High power fiber array assembly with built-in cooling - Patents.com

Abstract

An optical fiber array assembly for high power applications includes a support structure, an optical fiber array, a plurality of end caps, and a fluid conduit arrangement. The optical fiber array extends through the support structure and has a plurality of optical fibers extending in a common longitudinal direction. The plurality of end caps are arranged such that each of the end caps is attached to an end portion of one of the optical fibers. The fluid conduit arrangement has one or more conduits extending through the support structure. The one or more conduits are configured to support a flow of fluid therein for removing heat resulting from optical energy reflected back from the end caps into the support structure.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 313,998, filed February 25, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] There is an ever-increasing demand for high optical power delivered through optical fiber arrays for multiple applications such as laser cutting and welding, additive manufacturing, directed energy weapons, etc. Due to the high power of light transmitted in these systems, there is heat build-up in the optical fiber assemblies along with reflections from various optical elements and stray light energy. This heat needs to be reduced and dissipated so that the optical fiber arrays function efficiently and are not damaged. Summary of the Invention

[0003] According to one aspect of the subject matter described herein, an optical fiber array assembly for high power applications includes a support structure, an optical fiber array, a plurality of end caps, and a fluid conduit arrangement. The optical fiber array extends through the support structure and has a plurality of optical fibers extending in a common longitudinal direction. The plurality of end caps are arranged such that each of the end caps is attached to an end portion of one of the optical fibers. The fluid conduit arrangement has one or more conduits extending through the support structure. The one or more conduits are configured to support a flow of fluid therein for removing heat resulting from optical energy reflected back from the end caps into the support structure.

[0004] In another particular embodiment, the one or more conduits include at least one channel formed in the support structure.

[0005] In yet another particular embodiment, the one or more conduits include at least one tube extending through the support structure.

[0006] In another particular embodiment, the support structure includes a void positioned to receive the back-reflected optical energy. The one or more conduits include a first conduit having a first conduit segment that extends across the plurality of optical fibers in the optical fiber array, thereby receiving the back-reflected optical energy as light and / or heat that enters the support structure through a sidewall that defines the void.

[0007] In another particular embodiment, the first conduit segment extends across the plurality of optical fibers on a first side of the optical fiber array, and the array assembly further includes a second conduit having a second conduit segment extending across the plurality of optical fibers on a second side of the optical fibers opposite the first side of the optical fiber array.

[0008] In another particular embodiment, the first and second conduits each have an inlet and an outlet, respectively, through which fluid may enter and exit.

[0009] In another particular embodiment, the sidewalls of the cavity have an absorbing coating that absorbs the back-reflected optical energy.

[0010] In another particular embodiment, the support structure is transparent to the back-reflected optical energy and the fluid flowing within the one or more conduits includes an absorbing dye that absorbs the back-reflected optical energy.

[0011] In another particular embodiment, the optical fiber array assembly further includes a third conduit segment extending across the plurality of end caps to remove optical energy that is reflected back from the end caps and enters the support structure from the circumferential sidewalls of the end caps.

[0012] In another particular embodiment, the optical fiber array assembly further includes a closed-loop conduit containing a fluid having an absorbing die therein that absorbs the back-reflected optical energy, the closed-loop conduit being radially closer to the optical fibers than the first conduit such that heat absorbed by the closed-loop conduit flows through the support structure to the first conduit.

[0013] In another particular embodiment, the support structure includes upper and lower support structures that mate with one another with the optical fiber array positioned therebetween, the upper and lower support structures each including a corresponding notch that defines a gap when the upper and lower support structures are mated with one another.

[0014] In another particular embodiment, the one or more conduits include first and second conduits extending into the upper and lower support structures, respectively, the first and second conduits being symmetrically disposed relative to one another about a mating surface where the upper and lower support structures meet.

