Collimator array and method and system for aligning optical fibers to a lens array

What is claimed is:

1. A method for aligning optical fibers to a lens array having a substrate with a front surface providing a plurality of lenses in said lens array and a back surface for input or output of light for said lenses, said method comprising the steps of:

providing a planar reflective surface facing said front surface of said lens array;

locating the end of one of said fibers adjacent said back surface of said lens array to face one of said lenses of said array;

propagating light through said one of said fibers and said lens facing the fiber to said planar reflective surface, and receiving returned reflected light from said reflective surface through said one of said fibers and the lens facing the fiber;

adjusting the position of the end of said one of said fibers to change the amount of said returned reflected light received by the fiber to determine when the end of the fiber is at a position which provides a maximum amount of said returned reflected light; and

attaching the end of said one of said fibers to said back surface of lens array at said position which provides a maximum amount of said returned reflected light, in which said propagating, adjusting, and attaching steps are repeated for each of said fibers to different ones of said lenses of said array.

2. The method according to claim 1 further comprising the step of aligning said planar reflective surface substantially parallel with one of said front and back surfaces of said lens array.

3. The method according to claim 1 further comprising the steps of applying adhesive to the end of said one of the fibers, and attaching step further comprises the step of fixing said adhesive when the end of said one of said fibers is at said position providing a maximum amount of said returned reflected light.

4. The method according to claim 3 wherein said adhesive is a ultraviolet light curable adhesive, and said fixing step is carried out by applying ultraviolet light to cure said adhesive.

5. The method according to claim 1 wherein each end of said fibers has a ferrule through which the fiber extends and said ferrule has a front surface substantially planar with the end of said fiber.

6. The method according to claim 5 wherein said locating and adjusting steps are carried out with the aid of a holder having a surface shaped to receive said ferrule of one of said fibers and one or more openings to said surface of said holder, in which the said ferrule has an outer surface of which at least a portion is retained on said surface by said vacuum through said openings, and said holder has one or more stages coupled to said holder for translating said holder in different dimensions, and the end of each of said fibers is released from said holder after said attaching step to enable another one of said fibers to be retained in said holder for said locating and adjusting steps.

7. The method according to claim 5 wherein said locating step further comprises the steps of:

locating said end of said one of said fibers in said ferrule at a distance from said substrate to enable placement of adhesive upon said end of said fiber in said ferrule;

placing a drop of adhesive upon said end of said fiber in said ferrule; and

locating said end of said fiber in said coupler to a distance from said substrate which provides a gap into which said adhesive is located between the end of said one of said fibers and said back surface of said lens array, and wherein said attaching step further comprises the step of fixing said adhesive to bond said one of said fibers to said back surface at said position which provides a maximum amount of said returned reflected light.

8. The method according to claim 5 further comprises the steps of:

applying adhesive to the end of said one of the fibers; and

providing one or more regions along the front portion of the ferrule providing said front surface of the ferrule for retaining said adhesive when placed upon the end of the fiber and positioned adjacent said back surface of said lens array, wherein said attaching step further comprises the step of fixing said adhesive when the end of said one of said fibers is at said position providing a maximum amount of said returned reflected light.

9. The method according to claim 8 wherein said front portion of each said ferrule is chamfered, beveled, or has at least one groove providing a canal in said front surface of said ferrule.

10. The method according to claim 8 wherein said front surface of each said ferrule is angled with respect to said back surface of said lens array to provide said regions.

11. The method according to claim 8 wherein said front surface of each said ferrule is angled with respect to said back surface of said lens array, said front portion of each said ferrule is chamfered to provide said regions.

12. The method according to claim 1 wherein said locating, projecting, adjusting, and attaching steps are carried out for each of said fibers to different ones of said lens in succession in accordance with the order of said lenses in said array.

