Multichannel Optical Combiner Array

Abstract

The multi-channel optical coupler array has a coupler housing structure and longitudinal waveguides. At least one of the longitudinal waveguides is a missing core waveguide having an inner missing core with a first refractive index (N-1), an outer core with a second refractive index (N-2), and an outer cladding with a third refractive index (N-3). The refractive index transition between N-1 and N-2 has a function N(r), where r is the lateral distance from the inner missing core center. The function N(r) can be a smooth function with a positive average of the second derivative, or the function N(r) can be a step function with at least one step that approximates the smooth function. The coupler housing structure has a non-circular hole formed by a convex-shaped housing structural element.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application is a continuation-in-part of U.S. Application No. 17 / 452,173, entitled "Multi-Channel Optical Combiner Array," filed on October 25, 2021 (CHIRA.020P6), and claims the benefit of U.S. Provisional Application No. 63 / 147,128, entitled "Multi-Channel Optical Combiner Array," filed on February 8, 2021 (CHIRA.020PR6), and U.S. Provisional Application No. 63 / 203,052, entitled "Multi-Channel Optical Combiner Array," filed on July 6, 2021 (CHIRA.020PR7). U.S. Application No. 17 / 452,173 is also a continuation-in-part of U.S. Application No. 16 / 600,219 (CHIRA.020P5), filed on October 11, 2019, entitled “Passively Aligned Optical Coupler Array,” which is a continuation-in-part of U.S. Application No. 16 / 159,310 (CHIRA.020P3), filed on October 12, 2018, entitled “Passively Aligned Optical Coupler Array,” which is a continuation-in-part of U.S. Application No. 15 / 811,462 (CHIRA.020P1), filed on November 13, 2017, entitled “Multi-Channel Optical Coupler Array,” which is a continuation-in-part of U.S. Application No. 15 / 811,462 (CHIRA.020P1), filed on March 15, 2017, entitled “Multi-Channel Optical Coupler Array.” No. 15 / 459,730 (CHIRA.020A), entitled “Multi-Channel Optical Coupler Array,” which claims the benefit of U.S. Provisional Application No. 62 / 417,180 (CHIRA.020PR), filed November 3, 2016; and No. 14 / 306,217 (CHIRA.034A), entitled “Optical Component Assembly for Use With Optical Apparatus,” which claims the benefit of U.S. Provisional Application No. 61 / 834,957, filed June 14, 2013; entitled “Optical Component Assembly for Use With Optical Apparatus,” which claims the benefit of U.S. Provisional Application No. 61 / 834,957, filed June 14, 2013.U.S. Application No. 15 / 811,462 also claims the benefit of U.S. Provisional Application No. 62 / 564,178 (CHIRA.020PR3), filed September 27, 2017, entitled “Multi-Channel Optical Coupler Array,” and is a continuation-in-part of U.S. Application No. 15 / 617,684 (CHIRA.042A), filed June 8, 2017, entitled “Configurable Polarization Mode Couplers,” and is a continuation-in-part of U.S. Application No. 15 / 459,730 (CHIRA.020A), filed March 15, 2017, entitled “Multi-Channel Optical Coupler Array.” No. 62 / 417,180, entitled "Multi-Channel Optical Coupler Array," filed November 3, 2016 (CHIRA.020PR), which is a continuation-in-part of U.S. application Ser. No. 14 / 306,217, entitled "Optical Component Assembly for Use With an Optical Apparatus," filed June 16, 2014 (CHIRA.034A), which claims the benefit of U.S. Provisional Application No. 61 / 834,957, entitled "Optical Component Assembly for Use With an Optical Apparatus," filed June 14, 2013. The entirety of each application referred to in this paragraph is expressly incorporated herein by reference.

[0002] The present disclosure generally relates to optical coupler arrays, e.g., multi-channel optical coupler arrays, for coupling, e.g., multiple optical fibers to at least one optical device. Some embodiments relate to coupling light to and from multiple fibers, e.g., one or more single mode fibers, few mode fibers, multimode fibers, multicore single mode fibers, multicore few mode fibers, and / or multicore multimode fibers. Some embodiments relate to coupling light to and from photonic integrated circuits (PICs) and to and from multicore fibers (MCFs). Some embodiments include passive coupling of one or more MCFs to a PIC device (e.g., to one or more waveguides at the end of the PIC). Some embodiments relate generally to devices for high power single mode laser sources and coherent combining of multiple optical fiber lasers to generate multi-kilowatt single mode laser sources. Some embodiments The present invention relates to monolithically designed phase-locked optical fiber components that can be manufactured with a very high degree of control over the precise positioning (e.g., lateral or cross-sectional positioning) of multiple waveguides in large quantities, and can be configurable to increase or optimize the fill factor of the component, which can be related to the ratio of the mode field diameter of each waveguide at its “output” end to the distance between adjacent waveguides. [Background technology]

[0003] Optical waveguide devices are useful in various high-tech industrial applications, especially in telecommunications. In recent years, these devices, including planar waveguides, two-dimensional or three-dimensional photonic crystals, multimode fibers, multicore single-mode fibers, multicore family-mode fibers, and multicore multimode fibers, have been increasingly employed in combination with conventional optical fibers. In particular, optical waveguide devices and multichannel devices based on waveguides with different refractive index contrasts and numerical apertures (NAs) than conventional optical fibers are advantageous and desirable in applications where conventional optical fibers are also utilized. However, there are significant challenges in interfacing heterogeneous NA waveguide devices and multichannel devices with conventional optical fibers, which have channel spacings smaller than the diameter of conventional optical fibers. For example, (1) the size difference between optical waveguide devices and conventional fibers (especially with respect to the difference in core size), (2) the NA difference between optical waveguide devices and conventional fibers, and (3) the channel spacings smaller than the diameter of conventional fibers. If these obstacles are not properly addressed, they may lead to increased insertion loss and reduced coupling coefficients at each interface.

[0004] For example, a conventional optical fiber-based optical coupler, as shown in FIG. 6 (prior art), can be constructed by inserting a standard optical fiber (used as the input fiber) into a capillary tube constructed of a material with a lower refractive index than the cladding of the input fiber. However, this method has many drawbacks. For example, the interface between the fiber cladding and the capillary tube is a lower quality light-guiding interface than the interface inside a standard optical fiber, and optical losses are expected. In addition, the capillary tube must be manufactured using expensive fluorine-doped materials, significantly increasing the cost of the coupler.

[0005] U.S. Pat. No. 7,308,173, entitled "Low Loss and High Coupling Coefficient Optical Fiber Coupler and Method for Manufacturing Same," which is incorporated herein in its entirety, advantageously addresses some of the problems discussed above by providing various embodiments of optical fiber couplers that can provide a low loss, high coupling coefficient interface between conventional optical fibers and optical waveguide devices.

[0006] Nevertheless, many challenges remain. With the proliferation of multi-channel optical devices (e.g., waveguide arrays), establishing low-loss, high-precision connections to arrays of low or high NA waveguides has often been problematic, especially since the spacing between the waveguides is very small, making coupling thereto more difficult. U.S. Patent No. 8,326,099 ("Optical Fiber Coupler Array," issued Dec. 4, 2012) seeks to address the above challenges in at least some of its embodiments by providing an optical fiber coupler array that provides a highly accurate, easy-to-align, high coupling coefficient interface between an optical waveguide device having multiple closely spaced waveguides and multiple optical fibers spaced at least a fiber diameter apart.

[0007] U.S. Patent Application Serial No. 8,712,199, entitled "Configurable Pitch-Reduced Optical Fiber Arrays," which is expressly incorporated herein by reference, discusses the importance of cross-sectional or lateral positioning accuracy (and in some cases precise cross-sectional positioning) of individual waveguides. Improved cross-sectional positioning accuracy of waveguides remains desirable.

[0008] It is also desirable to improve and / or optimize the optical coupling between a set of insulating fibers (e.g., single mode fibers) at one end and the individual modes (e.g., of a few mode or multimode fiber) and / or cores (e.g., of a multicore fiber) at the other end. Further coupling improvements may be desired.

[0009] It would also be desirable to improve and / or optimize the optical performance of the tapered multi-channel coupler by further improving and / or optimizing the design of both the lossy waveguide and the housing structure. Summary of the Invention

