Abstract:
The high speed data link includes a light modulating device having an output, a source of light of a certain wavelength and a superconductive material, which is switchable between superconducting and non-superconducting states. This light modulating device also includes an arrangement for switching the superconductive material to provide at the output a train of light pulses having the certain wavelength. The high speed data link further includes a wavelength changing device, for changing the wavelength of the light pulses, an optical fiber, for directing the train of wavelength changed light pulses away from the wavelength changing device, and an arrangement, for receiving the train of wavelength changed light pulses. The receiving arrangement includes a demultiplexer, for dividing the train of wavelength changed light pulses into a series of sub-trains of wavelength changed light pulses, and a series of optical receivers, each optical receiver detecting at least one of the sub-trains.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    The present application is a continuation-in-part of copending U.S. patent application Ser. No. 09/637,098 Attorney Docket Number PUZ-P001-C2 entitled “Light Modulation System including a Superconductive Plate Assembly for Use in a Data Transmission Scheme and Method, which is incorporated herein by reference. The aforementioned copending U.S. patent application Ser. No. 09/637,098 is a continuation of U.S. patent application Ser. No. 09/208,326 Attorney Docket Number PUZ-P001C, also entitled “Light Modulation System including a Superconductive Plate Assembly for Use in a Data Transmission Scheme and Method” and now issued U.S. Pat. No. 6,115,170, which is incorporated herein by reference. U.S. Pat. No. 6,115,170 is itself a continuation of U.S. patent application Ser. No. 08/643,642 Attorney Docket Number PUZ-P001, which is now issued U.S. Pat. No. 5,768,002 of Puzey. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates generally to fiber optic communications and, more particularly, to high speed data links for use with light modulation systems including a superconductive plate assembly in a data transmission scheme.  
           [0003]    The light modulation system as disclosed in U.S. Pat. No. 5,768,002 is capable of transmitting optical data signals at high data rates such as, for example, rates of terabits per second (Tbit/s) at a given wavelength over a single optical fiber. For example, the light modulation system can be used in a wavelength-division multiplexing (WDM) system to provide the optical data signal at a WDM channel.  
           [0004]    However, in order to achieve a complete data link capable of handling optical data signals at a single wavelength at Tbit/s rates, an optical receiver in the data link must be able to detect the optical data signals at Tbit/s rates. Such an optical receiver singly capable of detecting Tbit/s optical data signals of a single wavelength is not commercially available at the present time to the applicant&#39;s knowledge. Although optical detectors capable of detecting optical signals at a rate of 750 GHz or with response times on the order of picoseconds or less are known in the art, these devices are still in their experimental stages hence are not yet commercialized.  
           [0005]    Prior art data links have not had to deal with this problem of the unavailability of Tbit/s rate optical receivers because light modulation systems capable of transmitting optical data signals at Tbit/s rates at a given wavelength are not currently known at this time to the applicant&#39;s knowledge, with the exception of the light modulation system disclosed in U.S. Pat. No. 5,768,002. Existing high speed light modulation systems generally consist of a series of N light modulators, each light modulator corresponding to one channel out of N channels and producing optical data signals at rates of less than Tbit/s at a unique wavelength corresponding to a particular WDM channel out of a range of wavelengths λ 1 -λ N . The multitude of optical data signals over the range of wavelengths, each optical data signal having its own unique wavelength, are multiplexed onto an optical fiber. The multiplexed signal is received by a demultiplexer which separates the multiplexed signal into the separate optical data signals according to wavelength. The separated optical data signals are then detected by a plurality of optical detectors, each operating at less than Tbit/s rates.  
           [0006]    The prior art data link as a whole can be made to transmit data at Tbit/s rates by using a plurality of data sources, optical sources and optical detectors all operating at Gbit/s rates. For example, if a hundred optical sources are provided (i.e., N=100), with each optical source generating an optical signal at 10 Gbit/s and at a distinct wavelength out of the wavelength range λ 1  through λ 100 , then the aggregate optical data rate is one Tbit/s. Following transmission through an optical fiber, a WDM multiplexer combines the one hundred optical signals such that the resulting multiplexed signal contains all optical signals of the wavelength range λ 1  through λ 100 . The WDM demultiplexer then separates the multiplexed signal into distinct wavelengths to be detected by a hundred optical detectors, each detector operating at 10 Gbits/s. As a result, it is possible to transmit data using the prior art data link at an aggregate rate of 1 Tbit/s.  
