Abstract:
Multiple light beams are launched into a single optical fiber, each respective light beam with a corresponding signal. Each of the respective multi-beams are separated by launching each of the light at a different incidence angle and/or input position, into the optical fiber. In this way, each light beam is able to propagate independently according to its own trajectory inside the fiber. The resultant multi light beams propagate with respective counter cyclical orbital angular momentum with respective helical paths.

Description:
A claim for priority under 35 U.S.C. 120 is made for the filing date of provisional patent application 61/252,820, filed Oct. 19, 2009 
    
    
     FIELD OF INVENTION 
     Multiplexing multi optical channels of the same or different optical wavelengths, on a single fiber, with counter cyclical orbital angular momentum 
     BACKGROUND 
     The subject invention pertains to a method and apparatus for multiplexing in optical fiber communications, for example, as shown and described in U.S. Pat. No. 7,639,909, Method And Apparatus For Spatial Domain Multiplexing In Optical Fiber Communications. As shown therein, multiple light beams, are launched into a single optical fiber, each respective light beam with a corresponding signal. The respective multi-beam excitation and separation in a single optical fiber, as disclosed, is accomplished by launching one or more light beams, each at a different incidence angle and/or input position, into the optical fiber. In this way, each light beam is able to propagate independently according to its own trajectory inside the fiber. As shown and described in U.S. Pat. No. 7,639,909, the projection of the light beam is in an annular ring with a respective radius dependent on the launch angle or skew angle of the light beam into the optical fiber. 
     SUMMARY OF THE INVENTION 
     U.S. Pat. No. 7,639,909 and the disclosed invention is incorporated by reference. The invention, as disclosed in U.S. Pat. No. 7,639,909 is a system for producing propagating helical light rays in an optical carrier. It discloses projecting a light ray beam into an optic fiber at an incident angle θ n  relative to a numerical aperture θmax for the optic fiber. 
     As shown and disclosed in U.S. Pat. No. 7,639,909, for spatial domain multiplexing (SDM), multiple light beams are projected or launched into a single optical fiber at different respective incident angles, θ n . As shown in U.S. Pat. No. 7,639,909, using the known physical constraints of the fiber optic, a maximum angle of incidence which is the numerical aperture represented by Sine θ max  may be calculated. Multiple light beams may be projected into the fiber optic at separate respective discrete angles, or incident angles, θ n  within a numerical aperture θ max . For example, for a numerical aperture θ max =50 degrees and for a respective incidence angle for θ n  from approximately 0 degrees up to a maximum incidence angle θ n  equal to θ max , which is the maximum angle of incidence or projection of the light beam into the fiber optic, for θ n , the variation of conic shapes of output light, appearing in respective annular rings projected on a flat surface, may be observed as respective annular rings of varying radii responsive to the respective incident angle θ n  of the projected light beam into the optic fiber. 
     As shown and described in U.S. Pat. No. 7,639,909, the physical output angles for the respective annular rings illuminated on the projected flat surface may be determined and as shown in U.S. Pat. No. 7,639,909, FIG. 11, may be plotted. 
     As shown and disclosed in U.S. Pat. No. 7,639,909, the light beams projected into the optic fiber with an incident angle θ n  within the numerical aperture θ max  propagate with orbital angular momentum in a helical path in the direction of the longitudinal axis of the optic fiber. 
     According to the disclosed inventive principles, a plurality of light beams in separate respective channels, are projected or inserted into an optic fiber at opposite angles of incidence, within a numerical aperture θ max . The resultant light beams propagate with respective counter cyclical orbital angular momentum in respective helical paths in the longitudinal direction of the optic fiber. The resultant light beams, with opposite angles of incidence θ n , propagating with opposite angular momentum in counter rotating directions, clockwise and counterclockwise may occupy the same helical path but are counter cyclical with clockwise and counter clockwise orbital angular momentum and are non interfering, 
     Where, as shown and disclosed, according to the disclosed inventive principles as shown for a preferred embodiment, and in a best mode, a plurality of separate respective light beams may be projected or inserted into an end of the optic fiber, with opposite angles of incidence or projection, for example as shown in a preferred embodiment, with same, or approximately the same, complementary angles of incidence. 
