Abstract:
An optical switch ( 100 ) includes a first collimator ( 10 ), a second collimator ( 20 ), and an optical switching member ( 50 ), all encased in a shell ( 40 ). The first collimator retains an input fiber ( 1 ) and a first output fiber ( 2 ). The second collimator retains a second output fiber ( 3 ). The optical switching member includes a light-transmitting member ( 51 ), a piezoelectric actuator ( 30 ) and a reflector ( 52 ). When a controlling voltage is applied to the actuator, the actuator elongates and moves the reflector to block an optical signal from the input fiber to the second output fiber, and to reflect the signal to the first output fiber. When the controlling voltage is removed, the actuator moves the reflector out of the signal path, thus allowing the signal to go to the second output fiber.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an optical switch, and particularly to an optical switch which achieves a switching operation by employing a piezoelectric device to control the movement of a reflective element in the optical switch.  
           [0003]    2. Description of Related Art  
           [0004]    Optical signals are commonly transmitted in optical fibers, which provide efficient light channels through which the optical signals can pass. Recently, optical fibers have been used in various fields, including telecommunications, where light passing through an optic fiber is used to convey either digital or analog information. Efficient switching of optical signals between individual fibers is necessary in most optical processing systems or networks to achieve the desired routing of the signals.  
           [0005]    A typical optical switch has one or more light input port(s) and at least two light output ports for performing switching or logical operations to optical signals in a light transmitting line/system or in an integrated optical circuit. Factors for assessing the capability of an optical switch include low insertion loss (IL, &lt;1 db), good isolation performance (&gt;50 db), and fast switching speed (normally, tens of milliseconds).  
           [0006]    Conventional mechanical optical switches come in two different designs: where the optical components move, and where the fibers move. Moving fiber switches involve the actual physical movement of one or more of the fibers to specific positions to accomplish the transmission of a beam of light from one fiber end to another under selected switching conditions. Moving optical component switches, on the other hand, include optical collimating lenses which expand the beam of light from the fibers, and then, using moving prisms or mirrors, reswitch the expanded beam as required by the switching process.  
           [0007]    The moving fiber switches have a stringent tolerance requirement for the amount and direction of fiber movement. The tolerance is typically a small portion of the fiber core diameter for two fibers to precisely collimate to reduce loss. The fibers themselves are quite thin and may be subject to breakage if not properly protected. On the other hand, reinforcing the fibers with stiff protective sheaths makes the fibers less flexible, increasing the force required to manipulate each fiber into alignment. Thus these moving fiber optical switches share a common problem of requiring high precision parts to obtain precise positioning control and low insertion loss. This results in high costs and complicates manufacture of the switches. Moreover, frequently moving fibers to and fro is apt to damage or even break the fibers. The switching speed of these moving fiber optical switches is also slow.  
           [0008]    Conventional moving optical component switches have less stringent movement control tolerance requirements because of the collimating lenses. However, problems with fatigue during operation make these switches not very reliable. Furthermore, these switches are usually much more complex. These inevitably require higher cost and more complicated manufacture.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    An object of the present invention is to provide an optical switch which is easy to produce without requiring high precision components.  
           [0010]    Another object of the present invention is to provide an optical switch having a high switching speed.  
           [0011]    An optical switch in accordance with one embodiment of the present invention comprises first and second collimators, an optical switching member between the collimators, and a shell encasing the collimators and the switching member. The first collimator retains an input fiber and a first output fiber. The second collimator retains a second output fiber.  
           [0012]    The optical switching member comprises a piezoelectric actuator and a reflector. The reflector is attached to the piezoelectric actuator. A controllable voltage is applied to the piezoelectric actuator, causing an elongation of the piezoelectric actuator corresponding to the amplitude of the voltage. When no controlling voltage is applied to the piezoelectric actuator, the optical signals from the input fiber travel toward the second output fiber. When the controlling voltage is applied to the piezoelectric actuator, the piezoelectric actuator elongates, causing the reflector to be displaced into a path of the optical signals between the input fiber and the second output fiber. The optical signals from the input fiber are incident onto the reflector and are reflected to the first output fiber.  
           [0013]    Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a cross-sectional view of an optical switch according to the present invention before a controlling voltage is applied to a piezoelectric actuator.  
