Abstract:
An optical switch that any vibration or oscillation transmitted to the optical switch from the outside is substantially prevented from being transmitted to a movable electrode is provided. In an optical switch comprising: a stationary electrode; a movable electrode opposed to the stationary electrode with a predetermined space therebetween; and a mirror mounted to the movable electrode, wherein the movable electrode and the mirror are moved together by applying a voltage between the stationary electrode and the movable electrode thereby to switch the path of an incident optical signal to the optical switch, a buffer member provided with a diaphragm is attached to the bottom of the stationary electrode, and a vibration or oscillation is substantially prevented from being transmitted to the movable electrode by the damping effects of the diaphragm and the space area formed above the diaphragm.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an optical switch used in changing the path of an optical signal, and more particularly, to an optical switch configured such that even if a vibration or oscillation should be transmitted to the optical switch, the operating or performance characteristic of the optical switch is not deteriorated.  
           [0003]    2. Description of the Related Art  
           [0004]    For the purpose of changing the path of an optical signal propagating through an optical waveguide such as an optical fiber, various types of optical switches have been heretofore used. An example of the prior art optical switch will be described with reference to FIGS.  1  to  4 .  
           [0005]    [0005]FIG. 1 is a plan view illustrating a construction of the prior art optical switch, and FIG. 2 is a sectional view taken along the line  2 - 2  in FIG. 1 and looking in the direction indicated by the arrows. The illustrated switch SW comprises: a movable electrode supporting frame  10  of a generally square in plan; a stationary electrode substrate  8  of a generally square in plan that closes the interior space of the movable electrode supporting frame  10 ; a movable electrode plate  2  of a generally square in plan that is disposed substantially in parallel with the stationary electrode substrate  8  with a space or gap between them generally in the center of the top surface of the stationary electrode substrate  8 , that is, generally in the center of the movable electrode supporting frame  10 ; four elastic and flexible beams  21  for supporting the movable electrode plate  2  for up and down or vertical motion, each beam having a plurality of meanders or sharply turning portions, one end thereof being fixed to corresponding one of the four sides of the movable electrode plate  2  generally in the center of the side and the other end thereof being fixed to corresponding one of the four sides of the movable electrode supporting frame  10  generally in the center of the side; and a mirror  3  mounted on the center of the top surface of the movable electrode plate  2  along one diagonal line thereof.  
           [0006]    Generally in the center of each of the four sides of the movable electrode supporting frame  10  is formed a post-like connecting portion  211  protruding upwardly and formed integrally with the supporting frame  10 . The other end of each beam  21  is fixed to corresponding one of these connecting portions  211 .  
           [0007]    The movable electrode supporting frame  10  is configured by boring a generally square opening  12  through a silicon substrate of a generally square in plan, the opening  12  being bored concentrically with the silicon substrate. In case of boring the opening  12 , as will be easily understood from FIG. 2, it is preferable that the opening  12  is perforated such that the wall surface of the opening  12  has a taper or slant so that the bore (size) of the opening  12  is gradually increased toward the lower portion thereof, and also it is preferable that the outer wall surface of the generally square stationary electrode substrate  8  is formed so as to have the same taper or slant as that of the opening  12 . It is needless to say that the thickness of the stationary electrode substrate  8  is set to the same value as that of the silicon substrate (the depth of the opening  12 ). By such arrangements, it is possible to fit and fix the stationary electrode substrate  8  in the opening  12  of the movable electrode supporting frame  10  in the state that the stationary electrode substrate  8  is electrically insulated from the supporting frame  10  by inserting the stationary electrode substrate  8  into the opening  12  from the bottom side thereof. As a result, the movable electrode supporting frame  10  and the stationary electrode substrate  8  are integrally coupled and become one plate-like body of a generally square.  
