZ lumen bundle 30 acts like a unit of helical core with a helix factor (HL/L) equal to the average helix factor of the SZ lumen bundle 30 and with freely rotating ends, the cumulative tensile rigidity will increase linearly from the onset of strain in the center optical fibers 20 until all optical fibers 20 are fully engaged, i.e., when core strain is equal to the helix factor of the outermost optical fibers 20 in the lumen bundle 30.
As mentioned above, the membrane 22 of the lumen 24 may be able to be reconfigured into a 1×12 shape, which means that the lumen 24 acts essentially like an optical fiber ribbon. In this configuration, the amorphous membrane 22 will hold the optical fibers 20 side-by-side, providing the planarity needed for mass fusion splicing. Advantageously, the lumen 24 provides an advancement over conventional optical fiber ribbons which need more than 60% free space for performance adequate performance. Because the optical fibers 20 in the membranes 22 can act as loose fibers inside the optical fiber cable 10, less free space is required. In particular, the free space is less than 60%, less than 40%, or even as low as 20%. Thus, the lumens 24 can combine the advantages of both loose fibers and ribbons in terms of free space and mass fusion splicing.
Although the optical fibers 20 in the membrane 22 will likely not have the correct sequence (standard color sequence is blue, orange, green, brown, slate, white, red, black, yellow, violet, rose, aqua) for mass fusion splicing immediately upon flattening the lumen 24, the membrane 22 provides a processing aid to arrange the optical fibers 20 in the correct sequence. When the proper sequence is provided, the field technician can place the membrane 22 in a thermal stripper device and heat the membrane 22 so that the membrane 22 melts and sticks or bonds to the optical fibers 20. This makes the 1×12 configuration permanent, and after cooling, the lumen 24 can then be processed in the same way as a ribbon (e.g., stripped, cleaved, and spliced).
As discussed above, lumens 24 or the multi-lumens 26 may be stranded (such as SZ-stranded) in the lumen bundle 30 in embodiments, including a binder film 32 provided around switchbacks and the full length of the lumen bundle 30. The stranding provides the ability to bend the cable while minimizing tensile and contractive forces within any of the fibers. During cable bending, the optical fibers 20 must be able to shift position, moving longitudinally to relieve those forces so as not to cause attenuation or break the optical fibers 20. In some embodiments, because the membranes 22, 28, and lumen bundle 30 do not provide free space for the optical fibers 20 to increase fiber density by design, the lumens 24 and multi-lumens 26 may need the ability to move relative to each other in certain embodiments. To provide such motion, one or more embodiments of the optical fiber cable 10 include spherical powder (
In accordance with other aspects of the present disclosure, and as shown in
Having described the optical fiber cable 10, embodiments of a method for manufacturing an optical fiber cable 10 including a plurality of lumens 24 are provided. In one or more embodiments, each lumen 24 is constructed by extruding a membrane 22 around a plurality of optical fibers 20 and, optionally, a yarn 35. In one or more other embodiments, each lumen 24 is constructed by wrapping a membrane 22 around a plurality of optical fibers 20 and, optionally, a yarn 35. For example, a roll of membrane material can be unspooled and wrapped around the plurality of optical fibers 20. The wrapped membrane material can be joined around the plurality of optical fibers 20 using, e.g., laser welding, ultrasonic welding, or seam welding, among other possibilities.
The lumens 24, prepared according to any of the foregoing methods, are formed into a lumen bundle 30. In embodiments, the lumens 24 extend straight along the longitudinal axis in the cable core 18, and in other embodiments, the lumens 24 are stranded (e.g., S-stranded, Z-stranded, or SZ-stranded) along the longitudinal axis in the cable core 18.
In one or more embodiments, a plurality of lumens 24 are arranged into two or more multi-lumens 26 by extruding a membrane around the lumens 24 or wrapping and sealing a membrane material around the lumens 24.
In one or more embodiments, a binder film 32 is extruded around a plurality of lumens 24, a plurality of multi-lumens 26, or a combination of one or more lumens 24 with one or more multi-lumens 26.
