Optical waveguides – Optical fiber bundle
Reexamination Certificate
1999-08-16
2001-06-05
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Optical fiber bundle
C385S116000, C385S120000
Reexamination Certificate
active
06243520
ABSTRACT:
BACKGROUND
The fabrication of fused and flexible optical fiber bundles for the purpose of transmitting electromagnetic signals from a signal-receiving end to a signal-emitting end of the optical fiber bundle is an evolving technology.
Optical fiber bundles arranged in one and two-dimensional arrays of signal transmitting optical fibers can be used as “optical fiber interconnects” to connect one and two-dimensional arrays of electromagnetic signal sources (e.g., photodiode arrays) and detectors in order to eliminate data transmission bottlenecks that arise in advanced digital systems communicating over short distances, for example. The practical implementation and usefulness of optical fibers as “optical fiber interconnects” requires optimum alignment of the optical fibers at at least one of the signal-receiving and signal-emitting ends of the fibers within an optical fiber bundle. Precision alignment of the optical fiber ends into an array at at least one common end of an optical fiber bundle is important in order to achieve efficiency in signal reception by, and transmission through, the optical fibers in the optical fiber bundle. An important measure of precision is how far the position of the axial center of any given fiber deviates from its ideal position. That is, how precisely are the desired distances between the axial center of a particular fiber maintained with respect to the axial centers of its neighboring fibers in an array (i.e., “center-to-center spacing”). The problem may also be expressed in terms of how closely the positions of the axial centers of the fibers approximate their objective, ideal lattice positions. Despite extensive, industry-wide research and development efforts, precision alignment of optical fiber ends, for these and other applications, has proved to be a vexing and elusive obstacle.
In some cases, fixtures have been used in an attempt to achieve precisely aligned arrays of optical fiber ends. Specifically, individual fibers have been adhered to array blocks or other fixtures where they are held in place with epoxy, for example. Some versions of this technique have called for individual fibers to be feed through individual holes in an array block and then fixed in place with epoxy or placed and adhered in channels created by micromachining or lithography, for example. The effectiveness and the degree of precision achievable by such techniques standing alone are limited by the precision with which the channels can be formed and spaced and by the precision with which the optical fibers can be placed and set therein.
Representative of recent attempts to achieve precise two dimensional arrays of optical fibers is a method for aligning optical fibers described by C. V. Cryan in a paper entitled “Two-dimensional multimode fibre array for optical interconnects,”
Electronics Letters
, Vol. 34 No. 6, Mar. 19, 1998, p. 586. In the method described by Cryan, each optical fiber within the array is fabricated using the rod in tube method, as is known in the art. The fiber preform comprises a central core rod, a concentric inner cladding tube over the central core rod and a concentric outer cladding tube that fits over the inner cladding tube. Each fiber preform is then drawn into fused fiber rods using industry-standard equipment and methods. The diameter and cross-section of each fiber rod is carefully monitored and controlled during the drawing stage.
The resulting fused fiber rods are then aligned into a lattice configuration to form a modified array preform. According to Cryan, reasonably precise alignment of the fiber rods is possible due to their large diameter and flexural rigidity. The array preform is then drawn, fused and segmented to yield a multiplicity of array rods. During the draw stage of the array preform, the concentric outer glass tubes of the individual fiber rods within the array fuse with those of their neighboring rods thereby filling interstitial gaps within the array. The end faces of the array rods are polished perpendicular to the optical fiber rod axes to produce a straight, rigid optical fiber array. If desired, the rigid array can then be shaped in a heated former to produce a rigid data conduit.
Cryan further teaches that, when the outer concentric cladding tube of each optical fiber is an acid soluble glass, a flexible array can be fabricated by removing the acid soluble glass around each fiber along the length of the array rods, while a fused section is preserved at each end. As is known in the art, selective glass removal may be achieved by masking the ends of the array with an acid resistant coating and then leaching the array in a dilute acid solution to remove the unmasked glass between the ends.
Ultimately, Cryan's method involves the heating and drawing of bundled optical fibers to create a fused optical fiber bundle. As a matter of general observation, variability in the heating and drawing process renders very precise fiber alignment at the array face extremely difficult to achieve with regularity. Specifically, observation and experimentation indicate that the deviation from an ideal array is usually caused more by the relative positions of the optical fibers then by imperfections, inconsistencies or deviations in the fiber diameters and geometries themselves. This is because, during the heating and drawing process, the claddings of the constituent fibers in the bundle become very soft and molten-like allowing the fiber core to drift from its ideal lattice position.
For the foregoing reasons, there is a need for a reliable method and apparatus in which optical fibers are precisely aligned in an array.
SUMMARY
The present invention is directed to a method and apparatus which, in some versions thereof, may be applied to the problem of aligning the ends of optical fibers at a common end of an optical fiber bundle into a precise array so that the optical fiber bundle is suitable for use as an optical fiber interconnect.
In one embodiment, an optical fiber bundle having an aligned first end fiber array with features of the present invention includes a plurality of optical fibers each of which has a first end and a second end, a fiber core with an axial fiber center and a concentric cladding around the fiber core that extends between the first and second ends. The optical fiber bundle has at least a first common end proximate to which the optical fibers are secured in place by a first array fixture. The optical fibers are secured by the first array fixture such that a fiber segment adjacent the first end of each optical fiber protrudes from the first array fixture. The axial fiber centers, at the first ends of selected sets of optical fibers, are maintained in predetermined positions with respect to one another by a plurality of precision microspacers installed between the fiber segments and secured in contacting engagement therewith. More specifically, each fiber segment of a selected plurality of fiber segments belongs to at least one microspacer neighborhood wherein each microspacer neighborhood comprises at least two fiber segments secured in contacting engagement with a precision microspacer installed between the at least two fiber segments such that the axial fiber centers at the first ends of the at least two fiber segments are maintained in predetermined array positions with respect to one another.
The optical fiber bundle itself may be of various forms. One such form is to have an optical fiber bundle with a first end fiber array from which the constituent optical fibers extend and terminate at their second ends in no particular configuration and at various locations. In another form, the optical fibers may be aligned in one fiber array at their first ends and in another fiber array at their second ends. In such cases, the fiber arrays at opposite ends of the optical fibers in the optical fiber bundle may or may not be of similar configuration and, furthermore, may or may not form a coherent bundle. In another alternative form, the optical fibers having their first ends in the first end fiber array may de
Franco Louis J.
Palmer Phan T. H.
Schott Fiber Optics Inc.
LandOfFree
Optical fiber bundle having an aligned optical fiber array... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical fiber bundle having an aligned optical fiber array..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical fiber bundle having an aligned optical fiber array... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2495979