           [0008]    Further, as one method of electrically insulating the junction between the movable electrode plate  2  and the stationary electrode substrate  8 , it is considered that the stationary electrode substrate  8  will be formed out of an n-type silicon semiconductor, for example, and the movable electrode plate  2  will be formed out of a p-type poly-silicon semiconductor, thereby to form the p-n junction therebetween, and a reverse bias voltage or current will be applied to the p-n junction, which results in the electrical insulation between the movable electrode plate  2  and the stationary electrode substrate  8 . It goes without saying that the junction between the movable electrode plate  2  and the stationary electrode substrate  8  may also be electrically insulated by use of other methods.  
           [0009]    In addition, as will be easily understood from the sectional view of FIG. 2, the four beams  21 , the movable electrode plate  2 , the four connecting portions  211 , and the movable electrode supporting frame  10  are usually formed integrally with one another. That is, in case of forming the four connecting portions  211  on the movable electrode supporting frame  10  using a semiconductor integrated circuit manufacturing technique, the movable electrode plate  2  and the four beams  21  are formed at the same time. Consequently, the four beams  21 , the movable electrode plate  2 , the four connecting portions  211  and the movable electrode supporting frame  10  are formed integrally with one another. Since such manufacturing method for the optical switch SW is well known, the explanation thereof will be omitted here.  
           [0010]    Next, the operation of the optical switch SW constructed as discussed above will be described with reference to FIGS. 3 and 4.  
           [0011]    [0011]FIG. 3 is a plan view for explaining the above-constructed optical switch SW in practical use, wherein the optical switch SW is shown in plan view similar to FIG. 1. An input side optical waveguide, namely an optical fiber  4  in this example, for inputting an optical signal L into the optical switch SW is positioned at the left side of the optical switch SW in the drawing. An output side optical waveguide, namely an optical fiber  5  in this example, for transmitting the optical signal L supplied from the optical switch SW is aligned with the input side optical fiber  4  along a straight line passing through the mirror  3  at an angle of about 45° with the surface of the mirror  3 , and another output side optical waveguide, namely an optical fiber  6  in this example, for transmitting the optical signal L supplied from the optical switch SW is disposed on a straight line passing through the mirror  3  and orthogonal to the aforesaid straight line.  
           [0012]    [0012]FIG. 4 is a diagrammatical sectional view illustrating the manner that the optical switch SW shown in FIG. 3 is accommodated in a package  9  which is shown by only a pedestal  91  for putting the optical switch on the top thereof and fixing it thereto, and the peripheral or neighboring portion of the pedestal  91 . Further, the optical switch SW is shown by a sectional view taken along the line  4 - 4  in FIG. 3 and looking in the direction indicated by the arrows. The input side optical fiber  4  and the output side optical fiber  5  are not sectioned.  
           [0013]    As described above, since the mirror  3  is placed on the central portion of the movable electrode plate  3  along a diagonal line thereof, the optical signal L that is outputted from the output end of the input side optical fiber  4  and goes right on in a space is incident on the mirror  3  at an angle of about 45° with the surface of the mirror  3 . As a result, the optical signal L is reflected by the mirror  3  in the direction of forming an angle of 90° (forming a right angle) with the incident light (the optical signal L is outputted from the mirror  3  at an angle of about 45° which is the same as the incident angle), and is transmitted to the input end of the output side optical fiber  6 . In the specification, the transmission state of the optical signal L in which the optical signal L outputted from the input side optical fiber  4  is reflected by the mirror  3  and transmitted to the output side optical fiber  6  is defined as the steady state.  
