Mechanically actuated optical switch

[0002] 1. Field of the Invention

[0003] The present invention relates to optical switches, and more particularly, to mechanically actuated optical switches.

[0004] 2. Background

[0005] Optical switches have been developed for switching optical networks in broadband telecommunications systems. Because of increasing demand for high speed broadband data communications, optical wavebands including infrared and visible light wavelengths are increasingly being used as data carriers in telecommunications systems to satisfy the demand for high speed broadband data transmission. Conventional optical switches have been implemented in a typical optical fiber telecommunications network to switch the optical paths of information-carrying light to different optical fiber cables.

[0006] Conventional optical switches typically fall into two broad categories of non-integrated optical switches and integrated optical switches. Among the non-integrated optical switches, moving fibers have been used to change optical paths between different input or output fibers. In a conventional moving fiber switch, either the input optical fibers or the output optical fibers are moved mechanically to switch the optical path between different input or output optical fibers.

[0007] However, conventional moving fiber switches typically suffer from alignment problems because it is difficult to align the input and output fibers with a high degree of accuracy and repeatability. Alignment of single mode fibers can be especially difficult because of their small diameters. Even a slight misalignment between the selected input and output fibers through which optical transmission supposedly occurs may result in an unacceptably high insertion loss because the output fiber is not in the perfect position on the optical path to receive the light transmitted from the input fiber.

[0008] In order to avoid the problem of misalignment in a typical fiber moving switch, expensive and complicated mechanisms are usually required to move either the input or the output optical fibers to achieve acceptable alignment accuracy and repeatability. Furthermore, conventional moving fiber switches typically have slow switching speeds which may limit their applications in optical fiber communications networks which require high-speed switching operations.

[0009] Moving reflectors have also been used in conventional non-integrated optical switches to switch optical paths between different input or output optical fibers instead of moving the input or output fibers for optical alignment. Moving reflector switches are usually capable of faster switching operations than conventional moving fiber switches. However, conventional reflector switches typically also suffer from the problems of mechanical stability and repeatability. After a large number of repeated on and off switching operations, the optical reflectors in a conventional reflector switch may deviate from their designed reflection angles because of the problems with mechanical stability and repeatability. Even a slight deviation of reflection angle may cause the optical path of reflected light to be misaligned with a respective output fiber or another reflector which is supposedly positioned to receive the reflected light.

[0010] Therefore, there is a need for an optical switch with a high degree of reliability after a large number of repeated on and off switching operations which are typically required in modern optical fiber telecommunications networks. Furthermore, there is a need for an optical switch which provides accurate optical alignments between the reflectors and the optical fibers without requiring expensive or delicate mechanical assemblies for switching the reflectors between their on and off positions.

[0011] The present invention provides a mechanically actuated optical switch, roughly comprising a primary optical port, a plurality of secondary optical ports, a support plate having first and second surfaces opposite each other, a plurality of movable optical reflectors each capable of occupying an on position to reflect light from the primary optical port to a respective one of the secondary optical ports, and a plurality of actuators connected to the movable optical reflectors respectively to drive the optical reflectors between their on and off positions.

[0012] In an embodiment, light is transmitted from the primary or input optical port to the selected secondary or output optical port by using a single optical reflector to reflect the light on a first optical path from the primary optical port onto a second optical path leading to the selected secondary optical port. In another embodiment in which input and output optical fibers connected to the optical switch assembly are desired to be parallel to each other, a fixed primary reflector is provided on the support plate to reflect incoming light on the first optical path from the primary optical port onto a second optical path, and the movable secondary reflectors are positioned along the second optical path. When one of the secondary reflectors is selected to be switched to its on position while other secondary reflectors are in their off positions, light on the second optical path is reflected by the selected secondary reflector onto a third optical path leading to the respective secondary optical port for outputting the light.

[0013] In an embodiment, the on positions of the movable optical reflectors are above the first surface of the support plate whereas the actuators are positioned below the second surface of the support plate. In a further embodiment, the support plate is provided with apertures, and the actuators are connected to the movable optical reflectors respectively through a plurality of levers which are movably positioned through the apertures in the support plate to drive the respective movable optical reflectors.

[0014] A movable optical reflector is switched to its on position when it is moved by the lever away from the first surface of the support plate to a predetermined position above the first surface of the support plate to intercept light on an incident optical path. The movable optical reflector has a reflection surface angled with respect to the incident optical path when the movable optical reflector is in its on position to reflect the light onto a reflected optical path which eventually leads to one of the output optical fibers. When the movable optical reflector is switched from its on position to its of f position, it is moved by the lever away from the incident optical path toward the first surface of the support plate. In a further embodiment, the off position of the movable optical reflector is within the aperture in the support plate.

[0015] In an embodiment, the actuators comprise relay switches capable of generating repetitive movements in opposite directions. Either prisms or mirrors may be used as optical reflectors in the optical switch according to the present invention, although other types of optical reflectors may also be used. For each of the optical reflectors, the reflection surface may be angled at 45° with respect to its incident optical path to reflect the light onto a reflected optical path which is perpendicular to the incident optical path, although other reflection angles may also be used within the scope of the present invention.

