CN114008498A - Optical fiber, lighting device having the same, and method for forming the same - Google Patents
Optical fiber, lighting device having the same, and method for forming the same Download PDFInfo
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- CN114008498A CN114008498A CN202080045899.2A CN202080045899A CN114008498A CN 114008498 A CN114008498 A CN 114008498A CN 202080045899 A CN202080045899 A CN 202080045899A CN 114008498 A CN114008498 A CN 114008498A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0005—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being of the fibre type
- G02B6/001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being of the fibre type the light being emitted along at least a portion of the lateral surface of the fibre
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02295—Microstructured optical fibre
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
- G02B6/0003—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being doped with fluorescent agents
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
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Abstract
According to an embodiment of the present invention, an optical fiber is provided. The optical fiber includes a core region having a scattering structure defined therein, the scattering structure being twisted about a longitudinal axis of the core region, wherein the scattering structure is configured to scatter light propagating in the optical fiber out of the optical fiber. According to further embodiments of the present invention, there is also provided an illumination device having an optical fiber and a method for forming an optical fiber.
Description
Cross Reference to Related Applications
The present application claims priority from singapore patent application No.10201908040X filed on 2019, 8, 30, the contents of which are incorporated herein by reference in their entirety for all purposes.
Technical Field
Various embodiments relate to an optical fiber, an illumination device having the optical fiber, and a method for forming the optical fiber.
Background
Fig. 1 shows a prior art light-diffusing reflective optical fiber 190. The light-diffusing reflective optical fiber 190 includes a solid core 192 (e.g., silica or doped silica), a scattering core 194, and another solid core 196 (e.g., silica or doped silica). The light-diffusing reflective optical fiber 190 extracts the guided light from the optical fiber 190 using a small diffuser (e.g., void) 195. Scatterers 195 are generated during the preform fabrication step based on a chemical vapor deposition process. A preform containing a diffuser 195 is drawn into a light-diffusing reflective fiber 190 with a coating (or jacket) 198 (e.g., a low index polymer or glass) to provide physical strength and light guidance (the jacket 198 is not shown in side view for clarity). Therefore, chemical vapor deposition processes are essential to generate the scattering mechanism and to implement the diffusely reflecting optical fiber 190. However, such chemical vapor deposition processes are expensive and complex.
Disclosure of Invention
The invention is defined in the independent claims. Further embodiments of the invention are defined in the dependent claims.
According to one embodiment, an optical fiber is provided. The optical fiber may include a core region having a scattering structure defined therein, the scattering structure being twisted about a longitudinal axis of the core region, wherein the scattering structure is configured to scatter light propagating in the optical fiber out of the optical fiber.
According to one embodiment, a lighting device is provided. The lighting device may include a light source configured to provide light, and an optical fiber described herein configured to receive the light for propagation in the optical fiber.
According to one embodiment, a method for forming an optical fiber is provided. The method may include twisting a scattering structure in a core region of the optical fiber about a longitudinal axis of the core region, wherein the scattering structure is configured to scatter light propagating in the optical fiber out of the optical fiber.
Drawings
In the drawings, like reference numerals generally refer to like parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which:
fig. 1 shows a schematic view of a prior art light-diffusing reflective optical fiber.
Fig. 2A shows a schematic side view of an optical fiber according to various embodiments.
Fig. 2B shows a schematic view of a lighting device according to various embodiments.
Fig. 2C illustrates a method for forming an optical fiber according to various embodiments.
FIG. 3A shows a schematic diagram of an optical fiber having a twisted structure, in accordance with various embodiments.
Fig. 3B shows a schematic diagram of an optical fiber having a variable pitch torsional scattering structure, in accordance with various embodiments.
Fig. 3C shows a schematic diagram of an optical fiber having a torsional scattering structure and a scattering agent, in accordance with various embodiments.
Fig. 3D illustrates a schematic diagram of an optical fiber having a torsional scattering structure and a spectral modifier, in accordance with various embodiments.
Figure 3E illustrates a schematic diagram of an optical fiber having an external kink, in accordance with various embodiments.
Fig. 4A to 4J show cross-sectional views of various structures that satisfy the lateral refractive index and/or geometry characteristics for defining an optical fiber having a torsional scattering structure.
FIG. 5 shows a schematic diagram illustrating a scattering angle distribution of an optical fiber according to various embodiments.
Fig. 6A and 6B show schematic diagrams illustrating a manufacturing process for manufacturing a radiation fiber having a cross-sectional feature that is twisted along a fiber axis, in accordance with various embodiments.
Fig. 7 shows a microscope image of the fabricated optical fiber. The scale mark represents 20 μm.
Fig. 8A shows a schematic diagram illustrating an apparatus for fiber optic illumination, while fig. 8B shows a photograph of the illuminated fibers of various embodiments.
Detailed Description
The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the present invention. The various embodiments are not necessarily mutually exclusive, as some embodiments may be combined with one or more other embodiments to form new embodiments.
Embodiments described in the context of one of the methods or apparatuses are approximately valid for the other method or apparatus. Similarly, embodiments described in the context of methods are approximately valid for the apparatus, and vice versa.
