Abstract:
A 2×2 optical switch routs each light signal received from input ports to selected output. The optical switch has an adjustable light signal steering element, a fixed light signal steering element, and a steering element actuator. The adjustable light signal steering element is repositioned by the steering element actuator to selectively place one light signal received from the input ports such that the light signal is transferred from the input port to a selected output port. The fixed light signal steering element is placed in the path of each light signal such the light signals from the input ports is transferred to of mirrors, prisms, and light waveguides, default output ports, when the adjustable light steering element is removed from the path of each light signal.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates generally to optical transmission systems. More particularly this invention relates to devices that switch light signals from input ports to selected output ports connected to fiber optic transmission cables.  
         [0003]     2. Description of Related Art  
         [0004]     Optical switches, particularly 2×2 optical switches, are known in the art. Examples of such switches are the SW2×2-9N12-16 manufactured by Sercalo Microtechnology, Ltd., Principality of Liechtenstein and the F04635 manufactured by Poly-Scientific Fiber Optic Products of Northrop Grumman Corporation, Blacksburg Va. Each of these optical switches employ optical micro electromechanical systems to adjust mirrors to steer light signals from input ports to output ports. Generally, the input ports and the output ports are placed on opposing sides of the packaging of the optical switch.  
         [0005]     In many of the existing optical switches, six or more mirrors are used to steer the light signals from the input ports to the output ports. The additional mirrors add to the complexity of the optical path and increase the insertion loss and light dispersion of the switch. Further, having the connections for the input and output ports on opposing sides of the switch complicates the packaging and system structure of an optical network.  
         [0006]     U.S. Pat. No. 6,002,818 (Fatehi, et al.) describes a free-space optical signal switch. The optical signal switch employs a rotating prism for transmitter beam steering for controlling to which receiver an optical signal from a transmitter is directed.  
         [0007]     U.S. Pat. No. 6,415,067 (Copner, et al.) reveals a four port optical switch. The switch consists of two GRIN lenses. Each of the two GRIN lenses has two of the optical ports placed to receive light placed at their outer end face. A movable optical element in the form of a light transmissive wedge having a reflective surface is selectively moved into the path between the two GRIN lenses to direct a light signal from the first GRIN lenses to the second GRIN lens. The wedges have a reflective surface to direct light signals from one port of the two GRIN lenses to the adjacent port of the adjacent port on the same GRIN lens. A second wedge is employed to direct the light signal between different ports of the two GRIN lenses.  
         [0008]     U.S. Pat. No. 6,005,998 (Lee) teaches a scalable, non-blocking fiber optic matrix switch. The matrix switch has two arrays of light beam collimators arranged to face one another in free space, and a number of optical fibers coupled to each of the arrays. Each collimator has a tubular body with a fiber receiving part at one end, and a lens mounting part at an opposite end of the body. A lens fixed in the mounting part produces a collimated light beam from light emitted from an end of an optical fiber inserted in the fiber receiving part. First and second motor assemblies with corresponding positioning elements displace the collimator body so that its light beam is steered to a desired position along “X” and “Y” axes in response to operation of the motor assemblies. A signal carried on a fiber entering a first collimator in one array can be switched into a fiber of a second collimator in the opposite array, by displacing the collimators so as to direct the beam of the first collimator to align with a lens axis of the second.  
         [0009]     U.S. Pat. No. 6,259,835 (Jing) illustrates a mechanically actuated optical switch including stationary and movable optical reflectors. The movable reflectors are transferred between their on and off positions to switch an input optical signal to any one of multiple output optical fibers selected for transmitting the optical signal. The moveable reflectors are connected to an arm that is attached to a relay that causes the arm to selectively move. When the arm moves, the reflectors are placed in the path of the optical signal to transfer the signal to the output optical fibers.  
         [0010]     U.S. Pat. No. 6,285,022 (Bhalla) demonstrates a front accessible optical beam switch. The optical beam switch is designed for improved serviceability by mounting two fiber optic beam deflection arrays to face the front of a rack assembly. Inside the optical beam switch, a mirror is located behind each of the two fiber optic beam deflection arrays and used to reflect the light beams between the two fiber optic beam deflection arrays. A controller adjusts the angle of the mirror such that the two fiber optic beam deflection arrays.  
