Abstract:
The subject matter disclosed herein relates to a device and method for bundling optical fibers. The device has a receiving channel with a cavity for receiving the optical fibers. A cover with a protrusion is configured to be inserted into the cavity for compression of the optical fibers. The receiving channel has at least one hole in the receiving channel or the cover configured to receive any excess adhesive resulting from the compression of the optical fibers.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to optical fiber bundles and methods for making optical fiber bundles. 
         [0002]    Optical fiber bundles provide a mechanism for transferring light from a light source to a desired location. Such optical fiber bundles are utilized in a variety of fields including fiber-optic communications as well as illumination applications (e.g., medical applications, machining applications, and the like). For example, optical fibers may be used in flexible borescopes to illuminate a confined space and permit visualization. 
         [0003]    Optical fiber bundles are connected to a light source, such as a light emitting diode (LED). The optical fiber bundles are comprised of multiple optical fibers. As light leaves the light source, a portion of the emitted light enters each optical fiber that comprises the optical fiber bundle. A portion of this light is then transferred down the length of the optical fiber bundle to a remote terminus. The light exits the terminus and illuminates the target. The amount of illumination provided is a function of the amount of light that enters the optical fiber bundle. It is desirable to provide a mechanism to reduce the loss of light. Conventionally, optical fibers are fused or epoxied to form optical fiber bundles. The fusing methods require expensive tooling and high heat. The excessive heat can give rise to other processing problems. Epoxied fibers usually have lower packing fraction with around 30% lost light (i.e., 70% core packing fraction). 
         [0004]    The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    The subject matter disclosed herein relates to a device and method for bundling optical fibers. The device has a receiving channel with a cavity for receiving the optical fibers. A cover with a protrusion is configured to be inserted into the cavity for compression of the optical fibers. The receiving channel has at least one hole in the receiving channel or the cover configured to receive any excess adhesive resulting from the compression of the optical fibers. 
         [0006]    In a first exemplary embodiment, a ferrule for bundling optical fibers is disclosed. The ferrule comprises a receiving member with a receiving channel comprising a cavity for receiving the optical fibers. The ferrule includes a cover with a protrusion configured to be inserted into the cavity to compress the optical fibers. At least one hole is present in the receiving channel or the cover that receives any excess adhesive resulting from the compression of the optical fibers. 
         [0007]    In a second exemplary embodiment, an optical fiber bundle is disclosed. The optical fiber bundle comprises a plurality of elongated optical fibers with a ferrule disposed on an end portion thereof. The first ferrule comprises a receiving member with a receiving channel comprising a cavity for receiving the optical fibers. The ferrule includes a cover comprising a protrusion configured to be inserted into the cavity to compress the optical fibers. At least one hole is present in the receiving channel or the cover that receives any excess adhesive resulting from the compression of the optical fibers. 
         [0008]    In a third exemplary embodiment, a method for bundling optical fibers is disclosed. The method comprises the steps of disposing an end portion of an optical fiber within a receiving channel of a receiving member of a ferrule. The receiving channel comprises a cavity for receiving the optical fibers. An adhesive is introduced into the receiving channel. A cover with a protrusion is placed over the receiving channel and inserted into the cavity to compress the optical fibers. Excess adhesive is permitted to flow through a hole in the receiving channel or the cover that is configured to receive any excess adhesive resulting from the compression. The adhesive is permitted to set. 
