Bundle fiber and method for securing bundle fiber

Abstract

The present invention provides a bundled fiber in which the ends are fixed with glass, and in which the melting of the glass is prevented even when light with a wavelength range of 350 nm to 500 nm is incident on it, and a method for fixing the bundled fiber. [Solution] A bundle fiber is constructed using multiple optical fibers, and glass containing at least phosphoric acid but no lead, with a light transmittance of 95% or more for light in the wavelength range of 350 nm to 500 nm, is melted by heating. The molten glass is then filled between each optical fiber at the end of the bundle fiber, thereby fixing the end of the bundle fiber with glass. Furthermore, the bundle fiber is optically coupled to a light source in the wavelength range of 350 nm to 500 nm, preventing the glass fixing the end of the bundle fiber from overheating when the light enters the optical fiber.

Description

[Technical Field]

[0001] This invention relates to bundled fibers and a method for fixing bundled fibers. [Background technology]

[0002] With the increasing power output of laser processing machines, there is a demand for higher density of multiple optical fibers. One method for achieving this density is the use of bundled fibers, which are made by bundling multiple optical fibers together and inserting them into ferrules or sleeves. Light with a wavelength of 500 nm or less is used as the incident light on these bundled fibers. Even metallic materials such as copper and gold, which have high reflectivity in visible light, will experience absorption at wavelengths of 500 nm or less.

[0003] The ends of bundled fibers are fixed with an organic resin adhesive, such as epoxy resin (see Patent Document 1). However, when light with a wavelength of 350 nm to 500 nm is incident on each optical fiber of the bundled fiber, the temperature of the ends of the bundled fibers rises, and the organic resin adhesive deteriorates and burns due to the heat, which presents a problem.

[0004] Therefore, a method for forming bundle fiber terminals using glass (especially low-melting-point glass) instead of the aforementioned organic resin adhesive has been invented (see Patent Document 2). In Patent Document 2, the terminal (end) of the bundle fiber is fused by immersion in molten glass (low-melting-point glass), and lead-borate glass is mentioned as the type of glass. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 55-111908 [Patent Document 2] Japanese Patent Application Publication No. 01-114804 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the applicant's investigation revealed that when light at 405 nm, which falls within the wavelength range of 350 nm to 500 nm, is incident on the bundle fiber of Patent Document 2, the glass bonding the ends of the bundle fiber generates heat and melts. It was also found that this melting results in problems such as the movement of each optical fiber at the end of the bundle fiber, or the deposition of lead (Pb) in the glass.

[0007] The present invention has been made in view of the above problems, and aims to provide a bundled fiber in which the ends are fixed with glass, and in which melting of the glass is prevented even when light in the wavelength range of 350 nm to 500 nm is incident, and a method for fixing the bundled fiber. [Means for solving the problem]

[0008] The aforementioned problems are solved by the present invention as follows. Specifically, the bundle fiber of the present invention is composed of multiple optical fibers, glass is filled between each optical fiber at the end of the bundle fiber, the end of the bundle fiber is fixed with glass, the bundle fiber is optically coupled to a light source in the wavelength range of 350 nm to 500 nm, the glass contains at least phosphoric acid but does not contain lead, the light transmittance of light in the wavelength range of 350 nm to 500 nm is 95% or more, and the heat generation of the glass when light in the wavelength range of 350 nm to 500 nm is incident on the optical fiber is prevented.

[0009] Furthermore, the present invention's method for fixing bundled fibers is characterized by forming a bundled fiber with multiple optical fibers, melting a glass that contains at least phosphoric acid but does not contain lead, and has an optical transmittance of 95% or more for light in the wavelength range of 350 nm to 500 nm by heating, filling the spaces between each optical fiber at the end of the bundled fiber with the glass, and fixing the end of the bundled fiber with the glass. [Effects of the Invention]

[0010] According to the bundle fiber or bundle fiber fixing method of the present invention, when light with a wavelength range of 350 nm to 500 nm is incident on the optical fiber, heating and melting of the glass can be prevented. Therefore, movement of each optical fiber at the end of the bundle fiber, or lead deposition in the glass, can be prevented. [Brief explanation of the drawing]

