Abstract:
An apparatus includes a substrate having at least one opening through a top surface to a bottom surface, the substrate also having a first plurality of aligned grooves formed in the top surface and a plurality of fibers, where each of the plurality of fibers are positioned over the opening and in contact with the substrate within a corresponding one of the first plurality of grooves. In another aspect, a method of manipulating fibers includes placing a plurality of fibers on a substrate to extend over an opening formed through a top surface of the substrate to a bottom surface of the substrate, and flowing air through the opening to draw the plurality of fibers down towards the top surface of the substrate, and positioning each of said plurality of fibers in substantial alignment.

Description:
CLAIM OF PRIORITY 
     This application claims priority under 35 USC §119(e) to U.S. patent application Ser. No. 60/275,864, filed on Mar. 14, 2001, the entire contents of which are hereby incorporated by reference. 
     This application also claims priority under 35 USC §119(e) to U.S. patent application Ser. No. 60/275,863, filed on Mar. 14, 2001, the entire contents of which are hereby incorporated by reference. 
     This application also claims priority under 35 USC §119(e) to U.S. patent application Ser. No. 60/341,040, filed on Oct. 30, 2001, the entire contents of which are hereby incorporated by reference. 
     This application also claims priority under 35 USC §119(e) to U.S. patent application Ser. No. 60/340,915, filed on Oct. 30, 2001, the entire contents of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     This invention relates to manipulating and aligning fibers on a substrate. 
     BACKGROUND 
     It is often desirable to align multiple fibers into an array of parallel fibers. One method of accomplishing this is to place fibers into parallel grooves that have been formed in the surface of a substrate. Typically, the placement of the fibers into the grooves is performed manually and requires careful and precise operations by skilled operators. In some cases, it is desirable to align multiple “etched” fibers, i.e., fibers that have been stripped of their outer protective coatings and then etched to reduce the outer diameter of the fiber. 
     SUMMARY 
     According to an aspect of this invention, an apparatus includes a substrate having at least one opening through a top surface to a bottom surface, the substrate having a first plurality of aligned grooves formed in the top surface, and a plurality of fibers, wherein each of the plurality of fibers are positioned over the opening and in contact with the substrate within a corresponding one of the first plurality of grooves. 
     One or more of the following features may also be included: wherein the opening is horizontally longer in a first dimension than a second dimension relative to the top surface of the substrate, and wherein the first plurality of aligned grooves is formed substantially perpendicular to a side of the opening of the first dimension. Wherein the side of the first dimension is as least as wide as the combined diameters of the plurality of fibers. Wherein each of the plurality of fibers has a smaller diameter section held within one of the first plurality of grooves and wherein each of the plurality of fibers has a larger diameter section in contact with the substrate in an area spaced from the first plurality of grooves. Wherein the larger diameter sections of the fibers are placed in contact with each other in a plurality of rows. Wherein the substrate has a second plurality of grooves formed in the top surface that are spaced from the first plurality of grooves, and wherein the second plurality of grooves are substantially aligned with the first plurality of grooves. Wherein each of the plurality of fibers has a smaller diameter section held within one of the first plurality of grooves and a larger diameter section held within one of the second plurality of grooves. Wherein the second plurality of grooves are spaced further apart from each other than the first plurality of grooves. The apparatus may further include a bonding material holding the plurality of fibers to the substrate. The apparatus may further include a holding cap contacting the bonding material. 
     According to a further aspect of this invention an apparatus includes a substrate, the substrate having an opening through a top surface to a bottom surface, a plurality of fibers contacting the substrate substantially in parallel across the opening, wherein the sections of the plurality of fibers in contact with the substrate are substantially equal in diameter, wherein the opening facilitates a flow of air, and a bonding material holding the plurality of fibers to the substrate. 
     One or more of the following features may also be included: Wherein the opening is horizontally longer in a first dimension than a second dimension relative to the top surface of the substrate, and wherein the plurality of fibers are substantially perpendicular to a side of the opening of the first dimension. The apparatus may further include a holding cap contacting the bonding material. 
     According to a further aspect of this invention an apparatus includes a substrate, the substrate having a groove formed in a top surface and recess formed in a bottom surface, wherein the recess intersects with a lower portion of the groove and forms an opening in the lower portion of the groove, and wherein the opening facilitates a flow of air, a fiber, the fiber positioned within the groove, and a bonding material holding the fiber in the groove. 
     One or more of the following features may also be included: A plurality of fibers, wherein the substrate has a plurality of grooves formed in the top surface, wherein the recess intersects with a lower portion of at least one of the plurality of grooves and forms at least one opening in the lower portion of one of the plurality of grooves, and wherein each of the plurality of fibers are positioned within a corresponding one of the plurality of grooves, and a bonding material holding the plurality of fibers in the plurality of grooves. 