         [0015]    [0015]FIG. 2 is a cross-sectional view of the optical switch of FIG. 1 after a controlling voltage is applied to the piezoelectric actuator.  
         [0016]    [0016]FIG. 3 is a cross-sectional view of an alternate embodiment of the optical switch before a controlling voltage is applied to a piezoelectric actuator.  
         [0017]    [0017]FIG. 4 is a cross-sectional view of the optical switch of FIG. 3 after a controlling voltage is applied to the piezoelectric actuator. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    As shown in FIGS. 1 and 2, an optical switch  100  of the present invention comprises a first collimator  10 , a second collimator  20 , an optical switching member  50  and a shell  40 . The shell  40  is preferably made of glass or metal and accommodates the collimators  10 ,  20  and the switching member  50  therein.  
         [0019]    The first collimator  10  comprises a first port  4  and a first GRIN (graded index) lens  6 . A first space  8  is present between the first port  4  and the first GRIN lens  6 . Ends of an input fiber  1  and a first output fiber  2 , which are preferably not fused together, are received and retained in the first port  4 . The first port  4  has a slanted face  41  which is in close proximity to a reciprocally slanted face  61  of the quarter pitch first GRIN lens  6 . The second collimator  20  comprises a second port  5  and a second GRIN lens  7 . A second space  9  is present between the second port  5  and the second GRIN lens  7 . A second output fiber  3  is received and retained in the second port  5 . The second port  5  has a slanted face  53  which is in close proximity to a reciprocally slanted face  71  of the quarter pitch second GRIN lens  7 . The end sections of the input fiber  1  and the first and second output fibers  2 ,  3  are dejacketed. The core and cladding of each fiber are exposed, and the exposed cladding and core may or may not be tapered. The first GRIN lens  6  and the second GRIN lens  7  are used to collimate a light beam propagating along substantially a longitudinal axis of the collimators  10 ,  20 .  
         [0020]    The optical switching member  50  comprises a piezoelectric actuator  30 , a light-transmitting member  51 , and a reflector  52 . The light-transmitting member  51  can be, for instance, a transparent crystal. The piezoelectric actuator  30  is made of a piezoelectric material, such as aluminum nitride (AIN) or zinc If oxide (ZnO). The piezoelectric actuator  30  comprises two opposite sidewalls (not labeled) and two opposite ends (not labeled). One end of the piezoelectric actuator  30  is attached to the shell  40 . The other end of the piezoelectric actuator  30  is attached to the reflector  52  and the light-transmitting member  51 . Two sidewalls of the piezoelectric actuator  30  are in contact with the shell  40 . When a controlling voltage is applied to the piezoelectric actuator  30 , the piezoelectric actuator  30  elongates a predetermined length corresponding to the amplitude of the voltage applied, thereby moving the reflector  52 .  
         [0021]    The reflector  52  can be a thin, non-transparent plate made of metal, or it can be a second transparent crystal (not labeled) having a reflective film deposited on a rearward side of the second transparent crystal. The rearward side of the reflector  52  (and the rearward side of the second transparent crystal) faces away from a rearward facing second sidewall  32  of the light-transmitting member  51 .  
         [0022]    When the reflector  52  is comprised of the second transparent crystal, in order to achieve desired reflective performance, the reflective film normally comprises a reflective surface made of silver or another highly reflective material having a thickness of about 1 μm. Manufacture of such a reflector  52  can be accomplished using the following process:  
         [0023]    1) providing a transparent, substantially planar crystal as the second transparent crystal;  
         [0024]    2) forming the reflective surface by depositing a silver film or a film made of another highly reflective material on a rearward surface of the second transparent crystal to a thickness of about 1 μm;  
         [0025]    3) forming a reflective material overlay by depositing one or more layers of the same or a second highly reflective material over the reflective surface to increase reflective performance; and  
         [0026]    4) forming a protective film over the reflective material overlay. When assembling the completed second transparent crystal in the optical switch  100 , the protective film (not labeled) faces away from the second sidewall  32  of the light-transmitting member  51 .  