A cable jacket 12 is then extruded around the lumens 24, multi-lumens 26, or binder film 32, as the case may be. During extrusion of the cable jacket 12, the access feature 39 and the tactile locator features 37 may be formed in the cable jacket 12 through the use of specially-configured extrusion die-heads. A vacuum may be pulled during extrusion of the cable jacket 12, which squeezes the cable jacket 12 down around the lumens 24. Additionally or alternatively, the cable jacket 12 can be made thicker, which results in greater shrinkage during cooling, compressing the lumens 24. Advantageously, by compressing the cable jacket 12 around the lumens 24, the individual lumens 24 may be manufactured with a higher than desired free space, and the force of the cable jacket 12 on the lumens 24 in the cable core 30 can reconfigure the lumens 24 into shapes with lower free space within the optical fiber cable 10.
Having described the construction of the optical fiber cable 10, embodiments of optical fibers 20 having a construction specially adapted for high fiber density applications are described below in greater detail. In that regard, the discussion of the optical fibers will make reference to various technical terms, definitions of which are provided in the following paragraphs:
“Refractive index” refers to the refractive index at a wavelength of 1550 nm.
The “refractive index profile” is the relationship between refractive index or relative refractive index and waveguide fiber radius. The radius for each region of the refractive index profile is given by the abbreviations r1, r2, r3, r4, etc. and lower and upper case are used interchangeably herein (e.g., r1 is equivalent to R1).
The “relative refractive index percent” is defined as Δ%=100×(ni2-nc2)/2ni2, and as used herein ni is the refractive index of region i of the optical fiber and ne is the refractive index of undoped silica. As used herein, the relative refractive index is represented by A and its values are given in units of “%”, unless otherwise specified. The terms: delta, A, A %, % A, delta %, % delta, and percent delta may be used interchangeably herein. In cases where the refractive index of a region is less than the average refractive index of undoped silica, the relative index percent is negative and is referred to as having a depressed region or depressed index. In cases where the refractive index of a region is greater than the average refractive index of the cladding region, the relative index percent is positive.
An “updopant” is herein considered to be a dopant which has a propensity to raise the refractive index relative to pure undoped SiO2. Examples of updopants include GeO2 (germania), Al2O3, P2O5, TiO2, Cl, Br.
A “downdopant” is herein considered to be a dopant which has a propensity to lower the refractive index relative to pure undoped SiO2. Examples of down dopants include fluorine and boron.
“Chromatic dispersion”, herein referred to as “dispersion” unless otherwise noted, of a waveguide fiber is the sum of the material dispersion, the waveguide dispersion, and the inter-modal dispersion. In the case of single mode waveguide fibers, the inter-modal dispersion is zero. Zero dispersion wavelength is a wavelength at which the dispersion has a value of zero. Dispersion slope is the rate of change of dispersion with respect to wavelength.
“Effective area” is defined as:
where f(r) is the transverse component of the electric field associated with light propagated in the waveguide. As used herein, “effective area” or “Aeff” refers to optical effective area at a wavelength of 1550 nm unless otherwise noted.
The trench volume V3 is defined for a depressed index region
where rTrench,inner is the inner radius of the trench cladding region, rTrench,outer is the outer radius of the trench cladding region, ATrench(r) is the relative refractive index of the trench cladding region, and Ac is the average relative refractive index of the common outer cladding region of the glass fiber. In embodiments in which a trench is directly adjacent to the core, rTrench,outer is r2=r1 (outer radius of the core), rTrench,outer is 13, and ATrench is Δ3(r). In embodiments in which a trench is directly adjacent to an inner cladding region, rTrench,inner is 12>r1, rTrench,outer is r3, and ATrench is Δ3(r). Trench volume is defined as an absolute value and has a positive value. Trench volume is expressed herein in units of % Δ-micron2, % Δ-μm2, or %-micron2, %-μm2, whereby these units can be used interchangeably.
