Spatial division multiplexing using wavelength division multiplexing device (SDM-WDM device)

Abstract

The wavelength division multiplexer for space division multiplexing may comprise a wavelength division multiplexing fan-out device or a pump signal combiner for multicore fibers.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application is a continuation-in-part of U.S. patent application Ser. No. 18 / 118,011 (Attorney Docket No. CHIRA.044P1), filed March 6, 2023, entitled "Wavelength Division Multiplexing Apparatus for Space Division Multiplexing (SDM) (SDM-WDM Device)," which is a continuation-in-part of U.S. provisional application Ser. No. 63 / 416,859 (Attorney Docket No. CHIRA.045PR), filed October 17, 2022, entitled "Wavelength Division Multiplexing Apparatus for Space Division Multiplexing (SDM) (SDM-WDM Device)," which is a continuation-in-part of U.S. provisional application Ser. No. 63 / 416,859 (Attorney Docket No. CHIRA.045PR), filed November 11, 2022, entitled "Wavelength Division Multiplexing Apparatus for Space Division Multiplexing (SDM) (SDM-WDM Device)," which is a continuation-in-part of U.S. patent ... This application claims priority to U.S. Provisional Application No. 63 / 424,812 (Attorney Docket No. CHIRA.045PR2), entitled "Wavelength Division Multiplexing Apparatus for Spatial Division Multiplexing (SDM) (SDM-WDM Apparatus)," filed March 3, 2023, U.S. Provisional Application No. 63 / 488,421 (Attorney Docket No. CHIRA.045PR3), entitled "Wavelength Division Multiplexing Apparatus for Spatial Division Multiplexing (SDM) (SDM-WDM Apparatus)," filed February 23, 2021, and U.S. Patent Application No. 17 / 183,136 (Attorney Docket No. CHIRA.044A), entitled "Spatial Division Multiplexing Apparatus," filed February 23, 2021. U.S. Patent Application No. 18 / 118,011 is a continuation-in-part of U.S. Patent Application No. 17 / 183,136 (Attorney Docket No. CHIRA.044A), filed February 23, 2021, entitled "Spatial Division Multiplexing Apparatus," which claims priority to U.S. Provisional Application No. 62 / 980,884 (Attorney Docket No. CHIRA.044PR), filed February 24, 2020, entitled "Spatial Division Multiplexing Apparatus," and U.S. Provisional Application No. 63 / 001,814 (Attorney Docket No. CHIRA.044PR2), filed March 30, 2020, entitled "Spatial Division Multiplexing Apparatus." The entirety of each application referenced in this paragraph is expressly incorporated herein.

[0002] The present invention relates to optical coupler arrays, e.g., multi-channel optical coupler arrays, for coupling multiple optical fibers to at least one optical device. Some embodiments relate to techniques for coupling light into multiple optical fibers, including single-mode optical fibers, few-mode optical fibers, multimode optical fibers, multi-core single-mode optical fibers, multi-core few-mode optical fibers, and / or multi-core multimode optical fibers. Some embodiments relate to techniques for coupling light into photonic integrated circuits (PICs) and multi-core optical fibers (MCFs). Some embodiments may include wavelength division multiplexers for spatial division multiplexing (SDM) (SDM-WDM devices), including wavelength division multiplexing fan-out devices and pump signal combiners for MCFs. Some embodiments may include spatial division multiplexers (SDMs), including adapters between MCFs with different core patterns and / or add / drop multiplexers for MCFs. Some embodiments relate to high-power single-mode laser sources in general and to devices for coherently combining multiple optical fiber sources to generate multi-kilowatt single-mode laser sources. Some embodiments relate to phase-locked optical fiber components in single-chip designs that can be manufactured with very high precision control over the precise positioning (e.g., lateral or cross-sectional positioning) of multiple waveguides, and these components may be configurable to increase or optimize the fill factor of the component (the ratio of the mode field diameter at the "output" end of each waveguide to the distance between adjacent waveguides). [Background technology]

[0003] Optical waveguide devices are useful in a variety of high-tech industrial applications, and are particularly widely used in the field of communications. In recent years, there have been many advances in these devices, including planar waveguiding, two-dimensional or three-dimensional photonic crystals, multimode fibers, multicore single-mode fibers, multicore few-mode fibers, and multicore multimode fibers, which are used in combination with conventional optical fibers. Optical waveguide devices and multi-channel devices based on refractive index contrasts or numerical apertures (NA) different from those of conventional optical fibers have advantageous and desirable properties in applications where conventional optical fibers are also used. However, significant challenges exist when connecting optical waveguide devices or multi-channel devices with different NAs, where the channel spacing is less than the diameter of the conventional fiber, to conventional optical fibers. For example, at least some of the following obstacles may be encountered: (1) differences in size (especially core size) between the optical waveguide device and conventional optical fiber; (2) differences in NA between the optical waveguide device and conventional optical fiber; and (3) channel spacing smaller than the diameter of the conventional optical fiber. If these obstacles are not properly resolved, they may result in increased insertion loss and reduced coupling coefficient at each interface.

[0004] For example, a conventional optical fiber-based optical coupler, such as that shown in Figure 6 (Prior Art), can be constructed by inserting a standard optical fiber used as the input fiber into a capillary tube made of a material with a lower refractive index than the cladding of the input fiber. However, this approach has several drawbacks. For example, the interface between the fiber cladding and the capillary tube has poorer optical waveguiding properties than the interface within a standard optical fiber, potentially causing optical loss. Furthermore, the capillary tube must be fabricated from expensive fluorine-doped materials, significantly increasing the cost of the coupler.

[0005] No. 7,308,173, entitled "Optical Fiber Coupler Having Low Loss and High Coupling Coefficient and Method for Manufacturing the Same," is incorporated herein in its entirety. To address some of the problems discussed above, various embodiments of optical fiber couplers are provided that provide a low-loss, high-coupling coefficient interface between conventional optical fibers and optical waveguide devices.

[0006] However, several challenges remain. With the widespread adoption of multi-channel optical devices (e.g., waveguide arrays), establishing low-loss, high-precision connections to low- or high-NA waveguide arrays has presented challenges, particularly due to the very small spacing between the waveguides. U.S. Patent No. 8,326,099, "Optical Fiber Coupler Array," issued December 4, 2012 (herein incorporated by reference in its entirety), addresses these challenges by providing, at least in some embodiments, an optical fiber coupler array that provides a high-coupling coefficient interface and high-precision, easy alignment between a waveguide device having multiple closely spaced waveguides and multiple optical fibers spaced at least one optical fiber diameter apart.

