Light emitting optical fiber

Abstract

This invention belongs to the field of optical component technology, and particularly relates to a light-emitting optical fiber, comprising a fiber core with an average refractive index of n0, and a microstructure cladding covering the fiber core. The microstructure cladding includes two phases, one of which is arranged in an array within the other phase. The two phases are a high-refractive-index phase and a low-refractive-index phase, respectively. The high-refractive-index phase has a refractive index of n1, and the low-refractive-index phase has a refractive index of n2. The refractive index n1 of the high-refractive-index phase is greater than the average refractive index n0 of the fiber core, and the refractive index n2 of the low-refractive-index phase is less than the average refractive index n0 of the fiber core. A first protective layer and a second protective layer are sequentially coated around the microstructure cladding. Compared to polymer fiber cores, the light-emitting optical fiber provided by this invention has better weather resistance, is less prone to aging, has higher mechanical strength, and a simpler fabrication process. It is more conducive to light emission within the optical fiber, has a smaller variance in luminous intensity, and achieves total internal reflection, thereby ensuring higher luminous brightness.

Description

Technical Field

[0001] This invention belongs to the field of optical component technology, and particularly relates to a light-emitting optical fiber. Background Technology

[0002] Light-emitting fiber refers to a fiber where, during transmission, not only is the transmitted light transported from the incident end to the exit end, but a portion of the light also shines through the cladding, resulting in side-emitting light. Conventional optical fibers aim to minimize or eliminate light leakage from the fiber cladding, reducing non-inherent losses due to light scattering and thus improving transmission efficiency. However, the purpose of light-emitting fiber fabrication is to minimize inherent losses through appropriate fiber design, thereby increasing non-inherent losses and scattering losses. This enhances the brightness of side-emitting light. Most existing light-emitting fibers are polymer fibers, typically achieving side-emitting light by incorporating scattering particles into the cladding material or by creating scattering points through mechanical scratches in the cladding. This type of fiber presents several problems:

[0003] (1) The intrinsic loss of polymer optical fiber is very high, generally up to 500dB / km. The light loss is extremely high during transmission, resulting in very low brightness of the side-scattered light and very large brightness non-uniformity along the length of the fiber.

[0004] (2) Polymer optical fibers have poor weather resistance and are easily aged in environments such as high temperature and ultraviolet radiation, which affects the light transmission effect.

[0005] (3) Polymer optical fibers have poor mechanical properties. After long-term use, the material becomes brittle and is very easy to break. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this invention provides a light-emitting optical fiber. The purpose is to solve the technical problems of polymer optical fibers, which have high intrinsic loss, resulting in extremely high light loss during transmission, extremely low brightness of side-scattered light, and very large brightness non-uniformity along the fiber length; poor weather resistance, easily aging in high temperature, ultraviolet and other environments, thus affecting the light transmission effect; and poor mechanical properties, becoming brittle and easily breaking after long-term use.

[0007] The present invention provides a light-emitting optical fiber, the specific technical solution of which is as follows:

[0008] A light-emitting optical fiber includes a core with an average refractive index of n0. The core is covered with a microstructure cladding, which includes two phases. One phase is arranged in an array within the other phase. This array arrangement results in a smaller variance in luminous intensity and higher luminous brightness. The two phases are a high-refractive-index phase and a low-refractive-index phase, respectively. The high-refractive-index phase has a refractive index of n1, and the low-refractive-index phase has a refractive index of n2. n1 is greater than n0, and n2 is less than n0. The bottoms of both the high-refractive-index phase and the low-refractive-index phase are attached to the outer peripheral surface of the core. This attachment structure effectively protects the core and prolongs the axial propagation of light. At least one of the high-refractive-index phases and the low-refractive-index phase is structurally disconnected. This disconnection ensures total internal reflection within the disconnected phase structure, resulting in higher luminous brightness. The microstructure cladding is sequentially covered with a first protective layer and a second protective layer.

[0009] In some embodiments, the line connecting any two points on the axial section of the fiber core falls within the axial section of the fiber core. This achieves uniform light emission.

[0010] In some embodiments, the solid angle of the end face of the light-emitting optical fiber is less than 4π.

