Thermal Expansion Equilibrium Lateral Anderson Localized Optical Waveguide with Reduced Bending

Abstract

The present invention relates to a thermally expanded balanced transverse Anderson-localized optical waveguide with reduced curvature. The optical waveguide is formed from a fiber bundle comprising at least two distinct structural elements. The low curvature of the waveguide is achieved by a net CTE rate that is close to zero, which is achieved by repositioning some of the structural elements of the fiber bundle into different quadrants of the waveguide cross-section.

Description

Technical Field

[0001] The present invention relates to a thermally expanded equilibrium lateral Anderson localized optical waveguide for transmitting electromagnetic waves, particularly for transmitting image information, with reduced curvature, and to a method for manufacturing a waveguide, particularly an image guide.

Background Art

[0002] An image guide typically comprises a plurality of individual optical fibers, each having a core and a cladding surrounding the core. The optical fibers are assembled as a bundle and arranged in a cross-section within a grid having a one-to-one relationship between the light input surface and the light output surface to form a plurality of pixels. Basically, each pixel serves to transmit luminance values or color information through the image guide.

[0003] In practice, it is often desirable to have the highest possible resolution for an image guide. In principle, high resolution can be achieved by reducing the diameter of the individual optical waveguides. However, due to physical laws, as the diameter of the individual optical waveguides becomes smaller and smaller, the increasing rate of the electric field distribution in the transmission mode exceeds the dimensions of the optical waveguide, particularly the cladding, and the crosstalk between adjacent optical waveguides increases, and thus the blurring increases, so the resolution cannot be increased linearly.

[0004] One approach for providing an image guide with higher resolution is based on the wave phenomenon of transverse Anderson localization (TAL). This utilizes the fact that a random distribution of refractive indices across the cross-section of an image guide having simultaneous invariance of the refractive index for each fiber along the length of the image guide results in confinement of the coupled light within the cross-section due to destructive interference. In practice, for example, a number of individual fibers with different refractive indices can be combined to form a transverse Anderson localized optical waveguide. When a light beam is coupled into such a waveguide, the light beam propagates along the length of the waveguide with a limited lateral extension within the cross-section.

[0005] On the one hand, image guides based on the principle of lateral Anderson localization enable higher resolution. On the other hand, a random distribution of refractive indices can lead to drawbacks where the image quality of the transmitted image information, particularly image sharpness, may be subject to local variations or become difficult to control. For example, the image sharpness in a specific region of a cross-section may deviate from that in other regions of the cross-section.

[0006] Such non-uniformities actually make it difficult to generate image guides with specific quality standards. Depending on the quality criteria applied in manufacturing, a high level of defective products may occur. When the cross-sectional area of the image guide should have large dimensions, the above-mentioned problems may become even more severe. This particularly applies to faceplates, where the length or diameter of the edge of the cross-section can exceed several times the thickness of the faceplate.

[0007] In addition, the obstacles necessary to ensure high optical performance of the image guide may have an impact on other physical properties of the waveguide. For example, the waveguide may often have curved fibers even after being stretched during the fiber drawing process or even after the fiber bundle is manufactured. This can lead to several problems as follows. 1) Curvature may reduce the optical properties of the waveguide. Specifically, curvature may increase the noise level in the transmitted signal, thereby degrading the signal quality and image quality. 2) The fiber may be highly likely to suffer mechanical failure due to being under a certain tensile stress at one of the edges. 3) The fiber may be difficult to handle and may have low robustness, and it is not always possible to align the curved fiber within the optical fiber bundle.

[0008] The faceplate is usually several mm 2 ~ several cm 2It is a type of waveguide understood to be a group of fused optical fibers, often relatively short (e.g., a few millimeters), having an axis perpendicular to the faceplate surface with a possible cross-sectional area. The main characteristic of the faceplate is to enable image transmission in the same way, i.e., 1:1, or according to a rule, for example, by rotating from one faceplate surface to the opposite faceplate surface.

Summary of the Invention

Problems to be Solved by the Invention

[0009] Accordingly, an object of the present invention is to provide a waveguide, particularly an image guide, and a method for manufacturing the same, which can improve the uniformity across the cross-section of the waveguide, particularly the image sharpness. One aspect of the problem of the present invention is to make the uniformity across the cross-section more controllable and reproducible so that, for example, defective products during manufacturing can be avoided and waveguides that meet specific quality standards can be consistently manufactured. Another aspect of the present invention is to reduce the amount of curvature.

[0010] One aspect of the problem of the present invention is that it is possible to provide a waveguide, particularly an image guide, having a large cross-sectional area, using Anderson localization that simultaneously meets the aforementioned conditions, particularly the defined uniformity. This relates particularly to waveguides formed as faceplates.

Means for Solving the Problems

[0011] The present invention discloses a waveguide for transmitting electromagnetic waves using Anderson localization, particularly for transmitting image information from the proximal end to the distal end of the waveguide along a transport direction extending between the proximal end and the distal end. The waveguide comprises a fiber bundle extending along the transport direction and including a first structural element and a second structural element different from the first structural element. In some embodiments, the first structural element and the second structural element have different refractive indices regardless of the presence or absence of different cross-sectional areas. The fiber bundle is 0.1 meter -1It may have a radius of curvature (also referred to as "curvature" in this specification) and a net CTE rate of 0.01 ppm / K or less.

