Patent Publication Number: US-2002003919-A1

Title: Optical switch module

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to an optical switch for switching optical paths or an optical switch module for use in an optical add/drop multiplexing system, which is used in optical communication system.  
       RELATED ART  
       [0002] Compact optical switches using MEMS (Micro Electro Mechanical System) have been proposed, and one such example is a 4×4 matrix switch shown in FIG. 5. This optical switch is described in Abstract C-3-105, published in the general conference of The Institute of Electronics, Information and Communication Engineers in 2000.  
       [0003] As shown in FIG. 5( a ), there is a matrix chip  35  having a face  25  on its one end, to which four input-side optical fibers  1  are arranged in parallel. A lens array  26  is disposed between the input-side optical fibers  1  and the end face  25 . The lens array  26  includes lenses  27  each facing a connecting endface of each input-side optical fiber  1 . Four parallel-arranged output-side optical fibers  2  are faced to the other end face  28  of the matrix chip  35 . Another lens array  29  is disposed between the output-side optical fibers  2  and the end face  28 . The lens array  29  includes lenses  30 , each facing a connecting end face of each input-side optical fiber  2 .  
       [0004] The matrix chip  35  is sectioned into 16-pieces (4×4=16) of matrices. As shown in FIFS.  5 ( b ) and ( c ), each matrix is formed by arranging a moving electrode  23  on a fixed electrode substrate  21  via a frame substrate  22  and arranging a movable mirror  24  on the movable electrode  23 .  
       [0005] In the optical switch shown in FIG. 5, electrostatically driving the movable electrode  23  supported by a spring enables the moving mirror  24  in a direction (an up-and-down direction in the drawing) perpendicular to the surface of the fixed electrode substrate  21 , which switches optical paths.  
       [0006] For example, as shown in FIG. 5( b ) and ( c ), some of the moving mirrors  24  shown by the solid lines in FIG. 5( a ) are moved up higher than the upper surface of the frame substrate  22 , while the remaining mirrors  24  shown by broken lines shown in FIG. 5( a ) are drawn toward the fixed electrode substrate  21  so as to locate lower than the upper surface of the frame substrate  22 . This allows the moving mirrors  24  shown by the solid lines in FIG. 5( a ) to optically connect the input-side optical fibers  1  to the output-side optical fibers  2 .  
       [0007] Because each moving mirror  24  is disposed movably in the perpendicular direction to the surface of the fixed electrode substrate  21 , moving mirrors  24  located higher than the upper surface of the frame substrate  22  can be changed, whereby it is possible to change the combination of the input-side and output-side optical fibers  1  and  2  optically connected to each other.  
       [0008] The matrix switch shown in FIG. 5 is configured so that the switch is able to switch the optical paths into, for example, N×M ways (N, M: positive integer). However, the number of the moving mirrors  24  is required by “N×M” pieces, resulting in a complicated construction of the switch.  
       [0009] In addition, the optical switch shown in FIG. 5 has a problem that it does not have function of reflecting a plurality of incident light beams to a single output fiber for wavelength multiplexing systems, which is required for the optical switch. Additionally, there is another problem that it is impossible for the optical switch to have a configuration of switching N×M optical paths simultaneously.  
       SUMMARY OF INVENTION  
       [0010] The present invention provides an optical switch module for solving the above problems.  
       [0011] A first embodiment of the present invention is an optical switch module, which comprises:  
       [0012] (a) N-pieces of input-side optical fibers are disposed in line along an end of X-axis direction of a plane substrate;  
       [0013] (b) rotary mirrors, the number of which is the same as that of the input-side optical fibers, are aligned in line in optical axes of the input-side optical fibers on the substrate so that each mirror is free from interrupting optical paths of the remaining mirrors;  
       [0014] (c) M-pieces of output-side optical fibers are disposed in line along a Y-axis directional end of the substrate; and  
       [0015] (d) a drive mechanism for rotating the mirrors so that an optical signal received through any of the input-side optical fibers is reflected toward any of the output-side optical fibers.  
       [0016] A second embodiment of the present invention is an optical switch module, wherein both of the X-axis and the Y-axis are perpendicular to each other.  
       [0017] A third embodiment of the present invention is an optical switch module, wherein a line of the mirrors is inclined to either the X-axis or the Y-axis by an angle of 30 to 60 degrees.  
