All optical decoding systems for optical encoded data symbols Number:7,130,539 from the United States Patent and Trademark Office (PTO) owispatent

Title: All optical decoding systems for optical encoded data symbols

Abstract: The present invention provides an optical system for decoding, switching, demultiplexing, and routing of optical encoded data symbols, including: a plurality of optical paths having first and second terminals; a splitting mechanism for directing the encoded data symbols to each of the first terminals; a plurality of decoding devices for producing decoded signals in response to the encoded data symbols; and each of the optical paths includes, between the first and second terminals, at least one of the decoding devices to produce one of the decoded signals at one of the second terminals in response to one of the encoded data symbols.

Patent Number: 7,130,539 Issued on 10/31/2006 to Shahar,   et al.

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Inventors:	Shahar; Arie (Rye Brook, NY), Halberthal; Eldan (Rye Brook, NY)
Assignee:	Main Street Ventures, LLC (White Plains, NY)
Appl. No.:	10/640,018
Filed:	August 14, 2003

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Current U.S. Class:	398/46 ; 398/152; 398/166; 398/183; 398/212; 398/214; 398/57; 398/75
Current International Class:	H04J 14/00 (20060101); H04B 10/00 (20060101); H04B 10/04 (20060101); H04B 10/06 (20060101); H04J 14/02 (20060101)
Field of Search:	398/47,49,54,57,75,77,78,99,152,166,183,184,188,191,212,214

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References Cited [Referenced By]

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U.S. Patent Documents

	5900957		May 1999		Van Der Tol
	6057950		May 2000		Bergano
	6433904		August 2002		Swanson et al.
	6493350		December 2002		Hojo et al.
	6711313		March 2004		Takiguchi et al.
	2002/0167693		November 2002		Vrazel et al.

Primary Examiner: Singh; Dalzid
Attorney, Agent or Firm: Pearl Cohen Zedek Latzer, LLP

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Parent Case Text

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REFERENCE TO OTHER APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/405,697, filed Aug. 22, 2002, entitled "Streaming signal control system for digital communications", and of U.S. Provisional Patent Application Ser. No. 60/420,112, filed Oct. 21, 2002, entitled "Streaming signal control system for digital communications".

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Claims

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We claim:

1. An all-optical passive system for decoding, switching, demultiplexing, and routing of optical encoded data signals, the system comprising: a plurality of optical paths having first and second terminals; a splitting mechanism for directing the optical encoded data signals to each of said first terminals; and a plurality of decoding devices for producing optical decoded signals at said second terminals in response to said optical encoded data signals, wherein each of said optical paths includes, between said first and second terminals, at least one of said decoding devices, wherein each of said decoding devices includes: a splitter having an input and at least three splitting terminals; a combiner having an output and at least three combining terminals; and at least three radiation guides each having a length, an input, and an output, wherein each of said splitting terminals is associated with an input of one of said radiation guides and each of said combining terminals is associated with an output of one of said radiation guides, and wherein the lengths of said radiation guides are such that said decoding devices are able to produce an optical coincidence signal that reaches a desired intensity when the optical encoded data signal has at least three pulses separated by time periods corresponding to differences in propagation times between said radiation guides.

2. The system of claim 1 wherein each of said decoding devices further includes a threshold mechanism.

3. The system of claim 1 wherein said optical encoded data signals include a non-zero base line.

4. The system of claim 1 wherein said optical encoded data signals include at least one data pulse and at least one control pulse.

5. The system of claim 4 wherein said data pulse of one of said optical encoded data signals is also a control pulse of another of said optical encoded data signals.

6. The system of claim 4 wherein said control pulse of one of said optical encoded data signals is also a data pulse of another of said optical encoded data signals.

7. The system of claim 1 wherein said system is produced in a medium selected from a group of media including open space, radiation guides, fiber optics, waveguides, and planar waveguides fabricated on a chip.

8. The system of claim 1 wherein said system includes optical sensors at said second terminals.

9. The system of claim 1 wherein said optical paths comprise radiation guides.

10. The system of claim 1 wherein said optical encoded data signals are encoded with predetermined destinations.

11. The system of claim 10 wherein said predetermined destinations are encoded by said time periods.

12. The system of claim 1 wherein said system further includes threshold devices at said second terminals.

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Description

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FIELD OF THE INVENTION

The invention relates to communications systems and more particularly to the modulation and control of signals for example by interaction of energy in a stateless controller device.

BACKGROUND AND PRIOR ART

In the field of optical communication, there is a pressing need to improve the capacity of optical networks and the speed of switching at reasonable cost. These are attended by the related problems of efficient retrofit to existing infrastructure, ease of maintenance, reliability, etc. The physical media of optical fibers used in current generation optical networks have a tremendous as yet untapped reserve capacity. The reasons for this involve various bottlenecks, chief among them, the slow speed of switches for optical data. To switch optical data, either the data on an optically-modulated signal must be converted to electrical modulation and switched by electrical switches, switched by relatively slow state change switches such as electro-optical, or thermo-optical switches, or switched by slow mechanical switches like Micro Electro Mechanical Systems (MEMS). Although the electrical conversion and switching is slow it is still much faster than any technology available today for optical switching. The optical switches are too slow to handle information switching and thus are used only for system management and reconfiguration in which the recovery time that may be tolerated for such application is in the range of microseconds to milliseconds. Some of the switches are much faster than the recovery time of the system and some of them have a time response of 50 ns, but still they are too slow for being used for the purpose of data switching fast enough as to avoid storage, which inevitably involves conversion. Electrical switching is the only technology available today that is capable of acting as a switch in the sense of intelligent switching or packet switching, because of the storage capability. While the switching is intelligent, it is still slow and constitutes a major bottleneck in communication networks. To compensate for the slowness of electronic switching, substantial parallelism must be introduced into the design of switches resulting in high cost, large footprint and power consumption. These limitations are near their upper limits making them very difficult to scale.

