Abstract:
A logical element including an optical junction coupled to at least two optical inlets and to at least one optical outlet. Incoming light beams of coherent monochromatic light beams and the same uniform frequency are applied to the optical inlets, and their super-positioning is provided as an outgoing light beam(s) via the optical outlet to another logical element or to a light intensity gauge. The light intensity gauge measures light intensity in specific zone(s) of an interference pattern created by the outgoing light beam, dependent on phase shift difference between the components of the incoming light beams, and the measured intensity is correlated with intensity ranges predetermined to conjugate to logical integer values, such as Boolean or other integer numeric values. A multiplicity of logical elements can be installed to provide an optical processor. Parallel use of the same logical element is provided by the simultaneous application of sets of light beams. The sets do not interact with each other by means of differing characteristics, such as different frequencies, or polarizations of the sets. A corresponding method is also provided.

Description:
CROSS-REFERENCE TO RELATED CASE 
   This is a continuation of U.S. patent application Ser. No. 10/008,599, filed on Dec. 3, 2001 now abandoned, the entirety of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to optical signal processing and switching, and more particularly to multi-gate devices for processing optical energy in logical devices, switching, commutation and computing optical signals, light amplification, energy control, optical waveguides communication, data transmission and computer circuitry, including arithmetic and logic units. 
   BACKGROUND OF THE INVENTION 
   Contemporary technology prevalently involves electric currents for the operation of transistors and other electronic devices. The velocity of electric signals through conductors and semi-conductors, namely—the response time of the (semi)-conductor to the input of an electric signal, is bounded by the physical limits of electric currents. A prolonged response time curbs the operational efficiency of the electronic device. For example, the speed of electric current through a conducting medium is about 6,000 km/sec and through a semi-conductor, such as a PN transistor is about 100 km/sec. In a transistor, a small power electronic signal (“base”) is used to control the amplification of a second electronic signal (“collector”), whose output (“emitter”) is thus selectively amplified. A typical transistor includes semiconductor media in which the speed of electrons as information bearers is as mentioned above. A processor typically contains 1 Million to 10 Million transistors. 
   For example, Pentium III® processor manufactured by Intel® is known to include around 7.5 Million transistors. A typical electronic path in a transistor is 0.18 microns, thus a typical path in a processor could extend to 1.5 meters. The conduction of electric current through electronic devices, such as conductors, transistors, resistors, coils and capacitors, encounters inevitable retarding forces that decelerate the electrons and diminish the electric current. These forces lead to the heating of the electronic device (with impractical exceptions such as ‘super-conductors’). The intrinsic heating of transistors, which are condensed by millions in electronic devices such as processors, may lead to damaging overheating. Overheating is avoided by taking different measures. In case of processors, the processing speed is reduced and in case of electronic devices, the capacity of the electronic device is reduced. In all cases, the overheating of the electronic device is avoided in different ways, such as, installing cooling fins, electric fans, operating in a relatively cold environment, and the like). In order to reduce overheating, the electric current has to be limited. Operating at a lower current causes a transistor to operate at a lower switching rate, and thus, in case of a processor, the number of operations per unit time is reduced. For example, current Pentium IV® processors and their equivalents are designed to handle operations in the scale of Gigaflops (“flops” means—floating point operations per second), in a properly cooled environment. The passage of electric currents also requires minimal dimensions of the physical conductor and a minimal energy for the operation thereof, and is also subject to physical manufacturing limits. Minimal energy E is required, for instance, for turning a device on and off, and is given by E=ln2·k·T, wherein ln2 is the natural logarithm of 2, k is Boltzmann&#39;s constant, and T is the temperature of the device in degrees Kelvin. Kazimir&#39;s Effect, wherein electric current is blocked by the pressure exerted by the spontaneous appearance of external elementary particles, also requires minimal sizing of the conducting medium—above 50 nanometers—to avoid such blockage. In addition, a parallel use of an electronic device, namely—the simultaneous operation of a single device for performing multiple operations, is almost impossible due to the mutual interfering of electric currents within the device. 
   Devices known in the prior art involve optical signal manipulation. U.S. Pat. No. 5,093,802 issued to Hait, teaches the use of modulated input beams that are able to produce interference fringes. The interference fringes are separated into constructive interference component regions and destructive interference component regions. Thus, output from individual functions is provided, that results from the interference which occurs in the separated interference-fringe component regions. This provides a logic circuit element, wherein the Boolean value of such a component, which is associated with its brightness, will be a function of values of the input beams. Mask separators with holes, or holograms made up of many subholograms are used to separate fringe component regions, and to direct function interconnecting beams. 
   Another device is disclosed in U.S. Pat. No. 5,793,905 issued to Maier et al., which teaches the switching of two incoming linearly polarized beams having orthogonal polarization. The disclosed invention requires employment of GaAs crystal as an anisotropic, birefringent object, for affecting the polarization of the outgoing light, whose intensity depends strongly on the intensity of one of the incoming beams. Thus the device can operate as an optical equivalent of an electronic device based on transistors. 
   SUMMARY OF THE PRESENT INVENTION 
   It is an object of the present invention to provide a system and a method for performing logical functions with optical light waves while eliminating the necessity of using electronic currents for operating such functions, that overcome the disadvantages of the prior art. 
   In accordance with the present invention, there is thus provided a logical element having an optical junction, at least two optical inlets, coupled with the optical junction, and at least one optical outlet coupled with the optical junction. According to another aspect of the present invention, there is thus provided an optical circuitry incorporating a plurality of optical circuitry elements. The optical circuitry elements include at least one optical logical element. The optical logical element includes an optical junction, at least two optical inlets, coupled with the optical junction, and at least one optical outlet coupled with the optical junction. 
   According to a further aspect of the present invention, there is thus provided an optical device for performing a logical operation. The optical device includes an optical junction, at least two optical inlets for receiving at least two incoming light beams, and at least one optical outlet at which at least one outgoing light beam is emitted. The two incoming light beams are superposed at said optical junction, thereby producing at least one outgoing light beam. 