13. The method according to claim 1 wherein said planar reference surface is part of a mirror.

14. The method according to claim 1 wherein said projecting step further comprises providing light from a laser and passing said light through optics to said one of said fibers, and said adjusting step further comprises providing a detector for measuring the amount of reflected light in which said optics pass returned reflected light to said detector from said same one of said fibers.

15. The method according to claim 1 wherein at least said adjusting step is carried out automatically under control of a computer system.

16. The method according to claim 1 wherein said moving step comprising the step of moving the fiber interactively between two or more orthogonal dimensions until the fiber is at a position which provides a maximum amount of said returned reflected light.

17. A system for aligning optical fibers to a lens array comprising:

a lens array on a substrate having a back surface and a front surface providing a plurality of lenses in an array;

a plurality of optical fibers each having two ends in which one of said ends is positioned in a ferrule;

a reference member having a planar reflective surface facing said front surface of said lens array;

means for individually locating each of said fibers at their ferrule adjacent said back surface of said lens array to face a different one of said lenses of said array;

means for each of said fibers when located adjacent said lens array for propagating light through the fiber and said lens facing the fiber to said planar reflective surface, and receiving returned reflected light from said reflective surface of said reference member through the fiber and the lens facing the fiber;

means for each of said fibers when located adjacent said lens array for adjusting the position of the end of the fiber to change the amount of returned reflected light received by the fiber to determine when the fiber is at a position which provides a maximum amount of said returned reflected light; and

means for attaching the end of said fibers to said lens array at said position which provides a maximum amount of said returned reflected light.

18. The system according to claim 17 further comprising means for positioning one of said front and back surfaces of said lens array substantially parallel to said reflective surface of said reference member.

19. The system according to claim 18 wherein said means for positioning one of said front and back surfaces of said lens array comprises:

one or more stages coupled to said lens array to enable at least pivoting of said lens array on one or more rotational axes; and

means for illuminating and collecting reflected illumination at one or more wavelengths from said reference surface and one of said front and back surfaces of said substrate; and

means for determining when said reference surface of said reference member and said one of said front and back surfaces are substantially parallel in accordance with said reflected illumination.

20. The system according to claim 17 wherein said lenses provide for one of collimating and converging light from said fibers.

21. The system according to claim 17 wherein said locating means provides a gap between said end of each fiber to said lens array in which adhesive is located in said gap for enabling said attaching means when said end of fiber is at a position providing a maximum amount of reflected light.

22. The system according to claim 17 wherein said locating means and adjusting means is enabled at said ferrule for each of said fibers by a holder and one or more stages coupled to said holder capable of positioning said holder.

23. The system according to claim 22 wherein said holder having a surface shaped to receive said ferrule of one of said fibers and one or more openings to said surface of said holder, in which the ferrule is retained on said surface by vacuum through said openings.

24. The system according to claim 23 further comprising means for providing and controlling said vacuum to said holder.

25. The system according to claim 23 wherein said vacuum is applied to openings of said holder at one or more levels providing different amounts of suction, and said locating means enables said holder with said one of said fibers with said vacuum at a low level to allow said end of said one of said fibers to slip in said holder when said end of the fiber reaches said back surface of said lens array, and then said vacuum at a high level to position the end of said one of said fibers with respect to the back surface of the lens array.

26. The system according to claim 17 further comprising

means for applying adhesive to the end of said one of the fibers, wherein each said ferrule of said fibers has one or more regions along the front portion of the ferrule providing said front surface of the ferrule for retaining excessive said adhesive when placed upon the end of said one of said fibers and positioned adjacent said back surface of said lens array, and said attaching means having means for bonding said adhesive to said couple said fiber to said substrate.

27. The system according to claim 26 wherein said front portion of each said ferrule is chamfered, beveled, or has at least one groove providing a canal in said front surface of said ferrule.

28. The system according to claim 26 wherein said front surface of each said ferrule is angled with respect to said back surface of said lens array to provide said regions.