         [0011]     U.S. Pat. No. 6,385,364 (Abushagur) reveals an optical switch that guides data transmitting light beams along free space switching paths from one or more input optical fibers to one or more output optical fibers. The optical switch includes a microchip base member, diffractive, refractive or reflective optical elements positioned on carrier panels, and actuators for moving the carrier panels. The optical elements are able to be position by the actuators to guide light beams emitted by the input optical fibers in free space to the receiving output optical fibers. The actuators may be linear and/or rotary. Switching of light beams can be from one input port to one or many output ports, and vice versa, to form a free space optical cross-connect switch and router.  
         [0012]     U.S. Pat. No. 6,396,976 (Little, et al.) describes a two dimensional optical switch. An array of micromachined mirrors are arranged on a first substrate at the intersections of input and output optical paths and oriented at approximately forty-five degrees to the paths. An array of split-electrodes is arranged on a second substrate above the respective mirrors. Each split electrode includes a first electrode configured to apply an electrostatic force that rotates the mirror approximately ninety degrees into one of the input optical paths to deflect the optical signal along one of the output optical paths, and a second electrode configured to apply an electrostatic force that maintains the mirror position.  
         [0013]     U.S. Pat. No. 5,000,534 (Watanabe, et al.) shows an optical switch that includes at least one optical fiber exit terminal disposed in a plane, multiple optical fiber entrance terminals disposed in the plane, and a movable reflector disposed in the plane and angularly movable about a point in the plane for reflecting and/or refracting a light ray from the optical fiber exit terminal selectively into one of the optical fiber entrance terminals for thereby optically coupling the optical fiber exit terminal and to one of optical fiber entrance terminals.  
       SUMMARY OF THE INVENTION  
       [0014]     An object of this invention is to provide an optical switch for routing each light signal received from a plurality of input ports to selected output ports of a plurality of output ports.  
         [0015]     The accomplish at least this and other objects the optical switch has a plurality adjustable light signal steering elements, at least one fixed light signal steering element, and a steering element actuator. Each adjustable light signal steering element, when selectively placed in a path of one light signal received from one of the plurality of input ports, transfers the one light signal from the input port to a selected output port.  
         [0016]     Each adjustable light signal steering element has a light bending element which receives the light signal from at least one input port and directs the light signal to at least one selected output port. The light bending element is mounted on a light bending element carrier. The light bending element carrier is connected to the steering element actuator to selectively place the light bending element in the path of the light signals. The light bending element is constructed from reflective elements such as mirrors, refractive elements such as prisms or light waveguides, or diffractive elements such as lenses.  
         [0017]     The light bending element carrier causes the light bending element to move perpendicularly from an axis of the path of the light signal to selectively place the light bending element in the path of the light signal to steer the light signal to the selected output port. The light bending element carrier includes an arm connected such that the steering element actuator causes the arm to rotate and a bar connected to the arm. The light bending element is attached to the bar, such that the light bending element is moved perpendicularly to the axis of the light path when the arm is rotated.  
         [0018]     The fixed light signal steering element is placed in the path of each light signal such the light signals from the plurality of input ports is transferred to a group of default output ports of the plurality of output ports. The fixed light steering elements are constructed from reflective elements such as mirrors, refractive elements such as prisms or light waveguides, or diffractive elements such as lenses. The fixed light steering elements are a plurality of mirrors placed to guide the light signal from the input port to the default output port. In the preferred embodiment the input ports and the output ports are situated adjacently with no more than three mirrors accomplishing the steerage of the light signal for each fixed light steering element.  
         [0019]     The steering element actuator is in communication with the plurality of adjustable light signal steering elements to reposition the light signal steering elements such that a selected light signal steering element is placed in a path of one light signal received from one of the plurality of input ports to the selected output port. In the preferred embodiment, the steering element actuator is a relay that causes the selective placement of one light steering element in the path of at least one light signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIGS. 1 and 2  diagrammatically illustrate the structure of the optical switch of this invention.  