   In accordance with the present invention, there is also provided a method for performing logical functions using at least one group of light beams. Each group of light beams includes a plurality of light beams, and being defined by at least one property and shares a distinctive characteristic. The method includes the procedure of superposing the plurality of light beams in an optical junction, thereby producing at least one superposed light beam sharing the distinctive characteristic. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: 
       FIG. 1  is a schematic illustration of a system constructed and operative in accordance with a preferred embodiment of the present invention; 
       FIG. 2A  is a graphical illustration of two coherent light beams of equal frequency and the same phase shift, and the result of superposing these two light beams in a Fresnel zone, as known is the art; 
       FIG. 2B  is a graphical illustration of two coherent light beams of equal frequency but phase shift difference of 180 degrees, and the result of superposing these two light beams in a Fresnel zone, as known is the art; 
       FIG. 2C  is a graphical illustration of two coherent light beams of equal frequency and an arbitrary phase shift difference, and the result of superposing these two light beams in a Fresnel zone, as known is the art; 
       FIG. 3  is a schematic illustration of a system, constructed and operative in accordance with another preferred embodiment of the present invention; 
       FIG. 4A  is a schematic illustration of an electro-optic converter (EO), constructed and operative in accordance with a further preferred embodiment of the present invention; 
       FIG. 4B  is a schematic illustration of an opto-electric converter (OE), constructed and operative in accordance with another preferred embodiment of the present invention; 
       FIG. 5  is a schematic illustration of a system using a plurality of junction gates, constructed and operative in accordance with a further preferred embodiment of the present invention; 
       FIG. 6  is a schematic illustration of an optical processor constructed and operative in accordance with another preferred embodiment of the present invention; 
       FIG. 7  is a schematic illustration of a three-dimensional optical processor constructed and operative in accordance with a further preferred embodiment of the present invention; 
       FIG. 8  is a schematic illustration of a system constructed and operative in accordance with another preferred embodiment of the present invention; 
       FIG. 9  is a schematic illustration of a system for performing parallel processing with different polarizations, constructed and operative in accordance with a further preferred embodiment of the present invention; 
       FIG. 10A  is a schematic illustration of a polarization separator, which may be used for the polarization separator of  FIG. 9 , constructed and operative in accordance with another preferred embodiment of the present invention; 
       FIG. 10B  is a schematic illustration of a polarization separator, which may be used as a preferable embodiment for the separator of  FIG. 9 , constructed and operative in accordance with a further preferred embodiment of the present invention; 
       FIG. 11  is a schematic illustration of a system for performing parallel processing with different wavelengths, constructed and operative in accordance with another preferred embodiment of the present invention; 
       FIG. 12A  is a schematic illustration of a wavelength separator, which may be used as a preferable embodiment for the separator of  FIG. 11 , constructed and operative in accordance with a further preferred embodiment of the present invention; 
       FIG. 12B  is a schematic illustration of a wavelength separator, which may be used as another preferable embodiment for the separator of  FIG. 11 , constructed and operative in accordance with another preferred embodiment of the present invention; 
       FIG. 13  is a schematic illustration of an optical circuit portion including an optical inverter, constructed and operative in accordance with a further preferred embodiment of the present invention; 
       FIG. 14  is a schematic illustration of a circuit portion including an optical resistor, constructed and operative in accordance with another preferred embodiment of the present invention; 
       FIG. 15A  is a schematic illustration of an optical resistor, constructed and operative in accordance with a further preferred embodiment of the present invention; 
       FIG. 15B  is a schematic illustration of an optical resistor, constructed and operative in accordance with another preferred embodiment of the present invention; and 
       FIG. 16  is a schematic illustration of a method for operating the system of  FIG. 1 , operative in accordance with a further preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The present invention provides a system and a method for performing logical functions by employing optical light waves, thereby eliminating the use of electrical currents for operating such logical functions. A logical function is performed by superposing two incoming light beams at an optical junction, thereby producing an outgoing light beam. The phases and amplitudes of the incoming light beams define the characteristics of the outgoing light beam. A predetermined logical value—which is a function of the characteristics of the outgoing light beam, is determined when the outgoing light beam is detected. 
   Reference is now made to  FIG. 1 , which is a schematic illustration of an optical device, generally referenced  100 , constructed and operative in accordance with a preferred embodiment of the present invention. Device  100  includes an inlet  1 , an inlet  3  and an outlet  5 , all of which are capable of guiding waves there through. Inlets  1  and  3  and outlet  5  are coupled together to form an optical junction, or an optical gate, in which incoming light beams  7  and  9  are superposed in a common zone—in junction  11 , and emitted as outgoing light beams through outlet  5 . Wavelengths suitable for operation with device  100  are not bounded, except for radiation that is damaging to the physical elements involved. Suitable photon radiation may typically include visible light, infra-red, ultra violet, microwaves and so forth, and is also referenced herein below as “light”, “waves”, “light beams” or “optical frequencies”. 
   However, the present invention is not limited to any specific frequency range, and any electromagnetic beam suitable for guidance can be employed. Hence, conduction through wave-guides or conduits is applicable as long as the interaction of beams with the conveying medium or the sides of the conduit is insignificant. The conveying medium may include optical fiber, fluid (i.e., gaseous or liquid confined by a conduit “piping”), vacuum defined by the conduit geometry, and the like. It will be appreciated by those skilled in the art, that the fading of light in vacuum or in other media such as conventional optical fiber, is almost negligible for the purposes relevant to the present invention. 
   For example, a 633 nm light beam will lose coherence after traveling through 1 meter of a conventional fiber-optic wave-guide. The conduit sides reflect optical waves with a mirror like effect, namely—reflectivity of almost 100%, especially with aluminum coated side walls. The linking of inlets  1  and  3  in junction  11  is practically seamless, as known from the use of fiber-optic, vacuum or gaseous wave-guides. The geometrical acute angle between inlets  1  and  3  also ensures that incoming light beams will not practically “turn” or “leak” from inlet  1  to inlet  3  and vice versa. 
   When a coherent monochromatic light beam  7  encounters another monochromatic coherent light beam  9 , wherein both light beams have the same uniform frequency (wavelength) and polarization, but different phase shifts, the two light beams  7  and  9  will interfere to give a resultant “disturbance” or “interference” light beam  13 . It will be noted that the terms “phase” and “phase shift” are used herein synonymously. The irradiance of light beam  13 , also termed flux density or light intensity at a specific locus, is a function of the phase difference, a phenomenon known as interference. An interference pattern appears, when projected on a crossing surface, as alternately bright and dark concentric rings of varying flux density running perpendicular to the line of propagation of light beam  13 . 
   The central wave front of the light wave at outlet  5  conforms to a ‘Fresnel zone’. The central area of this pattern is of particular interest when such a plane is cut off around its center to check its light intensity. The light intensity can be measured using an optical detector such as a photovoltaic detector, a thermal photodetector, and the like. The device employed for measuring the intensity of the Fresnel zone is hereinafter referred to as a “screen”. 
   Reference is further made to  FIGS. 2A ,  2 B and  2 C.  FIG. 2A  is a graphical illustration of two coherent light beams of equal frequency and the same phase shift, and the result of superposing these two light beams in a Fresnel zone, as known is the art.  FIG. 2B  is a graphical illustration of two coherent light beams of equal frequency but phase shift difference of 180 degrees, and the result of superposing these two light beams in a Fresnel zone, as known is the art.  FIG. 2C  is a graphical illustration of two coherent light beams of equal frequency and an arbitrary phase shift difference, and the result of superposing these two light beams in a Fresnel zone, as known is the art. 
   The intensities of light beams  7  and  9  are substantially equal. Resultant interference light beam  13  is composed of the super-position of light beam  7  with light beam  9 . If both light beams  7  and  9  are of the same phase shift, namely—the phase shift difference is zero, then the resultant light beam  13  will be similar in its coherence and phase shift to light beams  7  and  9 . However, the amplitude of the electromagnetic field measured by the screen in the central Fresnel zone will be substantially equal to twice the amplitude of the electromagnetic field of each light beam, as illustrated in  FIG. 2A . 