[0011] [Figure 1] This is an explanatory diagram showing the fixing state of the bundle fiber end composed of seven optical fibers according to the first embodiment of the present invention. [Figure 2] This is an explanatory diagram showing the fixing state of the bundle fiber end composed of 12 optical fibers, according to a second embodiment of the present invention. [Figure 3] Figure 1 is a side view showing the structure of a bundle fiber. [Figure 4] This image shows the state of adhesion at the end of a bundle fiber according to an embodiment of the present invention. [Modes for carrying out the invention]

[0012] The first feature of this embodiment is that glass is filled between each optical fiber at the end of a bundle fiber composed of multiple optical fibers, fixing the bundle fiber end with glass, the bundle fiber is optically coupled to a light source in the wavelength range of 350 nm to 500 nm, the glass contains at least phosphoric acid but does not contain lead, has an optical transmittance of 95% or more for light in the wavelength range of 350 nm to 500 nm, and prevents the glass from heating up when light in the wavelength range of 350 nm to 500 nm is incident on the optical fiber.

[0013] The second feature is that a bundle fiber is composed of a plurality of optical fibers, and glass containing at least phosphoric acid and no lead and having a light transmittance of 95 (%) or more in the wavelength range of 350 (nm) or more and 500 (nm) or less is melted by heating, and the melted glass is filled between the respective optical fibers at the end of the bundle fiber to fix the end of the bundle fiber with glass, which is a method for fixing the bundle fiber.

[0014] According to these bundle fibers or the method for fixing the bundle fiber, since the light transmittance of the glass with respect to light in the wavelength range of 350 (nm) or more and 500 (nm) or less with a high energy density is set to 95 (%) or more, heat generation and melting of the glass when light in the wavelength range of 350 (nm) or more and 500 (nm) or less enters the optical fiber can be prevented. As a result, movement of each optical fiber at the end of the bundle fiber or precipitation of lead in the glass is prevented.

[0015] Also, the third feature is that the difference in the coefficient of thermal expansion between the optical fiber and the glass is 7.8×10 ( / ℃) or less, which is a method for fixing the bundle fiber.

[0016] According to this method for fixing the bundle fiber, when the glass is fixed between the respective optical fibers, crack generation in the glass is prevented.

[0017] Hereinafter, the bundle fiber according to the embodiment of the present invention will be described with reference to FIGS. 1 to 3. The bundle fiber 1 according to the present invention is composed of a plurality of optical fibers 2. The number of optical fibers 2 can be set to any number of 2 or more. In the first embodiment shown in FIG. 1, the number is 7, and in the second embodiment shown in FIG. 2, the number is 12. The respective optical fibers 2 are bundled to form one bundle fiber 1.

[0018] A portion of the bundled fiber 1 is bundled and held in place by a cylindrical retaining component 4. Furthermore, molten glass 3 is filled between each optical fiber 2 for a fiber axial length of 1 mm from the end of each optical fiber 2, as shown by the hatching in Figures 1 to 3. The ends of the bundled fiber 1 are fixed in place by this glass 3.

[0019] The optical fiber 2 is composed of a core and a cladding having a refractive index lower than that of the core, surrounding the core. The mode is not limited. Each optical fiber 2 has its coating stripped and its outer diameter is set to any dimension of 1 mm, i.e., 1000 μm or less. The optical fiber 2 is made of quartz glass, with a glass transition temperature of 1000 °C or higher, a softening point of approximately 1600 °C or higher, and a thermal expansion coefficient of 0.5 × 10⁻⁶ -6 It is ( / ℃).

[0020] The glass 3 that secures the ends of the bundle fiber 1 contains at least phosphoric acid (H3PO4) but does not contain lead (Pb), and has a bending point of 400°C or higher and less than 1000°C. It may also contain phosphorus (P), zinc (Zn), potassium (K), aluminum (Al), and silica (SiO2) as needed. Furthermore, the thermal expansion coefficient of glass 3 is 0.5 × 10⁻⁶. -6 ( / ℃) or higher 8.3 × 10 -6 The temperature is below ( / °C). The heating temperature of glass 3 is within a temperature range that is above the bending point of glass 3 and below the glass transition temperature of optical fiber 2.

[0021] When this glass 3 is heated, it melts and fills the space between each fiber 2 from the end along the fiber axial length to a depth of 1 mm, fixing each fiber 2 with the glass 3 and forming a bundle fiber 1.

