FAUs including passive alignment adhesive profiles and related methods

1. A fiber optic assembly comprising:

a support substrate having a first surface comprising a plurality of V-grooves;

a signal-fiber array supported on the first surface of the support substrate, the signal-fiber array comprising a plurality of optical fibers disposed in the plurality of V-grooves, wherein each of the plurality of optical fibers comprises a first exposed datum surface at a top of the optical fibers opposite the support substrate and wherein some of the plurality of optical fibers are defined as edge optical fibers and comprise a second exposed datum surface; and

an adhesive, disposed on the plurality of optical fibers and the support substrate, that bonds the plurality of optical fibers to each other and to the support substrate,

wherein the adhesive resides below a plane defined by the first datum surface to not interfere with mating of the first exposed datum surface or the second datum surface, and wherein the second exposed datum surface enables lateral alignment of the fiber optic assembly with a waveguide substrate, and wherein each optical fiber is spaced apart from adjacent optical fibers of the plurality of optical fibers at a precise pitch, and each optical fiber is directly adjacent an adjacent optical fiber.

2. The fiber optic assembly of claim 1 , wherein the fiber optic assembly does not comprise a lid disposed opposite the support substrate.

3. The fiber optic assembly of claim 1 , wherein the adhesive is disposed on the first surface between two optical fibers of the plurality of optical fibers.

4. The fiber optic assembly of claim 3 , wherein the height of the adhesive is less than half of the diameter of an optical fiber of the plurality of optical fibers.

5. The fiber optic assembly of claim 1 , wherein the adhesive is disposed in the plurality of V-grooves and excluded from the first surface between two optical fibers of the plurality of optical fibers.

6. A fiber optic assembly comprising:

a support substrate having a substantially planar surface;

a signal-fiber array supported on the planar surface of the support substrate, the signal-fiber array comprising a plurality of optical fibers, wherein each of the plurality of optical fibers comprises a first exposed datum surface at a top of the optical fibers opposite the support substrate and wherein some of the plurality of optical fibers are defined as edge optical fibers and comprise a second exposed datum surface; and

an adhesive, disposed on the plurality of optical fibers and the support substrate, that bonds the plurality of optical fibers to each other and to the support substrate,

wherein each optical fiber is spaced apart from adjacent optical fibers of the plurality of optical fibers at a precise pitch, and each optical fiber is directly adjacent an adjacent optical fiber, and

wherein the adhesive resides below a plane defined by the first datum surface to not interfere with mating of the first exposed datum surface or the second datum surface, and wherein the second exposed datum surface enables lateral alignment of the fiber optic assembly with a waveguide substrate.

7. The fiber optic assembly of claim 6 , wherein the adhesive comprises an adhesive profile having a plurality of raised peaks over at least a portion of each optical fiber of the plurality of optical fibers.

8. The fiber optic assembly of claim 7 , wherein a third datum surface is defined at a top surface of the adhesive profile defined by the plurality of raised peaks.

9. The fiber optic assembly of claim 8 , wherein the plurality of raised peaks are truncated to the plurality of optical fibers.

10. The fiber optic assembly of claim 8 , wherein the plurality of raised peaks are truncated to define a plurality of planar datum surfaces.

11. The fiber optic assembly of claim 8 , further comprising:

a lid disposed on the third datum surface.

12. The fiber optic assembly of claim 11 , wherein the lid comprises a trench configured to receive at least a portion of the adhesive profile or the plurality of optical fibers.

13. The fiber optic assembly of claim 7 , further comprising:

a photonic integrated circuit (PIC) substrate comprising a plurality of V-grooves configured to receive the plurality of raised peaks.

14. The fiber optic assembly of claim 6 , wherein the height of the adhesive between adjacent optical fibers is less than half of the diameter of an optical fiber of the plurality of optical fibers.

15. A fiber optic assembly comprising:

a support substrate having a planar surface;

a signal-fiber array supported on the planer surface of the support substrate, the signal-fiber array comprising a plurality of optical fibers, wherein each of the plurality of optical fibers comprises a first exposed datum surface at a top of the optical fibers opposite the support substrate and wherein some of the plurality of optical fibers are defined as edge optical fibers and comprise a second exposed datum surface; and

an adhesive, disposed on the plurality of optical fibers and the support substrate, that bonds the plurality of optical fibers to each other and to the support substrate,

wherein each optical fiber is spaced apart from adjacent optical fibers of the plurality of optical fibers at a precise pitch and each optical fiber is directly adjacent an adjacent optical fiber, and

wherein a datum surface is defined on an outer surface of each edge optical fiber of the plurality of optical fibers.

16. The fiber optic assembly of claim 15 , further comprising:

a photonic integrated circuit (PIC) substrate comprising a plurality of waveguides, wherein the plurality of optical fibers is aligned with the plurality of waveguides.

17. The fiber optic assembly of claim 16 , wherein the PIC substrate comprises a notch configured to receive the plurality of optical fibers therein, and

wherein the datum surface on each of the edge optical fibers defines an interface of the plurality of optical fibers, and the notch enabling passive alignment of the plurality of optical fibers to the plurality of waveguides.

18. The fiber optic assembly of claim 14 , wherein the adhesive defines a spacer region on the planar surface, wherein a height of the spacer region corresponds to a depth of the plurality of waveguides below a top surface of the PIC substrate.

19. The fiber optic assembly of claim 13 , wherein the adhesive defines at least one alignment feature configured to enable passive alignment of the fiber optic assembly.

20. The fiber optic assembly of claim 19 , wherein the at least one alignment feature comprises a raised feature.

21. The fiber optic assembly of claim 19 , wherein the at least one alignment feature comprises a recessed feature.

22. The fiber optic assembly of claim 19 , wherein the at least one alignment feature is positioned at a horizontal offset and a vertical offset spaced away from the plurality of optical fibers.

23. A method of fabricating a fiber optic assembly comprising:

placing a signal-fiber array on a first surface of a support substrate, the signal-fiber array comprising a plurality of optical fibers disposed in a plurality of V-grooves disposed on the first surface of the support substrate;

applying an adhesive on the plurality of optical fibers and the support substrate for bonding the plurality of signal optical fibers to each other and to the support substrate,

pressing a release pad onto the adhesive, signal-fiber array, and support substrate;

curing the adhesive;

deforming the release pad and thereby controlling and limiting the flow of the adhesive around the pressed released pad; and

removing the release pad,

wherein a first datum surface is disposed at a top of each of the plurality of optical fibers opposite the support surface, wherein each optical fiber is spaced apart from adjacent optical fibers of the plurality of optical fibers at a precise pitch, and each optical fiber is directly adjacent an adjacent optical fiber.

24. A method of fabricating fiber optic assembly comprising:

placing a signal-fiber array on a planar surface of a support substrate, the signal-fiber array comprising a plurality of optical fibers;

applying an adhesive on the plurality of optical fibers and the support substrate;

pressing a release pad onto the adhesive, signal-fiber array, and support substrate; deforming the release pad and thereby controlling and limiting the flow of the adhesive around the pressed released pad;

curing the adhesive; and

removing the release pad,

wherein each optical fiber is spaced apart from adjacent optical fibers of the plurality of optical fibers at a precise pitch, and each optical fiber is directly adjacent an adjacent optical fiber.