[0010] The exemplary embodiments described herein have innovative features, no single one of which is essential or solely responsible for its desirable attributes. Without limiting the scope of the claims, some of the more advantageous features are summarized below. Example I 1. A multi-channel optical coupler array for optically coupling a plurality of optical fibers to an optical device, comprising: an elongated optical element having a first end operable to optically couple with the plurality of optical fibers and a second end operable to optically couple with the optical device; a common unitary coupler housing structure; and a plurality of longitudinal waveguides, each of the plurality of longitudinal waveguides having capacity for at least one optical mode of a predetermined mode field profile, each embedded in the common unitary housing structure proximate the second end, at least one of the plurality of longitudinal waveguides being a lost core waveguide, each of the at least one lost core waveguide comprising an inner lost core, an outer core, and an outer cladding, the inner lost core having an inner lost core center and having a first refractive index (Nl), a first inner core size (ICS-I) at the first end and a second inner core size (ICS-2) at the second end, the outer core extending between the inner lost core and the inner core, the outer cladding longitudinally surrounds the outer core, has a second refractive index (N-2), has a first outer core size (OCS-I) at the first end and a second outer core size (OCS-2) at the second end, the outer cladding longitudinally surrounds the outer core, has a third refractive index (N-3), has a first cladding size at the first end and a second cladding size at the second end, and the common single coupler housing structure comprises a laterally continuous medium having a fourth refractive index (N-4) surrounding a plurality of longitudinal waveguides, wherein a predetermined relative magnitude relationship between said first, second, third and fourth refractive indices (N-1, N-2, N-3 and N-4, respectively) is the following magnitude relationship: N-1>N-2>N-3, where the refractive index transition between N-1 and N-2 has a function N(r), where r is the lateral distance from the center of said inner missing core, and whose second derivative is d 2 N(r) / dr 2a total volume of the medium in the common single coupler housing structure is greater than a total volume of all the missing core waveguide inner cores and the outer cores in the common single coupler housing structure, the first inner missing core size (ICS-I) and the first outer core size (OCS-I) are simultaneously gradually reduced along the optical element between the first end and the second end according to a predetermined reduction profile until the second inner missing core size (ICS-2) and the second outer core size (OCS-2) are reached, and the function N(r) is a smooth function having a positive mean of a derivative, or the function N(r) is a step function having at least one step that approximates a smooth function having a positive mean of the second derivative, the second inner missing core size (ICS-2) is selected to be insufficient to guide light therethrough, the second outer core size (OCS-2) is selected to be sufficient to guide at least one optical mode, light traveling from the first end to the second end escapes from the inner missing core to the corresponding outer core proximate the second end, a common single coupler housing structure proximate to the first end having a cross-sectional configuration of a laterally continuous structure having at least one hole, the at least one hole containing at least one of the plurality of longitudinal waveguides, and forming a gap between the coupler housing structure and at least one of the plurality of longitudinal waveguides. 2. The multi-channel optical combiner array of Example 1, wherein the function N(r) is a smooth function having a positive mean of the second derivative. 3. The multi-channel optical combiner array of Example 1, wherein the function N(r) is a step function having at least one step that approximates a smooth function having a positive mean of the second derivative. 4. The multi-channel optical combiner array of example 3, wherein the function N(r) comprises one step. 5. The multi-channel optical combiner array of example 3, wherein the function N(r) comprises two steps. 6. The multi-channel optical combiner array of Example 3, wherein the function N(r) consists of three steps. 7. A multi-channel optical combiner array as described in Example 3, wherein the step function includes corner points, at least some of the corner points being above or below a smooth function having a positive average of the second derivative. 8. A multi-channel optical coupler array as described in any one of Examples 1 to 7, wherein the at least one hole comprises at least one non-circular hole formed by multiple protrusions of the coupler housing structure. 9. A multi-channel optical coupler array as described in any one of Examples 1 to 7, wherein the at least one hole comprises at least one hole formed by a tube surrounded by multiple protrusions of the coupler housing structure. 10. A multi-channel optical coupler array for optically coupling a plurality of optical fibers to an optical device, comprising: an elongated optical element having a first end operable to optically couple with the plurality of optical fibers and a second end operable to optically couple with the optical device; a common unitary coupler housing structure; and a plurality of longitudinal waveguides, each having capacity for at least one optical mode of a predetermined mode field profile, each embedded in the common unitary housing structure proximate the second end, at least one of the plurality of longitudinal waveguides being a lost core waveguide, each of the at least one lost core waveguide comprising an inner lost core, an outer core, and an outer cladding, the inner lost core having a first refractive index (Nl) and having a first inner core size (ICS-I) at the first end and a second inner core size (ICS-2) at the second end, the outer core longitudinally surrounding the inner core and having a second refractive index (N-2) and a first outer core size (OCS- the first, second, third and fourth refractive indices (N-4) surrounding the plurality of longitudinal waveguides, the outer cladding having a third refractive index (N-3), a first cladding size at the first end and a second cladding size at the second end, the common unitary coupler housing structure comprising a transversely continuous medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, the first, second, third and fourth refractive indices (N-4, respectively) being in the range of 0.5 to 1.0 .mu.m. and a predetermined relative size relationship between the inner cores (N1, N-2, N-3 and N-4) is comprised of the following size relationship (N-1>N-2>N-3), the total volume of the medium or the common single coupler housing structure is greater than the total volume or the outer cores of all the lost core waveguide inner cores and the outer cores enclosed within the common single coupler housing structure, and the first inner lost core size (ICS-I) and the first outer core size (OCS-I) are a predetermined reduced profile. According to a preferred embodiment of the present invention, the optical element is gradually reduced in size along the optical element between the first end and the second end until it reaches the second inner missing core size (ICS-2) and the second outer core size (OCS-2), the second inner missing core size (ICS-2) being selected to be insufficient to guide light therethrough and the second outer core size (OCS-2) being selected to be sufficient to guide at least one optical mode, and light traveling from the first end to the second end escapes from the inner missing core to the corresponding outer core proximate the second end and is guided by the second outer core size (OCS-2). light traveling from one end of the coupler housing structure toward the first end travels from the outer core to the corresponding inner lost core proximate the first end, the common single coupler housing structure proximate the first end has a cross-sectional configuration consisting of a laterally continuous structure having at least one hole, the at least one hole including at least one of the plurality of longitudinal waveguides forming a gap between the coupler housing structure and at least one of the plurality of longitudinal waveguides, and the at least one hole comprises at least one non-circular hole formed by a plurality of protrusions of the coupler housing structure. 11. A multi-channel optical coupler array for optically coupling a plurality of optical fibers to an optical device, comprising: an elongated optical element having a first end operable to optically couple with the plurality of optical fibers and a second end operable to optically couple with the optical device; a common unitary coupler housing structure; and a plurality of longitudinal waveguides, each having capacity for at least one optical mode of a predetermined mode field profile, each embedded in the common unitary housing structure proximate the second end; at least one of the plurality of longitudinal waveguides is a lost core waveguide, each of the at least one lost core waveguide comprising an inner lost core, an outer core, and an outer cladding, the inner lost core having a first refractive index (Nl) and a first inner core size (ICS-I) at the first end; the outer core longitudinally surrounds the inner core and has a second refractive index (N-2); the outer core longitudinally surrounds the inner core and has a first outer core size (OCS-I) at the first end and a second outer core size (OCS-2) at the second end; the outer cladding longitudinally surrounds the outer core and has a third refractive index (N-3); the outer cladding and the common single coupler housing structure comprise a transversely continuous medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides; and a predetermined relative magnitude relationship between the first, second, third and fourth refractive indices (Nl, N-2, N-3 and N-4, respectively) comprises the following magnitude relationship: N-1>N-2>N-3; a total volume of the medium or the common single coupler housing structure is greater than a total volume or the outer cores of all the missing core waveguide inner cores and outer cores enclosed within the common single coupler housing structure, the first inner missing core size (ICS-I) and the first outer core size (OCS-I) are simultaneously gradually reduced according to a predetermined reduction profile between the first end and the second end along the optical element until the second inner missing core size (ICS-2) and the second outer core size (OCS-2) are reached, the second inner missing core size (ICS-2) being selected such that it is insufficient to guide light therethrough, and the second outer core size (OCS-2) is selected such that it is insufficient to guide light therethrough, and the second outer core size (OCS-2) is selected such that it is insufficient to guide light therethrough, and the first outer core size (OCS-2) is selected such that it is insufficient to guide light therethrough, and the second ... inner missing core size (ICS-2) is selected such that it is insufficient to guide light therethrough, and the second outer core size (OCS-2) is selected such that it is insufficient to guide light therethrough, and the second outer core size (OCS-2) is selected such that it is insufficient to guide light therethrough, and the second outer core size (OCS-2) is selected such that it is insufficient to guide light therethrough, and the second outer core size (OCS-2) is selected such -2) is selected to be sufficient to guide at least one optical mode, light traveling from the first end to the second end escapes from the inner missing core to the corresponding outer core proximate the second end, and light traveling from the second end to the first end travels from the outer core to the corresponding inner missing core proximate the first end, the common single coupler housing structure proximate the first end has a cross-sectional configuration of a laterally continuous structure having at least one hole, the at least one hole comprising at least one of the plurality of longitudinal waveguides forming a gap between the coupler housing structure and at least one of the plurality of longitudinal waveguides, and the at least one hole is formed by a hole extending through the common single coupler housing structure. The structure is characterized by having at least one hole formed by a tube surrounded by a plurality of protrusions. 12. A multi-channel optical coupler array, comprising an elongated optical element having a first end and a second end, the first end and the second end operable to optically couple with a plurality of optical fibers, optical devices, or combinations thereof, the optical element comprising a coupler housing structure and a plurality of longitudinal waveguides, the plurality of longitudinal waveguides disposed relative to one another, each having capacity for at least one optical mode, the plurality of longitudinal waveguides being arranged adjacent the second end to the longitudinal waveguides. embedded within a housing structure, the plurality of longitudinal waveguides including at least one lost core waveguide, the at least one lost core waveguide comprising an inner lost core, an outer core, and an outer cladding, the inner lost core having a first refractive index (Nl) and having an inner core size, the outer core longitudinally surrounding the inner core and having a second refractive index (N-2), the outer cladding longitudinally surrounding the outer core and having a third refractive index (N-3) and having a cladding size, the coupler housing structure comprises a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, where N-1>N-2>N-3; a size of the inner core, a size of the outer core, and a spacing between the plurality of longitudinal waveguides decrease along the optical element from the first end to the second end, such that at the second end, a size of the inner core is insufficient to guide light therethrough and a size of the outer core is sufficient to guide at least one optical mode; the coupler housing structure proximate to the first end includes at least one hole, the at least one hole including at least one of the plurality of longitudinal waveguides forming a gap between the coupler housing structure and at least one of the plurality of longitudinal waveguides, the at least one hole being composed of at least one non-circular hole formed by a plurality of protrusions of the coupler housing structure. 13. The optical coupler array of example 12, wherein the coupler housing structures comprise a common single coupler housing structure. 14. The optical coupler array of any of Examples 12-13, wherein the medium is a laterally continuous medium. 15. An optical coupler array described in any of Examples 12 to 14, wherein the total volume of the medium in the coupler housing structure is greater than the total volume of all inner cores and outer cores of at least one lost core waveguide confined within the coupler housing structure. 16. An optical coupler array described in any of Examples 12 to 15, wherein the size of the inner core, the size of the outer core, and the spacing between the multiple longitudinal waveguides simultaneously decrease gradually from the first end to the second end. 17. An optical coupler array as described in any of Examples 12 to 16, wherein, proximate the second end, the coupler array is configured such that there is substantially no gap between the coupler housing structure and at least one of the plurality of longitudinal waveguides. 18. The optical coupler array of any one of examples 12 to 17, wherein the at least one hole comprises a plurality of holes. 19. The optical coupler array of example 18, wherein at least one of the holes has a different dimension than another one of the holes. 20. The optical coupler array of any of Examples 18-19, wherein at least one of the holes has a different shape than another one of the holes. 21. The optical coupler array of any one of examples 18 to 20, wherein the holes are insulated. 22. An optical coupler array according to any one of examples 18 to 20, in which some holes are connected. 23. The method according to any one of Examples 12 to 22, wherein the at least one hole is formed by a tube surrounded by a plurality of protrusions of the coupling housing structure. Optical coupler array mounted on the substrate. 24. A method for manufacturing an optical coupler array according to any one of Examples 12-23, comprising forming at least one hole by a tube surrounded by a plurality of protrusions of a coupler housing structure. 25. A multi-channel optical coupler array comprising an elongated optical element having a first end and a second end, the first end and the second end operable to optically couple with a plurality of optical fibers, optical devices, or combinations thereof, the optical element comprising a coupler housing structure and a plurality of longitudinal waveguides disposed relative to one another within the housing structure, the coupler housing structure proximate the first end comprising at least one hole, the at least one hole comprising at least one of the plurality of longitudinal waveguides forming a gap between the coupler housing structure and at least one of the plurality of longitudinal waveguides, the at least one hole being comprised of at least one non-circular hole formed by a plurality of protrusions of the coupler housing structure. 26. An optical coupler array as described in Example 25, wherein adjacent the second end, the coupler array is configured such that there is substantially no gap between the coupler housing structure and at least one of the plurality of longitudinal waveguides. 27. The optical coupler array of any one of examples 25-26, wherein at least one hole comprises a plurality of holes. 28. The optical coupler array of any of examples 25-27, wherein at least one of the holes has a different dimension than another one of the holes. 29. The optical coupler array of any of examples 25-28, wherein at least one of the holes has a different shape than another one of the holes. 30. The optical coupler array of any one of examples 25 to 29, wherein the holes are insulated. 31. An optical coupler array according to any one of examples 25 to 29, in which some holes are connected. 32. The optical coupler array of any one of Examples 25 to 31, wherein at least one of the plurality of longitudinal waveguides comprises a non-disappearing core waveguide. 33. The optical coupler array according to any one of Examples 25 to 32, wherein at least one of the plurality of longitudinal waveguides comprises an extinct core waveguide. 34. The optical coupler array of any one of Examples 25 to 33, wherein the at least one hole comprises at least one hole formed by a tube surrounded by a plurality of protrusions of the coupler housing structure. 35. A method for manufacturing an optical coupler array according to any one of Examples 25-34, comprising forming at least one hole by a tube surrounded by a plurality of protrusions of a coupler housing structure. Example II 1. A multi-fiber array comprising a plurality of optical couplers, each optical coupler of the plurality of optical couplers configured to optically couple at least one optical fiber waveguide to at least one waveguide of an optical device, the plurality of optical couplers comprising: an elongated optical element having a first end operable to optically couple with the at least one optical fiber waveguide and a second end operable to optically couple with the optical device; a common single coupler housing structure; and at least one longitudinal waveguide having capacity for at least one optical mode embedded in the common single coupler housing structure, the common single coupler housing structure having an outer cross-sectional shape having a first side and a second side, the multi-fiber array comprising an alignment carrier, the alignment carrier including one or more flats configured to be coupled to the second side of the housing structure to couple the plurality of optical couplers. 2. The multi-fiber assembly of example 1, wherein the second side of the housing structure includes one or more flats configured to mate with the one or more flats of the alignment carrier. Ibaalei. 3. The multi-fiber array of any of the preceding examples, wherein the first side of the housing structure comprises one or more curved portions. 4. A multi-fiber array as described in any of the preceding examples, wherein the one or more flat portions of the alignment carrier define a V-groove and the second side of the housing structure defines one or more curved portions. 5. A multi-fiber array as described in any of the preceding examples, wherein the alignment carrier has at least two flat portions configured to be coupled with at least two flat portions of one of the second sides of one of the housing structures. 6. A multi-fiber array as described in any of the preceding examples, wherein the alignment carrier extends laterally beyond the second side of one of the housing structures on at least one side. 7. A multi-fiber array as described in any preceding example, wherein the alignment carrier extends laterally on both sides beyond the second side of one of the housing structures. 8. A multi-fiber array according to any of the preceding examples, wherein the alignment carrier comprises a carrier plate. 9. A multi-fiber array as described in any of the preceding examples, wherein the first side of the common single coupler housing structure is configured to be positioned within a V-groove of the optical device or a carrier of the optical device such that the first side contacts a wall of the V-groove. 10. The multi-fiber array of example 9, wherein the alignment carrier is configured to be positioned on an upper surface of the V-groove. 11. The multi-fiber array of any one of examples 9 to 10, wherein the alignment carrier is configured not to rest on an upper surface of the V-groove. 12. The multi-fiber optic array of any of Examples 9-11, wherein the position of the V-groove is registered relative to the position of the at least one waveguide of the optical device. 13. The multi-fiber array of Example 12, wherein the position of the V-groove is registered relative to the position of the at least one waveguide of the optical device such that the at least one waveguide of the optical device is aligned with the at least one longitudinal waveguide of one of the optical couplers with an optical coupling efficiency of between 50% and 100%. 14. The multi-fiber array according to example 13, wherein the optical coupling efficiency is 80% or more and 100% or less. 15. The multi-fiber array of any of the preceding examples, wherein the optical coupler is configured to optically couple one end of the at least one multicore fiber waveguide to at least one waveguide of the optical device. 16. A multi-fiber array as described in any of the preceding examples, wherein the second side of the housing structure is spaced a distance from at least one longitudinal waveguide of one of the optical couplers such that insertion loss is low from the first end to the second end. 17. A multi-fiber array as described in any of the preceding examples, wherein the second side of the housing structure is positioned at a distance from at least one longitudinal waveguide of one of the optical couplers such that waveguiding properties are maintained from the first end to the second end. 18. A multi-fiber array according to any of the preceding examples, wherein the at least one longitudinal waveguide of one of the optical couplers comprises a core of a multicore fiber, and a common single coupler housing structure comprises a cladding. 19. The multi-fiber array of example 18, wherein the multi-core fiber is flexible. 20. The multi-fiber array of any of the preceding examples, wherein at least one of the optical couplers is configured to optically couple a plurality of optical fibers to an optical device, the elongated optical elements having first ends operable to optically couple with the plurality of optical fibers, an intermediate cross section, and a second end operable to optically couple with the optical device, the elongated optical elements each spaced apart from one another and each having at least a plurality of longitudinal waveguides each having capacity for one optical mode and embedded in the common single housing structure proximate the second end, at least one of the plurality of longitudinal waveguides being a missing core waveguide, each of the at least one missing core waveguide comprising an inner missing core, an outer core and an outer cladding, the inner missing core having a first refractive index (Nl), a first inner core size (ICS-1) at the first end, an intermediate inner core size (ICS-IN) at the intermediate cross section and an outer cladding at the second end; the outer core longitudinally surrounds the inner core and has a second refractive index (N-2), the outer core longitudinally surrounds the inner core and has a first outer core size (OCS-1) at the first end and an intermediate outer core size (OCS-IN) at the intermediate cross section and a second outer core size (OCS-2) at the second end, the outer cladding longitudinally surrounds the outer core and has a third refractive index (N-3), and the first cladding size at the first end and the second cladding size at the second end are the common unitary coupler housing structure comprises a laterally continuous medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, the relative magnitude relationship between the first, second, third and fourth refractive indices (Nl, N-2, N-3 and N-4, respectively) being the following magnitude relationship (N-1>N-2>N-3) and N-3), and a total volume of the medium in the common unitary coupler housing structure is greater than a total volume of all the missing core waveguide inner cores and the outer cores confined within the common unitary coupler housing structure. wherein the first inner missing core size (ICS-1), the first outer core size (OCS-1), and the spacing between the plurality of longitudinal waveguides are simultaneously and gradually reduced between the first end and the second end along the optical element according to a reduction profile until the second inner missing core size (ICS-2) and the second outer core size (OCS-2) are reached, and the intermediate inner missing core size (ICSIN) is selected such that it is insufficient to guide light therethrough, and the intermediate outer core size (OCS-IN) is selected such that the first inner missing core size (ICS-1), the first outer core size (OCS-1), and the spacing between the plurality of longitudinal waveguides are simultaneously and gradually reduced between the first end and the second end along the optical element according to a reduction profile until the second inner missing core size (ICS-2) and the second outer core size (OCS-2) are reached,a first outer core size (OCS-1) selected to be sufficient to guide at least one optical mode, and a second outer core size (OCS-2) selected to be insufficient to guide light therethrough; light traveling from the first end toward the second end escapes from the inner lost core to the corresponding outer core proximate the intermediate cross section and from the outer core proximate the second end to a coupled waveguide formed by at least two outer cores; at least one guided mode of light traveling from the second end toward the first end travels from the coupled waveguide formed by at least two outer cores to the outer core proximate the intermediate cross section and from the outer core to the corresponding inner lost core proximate the first end; the common single coupler housing structure has an outer cross-sectional shape including a first side comprised of one or more curved portions, and the second side is spaced apart from the plurality of longitudinal waveguides such that guiding properties are maintained and not disturbed; Example III 1. An optical coupler array for optically coupling a plurality of optical fibers to an optical device, comprising: an elongated optical element having a first end operable to optically couple with said plurality of optical fibers, an intermediate cross section, and a second end operable to optically couple with said optical device; and a plurality of longitudinal waveguides, each of said plurality of longitudinal waveguides being spaced apart from one another at a predetermined distance, each of said plurality of longitudinal waveguides having a capacity for at least one optical mode of a predetermined mode field profile, each of said plurality of longitudinal waveguides being embedded in said common unitary housing structure proximate said second end, and at least one of said plurality of longitudinal waveguides being disposed adjacent said second end. At least one of the at least one missing core waveguides comprises an inner missing core, an outer core, and an outer cladding, the inner missing core having a first refractive index (Nl), a first inner core size (ICS-1) at the first end, an intermediate inner core size (ICS-IN) at the intermediate cross section, and a second inner core size (ICS-2) at the second end, the outer core longitudinally surrounding the inner core and having a second refractive index (N-2), a first outer core size (OCS-1) at the first end, an intermediate inner core size (ICS-IN) at the intermediate cross section, and a second inner core size (ICS-2) at the second end. the common unitary coupler housing structure comprises a transversely continuous medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, the first, second, third and fourth refractive indices (N1, N-2, N-3, N-4, N-5, N-6, N-7, N-8, N-9, N-10, N-11, N-12, N-13, N-14, N-15, N-16, N-17, N-18, N-19, N-20, N-21, N-22, N-23, N-24, N-25, N-26, N-27, N-28, N-30, N-31, N-32, N-33, N-34, N-35, N-36, N-37, N-38, N-40, N-41, N-42, N-43, N-44, N-45, N-46, N-47, N-58, N-69, N-70, N-81, N-92, N-103, N-114, N-125, N-135, N-146, N-157, N-168, N-179, N-204, N-215, N-225, N-236, N-379, N-44, N-45, N-59, N-61, N-72, N-83, ​​N-94, N-105, N-116, N-126, N-137, N-145, N-158, N-169, N-179, N-185, N-196, N-197, N-198, N-199, N-204, N-2199, N-225, N-236, N-379, N-4 a predetermined relative size relationship between the first and second longitudinal waveguides (N-3 and N-4) comprising the following size relationship (N-1>N-2>N-3), a total volume of the medium in the common single coupler housing structure is greater than a total volume of all of the lost core waveguide inner cores and the outer cores confined within the common single coupler housing structure, the first inner lost core size (ICS-1), the first outer core size (OCS-1), and the predetermined spacing between the plurality of longitudinal waveguides are adjusted to a predetermined reduced profile along the first end of the optical element, and the second end, the intermediate inner missing core size (ICS-IN) is selected to be insufficient to guide light therethrough, the intermediate outer core size (OCS-IN) is selected to be sufficient to guide at least one optical mode, and the second outer core size (OCS-2) is selected to be insufficient to guide light therethrough, proceeding from the first end towards the second end. light escapes from the inner lost core to the corresponding outer core proximate the intermediate cross section and from the outer core to a coupled waveguide formed by at least two adjacent outer cores proximate the second end, at least one guided mode of light traveling from the second end towards the first end travels from the coupled waveguide formed by the at least two adjacent outer cores to the outer core proximate the intermediate cross section and from the outer core to the corresponding inner lost core proximate the first end, and the common single coupler housing structure comprises:The waveguide has an outer cross-sectional shape with a first side having one or more curved portions and a second side having one or more flat portions, the second side being spaced apart from the plurality of longitudinal waveguides such that the waveguide properties are maintained and not disturbed. 2. The optical coupler array of example 1, wherein the outer cross-sectional shape is a D-shape. 3. The optical coupler array of example 1 or 2, further comprising an alignment carrier including one or more flats configured to be coupled to the second side so as to extend laterally beyond the second side on at least one side. 4. The optical coupler array of example 3, wherein the alignment carrier extends laterally beyond the second side on both sides. 5. An optical coupler array as described in any of the preceding examples, wherein the first side is configured to be positioned within the V-groove so that the first side contacts a wall of the V-groove. 6. The optical coupler array of example 5, wherein the alignment carrier is disposed on an upper surface of the V-groove or configured to be disposed on an upper surface of the V-groove. 7. The optical coupler array according to any one of Examples 3 to 6, wherein the alignment carrier comprises a carrier plate. 8. An optical coupler for optically coupling at least one optical fiber waveguide to at least one waveguide of an optical device, comprising: an elongated optical element; a common single coupler housing structure; and at least one longitudinal waveguide, the elongated optical element having a first end operable to optically couple with the at least one optical fiber waveguide and a second end operable to optically couple with the optical device, the at least one longitudinal waveguide having a capacity for at least one optical mode, each embedded in the common single housing structure, the common single coupler housing structure having an outer cross-sectional shape with a first side and a second side, the common single coupler housing structure including one or more portions complementary to the second side of the housing structure, the alignment carrier extending laterally beyond the second side on at least one side. The connector is configured to be coupled to the connector. 9. An optical coupler as described in Example 8, wherein the first side of the housing structure comprises one or more curved portions, the second side of the housing structure comprises one or more flat portions, and the one or more portions of the alignment carrier comprise one or more flat portions. 10. The optical coupler of any one of examples 8 to 9, wherein the outer cross-sectional shape is D-shaped. 11. The optical coupler of example 8, wherein the outer cross-sectional shape is a polygon. 12. The optical coupler of any of Examples 8-11, wherein the alignment carrier extends laterally beyond the second side on both sides. 13. The optical coupler of any of Examples 8 to 12, wherein the first side is configured to be positioned within the V-groove such that the first side contacts a wall of the V-groove. 14. The optical coupler of example 13, wherein the alignment carrier is disposed on an upper surface of the V-groove or configured to be disposed on an upper surface of the V-groove. 15. The optical coupler according to any one of Examples 8 to 14, wherein the alignment carrier is made of a carrier plate. 16. An optical coupler described in any of Examples 13 to 15, wherein the V-groove is part of the optical device or a carrier of the optical device, and the position of the V-groove is registered relative to the position of the at least one waveguide of the optical device. 17. The optical coupler of Example 16, wherein the position of the V-groove is registered relative to the position of the at least one waveguide of the optical device such that the at least one waveguide of the optical device is aligned with the at least one longitudinal waveguide with an optical coupling efficiency between 50% and 100%. 18. The optical coupler of example 17, wherein the optical coupling efficiency is 80% or more and 100% or less. 19. The optical coupler of Example 8, wherein the second side of the housing structure comprises one or more curved portions and the one or more portions of the alignment carrier comprise a V-groove. 20. The optical coupler of Example 8, wherein the second side of the housing structure is comprised of one or more curved portions, and the one or more portions of the alignment carrier are comprised of one or more curved portions. 21. An optical coupler described in any of Examples 8 to 20, wherein a first end of the elongated optical element is operable to optically couple to a multicore fiber operable to optically couple to the at least one optical fiber waveguide. 22. The optical coupler of Example 21, wherein the multicore fiber is operable to optically couple with a second optical coupler operable to optically couple with the at least one optical fiber waveguide. 23. The optical coupler of any of Examples 8 to 22, wherein a first end of the elongated optical element is optically coupled to a multicore fiber operable to optically couple to the at least one optical fiber waveguide. 24. The optical coupler of example 23, wherein the multicore fiber is optically coupled to a second optical coupler operable to optically couple to the at least one optical fiber waveguide. Example IV 1. A multi-channel optical coupler array for optically coupling a plurality of optical fibers to an optical device, comprising: an elongated optical element; a common unitary coupler housing structure; and a plurality of longitudinal waveguides, the elongated optical element having a first end operable to optically couple with the plurality of optical fibers and a second end operable to optically couple with the optical device, the plurality of longitudinal waveguides each spaced at a predetermined distance from one another, each having capacity for at least one optical mode of a predetermined mode field profile, each embedded in the common unitary housing structure proximate the second end, at least one of the plurality of longitudinal waveguides being a lost core waveguide, each of the at least one lost core waveguide comprising an inner lost core, an outer core, and an outer cladding, the inner lost core having a first refractive index (Nl) and a first inner core size (IC) at the first end. the outer core has a second refractive index (N-2), a first outer core size (OCS-I) at the first end and a second outer core size (OCS-2) at the second end; the outer cladding longitudinally surrounds the outer core, has a third refractive index (N-3), a first cladding size at the first end and a second cladding size at the second end; the single coupler housing structure comprises a laterally continuous medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, the predetermined relative magnitude relationship between the first, second, third and fourth refractive indices (Nl, N-2, N-3 and N-4, respectively) being the following magnitude relationship (N-1>N-2>N-3), and the total volume of the medium or the common single coupler housing structure is less than the total volume or the outer core of all the lost core waveguides inner cores and the outer cores confined within the common single coupler housing structure. Largely, the first inner missing core size (ICS-I), the first outer core size (OCS-I), and the predetermined spacing between the plurality of longitudinal waveguides are simultaneously and gradually reduced according to a predetermined decreasing profile between the first end and the second end along the optical element until the second inner missing core size (ICS-2) and the second outer core size (OCS-2) are reached, the second inner missing core size (ICS-2) being selected to be insufficient to guide light, and the second outer core size (OCS-2) being selected to be insufficient to guide light, is selected to be sufficient to guide at least one optical mode, light traveling from the first end to the second end escapes from the inner lost core to the corresponding outer core proximate the second end, and light traveling from the second end to the first end travels from the outer core to the corresponding inner lost core proximate the first end, and the common single coupler housing structure proximate the first end has one of the following cross-sectional configurations: a ring and a continuous structure, the ring surrounding the plurality of longitudinal waveguides, and the continuous structure having a plurality of laterally continuous holes;At least one of the holes includes at least one of the longitudinal waveguides. 2. A multi-channel optical coupler array comprising: an elongated optical element; a coupler housing structure; and a plurality of longitudinal waveguides, the elongated optical element having a first end and a second end, the first end and the second end operable to optically couple with a plurality of optical fibers, optical devices, or combinations thereof, the plurality of longitudinal waveguides being a plurality of longitudinal waveguides arranged relative to one another, each having capacity for at least one optical mode, the housing structure being configured to couple the elongated optical element to a plurality of longitudinal waveguides, the plurality of longitudinal waveguides being ... embedded in said plurality of longitudinal waveguides, said plurality of longitudinal waveguides comprising at least one lost core waveguide, each of said at least one lost core waveguide comprising an inner lost core, an outer core and an outer cladding, said inner lost core having a first refractive index (Nl) and having an inner core size, said outer core longitudinally surrounding said inner core, having a second refractive index (N-2) and having an outer core size, said outer cladding longitudinally surrounding said outer core, having a third refractive index (N-3) and having a cladding size, a coupling housing structure comprising a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, where N-1>N-2>N-3; a size of the inner core, a size of the outer core, and a spacing between the plurality of longitudinal waveguides decreasing along the optical element from the first end to the second end, such that at the second end, a size of the inner core is insufficient to guide light therethrough and a size of the outer core is sufficient to guide at least one optical mode; and the coupling housing structure proximate the first end has one of the following cross-sectional configurations: a ring; and a structure having a plurality of holes, the ring being a ring surrounding the plurality of longitudinal waveguides, with a gap between the ring and the plurality of longitudinal waveguides, the structure having a plurality of holes having at least one hole for at least one of the plurality of longitudinal waveguides. 3. The optical coupling of Example 2, wherein the coupler housing structure is a common single coupler housing structure. Container array. 4. An optical coupler array as described in any of the preceding examples, wherein adjacent the first end, one of the plurality of longitudinal waveguides extends outside the coupler housing structure. 5. An optical coupler array as described in any of the preceding examples, wherein adjacent the first end, one of the plurality of longitudinal waveguides is disposed within the coupler housing structure and does not extend beyond the coupler housing structure. 6. An optical coupler array as described in any of the preceding examples, wherein adjacent the first end, one of the plurality of longitudinal waveguides is disposed in an outer cross-sectional boundary region of the coupler housing structure and does not extend beyond the coupler housing structure. 7. The optical coupler array of any of Examples 2-6, wherein the medium is a laterally continuous medium. 8. The optical coupler array of any of Examples 2-7, wherein a total volume of the medium in the coupler housing structure is greater than a total volume of all inner cores and outer cores of at least one lost core waveguide confined within the coupler housing structure. 9. An optical coupler array described in any one of Examples 2 to 8, wherein the size of the inner core, the size of the outer core, and the spacing between the multiple longitudinal waveguides simultaneously decrease gradually from the first end to the second end. 10. An optical coupler array as described in any preceding example, wherein proximate the second end, the coupler array is configured with substantially no gap between the coupler housing structure and the plurality of longitudinal waveguides. 11. An optical coupler array according to any preceding example, wherein one of the cross-sectional configurations is a ring that surrounds the plurality of longitudinal waveguides. 12. The optical coupler array of example 11, wherein the plurality of longitudinal waveguides is a hexagonal arrangement. 13. The optical coupler array of any one of Examples 11-12, wherein the ring has a circular inner cross section. 14. The optical coupler array of any one of Examples 11-12, wherein the ring has a non-circular inner cross-section. 15. The optical coupler array of example 14, wherein the inner cross section is hexagonal. 16. The optical coupler array of example 14, wherein the inner cross section is D-shaped. 17. The optical coupler array of any one of Examples 11 to 16, wherein the ring has a circular outer cross section. 18. The optical coupler array of any one of Examples 11 to 16, wherein the ring has a non-circular outer cross-section. 19. The optical coupler array of example 18, wherein the outer cross section is hexagonal. 20. The optical coupler array of example 18, wherein the outer cross section is D-shaped. 21. The optical coupler array according to any one of Examples 1 to 10, wherein one of the cross-sectional configurations is a structure having a plurality of holes. 22. The optical coupler array of example 21, wherein the holes are in a hexagonal arrangement. 23. The optical coupler array of example 21, wherein the holes are a rectangular array. 24. The optical coupler array of example 21, wherein the plurality of holes are defined in an XY array. 25. The optical coupler array of any one of examples 21-24, wherein the at least one hole is made of a non-waveguide material. 26. The optical coupler array of any one of Examples 21 to 25, wherein the at least one hole has a circular cross-section. 27. The optical coupler array of any one of Examples 21-26, wherein the at least one hole has a non-circular cross-section. 28. The optical coupler array of example 27, wherein the non-circular cross section is D-shaped. 29. The optical coupler array of any of examples 21-28, wherein at least one of the holes has a different dimension than another one of the holes. 30. The optical coupler array of any of Examples 21-29, wherein at least one of the holes has a different shape than another one of the holes. 31. The optical coupler array of any one of Examples 21 to 30, wherein the holes are insulated. 32. The optical coupler array according to any one of Examples 21 to 30, wherein the portion of the holes are in communication with each other. 33. An optical coupler array according to any preceding example, wherein the at least one missing core waveguide comprises a single mode fiber. 34. An optical coupler array according to any preceding example, wherein the at least one missing core waveguide comprises a multimode fiber. 35. An optical coupler array according to any preceding example, wherein the at least one missing core waveguide is made of polarization-maintaining fiber. 36. A multi-channel optical coupler array comprising: an elongated optical element; a coupler housing structure; and a plurality of longitudinal waveguides, the elongated optical element having a first end and a second end, the first end and the second end operable to optically couple with a plurality of optical fibers, optical devices, or combinations thereof, the plurality of longitudinal waveguides disposed relative to one another, each having a capacity for at least one optical mode, and embedded in the housing structure, the plurality of longitudinal waveguides comprising at least one lost core waveguide, each of the at least one lost core waveguides comprising an inner lost core, an outer core, and an outer cladding, the inner lost core having a first refractive index (Nl) and having a size of the inner core, the outer core longitudinally surrounding the inner core, having a second refractive index (N-2) and having a size of the outer core, the outer cladding longitudinally surrounding the outer core. a cladding size of N-1>N-2>N-3, the coupler housing structure being made of a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, N-1>N-2>N-3, the size of the inner core, the size of the outer core, and the spacing between the plurality of longitudinal waveguides decreasing along the elongated optical element from the first end to the second end, at the second end, the size of the inner core is insufficient to guide light and the size of the outer core is sufficient to guide at least one optical mode, the coupler housing structure proximate the first end has a cross-sectional configuration including at least one hole, the at least one hole including at least one of the plurality of longitudinal waveguides, the hole being larger than at least one of the plurality of longitudinal waveguides such that at least one of the plurality of longitudinal waveguides is laterally movable relative to the coupler housing structure. 37. The optical coupler array of example 36, wherein the coupler housing structure comprises a common single coupler housing structure. 38. The optical coupler array of any of Examples 36-37, wherein adjacent to the first end, one of the plurality of longitudinal waveguides extends outside the coupler housing structure. 39. The optical coupler array of any of Examples 36-38, wherein adjacent to the first end, one of the plurality of longitudinal waveguides is disposed within a coupler housing structure. 40. The optical coupler array of any one of Examples 36-39, wherein the medium is a laterally continuous medium. 41. An optical coupler array described in any of Examples 36 to 40, wherein the total volume of the medium in the coupler housing structure is greater than the total volume of all inner cores and outer cores of at least one lost core waveguide confined within the coupler housing structure. 42. An optical coupler array described in any of Examples 36 to 41, wherein the size of the inner core, the size of the outer core, and the spacing between the multiple longitudinal waveguides simultaneously decrease gradually from the first end to the second end. 43. An optical coupler array as described in any of Examples 36 to 42, wherein adjacent the second end, the coupler array is configured such that there is substantially no gap between the coupler housing structure and the plurality of longitudinal waveguides. 44. The optical coupler array of any one of Examples 36 to 43, wherein the at least one hole comprises a single hole, and at least one of the plurality of vertical waveguides comprises a plurality of vertical waveguides. 45. The optical coupler array of example 44, wherein the plurality of longitudinal waveguides are in a hexagonal arrangement. 46. ​​The optical coupler array of any one of Examples 44-45, wherein the single hole has a circular cross section. 47. The optical coupler array of any one of Examples 44-45, wherein the single hole has a non-circular cross-section. 48. The optical coupler array of example 47, wherein the non-circular cross-section is hexagonal. 49. The optical coupler array of example 47, wherein the non-circular cross section is D-shaped. 50. The optical coupler array of any one of Examples 44 to 49, wherein the coupler housing structure has a circular outer cross-section. 51. The optical coupler array of any one of Examples 44 to 49, wherein the coupler housing structure has a non-circular outer cross-section. 52. The optical coupler array of example 51, wherein the outer cross section is hexagonal. 53. The optical coupler array of example 51, wherein the outer cross section is D-shaped. 54. The optical coupler array of any one of Examples 36 to 43, wherein the at least one hole comprises a plurality of holes. 55. The optical coupler array of example 54, wherein the plurality of holes are in a hexagonal arrangement. 56. The optical coupler array of example 54, wherein the plurality of holes are in a rectangular array. 57. The optical coupler array of example 54, wherein the plurality of holes are defined by an XY array. 58. The optical coupler array of any one of Examples 54-57, wherein one or more of the plurality of holes is made of a non-waveguide material. 59. The optical coupler array of any one of Examples 54-58, wherein one or more of the plurality of holes has a circular cross-section. 60. The optical coupler array of any one of Examples 54-59, wherein one or more of the plurality of holes has a non-circular cross-section. 61. The optical coupler array of example 60, wherein the non-circular cross section is D-shaped. 62. The optical coupler array of any of Examples 54-61, wherein one or more of the plurality of holes has a different dimension than another one of the holes. 63. The optical coupler array of any of Examples 54-62, wherein one or more of the plurality of holes has a different shape than another one of the holes. 64. The optical coupler array of any one of Examples 54-63, wherein the holes are insulated. 65. The optical coupler array of any one of Examples 54 to 63, wherein some of the holes are connected. 66. The optical coupler array of any one of Examples 54 to 65, wherein the at least one missing core waveguide is made of a single mode fiber. 67. The optical coupler array of any one of Examples 54 to 66, wherein the at least one missing core waveguide is made of a multimode fiber. 68. The optical coupler array of any one of Examples 54 to 67, wherein the at least one missing core waveguide is made of polarization-maintaining fiber. Example V 1. A multi-channel optical coupler array for optically coupling a plurality of optical fibers to an optical device, comprising: an elongated optical element; a common unitary coupler housing structure; and a plurality of longitudinal waveguides, the elongated optical optical element having a first end operable to optically couple with the plurality of optical fibers and a second end operable to optically couple with the optical device, the plurality of longitudinal waveguides each spaced at a predetermined distance from one another, each having capacity for at least one optical mode of a predetermined mode field profile, each embedded in the common unitary housing structure, at least one of the plurality of longitudinal waveguides being a lost core waveguide, each of the at least one lost core waveguide comprising an inner lost core, an outer core, and an outer cladding, the inner lost core having a first refractive index (Nl). the outer core longitudinally surrounds the outer core and has a second refractive index (N-2), the outer core longitudinally surrounds the inner core and has a first inner core size (ICS-I) at the first end and a second inner core size (ICS-2) at the second end, the outer cladding longitudinally surrounds the outer core and has a third refractive index (N-3), the outer cladding longitudinally surrounds the outer core and has a first cladding size at the first end and a second outer core size (OCS-I) at the second end, a second cladding size, the outer cladding and the common unitary coupler housing structure comprising a laterally continuous medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, a predetermined relative magnitude relationship between the first, second, third and fourth refractive indices (Nl, N-2, N-3 and N-4, respectively) comprising the following magnitude relationship (N-1>N-2>N-3), and a total volume of the medium or the common unitary coupler housing structure is less than or equal to the total volume of all the missing core waveguides, inner core ... and a total volume of the outer core or greater than the outer core, the first inner missing core size (ICS-I), the first outer core size (OCS-I), and the predetermined spacing between the plurality of longitudinal waveguides are simultaneously and gradually reduced according to a predetermined decreasing profile between the first end and the second end along the optical element until the second inner missing core size (ICS-2) and the second outer core size (OCS-2) are reached, and the second inner missing core size (ICS-2) is selected such that it is insufficient to guide light. a second outer core size (OCS-1) selected to be sufficient to guide at least one optical mode, light from the first end toward the second end escaping from the inner lost core to the corresponding outer core proximate the second end, and light from the second end toward the first end traveling from the outer core to the corresponding inner lost core proximate the first end, and the common single coupler housing structure proximate the first end having one of the following cross-sectional configurations: a ring and a continuous structure having a plurality of holes, at least one hole, and the ring isThe plurality of longitudinal waveguides are surrounded, and one of the at least one hole includes at least one of the plurality of longitudinal waveguides. 2. A multi-channel optical coupler array for optically coupling a plurality of optical fibers to an optical device, comprising: an elongated optical element; a coupler housing; and a plurality of longitudinal waveguides, the elongated optical element having a first end operable to optically couple with the plurality of optical fibers and a second end operable to optically couple with the optical device, the plurality of longitudinal waveguides each spaced apart from one another, each having capacity for at least one optical mode, and each attached to the housing structure. embedded in the optical waveguide, at least one of the plurality of longitudinal waveguides is a missing core waveguide, each of the at least one missing core waveguides comprising an inner missing core, an outer core, and an outer cladding, the inner missing core having a first refractive index (Nl) and a first inner core size (ICS-I) at the first end and a second inner core size (ICS-2) at the second end, the outer core longitudinally surrounding the inner core and having a second refractive index (N-2) and a first outer core size (ICS-3) at the first end, (OCS-I) and a second outer core size (OCS-2) at the second end, the outer cladding longitudinally surrounds the outer core and has a third refractive index (N-3), a first cladding size at the first end and a second cladding size at the second end, the coupler housing structure comprises a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, the first, second, third and fourth refractive indices (Nl, N-2, N-3 and N-4, respectively). ICS-I), the first outer core size (OCS-I), and the spacing between the plurality of longitudinal waveguides decrease along the optical element between the first end and the second end until reaching the second inner missing core size (ICS-2) and the second outer core size (OCS-2), and the second inner missing core size (ICS-2) is insufficient to guide light therethrough. and the second outer core size (OCS-2) is sufficient to guide at least one optical mode, light proceeding from the first end to the second end escapes from the inner lost core to the corresponding outer core proximate the second end, and light proceeding from the second end to the first end travels from the outer core to the corresponding inner lost core proximate the first end, and the coupler housing structure proximate the first end has a cross-sectional shape of either a ring surrounding the plurality of longitudinal waveguides or a structure having a plurality of holes, at least one hole of the plurality of holes comprising at least one of the plurality of longitudinal waveguides. Example VI 1. A multi-channel optical coupler array for optically coupling a plurality of optical fibers to an optical device, comprising: an elongated optical element; a common unitary coupler housing structure; and a plurality of longitudinal waveguides, the elongated optical element having a first end operable to optically couple with the plurality of optical fibers, an intermediate cross section, and a second end operable to optically couple with the optical device, the plurality of longitudinal waveguides each spaced apart from one another by a predetermined distance, each having capacity for at least one optical mode of a predetermined mode field profile. and each of the plurality of longitudinal waveguides is embedded in the common unitary housing structure adjacent the second end, at least one of the plurality of longitudinal waveguides is a missing core waveguide, each of the at least one missing core waveguide comprises an inner missing core, an outer core, and an outer cladding, the inner missing core having a first refractive index (Nl), a first inner core size (ICS-I) at the first end, an intermediate inner core size (ICS-IN) at the intermediate cross section, and a second inner core size (ICS-2) at the second end, the outer core being a first refractive index (Nl) of the inner core, a first outer core size (OCS-I) at the first end, an intermediate outer core size (OCS-IN) at the intermediate cross section, and a second outer core size (OCS-2) at the second end; an outer core and a second cladding having a second refractive index (N-2), longitudinally surrounding the outer core and the outer core, a third refractive index (N-3), a first cladding size at the first end, and a second cladding size at the second end; and the common single coupler housing structure is configured to couple the plurality of longitudinal waveguides to the plurality of longitudinal waveguides. a laterally continuous medium having a fourth refractive index (N-4) surrounding said first, second, third and fourth refractive indices (Nl, N-2, N-3 and N-4, respectively), a predetermined relative magnitude relationship between said first, second, third and fourth refractive indices (Nl, N-2, N-3 and N-4, respectively) is the following magnitude relationship (N-1>N-2>N-3), a total volume of said medium or said common single coupler housing structure is greater than a total volume or said outer cores of all said lost core waveguide inner cores and said outer cores confined within said common single coupler housing structure, said first inner lost core size (ICS-I),The first outer core size (OCS-I) and the predetermined spacing between the plurality of longitudinal waveguides are simultaneously and gradually reduced according to a predetermined reduction profile between the first end and the second end along the optical element until the second inner missing core size (ICS-2) and the second outer core size (OCS-2) are reached, the intermediate inner missing core size (ICSIN) being selected to be insufficient to guide light therethrough, the intermediate outer core size (OCS-IN) being selected to be sufficient to guide at least one optical mode, and the second outer core size (OCS-2) being , selected to be insufficient to guide light therethrough, light traveling from the first end toward the second end escaping from the inner missing core to the corresponding outer core proximate the intermediate cross section and from the outer core to a coupled waveguide formed by at least two adjacent outer cores proximate the second end, at least one guided mode of light traveling from the second end toward the first end traveling from a coupled waveguide formed by at least two adjacent outer cores to the outer core proximate the intermediate cross section and from the outer core to the corresponding inner missing core proximate the first end, The common single coupler housing structure proximate the first end has a cross-sectional configuration of a laterally continuous structure having at least one hole, the at least one hole containing at least one of the plurality of longitudinal waveguides, and the coupler housing structure and the plurality of longitudinal waveguides are connected to each other. A gap is formed between at least one of the longitudinal waveguides. 2. A multi-channel optical coupler array comprising an elongated optical element, a coupler housing structure, and a plurality of longitudinal waveguides, the elongated optical element having a first end, a mid-section, and a second end, the plurality of longitudinal waveguides each spaced apart from one another, each having a capacity for at least one optical mode, each disposed within the housing structure, at least one of the plurality of longitudinal waveguides being a lost core waveguide, each of the at least one lost core waveguide comprising an inner lost core, an outer core, and an outer cladding. the inner missing core has a first refractive index (Nl), a first inner core size (ICS-I) at the first end, an intermediate inner core size (ICS-IN) at the intermediate cross-section, and a second inner core size (ICS-2) at the second end; the outer core longitudinally surrounds the inner core and has a second refractive index (N-2), a first outer core size (OCS-I) at the first end, an intermediate outer core size (OCS-IN) at the intermediate cross-section, and a second outer core size (OCS-2) at the second end. the outer cladding longitudinally surrounds the outer core and has a third refractive index (N-3), a first cladding size at the first end and a second cladding size at the second end; the coupler housing structure is comprised of a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, and a relative magnitude relationship between the first, second, third and fourth refractive indices (Nl, N-2, N-3 and N-4, respectively) is the following magnitude relationship: N-1>N-2>N-3; an inner missing core size (ICS-I), the first outer core size (OCS-I), and the spacing between the plurality of longitudinal waveguides decrease between the first end and the second end along the optical element, the intermediate inner missing core size (ICSIN) is insufficient to guide light thereto, the intermediate outer core size (OCS-IN) is sufficient to guide at least one optical mode, and the second outer core size (OCS-2) is insufficient to guide light thereto, and light traveling from the first end towards the second end isAt least one guided mode of light escaping from the inner lost core to the corresponding outer core proximate the intermediate cross section, and from the outer core to a coupled waveguide formed by at least two adjacent outer cores proximate the second end, traveling from the second end toward the first end, travels from the coupled waveguide formed by the at least two adjacent outer cores to the outer core proximate the intermediate cross section, and from the outer core to the corresponding inner lost core proximate the first end. [Brief description of the drawings]