[0012] At least two different types of structural elements can be used, namely, a first type having a first refractive index and a second type having a second refractive index different from the first refractive index. Thus, the plurality of structural elements may include at least one structural element of the first type as well as at least one structural element of the second type. Of course, three or more different types, for example, three different types of structural elements may be used.

[0013] The structural elements can each extend along the transport direction and across the cross-section of the waveguide such that a plurality of cross-sectional regions each corresponding to a cross-section of a single structural element are defined within the cross-section of the waveguide. Thus, the structural elements can extend side by side along the transport direction of the waveguide, in particular parallel to each other, and their cross-sections can each occupy a planar portion of the cross-section of the waveguide, and thus can each define a cross-sectional region of the cross-section of the waveguide. The cross-sectional regions can in particular correspond in this way to the surface regions formed by the structural elements when looking at the cross-section of the waveguide, for example, the light incident surface or the light output surface.

[0014] According to some embodiments of the present invention, the first structural element may be different from the second structural element by its refractive index, cross-sectional area, and / or composition.

[0015] In some embodiments, the physical arrangement of each structural element relative to the other structural elements is mathematically determined during the manufacture of the waveguide such that the fiber bundle has a net CTE rate of 0.01 ppm / K or less.

[0016] The cross-sectional area of the structural element may have a non-uniform geometry with respect to each other, for example, a non-uniform diameter. However, the geometry of the cross-sectional area can also be of the same type. In addition, a waveguide including a plurality of fiber bundles fused to each other can be twisted (e.g., inverted) around the central axis of the waveguide to form an inverted waveguide in a non-limiting example as disclosed in U.S. Patent No. 11,079,538, the entire content of which is incorporated herein by reference.

[0017] In some embodiments, each fiber has a diameter, and in a non-limiting example as disclosed in U.S. Patent No. 11,079,538, the entire content of which is incorporated herein by reference, the diameter of the fiber varies according to the radial displacement of the fiber from the central bundle axis.

[0018] The structural element can be arranged such that the electromagnetic wave transmitted by the waveguide remains localized in a direction extending laterally with respect to the propagation direction, and at the same time can reduce the curvature of the fiber during the fiber drawing process. The curvature occurs when the fiber bundle bends along its length. Specifically, the curvature can increase the noise level in the transmitted signal and degrade the signal quality and image quality. Also, since the structural element is under a certain tensile stress at one of its edges, the curvature increases the likelihood that the structural element will experience mechanical failure. The curvature also makes it difficult to handle the structural element and incorporate it into the bundle of the structural element.

[0019] The structural element can be mathematically arranged such that the waveguide has a reproducible structure, in particular such that a further waveguide having the same or substantially the same structure as the waveguide can be manufactured.

[0020] One method for manufacturing a fiber bundle with minimized bending and other advantages is to arrange the first and second structural elements during the manufacture of the fiber bundle such that the fiber bundle has a net CTE rate of 0.01 ppm / K or less. This value is calculated mathematically as described herein. An individual fiber bundle having a net CTE rate within this range is considered to be "balanced" with respect to CTE, and since such individual bundles are balanced, a waveguide formed by fusing a large number of such balanced fiber bundles is itself balanced.

[0021] The ratio of the total cross-sectional area of the first structural element to the total cross-sectional area of the second structural element can be, for example, in the range of 1:150 to 150:1, 1:100 to 100:1, 1:50 to 50:1, 1:10 to 10:1, 3:7 to 7:3, 4:6 to 6:4, or 5:5. This can also be understood as the filling degree.

[0022] The refractive index of the first structural element and the refractive index of the second structural element differ by at least 10 -4 only, for example, at least 10 -3 only, for example, at least 10 -2 only, for example, at least 10 -1 only, for example, at least 1 only, for example, at least 2 only, for example, at least 3 only, for example, at least 4 only and may be different.

[0023] Regarding the lateral extent of the structural element, it may be provided that at least one cross-sectional area has a minimum lateral extent of 100 nm to 50 μm, 400 nm to 20 μm, or 1 μm to 16 μm.

[0024] Furthermore, it may be provided that at least one cross-sectional area has a diameter that is 0.1 times to 10 times the average wavelength, particularly preferably 0.2 times to 5 times the average wavelength, or 0.5 times to 2 times the average wavelength of the wavelength range of the electromagnetic wave to be transmitted.

[0025] Regarding the geometric shape of the structural element, the structural element may be given a non-circular or polygonal geometry, such as a pentagonal or hexagonal geometry.

[0026] The first structural element can in particular be formed, for example, as having a first medium or as a monolithic substrate from the first medium, and the first medium has a first refractive index. The second structural element may be formed as a cavity within the substrate, and the cavity preferably forms a second refractive index by the refractive index of, for example, a liquid, air, or gas that may be present as the medium within the cavity. The second type of structural element can in particular be formed, for example, as having a second medium or as a monolithic substrate from the second medium, and the second medium has a second refractive index. One or more of the monolithic substrates of the first medium can be fused to one or more of the monolithic substrates of the second medium in order to form a waveguide comprising a plurality of first substrates and a plurality of second substrates before pulling and straightening the fused substrates.

[0027] The cavity within the substrate can be formed as a filamentous channel, i.e., a channel having a cross-sectional area that is significantly smaller compared to the cross-sectional area of a waveguide that can be introduced into the substrate, for example, in particular using a laser beam of an ultrashort pulse laser. Furthermore, the filamentous channel within the substrate can be reprocessed chemically or physically by an etching process, for example, to smooth the contour of the filamentous channel.

