JP2002182059A - Device for optical connection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce transmission loss generated when optically connecting an optical fiber with a large emission area and an optical fiber or a light- receiving semiconductor with a small incidence area. SOLUTION: An optical fiber and an optical fiber or an optical fiber and a light-receiving semiconductor are optically connected by interposing a light transmission body having a multitube- or multilayer-shaped light transmission body whose diameter is tapered from a central part toward an outer peripheral part. The light transmission body and an optical transmission body have a shape tapering off from a large optical fiber toward a small optical fiber or the light-receiving semiconductor. The refractive index of the optical transmission body is preferably nearly equivalent to the refractive index of the optical fiber. A flexible light transmission body is preferably mounted on one side or both sides of the connection end surface of the optical transmission body. About the characteristics of the light transmission body, its refractive index is preferably nearly equivalent to that of the optical fiber, and its hardness is preferably 50 deg. or less in JIS (A type).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for optically connecting an optical fiber to an optical fiber or a light receiving semiconductor. In particular, the present invention relates to a practical device for optically connecting signal light from an optical fiber having a large emission area to an optical fiber or a light receiving semiconductor in a small incidence area, and a practical apparatus for reducing optical transmission loss at the time of connection.

[0002]

2. Description of the Related Art The transmission efficiency of an optical transmission line using an optical fiber is greatly affected by a connection loss at an optical connection between optical fibers in the optical transmission line or between an optical fiber and another optical component. In particular, when the optical connection surface is narrowed, a large loss occurs and becomes a problem. This corresponds to the case where an optical fiber having a large exit diameter is connected to a light receiving semiconductor having a small incident diameter. If the two parts are simply connected directly, naturally only the area ratio between the incident diameter and the exit diameter is effectively transmitted.

[0003] In view of this, there has been proposed a structure for optically connecting a tapered light guide surrounded by a reflection surface as disclosed in Japanese Patent Application Laid-Open No. 10-221773. However, this structure is only effective if a light guide with a very long path is possible. It is theoretically difficult to collect random outgoing light from an optical fiber at a short distance.In particular, signal light with a large outgoing angle is attenuated through many reflections inside the light guide path and reaches the light receiving semiconductor or conversely. The signal light may return to the optical fiber.

[0004] Even the conventional method of interposing a lens causes considerable connection loss. When a rod lens is used, there is a problem similar to that of JP-A-10-221773. When a convex lens is used, it is known that a phenomenon such as reflection occurs and a large connection loss of several dB is caused. The ball lens has a function of collecting parallel light or point light, but it is difficult to effectively collect random light.

Heretofore, the above-mentioned problem has not occurred since the optical fiber is a quartz fiber having a small core diameter and the light receiving portion of the light receiving semiconductor is larger than the core diameter of the quartz fiber. Rather, precision processing technology for optically connecting to a fine-diameter quartz fiber has been a problem.

[0006] Recently, plastic optical fibers (referred to as POF) have become available. For example, polymethyl methacrylate POF (Mitsubishi Rayon, Toray, etc.) and fluororesin POF (Asahi Glass) are commercially available. As a result, optical connection in which the optical transmission path is narrowed has become a real problem, and practical use of a technique for reducing the connection loss has been strongly demanded.

[0007] Further, it is required to reduce, not negligible, optical transmission loss depending on positioning and adhesion at the time of optical connection. For example, it is important to reduce connection loss due to misalignment, inclination, gap, and the like.

The inventor of the present invention has devotedly studied the above problem and devised a structure for efficiently transmitting random outgoing light from an optical fiber. In particular, the present invention proposes a connection device with extremely small connection loss during optical transmission from a large-diameter optical fiber to a small-diameter optical fiber or a light-receiving semiconductor.

[0009]

The present invention relates to a technique for reducing transmission loss at the time of optically connecting an optical fiber to an optical fiber and an optical fiber to a light receiving semiconductor.

[0010]

SUMMARY OF THE INVENTION According to the present invention, an optical signal is transmitted by passing a random signal light emitted from an optical fiber through a multi-tubular or multi-layered optical transmission body which becomes thinner or thinner from the center to the outer periphery. It is an object of the present invention to provide an optical connection device for effectively transmitting data to a fiber or a light receiving semiconductor.

According to a first aspect of the present invention, in a connection structure for optically coupling an optical fiber to an optical fiber and an optical fiber to a light receiving semiconductor, a columnar optical transmission body is bundled so that the diameter decreases from the center to the outer periphery. A multi-tubular light guide, a multilayer light guide in which a tubular light transmitter or a film-like light transmitter is stacked so that the thickness decreases from the center to the outer periphery. This is an optical connection device.

A second aspect of the present invention is an optical connection device characterized in that a light guide is tapered in a light transmission direction during optical transmission from a large optical fiber to a small optical fiber or a light receiving semiconductor.

A third aspect of the present invention is an optical connection device, wherein the refractive index of the optical transmission body is substantially equal to the refractive index of the optical fiber.