The term “a-profile” refers to a relative refractive index profile, expressed in terms of Δ(r) which is in units of “%”, where r is radius, which follows the equation,
where r0 is the point at which Δ(r) is maximum, r1 is the point at which Δ(r) % is zero, and r is in the range ri≤r≤rf, where A is defined above, r1 is the initial point of the α-profile, rf is the final point of the a-profile, and a is an exponent which is a real number.
The mode field diameter (MFD) is measured using the Peterman II method wherein,
Mode field diameter depends on the wavelength of the optical signal in the optical fiber. Specific indication of the wavelength will be made when referring to mode field diameter herein. Unless otherwise specified, mode field diameter refers to the LP01 mode at the specified wavelength.
The theoretical fiber cutoff wavelength, or “theoretical fiber cutoff”, or “theoretical cutoff”, for a given mode, is the wavelength above which guided light cannot propagate in that mode. A mathematical definition can be found in Single Mode Fiber Optics, Jeunhomme, pp. 39-44, Marcel Dekker, New York, 1990 wherein the theoretical fiber cutoff is described as the wavelength at which the mode propagation constant becomes equal to the plane wave propagation constant in the outer cladding. This theoretical wavelength is appropriate for an infinitely long, perfectly straight fiber that has no diameter variations.
Fiber cutoff is measured by the standard 2 m (2 meter) fiber cutoff test, FOTP-80 (EIA-TIA-455-80), to yield the “fiber cutoff wavelength”, also known as the “2 m fiber cutoff” or “measured cutoff.” The FOTP-80 standard test is performed to either strip out the higher order modes using a controlled amount of bending, or to normalize the spectral response of the fiber to that of a multimode fiber.
Cabled cutoff wavelength, or “cabled cutoff” as used herein, refers to the 22 m (22 meter) cabled cutoff test described in the EIA-445 Fiber Optic Test Procedures, which are part of the EIA-TIA Fiber Optics Standards, that is, the Electronics Industry Alliance—Telecommunications Industry Association Fiber Optics Standards.
Unless otherwise noted herein, optical properties (such as dispersion, dispersion slope, etc.) are reported for the LP01 mode.
Referring to
In one or more embodiments, the cladding region 44 includes a cladding layer (e.g., second cladding layer 48) having a trench volume of greater than about greater than about 25% Δ-μm2. In one or more embodiments, the trench volume is greater than about 30% Δ-μm2, greater than about 40% Δ-μm2, greater than about 50% Δ-μm2, or greater than about 60%% Δ-μm2. In one or more embodiments, the trench volume is less than about 70% Δ-μm2, less than about 65% Δ-μm2, or less than about 60% Δ-μm2. In one or more embodiments, the trench volume is from about 25% Δ-μm2 to about 70% Δ-μm2, about 30% Δ-μm2 to about 70% Δ-μm2, about 40% Δ-μm2 to about 70% Δ-μm2, about 50% Δ-μm2 to about 70% Δ-μm2, about 60% Δ-μm2 to about 70% Δ-μm2, about 30% Δ-μm2 to about 60% Δ-μm2, about 30% Δ-μm2 to about 50% Δ-μm2, about 30% Δ-μm2 to about 40% Δ-μm2, about 40% Δ-μm2 to about 60% Δ-μm2, or about 50% Δ-μm2 to about 60% Δ-μm2. For example, the trench volume is about 30% Δ-μm2, about 35% Δ-μm2, about 40% Δ-μm2, about 45% Δ-μm2, about 46%%Δ-μm2, about 47%Δ-μm2, about 48%%Δ-μm2, about 49%Δ-μm2, about 50%Δ-μm2, about 55% Δ-μm2, about 60% Δ-μm2, about 61% Δ-μm2, about 62% Δ-μm2, about 68% Δ-μm2, about 69% Δ-μm2, about 70% Δ-μm2, or any trench volume between these values.