[0016] In an embodiment, a plurality of lenses are provided adjacent terminations of the input and output optical fibers to collimate light on the respective optical paths. In a further embodiment, the lenses and end portions of the respective optical fibers are housed in a plurality of collimator assemblies which are fixedly connected to the first surface of the support plate. In yet a further embodiment, the collimator assemblies are connected to the first surface of the support plate by laser welding for improved mechanical stability and reliability.

[0017] Advantageously, the mechanically actuated optical switch according to the present invention can be implemented in an optical fiber telecommunications network which requires a large number of frequent switching operations with a high degree of mechanical reliability and repeatability for accurate optical alignments. Furthermore, optical switching can be achieved with a high degree of reliability without requiring expensive or delicate mechanisms for actuating the movable optical reflectors in the optical switch according to the present invention.

[0018] The invention will be described with respect to particular embodiments thereof, and references will be made to the drawings in which:

[0019] FIG. 1 shows a top plan view of an embodiment of a mechanically actuated optical switch according to the present invention;

[0020] FIG. 2 shows a top plan view of another embodiment of the optical switch according to the present invention;

[0021] FIG. 3 shows another embodiment of the optical switch according to the present invention;

[0022] FIG. 4 shows another embodiment of the optical switch according to the present invention;

[0023] FIG. 5 shows a top plan view of yet another embodiment of the optical switch according to the present invention;

[0024] FIG. 6 shows a sectional view of an embodiment of a mechanical assembly for actuating the movable optical reflectors in the optical switch according to the present invention;

[0025] FIG. 7 shows a sectional view of another embodiment of a mechanical assembly for actuating the movable optical reflectors in the optical switch according to the present invention;

[0026] FIG. 8 shows a sectional view of another embodiment of the mechanical assembly similar to FIG. 6, with the additions of a magnet and a solenoid for faster switching of the optical switching element from its off position to its on position; and

[0027] FIG. 9 shows a sectional view of another embodiment of the mechanical assembly similar to FIG. 7, with the additions of a magnet and a solenoid for faster switching of the optical switching element from its off position to its on position.

[0028] FIG. 1 shows a top plan view of an embodiment of a mechanically actuated optical switch according to the present invention. A support plate 2 is provided with a plurality of apertures 4a, 4b, 4c, . . . 4mto allow mechanical movements of optical reflectors 6a, 6b, 6c, . . . 6m, respectively, when they are switched between their on and off positions. Two or more optical reflectors may share a single aperture in a different embodiment. In another embodiment, all of the movable optical reflectors 6a, 6b, 6c, . . . 6mmay share a single elongated aperture instead of the apertures as shown in FIG. 1. In an embodiment, the movements of the optical reflectors 6a, 6b, 6c, . . . 6mare roughly perpendicular to the support plate 2.

[0029] In the embodiment shown in FIG. 1, an input optical fiber 8 and a plurality of output optical fibers 10a, 10b, 10c, . . . 10mand 10nare positioned to provide input and output optical paths to the switch through a primary optical port 12 and a plurality of secondary optical ports 14a, 14b, 14c, . . . 14mand 14n, respectively. A plurality of collimator lenses including a primary lense 16 and a plurality of secondary lenses 18a, 18b, 18c, . . . 18mand 18nare provided on the respective optical paths adjacent the primary optical port 12 and the secondary optical ports 14a, 14b, 14c, . . . 14mand 14n, respectively.

[0030] In a further embodiment, a plurality of collimator assemblies are provided on a first surface which is the top surface 20 of the support plate 2. In the embodiment shown in FIG. 1, a first collimator assembly 22 is positioned on the first surface 20 of the support plate 2 to house the primary len 16. A plurality of additional collimator assemblies 24a, 24b, 24c, . . . 24mand 24nare positioned on the first surface 20 of the support plate 2 to house the secondary lenses 18a, 18b, 18c, . . . 18mand 18n, respectively. The input optical fiber 8 and the output optical fibers 10a, 10b, 10c. . . 10mand 10nhave terminations forming the primary optical port 12 and secondary optical ports 14a, 14b, 14c, . . . 14mand 14n, respectively.

[0031] In the embodiment shown in FIG. 1, the first collimator assembly 22 houses an end portion 26 of the input optical fiber 8 adjacent its termination as well as the primary lens 16. Furthermore, the additional collimator assemblies 24a, 24b, 24c, . . . 24mand 24nhouse the end portions 28a, 28b, 28c, . . . 28mand 28nof the output optical fibers 10a, 10b, 10c, . . . 10mand 10nadjacent their terminations in addition to the secondary lenses 18a, 18b, 18c, . . . 18mand 18n, respectively. In a further embodiment, the collimator assemblies 22 and 24a, 24b, 24c, . . . 24nare fixedly connected to the first surface 20 of the support plate 2 by laser welding to ensure that they are positioned at desired locations on the first surface 20 of the support plate 2 with a high degree of mechanical stability. Stable optical paths can thus be established between the collimator assemblies and their respective optical reflectors.

