Abstract:
An optical fiber switch circuit combines optical fiber switches that are capable of switching the connection of many circuits at the same time by using fewer actuators. The optical fiber switch circuit combines at least one N x 2N, N being equal or greater than 1 optical fiber switch which employs optical fibers for switching the connection of an N number of movable optical fibers from one N number of fixed optical fibers of a 2N number of fixed optical fibers to the other N number of fixed optical fibers at the same time.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical fiber switch member and optical fiber switching circuits used for an optical fiber communications system. More particularly, it relates to an optical fiber switch circuit composed of at least one N×2N (N&gt;1) switch optical fiber member capable of switching the connections of an N number of switches at the same time by a single actuator. 
     2. Description of the Related Art 
     A 1×2 optical fiber switch, such as the one disclosed in U.S. Pat. No. 5,434,936 is known. First and second fixed optical fibers are adhesively fixed on the bottoms of oppositely provided V grooves in such a manner that the distal end surfaces thereof are aligned. The outer surfaces of movable optical fibers are provided with films made of a magnetic material, the portions provided with the films made of the magnetic material being disposed in a magnetic field of a permanent magnet. The portions coated by the films are driven and displaced toward the first and second fixed optical fibers alternately by changing the magnetic force acting on the films made of the magnetic material by actuators constituted by the permanent magnet and a solenoid coil, thus switching the connection. 
     Referring to FIG. 7, an optical fiber switch circuit constructed using the 1×2 optical fiber switchs mentioned above will be described. FIG. 7 shows the circuit corresponding to a case constituted by connecting seven 1×2 optical fiber switches. 
     In FIG. 7, the movable optical fibers of 1×2 optical fiber switches  201  through  207  are driven by actuators making use of the foregoing solenoid coils and magnetism. 
     A typical way to construct an optical fiber switch circuit switch members each having one input and 4 outputs employing such 1×2 optical fiber switches, is to connect seven 1×2 optical fiber switches in series as illustrated in FIG.  7 . The optical fibers of the 1×2 optical fiber switches are connected by optical connectors or electric discharge fusion between the fibers. 
     The connection of the optical fiber switch of FIG. 7 is made as set forth below. To connect a port A with a port # 1 , the movable optical fibers of the 1×2 optical fiber switches  201 ,  202 , and  204  are respectively connected to the upper fixed optical fibers as illustrated. To connect the port A with a port # 5 , the movable optical fibers of the 1×2 optical fiber switch  201  is connected to the lower fixed optical fiber, and the movable optical fibers of the 1×2 optical fiber switch is  203  and are connected to the upper fixed optical fibers. The switching operation is accomplished by switching the polarity of the current flowing through the solenoid coil of the actuator provided for each of the 1×2 optical fiber switches  201  through  207 . 
     Hence, the optical fiber switch circuit configured as described above requires seven 1×2 optical fiber switches, seven control and drive circuits together with wiring therefor, and the connections of six pairs of optical fibers. This inevitably requires a large space for housing the switches themselves and their associated components and also leads to complicated wiring. Likewise, an optical fiber switch circuit having one input and 16 outputs requires fifteen 1×2 optical fiber switches, fifteen control and drive circuits together with wiring therefor and the connections of fourteen pairs of optical fibers. An optical fiber switch circuit having one input and 32 outputs requires thirty-one 1×2 optical fiber switches, thirty-one control and drive circuits together with wiring therefor and the connection of thirty pairs of optical fibers. 
     FIG. 8 shows the configuration of an optical fiber switch circuit having 2 inputs and 8 outputs. This optical fiber switch circuit is constituted by two pairs of optical fiber switch circuits each having one input and 4 outputs, namely, the optical fiber switch circuit comprised of three 1×2 optical fiber switches  208 ,  210 , and  211 , and the 1×4 optical fiber switch circuit comprised of three 1×2 optical fiber switches  209 ,  212 , and  213  as illustrated. The optical fiber switch circuit configured as described above requires six 1×2 optical fiber switches, six control and drive circuits and wiring therefor, and the connections of four pairs of optical fibers. Hence, as in the case of the foregoing optical fiber switch, circuit the sizes of the switches themselves respectively equipped with actuators increase, the wiring becomes complicated, and the number of connections of the optical fibers also increases. 
