Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
2002-06-11
2004-07-06
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S098000
Reexamination Certificate
active
06758609
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to optoelectronic and fiber optic components and, more particularly, to methods of joining optically coupled optoelectronic and fiber optic components.
BACKGROUND OF THE INVENTION
Optoelectronic and fiber optic components (collectively referred to hereinafter as “optoelectronic components”) convert electrical signals to visible or infrared radiation and/or vice-versa and/or serve as a waveguide for visible or infrared radiation. Examples of optoelectronic components include optical fibers, light guides, fiber optic connectors, fiber arrays, dense wavelength division multiplexers (DWDM), arrayed wave guides (AWG), couplers, lenses, gratings, filters, tunable lasers, vertical cavity surface emitting lasers (VCSEL), transmitters, receivers, transceivers, switches, modulators, routers, cross-connects, optomechanical switches, electro-optical switches, wavelength converters, repeaters, regenerators, optical amplifiers, optical sensors, photocells, solar cells, optoisolators, LEDs (light-emitting diodes), laser diodes, etc. Optoelectronic devices play an increasingly important role in many areas including telecommunications, photovoltaic power supplies, monitoring and control circuits, computer storage, optical fiber communications, medical devices, etc.
It is generally considered critical that optoelectronic components be assembled with high precision to assure proper optical alignment (referred to as optical “coupling”). In order to effectively couple optical signals between optical fibers and/or between optical fibers and other optical components, a fiber optic connector must maintain the precise alignment of the individual optical fibers in a predetermined manner such that the optical fibers will remain aligned as the fiber optic connector is mated with another fiber optic connector or with other types of optical devices. Conventional assembly techniques for joining optical fibers and/or components utilize a curable adhesive (e.g., epoxy) to attach optical fibers to a substrate.
The primary role of adhesives is to enable assembling complex shapes of similar or dissimilar materials. Of equal importance is the reliability of the joint/bond enabled by the adhesive chemistry. Adhesive selection is based on various criteria including the ability to provide a reliable joint over the life expectancy of the optoelectronic product and the ability to sustain environmental exposure during the operational life of the optoelectronic product. Some of the key adhesive properties guiding adhesive selection include: coefficient of thermal expansion, glass transition temperature, fracture toughness, modulus, moisture up-take, adhesive strength, cure shrinkage, viscosity and optical properties.
There are two main categories of adhesives used in optoelectronic packaging: reactive systems (referred to hereinafter as “thermal cure adhesives”) and photo-polymerizing systems (referred to hereinafter as “UV-curable adhesives”). Both types of adhesives require curing. Thermal cure adhesives require heat and UV-curable adhesives require a combination of ultraviolet (UV) radiation and heat. However, the properties of these two types of adhesives are different. Thermal cure adhesives are typically more stable post-cure than UV-curable adhesives and typically result in less moisture pick-up and better mechanical properties. Unfortunately, thermal cure adhesives may require a long cure time. In contrast, UV-curable adhesives cure much faster than thermal cure adhesives. Accordingly, UV-curable adhesives are often the preferred choice for rapid assembling of optoelectronic components. In operation, optoelectronic components are joined to create an assembly, an adhesive is applied to an interface between the components, and then the components are aligned and exposed to UV radiation to partially cure the adhesive prior to moving the assembly to a thermal cure station for completion of the cure.
A limitation of UV-curable adhesives is that line of sight is required for UV radiation to reach an adhesive to be cured in order to trigger the photo-initiators responsible for cure. Unfortunately, special design configurations of optoelectronic component assemblies may obstruct light paths, thereby creating a shadow at an interface. The shadowing effect may result in poor curing of the adhesive.
To align optoelectronic components being assembled, a light source (e.g., a laser) transmits light through the optoelectronic components being assembled and a photodetector measures the amount of light passing therethrough. The positions of the optoelectronic components are incrementally adjusted relative to each other (typically via mechanical nano-positioner devices) until the light transmitted therethrough reaches a maximum (i.e., when exact alignment is achieved), at which time, the optoelectronic components are “tacked” together in the aligned position by partially curing an adhesive at the interface (or joint) of the optoelectronic components. This partial curing is conventionally performed by irradiating the adhesive resin with UV radiation or with heat in the case of thermal cure adhesives such as epoxies.
Since the curing of thermal adhesives can cause movement of optoelectronic components relative to each other, alignment of optoelectronic components must be maintained during the curing process. Unfortunately, conventional adhesive resins may take a relatively long period of time to fully cure, which may increase the likelihood that misalignment will occur. In addition, UV-curable adhesive resins may absorb moisture that may cause deterioration of the adhesive and lead to loss of component alignment during subsequent use of the optoelectronic device. Also, conventional adhesive resin curing techniques may produce residual stresses in bonds between optoelectronic components that may cause undesirable creep and misalignment between adhesively joined optoelectronic components.
With the ever-increasing demand for optoelectronic components, there is a need for rapid, cost-effective methods of aligning and joining optoelectronic components for both in-situ and post curing processes. Furthermore, an adhesive curing method/technology that combines both in-situ and post curing is needed.
SUMMARY OF THE INVENTION
In view of the above discussion, both in-situ and post-cure methods of joining optoelectronic components such that they are optically coupled are provided. Methods according to the present invention may be utilized to join various types of optoelectronic components (e.g., optical fibers in adjacent end-to-end relationship, optical fibers to the active regions of various optoelectronic components, etc.)
An in-situ method of joining optoelectronic components according to an embodiment of the present invention includes positioning optoelectronic components in adjacent relationship such that light signals can pass therebetween, applying a curable resin having adhesive properties to an interface of the optoelectronic components, passing light signals between the optoelectronic components, aligning the optoelectronic components relative to each other such that the signal strength of light signals passing between the optoelectronic components is substantially maximized, and irradiating the interface with electromagnetic radiation to rapidly cure the resin such that the aligned optoelectronic components are fixedly joined. Irradiating the interface with electromagnetic radiation may include irradiating with non-ionizing radiation in the Radio Frequency (RF) and microwave regimes, according to embodiments of the present invention. Electromagnetic radiation can be applied using various applicators according to embodiments of the present invention, including fixed frequency, single mode microwave applicators, RF stray field applicators, capacitive heating applicators, and a variable frequency microwave (VFM) applicators. Moreover, microwave energy and RF energy can be used interchangeably.
Microwave applicators according to embodiments of the present invention may de
Ahmad Iftikhar
Fathi Zakaryae
Garard Richard S.
Geisler William L.
Wander Joseph M.
Knauss Scott A
Lambda Technologies
Myers Bigel & Sibley & Sajovec
Sanghavi Hemang
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