Abstract:
An optical Internet Protocol switching method and system are disclosed for switching data packets entirely in the optical domain. The method of the present invention includes the steps of receiving a plurality of data packets at an optical switch and extracting the header information for each data packet for processing at a control unit. The data packets can be demultiplexed at a plurality of demultiplexers and each data packet assigned a different internal wavelength. The method of the present invention can route each data packet to one or more delay buffers based on a current output status. The data packets can be combined into a single output from the delay buffers and broadcast to a plurality of outputs channels. The method of the present invention can select one or more data packets to output through at least one of the output channels and can convert the assigned internal wavelengths of the selected data packets to their original wavelength using a tunable wavelength converter. The selected data packets can be multiplexed together for transmission on an output Wave Division Multiplexing (“WDM”) fiber.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    Data traffic on networks, particularly on the Internet, has increased dramatically over the past several years, and this trend will continue with the introduction of new services that require more bandwidth. The dramatic increase in Internet Protocol (“IP”) traffic is leading to a realization that the equipment lines in corporate networks, and in the IP router capacity itself, may not keep up with the demand for more bandwidth. The large volume of Internet traffic requires a network with high capacity switching routers capable of routing data packets with variable lengths and bursty arrival.  
           [0002]    Current electronic IP switching routers will become difficult, if not impossible, to scale with the increase in IP traffic. Optical data packet switching routers can overcome the difficulties in electronic routers. In particular, the emergence of dense wavelength division multiplexing (“DWDM”) technology has helped to overcome the bandwidth problem encountered by current optical networks. A single DWDM optical fiber can carry in excess of 10 terabits of data per second. However, because current switching technologies are capable of switching data at rates of only 1 to 10 gigabits per second, current optical networks use only a small fraction of the bandwidth available on a single optical fiber.  
           [0003]    Different optical data packet switching architectures exist that can provide all optical solutions for fast data packet switching. One approach is the use of a broadcast and select switch. Broadcast and select switches can provide a solution for data packet switching with native broadcast and multicast functions entirely in the optical domain. Broadcast and select switches can have a single wavelength for each input/output fiber. Semiconductor Optical Amplifiers (“SOAs”) can be used as gates for selecting data packets to be routed. The selected data packets can be sent to different Fiber-Delay Line (“FDL”) buffers. The select matrix at the output of the broadcast and select switch can then choose and forward the data packets for transmission.  
           [0004]    Using WDM-based input/output fibers, prior art switching architectures can take advantage of wavelength routing and fast SOA switch blocks to provide data packet switching. Each data packet on an individual wavelength at a fiber can be processed and possibly wavelength-converted before it enters a space switch matrix. A single SOA gate is used to handle each individual wavelength in these architectures to prevent cross talk inside the active components.  
           [0005]    However, current broadcast and select switches cannot be directly migrated to a WDM input/output for each port. Other architectures suitable for WDM systems are available, but they do not include broadcast and multicast functions at the switch level. Also, some prior art architectures, such as arrayed waveguide (“AWG”) based architectures, use AWG&#39;s and Fiber Delay Line buffers for each wavelength channel, which can make for a physically very large switch.  
           [0006]    Although approaches other than broadcast and select switches have also been advocated for using optical technology in place of electronic switching systems, the limitations of optical component technology have largely limited optical switching to facility management applications. For example, another approach, called optical burst switch networking, attempts to make the best use of optical and electronic switching technologies. The electronics provide dynamic control of system resources by assigning individual user data bursts to channels of a DWDM fiber, while the optical technology is used to switch the user data channels entirely in the optical domain.  
           [0007]    However, previous optical burst switch networks designed to directly handle end-to-end data user channels have been disappointing and have shown the limitations of current optical components. For example, one prior art optical burst switch network utilized ATM switches in the control network that made the design of the control network more complicated and less efficient. Other prior art optical burst switch networks use electronic buffers in the optical routers, thus the optical burst switch network is not entirely optical. Electronic buffers cannot provide end-to-end transparent optical paths for data packet switching.  
         SUMMARY OF THE INVENTION  
         [0008]    Therefore a need exists for an optical IP switching router architecture that can switch IP data packet payloads in an all-optical manner without converting the entire data packet from an optical to an electric format. By eliminating the optical-to-electric conversion of the entire data packet, the optical IP switching router architecture of the present invention can provide an end-to-end transparent optical path for data packets.  
           [0009]    A further need exists for an optical IP switching router architecture with fast data packet switching capability.  
           [0010]    A still further need exits for an optical IP switching router architecture that can be directly migrated to a WDM input/output for each switch port.  