29. The system according to claim 26 wherein said front surface of each said ferrule is angled with respect to said back surface of said lens array, said front portion of each said ferrule is chamfered to provide said regions.

30. The system according to claim 17 further comprising means for maintaining the substrate of said lens array in a fixed relationship with said reflective surface of said reference member.

31. A system for aligning optical fibers to a lens array comprising:

a lens array on a substrate having a back surface and a front surface providing a plurality of lenses in an array;

a plurality of optical fibers each having one end for attachment to the lens array;

a reference member having a reflective surface facing said front surface of said lens array;

means for locating the one end of each of said fibers adjacent said back surface of said lens array to face a different one of said lenses of said array;

means for each of said fibers when located adjacent said lens array for propagating light through the fiber and said lens facing the fiber to said reflective surface, and receiving returned reflected light from said reflective surface of said reference member through the fiber and the lens facing the fiber;

means for each of said fibers when located adjacent said lens array for adjusting the position of the end of the fiber to change the amount of returned reflected light received by the fiber to determine when the fiber is at a position which provides a maximum amount of said returned reflected light; and

means for attaching the end of said fibers to said lens array at said position which provides a maximum amount of said returned reflected light.

32. The system according to claim 31 wherein at least one end of each of said fibers has a ferrule through which the fiber extends and said ferrule has a front surface substantially planar with the end of said fiber, wherein said attaching means comprises means for attaching the end of fibers by an adhesive material, and each said ferrule having at least one region along its front surface for retaining any excessive amounts of said adhesive.

33. A collimator array comprising:

an array of a plurality of lenses located on a substrate having a back surface;

a plurality of optical fibers each having one end coupled by adhesive to said back surface of said substrate in optical communication to a different one of said lenses; and

a ferrule at said one end of each of said fibers having at least one region for retaining excess of said adhesive joining said the fiber to said lens array to avoid the adhesive protruding upon said back surface of said substrate.

34. The collimator array according to claim 33 wherein said ferrule at said one end of each of said fibers is one of chamfered, angled, chamfered and angled, or has at least one groove, to provide said region for retaining excess adhesive.

35. A collimator array comprising an array of a plurality of lenses located on a substrate having a substantially flat back surface in which each said array has an optical axis, and a plurality of optical fibers each having one end coupled by adhesive to the part of said back surface of said substrate being substantially flat and coaxially with the optical axis of a different one of said lenses, in which each of said fiber are individually positioned with respect to said array.

36. A system for attaching optical fibers to a lens array comprising:

a lens array on a substrate having a back surface and a front surface providing a plurality of lenses in an array;

a plurality of optical fibers each having one end for attachment to the lens array;

a holder for retaining the end of each one of the fibers for attachment to the lens array having stages for moving the holder, in which said holder is located adjacent said back surface of said lens array to face one of said lenses of said array;

a reference member having a reflective surface facing said front surface of said lens array;

a source for illumination and optics for illuminating the one of said fibers in said holder with illumination from said source and receiving returned illumination from the one of said fibers in said holder from said reflective surface of said reference member via one of said lenses of the lens array;

a detector for receiving at least the returned illumination from said optics and measuring the amount of the returned illumination;

each of said fibers when retained in said holder is located using one of more of said stages to a position enabling a maximum amount of said returned illumination at said detector in which said returned illumination propagated through the fiber through one of said lenses of the array from the reflective surface; and

adhesive material located between each of said fibers when retained in said holder and the back surface of said lens array capable of attaching the fiber to the lens array when the fiber is at the position providing maximum amount of said returned illumination at said detector.

37. The system according to claim 36 wherein the one end of each of said fibers for attachment to the array extends through a ferrule.

38. The system according to claim 37 wherein each said ferrule has a front surface having at least one region for retaining any excessive amounts of said adhesive when attached to said lens array.

39. The system according to claim 36 wherein said substrate of the lens array is located in a fixture having one or more stages for indexing the lens array to present each of said fibers when retained in said holder to a different lens of the array for attachment of the fiber to the array.