Currently, there is no all-optical analog to the network switches used in networks.

In addition to the switching process per se, the process of generating optical signals--the modulation itself--is slow because of the rise and fall times of current optical modulators. As a result, symbols are much longer than need be, thereby limiting the bandwidth to a level substantially below the potential of the optical media.

A technique called Wavelength Division Multiplexing (WDM) and a refinement called, Dense Wavelength Division Multiplexing (DWDM) are currently used to increase the capacity of optical media using current modulation technology. WDM or DWDM methods increase the transmission rate by creating parallel information channels, each channel being defined by a different light frequency. Another method, Time Division Multiplexing (TDM) exists in which multiple data sequences are interleaved in time-division fashion on a common medium.

WDM or DWDM methods increase the transmission rate by using parallel information channels. The information in each optical channel is carried by a different light frequency. The light frequencies of the channels are combined together and are inserted into the input of a single optical fiber. The combined light frequencies at the output of the fiber are separated into different parallel channels, one for each specific light frequency. Although DWM and DWDM have the ability to increase the capacity of a fiber, the number of channels that may be defined has a practical upper limit because of the limited bandwidth of the fiber (optical properties are attuned to a narrow range of frequencies) and because of the ability of the laser sources to contain their energy in very narrow frequency bands.

Even if the line-width of the lasers would be made sufficiently narrow to allow the addition of more channels, the number of channels cannot be increased without limit. Increasing the number of channels results in channel crosstalk. Crosstalk results from nonlinear effects that occur within fiber media when subjected to the intense electrical fields produced when a high channel count is used. In TDM, the bits of several parallel channels at the same light frequency are interleaved in a predetermined periodic order to create a single serial data stream. This method is very effective when using a buffer, which accumulates and compresses the data of several channels into a dense serial data stream of a single channel by reorganizing this data with suitable delays. However the data rate permitted by this method, as well as others, is still limited by the data rate and duty cycle of the modulators or the light sources (DFB and DBR lasers) themselves when direct modulation is used. That is, in direct modulation, the power to the laser is switched on and off. The rate at which this can occur has a physical upper limit due to the relatively long recovery time of the lasers and it produces chromatic dispersions due to broadening of the emitted spectral line of the modulated lasers. This is caused by spontaneous emission, jittering, and shifting of the gain curve of the lasers during the current injection. Where modulation is performed in an indirect manner, by modulators, the lasers are operated in a Continuous Wave (CW) mode and separate modulators perform the modulation of the beam. The modulators are usually made from interference devices such as Mach-Zender's, directional couplers and active half wave-plates combined with polarizers and analyzers. However, an electro-optical device must be activated to modulate the beam and thereby produces phase shifts and polarization changes. Such changes involve the creation and removal of space charges, which change the density of the charge carriers within these electro-optic materials. The formation rate of the space charges is mainly dependent upon the speed and the magnitude of the applied voltage and can be on the order of sub nanoseconds. The charge removal is usually slower and is mainly dependent upon the relaxation time of these materials (lifetime of charge carriers) and can be relatively long. Accordingly, the width of the pulses and the duty cycle of the modulation are dependent limited by the long off-time (latency) of the modulators.

These same rise and fall time limitations impose similar limits on the abilities of switches to direct light along alternative pathways according to routing commands and data. At present, there are two major classes of optical switches. In one class, optical signals are converted to electrical signals, routed and switched conventionally, and optical signals generated anew at the output. As discussed above, the process of conversion is costly and the reduction of switching time is limited since the switching time includes delays due to reading, processing of destinations, reconfiguration delays, device I/O, and regeneration of the optical signals. Thus the switching time is slow requiring many parallel channels to obtain throughput making such switches scale poorly, costly, and otherwise problematic. In optical applications, this class of switches goes by the identifier OEO, which stands for signals medium conversion, from the optical domain to the electrical domain and then back to the optical.

A second class of optical switch, which is often very slow to reconfigure, goes by the identifier OO, which stands for optical-optical, as the signals are maintained thoroughly in the optical domain. In these switches, no conversion of optical signals to electrical signals takes place. Instead, the optical energy is routed by means of some sort of light diversion process such as a switchable mirror. In one system, micromechanical actuators or so-called Micro Electro Mechanical System (MEMS), use electrostatic forces to mechanically move microscopic mirrors in response to electrical routing signals. The speed of such switches is very limited by the slow response of the devices used to perform switching, for example, MEMS mechanism. The result is that no OO switch is capable of packet switching and is only applicable where the granularity of data signals is extremely high, such that the delays required for configuration represent a small fraction of the time required for transmitting. These devices are applicable in the core portions of networks and do not address the bottleneck problems inherent electronic switches.

At present, the highest bit rate being deployed is about 10G bits per second per channel. Higher bit rates designs, such as 40G bit per second per channel, are mainly challenged by developing high bit rate devices, improve optical signal-to-noise ratio and compensate for dispersion. Present high speed 10G bits per second devices are limited by the modulation rate of the modulators, the pulse width that they produce, and the switching time of the electronic switches.

There is a need for reliable mechanisms for exploiting the physical potential of fiber optic media in terms of data rate, switching, and cost.

In optical communication networks there is a need for fast, reliable, and inexpensive systems capable of demultiplexing information. One solution for such a need is provided by Passive Optical Networks (PON) that passively demultiplex the information, by splitters, into multiple customers. Such PON systems have a common use in applications for the last-mile. However such a solution suffers from security problems since every attached PON network customers receives the whole information of all other network customers, regardless of the targeted customer. Accordingly it is desired to produce an inexpensive, simple demultiplexing system in which each customer receives the information in a direct manner and only the information designated specifically to him.