Features described in the context of one embodiment may be correspondingly applicable to the same or similar features in other embodiments. Features described in the context of one embodiment may be correspondingly applicable to other embodiments, even if the features are not explicitly described in these other embodiments. Furthermore, additions and/or combinations and/or substitutions described for features in the context of one embodiment may be correspondingly adapted for the same or similar features in other embodiments.
In the context of various embodiments, the phrase "at least substantially" may include "exactly" and reasonable differences.
In the context of various embodiments, the term "about" as applied to numerical values encompasses precise values and reasonable differences.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
As used herein, a phrase in the form of "at least one of a or B" may include a or B, or both a and B. Accordingly, a phrase comprising other listed items in the form of "at least one of a or B or C" may include any and all combinations of one or more of the associated listed items.
Various embodiments may provide a twisted optical fiber having a twisted or helical path for outwardly scattering light.
Various embodiments may provide a design and manufacturing method of a radiation fiber. Radiation fibers may find interesting applications in decoration and lighting in small areas, such as consumer electronics, automotive, architectural and medical industries, to name a few, where bulky lighting devices cannot be arranged. The techniques disclosed herein may provide a method for obtaining one or more optical radiation fibers that provide easy manipulation of light scattering intensity over a distance. The radiation fiber can be realized by a simple and low-cost manufacturing route, and can also allow post-manufacturing control of the scattering intensity.
In contrast to known optical fibers, such as the light-diffusing reflective optical fiber 190 (FIG. 1), the techniques disclosed herein do not involve expensive and complex chemical vapor deposition processes. The techniques disclosed herein may provide an optical fiber having a radiation mechanism that utilizes a twisted structure. In various embodiments, the twisted structure or light pipe structure may have cross-sectional geometry and/or refractive index features that allow the twist to be observed when viewed laterally. The light guide structure (or optical fiber) may have a core of transparent material and a surrounding cladding of lower refractive index material that scatters light when twisted about the axis of the light guide structure (or optical fiber).
Fig. 2A shows a schematic side view of an optical fiber 200 according to various embodiments. The optical fiber 200 includes a core region 202 having a scattering structure 204 defined therein, the scattering structure 204 being twisted about a longitudinal axis 205 of the core region 202, wherein the scattering structure 204 is configured to scatter light (represented by solid arrows 222) propagating in the optical fiber 200 out of the optical fiber 200 (externally scattered light represented by open arrows 223).
In other words, an optical fiber 200 may be provided, and the optical fiber 200 may provide the external scattered light 223. Such optical fibers 200 may provide illumination for the surrounding environment. The optical fiber 200 may comprise an (optical) core region (for light propagation or transmission) within which the scattering structure 204 is defined. The scattering structure 204 may be twisted (or wound), for example in a helical manner, about a longitudinal axis 205 of the core region 202. Thus, the scattering structures 204 may extend longitudinally (either lengthwise or in the direction of the length of the core region 202 or along the length of the core region 202). Longitudinal axis 205 may include or may refer to any axis extending longitudinally, including, for example, a central axis of core region 202. The scattering structure 204 may scatter (or emit) light 222 propagating in the optical fiber 200 (or through the optical fiber 200) out of the optical fiber to provide externally scattered light 223. In some embodiments, the twisted scattering structure 204 may have multiple loops along the length of the core region 202.
The core region 202 may be configured to transmit light. The light 222 may propagate in the core region 202 and may then be scattered out (e.g., light 223) when the propagating light 222 encounters the scattering structure 204. For example, the light 222 may be scattered as the light 222 encounters the interface between the core region 202 and the scattering structure 204.
In various embodiments, the light 222 may not propagate in the scattering structure 204, for example, when the scattering structure 204 comprises air or may be an air scattering structure 204, or when the refractive index of the scattering structure 204 is lower than the refractive index of the core region 202. This may mean that the scattering structure 204 may not be suitable for guiding light in the scattering structure, or that the scattering structure 204 may not be a light transmitting structure. In other embodiments, the light 222 may propagate in the scattering structure 204 with a higher index of refraction than the core region 202. This may mean that light may be guided in the scattering structure 204 and that the scattering structure 204 may scatter light outwards due to the torsional properties of the scattering structure 204.
The core region 202 may be solid, e.g., completely solid. The core region 202 may comprise a high (refractive) index material. By way of non-limiting example, the core region 202 may comprise glass or a polymer.
In various embodiments, the scattering structure 204 may be disposed within the core region 202, or may be integral with the core region 202, or may be part of the core region 202. Accordingly, a twisted scattering structure 204 is provided within the core region 202 for scattering light 222 outward.
The direction of twist of the scattering structure 204 may be along the longitudinal direction of the core region 202. The scattering structure 204 may follow a curved twisted (e.g., helical) path or a curved shaped helical path. However, it should be understood that other shapes may be possible, for example, the scattering structure 204 may follow a twisted (e.g., helical) path that is a square helical path.
The optical fiber 200 may be a radiation fiber, which means that light 222 propagating in the optical fiber 200 may be emitted from the optical fiber 200 in the form of externally scattered light 223.
