JPH1138245A - Optical waveguide for optical interconnection and optical back wiring board(bwb) - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide for circuit substrate connection and to provide a small size optical BWB. SOLUTION: The optical waveguide 100 is provided with an optical transmission medium 3, in which the thickness is L, the cross-section is a square shape, both end surfaces 1 are coated with no-reflection films 10 and other side surfaces are coated with all-reflection films 12, an input window 4, which is provided on one of side surfaces 11 by removing the film 12, an output window 5, which is provided on the same surface 11 by removing the film 12 that is positioned with the interval having multiple of integer m of a unit length n from the window 4, for example 3n, an input prism 6, which is provided at the position of the window 4, reflects the light beams, that are normally incident on the surface 11, with an angle θ=tan<-1> (n/2L) with respect to the normal and emits the beams in the longitudinal direction of the waveguide 100 and an output prism 7 which is provided at the position of the widow 5, reflects the light beams made incident from the waveguide 100 with the angle θ with respect to the normal and emits the light toward the surface 11 vertically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical back wiring for mounting a plurality of circuit boards including an optical circuit in a detachable manner and transmitting an electric signal and an optical signal from one circuit board to another circuit board. The present invention relates to a board and an optical waveguide thereof.

[0002]

2. Description of the Related Art The above-mentioned optical back wiring board (rear wiring board, hereinafter referred to as optical BWB) is composed of wiring for transmitting electric signals between circuit boards, an optical waveguide for transmitting optical signals, and
An electrical connector and an optical connector for connecting these wirings, the optical waveguide and each circuit board are provided.

In general, an optical fiber is used as an optical waveguide for connecting an optical circuit between a motherboard, a package, and the like, and a light emitting end and an incident end of the circuit are connected to an optical fiber by an optical connector. It is necessary to precisely align the optical axis with the fiber, and various connecting means for that purpose have been disclosed.

[0004] For example, as disclosed in Japanese Patent Application Laid-Open No. 58-12451, in signal transmission between a motherboard and a package mounted on the motherboard, a multiplexing circuit for multiplexing electric signals on the package, An electric / optical conversion circuit and a light emitting element for converting a multiplexed signal into an optical signal,
An optical-to-electrical conversion circuit and a light-receiving element for converting an optical signal to an electric signal, and a demultiplexing circuit for demultiplexing the electric signal converted by the optical-to-electrical conversion circuit, and forming an optical waveguide on a motherboard; A method of optically coupling a light emitting element and a light receiving element on a package with each other is known.

Japanese Patent Application Laid-Open No. 63-202723 discloses a light-emitting device, an optical waveguide for guiding light emission of the light-emitting device, and an optical waveguide attached to the optical waveguide for transmitting propagating light out of the waveguide. A light deflector that has a diffraction grating that emits light to the substrate, and deflects the angle of the emitted light by applying an electrical signal; and a light converging optical system that converges the emitted light to a light receiving element on a receiving substrate. An optical connection device is disclosed.

[0006]

However, the above-mentioned prior art 1 is a connection between a motherboard and a package mounted on the motherboard, but is a connection within the same substrate. A connection between circuit boards in the same board or in the same plane by a fiber or the like. In each case, a large space is required in an optical connector section as an optical BWB for mounting a plurality of circuit boards in parallel and connecting them to each other. There was a problem.

An object of the present invention is to provide a small-sized optical BWB on which a plurality of circuit boards having an optical interface are mounted and optical signals can be connected between the circuit boards, and an optical waveguide thereof.

[0008]

The optical waveguide for optical interconnection according to the present invention has a rectangular cross section having a thickness L between opposing surfaces, and a total reflection film is provided inside each side surface which is linearly extended in the longitudinal direction. A light transmitting medium coated with an anti-reflection film on both end surfaces, an input window provided by removing a part of the total reflection film on one side in the longitudinal direction of the light transmitting medium, and the same side as the input window The output window is provided above and the portion of the total reflection film is removed from the input window at a distance of an integer m times the unit length n, and the output window is provided at the input window portion and vertically incident on the side surface. An input prism that refracts light at an angle θ = tan −1 (n / 2L) with respect to the normal line and emits the light in the longitudinal direction in the light transmitting medium; Incident at an angle θ to the line It was to refract light and an output prism emitted perpendicular to the side surface.

In addition, on the same side surface between the input window and the output window, one or more total reflection films at integer x positions up to m-1 are removed at intervals of an integral multiple of the unit length n. When the transmittance is from 1 / (x + 1) to 1/2 toward the output window from the one closer to the input window, 1 /
x, 1 / (x-1),. . . An intermediate window coated with a permeable membrane that changes step by step is provided,
Further, a prism similar to the output prism may be provided in each of these intermediate windows.

