Abstract:
An optical switch is disclosed having 4-ports. The switch consists of a first GRIN lens having 2 ports adjacent its outwardly facing end face. A second GRIN lens is disposed to receive light from the first GRIN lens and has two ports adjacent its outer end face. In a first state, a first port from the first GRIN lens couples light with a first output port of the second GRIN lens. In a second state, a movable optical element in the form of a light transmissive wedge having a reflective surface, is disposed in the path between first and second GRIN lens, providing a connection between a port of the first GRIN lens and a second port of the second GRIN lens. In a third connect state, the reflective surface of the wedge connects a port of the first GRIN lens and an output port in the same first GRIN lens. Hence an N×M optical switch is disclosed.

Description:
This application is a continuation-in-part of Ser. No. 09/334,502 filed Jun. 17, 1999, now U.S. Pat No. 6,154,585. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to optical switches and more particularly, to an optical switch having a movable wedge or a plurality of movable wedges, which serve to steer a beam of light. 
     BACKGROUND OF THE INVENTION 
     Optical switches of various kinds are well known for selectively switching light from a waveguide, such as optical fibre or light-conducting path, to another. 
     To fulfill this requirement, it has been well known to provide 2×2 optical switches having two ports on each side, wherein the switch is configurable to make a connection between ports  1  and  2  and simultaneously to provide a connection between ports  3  and  4 . Alternatively, such switches are configurable to provide simultaneous connections between ports  1  and  4 , and ports  3  and  2 . Hence these prior art switches have two states; a first state wherein two bar connections are formed and a second state wherein 2 cross connections are formed. Providing suitable coupling in both switching states, and providing a switch that is fast enough, and tolerant of physical disturbances is a daunting task most switch manufacturers face. 
     A well known optical switch made by JDS Fitel Inc. has been sold in the United States since Feb. 11, 1992 under the product number SR22xx-ONC. This optical switch includes a pair of GRaded INdex (GRIN) lenses having a reflector or mirror that can be selectively disposed therebetween. Each GRIN lens has two ports offset from the optical axis (OA) of the lens. 
     In a graded index medium that has a refractive index that varies with position, optical rays follow curved trajectories, instead of straight lines. By judicious selection of the refractive index, a GRIN rod can behave like a conventional optical element such as a prism or a lens. Lenses of this type are produced under the trade name “SELFOC”; the mark is registered in Japan and owned by the Nippon Sheet and Glass Co. Ltd. GRIN lenses are used extensively as a means of coupling optical signals from one waveguide such as an optical fiber, to another, for example, in optical switches. The use of GRIN lens provides a number of advantages over other conventional lenses. For example, GRIN lenses are relatively inexpensive, compact, and furthermore have parallel flat end faces. In particular, the flat end face of the GRIN lens allows a single lens to be used as a means of collimating or focusing light. 
     An optical arrangement is shown in FIG. 1, wherein two quarter pitch GRIN lenses  10   a and  10   b  are disposed so that their collimating ends are adjacent one another in a back-to-back relationship. A very thin optical element in the form of a filter  12  is sandwiched therebetween. The filter  12  can be coated directly on one of the inwardly facing end faces of the lenses, or alternatively may be coated on a substrate that is anti-reflection coated and sandwiched between the two GRIN lenses  10   a  and  10   b . It should be noted, that the optical axes of the input/output fibres  11   a  and  11   b  are parallel with the optical axes of the two GRIN lenses. Since the beam traversing the lenses  10   a  and  10   b  about the filter element  12  is at a location substantially coincident with the optical axes of the GRIN lenses, the light input orthogonal to the end face of the lens  10   a  at port P 1 , propagates through the filter  12  and through the second lens  10   b  and exits at port P 2  as a focused beam that is parallel to the input beam and the optical axes of the lenses  10   a  and  10   b.    
     FIG. 2 illustrates an offset that occurs when a gap is present between a pair of coaxial GRIN lenses  12   a  and  12   b.  The beam exiting the lens  12   a  intersects the end face equidistant from the optical axis indicated by lines  20   a  and  20   b , which define the outer most limits of the beam as it traverses the lens  12   a  end face. However, due to the gap between the lenses  12   a  and  12   b , the beam traverses the inwardly facing end face of the lens  12   b  having its outermost limits defined by the locations  22   a  and  22   b  which are not equidistant from the optical axis OA of the second lens  12   b . This beam shift downward results in the output beam being directed upward along the optical axis of the optical fibre  14   b . Accordingly, substantial coupling losses may occur between an input port on a first GRIN lens and an output port on a second GRIN lens, when the input and output ports are disposed adjacent the optical axes of the two GRIN lenses, and wherein a gap separating the GRIN lenses causes a beam propagating from the input port through the first GRIN lens to be shifted as it traverses the element towards the output port and enters the second lens at an offset to the optical axis of the lens. To overcome this disadvantage and to provide a more efficient optical coupling, the fibre  14   b  is provided at an angle θ&gt;0 degrees with respect to the optical axis of the lens. 
