WO2018006160A1

WO2018006160A1 - Optical element and method of making the same

Info

Publication number: WO2018006160A1
Application number: PCT/CA2017/050721
Authority: WO
Inventors: Jean-François VIENS; Abdelouahab BENNINI
Original assignee: Iglass Optical Technologies Inc
Current assignee: Iglass Optical Technologies Inc
Priority date: 2016-07-04
Filing date: 2017-06-13
Publication date: 2018-01-11
Anticipated expiration: 2019-01-04

Abstract

The invention relates to an optical element for point-to-point energy distribution comprising: a bundle of optically-transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons.

Description

OPTICAL ELEMENT AND METHOD OF MAKING THE SAME

This application claims priority to US provisional patent application serial number 62/358,096 filed 4 July 2016.

FIELD OF THE INVENTION

The present disclosure relates generally to optical devices, and more particularly to optical systems incorporating non-imaging optical components, and more specifically to a flexible optical element for optical light distribution, and to a method of making the same. BACKGROUND OF THE INVENTION

Concentration, confinement, and distribution of optical light is used in many applications pertaining to solar energy, energy storage, building illumination, distribution of radiant power, laser materials processing, laser surgery, detection of optical signals, fluoroscopy, and the like. Among many possible applications, the present disclosure relates to optical devices and optical cables that may be used, for example, to collect, concentrate, and distribute light from the Sun or other angularly extended non-coherent light sources from one location to another location spaced by some physical distance. It is well known in the art of solar energy that photo-voltaic solar cells for electrical energy production have limited efficiencies and very high cost of electricity production. For example, the cost per kilowatt- hour is still about five times that of conventional electric power production. To compete with other energy sources, the efficiency of production of energy from the Sun should be drastically improved. There are many applications such as heating and drying where the photo-voltaic solar energy conversion is not required, and where the photo-thermal solar energy conversion can be advantageously used to store energy in the form of heat with significant cost benefits compared to photo-voltaic schemes. These applications require devices and methods for flexible optical distribution of radiant power, particularly radiant power having very high power densities, wherein the distribution may go from any point A (e.g. solar concentrator) to any point B (e.g. heat chamber) efficiently along any desired pathways determined by building or terrain layout or any other physical constraints. Other applications such as solar-thermal energy storage applications may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (heat storage unit) efficiently along any desired pathways determined by building or terrain layout. Other applications such as concentrated photo-voltaic applications may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (photo-voltaic cell) efficiently along any desired pathways determined by building or terrain layout.

Other applications such as architectural lightning may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (building illumination unit) efficiently along any desired pathways determined by building or terrain layout.

Other applications such as industrial materials cutting may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (laser source) to point B (material cutting platform) efficiently along any desired pathways determined by building or industrial facilities layout.

Other applications such as biological pathogen detection may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (fluorescing optical source) to point B (optical sensor) efficiently along any desired pathways determined by laboratory layout.

Other applications such as in biomedicine and non-invasive laser surgery may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (high-intensity light source) to point B (organic tissue) efficiently along any desired pathways determined by laboratory, surgical room, or body tract layout. These point-to-point optical energy distribution applications may involve radiant power levels of very high optical power densities, of up to 10⁷ W/m² or higher, which may instantly burn materials not tolerant to high radiation, such as the acrylate material coating of conventional glass fiber optics. In addition, these applications may require large optical collecting areas, of up to 10³ cm² or larger, which are not easily provided by bundles comprising a reasonable number of conventional glass fiber optics. In addition, these applications may require an efficient transfer of lightwave energy that provides tolerance to millimeter-scale mis-alignments, which are not easily provided for systems comprising complex opto-mechanical alignment devices and costly micro-mechanical parts. In addition, these applications may require cost-effective figures with respect to point-to-point optical energy distribution, of a maximum of a few US dollars per meter of distribution, which are not easily provided by bundles comprising a large number of conventional glass fiber optics.

Therefore it is desirable to provide optical cable devices and methods for the concentration, confinement, and distribution of optical light that overcome the above and other problems. DESCRIPTION OF PRIOR ART

Many disclosures provide for optical cables that guide and harvest light waves from one point to another point, wherein the optical cables are made from a plurality of conventional optical fibers arranged side-by-side in a ribbon-like cable structure. Disclosures, such as U.S. Pat. No. 9,020,313, U.S. Pat. No. 9,052,459, U.S. Pat. No. 9, 176,292, U.S. Pat. No. 9,256,041 , U.S. Pat. No. 9,341 ,805, U.S. Pat. No. 9,360,646, U.S. Pat. No. 9,459,422, U.S. Pat. No. 9,494,764, and U.S. Pat. No. 9,651 ,754 described ribbon-like, side-by-side optical fiber arrangement structures, wherein very high optical power densities of up to 10⁷ W/m² or higher may instantly burn materials not tolerant to high radiation, especially the acrylate coating of conventional optical fibers. Among these disclosures, none can provide safe energy distribution of radiant power having very high optical power densities, of up to 10⁷ W/m² or higher, and none can provide energy distribution of radiant power over large optical collecting areas, of up to 10³ cm² or larger. In addition, these disclosures do not provide cost-effective figures with respect to point-to-point optical energy distribution, wherein the bill of materials for any such structures comprising hundreds of fibers may attain hundreds or thousands of US dollars per meter of distribution.

Other disclosures provide for ribbon structures that may provide tolerance to high radiation or may provide large collecting areas, such as U.S. Pat. No. 6,858,306, U.S. Pat. No. 7,043,881 , U.S. Pat. No. 7,423,286, and U.S. Pat. No. 8,980,062. However, the materials or structural arrangement specifications involved in these disclosures do not provide for an efficient transfer of lightwave energy about a lengthwise axis of a cable.

U.S. Pat. No. 4,498,460 issued to K.Mori provides a solar collector having a lens for converging sunlight and a fiber optic cable having a light receiving end located at a focal point of the lens. U.S. Pat. No. 4,529,830 issued to M.Daniel provides an apparatus for collecting, distributing and utilizing solar radiation includes a solar collection panel having an array of solar gathering cells which provide radiation to a light collecting unit. U.S. Pat. No. 4,723,826 issued to R.Whitaker provides a fiber optic solar collector employing a matrix of lenses mounted in an enclosure. US. Pat. No. 5,501 ,743 issued to M.Cherney provides a multiplicity of circularly shaped solar-light collectors and respective optical fibers assigned to said collectors and transmitting light therefrom. US. Pat. No. 7,339,739 issued to L.Kinney provides an apparatus consisting of a solar energy collector means including a modified Cassegrainian optical system. Pat. No. 7,973,235 issued to J.Muhs provides a small-aperture solar energy distribution system comprising at least one fiber having no conic surfaces. These disclosures generally relate to tightly aligned optical apparatuses, wherein the coupling of light between the collector and the distributor requires complex opto-mechanical alignment devices and costly micro-mechanical parts to achieve efficient transfer of lightwave energy to the distributor. In the prior art, slight micron-size mis-alignments generally result in high optical losses. These approaches yield many undesirable attributes such as high costs, fragility, and low tolerance to misalignments; whereas the optical element of the present invention provides tolerance to millimeter-scale mis-alignments and light confinement within the optical element itself resulting in robust integration without costly micro-mechanical parts. SUMMARY OF THE INVENTION

This invention is being shown and described herein with reference to a flexible optical cable for the concentration, confinement, and distribution of optical light, wherein the distribution of optical light may go from point A to point B efficiently along any desired pathways determined by building or terrain layout or any other constraints. The flexible optical cable of the present invention provides safe energy distribution of radiant power of very high optical power densities, of up to 10⁷ W/m² or higher. In addition, it provides energy distribution of radiant power over large optical collecting areas, of up to 10³ cm² or larger. In addition, it provides an efficient and cost-effective point-to-point transfer of lightwave energy about a lengthwise axis of said cable. In addition, it provides tolerance to millimeter-scale mis-alignments across a lengthwise axis of said cable resulting in robust integration without costly micro-mechanical parts. More specifically, the invention relates to a flexible optical element or flexible optical cable for point-to-point energy distribution and method of making the same, comprising: a bundle of optically-transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons. Furthermore, the flexible optical cable of the present invention may comprise a bundle, or a group, or a plurality, of mating glass ribbons that may exhibit chiral symmetry about a lengthwise axis of said cable, and that may exhibit a C2 rotation symmetry about a cross-section plane of said cable.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 : There is shown one embodiment of the optical element of the present invention, comprising a bundle of ribbons, and comprising a sheath providing a hermetic enclosure of said bundle of ribbons.

FIGURE 2: There is show one embodiment of the optical element of the present invention, comprising a bundle of ribbons schematized sideways along the lengthwise axis of said optical element, wherein light is being refracted within the plurality of ribbon-air interfaces by total internal reflection.