An optical BWB according to the present invention includes any one of the above optical interconnection optical waveguides, an electrical connector arranged at intervals of a unit length n and connected to a terminal of an electrical signal on a circuit board, and an input of the optical waveguide. An optical connector for connecting an optical interface unit of the circuit board to the window, the output window, and the intermediate output window;

[0011]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of one embodiment of the optical waveguide for optical interconnection of the present invention.

Referring to FIG. 1, an optical waveguide 100 of this embodiment is shown.
Has a rectangular cross section in which the antireflection film 10 is coated on both longitudinal end surfaces 1 extending in a straight line, and the total reflection film 12 is coated on each of the other longitudinal sides. The input window 4 provided by removing the total reflection film 12 on a part of the one side surface 11 coated with the light transmission medium 3 and the total reflection film 12, and on the same side surface 11 as the input window 4, And the input window 4
1, is provided at the position of an output window 5 provided by removing the total reflection film 12 at positions spaced by an integer m times the unit length n, for example, 3 times in FIG.
The light perpendicularly incident on the side surface 11 is angled with respect to the normal θ = t
An input prism 6 refracted to an-1 (n / 2L) and emitted in the longitudinal direction in the light transmitting medium, and provided at the position of the output window 5, and enters the light transmitting medium at an angle [theta] with respect to the normal line. And an output prism 7 that refracts the reflected light and emits the light perpendicular to the side surface 11.

By using the optical waveguide 100 having such a structure, an optical signal incident on the input window 4 and perpendicular to the side surface 11 is incident on the input prism 6 at an angle θ with respect to a normal line.
And is guided in the longitudinal direction in the optical waveguide 100. When the total reflection is repeated between the side surface 11 and the opposing surface at an angle θ with respect to the normal of 2m−1 times, that is, five times in the example of the drawing, and reaches the output window 5, the light is refracted by the output prism 7 and is output. 5 is emitted perpendicularly to the side surface 11. Therefore, an optical signal incident on the optical waveguide 100 from the circuit A disposed opposite to the input window 4 is:
Since the light is emitted in parallel to the circuit B disposed opposite the output window 5, the circuit A and the circuit B can be optically connected.

Next, another embodiment of the optical waveguide for optical interconnection of the present invention will be described with reference to the drawings.

As shown in FIG. 2, the optical waveguide 200 of the second embodiment has an interval of an integral multiple of the unit length n between the input window 4 and the output window 5 of the first embodiment. And at least one integer x up to m-1 (here, two places), the total reflection film is removed, and the transmittance becomes 1 / (x +
From 1) to 1/2, 1 / x, 1 / (x-1),. . .
, An intermediate window coated with a permeable film 13 that changes step by step (in the illustrated example, the transmittance is 1/3 and 1 /
Two intermediate windows 30 and 31) coated with two transmission films 13 are provided, and an output prism 7 similar to the output prism 7 is provided in each of these intermediate windows.

The optical signal incident from the input window 4 is totally reflected inside the optical waveguide 200 and first reaches the intermediate window 30. When the optical signal reaches the intermediate window 30, 1/3 of the incident light is refracted by the transmission film having the transmittance of 1/3. Then, the light is vertically emitted out of the optical waveguide from the intermediate window 30, and the remaining ２ is reflected into the optical waveguide 200. The optical signal reflected into the optical waveguide 200 is refracted in the next intermediate window 31 by 2/3 × 1/2 = 1/3 of the incident light due to the transmission film having the transmittance of て. From the optical waveguide 200, and the remaining 1/3 is reflected into the optical waveguide 200. The remaining 1/3 is vertically emitted from the last output window 5 to the outside of the optical waveguide 200.

That is, each intermediate window 30, 31
And 1/3 of the incident light are equally distributed and output from the output window 5.

The intermediate window has a unit length n on the side surface 11.
It is not always provided at each reflection point. The total reflection film 12 at the reflection point where the intermediate window is not provided is not removed, and the transmittance of the transmission film coated on each intermediate window is an input window represented by a multiple of the unit length n or an output window. Not the distance from the window,
It depends on the number x of arranged intermediate windows and the arrangement order.

Next, an optical BWB 300 using the above-described optical waveguide 100 will be described with reference to FIG.

The optical BWB 300 shown in FIG. 3 is composed of an optical waveguide for optical interconnection in which two optical waveguides 100 shown in FIG. 1 are arranged in parallel, and circuit boards 20a and 20b having both an optical interface and an electrical interface. Optical connectors 23a and 23b to which optical interfaces can be connected
And an electrical connector 2 to which electrical interfaces of the circuit boards 20a and 20b and other circuit boards (not shown) can be connected.
And 2.

The two optical waveguides 100 are arranged such that one input window 4 and the other output window 5 are arranged side by side.
Both ends are connected to either one of the optical connectors 23a and 23b, and when the circuit board 20a or 20b is mounted, both the one input window 4 and the other output window 5 are arranged on the optical interface of the circuit board. Connected at the same time.

