Multimode Optical Fiber Attenuation Measurement Directional Asymmetry
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Solution Overview
Problem
Conventional methods for measuring optical power attenuation in multimode optical fiber links using the LSPM and OTDR approaches often yield different results due to asymmetry, leading to discrepancies when measuring in different directions, necessitating an improved method for direction-independent optical power attenuation measurement.
Innovation Solution
The implementation of a system and method that controls the modal distribution of test light both before launch into the multimode DUT and before detection using a launch mode conditioner and a receive mode filter, respectively, to induce preferential attenuation of high-order optical fiber modes, ensuring similar optical power attenuation values regardless of measurement direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional LSPM or OTDR approaches are used for optical power attenuation measurement, then measurement can be performed, but measurement precision deteriorates due to asymmetry and differential mode attenuation leading to unrepeatable and irreproducible results
Solution Approach 1:
The patent changes the modal distribution parameters of test light by using mode conditioners (mandrel wrapping, mode filter, or mode scrambler) to transform the light distribution before it enters the DUT. This ensures that the test light has a controlled, standardized modal distribution that eliminates differential mode attenuation effects, thereby improving both measurement precision and reproducibility across different measurement directions and setups.
Solution Approach 2:
The patent applies preliminary mode conditioning to the test light before it is launched into the DUT. By pre-controlling the modal distribution using mode conditioners, the measurement system eliminates the source of asymmetry and irreproducibility before the measurement process begins, ensuring consistent results regardless of measurement direction or setup variations.
2Reliability
If mode conditioners are added to control modal distribution, then measurement reproducibility improves, but device complexity increases
Solution Approach 1:
The patent presents multiple mode conditioning techniques (mandrel wrapping, mode filter, mode scrambler) that can be used interchangeably to achieve the same goal of controlling modal distribution. This universal approach allows practitioners to select the most suitable method based on available equipment and specific measurement requirements, reducing the perceived complexity by showing that different components can fulfill the same function.
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 results in significantly reduced variations between measurements taken in different directions, providing more consistent and reproducible optical power attenuation values, thereby addressing the asymmetry issues in conventional techniques.
Implementation Method 1
inducing a preferential attenuation of high-order optical fiber modes of the test light along the first multimode device and along the second multimode device
Data Source
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AI summary
There is provided a method for measuring an optical power attenuation value of a multimode DUT. The method generally has, using an optical source, propagating test light along a multimode device link having a first multimode device, the multimode DUT and a second multimode device serially connected to one another; said propagating including inducing a preferential attenuation of high-order optical fiber modes of the test light along the first multimode device and along the second multimode device; using an optical power detector, detecting an optical signal resulting from the propagation of the test light along the multimode device link and transmitting an output signal based on the detected optical signal; and using a processor, determining the optical power attenuation value of the multimode DUT based on the output signal.