Background Of The Invention Generally, lateral emitting or leakage of light flux from a fiber optic cable is known to be used is such areas as aesthetic lighting or safety illumination. The fiber optic cable often has a plurality of individual optical or fiber optic strands, e. g., formed of plastic or glass, which are bundled together by a transparent or translucent jacket and positioned so that at least one light source optically coupled to at least one end of emits lights into the at least one end of the fiber optic cable. The light from the source is then distributed throughout the length of the fiber optic cable and is emitted laterally from the surface of the jacket. This laterally emitted light can then be used in various applications including, for example, back-lighting or surface illumination for swimming pools, spas, ponds, or waterfalls. The fiber optic cable has many advantages over other lighting techniques, e. g., neon tubes, incandescen.-lamps, or

other discrete light source, such as cable flexibility, immunity from electrical shock and noise, and low cost.

Fiber optic cables which are often used in these applications can include a light-scattering scheme to enhance the lateral emission of light from the cable. For example, the plurality of individual strands can be bundled and twisted together. More specifically, this prior technique generally involves twisting the individual optical fiber strands, e. g., about 7-14 strands, into a sub-bundle. This is generally achieved by rotating a plurality of fibers around a fixed closing die to produce the sub-bundle.

A plurality of sub-bundles, e. g., about 3-10, are then rotated into a fixed closing die to produce a fiber optic cable, e. g., having about 40-140 individual fiber optic strands. Because this technique relies primarily on tension and force at the closing die, any fractures in fiber optic cladding which may occur then generally occur in groups of 7-14 fiber optic strands and greatly reduces the uniformity of fractures to the individual strands. This twisting technique, in turn, also results in rapid light emission drop-off and little control to structurai cladding uniformity.

Examples of some some these twisting techniques are illustrated in U. S. Patent No. 5,345,531 by Keplinger et al. titled"Optical Fiber Lighting Apparatus and Method,"U. S. Patent No. 5,617,497 by Kingstone titled"Lateral Illumination Fiber Optic Cable Device And Method Of Manufacture,"U. S. Patent No. 5,333,228 by Kingstone titled"Lateral Illumination Fiber Optic Cable Device And Method Of Manufacture," and U. S. Patent No. 5,333,228 by Kingstone titled "Lateral Illumination Fiber Optic Cable Device And Method Of Manufacture."

In addition, with these prior techniques the elongation of the strands is generally induced by relatively high back tension on the individual strands and even more back tension can occur when attempts to control back lash are implemented so that the total back tension can be in the range of about 850-1500 grams. This high back tension, in turn, greatly impacts attenuation losses. For example, the initial attenuation characteristics of a plastic optical fiber strand is approximately 135 dB/Km, and the effect of accumulated back tension can change the attenuation of the plastic optical fiber strand to approximately 1200 dB/Km to 2700 dB/Km which dramatically effects performance of the individual strands.

Other techniques, for example, for increasing laterally emitting light include spreading the strands into a flat strip such as illustrated in U. S. Patent No. 4,763,984 by Awai et al. titled"Lighting Apparatus And Method"and forming a track for cable or portions of cable to positioned therealong such as illustrated in U. S. Patent No. by Kingstone titled Lateral Illumination Fiber Optic Cable Device And Method Of Manufacture." These prior techniques also generally lack uniformity in the light emission throughout the length of the cable, strip, or track. Further, complex and costly systems are often required to manufacture cable, strips, or tracks such as illustrated in the apparatus or system of U. S. Patent No. 5,376,201 by Kingstone titled"Method Of Manufacturing An Image Magnification Device." Generally, PMMA optical fiber based optical cables have a predetermined index of refraction that is a function of the core diameter and of the characteristics of the cladding (jacketing) that is present.

Historically, only 0.75 mm diameter PMMA fiber has been used in the production and manufacturing of laterally light emitting fiber optic cable.

Examples of some of this PMMA fiber usage can be found in U. S. Patent No. 5,345,531 (Keplinger et al., "Optical fiber lighting apparatus and method"); U. S.