It should be understood that more than one scattering structure 204 may be defined in the core region 202. In other words, the core region 202 may include a plurality of scattering structures 204 defined therein, each scattering structure 204 extending longitudinally and twisted about a longitudinal axis 205 of the core region 202, and each scattering structure 204 configured to scatter light 222 propagating in the optical fiber 200 out of the optical fiber 200. Each scattering structure 204 may be spaced apart from another scattering structure 204.
In various embodiments, the scattering structures 204 may have a refractive index that is different from the refractive index of the core region 202. The scattering structures 204 may be higher or lower index structures than the core region 202.
The scattering structure 204 may comprise a solid material.
In various embodiments, void regions may be defined in the core region 202, which define the scattering structures 204. In other words, the scattering structure 204 may include or may be a void region. In this manner, the optical fiber 200 may include void regions or spaces in the core region 202 to define the scattering structures 204. The void region may be a hollow passage, e.g., a hollow passage having air therein. The void region may be an air region or an air channel.
The optical fiber 200 may also include a material filled in the void region such that the refractive index of the scattering structure 204 may be different from the refractive index of the core region 202. The material may be a solid material or a fluid (e.g., an index fluid), such as a high index material or a low index material. Thus, the refractive index of the scattering structure 204 may be higher or lower than the refractive index of the core region 202.
In various embodiments, the scattering structures 204 may be laterally offset from the central axis (or center) of the core region 202. It is understood that the central axis may be aligned with a center point or central region of the core region 202. The transverse direction of the core region 202 may be perpendicular to the longitudinal direction of the core region 202. The scattering structures 204 may be offset from the central axis in a radial direction of the core region 202.
In various embodiments, the scattering structures 204 may be twisted about the longitudinal axis 205 by an at least substantially constant lateral offset (T) (over the length throughout the core region 202 or along a portion of the length of the core region 202). This may mean that the lateral offset or spacing between the scattering structures 204 and the central axis of the core region 202 may be substantially constant or remain substantially the same at any point along the length of the core region 202. In other words, each point on the scattering structure 204 may be equidistant from the central axis of the core region 202. Thus, the scattering structures 204 may extend longitudinally with a constant lateral offset (T).
In various embodiments, the scattering structures 204 may be twisted about the longitudinal axis 205 by a variable lateral offset (T) (either throughout the length of the core region 202 or along a portion of the length of the core region 202). This means that the lateral offset (T) of the scattering structures 204 with respect to the central axis of the core region 202 varies along the longitudinal direction of the core region 202.
In various embodiments, the scattering structure 204 may be twisted (e.g., twisted in a helical manner) about the longitudinal axis 205 with an at least substantially constant period (or pitch P) of twist (over the length throughout the core region 202). Thus, the scattering structure 204 may extend longitudinally with a constant period of twist.
In various embodiments, the scattering structure 204 may be twisted (e.g., twisted in a helical manner) with a variable period of twist (or pitch P) about the longitudinal axis 205. Thus, the scattering structures 204 may extend longitudinally with a variable period of twist. This may mean that at one section of the fiber 200, there may be a greater number of loops of the torsional scattering structure 204 than another section of the fiber 200. The twist period may for example decrease along a length portion of the core region 202 in a longitudinal direction away from at least one input region of the optical fiber 200. The reduction in twist period over a section of the fiber 200 results in an increase in the number of loops of the scattering structure 204 over the section of the fiber 200. By reducing the twist period, a more uniform illumination may be provided over the length of the optical fiber 200 along a portion of the length of the core region 202. The input area of the optical fiber 200 may refer to an area where light 222 may be provided or fed into the optical fiber 200 for propagation. The input region of the optical fiber 200 may include an end region or end face of the optical fiber 200. By way of non-limiting example, the twist period may decrease in the longitudinal direction toward a central region or portion of the optical fiber 200, or toward the output region of the optical fiber 200.
In various embodiments, the size (e.g., cross-sectional dimension) of the scattering structures 204 (over the length throughout the core region 202, or along a portion of the length of the core region 202) may be variable. This means that the size of the scattering structures 204 varies along the longitudinal direction of the core region 202.
In various embodiments, the perimeter (or outer surface) of the core region 202 may have a non-circular (cross-sectional) shape that may be twisted (in a helical manner) about the longitudinal axis 205 to define the scattering structure 204. This may mean that the non-circular shape may be longitudinally twisted about longitudinal axis 205 along the length of core region 202. In the context of various embodiments, a non-circular shape may refer to a shape that is not a complete circle. The perimeter may have one or more portions that may be curved or may resemble portions of a circle, but the perimeter as a whole is not a complete circle. The perimeter may have one or more portions that may be curved and one or more portions that may be linear or straight. The perimeter may have, but is not limited to, an elliptical shape, an oval shape, a rectangular shape, or a triangular shape.
In various embodiments, the optical fiber 200 may comprise a (longitudinal) structure defined in the core region 202, wherein the perimeter of the structure may have a non-circular shape that may be twisted (in a helical manner) about the longitudinal axis 205 to define the scattering structure 204. The (longitudinal) configuration may be defined in the center of the core region 202, or may be defined in an off-center location. The (longitudinal) structure may or may not be a light transmitting structure, depending on the refractive index of the structure compared to the refractive index of the core region.