     FIG. 9 shows an optical fiber switch circuit, namely, a 4×4 matrix optical fiber switch circuit having 4 inputs and 4 outputs constituted by employing eight optical fiber switch members each having one input and 4 outputs. Each of reference numerals  214  through  221  is a composed of three 1×2 optical fiber switches. Sixteen optical fibers  222  are provided and connected as illustrated. The 4×4 matrix optical fiber switch shown in FIG. 9 is a matrix optical fiber switch circuit that has a function for connecting the optical fibers of an arbitrary port A, B, C, or D in the left column to an arbitrary port # 1 , # 2 , # 3 , or # 4  in the right column. The 4×4 matrix optical fiber switch circuit requires twenty-four 1×2 optical fiber switches and a circuit wiring for connecting twenty-four actuators. 
     Thus, the optical fiber switch circuits shown in FIGS. 7-9 pose a problem in that the size of the switch itself inevitably increases, the control and drive circuit and the wiring becomes more complicated, and the number of connections of optical fibers also increases as the number of the switching circuits increases. 
     The optical fiber switches employed for the optical fiber switch circuits described above are publicly known; however, the connection of the respective circuits has been made by the inventor and is not known to have been described previously. Therefore, the connection of the respective optical fiber switch circuits is not considered prior art. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a major object of the present invention to provide an optical fiber switch circuit that combines at least one 1×2optical fiber switch employing optical fibers used for simultaneously switching the connection of an N number of movable optical fibers from one N number of fixed optical fibers of a 2N number of fixed optical fibers to the other N number of fixed optical fibers, and another optical fiber switch in accordance with the present invention. 
     It is another object of the present invention to provide an optical fiber switch circuit having 1 input and 8 outputs. 
     It is yet another object of the present invention to provide an matrix optical fiber switch circuit having N inputs and N outputs. 
     It is a further object of the present invention to provide an optical fiber switch circuit having two inputs and 8 outputs. 
     In order to achieve the major object, an optical fiber switch circuit configured by connecting a plurality of optical fiber switches is provided in accordance with the present invention, said optical fiber switch comprising: an alignment member main body which has a plurality first and second V shaped grooves, said first and second grooves opposing each other to form pairs of V grooves extending parallel to a Z-axis are aligned in a Y-direction, substantially perpendicular to said z-direction and a slit traversing said V grooves in an X-direction; substantially perpendicular to said y and z directions a 2N number of first and second fixed optical fibers located in the main body on a first side of the slit, one of said first optical fibers being positioned in each of said first grooves and one of said second fixed optical fibers being positioned in each of said second grooves, an N number of movable optical fibers located in said main body on a second side of said slit opposite the first side thereof, one of said moveable optical fibers being positioned in each pair of grooves so that the distal ends thereof are opposed to said fixed optical fibers and may be brought in contact with either of pairs of V grooves; a resilient a drive member which is inserted in said slit and engaged with said N number of movable optical fibers, said drive member being driven by said resilient pin to move said N number of movable optical fibers to a first position to optically couple them to said first fixed optical fibers 2N number of fixed optical fibers by bringing them into contact with one of said paired V grooves, and to a second position to couple them to the other N number of fixed optical fibers of said 2N number of fixed optical fibers by bringing them into contact with the other of said paired V grooves; wherein said optical fiber switch circuit comprises at least an N×2N (N=1) optical fiber switch and an N×2N (N=2) optical fiber switch having two input terminals thereof connected to two output terminals of said optical 
     In order to achieve the another object, an optical fiber switch circuit is configured by connecting a plurality of optical fiber switches of the type described above said optical fiber switch circuit including a series connection of n switching members, said n switching members having  2   n−1  m optical fiber switches therein, a single drive member driving all of the optical fiber switches in each of said n switching members via said resilient pin. 
     In order to achieve the yet another object, an N×N (N≧4) matrix optical fiber switch circuit is provided in accordance with the invention, which is configured by disposing an N number of said 1×2N optical fiber switch circuits in parallel, by preparing two N×(N×2N) switch circuits having an N number of input terminals and an N×2N number of output terminals, and by connecting an N×2N number of output terminals of a first switch circuit and an N×2N number of output terminals of a second switch circuit. 
     A 4×4 matrix optical fiber switch circuit is configured by disposing four 1×4 optical fiber switch circuits in parallel, by preparing two 4×16 switch circuits having four input terminals and 4×4 output terminals, and by connecting sixteen output terminals of a first switch circuit and sixteen output terminals of a second switch circuit. 
