Abstract:
An apparatus for performing a polishing operation on a fiber of a fiber optic cable in a cable termination, including means to receive the termination with the fiber extending therefrom towards a polishing surface, an operating means to bring the extending fiber and the polishing surface together, means to move the polishing surface relative to the termination and the fiber with the fiber and polishing surface in contact, to perform polishing of the fiber, characterized in that the operating means includes a manually operable member which is pivotal about a pivot axis, and means to bring the extending fiber and polishing surface together in response to pivoting movement of the manually operable member in a direction transverse to the pivot axis.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an apparatus for performing a polishing operation on a fiber of a fiber optic cable in a cable termination. 
     DESCRIPTION OF THE PRIOR ART 
     Fiber optic cables transmit data as pulses of light along a fiber comprising a core contained in a cladding having a different refractive index. Typically the fiber may have a diameter of only 50-300 microns. To allow the light pulses to pass from the core of the fiber at a termination of the cable into another core where two cables are joined, or to data handling apparatus where the cable terminates, the fibre must be accurately aligned and optically prepared. 
     To achieve this, the fibre optic cable is terminated in a termination which holds the cable and provides for connection to another termination or other connector. The fibre of the cable is set relative to the termination with an adhesive, and an end of the fibre which projects from a surface of the termination is polished to an optical flat. 
     The polishing process is critical to achieving a required quality of transmission of the light pulses, as pool polishing can introduce cracks and deep scratches into the fibre which cannot be removed. Such cracks and deep scratches can seriously affect the quality of the light transmission, resulting in loss of bandwidth or even corrupted data. 
     Whereas the fibre could be polished manually, various apparatus are known for more automated polishing. In each case a polishing surface or film is used, and relative movement is performed between the polishing surfacing and the fibre optic core. 
     Polishing apparatus for use in a laboratory environment are known which comprise a glass plate on which polishing film is mounted, and a fixture to hold the termination with the fibre projecting from a surface thereof. However known such apparatus require a high degree of skill to achieve satisfactory results consistently. Furthermore such apparatus are not portable. 
     It is desirable to be able to perform a polishing operation on a fibre of a fibre optic cable in a cable termination in situ, for example on board an aircraft where fibre optic cables are used for data transmission. In such environments there may be no readily available power supply for operating a polishing apparatus, and polishing may need to be carried out in very confined spaces, where no work surface is available. Also the persons expected to carry out such polishing may not be skilled in that task. Because in situ there may be little spare length of fibre optic cable, re-working of cable terminations may not be possible. The problems of in situ fibre optic repair and the like are aggravated because of the variety of different termination types in use, some having spring loaded parts which means that the terminations require particular handling. 
     Hand held fibre optic polishing apparatus have been proposed, but by the nature of their construction, they have not performed adequately and have been unable to handle a variety of termination types. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention we provide an apparatus for performing a polishing operation on a fibre of a fibre optic cable in a cable termination, the apparatus including means to receive the termination with the fibre extending therefrom towards a polishing surface, an operating means to bring the extending fibre and the polishing surface together, means to move the polishing surface relative to the termination and the fibre with the fibre and polishing surface in contact, to perform polishing of the fibre, characterised in that the operating means includes a manually operable member which is pivotal about a pivot axis, and means to bring the extending fibre and polishing surface together in response to pivoting movement of the manually operable member in a direction transverse to the pivot axis. 
     Thus by virtue of the simple construction of the apparatus, a simply operated and versatile apparatus may be provided, particularly suited for hand held use in situ by unskilled persons. 
     The apparatus may comprise a body and the manually operable member may be mounted on the body, whilst the means to receive the termination may be provided by a support assembly which is moveable relative to the body in response to pivoting movement of the manually operable member. To facilitate its use in confined conditions by unskilled persons, the apparatus may have guide means to guide the movement of the support assembly relative to the body in a direction normal to the pivot axis of the manually operable member, so that the projecting fibre and polishing surface are reliably brought together in a desired relative orientation in response to a simple manual movement of the manually operable member. 
     In one construction the manually operable member may be pivoted at one end to the body and may act to move the support assembly through a lever which is also pivotally mounted on the body and preferably also to the support assembly. 
     To prevent too much pressure being applied between the polishing surface and the projecting fibre by operation of the manually operable member, preferably the support assembly comprises a first part on which the manually operable member acts, and a second part which provides the means to receive the termination, the first part being moveable relative to the second part when the support assembly has been moved relative to the body so as to bring the termination and projecting fibre optic core into contact with the polishing surface at a predetermined pressure. 