       [0018] A fourth embodiment of the present invention is an optical switch module, wherein the number N of the input-side optical fibers is equal to or different from the number M of the output-side optical fibers.  
       [0019] A fifth embodiment of the present invention is an optical switch module, wherein the number N of the input-side optical fibers and the number M of the output-side optical fibers are integers selected from numbers of 2 to 10.  
       [0020] A sixth embodiment of the present invention is an optical switch module, wherein the input-side optical fibers or the output-side optical fibers are provided with a collimator lens at ends thereof.  
       [0021] A seventh embodiment of the present invention is an optical switch module, wherein the input-side optical fibers or the output-side optical fibers are provided with a multi-mode fiber with collimating functions at ends thereof.  
       [0022] An eighth embodiment of the present invention is an optical switch module, wherein the drive mechanism for rotating the mirrors is provided with a electrostatic motor.  
       [0023] A ninth embodiment of the present invention is an optical switch module, wherein the plane substrate is made up of a rectangular semiconductor substrate. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0024]FIG. 1 shows an essential configuration of one embodiment of an optical switch according to the present invention.  
     [0025]FIG. 2 shows a variety of embodiments for the shape of a substrate and the arrangement of mirrors in the present invention.  
     [0026]FIG. 3 is an outlined view of an electrostatic motor for rotating a rotary mirror applied to the embodiment.  
     [0027]FIG. 4 explains a rotary mechanism installed in the electrostatic motor.  
     [0028]FIG. 5 exemplifies a conventional optical switch constructed using the MEMS technique. 
    
    
     DETAILED DESCRIPTION  
     [0029] Embodiments of the present invention will now be described based on the accompanying drawings. Although the following is described about embodiments of the present invention, the present invention will not be limited to such embodiments. It should be understood that the present invention includes various embodiments realized by a person of ordinary skill in the art by arbitrarily combining embodiments that are described hereinafter. In the following description, the identical or similar components to those of the conventional optical switch employ the same references, the description being avoided from being repeated. FIG. 1 shows an essential configuration of one embodiment of an optical switch according to the present invention, in which X- and Y-directions perpendicular to each other are designated as shown therein.  
     [0030] As shown in FIG. 1, a plurality of input-side optical fibers  1  ( 1   a  to  1   h ; eight fibers in this case) are disposed in parallel along an end face  25  of a rectangular semiconductor substrate  3  at a pitch of, for example, 250 μm. Additionally, a plurality of output-side optical fibers  2  ( 2   a  to  2   h ; eight fibers in this case) is disposed above an end face  28  in the right direction to the end face  25  at a pitch of for example 250 μm As the semiconductor substrate  3 , a silicon substrate having a thickness of, for example, 625 to 1000 μm is preferably used.  
     [0031] In the present embodiment, the input-side optical fibers  1   a  to  1   h  and the output-side optical fibers  2   a  to  2   h  are disposed at a pitch described above, a width required for disposing each set of the input-side optical fibers  1   a  to  1   h  and the output-side optical fibers  2   a  to  2   h  is about 1.75 mm. In addition, a distance from the input-side optical fiber  1   a,  which is located at an outermost position, to the end face  28  is 3 mm, while a distance from the output-side optical fiber  2   h,  which is located at an outermost position, to an end face  39  facing the end face  25  is 1 mm. In other words, the length of the X-directional end face of the semiconductor substrate  3  is about 5 mm and the length of the Y-directional end face  28  thereof is about 3 mm.  
     [0032] In the present embodiment, a plurality of rotary mirrors  4  ( 4   a  to  4   h ) are aligned in optical axes on the semiconductor substrate  3  in one-to-one correspondence to the input-side optical fibers  1   a  to  1   h.  The output-side optical fibers  2  are directed along light reflecting directions from the rotary mirrors  4 , respectively. Each mirror  4  is shaped into a micro-mirror of which width is about 150 μm and of which height is about 300 μm, for instance.  
     [0033] Each of the rotary mirrors  4   a  to  4   h , which corresponds to each of the input-side optical fibers  1   a  to  1   h,  is located in an optical axis extending from each of the input-side optical fibers  1   a  to  1   h.  At the same time, the rotary mirrors  4   a  to  4   h  are placed at different positions mutually shifted in the longitudinal directions (in the Y-direction) of the input-side optical fibers  1   a  to  1   h.  By way of example, the rotary mirrors  4   a  to  4   h  are arranged at a pitch of 350 μm in the Y-direction.  