         [0009]    This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which: 
           [0011]      FIG. 1  is an exemplary schematic depiction of a system for illuminating a target location using a borescope; 
           [0012]      FIG. 2  is a cross-section view of an exemplary optical fiber; 
           [0013]      FIG. 3  is a depiction of an optical fiber bundle that is comprised of a plurality of optical fibers; 
           [0014]      FIG. 4  is a cross-section view of the first ferrule of  FIG. 1 ; 
           [0015]      FIG. 5  is a perspective view of the first ferrule of  FIG. 1  showing holes; 
           [0016]      FIG. 6  is a depiction of a ferrule where the receiving channel has a U-shape; 
           [0017]      FIG. 7  is a depiction of a ferrule where the receiving channel has a circular shape; 
           [0018]      FIG. 8  is a depiction of a ferrule with multiple chambers; 
           [0019]      FIG. 9  is a flow diagram of one method of bundling optical fibers; and 
           [0020]      FIG. 10  is a depiction of another ferrule with multiple chambers. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]      FIG. 1  is an exemplary schematic depiction of a system  100  for illuminating a target location  102  using a borescope  104 . The borescope  104  comprises a light source  106  disposed within a housing  108 . Examples of suitable light sources include light emitting diodes (LEDs), arc lamps, and the like. The housing  108  comprises a fitting  110 . The fitting  110  is shaped to releasably receive a first ferrule  112  that connects to an optical fiber bundle  114 . 
         [0022]    Light from the light source  106  traverses the length of optical fiber bundle  114  from a first end portion  116  to a second end portion  118  where it exits a second ferrule  120 . The second ferrule  120  is substantially identical to the first ferrule  112 . Since the optical fiber bundle  114  is flexible, it can be maneuvered in or through a curved pathway  122  in device  124  to illuminate the target location  102 . In the exemplary embodiment of  FIG. 1 , the first ferrule  112  compresses the optical fibers which comprise the optical fiber bundle to minimize the amount of lost light. 
         [0023]      FIG. 2  is a cross-section view of an exemplary optical fiber  200 . The optical fiber  200  comprises an optically transparent core  202  and a cladding  204 . Space-limited illumination optical fibers attempt to maximize the cross-section area of the core  202  while minimizing the cross-section area of the cladding  202 . Any light that contacts the cladding  204  is not transmitted by the optical fiber bundle and is lost. 
         [0024]    As shown in  FIG. 3 , an optical fiber bundle  300  is comprised of a plurality of optical fibers  200  separated by gaps  302 . Any light that enters the gaps  302  is not transmitted through the length of the optical fiber bundle  300  and is lost, typically as radiated heat. Conventional epoxy packing, wherein the gaps  302  are filled with epoxy, provides about 70% core packing fraction wherein 70% of the cross sectional area is occupied by the core  202  and the remaining 30% is occupied by the cladding  204  and the gaps  302 . Packing by fusing provides about 90% core packing fraction but requires expensive tooling and undesirably high heat. As shown in  FIG. 3 , an adhesive  304  can be added in the gaps  302 . 
         [0025]    The first ferrule  112  (see  FIG. 1 ) provides a mechanism to tightly pack the optical fibers  200  when forming an optical fiber bundle  300 . The resulting optical fiber bundle  300  exceeds the core packing fraction of conventional epoxy packed bundles but does not require the expensive processing conditions of packing by fusing. 
         [0026]    The shape of the first ferrule  112  is designed to match the shape and size of a corresponding light source outlet. For example, a particular light source (e.g., an LED) may have a rectangular shape. Conventionally, a circular optical fiber bundle fails to capture the light that is emitted from the corners of such a rectangular light source. This results in a portion of the light from the light source being lost. Loss of a portion of the light wastes energy, results in excessive heat and is undesirable. Advantageously, the shape of the first ferrule  112  may be controlled to better match the shape of the light source. This results in a more efficient use of the light from the light source. 
