Frustrated total internal reflection bus and method of operation

An optical bus for processing an optical signal includes an optical waveguide and a switchplate. The switchplate has a first position spaced apart from the optical waveguide and a second position in proximal contact with a reflecting surface of the optical waveguide to frustrate the total internal reflection of the optical signal such that the optical signal exits the optical waveguide at an output location.

TECHNICAL FIELD OF THE INVENTION
 This invention relates to the field of frustrated total internal reflection
 devices and more particularly to a frustrated total internal reflection
 bus.
 BACKGROUND OF THE INVENTION
 Data is often communicated between components of a system via communication
 channels called buses. The capacity of a bus is defined by the number of
 bits of data that a bus can carry simultaneously. Data is communicated
 between buses or between buses and individual components of the system
 using switches. Electrical buses and switches are limited, however, in
 bandwidth capacity, speed, expandability, and susceptibility to cross-talk
 and interference.
 Buses and switches are often integrated in a backplane bus architecture for
 various systems applications. An important attribute of a backplane bus
 architecture is the number of components that can be plugged into the
 backplane. The ability to interconnect individual components,
 sub-assemblies, processors, and systems, using a backplane, is an
 important aspect of systems integration. Many applications today require
 that the number of slot connections in a backplane bus architecture be
 expandable to facilitate the interconnection of additional components to
 perform functions conceived after the backplane was designed. The
 expandability of traditional backplane bus architectures is limited,
 however, by fixed bandwidth, fixed slot connections, and other electrical
 and mechanical constraints.
 SUMMARY OF THE INVENTION
 In accordance with the present invention, a frustrated total internal
 reflection bus is provided that substantially eliminates or reduces
 disadvantages and problems associated with previous bus architectures.
 In accordance with one embodiment of the present invention, an optical bus
 for processing an optical signal includes an optical waveguide having a
 first reflecting surface and a second reflecting surface. A switchplate
 coupled to the optical waveguide has a first position spaced apart from
 the waveguide and a second position in proximal contact with the second
 reflecting surface of the waveguide to frustrate the total internal
 reflection of the optical signal such that the optical signal exits the
 waveguide at an output location on the first reflecting surface of the
 optical waveguide.
 Another embodiment of the present invention is a method for processing an
 optical signal that includes reflecting the optical signal at a first
 reflecting surface of an optical waveguide. The method concludes by
 placing a switchplate in proximal contact with a second reflecting surface
 of the optical waveguide to frustrate the total internal reflection of the
 optical signal such that the optical signal exits the optical waveguide at
 an output location on the first reflecting surface of the optical
 waveguide.
 Technical advantages of the present invention include a frustrated total
 internal reflection (FTIR) bus that includes, in one embodiment, an
 optical waveguide that propagates an optical signal by total internal
 reflection, and any number of switchplates coupled to the optical
 waveguide. The switchplates may be placed in proximal contact with
 reflecting surfaces of the optical waveguide to frustrate the total
 internal reflection of the optical signal such that it exits the optical
 waveguide at one or more selected output locations along the reflecting
 surfaces of the waveguide. The FTIR bus may also receive optical signals
 at one or more input locations along the reflecting surfaces of the
 waveguide. The present invention provides advantages over prior optical
 buses that are limited to inputting and outputting optical signals at an
 end of the bus. By supporting multiple input and output locations for an
 optical signal along the reflecting surfaces of an optical bus, the
 present invention provides scalable and expandable input/output
 capabilities. The input and output locations of the FTIR bus may be
 permanently configured, dynamically reconfigured, or both to provide a
 multitude of signal processing and routing capabilities. For example,
 switchplates may be added to the optical waveguide to expand the number of
 output locations along its reflecting surfaces.
 Further technical advantages of the present invention include optical
 devices coupled to the optical waveguide at the input and output locations
 to facilitate enhanced switching, multiplexing, and processing of the
 optical signal. Since prior optical buses are limited to inputting and
 outputting the optical signal at an end of the bus, attempts to couple
 optical devices at these input/output locations are constrained by the
 limited surface area at either end of the bus. Providing optical devices
 at input and output locations along the reflecting surfaces of the FTIR
 bus yields a higher packing density of these devices. In one embodiment,
 the FTIR bus may perform a signal splitter function so that multiple
 optical devices coupled to the optical waveguide at different output
 locations may share the optical signal.
