JP2001059922A - Light emitting and light guiding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize light transmission loss at the time of transmitting signal light from a light emitting element to optical fiber. SOLUTION: The optical fiber and this light emitting and light guiding device which is integrated with a light emitting element are connected and light transmission is executed. The device has a structure formed by connecting an end surface of a light guide body 3 and a light emitting surface of a light emitting element 2. The light guide body 3 is surrounded by a reflection surface and, therein, is filled with a light transmitting body 4. Further, the light transmitting body 4 is brought into contact with the light emitting part of the light emitting element 2. Refractive index of the light transmitting body 4 is preferably within the refractive index of the optical fiber 1±0.2. The light transmitting body 4 has the characteristic that the light transmitting body 4 is soft, or the light emitting element 2 side thereof is hard and the optical fiber 1 side thereof is soft. The hardness of the optical fiber 1 side of the light transmitting body 4 is preferably less than 60 deg. JIS (D) hardness. The flank of the optical fiber 1 of the light transmitting body 4 is preferably designed in such a manner that the central part is projected and the peripheral part is rugged. Resin for the light transmitting body 4 is preferably one kind selected from silicone resin, acrylic resin, epoxy resin, thermoplastic elastomeric resin and the derivatives of these resins.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a light-emitting and light-guiding device for optically joining a light-emitting element and an optical fiber, and relates to a technique for reducing a loss during optical transmission.

[0002]

2. Description of the Related Art A transmitting system using an optical fiber transmits a signal light through a light emitting device and an optical fiber via a lens. As the light emitting device, a device in which a light emitting element is sealed with a resin or a metal is used, and a light emitting diode (LE) is used.
D), an edge-emitting semiconductor laser (LD), a surface-emitting semiconductor laser (VCSEL), and the like are known.

[0003] The transmission performance of such an optical transmission system is greatly affected by the transmission efficiency of signal light, and not only the performance of the optical fiber and the light-emitting device but also the transmission loss of the connecting portion affects the communication performance. The current connection method involving a lens has a problem that a precision structure is required, the cost is high and the versatility is poor, and further, a connection loss of several dB to several tens dB is caused by reflection on the lens surface.

The present inventor has proposed a coupling structure in which a light guide having a light guide path surrounded by a reflection surface is interposed between a light emitting element and an optical fiber in order to reduce the connection loss (particularly, FIG. 1). Kaihei 10-221574).

After the above-mentioned proposal, further studies for practical use have been earnestly conducted. When the light emitting element and the optical fiber are connected by a light guide, the light guide is directly connected to the light emitting element to have a structure capable of being separated and connected to the optical fiber. Is important.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for reducing a loss at the time of connection between a light emitting element and an optical fiber, and proposes a lensless light emitting and guiding device having excellent connection performance.

[0007]

SUMMARY OF THE INVENTION The present invention is an apparatus for transmitting signal light from a light emitting element to an optical fiber through a light guide having a light guide path surrounded by a reflective surface and filled with a light transmitting body. The light-emitting and light-guiding device is characterized in that the light-emitting surface of the light-emitting element and the end face of the light guide are coupled to each other and the light-emitting portion of the light-emitting element and the light-transmitting body are in contact with each other. According to a second aspect of the present invention, the light emitting surface of the light emitting element has a structure having an electrode on an outer peripheral portion and a light emitting portion on a central portion, and the light emitting surface is electrically connected to an end surface of the light guide. Item 2. A light-emitting and light-guiding device according to item 1. According to a third aspect of the present invention, there is provided the light-emitting and light-guiding device according to the first or second aspect, wherein the optical fiber and the light guide are connectable and separable.

According to a fourth aspect of the present invention, the core of the optical fiber is larger than the dimension of the light emitting portion of the light emitting element, and the optical fiber has a light guide path which tapers from the optical fiber toward the light emitting element. It is a light-emitting light-guiding device.

According to a fifth aspect of the present invention, the light transmitting body has a characteristic of being flexible or softening from the light emitting element side toward the optical fiber side, and the hardness of the optical fiber side is JIS (D) 60 degrees or less. The light-emitting and light-guiding device according to claim 1, wherein: A sixth aspect of the present invention is the light-emitting and light-guiding device according to any one of the first to fifth aspects, wherein the refractive index of the light transmitting body is within ± 0.2 of the refractive index of the optical fiber.

