Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1999-06-28
2001-06-19
Ngo, Hung N. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S024000, C385S034000
Reexamination Certificate
active
06249625
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is related to optical fibers and their manufacturing methods and, in particular, to optical fiber subassemblies in which a plurality of separate optical fibers are joined together.
A standard optical fiber has a relatively simple structure with a central core and a surrounding cladding. The core has one index of refraction and the cladding has a different index of refraction (typically less than the core index of refraction). The core and cladding have constant diameters along the length of the fiber. Depending upon the diameter of the core, the optical fiber can be a single mode fiber or a multimode fiber.
Variations from the standard optical fiber include fibers with multiple cores in which two or three parallel cores of constant diameters are enclosed by the surrounding cladding. As in the case of standard optical fibers, such multiple core fibers are manufactured with preforms and drawing techniques. Examples of such fibers include the polarization-maintaining optical fiber with its characteristic “mouse ears” cross-section. Another variation from the standard optical fiber is the thermally expanded core optical fiber in which the single core of the fiber is gradually enlarged in a taper. Such fibers are often used as light receptors because of the larger cross-sectional area of the core.
Recently optical devices have been developed in which two or more optical fibers are held in a sleeve. Light is transmitted (and received) through the end facets of the optical fibers. Such optical devices include WDM (Wavelength Division Multiplexing) couplers, add/drop multiplexers, tunable filters, optical switches, and so forth. See, for example, Nonetheless, it remains desirable to lower the manufacturing costs and reliability of these optical devices. For some purposes, the thermally expanded core optical fibers may be used since the larger cores increase manufacturing tolerances. However, such fibers are relatively expensive.
Hence there is a continued need for improvements in the manufacture of fiberoptic devices. The present invention provides for such an improvement for many fiberoptic devices.
SUMMARY OF THE INVENTION
The present invention provides for a joined optical fiber subassembly comprising first, second and third sections. The first section has a plurality of separate optical fibers with each optical fiber having a core and cladding, which encloses the core of the optical fiber. The second section, which adjoins the first section, has the optical fibers joined so that a single cladding encloses the cores of the optical fibers. The diameter of the single cladding in this section decreases in a taper away from the first section and the diameter of each core of the optical fibers increases in a taper away from said first section. The third section, which adjoins the second section, has the single cladding enclosing the cores of the optical fibers and having a constant diameter. The cores of the optical fibers in this section also have constant diameters.
With the joined optical fiber subassembly as a constituent element, the present invention also provides for a subunit which can be used in many fiberoptic devices. The subunit has a sleeve with a central longitudinal channel and an end face. The channel holds the third section of the joined optical fiber subassembly and the end facets of the cores of the optical fibers are co-planar with the sleeve end face. The subunit also has a quarter-pitch GRIN lens which has an end face proximate the sleeve end face. By arranging the location of the core end facets with respect to the optical axis of the GRIN lens, the paths of the light to and from the cores of the third section through the GRIN lens can be adjusted according to the requirements of the fiberoptic device.
REFERENCES:
patent: 4355863 (1982-10-01), Aulich et al.
patent: 5067792 (1991-11-01), Lloyd
patent: 5555330 (1996-09-01), Pan et al.
patent: 5742712 (1998-04-01), Pan et al.
patent: 5764830 (1998-06-01), Pan et al.
E-Tek Dynamics, Inc.
Ngo Hung N.
Townsend and Townsend / and Crew LLP
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