Patent Publication Number: US-9835812-B2

Title: Multi-optical fiber aggregate

Description:
This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 62/200,815 filed on Aug. 4, 2015, the content of which is relied upon and incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present disclosure general relates to optical fibers. More particularly, the present disclosure relates to multi-fiber aggregates. 
     BACKGROUND 
     Optical fiber has become accepted as a viable alternative to traditional materials used for data signal communication. Optical fiber is now widely utilized in a variety of electronic devices to facilitate the high-speed communication of data signals at high bandwidths. However, in addition to increases in the speed and bandwidth of the electronic components in data communication devices, optical fiber users are attempting to place ever more optical fibers in ever-smaller spaces. However, packing fibers into tight spaces can cause undesirable attenuation. 
     Optical fiber ribbons provide one way to densely pack a plurality of optical fibers. Often, individual coated optical fibers are made, arranged in parallel to one another, and then coated with a collective coating layer and formed into a ribbon shape. However, such ribbon designs limit the density with which the optical fibers can be positioned in the ribbon. Also, such shape limits the bending capabilities of the ribbon. Furthermore, the cores of the individual optical fibers in the ribbon are often not aligned in a manner that allows for precise coupling to standard connectors or other fiber arrays. 
     The use of optical fiber waveguides with multiple cores sharing a single outer glass cladding has been proposed as a means of increasing the bandwidth density of communications systems. However, the difficulty of fabricating multicore waveguides places a practical constraint on the features of the individual cores. Furthermore, the inclusion of many cores can result in large diameter waveguide structures. To maintain a given level of reliability, larger diameter glass structures are limited to larger minimum bending radii, which can complicate the routing of fibers in many applications. In addition, multicore fibers (MCF) are sensitive to external perturbations such as bending and twisting and increased cross-talk, increased loss, and decreased transmission performance have been observed with increased bending diameter of MCF relative to single core fibers. 
     SUMMARY 
     According to an embodiment of the present disclosure, a multi-fiber aggregate is provided. The multi-fiber aggregate includes at least two optical fibers, each of the at least two optical fibers having a core member formed from a silica-based glass and an outer cladding layer formed from a silica-based glass surrounding and in direct contact with the core member. The multi-fiber aggregate also includes a polymeric binding coating surrounding the at least two optical fibers and holding the at least two fibers in a predetermined geometry. 
     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 embodiment(s), and together with the description serve to explain principles and operation of the various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be understood more clearly from the following description and from the accompanying figures, given purely by way of non-limiting example, in which: 
         FIG. 1A  illustrates a cross section of an optical fiber according to an embodiment of the present disclosure; 
         FIG. 1B  is a schematic diagram that depicts refractive index as a function of fiber radius for the optical fiber of  FIG. 1A ; 
         FIG. 2A  illustrates a cross section of an optical fiber according to an embodiment of the present disclosure; 
         FIG. 2B  is a schematic diagram that depicts refractive index as a function of fiber radius for the optical fiber of  FIG. 2A ; 
         FIG. 3A  illustrates a cross section of an optical fiber according to an embodiment of the present disclosure; 
         FIG. 3B  is a schematic diagram that depicts refractive index as a function of fiber radius for the optical fiber of  FIG. 3A ; 
         FIG. 4A  illustrates a cross section of an optical fiber according to an embodiment of the present disclosure; 
         FIG. 4B  illustrates a cross section of an optical fiber according to an embodiment of the present disclosure; 
         FIG. 4C  illustrates a cross section of an optical fiber according to an embodiment of the present disclosure; 
         FIG. 5A  illustrates a cross section of an optical fiber according to an embodiment of the present disclosure; 
         FIG. 5B  illustrates a cross section of an optical fiber according to an embodiment of the present disclosure; 
         FIG. 6  illustrates a cross sections of an optical fiber according to an embodiment of the present disclosure; 
         FIG. 7  illustrates a cross section of multi-optical fiber aggregate according to an embodiment of the present disclosure; 
         FIG. 8  illustrates a cross section of multi-optical fiber aggregate according to an embodiment of the present disclosure; 
         FIG. 9  illustrates a cross section of multi-optical fiber aggregate according to an embodiment of the present disclosure; 
         FIG. 10  illustrates a cross section of multi-optical fiber aggregate according to an embodiment of the present disclosure; 
         FIG. 11  illustrates a cross section of multi-optical fiber aggregate according to an embodiment of the present disclosure; 
         FIG. 12  illustrates a cross section of multi-optical fiber aggregate according to an embodiment of the present disclosure; and 
         FIG. 13  illustrates a cross section of multi-optical fiber aggregate according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiment(s), an example(s) of which is/are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. 