FIGURE 3: There is shown one embodiment of the optical element of the present invention, comprising a bundle of ribbons of equal widths to form an overall square cross- section providing a C2 cross-sectional rotation symmetry properties to the bundle, and exhibiting a chiral symmetry about a lengthwise axis of said optical element, that may bend preferentially along any given direction under a torque applied perpendicular to the plane of said ribbons.

FIGURE 4: There is shown one embodiment of the optical element of the present invention, comprising a bundle of ribbons of unequal widths to form an overall circular cross-section.

FIGURE 5: There is shown one embodiment of the optical element of the present invention, comprising a bundle of ribbons of equal widths to form an overall rectangular cross-section providing a C2 cross-sectional rotation symmetry properties to the bundle, and exhibiting a chiral symmetry about a lengthwise axis of said optical element. FIGURE 6: There is shown one embodiment of the optical element of the present invention, comprising an optical coupling between two optical elements of similar characteristics.

FIGURE 7: There is shown one embodiment of the optical element of the present invention, comprising a coupler providing at least one end of the optical element for butt optically coupling said bundle of ribbons.

FIGURE 8: There is shown one embodiment of the optical element of the present invention, comprising a bundle of ribbons having rectangular cross-sectional shapes providing a C2 cross-sectional rotation symmetry properties to the bundle, and a chiral symmetry arising from a three-dimensional right-handed helical shape.

FIGURE 9: There is shown one embodiment of the optical element of the present invention, comprising a bundle of ribbons that may bend preferentially along any given direction under a torque applied perpendicular to the plane of said ribbons.

FIGURE 10: There is shown one embodiment of the optical element of the present invention, wherein the proximal end of the said optical element is adjacent to a light concentrating unit formed by a combination of an optical lens and at least one element of large optical aperture.

FIGURE 11 : There is shown one embodiment of the method for, or sequence of manufacturing for, making the optical element of the present invention. DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that certain descriptions of the present invention have been simplified to illustrate only those elements and limitations that are relevant to a clear understanding of the present invention, while eliminating, for purposes of clarity, other elements. Those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements and/or limitations may be desirable in order to implement the present invention. However, because such other elements and/or limitations may be readily ascertained by one of ordinary skill upon considering the present description of the invention, and are not necessary for a complete understanding of the present invention, a discussion of such elements and limitations is not provided herein. As such, it is to be understood that the description set forth herein is merely exemplary to the present invention and is not intended to limit the scope of the claims.

The present disclosure relates to a non-imaging optical element, and more specifically to a flexible optical cable for optical light concentration, confinement and distribution, and to a method for making the same.

According to an aspect of the invention, there is provided a flexible optical cable for point- to-point energy distribution comprising: a bundle of optically-transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons. Furthermore, the flexible optical cable of the present invention may comprise a bundle, or a group, or a plurality, of mating glass ribbons that may exhibit chiral symmetry about a lengthwise axis of said cable, and may comprise a C2 rotation symmetry about a cross-section plane of the cable.

As used herein, the term "optical cable" is intended to refer to a lengthwise optical element which guides and distributes optical light from a proximal to a distal end.

Also, as used herein, the term "total internal reflection" is intended to refer to a phenomenon that happens when a propagating light wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is greater than the critical angle, the light wave cannot pass through and is entirely reflected.

Also, as used herein, the term "cross-section" is intended to refer to a surface that is formed by making a straight cut through a three-dimensional object, especially at right angle to a given axis.

Also, as used herein, the terms "ribbon" or "glass ribbon" are intended to refer to a thin band of material, having a materials composition that may be selected from glass materials, and having a thickness substantially smaller than its width and its length.

Also, as used herein, the term "point-to-point" is intended to refer to a direct connection between two nodes or endpoints along a straight or curved connection line. Also, as used herein, the term "C2 rotation symmetry" is intended to refer to the Cn geometrical point group designation (with n=2) wherein an object looks the same after a 2-fold amount of rotation, or 180 degrees rotation, across a given rotation axis.

Also, as used herein, the term "chiral symmetry" is intended to refer to a symmetry group wherein an object exhibits a shape that is not identical to its mirror image, or that cannot be superposed on its mirror image, or, more precisely, that cannot be mapped to its mirror image by rotations and translations alone. Objects with helical shapes, twisted shapes, or bannister shapes exhibit chiral symmetry.

According to an aspect of the invention, there is provided a flexible optical cable for point- to-point energy distribution comprising: a bundle of optically-transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons. Furthermore, the flexible optical cable of the present invention may comprise a bundle, or a group, or a plurality, of mating glass ribbons that exhibits chiral symmetry about a lengthwise axis of said cable, and a C2 rotation symmetry about a cross-section plane of said cable.

Referring to Figure 1 , there is shown one embodiment of the flexible optical cable of the present invention, comprising a bundle, or a group, or a plurality, of mating glass ribbons [21] [22] [23] [24] [25]; wherein said glass ribbons extend from a proximal end [30] to a distal end [40] about a lengthwise axis of said cable [10]. The bundle of mating glass ribbons consists of a close-packed assembly of thin bands selected from optically- transparent glassy materials, such as silica glass, wherein each band exhibits a length much larger than its thickness, and wherein each band exhibits a width much larger than its thickness. In some embodiments, each band may exhibit a width 10 times larger than its thickness, or more. Also referring to Figure 1 , the two-dimensional cross-section of the flexible optical cable of the present invention may exhibit a C2 rotation symmetry about a cross-section plane of said cable, especially when referring to the cross-sectional surface that is formed by making a straight cut through said optical cable at right angle to the lengthwise axis of said cable [10]. Specifically, the cross-sectional shape of the optical cable, anywhere from the proximal end [30] to the distal end [40], may look substantially the same after a 2-fold amount of rotation, or 180 degrees rotation, across an axis coincident with the lengthwise axis of said cable [10]. Said ribbons may have equal widths to form a rectangular cross-section from the proximal end [30] to the distal end [40] of the cable. Also referring to Figure 1 , the flexible optical cable of the present invention may exhibit chiral symmetry about a lengthwise axis of said cable, wherein the chiral symmetry may arise from the three-dimensional twisted shape of said bundle of glass ribbons, meaning that the three-dimensional shape of the optical cable cannot be mapped to its mirror image by rotations and translations alone. In some embodiments, said chiral symmetry may relate to a three-dimensional twisted shape, or helical shape, or bannister shape, being right-handed or left-handed in direction, that undergoes a 90 degree rotation within at least a length of 100 meters, preferably within a length of 10 meters, more preferably within a length of 1 meter and most preferably within a length of 0.1 meters, about a lengthwise axis of said cable, said length being comprised anywhere within the boundary formed from the proximal end [30] to the distal end [40] of said cable.

Still referring to Figure 1 , there is shown one embodiment of the flexible optical cable of the present invention, comprising a bundle, or a group, or a plurality, of mating glass ribbons [21] [22] [23] [24] [25]; wherein said glass ribbons extend from a proximal end [30] to a distal end [40] about a lengthwise axis of said cable [10], and comprising a sheath [12] providing a hermetic enclosure of said bundle of glass ribbons. Said sheath [12] may comprise a lengthwise combination of fire-proof materials, or mechanically robust jacket materials, or any other flexible protective materials, or combination thereof, arranged in a hermetic cladding structure around said bundle of ribbons, being proximal [14] to said ribbons or radially more distanced [13] from said ribbons, for protecting said bundle of ribbons from any thermal, mechanical, or chemical constraints, or any other physical constraints present in a given environment, which may exert significant stress upon said sheath [12], and which may, in the absence of sheath, affect or damage said bundle of ribbons, or may reduce the efficiency at which optical total internal reflection occurs through said ribbons. Physical constraints present in a given environment may include water, humidity, dust, dirt, heat, abrasion, mechanical pressure, or mechanical torque or a combination thereof. According to an aspect of the invention, there is provided a flexible optical cable for point-to-point energy distribution comprising: a bundle of optically- transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons. Furthermore, the flexible optical cable of the present invention may comprise a connector provided at least one end of the cable for hermetically sealing said bundle of ribbons.