In various embodiments, at least a portion of the optical fiber 200 may be twisted externally (in a helical manner). This may mean that the entire portion of the optical fiber 200 itself may be arranged or defined in the form of a (helical) twist. The external twist of the fiber 200 may be temporarily or permanently induced or generated. In various embodiments, the entire fiber 200 may be twisted externally (in a helical manner), meaning that the entire fiber 200 may be arranged, bent, or crimped in a (helical) twisted manner.
The optical fiber 200 may further comprise an (outer) cladding (or cladding region or jacket) arranged around the core region 202. The cladding may comprise a low index material, or at least the refractive index of the cladding may be lower than the refractive index of the core region 202. As non-limiting examples, the cladding may comprise glass or polymer.
The optical fiber 200 may also include a plurality of scattering agents configured to scatter light 222 propagating in the optical fiber 200 out of the optical fiber 200. This may mean that the scattering agent may interact with the light 222 and scatter the light 222 out of the optical fiber 200 as external scattered light 223. The scattering agent may be used to adjust the scattering intensity of the optical fiber 200. The scattering agent may be disposed in the core region 202 and/or the cladding of the optical fiber 200.
The optical fiber 200 may also include a plurality of spectral modifiers configured to emit a composite light of different wavelengths in response to interaction with the light 222 propagating in the optical fiber 200. This means that the combined light and light 222 have different wavelengths (or colors or chromatograms). The combined light may be emitted from the optical fiber 200 as external scattered light 223. For example, the spectral modifier may absorb light 222 and, in response to the absorption, generate a resultant light of a different wavelength than the wavelength of the propagating light 222. In this manner, the spectral modifier can change the wavelength (or spectrum) of light scattered out of the optical fiber 200. The spectral modifier may comprise a phosphor and/or an (optical) absorber. A spectral modifier may be disposed in the core region 202 and/or the cladding of the optical fiber 200.
In the context of various embodiments, it should be understood that the term "twist" or "twisted" may include any twisting structure or path, including, but not limited to, twists having a constant pitch, twists having a variable pitch, twists in a forward direction, twists in a reverse direction, twists in a clockwise direction, twists in a counter-clockwise direction, or any combination thereof. As a non-limiting example, one section of twist may have a constant pitch, while another section of twist may have a different constant or variable pitch. As a further non-limiting example, one section of the structure may be twisted in a forward direction while another section of the structure may be twisted in an opposite direction (or have a clockwise twist and a counter-clockwise twist). The change of direction may occur multiple times. The change in direction may occur periodically or randomly.
In the context of various embodiments, the term "twist" may include reference to "helical twist. This may mean, for example, that the scattering structure 204 may be twisted in a helical manner about the longitudinal axis 205 of the core region 202.
Fig. 2B shows a schematic diagram of a lighting device 220 according to various embodiments. The lighting device 220 comprises a light source 221 configured to provide light (represented by arrow 222 b), and an optical fiber 200b, the optical fiber 200b being configured to receive the light 222b for propagation in the optical fiber 200b (or through the optical fiber 200 b). The optical fiber 200b may be optically coupled to a light source 221. The optical fiber 200b may be configured to receive light 222 b. The optical fiber 200b may be as described in the context of the optical fiber 200 of fig. 2A. In various embodiments, the light source 221 may be a laser, such as a laser diode.
Fig. 2C illustrates a method 230 for forming an optical fiber, according to various embodiments. In the method, a scattering structure is twisted about a longitudinal axis of a core region in the core region of the optical fiber, wherein the scattering structure is configured to scatter light propagating in the optical fiber out of the optical fiber.
It should be understood that the description in the context of the optical fiber 200 may apply accordingly to the method 230 for forming an optical fiber.
Various embodiments or techniques will now be described in further detail.
As a non-limiting example, a glass rod or preform having an off-center scattering structure or core (e.g., air holes) may be used to create cross-sectional geometry and/or refractive index features. Such rods can be drawn into optical fibers having a scattering structure or core that is twisted along the axis of the fiber to form a transversely visible twisted structure. Fig. 3A shows a schematic diagram of an optical fiber 300 having a twisted scattering structure (or helical scattering core) 304 (e.g., air channel) according to various embodiments. The optical fiber 300 may include a solid core 302 (e.g., glass or polymer) within which solid core 302 a torsional scattering structure 304 may be defined, the torsional scattering structure 304 having refractive index and/or geometric shape characteristics across a cross-section of the optical fiber 300. It should be understood that "twisting" may refer to any rotation of an element about its axis (e.g., the longitudinal axis of the element in an untwisted state) or about the longitudinal axis of a structure in which the twisting element is defined, including but not limited to variable twisting, reverse direction twisting, or a random combination of various forms of twisting. The optical fiber 300 may also include a coating (or jacket) 306 (e.g., a low index polymer or glass). For clarity, the sheath 306 is not shown in side view.
Parameters associated with the helical structure 304 may include pitch (or twist period) P and lateral offset T. The pitch P may refer to the distance between two consecutive points on the helical structure 304 that are aligned with each other along an axis parallel to the longitudinal axis of the optical fiber 300. The lateral offset T may refer to the distance of the spiral structure 304 from the center or central axis of the optical fiber 300 in the vertical direction. The pitch P may be constant or variable along the length of the fiber 300. The lateral offset T may be constant along the length of the optical fiber 300. Fig. 3B shows a schematic view of an optical fiber 300B having a torsional scattering structure 304B, wherein the torsional scattering structure 304B has a variable pitch. As can be observed, the period of the twisted structure 304b extends from P as the structure 304b extends longitudinally within the core region 302b1Decrease to P2. It should be understood that the optical fiber 300b may have an outer cladding or jacket.