     The singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. The endpoints of all ranges reciting the same characteristic are independently combinable and inclusive of the recited endpoint. All references are incorporated herein by reference. 
     The phrase “refractive index profile,” as used herein, refers to the relationship between refractive index or relative refractive index and the dimensions of the optical fiber. 
     The phrase “relative refractive index,” as used herein, is defined as Δ %=100×(n i   2 −n REF   2 )/2n i   2 , where n i  is the maximum refractive index in region i, unless otherwise specified. The relative refractive index percent is measured at the wavelength of intended operation, often approximately 850 nm, 1300 nm, or 1550 nm unless otherwise specified. Unless otherwise specified herein, n REF  is the average refractive index of the outer cladding region of the optical fiber, which can be calculated, for example, by taking “N” index measurements (n c1 , n c2 , . . . , b cN ) of the outer cladding region (which may be, for example, undoped silica), and calculating the average refractive index by: 
     
       
         
           
             
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     As used herein, the relative refractive index is represented by Δ % and its values are given in units of “%,” unless otherwise specified. In cases where the refractive index of a region is less than the reference index n REF , the relative index percent is negative and is referred to as a reduced refractive index region or referred to as having a depressed region or depressed-index, and the minimum relative refractive index is calculated at the point at which the relative refractive index is most negative unless otherwise specified. In cases where the refractive index of a region is greater than the reference index n REF , the relative index percent is positive and the region can be said to be raised or to have a positive index. 
     The term “α-profile” or “alpha profile” refers to a relative refractive index profile of the core members, expressed in terms of Δ(r) which is in units of “%”, where r is the radius of the core region, which follows the equation:
 
Δ( r ) %=Δ( r   o )(1−[| r−r   o |/( r   1   −r   o )] α ),
 
where r o  is the point at which Δ(r) is maximum, r 1  is the point at which Δ(r) % is zero with respect to the outer cladding region, and r is in the range r i ≦r≦r f , where Δ is defined above, r i  is the initial point of the α-profile, r f  is the final point of the α-profile, and α is an exponent which is a real number. For a profile segment beginning at the centerline of a core region (r=0), the α-profile has the simpler form:
 
Δ( r ) %=Δ(0)(1−[| r |/( r   1 )] α ),
 
where Δ(0) is the refractive index delta at the centerline of the core region.
 
     A cross section of an optical fiber according to an embodiment of the present disclosure is illustrated in  FIG. 1A . The optical fiber  100  includes a core region  102  and an outer cladding region  104  surrounding the core region  102 . As shown, the outer circumference of the outer cladding region  104  has a substantially circular shape. The core region  102  of optical fiber  100  is generally formed from silica-based glass and has a core index of refraction n 1  and a core relative refractive index Δ 1  relative to the outer cladding region  104 . The silica-based glass of the core region  102  is typically doped with one or more dopants which increases the index of refraction of the core region  102 , though the cladding can be doped with one or more dopants that reduce its index of refraction to achieve a similar difference relative to the core. For example, the core region  102  may include silica-based glass doped with germanium such as when the core region  102  comprises silica (SiO 2 ) glass up-doped with germania (GeO 2 ). However, dopants other than germania may be utilized in the core region  102 , including, without limitation, TiO 2 , ZrO 2 , Nb 2 O 5  and/or Ta 2 O 5 . Such dopants may be incorporated in the core region  102  either individually or in combination in order to obtain the desired core index of refraction n 1  and relative refractive index Δ 1 . The core region  102  may contain from about 4.0 wt. % to about 40 wt. % GeO 2 . For example, the core region  102  may include from about 4.0 wt. % to about 6.5 wt. % GeO 2 , from about 5.0 wt. % to about 6.0 wt. % GeO 2 , or even from about 5.2 wt. % to about 5.5 wt. % GeO 2 , which increases the index of refraction n 1  of the core members  102  relative to undoped silica glass. In addition, the relative refractive index Δ 1  of the core region  102  relative to outer cladding region  104  is greater than about 0.2%. For example, the relative refractive index Δ 1  of the core region  102  relative to outer cladding region  104  may be greater than about 0.3%, or even from about 0.2% to about 2%. 