     In order to achieve a further object, an optical fiber switch circuit configured by connecting a plurality of optical fiber switches is provided in accordance with the present invention, said optical fiber switch being an N×2N optical fiber switch comprising: 
     an alignment member main body which has an N (N≧1) number of pairs of V grooves which are oppositely provided such that they are parallel to a Z-axis and aligned in a Y-direction, and a single slit formed across said V grooves in an X-direction; a 2N number of fixed optical fibers disposed in contact with the bottoms of said respective V grooves; an N number of movable optical fibers which are provided so that the distal ends thereof are opposed to said fixed optical fibers and may be brought in contact with either of pairs of V grooves; a drive member which is inserted in said slit and engaged with said N number of movable optical fibers and which is guided so as to be movable in the X-direction; and a single actuator which is engaged with said drive member and which is joined to said drive member to reciprocate it so as to move said N number of movable optical fibers to a first position to connect them to one N number of fixed optical fibers of said 2N number of fixed optical fibers by bringing them into contact with one of said paired V grooves, and to a second position to connect them to the other N number of fixed optical fibers of said 2N number of fixed optical fibers by bringing them into contact with the other of said paired V grooves; wherein said optical fiber switch circuit comprises at least an N×2N (N=2) optical fiber switch and an N×2N (N=4) optical fiber switch having four input terminals thereof connected to four output terminals of said optical fiber switch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a front sectional view of an embodiment of the main body portion of an N×2N (N=4) optical fiber switch member in accordance with the present invention. 
     FIG. 1B shows a side sectional view of the embodiment at the line A—A. 
     FIG. 1C shows a side sectional view of the embodiment at the line B—B. 
     FIG. 1D is a top sectional view of the embodiment, movable optical fibers being located at a neutral position. 
     FIG. 1E is a side sectional view illustrative of the embodiment in a coupled state. 
     FIG. 1F is a side sectional view illustrative of the embodiment in another coupled state. 
     FIG. 2A is a top sectional view illustrative of a first coupling position of the embodiment. 
     FIG. 2B is a top sectional view illustrative of a second coupling position of the embodiment. 
     FIG. 3A is a diagram illustrative of an N×2N optical fiber switch, member or optical fiber switch which has been described with reference to FIG.  1 A through FIG. 2B, when it has been set to N×2N (N=1). 
     FIG. 3B is a diagram illustrative of the N×2N optical fiber switch member that has been set to N×2N (N=2). 
     FIG. 3C is a circuit diagram illustrative of the N×2N optical fiber switch member that has been set to N×2N (N=4). 
     FIG. 4A is a circuit diagram showing an 1 optical fiber switching circuit at a first connecting position thereof, the optical fiber switching circuit being constituted by connecting in series the 1×2 optical fiber switch member, the 2×4 optical fiber switch member, and the 4×8 optical fiber switch member shown in FIG.  3 A through FIG.  3 C. 
     FIG. 4B is a circuit diagram showing the optical fiber switching circuit of FIG. 4A at a second connecting position thereof. 
     FIG. 4C is a circuit diagram showing the optical fiber switching circuit of FIG. 4A at a third connecting position thereof. 
     FIG. 4D is a circuit diagram showing the optical fiber switching circuit of FIG. 4A at a fourth connecting position thereof. 
     FIG. 4E is a circuit diagram showing the optical fiber switching circuit of FIG. 4A at a fifth connecting position thereof. 
     FIG. 4F is a circuit diagram showing the optical fiber switching circuit of FIG. 4A at a sixth connecting position thereof. 
     FIG. 4G is a circuit diagram showing the optical fiber switching circuit of FIG. 4A at a seventh connecting position thereof. 
     FIG. 4H is a circuit diagram showing the optical fiber switching circuit of FIG. 4A at an eighth connecting position thereof. 
     FIG. 5A is a diagram showing a optical fiber switching circuit at a first connecting position thereof, the optical fiber switch being constituted by connecting in series the 2×4 optical fiber switch member and the 4×8 optical fiber switch member shown in FIG.  3 B and FIG.  3 C. 
     FIG. 5B is a circuit diagram showing the optical fiber switching circuit of FIG. 5A at a second connecting position thereof. 
     FIG. 5C is a circuit diagram showing the optical fiber switching circuit of FIG. 5A at a third connecting position thereof. 
     FIG. 5D is a circuit diagram showing the optical fiber switching circuit of FIG. 5A at a fourth connecting position thereof. 
     FIG. 6 is a circuit diagram showing a matrix optical fiber switching circuit of FIG. 5A circuit composed by using N×2N optical fiber switchs. 
