WO2002103403A2

WO2002103403A2 - Method of forming an ordered optic fiber array and connector arrangement for same

Info

Publication number: WO2002103403A2
Application number: PCT/US2001/043222
Authority: WO
Inventors: Armin Plichta; Peter Brix; Klaus Gerstner; Dirk Schlatterbeck; Michael Weisser; Martin Sommer; Robert A. Rubino, Jr.; Jeffrey A. Bonja; Richard Strack; Inka Henze
Original assignee: Schott Glas Carl-Zeiss-Stiftung Trading As Schott Glas And Carl-Zeiss-Stiftung; Carl Zeiss AG; Schott Glaswerke AG
Current assignee: Schott Glas Carl-Zeiss-Stiftung Trading As Schott Glas And Carl-Zeiss-Stiftung; Schott AG; Carl Zeiss AG
Priority date: 2000-11-16
Filing date: 2001-11-16
Publication date: 2002-12-27
Anticipated expiration: 2003-05-16
Also published as: WO2002103403A3; AU2001297945A1

Abstract

A method of forming an ordered optic fiber array is provided by forming an array of holes (12) in a glass block (10) based on an enlarged pattern of a desired precision array, heating and drawing the glass block from a first end thereof, and reducing an outside dimension of the glass block and the array of holes to a predetermined size for the precision array. A portion of the alignment block body (18) is separated to form at least one fiber alignment plate (14), and optic fibers (22) are attached. This can be used in a connector arrangement (30) for optic fibers (22) having first and second fiber alignment plates (32, 34) being located on a floating mount. Alignment structures are located on the alignment plate (16) for precise alignment. Another method of assembling an ordered optic fiber array can be used in which optic fibers are positioned with a computer-controlled manipulator and adhered to a substrate.

Description

[0001] METHOD OF FORMING AN ORDERED OPTIC FIBER ARRAY AND CONNECTOR ARRANGEMENT FOR SAME

[0002] BACKGROUND

[0003] The present invention relates to methods of assembling and aligning optic fibers into two-dimensional arrays, and a connector arrangement that can be utilized with such arrays.

[0004] Optic signal transmission, for example for transferring digital data within or between computers in a high speed computing system or for other applications, such as digital communications, requires precise alignment of the optic fibers with the signal emitters and detectors in order to avoid loss of light and low coupling efficiency. It was previously known to manually align and bond each fiber in position. However, this was an expensive and time-consuming process that was only commercially feasible for a small number of optic fibers, and is too costly to scale up to the larger arrays currently being contemplated and used for optical data transfer.

[0005] One known system which attempts to address this utilizes perforated guide and securing plates having a desired array of apertures formed by photolithographic means. The apertures are arranged to match a desired emitter or detector array or may be used on opposing sides of a mating coupling for a bundled array of optic fibers. However, each fiber must be individually inserted into an aperture and secured, and photo-lithographic etching processes produce funnel shaped holes, due to the longer etchant exposure time near the surface of the plate. This allows the fiber ends to be inserted at an angle, instead of normal to the face of such plates, unless multiple plates are utilized, which increases the production costs and can make assembly more difficult since the fiber ends must each be inserted through two aligned openings. [0006] The assembled array of ends is preferably mounted in a coupling body, which can then be connected to an opposing coupling half, or can be connected directly to an emitter or detector array. Such connections require precise alignment in order to avoid coupling losses. This alignment is generally done utilizing pins on one side, with complementary openings in the other side which must be precisely sized and aligned in order to accurately align the optic fiber ends, which can be as small as 10 microns in diameter. This type of arrangement is prone to damage and wear with repeated use, and often results in poorer alignment and optical signal losses increasing due to coupling inefficiencies. This is especially true for the common arrangement which utilizes metallic alignment pins arranged on the coupling body which are inserted into holes in a polymer or silicon based substrate. The assembly of the pins in a precision manner with one side of the coupling also introduces another step as well as additional costs in production. [0007] It would be desirable to provide an improved method of forming an optic fiber array and a connector which would both reduce cost and increase the connector life by improving upon the conventional alignment plate processes. [0008] It would also be desirable to have the possibility of forming such optic fiber arrays without the need for such precision plates or other auxiliary alignment structures. By definition, apertures in such alignment plates must have a greater diameter than the diameter of the fibers to be inserted therein, compromising the positional accuracy of the placed fiber. The manufacture of such perforated plates or other alignment structures is also expensive due to the required positional precision for locating the optic fibers. Spacing between fibers is also limited due to the required areas between perforations in an alignment plate, or due to the thickness of stackable V-groove plates which have also been used in the past to assemble an ordered two-dimensional array of optic fibers. [0009] SUMMARY