         [0027]    The light-transmitting member  51  has a forward facing first sidewall  31  and the rearward facing second sidewall  32 . The first and second sidewalls  31 ,  32  are parallel to each other and are perpendicular to the path of the light beams. The reflector  52  abuts the second sidewall  32 . When the piezoelectric actuator  30  is actuated, the reflector  52  is moved by the piezoelectric actuator  30  in a direction parallel to the second sidewall  32  of the light-transmitting member  51 . The light-transmitting member  51  helps maintain the reflector  52  in alignment perpendicular to the path of the light beams and prevents the reflector  52  from veering out of alignment.  
         [0028]    [0028]FIG. 1 shows the optical switch  100  of the present invention before the controlling voltage is applied to the piezoelectric actuator  30 . The reflector  52  is in a first, retracted position. Light beams from the input fiber  1  enter the first space  8 . The first GRIN lens  6  collimates the light beams into parallel light beams. The parallel light beams strike the light-transmitting member  51 . Since the material of the light-transmitting member  51  is transparent to the light beams, the light beams are transmitted through the light-transmitting member  51 . The second GRIN lens  7  collimates the parallel light beams after they have passed through the light-transmitting member  51 . The second output fiber  3  in the second port  5  receives the light beams collimated by the second GRIN lens  7 .  
         [0029]    [0029]FIG. 2 shows the optical switch  100  of the present invention after controlling voltage is applied to the piezoelectric actuator  30 . The piezoelectric actuator  30  elongates a predetermined amount corresponding to the amplitude of the voltage applied, moving the light-transmitting member  51  and the reflector  52  in a direction to have the reflector  52  block the path of the light beams. The reflector  52  is thus in a second, extended position. The light beams from the input fiber  1  enter the first space  8 . The first GRIN lens  6  collimates the light beams into parallel light beams. The parallel optical signals pass through the light-transmitting member  51  and hit the reflector  52 , whereupon they are reflected back through the first GRIN lens  6 . After being collimated by the first GRIN lens  6 , they are received by the first output fiber  2 . When the controlling voltage is removed from the piezoelectric actuator  30 , the piezoelectric actuator  30  contracts, retracting the light-transmitting member  51  and the reflector  52  in an opposite direction, thereby moving the reflector  52  out of the path of the light beams. The light beams from the input fiber  1  transmitted through the first collimator  10  can then pass through the second collimator  20  and enter the second output fiber  3 . By controlling the voltage applied to the piezoelectric actuator  30 , the elongation of the piezoelectric actuator  30  is controlled and the direction of the transmission of the light beams from the input fiber  1  is controlled to be received either by the first output fiber  2  or by the second output fiber  3 .  
         [0030]    [0030]FIGS. 3 and 4 show an alternate embodiment of an optical switch  100 A. This alternate embodiment optical switch  100 A comprises a first collimator  10   a , a second collimator  20   a , an optical switch member  50   a  and a shell  40   a . The first collimator  10   a  and the second collimator  20   a  are identical to the first collimator  10  and the second collimator  20  of the optical switch  100  described above and shown in FIGS. 1 and 2. Consequently, numerals used in FIGS. 3 and 4 are similar to those used in FIGS. 1 and 2 for corresponding parts. The optical switching member  50   a  comprises a piezoelectric actuator  30   a,  a light-transmitting member  51   a,  and a reflector  52   a.  One end of the piezoelectric actuator  30   a  is attached to the shell  40   a . The other, opposite end of the piezoelectric actuator  30   a  is attached to the reflector  52   a.  One sidewall of the piezoelectric actuator  30   a  is in contact with the light-transmitting member  51   a.  The other sidewall is in contact with the shell  40   a . A rearward side of the reflector  52   a  faces away from a rearward facing second sidewall  32   a  of the light-transmitting member  51   a.  The light-transmitting member  51   a  has a forward facing first sidewall  31   a  opposite the rearward facing second sidewall  32   a.  The first and second sidewalls  31   a,    32   a  are parallel to each other and are perpendicular to the path of light beams entering the optical switch  100 A. A portion of the first sidewall  31   a  abuts the shell  40   a . The reflector  52   a  and the piezoelectric actuator  30   a  abut the second sidewall  32   a . When a controlling voltage is applied to the piezoelectric actuator  30   a,  the piezoelectric actuator  30   a  elongates a predetermined length corresponding to the amplitude of the voltage applied, thereby moving the reflector  52   a  in a direction parallel to the second sidewall  32   a  of the light-transmitting member  51   a.  The light-transmitting member  51   a  helps maintain the reflector  52   a  in alignment perpendicular to the path of the light beams and prevents the reflector  52   a  from veering out of alignment.  
