JP2004021154A - Optical transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission device improved in the utilization efficiency of light radiated from a light emitting element. <P>SOLUTION: The optical transmission device is equipped with a light transmissive medium 23 having an inclined (45°) surface 22 and a light emitting element 24 whose beam spread angle is different in two orthogonal directions at an optical signal incident part 21. An optical signal 25 radiated from the light emitting element 24 is reflected on the inclined surface 22 after it is made incident on the medium 23, and propagated in a leftward direction in figure in the medium 23. The light emitting element 24 is arranged with respect to the incident part 21 so that a direction where the beam spread angle is narrow may be positioned in the inclined direction of the inclined surface 22. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical transmission device using a translucent medium that transmits an optical signal between a plurality of circuit boards or devices.
[0002]
[Prior art]
Conventionally, transmission and reception of signals between circuit boards and devices has been conventionally performed using an electric bus. However, electric buses have insufficient fan-out, making it difficult to respond to high-speed signals (Iwao Hayashi: "Integration of Light and Electron-Limits of Silicon Integrated Circuits and Optical Interconnection", Applied Physics, vol. .65, No. 8, pp. 824-831, 1996).
[0003]
On the other hand, Japanese Patent Application Laid-Open No. 2-41042 discloses an optical data bus in which light emitting / receiving devices are arranged on both front and back surfaces of each circuit board, and the light emitting / receiving devices on adjacent circuit boards are spatially coupled by light. Has been proposed. However, this technology requires high cost and large latency because optical / electrical conversion is required for each communication between adjacent circuit boards, and uses free space propagation, so positioning is severe, and crosstalk and dust Has the disadvantage of being weak.
[0004]
Japanese Patent Application Laid-Open No. S61-196210 proposes a technique for optically coupling circuit boards through an optical path constituted by a diffraction grating and a reflection element arranged on a plate surface. However, this technique has a problem that light emitted from one point can be connected only to a fixed point, so that many-to-many connection cannot be performed.
[0005]
In view of such circumstances, Japanese Patent Application Laid-Open No. 2002-62457 discloses a method in which a plurality of steps are provided at one end of a translucent medium for forming a light input / output section, and an optical signal incident from the input / output section is provided at the other end. There has been proposed an optical signal transmission device provided with a reflection means for reflecting light. In this device, an optical signal from a light emitting element is incident from one input / output unit, propagates in a light transmitting medium, is reflected by a reflection unit, propagates again in the light transmitting medium, and passes through a plurality of input / output units. The light is emitted to a plurality of light receiving elements provided correspondingly.
[0006]
[Problems to be solved by the invention]
This type of optical transmission device uses, for example, an edge-emitting laser diode as a light emitting element. The beam emitted from the edge-emitting laser diode has an elliptical shape, and the divergence angle is defined by FWHM (Full Width at Half Maximum). When the laser beam is incident on the inclined surface of the translucent medium constituting the optical transmission device, ideally all the incident light should be totally reflected on the inclined surface, but a part of the divergent incident light May escape from the translucent medium to the outside. In such a case, there is a problem that utilization efficiency of light emitted from the light emitting element is reduced.
[0007]
Therefore, an object of the present invention is to provide an optical transmission device in which the utilization efficiency of light emitted from a light emitting element is improved.
[0008]
[Means for Solving the Problems]
The above object is an optical transmission device including a translucent medium having an inclined surface at least at an incident portion of an optical signal and a light emitting element having a different beam divergence angle in two orthogonal directions, wherein the light emitting element is This is achieved by an optical transmission device disposed with respect to the incident portion such that a direction in which the beam divergence angle is narrow is located in the inclination direction of the inclined surface.
[0009]
Further, the optical transmission device according to the present invention has a light-transmitting medium having a step-like stepped portion provided with a plurality of optical signal input / output sections each having an inclined surface at one end and a vertical surface at the other end. An optical transmission device comprising a medium and a light-emitting element having a different beam spread angle in two orthogonal directions, wherein the light-emitting element is positioned such that a narrow beam spread angle is located in a direction in which the inclined surface is inclined. It is arranged with respect to the input / output unit. Here, a reflection portion or a reflection diffusion portion for an optical signal can be provided at the other end of the translucent medium.
[0010]
Further, the optical transmission device according to the present invention is characterized in that a light-transmitting medium having at least a vertical surface at an incident portion of an optical signal and an inclined surface at least at an emitting portion, and a light emitting device having different beam divergence angles in two orthogonal directions. An optical transmission device comprising: a light-emitting element, wherein the light-emitting element is arranged with respect to the incident portion such that a direction in which a beam divergence angle is narrow is positioned in a direction in which the inclined surface is inclined. Here, a diffusion portion for an optical signal can be provided at the incident portion of the translucent medium.