         [0021]      FIG. 3  is a perspective view of the optical switch of this invention  
         [0022]      FIG. 4  is a top plan view of the optical switch of this invention illustrating the paths of the light signals in the normal mode of operation.  
         [0023]      FIG. 5  is a top plan view of the optical switch of this invention illustrating the paths of the light signals in the loop back mode of operation. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     An optical 2×2 switch often has a normal mode, where a first input port receives a first light signal from a first fiber optic cable and conveys the first light signal to a second output port. A second input port receives a second light signal from a second fiber optic cable and conveys the second light signal to a first output port. This structure is particularly useful for a communication network having two systems connected with two fiber optic cables for essentially full duplex communications. The 2×2 switch is used to provide a mechanism to allow each system to diagnose problems within the communications network. The switch is set from the normal mode to a loop back mode where the first input port is connected to the first output port and the second input port is connected to the second output port. This allows each system connected to the communication network to transmit diagnostic signals and to receive the signals for determining the functioning of the components of the network, with the single point of failure being only the 2×2 switch.  
         [0025]     Refer now to  FIG. 1  for an explanation of the basic structure and function of the 2×2 switch of this invention. The input port  10  is aligned appropriately and bonded to the switch housing  5 . A fiber optic cable  15  from a first of two systems transmitting the first light signal  20  is connected to the input port  10 . The input port  10  is a collimator that receives the light signal and collimates the signal to remove any dispersion from passage of the light signal  20  through the fiber optic cable  15 . In the preferred embodiment, the collimator  10  is either soldered or attached to the housing  5  with an adhesive such as an epoxy.  
         [0026]     The light signal  20  is transferred from the input port  10  to a light bending or steering device  60 . The light bending or steering device  60  is reflective elements such as mirrors, refractive elements such as prisms or light waveguides, or diffractive elements such as lenses. In the preferred embodiment, the light bending or steering device  60  is a mirror. The mirror  60  reflects the light signal  20  to the second output port  25 . The second output port  25  is a collimator similar to that of the first input port  10  and is similarly aligned and attached to the switch housing  5 . The alignment of the second output port  25  is such that the light signal  20  as reflected from the mirror  60  impinges upon the second output port  25 . The second output port is connected to the fiber optic cable  30 . The fiber optic cable  30  is connected to the second system for reception of the light signal  20 . The collimator of the second output port  25  collimates the light signal  20  for removal of any dispersion resulting in the free space transmission and reflection from the mirror  60 .  
         [0027]     The second input port  35  is a collimator similar to the first input port  10 . The second input port is connected to the fiber optic cable  49 . The fiber optic cable is connected to the second system, which transmits the second light signal  45 . As described for the first input port  10 , the second input port  35  is a collimator that collimates the light signal  45  to remove dispersion resulting as a result of the passage of the light signal  45  through the fiber optic cable  40 . The collimator of the input port  35  is aligned appropriately and bonded to the switch housing  5 . In the preferred embodiment, the collimator  35  is either soldered or attached to the housing  5  with an adhesive such as an epoxy.  
         [0028]     The light signal  45  is transferred from the input port  35  to the mirror  60 . The mirror  60  reflects the light signal  45  to the first output port  50 . The first output port  50  is a collimator similar to that of the first input port  10  and is similarly aligned and attached to the switch housing  5 . The alignment of the first output port  50  is such that the light signal  20  as reflected from the mirror  60  impinges upon the first output port  50 . The first output port  50  is connected to the fiber optic cable  55 . The fiber optic cable  55  is connected to the first system for reception of the light signal  45 . The collimator of the first output port  50  collimates the light signal  45  for removal of any dispersion resulting in the free space transmission and reflection from the mirror  60 .  
         [0029]     The mirror  60  is attached to the moveable bar  65 . The moveable bar  65  is mounted to the rod  70  and the rod  70  has the connector  75 . The connector  75  is in contact with the moving plunger of the relay  80 . When the relay is not activated, the plunger has the connector  75  at a resting position such the rod  75  is at an initial position, with the moveable bar  65  set to have the mirror  60  as shown.  