[0010] Briefly stated, the present invention provides a method of forming an ordered optic fiber array. The method includes the steps of (a) forming an array of holes in a glass block based on an enlarged pattern of a desired precision array, (b) heating and drawing the glass block from a first end thereof, reducing an outside dimension of the glass block and the array of holes to a predetermined size for the precision array to form an alignment block body, (c) separating a portion of the alignment block body to form at least one fiber alignment plate, and (d) attaching optic fibers in the array of holes in the fiber alignment plate. [0011] In another aspect, the invention provides a connector arrangement for optic fibers. The connector arrangement includes first and second fiber alignment plates, with at least one of the first and second fiber alignment plates being located on a floating mount. At least a first type of alignment structure is located on the first fiber alignment plate, and a second complementary alignment structure is located on the second fiber alignment plate.

[0012] In another aspect, the invention provides a method of assembling an ordered optic fiber array. The method includes the steps of: (a) positioning a Mth optic fiber with a computer controlled manipulator so that an end thereof contacts a substrate at a defined mth location, (b) activating an adhesive between the end of the Mth optic fiber and the substrate, and (c) repeating steps (a) and (b) for M= 1 through X optic fibers such that the ends of the optic fibers define the ordered optic fiber array.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The foregoing summary, as well as the following detailed description of the preferred embodiments of the invention will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements shown.

[0015] Figure 1 is a glass block having an array of holes based on an enlarged pattern of a desired precision array used for forming an ordered optic fiber array in accordance with the present invention.

[0016] Figure 2 is a schematic diagram of the glass block of Figure 1 being drawn to form an alignment block body.

[0017] Figure 3 is a cross-sectional view taken along lines 3-3 in Figure 2 showing a separated portion of the alignment block body used to form one fiber alignment plate.

[0018] Figure 4 is a cross-sectional view through the fiber alignment plate of

Figure 3 illustrating the insertion of an optic fiber into one of the holes in the array.

[0019] Figure 5 is a cross-sectional view of first and second fiber alignment plates in accordance with a second embodiment of the invention used for making a connection arrangement.

[0020] Figure 6 is a perspective view showing an alternate embodiment of the alignment features used on the fiber alignment plates.

[0021] Figure 7 is a perspective view of a second alternate embodiment of the alignment structures used on the fiber alignment plates.

[0022] Figure 8 is a perspective view of a computer controlled manipulator for placing optic fibers on a substrate or alignment plate.

[0023] Figure 9 is a cross-sectional view of fibers bonded on a substrate being held in position relative to one another via a cast adhesive or potting compound.

[0024]DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0025] Certain terminology is used in the following description for convenience only and is not considered limiting. The words "right", "left", "lower" and "upper" designate directions in the drawings to which references made. This terminology includes the words specifically noted above, derivatives thereof and words of similar import. Additionally, the terms "a" and "one" are defined as including one or more of the referenced item unless specifically noted. The term "array" as used herein is intended to include any type of two-dimensional arrangement of fiber ends, such as for a flexible image bundle. [0026] Referring now to Figure 1-4, a method of forming an order optic fiber array will be described in detail. Figure 1 illustrates a glass block 10 having an array of holes 12 formed therein. The holes 12 are arranged in a desired pattern which is an enlarged version of a desired precision array holes 16 in a fiber alignment plate 14, as shown in Figure 3. The array of holes 12 in the glass block 10 is preferably formed by boring utilizing a multi-spindle machine. However, the array may be formed by precision boring each hole 12 individually while the glass block 10 is mounted on a precision X-Z table and is indexed to each individual hole position in the array.