[0032] In the embodiment shown in FIG. 1, a primary optical reflector 30 is positioned on the first surface 20 of the support plate 2 to receive incoming light on a first optical path 32 from the primary optical port 12. The primary reflector 30, which comprises a prism as shown in FIG. 1, has a reflection surface 34 which is angled at 45° with respect to the first optical path 32. The light reflected from the primary reflector 30 travels along a second optical path 36 before it reaches one of the movable optical reflectors, such as the first movable optical reflector 6aas shown in FIG. 1, which is in its on position to intercept the light on the second optical path 36.

[0033] The movable optical reflector 6a, which is shown as a prism in FIG. 1, has a reflection surface 37 which is angled at 45° with respect to the second optical path 36 to reflect the light onto a third optical path 38. Light on the third optical path 38 is transmitted through the collimator lens 18ain the collimator assembly 24ato the respective secondary optical port 14awhich leads to the output optical fiber 10a. Because light transmission has the property of reciprocity, incoming light can also be transmitted from the optical fiber 10athrough the collimator lens 18ato the secondary reflector 6awhen it is in the on position to reflect the light onto the second optical path 36. The light is then reflected by the primary reflector 30 to the primary optical port 12 through the collimator lens 16. The collimator lenses are positioned to collimate light travelling between the respective optical ports and the optical reflectors because light transmitted from an optical fiber termination tends to disperse as it travels into free space beyond the termination.

[0034] When the optical reflector 6ais in its on position as shown in FIG. 1, light transmitted from the input optical fiber 8 is output to the output optical fiber 10a, regardless of whether other movable optical reflectors 6b, 6c, . . . 6mare in their on or off positions. If the movable optical reflector 6ais in its off position while the movable optical reflector 6bis in its on position, for example, the light transmitted from the input optical fiber 8 is switched to the output optical fiber 10b, regardless of whether subsequent movable optical reflectors 4c. . . 4mare in their on or off positions.

[0035] The last optical reflector 6n, which is fixedly positioned on the first surface 20 of the support plate 2 in the embodiment shown in FIG. 1, reflects the input light reflected from the fixed primary optical reflector 30 to the output optical fiber 10nonly if all of the movable optical reflectors 6a, 6b, 6c, . . . 6mare in their off positions. The output optical port 14nis thus the default optical output when all of the movable optical reflectors are switched off. In an alternate embodiment, the last optical reflector 6ncomprises a movable optical reflector identical to the movable optical reflectors 6a, 6b, . . . 6m.

[0036] In FIG. 1, all of the secondary optical reflectors including optical reflectors 6a, 6b, 6c, . . . 6mand 6nas well as the primary optical reflector 30 are shown as prisms. Because the collimator assemblies are positioned above the first surface 20 of the support plate 2 in the embodiment shown in FIG. 1, all of the optical paths are above the first surface 20 of the support plate 2. Any one of the movable optical reflectors 6a, 6b, 6c, . . . 6mcan be switched on when it is in a position to intercept the second optical path 36 above the first surface 20 of the support plate 2. Furthermore, each of the movable optical reflectors 6a, 6b, 6c, . . . 6mcan be switched to its off position by moving the optical reflector away from the second optical path 36 toward the first surface 20 of the support plate 2. In an embodiment, each of the movable optical reflectors can be switched to its off position by moving into the respective aperture in the support plate 2.

[0037] The switching operations of the movable optical reflectors 6a, 6b, 6c, . . . 6mare achieved by a plurality of actuators 40a, 40b, 40c, . . . 40mwhich are capable of moving the optical reflectors 6a, 6b, 6c, . . . 6mrespectively between their on and off positions. In an embodiment, the actuators 40a, 40b, 40c, . . . 40mare connected to the movable optical reflectors 6a, 6b, 6c, . . . 6mthrough a plurality of levers 42a, 42b, 42c, . . . 42m, respectively, to transfer mechanical movements generated by the actuators to the movable optical reflectors. In an embodiment, the actuators 40a, 40b, 40c, . . . 40mand the respective levers 42a, 42b, 42c, 42mare located below a second surface (not shown in the top plan view of FIG. 1) which is opposite the top surface 20 of the support plate 2. Embodiments of actuator assemblies for switching the movable optical reflectors 6a, 6b, 6c, . . . 6mwill be described below in reference to the sectional views of FIGS. 6 and 7.

[0038] In an embodiment, the actuators 40a, 40b, 40c, . . . 40mare controlled by a control circuit 44 which supplies control voltages to the actuators to switch the movable optical reflectors 6a, 6b, 6c, . . . 6mbetween their on and off positions. In an embodiment, the actuators 40a, 40b, 40c, . . . 40mcomprise conventional solenoid relay switches which are known to a person skilled in the art. The control circuit 44 may be designed to supply control voltages to the solenoid relay switches in a conventional manner which is apparent to a person skilled in the art.

