Abstract:
Systems and methods are presented herein to achieve data privacy in the optical realm such that electronic encryption bottlenecks are removed, potentially increasing data transmission speeds to the limit of fiber optic media. In this regard, privatizing an optical data transmission may include dynamically altering a temporal length of data bits in an optical data transmission or dynamically altering a temporal length of data frames in an optical data transmission. For example, in a two-dimensional OCDMA signal, the temporal length of data bits may be altered by changing the number of time chips on a per bit basis (e.g., using OCDMA signatures having different temporal lengths). In an optical data bit scrambling signal, the temporal length of data frames may be altered by changing the number of time slices on a per data frame basis.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to the privacy of an optical data transmission and, more particularly, to enhancing the privacy of the optical data transmission by dynamically altering the temporal length of an Optical Code Division Multiple Access signature or an optical data frame used to transmit data. 
     BACKGROUND OF THE INVENTION 
     Optical communications are typically implemented by transmitting data through fiber-optic links because light is less prone to optical dispersion through fiber-optic links as opposed to other mediums, such as air. These optical communications use light to convey data to an intended receiver through the fiber-optic link, through “on-off keying” of the wavelength. For example, a binary signal (i.e., a signal of logical 1&#39;s and logical 0&#39;s) is transmitted through a fiber-optic link with the light switching on and off. 
     Demand on communications has dictated that optical fiber be shared among users. One method of sharing involves assigning specific time periods to individual users and is called Time Division Multiplexing (“TDM”). During a period of time in TDM, a single user transmits data and other users wait for their time period. Another method of sharing involves assigning specific wavelengths of light to individual users and is called Wavelength Division Multiplexing (“WDM”). In WDM, each user has a specific wavelength of light and may transmit data on that wavelength at any time, but no other user may use that wavelength. Optical Code Division Multiple Access (“OCDMA”) is yet another method to share the optical fiber among a number of users. In OCDMA, each user is assigned a unique code that is composed of temporal and wavelength components. This unique OCDMA signature may be thought of as a unique identifier or thumbprint on a data stream. For a user to receive a data stream, the user must detect a data stream having an appropriate OCDMA signature. 
     As with other forms of communications, such as radio frequency communications, it is often preferable to encrypt data being transmitted to maintain data privacy. In optical communications, data is typically encrypted in the electronic realm prior to optical transmission in order to achieve data privacy. Once encrypted, the data may be optically transmitted using one of the methods discussed hereinabove. Encryption in the electronic realm, however, often introduces a bottleneck (i.e., a communication slowdown) to the transmission of data because, among other reasons, electronic switching speeds are simply slower than optical transmission speeds. 
     BRIEF SUMMARY OF THE INVENTION 
     Typically, data transmission speed through fiber optic media is significantly faster than the processing speed of acceptable encryption electronics. By achieving data privacy in the optical realm, electronic encryption bottlenecks may be removed, potentially increasing data transmission speeds to the limit of fiber optic media. In this regard, the invention is generally directed to privatizing an optical data transmission by dynamically altering a temporal length of data bits or data frames in the optical data transmission. For example, a number of time chips in a two-dimensional OCDMA signal may be successively varied according to a predetermined sequence whereas, in optical data bit scrambling, successive data frames are dynamically varied by changing the number of time slices. These and other aspects of the invention may advantageously provide for secure data transmissions with relatively fast data transmission speeds. 
     A first aspect of the invention generally relates to privatizing an optical data transmission through using a plurality of OCDMA signatures, at least two of which have different temporal lengths. What may be characterized as a “series” is repeated a plurality of times to define the optical data transmission. In each series, an OCDMA signature is selected, a single data bit is converted into an optical signal based upon this OCDMA signature, and this optical signal is thereafter transmitted. The selected OCDMA signature in at least one series has a different temporal length than the selected OCDMA signature from at least one other series. 
