Abstract:
An optical switch includes an optical input terminal, a first deflector disposed to receive light from the optical input terminal, controlled to change its deflection angle, second deflectors arranged in a substrate, the first deflector transmits light from the optical input terminal to one of the second deflectors selectively, and optical output terminals disposed to receive light from the second deflectors, the second deflectors transmit light from the first deflector to the optical output terminals.

Description:
FIELD OF THE INVENTION 
     The invention relates to an optical switch, which connects selectively an optical input terminal with an optical output terminal. 
     BACKGROUND OF THE INVENTION 
     A conventional micro-mechanical optical switch is described, for example, in Photonics Technology Letters, vol. 10, pp. 525-527, April, 1998. An optical switch described in this publication includes input optical fibers disposed along one side of a rectangular substrate, output optical fibers disposed along the crossing side, and movable mirrors arranged in a matrix on the substrate. The movable mirrors further include actuators that convert electric energy into mechanical actions. 
     Each of the movable mirrors reflects light toward determined direction. Therefore, required number of the movable mirrors is product between the number of input ports and output ports. 
     In general, the number of the mirrors in a single substrate is limited to around 2500, because cubic content of the actuator is larger than the mirror. When numbers of the input ports and the output ports are equal, those numbers are respectively limited to around 50. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide an optical switch, which solve the above-described problem. According to the present invention, such an optical switch includes an optical input terminal, a first deflector disposed to receive light from the optical input terminal, controlled to change its deflection angle, second deflectors arranged in a substrate, the first deflector transmits light from the optical input terminal to one of the second deflectors selectively, and optical output terminals disposed to receive light from the second deflectors, the second deflectors transmit light from the first deflector to the optical output terminals. 
     Therefore, the optical switch has same number of optical input and output terminals as the deflectors. As s result, the number of the optical input and output terminals is increased. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The objects and features of the invention will become more apparent from the consideration of the following detailed description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is an oblique view of a first embodiment according to the invention. 
     FIG. 2 is a schematic view of a movable lens of the first embodiment. 
     FIG. 3 is a schematic view illustrating steering of light by the movable lens of the first embodiment. 
     FIG. 4 is an oblique view of a second embodiment according to the invention. 
     FIG. 5 is a schematic view illustrating deflection of light by the second embodiment. 
     FIG. 6 is a schematic view of a third embodiment according to the invention. 
     FIG. 7 is a schematic view of a fourth embodiment according to the invention. 
     FIG. 8 is a schematic view illustrating locations of movable deflector lenses of the fourth embodiment. 
     FIG. 9 is a schematic view of a modification of the fourth embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     &lt;The first embodiment&gt; 
     Referring to FIG. 1, the first embodiment of the invention, an optical switch  100  comprises output optical fibers  103 , deflector lenses  102 , an input optical fiber  105  and a movable lens  104 . 
     The deflector lenses  102  are formed in, for example, a silicon substrate  101   a  and are arranged in matrix formation. The output optical fibers  103  are disposed in association with the deflector lenses  102  so as to receive light from the lenses  102 . 
     The movable lens  104  is formed in, for example, a silicon substrate  101   b . The input optical fiber  105  is disposed in association with the movable lens  104 . The movable lens  104  deflects light so as to connect optically between the input fiber  105  and a specified deflector lens  102 . 
     The movable lens  104  changes its position to deflect incoming light. Various types of movable lens based on, for example, micro-mechanical technology can be used as the movable lens  104 . 
     FIG. 2 illustrates the movable lens  104 . In FIG. 2, actuators  21 X and  21 Y actuate levers  23  X and  23 Y by piezoelectric effect so as to move a lens holder  26  in X and Y directions. Sliders  24 X and  24 Y move levers  25 X and  25 Y connected to the lens holder  26 . 
     In the first embodiment, the deflector lenses  102  only receive the light from the lens  105 . Therefore, the lenses  102  are not required to be movable. The deflector lenses  102  are employed as optical elements which generate refraction or diffraction. For example, a lens array made by ion exchange or a lens array of CGH (Computer Generated Hologram) type is employed for the deflector lenses  102 . 
     Referring to FIG. 3, the steering of the light by the lens  104  is described. 
     Because of distance between a central axis of luminous flux and a central axis of the movable lens  104 , the luminous flux is deflected to direction  51   b  from direction  51   a.    
     Operating the actuator  21 X and  21 Y, the movable lens  104  is moved in X and Y directions. Therefore, the luminous flux is deflected in −X and −Y directions on a plane of the substrate  101   b . When distance between the input optical fiber  105  and the movable lens  104  is S and amount of the gap of those axes is δ, deflection angle θ is tan −1 (δ/S). For example, when the distance S is about 500 μm and the gap δ is 10 μm, the deflection angle θ is about 1 degree. In FIG. 3, a reference symbol T represents distance between the movable lens  104  and the lens  102 . 
     &lt;The second embodiment&gt; 
     Referring to FIG. 4, the second embodiment of the invention, an optical switch  200  further comprises plural input optical fibers  205 . 
     Plural deflector lenses  202  are formed in, for example, a silicon substrate  201   a  and are arranged in matrix formation. Output optical fibers  203  are disposed in association with the deflector lenses  202  so as to receive light from lenses  202 . 
     The movable lenses  204  are formed in, for example, a silicon substrate  201   b  and are arranged in matrix formation. The input optical fibers  205  are disposed in association with the movable lens  204 . The movable lenses  204  deflect light so as to connect optically between the input fibers  205  and a specified deflector lens  202 . 
