Patent Publication Number: US-2005135772-A1

Title: Optical fiber for a laser device having an improved tip diffuser and method of making same

Description:
RELATED APPLICATIONS  
      This patent application cross references and incorporates by reference the following co-pending, commonly assigned patent applications filed on even date herewith: “OPTICAL FIBER FOR A LASER DEVICE HAVING AN IMPROVED DIFFUSER SLUG AND METHOD OF MAKING SAME”, attorney docket END 5215, U.S. Ser. No. ______; and “OPTICAL FIBER TIP DIFFUSER AND METHOD OF MAKING SAME”, attorney docket END-5243, U.S. Ser. No. ______, 
    
    
     BACKGROUND OF THE INVENTION  
      The present invention relates generally to an optical fiber for use with a laser device and, more particularly, to an optical fiber having an improved diffuser configuration at its distal end for performing the dual functions of scattering light and providing a temperature signal.  
      Currently, surgeons employ medical instruments which incorporate laser technology in the treatment of benign prostatic hyperplasia, also commonly referred to as BPH. BPH is a condition of an enlarged prostate gland, where such gland having BPH typically increases in size by about two to four times. The laser energy employed by the surgeons to treat this condition is delivered by an optical fiber which must be able to distribute light radially in a predictable and controlled manner. During the course of such treatments, one parameter of great importance is the temperature of the tissue being treated. For example, one current recommendation for forming lesions in the prostate as a treatment for BPH is to heat a small volume of tissue to 85° C. for a designated time period depending on fiber and laser design. It will be appreciated that heating the tissue to a lesser temperature has the effect of incomplete lesion formation, while heating the tissue to a higher temperature can cause excessive tissue damage. Accordingly, the ability to accurately measure the temperature of the optical fiber tip during treatment is of primary concern.  
      It will be understood that there are several known ways of performing the temperature monitoring function for a laser system. One approach has been utilized in laser treatment systems known as the “Indigo 830e Laseroptic Treatment System” and the “Indigo Optima Laseroptic Treatment System,” both of which are manufactured by Ethicon EndoSurgery, Inc. of Cincinnati, Ohio, the assignee of the present invention. Methods of providing an optical fiber with a diffuser end are disclosed in U.S. Pat. No. 6,522,806 to James, IV et al., U.S. Pat. No. 6,361,530 to Mersch, and U.S. Pat. No. 5,946,441 to Esch. Each of these methods utilize the principle of relying upon the temperature dependence of the fluorescent response of a slug of material at the fiber tip to an optical stimulus as described in U.S. Pat. Nos. 5,004,913 and 4,708494 to Kleinerman. More specifically, a pulse of pump energy causes a fluorescence pulse in an alexandrite slug which is delayed by a time interval corresponding to a temperature of the material.  
      It will be appreciated from each of the aforementioned patents that the slug is composed of a cured mixture of alexandrite particles and an optical adhesive which is cured in place. The current manufacture and assembly of such slugs is considered both complex and tedious. In an exemplary process, the slugs are formed in batches by sprinkling ground alexandrite into several tiny cavities in a mold placed on a vibratory plate. The alexandrite particles are then covered with an optical coupling adhesive, after which a vacuum is drawn and the mixture is cured within the mold using either heat or ultraviolet light. The slugs are removed from the mold as a batch and placed individually into the distal sleeve tip against the end of the fiber optic glass during assembly.  
      While various improvements have been made in the basic slug manufacturing process, they are all based on the slug being a mixture of alexandrite and adhesive and therefore have similar disadvantages. One disadvantage is that a portion of the final molded configuration is used as structural support, which results in substantial waste of the expensive alexandrite material. The manufacturing process is considered to be lengthy and requires the use of specialized equipment and highly trained operators. Moreover, the ratio of alexandrite to the ultraviolet binder (i.e., its concentration) in each individual cavity of the slug mold is not precisely controlled, which results in a variation of the slug composition and its resulting performance. It will also be understood that assembly of the slug within the distal tip of the optical fiber is difficult since the slug is unidirectional, the size of the components in the optical fiber is extremely small, direct visualization is not available, and neither mechanical positioning nor final mechanical interlock is provided between the components.  
