Single mode optical fiber assembly using heat curable adhesive

Details Single mode optical fiber assembly using heat curable adhesive Single mode optical fiber assembly using heat curable adhesive

2001-04-11

2004-03-02

Prasad, Chandrika (Department: 2839)

Optical waveguides

With disengagable mechanical connector

Optical fiber to a nonfiber optical device connector

C385S080000

Reexamination Certificate

active

06698940

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method for assembling an optical assembly comprising parts requiring relatively precise positioning, and more specifically to a method for efficiently assembling an optical transceiver module used to receive and transmit optical signals.
2. Description of Related Art
In optical communication systems, it is very important of an optical assembly for receiving and transmitting optical signals, and converting electrical signals into corresponding optical signals, and vice verse in an optical transceiver module. The optical assembly comprises parts which need precise positional alignment. Thus the assembling is relatively difficult. Therefore, a variety of methods for assembling have been developed.
The optical assembly comprises a support member having a first junction surface, and a cap member having a second junction surface. One conventional way to make the assembly is to secure the cap member to the support member by applying a heat curable adhesive, such as heat curable epoxy, between the junction surfaces. To ensure proper alignment between the support member and the cap member, during the process of assembling, the cap member and the support member are held in an adjusting device with the first junction surface engaging the second junction surface. A positional adjustment is performed on the support member and/or the cap member to obtain the desired alignment. The heat curable adhesive is then applied to the junction surfaces.
The optical assembly is securely clamped by a clamping device, and then moved into a curing oven to cure the adhesive. The entire process is unduly complicated.
Furthermore, such a method is not suitable for single mode fiber transmission systems because the diameter of a single mode fiber is between 6 &mgr;m and 10 &mgr;m. A 0.5 &mgr;m relative displacement of assembled components may result in a poor transmission. While the clamped optical assembly is being moved into the curing oven, the assembly is vulnerable to impact or other unwanted force. This can result in relative displacement and thus poor alignment between components of the assembly. In addition, temperature gradient occurring during the curing process may cause non-uniform heating of the assembly. This can also result in displacement of components.
Another conventional method for assembling an optical assembly is disclosed in U.S. Pat. No. 4,969,702 (shown in FIG.
1
). The optical assembly comprises a laser diode (LD)
12
, a support member
14
, a lens
16
and a cap member
18
. The laser diode
12
is fixedly positioned in the support member
14
to generate light outputs at particular wavelengths. The lens
16
is positioned with respect to the laser diode
12
. The cap member
18
has a through hole
22
. An optical fiber
24
placed in a ferrule
26
is secured in the through hole
22
. An ultraviolet curable (UV) epoxy is applied between the cap member
18
and the support member
14
, with the optical fiber
24
in approximate alignment with the laser diode
12
and the lens
16
. Thus light outputs of the laser diode
12
are coupled to the optical fiber
24
through the lens
16
. The support member
14
and the cap member
18
are then placed in an adjusting device, for precise adjustment of the relative position of the cap member
18
and the support member
14
. The assembly is then exposed to UV light to cure the epoxy. At least one of the components must be transparent, to ensure proper exposure of the epoxy to the UV light. Furthermore, the adjusting device must have a sophisticated design to ensure such proper exposure. Thus the material of the components and the design of the adjusting device are both restricted.
Still another conventional method for assembling an optical assembly is disclosed in U.S. Pat. No. 5,073,047 (shown in FIG.
2
). The optical assembly comprises a light source
15
, a holder
19
, a housing
17
and a receptacle
1
. The light source
15
is fixedly positioned in the holder
19
. The holder
19
with the light source
15
therein and the housing
17
are solidly welded together by means of a laser beam
16
. The housing
17
and the receptacle
1
are solidly welded together by means of a laser beam
18
after positional alignment. The components solidly welded by the laser beams
16
,
18
must be made of metal, and a costly laser device must be used.
Yet another conventional method for assembling an optical assembly uses an instant glue in order to reduce costs. The method comprise the steps of placing a support member and a cap member in an adjusting device, operating the adjusting device to properly align the members, and applying an instant glue between the members. The instant glue solidifies quickly and joins the support member and the cap member together. However, the instant glue can solidify only when it contacts vapor. Since vapor concentration may vary from point to point in a three dimensional space, and since it is difficult to control vapor concentration, a non-uniform curing may occur. This can result in poor alignment between the two members.
In view of above-described drawbacks of the prior art, there is a great need to provide a method for efficiently and effectively assembling an optical assembly having parts requiring relatively precise orientations.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for efficiently and rapidly assembling an optical assembly having parts requiring relatively precise orientations.
In accordance with the present invention, a method for assembling an optical assembly comprising a base member having a first junction surface and a receptacle having a second junction surface is disclosed. The method comprises the steps of: providing a base member retaining a photoelectric component therein and having a first junction surface; providing a receptacle retaining an optical fiber therein and having a second junction surface; bringing the receptacle and the base member together so that the first and second junction surfaces engage each other; applying a heat curable adhesive between the junction surfaces; providing a heating device having a heat energy emitting part to surround the junction surfaces; and actuating the heating device to generate heat in the heat energy emitting part to heat and cure the heat curable adhesive, thereby securing the base member and the receptacle together. If desired, a cooling step may be performed after the heating step. The heating device may comprise an electric heating element, such as a resistance wire. Alternatively, the heating device may comprise piping for directing heated air streams toward the adhesive.


REFERENCES:
patent: 4969702 (1990-11-01), Anderson
patent: 5708741 (1998-01-01), DeVeau
patent: 5862303 (1999-01-01), Adar et al.
patent: 6496624 (2002-12-01), Hikita et al.
patent: 2002/0061723 (2002-05-01), Duescher

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