U.S. Pat. No. 5,060,305 entitled "Self Clocked, Self Routed Photonic Switch" filed Oct. 22, 1991 and U.S. Pat. No. 6,160,652 entitled "Optical Address Decoder" filed Dec. 12, 2000, disclose systems and devices for decoding headers in an architecture of sending information by payloads where the destinations of the payloads are encoded in the headers.

The design of the embodiments according to the present invention allows simple direct demultiplexing of the information without the use of headers and payloads. Thus the embodiments of the present invention are simpler, more reliable, faster, and less expensive than the embodiments disclosed by U.S. Pat. Nos. 5,060,305 and 6,160,652.

Accordingly, it is an object of the present invention to provide a passive, inexpensive, and reliable system for direct switching, routing, multiplexing and demultiplexing of information;

Another object of the present invention is to provide passive and fast systems for direct switching, routing, multiplexing and demultiplexing of information in which each customer may receives information directed only to him;

Another object of the present invention is to provide a fast system for direct switching, routing, multiplexing and demultiplexing of information that may include a threshold mechanism and switch the information in a direct manner;

Another object of the present invention is to provide a fast system for direct switching, routing, multiplexing and demultiplexing of information across multiple decoding/switching/routing/demultiplexing layers;

Another object of the present invention is to provide a fast system for direct switching, routing, multiplexing and demultiplexing of information to form cross connection switching and cross-connection boxes for decoding/switching/routing/demultiplexing of information;

Another object of the present invention is to provide a fast system for direct switching, routing, multiplexing and demultiplexing of information that may include a threshold mechanism and in which each customer receives information directed only to him;

Another object of the present invention is to provide fast systems for direct switching, routing, multiplexing and demultiplexing of information including coincidence gates or decoding devices that may be stateless;

Another object of the present invention is to provide coincidence gates that include a summing gate that may be of one of the type of dielectric and metallic beam-splitters, dual gratings, high density gratings, array of radiation guide gratings, Array of Waveguide Gratings (AWG), polarization beam-splitters, directional couplers, and Y-junctions;

Another object of the present invention is to provide coincidence gates that may be produced in any of the media including, open space, radiation guides, fiber optics, wave guides, and planar wave guides fabricated on a chip;

Another object of the present invention is to provide coincidence gates including summing gates that may sum the control and the data signal coherently or non-coherently;

Another object of the present invention is to provide coincidence gates including summing gates that may sum the control and the data signal coherently and have closed loop phase control;

Another object of the present invention is to provide coincidence gates including electrical or optical threshold mechanisms;

Another object of the present invention is to provide coincidence gates that may receive in their inputs control and data signal for a single source or from different sources;

Another object of the present invention is to provide coincidence gates including summing gates that may sum the control and the data signal and have closed loop clock recovery control;

Another object of the present invention is to provide a method and apparatuses to increase the rate of information transmitted using narrow pulse generators and shapers and dense interleaving to produce high dense multiplexing and demultiplexing;

Another object of the present invention is to provide codes with predetermined destinations including at least one control pulse and one data pulse;

Another object of the present invention is to provide codes with predetermined destinations including multiple control pulses;

Another object of the present invention is to provide codes constructed from a plurality of pulses with predetermined destinations including multiple control pulses to route, switch or demultiplex information across multiple routing, switching and demultiplexing layers;

Another object of the present invention is to provide symbol configurations, summing gates, and control pulses for increasing the ratio between coincidence pulses and non-coincidence pulses produced by coincidence gates;

Another object of the present invention is to provide coincidence gates including delay lines;

Another object of the present invention is to provide coincidence gates including variable delay lines;

Another object of the present invention is to provide coincidence gates including delay lines compactly produced on a chip;

Another object of the present invention is to provide optical cross-connection boxes capable of information self routing;

Another object of the present invention is to provide a self routing, switching and demultiplexing mechanism that maintains synchronization;

Another object of the present invention is to provide a self routing, switching and demultiplexing mechanism across DWDM systems that may include multiple switching layers;

Another object of the present invention is to provide embodiments designed to multiplex/demultiplex symbols with predetermined addresses including management of guard band between symbols, and,

Still another object of the present invention is to provide embodiments designed to multiplex/demultiplex symbols with predetermined addresses modulated by any combination of time, phase, and polarization modulation.

SUMMARY OF THE INVENTION

An all-optical system for modulating, switching, multiplexing, demultiplexing, and routing signals, for example digital signals in an optical medium, employs control units that direct energy according to a coincident control signal which may be in the same form as the digital signal. Briefly, in an embodiment where the signals are optical, any of a variety of different interactions between light inputs results in a combined output with a different magnitude when both inputs coincide than when they do not. For example, an energy summer produces an output whose power is proportional to the sum of the two inputs when the two inputs coincide and whose power is proportional to the individual inputs when the two inputs do not coincide. In an example embodiment, a control signal determines the power level of the output based on some addressing technique by combining the control signal at one input with a data signal at the other input. The control and the data signals may arrive from the same source of from different sources. The resulting signal has a higher magnitude when control and data signals are combined than when not. The output may be received by an optical-electrical transducer (e.g., a photodiode circuit) or an all optical threshold device configured to discriminate signals above a predefined threshold (electronically or optically) from signals below the predefined threshold. In such a receiver, data signals that are summed with a control signal are accepted as received data, while signals that are not summed (and, as a result, having a power magnitude below the threshold) are rejected. In an application of this example using a summer, a transmitter modulates a light beam to form pulses, each representing a bit consisting of a data pulse and a control pulse whose spacing represents a destination address. The modulated beam is applied in parallel to a set of summers. Each summer has a non-delayed input and a delayed input (or two inputs when each input has a different delay). Each summer has a respective delay at its delayed inputs (or between its inputs) such that a given spacing between the data and control pulses causes a coincidence at only one of the summers. The outputs of all the summers are sent to respective receivers, each configured to reject signals whose magnitude is below a specified threshold. Only one receiver will accept the data pulses "addressed" for the gate (i.e. whose spacing corresponds to that gate's control input's delay) connected to that receiver. In this embodiment, pulse-pairs will produce a single output pulse whose magnitude meets a threshold only at a single receiver. This function results in, effectively, a routing of each data bit to a selected receiver over a channel connected to multiple receivers.

