Abstract:
An optical switch provides the ability to broadcast one input signal to multiple output channels and to combine multiple input signals into single output channel. The signal broadcast pattern is reconfigurable. One or more diffractive optical elements are used in the switch.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to an optical switch capable of broadcasting one or more input signals to multiple output channels in a reconfigurable broadcast pattern, and combining multiple input signals into one output channel. 
         [0003]    2. Description of the Related Art 
         [0004]    Conventional optical switches receive and direct a single input signal to a single selected output. To broadcast an input signal to all output ports, some optical switches require an additional output port, N input ports as well as a 1×N splitter positioned between the output port and N input ports. To implement broadcasting, the input signal is switched to the added output port and is split by the 1×N splitter into multiple signals that are each fed back to a respective added input port. Each of the multiple added input ports then redirect their respective signal to a respective output port. The approaches used in conventional optical switches do not provide for transmitting a single input signal to multiple, reconfigurable outputs. Optical switches that utilize the conventional 1×N splitter require an additional output port and N input ports, increase insertion loss, add to complexity and cost. Additionally, this broadcasting method does not provide a reconfigurable broadcast pattern; as a result, it wastes optical power when 1-to-N broadcasting is not necessary (e.g., when only need 1-to-M, and M&lt;N). 
         [0005]    Additionally, conventional optical switches lack beam-combining capability. 
       SUMMARY OF THE INVENTION 
       [0006]    At least one adjustable input light director is positioned to direct input light to a diffractive optical Element (DOE). The DOE diffracts the light into one or more light beams. Each of a plurality of output light directors, is positioned to receive and redirect a respective one or more of the light beams along a respective optical channel. 
         [0007]    A method for optical switching comprises selecting between an intermediate light director or a diffractive optical element (DOE), directing input light to the selected DOE or intermediate light director, the DOE diffracting the input light into one or more light beams, and redirecting the one or more light beams into respective optical output channels. 
         [0008]    An optical switch comprises one or more output light directors which direct received light into respective output channels and one or more diffractive optical elements (DOE), each of which has a unique, fixed diffraction pattern such that light directed onto the DOE is broadcast to a respective one or more of the reflectors, and at least one adjustable input light director positioned to direct input light onto a selected DOE. 
         [0009]    An optical switch comprises at least one diffractive optical element (DOE) and one or more adjustable input light directors for receiving and directing a plurality of input light beams to a selected DOE, so that the selected DOE combines the input light beams into a single beam along an output channel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic diagram illustrating one embodiment of an optical switch that receives a single input light beam and uses one or more DOEs for diffracting an input light. 
           [0011]      FIGS. 2(   a )-( c ) are schematic diagrams illustrating some of the many diffraction patterns and output light created when a single input light signal is diffracted by one or more DOEs or by an optional intermediate reflector. 
           [0012]      FIG. 3  is a schematic diagram illustrating combining multiple input light beams into one output channel through a DOE. 
           [0013]      FIG. 4  is a flow diagram illustrating a method for optical switching using a DOE. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    The term “broadcast” used herein can refer to diffract light into multiple copies. The elements described herein may be used in different combinations and may be substituted. 
         [0015]      FIG. 1  shows one embodiment in which an input signal  102  is initially received by an input collimator  104  and directed to an input light director  106  (“M 1 ”), which is preferably a reflector, such as a rotatable micromirror, although other devices that perform the same or similar function may be used. Preferably, a computer or other controller device controls M 1 &#39;s rotation automatically. The computer/controller selects a direction or output light path using either a pre-programmed value, one that adjusts to real-time events, or one set by an operator. Where larger mirrors are used, or in the absence of a computer/controller device, M 1  may be rotated manually to select the output direction/path of the reflected light. 
         [0016]    As shown in  FIG. 1 , M 1 &#39;s rotation to a particular position allows it to reflect light to a selected DOE, or to an optional intermediate light director  122  (“M 2 ”). One or more DOEs such as  124  and  126  (“DOE 1 ” and “DOE 2 ”, respectively) and/or one or more intermediate light directors such as M 2  are preferably arranged in an array  120  for selection by M 1  through its rotational position. 
         [0017]    Each DOE is configured to diffract the input light beam into one or more beams, each of which is incident on a respective output light directors.  FIG. 1  shows one embodiment of output light directors  112 ,  114 , and  116  preferably arranged in an array, such as micromirror array  110 . Additional or fewer output light directors can be used. 
         [0018]    Each DOE preferably creates a unique diffraction pattern, which is defined by the number of diffracted beams created by the DOE and the relative direction in which the diffracted beams travel from the DOE. To produce the diffraction pattern, the DOE can be a computer-generated hologram with holographic fringes formed on the surface of a substrate (for example, a glass substrate) through chemical etching, laser scribing, stamping or other fabrication methods. The DOE can also be a thin or thick volume hologram with holographic fringes formed inside the volume of a holographic medium through exposure to the light interference patterns. Each DOE is preferably affixed to an array  120 , but can also be individually rotated to control and adjust the output direction of the entire diffraction light pattern from the DOE. 
