JP2005148115A - Optical coupling module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical coupling module with which the coupling efficiency of a light source and an optical fiber housed in a case can be improved. <P>SOLUTION: The optical coupling module 1 comprises an LED chip 23 as the light source and the case 10 having an internal space 12 to house the LED chip. An opening 11 which the incident end face 21 of the optical fiber 20 faces is formed on the side face 14d of the case 10. The bottom face 13a, the upper face 13b, side faces 14a, 14b, 14c and 14d of the case 10 are all mirror reflection faces plated with silver. The LED chip 23 has a wide directivity angle, and light emitted from the LED chip 23 toward the side face 14 and reflected on the side face 14b, in addition to light emitted from the LED chip 23 toward the incident end face 21, is also introduced into the optical fiber 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical coupling module that couples light emitted from a light source to an optical fiber, and more particularly to an optical coupling module that houses a light source in a housing.

  Conventionally, various types of optical coupling modules for coupling light emitted from a light source to an optical fiber have been used. As the light source, a light-emitting element such as a small and inexpensive LED is increasingly used. Usually, the LED emits light in all directions, and even a surface-emitting LED, for example, emits light not only in a direction perpendicular to the light emitting surface but also in multiple directions. For this reason, there has been proposed an optical coupling module that includes a reflection portion and efficiently introduces light emitted in these multi-directional directions into an optical fiber.

Further, for the purpose of reducing the size and cost of the optical coupling module, a module has been proposed in which the housing itself that accommodates the light source is used as a reflecting portion (see, for example, Patent Document 1 or Patent Document 2).
Japanese Patent Laid-Open No. 5-113527 Japanese Patent Laid-Open No. 5-190910

  In the optical coupling module described in Patent Document 1, a light source is attached to one end of a housing that holds an LED, an incident end of an optical fiber is attached to the other end, and a light scattering portion including a diffuse reflection surface is provided at the center. The light emitted from the LED toward the incident end of the optical fiber is directly introduced into the optical fiber, but the light emitted in the other direction is partially reflected after being reflected by the scattering reflection surface. Is introduced into the optical fiber. Since light is scattered in multiple directions on the scattering reflection surface, light scattered from the scattering reflection surface, that is, light emitted in directions other than the direction of the incident end of the optical fiber, is introduced into the optical fiber at a low rate. There is a problem that the efficiency does not increase so much.

  In addition, in the optical coupling module described in Patent Document 2, a housing is constituted by a light scattering reflection part in which a light source is arranged and a specular reflection part in which an incident end of an optical fiber is arranged, and the optical fiber incident surface from the LED. The light emitted in this direction is directly introduced into the optical fiber, and the light emitted in the other direction is scattered by the specular reflection surface and the irregular reflection surface or the irregular reflection surface, and a part thereof is introduced into the optical fiber. For this reason, there is also a problem that the coupling efficiency is not improved so much because the ratio of light emitted to directions other than the direction of the incident end of the optical fiber is small.

  In view of the above problems, an object of the present invention is to provide an optical coupling module capable of improving the coupling efficiency between a light source housed in a housing and an optical fiber.

An optical coupling module according to the present invention includes a light source that emits light,
It has an opening which accommodates the light source and has an incident end face of an optical fiber facing, and an inner surface opposite to the opening has a casing made of a specular reflection surface that regularly reflects light emitted from the light source. Is. Here, the “specular reflection surface” means a surface having a reflectivity for regular reflection of light of 80% or more.

  The light source may be an LED. Moreover, this LED may be formed on a transparent substrate.

  The light source may be composed of a plurality of LEDs arranged linearly in the optical axis direction of the optical fiber.

  The optical module is transparent to the light emitted from the light source, and is filled with a resin having a refractive index close to the refractive index of the optical fiber compared to the refractive index of air. It may be. In addition, it is preferable that the refractive index of resin is close to the refractive index of an optical fiber, and it is more preferable if it is substantially equal. Specific examples of the resin include silicone-based and acrylate-based resins. Further, it is necessary that the resin is filled at least between the incident end face of the optical fiber and the light source, and it is more preferable to fill the entire inner section.

