OTDR Receiver Sensitivity Switching for Range-Extended Fiber Traces
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Solution Overview
Problem
Conventional OTDR devices are limited by their operational range, which is constrained by the amount of optical power that can be launched into a fiber link, the fiber link length, and the time users are willing to wait for an OTDR trace, leading to saturation issues and loss of information.
Innovation Solution
The OTDR device generates an OTDR probe trace using a lower sensitivity level to avoid saturation, identifies transition points, and then transitions to a higher sensitivity level at specific points to extend the range, producing an OTDR range-extended trace.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the optical power launched into the fiber link is increased to extend the operational range, then the measurement range is improved, but saturation issues occur causing loss of information
Solution Approach 1:
The patent applies dynamics by making the receiver sensitivity adjustable and variable during the measurement process. The receiver sensitivity is dynamically changed based on the distance from the measurement origin, allowing the system to adapt to different signal strength conditions along the fiber link without requiring fixed high power that would cause saturation.
Solution Approach 2:
The patent changes the receiver sensitivity parameter as a function of distance. By adjusting the receiver sensitivity dynamically based on the measured distance, the system can detect weak signals from distant points without being saturated by strong signals from near points, thus extending operational range while preventing information loss.
2Measurement precision
If the receiver sensitivity is increased to detect weak signals from distant fiber points, then the measurement precision is improved, but saturation occurs for near portions causing loss of information
Solution Approach 1:
The patent applies local quality by making the receiver sensitivity dependent on the local distance condition. Different regions of the fiber link (near vs. distant) are measured with appropriately adjusted sensitivity levels, allowing high sensitivity for distant weak signals while maintaining lower sensitivity for near strong signals, thus preventing saturation in both regions.
Solution Approach 2:
The receiver sensitivity is dynamically adjusted based on the distance parameter. As the measurement progresses along the fiber link, the sensitivity is changed to match the expected signal strength at each distance, enabling precise detection of distant signals without saturating on near signals.
3Measurement precision
If the measurement time is extended to improve the accuracy of OTDR traces, then the measurement precision is improved, but the productivity is reduced due to longer wait time
Solution Approach 1:
The patent performs preliminary action by first measuring the distance to the far end of the fiber link before conducting the main OTDR measurement. This preliminary distance information is used to pre-calculate and set the optimal receiver sensitivity profile, allowing the main measurement to be completed more quickly with appropriate sensitivity settings from the outset, thus improving both accuracy and reducing time.
Solution Approach 2:
The system uses feedback from the preliminary distance measurement to adjust the receiver sensitivity settings for the main measurement. The measured distance information feeds back into the control system to optimize the sensitivity profile, enabling more accurate measurements to be obtained in less time through adaptive settings.
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 effectively extends the operational range of the OTDR device with minimal time increase, providing accurate OTDR traces by avoiding saturation and ensuring reliable measurements across both near and far portions of the fiber link.
Implementation Method 1
an optical receiver for detecting light from the optical source that is back-reflected by the optical fiber
Data Source
AI summary
An optical time domain reflectometry (OTDR) device includes an optical transmitter, an optical receiver with multiple operating settings, an optical coupler, and a processor. The optical transmitter generates a probe signal comprising a train of pulses. The optical receiver generates time-varying measurements of a back-reflected signal resulting from injection of respective pulses of the probe signal into an optical fiber link. The optical coupler injects the probe signal from the optical transmitter into the optical fiber link and directs the back-reflected signal from the optical fiber link to the optical receiver. The processor generates a probe trace of the optical fiber link from first time-varying measurements of the back-reflected signal, identifies an intra-scan first transition point from the probe trace, and generates a range-extended trace of the optical fiber link from second time-varying measurements of the back-reflected signal in which the optical receiver transitions from a first operating setting to a second operating setting at the intra-scan first transition point.