OTDR Zeroing Device Using Idle Time Feedback
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Solution Overview
Problem
Manual zeroing methods for OTDRs are not intelligent, and automatic zeroing methods introduce errors in the waveform, affecting the accuracy of measurements.
Innovation Solution
A zeroing method and device for OTDRs that send a zeroing signal before starting the device, utilizing a low noise amplifier to adjust for offset voltage, allowing for intelligent zeroing and minimizing waveform distortion during testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual zeroing method is used, then zeroing function can be completed well, but it increases the manual complexity of the test
Solution Approach 1:
The system performs zeroing automatically using internal circuitry and control logic without requiring external manual intervention. The microprocessor controls the zeroing process by adjusting the operational amplifier's offset voltage based on stored calibration data, making the system self-sufficient in maintaining measurement accuracy.
2Ease of operation
If automatic zeroing method is used, then intervention by software is not required, but the direct current component and low frequency component will be affected, resulting in worse tested waveform
Solution Approach 1:
The system performs zeroing adjustments before actual measurements are taken, using pre-stored calibration data from the look-up table. By completing the zeroing process in advance and storing the results, the system eliminates the need for continuous software intervention during measurements while preserving waveform integrity.
Solution Approach 2:
The system dynamically adjusts the operational amplifier's offset voltage based on temperature and other environmental conditions by referencing stored calibration data. This dynamic adjustment mechanism allows the system to adapt to changing conditions without continuous software control, maintaining both ease of operation and measurement precision.
3Measurement precision
If higher link gain is designed to detect small signals, then small signals can be detected, but the offset voltage influence is amplified, occupying larger dynamic range of ADC
Solution Approach 1:
The system uses a feedback mechanism where the microprocessor reads the offset voltage from the ADC, compares it with stored calibration data, and automatically adjusts the operational amplifier's offset voltage through a digital-to-analog converter. This closed-loop feedback system continuously compensates for offset voltage, allowing high link gain to be maintained without permanently occupying ADC dynamic range.
Data Source
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AI summary
A zeroing method and zeroing device for an optical time-domain reflectometer (OTDR) are disclosed. The zeroing method includes: before starting the optical time-domain reflectometer, when a laser device is in an off state, sending a zeroing signal; and performing zeroing processing according to the zeroing signal. In the embodiments of the present invention, the feedback zeroing can be performed on a receiving circuit by utilizing the idle time prior to a test or during the test, thus the influence of an offset voltage is reduced, and a problem of operational-amplifier zero drift also can be solved in the meantime, which improves a detectability of the OTDR, and overcomes a disadvantage that a manual zeroing method is not intelligent and a measured waveform introduced in an automatic zeroing method is bad.