     Various refinements exist of the features noted in relation to the first aspect of the present invention. Further features may also be incorporated in the first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. A plurality of OCDMA signatures may be available for the OCDMA signature selection that is made in relation to each series. In one embodiment, the OCDMA signature that is used in one series is of a different temporal length than the OCDMA signature that is used by each adjacent series. Stated another way, the OCDMA signature that is used in relation to any particular bit has a different temporal length than the OCDMA signature that is used in relation to the immediately preceding-in-time bit. However, the OCDMA signatures may be selected in any appropriate manner so long as the optical data transmission has at least two OCDMA signatures having different temporal lengths (e.g., a first OCDMA signature having a first temporal length could be used for two adjacent bits, and then a second OCDMA signature have a different, second temporal length could be used for the next two bits). 
     In the case of the first aspect, the optical signal may be configured with a plurality of optical wavelengths. For example, the optical data transmission may be a two-dimensional OCDMA signal. 
     A second aspect of the invention is generally directed to a method of privatizing an optical data transmission, as well as a system that incorporates this functionality. The method includes a step of generating both a scramble pattern and a frame temporal length for a data frame. The method also includes the steps of assigning at least one data bit to at least one element within the data frame based upon the scramble pattern and transmitting the data frame after the assigning step. The method then repeats the steps of generating, assigning, and transmitting a plurality of times, with at least one execution of the generating step using a different scramble pattern and a different frame temporal length than another execution of the generating step. 
     Various refinements exist of the features noted in relation to the second aspect of the present invention. Further features may also be incorporated in the second aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The method may further include a step of configuring the optical signal with a plurality of optical wavelengths. For example, the optical data transmission may be an optical data bit scrambling signal having a plurality of optical wavelengths. The step of generating both a scramble pattern and a frame temporal length for a data frame may include the step of establishing a substantially constant time slice duration for each data frame. The step of assigning at least one data bit to at least one element within the data frame based upon the scramble pattern may include the step of electronically retrieving the single data bit from storage. 
     A third aspect of the invention is generally directed to privatizing an optical data transmission having what may be characterized as a plurality of optical data segments. What may be characterized as a “series” is repeated a plurality of times to define the optical data transmission. In each series, a temporal length of an optical data segment is established, data is thereafter embedded in this optical data segment, and thereafter this optical data segment is transmitted. The temporal length of at least two of the optical data segments in the optical data transmission are of different magnitudes in the case of the third aspect. 
     Various refinements exist of the features noted in relation to the third aspect of the present invention. Further features may also be incorporated in the third aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. In one embodiment, each optical data segment in the optical data transmission has a different temporal length than each adjacent optical data segment in the optical data transmission. Stated another way, the temporal length of the optical data segment is changed on each execution of the noted series. Stated yet another way, the temporal length of the optical data segment that is used in the execution of one particular series is different than the temporal length of the optical data segment that was used in the execution of the immediately previous-in-time series. However, any appropriate pattern may be used for establishing the temporal length of each optical data segment in the optical data transmission, so long as at least two optical data segments in the optical data transmission have different temporal lengths. 
     A single data bit may be embedded in each optical data segment of the optical data transmission in the case of the third aspect. Multiple data bits may also be embedded in each optical data segment of the optical data transmission. One or more optical data segments in the optical data transmission could include a single data bit, while one or more optical data segments in the optical data transmission could include multiple data bits. It also may be such that a common number of data bits are embedded in each optical data segment of the optical data transmission. 
     Each optical data segment in the case of the third aspect may be characterized as including a plurality of time chips, where each time chip includes a plurality of wavelength slots, and where each time chip is of a common temporal length. The number of time chips in the optical data segments may be established in any appropriate manner such that at least two optical data segments in the optical data transmission use a different number of time chips. For instance, the number of time chips used by a particular optical data segment may be different than the number of time chips used by an immediately previous-in-time to optical data segment in the optical data transmission. 
