Phase Chip Frequency-Bins Optical Code Division Multiple Access

Abstract

Apparatus and system for transmitting and receiving optical code division multiple access data over an optical network. The apparatus comprises a spectral phase decoder for decoding the encoded optical signal to produce a decoded signal, a time gate for temporally extracting a user signal from the decoded signal, and a demodulator that is operable to extract user data from the user signal. The system preferably comprises a source for generating a sequence of optical pulses, each optical pulse comprising a plurality of spectral lines uniformly spaced in frequency so as to define a frequency bin, a data modulator associated with a subscriber and operable to modulate the sequence of pulses using subscriber data to produce a modulated data signals and a Hadamard encoder associated with the data modulator and operable to spectrally encode the modulated data signal to produce an encoded data signal.

1 . An apparatus for receiving a desired encoded optical signal comprising equally spaced coherent phase-locked spectral lines in the presence of other differently and orthogonally encoded synchronous, co-polarized optical signals which occupy the same wavelength channel and bit period, comprising:
 a spectral phase decoder comprising a means for individually phase shifting each of the equally spaced, coherent phase-locked spectral lines of the encoded optical signal with respect to the other spectral lines in accordance with a predetermined code which code is one of a set of more than two mutually orthogonal codes, for decoding the encoded optical signal to produce a decoded signal in which the desired encoded optical signal is reconstituted and occupies a small part of the bit period, and the other differently encoded signals have minimal optical power in that part of the bit period;   a synchronous optical time gate for temporally extracting the desired coded signal from the decoded composite signal by synchronously selecting only the portion of the bit period in which the desired signal resides; and   a demodulator that is operable to extract user data from the user desired coded signal.   
     
     
         2 . The apparatus of  claim 1 , wherein the spectral phase decoder comprises a set of spectrally selective phase shifters that are operable to conjugate the set of phase shifts used to encode the desired encoded optical signal. 
     
     
         3 . The apparatus of  claim 1 , wherein the desired encoded optical signal comprises a signal encoded using a code chosen from among a set of more than two orthogonal codes. 
     
     
         4 . The apparatus of  claim 3 , wherein the set of orthogonal codes comprises a set of Hadamard codes. 
     
     
         5 . The apparatus of  claim 1 , wherein the spectral phase decoder comprises at least one ring resonator. 
     
     
         6 . (canceled) 
     
     
         7 . The apparatus of  claim 1 , wherein the synchronous optical time gate is operative to filter multi-user interference energy that falls outside a time interval in which the user desired coded signal is located. 
     
     
         8 . An optical system for transporting data, comprising:
 a plurality of transmitting systems each associated with a data stream for transmitting data and a plurality of receiving systems each adjustable to receive data from a preselected transmitting system;   a plurality of coherent sources each associated with a respective transmitting system for generating a sequence of optical pulses, each optical pulse comprising equally spaced, coherent phase-locked spectral lines confined within a predetermined WDM channel spectral bandwidth;   a plurality of data modulators each associated with a respective transmitting system and operable to modulate the sequence of pulses from a plurality of transmitting systems using the data to produce a plurality of modulated data signals;   a spectral phase encoder associated with the plurality of data modulators comprising means for individually phase shifting each equally spaced, coherent phase-locked spectral line with respect to the other spectral lines in accordance with a predetermined code which code is one of a set of two or more mutually orthogonal codes to produce an encoded data signal;   a multiplexer for combining the encoded data signals into a composite transport data signal wherein each transmitted data signal shares the same spectral bandwidth during transmission of the transport data signal to a decoder;   a spectral phase decoder for decoding one of the encoded data signals comprising means for individually phase shifting each equally spaced, coherent phase-locked spectral line with respect to the other components in accordance with a predetermined code which is the conjugate of the code used to encode said data signal to produce a decoded data signal; and   a time gate coupled to said spectral phase decoder to temporarily extract the decoded signal associated with a predetermined transmitting system from the multi-data stream interference energy that falls outside a time interval in which the desired user signal is located.   
     
     
         9 . The system of  claim 8 , wherein the source comprises a mode locked laser wherein each of the plurality of equally spaced, coherent phase-locked spectral lines are approximately equal in amplitude and phase locked. 
     
     
         10 . The system of  claim 8 , wherein the set of orthogonal codes comprises a set of Hadamard codes that applies a unique spectral phase component to each of the plurality of spectral lines. 
     
     
         11 . (canceled) 
     
     
         12 . (canceled) 
     
     
         13 . (canceled) 
     
     
         14 . (canceled) 
     
     
         15 . (canceled) 
     
     
         16 . A method for preparing data for transport over an optical network, comprising:
 generating a sequence of optical pulses, each optical pulse comprising a plurality of equally spaced, coherent phase-locked spectral lines confined within a predetermined WDM channel spectral bandwidth;   modulating the sequence of optical pulses using a data stream to produce a modulated data signal; and   spectrally phase encoding the modulated data signal using one of a set of two or more orthogonal codes to produce an encoded data signal by individually phase shifting each spectral component of the modulated signal with respect to the other components in accordance with a predetermined code which code is one of a set of two or more mutually orthogonal codes.   
     
     
         17 . (canceled) 
     
     
         18 . The method of  claim 16 , wherein said modulating comprises confining the modulated data signal to a bandwidth no greater than the spectral spacing between two adjacent spectral lines comprising the optical pulse. 
     
     
         19 . The method of  claim 16 , further comprising demodulating the data stream signal to reproduce the transmitted data. 
     
