Optical waveguide and method for manufacturing the optical waveguide

Abstract

The present invention relates to an optical waveguide 1, which is transparent to a guided optical light beam 100 having a wavelength greater than 180 nm. The waveguide 1 comprises at least one core 10 for guiding light 100, made of a first material with a first refractive index n1, and a cladding 20 at least partially made of a thermoplastic elastomer TPE, the innermost layer of which has a refractive index n2 smaller than the refractive index n1 of the outermost layer of the core 10. The present invention also relates to a medical device and a waveguide sensor comprising the optical waveguide 1 of the present invention. The present invention further relates to a method for manufacturing the optical waveguide 1. The method is based on the realization of a solid thermoplastic elastomer preform 200 or a preform 204 with a central opening 202'. To realize the optical waveguide 1 of the present invention, the core of the preform is filled and cured before or after stretching the preform 200, 204 to a predetermined length and predetermined lateral dimensions. The present invention also relates to a 3D printing method for realizing the preform 200, 204.

Description

Technical Field

[0001] The present invention relates to the field of optical waveguides. More particularly, the present invention relates to flexible optical waveguides, such as optical fibers or planar waveguides, which can be advantageously used in applications and devices where it is difficult to supply light to a remote target, the optical path is small, and may have short bends and / or complex shapes. The present invention relates to flexible optical waveguides having biocompatibility and stretchability and based on the use of elastomers. The present invention proposes a solution for applications where damage to the optical waveguide would result in dramatic consequences.

Background Art

[0002] Optical waveguides constitute a means for supplying light to a remote target and may be deployed over long distances, through narrow spaces and sometimes harsh environments. Optical waveguides in the form of fiber optics, fiber bundles, or planar waveguides have been developed for a wide range of applications, such as telecommunication, industrial, and medical applications. In the case of telecommunication applications, the focus is mainly on processes that enable very long distances with very low absorption, mainly in the infrared range. In other applications, such as industrial machinery or medical applications, this requirement is usually not present, but there are other requirements, such as the mechanical properties of the optical waveguide or the compatibility requirements that are essential in chemical, biochemical, or medical environments. For example, in the case of medical implants, biocompatibility is the main requirement. This biocompatibility often leads to other requirements, such as mechanical security requirements.

[0003] For example, glass optical fibers for implants in the human body face many difficulties, such as biocompatibility or breakability, which can be dramatic in such applications. Furthermore, since the manufacturing steps of implants are complex, highly flexible optical waveguides are often required for the manufacture of implants.

[0004] Most existing optical waveguides are based on glass or plastic fibers and are not suitable for some medical applications, such as implants.

[0005] In order to realize an optical fiber having improved mechanical properties and / or medical or biochemical compatibility, several attempts have been made in the past. For example, polyurethane (PU) has been widely used in the field of optical fibers for coating design for cable production and fiber optic tubes.

[0006] Several solutions have been proposed to improve the mechanical properties of bent fibers. For example, Japanese Patent Laid-Open No. 59-111952 and International Publication No. 2003 / 091178 A2 propose using polyurethane to enhance the adhesion of the coating on the glass fiber and protect the fiber from the effects of minute bending. PU has also been used to reinforce optical fibers to enhance the corrosion resistance and weather resistance of aerial optical cables, as described in Chinese Patent Publication No. 107589507. Also, for example, Chinese Patent Publication No. 206431340 describes the use of PU to further enhance the resistance of optical fibers for medical applications. Further, U.S. Patent Application Publication No. 2013 / 243948 proposes using PU in a complex coating structure to correct the drawbacks of the primary coating.

[0007] In the field of fiber optic protection tube applications for handling in the manufacture of optical cables, Chinese Patent Publication No. 203275734 proposes a polymer such as PU simply as an additional component to enhance the flexibility of the cable.

[0008] Other literature in the field of optical fibers proposes using PU as a cladding-free optical fiber. For example, U.S. Patent No. 4915473 A discloses a pressure sensor by using a PU fiber in which the light transmittance is inversely proportional to the pressure applied to the fiber. Also, U.S. Patent Application Publication No. 2008 / 0089088 A1 describes the use of a cladding-free PU fiber that causes side scattering for writing and decorative applications.

[0009] U.S. Patent No. 4,893,897 describes a flexible optical fiber for in vivo use in living mammalian tissues. The document, U.S. Patent No. 4,893,897, describes a manufacturing process that uses two materials, such as polystyrene and aliphatic PU, to produce the core and cladding of the fiber. This process is ultimately based on the melting and coextrusion of the two materials to produce a fiber-shaped preform that is drawn down to the required final optical fiber dimensions. The main constraint in the manufacture of U.S. Patent No. 4,893,897 is that the cladding material must have a lower melt viscosity than the melt viscosity of the core.

[0010] Another document, Japanese Patent Laid-Open No. 62-269905, describes a method of manufacturing a flexible optical fiber by injecting a liquid PU resin into a hollow flexible fiber and then polymerizing this liquid resin using UV light. The photocurable liquid resin can be, for example, polyurethane poly(meth)acrylate alone, but may also be a monovinyl compound such as an alkyl (meth)acrylate or other materials. The materials used in the production of the hollow fiber were polytetrafluoroethylene, ethylene-vinyl acetate copolymer, vinyl chloride resin, and other types of materials. The hollow fiber needs to be extruded using a concentric annular die. The liquid resin is then extruded from one side and suctioned from the opposite side of the hollow fiber using a vacuum pump. The polymerization of the liquid core is carried out using UV light. In the production of this hollow fiber, due to the large influence of absorption, a very low-quality surface is produced that results in an unacceptable light transmittance.

[0011] In the literature <JP-A-54-47667> which describes a glass core covered with a silicone cladding layer, the initial use of optical silicone for producing optical fibers was described. The use of silicone as a coating for glass optical fibers has been described in several documents such as <JP-A-62-30152>, <JP-A-01-286939>, and Chinese Patent Publication No. 108977069. Such fibers are still not acceptable for some applications such as medical implants, even when using a silicone cladding.

[0012] Polymer fibers such as silicone fibers are described, for example, in US Patent No. 5237638A. The production of such polymer fibers is achieved by immersing an extruded core in a cladding solution and then curing the cladding. As described in US Patent No. 5692088A, a liquid silicone can be used to produce a fluid light guide. Such a liquid silicone waveguide uses a flexible tube of a liquid polymer where a specific film fixed to the inner surface serves as the cladding while the core is the fluid silicone. This technique can be used to produce a flexible catheter with a fluid core for laser ablation, as described in US Patent No. 9700655B2. The silicone light guide uses a non-curable fluid silicone, the cladding is achieved by a specific treatment of the inner surface of the tube, and the guiding sizes are on another order of magnitude. Such optical fibers are limited to cores with a large cross-section and it is difficult to reproduce a production process corresponding to the required optical properties. Also, such types of optical fibers are only used in optical distribution systems where the core diameter is not very important. For sensing applications, single-mode operation is more suitable.

[0013] In U.S. Patent Application Publication No. 2012 / 244,143 and Chinese Published Patent No. 107,907,484, highly stretchable optical fibers are described. The document, U.S. Patent Application Publication No. 2012 / 244,143, proposes the use of silk, while the documents, Chinese Published Patent No. 107,907,484 and U.S. Patent Application Publication No. 2016 / 177,002, describe the use of hydrogels. Silk- or hydrogel-based approaches are not useful for other applications or configurations, such as using this approach to obtain information from optically resonant cavities, such as Fabry-Perot cavities, located at the ends of waveguides.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

Patent Document 12

Patent Document 13

[0015] [Non-Patent Document 1] A. Sharon et al., "Resonating grating-waveguide structures for visible and near-infrared radiation", J. Opt. Soc. Am., Vol. 14, No. 11, pp. 2985 - 2993, 1997 [Summary of the Invention] [Problems to be Solved by the Invention]

[0016] Therefore, existing waveguides based on glass or plastic fibers are not suitable for a wide range of applications such as implants or other medical uses, and thus improved waveguides such as optical fibers are needed. [Means for Solving the Problems]

[0017] The inventors of the present invention have found a solution to the problems discussed above by realizing an optical waveguide such as an optical fiber having a cladding made of a thermoplastic elastomer (TPE) such as polyurethane. The manufacturing process of the fiber and waveguide of the present invention realizes a wide range of advantages, such as reducing the complexity specific to the production of optical waveguides to a level where implant manufacturers can at least partially produce their own optical waveguides.

[0018] More precisely, the present invention is realized by an optical waveguide comprising a core layer defining a longitudinal axis Z and a cladding layer surrounding the core layer. The core layer and the cladding layer are configured to transmit an optical beam having a wavelength exceeding 180 nm along the longitudinal axis Z. A cladding (20) comprising an outermost layer and at least an innermost layer in contact with the outermost layer of the core. The outermost layer of the core is made of a material having a first refractive index. The innermost layer of the cladding is made of a thermoplastic elastomer (TPE) having at least partially a second refractive index (n2) smaller than the first refractive index (n1).

[0019] In one embodiment, at least one layer of the thermoplastic plastic (TPE) is one of a styrene block copolymer (TPE-s), a thermoplastic polyolefin elastomer (TPE-o), a thermoplastic vulcanizate (TPE-v or TPV), a thermoplastic polyurethane (TPU), a thermoplastic copolyester (TPE-E), a thermoplastic polyamide (TPE-A), or an unclassified thermoplastic elastomer (TPZ). In one embodiment, the core l is made of a polymer, optionally silicone.

[0020] The thermoplastic plastic is preferably a thermoplastic plastic defined according to ISO standard 18064.

[0021] In one embodiment, the cladding layer comprises at least one additional layer of a thermoplastic plastic (TPE) made of thermoplastic polyurethane (TPU), styrene block copolymer (TPE-s), thermoplastic polyolefin elastomer (TPE-o), thermoplastic vulcanizate (TPE-v or TPV), thermoplastic copolyester (TPE-E), thermoplastic polyamide (TPE-A), or unclassified thermoplastic elastomer (TPZ).