     [0034] The maximum rotation angle of the rotary mirror  4   a,  which is located nearest to the end face  28 , is 35 degrees and its rotation angle is changeable in eight steps of 0, 5, 10, 15, 20, 25, 30 and 35 degrees. Meanwhile, a rotation angle of 0 degree for each of the rotary mirrors  4   a  to  4   h  means that each rotary mirror is able to exactly reflect a light beam to the output-side optical fiber  2   a  located closest to the end face  25 .  
     [0035] The maximum rotation angle of the rotary mirror  4   b,  which is located next to the rotary mirror  4   a,  is 33 degrees and its rotation angle is changeable in eight steps at every 4.7 degrees. Like this, each of the remaining mirrors  4   b  to  4   h  is changeable in rotation angle in eight steps at every appropriately set angle. The final mirror  4   h  can be rotated by 18 degrees at maximum and its rotation angle is changeable in eight steps at every 2.6 degrees.  
     [0036] In this way, each of the angles of the rotary mirrors  4   a  to  4   h  can be switched over in the eight steps, which makes it possible to arbitrarily combine the eight input-side optical fibers  1   a  to  1   h  and the eight output-side optical fibers  2   a  to  2   h . This switchable configuration is generalized to design in a manner such that the mirrors are equal in number to the input-side optical fibers and equal in the number of steps of rotation angle to the output-side optical fibers. Such design makes it possible to connect each of the input-side optical fibers  1   a  to  1   h  to all of the output-side optical fibers  2   a  to  2   h.    
     [0037] A collimator lens  9  is secured on each of connecting end faces of the input-side optical fibers  1 , whilst a collimator  10  is secured on each of connecting end faces of the output-side optical fibers  2 . The collimator lenses can be replaced by multi-mode fibers with collimating function.  
     [0038] In the present embodiment, the collimator lens  9  secured to the connecting end face of each input-side optical fiber  1  is constructed to convert input light, which has traveled through the input-side optical fiber  1 , to parallel light rays at an efficiency of approximately 100 percent and sends out the parallel light rays toward a given rotary mirror  4 .  
     [0039] The collimator lens  10  secured on the connecting end face of each output-side optical fiber  2  has a light-receiving angle which allows a given output-side optical fiber  2  to receive light reflected by the rotary mirrors  4  at an efficiency of substantially 100 percent (in the present embodiment, a maximum light-receiving angle è=70 degrees). In the present embodiment, securing both collimator lenses  9  and collimators  10  enables reflected light from the rotary mirrors  4  to be optically connected to all the output-side optical fibers  2 , as long as the rotary mirrors  4  are located in an area other than the hatched areas on the substrate  3 , as shown in FIG. 1. From a viewpoint of manufacturing, it is preferable that the mirrors be aligned straight at an angle of 30 to 60 degrees to both of the X- or Y-axes mutually crossing at the right angle, as shown in FIG. 1.  
     [0040] Although the above embodiment employs the rectangular substrate and the mirrors are arranged thereon, the present invention is not limited to the shape and arrangement. Alternative shapes and arrangement, to which the present invention can also be applied, are shown in FIGS.  2 ( a ) to  2 ( f ). The arrangement shown in FIG. 2( a ) is the same as that in FIG. 1. The arrangement shown in FIG. 2( b ) is realized by rotating the alignment of the mirrors in FIG. 2( a ) by about 90 degrees. In each of FIGS.  2 ( c ) to  2 ( f ), the substrate is shaped into a parallelogram, where the mirrors can be arranged in a similar way to the alignment shown in each of FIGS.  2 ( a ) and ( b ). In the shape of the substrate and arrangement of the mirrors, when taking less noise into account, it is preferable that a light reflection angle á at each mirror is as small as possible. From this point of view, the examples shown in FIG. 2( a ), ( b ) and ( d ) is preferable to the remaining examples.  
     [0041] In the above configurations, each of the number N of the input-side optical fibers and the number M of the output-side optical fibers is four, but the numbers N and M are not limited so. Each of the numbers N and M for practically available optical switch modules is 2 to 10. When the numbers N and M are more than 10, the reflection angle is widened, thereby providing a broader reflection flux of light, which is undesirable. In contrast, when the numbers N and M are less than two, it is considered that that the optical switch module provided in the present invention is slightly complicated, compared to such numbers of optical fibers. Further, it is not always required that the numbers N and M be equal to each other, but those may be different integers from each other. Furthermore, though it is general that the X-axis and Y-axis crossing at the right angle, the present invention is not confined to such an angular configuration. As long as the condition that the light reflection angle á is for example an amount of 150 degrees or less is maintained, both X-axis and Y-axis are not required to be crossed at the right angle.  