     The light beams may be projected into the fiber optic at respective points with the same or approximately the same displacement from the longitudinal axis of the optical fiber, for example, with respect to a locus describing a diameter of the optic fiber, or a locus describing a chord across the end of the optic fiber. As shown in a preferred embodiment, the light beams may be projected into the fiber optic a single coincident point. 
     However, the invention is not limited to the disclosed preferred embodiment but may be practiced, as shown herein, with a plurality of light beams projected or inserted into an optic fiber, with each respective light beam projected or inserted with a varying angle of incidence θ n  within a the numerical aperture θ max . Each of the projected light beams may be located at any selected random point on the end of the optic fiber and at any distance from any other of a plurality of projected light beams, relative to the locations where the other respective light beams are projected or inserted, into the fiber optic. 
     Projection of the light beams with opposed or opposite angles of incidence, for example θ 1  and θ 2  each within the maximum numerical aperture θ max , will cause the respective light will beams to propagate in the longitudinal axis direction of fiber optic, with respective counter cyclical orbital angular momentum (OAM) in a helical path. 
     As would be understood by those skilled in the art, by opposed or opposite angles of incidence is meant angles with opposed or opposite slopes. 
     The projections of the respective light beams, propagating in counter cyclical helical paths projected on a two dimensional plane, will produce light patterns in respective annular rings, with respective ring radii, as would be understood by those skilled in the art. Where the incident angles are opposite and approximately complementary, for example, the respective ring radii will be approximately the same. 
     As would be understood by those skilled in the art, an X, Y coordinate system for the end of the optic fiber, may be at any referenced location for an X axis and Y axis, on a circumference locus described by 2πr, where r is any radial distance from the Z axis, or longitudinal axis, of the fiber optic end, to a maximum radius for a fiber optic. 
     According to the principals of the disclosed invention, and for a preferred embodiment shown in a best mode, where the respective light beams, are projected into the optic fiber at approximately opposite and complementary angles, for example θ 1  and θ 2 , at opposed locations separated by the longitudinal or Z axis of the fiber optic, the respective light beams propagate in two optical channels describing similar countercyclical rotating helical paths inside the optic fiber with opposite, orbital angular momentum (OAM) and will project light in annular rings of approximately the same radii. 
     According to the disclosed inventive principles, two light beams at the same wavelength with opposite orbital angular momentum, clockwise and counter clockwise, can be simultaneously transmitted in the direction of the optic channel longitudinal or Z axis of the optic fiber, without interference, as shown and taught, according to the disclosed inventive principles. 
     At the output of the fiber optic, the respective light beams, with counter cyclical orbital angular momentum, propagate the same or similar set of X and Y coordinates, relative to a referenced X and Y coordinate system established at the input and output end planes of the optical fiber. The two countercyclical light beams may be projected on a projection plane or on a two dimensional surface, relative to the same X and Y coordinates. 
     As shown and described, according to the disclosed inventive principles, the projected radial displacement or radii of the respective annular rings will depend on the light beam projection variables, for example, the selected location and the incidence angle, θ 1  and θ 2 , at which the respective light beams are projected or inserted in the input end of the fiber optic. In a preferred embodiment, to preserve bandwidth, the countercyclical light beams may be projected into a fiber optic with opposite or complementary angles and at opposed locations relative to the X, Y, Z, axis so the helical propagation of the two counter cyclical light beams are with the same helical radius and the annular projections of the two countercyclical light beams have the same annular radius. 
     According to the disclosed inventive principles and as shown for a preferred embodiment, the two respective light channels with counter cyclical orbital momentum, (OAM), in the clockwise and counterclockwise, directions, are non interfering, which may be separately verified, by using the opposite OAM of each light beam in a novel detector as shown and described according to the disclosed inventive principals and in a preferred embodiment. 
     As shown by the disclosed inventive principles and as shown in preferred embodiment, a plurality of counter cyclical helically propagating light beams, with opposite orbital angular momentum (OAM), from a plurality of light beams projected into a fiber optic with complementary or opposite angles of incidence and at opposed locations, projecting annular rings with the same radii, may be separately detected by an annular detector with light responsive elements in the orbital or rotating paths of light beams. 