[0011] In the drawings, like reference characters indicate corresponding or similar elements throughout the various views.

[0012] [Figure 1A] FIG. 1A is a schematic diagram of a side view of a first exemplary embodiment of an optical fiber coupler array comprising at least one dissipative core waveguide (VC waveguide), illustratively illustrated therein as a single VC waveguide, and at least one Non-VC waveguide, illustratively illustrated therein as a plurality of Non-VC waveguides, illustratively arranged symmetrically adjacent to the single VC waveguide. [Figure 1B] FIG. 1B is a schematic diagram of a side view of a second exemplary embodiment of an optical fiber coupler array having at least one lost core waveguide (VC waveguide) illustratively illustrated therein as a single VC waveguide and at least one Non-VC waveguide illustratively illustrated therein as a single Non-VC waveguide, the optical fiber coupler array being arranged in parallel proximity to an exemplary single VC waveguide, with a portion of the optical fiber coupler array configured to configure a higher inter-channel spacing magnitude at its second (smaller) end than the corresponding inter-channel spacing magnitude at the second end of the optical fiber coupler array of FIG. 1A. [Figure 1C]FIG. 1C is a schematic diagram of a side view of a third exemplary embodiment of an optical fiber coupler array comprising a plurality of VC waveguides and a plurality of Non-VC waveguides arranged asymmetrically relative to one another in a longitudinal direction, at least some of the plurality of Non-VC waveguides having different types and / or different characteristics. [Figure 1D] FIG. 1D is a schematic diagram of a side view of a fourth exemplary embodiment of an optical fiber coupler array configured for fan-in and fan-out connections and consisting of a pair of optical fiber coupler components having a multi-core optical fiber element connected between the second (smaller sized) ends of the two optical fiber coupler components. [Figure 2A] FIG. 2A is a schematic diagram of a side view of a fifth exemplary embodiment of an optical fiber coupler array comprising a plurality of longitudinally adjacent VC waveguides at least partially embedded within a single common housing structure, each of the plurality of VC waveguides being connected to a corresponding elongated optical device (such as an optical fiber) at a specific first connection location, at least a portion of which extends outside the single common housing structure by a predetermined length, and each specific first connection location being disposed within the single common housing structure. [Figure 2B] FIG. 2B is a schematic diagram of a side view of a sixth exemplary embodiment of an optical fiber coupler array comprising a plurality of longitudinally adjacent VC waveguides at least partially embedded within a single common housing structure, each of the plurality of VC waveguides being connected to a corresponding elongated optical device (such as an optical fiber) to which it is spliced ​​at a specific second splice location, at least a portion of which extends outside the single common housing structure by a predetermined length, and each specific second connection location being disposed in an outer cross-sectional boundary area of ​​the single common housing structure. [Figure 2C]FIG. 2C is a schematic diagram of a side view of a seventh exemplary embodiment of an optical fiber coupler array comprising a plurality of longitudinally adjacent VC waveguides at least partially embedded within a single common housing structure, each of the plurality of VC waveguides being connected to a corresponding elongated optical device (such as an optical fiber) at a specific third connection location, at least a portion of which extends outside the single common housing structure by a predetermined length, and each specific third connection location being disposed outside the single common housing structure. [Figure 2D] FIG. 2D is a schematic diagram of a side view of an alternative embodiment of an optical fiber coupler array, comprising multiple longitudinally adjacent VC waveguides at least partially embedded within a single common housing structure, configured at its second end to increase, improve, and / or optimize optical coupling to a free-space based optical device, such as a lens followed by other optical components, as shown in FIG. 2D; or (2) a device, such as a coreless glass element, that can be fusion spliced ​​to the end of the second coupler, which can function as an end cup for power density reorganization at the glass-air interface or a Talbot mirror for phase locking of the coupler's waveguides in a Talbot cavity geometry. [Figure 3A] 3A is a schematic diagram of a cross-sectional view of a first alternative embodiment of the optical fiber coupler array of FIGS. 1D-2D, said 1D-2D, optionally including fiducial elements operable to provide visual identification of waveguide placement / characteristics (such as alignment), which may be located in one of several categories of cross-sectional areas. [Figure 3B] FIG. 3B is a schematic diagram of a cross-sectional view of a first alternative embodiment of the optical fiber coupler array of FIG. 1A, in which at least one VC waveguide, illustratively illustrated therein as a single VC waveguide, is disposed along a central longitudinal axis of a single common housing structure and is surrounded by a plurality of parallel proximal symmetrically disposed Non-VC waveguides. [Figure 3C]FIG. 3C is a schematic diagram of a cross-sectional view of a first alternative embodiment of the optical fiber coupler array of FIG. 3B above, in which the volume of a single common housing structure medium surrounding all of the waveguide sections embedded therein exceeds the combined volume of the inner and outer cores of the VC waveguide sections embedded within the single common housing structure. [Figure 3D] FIG. 3D is a schematic diagram of a cross-sectional view of a second alternative embodiment of the optical fiber coupler array of FIG. 3B above, in which at least one VC waveguide arranged along a central longitudinal axis of a single common housing structure is comprised of multiple VC waveguides, and the volume of the medium of the single common housing structure surrounding all of the sections of the waveguides embedded therein exceeds the combined volume of the inner cores and outer cores of the sections of the multiple VC waveguides embedded within the single common housing structure. [Figure 3E] FIG. 3E is a schematic illustration of a cross-sectional view of a first alternative embodiment of the optical fiber coupler array of FIG. 3D, further including a central waveguide channel operable to provide an optical pump function therethrough. [Figure 3F] FIG. 3F is a schematic diagram of a cross-sectional view of a second alternative embodiment of the optical fiber coupler array of FIG. 3D, in which the VC waveguides disposed along the central longitudinal axis of the single common housing structure are of a different type and / or are of different properties than the remaining multiple VC waveguides, and if selected to be comprised of an enlarged inner core, may be advantageously utilized to increase or optimize optical coupling to different types of optical pump channels of various optical devices. [Figure 3G] Figure 3G is a schematic diagram of a cross-sectional view of a third alternative embodiment of the optical fiber coupler array of Figure 3B, in which at least one VC waveguide, illustratively illustrated therein as a single VC waveguide, is arranged as a side channel offset from the central longitudinal axis of a single common housing structure, such that this embodiment of the optical fiber coupler array can be readily used as a fiber optical amplifier and / or laser when spliced ​​to a double clad optical fiber having a non-concentric core for improved optical pump efficiency. [Figure 3H]FIG. 3H is a schematic diagram of a cross-sectional view of a first alternative embodiment of the optical fiber coupler array of FIG. 3G above, in which at least one VC waveguide, illustrated therein as a side channel off-center positioned single VC waveguide by way of example, constitutes polarization maintaining properties and has its polarization axis aligned with respect to its lateral off-center position. [Figure 3I] FIG. 3I is a schematic diagram of a cross-sectional view of a fourth alternative embodiment of the optical fiber coupler array of FIG. 3B above, in which a single centrally located VC waveguide and multiple Non-VC waveguides each have polarization-maintaining properties (shown only by way of example as induced by a rod-shaped stress member and can easily be alternately induced by various other stresses or equivalent designs) and corresponding polarization axes, all of which are aligned with each other. [Figure 3J] 3J is a schematic diagram of a cross-sectional view of a first alternative embodiment of the optical fiber coupler array of FIG. 3I. Any polarization maintaining properties of the waveguides are solely due to the non-circular cross-sectional shape of the core (or outer core in the case of VC waveguides) of each waveguide, shown by way of example only as being at least partially elliptical, and optionally representative of a particular cross-sectional geometric arrangement of the waveguides of the optical coupler array, including at least one waveguide placement indicating element disposed in an outer region of the single common housing structure, the waveguide placement indicating element operable to facilitate passive alignment of the second end of the optical coupler array to at least one optical device such that the particular cross-sectional geometric waveguide arrangement may be readily identified from at least one of visual and physical inspection of the single common coupler housing structure. [Figure 3K] FIG. 3K is a schematic diagram of a cross-sectional view of a fifth alternative embodiment of the optical fiber coupler array of FIG. 3B above, in which a single centrally located VC waveguide includes polarization-maintaining properties (shown by way of example only as induced by a rod-shaped stress member, and which may readily and alternately be induced by various other stresses or equivalent designs) and corresponding polarization axis, and optionally includes multiple optional waveguide placement indicating elements of the same or different types, as described in connection with FIG. 3J. [Figure 3L]FIG. 3L is a schematic diagram of a cross-sectional view of a second alternative embodiment of the optical fiber coupler array of FIG. 3I above, in which the single common housing structure is comprised of a cross-section having a non-circular geometric shape (shown as a hexagon by way of example), and the polarization axes of the waveguides are aligned with each other and with the geometric shape of the single common housing structure cross-section, optionally further comprising a waveguide placement indicating element as described in connection with FIG. 3J. [Figure 4] FIG. 4 is a schematic isometric view showing an example of a connection of the second end (i.e., “tip”) of the optical fiber coupler array in a proximal open-air optical coupling alignment configuration to multiple vertical coupling elements of an optical device, which can be easily transitioned to a butt coupling configuration with full physical contact between the optical fiber coupler array second end and the vertical coupling elements. [Diagram 5] FIG. 5 is a schematic isometric view showing an example connection of a second end (i.e., "tip") of an optical fiber coupler array connected to multiple end coupling elements of an optical device in a butt coupling configuration, which can be easily shifted to one of several alternative coupling configurations, including a proximal open-air optical coupling alignment configuration, and / or an angled alignment coupling configuration. [Figure 6] FIG. 6 is a schematic diagram of a cross-sectional view of a previously known optical fiber coupler having various drawbacks and shortcomings that are readily overcome by the various embodiments of the optical fiber coupler arrays of FIGS. 1A-5. [Figure 7] FIG. 7 is a schematic diagram in various views of a flexible pitch reduced fiber optic coupler array (PROFA). [Figure 8] 8 is a schematic diagram of a cross-sectional view of an example housing structure configuration proximate a first end of an optocoupler array, the cross-sectional view being perpendicular to the longitudinal direction or length of the optocoupler array. [Figure 9] FIG. 9 is a schematic diagram of a cross-sectional view of another example configuration of a housing structure in a location proximate to a first end of an optical coupler array. [Figure 10] FIG. 10 is a schematic diagram of an additional exemplary optical combiner array in various views. [Figure 11]FIG. 11 is a schematic diagram of an additional exemplary optical combiner array in various views. [Figure 12A] 12A is a schematic diagram of an exemplary optical coupler array and an optical device. The exemplary coupler array can be configured to provide passive alignment with the optical device; [Figure 12B] FIG. 12B is a schematic diagram of a coupling between the exemplary optical coupler array and an optical device shown in FIG. 12A. [Figure 12C] FIG. 12C is a schematic diagram of an exemplary mechanical feature in a V-groove of the optical device shown in FIG. 12A. [Figure 13] FIG. 13 shows a schematic example of a multi-fiber array disposed above an optical device. [Figure 14] FIG. 14 shows a schematic example of a multi-fiber array disposed above an optical device. [Figure 15] FIG. 15 shows a schematic example of a multi-fiber array disposed above an optical device. [Figure 16] FIG. 16 is an example of a refractive index profile of an missing core waveguide that can be used in a multi-channel optical coupler array. [Figure 17] FIG. 17 is an example of a modified refractive index profile of a missing core waveguide that can be used in a multi-channel optical coupler array. [Figure 18] FIG. 18 is an example of a modified refractive index profile of a missing core waveguide that can be used in a multi-channel optical coupler array. [Figure 19] FIG. 19 is an example of a modified refractive index profile of an missing core waveguide that can be used in a multi-channel optical coupler array. [Figure 20] FIG. 20 is an example of a modified refractive index profile of a missing core waveguide that can be used in a multi-channel optical coupler array. [Figure 21] 21 is a schematic diagram of a cross-sectional view illustrating an example configuration of an empty housing structure proximate a first end of an optical coupler array, the cross-section being perpendicular to the longitudinal direction or length of the optical coupler array. [Figure 22]22 is a schematic diagram of a cross-sectional view of an example housing structure having at least one lost core waveguide located proximate a first end of an optical coupler array, the cross-sectional view being perpendicular to the longitudinal direction or length of the optical coupler array. [Figure 23] 23 is a schematic diagram of a cross-sectional view of another example configuration of an empty housing structure proximate a first end of an optical coupler array, the cross-sectional view being perpendicular to the longitudinal direction or length of the optical coupler array. [Figure 24] 24 is a schematic diagram of a cross-sectional view of another example configuration of a housing structure having at least one lost core waveguide disposed adjacent a first end of the optical coupler array, the cross-sectional view being perpendicular to the longitudinal direction or length of the optical coupler array. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Various embodiments include a multi-channel optical coupler array for providing low-loss coupling between a set of individual isolated optical fibers and an optical device having at least one optical channel, allowing for large separation between the individual optical fibers and small separation between the optical channels at the device interface. In some embodiments, the coupler array can have an increased taper draw ratio (e.g., an increase in the ratio of the spacing at the undrawn end divided by the spacing at the drawn tapered end), which can increase the reduction in channel spacing between the undrawn and drawn ends of the coupler array. In some embodiments, various embodiments can be useful for coupler arrays having a relatively large draw ratio. In some embodiments, various embodiments are useful for coupler arrays having a relatively small draw ratio.

[0014] Photonic integrated circuits (PICs) are packaged using optical and electronic interfaces as well as thermal-mechanical management. One major challenge in PIC packaging, both technical and economic, involves fiber coupling from the optical fiber infrastructure to an individual optical waveguide, or multiple waveguides, of a particular PIC. Various embodiments described herein relate to optical coupler arrays configured to couple light from one or more optical fibers into a waveguide at the end of a PIC. In some implementations, the optical coupler arrays may be configured to passively align with one or more waveguides of the PIC.

[0015] In some cases, improved cross-sectional (or lateral) positioning of the waveguides is desirable in many multi-channel optical coupler arrays. In the present disclosure, some embodiments of the housing structure (e.g., a possibly common single coupler housing structure) can enable self-aligned placement of the waveguides at a location proximate to a first end (e.g., a circular (as shown in FIG. 8) or hexagonal close-contact placement in a housing structure having a hexagonal inner cross-section) and improved (possibly exact or near-exact) cross-sectional positioning of the waveguides at the second end.

[0016] In a variety of applications, including optical communications and sensing, photonic integrated circuit (PIC) packages with low vertical (perpendicular to the PIC plane) profiles may also be desirable, which is easily achievable with edge couplers but may require significant vertical length with surface couplers.

[0017] It would therefore be advantageous to provide various embodiments of pitch reduced optical fiber array (PROFA) based flexible optical fiber array components that can be configured and potentially optimized to maintain all channels discrete with sufficiently low crosstalk while providing sufficient flexibility to accommodate low profile packaging. It would further be desirable to provide a PROFA based flexible optical fiber array component that is comprised of a flexible portion that provides mechanical isolation of the "PROFA-PIC interface" from the remainder of the PROFA, resulting in increased stability with respect to environmental variations including temperature changes and mechanical shock and vibration. It would further be desirable to provide a PROFA based flexible optical fiber array that is comprised of multiple coupler arrays, each with multiple optical channels.

[0018] Certain embodiments are directed to optical fiber coupler arrays that can provide a highly accurate, easy to match, low-loss, high coupling coefficient interface between a plurality of optical fibers (or other optical devices) having a first inter-channel spacing and an optical device having a plurality of waveguide interfaces having a second, smaller inter-channel spacing. Advantageously, in various embodiments, each of the large size end and the small size end of the optical fiber coupler array can be configured to have correspondingly different (i.e., large vs. small) inter-channel spacings, where the inter-channel spacings of each of the large and small ends of the optical coupler array can be easily matched to the corresponding respective first inter-channel spacings of the plurality of optical fibers at the large optical coupler array end and the second inter-channel spacings of the plurality of waveguide interfaces of the optical device at the small optical coupler array end.

[0019] In various of its embodiments, the optical coupler array includes a plurality of waveguides (at least one of which may optionally be polarization maintaining) comprised of at least one gradually decreasing "vanishing core fiber" at least partially embedded within a common housing structure. Alternatively, in various additional of its embodiments, the coupler array may be configured for use with at least one of an optical fiber amplifier and an optical fiber laser.

