Optical waveguides – With disengagable mechanical connector – Structure surrounding optical fiber-to-fiber connection
Reexamination Certificate
1999-09-24
2001-07-17
Epps, Georgia (Department: 2873)
Optical waveguides
With disengagable mechanical connector
Structure surrounding optical fiber-to-fiber connection
C385S076000, C385S078000, C385S094000
Reexamination Certificate
active
06261006
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of environmentally sealing fiber optic cable assemblies, and in particular to a method of sealing fiber optic cable assemblies from moisture by coating the prepared fiber terminations with a conformal coating before assembly to a coupler, connector, or backplane. The invention also relates to fiber optic cable assemblies in which the terminations have been environmentally sealed to protect the fiber from environmental degradation, and in particular to fiber optic cable assemblies having conformally coated fiber terminations.
2. Description of Related Art
It is well known that moisture can degrade the optical performance of fiber optic cable assemblies. In order to protect the fibers in a cable from moisture absorption, acrylate such as Corning's CPC6® and polyimide coatings are applied directly to the glass fibers to create a barrier to moisture.
While acrylate or polyimide coatings protect individual fibers during shipment and before preparation for termination, in order to terminate the fibers to a connector or alignment ferrule, the coating must be removed, leaving the fibers vulnerable to degradation due to moisture and other contaminants. The problem of fiber degradation due to exposure of the bare fibers following preparation for termination is especially significant in two situations: (1) following termination to an alignment ferrule but before installation, in an assembly plant or in the field, of the alignment ferrule in a fiber optic connector or coupler, and (2) in backplane terminations and other coupler assemblies where mechanical sealing is difficult and potting undesirable.
The first situation often arises because, during assembly of a fiber optic connector or housing, the fibers are often pre-terminated to alignment ferrules in one section of an assembly plant, and not installed in a sealed connector until later. Following termination to the ferrule, the terminated fibers must be stored until needed by the worker or section of the plant that assembles the fibers to the connectors or couplers. Storing and assembling the fiber optic connectors in clean rooms would be prohibitively expensive, and so the fibers are vulnerable during the period between termination to the ferrule and assembly to the connector or coupler, even where the connector or coupler in which the terminated fiber and ferrule is to be installed is adequately sealed.
It is also common for fibers to be pre-terminated to a ferrule and carried by workers for installation in the field, prior to which the portions of the fibers that have been exposed in preparation for termination are unprotected. Fiber optic terminations often require very high tolerances, and significant damage can occur during the interval between preparation of the cable for termination and the actual termination.
The second situation arises in applications, such as those involving optical backplanes of the type disclosed in U.S. patent application Ser. No. 09/006,193, field Jan. 12, 1998, now U.S. Pat. No. 5,980,312, herein incorporated by reference, where it is impractical to use mechanical sealing arrangements. While potting would solve the problem of degradation due to moisture, potting limits the flexibility of the fiber optic cables and makes it difficult to repair and replace individual cable assemblies, which is essential in backplane installations.
In view of the above, a need exists for a environmental sealing method and arrangement which can be used to seal a fiber optic termination immediately following termination of the fiber to an alignment ferrule or connector, thereby protecting the fiber even before it is installed in a sealed connector or coupling arrangement, and avoiding the need for potting in applications where the terminations would otherwise be completely unprotected.
SUMMARY OF THE INVENTION
It is accordingly a first objective of the invention to provide a method of protecting optical fibers after preparation of the fibers for termination and/or installation in an alignment ferrule, but before termination or installation in a sealed fiber optic connector or coupling arrangement.
It is a second objective of the invention to provide a method of protecting optical fibers for use in optical backplanes and other coupling arrangements in which the fibers would otherwise be unprotected or not adequately protected, and to eliminate the need for potting of the fibers or fiber terminations in order to protect them from environmental degradation.
It is a third objective of the invention to provide a method of environmental sealing fiber optic cable assemblies that does not require modification of the cable fiber termination procedure, and that can be carried out in a simple coating step.
It is a fourth objective of the invention to provide an environmental sealing arrangement for fiber optic cable assemblies that can be used to protect the cable assemblies prior to termination, that does not require mechanical seals, that eliminates the need for potting, and that can be carried out in a single coating step.
These objectives are achieved, in accordance with the principles of a preferred embodiment of the invention by providing a method of environmentally sealing fiber optic cable assemblies, and also an environmentally sealed fiber optic cable assembly, in which the fiber optic cable is terminated to the connector in a conventional fashion, polished and completed as would ordinarily be done, but in which the entire assembly or at least the termination/connector portion is coated with a conformal coating to provide an effective moisture barrier without restricting the flexibility of the cable.
In an especially preferred embodiment of the invention, the conformal coating is a MIL-I-46058 XY conformal coating, also known as Parylene.
In one application of the principles of the preferred embodiment, the conformal coating is applied to an alignment ferrule such as a Mechanical Transfer (MT) connector or ferrule following termination of a fiber to the ferrule and polishing, the conformal coating thereby protecting the polished connector/terminus interface from damage prior to installation in an MT coupler assembly. Because the mating face of the ferrule is polished before application of the coating, it can easily be peeled off from the mating face during coupling so that the conformal coating does not interfere with mating of the respective ferrules, or with transmission of light through the ends of the fibers.
Although the example of an MT ferrule is used to illustrate the principles of the invention, those skilled in the art will appreciate that the principles of the invention will be applicable to a wide variety of different fiber optic termination arrangements, and that the invention is not to be limited to any particular type of fiber optic connector, coupler, or terminus, but rather is intended to cover any fiber optic termination arrangement in which protection of the fibers or termination is necessary or desired.
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Amphenol Corporation
Blank Rome Comisky & McCauley LLP
Epps Georgia
Spector David N.
LandOfFree
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