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

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

[0009] The embodiments described herein include innovative features, no single one of which is essential or solely responsible for its desirable characteristics. Some advantageous features, without limiting the scope of the claims, are summarized below. example 1. A plurality of optical fibers transmitting light of at least two wavelengths W-1 and W-2 are provided. 1. An optical coupler array for optically coupling to an optical device, comprising: an elongated optical element having a first end and a second end, the first end operable to optically couple with the plurality of optical fibers and the second end operable to optically couple with the optical device; a common single coupler housing structure; A joint; a plurality of longitudinal waveguides; the plurality of longitudinal waveguides include at least one first waveguide and at least one second waveguide, each of the plurality of waveguides being spaced apart from one another and having a capacity of at least one optical mode of a mode field profile and a corresponding propagation constant, and embedded in the common single housing structure, at least one of the plurality of longitudinal waveguides being a lost core waveguide, each of the lost core waveguides being: an inner lossy core, an outer core, and an outer cladding; the inner disappearing core has a first refractive index (N-1) and a first inner core size (ICS-1) at the first end 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-1) 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 has a second cladding size at the second end; The common single coupler housing structure comprises a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, and the relative magnitude relationships of the first, second, third and fourth refractive indices (N-1, N-2, N-3 and N-4, respectively) satisfy the following magnitude relationship: (N-1>N-2>N-3), wherein a total volume of the medium of the common single coupler housing structure is greater than a total volume of the inner cores and outer cores of all of the missing core waveguides enclosed in the common single coupler housing structure, and the first inner missing core size (ICS-1), the first outer core size (OCS-1), and the spacing of the plurality of longitudinal waveguides are simultaneously and stepwise changed according to a profile 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 selected to be insufficient in size to conduct light, and the second outer core size (OCS-2) is selected to be sufficient in size to conduct at least one optical mode, thereby light traveling from the first end to the second end escapes from the inner lost core to the corresponding outer core near the second end; light traveling from the second end to the first end travels from the outer core to the corresponding inner lost core near the first end; an optical coupler array, wherein at least one of the lost core waveguides is positioned at a coupling distance from another longitudinal waveguide in the coupling portion located near the second end, and the coupling distance and a length of the coupling portion are configured to couple light of wavelength W-1 in at least one core mode of the at least one lost core waveguide with at least one core mode of another longitudinal waveguide while allowing light of wavelength W-2 to continue propagating in the other longitudinal waveguide. 2. The optical coupler array of Example 1, wherein near the second end, the light of wavelength W-1 and the light of wavelength W-2 are coupled into the same mode of the other longitudinal waveguide. 3. The optical coupler array of Example 1, wherein the first inner extinctive core size (ICS-1), the first outer core size (OCS-1), and the spacing of the plurality of longitudinal waveguides simultaneously and stepwise decrease along the optical element to the coupling portion between the first end and the second end, and simultaneously and stepwise increase from the coupling portion to the second end until reaching the second inner extinctive core size (ICS-2) and the second outer core size (OCS-2). 4. The optical coupler array of Example 1, wherein the first inner missing core size (ICS-1), the first outer core size (OCS-1), and the spacing between the multiple longitudinal waveguides are simultaneously and stepwise reduced along the optical element between the first end and the second end until the second inner missing core size (ICS-2) and the second outer core size (OCS-2) are reached. 5. The optical coupler array of Example 1, wherein one of the wavelengths W-1 and W-2 is a signal light, and the other of the wavelengths W-1 and W-2 is a pump light. 6. The optical coupler array of example 5, wherein the signal light is 1550 nm and the pump light is 980 nm. 7. The optical coupler array of Example 1, wherein one of the wavelengths W-1 and W-2 is a signal light, and the other of the wavelengths W-1 and W-2 is another signal light. 8. The optical coupler array of example 7, wherein the signal light is 1550 nm and the other signal light is 1310 nm. 9. The optical coupler array of Example 1, comprising an access region providing access to at least one of the plurality of waveguides between the first end and the second end. 10. The optical coupler array of example 1, wherein the coupling portion is substantially linear. 11. The optical coupler array of example 1, wherein the coupling portion has a neck portion. 12. The optical coupler array of Example 1, wherein the plurality of longitudinal waveguides comprises at least one waveguide configured not to couple light with other waveguides of the plurality of longitudinal waveguides of the optical coupler array. 13. A multicore fiber wavelength division multiplexer (MCF-WDM), comprising: a WDM fan-out device; a non-WDM fan-out device; the WDM fan-out device comprises a plurality of first longitudinal waveguides having at least one waveguide configured to propagate light at a first wavelength and at least one waveguide configured to propagate light at a second wavelength, and is configured to couple light at the first wavelength and light at the second wavelength into cores of a multicore fiber; 14. The multicore fiber wavelength division multiplexer of Example 13, wherein the non-WDM fan-out device comprises a plurality of second vertical waveguides, each waveguide of the plurality of second vertical waveguides configured to not couple light with other waveguides of the second plurality of vertical waveguides of the non-WDM fan-out device. 15. The MCF-WDM of Example 13, wherein the first vertical waveguide path comprises at least one waveguide configured to not couple light with other waveguides of the first vertical optical path of the WDM fan-out device. 15. The MCF-WDM of Example 13, further comprising one or more isolators, gain-flattening filters, couplers, attenuators, and / or fiber Bragg gratings. 16. An amplifier comprising two of the MCF-WDMs of Example 13 and a gain medium disposed therebetween. 17. The amplifier of Example 16, wherein the gain medium is an active MCF, the active MCF having at least one set of nearest neighbor cores and at least two sets of next-nearest neighbor cores, the next-nearest neighbor cores transmitting light in the same direction and the nearest neighbor cores transmitting light in opposite directions, one of the two MCF-WDMs coupling pump light into at least one set of the at least two sets of next-nearest neighbor cores at one end of the active MCF, and the other of the two MCF-WDMs coupling pump light into the other set of the at least two sets of next-nearest neighbor cores at the other end of the active MCF. 18. The amplifier of example 16, wherein the gain medium is an erbium-doped fiber. 19. The amplifier of example 16, further comprising a monitoring channel. 20. An optical coupler array for optically coupling a plurality of optical fibers transmitting at least two wavelengths W-1 and W-2 of light to an optical device, comprising: an elongated optical element having a first end operable to optically couple to the plurality of optical fibers and a second end operable to optically couple to the optical device; a common single coupler housing structure; A joint; a plurality of longitudinal waveguides; the plurality of longitudinal waveguides include at least one first waveguide and at least one second waveguide, each of the plurality of longitudinal waveguides having a capacity and a corresponding propagation constant of at least one optical mode of a mode field profile; at least one of the plurality of longitudinal waveguides is a lost core waveguide; an optical coupler array, wherein at least one of the lost core waveguides is positioned at a coupling distance from another longitudinal waveguide at the coupling portion proximate the second end, the coupling distance and a length of the coupling portion being configured to couple light at wavelength W-1 of at least one core mode of the at least one lost core waveguide with at least one core mode of the other longitudinal waveguide while continuing propagation of light at wavelength W-2 in the other longitudinal waveguide. 21. Each of the plurality of longitudinal waveguides is spaced apart from one another, and each of the lost core waveguides comprises an inner lost core, an outer core, and an outer cladding; the inner disappearing core has a first refractive index (N-1) and a first inner core size (ICS-1) at the first end and a second inner core size (ICS-2) at the second end; the outer core longitudinally surrounds the inner core, has a second refractive index (N-2), and has a first outer core size (OCS-1) 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), and has a first cladding size at the first end and a second cladding size at the second end; The common single coupler housing structure comprises a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, and the relative magnitude relationships of the first, second, third and fourth refractive indices (N-1, N-2, N-3 and N-4, respectively) satisfy the following magnitude relationship: (N-1>N-2>N-3), wherein a total volume of the medium of the common single coupler housing structure is greater than a total volume of the inner cores and the outer cores of all the lost core waveguides enclosed in the common single coupler housing structure, and the first inner lost core size (ICS-1), the first outer core size (OCS-1), and the spacing of the plurality of longitudinal waveguides are simultaneously and stepwise changed along the optical element between the first end and the second end according to a profile until reaching the second inner lost core size (ICS-2) and the second outer core size (OCS-2), wherein the second inner lost core size (ICS-2) is selected to be insufficient in size to conduct light, and the second outer core size (OCS-2) is selected to be sufficient in size to conduct at least one optical mode, whereby light traveling from the first end to the second end escapes from the inner lost core to the corresponding outer core near the second end, 21. The optical coupler array of example 20, wherein light traveling from the second end to the first end travels from the outer core to a corresponding inner lost core near the first end. 22. The optical coupler array of example 20, wherein each of the plurality of longitudinal waveguides is embedded in the common single housing structure. 23. An optical coupler array as described in Example 20, wherein, proximal to the second end, the light of wavelength W-1 and the light of wavelength W-2 are coupled into the same mode of another longitudinal waveguide. 24. An optical coupler array as described in Example 21, wherein the size of the first inner missing core (ICS-1), the size of the first outer core (OCS-1), and the spacing of the plurality of longitudinal waveguides are simultaneously and stepwise decreased between the first end and the second end from the optical element to the coupling portion, and are simultaneously and stepwise increased from the coupling portion to the second end until they reach the second inner missing core size (ICS-2) and the second outer core size (OCS-2). 25. The first inner lost core size (ICS-1), the first outer core size (OCS ICS-1 and the second outer core size (OCS-2) are simultaneously and stepwise decreased along the optical element from the first end to the second end until the second inner lost core size (ICS-2) and the second outer core size (OCS-2) are reached. 26. The optical coupler array of Example 20, wherein one of the wavelengths W-1 and W-2 is a signal light, and the other of the wavelengths W-1 and W-2 is a pump light. 27. The optical coupler array of example 26, wherein the signal light is 1550 nm and the pump light is 980 nm. 28. The optical coupler array of Example 20, wherein one of the wavelengths W-1 and W-2 is a signal light, and the other of the wavelengths W-1 and W-2 is another signal light. 29. The optical coupler array of example 28, wherein the signal light is 1550 nm and the other signal light is 1310 nm. 30. The optical coupler array of example 20, further comprising an access area providing access to at least one of the plurality of waveguides between the first end and the second end. 31. The optical coupler array of example 20, wherein the coupling portion is substantially linear. 32. The optical coupler array of example 20, wherein the coupling portion has a neck portion. 33. An optical coupler array as described in Example 20, wherein the plurality of longitudinal waveguides includes at least one waveguide configured not to couple light with other waveguides of the plurality of longitudinal waveguides of the optical coupler array. Additional example 1 1. A double tapered elongated optical coupler array, A housing structure; a first end; The middle part and A second end portion; a first tapered portion disposed between the first end portion and the intermediate portion; a second tapered section disposed between the second end and the intermediate section, the optical coupler array having an outer diameter that tapers from the first end toward the intermediate section and tapers from the intermediate section toward the second end; a plurality of spatial optical channels configured to optically couple with at least one of a first multi-channel optical device having a first lateral channel pattern at the first end or a second multi-channel optical device having a second lateral channel pattern at the second end; The plurality of spatial optical channels comprises at least one transmission channel, the transmission channel being capable of coupling with at least one optical channel of the first multi-channel optical device and at least one optical channel of the second multi-channel optical device, the at least one transmission channel being embedded in a first end and / or a second end of a housing structure; The optical combiner array is capable of performing at least one of the following functions: or accommodating different first and second lateral channel patterns between the first and second multi-channel optical devices; providing access to at least one optical channel of the first multi-channel optical device or the second multi-channel optical device. 2. The at least one pass-through channel is a lost core waveguide; an inner lossy core, an outer longitudinal structural element, and an outer cladding; the inner disappearing core has a first refractive index (N-1), a first inner core size (ICS-1) at the first end, a second inner core size (ICS-2) at the second end, and an intermediate inner core size (ICS-IN) at the intermediate portion; The outer longitudinal structural element longitudinally surrounds the inner core and has a second refractive index (N-2), a first outer core size (OCS-1) at the first end, and a second outer core size (OCS-2) at the second end. size (OCS-2), and an intermediate outer core size (OCS-IN) in the intermediate section; the outer cladding longitudinally surrounds the outer core and has a third refractive index (N-3); the first, second, and third refractive indices (N-1, N-2, and N-3) have a relative magnitude relationship satisfying the following magnitude relationship: (N-1 > N-2 > N-3); the first inner missing core size (ICS-1) and the first outer core size (OCS-1) increase simultaneously and stepwise from the first end to the middle section and decrease simultaneously and stepwise from the middle section to the second end according to a profile along the housing structure; the first and second inner missing core sizes (ICS-1 and ICS-2) are insufficient to conduct light; and the first and second outer core sizes (OCS-1 and OCS-2) are sufficient to conduct at least one optical mode, whereby light traveling from the first end to the middle section couples from the outer core to the inner missing core, and subsequently light traveling from the middle section to the second end escapes from the inner missing core to the outer core near the second end. 3. The at least one transmission channel is an expanded core waveguide, comprising an expanded core and an outer cladding; the expanded core has a core refractive index (NCO) and has a first expanded core size (ECS-1) at the first end, a second expanded core size (ECS-2) at the second end, and an intermediate expanded core size (ECS-IN) therebetween; the outer cladding longitudinally surrounds the expanded core and has a cladding refractive index (NCL); the first expanded core size (ECS-1) increases stepwise from the first end to the intermediate section and decreases stepwise from the intermediate section to the second end according to a profile along the housing structure; the first and second expanded core sizes (ECS-1 and ECS-2) and the refractive indices NCO and NCL match the waveguiding characteristics of one channel of the first and second multi-channel optical devices, respectively; and the intermediate expanded core size (ECS-IN) has a larger mode volume than one channel of the first and second multi-channel optical devices, such that light propagating from the first end to the intermediate section and from the intermediate section to the second end propagates in at least one lowest order mode. 4. The first and second transverse channel patterns in the first and second optical devices are different from each other; a lateral channel pattern similar to the first lateral channel pattern is formed in the first tapered portion, and a lateral channel pattern similar to the second lateral channel pattern is formed in the second tapered portion; The first and second tapered portions each include: A tapered housing structure; a plurality of longitudinal waveguides; each of the plurality of longitudinal waveguides is spaced apart from one another, is capable of propagating at least one optical mode, and is embedded proximate to a corresponding first or second end of the tapered housing structure; at least one of the plurality of longitudinal waveguides is a transmission channel common to both the first and second tapered sections; 2. The optical coupler array of Example 1, wherein the housing structure has the first and second tapered portions and a connecting sleeve. 5. The housing structure is a single monolithic coupler housing structure consisting of the first tapered section, the intermediate section, and the second tapered section, the intermediate section having an access area and at least one access optical channel, the access optical channel being accessed from the outside space into the housing structure through a waveguide, and having at least one first or second multi-channel. 10. The optical coupler array of Example 1, which provides access to at least one optical channel in a channel optical device. 6. The at least one access optical channel provides access to at least one optical channel of the first or second multi-channel optical device and constitutes an erased core waveguide; an inner vanishing core and an outer longitudinal structural element; the inner disappearing core has a first refractive index (N-1), a first inner core size (ICS-1) at the first end, and an intermediate inner core size (ICS-IN) at the middle portion; and the outer longitudinal structural element comprises an outer core and an outer cladding; the outer core longitudinally surrounds the inner core, has a second refractive index (N-2), has a first outer core size (OCS-1) at the first end, and has an intermediate outer core size (OCS-IN) at the intermediate portion; the outer cladding longitudinally surrounds the outer core and has a third refractive index (N-3); the first inner missing core size (ICS-1) and the first outer core size (OCS-1) increase simultaneously and stepwise from the first end to the intermediate portion according to a profile along an optical housing structure, the first inner missing core size (ICS-1) being insufficient to conduct light, and the first outer core size (OCS-1) being sufficient to conduct at least one optical mode, whereby light traveling from the first end to the intermediate portion couples from the outer core to the inner missing core. 7. The optical coupler array of Example 6, wherein the at least one access optical channel is a standard optical fiber fusion spliced ​​to the missing core waveguide, the fusion location being located outside the housing structure, and the missing core waveguide is configured to pass through an access area from external space into the housing structure. 8. The optical coupler array of Example 6, wherein the at least one access optical channel comprises a standard optical fiber fusion spliced ​​to an missing core waveguide, the fusion splice location is configured within the housing structure, and the standard optical fiber is configured to pass through an access area from external space into the housing structure. 9. The optical coupler array of Example 1, wherein the first and second multi-channel optical devices are multi-core fibers connected to opposite ends of the housing structure. 10. The optical coupler array of Example 5, wherein the first and second multi-channel optical devices are two ends of the same span of multi-core fiber having a circumferential core arrangement pattern, circumferentially numbered 1, 2, ...N, and wherein a connection direction at the first end couples at least one access optical channel to core number 1, and a connection direction at the second end couples core number 1 to core number 2 at the first end via at least one pass-through channel, core number 2 to core number 3, and thus core number N-1 is coupled to core number N, and core number N is coupled to a second of the at least one access optical channel at the second end. 11. The optical coupler array of Example 1, wherein the plurality of spatial optical channels disposed within the housing structure form a first transverse channel pattern at the first end and a second transverse channel pattern at the second end, the second transverse channel pattern being different from the first transverse channel pattern. 12. The optical coupler array of Example 1, further comprising an optical fiber, the optical fiber having the first end disposed within the housing structure and the second end disposed outside the housing structure. 13. The optical coupler array of example 12, wherein the first ends of the optical fibers are disposed at the first end or the second end of the housing structure. 14. The optical coupler array of example 12, wherein the optical fiber exits the housing structure through a central portion of the housing structure. 15. The optical coupler array of Example 12, wherein the optical fiber comprises two optical fibers, one of which has a first end disposed at a first end of the housing structure and the other of which has a first end disposed at a second end of the housing structure. 16. The optical coupler array of Example 1, wherein the middle section is bent at an angle of 90° to 170°. 17. The optical coupler array of Example 1, wherein the at least one transmission channel has no joints within the housing structure. 18. The optical coupler array of Example 1, wherein at least one of the first or second multi-channel optical devices has at least one multimode optical channel. 19. The optical coupler array of example 18, wherein the multimode optical channel is the inner cladding of a double-clad multicore fiber. 20. The optical coupler array of Example 5, wherein the first and second multi-channel optical devices are both multi-core fibers, the cores of the multi-core fibers are coupled via transmission channels, and the at least one access optical channel is a multimode fiber coupled to a cladding mode of an inner cladding of a dual-clad multi-core fiber. Additional example 2 1. A double tapered elongated optical coupler array, A housing structure; a first end; The middle part and a first tapered portion located between the first end portion and the intermediate portion; a second tapered portion located between the second end portion and the intermediate portion; at least one transmission channel; the first tapered section and the second tapered section have a contour that tapers from the first end toward the intermediate section and tapers from the intermediate section toward the second end, the contour having a plurality of spatial optical channels configured to optically couple with at least one of a first multi-channel optical device having a first lateral channel pattern at the first end and a second multi-channel optical device having a second lateral channel pattern at the second end; the at least one transmission channel functions to directly couple at least one optical channel of the first multi-channel optical device with at least one optical channel of the second multi-channel optical device, the at least one transmission channel being embedded in the first end and the second end of the housing structure; The optical combiner array is operable to perform at least one function of accommodating different first and second lateral channel patterns between the first and second optical devices, and providing direct access to at least one optical channel of the first or second multi-channel optical device. 2. The at least one transmission channel is a lost core waveguide and comprises an inner lost core and an outer longitudinal structural element; the inner disappearing core has a first refractive index (N-1), a first inner core size (ICS-1) at the first end, a second inner core size (ICS-2) at the second end, and an intermediate inner core size (ICS-IN) at the intermediate portion; the outer longitudinal structural element comprises an outer core and an outer cladding; the outer core longitudinally surrounds the inner core and has a second refractive index (N-2); a first outer core size (OCS-1) at a first end, a second outer core size (OCS-2) at the second end, and an intermediate outer core size (OCS-IN) at the intermediate portion; the outer cladding portion is disposed to surround the outer core in the longitudinal direction and has a third refractive index (N-3); The relative magnitude relationship between the first, second, and third refractive indices (N-1, N-2, and N-3, respectively) satisfies the following magnitude relationship: (N-1>N-2>N-3); 10. The coupler array of Example 1, wherein the first inner lost core size (ICS-1) and the first outer core size (OCS-1) are configured to simultaneously and incrementally increase from the first end to the intermediate section and simultaneously and incrementally decrease from the intermediate section to the second end according to a predetermined profile along the housing structure, the first and second inner lost core sizes (ICS-1 and ICS-2) being selected to be insufficient to conduct light, and the first and second outer core sizes (OCS-1 and OCS-2) being selected to be sufficient to conduct at least one optical mode, such that light traveling from the first end to the intermediate section couples from the outer core to the inner lost core, and subsequently light traveling from the intermediate section to the second end escapes from the inner lost core to the outer core near the second end. 3. The at least one transmission channel is an expanded core waveguide; an expanded core and an outer cladding; the expanded core has a core refractive index (NCO) and has a first expanded core size (ECS-1) at the first end, a second expanded core size (ECS-2) at the second end, and an intermediate expanded core size (ECS-IN) therebetween; the outer cladding longitudinally surrounds the expanded core and has a cladding refractive index (NCL); the first expanded core size (ECS-1) increases stepwise from the first end to the intermediate section and decreases stepwise from the intermediate section to the second end according to a predetermined profile along the housing structure; the first and second expanded core sizes (ECS-1 and ECS-2) and the refractive indices NCO and NCL are selected to match the optical waveguiding characteristics of at least one channel in the first and second multi-channel optical devices, respectively; and the intermediate expanded core size (ECS-IN) is selected to have a larger mode volume than at least one channel in the first and second multi-channel optical devices, such that light propagating from the first end to the intermediate section and from the intermediate section to the second end continues to propagate in at least one lowest order mode. 4. The first and second horizontal channel patterns in the first and second optical devices are different; a transverse channel pattern similar to the first transverse channel pattern is formed in the first tapered portion, and a transverse channel pattern similar to the second transverse channel pattern is formed in the second tapered portion; Each of the first tapered portion and the second tapered portion has A tapered housing structure; a plurality of longitudinal waveguides; the plurality of longitudinal waveguides are spaced apart from one another at predetermined intervals, each capable of accommodating at least one optical mode having a predetermined mode field profile, and are embedded near a corresponding first or second end of the tapered housing structure; at least one of the plurality of longitudinal waveguides is a transmission channel common to both the first and second tapered sections; 4. The optical coupler array of Example 2 or 3, wherein the housing structure comprises the first and second tapered portions and a connecting sleeve. 5. The housing structure is a single monolithic coupler housing structure; The first tapered portion; The middle part and a second tapered portion; the intermediate portion comprises an access area and includes at least one direct access optical channel; the direct access optical channel comprises a waveguide that directs light from external space into the housing structure through the access area to provide direct access to at least one optical channel in at least one first or second multi-channel optical device; The combiner array of Examples 2 or 3. 6. At least one direct-access optical channel providing direct access to at least one optical channel of the first multi-channel optical device is a direct-access lost-core waveguide; an inner lossy core, an outer longitudinal structural element, and an outer cladding; The inner disappearing core has a first refractive index (N-1), a first inner core size (ICS-1) at the first end, and an intermediate inner core size (ICS-IN) at the middle portion. the outer longitudinal structural element is an outer core that longitudinally surrounds the inner core and has a second refractive index (N-2), a first outer core size (OCS-1) at the first end, and an intermediate outer core size (OCS-IN) at the intermediate portion; and the outer cladding longitudinally surrounds the outer core and has a third refractive index (N-3); 10. The coupler array of Example 5, wherein the relative magnitude relationship between the first, second, and third refractive indices (N-1, N-2, and N-3) satisfies the following magnitude relationship: (N-1>N-2>N-3); the first inner missing core size (ICS-1) and the first outer core size (OCS-1) increase simultaneously and stepwise from the first end to the intermediate section according to a predetermined profile along the optical housing structure; the first inner missing core size (ICS-1) is selected to be insufficient in size to conduct light, and the first outer core size (OCS-1) is selected to be sufficient in size to conduct at least one optical mode, whereby light traveling from the first end to the intermediate section couples from the outer core to the inner missing core. 7. The coupler array of Example 6, wherein the at least one direct access optical channel is a fusion splice between a standard optical fiber having a connection location outside the housing structure and a direct access lost core waveguide, the direct access lost core waveguide being configured to pass through an access region from external space into the housing structure. 8. The coupler array of Example 6, wherein the at least one direct access optical channel comprises a standard optical fiber fusion spliced ​​to the direct access lost core waveguide, the fusion splice location is configured to be within a housing structure, and the standard optical fiber is configured to pass through an access area from external space into the housing structure. 9. The coupler array of Example 1, wherein the first and second multi-channel optical devices are multi-core fibers connected at both ends to the housing structure. 10. The coupler array of Example 5, wherein the first and second multi-channel optical devices are opposite ends of the same span of a multi-core fiber having a circumferential core arrangement pattern, for example, a multi-core fiber having cores numbered 1, 2, ..., N in the circumferential direction, and the connection direction at the first end is such that core number 1 is coupled to core number 2 of the first end via at least one pass-through channel, core number 2 is coupled to core number 3, core number N-1 is coupled to core number N, and core number N is finally coupled to a second of the at least one direct access optical channel at the second end. 11. An optical coupler array comprising: a housing and a plurality of spatial light channels; The housing includes: a first end; A second end portion; an intermediate portion disposed between the first end portion and the second end portion; a first tapered portion disposed between the first end portion and the intermediate portion; a second tapered portion disposed between the second end portion and the intermediate portion; The optical combiner array, wherein the plurality of spatial optical channels are disposed within a housing and form a first transverse channel pattern at the first end and a second transverse channel pattern at the second end, the second transverse channel pattern being different from the first transverse channel pattern. 12. An optical coupler array comprising: a housing, a plurality of spatial light channels, and an optical fiber; The housing includes: a first end; A second end portion; an intermediate portion located between the first end and the second end; a first tapered portion located between the first end portion and the intermediate portion; a second tapered portion located between the second end portion and the intermediate portion, the plurality of spatial light channels are disposed within a housing and define a first transverse channel pattern at the first end and a second transverse channel pattern at the second end; The optical fibers have first ends disposed within the housing and second ends disposed outside the housing. 13. The optical coupler array of example 12, wherein the first ends of the optical fibers are disposed at the first end or the second end of the housing. 14. The optical fiber exits the housing through a middle portion of the housing; The optical coupler array of example 12 or example 13. 15. The optical coupler array of any of Examples 12 to 14, wherein the optical fiber comprises two optical fibers, one of which has a first end of the optical fiber disposed at a first end of the housing and the other of which has a first end of the optical fiber disposed at a second end of the housing. 16. The optical coupler array of any of Examples 12 to 15, wherein the optical fiber comprises an add and / or drop channel. 17. The optical coupler array of any of Examples 12-16, wherein the second horizontal channel pattern is different from the first horizontal channel pattern. 18. The optical coupler array of any of Examples 11-17, wherein the plurality of spatial optical channels comprises an evanescent core waveguide. 19. The optical coupler array of any of Examples 11-18, wherein the plurality of spatial optical channels comprises expanded core waveguides. 20. The optical coupler array of any of Examples 11-19, wherein the array forms a gyroscope. 21. The optical coupler array of any of Examples 11-20, wherein each of the spatial optical channels does not include a joint within the housing. 22. The optical coupler array of any one of Examples 11 to 21, wherein the intermediate portion is bent at an angle of 90° to 170°. 23. The optical coupler array of any of Examples 1-10, wherein the at least one through channel does not include a joint within the housing structure. 24. The optical coupler array of any of Examples 1-10 or 23, wherein the intermediate section is bent at an angle of 90° to 170°. 25. The optical coupler array of example 1, wherein at least one of the first or second multi-channel optical devices has at least one multimode optical channel. 26. The optical coupler array of example 25, wherein the multimode optical channel is the inner cladding of a double-clad multicore fiber. 27. The optical coupler array of example 26, wherein direct access is provided to at least one optical mode of said multimode optical channel. 28. The coupler array of Example 27 and Example 5, wherein the first and second multi-channel optical devices are both multi-core fibers, the cores of the multi-core fibers are coupled via transparent channels, and the at least one direct access optical channel is a multimode fiber coupled to a cladding mode of an inner cladding of a dual-clad multi-core fiber. 29. The optical coupler array of example 12, wherein the optical fiber is a multimode optical fiber and has a configuration that provides access to said multimode optical channels. 30. The optical coupler array of Example 29, wherein the multimode optical channel is the inner cladding of a double-clad multicore fiber. Additional example 3 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 single 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; a plurality of longitudinal waveguides disposed at predetermined intervals from one another, each capable of transmitting at least one optical mode having a predetermined mode field profile, embedded in the common single housing structure proximate the second end, at least one of the plurality of longitudinal waveguides being a lost core waveguide, the lost core waveguide comprising: an inner lossy core, an outer core, and an outer cladding; The inner lost core has a first refractive index (N-1), a first inner core size (ICS-1) at the first end, 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-1) 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 second refractive index (N-2), a first outer core size (OCS-1) at the first end, and a second outer core size (OCS-2) at the second end; a third refractive index (N-3), a first cladding size at a first end, and a second cladding size at a second end; the common single coupler housing structure has a laterally continuous medium surrounding the plurality of longitudinal waveguides, the medium having a fourth refractive index (N-4); and a predetermined relative magnitude relationship between the first, second, third, and fourth refractive indices (N-1, N-2, N-3, and N-4, respectively) has 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 of the inner cores and a total volume of the outer cores of all the lost core waveguides enclosed within the common single coupler housing structure, and the first inner lost core size (ICS-I), the first outer core size (OCS-I), and the predetermined distance between the plurality of longitudinal waveguides are simultaneously and stepwise decreased along the optical element from a first end to a second end according to a predetermined decreasing profile, until a second inner lost core size (ICS-2) and a second outer core size (OCS-2) are reached, wherein the second inner lost core size (ICS-2) is selected to be a size insufficient to conduct light, and the second outer core size (OCS-2) is selected to be a size sufficient to conduct at least one optical mode, thereby An optical coupler array in which light traveling from the first end to the second end escapes from an inner disappearing core to a corresponding outer core near the second end, and light traveling from the second end to the first end travels from the outer core to a corresponding inner disappearing core and back to the inner disappearing core near the first end, and a common single coupler housing structure located near the first end is a ring surrounding multiple waveguides, a laterally continuous structure having multiple holes, at least one hole having one of the cross-sectional configurations of multiple longitudinal waveguides. 2. 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 are operable to optically couple to a plurality of optical fibers, optical devices, or a combination thereof, and the optical element comprises: a coupler housing structure; a plurality of longitudinal waveguides; The plurality of longitudinal waveguides are a plurality of longitudinal waveguides arranged relative to one another, each capable of propagating at least one optical mode, the plurality of longitudinal waveguides being embedded in the housing structure, the plurality of longitudinal waveguides comprising at least one lost core waveguide, the at least one lost core waveguide comprising: an inner lossy core, an outer core, and an outer cladding; the inner disappearing core has a first refractive index (N-1) and an inner core size; 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; a size of the inner core, a size of the outer core, and a spacing between the plurality of longitudinal waveguides are configured to decrease from the first end to the second end of the optical element, wherein at the second end, a size of the inner core is insufficient to conduct light and a size of the outer core is sufficient to conduct at least one optical mode; an optical coupler array, wherein the coupler housing structure proximate the first end has either a cross-sectional configuration of a ring surrounding the plurality of longitudinal waveguides and a gap between the ring and the plurality of longitudinal waveguides, or a cross-sectional configuration of a structure having a plurality of holes, at least one of which includes at least one of the plurality of longitudinal waveguides. 3. The optical coupler array of Example 2, wherein the coupler housing structure comprises a common single coupler housing structure. 4. The optical coupler array of any preceding example, wherein near the first end, one of the plurality of longitudinal waveguides extends outside the coupler housing structure. 5. The optical coupler array of any preceding example, wherein near the first end, one of the plurality of longitudinal waveguides is disposed within a coupler housing structure and does not extend outside of the coupler housing structure. 6. The optical coupler array of any preceding example, wherein near 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 protrude outside the coupler housing structure. 7. The optical coupler array of any of Examples 2 to 6, wherein the medium is a laterally continuous medium. 8. The optical coupler array of any of Examples 2 to 7, wherein a total volume of the medium within the optical coupler housing structure is greater than a total volume of all inner cores and outer cores of at least one lost core waveguide enclosed within the optical coupler housing structure. 9. The optical coupler array of any 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 decrease simultaneously and stepwise from the first end to the second end. 10. The optical coupler array of any preceding example, wherein there is substantially no spacing between the coupler housing structure and the plurality of longitudinal waveguides near the second end. 11. The optical coupler array of any preceding example, wherein the annular cross-sectional shape surrounding the plurality of longitudinal waveguides is one of the cross-sectional shapes of the plurality of longitudinal waveguides. 12. The optical coupler array of example 11, wherein the plurality of longitudinal waveguides are arranged in a hexagonal pattern. 13. The optical coupler array of any of Examples 11-12, wherein the ring has a circular internal cross section. 14. The optical coupler array of any of Examples 11-12, wherein the ring has a non-circular internal cross section. 15. The optical coupler array of example 14, wherein the internal 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 of Examples 11 to 16, wherein the outer cross section of the ring is circular. 18. The optical coupler array of any of Examples 11-16, wherein the outer cross section of the ring is non-circular. 19. The optical coupler array of Example 18, wherein the outer cross section shape is hexagonal. 20. The optical coupler array of example 18, wherein the outer cross-sectional shape is D-shaped. 21. The optical coupler array of 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 in a rectangular arrangement. 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 of Examples 21-24, wherein the at least one hole is made of a non-light-guiding material. 26. The optical coupler array of any of Examples 21-25, wherein the at least one hole has a circular cross section. 27. The optical coupler array of any 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 the dimensions of at least one hole are different from the dimensions of the other holes. 30. The optical coupler array of any of Examples 21-29, wherein at least one hole has a different shape than the other holes. 31. The optical coupler array of any of Examples 21-30, wherein the holes are isolated from each other. 32. The optical coupler array of any of Examples 21 to 30, wherein some of the holes are connected. 33. The optical coupler array of any preceding example, wherein the at least one lost core waveguide comprises single mode fiber. 34. The optical coupler array of any preceding example, wherein at least one missing core waveguide comprises multimode fiber. 35. The optical coupler array of any preceding example, wherein at least one of the disappearing core waveguides comprises polarization-maintaining fiber. 36. A multi-channel optical combiner array comprising: an elongated optical element; The elongated optical element has a first end and a second end, the first end and the second end being optically coupleable to a plurality of optical fibers, an optical device, or a combination thereof, and the optical element comprises: a coupler housing structure; a plurality of longitudinal waveguides arranged one above the other, Each of the plurality of longitudinal waveguides has the ability to accommodate at least one optical mode, the plurality of longitudinal waveguides are embedded in the housing structure, and the plurality of longitudinal waveguides comprise at least one lost core waveguide, the at least one lost core waveguide comprising: an inner lossy core, an outer core, and an outer cladding; the inner disappearing core has a first refractive index (N-1) and an inner core size; 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 includes 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 are configured to decrease from the first end to the second end of the elongated optical element, wherein at the second end, a size of the inner core is insufficient to conduct light and a size of the outer core is sufficient to conduct at least one optical mode; 37. The optical coupler array of Example 36, wherein the coupler housing structure proximate the first end has a cross-sectional configuration including at least one hole, the at least one hole comprising at least one of the plurality of longitudinal waveguides, the hole being larger than at least one of the plurality of longitudinal waveguides, and the at least one longitudinal waveguide being laterally movable relative to the coupler housing structure. 38. Near the first end, one of the plurality of longitudinal waveguides is disposed within the coupler housing. The optical coupler array of any of Examples 36-37 extending outside the structure. 39. The optical coupler array of any of Examples 36-38, wherein one of the plurality of longitudinal waveguides is disposed within a coupler housing structure near the first end. 40. The optical coupler array of any of Examples 36-39, wherein the medium is a laterally continuous medium. 41. An optical coupler array according to any of Examples 36 to 40, wherein the total volume of the medium within the coupler housing structure is greater than the total volume of all inner cores and outer cores of at least one lost core waveguide enclosed within the coupler housing structure. 42. The optical coupler array of 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 decrease simultaneously and stepwise from the first end to the second end. 43. The optical coupler array of any of Examples 36-42, wherein there is substantially no gap between the coupler housing structure and the plurality of longitudinal waveguides near the second end. 44. The optical coupler array of any of Examples 36 to 43, wherein the at least one hole is a single hole and the at least one longitudinal waveguide is composed of multiple longitudinal 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 of Examples 44-45, wherein the single hole has a circular cross section. 47. The optical coupler array of any 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 of Examples 44-49, wherein the optical coupler housing structure has a circular outer cross section. 51. The optical coupler array of any of Examples 44-49, wherein the optical 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 of Examples 36-43, 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 arrangement. 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 of Examples 54-57, wherein one or more of the plurality of holes comprises a non-light-guiding material. 59. The optical coupler array of any 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 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 the other 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 the other holes. 64. The optical coupler array of any of Examples 54-63, wherein the holes are isolated from each other. 65. The optical coupler array of any of Examples 54 to 63, wherein some of the holes are connected. 66. The optical coupler array of any of Examples 54-65, wherein the at least one lost core waveguide comprises a single mode fiber. 67. The optical coupler array of any of Examples 54-66, wherein at least one missing core waveguide comprises a multimode fiber. 68. The optical coupler array of any of Examples 54-67, wherein at least one of the disappearing core waveguides comprises polarization-maintaining fiber. Additional example 4 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 single coupler housing; the elongated optical element having a first end operable to be optically coupled to the plurality of optical fibers and a second end operable to be optically coupled to the optical device; The common unitary coupler housing structure has a plurality of longitudinal waveguides arranged at predetermined intervals from one another, each of the longitudinal waveguides capable of propagating at least one optical mode having a predetermined mode field profile, embedded in the common unitary housing structure, at least one of the longitudinal waveguides being a missing core waveguide, each of the missing core waveguides having an inner missing core, an outer core, and an outer cladding, the inner missing core having a first refractive index (N-1), a first inner core size (ICS-1) at the first end, and a second inner core size (ICS-2) at the second end, the outer core being a first refractive index (N-1) of the inner cladding. the common single coupler housing structure has a laterally continuous medium surrounding the plurality of longitudinal waveguides, and a predetermined relative magnitude relationship between the first, second, third and fourth refractive indices (N-1, N-2, N-3 and N-4) satisfies 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 of the inner cores and a total volume of the outer cores of all lost core waveguides enclosed within the common single coupler housing structure, the first inner lost core size (ICS-I), the first outer core size (OCS-I), and the predetermined distance between the plurality of longitudinal waveguides are simultaneously and stepwise decreased along the optical element from the first end to the second end according to a predetermined decrease profile, decreasing until a second inner lost core size (ICS-2) and a second outer core size (OCS-2) are reached, the second inner lost core size (ICS-2) is selected to be large enough not to conduct light, and the second outer core size (OCS-2) is selected to be large enough to conduct at least one optical mode, whereby light traveling from the first end to the second end escapes from an inner lost core to a corresponding outer core near the second end, and light traveling from the second end to the first end travels from an outer core to a corresponding inner lost core near the first end; an optical coupler array, wherein the common single coupler housing structure near the first end has a cross-sectional configuration of either a ring surrounding a plurality of longitudinal waveguides, a continuous structure having a plurality of holes, or a structure having at least one hole containing 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 structure; the elongated optical element having a first end operable to be optically coupled to a plurality of the plurality of optical fibers and a second end operable to be optically coupled to the optical device; The coupler housing structure has a plurality of longitudinal waveguides spaced apart from one another, each of the longitudinal waveguides capable of propagating at least one optical mode and embedded in the housing structure, at least one of the longitudinal waveguides being a lost core waveguide, each of the lost core waveguides having an inner lost core, an outer core, and an outer cladding, the inner lost core having a first refractive index (N-1) and a first inner core size (ICS-1) 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 the coupler housing structure includes a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, the first, second, third and fourth refractive indices (N-1, N-2, N-3 and N-4) having a relative magnitude relationship as follows: N-1>N-2>N-3; the first inner missing core size (ICS-I), the first outer core size (OCS-I), and the spacing between the plurality of longitudinal waveguides decrease along the optical element from the first end to the second end, this decrease continuing 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 insufficient to conduct light and the second outer core size (OCS-2) being sufficient to conduct at least one optical mode, whereby light traveling from the first end to the second end escapes from the inner vanishing core to the corresponding outer core near the second end, and light traveling from the second end to the first end travels from the outer core to the corresponding inner vanishing core; An optical coupler array, wherein the coupler housing structure near the first end has either a cross-sectional configuration of a ring surrounding a plurality of longitudinal waveguides or a structure having a plurality of holes, at least one of which contains at least one of the plurality of longitudinal waveguides. Additional example 5 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 single coupler housing structure; the elongated optical element having a first end operable to optically couple to an optical fiber, an intermediate cross section, and a second end operable to optically couple to the optical device; the common unitary coupler housing structure has a plurality of longitudinal waveguides spaced apart from one another at predetermined intervals, each of the plurality of longitudinal waveguides capable of transmitting at least one optical mode having a predetermined mode field profile, and is embedded proximate to the second end of the common unitary housing structure, at least one of the plurality of longitudinal waveguides being a lost core waveguide, the at least one lost core waveguide having an inner lost core, an outer core, and an outer cladding; the inner lost core has a first refractive index (N-1), a first inner core size (ICS-I) at the first end, an intermediate inner core size (ICS-IN) at the mid-cross section, and a second inner core size (ICS-2) at the second end; the outer core longitudinally surrounds the inner core and has the 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 mid-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 common single coupler housing structure comprises a laterally continuous medium surrounding the plurality of longitudinal waveguides; a fourth refractive index (N-4) of the medium, and a predetermined relative size relationship between the first, second, third, and fourth refractive indices (N-1, N-2, N-3, and N-4, respectively) comprises the following size 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 of the inner cores and a total volume of the outer cores of all the lost core waveguides confined within the common single coupler housing structure; the first lost core inner size (ICS-I), the first outer core size (OCS-I), and the predetermined distance between the plurality of longitudinal waveguides are set to simultaneously and stepwise decrease according to a predetermined decrease profile along the optical element from the first end to the second end, and the decrease is wherein the intermediate inner extinction core size (ICS-IN) is selected to be large enough to not conduct light, the intermediate outer core size (OCS-IN) is large enough to conduct at least one optical mode, and the second outer core size (OCS-2) is selected to not conduct light, whereby an optical coupler array, wherein light traveling from the first end to the second end escapes from an inner lost core to a corresponding outer core near the intermediate cross section and further escapes to a composite waveguide formed by at least two adjacent outer cores near the second end; at least one waveguide mode of light traveling from the second end to the first end travels from a composite waveguide formed by at least two adjacent outer cores to the outer core near the intermediate cross section and from the outer core to the corresponding inner lost core near the first end; and a common single coupler housing structure located proximal to the first end has a cross-sectional configuration having a laterally continuous structure with at least one hole, the at least one hole having at least one longitudinal waveguide forming a space between the coupler housing structure and the at least one longitudinal waveguide. 2. A multi-channel optical combiner array, comprising: an elongated optical element; and a coupler housing structure; the elongated optical element has a first end, an intermediate cross section, and a second end; the coupler housing structure has a plurality of longitudinal waveguides spaced apart from one another, each of the plurality of longitudinal waveguides capable of propagating at least one optical mode, and is disposed within the housing structure, at least one of the plurality of longitudinal waveguides having an inner dissipative core, an outer core, and an outer cladding; The inner lost core has a first refractive index (N-1) and 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, and the outer core longitudinally surrounds the inner core and has a second refractive index (N-2) and 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 (ICS-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 has a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides; and the relative magnitude relationships of the first, second, third, and fourth refractive indices (N-1, N-2, N-3, and N-4, respectively) satisfy the following magnitude relationship: N-1>N an optical coupler array, wherein the first inner missing core size (ICS-I), the first outer core size (OCS-I), and spacing between the plurality of longitudinal waveguides decrease along the optical element from the first end to the second end, the intermediate inner missing core size (ICS-IN) is insufficient to guide light, 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 such that light traveling from the first end to the second end escapes from an inner missing core to a corresponding outer core near the mid-cross section and escapes to a composite waveguide formed by at least two adjacent outer cores near the second end, and at least one waveguide mode of light traveling from the second end to the first end travels from a composite waveguide formed by at least two adjacent outer cores to the outer core near the mid-cross section and from the outer core to a corresponding inner missing core near the first end. [Brief explanation of the drawings]

[0010] In the drawings, the same reference numbers indicate corresponding or similar elements in each figure.