         [0027]      FIG. 4  depicts a cross-section of the first ferrule  112  taken perpendicular to the axis of optical fiber bundle  114 . In the embodiment of  FIG. 4 , the first ferrule  112  has a rectangular shape. The first ferrule  112  comprises a receiving member  400  and a cover  402 . The receiving member  400  comprises a receiving channel  404  with a cavity  422  for receiving a plurality of optical fibers  200  (see  FIG. 2 ). Collectively, these optical fibers  200  form the optical fiber bundle  300  (see  FIG. 3 ). The receiving channel  404  is formed by three surfaces of the receiving member  400  including a first surface  406 , a second surface  408  and a third surface  410 . In the exemplary embodiment depicted, the first surface  406  and the second surface  408  are both connected to the third surface  410  to form a monolithic receiving member  400 . In the exemplary embodiment, the cover  402  comprises a lid  412  and a protrusion  414  that extends from the lid  412  to provide a fourth surface  416 . The cover  402  can be monolithic with the lid  412  and protrusion  414  integrated into a single piece. In the exemplary embodiment, the protrusion  414  is a flat protrusion and has a width  420  that is slightly smaller than a width  432  of the cavity  422  to permit the protrusion  414  to securely mate with the cavity  422 . While in the exemplary embodiment, the cover  412  comprises a lid  414  having a width  418  that is larger than the width  420  of the protrusion  414  and that is substantially the same width  419  as the receiving member  400 , in another embodiment the cover  412  can be provided with a lid  414  that has a width  418  that is smaller than the width  420  of the protrusion  420 . In yet another embodiment, the cover  412  can be provided without a lid  414 , such that the cover  412  is of a substantially uniform width (i.e., the width  420  of the protrusion  416 ). 
         [0028]    Referring again to the exemplary embodiment of  FIG. 4 , the lid  412  and the receiving member  400  can both have substantially the same width  418  to produce a ferrule with a substantially rectangular cross-section. The width  418  may be, for example 3.5 millimeters and the thickness  424  of the receiving member  400  may be, for example 4.0 millimeters. In another embodiment, the ferrule  112  has a substantially square cross-section. The sides  434  and bottom  436  of the first ferrule  112  may have a thickness  426  of 1.0 millimeters and receiving channel  404  may be 1.5 millimeters in width. In one embodiment, the width  438  of receiving channel  404  is uniform over its entire depth  428 , including the width  432  of the cavity  422 . In another embodiment, the width  438  of receiving channel  404  may increase or decrease over its depth  428 . The lid  412  may have a thickness  426  that is 1.0 millimeters thick while the protrusion  414  may have a thickness  430  of, for example, 1.5 millimeters. The cross-sectional shape of the receiving channel  404  may be square, rectangular or any other suitable shape. Examples of other suitable cross-sectional shapes are shown in  FIG. 6  and  FIG. 7 . 
         [0029]      FIG. 5  is a perspective view of the first ferrule  112  showing holes  500 . In the embodiment depicted, the holes  500  are rectangular with a width  502  and a height  504 . In one embodiment, the holes  500  are rectangular with the width  502  being about 1.5 millimeters. In another embodiment, the holes are square. In yet another embodiment, the holes are circular. The first ferrule  112  has a length  506  which, in one embodiment, is about 18 millimeters. The holes  500  are spaced from the front and top surfaces, as viewed in  FIG. 5  of first ferrule  112  by distances  508 ,  510 . In one embodiment, the distance  508  is selected to correspond to the thickness  430  of the protrusion  414 . In such an embodiment, the height  504  of the hole may be substantially equal to the depth  428  of the receiving channel  404  minus the thickness  430  of the protrusion  414 . In one embodiment, distance  508  is about 1 millimeter and distance  510  is about three millimeters. Each of the holes  500  is spaced from an adjacent hole by a distance  512 . In one embodiment, distance  512  is about 1.5 millimeters. In the exemplary embodiment of  FIG. 5 , the cover  402  comprises at least one hole  500 . 