[0027] As shown in Figure 2, the glass block 10 is heated and drawn in a glass drawing tower. At least a portion of the glass block 10 to be drawn is heated utilizing heaters 20, and the block 10 is than drawn to reduce an outside dimension of the glass block 10 and the array of holes to a predetermined size for the precision array in order to form an alignment block body 18. The draw can be done as a single draw, or in a multi-draw process.

[0028] A portion of the alignment block body 18 is separated to form at least one fiber alignment plate 14, as shown in Figure 3. Preferably, the precision drawing process produces an alignment block body which can be separated into many fiber alignment plates having nearly identical precision arrays of holes 16 formed therein with the desired spacing and tolerance. Due to the precise drawing process, tolerances of +/- 0.0001 in the array of holes 12 in the glass block 10 are also reduced along with the relative size and spacing of the holes, so that tolerances on the order of a few microns can be obtained. Additionally, the sides of the holes 16 in the precision array have straight side walls, which eliminates the problem of the funnel shaped holes produced by photo lithographic etching methods. [0029] To form an optic fiber array, optic fibers 22 are inserted in the precision array of holes 16 in the fiber alignment plate 14. This can be done manually or using an automated insertion method. Once the optic fibers 22 are inserted into the holes 16 of the fiber alignment plate 14 and held in position, for example with a UV curable adhesive, to form the array, the free end is preferably ground and polished for low loss insertion and transmission of optic signals. The alignment plate 14 provides the advantage of holding all of the fiber ends generally normal to the surface of the plate due to the straight sided holes 16 in the precision array. This provides an improvement over the prior known alignment plates, which required two separate plates in order to accurately hold the fibers. [0030] Referring to Figure 5 , in order to make a connector arrangement 30 for optic fibers, first and second fiber alignment plates 32 and 34 are provided, with at least one of the first and second fiber alignment plates 32, 34 being located on a floating mount 36. The fiber alignment plates 32, 34 may be formed in the manner described above in connection with the fiber alignment plate 16, which has preferably been machined or etched in order to form an alignment structure. Preferably, the first fiber alignment plate 32 includes a first type of alignment structure 38, and a second complementary alignment structure 40 is located on the second fiber alignment plate 34. In the embodiment shown in Figure 5, the first type of alignment structure 38 may be a protrusion and the second type of alignment structure 40 may be a matching opening. As shown in Figure 5, a combination of first and second alignment structures 38, 40 may be used on each of the first and second fiber alignment plates 32, 34 such that the first fiber alignment plate 32 includes a protrusion 38 and an opening 40' and the second fiber alignment plate 34 includes a complementary opening 40 and a complementary protrusion 38'. [0031] The alignment structures 38, 40 are preferably produced by a semiconductor lithographic process on the fiber alignment plates 32, 34. The array of holes 42 which receive the optic fibers 22 may also be produced by lithographic means or by the method as described above. Alternatively, the fiber alignment plates 32, 34 could be in the form of substrates without fiber receiving holes to which the ends of optic fibers arranged in an ordered array have been bonded. [0032] Preferably, the first fiber alignment plate 32 is located on the floating mount 36, and the floating mount is formed by an elastic material located in a plug body 44. The elastic material may be a synthetic or natural rubber or any other suitable elastic material. Preferably, the elastic material allows movement of at least 10 microns in the X (left-right) and Z (into and out of paper) directions. Additionally, the elastic material allows and angular displacement of up to 5 ° about the Y (vertical) axis. The elastic material used to form the floating mount 36 is also compressible and exerts pressure against the other of the first and second alignment plates 32, 34 which does not include the floating mount 36 in order to provide firm contact between the alignment plates 32, 34 in order to provide a low loss connection.