     It is also possible, as shown in FIG. 3, to launch the beam  30  at a judiciously selected angle θ S  at the left input end face of the GRIN lens  16   b  in such a way that the beam is selectively directed towards a desired output port location at the right output end face of the GRIN lens  16   b . Moreover, by ensuring that the beam has its centre substantially coincident with the optical axis OA of the lens, the beam thus propagates through the lens  16   b  and exits the output end of the lens parallel to the OA of the lens. From a manufacturing standpoint, when using GRIN lenses in switches or routers, it is preferable to use a transmissive switching optical element, in which zero or a number of internal reflections in each plane, and/or any number of refractions, are imposed on the incident light between the lenses rather than a reflective element imposing one reflection, to route, shift, or direct a beam from one port to an alternate port when the element is disposed between lenses. Thus, by providing a transmissive element such as a prism, the switch is much less sensitive to angular deviation and misalignment of the element than a switch using a reflective element such as a mirror. For example, in comparing angular sensitivity based on a 0.05 dB excess insertion loss criterion, an existing single mirrorbased switch has a typical angular tolerance of 0.007 degrees. An existing prism-based switch has an angular tolerance of 0.03 degrees, whereas the transmissive optical wedge-based switch described in accordance with this invention has an angular tolerance of 1.4 degrees. 
     It is an object of the instant invention to provide an improved optical switch having a transmissive wedge movable between two GRIN lenses for changing the angle of the collimated beam by a selected amount so that the output beam exits the output end face substantially parallel to the optical axis of the GRIN lenses, regardless of the connect state. 
     It is an object of this invention to provide a relatively inexpensive and easy to manufacture switch that will serve as an N×M optical switch. 
     SUMMARY OF THE INVENTION 
     In accordance with this invention, there is provided an optical switch comprising: 
     at least one input port on one side for launching an optical signal along an input optical path; 
     at least two output ports on an opposite side for receiving the optical signal, a first of the at least two output ports optically coupled to the at least one input port; and 
     a light transmissive wedge having at least two non-parallel surfaces, the wedge movable into and out of the input optical path, the wedge movable at least between first, second, and third positions corresponding to first, second, and third connect states, respectively. 
     In accordance with this invention, there is provided a method for switching a beam of light from one of a plurality of output ports to another, comprising the step of: 
     receiving at an input port a beam of light parallel to the optical axis of a first GRIN lens, the first GRIN lens for collimating the beam of light; 
     transmitting the optical signal along an optical path to a second GRIN lens optically coupled to the plurality of output ports, the second GRIN lens for focussing the beam of light; and 
     inserting a wedge in the optical path for modifying the optical path so that the signal switches from one of the plurality of output ports and so that the beam of light exits the second GRIN lens at a predetermined output port of the plurality of output ports substantially parallel to the optical axis of the GRIN lens. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention will now be described in conjunction with the drawings in which: 
     FIG. 1 is a prior art side view of a conventional block diagram depicting an optical device having a pair of coaxial GRIN lenses and a very thin filtering element disposed therebetween; 
     FIG. 2 is a side view of a prior art diagram of a coupling system wherein losses are reduced by angling a receiving output fibre with respect to the angle of the input fibre; 
     FIG. 3 is a side view of a diagram of a GRIN lens receiving a collimated beam concentric with the optical axis and angled such that it exits the lens at a selected output port parallel to the optical axis of the lens; 
     FIG. 4 a  is a side view of a diagram showing the first connect state in accordance with the invention wherein a beam of light is collimated and focussed by a pair of coaxial GRIN lenses; 
     FIG. 4 b  is a side view of a diagram showing the second connect state in accordance with the invention wherein a beam of light is collimated and focussed by a pair of coaxial GRIN lenses having a first light transmissive asymmetric wedge disposed therebetween; 
     FIG. 4 c  is a side view of a diagram showing the third connect state in accordance with the invention wherein a beam of light is collimated, reflected on a reflective surface of the wedge, and focussed by a GRIN lens; 