           [0014]    In the above steady state, in case of applying a predetermined voltage between the movable electrode plate  2  and the stationary electrode substrate  8  to generate an electrostatic force between the both electrodes in such manner that they are attracted each other, the beams  21  are elastic and flexible and the stationary electrode substrate  8  is immovable, and hence the movable electrode plate  2  is driven downwardly toward the stationary electrode substrate  8 . Accordingly, if a voltage applied between the movable electrode plate  2  and the stationary electrode substrate  8  is controlled to displace or drive the movable electrode plate  2  downwardly so that the mirror  3  fixed to the top surface of the movable electrode plate  2  is displaced or driven downwardly to a position where the mirror  3  is out of the optical path on which any optical signal outputted from the input side optical fiber  4  goes right on, the optical signal L outputted from the input side optical fiber  4  will go right on without being reflected by the mirror  3  and be transmitted to the output side optical fiber  5 . Thus, the optical signal L incident on the optical switch SW can be switched to any one of the two output side optical fibers  5  or  6  for transmission of it therethrough. In other words, the above-configured optical switch SW is capable of switching in space the path of an optical signal propagating through an optical waveguide or optical transmission line (path) without any intervention of a solid state optical waveguide.  
           [0015]    However, as shown in FIG. 4, in case the optical switch SW is accommodated in the package  9 , the bottom surface of the stationary electrode substrate  8  of the optical switch SW is fixed directly to the pedestal  91  of a generally square in plan formed on the package  9  by an appropriate adhesive agent, for example. For this reason, if a mechanical vibration or oscillation is transmitted to the package  9  from the outside thereof, the vibration is transmitted to the movable electrode plate  2  through the pedestal  91  of the package  9 , the stationary electrode substrate  8  of the optical switch SW, the movable electrode supporting frame  10 , the connecting portions  211 , and the beams  21  in order of the description. As a result, the movable electrode plate  2  vibrates, and hence the mirror  3  secured to the movable electrode plate  2  vibrates, which results in a drawback that the operating characteristic of the optical switch SW is deteriorated.  
         SUMMARY OF THE INVENTION  
         [0016]    It is an object of the present invention to provide an optical switch that the operating characteristic thereof is not influenced for bad by a vibration or oscillation.  
           [0017]    It is another object of the present invention to provide an optical switch that any vibration or oscillation transmitted to a package is decreased by damping effects of a diaphragm and a space area thereby to prevent the vibration or oscillation from being transmitted to a movable electrode of the optical switch.  
           [0018]    In order to accomplish the foregoing objects, in one aspect of the present invention, there is provided an optical switch which comprises: a stationary electrode; a movable electrode opposed to the stationary electrode with a predetermined space therebetween; and a mirror mounted to said movable electrode, wherein the movable electrode and the mirror are moved together by applying a voltage between the stationary electrode and the movable electrode thereby to switch the path of an incident optical signal to the optical switch, and being characterized in that a buffer member provided with a diaphragm is attached to the bottom of the stationary electrode.  
           [0019]    In a preferred embodiment, the aforesaid buffer member comprises: a diaphragm of a predetermined thickness; a peripheral wall formed on and integrally with the periphery of the diaphragm for supporting the diaphragm and including a first frame-like portion protruding upwardly from the top surface of the diaphragm and a second frame-like portion protruding downwardly from the bottom surface of the diaphragm; at least one ventilating cutout formed in the first frame-like portion of the peripheral wall on the top surface side of the diaphragm; and a pedestal mount portion formed on and integrally with substantially the central portion of the bottom surface of the diaphragm and protruding downwardly.  
           [0020]    In addition, the first frame-like portion of the peripheral wall of the buffer member on the top surface side of the diaphragm is joined with the bottom surface of the stationary electrode to form a space area communicating with the outside atmosphere through only the cutout between the top surface of the diaphragm and the bottom surface of the stationary electrode, and an external vibration or oscillation is substantially prevented from being transmitted to the movable electrode by the damping effects of the diaphragm and the space area.  
           [0021]    In a specific example, the height of the first frame-like portion of the peripheral wall of the buffer member on the top surface side of the diaphragm is about 5 μm, and the space area having its thickness of about 5 μm is formed between the top surface of the diaphragm and the bottom surface of the stationary electrode.  