     As shown for a preferred embodiment, detection may be by interfering with the counter cyclical propagating light beams helically projected in respective rotational directions and detecting the change in the response of the light responsive elements at selected locations subject to interference to the respective counter cyclical light beams. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows in schematic form, projecting two light beams into the planar end of a fiber optic, at opposite launch angles and generating two contra cyclical light beams, propagating in the Z or longitudinal axis of the fiber optic with opposite orbital angular momentum. 
         FIG. 1   a  shown in schematic form the insertion or of separate light beams, as shown in  FIG. 1 , at approximately complementary angles θ 1  and θ 2 , at opposed locations at the fiber optic end, shown as a plane. 
         FIG. 1   b  shows in schematic form the two countercyclical light beams with opposed orbital angular momentum, propagating in a helical path in the direction of the Z or longitudinal axis of the fiber optic, and in counter clockwise and clockwise, directions 
         FIG. 1   c  shows in schematic form the projections of the two countercyclical light beams on a two dimensional surface, as shown in  FIG. 1 , with opposed orbital angular momentum, and showing the skew angles of the shadows produced in the projected annular rings by an interfering object shown as a wire place to interfere with the projection light path and as projected with the annular rings, parallel to the referenced object or the X axis of the fiber optic. 
         FIG. 1   d  shows in an exploded view, the separate projections of the two countercyclical light beams with opposed orbital angular momentum, as shown in  FIGS. 1 and 1   c , as two annular rings with the respective shadows cast by an interfering object shown as a wire across the X axis of fiber optic, and with the shadows shown in each projected annular ring shown rotated from the projected X axis of the fiber optic or the spatial projection of the interfering object, on the two dimensional surface, by equal and opposite skew angles [±γ 11 , ±γ 13 ]. 
         FIG. 1   e  shows in schematic form, two light beams, for example the light beams, projected into end of the fiber optic at the same random coincident location and at a selected opposite incidence angles θ 1 , θ 2 , to produce counter cyclical helically propagating light beam with opposite OAM, and annular ring projections of the light beams, with the same radii. 
         FIG. 1   f  shows in schematic form, a single light beam projected into the end of the fiber optic at a selected random location and at a selected incidence angle θ 2  to produce a cyclical helically propagating light beam with OAM, and an annular ring projection of the light beam. 
         FIG. 1   g  shows in schematic form, a single light beam projected into the end of the fiber optic at a selected random location and at a selected incidence angle θ 1 , to produce a cyclical helically propagating light beam with OAM, and an annular ring projection of the light beam. 
         FIG. 1   h  shows in schematic form, two light beams, for example the light beans as shown in  FIG. 1   f  and  FIG. 1   g , projected into end of the fiber optic at a random selected locations and selected opposite incidence angles θ 1 , θ 2 , to produce cyclical helically propagating light beam with opposite OAM, and annular ring projections of the light beams with respective radii. 
         FIG. 2  shows, in schematic form, the projection of the two contra cyclical light beams, as shown in  FIGS. 1 ,  1   c , and  1   d , on a two dimensional surface with the respective shadows produced by an interfering object, shown as a wire across the X axis of fiber optic, with the shadow shown rotated from the projected X axis of the wire, on the two dimensional surface, by equal and opposite skew angles [±γ 11 , ±γ 13 ]. 
         FIG. 3  shows in schematic form, a detector for detecting each of two countercyclical rotating light beams, as shown in  FIGS. 1 ,  1   c , and  1   d.    
         FIG. 3   a  is a schematic view, shows the detector shown in  FIG. 3 , in a side view. 
         FIG. 3   b  is the truth table logic diagram showing how the signals produced from each of detector segments as shown in  FIG. 3 , may logically be used to separately detect the counter rotating beams, each with opposite orbital angular momentum, projected with the projections of a standard beam without orbital angular momentum. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     According to the disclosed inventive principles, and in a preferred embodiment, as shown in  FIG. 1  and  FIG. 1   a , two light beams  11  and  13  are projected, into an optic fiber  15  at respective opposite or opposed angles of incidence θ 1 , θ 2 , with respect to the longitudinal Z axis of the optic fiber and points  25 ,  27 , on a locus at end  17 , shown in a preferred embodiment as a planar end. 