     According to embodiments of the present disclosure, the core region  102  may have a step-index profile, or, alternatively, the core region  102  may have a graded index. The core region  102  may have an α-profile with an α-value which defines the index of refraction of the core region  102  as a function of the radius of the core region  102 . Where the core region  102  has an α-profile, the α-value of the α-profile may be in a range from about 1.9 to about 2.2 as measured at 1300 nm. Where the core region  102  has a graded index and/or an α-profile, the core region  102  may have a relative refractive index percent Δ 1  relative to outer cladding region  104  and a maximum relative refractive index percent Δ 1Max  of greater than about 0.5% and less than about 2.2%, for example, at least about 0.6%, or at least about 1.0%, or at least about 1.5% or even at least about 2.0%. 
     The optical fiber  100  may be a single mode optical fiber having a core region  102  with a diameter of less than or equal to about 15 microns. For example, the core region  102  may have a diameter of between about 3 microns and about 10 microns, or between about 6 microns and about 9 microns, or even between about 7 microns and about 8 microns. The optical fiber  100  may be single moded at wavelengths from about 1260 nm to about 1700 nm. Alternatively, the optical fiber  100  may be single-moded at wavelengths from about 1500 nm to about 1700 nm. 
     Alternatively, the optical fiber  100  may be a multi-mode optical fiber having a core region  102  with a diameter of greater than or equal to about 15 microns. For example, the core region  102  may have a diameter of between about 15 microns and about 65 microns, or between about 25 microns and about 50 microns, or even between about 35 microns and about 50 microns. Multi-mode optical fibers may support the propagation of multiple modes at their operation wavelength and are often used from about 830 nm to about 880 nm. Alternatively, the multi-mode optical fibers may support propagation of multiple modes at wavelengths from about 1020 nm to about 1100 nm, but other wavelength ranges known in the field of optical communication can be used. The core region  102  of the multi-mode optical fiber may generally have a graded refractive index profile. More specifically, the core region of the multi-mode optical fiber may generally have a graded index α profile with an α value of between about 1.9 to about 2.1, as described above. 
     Referring again to  FIG. 1A , the outer cladding region  104  is formed from silica-based glass (SiO 2 ) with an index of refraction n 2  which is less than the index of refraction n 1  of the core region (i.e., n 2 &lt;n 1 ), which yields a refractive index profile as depicted in  FIG. 1B . According to embodiments of the present disclosure, the outer cladding region  104  has an outer diameter of less than about 125 microns. For example, the outer cladding region  104  may have an outer diameter of between about 40 microns and about 120 microns, or between about 60 microns and about 80 microns. The outer cladding region  104  may be formed from pure silica-based glass without any dopants which change the index of refraction of silica, such as up-dopants (i.e., germanium and the like) or down-dopants (i.e., boron, fluorine and the like). Alternatively, the outer cladding region  104  may include one or more up-dopants which increase the refractive index of the silica glass, or one or more down-dopants which decrease the refractive index of the silica glass, so long as the cladding index of refraction n 2  is less than the core index of refraction n 1  and the relative refractive index Δ 1  of the core region  102  relative to the outer cladding region  104  is greater than about 0.2%. For example, the relative refractive index Δ 1  of the core region  102  relative to the outer cladding region  104  may be greater than or equal to about 0.3%, or may be between 0.2% and about 2%. 
