OVNA Phase Distortion Mitigation via Reference Delay Array
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Solution Overview
Problem
Optical vector network analyzers (OVNAs) face limitations due to nonlinearities and phase noise in the optical-frequency sweep of tunable laser sources, leading to spectral spreading and reduced signal intensity, which worsen spatial resolution and limit the accuracy of optical component characterization.
Innovation Solution
An OVNA system employing an array of reference delays to estimate distance-variant phase distortion during the optical-frequency sweep, allowing for phase correction of digital electrical signals, thereby enhancing the accuracy of optical component characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tunable laser source is used for optical-frequency sweep in OFDR-based OVNA, then the system can measure complex transfer functions of optical components, but nonlinearities and phase noise in the frequency sweep cause spectral spreading and reduced signal intensity
Solution Approach 1:
The patent applies preliminary action by measuring the phase distortion of the tunable laser source beforehand using a reference optical path with known characteristics. The measured phase distortion data is then stored and used to correct subsequent measurements, eliminating the need for real-time correction and enabling accurate optical characteristic measurements despite laser nonlinearities
Solution Approach 2:
The patent implements feedback by continuously monitoring the phase distortion of the laser source through a reference measurement path and using this information to correct the measurement signals. The system calculates phase distortion from reference interference signals and applies this correction to the DUT measurement signals, creating a closed-loop correction mechanism that maintains measurement accuracy
2Measurement precision
If phase correction is applied to compensate for distance-variant phase distortion, then the accuracy of optical characteristic determination is improved, but the system complexity increases due to additional reference delays and signal processing
Solution Approach 1:
The patent applies segmentation by dividing the optical path into multiple discrete delay stages, each introducing a specific time delay. This segmented approach allows the system to measure phase distortion at different delay points and reconstruct the distance-variant phase distortion profile, enabling correction without requiring a completely complex redundant system
Solution Approach 2:
The patent uses an intermediary approach by introducing a reference optical path that does not include the device under test but experiences the same laser phase distortion. This reference path acts as a mediator to isolate and measure the laser's phase distortion separately, which is then used to correct the main measurement path without directly modifying the DUT measurement setup
3Productivity
If the optical-frequency sweep rate is increased to improve measurement speed, then productivity is enhanced, but phase noise and nonlinearities worsen leading to greater spectral spreading
Solution Approach 1:
The patent implements feedback by measuring the actual phase distortion at each frequency sweep and using this information to correct the measurement signals in real-time. This feedback mechanism allows the system to maintain high measurement speeds while compensating for the increased phase noise and nonlinearities that occur at higher sweep rates
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the phase correction based on the measured phase distortion characteristics. The system calculates correction parameters from the reference measurements and applies these parameters to compensate for frequency-dependent phase errors, enabling accurate measurements even at high sweep rates where nonlinearities are more pronounced
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 phase correction significantly improves the determination of optical characteristics, such as complex transfer functions and mode-dependent loss, by reducing noise and maintaining high spatial resolution over the measurement range.
Implementation Method 1
a first optical interferometer connected to mix first and second relatively delayed parts of the probe light to generate one or more first optical interference signals
Data Source
AI summary
An OVNA system employing an array of reference delays to estimate distance-variant phase distortion in probe light during an optical-frequency sweep thereof. The estimated distance-variant phase distortion is then used to perform a phase correction for the digital electrical signals generated in response to the probe light being passed through a device under test (DUT) during the same optical-frequency sweep. Advantageously, the performed phase correction enables the OVNA system to provide a more-accurate determination of certain optical characteristics of the DUT than that achievable without such phase correction.