     By opposed or opposite angles is understood to mean angles θ 1 , θ 2  with opposite slopes. The planar end  17  of the optic fiber end is shown and described by planar coordinate axes X and Y and by fiber optic longitudinal axis Z along the axis of the optic fiber  15 . As would be known to those skilled in the art, and as shown in  FIG. 1 , the X and Y axes may be rotated about the Z axis, to any referenced position, on a circumferential locus described by 2πr, where r is any radial distance from the center or z axis of the fiber optic. 
     For reference purposes only, the fiber optic  15  is shown with a first section  18  and a second section  20 , disposed on opposite sides and separated by the longitudinal Z axis. As shown in a preferred embodiment, the first section  18  and second section  20 , are separated by, and are on opposite sides of, the Y-Z plane, as shown in  FIGS. 1 and 1   a.    
     As shown and described, according to the disclosed principles of the invention, the random selected locations for inserting or projecting the opposed light beams into the fiber optic  15  may be in the same section, for example section  18 , or in opposed sections  18  and  20 , or at locations displaced at different displacements from the longitudinal Z axis of the fiber optic  15  or displaced with the same displacement from the fiber optic  15  longitudinal axis. 
     The terms as used herein, namely point, or location, or selected location, or random location, or random selected location, or selected random location, or selected point, or random point, or random selected point, or selected random point, is meant the location of the point or points, on the fiber optic at which the light beams are projected or inserted, into the fiber optic. 
     The helical paths of light beams  11  and  13 , with counter cyclical orbital angular momentum, are shown in  FIG. 1 , in the fiber optic  15  and in  FIG. 1   b , superposed on an X axis, Y axis and Z axis coordinate system. 
     According to the disclosed inventive principles, for a preferred embodiment, as shown in  FIG. 1  and  FIG. 1   a , two light beams  11  and  13  are projected, into, and intersect with the fiber optic  15  at two opposed points  25 ,  27 , on a reference fiber optic  15 , first locus  34 , shown in a preferred embodiment as the X axis. The beams  11  and  13  are inserted or projected or injected, into the optic fiber planar end  13 , at opposite angles and as shown in a preferred embodiment, as complementary or approximately complementary angles, θ 1 , and θ 2 . According to the inventive principles and in a preferred embodiment, the angles may be at, or approximately at opposite angles θ 1 , and θ 2  for example, for light beam  13  and  11 , respectively. 
     As shown by the disclosed inventive principles, the projection of the incident light beams, for example  11  and  13 , may be at selected random locations, as shown for example in  FIGS. 1   e ,  1   f ,  1   g , and  1   h.    
       FIG. 1   b , shows the two light beams  13  and  11 , may be projected to a on a second locus  36  at locations  46  and  38 , respectively. As shown in a preferred embodiment, the second locus  36  may be a chord parallel to, or at a 0° angle to the referenced X axis. However, as would be understood by those skilled in the art, the locus of the chord  36  or the diameter  34  may be at any rotational angle with reference to the X axis, at the fiber optic, end  17  and the incidence angles for θ 1 , and θ 2 , may be any selected angles within the maximum aperture θ max . 
     Projection of light beams  13  and  11 , into the planar end  17  of the optic fiber  15 , at opposed or opposite incidence angles θ 1 , and θ 2 , for example, to points  25 ,  27 , as shown on first locus  34 , causes the light beams  13  and  11  to propagate in two contra cyclical or counter rotating cyclical light beams, respectively, propagating helically in the respective light beam paths shown as respective paths  13  and  11 , each light beam with opposite orbital angular momentum, and each light beam  11  and  13  propagating along the optic fiber longitudinal Z axis to the opposite end  29  of the fiber optic  15 , as shown where the light beams  13  and  11  are projected in two annular rings, as shown schematically, by numerals  33  for light bean  13  and  31  for light beam  11 . 