           [0011]    An even further need exists for a WDM optical IP switching router architecture with the capability to include broadcast and multicast functions at the switch level. Multicast and/or broadcast functions in such a switch can be implemented in either the wavelength domain at the switch input or by a select matrix at the switch output.  
           [0012]    A still further need exists for an optical IP switching router architecture that combines optical space switches with optical wavelength converters to improve the flexibility and throughput of optical networks. Such an architecture can provide an optical IP data packet router structure for fast all-optical data packet switching in a WDM system.  
           [0013]    An even further need exists for an optical IP switching router architecture that uses WDM at both the switch input and the switch output, and thus provides full wavelength domain flexibility for data packet switching among nodes of core data networks.  
           [0014]    A still further need exists for an optical IP switching router architecture that can combine fast SOA gates and wavelength converters at the switch input to resolve conflicts in the wavelength domain. Such an architecture can provide for switching IP data packets in a completely optical manner.  
           [0015]    An even further need exists for an optical IP switching router architecture with reduced component requirements and reduced physical size, as compared to previous such architectures.  
           [0016]    The present invention provides an optical IP switching system and method that substantially eliminates or reduces disadvantages and problems associated with previously developed systems and methods for switching optical data packets across a network.  
           [0017]    More specifically, the present invention provides an optical IP switching method and system for switching data packets entirely in the optical domain. The method of the present invention includes the steps of receiving a plurality of data packets at an optical switch and extracting the header information for each data packet for processing at a control unit. The data packets can be demultiplexed at a plurality of demultiplexers and each data packet assigned a different internal wavelength. The method of the present invention can route each data packet to one or more delay buffers based on a current output status. The data packets can be combined into a single output from the delay buffers and broadcast to a plurality of outputs channels. The method of the present invention can select one or more data packets to output through at least one of the output channels and can convert the assigned internal wavelengths of the selected data packets to their original wavelength using a tunable wavelength converter. The selected data packets can be multiplexed together for transmission on an output Wave Division Multiplexing (“WDM”) fiber.  
           [0018]    The present invention provides an important technical advantage of an optical IP switching router architecture that can switch IP data packet payloads in an all-optical manner.  
           [0019]    The present invention provides another technical advantage of an optical IP switching router architecture with fast data packet switching capability.  
           [0020]    A still further technical advantage of the optical IP switching router architecture of the present invention is that it can be directly migrated to a WDM input/output for each port.  
           [0021]    An even further technical advantage of the optical IP switching router architecture of the present invention is its ability to include broadcast and multicast functions at the switch level.  
           [0022]    Yet another technical advantage of the optical IP switching router architecture of the present invention is that it can combine optical switches with optical wavelength converters to improve the flexibility and throughput of optical networks.  
           [0023]    Still another technical advantage of the optical IP switching router architecture of the present invention is the ability to use WDM at both the switch input and the switch output to provide full wavelength domain flexibility for data packet switching among nodes of core data networks.  
           [0024]    Even further, the optical IP switching router architecture of the present invention provides the technical advantage of combining fast SOA gates and wavelength converters at the switch input to resolve conflicts in the wavelength domain.  
           [0025]    Yet another technical advantage of the optical IP switching router architecture of the present invention is its reduced component requirements, which can reduce the physical size of a switching router as compared to previous such architectures.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features and wherein:  
         [0027]    [0027]FIG. 1 is a block diagram of an optical IP switching router incorporating an embodiment of the optical IP switching router architecture of the present invention;  
         [0028]    [0028]FIGS. 2 a  and  2   b  are block diagrams of an embodiment of the present invention that segregates broadcast/multicast functions; and  
         [0029]    [0029]FIG. 3 is a close-up block diagram of space switch  18  of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]    Preferred embodiments of the present invention are illustrated in the FIGUREs, like numerals being used to refer to like and corresponding parts of the various drawings.  
         [0031]    [0031]FIG. 1 shows one embodiment of the optical IP switching router architecture for IP data packet switching of the present invention. Optical switch  10  can have 1 to N input WDM fibers  12 , where N is an arbitrary number whose value is only limited by size and technology constraints, as discussed more fully below. Input WDM fibers  12  can carry optical data packets consisting of payload databits and data packet header information. Header information can be extracted and processed electronically via Control Unit  20 . The remainder of a data packet can pass through optical switch  10  in an entirely optical format and output from optical switch  10  on one of N output WDM fibers  48 . Control Unit  20  can direct the operation of the various components of optical switch  10  to insure the IP data packets are routed to the correct output. Control unit can perform this function by updating the control information for input wavelength converters  16 , space switches  18 , input SOAs  22 , output SOAs  42 , and output wavelength converters  44 .  