           [0022]    In addition, the diaphragm of the buffer member is formed from a generally square or rectangular silicon substrate, and the peripheral wall of a generally square or rectangle formed on and integrally with the periphery of the diaphragm and the pedestal mount portion formed on and integrally with substantially the central portion of the bottom surface of the diaphragm are also formed from said silicon substrate, and the cutout reaching the top surface of the diaphragm is formed on the generally square or rectangular first frame-like portion of the peripheral wall on the top surface side of the diaphragm at opposed positions thereof.  
           [0023]    With the construction as described above, between the bottom of the stationary electrode and the top surface of the diaphragm of the buffer member is formed a space area communicating with the outer atmosphere through only the cutout. Since the space area acts like an air cushion, its damping effect to a vibration or oscillation is remarkable as well as the diaphragm. Consequently, even if an external mechanical vibration or oscillation should be transmitted to the optical switch, the vibration is decreased by the damping effects of the diaphragm and the space area, and hence is substantially not transmitted to the movable electrode plate.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    [0024]FIG. 1 is a plan view showing an example of the prior art optical switch;  
         [0025]    [0025]FIG. 2 is a sectional view taken along the line  2 - 2  in FIG. 1 and looking in the direction indicated by the arrows;  
         [0026]    [0026]FIG. 3 is a diagrammatical plan view for explaining the optical switch shown in FIG. 1 in practical use;  
         [0027]    [0027]FIG. 4 is a diagrammatical sectional view illustrating the manner that the optical switch shown in FIG. 3 is accommodated in a package;  
         [0028]    [0028]FIG. 5 is a plan view showing an embodiment of the optical switch according to the present invention;  
         [0029]    [0029]FIG. 6 is a sectional view taken along the line  6 - 6  in FIG. 5 and looking in the direction indicated by the arrows;  
         [0030]    [0030]FIG. 7 is a rear view of FIG. 5;  
         [0031]    [0031]FIG. 8 shows the buffer member shown in FIGS. 6 and 7, FIG. 8A is a plan view of the buffer member, FIG. 8B is a right side view of FIG. 8A, FIG. 8C is a sectional view taken along the line  8 C- 8 C in FIG. 8A and looking in the direction indicated by the arrows, and FIG. 8D is a rear view of FIG. 8A;  
         [0032]    [0032]FIGS. 9A to  9 J are sectional views and plan views for explaining the manufacturing processes of the buffer member shown in FIG. 8; and  
         [0033]    [0033]FIG. 10 is a diagrammatical sectional view illustrating the manner that the optical switch shown in FIGS.  5  to  7  is accommodated in a package. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]    The preferred embodiment of the present invention will now be described in detail with reference to FIGS.  5  to  10 . The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth hereinafter; rather, the embodiment is provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.  
         [0035]    [0035]FIG. 5 is a plan view showing an embodiment of the optical switch according to the present invention, FIG. 6 is a sectional view taken along the line  6 - 6  in FIG. 5 and looking in the direction indicated by the arrows, and FIG. 7 is a rear view of FIG. 5. The optical switch SWB in this embodiment comprises: an optical switch part  70  that may have the same construction as that of the prior art optical switch SW shown in FIGS. 1 and 2 and discussed above; and a buffer member or shock absorbing member  83  joined with the bottom of the optical switch part  70 . Accordingly, the optical switch part  70  used in this embodiment may have the same construction as that of the prior art optical switch SW shown in FIGS. 1 and 2 and discussed above, and hence portions or elements in FIGS. 5 and 6 corresponding to those in FIGS. 1 and 2 will be shown by the same reference characters affixed thereto, and the explanation thereof will be omitted unless it is necessary.  
         [0036]    Next, the buffer or shock absorbing member  83  attached to the bottom of the optical switch part  70  will be described in detail with reference to FIG. 8 in addition to FIGS.  5  to  7 .  