Fig. 3C shows a schematic diagram of an optical fiber 300C, the optical fiber 300C having a torsional scattering structure 304C defined in a core region 302C of the optical fiber 300C. The optical fiber 300c may also include a plurality of scattering agents (represented by filled circles 340 c) for scattering light in the optical fiber 300c out of the optical fiber 300 c. It should be understood that the optical fiber 300c may have an outer cladding or jacket. Additionally or alternatively, a scattering agent may be provided in the outer cladding.
Fig. 3D shows a schematic diagram of an optical fiber 300D, the optical fiber 300D having a torsionally dispersive structure 304D defined in a core region 302D of the optical fiber 300D. The optical fiber 300d may also include a plurality of spectral modifiers (represented by open circles 340 d) to modify the spectrum of the externally scattered light. The spectral modifier 340d may comprise a phosphor and/or an (optical) absorber. It should be understood that the optical fiber 300d may have an outer cladding or jacket. Additionally or alternatively, a spectral modifier may be provided in the outer cladding.
A non-limiting example of scattering operation will now be described with reference to the optical fiber 300 of fig. 3A. When a suitable preform is drawn into an optical fiber by spinning, the introduced eccentric helical structure 304 may be a low index region or a high index region that satisfies the desired refractive index and/or geometry cross-sectional characteristics that can produce observable twist. As non-limiting examples, the spiral structure 304 may be an air channel or a channel filled with a low index material or fluid or a high index material or fluid. The scattering intensity of the helical structure 304 may vary depending on at least one of the number, size, position (or offset T), or twist pitch (P) of the introduced scattering structures (e.g., scattering agents). In the context of various embodiments, the size of the spiral structure 304 may be between about 1/50 and about 1/2 of the fiber diameter, the offset may be between about 1/100 and about 1/2 of the fiber diameter, the pitch may be between about 1mm and about 100mm, and the number of scattering structures may be between about 1 and about 100. For example, a larger lateral offset T and/or a shorter pitch P may cause stronger scattering. In practice, twists with variable pitch may be constructed or defined along the fiber, which may be used to create fibers with one or more higher or lower scattering regions, as desired. For example, the introduced variable pitch along the length of the fiber may control the degree of longitudinal scattering, e.g., to compensate for the natural attenuation of light intensity along the length. In this way, more uniform illumination may be provided across the entire fiber. As non-limiting examples, a stronger scattering region (e.g., having a shorter pitch P) may be defined towards the light outcoupling end region of the optical fiber, and a weaker scattering region (e.g., having a longer pitch P) may be defined in a longitudinal direction away from the light outcoupling end region (e.g., towards the light entrance end of the optical fiber). As will be described further below, variable pitch can be achieved by controlling the spin speed during the fiber draw stage.
It should be appreciated that in addition to the built-in twist path of the cross-sectional features described above, which may be introduced during the fiber draw process, additional twist may be introduced during the fiber post-fabrication process to adjust the degree of scattering. Thus, the radiation fibers of various embodiments may allow post-processing, such as external twisting, to modify or mitigate the scattering angle and/or scattering intensity. Post-treatment may be applied to the entire fiber length or to desired local sections. It will also be appreciated that permanent twist may be imparted to the optical fiber by local heating (e.g., heating at a particular location of the optical fiber) to the extent that viscous flow of the fiber material may occur while applying twist, such that once the heating is removed and the fiber material cools, the twist may be condensed. Fig. 3E shows a schematic of an optical fiber 300E having an external twist that may be induced temporarily or permanently as described above. The optical fiber 300e may include a core region 302e, which core region 302e may be twisted (in a helical manner) about an axis 342 (e.g., a longitudinal axis of the optical fiber 300e when in an untwisted state). Each point on the fiber 300e may be equidistant from the axis 342. For ease of understanding, the torsional scattering structures defined in the core region 302e are not shown. It should be understood that the optical fiber 300e may have an outer cladding or jacket.
It should be understood that two or more of the embodiments shown in fig. 3A-3E may be combined together in any manner.
A number of non-limiting examples of structures having cross-sectional geometries and/or refractive index features are shown in fig. 4A-4J. It will be appreciated that when preforms having the cross-sectional geometry and/or refractive index characteristics shown are drawn into respective optical fibers, for example using spinning, these structures may form a twist in the respective optical fibers that is recognizable or observable along the fiber axis when viewed transversely. It should be understood that the designs shown in fig. 4A-4J may not be mutually exclusive to each other.
Referring to fig. 4A-4C and 4I-4J, the black regions 454A, 454b, 454C, 454I, 454J represent regions or structures having a different index of refraction (e.g., a higher or lower index of refraction) as compared to the surrounding material 450a, 450b, 450C, 450I, 450J, which defines the core region material of the fiber as it is drawn. The structures 454a, 454b, 454c, 454i, 454j may be individual air holes and/or include an index material for providing a desired index of refraction.