Patent No. 5,617,497 (Kingstone,"Lateral illumination fiber optic cable device and method of manufacture"); and U. S. Patent No. 5,333,228 (Kingstone,"Lateral illumination fiber optic cable device and method of manufacture").

Fiber optic cables used in various applications including, for example, back-lighting or surface illumination for swimming pools, spas, ponds, fountains, or waterfalls, for decorative outlining of buildings, scripting for signs and advertisement displays, etc., may include a light-scattering scheme to enhance the lateral emission of light from the cable. For example, the plurality of individual strands can be twisted and bundled together. More specifically, about 7 to 14 strands can be twisted into a sub-bundle by rotating a plurality of fibers around a fixed closing die to produce the sub-bundle. A plurality of sub-bundles, e. g. about 3 to 10, are then rotated (twisted) into a fixed closing die to produce a fiber optic cable, e. g. having about 40 to 140 individual fiber optic strands.

These techniques, which have all made exclusive use of 0.75mm diameter PMMA fiber optic strands, allow for limited lateral light transmission due to the low refractive index (1.495) of the 0.75 mm diameter PMMA fiber optic strands. These techniques also generally lack sufficient light throughput due to the low numerical aperture (0.46) of 0.75 mm diameter PMMA optical fiber strands. This combination results in a low light acceptance angle of 55 degrees. The use of 0.75mm diameter PMMA optical fiber strand has been

the standard within the industry for all prior techniques for forming laterally light emitting fiber optic cable.

The formulae for representing the intermodal dispersion-propagation delay between modes and the refractive index of PMMA by wavelength are seen on pages 17 and 18. Those formulae are used for calculation of the bandwidth of a fiber having a core with an index of refraction of nl, surrounded by a cladding with an index of refraction of n2. Where numerical aperture determines total internal reflection: NA= sin A = (n.--n2-ì NA= Nominal numerical aperture A= entrance (acceptance) angle nl= index of refraction of the fiber medium (PMMA) n2= index of refraction of the cladding.

This is based on"Snell's"law for determining the numerical aperture (NA) of a fiber. When light encounters a surface of a different index of refraction, it is refracted in a relationship of hlsinsil= n2sinsi2 hi= index of refraction of the first media = PMMA core il =angle of incidence from first media h2= index of refraction of the second media (cladding) i2= resulting angle in the second media Although it is frequently applied for rays across the fiber optic edge, it really is derived for the meridian ray (of center ray) only. Light must enter into the fiber from a medium with an index of refraction close to 1 (e. g. air or space).

A ray that encounters the exterior fiber face with an angle of less than or equal to the acceptance angle will undergo total in--vernal reflection when it

encounters the difference in index of refraction between the cladding and the fiber (PMMA) media. The numerical aperture can be"tuned"for larger NA by making the difference between the core and cladding greater.

The historically used 0.75 mm diameter PMMA fiber has a core diameter of 0.735 mm. The refractive index of the core is 1.495 and the refractive index of the cladding is 1.402. The numerical aperture is 0.46 and the light acceptance angle (2er) is 55°. This has remained as a constant within the industry to date.

Summary Of The Invention In view of the foregoing background, the present invention advantageously provides an apparatus and method for forming laterally light emitting fiber optic cable which generally uniformly distributes light for lateral emission from the outer surface thereof throughout the length of the cable and laterally emits a high amount of light, e. g., increased intensity, from the outer surface of the cable. By increasing or controlling the uniform distribution and intensity of the light with a correspondingly similar light source (s), a user thereof advantageously improves light emission qualities of the fiber optic cable for desired applications. The present invention also advantageously provides a less costly and less complex apparatus and method of forming laterally emitting fiber optic cable having generally uniform light distribution and increased intensity. Additionally, the present invention advantageously provides an apparatus and method which control cladding fracture uniformity effecting individual plastic optical fiber strands and thereby greatly reduce the attenuation losses to the individual strands of optical fiber as well as to the overall attenuation of the plurality of strands which form a laterally emitting fiber optic cable.