     Optionally, optical fiber  100  may further include at least one coating layer  120  which surrounds and directly contacts the outer cladding region  104 . The coating layer  120  is configured to protect the surface of the glass fiber and provides mechanical isolation from the external environment and generally has a thickness of about 10 microns to about 150 microns. The coating layer  120  typically has a refractive index n ct  that is greater than or equal to the refractive index n 2  of the outer cladding region  104 . The coating layer  120  may include a primary coating layer  122  and a secondary coating layer  124 . The primary coating layer  122  surrounds and directly contacts the outer cladding region  104  and is formed of relatively soft polymer materials. The primary coating layer  122  has a thickness from about 5.0 microns to about 75 microns. The secondary coating layer  124  is formed around and directly contacts the primary coating layer  122  and has a thickness from about 5.0 microns to about 75 microns. The secondary coating layer  124  is generally formed from polymer materials which are relatively harder than the polymer materials from which the primary coating layer  122  is formed. More specifically, the primary coating layer  122  may exhibit a Young&#39;s modulus less than about 100 MPa (for example, less than about 50 MPa, or even less than about 10 MPa), while the secondary coating layer  124  may exhibit a Young&#39;s modulus greater than about 500 MPa (for example greater than about 700 MPa, or even greater than about 900 MPa). The materials used in the primary and secondary coating layers are typically UV curable urethane acrylate coating materials. For example, the primary and secondary coatings may include materials similar to those disclosed in U.S. Pat. Nos. 6,849,333 and 6,775,451, the specifications of which are incorporated by reference in their entirety. 
     While the embodiment of the optical fiber  100  of  FIG. 1A  is depicted with an coating layer  120  which comprises a primary coating layer  122  and a secondary coating layer  124 , it should be appreciated that, in other embodiments, the coating layer  120  only comprises primary coating layer  122 . Further, it should be appreciated that the coating layer  120  is optional and that, in some embodiments, optical fiber  100  may be formed without an coating layer  120 . 
     A cross section of an optical fiber according to an embodiment of the present disclosure is illustrated in  FIG. 2A . As shown, the optical fiber  200  includes a core region  202 , an inner cladding region  206  surrounding the core region  202 , a reduced refractive index region  208  surrounding inner cladding region  206 , and an outer cladding region  204  surrounding the reduced refractive index region  208 . As shown, the outer circumference of the outer cladding region  204  has a substantially circular shape. Optical fiber  200  may optionally include at least one optical coating layer, such as described above, which surrounds and directly contacts the outer cladding region  204 . 
     The inner cladding region  206  generally has an index of refraction n 3  that is substantially equal to the index of refraction n 2  of the outer cladding region  204  and a radial thickness of greater than about 1 micron. For example, the inner cladding region  206  may have a radial thickness of between about 1 micron and about 13 microns, or even between about 3 microns and about 9 microns. The reduced refractive index region  208  generally has an index of refraction n 4  and a radial thickness from about 1 micron to about 20 microns. For example, the radial thickness of the reduced refractive index region  208  may be between about 1 micron and about 10 microns, or even between about 1 micron and about 5 microns. The index of refraction n 4  of the reduced refractive index region  208  is such that n 4 ≦n 2 ≦n 1  which yields a refractive index profile as depicted in  FIG. 2B . 
     The reduced refractive index region  208  may include silica glass down-doped with fluorine. For example, the reduced refractive index region  208  may include between about 0.36 wt. % and about 3.6 wt. % fluorine, or between about 0.72 wt. % and about 2.5 wt. % fluorine, or even between about 1.4 wt. % and about 2.5 wt. % fluorine such that the relative refractive index percent Δ 3  of the reduced refractive index region  208  relative to outer cladding region  204  is less than about −0.1%, or even less than about −0.4%, or is between about −0.4% to about −0.7%. 
     A cross section of an optical fiber according to an embodiment of the present disclosure is illustrated in  FIG. 3 . The optical fiber  300  includes a core region  302 , a reduced refractive index region  308  surrounding the core region  302 , and an outer cladding region  304  surrounding the reduced refractive index region  308 . As shown, the outer circumference of the outer cladding region  304  has a substantially circular shape. Optical fiber  300  has the same features as optical fiber  200  shown in  FIG. 2A  with the exception that optical fiber  300  does not include an inner cladding region. Optical fiber  300  may optionally include at least one optical coating layer, such as described above, which surrounds and directly contacts the outer cladding region  304 . 