[0020] Each of the various embodiments of the optical coupler array advantageously comprises at least one "vanishing core" (VC) fiber waveguide, for example, as described below in connection with VC waveguide 30A of optical coupler array 10A of FIG. 1A.

[0021] It should also be noted that the term "optical device" as used generally herein applies to virtually any single or multi-channel optical device or any type of optical fiber, including but not limited to standard / conventional optical fibers. For example, optical devices to which a coupler array may be advantageously coupled may include, but are not limited to, one or more of the following: Free-space based optical devices, an optical circuit having at least one input / output edge-coupled port; an optical circuit having at least one optical port formed of a vertical coupling element; Multimode (MM) optical fiber, Double-clad optical fiber, Multi-core (MC) optical fiber, Large mode area (LMA) fiber, Double-clad multi-core optical fiber, Standard / conventional optical fiber, Custom fiber optics, and / or Additional optical combiner arrays

[0022] Additionally, while the term "fusion splice" is utilized in the various descriptions of exemplary embodiments of coupler arrays provided below with respect to the interconnections between the various optical coupler array components and between the various optical coupler array components and the optical device(s), it should be noted that any other form of waveguide or other coupler array component connection technique or methodology may be readily selected and utilized, including but not limited to mechanical connections, as a matter of design choice or need without departing from the spirit of the present invention.

[0023] Referring now to FIG. 1A, a first exemplary embodiment of an optical fiber coupler array is shown. 1A, a pair of Non-VC waveguides 32A-1, 32A-2 are shown symmetrically adjacent to one side of the exemplary single VC waveguide 30A, and the section of the VC waveguide 30A located between positions B and D in FIG. 1A is embedded in the common housing structure 14A.

[0024] Before describing the coupler array 10A and its components in more detail, it is useful to provide a detailed overview of the VC waveguide 30A that is advantageously utilized in each of the various embodiments of the coupler arrays of FIGS. 1A-5, both exemplary and alternative embodiments.

[0025] The VC waveguide 30A has a larger end (proximal to position B shown in FIG. 1A) and a tapered smaller end (proximal to position C shown in FIG. 1A), and comprises an inner core 20A (made of a material with an effective refractive index of N-1), an outer core 22A (made of a material with an effective refractive index of N-2 smaller than the material of N-1), and a cladding 24A (made of a material with an effective refractive index of N-3 smaller than the material of N-2).

[0026] Advantageously, the outer core 22A functions as an effective cladding at the large end of the VC waveguide 30A that supports the "M1" spatial propagation mode within the inner core 20A, where M1 > 0. The refractive indices N-1 and N-2 are preferably selected such that the numerical aperture (NA) at the large end of the VC waveguide 30A matches the NA of the optical device (e.g., an optical fiber) to which it is connected (e.g., at connection position 36A-1 (e.g., a fusion splicer, connection position 36A-1) of an optical device 34A-1 consisting of a standard / conventional optical fiber connected to the VC waveguide 30A at connection position 36A-1). The dimensions of the inner and outer cores (20A, 22A) are preferably selected such that the connected optical device (e.g., optical device 34A-1) has substantially the same mode field dimension (MFD).) In the following, the cross-section of the VC or non-VC waveguide may not be circular, resulting in a non-circular mode profile, so the mode field dimension is used instead of the generally used mode field diameter (MFD). Thus, the mode field dimension includes both the mode size and the mode shape and is equal to the mode field diameter in the case of a circularly symmetric mode.

[0027] During the manufacture of the coupler array 10A from a suitably configured preform (consisting of a VC waveguide 30A preform having corresponding inner and outer cores 20A, 22A, and cladding 24A), as the coupler array 10A preform is tapered according to at least one predetermined reduced profile, the inner core 20A becomes too small to support all M1 modes. The number of spatial modes supported by the inner core at the second (tapered) end is M2, where M2 < M1. In the case of a single-mode waveguide, since M1 = 1 (corresponding to two polarization modes), M2 = 0, meaning the inner core is too small to support light propagation. The VC waveguide 30A functions as if it were composed of a single core with an effective refractive index close to N-2 surrounded by a cladding of a lower refractive index N-3.

[0028] During fabrication of the coupler array 10A, the inter-channel spacing S-1 at the larger end of the coupler array 10A (position B, FIG. 1A) decreases in value to the inter-channel spacing S-2 at the smaller end of the coupler array 10A (position C, FIG. 1A) in proportion to the pull-in ratio selected for fabrication. Meanwhile, the MFD value (or the inverted NA value of the VC waveguide 30A) decreases, increases, or decreases depending on the selected difference in refractive indices, (N-1 to N-2) and (N-2 to N-3). or can be maintained, depending on the desired application of the optical coupler array 10A, as described below.

[0029] The ability to independently control the inter-channel spacing and MFD values ​​at each end of the optical coupler array is a highly advantageous feature of certain embodiments. Furthermore, the ability to match MFD and NA values ​​through the size and shape of the inner core 20A and outer core 22A and the corresponding selection of the values ​​of N-1, N-2, and N-3 allows the optical coupler array to be utilized to couple to a variety of waveguides without the need to use lenses.

[0030] In its various embodiments, the properties of the VC waveguide allow light to continue to propagate through the waveguide core along its length when its diameter is significantly reduced, advantageously reducing light loss due to interface imperfections or contamination, and allowing a wide range of materials to be used for the medium 28A of the common housing structure 14A (described below), including, but not limited to: (a) Non-optical material (because the light is concentrated inside the waveguide core), (b) an absorbing or scattering material with a refractive index greater than that of a standard / conventional fiber to reduce or increase crosstalk between channels; and (c) Pure silica (e.g., the same material used in most standard / conventional fiber claddings to facilitate splicing to multicore, double-clad, or multimode fibers)

[0031] Preferably, according to a particular embodiment, the desired relative values ​​of NA-1 and NA-2 (at corresponding ends of the coupler array 10A, e.g., NA-1 corresponds to the large end of the coupler array 10A and NA-2 corresponds to the small end of the coupler array 10A, respectively) may be determined by selecting values ​​of the refractive indices N1, N2, N3 of the coupler array 10A and configuring them according to at least one of the following relationships, which are selected based on the desired relative numerical apertures at each end of the coupler array 10A: [Table 1]

[0032] In general, the NA of any type of fiber is determined by the following formula:

number

[0033] When the above formula is used, it should be noted that the relationship between NA and the acceptance angle of a fiber is only an approximation. In particular, fiber manufacturers sometimes quote the "NA" of a single-mode (SM) fiber based on the above formula, even though the acceptance angles of SM fibers are quite different and cannot be determined from the refractive index alone.

[0034] According to certain embodiments, as used herein, the various NA values ​​are preferably core and n claddingThe effective refractive indexes of both N1, N2, N3, and N4 are determined by using the effective refractive indexes of both N1, N2, N3, and N4 because the effective refractive index determines the propagation of light and is more meaningful in the case of structured waveguides utilized in various embodiments. Also, the lateral refractive index profile inside the waveguide may not be flat but may vary around values ​​N1, N2, N3, or N4. Furthermore, the transition between regions having refractive indices N1, N2, N3, and N4 may not be as sharp as a step function due to dopant diffusion or some other intentional or unintentional factor, but may be a smooth function connecting the values ​​of N1, N2, N3, and N4. Coupling design or optimization may include varying both the values ​​of N1, N2, N3, and N4 and the size and shape of the regions having the respective indices.

[0035] Returning now to FIG. 1A, the common coupling structure 14A consists of a medium 28A in which a section of the VC waveguide 30A located between positions B and D in FIG. 1A is embedded, which may include, but is not limited to, at least one of the following materials: Materials that have properties that prohibit the propagation of light, Materials with light absorbing optical properties, Materials with light scattering optical properties, a material having optical properties selected such that a fourth refractive index (N-4) is greater than the third refractive index (N-3); and / or A material having optical properties selected such that said fourth refractive index (N-4) is substantially equal to said third refractive index (N-3).

[0036] At the large end of the optical coupler array 10A (proximate position B in FIG. 1A), the VC waveguides 30A are spliced ​​to corresponding respective elongated optical devices 34A-1 (e.g., optical fibers, etc.) at specific splice locations 36A-1 (shown, by way of example, as being located inside the common housing structure 14A), at least a portion of which extends outside the common housing structure 14A by a predetermined length 12A, while the non-VC waveguides 32A-1, 32A-2 are connected to corresponding respective elongated optical devices 34A-2, 34A-3 (e.g., optical fibers, etc.) at specific connection locations 36A-2, 36A-3, respectively (located outside the common housing structure 14A), and also extend outside the common housing structure 14A by a predetermined length 12A.

[0037] Optionally, the coupler array 10A can also include a substantially uniform diameter tip 16A (shown between positions C and D in FIG. 1A) for coupling with the interface 42A of the optical waveguide device 40A at the array interface 18A. The uniform diameter tip 16A can be useful in certain interface applications, such as those shown in FIG. 1D, 4, and 5. Alternatively, the coupler array 10A can be fabricated without the tip 16A (or the tip 16A can be removed after fabrication) such that coupling with the optical device interface 42A occurs at the coupler array 10A interface at position C in FIG. 1A.

[0038] In an alternative embodiment, when the optical device 40A is made of a double-clad fiber, the coupling When the small end of the transducer array 10A is coupled (e.g., fusion spliced) to the optical device interface 42A, at least a portion of the common housing structure 14A adjacent the splice location (such as at least a portion of the tip 16A) may be coated with a low index medium (not shown) and extends over the splice location and into the outer cladding of the dual clad fiber optic device 40A (and optionally over a portion of the outer cladding of the dual clad fiber optic device 40A adjacent the splice location).

[0039] 1B, a second exemplary embodiment of an optical fiber coupler array is shown as coupler array 10B. Coupler array 10B includes a common housing structure 14B, at least one VC waveguide, shown as a single VC waveguide 30B in FIG. 1B by way of example, and at least one Non-VC waveguide, shown as a single Non-VC waveguide in FIG. 1B by way of example, as a single Non-VC waveguide 32B, arranged parallel to and adjacent to VC waveguide 30B, such that a portion of optical coupler array 10B is configured to have a larger inter-channel spacing value S2' at its small end than the corresponding inter-channel spacing value S2 at the small end of optical coupler array 10A in FIG. 1A. This configuration can be readily implemented by cutting the optical fiber coupler array 10A laterally at location C', thus creating a common housing structure 14B that is shorter than the common housing structure 14A, and thus creating a new, larger diameter array interface 18B having a larger inter-channel spacing value S2'.

[0040] 1C, a third exemplary embodiment of an optical fiber coupler array is shown as coupler array 10C. Coupler array 10C is composed of a plurality of VC waveguides, shown as VC waveguides 30C-1, 30C-2 in FIG. 1C, and a plurality of Non-VC waveguides, shown as Non-VC waveguides 32C-1, 32C-2 in FIG. 1C. The plurality of Non-VC waveguides, shown as Non-VC waveguides 32C-1, 32C-2, 32C-a in FIG. 1C, are all longitudinally asymmetrically arranged with respect to each other, and at least some of the plurality of Non-VC waveguides are of different types and / or different characteristics (such as single mode or multimode or polarization maintaining), e.g., Non-VC waveguides 32C-1, 32C-2 are of different types or characteristics different from Non-VC waveguide 32C-a. Furthermore, either the VC or non-VC waveguides (e.g., non-VC waveguide 32C-a, etc.) can easily extend beyond the common housing structure of the coupler array 10C for any desired length and only need to be spliced ​​to an optical device in its vicinity.

[0041] 1D, there is shown a fourth exemplary embodiment of an optical fiber coupler array configured for multi-core fan-in and fan-out connections, designated as a coupler array 50. The coupler array 50 is comprised of a pair of optical fiber coupler array components (10D-1, 10D-2) with a multi-core optical fiber element 52 connected (e.g., by fusion splicing at locations 54-1, 54-2) between the second (smaller sized) ends of the two optical fiber coupler array components (10D-1, 10D-2). Preferably, at least one of the VC waveguides in each of the coupler array components (10D-1, 10D-2) is configured to increase or maximize optical coupling to a corresponding selected core of the multi-core optical fiber element 52 while decreasing or minimizing optical coupling to all other cores.

[0042] 2A, a fifth exemplary embodiment of an optical fiber coupler array is shown as coupler array 100A. Coupler array 100A is comprised of a plurality of longitudinally adjacent VC waveguides, shown for illustrative purposes only as a plurality of VC waveguides 130A-1, 130A-2, at least partially embedded in a single common housing structure 104A. Each of the plurality of VC waveguides 130A-1, 130A-2 is associated with a particular spline. At the splice locations 132A-1, 132A-2, a corresponding respective elongated optical device 134A-1, 134A-2 (such as an optical fiber) is spliced, at least a portion of which extends outside the common housing structure 104A by a predetermined length 102A, and each particular splice location 132A-1, 132A-2 is disposed within the common housing structure 104A.

[0043] Referring now to FIG. 2B, a sixth exemplary embodiment of a fiber optic coupler array is shown as coupler array 100B.

[0044] The coupler array 100B is comprised of a plurality of longitudinally adjacent VC waveguides, shown for illustrative purposes only as a plurality of VC waveguides 130B-1, 130B-2, at least partially embedded in a single common housing structure 104B. Each of the plurality of VC waveguides 130B-1, 130B-2 is spliced ​​to a corresponding respective elongated optical device 134B-1, 134B-2 (such as an optical fiber) at a specific splice location 132B-1, 132B-2, at least a portion of which extends outside the common housing structure 104B by a predetermined length 102B, with each specific splice location 132B-1, 132B-2 being disposed in an outer cross-sectional boundary region of the common housing structure 104B.

[0045] Referring now to FIG. 2C, a seventh exemplary embodiment of an optical fiber coupler array is shown as coupler array 100C.

[0046] The coupler array 100C is comprised of a plurality of longitudinally adjacent VC waveguides, shown for illustrative purposes only as a plurality of VC waveguides 130C-1, 130C-2, at least partially embedded in a single common housing structure 104C. Each of the plurality of VC waveguides 130C-1, 130C-2 is spliced ​​to a corresponding respective elongated optical device 134C-1, 134C-2 (such as an optical fiber) at a particular splice location 132C-1, 132C-2, at least a portion of which extends outside the common housing structure 104C by a predetermined length 102C, and each particular splice location 132C-1, 132C-2 is disposed outside the common housing structure 104C.

[0047] 2D, an alternative embodiment of an optical fiber coupler array is shown as a coupler array 150. The coupler array 150 is composed of a number of longitudinally adjacent VC waveguides at least partially embedded in a single common housing structure configured at its second end to increase or optimize optical coupling to a free-space-based optical device 152. The free-space-based optical device 152 may be composed of an additional optical device component 156 following a lens 154, which may be composed of a MEMS mirror or a volume Bragg grating, as an example. The combination of the coupler and the free-space-based optical device 152 may be used as an optical switch or WDM device for spectral combining or decoupling of optical signals 160b (representative of the optical coupler array 150 output optical signal 160a after passing through the lens 154). In this case, one of the fibers may be used for input and all the others for output, or vice versa. In another embodiment, the free space based device 152 can be fusion splicable to the end of the second coupler. This device can be a coreless glass element and can act as an end cup for power density realignment at the glass-air interface. In another modification, the coreless element can act as a Talbot mirror for phase locking of the coupler waveguides in a Talbot cavity geometry.

[0048] Before describing the various embodiments shown in FIGS. 3A-3L in more detail, please refer to FIGS. 3A-3L. Before describing the various embodiments shown in FIGS. 3A-3L in more detail, please refer to FIGS. 3A-3L. It should be understood that whenever "one or more" combiner components / elements are shown, the specific quantities of such combiner components / elements that may be provided in the corresponding embodiment of a combiner array may be selected as a matter of need or design choice (e.g., based on the intended industrial application of the combiner array) without departing from the spirit of the invention. Thus, in the various FIGS. 3A-3L, a single or individual combiner array component / element is identified by a single reference number, while each plurality of combiner components / elements is identified by a designation following the reference number, "(1..n)", where "n" is the desired number of combiner elements / components (and this may have a different value in any particular combiner array embodiment described below).

[0049] Also, all the waveguides VC and non-waveguides VC are shown only as examples with circular cross sections of the inner and outer cores and claddings. Other shapes of the cross sections of the inner and outer cores and claddings (e.g., hexagonal, rectangular or square) can be utilized without departing from the present invention. The specific selection of the shape is based on various requirements such as the channel shape, the channel position shape (e.g., hexagonal, rectangular or square lattice) or the axial polarization alignment mode of the optical device.

[0050] Similarly, unless otherwise noted below, the sizes, relative sizes, relative positions, and compositional material selections are not limited to the exemplary sizes, relative sizes, relative positions, and compositional material selections shown below in connection with the detailed description of the coupler array embodiments of Figures 3A-3L, so long as the various relationships below are observed (e.g., the relative quantity relationships below for optical coupler arrays 200C and 200D of Figures 3C and 3D, and the feature defined below in connection with coupler array 200H of Figure 3H in which PM VC waveguide 204H is longitudinally disposed laterally off-center from the central longitudinal axis of coupler array 200H). Rather, they may be selected by one of ordinary skill in the art as a matter of convenience or design choice without departing from the spirit of the invention.

[0051] Finally, it should be noted that each of the various single common housing structural components 202A-202L of the various coupler arrays 200A-200L of Figures 3A-3L may be composed of a medium having a refractive index N-4 value according to an applicable one of the above-mentioned relationships with the refractive indexes N-1, N-2, and N-3 values ​​of the other coupler array components, and may be composed of a medium having properties and characteristics selected from the various contemplated exemplary medium composition parameters described above in connection with medium 28A of Figure 1A.

[0052] 3A, a first alternative embodiment of the optical fiber coupler array embodiment of FIGS. 1D-2D is shown. It is shown as a coupler array 200A in which all of the waveguides are VC waveguides. The coupler array 200A comprises a single common housing 202A and a plurality of VC waveguides 204A-(1...n), where n is equal to 19, centrally disposed along a central longitudinal axis of the housing 202A, by way of example only. The coupler array 200A may also optionally include at least one fiducial element 210A, operable to provide the coupler array with one or more useful properties, including, but not limited to, Allows visual identification of the coupler array waveguide arrangement (at least one of the ends of the coupler array); and Facilitating passive alignment of at least one of the coupler array ends with at least one optical device.

[0053] Additionally, optical coupler array embodiments including at least one polarization-maintaining VC waveguide (FIG. 3H When deployed in a light coupler array embodiment (such as the light coupler array embodiment described below in connection with FIG. 3L), the fiducial element can be further operable as follows: Allows visual identification of specific polarization axis alignment modes of the optical combiner array (as described below in connection with Figures 3H-3L). Serves as a geometrically positioned reference point for aligning one or more polarization axes of the PM waveguides of a particular optical coupler array.

[0054] Fiducial element 210A may comprise any of a variety of types of fiducial elements known in the art, selected as a matter of design choice or convenience without departing from the spirit of the invention, and may, for example, be a dedicated elongated element disposed longitudinally within common housing structure 202A at one of various cross-sectional locations (such as locations X or Y shown in FIG. 3A ). Alternatively, fiducial element 210A may be comprised of a dedicated channel not used for non-fiducial purposes, for example replacing one of waveguides 204A-(1...n), shown by way of example only at location Z in FIG.

[0055] 3B, a first alternative embodiment of the optical fiber coupler array 10A of FIG. 1A described above is shown as coupler array 200B comprising a single housing structure 202B, at least one VC waveguide, exemplarily shown in FIG. 3B as VC waveguide 204B, and, by way of example only, a plurality of Non-VC waveguides 206B-(1...n), where n is equal to 18. The VC waveguide 204B is disposed along a central longitudinal axis of the common housing structure 202B and is circumferentially symmetrically surrounded by a plurality of proximal parallel Non-VC waveguides 206B-(1...n).

[0056] 3C, a first alternative embodiment of the optical fiber coupler array 200B of FIG. 3B described above is shown as a coupler array 200C comprised of a single housing structure 202C, a VC waveguide 204C, and a plurality of Non-VC waveguides 206C-(1...n), where n is equal to 18, by way of example only. The VC waveguide 204C is disposed along a central longitudinal axis of the common housing structure 202C and is circumferentially and symmetrically surrounded by a plurality of proximal parallel Non-VC waveguides 206C-(1...n). The coupler array 200C is configured such that the volume of the common housing structure 202C medium surrounding the sections of all the waveguides embedded therein (i.e., the VC waveguide 204C and the multiple Non-VC waveguides 206C-(1...n)) exceeds the combined volume of the inner and outer cores of the sections of the VC waveguide 204C embedded within a single common housing structure 202C.

[0057] 3D, a first alternative embodiment of the optical fiber coupler array 200C of FIG. 3C described above is shown as a coupler array 200D comprising a single housing structure 202D, a plurality of VC waveguides 204D-(1...N), where N is, by way of example only, equal to 7, and a plurality of Non-VC waveguides 206D-(1...n), where n is, by way of example only, equal to 12. The plurality of VC waveguides 204D-(1...N) are disposed along a central longitudinal axis of the common housing structure 202D and are circumferentially symmetrically surrounded by a plurality of proximal parallel Non-VC waveguides 206D-(1...n). The coupler array 200D is configured such that the volume of the medium of the common housing structure 202D surrounding all of the waveguide sections embedded therein (e.g., the multiple VC waveguides 204D-(1...N) and the multiple Non-VC waveguides 206D-(1...n) exceeds the combined volume of the inner and outer cores of the multiple VC waveguides 204D-(1...N) sections embedded within the single common housing structure 202D.

[0058] 3E, a first alternative embodiment of the optical fiber coupler array 200D of FIG. 3D described above is shown as a coupler array 200E comprising a single housing structure 202E, a plurality of VC waveguides 204E-(1...N), where N is equal to 6, by way of example only, a plurality of Non-VC waveguides 206E-(1...n), where n is equal to 12, by way of example only, and a separate single Non-VC waveguide 206E'. The Non-VC waveguide 206E' is preferably operable to provide an optical pumping function therethrough and is positioned along a central longitudinal axis of the common housing structure 202E and is circumferentially and symmetrically surrounded by proximal parallel multiple VC waveguides 204E-(1...N), which are in turn circumferentially and symmetrically surrounded by proximal parallel multiple Non-VC waveguides 206E-(1...n).

[0059] 3F, a second alternative embodiment of the optical fiber coupler array 200B of FIG. 3B described above is a single housing structure 202F, a plurality of VC waveguides 204F-(1..N), where by way of example only, N is equal to 6, a separate single VC waveguide 204F', and a plurality of Non-VC waveguides 206F-(1..n), preferably each comprised of an enlarged inner core of sufficient diameter to increase or optimize optical coupling to different types of optical pump channels of various optical devices to which the coupler array 200F may be advantageously coupled. The VC waveguide 204F' is disposed along a central longitudinal axis of the common housing structure 202F and is circumferentially and symmetrically surrounded by proximal parallel multiple VC waveguides 204F-(1..N), which in turn are circumferentially and symmetrically surrounded by proximal parallel multiple non-VC waveguides 206F-(1..N).

[0060] 3G, a third alternative embodiment of the optical fiber coupler array 200B of FIG. 3B described above is shown as a coupler array 200G comprising a single housing structure 202G, at least one VC waveguide, exemplarily shown in FIG. 3G as VC waveguide 204G, and a plurality of Non-VC waveguides 206G-(1...n), where n is equal to 18, by way of example only. The VC waveguides 204G are arranged as side channels offset from a central longitudinal axis of the single common housing structure 202G such that the optical fiber coupler array 200G can be easily used as a fiber optical amplifier and / or laser when spliced ​​to a double clad optical fiber (not shown) having a non-concentric core to improve optical pumping efficiency. It should be noted that since a double-clad fiber is a fiber in which both the core and the inner cladding have light-guiding properties, most optical fiber types, such as SM, MM, LMA, or MC (multicore), with or without polarization maintaining, and even standard (e.g., conventional) single-mode optical fibers, can be converted into double-clad fibers by coating (or re-coating) the fiber with a low-index medium (forming the outer cladding).

[0061] Optionally, when the second end of the coupler array 200G is spliced ​​to a double-clad fiber (not shown), at least a portion of the common housing structure 202G proximate the splice point with the double-clad fiber (not shown) may be coated with a low-index medium that extends beyond the splice point to the outer cladding of the double-clad fiber (optionally extending beyond a portion of the outer cladding proximate the splice point).