[0039] In an embodiment, only one of the actuators is selected at a time to drive a respective one of the movable optical reflectors 6a, 6b, 6c, . . . 6mto its on position to reflect the light from the second optical path 36 onto a respective third optical path leading to the respective output optical port. Alternatively, the actuators may be controlled in such a manner that only the movable optical reflectors ahead of the selected movable optical reflector are switched to their off positions to allow the light on the second optical path 36 to reach the selected movable optical reflector, which is in its on position. For example, if the movable optical reflector 6cis selected for reflecting the light from the primary reflector 30 to the output optical port 14c, only the movable optical reflectors 6aand 6bahead of the selected optical reflector 6calong the second optical path 36 need be switched off, even if some or all of the subsequent movable optical reflectors including the movable optical reflector 6mare in their on positions.

[0040] As described above, the last optical reflector 6nis the default reflector for switching the incoming light from the input optical fiber 8 to the last output optical fiber 10nwhen all of the movable optical reflectors 6a, 6b, 6c, . . . 6mare switched to their off positions. Although the first and last optical reflectors 30 and 6nare shown as fixed reflectors on the first surface 20 of the support plate 2, these reflectors may also be movable optical reflectors in a different embodiment, with switching movements between their on and off positions controlled by additional actuators. Various reflector arrangements can be made which are within the scope of the present invention.

[0041] FIG. 2 shows a top plan view of another embodiment of the mechanically actuated optical switch according to the present invention, with an input optical fiber 48 leading to a primary or input optical port 50 and positioned perpendicular to a plurality of output optical fibers 54a, 54b, 54c, . . . 54mand 54nleading to secondary or output optical ports 52a, 52b, 52c, . . . 52mand 52n, respectively. Compared to the embodiment shown in FIG. 1, the light incoming from the input optical port 50 as shown in FIG. 2 is reflected by only one optical reflector before it travels to one of the output optical ports.

[0042] In the embodiment shown in FIG. 2, a plurality of movable optical reflectors 56a, 56b, 56c, . . . 56mare switchable between their on and off positions by a plurality of actuators 58a, 58b, 58c, . . . 58m.Each of the movable optical reflectors 56a, 56b, 56c, . . . 56mis positioned along a first optical path 60 leading from the input optical port 50. When a movable optical reflector is in its on position, it reflects the incoming light on the first optical path 60 to a respective one of the output optical ports 52a, 52b, 52c, . . . 52m.Furthermore, a fixed optical reflector 56nis positioned last along the first optical path 60 in the optical switch assembly and serves as the default reflector to reflect the incoming light to the last output optical port 52nonly if all of the movable optical reflectors 56a, 56b, 56c, . . . 56mare in their off positions.

[0043] In the embodiment shown in FIG. 2, all of the optical reflectors 56a, 56b, 56c, . . . 56mand 56ncomprise prisms with reflection angles set at 45° with respect to the first optical path 60. In this embodiment, the insertion loss for the optical switch may be reduced by about 0.1 dB to about 0.2 dB compared to the embodiment shown in FIG. 1 because only one prism instead of two is used to switch the light from the primary optical port to a selected secondary optical port in the embodiment shown in FIG. 2.

[0044] In an embodiment, a primary collimator lens 62 is provided adjacent the primary optical port 50 to collimate the light travelling along the first optical path 60. In a similar manner, a plurality of secondary collimator lenses 64a, 64b, 64c, . . . 64mand 64nare provided adjacent the secondary optical ports 52a, 52b, 52c, . . . 52mand 52n, respectively, to focus the light travelling along the respective optical paths from the optical reflectors to the secondary optical ports.

[0045] In a further embodiment, a first collimator assembly 66 is provided on the first surface 20 of the support plate 2 to house the primary collimator lens 62 as well as an end portion 68 of the input optical fiber 48 adjacent its termination. In a similar manner, a plurality of additional collimator assemblies 70a, 70b, 70c, . . . 70mand 70nare provided on the first surface 20 of the support plate 2 to house the secondary collimator lenses 64a, 64b, 6c, 64mand 64nas well as end portions 72a, 72b, 72c, . . . 72mand 72nof the output optical fibers 54a, 54b, 54c, . . . 54mand 54nadjacent their terminations, respectively. In yet a further embodiment, the collimator assemblies 66, 70a, 70b, 70c, . . . 70mand 70nare fixedly connected to the first surface 20 of the support plate 2 by laser welding for a high degree of mechanical rigidity and reliability to ensure accurate alignments of optical paths between the optical reflectors and the input and output optical ports.

[0046] FIG. 2 also shows the actuators 58b, 58b, 58c, 58mfor mechanical switching of the movable optical reflectors 56a, 56b, 56c, . . . 56mbetween their on and off positions. In an embodiment, a plurality of levers 74a, 74b, 74c, . . . 74mare connected between the actuators 58a, 58b, 58c, . . . 58mand the movable optical reflectors 56a, 56b, 56c, . . . 56m, respectively to transfer mechanical movements generated by the actuators to the movable optical reflectors. In an embodiment, the actuators and the levers for switching the movable optical reflectors are located below the second surface opposite the first surface 20 of the support plate 2. In an embodiment, the actuators 58a, 58b, 58c, . . . 58mcomprise conventional solenoid relay switches which are known to a person skilled in the art. Examples of mechanical assemblies for actuating the movable optical reflectors 56a, 56b, 56c, . . . 56mwill be described below in reference to the sectional views of FIGS. 6 and 7.