           [0007]    It is submitted, however, the aforedescribed prior art data link has a number of disadvantages. In order to increase the total data transmission rate of the prior art data link above approximately 1 Tbit/s, the number of channels, and hence the number of data sources and optical sources used in the data link, must be increased. This condition may be satisfied by narrowing the wavelength differences between channels thus fitting more channels into a given wavelength range λ 1  through λ N  and/or widening the wavelength range between λ 1  and λ N . However, narrowing the wavelength differences between the channels increases the probability of data transmission error due to potential optical signal overlap and crosstalk and puts a greater demand on the WDM demultiplexer to accurately separate the optical signals into the distinct wavelengths. As is well known in the art, there is only a finite range available for use as the wavelength range λ 1  through λ N , outside of which significant optical signal loss occurs due to the material properties of the optical fiber as well as other components of an optical communication system, such as repeaters and amplifiers. Therefore, the wavelength range cannot be widened indefinitely using currently available technology, hence it is difficult to increase the number of channels to increase the data transmission rate. Furthermore, increasing the number of different wavelengths traveling simultaneously through the optical fiber also increases the probability of occurrence of undesired, nonlinear optical effects during transmission. Care must be taken to avoid such nonlinear optical effects, thus adding to the overall complexity and cost of this prior art data link at faster data transmission rates. Still further, WDM channels require a guard band on either side of the specific channel wavelength in order to reduce wavelength overlap and crosstalk between channels. Since no data can be transmitted on the guard band, the wavelengths used in the guard band are essentially wasted bandwidth.  
           [0008]    The present invention provides a high speed data link which serves to resolve the problems described above with regard to prior art data links in a heretofore unseen and highly advantageous way and which provides still further advantages.  
         SUMMARY OF THE INVENTION  
         [0009]    As will be described in more detail hereinafter, there is disclosed herein a high speed data link including a transmitting arrangement having a transmitter output. The transmitting arrangement includes a source of light having a certain wavelength. The transmitting arrangement further includes a layer of superconductive material through which the light from the source must pass before the light can reach the transmitter output. The superconductive material is switchable between a superconducting state in which the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. Still further, the transmitting arrangement includes an arrangement for switching the superconductive material between its superconducting and non-superconducting states to provide a train of light pulses having the certain wavelength and containing optical data. The transmitting arrangement further includes a wavelength changing device, which is optically coupled to the layer of superconductive material, for changing the wavelength of the light pulses and providing a train of wavelength changed light pulses containing optical data at the transmitter output. The high speed data link also includes an optical fiber, one end of which is optically coupled to the transmitter output, for directing the train of wavelength changed light pulses away from the transmitting arrangement. Additionally, the high speed data link includes a receiving arrangement optically coupled to an opposing end of the optical fiber. The receiving arrangement includes an all-optical demultiplexer for dividing the train of wavelength changed light pulses into a series of sub-trains of wavelength changed light pulses. The receiving arrangement further includes a series of optical receivers, each optical receiver being designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses.  
           [0010]    In another aspect of the invention, the transmitting arrangement of the high speed data link includes a series of light modulating devices for generating a series of trains of light pulses over a specified range of wavelengths. Each light modulating device has a light output and provides at its output one of the trains of light pulses, and the light pulses of each train of light pulses have an assigned wavelength out of the specified range of wavelengths. Each light modulating device includes a source of light having a given wavelength and a layer of superconductive material through which the light from the source must pass before the light can reach the light output of that light modulating device. The superconductive material is switchable between a superconducting state in which the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. Each light modulating device further includes an arrangement for switching the superconductive material between its superconducting and non-superconducting states to provides a train of light pulses having the given wavelength and containing optical data. In addition, each light modulating device includes a wavelength changing device, optically coupled to the layer of superconductive material, for changing the wavelength of the light pulses from the given wavelength into the assigned wavelength and providing a train of wavelength changed light pulses containing optical data at the light output such that no two light modulating devices in the series of light modulating devices generate trains of light pulses at the same assigned wavelength out of the specified range of wavelengths. The transmitting arrangement further includes a WDM multiplexer optically coupled to the light outputs of the series of light modulating devices for reading the series of trains of wavelength changed light pulses in parallel and combining the series of trains of wavelength changed light pulses into a multiplexed signal at the transmitter output of the transmitting arrangement. An optical fiber, one end of which is optically coupled to the transmitter output, directs the multiplexed signal away from the transmitting arrangement. The high speed data link further includes a receiving arrangement including a WDM demultiplexer, optically coupled to an opposing end of the optical fiber, for receiving the multiplexed signal and separating the multiplexed signal back into the series of trains of wavelength changed light pulses. Further, the receiving arrangement includes a series of light receiving devices configured to receive the series of trains of wavelength changed light pulses. Each of the receiving arrangements is optically coupled to the WDM demultiplexer and is designed to receive at least one of the trains of wavelength changed light pulses of a particular wavelength out of the specified range of wavelengths. Moreover, each of the receiving arrangements includes an all-optical demultiplexer for dividing the train of wavelength changed light pulses into a series of sub-trains of wavelength changed light pulses. Additionally, each of the receiving arrangements further includes a series of optical receivers, each of which is designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses.  