[0011] In some embodiments, the microstructure cladding has air holes. The air holes in the microstructure cladding also ensure uniform light emission.

[0012] In some embodiments, the low-refractive-index phase is arranged in an array within the high-refractive-index phase, and the low-refractive-index phase has one or more shapes and structures selected from triangular prism, polygonal prism, cylindrical, polygonal frustum, frustum, and cone.

[0013] In some embodiments, the refractive index of the first protective layer is n3, the refractive index of the second protective layer is n4, and n3 and n4 are greater than or less than n2.

[0014] In some embodiments, the fiber core material is one or more of quartz glass, borate glass, germanate glass, silicate glass, phosphate glass, fluoride glass, and oxyhalide glass, and is a homogeneous phase. Using glass for the fiber core, compared to polymer cores, offers better weather resistance, is less prone to aging, has higher mechanical strength, and a simpler manufacturing process. Furthermore, the convex cross-section of the core is more conducive to light emission within the fiber, ensuring uniformity and high emission capacity.

[0015] In some embodiments, the high refractive index phase is made of one or more of quartz glass, borate glass, germanate glass, silicate glass, fluoride glass, and oxyhalide glass; the low refractive index phase is made of one or more of air, gas mixtures, phosphate glass, fluoride glass, and oxyhalide glass.

[0016] Preferably, the low-refractive-index phase is made of air, meaning the microstructure layer is formed by short-pulse laser etching or chemical etching to create a circumferentially uniformly distributed arrangement, with the arrangement length less than or equal to the thickness of the microstructure layer, forming a frustum-shaped, conical, or corn-stick-shaped pore structure. The laser-etched air holes can uniformly scatter light, guiding it into the protective layer and achieving uniform light output; it also effectively enhances the heat dissipation of the optical fiber, reducing its heat dissipation cost.

[0017] In some embodiments, the first protective layer is one or more transparent optical materials selected from silicone resin, fluororesin and UV-curable resin, oxide transparent glass or ceramic, fluoride transparent glass or ceramic, nitride transparent glass or ceramic, oxynitride transparent glass or ceramic, oxysulfide transparent glass or ceramic, sulfide transparent glass or ceramic, and selenide transparent glass or ceramic; the second protective layer is one or more transparent optical materials selected from polymethyl methacrylate, polystyrene, polycarbonate, polydiallyl diethylene glycol carbonate, styrene-propanenitrile copolymer, transparent polyamide, oxide transparent glass or ceramic, fluoride transparent glass or ceramic, nitride transparent glass or ceramic, oxynitride transparent glass or ceramic, oxysulfide transparent glass or ceramic, sulfide transparent glass or ceramic, and selenide transparent glass or ceramic.

[0018] The present invention has the following beneficial effects: (1) The two-phase design of the microstructure cladding can restrict some light to be transmitted in the fiber core area, effectively enabling long-distance light transmission; the uniform and orderly distribution of the low-refractive-index phase of the microstructure cladding can allow light to be scattered to the protective layer through the low-refractive-index phase, resulting in a smaller variance in luminous intensity and higher luminous brightness. The structure of the high-refractive-index phase and the low-refractive-index phase attached to the fiber core can effectively protect the fiber core and extend the propagation of light in the axial direction; the two phases are not connected, which can ensure total internal reflection of light in the structure of the non-connected phases, resulting in higher luminous brightness.

[0019] (2) The first protective layer provides protection for the microstructure cladding, while the second protective layer provides overall protection for the optical fiber and improves its mechanical strength.

[0020] In summary, compared with polymer fiber cores, the light-emitting optical fiber provided by this invention has good weather resistance, is not easy to age, has high mechanical strength, and has a simple manufacturing process. It is more conducive to light emission within the optical fiber, has a smaller variance in light intensity, and achieves total internal reflection, thereby ensuring higher light brightness. Attached Figure Description

[0021] Figure 1 This is a three-dimensional structural schematic diagram of a light-emitting optical fiber according to Embodiment 1 of the present invention;

[0022] Figure 2 This is a three-dimensional structural diagram of the fiber core and microstructure cladding in a light-emitting optical fiber according to Embodiment 1 of the present invention;

[0023] Figure 3 These are cross-sectional views of the microstructure cladding in different axial directions in Embodiment 1 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0025] An optical fiber for emitting light includes a fiber core 1, a microstructure cladding 2 covering the fiber core 1, and a first protective layer 3 and a second protective layer 4 sequentially covering the microstructure cladding 2. The fiber core 1 is made of one or more of the following: quartz glass, borate glass, germanate glass, silicate glass, phosphate glass, fluoride glass, and oxyhalide glass; the line connecting any two points on the axial section of the fiber core 1 falls within the axial section of the fiber core 1, and the end face of the fiber core 1 is a convex arc surface.