[0028] Specifically, when the waveguide is formed as a substrate having a cavity but is formed independently thereof, the waveguide may have an extension in a cross-section larger than that along the transport direction. Specifically, the waveguide may be formed as a faceplate.

[0029] The waveguide may be given a cross-sectional area of 1.0 to 50 square centimeters.

[0030] The cross-sectional diameter of the waveguide may be at least twice as large, at least five times as large, or at least ten times as large as the length of the waveguide along the transport direction.

[0031] The substrate having cavities can be fabricated or manufactured in various ways. The cavities within the substrate can be formed, for example, by additional construction of the substrate by a 3D printing process. Alternatively or additionally, the cavities may be introduced into the substrate in a subtractive manner, in particular as holes introduced into the substrate by a polishing material processing method, such as mechanical drilling. Depending on the method used, the holes are not limited to a circular geometry only.

[0032] The waveguide may be manufactured in a multi-train process, especially when the waveguide comprises at least a second plurality of structural elements in addition to the plurality of structural elements. The waveguide has, in cross-section, at least two surface regions each containing a cross-sectional region of one of the two pluralities of structural elements, which may have the same structure apart from rotation and / or reflection.

[0033] With respect to the length of the waveguide along the transport direction, especially when the waveguide is formed as a faceplate, the waveguide may be provided with a length along the transport direction of less than 10 millimeters, less than 6 millimeters, or less than 5 millimeters.

[0034] However, generally, the waveguide may also be provided with a length along the transport direction of at least 10 millimeters, at least 20 millimeters, at least 50 millimeters, or at least 100 millimeters.

[0035] When the waveguide is formed as a substrate having cavities, the cavities within the substrate, in particular the filamentous channels and / or holes, may be filled with a second medium, which has a second refractive index.

[0036] Regarding the material, at least one structural element, in particular a first structural element, in particular a structural element formed as a substrate, may be provided to contain or consist of one or more of the following materials as a medium: glass (including non-oxide materials such as oxides and chalcogenides), fused silica, polymer, crystal, single crystal, polycrystalline material and / or glass-ceramic.

[0037] Furthermore, at least one structural element, in particular a first structural element, in particular a structural element formed as a substrate, may contain or consist of a chalcogenide containing at least one element from a group containing oxygen, sulfur, selenium and tellurium, and at least one element from a group containing arsenic, germanium, phosphorus, antimony, lead, boron, aluminum, gallium, indium, titanium, sodium, in particular in an attenuation of less than 100 dB / m, in particular less than 50 dB / m, in particular less than 10 dB / m, in particular less than 1 dB / m in the transmitted wavelength range, in particular 2 μm to 20 μm, and in particular an infrared transmitting material.

[0038] Furthermore, the optically active material may be provided, for example, as part of a medium or filling, and / or as a layer or coating or other modification on the surface of an assembly of structural elements formed as rods or tubes. Thus, for example, a modification of the induced electromagnetic field in the sense of amplification or conversion can be realized.

[0039] A further structural element, in particular a second structural element, may contain or consist of the same or different materials.

[0040] The first structural element may in particular be formed as a rod or tube having or made of a first medium, and the first medium has a first refractive index.

[0041] The second structural element can in particular be formed as a rod or tube having or from a second medium and / or as a cavity within the first structural element, the second medium having a second refractive index, the cavity forming the second refractive index or being filled with a second medium having the second refractive index.

[0042] Specifically, if the second structural element can exist as a cavity filled within the first structural element, the structural element may be formed as a core-shell system such that the core corresponds to the filled cavity.

[0043] The rod or tube should not be understood only as having a circular cross-sectional geometry.

[0044] The invention further relates to a method for manufacturing an optical waveguide, in particular an optical waveguide having one or more of the features described herein for transmitting an electromagnetic wave from the proximal end to the distal end of the optical waveguide along a propagation direction extending between the proximal end and the distal end, the method comprising forming a fiber bundle extending along the propagation direction and comprising a first structural element and a second structural element different from the first structural element, whereby the electromagnetic wave captured at the proximal end is restricted within a cross-sectional region transverse to the propagation direction due to the difference between the first structural element and the second structural element, and the forming step comprises arranging the first structural element and the second structural element within the fiber bundle such that the fiber bundle has a curvature of 0.1 meter -1 as follows.

[0045] Embodiments of the invention are described below with reference to the figures described.

Brief Description of the Drawings

[0046]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10A

Figure 10B

Figure 10C

Figure 11A

Figure 11B

Figure 12A

Figure 12B

Figure 13A

Figure 13B

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

BEST MODE FOR CARRYING OUT THE INVENTION

[0047] FIG. 1 shows various main examples of a waveguide (100) that can be used particularly as an image guide. The waveguides (100) shown in cross-section each comprise a plurality of structural elements (10), each of which extends here along the conveyance direction of the waveguide (100) perpendicular to the figure, and each of which extends proportionally across its cross-section. Each of the structural elements (10) thus defines a cross-sectional area (20), that is, a proportion of the area of the cross-section of the waveguide (100). The examples of waveguides shown each have at least two different types of structural elements with different refractive indices. These main embodiments serve to show some variations of the non-uniformity and may deviate in detail from the deterministic positioning of the structural elements determined according to the present invention.