In the above example, a simple summer can be fabricated from a Y-junction, directional coupler or a beam splitter, all commonly used in optical communications circuits. For example, it can also be fabricated from other optical devices used for energy summing, such as, transmitting and reflecting grating, fiber grating or other coupling devices. The light energy is preferably formed of light of a range of propagation modes, frequencies, phases or any combination between them, so that the signal power summing effect is produced non-coherently. Alternatively, the light at one input can be a different frequency than the light at the other input with the gate output being a mixture of the two input frequencies.

In further embodiments, the gate directs a substantial fraction of the energy pulses (including symbols) in a data signal to a first output when light from its two inputs are coincident, in its summing region, and to a second output when there is no coincidence. This effect can be produced by coherent summing, for example by means of a beam-splitter or directional coupler. In these embodiments, the interaction is coherent resulting in interference between the light signals applied at the two inputs. The power of the output when the input energy is coincident, in these latter embodiments, may be greater than the sum of the energy produced at the outputs in non coincidence situations. Several variations on these embodiments are described:

In one embodiment, the E-fields of the two input signals are summed providing an output whose power is up to four times the power of either output when one input alone provides a signal (assuming the two inputs have the same power level);

In another embodiment, the E-fields of the two input signals are summed. The resultant output is added to a signal generated by a separate source whose E-field magnitude is some fraction of that of the output resulting from coincidence of the inputs and out of phase with it such that the magnitude ratio of the signal at the coincidence output in a coincidence state to the signal in a non-coincidence state is increased. For example, if the E-field of the constant source is one half the magnitude of the non-coincidence signal at the coincidence output and out of phase with it, the energy magnitude of the signal in a coincidence state at the coincidence output will be nine times the magnitude of the non-coincidence signal at that output.

In a further embodiment, the pulses may be formed such that there is a negative E-field added to them, whose amplitude is, for example, a third of the E-field of the pulses and 180 degrees out of phase. Then, when the pulses are added coherently, the coincidence pulse power level is up to nine times (for the -1/3, +1 example) greater than that of the level of the non-coincidence pulses or the "floor" level between the pulses. In an additional embodiment, pulses with E-fields having different polarizations may be summed to generate, by vector addition, a pulse with a different polarization angle matching that of a polarization filter such that the energy of either component is substantially more attenuated than that of the sum. The ratio between the output energies of the signals in a non-coincidence state and a coincidence state, at the coincidence output, is depend on whether polarization filter is used or not in the output(s) of the control device. It also depends on the relative polarization orientation between the inputs beams. When pulses, whose E-fields at respective inputs are in phase, but with a difference in polarization angle of .pi./2, are summed by a polarizing beam splitter, the above ratio at the output is 4:1 when a polarization filter is used at the output and 2:1 when such a filter is not used. This ratio can be increased to 9:1 by adding CW field, with the appropriate magnitude phase and polarization, to each of the inputs or to the summed outputs. It is also possible to select one of two outputs providing the coincidence behavior by changing the phase of one of the inputs relative to the other.

Other control mechanisms may be employed besides the addressing scheme mentioned above. For example, a pulse sequence could be compared in a gate, such as described above, to a predefined pulse sequence defining an address. The gate may be configured such that if the addresses match, high-level signals are output due to consistent in the gate. Alternatively, the gate may be configured such that if the addresses match, only low-level signals are output due to non-coincidence in the gate. Other modulation schemes could also be used in connection with the present invention, for example, phase modulation, polarization modulation or any combination of them.

Phase modulation is produced by the relative phase between the data and control signals. When a control signal and a data signal are coincident with equal phases, at respective inputs of a control unit, most of the data signal energy is directed to one output (the coincidence output for phase matching). Alternatively, when a control signal and a data signal are coincident with opposite phases, at the same respective inputs of a control unit, most of the data signal energy is directed to the other output (the coincidence output for anti-phase). Accordingly, the appearance of a high-energy signal in one of the outputs of the control unit depends on the coincidence and the phase conditions.

Polarization modulation is produced by the relative polarization between the data and control signals. When a control signal and a data signal are coherent and polarized along the same direction, at respective inputs of a control unit (even if the control unit is polarization-insensitive), most of the data signal energy is directed to one output: the coincidence output corresponding to phase matching. Alternatively, when the control unit is polarization-sensitive and receives, at its respective inputs, control and data signals that are polarized along directions that are normal to each other, most of the data signal energy is directed to one of the outputs of the control unit. The coincidence output can be selected by the relative polarization orientation and phase between the energy at the inputs of the control unit. Accordingly, the appearance of a high-energy signal in one of the outputs of the control unit depends on the coincidence, the phase, and the polarization conditions.

Combined modulation can be achieved by any combination of the modulation methods, i.e., time, phase, and polarization. A combination of modulation methods increases the number of independent parameters that each symbol contains and thus increases the amount of information that each symbol can carry.