[0062] Reference is now made to Figures 3H-3L. With reference to Figures 3H-3L, in various alternative exemplary embodiments of the optical coupler, at least one of the VC waveguides utilized therein, and in certain embodiments, optionally at least one of the non-VC waveguides, may include polarization-maintaining (PM) properties. As an example, the PM properties of a VC waveguide may result from a pair of longitudinal stress rods (or via other stress elements) positioned either outside the inner core and inside or outside the outer core within the VC waveguide, and the PM properties may be achieved with non-circular inner or outer core geometries, or other PM-guiding optical fiber configurations (such as bowtie or elliptical clad PM fiber, etc.). ) In various embodiments of optical fibers in which at least one PM waveguide (VC and / or non-VC) is utilized, the alignment of the axis of the PM waveguide (or waveguides) according to a particular polarization axis alignment mode may be involved.

[0063] According to certain embodiments, the polarization axis alignment mode may consist of at least one of, but is not limited to, the following: Alignment of the polarization axis of the PM waveguide with the polarization axis of other PM waveguides in the optical coupler. For off-center PM waveguides: Alignment of the polarization axis of the PM waveguide with its cross-sectional (geometric) position in the optical coupler. In case the single common housing structure of the optical coupler consists of a non-circular geometric shape (as shown by way of example in Fig. 3L): the axial alignment of the polarization axes of the PM waveguides with respect to the geometric features of the outline of the common housing structure; In an embodiment of an optical coupler including one or more waveguide alignment indicators described below in connection with FIGS. 3J-3L, the polarization axis of the PM waveguide is axially aligned to at least one geometric characteristic thereof: axial alignment of the polarization axis to at least one geometric characteristic of the PM waveguide; As described above in connection with FIG. 3A, in an embodiment of an optical coupler including at least one fiducial element 210A: axial alignment of the polarization axis of the PM waveguide with respect to the geometric position of the at least one fiducial element 210A.

[0064] The selection of a particular type of polarization axis alignment mode for various embodiments of the optical couplers is preferably governed by at least one axis alignment criterion, which may include, but is not limited to: alignment of the polarization axes of the PM waveguides in a geometry that enhances or maximizes PM properties, and / or satisfies at least one requirement of one or more intended industrial applications for the coupler array.

[0065] 3H, a first alternative embodiment of the optical fiber coupler array 200G of FIG. 3G described above is shown as a coupler array 200H comprising a single housing structure 202H, at least one VC waveguide, exemplarily shown in FIG. 3H as a PM VC waveguide 204H having polarization maintaining properties, and a plurality of Non-VC waveguides 206H-(1...n), only exemplarily, where n is equal to 18. The PM VC waveguides 204H are arranged as side channels offset from a central longitudinal axis of the single common housing structure 202H, and configure polarization axes exemplarily aligned with respect to the lateral off-center position of the PM VC waveguides 204H.

[0066] 3I, a fourth alternative embodiment of the optical fiber coupler array 200B of FIG. 3B described above is shown as a coupler array 200I comprising a single housing structure 202I, at least one VC waveguide, exemplarily shown in FIG. 3I as PM VC waveguide 204I having polarization-maintaining properties, and a plurality of PM Non-VC waveguides 206I-(1...n), where n is equal to 18, each also having polarization-maintaining properties. The PM VC waveguide 204I is disposed along a central longitudinal axis of the common housing structure 202I and is circumferentially and symmetrically surrounded by a plurality of proximal parallel PM Non-VC waveguides 206I-(1...n). As an example, the coupler array 200I configures a polarization axis aligned mode in which the polarization axes of the PM VC waveguide 204I and the plurality of PM Non-VC waveguides 206I-(1...n) are aligned with each other. The PM properties of the PM VC waveguide 204I and the plurality of PM Non-VC waveguides 206I-(1...n) are shown as induced by rod stress members by way of example only (and may easily be induced alternately by various other stresses or equivalent designs).

[0067] Referring now to FIG. 3J, the first fiber optic coupler array 200I of FIG. 3I above An alternative embodiment is shown as a coupler array 200J comprising a single housing structure 202J, at least one VC waveguide, exemplarily shown in Fig. 3J as PM VC waveguide 204J having polarization-maintaining properties, and a plurality of PM Non-VC waveguides 206J-(1...n), exemplarily only, with n equal to 18, each also having polarization-maintaining properties. The PM VC waveguide 204J is disposed along a central longitudinal axis of the common housing structure 202J and is circumferentially symmetrically surrounded by a plurality of proximal parallel PM Non-VC waveguides 206J-(1...n). The PM characteristics of PM VC waveguide 204J and the plurality of PM Non-VC waveguides 206J-(1...n) are shown by way of example only as resulting from the non-circular cross-sectional shape of each of the plurality of PM Non-VC waveguides 206J-(1...n) cores (and the non-circular cross-sectional shape of the outer core of PM VC waveguide 204J).

[0068] The coupler array 200J optionally represents a particular cross-sectional geometric waveguide arrangement of the waveguides (i.e., PM VC waveguide 204J and the plurality of PM Non-VC waveguides 206J-(1...n) of the optical coupler array 200J such that the particular cross-sectional geometric waveguide arrangement may be readily identified from at least one of visual inspection and physical inspection of the common coupler housing structure 202J sufficient to inspect the waveguide placement indicator element 208J. Preferably, the waveguide placement indicator element 208J may be further operatively configured to facilitate passive alignment of the second end of the optical coupler array 200J to at least one optical device (not shown).

[0069] The waveguide placement indicator 208J may be comprised of one or more of, but is not limited to, a color marking and / or a physical indicator (such as a groove or other modification of the common housing structure 202J exterior surface, or an element or other member disposed thereon) applied to the common housing structure 202J exterior surface. Alternatively, the waveguide placement indicator 208J may actually be comprised of a specific modification to, or definition of, the cross-sectional geometry of the common housing structure 202J (such as, for example, the hexagonal shape of the common housing structure 202L of FIG. 3L described below, or another geometric shape).

[0070] As an example, the coupler array 200J can be configured in a polarization axis aligned mode in which the polarization axes of the PM VC waveguide 204J and each of the multiple PM Non-VC waveguides 206J-(1...n) are aligned with each other or with the waveguide orientation indicator 208J.

[0071] 3K, a fifth alternative embodiment of the optical fiber coupler array 200B of FIG. 3B above is shown as a coupler array 200K comprising a single housing structure 202K, at least one VC waveguide, exemplarily shown in FIG. 3K as a PM VC waveguide 204K having polarization-maintaining properties, and a plurality of Non-VC waveguides 206K-(1...n), where n is equal to 18, by way of example only. The PMVC waveguide 204K is disposed along a central longitudinal axis of the common housing structure 202K and is circumferentially symmetrically surrounded by a plurality of proximal parallel PM non-VC waveguides 206K-(1...n). The PM properties of the PM non-VC waveguide 204K are shown only as induced by a rod stress member by way of example (they may be easily and alternately induced by various other stresses, or equivalent approaches). Coupler array 200K may optionally be comprised of a plurality of waveguide placement indicator elements, shown for illustrative purposes only as waveguide placement indicator elements 208K-a and 208K-b, each of which may be the same or of a different type, as described above in connection with waveguide placement indicator element 208J of FIG. 3J.

[0072] 3L, a second alternative embodiment of the optical fiber coupler array 200I of FIG. 3I above is shown having a cross-sectional shape having a non-circular geometric shape (shown as a hexagon by way of example). 3L is illustrated as a coupler array 200L comprised of a single housing structure 202L consisting of a VC waveguide having polarization-maintaining properties, and at least one VC waveguide having polarization-maintaining properties, as shown by way of example in FIG. 3L. 3L is illustrated as a PM VC waveguide 204L having polarization-maintaining properties, and a plurality of PM non-VC waveguides 206L-(1...n), where n is equal to 18 by way of example only, each also having polarization-maintaining properties. The PM-VC waveguide 204L is disposed along a central longitudinal axis of the common housing structure 202L and is circumferentially symmetrically surrounded by a plurality of proximally parallel PM-Non-VC waveguides 206L-(1...n).

[0073] As an example, the coupler array 200L configures a polarization axis aligned mode in which the polarization axes of the PM VC waveguide 204L and the plurality of PM Non-VC waveguides 206L-(1...n) are aligned with each other and with the cross-sectional geometry of the common housing structure 202L. The PM characteristics of the PM-VC waveguide 204L and the plurality of PM-Non-VC waveguides 206L-(1...n) are shown as induced by rod stress members only as an example (they may be easily and alternately induced by various other stresses or equivalent designs). The coupler array 200K can optionally configure a waveguide placement indicator 208L-a that can configure any of the configurations described above in connection with the waveguide placement indicator 208J of FIG. 3J.

[0074] Referring now to FIG. 4 , the second end 302 (i.e., the “tip”) of the optical fiber coupler array is shown as being in the process of connecting to a plurality of vertical coupling elements 306 of an optical device 304 in, by way of example, a close-proximity open-air optical coupling alignment configuration that can be easily transitioned to a butt-coupled configuration by full physical contact between the optical fiber coupler array second end 302 and the vertical coupling elements 306.

[0075] Referring now to FIG. 5 , a second end 322 (i.e., “tip”) of the optical fiber coupler array is shown as being in the process of connecting to a plurality of end coupling elements 326 of an optical device 324 in, by way of example, a butt coupling configuration, which can be readily transitioned to one of several alternative coupling configurations, including a proximal open-air optical coupling alignment configuration, and / or an angled aligned coupling configuration.

[0076] In at least one alternative embodiment, the optical coupler array (i.e., optical coupler arrays 200D-200L of FIGS. 3C-3L, etc.) may be readily configured to pump optical fiber lasers and / or optical fiber amplifiers (or equivalent devices). In a preferred embodiment thereof, the pumpable coupler array comprises a central channel (i.e., waveguide) configured to transmit a signal (i.e., functioning as a "signal channel") that is subsequently amplified or utilized to generate oscillations, and at least one additional channel (i.e., waveguide) configured to provide an optical pumping function (i.e., each functioning as a "pump channel"). In various exemplary alternative embodiments thereof, the pumpable coupler array may include the following, in any desired combination thereof: At least one of the following signal channels: at least one predetermined signal wavelength; or a single-mode signal channel configured for increased or optimal coupling with a single-mode amplifying fiber at an oscillation wavelength; a multimode signal channel configured for increased or optimal coupling with a multimode amplifying fiber at at least one predetermined signal wavelength or oscillation wavelength; and Increased coupling to a single-mode pump source at at least one given excitation wavelength a single-mode pump channel configured to optimize coupling with a multimode pump source at at least one predetermined excitation wavelength; and a multimode pump channel configured to increase or optimize coupling with a multimode pump source at at least one predetermined excitation wavelength.

[0077] Optionally, to increase or maximize pump efficiency, the pump-enabled coupler array may be configured to selectively utilize fewer than all of the available pumping channels. It should also be noted that, as a matter of design choice, without departing from the spirit of the invention, the pump-enabled coupler array may be configured to include: a. at least one signal channel, each positioned at a predetermined desired location within the coupler array structure; b. at least one pump channel, each pump channel disposed at a predetermined desired location within the coupler ray structure; and c. Optionally—at least one additional waveguide for at least one additional purpose other than signal transmission or pump (e.g., fiducial marks for alignment, for fault detection, for data transmission, etc.).

[0078] Advantageously, the pump channel may be located at any lateral position within the coupler along the central longitudinal axis. The pump channel may also be constructed of at least one of the following optical fiber types, including but not limited to SM, MM, LMA, or VC waveguides. Optionally, any of the optical fibers (regardless of fiber type) utilized as the optical pump channel of the coupler may have polarization-maintaining properties.

[0079] In this case, the signal channels of the coupler array are configured or optimized to couple to the signal channels of the double-clad fiber, and each of the at least one pump channel is configured or optimized to couple to the inner cladding of the double-clad fiber.

[0080] In essence, the optical coupler arrays illustrated in the various embodiments can also be readily implemented as high density, multi-channel, optical input / output (I / O) for fiber-to-chip and fiber-to-optical waveguide. Optical fiber couplers can be readily constructed with at least the following features: Dramatically reduced channel spacing and device footprint (compared to conventional solutions) Scalable channel count All-glass optical path Easily butt or join dense surfaces together without the need for lenses, air gaps, or beam spreading media -Can be manufactured using semi-automated production processes A wide range of customizable parameters, including wavelength, mode field size, channel spacing, array configuration, and fiber type

[0081] The optical fiber coupler of the present invention may be advantageously utilized in at least the following applications, as a matter of design choice or convenience, without departing from the spirit of the invention. Coupling to a waveguide PIC or PCB based (single mode or multimode) Multi-core fiber Chip edge (1D) or chip face (2D) bonding Application-optimized NA · Package alignment requirements · Chip processing requirements / waveguide uptapering -Easy setting of polarization maintenance characteristics Coupling to chip-based devices: VCSELs, photodiodes, vertical coupling gratings, etc. Laser Diode Coupling ·High-density equipment input / output (I / O)

[0082] Thus, when implemented, the various exemplary embodiments of the fiber optic coupler constitute at least the following advantages over currently available competitive solutions: Unprecedented density ·Low loss coupling (≦0.5dB) - Operational stability Form factor support Wide spectral range Matching NA Scalable channel count Polarization maintenance

[0083] Referring now to FIG. 7, at least one exemplary embodiment of a flexible optical coupler array is shown as a flexible pitch reduced optical fiber coupler array (PROFA) coupler 450. Various features of the exemplary PROFA coupler may be described with respect to FIG. 7, however, any of the features described above may be implemented in any combination with the flexible PROFA coupler. For example, any of the features described with respect to FIG. 1A-5 may be utilized in the flexible PROFA coupler. FIG. 1A-5 may be utilized with the flexible PROFA coupler. Additionally, any of the features described with respect to FIG. 1A-5 may be utilized with the flexible PROFA coupler. FIG. 1A-5 may be combined with the features described with respect to FIG. 7.

[0084] With continued reference to FIG. 7, the exemplary flexible PROFA coupler 450 shown in FIG. 7 can be configured for use in applications where an interconnect is desired that has low crosstalk and is flexible enough to accommodate low profile packaging. The vanishing core approach described herein and in U.S. Patent Application Publication No. 2013 / 0216184, entitled "Configurable Pitch Reduced Optical Fiber Array," which is incorporated herein in its entirety, can, for example, butt-couple a plurality of optical fibers to an optical device (e.g., an array of vertical grating couplers (VGCs)). If the cross-sectional structure of the coupler 450 has an additional layer of refractive index N-2A, even lower than N2, as described herein and in U.S. Patent Application Publication No. 2013 / 0216184, the vanishing core approach can once again be utilized to further reduce the outer diameter without substantially compromising channel crosstalk. This further reduction can advantageously provide certain embodiments having a flexible region of reduced cross section between the first and second ends.

[0085] In some preferred embodiments, the difference (N-2A minus N-3) is greater than the difference (N-2 minus N-2A) or (N-1 minus N-2), resulting in a high NA, bend insensitive waveguide when the light is guided by an additional layer having a refractive index of N-2A. Also, in some preferred embodiments, the outer diameter of coupler 450 can be reduced longitudinally from one end to form a flexible region and then expanded longitudinally toward the second end, resulting in a low NA waveguide with a larger coupling surface area at the second end.

[0086] For example, as shown in FIG. 7, a particular embodiment of the optical coupler array 450 may be comprised of an elongated optical element 1000 having a first end 1010, a second end 1020, and a flexible portion 1050 therebetween. The optical element 1000 may include a coupler housing structure 1060 and a plurality of longitudinal waveguides 1100 embedded in the housing structure 1060. The waveguides 1100 may be arranged relative to one another in a cross-sectional geometric waveguide arrangement. In FIG. 7, an exemplary cross-sectional geometric waveguide arrangement of the waveguides 1100 at the first end 1010, the second end 1020, and a position within the flexible portion 1050 is shown. 7, a cross-sectional geometric waveguide arrangement of the waveguide 1100 for an intermediate location 1040 between the first end 1010 and the flexible portion 1050 is also shown. As illustrated by the shaded area in the cross section and described herein, light can be guided through the optical element 1000 from the first end 1010 to the second end 1020 via the flexible portion 1050. As also shown in FIG. 7, this can result in a structure that provides sufficient flexibility (e.g., at the flexible portion 1050) to accommodate a low profile package while keeping all channels discrete with sufficiently low crosstalk.

[0087] The level of crosstalk and / or flexibility may depend on the application of the array. For example, in some embodiments, low crosstalk may be considered to be in the range of -45 dB to -35 dB, and in other embodiments, low crosstalk may be considered to be in the range of -15 dB to -5 dB. Thus, the level of crosstalk is not particularly limited. In some embodiments, the crosstalk is -55 dB or less, -50 dB or less, 45 dB or less, -40 dB or less, -35 dB or less, -30 dB or less, -25 dB or less, -20 dB or less, -15 dB or less, -10 dB or less, 0 dB or less, or any value therebetween (e.g., -37 dB or less, -27 dB or less, -17 dB or less, -5 dB or less, etc.). In some embodiments, the crosstalk can be within a range formed from -50 dB to -40 dB, -40 dB to -30 dB, -30 dB to -20 dB, -20 dB to -10 dB, -10 dB to 0 dB, -45 dB to -35 dB, -35 dB to -25 dB, -25 dB to -15 dB, -15 dB to -5 dB, -10 dB to 0 dB, any combination of these ranges, or any value from -55 dB to 0 dB (e.g., -52 dB to -37 dB, -48 dB to -32 dB, etc.).

[0088] The flexibility may also depend on the application of the array. For example, in some embodiments, good flexibility of the flexible portion 1050 may constitute a bend of at least 90 degrees, while in other embodiments, a bend of at least 50 degrees may be acceptable. Thus, the flexibility is not particularly limited. In some embodiments, the flexibility may be at least 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, 80 degrees, 90 degrees, 100 degrees, 110 degrees, 120 degrees, or at least any value therebetween. In some embodiments, the flexible portion 1050 can bend in a range formed by any of these values, for example, from 45 degrees to 55 degrees, from 50 degrees to 60 degrees, from 60 degrees to 70 degrees, from 70 degrees to 80 degrees, from 80 degrees to 90 degrees, from 90 degrees to 100 degrees, from 100 degrees to 110 degrees, from 110 degrees to 120 degrees, or any combination of these ranges, or a range formed by any value within these ranges (e.g., 45 degrees to 55 degrees, from 50 degrees to 60 degrees, from 60 degrees to 70 degrees, from 70 degrees to 80 degrees, from 80 degrees to 90 degrees, from 90 degrees to 100 degrees, from 100 degrees to 110 degrees, from 110 degrees to 120 degrees, or any combination of these ranges, or ...). In other embodiments, the flexible portion 1050 can bend more or less than these values. Bending may typically be associated with light scattering. However, various embodiments can be configured to bend as described herein (e.g., in one of the ranges described above) and achieve relatively low crosstalk as described herein (e.g., in one of the ranges described above).

[0089] In various applications, the flexible portion 1050 may not bend during use, but flexibility may be desired to decouple the first end 1010 or the second end 1020 from other portions of the coupler array 450. For example, the flexible portion 1050 of the flexible PROFA coupler 450 can provide mechanical isolation of the first end 1010 (e.g., the PROFA-PIC interface) from the remainder of the PROFA, resulting in improved stability against environmental variations, including temperature changes and mechanical shock and vibration.

[0090] 7, the coupler array 450 may be operable to optically couple with a plurality of optical fibers 2000 and / or optical devices 3000. The optical fibers 2000 and optical devices 3000 may include any of those described herein. The coupler array 450 couples optically with a plurality of waveguides 1100 at a first end 1010. 7 illustrates all of the waveguides 1100 as VC waveguides. However, one or more non-VC waveguides may be used. Furthermore, while FIG. 7 illustrates seven VC waveguides, any number of VC and / or Non-VC waveguides may be used.

[0091] As also shown in cross section, each of the waveguides 1100 can be disposed in an individual corresponding cross-sectional geometric location relative to the other waveguides of the plurality of waveguides 1100. Although Figure 7 shows a waveguide surrounded by six other waveguides, the cross-sectional geometric waveguide arrangement is not limited and can include any arrangement known in the art or yet to be developed, including any of those shown in the figure.

[0092] As described herein, the VC waveguide 1101 can include an inner core (e.g., inner missing core) 1110, an outer core 1120, and an outer cladding 1130 having refractive indices N-1, N-2, and N-3, respectively. As shown in FIG. 7, the VC waveguide 1101 can also include a second outer core 1122 (e.g., between the outer core 1120 and the outer cladding 1130) having a refractive index N-2A. Just as the outer core 1120 can longitudinally surround the inner core 1110, the second outer core 1122 can longitudinally surround the outer core 1120, with the outer cladding 1130 longitudinally surrounding the second outer core 1122. In various embodiments, the relationship between the refractive indices of the inner core 1110, the outer core 1120, the second outer core 1122, and the outer cladding 1130 may advantageously be N-1>N-2>N2-A>N-3. Such a relationship allows each surrounding layer to act as an effective cladding for the layers therein (e.g., the outer core 1120 may act as an effective cladding for the inner core 1110, and the second outer core 1122 may act as an effective cladding for the outer core 1120). Thus, the use of the second outer core 1122 may provide an additional set of cores and claddings.

[0093] By including the second outer core 1122 having a refractive index N-2A, certain embodiments can achieve a higher NA (e.g., compared to without the second outer core 1122). In various embodiments, the difference (N-2A minus N-3) can be greater than the difference (N-2 minus N-2A) or (N-1 minus N-2) to result in a relatively high NA. Increasing the NA can reduce the MFD and allow the channels (e.g., the waveguides 1100) to be closer together (e.g., closer spacing between the waveguides 1100) without compromising crosstalk. Thus, the coupler array 450 can further reduce the cross section (e.g., compared to without the second outer core 1122) to provide a reduced area when the light is guided by the second outer core 1122. By providing a reduced area between the first end 1010 and the second end 1020, certain embodiments may include a flexible portion 1050 that may be more flexible than the areas proximate the first end 1010 and the second end 1020.

[0094] For example, the size of the inner core 1110, the size of the outer core 1120, and the spacing between the waveguides 1100 can decrease (e.g., simultaneously and gradually in some embodiments) along the optical element 1000 from the first end 1010 to the intermediate position 1040, such that at the intermediate position 1040, the size of the inner core 1110 is insufficient to guide light therethrough and the size of the outer core 1120 is sufficient to guide at least one optical mode. In certain embodiments, each waveguide 1100 can have capacity for at least one optical mode (e.g., single mode or multimode). For example, at the first end At 1010, the VC waveguide 1101 can support multiple spatial modes (M1) within the inner core 1110. At the intermediate position 1040, in various embodiments, the inner core 1110 may no longer be able to support all M1 modes (e.g., unable to support propagation of light). However, in some such embodiments, at the intermediate position 1040, the outer core 1120 may support all M1 modes (and possibly additional modes). In this example, light traveling within the inner core 1110 from the first end 1010 to the intermediate position 1040 may escape from the inner core 1110 to the outer core 1120 such that the light can propagate within both the inner core 1110 and the outer core 1120.

[0095] In addition, the size of the outer core 1120, the size of the second outer core 1122, and the spacing between the waveguides 1100 can decrease (e.g., simultaneously and gradually in some embodiments) along the optical element 1000, for example, from the intermediate position 1040 to the flexible portion 1050, such that at the flexible portion 1050, the size of the outer core 1120 is insufficient to guide light thereto and the size of the second outer core 1122 is sufficient to guide at least one optical mode thereto. In certain embodiments, at the intermediate position 1040, the VC waveguide 1101 can support all M1 modes in the outer core 1120. At the flexible portion 1050, in various embodiments, the outer core 1120 may no longer be able to support all M1 modes (e.g., may not be able to support the propagation of light). However, in some such embodiments, at the flexible portion 1050, the second outer core 1122 may be able to support all M1 modes (and possibly additional modes). In this example, light traveling within the outer core 1120 from the intermediate position 1040 to the flexible portion 1050 can escape from the outer core 1120 to the second outer core 1122 so that the light can propagate within the inner core 1110, the outer core 1120, and the second outer core 1122.

[0096] Additionally, the size of the outer core 1120, the size of the second outer core 1122, and the spacing between the waveguides 1100 can expand (e.g., simultaneously and gradually in some embodiments) along the optical element 1000 from the flexible portion 1050 to the second end 1020 such that at the second end 1020, the size of the second outer core 1122 is insufficient to guide light thereto and the size of the outer core 1120 is sufficient to guide at least one optical mode thereto. In certain embodiments, in various embodiments, at the second end 1020, the second outer core 1122 may no longer be able to support all M1 modes (e.g., may not be able to support the propagation of light). However, in some such embodiments, at the second end 1020, the outer core 1120 may support all M1 modes (and in some cases, may support additional modes). In this example, light traveling within the second outer core 1122 from the flexible portion 1050 to the second end 1020 can only propagate back within the inner core 1110 and outer core 1120 .

[0097] It will be understood that light traveling from the second end 1020 to the first end 1010 may behave in the opposite manner. For example, the size of the outer core 1120, the size of the second outer core 1122, and the spacing between the waveguides 1100 may decrease (e.g., simultaneously and gradually in some embodiments) along the optical element 1000 from the second end 1020 to the flexible portion 1050, such that at the flexible portion 1050, the size of the outer core 1120 is insufficient to guide light thereto, and the size of the second outer core 1122 is sufficient to guide at least one optical mode thereto.