More particularly, an apparatus and methods are provided for forming a fiber optic cable having a plurality of micro-bends in a relatively uniform pattern in each of a plurality of plastic fiber optic strands thereof to thereby increase the amount of light laterally and uniformly transmitted from the fiber optic cable. The apparatus preferably includes a supply having a plurality of plastic fiber optic strands, micro-bend forming means positioned downstream from the supply and positioned to individually receive each of the plurality of plastic fiber optic strands in a spaced-apart relation for forming a plurality of micro-bends in a relatively uniform pattern in each of the plurality of strands, strand guiding means positioned downstream from the micro-bend forming means and positioned to receive each of the plurality of micro-bend strands for guiding the plurality of spaced- apart, micro-bent strands into an abuttingly contacting relation, and wrapping means positioned downstream from the strand guiding means for wrapping a jacket, e. g., an inner cable jacket, of material such as Mylar or Teflon around the plurality of abuttingly contacting strands so as to form a cable having a plurality of individually micro-ben fiber optic strands.

Additionally, the apparatus can also advantageously include encasing means positioned downstream from the wrapping means for encasing the inner cable jacket with an outer cable jacket, cable pulling means positioned downstream from the encasing means for pulling the encased cable of the plurality of micro-bent fiber optic strands from the supply and through the micro-bend forming means, the guiding means, the wrapping means, and the encasing means, and cable collecting means positioned downstream from the cable pulling means for collecting the cable having the plurality of micro-bent fiber optic strands.

The term micro-ben as used herein throughout refers to micro-flexures or fractures in fiber cladding of individual fiber optic strands. These micro-bends preferably occur due to rotation or twisting of the individual fiber optic strands in a positive direction from 1-360 degrees of rotation either in a clockwise or counter-clockwise direction. The ratio of rotation or twist preferably is from 1-360 degrees and during 1-50 meters per minute of travel. The back tension is preferably from 100-300 grams total to any individual fiber optic strand by the use of either a mechanical, electrical, or electro-mechanical braking system on the supply, e. g., a spool pay-out to control backlashing.

This, in turn, can have the effect of controlling attenuation losses from 100-500 dB/Km which improves attenuation control.

The present invention also advantageously provides a plastic fiber optic cable for increasing lateral transmission of light therefrom. The cable preferably includes a plurality of plastic fiber optic strands. Each strand has a plurality of micro-bends formed therein in a relatively uniform pattern. At least one jacket, e. g., formed of Mylar, Teflon, or translucent plastic material, preferably is formed around the plurality of plastic fiber optic strands.

According to other embodiments of a fiber optic cable of the present invention, the fiber optic cable can advantageously include an inner core around which the plurality of strands is positioned. The plurality of strands, for example, can each extend generally parallel to each other and generally parallel to the lengthwise extent of the core or each of the plurality of strands can be twisted about the core, e. g., in sub-bundles. The core also can include a fluid such as water which can advantageously be used for fountains, pools, spas, or other water lighting applications. Further, the sub-bundles can also be

advantageously be tiered or nested about the core as well.

The apparatus and method of forming micro- bends in a generally uniform pattern in individual fiber optic strands advantageously can be used with existing methods of forming fiber optic cable and with existing types of fiber optic cable configurations to add control and uniformity to lateral light emission on these existing technologies. For example, by decreasing the amount of back tension currently required on existing fiber optic cable production, more uniformity and control of attenuation can be achieved.

This, in turn, allows the overall cladding fracture to be controlled to a much greater extent, enhances light emission uniformity, and provides a more uniform lateral light emission drop-off.

Methods of forming a fiber optic cable are also provided according to the present invention. A method preferably includes the steps of forming a plurality of micro-bends in each of a plurality of fiber optic strands, positioning each of the plurality of strands closely adjacent at least one other of the plurality of strands, and forming a jacket around the plurality of micro-bent strands. The plurality of micro-bends preferably are formed in a generally uniform pattern in each of the plurality of fiber optic strands.