[0047] Referring to FIG. 2, a control circuit 44 is connected to the actuators 58a, 58b, 58c, . . . 58mto supply control voltages for the actuators to generate mechanical movements. In a manner similar to the actuation of movable optical reflectors described above in reference to FIG. 1, each of the movable optical reflectors 56a, 56b, 56c, . . . 56mcan be switched by the respective actuator from its on position to its off position by moving the relector toward the first surface 20 of the support plate 2 away from the first optical path 60, or from its off position to its on position by moving away from the first surface 20 of the support plate 2 to a designated location above the first surface of the support plate 2 to intercept the first optical path 60.

[0048] For example, when the movable optical reflector 56ais switched to its on position, the incident light on the first optical path 60 is reflected by its reflection surface 76, which is shown as being angled at 45° with respect to the first optical path 60, to reflect the light onto a second optical path 78 which leads to the respective output optical port 52a.Because light has the property of reciprocity, the optical port 52acan be used as an input optical port to transmit light through the respective collimator lens 64ato the movable optical reflector 56a, which when in its on position reflects the light onto the optical path 60 leading to the optical port 50.

[0049] Any one of the movable optical reflectors 56a, 56b, 56c, . . . 56mcan be selected to be switched on to reflect incoming light on the first optical path 60 onto a respective second optical path leading to a respective one of the output optical fibers 54a, 54b, 54c, . . . 54m, as long as the movable optical switches preceding the selected optical switch along the first optical path 60 are in their off positions. For example, if the movable optical reflector 56bis switched to its on position while the movable optical reflector 56awhich precedes the movable optical reflector 56balong the first optical path 60 is in its off position, then the output optical fiber 54bis selected to receive the light transmitted from the input optical fiber 48, regardless of whether other movable optical reflectors including the movable optical reflectors 56cand 56m, which are located subsequent to the selected movable optical reflector 56balong the first optical path 60, are in their on or off positions.

[0050] In an embodiment, only one of the movable optical reflectors 56a, 56b, 56c, . . . 56mis selected at a time by the control circuit 44 to be switched to its on position to reflect light from the primary optical port 50 to the selected secondary optical port. In an alternate embodiment, the movable optical reflectors located subsequent to the optical reflector selected for the optical switching operation can remain in their on or off positions without being switched, since they have no effect on the optical switching operation. Only the movable optical reflectors located ahead of the optical reflector along the first optical path 60 need be switched off to allow light on the first optical path to reach the selected optical reflector.

[0051] In the embodiment shown in FIG. 2, a fixed optical reflector 56nis positioned on the first surface 20 of the support plate 2 to intercept light on the first optical path 60 when all of the movable optical reflectors 56a, 56b, 56c, . . . 56mare in their off positions. The fixed optical reflector 56nis thus the default reflector for switching the light transmitted from the input optical fiber 48 to the output optical fiber 54nonly if all of the movable optical reflectors 56a, 56b, 56c, . . . 56mare turned off by the control circuit 44. Alternatively, the last optical reflector 56nmay also be a movable reflector switched by an additional acutator. The control circuit 44 for supplying the control voltages to the actuators 58a, 58b, 58c, . . . 58mmay be implemented in a conventional manner which is apparent to a person skilled in the art.

[0052] FIG. 2 also shows a plurality of apertures 80a, 80b, 80c, . . . 80min the support plate 2 aligned with the movable optical reflectors 56a, 56b, 56c, . . . 56m, respectively. In an embodiment, each of the movable optical reflectors is switched to its off position by moving into the respective aperture in the support plate 2. Alternatively, each of the movable optical reflectors 56a, 56b, . . . 56mmay be switched to its off position by moving lower from the first optical path 60, which is above the first surface 20 of the support plate 2, to a position which is still above the first surface 20 of the support plate 2 but completely away from the first optical path 60. In yet another embodiment, the of f position of the movable optical reflector is below the second surface of the support plate 2.

[0053] Although FIG. 2 shows that a separate aperture is provided for each one of the movable optical reflectors, other aperture arrangements can also be made. For example, a plurality of elongated apertures may be provided in the support plate 2 to allow switching movements of two or more adjacent movable optical reflectors through each of the apertures. In another embodiment, all of the movable optical reflectors may be switched between their on and off positions through a single elongated aperture in the support plate 2.

[0054] FIG. 3 shows another embodiment of the mechanically actuated optical switch according to the present invention. The embodiment shown in FIG. 3 is similar to the embodiment shown in FIG. 1 and described above, except that the prisms 30, 6a, 6b, 6c, . . . 6mand 6nin FIG. 1 are replaced by a plurality of mirrors 84, 86a, 86b, 86c, . . . 86mand 86nin FIG. 3, respectively. It is apparent to a person skilled in the art to use either prisms or mirrors as optical reflectors in a mechanically actuated optical switch, although other types of optical switching elements can also be used within the scope of the present invention. For infrared optical wavelengths in the range of about 1500 nm to about 1550 nm, which are typically used in many conventional optical fiber communications systems, prisms may provide an advantage of slightly lower insertion loss over conventional mirrors.