[0011] [Figure 1A] FIG. 1A is a schematic diagram of a side view illustrating an example of a first embodiment of an optical fiber coupler array including at least one lost core waveguide (VC waveguide), shown as a single VC waveguide by way of example, and at least one non-VC waveguide (shown as multiple non-VC waveguides by way of example) symmetrically positioned proximal to the exemplary single VC waveguide. [Figure 1B] 1B is a schematic diagram of a side view of a second embodiment of an optical fiber coupler array, including at least one lost core waveguide (VC waveguide). In this figure, a single VC waveguide is shown as an example, and at least one non-VC waveguide is shown. In this figure, a single non-VC waveguide is shown as an example, positioned in parallel and adjacent to the exemplary single VC waveguide, and a portion of the optical fiber coupler array is configured such that the inter-channel spacing at its second end (smaller end) is larger than the inter-channel spacing at the second end (smaller end) of the optical fiber coupler array of FIG. 1A. [Figure 1C] FIG. 1C is a schematic side view of a third example optical fiber coupler array having a plurality of VC waveguides and a plurality of non-VC waveguides arranged asymmetrically relative to one another in the longitudinal direction, where at least some of the non-VC waveguides have different types and / or different characteristics. [Figure 1D] FIG. 1D is a schematic diagram of a side view illustrating a fourth embodiment of an optical fiber coupler array configured to support fan-in and fan-out connections, including a pair of optical fiber coupler components with a multi-core optical fiber element connected between the second (smaller) ends of the two optical fiber coupler components. [Figure 2A]2A is a schematic diagram showing a side view of an optical fiber coupler array in a fifth embodiment, comprising a plurality of vertically adjacent VC waveguides at least partially embedded within a single common housing structure, each VC waveguide being spliced ​​to a corresponding elongated optical device (e.g., an optical fiber) at a specific first connection location, at least a portion of which extends outward from 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 side view of a sixth embodiment of an optical fiber coupler array, comprising a plurality of vertically adjacent VC waveguides at least partially embedded within a single common housing structure, each VC waveguide being joined to a corresponding extended optical device (e.g., an optical fiber) at a specific second connection location, at least a portion of which extends outward from the single common housing structure by a predetermined length, and each specific second connection location being located in an outer cross-sectional boundary area of ​​the single common housing structure. [Figure 2C] 2C is a schematic diagram showing a side view of a seventh embodiment of an optical fiber coupler array, comprising a plurality of vertically adjacent VC waveguides at least partially embedded within a single common housing structure, each VC waveguide being spliced ​​with a corresponding extended optical device (e.g., 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 located outside the single common housing structure. [Figure 2D]FIG. 2D is a side view schematic diagram illustrating an alternative embodiment of an optical fiber coupler array having multiple vertically adjacent VC waveguides at least partially embedded in a single common housing structure, the second end of which is configured to increase, improve, and / or optimize optical coupling to a free-space-based optical device, where the free-space-based device can be either (1) a stand-alone device (e.g., a lens followed by other optical components as shown in FIG. 2D ) or (2) a device that can be fusion-bonded to the end of the second coupler (e.g., a coreless glass element that acts as an end cup for power density reduction at the glass-air interface or as a Talbot mirror for phase-locking the coupler waveguides in a Talbot cavity geometry). [Figure 3A] Figure 3A is a schematic diagram showing a cross-sectional view of a first alternative embodiment of the optical fiber coupler array shown in Figures 1D-2D, and optionally, a reference element having the function of providing visual identification of the waveguide placement / characteristics (e.g., alignment) can be placed in one of multiple cross-sectional area categories. [Figure 3B] FIG. 3B is a schematic diagram of a cross-sectional view of a first alternative embodiment of the optical fiber coupler array shown in FIG. 1A, in which at least one VC waveguide (shown as a single VC waveguide by way of example) is arranged along the central longitudinal axis of a single common housing structure and is surrounded by a plurality of parallel, closely spaced, symmetrically arranged non-VC waveguides. [Figure 3C] FIG. 3C is a schematic diagram showing a cross-sectional view of a first alternative embodiment of the above-described optical fiber coupler array of FIG. 3B, in which the volume of the medium of the single common housing structure surrounding all of the waveguide sections embedded within the single common housing structure exceeds the combined volume of the inner cores and outer cores of the VC waveguide sections embedded within the single common housing structure. [Figure 3D]3D is a schematic cross-sectional view showing a second alternative embodiment of the optical fiber coupler array shown in FIG. 3B, wherein at least one VC waveguide arranged along the central longitudinal axis of the single common housing structure is comprised of multiple VC waveguides, and the volume of the single common housing structure medium surrounding all the waveguide sections embedded within the single common housing structure exceeds the total volume of the inner and outer cores of the multiple VC waveguide sections embedded within the single common housing structure. [Figure 3E] FIG. 3E is a schematic cross-sectional view of a first alternative embodiment of the fiber optic coupler array shown in FIG. 3D, further comprising a central waveguide channel through which optical pumping can be provided. [Figure 3F] Figure 3F is a schematic cross-sectional view showing a second alternative embodiment of the optical fiber coupler array shown in Figure 3D, and Figure 3F is a schematic cross-sectional view showing a first alternative embodiment of the optical fiber coupler array shown in Figure 3D.If the VC waveguides arranged along the central longitudinal axis of a single common housing structure are selected to be of a different type or have different characteristics from the remaining multiple VC waveguides and to have an enlarged inner core, they can be advantageously used to increase or optimize optical coupling with various optical devices having different types of optical pump channels. [Figure 3G] FIG. 3G is a schematic diagram showing a cross-sectional view of a third alternative embodiment of the optical fiber coupler array of FIG. 3B, in which at least one VC waveguide (shown as a single VC waveguide by way of example) is positioned at an offset position from the central longitudinal axis of a single common housing structure, and this optical fiber coupler array embodiment can be readily utilized as a fiber optical amplifier or laser when coupled with a double-clad optical fiber having a non-concentric core, which is useful for improving optical pump efficiency. [Figure 3H]FIG. 3H is a schematic cross-sectional view showing a first alternative embodiment of the optical fiber coupler array shown in FIG. 3G above, in which at least one VC waveguide (shown, by way of example, as a single VC waveguide offset from the center) has polarization-maintaining properties and is positioned so that its polarization axis coincides with its lateral offset position. [Figure 3I] FIG. 3I is a schematic cross-sectional view illustrating a fourth alternative embodiment of the optical fiber coupler array shown in FIG. 3B, in which a single centrally located VC waveguide and multiple non-VC waveguides each have polarization-maintaining properties (shown as induced by a rod stress member by way of example, but easily substituted by other stresses or equivalent designs) and corresponding polarization axes, all of which are coincident with one another. [Figure 3J] 3J is a schematic diagram illustrating a first alternative embodiment of FIG. 3I, in which the polarization-maintaining properties of all waveguides arise solely from the non-circular cross-sectional shape (e.g., at least a portion of an ellipse) of the core (or outer core, in the case of a VC waveguide) of each waveguide, and optionally includes at least one waveguide orientation indicator located in an outer region of the single common housing structure, which indicates a particular cross-sectional geometrical arrangement of the waveguides of the optical coupler array so that the particular cross-sectional geometrical waveguide arrangement can be easily identified from a visual or physical inspection of the single common housing structure. The waveguide orientation indicator further functions to facilitate passive alignment of the second end of the optical coupler array to at least one optical device. [Figure 3K] FIG. 3K is a cross-sectional view showing a fifth alternative embodiment of the optical fiber coupler array shown in FIG. 3B, in which a single centrally located VC waveguide has polarization-maintaining properties (shown as induced by a rod stress member by way of example, but easily substituted by other stress or equivalent designs), has a corresponding polarization axis, and optionally includes multiple optional waveguide placement indicator elements of the same or different type as those described in FIG. 3J. [Figure 3L]FIG. 3L is a schematic diagram illustrating a second alternative embodiment of the optical fiber coupler array of FIG. 3I, in which the single common housing structure has a cross-section with a non-circular geometric shape (shown as a hexagon, for example), and the polarization axes of the waveguides are aligned with each other and with the cross-sectional geometric shape of the single common housing structure, and optionally further includes a waveguide placement indicator element as described in FIG. 3J. [Figure 4] FIG. 4 is a schematic isometric view illustrating an example of the connection of the second end (i.e., “tip”) of an optical fiber coupler array in the process of connecting to multiple vertical coupling elements in an optical device in a close, open-air optical coupling arrangement, showing a configuration that can be easily transitioned to a butt-coupled configuration due to full physical contact between the second end of the optical fiber coupler array and the vertical coupling elements. [Figure 5] FIG. 5 is a schematic isometric view illustrating an example in which the second end (i.e., “tip”) of an optical fiber coupler array is connected to multiple edge coupling elements of an optical device in a butt coupling configuration, which can be easily switched to multiple alternative coupling configurations, including a close-in open-air optical coupling arrangement or an angle-adjusted coupling arrangement. [Figure 6] FIG. 6 is a schematic diagram illustrating a cross-sectional view of a conventionally known optical fiber coupler having various drawbacks and deficiencies that are readily overcome by the various embodiments of the optical fiber coupler arrays shown in FIGS. 1A-5. [Figure 7] FIG. 7 is a schematic diagram showing various views of a flexible pitch-reduced optical fiber (PROFA). [Figure 8] 8 is a schematic diagram illustrating a cross-sectional view of an exemplary configuration of a housing structure near a first end of an optical coupler array, the cross-sectional view being taken perpendicular to the longitudinal direction or length of the optical coupler array. [Figure 9] FIG. 9 is a schematic diagram illustrating a cross-sectional view of another exemplary configuration of a housing structure near a first end of an optical coupler array. [Figure 10] FIG. 10 is a schematic diagram (multiple views) of an additional exemplary optical coupler arrangement. [Figure 11] FIG. 11 is a schematic diagram (multiple views) of an additional exemplary optical coupler arrangement. [Figure 12A] FIG. 12A is a schematic diagram of an exemplary spatial division multiplexer. [Figure 12B] FIG. 12B is a schematic diagram of an exemplary spatial division multiplexer. [Figure 12C] FIG. 12C is a schematic diagram of an exemplary spatial division multiplexer. [Figure 13] FIG. 13 is a schematic diagram of an exemplary adapter with pattern adaptation. [Figure 14] FIG. 14 is a schematic diagram of an exemplary channel add-drop multiplexer. [Figure 15] FIG. 15 is a schematic diagram of an exemplary multiplexer that combines pattern adaptation and channel add / drop. [Figure 16] FIG. 16 is a schematic diagram of an exemplary multiplexer having a curved housing structure. [Figure 17] FIG. 17 is a schematic diagram of an exemplary multiplexer having an additional multimode channel. [Figure 18A] FIG. 18A is a schematic diagram of an exemplary WDM-fanout device. [Figure 18B] FIG. 18B is a schematic diagram of an exemplary MCF-WDM device. [Figure 19A] FIG. 19A is a schematic diagram of a cross-sectional view of an exemplary composite SDM-WDM device. [Figure 19B] 1A-1C are schematic diagrams of side views of various examples of composite SDM-WDM devices. [Figure 19C] 1A-1C are schematic diagrams of side views of various examples of composite SDM-WDM devices. [Figure 19D] 1A-1C are schematic diagrams of side views of various examples of composite SDM-WDM devices. [Figure 19E] 1A-1C are schematic diagrams of side views of various examples of composite SDM-WDM devices. [Figure 19F] 1A-1C are schematic diagrams of side views of various examples of composite SDM-WDM devices. [Figure 20] FIG. 20 is a schematic diagram of a cross-sectional view of an example MCF-WDM device with an access region. [Figure 21A] FIG. 21A is a schematic diagram illustrating a cross-sectional view of an exemplary composite SDM-WDM device. [Figure 21B] FIG. 21B is a schematic diagram illustrating an exemplary configuration utilizing the device shown in FIG. 21A. [Figure 22] FIG. 22 is a schematic diagram of another exemplary configuration utilizing the device shown in FIG. 21A. [Figure 23] FIG. 23 is a schematic diagram of another exemplary configuration utilizing the device shown in FIG. 21A. [Figure 24] FIG. 24 is a schematic diagram of another exemplary configuration utilizing the apparatus shown in FIG. 21A. [Figure 25A] FIG. 25A is a schematic diagram of a side view of an exemplary SDM-WDM composite device. [Figure 25B] FIG. 25B is a microscope image showing a cross section of the tapered end of the exemplary four-core WDM combiner 2500. [Figure 25C] FIG. 25C is a microscope image showing a cross section of an exemplary four-core MCF 2550. [Figure 26A] FIG. 26A is an end-face alignment mode image of an exemplary four-core WDM combiner and MCF before splicing. [Figure 26B] FIG. 26B is an end-face alignment mode image of an exemplary four-core WDM combiner and MCF before splicing. [Figure 26C] FIG. 26C shows an exemplary packaged device of a fusion-spliced ​​four-core WDM combiner and MCF. [Figure 27A] FIG. 27A shows the total insertion loss of four pump channels and four signal channels when an exemplary four-core WDM combiner is fusion-connected to a 5-meter four-core MCF and a non-WDM fan-out device. [Figure 27B] FIG. 27B shows the C-band signal channel loss for four signal channels when the exemplary 4-core WDM combiner is fusion spliced ​​to a 4-core MCF and a non-WDM fan-out device over 5 meters. [Figure 28A]1 shows the measured insertion loss, polarization dependent loss, and crosstalk of the second and fourth diagonal signal channels of an exemplary four-core WDM combiner, respectively. [Figure 28B] 1 shows the measured insertion loss, polarization dependent loss, and crosstalk of the second and fourth diagonal signal channels of an exemplary four-core WDM combiner, respectively. [Figure 28C] 1 shows the measured insertion loss, polarization dependent loss, and crosstalk of the second and fourth diagonal signal channels of an exemplary four-core WDM combiner, respectively. [Figure 29] FIG. 29 shows an example packaged MCF-WDM device. DETAILED DESCRIPTION OF THE INVENTION

[0012] Various embodiments described herein provide improved wavelength division multiplexing devices (e.g., wavelength division multiplexing fan-out devices and pump signal combiners for multicore fibers (MCFs)) for spatial division multiplexing (SDM-WDM devices). Various embodiments described herein provide improved spatial division multiplexing (SDM). Some components can include adapters between multicore fibers (MCFs) with different core patterns. Some examples may include add-drop multiplexers for MCFs. Some designs may include multiplexers with pattern adaptation and channel add-drop.

[0013] In many multi-channel optical coupler arrays, improved cross-sectional (or lateral) positioning of the waveguides may be desirable. In one embodiment of the present disclosure, the housing structure (e.g., a common single coupler housing structure in some cases) allows for self-aligning waveguide placement in a position close to a first end (e.g., a circular (as shown in FIG. 8) or hexagonal close placement in a housing structure having a hexagonal interior cross-section) and allows for improved (in some cases precise or near-precise) cross-sectional positioning of the waveguides at the second end.

[0014] Packaging photonic integrated circuits (PICs) with a low vertical profile (perpendicular to the plane of the PIC) can be desirable in a variety of applications, including optical communications and sensing. While this is easily achievable with edge couplers, surface couplers can require significant vertical lengths.

[0015] Therefore, it would be advantageous to provide various embodiments of a pitch-reduced optical fiber (PROFA)-based flexible optical fiber component that can be configured and optimized to provide sufficient flexibility for low-profile packaging while maintaining all channels discrete with sufficiently low crosstalk. It would also be desirable to provide a PROFA-based flexible optical fiber component with a flexible portion that provides mechanical isolation of the "PROFA-PIC interface" from the rest of the PROFA, improving stability against environmental variations, including temperature changes and mechanical shock and vibration. It would also be desirable to provide a PROFA-based flexible optical fiber that combines multiple coupler arrays (each array having multiple optical channels) to form an optical multi-port input / output (IO) interface.

[0016] Certain embodiments provide an optical fiber coupler array that provides low loss, high coupling coefficient, high precision, and easy alignment between a plurality of optical fibers (or other optical devices) and an optical device having a plurality of waveguide interfaces with a second smaller inter-channel spacing. Advantageously, in various embodiments, the large size end and the small size end of the optical fiber coupler array can each be configured with a corresponding different (i.e., large vs. small) inter-channel spacing, such that the respective inter-channel spacings at the large and small ends of the optical fibers can be easily matched to a corresponding first inter-channel spacing of the plurality of optical fibers at the large optical fiber end and a second inter-channel spacing of the plurality of waveguide interfaces of the optical device at the small optical fiber end.

[0017] In various embodiments, the optical coupler array includes a plurality of waveguides, at least one of which is optionally polarization-maintaining, including at least one "missing core fiber" at least partially embedded within a common housing structure. Furthermore, in various additional embodiments, the coupler array is configured to enable use with at least one of either an optical fiber amplifier or an optical fiber laser.

[0018] Various embodiments of the optical coupler array advantageously include at least one "cancellation core" (VC) waveguide, as described below in connection with, for example, VC waveguide 30A of optical coupler array 10A shown in FIG. 1A.

[0019] Additionally, the term "optical device," as used generally herein, applies to any type of optical fiber, including, but not limited to, single-channel or multi-channel optical devices, or standard / conventional optical fibers. For example, optical devices that may be advantageously coupled with an optical coupler array include, but are not limited to, any 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 with 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 array.

[0020] Furthermore, while the term "fusion splice" is used in various descriptions of exemplary embodiments of optical coupler arrays described below to refer to connections between various components of an optical coupler array and between various components of an optical coupler array and optical devices, it should be noted that other forms of connection techniques or methods for waveguides or other optical coupler array components, including but not limited to mechanical connections, may be selected and utilized depending on design choice or need without departing from the spirit of the invention.

[0021] Referring to FIG. 1A, a first embodiment of an optical fiber coupler array is shown as optical coupler array 10A. This array comprises a common housing structure 14A, described below, at least one VC waveguide, including a single VC waveguide 30A as illustrated in FIG. 1A, and at least one non-VC waveguide, including non-VC waveguides 32A-1 and 32A-2, as illustrated in FIG. 1A. As illustrated in FIG. 1A, non-VC waveguides 32A-1 and 32A-2 are shown as a pair, each symmetrically positioned adjacent one side of the exemplary single VC waveguide 30A. Here, the section of VC waveguide 30A between positions B and D in FIG. 1A is embedded in common housing structure 14A.

[0022] Before describing the coupler array 10A and its components in detail, it is useful to provide a detailed overview of the VC waveguide 30A, exemplary and alternative embodiments thereof, which are advantageously utilized in each of the coupler array embodiments shown in FIGS. 1A-5.

[0023] VC waveguide 30A has a large end adjacent to position B in FIG. 1A and a tapered small end adjacent to position C in FIG. 1A, and is composed of inner core 20A made of a material with an effective refractive index N-1, outer core 22A (made of a material with an effective refractive index N-2 that is smaller than N-1), and cladding 24A (made of a material with an effective refractive index N-3 that is smaller than N-2).

[0024] Preferably, the outer core 22A functions as an effective cladding when the VC waveguide 30A supports a "M1" spatial propagation mode (where M1 > 0) within the inner core 20A at the large end of the VC waveguide 30A. 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 connected optical device (e.g., optical device 34A-1, etc.). It is selected to match the NA of a standard / conventional optical fiber connected to the VC waveguide 30A at the connection position 36A-1 (e.g., by fusion splicing, mechanical connection, or other fiber connection designs). On the other hand, the dimensions of the inner and outer cores (20A, 22A) are selected such that the connected optical device (e.g., optical device 34A-1) has substantially the same mode field dimension (MFD). Hereinafter, when the cross-section of the VC or non-VC waveguide is not circular, a non-circular mode profile occurs, so the mode field dimension is used instead of the generally used mode field diameter (MFD). Thus, the mode field dimension encompasses both the size and shape of the mode and is equal to the mode field diameter in the case of a circularly symmetric mode.

[0025] When manufacturing the coupler array 10A from a preform of appropriate configuration (including the VC waveguide 30A preform, having the corresponding inner core 2 0A, outer core 22A, and cladding 24A), as the coupler array 10A preform is thinned according to at least one predefined thinning profile, the inner core 20A becomes not large enough to support all M1 modes. The number of spatial modes supported by the inner core at the second (tapered) end is M2, and M2 < M1. In the case of a single-mode waveguide (M1 = 1, corresponding to two polarization modes), M2 = 0, and the inner core is not large enough to support light propagation. The VC waveguide 30A functions as a single-core fiber with an effective refractive index N-2 surrounded by a cladding of refractive index N-3.

[0026] During fabrication of the coupler array 10A, the inter-channel spacing S-1 at the large end of the coupler array 10A (position B in Figure 1A) decreases to S-2 at the small end of the coupler array 10A (position C in Figure 1A). The inter-channel spacing S-2 at the small end of the coupler array 10A (position C in Figure 1A) decreases in proportion to the stretch ratio selected during fabrication. Meanwhile, the MFD value (or the inverse NA value of the VC waveguide 30A) may be decreased, increased, or maintained depending on the selected refractive index differences (N-1 - N-2) and (N-2 - N-3). This selection is determined by the application of the coupler array 10A.

[0027] The ability to independently control the inter-channel spacing and MFD values ​​at either end of the optical coupler array is a highly advantageous feature of certain embodiments. Furthermore, the ability to match MFD and NA values ​​by correspondingly selecting the size and shape of the inner core 20A and outer core 22A and the values ​​of N-1, N-2, and N-3 allows for coupling to a variety of waveguides without the use of lenses.

[0028] In various embodiments, the property of VC waveguides that light continues to propagate along the core even when the diameter is significantly reduced reduces light loss due to interfacial imperfections and contamination, allowing a wider range of materials to be used as the medium 28A of the common housing structure 14A (described below), including, but not limited to: (a) non-optical materials (because light is concentrated within the waveguide core); (b) absorbing or scattering materials, or materials with refractive indices greater than that of standard / conventional fibers (to reduce or increase crosstalk between channels); and (c) Pure silica (e.g., to use the same cladding material as standard / conventional fibers and to facilitate splicing to multicore, double-clad, or multimode fibers).

[0029] Preferably, according to a particular embodiment, the desired relative values ​​of NA-1 and NA-2 at corresponding ends of coupler array 10A (e.g., NA-1 corresponding to the large end of coupler array 10A, and NA-2 corresponding to the small end of coupler array 10A, and the respective values ​​of NA-1 and NA-2, if desired) can be determined by selecting values ​​for refractive indices N1, N2, and N3 of coupler array 10A and configuring them according to at least one of the following relationships selected based on the magnitude of the desired relative numerical aperture at each end of coupler array 10A: JPEG2025536527000002.jpg52168

[0030] In general, the NA of any type of optical fiber is determined by the following formula: where n core and n clad are the refractive indices of the core and cladding of the optical fiber, respectively. JPEG2025536527000003.jpg1874

[0031] When using the above formula, it is important to note that the relationship between NA and the acceptance angle of the fiber is only an approximation. In particular, fiber manufacturers often indicate the "NA" of single-mode (SM) fiber based on the above formula, but the acceptance angle of single-mode fiber cannot be determined from the refractive index alone, and is actually a different value.