[0011]
In addition, an optical data bus system that transmits data by an optical signal can be configured by using these optical transmission devices.
With this configuration, the efficiency of using light emitted from the light emitting element can be improved.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. Before that, first, a phenomenon in which a part of an incident light beam escapes from a translucent medium to the outside will be described.
[0013]
FIG. 1 is a diagram illustrating an example of a path of light incident on a translucent medium having an inclined surface. As shown in the figure, the light-transmitting medium 1 has an inclined surface 2, and a light-emitting element 3 is arranged near the light-transmitting medium 1. The refractive index of the surrounding transparent medium n _1, the refractive index of the transparent medium 1 n _2, the half-value of the spread angle of the beam emitted from the light-emitting element 3 and phi _1. Focusing on the outermost ray of the beam, the light beam is incident on the transparent medium 1 at an incident angle phi _1, reaches the inclined surface 2 is refracted at refraction angle phi _2. Here, if the inclined surface 2 has an inclination of 45 °, although this ray reaches the inclined surface 2 at an incident angle (45 ° -.phi _2), the angle of incidence (45 ° -.phi ₂₎ is the critical angle ( φ _c ), that is, φ ₁ > sin ⁻¹ {n ₂ / n ₁ · sin (45 ° −φ _c )}
In the case of, the incident light beam escapes to the outside from the translucent medium. For example, when n ₁ = 1.0 (assuming air) and n ₂ = 1.525 (assuming polyolefin), light rays with φ ₁ > 6.14 ° pass through the translucent medium to the outside. . Therefore, by arranging the light emitting element such that the direction in which the beam divergence angle is narrow is located in the direction of inclination of the inclined surface, it is possible to suppress the escape of light rays from the inclined surface to the outside, and the efficiency of use of light emitted from the light emitting element Can be improved.
[0014]
2A and 2B are diagrams showing an embodiment of the optical transmission device according to the present invention, wherein FIG. 2A is a plan view, FIG. 2B is a side view, and FIG. 2C is a perspective view. In this embodiment, as shown in the figure, a light-transmitting medium 23 having an inclined (45 °) surface 22 at an incident portion 21 of an optical signal, and a beam in two orthogonal directions (X direction and Y direction in the figure). And light emitting elements 24 having different spread angles. The light emitting element 24 is arranged with respect to the incident part 21 so that the direction in which the beam spread angle is narrow is located in the inclination direction (Y direction) of the inclined surface 22. The light emitting element 24 is fixed to, for example, a circuit board (not shown).
[0015]
In FIG. 2, an optical signal 25 emitted from a light emitting element 24 is incident on a light transmitting medium 23, is reflected on the inclined surface 22, and propagates inside the light transmitting medium 23 to the left in the figure. In the present embodiment, since the light emitting elements are arranged so that the direction in which the beam divergence angle is narrower is located in the direction of inclination of the inclined surface, the amount of light rays that escape from the inclined surface to the outside can be suppressed, and as a result, the light Usage efficiency can be improved.
[0016]
3A and 3B are diagrams showing another embodiment of the optical transmission device according to the present invention, wherein FIG. 3A is a plan view, FIG. 3B is a side view, and FIG. 3C is a perspective view. In this embodiment, as shown in the figure, a transparent step having a stepped step portion having a plurality of optical signal input / output portions 32 each having an inclined (45 °) surface 31 at one end and a vertical surface 33 at the other end. An optical medium 34, a light emitting element 35 having a different beam divergence angle in two orthogonal directions (X direction and Y direction in the figure), and a plurality of light receiving elements 36 are provided. On the vertical surface 33 at the other end of the translucent medium, a reflection part (or reflection diffusion part) 37 for an optical signal is provided. The light emitting element 35 is arranged with respect to the incident / emission unit 32 such that the direction in which the beam divergence angle is narrow is located in the inclination direction (Y direction) of the inclined surface 31. The light emitting element 35 and the plurality of light receiving elements 36 are respectively fixed to, for example, a circuit board (not shown).
