Optical Transmitter Phase Noise Reduction via Feedback Control
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Solution Overview
Problem
Wavelength division multiplexed (WDM) optical communication systems face performance penalties due to phase noise, particularly lower frequency portions of the optical signal phase noise spectrum, which interfere with signal modulation, transmission, and processing, leading to higher bit rate errors.
Innovation Solution
An optical system that includes an optical source, a frequency change detection device, a photodetector, an integrator, and a controller to convert the detected frequency change into an electrical signal and provide a feedback current to the optical source, reducing phase noise without affecting the signal's linewidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If phase noise reduction is implemented using conventional methods, then phase noise is reduced, but signal linewidth is also reduced which affects signal quality
Solution Approach 1:
The patent implements a feedback control system where the optical signal is detected, phase noise is identified, and a compensating signal is fed back to the optical source to reduce phase noise while maintaining signal linewidth through selective frequency component processing
Solution Approach 2:
The patent extracts only the problematic low-frequency phase noise components from the optical signal using a bandpass filter, leaving the signal linewidth and other frequency components intact, thereby reducing phase noise without affecting signal quality
2Reliability
If phase noise is reduced, then transmission performance improves, but system complexity increases due to additional compensation components
Solution Approach 1:
The patent introduces an intermediary detection and processing system that bridges the optical signal and the control mechanism, using photodetectors and signal processors to convert optical phase variations into electrical control signals for feedback, thereby managing complexity through modular functional blocks
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
The system effectively reduces phase noise, thereby improving transmission performance by minimizing bit rate errors and maintaining signal quality across the frequency spectrum.
Implementation Method 1
a photodetector to receive the first optical signal and provide an electrical signal that is indicative of the change in frequency of the first optical signal
Data Source
AI summary
An optical transmitter may include an optical source to provide a first optical signal having a varying frequency; an optical circuit to receive a portion of the first optical signal and provide a second optical signal corresponding to a change in frequency of the first optical signal; a photodetector to receive the first optical signal and provide an electrical signal that is indicative of the change in frequency of the first optical signal; an integrator to receive the electrical signal and provide an inverted electrical signal; and a controller to process the inverted electrical signal and provide a current, associated with the inverted electrical signal, to the optical source. The optical source may reduce the phase noise associated with the first optical signal based on the current.