[0032] In accordance with certain embodiments herein, n core and n claddingIt is preferable to determine various NA values ​​using the effective refractive index of N1, N2, N3, or N4. This is because the effective refractive index determines light propagation and is meaningful for the structured waveguides used in various embodiments. Furthermore, the lateral refractive index profile within the waveguide may not be flat but may vary around the values ​​of N1, N2, N3, or N4. Furthermore, due to dopant diffusion and other intentional or unintentional factors, the transitions between regions having refractive indices N1, N2, N3, and N4 may not be as sharp as step functions but may be smooth functions connecting the values ​​of N1, N2, N3, and N4. Coupling design or optimization may involve varying the values ​​of N1, N2, N3, and N4 as well as the size and shape of the regions having the respective refractive indices.

[0033] Returning to FIG. 1A, the common coupling structure 14A consists of a medium 28A in which a section of the VC waveguide 30A between locations B and D in FIG. 1A is embedded, the medium 28A including, but not limited to, at least one of the following materials: Materials that have properties that inhibit the propagation of light, Materials with light-absorbing optical properties, Materials with light-scattering optical properties, a material with optical properties selected such that the fourth refractive index (N-4) is greater than the third refractive index (N-3), and / or A material having optical properties selected such that the fourth refractive index (N-4) is substantially equal to the third refractive index (N-3).

[0034] At the large end of the optical coupler array 10A (close to position B in FIG. 1A ), the VC waveguides 30A are connected to corresponding extended optical devices 34A-1 (e.g., optical fibers) at specific connection locations 36A-1 (shown as an example located within the common housing structure 14A), at least portions of which extend outside the common housing structure 14A by a predetermined length 12A. Meanwhile, the non-VC waveguides 32A-1, 32A-2 are connected to corresponding extended optical devices 34A-2, 34A-3 (e.g., optical fibers) at specific connection locations 36A-2, 36A-3 (located outside the common housing structure 14A), at least portions of which extend outside the common housing structure 14A by a predetermined length 12A.

[0035] Optionally, coupler array 10A may include a substantially uniform diameter tip 16A for coupling to interface 42A of optical waveguide device 40A, as shown between positions C and D in FIG. 1A. This uniform diameter tip 16A may be useful in certain interface applications, such as those shown in FIGS. 1D, 4, and 5. , the coupler array 10A can be manufactured without the tip 16A (or the tip 16A can be removed after manufacturing) and configured so that coupling with the optical device interface 42A occurs at the interface of the coupler array 10A at position C in FIG. 1A.

[0036] In another embodiment, when the optical device 40A is constructed from a dual-clad fiber, when the small end of the coupler array 10A is coupled (e.g., fusion spliced) to the optical device interface 42A, a portion of the common housing structure 14A (e.g., a portion of the tip 16A) adjacent to the splice location is coated with a low refractive index medium (not shown) and extends beyond the splice location to the outer cladding of the dual-clad optical fiber optical device 40A (and optionally extends beyond a portion of the outer cladding of the dual-clad optical fiber optical device 40A adjacent to the splice location).

[0037] Referring to FIG. 1B, a second embodiment of an optical fiber coupler array is shown as coupler array 10B. Coupler array 10B comprises a common housing structure 14B, at least one VC waveguide, shown as a single VC waveguide 30B in FIG. 1B, and at least one non-VC waveguide, shown as a single non-VC waveguide 32B in FIG. 1B, arranged in parallel proximity to VC waveguide 30B. Here, 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 shown in FIG. 1A. This configuration can be easily achieved by transversely cleaving optical fiber 10A at location C′, thereby shortening common housing structure 14B relative to common housing structure 14A and creating a new, larger-diameter array interface 18B, which has a larger inter-channel spacing value S2′.

[0038] Referring to FIG. 1C, a third embodiment of an optical fiber coupler array is shown as coupler array 10C. Coupler array 10C includes a plurality of VC waveguides, VC waveguides 30C-1 and 30C-2 shown in FIG. 1C, and a plurality of non-VC waveguides, non-VC waveguides 32C-1, 32C-2, and 32C-a shown in FIG. 1C, all of which are arranged longitudinally and asymmetrically relative to one another. Here, at least some of the non-VC waveguides have different types and / or characteristics (e.g., single-mode or multimode, polarization-maintaining, etc.). For example, non-VC waveguides 32C-1 and 32C-2 are different types or have different characteristics from non-VC waveguide 32C-a. Furthermore, either the VC or non-VC waveguide (e.g., non-VC waveguide 32C-a) can extend beyond the common housing structure of coupler array 10C by any length and need to be connected to a nearby optical device.

[0039] 1D , a fourth example of an optical fiber coupler array configured to support multicore fan-in and fan-out connections is shown as coupler array 50. Coupler array 50 comprises a pair of optical fiber coupler array components (10D-1 and 10D-2), with a multicore optical fiber element 52 connected between the second (smaller) ends of the two optical fiber coupler array components (10D-1, 10D-2) (e.g., by fusion splicing at locations 54-1 and 54-2). Preferably, at least one VC waveguide within each optical fiber coupler array component (10D-1, 10D-2) is configured to increase or maximize optical coupling to a corresponding selected core of the multicore optical fiber element 52 and reduce or minimize optical coupling to all other cores.

[0040] Referring to FIG. 2A, a fifth embodiment of the optical fiber coupler array is shown as coupler array 100A. The coupler array 100A is comprised of a plurality of vertically adjacent VC waveguides, shown as a plurality of VC waveguides 130A-1, 130A-2, at least partially embedded in a single common housing structure 104A (by way of example only). Each VC waveguide 130A-1, 130A-2 is connected at a specific connection location 132A-1, 132A-2, respectively, to a corresponding extended optical device 134A-1, 134A-2 (e.g., an optical fiber), at least a portion of which extends outward from the common housing structure 104A a predetermined length 102A, and each specific connection location 132A-1, 132A-2 is disposed within the common housing structure 104A.

[0041] Referring to FIG. 2B, a sixth embodiment of an optical fiber coupler array is shown as coupler array 100B.

[0042] The coupler array 100B comprises a plurality of longitudinally adjacent VC waveguides, illustratively shown as a plurality of VC waveguides 130B-1, 130B-2, at least partially embedded in a single common housing structure 104B. Each VC waveguide 130B-1, 130B-2 is spliced ​​to a corresponding extended optical device 134B-1, 134B-2 (e.g., an optical fiber) at a specific connection location 132B-1, 132B-2, respectively, at least a portion of which protrudes outside the common housing structure 104B by a predetermined length 102B, and each specific connection location 132B-1, 132B-2 is located in an outer cross-sectional boundary region of the common housing structure 104B.

[0043] Referring to FIG. 2C, a seventh embodiment of an optical fiber coupler array is shown as coupler array 100C.

[0044] The coupler array 100C comprises a plurality of longitudinally adjacent VC waveguides, illustratively shown as a plurality of VC waveguides 130C-1, 130C-2, at least partially embedded in a single common housing structure 104C. Each VC waveguide 130C-1, 130C-2 is connected at a specific connection location 132C-1, 132C-2 to a corresponding extended optical device 134C-1, 134C-2 (e.g., an optical fiber), at least a portion of which protrudes outward from the common housing structure 104C by a predetermined length 102C, and each specific connection location 132C-1, 132C-2 is located outside the common housing structure 104C.

[0045] Referring to FIG. 2D , an alternative embodiment of an optical fiber coupler array is shown as coupler array 150. Coupler array 150 consists of multiple longitudinally adjacent VC waveguides at least partially embedded in a single common housing structure, with the second end configured to increase or optimize optical coupling to free-space-based optical device 152. Free-space-based optical device 152 includes lens 154 followed by an additional optical device component 156, which may include, for example, a MEMS mirror or a volume Bragg grating. The combination of the coupler and free-space-based optical device 152 can be used as an optical switch or WDM device to spectrally combine or split optical signal 160b (representative of output optical signal 160a of optical coupler array 150 after passing through lens 154). In this case, one of the fibers is used as an input and the other as an output, or vice versa. In another embodiment, free-space-based device 152 can be configured to be fusion-splicable to the end of a second coupler. This device can be a coreless glass element that acts as an end cup for power density reduction at the glass-air interface. In another variation, the coreless element acts as a Talbot mirror that allows phase locking of the coupler waveguides in a Talbot cavity geometry.

[0046] Before describing each embodiment shown in FIGS. 3A to 3L in detail, it is important to note that the words "multiple" or "at least" may be used in the figures. Where the phrase "at least one" is used, the specific quantity of such coupler components / elements provided in the corresponding coupler array embodiment may be selected as needed or by design choice (e.g., based on the intended industrial application of the coupler array) without departing from the spirit of the present invention. Accordingly, in each of FIGS. 3A-3L , a single or individual coupler array component / element is identified by a single reference number, and multiple coupler components / elements are identified by appending a "(1..n)" designation to the reference number, where "n" is the desired number of multiple coupler elements / components (which may have different values ​​in specific coupler array embodiments described below).

[0047] Additionally, all VC and Non-VC waveguides are shown illustratively with only circular cross sections of the inner and outer cores and cladding. Other shapes (e.g., hexagonal, rectangular, or square) of the cross sections of the inner and outer cores and cladding can be used without departing from the scope of the present invention. The specific choice of shape is determined based on requirements such as the channel shape of the optical device, the channel position geometry (e.g., hexagonal, rectangular, or square lattice), or the axial polarization alignment mode.

[0048] Similarly, unless otherwise specified below, as long as the various relationships defined below (e.g., the following relative volume relationships for optical coupler arrays 200C and 200D shown in Figures 3C and 3D, and the feature in Figure 3H that PM VC waveguide 204H is laterally offset from the longitudinal central axis of coupler array 200H) are observed, the sizes, relative sizes, relative positions, and selection of construction materials are not limited to the exemplary sizes, relative sizes, relative positions, and selection of construction materials shown in the detailed description of the coupler array embodiments of Figures 3A to 3L, and can be selected by one of ordinary skill in the art as a matter of convenience or design choice.

[0049] Finally, the various single common housing structural components 202A-202L of the various coupler arrays 200A-200L shown in Figures 3A-3L can each be constructed from a medium having a refractive index N-4 value in accordance with applicable ones of the relationships described above. The various single common housing structural components 202A-202L shown in Figures 3A-3L are constructed from a medium having a refractive index N-4 value in accordance with applicable relationships with the refractive index N-1, N-2, and N-3 values ​​of the other coupler array components described above, and have properties and characteristics selected from the various contemplated exemplary medium composition parameters described above in connection with medium 28A of Figure 1A.

[0050] 1D-2D is shown as coupler array 200A in which all of the waveguides are VC waveguides. Coupler array 200A comprises a single common housing structure 202A and a plurality of VC waveguides 204A-(1 ..n), where n is illustratively 19, centrally disposed along a central longitudinal axis of housing structure 202A. Coupler array 200A may further comprise at least one optional reference element 210A that imparts one or more useful characteristics to the coupler array, including, but not limited to, the following: Making the waveguide arrangement of the coupler array visually identifiable at at least one end of the coupler array; and Facilitate passive alignment with at least one optical device.

[0051] Furthermore, in optical coupler array embodiments that include at least one polarization-maintaining VC waveguide (eg, the optical coupler array embodiments described below in connection with FIGS. 3H-3L), the reference element further has the following functions. Allows visual identification of specific polarization axis alignment modes of the optical combiner array (e.g., as described below in connection with Figures 3H-3L), and Alignment of one or more polarization axes of PM waveguides in a particular optical coupler array It serves as a geometrically positioned reference point for the ment.

[0052] Reference element 210A can include any of a variety of known reference elements selected based on design choice or convenience without departing from the spirit of the invention. For example, it can be a dedicated elongated element located at various cross-sectional locations (e.g., locations X or Y shown in FIG. 3A) within the longitudinal direction of common housing structure 202A. Alternatively, reference element 210A can constitute a dedicated channel not used for non-reference purposes, e.g., replacing one of waveguides 204A-(1 ..n) illustratively shown at location Z in FIG. 3A.

[0053] 3B, a first alternative embodiment of the above-described optical fiber coupler array 10A of FIG. 1A is shown as coupler array 200B, and includes a single housing structure 202B, a VC waveguide 204B illustratively shown in FIG. 3B, at least one VC waveguide consisting of VC waveguides 206-(1 .. n), where n is equal to 18, and at least one non-VC waveguide consisting of VC waveguides 206-(1 .. n), where n is illustratively equal to 18. VC waveguide 204B is disposed along a central longitudinal axis of common housing structure 202B and is circumferentially and symmetrically surrounded by a plurality of closely spaced, parallel non-VC waveguides 206B-(1 .. n).

[0054] Referring to FIG. 3C, a first alternative embodiment of the optical fiber coupler array 200B shown in FIG. 3B is shown as a coupler array 200C consisting 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 for illustrative purposes only. The VC waveguide 204C is disposed along the central longitudinal axis of the common housing structure 202C and is circumferentially and symmetrically surrounded by a plurality of closely spaced, parallel non-VC waveguides 206C-(1...n). The coupler array 200C is configured such that the volume of the medium of the common housing structure 202C (i.e., the portion surrounding the embedded sections of the VC waveguide 204C and the plurality of non-VC waveguides 206C-(1...n)) exceeds the combined volume of the inner and outer cores of the VC waveguide 204C and the sections of the plurality of non-VC waveguides 206C-(1...n). That is, the VC waveguide 204C and the plurality of non-VC waveguides 206C-(1..n) are configured to exceed the combined volume of the inner and outer cores of the section of VC waveguide 204C embedded within a single common housing structure 202C.

[0055] 3C, the first alternative embodiment of the optical fiber coupler array 200C shown in FIG. 3D is shown as a coupler array 200D consisting of a single housing structure 202D, VC waveguides 204D-(1 ..N) (where N is illustratively 7) and non-VC waveguides 206D-(1 ..n) (where n is illustratively 12). The multiple VC waveguides 204D-(1 ..N) are arranged along a central longitudinal axis of the common housing structure 202D and are circumferentially and symmetrically surrounded by multiple closely spaced, 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 (e.g., the plurality of VC waveguides 204D-(1..N) and the plurality of non-VC waveguides 206D-(1..n)) embedded therein exceeds the sum of the volumes of the sections' inner and outer cores. For example, the plurality of VC waveguides 204D-(1..N) and the plurality of non-VC waveguides 206D-(1..n) are configured such that the combined volume of the inner and outer cores of the plurality of VC waveguides 204D-(1..N) sections embedded within a single common housing structure 202D.

[0056] Referring to FIG. 3E, a first alternative embodiment of the above-described optical fiber coupler array 200D of FIG. 3D is shown as coupler array 200E, which includes a single housing structure 202E, a plurality of VC waveguides 204E-(1 ..N), where N is illustratively equal to 6, a plurality of non-VC waveguides 206E-(1 ..n), where n is illustratively equal to 12, and a separate single non-VC waveguide. The non-VC waveguide 206E' is preferably operable to provide an optical pumping function and is disposed along a central longitudinal axis of the common housing structure 202E and is circumferentially and symmetrically surrounded by a plurality of adjacent, parallel VC waveguides 204E-(1..N), which in turn are circumferentially and symmetrically surrounded by a plurality of adjacent, parallel non-VC waveguides 206E-(1..n).

[0057] Referring to Figure 3F, a coupler array 200F is shown as a second alternative embodiment of the optical fiber coupler array 200B of Figure 3B, which is comprised of a single housing structure 202F, VC waveguides 204F-(1 ..N) (where N is illustratively 6), a separate single VC waveguide 204F', and a plurality of non-VC waveguides 206F-(1 ..n) (where n is illustratively 12). These waveguides are preferably each configured with an enlarged inner core having a sufficient diameter to increase or optimize optical coupling with different types of optical pump channels in the various optical devices to which the optical coupler array 200F can be advantageously coupled. The VC waveguide 204F' is disposed along the central longitudinal axis of the common housing structure 202F and is circumferentially and symmetrically surrounded by a plurality of closely spaced parallel VC waveguides 204F-(1..N), which are in turn circumferentially and symmetrically surrounded by a plurality of closely spaced parallel non-VC waveguides 206F-(1..n).

[0058] Referring to Figure 3G, a coupler array 200G is shown as a third alternative embodiment of the optical fiber coupler array 200B of Figure 3B, which is comprised of a single housing structure 202G, a VC waveguide 204G as illustrated in Figure 3G, and a plurality of non-VC waveguides 206G-(1...n), where n is illustratively 18. The VC waveguides 204G are arranged as side channels offset from the central longitudinal axis of the single common housing structure 202G, which allows the optical fiber coupler array 200G to be easily used as an optical fiber amplifier or laser when coupled with a double-clad optical fiber (not shown) having a non-concentric core. It's important to note that because double-clad fiber is a fiber with optical guiding properties in both the core and the inner cladding, most optical fiber types, whether polarization-maintaining or not, such as SM, MM, LMA, or MC (multicore), and even most optical fiber types, including standard (e.g., conventional) single-mode optical fiber, can be converted to double-clad fiber by coating (or recoating) the fiber with a low-index medium (which forms the outer cladding).

[0059] Optionally, if the second end of the coupler array 200G is to be connected to a double-clad fiber (not shown), a portion of the common housing structure 202G near the junction point is coated with a low refractive index medium that extends beyond the junction point to the outer jacket of the double-clad fiber (and, if necessary, also extends to a portion of the jacket near the junction point).

[0060] 3H-3L, in various alternative embodiments of optical couplers, at least one of the VC waveguides used in the optical couplers, and optionally in certain embodiments, at least one of the VC waveguides, has polarization-maintaining (PM) properties. For example, the PM properties of a VC waveguide may result from a pair of longitudinal stress bars positioned outside the inner core and inside or outside the outer core of the VC waveguide. Alternatively, the PM properties may result from a non-circular inner or outer core shape or other PM-inducing optical fiber configuration (e.g., bowtie or elliptical clad PM fiber). In various embodiments of optical fibers in which at least one PM waveguide (VC and / or non-VC) is used, the axial orientation of the PM waveguide (or waveguides) may be performed according to a particular polarization axis orientation mode.

[0061] In certain embodiments, the polarization axis configuration modes include, but are not limited to, at least one of the following: Axial alignment of the polarization axis of the PM waveguide with the polarization axis of other PM waveguides in the optical coupler; Axial alignment of the polarization axis of the PM waveguide with its cross-sectional (geometric) location within the optical coupler, if the PM waveguide is off-center; When the single common housing structure of the optical coupler has a non-circular geometry (e.g., as illustrated in FIG. 3L): axially align the polarization axis of the PM waveguide with the geometric features of the outer shape of the common housing structure; In optical coupler embodiments including one or more waveguide alignment features described below with reference to FIGS. 3J-3L, axially aligning the polarization axis of the PM waveguide with at least one geometric characteristic thereof; In optical coupler embodiments that include at least one reference element 210A as described in connection with FIG. 3A above, the polarization axis of the PM waveguide is axially aligned with the geometric position of the at least one reference element 210A.

[0062] In various optical coupler embodiments, the selection of a particular polarization axis alignment mode is preferably determined by at least one axis alignment criterion, including, but not limited to, aligning the polarization axes of the PM waveguides in a geometry that increases or maximizes PM properties and / or satisfies one or more requirements of the intended industrial application of the coupler array.

[0063] Referring to Figure 3H, as a first alternative embodiment of the above-described optical fiber coupler array 200G of Figure 3G, coupler array 200H is shown, which is composed of a single housing structure 202H, a PMVC waveguide 204H having polarization-maintaining properties as illustrated in Figure 3H, and a plurality of non-VC waveguides 206H-(1...n), where n is illustratively 18. PMVC waveguides 204H are arranged as side channels offset from the central longitudinal axis of the single common housing structure 202H, e.g., with their polarization axes aligned relative to the off-center lateral positions of PMVC waveguides 204H.

[0064] Referring to Figure 3I, a fourth alternative embodiment of the optical fiber coupler array 200B of Figure 3B is shown as coupler array 200I, which is composed of a single housing structure 202I, a polarization-maintaining PMVC waveguide 204I, and a plurality of PM non-VC waveguides 206I-(1...n) (n is illustratively 18) with polarization-maintaining properties, as illustrated in Figure 3I. The PMVC waveguide 204I is arranged along the central longitudinal axis of the common housing structure 202I and is circumferentially and symmetrically surrounded by a plurality of closely spaced, parallel PM non-VC waveguides 206I-(1...n). For example, coupler array 200I employs a polarization-axis-matched mode in which the polarization axes of the PMVC waveguide 204I and the plurality of PM non-VC waveguides 206I-(1...n) are aligned with each other. The PM characteristics of PMVC waveguide 204I and multiple PM non-VC waveguides 206I-(1..n) are shown as being induced by rod stress members for illustrative purposes only (these stresses can easily be substituted by other stresses or equivalent designs).

[0065] Referring to Figure 3J, a first alternative embodiment of the above-described optical fiber coupler array 200I of Figure 3I is shown as coupler array 200J, which is comprised of a single housing structure 202J and, as illustrated in Figure 3J, a PMVC waveguide 204J having polarization-maintaining properties and a plurality of PM non-VC waveguides 206J-(1 .. n) having polarization-maintaining properties, where n is illustratively 18. The PMVC waveguide 204J is disposed along the central longitudinal axis of the common housing structure 202J and is circumferentially and symmetrically surrounded by a plurality of closely spaced, parallel PM non-VC waveguides 206J-(1 .. n). The PM characteristics of the PMVC waveguide 204J and the plurality of PM non-VC waveguides 206J-(1..n) are shown, for purposes of illustration only, as resulting from the non-circular cross-sectional shape (which is, by way of example only, at least partially elliptical) of the core of each of the plurality of PM non-VC waveguides 206J-(1..n) (and resulting from the non-circular cross-sectional shape of the outer core of the PMVC waveguide 204J).

[0066] The coupler array 200J optionally includes at least one waveguide placement indicator element 208J disposed in an exterior region of the common housing structure 202J that enables a particular cross-sectional geometrical arrangement of the waveguides of the optical coupler array 200J (i.e., of the PMVC waveguide 204J and the plurality of PM non-VC waveguides 206J-(1 ..n)) to be readily identified by visual or physical inspection of the common coupler housing structure 202J to an extent sufficient to inspect the waveguide placement indicator element 208J. Preferably, the waveguide placement indicator element 208J can 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).

[0067] The waveguide placement indicator element 208J may include, but is not limited to, any one or more of the following: a color marking and / or a physical indicator (e.g., a groove or other modification of the outer surface of, or an element or other component disposed thereon) applied to the outer surface of the common housing structure 202J; or, the waveguide placement indicator element 208J may constitute a specific modification or definition of the cross-sectional geometry of the common housing structure 202J itself (e.g., the hexagonal shape of the common housing structure 202L shown in FIG. 3L, or other geometric shape).

[0068] For example, the coupler array 200J can include a polarization axis coincident mode in which the polarization axes of each PMVC waveguide 204J and the plurality of PM non-VC waveguides 206J-(1..n) are coincident with each other or with respect to the waveguide placement indicator element 208J.

[0069] Referring to FIG. 3K, a fifth alternative embodiment of the optical fiber coupler array 200B of FIG. 3B is shown, which includes a single housing structure 202K and at least one VC waveguide, as shown in FIG. 3K. As illustrated in FIG. 3K, the coupler array 200K is comprised of a polarization-maintaining PMVC waveguide 204K and a plurality of non-VC waveguides 206K-(1...n), where n is illustratively 18. The PMVC waveguide 204K is disposed along the central longitudinal axis of the common housing structure 202K and is circumferentially and symmetrically surrounded by a plurality of closely spaced, parallel PM non-VC waveguides 206K-(1...n). The PM properties of the PM VC waveguide 204K are shown, by way of example only, as induced by rod stress members (although these stresses can easily be substituted by other stresses or equivalent techniques). Coupler array 200K may optionally include a plurality of waveguide placement indicator elements, shown by way of example as waveguide placement indicator elements 208K-a and 208K-b, which may be the same type as waveguide placement indicator element 208J of FIG. 3J above or a different type.