[0048] Such a waveguide (100) for transmitting an electromagnetic wave from the proximal end (2) to the distal end (4) of the waveguide along a transport direction (5) extending between the proximal end and the distal end may comprise a fiber bundle (1) extending along the transport direction (5) and comprising a first structural element (10a) and a second structural element (10b) different from the first structural element (10a), whereby the electromagnetic wave captured at the proximal end (2) is restricted within a cross-sectional region transverse to the transport direction (5) due to the difference between the first structural element (10a) and the second structural element (10b), and the fiber bundle (1) is 0.1 meter -1 has the following curvature. As explained above, the curvature of the present invention is a reduced amount of curvature compared to conventional Anderson localization fiber bundles that can reduce the potential for noise, reduce the potential for mechanical failure, and increase the potential for incorporating the fiber bundle into the waveguide (100). For a description of the cross-section of the fiber bundle (1) composed of a plurality of first and second structural elements (10), see FIG. 17A, and for a description of a partial cross-section of the waveguide (100) composed of a plurality of fiber bundles (1), see FIG. 17B.

[0049] As shown in FIG. 14, the curvature is measured by placing the fiber bundle on a plane, then measuring the length L of the fiber bundle along the image transport direction, then measuring the height H which is the distance between the midpoint of the fiber bundle and the axis intersecting the centers of the image input end and the image output end of the fiber bundle, and then calculating the radius of curvature R using the following formula. Curvature (meter -1 The unit) is the reciprocal of R.

Equation

[0050] In some embodiments, the curvature is 0.1 meter -1 or less, 0.09 meter -1 or less, 0.08 meter -1 or less, 0.07 meter -1 or less, 0.06 meter -1 or less, 0.05 meter -1Hereinafter, 0.04 meters -1 Hereinafter, 0.03 meters -1 Hereinafter, 0.02 meters -1 Hereinafter, 0.01 meters -1 Hereinafter, and / or 0 meters -1 exceeding.

[0051] The fiber bundle can have a net CTE rate of 0.0100 ppm / K or less, 0.0075 ppm / K or less, 0.0050 ppm / K or less, 0.0025 ppm / K or less, and / or 0 m or more. One way to achieve the desired curvature described herein is to manufacture the fiber bundle such that the fiber bundle has a net CTE rate. The calculation of the net CTE rate and the method of manufacturing the fiber bundle to achieve the net CTE rate are described herein.

[0052] The waveguide (100) shown in cross-section in FIG. 1(a) has a first structural element 10a formed as a substrate that houses a plurality of second structural elements 10b. Thereby, the second structural element 10b may be formed, for example, as a cavity or hollow channel that extends along the transport direction within the first structural element 10a. In this case, the first structural element 10a formed as a substrate includes a first material having a first refractive index, and the second structural element 10b formed, for example, as a cavity forms a second refractive index, for example, by air or another gas contained therein. In this case, the cross-sectional area 20 of the first structural element corresponds to the cross-sectional area of the waveguide (100) minus the holes within this area defined by the cavity, and the cross-sectional area 20 of the second structural element 10b corresponds to the cross-sectional area of each cavity. However, the cavity within the body may also be filled with a second material so that the cavity corresponds to the cavity filled with the second structural element 10b. As schematically shown in the figure, the cross-sectional areas 20 of the second structural elements 10b are non-uniform in that their positions are distributed non-uniformly across the cross-section, especially not on a periodic lattice. However, at the same time, the positions of the structural elements are mathematically determined as described in more detail herein.

[0053] The waveguide (100) shown in cross-section in Fig. 1(b) has two types of structural elements 10a, 10b, namely, one structural element 10a formed as a substrate and having a first refractive index, and a plurality of structural elements 10b having a second refractive index different therefrom. In the example shown here, the cross-sectional regions 20 of the second structural elements 10b not only are arranged non-uniformly but also have a non-uniform geometry, in this case a non-uniform diameter.

[0054] The waveguide (100) shown in cross-section in Fig. 1(c) also has two types of structural elements 10a, 10b, and the cross-sectional regions of the second structural elements 10b are each arranged in the first structural element 10a, in particular as a core-sheath system. Thus, in this case, a plurality of first structural elements 10a and a plurality of second structural elements 10b are provided. The structural elements or their cross-sectional regions are formed non-uniformly in that the first structural elements 10a (accommodating the second structural elements 10b) are arranged non-uniformly, in particular aperiodically, across the cross-section of the waveguide (100), and this arrangement is mathematically determined.

[0055] The waveguides (100) shown in cross-section in Figs. 1(d) and (e) correspond in some respects to the waveguides (100) shown in Figs. 1(a) and (b), respectively, but have three types of structural elements 10a, 10b, 10c having different refractive indices. Specifically, the cavities in the structural elements 10a formed as substrates may be filled with different media. Thus, the structural elements 10b, 10c have non-uniformity in that their refractive indices are different from each other.

[0056] The fiber bundle is -1 manufactured to have the following curvature. One way to achieve this curvature is to manufacture the fiber bundle such that the fiber bundle has a net CTE rate of 0.01 ppm / K or less.

[0057] The net CTE rate is calculated mathematically as follows.