      In an alternate variation of the current manufacturing process, an uncured mixture of alexandrite and adhesive may be directly applied to the end of the fiber and cured into place. This may be accomplished by dispensing the mixture within the tubing directly onto the end of the glass core, loading it into a sleeve or other carrier and seating the sleeve, or by dipping the core end into adhesive and then into the alexandrite particles. It has been found in this process, however, that application of a consistent amount of the mixture in the proper location is difficult to achieve and monitor on a production basis.  
      Thus, in light of the foregoing, it would be desirable for a slug, as well as a method of making and assembling such slug in an optical fiber, to be developed which overcomes the disadvantages associated with the alexandrite and adhesive composition and manufacturing processes described herein. It is also desirable that such slug would assist in centering the slug on the distal surface of the optical fiber and assuring contact between the core fiber and an outer sleeve, whereby the dual functions of light scattering and temperature sensing are optimized. Further, it is highly desirable for the light-scattering material and the sleeve of the diffuser portion for such optical fiber to be formed in an integral manner. In an alternative configuration, it would be desirable for the separate slug to be eliminated from the optical fiber and replaced with a tip diffuser having light scattering and temperature sensing capabilities which can be assembled to the distal end of the optical fiber.  
     BRIEF SUMMARY OF THE INVENTION  
      In a first exemplary embodiment of the invention, an optical fiber for use with a laser device including a source of light energy is disclosed, where the optical fiber has a proximal end in communication with the light source and a distal end positionable at a treatment site. The optical fiber includes: a core having a proximal portion, a distal portion and a distal face proximate the distal end of the optical fiber; a layer of cladding radially surrounding the core from the core proximal portion to a point adjacent the core distal portion; a sleeve radially surrounding the cladding layer composed essentially of a predetermined type of material; and, a tip diffuser radially surrounding the core distal portion including light-scattering material molded with substantially the same type of material utilized for the sleeve, wherein the light-scattering material fluoresces in a temperature dependent manner upon being stimulated by light. More specifically, the tip diffuser is an open sleeve and the designated point of the cladding layer is adjacent the core distal portion so that a layer of optical coupling material is located between the core distal portion and the tip diffuser.  
      In a second exemplary embodiment of the invention, an optical fiber for use with a laser device including a source of light energy is disclosed, where the optical fiber has a proximal end in communication with the light source and a distal end positionable at a treatment site. The optical fiber includes: a core having a proximal portion, a distal portion and a distal face proximate the distal end of the optical fiber; a layer of cladding radially surrounding the core from the core proximal portion to a point adjacent the core distal portion; a sleeve radially surrounding the cladding layer composed essentially of a predetermined type of material; and, a tip diffuser radially surrounding the core distal portion including light-scattering material molded with substantially the same type of material utilized for the sleeve, wherein the light-scattering material fluoresces in a temperature dependent manner upon being stimulated by light. More specifically, the tip diffuser is a solid rod having a proximal portion for receiving a part of the core distal portion and a distal portion having a penetrating tip. The designated point of the cladding layer is adjacent the distal face of the core so that a layer of optical coupling material is located between the core distal face and the tip diffuser.  