[0070] Referring to Figure 3L, a coupler array 200L is shown as a second alternative embodiment of the optical fiber coupler array 200I shown in Figure 3I. The coupler array 200L comprises a single housing structure 202L having a cross-section with a non-circular geometric shape (e.g., hexagonal) and is composed of at least one VC waveguide (shown in Figure 3L as a polarization-maintaining PMVC waveguide 204L, e.g., polarization-maintaining PM non-VC waveguides 206L-(1...n) (e.g., n=18). The PMVC waveguide 204L is arranged along the central longitudinal axis of the common housing structure 202L and is circumferentially and symmetrically surrounded by a plurality of closely spaced, parallel PM non-VC waveguides 206L-(1...n).

[0071] For example, the coupler array 200L has a polarization axis coincident mode in which the polarization axes of the PMVC waveguide 204L and the plurality of PM non-VC waveguides 206L-(1 .. n) are coincident with each other and with the cross-sectional geometry of the common housing structure 202L. The PM characteristics of the PMVC waveguide 204L and the plurality of PM non-VC waveguides 206L-(1 .. n) may be, by way of example only, a rod stress member. (These stresses can be easily substituted with other stresses or equivalent designs.) Coupler array 200K can optionally include waveguide placement indicator elements 208L-a including any of the configurations described above in connection with waveguide placement indicator element 208J of FIG. 3J.

[0072] 4, the second end 302 (or "tip") of the optical fiber coupler array is shown in the process of being connected in a close, open-air optical coupling arrangement with, by way of example, multiple vertical coupling elements 306 of an optical device 304. This arrangement can be easily converted to a butt-coupled configuration due to the full physical contact between the second end 302 of the optical fiber coupler array and the vertical coupling elements 306.

[0073] In Figure 5, the second end 322 (i.e., "tip") of the optical fiber coupler array is shown in a butt-coupled configuration, by way of example, in the process of connecting with a plurality of edge coupling elements 326 of an optical device 324. This configuration can be easily switched to a number of alternative coupling configurations, including a close-in open-air optical coupling arrangement or an angle-tuned coupling arrangement.

[0074] In at least one alternative embodiment, the optical coupler array (e.g., optical coupler arrays 200D through 200L shown in Figures 3C-3L) can be readily configured to drive optical fiber lasers and / or optical fiber amplifiers (or equivalent devices). In a preferred embodiment, the pumped coupler array includes a central channel (i.e., waveguide) that carries a signal (i.e., functions as a "signal channel") and is subsequently utilized for amplification or lasing, and at least one additional channel (i.e., waveguide) configured to provide optical pumping functionality (i.e., each functions as a "pump channel"). In various exemplary alternative embodiments, the pumped coupler array can include the following elements in any combination: At least one of the following signal channels: a single-mode signal channel (configured to increase or optimize coupling into a single-mode amplifying fiber at at least one predetermined signal or lasing wavelength), a multimode signal channel (configured to increase or optimize coupling into a multimode amplifying fiber at at least one predetermined signal or lasing wavelength), and At least one of the following pump channels: a single-mode pump channel (configured to increase or optimize coupling with a single-mode pump source at at least one predetermined pump wavelength), a multi-mode pump channel (configured to increase or optimize coupling with a multi-mode pump source at at least one predetermined pump wavelength).

[0075] Optionally, to improve or maximize pump efficiency, the pump-compatible coupler array can be configured to selectively utilize a subset of all available pump channels. Also, as a design choice, without departing from the spirit of the invention, the pump-compatible coupler array can be configured to include the following configurations: a. at least one signal channel, each positioned at a predetermined desired location within a combiner array structure; b. at least one pump channel, each positioned at a predetermined desired location within the coupler array structure; and c. Optionally—at least one additional waveguide for at least one additional purpose other than signal transmission or pump (e.g., physical marker for alignment, fault detection, data transmission, etc.).

[0076] Preferably, the pump channel can be positioned at any lateral location within the coupler, including along the central longitudinal axis. The pump channel can be SM, MM, LMA, or V. The coupler may be constructed from at least one optical fiber type, including but not limited to a C waveguide. Optionally, the optical fiber (regardless of fiber type) used as the optical pump channel in the coupler may have polarization-maintaining properties.

[0077] In yet another embodiment, the pumped coupler array can be configured to be optimized for coupling with a double-clad fiber, where the signal channels of the coupler array are configured or optimized for coupling with the signal channels of the double-clad fiber and at least one pump channel is configured or optimized for coupling with the inner cladding of the double-clad fiber.

[0078] Essentially, the optical coupler arrays illustrated in the various embodiments can be readily implemented as high-density, multi-channel, optical input / output (I / O) for fiber chips and fiber waveguides. Optical fiber couplers can readily have at least the following characteristics: Significantly reduced channel spacing and device area compared to previously known solutions, Scalable channel count, All-glass optical path, Easily butt-bonded or spliced ​​on dense surfaces without the need for lenses, air gaps, or beam-diffusing media; -Can be manufactured using semi-automated manufacturing processes, Extensive customizable parameters: wavelength, mode field size, channel spacing, array configuration, fiber type

[0079] The fiber optic coupler may be advantageously utilized in the following applications, depending on design choice or convenience, without departing from the spirit of the invention: Coupling to waveguides PIC or PCB based (single mode or multimode) Multi-core fiber Chip edge (1D) or chip face (2D) bonding Application-optimized NA (numerical aperture), taking into account the following factors: Packaging alignment requirements Chip processing requirements / waveguide uptapering Polarization maintenance characteristics can be easily set Coupling to chip-based devices: e.g. VCSELs, photodiodes, vertical coupling gratings Laser diode coupling High-density equipment input / output (I / O)

[0080] Thus, when implemented, various embodiments of the fiber optic coupler have at least the following advantages over currently available competitive solutions: Breakthrough density ·Low loss coupling (≦0.5dB) ·Operation stability Form factor support Wideband spectral range ·Suitable NA Scalable channel count Maintains polarization

[0081] Referring to FIG. 7, a flexible pitch-reduced optical fiber (PROFA) coupler 450 is shown. At least one exemplary embodiment of a flexible optical coupler array is shown. Various features of an exemplary PROFA coupler are described with reference to FIG. 7 , and any of the features described above can be implemented in any combination with a flexible PROFA coupler. For example, any of the features described with reference to FIGS. 1A-5 can be used with a flexible PROFA coupler. Furthermore, any of the features described with reference to FIGS. 1A-5 can be combined with the features described with reference to FIG. 7 .

[0082] Continuing to refer to Figure 7, the exemplary flexible PROFA cooler 450 shown in Figure 7 is configurable for use in applications requiring interconnections with sufficient flexibility for low crosstalk and low profile packaging. As described herein and in U.S. Patent Application Publication No. 2013 / 0216184, entitled "Configurable Pitch Reduced Fiber Optic Arrays," which is incorporated herein in its entirety, multiple It is possible to construct a pitch-reduced optical fiber (PROFA) coupler / interconnect that can optically couple an optical fiber to an optical device (e.g., a PIC). The coupler can be butt-coupled to an array of vertical grating couplers (VGCs). If the cross-sectional structure of coupler 450 includes an additional layer of refractive index, the coupler can be butt-coupled to an array of vertical grating couplers (VGCs). For example, it is possible to construct a fiber optic (PROFA) coupler / interconnect that can optically couple to a PIC and end-couple to an array of vertical grating couplers (VGCs). The cross-sectional structure of coupler 450 can again utilize a vanishing core approach, as described herein and in U.S. Patent Application Publication No. 2013 / 0216184, to further reduce the outer diameter without substantially compromising channel crosstalk. This further reduction, in certain embodiments, provides the advantage of providing a flexible region of reduced cross-section between the first and second ends.

[0083] In some preferred embodiments, the difference (N-2A-N-3) is greater than the difference (N-2-N-2A) or (N-1-N-2), which results in a high NA, bend-insensitive waveguide when the light is guided by an additional layer (with refractive index N-2A). Also, in some preferred embodiments, the outer diameter of coupler 450 is reduced longitudinally from one end to form a flexible region, and then the outer diameter is expanded longitudinally toward the second end to result in a low NA waveguide with a larger coupling surface area at the second end.

[0084] For example, as shown in FIG. 7 , a particular embodiment of an optical coupler array 450 can include an elongated optical element 1000 having a first end 1010, a second end 1020, and a flexible portion 1050 therebetween. The optical element 1000 can include a housing structure 1060 and a plurality of longitudinal waveguides 1100 embedded in the housing structure 1060. The waveguides 1100 are arranged in a cross-sectional waveguide geometry relative to one another. Exemplary cross-sectional waveguide geometry of the waveguides 1100 at the first end 1010, the second end 1020, and positions within the flexible portion 1050 are shown in FIG. 7 . The cross-sectional waveguide geometry of the waveguides 1100 at an intermediate position 1040 between the first end 1010 and the flexible portion 1050 is also shown. As shown by the shaded area in the cross section and described below, light is guided from the optical element 1000 via the first end 1010 through the flexible section 1050 to the second end 1020. As also shown in Figure 7, this provides a structure that isolates all channels with sufficiently low crosstalk while providing sufficient flexibility (e.g., via the flexible section 1050) to accommodate low-profile packaging.

[0085] The level and / or flexibility of crosstalk may vary depending on the application of the array. For example, in some embodiments, low crosstalk is considered to be in the range of -45 dB to -35 dB, and in other embodiments, low crosstalk is considered to be in the range of -15 dB to -5 dB. Thus, the level of crosstalk is not particularly limited. In some embodiments, crosstalk may be in the range of -55 dB, -50 dB, -45 dB, -40 dB, -35 dB, -30 dB, -25 dB, -20 dB, It may be -15 dB, -10 dB, 0 dB, or any value therebetween (e.g., -37 dB or less, -27 dB, -17 dB, -5 dB, etc.). In some embodiments, the crosstalk may be between -50 dB and -40 dB, between -40 dB and -30 dB, between -30 dB and -20 dB. 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 range formed from any value between -55 dB and 0 dB (e.g., -52 dB to -37 dB, -48 dB to -32 dB, etc.).

[0086] The flexibility also depends on the application of the array. For example, in some embodiments, good flexibility of the flexible portion 1050 can include bending at least 90 degrees, while in other embodiments, bending at least 50 degrees may be acceptable. Thus, the flexibility is not particularly limited. In some embodiments, the flexibility can 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 any value between these values. In some embodiments, the flexible portion 1050 can bend within a range formed by any of these values. For example, 45°-55°, 50°-60°, 60°-70°, 70°-80°, 80°-90°, 90°-100°, 100°-110°, 110°-120°, or a combination of these ranges, or a range formed by any value within these ranges (e.g., 50°-65°, 50°-85°, 65°-90°, etc.). In other embodiments, flexible portion 1050 may bend more or less than these values. Bending is typically associated with light scattering. However, various embodiments can be configured to bend as described herein (e.g., within any of the ranges described above) while simultaneously achieving relatively low crosstalk as described herein (e.g., within any of the ranges described above).

[0087] In various applications, the flexible portion 1050 may not bend during use, but flexibility may be desired to isolate 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 mechanically isolates the first end 1010 (e.g., the PROFA-PIC interface) from the rest of the PROFA, improving stability against environmental variations, including temperature changes and mechanical shock and vibration.

[0088] In the example shown in FIG. 7 , the coupler array 450 can be optically coupled to a plurality of optical fibers 2000 and / or optical devices 3000. The optical fibers 2000 and optical devices 3000 can include any of those described herein. The coupler array 450 can be coupled to the optical fibers 2000 via a plurality of waveguides 1100 at the first end 1010. Additionally, the coupler array 450 can be coupled to the optical devices 3000 via a plurality of waveguides 1100 at the second end 1020. As described herein, the plurality of waveguides 1100 can include at least one VC waveguide 1101. FIG. 7 depicts all of the waveguides 1100 as VC waveguides; however, one or more non-VC waveguides can also be used. Additionally, although seven VC waveguides are shown in FIG. 7 , any number of VC and non-VC waveguides can be used.

[0089] As also shown in the cross-sectional view, each of the plurality of waveguides 1100 can be positioned at an individual corresponding cross-sectional geometric location relative to the other waveguides. While Figure 7 shows a waveguide surrounded by six other waveguides, the cross-sectional geometric waveguide arrangement is not limited and can include any known or later developed arrangement, including those shown in Figures 3A-3L.

[0090] As described herein, the VC waveguide 1101 includes an inner core (e.g., an inner lossy core) 1110, an outer core 1120, and an outer cladding having refractive indices N-1, N-2, and N-3. 7, the VC waveguide 1101 may include a secondary outer core 1122 (e.g., having a refractive index N-2A) disposed between the outer core 1120 and the outer cladding 1130. Because the outer core 1120 is disposed to vertically surround the inner core 1110, the secondary outer core 1122 vertically surrounds the outer core 1120, and the outer cladding 1130 is disposed to vertically surround the secondary outer core 1122. In various embodiments, the refractive index relationship of the inner core 1110, outer core 1120, secondary outer core 1122, and outer cladding 1130 advantageously follows the relationship N-1>N-2>N-A>N-3. In this relationship, each surrounding layer effectively functions as a cladding for the inner layer (e.g., outer core 1120 functions as a cladding for inner core 1110, and secondary outer core 1122 functions as a cladding for outer core 1120). Thus, secondary outer core 1122 can be used to provide additional core and cladding sets.

[0091] By including the secondary outer core 1122 with refractive index N-2A, a higher NA (e.g., compared to not having the secondary outer core 1122) can be achieved in certain embodiments. In various embodiments, the difference (N-2A-N-3) is designed to be larger than the difference (N-2-N-2A) or (N-1-N-2), thereby achieving a relatively high NA. Increasing the NA can decrease the MFD and allow the channels (e.g., waveguides 1100) to be closer together (e.g., by reducing the spacing between the waveguides 1100) without compromising crosstalk. Thus, the cross-sectional dimensions of the coupler array 450 can be further reduced, reducing the area through which light is guided by the secondary outer core 1122, compared to when the secondary outer core 1122 is not present. By reducing the area between the first end 1010 and the second end 1020, some embodiments can include a flexible section 1050 that is more flexible than the areas proximate the first end 1010 and the second end 1020.

[0092] 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 from the first end 1010 to the intermediate position 1040 of the optical element 1000. Thus, at the intermediate position 1040, the size of the inner core 1110 is insufficient to conduct light, and the size of the outer core 1120 is sufficient to conduct at least one optical mode. In certain embodiments, each waveguide 1100 is capable of transmitting at least one optical mode (e.g., single mode or multimode). For example, at the first end 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 optical propagation). However, in some such embodiments, the outer core 1120 may be able to support all M1 modes (and possibly additional modes) at the intermediate position 1040. In this example, light propagating from the inner core 1110 to the first end 1010 to the intermediate position 1040 escapes from the inner core 1110 to the outer core 1120 and can propagate in both the inner core 1110 and the outer core 1120.

[0093] Additionally, the size of the outer core 1120, the size of the secondary outer core 1122, and the spacing between the waveguides 1100 can decrease along the waveguide 1000 (e.g., from the intermediate position 1040 to the flexible section 1050), e.g., from the intermediate position 1040 to the flexible section 1050. For example, the size can decrease along the optical element 1000 from the intermediate position 1040 to the flexible section 1050. This allows the size of the outer core 1120 to be insufficient to conduct light at the flexible section 1050, while the size of the secondary outer core 1122 is sufficient to conduct at least one optical mode. In certain embodiments, at the intermediate position 1040, the VC waveguide 1101 can support all M1 modes within the outer core 1120. At the flexible section 1050, in various embodiments, the outer core 1120 would be unable to support all M1 modes (e.g., unable to support light propagation). However, in some such embodiments, in the flexible section 1050, the secondary outer core 1122 can support all M1 modes (and in some cases, additional modes). In this example, light traveling from the intermediate position 1040 to the flexible section 1050 escapes from the outer core 1120 to the secondary outer core 1122 and can propagate within the inner core 1110, the outer core 1120, and the secondary outer core 1122.

[0094] Additionally, the size of the outer core 1120, the size of the secondary outer core 1122, and the spacing between the waveguides 1100 can be expanded (e.g., simultaneously and gradually in some cases) from the flexible portion 1050 of the optical element 1000 along the second end 1020, such that at the second end 1020, the size of the secondary outer core 1122 is insufficient to conduct light and the size of the outer core 1120 is sufficient to conduct at least one optical mode. In certain embodiments, at the second end 1020, in various embodiments, the secondary outer core 1122 may be unable to support all M1 modes (e.g., unable to support optical propagation). However, in some such examples, at the second end 1020, the outer core 1120 may be able to support all M1 modes (and possibly additional modes). In this example, light traveling within the secondary outer core 1122 from the flexible section 1050 to the second end 1020 propagates back within the inner core 1110 and outer core 1120 only.

[0095] It will be appreciated that light propagating from the second end 1020 to the first end 1010 exhibits the opposite behavior. For example, the size of the outer core 1120, the size of the secondary outer core 1122, and the spacing between the waveguides 1100 decrease along the waveguide 1000 from the second end 1020 to the flexible portion 1050 (e.g., simultaneously and gradually in some cases) such that at the flexible portion 1050, the size of the outer core 1120 is insufficient to conduct light and the size of the secondary outer core 1122 is sufficient to conduct at least one optical mode.

[0096] The reduction in the cross-sectional size of the core and cladding can advantageously provide rigidity and flexibility in the coupler array 450. Rigidity at the first end 1010 and the second end 1020 may be desirable because the optical fibers 2000 and / or optical devices 3000 can be fused to the ends 1010, 1020 of the coupler array 450. However, flexibility may also be desirable so that the coupler array can be bent for connection to low-profile integrated circuits. In certain embodiments, a flexible section 1050 between the first end 1010 and the second end 1020 can provide a flexible section 1050 therebetween while still providing relative rigidity between the first end 1010 and the second end 1020. The flexible section extends the length of the optical element 1000 and mechanically isolates the first end 1010 and the second end 1020. For example, the flexible section 1050 mechanically isolates the first end 1010 from the region between the flexible section 1050 and the second end 1020. As another example, the flexible portion 1050 can mechanically isolate the second end 1020 from the region between the first end 1010 and the second end 1020. Such mechanical isolation provides stability to the first end 1010 and the second end 1020, making them resistant to environmental variations, such as temperature changes and mechanical shock and vibration. The length of the flexible portion 1050 is not particularly limited and can vary depending on the application. In some examples, the length is in the ranges of 2-7 mm, 3-8 mm, 5-10 mm, 7-12 mm, or 8-15 mm. It can also be any combination of these ranges, or any range formed from any value between 2 mm and 20 mm (e.g., 3 mm-13 mm, 4 mm-14 mm, 5 mm-17 mm, etc.). In other examples, the length of the flexible portion 1050 can be shorter or longer.

[0097] At the same time, flexible section 1050 is flexible. In many cases, flexible section 1050 has a cross-sectional size substantially similar to the cross-sectional size of waveguide 1100 along its entire length. In certain embodiments, the flexible portion 1050 can have a cross-sectional size that is smaller than the cross-sectional size of the first end 1010 and the second end 1020. This smaller cross-sectional size makes the flexible portion 1050 more flexible than the regions proximate the first end 1010 and the second end 1020. The smaller cross-sectional size can result from a reduction in the size of the core and cladding. An optional post-etch process may be desirable to further reduce the diameter of the flexible length of the flexible PROFA cooler 450.

[0098] In some embodiments, the flexible section 1050 is more flexible than standard SMF28 fiber. In some embodiments, the flexible section 1050 bends at or above 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 any value between these values. In some embodiments, the flexible section 1050 bends within a range formed by any of these values. For example, 45 degrees to 55 degrees, 50 degrees to 60 degrees, 60 degrees to 70 degrees, 70 degrees to 80 degrees, 80 degrees to 90 degrees, 90 degrees to 100 degrees, 100 degrees to 110 degrees, 110 degrees to 120 degrees, or any combination of these ranges, or a range formed by any value within these ranges (e.g., 50 degrees to 65 degrees, 50 degrees to 85 degrees, 65 degrees to 90 degrees, etc.). In other embodiments, the flexible portion 1050 may bend more or less than these amounts. As described herein, in various applications, the flexible portion 1050 does not bend during use, but flexibility may be desirable to separate the first end 1010 or the second end 1020 from other portions of the coupler array 450.

[0099] 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 described herein (e.g., pure silica). The medium may also include glass, such that the coupler array 450 is 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 inner cores 1110, outer cores 1120, and middle cores 1122 of the VC waveguides enclosed within the coupler housing structure 1060.

[0100] In some embodiments, each waveguide can be configured to couple with an optical fiber 2000 and / or an optical device 3000 inside, outside, or at a boundary region of the coupler housing structure 1060, as shown in FIGS. 1A-2D . Because the optical fiber 2000 and the optical device 3000 are different at each end, the first end 1010 and the second end 1020 can be configured to correspond to the optical fiber 2000 or optical device 3000 to be connected. For example, the MFD at the first end 1010 and / or the second end 1020 of the VC waveguide can be configured (e.g., using core size) to match or substantially match the MFD of the optical fiber 2000 or optical device 3000 to be coupled. Furthermore, the NA at the first end 1010 and / or the second end 1020 of the VC waveguide 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 be coupled. The refractive index can be varied in any manner, by known techniques (e.g., doping the waveguide glass) or methods to be developed in the future. In various embodiments described herein, the difference (N-1-N-2) is greater than the difference (N-2-N-2A), such that the NA of the first end 1010 is greater than the NA of the second end 1020. In other embodiments, the NA of the first end 1010 is less than the NA of the second end 1020, such that the difference (N-1-N-2) is less than the difference (N-2-N-2A). Still other embodiments may be used. In an embodiment, the NA of the first end 1010 is configured to be equal to the NA of the second end 1020 such that the difference (N-1-N-2) is equal to (N-2-N-2A). The VC waveguide can include single mode fiber, multimode fiber, and / or polarization maintaining fiber, including but not limited to the fiber types described herein.

[0101] The size of the core and cladding (1110, 1120, 1122, 1130) (e.g., outer diameter if circular, outer cross-sectional dimension if non-circular) is not particularly limited. In some embodiments, the size of the inner core 1110 and / or outer core 1120 is 1-3 microns, 2-5 microns, 4-8 microns, 5-10 microns, any combination of these ranges, or any range formed from the 1-10 micron range (e.g., 2-8 microns, 3-9 microns, etc.). However, the size can be larger or smaller. For example, the size of the inner core 1110 and / or outer core 1120 can range from submicrons to several microns, tens of microns, or hundreds of microns, depending on the wavelength and / or the number of modes desired.

[0102] Furthermore, the difference in refractive index (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 difference in refractive index is 1.5×10 -3 ~2.5×10 -3 , 1.7×10 -3 ~2.3×10 -3 , 1.8×10 -3 ~2.2×10 -3 , 1.9×10 -3 ~2.1×10 -3 , 1.5×10 -3 ~1.7×10 -3 , 1.7×10 -3 ~1.9×10 -3 , 1.9×10 -3 ~2.1×10 -3 , 2.1×10 -3 ~2.3×10 -3 , 2.3 × 10 -3 ~2.5×10 -3 , any combination of these ranges, or 1.5 x 10 -3 ~2.5×10 -3 Any range formed from any value of . In other examples, the exponent difference may be larger or smaller.

[0103] 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 Packaging Header Apparatus," and incorporated herein in its entirety, multiple flexible PROFA couplers (e.g., coupler 450), each having multiple optical channels, can be combined to advantageously 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.

[0104] 8 and 9, exemplary cross-sectional views of a housing structure near a first end of a multi-channel optical coupler array are shown. The cross-sectional views are perpendicular to the longitudinal direction or length of the optical coupler array. Some such configurations improve the cross-sectional or lateral (or lateral) positioning of the waveguides at the first end, allowing for self-aligning waveguide placement proximate the first end (e.g., a hexagonal close-up placement in a housing structure having a circular interior cross-section, as shown in FIG. 8). For example, a hexagonal close-up placement in a housing structure having a circular (as shown in FIG. 8) or hexagonal interior cross-section) and improved (in some cases precise or near-precise) cross-sectional positioning of the waveguides at the second end. Such configurations allow for alignment during manufacturing, allowing for desired precision in the cross-sectional positioning of the waveguides at the second end.

[0105] Although various features of the exemplary optical combiner array are described with reference to Figures 8 and 9, any of the features described above (e.g., those described in connection with the above figures or examples) can be implemented in any combination in a multi-channel optical combiner array. For example, any of the features described with respect to Figures 1A-5 and 7 can be utilized in a multi-channel optical combiner array and combined with the features described with respect to Figures 8 and 9.

[0106] For example, referring to the embodiment shown in Figures 1A-2D, the coupler array has two ends: a first (larger) end and a second (smaller) end. The two ends are spaced apart along the longitudinal direction (z-direction). For example, in Figure 1A, the first end is adjacent to position B, and the second end is adjacent to positions C and D.