     FIG. 5 a  is a side view of a diagram showing a fourth connect state in accordance with an other embodiment of the invention wherein a beam of light is collimated and focussed by a pair of coaxial GRIN lenses having a first and a second light transmissive asymmetric wedge disposed therebetween; 
     FIG. 5 b  is a side view of a diagram showing a fifth connect state in accordance with another embodiment of the invention wherein the first wedge is moved out of the path of the beam of light and the second wedge is into the path of the beam and disposed between a pair of coaxial GRIN lenses; 
     FIG. 5 c  is a side view of a diagram showing a sixth connect state in accordance with an embodiment of the invention wherein a beam of light is collimated by a GRIN lens, refracted through the first wedge, reflected on a reflective surface of the second wedge, sent back to the first wedge and focussed by the same GRIN lens; 
     FIG. 5 d  is a side view of a diagram showing a seventh connect state in accordance with an embodiment of the invention wherein a beam of light is collimated, reflected on a reflective surface of the second wedge, and focussed by a GRIN lens whereas the first wedge is moved out of the path of the beam of light; 
     FIG. 6 a  is a side view diagram showing a connect state in accordance with an embodiment of the invention wherein two beams of light are collimated and focussed by a pair of coaxial GRIN lens; 
     FIG. 6 b  is a side view diagram showing a connect state in accordance with an embodiment of the invention wherein two beams of light are collimated and focussed to two output ports by a pair of coaxial GRIN lenses having a light transmissive asymmetric wedge disposed therebetween; 
     FIG. 6 c  is a side view diagram showing a connect state in accordance with an embodiment of the invention wherein two beams of light are collimated, reflected on the reflective surface of a wedge and focussed by a GRIN lens to two output ports located on the same side as the input ports; 
     FIG. 7 a  shows a perspective view of a multifaceted wedge; 
     FIG. 7 b  is a perspective view of another multifaceted wedge; and, 
     FIG. 7 c  is a perspective view of a multifaceted wedge having reflective areas. 
    
    
     DETAILED DESCRIPTION 
     Preferred embodiments of this invention are based on the use of a light transmissive wedge or a wedge having a light transmissive region such as shown in FIGS. 4 b  and  4   c.    
     FIG. 4 a  shows the first connect state of the optical switch in accordance with an embodiment of the invention wherein a wedge  50  is moved out of the beam path. A pair of quarter pitch GRIN lenses  18   a  and  18   b , having end faces parallel to each other, disposed back to back sharing the same optical axis are slightly spaced apart. Two lo optical waveguides  40   a  and  40   b  are shown coaxial with and coupled to the lenses along the optical axis of the lenses  18   a  and  18   b  shown by a dotted line. A beam profile is also shown within the lenses  18   a  and  18   b  as if light was launched from the waveguide  40   a  to the respective lens  18   a  and exited the lens  18   b  at output  1  to the waveguide  40   b.    
     FIG. 4 b  illustrates the second connect state wherein an actuator, for example in a form of a three-position actuator  100 , moves the wedge  50  into the path of the beam between the coaxial GRIN lenses  18   a  and  18   b . The wedge  50  is defined herein as an optical medium an having two non-parallel surfaces, which for exemplary purposes are shown as input end  51  and output end  52 . The angle between the two non-parallel surfaces and the centre thickness of the wedge are judiciously chosen to give optimal fibre coupling. Either the upper half or the lower half area of the wedge facing the collimating GRIN lens is coated with a reflective coating. Similarly, either the other of the upper half or the lower half area of the wedge facing the collimating GRIN lens is light transmissive. The input end face  51  of the wedge  50  is facing the end face  19   a  of the GRIN lens  18   a ; the angle existing between the surface  51  and the optical axis of the GRIN lens  18   a  is substantially about 90°. The output end face  52  of the wedge  50  is facing the input end  19   b  of the second GRIN lens  18   b ; the second non parallel surface  52  is not normal to the optical axis of the GRIN lens  18   b.    
     In operation, in this embodiment, a beam of light parallel to the optical axis is launched into the input end of the GRIN lens  18   a ; at the end face  19   a , the collimated beam concentric with the optical axis of the lens exits the lens and is incident on the transmissive surface  50   a  of the wedge  50 . The beam is slightly refracted into the wedge and exits the wedge  50  at the face  52  oriented towards the input end  19   b  of the lens  18   b.    