[0017]
In FIG. 3, an optical signal 38 emitted from a light emitting element 35 enters a light transmitting medium 34 from one of the input / output sections 32, is reflected by the inclined surface 31, and passes through the inside of the light transmitting medium 34 in the left of the figure. Propagation in the direction. Then, the optical signal is reflected (diffused) by the reflection section (reflection / diffusion section) 37, propagates in the light-transmitting medium 34 in the opposite direction, and is emitted from each of the input / output sections 32 to the light receiving element 36. In the present embodiment, since the light emitting elements are arranged so that the direction in which the beam divergence angle is narrower is located in the direction of inclination of the inclined surface, the amount of light rays that escape from the inclined surface to the outside can be suppressed, and as a result, the light Usage efficiency can be improved.
[0018]
4A and 4B are diagrams showing another embodiment of the optical transmission device according to the present invention, wherein FIG. 4A is a plan view, FIG. 4B is a side view, and FIG. 4C is a perspective view. In the present embodiment, as shown in the figure, a light-transmitting medium 44 having a vertical surface at an optical signal incident portion 41 and an inclined (45 °) surface 43 at an output portion 42 and two orthogonal directions (FIG. A light-emitting element 45 having a different beam spread angle between the middle X direction and the Y direction). The light emitting element 45 is arranged with respect to the incident portion 41 such that the direction in which the beam divergence angle is narrow is located in the inclination direction (Y direction) of the inclined surface 43. In this incident part, a diffusion part 46 for an optical signal is provided. On the other hand, a light receiving element 47 is arranged in each of the emission sections 42 in correspondence with each other.
[0019]
In FIG. 4, an optical signal 48 emitted from a light emitting element 45 is diffused by a diffusion section 46, propagates in a translucent medium 44 rightward in the figure, and is emitted from each emission section 42 to a light receiving element 47. In this embodiment, since the light emitting elements are arranged so that the direction in which the beam divergence angle is narrow is located in the inclination direction (Y direction) of the inclined surface (the Z direction in the vertical plane of the incident portion), the light emitting element is located outside the inclined surface. It is possible to suppress the amount of light passing through the light source, thereby improving the light use efficiency.
[0020]
FIG. 5 is a diagram for explaining a simulation of the insertion loss (dB) at the light emitting portion when the arrangement direction of the light emitting elements is rotated by 90 ° in FIG. 3C, and FIG. -Parameters, (b) are simulation results. As shown in FIG. 5A, in this simulation, the beam divergence angle of the light source (light emitting element) is 8 × 20 °, the light receiving diameter of the light receiving unit is φ0.8 mm, the coupling distance is 1.2 mm, and the reflection type diffusion unit Has a diffusion angle of 0.2 × 40 °, a translucent medium having a thickness of 1.5 mm, a width of 8 mm, a mixing length of 100 mm, a step length of 13.25 mm, and a refractive index of 1.49 (for example, polymethyl Methacrylate) and the number of branches (the number of nodes) was set to 8. Here, the mixing length is a length of a portion excluding a step-shaped step portion formed at one end of the light transmitting medium, and the step length is a length of each step-shaped step portion, and the number of branches The (number of nodes) corresponds to the number of steps (incoming and outgoing portions) having a step-like shape.
[0021]
According to the simulation result shown in FIG. 5B, the maximum insertion loss is 18.4 dB in the embodiment of the present invention and 20.0 dB in the embodiment rotated by 90 °. That is, according to the embodiment of the present invention, the insertion loss can be reduced by 1.6 dB as compared with the case where the arrangement direction of the light emitting elements is rotated by 90 °.
[0022]
In the present invention, the light emitting element is not limited to the edge emitting laser diode (LD), but may be a surface emitting laser (VCSEL) or a light emitting diode (LED).
Further, the shape of the translucent medium is not limited to the above-described one, and may be any shape having an obliquely inclined surface at the entrance / exit portion, such as the forms shown in FIGS. 6A and 6B are diagrams showing another embodiment of the optical transmission device according to the present invention, wherein FIG. 6A is a plan view and FIG. 6B is a side view. In the present embodiment, as shown in the figure, a stepped step portion having an inclined (45 °) surface 61 at one end and a plurality of optical signal input / output portions, and a vertical surface 62 and an inclined (45 °) a light-transmitting medium 64 having an input / output portion having a surface 63; A reflection portion (or a reflection diffusion portion) of an optical signal is provided at a position other than the entrance / exit portion of the vertical surface 62 at the other end of the translucent medium. In the present embodiment, a light emitting element (not shown) is arranged such that the direction in which the beam divergence angle is narrow is located in the direction of inclination of the inclined surface 61 or the inclined surface 63. Thus, the amount of light rays that escape from the inclined surface to the outside can be suppressed, and the light use efficiency can be improved. FIGS. 7A and 7B are diagrams showing another embodiment of the optical transmission device according to the present invention, wherein FIG. 7A is a perspective view and FIG. 7B is a side view. In this embodiment, as shown in the figure, a translucent medium 73 having trapezoidal cross sections having inclined (45 °) surfaces 71 and 72 at both ends and a plurality of optical signal input / output sections is provided. A plurality of light emitting elements 74 are arranged on the inclined surface 71 side, and a plurality of light receiving elements 75 are arranged on the inclined surface 72 side. In this embodiment, the light emitting elements 74 are arranged such that the direction in which the beam divergence angle is narrow is located in the direction of inclination of the inclined surface 71. Thus, the amount of light rays that escape from the inclined surface 71 to the outside can be suppressed, and the light use efficiency can be improved.