[0107] In some embodiments, one function of the first end (the end proximate position B) is to enhance positional accuracy or approximate positional encapsulation of the waveguides 30A, 32A-1, and 32A-2. For example, the coupler housing structure 14A near the first end (proximate position B) may circumferentially surround, for example, a portion of the length of the waveguides 30A, 32A-1, and 32A-2, but need not completely encapsulate the ends of the waveguides 30A, 32A-1, and 32A-2. In such cases, the waveguides 30A, 32A-1, and 32A-2 may extend outside the coupler housing structure 14A, e.g., longitudinally. 1A, near the first end, the end of waveguide 30A is disposed within coupler housing structure 14A, while the ends of waveguides 32A-1 and 32A-2 extend outside coupler housing structure 14A, for example, in a direction parallel to the z direction (longitudinal direction). In FIG. 2B, near the first end, the ends of waveguides 130B-1 and 130B-2 are disposed in an outer cross-sectional boundary region of coupler housing structure 14A, and do not extend outside coupler housing structure 14A, for example, in a direction parallel to the z direction (z direction).

[0108] In various embodiments, one function of the second ends (proximate positions C and D) is to embed the waveguides 30A, 32A-1, 32A-2 in a housing structure (e.g., a common housing structure in some cases) with improved (in some cases precise or near-precise) cross-sectional positional accuracy. For example, the waveguides 30A, 32A-1, 32A-2 proximate the second ends (proximate positions C and D) are embedded so as to be circumferentially surrounded, for example, by the continuous coupler housing structure 14A. In FIG. 1A , near the second ends, the ends of the waveguides 30A, 32A-1, 32A-2 are longitudinally disposed in the outer cross-sectional boundary region of the coupler housing structure 14A. In some embodiments, near the second ends, one or more ends of the waveguides are within or extend longitudinally outside the coupler housing structure 14A.

[0109] To improve positional accuracy, in some embodiments, an exemplary cross-sectional arrangement of a housing structure, as shown in FIG. 8, can be located near the first end. The cross-section is perpendicular to the longitudinal direction or length of the optical coupler array. As shown in FIG. 8, a coupler array 800 can include a housing structure 801 having an annular lateral (or side) arrangement surrounding a plurality of longitudinal waveguides 805 in a longitudinally proximate position near the first end. A gap, such as an air gap, separates the plurality of longitudinal waveguides 805 from the surrounding ring. Some such configurations enable a self-aligning waveguide arrangement in a position proximate the first end (e.g., a circular (as shown in FIG. 8) or hexagonal proximate position in a housing structure having a hexagonal interior cross-section).

[0110] 8, the waveguides 805 are arranged in a hexagonal configuration, although other configurations are possible, such as square, rectangular, etc.

[0111] The ring can have a circular or non-circular inner cross-section 801a in the transverse direction (i.e., perpendicular to the longitudinal direction or length of the optical coupler array). For example, the inner cross-section 801a can be circular, elliptical, D-shaped, square, rectangular, hexagonal, pentagonal, octagonal, or other polygonal shape. The inner cross-section 801a does not have to follow the arrangement of the waveguides 805. For example, four waveguides arranged in a square arrangement could fit within the inner circular cross-section. As another example, as shown in FIG. 8, the inner cross-section 801a is circular and the waveguides 805 are arranged in a hexagon. In some embodiments, a circular inner cross-section as shown in FIG. 8 is preferred. The ring has a unique shape that allows for a tight hexagonal arrangement. Other interior cross-sectional shapes, such as squares or rectangles, can also be used, allowing for waveguide arrangements other than hexagons. In some cases, the air gap can be reduced by making the interior cross-section 801 a similar to the arrangement of the waveguides 805. For example, for a hexagonal arrangement of waveguides 805, the interior cross-section 801 a of the ring can be hexagonal to reduce the air gap between the interior cross-section 801 a and the waveguides 805.

[0112] The outer cross-section 801b (lateral, e.g., perpendicular to the longitudinal or length direction of the optical coupler array) can be circular or non-circular. For example, the outer cross-section 801b can be circular, elliptical, hexagonal, D-shaped (e.g., for flat surfaces that allow for easy rotational alignment, to achieve passive axial alignment of the coupler), square, rectangular, pentagonal, octagonal, or other polygonal shape. In FIG. 8 , the outer cross-sectional shape 801b (e.g., circular) follows the shape of the inner cross-sectional shape 801a (e.g., circular). However, in some embodiments, the outer cross-sectional shape 801b need not be similar to the inner cross-sectional shape 801a. One function of the inner cross-sectional shape is to improve lateral positioning accuracy near the second end, and one function of the outer cross-sectional shape is to enable passive axial positioning of the coupler without illuminating the coupler with light (e.g., positioning can be performed without illuminating the coupler with light). 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.

[0113] FIG. 9 illustrates a cross-sectional configuration of another example housing structure near a first end. As shown in FIG. 9, a coupler array 850 can include a housing structure 851 having a structure (e.g., a continuous structure in some cases) with a plurality of holes 852. At least one of the holes 852 can include at least one longitudinal waveguide 855. A gap, such as an air gap, separates the plurality of longitudinal waveguides 855 from the surrounding housing structure 851. As described with respect to the example illustrated in FIG. 8, the outer cross section can be circular, elliptical, hexagonal, D-shaped, square, rectangular, pentagonal, octagonal, or other polygonal shape. Some such configurations allow for passive alignment at one or both ends of the coupler array. While the exemplary configuration illustrated in FIG. 8 may simplify manufacturing in some cases, the exemplary configuration illustrated in FIG. 9 allows for any lateral waveguide arrangement.

[0114] While FIG. 9 shows an exemplary configuration having six holes 852, other numbers of holes are possible. The holes 852 in this exemplary 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. While the arrangement of the holes 852 is shown as a 3×2 array, other arrangements are possible. For example, the hole arrangement pattern may be hexagonal, square, rectangular, or defined by an XY array that defines the location of the holes in the XY plane.

[0115] FIG. 9 shows the waveguides 855 in all of the holes 852 as vanishing core (VC) waveguides. However, while at least one waveguide is a VC waveguide in this example, one or more of the holes 852 may include a non-vanishing core (Non-VC) waveguide. The VC or Non-VC waveguides 855 may 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 may be hollow or filled with other materials (e.g., non-waveguide materials), such as to function as fiducial marks. One or more of the holes 852 may be filled with a single waveguide 855 (in some preferred configurations) or multiple waveguides 855, as shown in FIG. 9 . Depending on the design, one or more of the holes 852 may have the same or different shape as the other holes 852, e.g., waveguides of different shapes and dimensions (e.g., cross-sectional shape, diameter, major / minor axis dimensions of an ellipse, etc.). The hole 852 is configured to accommodate the waveguide 855. The cross section of the hole 852 can be circular or non-circular. For example, the cross section can be circular, elliptical, hexagonal, D-shaped (e.g., to allow passive axial alignment of polarization-maintaining (PM) channels), square, rectangular, pentagonal, octagonal, or other polygonal. As shown, the cross section of the hole 852 near the first end is often larger than the cross section of the waveguide 855, thereby forming a gap between the inner surface 851 a of the coupler housing structure 851 and the waveguide 855.

[0116] The coupler housing structure (e.g., 801 in FIG. 8 or 851 in FIG. 9) can include a medium made of a wide range of materials as described herein. As 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, which can provide 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 inner and outer cores of the VC waveguides enclosed within the coupler housing structure 801, 851, which can provide reliable embedding of all VC waveguides within the housing structure for stable performance in some embodiments.

[0117] In certain embodiments, the exemplary configurations shown in FIGS. 8 and 9 can improve the manufacturability of the device by improving the lateral (transverse) positional accuracy of the waveguide. For example, at the second end, this lateral position is defined, for example, in the x and / or y directions, with the z direction being the length direction of the coupler array (e.g., from the first end to the second end). In various manufacturing techniques, an assembly consisting of a waveguide (e.g., 805 in FIGS. 8 and 855 in FIGS. 9) and a coupler housing structure (e.g., 801 in FIGS. 8 or 851 in FIGS. 9) is heated and stretched to form the second end, as shown in the cross-sectional side views of FIGS. 3A-3L. Referring to FIG. 8, the waveguide 805 is inserted into a coupler housing structure 801 that has a ring shape in a cross section perpendicular to the longitudinal or longitudinal direction of the optical coupler array (e.g., the illustrated xy plane). As described above, placing a gap, such as an air gap, between the coupler housing structure 801 and the waveguides 805 allows the waveguides to move laterally (in the x and / or y directions) relative to the coupler housing structure 801. As shown in FIG. 9 , one or more waveguides 855 can be inserted into an optical coupler housing structure 851 having a plurality of holes 852 in a cross section (e.g., the x-y plane shown) perpendicular to the longitudinal direction or length of the optical coupler array. This allows the waveguides 855 to be passively positioned within the housing structure 851. Placing a gap, such as an air gap, between the coupler housing structure 851 and the waveguides 855 allows the waveguides to move laterally (in the x and / or y directions) relative to the coupler housing structure 851. For closely spaced waveguide arrangements (e.g., hexagonal), this movement capability allows for more precise positioning of the cross-sectional position at the second end after fabrication.

[0118] Referring to FIG. 1A, the coupler array may include multiple longitudinal waveguides 30A, 32A-1, and 32A-2, each including at least one VC waveguide 30A. The VC waveguide 30A has an inner core 20A and an outer core 22A. The spacing between the inner core 20A, the outer core 22A, and the waveguides 30A, 32A-1, and 32A-2 decreases (e.g., simultaneously and gradually in some cases) from the first end (near position B) to the second end (near positions C and D). For example, the spacing decreases from S-1 to S-2. In various embodiments, the cross-sectional layout of the first end (near position B) is shown in FIG. 8 or FIG. 9, and the cross-sectional layout of the second end (near positions C and D) is shown in FIG. 3A-3L or FIG. 7. In some embodiments, there is substantially no gap between the coupler housing structure and the waveguide near the second end, with some gaps filled with the housing material and other gaps filled with the cladding material of the waveguide. The cross-sectional configuration of the first end described above improves the cross-sectional or lateral position of the waveguide at the second end. This allows the waveguide at the second end to be more easily integrated into the optical device. The device is appropriately positioned laterally (e.g., in the x and / or y directions) relative to the chair.

[0119] 10 and 11, yet another example of an optical coupler array 4000, 5000 is shown. The optical coupler array 4000, 5000 can be configured to couple light between multiple optical fibers having different mode fields and / or core sizes. In some examples, the coupler array 4000, 5000 can be configured to provide coupling between individual isolated optical fibers 2000 and an optical device 3000 having at least one optical channel that allows propagation of multiple optical modes. In some preferred embodiments, all of the isolated optical fibers 2000 are identical (or in some cases, different), and the optical device 3000 can include at least one few-mode fiber, multimode fiber, multi-core single-mode fiber, multi-core few-mode fiber, and / or multi-core multimode fiber. 1A-5, various embodiments 4000, 5000 can include a further reduction in the taper diameter, which allows light to escape the outer core 4120, 5120 and propagate in the composite waveguide 4150, 5150 formed by at least two adjacent cores. Accordingly, various embodiments described herein can be configured to couple light between fibers with different mode fields and / or core shapes or sizes. Advantageously, some coupler array embodiments can improve and / or optimize optical coupling between one or more of single-mode fiber, few-mode fiber, multimode fiber, multi-core single-mode fiber, multi-core few-mode fiber, and / or multi-core multimode fiber.

[0120] Various features of the exemplary coupler array are described with reference to FIGS. 10 and 11 , although the described features can be implemented in any combination with the coupler arrays described with reference to FIGS. 1A-5 and 7 . Additionally, any feature described in FIGS. 1A-5 and 7 can be combined with any feature described in FIGS. 10 and 11 . For example, the exemplary coupler arrays 4000 and 5000 are shown using housing structures 4060 and 5060 similar to the housing structures 801 and 851 shown in FIGS. 8 and 9 . In these examples, the cross-sectional configuration of the housing structures 4060 and 5060 can include a structure having multiple holes (e.g., multiple holes), as shown in FIG. 10 , or a structure including a single hole surrounded by a ring (e.g., single hole), as shown in FIG. 11 . However, other housing structures can also be used. For example, the housing structures described in FIGS. 1A-5 and 7 can be used.

[0121] 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 housing structure 4060 and a plurality of longitudinal waveguides 4100 disposed within the housing structure 4060. The waveguides 4100 are arranged in a cross-sectional geometric waveguide arrangement relative to one another. FIG. 10 illustrates exemplary cross-sectional geometric waveguide arrangements of the waveguides 4100 at the first end 4010, the intermediate cross-section 4050, and the second end 4020. As indicated by the shaded portions in the cross-sections and as described below, light is directed from the optical element 4001 through the first end 4010, through the intermediate cross-section 4050, and to the second end 4020.

[0122] As shown in FIG. 10 , proximal to (e.g., adjacent to) the first end 4010, the housing structure 4060 (e.g., a common single coupler housing structure in some examples) can have a cross-sectional shape with a structure (e.g., a laterally continuous structure in some examples) having multiple holes 4062. FIG. 10 shows an example configuration with three circular holes 4062-1, 4062-2, 4062-3. However, the hole shape, number of holes, and / or hole arrangement are not particularly limited and may include other shapes, numbers, and / or arrangements, including those described in FIG. 9 . At least one of the holes 4062 can include at least one vertical waveguide 4100. A gap, such as an air gap, separates the plurality of vertical waveguides 4100 from the surrounding housing structure 4060 proximate the first end 4010. In some embodiments, there can be substantially no gap between the coupler housing structure 4060 and the waveguides 4100 at the intermediate location 4050 and / or the second end 4020. For example, one or more gaps can be filled with housing material and / or waveguide cladding material. As described herein, in some embodiments, there can be a gap between the coupler housing structure 4060 and the waveguides 4100 near the first end 4010, but substantially no gap between the coupler housing structure 4060 and the waveguides 4100 near 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 location 4050 , and / or the second end 4020 .

[0123] As described herein, the coupler array 4000 can be optically coupled to a plurality of optical fibers 2000 and / or optical devices 3000. The coupler array 4000 can couple to the optical fibers 2000 via a plurality of waveguides 4100 near the first end 4010 and / or to the optical devices 3000 via a plurality of waveguides 4100 near the second end 4020. The coupler array 4000 can be connected (e.g., via a fusion splice 2001) and / or to the optical devices 3000 via a plurality of waveguides 4100 near the second end 4020 (e.g., via a fusion splice not shown). In FIG. 10, three waveguides 4100 are shown for each of the three holes 4062-1, 4062-2, and 4062-3. However, any number of waveguides 4100 can be used for each hole 4062. In some embodiments, the number of waveguides 4100 may be equal to the number of optical fibers 2000 (e.g., nine waveguides coupled to nine optical fibers). In other embodiments, the number of waveguides 4100 in at least one hole may be equal to the number of optical modes supported by a corresponding few-mode or multimode waveguide in device 3000 (e.g., three waveguides in each of three holes coupled to three three-mode cores of a multicore fiber). In various embodiments, the waveguides 4100 are positioned at a fixed distance (e.g., a predetermined distance in some cases) from one another within each hole 4062. In preferred embodiments of a multi-hole configuration, each hole 4062-1, 4062-2, 4062-3 contains all of the waveguides (e.g., fibers) that couple to at least one particular core of a few-mode, multimode, and / or multicore fiber in the optical device. In other embodiments, one or more additional fibers and / or dummy fibers (e.g., those that do not conduct light) may be used to create a particular geometry of active waveguide fibers.

[0124] In various embodiments, the plurality of waveguides 4100 are capable of accommodating at least one optical mode (e.g., a predefined mode field profile in some cases). The plurality of waveguides 4100 can include at least one lost-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. In this description, the VC waveguide 4101 can include an inner core (e.g., an inner lost-core) 4110, an outer core 4120, and an outer cladding 4130 having refractive indices N-1, N-2, and N-3. The outer core 4120 longitudinally surrounds the inner core 4110, and the outer cladding 4130 longitudinally surrounds the outer core 4120. As described herein, the relative magnitude relationship of the refractive indices of the inner core 4110, outer core 4120, and outer cladding 4130 is advantageously N-1>N-2>N-3.

[0125] In various embodiments, a housing structure 4060 is disposed to surround the waveguide 4100. The coupler housing structure 4060 may include a medium 4140 having a refractive index N-4. The medium 4140 may be any of those described herein. In some examples, the total volume of the medium 4140 within the coupler housing structure 4060 may be greater than the total volume of all of the inner cores 4110 and outer cores 4120 of the VC waveguides contained within the coupler housing structure 4060. In some examples, the waveguides 4100 are embedded in the housing structure 4060 (e.g., near the second end 4020).

[0126] In certain embodiments, the waveguide dimensions of the inner core 4110, the waveguide dimensions, refractive index, and / or numerical aperture (NA) of the outer core 4120 are selected to increase or optimize coupling to the individual fibers 2000. In various embodiments, the waveguide dimensions, refractive index, NA of the outer core 4120, and / or dimensions of the cladding 4130 are selected to increase or optimize coupling to the optical device 3000. Various examples described herein incorporate the reflection-reducing properties of pitch-reduced optical fibers described in U.S. patent application Ser. No. 14 / 677,810, entitled "Optimized Configurable Pitch-Reduced Optical Fiber Coupler Array," which is incorporated herein in its entirety. For polarization control, portions of the outer core 4120 are formed with non-circular cross-sections (e.g., elliptical shapes as shown in FIG. 10 ), and specific configurations of the outer core 4120 can be used to increase or optimize optical coupling. The various embodiments described herein incorporate the properties of any of the optical polarization mode couplers described in US patent application Ser. No. 15 / 617,684, entitled "Configurable Polarization Mode Coupling."

[0127] 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 can be configured to decrease (e.g., decrease simultaneously and in stages in some cases) from the first end 4010 of the optical element 4001 to an intermediate position or cross section 4050. In some examples, a predetermined decrease profile is used. In the example shown in FIG. 10 , at the intermediate position 4050, the inner core 4110 is insufficient to conduct light, and the outer core 4120 is sufficient to conduct at least one optical mode (e.g., a spatial mode).

[0128] In some embodiments, each core of the waveguide 4100 has the capacity to accommodate 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 multiple spatial modes (M1) within the inner core 4110. At the intermediate position 4050, in various embodiments, the inner core 4110 may be unable to support all M1 modes (e.g., unable to support light propagation). However, in some such embodiments, at the intermediate position 4050, the outer core 4120 may be able to support all M1 modes (and possibly support additional modes). In this example, light propagating from the inner core 4110 to the first end 4010 to the intermediate position 4050 can escape from the inner core 4110 to the outer core 4120 and propagate within the outer core 4120.

[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 be further reduced (e.g., simultaneously and in stages in some instances) from the intermediate position 4050 along the second end 4020 of the optical element 4001. In the example shown in FIG. 10 , at the second end 4020, the outer core 4120 may be insufficient to conduct light.

[0130] In some embodiments, at the intermediate position 4050, the VC waveguide 4101 can support all M1 modes in 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., may not be able to support optical propagation). However, in some such embodiments, at the second end 4020, a composite core 4150 comprised of at least two cores may be able to support all M1 modes of all the waveguides 4101 (and possibly additional modes). In this example: Light propagating within the outer core 4120 from the intermediate position 4050 to the second end 4020 can escape from the outer core 4120 to and propagate within a composite waveguide 4150 formed by at least two outer cores (e.g., two or more adjacent cores). In the example shown in Figure 10, each composite waveguide 4150 is formed from three outer cores. However, in some embodiments, the composite waveguides 4150 may be formed from a different number of outer cores.

[0131] It will be understood that light traveling from the second end 4020 to the first end 4010 exhibits the opposite behavior. For example, in some embodiments, light travels from a composite waveguide 4150 formed from at least two adjacent outer cores to at least one outer core 4120 proximate the intermediate cross section 4050, and then travels from the outer core 4120 to a corresponding inner core 4110 proximate the first end 4010. In the example shown in FIG. 10 , each composite waveguide 4150 can support three propagation modes. Each propagation mode traveling from the second end 4020 to the first end 4010 can be coupled to a corresponding outer core 4120 proximal to the intermediate cross section 4050 and travel from the outer core 4120 to a corresponding inner core 4110 proximal to the first end 4010.

[0132] 11 , exemplary embodiment 5000 has a similar configuration to exemplary embodiment 4000 shown in FIG. 10 . One difference is that the cross-sectional configuration of housing structure 5060 includes a structure having a single hole 5062 instead of multiple holes 4062. Similar to exemplary embodiment 4000 shown in FIG. 10 , optical element 5001 can include housing structure 5060 (e.g., including medium 5140) and multiple longitudinal waveguides 5100 disposed within housing structure 5060. Waveguides 5100 are positioned relative to one another in a cross-sectional geometric waveguide arrangement within hole 5062. As shown, light is guided from a first end 5010 of optical element 5001 through an intermediate cross section 5050 to a second end 5020.

[0133] As described herein, gaps may be formed between the plurality of longitudinal waveguides 5100 and the surrounding housing structure 5060. In some embodiments, there may be substantially no gap between the coupler housing structure 5060 and the waveguides 5100 near the intermediate location 5050 and / or the second end 5020. For example, while FIG. 11 shows a gap near the second end 5020, 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 near the first end 5010, the intermediate location 5050, and / or the second end 5020.

[0134] In various embodiments, the plurality of waveguides 5100 can include at least one VC waveguide 5101. FIG. 11 shows 37 waveguides 5100, all 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 can be used. As described herein, one or more dummy fibers can be used to create a particular geometric arrangement 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.

[0135] In certain embodiments, the waveguide dimensions of the inner core 5110, the waveguide dimensions of the outer core 5120, the dimensions, refractive index, and / or numerical aperture (NA) of the cladding 5130 are selected to increase or optimize coupling to individual fibers 2000 and / or optical devices 3000. In some examples, 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 decrease from the first end 5010 to the second end 5020 of the optical element 5001. In the example shown in FIG. 11 , at the intermediate position 5050, the inner cores 5110 of some waveguides 5100 are insufficient to conduct light, and the outer cores 5120 of some waveguides 5100 are sufficient to conduct at least one optical mode (e.g., spatial mode). In this example, near the second end 5020, the outer cores 5120 may be insufficient to conduct light. Thus, in some embodiments, light traveling within the outer cores 5120 from the intermediate position 5050 to the second end 5020 can escape the outer cores 5120 into and propagate within a composite waveguide 5150 formed by at least two outer cores (e.g., two or more adjacent cores). In the example shown in FIG. 11 , each composite waveguide 5150 is formed from three outer cores, although the composite waveguides 5150 may be formed from other numbers of outer cores. The remaining cores (eg, waveguide cores or dummy fibers) may or may not guide the light. Light propagating from the second end 5020 to the first end 5010 exhibits the opposite behavior.

[0136] Spatial division multiplexing (SDM) can be used to overcome the capacity limitations of a single fiber. To enable the deployment of multicore fibers (MCFs), it is desirable to develop optical fiber components that allow access to individual cores of the MCF as a way to achieve SDM. This application addresses some of such components, and relates to adapters between MCFs with different core patterns and / or add-drop multiplexers for MCFs.

[0137] As shown in Figures 12A-12C, both functions can be realized by combining or separating two separate fan-in / fan-out devices with pigtail fibers connected as indicated by the stars. Figure 12A shows single-channel add / drop, Figure 12B shows pattern adaptation, and Figure 12C shows the combination of pattern adaptation and channel add / drop. However, there are several considerations: (1) high insertion loss involving the sum of the two fan-out devices, (2) large size of the combined components, and (3) high assembly costs.

[0138] To address these factors, in various embodiments, the present disclosure provides a spatial division multiplexer that includes a dual-tapered extension optical element that can provide a low-loss connection between two similar or dissimilar MCFs or other multi-channel optical devices without splicing the pass-through channels. FIG. 13 is a schematic diagram of an exemplary dual-tapered extension optical coupler array. The coupler array 6000 can include a housing structure 6005, a first end 6010, a middle section 6015, and a second end 6020. The coupler array 6000 can include a first tapered section 6030 and a second tapered section 6040. The first tapered section 6030 is disposed between the first end 6010 and the middle section 6015, and the second tapered section 6040 is disposed between the second end 6020 and the middle section 6015. In various designs, the housing structure 6005 can include a first tapered section 6030, a second tapered section 6040, and a connecting sleeve 6035 disposed therebetween. In FIG. 13 , the outer diameter of the coupler array 6000 tapers from the first end 6010 toward the middle section 6015 and tapers from the middle section 6015 toward the second end 6020. The coupler array 6000 can include multiple spatial light channels 6050. For example, the pass-through channels can include erased-core waveguides (e.g., those described herein) or expanded-core waveguides (e.g., waveguides with a larger core size than standard optical fibers) or other types of waveguides that can taper up or down while maintaining optical propagation. The spatial light channels 6050 (e.g., via one or more pass-through channels) can be configured to optically couple the first optical device 6070 and the second optical device 6080. For example, the at least one pass-through channel is operable to couple (e.g., directly couple) at least one optical channel of the first optical device 6070 with at least one optical channel of the second optical device 6080. In various embodiments, the pass-through channel is located within the housing structure 6005. can be embedded in the first end 6010 and / or the second end 6020 of the housing structure 6005. In various designs, individual ones of the spatial light channels 6050 (e.g., transmission channels) do not include joints within the housing structure 6005.