         [0032]    Input WDM fibers  12  can contain multiple data packets each having different wavelengths as they arrive at input demultiplexers  14 . Optical switch  10  can have from 1 to N input demultiplexers, one each corresponding to each of the 1 to N input WDM fibers  12 . Input demultiplexers  14  can separate out the multiple wavelength data packets arriving on WDM fibers  12  and can forward each individual wavelength signal (data packet) along a wavelength fiber  15  to an input wavelength converter  16 . Incoming data packets can thus be demultiplexed at the input to optical switch  10  and have a different internal wavelength assigned.  
         [0033]    Each incoming data packet can be assigned to a different wavelength by input wavelength converters  16 . Each input WDM fiber  12  can carry up to n wavelengths that can be assigned to incoming data packets, where n is an arbitrary number determined by the capacity of available switching technology. Because there are up to N WDM fibers  12  and each of the WDM fibers  12  can have up to n wavelengths assigned to it, the total number of possible wavelengths is N×n. Currently, each input WDM fiber  12  can carry up to 32 wavelengths. The optical IP switching router architecture of the present invention, however, is scalable to a greater number of wavelengths.  
         [0034]    In the embodiment of the present invention shown in FIG. 1, input wavelength converters  16  are tunable wavelength converters. However, input wavelength converters  16  can also be fixed wavelength converters. When input wavelength converters  16  are fixed, the wavelength of each data packet coming out of a particular wavelength converter  16  can be a fixed (assigned) wavelength. This provides the capability of being able to carry on the same fiber all of the data packets having a particular wavelength (i.e., the same fiber will always carry the same wavelength data packets). By using fixed wavelength converters  16 , it is possible to avoid using a control data input from control unit  20  to control wavelength converters  16 , since a given fixed wavelength converter  16  will only convert data packets to a single wavelength. Despite the need for a control signal, however, tunable wavelength converters can provide more expansion capabilities and greater flexibility than fixed wavelength converters.  
         [0035]    Tunable input wavelength converters  16  of FIG. 1 can convert the wavelength of an incoming data packet along wavelength fibers  15  to any internal wavelength (including the same wavelength as the data packet had when arriving at tunable wavelength converter  16 ). Wavelength conversion can be performed to avoid conflicts that may exist when two or more data packets are destined for the same output. If each of two or more wavelength fibers  15  carry a data packet whose output destination is the same (i.e., each data packet has the same initial wavelength), there exists a potential for a conflict to occur as the data packets are routed to the intended output WDM fiber  48 , with a corresponding potential loss of data. To avoid this conflict, one or more tunable wavelength converters  16  can, upon direction from control unit  20 , convert the wavelengths of one or more of the same wavelength data packets to different unused wavelength(s).  
         [0036]    Conflicts between data packets can occur because all data packets, regardless of which input WDM fiber  12  they arrived on, can be sent along the same path through optical switch  10 . Before a data packet is ultimately routed to its respective output, it can potentially conflict with another data packet having the same wavelength. If two or more data packets have the same wavelength upon arrival, tunable input wavelength converter  16  can convert the wavelength of at least one of the data packets to avoid conflict. Thus, two or more data packets having the same initial wavelength can be routed to the same switch output without conflict because at least one data packet&#39;s wavelength can be converted to a different, nonconflicting wavelength.  
         [0037]    Control unit  20  can provide a control signal to input wavelength converters  16  to control the conversion of data packet wavelengths. Although optical switch  10  is an optical switch architecture, a separate layer of electronics can be used to control optical switch  10 . Control unit  20  can provide control information based on extracted header information from each data packet carried on the N WDM input fibers  12 .  
         [0038]    Header information can be extracted from each data packet before the data packet arrives at input demultiplexers  14 . The header information is forwarded to control unit  20  through input optical-to-electric converters  50 , which can convert the header information from an optical to an electric format. Control unit  20  can determine from the extracted header information what wavelengths are being used within each input WDM fiber  12 . Control unit  20  can provide a control signal to optical switch  10  to route and/or convert the wavelength of the data packet payloads, based on their header information, so that each of the data packet payloads reaches its intended switch output without conflict or loss/corruption of data. If a possibility of overlap/conflict between two or more data packet payloads exists, control unit  20  can issue an appropriate control signal to input wavelength converters  16  to convert the wavelengths of one or more data packet payloads, as discussed above, to avoid the potential conflict. Control unit  20  can track every data packet wavelength so that it does not cause a conversion to occur that avoids one conflict only to cause another. Data packet wavelengths are converted to currently free wavelengths.  