  An optical coupling module according to the present invention includes a light source that emits light, an opening that accommodates the light source and faces an incident end face of an optical fiber, and an inner surface that faces the opening reflects specularly the light emitted from the light source. Since it has a housing made of a reflecting surface, a part of the light emitted from the light source in a direction other than the direction of the incident end of the optical fiber is reflected by the specular reflecting surface and then reflected by the irregular reflecting surface. Without being introduced into the optical fiber. Since light is specularly reflected at the specular reflection surface, light emitted in directions other than the direction of the incident end of the optical fiber is efficiently introduced into the optical fiber, and the coupling efficiency between the light source and the optical fiber is improved. In addition, since the inner surface of the casing is a specular reflection surface, it is not necessary to separately provide a specular reflection section in the casing, and the optical coupling module is not increased in size and structure.

  When an LED is used as the light source, an inexpensive optical coupling module can be provided. In addition, when an LED formed on a transparent substrate is used as the light source, the rate at which the light reflected by the specular reflection surface is absorbed or scattered by the LED substrate is reduced, and the coupling efficiency can be further improved. .

  If the light source is composed of a plurality of LEDs arranged linearly in the optical axis direction of the optical fiber, more light can be introduced into the optical fiber.

  In general, the reflectance between media having different refractive indexes increases as the difference in refractive index increases. For this reason, if the refractive index difference is reduced, the reflectance decreases. In the optical coupling module according to the present invention, the inside of the casing is filled with a resin that is transparent to light emitted from the light source and has a refractive index close to the refractive index of the optical fiber compared to the refractive index of air. In this case, the light reflectance at the incident end face of the optical fiber is reduced, and the coupling efficiency is further improved. When this resin is filled in the entire inner section of the housing, the light source and the incident end of the optical fiber are securely fixed by the resin, and it is possible to prevent the positional deviation of the light source and the dropping of the optical fiber. .

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partially broken plan view of an optical coupling module according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line 2-2 shown in FIG.

  As shown in FIGS. 1 and 2, the optical coupling module 1 includes a housing 10 having an opening 11 to which an optical fiber 20 is attached, and an LED housed in an internal space 12 of the housing 10. It is comprised from the chip | tip 23 and the resin 24 with which the empty space of the internal space 12 is filled. The outer shape of the housing 10 is a square columnar shape having a length of 520 μm, a width of 550 μm, and a height of 310 μm, and a rectangular columnar internal space 12 having a length of 320 μm, a width of 350 μm, and a height of 110 μm is provided therein. . A circular opening 11 having a diameter of 110 μm is formed in one of the side surfaces of the housing 10 in the center. Further, as shown in FIGS. 1 and 2, the internal space 12 includes a lower surface 13a, an upper surface 13b, and side surfaces 14a, 14b, 14c, and 14d. The opening 11 is provided in the side surface 14d. Further, the surfaces 13a, 13b, 14a, 14b, 14c and 14d constituting the internal space 12 are all specular reflecting surfaces plated with silver.

  The optical fiber 20 has a cladding diameter of 110 μm and a core diameter of 100 μm. The optical fiber 20 is attached to the opening 11 such that the incident end face 21 at the tip protrudes from the side face 14 d to the internal space 12 of the housing 10 by 30 μm.

  The LED chip 23 is a GaN-based LED formed on a sapphire substrate, which is a transparent substrate, and has a chip size of 260 μm in length, 260 μm in width, and 60 μm in height. The LED chip 23 is disposed on the lower surface 13a so that the center position is located at a distance of 160 μm from the side surface 14a and the side surface 14b, and the side surface of the chip is parallel to the side surfaces 14a to 14d. An anode electrode and a cathode electrode (not shown) are formed on the surface of the LED chip 23 and are connected to a power source by a wiring (not shown).

  When the light emitted from the LED chip 23 is coupled to the optical fiber 20, the light emitted from the LED chip 23 toward the incident end face 21 of the optical fiber 20 is directly reflected by the optical fiber 20. To be introduced. The light emitted in the direction of the side surface 14 b is specularly reflected by the side surface 14 b, passes through the LED chip 23, and is introduced into the optical fiber 20. Further, part of the light emitted from the LED chip 23 in the other direction is also reflected and introduced into the optical fiber 20. The resin 24 is transparent to the light emitted from the LED chip 23 and has a refractive index substantially equal to the refractive index of the core of the optical fiber 20. For this reason, the light emitted from the LED chip 23 is hardly absorbed by the resin 24, and the reflectance at the incident end face 21 of the optical fiber 20 is also small.