         [0019]    In addition to directing light to one or more DOEs, M 1  can also direct light to the intermediate light director M 2 , which is preferably a micromirror. Rather than diffract the input light into multiple copies, M 2  reflects the input light signal to a single output path. Like M 1 , M 2  is also rotatable to adjust the direction of its output ray, and can be computer controlled. The rotatability of M 2  enables it to select a single output path among many, rather than being limited to only one fixed output path, which allows for implementing a 1×N switch (where N is the number of output ports). 
         [0020]    The DOE and optional intermediate light director M 2  direct light to a set of rotatable output light directors  112 ,  114 , and  116  that can be arranged as an array  110 , which is preferably a micromirror array. Like M 1  and M 2 , the position of the output light directors can be set either manually or by a controller or computer to direct light out to a set of output collimators. Angular dispersion caused by a DOE that may introduce angle deviation at the output light directors, can be compensated through the rotation of the output light directors, so that the switch can work with light over a certain wavelength band, for example an entire C band (from 1530 nm to 1565 nm). Each output light director directs the light beam from DOE (or M 2 ) to a respective output collimator. Rotation of the output directors allows maximum light coupling into the output ports via the collimators. Where a single DOE diffracts the light into multiple beams, the output light directors that receive each of the multiple beams redirect the beam to a respective output collimator. Additionally, M 1 , M 2  and the output light directors may be rotated/adjusted independently, or in coordination with one another, to output one or more copies of the input light ray. 
         [0021]      FIGS. 2(   a ) ( b ) and ( c ) illustrate some examples of output patterns that can be generated using light director M 1 , DOEs, optional intermediate light director M 2 , and the set of output light directors. Other light patterns are also contemplated, and no embodiment is limited to the specific light patterns, paths or number of elements and their positions depicted in the Figures. 
         [0022]      FIG. 2(   a ) illustrates one example of a light pattern created when DOE 1  is selected by M 1 . In  FIG. 2(   a ), M 1  is rotated to direct light from an optional input collimator  104  to DOE 1 . In this example, DOE 1  diffracts the light from M 1  into two light beams. One light beam is directed to output light director  114  and the other to output light director  116 . DOE 1  can alternatively be fabricated to generate more or fewer light beams, and/or to transmit the beams to a different combination of output light directors. Additionally, DOE 1  itself may optionally be rotatable to select a different combination of output light directors. The output light directors can also be rotated to redirect the light from the DOEs to the respective output collimators. In this example, output light directors  112  and  114  reflect the light onto output collimators  130  and  132 , respectively. 
         [0023]      FIG. 2(   b ) shows an example of a light pattern created when M 1  is rotated to select DOE 2 , so that light from the optional input collimator  104  is directed onto DOE 2 . In this example, DOE 2  is fabricated to diffract the input light into three output beams. Each beam is directed to a respective output light director  112 ,  114 , and  116  to broadcast the input light to all output light directors and collimators. DOE 2  can also be configured to diffract the incoming light into fewer or more light beams, and to transmit beams to a different combination of output light directors. 
         [0024]    In the example depicted in  FIG. 2(   c ), M 1  is rotated to direct the input light ray to intermediate light director M 2 . M 2  is preferably a mirror, although any other reflective, deflective, and rotatable element can also be used. In this example, M 2  is rotated to direct the input light to output light director  114 , which in turn is positioned to receive and direct the reflected light to output collimator  132 . Alternatively, M 2  could be rotated to direct the light to either output light director  112  or  116 , which are rotated to direct light to output collimators  130  and  134 , respectively. In this manner, a single input light signal can be directed to a single and any output. 
         [0025]    By flipping the input and output ports in  FIG. 2 , the same switch is able to implement a beam-combining function as illustrated in  FIG. 3 . In  FIG. 3 , one or more input collimators  372 ,  374 , and  375  are arranged to receive input light beams  352 ,  354 , and  356 , and direct them to their respective light directors,  312 ,  314 , and  316 . These light directors are shown as input micromirror array in  FIG. 3 . In the absence of input collimators  372 ,  374 , and  375 , light rays  352 ,  354 , and  356  are incident directly on the input light directors. The input light directors redirect the incoming beams to one DOE (e.g., DOE 2 ). The DOE is designed to combine the incoming beams into a single beam and redirect it to output light director  390  shown in  FIG. 3 . The input light directors,  312 ,  314  and  316  are preferably reflectors, such as mirrors, and are preferably rotatable to direct the light to a single selected DOE. In  FIG. 3 , the selected DOE is  326 . The DOEs are preferably arranged in an array format  320 , and the output light director  390  is preferably a reflector, such as a mirror, and is preferably rotatable to direct the light to an output collimator,  330 . Additionally, each DOE may be rotatable. 
         [0026]      FIG. 4  illustrates a method for optical switching comprising selecting a intermediate light director (preferably a mirror) or a diffractive optical element (DOE) for each input light from one or more DOEs, directing input light to the selected DOE said diffractive optical element, or the said intermediate light director, diffracting said input light into one or more light rays with said DOE or redirecting the light with the said intermediate light director, and redirecting said one or more light rays into respective optical output channels. 
         [0027]    While various implementations and embodiments of the optical switch with beam broadcasting capabilities system have been described, it will be apparent to those of ordinary skill in the art that many more are possible.