     Each optical data segment in the case of the third aspect may also be characterized as including a plurality of elements in a two-dimensional array of time versus wavelength, where each element is of the same temporal length. The manner in which data is disbursed in each optical data segment may be controlled in any appropriate manner. For instance, each optical data segment in the optical data transmission may use a different dispersion pattern for data contained therein than the immediately previous-in-time optical data segment in the optical data is transmission. In one embodiment, both the number of elements and the dispersion pattern are changed for each adjacent optical data segment in the optical data transmission. 
     The third aspect may be implemented in any appropriate manner. For instance, different OCDMA signatures having different temporal lengths may be used. In this regard, the various features discussed above in relation to the first aspect may be used by this third aspect as well. The manner in which the temporal length of each optical data segment of the optical data transmission may be controlled in any appropriate manner (e.g., using an appropriate algorithm), the manner in which data is embedded in each optical data segment of the optical data transmission may be controlled in any appropriate manner (e.g., using an appropriate algorithm), or both. For instance, the various features discussed above in relation to the second aspect may be used by this third aspect as well. 
     Although the aspects of the invention generally provide for methods of privatizing optical data transmissions, those skilled in art should readily recognize that the invention is not limited to such methods. Rather, these aspects may be implemented with an optical communication system. For example, an electrical to optical converter may be configured to perform various steps described herein, such as changing a temporal length of optical data and transmitting the optical data. 
    
    
     
       BRIEF DESCRIPTION OF THE INVENTION AND THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a signaling diagram illustrating wavelength versus time for a prior art two-dimensional OCDMA signal. 
         FIG. 2  is a signaling diagram illustrating wavelength versus time for a prior art optical data bit scrambling signal. 
         FIG. 3  is a signaling diagram illustrating dynamic temporal duration optical transmission privacy for a two-dimensional OCDMA signal. 
         FIG. 4  is a signaling diagram illustrating dynamic temporal duration optical transmission privacy for an optical data bit scrambling signal. 
         FIG. 5  is a block diagram of an optical transmitter that utilizes dynamic temporal duration. 
         FIG. 6  is a block diagram illustrating a receiver that utilizes dynamic temporal duration. 
         FIG. 7  is a flow chart illustrating a transmission operation that utilizes dynamic temporal duration. 
         FIG. 8  is a flow chart illustrating a reception operation that utilizes dynamic temporal duration. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  illustrate prior art optical signals comprising a plurality of wavelengths (i.e., illustrated along axis  101 ) versus time (i.e., illustrated along axis  102 ).  FIG. 1  illustrates a prior art two-dimensional OCDMA signal  100 , while  FIG. 2  illustrates a prior art optical data bit scrambling signal  200 . 
     In two-dimensional OCDMA signal  100 , each data bit  105  is represented by an OCDMA signature. The data bit is divided into a number of time chips  110  and spread across a number of wavelength slots  115 . Certain elements of this two-dimensional array are occupied (e.g., labeled  120 ) and represent a unique OCDMA signature for a single data bit in the data stream. An element is deemed occupied when a pulse of light is transmitted at a wavelength and duration that corresponds to the element. If all of the array elements for a particular OCDMA signature are occupied, a logical “1” is interpreted. If the number of array elements occupied is less than a certain threshold for a particular OCDMA signature, a logical “0” is interpreted. 
     The elements that are not needed for the particular OCDMA signature remain unoccupied (e.g., labeled  125 ) and available for OCDMA signatures of other data streams. For example, each OCDMA signature is composed of the same number of time chips  110 , wavelength slots  115 , and occupied elements  120 . To achieve privacy, the OCDMA signature for a particular data stream may be selected from a pool of OCDMA signatures according to a predetermined sequence. Other data streams then simply use other OCDMA signatures that do not correspond. 
     In two-dimensional OCDMA signal  100 , each transmitted data bit  105  has the same fixed number of time chips  110  as a previous data bit  105 . For example, each data bit  105  (i.e., bits  1 ,  2 ,  3 , etc.) of two-dimensional OCDMA signal  100  is divided into an array of four time chips  110  and eight wavelength slots  115 . In each array, four elements are selected and occupied according to the OCDMA signature. Each successive data bit  105  is represented by a different OCDMA signature selected from a pool of OCDMA signatures according to a predetermined sequence. 
