Patent Application
20150192739
Multicore optical fiber has many positive attributes, chiefly due to the separation of the cores fern the fiber's neutral axis. This property enables the fiber to be used for differential strain measurements (typically using fiber Bragg gratings) in free space or while attached to a sub-structure. Became cores opposite of the neutral, axis experience tension and compression, the resultant strain vector reveals information about the bending amplitude and orientation.
Despite the potential advantages of multicore fiber, there are numerous drawbacks to using this type of fiber for optical devices. The first drawback is this fiber's availability. Few manufacturers produce molts core fiber, and those that do, either produce a single design or are unwilling to draw limited quantities of specialty fiber, furthermore, because most newly designed fibers require multiple iterations between the end user and the manufacturer, the process can become cost-prohibitive. The second drawback is that connecting to the fiber is challenging and often unreliable. Because the fiber has multiple cores, each core most be addressed to obtain the measurement signal This is commonly achieved by using a fiber fan-out, a custom fiber optic switch, or tapering the fiber and splicing to a conventional single mode fiber. These methods typically have high insertion losses and limit the operating performance of the sensor. The third drawback is that inscribing the sensors within the fiber is difficult and can lead to reproducibility issues. Depending on the geometry, peripheral cores or internal structure within the fiber can also obscure distal cores during the exposure procedure, making it necessary to perform multiple exposures, shadow certain cores from exposure, or index match the exposure.
To address these limitations. Applicant conceived a novel solution involving a bundling of several single mode optical fibers in a geometry reminiscent of a multicore fiber. Applicants solution involved use of commercially available single mode fibers that are stacked and attached along their tangential contact points. The resultant multi-fiber bundle (“MFB”) provides a mechanically sound, multicore optical structure with individual fiber pigtails available for connectorization. Additionally, because the process cars be highly localized or implemented at low temperatures according to an embodiment of the invention, the MFB can be fabricated with optical fibers containing fiber Bragg gratings (“FBGs”) or other optical structures that would anneal or otherwise be destroyed upon heating.
An embodiment of the invention includes a method of manufacturing a multi-fiber bundle. The multi-fiber bundle includes a multi-fiber bundle neutral axis. The multi-fiber bundle includes at least three optical fibers. The at least three optical fibers includes respective optical, fiber neutral axes. The at least three optical fibers are registered such that at least a portion of the multi-fiber bundle neutral axis remains at a constant distance from at least a portion of the respective optical fiber neutral axes. The at least three optical fibers are coated with an optical fiber coating material lire at least three coated optical fibers are cured.
Another embodiment includes a method of manufacturing a multi-fiber bundle. The multi-fiber bundle includes a multi-fiber bundle neutral axis. The multi-fiber bundle includes at least three optical fibers. The at least three optical fibers includes respective optical fiber neutral axes. The at least three optical fibers includes scams. The scams include tangential locations of the at least three optical fibers. The at least three optical fibers are registered such that at least a portion of the multi-fiber bundle neutral axis remains at a constant distance from at least a portico of the respective optical fiber neutral axes. The seams of the at least three optical fibers are fused.
Applicant has determined that the utilization of an MFB in place of a multicore fiber, in accordance to one or more embodiments of the instant invention, has several advantages. First, because a single mode fiber, for example, is used to form the MFB, the amount of available optical fiber is significantly increased. There are numerous fiber manufacturers capable of making excellent single mode fiber and at a reduced cost when compared to a multicore fiber counterpart. Using single mode fiber also enables the capability of bundling fibers with vastly different core parameters and host materials (generally not achievable with multicore fiber). Second, by bundling individual fibers, the connectivity issue becomes nonexistent. Because each fiber end is free, connecting to the MFB is achieved by splicing to the individual fibers. Fusing the fibers or using silica coatings also provides thermal and mechanical robustness to the MFB. Since the host material is same, thermal uniformity across the bundle prevents non-uniform strain transfer. Lastly, the fibers can be modified prior to bundling to facilitate the incorporation of complicated structures within the fiber. This allows the fibers to be individually treated before they are integrated into a MFB. Some examples might include writing FBG arrays into the fibers (e.g., via “strip and re-coat” or in-line with a draw tower) or writing microstructures into the fibers using ultrafast laser processing. Because standard writing and processing techniques are already employed, the added complication of rotational alignment (as with conventional multicore fiber) is not necessary and greatly simplifies the manufacturing of optical devices.
An embodiment of the invention includes a method of manufacturing a multi-fiber bundle 10, for example, as described by way of illustration in
Optionally, the at least three optical fibers 30, 32, 34 include at least one of a standard single mode optical fiber, a standard multi-mode optical fiber, a standard gradient index optical fiber, a standard microstructured optical fiber, and a standard photonic crystal optical fiber. The at least three optical fibers include respective standard in-fiber refractive index structures, the respective in-fiber refractive index structures including at least one of a standard fiber Bragg grating, a standard long period grating, a standard super-structure grating, a standard tilted, grating, and a standard constant index change region.