   Thus, the intensity measured will be equal to four times the intensity of each incident light beam (the intensity is proportional to the amplitude, squared). If the phase shift difference between the two light beams  7  and  9  is half a cycle, commonly termed as ‘π’ in units of radian, wherein 2π radians define a complete cycle, then the intensity measured by the screen is zero. This phenomenon is known as destructive interference, as illustrated in  FIG. 2B . Other phase shift differences will provide intermediate resultant intensities, e.g., π/2 phase shift difference will yield a measurement with intensity approximately equal to 2 times the intensity of each light beam  7  or  9 , as is illustrated in  FIG. 2C . 
   To achieve the above described Fresnel Zone effect, a uniform polarization and frequency coherent light should be applied with known phase shift difference at inlets  1  and  3 . If the phase shift difference is zero, a bright central Fresnel Zone will appear on screen  15  (confer  FIG. 2A ). If the phase difference is π, a dark central zone will appear on screen  15  ( FIG. 2B ). In general, if the wave functions ψ 1  and ψ 2 , representing light beams  7  and  9 , respectively, are given by:
 
ψ 1   =A   1 ·cos(ω t+ψ   1 ) and ψ 2   =A   2 ·cos(ω t+ψ   2 )  (1)
 
wherein for i=1, 2, A i  is a constant representing the amplitude, and φ i  is the phase shift, then the resultant average wave function ψ of the resultant light beam  13  measured at screen  15  is given by:
 
ψ=√(ψ 1 +ψ 2 ) 2   =√[A   1   2   +A   2   2 +2 A   1   A   2  cos(φ 2 −φ 1 ].  (2)
 
If, for example, A 1 =A 2  and φ 2 −φ 1 =π, then:
 
ψ=√[ A   1   2   +A   1   2 +2 A   1   2  cos(φ 2 −φ 1 )]  (3)
 
But cos(φ 2 −ψ 1 )=cos(π)=(−1). Thus:
 
ψ=√[ A   1   2   +A   1   2 +2 A   1   2 (−1)]=0.  (4)
 
This is equivalent to an “optical-minimum” at the central Fresnel Zone.
 
   The generation of two such light beams with the same amplitude A and the same frequency ω, is possible, for example, by a single source that generates both light beams, and where the phase shift φ is provided by a suitable shifter that retains the frequency and shifts the phase. The use of fibers of different lengths by which the path length determines the number of wavelengths (or cycles) that pass there through, is one such simple shifter. The use of retarding material for the path of one of the light beams or the use of birefringent material that splits the light beams in different paths with different lengths, or retarding material properties are examples of other such shifters. 
   Device  100  of  FIG. 1  can be readily applied as an optical analog of a logical transistor, i.e.: performing a logical function similar to logical electronic devices based on transistors, such as AND, OR, XOR, or NOR gates, disregarding amplification effects of transistors. For example, a destructive interference at outlet  5  may be considered as a binary 0 and a constructive interference as a binary 1 (or vice versa). Accordingly, device  100  may be referred to as an optical gate, junction or transistor. Device  100  can be installed by the hundreds, thousands and even more, in a single device to construct a multiple states system or a processor, in combinations similar to those typical of conventional electronic devices. The difference is the way in which the states are defined, which is optical rather than electrical. 
   The manufacture of a multiplicity of optical junctions like device  100  in a single processor is feasible, by using slices of tapes in which tracks are carved by employing nano-technological principles, or by the use of laser such as an ultra violet hot laser having a beam size of 1 nanometer, for carving a track or a path for the light in the substrate. 
   According to another aspect of the present invention, electronic signals are converted to optical signals before entering the processor of the present invention and the optical signals at the output of the processor are converted back to electronic signals. In this manner, it is possible to incorporate the processor of the present invention with conventional electronic elements, such as communication interface, input/output device, memory modules, network controller, and the like. 
   Reference is now made to  FIGS. 3 ,  4 A and  4 B.  FIG. 3  is a schematic illustration of a system, generally referenced  300 , constructed and operative in accordance with a preferred embodiment of the present invention.  FIG. 4A  is a schematic illustration of an electro-optic converter (EO), generally referenced  320 , constructed in accordance with another preferred embodiment of the present invention.  FIG. 4B  is a schematic illustration of an opto-electric converter (OE), generally referenced  340 , constructed in accordance with a further preferred embodiment of the present invention. 
   With reference to  FIG. 3 , system  300  includes an electro-optic converter  303 , an optical element  307  (which may include an optical gate or an optical processor), and an opto-electric converter  311 . Optical element  307  is coupled to electro-optic converter  303  and to opto-electric converter  311 . Optical element  307  includes one or more components similar to device  100  ( FIG. 1 ). Examples of optical processors are further elaborated herein below with reference to  FIGS. 5 ,  6  and  7 . 
   An input electrical signal  301  enters electro-optic converter  303 . Electro-optic converter  303  converts input electrical signal  301  into an input optical signal  305 , and sends input optical signal  305  to optical element  307 . Optical element  307  receives input optical signal  305 , processes it, and sends an output optical signal  309  to opto-electric converter  311 . Opto-electric converter  311  converts output optical signal  309  into an output electrical signal  313 . 
   With reference to  FIG. 4A , electro-optic converter  320  includes a transistor  323 , conducting wires  325 ,  327 ,  329  and  331 , and a light-emitting diode (LED)  321 . A LED is an electrical element having the property, that a current flowing there through causes it to emit light at an intensity proportional to the current. Conducting wire  329  is coupled to LED  321  and to the emitter (e) of transistor  323 . The collector (c) and base (b) of transistor  323  are coupled to conducting wires  327  and  325 , respectively. LED  321  is further coupled to conducting wire  331 . Conducting wire  331  is grounded (i.e., its potential is referenced zero). The potential at collector (c) of transistor  323  is V cc . An electrical signal passes through conducting wire  325  and is received at the base (b) of transistor  323 . The potential difference between the collector and the base of transistor  323  causes transistor  323  to amplify the signal and send the amplified signal through its emitter (e) to conducting wire  329 . LED  321  receives the amplified signal from conducting wire  329 . The current flowing through LED  321  causes it to emit an optical signal  333  proportional to the amplified electric signal. 