     According to a further aspect of this invention a method of manipulating fibers, the method includes placing a plurality of fibers on a substrate to extend over an opening formed through a top surface of the substrate to a bottom surface of the substrate, and flowing air through the opening to draw the plurality of fibers down towards the top surface of the substrate, and positioning each of the plurality of fibers in substantial alignment. 
     One or more of the following features may also be included: Wherein the opening is horizontally longer in a first dimension than a second dimension relative to the top surface of the substrate, and wherein the placing includes placing the plurality of fibers approximately perpendicular to a side of the opening of the first dimension. Wherein the positioning further includes positioning one of the plurality of fibers within a corresponding one of a plurality of grooves formed in the top surface of the substrate proximate to the opening. 
     According to a further aspect of this invention a method of providing an airflow opening in a substrate, the method includes forming a groove in a top surface of a substrate, and forming a recess in a bottom surface of the substrate, wherein the recess intersects a lower portion of the groove, and wherein the intersection between the recess and the groove forms an opening in a lower portion of the groove and facilitates a flow of air through the opening. 
     One or more of the following features may also be included: Wherein forming a groove further includes forming a plurality of grooves in the top surface of the substrate, wherein the recess intersects with a lower portion of at least one of the plurality of grooves. 
     Embodiments of the invention may have one or more of the following advantages. For example, they enable an operator to quickly and easily align a set of fibers on a substrate using the forces associated with a flow of air. They also enable an operator to align fibers with a minimal amount of handling which reduces the possibility of damage to individual fibers. Moreover, by using the apparatus and methods of the invention, the forces associated with a flow of air can be used to hold a set of fibers against a substrate, after the fibers are aligned, and allow an application of bonding material to all of the fibers simultaneously, that is, without requiring tacking or bonding of individual fibers as they are placed. Furthermore, some of the embodiments allow for an alignment of a set of etched fibers into a “fan-out” pattern, i.e., placing a set of etched fiber ends within a set of closely-spaced grooves formed in a substrate, and positioning the larger diameter sections of the same set of fibers into a more widely-spaced pattern in an area away from the grooves. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     DESCRIPTION OF DRAWINGS 
     FIG. 1A shows a first embodiment of a fiber alignment substrate having an airflow slot and one set of grooves; 
     FIG. 1B shows a second embodiment of a fiber alignment substrate having an airflow slot and two sets of grooves; 
     FIG. 2 shows the substrate of FIG. 1A mounted on an airflow fixture; 
     FIG. 3 shows a third embodiment of a fiber alignment substrate having an airflow slot but without grooves; 
     FIGS. 4A-4B shows a stacked set of fibers on a substrate; 
     FIG. 5A shows a grooved substrate with airflow slots; and 
     FIG. 5B shows the grooved substrate of FIG. 5A with airflow slots and airflow holes. 
    
    
     DETAILED DESCRIPTION 
     A set of fibers is aligned on a substrate by placing the fibers across an opening in the substrate and applying an airflow through the opening. A pressure differential created by the airflow causes the fibers to be pulled down onto the substrate. The forces associated with the airflow through the opening enables an operator to adjust the position of the fibers while the airflow holds the repositioned fibers in place. The airflow is continued until a bonding material and a holding cap is applied over the aligned fibers, at which point the airflow is turned off or reduced. 
     Referring to FIGS. 1A and 2, a substrate  100 A includes a set of closely-spaced grooves  130  formed next to an airflow opening  120  and a fan-out area  140  spaced away from opening  120 . An airflow fixture  200  includes an airflow opening  220  formed through the top surface of fixture  200 . Airflow opening  220  aligns with airflow opening  120  when substrate  100 A is placed onto the top surface of fixture  200 . Fixture  200  also includes a hollow airflow connector  210  attached to a side surface of fixture  200  and an airflow channel  212 , formed within fixture  200  and airflow opening  220  to airflow connector  210 . In use, an operator places substrate  100 A onto the top surface of fixture  200  and then places a set of etched fibers  110  across opening  120  and substrate  100 A. A vacuum source (an “airflow source”-not shown) is connected to airflow connector  210  to create a downward airflow  230 , through airflow opening  220  and opening  120 , and an outward airflow  215  from fixture  200 . Downward airflow  230  creates a differential pressure that pulls fibers  110  down onto the top of substrate  100 A, i.e., downward airflow  230  from the top of substrate  100 A causes fibers  110  to experience a higher pressure above opening  220  and  120  and a lower pressure below. 
