WO2019083920A1

WO2019083920A1 - Light diffusing optical fibers for guiding and scattering ultraviolet light

Info

Publication number: WO2019083920A1
Application number: PCT/US2018/056985
Authority: WO
Inventors: Trista Nicole Hesch; Stephan Lvovich Logunov; Manuela Ocampo
Original assignee: Corning Incorporated
Priority date: 2017-10-24
Filing date: 2018-10-23
Publication date: 2019-05-02
Also published as: EP3701186A1; CN111279124A; CN111279124B; JP7270620B2; JP2021500623A

Abstract

A light diffusing optical fiber that includes a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a thermoplastic polymer coating layer surrounding and contacting the cladding. The plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber. The core includes glass doped with 300 ppm or more of a hydroxyl material. The cladding includes glass doped with 300 ppm or more of a hydroxyl material. Further, the thermoplastic polymer coating layer is doped with a plurality of scattering particles.

Description

LIGHT DIFFUSING OPTICAL FIBERS FOR GUIDING AND SCATTERING ULTRAVIOLET LIGHT

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S.

Provisional Application Serial No. 62/724,870, filed on August 30, 2018, U.S. Provisional Application Serial No. 62/607,401 filed on December 19, 2017, and U.S. Provisional Application Serial No. 62/576,237 filed on October 24, 2017, the contents of each are relied upon and incorporated herein by reference in their entirety.

BACKGROUND

[0002] The present disclosure relates to light diffusing optical fibers. More specifically, the present disclosure relates to light diffusing optical fibers for guiding and scattering ultraviolet light propagating along the light diffusing optical fiber.

BRIEF SUMMARY

[0003] According to one embodiment, a light diffusing optical fiber includes a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a thermoplastic polymer coating layer surrounding and contacting the cladding. The plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber. The core includes glass doped with 300 ppm or more of a hydroxyl material. The cladding includes glass doped with 300 ppm or more of a hydroxyl material. Further, the thermoplastic polymer coating layer is doped with a plurality of scattering particles.

[0004] In another embodiment, a light diffusing optical fiber includes a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, a primary coating layer surrounding the cladding, and a thermoplastic polymer coating layer surrounding the primary coating layer such that the primary coating layer is disposed between the cladding and the thermoplastic polymer coating layer. The plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber. The core includes glass doped with 300 ppm or more of a hydroxyl material. The cladding includes glass doped with 300 ppm or more of a hydroxyl material. The primary coating layer includes a cycloaliphatic epoxy having an absorbance of about 0.04 or less per 100 μπι of layer thickness at a wavelength of about 250 nm or more. Further, the primary coating layer includes a plurality of scattering particles doped within the cycloaliphatic epoxy.

[0005] In yet another embodiment, a light diffusing optical fiber includes a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a coating layer surrounding the cladding. The plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that when guided light propagates along the core, a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber. The core includes glass doped with 300 ppm or more of a hydroxyl material. The cladding includes glass doped with 300 ppm or more of a hydroxyl material. The coating layer is doped with a plurality of scattering particles. Further, when guided light having a wavelength of about 250 nm or greater propagates along the core and a portion of the guided light diffuses through the outer surface, the light diffusing optical fiber comprises a scattering efficiency of from about 0.4 or greater.

[0006] Although the concepts of the present disclosure are described herein with primary reference to light diffusing optical fibers for guiding and scattering ultraviolet light, it is contemplated that the concepts will enjoy applicability to any optical fiber.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0007] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0008] Fig. 1 schematically depicts an illumination system comprising a light output device and a light diffusing optical fiber, according to one or more embodiments shown and described herein;

[0009] Fig. 2A schematically depicts a cross section of a light diffusing optical fiber, according to one or more embodiments shown and described herein;

[0010] Fig. 2B schematically depicts a cross section of the light diffusing optical fiber of Fig. 2A, according to one or more embodiments shown and described herein;

[0011] Fig. 3 A schematically depicts a cross section of another embodiment of a light diffusing optical fiber, according to one or more embodiments shown and described herein;

[0012] Fig. 3B schematically depicts a cross section of the light diffusing optical fiber of Fig. 3A, according to one or more embodiments shown and described herein;

[0013] Fig. 4A schematically depicts a cross section of another embodiment of a light diffusing optical fiber, according to one or more embodiments shown and described herein;

[0014] Fig. 4B schematically depicts a cross section of the light diffusing optical fiber of Fig. 4A, according to one or more embodiments shown and described herein;

[0015] Fig. 5 graphically depicts the absorbance of ultraviolet light for various polymer materials, according to one or more embodiments shown and described herein;

[0016] Fig. 6 graphically depicts the scattering efficiency of ultraviolet light for various embodiments of light diffusing optical fibers, according to one or more embodiments shown and described herein;

[0017] Fig. 7A is an image of a light diffusing fiber light delivery system, according to one or more embodiments; and [0018] Fig. 7B. is a graph showing the efficacy of a known light diffusing fiber (un- bolded line) and the efficacy of a light diffusing fiber according to one or more embodiments (bold line).

DETAILED DESCRIPTION

[0019] Referring now to Fig. 1, an illumination system 100 comprises a light diffusing optical fiber 110 optically coupled to a light output device 102 that includes a light source 152. The light diffusing optical fiber 110 comprises a first end 112, a second end 114 opposite the first end 112. Cross sections of embodiments of the light diffusing optical fiber are depicted in Figs. 2A-4C. For example, Figs. 2A and 2B depict cross sections of the light diffusing optical fiber 110, Figs. 3A and 3B depict cross sections of a light diffusing optical fiber 210, and Figs. 4A and 4B depict cross sections of a light diffusing optical fiber 310. Each light diffusing optical fiber 110, 210, 310 described herein comprises a core 120, 220, 320, a cladding 122, 222, 322 surrounding the core 120, 220, 320, an outer surface 128, 228, 328, and a plurality of scattering structures 125, 225, 325 positioned within the core 120, 220, 320, the cladding 122, 222, 322, or both the core 120, 220, 320 and the cladding 122, 222, 322.

[0020] As used herein, the "outer surface" 128, 228, 328 refers to the outermost surface of the light diffusing optical fiber 110, 210, 310. In the embodiments depicted in Figs. 2A and 2B, the outer surface 128 is a surface of a secondary polymer coating layer 132, in the embodiments depicted in Figs. 3A and 3B, the outer surface 228 is a surface of a thermoplastic polymer coating layer 234, and in the embodiments depicted in Figs. 4A and 4B, the outer surface 328 is a surface of a thermoplastic polymer coating layer 334. Further, the plurality of scattering structures 125, 225, 325 are configured to scatter guided light (e.g., light output by the light output device 102 that is propagating along the light diffusing optical fiber 110, 210, 310) toward the outer surface 128, 228, 328 of the light diffusing optical fiber 110, 210, 310 such that a portion of the guided light diffuses through the outer surface 128 along a diffusion length of the light diffusing optical fiber 110, 210, 310. Further, the light diffusing optical fiber 110, 210, 310 will may comprise a length (e.g., a length between the first end 1 12 and the second end 1 14) of from about 0.15 m to about 100 m, for example, about 100 m, 75 m, 50 m, 40 m, 30 m, 20 m, 10 m, 9 m, 8 m, 7 m, 6 m, 5 m, 4 m, 3 m, 2 m, 1 m, 0.75 m, 0.5 m, 0.25 m, 0.15 m, or 0.1 m.

[0021] As used herein, "diffusion length," is the length of the light diffusing optical fiber

110 extending from the first end 112 of the light diffusing optical fiber 110 (or from any end receiving input light) to a location along the length of the light diffusing optical fiber 110 where 90% of the guided light has diffused from the light diffusing optical fiber 1 10. The diffusion length may be in a range from about 0.1 m to about 100 m, for example, from about 0.2 m to about 100 m, from about 0.25 m to about 100 m, from about 0.3 m to about 100 m, from about 0.35 m to about 100 m, from about 0.4 m to about 100 m, from about 0.5 m to about 100 m, from about 0.55 m to about 100 m, from about 0.6 m to about 100 m, from about 0.65 m to about 100 m, from about 0.7 m to about 100 m, from about 0.75 m to about 100 m, from about 0.8 m to about 100 m, from about 0.85 m to about 100 m, from about 0.9 m to about 100 m, from about 1 m to about 100 m, from about 2 m to about 100 m, from about 3 m to about 100 m, from about 4 m to about 100 m, from about 5 m to about 100 m, from about 10 m to about 100 m, from about 20 m to about 100 m, from about 30 m to about 100 m, from about 40 m to about 100 m, from about 50 m to about 100 m, from about 0.1 m to about 90 m, from about 0.1 m to about 80 m, from about 0.1 m to about 70 m, from about 0.1 m to about 60 m, from about 0.1 m to about 50 m, from about 0.1 m to about 40 m, from about 0.1 m to about 30 m, from about 0.1 m to about 20 m, or from about 0.1 m to about 10 m., As used herein, the term "light-diffusing" means thatlight scattering is substantially spatially continuous along at least a portion of the length of the light diffusing optical fiber 110, i.e., there are no substantial jumps or discontinuities such as those associated with discrete (e.g., point) scattering. Thus, the concept of substantially continuous light emission or substantially continuous light scattering as set forth in the present disclosure refers to spatial continuity. Further, as used herein, "uniform illumination" refers to illumination along the length of the light diffusing optical fiber 1 10 in which the intensity of light emitted from the light diffusing optical fiber 110 does not vary by more than 25% over the specified length. It should be understood that the above definitions also apply to the light diffusing optical fibers 210, 310 of Figs. 2A-4B.

