Abstract:
A portable optical-fiber cutter is used to slice a first optical-fiber at an advantageous angle to control reflections and at a suitable length to mate with a similar second optical-fiber that was pre-sliced at a complementary angle in the factory and configured as a receptacle for the first optical-fiber. This technique avoids the need for installation of two-ended, factory pre-connectorized optical-fiber cable and permits usage of a narrow-diameter protective “microduct” to enclose the optical fiber cable rather than requiring large-diameter protective duct to allow passage of a pre-connectorized connector there-through. Space is saved, particularly in large multi-unit apartment buildings where available space may be at a premium for large bundles of multiple optical cables. This technique also results in saving large amounts of technician-installer time when compared with the current time-consuming technique of fusion splicing.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to apparatus and method for facilitating installation of optical-fiber (fiber optic) cable used for communication purposes and, more particularly, for mechanically splicing optical-fiber cable in the field during installation in a manner that results in an efficient optical interface without producing harmful light reflections. 
   2. Description of Prior Art 
   The evolution of communication technology is in the direction of ever-faster communication with ever-increasing bandwidth. Optical-fiber cable offers these improvements over copper wire, but imposes challenges which copper wire technology did not present. For example, copper wires can be readily spliced and/or soldered together, where the resultant contact or joint almost always offers good electrical conductivity without inhibiting communication, but not so with optical-fiber cable. Optical-fiber cable (also known as fiber-optic cable), made from glass, is not capable of being readily spliced in a time-efficient manner, as compared with copper wire splices. Optical-fiber uses light energy as its communication medium rather than the familiar flow of electrons, i.e., “electricity”, used in copper wire. A bad optical “joint” can attenuate forward light transmission and cause reflection of light waves back to the light source which can interfere with operation of the light source and become a major problem. 
   The assignee of the present invention is a large telecommunications company which is installing optical-fiber cable (fiber optics) to its present and future customer base. When installing this fiber into apartment houses or multiple dwelling units (MDU&#39;s), the current technique is to bring the optical-fiber cable from, for example, a pole on the street to an external terminal affixed to the outside of the MDU building. From that connection point, a path is created to each apartment unit by using “microduct” which is a protective casing which may have an inside diameter of approximately 0.25-0.50 inches. A fiber optic cable which may have an outside diameter of approximately 0.125 inches containing a clad optical strand along the longitudinal axis of the cable is pulled through the microduct into each dwelling unit. For a two-hundred unit apartment building, for example, two-hundred separate microducts each containing its own optical cable with centralized and clad glass optical strand is connected from the external terminal, each microduct going to one of the two-hundred apartments respectively. 
   Today, fiber optic cable of pre-determined lengths with factory-connectorized both ends can be readily obtained. The connectors of these connectorized ends then can readily plug into jacks which are designed to matingly-accept the connectors. Although this would eliminate the need for splicing optical-fiber cable in the field, a connector is too large to fit into and through the microduct. The cross-sectional dimension of these connectors can be at least an order of magnitude larger than the outside diameter of the fiber optic cable for which they act as terminations. Larger diameter microduct could be used to accommodate pre-connectorized optical-fiber cable, but with a large apartment building (e.g., 200 units) a space issue develops—there simply isn&#39;t enough space to bundle 200 “large-diametered” microducts and run them up a wall inside a building prior to their being dispersed to the 200 dwelling units. That would require too much space. Thus, the small inside diameter microduct is used which requires elimination of one pre-connectorized end. Indeed, each un-connectorized or “raw” glass fiber end is fed through the microduct into one of the dwelling units. That raw end then needs to be properly and optically coupled to something that would serve to continue the light energy communication to its intended destination. There could be an optical coupling to a raw glass end of another optical cable in an apartment, the other end of the other optical cable being pre-connectorized and connectable to a wall plate, or the equivalent, mounted in the apartment. In other words, an optical cable splice of the two “raw” optical-fiber ends needs to be performed in the apartment unit. 
