Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
1998-08-24
2001-03-20
Nguyen, Thong (Department: 2872)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S088000, C385S049000
Reexamination Certificate
active
06203212
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to fiber optic devices and more particularly to an optical subassembly for use in fiber optical systems.
DESCRIPTION OF THE RELATED ART
When manufacturing a fiber optic device for interconnecting optical fibers, it may be beneficial to fabricate a portion of the device as an optical subassembly, which can be tested as a separate unit. For example, the optical subassembly may include a semiconductor light source or photodetector, and other optical components. If the optical subassembly is a transmission type, a semiconductor light source will typically be included in the optical subassembly. On the other hand, if the optical subassembly is a reception type, the optical subassembly will include a photodetector.
One major type of optical subassembly utilizes a transistor outline (TO) can package containing a semiconductor light source or a photodetector. An optical subassembly utilizing a TO can package is described in U.S. Pat. No. 5,537,504 to Cina et al. The optical subassembly of Cina et al. includes a molded plastic housing having a TO can package attached to one end of the housing. Epoxy type adhesive is used to attach the housing to the TO can package. The optical subassembly of Cina et al. also includes a lens that is placed within the molded plastic housing between the TO can package and an optical fiber.
A concern with optical subassemblies utilizing a TO can package is that TO can packages are relatively expensive. In addition, TO can packages do not typically accommodate a high density of electrical inputs and outputs, and are not compatible with most commercially available high-speed semiconductor assembly equipment. Furthermore, TO cans are bulk and result in electrical parasitics (e.g. capacitance, resistance, inductance) that limit the high-speed performance of such packages.
Another major type of optical subassembly utilizes a submount, e.g., a micro-machined silicon micro-bench, to support an optoelectronic device and other optical components. The submount is typically a semiconductor substrate having a number of etched depressions for affixing the device and components onto the submount. U.S. Pat. No. 5,264,392 to Gaebe et al. describes an optical subassembly having a silicon-based submount. The submount supports a cylindrically-shaped graded-index (GRIN) lens, an optical isolator, an optoelectronic device, and a spherical lens.
A concern with optical subassemblies utilizing a submount is that, similar to the TO can type optical subassemblies, submounts are generally expensive. In addition, quality material for fabrication of the submounts is presently available from only a limited number of vendors.
While known optical subassemblies operate well for their intended purposes, improvements in performance and reduction in fabrication cost are desired. In particular, low cost package designs which permit the assembly of multiple optical sources or detectors in a small volume are needed.
SUMMARY OF THE INVENTION
An optical subassembly and a method of fabricating the same utilize a subassembly body that is formed by molding the subassembly body onto a substrate. Preferably, the subassembly body is formed of a polymeric material that can be molded into a precise shape directly onto the substrate. The subassembly body and the substrate become an integral unit when the molded polymeric material is polymerized.
In a first embodiment of the invention, the optical subassembly facilitates transmission or reception of light signals that are propagating exclusively in a single plane. The optical subassembly of the first embodiment includes an optical element, the subassembly body, the substrate, an optoelectronic device, and a transmitter or receiver integrated circuit (IC) chip. As stated above, the subassembly body and the substrate form an integral unit. The other components are attached to the integral unit. The optoelectronic device and the transmitter/receiver IC chip may be affixed to substrate, while the optical element is affixed to the molded subassembly body. Preferably, the substrate is a flexible circuit having a number of electrical traces. The flexible circuit may be composed of a polymer material. The optoelectronic device may be a light source and/or detector that is affixed to one side of the flexible circuit, while the transmitter/receiver IC chip is affixed to the opposite side. Alternatively, the transmitter/receiver IC chip may be affixed to the same side of the flexible circuit with respect to the light source and/or detector. The position of the transmitter/receiver IC chip on the flexible circuit is not critical to the invention. The optoelectronic device is positioned on the substrate such that the optoelectronic device is located within an opening in the subassembly body.
The optoelectronic device and the transmitter/receiver IC chip may be affixed to the substrate using a conductive epoxy, solder, or other comparable material. In addition, the optoelectronic device and the transmitter/receiver IC chip may be electrically connected to the substrate by wire connections or via flip chip contacts. Additional optoelectronic devices and their associated transmitter/receiver IC chips may be affixed to the substrate.
The optical element is preferably attached to the subassembly body. The rearward face of the optical element is positioned such that the opening of the subassembly body containing the optoelectronic device becomes an enclosed cavity that encapsulates the optoelectronic device. The optical element may be one or more lenses or other optics designed to provide an efficient coupling of optical fibers to the optoelectronic device. The optical element may incorporate mechanical stand-offs to ensure that proper spacing is maintained between the optical fibers and the optical element when a fiber optic ribbon cable is attached to the optical subassembly.
A second embodiment of the invention includes the same components of the optical subassembly as the first embodiment of the invention, but with a different configuration of the optical element, the subassembly body, and the substrate. The configuration of the optical subassembly in accordance with the second embodiment is primarily designed to accommodate light signals that are emitted or received in a first direction by the optoelectronic device. However, the light signals are transmitted to or received from optical fibers in a direction that is perpendicular to the first direction. This is rendered possible by an optical element which provides a 90 degree optical turn for light signals in order to redirect horizontally propagating light signals from the optical fibers into a vertical direction, or direct vertically propagating lights signals from the optoelectronic device into a horizontal direction. The optical element may include optical guiding veins or channels to change the propagating direction of lights signals.
To facilitate the change in the propagating direction of light signals, the subassembly body is configured such that the optical element is attached to the forward face of the subassembly body, while the substrate is located at the bottom of the subassembly body. The optoelectronic device is affixed to the substrate to receive or emit light signals in a vertical direction. In the second embodiment, the optoelectronic device and the transmitter/receiver IC chip are affixed to the same side of the substrate. However, the location of the transmitter/receiver IC chip on the substrate is not critical to the invention. Similar to the first embodiment, additional optoelectronic devices and their associated transmitter/receiver IC chips may be affixed to the substrate to couple more optical fibers.
A method of fabricating an optical subassembly in accordance with the invention initially involves a step in which a substrate having electrical traces is provided. The substrate can be provided in a panel form to fabricate a number of the optical subassemblies in a parallel fabrication manner. Preferably, the substrate is a flexible circuit containi
Giboney Kirk S.
Rosenberg Paul K.
Yuen Albert T.
Agilent Technologie,s Inc.
Nguyen Thong
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