[0022] In an embodiment, the waveguide is an optical fiber, optionally a single-mode optical fiber. In a variant, the optical waveguide has a first lateral face with a first width W1 and a second face with a second width W2 greater than the first width W1, the widths W1, W2 being defined in a plane X-Y orthogonal to the longitudinal axis Z and defined by any cross-section.

[0023] In one embodiment, the core layer is at least partially made of thermoplastic polyurethane (TPU), styrene block copolymer (TPE-s), thermoplastic polyolefin elastomer (TPE-o), thermoplastic vulcanizate (TPE-v or TPV), thermoplastic copolyester (TPE-E), thermoplastic polyamide (TPE-A), or unclassified thermoplastic elastomer (TPZ). In a particular implementation, the core layer may have a refractive index of less than 1.3, less than 1.2, or less than 1.1. In an advantageous embodiment, the inner surface of the cladding layer can comprise a metal layer and / or a dielectric layer arranged to reflect the light input-coupled into the core layer. Such a reflective layer enables the core layer to be used in a non-solid optical waveguide such as a layer of oil.

[0024] In an embodiment, the optical waveguide is configured to guide less than 100 modes, preferably less than 20 modes, more preferably less than 5 modes, defined in at least one longitudinal plane (X-Z, Y-Z). This is achieved by providing a core layer having a minimum diameter of less than 10 μm, less than 5 μm, or less than 2 μm, depending on the number of modes, as is well known for the wavelength of light guided within the core of the optical waveguide. In a variant, the optical waveguide is a tapered optical waveguide having at least two different cross-sections. The tapered optical waveguide has advantages, for example, in medical instruments that must have a tip of the optical waveguide where the diameter is very small up to the end of the optical waveguide.

[0025] In an embodiment, the light transmittance (T0) of the waveguide exceeds 50% for input-coupled light having a wavelength between 180 nm and 25 μm, and the optical waveguide has a length of less than 1 m, preferably less than 0.5 m, more preferably less than 0.25 m. In a variant, the light transmittance (T0) exceeds 80%, preferably exceeds 90%, for input-coupled light having a wavelength between 300 nm and 5 μm, preferably between 350 nm and 2 μm, even more preferably between 400 nm and 700 nm. The transmittance is a function of the materials used and possibly the doping of the materials, the wavelength of the induced light, and the length. These parameters are selected depending on the application, for example, for surgical devices where IR, visible light, or UV light will be used, depending on the required dimensions.

[0026] In an advantageous embodiment, the optical waveguide is configured to be elastically stretchable up to at least 10%, preferably at least 20%, more preferably at least 30% of the length (L) of the optical waveguide, whereby the light transmittance (T2) is maintained at at least 90% of the transmittance (T0) of the optical waveguide before being stretched after being stretched. The stretchable waveguide is particularly useful in instruments or locations where there is little available space and where it may be necessary to bend and / or stretch the optical waveguide.

[0027] The present invention also relates to an optical waveguide bundle comprising at least three optical waveguides.

[0028] The present invention also relates to a medical device comprising at least one optical waveguide of the present invention. The medical device may be a cochlear implant. In another aspect, the present invention also relates to an optical sensor comprising at least one optical waveguide of the present invention and an optical cavity sensor head disposed on the optical waveguide, the sensor head comprising an optical cavity closed by a flexible membrane.

[0029] The present invention is also realized by a method for manufacturing the described optical waveguide and includes the following steps (A to D). A) Realizing a hollow preform made of a thermoplastic elastomer, preferably thermoplastic polyurethane (TPU). B) Producing a core portion of the preform and filling the hole of the hollow preform to realize a filled preform. C) Reducing the diameter of the preform and stretching the preform to obtain an optical waveguide having a predetermined length L and a predetermined cross-section.

[0030] In one embodiment, the material of the core portion is a thermoplastic plastic (TPE) selected from among thermoplastic polyurethane (TPU), styrene block copolymer (TPE-s), thermoplastic polyolefin elastomer (TPE-o), thermoplastic vulcanizate (TPE-v, TPV), thermoplastic copolyester (TPE-E), thermoplastic polyamide (TPE-A), or unclassified thermoplastic elastomer (TPZ), and the thermoplastic plastic is defined according to ISO standard 18064.

[0031] In one embodiment, steps B and C are replaced by steps B' to D'. B') Reducing the diameter of the preform and stretching the preform until a capillary having a predetermined length (L) and a predetermined cross-section is formed, the capillary having a central opening with a predetermined cross-section during stretching. C’) A step of introducing liquid silicone into the central opening of the preform. D’) A step of polymerizing the liquid silicone to form an optical waveguide having a core made of the polymerized liquid silicone.

[0032] In one embodiment, steps C’ and D’ are replaced by steps E’ through G’. E’) A step of introducing liquid silicone during step B’ of reducing the diameter of the preform. F’) A step of maintaining the liquid silicone in a liquid state until the previous form of the optical waveguide obtains a predetermined length (L) and a predetermined cross-section during the step of reducing the diameter of the preform. G’) A step of thermally polymerizing the liquid silicone and the capillary tube to form an optical waveguide.

[0033] In one embodiment, steps B’, C’ and D’ are replaced by steps H’ through J’. H’) A step of introducing a liquid polymer into the central opening of the hollow preform after step A. I’) A step of reducing the diameter of the preform filled with the liquid polymer and stretching the filled preform until a capillary tube filled with the liquid polymer is formed, the capillary tube having a predetermined length (L) and a predetermined cross-section, and stretching. J’) A step of applying UV light to polymerize the liquid polymer. In a variant, the liquid polymer is liquid silicone or liquid siloxane.

[0034] The present invention is also realized by a method for manufacturing an optical waveguide by first realizing a complete preform using a 3D technique including the following steps (A’’ to B’’). A’’. A step of realizing a preform made entirely by 3D printing technique, the preform comprising a core portion forming the core of the optical waveguide and an outer portion forming the cladding of the optical waveguide. A step of stretching a preform to obtain an optical waveguide having a predetermined length L and a predetermined cross-section.

[0035] In one embodiment, the core portion and the outer portion of the preform are realized by 3D printing of successive layers, each of the successive layers comprising a central portion and an outer portion, the central portion having a first refractive index n1 at least on the side of the outer portion, and the outer portion having a second refractive index n2 that is smaller than the first refractive index n1 at least partially on the side of the inner portion, and is made of a thermoplastic elastomer (TPE).

[0036] In an advantageous embodiment, the 3D system can comprise an X, Y, and Z displacement mechanism for one or more nozzles having a positional accuracy of less than 10 μm, optionally less than 5 μm, and preferably less than 2 μm if possible. In an advantageous variant, the volume deposition rate of the TPE filament, preferably a TPU filament, is faster than 10 mm 3 / s, and may be faster than 24 mm 3 / s in some cases.

[0037] In one embodiment, the central portion and the outer portion of the successive layers are made of a thermoplastic elastomer (TPE) selected at least partially from among thermoplastic polyurethane (TPU), styrene block copolymer (TPE-s), thermoplastic polyolefin elastomer (TPE-o), thermoplastic vulcanizate (TPE-v or TPV), thermoplastic copolyester (TPE-E), thermoplastic polyamide (TPE-A), or unclassified thermoplastic elastomer (TPZ).

[0038] In a variant, at least two of the successive layers are layers having different shapes or different material compositions.

[0039] In an embodiment, at least one additional layer is disposed on the preform, and the additional layer is made of a thermoplastic elastomer (TPE) layer selected from among thermoplastic polyurethane (TPU), styrene block copolymer (TPE-s), thermoplastic polyolefin elastomer (TPE-o), thermoplastic vulcanizate (TPE-v, TPV), thermoplastic polyurethane (TPU), thermoplastic copolyester (TPE-E), thermoplastic polyamide (TPE-A), or unclassified thermoplastic elastomer (TPZ), and the thermoplastic elastomer is defined according to ISO standard 18064.

[0040] The present invention is also realized by the method of using the optical waveguide of the present invention related to surgical instruments during surgery. In a variant, the method of use can be carried out with respect to tracking the position of the surgical instrument and / or tracking the optical properties of the tissue near the tip of the surgical instrument.

Brief Description of the Drawings

[0041]

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Mode for Carrying Out the Invention

[0042] The present invention will be described in connection with examples and with reference to the accompanying drawings, but the present invention is not limited thereto. The drawings to be described are only schematic and not restrictive. In the drawings, the sizes of some elements are exaggerated and may not be drawn to a certain scale for the purpose of explanation. The dimensions and relative dimensions do not coincide with the actual reduction for the practice of the present invention.

[0043] As used herein, the term "optical waveguide" (also defined as waveguide), when used in this specification, encompasses all types of homogeneous or inhomogeneous, and / or tapered optical waveguides, such as single-mode fibers and multi-mode fibers, and further encompasses single-mode and multi-mode planar optical waveguides, as well as waveguide bundles comprising a plurality of optical fibers, planar optical waveguides, or mixtures thereof. Waveguide 1 has a longitudinal axis defined as the central virtual axis of waveguide 1, which is defined in the guiding direction of the optical light beam 100 within waveguide 1. The guiding of light can be carried out by total internal reflection (TIR), or by using reflective or diffractive layers or structures. In the case of a single-mode waveguide, only one mode is guided through the core of the waveguide. The virtual axis defines the directions to the Z-axis and two orthogonal axes X, Y, or the Z-axis. In this specification, the cross-section is a section defined in the X-Y plane. The longitudinal cross-section is defined in a plane containing the Z-axis.

[0044] The terms "clad" and "core" are also defined as clad layer and core layer, and may be layers that do not have a circular cross-section. This also applies to the core and clad of the aforementioned preform, and the same is true for the optical waveguide realized by the core and clad.