[0023]
Using these optical transmission devices, an optical data bus system for transmitting data by optical signals can be configured. With this configuration, it is possible to improve the light use efficiency in the optical bus system. Furthermore, if a signal processing device having a plurality of circuit boards is configured, signal transmission between arbitrary circuit boards becomes possible, and an optical bus system having high resistance to environmental changes such as temperature change and dust can be obtained.
[0024]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the optical transmission apparatus which improved the utilization efficiency of the light radiated from the light emitting element can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a path of light incident on a translucent medium having an inclined surface.
FIGS. 2A and 2B are diagrams showing an embodiment of the optical transmission device according to the present invention, wherein FIG. 2A is a plan view, FIG. 2B is a side view, and FIG.
3A and 3B are diagrams showing another embodiment of the optical transmission device according to the present invention, wherein FIG. 3A is a plan view, FIG. 3B is a side view, and FIG. 3C is a perspective view.
4A and 4B are diagrams showing another embodiment of the optical transmission device according to the present invention, wherein FIG. 4A is a plan view, FIG. 4B is a side view, and FIG.
FIGS. 5A and 5B are diagrams for explaining a simulation of insertion loss at the emission part when the arrangement direction of the light emitting elements is rotated by 90 °, where FIG. 5A is a simulation parameter, and FIG. 5B is a simulation result. is there.
FIGS. 6A and 6B are diagrams showing another embodiment of the optical transmission device according to the present invention.
FIGS. 7A and 7B are diagrams showing another embodiment of the optical transmission device according to the present invention.
[Explanation of symbols]
Reference Signs List 21 Incident part 22 Inclined (45 °) surface 23 Translucent medium 24 Light emitting element 25 Optical signal

Claims (7)

An optical transmission device comprising: a light-transmitting medium having an inclined surface at least at an optical signal incident portion; and a light emitting element having a different beam divergence angle in two orthogonal directions, wherein the light emitting element has an inclined surface. An optical transmission device, wherein the optical transmission device is disposed with respect to the incident portion such that a direction in which a beam divergence angle is narrow is located in a tilt direction. A light-transmitting medium having a stepped stepped portion having a plurality of optical signal input / output sections each having an inclined surface at one end of the light-transmitting medium and a vertical surface at the other end; and a beam spread in two orthogonal directions. An optical transmission device comprising a light emitting element having a different angle, wherein the light emitting element is disposed with respect to the incident / exit unit such that a direction in which a beam divergence angle is narrow is located in a direction in which the inclined surface is inclined. An optical transmission device characterized by the above-mentioned. A translucent medium having a step-like stepped portion having a plurality of optical signal input / output portions each having an inclined surface at both ends of the translucent medium, and a translucent medium having a vertical surface at a part of the other end, and two orthogonal directions And a light emitting element having a different beam divergence angle in the light transmission element, wherein the light emitting element is disposed with respect to the incident / emission unit such that a narrow beam divergence angle is located in a direction of inclination of the inclined surface. An optical transmission device, comprising: The optical transmission device according to claim 2, wherein a reflection portion or a reflection diffusion portion for an optical signal is provided at the other end of the light transmitting medium. An optical transmission device comprising: a light-transmitting medium having at least a vertical surface at an incident portion of an optical signal and having an inclined surface at least at an output portion; and a light-emitting element having different beam spread angles in two orthogonal directions. An optical transmission device, wherein the light emitting element is arranged with respect to the incident portion such that a direction in which a beam divergence angle is narrow is located in an inclination direction of the inclined surface. 6. The optical transmission device according to claim 5, wherein a light signal diffusion portion is provided at an incident portion of the light transmitting medium. An optical data bus system for transmitting data by an optical signal using the optical transmission device according to any one of claims 1 to 6.

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