[0055] FIG. 4 shows another embodiment of the mechanically actuated optical switch according to the present invention similar to the embodiment shown in FIG. 2 and described above, except that the prisms 56a, 56b, 56c, . . . 56mand 56nas shown in FIG. 2 are replaced by a plurality of mirrors 88a, 88b, 88c, . . . 88mand 88nin FIG. 4, respectively. Whereas the reflection surface of a prism is behind the triangular prism medium and light travels through the prism medium before and after it is reflected by the reflection surface, a mirror has a reflection surface which reflects light directly in free space. Although prisms generally have lower insertion losses when used as optical reflectors at infrared wavelengths in the range of about 1500 nm to about 1550 nm, mirrors may also be used as optical reflectors in some applications.

[0056] FIG. 5 shows a top plan view of yet another embodiment of the mechanically actuated optical switch according to the present invention, with parallel output optical fibers arranged for transmitting output light in opposite directions. In this embodiment, an input optical fiber 90 has a termination forming a primary optical port 92, and a first collimator assembly 94 is positioned to house an end portion 96 of the input optical fiber 90 adjacent its termination and a primary collimator lens 98, which collimates the input light from the primary optical port 92 to form a substantially parallel light beam.

[0057] A plurality of output optical fibers 100a, 10b, . . . 100hare provided for the optical switch. The output optical fibers 100b, 100d, 100fand 100hare arranged on the same side of the optical switch as the input optical fiber 90, while the output optical fibers 100a, 100c, 100eand 100gare arranged on an opposite side of the optical switch. The output optical fibers 100a, 100b, . . . 100hhave terminations forming the output optical ports 102a, 102b, . . . 102h, respectively, for the optical switch.

[0058] In an embodiment, a plurality of additional collimator assemblies 104a, 104b, . . . 104hare provided for housing end portions 106a, 106b, . . . 106hof the output optical fibers 100a, 100b, . . . 100has well as their associated collimator lenses 108a, 108b, 108h, respectively. In an embodiment, the collimator assemblies 94 and 104a, 104b, . . . 104hare connected to the first surface 20 of the support plate 2 by laser welding for mechanical rigidity and stability.

[0059] In the embodiment shown in FIG. 5, a plurality of movable optical reflectors 110a, 110b, . . . 110gand a fixed optical reflector 110hare provided. The support plate 2 has a plurality of apertures to facilitate mechanical movements of the movable optical reflectors between their on and off positions. In the embodiment shown in FIG. 5, three elongated apertures 112, 114 and 116 are provided for the movable optical reflectors 110b, 110c, . . . 110g.Each of the elongated apertures 112, 114 and 116 is positioned to allow mechanical movements of two adjacent optical reflectors. For example, the movable optical reflectors 110band 110cshare a single aperture 112 while the movable optical reflectors 110dand 110eshare a single aperture 114.

[0060] A smaller aperture 118 is provided to allow mechanical movements by the first movable optical reflector 110a.The last optical reflector 110h, which is shown as a fixed reflector in this embodiment, is connected to the first surface 20 of the support plate 2 and is positioned to reflect light to the collimator assembly 104hleading to the output optical fiber 100honly if the first movable optical reflector 110ais switched on while all of the other movable optical reflectors 110b, 110c, . . . 110gare switched off.

[0061] FIG. 5 shows an example of optical paths formed between the input optical fiber 90 and the output optical fiber 100ewhen the movable optical reflectors 110aand 110eare in their on positions and the movable optical reflectors 110b, 110cand 110dare in their off positions. When the first movable optical reflector 110ais in its on position, light transmitted from the input optical fiber 90 on a first optical path 122 is reflected by the first movable optical reflector 110aonto a second optical path 124. If the movable optical switch 110eis in its on position while the movable optical reflectors 110b, 110cand 110dare in their off positions, light on the second optical path 124 is reflected by the movable optical reflector 110eonto a third optical path 126 which leads to the collimator assembly 104efor the output optical fiber 010e.

[0062] If, on the other hand, the movable optical reflector 110dis switched to its on position, light on the second optical path 124 is reflected by the movable optical reflector 110dto the collimator assembly 104dfor the output optical fiber 110d.If the first movable optical reflector 110ais switched to its off position, light transmitted from the input optical fiber 90 travels straight to the output optical fiber 100athrough the collimator lenses 98 and 108a, regardless of whether other movable optical reflectors 110b, 110c, . . . 110gare in their on or off positions.

[0063] In the embodiment shown in FIG. 5, a plurality of actuators 128a, 128b, . . . 128gare provided below the second surface of the support plate 2 for switching the respective movable optical reflectors 110a, 110b, . . . 110gbetween their on and off positions. A plurality of levers 130a, 130b, . . . 130gare connected between the actuators 128a, 128b, . . . 128gand the movable optical reflectors 110a, 110b, . . . 110g, respectively, to transfer mechanical movements from the actuators to the movable optical reflectors. In the embodiment shown in FIG. 5, four actuators 128a, 128b, 128dand 128fare arranged on one side of the optical reflector array while three actuators 128c, 128eand 128gare arranged on an opposite side of the reflector array to provide adequate spacing for the mechanical assemblies below the second surface of the support plate 2 and to distribute the weight of the optical switch more evenly across the support plate 2.