       FIGS. 4A-4C  illustrate cross sections of optical fibers which are similar to optical fiber  100  shown in  FIG. 1A , but have various additional features relative to optical fiber  100 .  FIG. 4A  shows an optical fiber  400 A including an outer cladding region  404 A and an elliptical core region  402 A having a radius R 1  in a first dimension and radius R A  in a dimension perpendicular to the first dimension, where one of R 1  and R A  is greater than the other of R 1  and R A .  FIG. 4B  shows a multicore optical fiber  400 B having an outer cladding region  404 B and at least two core regions  402 B,  402 B′. It should be appreciated that a multicore optical fiber such as the one shown in  FIG. 4B  may include any number of cores.  FIG. 4C  shows an optical fiber  400 C having a core region  402 C and an outer cladding region  404 C which includes and/or is surrounded by at least two stress rods  410 C,  410 C′ positioned on diametrically opposite sides of the core region  402 C. The at least two stress rods  410 C,  410 C′ may be situated such that they touch the core region  402 C. Alternatively, the at least two stress rods  410 C,  410 C′ may be situated in close proximity to the core region  402 C, such as within 10 microns. For example, an edge of one of the at least two stress rods  410 C,  410 C′ may be located between about 0.1 microns and about 5.0 microns from an edge of the core region  402 C. The radius of the at least two stress rods  410 C,  410 C′ may be greater than the edge-to-edge distance between the core region  402 C and one of the at least two stress rods  410 C,  410 C′. Additionally, the edge-to-edge distance is less than the diameter of the core region  402 C. The cross-section of the at least two stress rods  410 C,  410 C′ may be circular, but may optionally be of other shapes. The at least two stress rods  410 C,  410 C′ may be of equal or non-equal size. The at least two stress rods  410 C,  410 C′ may have a radius of between about 2.5 μm and about 20 μm. For example, the at least two stress rods may have a radius of between about 5.0 μm and about 15 μm, or between about 10 μm and about 25 μm, or even between about 10 μm and about 20 μm. Optical fibers  400 A,  400 B,  400 B may optionally include at least one optical coating layer, such as described above, which surrounds and directly contacts the outer cladding region  404 A,  404 B,  404 C. 
     Cross sections of optical fibers according to embodiments of the present disclosure are illustrated in  FIGS. 5A-5B . For purposes of illustration, the optical fibers of  FIGS. 5A-5B  are shown having the features of optical fiber  100  shown in  FIG. 1A . However, it should be appreciated that the optical fibers of  FIGS. 5A-5B  may include any of the features of the optical fibers shown in  FIG. 2, 3 or 4A-4C . As shown, the optical fibers  500 A,  500 B have core regions  502 A,  502 B respectively, and the same features of optical fiber  100  of  FIG. 1A , with the exception that at least a portion of the outer perimeter of the outer cladding region  504 A,  504 B is substantially flat. As used herein, the term “flat” is meant to describe a portion of an optical fiber that continues in approximately a single plane and is curved or rounded significantly less than an extension of the adjacent rounded surfaces. As shown in  FIG. 5A  the perimeter of the outer cladding region  504 A may have a flat portion  512 A with the rest of the perimeter being substantially circular. As shown in  FIG. 5B , the perimeter of the outer cladding region  504 B may have at least two flat portions  512 B,  512 B′ with the other portions of the perimeter being substantially curved portions. Optical fibers  500 A,  500 B may optionally include at least one optical coating layer, such as described above, which surrounds and directly contacts the outer cladding region  504 A,  504 B. 
     A cross section of an optical fiber according to an embodiment of the present disclosure is illustrated in  FIG. 6 . As shown, the optical fiber  600  has a core region  602  and an outer cladding region  604 . For purposes of illustration, the optical fiber  600  is shown having the features of optical fiber  100  shown in  FIG. 1A . However, it should be appreciated that opt cal fiber  600  may include any of the features of the optical fibers shown in  FIG. 2, 3  or  4 A- 4 C. As shown, the optical fiber  600  has the same features of optical fiber  100  of  FIG. 1A , with the exception that the outer perimeter of the outer cladding region  604  has a non-circular shape. As shown in  FIG. 6 , optical fiber  600  has four edges that have portions that are substantially flat. As measured from flat edges of the outer cladding 604 situated opposite each other, optical fiber  600  has a width of less than about 125 microns. For example, optical fiber  600  may have a width of between about 40 microns and about 120 microns, or between about 60 microns and about 80 microns. Optical fiber  600  may optionally include at least one optical coating layer, such as described above, which surrounds and directly contacts the outer cladding region  604 . 