In some embodiments, the outer trench radius (corresponding to R3 in the embodiment of
In one or more embodiments, the core 42 and cladding region 44 are comprised of a glass material. In one or more embodiments, the core is comprised of germania-doped silica, and the trench (e.g., second cladding layer 48 in the embodiment of
In one or more embodiments, the core 42 has a first radius R1 that is from 4 microns to 6 microns. In one or more embodiments, the first cladding layer 46 has a second radius R2, the second cladding layer 48 has a radius R3, and the third cladding layer has a radius R4. In one or more embodiments, the second radius R2 is from 7 microns and 13 microns. In one or more embodiments, the third radius R3 is from 11 microns and 20 microns. In one or more embodiments, the fourth radius R4 is from 60 microns to 65 microns. The cladding region 44 defines a maximum cross-sectional dimension of the glass of the optical fiber 20. In embodiments in which the optical fiber 20 has a circular end or cross-section, the maximum cross-sectional dimension is a glass diameter Dg of the optical fiber 20. In one or more embodiments, the glass diameter Dg is from 120 microns to 130 microns.
For the purpose of this disclosure, the refractive index in each of the core 42, first cladding layer 46, and second cladding layer 48 are defined with respect to the refractive index Δ4 of the third cladding layer 50, i.e., Δ4=0% Δ. As shown in
In one or more embodiments, the core 42 is a step index with a core alpha of greater than 10. In other embodiments, the core 42 is a graded index core having a core alpha between 1.5 and 5. The core alpha is defined as an exponent a wherein the refractive index in the core 42 as a function of radial position is described by the refractive index relation Δ% (r)=Δ1,max*[1−(r/R1)α].
Disposed around the cladding region 44 is a coating 52 that surrounds and encapsulates the glass core 42 and cladding region 44. In embodiments, the coating 52 is configured to provide mechanical protection for the optical fiber 20. In one or more embodiments, the coating 52 includes an inner or primary coating 54 and an outer or secondary coating 56. In one or more embodiments, the primary coating 54 directly contacts the cladding region 44, and the secondary coating 56 directly contacts the primary coating 54. In one or more embodiments, the secondary coating 56 defines the outermost surface of the optical fiber 20. However, in one or more other embodiments, the optical fiber 20 further includes a color layer 58, which may be used to identify the optical fiber 20. In embodiments in which the color layer 58 is included, the color layer 58 may define the outermost surface of the optical fiber 20.
In one or more embodiments, the coating 52 has a thickness in the range of 22-45 microns, or in the range of 22-40 microns, or in the range of 22-35 microns. In one or more embodiments, the coating 52 has a ratio of the thickness of the secondary coating 56 to the thickness of the primary coating 54 in the range of 0.65 to 1.0. According to one or more other embodiments, the ratio of the secondary coating 56 thickness to the primary coating 54 thickness may be in the range of 0.70 to 0.95, more particularly in the range of 0.75 to 0.90, and most particularly in the range of 0.75 to 0.85. In one or more embodiments, the primary coating 54 may have a thickness in the range of 12-25 microns, or in the range of 12-22 microns, or in the range of 12-19 microns. In one or more embodiments, the secondary coating 56 may have a thickness in the range of 10-20 microns, or in the range of 10-18 microns, or in the range of 10-16 microns. In one or more embodiments, the color layer 58 may have a thickness equal to or less than 10 microns, more particularly equal to or less than 8 microns, and more particularly in the range of 2-8 microns.
In one or more embodiments, the optical fiber 20 has an overall fiber diameter Df equal to or less than 210 microns. More specifically, in one or more embodiments, the overall fiber diameter Df may be in the range of 160-210 microns, or in the range of 160-200 microns, or in the range of 160-190 microns, or in the range of 160-180 microns, or in the range of 160-170 microns, or in the range of 170-210 microns, or in the range of 170-200 microns, or in the range of 170-190 microns, or in the range of 170-180 microns, or in the range of 180-210 microns, or in the range of 180-200 microns, or in the range of 180-190 microns.