Still referring to Figure 1 , said sheath [12] may comprise a lengthwise combination of jacket materials or other flexible protective materials, wrapped proximal [14] or more distanced [13] from the ribbons, or arranged as an inner [14] and outer [13] protective hermetic cladding structure around said bundle of ribbons. Said inner [14] cladding structure may consist of a tube-like hollow-core material, semi-rigid in nature, holding and retaining the bundle of ribbons in place inside said cable, wherein said hollow-core cross- section being larger than cross-section of said bundle of ribbons. Said inner [14] cladding structure may be a retaining structure that retains into a close-packed bundle the group of individual ribbons without affecting, attenuating, dispersing, scattering, or radiating away light guided by total internal reflection within the bundle of ribbons. Said retaining structure may consist or comprise at least one retaining rings, or retaining clamps, or retaining ferrules, or any other retaining elements, that may be regularly-spaced, or periodically- spaced, along the lengthwise axis of the cable, and that may hold in place the bundle from the corners of the ribbons, at specific locations along the cable, without touching significantly the flat surfaces of the ribbons, and that may hold in place the chiral shape of said bundle of ribbons without touching significantly the flat surfaces of the ribbons. Said sheath [12] may comprise an inner [14] cladding structure that may consist of a retaining structure that comprises a lengthwise combination of toroid-shaped retaining rings, or toroid-shaped retaining annuluses, or toroid-shaped retaining clamps, or toroid-shaped retaining ferrules, or any other toroid-shaped retaining elements, exhibiting an inner diameter substantially equivalent to the diagonal extent of the bundle of ribbons [21] [22] [23] [24] [25], and exhibiting an outer diameter substantially equivalent to the inner extent of the outer cladding [13] of said sheath [12]. Said retaining structure may hold tight the bundle of ribbons at specific locations along the cable, while touching only the corners of the ribbons forming the diagonal extent of the bundle, and without touching significantly the flat surfaces of the ribbons. Said retaining structure placed along the inner [14] cladding structure may consist of optically-transparent, temperature-resistant, semi-rigid, materials compositions that may be selected from glass materials or any other materials. Said outer [13] cladding structure may consist of a tube-like hollow-core material, semirigid in nature, arranged as an hermetic cladding structure around said bundle of ribbons for protecting and jacketing said bundle of ribbons from any thermal, mechanical, or chemical constraints, or any other physical constraints present in a given environment. Said outer [13] cladding structure may consist of mechanically-strong, temperature- resistant, chemically-resistant, fire-proof, composite materials, or metallic materials, or any other materials. Said sheath [12] providing a hermetic enclosure of said bundle of glass ribbons and protecting said bundle from any physical constraints present in a given environment that may include water, humidity, dust, dirt, heat, abrasion, mechanical pressure, or mechanical torque, or a combination thereof.

This invention is being shown and described herein with reference to a flexible optical cable for the concentration, confinement, and distribution of optical light, wherein said group of glass ribbons [21] [22] [23] [24] [25] refracts optical light by total internal reflection, and wherein the distribution of optical light may go from the proximal end [30] to the distal end [40] efficiently along the lengthwise axis of said cable [10] as the cable may bend and curve through any desired pathways determined by building or terrain layout or any other physical constraints. Therefore, the main attributes sought for the flexible optical cable of the present invention relate to 1) the confinement of optical light, and 2) the flexible point- to-point distribution of light along any desired pathways.

First, the confinement of optical light is such that any light wave propagating substantially along the lengthwise axis of said cable [10] may enter with substantial optical efficiency through the proximal end [30] of the optical element, and may stay confined inside the group of optically-transparent glass ribbons by total internal reflection. Referring to Figure 2, there is shown an embodiment of the optical cable of the present invention, schematized sideways along the lengthwise axis of said cable [10]. Input lightwaves [80][81][82][83][84] emitted from a light source [15] and propagating substantially along the lengthwise axis of said cable [10] may enter with substantial optical efficiency through the proximal end [30] of the optical cable, and may stay confined inside the group of optically-transparent ribbons [21] [22] [23] [24] [25] by being refracted within the plurality of ribbon-air interfaces [26] [27] [28] [29] by total internal reflection [91] [92] [93] [94] [95]. Said light waves may then exit [85] [86] [87] [88] [89] the optical cable through the distal end [40] with minimal optical loss provided that the group of ribbons are selected from optically transparent materials having smooth, well-polished surfaces. The mechanism of total internal reflection [91] [92] [93] [94] [95] provides confinement of optical light into the optical cable, from the proximal end [30] to the distal end [40], provided that the plurality of ribbon-air interfaces [26] [27] [28] [29] are not contaminated by, or in contact with, any impurities or foreign substances throughout the length of the optical cable, such as water or dirt that may absorb, scatter, or radiate away light guided by total internal reflection. The bundle of ribbons thus form a light guide through which optical light is confined and distributed along the lengthwise axis of said cable [10] by total internal reflection. The optical efficiency at which a light wave enters the optical cable is determined by the cross-sectional dimension of the proximal end [30], specifically the cross-sectional dimension where total internal reflection takes place at the proximal end [30], which defines the optical aperture of the optical cable; by the close-packing of glass ribbons [21] [22] [23] [24] [25] in the bundle, which defines the fraction of space occupied by the cross-sectional lattice arrangement of ribbons in the bundle; and by the refractive index of the glass ribbons [21] [22] [23] [24] [25] which defines the numerical aperture of the optical cable. Large optical aperture, large numerical aperture, close-packing ribbon arrangement, and high optical transparency maximize the optical efficiency of the optical cable, or maximize the proportion of light entering the proximal end [30] of the optical cable, staying confined inside the group of glass ribbons [21] [22] [23] [24] [25] by total internal reflection, and leaving the distal end [40] of the optical cable along the lengthwise axis of said cable [10]. The bundling of many individual optically-transparent ribbons provide the desired and necessary attribute of enlarging the optical aperture and improving the optical efficiency of the optical cable. In some embodiments, said light source [15] may be the Sun, or a Light Emitting Device (LED), or a laser, or a lamp, or a thermal element, or a fluorescent source, or any other light source or combination thereof.

Second, the flexible distribution of light along any desired pathways is such that the optical cable, from the proximal end [30] to the distal end [40], may have sufficient mechanical flexibility and adaptability to bend and curve along any directions or orientations in order to conform to any physical constraints, such as building or terrain layouts. This mechanical flexibility attribute is made possible by the small bending stiffness of the bundle of thin ribbons. Specifically, the high mechanical flexibility is attributable to the small second moment of inertia perpendicular to the plane of every ribbon comprised in the optical cable. In the art of structural engineering, the second moment of inertia of the cross-section of an object is an important property used in bending stiffness calculations under a mechanical torque applied to the object. The bending stiffness perpendicular to the plane of an individual ribbon is proportional to its thickness t raised to the cube, t³, and the bending stiffness of a bundle comprising N individual and independent ribbons is proportional to Nt³. This value of bending stiffness is only 1//V²that of the bending stiffness of a single beam of material of the same total thickness Nt, which is proportional to ΝΨ. For example, a bundle comprising 10 individual and independent glass ribbons will have a bending stiffness of only 1 % that of single beam of glass of the same total thickness. Therefore, the bundling of N individual and independent ribbons in the optical cable provide the desired and necessary attribute of high mechanical flexibility as compared to an optical cable comprising a single beam of material of the same total thickness.

It will be appreciated that the abovementioned mechanical flexibility attribute is possible for ribbons having axially-elongated cross-sectional shapes, such as rectangular, elliptical, or other axially-elongated cross-sectional shapes, and such that the small second moment of inertia perpendicular to the plane of every ribbon is attributable to ribbons having a thickness substantially smaller than its width and its length. For example, the bending stiffness perpendicular to the plane of an individual rectangular-shaped ribbon is proportional to its thickness t raised to the cube, I³, whereas the bending stiffness parallel to the plane is proportional to its width w raised to the cube, w³; therefore an individual rectangular-shaped ribbon exhibits (w/t)³ times more mechanical flexibility perpendicular to its plane. In some embodiments, each ribbon may exhibit a width 10 times larger than its thickness, or more, which may relate to 1000 times more mechanical flexibility perpendicular to its plane, or more. Also, it will be appreciated that the abovementioned mechanical flexibility attribute for a bundle of independent ribbons is attributable to an axially-aligned packing of ribbon exhibiting axially-elongated cross-sections, such that all the ribbons are bundled and aligned along the same direction, and such that the two- dimensional cross-section of a bundle comprising N individual and independent ribbons exhibits a substantial C2 rotation symmetry when referring to the cross-sectional surface that is formed by making a straight cut through said group of ribbons at right angle to the lengthwise axis of said cable [10]. More generally, said ribbons may be assembled or bundled in an ordered manner such as to obtain substantially an order of rotation symmetry n intended to refer to the Cn geometrical point group designation (with n that may be equal to 2) wherein the two-dimensional cross-section of the bundle of ribbons looks the same after a n-fold amount of rotation, or 360/n degrees rotation, at right angle to a given lengthwise axis. Said C2 rotation symmetry only refers to the two-dimensional cross-sectional shape of the bundle of ribbons at right angle to the lengthwise axis of said cable, not to its three-dimensional shape. Also, it will be appreciated that the abovementioned mechanical flexibility attribute is possible for a bundle of un-bonded ribbons, wherein every ribbon comprising the optical cable may be free to move with respect to the other ribbons along a substantial portion of the lengthwise axis of said cable, or may be in partial contact with the other ribbons, or may be spaced by a thin layer of air or vacuum to provide for low mechanical friction at the ribbon interfaces.