     In the second embodiment, the deflector lenses  202  are movable so as to receive light from any of the input optical fibers  205 . The structure of the deflector lenses  202  and the movable lenses  204  are same as the movable lens  104  in the first embodiment. 
     Referring to FIG. 5, the deflection through the lenses  202  and  204  described. Light  31  from an input fiber  205   a  enters an output fiber  203   a  through the movable lenses  204   a  and  202   a . In this case, the lenses  202   a  and  204   a  are in those initial positions. On the other hand, light  32  from an input optical fiber  205   b  enters an output optical fiber  203   b  through the movable lenses  204   b  and  202   b . In the latter case, the lenses  202   b  and  204   b  change the position so as to deflect the light  32  from the input fiber  205   b  to the output fiber  203   b.    
     &lt;The third embodiment&gt; 
     Referring to FIG. 6, the third embodiment of the invention, an optical switch  300  is described. 
     Plural deflector lenses  302  are formed in, for example, a silicon substrate  301   a  and are arranged in matrix formation. Output optical fibers  303  are disposed in association with the deflector lenses  302  so as to receive light from the lenses  302 . 
     The movable lenses  304  are formed in, for example, a silicon substrate  301   b  and are arranged in matrix formation. The input optical fibers  305  are disposed in association with the movable lens  304 . The movable lenses  304  deflect light so as to connect optically between the input fibers  305  and a specified deflector lens  302 . 
     In the third embodiment, the deflector lenses  302  are movable so as to receive light from any of the input optical fibers  305 . The structure of the optical switch  300  is basically same as the optical switch  200  in the second embodiment. 
     The optical switch  300  further comprises a reflector  306  disposed between the substrate  301   a  and the substrate  301   b . The reflector  306  has penetrative areas and reflective areas spatially. In FIG. 6, when the movable lens  304  is in a specified position, light form the input optical fiber  305   a  pass through the reflector  306 , and then enters the output optical fiber  301   a . When the movable lens  304  is in another specified position, the light from the input fiber  305   a  is reflected by the reflector  306 , and then enters the input optical fiber  305   b.    
     As the reflector  306 , for example, a corner-cube or a beamsplitter can be used. Moreover, the reflector  306  may be switched for total reflection or total penetration. 
     &lt;The fourth embodiment&gt; 
     Referring to FIG. 7, the fourth embodiment of the invention, an optical switch  400  is described. The optical switch  400  employs two sets of input optical fibers and movable lenses, and two sets of output optical fibers and movable lenses. 
     First, the two sets of the output optical fibers and the lenses are described. Movable deflector lenses  402   b  are formed in, for example, a silicon substrate  401   aa  and are arranged in matrix formation. Output optical fibers  403   b  are disposed in association with the movable lenses  402   b  so as to receive light from the lenses  402   b . Movable deflector lenses  402   a  are formed in, for example, a silicon substrate  401   ab  and are arranged in matrix formation. Output optical fibers  403   a  are disposed in association with the movable lenses  402   a  so as to receive light from the lenses  402   a.    
     Then, the two sets of the input optical fibers and the lenses are described. Movable deflector lenses  404   a  are formed in, for example, a silicon substrate  401   ba  and are arranged in matrix formation. Input optical fibers  405   a  are disposed in association with the movable lenses  404   a . Movable deflector lenses  404   b  are formed in, for example, a silicon substrate  401   bb  and are arranged in matrix formation. Input optical fibers  405   b  are disposed in association with the movable lenses  404   b.    
     In the optical switch  400 , on the output side, the substrates  401   aa  and  401   ab  are disposed at right angle. On the input side, the substrates  401   ba  and  bb  are also disposed at right angle. The substrate  401   aa  of the output side is opposite to the substrate  401   bb  of the input side, and the substrate  401   ab  of the output side is opposite to the substrate  401   ba  of the input side. Therefore, the substrates  401   aa ,  401   ab ,  401   ba  and  401   bb  are arranged in rectangular formation. A beamsplitter  406  is disposed inside the formation. 
     Light from the input optical fiber  405   a  enters the output fiber  403   a . According to the deflection angle of the lens  404   a , split light enters the  403   b  through the beamsplitter  406 . On the other hand, another light from the input optical fiber  405   b  enters the output optical fiber  403   b . According to the deflection angle of the lens  404   b , split light enters the  404   b  through the beamsplitter  406 . 
     In FIG. 7, imaginary input optical fibers  405   b ′ are arranged among the input fibers  405   a  and imaginary output fibers  403   b ′ are arranged among the input fibers  403   a . Then, imaginary light from the imaginary input fiber  405   b ′ enters the imaginary output fiber  403   b′.    
     The imaginary light described above overlaps a mirror image of the light from the input optical fiber  405   b  to the output optical fiber  403   b . Instead of increasing density of the optical fibers connected to the substrate, the optical switch  400  employs two sets of the output optical fibers  405   a  and  405   b , and two sets of input optical fibers  403   a  and  403   b.    
     As shown in FIG. 8, locations of the lenses  402   b  of the substrate  401   aa  are arranged not to overlap mirror images of the lenses  402   a  of the substrate  401   ab.    
     FIG. 9 shows a modification of the fourth embodiment. In FIG. 9, larger number of the substrates and beamsplitters are employed in order to increase the number of the optical terminals. Reference symbols “a” through “h” represent substrates connected with optical input/output terminals. A reference symbol M represents beamsplitters. A reference symbol ab represents a composite image of the terminals on the substrates a and b. Reference symbols cd, ef and gh represent composite images likewise. 
     As decribed above, according to the invention, the optical switch has same number of input and output optical fibers as the deflectors. Therefore, comparing to the conventional optical switch, the number of the terminals is increased.