     
         20 . The method of  claim 16 , wherein the set of mutually orthogonal codes is a set of Hadamard codes. 
     
     
         21 . An apparatus for receiving a plurality of mutually orthogonal, spectrally phase encoded optical signals which simultaneously occupy the same optical frequency domain, in which each encoded optical signal comprises a plurality of uniformly spaced spectral lines, all of which are modulated with data associated with each user of a plurality of users, and the modulated signals are encoded by imposing predetermined relative phase shifts between spectral lines according to the code assigned to each user, comprising:
 a spectral phase decoder for decoding a selected encoded optical signal to produce a decoded signal that occupies a finite sampling interval while at the same time nulling the optical power of the other encoded optical signals during the sampling time;   an optical time gate for temporally extracting the selected optical signal and rejecting other interfering optical signals, all of which occupy the same frequency domain; and   a demodulator and detector that is operable to extract user data from the selected optical signal.   
     
     
         22 . The apparatus of  claim 21 , wherein the spectral phase decoder separates the individual spectral components of the signal, individually shifts the phase of each of the spectral components and coherently recombines the frequency components, so that the decoder is operable to conjugate the phase code used to encode the encoded optical signal. 
     
     
         23 . The apparatus of  claim 21 , wherein the encoded optical signal comprises a signal encoded using a set of two or more orthogonal codes. 
     
     
         24 . The apparatus of  claim 23 , wherein the set of orthogonal codes comprises a set of Hadamard codes. 
     
     
         25 . The apparatus of  claim 21 , wherein the optical time gate is operative to filter multi-user interference energy that falls outside a time interval in which the user signal is located. 
     
     
         26 . An optical system for transporting data, comprising:
 a source for generating a sequence of optical pulses, each optical pulse comprising a plurality of spectral lines uniformly spaced in frequency with fixed absolute frequency and relative phase;   a set of data modulators each associated with a user and operable to modulate the sequence of pulses using user data to produce a modulated data signal;   a set of encoders imparting a plurality of orthogonal codes each associated with one of the data modulators and operable to spectrally encode the modulated data signal to produce an encoded data signal; and   a set of decoders each of which is a conjugate match to one of the encoders, for spectrally decoding a specified encoded data signal to produce a set of decoded data signals.   
     
     
         27 . The system of  claim 26 , wherein the source comprises a mode locked laser wherein each of the plurality of spectral lines is approximately equal in amplitude and phase locked. 
     
     
         28 . The system of  claim 27 , wherein the encoder comprises a spectral phase encoder that applies a phase shift defined by a code applied to each of the plurality of spectral lines. 
     
     
         29 . The system of  claim 28 , wherein the code is chosen from a set of two or more mutually orthogonal codes. 
     
     
         30 . The system of  claim 29  wherein the set of two or more mutually orthogonal codes comprises a set of Hadamard codes. 
     
     
         31 . The system of  claim 26 , further comprising a plurality of additional modulators each associated with respective additional users and each operable to modulate the sequence of pulses using data associated with one of the plurality of additional users to produce a plurality of additional modulated data signals. 
     
     
         32 . The system of  claim 31  further comprising a plurality of additional mutually orthogonal encoders each associated with a respective one of the additional modulators and operable to spectrally encode a respective one of the plurality of additional modulated data signals to produce a plurality of additional encoded data signals. 
     
     
         33 . The system of  claim 32 , wherein each of the additional mutually orthogonal encoders associates a respective spectral phase code with each of the additional users. 
     
     
         34 . The system of  claim 33  wherein the respective spectral phase codes are Hadamard codes. 
     
     
         35 . The system of  claim 32 , further comprising an optical combiner for bit-synchronously combining the encoded data signals into a composite transport data signal wherein each user shares the same spectral bandwidth during transmission. 
     
     
         36 . The system of  claim 35 , wherein the same spectral bandwidth for a group of users is limited to a transparent window in a WDM network. 
     
     
         37 . The system of  claim 26  further comprising an optical time gate coupled to the output of the matching decoder and operable to temporally extract a user data signal from the decoded signals. 
     
     
         38 . A method for preparing data for transport over an optical network, comprising:
 generating a sequence of optical pulses, each optical pulse comprising a plurality of equally spaced, coherent phase-locked spectral lines confined within a predetermined WDM channel spectral bandwidth;   modulating the sequence of optical pulses using user data to produce a modulated data signal; and   spectrally phase encoding the modulated data signal using a set of two or more orthogonal codes to produce an encoded data signal.   
     
     
         39 . The method of  claim 38 , further comprising applying a unique phase shift to each of the plurality of spectral lines as prescribed by a code from a set of two or more mutually orthogonal codes. 
     
     
         40 . The method of  claim 39  wherein the set of mutually orthogonal codes are Hadamard codes. 
     
     
         41 . The method of  claim 38 , wherein modulation induced broadening of the spectral lines is substantially confined to a frequency bin, which is defined as a portion of optical bandwidth of width less than the separation between two adjacent lines in the plurality of spectral lines comprising the pulses. 
     
     
         42 . The method of  claim 41  wherein the entire spectral content of each modulation broadened spectral line is phase encoded by a single unique phase shift. 
     
     
         43 . The method of  claim 38  further comprising spectral phase encoding and decoding of a single user's modulated data signal comprises associating one of a set of two or more orthogonal codes with each of the plurality of spectral lines. 
     
     
         44 . The method of  claim 43  wherein the set of two or more orthogonal codes are Hadamard codes.