[0022] Referring again to Fig. 1, the light output device 102 is optically coupled to the first end 112 of the light diffusing optical fiber 110 (or in other embodiments, the light diffusing optical fibers 210 or 310) such that light output by the light source 152 of the light output device 102 may irradiate the end face 116 of the first end 1 12 of the light diffusing optical fiber 1 10 and enter the light diffusing optical fiber 110. The light source 152 may comprise a light-emitting diode (LED), a laser diode, or the like. For example, the light source 152 may comprise a multimode laser diode, single mode laser diode, a SiP laser diode, a VCSEL laser diode, or another type of semiconductor laser diode. Further, the light source 152 may be configured to generate light in the 200 nm to 2000 nm wavelength range. [0023] In some embodiments, the light source 152 may be configured to generate or may generate light in the 200 nm to 2000 nm wavelength range. For example, the light source 152 may be an ultraviolet (UV) or near UV light source configured to emit light at a wavelength of from about 200 nm to about 500 nm, from about 200 nm to about 500 nm, from about 220 nm to about 500 nm, from about 240 nm to about 500 nm, from about 250 nm to about 500 nm, from about 260 nm to about 500 nm, from about 280 nm to about 500 nm, from about 300 nm to about 500 nm, from about 320 nm to about 500 nm, from about 340 nm to about 500 nm, from about 350 nm to about 500 nm, from about 360 nm to about 500 nm, from about 380 nm to about 500 nm, from about 400 nm to about 500 nm, from about 200 nm to about 480 nm, from about 200 nm to about 460 nm, from about 200 nm to about 450 nm, from about 200 nm to about 440 nm, from about 200 nm to about 420 nm, from about 200 nm to about 410 nm, from about 375 nm to about 475 nm, from about 380 nm to about 460 nm, from about 390 nm to about 450 nm, from about 400 nm to about 440 nm, from about 400 nm to about 430 nm, from about 400 nm to about 420 nm, from about 400 nm to about 410 nm, or from about 402 nm to about 408 nm. In one or more embodiments, the light source may be configured to generate or may generate light having a wavelength of, for example, about 225 nm, 250 nm, 275 nm, 300 nm, 325 nm, 350 nm, 375 nm, 400 nm, 405 nm, 415 nm, 425 nm, 435 nm, 445 nm, 450 nm, 475 nm, or the like, such as about 300 nm to about 460 nm. The light output device 102 may further comprise additional optical components such a lens, an optical delivery fiber, or the like, positioned between and optically coupled to the light source 152 and the first end 1 12 of the light diffusing optical fiber 1 10 to facilitate the input of light into the light diffusing optical fiber 1 10. Moreover, these additional optical components, such as an optical delivery fiber, may allow the light source 152 to be spatially separated from the light diffusing optical fiber 1 10.

[0024] In operation, because light emitted by the light source 152 is scattered into the surrounding environment by the light diffusing optical fiber 110, the light source 152 may be positioned at a location remote from the light diffusing optical fiber 1 10. Accordingly, any thermal heat generated by the light source 152 may be transferred away from the light source 152 to locations remote from both the light source 152 and the light diffusing optical fiber 1 10. Thus, the temperature of the light diffusing optical fiber 1 10 may remain substantially similar to the ambient temperature of the surrounding environment and the lighting unit may be described as a thermally "cool" lighting unit. Further, spatially separating the light diffusing optical fiber 110 and the light source 152 may provide additional design flexibility to the illumination system 100.

[0025] Referring now to Figs. 2A-4B, each of the light diffusing optical fibers 110, 210, 310, are configured to induce scattering through the outer surface 128, 228, 328 with a high scattering efficiency, in particular, when the guided light propagating along the length of the light diffusing optical fiber 110, 210, 310 comprise wavelengths in the ultraviolent range (e.g., from about 200 nm to about 500 run). As used herein, "scattering efficiency" refers to the percentage of light scattering outward from the core 120, 220, 320 of the light diffusing optical fiber 110, 210, 310 towards the outer surface 128, 228, 328 that in not absorbed, blocked, or otherwise lost, and in fact exits the outer surface 128, 228, 328. While not intending to be limited by theory, a percentage of light scattering from the core 120, 220, 320 may be absorbed by the one or more additional layers of the light diffusing optical fiber 1 10, 210, 310 surrounding the cladding 122, 222, 322. However, the light diffusing optical fibers 110, 210, 310 described herein limit absorption of UV light scattering through the outer surface 128, 228, 328 and facilitate high scattering efficiency at UV wavelengths.

[0026] Referring still to Figs. 2A-4B, the core 120, 220, 320 and the cladding 122, 222, 322 of each of the light diffusing optical fibers 110, 210, 310 may comprise a glass, such as silica glass, doped with a hydroxyl material (e.g., a hydroxyl doped glass core and a hydroxyl doped glass cladding). As used herein, "hydroxyl doped" refers to a glass comprising 300 ppm or more of a hydroxyl material, for example hydroxyl ions (OH), excess oxygen (which may be added to the glass), or the like. While not intending to be limited by theory, doping the core 120, 220, 320 and the cladding 122, 222, 322 with a hydroxyl material may be advantageous at UV wavelengths. While glass cores and claddings having a low hydroxyl content (e.g., hydroxyl content of less than 300 ppm) have increased transmissivity at higher wavelengths (e.g., wavelengths in the visible range, near infrared (NIR) range, and infrared range), they also incur increased absorption losses at wavelengths in the UV range because lowering the hydroxyl content in the glass increases the number and/or size of oxygen deficiency centers in the glass. As used herein, "oxygen deficiency center" refers to formation of broken bonds of silica having an oxygen vacancy. While not intending to be limited by theory, oxygen deficiency centers in the core 120, 220, 320 and the cladding 122, 222, 322 absorb light comprising a wavelength in the UV range, which darkens the core 120, 220, 320 and the cladding 122, 222, 322 and reduces the percentage of light scattered outward from the core 120, 220, 320 by the scattering structures 125, 225, 325 that diffuses through the outer surface 128, 228, 328 of the light diffusing optical fiber 1 10, 210, 310. While not intending to be limited by theory, under UV radiation, different "color centers" can be developed in fused silica. The origin of a color center may be related to ionization of the fused silica. While still not intending to be limited by theory, color centers may react with OH to form stable non-absorbing species. In some embodiments, the light diffusing optical fiber 1 10, 210, 310 may be hydroxyl doped by hydrogen loading the silica of the light diffusing optical fiber 1 10, 210, 310 with high pressure and temperature.

[0027] Moreover, while not intending to be limited by theory, some polymer materials, such as some UV curable polymers, are highly absorptive of UV light. Thus, it is advantageous to limit the number and thickness of polymer layers of the light diffusing optical fiber 1 10, 210, 310 and use polymer layers with limited absorption of UV light. For example, in each embodiment depicted in Figs. 2A-4B, the cladding 122, 222, 322 comprises glass (e.g., hydroxyl doped glass). Further, each of the embodiments of the light diffusing optical fiber 1 10, 210, 310 described herein comprise at least one polymer layer surrounding the cladding 122, 222, 322, however, as described in more detail below, each of these polymer layers comprise low absorption of UV light.

[0028] Referring now to Figs. 2A and 2B, cross sections the light diffusing optical fiber 1 10 comprising the core 120, the cladding 122 surrounding the core 120, the outer surface 128 and the plurality of scattering structures 125 are depicted. The core 120 comprises a glass core (e.g., silica) doped with a hydroxyl material (e.g., silica comprising about 300 ppm or more of a hydroxyl material). The cladding 122 comprises a glass cladding (e.g., F-doped silica or F(fluorine)/B(boron) co-doped silica having a lower refractive index than the refractive index of the core 120) doped with a hydroxyl material (e.g., F-doped silica or F(fluorine)/B(boron) co-doped silica comprising about 300 ppm or more of a hydroxyl material). The light diffusing optical fiber 1 10 further comprises a primary polymer coating 130 surrounding the cladding 122 and the secondary polymer coating layer 132 surrounding the primary polymer coating 130.

[0029] Referring still to Figs. 2A and 2B, the scattering structures 125 may occur throughout the core 120 (as depicted in Figs. 2A and 2B), or may occur near the interface of the core 120 and the cladding 122 (e.g., the core-cladding boundary), or may occur in an annular ring within the core 120. The scattering structures 125 may comprise gas filled voids, scattering particles, such as ceramic materials, dopants, or the like. Some examples of light-diffusing optical fibers having randomly arranged and randomly sized voids (also referred to as "random air lines" or "nanostructures" or "nano-sized structures") are described in U.S. Pat. No. 7,450,806, and in U.S. Pat. Application Ser. No. 12/950,045, 13/097,208, and 13/269,055, herein incorporated by reference in their entirety. Alternatively, the light diffusing optical fiber 110 may have a "roughened" core 120, where the irregularities on the surface of the core 120 at the core-cladding boundary causes light scatter. Other types of light diffusing optical fibers may also be utilized. In operation, the light diffusing optical fiber 110 may undergo scattering-induced attenuation (i.e., attenuation due to light lost through the outer surface 128 of the light diffusing optical fiber 110, not due to absorption of scattering particles within the light diffusing optical fiber 110) about 50 dB/km or greater, for example from about 100 dB/km to about 60000 dB/km at an illumination wavelength (e.g., the wavelength(s) of emitted radiation).

[0030] In embodiments in which the scattering structures 125 comprise gas filled voids, the gas filled voids may be arranged in a random or organized pattern and may run parallel to the length of the light diffusing optical fiber 110 or may be helical (i.e., rotating along the long axis of the light diffusing optical fiber 110). Further, the light diffusing optical fiber 110 may comprise a large number of gas filled voids, for example more than 50, more than 100, or more than 200 voids in the cross section of the fiber. The gas filled voids may contain, for example, SO2, Kr, Ar, CO2, N2, O2, or mixtures thereof. However, regardless of the presence or absence of any gas, the average refractive index in region of the core 120, the cladding 122, or the core-cladding boundary that comprises the plurality of scattering structures 125 is lowered due to the presence of voids. Further, the plurality of scattering structures 125 such as voids can be randomly or non-periodically disposed in the core 120, the cladding 122, or the core-cladding boundary, however, in other embodiments the voids may be periodically disposed.

[0031] The cross-sectional size (e.g., diameter) of the voids, such as gas filled voids (or other scattering particles) may be from about 10 nm to about 10 μπι and the length may vary from about 1 μπι to about 50 m. In some embodiments, the cross sectional size of the voids (or other scattering particles) is about 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 250 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 1 um, 2 um, 3 μιη, 4 um, 5 μιη, 6 μιη, 7 μιη, 8 um, 9 μτη, or 10 um. In some embodiments, the length of the voids is about 1 um, 2 um, 3 um, 4 μιη, 5 μτη, 6 μιη, 7 μm, 8 um, 9 μm, 10 μιη, 20 μm, 30 μm, 40 μιη, 50 μm, 60 μιη, 70 μm, 80 μm, 90 μιη, 100 μιη, 200 μιη, 300 μιη, 400 μιη, 500 μιη, 600 μιη, 700 μιη, 800 μιη, 900 μιη, 1000 μτη, 5 mm, 10 mm, 50 mm, 100 mm, 500 mm, 1 m, 5 m, 10 m, 20 m, or 50 m.