     If required, the final placement of fibers  110  into grooves  130  is performed manually, by an operator who manipulates fibers  110  with a small instrument, such as a small pick or brush (not shown) while downward airflow  230  is continued. Each of the individual fibers in set  110  has smaller-diameter etched ends  112  and larger-diameter non-etched sections  114 . In use, the operator nudges or brushes the fibers on or near the substrate  100 A. The forces applied by the operator are sufficient to temporarily overcome the airflow forces produced by the airflow through opening  120 . By temporarily overcoming the airflow forces and nudging or brushing the fibers, the operator is able to reposition the etched ends  112  of individual fibers  110  into grooves  130 , while the continued downward airflow  230  causes a downward force to pull fibers  110  toward the substrate and into grooves  130 . Sideward airflow forces  240 A and  240 B are also applied to the set of fibers  110 , as a result of the design of the airflow opening  120  and the nature of the flow of air around the opening. Sideward airflows  240 A and  240 B cause inward forces to be applied to the fibers  110 , i.e., causing the application of forces in the same horizontal plane as the top surface of substrate  100 A but perpendicular to the longitudinal axis of the fibers  110  causing the set of fibers  110  to be pushed toward each other. The sideward airflow forces are controlled by the strength (amount) of airflow applied to airflow connector  210  and by the length of channel  120 . The airflow source is left on to hold etched ends  112  of fibers  110  in grooves  130  while the operator positions non-etched sections  114  of fibers  110  into a more widely-spaced row in fan-out area  140 . The airflow is continued after the fibers  110  are positioned and the operator applies a bonding material (not shown), e.g epoxy or glue, to fibers  110  and substrate  110 A, and then positions a holding cap  150  over and onto the bonding material, at which point the airflow may be turned off or reduced. Holding cap  150  may include a set of grooves formed in the surface contacting fibers  160  that match the alignment pattern of fibers  160 . 
     Referring to FIG. 1B, a second embodiment of a fiber alignment substrate  100 B includes all of features of substrate  100 A, and also includes a second set of grooves  160 B formed in the top surface of substrate  100 B in the fan-out area  140  for holding the non-etched sections  114  of etched fibers  110  in alignment. Grooves  160 B are more widely-spaced than grooves  130  and are formed to an appropriate depth to hold non-etched sections  114  of fibers  110 . The placement of etched fibers  110  on substrate  100 B is similar to that described before in connection with substrate  100 A, i.e., in use, substrate  100 B is placed on airflow fixture  200 , and a flow of air through opening  120  enables an operator to position the etched fiber ends  112  within grooves  130  and then position the non-etched sections  114  of fibers  110  within more widely-spaced grooves  160 B. 
     In the embodiments discussed above the etched fibers  110  were placed on a substrate  100 A or  100 B in a “fan-out” pattern, i.e., a closely-spaced pattern at the etched ends  112  and a more widely-spaced pattern at the non-etched sections  114  of fibers  110 . When placing fibers that have varying outer diameters, or, when placing fiber with varying separation distances across a single substrate, the use of grooves formed in the substrate surface with accurate center-to-center distances between them is necessary to ensure accurate center-to-center distances between the fibers. In contrast, when aligning fibers together that have approximately equal outer diameters, the center-to-center distance between the fibers may be established, in part, by the outer diameter of the fibers and without using grooves. 
     Referring to FIG. 3, when aligning a set of fibers  310  that have approximately equal outer diameters, a fiber alignment substrate  300  includes a top surface that is flat (i.e., without grooves formed in the surface). Substrate  300  includes an airflow opening  320 , and, in use, substrate  300  is placed on airflow fixture  200  and a downward airflow  360  is passed through opening  320 , that enables an operator to align fibers  310  on substrate  300 . Downward airflow  360  causes fibers  310  to be held down on the top surface of substrate  300  while the operator applies a bonding material (not shown) and then a holding cap  350  over and onto the bonding material. Holding cap  350  may include a set of grooves formed in the surface contacting fibers  310  that match the alignment pattern of fibers  310 . 
     In the embodiments discussed above, the shape of the airflow openings  120  and  320  in the top surface of substrate  100 A,  100 B and  300 , respectively, are rectangular relative to the top surface of each substrate, with the longest sides of openings  120  and  320  being roughly perpendicular to the longitudinal axis of the grooves and the fibers being placed. The length of the longer-sides of openings  120  and  320  is slightly longer than the combined width of the diameters of the set of fibers being placed when all of the fibers in the set are placed side-by-side. This longer-side length can be increased to increase the access to manipulate the fibers from the side of or below the set of fibers. 