[0045] The type of the optical waveguide 1 of the present invention is selected according to the type of application, or geometric constraints, and the geometric shape and operating temperature requirements of the device in which the optical waveguide 1 is implemented. Typical but not exclusive, the following options are available. - Single fiber: for transmitting intensity, polarization, and spectral information - Fiber bundle: for image transmission and light beam irradiation - Multicore optical waveguides such as multicore optical fibers - Planar waveguide: for transmitting intensity, polarization, and spectral information, as well as for image transmission and illumination light beam - Fan-in / fan-out optical device

[0046] In this specification, the usage and optical functions of the optical waveguide 1, which is also defined as a waveguide such as the optical fiber 1 and the optical fiber bundle 300, are well known to those skilled in the field of guided optics and will not be described further here. Methods of constructing an optical fiber device suitable for irradiating an object and collecting the light reflected or transmitted by such an object are also known. The present invention proposes an optical waveguide such as an optical fiber and a manufacturing procedure for such a fiber. As will be described in more detail, one of the preferred manufacturing methods involves realizing a hollow-shaped preform 204 of a thermoplastic elastomer (TPE), such as a preform of thermoplastic polyurethane (TPU) that can be thermally stretched to obtain a very flexible TPU capillary 2000. The waveguide 1 of the present invention is realized by filling the hollow-shaped preform 204 with a polymer and pulling the preform to obtain a thin waveguide 1, or by first realizing a solid capillary and filling the capillary with a liquid polymer. Various methods for curing the liquid polymer in the core 10 will be further described. The liquid used to form the core 10 of the waveguide 1 is preferably silicone or siloxane.

[0047] In a first aspect, the present invention proposes a new biocompatible and highly stretchable optical waveguide 1 with a significantly reduced multimode effect by using a low-cost, biocompatible, and optically transparent material. The present invention relates to the use of a thermoplastic elastomer (TPE) for the cladding of the optical waveguide 1 and a preform for making the cladding. The cladding 20 of the waveguide 1 of the present invention consists at least partially of a thermoplastic elastomer (TPE), preferably a TPU elastomer. The cladding is made from a hollow preform 204 consisting at least partially or entirely of thermoplastic polyurethane. The core 10 of the optical waveguide may be a different type of TPE than that used for the cladding, as further described, or a liquid silicone polymerized within the tubular-shaped cladding that is realized. The present invention is not limited to waveguides having a solid core. The optical waveguide 1 may also be a hollow waveguide consisting only of a capillary tube made of an elastomer consisting at least partially of thermoplastic polyurethane (TPU) and having a coating such as a reflective metal coating or a dielectric coating further described herein on the inner surface of the capillary tube.

[0048] It should be understood that the optical waveguide 10 of the present invention may be arranged in a wide variety of forms and geometries, or may be arranged in any configuration within the medical device 2. In a first aspect, the present invention relates to an optical waveguide 1 comprising a core layer 10 defining a longitudinal axis Z and a cladding layer 20 surrounding the core layer 10. The optical waveguide 1 has an input coupling surface 31 for input-coupling an optical beam 110 into the core layer 10 and an output coupling surface 51 for output-coupling light 120 out of the core layer 10. The core layer 10 and the cladding layer 20 are configured to transmit a guided optical beam 100 through the core layer 10 along the longitudinal axis Z from the input coupling surface 31 to the output coupling surface 51, and the guided optical beam 100 has a wavelength longer than 180 nm. In all embodiments of the present invention, the cladding layer of the optical waveguide 1 is at least partially made of a thermoplastic elastomer (TPE) that is a thermoplastic rubber. TPE is a thermoplastic elastomer and is usually part of a class of copolymers of plastic and rubber or a physical mixture of polymers, consisting of materials having both thermoplastic and elastic properties. Thermoplastic plastic parts are relatively easy to manufacture, for example, by injection molding. Thermoplastic elastomers offer the advantages of both rubber materials and plastic materials. The advantage of using a thermoplastic elastomer such as TPU as at least the material of the cladding of the optical waveguide 1 of the present invention is the surprising ability to stretch to a moderate amount of elongation and return to almost the original shape, resulting in a longer lifespan and better physical range than other materials. The main difference between a thermosetting elastomer and a thermoplastic elastomer such as TPU is the type of cross-linking bond in their structures. In fact, the cross-linking characteristics are an important structural factor that gives high elastic characteristics to the optical waveguide of the present invention. TPE is well known and will not be described further here.

[0049] There are generally six classes of commercial TPEs (designated by ISO standard 18064). - Styrene block copolymer, TPS (TPE-s) - Thermoplastic polyolefin elastomer, TPO (TPE-o) - Thermoplastic vulcanizate, TPV (TPE-v or TPV) - Thermoplastic polyurethane, TPU (TPU) - Thermoplastic copolyester, TPC (TPE-E) - Thermoplastic polyamide, TPA (TPE-A) - Unclassified thermoplastic elastomer, TPZ

[0050] The cladding, as used herein, is at least partially composed of TPE, but various other TPE materials may be combined to form the cladding layer. In a preferred embodiment, the entire cladding layer is made of TPE, preferably entirely, and particularly preferably made of TPU, which is quite suitable for specific applications such as medical devices.

[0051] All of the aforementioned TPEs can be used to implement the preform 200 and the optical waveguide 1 of the present invention. TPU is a preferred option among these TPE materials. The reason is that, as will be explained in more detail, TPU has the best combination of a thermoplastic and a rubber (a thermosetting material) for the desired properties of the optical waveguide 1 of the present invention. The cladding layer 20 may be a homogeneous layer, or it may be composed of at least two parts with different layer compositions. The cladding may be made of at least one layer formed of a homogeneous TPE layer, or it may be made of a heterogeneous TPE layer. In a variant, the TPE layer may be provided with at least one other layer made of TPE on at least one of the sides of the TPE layer. Using this, for example, an optical waveguide 1 with a refractive index distribution type having a plurality of TPE layers with different refractive indices can be realized. The other TPE layer may be a heterogeneous layer that can have a diameter that varies along the length of the cladding layer. Such a heterogeneous layer, as will be further explained, has a mechanical function, is incorporated into the cladding of the waveguide, and may be an outer layer that can be used to improve the mechanical adhesion, clamping, gripping, or sliding of the device.

[0052] The core layer 10 is made of a first material having a first refractive index n1, and the cladding layer 20 is made of at least one layer that is at least partially composed of a TPE, such as a TPU, and has a second refractive index n2 that is smaller than the first refractive index n1.

[0053] In certain cases, the optical waveguide 1 is a capillary tube made of at least one cladding layer with an internal reflection layer, and the core layer 10 may be air or vacuum, or a liquid such as oil. In such cases, the waveguide has closures at both ends of the capillary tube structure.

[0054] The refractive index values of the core and / or the cladding layers 10l, 20 can cover a wide range for both materials. For example, n2 may be between 1.49 and 1.57, and n1 may be between 1.52 and 1.60. It should be understood that in a preferred embodiment, the core 10 and the cladding 20 of the optical waveguide may each be a uniform layer having a uniform refractive index n1, n2. The cladding is in contact with the core. Similar to the core 10, the cladding 20 may also be provided with another layer in contact therewith. The inner layer of the cladding 20 is in contact with the outer layer of the core 10 to ensure total reflection. The core 10 and the cladding 20 may consist of a series of layers having different individual refractive indices. The core and / or the cladding may have a continuously varying refractive index distribution across the diameter of the core 10 and / or the cladding 20, which can be achieved by doping the polymer deposited during the manufacture of the core and / or the cladding. Anyway, the refractive index of the outermost layer of the core 10 has a refractive index greater than that of the innermost layer of the cladding 20, and the innermost layer and the outermost layer are in contact.

[0055] The proposed limit of the effective length of the optical waveguide 1 can be the penetration length of the core material, for example, when using liquid silicone or another TPU composition as the core material to be introduced into the capillary of the TPE, as further explained in the method paragraph. TPU is a preferred option among TPEs as it has rubber-like elasticity, high tear and abrasion resistance, high elongation at break, and excellent thermal stability. In addition, TPU is also resistant to oils, greases, and various solvents. TPU is also the hardest among TPEs and can be printed using 3D techniques as further explained. Using TPU, complex internal and external structures of the optical waveguide 1 can be manufactured. TPU can further be prepared in a wide range of colors, has low shrinkage, and is excellent for applications where vibration damping and impact resistance are important. Due to these properties, the waveguide 1 made of TPU is particularly suitable for medical applications. For applications where such stringent requirements are not essential, the cladding and possibly the core of the waveguide 1 may also be made of another type of TPE. Various manufacturing methods are possible as further explained, and each of the various other methods can achieve various geometries and various lengths according to the application and the required throughput or diversity of strength required. Nevertheless, a typical optical waveguide 1 is an optical fiber having a fiber length of about 10 cm, for example, in the case of a medical implant, but it may be longer. For example, for a distance on the scale of an organ spanning 10 cm in the case of a human, a length of 10 cm would be sufficient (Reference 5).

[0056] In a preferred embodiment, the lineal loss of the optical waveguide 1 does not exceed 0.5 to 1 dB / cm, whereby a total loss of up to 10 to 20 dB is ensured for a round trip of a 10 cm long waveguide. The bending loss is very important for the use as a snail implant where the waveguide 1 needs to be arranged at a narrow radius (1 to 2 mm at the distal end) where the inside of the snail can be seen (Reference 3). However, such radii are incremental and the waveguide 1 may be arranged through sections having a very short bending radius of only a few millimeters. For example, in order to provide some margin to the ultimately acquired signal resulting from a resonant cavity at the tip of the fiber, it is essential that for a bending radius of about 5 mm, the loss is less than 5 dB on a round-trip basis over a fiber length of 30 mm corresponding to the average snail length. This constraint is clearly caused by the attenuation of the waveguide itself. If the attenuation of the fiber is much lower than the 0.5 to 1 dB / cm defined above, the margin available for the bending loss will be greater.