  With these configurations, in the optical coupling module 1, in addition to the light directly introduced into the optical fiber 20, the light specularly reflected by the side surface 14 b is also introduced into the optical fiber 20. The coupling efficiency with 20 can be improved. Furthermore, since the LED chip 23 is used as the light source, an inexpensive optical coupling module can be provided. Further, since the LED chip 23 is formed on the transparent substrate, the light that is specularly reflected in the housing 10 is less likely to be absorbed or scattered by the substrate of the LED chip 23, and the coupling efficiency is further improved.

In addition, since the resin 24 is filled in the empty space of the internal space 12 of the housing 10, the reflectance at the incident end face 21 of the optical fiber 20 is reduced, and the coupling efficiency is further improved. Further, since the resin 24 is filled in the entire inner section 12 of the housing 10, the LED chip 23 and the incident end face 21 of the optical fiber 20 are securely fixed by the resin 24, so that the positional deviation of the LED chip 23 and the optical fiber 20 Positional displacement or dropout of the incident end face 21 is prevented. Specific examples of the resin 24 include silicone-based and acrylate-based resins.

  Moreover, in this Embodiment, although each surface 13a, 13b, 14a, 14b, 14c, and 14d is comprised from the plane, it is not limited to this, A curved surface can also be used as each surface. When using curved surfaces, it is preferable to determine the shape of the curved surface so that the light reflected by these surfaces is reflected in the direction of the incident end face 21 of the optical fiber 20.

  Next, the optical coupling module 2 which is the 2nd Embodiment of this invention is demonstrated using FIG. 3 and FIG. 3 is a partially broken plan view of the optical coupling module 2, and FIG. 4 is a cross-sectional view taken along line 4-4 shown in FIG.

  As shown in FIGS. 3 and 4, the optical coupling module 2 includes a housing 30 having an opening 31 to which the optical fiber 20 is attached, and three housings housed in an internal space 32 of the housing 30. The LED chip 41a, 41b and 41c and the resin 35 filled in the empty space of the internal space 32 are configured. The outer shape of the housing 30 is a rectangular column shape having a length of 520 μm, a width of 1140 μm, and a height of 310 μm, and a rectangular columnar internal space 32 having a length of 320 μm, a width of 940 μm, and a height of 110 μm is provided therein. . A circular opening 31 having a diameter of 110 μm is formed in the center of one of the side surfaces of the housing 30. Further, as shown in FIGS. 3 and 4, the internal space 32 includes a lower surface 33a, an upper surface 33b, and side surfaces 34a, 34b, 34c and 34d. An opening 31 is provided on the side surface 34d. Further, the surfaces 33a, 33b, 34a, 34b, 34c and 34d constituting the internal space 32 are all specular reflection surfaces subjected to silver plating.

  The optical fiber 20 has a cladding diameter of 110 μm and a core diameter of 100 μm. The optical fiber 20 is attached to the opening 31 such that the incident end face 21 at the tip protrudes 30 μm from the side face 34d.

  The LED chips 41a, 41b, and 41c are GaN-based LEDs formed on a sapphire substrate, which is a transparent substrate, and have a chip size of 260 μm in length, 260 μm in width, and 60 μm in height. The LED chip 41a is disposed on the lower surface 33a so that the center position is located at a distance of 160 μm from the side surface 34a and the side surface 34b. The LED chip 41b is disposed on the lower surface 33a so that the center position is located 450 μm away from the side surface 34b and 160 μm away from the side surface 34a. The LED chip 41c is arranged on the lower surface 33a so that the center position is located 730 μm away from the side surface 34b and 160 μm away from the side surface 34a. Each LED chip 41a, 41b and 41c has an anode electrode and a cathode electrode (not shown) formed on the surface thereof, and is connected to a power source by a wiring (not shown).

  When the light emitted from the LED chips 41a, 41b and 41c is coupled to the optical fiber 20, the light emitted from the LED chips 41a, 41b and 41c is directed toward the incident end face 21 of the optical fiber 20. The emitted light is directly introduced into the optical fiber 20. The light emitted in the direction of the side surface 34b is specularly reflected by the side surface 34b, passes through the LED chips 41a, 41b, and 41c, and is introduced into the optical fiber 20. A part of the light emitted from each LED chip 41 a, 41 b and 41 c in the other direction is also reflected and introduced into the optical fiber 20.