      In a third exemplary embodiment of the invention, a method of making an improved diffuser in an optical fiber for use with a laser device is disclosed, wherein the optical fiber includes a core having a proximal portion, a distal portion, and a distal surface and a sleeve composed essentially of a predetermined type of material radially surrounding the core from the proximal portion to the distal portion. The method includes the following steps: molding a light-scattering material with the same type of material as the sleeve into a tip diffuser having a predetermined length and geometry, wherein the light-scattering material fluoresces in a temperature dependent manner upon being stimulated by light; inserting the tip diffuser over at least a portion of the core distal portion; and, attaching the tip diffuser at a first end to a distal end of the sleeve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a diagrammatic view of a laser system utilized for performing medical procedures which includes the optical fiber of the present invention;  
       FIG. 2  is an enlarged, partial sectional view of the optical fiber depicted in  FIG. 1 , where the penetrating tip has not been formed;  
       FIG. 3  is an enlarged, partial sectional view of the optical fiber depicted in  FIGS. 1 and 2 , where the penetrating tip has been formed;  
       FIG. 4  is an enlarged, sectional view of the slug in the optical fiber as depicted in  FIGS. 2 and 3 ;  
       FIG. 5  is an enlarged, sectional view of a first alternative embodiment for the slug depicted in  FIGS. 2 and 3 ;  
       FIG. 6  is an enlarged, sectional view of a second alternative embodiment for the slug depicted in  FIGS. 2 and 3 ;  
       FIG. 7  is an enlarged, sectional view of the slug depicted in  FIG. 4  including a feature formed in one end thereof for interfacing with an assembly tooling spaced therefrom;  
       FIG. 8  is an enlarged, sectional view of the slug depicted in  FIG. 4  including an alternative feature formed in one end thereof for interfacing with an assembly tooling spaced therefrom;  
       FIG. 9  is an enlarged, partial sectional view of a first alternative embodiment for the optical fiber depicted in  FIGS. 1-3 , where a tip diffuser is in a detached position and the penetrating tip has not been formed;  
       FIG. 10  is an enlarged, partial sectional view of the optical fiber depicted in  FIG. 9 , where the tip diffuser is in the attached position and the penetrating tip has been formed;  
       FIG. 11  is an enlarged, partial sectional view of a second alternative embodiment for the optical fiber depicted in  FIGS. 1-3 , where a tip diffuser is in the attached position and the penetrating tip has been formed;  
       FIG. 12  is an enlarged, partial sectional view of a fourth alternative embodiment for the optical fiber depicted in  FIGS. 1-3 , where a tip diffuser including a ring-shaped portion made of light scattering material and the sleeve material is in the attached position and the penetrating tip has been formed; and,  
       FIG. 13  is an enlarged, partial sectional view of a third alternative embodiment for the optical fiber depicted in  FIGS. 1-3 , where a tip diffuser incorporating a ring-shaped slug made of light scattering material is in the attached position and the penetrating tip has been formed. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring now to the drawings in detail, wherein identical numerals indicate the same elements throughout the figures,  FIG. 1  depicts schematically a medical instrument  10  for diffusing light from an optical fiber  12 . Medical instrument  10  includes a source of light energy  14 , which preferably is a laser. Optical fiber  12  connects into light energy source  14  through the intermediary of a connector  16  which is attached to a connection port  18  leading to a diffuser portion  20  of optical fiber  12 . A typical connector and connection port of this kind which can be utilized for medical instrument  10  is the Optima laser which is sold by Ethicon Endo-Surgery in Cincinnati, Ohio. It will be appreciated that optical fiber  12  with the attached connector  16  may be provided and sold separately from light energy source  14  as an optic fiber assembly.  
      More specifically, optical fiber  12  includes a proximal end  22  in communication with light energy source  14  which transmits light to a distal end  24  including diffuser portion  20  that is utilized to diffuse light at a treatment site. Optical fiber  12  further includes a plurality of assembled components which enable it to function in an intended manner, as in the case for the treatment of BPH. It will be seen from  FIGS. 2 and 3  that optical fiber  12  includes a core  26  which extends substantially through the center of optical fiber  12 . Core  26 , which is typically made of silica glass, has a proximal portion  28  in communication with light energy source  14  and functions to transmit light to a distal portion  30  that is located within diffuser portion  20 . It will be understood that distal portion  30  includes a distal face  32 . In this way, diffuser portion  20  functions to diffuse the light energy received from proximal portion  28 . A layer of cladding  34  is preferably provided so as to radially surround core  26  from core proximal portion  28  to a point adjacent to core distal portion  30 . Cladding layer  34 , which protects core  26  by imparting a mechanical support thereto, preferably has an index of refraction lower than that of the material used to create core  26  so as to contain or block the light transmitted through optical fiber  12  from emerging radially from core  26 .  
      Optical fiber  12  further includes a layer  36  of optical coupling material which preferably radially surrounds at least a portion  38  of core distal portion  30  and possibly a portion of cladding layer  34 . Exemplary optical coupling materials include: XE5844 Silicone, which is made by General Electric Company; Uv50 Adhesive, available from Chemence, Incorporated in Alpharetta, Ga.; and, 144-M medical adhesive, which is available from Dymax of Torrington, Conn. Optical coupling layer  36  preferably has a higher index of refraction than core  26  so that light exits core  26 .  
