Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1998-03-13
2001-04-24
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S088000, C385S092000
Reexamination Certificate
active
06222967
ABSTRACT:
This application is based on patent application Ser. No. 58,876/1997 filed Mar. 13, 1997, Ser. No. 198,083/1997 filed Jul. 24, 1997 and No. 27,558/1998 filed Feb. 9, 1998 in Japan, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a packaging platform capable of accurately and easily connecting one or more optical fibers to one or more optical components having functions, such as optical detection, optical signal branching, optical multiplexing, optical switching and optical modulation; and an optical module comprising one or more optical components and such one or more packaging platforms.
2. Description of the Prior Art
In an optical component using a planar optical waveguide circuit, connection between an optical waveguide and an optical fiber requires alignment precision of the order of microns. Simplifying this connection is very important in reducing the manufacturing cost. An optical component which processes fast signals involves fine electrical wiring, and thus requires a fan-out structure for electrical connection. An optical device generally needs sealing to achieve reliability. In an optical module having structures for a fiber pigtail and electrical wiring, it is necessary to seal large capacity regions above these structures. This has caused problems relating to packaging capacity and sealing effect.
Some structures of conventional optical modules are described below.
CONVENTIONAL EXAMPLE 1
“Self-aligned flip-chip assembly of photonic devices with electrical and optical connections”, M. J. Wale, et al., IEEE Trans. Comp., Hybrids, Manufac. Technol., Vol. 13, No. 4 (1990)
FIG. 1
is a conventional example of a packaging structure which provides an optical connection between an optical waveguide and an optical fiber. This example realizes a structure in which an optical fiber
2
is fixed onto a V-shaped groove of an Si substrate
3
and connected to an optical waveguide
1
a
of an optical component
1
. The optical waveguide
1
and the V-grooved substrate
3
are automatically aligned by the surface tension of solder bonds
3
-
31
. The optical fiber
2
can thus be accurately positioned by a V-groove
3
a
. Since the positions of the optical fiber
2
and the optical waveguide
1
need to be determined accurately, however, packaging becomes laborious. According to this example, automatic alignment by the solder
3
-
31
is employed. To make the effect of surface tension during soldering work, optimization of the reflow conditions is required.
CONVENTIONAL EXAMPLE 2
“High impedance, high frequency crosstalk characteristics of a photodiode array and subcarriers”, Kondo et al., 1994 Spring Conference of the Institute of Electronics, Information and Communications Engineers of Japan, ref. C-297
FIG. 2
shows a conventional example of packaging an optical component having an electrode. An active optical component is frequently used in high speed optical transmission. Thus, electrical wirings, etc. should be integrated. To package such a component as a module, a lead for taking out the electrode for connection to the outside should be formed. According to this example, an arrayed 4-channel optical device (photodiode)
1
-
3
is mounted on an optical component
1
. From there, electrodes
1
-
4
for bonding are extended, and then bonding wires
101
, chip resistors
102
, and the bonding wires
101
are further provided, followed by lead wires
3
-
30
of a package (packaging platform)
3
. As noted from this, packaging of an optical component with integrated parts requires an electrode withdrawal structure and wire bonding.
CONVENTIONAL EXAMPLE 3
“A study of automatic assembly of a non-adjustment packaging module”, Nakagawa G. et al., 1995 Electronics Society Conference lecture papers of the Institute of Electronics, Information and Communications Engineers of Japan, ref. C-187
FIG. 3
shows a conventional example of a hermetically sealed optical module. An optical device (laser diode)
1
-
3
forms an optical component
1
attached onto an Si substrate. On a package
3
as a packaging platform, there are mounted an electric cable
3
-
40
for electric signal transmission and an optical fiber
2
. The optical fiber
2
is fixed onto the Si substrate by a cover
5
. After these steps, a sealing cover
3
-
50
is hermetically applied such that the entire optical component
1
is sealed, thereby providing a structure for a completely hermetic state. Such hermetic sealing requires a special container, making the packaging volume large. In addition, the use of the electric cable for electric signal transmission tends to lengthen the transmission distance. The resulting structure makes it difficult to accommodate a high frequency signal because is of electric characteristics. As long as such a sealing form is employed, the more complicated the electrical wirings become, the larger the packaging volume and the worse the deterioration of signals will be.
As seen in the above conventional examples, packaging of an optical component required the optical axis alignment of the optical waveguide and the optical fiber, and the structure for taking out an electrode from a fine electrode. Moreover, strict sealing was required, thereby imposing a severe burden on packaging.
In an optical module using a planar optical waveguide circuit, as described above, connection between the optical waveguide and an optical fiber has so far required a high accuracy aligning apparatus or an advanced packaging technique for performing precision positioning, even when a fiber guide structure is used.
Another example is the production of an optical switch utilizing a thermooptic effect, or an optical module having an active portion on an optical waveguide circuit, such as a hybrid optical module having an optical semiconductor device packaged on an optical waveguide substrate. This production has posed the problem of electrical connection as well as the above-mentioned optical fiber connection. That is, wire bonding is needed to connect the electrical wiring portion of the optical waveguide circuit to another part such as a package. In handling a fast signal by use of the characteristics of an optical signal, in particular, a high density electrical wiring is required of the optical module. Needs also exist to eliminate the routing of the electrical wiring or provide a microstructure to an electrical pad or the like. The step of electrical connection, such as bonding the wiring onto a miniscule electrode pattern, is also complicated.
The above hybrid optical module has further required sealing of the surroundings of the optical semiconductor device, and needed for this purpose is the step of mounting a sealing cover. This method has caused problems such as an increased volume of the optical module, or an adverse influence on electrical signals due to an increased electrical wiring length associated with the increased volume.
The conventional way of packaging an optical waveguide circuit module, as described above, has required many steps such as an electrical connecting step and a sealing step as well as an optical fiber connecting step. Also, precise alignment has been required.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a packaging platform which can simplify all packaging steps including electrical connection and sealing as well as optical connection in connecting one or more optical components to one or more optical fibers and can improve the dimensional accuracy of alignment, an optical module comprising the packaging platform, and methods for producing the packaging platform and the optical module.
In one aspect, the present invention is directed to a packaging platform for achieving optical coupling between one or more optical waveguides of an optical component having the optical waveguides and one or more optical fibers; the packaging platform including a reference structure portion for performing the horizontal and vertical positioning of the optical component, and
Amano Michiyuki
Hashimoto Toshikazu
Hikita Makoto
Imamura Saburo
Kato Kuniharu
Bovernick Rodney
Frank Robert J.
Kim Ellen E.
Nippon Telegraph and Telephone Corporation
Venable
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