   With reference to  FIG. 4B , opto-electric converter  340  includes a transistor  343 , conducting wires  345 ,  347 ,  349  and  351 , and a photodiode  341 . A photodiode is an electrical element having the property, that the incoming light causes it to release electrons for conduction of electricity, wherein the number of electrons released for conduction is proportional to the intensity of the light. Hence, the resistance of photodiode  341  to electric current is inversely proportional to the intensity of the incoming light. Conducting wire  347  is coupled to photodiode  341  and to the base (b) of transistor  343 . The collector (c) and emitter (e) of transistor  343  are coupled to conducting wires  351  and  349 , respectively. Photodiode  341  is grounded through conducting wire  345 . The potential at collector (c) of transistor  343  is V cc . An optical signal  353  is received at photodiode  341 , causing it to conduct electricity. The potential difference between the two sides of photodiode  341  produces a current (i.e., an electrical signal) proportional to the intensity of optical signal  353 . Transistor  343  amplifies the electrical signal and sends the amplified signal to the emitter (e) of transistor  343 . 
   It is noted that similar electro-optic and opto-electric converters can be used without the use of transistors. However, the use of transistors allows controlling the amplification of the electrical and optical signals. The use of converters such as the exemplary converters illustrated in  FIGS. 4A and 4B  enables the integration of a junction gate into electronic systems. However, it is apparent that a fully optical apparatus—in which all electrical transistors and processors are replaced by equivalent optical devices, reduces and may even eliminate entirely the necessity to use converters. A Personal Computer (PC), other computers, and appliances, or computer integrated apparatus, may be replaced by equivalent optical devices. In particular, for devices that already incorporate optical technologies, such as display monitors, optical communication and switching apparatus, the direct application of the present invention without conversion is apparent. 
   According to another aspect of the present invention, an optical processor is constructed by interconnecting a plurality of optical gates. Incoming light beams enter the optical processor at one end thereof, the optical gates process the incoming light beams and a plurality of outgoing light beams exit the optical processor. A plurality of detectors detects the outgoing light beams, thereby providing the result of the processing procedure. 
   Reference is now made to  FIGS. 5 ,  6  and  7 .  FIG. 5  is a schematic illustration of a system, generally referenced  400 , using a plurality of junction gates, constructed and operative in accordance with a preferred embodiment of the present invention.  FIG. 6  is a schematic illustration of an optical processor, generally referenced  450 , constructed and operative in accordance with another preferred embodiment of the present invention.  FIG. 7  is a schematic illustration of a three-dimensional optical processor, generally referenced  470 , constructed and operative in accordance with a further preferred embodiment of the present invention. 
   With reference to  FIG. 5 , system  400  includes junction devices  401 ,  411 ,  421  and  431 , and a screen  439 . Device  401  includes inlets  403  and  405  and an outlet  407 . Device  411  includes inlets  413  and  415  and an outlet  417 . Device  421  includes inlets  423  and  425  and an outlet  427 . Device  431  includes inlets  433  and  435  and an outlet  437 . Outlet  407  of device  401  is coupled to inlet  423  of device  421 . Outlet  417  of device  411  is coupled to inlet  425  of device  421 . Outlet  427  of device  421  is coupled to inlet  433  of device  431 . Outlet  437  of device  431  is coupled to screen  439 . System  400  illustrates the incorporation of a plurality of devices in an optical circuit. The output light beam in outlet  437  of device  431  is the superposition of the input light beams in inlets  403 ,  405 ,  413 ,  415  and  435 . Thus, the signal which exits outlet  437  and enters screen  439  is a function of the signals which enter inlets  403 ,  405 ,  413 ,  415  and  435 . Accordingly, system  400  can represent a logical function with multiple inputs and a single output. 
   With reference to  FIG. 6 , processor  450  includes processor inlets  451   1 ,  451   2 ,  451   3 ,  451   4 ,  451   5  and  451   6 , junction gates  453 ,  455 ,  457 ,  459 ,  461  and  463 , and processor outlets  465   1 ,  465   2  and  465   3 . Each of the junction gates  453 ,  455 ,  457 ,  459 ,  461  and  463 , includes two gate inlets and one gate outlet. Some of the inlets and outlets of processor  450  and of the junction gates  453 ,  455 ,  457 ,  459 ,  461  and  463 , are interconnected by conveying media such as optical fibers, and the like. Processor inlet  451 , is coupled to the first inlet of junction gate  453 . Processor inlet  451   2  is coupled to the second inlet of junction gate  453  and to the first inlet of junction gate  455 . Processor inlet  451   3  is coupled to the second inlet of junction gate  455 . Processor inlet  451   4  is coupled to the second inlet of junction gate  457 . Processor inlet  451   5  is coupled to the second inlet of junction gate  461 . Processor inlet  451   6  is coupled to the second inlet of junction gate  463 . The outlet of junction gate  453  is coupled to processor outlet  465   1  and to the first inlet of junction gate  459 . The outlet of junction gate  455  is coupled to the first inlet of junction gate  457 . The outlet of junction gate  457  is coupled to the second inlet of junction gate  459 . The outlet of junction gate  459  is coupled to the first inlet of junction gate  461 . The outlet of junction gate  461  is coupled to processor outlet  465   2  and to the first inlet of junction gate  463 . The outlet of junction gate  463  is coupled to processor outlet  465   3 . Optical processor  450  receives up to six optical signals at processor inlets  451   1 ,  451   2 ,  451   3 ,  451   4 ,  451   5  and  451   6 . The optical signals pass through some of the junction gates in processor  450 , according to the couplings described hereinabove, and are superposed accordingly. The processed signals are sent through processor outlets  465   1 ,  465   2  and  465   3 . The signals at processor outlets  465   1 ,  465   2  and  465   3  depend on the intensities and the phase shifts of the signals which enter processor inlets  451   1 ,  451   2 ,  451   3 ,  451   4 ,  451   5  and  451   6 . 
   With reference to  FIG. 7 , three-dimensional processor  470  includes top layer  471   1 , middle layer  471   2  and bottom layer  471   3 . Each of the top layer  471   1 , middle layer  471   2  and bottom layer  471   3  is similar to optical processor  450  ( FIG. 6 ), although the configuration of the gates thereof and the interconnections between the gates, is not restricted to the example illustrated in  FIG. 6 . Top layer  471   1  includes contact points  473  and  475 . Middle layer  471   2  includes contact points  477 ,  479  and  481 . Bottom layer  471   3  includes contact points  483 ,  485 ,  487  and  489 . Three-dimensional processor  470  may further include additional layers below bottom layer  471   3  (denoted by dots below bottom layer  471   3 ) or above top layer  471   1 . Some of the contact points of the different layers are interconnected by conveying media such as optical fibers, and the like. Contact point  477  is coupled to contact point  483 . Contact point  479  is coupled to contact point  485 . Contact point  473  is coupled to contact point  487 . Contact point  481  is coupled to contact point  475  and to contact point  489 . The arrows on the connection lines in  FIG. 7  illustrate a possible direction of flow of light. According to the example set forth in  FIG. 7 , light flows from contact points  483 ,  479  and  487  to contact points  477 ,  485  and  473 , respectively, and from contact point  481  to contact points  475  and  489 . It is noted, however, that the same three-dimensional processor can be used with different directions of flow. 
