Method and system for a polarization mode dispersion tolerant optical homodyne detection system with optimized transmission modulation
DCFirst Claim
1. A method of optical communication in an optical communication system, comprising the steps of:
- providing a quadrature modulated optical data signal by a transmitter, the optical data signal including two data bands separated in frequency, each data band having in-phase and quadrature components;
during transitional states of the quadrature modulated optical data signal in which data symbols change in value, reducing, by the transmitter, the power to zero such that transmitted power decreases to zero at approximately a mid point of the transitional states;
combining the optical data signal with a side carrier at a single frequency between the two data bands of the optical data signal;
transmitting, by the transmitter, the combined optical data signal;
receiving, by a receiver, the combined optical data signal;
separating, at the receiver, the side carrier from the two data bands of the combined optical data signal;
increasing an amplitude of the side carrier;
modulating the side carrier into two shifted side carriers, one of the two shifted carriers being shifted in frequency to the middle of each of the respective two data bands; and
correcting, at the receiver, for polarization mode dispersion on the combined signal by adjusting a polarization state of each of the two shifted side carriers to match a polarization state of the one of the two data bands at which the respective shifted side carrier is centered.
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Abstract
An optical homodyne communication system and method in which a side carrier is transmitted along with data bands in an optical data signal, and upon reception, the side carrier is boosted, shifted to the center of the data bands, and its polarization state is matched to the polarization state of the respective data bands to compensate for polarization mode dispersion during transmission. By shifting a boosted side carrier to the center of the data bands, and by simultaneously compensating for the effects of polarization mode dispersion, the provided system and method simulate the advantages of homodyne reception using a local oscillator. The deleterious effects of chromatic dispersion on the data signals within the data bands are also compensated for by applying a corrective function to the data signals which precisely counteracts the effects of chromatic dispersion.
29 Citations
22 Claims
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1. A method of optical communication in an optical communication system, comprising the steps of:
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providing a quadrature modulated optical data signal by a transmitter, the optical data signal including two data bands separated in frequency, each data band having in-phase and quadrature components; during transitional states of the quadrature modulated optical data signal in which data symbols change in value, reducing, by the transmitter, the power to zero such that transmitted power decreases to zero at approximately a mid point of the transitional states; combining the optical data signal with a side carrier at a single frequency between the two data bands of the optical data signal; transmitting, by the transmitter, the combined optical data signal; receiving, by a receiver, the combined optical data signal; separating, at the receiver, the side carrier from the two data bands of the combined optical data signal; increasing an amplitude of the side carrier; modulating the side carrier into two shifted side carriers, one of the two shifted carriers being shifted in frequency to the middle of each of the respective two data bands; and correcting, at the receiver, for polarization mode dispersion on the combined signal by adjusting a polarization state of each of the two shifted side carriers to match a polarization state of the one of the two data bands at which the respective shifted side carrier is centered. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of reducing the transmitted power of a quadrature modulated optical data signal, comprises the steps of:
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providing a quadrature modulated optical data signal by a transmitter; during all transitional states of the quadrature modulated optical data signal in which data symbols can change in value, reducing, by the transmitter, the power to zero such that transmitted power decreases to zero at approximately a mid point of each of the transitional states; combining the quadrature modulated optical data signal with a side carrier; and transmitting the side carrier with the quadrature modulated optical data signal. - View Dependent Claims (13)
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14. An optical data signal transmitter comprising:
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a Mach-Zender modulator, the Mach-Zender modulator receiving an input optical signal and modulating a pair of side carriers onto the input optical signal, outputting an optical carrier signal; and at least two phase modulators, the at least two phase modulators receiving the optical carrier signal and each generating an optical data signal by modulating a pair of data signals onto at least two data bands; wherein the data bands are spread in frequency when modulated onto the optical carrier signal, the spreading causing an amplitude of the optical data signal to be reduced to zero during all transitional state between any pair of data symbol, in which the data symbols can change in value.
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15. An optical data signal transmitter comprising:
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a Mach-Zender modulator, the Mach-Zender modulator receiving an input optical signal and modulating a pair of side carriers onto the input optical signal, outputting an optical carrier signal; at least two phase modulators, the at least two phase modulators receiving the optical carrier signal and each generating an optical data signal by modulating a pair of data signals onto at least two data bands; a second Mach-Zender modulator, the second Mach-Zender modulator imprinting the input optical signal with an identification code to generate a TX ID, the identification code including information concerning the transmitter; and a combiner, the combiner attaching the TX ID to the optical data signal; wherein the data bands are spread in frequency when modulated onto the optical carrier signal, the spreading causing an amplitude of the optical data signal to be reduced to zero during transitions between data symbols. - View Dependent Claims (16, 17)
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18. An optical data signal comprising:
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a Mach-Zender modulator, the Mach-Zender modulator receiving an input optical signal and modulating a pair of side carriers onto the input optical signal, outputting an optical carrier signal; and at least two phase modulators, the at least two phase modulators receiving the optical carrier signal and each generating an optical data signal by modulating a pair of data signals onto at least two data bands; wherein the data bands are spread in frequency when modulated onto the optical carrier signal, the spreading causing an amplitude of the optical data signal to be reduced to zero during transitions between data symbols; and wherein the pair of side carriers is modulated onto the input optical signal at both above and below a reference frequency of the input optical signal. - View Dependent Claims (19)
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20. A method of reducing the transmitted power of a quadrature modulated optical data signal, comprising the steps:
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providing a quadrature modulated optical data signal by a transmitter; during all transitional states of the quadrature modulated optical data signal in which data symbols can change in value, reducing, by the transmitter, the power to zero such that transmitted power decreases to zero at approximately a mid point of each of the transitional states; and spreading orthogonal data signals onto two side carriers of an optical signal to obtain the quadrature modulated optical data signal. - View Dependent Claims (21)
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22. A method of reducing the transmitted power of a quadrature modulated optical data signal, comprising the steps:
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providing a quadrature modulated optical data signal by a transmitter; during all transitional states of the quadrature modulated optical data signal in which data symbols can change in value, reducing, by the transmitter, the power to zero such that transmitted power decreases to zero at approximately a mid point of each of the transitional states, where data signals are in effect spread out by approximately fifty percent in the frequency domain equivalent to a multiplication by a sine wave at half the data rate, and results in each symbol returning to zero at approximately a mid-point of the transitional states.
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Specification