 The present invention further includes any number of input FTIR buses and
 output FTIR buses that interface at selected locations to form an FTIR bus
 matrix. The interfaces between the FTIR buses of the matrix may be
 permanently configured, dynamically reconfigured, or both, to provide even
 more enhanced switching and multiplexing capabilities for processing the
 optical signal. Other technical advantages of the present invention are
 evident to one skilled in the art from the attached description, figures,
 and claims.

DETAILED DESCRIPTION OF THE INVENTION
 FIG. 1 illustrates a frustrated total internal reflection (FTIR) bus 10
 that includes a first refractive material 12 having an index of refraction
 n.sub.1, a second refractive material 14 having an index of refraction
 n.sub.2, and a third refractive material 16 having an index of refraction
 n.sub.3. FTIR bus 10 further includes switchplates 20, actuators 22, and
 an optical device 24. First refractive material 12 has critical angles of
 refraction 18a and 18b that comprise threshold angles above which light
 traveling in refractive material 12 will be totally internally reflected
 by the interfaces between material 12 and materials 14 and 16,
 respectively, provided index of refraction n, is different from index of
 refraction n.sub.2 and index of refraction n.sub.3.
 In general, optical device 24 introduces an optical signal 26 into first
 refractive material 12 such that it travels along the length of material
 12 totally internally reflecting at angles equal to or greater than
 critical angles of refraction 18a or 18b each time signal 26 contacts an
 interface between material 12 and material 14 or 16, respectively. An
 actuator 22 places a switchplate 20 into proximal contact with refractive
 material 12 at the interface between material 12 and material 14 or 16 to
 frustrate the total internal reflection of signal 26 and to reflect
 optical signal 26 at an angle 28 less than critical angle of refraction
 18a or 18b such that optical signal 26 exits refractive material 12.
 First refractive material 12 comprises an optical waveguide, referred to as
 optical waveguide 12, formed by an arrangement of prisms, rhomboids, or
 any other suitable optically transmissive material that has a first
 reflecting surface 30 and a second reflecting surface 32. Reflecting
 surface 30 may be parallel with reflecting surface 32 or at any suitable
 angle with respect to surface 32 to control the angle of refraction of
 optical signal 26. In one embodiment, the distance between surfaces 30 and
 32 measures approximately one millimeter. First refractive material 12 has
 an index of refraction n, that characterizes the ratio of the speed of
 light in a vacuum to the speed of light in material 12. First refractive
 material 12 may be selected to provide a particular index of refraction n,
 at a particular wavelength of optical signal 26.
 Second refractive material 14 and third refractive material 16 comprise air
 or any other suitable substance that have indices of refraction, n.sub.2
 and n.sub.3, lower than that of first refractive material 12. Accordingly,
 if optical signal 26 propagates through refractive material 12 at angles
 equal to or above critical angles of refraction 18a or 18b, then the
 interfaces between material 12 and materials 14 or 16 totally internally
 reflect optical signal 26. The following description of the present
 invention is detailed with reference to a particular embodiment in which
 index of refraction n.sub.2 of material 14 equals index of refraction
 n.sub.3 of material 16 and, accordingly, critical angle of refraction 18a
 equals critical angle of refraction 18b. Therefore, critical angles of
 refraction 18a and 18b are collectively referred to hereinafter as
 critical angle of refraction 18. It should be understood, however, that
 index of refraction n.sub.2 may be the same as or different from index of
 refraction n.sub.3, and critical angle of refraction 18a may be the same
 as or different from critical angle of refraction 18b, without deviating
 from the scope of the present invention.