     As shown in a preferred embodiment, in  FIG. 1   a , the light beams  11  and  13  are inserted or projected into end  17  of fiber optic  15  on a locus shown as the X axis  34  or along a locus describing a chord  36 , and at points opposed across, and separated by, the longitudinal Z axis. 
     The locations of the points where the light beams  11  and  13 , shown in a preferred embodiment at points  25 ,  27  and  38 ,  46 , and the angles of injection, θ 1 , and θ 2 , may be varied without departing from the disclosed inventive principles. 
     In accordance with the disclosed inventive principles, projection of a plurality of light beams, into the fiber optic with opposite incidence angles, each within the numerical aperture θ max , will produce countercyclical rotating light beams opposite orbital angular momentum (OAM) propagating in the direction of the optical axis of the fiber optic. Varying the incident angle θ n , for example by increasing it up to the numerical aperture θ max  will produce projected annular rings,  33  and  31  with increasing radii. Varying the points where the light beams are projected into the fiber optic, for example, displaced away from the longitudinal axis of the fiber optic will produce projected annular rings  31 ,  33  with increasing radii. 
     As shown for a preferred embodiment, the light beams  11  and  13  are inserted or projected into the optic fiber end at points opposed across, and separated by the longitudinal Z axis and in respective separate parts  18  and  20 , of the fiber optic  15  shown in a preferred embodiment as separated by the Y-Z plane, as shown in  FIG. 1  and  FIG. 1   a . However, as would be understood by those skilled in the art, the projected light beams may be inserted into the fiber optic  15 , in the same part of the fiber optic, for example in part  18  or in part  19 , or at the same point, as shown in  FIG. 1   e  or at selected random points as shown in  FIGS. 1   f ,  1   g ,  1   h , and the invention is not limited to the selected random insertion points, shown as examples, in  FIGS. 1   a ,  1   c ,  1   d ,  1   e ,  1   f ,  1   g.    
     The projection of the two counter rotating light beams  11  and  13 , with respective counter rotating orbital angular momentum, from fiber optic end  29  onto a two dimensional surface, is shown schematically in  FIGS. 1 ,  1   c ,  1   d  in an exploded view and in  FIG. 2 , by annular ring projections shown by  33  for light beam  13  and  31  for light beam  11 . 
     The counter cyclical orbital angular directions, clockwise and counterclockwise, of the annular ring projections  31  and  33 , is as shown schematically by the counterclockwise arrow  31   a  for annular projection  31  for light beam  11  and clockwise arrow  33   a  for annular projection  33  for light beam  13 . 
     The radius of the annular light projections, shown for example, in  FIGS. 1 ,  1   c ,  1   d , and  2 , as annular ring projections  33  and  31 , in the contra cyclical directions, shown arrows  31   a  and  33   a , may be varied according to the disclosed inventive principles, by varying the selected projection angles θ 1 , and θ 2  and the selected insertion or projection points, for the light beams, as shown for example, in a preferred embodiment as selected locations  25  and  27 , on first locus  34 , or the locations  38  and  46 , on second locus  36 , or as shown, for example, by the projection of annular rings  31  and  33 , produced by the insertion of light beam  11  at selected random insertion point  25 , and beam  13  at selected random insertion point  46 , as shown in  FIGS. 1   f ,  1   g ,  1   h , and as would be understood by those skilled in the art, the principles of the invention include all selected random point for the insertion of the light beams, for example  11  and  13 , in any X, Y, coordinate position. 
     As shown in  FIGS. 1 ,  1   c , and  1   d , shadows  35 ,  37 ,  39  and  41  are shown n the annular ring projections  31  and  33 , as would be projected by an interfering object, for example, wire  43  placed in the light path of projected light beams  11  an  13 , as shown in  FIG. 2 . 
     As shown in  FIGS. 1 ,  1   c ,  1   d , and  2 , where the interfering wire object, shown as wire  43  is located on a locus opposed to the fiber optic end  29 , and parallel to the X axis, the shadows  35 ,  41 , are shown on annular ring projection  31  and shadows  37 ,  39 , are shown on annular ring projection  33 . 