[0015] This Summary is provided to introduce various concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Moreover, the claimed subject matter is not limited to implementations that solve any or all of the disadvantages noted in any part of this disclosure. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic exploded perspective view of an example of a high power fiber array assembly. [Diagram 2] 2 is a front view of the fiber array assembly shown in FIG. 1. [Diagram 3] FIG. 1 is a schematic diagram of optical energy propagating within one of the optical fibers and the surrounding end cap employed in a high power fiber array assembly. [Figure 4] 2A-2C are different views of one embodiment of cooling channels that may be incorporated into the high-power fiber array assembly shown in FIG. 1 to mitigate adverse thermal effects. [Diagram 5] 2A-2C are different views of one embodiment of cooling channels that may be incorporated into the high-power fiber array assembly shown in FIG. 1 to mitigate adverse thermal effects. [Figure 6] 2A-2C are different views of one embodiment of cooling channels that may be incorporated into the high-power fiber array assembly shown in FIG. 1 to mitigate adverse thermal effects. [Figure 7] 11A-11C are different views of another embodiment of a high-power fiber array assembly in which one or more additional cooling channels are located above and / or below the fiber end caps to keep the end caps cool. [Figure 8] 11A-11C are different views of another embodiment of a high-power fiber array assembly in which one or more additional cooling channels are located above and / or below the fiber end caps to keep the end caps cool. [Figure 9] 11A-11C are different views of another embodiment of a high-power fiber array assembly in which one or more additional cooling channels are located above and / or below the fiber end caps to keep the end caps cool. [Figure 10] 11A-11C are different views of another embodiment of a high-power fiber array assembly in which lower and upper cooling channels each have a closed-loop cooling channel associated therewith. [Figure 11] 11A-11C are different views of another embodiment of a high-power fiber array assembly in which lower and upper cooling channels each have a closed-loop cooling channel associated therewith. [Figure 12] 11A-11C are different views of another embodiment of a high power fiber array assembly in which the cooling conduits are formed from tubes extending through the support structure. [Figure 13] 11A-11C are different views of another embodiment of a high power fiber array assembly in which the cooling conduits are formed from tubes extending through the support structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] FIG. 1 shows a schematic exploded perspective view of one example of a high power fiber array assembly that may incorporate cooling conduits such as channels or tubes to remove heat that may build up as a result of high power being employed. An array of optical fibers 1 is secured between a lower support structure 3a and an upper support structure 3b that, when mated, together define the support structure 3. Fiber end caps 2 are attached to the end portions of the optical fibers 1 from which the light propagating therein exits. If the energy density becomes too high, the end faces of the fibers may be damaged, which may result in failure of the array. This damage occurs at the glass-air interface. Fiber end caps 2, which may be fused to the optical fiber end faces, reduce this damage by allowing a larger area for the light to exit, resulting in a reduction in the energy density at the glass-air interface, which in turn reduces or eliminates the damage caused to the optical fibers 1. FIG. 2 shows the front of the fiber array assembly with the fiber end caps 2 visible between the lower support structure 3a and the upper support structure 3b. Please note that in Figures 1 and 2 and subsequent figures, like elements are represented by like reference numerals.

[0018] The optical fibers 1 are generally arranged parallel to one another and extend longitudinally along the lower support structure 3a. The lower support structure 3a includes a notch 30a having a longitudinal width across which each of the optical fibers 1 traverses. The notch 30a is defined by the sidewalls of ridges 31 and 33. A corresponding notch 30b is located in the upper support structure 3b.

[0019] Fiber end cap 2 is supported by ridge 31 and may sit within a V-groove defined therein. Similarly, optical fiber 1 may be supported by ridges 32 and 33. In some cases, a suitable adhesive, such as epoxy, may be used to secure end cap 2 and optical fiber 1 to the support structure. Note that optical fiber 1 is generally surrounded by a fiber jacket, which has been removed in the area including where optical fiber 1 traverses the width of notch 30a as seen in FIG.

[0020] The upper support structure 3b and the lower support structure 3a can be formed from a wide range of different materials, illustrative examples may include glasses, metals and metal alloys, etc. that are transparent to the operating wavelengths of light used in the high power fiber array assembly.

[0021] FIG. 3 shows in more detail the fiber end cap 2 surrounding the emitting end of one of the optical fibers 1. As shown, light 20 propagates from the optical fiber 1 into the end cap 2 and exits the end cap 2 as light 21 that is spread over a wider area compared to the light propagating within the optical fiber 1. Also shown is light 22 that reflects back through the fiber end cap 2. The back-reflected light 22 exits the fiber end cap 2 as light 23 at various points along the circumference of the end cap 2 as well as at the input surface where the optical fiber 1 contacts the end cap 2. This light can be absorbed by the support structure and converted to heat, which is then contained within the fiber array assembly. However, increased power can cause the fiber assembly to get hotter, resulting in failure of various components of the fiber array assembly, such as the epoxy used to construct the fiber array assembly. The epoxy can outgas from particles that can reach the end face of the optics, resulting in further failure.