     [0042]FIG. 3 shows a perspective view of an electrostatic motor (also, referred to as an electrostatic actuator) adopted as a rotary drive mechanism for each rotary mirror  4 . This electrostatic motor will now be outlined. As shown in FIG. 3, the rotary mirror  4  is secured on a rotor  7 . On the outer circumferential surface of the rotor  7  are provided with protrusions  8  each extending outward, which are located at intervals in the circumferential direction. Stators  5  that consist of divided pieces each opposing to the protrusions  8  of the rotor  7  are disposed at intervals.  
     [0043] In the electrostatic motor for driving each mirror  4 , the diameter of the rotor  7  is for example 250 μm and the outer diameter of the divided stator  5  is for example 500 μm. The numbers of protrusions  8  and stators  5  are designated according to the rotation angle. The stators  5 , which neighbor on each other, are disposed, by way of example, at intervals of a certain angle {grave over ( 1 )} which corresponds to a rotation angle of each of the mirrors  4   a  to  4   h  at the center of the rotor  7 . For example, the angle ì is 5 degrees for the rotary mirror  4   a.    
     [0044] The rotor of the electrostatic motor is formed of P-type or N-type of semiconductor that accepts supply of positive and negative direct currents. On the other hand, pulsed current is supplied to the stators  5  to rotate them stepwise.  
     [0045] The operational principle of each rotary mirror  4  will now be described with reference to FIG. 4. For instance, in the configuration shown in FIG. 4, the protrusions  8   a ,  8   b,    8   c,  . . . are charged positively. In contrast, the stators  5  adopt an alternating charge manner. Specifically, the divided pieces of the stators  5  are charged positively or negatively every other piece and their charge are changed at each time specified in a driving sequence. So at a certain time, the divided pieces  5   a,    5   c,    5   e,  . . . are charged positively, while the divided pieces  5   b,    5   d,    5   f,  . . . are charged negatively.  
     [0046] This charging causes Coulomb&#39;s forces. In addition, design is made such that, when making the protrusion  8   a  face to the divided piece  5   a  of the stator, the next protrusion  8   b  is located between the stator divided pieces  5   b  and  5   c.  Therefore, the operating forces are shifted from the center to yield a torque in the rotary direction, which causes the rotor  7  to rotate. Accordingly, controlling current generated in the direct electric circuit sequentially in time enables the mirror  4  to rotate by an arbitrary amount of angle. In other words, this makes it possible to obtain any rotation angle of the rotary mirror  4 .  
     [0047] Alternatively, as an opposed way to the above, the protrusions  8   a ,  8   b,    8   c,  . . . may be charged negatively. It is enough that in the divided pieces  5 , the polarities thereof are set to be alternating every other piece. This kind of charge can be realized by connecting the whole protrusions  8  to a single direct electric charge and connecting the divided pieces  5  to a positive charge or a negative charge of direct alternating electric circuits, piece by piece.  
     [0048] Hence, for example, when the mirror  4   a  is rotated to an angle of 0 degrees, the light coming through the input-side optical fiber  1   a  is reflected by the rotary mirror  4   a  toward the output-side optical fiber  2   a , and is transmitted. When the mirror  4   a  is rotated to an angle of 5 degrees, the light coming through the input-side optical fiber  1   a  is reflected by the rotary mirror  4   a  toward the output-side optical fiber  2   b , and is transmitted.  
     [0049] As explained the light coming through the input-side optical fiber  1   a  is reflected by the rotary mirror  4   a  toward each of the out-put optical fiber  2   a  to  2   h  by changing the angle of the rotary mirror  4   a  by 5 degrees each time.  
     [0050] Similarly, the rotation angle step of each of the rotary mirrors  4   b  to  4   h  is defined for each of the mirrors  4   b  to  4   h . Changing of the rotation angle step by step causes the light which is input through each of the input-side optical fibers  1   b  to  1   h  to be reflected by any of the rotary mirrors  4   a  to  4   h  toward any of the output-side optical fibers  2   a  to  2   h,  and is outputted through the optical fibers  2 .  