[0098] The reduction in cross-sectional size of the core and cladding can advantageously provide stiffness and flexibility to the coupler array 450. Rigidity at the first end 1010 and the second end 1020 may be desirable because the optical element 1000 may be fused to the ends 1010, 1020 of the coupler array 450. However, it may also be desirable for the coupler array to be flexible so that it can be bent to connect with low profile integrated circuits. In certain embodiments, a flexible portion 1050 between the first 1010 and second 1020 ends may be provided therebetween, while allowing the first 1010 and second 1020 ends to be relatively rigid. The flexible portion may extend the length of the optical element 1000 and may mechanically isolate the first 1010 end and the second 1020 end. For example, the flexible portion 1050 may mechanically isolate the first end 1010 from the area between the flexible portion 1050 and the second end 1020. As another example, the flexible portion 1050 can mechanically isolate the second end 1020 from the area between the first end 1010 and the flexible portion 1050. Such mechanical isolation can provide stability to the first end 1010 and the second end 1020 with respect to environmental variations including, for example, temperature changes, mechanical shock and vibration. The length of the flexible portion 1050 is not particularly limited and can depend on the application. In some examples, the length can be 2-7 mm, 3-8 mm, 5-10 mm, 7-12 mm, 8-15 mm, any combination of these ranges, or any range formed from any value between 2-20 mm (e.g., 3-13 mm, 4-14 mm, 5-17 mm, etc.). In other examples, the length of the flexible portion 1050 can be shorter or longer.

[0099] At the same time, the flexible portion 1050 can provide flexibility. In many embodiments, the flexible portion 1050 can have a substantially similar cross-sectional size (e.g., the cross-sectional size of the waveguide 1100) extending over the length of the flexible portion 1050. In certain embodiments, the cross-sectional size at the flexible portion 1050 can be configured to be smaller than the cross-sectional size at the first end 1010 and the second end 1020. By having a smaller cross-sectional size, the flexible portion 1050 can be more flexible than the regions proximate the first 1010 and second 1020 ends. The smaller cross-sectional size can result from a reduction in the size of the core and cladding. An optional post-etching process may be desirable to further reduce the diameter of the flexible length of the flexible PROFA coupler 450.

[0100] In some embodiments, the flexible portion 1050 can be more flexible than a standard SMF28 fiber. In some embodiments, the flexible portion 1050 can bend at least 45 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, 80 degrees, 90 degrees, 100 degrees, 110 degrees, 120 degrees, or at least any value therebetween. In some embodiments, the flexible portion 1050 can bend in a range formed by any of these values, for example, from 45 degrees to 55 degrees, from 50 degrees to 60 degrees, from 60 degrees to 70 degrees, from 70 degrees to 80 degrees, from 80 degrees to 90 degrees, from 90 degrees to 100 degrees, from 100 degrees to 110 degrees, from 110 degrees to 120 degrees, or any combination of these ranges, or a range formed by any value within these ranges (e.g., from 50 degrees to 65 degrees, from 50 degrees to 85 degrees, from 65 degrees to 90 degrees). In other embodiments, the flexible portion 1050 can bend more or less than these amounts. As described herein, in various applications, the flexible portion 1050 may not bend during use, but flexibility may be desired to decouple the first 1010 end or the second 1020 end from other portions of the coupler array 450.

[0101] The coupler array 450 may include a coupler housing structure 1060. For example, the coupler housing structure 1060 may include a common single coupler housing structure. In certain embodiments, the coupler housing structure 1060 may include a medium 1140 (e.g., having a refractive index N-4) surrounding the waveguides 1100. In some examples, N-4 is greater than N-3. In other examples, N-4 is equal to N-3. The medium 1140 may include any medium as described herein (e.g., pure silica). The medium may also be a common component of the coupler array 450. 50 may be an all-glass coupler array. The waveguides 1100 may be embedded within the medium 1040 of the housing structure 1060. In some examples, the total volume of the medium 1140 of the coupler housing structure 1060 may be greater than the total volume of all of the inner and outer cores 1110, 1120, 1122 of the VC waveguides enclosed within the coupler housing structure 1060.

[0102] In some embodiments, each waveguide may be coupled to an optical fiber 2000 and / or optical device 3000 at a location inside, outside, or at a boundary region of the coupler housing structure 1060, as shown in, for example, FIG. 1A to 2D. Because the optical fiber 2000 and optical device 3000 may be different at each end, the first end 1010 and the second end 1020 may each be configured for the optical fiber 2000 or optical device 3000 to which it is coupled. For example, the MFD of the VC waveguide at the first end 1010 and / or the second end 1020 may be configured (e.g., using the core size) to match or substantially match the MFD of the optical fiber 2000 or optical device 3000 to which it is coupled. Additionally, the NA of the VC waveguide at the first 1010 end and / or the second 1020 end can be configured (e.g., using refractive index) to match or substantially match the NA of the optical fiber 2000 or optical device 3000 to which it is coupled. The refractive index can be modified by any method known in the art (e.g., doping the waveguide glass) or yet to be developed. In various embodiments, as described herein, the difference (N-1 minus N-2) can be greater than the difference (N-2 minus N-2A) such that the NA at the first end 1010 is greater than the NA at the second end 1020. In other embodiments, the difference (N-1 minus N-2) can be less than the difference (N-2 minus N-2A) such that the NA at the first end 1010 is less than the NA at the second end 1020. In yet other embodiments, the difference (N-1 minus N-2) can be equal to (N-2 minus N-2A), such that the NA at the first end 1010 is equal to the NA at the second end 1020. The VC waveguide can include any of the fiber types described herein, including but not limited to single mode fiber, multimode fiber, and / or polarization-maintaining fiber.

[0103] The size of the core and cladding (1110, 1120, 1122, 1130) (e.g., outer cross-sectional diameter if circular, outer cross-sectional dimension if not circular) is not particularly limited. In some embodiments, the core size of the inner core 1110 and / or outer core 1120 can be 1-3 microns, 2-5 microns, 4-8 microns, 5-10 microns, any combination of these ranges, or any range formed from any value between 1 and 10 microns (e.g., 2-8 microns, 3-9 microns, etc.). However, the size can be larger or smaller. For example, the core size of the inner core 1110 and / or outer core 1120 can range from submicrons to many microns, tens of microns, hundreds of microns, depending on, for example, the desired wavelength and / or number of modes.

[0104] Furthermore, the refractive index difference (e.g., between N-1 and N-2, between N-2 and N-2A, and / or between N-2A and N-3) is not particularly limited. In some examples, the refractive index difference is less than 1.5x10 -3 From 2.5x10 -3 , 1.7x10 -3 From 2.3x10 -3 , 1.8x10 -3 From 2.2x10 -3 , 1.9x10 -3 From 2.1x10 -3 , 1.5x10 -3 From 1.7x10 -3 , 1.7x10 -3 From 1.9x10 -3 Up to 1.9x10 -3 From 2.1x10 -3 Up to 2.1x10 -3 From 2.3x10 -3 Up to 2.3x10 -3 From 2.5x10 -3 up to 1.5x10, any combination of these ranges, or -3 From 2.5x10 -3 Any range formed from any value up to In other examples, the exponent difference may be larger or smaller.

[0105] As described herein, the optical device 3000 can include a PIC. The PIC can include an array of VGCs. Also, as described in U.S. Patent Application Publication No. 2012 / 0257857, entitled "High Density Optical Package Header Apparatus," which is incorporated herein in its entirety, multiple flexible PROFA couplers (such as coupler 450), each having multiple optical channels, can be advantageously combined together to form an optical multi-port input / output (IO) interface. In this manner, the optical multi-port IO interface can include multiple optical coupler arrays, at least one of which can include the optical coupler array 450 described herein.

[0106] 8 and 9, exemplary cross-sectional views of housing structures proximate a first end of a multi-channel optical coupler array are shown. The cross-sectional views are orthogonal to the longitudinal or length of the optical coupler array. Some such configurations provide improved cross-sectional or lateral (or transverse) positioning of the waveguides at the first end, allowing for self-aligned placement of the waveguides proximate the first end (e.g., circular (as shown in FIG. 8) or hexagonal tight placement in a housing structure having a hexagonal interior cross-section) and improved (possibly exact or near exact) cross-sectional positioning of the waveguides at the second end. Such configurations can also be aligned during manufacture so that the cross-sectional positioning of the waveguides at the second end is precisely positioned as desired.

[0107] Although various features of the exemplary optical combiner array may be described with respect to Figures 8 and 9, any of the features described above (e.g., with respect to any of the figures or embodiments described above) may be implemented in any combination with a multi-channel optical combiner array. For example, any of the features described with respect to Figures 1A-5 and 7 may be utilized. Figures 1A-5 and 7 may be utilized in a multi-channel optical combiner array and may be combined with any of the features described with respect to Figures 8 and 9.

[0108] For example, referring to the exemplary embodiment shown in Figures 1A-2D, there are two ends of the coupler array: a first (large) end and a second (small) end. The two ends are spaced apart longitudinally (along the z-direction). For example, in Figure 1A, the first end is proximate to location B and the second end is proximate to locations C and D.

[0109] In certain embodiments, one of the functions of the first end (proximate position B) is to seal the waveguides 30A, 32A-1, 32A-2 with increased or approximate positioning accuracy. For example, the coupler housing structure 14A proximate the first end (proximate position B) can seal, e.g., circumferentially surround, a portion of the length of the waveguides 30A, 32A-1, 32A-2, but not necessarily completely seal the ends of the waveguides 30A, 32A-1, 32A-2. In some such implementations, the waveguides 30A, 32A-1, 32A-2 may or may not extend (e.g., longitudinally) outside the coupler housing structure 14A. In Fig. 1A, adjacent to the first end, the end of the waveguide 30A is disposed within the coupler housing structure 14A, while the ends of the waveguides 32A-1, 32A-2 extend outside the coupler housing structure 14A, e.g., longitudinally (in a direction parallel to the z-direction). In Fig. 2B, adjacent to the first end, the ends of the waveguides 130B-1, 130B-2 are disposed in a cross-sectional boundary region outside the coupler housing structure 14A, and do not extend outside the coupler housing structure 14A, e.g., longitudinally (in a direction parallel to the z-direction).

[0110] In various embodiments, one of the functions of the second end (proximate positions C and D) is to accommodate the waveguides 30A, 32A-1, 32A-2 in a housing structure (e.g., in some cases a common housing) with improved (in some cases accurate or near accurate) cross-sectional positioning. structure). For example, the waveguides 30A, 32A-1, 32A-2 proximate the second ends (proximate positions C and D) may be embedded, e.g., circumferentially surrounded by the continuous coupler housing structure 14A. In FIG. 1A, proximate the second ends, the ends of the waveguides 30A, 32A-1, 32A-2 are longitudinally disposed at the outer cross-sectional boundary region of the coupler housing structure 14A. In some embodiments, proximate the second ends, one or more ends of the waveguides may be disposed within the coupler housing structure 14A or may extend longitudinally outside the coupler housing structure 14A.

[0111] To achieve improved positioning, some embodiments may include an exemplary cross-sectional configuration of a housing structure shown in FIG. 8 proximate the first end. The cross-section is orthogonal to the longitudinal direction or length of the optical coupler array. As shown in FIG. 8, the coupler array 800 may include a housing structure 801 having a lateral (or transverse) configuration of a ring surrounding a plurality of longitudinal waveguides 805 longitudinally proximate the first end. A gap, such as an air gap, may separate the plurality of longitudinal waveguides 805 from the surrounding ring. Some such configurations may allow for self-aligned placement of the waveguides proximate the first end (e.g., a circular (as shown in FIG. 8) or hexagonal tightly-fitting arrangement in a housing structure having a hexagonal interior cross-section).

[0112] In the example configuration shown in Figure 8, the waveguides 805 are arranged in a hexagonal configuration, although other configurations are possible, e.g., square, rectangular, etc.

[0113] The ring may have an inner cross section 801a (transverse, i.e., perpendicular to the longitudinal or length of the optical coupler array) that is circular or non-circular. For example, the inner cross section 801a may be circular, elliptical, D-shaped, square, rectangular, hexagonal, pentagonal, octagonal, other polygonal, etc. Also, the inner cross section 801a does not necessarily follow the arrangement of the waveguides 805. For example, four waveguides arranged in a square can be confined to the inner circular cross section. As another example, as shown in FIG. 8, the inner cross section 801a is circular, but the waveguides 805 are arranged in a hexagon. In some embodiments, a circular inner cross section as shown in FIG. 8 may be a preferred shape that can enable a close-packed hexagonal arrangement. Also, other inner cross section shapes, such as square or rectangular, can be used, which can enable non-hexagonal waveguide arrangements. In some examples, the inner cross section 801a may be similar to the arrangement of the waveguides 805 to reduce empty space. For example, in the case of a hexagonal arrangement of waveguides 805 , the inner cross section 801 a of the ring may be hexagonal to reduce the empty space between the inner cross section 801 a and the waveguides 805 .

[0114] The outer cross-section 801b (lateral, e.g., perpendicular to the longitudinal or length of the optical coupler array) may be circular or non-circular. For example, the outer cross-section 801b may be circular, elliptical, hexagonal, D-shaped (e.g., to provide passive axial alignment of the couplers, while flat surfaces allow for easy rotational alignment), square, rectangular, pentagonal, octagonal, other polygonal, etc. In FIG. 8, the outer cross-section 801b (e.g., circular) follows the shape of the inner cross-section 801a (e.g., circular). However, in some embodiments, the outer cross-section 801b need not be similar to the inner cross-section 801a. One function of the inner cross-sectional shape is to allow for improved lateral positional accuracy in the vicinity of the second end, and one function of the outer cross-sectional shape is to allow for passive axial alignment of the couplers (e.g., alignment can be performed without launching light into the couplers). In some configurations, it may be preferable to substantially maintain the outer cross-sectional shape from the first end to the second end to facilitate passive alignment at one or both ends of the coupler array.

[0115] FIG. 9 illustrates another exemplary cross-sectional configuration of the housing structure proximate the first end. As shown in FIG. 9, the coupler array 850 can include a housing structure 851 having a configuration (e.g., a possibly continuous configuration) with a plurality of holes 852. At least one of the holes 852 can include at least one of the longitudinal waveguides 855. A gap, such as an air gap, can separate the plurality of longitudinal waveguides 855 from the surrounding housing structure 851. As with the description related to the embodiment shown in FIG. 8, the outer cross section can be circular, elliptical, hexagonal, D-shaped, square, rectangular, pentagonal, octagonal, other polygonal, etc. Some such configurations can allow passive alignment at one or both ends of the coupler array. The example configuration shown in FIG. 8 may allow for simpler fabrication in some cases, while the example configuration shown in FIG. 9 may allow for arbitrary lateral waveguide positioning.

[0116] FIG. 9 shows an example configuration having six holes 852, although other numbers of holes are possible. The holes 852 in this example configuration may be isolated, or some or all of the holes 852 may be connected. For example, as shown in FIG. 9, a first hole 852-1 is isolated from a second hole 852-2. However, in some configurations, a first hole 852-1 may be connected to at least one second hole 852-2. Although the arrangement of holes 852 is shown as a 3×2 array, other arrangements are possible. For example, the arrangement pattern of holes may be hexagonal, square, rectangular, or defined by an XY array that defines the location of the holes in the cross section.

[0117] FIG. 9 shows all holes 852 with waveguides 855 illustrated as vanishing core (VC) waveguides. However, while at least one of the waveguides in this example is a VC waveguide, one or more of the holes 852 can include a non-vanishing core (Non-VC) waveguide. The VC or Non-VC waveguides 855 can include any of the waveguides described herein, such as single mode fiber, multimode fiber, polarization maintaining fiber, etc. In some embodiments, one or more of the holes 852 can be empty or have other (e.g., non-waveguide) material disposed therein, for example, to act as a fiducial mark. One or more of the holes 852 can have a single waveguide 855 (in some preferred configurations) disposed therein, or multiple waveguides 855 disposed therein, as shown in FIG. 9. Depending on the design, one or more holes 852 may be identical to or different from another hole 852, for example, to accommodate waveguides 855 of different shapes and dimensions (e.g., cross-sectional shapes, diameters, major / minor elliptical dimensions, etc.). The cross-section of the hole 852 may be circular or non-circular. For example, the cross-section may be circular, elliptical, hexagonal or D-shaped (e.g., to provide passive axial alignment of polarization-maintaining (PM) channels), square, rectangular, pentagonal, octagonal, other polygonal, etc. As shown, in many cases, the cross-section of the hole 852 proximate the first end is larger than the cross-section of the waveguide 855 such that a gap is disposed between the inner surface 851a of the coupler housing structure 851 and the waveguide 855.

[0118] The coupler housing structure (e.g., 801 in FIG. 8 or 851 in FIG. 9) can include a medium from a wide range of materials as described herein. As also described herein, the medium of the coupler housing structure 801, 851 can have a refractive index (N-4). The medium can be a laterally continuous medium. This can allow for a robust housing structure with improved lateral positioning accuracy in some embodiments. In some embodiments, the total volume of the medium of the coupler housing structure 801, 851 can be greater than the total volume of all the inner and outer cores of the VC waveguides confined within the coupler housing structure 801, 851, providing that in some embodiments all the VC waveguides are securely embedded within the housing structure, allowing for stable performance).

[0119] In certain embodiments, the exemplary configurations shown in Figures 8 and 9 may enable improved manufacturability of the device, for example, due to improved cross-sectional (lateral) positioning of the waveguide at the second end. This lateral position may be defined, for example, in the x and / or y directions, and z is the direction along the length coupler array (e.g., from the first end to the second end). In various manufacturing approaches, an assembly consisting of a waveguide (e.g., 805 in FIG. 8 and 855 in FIG. 9) and a coupler housing structure (e.g., 801 in FIG. 8 or 851 in FIG. 9) may be heated and stretched to form a second end, as shown in the side cross-sectional views shown in FIGS. 3A-3L. Referring to FIG. 8, the waveguide 805 may be inserted into a coupler housing structure 801 having a ring configuration (in a cross-section perpendicular to the longitudinal direction or length of the optical coupler array, e.g., in the xy plane shown). As mentioned above, a gap such as an air gap may be disposed between the coupler housing structure 801 and the waveguide 805 to allow lateral movement (in the x and / or y directions) of the waveguide relative to the coupler housing structure 801. 9, one or more waveguides 855 can be inserted into a coupler housing structure 851 having a number of holes 852 (e.g., when viewed in a cross section perpendicular to the longitudinal direction or length of the optical coupler array, e.g., in the xy plane as shown) in which the waveguides 855 can be passively aligned within the housing structure 851. A gap, such as an air gap, can be disposed between the coupler housing structure 851 and the waveguides 855 to allow lateral movement (in the x and / or y directions) of the waveguides relative to the coupler housing structure 851. When the waveguides are densely spaced (e.g., hexagonal), this movement capability can result in more accurate cross-sectional positioning at the second end after fabrication.

[0120] Referring to FIG. 1A, the coupler array can include a plurality of longitudinal waveguides 30A, 32A-1, 32A-2 having at least one VC waveguide 30A having an inner core 20A and an outer core 22A. The spacing between the inner core 20A, the outer core 22A, and the plurality of waveguides 30A, 32A-1, 32A-2 can decrease (e.g., gradually, sometimes simultaneously) from a first end (near position B) to a second end (near positions C and D). In various embodiments, the cross-sectional configuration at the first end (near position B) can be shown as in FIG. 8 or FIG. 9, while the cross-sectional configuration at the second end (near positions C and D) can be shown in FIG. 3A-3L or FIG. 7. In some embodiments, proximate the second end, there is substantially no gap between the coupler housing structure and the waveguide, some gaps are filled by the housing material, and some gaps are filled by the waveguide cladding material. As a result of the described cross-sectional configuration at the first end, the cross-sectional or lateral positioning of the waveguide at the second end can be improved. Thus, the waveguide at the second end can be properly aligned laterally (e.g., in the x-direction and / or y-direction) with the optical device.

[0121] 10 and 11, further exemplary embodiments of the optical coupler array 4000, 5000 are shown. The coupler array 4000, 5000 can be configured to couple between multiple optical fibers, such as between optical fibers having different mode fields and / or core sizes. In some implementations, the coupler array 4000, 5000 can be configured to provide coupling between a set of individual insulated optical fibers 2000 and an optical device 3000 having at least one optical channel that allows the propagation of multiple optical modes. In some preferred embodiments, all the insulated optical fibers 2000 can be identical (or in some embodiments different), and the optical device 3000 can include at least one few-mode fiber, multimode fiber, multicore single mode fiber, multicore few-mode fiber, and / or multimode fiber. In comparison with the specific embodiments described herein with respect to the figures, the various embodiments described herein with respect to FIGS. 1A-5 are to be referred to FIGS. 1A-5. 1A-5, various embodiments 4000, 5000 may include further reduction in the taper diameter, which allows light to exit the outer core 4120, 5120 and propagate in a coupled waveguide 4150, 5150 formed by at least two adjacent cores. Thus, various embodiments described herein may include: The coupler array may be configured to optically couple between fibers having dissimilar mode fields and / or core shapes or sizes. Advantageously, some embodiments of the coupler array may improve and / or optimize optical coupling between one or more of single mode fibers, few mode fibers, multimode fibers, multicore single mode fibers, multicore few mode fibers, and / or multicore multimode fibers.

[0122] Various features of the exemplary coupler array will now be described with respect to Figures 10 and 11, however the described features may be implemented in any combination with the coupler array described with respect to Figures 10 and 11. Any of the described features may be implemented in any combination with the coupler array described with respect to Figures 1A-5 and 7. 1A-5 and 7. Additionally, any of the features described with respect to Figures 1A-5 and 7 may be combined. Any of the features described with respect to Figures 1A-5 and 7 may be combined with any of the features described with respect to Figures 10 and 11. Any of the features described with respect to 10 and 11 may be combined. For example, the exemplary coupler array 4000, 5000 is illustrated utilizing housing structures 4060, 5060 similar to the housing structures 801, 851 illustrated in Figures 8-9. In these examples, the cross-sectional configuration of the housing structure 4060, 5060 may include a structure having multiple holes (e.g., multi-hole), as shown in FIG. 10, or may include one hole (e.g., a single hole surrounded by a ring), as shown in FIG. 11. However, other housing structures may be used. For example, the housing structures described with respect to FIGS. 1A-5 and 7 may be used.

[0123] 10, a particular embodiment of a multi-channel optical combiner array 4000 can include an elongated optical element 4001 having a first end 4010, an intermediate position or cross section 4050, and a second end 4020. The optical element 4001 can include a combiner housing structure 4060 and a plurality of longitudinal waveguides 4100 disposed within the housing structure 4060. The waveguides 4100 can be disposed relative to one another in a cross-sectional geometrical waveguide arrangement. In FIG. 10, an exemplary cross-sectional geometrical waveguide arrangement of the waveguides 4100 relative to the first end 4010, the intermediate cross section 4050, and the second end 4020 is shown. As illustrated by the shaded area in the cross section and described herein, light can be guided through the optical element 4001 from the first end 4010, through the intermediate cross section 4050, to the second end 4020.

[0124] As shown in FIG. 10, proximate (e.g., adjacent) the first end 4010, the housing structure 4060 (e.g., a possibly general single coupler housing structure) can have a cross-sectional configuration of a structure (e.g., a possibly laterally continuous structure) having a plurality of holes 4062. FIG. 10 shows an example configuration having three circular holes 4062-1, 4062-2, 4062-3. However, the shape of the holes, the number of holes, and / or the arrangement of the holes are not particularly limited and can include other shapes, numbers, and / or arrangements, including those described with respect to FIG. 9. At least one of the holes 4062 can include at least one of the longitudinal waveguides 4100. A gap, such as an air gap, may separate the plurality of longitudinal waveguides 4100 from the surrounding housing structure 4060 proximate the first end 4010. In some embodiments, there may be substantially no gap between the coupler housing structure 4060 and the waveguide 4100 at the intermediate location 4050 and / or the second end 4020. For example, one or more gaps may be filled by the housing material and / or the waveguide cladding material. As described herein, in some embodiments, there may be a gap between the coupler housing structure 4060 and the waveguide 4100 proximate the first end 4010, but there may be substantially no gap between the coupler housing structure 4060 and the waveguide 4100 proximate the second end 4020 (or vice versa). In some embodiments, there may be substantially no gap between the coupler housing structure 4060 and the waveguide 4100 near the first end 4010, the intermediate position 4050, and / or the second end 4020.