[0057] The standard attenuation values are 0.79 dB / cm at 1550 nm and 0.46 dB / cm at 1300 nm. The attenuation value is lower at 633 nm than at 0.79 dB / cm at 1550 nm and 0.46 dB / cm at 1300 nm. Therefore, an optical waveguide length exceeding 2 m can be used. Experimental data show that the optical waveguide 1 of the present invention has less attenuation in the visible part of the spectrum than in the infrared part of the spectrum.

[0058] In a preferred embodiment, the optical waveguide 1 is a single-mode or multimode fiber as shown in FIG. 1. The cross-section 30 of the core 10 and the cross-section 40 of the cladding 20 may be uniform over the length of the waveguide 1, or may vary as shown in FIG. 4.

[0059] In one embodiment shown in FIG. 3, the optical waveguide 1 has a first lateral surface 1c having a first width W1 and a second side surface 1b having a second width W2 greater than the first width W1. The widths W1 and W2 are defined in an arbitrary cross-section defined in a plane X-Y orthogonal to the longitudinal axis Z. FIG. 3 shows a planar optical waveguide 1 having a rectangular cross-section, but other cross-sections such as an elliptical cross-section or a trapezoidal cross-section may be possible.

[0060] In the embodiment shown in FIG. 4, the optical waveguide 1 is a tapered waveguide 1 having a tapered shape in at least one plane including the longitudinal axis Z. FIG. 4 shows the changing shapes and / or dimensions of the cross-sections 42, 44.

[0061] In one embodiment, the core layer 10 is made of a polymer. This polymer may be silicone.

[0062] In a variant, the core layer may be a liquid. This can be achieved by providing a very small core diameter capillary tube such that the liquid is retained in a confined state inside the optical waveguide 1. In one variant, the input and output areas of the waveguide having a liquid core may have windows for confining the liquid core so that the liquid stays inside the waveguide 1.

[0063] In one embodiment, a reflective layer may be disposed between the core layer 10 and the cladding layer 20, and the reflective layer is disposed inside the core layer 10 so as to enable total reflection and guiding of the guided light input-coupled to the core layer 20. The reflective layer may be a metal layer, a dielectric layer, or a combination thereof.

[0064] In one embodiment, the optical waveguide 1 is an optical fiber, and the core layer 10 and the cladding layer 20 are configured to guide a plurality of modes less than 100, preferably less than 20, more preferably less than 5. In one embodiment, the optical waveguide 1 is a single-mode fiber.

[0065] In one embodiment, the optical waveguide 1 is configured to guide modes less than 100, preferably less than 20, more preferably less than 5, defined in at least one longitudinal plane X-Z, Y-Z.

[0066] In one embodiment, the optical waveguide 1 is a tapered optical waveguide having at least two different cross-sections 42, 44.

[0067] The optical waveguide 1 has an optical transmittance T0 defined as the ratio of the intensity I2 of the output-coupled light 120 to the intensity I1 of the input-coupled light, I2 / I1. In one embodiment, the optical waveguide 1 has a practical length of less than 2 m, preferably less than 0.5 m, more preferably less than 0.25 m, and the intensity I2 of the output-coupled light 120 can be greater than 10% of the intensity T0 of the input-coupled light 110, preferably greater than 30%, for the input-coupled light having a wavelength between 180 nm and 25 μm.

[0068] In one embodiment, in the effective length of the optical waveguide 1, for the input-coupled light having a wavelength between 300 nm and 5 μm, preferably between 350 nm and 2 μm, more preferably between 400 nm and 700 nm, it has an optical transmittance exceeding 80%, preferably exceeding 90%. For example, in the case of a medical implant, the effective length is typically 10 - 20 cm.

[0069] In one embodiment, the optical waveguide 1 can elastically stretch up to at least 10% of the length L of the optical waveguide, whereby the optical transmittance T2 after stretching is maintained at at least 50%, preferably at least 70%, more preferably at least 90% of the transmittance T0 of the optical waveguide 1 before stretching.

[0070] One of the essential features of the optical waveguide 1 is that it can be stretched while substantially maintaining the optical guiding characteristics of the optical waveguide. In the case of the hollow-core waveguide 1 made of TPU, the core 10 is air or vacuum, and a stretch ratio of 600% is possible before the waveguide 1 breaks. In the case of the optical waveguide 1 having a core 10 made of silicone, depending on the adhesion characteristics between the core layer 10 and the cladding layer 20, the possible stretch ratio before fracture may be similar. Depending on the selected core material layer, the core layer may be damaged or fractured before the cladding layer is damaged, so the fracture limit may also depend on the elongation characteristics of the core layer. A typical silicone core layer can have a maximum stretch ratio of 50% before fracture.

[0071] In one embodiment, an adhesive layer or an anti-friction layer may be provided on the inner surface of the capillary 2000 before introducing the liquid core material. This provides a method for improving the fracture limit or the possibility of mechanical damage of the waveguide 1, for example, in situations where the radius of curvature is small and / or the traction force is large.

[0072] In an advantageous embodiment, the optical waveguide 1 can be at least partially made conductive, which is possible by using a conductive TPU material for the preform and also for the core and / or cladding of the optical waveguide. As will be further explained, 3D printing techniques can also make it possible to embed at least one electrical and conductive wire in the filled or hollow preforms 200, 204 and thus in the optical waveguide 1, which can be very useful in some medical devices. In a variant, the preforms 200, 204 may be doped preforms or preforms containing powders such as conductive powders or substances. This may help to realize the optical waveguide 1, which may be partially conductive or thermally conductive. In a variant, only the cladding 20 of the optical waveguide 1 can be made conductive or thermally conductive.

[0073] The present invention can also be realized by the optical waveguide bundle 300 shown in FIG. 5, which, as shown, comprises at least three optical waveguides 1a, 1b, 1c. In a variant 7, the optical fiber 1 may be arranged within such a fiber bundle 300, which comprises an outer mantle 302 and an inner filling material 304.

[0074] In the embodiments shown in FIGS. 6 to 9, the optical waveguides 1’, 1’’, 1’’’, 1’’’’ can comprise a plurality of core layers 10’, 10’’, 10’’’, 10’’’’.

[0075] In an embodiment, the cladding layer can comprise at least two layers, at least one of which comprises a TPU polymer or consists entirely of a TPU polymer. In an embodiment, the cladding layer may comprise, for example, at least five layers that enable the realization of a refractive index profile waveguide. In a variant, the core 10 may also consist of at least two different layers, both of which may be TPU layers or another type of TPE layer.

[0076] In an embodiment, the optical waveguide (1) may be a polarization maintaining waveguide (1). This can be realized by incorporating a polarization substance into the preform and may be added by 3D printing as described herein.

[0077] It should be understood that the optical waveguide 1 of the present invention is not limited to only the waveguide 1 comprising the core layer 10 and the cladding layer 20. Furthermore, the core layer 10 and / or the cladding layer 20 may comprise a structured part having an optical function. A typical optical structure can be a diffraction grating, such as a local diffraction grating or a distributed grating, as shown in FIG. 13. Also, a hologram type structure or layer can be arranged in or on the optical waveguide 1.

[0078] In an advantageous embodiment, at least a part of the waveguide 1 is arranged according to a resonant waveguide grating (RWG). The RWG is described, for example, below. - A. Sharon et al., "Resonating grating-waveguide structures for visible and near-infrared radiation", J. Opt. Soc. Am., Vol. 14, No. 11, pp. 2985 - 2993, 1997

[0079] The RWG is made using a multilayer configuration, combining a sub-wavelength grating and a thin waveguide. When incident light is diffracted by the grating and matched to the mode of the waveguide, resonance occurs. Since most of the spectrum of the input coupled light is not coupled into the waveguide, strong spectral effects are realized in reflection and / or transmission. This is the fact that the RWG is a corrugated waveguide and acts as a waveguide grating. Using an RWG as a seal can achieve a unique optical effect that is very difficult to identify and replicate. The RWG is generally designed to have a spatial periodicity shorter than the operating wavelength, so it is called a "sub-wavelength" structure or sub-wavelength device. The RWG ultimately has a periodicity that is close to, slightly larger than, the operating wavelength. In many cases, the period is much shorter than the free-space wavelength used, for example, one-third of the free-space wavelength. Because of the small periodicity of the RWG, various diffraction orders become impossible, which differentiates the RWG from a much simpler diffractive optical element (DOE).

[0080] Using an RWG can achieve unique input and output coupling optical effects, for example, by enabling high input and / or output coupling efficiency, or can couple input and output more efficiently or at a predetermined angle that is impossible with the use of normal diffraction gratings such as binary diffraction gratings. The RWG can realize an inexpensive waveguide with very efficient optical coupling efficiency, which may depend on a specific predetermined wavelength depending on the design, and may be realized using an embossing technique. In a modification not shown in the figure, at least one of the side surfaces of the waveguide 1 is arranged as an input coupling surface and / or an output coupling surface continuously or discontinuously over at least 50% of the total length of the waveguide. The input coupling surface and / or the output coupling surface can be configured as an RWG.

[0081] The present invention can also be realized by an optical system or a sensor including at least one optical waveguide 1 described herein. In one example, the resonant cavity is arranged as the tip of the optical waveguide 1 of the present invention. Information can be obtained from the resonant cavity using a low-cost telecom-grade LED as a light source. In such a device, a useful interference fringe needs to be visible with a cavity length of about 200 - 300 μm.

[0082] The present invention can also be realized by an optical waveguide sensor including a resonant cavity 520 arranged at the tip, where a deformable diaphragm 530 is fixed to the output end of the optical waveguide. The cavity 520 can have another function other than the resonance effect. For example, the cavity can change the optical intensity of the light beam returned to the fiber 1 due to the deformation of the membrane. In an embodiment, the cavity 520 may be filled with a liquid such as air or oil.

[0083] The present invention can also be realized by a pressure sensor including the optical waveguide of the present invention. The pressure sensor may depend on the influence of bending or stretching on the intensity transmitted through the optical waveguide, as further described in the experimental section.