According to a seventh aspect of the present invention, there is provided the light-emitting and light-guiding device according to any one of the first to sixth aspects, wherein the connection surface of the light transmitting body on the optical fiber side has a convex shape in the optical fiber direction. According to an eighth aspect of the present invention, there is provided the light-emitting and light-guiding device according to any one of the first to seventh aspects, wherein an outer peripheral portion of the light transmitting body on the optical fiber side has a shape subjected to uneven processing to allow air to escape. Device.

According to a ninth aspect, the light transmitting member is selected from the group consisting of silicone resin, acrylic resin, epoxy resin, thermoplastic elastomer resin, and derivatives of these resins.
The light-emitting and light-guiding device according to claim 1, wherein the light-emitting and light-guiding device is a seed.

In order to efficiently transmit the signal light from the light emitting element, it is important to prevent the signal light from leaking and to join the light emitting element and the light guide at the shortest distance. That is, it is effective to integrate the light emitting surface of the light emitting element and the end face of the light guide so that the light emitting portion of the light emitting element is in contact with the light transmitting body. To do this,
It is important that the optical semiconductor is used not in a device sealed with metal or resin but in an element state and directly coupled to the light guide. Since current light emitting devices are designed on the premise of a lens structure, the size of the light emitting surface is large and the distance to the element is long.
That is, when the current light emitting device is used, signal light is not effectively transmitted due to light leakage, scattering or reflection (for example, see Japanese Patent Application Laid-Open No. 10-2).
61821).

Even when a light emitting element is used, a loss due to dispersion of signal light occurs when the light guide is coupled to the entire light emitting element or the entire module portion electrically connected by gold wires. It is necessary to directly connect the transmitting portions to minimize transmission loss. It is preferable to use a module dedicated to light transmission in which only the light emitting part of the light emitting element is exposed, or to electrically connect the outer peripheral electrode part of the light emitting element and the end face of the light guide to prevent light leakage to parts other than the light transmitting part. L which requires an electrode on the light emitting surface
In the case of ED and VCSEL, the electrodes are arranged on the outer peripheral part of the light emitting surface and the light emitting part is located at the center part, the electrode of the light guide is connected to the electrode of the light emitting element, and the light transmitting body is connected to the light emitting part of the light emitting element By doing so, transmission loss can be minimized.

When the light emitting element and the light guide are integrated, it is preferable that the optical fiber side of the light guide has a structure capable of connection and separation. It is functional that the light emitting element is mounted and fixed on the main body of the optical communication device or the attached equipment, and leaving the degree of freedom on the other optical fiber side provides practicality.

It is preferable that a core size of the optical fiber is larger than a size of a light emitting portion of the light emitting element, and that the optical fiber has a light guide path that tapers from the optical fiber side toward the light emitting element side. This structure is important as a simple connection technique when a plastic optical fiber having a large core size is used.

The light transmitting body is required to protect the light emitting element from the environment (confidentiality and reliability). It is necessary for the light transmitting body to protect the light emitting element from external pressure and moisture. Since the light emitting element is very sensitive to fluctuations in pressure, temperature and humidity, the light transmitting body is required to have a function of buffering stress and firmly protecting the light emitting element from water intrusion. That is,
The light transmitting body has the property of being flexible or becoming rigid continuously or stepwise from the optical fiber side to the light emitting element side, and the optical fiber side hardness of the light transmitting body is 60 degrees or less according to JIS (D). preferable. If it is too hard, the adhesion to the optical fiber will be poor, resulting in loss of signal light during optical transmission.

It is preferable that the refractive index of the light transmitting body is substantially the same as that of the optical fiber. At least, the difference in refractive index between the light transmitting body and the optical fiber is preferably within ± 0.2. If the difference is too large, light transmission loss due to reflection or the like is caused. A method for adjusting the refractive index of the light transmitting body is known (eg, POF CONFE).
RANCE '97, JP-A-11-43605).

In the case where the light-emitting light guide device is connected to the optical fiber, when air is involved in the connection surface between the light transmitting body and the optical fiber, the light causes transmission loss due to phenomena such as reflection, scattering and refraction.
For this reason, it is effective to provide a shape or device that does not involve air in the connection surface.