[0032] Referring still to Figs. 2A and 2B, the primary polymer coating 130 may comprise a substantially clear layer surrounding the core 120 and cladding 122 for ease of mechanical handling, for example, a polymer coating. Further, the secondary polymer coating layer 132 may be positioned surrounding the core 120, the cladding 122, and the primary polymer coating 130. The secondary polymer coating layer 132 operates as a scattering layer and comprises a base material (for example, a polymer) and a plurality of scattering particles 135 positioned in the base material. In operation, the secondary polymer coating layer 132 may facilitate uniform angular scattering over a large angular range (e.g., 40 to 120°, or 30° to 130°, or 15 to 150°). For example, the light diffusing optical fiber 110 is configured to provide substantially uniform illumination due to scattering, such that the difference between the minimum and maximum scattering illumination intensity is less than 50% of the maximum scattering illumination intensity, for all viewing angles between 40 and 120 degrees.

[0033] The scattering particles 135 comprise a refractive index differential from the base material of the secondary polymer coating layer 132 (e.g. a base polymer having a refractive index of about 1.5) of more than 0.05 (e.g., the difference in refractive indices between the base material and each scattering particle 135 is greater than 0.05). In some embodiments, the difference in refractive indices between the base material and the each scattering particle 135 is at least 0.1. That is, the index of refraction of each scattering particle 135 may be at least 0.1 larger than the index of refraction of the base material (e.g., of the polymer or other matrix material) of the secondary polymer coating layer 132. Further, to limit the absorption of UV light traversing the secondary polymer coating layer 132, the scattering particles 135 comprise a material having low absorbance of UV light (e.g., low absorption scattering materials). Example low absorption materials scattering materials having a refractive index greater than the base material (e.g., greater than about 1.5) include aluminum oxide (AI2O3) having a refractive index of about 1.77, barium sulfate (BaSO- having a refractive index of about 1.636, gas voids such as microbubbles with refractive index of about 1, or the like. Further, in some embodiments, the scattering particles 135 may instead or in addition comprise gas voids or microbubbles.

[0034] Further, the cross-sectional size of each scattering particle 135 within the secondary polymer coating layer 132 may comprise 0.1λ to 10λ, where λ is the wavelength of light propagating through the light diffusing optical fiber 1 10. In some embodiments, the cross-sectional size of each scattering particle 135 is greater than 0.2λ and less than 5λ, for example, between 0.5λ and to 2λ. For example, the cross-sectional size of each scattering particle may comprise from about 20 nm to about 5 μπι, for example, about 50 nm, 75 nm, 100 nm, 150 nm, 200 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1 μιη, 1.1 um, 1.2 μιη, 1.3 μιη, 1.4 μιη, 1.5 μιη, 1.6 μιη, 1.7 μιη, 1.8 μιη, 1.9 μτη, 2 μιη, 2.1 μιη, 2.2 μιη, 2.3 μτη, 2.4 μιη, 2.5 μιη, 2.6 μιη, 2.7 μιη, 2.8 μτη, 2.9 μιη, 3 μιη, 3.1 μιη, 3.2 μιη, 3.3 μιη, 3.4 μτη, 3.5 μιη, 3.6 μιη, 3.7 μιη, 3.8 μιη, 3.9 μτη, 4 μιη, 4.1 μιη, 4.2 μm, 4.3 μιη, 4.4 μm, 4.5 μm, 4.6 μιη, 4.7 μm, 4.8 μιη, 4.9 μm, or the like. Further, the scattering particles 135 in the secondary polymer coating layer 132 may comprise from about 0.005% to 70% by weight of the secondary polymer coating layer 132, for example, 0.01 % to 60%, 0.02% to 50%, or the like.

[0035] In some embodiments, the plurality of scattering particles 135 may be disposed within a sublayer of the secondary polymer coating layer 132. For example, in some embodiments, the sublayer may have a thickness of about 1 μιη to about 5 μιη. In other embodiments, the thickness of the particle sublayer and/or the concentration of the scattering particles 135 in the secondary polymer coating layer 132 may be varied along the axial length of the light diffusing optical fiber 110 so as to provide more uniform variation in the intensity of light scattered from the light diffusing optical fiber 1 10 at large angles (i.e., angles greater than about 15 degrees). For example, the angular illumination for all viewing angles between 40 and 120 degrees is within 50% of maximum illumination, and in some embodiments within 30%. In some embodiments, the angular illumination for all viewing angles between 40 and 120 degrees is within 30% of maximum illumination, and in some embodiments within 25%.

[0036] Referring now to Figs. 3 A and 3B, cross sections the light diffusing optical fiber

210 comprising the core 220, the cladding 222 surrounding the core 220, scattering structures

225 and a thermoplastic polymer coating layer 234 surrounding and contacting the cladding

222 are depicted. The core 220 comprises a glass core (e.g., silica) doped with a hydroxyl material (e.g., silica comprising about 300 ppm or more of a hydroxyl material). The cladding 222 comprises a glass cladding (e.g., F-doped silica or F(fluorine)/B(boron) co- doped silica having a lower refractive index than the refractive index of the core 220) doped with a hydroxyl material (e.g., doped silica or F(fluorine)/B (boron) co-doped silica comprising about 300 ppm or more of a hydroxyl material). The scattering structures 225 may occur throughout the core 220 (as depicted in Figs. 3A and 3B), or may occur near the interface of the core 220 and the cladding 222 (e.g., the core-cladding boundary), or may occur in an annular ring within the core 220. The scattering structures 225 may comprise any of the scattering structures 125 described above with respect to the light diffusing optical fiber 110, for example, gas filled voids, scattering particles, such as ceramic materials, dopants, or the like.

[0037] The thermoplastic polymer coating layer 234 comprises a fluorinated polymer material such as polytetrafluoroethylene (PTFE), such as Teflon™, ethylene- tetrafluoroethylene (ETFE), such as Tefeel™, polyethylene terephthalate (PET), fluorinated ethylene propylene (FEP), perfluoroalkoxy alkane (PFA), PEEK (polyetheretherketone), Nylon, and any other fluorinated extrudable polymer. The thermoplastic polymer coating layer 234 comprises low absorbance of UV light (as described in more detail with respect to graph 50 of Fig. 5, below) and is a hard plastic material, which provides a protective coating layer surrounding the core 220 and the cladding 222. In the embodiment depicted in Figs. 3 A and 3B, the thermoplastic polymer coating layer 234 is in direct contact with the cladding 222 and thus, no intervening layers are positioned between the cladding 222 and the thermoplastic polymer coating layer 234, limiting the amount of UV light scattering outward from the core 220 towards the outer surface 228 that is absorbed, blocked or otherwise prevented from exiting the outer surface 228.

[0038] Further, as depicted in Figs. 3A and 3B, scattering particles 235 are disposed in the thermoplastic polymer coating layer 234. The scattering particles 235 disposed within the thermoplastic polymer coating layer 234 may comprise any of the scattering particles 135 described above with respect to the light diffusing optical fiber 110. The thermoplastic polymer coating layer 234 may comprise a refractive index of from about 1.30 to about 1.35. The scattering particles 235 may comprise low absorption scattering materials having a refractive index greater than the refractive index of the thermoplastic polymer coating layer 234, for example, AI2O3 having a refractive index of about 1.77, BaS04 having a refractive index of about 1.636, silicon dioxide (S1O2) having a refractive index of about 1.46, or the like. Note that because the thermoplastic polymer coating layer 234 comprises a refractive index that is lower than the secondary polymer coating layer 132, materials may be used as scattering particles 235 that are not available as scattering particles 135. In particular, S1O2 may be used as a material of scattering particles 235, which may be advantageous because S1O2 is transparent to light having a wavelength of about 200 nm and greater, thereby reducing absorption loss caused by the scattering particles 235 in the UV range. Further, in some embodiments, the scattering particles 235 may instead or in addition comprise gas voids or microbubbles.

[0039] In some embodiments, the thermoplastic polymer coating layer 234 may be applied directly to the cladding 222 of the light diffusing optical fiber 210 during a fiber draw process. For example, while not intending to be limited by theory, the core 220 and the cladding 222 may be drawn from an optical fiber preform, though a draw furnace, which heats the optical fiber preform, and a fiber coating unit, which applies the thermoplastic polymer coating layer 234 to the cladding 222 of the light diffusing optical fiber 210. Further, after the thermoplastic polymer coating layer 234 is applied, the light diffusing optical fiber 210 reaches a fiber collection unit, which may comprise one or more drawing mechanisms and tensioning pulleys to provide tension to the light diffusing optical fiber 210 and facilitate winding the light diffusing optical fiber 310 onto a fiber storage spool.

[0040] During the drawing process, applying the thermoplastic polymer coating layer 234 before the light diffusing optical fiber 210 reaches the fiber collection unit prevent mechanical contact between the cladding 222 and the one or more drawing mechanisms of the fiber collection unit, which may prevent damage to the glass of the cladding 222. However, in other embodiments, the thermoplastic polymer coating layer 234 is applied to the light diffusing optical fiber 210 after the light diffusing optical fiber 210 is drawn, for example, using off-draw equipment, such as conventional extruding equipment. Thus, in embodiments in which the thermoplastic polymer coating layer 234 is applied after a draw process, it may be desirable to apply a coating layer onto the cladding 222 during the draw process to prevent damage to the glass of the cladding 122 caused by the drawing mechanisms and tensioning pulleys of the fiber collection unit. An example light diffusing optical fiber having a polymer layer between a cladding and a thermoplastic polymer coating layer is the light diffusing optical fiber 310, described below. [0041] Referring now to Figs. 4A and 4B, cross sections the light diffusing optical fiber 310 comprising the core 320, the cladding 322 surrounding the core 320, scattering structures 325, a primary coating layer 330 surrounding the cladding 322, and a thermoplastic polymer coating layer 334 surrounding the primary coating layer 330 such that the primary coating layer 330 is disposed between the cladding 322 and the thermoplastic polymer coating layer 334 are depicted. The core 320 comprises a glass core (e.g., silica) doped with a hydroxyl material (e.g., silica comprising about 300 ppm or more of a hydroxyl material). The cladding 322 comprises a glass cladding (e.g., F-doped silica or F(fluorine)/B(boron) co- doped silica having a lower refractive index than the refractive index of the core 320) doped with a hydroxyl material (e.g., doped silica or F(fluorine)/B (boron) co-doped silica comprising about 300 ppm or more of a hydroxyl material). The scattering structures 325 may occur throughout the core 320 (as depicted in Figs. 4A and 4B), or may occur near the interface of the core 320 and the cladding 322 (e.g., the core-cladding boundary), or may occur in an annular ring within the core 320. The scattering structures 325 may comprise any of the scattering structures 125 described above with respect to the light diffusing optical fiber 1 10, for example, gas filled voids, scattering particles, such as ceramic materials, dopants, or the like.

