Optical switching apparatus

Abstract

An optical matrix switch station ( 1 ) is shown mounting a plurality of optical switch units ( 15, 17 ), each of which includes a mirror ( 29 ), moveable in two axes, for purpose of switching optical beams from one optical fiber to another. A mirror assembly ( 41 ) includes a single body of silicon comprising a frame portion ( 43 ), gimbals ( 45 ), mirror portion ( 47 ), and related hinges ( 55 ). Magnets ( 53, 54 ) and air coils ( 89 ) are utilized to position the central mirror surface ( 29 ) to a selected orientation. The moveable mirror and associated magnets along with control LED's ( 71 ) are hermetically packaged in a header ( 81 ) and mounted with the air coils on mounting bracket ( 85 ) to form a micromirror assembly package ( 99 ) mounted in each optical switch unit.

What is claimed:  
     
         1 . Optical switching apparatus comprising, 
 a header having a bottom wall and upwardly extending side walls forming a recess, a platform formed along the side walls spaced above the bottom wall,    a micromirror formed from a single piece of material having an outer frame portion lying in a plane and supported on the platform, an intermediate rotational gimbals portion hinged to the frame portion and movable relative to the frame portion about a first axis and an inner rotational mirror portion having a reflective, upper face surface formed with a radius of curvature of at least 2 meters hinged to the gimbals portion for movement of the mirror portion relative to the gimbals portion about a second axis, at least one magnet attached to one of the rotational portions, and    at least one electromagnetic coil assembly disposed in close proximity to the mirror assembly for applying selected forces to the at least one magnet for causing desired movement of the gimbals portion and the mirror portion along the two axes to reflect an optical beam directed to the mirror portion in a selected direction.    
     
     
         2 . Optical switching apparatus according to  claim 1  in which the gimbals portion is hinged to the frame portion by a pair of hinges spaced apart along the first axis and the mirror portion is hinged to the gimbals portion by a pair of hinges spaced apart along the second axis.  
     
     
         3 . Optical switching apparatus according to  claim 1  in which the axes are disposed 90 degrees relative to one another.  
     
     
         4 . Optical switching apparatus according to  claim 1  further comprising a plurality of light emitting diodes mounted on the frame portion for providing control signals.  
     
     
         5 . Optical switching apparatus according to  claim 1  further comprising a pair of magnets for driving movement of the gimbals portion disposed on spaced apart locations of the gimbals portion along the second axis and a pair of magnets for driving movement of the mirror portion disposed on spaced apart locations of the mirror portion along the first axis.  
     
     
         6 . Optical switching apparatus according to  claim 5  in which each magnet comprises a set of an upper magnet attached to an upper face surface of the respective gimbals portion and mirror portion and a lower magnet attached to a lower surface of the respective gimbals portion and mirror portion, the respective upper and lower magnets of a set being in alignment with each other.  
     
     
         7 . Optical switching apparatus according to  claim 1  in which the at least one electromagnetic coil assembly is disposed in engagement with the bottom wall of the header, a respective coil assembly being in alignment with each spaced apart magnet location.  
     
     
         8 . Optical switching apparatus according to  claim 7  in which each coil assembly comprises a bobbin having a spool on which a coil is wound and an aluminum plate portion between the respective coil and the bottom wall of the header, the bobbins having a massive heat sink portion of heat conductive material relative to the respective coils on a side of the coils remote from the plate portion.  
     
     
         9 . Optical switching apparatus according to  claim 8  further comprising a flex circuit electrically connected to the coils and to the LED's and a mounting bracket formed of heat conductive material, the flex circuit received on the mounting bracket, the mounting bracket being relatively massive relative to the coil assemblies, the header mounted on the mounting bracket with the coil assemblies therebetween and heat conductive potting material disposed between the header on one side and the flex circuit and the mounting bracket on another side.  
     
     
         10 . Optical switching apparatus according to  claim 5  further comprising a push-pull drive for exciting the magnets.  
     