Referring to Figure 3, there is shown one embodiment of the flexible optical cable of the present invention, comprising a bundle, or a group, or a plurality, of mating glass ribbons [21] [22] [23] [24] [25]; wherein said glass ribbons extend from a proximal end [30] to a distal end [40] about a lengthwise axis of said cable [10]. The sheath providing a hermetic enclosure of said bundle is being omitted in this figure for sake of clarity. Due to the abovementioned small bending stiffness properties perpendicular to the plane of the ribbons, the bundle of mating glass ribbons being shown herein may bend preferentially along the x-axis [31] [32] under a torque applied perpendicular to the plane of the ribbons near the proximal end [30] of the optical cable. Also, the bundle of mating glass ribbons being shown herein may bend preferentially along the y-axis [41 ] [42] under a torque applied perpendicular to the plane of the ribbons near the distal end [40] of the optical cable. Throughout the lengthwise axis of said cable [10], these preferential bending properties may occur along any (x,y,z) three-dimensional directions according to the chiral symmetry properties of the bundle of ribbons, and also may occur along any +/- orientations according to the C2 rotational symmetry properties of the cross-sectional shape of the bundle of ribbons. Therefore, the chiral symmetry properties of the optical cable, and the C2 rotational symmetry properties of its cross-section, are necessary attributes that provide three-dimensional mechanical flexibility to the optical cable along any directions or orientations. It will be appreciated that this three-dimensional mechanical flexibility attribute is possible for an optical cable having a bundle of ribbons exhibiting a substantial chiral morphology that may arise from a three-dimensional twisted shape, or helical shape, or bannister shape, being right-handed or left-handed in direction, encompassing at least 90 degrees along the lengthwise axis of said cable. In some embodiments, said chiral morphology may relate to said ribbons being twisted-coiled, or helical-coiled, or bannister-coiled. In some embodiments, said chiral morphology or twist undergoes a 90 degree rotation within the lengthwise axis of said cable in order to provide three-dimensional mechanical flexibility along the lengthwise axis of said cable. In some embodiments, said twist undergoes a 90 degree rotation within a length of 0.1 meters, or within a length of 1 meters, or within a length of 10 meters, or within a length of 100 meters along the lengthwise axis of said cable. In some embodiments, said twist undergoes a 360 degree rotation within a length of 0.1 meters, or within a length of 1 meters, or within a length of 10 meters, or within a length of 100 meters along the lengthwise axis of said cable. Also, in some embodiments, the chiral symmetry may be intrinsic to the bundle of ribbons, such that the chiral symmetry may arise inherently (intrinsic) from the thermal process of forming twisted ribbons. Also, in some embodiments, the chiral symmetry may be extrinsic to the bundle of ribbons, such that the chiral symmetry may arise from an external (extrinsic) torque applied to un-twisted ribbons, such as a torque that may be applied within the sheath [12] by the retaining structure placed along the inner [14] cladding structure, as referring to Figure 1. Also, in some embodiments, the chiral symmetry may occur, or take place, prior or posterior to being arranged in said sheath providing a hermetic enclosure of said bundle. Also, in some embodiments of the present invention, said chiral symmetry may be intrinsic or extrinsic, or a combination thereof, to the bundle of ribbons. In some embodiments of the present invention, said ribbons are arranged in said sheath to have a chiral symmetry.

Referring to Figure 4, there is shown one embodiment of the flexible optical cable of the present invention, comprising a bundle, or a group, or a plurality, of mating glass ribbons [21] [22] [23] [24] [25]; wherein said ribbons extend from a proximal end [30] to a distal end [40] about a lengthwise axis of said cable [10]. The bundle of ribbons may consist of a close-packed assembly of thin ribbons of unequal widths to form an overall circular cross-section from the proximal end [30] to the distal end [40] of the cable.

Referring to Figures 1 , 3 and 4, the flexible optical cable of the present invention may comprise a bundle of 2 to 10,000 independent ribbons, or more, wherein every ribbon comprising the optical cable may be in partial contact with the other ribbons, or may be spaced by a thin layer of air or vacuum, or may be similar or different in shape to the other glass ribbons, or may have axially-elongated cross-sectional shapes to provide for the C2 rotation symmetry properties of the group. The cable as defined may comprise ribbons of less than 4 mm thick and greater than 1 mm thick; or ribbons less than 1 mm thick and greater than 0.25 mm thick; or ribbons less than 0.25 mm thick and greater than 0.1 mm and greater than 0.01 mm, preferably 0.02 mm, thick. The width, and length, of every ribbon comprised in the optical cable may be in the range 1 mm to 1000mm, and 0.1 m to 1000m, respectively. Said bundle of ribbons may thus provide large optical collecting areas, of up to 10³ cm² or larger. The ribbons may be selected from optical grade material, or optical grade glass, or optically-transparent glassy materials, such as silica glass, glass- ceramic, float glass, plexi-glass, polymer, or other optically-transparent well-polished glass-like materials, or a combination thereof, which provide optical transparency properties to the bundle of ribbons. The ribbons may have an optical numerical aperture larger than 0.15 to efficiently confine light by total internal reflection. The bundle of mating ribbons may exhibit substantial chiral symmetry, wherein the chiral symmetry may arise from a three-dimensional twisted shape, or helical shape, or bannister shape, being right- handed or left-handed in direction, such that the bundle of ribbons cannot be mapped to its mirror image by rotation and translation operations alone. Said ribbons may be twisted, or helically coiled, about the lengthwise axis of said cable, wherein said twist or helicity undergoes at least a 90 degree rotation within a length of 10 meters about the lengthwise axis of said cable. The optical cable of the present invention is not limited to these specific dimensions, shapes, or specifications.

Referring to Figure 5, there is shown one embodiment of the flexible optical cable of the present invention, comprising a bundle, or a group, or a plurality, of mating glass ribbons [21] [22] [23]; wherein said ribbons extend from a proximal end [30] to a distal end [40] about a lengthwise axis of said cable [10]. The sheath providing a hermetic enclosure of said bundle is being omitted in this figure for sake of clarity. The embodiment being shown herein refers to a group of glass ribbons having rectangular cross-sectional shapes providing a C2 cross-sectional rotation symmetry properties to the bundle, and a chiral symmetry arising from a three-dimensional left-handed twisted shape, such that the bundle cannot be mapped to its mirror image by rotation and translation operations alone. It will be appreciated that the optical cable may be optically coupled to a plurality of other optical cables of similar characteristics. Referring to Figure 6, there is shown one embodiment of the optical cable [1] of the present invention, comprising a bundle of mating glass ribbons [21] [22] [23] that exhibits a chiral symmetry about a lengthwise axis of said cable [10], and a rectangular cross-sectional shapes providing a C2 cross-sectional rotation symmetry properties to said bundle of ribbons. Said optical cable [1] may be optically coupled to another optical cable [2] of similar characteristics, wherein the bundle of mating glass ribbons [21] [22] [23] of the first optical element [1] are joined [70] to the bundle of mating glass ribbons [24] [25] [26] of the second optical element [2] about the lengthwise axes of said cables [10] [11]. The joining interface [70] may be arranged and fixed using a coupler such that the distal faces of every glass ribbons [21] [22] [23] of the first optical cable [1] are in co-alignment [71][72][73] with the proximal faces of every respective glass ribbons [24] [25] [26] of the second optical cable [2], and such that the lengthwise axes of the first optical cable [10] and of the second optical cable [1 1] are in co-alignment, and such that the proportion of light leaving the distal end [40] of the first optical cable [1] and entering the proximal end [50] of the second optical cable [2] is maximized, and such as to provide an efficient transfer of lightwave energy from the first [1] to the second [2] optical cable. Said joining interface [70] may be straight-cut or angle- cut with respect to the lengthwise axes of said cables [10] [11].

As used herein, the term "optical coupling" is intended to refer to a transfer of lightwave energy from one optical medium to another optical medium. Also, as used herein, the term "butt coupling" is intended to refer to a transfer of lightwave energy from one optical cable to another optical cable. According to an aspect of the invention, there is provided a flexible optical cable for point- to-point energy distribution comprising: a bundle of optically-transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons. Furthermore, the flexible optical cable of the present invention may comprise a coupler provided at least one end of the cable for butt optically coupling said bundle of ribbons. Referring to Figure 7, there is shown two similar embodiments of the flexible optical cable of the present invention, each comprising a bundle of optically-transparent ribbons [20]; and a sheath providing a hermetic enclosure of said bundle [12]; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said bundle of ribbons [20], and further comprising a coupler element, of either male [16] or female [17] polarity, provided at least one end of the cable for butt optically coupling said bundle of ribbons [20]. Referring to Figures 6 and 7, the joining interface [70] may be arranged and fixed using a coupler, of either male [16] or female [17] polarity, such that the distal faces [40] of every glass ribbons [21] [22] [23] of the first optical cable [1] are in co-alignment [71][72][73] with the proximal faces [50] of every respective glass ribbons [24] [25] [26] of the second optical cable [2], providing an efficient transfer of lightwave energy across the coupler [16] [17]. In some embodiments, the coupler [16] [17] may comprise additional optical elements such as carousels, cassettes, splitters, rotators, routers, attenuators, liquid crystal devices, or switches, or any other optical elements or a combination thereof, to optically couple one cable to a plurality of other cables, or to optically switch one cable to a plurality of other cables.

