Polarization-Sensitive OFDR for Long-Distance Disturbance Sensing
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Solution Overview
Problem
Current methods for distributed disturbance and stress sensing in long-distance optical fibers are limited to sensing distances less than 80 km and have low spatial resolution, primarily offering discrete single-point measurements.
Innovation Solution
The implementation of a polarization-sensitive optical frequency domain reflectometry (P-OFDR) system, which includes a laser optical frequency and phase monitoring module, phase modulation in the reference arm, and a polarization generating and splitting module, enhances sensitivity and signal-to-noise ratio, enabling distributed disturbance sensing by analyzing polarization information and Rayleigh backscattering along the optical fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If traditional OFDR methods are used, then the system structure is simple, but the sensing distance is limited to less than 80 km
Solution Approach 1:
The patent segments the optical signal processing into multiple polarization components (parallel and perpendicular to reference polarization). By separately detecting and processing these polarization components through polarization beam splitters and balanced photodetectors, the system extends sensing distance beyond 80 km while managing complexity through modular polarization-diversity detection architecture.
Solution Approach 2:
The patent introduces polarization state as an additional dimension for signal discrimination. By encoding disturbance information in polarization state changes and using polarization-sensitive detection, the system achieves extended sensing range and improved signal-to-noise ratio without simply increasing optical power or reducing attenuation.
2Manufacturing precision
If traditional OFDR methods are used, then the device complexity is low, but the spatial resolution is low (>10 m)
Solution Approach 1:
The patent uses polarization beam splitters to segment the detected light into orthogonal polarization components, with each component processed through separate detection channels. This segmentation enables precise spatial resolution down to centimeters by allowing independent analysis of polarization-state-dependent backscattered light from different spatial locations.
Solution Approach 2:
The patent changes the detection parameter from simple intensity measurement to polarization state measurement. By monitoring changes in polarization state (through Stokes parameters or Jones matrix analysis) of the backscattered light, the system achieves high spatial resolution and sensitivity to disturbances while using standard OFDR wavelength sweeping techniques.
3Productivity
If traditional OFDR methods are used, then the system is simple, but it only provides discrete single-point sensing
Solution Approach 1:
The patent implements continuous distributed sensing along the entire optical fiber length by combining OFDR wavelength sweeping with polarization-sensitive detection. The system continuously measures polarization state changes at all positions along the fiber simultaneously, providing continuous multi-point sensing coverage rather than discrete single-point measurements, achieving over 200 km sensing range.
Solution Approach 2:
By adding polarization state analysis as an additional measurement dimension to traditional OFDR, the system transforms single-point discrete sensing into continuous distributed sensing. The polarization-diversity detection architecture enables simultaneous measurement of disturbance characteristics at multiple locations along the fiber, extending sensing coverage to over 200 km.
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 extends the sensing range beyond 200 km, achieves high spatial resolution up to centimeters, and allows for continuous multi-point sensing, making it suitable for real-time monitoring in applications like electric power, communication cables, and oil and gas pipelines.
Implementation Method 1
OFDR technique use the high-coherent laser to achieve high-speed and linear wavelength scanning
Implementation Method 2
the reference arm is coherent by the reflected light of Faraday reflector and single-mode optical fiber backscattering light (i.e. Rayleigh reflected light)
Implementation Method 3
the reference arm is coherent by the reflected light of Faraday reflector
Implementation Method 4
the two arm lights with different frequency are interfered to form beat-frequency at the interference end
Implementation Method 5
When external disturbance (e.g. vibration and stress) occurs on the sensing optical fibers, the porization information (such as birefringence) and Rayleigh backscattering information of the sensing fiber can be changed
Implementation Method 6
polarization maintaining optical fiber
Data Source
AI summary
This invention relates to a distributed disturbance sensing device based on polarization sensitive optical frequency domain reflectometry (OFDR) and the related demodulation thereof. The device, adopting OFDR, polarization controlling and analysis techniques, consists of a ultra-narrow linewidth tunable laser source module, polarization generating and polarization splitting balanced detecting module, laser source optical frequency and phase monitoring module, high-speed optical switch and so on to establish a large-scale and long-distance optical sensing network. The demodulation method consists of analysis the polarization information from sensing optical fiber, the method of suppressing and compensating of the non-linear optical frequency and the laser phase noise, super-resolution analyzing, advanced denoising method and the polarization information analysis method based on Jones and Mueller's matrices using distributed wave plate model of optical fiber.