     [0051] As described above, in the present embodiment, controlling the rotation angles of the rotary mirrors  4   a  to  4   h  makes it possible to output the light received through any of the input-side optical fibers  1   a  to  1   h  through any of the output-side optical fibers  2   a  to  2   h.  Accordingly, there can be provided a 8×8 optical switch or an optical add/drop multiplexing apparatus capable of freely changing combinations between the input-side optical fibers  1   a  to  1   h  and the output-side optical fibers  2   a  to  2   h  in a controlled manner.  
     [0052] In addition, in the case that the rotation angles of all rotary mirrors  4   a  to  4   h  are set to zero degree, the light rays input through all of the input-side optical fibers  1   a  to  1   h  can be multiplexed to be output through the single output-side optical fiber  2   a . As understood from this example, the optical switch according to the present embodiment can be used as an optical switch module that has a function of freely combining optical waves.  
     [0053] Further, the present embodiment provides a compact and elaborate configuration in which the rotary mirrors  4   a  to  4   h  are formed on the semiconductor substrate  3  using the semiconductor processing technique. In addition, it is enough to provide the rotary mirrors  4   a  to  4   h  of which number is the same as that of the input-side optical fibers  1   a  to  1   h,  which can lower largely in the number of mirrors, compared to the conventional matrix switch.  
     [0054] In the present embodiment, the electrostatic force can be used to switch the rotation angles of each of the rotary mirrors  4   a  to  4   h  with ease. This provides easier switching of optical paths and optical multiplexing.  
     [0055] In comparison, the conventional optical switch shown in FIG. 5 does not have function of reflecting a plurality of incident light beams to a single output fiber for wavelength multiplexing systems, which is required for the optical switch. Additionally, the conventional optical switch does not provided a possibility of switching N×M optical paths simultaneously.  
     [0056] In contrast, the present embodiment uses the semiconductor substrate  3  as a substrate for the switch and the rotary mirrors  4  formed by using the semiconductor etching processing technique It is therefore possible to form the rotary mirrors with precision as can be obtained in processing of semiconductors, with the result that greatly compact optical switch modules can be constructed with precision It is preferred to plate the reflection surfaces of the mirrors  4  with gold or aluminum for raising efficiency of their reflections. How to produce the mirrors and electrostatic motors is disclosed in detail in, for example, “IEEE, pages 26-31, Vol, 5, No.1 (1999).” The outline of the disclosure is that masks to form mirrors and motors to be produced are prepared, and etching is repeated using photo resist so as to finally form electrostatic motors with mirrors on a substrate.  
     [0057] The present invention is not restricted to the foregoing embodiments, but can be practiced in a variety of other embodiments. For instance, the alignment pitch of the rotary mirrors  4   a  to  4   h  and the rotation angle of each of the rotary mirrors  4   a  to  4   h , which are applied to the optical switch of the present invention, are not restricted to the values described in the foregoing embodiment. Appropriate variation may be set for those parameters. The alignment pitch of the rotary mirrors  4   a  to  4   h  can be determined, by way of example, by such parameters as maximum light-receiving angles of the collimator lenses  9  and  10  secured on the connecting end faces of the input-side and output-side fibers  1  and  2 , waists of beams after being collected by the collimator lenses  9  and  10 , the size of a chip, and/or a geometry that removes a light beam reflected by a certain rotary mirror  4  from being interrupted by another rotary mirror  4 .  
     [0058] Though being rotated by the electrostatic motor in the foregoing present embodiment, each of the rotary mirrors  4  may be rotated using a stepping motor based on electromagnetic force. Alternatively each mirror is possible to have rotating means based on both electrostatic force and electromagnetic force.  
     [0059] In the foregoing embodiment, each of the input-side optical fibers  1  and the output-side optical fibers  2  is set to eight in number, but those numbers of optical fibers  1  and  2  are not limited to so. An appropriately set number is available. Although there is no intention to limit the number, the number of the optical fibers is preferably chosen from integers of 2 to 10.  
     [0060] For instance, the output-side optical fibers  2  can be formed such that they are larger in number than the input-side optical fibers  1 , wherein there is excessive output-side optical fibers as reserve fibers which are usually out of use. In cases where the output-side optical fibers  2  or a counter party to which any of the output-side optical fibers  2  is connected is out of order, or the lines connected such as telephone lines are changed, malfunctioned optical paths are switched over to the reserve output-side optical fibers  2 .  