   According to another aspect of the present invention, an optical system includes a plurality of inlets and an outlet. Incoming light beams enter the optical system through each of the inlets, and an outgoing light beam which is a superposition of the incoming light beams exits through the outlet of the optical system. A detector located at the outlet, detects the outgoing light beam and produces a logical signal according to the properties of the outgoing light beam. 
   Reference is now made to  FIG. 8 , which is a schematic illustration of a system, generally referenced  490 , constructed and operative in accordance with a further preferred embodiment of the present invention. System  490  includes a first inlet  491 , a second inlet  493 , a third inlet  495 , a fourth inlet  497 , and an outlet  498 . System  490  operates in a manner similar to system  100  ( FIG. 1 ), except that system  490  has four inlets rather than two. The light beams which enter inlets  491 ,  493 ,  495  and  497  are superimposed at outlet  498 . A measuring device such as screen  499  may be connected to outlet  498 , directly or indirectly, whereby the superimposed light beam at outlet  498  eventually strikes screen  499 . The measurement by screen  499  at the central Fresnel zone depends on the intensities and the relative phase-shift of the light beams which enter inlets  491 ,  493 ,  495  and  497 . For example, if the light beams are of the same polarization, frequency, amplitude and phase shift (i.e. the phase shift difference among all the light beams is zero), then the amplitude of the superimposed light beam measured by screen  499  at outlet  498 , is four times the amplitude of the light beam at each of the inlets  491 ,  493 ,  495  and  497 . Furthermore, the intensity measured by screen  499  at outlet  498 , is sixteen times the intensity of the light beam at each of the inlets  491 ,  493 ,  495  and  497  (i.e., the total intensity equals accumulation of four “amplitudes”, all squared). If, however, two of the light beams are out-of-phase compared to the other two (π phase shift difference), then the measured intensity is zero. If three of the light beams are in phase but one of the light beams is “zero” (i.e., the beam has zero intensity or it is composed of two equal components in antiphase), then the resulting amplitude is 3 times the amplitudes of the incoming light beams and the intensity at the outlet is 9 times their intensities. Moreover, if the amplitude of a light beam at an inlet is different from the amplitude of other light beams at other inlets, then the amplitude of the light beam at the outlet is substantially equal to the sum or the difference between the amplitudes of these two light beams, if these two light beams are in-phase or out-of-phase, respectively. System  490  can be used to perform non-Boolean operations. For example, if screen  499  (or other measuring device) distinguishes between different values of a measured intensity, then system  490  can be used as an adding machine for adding together four numbers. If screen  499  does not distinguish between different values of the measured intensity, then the non-Boolean results (i.e., values of the amplitude which may take on more than two different values) can still be used in intermediate processing procedures. For example, system  490  can be used for determining whether the sum of a plurality of input numbers exceeds a certain threshold. System  490  may also be used as a Boolean logic gate, which is relatively simple to implement in comparison to devices prevalent in conventional electronics. For example, the intensities, frequencies and polarizations of the input light beams are substantially equal, and the light beams are in phase (or in antiphase with each other). Furthermore, screen  499  does not distinguish between different levels of intensities, and the threshold for distinguishing between “one” and “zero” is 10 times the input light beam intensities. In this case, the result will be a Boolean “one” only if the four light beams are in phase. Thus, system  490  can be used as a Boolean AND gate with four input channels. Non-Boolean algebra may be employed with system  490  as well as with analogous systems having a different, N number, of input channels, as long as the output light beam contains N different modes that can be detected by screen  499 . 
   According to another aspect of the present invention, there is thus provided a method and a system for performing multiple logical or switching actions in parallel. This aspect applies with further significance to parallel processing in a single processor. For the sake of simplifying this example, a processor is considered a device which includes a plurality of simple optical gates or junctions, such as those described herein above in connection with  FIGS. 1 and 8 . This allows increasing the power of an optical gate, junction or a processor, thereby allowing manifold increase in computation power. 
   One example of this aspect of the invention, concerns an alternative parallel-use technique that involves different polarizations with the same junction gate or processor. Two light beams which are linearly polarized in orthogonal directions can be used in the same junction gate without interfering with each other. In the description that follows, light which is linearly polarized in the plane of the drawing shall be referred to as vertically polarized light, and light which is linearly polarized perpendicular to the plane of the page shall be referred to as horizontally polarized light. In  FIGS. 9 ,  10 A and  10 B, described herein below, dots indicate horizontally polarized light and arrows indicate vertically polarized light. 
   According to another aspect of the present invention, a polarization separator is coupled to the outlet of a junction gate. The polarization separator emits two outgoing light beams of two different polarizations, when two incoming light beams each polarized at both of these polarizations, enter the junction gate through each of the two inlets of the junction gate. 
   Reference is now made to  FIG. 9 , which is a schematic illustration of a system, generally referenced  500 , for performing parallel processing with different polarizations, constructed and operative in accordance with a preferred embodiment of the present invention. System  500  includes a junction gate  501 , a polarization separator  509 , a first output channel  511 , and a second output channel  513 . A first screen  515  and a second screen  517  represent intensity measuring devices for performing logical operations, in analogy to screen  15  of  FIG. 1 . Junction gate  501  includes a first gate inlet  503 , a second gate inlet  505 , and a gate outlet  507 . Polarization separator  509  is coupled to gate outlet  507  and to output channels  511  and  513 . Output channels  511  and  513  are coupled to screens  515  and  517 , respectively. Incoming light beams  519  and  521  simultaneously enter gate inlets  503  and  505 , respectively. Light beams  519  and  521  are each composed of two orthogonal polarization direction represented by a “horizontally” polarized component and a “vertically” polarized component. Light beams  519  and  521  are superimposed in gate outlet  507  to produce an interference light beam  523 . Interference light beam  523  enters gate  507  as input to polarization separator  509 . Polarization separator  509  separates the components of the interference light beam  523 , whose polarizations are orthogonal. Accordingly, polarization separator  509  sends a horizontally polarized light beam  525  to first output channel  511 , and a vertically polarized light beam  527  to second output channel  513 . Light beams  525  and  527  are received at screens  515  and  517 , respectively for performing logical operation in analogy to operations described with reference to  FIG. 1 . Thus, the horizontally polarized signals and the vertically polarized signals are each processed without interfering with each other. It will be noted that a multiplicity of gate inlets may be employed, such as in analogy to the four gates described in reference to  FIG. 8 , and that the embodiment illustrated in  FIG. 9  is reduced to two gate inlets  503  and  505  for the sake of simplicity of description. 