In one or more embodiments, the primary coating layer 54 has an elastic modulus (also referred to herein as “elastic modulus”) of less than 1 MPa and a Tg (glass transition temperature) of less than −20° C., and the secondary coating layer 24 has an elastic modulus of greater than 1500 MPa and a Tg of greater than 65° C.
The primary coating 54 may be made of a known primary coating composition. For example, the primary coating composition may have a formulation listed below in Table 2 which is typical of commercially available primary coating composition.
where the oligomeric material may be prepared from H12MDI, HEA, and PPG4000 using a molar ratio n:m:p=3.5:3.0:2.0, H12MDI is 4,4′-methylenebis(cyclohexyl isocyanate) (available from Millipore Sigma), HEA is 2-hydroxyethylacrylate (available from Millipore Sigma), PPG4000 is polypropylene glycol with a number average molecular weight of about 4000 g/mol (available from Covestro), SR504 is ethoxylated(4)nonylphenol acrylate (available from Sartomer), NVC is N-vinylcaprolactam (available from Aldrich), TPO (a photoinitiator) is (2,4,6-trimethylbenzoyl)-diphenyl phosphine oxide (available from BASF), Irganox 1035 (an antioxidant) is benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxythiodi-2,1-ethanediyl ester (available from BASF), 3-acryloxypropyl trimethoxysilane is an adhesion promoter (available from Gelest), and pentaerythritol tetrakis(3-mercaptopropionate) (also known as tetrathiol, available from Aldrich) is a chain transfer agent. The concentration unit “pph” refers to an amount relative to a base composition that includes all monomers, oligomers, and photoinitiators. For example, a concentration of 1.0 pph for Irganox 1035 corresponds to 1 g Irganox 1035 per 100 g combined of oligomeric material, SR504, NVC, and TPO.
The secondary coating 56 may be made of a known secondary coating composition. The secondary coating may be prepared from a composition that exhibits high elastic modulus. Higher values of elastic modulus may represent improvements that make the secondary coating prepared for the coating composition better suited for small diameter optical fibers. More specifically, the higher values of elastic modulus enable use of thinner secondary coatings on optical fibers without sacrificing performance. Thinner secondary coatings reduce the overall diameter of the optical fiber and provide higher fiber counts in cables of a given cross-sectional area. The elastic modulus of secondary coatings prepared as the secondary coating composition may be equal to or greater than 1500 MPa, more particularly about 1800 MPa or greater, or about 2100 MPa or greater and about 2800 MPa or less or about 2600 MPa or less. The results of tensile property measurements prepared from various curable secondary compositions are listed below in Table 3.
A representative curable secondary coating composition is listed below in Table 4.
SR601 is ethoxylated (4) bisphenol A diacrylate (a monomer). SR602 is ethoxylated (10) bisphenol A diacrylate (a monomer). SR349 is ethoxylated (2) bisphenol A diacrylate (a monomer). Irgacure 1850 is bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide (a photoinitiator).
Secondary coating compositions (A) and (SB) are listed in Table 5.
PE210 is bisphenol-A epoxy diacrylate (available from Miwon Specialty Chemical, Korea), M240 is ethoxylated (4) bisphenol-A diacrylate (available from Miwon Specialty Chemical, Korea), M2300 is ethoxylated (30) bisphenol-A diacrylate (available from Miwon Specialty Chemical, Korea), M3130 is ethoxylated (3) trimethylolpropane triacrylate (available from Miwon Specialty Chemical, Korea), TPO (a photoinitiator) is (2,4,6-trimethylbenzoyl)diphenyl phosphine oxide (available from BASF), Irgacure 184 (a photoinitiator) is 1-hydroxycyclohexyl-phenyl ketone (available from BASF), Irganox 1035 (an antioxidant) is benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxythiodi-2,1-ethanediyl ester (available from BASF). DC190 (a slip agent) is silicone-ethylene oxide/propylene oxide copolymer (available from Dow Chemical). The concentration unit “pph” refers to an amount relative to a base composition that includes all monomers and photoinitiators. For example, for secondary coating composition A, a concentration of 1.0 pph for DC-190 corresponds to 1 g DC-190 per 100 g combined of PE210, M240, M2300, TPO, and Irgacure 184.