   The current method of making such a splice involves melting the ends of the glass strands where they touch in what is called a “fusion” splice. This may be analogous to welding two pieces of metal together. The glass strands are only microns in diameter, possibly on the order of 100 microns or less. (One micron is one-thousandth of a millimeter or about 0.000039 inch.) In the fusion splice, the strands are cut at right angles to the axis of the strand. The fusion splice, involving an electrical arc, is sufficiently good to avoid both substantial forward transmission light-loss and substantial problematical light reflection, the latter of which otherwise could be reflected back to the light source causing serious problems. However, a major drawback in performing the fusion splice is the very long time required for a technician to perform the splice—some 45 minutes or longer per splice. When outfitting a 200 unit apartment building, for example, this can result in a large man-hour impact, negatively impacting the costs of installation. 
   What is needed is a technique for providing a splice between two glass strand ends of mere microns in diameter, each contained within its own optical-fiber cable, in a quick and efficient manner as compared with the present forty-five minute splice-time needed for a fusion splice, and which provides a splice that (1) does not significantly attenuate forward transmission of the light signal and (2) does not return light reflections from the splice via the optical-fiber back to the light source, otherwise causing damage or deteriorated operation. The present invention is a welcome solution to these drawbacks of the prior art. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a method and an apparatus for operatively coupling two optical-fibers through which electromagnetic energy signals, such as visible light signals, are transmitted for communication purposes. The invention is not limited to wavelengths of light in the visible spectrum, and is also intended to operate with electromagnetic energy signals in the infra-red spectrum and beyond and in the ultra-violet spectrum and beyond. 
   The method includes mechanically slicing a raw end of one of the fibers at a pre-determined non-right angle relative to the longitudinal axis of that fiber and at a pre-determined distance from the face of a connector-clamp holding that fiber. This provides a first sliced end. The other optical-fiber has a raw end which is mechanically sliced at the complement of the pre-determined angle. This provides a second sliced end. The second sliced end is held in a manner to form a receptacle for the first sliced end. The first and second sliced ends are mechanically bound together in a substantially coplanar and congruent interface, whereby the interface transmits substantially all of the energy associated with the light signals and reflects any of the energy not transmitted therethrough in a manner to avoid transmission of reflected energy back to the source of the light energy. The second sliced end is held within a pluggable jack. The pluggable jack is mountable within a wall plate. The raw end of the one of the fibers is mechanically sliced by way of a portable diamond wheel cutter, allowing an optical cable installer to obtain the first sliced end at the site where the pluggable jack shall be mounted into the wall plate. The connector clamp holding the one of the fibers and the pluggable jack holding the other of the fibers have complementary keying means. When the keying means are fully mated, the first and second sliced ends form the substantially coplanar and congruent interface. 
   The apparatus includes a connector-clamp for holding the one of said fibers and a mechanical slicer adapted to grip said connector clamp and slice a raw end of the fiber at a pre-determined non-right angle relative to the axis of the fiber and at a pre-determined distance from the face of the connector-clamp, thereby providing a first sliced end. A pluggable jack is also provided which includes the other of the two fibers which was pre-sliced at the complement of the predetermined non-right angle, thereby providing a second sliced end. The jack forms a receptacle for the first sliced end. Means for binding together the first and second sliced ends in a substantially coplanar and congruent interface are provided. Therefore, the interface transmits substantially all of the energy associated with the light signals through the interface. Any and all light energy reflected from the interface and not transmitted therethrough is reflected in a manner to avoid transmission of the reflected energy back to the light energy source. 