[0026] The microstructure cladding 2 comprises at least two phases, one of which is arranged in an array within the other, meaning that one phase is regularly and periodically embedded discretely within the other phase. Based on refractive index, it is divided into a high-refractive-index phase 21 and a low-refractive-index phase 22. The high-refractive-index phase 21 is made of one or more of the following: quartz glass, borate glass, germanate glass, silicate glass, phosphate glass, fluoride glass, and oxyhalide glass. The low-refractive-index phase 22 is made of, but is not limited to, air, gas mixtures, fluoride glass, and oxyhalide glass. In some embodiments, the bottoms of both the high-refractive-index phase 21 and the low-refractive-index phase 22 are attached to the outer peripheral surface of the fiber core 1, and the angle between the major axis of both phases and the lateral section of the fiber core 1 is 10–170°. In some embodiments, the proportion of the total volume of the low-refractive-index phase 22 to the volume of the microstructure cladding 2 is called the phase ratio, which varies regularly along the axial direction of the fiber core 1, such as a linear or sinusoidal function. Preferably, the phase ratio is smaller in the head and tail regions of the optical fiber, and larger in the middle of the optical fiber, thereby making the scattering efficiency in the middle higher and improving the light output uniformity of the optical fiber along its entire length.

[0027] In some embodiments, the low-refractive-index phase 22 is arranged in an array within the high-refractive-index phase 21, and the low-refractive-index phase 22 has one or more shapes and structures selected from triangular prism, polygonal prism, cylindrical, polygonal frustum, frustum, and cone.

[0028] The first protective layer 3 is a transparent optical material, which is one or more of the following: silicone resin, fluororesin and UV-curable resin, oxide transparent glass or ceramic, fluoride transparent glass or ceramic, nitride transparent glass or ceramic, oxynitride transparent glass or ceramic, oxysulfide transparent glass or ceramic, sulfide transparent glass or ceramic, and selenide transparent glass or ceramic; the second protective layer 4 is a transparent optical material, which is one or more of the following: polymethyl methacrylate, polystyrene, polycarbonate, polydiallyl diethylene glycol carbonate, styrene-propanenitrile copolymer, transparent polyamide, oxide transparent glass or ceramic, fluoride transparent glass or ceramic, nitride transparent glass or ceramic, oxynitride transparent glass or ceramic, oxysulfide transparent glass or ceramic, sulfide transparent glass or ceramic, and selenide transparent glass or ceramic.

[0029] The refractive index relationship between the core 1 and the two phases of the microstructure layer is: n1 > n0, n0 > n2; where the average refractive index of the core 1 is n0, the refractive index of the high-refractive-index phase 21 is n1, and the refractive index of the low-refractive-index phase 22 is n2. Based on the relationship n1 > n0 and n0 > n2, it can be concluded that when light propagates between the core 1 and the high-refractive-index phase 21, it cannot leak through the high-refractive-index phase 21 and can only undergo total internal reflection within the core 1 layer. When light propagates between the core 1 and the low-refractive-index phase 22, since the refractive index of the core 1 is higher than that of the low-refractive-index phase 22, the light is scattered from the low-refractive-index phase, achieving the effect of light emission. The refractive index of the first protective layer is n3, and the refractive index of the second protective layer is n4. n3 and n4 are greater than or less than n2.

[0030] Example 1

[0031] This embodiment provides a light-emitting optical fiber, the specific technical solution of which is as follows:

[0032] like Figure 1 As shown, a light-emitting optical fiber includes a fiber core 1, a microstructure cladding 2 covering the fiber core 1, and a first protective layer 3 and a second protective layer 4 sequentially covering the microstructure cladding 2.