[0064] In a different embodiment, all of the actuators and levers below the second surface of the support plate 2 may be arranged on one side of the reflector array if spacing is not a problem. Furthermore, instead of the aperture arrangement shown in FIG. 5, a separate aperture may be provided for each of the movable optical reflectors, or alternatively, more than two movable optical reflectors may share a single elongated aperture. In yet another embodiment, only one elongated aperture is provided in the support plate 2 to allow mechanical movements of all of the movable optical reflectors 110a, 110b, . . . 110g.Although the optical reflectors 110a, 110b, 110hare shown as prisms in FIG. 5, mirrors can also be used as optical reflectors within the scope of the present invention.

[0065] FIG. 6 shows a sectional view of an embodiment of a mechanical assembly for actuating a movable optical reflector obtained along sectional line 101—101 in FIG. 5. In this embodiment, the mechanical assembly is provided below the second surface 132 of the support plate 2 except for an end portion 134 of the lever 130fwhich supports the movable optical reflector 110f.The end portion 134 of the lever 130fis movable through the aperture 116 in the support plate 2 to drive the optical reflector 110fbetween its on and off positions. The location of the mechanical assembly below the second surface 132 of the support plate 2 avoids the blockage of optical paths above the first surface 20 of the support plate 2 and frees the first surface 20 of the support plate 2 from being cluttered with mechanical elements.

[0066] In the embodiment shown in FIG. 6, the actuator 128fcomprises a conventional solenoid relay switch, which is capable of generating repetitive movements in opposite directions controlled by voltages generated by a conventional control circuit 44. The mechanical movements generated by the relay switch 128fare transferred to the lever 130fthrough a flexible connector 136, which in an embodiment comprises a pair of bent metal wires 136aand 136b.The lever 130f, which is pivotably supported by a stable axle assembly 138, transfers the mechanical movements generated by the relay switch 128fto the movable optical reflector 110f.As shown in FIG. 6, the axle assembly 138 is supported by a fixed member 140 which is connected to the second surface 132 of the support plate 2.

[0067] Because the movable optical reflector 110fhas its designated on and off positions, two fixed blocks 142 and 144 are provided on the second surface 132 of the support plate 2 to stop further movements of the lever 130fto set the optical reflector 110fin its on and off positions. In an embodiment, a contact pad 146 is provided on the lever 130fopposite the first fixed block 142, such that when the contact pad 146 is in contact with the first fixed block 142, the optical reflector 110fis stopped in its designated on position. The second fixed block 144 is positioned to stop the lever 130ffrom moving farther in the opposite direction after the optical reflector 110freaches its off position. Further details of the mechanical assembly as shown in FIG. 6 are described in U.S. patent application Ser. No. 09/416,444, titled “Actuator Assembly for Optical Switches”, filed Oct. 12, 1999, which is incorporated herein by reference.

[0068] FIG. 7 shows a sectional view of another embodiment of a mechanical assembly for actuating the movable optical reflectors in the optical switch according to the present invention. In this embodiment, the actuator comprises a conventional solenoid relay switch 150, which is capable of generating repetitive mechanical movements in opposite directions controlled by voltages generated by a conventional control circuit 44. In this embodiment, the relay switch 150 is vertically mounted to a fixed member 152 which also supports a stable axle assembly 154. A lever 156 is pivotably supported by the axle assembly 154 to drive a movable optical reflector 158 between its on and off positions.

[0069] In the embodiment shown in FIG. 7, a flexible connector 160 is connected between the relay switch 150 and the lever 156 to transfer mechanical movements generated by the relay switch 150 to the lever 156. In an embodiment, the flexible connector 160 comprises two bent metal wires 160aand 160b.In FIG. 7, two fixed blocks 162 and 164 are provided on the second surface 132 of the support plate 2 to stop the lever 156 from moving farther when the movable optical reflector 158 reaches its designated on and off positions.

[0070] In an embodiment, a contact pad 166 is provided on the lever 156 opposite the first fixed block 162. When the movable optical reflector 158 reaches its designated on position, the contact pad 166 is in contact with the first fixed block 162. The second fixed block 164 stops the lever 156 from moving farther in the opposite direction when the movable optical reflector 158 reaches its off position. Further details of the mechanical assembly as shown in FIG. 7 are also described in U.S. patent application Ser. No. 09/416,444, titled “Actuator Assembly for Optical Switches”, filed Oct. 12, 1999, which is incorporated herein by reference.

[0071] FIGS. 8 and 9 show further embodiments of mechanical assemblies for the optical switch according to the present invention. FIG. 8 shows an embodiment of the mechanical assembly similar to that which is shown in FIG. 6 and described above, with the additions of a magnet 170 which is connected to the contact pad 146 on the lever 130fand a solenoid 172 which is connected to the second surface 132 of the support plate 2. In an embodiment, the magnet 170 is a permanent magnet which generates a strong magnetic field. The solenoid 172 is connected to the second surface 132 of the support plate 2 at a position opposite the contact pad 146 and the magnet 170. In an embodiment, the solenoid 172 is positioned within the first metal block 142, which is provided with a hollow interior to house the solenoid 172.