           [0011]    In still another aspect of the invention, a method for providing a high speed data link is disclosed. Accordingly, a train of light pulses containing optical data is transmitted. In this transmitting step, light having a certain wavelength is generated and directed onto a layer of superconductive material, which is switchable between a superconducting state in which the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. The superconductive material is switched between its superconducting and non-superconducting states for generating a train of light pulses having the certain wavelength . The wavelength of the light pulses is then changed to provide a train of wavelength changed light pulses containing optical data. The train of wavelength changed light pulses is directed to a desired location then received at the desired location and divided into a series of sub-trains of wavelength changed light pulses. Additionally, the series of sub-trains of wavelength-changed light pulses are detected using a series of optical receivers, each of which is designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses.  
           [0012]    In yet another aspect of the invention, an alternative method for providing a high speed data link is disclosed. Accordingly, a multiplexed signal containing optical data is transmitted. In this transmitting step, light of a given wavelength is generated and directed onto a layer of superconductive material, which is switchable between a superconducting state in which the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. The superconductive material is switched between its superconducting and non-superconducting states for generating a train of light pulses having the given wavelength and containing optical data. The wavelength of the light pulses is changed from the given wavelength to an assigned wavelength out of a specified range of wavelengths. The steps of light generation, switching of the superconductive material and wavelength changing are repeated to provide a series of trains of wavelength changed light pulses, each of which trains of wavelength changed light pulses contains optical data and has a distinct, assigned wavelength out of the specified range of wavelengths in such a way that no two trains of wavelength changed light pulses in the series of trains of wavelength changed light pulses have the same assigned wavelength out of the specified range of wavelengths. The series of trains of wavelength changed light pulses are read in parallel and combined into a multiplexed signal containing optical data. The multiplexed signal is directed to a desired location and received at the desired location where the received, multiplexed signal is separated back into the series of trains of wavelength changed light pulses. Each of the trains of wavelength changed light pulses is divided into a series of sub-trains of wavelength changed light pulses. The series of sub-trains of wavelength is detected using a series of optical receivers, each of which is designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses of a particular, assigned wavelength out of the specified range of wavelengths.  
           [0013]    In still yet another aspect of the present invention, an optical communication system for use with a communication satellite is disclosed. The optical communication system includes means for transmitting a train of light pulses containing optical data. Transmitting means has a transmitter output and includes a source of light having a certain wavelength and a layer of superconductive material through which the light from the source must pass before the light can reach the transmitter output. The superconductive material is switchable between a superconducting state in which the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. Transmitting means also includes an arrangement for switching the superconductive material between the superconducting and non-superconducting states for providing a train of light pulses having the certain wavelength and containing optical data. Transmitting means also includes a wavelength changing device optically coupled to the layer of superconductive material for changing the wavelength of the light pulses and providing a train of wavelength changed light pulses containing optical data at the transmitter output. The optical communication system also includes means for directing the train of wavelength changed light pulses from the transmitter output to the communication satellite, which redirects the train of wavelength changed light pulses toward a desired location, and means for intercepting the train of redirected, wavelength changed light pulses from the satellite at the desired location. The optical communication system further includes means for receiving the train of redirected, wavelength changed light pulses intercepted by the intercepting means. Receiving means includes an all-optical demultiplexer for dividing the train of redirected, wavelength changed light pulses into a series of sub-trains of wavelength changed light pulses and a series of optical receivers, each of which is designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses. 
       
    
    
     BRIEF DESCRIPTION OF THEIR DRAWINGS  
       [0014]    The present invention may be understood by reference to the following detailed description taken in conjunction with the drawings briefly described below.  
         [0015]    [0015]FIG. 1 is a diagrammatic illustration of a data link designed in accordance with the present invention and employing a superconducting layer and a wavelength converting device to modulate light.  
         [0016]    [0016]FIG. 2 is a diagrammatic illustration of an alternative embodiment of a data link designed in accordance with the present invention.  
         [0017]    [0017]FIG. 3 is a diagrammatic illustration of yet another embodiment of a data link manufactured in accordance with the present invention.  
         [0018]    [0018]FIGS. 4A and 4B are diagrammatic illustrations of alternative embodiments of an optical transmitter as shown in FIG. 3.  
         [0019]    [0019]FIGS. 5A, 5B and  5 C are diagrammatic illustrations of alternative embodiments of an optical communication system designed in accordance with the present invention.  