[0084] In an embodiment, the medical device is an implant to be used within the cochlea. FIG. 14 shows a cochlear implant 600 having a central portion 606 to be inserted into a human ear. The mechanical guiding structure 606 is disposed in the central portion and includes at least one optical waveguide 1 according to the present invention.

[0085] In an advantageous embodiment, the medical device can include at least one optical waveguide 1 of the present invention to supply a UV light beam to a predetermined location, for example, to disinfect a location within a living body. It should be generally understood that at least one end of the optical waveguide 1 can have a shape that can be used for optical functions such as deflection, focusing, or divergence of an input-coupled or output-coupled light beam. The shape can be realized during the manufacturing process of the waveguide 1, for example, by heating the end to provide a rounded shape at the end of the waveguide.

[0086] The waveguide 1 of the present invention can be used for optogenetics as described in reference 18. The present invention also relates to a device to be used in optogenetics that includes at least one waveguide 1 according to the present invention.

[0087] The waveguide 1 of the present invention can also be used to track a surgical instrument in real time, for example, to generate position identification information at the tip of the instrument or to monitor the light information at the tip of the optical waveguide at the surgical intervention site. Accordingly, the present invention also relates to a surgical instrument including the optical waveguide of the present invention.

[0088] In a second aspect, the present invention relates to the manufacture of the aforementioned optical waveguide 1 and includes steps (A, B, C). A. A step of realizing a hollow-shaped preform 204 having a central opening 202', which is made of at least partially a thermoplastic elastomer (TPE), preferably TPU. The hollow-shaped preform 204 has an innermost layer that is a TPE elastomer having a second refractive index n2, which is substantially within 10% of the refractive index of the cladding of the optical waveguide 1 to be formed by the method of the present invention. In a variant, the entire hollow preform 204 may be made of a TPE elastomer having a second refractive index n2. B. A step of filling the central opening 202' of the hollow-shaped preform 204 to create the core portion 202 of the filled preform 200. The core portion 202 has an outermost layer that is made of a material having a first refractive index n1 that is greater than the second refractive index. In a variant, the entire core portion 202 may be made of a material having a second refractive index n2. C. A step of reducing the diameter of the preform 200 and stretching the preform until an optical waveguide 1, typically an optical waveguide having a predetermined length L and a predetermined cross-section 40, 41, is formed.

[0089] It should be understood that the refractive indices of the core 10 and the cladding 20 of the optical waveguide 1 are substantially the same as the refractive indices of the core portion and the wall of the hollow-shaped preform 204, respectively, within 10% of the error after step C of reducing them.

[0090] In one embodiment, the preform 200 of step A is made by the first injection into a mold, typically a cylindrical mold. This mold is preferably a metal or ceramic mold. The role of the cylindrical insert is to realize a preform having a central hole 202 which is also defined as a central opening. FIG. 19 shows an example of a realized TPU preform 200 comprising an outer portion 204 which is also defined as the wall of the preform, and a central opening 202 to be filled with the material constituting the core 10 of the optical waveguide when extended from the preform 200. The outer portion 204' forms the cladding 20 of the optical waveguide when extended, and the inner portion 202 forms the core 10 of the optical waveguide 1 when extended. In a variant, the hollow preform may also first be extended to a specific length to realize a thin tube of TPE to be filled with the core material and polymerized.

[0091] In an advantageous embodiment, the cylindrical preform 204 of step A is made by 3D printing techniques in step A.

[0092] In one embodiment, the filling step B is carried out, for example, using an injection technique after step A has been executed.

[0093] In an advantageous embodiment, steps A and B are carried out simultaneously using a 3D printing technique. The core and cladding layers of the preform are constructed using such a 3D printing technique by adding successive layers. In each of such layers, a different PME elastomer is printed inside a layer of TPU, preferably an annular layer. TPU is a preferred choice among TPEs as it enables adhesion between layers and allows for printing that is stronger and more durable than other TPEs. The use of the optical waveguide 1 of the present invention focuses on special waveguides such as those required for medical devices. Thus, a slow printing speed can be tolerated in order to realize a preform that may have a very complex shape. Since the length required for the use of the present invention is short, the time required to process the preform 200 may be much longer than the time normally required for telecommunication preforms, but it is acceptable. Thousands of short optical waveguides can be provided from one preform.

[0094] FIG. 28 shows a method of forming a fully filled preform 200 using a 3D machine 500. In the illustrated example of FIG. 28, a single nozzle 502 supplies a polymer stream 504. In the example of FIG. 28, the core portion 202 and the outer portion 204' of the preform 200 are realized by 3D printing of successive layers 200a-200c. FIG. 28 shows only the first three layers 200a-200c formed during the 3D printing operation. Each of the successive layers 200a-200c includes a central portion 202a-202c and an outer portion 204'a-204'c, where the central portions 202a-202c have a first refractive index n at least on the side surfaces of the outer portion, and the outer portions 204'a-204'c have a second refractive index n2 that is at least partially smaller than the first refractive index n1 up to at least the side surfaces of the inner portions 202a-202c, and are made of a thermoplastic elastomer (TPE). In an embodiment, several variations to the 3D printing process are possible. For example, during the steps of each layer, a plurality of central portions can be deposited. As explained herein, the advantage of using 3D printing is that it can realize a core portion and / or an outer portion of a complex shape of the preform 200, as shown in the examples of FIGS. 25-27.

[0095] In an embodiment, the material of the core portion 202 of the preform 200 may be a thermoplastic elastomer (TPE) selected from among styrene block copolymers (TPE-s), thermoplastic polyolefin elastomers (TPE-o), thermoplastic vulcanizates (TPE-v, TPV), thermoplastic polyurethanes (TPU), thermoplastic copolyesters (TPE-E), thermoplastic polyamides (TPE-A), or unclassified thermoplastic elastomers (TPZ), and the thermoplastic is defined according to ISO standard 18064.

[0096] Advantages and further details regarding the use of TPE, preferably TPU, for the preform and the optical waveguide 1 of the present invention are explained in more detail herein.

[0097] Elastomers are based on relatively long polymer chains that have a high degree of mobility and flexibility. These chains are linked to a network structure that prevents the chains from flowing past each other when an external stress is applied. The structure is a two-phase material where one phase is a hard solid and the other phase is the elastomer. The elastomer phase provides the elasticity of the material, and the solid phase results in physical cross-links that maintain the strength of the material. When processing such materials, two different glass transition temperatures are involved, one being the glass transition temperature Te of the elastic polymer and the other being the glass transition temperature Th of the hard phase, with Th > Te. The material is basically brittle and hard in both phases when the temperature T < Te, and the material begins to become a viscous fluid when T > Th, so it is necessary to use it basically between these two temperatures. This is important in the production of optical waveguides such as optical fibers due to the fact that a step-index refractive index is required as a basic configuration for weakly guiding fibers, and thus two different polymers such as two different types of TPU are required. Care must be taken in the selection of the two TPU materials required to create a step-index profile. The temperature is usually well below 0 °C and is not much of an issue in the selection. However, one of the two polymers, for example, one of the two different types of TPU, will begin to melt at a lower temperature than the other TPU, so Th will have a direct impact on the drawing of the fiber. Furthermore, if the heating system is not properly designed, it will create a non-uniform radial heat distribution in the preform, increasing the effect of the difference from Te.

[0098] In an exemplary embodiment, to produce an optical fiber, two types of TPU are used, namely, Elastollan 1185A and Elastollan 1185A10W from BASF, which have refractive indices nd of 1.505 and 1.553, respectively. Since the processing temperatures of both TPUs are relatively similar, an appropriate drawing temperature can be easily selected.

[0099] In a typical implementation, the preforms 200, 204 can be realized in a two-step injection molding process using, for example, an Arburg Allrounder 170S injection machine. The first injection is performed along the cylindrical axis in a cylindrical mold having dimensions of 15 mm in diameter and 100 mm in length, using a cylindrical insert in the center. In a preferred embodiment, the preform of the first step generates a cladding portion of the fiber by using Elastollan 1185A TPU. The second injection can be realized by using Elastollan 1185A10W to fill the holes and create the core portion of the preform.

[0100] In an embodiment, the extruder of the 3D printer has a completely sealed, PTFE-lined filament guide to prevent the filament from buckling during the printing process.

[0101] In a variant, the inner diameter of the nozzle is 0.25 mm, and in some cases, it can be as small as 0.1 mm. An internal pressure system can be provided to supply a smooth PTE filament, preferably a PTU filament.

[0102] The 3D system can be equipped with an X, Y, and Z-direction displacement mechanism for one or more nozzles having an accuracy of less than 10 μm, and in some cases, less than 5 μm, and preferably less than 2 μm, to achieve a precise structure of the model. In an advantageous variant, the volume deposition rate is faster than 10 mm 3 / second, and in some cases, it can be faster than 24 mm 3 / second. The viscosity of TPU at the rated nozzle temperature is much lower compared to rigid thermoplastic plastics. This enables high intermolecular diffusion or healing during the FDM process. Therefore, TPU is a more suitable choice than other polymers for realizing optical waveguide preforms.

[0103] In an embodiment, the filled or hollow preforms 200, 204 may be made of at least one layer of a TPE, preferably TPU, on which at least one additional layer is disposed. Such an additional layer can be realized on the inner wall of the cylindrical opening of the TPE layer or on the outer surface of the TPE layer.

[0104] The preforms 200, 204, which are at least partially made of TPE, preferably TPU, can comprise a plurality of layers having a predetermined order of refractive indices, such that, for example, a refractive index profile layer is provided in the core layer 10 of the optical fiber 1 when realized by stretching the preform 200. Realizing an optical waveguide having a refractive index profile around the core 10 of the optical waveguide has several advantages with respect to the propagation characteristics of the guided light beam. The refractive index profile can be adapted to control the type and number of guided modes in the optical waveguide 1.

[0105] In an advantageous embodiment, as will be commented in more detail in the experimental paragraph, the inner surface of the TPE-based preforms 200, 204, preferably preforms made of TPU, is polished to enhance the smoothness of the surface of the preform in order to reduce the optical losses due to the interface between the core and the cladding of the optical fiber to be produced.