[0139] The first optical device 6070 and / or the second optical device 6080 can include MCFs or other multi-channel optical devices. The transverse channel patterns of the optical devices 6070, 6080 can be configured arbitrarily, for example, depending on the application. In some examples, the transverse channel patterns of the optical devices 6070, 6080 are similar. In other examples, the transverse channel patterns of the optical devices 6070, 6080 are different. For example, as shown in FIG. 13 , the transverse channel patterns can include two rows of channels in one device 6070 and a circumferential channel pattern in the other device 6080, achieving pattern adaptation (e.g., transforming the spatial pattern of one channel into another, different spatial pattern). In some such designs, the spatial optical channels 6050 disposed within the housing 6005 form transverse channel patterns at the first end 6010 and the second end 6020 that can be similar to the transverse channel patterns of the first optical device 6070 and the second optical device 6080, respectively. For example, the first tapered portion 6030 may have a lateral channel pattern similar to the lateral channel pattern of the first optical device 6070, and the second tapered portion 6040 may have a lateral channel pattern similar to the lateral channel pattern of the second optical device 6080.

[0140] In various embodiments, the first tapered section 6030 and / or the second tapered section 6040 can include a tapered housing structure and multiple longitudinal waveguides (e.g., portions of the spatial optical channel 6050). Individual ones of the longitudinal waveguides can be positioned at a fixed distance (e.g., a predetermined distance in some cases) from one another, can be capable of accommodating at least one optical mode (e.g., a mode having a predetermined mode field profile), and can be embedded in the tapered housing structure near the corresponding first or second end 6010, 6020. At least one longitudinal waveguide can be a through channel common to both the first tapered section 6030 and the second tapered section 6040.

[0141] In some embodiments, at least one through channel can include a lost-core waveguide, for example, as described herein. In some embodiments, at least one through channel can include an expanded-core waveguide, such as a waveguide having a core size larger than that of a standard optical fiber. In some examples, the expanded-core waveguide can include an expanded core having a core refractive index (NCO). The expanded core can have a first expanded core size (ECS-1) at the first end 6010, a second expanded core size (ECS-2) at the second end 6020, and an intermediate expanded core size (ECS-IN) at an intermediate portion 6015 therebetween. The expanded-core waveguide can also include an outer cladding that longitudinally surrounds the expanded core. The outer cladding can have a cladding refractive index (NCL). The relative magnitude relationship of the refractive indices can include the following magnitude relationship: NCO > NCL. In some examples, the first expanded core size (ECS-1) is formed according to a predetermined profile, for example, along the housing structure 6005, such that it gradually increases from the first end 6010 to the intermediate portion 6015 and gradually decreases from the intermediate portion 6015 to the second end 6020. In some examples, the first expanded core size (ECS-1) and the second expanded core size (ECS-2) and the refractive indices NCO and NCL may match (e.g., selected in some cases to substantially match) the optical waveguiding characteristics of at least one channel of the first optical device 6070 and / or the second optical device 6080. In some examples, the intermediate expanded core size (ECS-IN) has (e.g., selected in some examples) a larger mode volume than at least one channel of the first optical device 6070 and the second optical device 6080, such that light propagating from the first end 6010 to the intermediate portion 6015 and from the intermediate portion 6015 to the second end 6020 is at least partially Both continue to propagate in one lowest-order mode.

[0142] 14-15 are schematic diagrams of other exemplary double-taper extension optical coupler arrays configured to optically couple a first optical device and a second optical device. In some embodiments, the coupler arrays can be configured to provide access (e.g., direct access) to at least one optical channel of the first optical device and / or the second optical device. Similar to the exemplary coupler array 6000 of FIG. 13, each optical coupler array of FIGS. 14-15 includes a housing structure 7005, 8005; a first end portion 7010, 8010; a middle portion 7015, 8015; a second end portion 7020, 8020; a first tapered portion 7030, 8030; and a second tapered portion 7040, 8040. In some designs, the housing structure 7005, 8005 can be a single monolithic cooler housing structure consisting of a first tapered section 7030, 8030; an intermediate section 7015, 8015; and a second tapered section 7040, 8040. A spatial light channel 7050, 8050 (e.g., via one or more through channels) can be configured to optically couple the first optical device 7070, 8070 and the second optical device 7080, 8080.

[0143] As shown in FIGS. 14-15 , the access region 7016, 8016 in the intermediate section 7015, 8015 has one or two access channels (e.g., direct access channels) 7051, 7052 ( FIG. 14 ) and 8051, 8052 ( FIG. 15 ) (e.g., standard optical fiber, lost core waveguide, expanded core waveguide, etc.) connected (e.g., directly connected) at first and / or second ends of those access channels to the optical devices 7070, 8070 of FIG. 14 and 8070, 8080 of FIG. 15 . For example, one or more optical waveguides may connect the optical devices 7070, 8070 of FIG. 14 and 8070, 8080 of FIG. 15 to the access region 7016 from external space. 6, 8016 into the housing structure 7005, 8005 and provide access to at least one optical channel of the first optical device 7070, 8070 or the second optical device 7080, 8080. The optical waveguides (e.g., optical fibers) 7051, 7052, 8051, 8052 can have a first end disposed within the housing structure 7005, 8005 and a second end disposed outside the housing structure 7005, 8005. For example, the first ends of the waveguides 7051, 7052, 8051, 8052 can be connected to the first end 7010 of the housing structure 7005, 8005. Or may be located at the second end 7020. The waveguides 7051, 7052, 8051, 8052 may exit the housing structures 7005, 8005 through intermediate portions 7015, 8015 of the housing structures 7005, 8005.

[0144] As shown in Figures 14-15, an access channel 7051, 8051 is connected to a first optical device 7070, 8070 at a first end 7010, 8010 of the coupler array 7000, 8000, and an access channel 7052, 8052 is connected to a second optical device 7080, 8080 at a second end 7020, 8020 of the coupler array 7000, 8000. In some embodiments, one channel 7051, 8051 functions as a "drop" channel that extracts an optical signal from the SDM transmission line, and the other channel 7052, 8052 functions as an "add" channel that replaces the dropped signal with a new signal. This add-drop function can be achieved without pattern adaptation (e.g., for optical devices 7070, 7080 with similar transverse channel patterns), as shown in Figure 14. Alternatively, this may be achieved with pattern adaptation, such as creating an access region 8016 in the connecting sleeve (e.g., as shown in FIG. 15, creating an access region 8016 in the connecting sleeve). While FIGS. 14-15 show examples of one "add" channel and one "drop" channel, some optical coupler arrays may be configured to provide one or more "add" and / or "drop" channels. Furthermore, some optical coupler arrays may be configured to provide only one or more "add" channels or only one or more "drop" channels.

[0145] In various embodiments, at least one access optical channel 7051, 7052, 8051, 8052 can be a missing core waveguide. For example, at least one access optical channel 7051, 7052, 8051, 8052 can provide access to at least one optical channel of the first optical device 7070, 8070 and / or the second optical device 7080, 8080 and can be a missing core waveguide. In some such cases, at least one access channel 7051, 7052, 8051, 8052 is configured to fusion splice a standard optical fiber to the access missing core waveguide, with the fusion location located outside the housing structure 7005, 8005, and arranged so that the access missing core waveguide passes from the access region 7015, 8015 through external space into the housing structure 7005, 8005. In some examples, the splice location is located within the housing structure 7005, 8005 and is configured such that a standard optical fiber enters the housing structure 7005, 8005 from the exterior space through the access area 7015, 8015.

[0146] Another application of the present disclosure includes fiber optic gyroscopes, where access to a single channel of a looped MCF is desired. In some designs, two ends of the same span of MCF are connected to the first and second ends of the device shown in FIG. 14 (e.g., forming a fiber loop within the fiber optic gyroscope). In various embodiments, the MCF has a circumferential core arrangement pattern, e.g., numbered along the circumferential direction: core number 1 or channel 1, core number 2 or channel 2, ... core number N or channel N. The connection direction at the first end 7010 couples at least one access channel 7051 to core number 1, and the connection direction at the second end 7020 couples core number 1 to core number 2 at the first end 7010 via at least one pass-through channel. Core number 2 is then coupled to core number 3, and this process continues until core number N-1 is coupled to core number N, which is then coupled to the second access channel 7052 at the second end 7020. For example, the MCF may be configured to be axially twisted such that an optical signal from drop channel 7051 is coupled to channel 1 of the MCF 7070 at the first end 7010. At the second end 7020, the optical signal is coupled to the pass channel of the spatial optical channel 7050, after which the signal is coupled to channel 2 of the MCF 7070 at the first end 7010. In a similar manner, core number 2 is coupled to core number 3, and so on until core number N-1 is coupled to core number N, and finally core number N is coupled to the "add" channel 7052 at the second end 7020.

[0147] In various embodiments, the housing structure is constructed of a material selected depending on the application, such as glass, metal, or polymer. The channels can be embedded in a portion of the housing structure. For example, the channels can be embedded in the housing structure near the tapered end(s). In some examples, the channels can be embedded 40%, 45%, 50%, 55%, 60% (or any range formed by these values) of the tapered length. In some designs, the channels are embedded throughout the housing structure. In some examples, a gap (e.g., air-filled or filled with a filler material, or a combination thereof) exists in the middle section (e.g., the larger diameter section). The housing structure is substantially linear (e.g., linear or in the range of 175° to 185°). Figure 16 is a schematic diagram of an optical coupler array 9000 configured to optically couple a first optical device 9070 and a second optical device 9080. The coupler array 9000 can include a first end 9010, a second end 9020, a first tapered section 9030, and a second tapered section 9040. The optical coupler array 9000 can include a plurality of spatial optical channels 9050, such as pass-through channels. As shown in FIG. 16 , the housing structure 9005 (e.g., a middle section) can be formed to be bent. In some examples, the housing structure 9005 can include a bendable flexible section. In some examples, the housing structure 9005 can include a rigid bending section. In various examples, the housing structure 9005 can be bent at 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, etc., or any range formed by these values ​​(e.g., 90°-170°, 90°-150°, 90°-130°, etc.). The bend angle may be 90 degrees as shown, or 180 degrees depending on the application requirements. Figure 16 shows an example of pattern adaptation. Also, in either a straight or bent configuration, add-drop multiplexing or a combination of pattern adaptation and add-drop multiplexing may be desirable.

[0148] In some embodiments, the optical coupler array can be configured to couple with at least one optical device having at least one multimode optical channel. For example, the multimode optical channel can be the inner cladding (e.g., for pump transmission) of a dual-clad multicore fiber. In some examples, configurations can be made to provide direct access to at least one optical mode of the multimode optical channel. FIG. 17 illustrates such an example, where the optical coupler array 9100 couples a first optical device 9170 (e.g., a single-clad MCF) at a first end 9110 with a second optical device 9180 (e.g., a dual-clad MCF having an inner cladding 9181 and an outer cladding 9182) at a second end 9110. The coupled multichannel optical devices 9170, 9180 can include multicore fibers whose cores are coupled via spatial optical channels 9150 (e.g., pass-through channels (e.g., signal channels)). At least one access (eg, direct access) optical channel 9152 may include a multimode fiber coupled to at least one cladding mode of an inner cladding 9181 of a dual-clad multicore fiber 9180 .

[0149] 17 , the signal channel is a pass-through channel of the spatial optical channel 9150 from the core of the single-clad MCF 9170 at the first end 9110 and connected to the core of the dual-clad MCF 9180 at the second end 9120. The core of the dual-clad MCF 9180 can be single-mode, few-mode, or multimode. The spatial optical channel 9150 (e.g., the pass-through channel) can be a multimode or lost-core waveguide. As shown, the core at the second end 9120 of the optical coupler array 9100 can be configured to match (e.g., substantially match) the core of the dual-clad MCF 9180. For example, in some embodiments, the pass-through channel is an lost-core channel having a single-mode core at the second end 9120 and configured to match (e.g., substantially match) the single-mode core of the dual-clad MCF 9180. In some examples, when a pass-through channel is formed, both ends (e.g., tapered ends) are configured to match the core of the dual-clad MCF 9180. For example, both ends of the pass-through channel can be single-mode (or few-mode or multi-mode) to match the single-mode (or few-mode or multi-mode) core of the dual-clad MCF 9180. The access channels 9152 passing through the access region 9116 can be coupled to cladding modes. As shown in FIG. 17 , at least one access channel 9152 can include a pump channel coupled to a cladding mode (e.g., inner cladding 9181) at the second end 9120 of the dual-clad MCF 9180. The dual-clad MCF 9180 is an active fiber, with one or more cores doped with erbium or other active elements, and capable of amplifying light when pumped with other light waves. As shown, in some embodiments, the access region 9116 provides access to at least one pump channel (only one additional channel is shown), and the signal channel is a pass-through channel 9150. A drop channel may be provided for at least one pump channel, which is useful for pump reuse at the opposite end of the double-clad MCF 9180.The add / drop pump channels are coupled to the cladding of the MCF, and their cross-sectional locations do not necessarily coincide with the cores of the MCF (e.g., they are coupled to the inner cladding of a double-cladding multicore fiber). As in Figure 3E, the pump channels are conventional single-core multimode pump transmission fibers, not erased-core fibers. In some cases, the pump channels may be erased-core fibers. The number of pump channels can be one or more. Within one device, a combination of pump and signal adding functions, pump and signal dropping functions, and / or pattern adaptation can be realized.

[0150] As one way to realize SDM that enables the deployment of multicore fibers (MCFs), it is desirable to develop optical fiber components that allow access to individual cores of MCFs at two wavelengths (e.g., pump and signal wavelengths). This application addresses some of such components: wavelength division multiplexing (WDM) fan-out devices and pump-signal combiners for MCFs.

[0151] As shown in Figures 18A and 18B, these functions can be realized by combining a WDM device with a fan-out (or fan-in) device, or by combining a WDM device with two fan-in / fan-out devices and connecting the pigtail fibers as indicated by the stars. Figure 18A shows a WDM fan-out device 1810, and Figure 18B shows an MCF-WDM device 1820. In Figure 18A, the WDM-fan-out device 1810 consists of a WDM device 1811, a fan-out (or fan-in) device 1812, and a connection 1815 between them. The WDM device 1811 can be, for example, a wavelength combiner (e.g., a 980 / 1550 combiner) that combines light of a first wavelength (wavelength-1 or W-1) with light of a second wavelength (wavelength-2 or W-2). The light of the first wavelength includes signal light at 1550 nm, and the light of the second wavelength includes pump light at 980 nm (or vice versa). Other examples are also possible. The light at the first wavelength and the light at the second wavelength are coupled into one core 1816 of an output MCF 1817. In some cases, the MCF 1817 may comprise an Er-doped fiber. In FIG. 18B, an MCF-WDM device 1820 combines a WDM device 1821 with two fan-in / fan-out devices 1822, 1824 and a splice 1825 connected therebetween. The MCF-WDM 1820 includes an input MCF 1826 and an output MCF 1827. In some cases, the input MCF 1826 includes a transmission MCF. In some cases, the output MCF 1827 includes an Er-doped fiber.

[0152] However, the following points must be taken into consideration: (1) high insertion loss (including the sum of the WDM component and one or two fan-out devices), (2) large size of the combined components, and (3) high assembly cost.

[0153] To address these factors, various embodiments of the present disclosure may integrate WDM functionality into a spatial division multiplexer. Figure 19A illustrates a cross-sectional view of an exemplary WDM fan-out device (e.g., a combined SDM-WDM device) 1910. Light of wavelength W-1 is combined with light of wavelength W-2 in a core of an MCF (e.g., the core of an MCF coupled to the WDM fan-out device 1910). For example, a signal (e.g., 1550 nm) or multiple signals (e.g., signals in the C-band from 1520 to 1570 nm) and pump light (e.g., 980 nm) may be combined in the core of the MCF. As another example, two signals (e.g., 1550 nm and 1310 nm) may be combined in the core of the MCF. In the example illustrated in Figure 19A, a 1550 nm signal light and a 980 nm pump light may be combined in each core of a four-core MCF. For example, in FIG. 19A, WDM fan-out device 1910 represents four WDMs (1911A, 1911B, 1911C, and 1911D) with four pairs of adjacent waveguides. Each pair of adjacent waveguides 1911A, 1911B, 1911C, and 1911D includes a first waveguide for light of a first wavelength (W-1) and a second waveguide for light of a second wavelength (W-2). The W-1 and W-2 light output from WDMs 1911A, 1911B, 1911C, and 1911D are coupled to each core of a four-core MCF coupled to WDM fan-out device 1910. Other designs may include more or fewer WDMs or more or fewer cores in the MCF. The number of WDMs and the number of cores are not particularly limited. FIGS. 19B-19F are side views showing various examples of a WDM fan-out taper device 1910. In FIG. 19B, at the tapered end, a composite waveguide 1913 formed from the outer cores of the signal channel and the pump channel guides light of both wavelengths and couples it to corresponding cores 1916 of an MCF 1917. In some embodiments, the signal light is coupled to the lowest-order mode of the MCF core, and the pump light is coupled to a set of modes with a corresponding coupling coefficient. In this case, the wavelength coupling can be broadband, but the two wavelengths are coupled to a set of modes with corresponding coupling coefficients in the MCF core. For example, the signal light is coupled to the lowest-order mode of the output waveguide, and the pump light is coupled to a higher-order mode (e.g., a second-order mode) of the output waveguide.

[0154] In various embodiments, light of different wavelengths coming from different input waveguides (e.g., the lowest-order modes of the input waveguides) can be coupled into the same mode (e.g., the lowest-order mode) of an output waveguide. In Figures 19C, 19D, 19E, and 19F, composite waveguides are not formed at the MCF interfaces; instead, MCF cores 1926, 1936, 1946, and 1956 are coupled to one of the input waveguides 1923, 1933, 1943, and 1953. In the examples shown in Figures 19C and 19D, wavelength coupling can be achieved by forming necks (e.g., neck couplings) 1928 and 1938. In contrast, in the examples shown in Figures 19E and 19F, wavelength coupling can be achieved by small waveguide splits (e.g., substantially linear couplings) 1948 and 1958 near the second end. At these couplers 1928, 1938, two wavelengths are coupled into one waveguide (e.g., FIG. 19C) or the other waveguide (e.g., FIG. 19D) and then into the corresponding MCF cores 1926, 1936. Similarly, the examples shown in FIGS. 19E and 19F can be configured to couple the MCF cores into the inner (e.g., as shown in FIG. 19F) or outer cores (e.g., as shown in FIG. 19E) at the tapered ends. In various designs of necked and near-linear couplers, the waveguides are positioned close to each other, so that light of one wavelength (e.g., W-1 or W-2) remains in its own waveguide, while light of the other wavelength is coupled into the other waveguide. The W-1 and W-2 optical signals can propagate within the same output waveguide. Design parameters include the waveguide separation distance and the coupler length. In various cases, the coupling distance between the waveguides is configured to couple light of a wavelength (e.g., W-1 or W-2) of at least one core mode of one waveguide to at least one core mode of the other waveguide while continuing or maintaining propagation of light of other wavelengths (e.g., W-2 or W-1) in the other waveguide.

[0155] In various cases, the neck portions 1928, 1938 can be fabricated similarly to some embodiments shown in FIG. 7. For example, in some cases, the first inner eliminated core size (ICS-1), the first outer core size (OCS-1), and the spacing between the multiple longitudinal waveguides gradually decrease simultaneously from the first end along the second end of the optical element to an intermediate position (e.g., the neck junction), and then gradually increase simultaneously from the intermediate position to the second end, continuing until the second inner eliminated core size (ICS-2) and the second outer core size (OCS-2) are reached. Some embodiments may be flexible, while other embodiments may be inflexible.

[0156] Any of the exemplary embodiments of the composite SDM-WDM device described above can be fusion spliced ​​into a fan-out device to perform the function of an MCF-WDM device. To fabricate a single device with a reduced number of splices, one or more channels (e.g., pump channels) can be introduced through the access region of a modified MCF add-drop multiplexer, as shown in FIG. 14 or FIG. 15. One or both of the "direct access channels" can be used to introduce the pump channels for providing co-directional and / or counter-directional pump light. In this case, the cross-section of the access region is modified (e.g., side-polished region for fiber access) from the add-drop multiplexer design shown in FIG. 20. In this example, cross-section 1950 includes a side-polished region that provides an access hole for accessing the optical fiber carrying W-2 (e.g., 980 nm pump light). 19A shows the state after the optical fiber carrying the light of W-2 has been installed.

[0157] Various embodiments described herein may be modified from the examples shown. For example, the number of WDMs in a WDM fanout device and / or the number of cores in an MCF may differ from those shown and described. For example, the number of WDMs in a WDM fanout device is not limited to the number of WDMs shown. As another example, the number of cores in an MCF is not limited to the number of cores shown. Furthermore, the number of WDMs in a WDM fanout device and the number of cores in an MCF may differ from each other. For example, the number of WDMs in a WDM fanout device does not need to match the number of cores in an MCF to which the WDM fanout device is connected.

[0158] 19A shows a WDM-fanout device 1910 in which four WDMs 1911A, 1911B, 1911C, and 1911D are represented by four pairs of adjacent waveguides. Each pair of adjacent waveguides includes a first waveguide for light of a first wavelength (e.g., wavelength-1 or W-1) and a second waveguide for light of a second wavelength (e.g., wavelength-2 or W-2). For example, W-1 is a signal light at 1550 nm and W-2 is a pump light at 980 nm. In another example, W-1 is a pump light and W-2 is a signal light. Other wavelengths are possible.

[0159] As described herein, the number of light propagating through adjacent first and second waveguides of a WDM fanout device 1910 can match the number of cores of the MCF (e.g., four WDMs for a four-core MCF), as shown in FIGS. 19B-19F. However, the number of WDMs in the WDM fanout device 1910 can be less than the number of cores of the MCF. FIG. 21A is a schematic diagram of a cross-section of such an exemplary SDM-WDM composite device 1960. In FIG. 21A, the cross-section of the exemplary SDM-WDM device 1960 is composed of two WDMs 1961A, 1961D (e.g., two pairs of adjacent W-1 / W-2 waveguides) and two single waveguides 1961B, 1961C (e.g., two waveguides with no adjacent waveguides) that can be configured to be coupled to a four-core MCF.

[0160] The first WDM 1961A is represented by a pair of adjacent waveguides at the top left of the cross-sectional view, and the second WDM 1961D is represented by another pair of adjacent waveguides at the bottom right of the cross-sectional view. The other two waveguides 1961B and 1961C at the top right and bottom left of the cross-sectional view can each be single waveguides. For example, the single waveguides 1961B and 1961C can be configured so that they do not couple light with other waveguides in the SDM-WDM device 1960.

[0161] Some of these examples can be used to transmit co-propagating and counter-propagating light. For example, the SDM-WDM device 1960 shown in FIG. 21A is a WDM fanout device D1 that can be configured to connect to a four-core MCF1, where diagonal cores of the MCF1 can transmit co-directional light (e.g., two diagonal cores transmit light in the same direction as each other, and the remaining two diagonal cores transmit light in the same direction as each other) and adjacent cores can be configured to transmit counter-propagating light (e.g., two adjacent cores transmit light in opposite directions from each other). The MCF1 can be a transmission MCF or an erbium-doped fiber (EDF), i.e., an erbium-doped MCF. In some embodiments, the device can be used as an amplifier. In some examples, the MCF1 can be a submarine SDM link that provides a communications link below the surface of the water, such as in the sea or ocean.

