Substrate with optical waveguide and method of making the same

Details Substrate with optical waveguide and method of making the same Substrate with optical waveguide and method of making the same

1999-03-05

2001-05-22

Lee, John D. (Department: 2874)

Optical waveguides

With optical coupler

Particular coupling structure

C385S014000, C385S049000

Reexamination Certificate

active

06236786

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a substrate provided with an optical waveguide through which a light signal is transmitted and a method of making such a substrate.
2. Description of the Related Art
A substrate with an optical waveguide has recently been proposed which is provided with an optical waveguide so that light signals and electric signals are simultaneously treated. For example, the prior art has proposed a construction in which an optical waveguide is provided on one of two sides of a substrate and a reflecting face serving as direction changing means and a light-sensitive element are disposed at one end side of the optical waveguide. In this construction, a light signal introduced into the optical waveguide is reflected on the reflecting face so that the direction of the light signal is changed to the light-sensitive element side. The light signal is then sensed by the light-sensitive element.
In the above-described construction, however, it is only at one side of the substrate that the light signal is transmitted. In other words, the transmitting direction of the light signal can be changed only two-dimensionally or on a plane. As a result, a region used for the light signal transmission is limited in a single substrate.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a substrate with an optical waveguide in which the substrate can be effectively used for the light signal transmission and which can cope with high-densification of the substrate.
Another object of the invention is to provide a method of making a substrate with an optical waveguide in which the optical waveguide can be desirably made in the substrate.
The present invention provides a substrate with an optical waveguide comprising a substrate having a through hole and two sides, a first optical waveguide defined in the through hole of the substrate so as to linearly extend between both sides of the substrate, a second optical waveguide defined on at least one of the sides of the substrate, and direction changing means for changing a transmitting direction of a light signal from either one of the first and second optical waveguides to the other, each optical waveguide including a core layer for transmitting the light signals and a clad layer formed around the core layer.
According to the above-described substrate, the first optical waveguide can optically connect between both sides of the substrate. Consequently, since the optical waveguides through which the light signal is transmitted are provided on both sides of the substrate respectively, the substrate can be used effectively. Further, the first optical waveguide is defined in the through hole of the substrate. Consequently, the light signal can be transmitted from one side to the other side at any location of the substrate and accordingly, a transmission pattern of the light signal can be designed more freely.
In this construction, the transmitting efficiency of the light signal can further be improved. Further, two second optical waveguides are preferably defined at both sides of the substrate respectively. Additionally, the substrate is preferably made of polyimide.
In another preferred form, the substrate further comprises signal converting means provided on said other side of the substrate for converting the light signal received via the first optical waveguide to a corresponding electric signal, and an electric circuit section into which the electric signal is supplied. According to this construction, the light signal transmitted via, for example, an external optical fiber network is received at said one side of the substrate and further transmitted via the first optical waveguide to said other side of the substrate, where the light signal is converted to the electric signal by the signal converting means. When the electric signal is thereafter supplied to an electric or electronic circuit, the light signal can be used so that information is transmitted at high speeds or over a wide band between electric circuit sections of respective substrates connected together via the network.
The invention also provides a method of making a substrate with an optical waveguide, the substrate having a through hole and two sides and comprising a first optical waveguide defined in the through hole of the substrate so as to linearly extend between both sides of the substrate, a second optical waveguide defined on at least one of the sides of the substrate, and direction changing means for changing a transmitting direction of a light signal from either one of the first and second optical waveguides to the other. The method comprises the steps of immersing the substrate in a resin liquid for making the first optical waveguide so that the through hole is filled with the resin liquid, and hardening the resin liquid after the immersing step, thereby making the first optical waveguide.
According to the above-described method, the first optical waveguide can be made desirably and readily.
The invention further provides a method of making a substrate with an optical waveguide, the substrate having a through hole and two sides and comprising a first optical waveguide including a core layer linearly formed between both sides of the substrate for propagating a light signal and a clad layer covering the core layer, a second optical waveguide defined on at least one of the sides of the substrate, and direction changing means for changing a transmitting direction of a light signal from either one of the first and second optical waveguides to the other. The method comprises the steps of disposing a metal die having one open end at the substrate side along a route of the second optical waveguide so that the other end of the die covers an opening of the through hole, and filling the die with a resin liquid for forming the optical waveguides, and hardening the resin liquid subsequently to the filling step, thereby forming the first and second optical waveguides.
According to the above-described method, the first and second optical waveguides are simultaneously formed by using the metal die. Consequently, steps of manufacturing the substrate can be simplified. Further, since the first and second optical waveguides are integrally formed, no boundary between them is formed. Consequently, a reflection loss resulting from transmission of the light signal between both waveguides can be reduced to a large extent.


REFERENCES:
patent: 3663194 (1972-05-01), Greenstein et al.
patent: 4070516 (1978-01-01), Kaiser
patent: 4472020 (1984-09-01), Evanchuk
patent: 5125054 (1992-06-01), Ackley et al.
patent: 5200631 (1993-04-01), Austin et al.
patent: 5898803 (1999-04-01), Mueller-Fieldler et al.

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