[0022] 4, 5, and 6 show an embodiment of cooling channels that may be incorporated into the high-power fiber array assembly shown in FIG. 1 to mitigate adverse thermal effects. FIG. 4 is a side view in which optical fibers 1 are positioned in a horizontal plane extending into the page. FIGS. 5 and 6 are perspective views of the fiber array assembly without the upper support structure 3b and with the upper support structure 3b in place, respectively. As shown, the lower cooling channels 4a are formed in the lower support structure 3a and the upper cooling channels 4b are formed in the upper support structure 3b. The lower cooling channels 4a each have inlet and outlet channel segments through which the cooling fluid (e.g., liquid such as distilled water or other with higher heat capacity, gas such as nitrogen, etc.) enters and exits the lower cooling channel 4a. In this example, the inlet and outlet channel segments extend largely parallel to the optical fibers 1. The transverse channel segments are in fluid communication with the inlet and outlet channel segments and extend across the array of optical fibers 1 parallel to the side walls of the notch 30a. That is, the inlet and outlet channel segments and the side channel segments form a continuous channel, and the side channel segments extend parallel to the side walls of the notch 30b. In the examples shown in Figures 4 and 6, the upper cooling channel 4b is disposed in a symmetrical manner relative to the upper cooling channel, but this is not required. Furthermore, in some embodiments, only one of the lower cooling channel 4a and the upper cooling channel 4b may be employed.

[0023] As best seen in the side view of Figure 4, reflected light 23 diffusing from the fiber end cap 2 back towards the optical fiber 1 enters the void defined by the upper and lower notches 30b and 30a and is then absorbed as light and heat energy 8 by the sidewalls of the notches 30b and 30a defined in the upper and lower support structures. The transverse channel segments are located in the support structure as close to the void as practical, thereby maintaining structural integrity. In this manner, the transverse channel segments can absorb light and / or heat 8 that enters the support structure after traversing the void.

[0024] In some embodiments, an absorbing material may be coated on the sidewalls of the upper and lower notches 30a, 30b to absorb light reflected back from the fiber end cap 2. In an alternative embodiment, if the support structure is made of a material such as glass that is transparent to the optical energy in the optical fiber, the cooling fluid in the cooling conduit may include an absorbing dye to absorb the reflected light that enters the support structure.

[0025] In some embodiments, the cooling channels 4a and 4b may have diameters ranging from as little as a millimeter to several millimeters, depending on a variety of factors, including the number and size of the optical fibers in the array and the amount of power transmitted through them. Generally, the diameter of the cooling channels is larger than the diameter of the optical fibers, and may range from hundreds of microns to more than a millimeter in some typical high-power applications. The cooling channels may be formed by any suitable technique, such as laser etching using a femtosecond laser, or by 3D printing techniques that may be used to form the support structure.

[0026] 7-9 show another embodiment of the high power fiber array assembly in which one or more additional cooling channels are positioned above and / or below the fiber end cap 2 to keep the end cap 2 cool. The additional cooling channels can cool the fiber end cap 2 by receiving light and heat 13 exiting from the outer periphery of the fiber end cap 2. FIG. 7 is a side view in which the optical fibers 1 are placed in a horizontal plane extending into the page. FIGS. 8 and 9 are two different perspective views of the fiber array assembly without the upper support structure 3b in place. In this embodiment, the forward lower and upper cooling channels 11a and 11b have transverse segments that extend below and above the end cap 2, respectively. In this embodiment, the forward lower and upper cooling channels 11a and 11b are formed as branches of the lower and upper cooling channels 4a and 4b. In an alternative embodiment, the forward lower and upper cooling channels 11a and 11b are independent of the lower and upper cooling channels 4a and 4b and therefore have separate amounts of fluid flowing through them.

[0027] 10-11 show yet another embodiment of a high power fiber array assembly in which the lower and upper cooling channels 4a, 4b each have a closed-loop cooling channel associated therewith. FIG. 10 shows a side view and FIG. 11 shows an exploded perspective view. As shown, the lower cooling channel 4a is associated with the lower closed-loop cooling channel 16a and the upper cooling channel 4b is associated with the upper closed-loop cooling channel 16b. The lower and upper closed-loop cooling channels 16a, 16b are radially closer to the optical fiber 2 than the lower and upper cooling channels 4a, 4b, thereby better receiving the energy caused by the light reflected back from the fiber end cap 2. In those embodiments employing a transmissive support structure, the lower and upper closed-loop cooling channels 16a, 16b can include an absorbing die to better absorb the light that enters the support structure 3 and heats the fluid in the closed-loop channels. As shown by arrows 18 in FIG. 10, heat from the lower closed-loop cooling channel 16a and the upper closed-loop cooling channel 16b flows into the lower cooling channel 4a and the upper cooling channel 4b, respectively, where the heat is removed from the fiber array assembly by the fluid flowing therethrough.