40. The system according to claim 39 wherein said stages of said holder present each of said fibers when retained in said holder to a different lens of the array for attachment of the fiber to the array.

41. The system according to claim 36 further comprising a computer system coupled to said stages of said holder to enable locating each of fibers when retained in the holder to a position enabling a maximum amount of said returned illumination at said detector.

42. The system according to claim 36 wherein said stages of said holder are manually positioned to locate each of fibers when retained in the holder to a position enabling a maximum amount of said returned illumination at said detector.

43. The system according to claim 36 wherein the amount of returned illumination detected by the detector is recorded for each of said fibers when attached to said lens array to provide a measure of insertion loss.

Description Submit all comments and votes

FIELD OF THE INVENTION

The present invention relates to a method and system for aligning optical fibers to a lens array, and relates particularly to, a method and system for aligning optical fibers to a lens array in which each fiber is aligned at the focal point of a different lens of the array and then attached to the array, such that beams emitted from lenses of the array are pointing in the same direction, i.e., parallel to each other, when light is provided to their respective fibers. The invention further relates to a collimator array provided by the assembly of the lens array and such aligned optical fibers.

BACKGROUND OF THE INVENTION

In the fabrication of optical devices, it is often desirable to produce a set of collimated optical signals (e.g., beams), each encoded with information from a different source. Monolithic one or two-dimensional arrays of collimating elements may be used in which each collimating element is coupled to a different optical path (e.g. an optical fiber) to provide this set of collimated optical signals. Such a lens array, referred to as a microlens array herein, may consist of a plurality of lens elements formed into a single substrate, or plate, of material, or integrated onto such substrate. This material may be, for example, of plastic (polymers), glass, silicon, or silica. Each optical fiber is attached to the back surface of the substrate for illuminating a different one of the lenses in the array. The end of each optical fiber should be aligned at the focal point of its respective lens to enable optimal light beam collimation, focusing, or maximum light coupling (minimum insertion loss) into another similarly produced lens. Moreover, such alignment should provide collimated beams aligned parallel to each other from lenses when light is provided to their respective fibers. Positioning the optical fibers so that the optical beams emerging from the collimator array are highly collimated and collimated parallel to each other is a difficult task, becoming even more difficult with increased density of lens in the array.

One possible method of alignment is to use a complex structure of a matrix of optical fibers which may be provided by threading optical fibers into holes of a substrate and then polish the ends of the fibers to be aligned to the array. The complex structure is oriented and attached to the lenses of the array to couple illumination from fibers to lenses of the array. This however does not assure that the ends of the fibers are each properly located at the focal point of each lens, or that one of more of the ends of the fibers are not tilted to effect orientation of beams from lenses.

The complex structure for fiber alignment may be fabricated into one side of the substrate containing the microlens array. For example, U.S. Pat. No. 5,346,583 describes a method for aligning optical fibers with a microlens array in which one side of a substrate contains the microlens array and the other side has an array of circular apertures each aligned with the central axis of one of the lenses of the array. Optical fibers are inserted into these apertures, such that the ends of the fibers are aligned in a common plane with respect to the lenses. The substrates' sides are produced by a photolithographic mask and etching processes on each side of the substrate. This method thus requires two masks, which must be precisely aligned with each other, otherwise the central axis of the lenses will not align with the circular apertures. Laser beams are directed through a slot in each mask for mask-to-mask alignment. This may improve enmasse alignment of optical fibers, but such manufacture increases the cost of the microlens array, and does not account for variations which often occur in the focal length between different microlenses of the array. Thus, it would be desirable to align multiple fibers to a microlens array, without requiring a complex structure for enmasse fiber alignment.