         [0030]    In use, the optical fibers  200  (see  FIGS. 2 and 3 ) are disposed within the receiving channel  404  and an adhesive  304  is added. In one embodiment, the optical fibers  200  are brushed with an adhesive  304 . The cover  402  is then disposed above the receiving channel  404  and pressed in a downward direction such that the protrusion  416  compresses the optical fibers  200 . This compression minimizes the gaps between the optical fibers  200 . The adhesive  304  may be present in any remaining gaps  302  (see  FIG. 3 ). The compression forces excess adhesive  304  into at least one hole  500  (see  FIG. 5 ) to further minimize the gaps  302  between the optical fibers  200 . A portion of the adhesive  304  contacts the protrusion  416 . After the adhesive  304  cures, the cured adhesive  304  holds the cover  402  to the receiving member  400  to form first ferrule  112 . In one embodiment, excess adhesive  304  cures within the holes  500 . Examples of adhesives  304  include epoxies and other similar liquid fixing agents. In the exemplary embodiment depicted in the figures, the holes  500  are present on the first surface  406  and the second surface  408 . In other embodiments, one or more holes may be present on the first surface  406 , the second surface  408 , the third surface  410 , the fourth surface  416  and any combinations thereof 
         [0031]      FIG. 6  is a depiction of a ferrule  600  where the receiving channel  602  has a U-shape cross-section formed by curved surfaces  604  that connect a third surface  606  to a first surface  608  and to a second surface  610  to provide the third surface  606  with a concave shape. The embodiment of  FIG. 7  is similar to  FIG. 6  except in that cover  700  has a protrusion  702  that is concave. When the cover  700  is connected to the receiving member  704  a circular receiving channel  706  is formed. In another embodiment, an elliptical receiving channel is formed. 
         [0032]      FIG. 8  is a depiction of a ferrule  800  with multiple chambers for multiple optical fiber bundles  300 . In the exemplary embodiment, a first chamber  802  and a second chamber  804  are separated by a plate  806 . Such multiple chambered ferrules are useful when a housing has multiple light sources. A first plurality of optical fibers are disposed within the first chamber  802 . The plate  806  is then added to the ferrule. Thereafter a second plurality of optical fibers are disposed within the second chamber  804  before sealing with a cover  808 . Such an embodiment is useful for preventing the first plurality and second plurality of optical fiber bundles  300  from being intermixed. When two light sources are used (e.g. two different wavelengths) separating the optical pathways permits controlled use of one of the two wavelengths. In the embodiment of  FIG. 8 , the plate  806  is horizontal such that the first chamber  802  and the second chamber  804  are vertically stacked. In such an embodiment, the plate  806  extends a direction that is substantially parallel to the cover  808 . In another embodiment, shown in  FIG. 10 , the plate  1006  is vertical such that first and second chambers  1002 ,  1004  are horizontally arranged. In such an embodiment, the cover includes first and second protrusions that correspond to the first and second chambers. The plate  1006  extends in a direction that is substantially perpendicular to a cover  1008 . In such embodiments, the plate may be a distinct piece with regard to the receiving member or the plate may be monolithic with regard to the receiving member. In the embodiment of  FIG. 10 , the cover  1008  comprises a first protrusion  1014  and a second protrusion  1015  configured to compress first chamber  1002  and second chamber  1004 , respectively. 
         [0033]    Referring to  FIG. 9  and method  900  shown therein, in operation first ends of a plurality of optical fibers are disposed within a receiving channel of a ferrule in step  902 . A liquid adhesive  304  is introduced into the receiving channel in step  904 . The adhesive  304  may be introduced directly or the adhesive  304  may be introduced by first being brushed on the optical fibers. In step  906 , a cover is placed on the receiving channel and pushed downward such that a protrusion on the cover compresses the optical fibers. Excessive adhesive  304  is permitted to flow into at least one hole in the ferrule in step  908 . In step  910  the adhesive  304  is permitted to set. The first ends of the optical fibers may be subjected to cutting and polishing operations to produce smooth ends. 
         [0034]    The ferrules described in this specification may be formed of any material that will withstand the operating temperature of the light source. In one embodiment, the ferrule is formed of a metal, such as aluminum, to better dissipate heat. 
         [0035]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.