 Switchplates 20 comprise any suitable refractive material having a contact
 surface 40 and a reflective surface 42. Each switchplate 20 may be formed
 in many configurations without deviating from the inventive concepts of
 the present invention. A switchplate 20 couples to material 12 in proximal
 contact with either first reflecting surface 30 or second reflecting
 surface 32. The distance between each switchplate 20 is selected in
 response to the magnitude of critical angle of refraction 18 of material
 12. Accordingly, the distance between each switchplate 20 may be selected
 by adjusting the indices of refraction, n.sub.1, n.sub.2, or n.sub.3, of
 materials 12, 14, or 16. In one embodiment, as critical angle of
 refraction 18 increases, switchplates 20 are spaced further apart from
 each other. Conversely, as critical angle of refraction 18 decreases,
 switchplates 20 are spaced closer together.
 Reflective surface 42 of switchplate 20 is at bias angle 44 in one or more
 planes with respect to contact surface 40 to direct optical signal 26 to a
 selected output location 46 on either of reflecting surfaces 30 or 32 when
 switchplate 20 is in proximal contact with material 12. The reflectivity
 of surface 42 may be caused by total internal reflection or by reflective
 material. It is noted that reflective surface 42 of switchplate 20 may
 also be non-reflective or optically absorbing.
 Switchplate 20 has a first position spaced apart from refractive material
 12 and a second position in proximal contact with refractive material 12
 to frustrate the total internal reflection of optical signal 26. The term
 proximal contact refers not only to direct contact between switchplate 20
 and refractive material 12, but also contemplates any spacing or partial
 contact between switchplate 20 and refractive material 12 to frustrate the
 total internal reflection of signal 26 to a desired degree. In one
 embodiment, the spacing between switchplate 20 and first refractive
 material 12 may be controlled to perform a variable signal splitter or
 attenuator function.
 Actuators 22 comprise a piezoelectric device, a bimorph transducer, or any
 other suitable material that displaces switchplate 20 in response to an
 electrical, thermal, or other appropriate control signal. Activating and
 deactivating actuator 22 coupled to switchplate 20 causes actuator 22 to
 bring switchplate 20 into and out of proximal contact with refractive
 material 12. U.S. Pat. No. 5,555,327 and U.S. patent application Ser. No.
 08/923,953 disclose a variety of techniques and components to construct
 switchplates 20, actuators 22, and combinations thereof that may be used
 with FTIR bus 10, and are herein incorporated by reference.
 Optical device 24 is coupled to first refractive material 12 at an input
 location 48. Optical device 24 may comprise a prism, a rhomboid, or any
 other suitable configuration of optically transmissive materials. In one
 embodiment, optical device 24 has an index of refraction similar to that
 of first refractive material 12 to allow the introduction of optical
 signal 26 into first refractive material 12 from either second refractive
 material 14 or third refractive material 16 without violating Snell's law.
 In another embodiment, optical device 24 is positioned at a particular
 angle in relation to the interface between first refractive material 12
 and either of second refractive material 14 or third refractive material
 16 to allow the introduction of optical signal 26 into first refractive
 material 12 without violating Snell's law. Optical device 24 may couple to
 first refractive material 12 at multiple input locations 48 along
 reflecting surfaces 30 or 32 or at either end of optical waveguide 12 to
 provide enhanced switching capabilities.
 Optical signal 26 comprises visible light, infrared radiation, ultraviolet
 radiation, or any other suitable optical beam. In one embodiment, optical
 signal 26 comprises optical energy emitted by a nominally collimated
 optical source. In a particular embodiment, optical signal 26 comprises
 optical energy emitted from a laser or light emitting diode (LED) at a
 wavelength ranging from approximately 1.3 to 1.6 microns.
 In operation, optical device 24 introduces optical signal 26 into first
 refractive material 12 such that it propagates along the longitudinal axis
 of material 12 totally internally reflecting at angles equal to or greater
 than critical angle of refraction 18 each time it contacts an interface
 between material 12 and materials 14 or 16, such as reflecting surfaces 30
 or 32. To change the path of optical signal 26, a selected actuator 22 is
 activated. Activating an actuator 22 brings an associated switchplate 20
 into proximal contact with first refractive material 12 such that optical
 signal 26 enters switchplate 20 and reflects at an angle 28 less than
 critical angle of refraction 18. This causes optical signal 26 to exit
 first refractive material 12 at output location 46 in accordance with
 Snell's law.