   The apparatus further includes a pluggable jack which is mountable into a wall plate, along with means for utilizing a portable diamond wheel cutter to allow an optical-fiber cable installer to obtain the first sliced end at the site of installation of the pluggable jack into the wall plate. Also, keying means located on the connector-clamp with complementary keying means located on the pluggable jack are provided, for ensuring proper orientation between connector-clamp and pluggable jack when mated. The substantially coplanar and congruent interface is formed when keying means and complementary keying means are fully mated. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a front view of an exemplary schematic diagram of a commercially-available mountable wall plate into which an embodiment of the present invention is pluggable; 
       FIG. 1B  is the side view of  FIG. 1A ; 
       FIG. 2A  is a cross-sectional view of an exemplary pluggable jack holding an optical-fiber having a pre-sliced end; 
       FIG. 2B  is a cross-sectional view of an exemplary connector-clamp holding an optical-fiber having a sliced end; 
       FIG. 2C  is a frontal elevation view of the connector clamp in its relationship to  FIG. 2B , showing the section taken therethrough which is reflected by  FIG. 2B ; and 
       FIG. 2D  is a perspective view of the connector clamp of  FIGS. 2B and 2C . 
       FIG. 3  is a schematic diagram of an exemplary embodiment of a portable diamond wheel cutting mechanism of the type that may be used in or with the present invention and shown supporting the pluggable jack and optical-fiber of  FIGS. 2B-2D ; and 
       FIG. 4  is a schematic view of the two optical-fibers in their mated position showing, on edge, the coplanar and congruent interface there-between, long with light energy source and light energy receiver. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  depicts a commercially-available, mountable, wall plate into which an embodiment of the present invention is pluggable. Wall plate  101  is shown in front view at the left side of  FIG. 1  and is shown in side view at the right side of  FIG. 1 . Wall plate  101  includes mounting apertures  102  and  103 . Phone line designator  106  identifies aperture  104  as line “1” and line designator  107  identifies aperture  105  as line “2.” Jack  108 , which includes an embodiment of the present invention (to be described), is shown mounted in aperture  104 . Another jack  109  is shown mounted in aperture  105 . Apertures  110  and  111  may be familiar-looking phone-jack apertures into which telephone lines would ordinarily be plugged if this wall plate were being used directly with telephones (telephone lines not shown). However, in this instance, fiber optic jumpers (not shown) would be plugged into these apertures, those jumpers operatively coupled to, for example, a fiber optic network terminal (not shown). There could then be operative couplings from that fiber optic network terminal to installed consumer-related equipment such as TV, telephone, computer, etc. 
     FIG. 2  depicts the present invention in four related views.  FIG. 2A  is a cross-sectional view of an exemplary pluggable jack holding an optical-fiber having a pre-sliced end. Pluggable jack  108  is the same jack  108  shown in  FIG. 1 . Optical-fiber  201  is shown sliced at an angle which is other than a right angle relative to its longitudinal axis. In a preferred embodiment this angle is angularly-displaced from that right angle by approximately eight (8) degrees. In other words, this preferred embodiment angle is angularly displaced from its own longitudinal axis by eighty two (82) degrees measured in a clockwise direction from its axis. Optical-fiber  201  is circumferentially supported by optical cable insulation and support material  202  in a firm manner which constrains optical-fiber  201  from being displaced in a radial direction. This material can be made from plastic, its properties including resistance to expansion and contraction when exposed to temperature variations. Funnel  203  forms an aperture designed to accept and guide another like fiber to its center, and is similarly circumferentially supported by similar insulation and support material  204 . Female keying means  205  is shown in the upper right of  FIG. 2A , and the far inside face of the female keying means is shown in this view. 
     FIG. 2B  is a cross-sectional view of a portion of an exemplary connector-clamp or “shoe”  209  holding an optical-fiber with a sliced end. The cross section is taken vertically through the axis of the optical-fiber, as shown in  FIG. 2C  which is a frontal view of the connector clamp of  FIG. 2B , and reference may be made to both Figs. in this description. Glass fiber  201 A has been sliced (to be described below) at an angle which is complementary to the angle to which optical-fiber  201  in  FIG. 2A  has been sliced and at a protrusion length L 2  which is equal to length L 1  of  FIG. 2A , in accordance with principles of the present invention. Optical-fiber cladding  210 , tightly circumscribes optical-fiber  210 A (which is circular in transverse cross section) and is a dielectric which supports fiber  210 A while being capable of absorbing light energy directed at it, and typically can be white. Insulation  211  circumscribes cladding  210 , although not as tightly as the cladding-glass fit, offers substantial physical protection and electrical/optical insulation for the optical-fiber which it contains, and typically can be approximately 0.125 inches in outside diameter in yellow color. Colors are immaterial to the principles of operation of the present invention. 
