Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
2000-10-27
2002-11-12
Patel, Tulsidas (Department: 2839)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
C385S092000, C385S094000
Reexamination Certificate
active
06478477
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a planar packaged optical module, and in particular a planar packaged optical module which reciprocally or unilaterally converts electrical signals and optical signals.
2. Description of the Related Art
A planar packaged optical module is an electronic part which reciprocally or unilaterally converts electrical signals and optical signals, and is principally used in key equipment for optical communications. Such a planar packaged optical module generally has a structure like the one illustrated in
FIGS. 4 and 5A
.
That is, a planar packaged optical module generally has a housing
50
formed of epoxy resin or the like with a lid (in
FIG. 5A
, the lid is indicated with a broken line
62
), an Si substrate
52
provided within the housing
50
, a semiconductor laser device
54
(hereinafter referred to as an LD) provided on the Si substrate
52
, a ferrule
56
which is adhered by an adhesive to the housing in a state in which the ferrule
56
is passed through the housing
50
, and an optical fiber
58
which is adhesively retained within the ferrule
56
and is adhered to the Si substrate
52
in a state in which the optical fiber
58
is disposed so that one end surface of the optical fiber
58
opposes an active layer of the LD
54
.
The Si substrate
52
is provided with an optical fiber mounting portion
52
a
and an LD mounting portion
52
b
which are separated by a separation groove
52
c
. A V-groove for mounting the optical fiber is formed on the optical fiber mounting portion
52
a
along a direction perpendicular to the separation groove
52
c
. The LD
54
which converts electrical signals inputted from the outside into optical signals is fixedly provided on the LD mounting portion
52
b.
The optical fiber
58
is disposed at a position such that one end surface of the optical fiber
58
precisely opposes the active layer of the LD
54
. The optical fiber
58
is retained within the ferrule
56
at a notch portion of the housing
50
. Within the housing
50
, in a state in which a glass plate
60
which prevents the optical fiber
58
from rising up out of the V-groove is provided, the contact surface of the optical fiber
58
is adhesively fixed in the V-groove (not illustrated), which is provided on the optical fiber mounting portion
52
a
, by an adhesive
67
of UV hardenability or the like. The end surface of the optical fiber
58
which opposes the active layer of the LD
54
is stress-ruptured to a mirror-finished surface, while the other end surface of the optical fiber
58
is polished to a convex spherical surface.
The ferrule
56
which retains the optical fiber
58
at a notch portion of the housing
50
is structured to be substantially cylindrical. The ferrule
56
adhesively retains at the inner peripheral surface thereof the optical fiber
58
with an adhesive, while the outer peripheral surface of the ferrule
56
is fixed to the housing
50
with an adhesive. The adhesive which fixes the ferrule
56
to the housing
50
and the adhesive which fixes the optical fiber
58
to the inside of the ferrule
56
are epoxy resin adhesives which have a glass-transition temperature Tg of about 125° C.
In the planar packaged optical module of the structure described above, lead portions
72
are placed on electrodes
82
of a distribution substrate
80
with solder balls
84
interposed between the lead portions
72
and the electrodes
82
, as illustrated in FIG.
6
A. Thereafter, the electrodes
82
of the distribution substrate
80
and the lead portions
72
are electrically bonded by leaving them for about thirty seconds in a high-temperature environment at 240° C., as illustrated in FIG.
6
B.
In the planar packaged optical module of the structure described above, the housing and the ferrule, and the ferrule and the optical fiber are respectively adhered to one another with an adhesive made of a resin, and the glass-transition temperature Tg of these adhesives is of a range of from about 100° C. to about 125° C.
When the electrodes
82
of the distribution substrate
80
are bonded with the lead portions
72
by solder balls or the like in a high-temperature environment at 240° C. for a bonding time of thirty seconds, the adhesive which binds the housing and the ferrule and the adhesive which binds the ferrule and the optical fiber undergo glass-transition and harden once they have softened at almost the same time.
Because the adhesive which binds the housing and the ferrule and the adhesive which binds the ferrule and the optical fiber are fixed once they have softened at virtually the same time, sometimes the optical fiber slips out of position in the direction in which it is drawn into the housing at the time the adhesives have softened, as illustrated in FIG.
5
B.
When such positional displacement occurs, the output variance from the optical fiber ends up exceeding 1 dB and noise increases. Therefore, there has been the drawback in that bonding by a reflow soldering which uses solder balls or the like is difficult.
SUMMARY OF THE INVENTION
In order to overcome such drawbacks, an object of the present invention is to provide a planar packaged optical module in which shifting of an optical fiber and a ferrule from their design positions and positional displacement of the optical fiber within the ferrule resulting from a movement of the optical fiber therein can be prevented, and which is suitable for reflow soldering.
In order to achieve this object, the invention according to the first aspect is a planar packaged optical module which includes a conversion device provided on a substrate within a housing and when supplied with one of an electric signal and an optical signal substantially converts one into the other; an optical fiber retained by a retaining member adhered to the housing and fixed on the substrate such that an end surface of the optical fiber opposes the conversion device; a first adhesive which adheres the housing and the retaining member to one another, the first adhesive substantially formed of a resin having a predetermined glass-transition temperature; and a second adhesive which adheres the retaining member and the optical fiber to one another, the second adhesive substantially formed of a resin having a glass-transition temperature greater than that of the first adhesive.
In the invention according to the first aspect, the glass-transition temperature of the second adhesive, which adheres the retaining member and the optical fiber to one another, is higher than the glass-transition temperature of the first adhesive, which adheres the housing and the retaining member to one another. Therefore, the time at which the adhesive between the housing and the retaining member softens and hardens and the time at which the adhesive between the retaining member and the optical fiber softens and hardens are staggered. In particular, the second adhesive which adheres the retaining member and the optical fiber to one another softens and hardens after the first adhesive which adheres the housing and the retaining member to one another softens and hardens.
Accordingly, displacement of the optical fiber due to movements of the optical fiber within the retaining member in an environment having a temperature higher than the glass-transition temperature of the adhesives at the time of reflow soldering and the like can be prevented, and the planar packaged optical module becomes suitable for reflow soldering.
It is preferable that the adhesives are thermoplastic resin adhesives. It is further preferable that the thermoplastic resin adhesives are epoxy resin adhesives.
As described above, according to the first aspect of the invention, effects can be obtained in that shifting of the retaining member from its design position in a high-temperature environment at the time of reflow soldering, and positional displacement of the optical fiber caused by a movement of the retaining member, can be prevented.
For this reason, because the planar packaged receptacle optical
Oki Electric Industry Co,. LTD
Patel Tulsidas
Prasad Chandrika
Rabin & Berdo PC
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