[0058] In the case of a waveguide formed by combining a plurality of structural elements to form a fiber bundle and then combining a plurality of fiber bundles to form a waveguide, since a single fiber bundle is a repeating unit that forms the waveguide, calculations are performed across the cross-section of a single fiber bundle. In the case of a waveguide formed by combining a plurality of structural elements to form the entire waveguide without an intermediate step of forming and combining a plurality of fiber bundles together, since there is no single repeating unit of the fiber bundle, calculations are performed across the cross-section of the entire waveguide. When a waveguide is formed by combining two or more different fiber bundles, the calculations are performed individually across the cross-section of each fiber bundle. If it is not possible to identify individual fiber bundles, for example, when a manufactured waveguide is analyzed to determine its characteristics, calculations are performed across the cross-section of the smallest recognizable repeating unit, and if there are two or more different recognizable repeating units, calculations are performed across the cross-section of each of those repeating units.

[0059] The first step of the calculation is to obtain an actual image of the reference fiber bundle at a resolution of at least 20 pixels and bisect the cross-section along its two main axes, specifically the horizontal x-main axis and the vertical y-main axis of the Cartesian coordinate system. The two main axes are orthogonal to each other and centered on the geometric center of the fiber bundle, for example, the geometric center of the hexagonal cross-section shown in Figure 2A or the geometric center of the circular cross-section shown in Figure 2B. Figures 2A and 2B show that this bisection creates four quadrants, where quadrant 1 is opposite quadrant 3 and quadrant 2 is opposite quadrant 4. For cross-sectional shapes that are not symmetric, such as polygons or circles, two additional main axis bisections are created at the geometric center to create four quadrants.

[0060] Next, the coordinate (0,0) is assigned to the geometric center, and the CTEs along the x-axis and y-axis are calculated as follows:

Equation

[0061] The net CTE rate is

Number

[0062] If the net CTE rate is not 0.01 ppm / K or less, this may indicate that the fiber bundle does not have a desirable curvature of 0.1 meter -1 or less. To achieve this desirable curvature for the next fiber bundle to be manufactured, the position of each structural element within the next fiber bundle to be manufactured may need to be repositioned relative to its adjacent structural elements such that the net CTE rate resulting from the newly manufactured fiber bundle is 0.01 ppm / K or less. For example, this repositioning may involve moving the position of one or more of the first and second structural elements, and thus their x and y coordinates, relative to the other structural elements, such that when the net CTE rate calculation is performed for the new fiber bundle, the new fiber bundle has a net CTE rate of 0.01 ppm / K or less, and thus the new fiber bundle is likely to have a curvature of 0.1 meter -1 or less. This repositioning / relocation of the positions of the first and second structural materials is performed multiple times as necessary until a net CTE rate of 0.01 ppm / K or less is achieved.

[0063] One possible way to determine which optical structural elements should be repositioned is α x and α yIt is to consider the signs and magnitudes. For example, 1) the positive sign of α x and the positive sign of α y mean that the structural elements in the first quadrant have an excessive number of higher expansion structural elements, and a certain number of high-expansion structural elements from the first quadrant should be replaced by an equal number of low-expansion structural elements from the third quadrant facing it. 2) The negative sign of α x and the positive sign of α y mean that the structural elements in the second quadrant have an excessive number of higher expansion structural elements, and a certain number of high-expansion structural elements from the second quadrant should be replaced by an equal number of low-expansion structural elements from the fourth quadrant facing it. 3) The negative sign of α x and the negative sign of α y mean that the structural elements in the third quadrant have an excessive number of higher expansion structural elements, and a certain number of high-expansion structural elements from the third quadrant should be replaced by an equal number of low-expansion structural elements from the first quadrant facing it. 4) The positive sign of α x and the negative sign of α y mean that the structural elements in the fourth quadrant have an excessive number of higher expansion structural elements, and a certain number of high-expansion structural elements from the fourth quadrant should be replaced by an equal number of low-expansion structural elements from the second quadrant facing it.

[0064] In addition to, or instead of, performing the replacement between opposite quadrants, the replacement can also be performed between adjacent quadrants. Also, the replacement can be performed within the same quadrant by bringing the high-expansion structural elements closer to the 0,0 coordinate, which may lead to the aggregation and partial symmetry of the high-expansion structural elements. Furthermore, between any of these replacements, other high and low thermal expansion structural elements may need to be rearranged to avoid creating a regular pattern with symmetry that does not promote Anderson localization.

[0065] This replacement of the high thermal expansion structural elements with low thermal expansion structural elements can be carried out until a desirable new CTE rate, such as 0.015 m or less, is achieved.

[0066] Figure 3 shows two further examples of a waveguide (100) that can be used in particular as an image guide. The waveguide (100) comprises a plurality of first and second structural elements 10, each of which extends from the proximal end 2 to the distal end 4 of the waveguide (100) along the transport direction 5 and is, for example, rod-shaped.

[0067] The waveguide (100) shown in Fig. 3(a) has a plurality of first structural elements 10a and a plurality of second structural elements 10b. The structural elements have a non-uniform arrangement in that the first structural elements 10a and the second structural elements 10b are non-uniformly arranged and / or distributed, and the arrangement and / or distribution should be determined mathematically as described herein in order to achieve a desired net CTE rate and thus a desired curvature. However, Fig. 3 does not necessarily show an arrangement that achieves a desired net CTE rate or curvature.

