Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1999-02-18
2001-04-10
Spyrou, Cassandra (Department: 2872)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S091000, C385S094000
Reexamination Certificate
active
06213650
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bonding method of optical members which are positioned with high accuracy; and, in particular, to a bonding method applicable to producing an optical module employed in optical communications. The optical module contains a semiconductor device such as a light-receiving device or a light-emitting device and provides a configuration for optically coupling an optical fiber and the semiconductor device to each other with high accuracy.
2. Related Background Art
A conventional optical module in which an optical fiber acting as a transmission medium for signal light and a semiconductor device such as a light-receiving device or light-emitting device are optically coupled to each other. Such modules employ a structure for maintaining the optically coupled state between the optical fiber and the semiconductor device by integrally encapsulating a condenser lens and a plane reflecting surface, which are disposed in the optical path between an end face of the optical fiber and the semiconductor device. The conventional optical module, for example, Japanese Patent Application Laid-Open No. 63-090866 discloses an optical receiver module configured such that light emitted from an end face of an optical fiber and passed through a condenser lens is reflected by a plane reflecting surface to be incident on the light-receiving surface of a light-receiving device.
SUMMARY OF THE INVENTION
Having studied conventional methods of making an optical module, the inventors have found the following problems. In the conventional methods, a condenser lens and a plane reflecting mirror are integrally encapsulated with a transparent resin together with a semiconductor device. It is necessary to establish optical axis alignment between the condenser lens, the plane reflecting mirror and semiconductor device, and encapsulate them with a resin after the position of the semiconductor device is set with a sufficiently high accuracy. However, it has been quite difficult to improve the positioning accuracy of such a semiconductor device, and prevent the position from shifting during the encapsulation. The conventional methods have been unsuitable for making an optical module employed in the field of optical communications.
Although the conventional optical module is applicable to fields which do not require a relatively high accuracy, e.g., a field which allows a relatively broad luminous flux incident on a light-receiving device having a large light-receiving area, it can not be used for a field in which a very high aligning accuracy is required such as optical communications. This is because the core diameter of the optical fiber is only about a few &mgr;m and the light-receiving area of the light-receiving device is only about several hundred square &mgr;m. When an optical module for optical communications is manufactured by employing a conventional technique, there is a possibility that detrimental effects such as the lowering of the optical coupling efficiency between the optical fiber and the semiconductor device will occur.
In recent years, as the transmission speed in optical fiber communications has been reaching a GHz band, there has been a demand for developing an optical module which can attain a higher aligning accuracy. If the position of the plane reflecting mirror or the like shifts at the resin encapsulation (at the member-fixing step) after the alignment, then even the aligning accuracy that was once attained may deteriorate.
In order to overcome such problems, it is an object of the present invention to provide a bonding method which is applicable to fields in which positions between members with high accuracy is required. For example, when applied to making an optical module having a configuration in which alignment can be adjusted much more easily than conventional methods and making it possible to reduce the number of its components, the bonding method according to the present invention effectively prevents the optical coupling efficiency of the once-adjusted members from deteriorating.
The optical module fabricated by the method according to the present invention comprises: a housing having a mounting surface for mounting a semiconductor device; a sleeve, extending along a predetermined direction from a side wall of the housing, for supporting a ferrule attached to a front end of an optical fiber; and an optical reflecting member having a curved reflecting surface, which is put in the housing, for optically coupling the optical fiber and the semiconductor device to each other. In this method, in particular, the optical reflecting member having a reflecting surface with a predetermined form for optically coupling the semiconductor device and the optical fiber to each other is fixed at a predetermined position in the housing.
The semiconductor device encompasses, at least, a light-emitting device and a light-receiving device. The optical module encompasses an optical transmitter module in which a light-emitting device is mounted, while the light-emitting surface of the light-emitting device and the end face of an optical fiber are optically coupled to each other; and an optical receiver module in which a light-receiving device is mounted, while the light-receiving surface of the light-receiving device and the end face of an optical fiber are optically coupled to each other.
In particular, the reflecting surface of the optical reflecting member preferably has a concave surface form coinciding with a portion of a virtually defined rotational ellipsoid. In order to attain a high aligning accuracy, the optical reflecting member having such a specific form is installed at a predetermined position in the housing such that the end face of the optical fiber coincides with the first focal point of the rotational ellipsoid, whereas the main surface of the semiconductor device (the light-emitting surface in the light-emitting device or the light-receiving surface in the light-receiving device) coincides with the second focal point of the rotational ellipsoid.
In the optical receiver module, even if a signal luminous flux is emitted from the end face of the optical fiber with an angle, it will be reflected by a certain portion of the reflecting surface and reach the light-receiving surface of the light-receiving device as long as the light exit end face coincides with the first focal point. On the other hand, in the case of the optical transmitter module, the light emitted from the light-emitting surface of the light-emitting device with an angle also reaches the end face of the optical fiber due to the action of the reflecting surface mentioned above.
When making an optical module provided with a configuration mentioned above, the most important point is the positional deviation of the optical reflecting member. In particular, the optical reflecting member is installed at a predetermined position in the housing such that the end face of the optical fiber opposing the reflecting surface coincides with the first focal point of the rotational ellipsoid, whereas the main surface of the semiconductor device (e.g., the light-receiving surface in the light-receiving device) opposing the reflecting surface coincides with the second focal point of the rotational ellipsoid. If the optical reflecting member positionally shifts after such an aligning operation, there will be a possibility of insufficient alignment accuracy.
The method of making an optical module according to the present invention comprises the steps of installing the optical reflecting member at a given position on the mounting surface in the housing with an adhesive and preventing the optical reflecting member from positionally shifting by using a holding member such as a magnet generating a magnetic force against the housing. Specifically, the holding member is provided with a protrusion adapted to engage a depression formed in the upper face of the optical reflecting member. When the holding member is attached to the housing, the protrusion engages the depre
Kumagai Seiji
Moriyama Yutaka
Sawada Sosaku
Smith Gambrell & Russell
Spyrou Cassandra
Sumitomo Electric Industries Ltd.
Treas Jared
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