      In the embodiment of the invention depicted in  FIGS. 2 and 3 , a slug  40  positioned adjacent distal face  32  functions to scatter light back through core  26  and thereby raise the intensity of the light in diffuser portion  20 . Slug  40 , as discussed previously herein, has heretofore been composed essentially of a light-scattering material and an adhesive. Typical scattering materials have included aluminum oxide, titanium dioxide, and diamond power, but alexandrite has been found to be a preferred material. This is because alexandrite not only is able to perform the light-scattering function, but it also exhibits a temperature dependent optical fluorescence decay rate upon being stimulated by light of a predetermined wavelength. Accordingly, the alexandrite is able to emit a light signal back through core  26  from which a temperature for diffuser portion  20  can be determined and controlled. It will be appreciated that the adhesive generally mixed with the light-scattering material may or may not be the same as for optical coupling layer  36 .  
      It will be noted that optical fiber  12  also preferably includes a sleeve  42  which radially surrounds optical coupling layer  36  and slug  40 . A buffer layer  43  is preferably positioned radially between sleeve  42  and cladding layer  34  upstream of and perhaps into diffuser portion  20 . Sleeve  42  is composed essentially of a predetermined type of material which preferably has an index of refraction higher than the material used for optical coupling layer  36 . Further, such material is preferably flexible, is non-absorbent of laser energy in the wavelengths of interest, has a high melt temperature, and is optically diffusing. A preferred material for sleeve  42  having the desired characteristics is perfluoroalkoxy (PFA) impregnated with barium sulfate, where the barium sulfate particles assist in scattering light energy evenly outward to the tissue at the treatment site. Other materials optically transparent to the appropriate wavelengths may be used to construct sleeve  42 , including Ethylenetetraflouroethylene (ETFE) and other types of flouropolymers.  
      Turning back to slug  40 , the present invention involves molding the alexandrite (or other light-scattering material having similar temperature dependent properties when stimulated by light) with substantially the same type of material utilized for sleeve  42 . It will be appreciated that a preferred concentration of the alexandrite in slug  40  exists and is dependent upon the configuration and composition of slug  40 . In the case where slug  40  is a substantially homogeneous mixture of alexandrite and perfluoroalkoxy with approximately 10% barium sulfate (see  FIG. 4 ), the preferred concentration of alexandrite therein is in a range of approximately 25-75% by weight.  
      With respect to the overall configuration of slug  40 , it will be seen that slug  40  preferably radially surrounds a portion  44  of core distal portion  30 . Accordingly, a feature  46  is preferably incorporated into a first end  48  of slug  40  for centering slug  40  onto core distal portion  30 . Further, slug  40  preferably includes a negative feature  50  formed into a second end  52  thereof for interfacing with a positive assembly tooling  54  (see  FIG. 7 ). Alternatively, a positive feature  56  is preferably formed into second end  52  thereof for interfacing with a negative assembly tooling  58  (see  FIG. 8 ). In either case, insertion of slug  40  onto core distal portion  30  is facilitated. It will be appreciated, however, that differing the tooling feature from the centering feature assists in preventing misassembly. Because slug  40  essentially consists of the same type of material as that utilized for sleeve  42 , and an interior surface  60  of sleeve  42  is preferably abraded to include grooves  62  or other variable surface characteristics, slug  40  achieves a mechanical connection with sleeve  42  via a physical bonding during the formation of a penetrating tip  64  on sleeve  42 . In particular, the material of slug  40  melts and bonds with the material of sleeve  42  since they have substantially the same melting points.  
      It will also be seen that additional embodiments of slug  40  are depicted in  FIGS. 5 and 6  which differ from the substantially homogeneous mixture represented in  FIG. 4 . In  FIG. 5 , slug  66  includes a first portion  68  consisting essentially of a light-scattering material (e.g., alexandrite or any other material having similar properties and characteristics) which is positioned adjacent to core distal face  32 . In addition, slug  66  includes a second portion  70  consisting essentially of the same type of material utilized for sleeve  42  (e.g., perfluoroalkoxy with barium sulfate particles or any other material having similar properties and characteristics). Second slug portion  70  is preferably molded so as to be positioned around first slug portion  68  and portion  44  of core distal portion  30 .  