 Deactivating actuator 22 brings switchplate 20 out of proximal contact with
 first refractive material 12. Once switchplate 20 is spaced apart from
 first refractive material 12 a sufficient distance, approximately two
 times the wavelength of optical signal 26 in material 12, for example,
 then optical signal 26 again reflects by total internal reflection at
 reflecting surfaces 30 and 32 of material 12. Controlling the activation
 of actuators 22 controls the separation between switchplates 20 and first
 refractive material 12. This allows FTIR bus 10 to be used for switching,
 modulating, or otherwise processing optical signal 26. By supporting input
 and output locations for optical signal 26 along reflecting surfaces 30
 and 32 of optical waveguide 12 as well as either end of waveguide 12, FTIR
 bus 10 provides scalable and expandable input/output capabilities.
 FIG. 2 illustrates another embodiment of FTIR bus 10 that provides a
 variable signal splitter or attenuator function. In this embodiment, a
 selected actuator 22 may position an associated switchplate 20 in relation
 to first refractive material 12 such that a portion of optical signal 26
 propagating through material 12 is reflected at reflecting surface 30 or
 32 of material 12 and a portion of optical signal 26 is reflected at
 reflective surface 42 of switchplate 20. For example, reflecting surface
 32 of material 12 reflects a portion of optical signal 26 as a first
 optical beam 26a and reflective surface 42 of switchplate 20 reflects a
 portion of optical signal 26 as a second optical beam 26b. First optical
 beam 26a continues propagating along the longitudinal axis of material 12
 reflecting at angles equal to or greater than critical angle of refraction
 18 each time it contacts an interface between material 12 and another
 refractive material 14 or 16. Second optical beam 26b reflects at an angle
 50 less than critical angle of refraction 18 such that it exits material
 12 at output location 46 according to Snell's law. In one embodiment,
 angle 50 equals angle 28.
 Actuators 22 may control the spacing of associated switchplates 20 with
 relation to material 12 to any desired degree. The degree of spacing
 between switchplates 20 and material 12 determines the portion of optical
 signal 26 reflected as signal 26a and the portion of optical signal 26
 reflected as signal 26b. Signals 26a and 26b may exit optical waveguide 12
 at different output locations along reflecting surfaces 30 or 32 of
 optical waveguide 12 or at either end of waveguide 12. By splitting
 optical signal 26 into signals 26a and 26b, FTIR bus 10 provides enhanced
 switching and multiplexing capabilities.
 FIG. 3 illustrates another embodiment of FTIR bus 10 that includes output
 devices 52, such as output devices 52a-52d, coupled to first refractive
 material 12. An output device 52 may comprise an optical device, an
 electrical device, a mechanical device, a thermal device, or any
 combination of optical, electrical, mechanical, or thermal devices that
 perform further propagation, switching, multiplexing, or other suitable
 processing on optical signal 26. Output devices 52 may couple to material
 12 at locations along reflecting surfaces 30 or 32 to provide a higher
 packing density of these devices.
 Although the following description of the present invention details the
 operation of FTIR bus 10 using an optical device 52, output device 52 may
 comprise any combination of optical, electrical, mechanical, or thermal
 devices, as described above. In a particular embodiment, an optical device
 52 may comprise an optical detector, a bundle of optical fibers, another
 FTIR bus 10, or a prism coupled to a lens, as illustrated in FIG. 3. It
 should be understood that FIG. 3 depicts switchplates 20 of FTIR bus 10
 performing a variable signal splitter function, as described above with
 reference to FIG. 2, for illustrative purposes only, and that switchplates
 20 of FIG. 3 may be strategically placed into or out of proximal contact
 with material 12 to any desired degree.
 In one embodiment, optical device 52a couples to but is spaced apart from
 first refractive material 12 at output location 46 to provide further
 processing capabilities on optical signal 26 that exits material 12 while
 maintaining the total internal reflection properties of material 12. In
 this embodiment, optical signal 26b exits material 12 at output location
 46 according to Snell's law and enters optical device 52a. Optical device
 52a performs further processing on signal 26b. For example, optical device
 52a may change the angle of optical signal 26b after it exits first
 refractive material 12. In another example, optical device 52a
 decollimates signal 26b to introduce it into another optical device 52,
 such as, for example, an optical fiber.
