Fibered Optical Path Inspection via Polarization Correlation
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Solution Overview
Problem
Conventional OTDR methods are not sensitive to mechanical disturbances that cause changes in light phase or polarization in optical fibers, limiting their ability to detect events like fiber bends or acoustic vibrations.
Innovation Solution
A method and system that use a computer-implemented system with a controller and detector to emit optical pulses into a fibered optical path, detect reflected signals, and determine correlation values between a reference signal and test signals to identify mechanical disturbances caused by birefringence, without requiring additional polarization measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional OTDR measures total return light, then signal-to-noise ratio is improved through averaging, but sensitivity to mechanical disturbances and polarization changes is lost
Solution Approach 1:
The patent segments the detection process into two independent components: intensity measurement (for SNR improvement) and polarization state measurement (for mechanical disturbance detection). By measuring both the intensity envelope and polarization state of backscattered light, the system can detect mechanical disturbances without sacrificing the SNR benefits of averaging.
Solution Approach 2:
The patent introduces polarization state as an intermediary parameter that mediates between the intensity signal and mechanical disturbances. By measuring changes in polarization state rather than relying solely on intensity changes, the system can detect mechanical disturbances while maintaining the ability to average for SNR improvement.
2Difficulty of detecting and measuring
If polarization sensitive OTDR is used to detect mechanical disturbances, then sensitivity to polarization changes is improved, but signal-to-noise ratio deteriorates due to differential measurements
Solution Approach 1:
The patent segments the measurement into intensity envelope detection (which can be averaged) and polarization state detection (which detects mechanical disturbances). This allows the intensity component to benefit from averaging for SNR improvement while the polarization component maintains sensitivity to mechanical disturbances.
Solution Approach 2:
The patent changes the measurement parameter from pure intensity (conventional OTDR) or differential polarization (standard polar-OTDR) to a combination of intensity envelope and polarization state. This parameter change enables simultaneous achievement of high SNR and mechanical disturbance detection sensitivity.
3Difficulty of detecting and measuring
If polarization sensitive OTDR measures differential signals, then mechanical disturbance detection is enabled, but inspectable distance is limited due to signal strength drop-off
Solution Approach 1:
The patent segments the detection function into intensity measurement (for distance measurement and SNR improvement) and polarization measurement (for mechanical disturbance detection). By using intensity envelope for the majority of the detection range and reserving polarization measurement for disturbance detection, the system extends the inspectable distance while maintaining mechanical disturbance detection capability.
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 allows for the detection of mechanical disturbances and polarization changes over longer distances than conventional OTDR, even when signals are below the minimum noise level, thereby enhancing the reliability of fiber inspection.
Implementation Method 1
causing a laser to emit at least one optical pulse into the fibered optical path
Implementation Method 2
detecting a plurality of reflected optical signals from the fibered optical path, the plurality of reflected optical signals having been reflected from a corresponding plurality of locations along the fibered optical path
Implementation Method 3
identifying a mechanical disturbance caused by birefringence in the fibered optical path
Data Source
AI summary
A method and system for inspecting polarization in a fibered optical path. The method being executed by a computer-implemented system comprising a controller and at least one detector communicatively coupled to the controller, the computer-implemented system being operatively connected to the fibered optical path, including: causing a laser to emit at least one optical pulse into the fibered optical path; detecting a plurality of reflected optical signals from the fibered optical path; determining a plurality of experimental correlation values based on the plurality of reflected optical signals and a reference signal function; and in response to a given experimental correlation value of the plurality of experimental correlation values being less than a threshold, identifying a mechanical disturbance caused by birefringence in the fibered optical path, the mechanical disturbance being located at a location of the plurality of locations corresponding to the given experimental correlation value.