[0033] Referring now to Figure 6, an alternate alignment structure is shown on the first and second fiber alignment plates 32, 34. Two V-grooves 48, 50, are formed in the face of the first fiber alignment plate 32. Three corresponding protrusions 52, 54, 56 are located in the second fiber alignment plate 34. These protrusions 52, 54, 56 provide the required X-Z alignment for the fiber alignment plates 32, 34 so that the corresponding ordered optic fiber arrays connected to the alignment plates 32, 34 are aligned.

[0034] Referring to Figure 7, a second alternate arrangement of the first and second type of alignment structures is shown on the first and second fiber alignment plates 32, 34. The first type of alignment structure located on the first fiber alignment plate 32 includes a centrally located depression 58 and a radially extending groove 60, which preferably extends in the X direction. The second alignment structure on the second fiber alignment plate 34 includes two protrusions 62 and 64. The central protrusion 62 centers the first and second fiber alignment plates 32, 34 with respect to each other, and the second protrusion 64 provides the correct angular alignment of the fiber alignment plates 32, 34. The first and second types of alignment structures as noted above are intended to merely exemplary, and those skilled in the art will recognize that other types of fiber alignment structures may be provided, if desired.

[0035] One or both of the fiber alignment plates 32, 34 may be mounted in plug bodies in order to form two mating plug halves which can be utilized to form the connector arrangement. Alternatively, one of the first and second fiber alignment plates 32, 34 may be a faceplate that does not include any holes. The faceplate would be mounted directly on an array of emitters or detectors and allow coupling of an ordered optic fiber array utilizing a fiber alignment plate 32, which is preferably mounted on a floating mount 36.

[0036] An alternate method of forming an ordered fiber optic array without the use of a fiber alignment plate is also provided. Referring now to Figures 8 and 9, in accordance the alternate method, a computer controlled manipulator 110, which preferably allows movement in the X, Y and Z directions is utilized. The computer controlled manipulator 110 has a holder 112 which can hold an optic fiber 114 at the end of a manipulator arm 116. The optic fiber 114 is positioned with the computer controlled manipulator 110 so that an end 118 thereof contacts a substrate 120 at a defined location. An adhesive is activated between the end 118 of the optic fiber 114 and the substrate 120. These steps are repeated for all of the required fibers for an optic fiber array. If the optic fiber 114 is considered to be a Mth optic fiber, then these steps are repeated for M=l through X optic fiber optic fibers, where X= the total number of optic fibers 114 required for the array, so that the ends 118 of the X optic fibers 114 are positioned to define the ordered optic fiber array and are held in position by the adhesive.

[0037] In order to assure precise positioning, preferably the substrate 120 comprises a faceplate which is mounted over a detector array having a plurality of optic signal detectors located in the desired positions. Preferably, each optic fiber 114 is connected to an optic signal emitter 130 which sends an optic signal toward the substrate 120 through the end 118 of the optic fiber. While gross positioning down to ten thousandths of an inch can be achieved using the computer controlled manipulator 110 based on a predetermined positioning program, the exact position of the optic fiber end 118 can be adjusted through a feedback system by sensing the optic signal strength of the signal from the optic signal generator 130 utilizing the array of detectors 140 upon which the substrate 120 is positioned. [0038] The adhesive used for bonding the ends 118 of the optic fibers 114 to the substrate 120 may be placed on the ends of the optic fiber 114 or may be placed upon the face of the substrate 120. The adhesive may be UV curable or may be a contact type adhesive which adheres upon contact. Alternatively, the adhesive may be applied by an applicator connected to the manipulator arm which places a drop of adhesive at the edge of the end 118 where it contacts the substrate 120. Preferably, if adhesive is applied utilizing a separate applicator, it is applied symmetrically on opposing sides of the optic fiber 114 to ensure that the optic fiber is not tilted by the adhesive curing on one side only of the optic fiber end 118. However, depending upon the adhesive, asymmetric application may be possible if the tilting of the optic fibers 114 is uniform. For a UV curable adhesive, preferably the adhesive may be activated by directing UV light through the optic fiber 114 using the optic signal generator 130 after the optic fiber 114 is positioned. [0039] While an array may be formed utilizing the substrate, as shown in