     FIG. 7 is a circuit diagram showing an optical fiber switch circuit composed by connecting seven conventional 1×2 circuit optical fiber switches. 
     FIG. 8 is a circuit diagram showing an optical fiber switch circuit composed by connecting six conventional 1×2 circuit optical fiber switches. 
     FIG. 9 is a circuit diagram showing a matrix optical fiber switch circuit composed by using twenty-four conventional 1×2 circuit optical fiber switches. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The embodiments of the optical fiber switch in accordance with the present invention will be described in detail in conjunction primarily with the accompanying drawings. 
     FIGS. 1A through 1F show the optical fiber switch main body and drive members of an embodiment of an N×2N optical fiber switch (N=4) used in an optical fiber switch circuit in accordance with the present invention. 
     FIG. 1A is a front sectional view of the embodiment of the main body of the N×2N (N=4) optical fiber switch in accordance with the present invention. 
     FIGS. 1B and 1C show side sectional views of the embodiment at the lines A—A and B—B, respectively, and FIG. 1D is a top sectional view of the embodiment, with the movable optical fibers being located at a neutral position. FIG. 1E is a side sectional view illustrative of the embodiment in a connected state, and FIG. 1F is a side sectional view illustrative of the embodiment in another connected state. 
     The N×2N optical fiber switch in accordance with the present invention is provided with parallel V grooves  3 , . . .  3  and  4 , . . .  4  for aligning an N number (N=4) of optical fibers. The parallel V grooves are formed in the opposed surfaces in the longitudinal direction (Z) of a first rectangular alignment member  1  and a second rectangular alignment member  2 , respectively. As will be discussed later, the alignment members  1  and  2  are joined facing each other with the fixed and movable optical fibers arranged in a rhombic space formed by the respective parallel V grooves  3 , . . .  3 , and  4 , . . .  4 . A single slit  12  is provided in a lateral direction (X) so that it extends across the V grooves  3 , . . .  3 , and  4 , . . .  4 . 
     As shown in FIG. 1B, first fixed optical fibers  7 , . . .  7  are bonded in the same spaces of the alignment V grooves  3 , . . .  3  and second fixed optical fibers  8 , . . .  8  are also bonded in the same spaces of the alignment V grooves  4 , . . .  4 , the height thereof being aligned, from one end (the left end in FIG. 1A) of the first alignment member  1  and the second alignment member  2 . The sheathed portions of the fixed optical fibers  7 , . . .  7 , and  8 , . . .  8  are supported by a mounting flange  5 . 
     As shown in FIG. 1C, the distal ends of the movable optical fibers  9 , . . .  9  are disposed at the center of the rhombic space formed by the alignment V grooves  3 , . . .  3  and the alignment V grooves  4 , . . .  4  from the other ends (the right end in FIG. 1A) of the first alignment member  1  and the second alignment member  2 . The sheathed portions of the movable optical fibers  9 , . . .  9  are supported by a mounting flange  10  of the movable side. 
     A drive member  13  is guided by the slit  12 , which is provided in the foregoing X direction of the alignment members  1  and  2 , so that it may reciprocate in the X direction. The slit  12  has a width of 1 mm or less; it receives the drive member  13  and guides it in a direction (X) perpendicular to an optical axis (Z). 
     The drive member  13  has slit grooves  14  and  16  as illustrated in FIGS. 1E and 1F, and the distal ends of the movable optical fibers  9 , . . .  9  are inserted in the slit groove  14 . An elastic pin  15  of an actuator, which will be discussed later, is engaged with the other groove  16 . 
     The drive member  13  is driven so as to elastically press the portions near the distal ends of the movable optical fibers against the aligning reference surfaces of the first fixed optical fibers and the second fixed optical fibers alternately with a predetermined pressing force. A guide cover  17  for preventing the drive member  13  from coming off is provided; it is fixed to the top surfaces of the alignment members  1  and  2  by bonding or screwing. 
     FIG. 1E is a diagram illustrating a state wherein the drive member  13  has been displaced to the right as indicated by the black arrow. In this case, the drive member  13  is driven by the elastic pin  15 , and as the drive member  13  is displaced, the four movable optical fibers  9  are moved to the right by the slit groove  14  until they come in contact with and are pressed against the surfaces of the V grooves  4  of the alignment member  2  and stop. 