         [0037]    The shock absorbing member  83  in this embodiment comprises: as is clear from FIG. 8, a diaphragm  831  of a generally square in plan; a frame-like peripheral wall  832  of a generally square in plan formed on and integrally with the periphery of the diaphragm  831  for supporting the diaphragm  831 ; one pair of ventilating cutouts  833  formed on the upper end surface of the frame-like peripheral wall  832  at two spots or places thereof opposed to each other; and a mount portion  834  of a generally square in plan to be mounted to a pedestal (hereinafter referred to as pedestal mount portion) formed on and integrally with substantially the central portion of the lower surface of the diaphragm  831  and protruding downwardly from the lower surface of the diaphragm  831 , the pedestal mount portion  834  being mounted on the pedestal  91  of the package  9  as described later.  
         [0038]    The outer measurement (size) of the peripheral wall  832  is set, as is apparent from FIG. 6, to the same value as that of the movable electrode supporting frame  10  of the optical switch part  70 . In addition, the peripheral wall  832  is provided with a first frame-like portion protruding upwardly from the top surface of the diaphragm  831  and a second frame-like portion protruding downwardly from the bottom surface of the diaphragm  831 . As is clear from FIGS. 8A and 8B, the pair of ventilating cutouts  833  are formed by cutting out two opposed spots of the first frame-like portion of the peripheral wall  832  protruding upwardly from the top surface of the diaphragm  831  until they are flush with the top surface of the diaphragm  831 . In this embodiment, though the cutouts  833  are formed at two spots of the first frame-like portion that are substantially symmetrical about the center of the diaphragm  831 , the number of the cutouts  833  and spots or places where the cutouts  833  are to be formed are not limited to the illustrated example. The pedestal mount portion  834  is set such that the height of the downward protrusion thereof becomes equal to the height of the second frame-like portion of the peripheral wall  832  protruding downwardly.  
         [0039]    The height of the first frame-like portion of the peripheral wall  832  protruding upwardly from the top surface of the diaphragm  831  is set to be considerably lower than that of the second frame-like portion of the peripheral wall  832  protruding downwardly from the bottom surface of the diaphragm  831 . Accordingly, in case the optical switch part  70  is joined with the shock absorbing member  83 , as will be easily understood from FIG. 6, between the bottom of the optical switch part  70  and the top surface of the diaphragm  831  of the shock absorbing member  83  is formed a space area S that is an air layer communicating with the outer atmosphere through the pair of the cutouts  833 . In other words, the height of the first frame-like portion of the peripheral wall  832  protruding upwardly from the top surface of the diaphragm  831  is set such that the space area S acting like an air cushion through the ventilating cutouts  833  can be formed between the bottom of the optical switch part  70  and the top surface of the diaphragm  831  of the shock absorbing member  83 .  
         [0040]    The shock absorbing member  83  constructed as discussed above is attached to the bottom of the optical switch part  70  by, for example, an appropriate adhesive agent, and thus, the optical switch SWB shown in FIGS.  5  to  7  is completed.  
         [0041]    Next, an example of the manufacturing method for the aforesaid shock absorbing member  83  will be described with reference to FIG. 9.  
         [0042]    At first, a silicon substrate having a predetermined shape and size (in this example, a generally square silicon substrate having a predetermined thickness and surface area) is prepared, and as shown in FIG. 9A, silicon dioxide (SiO 2 ) layers  835 A and  835 B are formed on both the top and bottom surfaces of the silicon substrate  830 , respectively, by thermal oxidation.  
         [0043]    Next, a photoresist, for example, is applied all over the surface of the silicon dioxide layer  835 A over the top surface of the silicon substrate  830 , and thereafter, portions of the photoresist corresponding to the shape of the diaphragm  831  and the shapes of the two cutouts  833  are removed respectively by a photoetching process.  
         [0044]    Then, portions of the silicon dioxide layer  835 A where the photoresist thereon have been removed are removed by etching. FIG. 9B is a plan view illustrating the state that portions of the silicon dioxide layer  835 A corresponding to the shape of the diaphragm  831  and the shapes of the two cutouts  833  have been removed by etching, and FIG. 9C is a sectional view taken along the line  9 C- 9 C in FIG. 9B and looking in the direction indicated by the arrows. This process exposes the top surface of the silicon substrate  830  in the shape of the diaphragm  831  and the shapes of the two cutouts  833 .  