According to a fourth aspect of the present invention, there is provided an optical connection device wherein a flexible light transmitting body is mounted on one or both sides of a connection end face of the light guide.

[0015] Claims 5 and 6 relate to a light transmitting body, the refractive index of which is equal to the refractive index of an optical fiber and the hardness of which is JIS (A type) 50 degrees or less. It is at least one selected from resins, epoxy resins, elastomer resins, and derivatives of these resins.

In the connecting device according to the present invention, the optical fiber and the optical fiber, and the optical fiber and the light receiving semiconductor are interposed with a light guide having a multi-tubular or multi-layered light transmitting body which becomes thinner or thinner from the center to the outer periphery. It is necessary to connect them.
The outer peripheral portion of the cylindrical, tubular, or film-shaped optical transmission body is surrounded by a reflection surface except for the connection end surface.

The light guide can be made by itself or a commercial product can be diverted. For example, a multi-tubular polymethyl methacrylate resin light guide can be produced by purchasing a pellet of the resin, melt drawing, surface reflection, convergence, and cutting smoothing. Also, POFs having different core diameters can be purchased and used as a light guide by subjecting them to focusing cutting and smooth processing. As the surface reflection processing, there is a method of coating with a fluororesin having a low refractive index or a highly reflective substance. Generally, methods such as plating, vapor deposition, and coating are often used.

In optical transmission from a large-diameter optical fiber to a small-diameter optical fiber or a light-receiving semiconductor, it is necessary that the light guide path and the light guide have a tapered shape in the light transmission direction. The specific shape is selected from a cone, a paraboloid, a spheroid, and the like in consideration of the characteristics of the light emitted from the optical fiber. Further, it is preferable that the cross-sectional dimension of the light guide is equal to the input / output port of the optical fiber or light receiving semiconductor to be connected.

It is preferable that a flexible light transmitting body is mounted on one or both sides of the connection end face of the light guide. When a gap is formed at the connection interface, optical transmission loss is caused by phenomena such as refraction and reflection.

It is preferable that the refractive index of the light transmitting body and the light transmitting body is substantially equal to that of the optical fiber (within ± 0.05 of the refractive index of the optical fiber). If the difference in the refractive index between the optical fiber and the light transmitting body or the light transmitting body is too large, light transmission loss due to reflection or the like is caused. The refractive index of the optical fiber is 1.35 to 1.6.
0, and the refractive indexes of the light transmitting body and the light transmitting body are also in this range.

Other characteristics required for the optical transmission body are the same as those of the optical fiber, such as light transmittance, weather resistance, heat resistance, and the like. Any resin that satisfies these conditions may be used, and various applicable transparent resins are commercially available from Asahi Kasei, Mitsui Chemicals, JSR and the like.

The light transmitting body is required to be flexible, and its hardness is preferably 50 degrees or less in JIS (A type). If it is too hard, the adhesion at the time of connection will be insufficient and a gap will be created, resulting in loss during optical transmission. Suitable resins include silicones, acrylics, epoxies, elastomers, and derivatives thereof. Commercial products can be selected from products such as Shin-Etsu Chemical Co., Toshiba Silicone, Toagosei, Nippon Kayaku, and Asahi Kasei.

FIG. 1 is a schematic view of an optical connection device according to the present invention. (1) is a cross-sectional view as viewed from the side in the connection direction. (2) is a diagram viewed from the connection direction.
(A) is a shape in which a columnar optical transmission body is bundled so as to decrease in diameter from the center to the outer periphery, (b) is a shape in which a cylindrical optical transmission body is superimposed on a tubular optical transmission body, (c) Is a light guide having a shape in which a film-shaped light transmitter is wound around a cylindrical light transmitter.

FIGS. 2A and 2B show some examples of the optical connection device according to the present invention (a cross-sectional view as viewed from the side in the connection direction. 1) A device incorporating only a light guide, 2) An apparatus having a light transmitting body mounted on one side, and 3) is an apparatus having a light transmitting body mounted on both sides. 21 is a light guide, 22 is a support, 23
Is a light transmitting body.

FIG. 3 is a view showing an example in which an optical fiber having a large core diameter and a light receiving semiconductor having a small light receiving diameter are connected using the optical connecting device of the present invention (cross-sectional view in the connection direction). 30
Is a POF, 31 is a light guide, 32 is a support, 33 is a light transmitting body, 35 is a light receiving semiconductor (element 36, light receiving surface 37), 39
Is a signal light.

FIG. 4 is a view showing an example in which an optical fiber and a light receiving semiconductor are connected in the same manner as in FIG. 3 using the optical connection device of JP-A-10-221773 (cross-sectional view in the connection direction). 40
Is a POF, 42 is a support, 44 is a light guide, 45 is a light receiving semiconductor (element 46, light receiving surface 47), and 49 is a signal light.

