Pseudorandom pulse code generators using electro-optical XOR gates
First Claim
1. A code generator generating pseudorandom digital codes comprising:
- a source of optical pulses;
a plurality of optical XOR gates each having at least two optical inputs and one optical output; and
optical fiber means interconnecting the optical outputs of selected of said XOR gates to selected inputs of other of said XOR gates in a pattern which generates a single optical output representing said pseudorandom digital code, said optic fiber means having lengths selected to effect selected delays in the transmission of light pulses between selected ones of said optical XOR gates.
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Abstract
Pseudorandom pulse code generators utilize XOR gates constructed of a pair of back to back parallel connected laser diodes, and fiber optic delay lines connecting the XOR gates to generate PN code sequences with tens of Gbits/s data rates. The single tap generator uses a fiber optic line of a length representing a selected number of delay stages connected to the optical output of the XOR gate and with optical splitters at the end of the delay line and at a selected delay stage feeding back optical signals to the optical inputs of the XOR gate to produce the PN sequence at the end of the delay line. Multi-tap generators utilize additional electro-optical XOR gates connected in serial-parallel, or preferably in a converging cascade arrangement to feed back pulses to the delay line. A syncopated PN code generator uses the electro-optical XOR gates to multiplex codes generated by syncopated pairs of relatively slow electronic shift register code generators with the required phase shifting provided by diffeence in the lengths of the optic fibers connected successive stages of XOR gates.
28 Citations
23 Claims
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1. A code generator generating pseudorandom digital codes comprising:
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a source of optical pulses; a plurality of optical XOR gates each having at least two optical inputs and one optical output; and optical fiber means interconnecting the optical outputs of selected of said XOR gates to selected inputs of other of said XOR gates in a pattern which generates a single optical output representing said pseudorandom digital code, said optic fiber means having lengths selected to effect selected delays in the transmission of light pulses between selected ones of said optical XOR gates. - View Dependent Claims (2, 3)
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4. A code generator for generating a pseudorandom optical pulse code from a series of input light pulses having a selected clock rate:
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at least one XOR gate having two optical inputs and one optical output; a fiber optic delay line having a length equal to a selected number of delay stages, with each delay stage length being equal to the speed of light in said fiber optic delay line divided by said clock rate, said fiber optic delay line having an input end connected to the optical output of said XOR gate and an output end at which said pseudorandom optical pulse code is generated; a first optical splitter adjacent said output end of said delay line feeding back light pulses appearing at the output end of said delay line to one of said optical inputs to said XOR gate; a second optical splitter inserted into said fiber optic delay line at a selected number of delay stages from the input end of said fiber optic delay line feeding back light pulses in said fiber optic delay line into the other optical input of said XOR gate; and an optical combiner injecting said input light pulses into said fiber optic delay line. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A code generator for generating a pseudorandom optical pulse code from a series of input light pulses comprising:
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a plurality of XOR gates having at least two optical inputs and a single optical output; optical fibers connecting said plurality of XOR gates in a converging cascade arrangement funneling optical pulses from a preselected number of said plurality of XOR gates to a single XOR gate; a fiber optic delay line having a plurality of delay stages between an input end and an output end with said input end connected to the optical input of said single XOR gate and with the pseudorandom optical pulse code being produced at the output end of said fiber optic delay line; a plurality of fiber optic splitters in said delay line connecting selected ones of said delay stages in said delay line to the optical inputs of said preselected number of XOR gates; and an optical combiner connected to the input end of said delay line injecting said input light pulses into said fiber optic delay line. - View Dependent Claims (16, 17, 18, 19)
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20. A code generator for generating pseudorandom optical pulse codes comprising:
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a clock generating clock pulses at a selected clock rate; a plurality of pairs of electronic pseudorandom code generators each generating an electronic pulse code in response to said clock pulses; means delaying clock pulses to one electronic pseudorandom code generator in each pair of electronic code generators by one half said clock rate; a first set of XOR gates having two electronic inputs and a single optical output, with each of said first set of XOR gates having its electronic inputs connected to one of said pairs of said electronic pseudorandom code generators; a second set of XOR gates having two optical inputs and two optical outputs; and pairs of optical fibers connecting said XOR gates in successive converging cascaded stages funneling pulses from said first set of XOR gates to a single XOR gate in said second set of XOR gates, said pairs of optical fibers comprising one optical fiber which exceeds the length of the other optical fiber in the pair by an amount which delays pulses transmitted by said one optical fiber by one half the bit width of pulses transmitted by the pair, optical pulses appearing at the optical output of said single XOR gate in said second set being said pseudorandom optical pulse code. - View Dependent Claims (21, 22, 23)
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Specification