Another method of forming a laterally light emitting fiber optic cable having enhanced and uniform light emitting capabilities preferably includes imparting a generally continuous twist in each of a plurality of plastic fiber optic strands moving along a predetermined path of travel so as to form a generally uniform pattern of micro-bends in each of the plurality of strands and bundling the plurality of micro-bent strands so as to define a laterally light emitting fiber optic cable.

An additional method of forming a laterally light emitting fiber optic cable preferably includes supplying a plurality of plastic fiber optic strands in spaced-apart relation, forming a plurality of micro- bends in each of the plurality of plastic fiber optic strands in a generally uniform pattern, guiding each of the plurality of spaced-apart and micro-bent strands into an abutting contact relation, and positioning a jacket of material around the plurality of strands.

In view of the foregoing background, another embodiment of the present invention advantageously provides improved materials comprising, and methods for manufacturina, laterally light emitting fiber cptic cable providing improved high lateral light emission.

In one embodiment of the invention, the intensity of laterally emitted light in increased by increasing the diameter of the core of PMMA optical fiber to 0.980 mm.

This 0.980 mm diameter fiber preferably is used in conjunction with a relatively thin cladding (jacket) having, for example, a thickness of 0.1 mm. This structure provides a ratio of core area to fiber cross- section of 96% and a concomitant increase of the numeric aperture-co 0.50, which in turn will increase the amount of light entering the PMMA core, known as the acceptance angle, to 60'. This structure can yield more light capacity and throughput than the prior art structures.

Brief Description Of The Drawincrs Some of the features, advantages, and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings in which: FIG. 1 is a block diagram of an apparatus for forming a laterally light emitting fiber optic cable

according to a first embodiment of the present invention; FIG. 2 is a perspective view of an apparatus for forming a laterally light emitting fiber optic cable according to a first embodiment of the present invention; FIG. 3 is a perspective view of a micro-bend former of an apparatus for forming a laterally light emitting fiber optic cable according to the present invention; FIG. 4 is an enlarged and fragmentary front elevational view of a micro-bend former of an apparatus for forming a laterally light emitting fiber optic cable according to the present invention; FIG. 5 is a side elevational view of a micro- bend former of an apparatus for forming a laterally light emitting fiber optic cable according to the present invention; FIG. 6 is a block diagram of an apparatus for forming a laterally light emitting fiber optic cable according to a second embodiment of the present invention; FIG. 7 is a perspective view of a micro-bend former, a strand bundle twister, and a strand guide of an apparatus for forming a laterally light emitting fiber optic cable according to a second embodiment of the present invention; FIG. 8 is a perspective view of a fiber optic cable having a plurality of strands which each include a plurality of micro-bends formed therein according to a first embodiment of a laterally light emitting fiber optic cable of the present invention; FIG. 9 is a sectional view of a fiber optic cable having a plurality of strands which each include a plurality of micro-bends formed therein and taken along line 9-9 of FIG. 8 according to a first

embodiment of a fiber optic cable of the present invention; FIG. 10 is a sectional view of a fiber optic cable having a plurality of strands which each include a plurality of micro-bends formed therein and taken along line 10-10 of FIG. 8 according to a first embodiment of a fiber optic cable of the present invention; FIG. 11 is a strand of a fiber optic cable having a plurality of micro-bends formed therein according to the present invention; FIG. 12 is a sectional view of a strand of fiber optic cable having a plurality of micro-bends formed therein and taken along line 12-12 of FIG. 11 according to the present invention; FIG. 13 is a sectional view of a strand of fiber optic cable having a plurality of micro-bends formed therein and taken along line 13-13 of FIG. 11 according to the present invention; FIG. 14 is a fragmentary view of a fiber optic cable having a plurality of strands each which includes a plurality of micro-bends formed therein according to a second embodiment of a fiber optic cable of the present invention; FIG. 15 is a sectional view of a fiber optic cable having a plurality of strands each which includes a plurality of micro-bends formed therein and taken along line 15-15 of FIG. 14 according to a second embodiment of a fiber optic cable of the present invention; FIG. 16 is a fragmentary view of a fiber optic cable having a plurality of strands each which includes a plurality of micro-bends formed therein according to a third embodiment of a fiber optic cable of the present invention; FIG. 17 is a sectional view of a fiber optic cable having a plurality of strands each which includes

