REFERENCE TO PENDING PRIOR PATENT APPLICATION 
     This is a division of pending prior U.S. patent application Ser. No. 09/281,406, filed Mar. 30, 1999, U.S. Pat. No. 6,404,969, by Parviz Tayebati et al. for OPTICAL SWITCHING AND ATTENUATION SYSTEMS AND METHODS THEREFOR, which patent application claims benefit of (i) U.S. Provisional Patent Application Serial No. 60/079,994, filed Mar. 30, 1998 by Tayebati et al. for OPTICAL SWITCHING USING MICRO-ELECTROMECHANICAL TECHNIQUE, and (ii) U.S. Provisional Patent Application Serial No. 60/105,940, filed Oct. 28, 1998 by Azimi et al. for VARIABLE OPTICAL ATTENUATOR. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to optical systems in general, and more particularly to switches and attenuators for use in optical systems. 
     BACKGROUND OF THE INVENTION 
     In many situations, it is necessary to switch or attenuate a light signal within an optical system. 
     By way of example but not limitation, in a typical optical system, it may be necessary to switch a light signal between a first line and a second line. 
     By way of further example but not limitation, in a typical optical system, it may be necessary to attenuate a light signal passing through a line. 
     OBJECTS OF THE INVENTION 
     One object of the present invention is to provide novel apparatus for switching a light signal in an optical system. 
     Another object of the present invention is to provide novel apparatus for attenuating a light signal in an optical system. 
     Still another object of the present invention is to provide a novel method for switching a light signal in an optical system. 
     Yet another object of the present invention is to provide a novel method for attenuating a light signal in an optical system. 
     SUMMARY OF THE INVENTION 
     These and other objects of the present invention are addressed by the provision and use of novel light switches and attenuators. In one form of the invention, a novel 2×2 crossbar switch is formed by positioning a movable reflector intermediate four fiberoptic lines. In another form of the invention, a 1×N switch is formed by providing a plurality of cantilevers each having a reflective surface thereon. In still another form of the invention, a novel light attenuator is formed by positioning a movable arm intermediate two fiberoptic elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Still other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings, wherein like numbers refer to like parts and further wherein: 
     FIG. 1 is a schematic side view showing a novel 2×2 crossbar switch in a first state; 
     FIG. 2 is a schematic side view showing the 2×2 crossbar switch of FIG. 1 in a second state; 
     FIG. 3 is a schematic side view showing an alternative form of 2×2 crossbar switch; 
     FIG. 4 is a schematic view showing a 1×N optical switch formed by a plurality of cantilevers; 
     FIG. 5 is a schematic view showing a novel light attenuator formed in accordance with the present invention; 
     FIG. 6 is a schematic view showing a portion of the light attenuator of FIG. 5 in various states of operation; 
     FIG. 7 is a schematic view showing the light attenuator of FIGS. 5 and 6 positioned between two fiberoptic elements; and 
     FIG. 8 is a schematic view showing the light attenuator of FIGS. 5 and 6 used in an alternative setting. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Looking first at FIG. 1, there is shown a novel 2×2 crossbar switch  5  formed in accordance with the present invention. Crossbar switch  5  utilizes a first lens  10  and a second lens  15  to connect a fiberoptic element  20  with a fiberoptic element  25 , and to connect a fiberoptic element  30  with a fiberoptic element  35 , when the 2×2 crossbar switch is in the state shown in FIG.  1 . 
     In accordance with the present invention, a substrate  40  is positioned between lenses  10  and  15 . Substrate  40  carries a comb drive  45  or some other type of actuation and a moving arm  50  thereon. A hole  55  is formed in moving arm  50  so that light can pass between fiberoptic element  20  and fiberoptic element  25 , and fiberoptic element  30  and fiberoptic element  35 , when the 2×2 crossbar switch is in the position shown in FIG. 1. A reflector  60 , spaced from hole  55 , is also carried by moving arm  55 . 
     In accordance with the present invention, when crossbar switch  5  is to be activated, comb drive  45  is activated so as to move moving arm  50 , whereby to position reflector  60  at the location where hole  55  previously sat. Reflector  60  causes fiberoptic element  20  to be connected to fiberoptic element  30 , and fiberoptic element  25  to be connected to fiberoptic element  35 , when the 2×2 crossbar switch is in the state shown in FIG.  2 . 
     Stated another way, in the switch state shown in FIG. 1, the light signal from fiberoptic element  20  goes through hole  55  in actuating (moving) arm  55  of comb drive  45  and couples to fiberoptic element  25 . Similarly, fiberoptic element  30  is coupled to fiberoptic element  35 . This is the “through connect” situation. When voltage is applied to comb drive  45 , arm  50  moves to a new position and brings reflector  60  in the path of the light beams, so that the switch is in the state shown in FIG.  2 . In this condition, a light signal from fiberoptic element  20  is reflected and couples back to fiberoptic element  30  and, in similar fashion, fiberoptic element  35  will be coupled to fiberoptic element  25 . FIG. 2 represents the “cross bar switching” state of the switch. 