         [0030]     Upon activation of the relay  80  to change from the normal mode of operation of  FIG. 1  to the loop back mode of operation as shown in  FIG. 2 , the plunger moves and the connector  75  causes the rod  70  to rotate. The rotation of the rod  70  causes the moveable bar  65  to move the mirror  60  in a motion perpendicular to the axis of the paths of the light signals  20  and  45  so that it is removed from the paths of the light signals  20  and  45  as shown in  FIG. 2 .  
         [0031]     Once the mirror  60  is removed from the paths of the light signals  20  and  45 , the light signals  20  and  45  now impinge upon the fixed light bending or steering device  90 . The fixed light bending or steering device  90  is reflective elements such as mirrors, refractive elements such as prisms or light waveguides, or diffractive elements such as lenses. In the preferred embodiment, is formed of the mirrors  92 ,  94 , and  96 . The mirrors  92 ,  94 , and  96  are placed and adhered to the switch housing  5  with an epoxy or a solder. The mirror  92  is aligned such the light signal  20  is transferred from the first input port  10  to the first output port  50 . The mirrors  94  and  96  are aligned such that the light signal  45  is transferred from the second input port  35  to the second output port  25 . This is the loop back mode of operation where the light signal  20 , as transmitted by the first system is received by the first system and the light signal  45  as transmitted by the second system is received by the second system. This allows for each system to diagnose problems of the communications network coupling the two systems. The structure of the switch as shown in  FIGS. 1 and 2  as is apparent is not restricted to having a normal mode and loop back mode, but may allow connection of the first and second system for communication to at least one other system with the first or second output being to the other system.  
         [0032]     Refer now to  FIG. 3  for a description of the preferred embodiment of the optical switch of this invention. The collimators of the first and second input ports  10  and  35  and the first and second output ports  50  and  25  are appropriately aligned and secured to the switch housing  5 . Fiber optic cables are guided through the openings  100  and  105  of the switch housing  5  and connected to the collimators of the first and second input ports  10  and  35  and the first and second output ports  50  and  25 .  
         [0033]     The mirror  60  is attached on the moveable arm  65 , which is connected to the relay  80  by the rod  70  and the connector  75 . The rod  70  is inserted and soldered to the movable arm  65 . The connector  75  is inserted and soldered to the rod  70 . The mirror  60  is soldered or adhered by epoxy onto the movable arm  65 . The rod  70  is then placed into the V-grooves of the supporting blocks  115  and  120 . The V-grooves of the supporting blocks  115  and  120  have a nickel coating to provide a smooth contact surface for the rod  70 . The v-groove springs  130  and  135  is placed on the rod  70  to apply pressure to control the friction between the rod and the v-groove. If the friction is either too large or too small, the rod  70  will not rotate properly. The arm spring  125  is placed upon the moveable arm  65  to limit the movement of the moveable arm  65  by applying a spring force from the top of the moveable arm  65 . The arm spring  125  consists of a stainless steel ball, copper spring, and a spring holder. The stainless steel ball, copper spring, and a spring holder are soldered together for better durability.  
         [0034]     The relay  80  is cut so that the moving plunger of the relay  80  is exposed and capable of contacting the connector  75 . When the plunger of the relay  75  moves upward, the connector  75  moves upward and rotates the rod  70 . The moveable arm  65  and mirror  60  then moves upward by the rotation of the rod  70 . When the relay  80  moves downward, the connector  75  moves downward and rotates the rod  70 . The moveable arm  65  and mirror  60  then moves downward.  
         [0035]     The switch housing  5  in the preferred embodiment has a width  140  of approximately 24 mm. The length  145  of the switch housing  5  is approximately 60 mm and the height  150  of the switch housing  5  is approximately 7 mm.  
         [0036]     Refer now to  FIGS. 4 and 5  for a review of the paths of the light signals  20  and  45 . When the moveable arm  65  and the mirror  60  are down as shown in  FIG. 4 , the light from input port  10  is transferred to output port  25 , and the light from input port  35  is transferred to output port  50  by reflection from the mirror  60 . This is the normal mode of operation. When the moveable arm  65  and mirror  60  are up as shown in  FIG. 5 , the light from input port  10  is reflected from the mirror  92  to output port  50 , and the light from input port  35  is reflected from the mirrors  94  and  96  to output port  25 . This is the loop back mode.  