         [0039]    At the output of input wavelength converters  16 , each data packet payload can have a different wavelength, even if one or more data packet payloads are going to the same optical switch  10  output. In the event that a large number of incoming data packets have the same wavelength and are going to the same switch output, a simple wavelength conversion may not be enough to avoid conflicts. To avoid a conflict, optical switch  10  can also include delay buffers  32  to insert an appropriate delay between one or more of the data packets intended for the same switch output. Delay buffers  32  can be Fiber Delay Line (“FDL”) buffers.  
         [0040]    Unlike prior art electronic switch routers, the present invention can operate without a dedicated delay buffer for every data packet input fiber coming into optical switch  10 , and can thus avoid the additional cost and reduced speed of prior art such systems. Prior art electronic switching systems require an optical-to-electric signal conversion for every channel (wavelength) coming into the switching router. Those prior art systems can extract and process header information to route the data packets, but to do so they must convert the entire data packet into electric form and temporarily store the data packet payload while processing the header information. This is both costly and slow because it requires a separate memory buffer for every wavelength to store the data packet payload while reading the header information.  
         [0041]    Because the minimum data packet size is typically fixed, as data transmission speed increases—for example, from the most popular speed today (155 megabytes per second) up to the currently possible 2.5 gigabyte or 10 gigabyte per second speeds—the amount of time that a switching router has to process each individual data packet decreases. Prior art methods that perform an optical-to-electric conversion of the entire data packet become overly problematical as transmission speeds increase due to limits in the data processing speed of prior art switches and routers. Additionally, optical-to-electric conversion is limiting in that individual data packets must be synchronized to recreate each data packet at the output to optical switch  10 .  
         [0042]    The optical IP switching router architecture of the present invention can avoid these problems by tapping a single channel (wavelength) on each input WDM fiber  12 . This channel can contain all of the control information for the input WDM fiber  12 . Additionally, the entire process, except for the header information extraction (control information extraction), is entirely optical. Furthermore, extraction of the header information requires manipulation of less data when compared to extraction of the entire data packet. The present invention allows multiple data packet payloads to be processed together in an optical format. This can provide the capability for much faster speeds than are possible with current switching technology. The present invention, for example, can process data through-puts in excess of 40 gigabits. The optical IP switching router architecture of the present invention is also transparent, meaning that optical switch  10  can operate independently of data transmission speed.  
         [0043]    Extracted header information is reassembled with the its respective data packet payload at the output of optical switch  10 . Electric-to-optical converters  60 , at the output of control unit  20 , can convert the header information back to an optical format to be reassembled with its associated data packet payload. The present invention thus can reduce the number of optical-to-electric conversions (and vice versa) from that of the prior art (one conversion for each wavelength) to just a single conversion for each input WDM fiber  12  to optical switch  10 .  
         [0044]    From input wavelength converter  16 , data packet payloads (each having a different wavelength) can be forwarded to one of 1 to N optical space switches  18 . Optical space switches  18  (one for each input WDM fiber  12 ) are similar to electronic space switches but operate entirely in the optical domain. Optical space switches  18  are shown in FIG. 1 as nxn space switches, but they can be scaled to fit any switch architecture. A nxn space switch, as shown in FIG. 1, splits each incoming signal into n signals identical to the incoming signal. As examples, three-by-three, four-by-four, five-by-five (and so on) space switches can split each incoming data packet signal into three, four and five individual signals (and so on), as the case may be.  
         [0045]    Input splitters  22  split the incoming signals within optical space switches  18 . Optical space switches  18  can have up to n input splitters each, corresponding to the n wavelengths carried on each input WDM fiber  12 . Input splitters  22  can split an incoming signal into as many component signals as required by optical space switch  18 (e.g., split into two signals for a n×n optical space switch  18 ). Once split, each signal can be forwarded to an input Semiconductor Optical Amplifier gate (SOA)  24 .  
         [0046]    Each input SOA  24  is like an on/off switch that can either pass a signal when “on,” or can block a signal from passing when “off.” Input SOAs  24  can be controlled by an input signal from control unit  20 . Each input SOA  24  can have a driver to control its operation. For example, if the current through an input SOA  24  is one value (e.g., 200 milliamps), then input SOA  24  can become transparent and pass an incoming signal through it. Alternatively, if the current through an input SOA  24  is a lesser value (e.g., 50 milliamps), the input SOA  24  can become obscure and absorb the optical signal, preventing transmission. Input SOAs  24  can provide the capability for fast data packet switching.  