     [0061] In the case of the optical switch wherein a large number of input light beams are multiplexed for use, there are some cases in which it is convenient to form the input-side optical fibers  1  larger in number than that of the output-side optical fibers  2 . Thus, the numbers of input-side and output-side optical fibers  1  and  2  can appropriately be determined based on such factors as specifications.  
     [0062] The present embodiment employs the configuration that the input-side optical fibers  1  are disposed in line along the end face  25  of the semiconductor substrate  3  and the output-side optical fibers  2  are disposed in line along the end face  28  thereof. However, the disposal embodiments of those optical fibers  1  and  2  are not limited to the disclosed example. It is enough that both input-side optical fibers  1  and output-side optical fibers  2  are optically coupled with each other via the rotary mirrors  4  on the substrate. As long as this condition is met, the fibers  1  and  2  may appropriately be disposed in other ways.  
     [0063] Moreover, in the foregoing embodiment, each rotary mirror  4  ( 4   a  to  4   h ) related to each input-side optical fiber  1  ( 1   a  to  1   h  ) is disposed in the optical axis of the optical fiber  1  and the rotary mirrors  4  are mutually shifted in position in the longitudinal direction (Y-axis direction) of the input-side optical fibers  1 . However, the disposal embodiment of the rotary mirrors  4  is not limited to such embodiment. In this case, the rotary mirrors  4  may also be set appropriately if only each rotary mirror  4  is disposed on the substrate correspondingly to each input-side optical fiber  1  on a one-by-one basis and reflects light toward a specified output-side optical fiber  2 .  
     [0064] The present invention provides the following advantages. The present invention is constructed such that, correspondingly to each of a plurality of input-side optical fibers, a rotary mirror to reflect light coming through each input-side optical fiber is aligned on a substrate, while a plurality of output-side optical fibers are disposed to receive reflected light from the rotary mirrors. Accordingly changing rotation angles of the rotary mirrors enables the light coming through the input-side optical fibers to be outputted to any or all of the output-side optical fibers. It is therefore possible to freely switch optical paths.  
     [0065] In switching the optical paths, controlling the rotation angles of selected ones or all of the rotary mirrors makes it possible to reflect light coming through a plurality of arbitrary input-side optical fibers toward any one of the output-side optical fibers, thus the reflected light being transmitted. Accordingly, multiplexing of light that was not conducted by the conventional optical switch can be conducted.  
     [0066] Thanks to the present invention wherein a plurality of input-side optical fibers are disposed in parallel, a plurality of rotary mirrors are placed in their optical axes one by one, and the rotary mirrors are mutually shifted in position in the longitudinal directions of the input-side optical fibers, the optical switches according to the present invention can be designed with ease and efficiency for optical connection between the input-side and output-side optical fibers can be improved.  
     [0067] Because collimator lenses are individually secured on connecting end faces of at least one of the input-side optical fibers and the output-side optical fibers, the collimator lenses enables a steady optical connection between the input-side and output-side optical fibers.  
     [0068] Moreover, each of the collimator lenses secured on the connecting end faces of the input-side optical fibers is able to pass light coming through each input-side optical fiber toward each rotary mirror at an efficiency of substantially 100 percent. Each of the collimator lenses secured on the connecting end faces of the output-side optical fibers has a light-receiving angle that allows the light reflected by any mirror to be passed to each output-side optical fiber at an efficiency of substantially 100 percent. Therefore, optical connections between the input-side and output-side optical fibers via those collimator lenses can be realized in an improved condition.  
     [0069] There is also provided a further configuration wherein rotating means is provided which rotates the rotary mirrors with at least one of an electrostatic force and an electromagnetic force. Therefore, the rotary mirrors can be rotated with ease and with precision by the electrostatic or electromagnetic force, thereby contributing to a more improved optical connection.  
     [0070] In addition, the substrate and rotary mirrors, which are made of semiconductors such as silicon, are formed using the highly developed semiconductor processing technique. As a result, very compact-sized and accurately-operated optical switches can be manufactured.  
     [0071] There is also provided a construction in which the number of the input-side optical fibers is different from that of the output-side optical fibers. For example, if the output-side optical fibers are larger in number than that of the inputs-side optical fibers, the optical switch which makes it easier to cope with troubles or line changes can be provided. By contrast, the number of the input-side optical fibers is greater than that of the output-side optical fibers, an optical switch module convenient for multiplexing wavelengths can be constructed.