[0042] The thermoplastic polymer coating layer 334 may comprise any of the fluorinated polymer materials of the thermoplastic polymer coating layer 234, such as polytetrafluoroethylene (PTFE), such as Teflon™, ethylene-tetrafluoroethylene (ETFE), such as Tefeel™, polyethylene terephthalate (PET), fluorinated ethylene propylene (FEP), perfluoroalkoxy alkane (PFA), PEEK (polyetheretherketone), Nylon, and any other fluorinated extrudable polymer. The thermoplastic polymer coating layer 334 comprises low absorbance of UV light and is a hard plastic material, which provides a protective coating layer surrounding the core 320, the cladding 322, and the primary coating layer 330.

[0043] The primary coating layer 330 comprises a UV curable coating layer, such as cycloaliphatic epoxy. While cycloaliphatic epoxy is UV curable, the photo-initiator used to cure the cycloaliphatic epoxy is UV absorptive but is removable after the cycloaliphatic epoxy is cured, for example, by bleaching the cycloaliphatic epoxy, and the resultant cured cycloaliphatic epoxy comprises low absorbance of UV light, as described in more detail below with respect to graph 50 of Fig. 5 , below. In some embodiments, the photo -initiator comprises (p-isopropylphenyl)(p-methylphenyl)iodonium tetrakis(pentafluorophenyl)borate. Further, the primary coating layer 330 may comprise a thickness of from about 5 μιη to about 20 μιη, for example, from about 10 μιη to about 15 μιη. It may be advantageous for the primary coating layer 330 to be thin because some UV may still be absorbed by the primary coating layer 330 and a thinner layer minimizes this absorption.

[0044] Referring still to Figs. 4A and 4B, the primary coating layer 330 is doped with a plurality of scattering particles 335, which may comprise any of the scattering particles 135 described above with respect to the light diffusing optical fiber 110. For example, the scattering particles 335 may comprise low absorption scattering materials having a refractive index greater than the cycloaliphatic epoxy of the primary coating layer 330 (which comprises a refractive index of about 1.41), for example, AI2O3 having a refractive index of about 1.77, BaS04 having a refractive index of about 1.636, particles made from thermoplastic polymer such as polytetrafluoroethylene (PTFE), such as Teflon™, ethylene- tetrafluoroethylene (ETFE), such as Tefeel™, polyethylene terephthalate (PET), fluorinated ethylene propylene (FEP), perfluoroalkoxy alkane (PFA), PEEK (polyetheretherketone), Nylon, and any other fluorinated polymer, or the like. Further, in some embodiments, the scattering particles 335 may instead or in addition comprise gas voids or microbubbles. Moreover, while Figs. 4A and 4B depict that the plurality of scattering particles 335 are disposed in the primary coating layer 330, the plurality of scattering particles 335 may alternatively or additionally be disposed in the thermoplastic polymer coating layer 334.

[0045] Referring again to Figs. 1, 2B, 3B, and 4B, in operation, unscattered, guided light (such as UV light output by the light source 152 of the light output device 102) propagates along the light diffusing optical fiber 110, 210, 310 in the direction shown by arrow 10. Scattered light is shown exiting the light diffusing optical fiber 110, 210, 310 in the direction shown by arrow 12 at a scattering angle 0s, which is the angular difference between the propagation direction 10 of guided light propagating along the light diffusing optical fiber 110, 210, 310 and the direction 12 of the scattered light when it leaves light diffusing optical fiber 110. In some embodiments, the intensities of the spectra when the scattering angle 0s is between 15° and 150°, or 30° and 130° are within ±50%, ±30%, ±25%, ±20%, ±15%, ±10%, or ±5% as measured at the peak wavelength. In some embodiments, the intensities of the spectra when the scattering angle 0s is between all angles within 30° and 130°, or 40° and 120° are at least within ±50%, for example ±30%, ±25%, ±20%, ±15%, ±10%, or ±5% as measured at the peak wavelength. Accordingly, each light diffusing optical fiber 110, 210, 310 is configured to provide substantially uniform illumination due to scattering, such that the difference between the minimum and maximum scattering illumination intensity is less than 50% of the maximum scattering illumination intensity, for all viewing angles between at least 40 degrees and 1 10 degrees, for example for all viewing angles between 40 degrees and 120 degrees. According to some embodiments, the difference between the minimum and maximum scattering illumination intensity is not greater than 30% of the maximum scattering illumination intensity.

[0046] Referring again to Figs. 2A-4B, each light diffusing optical fiber 110, 210, 310 may have a scattering induced attenuation loss of greater than about 0.2 dB/m at a wavelength of 550 nm. For example, in some embodiments, the scattering induced attenuation loss (attenuation loss due to the scattering structures 125, 225, 325, such as air lines) may be greater than about 0.5 dB/m, 0.6 dB/m, 0.7 dB/m, 0.8 dB/m, 0.9 dB/m, 1 dB/m, 1.2 dB/m, 1.4 dB/m, 1.6 dB/m, 1.8 dB/m, 2.0 dB/m, 2.5 dB/m, 3.0 dB/m, 3.5 dB/m, or 4 dB/m, 5 dB/m, 6 dB/m, 7 dB/m, 8 dB/m, 9 dB/m, 10 dB/m, 20 dB/m, 30 dB/m, 40 dB/m, or 50 dB/m at 550 nm. In some embodiments, the average scattering loss of the light diffusing optical fiber 1 10, 210, 310 is greater than 50 dB/km, and the scattering loss does not vary more than 20% (i.e., the scattering loss is within ±20% of the average scattering loss, for example within ± 15%, or within ± 10%) over any given fiber segment of the light diffusing optical fiber 110. In some embodiments, the average scattering loss of the light diffusing optical fiber 1 10, 210, 310 is greater than 50 dB/km, and the scattering loss does not vary more than 20% (i.e., the scattering loss is within ±20% of the average scattering loss, for example within ± 15 %, or even within ± 10%) over any given fiber segment of the light diffusing optical fiber 1 10, 210, 310 of from about 0.2 m to about 50 m, for example, 0.5 m, 1 m, 2 m, 5 m, 10 m, 15 m, 20 m, 25 m, 30 m, 35 m, 40 m, 45 m, or the like.

[0047] Referring now to Fig. 5, a graph 50 depicts the absorbance of UV light from 200 nm to 400 nm in sample material layers comprising a thickness of about 100 um. One sample material layer is a cycloaliphatic epoxy comprising a thickness of about 100 μπι, such as the cycloaliphatic epoxy of the primary coating layer 330 of the light diffusing optical fiber 310, which is represented by line 52. Another sample material layer comprising a thickness of about 100 μπι is PTFE, such as the thermoplastic polymer coating layer 234 of light diffusing optical fiber 210 and the thermoplastic polymer coating layer 334 of the light diffusing optical fiber 310, which is represented by line 54. As depicted by line 52, the cycloaliphatic epoxy comprises an absorbance per 100 μιη of thickness of about 0.0005 at 400 nm, about 0.001 at 375 nm, about 0.002 at 350 nm, about 0.004 at 325 nm, about 0.012 at 300 nm, about 0.025 at 275 nm, and about 0.035 at 250 nm. Further, as depicted by line 54, the PTFE comprises an absorbance per 100 μιη of thickness of about 0.003 at 400 nm, about 0.004 at 375 nm, about 0.006 at 350 nm, about 0.008 at 325 nm, about 0.01 at 300 nm, about 0.013 at 275 nm, about 0.0175 at 250 nm, about 0.024 at 225 nm, and about 0.032 at 200 nm.

[0048] Referring still to Fig. 5, the cycloaliphatic epoxy (line 52) comprises an absorbance per 100 μιη of thickness of about 0.01 or less for light comprising a wavelength of about 310 nm or more. The cycloaliphatic epoxy (line 52) comprises an absorbance per 100 μιη of thickness of about 0.02 or less for light comprising a wavelength of about 250 nm or more. The cycloaliphatic epoxy (line 52) comprises an absorbance per 100 μιη of thickness of about 0.03 or less for light comprising a wavelength of about 270 nm or more. Further, the cycloaliphatic epoxy (line 52) comprises an absorbance per 100 μιη of thickness of about 0.04 or less for light comprising a wavelength of about 245 nm or more. The PTFE (line 54) comprises an absorbance per 100 μιη of thickness of about 0.01 or less for light comprising a wavelength of about 300 nm or more. The PTFE (line 54) comprises an absorbance per 100 μιη of thickness of about 0.02 or less for light comprising a wavelength of about 240 nm or more. Further, the PTFE (line 54) comprises an absorbance per 100 μιη of thickness of about 0.03 or less for light comprising a wavelength of about 205 nm or more.

[0049] Referring now to Fig. 6, graph 70 depicts the scattering efficiency of various light diffusing optical fiber embodiments for light comprising a wavelength of from about 300 nm to about 500 nm. As stated previously, "scattering efficiency" refers to the percentage of light scattering outward from the core 120, 220, 320 of the light diffusing optical fiber 110, 210, 310 towards the outer surface 128, 228, 328 that in not absorbed, blocked, or otherwise lost, and in fact exits the outer surface 128, 228, 328. In Fig. 6, line 72 represents a previous embodiment of a light diffusing optical fiber, line 74 represents the light diffusing optical fiber 110, line 76 represents the light diffusing optical fiber 210, and line 78 represents the light diffusing optical fiber 310. As depicted in Fig. 6, the light diffusing optical fibers 110, 210, 310 described herein comprise higher scattering efficiencies of UV light than previous light diffusing optical fibers. [0050] Referring still to Fig. 6, line 74 depicts that the light diffusing optical fiber 1 10 comprises a scattering efficiency of about 0.1 or more for light comprising a wavelength of about 350 nm or more, a scattering efficiency of about 0.4 or more for light comprising a wavelength of about 375 nm or more, a scattering efficiency of about 0.6 or more for light comprising a wavelength of about 400 nm or more, and a scattering efficiency of about 0.8 or more for light comprising a wavelength of about 425 nm or more. Line 76 depicts that the light diffusing optical fiber 210 comprises a scattering efficiency of about 0.5 or more for light comprising a wavelength of about 300 nm or more, a scattering efficiency of about 0.65 or more for light comprising a wavelength of about 325 nm or more, a scattering efficiency of about 0.75 or more for light comprising a wavelength of about 350 nm or more, a scattering efficiency of about 0.8 or more for light comprising a wavelength of about 375 nm or more, and a scattering efficiency of about 0.9 or more for light comprising a wavelength of about 400 nm or more. Further, while not depicted in Fig. 6, light diffusing optical fiber 210 comprises a scattering efficiency of about 0.4 or more for light comprising a wavelength of about 250 nm or more, such as a scattering efficiency of about 0.5 or more. Moreover, line 78 depicts that the light diffusing optical fiber 310 comprises a scattering efficiency of about 0.3 or more for light comprising a wavelength of about 350 nm or more, a scattering efficiency of about 0.6 or more for light comprising a wavelength of about 375 nm or more, a scattering efficiency of about 0.8 or more for light comprising a wavelength of about 400 nm or more, and a scattering efficiency of about 0.9 or more for light comprising a wavelength of about 425 nm or more.