     In  FIG. 2 , optical data bit scrambling signal  200  comprises a plurality of wavelength channels  215  such that each individual data stream is scrambled across both time (i.e., illustrated along axis  102 ) and wavelength (i.e., illustrated along axis  101 ). Optical data bit scrambling signal  200  is configured as a plurality of data frames  205 , with each individual data frame  205  composed of a matrix having the same number of time slices  210  and wavelength channels  215 . Time slices  210  have equal time intervals that correspond to data bits  216  of a source data stream (i.e., occupied locations  220  of bits  1 ,  2 ,  3 , etc.) and to unoccupied locations  225 . 
     In a data frame  205 , a specific number of data bits occupy locations  220  in a matrix of time slices  210  and wavelength channels  215 . For example, each of occupied locations  220  contains a specific data bit from the source data stream and is represented by a pulse of light. A binary zero is represented by the absence of light in the matrix (i.e., unoccupied locations  225 ). Matrix locations that are not needed for a particular data stream bit scrambling remain unoccupied  225  and are available for bit scrambling transmissions of other data streams. For each data frame  205 , a unique bit scrambling pattern is selected. For an enhancement to privacy, the bit scrambling pattern for a particular data stream may be selected from a pool of bit scrambling patterns according to a predetermined sequence. 
     In optical data bit scrambling, each data frame  205  has the same fixed number of time slices  210  as the previous data frame  205 . For example, each data frame  205  (e.g., data frames A, B, C, etc.) are divided into a matrix of four time slices  210  and four wavelength channels  215 . In each data frame  205 , four locations are selected according to a bit scrambling pattern. Four data bits in the data stream occupy those selected locations (e.g., bits  1 ,  2 ,  3  and  4  occupy frame A). For each successive data frame  205 , a different bit scrambling pattern is selected from a pool of bit scrambling patterns according to a predetermined sequence. 
       FIG. 3  illustrates two-dimensional OCDMA signal  300  utilizing dynamic temporal durations to enhance privacy of optical communications. As with the prior art two-dimensional OCDMA signal  100  of  FIG. 1 , each data bit  305  is represented by an OCDMA signature. The OCDMA signature is a two-dimensional array comprised of a number of time chips  110  and a number of wavelengths slots  115 . However, the OCDMA signature for each successive data bit  305  dynamically varies with respect to the number of time chips  110  that make up each two-dimensional array. For example, adjacent data bits  305  may differ in terms of the number of time chips  110 . Note that the period of time for each time chip  110  is constant, while the duration of data bits  305  is dynamic or variable/varying. 
     The number of time chips  110  in each successive OCDMA signature may be varied according to a predetermined sequence. For example, each successive data bit  305  may be represented by a different OCDMA signature selected from a pool of OCDMA signatures. Each OCDMA signature may have a particular number of time chips that determines the number of time chips  110  in a data bit  305 . The number of occupied elements  120  in each successive OCDMA signature may also be varied according to a predetermined sequence, such as a substantially random sequence. 
       FIG. 4  illustrates optical data bit scrambling signal  400  signal utilizing dynamic temporal durations to enhance privacy of optical communications. As with prior art optical data bit scrambling  200 , optical data bit scrambling signal  400  is configured as a plurality of data frames  405 , with each individual data frame  405  composed of a matrix of time slices  210  and wavelength channels  215 . Differing from optical data bit scrambling signal  400  is that successive data frames  405  are dynamically varied with respect to the number of time slices  210 . The period of each time slice  210  is constant, while the overall duration of each data frame  405  is dynamic or variable/varying. 
     The number of time slices  210  in each successive data frame  405  may be varied according to a predetermined sequence. For example, each successive data frame  405  may be populated by a different scrambling pattern selected from a pool of scrambling patterns. Each scrambling pattern may have a number of time slices that determines the number of time slices  210  in a given data frame  405 . The number of occupied locations  220  in each successive scrambling pattern may also be varied according to the predetermined sequence. 
