OFDR Polarization Dependent Path Length Shifter
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Solution Overview
Problem
Existing Optical Frequency Domain Reflectometry (OFDR) systems require two separate measurements for orthogonal input polarizations, leading to errors due to environmental changes and reduced update rates when one measurement is corrupted, and suffer from calibration inaccuracies between polarizations.
Innovation Solution
An OFDR system with a polarization dependent optical path length shifter (PDOPS) that creates two distinct polarization states with different optical path lengths, allowing for simultaneous measurement of both polarizations in a single scan, thereby avoiding overlap and reducing errors and calibration issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two separate measurements are performed for orthogonal input polarizations, then polarization fading can be addressed, but measurement time increases and reliability decreases due to environmental changes between measurements
Solution Approach 1:
The patent combines two separate polarization measurements into a single measurement by using a polarization beam splitter to separate orthogonal polarization components and process them simultaneously through the same optical path, eliminating time separation between measurements and preventing environmental changes from affecting measurement reliability
Solution Approach 2:
The system dynamically adjusts polarization states using polarization controllers to ensure that orthogonal polarization components are properly separated and measured, adapting to changing environmental conditions while maintaining measurement accuracy in a single scan
2Reliability
If two separate measurements are performed for orthogonal input polarizations, then complete polarization information can be obtained, but update rate decreases when one measurement is corrupted
Solution Approach 1:
The patent merges the measurement of orthogonal polarization states into a single simultaneous measurement process, so that both polarization components are acquired in one scan. This eliminates the need to repeat measurements when one is corrupted, maintaining high update rates while ensuring complete polarization information is obtained
Solution Approach 2:
The polarization beam splitter acts as an intermediary that separates orthogonal polarization components from a single input beam, allowing both to be measured simultaneously. This intermediary device enables complete polarization information acquisition without requiring separate measurements, thus maintaining high update rates even when environmental conditions change
3Reliability
If polarization-diverse detection is used with a polarizing beam splitter, then polarization fading is resolved, but device complexity increases
Solution Approach 1:
The patent uses a polarizing beam splitter that serves multiple functions: separating orthogonal polarization components, directing them to appropriate detectors, and enabling simultaneous measurement of both polarization states. This multi-functional component resolves polarization fading while minimizing the increase in device complexity by using a single versatile optical element
Data Source
AI summary
There is presented an optical frequency domain reflectometry (OFDR) system (100) comprising a first coupling point (15) arranged for splitting radiation into two parts, so that radiation may be emitted into a reference path (16) and a measurement path (17). The system further comprises an optical detection unit (30) capable of obtaining a signal from the combined optical radiation from the reference path and the measurement path via a second coupling point (25). The measurement path (17) comprises a polarization dependent optical path length shifter (PDOPS, PDFS, 10), which may create a first polarization (PI) and a second polarization (P2) for the radiation in the measurement path, where the optical path length is different for the first and second polarizations in the measurement path. This may be advantageous for obtaining an improved optical frequency domain reflectometry (OFDR) system where e.g. the two measurements for input polarizations may be performed in the same scan of a radiation source.