         [0031]    [0031]FIG. 3 shows the optical switch  100 A before the controlling voltage is applied to the piezoelectric actuator  30   a.  The reflector  52   a  is in a first, retracted position. Light beams from the input fiber  1   a  enter the first space  8   a.  The first GRIN lens  6   a  collimates the light beams into parallel light beams. The parallel light beams strike the light-transmitting member  51   a.  The light beams are transmitted through the light-transmitting member  51   a.  The second GRIN lens  7   a  collimates the parallel light beams after they have passed through the light-transmitting member  51   a.  The second output fiber  3   a  in the second port  5   a  receives the light beams collimated by the second GRIN lens  7   a.    
         [0032]    [0032]FIG. 4 shows the optical switch  100 A after controlling voltage is applied to the piezoelectric actuator  30   a . The piezoelectric actuator  30   a  elongates a predetermined amount corresponding to the amplitude of the voltage applied, moving the reflector  52   a  in a direction parallel to the second sidewall  32   a  of the light-transmitting member  51   a.  After controlling voltage is applied, the reflector  52   a  is thus in a second, extended position, as shown in FIG. 4, where the reflector  52   a  blocks the path of the light beams. The light beams from the input fiber  1   a  enter the first space  8   a.  The first GRIN lens  6   a  collimates the light beams into parallel light beams. The parallel light beams pass through the light-transmitting member  51   a  and hit the reflector  52   a,  whereupon they are reflected back through the light-transmitting member  51   a  and the first GRIN lens  6   a.  After being collimated by the first GRIN lens  6   a,  they are received by the first output fiber  2   a . When the controlling voltage is removed from the piezoelectric actuator  30   a,  the piezoelectric actuator  30   a  contracts, retracting the reflector  52   a  in an opposite direction, thereby moving the reflector  52   a  out of the path of the light beams. The light beams from the input fiber  1   a  transmitted through the first collimator  10   a  can then pass through the second collimator  20   a  and enter the second output fiber  3   a.  By controlling the voltage applied to the piezoelectric actuator  30   a,  the elongation of the piezoelectric actuator  30   a  is controlled and the direction of the transmission of the light beams from the input fiber  1   a  is controlled to be received either by the first output fiber  2   a  or by the second output fiber  3   a.    
         [0033]    The operation of the optical switch embodiments  100 ,  100 A is readily comprehended by examining, respectively, FIGS. 1 and 2 and FIGS. 3 and 4. The optical fibers, fiber ends, and collimators need not be moved to effect switching, as in many prior art switches. In fact, the only optical elements which move in the embodiments of the present invention are the reflector  52  and the light-transmitting member  51  (in the switch  100 ), and the reflector  52   a  (in the switch  100 A). Since the light-transmitting member  51 , the reflector  52 , and the reflector  52   a  can be small, thin, two-sided, and of a conventional construction, the weight of the light-transmitting member  51 , the reflector  52 , and the reflector  52   a  can be kept low, reducing the load on the piezoelectric actuators  30 ,  30   a.    
         [0034]    The switching speeds of the optical switch embodiments  100 ,  100   a  are determined by the speed of movement of the piezoelectric actuators  30 ,  30   a  and are, in general, greater than 1 kHz/s. Therefore, the switching speeds of the optical switch embodiments  100 ,  100   a  are faster than those of conventional switches that require movement of fiber optic components.  
         [0035]    The optical switch embodiments  100 ,  100 A of the present invention are both simple and efficient. Both are economical to manufacture and both are capable of efficiently controlling the direction of transmission of optical signals. None of the parts utilized in the switches requires high precision machining and assembly can be accurately carried out without using expensive equipment or highly skilled personnel. Both switch embodiments are completely self-contained and the piezoelectric actuators  30 ,  30   a  are completely electrically operated.  
         [0036]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.