 In another embodiment, optical device 52b couples to and is placed in
 proximal contact with first refractive material 12 at a selected location
 where optical signal 26a is normally totally internally reflected by the
 interface between first refractive material 12 and either second or third
 refractive materials 14 or 16. In this embodiment, optical device 52b
 comprises an optically transmissive material having an index of refraction
 suitable to frustrate the total internal reflection of optical signal 26a
 by material 12 such that optical signal 26a exits material 12 irrespective
 of the angle of refraction of optical signal 26a in comparison to critical
 angle of refraction 18. In a particular embodiment, optical device 52b
 couples to material 12 using an actuator 22, and has a first position
 spaced apart from material 12 and a second position in proximal contact
 with material 12 to frustrate the total internal reflection of signal 26a.
 For example, an optical signal 26a propagating through first refractive
 material 12 with an angle of refraction equal to or greater than critical
 angle of refraction 18 will exit first refractive material 12 provided
 optical device 52b having a suitable index of refraction is placed in
 proximal contact with material 12 at a selected location where optical
 beam 26a contacts the interface between material 12 and either of
 materials 14 or 16. This embodiment provides an alternative method by
 which optical signal 26 may exit first refractive material 12, based on
 the location of optical beam 26a and independent of its angle of
 refraction.
 In yet another embodiment, optical devices 52c and 52d comprise additional
 FTIR buses 10 that may receive optical signal 26. Upon receiving optical
 signal 26, the FTIR buses 10 of optical devices 52c and/or 52d may
 propagate optical signal 26 by total internal reflection as described
 above with reference to FIGS. 1 and 2. In a particular embodiment, optical
 device 52d couples to FTIR bus 10 at an angle to adjust the angle of
 refraction of optical signal 26 within optical device 52d.
 FIG. 4 illustrates an arrangement 60 of FTIR buses 10. In this embodiment,
 a single actuator 22 may place a single switchplate 20 into and out of
 proximal contact with one or more FTIR buses 10. Therefore, a single
 switchplate 20 may simultaneously frustrate the total internal reflection
 of multiple optical signals 26 propagating through FTIR buses 10 of
 arrangement 60, using the techniques described above with reference to
 FIGS. 1 and 2. Placing a single switchplate 20 into and out of proximal
 contact with one or more FTIR buses 10 to frustrate simultaneously the
 total internal reflection of one or more associated optical signals 26
 facilitates more precise and enhanced switching capabilities. For example,
 multiple optical signals 26 may be switched in tandem in response to a
 single control signal. Furthermore, this embodiment conserves power by
 activating a single actuator 22 to control one or more optical signals 26.
 Although FIG. 4 illustrates FTIR buses 10 arranged in proximal contact with
 each other, FTIR buses 10 may also be arranged spaced apart from each
 other. In a particular embodiment, a single FTIR bus 10 is provided that
 has sufficient width to support the propagation of multiple optical
 signals 26 along its longitudinal axis. In this embodiment, one or more
 switchplates may frustrate the total internal reflection of the multiple
 optical signals simultaneously.
 FIG. 5 illustrates a top view of one embodiment of an FTIR bus matrix 70
 that includes input FTIR buses 10a-10c and output FTIR buses 10x-10z (FTIR
 buses 10a-10c and FTIR buses 10x-10z are generally referred to as FTIR
 buses 10). Although the following description of FIG. 5 is detailed with
 reference to switching an optical signal 26 from an input FTIR bus 10 to
 an output FTIR bus 10, it should be understood that the present invention
 contemplates bidirectional communication of optical signal 26 between
 input FTIR buses 10 and output FTIR buses 10. Therefore, input FTIR bus 10
 and output FTIR bus 10 may each perform both input and output
 communication of optical signal 26.