It is preferable that the connecting surface of the light transmitting body on the optical fiber side has a convex and concave shape, and air is pushed out from the central portion to the outer peripheral portion by a pressing force at the time of connection so as to be in close contact therewith. Specific shapes include a spherical shape, a parabolic shape, a conical shape, and a pyramid shape. It is also effective to create an escape route in the outer peripheral portion of the light transmitting body on the optical fiber side and forcibly discharge air bubbles by pressing force at the time of connection. For example, it is preferable to apply a wave-like, triangular or groove-like processing to the optical fiber side connection outer peripheral portion. In this case, it is particularly preferable to use it in combination with the convex shape of the connection surface.

As the resin of the light transmitting body, those having excellent light transmitting properties, adjustable hardness, and proven in the semiconductor field or the optical field are preferable. It is preferable to select one kind of a silicone resin, an acrylic resin, an epoxy resin, a thermoplastic elastomer resin, and derivatives of these resins.
When a plurality of resins are used, problems such as water intrusion and optical transmission loss may occur depending on the state of the contact interface. Commercial products can be selected from product catalogs of Shin-Etsu Chemical, Toshiba Silicone, Toagosei, Nippon Kayaku, Asahi Kasei, etc.
Derivatives of these resins can also be produced and used using known techniques. (JP-A-59-133220, JP-A-62-167317, JP-A-3-22553, JP-A-10-17776, JP-A-10-110102, and JP-A-10-261821).

FIG. 1 is a view showing an example of a light-emitting and light-guiding device according to the present invention (a view in which the connection direction is viewed from the side). (1)
Shows a state where the light guide and the light emitting element are integrated, and (2) shows a state before the integration. 1 is an optical fiber, 2 is a light emitting element, 3
Is a light guide, and 4 is a light transmitting body. The optical fiber connection surface 5 of the light transmitting body is spherical. An electrode 6 is arranged on the light emitting element side end surface of the light guide and is coupled to the light emitting element electrode 8 of the light emitting element.

FIG. 2 is a diagram showing another example of the light-emitting and light-guiding device according to the present invention. (3) is a diagram viewed from the optical fiber side. 1 is an optical fiber, 2 is a light emitting element, 23 is a light guide, 24a is a flexible light transmitting body, 24b is a rigid light transmitting body, and 29 is an insulating resin. The shape of the connection surface on the optical fiber side of the light transmitting body is such that the central portion 25C is conical and the outer peripheral portion 25d is a cut hexagonal pyramid. The light emitting portion of the light emitting element is sealed with a light transmitting body, and the back surface of the light emitting element is sealed with an insulating resin. or,
A mechanism for temporarily fixing the optical fiber to the light guide light emitting device may be provided. An attachment / detachment mechanism (existing technology such as a spring, a screw, and a groove) used in a general connector can be used.

FIG. 3 is a view showing an example of a light-emitting and light-guiding device having a structure similar to that of the present invention. The light emitting element 2 is integrated with the light guide 33 which is surrounded by the reflection surface and is filled with the light transmitting body 34, but is connected using the gold wire 31 by a conventional method, which is regarded as an inefficient lensless connection. be able to.

FIG. 4 is a diagram showing an example of a connection structure using a conventional lens. The optical fiber 1 and the resin-sealed light emitting device transmit signal light via a quartz ball lens 40. The resin-sealed light emitting device includes a light emitting element 2, a gold wire 41,
The light emitting side electrode 48 and the transparent epoxy resin 44 are used.

FIG. 5 shows a general-purpose resin-sealed light emitting device LED.
FIG. 3 is a diagram illustrating an example of the optical fiber (a diagram viewed from the optical fiber direction).
In the transparent epoxy resin 54, a light emitting element (light emitting section 5) is provided.
0, the light emitting side electrode 58) and the gold wire 51 can be seen. That is,
Since the signal light from the light emitting portion of the light emitting element is not only blocked by the electrodes but also dispersed and transmitted via the epoxy resin sealing the entire module, the signal light is difficult to be effectively transmitted to the optical fiber.

FIG. 6 is a view showing an example of the metal-sealed light emitting device VCSEL (as viewed from the optical fiber direction). In the glass window 65, the light emitting element 2 (the light emitting section 6)
0, the light emitting side electrode 68) and the gold wire 61 can be seen. The signal light from the light emitting portion of the light emitting element is disturbed and transmitted to the optical fiber (dispersion in the device, reflection on the glass surface). .

