Photonic Phase Noise Measurement Using Wavelength Multiplexing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for measuring phase noise in RF, microwave, or millimeter signals struggle with high noise floors and require extensive fiber lengths, which are bulky and costly, while also relying on multiple fiber delay lines that increase system size and noise artifacts.
Innovation Solution
The implementation of a photonic-based cross-correlation homodyne detection system using shared optical components, such as lasers and modulators, and optical polarization techniques to reduce fiber length and noise, allowing for multiple delays over a single fiber, and employing Faraday rotator mirrors to halve the required fiber length while maintaining effective phase noise measurement capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple fiber delay lines are used for phase noise measurement, then measurement accuracy is improved, but system size and noise floor increase
Solution Approach 1:
The patent combines multiple delay line functions into a single optical fiber by using wavelength division multiplexing. Multiple wavelengths are propagated through the same fiber simultaneously, each carrying phase noise information at different delay times. This merging approach maintains the measurement accuracy benefits of multiple delay lines while dramatically reducing system size and eliminating the noise artifacts associated with having multiple separate fiber cables.
Solution Approach 2:
The single optical fiber serves multiple functions by simultaneously acting as multiple delay lines for different wavelengths. Each wavelength experiences a different effective delay based on its propagation characteristics, allowing the single fiber to provide the diverse delay paths needed for accurate phase noise measurement without requiring separate physical delay lines for each wavelength.
2Measurement precision
If multiple fiber delay lines are used for phase noise measurement, then measurement accuracy is improved, but noise floor increases
Solution Approach 1:
By merging multiple delay functions into a single fiber using wavelength division multiplexing, the patent eliminates the noise artifacts generated by having multiple separate fiber cables. The single fiber configuration removes sources of differential thermal expansion, mechanical stress, and connection noise that would otherwise increase the noise floor and degrade measurement accuracy.
3Measurement precision
If long fiber lengths are used for delay, then phase noise measurement capability is improved, but system size and cost increase
Solution Approach 1:
The patent changes the parameter of delay by using different wavelengths instead of different fiber lengths. By propagating multiple wavelengths through the same fiber, the system achieves different effective delays based on wavelength-dependent propagation characteristics, eliminating the need for multiple long fiber cables of different lengths and significantly reducing overall system size and cost.
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 significantly reduces the noise floor by averaging uncorrelated noise and decreases the physical length of fiber delay lines, resulting in a more compact, efficient, and accurate phase noise measurement system with improved sensitivity and reduced system size.
Implementation Method 1
a shared optical modulator that modulates the laser light at the first and second wavelengths to produce modulated laser light that carries the oscillation signal
Implementation Method 2
a wavelength-selective optical device that separates the modulated laser light output by the shared optical delay into a first modulated laser beam at the first wavelength and a second modulated laser beam at the second wavelength
Implementation Method 3
a Faraday rotator mirror coupled to the fiber delay line to reflect light back to the fiber delay line by rotating optical polarization by 90 degrees
Implementation Method 4
a photodetector coupled to receive light from the third port of the photonic beam combiner to generate a detector signal
Implementation Method 5
a signal mixer that mixes the detector signal and the phase-shifted oscillator signal to produce the output signal
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Techniques and devices for measuring phase noise in radio frequency (RF), microwave, or millimeter signals based on photonic delay.