     The angle of the surface  52  with respect to the end face  19   b  of the lens  18   b  is chosen to ensure that the light enters the input end  19   b  of the lens  18   b  and is directed towards an output port  2 . The substantial coincidence of the beam of light with the optical axis allows the focussed beam to exit the lens  18   b  substantially parallel to the optical axis at the output port  2 . 
     The third connect state is illustrated in FIG. 4 c . The three-position actuator  100  moves the wedge  50  into the path of the beam between the coaxial GRIN lenses  18   a  and  18   b . The wedge  50  is the same wedge described previously. The wedge is placed such that the reflective surface  50   b  of the surface  51  faces the end face  19   a  of the lens  18   a.    
     A beam of light parallel to the optical axis is launched into the input end of the GRIN lens  18   a ; at the end face  19   a  of the GRIN lens  18   a , the collimated beam substantially concentric with the optical axis of the lens exits the lens and is incident on the reflective surface  50   b  of the wedge  50 . The beam is then reflected back into the same GRIN lens  18   a . The angle between the surface  51  and the optical axis is substantially about 90°. The exact angle is chosen to ensure that the collimated light is redirected toward output port  3 . Moreover, the reflective beam of light is substantially concentric with the optical axis of the lens, thus the focussed beam exits the lens  18   a  substantially parallel to the optical axis at the output port  3  located on the same end face that the input beam was launched through. 
     It is also within the scope and spirit of the present invention to provide and add a plurality of wedges between two substantially coaxial GRIN lenses and to increase the number of ports. For example, by adding one or more movable wedges  60  similar but not identical to the wedge  50  previously described, between the output surface  52  of the wedge  50  and the input end  19   b  of the lens  18   b , the number of output ports is changed. Such an embodiment is shown in FIG. 5 that details the different connect states achieved when a second movable asymmetric light transmissive wedge  60  having two non-parallel to each other surfaces forming an input end  61  and an output end  62  is inserted into the switch. The second wedge  60  is moved in or out of the path of the beam of light with a second three-position actuator  200 . In FIG. 5 a,  the three-position actuator  200  moves the wedge  60  into the path of the beam between the wedge  50  and the input face of the GRIN lens  18   b . The input end face  61  of the wedge  60  is oriented towards the output end face  52  of the wedge  50 ; the output end face  62  of the wedge  60  is oriented towards the input end  19   b  of the second GRIN lens  18   b.    
     In such configuration, a beam of light parallel to the optical axis is launched into the input end of the GRIN lens  18   a ; at the end face  19   a  of the GRIN lens  18   a , the collimated beam concentric with the optical axis of the lens exits the lens and is incident on the transmissive surface  50   a  of the wedge  50 . The beam is then slightly refracted into the wedge and exits the wedge at the surface  52  oriented towards the transmissive surface  60   a  of the wedge  60 ; the beam is slightly bent into the wedge  60  and exits the wedge at the surface  62  oriented towards the input end  19   b  of the lens  18   b . The angle of the surfaces  61  with respect to the optical axis on one hand and the angle of the surface  62  with respect to the optical axis on another hand are chosen to ensure that the light enters the input end  19   b  of the lens  18   b  and is directed towards an output port  4 . The coincidence of the beam of light with the optical axis makes the focussed beam exiting the lens  18   b  substantially parallel to the optical axis at the output port  4 . 
     FIG. 5 b  shows a fifth connect state wherein the three-position actuator  100  moves the wedge  50  out of the path of the beam whereas the three-position actuator  200  places the wedge  60  into the path of the beam of light between the coaxial GRIN lenses  18   a  and  18   b . Because of the absence of the wedge  50 , the beam of light exiting the output end  19   a  of the lens  18   a  propagates through the air before contacting the input transmissive surface  60   a  of the wedge  60 . The beam of light is refracted into the wedge  60  and exits the wedge at the output surface  62  oriented towards the input end  19   b  of the lens  18   b . The angle of the surfaces  61  and  62  with respect to the optical axis are chosen to ensure that the light enters the input end  19   b  of the lens  18   b  and is directed towards an output port  5 . The coincidence of the beam of light with the optical axis makes the focussed beam exiting the lens  18   b  substantially parallel to the optical axis at the output port  5 . 