     Desirably guide means are provided between the first and second parts of the support assembly to allow relative movement therebetween, and resilient means act between the first and second parts of the support assembly to resist relative movement therebetween until the predetermined pressure is applied by the manually operable member. Thus the first and second parts will move in concert in response to movement of the manually operable member to bring the polishing surface and projecting fibre together, but in the event that excess pressure is applied, the resilient means will permit of continued movement of the first part, movement of the second part is relieved. 
     The means which receive the termination may comprises an opening in the support assembly, preferably in the second part of the assembly, the opening being adapted so that the fibre extends from the termination in a direction substantially normal to the direction of movement of the support assembly relative to the body. To enable the apparatus to be used with a variety of termination types the opening may be provided in a removable insert which is adapted to receive a termination of a particular configuration and thus which may readily be exchanged for a removable insert which is adapted to receive a termination of another particular configuration. 
     In addition to any resilient means which act between the first and second parts of the support assembly, resilient means may act between the body and the support assembly to resist movement of the termination and projecting fibre towards the polishing surface in response to operation of the manually operable member, thus to improve control of the polishing process and to move the support assembly away from the polishing surface when the manually operable member is released. 
     An apparatus according to the invention may include a motor to move the polishing surface relative to the termination, and a housing for a power supply for the motor so that no external drive means or power supply is required. 
     For most efficient use of the polishing surface the polishing surface may be moved relative to the termination by a transmission which provides for relatively eccentric motion of the polishing surface relative to the termination. 
     According to a second aspect of the invention we provide a method of performing a polishing operation on a fibre of a fibre optic cable in a termination of the cable utilising a portable hand held apparatus including means to receive the termination with the fibre extending therefrom towards a polishing surface, an operating means to bring the extending fibre and the polishing surface together, means to move the polishing surface relative to the termination and the fibre with the fibre and polishing surface in contact, to perform polishing of the fibre, the method comprising manually operating a manually operable member by pivoting the member about a pivot axis to bring the extending fibre and polishing surface together. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described with reference to the accompanying drawings in which: 
     FIG. 1 is a plan view of a polishing apparatus in accordance with the invention; 
     FIG. 2 is a side sectional view along the line A—A of the apparatus of FIG. 1; 
     FIGS. 3 a  to  3   d  is a schematic illustration of a fibre optic cable termination procedure which includes a polishing process for which the apparatus of FIG. 1 may be used. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, an apparatus  10  for performing a polishing operation on a fibre  11  of a fibre optic cable  12  in a cable termination  14  is illustrated. 
     A typical fibre optic cable termination procedure is as follows. 
     First, the fibre optic cable  12  is prepared by stripping back outer layers  15  thereof to leave a projecting length of fibre  11  comprising a core surrounded by cladding (not shown). The projecting fibre  11  is then inserted into a termination  14  which in the example shown in FIG. 3 a  is a metal ferrule  16  having a ceramic part  17  with a central opening to receive the fibre  11 . The ferrule  16  has a female screw thread (not seen) by which the termination  14  is connectable to a corresponding male threaded termination of another fibre optic cable, or a male threaded part of a data handling machine or the like. 
     The projecting length of the fibre  11  is such that when inserted, with the outer layers  15  received by the ferrule  16 , a portion  11   a  of the fibre  11  projects outwardly of the ceramic part  17  as seen in FIG. 3 b.    
     The fibre  11  is set in the ceramic salt  17  by means of an adhesive, usually an epoxy adhesive, which may be introduced into the ferrule  16  ahead of the fibre  11 , so that as the fibre  11  is introduced, some of the adhesive is ejected from the opening in the ceramic  17 , as indicated at  19  in FIG. 3 b , to form a dome of adhesive about the projecting fibre portion  11   a . 
     Next the cable  12  is secured relative to the termination  14  by curing the epoxy  19  e.g. by applying heat, or is simply allowed to cure. The projecting portion  11   a  is then shortened by a cleaving process, to leave a short projecting length only, as seen in FIG. 3 c , projecting from an end surface of the ceramic part  17  of the termination. The fibre  11  can then be polished to an optical flat  21  as indicated in FIG. 3 d , which polishing will also remove the dome of epoxy  19 . 
     Referring particularly to FIGS. 1 and 2, a polishing apparatus  10  includes an opening  22  in a removable insert  23  to receive the termination  14  with the fibre  11  extending from the end surface  21  of the termination  14  towards a polishing surface  25  which in this example is a very fine grade polishing film. 
     An operating means  26  is provided to bring the extending fibre  11  and the polishing surface  25  together. The operating means  26  comprises a manually operable handle member  28  which is pivotal about a pivot axis B. This may be achieved by an operator holding a body  30  of the apparatus  10  with his fingers about the handle  28 . As the handle  28  pivots about axis B, the handle  28  acts on a lever  31  which is also pivoted at one end  29  thereof to the body  30 , but for movement about an axis C, the axes B and C being parallel to but spaced from one another, the handle  28  bearing on a roller  33  between the handle  28  and lever  31 . As the handle  28  is pivoted about axis B, the lever  31  is caused to pivot about axis C. 