In fiber optic connections, techniques have been developed for aligning an individual optical fiber to a GRIN (graduated refractive index) lens. For example, in U.S. Pat. Nos. 4,509,827 and 4,545,643, a mirrored surface is positioned substantially orthogonal relative to the axis of a GRIN lens to autocollimate a light beam transmitted through a fiber. The fiber is positioned relative to the lens such that the returned signals from the mirrored surface is maximized. An adhesive then secures the fiber to the lens. In a further example of fiber optics connection, U.S. Pat. No. 4,637,683 aligns an optical fiber to a GRIN lens having a reflective surface coating on the side of the lens opposite from the fiber, where the reflective surface provides a reference plane. The optical fiber is positioned relative to the GRIN lens to maximize the reflected light from the reference plane. Such methods of U.S. Pat. Nos. 4,509,827, 4,545,643 and 4,637,683 are limited to alignment of a single fiber to a single GRIN lens rather than alignment of multiple optical fibers to a microlens array.

Other alignment methods for aligning an individual fiber to a lens use transmitted, rather than reflected light. U.S. Pat. No. 5,009,482, describes joining an optical fiber with a spherical lens by detecting the amount of light transmitted by the lens into the fiber, and iteratively positioning the fiber relative to the lens to maximize the amount of detected light. In European Pat. Publication EP 0619505B1, multiple separate GRIN lens are aligned with optical fibers in a structure mechanically providing an optical collimator array. Light is passed along the optical fibers and beams emitted from the GRIN lenses are imaged on a CCD camera and shown on a monitor coupled to the CCD camera. The centers of the beams in the image are used to adjust the position of fibers and lens to provide the desired output from the optical collimation array.

Often optical fiber have a ferrule coupled about one of their ends having a front surface planar with the end of the fiber to be attached to a microlens array. In attaching individual fibers to the array, excess adhesive used in joining the fiber to the array protrudes from the location where the ferrule attaches to the back surface of the lens array's substrate. Often such protruding adhesive forms a bead or runs along the back surface of the array's substrate. This can be a problem since the protruding adhesive can interfere with attachment of other neighboring fibers to the array. Thus, it would be desirable to avoid protruding adhesive in the attachment of fibers to the microlens array.

SUMMARY OF THE INVENTION

Accordingly, it is the principal object of the present invention to provide an improved method and system for aligning optical fibers to a lens array in which each fiber is aligned to a different lens to obtain proper collimation, focusing, or maximum light coupling, without enmasse alignment techniques of the prior art.

It is another object of the present invention to provide an improved method and system for aligning optical fibers to a lens array to obtain optical signals or beams aligned parallel to each other from lenses of the array when respective fibers receive illumination providing such optical signals.

A further object of the present invention is to provide an improved method and system for aligning optical fibers to a lens array in which alignment can be performed either manually, or automatically by a programmed computer.

A still further object of the present invention is to provide an improved method and system for aligning optical fibers to a lens array which avoid excessive adhesive used in joining fibers to the lens array from protruding upon the back surface of the lens array and interfering with attachment of other neighboring fibers to the array.

Briefly described, the present invention embodies a method for aligning optical fibers to a lens array in which the lens array has a substrate with a front surface providing a plurality of lenses in the array, and a back surface for input (or output) of light for the lenses. The method includes providing a planar reflective surface facing the front surface of the lens array, aligning the planar reflective surface substantially parallel with the front surface of the lens array such that the optical axes of the lenses of the array are substantially perpendicular to the planar reflective surface, locating the end of one of the fibers to be aligned adjacent the back surface of the lens array to face one of the lenses of the array, applying an adhesive material, such as ultraviolet light curable liquid adhesive, to the end the fiber, propagating light through the fiber and the lens facing the fiber to the reflective surface, and receiving returned reflected light from the reflective surface through the one of the fibers and the lens facing the fiber, adjusting the position the end of the one of the fibers to change the amount of the returned reflected light received by the fiber to determine when the end of the fiber is at a position which provides a maximum (or peak) amount (or power) of the returned reflected light, and attaching the end of the one of the fibers to the back surface of lens array at the position which provides a maximum amount (or power) of the returned reflected light. Such attachment may be facilitated by using a radiation source that provides ultraviolet light to cure liquid adhesive, in the case where an ultraviolet light curable adhesive is used. The propagating, adjusting, and attaching steps are repeated for each of the fibers to different ones of the lenses of the array until all fibers are coupled to the lenses of the array. Thus, a single reflective surface is provided and each fiber is aligned to maximize the reflected light from this reflective surface received through the fiber and its respective lens, and then the fiber is attached to the substrate. Since each of the aligned fibers and lenses are aligned to the same reflective surface, their beams will be parallel to each other when their respective fibers are illuminated. Although preferably the planar reflective surface is substantially parallel with the substrate of the lens array, the reflective surface need only be in a fixed relationship with the lens array during alignment and attachment of the fibers to the substrate to assure that such beams will be parallel with respect to each other.

