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US 10,833,767 B2Granted
Self-homodyne carrier multiplexed transmission system and method for coherent optical links
AssigneeIndian Institute of Technology Bombay
InventorsShalabh Gupta, Rashmi Kamran, Anghan Mehul Popatbhai
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Abstract
Embodiments herein provide a self-homodyne coherent optical transmission system (Self-Homodyne system) where an optical carrier is polarization multiplexed with a modulated signal and is transmitted over the optical fiber. An Adaptive polarization control is used by the receiver for simplifying a signal processing in the receiver. Analog processing may be used for implementing LO less receiver. Transmitter uses a phase modulated carrier in place of an unmodulated carrier.
Claims13
A self-homodyne coherent optical transmission system, comprising:
- a transmitter, comprising:
- a laser for generating an optical carrier,
- a polarization beam splitter for splitting the optical carrier into two orthogonal polarizations,
- at least one modulator for modulating a polarization signal for one of the two orthogonal polarizations, wherein a modulation technique for modulating the polarization signal comprises one of an m-QAM modulation technique or an m-PSK modulation technique,
- a polarization beam combiner for combining an unmodulated carrier in other polarization with a modulated signal, wherein an output of the polarization beam combiner is transmitted through a fiber channel,
- wherein the optical carrier in one polarization is multiplexed with a message signal modulated over the carrier in another polarization and is transmitted over the fiber channel;
- and
- a receiver for receiving a message signal from transmitter through the fiber channel and demodulating the message signal using a polarization multiplexed carrier as a local oscillator, the receiver comprising:
- at least one 90° optical hybrid for combining a carrier and a modulated signal in the message signal, comprising at least one polarization beam splitter that splits the incoming optical signal from the fiber channel into two orthogonal polarizations,
- at least two balanced photo-detectors for converting an optical output of the at least one 90° optical hybrid into electrical signals, and
- a polarization controller for applying an adaptive polarization control mechanism for separating the modulated signal and the carrier at the receiver in two independent polarization components;
- wherein the adaptive polarization control mechanism is performed by the receiver for feedback control of the polarization controller for minimizing an amount of cross-polarization to separate the modulated signal and the carrier into two independent polarization components;
- and
- wherein optical power from at least one of the at least one polarization beam splitter outputs is further split, and given to at least one photodetector, and wherein output from the at least one photodetector is used for performing the adaptive polarization control mechanism by at least one of maximization of power in one polarization and minimization of power in other polarization.
11 more elements
A receiver in a self-homodyne coherent optical transmission system, the receiver comprising:
- at least one 90° optical hybrid for combining a carrier and a modulated signal in a message signal, received from a transmitter, wherein the message signal is demodulated by using a polarization multiplexed carrier as a local oscillator, comprising at least one polarization beam splitter that splits the incoming optical signal from the fiber channel into two orthogonal polarizations;
- at least two balanced photo-detectors for converting an optical output of the at least one 90° optical hybrid into electrical signals;
- and
- a polarization controller for applying an adaptive polarization control mechanism for separating the modulated signal and the carrier at the receiver in at least two independent polarization components;
- wherein the adaptive polarization control mechanism is performed by the receiver by using electronics for identifying an amount of cross-polarization from each of received signal parameters for feedback control of the polarization controller for minimizing the amount of cross-polarization comprising at least one polarization beam splitter that splits the incoming optical signal from the fiber channel into two orthogonal polarizations;
- and
- wherein optical power from at least one of the at least one polarization beam splitter outputs is further split, and given to at least one photodetector, and wherein output from the at least one photodetector is used for performing the adaptive polarization control mechanism by at least one of maximization of power in one polarization and minimization of power in other polarization.
4 more elements
A method for receiving signal in a self-homodyne coherent optical transmission system, the method comprising:
- receiving, a message signal from a transmitter through an optical fiber channel;
- applying, through a polarization controller, an adaptive polarization control mechanism for separating a modulated signal and a carrier at the receiver in at least two independent polarization components;
- wherein the adaptive polarization control mechanism is performed by the receiver by using electronics for identifying an amount of cross-polarization from each of received signal parameters for feedback control of the polarization controller for minimizing the amount of cross-polarization to separate the modulated signal and the carrier into two independent polarization components;
- combining, through at least one 90° optical hybrid, a carrier in one polarization and a modulated signal in the other polarization after a polarization rotator with one polarization signal;
- and
- converting, through at least two balanced photo-detectors, an optical output of the at least one 90° optical hybrid into electrical signals;
- and
- wherein optical power from at least one of at least one polarization beam splitter outputs is further split, and given to at least one photodetector, and wherein output from the at least one photodetector is used for performing the adaptive polarization control mechanism by at least one of maximization of power in one polarization and minimization of power in other polarization.
5 more elements
Dependencies are inferred from the claim text.