   Three circumferential clamps are provided. Optical clamp  206  tightly holds optical-fiber  201 A, and can be fashioned from plastic material which has a slight resilience to enable it to tightly choke the optical-fiber without cracking it. Cladding clamp  207  has an inside diameter slightly smaller than the outside diameter of the cladding and also contains small protrusions or teeth (not shown) from its surface configured to bite and hold white cladding  210 . Typically, the white cladding has a degree of resilience to it and may typically have a 250 micron outside diameter, compared with the inside diameter of the cladding clamp measured between oppositely disposed protrusions at approximately 200 microns. This is a sufficient diameter-differential to cause a choking force on the white cladding/optical-fiber combination to render the combination immovable, both axially and rotationally. The teeth merely hold the cladding without penetrating it sufficiently to touch its optical-fiber center which may have a diameter approximately 100 microns. And, insulation clamp  208  circumscribes the yellow insulation  211  in a manner similar to the other clamps to add stability, but applies less force than the other clamps to allow some movement between the white cladding and its encapsulating yellow insulation to permit the cladded optical fiber to be pulled through the insulation, if need be. The reason for these clamps shall be explained more fully below. 
   Connector clamp  209  can be square, rectangular, or some other shape in cross section, formed of hard plastic material. It encompasses and provides radially-directed force for the three clamps discussed above as it pushes in a radial direction against the clamping materials. It has a front face which is formed with a conical flare, rim  212  of that flare being shown in  FIG. 2C . In one embodiment the flare is configured to mate exactly with the opening of funnel  203 . In another embodiment, to allow some “wiggle” room for optical fiber  201 A in the event that optical fiber  201 A is microns too long, the flare may be partially or completely eliminated, which would allow the optical fiber to push and displace in a direction other than pushing only directly against optical fiber  201 . Male keying means  205 A is shown at the top of connector clamp  209  and is designed to permit only one orientation of insertion of connector clamp  209  into pluggable jack  108 . This is crucial for connector clamp bodies with square or rectangular transverse cross sections. 
     FIG. 2D  is a perspective view of connector clamp  209  of  FIGS. 2B and 2C , with optical-fiber  201 A, male keying means  205 A and rim  212  being shown. It should be understood that the dimensional proportions in  FIGS. 2A-2D  are intentionally not depicted accurately for purposes of enhancing clarity of presentation. The diameter of the optical-fiber may be on the order of 100 microns or less (0.0039 inch), and it is not feasible to show a cleaved angle on that fiber if it were held to its rightful proportion with respect to, for example, connector clamp  209  which could be square shaped with each edge being on the order of 0.25 inch, almost 100 times larger. Also, the angle of slice or cleavage is shown at an angle which is more than the preferred embodiment of eight degrees, again to enhance clarity of presentation. 
     FIG. 3  is a schematic diagram of an exemplary embodiment of a portable diamond wheel optical-fiber cutter mechanism  300  of the type that may be used in or with the present invention and shown supporting the pluggable jack and optical-fiber of  FIGS. 2B-2D . Diamond wheel cutter base  301  is shown supporting connector clamp  209 . Connector clamp  209  can lie in a conforming channel (not shown) formed in cutter base  301 . The channel shown conforms to connector clamp  209  in the embodiment without a conical flare. If a connector clamp having a conical flare is being used by the technician/installer, a different cutter mechanism  300  having a channel shape that matingly receives the conical flare (not shown) would be used. Also clamp body  209  can be held securely in place by other clamps, not shown. Optical-fiber  201 A (again in exaggerated dimension) is shown protruding from clamp body  209  in the left direction, while insulation  211 , encompassing cladding  210  (not shown) which encompasses optical-fiber  201 A (not shown) protrudes from clamp body  209  in the right direction. Optical-fiber  201 A also lies in a channel (not shown) formed within base  301 . Groove  307  lies underneath optical-fiber  201 A and intersects the channel holding optical-fiber  201 A, thereby removing support at the intersection. Attached to mechanism body  301  by hinge  303  is diamond blade chassis  302  which holds, in one embodiment, rotatable diamond blade  308 . In another embodiment, diamond blade  308  does not rotate. Also shown are grooves  306 ,  307 A and  309 , as well as hand control  305  which is attached to cutter  308 . 
