Photon Detector Segmentation for Optical Fiber Reflection Measurement
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Solution Overview
Problem
Conventional optical time domain reflectometry (OTDR) devices face challenges in simultaneously achieving high spatial/temporal resolution and sensitivity due to saturation issues with photon detectors during high reflection events in optical fibers, leading to incomplete measurement of reflection levels after powerful reflection events.
Innovation Solution
The use of two photon detectors, where one acts as a peak detector to identify high-level reflections and temporarily isolate the second detector from saturation, allowing it to maintain a long measuring window without being overwhelmed by high-level reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single photon detector is used to measure optical fiber reflections, then high sensitivity and temporal resolution are achieved, but the detector becomes saturated by high-level reflections causing loss of measurement data in subsequent time intervals
Solution Approach 1:
The single photon detector is divided into two functional segments: a peak detector portion that identifies high-level reflections and triggers isolation, and a measuring portion that continuously collects reflection data. This segmentation allows each portion to specialize in its function, preventing saturation while maintaining measurement capability.
Solution Approach 2:
An optical isolator is introduced as an intermediary component between the optical fiber and the measuring portion of the photon detector. The isolator remains transparent during normal operation but can be activated to block high-level reflections from reaching the measuring portion, preventing saturation while allowing continuous measurement of lower-level reflections.
2Measurement precision
If the measuring window is shortened to avoid saturation from high-level reflections, then measurement precision after reflection events is improved, but the overall measurement efficiency and coverage of the optical fiber decreases
Solution Approach 1:
The peak detector operates continuously in advance to monitor for high-level reflections and trigger isolation before the measuring portion becomes saturated. This preliminary detection and isolation action prevents saturation from occurring, allowing the measuring window to remain open and continuous without needing to be shortened.
3Measurement precision
If photon counting is used to achieve high temporal resolution, then sensitivity is improved, but the dynamic range is limited causing saturation at high backscatter levels
Solution Approach 1:
The photon detector is segmented into a peak detector that handles high-level signals and a measuring portion that handles low-level signals with high temporal resolution. This allows the system to maintain photon counting capability for precise temporal measurement while extending the effective dynamic range through the peak detector's ability to identify and isolate high-level events.
Solution Approach 2:
The optical isolator acts as a dynamic intermediary that selectively blocks high-level reflections from reaching the photon-counting measuring portion, preventing saturation and extending the usable dynamic range while preserving the high temporal resolution capability of photon counting for lower-level reflections.
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 enables precise and quick measurement of optical fiber reflections, including those after high-level events, by preventing saturation and allowing continuous data collection beyond initial reflection points, thus improving measurement efficiency and accuracy.
Implementation Method 1
measuring means (3300) comprising a first photon detector (3310) and a second photon detector (3311)
Implementation Method 2
emitting means (3100) connected to the optical fiber (1400) and configured to emit light into the optical fiber (1400)
Data Source
AI summary
The present invention relates to a measuring device (3000) for measuring reflection in an optical fiber (1400), the device comprising: emitting means (3100) connected to the optical fiber (1400) and configured to emit light into the optical fiber (1400), measuring means (3300) connected to the optical fiber (1400) and configured to receive a reflected light from the optical fiber (1400), wherein the measuring means comprises a first photon detector (3310) and a second photon detector (3311), wherein the operation of the second photon detector (3311) and/or the reflected light reaching the second photon detector (3311) is controlled based on an output of the first photon detector (3310).