[0028] Figures 12 and 13 show another embodiment of a high power fiber array assembly in which the cooling conduits are formed from tubes 17a and 17b that extend through the support structure 3. Figure 12 is a side view and Figure 13 is an exploded perspective view. As shown, tubes 17a and 17b extend through gaps defined by notches 30a and 30b formed in the lower and upper support structures 3a and 3b. In the example shown, tube 17b extends into the gap above the optical fiber array and tube 17a extends into the gap below the optical fiber array.

[0029] It should be noted that various features of the illustrative embodiments described above may be combined in different embodiments as would occur to one of ordinary skill in the art. For example, in some embodiments, the high power fiber array assembly may incorporate cooling conduits formed from channels and tubes. As another example, in some embodiments, closed loop cooling channels may be located only in one of the upper or lower support structures, while the other of the upper or lower support structures may include forward cooling channels to keep the end cap cool. More generally, the number of conduits and the particular configuration of the conduits shown in the depicted embodiments are presented for illustrative purposes only and are not intended to limit the types or kinds of conduit devices that may be incorporated to remove heat resulting from light energy reflecting back from the end cap into the support structure.

[0030] The above description has been described with reference to specific embodiments for purposes of explanation. However, the illustrative embodiments are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments have been chosen and described to best explain the principles of the embodiments and their practical application, thereby enabling others skilled in the art to best utilize the embodiments and various modifications that may be suitable for the particular use contemplated. Thus, the present embodiments should be considered as illustrative and not restrictive, and the invention is not limited to the details given herein, but may be modified within the scope of the appended claims and their equivalents.

Claims

1. 1. An optical fiber array assembly for high power applications, comprising: A support structure; an optical fiber array extending through the support structure and having a plurality of optical fibers extending in a common longitudinal direction; a plurality of end caps, each end cap positioned to be attached to an end portion of one of the optical fibers; and a fluid conduit arrangement having one or more conduits extending through the support structure, the one or more conduits configured to support a flow of fluid therein to remove heat resulting from optical energy reflected back from the end caps and entering the support structure.

2. The optical fiber array assembly of claim 1 , wherein the one or more conduits comprises at least one channel formed in the support structure.

3. The optical fiber array assembly of claim 1 , wherein the one or more conduits include at least one tube extending through the support structure.

4. 2. The optical fiber array assembly of claim 1, wherein the support structure includes a void positioned to receive back-reflected optical energy, and the one or more conduits include a first conduit having a first conduit segment extending across a plurality of optical fibers in the optical fiber array, thereby receiving back-reflected optical energy as light and / or heat that enters the support structure through a sidewall defining the void.

5. 5. The optical fiber array assembly of claim 4, further comprising a second conduit having a first conduit segment extending across a plurality of optical fibers on a first side of the optical fiber array and a second conduit segment extending across a plurality of optical fibers on a second side of the optical fibers opposite the first side of the optical fiber array.

6. 6. The fiber optic array assembly of claim 5, wherein said first and second conduits each have an inlet and an outlet, respectively, through which fluid enters and exits.

7. 5. The optical fiber array assembly of claim 4, wherein a sidewall of the cavity has an absorbing coating that absorbs back-reflected optical energy.

8. 10. The optical fiber array assembly of claim 1, wherein the support structure is transparent to back-reflected optical energy and the fluid flowing within the one or more conduits includes an absorbing die that absorbs the back-reflected optical energy.

9. 5. The optical fiber array assembly of claim 4, further comprising a third conduit segment extending across the plurality of end caps to remove optical energy that is reflected back from the end caps and enters the support structure from a circumferential sidewall of the end cap.

10. 5. The optical fiber array assembly of claim 4, further comprising a closed-loop conduit containing a fluid having an absorbing die therein for absorbing back-reflected optical energy, the closed-loop conduit being radially closer to the optical fibers than the first conduit such that heat absorbed by the closed-loop conduit flows through a support structure to the first conduit.

11. 2. The optical fiber array assembly of claim 1, wherein the support structure includes upper and lower support structures that mate with one another with the optical fiber array positioned therebetween, the upper and lower support structures each including a corresponding notch that defines a gap when the upper and lower support structures are mated with one another.

12. 12. The optical fiber array assembly of claim 11, wherein the one or more conduits include first and second conduits extending into the upper and lower support structures, respectively, the first and second conduits being symmetrically positioned relative to one another about a mating surface where the upper and lower support structures meet.

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