[0027]

Embodiments of the present invention will be described. The present invention
In an optical transmission system which is optically coupled with a light guide 3, 23 which is surrounded by a reflective surface between the optical fiber 1 and the light emitting element 2 and which is filled with light transmitting bodies 4, 24, the light transmitting element This is a light-emitting and light-guiding device having a structure in which a light-emitting surface and an end face of a light guide are directly coupled to each other, and the optical fiber and the light guide can be connected and separated. The light emitting portion of the light emitting element is sealed with a light transmitting body, and the light transmitting body has optical fiber side connection surfaces 5 and 25. By using the light-emitting and light-guiding device of the present invention, it is possible to reduce the loss during optical transmission. Hereinafter, specific examples will be described with reference to examples and comparative examples.

[0028]

Embodiment 1 The light emitting and light guiding device of FIG. 1 in which a step index type acrylic optical fiber (core diameter 0.9 mm, manufactured by Mitsubishi Rayon) and an outer electrode type LED (light emitting portion 0.3 mmφ, manufactured by NEC) are integrated. And connected. The inner surface of the light guide is subjected to a plating process capable of highly reflecting light. The light transmitting body is made of a silicone-modified epoxy resin (manufactured by Nippon Kayaku) having an optical fiber side hardness of JIS (D) 30 degrees. The optical fiber and the light-emitting light-guiding device were connected, and the optical transmission loss was measured to be 0.8 dB.

The light refractive index is 1.50 for the optical fiber and 1.51 for the silicone-modified epoxy resin. Resin hardness is JI
Measured according to S (using durometer). The light transmitting body was injected into the light guide and cured while continuously changing the mixing ratio of the resin having a high silicone modification rate and the resin having a low silicone modification rate, and having a gradient hardness on the light emitting element side.

[0030]

Embodiment 2 A great index type acrylic optical fiber (core diameter: 0.5 mm, refractive index: 1.5 to 1.6, made by Clave) was connected to the light-emitting and light-guiding device of FIG. The element used was an outer peripheral electrode type LED (light emitting portion 0.2 mmφ) manufactured by Hitachi, Ltd. As the light transmitting body, two types of acrylic-modified epoxy resins having a hardness of 10 degrees and 50 degrees (refractive index: 1.50, manufactured by Toagosei Co., Ltd.) were used. The optical transmission loss in this case was 0.5 dB.

[0031]

[Embodiment 3] Fluorine type optical fiber (core type 0.3 mm,
(Refractive index: 1.35, manufactured by Asahi Glass Co., Ltd.) and the light-emitting light-guiding device of FIG. The light emitting element used was an outer electrode type VCSEL (light emitting part: 0.1 mmφ, manufactured by Samsung Electronics), and the light transmitting body was a vinyl-modified silicone resin (hardness on the optical fiber side: 40 degrees, refractive index: 1.43). The outer peripheral portion of the light transmitting body on the optical fiber side has a shape that allows air to escape when the optical fiber is pressed, and also has a function of assisting alignment and temporary fixing of the optical fiber.
In the present embodiment, a loss of 0.3 dB occurs in the optical transmission.

[0032]

[Examination Example 1] An optical fiber and a light emitting element were connected by a light guide in the same manner as in Example 1 except that a commercially available epoxy resin (Nitto Denko, refractive index 1.55) was used as a light transmitting body. In this case, the optical transmission loss at the connection was 3.4 dB. It is considered that the epoxy resin as the light transmitting body is hard as JIS (D) 70 degrees, and the optical fiber connection surface does not adhere to each other, causing loss. The epoxy resin used for the light transmitting body was mainly composed of bisphenol A type epoxy resin and phthalic anhydride.

[0033]

[Study Example 2] An optical fiber was connected in the same manner as in Example 2 using the light emitting / guiding device of FIG. The optical transmission loss in this case is 4.
It was 8 dB. It is considered that the signal light was dispersed and the efficiency was deteriorated due to the connection structure by the gold wire.

[0034]

[Examination Example 3] An optical fiber and an optical semiconductor were connected by a light guide in the same manner as in Example 3 except that a general-purpose urethane-modified synthetic rubber (manufactured by Takeda Chemical Industries) was used as a light transmitting body. In this case, the connection portion optical transmission loss was as high as 4.4 dB. It is considered that a loss due to reflection occurred because the refractive index of the light transmitting body was as high as 1.58.