     An opposite end  32  of the lever  31  is pivoted to a support assembly  34 , to pivot about a pivot axis D. As a result of handle  28  movement, the support assembly  34  moves relative to the body  30  as hereinafter described. 
     Within the body  30  there is provided a motor  35 , and a power pack (battery)  36 . The motor  35  is operated by a switch  37  but could be operated via a microswitch for example, upon handle  28  movement. 
     The motor  35  drives the polishing surface  25  through a transmission  41  so that the polishing surface  25  undergoes an eccentric movement in a plane P beneath the termination  14 . 
     The support assembly  34  is mounted on the body  30  by a first guide means provided by four pillars  42   a  to  42   d . Each pillar  42   a  to  42   d  has an end stop  43 , and the support assembly  34  can move up and down guided along the pillars  42   a  to  42   d  (only up as far as the stops  43  allow) with the pillars  42   a  to  42   d  each received in a corresponding opening of a first part  44  of the support assembly  34 , the first part  44  comprising a plate-like part. 
     Within an opening  46  of the first plate-like part  44  of the support assembly  34 , there is mounted a second plate-like part  48  which provides an opening  49  for the insert  23  which provides the opening  22  to receive the termination  14 . The opening  49  for the insert  23  has, in this example, three inwardly extending sprung plungers  47 , which are receivable in e.g. a groove provided in the insert  23 , for the purposes of retaining the insert  23  in the opening  49 . The insert  23  is of top-hat shape, a brim  50  of the hat sitting on the second plate-like part  48  to prevent the insert  23  passing downwardly as seen in FIG. 2 of the drawings, through the second plate-like part  48 . 
     The second plate-like part  48  is mounted with respect to the first plate-like part  45  on three pillars  51   a  to  51   c , each pillar  51   a  to  51   c  providing a second guide means in the event of there being relative movement between the first plate-like part  44  and the second plate-like part  48 . However such relative movement is resisted by resilient biasing means comprising springs  52   a  to  52   c , one being provided on each of the pillars  51   a  to  51   c.    
     By virtue of the first guide means  42   a - 42   d  guiding the first plate-like part  44  movement, when the handle  28  is operated by pivoting towards the body  30 , the movement of the lever  31  will cause the first plate-like part  44  and hence the second plate-like part  48  and thus the termination  14 , to move towards the polishing surface  25 , to bring the projecting fibre portion  11   a  into contact with the polishing surface  25 . The pillars  42   a  to  42   d  of the first guide means may carry resilient biasing means  56  comprising springs which act between the body  30  and the first plate-like part  44 , to resist handle  28  movement and thus improve the control of the polishing process. However the force of those springs  56  may be readily overcome by the normal operation of the handle  28 . 
     Thus with the motor  35  switched on and the polishing surface  25  performing its eccentric movement, the projecting fibre  11  may be moved towards the moving polishing surface  25  to polish away the dome of epoxy  19  and the projecting length of the fibre  11 . 
     If too great a pressure is applied to the handle  28  by the operator, excess pressure greater than the force applied between the first and second plate-like parts  44 , 48  by the springs  52   a  to  52   c  of the second guide means  51   a - 51   c , will be relieved by the springs  51   a  to  51   c , so that the first plate-like part  44  may continue to be moved by the handle operation, but the second plate-like part  48  will not continue to move towards the polishing surface  25 . 
     Handle  28  movement is eventually arrested by a stop  59  of the body  30 . 
     It will be appreciated that the insert  23  providing the receiving opening  22  for the termination  14  may be removed from the opening  49  in the second plate-like part  48 , and may be replaced with a different insert having an opening adapted to receive a different kind or configuration of termination. 
     Various modifications may be made without departing from the scope of the invention. 
     For example although eccentric polishing surface  25  movement is preferred, in another arrangement an orbital or even circular movement may be performed by the transmission  41 . The first and second plate-like members  44 , 48  may be of other configurations than shown, as may the first and/or guide means  42   a - 42   d  and  51   a - 51   c  which mount them. 
     Instead of a lever  31  arrangement as shown, an alternative mechanism for transmitting the pivotal movement of the handle  28  to a linear movement of the support assembly  34  to bring the projecting fibre portion  11   a  and the polishing surface  25  together, may alternatively be provided. 
     The battery pack  36  may be rechargeable, or if desired the apparatus  10  may be powered by external means where an external power supply is conveniently available.