A ferrule, or other type of coupler or connector, is provided about each end of the fibers when aligned and attached to the substrate of the lens array. Each ferrule may have one or more regions (structures or features) for retaining excessive adhesive joining the fiber to the lens array to avoid such excessive adhesive protruding upon the back surface of the substrate and interfering with placement of other fibers to the lens array. These regions are located at the front portion or surface of the ferrule facing the array's substrate and provided by a chamfered front surface, a groove providing an annular canal in the front surface of the ferrule, or a combination thereof. The front surface of each ferrule may be angled with respect to the back surface of the substrate to provide the regions with or without being chamfered or having a canal. Alternatively, the fibers may be attached to the lens array without ferrules.

A system embodying the method for aligning optical fibers to a lens (or microlens) array is also provided, including, a lens array having a substrate with a back surface and a front surface providing the lenses of the array, optical fibers each having two ends in which one of ends may be positioned in a ferrule to provide a ferruled fiber, a reference member having a planar reflective surface facing the front surface of the lens array in which the front surface of the lens array is parallel to the reflective surface of the reference member such that the optical axes of the lenses of the array are substantially perpendicular to the planar reflective surface. A vacuum actuated holder is provided capable of retaining the fiber in its ferrule. The holder is pivotable such that when a fiber in its ferrule is retained, the ferrule faces the substrate in a fixed relationship, preferably parallel, to the substrate. Each of the fibers are individually loaded onto the holder and positioned to face a different one of the lenses of the substrate, in which the holder has translation stages capable of moving the end of the fiber in x,y,z orthogonal dimensions. At the end of the fiber an adhesive material is applied, such as an ultraviolet light curable adhesive, with a precise syringe. Each fiber when located adjacent the substrate, a laser beam is directed (propagated) through the fiber and the lens facing the fiber to the reflective surface, and returned reflected light from the reflective surface of the reference member passes through the fiber and the lens facing the fiber onto a detector. Optics are provided to pass light to each fiber and direct returned reflected light to a detector for measuring the amount (or power) of the reflected light. The stages coupled to the holder are each iteratively moved in x, y, or z to adjust the position of the end of the fiber to change the amount (or power) of returned reflected light received by the fiber to determine when the fiber in the coupler has moved to a position which provides a maximum amount (or power) of returned reflected light. The fiber is bonded to the back surface of the substrate at the position which provides a maximum amount (or power) of returned reflected light, such as applying ultraviolet light when an ultraviolet curable adhesive is used. The fiber is released from holder and another fiber is positioned in the holder, and then aligned and bonded to the array's substrate, and so forth until all fibers are attached to the array. For each fiber to be aligned, the lens array is indexed to the next lens in the array by adjusting the position of the substrate of the lens array by using x,y translation stages coupled to the substrate, or the holder of the fiber may be moved using its x,y stages to index to the next lens.