Structures having non-circular cross-sectional shapes may be provided. For example, the structure 454a may be a straight line (or a rectangle) extending in a radial direction, but any line that may extend in any direction and/or have any suitable shape may be suitably employed, such as a zig-zag line, a curved line, and the like. The structures 454i may have a square cross-section, while the structures 454j may have an elliptical or oval cross-section. However, other non-circular shapes may be provided, such as rectangular, triangular or any suitable (polygonal) shape. While the structures 454i, 454j are shown positioned at the center of the respective surrounding material 450i, 450j, it should be understood that the structures 454i, 454j may be positioned at any off-center location.
The structures 454b, 454c have a circular shape, but may take any suitable (polygonal) shape. The structures 454b may be coaxially aligned and opposed to each other. Structures 454c may be aligned symmetrically or asymmetrically with respect to each other.
The structures 454a, 454b, 454c, 454i, 454j define scattering structures when spun into an optical fiber. When spun into an optical fiber, the structures 454a, 454b, 454c are longitudinally twisted along the fabricated optical fiber to define scattering structures. When spun into an optical fiber, the perimeter of the structures 454i, 454j having a non-circular shape are longitudinally twisted along the fabricated optical fiber to define scattering structures. In the fabricated optical fiber, light may propagate in the core with the materials 450a, 450b, 450c, 450i, 450j and be scattered as it encounters the twisted structures defined by the structures 454a, 454b, 454c, 454i, 454 j.
Preforms having a perimeter that is non-circular in shape may be used, as shown in the non-limiting examples of fig. 4D-4H. Preforms having a structure or shape in which circular symmetry is broken may be used, for example, as shown in fig. 4D and 4E. Non-circular shapes, such as elliptical or oval as shown in FIG. 4F, rectangular as shown in FIG. 4G, and triangular as shown in FIG. 4H, may also be used. However, it should be understood that any suitable (polygonal) shape may be provided. In optical fibers spun from preforms having the structures shown in fig. 4D-4H, light may propagate in the core with materials 450D, 450e, 450f, 450g, 450H and may be scattered as the light encounters the fiber air or fiber polymer jacket interface (e.g., intersects the twisted structure of the fiber).
The preform materials 450a, 450b, 450c, 450d, 450e, 450f, 450g, 450h, 450i, 450j may comprise any transparent glass or polymer material that can be drawn into an optical fiber. The drawn fiber may be clad with an additional outer layer to serve as a cladding layer to construct a core and cladding structure (or to implement a waveguide structure) for guiding light. If the structure is made of a flexible polymeric material and is directly exposed to air, the outer layer may not be needed.
It should be understood that two or more of the embodiments shown in fig. 3A-3E and 4A-4J may be combined together in any manner.
In addition to the scattering intensity, various embodiments may allow modification of the scattering angle distribution. For example, referring to FIG. 5, FIG. 5 illustrates a scattering angle distribution of an optical fiber 500 having a helical scattering structure 504 by providing an incident light 530 to the optical fiber 500 at a backscattering angle θbIn contrast, the scattering is in the forward direction by a forward scattering angle θfAnd may be stronger. Forward scattering angle thetafMay be modified or mitigated by adjusting one or more design parameters (e.g., pitch P and/or offset T). For example, short pitch and large offset may increase θb。
The radiation fibers of the various embodiments can be manufactured without involving the use of expensive and complex chemical vapor deposition processes. An exemplary method of manufacturing such an optical fiber will now be described. Referring to fig. 6A, glass rod 650 may be drilled to form or define holes or voids 654 along rod 650. The introduced holes 650 may provide lateral geometry and/or refractive index features. Additional high or low index materials may be inserted or introduced into the holes 654. The prepared preform 656 can be drawn into an optical fiber in a draw tower by heating in a furnace until the material becomes viscous. During the drawing process, referring to fig. 6B, preform 656 can be rotated (spinning motion represented by arrow 658) at a desired rate to produce optical fiber 600 having a torsional scattering structure defined by void structures 654. The spin rate and/or the draw speed may determine the pitch P of the twisted structure. Higher spin rates may result in shorter pitches and therefore stronger scattering, while lower spin rates may result in longer pitches and therefore weaker scattering. If the spin rate is varied during fiber draw, the resulting fiber 600 can have a variable pitch along the length of the fiber 600. Thereby, the scattering intensity becomes variable, which may help to achieve a more uniform illumination along the fiber 600. During the drawing process, a pressure control (represented by arrow 659) may be applied to establish a positive pressure in the gas holes 654 to prevent the holes 654 from closing under the action of surface tension. As a non-limiting example, as one form of pressure control, air may be supplied into holes 654 to prevent holes 654 from closing or collapsing.
During fiber draw, a low index polymer coating (e.g., a UV curable fluoroacrylate or a thermally curable silicone) may be applied to provide light guidance and physical strength to the fiber. Additionally, a scattering body or agent may be incorporated into the polymer resin used to form the cladding (or outer jacket) to adjust the scattering intensity. Color tuning may also be provided, which may include phosphors or absorbers that may modify the spectrum of scattered light. For example, the phosphor or the absorber may be provided in a (polymer) cladding.