         [0020]    [0020]FIG. 6 is a diagrammatic illustration of an embodiment of an electrical receiver suitable for use in the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0021]    Turning now to the drawings, wherein like components are indicated by like reference numbers throughout the various figures, attention is immediately directed to FIG. 1, which illustrates one embodiment of a high speed data link, generally indicated by the reference numeral  100 , fabricated in accordance with the present invention. Data link  100  includes a transmitter arrangement  112 , optical fiber  113  and receiver arrangement  114 . Transmitter arrangement  112  includes a data source  116  which provides data input  117  to a superconducting arrangement  118 . Data source  116  can be, for example, a high speed modulating circuit, electronic signal generator, serializer, SONET Add/Drop multiplexer, ATM switch or a combination thereof. Superconducting arrangement  118  is switched between a normal state and a superconducting state according to data input  117 . A light source  120  is used to generate light  122  at a wavelength λ 0  directed toward superconducting arrangement  118 . Light source  120  may be a laser, light emitting diode, etc., as is commonly known in the art. By way of example and not a limitation, a quantum cascade (QC) laser is suitable for use as light source  120 . QC lasers are capable of emitting light over a variety of infrared wavelengths that are compatible with superconducting arrangement  118 , ranging from a few microns to tens of microns at high peak powers of hundreds of milliwatts (See, for example, A. Tredicucci, et al, “High-power inter-miniband lasing in intrinsic superlattices,” Applied Physics Letters, 72 (19), pp. 2388-2390). QC lasers are also tunable, thus allowing more flexibility in the specification of superconducting arrangement  118 . Other examples of appropriate light sources include a bismuth antimony BiSb laser (see, for example, A. G. Alksanyan, et al, “Semiconductor laser made of Bi 1-x Sb x ,” Soviet Journal of Quantum Electronics, vol. 14, no. 3, pp. 336-8), germanium laser and gas lasers, such as a laser including a carbon dioxide-pumped cavity with methanol.  
         [0022]    Continuing to refer to FIG. 1, superconducting arrangement  118  is designed in such a way that it is transparent to light of wavelength λ 0  when it is in its normal state, and blocks the transmission of light of wavelength λ 0  when it is in its superconducting state. As a result, light  122  is blocked or transmitted according to data input  117 , and light  122  is modulated by superconducting arrangement  118  to produce a series of optical pulses  123  at wavelength λ 0 . The details of the switching mechanism of superconducting arrangement  118  are described in detail in U.S. Pat. No. 5,768,002.  
         [0023]    Still referring to FIG. 1, it should be noted that the wavelength λ 0  of light  122  and optical pulses  123  is chosen such that wavelength λ 0  is transmitted or blocked by superconducting arrangement  118  depending on whether superconducting arrangement  118  is in its normal or superconducting state. As described in U.S. Pat. No. 5,768,002, superconducting arrangement  118  can perform the function of encoding data input  117  as optical pulses  123  when the wavelength λ 0  is in the far infrared (IR) range (approximately 14 μm or greater). For example, the wavelength λ 0 =25 μm is chosen in the embodiment of the present invention shown in FIG. 1. Unfortunately, since light of far IR wavelengths attenuate rapidly during transmission through conventional, silica glass optical fiber, it is not practical to directly transmit optical pulses of far IR wavelengths through the optical fiber  113 . To counter this problem, optical pulses  123  are directed into a wavelength converting device  125 , which converts optical pulses  123  at the wavelength λ 0  into optical pulses  126  at a shorter wavelength λ conv . The wavelength λ conv  are in the range of approximately 0.5 to 2 μm, preferably on the order of 1.3 or 1.5 μm so as to be compatible with conventional optical fibers. Optical pulses  126  are then directed into one end of optical fiber  113 .  
         [0024]    Optical pulses  126  shown in FIG. 1 are received at an opposing end of optical fiber  113  by receiving arrangement  114 . Receiving arrangement  114  includes an all-optical (AO) demultiplexer  132 . AO demultiplexer  132  divides optical pulses  126  into a plurality of low data rate, optical pulses  126 ′ also with wavelength λ conv . Then, each set of divided, low data rate, optical pulses  126 ′ are detected by an optical detector  134 . For example, AO demultiplexer  132  can be designed to divide optical pulses  126  such that a first data bit goes to a first optical detector, a second data bit goes to a second optical detector, and so on. The optical detectors are, for example, a plurality of interchangeable, generic detectors designed to be sensitive to light of wavelength λ conv . Therefore, while transmitter arrangement  112  generates optical data signals at Tbit/s rates at wavelength λ conv  receiver arrangement  114  is able to detect the Tbit/s rate optical data signals using Gbit/s detectors by dividing optical pulses  126  into slower optical pulses  126 ′, thus achieving Tbit/s rate transmission through data link  100 .  