         [0045]    Next, the exposed portions of the silicon substrate  830  in the shape of the diaphragm  831  and the shapes of the two cutouts  833  are removed by a predetermined thickness, in the order of 5 μm (micrometers) in this example, by etching. The result is shown in FIGS. 9D and 9E. FIG. 9D is a plan view thereof and FIG. 9E is a sectional view taken along the line  9 E- 9 E in FIG. 9D and looking in the direction indicated by the arrows. Upon completion of this process, the top surface of the silicon substrate is exposed in a generally square portion which will become the top surface of the diaphragm  831  and small rectangular portions corresponding to the two cutouts  833 , the generally square frame-like peripheral wall  832  having its height of 5 μm is formed at the periphery of the top surface of the diaphragm  831 , and the two cutouts  833  are formed at substantially symmetrical positions about the center of the diaphragm  831  (at the positions of bilateral symmetry in the drawing).  
         [0046]    Next, a photoresist, for example, is applied all over the surface of the silicon dioxide layer  835 B over the bottom surface of the silicon substrate  830 , and thereafter, a generally square portion of the photoresist corresponding to the shape of the diaphragm  831  except a generally square portion of the photoresist located at the central portion thereof corresponding to the shape of the pedestal mount portion  834  is removed by a photoetching process.  
         [0047]    Then, a portion of the silicon dioxide layer  835 B where the photoresist thereon have been removed is removed by etching. FIG. 9F is a plan view illustrating the state that a portion of the silicon dioxide layer  835 B corresponding to the shape of the diaphragm  831  except a portion thereof corresponding to the shape of the pedestal mount portion  834  has been removed by etching, and FIG. 9G is a sectional view taken along the line  9 G- 9 G in FIG. 9F and looking in the direction indicated by the arrows. This process leaves a generally square frame-like silicon dioxide layer  835 B and a generally square silicon dioxide layer  835 B at the periphery and central portion of the bottom surface of the silicon substrate  830 , respectively, and therefore, the bottom surface of the silicon substrate  830  is exposed in the shape of the diaphragm  831  except the central portion of the bottom surface.  
         [0048]    Next, the exposed portion of the bottom surface of the silicon substrate  830  is removed by a predetermined thickness, in the order of 300 μm in this example, by etching. The result is shown in FIGS. 9H and 9I. FIG. 9H is a plan view thereof and FIG. 9I is a sectional view taken along the line  9 I- 9 I in FIG. 9H and looking in the direction indicated by the arrows. Upon completion of this process, the bottom surface of the silicon substrate is exposed in a generally square portion which will become the bottom surface of the diaphragm  831  except a generally square island-like portion located at the central portion of the silicon substrate, the generally square frame-like peripheral wall  832  having its height of 300 μm is formed at the periphery of the bottom surface of the diaphragm  831 , and the generally square pedestal mount portion  834  having its height of 300 μm is formed at the central portion of the bottom surface of the diaphragm  831 .  
         [0049]    Further, in this embodiment, the thickness of the original silicon substrate  830  not etched is selected such that the thickness of the diaphragm  831  falls within the range from several μm to several tens μm after it has been etched. Since the thickness of the diaphragm  831  may be changed within a range in which a diaphragm can give a large damping effect to a vibration or oscillation, it is not always limited to the values of the embodiment.  
         [0050]    Next, as shown in FIG. 9J, the remaining silicon oxide layers  835 A and  835 B on both the top and bottom surfaces of the silicon substrate  830  are removed. Thus, the shock absorbing member or buffer member  83  of this embodiment shown in FIG. 8 can be obtained.  