     As described before in connection with substrate  100 A and  100 B, the placement of etched fibers on a substrate may result in a “fan-out” pattern, i.e., where the etched ends are placed in a more closely-spaced pattern and the non-etched sections are placed in a more widely spaced single row that is spaced away from the etched ends. Referring to FIG. 4A and 4B, an alternative pattern is shown for positioning the larger-diameter section of a set of etched fibers  520 A- 520 N and  530 A- 530 M on a substrate  500 , i.e. placing the non-etched section of fibers  520 A- 520 N and  530 A- 530 M in multiple rows with a first row of fibers  520 A- 520 N placed into a set of grooves  510 A- 510 N formed on a substrate  500  and a second row of fibers  530 A- 530 M placed above the first row  520 A- 520 N. More specifically, the second row of fibers  530 A- 530 M is placed between the grooves formed between the pairs of fibers of the first row of fibers  520 A- 520 N. An airflow  540  is applied next to the fibers through an airflow slot  550  to create a pressure differential above and below fibers  520 A- 520 N and  530 A- 530 N during placement and to hold the fibers in place until bonded together and to substrate  500 . The placement pattern shown in FIGS. 4A and 4B reduces the required width of the substrate  500  for a given number of fibers being placed. 
     Referring to FIGS. 5A and 5B, another way of creating airflow openings through a grooved substrate is to drill or form holes  640  in the lower portion of a set of grooves  612 A- 612 F formed in a top surface of substrate  610 . An airflow from the top surface of substrate  610  and into holes  640  causes a pressure differential above and below the holes  640  which may be used to manipulate and hold fibers within the grooves  612 A- 612 F. However, aligning smaller-diameter etched fibers as closely as possible requires grooves that are more closely spaced and shallower than the grooves required when aligning full-diameter fibers. More specifically, in one application, the etched fibers ends may be on the order of 50 um in diameter and require a set of grooves each of which are approximately 50 um wide and 50 um in depth. To avoid removing too much material from these closely-spaced grooves when forming or drilling holes  640 , the maximum diameter of the hole is limited. Therefore, the fabrication of the holes is difficult and requires a large number of holes to achieve the desired airflow through the grooves. An alternative way of creating airflow openings through a grooved substrate  610  is to create (for example, by an etching process) a recess  620  in the back of substrate  610  that intersects with the lower portion of grooves  612 A- 612 F, thereby creating openings  630  in the lower portion of grooves  612 A- 612 F. By forming recess  620  to a known depth into the back of substrate  610 , openings  630  are created that allow the desired airflow but without causing the removal of an excessive amount of material from grooves  612 A- 612 F. 
     A problem with some bonding materials and methods is that voids may be created and may remain in the cured bonding material, e.g., air bubbles. Typically, following bonding and curing, the substrate and fiber ends are ‘lapped back’ to a desired length and/or angle. The lap back procedure uses a grinding material to grind off and polish the fiber ends and the substrate, and, therefore it exposes voids in the bonding materials. Lapping back a fiber that is near a void in the bonding material may cause the fiber to shift and/or be damaged. To address the problem of voids in the bonding material, in an embodiment, the airflow is left on during the application of the bonding material and the holding cap or holding substrate. The differential pressures created by the airflow cause the bonding material to be drawn into the grooves and along the fibers to even out the application and reduce the number of voids between the fibers, the holding cap or holding substrate. 
     Though we have described specific embodiments, we do not intend to imply there are not other ways to implement some of the features of those embodiments. For example, we mentioned epoxy or glue as the means by which various elements are attached to each other. However, any appropriate method which affixes one element to another could be used, such as fusing or soldering. If the bonding material requires thermal curing, the fiber alignment substrate and/or the airflow fixture may be placed in an oven to speed the curing. The holding cap may be larger or smaller than shown in the attached figures and may contact not only the aligned fibers held within grooves but may also contact the non-etched fiber sections placed in the fan-out areas. Also, although a single rectangular slot placed directly behind grooves in the substrate was described, any number of through holes of various shapes, sizes and locations could also be used to hold the fibers against the substrate and to orient the fibers relative to one another. In addition, other hole shapes, sizes and locations may be used to aid in the application of bonding material. Also, instead of having an operator manipulate the fibers to position them, an automated mechanical arm with a tool of the appropriate size could be used to manipulate the fibers, for example, from either the side of the fibers or through the airflow opening below the substrate, to raise, and position the fibers. The vacuum source described previously may be implemented as a vacuum pump or as a “Bernoulli effect” vacuum generator, for example. 
     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.