[0022] A portion of each optical fiber 2, excluding the portion with an axial length of 1 mm from the end, is bundled and held by a retaining component 4 along the circumferential direction of each optical fiber 2. Examples of retaining components 4 include cylindrical parts such as ferrules, pipes, or sleeves. The retaining component 4 only needs to have a circular inner circumference. Furthermore, the entire component is formed into a cylindrical shape by integral molding or assembly. The material of the retaining component 4 can be arbitrarily selected, but in this embodiment, examples include zirconia, stainless steel (SUS: Steel Special Use Stainless), and glass.

[0023] The bundle fiber 1 formed in this manner is optically coupled to a light source (not shown). The wavelength range of the light incident from the light source into each optical fiber 2 is between 350 nm and 500 nm, within the wavelength range from ultraviolet A (UVA) to blue light.

[0024] The light energy E of the light incident from the light source into bundle fiber 1 is expressed by the following equation 1.

[0025]

number

[0026] As shown in equation 1, the shorter the wavelength λ (m) of light, the stronger the light energy E becomes. The wavelength range from 350 nm to 500 nm is a relatively short wavelength range within the overall wavelength range of light, so the light energy E is strong in this range. In this embodiment and this embodiment, the overall wavelength range of light is considered to be from 315 nm to 830 nm, and the explanation continues below. Note that E: light energy (J), h: Planck constant (6.62607 × 10⁻¹⁰). -34 (Js)), ν: frequency (Hz), c: speed of light in a vacuum (2.99792458 × 10⁻¹⁸) 8 (m / s), where λ is the wavelength (m) of light (electromagnetic wave) in a vacuum.

[0027] Based on the applicant's investigation, it was found that lead precipitation occurred due to the melting of the glass. Therefore, the causal relationship between the presence of lead and the melting of the glass was first investigated. It was then confirmed that by first making the glass lead-free, lead precipitation in the glass was prevented when light in the wavelength range of 350 nm to 500 nm was incident from the light source into the optical fiber 2.

[0028] However, further investigations by the applicant revealed that simply removing lead from the glass's composition is insufficient. When light with a wavelength range of 350 nm to 500 nm is incident from the light source into the optical fiber 2 after the glass has been fixed, the glass generates heat, which causes it to melt.

[0029] As a result of further investigation into the causes of heat generation and melting of glass, the applicant found that, assuming the glass is lead-free, the inclusion of phosphoric acid can prevent heat generation and melting of the glass. Specifically, the applicant found that the light transmittance of the glass changes due to the inclusion of phosphoric acid.

[0030] Furthermore, it was found that by setting the threshold for light transmittance at which heating and melting of the glass are prevented when light in the wavelength range of 350 nm to 500 nm, where the light energy E is relatively high, is incident on the optical fiber 2, heating and melting of the glass can be prevented even when such light is incident. Therefore, in the present invention, the light transmittance of the glass 3 for light in the wavelength range of 350 nm to 500 nm is set to 95% or higher.

[0031] Next, the method for fixing the bundle fiber 1 will be explained. First, multiple and arbitrary numbers of optical fibers 2 are prepared as optical fibers constituting the bundle fiber 1. Meanwhile, as described above, glass 3 is also prepared, which contains at least phosphoric acid but does not contain lead, has a bending point of 400°C or higher and less than 1000°C, and has an optical transmittance of 95% or higher for light in the wavelength range of 350 nm or higher and 500 nm or lower.

[0032] The immersion of the glass 3 between each optical fiber 2 may be done by placing the glass 3 beforehand at the ends of the optical fiber 2 and melting it by heating before immersion, or by preparing the glass 3 by heating in a melting bath and immersing the ends of each optical fiber 2 with a fiber axial length of 1 mm.

[0033] The molten glass 3 is filled between each optical fiber 2 at the end of the bundle fiber 1 using one of the above methods. After filling, the bundle fiber 1 is cooled to fix the end of the bundle fiber 1 with the glass 3.

[0034] For heating and melting glass 3, one of the following heating methods can be selected: heating by laser irradiation, heating by a heater, heating by electrical discharge, or heating by a lamp.

[0035] The bundle fiber 1, whose ends have been fixed by the above process, is optically coupled to a light source in the wavelength range of 350 nm to 500 nm.