     A sixth connect state is illustrated in FIG. 5 c . The three-position actuators  100  and  200  move the wedges  50  and  60  into the path of the beam between the coaxial GRIN lenses  18   a  and  18   b . The wedge  50  is moved in a position allowing the beam of light to pass therethrough in its second connect state, i.e., the transmissive surface  50   a  is oriented towards the end face  19   a  of the lens  18   a . The wedge  60  is placed such that the reflective surface  60   b  of the surface  61  is oriented towards the end  52  of the wedge  50 . 
     A beam of light parallel to the optical axis is launched into the input end of the GRIN lens  18   a ; at the end face  19   a  of the GRIN lens  18   a , the collimated beam concentric with the optical axis of the lens exits the lens and enters the input transmissive face  50   a  of the wedge  50 ; the beam is bent into the wedge and exits the wedge  50  at the output end  52  to propagate to the wedge  60  where it contacts the reflective surface  60   b  of the wedge  60 . The beam is reflected back into the wedge  50 . The beam is refracted again while propagating through the wedge  50  and is directed towards a selected output port  6 , located on the same end face that the input beam was launched through. Moreover, the reflective beam of light is substantially concentric with the optical axis of the lens, thus the focussed beam exits the lens  18   a  substantially parallel to the optical axis at the output port  6 . 
     FIG. 5 d  shows a seventh connect state where the wedge  50  is moved out of the path of the beam by the three-position actuator  100  whereas the three-position actuator  200  positions the reflective surface  60   b  of the wedge  60  in the path of the beam of light. 
     In such configuration, a beam of light parallel to the optical axis is launched at the input end of the GRIN lens  18   a ; at the end face  19   a  of the GRIN lens  18   a , the collimated beam concentric with the optical axis of the lens exits the lens to contact the reflective surface  60   b  of the wedge  60 . The beam is then reflected back into the same GRIN lens  18   a . The angle of the surface  61  is chosen to ensure that the collimated light is redirected toward output port  7 . Moreover, the reflective beam of light is substantially concentric with the optical axis of the lens, thus the focussed beam exits the lens  18   a  substantially parallel to the optical axis at the output port  7  located on the same end face that the input beam was launched through. 
     FIGS. 6 a ,  6   b  and  6   c  illustrate an embodiment wherein additional input ports are provided. For clarity, each beam of light is represented by a single ray of light. One optical path is shown with a solid line and the other is shown with a dashed line. Only one wedge  50  is shown in this embodiment. FIG. 6 a  shows a connect state when the wedge  50  is moved out of the optical paths. A beam of light parallel to, and off the optical axis of the GRIN lenses  18   a  and  18   b , launched into input port  110  is directed towards an output port A. 
     Another beam of light parallel to, and off the optical axis of the GRIN lenses  18   a  and  18   b  launched into input port  120  is directed towards an output port B. The substantial coincidence of the beams of light with the optical axis allows the focussed beams to exit the lens  18   b  substantially parallel to the optical axis at the output ports A and B. 
     FIG. 6 b  shows the paths of the beams of light when the wedge  50  is moved between the two GRIN lenses  18   a  and  18   b  such that the transmissive surface  50   a  of the wedge  50  is placed between the end face  19   a  of the GRIN lens  18   a  and the input face  19   b  of the GRIN lens  18   b . The beam of light launched from the input port  110  is optically coupled to an output port C, and the beam of light launched from the input port  120  is optically coupled to an output port D. The characteristics and displacement (or position) of the wedge allow the beams of light to exit the GRIN lens  18   b  substantially parallel to the optical axis of the lenses. 
     In FIG. 6 c , the actuator  100  has moved the wedge  50  between the two GRIN lenses  18   a  and  18   b  so that the reflective surface  50   b  of the wedge  50  is oriented towards the end face  19   a  of the GRIN lens  18   a . In such a configuration, the beam of light launched from input port  110  is reflected back to the GRIN lens  18   a  and directed towards an output port E located on the same side of the input port  110 . Similarly, the beam of light launched from input port  120  is reflected back to the GRIN lens  18   a  and focussed at an output port F located on the same side of the input port  120 . The characteristics of the wedge allow the beams of light to exit the GRIN lens  18   b  substantially parallel to the optical axis of the lens. 