         [0037]     The mirrors  60 ,  92 ,  94 , and  96  as employed in the present invention have certain losses. Typically these losses of each mirror is 0.05˜0.1 dB. The alignment is accomplished during assembly and cannot be done during field service. Small grooves are machined in the housing of the mirrors  60 ,  92 ,  94 , and  96  to guide the light signals  20  and  45  from first and second input ports  10  and  65  and to the first and second output ports  50  and  25 . These grooves facilitate the alignment process and improve accuracy.  
         [0038]     The assembly and alignment of the switch of this invention begins to by placing the collimator of the first input port  10  on the surface of the switch housing  5 . The collimator of first input port  10  is attached to the switch housing  5 . The mirror  60  is set such that the light signal  20  from first input port  10  is transferred to the collimator of the second output port  35  collimator of the second output port  25  is aligned and attached to the switch housing  5 . The collimator of second input port  35  is then attached onto the switch housing  5 . The mirror  60  is set such that the light signal  45  from second input port  35  is transferred to the collimator of the first output port  50 . The collimator of the first output port  50  is aligned and attached to the switch housing  5 . The relay  80  is activated forcing the mirror  60  to move upward. The mirror  92  is aligned and adjusted such that the light signal  20  from the collimator of first input port  10  is transferred to the collimator of the first output port  50 . The mirror  92  is then soldered or adhered with epoxy to the switch housing  5 . The mirrors  94  and  96  are aligned and adjusted such that the light signal  45  from the collimator of second input port  35  is transferred to the collimator of the second output port  25 . The mirrors  94  and  96  are soldered to the switch housing  5 .  
         [0039]     In the preferred embodiment, two pieces of materials are between each of the collimators  10 ,  25 ,  35 , and  50  and the switch housing  5 . A piece of printed circuit board (PCB) (3.2×7.6×0.4 mm W×L×H) is bounded to the switch housing with epoxy 153ND or 353ND4. A collimator holder (3.2×8 mm W×L×H) is bounded to the PCB with epoxy (type 353ND or 353ND4 epoxy) for each of the collimators  10 ,  25 ,  35 , and  50 . Each collimator holder is aluminum with a gold coating to enable soldering to each of the collimators. The PCB insulates the switch housing  5  from heat when soldering when each of the collimators  10 ,  25 ,  35 , and  50  is soldered to the collimator holder. Finally, two screws secure both the PCB and collimator holder to the switch housing  5 .  
         [0040]     The mirrors  60 ,  92 ,  94 , and  96  each have two coatings. One side of each of the mirrors  60 ,  92 ,  94 , and  96  is coated with solderable gold and the coating on the opposing side of the mirrors  60 ,  92 ,  94 , and  96  are reflective. The reflective coating consists of five layers as listed in table 1.  
                                                             TABLE 1                               Packing   Refractive   Extinction           Layer   Material   Density   Index   Coefficient   Thickness                                Medium   Air       1.0000   0.0           1   Si   1.0   3.8000   0.001   0.25 μm           (lossy)           2   SiO2   1.0   1.14464   0.0   0.25 μm       3   Si   1.0   3.8000   0.001   0.25 μm           (lossy)           4   SiO2   1.0   1.4464   0.0   0.25 μm       5   Al   1.0   2.0381   12.6904700   0.25 μm       Substrate   Glass           1.5073                  
 
         [0041]     Packing density is the fraction of a volume filled by a given collection of solids. Extinction coefficient is the fraction of light lost to scattering and absorption per unit distance in a participating medium and is normally given in standard units as a fraction per meter.  
         [0042]     The 2×2 switch of this invention, as described, provides a packaging structure that allows the fiber optic cables to enter the switch housing on the same side. Further, the 2×2 switch of this invention implements the switch using four mirrors, as opposed to the six mirrors of the prior art. This allows the placement of the 2×2 switch in a rack and panel environment for each of construction of a communication network. Minimizing the number of mirrors reduces the losses and dispersion to the light signals.  
         [0043]     While this invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.