  The resin 35 is transparent to the light emitted from the LED chips 41a, 41b and 41c, and has a refractive index substantially equal to the refractive index of the core of the optical fiber 20.

  With these configurations, in the optical coupling module 2, in addition to the light directly introduced into the optical fiber 20, the light specularly reflected by the side surface 34 b is also introduced into the optical fiber 20, so that the LED chips 41 a and 41 b that are light sources and The coupling efficiency between 41c and the optical fiber 20 can be improved.

  Further, the coupling efficiency can be improved by a simple structure in which the inner surface of the housing 30 that accommodates the LED chips 41a, 41b, and 41c is a reflecting mirror surface. Furthermore, since the LED chips 41a, 41b and 41c are used as the light source, an inexpensive optical coupling module can be provided. Further, since the LED chips 41a, 41b, and 41c are formed on the transparent substrate, the light that is specularly reflected in the housing 30 is hardly absorbed or reflected by the LED chips 41a, 41b, and 41c, and the coupling efficiency Is further improved. Since the resin 35 is filled in the empty space of the internal space 32 of the housing 30, reflection at the incident end face 21 of the optical fiber 20 is reduced and the coupling efficiency is further improved. Further, since the resin 35 is filled in the entire inner section 32 of the housing 30, the LED chips 41a, 41b and 41c and the incident end face 21 of the optical fiber 20 are securely fixed by the resin 35, and the LED chips 41a, 41b and 41c are fixed. Misalignment of the incident end face 21 of the optical fiber 20 is prevented. Specific examples of the resin 35 include silicone-based and acrylate-based resins.

  Further, since three LED chips 41 a, 41 b and 41 c are accommodated in the housing 30, more light can be introduced into the optical fiber 20. Note that the number of LED chips to be accommodated can be appropriately increased or decreased depending on the size of the housing and the LED chips. Alternatively, the LED chip may be turned upside down and fixed to the upper surface 33b, and light emitted from both the LED chip fixed to the lower surface 33a and the LED chip fixed to the upper surface 33b may be introduced into the optical fiber. When the core system of the optical fiber is large with respect to the height of the LED chip, more light can be introduced into the optical fiber by such an arrangement.

  In the present embodiment, each of the surfaces 33a, 33b, 34a, 34b, 34c, and 34d is a flat surface, but the present invention is not limited to this, and curved surfaces can be used as the respective surfaces. When using curved surfaces, it is preferable to determine the shape of the curved surface so that the light reflected by these surfaces is reflected in the direction of the incident end face 21 of the optical fiber 20.

  Next, the optical coupling module 3 which is the 3rd Embodiment of this invention is demonstrated using FIG. 5 and FIG. FIG. 5 is a partially broken plan view of the optical coupling module 2, and FIG. 6 is a cross-sectional view taken along line 6-6 shown in FIG.

  As shown in FIGS. 5 and 6, the optical coupling module 3 includes a housing 50 having an opening 51 to which an optical fiber 60 is attached, and an LED housed in an internal space 52 of the housing 50. The chip 23 and the resin 55 filled in the empty space of the internal space 52 are configured. The outer shape of the housing 50 is a rectangular columnar shape having a length of 520 μm, a width of 350 μm, and a height of 520 μm, and a rectangular columnar internal space 52 having a length of 320 μm, a width of 150 μm, and a height of 320 μm is provided therein. . A circular opening 51 having a diameter of 260 μm is formed in the center of one of the side surfaces of the housing 50. Further, as shown in FIGS. 5 and 6, the internal space 52 includes a lower surface 53a, an upper surface 53b, and side surfaces 54a, 54b, 54c and 54d. The opening 51 is provided on the side surface 54d. Further, the surfaces 53a, 53b, 54a, 54b, 54c and 54d constituting the internal space 52 are all specular reflecting surfaces plated with silver.

  The optical fiber 60 has a cladding diameter of 260 μm and a core diameter of 230 μm. The optical fiber 60 is attached to the opening 51 so that the incident end face 61 at the tip protrudes 50 μm from the side face 54 d to the internal space 52 of the housing 50.

  The LED chip 23 is a GaN-based LED formed on a sapphire substrate, which is a transparent substrate, and has a chip size of 260 μm in length, 260 μm in width, and 60 μm in height. As shown in FIGS. 5 and 6, the LED chip 23 is fixed with a transparent adhesive so that the substrate side is in contact with the side surface 54b. The center position is arranged to coincide with the center of the side surface 54a. An anode electrode and a cathode electrode (not shown) are formed on the surface of the LED chip 23 and are connected to a power source by a wiring (not shown).