An autocollimator, interferometer, or other aligning mechanism, may be used to locate a reference member providing the planar reflective surface substantially parallel with respect to one or more flat reflective areas on the front or back surface of the lens array's substrate. The autocollimator or interferometer may be used during the alignment of each fiber to assure that the reflective surface is maintained substantially parallel with the substrate.

The movement of the stages of the holder to locate the position of maximum light reflectance may be carried out manually, or automatically by a computer system coupled to the stages and programmed to locate the maximum level (or power) of reflected light. The computer system operates the stages of the holder as a robotic arm to pick up each fiber by its ferrule from a fixture or cassette and locate and align the fiber when in the holder to one of the lenses in the array, as described above. The computer system controls vacuum to holder to retain the fiber in the holder and release the fiber after attachment to the lens array. The computer system may further control stages coupled to the precision syringe, such that prior to alignment of each fiber facing the lens array, the tip of the syringe may be positioned and adhesive applied to the fiber. After alignment of each fiber to a lens array, the computer system may also control the light source for curing the adhesive to bond the fiber to the substrate.

In addition to providing proper alignment, the system may be used to enable measurement of insertion loss for each fiber-lens pair as the lens array is assembled with fibers. This may be achieved by recording the power of the reflected light after each fiber is aligned and attached to the substrate.

A collimator array is also provided having such aligned optical fibers including, an array of lenses located on a substrate having a substantially flat back surface, and optical fibers each having one end coupled by an adhesive material to the back surface of the substrate in optical communication to a different one of the lenses in which each of the fiber are individually positioned with respect to the array. Each of the fibers may have a ferrule having regions for retaining excess adhesive material joining the fiber to the lens array to avoid the adhesive protruding upon the back surface of the substrate.

Although the lens array is described as having convex lens or elements for collimating light from fibers, and are not limited to collimating lenses, as such lens arrays may have lens for converging (or focusing) light. Further, the lens may operate to receive optical signals into the fibers or send optical signals received from the fibers. The lenses of the array may be surface relief, gradient index, or GRIN type lenses, or a combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects, features and advantages of the invention will become more apparent from a reading of the following description in connection with the accompanying drawings, in which:

FIG. 1 is a front view of an example of the convex lens array having a substrate;

FIG. 1A is a side view of the example of a convex lens array of FIG. 1;

FIG. 1B is a front perspective view of another example of a lens array;

FIG. 1C is a back perspective view of the lens array of FIG. 1B in which four ferruled fibers are shown attached;

FIG. 2 is an optical diagram of the end of an optical fiber in a ferrule adhesively coupled to one of the lens of the array of FIGS. 1 and 1B in which proper optical alignment is provided to obtain a collimated light;

FIGS. 3-5 are optical diagrams similar to FIG. 2 showing examples of different optical misalignment of the fiber with respect to one of the lens of the array and its negative effect on collimating light from the lens;

FIG. 6A is a schematic view of the end of an optical fiber in a ferrule adhesively coupled to the back surface of the substrate of the lens array showing the ferrule having no regions, i.e., structures along its front surface, to retain excessive adhesive material;

FIG. 6B is a schematic view of the end of an optical fiber in a ferrule adhesively coupled to the back surface of the substrate of the lens array showing the ferrule having a chamfered front surface to provide regions to enable retaining of excessive adhesive material;

FIG. 6C is a schematic view of the end of an optical fiber in a ferrule adhesively coupled to the back surface of the substrate of the lens array showing the ferrule having an angled front surface and no chamfered regions;

FIG. 6D is a schematic view of the end of an optical fiber in a ferrule adhesively coupled to the back surface of the substrate of the lens array showing the ferrule having an angled front surface with a chamfered front surface to provide regions to enable retaining of excessive adhesive material;

FIG. 7 illustrates the ends of the optical fibers having different types of ferrules with no regions for retaining adhesive material, a chamfered front surface, angled front surface, and annular canal in the front surface of the ferrule when adhesive material is applied to the end of the fiber, and after the ferrules are attach