[0068] The waveguide (100) shown in Fig. 3(b) comprises a plurality of structural elements 10. In this example, the cross-sectional area of the structural elements has a non-uniform geometry. Specifically, the geometry may be different in that the diameters of the structural elements or their cross-sectional areas are different from each other. Furthermore, the structural elements 10 in each of Figs. 3(a) and 3(b) can exhibit non-uniformity in that the refractive indices of the structural elements are different from each other. In this regard, a discrete number of different refractive indices, for example 2, 3, 4, etc. may be provided.

[0069] Figure 4 shows a cross-section of a fiber bundle (1) corresponding to the waveguide (100) shown in Fig. 3(a) in some embodiments. The fiber bundle (1) shown in Fig. 4 has a plurality of, in particular rod-shaped, structural elements 10, namely a plurality of first structural elements 10a and a plurality of second structural elements 10b, and the structural elements 10 are arranged in a cross-section on a hexagonal lattice. At least one of the structural elements 10, or its cross-sectional area 20, is equidistant from, and preferably adjacent to, six directly adjacent structural elements 10, or their cross-sectional areas 20.

[0070] FIG. 5 shows the steps of a method for manufacturing a waveguide by the multi-draw method. In this process, a plurality of waveguides are assembled to form a preform 30 and drawn to a certain length (FIG. 5a). The waveguides can be, for example, the arrangement of the structural elements 10, 20 or 10a, b according to FIG. 4, or an alternative arrangement such as those shown in FIGS. 1(a)-(e), and they may already be drawn in a known manner. Ideally, the structural elements are positioned relative to each other to achieve the desired net CTE rate.

[0071] Next, the assembled elongated waveguide (“multi-fiber”) is disassembled into sections and reassembled into a preform 40 (FIG. 5b, “multi-multi-assembly”). Then, the preform 40 is drawn to a certain length again (FIG. 5c), and if necessary, divided into sections and reassembled (FIG. 5d). Finally, the assembly thus obtained can be fused, particularly under vacuum, by applying heat and / or pressure (FIG. 5e).

[0072] Referring to FIG. 6, a fiber bundle (“multi-fiber”, here “M1”) drawn and assembled to a certain length can be assembled without rotating relative to each other (FIG. 6a) or rotated relative to each other during assembly into a further preform (FIG. 6b). Further, during assembly, sections from at least two different assembled fiber bundles (“M1”, “M2”) drawn to a certain length can be assembled without rotating relative to each other (FIG. 6c) or rotated relative to each other (FIG. 6d). Similar to the arrangements shown in FIGS. 6a and 6b, when the first preform is assembled, the fiber bundles can be arranged without rotating relative to each other, or rotated and arranged, or arranged.

[0073] Referring to FIG. 7, various embodiments of the non-uniformity of the structural elements are described again below by way of example. As described, the structural elements, particularly their cross-sectional regions, are characterized on the one hand by non-uniformity with respect to each other, and on the other hand by the regularity with respect to the effect that the non-uniformity of the structural elements is predetermined so as to achieve a desired net CTE rate.

[0074] FIG. 7 shows several fiber bundles (1), each having a plurality of structural elements of a first type and a plurality of structural elements of a second type (and sometimes further types in FIG. 7d). Specifically, the fiber bundles (1) shown here have no matrix material, rather the structural elements are adjacent to each other. The fiber bundles (1) shown in FIG. 7 have in common that different types of structural elements, particularly their cross-sectional regions, are periodically positioned so as to achieve a desired net CTE rate.

[0075] FIG. 7a approximately shows a fiber bundle (1) having a plurality of structural elements 10a and a plurality of structural elements 10b with different refractive indices.

[0076] FIG. 7b shows a fiber bundle (1) having a plurality of structural elements 10d and a plurality of structural elements 10e with different refractive indices and different sub-structures, the sub-structures being defined by sub-structural elements 10a and 10b (having refractive indices a and b) and 10a and 10c (having refractive indices a and c), respectively. The sub-structures here are such that the structural elements 10d and 10e are formed as a core-shell system, with the cores being different.

[0077] FIG. 7c similarly shows a fiber bundle (1) having a plurality of structural elements 10d and a plurality of structural elements 10e with different refractive indices and different sub-structures, the sub-structures being defined by sub-structural elements 10a and 10b (having refractive indices a and b) and 10c and 10b (having refractive indices c and b), respectively. The sub-structures here are such that the structural elements 10d and 10e are formed as a core-clad system, with the clads being different.

[0078] FIG. 7d similarly shows a fiber bundle (1) having a plurality of structural elements 10e, a plurality of structural elements 10f, a plurality of structural elements 10g, and a plurality of structural elements 10h having different refractive indices and different sub-structures, the sub-structures being represented by sub-structural elements 10a and 10b (having refractive indices a and b), 10a and 10c (having refractive indices a and c), 10b and 10d (having refractive indices b and d), and 10c and 10d (having refractive indices c and d), respectively. The sub-structures here are such that the structural elements 10e, 10f, 10g, and 10h are formed as a core-shell system, with both the shell and the core being different.

[0079] FIG. 7e shows a fiber bundle (1) having a plurality of structural elements 10c and a plurality of structural elements 10d having different geometries and different sub-structures, the sub-structure of the structural element 10c being defined by sub-structural elements 10a and 10b (having refractive indices a and b and a first core diameter), and the sub-structure of the structural element 10d being defined by sub-structural elements 10a and 10b (having refractive indices a and b and a second core diameter).

