Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1999-07-13
2001-01-30
Ngo, Hung N. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S083000, C385S094000
Reexamination Certificate
active
06181854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical module and a manufacturing method therefor.
2. Description of the Related Art
In recent years, the development of an optical access network has been actively carried out. For realization of the optical access network, reducing the cost of an optical device and/or an optical module is a very important subject. Further, in encapsulating an optical element for making conversion from light to electricity or conversion from electricity to light, a further cost reduction is necessary, and it is required to realize an optical module which can simply encapsulate the optical element and can ensure a sufficient reliability.
In many optical modules at present, a metal package or a ceramic package is used to ensure reliability, and the package is hermetically sealed by welding or soldering, so that the cost of each optical module becomes very high. It is therefore an important subject for the cost reduction of an optical module to simplify an encapsulation method for an optical element. As an example of a method of simply hermetically sealing an optical module, there has been proposed a method including the steps of applying a resin to the entire surface of a substrate on which an optical element is mounted, and next curing the resin to hermetically seal the optical element (Mitsuo Fukuda et al., “Plastic Packaging of Semiconductor Laser Diode”, Electronic Components and Conference, 1996, pp 1101-1108).
An optical module such as a light emitting module or a photodetecting module is required to be connected to an optical connector, so as to launch an optical signal to an optical fiber transmission line or to receive an optical signal from an optical fiber transmission line, and it is accordingly necessary to realize an optical module allowing the connection to the optical connector with a simple structure. However, in the case that a resin is applied to the entire surface of a substrate on which an optical element is mounted, and the resin is next cured to hermetically seal the optical element as described in the above literature, there is a possibility of separation of the resin from the substrate or generation of cracks or the like in the resin due to a difference in coefficient of linear expansion between the substrate and the resin. Furthermore, the substrate may be broken by a residual stress in the resin.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a low-cost, high-reliability optical module which can be easily connected to an optical fiber transmission line.
In accordance with an aspect of the present invention, there is provided an optical module comprising a plurality of leads; a substrate having a first groove and a plurality of conductor patterns electrically connected to the leads; a ferrule having a center hole in which an optical fiber is inserted and fixed, a first end, and a second end, the ferrule being mounted in the first groove of the substrate so that the first end projects from an end surface of the substrate; an optical element mounted on the substrate for making conversion between light and electricity; a first resin for covering at least the optical element and the second end of the ferrule, the first resin having transparency to the light; and a second resin for enclosing all of the leads, the substrate, the ferrule, the optical element, and the first resin except the first end of the ferrule and a part of each of the leads.
Preferably, the optical module further comprises a block having a second groove, the block being fixed to the substrate so that the second groove holds the ferrule. In this optical module, each of the first groove and the second groove preferably has a trapezoidal cross section.
In the optical module according to the present invention, an optical coupling portion between the optical element and the second end of the ferrule is covered with the transparent first resin, so that the optical fiber in the ferrule and the optical element can be optically coupled together through the transparent first resin, thus configuring the optical coupling portion without a space. All of the components except the first end of the ferrule and a part of each of the leads are enclosed by the second resin molded, thereby firmly fixing the ferrule to the substrate. Accordingly, it is possible to provide a receptacle type optical module having a sufficient strength against an external force applied to the optical module in connecting or disconnecting an optical connector with respect to the optical module while employing a resin sealed structure superior in productivity. Since the optical module according to the present invention is sealed with resin, greatly stable characteristics can be exhibited against environmental changes such as temperature changes or humidity changes.
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.
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Hakogi Hironao
Kojima Takashi
Miura Kazunori
Shimano Yoshio
Yamamoto Naoki
Fujitsu Limited
Ngo Hung N.
Staas & Halsey , LLP
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