   Reference is now made to  FIG. 10A , which is a schematic illustration of a polarization separator, generally referenced  530 , constructed and operative in accordance with a further preferred embodiment of the present invention. Polarization separator  530  may be used for polarization separator  509  in  FIG. 9 . Polarization separator  530  includes a birefringent material  531 . An incoming light beam  533  is received at one side of birefringent material  531 . The plane of incidence of light beam  533  lies on the plane of the drawing. The optical axis  535  of birefringent material  531  also lies on the plane of the drawing. Light-beam  533  is composed of horizontally and vertically polarized components. Due to the difference in the index of refraction of birefringent material  531  for horizontally and vertically polarized light, light beam  533  is split in birefringent material  531  into a first light beam  537  containing the vertically polarized component of light beam  531  in the plane of the drawing (also known as the “e”-ray), and a second light beam  539  containing the horizontally polarized component of light beam  531  in perpendicular to the plane of the drawing (also known as the “o”-ray). Light beams  537  and  539  travel in slightly different directions in birefringent material  531 , and exit birefringent material  531  at different locations. This phenomenon is known as double refraction. With reference to  FIG. 9 , system  530  directs light beams  537  and  539  (referenced  527  and  525  in  FIG. 9 ) to output channels  511  and  513 , respectively. Thus, the horizontally and vertically polarized components of light beam  533  (referenced  523  in  FIG. 9 ) are separated and can be processed separately. 
   According to another aspect of the present invention, two polarizers whose orientation of polarization is substantially 90 degrees apart, receive light beams from a beam splitter. Each polarizer emits an outgoing light beam in a single plane of polarization and filtering other polarizations, when an incoming light beam polarized at two different polarizations (or more polarizations), enters the beam splitter. Two such polarizers for selectively directing polarized light at a first plane and directing another polarized light at another plane normal to the first plane, may be employed in different times or locations to provide two polarized beams of light at two different polarizations. 
   Reference is now made to  FIG. 10B , which is a schematic illustration of a polarization separator, generally referenced  550 , constructed and operative in accordance with yet another preferred embodiment of the present invention. Polarization separator  550  may be used for polarization separator  509  in  FIG. 9 . Polarization separator  550  includes a beam splitter  551 , a first polarizer  553  and a second polarizer  555 . An incoming light beam  557  is received at beam splitter  551 . Incoming light beam  557  is composed of horizontally polarized components and vertically polarized components. Beam splitter  551  splits incoming light beam  557  into a first light beam  559  and a second light beam  561 . The characteristics of light beams  559  and  561  is substantially the same as the characteristics of incoming light beam  557 , however the intensities of light beams  559  and  561  are less than the intensity of incoming light beam  557 . This is so, because the sum of the intensities of light beams  559  and  561  is substantially equal to the intensity of incoming light beam  557 . Beam splitter  551  directs light beams  559  and  561  to first polarizer  553  and to second polarizer  555 , respectively. The orientation of polarization of first polarizer  553  is substantially the same as the orientation of the horizontal component of incoming light beam  557 . The orientation of polarization of second polarizer  555  is substantially the same as the orientation of the vertical component of incoming light beam  557 . Thus, first polarizer  553  blocks the vertical component of incoming light beam  557  and second polarizer  555  blocks the horizontal component of incoming light beam  557 . A light beam  563  which exits first polarizer  553  is polarized with the horizontal component of incoming light beam  557  and a light beam  565  which exits second polarizer  555  is polarized with the vertical component of incoming light beam  557 . 
   With reference also to  FIG. 9 , polarization separator  550  directs light beams  563  and  565  (referenced  525  and  527  in  FIG. 9 ) to output channels  511  and  515 , respectively. Thus, the horizontally and vertically polarized components of light beam  557  (referenced  523  in  FIG. 9 ) are separated and may be processed separately. It is noted that polarization separator  550  reduces the intensity of each polarized component. Alternatively, a light beam of different wavelengths can be separated to different light beams, each at one of these wavelengths. This concept facilitates the use of a processor for parallel operations. The wavelengths can be sufficiently spaced apart, in order to avoid interference there between, thus allowing simultaneous use of the same medium for multiple switching or processing. 
   According to another aspect of the present invention, a wavelength separator is coupled to the outlet of an optical device, such as a junction, a gate or other optical element as shown with reference to  FIGS. 1 ,  3 ,  5 – 8 , and the like. The wavelength separator emits a plurality of outgoing light beams at different wavelengths, when two (or more) incoming light beams, each composed of a plurality of wavelengths, enter the optical element through the inlets thereof. 
   Reference is now made to  FIG. 11 , which is a schematic illustration of a system, generally referenced  600 , for performing parallel processing with different wavelengths constructed and operative in accordance with another aspect of the present invention. System  600  includes a junction gate  601 , a wavelength separator  609 , a plurality of N output channels  611   1 ,  611   2  and  611   N . Junction gate  601  includes a plurality of L inlets  603   1 ,  603   2  and  603   L  and an outlet  607 . A plurality of screens  613   1 ,  613   2 , and  613   N  or other measuring devices are associated to output channels  611   1 ,  611   2  and  611   N , respectively. Wavelength separator  609  is coupled to outlet  607  and to output channels  611   1 ,  611   2  and  611   N . Incoming light beams  615   1 ,  615   2  and  615   L  simultaneously enter inlets  603   1 ,  603   2  and  603   L , respectively. Incoming light beams  615   1 ,  615   2  and  615   L  are each composed of a plurality of N components at wavelengths λ 1 , λ 2  and λ N . It is noted that “L” and “N” may be any natural numbers and that correlation between N and L is call for. It is further noted that the phase shift or the intensity of a component of incoming light beam  615   i  (i=1, 2, . . . , L) at one wavelength λ j  (j=1, 2, . . . , N), is not necessarily equal to the phase shift and the intensity of another component of the same incoming light beam  615   i , at a different wavelength λ k  (k=1, 2, . . . , N). However, all components of the same wavelength λ j  (j=1, 2, . . . , N) in all incoming beams  615   1 ,  615   2  until  615   L  substantially have the same intensities and phase or anti-phase shifts as required in a single frequency embodiments such as of  FIG. 1  or  FIG. 8 . A resultant superposed light beam  619  is produced at outlet  607 . Superposedlight beam  619  is the superposition of incoming light beams  615   1 ,  615   2  and  615   L . Hence, superposedlight beam  619  is composed of components at wavelengths λ 1 , λ 2  and λ N . Superposedlight beam  619  enters wavelength separator  609 . Wavelength separator  609  separates superposed light beam  619  to outgoing light beams  621   1 ,  621   2  and  621   N , at wavelengths λ 1 , λ 2  and λ N , respectively. An outgoing light beam  621   i  (i=1, 2, . . . , N) groups together components of the same corresponding wavelength λ i , which components originate from all the incoming light beams  615   1 ,  615   2  and  615   L . In agreements with the terminology herein, all the L components with the same wavelength λ i  are said to belong to the same group “i” of light beams. Wavelength separator  609  directs outgoing light beams  621   1 ,  621   2  and  621   N  to output channels  611   1 ,  611   2  and  611   N , respectively. Screens  613   1 ,  613   2  and  613   N  receive light beams  621   1 ,  621   2  and  621   N , respectively, from output channels  611   1 ,  611   2  and  611   N , respectively. Screens  613   1 ,  613   2  and  613   N  can detect the properties of light beams  621   1 ,  621   2  and  621   N , namely—amplitudes and phase shifts, in analogy to the description in reference to  FIG. 1 . It is noted that separation of wavelengths facilitates parallel processing, without interaction among the different-wavelength components. This is subject to transfer of energy or “quark” from “hot” photons to “cold” photons which can distort the signal (for example, infra red laser is 3 degrees Kelvin hotter than Na laser). No signal distortion is expected to occur at similar wavelengths. Examples of wavelength separators include prisms, splitters, filters, and the like. 