         [0025]    Data link  100  takes advantage of the high data rate that is possible with a transmitter arrangement based on a superconducting arrangement to provide a complete, high speed data link. Transmitter arrangement  112  as shown in FIG. 1 is capable of encoding data input  117  onto optical pulses  126  of wavelength λ conv  at data rates of approximately 1 Tbit/s. Unlike the aforementioned prior art data link which requires a plurality of data sources and optical sources operating simultaneously at different wavelengths to achieve an aggregate data transmission rate of 1 Tbit/s, transmitter arrangement  112  is singly capable of transmitting optical data in the form of optical pulses at 1 Tbit/s rates at a single wavelength. It is submitted that this feature of optical source  10  is highly advantageous in at least one respect since, by splitting optical pulses  126  into low data rate, optical pulses  126 ′, receiver arrangement  114  is able to detect the high data rate, optical pulses  126  using a series of low speed detectors without the need to use multiple wavelengths and a WDM demultiplexer.  
         [0026]    It should also be understood that only one wavelength, wavelength λ conv , is transmitted through optical fiber  113  of data link  100  illustrated in FIG. 1. Therefore, potential problems associated with the prior art data such as crosstalk and nonlinear optical effects due to the presence of multiple wavelengths in the optical fiber are eliminated in data link  100 . Furthermore, data link  100  does not require the use of a guard band, thus the available bandwidth outside of wavelength λ conv  is not wasted.  
         [0027]    An additional advantage associated with data link  100  resides in the fact that data link  100  is readily up-scalable. Since the overall, data transmission rate depends mainly on the speed at which superconducting arrangement  118  can be modulated, as faster materials or switching schemes are developed for the superconducting arrangement such that transmitter arrangement  112  produces higher rate optical pulses  126 , additional optical detectors  134  can be added in receiver arrangement  114  to accommodate the increased data rate without a need to develop faster optical detectors than are currently available commercially today. As faster optical detectors do become available, the number of optical detectors may be accordingly decreased, thus potentially simplifying the high speed data link of the present invention.  
         [0028]    Attention is now directed to FIG. 2 in conjunction with FIG. 1. FIG. 2 illustrates another data link produced in accordance with the present invention, generally indicated by the reference number  200 . Data link  200  includes a transmitter arrangement  212  as well as optical fiber  113  and receiver arrangement  114 , the latter two components being essentially identical to the corresponding components of data link  100  illustrated in FIG. 1 with like reference numbers. Therefore, the discussion of data link  200  will concentrate on transmitter arrangement  212  which is modified with respect to transmitter arrangement  112  of data link  100 .  
         [0029]    Like transmitter arrangement  112  of FIG. 1, transmitter arrangement  212  shown in FIG. 2 includes light source  120  which generates light  122  of wavelength λ 0  directed towards superconducting arrangement  118 . Superconducting arrangement  118  is switched between its normal and superconducting states according to data input  117 , thus generating optical pulses  123  of wavelength λ 0 . Optical pulses  123  are directed into wavelength converting device  125  which converts optical pulses  123  of wavelength λ 0  into optical pulses  126  of wavelength λ conv .  
         [0030]    However, the way in which data input  117  is generated is different in transmitter arrangement  212  as compared to that of transmitter arrangement  112 . Transmitter arrangement  212  includes a plurality of optical transmitters  150  and  152  arranged to transmit optical modulation pulses in parallel into an optoelectronic (OE) multiplexer  154 . OE multiplexer  154  reads the optical modulation pulses in parallel then serializes the electrical data from the optical modulation pulses, thus generating data input  117 . It should be noted that data input  117  is a serial, electrical signal. For example, commercially-available, 10 Gbit/s optical transmitters, which are well-known in the art, are suitable for use as optical transmitters  150  and  152 . OE multiplexer  154  can be designed to generate data input  117  at rates of one Tbit/s or higher depending on the number of optical transmitters used. In this way, slower optical transmitters can be multiplexed to generate high speed data signals for switching superconducting arrangement  118 , and optical pulses  126  are generated at rates of Tbit/s or higher. OE multiplexer  154  is, for instance, a multiplexer based on Josephson Junction circuitry. Alternatively, the plurality of optical transmitters  150  and  152  and OE multiplexer  154  is replaceable by a system of a plurality of fiber optic transmitters, receivers, optical fibers and a high speed shift register, as described in U.S. Pat. No. 5,768,002.  