[0036] With the above configuration of bundle fiber 1 or method of fixing bundle fiber 1, the light transmittance of glass 3 for light in the wavelength range of 350 nm to 500 nm, which has a high energy density, is 95% or more. Therefore, when light in the wavelength range of 350 nm to 500 nm is incident on the optical fiber 2, heating and melting of glass 3 can be prevented. As a result, movement of each optical fiber 2 at the end of bundle fiber 1, or lead deposition in glass 3, is prevented.

[0037] The phosphoric acid content that yields the aforementioned effect is approximately 40-45 (mol%).

[0038] Furthermore, the difference in thermal expansion coefficients between optical fiber 2 and glass 3 is 7.8 × 10 -6 It is desirable to set the temperature to ( / °C) or lower. This is because it prevents crack formation in the glass 3 when the glass 3 is fixed between each optical fiber 2. The difference in thermal expansion coefficients is 7.8 × 10 -6( / ℃) In the case of super, in the glass 3 having a composition containing phosphoric acid and not containing lead, it was confirmed by the study of the applicant that cracks occur during fixation.

[0039] Examples according to the present invention will be described below, but the present invention is not limited only to the following examples. Descriptions overlapping with the above embodiments will be omitted or simplified.

Example

[0040] As shown in FIG. 4, a bundle fiber according to this example was constituted by seven optical fibers. Each optical fiber was bundled and held by an integrally formed cylindrical zirconia ferrule as a holding component. The inner diameter of the ferrule is 377 (μm).

[0041] Furthermore, as shown in FIG. 4, glass melted between each optical fiber having a fiber axial direction length of 1 (mm) from the end of each optical fiber was filled, and the end of the bundle fiber was fixed with glass.

[0042] Each optical fiber constituting the bundle fiber is a step index (SI: Step Index) type fiber, the coating is stripped, the core diameter is 105 (μm), the cladding diameter is 125 (μm), and the thermal expansion coefficient is 0.5×10 -6 ( / ℃).

[0043] The glass contains phosphoric acid (H3PO4) and does not contain lead (Pb), and further contains phosphorus (P), zinc (Zn), potassium (K), aluminum (Al), and silica (SiO2). The content of phosphoric acid is 40 to 45 (mol%), the yield point is 450 to 505 (℃), the thermal expansion coefficient is 5.6×10 -6 ~8.3×10 -6 ( / ℃), and the heating temperature is 500 to 800 (℃).

[0044] Such glass was disposed at the end of the optical fiber, heated by laser irradiation and immersed between each optical fiber, and the end of the bundle fiber was fixed with glass.

[0045] The difference in thermal expansion coefficients between each optical fiber and glass is 7.8 × 10⁻⁶. -6 Set to ( / °C) or lower.

[0046] After fixing each optical fiber with glass, a lightfastness test was performed on the optical fibers of the bundle fiber by continuously irradiating them with light of a wavelength of 405 nm and an output of 10 W from a light source for 2000 hours. The light transmittance of the glass to 405 nm light was 99%.

[0047] As a result, it was confirmed that no melting or deterioration occurred in the glass even after 2000 hours.

[0048] Furthermore, the difference in thermal expansion coefficients between the optical fiber and glass is 7.8 × 10⁻⁶ -6 By setting the temperature to below ( / °C), it was confirmed that crack formation in the glass was prevented when the glass bonded between each optical fiber. [Explanation of Symbols]

[0049] 1 bundle fiber 2 Optical Fibers 3 Glass 4. Retaining parts

Claims

1. Glass is filled between each optical fiber at the end of a bundle fiber composed of multiple optical fibers, and the bundle fiber end is fixed with glass. The bundled fiber is optically coupled to a light source in the wavelength range of 350 nm to 500 nm. The glass contains at least phosphoric acid and is lead-free, and has a light transmittance of 95% or more for light in the wavelength range of 350 nm to 500 nm. A bundled fiber that prevents the glass from overheating when light with a wavelength range of 350 nm to 500 nm is incident on the optical fiber.

2. A bundle fiber is formed using multiple optical fibers, A glass containing at least phosphoric acid but free of lead, and having a light transmittance of 95% or more for light in the wavelength range of 350 nm to 500 nm, is melted by heating. Molten glass is filled between each optical fiber at the end of the bundle fiber, A method for securing bundled fibers by fixing the ends of the bundled fibers with glass.

3. The difference in thermal expansion coefficients between the optical fiber and the glass is 7.8 × 10 -6 The method for fixing bundle fibers according to claim 2, wherein the temperature is less than or equal to ( / °C).

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