[0033] like Figure 2 As shown, in this embodiment, the fiber core 1 is cylindrical, and the material of the fiber core 1 of the light-emitting optical fiber is quartz glass with a purity of 99.99%-99.99999%.

[0034] The microstructure cladding 2 contains at least two phases, one phase is embedded in the other phase in a circular array, that is, one phase is regularly and periodically embedded in the other phase, and is divided into a high refractive index phase 21 and a low refractive index phase 22 according to the refractive index. In this embodiment, the high refractive index phase 21 is made of borate, and the low refractive index phase 22 is made of air holes, that is, circumferentially uniformly distributed frustum or conical air holes are etched in the microstructure layer. The design of the air holes mainly serves two purposes: (1) light guiding, so that the light scattered between the fiber core 1 and the low refractive index phase can be discharged, so as to achieve the effect of side light emission; (2) heat dissipation, so that the heat generated by the light during transmission can be dissipated through the air holes. Figure 3 The invention presents cross-sectional views of the microstructure cladding 2 in different axial directions, which are significantly different from the materials and structures of currently commonly used side-emitting optical fibers. This optical fiber improves the side-emitting ability of the optical fiber, enabling light to be transmitted over longer distances, while ensuring the uniformity of side-emitting light.

[0035] In this embodiment, the first protective layer 3 is a transparent silicate glass material, which provides protection for the microstructure cladding layer 2.

[0036] In this embodiment, the second protective layer 4 is made of transparent polystyrene material, which provides protection for the optical fiber as a whole and improves its mechanical strength.

[0037] Example 2

[0038] In this embodiment, the core 1 is made of silicate glass, the high refractive index phase 21 is made of germanate glass, and the low refractive index phase 22 is made of oxyhalide glass (this material corresponds to the experimental data in the table, and has better brightness). The fluoride glass can precipitate two phases by annealing heat treatment at a certain temperature and time, and one phase in the glass is regularly, periodically, and discretely embedded in the other phase. The rest of the technical solutions are the same as in Embodiment 1.

[0039] Example 3

[0040] In this embodiment, the core 1 is made of quartz glass, and in the microstructure cladding 2, the high refractive index phase material is fluoride glass, the low refractive index phase material is phosphate glass, and the rest of the technical solutions are the same as in Embodiment 1.

[0041] With the same structural design in all three embodiments, the material selection differs, resulting in the following experimental data on gloss intensity:

[0042]

[0043] The luminous intensity of all three embodiments was above 2100 cd, and the overall variance of the embodiments decreased from large to small.

[0044] Another set of side-emitting intensity measurements for the light-emitting fiber of this invention is provided: The side-emitting intensity measurements were performed using an InGaAs detector with a probe diameter of 1 mm and a test area of ​​0.8 mm². 2 The measurable wavelength range is 500-1700nm. This detector converts the optical signal transmitted from the side of the optical fiber within the detection area into an electrical signal and transmits it to the data acquisition device, i.e., an oscilloscope. The experiment uses a red light source to provide infrared light of constant intensity. This source consists of a power supply, a laser, and a collimator at the end of the optical fiber. The maximum power of the light source is 1.1W, the brightness is adjustable, and the spot diameter is 15mm. During the experiment, the optical fiber is moved using an electric translation stage while the detector position remains unchanged, and the lateral emission intensity at each test point on the optical fiber is measured.

[0045] The testing steps are as follows:

[0046] 1) Connect the light source, motorized translation stage, detector, and oscilloscope in sequence. Connect the detector to a 50Ω coaxial cable, with the other end of the cable connected to the oscilloscope;

[0047] 2) Set the running speed of the electric translation stage to 300Hz, the motion mode to relative motion, the displacement unit to mm, adjust the initial position of the electric translation stage to 10mm, set the movement distance to 5mm each time, and record the position points as P0, P1...P9, P10 in sequence.

[0048] 3) Fix the fiber under test (outside the test area) flat on the electric translation stage with tape, and couple the fiber and the light source with a coupling length of 20mm;

[0049] 4) Adjust the probe position of the detector so that it is vertically aligned with the P0 position of the fiber processing section under test, and finally adjust the distance between the detector and the test point of the fiber to 5mm.