Referring to Figure 8, there is shown one embodiment of the flexible optical cable of the present invention, comprising a bundle, or a group, or a plurality, of mating glass ribbons [21] [22] [23]; wherein said ribbons extend from a proximal end [30] to a distal end [40] about a lengthwise axis of said cable [10]. The sheath providing a hermetic enclosure of said bundle is being omitted in this figure for sake of clarity. The embodiment being shown herein refers to a bundle of ribbons having rectangular cross-sectional shapes providing a C2 cross-sectional rotation symmetry properties to the bundle, and a chiral symmetry arising from a three-dimensional right-handed helical shape, such that the bundle cannot be mapped to its mirror image by rotation and translation operations alone.

Referring to Figures 8 and 9, there is shown the same embodiment of the optical cable of the present invention. Due to the abovementioned small bending stiffness properties perpendicular to the plane of the ribbons, the group of mating ribbons [21 ] [22] [23] being shown herein may bend preferentially along the x-axis [31 ], or may bend preferentially along the y-axis [41 ], under a torque applied perpendicular to the plane of the ribbons at specific locations along the lengthwise axis of said cable [10]. It can be seen that, throughout the axis [10], these preferential bending properties may occur along any (x,y,z) three-dimensional directions according to the chiral symmetry properties of the optical cable, and also may occur along any +/- orientations according to the C2 rotational symmetry properties of its cross-section.

According to an aspect of the invention, there is provided a flexible optical cable for point- to-point energy distribution comprising: a bundle of optically-transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons. Said ribbons may further comprise treatments, such as optical polishing, thin-film coating, UV hardening, laser writing, or any other treatments or combination thereof that provide for added optical functions. Said optical functions may relate to higher optical transparency, higher total internal reflection efficiency, graded refractive index for optical mode preservation, stronger radiation tolerance, etc. , for one or several of the ribbons included in the optical cable. According to an aspect of the invention, there is provided a flexible optical cable for point- to-point energy distribution comprising: a bundle of optically-transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons. Furthermore, the flexible optical cable of the present invention may comprise a light concentrating unit optically coupled to at least one end of said cable. According to an aspect of the invention, there is provided an optical cable [1] wherein said light concentration unit is to be adjacent to the proximal end [30] of said cable. Said light concentrating unit may consist of a lens, or a mirror, or a prism, or an optical grating, or a liquid crystal device, or any other refractive or reflective optical element or combination thereof, provided at least one end of the cable for butt optically coupling said bundle of ribbons to said energy along the lengthwise axis of said cable. Furthermore, the flexible optical cable of the present invention may comprise a light concentrating unit wherein said light concentrating unit consists of an optical lens having: an optical axis, and a front surface comprising a conic shape with a directrix perpendicular to said optical axis.

As used herein, the term "conic" is intended to refer to a geometrical curve obtained as the intersection of a right circular cone with a plane. A conic may be elliptic, parabolic or hyperbolic shape. A defining condition depends on a fixed point F (the focus), a line L (the directrix) and a number E (the eccentricity) wherein the conic consists of the locus of all points whose distance to F equals E times their distance to L.

As used herein, the term "directrix" is intended to refer to a line L which, together with the point known as the focus F, serves to define a conic section as the locus of points whose distance from the focus is proportional to the horizontal distance from the directrix, with a number E (the eccentricity) being the constant of proportionality. Referring to Figure 10, there is shown one embodiment of the flexible optical cable of the present invention, wherein the proximal end [30] of said cable [1] is adjacent to a light concentrating unit consisting in an optical lens [100]. Said optical lens [100] comprises a front conic surface [101] consisting of at least one conic surface having a directrix perpendicular to the optical axis [110]. Alternatively, said optical lens [100] may comprise a front conic surface [101] consisting of at least one conic surface having a directrix perpendicular to the optical axis [1 10], joined longitudinally [102] to a back conic surface [103] consisting of at least one conic surface having a directrix parallel to the optical axis [1 10]. The optical lens [100] may be selected from optical-grade well-polished glassy materials, such as silica glass, glass-ceramic, float glass, plexi-glass, polymer, or other optically-transparent glass-like materials, or a combination thereof, which provide optical transparency properties to the optical lens. The diameter of the front conic surface [101] may be in the range from 1 mm to 100mm, not limited to these specific dimensions. The embodiment includes a physical joining of the distal end [105] of optical lens to the proximal end [30] of the cable, aligned such that the lengthwise axis of said cable [1] share substantially the same direction as the optical axis [1 10] of the optical lens [100], in order to provide efficient optical coupling and efficient transfer of lightwave energy between the optical lens [100] and the optical cable [1], wherein said transfer of lightwave energy is achieved about a lengthwise axis of said cable by optical total internal reflection through said optical lens [100] and through said optical cable [1 ] that comprises a bundle of ribbons [20], and wherein said transfer of lightwave energy is mediated by a coupler element [16], of either male or female polarity, provided the distal end [105] of said optical lens for butt optically coupling the proximal end [30] of said cable.

Still referring to Figure 10, there is provided an optical lens [100] comprising a front conic surface consisting of at least one conic surface having a directrix perpendicular to the optical axis, joined to a back conic surface consisting of at least one conic surface having a directrix parallel to the optical axis; wherein said back conic surface refracts optical light by total internal reflection; and wherein said back conic surface is optically coupled to a group of glass ribbons forming the optical cable [1] of the present invention. Specifically, the proximal end [30] of the optical cable [1] may be optically coupled to the distal end [105] of the optical lens, such that the such that the lengthwise axis of said cable [10] share substantially the same direction as the optical axis [110] of the front conic surface [101] and back conic surface [103].

Still referring to Figure 10, the shape of the front conic surface [101] comprises a directrix perpendicular to the optical axis [110] and may be described by a mathematical equation associated to a quadratic vectorial form given by Q(x) = x^TAx, Where the vector x relates to a real space x eR" such that for the three dimensional Cartesian coordinates depicted in Figure 1 the vector becomes x = [x y zf. The 3x3 matrix A relates to the set of conic coefficients describing the front conic surface [101]. For a pure conic shape, the quadratic term Q(x) becomes zero, Q(x) = 0. Non-quadratic terms about the (x,y,z) coordinates may be present in the shape of the front conic surface [101] such that Q(x) = Q(x,y,z) becomes non-zero. In some embodiments, the shape of the front conic surface [101] comprises a directrix perpendicular to the optical axis [1 10] and relates to a conic surface of revolution about the z-axis such that r² = x²+y² and x = [r z]^T, and may contain non-quadratic terms about the r-axis, such that the mathematical equation associated to the quadratic form reduces to a two-dimensional form: z² - 2Rr + (K + l)r² = Q(r) = a₀ + a_?r + a₂r² + a₃fi +... , where z is the conic amplitude parallel to the optical axis; r the radial distance from the optical axis; the conic constant; and R the vertex radius at r = 0, and a_n are a set of non- quadratic (or aspheric) terms. This formulation is used in geometric optics to specify oblate elliptical (K > 0), spherical (K = 0), prolate elliptical (0 > K > -1), parabolic (K = -1), and hyperbolic (K < -1) conic shapes. The present invention is not limited to any specific conic constants, vertex radiuses or aspheric terms for the shape of the front conic surface [101]. In some embodiments, the angular symmetry of the front conic surface [101] may be broken to a polygonal cross-section to form a triangular, or square, or pentagonal, or hexagonal, any other polygonal cross-section different than the circular cross-section depicted in Figure 10.

Still referring to Figure 10, the shape of the back conic surface [103] comprises a directrix parallel to the optical axis [1 10] and may be described by a mathematical equation associated to a quadratic vectorial form given by: Q(x') = χ'^τΒχ' , where the vector x' relates to a real space x' e R" and, since the directrix is now parallel to the optical axis, relates to the reflection about the (x+z)-ax\s of the previous vector x = [x y z]^T, such that x' = [z y x]^T. The 3x3 matrix B relates to the set of conic coefficients describing the back conic surface [103]. For a pure conic shape, the quadratic term Q(x) becomes zero, Q(x) = 0. Non-quadratic terms about the (x,y,z) coordinates may be present in the shape of the front conic surface [101] such that Q(x') = Q(z,y,x) becomes non-zero. In some embodiments, the shape of the back conic surface [103] comprises a directrix parallel to the optical axis [1 10] and relates to a conic surface of revolution about the z-axis such that r² = x²+y² and x' = [z rf, and may contain non-quadratic terms about the z-axis, such that the mathematical equation associated to the quadratic form reduces to a two-dimensional form: r² - 2R'z + (K' + 1)z² = Q(z) = b₀ + biz + b₂z² + b₃z³ +... , where K' is the conic constant, R' the vertex radius near the distal end of the back conic lens [105], and b_n are a set of non-quadratic (or aspheric) terms for the back conic surface [103]. This formulation is used in geometric optics to specify oblate elliptical (K' > 0), spherical (K' = 0), prolate elliptical (0 > K' > -1), parabolic (K' = -1), and hyperbolic (K' < -1) conic shapes. The optical lens is not limited to any specific conic constants, vertex radiuses or aspheric terms for the shape of the back conic surface [103]. In some embodiments, the angular symmetry of the back conic surface [103] may be broken to a polygonal cross-section to form a triangular, or square, or pentagonal, or hexagonal, or any other polygonal cross- section different than the circular cross-section depicted in Figure 10. The longitudinal join [102] between the front conic surface [101] and back conic surface [103] may be perpendicular to the optical axis [110] of the lens, not limited to any specific length or shape. The proximal diameter of the back conic surface [104] may be substantially similar to the diameter of the front conic surface [101], in the range from 1 mm to 100mm, whereas the distal diameter of the back conic surface [105] may be substantially smaller than its proximal diameter [104], in the range from 0.01 mm to 10mm. The overall length of the back conic surface [103] along its optical axis, from its proximal end [104] to its distal end [105], may be in the range from 10mm to 1000mm. The front [101] and back conic surface [103] are not limited to these specific dimensions.