     Various multi-optical fiber aggregates in accordance with embodiments of the present disclosure will now be described. As used herein, the term “aggregate” is meant to describe at least two optical fibers held together by a polymeric binding coating. Embodiments of the present disclosure provide multi-optical fiber aggregates having high spatial density. Employment of optical fibers having diameters or widths as described herein reduces the size of the aggregates as compared to conventional optical fiber ribbons and also permits the inclusion of a greater number of cores than are commonly employed in conventional optical fiber ribbons. Furthermore, employment of optical fibers as described herein permits reduced distances between adjacent cores as compared to conventional optical fiber ribbons. 
       FIGS. 7-9  illustrate cross sections of various multi-optical fiber aggregates in accordance with embodiments of the present disclosure. For purposes of illustration, the aggregates of  FIGS. 7-9  are shown with a plurality of optical fibers each having the features of optical fiber  100  shown in  FIG. 1 . However, it should be appreciated that the optical fibers of the aggregates of  FIGS. 7-9  may include any of the features of the optical fibers shown in  FIG. 1, 2, 3, 4A-4C or 6 , and that, according to certain embodiments, the aggregates may include combinations of optical fibers having different features. 
     A cross section of a multi-optical fiber aggregate according to an embodiment of the present disclosure is illustrated in  FIG. 7 . As shown, the multi-optical fiber aggregate  700  includes a plurality of optical fibers  100  and a polymeric binding coating  750  surrounding the plurality of optical fibers  100  and holding the plurality of optical fibers  100  in a predetermined geometry. The optical fibers  100  may be oriented such that a portion of each optical fiber  100  physically contacts a portion of at least one adjacent optical fiber  100 . Alternatively, the optical fibers may be oriented such that a portion of each optical fiber  100  is less than about 15 microns from a portion of at least one adjacent optical fiber  100 . For example, a portion of each optical fiber  100  may be less than about 10 microns, or less than about 5.0 microns, or even about 1.0 micron from a portion of at least one adjacent optical fiber  100 . The aggregate  700  shown in  FIG. 7  includes a plurality of optical fibers  100  oriented in parallel in a single plane. While the aggregate  700  of  FIG. 7  includes four optical fibers, it should be appreciated that aggregates according to embodiments of the present disclosure include at least two optical fibers and may include any number of optical fibers. 
     A cross section of a multi-optical fiber aggregate according to an embodiment of the present disclosure is illustrated in  FIG. 8 . As shown, the multi-optical fiber aggregate  800  includes a plurality of optical fibers  100  and a polymeric binding coating  850  surrounding the plurality of optical fibers  100  and holding the plurality of optical fibers  100  in a predetermined geometry. The optical fibers  100  may be oriented such that a portion of each optical fiber  100  physically contacts a portion of at least one adjacent optical fiber  100 . Alternatively, the optical fibers may be oriented such that a portion of each optical fiber  100  is less than 15 microns from a portion of at least one adjacent optical fiber  100 . For example, a portion of each optical fiber  100  may be less than about 10 microns, or less than about 5.0 microns, or even about 1.0 micron from a portion of at least one adjacent optical fiber  100 . The aggregate  800  shown in  FIG. 8  includes two sets of two optical fibers  100  with each set of optical fibers  100  being oriented in different parallel planes. For example, a first set is oriented such that the optical fibers  100  are bisected by a first horizontal plane  892 , and a second set is oriented such that the optical fibers  100  are bisected by a second horizontal plane  894  which is parallel with the first plane  892 . Additionally, optical fibers in the first set may be offset from optical fibers  100  in the second set such that they are not bisected by the same vertical plane. For example, an optical fiber  100  of the first set is oriented such that it is bisected by a first vertical plane  896 , and an optical fiber  100  of the second set is oriented such that it is bisected by a second vertical plane  898  which is parallel with the first vertical plane  892 . While the aggregate  800  of  FIG. 8  includes four optical fibers oriented in two planes, it should be appreciated that aggregates according to embodiments of the present disclosure include at least two optical fibers and may include any number of optical fibers oriented in any number of parallel planes. 