         [0031]    Referring now to FIG. 3, a diagrammatic illustration of still another embodiment of a data link manufactured in accordance with the present invention, generally indicated by reference numeral  300 , is shown. Data link  300  includes a transmitter arrangement  312 , an optical fiber  313  and a receiver arrangement  314 . Transmitter arrangement  312  includes a series of optical transmitters  212 ′. Each optical transmitter  212 ′ is identical to transmitter arrangement  212  illustrated in FIG. 2 with a modification that optical transmitter  212 ′ is designed to generate optical pulses  126 ′ of a particular wavelength out of the wavelength range λ conv1  to λ convN  in such a way that no two optical transmitters generate optical pulses  126 ′ at the same wavelength. As described in the discussion of FIG. 2, each optical transmitter  212 ′ is capable of generating optical pulses  126 ′ at rates of Tbit/s or higher.  
         [0032]    The series of optical pulses  126 ′ are directed into a WDM multiplexer  324  which combines the series of optical pulses  126 ′ such that the series of optical pulses  126 ′, each set of optical pulses  126 ′ having a distinct wavelength out of the wavelength range λ conv1  to λ convN , are together directed into optical fiber  313  as optical pulses  326 . Optical pulses  326  contains all sets of optical pulses  126 ′ such that all optical data encoded into the series of optical pulses  126 ′ are transmitted down optical fiber  313  simultaneously. In this way, optical pulses  326  carries optical data signals at an aggregate rate which is greater than Tbit/s.  
         [0033]    Optical pulses  326  are transmitted through optical fiber  313  and into receiver arrangement  314 , where optical pulses  326  are received by a WDM demultiplexer  332 . WDM demultiplexer  332  separates optical pulses  326  back into the series of optical pulses  126 ′ according to wavelength. Each set of optical pulses  126 ′ is directed into an optical receiver  114 ′, which is identical to receiver arrangement  114  of FIG. 1 with a modification that AO demultiplexer  132  is designed to divide a set of optical pulses  126 ′ of at least one particular wavelength out of the wavelength range λ conv1  to λ convN  into a plurality of low data rate, optical pulses  126 ”. Thus, each optical receiver  114 ′ is capable of receiving optical pulses  126 ′ at rates of Tbit/s or higher. Furthermore, by using a WDM demultiplexer and a plurality of wavelengths with each wavelength carrying optical data at rates of Tbit/s, receiver arrangement  314  is able to receive optical data at an aggregate rate of much higher than Tbit/s.  
         [0034]    Turning to FIGS. 4A and 4B, two possible alternatives for the optical transmitter  212 ′ are illustrated. Although two specific schemes for the optical transmitter are shown, these configurations are not to be considered as limiting. Various modifications may be made to the optical transmitter alternatives shown in FIGS. 4A and 4B while keeping with the spirit of the present invention.  
         [0035]    [0035]FIG. 4A is a diagrammatic illustration of an optical transmitter  212 ′A, which is the X th  optical transmitter in a series of N optical transmitters. Optical transmitter  212 ′A includes a wavelength converting device  125 ′ with a pump laser  340  and a nonlinear optical crystal  342 . Pump laser  340  provides a pump beam  344  of a predetermined wavelength λ pX  directed at nonlinear optical crystal  342 . Optical pulses  123  from superconducting arrangement  118  are also incident on nonlinear optical crystal  342 . Since the specific wavelength generated by the wavelength converting device  125 ′ depends on the material characteristics of nonlinear optical crystal  342  and the wavelength of pump laser  340 , the predetermined wavelength λ pX  of pump beam  344  is selected such that optical pulses  123  of wavelength λ 0  are converted into optical pulses of a particular wavelength λ convX  out of the wavelength range λ conv1  to λ convN . By using identical nonlinear optical crystals  342  in all optical transmitters  212 ′ and selecting a suitable pump laser wavelength λ pX  for each wavelength converting device  125 ′, the series of optical transmitters  212 ′ are designed in such a way that each optical transmitter  212 ′ generates optical pulses  126 ′ of a particular wavelength out of the wavelength range λ conv1  to λ convN  and no two optical transmitters generate optical pulses  126 ′ at the same wavelength. For example, each optical transmitter  212 ′ is equipped with a distinct pump laser which lases at the specific pump wavelength λ pX . Alternatively, every optical transmitter  212 ′ is equipped with an identical, tunable pump laser and each tunable pump laser is programmed at the factory or in the field to the appropriate wavelength λ pX . In yet another implementation, all wavelength converting devices includes identical pump lasers and a suitable nonlinear optical crystal can be selected for each wavelength converting device  125 ′ such that that each optical transmitter  212 ′ generates optical pulses  126 ′ of wavelength λ convX  out of the wavelength range λ conv1  to λ convN  and no two optical transmitters generate optical pulses  126 ′ at the same wavelength. As another possibility, all wavelength converting devices may include identical pump lasers and nonlinear optical crystals, with each nonlinear optical crystal being provided with, for example, a temperature and/or current control device to tune the material properties of the nonlinear optical crystal such that that each optical transmitter  212 ′ generates optical pulses  126 ′ of wavelength λ convX  out of the wavelength range λ conv1  to λ convN  and no two optical transmitters  212 ′A generate optical pulses  126 ′ at the same wavelength. It should be noted that all components (other than wavelength converting device  125 ′) of optical transmitter  212 ′A are essentially the same as those of optical transmitter  212  shown in FIG. 2.  