       FIG. 5  is a block diagram of optical transmitter  500  that utilizes dynamic temporal duration to enhance privacy of an optical data transmission. In this embodiment, a sequence of settings may be determined before data is transmitted optically. For example, transmitter  500  may include sequencer  505  which may be configured to establish settings prior to transmission for either two-dimensional OCDMA signal  300  of  FIG. 3  or optical data bit scrambling signal  400  of  FIG. 4 . For two-dimensional OCDMA signal  300 , these settings may include determination of an OCDMA signature based at least in part on a number of time chips  110  and/or a number of occupied elements  120 . For optical data bit scrambling signal  400 , these settings may include a determination of a bit scrambling pattern (e.g., based at least in part on a number of time slices  210  in a data frame  405  and/or a number of occupied locations  220  in a data frame  405 ). 
     With the settings established, generator  510  may generate the appropriate code. For example, generator  510  may generate an OCDMA signature having a number of time chips  110  as determined by sequencer  505  to control the number of time chips  110  in a data bit  305  of two-dimensional OCDMA signal  300 . Alternatively, generator  510  may generate a scramble pattern having a number of time slices  210  as determined by sequencer  505  to control the number of time slices  210  in a data frame  405  of optical data bit scrambling signal  400 . Although discussed in terms of code generation, those skilled in the art should readily recognize that the code may be pregenerated and selected from, for example, a database of codes (e.g., a plurality of OCDMA signatures or a plurality of scrambling patterns). 
     Electrical to optical converter  515  uses the generated code to convert electronic data to an optical signal. For example, electrical to optical converter  515  may receive the generated code from generator  510  to configure a number of time chips  110  for two-dimensional OCDMA signal  300  on a per data bit  305  basis. Alternatively, electrical to optical converter  515  may use the generated code to configure a number of time slices  210  for optical data bit scrambling signal  400  on a per data frame  405  basis. Once the data bits  305  or data frames  405  are configured, electrical to optical converter  515  may use the generated code to format the data within the data bits  305  or data frames  405 , respectively. 
       FIG. 6  is a block diagram of optical receiver  600  that utilizes dynamic temporal duration to enhance privacy. Before data is received optically, a sequence of settings may be determined. This sequence of settings is generally the same as that used by transmitter  500  of  FIG. 5 . As such, receiver  600  may include certain components that are similar in nature to those of transmitter  500  to reverse the encoding (i.e., alteration of temporal durations) performed by transmitter  500 . For example, receiver  600  may include sequencer  505  to establish settings prior to reception of either two-dimensional OCDMA signal  300  of  FIG. 3  or optical data bit scrambling signal  400  of  FIG. 4 . For two-dimensional OCDMA signal  300 , these settings may again include determination of an OCDMA signature based at least in part on a number of time chips  110  and/or a number of occupied elements  120 . For optical data bit scrambling signal  400 , these settings may again include a determination of a bit scrambling pattern (e.g., based at least in part on a number of time slices  210  in a data frame  405  and/or a number of occupied locations  220  in a data frame  405 ). 
     With the settings established, generator  510  may generate the appropriate code. For example, generator  510  may generate an OCDMA signature having a number of time chips  110  as determined by sequencer  505  to correctly ascertain the number of time chips  110  in a received data bit  305  of two-dimensional OCDMA signal  300 . Alternatively, generator  510  may generate a scramble pattern having a number of time slices  210  as determined by sequencer  505  to ascertain the number of time slices  210  in a received data frame  405  of optical data bit scrambling signal  400 . Again, those skilled in the art should readily recognize that such codes may be selected rather than generated. 
     As receiver  600  is configured for receiving data, receiver  600  may include optical to electrical converter  615 . Optical to electrical converter  615  uses a generated code to convert electronic data to an optical signal. For example, optical to electrical converter  615  may receive the generated code from generator  510  to configure a number of time chips  110  for reception of two-dimensional OCDMA signal  300  on a per data bit  305  basis or to configure a number of time slices  210  for reception of optical data bit scrambling signal  400  on a per data frame  405  basis. Once the data bits  305  or data frames  405  are configured, optical to electrical converter  515  may use the generated code to extract the optical information from data bits  305  or data frames  405 , respectively, and convert that optical information to an electronic data signal. 