 In one embodiment, input FTIR buses 10 have first longitudinal axes and
 output FTIR buses 10 have second longitudinal axes substantially
 perpendicular to the first longitudinal axes. Although FIG. 5 is
 illustrated with three input and three output FTIR buses 10 arranged in a
 perpendicular manner, matrix 70 may include any number and arrangement of
 input and output FTIR buses 10. Each FTIR bus 10 of FTIR bus matrix 70
 includes a first refractive material 12, such as an optical waveguide, a
 second refractive material 14 (e.g., air), and a third refractive material
 16 (e.g., air), and any combination of switchplates 20, actuators 22,
 optical devices 24, and/or output devices 52, as described above with
 reference to FIGS. 1 through 3. In one embodiment, a spacer, a
 switchplate, or any other suitable optical device, couples an output FTIR
 bus 10 to an input FTIR bus 10 at an appropriate node. Although the
 following description is detailed with reference to coupling an output
 FTIR bus 10 above an input FTIR bus 10, an output FTIR bus 10 may couple
 above or below an input FTIR bus 10. Input and output FTIR buses 10 are
 spaced according to the critical angles of reflection 18 of the optical
 waveguides for each FTIR bus 10 and according to the thickness and bias
 angle 44 of each switchplate 20.
 In operation of FTIR bus matrix 70, an optical signal 26 propagates through
 an optical waveguide of an input FTIR bus 10a-10c in a direction indicated
 by either arrow 72 or arrow 74, totally internally reflecting at angles
 equal to or greater than critical angle of refraction 18 each time it
 contacts an interface between material 12 and materials 14 or 16. For
 example, signal 26 totally internally reflects at an angle equal to or
 greater than critical angle of refraction 18 at an interface 76 (indicated
 by a solid circle) between material 12 and material 14, and at an
 interface 78 (indicated by a dashed circle) between material 12 and
 material 16. Switchplates 20 of FTIR buses 10 may be selectively activated
 to frustrate the total internal reflection of signal 26 such that optical
 signal 26 exits an input FTIR bus 10 and enters an output FTIR bus 10 at
 an appropriate node 80 (indicated by opaque circles). A node 80 comprises
 an interface through which an optical signal 26 propagates when switched
 between an input FTIR bus 10 and an output FTIR bus 10. The optical signal
 26 then propagates along the longitudinal axis of the optical waveguide of
 the output FTIR bus 10 in a direction indicated by either arrow 82 or 84,
 totally internally reflecting at angles equal to or greater than critical
 angle of refraction 18 each time it contacts an interface between material
 12 and materials 14 or 16.
 In one embodiment, a first switchplate 20 coupled to an input FTIR bus 10
 and a second switchplate 20 coupled to an output FTIR bus 10 operate
 simultaneously to communicate optical signal 26 between an input FTIR bus
 10 and an output FTIR bus 10 at an appropriate node 80. For example, a
 first switchplate 20 of a particular input FTIR bus 10 is placed in
 proximal contact with material 12 at an interface 78 such that optical
 signal 26 enters the switchplate 20 and reflects at an angle less than
 critical angle of refraction 18 of the optical waveguide. As a result,
 optical signal 26 exits that input FTIR bus 10 and enters the optical
 waveguide of a corresponding output FTIR bus 10 at an appropriate node 80.
 A first configuration of bus matrix 70 positions the corresponding output
 FTIR bus 10 along input FTIR bus 10 in alignment with the first
 switchplate 20 such that switchplate 20 reflects optical signal 26 from
 interface 78 to node 80 along one plane. In this configuration of bus
 matrix 70, illustrated in FIGS. 5, 6A, and 6B, angle 44 of the first
 switchplate 20 may be biased in one plane such that optical signal 26
 exits the input FTIR bus 10 and enters the optical waveguide of the
 corresponding output FTIR bus 10 at node 80. A second configuration of bus
 matrix 70 positions the corresponding output FTIR bus 10 along input FTIR
 bus 10 offset from the first switchplate 20 such that first switchplate 20
 reflects optical signal 26 from interface 78 to node 80 along two planes.
 In this configuration, angle 44 of first switchplate 20 may be biased in
 one or more planes such that optical signal 26 exits the input FTIR bus 10
 and enters the optical waveguide of the corresponding output FTIR bus 10
 at node 80.