[0072] In the embodiment shown in FIG. 8, the control circuit 44 supplies an actuating voltage V to the actuator 128f.In an embodiment, the actuator 128fgenerates repetitive movements in opposite directions depending upon the changes in polarities of the actuating voltage V supplied by the control circuit 44. In the embodiment shown in FIG. 8, the actuating voltage V generated by the control circuit 44 is also supplied to the solenoid 172 through conductive lines 174 and 176. When the optical switching element 110fis switched from its off position to its on position, the voltage V supplied by the control circuit 44 forces a current through the solenoid 172 to generate a magnetic field for attracting the permanent magnet 170.

[0073] Because of the magnetic force of attraction between the permanent magnet 170 and the solenoid 172 when the optical switching element 110fis moved from its off position to its on position, the switching time for the optical switching element 110fto reach its on position from its off position can be reduced compared to the embodiment shown in FIG. 6 in which the optical switching element 110frelies solely upon the force generated by the relay switch 128fto move to its on position.

[0074] Referring to FIG. 8, when the control circuit 44 reverses the polarity of the actuating voltage V to cause the relay switch 128fto move the optical switching element 110ffrom its on position to its off position, the polarity of the voltage supplied to the solenoid 172 is also reversed. The current through the solenoid 172 thus flows in a reverse direction to generate a reverse magnetic field to repel the permanent magnet 170 downward away from the solenoid 172. The repelling force between the solenoid 172 and the permanent magnet 170 in addition to the force generated by the relay switch 128fcauses the optical switching element 110fto move quickly from its on position to its off position when the polarity of the actuating voltage V is reversed.

[0075] When the actuating voltage V is supplied to both the relay switch 128fand the solenoid 172 to move the optical switching element 110fto its on position, a strong magnetic force of attraction between the solenoid 172 and the permanent magnet 170 causes the contact pad 146 to move quickly toward the first metal block 142 in addition to the actuating force transferred from the relay switch 128fto the lever 130fthrough the flexible connector 136. The solenoid 172 and the permanent magnet 170 allow the switching time of the optical switching element 110ffrom its off position to its on position to be reduced to about 15 ms or less. After the optical switching element 110freaches its on position, the force of attraction between the permanent magnet 170 and the solenoid 172 ensures that the contact pad 146 is in secure contact with the first metal block 142. In an embodiment, the first metal block 142 comprises a nonferrous metal such as copper or aluminum. In a further embodiment, the contact pad also comprises a nonferrous metal.

[0076] FIG. 9 shows a sectional view of an embodiment of the mechanical assembly similar to that which is shown in FIG. 7 and described above, with the additions of a permanent magnet 182 attached to the contact pad 166 and a solenoid 180 on the second surface 132 of the support plate 2. In the embodiment shown in FIG. 9, the solenoid 180 is positioned within the first metal block 162. A hollow interior may be provided in the first metal block 162 to allow sufficient space for the solenoid 180. The control circuit 44, which supplies an actuating voltage V to the relay switch 150 for generating repetitive movements in opposite directions, also supplies the same actuating voltage V to the solenoid 180 through conductive lines 184 and 186.

[0077] When the actuating voltage V is applied to the relay switch 150 to move the optical switching element 158 from its off position to its on position, it also causes a current to flow through the solenoid 180 to produce a magnetic field for attracting the permanent magnet 182. With the additional force of magnetic attraction between the permanent magnet 182 and the solenoid 180, the optical switching element 158 can be switched from its off position to its on position within a shorter switching time. When the optical switching element 158 is switched from its on position to its off position, the polarity of the actuating voltage V is reversed to cause the relay switch to generate an opposite motion. The magnetic field produced by the solenoid 180 is also reversed, thereby repelling the permanent magnet 182 downward to move the optical switching element 158 from its on position to its off position.

[0078] In an embodiment, conventional solenoids with iron cores may be implemented to attract and to repel the permanent magnets 170 and 182 as shown in FIGS. 8 and 9, respectively. In an embodiment, the contact pads 146 and 166 in FIGS. 8 and 9 may have surfaces wider than the widths of the levers 130fand 156 to allow the permanent magnets 170 and 182 to be attached to the contact pads 146 and 166 at positions external to the levers 130fand 156, respectively. In another embodiment, the permanent magnets may be positioned inside the levers, provided that the levers are made of nonferrous metals. Although the solenoids 172 and 180 are shown as being positioned inside the first metal blocks 142 and 162 in FIGS. 8 and 9, respectively, the solenoids may also be positioned outside the respective first metal blocks in a different embodiment, as long as the solenoids are able to produce sufficiently strong forces of attraction and repulsion on the respective permanent magnets.

[0079] The invention has been described with respect to particular embodiments thereof, and numerous modifications can be made which are within the scope of the invention as set forth in the claims.