         [0047]    Based on a 40-byte data packet (the smallest data packet in the IP format) and a transmission speed of 10 gigabits per second, the time a gate can change state between ON and OFF between data packets is only about five to ten nanoseconds. To provide for fast data packet switching, the state of a switch, such as an input SOA  24 , must be changed in that five to ten nanosecond time period. Input SOAs  24  can currently perform this fast data packet switching.  
         [0048]    Buffers in fast data packet switching can be used to avoid conflicts between incoming data packets that may have the same optical switch  10  output destination. As discussed previously, conflicts can occur even after wavelength conflicts between incoming data packets have been resolved by input wavelength converters  16 . Two or more data packets going to the same switch output, even though they may be assigned different wavelengths, can arrive at optical switch  10  at the same time and hence still have the potential to conflict. To avoid this potential conflict, optical switch  10  can direct one or more of the data packets to different levels of delay in one or more of delay buffers  32 . Input SOAs  24 , with their capability for fast data packet switching, can be used to direct incoming data packets to different delay buffers  32 .  
         [0049]    The delay buffer  32  to which a data packet payload is directed determines the amount of delay inserted into that data packet. As shown in FIG. 1, the output of input SOAs  24  can be forwarded to any one of 1 to B input couplers  26 . Input couplers  26  can couple together all of the data packets coming into optical space switches  18  that require the same amount of delay. Input couplers  26  can send the coupled signals to the appropriate delay buffer  32 .  
         [0050]    Optical switch  10  can have  1  to B delay buffers  32 . Thus, each optical space switch  18  can take as inputs up to n input data packet payloads and output up to B coupled signals for delay. There is no particular relationship between n and B. The value of B can be determined by the performance desired from optical switch  10 . For example, if the data through-put is 10,000 data packets per second and the maximum acceptable loss desired is one data packet per second, then B may be made equal to, e.g. ten, corresponding to ten possible levels of delay. If out of the 10,000 data packets per second it is acceptable to lose ten data packets per second, then B might be made equal to a single delay buffer (i.e., B=1).  
         [0051]    Input couplers  26  forward the coupled data packets requiring the same level of delay to buffer couplers  28 . Buffer couplers  28  can couple together the data packets from each of the N optical space switches  18  that require the same amount of delay and forward the coupled data packets to the appropriate delay buffer  32 . Buffer couplers  28  can be the same technology as input couplers  26 , although perhaps of different sizes. This is because input couplers  26  can couple up to n data packet signals corresponding to the possible n wavelengths of each input WDM fiber  12 . Buffer couplers  28 , however, must be able to couple a number of data packet inputs equal to N, the number of input WDM fibers  12 , since each buffer coupler  28  receives a single signal from each optical space switch  18 .  
         [0052]    Optical switch  10  can have a number of delay buffers  32  equal to B. The number of delay buffers  32  can be scaled to any number, but is limited by cost of components. This is because as the number of delay buffers  32  increases, the number of input SOAs  24  required also increases. As previously discussed, the number of delay buffers  32  (the value of B) can be determined by the level of performance desired from optical switch  10 . Delay buffers  32  can provide an increasing level of delay, with the first delay level being a zero delay. Each subsequent delay buffer  32  can insert an additional unit level of delay, where a unit level of delay can be the average data packet length.  
         [0053]    Optical switch  10  can have the same number of delay buffers  32  as buffer couplers  28  and input couplers  26 , since the function of buffer couplers  28  and input couplers  26  is to direct data packets requiring the same level of delay to the appropriate delay buffer  32 . For example, if 64 wavelengths come into optical space switch  18  and B is equal to five (i.e., there are five input couplers  26 , five buffer couplers  28  and five levels of delay buffer  32 ), then there are five outputs from each optical space switch  18 . As discussed above, each data packet coming in at a different wavelength can be split into five identical signals by input splitters  22 , with each of these five signals requiring an input SOA  24 . Optical switch  10 &#39;s architecture can thus scale to very large component numbers very quickly, since the number of input SOAs  24  required is equal to (n×B).  
         [0054]    Once delay buffers  32  have inserted the appropriate level of delay into each of the data packets from input WDM fibers  12 , all of the data packets (potentially (n×N) different wavelengths) can be coupled together by buffer output coupler  34  into combined signal  39 . Combined signal  39  can be forwarded from buffer output coupler  34  to output splitter  36  along combined fiber  69 . Output splitter  36  can split combined signal  39  into its component data packets, at their respective different wavelengths, and forward the data packets onto one of N output fibers  38 .  