      With respect to  FIG. 6 , it will be seen that slug  72  therein includes a first portion  74  consisting essentially of a substantially homogeneous mixture of a light-scattering material and material of the same type utilized for sleeve  42  (e.g., alexandrite and perfluoroalkoxy with barium sulfate particles or other compositions having similar properties and characteristics), where first slug portion  74  is positioned adjacent to core distal face  32 . A second portion  76  of slug  72  consisting essentially of the same type of material utilized for sleeve  42  (e.g., perfluoroalkoxy with barium sulfate particles or any other material having similar properties and characteristics) is molded so as to be positioned around first slug portion  74  and portion  44  of core distal portion  30 .  
      In a second embodiment of the optical fiber (identified generally by reference numeral  78 ), it will be seen from  FIGS. 9 and 10  that slug  40  from  FIGS. 2 and 3  has been eliminated. Further, while core  26 , cladding layer  34 , and buffer layer  43  remain unchanged, a sleeve  80  is provided which radially surrounds cladding layer  34  but not core distal portion  30 . Accordingly, a tip diffuser  82  is provided which preferably surrounds core distal portion  30  and core distal face  32 . In this way, the area of core  26  which receives the most treatment light also receives the most marker light excitation. Thus, the temperature measurement is weighted more closely to the tissue being treated.  
      As discussed previously herein with respect to slug  40 , tip diffuser  82  preferably includes a light-scattering material (e.g., alexandrite or any other material having similar properties and characteristics) molded with substantially the same type of material utilized for sleeve  80 . Tip diffuser  82  includes a first end  84  which is positioned adjacent a distal end  86  of sleeve  80  and a second end  88  which preferably is formed into a penetrating tip  90 . It will be appreciated that first end  84  of tip diffuser  82  is preferably attached to sleeve distal end  86 , such as by heat staking or welding.  
      A layer  92  of optical coupling material is preferably located between core distal portion  30  and tip diffuser  82 . As seen in  FIGS. 9 and 10 , an interior surface  94  of tip diffuser  82  is preferably abraded to include grooves  96  or other variable surface characteristics so that a mechanical connection with optical coupling layer  92  is achieved and the disadvantage of index of refraction is overcome.  
      It will be appreciated that tip diffuser  82  is preferably a substantially homogeneous mixture of the light-scattering material and the material utilized for sleeve  80 . Further, a preferred concentration of alexandrite in tip diffuser  82  exists and is dependent upon the configuration and composition of tip diffuser  82 . In the case where tip diffuser  82  is a substantially homogeneous mixture of alexandrite and perfluoroalkoxy with approximately 10% barium sulfate, the preferred concentration of alexandrite therein is in a range of approximately 25-75%. It will be appreciated, however, that such concentration of alexandrite is likely to be less for tip diffuser  82  than for slug  40  described previously herein due to their respective orientations with regard to core distal portion  30 .  
       FIG. 11  depicts a third embodiment of an optical fiber identified generally by reference numeral  98 . Optical fiber  98  likewise includes core  26 , buffer layer  43 , and sleeve  80  as shown in  FIGS. 9 and 10 . A new tip diffuser  100  is utilized with optical fiber  98  which preferably is formed as a solid rod having a first end  102  positioned adjacent distal end  86  of sleeve  80  and a second end  104  which preferably terminates in a penetrating tip  106 . It will be appreciated that first end  102  of tip diffuser  100  is preferably attached to sleeve distal end  86 , such as by heat staking or welding.  
      Contrary to tip diffuser  82  of optical fiber  78 , tip diffuser  100  has a smaller portion  107  hollowed therefrom at first end  102  so that only a portion  108  of core distal portion  30  extends therein. It will be noted that a cladding layer  110  radially surrounding core  26  extends into core distal portion  30  to core distal face  32 . A layer  112  of optical coupling material is then preferably located between core distal face  32  and tip diffuser  100  to facilitate light emission from core distal portion  30 . This particular configuration, where cladding layer  110  extends further on core  26 , is effective for enhancing the flexibility of core distal portion  30  and thus rendering optical fiber  98  more compatible with certain flexible endoscopes.  