[0162] As shown within the dotted line in FIG. 21B, the SDM-WDM device 1960 (e.g., WDM fan-out device D1) shown in FIG. 21A is a fan-out device having a single waveguide. Device D1 is connected (e.g., via connection 1965) to device D2 (e.g., without adjacent waveguide pairs or WDMs). Device D2 can be any known or later-developed non-WDM fan-out device. In FIG. 21B, devices D1 and D2 are shown schematically as triangular shapes, but devices D1 and / or D2 may include tapered regions with optical fibers extending from the tapered regions (e.g., D1 and / or D2 may include portions of the fibers shown outside the triangular shapes). The two WDMs in device D1 couple light W-1 and light W-2, respectively, into corresponding cores of MCF1. In FIGS. 21A-21B, W-1 is the signal light at 1550 nm, and W-2 is the pump light at 980 nm. In other examples, W-1 is the pump light and W-2 is the signal light. In other examples, other wavelengths can be used. FIG. 21B shows pump light entering the input waveguide of device D1. In some cases, D1 and D2 are combined into one device similar to the device shown in FIG. 14, with the pump light entering the combined device D1 via a direct access channel in device D1 as described in FIG.

[0163] Light at wavelength W-1 is transmitted through device D2 from MCF2 (e.g., a transmission MCF), and light at wavelength W-2 is transmitted from a pump (e.g., a 980 nm pump). Device D1 combines light from W-1 and W-2 and couples the combined light into two diagonal cores of MCF1 (e.g., a four-core erbium-doped MCF), which transmits light from MCF2 to MCF1. Any of the coupling configurations shown in Figures 19B-19F can be used. The other two diagonal waveguides of device D1 transmit light received from MCF1 (e.g., a transmission MCF) to MCF2 (e.g., an erbium-doped MCF) through device D2.

[0164] In various examples, mode size and / or pattern adaptation features may be utilized when the mode field diameters and / or core patterns of the erbium-doped fiber and the transmission fiber are different. Splice protectors may or may not be used. All components included within the dotted line in FIG. 21B may be co-packaged as a single compact MCF-WDM device 1970.

[0165] FIG. 22 is a schematic diagram of another configuration 1980 that combines the device 1960 (e.g., WDM fan-out device D1) of FIG. 21A with a fan-out device D2 that omits the WDM, as shown by the dotted line. This configuration can mimic a single-core fiber optic bump pair that amplifies light in a counter-directional optical fiber pair. In various embodiments, the amplifier 1980 can include two MCF-WDMs 1970 (e.g., those shown in FIG. 21B) with an amplification medium MCF1 disposed therebetween. For example, in FIG. 22, the devices D1 and D2 within the dotted line are similar to the configuration 1970 shown in FIG. 21B. For example, signal light from MCF2 (e.g., a four-core transmission MCF) is transmitted through device D2 and coupled with pump light into MCF1 (e.g., an erbium-doped MCF) through device D1. This approach can provide co-propagating pumps (e.g., light W-1 and light W-2 propagate in the same direction) for all four cores of the erbium-doped 4C-MCF1,2, one from one end and two from the other end, as shown in Figure 22. While an erbium-doped fiber amplifier (EDFA) is shown, other implementations are applicable to other amplifiers, such as those using an amplification medium other than erbium-doped fiber.

[0166] As illustrated in FIG. 22, various implementations may include a pair of MCF-WDMs 1970 described herein with an amplification medium MCF1 disposed therebetween. The amplification medium may be an active MCF. The active MCF may include at least one pair of nearest neighbor cores and at least two pairs of next-nearest neighbor cores. The next-nearest neighbor cores may be configured to transmit light in the same direction, and the nearest neighbor cores may be configured to transmit light in opposite directions. One of the two MCF-WDMs 1970 may be attached to one end of the active MCF1. One of the two MCF-WDMs 1970 is configured to couple pump light into at least one pair of two next-neighbor cores at one end of the active MCF 1, and the other of the two MCF-WDMs 1970 is configured to couple pump light into another pair of two next-neighbor cores at the other end of the active MCF 1. One of the two MCF-WDMs at one end can be configured to couple pump light into at least one pair of two MCFs at one end of the active MCF 1. It can also be configured to couple pump light into another pair of two MCFs at one end of the active MCF 1. While the illustrated amplifier 1980 uses a four-core MCF 1, the number of cores is not limited to four. For example, the number of cores can be less than or greater than four. Furthermore, the core arrangement can form a square pattern, although non-square core patterns can be used in other embodiments.

[0167] Any of the coupling configurations shown in Figures 19B-19F can be used. Additional devices (e.g., one or more gain-flattening filters 1984 and / or one or more isolators 1985) can also be used. Mode size adaptation can be integrated into devices D1 and / or D2, for example, when MCF1 and MCF2 are different. Furthermore, core pattern adaptation can be achieved by providing devices D1 and D2 with different core patterns and / or corresponding spacing matching for MCF1 and MCF2, respectively. Splice protectors may or may not be used. All components included within the dotted line in Figure 22 can be co-encapsulated as a single compact MCF-WDM device 1970. In the reverse direction, light from MCF1 (e.g., an erbium-doped MCF) can be transmitted to MCF2 via devices D1 and D2.

[0168] FIG. 23 is a schematic diagram of another example configuration 1990 using the device 1960 shown in FIG. 21A. This configuration combines a WDM fan-out device (e.g., WDM fan-out device D1) with a WDM-free fan-out device D2. This configuration is similar to FIG. 22 and includes a monitoring channel (e.g., high-loss loopback 1989). As shown, additional devices (e.g., one or more gain-flattening filters 1984, one or more isolators 1985, one or more coolers 1986, one or more line build-out (LBO) attenuators 1987, and / or one or more fiber Bragg gratings 1988) can also be used. Mode size adaptation and / or pattern adaptation can also be utilized. Splice protectors may or may not be used. All components within the dotted lines in FIG. 23 can be co-encapsulated into a single, compact MCF-WDM device 1970. While various implementations are possible using currently available components, a more compact and efficient format may be realized.

[0169] Experimental example An example of a four-core wavelength division multiplexing (WDM) combiner (or WDM fanout device) employing a quenched-core approach similar to the device shown in FIG. 19F has been created. In this description, this combiner can pave the way to a compact four-core erbium-doped optical fiber amplifier (EDFA) 2400 shown in FIG. 24. The configuration 2400 in FIG. 24 is similar to the configuration in FIG. 22, which combines the device 1960 (e.g., WDM fanout device D1) shown in FIG. 21A with a fanout device D2 without WDM. The EDFA 2400 shown in FIG. 24 can combine the functions of four single-core EDFAs or two single amplifier pairs. In some designs, the use of two diagonal pump signal coupling channels at either end of a four-core erbium-doped optical fiber multicore fiber (MCF1) can achieve a four-core EDFA 2400 with reduced (and / or minimized) crosstalk due to co-propagating diagonals and counter-propagating adjacent channels. In Figure 24, the pump signal is provided by four 980 nm shared pump diodes 1976. In other examples, the number of pump diodes can be any number, e.g., 1, 2, 3, 5, 6, 7, 8, 9, 10, or any range formed by any of these values. A combiner 1986 (e.g., a 2x2 combiner) couples the pump diodes 1976 together for redundancy. to the WDM fan-out device D1. In other embodiments, any pump source and any type of coupler can be used.

[0170] FIG. 25A is a schematic side view of an exemplary SDM-WDM device (e.g., configured to couple a four-core WDM combiner 2500 with a four-core MCF 2550). The length of the device 2500 was 36 mm, including a 20 mm taper and a 4 mm coupling section 2510. FIG. 25B shows a microscope image 2500A of a cross section at the tapered end 2511 of the combiner 2500. FIG. 25C shows a microscope image 2500B of a cross section of an MCF 2550 positioned adjacent to the tapered end 2512 of the combiner 2500. In various embodiments, a coupler design using a disappearing-core approach can effectively reduce excess loss by bringing the waveguides closer together during the tapering process before the cores are actually coupled. In this example, in a configuration where pump channels p1, p2, p3, and p4 are arranged on the inside and signal channels s1, s2, s3, and s4 are arranged on the outside, increasing (and / or maximizing) the separation between the signal channels can reduce (and / or minimize) signal crosstalk. As shown in FIG. 25A, the spacing 2555 between the cores 2560 of the MCF 2550 is significantly larger than the spacing 2513 between the waveguides s1 and p1 carrying signal wavelengths W-1 and W-2. Advantageously, the lost-core fiber design allows for large draw ratios at both signal wavelengths W-1 and W-2. In the fabricated example, the pitch 2555 of the MCF cores 2560 was approximately 42 μm, and the initial pitch 2515 between the waveguides s1 and s4 carrying 1550 nm signals at the non-tapered end 2511 was 360-400 μm. The large stretch ratio (e.g., approximately 9:10) provided flexibility to adjust the initial spacing 2513 between the signal and pump waveguides s1 and p1 to increase (and / or optimize) coupling with the reduced diameter of the tapered end 2512. The length of the coupling section 2510 determines, at least in part, the coupling wavelength. Increasing (and / or optimizing) the signal-pump spacing 2513 can reduce (and / or minimize) losses in the signal and pump channels in the C-band from 1520-1570 nm and at 980 nm, enabling longer coupling lengths. In the illustrated example, all components of device 2500 (including the disappearing-core (VC) fiber and housing) are fabricated from silica-based glass, enabling conventional fusion splicing for fiber integration.The fabricated four-core WDM device 2500 (four pairs of pump-signal channels p1-s1, p2-s2, p3-s3, and p4-s4) was fusion-spliced ​​to a four-core MCF 2550 for 5-meter transmission. The fiber 2550 had four uniform cores 2560 with a mode field diameter (MFD) of ~10 μm at 1550 nm, a core spacing 2555 of 42 μm, and a core position accuracy of less than 0.1 μm. Using the end-view mode of a Fujikura FSM-100P+ fusion splicer, the pump and signal channels p and s of the device 2500 were aligned as shown in Figure 26A. The core 2560 of the four-core MCF 2550 was aligned with the "pump" channel p of the combiner 2500 as shown in Figure 26A. As shown in Figures 26A-26B, core 2560 of combiner 2500 was matched with the "pump" channel p of combiner 2500. After splicing with MCF 2550, combiner 2500 was packaged using a compact package design that was validated through extensive testing and submersion testing, resulting in device 2600, shown in Figure 26C. Multiple packaged combiner / fanouts employing similar VC fiber technology were tested to meet temperature, humidity, and other subsea application environmental requirements in addition to watt-level power handling capabilities. The other end of the 4-core MCF 2550 was fusion-spliced ​​with a non-WDM fanout device (such as fanout device D2 shown in Figure 24). This configuration enabled proof-of-concept, per-channel optimization, and measurements of insertion loss, polarization-dependent loss, return loss, and crosstalk.

[0171] The performance of a four-core WDM device 2500 fabricated with a stretching ratio of 9.1, an initial signal channel separation of 374 μm, a pump-signal separation of 130 μm, and a coupling length of 4 mm was measured. For the insertion loss measurement shown in Figure 27A, a broadband light source was used as the "pump" and "signal" single-core coupling. The pump channels were sequentially connected to the 2550 MCF cores via a non-WDM fan-out device, and an optical spectrum analyzer was connected to the 2550 MCF cores matched with the pump channels. As shown in Figure 27A, the dips at ~1550 nm for all pump channels were within ±8 nm, which is much smaller than the transmission bandwidth of the signal channels. This spectral proximity ensures low C-band loss for all four channels, as shown in Figure 27B. Using the same combiner-fan-out configuration and narrowband light source, the crosstalk (XT) in the pump channels was measured at 980 nm; the results are shown in Table 1. The average XT in the C-band for the signal channels is shown in Table 2. JPEG2025536527000004.jpg85107

[0172] Using the LUNA6415 OFDR, return losses of over 70 dB were measured for all combiner channels. Because the EDFA configuration of the fabricated 4-core WDM combiner 2500 has adjacent cores in a counter-propagating geometry (see Figure 24), additional high-resolution tunable laser measurements were performed on the signal and pump channels corresponding to diagonal cores 2 and 4. The measured insertion loss, polarization-dependent loss (PDL), and crosstalk (XT) in the C-band for these channels are shown in Figures 28A-28C. The insertion loss at 980 nm was less than 0.4 dB for both pump channels. PDL was less than 0.1 dB for both channels. The counter-propagating XT for adjacent channel pairs (2-1, 2-3, 4-1, 4-3) in the C-band was measured to be less than -70 dB.

[0173] In the pump configuration shown in FIG. 24, a WDM combiner D1 configured to couple with an MCF1, as shown within the dotted line, is co-enclosed with a non-WDM fan-out device D2 in a compact housing (dimensions: 58×25×5 mm) to form the MCF-WDM2900 shown in FIG. 29. The length of the housing can be 45 mm, 50 mm, 55 mm, 58 mm, 60 mm, 65 mm, etc., or any value between these values. The length of the housing can be any range formed by any of these values, for example, 45 mm to 65 mm, 50 mm to 65 mm, etc. The width of the housing can be 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, etc., or any value between these values. The width of the housing can be within any range formed by any of these values. Ranges can be, for example, 15 mm to 35 mm, 20 mm to 30 mm, etc. The height of the housing can be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc. The height of the housing can be within any range formed by any of these values. Ranges can be, for example, 3 mm to 10 mm, 3 mm to 8 mm, etc. Other dimensions are possible. In this case, the size of the illustrated enclosure may be limited by the long-term reliability of the bent pigtail fiber. The provided package provided a failure probability of less than 1 ppm over a 25-year lifetime. As shown within the dotted line in Figure 24, access to the single-core fiber between the combiner D1 and the fanout D2 can be provided as shown in Figures 14-15. Standard EDFA components (or combinations thereof) shown in Figures 22-23 can be incorporated into the package, maintaining the same footprint while increasing some height. Furthermore, instead of the four-core transmission MCF shown in Figure 24, four single-core or two dual-core transmission fibers can be used in this four-core EDFA configuration. Other numbers of fiber cores are also possible.

[0174] Thus, while fundamental novel features applied to preferred embodiments of the present invention have been shown, described, and pointed out, those skilled in the art will recognize that various omissions, substitutions, and changes may be made in the form and details of the illustrated apparatus and method, as well as in its operation, without departing from the spirit of the invention. For example, all combinations of elements and / or method steps that function in substantially the same way to achieve substantially the same function are expressly intended to be within the scope of the invention. Accordingly, the scope of the invention is limited only by the claims appended hereto.

Claims

1. an optical coupler array for optically coupling a plurality of optical fibers transmitting light of at least two wavelengths W-1 and W-2 to an optical device, an elongated optical element having a first end and a second end, the first end operable to optically couple with the plurality of optical fibers and the second end operable to optically couple with the optical device; a common single coupler housing structure; A joint; a plurality of longitudinal waveguides; the plurality of longitudinal waveguides having at least one first waveguide and at least one second waveguide, each of the plurality of longitudinal waveguides being spaced apart from one another and having a capacity of at least one optical mode of a mode field profile and a corresponding propagation constant, and embedded in the common single coupler housing structure, at least one of the plurality of longitudinal waveguides being a lost core waveguide, each of the lost core waveguides being: an inner lossy core, an outer core, and an outer cladding; the inner disappearing core has a first refractive index (N-1) and a first inner core size (ICS-1) at the first end and a second inner core size (ICS-2) at the second end; The outer core longitudinally surrounds the inner core, has a second refractive index (N-2), has a first outer core size (OCS-1) at the first end, and has 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 has a second cladding size at the second end; The common single coupler housing structure comprises a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, and the relative magnitude relationships of the first, second, third and fourth refractive indices (N-1, N-2, N-3 and N-4, respectively) satisfy the following magnitude relationship: (N-1>N-2>N-3), wherein a total volume of the medium of the common single coupler housing structure is greater than a total volume of the inner cores and outer cores of all of the lost core waveguides enclosed in the common single coupler housing structure, and the first inner lost core size (ICS-1), the first outer core size (OCS-1), and the spacing of the plurality of longitudinal waveguides are simultaneously and stepwise changed according to a profile along the optical element between the first end and the second end until reaching the second inner lost core size (ICS-2) and the second outer core size (OCS-2), and the second inner lost core size (ICS-2) is selected to be insufficient in size to conduct light, and the second outer core size (OCS-2) is selected to be sufficient in size to conduct at least one optical mode, thereby light traveling from the first end to the second end escapes from the inner lost core to the corresponding outer core near the second end; light traveling from the second end to the first end travels from the outer core to the corresponding inner lost core near the first end; an optical coupler array, wherein at least one of the lost core waveguides is positioned at a coupling distance from another longitudinal waveguide at the coupling portion located near the second end, and the coupling distance and the length of the coupling portion are configured to couple light of wavelength W-1 in at least one core mode of the at least one lost core waveguide with at least one core mode of another longitudinal waveguide while allowing light of wavelength W-2 to continue propagating in the other longitudinal waveguide.

2. 2. The optical coupler array according to claim 1, wherein near the second end, the light of wavelength W-1 and the light of wavelength W-2 are coupled into the same mode of the other longitudinal waveguide.

3. the first inner lost core size (ICS-1), the first outer core size (OCS-1), and a spacing between the plurality of longitudinal waveguides is simultaneously and stepwise decreased along the optical element to the coupling portion between the first end and the second end, and is simultaneously and stepwise increased from the coupling portion to the second end until the second inner optical core size (ICS-2) and the second outer core size (OCS-2) are reached.

4. 2. The optical coupler array of claim 1, wherein the first inner missing core size (ICS-1), the first outer core size (OCS-1), and the spacing of the plurality of longitudinal waveguides are simultaneously and stepwise decreased along the optical element between the first end and the second end until the second inner missing core size (ICS-2) and the second outer core size (OCS-2) are reached.

5. 2. The optical coupler array according to claim 1, wherein one of the wavelengths W-1 and W-2 is a signal light, and the other of the wavelengths W-1 and W-2 is a pump light.

6. 6. The optical coupler array of claim 5, wherein the signal light is 1550 nm and the pump light is 980 nm.

7. 2. The optical coupler array according to claim 1, wherein one of the wavelengths W-1 and W-2 is a signal light, and the other of the wavelengths W-1 and W-2 is another signal light.

8. 8. The optical coupler array of claim 7, wherein the signal light is 1550 nm and the other signal light is 1310 nm.

9. The optical coupler array of claim 1 , comprising an access region providing access to at least one of the plurality of longitudinal waveguides between the first end and the second end.

10. The optical coupler array of claim 1 , wherein the coupling portions are substantially linear.

11. The optical coupler array of claim 1 , wherein the coupling portion has a neck portion.

12. The optical coupler array of claim 1 , wherein the plurality of longitudinal waveguides comprises at least one waveguide configured not to couple light with other waveguides of the plurality of longitudinal waveguides of the optical coupler array.

13. 1. A multi-core fiber wavelength division multiplexer (MCF-WDM), comprising: a WDM fan-out device; a non-WDM fan-out device; the WDM fan-out device comprises a plurality of first longitudinal waveguides having at least one waveguide configured to propagate light at a first wavelength and at least one waveguide configured to propagate light at a second wavelength, and is configured to couple light at the first wavelength and light at the second wavelength into cores of a multicore fiber; the non-WDM fan-out device comprises a plurality of second vertical waveguides, each waveguide of the plurality of second vertical waveguides configured not to couple light with other waveguides of the plurality of second vertical waveguides of the non-WDM fan-out device.

14. The MCF-WDM of claim 13, wherein the first vertical waveguide comprises at least one waveguide configured not to couple light with other waveguides of the first vertical waveguide of the WDM fan-out device.

15. The MCF-WDM of claim 13, further comprising one or more isolators, gain-flattening filters, couplers, attenuators, and / or fiber Bragg gratings.

16. An amplifier comprising two of the MCF-WDMs of claim 13 and a gain medium disposed therebetween.

17. 17. The amplifier of claim 16, wherein the gain medium is an active MCF, the active MCF having at least one set of nearest neighbor cores and at least two sets of next nearest neighbor cores, the next nearest neighbor cores transmitting light in the same direction and the nearest neighbor cores transmitting light in opposite directions, one of the two MCF-WDMs at one end of the active MCF coupling pump light into at least one set of the at least two sets of next nearest neighbor cores, and the other of the two MCF-WDMs at the other end of the active MCF coupling pump light into the other set of the at least two sets of next nearest neighbor cores.

18. 17. The amplifier of claim 16, wherein the gain medium is an erbium-doped fiber.

19. The amplifier of claim 16 further comprising a monitoring channel.

20. an optical coupler array for optically coupling a plurality of optical fibers transmitting at least two wavelengths W-1 and W-2 of light to an optical device, the optical coupler array comprising: an elongated optical element having a first end operable to optically couple to the plurality of optical fibers and a second end operable to optically couple to the optical device; a common single coupler housing structure; A joint; a plurality of longitudinal waveguides; the plurality of longitudinal waveguides include at least one first waveguide and at least one second waveguide, each of the plurality of longitudinal waveguides having a mode field profile of at least one optical mode and a corresponding propagation constant; at least one of the plurality of longitudinal waveguides is a lost core waveguide; an optical coupler array, wherein at least one of the lost core waveguides is positioned at a coupling distance from another longitudinal waveguide at the coupling portion proximate the second end, the coupling distance and a length of the coupling portion being configured to couple light at wavelength W-1 of at least one core mode of the at least one lost core waveguide with at least one core mode of the other longitudinal waveguide while continuing propagation of light at wavelength W-2 in the other longitudinal waveguide.

21. each of the plurality of longitudinal waveguides is spaced apart from one another, and each of the lost core waveguides comprises an inner lost core, an outer core, and an outer cladding; the inner disappearing core has a first refractive index (N-1) and a first inner core size (ICS-1) at the first end and a second inner core size (ICS-2) at the second end; the outer core longitudinally surrounds the inner core, has a second refractive index (N-2), and has a first outer core size (OCS-1) 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), and has a first cladding size at the first end and a second cladding size at the second end; The common single coupler housing structure includes a medium having a fourth refractive index (N-4) surrounding the plurality of longitudinal waveguides, and the relative magnitude relationship of the first, second, third and fourth refractive indexes (N-1, N-2, N-3 and N-4, respectively) satisfies the following magnitude relationship: N-1>N-2>N-3, and the total volume of the medium of the common single coupler housing structure is a volume greater than the total volume of the inner cores and outer cores of all the lost core waveguides enclosed in the common single coupler housing structure, wherein the first inner lost core size (ICS-1), the first outer core size (OCS-1), and the spacing of the plurality of longitudinal waveguides are simultaneously and stepwise changed along the optical element between the first end and the second end according to a profile until reaching the second inner lost core size (ICS-2) and the second outer core size (OCS-2), wherein the second inner lost core size (ICS-2) is selected to be insufficient in size to conduct light, and the second outer core size (OCS-2) is selected to be sufficient in size to conduct at least one optical mode, whereby light traveling from the first end to the second end escapes from the inner lost core to a corresponding outer core near the second end; 21. The optical coupler array of claim 20, wherein light traveling from the second end to the first end travels from the outer core to a corresponding inner lost core near the first end.

22. 21. The optical coupler array of claim 20, wherein each of the plurality of longitudinal waveguides is embedded in the common unitary housing structure.

23. 21. The optical coupler array of claim 20, wherein, proximal to the second end, the light of wavelength W-1 and the light of wavelength W-2 are coupled into the same mode of another longitudinal waveguide.

24. 22. The optical coupler array of claim 21, wherein the first inner lost core size (ICS-1), the first outer core size (OCS-1), and the spacing of the plurality of longitudinal waveguides are simultaneously and stepwise decreased from the optical element to the coupling portion between the first end and the second end, and are simultaneously and stepwise increased from the coupling portion to the second end until reaching the second inner lost core size (ICS-2) and the second outer core size (OCS-2).

25. 22. The optical coupler array of claim 21, wherein the first inner missing core size (ICS-1), the first outer core size (OCS-1), and the spacing of the plurality of longitudinal waveguides are simultaneously and stepwise decreased along the optical element from the first end to the second end until reaching the second inner missing core size (ICS-2) and the second outer core size (OCS-2).

26. 21. The optical coupler array of claim 20, wherein one of the wavelengths W-1 and W-2 is a signal light, and the other of the wavelengths W-1 and W-2 is a pump light.

27. 27. The optical coupler array of claim 26, wherein the signal light is at 1550 nm and the pump light is at 980 nm.

28. 21. The optical coupler array according to claim 20, wherein one of the wavelengths W-1 and W-2 is a signal light, and the other of the wavelengths W-1 and W-2 is another signal light.

29. 30. The optical coupler array of claim 28, wherein the signal light is 1550 nm and the other signal light is 1310 nm.

30. 21. The optical coupler array of claim 20, further comprising an access area providing access to at least one of the plurality of waveguides between the first end and the second end.

31. 21. The optical coupler array of claim 20, wherein the coupling portions are substantially linear.

32. 21. The optical coupler array of claim 20, wherein the coupling portion has a neck portion.

33. 21. The optical coupler array of claim 20, wherein the plurality of longitudinal waveguides includes at least one waveguide configured not to couple light with other waveguides of the plurality of longitudinal waveguides of the optical coupler array.

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