[0051] Examples

[0052] All organisms used in the following examples are listed in Table 1. When available, well-characterized laboratory strains were used, otherwise clinical isolates were acquired from the Strong Memorial Hospital Clinical Microbiology Laboratory, Rochester, NY. S. aureus strain UAMS-1 1 12 is a stable small-colony variant of the common laboratory strain 8325-4 that harbors a hemB disruption. Unless otherwise noted, bacteria were grown for 16 h in Mueller-Hinton (MH) medium (Becton Dickinson, Franklin Lakes, NJ) at 37 °C on a rotary shaker at 225 rotations per min, serially diluted in 0.9% saline solution, and then processed as described below. Candida albicans cultures were grown overnight in Yeast Extract-Peptone-Dextrose (YPD) broth and processed. [0053] Table 1. Organisms used in these studies.

Species Strain Reference or Source

Enterococcus faecium 824-05 (19)

Staphylococcus aureus UAMS-1 (39)

UAMS-1 1 12 (19)

Staphylococcus epidermidis 1457 (40)

Klebsiella pneumoniae cKP1 (41)

Acinetobacter baumannii 98-37-09 (42)

Pseudomonas aeruginosa PA01 (43)

Enterobacter cloacae PMD1001 (19)

Streptococcus pyogenes Clinical isolate URMC¹

Candida albicans SC5314 (44)

Escherichia coli JM109 (45)

¹Strong Memorial Hospital Clinical Microbiology Laboratory, Rochester, NY

[0054] All assays were performed using 230 μτη (outer) diameter 22 cm diffusion length light diffusing fibers (Coming Incorporated; Corning, NY). As shown in Fig. 7A, ends of the fiber were connected to 750 mW 405 nm lasers (World Star Technologies; Ontario, CA) using FC/PC to FC/PC patch cable with 0.22 NA and 105 μπι core size (Thorlabs; Newton, NJ). Light diffusing fibers were placed in a 1 mm x 1 mm groove on a sheet of

polytetrafuoroethylene for increased reflection and to stabilize the fiber's configuration across experiments. Microorganisms within 96 well microtiter plates, colonizing agar or abiotic surfaces were positioned approximately 1 cm directly overtop the fiber's illumination path and irradiated at 405 nm to achieve the indicated light dose.

[0055] Light diffusing fiber treatment of bacteria inoculated onto agar plate surfaces.

Bacteria were either dispensed as a spot (20 μΐ volume) or spread (100 μΐ volume) directly onto MH agar plates at final concentrations of 1 x 10⁴ to 1 x 10⁸ cells per plate. Once dry, plates were inverted and the surface was placed within 1 cm of the light diffusing fiber light delivery or illumination path. Plates were treated at fluence rates ranging from 5 mW/cm² to 25 mW/cm² for 2 to 6 h. Fluence rates were measured at the beginning of each test using an ILT 1400 Photometer and XSL340A detector (International Light Technologies; Peabody, MA). Fluence (radiant energy in Joules/cm²) was calculated using the formula Fluence = (X)(Y)(3.6) J/cm², where X = power density in mW/cm², and Y = exposure time in hours. Following treatment, plates were incubated for 16 h at 37°C to determine colony forming units (CFU). Antimicrobial effects were determined by comparing the cell viability of each treatment regimen to mock-treated (light-shielded) cells. All organisms were evaluated a total of three times on separate days. [0056] Light diffusing fiber treatment of bacteria cultured in liquid media. To approximate standard antimicrobial minimum inhibitory concentration (MIC) testing parameters, approximately 5 x 10⁴ of the indicated bacterial species were inoculated (10 μΐ) in individual wells of a 96-well, round-bottom polystyrene microtiter plate (Corning, Inc., Corning NY) containing 190 μΐ MH medium. Cell suspensions were then treated at 5 mW/cm² to 25 mW/cm² for 2 to 6 hr. Following treatment, an aliquot of cells was removed, serially diluted in 0.9% saline solution and plated to enumerate CFU. Antimicrobial effects were determined by comparing the number of CFU of each treatment to that of mock-treated (light-shielded) cells. All organisms were evaluated at least three times on separate days.

[0057] Cytotoxicity testing. Human Colon 38 cells were grown to 50% and 100% confluence in McCoy's 5A medium in a 24 well plate. Half the plate was shielded and the other half was treated at 5 mW/cm², 10mW/cm², 25mW/cm², or 50 mW/cm² for 4 hours. Following treatment, the cells were stained by adding 0.1 volume of Alamar blue solution (Invitrogen, Eugene, OR) and incubated at 37°C (protected from light) for 4 hours. To measure cell viability a 100 μΐ aliquot was transferred into a 96 well plate to be read by a plate reader at a fluorescence excitation wavelength of 540-570 nm (peak excitation is 570 nm) and fluorescence emission at 580-610 nm (peak emission is 585 nm). Each condition was tested in quadruplet.

[0058] Light diffusing fiber treatment of S. aureus, A. baumannii and P. aeruginosa on abiotic surfaces. Approximately 1 x 10⁶ to 1 x 10⁸ CFU of the indicated organism in 20 μΐ 0.9% saline was inoculated onto approximately 1 cm² area of abiotic materials including fabric (Ameripride Services; Minnetonka, MN), silicone rubber, polystyrene, polypropylene (Nuc 96-well), and ceramic tile (Lowes, Mooresville, NC). Each material was placed in 24- well culture plates and allowed to dry for 24 to 48 hr at 37°C. Colonized surfaces were treated at 5 mW/cm², 10 mW/cm², or 25 mW/cm² for a total of 2, 4, or 6 hr. Bacteria were collected from treated surfaces by vigorous pipetting with 1 mL of 0.9% saline, serially diluted, and the recoverable CFU were enumerated by plating. The antimicrobial effects of each treatment regimen were determined by comparing the cell viability of each treatment to mock-treated cells. Additionally, two methods were used in parallel to ensure total viable bacterial recovery from each surface. First, 0.25 ml of 0.9% saline was added and the test surface was physically scraped using a spatula, transferred to a 96 well microtiter plate and the percent non-viable/viable organisms remaining was measured using a LIVE/DEAD stain at an excitation wavelength of 485 nm and emission wavelengths of 530 nm (SYTO 9; green) and 630 nm (propidium iodide; red) (Molecular Probes, Inc., Eugene, OR). Second, inoculated test surfaces were transferred to fresh culture medium after treatment, incubated for 16 h at 37°C on an orbital shaker and optical density (OD600nm) measured. All organisms were evaluated a total of three times on separate days for each abiotic material.

[0059] RESULTS:

[0060] The light diffusing fiber (according to one or more embodiments of this disclosure) used in these studies was developed to maximize 405 nm light emission and antimicrobial potential. The fiber is composed of 115 μπι high purity silica glass core with 0.05 - 0.3 μπι diameter gas filled voids randomly distributed throughout the core to increase light scattering. The fiber core was double clad with a 25 μπι thick fluorine-doped (F-doped) silica and a 40 um cycloaliphatic polymer containing - 0.1 μπι diameter alumina particles, both of which increase angular light scattering (data not shown), whereas the outer surface of the light diffusing fiber is coated with ~ 70 μπι fluorinated polymer (Perfluoroalkoxy, PFA) to protect the fiber yet retain its flexibility. Integrated sphere testing measures of the total light scattering across emission wavelengths revealed that the light diffusing fiber light delivery or illumination efficiency was improved in comparison to conventional visible light-diffusing fibers (unbolded line) and capable of greater than 90% emission at wavelengths >400 nm (Fig. 7B), suggesting that it may be ideal for antimicrobial 405 nm light delivery.

[0061] Light diffusing fiber 405 nm light delivery or illumination system exerts antimicrobial activity toward ESKAPE and other pathogens. LED-delivered 405 nm light (133 J/cm²) has been shown to effectively reduce the growth of both S. aureus and P. aeruginosa seeded onto agar plates by approximately 6-logio and 5.2-logio, respectively. Thus, as an initial evaluation of whether a light diffusing fiber light delivery or illumination system efficiently delivered 405 nm light approaching the antimicrobial effects of LED 405 nm exposure, 1 x 10⁶ CFU of exponential phase S. aureus strain UAMS-1 or P. aeruginosa strain PA01 were spread onto the surface of Mueller Hinton (MH) agar plates. One half of the plate was shielded from light exposure, whereas the other half was exposed to 10 mW/cm² 405 nm light for a total of 6 hrs (fluence = 216 J/cm²) and then incubated overnight to score bacterial growth. As shown in Fig. 7B (left), light diffusing fiber 405 nm light delivery effectively inhibited growth of irradiated S. aureus cells, whereas there were no discemable ablation of shielded cell growth. Similar antimicrobial effects were also observed in studies in which 10⁶ S. aureus CFU were spot plated (20 μΐ) in the light exposure field

(Fig. 7B.; right), providing an efficient means of performing replicate light exposure tests on a single petri plate. Parallel studies of P. aeruginosa cells revealed the organism to be

equally susceptible to the antimicrobial effects of a light diffusing fiber 405 nm light delivery (data not shown). Taken together, these results suggested that 405 nm light delivered via a light diffusing fiber illumination system is capable of producing an effective antimicrobial dose that approximates the antimicrobial performance of LED directed light exposure.