         [0055]    Combined signal  39  from output coupler  34  can carry all data going to all of optical switch  10 &#39;s outputs (every wavelength data packet). Buffer output coupler  34  can combine all the data packets that at a given time are ready to be forwarded to their respective outputs. For example, if input data packet  1  arrives at optical switch  10  at time t=0, input data packet  2  arrives at time t=1, and input data packet  3  arrives at time t=2, then if input data packet  1  is delayed two delay increments and input data packet  2  is delayed one delay increment and input data packet  3  is not delayed at all, all three data packets will arrive at buffer output coupler  34  at the same time. Buffer output coupler  34  can couple all three data packets into combined signal  39  and forward combined signal  39  to output splitter  36 .  
         [0056]    One reason for combining all of the data packets into a single combined signal  39  along a combined fiber  69  is that information arriving on distinct input WDM fibers  12  may be needed in a combined form at the output of optical switch  10 , along one or more different output WDM fibers  48 . Buffer output coupler  34  can provide this function by coupling all of the data packet outputs into combined signal  39 . Combined signal  39  can be split along perhaps different parameters and along different output WDM fibers  48  than that on which the data packets originally entered optical switch  10 . Information (data packets) that may have arrived at optical switch  10  along distinct input WDM fibers  12  can thus be appropriately delayed and recombined such that information from two or more input WDM fibers  12  can be combined into a single output WDM fiber  48 .  
         [0057]    Another advantage of combining all of the input data packets, regardless of their wavelength, into a single combined fiber  69  is that it can provide for a multicast/broadcast function, voice over IP, and video on demand. The optical IP switching router architecture of the present invention can provide these functions because coupling together the information coming into optical switch  10  into a combined fiber  69  allows every output from optical switch  10  to selectively receive all or part of the information carried on combined fiber  69 . Combined signal  39  need not be separately assigned to each switch output, but instead can serve as a source feed that every switch output can tap into. All or part of combined signal  39  can thus be routed to any or all switch outputs.  
         [0058]    Combined signal  39  can be forwarded by buffer output coupler  34  to output splitter  36 , which can split combined signal  39  into N individual signals having the same information as combined signal  39  and each carried on N output channels  38 . Output channels  38  can feed into N output demultiplexers  40 . Each output demultiplexer  40  can thus receive all the data coming into optical switch  10 .  
         [0059]    Output demultiplexers  40 , one for each of the N output WDM fibers  48 , can separate out the different wavelengths carried within combined signal  39 . On the downstream side of output demultiplexer  40   s  there can be up to (n×N) individual fibers  43 , one for each of the possible (n×N) different data packet wavelengths. On each individual fiber  43  there can be an output SOA  42  followed by an output wavelength converter  44 . Control unit  20  can provide a control signal to output SOAs  42  such that, in the same manner discussed for input SOAs  24 , a particular wavelength can either be allowed to pass through or can be absorbed.  
         [0060]    Each signal allowed to pass through an output SOA  42  can be forwarded to an output wavelength converter  44 . Output wavelength converters  44  are tunable wavelength converters. Output wavelength converters  44  perform the same function as input wavelength converters  16  and can convert the wavelength of a particular data packet. In particular, output wavelength converters  44  can convert the wavelength of a data packet at the output of optical switch  10  back to the original wavelength that data packet had at the input to optical switch  10 . At output couplers  46 , all of the wavelengths selected by control unit  20  through output SOAs  42  to comprise the signal for a particular output WDM fiber  48  are combined and forwarded from optical switch  10  along output WDM fibers  48 .  
         [0061]    On average, the number of inputs into output demultiplexers  40  equals the number of outputs from output coupler  46 . However, the number can differ at a particular point in time, depending on which wavelengths are allowed to go through, and which wavelengths are blocked by, output SOAs  42 . As previously discussed, data packets arriving at optical switch  10  along different input WDM fibers  12  can be combined at the output of optical switch  10  onto one or more output WDM fibers  48 . For example, a data packet could arrive at optical switch  10  along a single fiber (e.g., fiber  1 ) and be split and selected for output along every output WDM fiber  48 . This is one example of a multicast function data packet.  