     A cross section of a multi-optical fiber aggregate according to an embodiment of the present disclosure is illustrated in  FIG. 9 . As shown, the multi-optical fiber aggregate  900  includes a plurality of optical fibers  100  and a polymeric binding coating  950  surrounding the plurality of optical fibers  100  and holding the plurality of optical fibers  100  in a predetermined geometry. The optical fibers  100  may be oriented such that a portion of each optical fiber  100  physically contacts a portion of at least one adjacent optical fiber  100 . Alternatively, the optical fibers may be oriented such that a portion of each optical fiber  100  is less than 15 microns from a portion of at least one adjacent optical fiber  100 . For example, a portion of each optical fiber  100  may be less than about 10 microns, or less than about 5.0 microns, or even about 1.0 micron from a portion of at least one adjacent optical fiber  100 . The aggregate  900  shown in  FIG. 9  includes six optical fibers  100  surrounding a central optical fiber and forming a circular aggregate. While the aggregate  900  of  FIG. 9  includes seven optical fibers oriented in a circular geometry, it should be appreciated that aggregates according to embodiments of the present disclosure may include any number of optical fibers necessary to form a circular geometry. 
       FIGS. 10-11  illustrate cross sections of various multi-optical fiber aggregates in accordance with embodiments of the present disclosure. For purposes of illustration, the aggregates of  FIGS. 10-11  are shown with a plurality of optical fibers having the features of optical fiber  600  shown in  FIG. 6 . However, it should be appreciated that the optical fibers of the aggregates of  FIGS. 10-11  may include any of the features of the optical fibers shown in  FIG. 1, 2, 3 or 1A-4C , and that, according to certain embodiments, the aggregates may include combinations of optical fibers having different features. 
     A cross section of a multi-optical fiber aggregate according to an embodiment of the present disclosure is illustrated in  FIG. 10 . As shown, the multi-optical fiber aggregate  1000  includes a plurality of optical fibers  600  and a polymeric binding coating  1050  surrounding the plurality of optical fibers  600  and holding the plurality of optical fibers  600  in a predetermined geometry. The optical fibers  600  may be oriented such that a portion of each optical fiber  600  physically contacts a portion of at least one adjacent optical fiber  600 . Alternatively, the optical fibers may be oriented such that a portion of each optical fiber  600  is less than 15 microns from a portion of at least one adjacent optical fiber  600 . For example, a portion of each optical fiber  600  may be less than about 10 microns, or less than about 5.0 microns, or even about 1.0 micron from a portion of at least one adjacent optical fiber  600 . The aggregate  1000  shown in  FIG. 10  includes two sets of two optical fibers  600  with each set of optical fibers  600  being oriented in different parallel planes. While the aggregate  1000  of  FIG. 10  includes four optical fibers oriented in two planes, it should be appreciated that aggregates according to embodiments of the present disclosure include at least two optical fibers and may include any number of optical fibers oriented in any number of parallel planes. As a further example,  FIG. 11  illustrates a cross section of a multi-optical fiber aggregate having different sets of optical fibers  600  having different numbers of optical fibers  600 , where each set is oriented such that the optical fibers  600  are bisected by different parallel planes. As shown, the aggregate  1100  includes a first set of two optical fibers  600  bisected by a first horizontal plane  1160 , a second set of four optical fibers  600  bisected by a second horizontal plane  1170 , a third set of four optical fibers  600  bisected by a third horizontal plane  1180 , and a fourth set of two optical fibers  600  bisected by a second horizontal plane  1190 . 
       FIGS. 12-13  illustrate cross sections of various multi-optical fiber aggregates in accordance with embodiments of the present disclosure. For purposes of illustration, the aggregates of  FIGS. 12-13  are shown with a plurality of optical fibers having the features of optical fibers  500  shown in  FIGS. 5A-5C . However, it should be appreciated that the optical fibers of the aggregates of  FIGS. 12-13  may include any of the features of the optical fibers shown in  FIG. 1, 2, 3, 4A-4C or 6 , and that, according to certain embodiments, the aggregates may include combinations of optical fibers having different features. 
     A cross section of a multi-optical fiber aggregate according to an embodiment of the present disclosure is illustrated in  FIG. 12 . As shown, the multi-optical fiber aggregate  1200  includes a plurality of optical fibers  500 B each having two flat portions, and a polymeric binding coating  1250  surrounding the plurality of optical fibers  500 B and holding the plurality of optical fibers  500 B in a predetermined geometry. The optical fibers  500 B may be oriented such that a portion of each optical fiber  500 B physically contacts a portion of at least one adjacent optical fiber  500 B. Alternatively, the optical fibers may be oriented such that a portion of each optical fiber  500 B is less than 15 microns from a portion of at least one adjacent optical fiber  500 B. For example, a portion of each optical fiber  500 B may be less than about 10 microns, or less than about 5.0 microns, or even about 1.0 micron from a portion of at least one adjacent optical fiber  500 B. The aggregate  1200  shown in  FIG. 12  includes a plurality of optical fibers  500 B oriented in parallel in a single plane. While the aggregate  1200  of  FIG. 12  includes four optical fibers, it should be appreciated that aggregates according to embodiments of the present disclosure include at least two optical fibers and may include any number of optical fibers. 