     FIG. 1F is a diagram illustrating a state wherein the drive member  13  has been displaced to the left as indicated by the black arrow. In this case, as the drive member  13  is displaced, the four movable optical fibers  9  are moved to the left by the slit groove  14  until they come in contact with and are pressed against the surfaces of the V grooves  3  of the alignment member  1  and stop. The alignment members  1  and  2  employ a cemented carbide material to ensure higher machining accuracy and also to provide sufficiently high wear resistance to the repeated contact of the movable optical fibers. 
     FIGS. 2A and 2B are schematic representations illustrative of the principle regarding the driving mechanism and the push-to-align mechanism by the drive member  13  for the movable optical fibers  9 , . . .  9  according to the embodiment of the N×2N (N=4) optical fiber switch shown in FIGS. 1A through 1F. 
     FIG. 2A illustrates a state wherein the movable optical fibers  9 , . . .  9  have been lightly pressed against the V grooves of the alignment member  1  and opposed to and connected with the first fixed optical fibers  7 , . . .  7 . FIG. 2B illustrates a state wherein the movable optical fibers  9 , . . .  9  have been lightly pressed against the V grooves of the alignment member  2  and opposed to and connected with the second fixed optical fibers  8 , . . .  8 . The movable optical fibers  9 , . . .  9  are inserted and installed from the other ends of the alignment members  1  and  2  so that the distal ends thereof are aligned and that they provide a gap of  10  μm or less between themselves and the distal ends of the fixed optical fibers  7  and  8 . The distal ends of the optical fibers  7 ,  8 , and  9  are polished in advance so as to form them into inclined surfaces having an angle of θ degrees (where θ&gt;4 degrees) with respect to the surface perpendicular to the optical axis in order to reduce the light that reflects and returns (see FIG.  1 A). 
     The actuator for driving the drive member  35 , may be a publicly known solenoid magnet which creates the linear movement of the movable members by switching its current polarity, or a small motor which creates the movement by switching its current polarity for forward and reverse revolution. 
     FIGS. 3A through 3C show the circuit diagrams of a 1×2 optical fiber switch, a 2×4 optical fiber switch, and a 4×8 optical fiber switch when N=1, N=2, and N=4, respectively, in the foregoing N×2N optical fiber switch. 
     The 1×2 optical fiber switch shown in FIG. 3A is constituted by two fixed optical fibers  40  and  41  and one movable optical fiber  42 . The movable optical fiber  42  is connected to the fixed optical fibers  40  and  41  alternately by the drive member, and an optical fiber port A can be connected to optical fiber ports # 1  and # 2  alternately. 
     The 2×4 optical fiber switch circuit shown in FIG. 3B is composed of four fixed optical fibers  43  through  46  and two movable optical fibers  47  and  48 . The movable optical fibers  47  and  48  are connected to a pair of fixed optical fibers  43  and  45  and another pair of fixed optical fibers  44  and  46  alternately by the drive member. Optical fiber ports A and B can be connected to optical fiber ports # 1 , # 3  and # 2 , # 4  alternately and in synchronization. 
     The 4×8 optical fiber switch of FIG. 3C is composed of eight fixed optical fibers  49  through  56  and four movable optical fibers  57  through  60 . The movable optical fibers  57  through  60  are connected to a set of fixed optical fibers  49 ,  51 ,  53 , and  55  and another set of fixed optical fibers  50 ,  52 ,  54 , and  56  alternately by the drive member. Optical fiber ports A through D can be connected to optical fiber ports # 1 , # 3 , # 5 , and # 7 , and # 2 , # 4 , # 6 , and # 8  alternately and in synchronization. 
     Thus, the N×2N optical fiber switch used for an optical fiber switch circuit in accordance with the present invention includes the 2N number of fixed optical fibers comprised of a pair of the N number of fixed optical fibers, and the N number of movable optical fibers that are installed in the V groove array of a pair of alignment members. The optical fiber ports of the N number of circuits can be connected to other optical fiber ports composed of the N number of circuits, respectively, alternately and in synchronization by the reciprocating motion of the single drive member  13 . Hence, in the case of an optical fiber switch with a high integration of optical fiber ports, the switch volume can be made markedly smaller than the conventional optical fiber switch comprised of the combination of many 1×2 switches. Moreover, the number of actuators can be also decreased. As a result, the whole configuration can be simplified, leading to higher reliability of the circuitry. 
     The embodiments of the optical fiber switches constructed primarily by combining the optical fibers shown in FIGS. 3 A- 3 C will now be described. 