The electrical connectors 22 are arranged in one or more rows in parallel with the optical waveguide 100 at intervals of a unit length n, and the electrical connectors are electrically wired on the optical BWB. In each row, up to m + 1 electrical connectors 22 including a circuit board having only an electrical interface without an optical interface can be attached.

[0024]

As described above, the optical waveguide for optical interconnection of the present invention is provided with an input and output window having an input prism and an output prism on a light transmitting medium having a rectangular cross section and extending straight. The optical signal incident on the window is refracted and propagated to the output window while being reflected in the light transmitting medium, and then emitted from the output window, making it easy to connect the optical signal between two circuit boards mounted in parallel. There is an effect that can be realized.

Also, by providing an intermediate window having a transmission film at a reflection point between the input window and the output window, an optical signal incident from one circuit board can be distributed to a plurality of circuit boards and emitted. is there.

The optical back wiring board of the present invention has the effect of reducing the size and weight of the device and reducing power consumption by embedding the above-described optical waveguide in the board.

[Brief description of the drawings]

FIG. 1 shows an optical waveguide 1 for optical interconnection according to the present invention.
It is a longitudinal section of an example.

FIG. 2 is a longitudinal sectional view of another embodiment of the optical waveguide for optical interconnection of the present invention.

FIG. 3 is a perspective view of one embodiment of an optical back wiring board (optical BWB) of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 End surface 3 Light transmission medium 4, 5, 30, 31 Window 6 Input prism 7 Output prism 10 Non-reflection film 11 Side surface 12 Total reflection film 13 Transmission film 20a, 20b Circuit board 22 Electrical connector 23a, 23b Optical connector 100, 200 Light Optical waveguide for interconnection 300 Optical back wiring board, (optical BW
B)

Claims (5)

[Claims] An optical waveguide for optical interconnection connected between optical circuit boards and transmitting an optical signal from one optical circuit board to another optical circuit board, wherein the cross section is rectangular and the thickness between one opposing surfaces. L, a light-transmitting medium in which a total reflection film is coated inside each side surface that is linearly extended in the longitudinal direction, and a non-reflective film is coated on both end surfaces; and one longitudinal side surface of the light-transmitting medium. An input window provided by removing a part of the total reflection film, and a total reflection film of a portion on the same side surface as the input window and spaced from the input window by an integer m times the unit length n. An output window provided by removing the light; and a light that is provided on the input window and refracts light incident perpendicularly to the side surface at an angle θ that is an arctangent of (n / 2L) with respect to a normal line. Longitudinal direction in transmission medium And an output prism that is provided in the output window and that refracts light incident at the angle θ with respect to a normal line from within the light transmitting medium and emits the light perpendicularly to the side surface. Characteristic optical waveguide for optical interconnection. 2. A total reflection film at one or more integers x and at least m-1 at intervals of an integral multiple of a unit length n is removed on the same side surface between the input window and the output window. From the one whose transmittance is closer to the input window toward the output window, respectively, 1 / (x + 1) to 1 / x, 1 / (x−1),. . . 2. The method according to claim 1, wherein x intermediate windows coated with a permeable film that changes in a stepwise manner are provided, and each intermediate window is provided with an output prism similar to the output prism. Optical waveguide for optical interconnection. 3. A back wiring boat for performing circuit connection between mounted circuit boards, wherein the back wiring boat has a rectangular cross section having a thickness L between opposing surfaces, and is entirely provided inside each side surface extended linearly in the longitudinal direction. A light transmission medium coated with a reflection film, and a non-reflection film coated on both end surfaces; an input window provided by removing a part of a total reflection film on one side surface in a longitudinal direction of the light transmission medium; An output window which is provided on the same side as the input window, and which is provided by removing the total reflection film at a portion spaced from the input window by an integer m times the unit length n; and an output window provided at the input window portion. An input prism that refracts light incident perpendicular to the side surface at an angle θ that is an arctangent of (n / 2L) with respect to a normal line and emits the light in a longitudinal direction in the light transmitting medium; part An optical waveguide having an output prism that refracts light incident at the angle θ with respect to a normal from the light transmission medium and emits the light perpendicular to the side surface, at an interval equal to the unit length n. An electrical connector arranged and connected to the wiring for connection between circuit boards and an electrical interface unit of each circuit board; and an input window and an output window of the optical waveguide and an optical interface unit of each circuit board connected. An optical back wiring board comprising an optical connector. 4. The optical waveguide has a unit length n on the same side surface between the input window and the output window.
The total reflection film at one or more integer x positions is removed at intervals of an integer multiple of 1 to m−1, and the transmittance is changed from 1 near the input window toward the output window by 1
// (x + 1) to 1 / x, 1 / (x-1),. . . And a half of which is provided with an output prism similar to the output prism, and the intermediate window is provided with an output prism similar to the output prism. 4. The optical back wiring board according to claim 3, wherein each of the optical interface units has an optical connector connected thereto. 5. The optical back wiring board according to claim 3, wherein the light transmitting medium of the optical waveguide is disposed so as to be embedded in the optical back wiring board.