Still referring to Figure 10, the conical shape of the back conic surface [103], with its smooth tapering from its proximal end [104] to its distal end [105] along the optical axis [1 10], provides a means for increasing gradually the internal angle with respect to the normal to the surface at which the lightwave strikes the boundary of the back conic surface [103]. This gradual, non-discontinuous increase of the internal angle maximizes the proportion of light that strikes the boundary at an angle larger than the critical angle for total internal reflection along the whole length of the back conic surface [103]. Since the distal diameter of the back conic surface [105] may be substantially smaller than its proximal diameter [104], any light wave propagating substantially along the optical axis [1 10] and entering the front conic surface [101] may converge inside the back conic surface [103], refract within its surface by total internal reflection, and be optically coupled into the optical cable [1] at the junction between the distal end [105] of the optical lens [100] and the proximal end [30] of the optical cable [1], thus providing concentration and confinement of optical light from the proximal end [104] of the optical lens to the distal end [40] of the optical cable with minimal optical loss.

Those of ordinary skill in the art, upon considering the present description, will recognize that the back conic surface [103] of the present invention, by having a directrix parallel to the optical axis [1 10] and perpendicular to the front conic surface [101], provides the necessary attributes to concentrate and confine light by total internal reflection with an efficient transfer of lightwave energy; wherein the light concentration factor is proportional to the square ratio of the diameters of the proximal [104] (dw4) and the distal [105] (dws) ends of the back conic surface, η = (dwVdws)²-

It will be appreciated that ribbon materials and lens materials selected from optical grade materials, or optical grade glasses, or optically-transparent glassy materials, such as silica glass, glass-ceramic, float glass, plexi-glass, polymer, or other optically-transparent well- polished glass-like materials, or a combination thereof, may provide good optical transparency properties as well as good materials tolerance to intense light concentration factors. Materials may be selected according to the optical power density encountered for a specific application. For instance, air-clad polymer ribbons and lenses may tolerate solar concentration factors of η = 100, which corresponds to an optical power density of about

10⁵ W/m². Whereas air-clad plexi-glass ribbons and lenses may tolerate solar concentration factors of η = 1,000, which corresponds to an optical power density of about

10⁶ W/m². Whereas air-clad silica glass ribbons and lenses may tolerate solar concentration factors of η = 10,000, which corresponds to an optical power density of about 10⁷ W/m². Such high optical power density will burn instantly soft polymer materials such as the acrylate material coating of conventional optical fibers.

The mechanism of total internal reflection provides confinement of optical light into the optical lens and optical cable, provided that the plurality of glass-air surfaces are not contaminated by, or in contact with, any impurities or foreign substances throughout the optical path, such as water, dust, or dirt that may absorb, scatter, or radiate away light guided by total internal reflection. In some embodiments, said optical cable [1] and optical lens [100] may be cladded by a fire-proof jacket, a hermetically-sealed jacket, a thermal insulator, a tubing apparatus, or an overcoat, or any other protectors or a combination thereof to protect, shield or insulate these parts from the environment. Also, in some embodiments, specific parts of the optical element [1] and optical lens [100], such as the conic surfaces [101] [103], join [102], proximal ends [30] [104], or distal ends [40] [105], may be affixed to one or several connectors or metallic ferules for proper handling and clamping of the optical cable [1] to the optical lens [100]. According to an aspect of the invention, there is provided a flexible optical cable for point- to-point energy distribution comprising: a bundle of optically-transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons. The flexible optical cable of the present invention may further comprise a light concentrating unit optically coupled to at least one end of said cable, wherein said light concentrating unit consists of a combination of an optical lens adjacent to the proximal end of said cable, and at least one element of large optical aperture adjacent to said optical lens; wherein said element consists of a large lens, or a large mirror, or a large prism, or a large optical grating, or any other refractive or reflective optical element of large optical aperture or combination thereof. Referring to Figure 10, there is shown one embodiment of the optical cable [1] wherein the proximal end [30] is adjacent to a light concentrating unit formed by a combination of an optical lens [100] and at least one element of large optical aperture [130] adjacent to said optical lens [100]. Said at least one element of large optical aperture [130], said optical lens [100], and said optical cable [1] may be aligned such that the lengthwise axis of said cable [10] share substantially the same direction as the optical axes [1 10] of the optical lens [100] and of the element of large optical aperture [130], in order to provide efficient optical coupling and efficient transfer of lightwave energy between the element of large optical aperture [130], the optical lens [100] and the optical cable [1] combined.

Still referring to Figure 10, said element of large optical aperture [130] may consist of a large lens, or a large mirror, or a large prism, or a large optical grating, or any other refractive or reflective optical element or combination thereof. In some embodiments, said element [130] may consist of a large concave mirror, such as a large parabolic mirror. The optical aperture of the element [130] may be in the range from 100mm to 10,000mm or larger, not limited to these specific dimensions.

The present disclosure may relate to optical devices that can be used, for example, to collect, concentrate, and distribute light from the Sun or any other angularly-extended noncoherent light sources. It is therefore desirable to provide an optical cable with sufficient angular acceptance with respect to the optical axis of the light concentrating unit [110], enabling the off-axis collection of light with an efficient transfer of lightwave energy.

In some embodiments, an efficient transfer of lightwave energy from angularly-extended sources may be provided by placing the front conic surface [101] proximal to the focus point of said element of large optical aperture [130]. In such case, the focal length fi and off-axis angular acceptance θι of said element [130] may relate to the diameter d∑ of said front conic surface [101], where an efficient transfer of lightwave energy may be provided along the optical axis [110] according to design rules prescribed by the art of geometrical optics, according to which: fi tanOi < d∑. In some embodiments, the numerical aperture of said element [130] may relate to the curvature (i.e. conic coefficient and vertex radius) of the front conic surface [101] where an efficient transfer of lightwave energy may be provided along the optical axis [1 10] according to design rules prescribed by the art of geometrical optics.

In some embodiments, the diameter di and off-axis angular acceptance θι of said element [130] embedded in a medium of refractive index ni may relate to the size and numerical aperture NA of said optical cable [1], where an efficient transfer of lightwave energy may be provided along the optical axes [10][110] according to design rules prescribed by the art of geometrical optics, according to which: di ni sindi < d₃ NA. In some embodiments related to solar energy, where high concentration of solar light may be desirable, a concentration factor of η = (di/de)² to values above 1000 may be prescribed, for which a solar angular radius of θ₁ = 5 mrad determines NA > 0.15 to said optical cable [1]. For some applications that may use air-clad glass ribbons of NA = 1.05 for the optical cable [1], the attainable concentration factor could reach values above η = 20,000.

In some embodiments related to solar energy, where the capture of large solar power may be desirable, a 1 kilowatt capture would require an element of large optical aperture [130] of about di = 1.1 m in diameter. A concentration factor of η = 5000 and solar angular radius of θι = 5 mrad would require the use of a bundle of glass ribbons of NA > 0.35 and cross- section size of = 0.016m and a corresponding collecting area of 3 cm². An element [130] of focal ratio of F/2 would lead to d∑ > 0.021 m. Alternatively, the use of a bundle of air-clad glass ribbons of NA = 1.05 would increase the acceptance angle to θι = 14 mrad and thus provide significant tolerance to misalignments of solar tracking as long as the diameter of the front conic surface [101] is increased to d∑ > 0.031 m. Those of ordinary skill in the art, upon considering the present description pertaining to design rules prescribed by the art of geometrical optics, will recognize that the optical lens [100] of the present invention provides tolerance to millimeter-scale mis-alignments of the front conic surface [101] with respect to the optical axis [110], thus providing a low-cost approach to lightwave concentration not requiring micro-mechanical parts for optical alignment. The present invention is not limited to these specific dimensions.