[0080] FIG. 7f shows a fiber bundle (1) having a plurality of structural elements 10c and a plurality of structural elements 10d having different geometries and different sub-structures, the sub-structure of the structural element 10c being defined by sub-structural elements 10a and 10b (having refractive indices a and b and a core positioned at the center), and the sub-structure of the structural element 10d being defined by sub-structural elements 10a and 10b (having refractive indices a and b and a core positioned eccentrically).

[0081] FIG. 8a shows a photograph as an example of an optical fiber bundle (1) having a plurality of optical fibers having a first refractive index as a first structural element 10a and a plurality of optical fibers having a second refractive index as a second structural element 10b, an enlarged view thereof in FIG. 8b, and a sketch. In this case, the optical fibers of the structural elements 10a and 10b are positioned adjacent to each other, and the net CTE rate can be calculated. The structural elements of the first type 10a and the second type 10b may be surrounded by a structural element of a third type 10c formed as a cladding tube. The cladding tube may have a refractive index lower than both the refractive index of the structural element 10a of the first type and the refractive index 10b of the second type.

[0082] FIG. 9 shows a photograph of the optical fiber bundle (1) of FIG. 8a in its use as an image guide, transmitting an image indicating the number 5. Due to the non-uniformity in the arrangement of the structural elements, high-resolution image transmission based on the phenomenon of lateral Anderson localization is realized here.

[0083] In summary, there may be provided a waveguide (100) for transmitting an electromagnetic wave from a proximal end (2) of the waveguide (100) to a distal end (4) of the waveguide (100) along a transport direction (5) extending between the proximal end and the distal end. The waveguide (100) may have an optical fiber bundle (1) extending along the transport direction (5) and having a first structural element (10a) and a second structural element (10b) different from the first structural element (10a). The electromagnetic wave captured at the proximal end (2) may be restricted within a cross-sectional region transverse to the transport direction (5) due to the difference between the first structural element (10a) and the second structural element (10b). The optical fiber bundle (1) may have a net CTE rate of 0.01 ppm / K or less and a curvature of 0.1 meter -1 as follows.

[0084] The CTE of the first structural element (10a) may differ from the CTE of the second structural element (10b) by 5 ppm / K or less, or by 3,690 ppm / K or less when one of the structural elements is a cavity filled with air.

[0085] The fiber bundle (1) can include a plurality of first structural elements (10a) and a plurality of second structural elements (10b), and the waveguide (100) can include a plurality of fiber bundles (1). The total number of the first structural elements (10a) and the second structural elements (10b) in the fiber bundle (1) can be sufficient to manufacture a fiber bundle having, for example, 20 to 300 structural elements or 50 to 300 structural elements, such as a central polygonal unit, for example, 61 structural elements shown in FIG. 2.

[0086] One or more of the first structural elements (10a) can be fused with one or more of the one or more second structural elements (10b). The second structural element (10b) can be an air channel located within a matrix formed from the first structural element (10a). The individual first structural elements (10a) and the individual second structural elements (10b) do not need to be surrounded by a cladding.

[0087] The plurality of first structural elements (10a) and the plurality of second structural elements (10b) can be arranged non-uniformly when viewed in the cross-section of the fiber bundle (1). The first structural element (10a) and the second structural element (10b) can have the same composition but different diameters when viewed in the cross-section of the fiber bundle (1).

[0088] A method of manufacturing a waveguide (100) for transmitting an electromagnetic wave from a proximal end (2) of the waveguide (100) to a distal end (4) of the waveguide (100) along a transport direction (5) extending between the proximal end and the distal end can include determining an intended curvature of the waveguide (100) and manufacturing the waveguide (100) to achieve the intended curvature. The method can include forming a fiber bundle (1) that extends along the transport direction (5) and includes a first structural element (10a) and a second structural element (10b) different from the first structural element (10a), whereby an electromagnetic wave captured at the proximal end (2) is restricted within a cross-sectional region that crosses the transport direction (5) due to a difference between the first structural element (10a) and the second structural element (10b). The forming step can include arranging the first structural element (10a) and the second structural element (10b) within the fiber bundle (1) such that the fiber bundle (1) has a curvature of 0.1 meter -1 including arranging the first structural element (10a) and the second structural element (10b) within the fiber bundle (1) to have the following curvature.

[0089] Example: The following waveguides were prepared and analyzed.

[0090] Example 1: A glass fiber bundle having a plurality of first components with a CTE of 5 ppm / K and a plurality of second components with a CTE of 7.3 ppm / K was prepared. The position of each of the components was arbitrarily positioned as shown in FIG. 10A (the first components are shown linearly and the second components are shown wavy). The net CTE rate was 0.0383 ppm / K. The curvature was 0.083 meter -1 The generated image is shown in FIG. 15.

[0091] The first glass fiber bundle has an α of -0.0171 ppm / K x and an α of -0.342 ppm / K yand it means that there was an excess of high-expansion fibers in the third quadrant. To reduce the net CTE rate and the curvature, as shown in Figure 10B, some structural elements from the third quadrant were repositioned to the first and second quadrants, with an α of -0.0043 ppm / K x and an α of -0.0086 ppm / K y , thus, a second glass fiber bundle shown in Figure 10C with a net CTE rate of 0.0096 ppm / K was manufactured. The curvature was 0 to 0.01 meters -1 . The generated image is shown in Figure 16.