       FIG. 13  illustrates a similar aggregate as shown in  FIG. 12 . As shown, the multi-optical fiber aggregate  1300  includes a fiber arrangement  1360  having a plurality of optical fibers  500 B each having at least two flat portions, with two optical fibers  500 A, each having one flat portion, situated at each end of the plurality of optical fibers  500 B, where the flat portion of optical fibers  500 A faces a flat portion of an adjacent optical fiber  500 B of the plurality of optical fibers  500 B. The optical fibers  500 A,  500 B may be oriented such that a portion of each optical fiber  500 A,  500 B physically contacts a portion of at least one adjacent optical fiber  500 A,  500 B. Alternatively, the optical fibers may be oriented such that a portion of each optical fiber  500 A,  500 B is less than 15 microns from a portion of at least one adjacent optical fiber  500 A,  500 B. For example, a portion of each optical fiber  500 A,  500 B may be less than about 10 microns, or less than about 5.0 microns, or even about 1.0 micron from a portion of at least one adjacent optical fiber  500 A,  500 B The aggregate  1300  also includes a polymeric binding coating  1250  surrounding the fiber arrangement  1360  and holding the optical fibers  500 B in a predetermined geometry. The fiber arrangement  1360  shown in  FIG. 13  includes a plurality of optical fibers  500 B oriented in parallel in a single plane. While the fiber arrangement  1360  includes two optical fibers  500 B, it should be appreciated that the fiber arrangement may include any number of optical fibers  500 B. 
     According to embodiments of the present disclosure, the polymeric binding coating  750 ,  850 ,  950 ,  1050 ,  1150 ,  1250 ,  1350  may be formed from the same polymer materials as the secondary coating layer  124  described above. 
     Aggregates according to embodiments of the present disclosure include optical fibers spaced apart from one another such that the cross-talk between adjacent optical fibers is less than −25 dB. For example, cross-talk between adjacent optical fibers may be less than −30 dB, or less than −35 dB and, or even less than −40 dB. 
     Embodiments of the present disclosure provide multi-optical fiber aggregates which can be formed with repeatable geometries. Multi-optical fiber aggregates according to the embodiments of the present disclosure include a high optical fiber core density. For example, flat portions of the multi-optical fiber aggregates and the optical fiber of the aggregates, such as those shown in  FIGS. 10-13 , facilitate such high core density. Furthermore, the flat portions limit the movement of the optical fibers, and in turn, the optical fiber cores, when a polymeric binding coating is applied to the optical fibers during formation of a multi-optical fiber aggregate and maintains the optical fiber and optical fiber core relative positions. This in turn promotes high alignment tolerances when the multi-optical fiber aggregate are coupled to sources, detectors or other optical fiber portions. 
     As compared to other optical fiber solutions, the high optical fiber core density of the aggregates described herein decreases the amount of space needed to either house optical fiber, or to connect one location to another location via optical fiber. Additionally, the aggregates described herein have an increased bandwidth over a cross-section of the aggregate as compared to the bandwidth over the same cross-section of other optical fiber solutions. The high optical fiber core density of the aggregates described herein also promotes a reduction in the costs of source devices or other optical devices and components. The cost of such devices is directly related to the size of the devices and the size of the devices is generally proportional to the size of the device-fiber interface. By decreasing the size of the device-fiber interface, the high optical fiber core density can lead to a decrease in the size of the devices, and in turn, a decrease in the costs of such devices. 
     Additionally, the multi-optical fiber aggregate designs described herein enable forming separate and individual optical fibers prior to formation of the aggregate. This allows for quality and performance testing to be performed on the optical fibers prior to inclusion of the individual optical fibers in the aggregate, and ensures that all of the at least two optical fibers of the aggregate meet predetermined quality and performance standards. 
     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.