     FIG. 7 a  shows a multifaceted wedge  70  having at least two different wedged-shaped parts,  71  and  72 . The two wedged-shaped parts are disposed so that the wedge  71  is on the top of and in contact with the wedge  72 . The wedge  71  has at least two non-parallel surfaces  71   a  and  71   b  and at least two other surfaces  71   c  and  71   d , wherein the width of surface  71   c  is smaller than the width of the surface  71   d . The wedge  72  has at least two non-parallel surfaces  72   a  and  72   b , and at least two other surfaces  72   c  and  72   d , wherein the width of surface  72   c  is smaller than the width of the surface  72   d . The wedges are positioned so that the smallest surface  72   c  of the wedge  72  is below the largest surface  71   d  of the wedge  71 , and the largest surface  72   d  of the wedge  72  is below the smallest surface  71   c  of the wedge  71 . The angle between the two non-parallel surfaces and the centre thickness of the wedges  71  and  72  are selected so that, when the multifaceted wedge  70  is inserted between a pair of GIRN lenses, a beam of light incident thereon is refracted and directed towards a predetermined output port as described above. 
     FIG. 7 b  shows another example of a multifaceted wedge  80 . The wedge  80  has at least three wedged-shaped parts,  81 ,  82  and  83 . The general arrangement is that the wedge  81  is on top of and in contact with the wedge  82  which is on top of an in contact with the wedge  83 . The wedge  81  has at least two non-parallel surfaces  81   a  and  81   b  and at least two other surfaces  81   c  and  81   d , wherein the width of surface  81   c  is smaller than the width of the surface  81   d . The wedge  82  has at least two non-parallel surfaces  82   a  and  82   b , and at least two other surfaces  82   c  and  82   d , wherein the width of surface  82   c  is smaller than the width of the surface  82   d . The wedge  83  also has at least two non-parallel surfaces  83   a  and  83   b , and at least two other surfaces  83   c  and  83   d , wherein the width of surface  83   c  is smaller than the width of the surface  83   d . The angles between the two non-parallel surfaces and the centre thickness of each wedge  81 ,  82 , and  83  are different from one wedge to the other and are selected so that, when the multifaceted wedge  80  is inserted between a pair of GIRN lenses, a beam of light incident thereon is refracted and directed towards a predetermined output port as described above. In the embodiment shown in FIG. 7 b , the angle and thickness of the wedge  81  are smaller than the angle and thickness of the wedge  82  which are smaller than that of the wedge  83 . 
     FIG. 7 c  shows a multifaceted wedge  90  having at least two different wedged-shaped parts,  91  and  92 . The two wedged-shaped parts are disposed so that the wedge  91  is on the top of and in contact with the wedge  92 . The wedge  91  has at least two non-parallel surfaces  91   a  and  91   b  and at least two other surfaces  91   c  and  91   d , wherein the width of surface  91   c  is smaller than the width of the surface  91   d . The upper half area  91   a   T  of the non-parallel surface  91   a  is light transmissive, whereas the lower half area  91   a   R  of the same surface is reflective. The wedge  92  has at least two non-parallel surfaces  92   a  and  92   b , and at least two other surfaces  92   c  and  92   d , wherein the width of surface  92   c  is smaller than the width of the surface  92   d . The upper half area  92   a   T  of the non-parallel surface  92   a  is light transmissive, whereas the lower half area  92   a   R  of the same surface is reflective. The wedges are positioned so that the smallest surface  92   c  of the wedge  92  is below the largest surface  91   d  of the wedge  91 , and the largest surface  92   d  of the wedge  92  is below the smallest surface  91   c  of the wedge  91 . The angle between the two non-parallel surfaces and the centre thickness of the wedges  91  and  92  are selected so that, when the multifaceted wedge  90  is inserted between a pair of GIRN lenses, a beam of light incident thereon is either refracted or reflected towards a predetermined output port. 
     Other configurations and modes of operation can be readily adapted, by rearranging the position of the input port. For example, the input port may be positioned so that the input beam enters the input end face of the GRIN lens  18   a  substantially offset from the optical axis of the lens. Moreover, in the aforementioned description, for ease of explanation, the first lens has been denoted as the input lens wherein the second lens has been denoted as the output lens; of course, the present invention is not limited to use in this direction and can be used in an alternate manner wherein the second lens functions as the input end and the first lens as the output end. 
     Of course, numerous other embodiments may be envisaged, without departing from the spirit and scope of the invention. For example, the pitch of the GRIN lenses may be substantially different than a quarter pitch and or the reflective surface of the wedge may face the input face  19   b  of the second GRIN lens  18   b.    
     Other configurations of the wedges can easily be envisaged without departing from the spirit and scope of the invention. For example, angles and thickness&#39; of the multifaceted wedge  70  have been described similar in the two wedged-shaped parts  71  and  72 ; they may be different from one part to the other.