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Higher-order mode suppression technique for multimode sapphire fiber external Fabry-Perot interferometers
Optics Express
|February 25, 2022
Summary
A novel technique using multi-stage fiber coupling enhances demodulation stability and accuracy for sapphire fiber external Fabry-Perot interferometers. This method significantly reduces errors in optical phase and cavity length measurements.
Area of Science:
- Optoelectronics
- Fiber Optics Sensing
- Interferometry
Background:
- Sapphire fiber external Fabry-Perot interferometers are crucial for high-temperature sensing.
- Demodulation stability and accuracy are often limited by modal interference.
- Existing techniques struggle to mitigate the influence of higher-order modes.
Purpose of the Study:
- To propose and demonstrate a new signal-picking technique.
- To improve demodulation stability and accuracy in sapphire fiber interferometers.
- To overcome the limitations of conventional coupling methods.
Main Methods:
- Fusion splicing four multimode fibers with varying core diameters in sequence.
- Utilizing in-step core diameter changes to induce a filtering effect on higher-order modes.
- Implementing a multi-stage coupling approach to suppress unwanted modal interference.
Main Results:
- Suppressed additional phase on fundamental mode demodulation by five-fold compared to single-stage coupling.
- Reduced the standard deviation of demodulated optical phase by over two times.
- Achieved significant improvements in demodulation accuracy and stability.
Conclusions:
- The proposed multi-stage coupling technique effectively filters higher-order modes.
- This method offers a simple and robust solution for multimode sapphire fiber interferometer demodulation.
- The technique enhances the reliability of measurements in demanding environments.
