Photonic Phase Correction in pADCs for Remote Sampler Drift
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Solution Overview
Problem
Conventional photonic analog-digital converters (pADCs) face challenges in maintaining absolute phase difference between signal and reference branches due to environmental factors like temperature changes and vibrations, which can cause phase drift, leading to aliasing and reduced frequency bandwidth, especially in passive fiber remoting applications.
Innovation Solution
A photonic analog-digital converter (pADC) with photonic phase correction, utilizing a passive remote sampler (PRS) that measures environmental phase drift using a continuous-wave (CW) laser in a reverse optical path, and corrects phase errors with a phase shifter based on an electrical signal from a low-bandwidth photodiode, allowing for passive remote sampling and low-loss components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dithering tone is used for phase correction, then phase drift can be measured and corrected, but the frequency bandwidth is reduced and active powered components are required
Solution Approach 1:
The patent introduces a dithering tone as an intermediary signal to measure phase drift. This tone is modulated onto the optical carrier and allows the system to detect phase changes without requiring active powered components at the remote location. The dithering tone serves as a mediator between the phase drift phenomenon and the measurement capability, enabling precision phase correction while maintaining passive remote sampling.
2Measurement precision
If a dithering tone is used for phase correction, then phase drift can be measured and corrected, but active powered components are required which are incompatible with passive fiber remoting
Solution Approach 1:
The system uses the existing optical infrastructure and components to perform phase correction without requiring active powered components at the remote sampler. The dithering tone is generated and processed using passive optical elements and the existing photodetector, allowing the system to self-correct phase drift without additional active components, thus maintaining compatibility with passive fiber remoting applications.
3Device complexity
If environmental phase drift is not corrected, then the system remains simple, but phase aliasing occurs and overlaps with the RF signal
Solution Approach 1:
The patent implements a feedback mechanism where phase drift is continuously measured using the dithering tone and the phase difference is used to adjust the sampling timing or apply digital correction. This feedback loop ensures that phase drift does not cause aliasing or overlap with the RF signal, maintaining signal accuracy while using a relatively simple implementation that leverages existing system components.
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 solution effectively corrects environmental phase drift, ensuring accurate digitization of RF signals by maintaining phase alignment, even in remote and passive sampling scenarios, while using low-loss components.
Implementation Method 1
The sending side includes a source for the optical pulse (e.g., a mode locked laser (MLL)) and a photodetector for converting the CW laser (having traveled through the PRS) into an equivalent electrical signal.
Implementation Method 2
the pADC splits the optical pulse into a signal branch and a reference branch sent through separate optical fibers, of which only the signal branch is phase-modulated according to the RF signal of interest before recombination
Data Source
AI summary
A system and method for correcting environmental phase drift between signal and reference branches of a photonic analog-digital converter (pADC) with passive remote sampler (PRS) sends a continuous-wave (CW) laser from a base unit through the PRS in a reverse optical path to measure the phase drift. The CW optical signal is converted to an electrical signal from which a phase-error signal indicative of the phase drift is filtered out and sent to a phase shifter. The pADC sends an optical pulse through the PRS in a forward optical path; the signal pulse is phase-modulated according to a received radio frequency (RF) signal of interest. The phase-modulated optical pulses (e.g., signal and reference) are received at the base unit and the phase drift corrected out of the optical pulses via the phase shifter. The corrected optical pulses are demodulated to provide a digital counterpart to the RF signal of interest.