         [0062]    In prior art switching architectures, bottlenecks can occur at the output of a coupler, such as buffer output coupler  34 , because the output from the combined delay buffers  32  can have up to (n×N) wavelengths. Current switching technology is only capable of a total of 32 wavelengths on a single fiber, which limits the number of input WDM fibers  12  that can be used depending on the number of wavelengths per fiber. In the embodiment of this invention shown in FIG. 1, however, optical switch  10  can potentially process  256  different wavelengths per internal fiber. Therefore, if each input WDM fiber  12  can hold  32  wavelengths (n), then N can be equal to eight (i.e., there can be eight input WDM fibers  12 ). Furthermore, the optical IP switching router architecture of the present invention, because of its transparency to transmission speed, can be scaled up to some five to six terrabits per second. The capacity of the present invention is thus dependent upon, and limited by, the capacity of input WDM fibers  12  and output WDM fibers  48 . However, even with the current limitation of 32 wavelengths per fiber, the number of input WDM fibers  12  can be increased using the present invention.  
         [0063]    [0063]FIGS. 2 a  and  2   b  show another embodiment of the optical IP switching router architecture of the present invention. The embodiment of FIGS. 2 a  and  2   b  performs the same function as the embodiment of this invention shown in FIG. 1. However, the embodiment of FIGS. 2 a  and  2   b  has reduced component requirements. The embodiment of the present invention shown in FIGS. 2 a  and  2   b  can assign separate wavelengths to the multicast and broadcast functions at the input to optical switch  10 . A smaller number of output SOAs  42  can then be used as compared to the embodiment of FIG. 1. Further, the number of tunable output wavelength converters  44  can likewise be reduced.  
         [0064]    Because broadcast and multicast functions are not needed at all times, the embodiment of the optical IP switching router architecture of the present invention shown in FIGS. 2 a  and  2   b  can assign specific wavelengths to those functions. The embodiment of FIGS. 2 a  and  2   b  has limited broadcast and multicast functions as compared to the embodiment of FIG. 1 because not all data packets can be routed along all fibers. Broadcast and multicast data packets are instead segregated in the output channels (prior to output couplers  46 ) from unicast data packets. However, this is compensated for by the decrease in component costs. Dedicated wavelengths can be assigned to broadcast and multicast data packets because only about 10% to 20% of the total data transmitted through optical switch  10  at a given time is broadcast or multicast data.  
         [0065]    The embodiment of the present invention shown in FIGS. 2 a  and  2   b  is essentially identical to the embodiment shown in FIG. 1 up to buffer output coupler  34 . An exception is that input wavelength converters  16  must be tunable wavelength converters in the embodiment shown in FIGS. 2 a  and  2   b . Additionally, the embodiment of FIGS. 2 a  and  2   b  typically requires more wavelengths be available than in the embodiment of FIG. 1. These additional wavelengths are labeled in FIGS. 2 a  and  2   b  as λ x+1  up to λ x+m , where m is an arbitrary number chosen to satisfy the data throughput needs of the broadcast and multicast functions. The total number of wavelengths carried over optical switch  10  is therefore (N×n)+(m).  
         [0066]    On the downstream side of buffer output coupler  34  there are several differences in the embodiment of the present invention shown in FIGS. 2 a  and  2   b  from the embodiment of FIG. 1. Data packets arriving at input demultiplexers  14  along input WDM fibers  12  can be sent along wavelength fibers  15  to input wavelength converters  16  in the same manner as discussed above for FIG. 1. However, input wavelength converters  16  of FIGS. 2 a  and  2   b  serve the additional function of assigning one set of wavelengths to normal (unicast) IP data packets, and a different set of wavelengths to multicast and broadcast function data packets.  
         [0067]    Data packets arriving at tunable wavelength converters  16  can thus be assigned a wavelength dependent upon their intended optical switch  10  output. This can be accomplished by assigning only certain different internal wavelengths to each of output WDM fibers  48 . When a data packet arrives at optical switch  10  intended for a particular output WDM fiber  48 , one of the wavelengths set aside for that output WDM fiber  48  can be assigned to the data packet. If a subsequent data packet for the same output WDM fiber  48  arrives at optical switch  10 , another free wavelength set aside for that output WDM fiber  48  can be assigned to the subsequent data packet, and so on. Otherwise, the operation of the embodiment of optical switch  10  of the present invention shown in FIGS. 2 a  and  2   b  is substantially the same as described for the embodiment of optical switch  10  shown in FIG. 1.  