 A second switchplate 20 is placed in proximal contact with the optical
 waveguide of the corresponding output FTIR bus 10 such that optical signal
 26 enters the second switchplate 20. Reflective surface 42 of second
 switchplate 20 is biased at an angle in one or more planes in coordination
 with first switchplate 20 to reflect signal 26 such that it propagates
 along the longitudinal axis of the corresponding output FTIR bus 10
 reflecting at angles equal to or greater than critical angle of refraction
 18 of the optical waveguide.
 For example, in the first configuration of bus matrix 70, second
 switchplate 70 may be biased in one plane to reflect signal 26 such that
 it propagates along the longitudinal axis of the corresponding output FTIR
 bus 10. In the second configuration of bus matrix 70, second switchplate
 70 may be biased in one or more planes in coordination with angle 44 of
 first switchplate 70. In particular, if first switchplate 70 is biased in
 two planes to reflect signal 26 out of FTIR bus 10 at node 80, then second
 switchplate 70 may be biased in one plane to reflect signal 26 such that
 it propagates along the longitudinal axis of the corresponding output FTIR
 bus 10. If first switchplate 70 is biased in one plane to reflect signal
 26 out of FTIR bus 10 at node 80, then second switchplate 70 may be biased
 in two planes to reflect signal 26 such that it propagates along the
 longitudinal axis of the corresponding output FTIR bus 10. Therefore,
 signal 26 propagates along the longitudinal axis of the output FTIR bus 10
 in a direction indicated by either arrow 82 or arrow 84 depending upon
 bias angle 44 of second switchplate 20.
 In another embodiment, reflective surface 42 of a single switchplate 20
 placed in proximal contact with an optical waveguide of an input FTIR bus
 10 is biased in two or more planes. A first configuration of bus matrix 70
 positions a corresponding output FTIR bus 10 along input FTIR bus 10 in
 alignment with the switchplate 20 such that switchplate 20 reflects
 optical signal 26 from interface 78 to node 80 along one plane. In this
 configuration of bus matrix 70, angle 44 of switchplate 20 is biased in a
 first plane and a second plane. Switchplate 20 biased in the first plane
 reflects optical signal 26 at an angle that is less than critical angle of
 refraction 18 of the optical waveguide such that signal 26 exits the input
 FTIR bus 10 at a node 80. The same switchplate 20 biased in the second
 plane further reflects the optical signal 26 at an angle such that signal
 26 enters an optical waveguide of a corresponding output FTIR bus 10 at
 node 80 and propagates along the longitudinal axis of the output FTIR bus
 10 reflecting at angles equal to or greater than critical angle of
 refraction 18 of the optical waveguide.
 A second configuration of bus matrix 70 positions a corresponding output
 FTIR bus 10 along input FTIR bus 10 offset from the switchplate 20 such
 that switchplate 20 reflects optical signal 26 from interface 78 to node
 80 along two planes. In this configuration of bus matrix 70, angle 44 of
 switchplate 20 is biased in two or more planes. Switchplate 20 biased in a
 first plane and a second plane reflects optical signal 26 at an angle that
 is less than critical angle of refraction 18 of the optical waveguide such
 that signal 26 exits the input FTIR bus 10 at node 80. The same
 switchplate further reflects the optical signal at an angle such that
 signal 26 enters an optical waveguide of the corresponding output FTIR bus
 10 at node 80 and propagates along the longitudinal axis of the output
 FTIR bus 10 reflecting at angles equal to or greater than critical angle
 of refraction 18 of the optical waveguide. In this embodiment, therefore,
 a single switchplate 20 biased in two or more planes and placed in
 proximal contact with an optical waveguide of an input FTIR bus 10 may
 communicate optical signal 26 from an input FTIR bus 10 to an output FTIR
 bus 10 at an appropriate node 80 such that optical signal 26 propagates
 along the longitudinal axis of the output FTIR bus 10.
 By activating the appropriate actuators 22 and by placing the appropriate
 switchplates 20 in proximal contact with the appropriate optical
 waveguides, matrix 70 performs enhanced switching, multiplexing, and other
 suitable processing on optical signal 26. Specifically, by placing any
 particular pattern of switchplates 20 in proximal contact with the
 appropriate optical waveguides, matrix 70 generates a desired mapping of
 signals 26 from input FTIR buses 10a-10c to output FTIR buses 10x-10z, or
 vice versa. In one embodiment, an optical signal 26 from any input FTIR
 bus 10 may be switched to any output FTIR bus 10 if the designated output
 FTIR bus 10 is not already propagating another optical signal 26.