[0062] To further explore the antimicrobial potential of the light diffusing fiber light

delivery or illumination system, studies were expanded to provide higher resolution measures of the system's performance. In independent experiments 10⁴, 10⁶ and 10⁸5^*. aureus or P.

aeruginosa cells were challenged with various light intensities (5, 10, or 25 mW/cm²) and exposure times (2, 4, or 6 hr). Each experiment was repeated at least three times, and the

number of cells that were reproducibly and completely inhibited by each experimental

condition was recorded (Table 2). Results revealed that light diffusing fiber delivery of 405

nm light elicited a dose-dependent antimicrobial effect toward both test organisms. For S.

aureus, 2 hr, 25 mW/cm² (180 J/m²) treatment inhibited growth 10⁴ CFU, whereas both 4 and

6 hr treatment at the same fluence rate inhibited growth of 10⁶ cells. While 2 hr of 10

mW/cm² treatment did not display antimicrobial activity toward the organism, 4 hr (144 J/m²) and 6 hr (216 J/m²) treatment inhibited growth of 10⁴ and 10⁶ CFUs, respectively. S. aureus treatment with 5 mW/cm² did not exhibit detectable antimicrobial activity at 2 or 4 hr

exposure, whereas 6 hr (108 J/m²) treatment reduced growth of < 10⁴ cells. Compared to S.

aureus, P. aeruginosa displayed increased 405 nm light susceptibility; 2 hr treatment with 5

(36 J/m²), 10 (72 J/m²) and 25 mW/cm² (108 J/m²) treatment inhibited growth of 10⁴, 10⁶,

and > 10⁶ P. aeruginosa cells, respectively. From these studies, we concluded that a light diffusing fiber illumination system is capable of delivering an antimicrobial effect with

equipotency to standard LED systems.

Table 2. Antimicrobial effect on a semi-solid surface.

Viability Reduction^*

Species Treatment (hr) 25 mW cm² 10 mW cm² 5 mW cm² Minimum Fluence

Staphylococcus aureus 2 10⁴

4 10⁶ 10⁴ - 144 6 10^ 10^ < 10⁴

Pseudomonas aeruginosa 2 10⁷ 10⁶ < 10⁴

4 10⁶ 10⁶ < 10⁴ 72

6 10⁷ 10⁶ < 10⁴ Enterococcus faecium 2

4 < 10⁴ 540

6 10⁴

Staphylococcus epidermidis 2 10⁴ - -

4 10⁴ 10⁵ - 144

6 10⁷ 10⁷ -

Klebsiella pneumoniae 2

4 < 10⁴ < 10⁴ 144

6 10⁵ 10⁴ < 10⁴

Acinetobacter baumannii 2 10⁴

4 10⁴ 10⁴ 144

6 10⁴ < 10⁴ < 10⁴

Enterobacter sp. 2 < 10⁴

4 10⁵ < 10⁴ 360

6 10⁵ < 10⁴

Streptococcus pyogenes 2 < 10⁸ < 10⁸ < 10⁸

4 < 10⁸ < 10⁸ < 10⁸ 36

6 < 10⁸ < 10⁸ < 10⁸

Candida albicans 2 < 10⁴ < 10⁴

4 10⁶ < 10⁴ < 10⁴ 216

6 < 10⁷ 10⁶ < 10⁴

Escherichia coli 2 < 10⁴

4 10⁵ < 10⁴ 216

6 10⁶ 10⁵ < 10⁴

* < 10^x indicates more than 50% reduction in the indicated inoculum; ( - ) indicates no measurable reduction in inoculum.

** Minimum radiant energy (Fluence; Joules/cm²) required to achieve a 4-log reduction in viability.

[0063] Based on the system's performance toward these two organisms, studies were expanded to assess the system's antimicrobial performance toward the remaining members of the ESKAPE pathogens (Enterococcus faecium, Klebsiella pneumoniae, Acinetobacter baumannii, and Enterobacter cloacae), as well as other microbes of immediate healthcare concern including Streptococcus pyogenes, Escherichia coli, and the fungus Candida albicans. Results revealed that the light diffusing fiber 405 nm light delivery inhibited growth of each organism in a dose dependent manner (Table 2). For instance, E. coli treatment at 25 mW/cm² for 2, 4 or 6 hr resulted in < 10⁴, 10⁵, and 10⁶ reduction in CFU, respectively; six hours treatment with 10 and 5 mW/cm² resulted in a reduction of 10⁵ and 10⁴ CFU, respectively. Similar dose-dependent antimicrobial activity was observed for all other organisms evaluated, although the magnitude of the system's performance did vary for microbial species. Streptococcus pyogenes appeared to be the most susceptible, as all doses uniformly produced an approximately 8-log reduction in inoculum. Further, consistent with previously published reports, E. faecium appeared to be the most 405 nm-tolerant organism tested, displaying a 4-log decrease in cell viability but only at the highest dosing conditions (25 mW for 6 hr; 540 J/cm²). However, there was no significant reduction in the organism's survival at lower light exposures.

[0064] To facilitate comparison of the antimicrobial efficacy of light diffusing fiber to other technologies using 405 nm light reported in the literature, Table 2 also summarizes the radiant energy in J/cm² required to kill > 4-logio CFU of each test organism. As elaborated above, S. pyogenes appeared to be the most susceptible organism tested, demonstrating >4 log reduction in cell viability at 36 J/cm². Of the other species evaluated, P. aeruginosa was also highly susceptible to 405 nm light (72 J/cm²), followed by S. aureus, S. epidermidis, K. pneumoniae and A. baumannii (144 J/cm²). C. albicans, E. coli and E. cloacae appeared somewhat more blue light-tolerant (360 J/cm²), whereas E. faecium was the least susceptible, requiring 540 J/m² irradiation to achieve at least a 4 log reduction in CFU.

[0065] Effects of light diffusing fiber light delivery or illumination system-delivered 405 nm light toward ESKAPE pathogen-colonized abiotic surfaces. Colonization of fomite material is well-recognized to serve as a source of bacterial transmission. Thus, studies were expanded to assess the system's performance toward representatives of the ESKAPE pathogens when colonizing abiotic surfaces common to hospital environments, including polystyrene, fabric, silicone rubber, polypropylene and ceramic tile. Based, in part, on their observed high degree of 405 nm susceptibility on semi-solid agar surfaces combined with their propensity to colonize abiotic surfaces, we chose three representative ESKAPE pathogens for these studies; S. aureus and P. aeruginosa, which are commonly acquired nosocomial pathogens prevalent in the hospital environment, and A. baumannii, an environmental organism that is notoriously tolerant to desiccation, and a prominent cause of wound infections. Each abiotic surface was inoculated with 10⁸, 10⁷, or 10⁶ CFU S. aureus, P. aeruginosa or A. baumannii, dried for 24 to 48 hr, and then treated at 0, 5, 10, or 25 mW/cm² for 2, 4, or 6 hr. Bacterial cells were recovered by washing and the number of viable cells remaining was enumerated by plating; care was taken to ensure that all viable organisms were recovered.

[0066] The light diffusing fiber illumination system displayed modest decolonization properties toward P. aeruginosa and limited activity toward S. aureus adhered to each substrate (Table 3). More specifically, in comparison to mock-treated cells (shielded from light), P. aeruginosa exhibited a dose response dependent effect when adhered to cloth and polystyrene resulting in a maximum of 2-logio and 5-logio decrease in viability following 4 hr and 6 hr 25 mW/cm² treatment, respectively. P. aeruginosa exhibited a 2-logio to 3-logio decrease in recoverable cells when adhered to all other surfaces, with the exception of silicone rubber. For S. aureus, 6 hr. irradiation at 25 mW/cm² (540 J/m²) resulted in a maximum of 2 to 3-logio reduction in viability to the organism adhered to cloth, ceramic tile, polypropylene and polystyrene, whereas no antimicrobial activity was detected toward the organism when adhered to silicone rubber. Similarly, light diffusing fiber-delivered 405 nm light had no detectable antimicrobial effect toward baumannii on the tested colonized surfaces at any dose (< 540 J/m²).

Table 3. Antimicrobial effect abiotic surfaces.

Viability Reduction

Polvstvrene Treatment (hr) 25 mW cm² 10 mW cm² 5 mW cm²

Staphylococcus aureus 2 - - -

Pseudomonas aeruginosa

Acinetobacter baumannii

6

Polvoroovlene Treatment (hr) 25 mW cm² 10 mW cm² 5 mW cm²

Staphylococcus aureus 2 - - -

Pseudomonas aeruginosa

Acinetobacter baumannii

4 - 6

Ceramic Tile Treatment (hr) 25 mW cm² 10 mW cm² 5 mW cm²

Staphylococcus aureus 2 - - -

Pseudomonas aeruginosa

6 10³

Acinetobacter baumannii 2

4 - - - 6

Rubber Treatment (hr) 25 mW cm² 10 mW cm² 5 mW cm²

Staphylococcus aureus 2

4 - - - 6

Pseudomonas aeruginosa 2

Acinetobacter baumannii

4 - - - 6

Cloth Treatment (hr) 25 mW cm² 10 mW cm² 5 mW cm²

Staphylococcus aureus 2 - - -

4

6 10³

Pseudomonas aeruginosa 2

4 10⁴ _ _

6 10³ 10³

Acinetobacter baumannii 2 - - - 4

6 _

[0067] Taken together, these results indicate that the light diffusing fiber illumination system may be amenable to decolonizing P. aeruginosa and, to a lesser extent, S. aureus colonizing many abiotic surfaces common to the hospital setting. Yet, effective

decolonization would likely require significantly higher blue light doses than investigated here using either higher power and/or longer exposure times. Conversely, A. baumannii decolonization is not likely to be achievable, which is consistent with the organism's well- established hardiness and ability to tolerate disinfectants and long-term desiccation.

[0068] Comparison of light diffusing fiber-delivered 405 nm light on cultured eukaryotic cells and bacterial pathogens. We next explored the technology's potential as a therapeutic in the context of the host setting. In doing so, it was recognized that establishing blue light's therapeutic index (antimicrobial dose vs. human cell toxicity) is a requisite in characterizing whether the technology is likely to be applicable to treating infection without causing extensive, collateral host cell damage. Thus, human cell cytotoxicity measures were first used to establish a relative safe dose of blue light that displayed limited human cell cytotoxicity. To do so, human colon 38 cells grown to either 50% or 100% confluence and irradiated with various doses of 405 nm light for 4 hr. Cells irradiated at 144 J/cm² cells displayed between 96% and 100% metabolic activity of mock-treated cells, whereas higher doses resulted in significant reduction in cellular metabolism expected of human cell cytotoxic response (not shown). Thus we considered 144 J/cm² irradiation to be the maximum blue light dose tolerated by representative host cells, and set out to evaluate whether blue light could deliver therapeutically relevant antimicrobial activity toward ESKAPE pathogens during planktonic growth at < 144 J/cm².