When a control signal and a data signal are coincident at respective inputs of a control unit, most of the data signal energy is directed to one output and when the control signal is non-coincident with the data signal, most of the data signal energy is directed to another output or simply discarded. According to an embodiment, this "coincidence-gate" behavior is brought about by the interference of the control and data signals. Note that reference to one signal as a control signal and the other signal as a data signal is, at least in many embodiments, an arbitrary choice and may be used in the present specification simply to facilitate the description of the invention. The described addressing technique may include signals having multiple control pulses. The multiple control pulses are constructed such that they can only be decoded by a single combination of multiple coincidence gates. Such a technique may also be used for addressing across multiple layers of switching, demultiplexing or routing layers.

In an embodiment, the interference of light in the control and data signals is the result of applying one signal to a first diffraction grating that generates a first interference order diffraction pattern and the other signal to a diffraction pattern adjacent or interleaved with the first such that a different interference order is generated when both signals coincide on both gratings. In an example, the first grating may be a transmission grating with (broken or patterned) reflective surfaces between the transmission apertures defining a reflection grating. With such a device, one signal may reflect off of the reflective grating and the other signal may pass through the transmission grating. The reflection and transmission diffraction patterns of either signal produces first order diffracted radiation when only one signal falls on the device at given instant of time. But when both fall on the device at the same time, so that the effective pitch of the diffraction grating includes both the transmission and reflection grating, a lower order diffracted radiation results. In the case of the first order pattern, the number of lobes is higher and they have different intensities from that of the lower order diffraction pattern. With suitably spatially-located receivers, the energy may be directed in different directions from this type of interference device depending on the relative phase between the beams and whether the two signals are coincident or non-coincident. The coincidence gate may thus have a coincidence output to which higher energy is sent when the both inputs receive energy at the same time and a non-coincidence output to which energy is sent when the inputs receive energy at different times. Note, as should be clear to a person of ordinary skill, for the above interference type of coincidence gate to work properly, the phases of the inputs should be properly aligned to insure the energy from the gratings falls on the respective receivers. It should be understood that selecting certain outputs as coincident and non-coincident output may change and each output may serve both, a coincidence and non-coincidence output, depending on the specific application used.

An alternative device for producing a coincidence effect is to perform non-coherent summing. Laser light from a multimode laser or a Light Emitting Diode (LED) characterized by a distribution of wavelengths and/or phases can be modulated and summed non-coherently. In such an embodiment, the ratio of energies of the coincidence output and the non-coincidence outputs may not be as high as with coherent summing, but the effect is still strong enough to be usable for gating.

Using such interference devices, by suitable construction of an optical device, incident energy is directed along different paths depending on whether the data and control beams are coincident on the inputs of the device or non-coincident. The result is a basic component, mentioned above, called a coincidence gate. This gate may be used to control the path of a data signal. For example, by articulating a single data signal so that it contains pairs of pulses separated by a predefined spacing, and splitting this signal, sending one to one input of the coincidence gate and sending a delayed version to the other input of the coincidence gate, the signal will transmit a pulse of higher intensity at an output of a coincidence gate where the pulse spacing matches the delay than at the output of a coincidence gate where the pulse spacing is different from the delay. By sending such a spaced-pulse symbol to a number of different coincidence gates in parallel, each with a different delay, the articulated signal will, in effect, select an output according to the delay matching the spacing of the pulses in the signal. Thus, the optical signal carries a symbol (the pulse spacing) that selects which coincidence gate-device most of its energy will be sent through. This effect amounts to a basic switching function.

Note that the switching function can be layered by providing each output to another set of different gates each with another different delay. To articulate the signal for successive layers, the signal construction may be repeated in self-similar steps for every switch layer involved because each pulse pair only produces a single pulse at the output. The details of this process are described in the Detailed Description section along with supporting illustrations.

The coincidence device may also be used to create a modulator for dense signal transmission because of its rapid on-off response. That is, if two broad pulses are applied to the control and data inputs of a coincidence device with different time delays, the width of the pulse emerging from the coincidence output will be determined by the period during which both input pulses are incident on a gate. Thus, the coincidence effect can be used to generate pulses that are very narrow. Other devices are also discussed for forming narrow pulses. By combining multiple streams from such sources of narrow pulses into a common optical channel with respective delays, very dense streams of narrow pulses may be generated thereby increasing the bandwidth of an optical signal. A mirror-image process can then be used to demultiplex the dense data stream into respective channels with larger pulse spacing at a receiving end. Thus, the above description embodies a multiplexer/demultiplexer combination. Another way of forming dense pulse streams is to modulate multiple parallel channels fed by a mode locked laser and interleaving the pulses.

There are a number of alternative interference devices that may be used to create a coincidence gate. Y-junctions, directional couplers, fast-pitch diffraction gratings, beam splitters, and other examples discussed in the present specification may be used to form coincidence gates and produce a similar coincidence function. These examples are described in the Detailed Description section below along with supporting illustrations.

Also, in addition to the modulation and self-switching functions described above, the coincidence gate may be used as the basis for a switch controlled by an external control signal. Thus, a data signal from one source can be directed to an appropriate output of a layer of coincidence gates by sending an appropriately-timed control pulse to all of the gates. Alternatively, a single selected coincidence gate can have one of its outputs selected by an external control signal by transmitting a control signal to only the selected coincidence gate.

An additional layer of symbology may be added to an optical signal which may be used for switching purposes in coincidence gates employing the diffraction phenomenon. The propagation directions of the various diffraction orders may be varied by imposing different phase relationships between the data and control signals. By placing receivers in different locations, each set with different outputs, the coincidence gate may be configured to provide selectable outputs depending on the phase relationship between the pulses.