[0106] By 3D printing of the filled or hollow preforms 200, 204, which are at least partially made of TPE, preferably TPU, it is possible, if not difficult, to realize a dopant distribution that is impossible or difficult to achieve using conventional step-index optical fibers and standard injection techniques for manufacturing optical waveguide preforms. This is because the geometry of each layer created using the 3D printing process can be adapted. In a first aspect, there is an advantage in realizing microstructured and nanostructured optical waveguides 1, such as optical fibers. The manufacture of such fibers is often limited to methods suitable for specific materials only. In a second aspect, the outer and inner cross-sections can have a predetermined shape. The cross-section can be, for example, square or hexagonal over the entire length of the preform.

[0107] Furthermore, the cross-sectional shape may vary over a predetermined length of the preform. The preform may, for example, have a hexagonal cross-section over 80% of the length of the preform, and the two end portions may have another cross-sectional shape, for example, circular. In a variant, the preform may be made of a first type of TPE, such as a TPU elastomer, over a first length and made of another type of polymer, such as another type of TPE or TPU, over a second length. This can be easily achieved by 3D printing technology.

[0108] In an embodiment, the preforms 200, 204 and their optical waveguides 1 may have a Y-shape or any other shape that results in three or more branches in order to realize an optical waveguide 1 that can have N input coupling branches and M output coupling branches, where M is equal to or greater than N. A TPU-based optical waveguide may, for example, have two input coupling portions and four output coupling portions. Realizing this using injection techniques, while not impossible, would be very difficult as opposed to the 3D printing technique proposed in the present invention.

[0109] In other embodiments, the cladding 20 may be formed around at least one solid element, such as a solid shaft, such that the waveguide is firmly attached to the solid element without the need to adhere or fix it to the solid element. This eliminates the need to wrap or fix the waveguide 1 around or to such elements, which can be components of a medical device, and can reduce costs.

[0110] Realizing the preform using 3D printing techniques is particularly interesting in the framework of the present invention because the optical waveguide 1 can have a specific outer shape and / or inner shape that can be easily adapted within or on the surgical device. For example, a filled preform, i.e., a preform having a cladding and a filled core, can be realized such that there is at least one longitudinal opening in the cladding, for example, thereby allowing the optical waveguide 1 to be attached to a very thin guiding wire. In a variant, the preform, and thus the final optical waveguide, may have a surface with undulations in the length and / or width directions of the preform and the optical waveguide.

[0111] In another aspect, by realizing the preform using 3D printing techniques, a waveguide having a donut-shaped cross-section or a holey shape including two cores can be easily fabricated. In a variant, a preform and fiber housed in a hexagon may be realized in a 3D process. In other variants, the preform and the optical waveguide manufactured from the preform are also at least partially made of a photonic crystal.

[0112] In yet another aspect, by 3D printing a filled preform that is at least partially clad with a TPE, preferably a TPU, and / or is entirely realized with a TPU elastomer, it is possible to add mechanical form and function to the outside of the formed optical waveguide where attachment and fixation to a thin surgical instrument are important. For example, during 3D printing, side structures can be added to the preform, and then the optical waveguide can be realized. The side structures can be realized, for example, with a harder polymer. By using 3D printing techniques, at least two deposited layers can have different compositions. It would be particularly difficult to realize the shapes described above by using an injection technique to realize a TPU-based preform. This is mainly due to the limitations caused by the design complexity induced by injection molding as compared to 3D printing. Known drilling, extrusion, and injection molding, or mechanical adjustment of a TPU-based preform would be difficult and time-consuming. 3D printing of a TPU-based preform has a significant competitive advantage in realizing a waveguide with a TPU-based cladding, optionally with a TPU-based core.

[0113] Figures 25-27 show cross-sections of preforms of complex shapes that can be realized by 3D printing TPU preforms 200, 204. Such preforms 200, 204 may also be made of a TPE polymer.

[0114] In one variation, a hollow-shaped preform 204 is first formed, and then an elongated capillary filled with a polymer that can be different from a TPE elastomer such as silicone is realized. A variation of such a method includes the steps (A-D') schematically shown in FIG. 10. A) The step of realizing a hollow preform 204 that is at least partially made of a TPE elastomer as described above. Step B’) Reducing the diameter of the hollow preform 204 and stretching the preform until a capillary tube 2000 having a predetermined length L and a predetermined cross-section 40, 41 is formed, the capillary tube 2000 having a central opening 2002 with a predetermined cross-section 30, the stretching step. Step C’) Introducing liquid silicone 11 into the central opening 220 of the preform. Step D’) Polymerizing the liquid silicone to form an optical waveguide 1 having a core 10 made of the polymerized liquid silicone 11 and having a predetermined length L and an outer diameter D2. The diameter of the core is directly related to the ratio of the outer diameter D1 of the preform to the diameter of the opening of the preform. This is because this ratio does not change during step B’ of reducing the diameter.

[0115] In one embodiment, steps C’ and D’ are replaced by steps E’, F’, G’. Step E’) Introducing liquid silicone 11 during step B of reducing the diameter of the preform. Step F’) During the step of reducing the diameter of the preform 200, maintaining the liquid silicone in a liquid state until a previous form of the optical waveguide obtains a predetermined length (L) and a predetermined cross-section 40, 41. Step G’) Thermally polymerizing the liquid silicone 11 and the capillary tube 2000 to form the optical waveguide 1. In a variant, the capillary tube 2000 may be polymerized before the polymerization of the liquid silicone.

[0116] In one embodiment, steps B’, C’ and D’ are replaced by steps H, I, J. Step H’) After step A, introducing the liquid polymer 11 into the central opening 202’ of the hollow preform 204. Step I’) Reducing the diameter of the preform 204 filled with the liquid polymer 11 and stretching the filled preform 200 until a capillary tube 2000 filled with the liquid polymer 11 is formed, the capillary tube having a predetermined length L and a predetermined cross-section 40, 41, the stretching step. J) A step of polymerizing a liquid polymer by applying UV light.

[0117] In the step of one embodiment, the liquid polymer is a liquid silicone and, in some cases, a liquid siloxane.

[0118] In one embodiment of the method, the obtained optical waveguide 1 is a multimode optical fiber. In a variant, the obtained waveguide is a single-mode optical fiber.

[0119] In one embodiment, the obtained waveguide is an optical waveguide having a non-circular cross-section defined in any lateral plane X-Y. In an embodiment, the core 10 of the waveguide can have a very small cross-section that is less than 1 μm. Here, the process for achieving this will be described.

[0120] In order to reduce the fiber diameter during stretching, it will be necessary to adjust the stretching parameter, which is the winding speed at which the fiber diameter is reduced. For this purpose, both materials, TPU and silicone, must be processable in such a small geometry. With respect to silicone, this will be very easy since it remains liquid and follows the deformation of the TPU. If the final fiber diameter is not small enough and the silicone has not yet been polymerized, a new stretching process can be started to reduce the size of the fiber. This process is similar to that proposed in reference 16, where the introduced fiber is melted while the rotating rod winds the microfiber. In the case of the inventors, the melting will be carried out using the same heater that is used to stretch the fiber from the preform. Since the size of the incoming fiber is as small as 100 μm or less, it is necessary to achieve melting quickly so that there will be no time for the silicone to polymerize again. It is essential to wind around the rod rather than around a normal spool. The reason for this is that if the hot TPU fiber is not sufficiently cooled, the fibers will stick together. In the stretching of normal optical fibers, this cooling is carried out by removing the furnace and the winding spool.

[0121] In one embodiment, the length of the useful optical waveguide 1 is determined by cutting the optical waveguide until an acceptable light transmittance is obtained. Therefore, a transmittance measurement step can be performed to determine the ratio T1 / T0 of the light transmittance of the short optical waveguide, and then a new step F consisting of cutting the optical waveguide 1 to another predetermined length to generate a second short optical waveguide whose length is shorter than that of the first short optical waveguide follows. The second short optical waveguide has a transmittance ratio T2 / T1 that is greater than the transmittance ratio T1 / T0 of the first short optical waveguide.

[0122] In a modified example, micro- or nano-sized optical fibers can be realized. These diameters are usually 1 μm and may be less than 1 μm in some cases. When a preform made of a TPE such as TPU is filled with a UV-polymerizable adhesive or silicone, the liquid introduced into the central opening follows the deformation of the TPU cylinder when reducing the diameter of the preform. As a result, the central opening 2002 cannot be closed even when it reaches a micro-sized diameter during the pulling operation of the capillary tube. When a predetermined length and outer diameter are reached, the internal liquid is polymerized by UV light passing through the TPE or TPU.

[0123] The present invention also relates to a method for manufacturing a system that can be used to realize a fan-in / out optical system (Reference 17) and enables the connection of the output and input of a multi-core fiber (Reference 17). This method preferably includes the following steps. - A step of preparing a plurality of optical fibers having an uncured liquid core and typically having a diameter of 40 μm. - A step of aligning a plurality of fibers in a mechanical holder having a plurality of holes and a dispersion arrangement of the same fiber geometry as that of the multi-core fiber to form a bundle. The mechanical holder preferably has a cylindrical outer diameter that is equal to or larger than the multi-core fiber to be connected. - In one embodiment, the number of fibers introduced into the holder is seven, and they can be of various types. - The step of bonding the mechanical holder assembly, preferably using a UV adhesive, to fix all components together.

[0124] In one embodiment, the plurality of optical fibers have cores made at least partially of TPE. In a variant shown in FIG. 17, the preform is a composite preform. For example, the block 4000 can comprise two holders (as shown in FIG. 16) in which wires are arranged, and this structure can be overmolded by a cladding layer of TPE such as TPU as shown in FIG. 17. The preform 200 can be produced by injection molding, and the first half of the preform constitutes a multi-core preform. The other half is a plurality of, preferably seven, separate tubes that are directly aligned and connected to the first part of the preform comprising two holders.