[0069] Individual wells of a microtiter plate containing MH broth were inoculated with approximately 5 x 10⁴ of each pathogen and then treated with light diffusin fiber-delivered 405 nm light for 1, 2, or 4 hr, equaling approximately 31.3 J/cm², 62.7 J/cm², and 125.4 J/cm², respectively. The number of remaining CFU was enumerated by plating; each experimental condition was evaluated at least three times, and the average reduction in starting CFU was calculated (Table 4). Results revealed two distinct susceptibility phenotypes. S. aureus, S. epidermidis, and S. pyogenes were all highly susceptible to 405 nm irradiation. More specifically, S. pyogenes exhibited a complete loss of cell viability at all doses evaluated (> 31 J/cm²), whereas both S. aureus and S. epidermidis showed a dose dependent antimicrobial effect with a maximum and complete loss of cell viability at 125.4 J/cm², respectively. Conversely, the other organisms tested displayed no significant susceptibility toward 405 nm light during growth in liquid culture conditions. Collectively, these results suggest that the relatively low human cytotoxicity threshold necessitates careful consideration of the potential collateral damage associated with use of 405 nm light in the context of the host environment. Nonetheless, the two organisms that displayed the greatest therapeutic index, S. pyogenes and S. aureus, are predominant causes of bolus impetigo, indicating that a light diffusing fiber 405 nm light delivery or illumination system may represent a safe and attractive strategy for the therapeutic intervention of this serious bacterial skin infection.

Table 4. Antimicrobial effect planktonic growth conditions.

Viability Reduction¹

Organism 31.3 (±8.8) 62.7 (±17.7) 125.4 (±35.4) 250.8 (±70.8)

J/cm² J/cm² J/cm² J/cm²

Staphylococcus aureus

human serum

lung surfactant

Pseudomonas aeruginosa 10¹

Enterococcus faecium

Staphylococcus epidermidis 10¹ m 111 Klebsiella pneumoniae

Acinetobacter baumannii

10¹

Enterobacter sp.

Streptococcus pyogenes i§§ in in Candida albicans

Escherichia coli

¹Grey indicates conditions that elicited > 10² reduction in cell viability; - indicates no measurable effect.

[0070] Characterization of the effects of 405 nm light toward S. aureus disease- associated growth states. In comparison to S. pyogenes, S. aureus has greater propensity to cause a multitude of diverse infections ranging in severity from skin to lung disease and sepsis. Thus as an entree toward assessing the antimicrobial properties of light diffusing fiber 405 nm light delivery in conditions that approximate S. aureus disease settings, we assessed whether the light delivery or illumination system was capable of delivering antimicrobial activity toward the organism during growth in either human serum or mouse lung surfactant.

[0071] Accordingly, approximately 1 x 10⁵ exponential phase S. aureus cells were transferred to individual wells of a microtiter plate containing either 100% human serum or lung surfactant, and exposed to < 144 J/m² 405 nm light. During growth in human serum, 405 nm light delivered via a light diffusing fiber light delivery or illumination system resulted in a dose-dependent reduction in S. aureus viability, resulting in a 1.65 log and 2 log reduction in recoverable CFU when irradiated at 62.7 J/cm² and 125 J/cm², respectively. During growth in mouse lung surfactant, S. aureus appeared to be recalcitrant to low-dose exposures < 125 J/cm², but exhibited complete loss of viability at 250 J/cm² although this dose is expected to be detrimental to host cells (Table 4). Taken together, these results suggest that future 405 nm light delivery strategies may serve as an effective and safe approach to reducing S. aureus burden in the context of systemic infections, but the approach may not be effective/safe in treating lung infections.

[0072] High-intensity blue-violet light (having a wavelength range from about 405 nm to about 470 nm) has been demonstrated in the literature as an effective antimicrobial agent. Most of these studies use LEDs or other flood illumination sources. In these examples, the antimicrobial capabilities of 405 nm light delivered with a laser source and a light diffusing fiber of one or more embodiments. Since such light diffusing fibers deliver light radially along its length in a flexible and thin format, its geometric characteristics may be

advantageous for clinical applications. The light diffusing fiber light delivery or illumination system and 405 nm light displayed significant antimicrobial activity toward the ESKAPE bacterial pathogens, as well as Staphylococcus epidermidis, Streptococcus pyogenes and the fungal pathogen Candida albicans.

[0073] Aspect (1) of this disclosure pertains to a light diffusing optical fiber comprising: a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a thermoplastic polymer coating layer surrounding and contacting the cladding, wherein: the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber; the core comprises glass doped with 300 ppm or more of a hydroxyl material; the cladding comprises glass doped with 300 ppm or more of a hydroxyl material; and the thermoplastic polymer coating layer is doped with a plurality of scattering particles.

[0074] Aspect (2) of this disclosure pertains to the light diffusing optical fiber of Aspect (1), wherein the thermoplastic polymer coating layer comprises a fluorinated polymer material. [0075] Aspect (3) of this disclosure pertains to the light diffusing optical fiber of Aspect (2), wherein the fluorinated polymer material of the thermoplastic polymer coating layer comprises polytetrafluoroethylene, ethylene-tetrafluoroethylene, polyethylene terephthalate, fluorinated ethylene propylene, perfluoroalkoxy alkane, polyetheretherketone, or combinations thereof.

[0076] Aspect (4) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (1) through (3), wherein the plurality of scattering particles comprise A1203, BaS04, Si02, gas voids, or a combination thereof.

[0077] Aspect (5) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (1) through (4), wherein a cross-sectional size of each scattering particle of the plurality of scattering particles is from about 20 nm to about 5000 nm.

[0078] Aspect (6) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (1) through (5), wherein when guided light comprising a wavelength of about 250 nm or greater propagates along the core and a portion of the guided light diffuses through the outer surface, the light diffusing optical fiber comprises a scattering efficiency of from about 0.5 or greater.

[0079] Aspect (7) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (1) through (6), wherein the thermoplastic polymer coating layer comprises an absorbance of about 0.02 or less per 100 μπι of layer thickness at a wavelength of about 240 nm or more.

[0080] Aspect (8) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (1) through (7), wherein the glass of the core comprises silica glass and the glass of the cladding comprises F-doped silica glass.

[0081] Aspect (9) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (1) through (8), wherein the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along the diffusion length of the light diffusing optical fiber to provide a scattering induced attenuation of about 50 dB/km or more. [0082] Aspect (10) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (1) through (9), wherein the plurality of scattering particles of the thermoplastic polymer coating layer are configured such that a difference between the minimum and maximum scattering illumination intensity is less than 50% of the maximum scattering illumination intensity, for all viewing angles between 40 and 120 degrees.

[0083] Aspect (11) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (1) through (10), wherein the plurality of scattering structures comprise gas filled voids.

[0084] Aspect (12) of this disclosure pertains to a light diffusing optical fiber comprising: a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, a primary coating layer surrounding the cladding, and a thermoplastic polymer coating layer surrounding the primary coating layer such that the primary coating layer is disposed between the cladding and the thermoplastic polymer coating layer wherein: the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber; the core comprises glass doped with 300 ppm or more of a hydroxyl material; the cladding comprises glass doped with 300 ppm or more of a hydroxyl material; the primary coating layer comprises a cycloaliphatic epoxy having an absorbance of about 0.04 or less per 100 μπι of layer thickness at a wavelength of about 250 nm or more; and the primary coating layer comprises a plurality of scattering particles doped within the cycloaliphatic epoxy.

[0085] Aspect (13) of this disclosure pertains to the light diffusing optical fiber of Aspect

(12) , wherein the thermoplastic polymer coating layer comprises a fluorinated polymer material.

[0086] Aspect (14) of this disclosure pertains to the light diffusing optical fiber of Aspect

(13) , wherein the fluorinated polymer material of the thermoplastic polymer coating layer comprises polytetrafluoroethylene, ethylene-tetrafluoroethylene, polyethylene terephthalate, fluorinated ethylene propylene, perfluoroalkoxy alkane, or polyetheretherketone, or combinations thereof. [0087] Aspect (15) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (12) through (14), wherein the plurality of scattering particles comprise, A1203, BaS04, silica, fluorinated polymer particles, gas voids, or a combination thereof.

[0088] Aspect (16) of this disclosure pertains to the light diffusing optical fiber of any one of Aspects (12) through (15), wherein when guided light comprising a wavelength of about 375 nm or greater propagates along the core and a portion of the guided light diffuses through the outer surface, the light diffusing optical fiber comprises a scattering efficiency of from about 0.6 or greater.

[0089] Aspect (17) of this disclosure pertains to a light diffusing optical fiber comprising: a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a coating layer surrounding the cladding wherein: the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that when guided light propagates along the core, a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber; the core comprises glass doped with 300 ppm or more of a hydroxyl material; the cladding comprises glass doped with 300 ppm or more of a hydroxyl material; the coating layer is doped with a plurality of scattering particles; and when guided light comprising a wavelength of about 250 nm or greater propagates along the core and a portion of the guided light diffuses through the outer surface, the light diffusing optical fiber comprises a scattering efficiency of from about 0.4 or greater.

[0090] Aspect (18) pertains to the light diffusing optical fiber of Aspect (17), wherein the plurality of scattering particles of the coating layer are configured such that a difference between the minimum and maximum scattering illumination intensity is less than 50% of the maximum scattering illumination intensity, for all viewing angles between 40 and 120 degrees.

[0091] Aspect (19) pertains to the light diffusing optical fiber of Aspect (17) or Aspect (18), wherein the plurality of scattering particles comprise, A1203, BaS04, Si02, fluorinated polymer particles, gas voids, or a combination thereof. [0092] Aspect (20) pertains to the light diffusing optical fiber of any one of Aspects (17) through (19), wherein the coating layer doped with the plurality of scattering particles comprises a thermoplastic polymer coating layer.

[0093] Aspect (21) of this disclosure pertains to an illumination system comprising: a light diffusing optical fiber comprising a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a thermoplastic polymer coating layer surrounding and contacting the cladding, wherein, the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber, either one or both the core and the cladding comprises glass doped with a hydroxyl material; and the thermoplastic polymer coating layer is doped with a plurality of scattering particles; and a light output device configured to be coupled to either one of the first end or the second end of the light diffusing optical fiber, wherein the light output device comprises a light source that generates a light having a wavelength range from about 200 nm to about 500 nm.

[0094] Aspect (22) pertains to the illumination system of Aspect (21), wherein the light output device is coupled to the light diffusing optical fiber.