     
         11 . Optical switching apparatus according to  claim 1  further comprising a single magnet mounted on a lower face surface of the mirror portion.  
     
     
         12 . Optical switching apparatus according to  claim 11  further comprising a plurality of electromagnetic coil assemblies spaced apart adjacent to but out of alignment with the single magnet.  
     
     
         13 . Optical switching apparatus according to  claim 1  in which the piece is formed of silicon.  
     
     
         14 . Optical switching apparatus according to  claim 13  in which the mirror portion has a lower face surface and both the upper and lower face surfaces are polished thereby providing improved surface flatness.  
     
     
         15 . Optical switching apparatus according to  claim 2  in which the frame portion has spaced apart, inwardly extending stop tabs on either side of the first axis and the gimbals portion has an extension along the first axis fitting closely between the stop tabs to limit motion in the plane in which the gimbals portion lies.  
     
     
         16 . Optical switching apparatus to  claim 2  in which the gimbals portion has spaced apart, inwardly extending stop tabs on either side of the second axis and the mirror portion has an extension along the second axis fitting closely between the stop tabs to limit motion in the plane in which the mirror portion lies.  
     
     
         17 . Optical switching apparatus according to  claim 15  further comprising a projection formed on one of the stop tabs and the extension and extending toward the other of the stop tabs and the extension.  
     
     
         18 . Optical switching apparatus according to  claim 16  further comprising a projection formed on one of the stop tabs and the extension and extending toward the other of the stop tabs and the extension.  
     
     
         19 . Optical switching apparatus according to  claim 1  in which the header is ceramic and a glass window is attached to the header covering the recess, the glass window being attached with indium forming a hermetic seal with a selected atmosphere sealed in the recess.  
     
     
         20 . Optical switching apparatus according to  claim 1  further comprising a mounting bracket formed of heat conductive material, the header mounted on the bracket, the bracket being formed with a first portion having a pair of spaced apart surfaces lying in respective planes which intersect each other, 
 a package having a bottom wall, the bottom wall having an upwardly extending mounting pad formed with a second portion having a pair of complimentary, spaced apart surfaces, one of the first and second portions forming a concave cradle and the other of the first and second portions forming a convex protrusion received in the cradle, the first and second portions being fixed to one another.  
 
     
     
         21 . Optical switching apparatus according to  claim 19 , in which a bore is formed through the bracket intermediate to the spaced apart surfaces of the first portion and a threaded bore is formed between the pair of complementary, spaced apart surfaces of the second portion and the portions are fixed together by a threaded member received through the bore of the bracket and threaded into the threaded bore.  
     
     
         22 . Optical switching apparatus comprising, 
 a header having a bottom wall and upwardly extending side walls forming a recess, a platform formed along the sidewalls spaced above the bottom wall,    a micromirror assembly formed from a single piece of material having an outer frame portion lying in a plane and supported on the platform, an intermediate rotational gimbals portion hinged to the frame portion and movable relative to the frame portion about a first axis and an inner rotational mirror portion having a reflective, upper face surface hinged to the gimbals portion for movement of the mirror portion relative to the gimbals portion about a second axis, at least one magnet attached to one of the rotational portions, and    at least one electromagnetic coil assembly disposed in close proximity to the mirror assembly for applying selected forces to the at least one magnet for causing desired movement of the gimbals portion and the mirror portion along the two axes to reflect an optical beam directed to the mirror portion in a selected direction.    
     
     
         23 . A method for making a movable mirror comprising the steps of taking a piece of silicon and forming an outer frame portion, an intermediate gimbals portion connected by a hinge to the frame portion and an inner mirror portion connected by a hinge to the gimbals portion, attaching the mirror portion to the gimbals portion at locations on both sides of the respective hinge, attaching the gimbals portion to the frame portion at locations on each side of the respective hinge to prevent movement of the respective portions in a plane in which the piece lies and severing the attachment at each location at any selected time prior to use.