Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
1998-10-09
2001-12-18
Font, Frank G. (Department: 2877)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
C385S084000, C385S147000, C522S095000
Reexamination Certificate
active
06331080
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an adhesive composition for bonding an optical fiber to a suitable housing using light, in the visible and near-infrared ranges of the spectrum, to cure the adhesive. A colorant included in the adhesive composition provides evidence that the space between the optical fiber and the housing is filled prior to curing. The colorant further signals the point at which exposure to a light source is sufficient to cure the adhesive and bond the optical fiber within the housing.
2. Description of the Prior Art
Successful use of optical fiber cables for carrying, e.g. telecommunication signals depends upon maintaining axial alignment of the fiber along the length of the cable even though it may be subject to junctions held together by suitable connector or termination structures. Correct positioning of the optical fiber, within the connector or termination structure, represents a critical requirement for maintaining maximum signal transmission across a junction of precisely aligned fibers. Precise alignment relies upon the retention of a fixed spatial relationship between the fiber and the connector structure. When accurately established, correct spatial relationship ensures desirable fiber-to-fiber alignment during junction formation using interlocking connector or termination structures which may be subject to repeated engagement and disengagement. A convenient means to establish the correct spatial relationship between an optical fiber and a connector involves the use of a bonding material, usually an adhesive, for securing the fiber to an inner surface of the connector structure.
There are many examples of the use of adhesives, of various kinds, for bonding optical fibers inside connector structures. U.S. Pat. No. 4,588,256 discloses the use of hot melt adhesive, contained in an optical fiber mounting means, inside a connector. Upon heating of the optical fiber mounting means, the hot melt adhesive softens, allowing insertion of the optical fiber which becomes bonded to the mounting means when the adhesive cools and solidifies. Similarly, U.S. Pat. Nos. 4,984,865 and 5,048,915 employ thermoplastic adhesives for bonding an optical fiber within a connector structure. In both cases, a small amount of molten adhesive exudes from the tip of the connector under the force of insertion of the optical fiber into the heated thermoplastic adhesive. Upon cooling, a small drop of adhesive surrounds the glass fiber, at the tip of the connector. This drop formation, while suggesting that adhesive surrounds the optical fiber, does not provide confirmation that adhesive fills the connector. Such filling of the connector, to place adhesive in the space between the optical fiber and the inner wall of the connector, provides the optimum condition for securely bonding the fiber to the connector. Less than optimum bonding could lead to disruption in the position of the fiber relative to the connector with resultant loss of alignment between fibers present in connectors used to join lengths of optical cable together.
A means to indicate optimum bonding between optical fibers and connecting structures would be advantageous towards providing reliable optical fiber connections. Suitable indicating means would confirm bond formation capable of surviving forces associated with shock or extension of a connection. The current invention provides a means of indicating optimum bond formation using an colored adhesive composition, which, during bonding of the optical fiber inside a fiber connector structure, shows uniform coloring when the adhesive fills the space between the fiber and the connector in a first color. The adhesive is subject to curing by exposure to visible light, and as it cures, the first color changes to a second color at the initiation of cure.
Further, such adhesive should be of a viscosity small enough such that it is injectable, however, large enough, such that when injected it will remain in the desired area of the connector and not migrate to other areas.
SUMMARY OF THE INVENTION
The invention provides an adhesive which bonds an optical fiber to a fiber housing in an optical fiber connector. The adhesive contains a colorant to show that the space between the optical fiber and the housing is filled prior to curing the adhesive with light of wavelengths found in the visible and near-infrared ranges of the spectrum. As the adhesive cures the colorant further signals the point of sufficient exposure to light to bond the optical fiber within the housing.
More specifically, the invention provides an adhesive distribution and cure indicating composition for an optical fiber connection or termination, comprising: an adhesive having a viscosity from about 200 centipoise to about 5000 centipoise, a colorant, which is soluble in the adhesive to show how the adhesive distributes inside the connection or termination, the colorant having a first color before exposure to radiation of from about 400 to about 100 nanometers, but preferably from about 400 to about 700 nanometers, and a second color after such exposure, and an initiator system to cure the adhesive composition by exposure to such radiation, the composition preferably having a cure onset up to about 60 seconds with formation of the second color, more preferably up to about 30 seconds.
Preferably the adhesive component comprises at least one acrylate monomer. The adhesive is curable by light of wavelengths from about 400 to about 1100 nanometers, preferably from about 400 to about 700 nanometers, more preferably from about 400 to about 600 nanometers, which includes a portion of the blue and green area of the spectrum, most preferably between about 500 and about 600 nanometers. The adhesive composition cures and the colorant changes color in less than about 30 seconds, preferably less than about 25 seconds, most preferably less than about 15 seconds. The adhesive bonds strongly to the optical fiber and housing of the optical fiber connector.
The invention also provides a method for bonding an optical fiber to a connector.
As used herein, these terms have the following meanings.
1. The term “visible light” means electromagnetic radiation having wavelengths between about 400 nm and about 700 nm.
2. The term “near-infrared”, abbreviated “nIR”, means electromagnetic radiation having wavelengths between about 700 nm and about 1000 nm.
3. The term “holder” generally refers to the portion of an optical connector designed to secure an optical fiber inside the connector or termination.
4. The term “connector” means an article for aligning a first optical fiber with a second optical fiber by establishing contact between fiber ends and thereafter including a holding means to retain fiber end contact and fiber alignment.
5. The terms “connection” and “termination” mean the point at which the end of a first optical fiber is held in contact with the end of a second optical fiber. The terms “connector”, “connection”, and termination are used interchangeably.
6. The term “(meth)acrylate” includes both the acrylate and the methacrylate.
7. The terms “epoxy” and “epoxide” mean an organic resin having at least one oxirane ring which is polymerizable by ring opening.
8. The term “epoxy acrylate” means a material containing both an epoxide functionality and an acrylate functionality in the same molecule, or a blend containing both acrylte and epoxy functionality in separate molecules.
9. The terms “colorant” and “color component” are synonymous and mean a compound which has a visible color.
As used herein, all parts, percents, and ratios are by weight, unless specifically stated otherwise.
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patent: 3773706 (1973-11-01), Dunn
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patent: 4588256 (198
Cole Brian M.
Dower William V.
Oxman Joel D.
3M Innovative Properties Company
Fonseca Darla P.
Font Frank G.
Lee Andrew H.
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