      Tip diffuser  100  preferably includes a light-scattering material (e.g., alexandrite or any other material having similar properties and characteristics) molded with substantially the same type of material utilized for sleeve  80 . Once again, it will be appreciated that tip diffuser  100  is preferably a substantially homogeneous mixture of the light-scattering material and the material utilized for sleeve  80 . Further, a preferred concentration of alexandrite in tip diffuser  100  exists and is dependent upon the configuration and composition thereof. When tip diffuser  100  is a substantially homogeneous mixture of alexandrite and perfluoroalkoxy with approximately 10% barium sulfate, the preferred concentration of alexandrite therein is in a range of approximately 25-75%. It will be appreciated, however, that such concentration of alexandrite is likely to be less for tip diffuser  100  than for slug  40  described previously herein due to their respective orientations with regard to core distal portion  30 .  
      A fourth embodiment of an optical fiber  114  is depicted in  FIG. 12 . As seen therein, optical fiber  114  is configured to have core  26 , cladding layer  34 , buffer layer  43 , and sleeve  80  as described above with respect to  FIGS. 9 and 10 . Another tip diffuser  116  is provided which preferably surrounds core distal portion  30  and core distal face  32 . Further, tip diffuser  116  includes a first end  118  positioned adjacent distal end  86  of sleeve  80  and a second end  120  which preferably terminates in a penetrating tip  122 . It will be appreciated that first end  118  of tip diffuser  116  is preferably attached to sleeve distal end  86 , such as by heat staking or welding. It will be appreciated that an optical coupling layer  123  is shown as being provided between core distal portion  30  and tip diffuser  116 .  
      More specifically, as seen in the upper portion of  FIG. 12 , tip diffuser  116  preferably includes a first substantially ring-shaped portion  124  which is sized to fit radially around a designated section  126  of core distal portion  30 . Accordingly, first tip diffuser portion  124  is positioned axially at a middle section of core distal portion  30 ) along a longitudinal axis  133  through core distal portion  30 . It is preferred in this embodiment that core distal portion  30  extend at least to a midpoint in tip diffuser  116  so that the temperature sensing ability of first tip diffuser portion  124  is enhanced by receiving the strongest light. In this configuration, first diffuser tip portion  124  includes a first end  127  (same as first end  118  of tip diffuser  116 ) which is attached to sleeve distal end  86  (e.g., by heat staking or welding) and a second end  128 .  
      First diffuser tip portion  124  preferably consists of an exemplary light-scattering material (e.g., alexandrite or some other material exhibiting similar properties and characteristics) or a substantially homogeneous mixture of such light-scattering material and the material utilized for sleeve  80  (e.g., perfluoroalkoxy with barium sulfate particles or some material exhibiting similar properties and characteristics). Of course, a preferred concentration of alexandrite in first tip diffuser portion  124  exists and is dependent upon the configuration and composition thereof. When first tip diffuser portion  124  is a substantially homogeneous mixture of alexandrite and perfluoroalkoxy with approximately 10% barium sulfate, the preferred concentration of alexandrite therein is in a range of approximately 25-75%. It will be appreciated, however, that such concentration of alexandrite is likely to be less for first tip diffuser portion  124  than for slug  40  described previously herein due to their respective orientations with regard to core distal portion  30 .  
      Tip diffuser  116  further includes a second portion  130  which preferably radially surrounds a second section  132  of core distal portion  30  and terminates in penetrating tip  122 . Second tip diffuser portion  130 , which preferably is composed essentially of the same material utilized for sleeve  80 , includes an end  134  opposite penetrating tip  122  which is attached to second end  128  of first diffuser tip portion  124  (e.g., by heat staking or welding).  
      As seen in a bottom portion of  FIG. 12 , tip diffuser  116  may include a third substantially ring-shaped portion  136  which is sized to fit radially around an upstream or third section  138  of core distal portion  30 . Third tip diffuser portion  136 , which preferably consists essentially of the same type of material as sleeve  80 , is located adjacent sleeve distal end  86 A and includes a first end  140  (same as diffuser tip first end  118 ) and a second end  142  located opposite thereto. According, first end  140  of third diffuser section is attached to sleeve distal end  86 A (e.g., by means of heat staking or welding) and second end  142  thereof is attached to first end  127  of first tip diffuser portion  124 .  