         [0036]    An alternative scheme for an optical transmitter is shown in FIG. 4B, generally indicated by reference numeral  212 ′B. Each optical transmitter  212 ′B in this case is equipped with a generic, tunable laser as light source  120 ′ which emits light  122 ′ of wavelength λ X , where X=an integer between 1 and N corresponding to the X th  optical transmitter  212 ′B. All components (other than light source  120 ′) of optical transmitter  212 ′B are identical to those of optical transmitter  212  shown in FIG. 2. Light  122 ′ is directed at superconducting arrangement  118 , which in turn produces optical pulses  123 ′ of wavelength λ X . Each optical transmitter  212 ′B in the series of optical transmitters is provided with a generic wavelength converting device  125 . The wavelength λ X  of light  122 ′ produced at tunable laser of each optical transmitter  212 ′B is then tuned to provide light of a distinct wavelength such that wavelength converting device  125  converts the wavelength λ X  of optical pulses  123 ′ into optical pulses  126 ′ of a particular wavelength λ convX  out of the wavelength range λ conv1  to λ convN  and no two optical transmitters  212 ′B generate optical pulses  126 ′ at the same wavelength. The aforementioned QC laser is an example of a light source which is suitable for use as the tunable laser in this configuration. A bismuth laser, antimonide laser, germanium laser or a gas laser, such as a laser including a carbon dioxide-pumped cavity with methanol, may also be used in conjunction with an appropriate tuning mechanism (such as a temperature, current and/or magnetic field controller).  
         [0037]    It should be noted that the use of a tunable pump laser as pump laser  340  as shown in FIG. 4A or a tunable laser as light source  120 ′ as shown in FIG. 4B adds a routing capability to data link  300  of FIG. 3. By tuning the output wavelength of the series of optical transmitters  212 ′ in data link  300 , it is possible to direct data from any optical transmitter  212 ′ to any optical receiver  114 ′, thus routing the transmitted data to the desired recipient.  
         [0038]    Returning to FIG. 3, although data link  300  uses a plurality of wavelengths as in the aforedescribed prior art data link, it is submitted that data link  300  has advantages over the prior art data link. Since data link  300  is capable of transmitting at Tbit/s data rates on each train of wavelength converted optical pulses  126 ′, the selection of specific wavelengths out of the wavelength range λ conv1  to λ convN  is more flexible than in prior art data links, which depend on the packing of as many channels as possible into the limited wavelength range. Data link  300  can achieve multiple Tbit/s data rates with fewer constraints on the wavelengths chosen such that the wavelengths and channel spacings used can be specifically selected to reduce problems such as cross talk and nonlinear optical effects. In addition, although data link  300  requires the use of a guard band on either side of each channel wavelength, the fast data rate capability at each channel and the flexibility in wavelength selection allow more efficient use of the available bandwidth and higher data rates as compared to prior art WDM data links.  
         [0039]    Attention is now directed to FIGS.  5 A- 5 C, which illustrate alternative embodiments of an optical communication system designed in accordance with the present invention. FIGS.  5 A- 5 C show optical communication systems  400 A- 400 C, which correspond to high speed data links  100 ,  200  and  300  of FIGS.  1 - 3 , respectively, where optical fiber  113  is generally replaced by a satellite transmission system  413  in each of FIGS.  1 - 3 . The transmitter and receiver arrangements of FIGS.  5 A- 5 C are essentially the same as those shown in FIGS.  1 - 3 , respectively, therefore explanation of FIGS.  5 A-SC is restricted to the details of the satellite transmission system.  