[0095] Aspect (23) pertains to an illumination system comprising: a light diffusing optical fiber comprising a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, a primary coating layer surrounding the cladding, and a thermoplastic polymer coating layer surrounding the primary coating layer such that the primary coating layer is disposed between the cladding and the thermoplastic polymer coating layer wherein: the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber; the core and the clad comprise glass; the primary coating layer comprises a cycloaliphatic epoxy having an absorbance of about 0.04 or less per

100 μπι of layer thickness at a wavelength of about 250 nm or more; and the primary coating layer comprises a plurality of scattering particles doped within the cycloaliphatic epoxy; and a light output device configured to be coupled to either one of the first end or the second end of the light diffusing optical fiber, wherein the light output device comprises a light source that generates a light having a wavelength range from about 200 nm to about 500 nm.

[0096] Aspect (24) pertains to the illumination system of Aspect (23), wherein the light output device is coupled to the light diffusing optical fiber.

[0097] Aspect (25) pertains to an illumination system comprising: a light diffusing optical fiber comprising a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a coating layer surrounding the cladding wherein: the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that when guided light propagates along the core, a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber; either one of the core and the clad comprises glass doped with 300 ppm or more of a hydroxyl material; the coating layer is doped with a plurality of scattering particles; and when guided light comprising a wavelength of about 250 nm or greater propagates along the core and a portion of the guided light diffuses through the outer surface, the light diffusing optical fiber comprises a scattering efficiency of from about 0.4 or greater; and a light output device configured to be coupled to either one of the first end or the second end of the light diffusing optical fiber, wherein the light output device comprises a light source that generates a light having a wavelength range from about 200 nm to about 500 nm.

[0098] Aspect (26) pertains to the illumination system of Aspect (25), wherein the light output device is coupled to the light diffusing optical fiber.

[0099] For the purposes of describing and defining the present inventive technology, it is noted that reference herein to a variable being a "function" of a parameter or another variable is not intended to denote that the variable is exclusively a function of the listed parameter or variable. Rather, reference herein to a variable that is a "function" of a listed parameter is intended to be open ended such that the variable may be a function of a single parameter or a plurality of parameters. [00100] It is also noted that recitations herein of "at least one" component, element, etc., should not be used to create an inference that the alternative use of the articles "a" or "an" should be limited to a single component, element, etc.

[00101] It is noted that recitations herein of a component of the present disclosure being "configured" in a particular way, to embody a particular property, or function in a particular manner, are structural recitations, as opposed to recitations of intended use. More specifically, the references herein to the manner in which a component is "configured" denotes an existing physical condition of the component and, as such, is to be taken as a definite recitation of the structural characteristics of the component.

[00102] For the purposes of describing and defining the present inventive technology it is noted that the terms "substantially" and "about" are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The terms "substantially" and "about" are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[00103] Having described the subject matter of the present disclosure in detail and by reference to specific embodiments thereof, it is noted that the various details disclosed herein should not be taken to imply that these details relate to elements that are essential components of the various embodiments described herein, even in cases where a particular element is illustrated in each of the drawings that accompany the present description. Further, it will be apparent that modifications and variations are possible without departing from the scope of the present disclosure, including, but not limited to, embodiments defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

[00104] It is noted that one or more of the following claims utilize the term "wherein" as a transitional phrase. For the purposes of defining the present inventive technology, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term "comprising."

Claims

CLAIMS What is claimed is:

1. A light diffusing optical fiber comprising:

a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a thermoplastic polymer coating layer surrounding and contacting the cladding, wherein:

the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber;

the core comprises glass doped with 300 ppm or more of a hydroxyl material; the cladding comprises glass doped with 300 ppm or more of a hydroxyl material; and

the thermoplastic polymer coating layer is doped with a plurality of scattering particles.

2. The light diffusing optical fiber of claim 1 , wherein the thermoplastic polymer coating layer comprises a fluorinated polymer material.

3. The light diffusing optical fiber of claim 2, wherein the fluorinated polymer material of the thermoplastic polymer coating layer comprises polytetrafluoroethylene, ethylene- tetrafluoroethylene, polyethylene terephthalate, fluorinated ethylene propylene, perfluoroalkoxy alkane, polyetheretherketone, or combinations thereof.

4. The light diffusing optical fiber of any one of the preceding claims, wherein the plurality of scattering particles comprise AI2O3, BaS04, S1O2, gas voids, or a combination thereof.

5. The light diffusing optical fiber of any one of the preceding claims, wherein a cross- sectional size of each scattering particle of the plurality of scattering particles is from about 20 nm to about 5000 nm.

6. The light diffusing optical fiber of any one of the preceding claims, wherein when guided light comprising a wavelength of about 250 nm or greater propagates along the core and a portion of the guided light diffuses through the outer surface, the light diffusing optical fiber comprises a scattering efficiency of from about 0.5 or greater.

7. The light diffusing optical fiber of any one of the preceding claims, wherein the thermoplastic polymer coating layer comprises an absorbance of about 0.02 or less per 100 μπι of layer thickness at a wavelength of about 240 nm or more.

8. The light diffusing optical fiber of any one of the preceding claims, wherein the glass of the core comprises silica glass and the glass of the cladding comprises F-doped silica glass.

9. The light diffusing optical fiber of any one of the preceding claims, wherein the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along the diffusion length of the light diffusing optical fiber to provide a scattering induced attenuation of about 50 dB/km or more.

10. The light diffusing optical fiber of any one of the preceding claims, wherein the plurality of scattering particles of the thermoplastic polymer coating layer are configured such that a difference between the minimum and maximum scattering illumination intensity is less than 50% of the maximum scattering illumination intensity, for all viewing angles between 40 and 120 degrees.

1 1. The light diffusing optical fiber of any one of the preceding claims, wherein the plurality of scattering structures comprise gas filled voids.

12. A light diffusing optical fiber comprising:

a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, a primary coating layer surrounding the cladding, and a thermoplastic polymer coating layer surrounding the primary coating layer such that the primary coating layer is disposed between the cladding and the thermoplastic polymer coating layer wherein:

the core comprises glass doped with 300 ppm or more of a hydroxyl material; the cladding comprises glass doped with 300 ppm or more of a hydroxyl material;

the primary coating layer comprises a cycloaliphatic epoxy having an absorbance of about 0.04 or less per 100 μπι of layer thickness at a wavelength of about 250 nm or more; and

the primary coating layer comprises a plurality of scattering particles doped within the cycloaliphatic epoxy.

13. The light diffusing optical fiber of claim 12, wherein the thermoplastic polymer coating layer comprises a fluorinated polymer material.

14. The light diffusing optical fiber of claim 13, wherein the fluorinated polymer material of the thermoplastic polymer coating layer comprises polytetrafluoroethylene, ethylene- tetrafluoroethylene, polyethylene terephthalate, fluorinated ethylene propylene, perfluoroalkoxy alkane, or polyetheretherketone, or combinations thereof.

15. The light diffusing optical fiber of any one of claims 12-14, wherein the plurality of scattering particles comprise, AI2O3, BaS04, silica, fluorinated polymer particles, gas voids, or a combination thereof.

16. The light diffusing optical fiber of any one of claims 12-15, wherein when guided light comprising a wavelength of about 375 nm or greater propagates along the core and a portion of the guided light diffuses through the outer surface, the light diffusing optical fiber comprises a scattering efficiency of from about 0.6 or greater.

17. A light diffusing optical fiber comprising: a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a coating layer surrounding the cladding wherein:

the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that when guided light propagates along the core, a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber;

the coating layer is doped with a plurality of scattering particles; and when guided light comprising a wavelength of about 250 nm or greater propagates along the core and a portion of the guided light diffuses through the outer surface, the light diffusing optical fiber comprises a scattering efficiency of from about 0.4 or greater.

18. The light diffusing optical fiber of claim 17, wherein the plurality of scattering particles of the coating layer are configured such that a difference between the minimum and maximum scattering illumination intensity is less than 50% of the maximum scattering illumination intensity, for all viewing angles between 40 and 120 degrees.

19. The light diffusing optical fiber of claim 17 or claim 18, wherein the plurality of scattering particles comprise, AI2O3, BaS04, S1O2, fluorinated polymer particles, gas voids, or a combination thereof.

20. The light diffusing optical fiber of any one of claims 17-19, wherein the coating layer doped with the plurality of scattering particles comprises a thermoplastic polymer coating layer.

21. An illumination system comprising:

a light diffusing optical fiber comprising a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a thermoplastic polymer coating layer surrounding and contacting the cladding, wherein, the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber, either one or both the core and the cladding comprises glass doped with a hydroxyl material; and the thermoplastic polymer coating layer is doped with a plurality of scattering particles; and a light output device configured to be coupled to either one of the first end or the second end of the light diffusing optical fiber, wherein the light output device comprises a light source that generates a light having a wavelength range from about 200 nm to about 500 nm.

22. The illumination system of claim 21 , wherein the light output device is coupled to the light diffusing optical fiber.

23. An illumination system comprising:

a light diffusing optical fiber comprising a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, a primary coating layer surrounding the cladding, and a thermoplastic polymer coating layer surrounding the primary coating layer such that the primary coating layer is disposed between the cladding and the thermoplastic polymer coating layer wherein: the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber; the core and the clad comprise glass; the primary coating layer comprises a cycloaliphatic epoxy having an absorbance of about 0.04 or less per 100 μπι of layer thickness at a wavelength of about 250 nm or more; and the primary coating layer comprises a plurality of scattering particles doped within the cycloaliphatic epoxy; and

a light output device configured to be coupled to either one of the first end or the second end of the light diffusing optical fiber, wherein the light output device comprises a light source that generates a light having a wavelength range from about 200 nm to about 500 nm.

24. The illumination system of claim 23, wherein the light output device is coupled to the light diffusing optical fiber.

25. An illumination system comprising:

a light diffusing optical fiber comprising a first end, a second end opposite the first end, a core, a cladding surrounding the core, an outer surface, a plurality of scattering structures positioned within the core, the cladding, or both the core and the cladding, and a coating layer surrounding the cladding wherein: the plurality of scattering structures are configured to scatter guided light toward the outer surface of the light diffusing optical fiber such that when guided light propagates along the core, a portion of the guided light diffuses through the outer surface along a diffusion length of the light diffusing optical fiber; either one of the core and the clad comprises glass doped with 300 ppm or more of a hydroxyl material; the coating layer is doped with a plurality of scattering particles; and when guided light comprising a wavelength of about 250 nm or greater propagates along the core and a portion of the guided light diffuses through the outer surface, the light diffusing optical fiber comprises a scattering efficiency of from about 0.4 or greater; and

26. The illumination system of claim 25, wherein the light output device is coupled to the light diffusing optical fiber.