         [0068]    Output demultiplexers  40  can direct each data packet (wavelength) to the appropriate output WDM fiber  48 . Control unit  20  can provide the control signals to perform these data traffic routing functions. In this way, depending on the data packet type (e.g., whether it is a unicast or multicast/broadcast data packet), data packets can be converted to different wavelength groups, group, e.g, unicast in 1 to N×n and multicast from x to x+m, for routing to a particular output WDM fiber  48 . One set of wavelengths can be set aside for unicast data packets, based on the unicast data packet&#39;s intended output WDM fiber  48 . Similarly, another different set of wavelengths can be reserved for multicast/broadcast traffic. The total number of wavelengths is (N×n)+(m), where (N×n) wavelengths are for unicast traffic and (m) wavelengths are for multicast/broadcast traffic. For example, for unicast traffic, a first output WDM fiber  48  can be assigned wavelengths 1 to n, a second output WDM fiber  48  can be assigned wavelengths (n+1) to (2×n), and so on, up to the N th  output WDM fiber  48 . The N th  output WDM fiber  48  can be assigned wavelengths [(N−1×(n+1)] to (N×n).  
         [0069]    The output matrix for optical switch  10  can thus be made very simple and avoid the use of additional output SOAs  42  and output tunable wavelength converters  44  for the processing of unicast traffic. For multicast/broadcast data packets, wavelengths between x and (x+m) can be assigned to the data packets and the data packets broadcast to all output WDM fibers  48  in a manner similar to that discussed for the embodiment of FIG. 1.  
         [0070]    [0070]FIGS. 2 a  and  2   b  also can include up to N subsplitters  90  downstream of output splitter  36 . Subsplitters  90  can split combined signal  39  (which can include additional wavelengths λ x+1  up to λ x+m ) into two signals, one going to unicast demultiplexers  70 , the other going to broadcast demultiplexers  72 . Unicast demultiplexers  70  and broadcast demultiplexer  72  can discriminate based on wavelength. Unicast demultiplexers  70  can separate out all of the unicast wavelengths from combined signal  39  and forward them to fixed output wavelength converters  80 . Similarly broadcast demultiplexers  72  can filter out the broadcast/multicast data packet wavelengths and forward the respective data packets to output SOAs  42 .  
         [0071]    Unicast data packets can thus be sent directly to their intended output WDM fiber  48  based on their assigned wavelength. Each output WDM fiber  48  has its assigned wavelengths, which are the only wavelengths allowed through by the respective unicast demultiplexer  70 . The data packets output from fixed output wavelength converters  80  can be coupled together by output couplers  46  and transmitted as an output from optical switch  10  along their respective output WDM fiber  48 . Control unit  20  need not provide an input to the output portion of optical switch  10  to control the routing of the unicast data packets because they have been pre-selected at the input to optical switch  10  to go to a particular output WDM fiber  48 . The unicast data packets can be routed automatically through the operation of unicast demultiplexers  70 . Unicast demultiplexers  70  and broadcast demultiplexers  72  can be broadband filters that allow through only certain wavelengths.  
         [0072]    Output SOAs  42  and output tunable wavelength converters  44  of FIGS. 2 a  and  2   b  perform the same function as in the embodiment of the present invention shown in FIG. 1. Control unit  20  can likewise provide a control signal input to output SOAs  42  and output wavelength converters  44  to control which broadcast/multicast data packets are allowed through output SOAs  42 . Broadcast/multicast data packets allowed through output SOAs  42  can have their wavelengths converted by output tunable wavelength converters  44  to avoid conflicts in the same manner as discussed above with regards to FIG. 1. Data packets allowed through output SOAs  42  can be broadcast to every output WDM fiber  48 .  
         [0073]    The embodiments of the present invention shown in FIG. 1 and FIGS. 2 a  and  2   b  can both provide transparent optical data packet switching for internet traffic. They also can both provide multicast and broadcast functionality at the switch level. The active components in optical switch  10  of either embodiment can handle one wavelength at a time to reduce the cross-talk among channels.  
         [0074]    [0074]FIG. 3 is a close-up block diagram of an optical space switch  18  of the present invention as shown in FIG. 1 and FIGS. 2 a  and  2   b . Wavelength fibers  15  enter optical space switch  18  and progress through input splitter  22 , input SOAs  24 , and input couplers  26 , as described above as part of FIG. 1. The operation of optical space switch  18  can be controlled by control unit  20  as previously described.  
         [0075]    Although the present invention has been described in detail herein with reference to the illustrative embodiments, it should be understood that the description is by way of example only and is not to be construed in a limiting sense. It is to be further understood, therefore, that numerous changes in the details of the embodiments of this invention and additional embodiments of this invention will be apparent to, and may be made by, persons of ordinary skill in the art having reference to this description. It is contemplated that all such changes and additional embodiments are within the spirit and true scope of this invention as claimed below.