[0050] 5) Simultaneously turn on the light source and oscilloscope, set the power supply current to 0.5A, use the oscilloscope to automatically collect data, adjust the time value represented by each horizontal bar on the oscilloscope screen to 2s, and collect the voltage value of each test point of a single optical fiber in sequence.

[0051] 6) Repeat the above operation steps for each optical fiber of Examples 1, 2 and 3 after treatment, record the experimental data, and take the average value of each group of data as the measurement result.

[0052]

[0053] As shown in the table above, it can be observed that the single-sided emission voltage values ​​from P0 to P10 in Examples 1, 2, and 3 fluctuate around 35mV, with a fluctuation range of 1mV. This indicates that the luminescent optical fiber obtained by the present invention has uniform brightness and better performance. The smaller the voltage value, the greater the transmission loss, resulting in more and more optical signals leaking out from the fiber sheath and less optical signal reaching the end face. Consequently, the transmission loss of the optical fiber is greater, and the side emission intensity increases accordingly.

[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. The present invention is not limited to the examples described above. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A light-emitting optical fiber, characterized in that, The fiber includes a core with an average refractive index of n0. The core is covered with a microstructure cladding, which comprises two phases, one of which is arranged in an array within the other. The two phases are a high-refractive-index phase and a low-refractive-index phase, respectively. The high-refractive-index phase has a refractive index of n1, and the low-refractive-index phase has a refractive index of n2. n1 is greater than n0, and n2 is less than n0. The bottoms of both the high-refractive-index and low-refractive-index phases are attached to the outer peripheral surface of the core. At least one of the high-refractive-index phases and the low-refractive-index phase is structurally non-communicating. The microstructure cladding has air pores. The microstructure cladding is sequentially covered with a first protective layer and a second protective layer. The refractive index of the first protective layer is n3, and the refractive index of the second protective layer is n4. Both n3 and n4 are greater than or less than n2. The material of the low refractive index phase is air, that is, the microstructure layer is formed by short pulse laser writing or chemical etching to form a circumferentially uniformly distributed arrangement, the arrangement length of which is less than or equal to the thickness of the microstructure layer, forming a frustum-shaped, conical, or corn-stick-shaped pore structure.

2. The light-emitting optical fiber according to claim 1, characterized in that, The line connecting any two points on the axial section of the fiber core falls within the axial section of the fiber core.

3. The light-emitting optical fiber according to claim 1, characterized in that, The solid angle of the end face of the light-emitting optical fiber is less than 4π.

4. The light-emitting optical fiber according to claim 1, characterized in that, The core material is one or more of the following: quartz glass, borate glass, germanate glass, silicate glass, phosphate glass, fluoride glass, and oxyhalide glass.

5. The light-emitting optical fiber according to claim 1, characterized in that, The high refractive index phase is made of one or more of the following materials: quartz glass, borate glass, germanate glass, silicate glass, fluoride glass, and oxyhalide glass; the low refractive index phase is made of one or more of the following materials: air, gas mixture, phosphate glass, fluoride glass, and oxyhalide glass.

6. The light-emitting optical fiber according to claim 1, characterized in that, The first protective layer is one or more of the following transparent optical materials: silicone resin, fluororesin and UV-curable resin, oxide transparent glass or ceramic, fluoride transparent glass or ceramic, nitride transparent glass or ceramic, oxynitride transparent glass or ceramic, oxysulfide transparent glass or ceramic, sulfide transparent glass or ceramic, and selenide transparent glass or ceramic.

7. The light-emitting optical fiber according to claim 1, characterized in that, The second protective layer is one or more transparent optical materials selected from polymethyl methacrylate, polystyrene, polycarbonate, polydiallyl diethylene glycol carbonate, styrene-propanenitrile copolymer, transparent polyamide, oxide transparent glass or ceramic, fluoride transparent glass or ceramic, nitride transparent glass or ceramic, oxynitride transparent glass or ceramic, oxysulfide transparent glass or ceramic, sulfide transparent glass or ceramic, and selenide transparent glass or ceramic.

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