         [0040]    Satellite transmission system  413  in FIGS.  5 A- 5 C includes a reflector  415 A, which directs the optical pulses from the corresponding transmitter arrangement toward a satellite  417 . Satellite  417  then redirects the optical pulses toward a desired location where the redirected optical pulses are intercepted by an interceptor arrangement  415 B. The optical pulses intercepted by interceptor arrangement  415 B are received by the corresponding receiving arrangement. Reflector  415 A and interceptor arrangement  415 B are, for example, conformable mirrors (such as the micro-machined membrane mirror manufactured by SY Technology). Conformable mirrors are useful in the satellite transmission system of FIGS.  5 A- 5 C because they can be used to compensate for possible distortion of the optical pulses. Such distortion in the optical pulses are potentially produced during transmission to and from the satellite due to, for example, atmospheric disturbances. In the case of the embodiments of the optical communication systems shown in FIGS.  5 A- 5 C, wavelength converting device  125  in each of the transmitter arrangements may be adjusted to produce optical pulses at wavelengths appropriate for satellite communications, such as in the far-infrared wavelengths. Moreover, reflector  415 A, interceptor arrangement  415 B and/or satellite  417  can include an off-axis paraboloid (may be conformable) for focusing or collimating the optical pulses. The conformable mirror and/or off-axis paraboloid as well as other components used in satellite transmission system  413  should be compatible with wavelengths used in free space communication systems such as, for example, wavelengths in the mid-infrared range (3.5 μm, 8 to 12 μm, etc.). For example, wavelength converting device  125  can be configured to generate optical pulses  126  in the aforementioned mid-infrared range. Alternatively, a light source capable of producing light  122  in the mid-infrared range can be used as light source  120  in combination with a superconducting material compatible with the mid-infrared range as superconducting arrangement  118  such that frequency converting device  125  may be eliminated altogether. In other words, if light source  120  produces light in the mid-infrared range, superconducting arrangement  118  can be used to produce optical pulses  123  in the mid-infrared range such that optical pulses  123  may be directed toward satellite  417  without the need for frequency converting device  125 . An example of suitable superconducting materials include mercury-based superconductor materials, which have critical temperatures of 134° K and 164° K under pressure. According to the Bardeen Cooper Schreiffer theory a superconductor with a critical temperature of 164° K would have a critical wavelength of 11 μm. Therefore a superconductor arrangement  118  made form strained mercury cuprates can be used with light  122  with wavelengths greater than 11 μm. In this way, the high speed data link of the present invention is applicable to free-space communication systems as well as for optical fiber-based systems.  
         [0041]    Turning now to FIG. 6, an alternative option to the aforedescribed optical receivers  114  and  114 ′ is shown. FIG. 6 illustrates a receiver  514 , which is based on a superconducting detector  540  and is suitable for use in the high speed data link of the present invention. Such use of superconducting films as bolometers or photodetectors are known in the art (see, for example, U.S. Pat. No. 5,155,093 issued to Den et al., U.S. Pat. No. 5,600,172 issued to McDevitt et al. and Roman Soblewski, “Ultrafast dynamics of nonequilibrium quasiparticles in high-temperature superconductors,”  Superconducting and Related Oxides: Physics and Nanoengineering III , ed. by I. Bozovic and D. Pavuna, Proc. SPIE, 3481, 480-491 (1998)). When a train of light pulses containing optical data, such as optical pulses  126  of FIG. 1, is incident on superconducting detector  540 , optical pulses  126  are converted into a train of voltage spikes  542 . Voltage spikes  542  are received by an electrical demultiplexer  544 . Electrical demultiplexer  544  performs a task analogous to AO demultiplexer  132  of FIG. 1 in that, where as AO demultiplexer  132  divides optical pulses  126  into a plurality of low data rate, optical pulses  126 ′, electrical demultiplexer  544  divides voltage spikes  542  into a plurality of low data rate, voltage spikes  542 ′. Voltage spikes  542 ′ are received by a plurality of electrical detectors  548 , which can be low speed electrical detectors that are commercially available. Receiver  514  of FIG. 6 is usable in situations in which it may be desirable to use an electrical signal detection scheme rather than an optical signal detection scheme.  
         [0042]    Since the high speed data link and associated method disclosed herein may be provided in a variety of different configurations and the method may be practiced in a variety of different ways, it should be understood that the present invention may be embodied in many other specific ways without departing from the spirit or scope of the invention. For example, an optical detector may be configured in essentially unlimited number of ways to cooperate with an AO demultiplexer in such a way that a series of optical pulses are divided into lower rate, optical pulses by the AO demultiplexer and detected by the optical detector. Furthermore, additional optical devices such as, but not limited to, optical amplifiers, switches, routers, and repeaters may be inserted in-line with an optical fiber for transmitting optical pulses from a transmitter arrangement to a receiver arrangement. Still further, the optical fiber may be eliminated as the transmission medium between the transmitter and receiver arrangements. In this way, wavelengths outside of the optical fiber transmission window can be used and the data link of the present invention becomes applicable to data transmission using electromagnetic waves outside of the optical wavelength range (microwave data transmission, for example). Such modifications are considered to be within the scope of the present invention so long as the teachings herein are applied. Therefore, the present examples are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.