The present invention provides an optical system for decoding, switching, demultiplexing, and routing of optical encoded data symbols, including:

a plurality of optical paths having first and second terminals;

a splitting mechanism for directing the encoded data symbols to each of the first terminals;

a plurality of decoding devices for producing decoded signals in response to the encoded data symbols; and

each of the optical paths includes, between the first and second terminals, at least one of the decoding devices to produce one of the decoded signals at one of the second terminals in response to one of the encoded data symbols.

The present invention also provides an optical system for decoding, switching, demultiplexing, and routing of optical encoded data symbols, including:

a plurality of radiation guides having first and second terminals;

a splitting mechanism for directing the encoded data symbols to each of the first terminals;

a plurality of decoding devices, each of the decoding devices produces one of a plurality of decoded signals in response to one of the encoded data symbols; and

each of the radiation guides includes, between the first and second terminals, at least one of the decoding devices to produce one of the plurality of decoded signals at one of the second terminals in response to one of the encoded data symbols.

In another version, the present invention also provides an optical system for decoding, switching, demultiplexing, and routing of optical encoded data symbols, including:

a first plurality of radiation guides having first and second terminals;

a first splitting mechanism for directing the encoded data symbols to each of the first terminals of the radiation guides of the first plurality of radiation guides;

a plurality of decoding devices each of the decoding devices includes a second plurality of radiation guides, each of the radiation guides of the second plurality of radiation guides associated with one of the ports of a second splitting mechanism and with one of the ports of a combining mechanism, the decoding devices are arranged for producing decoded signals in response to the encoded data symbols; and

each of the optical paths includes, between the first and second terminals, at least one of the decoding devices to produce one of the decoded signals at one of the second terminals in response to one of the encoded data symbols.

While some of the embodiments of the invention are illustrated as being constructed in one of the media of open space, fiber optics, radiation guides, waveguides, and planar waveguides on a chip, each of them may be fabricated in any of these media. It also should be clear that while the descriptions below describe coincidence gates they are also decoding devices. While the optical encoded data symbols may also be described, below, as encoded signals, signals including information and control pulses, symbols, symbol signals, spaced-pulse symbols, pulse patterns and signals, it should be clear that they all may represent optical encoded data symbols as well as other signals defined by other terms that may describe equivalents to optical encoded data symbols.

The invention will be described in connection with certain preferred embodiments, with reference to the following illustrative figures so that it may be more fully understood. With reference to the figures, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to accompanying drawings, wherein:

FIGS. 1A, 1B, 1C and 1D are figurative illustrations of a gate having two inputs and two outputs showing the output signals at the gate outputs for different combinations of the input beams received at the gate inputs;

FIGS. 2A, 2B and 2C are schematic illustrations of a gate including a dielectric beam-splitter device having two inputs and two outputs and showing the output signals at the gate outputs for different combinations of the input beams received at the gate inputs;

FIGS. 3A, 3B and 3C are figurative illustrations of a gate including a metallic beam-splitter device having two inputs and two outputs and showing the output signals at the gate outputs for different combinations of the input beams received at the gate inputs;

FIGS. 4A, 4B, 4C, 4D and 4E schematically illustrate a gate made of a dual grating device having transmitting and reflecting gratings illustrated within a prism having two inputs and two outputs and showing the output signals at the gate outputs for different combinations of the input beams with different relative phases received at the gate inputs;

FIGS. 5A, 5B and 5C are figurative illustrations of a gate made of a Y-junction combiner device having two inputs and one output showing the output signal at the gate outputs for different combinations of the input beams received at the gate inputs;

FIGS. 6A, 6B and 6C are schematic illustrations of a gate constructed by a high pitch grating device illustrated within a prism having two inputs and two outputs showing the output signals at the gate outputs for different combinations of input beams received at the gate inputs;

FIGS. 7A and 7B schematically illustrate a gate made of an array of interleaved light guides having two inputs and one output and showing the gate where it is fabricated by optical fibers and planar waveguides, respectively;

FIGS. 8A, 8B, 8C and 8D are figurative illustrations of a gate including a polarizing beam splitter device and two output polarizes having two inputs and two outputs and showing the output signals at the gate outputs for different combinations of the input beams received at the gate inputs;

FIG. 8E is a schematic illustration of a gate produced by a directional coupler exhibiting behavior similar to the behavior of the gates illustrated by FIGS. 1A 1D, 2A 2C, 3A 3C, 4A 4E, 5A 5C, 6A 6C, 7A 7B and 8A 8D;

FIGS. 9A and 9B illustrate coincidence gates for symbol-selection mechanism in a situation where the gates are in non-coincidence and coincidence states, respectively;

FIG. 9C is a schematic illustration of a symbol copier that duplicates a single symbol to produce input symbols for a coincidence gate;

FIG. 9D schematically illustrates a one-to-two demultiplexer representing in general any one-to-many demultiplexer having output ports that each of them has a corresponding receiver that respond only to a specific corresponding symbol at the input;

FIG. 9E is a schematic illustration of series of symbols configured to produce time synchronized coincidence signals;

FIGS. 9F, 9G and 9H illustrate the coincidence and non-coincidence signals produced at the outputs of coincidence gates in response to input signals in the from of spaced-pulses symbol, spaced-notches symbol with non zero background, and spaced-pulses symbol including pulses with different widths, respectively;

FIG. 9I illustrates the spectral distributions of wide band non-coherent and narrow band coherent signals;

FIG. 10A is a schematic illustration of the field vectors of the signals received by a coincidence gate and their delayed vectorial coherent summing produced at the outputs of the coincidence gate;

FIG. 10B illustrates exemplary presentation of vectors illustrated by their magnitude and phase in a complex plane;

FIG. 10C is a schematic illustration of the field vectors of the signals and their non-zero background received by a coincidence gate and their enhanced delayed vectorial coherent summing produced at the outputs of the coincidence gate;