     The via-hole  65  in substrate  40  provides low insertion loss for the switch. Alternatively, substrate  40  can be anti-reflection coated. 
     The Grin-lenses  10  and  15  provide the proper bending of the light as shown in FIGS. 1 and 2. Alternatively, thermally expanded core (TEC) fiberoptic elements  20 A,  25 A,  30 A and  35 A can be used with appropriate mounts  70 ,  75  as shown in FIG.  3 . 
     Looking next at FIG. 4, there is shown a novel 1×N switch  100 . Switch  100  utilized three cantilevers  105 ,  110  and  115  formed on a substrate  120 . Cantilevers  105 ,  110  and  115  have reflective regions  105 R,  110 R and  115 R formed thereon, respectively. Cantilevers  105 ,  110  and  115  are positioned relative to one another, and relative to a reflective surface (e.g., a mirror)  120 , such that when the cantilevers are in a first state, an input beam  125  may be reflected off cantilever reflective region  105 R and reflective surface  120  so as to land on cantilever reflective region  110 R. However, when cantilever  105  is moved to a second position, e.g., by the application of an electric field, input beam  125  may be reflected off cantilever reflective region  105 R and reflective surface  120  so as to land on cantilever reflective region  115 R. 
     In the same way, properly positioned reflective surfaces  130  and  135  can direct light from reflective surface  110 R and  115 R to output ports  140 / 145  and  150 / 155 , respectively, depending on the position of cantilevers  110  and  115 , respectively. 
     Stated another way, input beam  125  reflects off the tip of cantilever  105 . This reflected beam is further reflected by surface  120  placed at an appropriate position, i.e., on top of the cantilevers. Hence, by double reflection, the beam  125  can land on reflective surface  110 R on the tip of cantilever  110 . With an applied voltage to cantilever  115 , the beam can be switched to reflective surface  115 R on cantilever  115 . In similar fashion, the beam  125  reflecting off cantilever  110  can be routed (via reflective surface  130 ) to positions  140  or  145  by the application of appropriate voltage to cantilever  110 ; or the beam  125  reflecting off cantilever  115  can be routed (via reflective surface  135 ) to positions  150  and  155  by the application of appropriate voltage to cantilever  115 . In this way, the input beam  125  can be selectively switched (i.e., routed) to output ports  140 ,  145 ,  150 , and  155 , as desired. 
     Looking next at FIGS. 5-7, there is shown an optical attenuator  200  also formed in accordance with the present invention. Optical attenuator  200  comprises a so-called “MEM&#39;s” (microelectromechanical) structure  205  disposed between two single mode fibers  210  and  215 . More particularly, MEM&#39;s structure  205  comprises a substrate  220  having an arm  225  extending therefrom, and an actuator  230  for moving arm  225  into and out of position between fibers  210  and  215 , whereby to selectively position the arm&#39;s mirror  235  into and out of the light path  240  extending between the two fibers (FIG.  6 ). The substrate  220  on which the microelectromechanically-activated arm  225  is fabricated is positioned perpendicular to the optical axis of the fibers (FIG.  7 ). 
     The actuator  230  may be any available electromechanical, thermal or magnetic based actuator. One example of an electromechanical actuator is the comb drive  245  shown in FIG.  5 . Mirror  235  may be positioned parallel to the substrate  220 , or preferably at an angle to the substrate, so as to avoid back reflection of the light back into the fiber. 
     In order to allow efficient coupling of light between fibers  210  and  215 , the substrate  220  has a via hole  250  (FIG. 7) on the back to allow the two fibers to be brought close to the arm  225  and to each other. 
     The MEM&#39;s structure  205  is designed such the light passing through the substrate  220  undergoes no residual reflections from the non-moving part. For example, the device is fabricated such that after processing, no part of the substrate  220  remains between the two fibers (FIG. 7) or the front and the back of the remaining part of the substrate are antireflection (AR) coated as shown at  255  using Si/SiO 2  or other multilayer films (FIG.  8 ).
Novel light switches and attenuators are disclosed. In one form of the invention, a novel 2x2 crossbar switch is formed by positioning a movable reflector intermediate four fiberoptic lines. In another form of the invention, a 1xN switch is formed by providing a plurality of cantilevers each having a reflective surface thereon. In still another form of the invention, a novel light attenuator is formed by positioning a movable arm intermediate two fiberoptic elements.