     As shown in  FIGS. 1   c  and  1   d , showing in schematic form, the annular right projections  31  and  33  are in the counter cyclical orbital directions of rotation  31   a  and  33   a . The shadows projected by the wire  43 , as shown in  FIG. 1 , located on the X axis of the fiber optic  15 , on annular ring  31 , for beam  11  and on annular ring  33  for beam  13 , are displaced at opposite respective skew angles ±γ 13 , and ±γ 11 , from a locus  44 , on the projection plane for the annular rings  31  and  33 , opposed to and parallel to the spatial projection of the X axis of the fiber optic  15 , or the wire  43 . 
     As would be understood by those skilled in the art, the angles θ 1 , and θ 2  may be varied without departing from the principles of the invention and the point of projection into the optic fiber end  17 , shown as  25 ,  27  or  36 ,  46 , in  FIG. 1  and  FIG. 1   a , may be varied without departing from the principles of the invention 
       FIG. 1   e  shows in schematic form, two light beams, for example the light beams  11  and  13 , projected into end of the fiber optic at the same random locations  25 ,  27 , and at selected opposite incidence angles θ 1 , θ 2 , to produce counter cyclical helically propagating light beam with opposite OAM, and annular ring projections of the light beams, with the same radii. 
       FIG. 1   f  shows in schematic form, a single light beam  11 , projected into the end  17  of the fiber optic at a random location  25  and at a selected incidence angle θ 2  to produce a cyclical helically propagating light beam with OAM, and an annular ring projection  31  of the light beam. 
       FIG. 1   g  shows in schematic form, a single light beam  13 , projected into the end of the fiber optic at a random location  46 , and at a selected incidence angle θ 1 , to produce a cyclical helically propagating light beam with OAM, and an annular ring projection  33 , of the light beam. 
       FIG. 1   h  shows in schematic form, two light beams,  11 ,  13 , for example the light beams, as shown in  FIG. 1   f  and  FIG. 1   g , projected into end  17 , of the fiber optic at a random locations  46  and  34 , and at a selected opposite incidence angles θ 1 , θ 2 , to produce cyclical helically propagating light beam with opposite OAM, and annular ring projections of the light beams with respective radii. 
     The projection of the shadow pairs  35 ,  41 , for annular ring  31  and  37 ,  39  for annular ring  33 , at respective opposite skew angles ±γ 13 , ±γ 11 , as shown schematically in  FIGS. 1   c  and  1   d , is the result of the counter cyclical orbital angular momentum of the light beams  11  and  13 , as explained herein. 
     As shown in a preferred embodiment, a interfering object, shown as a wire  43  placed in the projection path  42  of the counter cyclical light beams  11  and  13 , produces respective shadows  35 ,  41 ,  37 ,  39 , in the projected annular rings  31  and  33 . With respect to the spatial projection of the interfering wire  43 , the shadows  37 ,  39  and  35 ,  41 , are angularly displaced in the projection plane of the annular rings  31  and  33 , from the spatial projection of the interfering wire  43  or, for example, the X axis. 
     As shown schematically in  FIGS. 1   c  and  1   d , for beam  11  shown with orbital angular momentum in the counter clockwise direction  31   a , shadows  35 ,  41 , will be produced at skew angles ±γ 11  and for beam  13  shown with clockwise orbital momentum  33   a , in the clockwise direction will be produced at skew angles, ±γ 13 . As may be seen in  FIG. 1   d , showing schematically an exploded view of the annular rings  31  and  33  the skew angles ±γ 11  are shown for annular ring  31  and skew angles ±γ 13  are shown for annular ring  33 . 
     By annular ring  31  and annular ring  33 , as would be understood by those skilled in the art, is meant the annular ring projection of light on a projection plane by respective counter cyclical rotating light beams  11  and  13 , each with opposite orbital angular momentum. 