Optionally, registering the at least three optical fibers includes cold-drawing the at least three optical fibers through a standard aligning die 40, such as shown by way of illustration in
Alternatively, registering the at least three optical fibers 30, 32, 34 includes mounting the at least three optical fibers on a standard fiber mount 60, such as shown by way of illustration in
Optionally, a standard coating cup 110 is provided, for example as shown by way of illustration in
Optionally, coating the at least three optical fibers with an optical fiber coating material includes passing the at least three cold-drawn optical fibers through a coating cup to generate coated optical fibers 36, such as shown by way of illustration in
Optionally, the optical fiber coating material 150 comprises ultra-violet-curable epoxy, acrylate, and sol-gel. For example, the sol-gel includes aerogel, xerogel, or freeze-dried sol-gel.
Optionally, coring the at least three coated optical fibers comprises employing a standard curing station 170 including a standard heat source, such as shown by way of illustration in
Another embodiment includes a method of manufacturing a multi-fiber bundle 10. The multi-fiber bundle includes a multi-fiber bundle neutral axis. The multi-fiber bundle includes at least three standard optical fibers. The at least three optical fibers includes respective optical fiber neutral axes. The at least three optical fibers includes seams. The seams include tangential locations of the at least three optical fibers. The at least three optical fibers are registered such that at least a portion of the multi-fiber bundle neutral axis remains at a constant distance from at least a portion of the respective optical fiber neutral axes. The seams of the at least three optical fibers are fused.
Optionally, the at least three optical fibers include of a standard single mode optical fiber, a standard multi-mode optical fiber, a standard, gradient index optical fiber, a standard microstructered optical fiber, and/or a standard photonic crystal optical fiber. The at least three optical fibers include respective, standard in-fiber gratings. The respective, in-fiber gratings include a standard fiber Bragg grating, a standard long period grating, a standard super-structure grating, sad/or a standard tilted grating.
Optionally, registering the at least three optical fibers 30, 32, 34 comprises cold-drawing the at least three optical fibers through a standard aligning die, such as discussed above. Alternatively, registering the at least three optical fibers 30, 32, 34 includes mounting the at least three optical fibers on a standard fiber mount, such as discussed above.
Optionally, fusing the seams of the at least three optical fibers comprises laser welding the seams using at least one standard CO2 laser and/or a standard ultrafast laser. Optionally, fusing the seams of the at least three optical fibers comprises laser welding tire seams using a standard fixed laser, a standard scanning or rastering laser. One of ordinary skill in the art will readily appreciate that either the laser(s) must move, or the optical fibers must move, depending on the application. For example, one of ordinary skill in the art will recognize that multiple, fixed, standard lasers 250, 252, 254 can be used to fuse directly multiple scams of optical fibers moving past the lasers, such as shown by way of illustration in
Optionally, the at least three optical fibers include at least three metalized optical fibers. Optionally, the at least three moralized optical fibers are metalized with titanium and gold. For example, titanium is advantageously used as an adhesion layer for gold.
Optionally, the optical, fibers arc attached to, or held by, separated fiber mount wail blocks 300,302, 304,306. For example, standard solder 310 is positioned between the separated, fiber mount wall blocks 300, 302, 304, 306, as shown by way of illustration in
Optionally, the optical fibers are prepped for soldering by a standard brash 320 applying standard flux onto the optical fibers held, for example, by the fiber mount 60, such as shown by way of illustration in
Optionally, fusing the seams of the at least three optical fibers includes using a standard solder, such as shown by way of illustration in
It should be appreciated that various embodiments of the present invention may
be implemented as a sequence of computer-implemented acts or program modules running on a computing system and/or as interconnected machine logic circuits or circuit modules within the computing system. The implementation is a matter of choice dependent on the performance requirements of the computing system implementing the invention. Accordingly, logical operations including related algorithms can be referred to variously as operations, structural devices, acts or modules. It will be recognized, by one skilled in the art that these operations, structural devices, acts and modules may be implemented in software, firmware, special purpose digital logic, and any combination thereof without deviating from the spirit and scope of the present invention as described herein.
Although a particular feature of the disclosure may have been illustrated and/or described with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Also, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in the detailed description and/or in the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”.
This written description sets forth the best mode of the invention and provides
examples to describe the invention and to enable a person of ordinary skill in the art to make and use the invention. This written description does not limit the invention to the precise terms set forth. Thus, while the invention has been described in detail with reference to the examples set forth above, those of ordinary skill in the art may effect alterations, modifications and variations to the examples without departing from the scope of the invention.
These and other implementations are within the scope of the following claims.
This application claims priority to U.S. Provisional Patent Application Ser. No. 61/924,269, entitled “FABRICATION OF MULTI-FIBER OPTICAL SENSOR/” to Miller, which was filed on 7 Jan. 2014 and is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61924269 | Jan 2014 | US |