      In yet another alternative optical fiber embodiment (represented by reference numeral  143 ) depicted in  FIG. 13 , it will be seen that a tip diffuser  144  includes a first tip diffuser portion  146 , a second diffuser tip portion  148  and a third tip diffuser portion  150 . As indicated above with respect to tip diffuser  116 , third diffuser tip portion  150  is substantially ring-shaped, preferably consists essentially of the same type of material as sleeve  80 , and is sized to fit radially around a third or upstream section  152  of core distal portion  30 . Third diffuser tip portion  150  is located adjacent sleeve distal end  86  and includes a first end  154  and a second end  156  located opposite thereto.  
      Similarly, second diffuser tip portion  148  radially surrounds a second section  158  of core distal portion  30  and terminates in penetrating tip  160 . Second tip diffuser portion  148 , which preferably is composed essentially of the same material utilized for sleeve  80 , includes an end  162  opposite penetrating tip  160  which is attached to second end  156  of third diffuser tip portion  146  (e.g., by heat staking or welding).  
      It will be noted that first tip diffuser portion  146  is preferably sized and configured so that a first end  164  and at least a portion thereof is received within, or otherwise mated with, a feature  166  formed in a middle section  168  of third tip diffuser portion second end  156 . A similar feature  170  may be formed in a middle section  172  of second tip diffuser portion end  162  so that a second end  174  and at least a portion of first tip diffuser portion  146  is received therein or otherwise mated therewith. In particular, while features  166  and  170  are depicted as a female type, such features could alternatively have a male configuration which extends into complementary female portions formed in first and second ends  164  and  174 , respectively, of first tip diffuser portion  146 . In either case, first tip diffuser portion  146  will preferably radially surround a middle section  176  of core distal portion  30 .  
      In conjunction with the optical fiber embodiments described herein, one improvement related thereto is the method of making and assembling such optical fibers. With respect to optical fiber  12 , a method of making such optical fiber  12  includes an initial step of providing sleeve  42  radially around core  26  so that a length  178  of the open sleeve thereof extends beyond core distal face  32  a predetermined amount. The next step involves molding the light-scattering material with a material similar to that utilized for sleeve  42  to form slug  40 , where the light-scattering material fluoresces in a temperature dependent manner upon being stimulated by light. Thereafter, slug  40  is inserted into open sleeve length  178  so as to be positioned adjacent core distal face  32 . Open sleeve length  178  is then shaped into penetrating tip  64  having a predetermined geometry. It will be appreciated that slug  40  is also physically bonded to sleeve  42  during the tip shaping step. Also, it is preferred that optical coupling layer  36  be provided between core distal portion  30  and sleeve  42 .  
      It will be understood with regard to the physical features of slug  40  that the method further may include the step of molding feature  46  at first end  48  of slug  40  for centering slug  40  with core distal portion  30 . Another step may include the molding of negative feature  50  or positive feature  56  on second end  52  of slug  40  to facilitate placement of slug  40  on a corresponding assembly tooling  54  or  58 , respectively, for the inserting step.  
      With respect to the materials utilized for slug  40 , a preferred step is optimizing slug  40  with a predetermined concentration of the light-scattering material to the sleeve-type material utilized therewith. This can be different depending on the configuration and composition of slug  40 . In a first instance, this involves the step of mixing the light-scattering material and the same type of material as utilized for sleeve  42  into a substantially homogeneous mixture prior to the molding step. For slug  66 , the molding step further includes the steps of preloading the light-scattering material in a mold and compression molding the same type of material as utilized for sleeve  42  directly over and through the light-scattering material. The molding step for slug  72  further includes the following steps: mixing the light-scattering material and the same type of material as utilized for sleeve  42  into a substantially homogeneous mixture; molding first portion  74  of slug  72  with the mixture; and, molding second portion  76  of slug  72  from the same type of material as utilized for sleeve  42  so as to surround all but one side (that used to interface core distal face  32 ) of first slug portion  74 .  