       FIG. 7  is flow chart  700  illustrating the optical transmission of an optical signal that utilizes dynamic temporal duration to enhance privacy. A sequence of settings is negotiated between transmitter  500  of  FIG. 5  and receiver  600  of  FIG. 6 , in step  701 . It is not necessary for the entire sequence to be transferred between transmitter  500  and receiver  600 . Rather, it may only be necessary for the negotiation of the manner in which the sequence is to be generated. Afterwards, transmitter  500  uses the sequence to establish a temporal duration of the OCDMA signature or the data frame, in step  702 . Using this temporal duration, the OCDMA signature or bit scramble pattern is selected (e.g., an OCDMA signature for two-dimensional OCDMA signal  300  of  FIG. 3  or a scramble pattern for optical data bit scrambling signal  400  of  FIG. 4 ), in step  703 . The selected OCDMA signature or selected bit scramble pattern is used to convert the electrical data into an optical signal for transmission, in step  704 . 
     Once the optical signal is generated, a determination may be made regarding whether optical signal transmission is necessary, in step  705 . For example, once the last bit of two-dimensional OCDMA signal  300  or the last frame of optical data bit scrambling signal  400  has been transmitted, optical signal transmission may end in step  706 . However, if transmission of two-dimensional OCDMA signal  300  or optical data bit scrambling signal  400  is to continue, corresponding temporal durations are subsequently changed in step  707 . The process then returns to step  703  for recursion of steps  703 ,  704 , and  707 . 
       FIG. 8  is flow chart  800  illustrating the optical reception of an optical signal that utilizes dynamic temporal duration to enhance privacy. A sequence of settings is negotiated between transmitter  500  of  FIG. 5  and receiver  600  of  FIG. 6 , in step  801 . Again, it is not necessary for the entire sequence to be transferred between transmitter  500  and receiver  600 . Rather, it may only be necessary for the negotiation of the manner in which the sequence is to be generated. Afterwards, transmitter  500  uses the sequence to establish the temporal duration of the OCDMA signature or data frame, in step  802 . Using this temporal duration, the OCDMA signature or bit scramble pattern is selected (e.g., an OCDMA signature for two-dimensional OCDMA signal  300  of  FIG. 3  or a scramble pattern for optical data bit scrambling signal  400  of  FIG. 4 ), in step  803 . The selected OCDMA signature or selected bit scramble pattern is used to convert the optical signal into electronic data, in step  804 . 
     Once the electronic data is generated, a determination may be made regarding whether optical signal reception is necessary, in step  805 . For example, once the last bit of two-dimensional OCDMA signal  300  or the last frame of optical data bit scrambling signal  400  of  FIG. 4  has been received, optical signal reception may end in step  806 . However, if reception of two-dimensional OCDMA signal  300  or optical data bit scrambling signal  400  is to continue, corresponding temporal durations are subsequently changed in step  807 . The process then returns to step  803  for recursion of steps  803 ,  804 , and  807 . 
     While the above embodiments have been shown and described in sufficient detail so as to enable one skilled in the art to make and use the invention, the invention is not intended to be limited to these embodiments. Those skilled in the art should readily recognize that certain features may be implemented in different ways. For example, certain steps may be implemented optically and/or electronically (e.g., such as with optoelectronic components). Additionally, such features may be controlled via firmware and/or software. Those skilled in the art are readily familiar with optoelectronics, software and firmware. 
     The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described hereinabove are further intended to explain best modes known as practicing the invention and to enable others skilled in the art to utilize the invention in such or other embodiments with various modifications required by the particular application(s) or use(s) of the present invention. It is intended that the appended claims, therefore, be construed to include alternative embodiments to the extent permitted by the prior art.