[0125] As described herein, the coupler array 4000 may be operable to optically couple with a plurality of optical fibers 2000 and / or optical devices 3000. The coupler array 4000 may couple with the optical fibers 2000 via a plurality of waveguides 4100 proximate the first end 4010 (e.g., via fusion splices 2001) and / or may couple with the optical devices 3000 via a plurality of waveguides 4100 proximate the second end 4020 (e.g., via fusion splices not shown). In FIG. 10, three waveguides 4100 are shown in each of the three holes 4062-1, 4062-2, 4062-3. However, any number of waveguides 4100 may be used for each of the holes 4062. In some embodiments, the number of waveguides 4100 may be equal to the number of optical fibers 2000 (e.g., nine waveguides for coupling with nine optical fibers). In some other embodiments, the number of waveguides 4100 in at least one hole may be equal to the number of optical modes supported by the corresponding few-mode or multi-mode waveguides of the device 3000 (e.g., three waveguides in each of three holes to couple with three 3-mode cores of a multi-core fiber). In various embodiments, the waveguides 4100 may be spaced apart from one another (e.g., predetermined in some implementations) within each hole 4062. In some preferred embodiments of the multi-hole configuration, each hole 4062-1, 4062-2, 4062-3 may include all the waveguides (e.g., fibers) intended to couple to at least one particular core of the few-mode fiber, multimode fiber, and / or multi-core fiber of the optical device. In some other embodiments, one or more additional fibers and / or dummy fibers (e.g., that may not guide light) may be utilized to create a particular geometry of active guiding optical fiber waveguides.

[0126] In various embodiments, the plurality of waveguides 4100 can have capacity for at least one optical mode (e.g., possibly a predetermined mode field profile). The plurality of waveguides 4100 can include at least one missing core (VC) waveguide 4101. FIG. 10 illustrates all of the waveguides 4100 as VC waveguides. However, one or more non-VC waveguides can also be used. As described herein, the VC waveguide 4101 can include an inner core (e.g., an inner missing core) 4110, an outer core 4120, and an outer cladding 4130 having refractive indices N-1, N-2, and N-3, respectively. The outer core 4120 can longitudinally surround the inner core 4110, and the outer cladding 4130 can longitudinally surround the outer core 4120. As described herein, the relative magnitude relationship between the refractive indices of the inner core 4110, the outer core 4120, and the outer cladding 4130 may advantageously be N-1>N-2>N-3.

[0127] In various embodiments, the housing structure 4060 can surround the waveguide 4100. The coupler housing structure 4060 can include a medium 4140 having a refractive index N-4. The medium 4140 can include any of those described herein. In some examples, the total volume of the medium 4140 of the coupler housing structure 4060 can be greater than the total volume of all the inner and outer cores 4110, 4120 of the VC waveguides confined within the coupler housing structure 4060. In some examples, the waveguide 4100 can be embedded in the housing structure 4060 (e.g., near the second end 4020).

[0128] In certain embodiments, the inner core 4110 waveguide dimensions, the outer core 4120 waveguide dimensions , refractive index, and / or numerical aperture (NA) are selected to increase and / or optimize coupling to the individual fibers 2000. In various embodiments, the outer core 4120 waveguide dimensions, refractive index, NA, and / or cladding 4130 dimensions are selected to increase and / or optimize coupling to the optical device 3000. Various embodiments described herein may also include the reflection-reducing features of pitch-reduced optical fiber arrays described in U.S. application Ser. No. 14 / 677,810, entitled "Optimized Configurable Pitch-Reduced Optical Fiber Arrays," which is incorporated herein in its entirety. For polarization control, a portion of the outer core 4120 may be made to have a non-circular cross-section (e.g., elliptical as shown in FIG. 10), and a particular orientation of the outer core 4120 may be used to increase and / or optimize optical coupling. Various embodiments described herein may also include any of the features of optical polarization mode couplers described in U.S. application Ser. No. 15 / 617,684, entitled "Configurable Polarization Mode Couplers," which is incorporated herein in its entirety.

[0129] In some embodiments, the size of the inner core 4110, the size of the outer core 4120, the size of the cladding 4130, and / or the spacing between the waveguides 4100 may decrease (e.g., simultaneously and gradually, in some embodiments) along the optical element 4001 from the first end 4010 to an intermediate position or cross section 4050. In some embodiments, a predetermined reduction profile may be used. In the example shown in FIG. 10, at the intermediate position 4050, the inner core 4110 may be insufficient to guide light therethrough and the outer core 4120 may be sufficient to guide at least one optical mode (e.g., a spatial mode).

[0130] In some embodiments, each core of the waveguide 4100 can have capacity for at least one optical mode (e.g., single mode, few modes, or multiple modes). For example, at the first end 4010, the VC waveguide 4101 can support a number of spatial modes (M1) within the inner core 4110. At the intermediate position 4050, in various embodiments, the inner core 4110 may no longer be able to support all M1 modes (e.g., unable to support propagation of light). However, in some such embodiments, at the intermediate position 4050, the outer core 4120 may support all M1 modes (and possibly additional modes). In this example, light traveling within the inner core 4110 from the first end 4010 to the intermediate position 4050 can escape from the inner core 4110 to the outer core 4120 such that the light can propagate within the outer core 4120.

[0131] In some embodiments, the size of the inner core 4110, the size of the outer core 4120, the size of the cladding 4130, and / or the spacing between the waveguides 4100 may decrease further (e.g., simultaneously and gradually in some examples) along the optical element 4001 from the intermediate position 4050 to the second end 4020. In the example shown in Figure 10, at the second end 4020, the outer core 4120 may be insufficient to guide light thereto.

[0132] In certain embodiments, at the intermediate position 4050, the VC waveguide 4101 can support all M1 modes within the outer core 4120. At the second end 4020, the outer core 4120 may no longer be able to support all M1 modes (e.g., unable to support propagation of light). However, in some such embodiments, at the second end 4020, the combined core 4150 of at least two cores can support all M1 modes of all combined waveguides 4101 (and possibly support additional modes). In this example, light traveling within the outer core 4120 from the intermediate position 4050 to the second end 4020 is guided from the outer core 4120 by a combination of at least two outer cores (e.g., two or more adjacent cores) such that the light can propagate within the combined core. 10, each of the coupled waveguides 4150 is formed by three outer cores. However, in some embodiments, the coupled waveguides 4150 may be formed with another number of outer cores.

[0133] It will be appreciated that light traveling from the second end 4020 to the first end 4010 may behave in an inverse manner. For example, in some embodiments, light may travel from a coupled waveguide 4150 formed by at least two adjacent outer cores to at least one outer core 4120 proximate the intermediate cross section 4050, and from the outer core 4120 to a corresponding inner core 4110 proximate the first end 4010. In the example shown in FIG. 10, each of the combined waveguides 4150 may support three propagation modes. Propagating from the second end 4020 to the first end 4010, each propagation mode may be coupled to a corresponding outer core 4120 proximate the intermediate cross section 4050 and travel from the outer core 4120 to a corresponding inner core 4110 proximate the first end 4010.

[0134] 11, an exemplary embodiment 5000 includes similar features to the exemplary embodiment 4000 shown in FIG. 10. One difference is that the cross-sectional configuration of the housing structure 5060 includes a structure having a single hole 5062 instead of multiple holes 4062. Similar to the exemplary embodiment 4000 shown in FIG. 10, the optical element 5001 can include a coupler housing structure 5060 (e.g., including a medium 5140) and multiple longitudinal waveguides 5100 disposed within the housing structure 5060. The waveguides 5100 can be disposed relative to one another in a cross-sectional geometric waveguide arrangement within the holes 5062. As shown, light can be guided through the optical element 5001 from a first end 5010, through an intermediate cross-section 5050, and to a second end 5020.

[0135] As described herein, a gap can separate the multiple longitudinal waveguides 5100 from the surrounding housing structure 5060. In some embodiments, there may be substantially no gap between the coupler housing structure 5060 and the waveguides 5100 proximate the intermediate location 5050 and / or the second end 5020. For example, in FIG. 11, a gap is shown proximate the second end 5020, but in preferred embodiments, there may be substantially no gap between the coupler housing structure 5060 and the waveguides 5100. In some embodiments, there may be substantially no gap between the coupler housing structure 5060 and the waveguides 5100 proximate the first end 5010, the intermediate location 5050, and / or the second end 5020.

[0136] In various embodiments, the plurality of waveguides 5100 can include at least one VC waveguide 5101. FIG. 11 illustrates all 37 of the waveguides 5100 as VC waveguides 5101 in a hexagonal arrangement. However, any arrangement can be used. Additionally, any number of VC waveguides, non-VC waveguides, and / or dummy fibers may be used. As described herein, one or more dummy fibers can be utilized to create a particular geometry of active optical fiber waveguides. As described herein, the VC waveguide 5101 can include an inner lost core 5110, an outer core 5120, and an outer cladding 5130.

[0137] In certain embodiments, the inner core 5110 waveguide dimensions, outer core 5120 waveguide dimensions, cladding 5130 dimensions, refractive index, and / or numerical aperture (NA) can be selected to increase and / or optimize coupling to individual fibers 2000 and / or optical devices 3000. In some embodiments, the size of the inner core 5110, the size of the outer core 5120, the size of the cladding 5130, and / or the spacing between the waveguides 5100 may decrease along the optical element 5001 from the first end 5010 to the second end 5020. In the example shown in FIG. 11, at an intermediate position 5050, the inner core of a particular waveguide 5100 may be The outer core 5120 of a particular waveguide 5100 may be sufficient to guide at least one optical mode (e.g., spatial mode) while the outer core 5110 may be insufficient to guide light therethrough. In this example, proximate the second end 5020, the outer core 5120 may be insufficient to guide light therethrough. Thus, in some embodiments, light traveling in the outer core 5120 from the intermediate position 5050 to the second end 5020 may escape from the outer core 5120 into a combined waveguide 5150 formed by at least two outer cores (e.g., two or more adjacent cores) such that the light can propagate in the combined core. In the example shown in FIG. 11, each of the combined waveguides 5150 is formed by three outer cores, although the combined waveguides 5150 may be formed by another number of outer cores. The remaining cores (e.g., cores of waveguides or dummy fibers) may or may not guide light. Light traveling from the second end 5020 to the first end 5010 may behave in the opposite manner.

[0138] As described herein, various embodiments relate to optical coupler arrays configured to couple light from one or more optical fibers to an optical device, such as a photonic integrated circuit (PIC), or vice versa. In various implementations, one or more optical coupler arrays can include one or more features configured to passively align (e.g., laterally and / or axially) with one or more features of the optical device. Some such embodiments can advantageously provide passive alignment without time-consuming and costly active alignment, which may involve, for example, transmitting light through a waveguide structure, detecting coupling efficiency, and optimizing alignment between the waveguides of the coupler array and the optical device to optimize light coupling. Axial alignment is also desirable for polarization processing and multi-channel coupling.

[0139] FIG. 12A illustrates a schematic of an exemplary optical coupler array configured to provide passive alignment with an optical device such as a PIC. The exemplary optical coupler array 900 can include one or more longitudinal waveguides 930 within a housing structure 914. The housing structure 914 can have an outer cross-sectional shape consisting of a first side 914A and a second side 914B. The first side 914A can be configured to align with a feature 945 of the optical device 940. The second side 914B can be configured to align with a feature 945 of the optical device and / or a top surface 945B of the optical device 940 in some implementations. For example, the second side 914B can be substantially parallel to the top surface 945B of the feature 945 of the optical device and can be substantially linear. As another example, the second side 914B can be higher or lower (e.g., vertically) than the top surface 945B of the feature 945 of the optical device, but still be substantially parallel to the top surface 945B. In the example of FIG. 12A, the housing structure 914 has a D-shaped outer cross-sectional shape with a first side 914A consisting of a curved portion and a second side 914B consisting of a flat portion. The curved side 914A can be aligned with a feature 945 (e.g., a V-groove) of the optical device 940, and the flat side 914B can be aligned (e.g., substantially parallel) with the feature 945 of the optical device and / or the top surface 945B of the optical device 940. In some implementations, an alignment carrier 920 (e.g., a plate, block, wedge, etc.) having a first side 920A and a second side 920B can be disposed on the second side 914B of the housing structure 914 of the optical coupler array 900 to provide alignment with the feature 945 of the optical device and / or the top surface 945B of the optical device 940. FIG. 12B illustrates a schematic of an exemplary optical combiner array 900 aligned and coupled with the optical device 940 shown in FIG. 12A.

[0140] The optical combiner array 900 can be any optical combiner array known in the art or yet to be developed. The optical combiner array 900 can be any optical combiner array described herein. 1A-11. As an example, in some embodiments, the optical coupler array 900 can include a pitch-reduced optical fiber coupler array (PROFA) as described herein. The PROFA can be advantageously used to provide access to the individual channels. In various embodiments, the optical coupler array 900 can have a first end 901 and a second end 902. The optical coupler array 900 can be configured to optically couple with a plurality of optical fibers (not shown) at the first end 901 and to optically couple with an optical device 940 at the second end 902.

[0141] The optical coupler array 900 can include one or more optical waveguides 930. The number of waveguides is not particularly limited (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 40, 50, 75, 80, 90, 100, etc., or any range formed by such values). The optical waveguides 930 can be any optical waveguides known in the art or yet to be developed. For example, the optical waveguides 930 can include any waveguides described herein, such as a lost core waveguide or a non-lost core waveguide. The waveguides 930 can include optical fibers and are not limited with respect to the type of optical fiber, but can include any optical fiber, such as single mode fiber, few mode fiber, multimode fiber, polarization maintaining fiber, and / or any combination thereof. The one or more optical waveguides 930 can be disposed within a housing structure 914, such as a common single coupler housing structure. In some implementations, one or more optical waveguides 930 may be embedded in the housing structure 914. In some implementations, the waveguides 930 may comprise the core of the fiber and the housing 914 may comprise the cladding of the fiber. With reference to FIG. 12A, for example, a multi-core fiber (MCF) for multi-channel coupling may be used. In this case, the waveguides 930 are the core of the MCF and the housing 914 is the cladding. In some implementations, the MCF fiber may be manufactured separately and fusion spliced ​​to the end of the PROFA coupler, or the PROFA coupler may be manufactured with the MCF as an integral part of the PROFA coupler. For example, the MCF is formed as a relatively long and flexible end of the PROFA coupler. In some implementations, the PROFA coupler may or may not be used. For example, the optical coupler array 900 may be optically coupled to an MCF (not shown) at a first end 901. The MCF may be operable to optically couple to at least one optical fiber waveguide (e.g., multiple optical fibers or another optical device).In some implementations, the MCF may be optically coupled to a second optical coupler array (at an opposite end from the optical coupler array 900) that is operable to optically couple with at least one optical fiber waveguide (e.g., a plurality of optical fibers or another optical device). The second optical coupler array may be any optical coupler array disclosed herein, including any of the optical coupler arrays of Figures 1A-11. The optical coupler array 900 shown in Figures 1A-11 or 12A. Other examples are possible.

[0142] The optical coupler array 900 can have one or more features configured to passively align with one or more features of the optical device 940 (or to passively align with one or more features of the carrier or substrate of the coupler array 900 and / or the optical device 940). In some examples, the optical coupler array 900 can have one or more features that can passively align with one or more features of a common carrier / substrate of the coupler array 900 and the optical device 940. The features of the optical coupler array 900 can be aligned with one or more of the waveguides 930 of the optical coupler array 900 (e.g., the position of the first side 914a can be registered relative to the position of the waveguides 930 of the optical coupler array 900), and the features of the optical device 940 can be positionally registered with one or more of the waveguides 950 of the optical device 940 (e.g., the position of the V-groove 945 can be registered relative to the position of the waveguides 950 of the optical device 940). When features of the optical coupler array 900 mate or mate with features of the optical device 940, the waveguides 930 of the optical coupler array 900 are aligned (e.g., laterally and / or axially at the second end 902) with the waveguides 950 of the optical device 940. In some embodiments, features of the optical device 940 can accommodate reciprocally or complementary designed features of the optical coupler array 900. In some embodiments, features of the optical coupler array 900 can accommodate reciprocally or complementary designed features of the optical device 940.

[0143] In some implementations, the features of the optical coupler array 900 may include a particular shape of the housing structure 914, such as a shape complementary to the features 945 of the optical device 940 (or a shape complementary to the features of the carrier or substrate of the coupler array 900 and / or the optical device 940). For example, the housing structure 914 may have an outer cross-sectional shape with a first side 914A consisting of one or more curved portions (e.g., a circular or elliptical portion or portions). In some embodiments, the outer cross-sectional shape may include a second side 914B consisting of one or more flat portions (e.g., a flat or planar portion or portions). With reference to FIG. 12A, the housing structure 914 may have a D-shaped outer cross-sectional shape. For example, the housing structure 914 may have a curved side 914A and a flat side 914B. Other shapes, including any shape with flat and / or curved portions, may also be used (e.g., a square, a rectangle, a pentagon, a hexagon, an octagon, any other polygonal shape, a circle with flat portions, etc.). In various embodiments, the second side 914B can be positioned at a distance from the waveguide 930 such that the guiding properties are maintained and not disturbed. For example, the second side 914B can be positioned at a distance of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 wavelengths (or any range formed by such values) from the waveguide 930. In some embodiments, the second side 914B can be positioned such that the insertion loss is low (e.g., minimized in some embodiments). In some cases, the second side 914B can be positioned such that the polarization extinction ratio is high (e.g., maximized in some cases). The second side 914B can also be registered (e.g., in height) with the optical device 940.

[0144] 12A, an optical device 940 (e.g., a PIC) can include one or more waveguides 950 configured to couple with one or more waveguides 930 of an optical coupler array 900. FIG. 12A illustrates a PIC 940 having a single layer of waveguides 950. In some implementations, the optical device 940 can include multiple layers of waveguides 950. The optical coupler array 900 (e.g., made of MCF) can also include a corresponding two-dimensional array of waveguides 930. Features of the optical device 940 can include shapes within the device 940 (and / or within a common substrate with the optical coupler array 900). As an example, as shown in FIG. 12A, a chip / die edge 947 can be faceted to integrate features of a registered V-groove 945. The V-groove 945 can include angled walls 945A forming a V-shape. The V-groove 945 (or optical device 940) may also include a top surface 945B, for example, configured to align (e.g., be substantially parallel) with the second side 914B of the housing structure 914 of the optical coupler array 900. In some implementations, the V-groove 945 and / or the top surface 945B of the optical device 940 may be substantially parallel and substantially linear with the second side 914B of the housing structure 914 of the optical coupler array 900. In some examples, the V-groove 945 and / or the top surface 945B of the optical device 940 may be substantially parallel but lower or higher (e.g., in a vertical direction) than the second side 914B of the housing structure 914 of the optical coupler array 900. Other configurations are possible. The features of the V-groove 945 with the chip / die edge 947 may include one or more features for bonding and / or index alignment / filling. For example, as shown in FIG. 12C , features may be formed within a V-groove 945 (e.g., the walls 946 of the V-groove 945) that may allow the epoxy to flow and better adhere to the optical device 940. 45A). As another example, the features can include features 946B (e.g., protrusions, holes, pits, grooves, etc.) that enable the index-matching adhesive to have better mechanical adhesion to the chip / die edge 947. Other exemplary features of the optical device 940 can include other shapes that have flat surfaces (e.g., square or rectangular trenched structures, or hexagonal or octagonal trenched structures) and / or have curved surfaces. Some such examples can be useful, for example, to facilitate preferential or multiple orientation of the MCF.

[0145] 12B, the V-groove 945 of the optical device 940 can receive the housing structure 914 in the shape of the optical coupler array 900 (e.g., D-shaped). For example, the first side 914A of the housing structure 914 can be configured to be disposed within the V-groove 945 such that a shaped (e.g., curved in this example) portion of the first side 914A can contact and / or align with the shape of the optical device 940 (e.g., wall 945A of the V-groove 945). In some embodiments, the second side 914B can be configured to align with the V-groove 945 and / or the top surface 945B of the optical device 940 (e.g., substantially parallel). For example, the second side 914B can be substantially parallel and substantially straight with the V-groove 945 and / or the top surface 945B of the optical device 940. As another example, the second side 914B can be higher or lower (e.g., vertically) than the V-groove 945 and / or the top surface 945B of the optical device 940, but can be substantially parallel to the top surface 945B. By simply seating in the V-groove 945 and positioned upward against the facet edge 947 (e.g., edge-coupled), the optical coupler array 900 can advantageously self-align (e.g., automatically align) with the optical device 940 such that the waveguides 930 of the optical coupler array 900 can be laterally and axially aligned with the waveguides 950 of the optical device 940. In various embodiments, the waveguides 930 of the light coupler array 900 can be aligned with the waveguides 950 of the optical device 940 with a light coupling efficiency of between 50% and 100% (e.g., between 60% and 100%, between 70% and 100%, between 80% and 100%, between 90% and 100%). In some embodiments, one or more of the waveguides 930, 950 or surfaces thereof can be angled at the interface to reduce back reflections.

[0146] Additional alignment and / or bonding features are possible. For example, the optical coupler array 900, the optical device 940, and / or the carrier / substrate (not shown) can include alignment fiducials. As an example, the optical coupler array 900 can include a polarization-maintaining (PM) MCF configured to couple with the polarization-sensitive waveguide of the PIC. The alignment fiducials can be incorporated into the MCF, the PIC, the carrier / substrate, and / or any combination thereof. The alignment fiducials can be used by machine vision for coarse alignment, and self-alignment features achieve fine alignment. The fiducials can be any kind of visually identifiable feature, such as, for example, lithographically formed metal geometries (e.g., lines, corners, crosses, etc.). As another example, the mechanical bonding features can be used to facilitate, for example, compression bonding, solder bonding, laser welding, and / or the flow and retention of optical or mechanical adhesives. These can be, for example, copper bond pads, metallization to accept solder bumps, metal pads or lines for laser welding, grooves to increase surface or roughness to enhance mechanical adhesion, etc. Mechanical coupling features (e.g., reciprocal features in the optical coupler array 900 and optical device 940) can also be used for non-optical coupling, for example, for electrical or fluid transmission. For example, a fiber can transmit light, but can also have electrical (e.g., metal) and / or fluid (e.g., hole) waveguides that also transmit electricity or fluid. These can be, for example, PICs used in microfluidics, biological analysis, gas sensing, and / or for various input / output needs, such as electrical, fluid / gas, and / or optical. The array of waveguides in the optical coupler array 900 and / or the optical device 940 may be heterogeneous to include other mechanical or transmission coupling modes.

[0147] In some implementations, the optical coupler array 900 may include an alignment carrier 920 (e.g., a plate, a block, a wedge, etc.) disposed on and / or coupled to the second side 914B of the housing structure 914. The alignment carrier 920 may have a first side 920A and a second side 920B. In some implementations, the alignment carrier 920 may include one or more features configured to align with one or more features of the second side 914B of the housing structure 914, such as one or more features complementary to one or more features of the second side 914B of the housing structure 914. For example, the first side 920A of the alignment carrier 920 may include one or more flat portions (e.g., a portion or portions of a flat or planar shape) configured to align with one or more flat portions of the second side 914B of the housing structure 914. In some implementations, a flat portion of a first side 920A (e.g., lower side) of the alignment carrier 920 may be disposed on a flat portion of a second side 914B (e.g., upper side) of the housing structure 914. The shape of the second side 920B of the alignment carrier 920 is not particularly limited. For example, the second side 920B may include one or more flat and / or curved portions. The second side 920B may include a regular or irregular shape. The alignment carrier 920 may be advantageously configured to provide an axial alignment tool, for example, to enable a pick-and-place machine to properly position the optical coupler array 900 to provide alignment with the V-groove 945 and / or the top surface of the optical device 940. 12A-12B, the housing structure 914 can be designed such that the waveguide 930 is axially aligned with the waveguide 950 of the PIC when a top surface 945B of the PIC and a top surface 914B of the housing structure 914 of the optical coupler array 900 are substantially parallel. A pick-and-place tool can pick up the alignment carrier 920 by, for example, applying a vacuum to the top surface 920B and then place it on the housing structure 914.The top surface 914B of the housing structure 914 and / or the bottom surface 920A of the alignment carrier 920 of the optical coupler array 900 may include an adhesive (e.g., a pre-applied adhesive). The alignment carrier 920 and the housing structure 914 may be bonded by pressing the alignment carrier 920 against the housing structure 914, which may also be present on a suitable carrier, and the housing structure 914 may be axially aligned such that the housing structure 914 may be lifted and placed into the V-groove 945 and bonded therein, thereby aligning the waveguides 930 and 950. In some implementations, the alignment carrier 920 may extend laterally beyond the second side 914B of the housing structure 914 on at least one or both sides. The alignment carrier 920 may be configured to be located above (e.g., located above and / or on) the V-groove 945 or the top surface 945B of the optical device 940. In some embodiments, the alignment carrier 920 may not sit on and / or contact the V-groove 945 and / or the top surface 945 B of the optical device 940 .