 FIGS. 6A and 6B illustrate an optical signal 26 propagating along the
 longitudinal axis of input FTIR bus 10b in a direction indicated by arrow
 72. A switchplate 20 frustrates the total internal reflection of optical
 signal 26 such that it exits FTIR bus 10b, enters output FTIR bus 10y, and
 propagates along the longitudinal axis of FTIR bus 10y in a direction
 indicated by arrow 84. In particular, FIG. 6A illustrates a
 cross-sectional view of FTIR bus matrix 70 taken along lines 6A--6A of
 FIG. 5. FTIR bus matrix 70 includes the optical waveguide 12b of input
 FTIR bus 10b, the optical waveguides 12x-12z of output FTIR buses 10x-10z,
 and switchplates 20 coupled to optical waveguide 12b by actuators 22.
 Optical signal 26 propagates along the longitudinal axis of optical
 waveguide 12b totally internally reflecting at angles equal to or greater
 than critical angle of refraction 18 of optical waveguide 12b each time it
 contacts an interface between material 12 of optical waveguide 12b and
 materials 14 or 16. A selected actuator 22 places an associated
 switchplate 20 into proximal contact with optical waveguide 12b to
 frustrate the total internal reflection of optical signal 26 such that it
 exits optical waveguide 12b of input FTIR bus 10b and enters optical
 waveguide 12y of output FTIR bus 10y at node 80.
 FIG. 6B illustrates a cross-sectional view of FTIR bus matrix 70 taken
 along lines 6B--6B of FIG. 5. FTIR bus matrix 70 includes the optical
 waveguides 12a-12c of input FTIR buses 10a-10c, the optical waveguide 12y
 of output FTIR bus 10y, and switchplates 20 coupled to optical waveguide
 12y by actuators 22. As discussed above, optical signal 26 exits FTIR bus
 10b and enters output FTIR bus 10y at node 80. Actuator 22 places
 switchplate 20 in proximal contact with optical waveguide 12y of output
 FTIR bus 10y. In one embodiment, switchplate 20 of output FTIR bus 10y and
 switchplate 20 of input FTIR bus 10b are placed in proximal contact with
 the appropriate optical waveguides 12 simultaneously to provide a precise
 communication of signal 26 between FTIR buses 10b and 10y. Reflective
 surface 42 of switchplate 20 is at a bias angle 44 with respect to contact
 surface 40 to reflect signal 26 such that it propagates along the
 longitudinal axis of output FTIR bus 10y reflecting at angles equal to or
 greater than critical angle of refraction 18 of optical waveguide 12y. In
 one embodiment, reflective surface 42 of switchplate 20 reflects signal 26
 such that it propagates along the longitudinal axis of output FTIR bus 10y
 in a direction indicated by arrow 84. Although FIG. 6B is illustrated with
 reference to propagating signal 26 along the longitudinal axis of output
 FTIR bus 10y in a direction indicated by arrow 84, reflective surface 42
 of switchplate 20 may have a bias angle 44 sufficient to propagate signal
 26 along the longitudinal axis of output FTIR bus 10y in a direction
 indicated by arrow 82. In a particular embodiment, switchplate 20 is
 dynamically and selectively rotated about an appropriate axis to propagate
 signal 26 in a selected direction indicated by either arrow 82 or 84. Once
 switchplates 20 of input FTIR bus 10b and output FTIR bus 10y are placed
 in proximal contact with the appropriate optical waveguides, FTIR bus
 matrix 70 may communicate optical signal 26 bidirectionally between FTIR
 buses 10b and 10y.
 Although the present invention has been described in several embodiments, a
 myriad of changes, variations, alterations, transformations, and
 modifications may be suggested to one skilled in the art, and it is
 intended that the present invention encompass such changes, variations,
 alternations, transformations, and modifications as falls within the
 spirit and scope of the appended claims.