a plurality of micro-bends formed therein and taken along line 17-17 of FIG. 16 according to a third embodiment of a fiber optic cable of the present invention; FIG. 18 is a fragmentary view of a fiber optic cable having a plurality of strands each which includes a plurality of micro-bends formed therein according to a fourth embodiment of a fiber optic cable of the present invention; FIG. 19 is a sectional view of a fiber optic cable having a plurality of strands each which includes a plurality of micro-bends formed therein and taken along line 19-19 of FIG. 18 according to a fourth embodiment of a fiber optic cable of the present invention; FIG. 20 is a fragmentary view of a fiber optic cable having a plurality of strands each which includes a plurality of micro-bends formed therein according to a fifth embodiment of a fiber optic cable of the present invention; FIG. 21 is a sectional view of a fiber optic cable having a plurality of strands each which includes a plurality of micro-bends formed therein and taken along line 21-21 of FIG. 20 according to a fifth embodiment of a fiber optic cable of the present invention; and FIG. 22 is a perspective view of a fiber optic cable in the form of a relatively flat strip having a plurality of individual fiber optic strands which each include a plurality of micro-bends formed therein according to yet another embodiment of the present invention.

Detailed Description Of Preferred Embodiments The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may,

however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Ratner, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Prime or multiple prime notation where used indicates alternative embodiments.

Like numbers refer to like elements throughout.

FIGS. 1-2 illustrate an apparatus 30 for forming a fiber optic cable C having a plurality of micro-bends B in a relatively uniform pattern in each of a plurality of plastic fiber optic strands S thereof to thereby increase the amount of light laterally and uniformly transmitted from the fiber optic cable C according to the present invention. The apparatus 30 preferably includes a supply 40 having a plurality of spools 41 of plastic fiber optic strands S mounted to a frame defining a rack 45. The spools 41 are positioned on the rack 45, and each spool 41 is preferably controlled by a spool braking system, e. g., electro- mechanical or motor controlled as understood by those skilled in the art, connected to a control unit 25 to control backlash and tension in the individual strand S. The supply 40 also preferably includes a strand spacer 46 illustrated in the form of a strand spacer ring, e. g., formed of metal having a plurality of spaced apart guides or openings 47 formed therein for spacing and guiding the individual strands from the supply 40.

The apparatus 30 also preferably has micro- bend forming means, e. g., preferably provided by a micro-bend former 50, preferably positioned downstream from the supply 40 and positioned to individually

receive each of the plurality of plastic fiber optic strands S in a spaced-apart relation for forming a plurality of micro-bends B in a relatively uniform pattern in each of the plurality of strands S (see also FIGS. 3-5). The micro-bend former 50 preferably includes a housing 51, e. g., mounted on a floor pedestal 52 having a plurality of spaced-apart openings 53 formed therein and extending therethrough, e. g., through a position gathering ring 54 to position a single fiber optic strand S in each of the plurality of openings 53 and twisting means 55 positioned to abuttingly contact each of the plurality of strands S when positioned in the plurality of openings 53 for imparting generally continuous twists in each of the plurality of strands S to thereby form the plurality of micro-bends B therein in a relatively uniform pattern as the plurality of fiber optic strands S travel downstream. The twisting means 55, for example, can include a motor 59, a shaft 56 connected to the motor 54 for being rotatingly driven by the motor 54, and a fiber optic interface member 57 connected to the shaft 56 for abuttingly interfacing with each of the plurality of strands. The interface member 57 preferably includes an interface ring 58a formed of an elastomeric material which defines a fiber optic strand contact, friction drive belt mounted to a spline drive hears 58b. The spline drive gear 58b, in turn, is mounted to the drive shaft 56.