FIG. 10D is a schematic illustration of the field vectors of the signals received by a coincidence gate and their vectorial coherent summing produced at the coincidence output of the coincidence gate that is vectorially summed in opposite phase with CW radiation to produce enhanced contrast between the coincidence signal and the background signals;

FIG. 10E schematically illustrates the embodiment for producing the vectorial summing illustrated by FIG. 10D;

FIG. 10F is a schematic illustration of the output signal produced by the embodiment of FIG. 10E;

FIG. 11A illustrates a polarization based coincidence gate combined with contrast enhancer device to increase the contrast between the coincidence signal and the background;

FIG. 11B is a schematic illustration of the field vectors in various locations of the device of FIG. 11A shown in their corresponded time slots;

FIGS. 11C and 11D shows the intensities of the signals in various locations of the device of FIG. 11A;

FIG. 12A is a schematic illustration of an embodiment including a coincidence gate combined together with an optical threshold device to increase the contrast between the coincidence and the non-coincidence pulses;

FIGS. 12B and 12C illustrate the combined transmission function of an optical amplifier and an attenuator and the transmission function of an optical amplifier alone, respectively;

FIGS. 12D and 12E illustrate the signals propagating in the embodiment of FIG. 12A in various locations for non-coincidence and coincidence signals, respectively;

FIG. 12F illustrate an ideal and practical transmission function of an optical amplifier;

FIG. 12G is a schematic illustration for a modified design of the embodiment of FIG. 12A;

FIGS. 12H and 12K illustrate the signals propagating in the embodiment of FIG. 12G in various locations for non-coincidence and coincidence signals, respectively;

FIG. 13A is a general schematic illustration of a coincidence gate having two inputs and two outputs;

FIG. 13B illustrates a coincidence gate receiving input signals from different sources;

FIGS. 13C, 13D and 13E schematically illustrate specific design for closed loop phase control, general design for closed loop phase and clock recovery control, and closed loop phase and clock recovery control for multiple clients, respectively;

FIG. 13F schematically illustrates a system for selecting a desired time delay for a coincidence gate;

FIG. 13G is a schematic illustration of a system for enhancing the contrast between the coincidence signal and the background at the output of a coincidence gate;

FIG. 13H schematically illustrates a system including an optical threshold device for enhancing the contrast between the coincidence signal and the background at the output of a coincidence gate;

FIG. 13I is a general schematic illustration of a coincidence gate that may or may not include any combination between a coincidence gate and any other means accompanied to the gate;

FIG. 13J illustrate a design for a time delay selector;

FIG. 14A schematically illustrates a self demultiplexer system designed to demultiplex the input information having different symbols, into designated outputs port according to the predetermined destination encoded in the input symbols;

FIGS. 14B, 14C and 14D illustrate exemplary internal structures of the dividing device of the self demultiplexing system of FIG. 14A;

FIGS. 15A and 15B illustrate a device and an icon representing this device, respectively, designed for converting a single pulse into a symbol signal including pair of pulses;

FIG. 15C schematically illustrates a multiplexing system for interleaving symbols signals to form a dense stream of symbols that may be arranged in form of Time Division Multiplexing (TDM);

FIG. 15D is a schematic illustration of a duplicating device including circulating loop used to increase the density (rate) of the pulses;

FIG. 15E is a schematic illustration of a demultiplexer designed for self demultiplexing of symbol signals such as the interleaved symbol signals produced by the multiplexer of FIG. 15C;

FIGS. 15F and 15G schematically illustrate narrow pulse generators with and without threshold mechanism, respectively;

FIG. 15H is a schematic illustration of the signals produced at different locations in the narrow pulse generators of FIGS. 15F and 15G;

FIG. 15J schematically illustrates a multiplexer that receives optical pulses and interleaves them into high dense symbol signals including pulses that are narrower than the pulses at the input of the multiplexer;

FIG. 15K schematically illustrates the foregoing multiplexer/demultiplexer combinations as a generic schematic;

FIG. 15L schematically illustrates a contrast enhancer device used to increase the ratio between coincidence and non coincidence pulses in the multiplexer of FIG. 15J;

FIGS. 15M and 15N are schematic illustration of the generic multiplexers and demultiplexers of FIG. 15K that may have multiple inputs and outputs and arranged in different configurations;

FIG. 15P schematically illustrates a system for self demultiplexing over multiple layers;

FIGS. 15Q and 15R schematically illustrate self demultiplexers with and without data control, respectively;

FIG. 15S schematically illustrates a system for self n-by-m routing connection;

FIG. 15T schematically illustrates a many-to-one combiner alternative to the star combiner used in FIG. 15S;

FIGS. 16A, 16B and 16C schematically illustrates the construction of symbols designed for self demultiplexing/switching across multiple layers;

FIG. 16D is a schematic illustration of self demultiplexing/switching system across multiple layers;

FIG. 16E schematically illustrates a coincidence gate combined with electronic detectors and comparator (differential amplifier) to increase the contrast between the coincidence and the non-coincidence pulses;

FIG. 16F illustrates the intensities of the signals at the coincidence and the non-coincidence outputs of the coincidence gate of FIG. 16E and shows the coincidence signal produced at the output of the comparator of FIG. 16E;

FIG. 16G is a schematic illustration of the coincidence and non-coincidence signals produced at the different layers of self demultiplexing/switching system;

FIG. 17 schematically illustrates a self demultiplexing/switching/routing Wavelength Division Multiplexing (WDM) system including multiple layers of self Code Division Multiplexing/demultiplexing gates;

FIG. 18A is a schematic illustrations of a self routing/switching/demultiplexing system made of radiation guides and includes electronic threshold devices;