     As shown in  FIG. 1   a , the fiber optic  15 , with a radius r, is shown with an input end  17 , where light beams  11  and  13  are projected into the fiber optic  15 . As shown schematically, according to the inventive principles, and in a preferred embodiment, light beam  11  is projected into fiber optic end  17  on the locus  34  describing the diameter of the fiber optic  15 , which may be or may not be, parallel to an established X axis. Increasing or decreasing the insertion angles θ 1 , θ 2 , and will decrease or increase the radius of the projected annular rings  33  and  31 . 
     Moving the points of insertion  25  and  27 , or  38 ,  46 , closer to, or further from the longitudinal or Z axis, will decrease or increase the radius of the projected annular rings  33  and  31 . Accordingly the function and result of the disclosed invention and the way the function and result of the disclosed invention may be achieved, may be by varying the insertion angles θ 1 , and θ 2 , the location of the locus on the end  17  where the light beams are projected into the fiber optic  15 , the location of the points on the locus where the light beams, for example  11  and  13 , are projected into the fiber optic  15 , whether the locus for inserting the light beams is on the X axis of end  17 , or at a location displaced from the X axis, or the relative displacement of the points of insertion from the longitudinal Z axis, where the light beams are inserted. 
     As shown in  FIG. 2 , in a perspective schematic view, according to the disclosed inventive principles and in a preferred embodiment, an interfering object shown as a wire  43  is placed opposed to the output end  29  of the fiber optic  15 , and in a preferred embodiment, opposed to the X axis of the fiber optic  15 , displaced from end  29  and in the projection path  47  of the contra cyclical rotating light beams  11  and  13 , by a distance d. The projection of the contra cyclical light beam  11  and  13 , for example on a two dimensional surface, is shown schematically in  FIGS. 1 ,  1   c ,  1   d  and  2 , by the superposed rings shown schematically at rings  31 ,  33 , in  FIG. 2 , and separately in an exploded view in  FIG. 1   d . As shown, shadows  35  and  41 , made in annular ring  31 , by the projection of light beam  11 , across the interfering wire  43 , shown schematically with counter clockwise orbital angular momentum  31   a , on the wire  43  are displaced by equal and opposite skew angles ±γ 11 , from the spatial projection of wire  43  on the two dimensional plane of projection shown by annular ring  33 , relative to a line  44 , parallel to and opposed to the wire  43 . 
     Similarly, as shown, shadows  39 ,  37 , made in annular ring  33  by the projection of light beam  13 , shown schematically with clockwise orbital angular momentum  33   a , on interfering wire  43 , are displaced by opposite skew angles ±γ 13 , from the spatial projection of wire  43  on the plane of projection shown by annular ring  33 , relative to a line  44 , parallel to and opposed to the wire  43  or the spatial projection of the X axis of end  17 . 
     As shown herein, in a preferred embodiment, the ability to transmit two optical vortices in two (2) channels with the same orbital angular momentum but with opposite topological charge and with counter cyclical rotational directions, inside a single fiber simultaneously while preserving each light beam&#39;s orbital angular momentum and countercyclical rotational direction, permits simultaneous transmission of two optical channels at the same spatial location by using separate respective orbital angular momentum, in conjunction with intensity of light to detect signals instead of the conventional methods of employing intensity alone to detect the presence or absence of a signal. 
     An orbital angular detector which may be used to detect the counter rotating orbital angular light beams,  11  and  13 , as shown in  FIGS. 3 ,  3   a  and  3   b , where the projected respective annular rings  31 ,  33 , are projected with the same radii. 
     A segmented photo-detector, shown generally by numeral  60  with a planar body  62 , and two opposed ridges  62  and  64 . The ridges  64 ,  66 , are shown in a side view in the direction of arrow  68 , as light interfering structures arranged on the surface  70 , of photo detector  62 , at opposed diametric points  72 ,  74 , or 180° from each other. 
     The photo detector  60  is used to detect the information associated with one standard light beam in one optical channel without orbital angular momentum and two light beams  13 ,  11  in two other respective light channels with counter orbital angular momentum, possessing clockwise and counter clockwise orbital angular momentum, with reference to the truth table shown in  FIG. 3   b.    