   Reference is now made to  FIG. 12A , which is a schematic illustration of a wavelength separator, generally referenced  650 , constructed and operative in accordance with a further preferred embodiment of the present invention. Wavelength separator  650  may be used as a preferable embodiment for separator  609  in  FIG. 11 . Wavelength separator  650  includes a dispersive prism  651 . An incoming light beam  653  composed of a plurality of components at wavelengths λ 1 , λ 2  and λ N , enters dispersive prism  651 . Due to dispersion of the light wave in dispersive prism  651 , different components of incoming light beam  653  travel at different speeds within dispersive prism  651 . Hence, different components of incoming light beam  653  at different wavelengths, exit dispersive prism  651  in different directions. Thus, dispersive prism  651  splits oncoming light beam  653  to a plurality of outgoing light beams  655   1 ,  655   2 , and  655   N . Outgoing light beams  655   1 ,  655   2 , and  655   N  are at wavelengths of λ 1 , λ 2  and λ N , respectively. 
   According to another aspect of the present invention, a plurality of different wavelength filters receives light beams from a beam splitter. Each wavelength filter emits an outgoing light beam at a specific wavelength and blocks other wavelengths, when an incoming light beam composed of different wavelengths enters the beam splitter. 
   Reference is further made to  FIG. 12B , which is a schematic illustration of a wavelength separator, generally referenced  680 , constructed and operative in accordance with another preferred embodiment of the present invention. Wavelength separator  680  may be used as a preferable embodiment for separator  609  in  FIG. 11 . Wavelength separator  680  includes a beam splitter  687  and a plurality of wavelength filters  689   1 ,  689   2  and  689   N . Each of wavelength filters  689   1 ,  689   2  and  689   N  is a device which emits an outgoing light beam at a selected wavelength, when an incoming light beam composed of different wavelengths, enters a wavelength filter. Beam splitter  687  receives an incoming light beam  681 . Incoming light beam  681  is composed of a plurality of components at wavelengths λ 1 , λ 2  and λ N . Beam splitter  687  splits incoming light beam  681  to a plurality of light beams  683   1 ,  683   2  and  683   N . The splitting is equivalent to apportioning of light beam  681  into N Light beams and channeling each of so apportioned light beam  683   i  (i=1, 2, . . . N) into N different direction. 683  The characteristics of light beams  683   1 ,  683   2  and  683   N  are substantially the same as the characteristics of incoming light beam  681 . However, the intensities of each of light beams  683   1 ,  683   2  and  683   N  and even the sum of their intensities is equal or less than the intensity of incoming light beam  681 , (unless some intensity amplification is applied). Beam splitter  687  directs light beams  683   1 ,  683   2  and  683   N  to wavelength filters  689   1 ,  689   2  and  689   N , respectively. Wavelength filters  689   1 ,  689   2  and  689   N  emit outgoing light beams  685   1 ,  685   2  and  685   N , respectively, at wavelengths λ 1 , λ 2  and λ N , respectively. 
   It is noted that light sources suitable for application with the present invention are readily available. This is true for an optical system which may well include a plurality of optical elements, gates, junctions, constructed according to the present invention. Different light sources can be used together with a processor constructed according to the present invention, such as micro-lasers, masers—currently used in conventional CD writers or CD-ROM appliances, nano-lasers, hot diode lasers, natural sun light or other ambient light, and the like. The incoming light beam can enter a complex device such as an optical processor through a single inlet and directed to different regions in the processor or from several sources that provide light to key locations in the processor, using suitable filter, that filters out all wavelengths except those to be used. It is furthermore noted that in addition to optical transistors, other optical devices which operate similar to electronic devices, such as diodes, coils, capacitors, inverters, resistors, and the like, can be constructed according to the present invention. 
   According to another aspect of the present invention, a phase shifter is coupled to an inlet of a junction gate. The phase shifter shifts the phase of an incoming light beam entering the inlet, relative to the phase of another incoming light beam which enters the junction gate through another inlet of the junction gate. 
   Reference is now made to  FIG. 13 , which is a schematic illustration of an optical circuit portion, generally referenced  700 , constructed and operative in accordance with a further preferred embodiment of the present invention. Optical circuit portion  700  includes a junction gate  701  and a phase shifter  703 . One of the inlets of junction gate  701  is coupled to phase shifter  703 . Phase shifter  703  is a device which emits an outgoing light beam with a phase which is shifted relative to the phase of an incoming light beam entering phase shifter  703 . Phase shifter  703  is a light conveying medium, of a length different than the length of a reference conveying medium coupled to inlet  705  of junction gate  701 . Alternatively, phase shifter  703  is a conveying medium of a length substantially equal to the length of the reference conveying medium, but made of a material different from the material of the reference conveying medium, herein below referred to as “reference material”. It is noted that the types of phase shifters described herein above is not exhaustive and that phase shifter  703  can be constructed according to other concepts. If the index of refraction of the material of phase shifter  703  is different from that of the reference material, then a light beam travels through phase shifter  703 , at a speed different than the speed of another light beam which travels through the reference conveying medium. Thus phase shifter acquires different phase shift when reaching gate  701 . It is noted that optical circuit portion  700  may further include additional junction gates, fibers, other optical or non-optical devices, a combination thereof, and the like. Phase shifter  703  may be constructed so that light traveling there through acquires a phase shift of π. Hence, phase shifter  703  may operate as an optical inverter, or a logical NOT gate. 
   According to another aspect of the present invention, an optical resistor is coupled to a junction outlet of a junction gate. The optical resistor emits an outgoing light beam of an intensity that is lower than that of a resultant light beam which is a superposition of two incoming light beams entering the junction gate through each of the two inlets of the junction gate. 
   Reference is now made to  FIG. 14 , which is a schematic illustration of an optical circuit portion, generally referenced  750 , constructed and operative in accordance with another preferred embodiment of the present invention. Optical circuit portion  750  includes a junction gate  751  and an optical resistor  753 . Junction gate  751  includes junction inlets  755  and  757  and a junction outlet  759 . Junction outlet  759  is coupled to optical resistor  753 . Light beams  761  and  763  enter junction inlets  755  and  757 , respectively. Light beams  761  and  763  are superposed at junction outlet  759 , as described herein above in connection with  FIG. 1 , thereby producing a resultant light beam  765 . Resultant light beam  765  enters optical resistor  753  and optical resistor  753  emits an outgoing light beam  767 . The frequency spectrum, polarization components and phase shift components of light beams  765  and  767  are identical. However, light beam  767  has a lower intensity than light beam  765 . The intensity of light beam  767  may be proportional to the intensity of light beam  765  (i.e., the intensity of light beam  767  may be equal to a predetermined fraction of the intensity of light beam  765 ). Alternatively, optical resistor  753  may limit the intensity of light beam  767  to a predetermined cut-off value. For example, if incoming light beams  761  and  763  have an equal intensity I, then the intensity of superposed light beam  765  is 2I. If optical resistor  753  reduces the intensity of light beam  765  by 50%, then the intensity of light beam  767  is also I. This may be beneficial since light beam  767  has the same intensity as light beams  761  and  763 , and can thus be used in the same way as light beams  761  and  763 , for devices whose performance is affected by or is sensitive to light intensity. 