Strand guiding means, e. g., preferably provided by a strand guide 60, guide belts, or closer, preferably is positioned downstream from the micro-bend former 50 and positioned to receive each cf the

plurality of micro-bent strands S for guiding the plurality of spaced-apart, micro-ben strands S into an abuttingly contacting relation. The guiding operation, for example, can be achieved by a frusto-conical shaped housing 61, such as illustrated, and can include a motor 62 and drive belt 63. Guide belts or other closers can be used, alternatively, as well.

Wrapping means, e. g., preferably provided by a wrapper 70, is positioned downstream from the strand guide 60 for wrapping a jacket, e. g., an inner cable jacket Jl, of material around the plurality of abuttingly connecting strands S so as to form a cable C having a plurality of individually micro-bent fiber optic strands S. The wrapper 70, for example, can include a roll 72 or spool of material mounted to a frame member 73 and a wrap guide 74 for guiding the wrapping material around the bundle of strands S. The material of the wrapper 70 preferably includes at least one of either Mylar or Teflon, and the material preferably is overlappingly wrapped around the plurality of micro-bent strands S.

Additionally, the apparatus 30 can also advantageously include encasing means, e. g., preferably provided by an encaser 80, positioned downstream from the wrapper 70 for encasing the inner cable jacket J1 with an outer cable jacket J2. The encaser preferably encases or surrounds the inner jacket J1 with a translucent plastic material as it passes through a trough or channel 81. A pair of pipes 82,83 are connected to the trough 81 vo supply fluid plastic material and/or a coolant thereto. Cable pulling means, e. g., preferably provided by a cable puller 90 or

caterpillar-type device as understood by those skilled in the art, is positioned downstream from the encaser 80 for pulling the encased cable C of the plurality of micro-bent fiber optic strands S from the supply 40 and through the micro-ben former 50, the strand guide 60, the wrapper 70, and the encaser 80. The cable puller 90 preferably includes a drive motor 92 which drives a plurality of drive rolls 94. A pair of belts 95,96 are mounted to the drive rolls for contactingly engaging the outer jacket J2 of the cable C.

Also, cable collecting means, e. g., preferably provided by a spool collector 100, is positioned downstream from the cable puller 90 for collecting cable C having the plurality of micro-bent fiber optic strands S in a controlled manner. The spool collector 100 preferably includes a drive motor 102 for rotatingly driving the spool for take-up of the cable C. The spool collector 100 also preferably includes a cable guide 105 for guiding the cable onto the spool during rotation thereof. The cable guide 105 preferably includes a motor 106 mounted to a frame member 107 and an eyelet 108 connected to the motor 106 by a drive chain or other drive link. The eyelet 108 advantageously travels along the frame member 107 during take-up operation so that the cable C is collected onto the spool in a smooth and organized process.

Further, the apparatus 30 preferably has drive controlling means, e. g., a control unit 25, including one or more processing circuits, e. g., microprocessors, and/or associated control software as understood by those skilled in the art, connected at

least to the micro-bend former 50, the cable puller 90, and the spool collector 100, for controlling the drive of the same. The control unit 25 preferably includes synchronizing means, e. g., a timing synchronizer 26 of hardware and/or software, for synchronizing the drive of the micro-bend former 50, the cable puller 90, and the spool collector 100.

As best illustrated in FIGS. 6-7, and for alternate cable configurations (see FIGS. 16-21) for example, the apparatus 30'can also include strand bundle twisting means, e. g., preferably provided by a strand bundle twister 65, positioned downstream from the micro-bend former 50 for twisting individual strands S into sub-bundles prior to positioning or wrapping the inner jacket J1'around a plurality of these sub-bundles. The sub-bundles also can be positioned around an inner core I as well. The strand bundle twister 65 for example, can include another guide ring 68 mounted to a floor support stand. The guide ring 68 has an inner ring connected to the stand in a stationary manner and an outer ring surface which interfaces with a drive belt 67 driven by a drive motor 68. The guide ring 68 has a plurality of openings 69 extending therethrough and into which sub-groups or sub-bundles of fiberoptic strands pass. The drive belt 67 imparts a twist to the strands S as the strands pass through the opening. In turn, a plurality of twisted sub-bundles is the output of the stand bundle twister 65 and travel downstream to the stand guide 60'for initiating the formation of the cable C'', for example.