   In operation, consider  FIGS. 2 and 3  together. When a fiber optic installer is requested to install a large number of “fiber-drops” in a large apartment building, he/she carries with him/her the portable cutter mechanism  300 . While carried, chassis  302  is in a closed and locked position with diamond cutter wheel resting in groove  307  and with chassis  302  locked in place on top of base  301  by a latch (not shown). Of course, connector clamp  209  is not in its depicted position when cutter mechanism  300  is being transported with wheel chassis in locked position. Diamond wheel slicer  308 , in one embodiment, is driven by a small portable and battery-powered motor (both motor and rechargeable battery not shown). The rotational axis of the motor is canted or tilted at an angle with respect to that plane of the surface of chassis  302  which mates with the surface of cutter base  301  when the hinged chassis is in a closed position. That angle of tilt can be fixed at the preferred embodiment angle of eight degrees. Grooves  307  and  307 A are made sufficiently wide to allow for not only the width of cutter wheel  308  itself, but also to allow for the additional width needed due to the cant or tilt of the rotational axis of the wheel. The greater the tilt, the wider the groove or channel needs to be. 
   When an optical-fiber is to be cut, the following procedure is followed. The chassis is opened to the position shown in  FIG. 3 . A piece of optical-fiber cable is stripped by the technician to expose bare optical-fiber and a small amount of white cladding using a special hand tool which permits a precise amount of yellow insulation to be removed, exposing the white cladding beneath. The prepared optical-fiber with cladding and insulation is placed inside the body of connector clamp  209 , either by insertion from the far right end using a funnel mechanism built-into the right end of connector clamp  209  and not unlike that shown in  FIG. 2A , or by removing the top of clamp body  209 , laying the optical-fiber with cladding and insulation therein, and thereafter snapping-shut the clamp connector (removable top and snap-lock not shown in  FIG. 3 ). Connector clamp  209  with optical cable inserted therein are then placed into their respective channels (not shown) formed in base  301  for holding both connector clamp  209  and optical-fiber  201 A. 
   With cutter  308  positioned by hand adjuster  305  within groove  307 A to a position nearest hinge  303 , chassis  302  is carefully closed and latched. Groove  306  fits over and secures optical fiber  201 A. Alternatively, groove  306  may not be needed if the channel holding optical fiber  201 A is deep enough. With battery power turned on, cutter  308  rotates at high speed and at the canted angle discussed above. Using hand adjuster  305 , by sliding it transversely in groove  309 , the canted rotating wheel transversely slices through the optical-fiber at the prescribed angle and at the appropriate length L 2  In an alternative embodiment, cutter  308  does not rotate at high speed under battery power. Instead, by using hand adjuster  305 , cutter  308  may be drawn over the optical fiber which it scores allowing a clean break, or may be drawn back and forth over the optical fiber and thereby slicing it by result of the transverse motion. After multiple usages in this position, the diamond wheel can be hand-rotated to another position if and when the blade portion doing the slicing in its current position begins to get dull. 
