Optical waveguides – With optical coupler – With alignment device
Reexamination Certificate
2000-11-29
2002-12-10
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With optical coupler
With alignment device
C385S033000, C385S039000, C385S091000
Reexamination Certificate
active
06493489
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fiber-optic systems for telecommunication and data-communication applications. More specifically, it relates to a novel type of coupling modules for interconnecting fiber-optic components.
BACKGROUND OF THE INVENTION
The explosive growth of Internet traffic has imposed an unprecedented demand on the existing communications backbone-fiber-optic networks. As the demand for ever greater bandwidth grows, a particular challenge to fiber-optic equipment makers is to increase the bandwidth capacity of fiber-optic transceivers without increasing their overall physical dimensions, so that the users of the fiber-optic transceivers can attain higher bandwidth without increasing the sizes of their network switch boxes.
A crucial step in achieving greater bandwidth capacity while shrinking the package size lies in a simple and reliable way of coupling light between optoelectronic devices (e.g., lasers, light-emitting diodes, and photo-detectors) and optical fibers. This is a difficult task in a system where one or more optical fibers are brought into the proximity of optoelectronic devices by a fiber connector, for the fiber connector is typically aligned using passive alignment means which requires high precision and stringent tolerance. The task becomes more formidable when a fiber ribbon-connector is used to bring a plurality of optical fibers to an array of optoelectronic devices in a parallel fashion.
An effective way of coupling optical fibers in a fiber connector to their corresponding optoelectronic devices is to use an optical coupler that is embedded with optical lenses. The use of lenses to couple light has additional advantages of increasing the working distance and easing the mechanical tolerance imposed on the assembled components. This way of optical coupling, however, requires an accurate and reliable alignment amongst optical fibers in the fiber connector, optical lenses in the coupler, and optoelectronic devices that is to be maintained over a wide range of operating temperatures. In addition, such an optical coupler should be simple in assembly, therefore more reliable in alignment and lower in cost.
Furthermore, as the bandwidth increases, fiber-optic transceivers run at increasingly faster speeds. Accordingly, the manufacturing process for the fiber-optic transceivers has evolved from using electrical pins by way of wave solder processing to Ball Grid Array (BGA) by way of reflow processing. The latter is a surface mount technology. Given that the reflow processing typically occurs at a temperature around 220° C., the optical coupling devices along with other optical components in a high-speed fiber-optic transceiver must be able to withstand this high-temperature treatment, while maintaining their integrity and performance.
Various devices for the interconnections of optical fibers and for the coupling of optical fibers to optoelectronic components have been devised in the art. For instance, U.S. Pat. Nos. 5,574,814, 5,671,311, and 5,781,682 disclose several optical couplers. No optical lenses, however, are incorporated in these prior art coupling devices. Although optical lenses are implemented in an optical coupler disclosed by U.S. Pat. Nos. 5,002,357, the assembly housing of this coupler also contains a fiber connector and an electronic light pulse communication device among other things, thus making it bulky and less modular.
Depicted in
FIG. 1
is another prior art optical coupler that incorporates optical lenses. Optical coupler
100
comprises a transparent plastic plate
11
molded with a plurality of plastic lenses
12
. Since optical coupler
100
is entirely made of transparent plastic, it will not be able to withstand the high-temperature reflow processing for BGA described above, thus rendering it not applicable to high-bandwidth fiber-optic transceivers. Moreover, given that optical coupler
100
is not equipped with any alignment features, it would be difficult to optically align optical coupler
100
with other optical elements in an accurate and secure fashion.
As fiber-optic systems rapidly grow in modern communications networks, there exists a need for simple, effective, modular, versatile, and low-cost optical coupling devices for high-bandwidth fiber-optic transceivers.
SUMMARY
The aforementioned need in the art is provided by a coupling module for coupling light between two optical devices, such as an optical fiber connector and an optoelectronic device. In one embodiment of the present invention, a coupling module of the present invention comprises an alignment plate, one or more beam-shaping elements, and one or more alignment elements. The beam-shaping elements are embedded in one or more precision slots on the alignment plate, typically by way of press-fitting, such that their respective positions are secured within the alignment plate. The alignment elements, typically in the form of alignment pins and holes, are produced on the alignment plate in such a way that they effectively become an integral part of the alignment plate. The positions of the alignment elements are so chosen that they correspond to the alignment features on peripheral devices, such as a fiber connector and an optoelectronic device. The precision slots and alignment elements can be created in a single manufacturing process, thereby enabling the beam-shaping elements and alignment elements to be aligned in a simple, precise and secure way. Moreover, the relative physical arrangement between the beam-shaping elements and the alignment elements are configured such that once the alignment elements are engaged with the peripheral devices, accurate optical alignment between the peripheral devices and the coupling module is also attained. A coupling module thus constructed maintains a precise optical alignment that is less susceptible to change with temperature variations (e.g., during the high-temperature treatment described above) and other extraneous effects.
In an alternative embodiment of the present invention, the beam-shaping elements are embedded into the precision slots at an elevated temperature, whereby the precision slots expand and/or the alignment plate softens to allow the beam-shaping elements to be press-fit with relative ease. The use of a soft metal like copper for the alignment plate facilitates the press-fitting process. Subsequent cooling to a normal operating temperature then causes the beam-shaping elements to be compressed in their respective positions within the alignment plate. In the coupling module thus constructed, the beam-shaping elements are more firmly embedded in the alignment plate during the normal operation, thereby rendering a more enduring optical alignment.
In another embodiment of the present invention, the alignment plate is made to contain one or more “plungers”, comprising one or more foreign materials. The plungers are configured such that one or more gaps form between the embedded plungers and the remaining of the alignment plate, thereby providing one or more precision slots. The incorporation of the plungers in an alignment plate renders a variety of utilities and advantages. For instance, it is easier to create the precision slots by way of embedding the plungers in the alignment plate than having the precision slots directly machined out of the alignment plate, for a combined (and hence larger) area occupied by a plunger and the corresponding precision slot can be readily produced by way of stamping, or other suitable techniques. The plungers can also be of “thermal” type, namely, they are made of materials whose coefficients of thermal expansion are markedly different from that of the alignment plate. In this case, the alignment plate with the embedded “thermal plungers” are heated (or cooled) to an elevated (or lower) temperature, such that the precision slots expand to allow the beam-shaping elements to be press-fit into the precision slots with relative ease. Subsequently cooling (or warming) to a normal operating temperature causes the beam-shaping elemen
Babic Dubravko
Mertz Pierre H.
Alvesta Corporation
Rojas Omar
Sanghavi Hemang
Townsend and Townsend and Crew
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