It should be understood that preforms having structures or features as shown in fig. 4A-4J may be spun during fiber draw to produce fibers having twisted (e.g., helically twisted) scattering structures.
An alternative to the above-described drilling process is to use a stack-draw technique to build the cross-sectional geometry and/or refractive index features. Capillary tubes or doped silica rods with index lowering or raising elements may be stacked together with the silica rods to form a structure as a bundle. A build-up may be inserted into the jacket tube to hold the structure during fiber draw to form the preform. The preform may be spun during drawing to form a radiation fiber having a torsional scattering path defined by a capillary or a doped silica rod index lowering or raising element.
A radiation fiber made of silica is manufactured via the manufacturing process described with respect to fig. 6A and 6B, wherein the radiation fiber contains twisted air holes or channels, thus satisfying the above-described cross-sectional characteristics twisted along the fiber axis. A low index acrylate polymer coating is applied during the drawing process that can provide a nominal 0.45 Numerical Aperture (NA) for light injected into one end of the optical fiber and guided along the length of the optical fiber. A microscope image of a cross-section of the fabricated optical fiber 700 is shown in fig. 7. The fabricated radiation fiber 700 has a core region 702 with air holes 704, the air holes 704 being off-center and offset from the center of the fiber 700 by approximately 29 μm. Along the length of the fiber 500, the air holes 704 follow a twisted path with a 1cm pitch along the fiber 700 in order to scatter the light from the fiber 700. As shown in fig. 7, the diameter of the fiber 700 is measured to be about 220 μm and the size of the hole 704 is about 33 μm.
To demonstrate the scattering properties, the fabricated fiber can be illuminated, for example, using a blue Laser Diode (LD). Referring to fig. 8A, fig. 8A shows a schematic diagram of an apparatus 870 for fiber optic illumination, illustrating an illumination device having a light source (e.g., blue LD 872) and a radiation fiber 800, blue LD 872 may be butt-coupled to fiber 800. Blue light coupled into the fiber 800 propagates along the length and may be scattered by torsional scattering structures within the fiber 800. The output end of fiber 800 may be connected to another LD or mirror (M)874 to send light back toward the input end, making the illumination more uniform and enhancing the radiation intensity. Fig. 8B shows a photograph of a blue illumination fiber 800B using an 18 meter long radiation fiber.
If desired, the scattering intensity may be adjustable, meaning that the scattering intensity is made stronger or weaker by applying an external twist to the fiber 800, for example by clamping the fiber with external equipment and rotating the clamps relative to each other. Additionally or alternatively, the fiber 700 may be given a permanent twist by local heating to the point where viscous flow can occur while applying the twist together such that the twist is coagulated. Thus, the scattering intensity may become adjustable at any desired location along the fiber 800.
Design, fabrication, and illustration of a radiation fiber having a torsional scattering structure that is not cylindrically symmetric (e.g., in the form of a helical structure) is described herein. The techniques disclosed herein may provide a way to scatter light from an optical fiber according to one or more of the following.
(i) A light guide structure (or optical fibre) having a core of transparent material and a surrounding cladding of lower refractive index material which, when twisted about the axis of the light guide structure (or optical fibre), scatters light.
(ii) A twisted light guide fiber having one or more of:
an optical fiber having a cross-sectional geometry and/or refractive index characteristics such that when viewed laterally allows for viewing of twist;
here, twist may be understood to refer to any rotation of the fiber about its axis, including variable twist, reverse direction twist, or a random combination of various forms of twist;
twist with variable pitch can be used to create fibers with higher or lower dispersion regions at will;
a light guide fiber may refer to a light guide having a length substantially exceeding its width;
the optical fiber may include one or more transparent materials, such as silica, composite glass, or polymers;
the optical fiber may include a core and a cladding region to form a waveguide;
the optical fiber may include a mixed low index region and high index region;
or a single transparent material having a non-cylindrically symmetric cross-section, wherein the feature creating the non-cylindrical symmetry is a gas such as air or a vacuum or a solid such as one or more transparent materials;
it is to be understood that the optical fibers of various embodiments may be used with other forms of scattering or spectral modifiers, such as may be embedded in glass regions within the optical fiber or in coatings of low index or high index polymers, where the glass or polymer may contain at least one of scatterers, phosphors, or absorbers to change the intensity of scattering and/or change the color of the scattered light.
(iii) An apparatus for distributed lighting based on a light source and a radiation fiber, having one or more of:
the illumination intensity and distribution can be controlled by varying the twist pitch permanently introduced during manufacture;
the illumination intensity and angle distribution can be adjusted by externally twisting the manufactured optical fiber;
the permanent twist may be imparted to the fiber by local heating to the point that viscous flow can occur while applying the twist together so that the twist is coagulated.
While the present invention has been particularly shown and described with reference to particular embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is, therefore, indicated by the appended claims, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (18)
1. An optical fiber, comprising:
a core region comprising scattering structures defined therein, the scattering structures being twisted about a longitudinal axis of the core region,
wherein the scattering structure is configured to scatter light propagating in the optical fiber out of the optical fiber.
2. The optical fiber of claim 1, wherein the scattering structure has a refractive index different from a refractive index of the core region.