         [0051]    The optical switch SWB of this embodiment having the above-constructed shock absorbing member  83  attached thereto is used by housing it in a package  9  as shown in FIG. 10. The package  9  may be one that has the same construction as that of the prior art package  9  shown in FIG. 4, and is provided with a pedestal  91  on which the optical switch SWB is put and fixed thereto. The optical switch SWB is fixed within the package  9  by joining the bottom surface of the pedestal mount portion  834  formed integrally with the bottom surface of the diaphragm  831  of the optical switch SW with the top surface of the pedestal  91  by use of an appropriate adhesive agent, for example.  
         [0052]    With the construction as described above, between the bottom of the optical switch part  70  and the top surface of the diaphragm  831  of the shock absorbing member  83  is formed a space area S that is an air layer communicating with the outer atmosphere through only the pair of the cutouts  833 . Since the space area S acts like an air cushion, its damping effect to a vibration or oscillation is remarkable as well as the diaphragm  831 . As a result, if a mechanical vibration or oscillation should be generated in the outside of the optical switch SWB and transmitted to the package  9 , the vibration is completely or greatly decreased by the damping effects of the diaphragm  831  and the space area S existing in the way of the vibration transmission path, and hence is substantially not transmitted to the movable electrode plate  2 .  
         [0053]    Specifically explaining, between the outside of the optical switch SWB and the movable electrode plate  2  is formed the vibration transmission path in a serial manner constituted by the pedestal  91  of the package  9 , the pedestal mount portion  834  of the buffer member  83 , the diaphragm  831 , the space area S, the stationary electrode substrate  8 , the movable electrode supporting frame  10 , the connecting portions  211 , and the beams  21 . However, in this vibration transmission path are interposed the diaphragm  831  and the space area S each of which has a large damping effect, and so any external vibration or oscillation applied to the package  9  is completely or almost decreased by the multiplied damping effects of the diaphragm  831  and the space area S. As a result, the vibration or oscillation is not transmitted to the movable electrode plate  2 , or even if it should be transmitted to the movable electrode plate  2 , it is decreased to such an extremely weak one that the mirror  3  substantially does not vibrate. Accordingly, there is obtained a remarkable advantage that an optical switch can be provided the operating characteristic of which is not deteriorated even an external vibration or oscillation is transmitted to the package  9 . In addition, since the buffer member  83  is a thin and planar-shaped member having the diaphragm  831 , it is best suited for a member to be joined with the thin and planar-shaped optical switch part  70 .  
         [0054]    In the aforesaid embodiment, there has been illustrated a case that the buffer member  83  is attached to the optical switch part  70  having the same construction as that of the prior art optical switch shown in FIGS. 1 and 2. However, it is needless to say that the buffer member  83  of the above embodiment can be also attached to other known prior art optical switch or switches, and that the same function and effect can be obtained therefrom. For example, the buffer member  83  of the above embodiment can be also attached to an optical switch that comprises: a stationary electrode substrate made of an n-type or p-type silicon; two connecting portions; two elastic and flexible beams; and a movable electrode plate supported by the two beams, wherein the two connecting portions, the two elastic and flexible beams, and the movable electrode plate all are made of a p-type or n-type poly-silicon and are formed integrally with one another on the stationary electrode substrate without using a movable electrode supporting frame, and the same function and effect can be obtained therefrom.  
         [0055]    Further, it goes without saying that the number, shape and size of the connecting portions, the number, shape and size of the beams, shapes and sizes of the movable electrode plate, stationary electrode substrate, and the like, or shapes, sizes or the like of the diaphragm, peripheral wall, and cutout of the buffer member are not limited to the illustrated example, and can be modified, altered or changed variously if the need arises.  
         [0056]    While the present invention has been described with regard to the preferred embodiment shown by way of example, it will be apparent to those skilled in the art that various modifications, alterations, changes, and/or minor improvements of the embodiment described above can be made without departing from the spirit and the scope of the present invention. Accordingly, it should be understood that the present invention is not limited to the illustrated embodiment, and is intended to encompass all such modifications, alterations, changes, and/or minor improvements falling within the scope of the invention defined by the appended claims.