FIG. 5 is a view showing an example in which an optical fiber and a light-receiving semiconductor are connected using a convex lens as in FIG. 3 (cross-sectional view in the connection direction). 50 is a POF, 52 is a support, 54 is a convex lens, 55 is a light receiving semiconductor (element 56, light receiving surface 5).
7) and 59 are signal lights.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described with reference to Examples and Comparative Examples.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A POF (Toray, core diameter 0.5 mm, refractive index 1.50) 30 made of polymethyl methacrylate resin and a light receiving semiconductor 35 are manufactured by using the optical connection device (31, 32) of the present invention.
Was connected as shown in FIG. The light receiving semiconductor is the light receiving element 36
(Photodiode, Hamamatsu Photonics, light receiving diameter 0.2m
m) was flip-mounted on a flexible circuit board and prototyped. Further, a flexible light transmitting body 33 was mounted on the contact interface between the POF and the light guiding body 31. The connection loss of this embodiment was as small as 0.3 dB. It can be determined that the signal light 39 having a large emission angle from the POF is reflected within the light guide path and transmitted to the light receiving surface 37 of the light receiving semiconductor without fail.

The light guide was formed by stretching the POF of the embodiment to a core diameter of 0.2 mm, wrapping an optical transmission sheet made of polymethyl methacrylate resin around the core to a diameter of 0.5 mm, and then performing a tension processing into a truncated cone. After the cutting, the connection cross section was further polished. The optical transmission body was made into a sheet by forming a resin pellet into a sheet having a thickness of 0.02 mm and performing chrome plating on the surface.

The light transmitting material is an addition-reaction type diphenyl silicone raw material having a hardness of JIS (A) 15 degrees (Shin-Etsu Chemical Co., Ltd.)
Was cured by heating, and the refractive index was 1.50.

[0032]

Comparative Example 1 A POF and a light-receiving semiconductor were connected as shown in FIG. 4 in the same manner as in the example by using a connection device (42, 44) based on the invention of Japanese Patent Application Laid-Open No. 10-221773. The outer shape of the light guide is the same as that of the example, but the connection loss of this comparative example is 3.7 dB.
Met. The signal light is not effectively transmitted to the light receiving semiconductor, and for example, the cause may be that the signal light 49 having a large emission angle is reflected by the light guide and returns to the optical fiber to cause a loss. In this comparative example, no light transmitting body was attached.

[0033]

Comparative Example 2 A connecting device using a conventional convex lens (52,
54), the POF and the light receiving semiconductor are changed in the same manner as in the embodiment.
Connected like. The connection loss in this comparative example is 5.1 dB.
And was the largest. It is considered that the main cause is that the signal light 59 having a large emission angle is reflected on the lens surface and is not transmitted to the light receiving semiconductor.

[0034]

According to the present invention, the connection loss in the case of optically coupling an optical fiber having a large exit diameter with an optical fiber having a small incident diameter or a light receiving semiconductor can be greatly reduced.
In particular, it is expected to play a large role in the spread of optical communication using large-diameter POF, which is scheduled to be used for consumer use. According to the present invention, an inexpensive and easy-to-use general-purpose optical fiber optical connection device will be put to practical use, and the spread of an optical communication system to offices and homes will be remarkably promoted.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a light guide of the present invention.

FIG. 2 is a diagram showing an example of the optical connection device of the present invention.

FIG. 3 is a diagram showing a connection example using the optical connection device of the present invention.

FIG. 4 is a diagram showing an example of an optical connection according to the prior art.

FIG. 5 is a diagram illustrating an optical connection example using a convex lens.

[Explanation of symbols]

 30, 40, 50 POF 21, 31 Light guide 22, 32, 42, 52 Support 23, 33 Light transmitting body 35, 45, 55 Light receiving semiconductor 36, 46, 56 Light receiving element 37, 47, 57 Light receiving section 39, 49, 59 signal light 44 prior art light guide 54 convex lens

Claims (6)

[Claims] In a connection structure for optically coupling an optical fiber to an optical fiber and an optical fiber to a light-receiving semiconductor, a multi-tubular form in which cylindrical optical transmission bodies are bundled so that the diameter decreases from the center to the outer periphery. A light guide, a tubular light guide or a multi-layered light guide in which light guides on a film are stacked so as to decrease in thickness from a central portion toward an outer peripheral portion, and are connected by interposing and connecting. Device for connection. 2. An optical transmitter and a light guide according to claim 1, wherein the signal light is transmitted from the optical fiber to an optical fiber or a light receiving semiconductor having an incident portion smaller than an emitting portion of the fiber. Has a shape that tapers in the light transmission direction. 3. The refractive index of an optical transmission medium is ±±
3. The optical connection device according to claim 1, wherein the value is within 0.05. 4. The optical connection device according to claim 1, wherein a flexible light transmitting body is mounted on one or both sides of the connection end face of the light guide. . 5. The method according to claim 1, wherein the refractive index of the light transmitting member is equal to the refractive index of the optical fiber.
The optical connection device according to any one of claims 1 to 4, wherein the value is within 0.05. 6. The light transmitting body is at least one selected from a silicone resin, an acrylic resin, an epoxy resin, an elastomer resin and a derivative of these resins having a JIS (A type) hardness of 50 degrees or less. The optical connection device according to any one of claims 1 to 5, wherein: