Optical Comb Generator Phase Noise Cancellation
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Solution Overview
Problem
Optical communication systems face challenges in improving spectral efficiency without significant increases in inter-channel interferences, primarily due to noise and chromatic dispersion effects.
Innovation Solution
The system employs an optical transceiver with a transmitter-side comb generator that generates equally spaced carrier signals using a pilot carrier signal, which is also used by the receiver-side comb generator to produce frequency-locked signals for demodulation, effectively canceling phase noise and minimizing inter-channel interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher order modulation techniques are employed to increase bandwidth data transmission, then data transmission capacity is improved, but noise and inter-channel interferences increase
Solution Approach 1:
The patent segments the optical spectrum into multiple orthogonal frequency-division multiplexing (OFDM) subcarriers, each carrying a portion of the data stream. By dividing the high-order modulation into multiple lower-rate subcarriers with frequency spacing less than the baud rate, the system achieves high data capacity while reducing the impact of noise and interference on each individual subcarrier
Solution Approach 2:
The patent introduces a pilot carrier signal as an intermediary reference signal that is transmitted alongside the data-carrying subcarriers. This pilot signal serves as a mediator that enables the receiver to regenerate local carrier signals for coherent demodulation, thereby improving signal quality and reducing the effects of noise and channel impairments
2Productivity
If frequency spacing between carrier signals is reduced below baud rate to improve spectral efficiency, then spectral efficiency is improved, but inter-channel interferences increase
Solution Approach 1:
The patent employs dynamic carrier phase and frequency tracking by using the pilot carrier signal to continuously update and regenerate local carrier references at the receiver. This dynamic adaptation allows the system to maintain coherent detection despite the reduced frequency spacing between subcarriers, thereby achieving high spectral efficiency without excessive inter-channel interference
Solution Approach 2:
The patent changes the frequency spacing parameter between subcarriers to be less than the baud rate, which is unconventional. By combining this parameter change with pilot-based carrier regeneration and coherent detection, the system achieves improved spectral efficiency while managing inter-channel interference through precise frequency and phase synchronization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances spectral efficiency by reducing phase noise and improving signal quality, leading to better data throughput and error rates in optical communication systems.
Implementation Method 1
a transmitter-side optical comb generator configured to generate a plurality of transmitter-side carrier signals, the plurality of transmitter-side carrier signals being equally spaced in frequency
Implementation Method 2
a plurality of optical mixers, each optical mixer configured to mix one of the plurality of receiver-side carrier signals with a corresponding one of the plurality of received modulated carrier signals to generate a set of output signals
Data Source
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AI summary
This disclosure provides systems, methods, and apparatus for improving spectral efficiency of a communication system. The communication system can include a transmitter, a receiver and a communication link for communicating data between the transmitter and the receiver. The transmitter can employ a multi-carrier technique to transmit data to the receiver. The transmitter can generate a plurality of carrier signals using a receiver-side comb generator, one of which is sent to the transmitter as a pilot carrier signal combined with modulated carrier signals over an optical link. At the receiver the receiver-side comb generator uses the pilot carrier signal to generate a plurality of receiver-side carrier signals, which are used for detecting the modulated carrier signals. As the phase noise in the modulated carrier signals and the phase noise in the receiver-side carrier signals have the same characteristics, the phase noise is cancelled at the receiver, resulting in improved detection.