     FIG. 4A is a circuit diagram of an optical fiber switch circuit having one input (M=1) composed by connecting in series n switching members  61 - 63  the 1×2 optical fiber switch,  61  the 2×4 optical fiber switch  62 , and the 4×8 optical fiber switch  63  respectively shown in FIG.  3 A through FIG.  3 C. FIGS. 4A through 4 individually illustrate the shifted positions of the drive members of the respective switches when the connection of the port A is shifted from the port # 1  to the port # 8  in sequence in the optical fiber switch circuit. The state wherein the drive members of the 1×2 optical fiber switch  61 , the 2×4 optical fiber switch  62 , and the 4×8 optical fiber switch  63  have moved to the upper side is denoted as 0, and the state wherein they have moved to the lower side is denoted as 1. To connect the port A of the optical fiber to the port # 1  as shown in FIG. 4A, the positions of the three drive members are set to 0-0-0. For instance, to connect the port A of the optical fiber to the port # 6  as illustrated in FIG. 4F, the positions of the three drive members are set to 1-0-1. 
     As set forth above, it is extremely simple to connect the respective optical fiber ports of the optical fiber switch circuit shown in FIGS. 4A to  4 H comprised of the N×2N optical fiber switches (N=1, 2, 4) in accordance with the present invention. In other words, only three control circuits are required to operate the optical fiber switches easily by combining the upward or downward shifts of the three drive members in comparison with the conventional case in which seven 1×2 optical fiber switches have been operated by seven pairs of control circuits. 
     FIG. 5A is a circuit diagram of an optical fiber switch circuit having  2  inputs (M=2) composed by connecting in series the 2×4 optical fiber switch member and the 4×8 optical fiber switch member shown in FIG.  3 B and FIG.  3 C. FIGS. 5A through 5D individually illustrate the shifted positions of the drive members of the respective switches when the connection of the port A is shifted from the port # 1  to the port # 4 , and the port B is shifted from the port # 5  to the port # 8  in sequence in the optical fiber switch circuit. As previously mentioned, when the state wherein the drive members have moved to the upper side is denoted as 0, and the state wherein they have moved to the lower side is denoted as 1, the optical fiber switches can be easily operated merely by combining the upward or downward shifts of the two drive members as illustrated. 
     Thus, it can be easily understood that the embodiment permits easy operation of the optical fiber switches. In contrast to the conventional optical fiber switch circuit having two inputs and 8 outputs in which six optical fiber switches are operated by six pairs of control circuits, the embodiment makes it possible to operate the optical fiber switch circuit simply by combining the upward or downward shifts of two drive members moved by two control circuits. 
     FIG. 6 is a circuit diagram showing an embodiment of a matrix optical fiber switch circuit having 4 inputs and 4 outputs constituted by connecting two sets of optical fiber switch circuits comprised by connecting in series the 1×2 optical fiber switch and the 2×4 optical fiber switch shown in FIG. 2A and FIG.  2 B. The matrix optical fiber switch circuit of FIG. 6 is configured by two groups, one group including four optical fiber switches  64  through  67  in the left column each consisting of three 1×2 optical fiber switches and the other group including four optical fiber switches  68  through  71  in the right column each consisting of three 1×2 optical fiber switches. 
     As illustrated, four optical fibers A 1 , A 2 , A 3 , and A 4  of the four circuits of the optical fiber switch  64  in the left column are respectively connected to the four optical fiber switches  68  through  71  in the right column. Likewise, the four optical fibers of the four circuits of the remaining three optical fiber switches  65  through  67  in the left column are respectively connected to the four optical fiber switches  68  through  71  in the right column. 
     In this 4×4 matrix optical fiber switch circuit, ports A, B, C, and D of the four optical fiber switches  64  through  67  in the left column can be connected to any of ports # 1 , # 2 , # 3 , and # 4  of the four optical fiber switches  68  through  71  in the right column. Each of the eight optical fiber switches constituting the 4×4 matrix optical fiber switch in accordance with the present invention is configured by connecting one 1×2 optical fiber switch and one 2×4 optical fiber switch in series as mentioned above. Therefore, a total of 16 optical fiber switches, i.e. a total of  16  drive members and  16  actuators, are necessary. 
     Using the conventional 1×2 optical fiber switches to constitute the 4×4 matrix optical fiber switch enabling the equivalent circuit connection to that described above would require  24  switches and  24  actuators. 
     Hence, the 4×4 matrix optical fiber switch constructed by employing the optical fiber switch in accordance with the present invention permits a smaller size and more reliable operation.