[0125] FIG. 15 shows an example of an apparatus 4000 comprising a part of a preform with two holders 4004, 4004 arranged to preferably implement a fan-in / fan-out optical component.

[0126] FIG. 16 shows a portion of a preform with two holders of FIG. 15 for making fan-in / fan-out optical components, the two holders comprising a plurality of wires 4001 that are to be removed after injection of the TPE polymer. FIG. 16 shows two inserts with seven core pins prior to injection of the cladding. After overmolding the volume between the two holders 4002 and 4004, wires are present within that volume by the TPE layer 4003 (FIG. 16). Then, after cooling the TPE and pulling out the wires 4001, a plurality of axial holes remain that can accommodate introduction of another polymer such as silicone. The preform thus formed may be stretched to make a multi-core fiber or may be stretched or heated across the central portion of the preform to form a multi-core structure having a reduced diameter central portion that can be used in a fan-in / fan-out optical device.

[0127] FIG. 18 shows the demolding process of such a multi-core fiber after injection of the TPU layer 4003, which is the cladding layer shown in FIG. 17. FIG. 19 shows a multi-core fan-in / fan-out platform realized using the molds of FIGS. 16 and 17, after melting and stretching to reach the final desired diameter. The fan-in / fan-out component 4100 shown in FIG. 19 comprises two ends 4104, 4106 with spaced cores and an intermediate portion 4102 where the cores are closer together than in the two ends 4104 and 4106.

[0128] In order to reduce the size of the multi-core preform portion to the size of a normal fiber and to reduce the tube exiting the transition area to normal size, a melting and stretching process is realized in the transition area of the composite preform. In one embodiment, the fiber may be disposed within a ring or tube that forms something similar to a multi-core fiber structure. This structure is fixed by a thermal flash and then stretched thermally to reach the final diameter equal to that of the multi-core fiber to be connected.

[0129] The present invention also relates to an illumination device and an illumination method based on a usage method for changing the diameter of the core of an optical fiber. Such an illumination method includes the following steps. - Preparing the optical waveguide 1 described in this specification. - Introducing light into the core 10 of the optical waveguide 1. - Extending a part of the optical waveguide 1 in order to couple light from the core 10 to the side surface of the optical waveguide through the cladding 20.

[0130] In a variant, the extension may be periodically extended by an automatic mechanism. In one embodiment, a dopant can be incorporated into the TPE cladding layer in order to realize the light diffusion effect by the cladding layer. By incorporating the dopant, it becomes possible to make the extended part of the optical waveguide more visible, and thus to realize a lighting effect that is useful for, for example, optical decoration.

[0131] Experimental results a. Realization of an optical fiber with a TPU core and a TPU cladding In an exemplary process according to the present invention, three types of step-index optical fibers having the dimensions listed in Table 1 were realized. The V value for each fiber was determined considering the minimum diameter realized at three different wavelengths (633 nm, 830 nm, and 1300 nm). The estimated value of the corresponding number of modes was determined using Equation 1 and the numerical aperture (NA) 0.38. It was assumed that NA remains stable with respect to the wavelength, for example, without material dispersion. It can be noticed that the F3 fiber approaches the action of a few mode fiber (FMF) at wavelengths > 800 nm. The number of modes M is given by Equation (1) and depends on the V value, which is a dimensionless parameter that is often used in the category of step-index fibers. The V value is defined as follows.

Equation

[0132] The fiber 1 realized according to the process of the present invention was first visually evaluated under a microscope, white light was input-coupled, and induced within a fiber length of 40 cm. Subsequently, the cut-back method was used to measure the attenuation of the fiber. The obtained attenuation values are listed in Table 2, and except for a wavelength of 1300 nm, they are very similar to the values measured with a planar sheet of TPU polymer. At the third optical window (for example, 1550 nm), since strong attenuation was observed in this wavelength band, the attenuation was not measured. [Table 2]

[0133] The bending loss was measured using a set of sample fibers F3. The results are shown in FIG. 23. Fiber F3 was bent twice around a metal rod and manually maintained while the power signal was stable. Since the TPU fiber is very soft, any contact directly applies stress to the interface between the core and the cladding, and when the fiber bends, the light transmittance changes. Furthermore, in order to bend the fiber around the rod, a non-negligible elongation of the fiber inevitably occurs, causing additional losses. However, the fiber may sometimes be used in short lengths for applications that require a small bending radius.

[0134] By using the change in the transmission intensity of the optical waveguide 1, a pressure sensor or system can be realized in which the transmission intensity changes in response to the applied pressure or bending. FIG. 22 shows the experimental results of the change in intensity b by adhering a fiber to the outer surface of an inflatable balloon using an 8 cm long fiber made of a TPU core and a TPU cladding. FIG. 22 shows the detected change in intensity by inflating the balloon. The length of the fiber changed by up to 30%. The core dimensions changed by 30% from an initial 10 μm to 6.6 μm. The wavelength used was 633 nm. FIG. 24 shows the change in the number of modes as a function of the elongation received by the fiber, expressed in %. The initial length is shown as 0%, and 128% means that the length increased 2.28 times.

[0135] b.Realization of a fiber with a TPU cladding and a silicone core In the experimental process according to the present invention, a TPU-based capillary tube is filled with silicone to realize an optical fiber. In such a process of the TPU capillary tube 2000, the first step is to produce a clad preform 200, preferably by injection molding. The dimensions of the clad need to consider the ratio of the final clad diameter to the core fiber diameter in order to obtain a multi-mode fiber having a predetermined number of guided modes, or to ensure fiber and core sizes close to or equal to those of a standard single-mode fiber. The diameter of the clad needs to comply with the constraints of the dimensions to be molded, but also depends on the diameter of the initial central hole required for using an insert inside the mold. This insert is an important component of clad production because it can be bent by the flow of the hot polymer during the molding process. Based on such constraints and typical injection molding equipment, the typical diameter of the clad is up to 20 mm for a length of about 100 mm. The central hole diameter of the preform 200 is usually 1 mm or more due to the polymer flow stress during molding. A hole diameter of the preform of about 0.5 mm can be obtained. Another constraint of the insert is the quality of the insert surface and the adhesion to the TPU. The surface quality will directly affect the optical interface between the TPU and the silicone, and above all, the optical induction loss inside the final fiber. Therefore, surface treatment is generally necessary to reduce roughness and the adhesion force of the TPU. Once the clad preform is obtained, a capillary tube of a hair-thin TPU fiber is realized by a standard thermal fiber drawing process. Since the fiber length required for most of the applications concerned here is very short (10 - 15 cm), the shrinkage due to the taper and diameter variation is less, and thus the process constraints are relaxed.

[0136] Tests were conducted to achieve the intrusion of silicone into the small-diameter capillary tubes, and a glass capillary tube 2000 with a central hole of 15 μm and an outer diameter of 125 μm was used. Using the syringe technique, it is possible to inject silicone with a length of about 100 mm. By using the vacuum pump technique together with the syringe, it is possible to achieve an intrusion depth of more than 100 mm. By modifying the wettability of the inner wall of the capillary tube, and thus with the help of the force to fill the capillary tube, the initial intrusion length is improved. In addition, by using a more high-performance vacuum pump and enhancing the efficiency of the syringe on the opposite side of the fiber, an intrusion depth over a fiber length of up to 20 - 40 cm can be achieved.

[0137] In a typical silicone-based optical fiber, the core material is generally made of silicone used as an LED liquid encapsulant. This silicone is of the OLS-5291 type of the OPTOLINQ trademark, commercialized by Caplinq Corporation (Canada).

[0138] The cladding material was a TPU polymer that could be found in very flexible grades such as BASF's 1185A TPU. The cladding dimensions to be achieved could be 200 μm, the core diameter could be 50 μm, and the length of fiber 1 could be at least 250 mm. The fiber typically has a high numerical aperture of 0.32. The typical fiber achieved could stretch by about 50% without significant optical loss, that is, the optical fiber could be stretched up to 375 mm. Due to the large numerical aperture of fiber 1, the bending loss was less than 20 - 30%. This could not be achieved with other polymer-based fibers of the prior art, such as PMMA fibers. The tests showed that even when the optical fiber 1 of the present invention was crushed, the mechanical or optical properties of the optical fiber did not change. For example, even when a lateral force of 20 N - 30 N was applied, the optical fiber returned to its original shape without any change in its mechanical or optical properties.

[0139] The typical light transmittance of the optical waveguide 1 measured using an optical bench was as follows. - The attenuation at 633 nm was 0.2 to 0.3 dB / cm. - The attenuation at 1300 nm was 0.3 to 0.5 dB / cm. - The typical attenuation at 1550 nm was 0.6 to 0.9 dB / cm.

[0140] When the length of the optical waveguide 1 of the present invention is typically shorter than 100 mm, it can be used for some UV applications. In the case of UV, at a length of 50 mm, the estimated transmittance at 300 nm was about 30 to 60%, but the transmittance value can vary greatly depending on the type of polymer used and, of course, the UV wavelength. The transmittance below 300 nm is typically less than 20 to 10% when the fiber length is about 50 mm.

