MONOLITHIC MULTI-OPTICAL-WAVEGUIDE PENETRATOR OR CONNECTOR

Abstract

Methods and apparatus are provided for a monolithic multi-optical-waveguide penetrator or connector. One example apparatus generally includes a plurality of large diameter optical waveguides, each having a core and a cladding, and a body having a plurality of bores with the optical waveguides disposed therein, wherein at least a portion of the cladding of each of the optical waveguides is fused with the body, such that the apparatus is a monolithic structure. Such an apparatus provides for a cost- and space-efficient technique for feedthrough of multiple optical waveguides. Also, the body may have a large outer diameter which can be shaped into features of interest, such as connection alignment or feedthrough sealing features.

Claims

1. An apparatus for transmitting light along multiple pathways, comprising: a plurality of large diameter optical waveguides, each having a core and a cladding, wherein the apparatus is a monolithic structure; and a body having a plurality of bores with the optical waveguides disposed therein, wherein at least part of the cladding of each of the optical waveguides is fused with the body to form the monolithic structure and wherein the body comprises at least one orientation feature.

2. The apparatus of claim 1, wherein the at least one orientation feature comprises at least one flat surface formed in an outer diameter of the body and parallel to an axis of the body.

3. The apparatus of claim 1, wherein the body has at least two different outer diameters.

4. The apparatus of claim 3, wherein the body comprises a sealing surface between the at least two different outer diameters.

5. The apparatus of claim 4, wherein the sealing surface comprises a convex frustoconical section between the at least two different outer diameters.

6. The apparatus of claim 1, wherein a temperature coefficient of the cladding of each of the optical waveguides is about the same as a temperature coefficient of the body.

7. The apparatus of claim 1, wherein the body and the core and cladding of each of the optical waveguides comprise silica glass.

8. The apparatus of claim 1, wherein the body is a cylindrical capillary tube.

9. The apparatus of claim 1, wherein an outer diameter of the cladding of the large diameter optical waveguides is at least 1 mm.

10. An optical waveguide feedthrough assembly comprising the apparatus of claim 1, the optical waveguide feedthrough assembly further comprising: a housing, wherein the apparatus is at least partially disposed in the housing; and one or more annular sealing elements disposed between an inner surface of the housing and an outer surface of the apparatus.

11. The assembly of claim 10, wherein the annular sealing elements comprise at least one of v-ring seals, o-ring seals, or gasket members.

12. The assembly of claim 10, wherein the housing comprises metal and wherein the body and the core and cladding of each of the optical waveguides comprise silica glass.

13. The assembly of claim 10, wherein the housing comprises a cylindrical tube.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0024] FIG. 1 illustrates a cross-sectional view of a prior art optical waveguide feedthrough assembly.

[0025] FIG. 2 is a diagram conceptually illustrating a monolithic multi-waveguide structure, according to an embodiment of the present invention.

[0026] FIG. 3 is a diagram conceptually illustrating a monolithic multi-waveguide structure with a collapsed region and a larger outer diameter region, according to an embodiment of the present invention.

[0027] FIG. 4 is a diagram conceptually illustrating a monolithic multi-waveguide structure disposed in a housing with annulus seals disposed therebetween, according to an embodiment of the present invention.

[0028] FIG. 5 is a diagram conceptually illustrating two monolithic multi-waveguide connectors with locating features, according to an embodiment of the present invention.

[0029] FIG. 6 is a diagram conceptually illustrating splicing of optical fibers to a monolithic multi-waveguide structure, according to an embodiment of the present invention.

[0030] FIGS. 7 and 8 are flow diagrams illustrating example operations for forming a monolithic structure for transmitting light along multiple pathways.

DETAILED DESCRIPTION

[0031] As described above, current approaches to optical waveguide feedthroughs use glass to metal seals constructed from drawn cane. These approaches are limited to around 5 mm outer diameters without specialized equipment and thus are not capable of spreading out stress loads. The approaches are non-monolithic or limited to single waveguides, thus involving multiple duplicates to accommodate multiple waveguides. Similarly, the components are limited to single waveguide connections, or connections built up from single waveguide approaches.

[0032] Accordingly, what is needed are techniques and apparatus to reduce glass stress when sealing multiple fiber optic components against high pressure and to achieve high temperature multi-waveguide fiber optic cable fluid block and connectorization with low loss.

[0033] Embodiments of the present invention provide techniques and apparatus for a robust, reliable, high pressure optical waveguide feedthrough (penetrator) or connector that utilizes a monolithic glass structure. In one embodiment, the apparatus includes a plurality of large diameter optical waveguides, each having a core and a cladding, and a body having a plurality of bores with the optical waveguides disposed therein, wherein at least part of the cladding of each of the optical waveguides is fused with the body, such that the apparatus is a monolithic structure. In another embodiment, the apparatus includes a plurality of large diameter optical waveguides, each having a core and a cladding, wherein at least part of the cladding of each of the optical waveguides is fused with the cladding of another one of the optical waveguides, such that the apparatus is a monolithic structure.