   Reference is now made to  FIGS. 15A and 15B .  FIG. 15A  is a schematic illustration of an optical resistor, generally referenced  800 , constructed and operative in accordance with a further aspect of the present invention.  FIG. 15B  is a schematic illustration of another optical resistor, generally referenced  850 , constructed and operative in accordance with another aspect of the present invention. 
   With reference to  FIG. 15A , optical resistor  800  includes an inlet  801 , an outlet  803 , and an absorbent material  805 . A light beam  807  enters inlet  801 . Light beam  807  passes through absorbing material  805 . Absorbent material  805  absorbs a portion of light beam  807 . Optical resistor  800  emits a light beam  809  through outlet  803 . The frequency spectrum, polarization components and phase-shift components are identical for light beam  807  and  809 . However, light beam  809  has a lower intensity, since a portion of the intensity is absorbed by absorbent material  805 . It will be noted that absorbent material  805  is heated by the absorption of light, and that if such heating is significant, especially in devices that include a multiplicity of such resistors, it may require the cooling of resistor  800  or its neighboring elements. 
   With reference to  FIG. 15B , optical resistor  850  includes an inlet  851 , a first outlet  853 , and a second outlet  855 . A light beam  857  enters inlet  851 . Light beam  857  splits between the two outlets  853  and  855 . Light beam  857  is partially emitted through outlet  853  as a light beam  859 , and partially through outlet  855  as a light beam  861 . Thus, a portion of the intensity of light beam  857  is referenced to outlet  855  and is deprived from light beam  859 . The frequency spectrum, polarization components and phase shift components are substantially identical for light beams  857 ,  859  and  861 . However, the intensity of light beam  859  (as well as light beam  861 ) is lower than the intensity of light beam  857 , since a portion of the intensity is referenced to outlet  855 . Light beam  861  may be channeled to a “drainage”, in which part or all of such excessive light is collected from similar resistors or other excessive light sources. Thereby, such excessive light is eventually removed without producing significant heating. For example, optical conveyers may channel all drained light to a light emitter that emits the light toward a non damaging direction, such as the surrounding space. It will be noted that light beam  861  is not necessarily excessive and may be used for purposes similar to those for which light beam  859  is used, or other purposes. 
   Reference is now made to  FIG. 16 , which is a schematic illustration of a method for operating system  100  of  FIG. 1 , operative in accordance with another preferred embodiment of the present invention. In procedure  900 , a respective logical values is determined for each light beam of a group of light beams. Usually, the logical value is determined in pursuance of the properties of the light beam, such as phase shift or amplitude. For example, with reference to  FIG. 1 , assuming that light beams  7  and  9  are in anti-phase, logical values of “0” and “1” may be determined for light beams  7  and  9 , respectively. It is noted that the choice of the first logical value, (i.e., for light beam  7  in this case) depends on the predetermined system definitions, and that the second logical value (i.e., for light beam  9 ) depends on the phase shift difference between light beams  7  and  9 . 
   In procedure  902 , a group of light beams is produced from a light source (or a plurality of light sources). In the example set forth in  FIG. 1 , light beams  7  and  9  are produced from an external light source (not shown). In case of parallel processing, a plurality of groups of light beams are produced, each group with a distinctive characteristic such as a specific frequency or a specific polarity, which is common to the group but distinguishable with respect to other groups. In the example set forth in  FIG. 9 , two groups of light are produced. A first group has a first polarity direction and a second group has a second polarity direction which is orthogonal to the first polarity direction. In the example set forth in  FIG. 11 , N groups of light beams are applied through L incoming light beams. Each group “i” (i=1, 2, . . . N) of light beams distinctively shares a common wavelength λ i , that reach junction gate  601  in L components. Each component “j” (j=1, 2, . . . L) is a component of an incoming light beam  615   j . 
   In procedure  904 , a group of light beams is produced in response to electrical signals. In the example set forth in  FIG. 4A , optical signal  333  is produced in response to electrical signal  325 . It will be noted that procedure  904  is optional—it is employed only where association to electric circuitry is required. 
   In procedure  906 , the group of light beams is superposed in an optical junction, thereby producing a superposed light beam. In the example set forth in  FIG. 1 , light beam  13  is produced from superposing light beams  7  and  9 . In the example set forth in  FIG. 11 , light beam  619  is produced from superposing light beams  615   1 ,  615   2  and  615   L . 
   In procedure  908 , the superposed light beam is separated into components respective of the groups of light beams. It is noted that this procedure is applied only in cases where at least two groups of light beams are superposed in the optical junction gate. It is further noted that after separation, light beams of the same group are superposed together, while light beams from different groups are not superposed together. The characteristic common to each group but distinct in respect to other groups is used to separate between the groups. In the example set forth in  FIG. 11 , the N components of superposed light beam  619  originate from L light beams  615   1 ,  615   2 , and  615   L , which are then separated into N light beams  621   1 ,  621   2 , and  621   N , —each of which has a specific wavelength λ i , which is distinctively respective of one group of light beams only. In the example set forth in  FIG. 9 , the components of superposed light beam  523  are separated into outgoing light beams  525  and  527 , wherein light beam  525  is polarized in a direction normal to that of light beam  527 . In the example set forth in  FIG. 11 , the components of superposed light beam  619  are separated into N outgoing light beams  621   i , each such light beam has a distinctive wavelength λ i . 
   In procedure  910 , properties of the superposed light beam are detected. In the example set forth in  FIG. 1 , screen  15  is used to determine whether the components of light beam  13  are in phase, anti-phase or out of phase. The amplitude of the components can be used as an additional or an alternative property. 
   In procedure  912 , the logical values of the superposed light beam are determined from the detected properties thereof. For example, with reference to  FIG. 1 , assuming that the components of light beam  13  are identified in anti-phase at screen  15 , thus determining a logical value of “0” for light beam  13 . 
   In procedure  914 , an electrical signal is produced in response to the detected properties of the superposed light beam. This can be also in response or in correlation to the logical values determined in procedure  912 . With reference to  FIG. 3 , electrical signal  313  is produced in response to optical signal  309 . It will be noted that procedure  914  is optional—it is employed only where association to electric circuitry is required. 
   It will be appreciated by persons skilled in the art, that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims, which follow.