FIG. 18B schematically illustrates an exemplary threshold mechanism for the system of FIG. 18A that includes a comparator;

FIG. 19 schematically illustrates an optical delay line fabricated on a chip that includes optical couplers and mirror like edge surfaces;

FIGS. 20A and 20B schematically illustrate the configuration of FIG. 19 where the mirror like edge surfaces are replaced by Bragg reflector gratings;

FIGS. 20C and 20D are schematic illustrations of the implementation of the delay line of FIG. 19 in a coincidence gate with and without a phase shifter, respectively;

FIG. 20E schematically illustrates a delay line fabricated on a chip that includes an open core of a loop;

FIGS. 21A, 21B, 21C and 21D schematically illustrate four versions of multiplexing/demultiplexing systems for symbol signals;

FIGS. 21E, 21F, 21G, 21H and 21J schematically illustrate symbol signals, the artifact pulses that they produce and various arrangements of guard bands between the symbols;

FIG. 21K schematically illustrates narrow pulses arriving from multiple parallel channels and shows their multiplexing (interleaving) into a common channel in a form of symbol signals;

FIG. 21L is a schematic illustration of a multiplexing system that performs the multiplexing illustrated by FIG. 21K;

FIG. 22A is a schematic illustration of a coincidence gate designed to receive symbols containing more than two pulses for enhancing the contrast between coincidence and non-coincidence signals;

FIGS. 22B and 22C illustrate the signals propagating in the embodiment of FIG. 22A in various locations;

FIG. 22D schematically illustrates a switching/routing/demultiplexing system that eliminates the need for time guard bands between the data symbols and including combined coincidence gates;

FIG. 22E is a schematic illustration of an alternative design for a combined coincidence gate that may be used in the system of FIG. 22D;

FIG. 22F schematically illustrates the symbols that are demultiplexed by the system of FIG. 22D and shows that the symbols do not include time guard band and are closely packed;

FIGS. 23A 23F schematically illustrate the output signals at the outputs of a beam splitter for various input beams having various relative phases;

FIGS. 23G and 23H illustrate the coincidence and the non-coincidence signals at the outputs of a coincidence gate for a data symbol signal encoded by time and phase modulation;

FIGS. 23I and 23J illustrate multiplexing and demultiplexing systems for data symbol signals modulated by time space and relative phase between the pulses of the symbols, and

FIGS. 23K, 23L and 23M are schematic illustrations of data symbol signals appearring at various locations of the systems illustrated by FIGS. 23I and 23J.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIGS. 1A, 1B, 1C and 1D are figurative illustrations of a gate 100 that directs applied energy, for example, optical energy, based on an interaction between two sources, such as a control source and a source representing data. As discussed below, the gate 100 may permit the selective application of higher energy to an output port based on the timing and configuration of inputs by interaction of the inputs and without the requirement for a state change of the gate 100. A discussion of various embodiments that exhibit this behavior follows the discussion of FIGS. 1A, 1B, 1C and 1D.

Referring to FIG. 1A, a gate 100 has two inputs 5 and 10 and is configured such that when compatible energy signals are received simultaneously at the inputs 5 and 10, responsive outputs, at an output port 15, is obtained. For example, the inputs may be optical energy pulses whose phases are aligned to constructively interfere within the gate 100 or light beams whose polarization angles are in a predetermined relationship relative to each other and to filters within the gate 100. The gate 100 may be further configured such that if the energy received at the inputs has some other relationship (polarization angles, phase, or relative timing, for example) then a different output is obtained. The gate 100 may also, in embodiments, be configured to generate a different output signal at another output, for example output 20 where some of the energy is directed. For example, when a different relationship between the signals received at the inputs 10 and 5 exists, different signals may be output at such an additional output 20. Although only one additional output 20 is shown, more may be provided, depending on the embodiment.

In FIG. 1A, an input signal 40 includes an input symbol, represented here by a pulse 35 applied to input 5 of the gate 100. A second input 10 receives a different input symbol, represented here by the absence of a coinciding pulse (i.e., no input signal). An output signal 60, and where present other output signals represented by output 63, are responsive to the input signals. Here the output signals are represented by pulses 70 and 80 generated at outputs 15 and 20, respectively. The output signals are detected by sensors 90 and 95. Although gate 100 has two outputs 15 and 20 from which signals 60 and 63 are emitted and detected by sensors 90 and 95, respectively, a greater or lower number of outputs may be provided as will be clear from the discussion of specific embodiments below.

Referring now to FIG. 1B, the inputs signals change. Here, a different input signal 25 is represented by a pulse 30 applied to the input 10 of the gate 100 and no signal at input 5. A changed output signal 61 is represented by a pulse 71 generated at the output 15. In the illustrated case, the output may be substantially the same whether there is a pulse at input 5 or at input 10, but not coincident. Referring to FIG. 1C, when pulses 30 and 35 are applied to both inputs 10 and 5, respectively, a different output 62 results, which includes a pulse 72, which is different from either pulse 70 or 71.

By providing an appropriate detector, such as, detector 90, to the gate 100, it can be determined whether a signal was applied to either input 5 or 10 independently or to both in a certain temporal relationship. This may be determined by detecting the presence of a pulse 72 versus either pulse 70 or 71, for example, by comparing an intensity level of the respective pulses. Thus, for example, if a receiver is configured to detect only pulses of the form 72, a signal modulated to carry data and applied at one of the inputs 5 or 10 may be detected as such at the output 15 only when a "control signal" is applied at the other input 10 or 5 simultaneously and respectively. In this case, for example, a data signal at input 5 may be considered to be passed or blocked depending on the coincidence of a signal at input 10. Thus, one of the inputs can be regarded as a control input and the other as a data input. In FIG