In some embodiments related to solar energy, where the low cost of solar power may be desirable, a cost-performance analysis may prescribed in which the terms pertaining to the transmitted solar power are maximized with respect to the terms pertaining to the costs of the optical elements transmitting solar power. Said transmitted solar power is approximately proportional to ~ di²exp(-aL), where cf_? is the diameter of the large optical aperture [130], a and L the optical loss and length, respectively, of the bundle of mating glass ribbons in the optical cable [1]. Said optical loss a is approximately a combination of butt-coupling loss «_c, absorption loss a_m, and scattering loss a_s occurring at or within the optical cable [1], such that a ~ a_c I L + a_m + a_s. Said costs of the optical elements transmitting solar power are approximately related to the bill of materials pertaining to the glass ribbons within the optical cable [1], such that Cost ~ d₃ ²L. Therefore, improving the cost-performance figure may relate to decreasing , decreasing <¾, and decreasing the normalized cost-per-length of the bundle, which may relate to increasing the concentration factor η and the numerical aperture NA of the optical cable, as well as improving the optical transparency, smoothness and close-packing of the glass ribbons, among other things. Those of ordinary skill in the art, upon considering the present description pertaining to design rules prescribed by the art of geometrical optics and pertaining to cost-performance analysis, will appreciate that the optical cable [1] of the present invention provides the necessary attributes (i.e. large NA-1.0, close-pack bundle arrangement, ~$10 cost-per- length of the bundle, ^>10,000 concentration factor tolerance) for optimizing the transmitted solar power and reducing the concomitant costs as opposed to, for example, an optical cable made from a bundle of standard acrylate-coated optical fibers or from a bundle of acrylate-coated glass ribbons drawn from a standard fiber draw tower (i.e. small NA-0.2, loose-pack bundle arrangement, -$1000 cost-per-length of the bundle, ^<100 concentration factor tolerance).

In some embodiments, the lengthwise axis of said cable [10] and the optical axes [110] of the optical lens [100] and of the element of large optical aperture [130], may have coincident directions, and all axes may be maintained by a frame construct such as a tube, or a tubular chassis, or a truss, or any other frame with sufficient mechanical rigidity in order to provide efficient optical coupling and efficient transfer of lightwave energy between the element of large optical aperture [130], the optical lens [100] and the optical cable [1] combined. In some embodiments, said axes may be coincident to a light source such as the Sun, or a Light Emitting Device, or a Laser, or a Lamp, or a thermal element, or a fluorescent source, or any other light source or combination thereof. In some embodiments, said axes and said light source may be maintained coincident by a motorized tracker system such as an alt-azimuthal mount, or an equatorial mount, or a pivotal yoke, or a multi-stage mount, or any other robotic or motorized tracker system with servo control, or combination thereof.

It will be understood by those skilled in the art of optics that various changes in form and details may be made therein such that the optical cable [1], optical lens [100] and optical element [130] of the present invention can be used advantageously for the concentration, confinement, and distribution of optical light, wherein the distribution of optical light may go from point A (i.e. the front end of the element of large optical aperture [130]) to point B (i.e. the distal end of the optical cable [40]) efficiently along any desired pathways determined by the overall mechanical flexibility of the optical cable [1].

By virtue of the large optical aperture of the element [130]; and the substantial proximity of the front conic surface [101] to the focus point of the element [130]; and the total internal reflection occurring in the optical lens [100] and optical cable [1]; and the mechanical flexibility of the optical cable [1]; and the substantial alignment of their axes [10] [110], a lightwave impinging the optical aperture of the element of large optical aperture [130] may be concentrated, confined, and distributed efficiently all the way to the distal end of the optical cable [40], thereby distributing the concentrated lightwave energy flexibly and efficiently along any desired pathways. It will be appreciated that this invention is being shown and described herein with reference to a flexible optical cable for the concentration, confinement, and distribution of optical light, wherein the distribution of optical light may go from any point A to any point B efficiently along any desired pathways determined by building or terrain layout or any other constraints. According to the descriptions provided herein, the flexible optical cable of the present invention may provide safe energy distribution of radiant power of very high optical power densities, of up to 10⁷ W/m² or higher. In addition, it may provide energy distribution of radiant power over large optical collecting areas, of up to 10³ cm² or larger. In addition, it may provide an efficient and cost-effective point-to-point transfer of lightwave energy about a lengthwise axis of said cable, from any point to any point distanced across two-dimensional or three-dimensional space. In addition, it may provide tolerance to millimeter-scale mis-alignments across a lengthwise axis of said cable resulting in robust integration without costly micro- mechanical parts.

According to an aspect of the invention, there is provided a flexible optical cable for point- to-point energy distribution comprising: a bundle of optically-transparent ribbons; and a sheath providing a hermetic enclosure of said bundle; wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons. Said cable may further comprise a light absorbing unit optically coupled to at least one end of said cable. According to an aspect of the invention, there is provided an optical cable [1] wherein said light absorbing unit is to be adjacent to the distal end [40] of said cable. According to an aspect of the invention, said light absorbing unit may consist of a thermal unit for the transformation of light to heat energy, that may comprise heat-conducting, heat-convective, heat-radiative, or heat-capacitive, or heat-exchanging elements or combination thereof, such as a heat chamber, a heat accumulator, a cogeneration engine, an air-conditioning engine, a water-treatment engine, a fluidized bed reactor, or a thermal mass, or any other heat engine or thermodynamic engine. According to an aspect of the invention, said light absorbing unit may consist of a thermal unit for the transformation of light to heat energy, wherein said thermal unit is the heat engine for a heat chamber, a heat accumulator, a cogeneration engine, an air-conditioning engine, a water-treatment engine, a fluidized bed reactor, or a thermal mass, or any other heat engine or thermodynamic engine. Also, according to an aspect of the invention, said light absorbing unit may consist of a photo-transducing unit for the transformation of light to electrical energy, that may comprise photo-electric, photo-voltaic, or photo-conducting, or cogeneration elements or combination thereof, such as a solar cell, or an optical sensor, or a cogeneration engine. Also, according to an aspect of the invention, said light absorbing unit may consist of a photo-chemical unit for the transformation of light to chemical energy, that may comprise chemical reactors or photo-catalytic reactors or combination thereof, such as a photo-catalytic cell. Also, according to an aspect of the invention, said light absorbing unit may consist of a photo-absorptive unit for the transformation of light to entropy, that may comprise devices performing kinetic processes on material or biological elements or combination thereof. Said kinetic processes may include materials cutting, materials bonding, materials ablation, materials transformation, or any other kinetic processes or combination thereof. Those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to applications such as solar heating and drying that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (heat chamber) efficiently along any desired pathways determined by building or terrain layout.

Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to applications such as solar air conditioning that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (solar heat collector) efficiently along any desired pathways determined by building or terrain layout.

Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to applications such as solar water heating or solar water treatment that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (solar heat collector) efficiently along any desired pathways determined by building or terrain layout.

Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to applications such as a solar-fed fluidized bed reactor, or other reactor devices that may be used to carry out a variety of multiphase physical or chemical reactions, that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (solar heat collector) efficiently along any desired pathways determined by building or terrain layout. Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to thermal-solar energy storage applications that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (heat storage unit) efficiently along any desired pathways determined by building or terrain layout.

Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to photo-voltaic applications that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (photo-voltaic cell) efficiently along any desired pathways determined by building or terrain layout.

Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to electrical applications that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (cogeneration engine) efficiently along any desired pathways determined by building or terrain layout.

Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to applications such as architectural lightning that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (solar concentrator) to point B (building illumination unit) efficiently along any desired pathways determined by building or terrain layout. Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to applications such as industrial materials cutting that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (laser source) to point B (material cutting platform) efficiently along any desired pathways determined by building or industrial facilities layout. Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to applications such as biological pathogen detection that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (fluorescence optical source) to point B (optical sensor) efficiently along any desired pathways determined by laboratory layout.

Also, those of ordinary skill in the art, upon considering the present description of the invention, will recognize that other elements may be desirable in order to implement the present invention to applications such as in biomedicine and non-invasive laser surgery that may require devices and methods for flexible optical distribution of radiant power where the distribution may go from point A (high-intensity light source) to point B (organic tissue) efficiently along any desired pathways determined by laboratory, surgical room, or body tract layout.