[0141] Applications of the waveguide 1 of the present invention One of the important applications of the optical waveguide 1 of the present invention relates to implants, more particularly cochlear implants. In such applications, 3D printing of the TPU-based preforms described herein is particularly well-suited. The optical waveguide 1 is mounted at the tip of a pressure sensor that is disposed at the tip of the cochlear implant. The optical waveguide 1 is intended to minimize accidental structural damage within the cochlea. Recent studies have demonstrated pressure pulses corresponding to voice levels that cause severe impulse trauma resulting from inserting an electrode array into the sealed space of the cochlea during implantation. The solution of implementing the optical waveguide 1 of the present invention will enhance the reliability and flexibility of the surgery and improve the quality of the implant by avoiding any failures during the important process of implantation. The cost of cochlear implants, including surgery, can vary between $30,000 and $50,000. Although rare, surgical failures may result in a second surgery after the patient's recovery time, while implant malfunction (due to structural damage) can also occur in some cases. Furthermore, the remaining structures and nerve tissue within the cochlea are highly relevant to the sound quality experienced by the patient. The insertion process can cause significant trauma to this structure due to pressure pulses caused by the surgeon's manipulation and penetration of the important membrane. The new optical fiber techniques have revolutionized surgical procedures, can suppress the growth of fibrotic tissue, and can maintain the state of the cochlea in order to succeed in future regenerative medicine and enhance the therapeutic effect. Furthermore, implantable optical technologies can also improve postoperative rehabilitation by continuously monitoring physiological parameters. By enabling feedback measurement of important physiological or environmental parameters with the optical waveguide of the present invention, not only implant failures but also surgical failures can be dramatically reduced. The optical waveguide of the present invention further opens the door to long-term and highly localized monitoring of physiological parameters. This is very interesting as it allows for the early detection of medical problems and thus minimizes potential post-implantation trauma and the resulting surgeries.In addition, by enhancing the reliability of the implant and the consumables required for the surgery, solutions for reducing waste are also provided. The potential reduction in waste will continue to significantly enhance the energy efficiency of the implantation operation by reducing the likelihood of implant failure and the trauma that can occur due to failure, and further by preventing important surgeries from occurring from a long-term perspective.

[0142] Other important uses that may benefit from the optical waveguide 1 of the present invention include, but are not limited to, the following. - Ophthalmology. A pressure-sensitive device using the optical waveguide 1 is useful for cataract surgery. - Spinal traumatology. Post-operative pressure monitoring (vertebral or intervertebral disc replacement). - Cardiac traumatology. Blood flow and blood pressure monitoring after a heart attack, local microscopic surgery. - Cardiac surgery, plastic surgery, urology, and neurology. - Security and anti-counterfeiting applications. - Industrial sensor applications

[0143] The various uses of the waveguide of the present invention may create new markets as an entirely new class of optical waveguides. As an example, a Bragg grating may be provided on the TPU-based waveguide 1 to improve the sensitivity of the waveguide without requiring any additional sensors. The optical waveguide 1 of the present invention can be used by implant manufacturers, as described, to guide light to remote locations where it is dangerous to use glass optical fibers for sensing purposes. The optical waveguide 1 of the present invention can also be used in, for example, a fan / in-fan / out system as described in reference 15.

[0144] Still other applications are directed to decorative lighting devices. TPEs such as TPU clad may be doped with diffusing particles. In one example, by pulling a portion of the optical waveguide, light can be made somewhat visible at a portion where the core size has been reduced. In other applications, a Bragg grating may be disposed on the optical waveguide 1 of the present invention, which makes it possible to replace, for example, a SiO2-based optical waveguide or fiber. Such a waveguide 1 can be used in cryogenic applications where there is substantially no thermal expansion of SiO2.

[0145] Background Information and References [1] Gerd Keiser, Fei Xiong, Ying Cui and Perry Ping Shum, “Review of diverse optical fibers used in biomedical research and clinical practice”, Journal of Biomedical Optics 19(8), 080902 (August 2014) [2] Sedat Nizamoglu, Malte C. Gather, and Seok Hyun Yun, “All-Biomaterial Laser Using Vitamin and Biopolymers”, Adv. Mater. 2013, 25, 5943-5947 [3] M. Llera, T. Aellen, J. Hervas, Y. Salvade, P. Senn, S. Le Floch and H. Keppner, “Liquid-air based Fabry-Perot cavity on fiber tip sensor”, Opt. Express 24, 8054-8065 (2016) [4] Sara T. Parker, and al., “Biocompatible Silk Printed Optical Waveguides”, Adv. Mater.2009,21,2411-2415 [5] Myunghwan Choi, Matjaz Humar, Seonghoon Kim, and Seok-Hyun Yun, “Step-Index Optical Fiber Made of Biocompatible Hydrogels”, Adv. Mater. 2015, 27, 4081-4086; [6] M. Han, and A. Wang, “Exact analysis of low-finesse multimode fiber extrinsic Fabry-Perot interferometers”, Applied Optics (43), pp. 4659-4666, 2004; [7] Brandon W. Swatowski, Chad M. Amb, W. Ken Weidner, Ranjith S. John, Jeffrey D. Mitchell, “Advances in manufacturing of optical silicone waveguides for high performance computing” 2014 IEEE Avionics, Fiber-Optics and Photonics Technology Conference (AVFOP), ThB1, 2014 [8] Md Rejvi Kaysir, Alessio Stefani, Richard Lwin, and Simon Fleming, “Flexible optical fiber sensor based on polyurethane”, 2017 Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR), 2017 [9] Timo Stover and Thomas Lenarz, “Biomaterials in cochlear implants”, GMS Curr Top Otorhinolaryngol Head Neck Surg, 2009

[10] http: / / info.hotims.com / 45604-161

[11] Hugh L. Narcisco, Jr., “Silicone optical waveguide”, US5237638A, 1991

[12] Nathan N. Haese, and al. “Pressure sensor utilizing a polyurethane optical fiber”, US4915473A, 1989

[13] https: / / www.aliexpress.com /

[14] Herve Elettro. Elastocapillary windlass: from spider silk to smart actuators. Mechanics of the fluids [physics.class-ph]. UPMC, 2015.

[15] O.Shimakawa et al. Connector type fan-out device for multi-core fiber “, SEI Tech Review nr 77, pp.23-28, Oct.2013.

[16] [M. Sumetsky, Y. Dulashko, S. Ghalmi, “Fabrication of miniature optical fiber and microfiber coils”, Opt. Lasers Eng., 48 (2010), pp. 272-275].

[17] O. Shimakawa, H. Arao, M. Shiozaki, T. Sano, A. Inoue, "Connector type fan‐out device for multi‐core fiber", SEI Tech. Review, no. 77, pp. 23‐28, Oct. 2013.

[18] S.Chen et al., "Near-infrared deep brain stimulation via upconversion nano-particle-mediated optogenetics",Science 359, 2088, pp.679-684, Feb. 2018.

Claims

1. A method for manufacturing an optical waveguide (1), comprising: A. realizing a hollow preform (204) for forming a cladding (20) of the optical waveguide (1), the hollow preform (204) comprising an innermost layer made of a thermoplastic polyurethane (TPU) having at least partially a second refractive index (n2) and a central opening (202'); B. filling the central opening (202') of the hollow preform (204) to create a core portion of a preform (200) for forming a core of the optical waveguide (1), the core portion comprising an outermost layer having a first refractive index (n1) greater than the second refractive index (n2), the innermost layer being formed in contact with the outermost layer to realize a filled preform (200); C. reducing the diameter of the filled preform (200) and elongating the filled preform (200) to obtain an optical waveguide (1) having a predetermined length L and a predetermined cross-section (40, 41). A method for manufacturing an optical waveguide (1).

2. The method according to claim 1, wherein the central opening (202') of the hollow preform (204) is filled with a thermoplastic elastomer (TPE) selected from thermoplastic polyurethane (TPU), styrene block copolymer (TPE-s), thermoplastic polyolefin elastomer (TPE-o), thermoplastic vulcanizate (TPE-v, TPV), thermoplastic copolyester (TPE-E), thermoplastic polyamide (TPE-A), or unclassified thermoplastic elastomer (TPZ).

3. Steps B and C are:[[]] B') reducing the diameter of the hollow preform (204) and elongating the hollow preform (204) until a capillary tube (2000) having a predetermined length (L) and a predetermined cross-section (40, 41) is formed, the capillary tube (2000) having a central opening (2002) with a predetermined cross-section (30); C') introducing liquid silicone (11) into the central opening (202') of the hollow preform (204). D') polymerizing the liquid silicone (11) to form an optical waveguide (1) having a core (10) made of the polymerized liquid silicone (11); The manufacturing method according to claim 1, which is replaced by.

4. Steps C' and D' are E') introducing liquid silicone (11) during step B' of reducing the diameter of the hollow preform (204); F') during the step of reducing the diameter of the hollow preform (204), holding the liquid silicone in a liquid state until a previous form of optical waveguide obtains a predetermined length (L) and a predetermined cross-section (40, 41); G') thermally polymerizing the liquid silicone (11) and the capillary (2000) to form an optical waveguide (1); The manufacturing method according to claim 3, which is replaced by.

5. Steps B', C', and D' are H') after step A, introducing a liquid polymer (11) into the central opening (202) of the hollow preform (204) to realize a filled preform (200); I') reducing the diameter of the filled preform (200) filled with the liquid polymer (11) and stretching the filled preform (200) until a capillary (2000) filled with the liquid polymer (11) is formed, the capillary having a predetermined length (L) and a predetermined cross-section (40, 41); J') applying UV light to polymerize the liquid polymer; The manufacturing method according to claim 3, which is replaced by.

6. The method according to claim 5, wherein the liquid polymer is liquid silicone.

7. At least one additional layer is disposed on the hollow-shaped preform (204), the additional layer being made of a thermoplastic elastomer (TPE) selected from thermoplastic polyurethane (TPU), styrene block copolymer (TPE-s), thermoplastic polyolefin elastomer (TPE-o), thermoplastic vulcanizate (TPE-v, TPV), thermoplastic polyurethane (TPU), thermoplastic copolyester (TPE-E), thermoplastic polyamide (TPE-A), or unclassified thermoplastic elastomer (TPZ), the thermoplastic elastomer being defined according to ISO standard 18064, the manufacturing method according to any one of claims 1 to 6.

8. The method according to any one of claims 1 to 7, wherein the preform (200) is made of TPU by a 3D printing technique.

9. The method according to claim 8, wherein the preform (200) is made to realize a multi-core optical waveguide (1) having at least six openings and having at least six cores.

10. The method according to any one of claims 1 to 9, wherein the preform (200) and the optical waveguide (1) are made to have a non-uniform cross-section over a predetermined length, the cross-section being defined to be orthogonal to the lengths of the preform and the optical waveguide (1) respectively.

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