The study example shows that the light transmission loss is larger than that of the embodiment but smaller than that of the comparative example, and shows that the structure of the light-emitting and light-guiding device and the characteristics of the light transmitting body influence.

[0036]

Comparative Example As shown in FIG. 4, optical transmission was performed by a conventional method.
The optical fiber of Example 1 and a commercially available resin-sealed LED (3 m
m-square, manufactured by Toshiba) and connected via a ball lens (manufactured by Molex Japan). In this case, the connection part optical transmission loss is 13d.
B. It is considered that a part of the signal light was dispersed in the device, reflected on the lens surface, and did not reach the optical fiber.

[0037]

The light-emitting and light-guiding device of the present invention has a joint structure for directly coupling to a light-emitting element and connecting to an optical fiber. When the optical fiber and the light-emitting light-guiding device of the present invention are connected, optical transmission loss during optical communication becomes extremely small. That is, the present invention greatly contributes to increasing the versatility of the optical communication system.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a light emitting and light guiding device of the present invention.

FIG. 2 is a diagram showing an example of a light emitting and light guiding device of the present invention.

FIG. 3 is a diagram showing an example of a conventional light-emitting and light-guiding device using gold wire connection.

FIG. 4 is a diagram showing an example of a conventional lens connection structure.

FIG. 5 is a diagram illustrating an example of a resin-sealed light emitting device.

FIG. 6 is a diagram showing an example of a metal-sealed light emitting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 3, 23, 33 Light guide 4, 24, 34 Light transmitting body 5, 25 Optical fiber side surface of light transmitting body 6 Light emitting element side end face 8, 48, 58, 68 Light emitting side of light emitting element Electrode 29 Insulating resin 31, 41, 51, 61 Gold wire 40 Ball lens 44, 54 Transparent epoxy resin 50, 60 Light emitting portion of light emitting element 65 Glass window

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H037 AA01 BA02 CA38 DA03 DA04 DA16 5F041 DA07 DA26 DC22 DC66 EE03 EE06 FF14

Claims (9)

[Claims] An apparatus for transmitting signal light from a light emitting element to an optical fiber through a light guide having a light guide path surrounded by a reflecting surface and filled with a light transmitting body, and transmitting the signal light from the light emitting surface of the light emitting element. A light-emitting and light-guiding device, wherein an end face of a light-guiding body is connected to the light-emitting unit and a light-transmitting body is in contact with the light-emitting unit. 2. The light-emitting device according to claim 1, wherein the light-emitting surface of the light-emitting element has an electrode on the outer periphery and a light-emitting portion on the center, and the light-emitting surface is electrically connected to an end surface of the light guide. A light-emitting light guide device characterized by the above-mentioned. 3. The light-emitting and light-guiding device according to claim 1, wherein the optical fiber and the light-guiding body have a structure that can be connected and separated. 4. The light-emitting light guide according to claim 1, wherein a core size of the optical fiber is larger than a size of a light emitting portion of the light emitting element, and a light guide path tapering from the optical fiber side toward the light emitting element side. apparatus. 5. The light transmitting body is characterized in that it is flexible or softens from the light emitting element side to the optical fiber side, and the hardness of the optical fiber side is JIS (D) 60 degrees or less. The light-emitting and light-guiding device according to claim 1, wherein: 6. The light-emitting and light-guiding device according to claim 1, wherein the refractive index of the light transmitting body is within ± 0.2 of the refractive index of the optical fiber. 7. The optical fiber-side connecting surface of the light transmitting body has a convex shape such as a spherical shape, a parabolic shape, a conical shape, a pyramid shape, etc. in the optical fiber direction. The light-emitting and light-guiding device according to claim 6. 8. The method according to claim 1, wherein an outer peripheral portion of the light transmitting body on the optical fiber side is formed into a corrugated shape, a polygonal shape, a groove shape or the like in order to release air. A light-emitting and light-guiding device according to claim 7. 9. The method according to claim 1, wherein the light transmitting body is one selected from a silicone resin, an acrylic resin, an epoxy resin, a thermoplastic elastomer resin, and a derivative of these resins. A light-emitting and light-guiding device according to claim 8.