According to an aspect of the invention, there is provided a method of making or of manufacturing an optical cable comprising: providing a thin sheet of transparent material; cutting the thin sheet into ribbons; assembling a number of ribbons into a bundle; and, placing the bundle in a hermetic sheathing. Said method for manufacturing an optical cable may consist of obtaining ribbons selected from optically-transparent materials, such as silica glass, glass-ceramic, float glass, plexi-glass, polymer, or other optically- transparent glass-like materials, wherein said ribbons may be obtained by an extrusion process applied to a glass material at the viscous state, or by a cutting process applied to a large and thin sheet of solid glass material cut in many narrow ribbons, wherein said cutting comprises cutting with a water jet tool or scribing and breaking said ribbons from said large sheet of solid glass material. Said ribbons may be assembled or bundled in an ordered manner such as to obtain substantially an order of rotation symmetry n intended to refer to the Cn geometrical point group designation (with n that may be equal to 2) wherein the cross-section of the bundle of ribbons looks the same after a n-fold amount of rotation, or 360/n degrees rotation, at right angle to a given optical axis. Said bundle of ribbons may be inserted in a kiln and heated to a temperature substantially equivalent to the softening temperature of the material; followed by the application of a torque wherein said ribbons are twisted about a lengthwise axis of said cable in order to obtain a viscous strain conformal to a chiral shape. The "softening temperature" of the material is herein intended to refer to the temperature at which a material exhibits a dynamic viscosity of about 10^{6 6} Pa.s. Said bundle of ribbons may be strained at the viscous state in order to obtain a chiral symmetry of twisted shape, of helical shape, or of bannister shape. Heating is then followed by the decrease of temperature to anneal and solidify the bundle of ribbons. Said bundle of ribbons may be torqued during heating to obtain a permanent chiral shape, or may be torqued after heating when arranged in said sheath to have a chiral symmetry. Said method may further comprise affixing a fire-proof jacket, or a hermetically-sealed jacket, or one or several metallic ferules, or a combination thereof to the optical cable. Referring to Figure 1 1 , there is shown one embodiment of the method, or sequence, of manufacturing or making a flexible optical cable of the present invention: providing a thin sheet of transparent material [200]; then cutting [201] along the lengthwise axis [301] [302] [303] [304] [305] and across the lengthwise axis [401] [402] of said thin sheet of transparent material [200], in order to form [202] individual ribbons [21 1] [212] [213] [214] [215] [216]; then assembling [203] a number of ribbons into a bundle; then twisting said bundle into a twisted shape [205] or helical shape [204] about a lengthwise axis and heating to a temperature equivalent to the softening temperature of the material; then annealing and cooling said bundle; and, placing the bundle in a hermetic sheathing [206]. Still referring to Figure 1 1 , there is shown one embodiment of the method of manufacturing or making a flexible optical cable of the present invention: providing a front-end process [500] to be adapted within a glass industrial unit such as a float glass manufacturing unit, wherein a thin sheet of transparent float glass material is continually produced [200], then cut [201] along the lengthwise axis [301] [302] [303] [304] [305], and then cut across the lengthwise axis [401] [402], in order to form [202] individual ribbons of transparent float glass [211] [212] [213] [214] [215] [216], wherein said cut is performed in a continuous manner in the float glass manufacturing process and comprises scribing along and across the lengthwise axis and breaking said ribbons from said thin sheet of transparent float glass material; then providing a back-end process [600] to be adapted within an optical assembly unit that comprises assembling [203] a number of ribbons into a bundle; then twisting said bundle into a twisted shape [205] or helical shape [204] about a lengthwise axis and heating to a temperature equivalent to the softening temperature of the material; then annealing and cooling said bundle; and, placing the bundle in a hermetic sheathing [206]. Said cutting [201] sheet into individual ribbons, or said assembling [203] a number of ribbons into a bundle, or said heating to a temperature equivalent to the softening temperature, or combination thereof, may be followed by further treatments applied to individual ribbons, such as optical polishing, thin-film coating, UV hardening, laser writing, or any other treatments applied to individual ribbons or to a bundle of ribbons.

It is to be understood that the descriptions set forth herein are merely exemplary to the present invention and are not intended to limit the scope of the claims. While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

1 . A flexible optical cable for point-to-point energy distribution comprising: a bundle of optically-transparent ribbons; and

a sheath providing a hermetic enclosure of said bundle;

wherein said energy distribution is achieved about a lengthwise axis of said cable by optical total internal reflection through said ribbons.

2. The cable as defined in claim 1 , wherein said ribbons are made of optical grade material or optical grade glass.

3. The cable as defined in claim 1 , wherein said ribbons are made of transparent float glass.

4. The cable as defined in claim 1 , 2 or 3, wherein said ribbons are less than 3 mm thick and greater than 1 mm thick.

5. The cable as defined in claim 1 , 2 or 3, wherein said ribbons are less than 1 mm thick and greater than 0.25 mm thick.

6. The cable as defined in claim 1 , 2 or 3, wherein said ribbons are less than 0.25 mm thick and greater than 0.01 mm, preferably 0.02 mm, thick.

7. The cable as defined in any one of claims 1 to 6, wherein said ribbons are arranged in said sheath to have a chiral symmetry.

8. The cable as defined in any one of claims 1 to 7, wherein said bundle exhibit a C2 cross-sectional rotation symmetry about a lengthwise axis of said cable.

9. The cable as defined in any one of claims 1 to 7, wherein said ribbons are twisted about a lengthwise axis of said cable.

10. The cable as defined in claim 9, wherein said twist undergoes a 90 degree rotation within at least a length of 100 meters, preferably within a length of 10 meters, more preferably within a length of 1 meter and most preferably within a length of 0.1 meters.

1 1 . The cable as defined in claim 9, wherein said twist is intrinsic or extrinsic to said ribbons, or a combination thereof.

12. The cable as defined in any one of claims 1 to 1 1 , wherein said ribbons are twisted-coiled, or helical-coiled, or bannister-coiled.

13. The cable as defined in any one of claims 1 to 12, wherein said ribbons are of equal width to form a rectangular cross-section.

14. The cable as defined in any one of claims 1 to 13, wherein said ribbons are of unequal width to form a circular cross-section.

15. The cable as defined in any one of claims 1 to 14, further comprising a coupler provided at least one end of the cable for butt optically coupling said bundle of ribbons.

16. The cable as defined in any one of claims 1 to 14, further comprising a connector provided at least one end of the cable for hermetically sealing said bundle of ribbons.

17. The cable as defined in claim 1 , wherein said sheath comprises a lengthwise combination of fire-proof materials and mechanically robust jacket materials for protecting said bundle of ribbons.

18. The cable as defined in claim 1 , wherein said sheath comprises a lengthwise combination of toroid-shaped retaining rings, or toroid-shaped retaining annuluses, or toroid-shaped retaining clamps, or toroid-shaped retaining ferrules, or any other toroid-shaped retaining elements.

19. The cable as defined in any one of claims 1 to 18, further comprising a light concentrating unit to be optically coupled to at least one end of said cable.

20. The cable as defined in claim 19, wherein said light concentrating unit consists of a lens, or a mirror, or a prism, or an optical grating, or a liquid crystal device, or any other refractive or reflective optical element or combination thereof.

21 . The cable as defined in claim 19, wherein said light concentrating unit consists of an optical lens having a front surface comprising a conic shape with a directrix perpendicular to said optical axis.

22. The cable as defined in any one of claims 1 to 18, further comprising a light absorbing unit to be optically coupled to at least one end of said cable.

23. The cable as defined in claim 22, wherein said light absorbing unit consists of a thermal unit for the transformation of light to heat energy, such as heat- conducting, heat-convective, heat-radiative, or heat-capacitive, or heat- exchanging units or combination thereof.

24. The cable as defined in claim 23, wherein said thermal unit is a solar heat collector.

25. The cable as defined in claim 23, wherein said thermal unit is the heat engine for an air conditioning device.

26. The cable as defined in claim 23, wherein said thermal unit is the heat engine for a water heating device.

27. The cable as defined in claim 23, wherein said thermal unit is the heat engine for a fluidized bed reactor device.

28. The cable as defined in claim 22, wherein said light absorbing unit consists of a photo-transducing unit for the transformation of light to electrical energy, such as photo-electric, photo-voltaic, or photo-conducting, or cogeneration units or combination thereof.

29. The cable as defined in claim 22, wherein said light absorbing unit consists of a photo-chemical unit for the transformation of light to chemical energy, such as chemical reactors or photo-catalytic reactors or combination thereof.

30. The cable as defined in claim 22, wherein said light absorbing unit consists of a photo-absorptive unit for the transformation of light to entropy, that may comprise devices performing kinetic processes on material or biological elements such as materials cutting, materials bonding, materials ablation, materials transformation, or any other kinetic processes or combination thereof.

31 . The cable as defined in claim 1 , wherein said energy consists of the optical energy emitted by a light source such as the Sun, or a Light Emitting Device, or a Laser, or a Lamp, or a thermal element, or a fluorescent source, or any other light source or combination thereof, coincident about a lengthwise axis of said cable.

32. A method of manufacturing a flexible optical cable comprising:

providing a thin sheet of transparent material;

cutting the thin sheet into ribbons;

assembling a number of ribbons into a bundle;

placing the bundle in a hermetic sheathing.

33. The method as defined in claim 32, wherein said manufacturing comprises a front-end process wherein said thin sheet of transparent material is a float glass material, and wherein said float glass material is cut along and across its lengthwise axis in order to form said ribbons.

34. The method as defined in claim 32, wherein said ribbons are twisted about a lengthwise axis of said cable.

35. The method as defined in claim 32, further comprising thermal annealing said ribbons.

36. The method as defined in any one of claims 32 to 33, wherein said cutting comprises cutting with a water jet.

37. The method as defined in any one of claims 32 to 33, wherein said cutting comprises scribing and breaking said ribbons from said thin sheet.

38. The method as defined in any one of claims 32 to 37, wherein said transparent material is glass.