Optical waveguides – With optical coupler – Permanently fixed coupler
Reexamination Certificate
1998-07-31
2001-07-31
Spyrou, Cassandra (Department: 2872)
Optical waveguides
With optical coupler
Permanently fixed coupler
C385S045000, C385S049000, C385S051000, C385S088000, C385S089000, C385S092000, C385S094000, C174S256000, C174S260000, C257S783000, C257S792000
Reexamination Certificate
active
06269209
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical module and a sealing method therefor.
2. Description of the Related Art
In recent years, the development of an optical access network has been actively pursued. For realization of an optical access network, it is greatly important to reduce the cost of an optical device and/or an optical module. Also in sealing an optical element for performing opto-electric conversion or electro-optic conversion in an optical module, further cost reduction is required, and a method of easily sealing the optical element with a sufficient reliability is demanded.
In many optical modules at present, a metal package or ceramic package is used to ensure reliability and the package is hermetically sealed by welding or soldering, resulting in a very high cost of optical module. For cost reduction of an optical module, it is now important to simplify the sealing method for an optical element. As an example of simplification of the sealing method for an optical element, there has been proposed a method of applying a resin to the entire surface of a substrate on which an optical element is mounted and next curing the resin (Mitsuo Fukuda et al., “Plastic Packaging of Semiconductor Laser Diode”, Electronic Components and Conference, 1996, pp1101-1108).
In the case of applying a resin to the entire surface of a substrate on which an optical element is mounted and next curing the resin to seal the optical element as described in the above literature, there is a possibility that separation or cracking of the resin may occur because of a large difference in coefficient of thermal expansion between the substrate and the resin, or the substrate may be broken by a residual stress in the resin. The larger the thickness of the resin coating covering the optical element and the wider the range of spread of the resin coating, the larger the residual stress in the resin. Accordingly, the residual stress can be relaxed by thinly applying the resin to a minute area surrounding the optical element. However, the resin is generally in the form of gel, so that when dropped onto the substrate, it spreads widely on the substrate and it is difficult to apply the resin to only the minute area surrounding the optical element.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a low-cost high-reliability optical module by sealing only an optical element and its periphery with a resin.
It is another object of the present invention to provide a sealing method for a low-cost high-reliability optical module.
In accordance with an aspect of the present invention, there is provided an optical module comprising a substrate; an optical waveguide formed on said substrate and having a first end; an optical element mounted on said substrate so as to be optically coupled to said first end of said optical waveguide, for performing conversion between light and electricity; a transparent resin for covering at least an optical coupling portion between said optical waveguide and said optical element; and a thermoplastic resin for covering only said optical element and its periphery including said transparent resin to seal said optical element.
In accordance with another aspect of the present invention, there is provided an optical module comprising a substrate; an optical waveguide formed on said substrate and having a first end; an optical element mounted on said substrate so as to be optically coupled to said first end of said optical waveguide, for performing conversion between light and electricity; and an ultraviolet-curing resin for covering only said optical element and its periphery including an optical coupling portion between said optical waveguide and said optical element to seal said optical element.
In the optical module according to the present invention, only the optical element and its periphery are sealed with the resin, so that the residual stress in the resin can be reduced. Therefore, separation and cracking of the resin can be prevented to thereby ensure the cost reduction and reliability of the optical module.
In accordance with a further aspect of the present invention, there is provided a sealing method for an optical module including an optical waveguide formed on a substrate and having a first end, and an optical element mounted on said substrate so as to be optically coupled to said first end of said optical waveguide, for performing conversion between light and electricity, comprising the steps of applying a transparent resin to an optical coupling portion between said optical waveguide and said optical element; curing said transparent resin; applying a thermoplastic resin to only said optical element and its periphery; and curing said thermoplastic resin by cooling to thereby seal said optical element.
In accordance with a still further aspect of the present invention, there is provided a sealing method for an optical module including an optical waveguide formed on a substrate and having a first end, and an optical element mounted on said substrate so as to be optically coupled to said first end of said optical waveguide, for performing conversion between light and electricity, comprising the steps of applying an ultraviolet-curing resin to the entire surface of said substrate; laying a mask having an opening for exposing said optical element and its periphery over said substrate at a given height; directing ultraviolet radiation through said mask onto said ultraviolet-curing resin to thereby cure only a part of said ultraviolet-curing resin exposed to said opening; removing said mask; and removing the remaining uncured part of said ultraviolet-curing resin by using an organic solvent.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.
REFERENCES:
patent: 3911475 (1975-10-01), Szedon et al.
patent: 4001655 (1977-01-01), Voyles et al.
patent: 4717948 (1988-01-01), Sakai et al.
patent: 4758875 (1988-07-01), Fujisaki et al.
patent: 4803543 (1989-02-01), Inayoshi et al.
patent: 4948960 (1990-08-01), Simms et al.
patent: 5130780 (1992-07-01), Kumai et al.
patent: 5185835 (1993-02-01), Vial et al.
patent: 5825951 (1998-10-01), Kitamura
patent: 2207559 (1990-08-01), None
Fukushima Akira
Miura Kazunori
Nakagawa Goji
Nosaka Taizo
Tanaka Kazuhiro
Curtis Craig
Fujitsu Limited
Spyrou Cassandra
Staas & Halsey , LLP
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