The clastic modulus of the secondary coatings 56 made from compositions A, KB and SB were measured using the measurement techniques described below.
In particular, the curable secondary coating compositions were cured and configured in the form of cured rod samples for measurement of elastic modulus, tensile strength at yield, yield strength, and elongation at yield. The cured rods were prepared by injecting the curable secondary composition into Teflon® tubing having an inner diameter of about 0.025″. The rod samples were cured using a Fusion D bulb at a dose of about 2.4 J/cm2 (measured over a wavelength range of 225-424 nm by a Light Bug model IL390 from International Light). After curing, the Teflon® tubing was stripped away to provide a cured rod sample of the secondary coating composition. The cured rods were allowed to condition for 18-24 hours at 23° C. and 50% relative humidity before testing. Elastic modulus was measured using a Sintech MTS Tensile Tester on defect-free rod samples with a gauge length of 51 mm, and a test speed of 250 mm/min.
Tensile properties were measured according to ASTM Standard D882-97. The properties were determined as an average of at least five samples, with defective samples being excluded from the average.
The results show that secondary coatings prepared from compositions KB, A, and SB have clastic moduli higher than 1500 MPa. Secondary coatings with high clastic modulus as disclosed herein may be better suited for small diameter optical fibers. More specifically, a higher elastic modulus enables use of thinner secondary coatings on optical fibers, thereby enabling smaller fiber diameters without sacrificing performance. Thinner secondary coatings reduce the overall diameter of the optical fiber and provide higher fiber counts in cables of a given cross-sectional area.
Advantageously, an optical fiber 20 constructed as described above has several beneficial thermomechanical and optical properties as discussed below.
In terms of optical properties, coupling losses can be reduced by providing optical fibers with a mode field diameter that is matched to standard single mode fiber. In one or more embodiments, the optical fiber 20 is compliant with ITU-G.652.D and ITU-G.657.A2 specifications. Further, in one or more embodiments, the optical fiber 20 has a mode field diameter (MFD) at 1310 nm of at least 9 microns, or at least 9.1 microns, or at least 9.2 microns.
In one or more embodiments, the optical fiber 20 exhibits a cabled cutoff of less than 1260 nm and a zero dispersion wavelength of between 1300 nm and 1324 nm.
In one or more embodiments, the optical fiber 20 experiences a bend loss of less than 0.5 dB/turn at 1550 nm for one bend around a mandrel of diameter of 15 mm. In one or more embodiments, the optical fiber 20 experiences a bend loss of less than 0.1 dB/turn at 1550 nm for one bend around a mandrel of diameter of 20 mm. In one or more embodiments, the optical fiber 20 experiences a bend loss of less than 0.003 dB/turn at 1550 nm for one bend around a mandrel of diameter of 30 mm.
Exemplary embodiments of optical fibers 20 (Examples 1-4) that can be incorporated into a high fiber density optical fiber cable are provided in Table 6, below. Examples 1˜4 have triangular trenches (as shown in
Table 7 provides examples of optical fibers 20 having rectangular trenches (as shown in
Various modifications and alterations may be made to the examples within the scope of the claims, and aspects of the different examples may be combined in different ways to achieve further examples. Accordingly, the true scope of the claims is to be understood from the entirety of the present disclosure in view of, but not limited to, the embodiments described herein.
It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claims.
This application is a continuation of International Patent Application No. PCT/US2022/048972, filed Nov. 4, 2022, which claims the benefit of priority of U.S. Provisional Application No. 63/276,014, filed on Nov. 5, 2021, the content of which is relied upon and incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63276014 | Nov 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2022/048972 | Nov 2022 | WO |
| Child | 18648958 | US |