[0148] Other examples are possible. For example, the housing structure 914 of the optical coupler array 900 can have a second side 914B with a curved portion, and the alignment carrier 920 can have a first side 920A with a V-shape or curved portion. As described herein, the optical coupler array 900 can have a housing structure 914 with a first side 914A (e.g., a bottom surface) having a shape complementary to the feature 945 of the optical device 940 to provide passive alignment. For further alignment, in some implementations, the optical coupler array 900 can have a housing structure 914 with a first side 914A (e.g., a bottom surface) having a shape complementary to the feature 945 of the optical device 940. The alignment carrier 920 may include an alignment structure 914 having a first side 920A (eg, a bottom side) having a complementary shape to a second side 914B (eg, a top side) of the alignment structure 914.

[0149] Some implementations may include, for example, multiple optical coupler arrays coupled by an alignment carrier to form a multi-fiber array. FIG. 13 illustrates an exemplary multi-fiber array 1300 disposed above an optical device 1340. The exemplary multi-fiber array 1300 includes multiple optical couplers 1301. The multi-fiber array 1300 may include 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. optical couplers 1301. The number of optical couplers 1301 is not particularly limited. FIG. 13 illustrates four optical couplers 1301 for illustrative purposes. The optical couplers 1301 may include any of the optical coupler arrays described herein (including, for example, optical coupler array 900). The optical couplers 1301 may include one or more longitudinal waveguides 1330. The waveguides 1330 may include any of the waveguides described herein (including, for example, waveguide 930), including any lost core waveguides and / or non-lost core waveguides. In some embodiments, the waveguide 1330 may comprise a core of a multicore fiber. Some fibers may be flexible.

[0150] 13, the waveguides 1330 of the optical coupler 1301 can be embedded in a common single housing structure 1314. The housing structure 1314 can include any of the housing structures described herein (including, for example, the housing structure 914). In some implementations, the housing structure 1314 can include a cladding. As shown in FIG. 13, the housing structure 1314 has a first side 1314a that can be comprised of one or more curved portions. The housing structure 1314 has a second side 1314B that can be comprised of one or more flat portions. In various implementations, the flat portion(s) of the second side 1314B can be positioned at a distance from the waveguide 1330 such that the insertion loss is low from one end of the waveguide 1330 to the other end. In various embodiments, the flat portion(s) of the second side 1314B can be positioned at a distance from the waveguide 1330 such that the waveguiding properties are maintained from one end of the waveguide 1330 to the other.

[0151] Continuing to refer to FIG. 13, the optical coupler 1301 may be coupled together with an alignment carrier 1320. The alignment carrier 1320 may include any of the alignment carriers described herein (including, for example, the alignment carrier 920). The alignment carrier 1320 may include, for example, a plate, a block, a wedge, or the like. The alignment carrier 1320 may have a first side 1320A and a second side 1320B and may be disposed on a second side 1314B of the housing structure 1314 of the optical coupler 1301. Referring to FIG. 13, the first side 1320A of the alignment carrier 1320 may constitute one or more flat portions 1320A-1 coupled with one or more flat portions of the second side 1314B of the housing structure 1314 of the optical coupler 1301. In some implementations, the flat portion 1320A-1 of the alignment carrier 1320 may be adhered (e.g., with an adhesive) to a flat portion of the second side 1314B of the housing structure 1314 of the optical coupler 1301. As described herein, the alignment carrier 1320 can extend laterally beyond the second side 1314B of the housing structure 1314 of the optical coupler 1301 on at least one side (e.g., extending on both sides as shown in FIG. 13 ).

[0152] In Figure 13, the multi-fiber array 1300 is disposed over an exemplary optical device 1340. The optical device 1340 may include any of the optical devices described herein, including, for example, optical device 940. With reference to Figure 13, the optical device 1340 or a carrier for the optical device 1340 may include a V-groove 1345 and / or may include a wall 1345A and a top surface 1345B of the optical device 1340. A first side 1314A of the housing structure 1314 of the optical coupler 1301 may be disposed within the V-groove 1345. For example, the first side 1314A of the housing structure 1314 may contact the wall 1345A of the V-groove 1345. Other mutually or complementary designed shapes of the optical coupler 1301 and the optical device 1340 are possible, as described herein.

[0153] When the multi-fiber array 1300 is placed within the optical device 1340, the alignment carrier 1320 can be configured to align (e.g., be substantially parallel) with the top surface 1345B (e.g., V-groove 1345) of the optical device 1340. For example, the first side 1320A of the alignment carrier 1320 can be configured to sit on the top surface 1345B of the optical device 1340. In an embodiment, the alignment carrier 1320 can be configured to sit on the top surface 1345B of the optical device 1340. In some embodiments, the alignment carrier 1320 can be configured not to sit on the top surface 1345B of the optical device 1340. For example, in some embodiments, the alignment carrier 1320 can be shaped such that it does not contact the top surface 1345B of the optical device 1340. As another example, the second side 1314B of the housing structure 1314 of the optical coupler 1301 may be higher (e.g., vertically) than the top surface 1345B of the optical device 1340 such that the alignment carrier 1320 may also be higher than the top surface 1345B of the optical device 1340. In various embodiments, the alignment carrier 1320 may be aligned with (e.g., substantially parallel to) the top surface 1345B of the optical device 1340, even though it may not contact the top surface 1345B of the optical device 1340.

[0154] As described herein, the optical coupler 1301 may be configured to optically couple with at least one waveguide of the optical device 1340. In some implementations, the position of the optical device 1340 (e.g., the V-groove 1345) may be registered relative to the position of the waveguide of the optical device 1340. When the multi-fiber array 1300 is placed in the optical device 1340, the waveguide 1330 of the optical coupler 1301 may be aligned with the waveguide of the optical device 1340. In some examples, the waveguide 1330 of the optical coupler 1301 may be aligned with the waveguide of the optical device 1340 with an optical coupling efficiency of 50% to 100% (e.g., 60% to 100%, 70% to 100%, 80% to 100%, 90% to 100%, etc., or any range between any of these values).

[0155] When the multi-fiber array 1300 is disposed within the optical device 1340, each one of the optical couplers 1301 may be configured to optically couple one end of at least one optical fiber waveguide (e.g., one or more single mode fibers, few mode fibers, multimode fibers, multicore single mode fibers, multicore few mode fibers, and / or multicore multimode fibers) to a waveguide or waveguides of the optical device 1340.

[0156] As described herein, other mutually or complementary designed shapes of the alignment carrier of the optical coupler array and the housing structure are possible. For example, FIG. 14 shows a schematic of another example multi-fiber array 1400 disposed on an optical device 1440. The multi-fiber array 1400 has a plurality of optical couplers 1401 and an alignment carrier 1420. One or more of the optical couplers 1401 can include one or more longitudinal waveguides 1430 in the housing structure 1414. The alignment carrier 1420 has a first side 1420A and a second side 1420B. The optical couplers 1401 and the alignment carrier 1420 can include any of the features and / or combinations of features described herein, which are not all repeated herein.

[0157] As shown in FIG. 14, the first side 1414A of the housing structure 1414 of the optical coupler 1401 can be disposed in the optical device 1440. For example, the first side 1414A of the housing structure 1414 can configure one or more curved portions configured to be disposed in the walls 1445A of the V-groove 1445 in the optical device 1440. As also shown in FIG. 14, the first side 1420A of the alignment carrier 1420 can configure one or more V-grooves 1420A-1, and the second side 1414B of the housing structure 1414 of the optical coupler 1401 can configure one or more curved portions. In various embodiments, the curved portions of the housing structure 1414 can be disposed in the V-groove 1420A-1 of the alignment carrier 1420. Although four V-grooves 1420A-1 are shown in FIG. 14, the number of V-grooves 1420A-1 is not particularly limited. For example, the number of V-grooves 1420A-1 in the alignment carrier 1420 can be at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. (or any range formed by such values). In various embodiments, the number of V-grooves 1420A-1 in the alignment carrier 1420 can correspond to the number of optical couplers 1401. In some implementations, there may be more V-grooves 1420A-1 in the alignment carrier 1420 than the number of optical couplers 1401. In some implementations, there may be fewer V-grooves 1420A-1 in the alignment carrier 1420 than the number of optical couplers 1401. The v-grooves 1420A-1 in the alignment carrier 1420 may be the same or different in shape (e.g., wall slope) and / or size as the other v-grooves 1420A-1 in the alignment carrier. Also, the V-groove 1420A-1 in the alignment carrier 1420 can be the same or different in shape (e.g., slope of the walls) and / or size as the V-groove 1445 in the optical device 1440. For example, in FIG. 14 , the V-groove 1420A-1 in the alignment carrier 1420 is not the same size as the V-groove 1445 in the optical device 1440. In other examples, the V-groove 1420A1 in the alignment carrier 1420 may be the same size as the V-groove 1445 in the optical device 1440.

[0158] When the multi-fiber array 1400 is disposed within the optical device 1440, each one of the optical couplers 1401 can be configured to optically couple one end of at least one optical fiber waveguide to a waveguide or waveguides of the optical device 1440. In various implementations, the first side 1420A of the alignment carrier 1420 can be located on the top surface 1445B of the optical device 1440 (e.g., the top surface of the V-groove 1445). The alignment carrier 1420 may or may not contact the top surface 1445B of the optical device 1440.

[0159] 15 illustrates a schematic representation of another example multi-fiber array 1500 disposed above an optical device 1540. The multi-fiber array 1500 includes a plurality of optical couplers 1501 and an alignment carrier 1520. One or more of the optical couplers 1501 can include one or more longitudinal waveguides 1530 within a housing structure 1514. The alignment carrier 1520 has a first side 1520A and a second side 1520B. The optical couplers 1501 and the alignment carrier 1520 can include any of the features and / or combinations of features described herein, not all of which are repeated herein.

[0160] 15, the first side 1514A of the housing structure 1514 of the optical coupler 1501 can be disposed within the optical device 1540. For example, the first side 1514A of the housing structure 1514 can comprise one or more curved portions configured to be disposed within the walls 1545A of a V-groove 1545 in the optical device 1540. As also shown in FIG. 15, the first side 1520A of the alignment carrier 1520 can comprise a plurality of flat portions 1520A-1, and the housing structure 1514 of the optical coupler 1501 can be disposed within the walls 1545A of a V-groove 1545 in the optical device 1540. The fourth second side 1514B may define a plurality of flats configured to mate with the plurality of flats of the alignment carrier 1520.

[0161] In some implementations, the number of flat portions in the optical coupler 1501 may be the same as the number of corresponding flat portions 1520A-1 in the alignment carrier 1520. For example, in FIG. 15, for a given optical coupler 1501, there are two flat portions (e.g., forming an inverted V-shape, a ridge, a roof, etc.) of the second of the housing structure 1514, and there are two flat portions 1520A-1 (e.g., forming a V-groove) corresponding to the first side 1520A of the side 1514B alignment carrier 1520. The number of flat portions in a given optical coupler 1501 and / or the number of corresponding flat portions 1520A-1 in the alignment carrier 1520 is not particularly limited. For example, the number of flat portions may be 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. (or any range formed by such values).

[0162] In some implementations, the number of flat portions in the optical coupler 1501 may be different from the number of corresponding flat portions 1520A-1 in the alignment carrier 1520. As an example (not shown), an optical coupler 1501 having a second side 1514B with two flat portions may be disposed in three flat portions in the alignment carrier 1520. In some implementations, the number, shape, and / or size of flat portions for one optical coupler 1501 (and / or the number, shape, and / or size of corresponding flat portions 1520A-1 in the alignment carrier 1520) may be the same or different from the number, shape, and / or size of flat portions for another optical coupler 1501 (and / or the number, shape, and / or size of corresponding flat portions 1520A-1 in the alignment carrier 1520).

[0163] When the multi-fiber array 1500 is disposed within the optical device 1540, each one of the optical couplers 1501 can be configured to optically couple one end of at least one optical fiber waveguide to a waveguide or waveguides of the optical device 1540. In various implementations, the first side 1520A of the alignment carrier 1520 can be located on a top surface 1545B of the optical device 1540 (e.g., a top surface of the V-groove 1545). The alignment carrier 1520 may or may not contact the top surface 1545B of the optical device 1540.

[0164] In Figures 13, 14, and 15, the mutually or complementary designed shapes of the alignment carrier and the housing structure of the optical coupler are similar for different optical couplers in the multi-fiber array. In some cases, the mutually or complementary designed shapes can be combined with other mutually or complementary designed shapes. For example, any of the design shapes shown in Figures 13, 14, and / or 15 can be combined with other design shapes. For example, any of the design shapes shown in Figures 13, 14, and / or 15 can be combined with any of the other design shapes shown in Figures 13, 14, and / or 15. Other mutually or complementary designed shapes can also be used.

[0165] Multichannel optical coupler array with enhanced taper extraction ratio As described herein, a multi-channel optical coupler array can provide low-loss coupling between a set of individual isolated optical fibers and an optical device having at least one optical channel. This can allow for relatively large separation (e.g., lateral separation) between the individual optical fibers and relatively small separation (e.g., lateral separation) between the optical channels at the device interface. The large separation (e.g., lateral separation) can be important when standard jacketed fibers are utilized, keeping the fiber-to-fiber distance at least 250 micrometers, which is the diameter of a standard polymer jacket. may be preferred in various embodiments. An example of an optical device is a multicore fiber with a core-to-core distance of 30 micrometers. A multichannel optical coupler array coupling a standard jacket fiber to a multicore fiber may have a pull-in ratio of, for example, 250 / 30. Various embodiments of a multichannel optical coupler array may utilize one or more missing core waveguides, for example as described herein. In various embodiments, any of the multichannel optical coupler arrays described herein may have an increased taper pull-in ratio, which may allow for a significant reduction in channel spacing between the undrawn and drawn ends of the coupler array (e.g., the drawn end may have a significantly smaller channel spacing compared to the undrawn end). To achieve this goal, the example refractive index profile of the missing core waveguide shown in FIG. 16 may be modified as shown in FIG. 17. The refractive index transition between N-1 and N-2 may have a function N(r), where r is the lateral distance from the center of the inner evanescent core, and the second derivative d 2 N(r) / dr 2 The second derivative d 2 N(r) / dr 2A smooth N(r) profile, possibly with a positive average of N-2 to N-1, may be desirable in many cases. In some cases, a smooth N(r) profile from N-2 to N-1 may have a relatively gradual slope followed by a steep slope. In some cases, it may be of practical advantage to approximate the N(r) profile with a step function (e.g., having at least one step that approximates a smooth function with a positive average of the second derivative), as shown in Figures 18-20. Depending on the manufacturing parameters and application requirements of the evanescent core fiber, this step function may have one or more steps, for example, one, two, and three steps located between the N-1 to N-2 steps of refractive index, as shown in Figures 18, 19, and 20, respectively. One or more steps may have a refractive index less than N-1 and greater than N-2. In various designs, the evanescent core waveguide with a refractive index profile may be fabricated using chemical vapor deposition (CVD). In various embodiments, one or more steps can correspond to different physical regions of the waveguide, e.g., an annular region having a different refractive index than the regions having refractive indices N-1 and N-2. In some cases, one or more steps can have a decreasing refractive index with distance from the center of the waveguide, e.g., a step closer to the center of the waveguide can have a higher refractive index than another step further from the center. As shown in FIG. 19, some of the corner points of the step function have a positive average d 2 N(r) / dr 2 may be above or below a smooth N(r) profile with

[0166] In some embodiments, a larger draw ratio of the taper can make the waveguide propagation at the second end more sensitive to the quality of the interface between the cladding of the missing core waveguide and the common housing structure. A high draw ratio can reduce the thickness of the cladding, so that the evanescent tail of the propagating light wave extends to the housing structure. It may be desirable to intentionally introduce a concave gap in the cross section of the housing structure (e.g., between the missing core waveguide and the hole of the common housing structure) to improve the fusion quality of the coupler array. A housing structure with a concave gap can be created, for example, by adding a rod to a circular hole with the missing core waveguide before tapering, or by creating the entire housing structure by fusing appropriately sized elements, as shown in FIG. 21. Rods or elements with circular cross sections (e.g., cylindrical shapes) with different lateral dimensions (e.g., radii) can be used, for example, in certain embodiments. In the case of a concave gap, for example, there may be a well-defined closest point, ideally located symmetrically around the missing core waveguide in some embodiments, where fusing first begins. This is in contrast to circular or other hole shapes that do not create concave gaps, and fusion may begin uncontrollably at any point, resulting in voids or bubbles in the structure near the second end. In various designs, multiple convexities in the coupler housing structure may form one or more holes. Adjacent rods or elements may come together to create such multiple convexities. The arrangement of such convexities 21 and 22, one or more dissipative core waveguides, non-circular holes (eg, having concave gaps) can be formed.

[0167] FIG. 21 is a schematic diagram of a cross-sectional view illustrating an example configuration of an empty housing structure 2100 proximate a first end of an optical coupler array. The cross-sectional view is perpendicular to the longitudinal direction or length of the optical coupler array. As shown in FIG. 21, adjacent rods 2110 can form a protrusion 2120 of the coupler housing structure, which can form one or more non-circular holes 2130 (e.g., a concave shaped hole). As shown in FIG. 22, one or more of the holes can include at least one longitudinal waveguide 2140 (e.g., a lost core waveguide) that forms a gap 2150 between the coupler housing structure 2100 and the waveguide 2140.

[0168] Figure 23 is a schematic diagram of a cross-sectional view of another exemplary configuration of an empty housing structure 2300 at a location proximate to a first end of an optical coupler array. As shown in Figure 23, one or more of the holes 2330 can be formed by a tube 2335 within (e.g., surrounded by) a protrusion 2320 of the coupler housing structure. In some implementations, the tube 2335 can be a thin tube. In various embodiments, the tube can have a wall thickness of 1-90% of the waveguide diameter, e.g., 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 80%, 90% of the waveguide diameter, etc., or any range formed by any of these values, e.g., 1-50%, 5-50%, 10-50%, 1-40%, 5-40%, 10-40%, 1-30%, 5-30%, 10-30%, etc., of the waveguide diameter. In various embodiments, the tube has an inner diameter of 100.1-120% of the waveguide diameter, e.g., 100.1%, 100.2%, 100.3%, 100.4%, 100.5%, 101%, 102%, 103%, 104%, 105%, 110%, 115%, 120%, etc., of the waveguide diameter, or any range formed by any of these values, e.g., 100.1-105%, 100.1-110%, 100.1-115%, 100.5-105%, 100.5-110%, 100.5-115%, 100.5-120%, 101-105%, 101-110%, 101-115%, 101-120%, etc., of the waveguide diameter. In various embodiments, the tube can have an outer diameter that is the inner diameter plus twice the wall thickness.In various embodiments, the tube has an outer diameter that is 102.1-300% of the waveguide diameter, e.g., 102.1%, 102.2%, 102.3%, 102.4%, 102.5%, 103%, 104%, 105%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 225%, 250%, 275%, 300%, etc., or any range formed by any of these values, e.g., 102.1-150%, 102.2-100%, 102.3-100%, 102.4-100%, 102.5-100%, 102.6-100%, 102.7-100%, 102.8-100%, 102.9-100%, 110-120%, 130-140%, 150-160%, 170-180%, 190-190%, 200-225%, 250-275%, 300-200%, etc. 1-170%, 102.1-200%, 102.1-250%, 105-150%, 105-170%, 105-200%, 105-250%, 105-300%, 110-150%, 110-170%, 110-200%, 110-250%, 110-300%, 120-150%, 120-170%, 120-200%, 120-250%, 120-300%, 130-150%, 130-170%, 130-200%, 130-250%, 130-300%, etc. Other designs are possible. In some cases, the tube 2335 can be made of the same material as the rod. As shown in FIG. 24, one or more of the holes can include at least one longitudinal waveguide 2340 (e.g., an extinct core waveguide) that forms a gap 2350 between the coupler housing structure and the waveguide 2340.

[0169] Well-controlled fusion is beneficial for both increased and normal taper draw ratio devices. By creating structures with reduced and / or no voids / bubbles, microbending of the waveguide can be reduced and / or minimized, leading to improvements in loss, wavelength dependent loss, polarization dependent loss, and reduced inter-channel crosstalk, which are often the most critical parameters for coupler performance.

[0170] Thus, while the basic novel features of the invention as applied to its preferred embodiments have been shown, described and pointed out, it will be understood that various omissions and substitutions and changes in the form and details of the illustrated apparatus and methods, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, all combinations of those elements and / or method steps which perform substantially the same function in substantially the same way to achieve the same results are expressly intended to be within the scope of the invention. It is therefore intended to be limited only as indicated by the scope of the appended claims.

Claims

1. A multi-channel optical combiner array, comprising: an elongated optical element having a first end and a second end, the first end and the second end operable to optically couple with a plurality of optical fibers, an optical device, or a combination thereof; The optical element is a coupler housing structure; and a plurality of longitudinal waveguides disposed relative to one another within the housing structure; a coupler housing structure proximate the first end including at least one hole, the at least one hole including at least one of the plurality of longitudinal waveguides forming a gap between the coupler housing structure and at least one of the plurality of longitudinal waveguides, the at least one hole being composed of at least one non-circular hole formed by a plurality of protrusions of the coupler housing structure.

2. An optical coupler array as described in claim 1, wherein, adjacent the second end, the coupler array is configured such that there is substantially no gap between the coupler housing structure and at least one of the plurality of longitudinal waveguides.

3. An optical coupler array as described in claim 1 or 2, wherein the at least one hole consists of a plurality of holes.

4. The optical coupler array of claim 3, wherein at least one of the holes has a different dimension than another one of the holes.

5. An optical coupler array as described in claim 3 or 4, wherein at least one of the holes has a different shape than another one of the holes.

6. An optical coupler array as described in any one of claims 3 to 5, wherein the holes are insulated.

7. An optical coupler array as described in any one of claims 3 to 5, wherein some of the holes are connected.

8. An optical coupler array as described in any one of claims 1 to 7, wherein at least one of the plurality of longitudinal waveguides comprises a non-disappearing core waveguide.

9. An optical coupler array as described in any one of claims 1 to 8, wherein at least one of the plurality of vertical waveguides comprises a lost core waveguide.

10. Each of the plurality of longitudinal waveguides has a capacity for at least one optical mode, the plurality of longitudinal waveguides are embedded within the housing structure proximate the second end, and the disappearing core waveguide is An inner lost core, an outer core, and an outer cladding; the inner disappearing core has a first refractive index (N-l) and has a size of the inner core; the outer core longitudinally surrounds the inner core, has a second refractive index (N-2), and has an outer core size; the outer cladding longitudinally surrounds the outer core, has a third refractive index (N-3), and has a cladding size; the coupler housing structure comprises a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, where N-1>N-2>N-3; 10. The multi-channel optical coupler array of claim 9, wherein a size of the inner core, a size of the outer core, and a spacing between the plurality of longitudinal waveguides decrease along the optical element from the first end to the second end, at which the size of the inner core is insufficient to guide light therethrough and the size of the outer core is sufficient to guide at least one optical mode.

11. An optical coupler array as described in claim 10, wherein the coupler housing structure consists of a common single coupler housing structure.

12. An optical coupler array as described in claim 10 or 11, wherein the medium is a laterally continuous medium.

13. An optical coupler array as described in any of claims 10 to 12, wherein the total volume of the medium of the coupler housing structure is greater than the total volume of all inner cores and outer cores of at least one lost core waveguide confined within the coupler housing structure.

14. An optical coupler array as described in any of claims 10 to 13, wherein the size of the inner core, the size of the outer core, and the spacing between the multiple longitudinal waveguides gradually decrease simultaneously from the first end to the second end.

15. The optical coupler array of claim 10, wherein N-4 is greater than N-3.

16. An optical coupler array as described in any one of claims 10 to 15, wherein the medium of the common coupler housing structure is pure silica.

17. A multi-channel optical coupler array as described in any of claims 10 to 16, wherein the refractive index transition between N-1 and N-2 has a function N(r), where r is the lateral distance from the center of the inner missing core and whose second derivative is d2N(r) / dr2, and the function N(r) is a smooth function with a positive mean of the second derivative, or the function N(r) is a step function having at least one step that approximates a smooth function with a positive mean of the second derivative.

18. The multi-channel optical coupler array of claim 17, wherein the function N(r) is a smooth function having a positive mean of the second derivative.

19. The multi-channel optical coupler array of claim 17, wherein the function N(r) is a step function having at least one step that approximates a smooth function having a positive mean of the second derivative.

20. The multi-channel optical coupler array of claim 19, wherein the function N(r) has one step.

21. The multi-channel optical coupler array of claim 19, wherein the function N(r) has two steps.

22. The multi-channel optical coupler array of claim 19, wherein the function N(r) consists of three steps.

23. The multi-channel optical coupler array of claim 19, wherein the step function includes corner points, at least some of the corner points being above or below a smooth function having a positive average of the second derivative.

24. An optical coupler array as described in any one of claims 1 to 23, wherein the at least one hole comprises at least one hole formed by a tube surrounded by a plurality of protrusions of the coupler housing structure.

25. A method for manufacturing an optical coupler array as described in any one of claims 1 to 24, comprising forming at least one hole by a tube surrounded by a plurality of protrusions of a coupler housing structure.

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