     In a preferred embodiment, according to the disclosed inventive principles, a segmented annular photo detector  60  is as shown in  FIG. 3 . The photo detector  60 , is shown with segmented light responsive elements, for example photo diodes, as would be known to those skilled in the art, a, b, c, d, e, f, g, h, arranged on the annular photo detector surface  70 . Two ridges  64  and  66  are shown on the surface  70  of the photo detector  60 , as shown in  FIG. 3   a , showing a side view of detector  60 , from the direction of arrow  68  and arranged to interfere with the rotating light beams  11  and  13 , projected toward the ridge  62  and  64 , as shown by arrows  80  for light beam  11  or projected toward the ridge  62  and  64 , and as shown by arrows  78  for light beam  13 . 
     As shown in a preferred embodiment, the photo diode detector may be divided, for example, into six or more segments, such that four segments  81 ,  83 ,  85 ,  87 , shown adjacent to the ridges  62  and  64 , and two or more segments, b, c, g, h, displaced from the ridges  62 .  64 . 
     As shown for a preferred embodiment, for two of the adjacent segments (a &amp; e) ( 81 ,  85 ) adjacent to the ridges  62 ,  64 , the ridges  62 ,  64  will interfere with the clockwise (CW) light beam  13 , while for the two adjacent segments (h &amp; d) ( 83 ,  87 ), adjacent ridges  62 ,  64 , the ridges  62 ,  64 , will interfere with the counterclockwise (CCW) light beam  11 . 
     The interference by ridges  62  and  64 , with the light beams  11  and  13 , will reduce the light on photo detector segments  83 ,  87  and  81 ,  85 , respectively. This will lead to a reduced light intensity on the respective adjacent segments as compared to the standard segments, for example, as shown in a preferred embodiment, segments f, g, b and c, which are not adjacent the ridges  62 ,  64 . 
     Comparator circuits or other logic circuits can then be used to detect the presence or absence, or relative intensity, of one or both light beam channels and to detect the intensity of a standard light beam which is without orbital angular momentum, as would be known to those skilled in the art. As known to those skilled in the art, the comparator circuits would compare the relative electrical signals produced by the relative intensity of light on photo detectors a −h, to produce signals indicative of the relative light intensity on the respective photo detectors, as from the light beam  11  or  13  or from a standard light beam. The signals, reproduced in a logical truth table as shown in  FIG. 3   b , would indicate the presence or absence of the standard non rotating light bean, or the clockwise or counter clockwise, rotating light beams. 
     The truth table is presented in  FIG. 3   b , shows how the photo detector  60  with segmented detectors and opposed ridges  62 ,  64 , can be used to simultaneously detect the transmitted light in three light beams or channels, where one light beam is a standard light beam and two light beams are counter cyclical light beams with opposite orbital angular momentum. 
     As shown in  FIG. 3   b , the light beams or channels, shown as Only Standard, Only CW OAM (Clockwise Orbital Angular Momentum), Only CCW OAM (Counter Clockwise Orbital Angular Momentum), Standard+CW OAM, Standard+CCW OAM, (CW+CCW) OAM, and Standard+(CW+CCW) OAM, produces the signals shown in  FIG. 3   b , for the photo detectors a to h and  81 ,  83 ,  85 ,  87 , For example, a “0” signal indicates no light or reduced light on the respective photo detector, for example as a result of ridge  62  or  64 , interfering with rotating light beam  11  or  13 , a “1” indicates full light from one light beam on the respective photo detector and a “1+” indicates light from two (2) light beams on a respective photo detector, for example from the standard light channel and from the CC or CCW light beams  11  or  13 , where the light falls on the photo detector without interference from ridge  62  or  64 . 
     As would be known to those skilled in the art, and as explained for a preferred embodiment, the detector  60  detect the counter cyclical light beams, as shown for a preferred embodiment, beam  11  and  13 , with one ridge, for example ridge  62  and adjacent light detector segments ( 81 , a) and ( 83 , h) and as shown in the truth table columns a,  81  and h,  83 , in  FIG. 3   b.    
     As would be understood by those skilled in the art, the structure and arrangement shown for the preferred embodiment may be altered without departing from the disclosed inventive principles.