3. The optical fiber according to claim 1 or 2, wherein a void region is defined in the core region, the void region defining the scattering structure.
4. The optical fiber of claim 3, further comprising a material filled in the void region such that the refractive index of the scattering structure is different from the refractive index of the core region.
5. The optical fiber according to any of claims 1 to 4, wherein the scattering structure is laterally offset from a central axis of the core region.
6. The optical fiber of claim 5, wherein the scattering structure is twisted about the longitudinal axis at least a substantially constant lateral offset.
7. The optical fiber of claim 5, wherein the scattering structure is twisted about the longitudinal axis with a variable lateral offset.
8. The optical fiber according to any of claims 1 to 7, wherein said scattering structure is twisted around said longitudinal axis with an at least substantially constant period of twist.
9. The optical fiber according to any of claims 1 to 7, wherein the scattering structure is twisted around the longitudinal axis with a variable twist period.
10. The optical fiber of claim 9, wherein the twist period decreases along a length portion of the core region in a longitudinal direction away from at least one input region of the optical fiber.
11. The optical fiber according to any of claims 1 to 10, wherein the size of the scattering structure is variable.
12. The optical fiber according to any of claims 1 to 11, wherein a perimeter of said core region has a non-circular shape that is twisted about said longitudinal axis to define said scattering structure.
13. The optical fiber of any of claims 1 to 11, comprising a structure defined in the core region, wherein a perimeter of the structure has a non-circular shape that is twisted about the longitudinal axis to define the scattering structure.
14. The optical fiber of any of claims 1 to 13, wherein at least a portion of the optical fiber is twisted externally.
15. The optical fiber according to any one of claims 1 to 14, further comprising a plurality of scattering agents configured to scatter light propagating in said optical fiber out of said optical fiber.
16. The optical fiber according to any one of claims 1 to 15, further comprising a plurality of spectral modifiers configured to emit a composite light of different wavelengths in response to interaction with light propagating in the optical fiber.
17. An illumination device, comprising:
a light source configured to provide light; and
the optical fiber of any one of claims 1 to 16, configured to receive light for propagation in the optical fiber.
18. A method for forming an optical fiber, comprising twisting a scattering structure in a core region of the optical fiber about a longitudinal axis of the core region, wherein the scattering structure is configured to scatter light propagating in the optical fiber out of the optical fiber.
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| Application Number | Priority Date | Filing Date | Title |
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| SG10201908040X | 2019-08-30 | ||
| SG10201908040X | 2019-08-30 | ||
| PCT/SG2020/050498 WO2021040623A1 (en) | 2019-08-30 | 2020-08-27 | Optical fiber, lighting apparatus having the same, and method for forming the same |
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| CN114008498A true CN114008498A (en) | 2022-02-01 |
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| CN (1) | CN114008498A (en) |
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| US20060024008A1 (en) * | 2004-07-14 | 2006-02-02 | Almantas Galvanauskas | Composite waveguide |
| CN1898586A (en) * | 2004-10-24 | 2007-01-17 | 手性光子公司 | Chiral in-fiber polarizer apparatus and method |
| US20110292676A1 (en) * | 2010-05-28 | 2011-12-01 | Etkin | Chiral Fiber Apparatus and Method for Controllable Light Extraction from Optical Waveguides |
| US20120275180A1 (en) * | 2011-04-29 | 2012-11-01 | Leslie James Button | Light Diffusing Fibers and Methods for Making the Same |
| US20130088888A1 (en) * | 2011-10-07 | 2013-04-11 | Edward John Fewkes | Optical Fiber Illumination Systems and Methods |
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| EP0093998B1 (en) * | 1982-05-11 | 1987-09-02 | Kei Mori | Photoradiator |
| US20140355292A1 (en) * | 2013-05-30 | 2014-12-04 | Gabriel Krause | Fiber Optic Filament Lamp |
| JP6287421B2 (en) * | 2014-03-24 | 2018-03-07 | 株式会社デンソー | Light guide member, attachment for light guide member, illumination device |
| US11059747B2 (en) * | 2017-03-28 | 2021-07-13 | Corning Incorporated | Light diffusing optical fibers for emitting white light |
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2020
- 2020-08-27 WO PCT/SG2020/050498 patent/WO2021040623A1/en active Application Filing
- 2020-08-27 SG SG11202113104XA patent/SG11202113104XA/en unknown
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20060024008A1 (en) * | 2004-07-14 | 2006-02-02 | Almantas Galvanauskas | Composite waveguide |
| CN1898586A (en) * | 2004-10-24 | 2007-01-17 | 手性光子公司 | Chiral in-fiber polarizer apparatus and method |
| US20110292676A1 (en) * | 2010-05-28 | 2011-12-01 | Etkin | Chiral Fiber Apparatus and Method for Controllable Light Extraction from Optical Waveguides |
| US20120275180A1 (en) * | 2011-04-29 | 2012-11-01 | Leslie James Button | Light Diffusing Fibers and Methods for Making the Same |
| US20130088888A1 (en) * | 2011-10-07 | 2013-04-11 | Edward John Fewkes | Optical Fiber Illumination Systems and Methods |
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| WO2021040623A1 (en) | 2021-03-04 |
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