The terms micro-bend B or micro-bent as used herein throughout refers to micro-flexures or fractures

in fiber cladding of individual fiber optic strands S such as due to twisting at strong enough force or tension to cause the fracture. These micro-bends preferably occur due to rotation or twisting of the individual ber optic strands S in a positive direction from 1-360 degrees of rotation either in a clockwise or counter-clockwise direction. The ratio of rotation or twist will be from 1-360 degrees and from 1-50 meters per minute of travel. The back tension is preferably from 100-300 grams total to any individual fiber optic strand S by the use of either a mechanical, electrical, or electro-mechanical braking system on the supply, e. g., a spool pay-out to control backlashing.

This, in turn, can have the effect of controlling attenuation losses from 100-500 dB/Km which improves attenuation control.

For example, as understood by those skilled in the art, the plastic strands S are preferably formed of a polymethyl methacrylate ("PMMA") core, a fluorinated polymer cladding, and a structure having a step index type. Fiber optic strands S having a plurality of micro-bends B or micro-flexures of rotation a, , y of positive X, Y, and Z axes into the assigned direction along the line between 0^ and 180°.

The direction cosines, in turn, are cos a, cos , and cos Y and satisfy the equation: COS2 + cos + Cos2y = 1. Direction numbers a, b, c can be any three numbers proportional to the direction cosines. In other words, a=Kcos a, b=Kcosß, and c=Kcosy (with Kit0). The direction cosine of a line is the coordinates of the point a unit distance from the origin along its positive direction.

Assuming a numerical aperture ("N. A.") equals<BR> <BR> <BR> <BR> <BR> <BR> <BR> about 0.54 and an acceptance angle of 65°, then the bandwidth step index modulation of PMMA strands can be shown as follows: A. Intermodal dispersion: propagation delay between modes is represented by: <BR> <BR> <BR> <BR> <BR> <BR> <BR> ## [N.A.]2<BR> lm #(7-#)##<BR> <BR> nc where (n) is the refractive index of the core, (c) is light velocity in the vacuum, (A) is the difference of specific index, and v) is normalized frequency.

Material dispersion: for visible light from 398 nanometers to 1200 nanometers spectral content material dispersion oc is calculated by: o==-ld c dA c d The refractive index of PMMA by wave length is given by "Cauchy's"series as follows: n (2) =pO+A2-2 +BA2-4 where i, = 1.4779.

A= 5.0496 X 103 B= 6.9486 X 10' These figures are used for calculatlon of the bandwidth of the fiber.

The PMMA is an optical fiber cylindrical guide which permits the propagation of the visible light wave.

Forms in the mode of a"light"signal. According to the refraction index profile, it is possible to have these signals propagated in single mode or multi-mode fiber"step index."The dimensions of the multi-mode fibers are characterized by the cladding diameter and core diameter. The number of micro-bends can vary between a few per meter to several hundred per meter.

As the flex or"twist"becomes"tighter"micro-bending losses are introduced. The dimensions control between radii, is expected to be reasonably assured to tens of microns and perhaps less.

The index of refraction cf the cladding being smaller than that of the core, for example, from 50y (microns) to 3004 (microns) as compare to 500, u (microns) to 1500p (micron) for the core. Owing to this difference in the index of refraction between the materials constituting the core and cladding, light entering one end of the micro-flexed fiber is

propagated-nside the fiber itself and transmitted as a uniformly controlled brightness or"lateral light transmission along the line between 0° (degrees) and 180° (degrees) a unit distance from the crigin 6. Along its positive direction this method of micro-bending the individual fiber strand S allows a uniformly controlled fracturing of the fiber's clad to effect attenuation losses by effecting light wave transit times. This will cause lucent light leakage, the luminance of the light leakage can be increased or decreased under the influence of micro-bending or micro-flexure. The refracting and scattering actions of the light leaks at a high luminance. The cable C having the strands S constructed in this manner as described above is fabricated by twisting the individual optical fiber strands S and thereby form a rotational light leakage. formed therein according to the present invention.