      Regarding optical fibers  78 ,  98 ,  114  and  143  shown in  FIGS. 10, 11 ,  12 , and  13  respectively, it will be understood that the process of making them involves the step of molding the light-scattering material with the same type of material utilized for sleeve  80  into at least a portion of tip diffusers  82 ,  100 ,  116 , and  144 , respectively, having a predetermined length and geometry. Thereafter, the respective tip diffuser  82 ,  100 ,  116  or  144  is inserted over at least a portion of core distal portion  30 . The tip diffuser  82 ,  100 ,  116  or  144  is then attached at a first end  84 ,  102 ,  118 , or  154 , respectively, to distal end  86  of sleeve  80 . Of course, the process also involves the step of forming penetrating tip  90 ,  106 ,  122  and  160  at second end  88 ,  104 ,  120 , and  155 , respectively, for each tip diffuser  82 ,  100 ,  116 , and  144 . The formation of penetrating tips  90 ,  106 ,  122  and  160  may occur prior to or after the inserting step described above.  
      It will be noted with respect to optical fibers  78 ,  114  and  143  that the method preferably includes the step of providing layers  92 ,  123 , and  157 , respectively, of optical coupling material between core distal portion  30  and tip diffusers  82 ,  116 , and  143 . In order to provide a desired physical or mechanical connection between optical coupling layers  92 ,  123 , and  157  and interior surfaces  94 ,  125 , and  159  of tip diffusers  82 ,  116 , and  143 , respectively, interior surfaces  94 ,  125 , and  159  are preferably abraded prior to the inserting step. For optical fibers  78 ,  114 , and  143 , it will be seen that tip diffusers  82 ,  116 , and  144  thereof extend around substantially all of core distal portion  30 , whereas tip diffuser  100  of optical fiber  98  extends around only a small portion  108  of core distal portion  30 .  
      With regard to the composition of tip diffusers  82  and  100 , the process may further include the steps of mixing the light-scattering material and the same type of material utilized for sleeve  80  into a substantially homogeneous mixture and molding the mixture into such tip diffusers  82  and  100  having the predetermined length and geometry.  
      Regarding optical fibers  114  and  143 , the process preferably includes the following additional steps: mixing the light-scattering material and the same type of material utilized for sleeve  80  into a substantially homogeneous mixture; molding first tip diffuser portions  124  and  146  from the mixture into a ring shape sized to radially surround sections  126  and  176  of core distal portion  30 ; and, molding second tip diffuser portions  130  and  148  from the same type of material utilized for sleeve  80  to surround sections  132  and  158 . Additionally, such process preferably includes the step of attaching the respective first tip diffuser portions  124  and  146  and second tip diffuser portions  130  and  148  so as to have a common longitudinal axis  133  and  161  therethrough. Further steps may include forming penetrating tips  122  and  160  of predetermined geometry in second tip diffuser portions  130  and  148  and abrading interior surfaces  125  and  159  of tip diffusers  116  and  144 .  
      Optionally, the process may include the step of molding third tip diffuser portions  138  and  150  from the same type of material utilized for sleeve  80  into a ring shape sized to radially surround sections  138  and  152  of core distal portion  30 .  
      With respect to optical fiber  116 , it will be appreciated that first tip diffuser portion  124  is preferably configured so that the method thereof includes attaching first end  126  to sleeve distal end  86  or to second end  142  of third tip diffuser portion  136  by heat staking or welding. In either case, second end  128  thereof is attached to non-penetrating tip end  134  of second tip diffuser portion  130  and  148 , respectively.  
      With respect to optical fiber  143 , the manner of attaching first tip diffuser portion  146  involves the steps of forming feature  166  in second end  156  of third tip diffuser portion  150  and/or forming feature  170  in end  162  of second tip diffuser portion  148 . In this way, first tip diffuser portion  146  is mated with second and/or third tip diffuser portions  148  and  150 .  
      Having shown and described the preferred embodiment of the present invention, further adaptations of optical fibers  12 ,  78 ,  98 , and  114 , including slugs  40 ,  66  and  72  and/or sleeves  42  and  80  thereof, as well as the methods making and assembling such optical fibers, can be accomplished by appropriate modifications by one of ordinary skill in the art without departing from the scope of the invention.