Figure 9, it is preferable that the ends of the optic fibers 114 are affixed together utilizing an adhesive or a potting compound 132 which is poured or molded around the optic fibers 114 above the substrate 120. The substrate 120 may be removed and the ends of the optic fibers cut and polished in order to form an ordered optic fiber array.

[0040] While the preferred embodiments of the invention have been described in detail, the invention is not limited to the specific embodiments described above, which should be considered as merely exemplary. Further modifications and extensions of the present invention may be developed, and all such modifications are deemed to be within the scope of the present invention as defined by the appended claims.

Claims

CLAIMS What is claimed is:

1. A method of forming an ordered optic fiber array, comprising: forming an array of holes 12 in a glass block 10 based on an enlarged pattern of a desired precision array; heating and drawing the glass block from a first end thereof, reducing an outside dimension of the glass block and the array of holes to a predetermined size for the precision array to form an alignment block body; separating a portion of the alignment block body to form at least one fiber alignment plate; and attaching optic fibers in the array of holes in the fiber alignment plate.

2. The method of claim 1, further comprising separating the alignment block body into a plurality of fiber alignment plates.

3. The method of claim 1, wherein the array of holes in the glass block is formed by boring utilizing a multi-spindle machine.

4. The method of claim 1, further comprising mounting the fiber alignment plate in a floating arrangement on one side of a connector arrangement.

5. A connector arrangement for optic fibers, comprising first and second fiber alignment plates, at least one of the first and second fiber alignment plates being located on a floating mount; and at least a first type of alignment structure located on the first fiber alignment plate, and a second complementary alignment structure located on the second fiber alignment plate.

6. The connector arrangement of claim 5, wherein the alignment structures are produced by a semiconductor lithographic process.

7. The connector arrangement of claim 6, wherein the first alignment structure is a V-groove, and the second alignment structure is one of a complementary protrusion or a spherical bump.

8. The connector arrangement of claim 5, wherein the floating mount is an elastic material located in a plug body.

9. The connector arrangement of claim 8, wherein the elastic layer allows movement of 10 microns in the x and z directions, and allows an angular displacement of up to 5 °.

10. The connector arrangement of claim 9, wherein the elastic material is compressible and exerts pressure against the other of the first and second alignment plates.

11. Method of assembling an ordered optic fiber array, comprising:

(a) positioning a Mth optic fiber with a computer controlled manipulator so that an end thereof contacts a substrate at a defined mth location;

(b) activating an adhesive between the end of the Mth optic fiber and the substrate; and

(c) repeating steps (a) and (b) for M= 1 through X optic fibers such that the ends of the optic fibers define the ordered optic fiber array.

12. The method of claim 11, further comprising:

(d) affixing the ends of the optic fibers together; and (e) removing the substrate.

13. The method of claim 11, the adhesive is a UV curable adhesive, and the adhesive is activated by directing UV light through the Mth optic fiber after it is positioned.

14. The method of claim 11, further comprising sensing when the Mth optic fiber is aligned in the mth location by monitoring an optic signal transmitted through the Mth fiber.

15. The method of claim 11, wherein the adhesive is placed on one of the ends of the optic fibers and the substrate.

16. The method of claim 11, wherein the adhesive is applied automatically by an applicator after the end of the Mth optic fiber contacts the substrate.

17. The method of claim 16, wherein the adhesive is applied symmetrically on opposing sides of the Mth optic fiber.