[0092] Example 2: The first and second structural elements from Example 1 were arranged as shown in Figure 11A. The net CTE rate was 0.1213 ppm / K.

[0093] The first glass fiber bundle had an α of 0.1115 ppm / K x and an α of -0.0478 ppm / K y and it means that there was an excess of high-expansion fibers in the fourth quadrant. To reduce the net CTE rate and the curvature, some structural elements from the fourth quadrant were repositioned to the second and third quadrants, with an α of 0 ppm / K x and an α of 0 ppm / K y , thus, a second glass fiber bundle shown in Figure 11B with a net CTE rate of 0 ppm / K was manufactured.

[0094] Example 3: The first and second structural elements from Example 1 were arranged as shown in Figure 12A. The net CTE rate was 0.1051 ppm / K.

[0095] The first glass fiber bundle had an α of 0.0798 ppm / K x and an α of -0.0684 ppm / K yhaving, which means that there was an excess of high-expansion fibers in the fourth quadrant. To reduce the net CTE rate and the curvature, some structural elements from the fourth quadrant were repositioned to the second and first quadrants, with an α of 0 ppm / K x and an α of 0 ppm / K y , thus, a second glass fiber bundle shown in Figure 12B having a net CTE rate of 0 ppm / K was manufactured.

[0096] Example 4: The first and second structural elements from Example 1 were arranged as shown in Figure 13A. The net CTE rate was 0.0756 ppm / K.

[0097] The first glass fiber bundle had an α of 0.0750 ppm / K x and an α of 0.0100 ppm / K y having, which means that there was an excess of high-expansion fibers in the first quadrant. To reduce the net CTE rate and the curvature, some structural elements from the first quadrant were repositioned to the third and fourth quadrants, with an α of 0 ppm / K x and an α of 0 ppm / K y , thus, a second glass fiber bundle shown in Figure 13B having a net CTE rate of 0 ppm / K was manufactured.

Claims

1. A waveguide (100) for transmitting electromagnetic waves, wherein the electromagnetic waves are transmitted along a propagation direction (5) extending between a proximal end (2) and a distal end (4) of the waveguide (100) from the proximal end (2) to the distal end (4) of the waveguide (100), the waveguide (100) comprises a fiber bundle (1), the fiber bundle (1) extends along the propagation direction (5), and has a random arrangement of a first structural element (10a) and a second structural element (10b) different from the first structural element (10a), whereby the electromagnetic waves captured at the proximal end (2) are limited within a cross-sectional area transverse to the propagation direction (5) due to the difference between the first structural element (10a) and the second structural element (10b), The fiber bundle (1) has a curvature of 0.1 meter or less －１ and has the following curvature Waveguide (100).

2. The fiber bundle (1) has a curvature exceeding 0.1 to 0 meters －１ and has the curvature exceeding the above value The waveguide according to claim 1.

3. The fiber bundle (1) has a net CTE rate of 0.01 ppm / K or less, The waveguide according to claim 1.

4. The fiber bundle (1) has a net CTE rate of 0 to 0.01 ppm / K, The waveguide according to claim 1.

5. The CTE of the first structural element (10a) differs from the CTE of the second structural element (10b) by 5 ppm / K or less, The waveguide according to claim 1.

6. The fiber bundle (1) comprises a plurality of first structural elements (10a) and a plurality of second structural elements (10b), The waveguide according to claim 1.

7. The waveguide (100) comprises a plurality of fiber bundles (1), The waveguide according to claim 6.

8. The fiber bundle (1) comprises a total number of 20 to 300 first structural elements (10a) and a plurality of second structural elements (10b), The waveguide according to claim 6.

9. One or more of the first structural elements (10a) are fused with one or more of the second structural elements (10b), The waveguide according to claim 1.

10. The second structural element (10b) is an air channel located within a matrix formed from the first structural element (10a), The waveguide according to claim 1.

11. Individual first structural elements (10a) and individual second structural elements (10b) are not surrounded by a cladding, The waveguide according to claim 1.

12. The plurality of the first structural elements (10a) and the plurality of the second structural elements (10b) are arranged non-uniformly when viewed in the cross-section of the fiber bundle (1). The waveguide according to claim 1.

13. A method of manufacturing a waveguide (100) for transmitting electromagnetic waves, wherein the electromagnetic waves are transmitted from the proximal end (2) of the waveguide (100) to the distal end (4) of the waveguide (100) along a transport direction (5) extending between the proximal end and the distal end, and the method comprises determining an intended curvature of the waveguide (100); manufacturing the waveguide (100) so as to realize the intended curvature; A method comprising.

14. A method of manufacturing a waveguide (100) for transmitting electromagnetic waves, wherein the electromagnetic waves are transmitted from the proximal end (2) of the waveguide (100) to the distal end (4) of the waveguide (100) along a transport direction (5) extending between the proximal end and the distal end, the method comprising forming a fiber bundle (1) extending along the transport direction (5) and comprising a first structural element (10a) and a second structural element (10b) different from the first structural element (10a), whereby electromagnetic waves captured at the proximal end (2) are confined within a cross-sectional region transverse to the transport direction (5) due to a difference between the first structural element (10a) and the second structural element (10b). The forming step comprises arranging the first structural element (10a) and the second structural element (10b) within the fiber bundle (1) such that the fiber bundle (1) has a curvature of 0.1 meter or less. －１ ​ Method.

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