[0034] Although the reduced stress and other benefits provided by such monolithic structures are also applicable to a single (large diameter) optical waveguide fused into a larger capillary, only monolithic structures supporting multiple optical waveguides are described in detail below. From this description, the ideas disclosed herein can be adapted to a capillary tube having only a single bore for supporting one optical waveguide.

[0035] As used herein, optical fiber, glass plug, and the more general term optical waveguide refer to any of a number of different devices that are currently known or may later become known for transmitting optical signals along a desired pathway. For example, each of these terms can refer to single mode, multi-mode, birefringent, polarization-maintaining, polarizing, multi-core or multi-cladding optical waveguides, or flat or planar waveguides. The optical waveguides may be made of any glass (e.g., silica, phosphate glass, or other glasses), of glass and plastic, or solely of plastic. For high temperature applications, optical waveguides composed of a glass material are desirable. Furthermore, any of the optical waveguides can be partially or completely coated with a gettering agent and/or a blocking agent (such as gold) to provide a hydrogen barrier that protects the waveguide.

[0036] An Example Monolithic Multi-Optical-Waveguide Penetrator

[0037] FIG. 2 conceptually illustrates a monolithic structure 200 with multiple optical waveguides fused with multiple bores of a capillary tube 202. Embodiments of the present invention, such as the monolithic structure 200, may be used in place of the optical waveguide element 14 of FIG. 1. As shown, the monolithic structure 200 includes a capillary tube 202 and a plurality of large-diameter optical waveguides 204, each waveguide having a core and a cladding. Before fusing, the capillary tube 202 had a plurality of bores running through the length of the capillary tube 202. Although four bores are shown in FIG. 2 as an example, the tube 202 may include more or less than four bores, which may depend on the number of optical waveguides desired for a particular application. The plurality of optical waveguides 204 are inserted into the bores. As used herein, a large-diameter optical waveguide (also known as a cane waveguide) generally refers to an optical waveguide having an outer diameter (of the cladding) which is greater than or equal to 1 mm (and preferably at least 3 mm). The capillary tube 202 has a larger outer diameter than the outer diameter of the large-diameter optical waveguides 204.

[0038] After insertion of the waveguide 204, the capillary tube 202 is subjected to heat in one or more selected regions to fuse the capillary tube 202 and the optical waveguides 204 (at least within the collapsed region(s)). Typically performed with vacuum assist, this fusing collapses the bores of the capillary tube 202 around the cladding of the optical waveguides 204 to form a single monolithic structure. The monolithic structure 200 is able to conduct light energy through multiple paths and effectively increases the outer diameter of the plurality of optical waveguides 204.

[0039] In some embodiments, the capillary tube 202 and/or the core and cladding of each optical waveguide 204 are composed of silica glass, such as quartz. In some embodiments, the optical waveguides 204 may be 1 mm quartz cane waveguides for 1550 nm light. For some embodiments, the cladding of each optical waveguide 204 and capillary tube 202 have about the same temperature coefficient.

[0040] The capillary tube 202 may be a cylinder or have any of various other suitable shapes. The capillary tube 202 may be made of quartz formed by drawing or drilling (e.g., multibore tubing offered by Friedrich & Dimmock, Inc. of Milleville, N.J.). The capillary tube 202 may be shaped by grinding, machining, or other means to form any feature of interest.

[0041] According to one embodiment, the capillary tube 202 may be shaped to form geometries important to sealing and stress reduction. For example, FIG. 3 illustrates another monolithic structure 300, similar to the monolithic structure 200 of FIG. 2, where the capillary tube 202 includes a collapsed region 306 (wherein fusing of the bores and optical waveguides 204 has occurred) and a shaped sealing region 308. In the embodiment shown in FIG. 3, the sealing region 308 has a convex frustoconical shape. The tapered ends of the convex frustoconical shaped sealing region 308 form sealing surfaces that are large compared to the outer diameter of the optical waveguides 204 and the collapsed region 306. In this manner, when the monolithic structure 300 is disposed in a wellhead feedthrough assembly, for example, downhole pressure may be distributed on the monolithic structure 300 in a desired manner, with a surface reacting force acting on the sealing surface furthest away from the collapsed region.

[0042] In some embodiments, as shown in FIG. 4, the monolithic structure 200 may further include one or more annulus seals 410 (e.g., Accuseal, offered by Weatherford International with headquarters in Houston, Tex.) around the capillary tube 202 in collapsed region 306. The annulus seals 410 may be any of various suitable sealing elements, such as v-ring seals, chevron seals, o-ring seals, gasket seals, etc. The annulus seals 410 see internal pressure within a metal housing 412 corresponding to the outer diameter of the annulus seals 410. The glass, however, sees internal pressure within the metal housing corresponding to the smaller outer diameter of the capillary tube 202 in the collapsed region 306. According to some embodiments the annulus seals 410 seal an annulus around the smaller diameter collapsed region 306, while sealing region 308 has a larger outer diameter and thus reacts to the axial force on the optical waveguide 204 over a much larger area (surface reacting force) which provides reduced stress on the glass.