   The location of the channel which holds connector clamp  209  with respect to location of channel  307  is precisely set to ensure that length L 2  is achieved. Thereafter, chassis  302  is opened, the snap (not shown) holding down connector clamp  209  is released, and connector clamp  209  is removed from base  301 . Optical-fiber  201 A can be cleaned with alcohol, to remove any debris from the fiber due to the cutting process. Connector clamp  209  is then oriented by the technician so that its male keying means  205 A is aligned with female keying means  205 , and is then inserted into aperture  213  as suggested by the juxtaposition of  FIGS. 2B and 2A . When optical-fiber  201 A makes contact with funnel  203 , the relatively wide funnel mouth guides the optical-fiber into position so that its axis and the axis of optical-fiber  201  tend to become co-linear. Upon complete insertion, the face of optical-fiber  201 A (which is now elliptical in shape because of the angular cut) is pressed against the elliptical face of optical-fiber  201 . The conical flare on the face of connector clamp  209  in one embodiment may be designed to mate substantially with funnel  203 , and connector clamp  209  is locked into place with pluggable jack  108 , by locking means (not shown). In other embodiments, the conical flare on the face of connector clamp  209  may be configured to allow a small gap between connector clamp  209  and the cylindrical surface of optical fiber  201 A to allow wiggle-room or play in a radial direction for optical fiber  201 A after insertion, or may be completely eliminated to allow even more wiggle-room, to properly manage the situation where L 2  may be a few microns too long relative to length L 1 . 
   Accordingly, equality of lengths L 1  and L 2  is important. Also it is important that the pre-sliced angle of optical-fiber  201  and the field-sliced angle of optical-fiber  201 A be complementary. Accuracy of these angles is important in order to (1) make the elliptical sliced end of fiber  201  substantially coplanar with the elliptical sliced end of fiber  201 A and (2) make the elliptical sliced end of fiber  201  substantially congruent (congruence=100% overlap) with the elliptical sliced end of fiber  201 A, in order to pass maximum light energy therethrough with minimum attenuation and concomitantly minimize reflected light energy therefrom. The bigger the gap between, and the less overlap of, the sliced ends after insertion, the bigger the transmission loss. When a state of coplanar congruency is achieved, the longitudinal axes of portions of optical-fibers  201  and  201 A contained within pluggable jack  108  and connector clamp  209  respectively are substantially co-linear. 
   To further ensure the appropriate interface between the two optical-fibers, the following technique may be employed. On the one hand, a thin coating of indexing gel may be applied to the tip of optical-fiber  201 A after cleaning with alcohol, which passes light and offers a means of adding a few microns “length” to optical-fiber  201 A, if needed. On the other hand, the above-noted loosening or complete elimination of the conical flare on the face of connector clamp  209  allows a radial-direction wiggle room for optical fiber  201 A, so that there is the slightest “give” to optical-fiber  201  if optical-fiber  201 A is a few microns too long. By using both of these techniques together, a few microns difference in either direction between lengths L 1  and L 2  is accounted for, ensuring an optimum connection. 
   Periodically, the portable slicer  300  can be returned to the factory to be re-aligned if necessary. For example, realignment can be accomplished by using a test jig having a standard optical-fiber embedded therein. Optical-fibers sliced by the returned portable slicer can be tested against the standard fiber in the test jig. Adjustment to the slicer under test is made until optical-fibers sliced in that slicer produce maximum light energy throughput. Other realignment techniques could be used. 
     FIG. 4  is a schematic view of the two optical-fibers  201  and  201 A in their mated position showing, on edge, a coplanar and congruent interface  401  therebetween. As a result of this optimum interface, virtually all light from the depicted light source that reaches the interface will pass through it and virtually none of the light reaching the interface will be reflected from it. Any light that is reflected from it is reflected into the cladding containing the optical-fiber. One property of that cladding is to absorb reflected light and attenuate it, thereby inhibiting or preventing it from being transmitted back to the light source. Any reflected light reaching the light source would interfere with the light source signal being generated. As shown, the light source may be positioned in a telecommunications company&#39;s central office, and the light receiver may be positioned inside an apartment unit of a telecommunications consumer who uses communication devices such as telephone, television, Internet or other communications gear which are fed signals via the installed optical-fiber connection. 
   The present embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the invention, therefore, is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.