  When the light emitted from the LED chip 23 is coupled to the optical fiber 60, the light emitted from the LED chip 23 toward the incident end face 61 of the optical fiber 60 is directly reflected by the optical fiber 60. To be introduced. The light emitted in the direction of the side surface 54 b is specularly reflected by the side surface 54 b, passes through the LED chip 23, and is introduced into the optical fiber 60. Further, part of the light emitted from the LED chip 23 in the other direction is also reflected and introduced into the optical fiber 60. The resin 55 is transparent to the light emitted from the LED chip 23 and has a refractive index that is substantially equal to the refractive index of the core of the optical fiber 60. For this reason, the light emitted from the LED chip 23 is hardly absorbed by the resin 55, and the reflectance at the incident end face 61 of the optical fiber 60 is also small.

  With these configurations, in the optical coupling module 3, in addition to the light emitted from the front surface of the LED chip 23 and directly introduced into the optical fiber 60, the light emitted from the back surface of the LED chip 23 and specularly reflected by the side surface 54b is also generated. Since it is introduced into the optical fiber 60, the coupling efficiency between the LED chip 23, which is a light source, and the optical fiber 60 can be improved. Furthermore, since the LED chip 23 is used as the light source, an inexpensive optical coupling module can be provided. Further, since the LED chip 23 is formed on the transparent substrate, the light that is specularly reflected in the housing 50 is less likely to be absorbed or scattered by the substrate of the LED chip 23, and the coupling efficiency is further improved. Since the resin 55 is filled in the empty space of the internal space 52 of the housing 10, the reflectance at the incident end face 61 of the optical fiber 60 is reduced, and the coupling efficiency is further improved. Further, since the resin 55 is filled in the entire inner section 52 of the housing 150, the incident end face 61 of the LED chip 23 and the optical fiber 60 is securely fixed by the resin 55, and the positional deviation of the LED chip 23 and the optical fiber 60 Positional displacement or dropout of the incident end face 61 is prevented. Specific examples of the resin 55 include silicone-based and acrylate-based resins.

  In the present embodiment, each of the surfaces 53a, 53b, 54a, 54b, 54c, and 54d is composed of a flat surface. However, the present invention is not limited to this, and curved surfaces can be used as the respective surfaces. When using curved surfaces, it is preferable to determine the shape of the curved surface so that the light reflected by these surfaces is reflected in the direction of the incident end face 61 of the optical fiber 60.

  In each embodiment, as the LED chip, an LED chip having a face-up structure may be used, or an LED chip having a face-down structure may be used. As the casing, an integrally formed casing may be used, or a casing formed by combining a substrate on which an LED chip is disposed and a cover provided on the substrate may be used. .

The partially broken plan view of the optical coupling module which is 1st Embodiment Cross section of optical coupling module The partially broken top view of the optical coupling module which is 2nd Embodiment Cross section of optical coupling module The partially broken top view of the optical coupling module which is 3rd Embodiment Cross section of optical coupling module

Explanation of symbols

1, 2, 3 Optical coupling module 10, 30, 50 Housing 11, 31, 51 Opening 12, 32, 52 Internal space 13a, 33a, 53a Lower surface 13b, 33b, 53b Upper surface 14a, 14b, 14c, 14d Side surface 20, 60 Optical fiber 23, 41a, 41b, 41c LED chip 24, 35, 55 Resin 34a, 34b, 34c, 34d Side surface 54a, 54b, 54c, 54d Side surface

Claims (5)

A light source that emits light;
It has an opening which accommodates the light source and has an incident end face of an optical fiber facing, and an inner surface opposite to the opening has a casing made of a specular reflection surface that regularly reflects light emitted from the light source. Optical coupling module. The optical coupling module according to claim 1, wherein the light source is an LED. The optical coupling module according to claim 2, wherein the LED is formed on a transparent substrate. 4. The optical coupling module according to claim 2, wherein the light source includes a plurality of LEDs arranged linearly in the optical axis direction of the optical fiber. The housing is filled with a resin that is transparent to light emitted from the light source and has a refractive index close to the refractive index of the optical fiber compared to the refractive index of air. Item 5. The optical coupling module according to any one of Items 1 to 4.

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