[0043] An Example Monolithic Multi-Optical-Waveguide Connector

[0044] In some embodiments, the capillary tube 202 may be shaped to form geometries important to alignment of two monolithic multi-optical-waveguide connectors. As shown in FIG. 5, the capillary tube 202 may be shaped to include at least one locating feature 514. In the embodiment shown in FIG. 5, the locating feature 514 is a flat (i.e., a flat surface) along a length of the capillary tube 202. The flat is formed in an outer diameter of the capillary tube 202 and is parallel to an axis of the capillary tube 202. The capillary tube 202 may be divided (e.g., by cutting or dicing) in the collapsed region 306 to form a connector pair. The locating feature 514 allows the optical waveguides 204 to be realigned within the desired submicron alignment. In one embodiment, the parted capillary tube 202 may be realigned by butting the diced ends 512 against one another and using the flat (locating feature 514) to precisely align the outer diameter, thereby also aligning the optical waveguides 204. This is particularly useful for undersea wet connects. In some embodiments, the ends 512 of the cut portion may have a polished face. In some embodiments, rather than having flat faces, the diced ends 512 may be aligned and connected using male/female connectors, where each end 512 is shaped to mate with the other end 512.

[0045] As shown in FIG. 6, in some embodiments, individual optical waveguides 204 may be spliced using a cone or carrier splice at 616, for example, with optical fibers 618. In carrier splicing, for example, all but one of the carriers (which may be the optical waveguides 204) are pulled back, the remaining carrier is spliced, and this process is repeated for each carrier. In another embodiment, the carriers may be spliced using large diameter splicing (LDS) to the ends of the cane waveguides.

Example Methods for Making a Monolithic Multi-Optical-Waveguide Penetrator or Connector

[0046] FIG. 7 is a flow diagram illustrating example operations 700 for forming an apparatus for transmitting light along multiple pathways. The operations 700 begin, at 702, by positioning a plurality of large diameter optical waveguides (e.g., waveguides 204), each having a core and a cladding, in a plurality of bores of a body (e.g., the cylindrical capillary tube 202 of FIG. 2). According to some embodiments, the bores may be drilled in the body prior to positioning the optical waveguides in the bores. For other embodiments, the body having the plurality of bores may be drawn from a preform having a plurality of bores.

[0047] At 704, at least a portion of the cladding of each of the optical waveguides is fused with the body, such that the apparatus resulting therefrom is a monolithic structure (e.g., structure 200). For some embodiments, at least one orientation feature may be formed in the body before the fusing at 704 or in the apparatus after the fusing.

[0048] At 706, the apparatus may be diced in the fused portion to form two apparatuses. Each of the two apparatuses may be a monolithic structure (e.g., if the dicing occurs in the collapsed region 306). For some embodiments, an end face of at least one of the two apparatuses may be polished at 707. For some embodiments, at least one orientation feature may be formed in the two apparatuses (e.g., in the end faces 512 of the two apparatuses).

[0049] At 708, the end faces of the two apparatuses may be butted together, such that the optical waveguides in the two apparatuses are aligned. The optical waveguides may be aligned using at least one orientation feature (e.g., locating feature 514) in at least one of the two apparatuses. In some embodiments, the orientation feature may be at least one flat surface formed in an outer diameter of the body and parallel to an axis of the body.

[0050] At 710, a plurality of optical fibers (e.g., fibers 618) may be spliced (e.g., at 616) to the plurality of large diameter optical waveguides. The splicing may involve cone splicing or carrier splicing.

[0051] For some embodiments, a monolithic structure as described above may be formed without using a body (e.g., a capillary tube). For example, FIG. 8 is a flow diagram illustrating example operations 800 for forming an apparatus for transmitting light along multiple pathways by fusing the claddings of multiple large diameter optical waveguides together. The operations 800 may begin, at 802, by positioning a plurality of large diameter optical waveguides (e.g., waveguides 204), each having a core and a cladding, adjacent one another (e.g., in a bundle).

[0052] At 804, at least a portion of the cladding of each of the optical waveguides is fused with the cladding of another one of the optical waveguides, such that the apparatus resulting therefrom is a monolithic structure. This fusing may be performed in the same region on each of the optical waveguides, such that the monolithic structure may be used as an optical feedthrough.

[0053] Many of the operations 700 of FIG. 7 described above may also be performed for the monolithic structure formed according to the operations 800 of FIG. 8. For example, the apparatus may be diced in the fused portion to form two apparatuses, which may be polished and later butted together (e.g., using one or more orientation features for alignment).

[0054] Embodiments of the invention heretofore can be used and have specific utility in applications within the oil and gas industry. Further, it is within the scope of the invention that other commercial embodiments/uses exist with one such universal sealing arrangement shown in the figures and adaptable for use in (by way of example and not limitation) industrial, chemical, energy, nuclear, structural, etc. While the foregoing is directed to preferred embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.