As perhaps best illustrated in FIGS. 8-21, the present invention also advantageously provides a plastic fiber optic cable C for increasing lateral transmission of light therefrom. The cable C preferably includes a plurality of plastic fiber optic strands S as described herein above (see FIGS. 8-15).

Each strand S has a plurality of micro-bends B formed therein as described herein above in a relatively uniform pattern. The strands, as illustrated, extend generally parallel to each other and parallel to the axis of the extent of the one or more jackets J1, J2.

At least one jacket, e. g., inner cable jacket J1 formed of Mylar, Teflon, or translucent plastic material, preferably is formed around the plurality of plastic fiber optic strands S. Alternatively, as illustrated in FIGS. 14-15, the individual strands S'can be twisted into sub-bundles prior to wrapping and/or encasing the sub-bundles.

According to other embodiments of a fiber optic cable or the present invention, the fiber optic cable C''can advantageously include an inner core I around which the plurality of strands S''is positioned (see FIGS. 16-21). The plurality of strands S'', for example, can each extend generally parallel to each other and generally parallel to the lengthwise extent of the core I or each of the plurality of strands S'' can be twisted about the inner core I. As perhaps best illustrated in FIGS. 18-19, the inner core I'also can include a fluid F such as water which can advantageously be used for fountains, pools, spas, or other water lighting applications. The fluid F, for example, can be positioned in a translucent or transparent tube T which in combination with the fluid defines the core of the cable C''. Further, as illustrated in FIGS. 20-21, the fiber optic sub-bundles can advantageously be nested in a plurality, e. g., two or more, tiers of sub-bundles about the inner core I so that light can also readily be emitted from regions R between adjacent bundles. The inner sub-bundles can also advantageously be formed of smaller diameter individual fiber optic strands S''and can have a fewer number of strands S''within the sub-bundles for more efficient packing within a jacket Jl''and for more efficient lateral light emission qualities.

FIG. 22 illustrates yet another embodiment of a fiber optic cable Cl"in the form of a relatively flat strip having a plurality of individual fiber optic strands S which each include a plurality of micro-bends B formed therein according to the present invention.

This embodiment also preferably includes a translucent outer jacket J'"which readily allows laterally emitted

light to emit therefrom. As will be understood by those skilled in the art, this arrangement also illustrates the individual strands S being positioned in a side-by-side, e. g., preferably abuttingly contacting, relation so that light can be emitted from both sides of the relatively flat outer jacket J'".

As illustrated in FIGS. i-21, methods of forming a fiber optic cable C are also provided according to the present invention. A method preferably includes the steps of forming a plurality of micro-bends B in each of a plurality of fiber optic strands S, positioning each of the plurality of strands S closely adjacent at least one other of the plurality of strands S, and forming a jacket J1 around the plurality of micro-bent strands S. The plurality of micro-bends B preferably are formed in a generally uniform pattern in each of the plurality of fiber optic strands S.

Another method of forming a laterally emitting fiber optic cable C having enhanced and uniform light emitting capabilities preferably includes imparting a generally continuous twist in each of a plurality of plastic fiber optic strands S moving along a predetermined path of travel so as to form a generally uniform pattern of micro-bends B in each of the plurality of strands S and bundling the plurality of micro-bent strands S so as to define a laterally emitting fiber optic cable C.

An additional method of forming a laterally emitting fiber optic cable C preferably includes supplying a plurality of plastic fiber optic strands S in spaced-apart relation, forming a plurality of micro- bends B in each of the plurality of plastic fiber optic strands in a generally uniform pattern, guiding each of the plurality or spaced-apart and micro-bent strands S into an abutting contact relation, and positioning a jacket J1 of material around the plurality of strands 5 S.

Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.