Optical Transmitter Using Nyquist Pulse Shaping
First Claim
Patent Images
1. An optical data transmitter comprising:
- a) a symbol generator that generates a stream of symbols having a symbol rate at an output;
b) a Nyquist filter having an input that is electrically connected to the output of the symbol generator, the Nyquist filter generating a Nyquist filtered stream of symbols; and
c) an optical modulator having an electrical input that is coupled to the output of the Nyquist filter, the optical modulator modulating an optical beam with the Nyquist filtered stream of symbols to generate a modulated optical beam, wherein the symbol rate is greater than a bandwidth of the modulated optical beam.
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Abstract
An optical data transmitter includes a symbol generator that generates a stream of symbols having a symbol rate. A Nyquist filter that is electrically connected to the symbol generator generates a Nyquist filtered stream of symbols. An optical modulator modulates an optical beam with the Nyquist filtered stream of symbols to generate a modulated optical beam. The symbol rate is greater than a bandwidth of the modulated optical beam.
26 Citations
33 Claims
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1. An optical data transmitter comprising:
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a) a symbol generator that generates a stream of symbols having a symbol rate at an output; b) a Nyquist filter having an input that is electrically connected to the output of the symbol generator, the Nyquist filter generating a Nyquist filtered stream of symbols; and c) an optical modulator having an electrical input that is coupled to the output of the Nyquist filter, the optical modulator modulating an optical beam with the Nyquist filtered stream of symbols to generate a modulated optical beam, wherein the symbol rate is greater than a bandwidth of the modulated optical beam. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An N-bit quadrature amplitude modulation optical data transmitter comprising:
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a) a symbol generator that generates a plurality of N-bit streams of symbols having a symbol rate at an output; b) a splitter having an input that is coupled to the output of the symbol generator, the splitter directing a first N/2-bit stream of symbols to a first output and a second N/2-bit stream of symbols to a second output; c) an I-channel comprising; i. a first digital-to-analog converter having an input that is electrically connected to the first output of the splitter, the first digital-to-analog converter generating an analog signal representing the first N/2-bit stream of symbols at an output; ii. a first Nyquist filter having an input that is coupled to the output of the first digital-to-analog converter, the first Nyquist filter generating an I-channel Nyquist filtered N/2-bit stream of symbols; and iii. a multiplier that multiplies the first Nyquist filtered N/2-bit stream of symbols by a cosine function optical waveform to generate a first N/2 bit Nyquist filtered stream of symbols at an output; d) a Q-channel comprising; i. a second digital-to-analog converter having an input that is electrically connected to the second output of the splitter, the second digital-to-analog converter generating an analog signal representing the second N/2-bit stream of symbols at an output; ii. a second Nyquist filter having an input that is coupled to the output of the second digital-to-analog converter, the second Nyquist filter generating a Q-channel Nyquist filtered N/2-bit stream of symbols; and iii. a multiplier that multiplies the second Nyquist filtered N/2-bit stream of symbols by a sine function optical waveform to generate a first N/2 bit Nyquist filtered stream of symbols at an output; and e) an optical combiner having a first optical input that is coupled to the I-channel and a second optical input that is coupled to the Q-channel, the optical combiner producing a combined optical beam with the first and second N/2-bit Nyquist filtered stream of symbols to generate a modulated optical beam, wherein the symbol rate is greater than N times a bandwidth of the modulated optical beam. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A method of optically modulating a stream of symbols, the method comprising:
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a) generating a stream of symbols having a symbol rate; b) filtering the stream of symbols with a Nyquist filter; and c) modulating an optical beam with the filtered stream of symbols thereby generating a modulated optical beam, wherein the symbol rate is greater than a modulation bandwidth of the modulated optical beam. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification