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Direct phase reading in two-mode fiber sensors and sensor arrays
Optics Letters
|October 2, 2009
Summary
A new signal processing method uses frequency shifters in two-mode fiber sensors. This approach enables direct phase shift measurement with minimal crosstalk for cascaded sensing regions.
Area of Science:
- Optics and Photonics
- Fiber Optic Sensing
- Signal Processing
Background:
- Two-mode fiber in-line interferometric sensors offer a platform for various sensing applications.
- Traditional methods for interrogating these sensors can be complex or limited in performance.
Purpose of the Study:
- To present a novel signal-processing scheme for two-mode fiber in-line interferometric sensors.
- To enable direct measurement of optical phase shifts using frequency shifters.
Main Methods:
- Utilizing frequency shifters as directional couplers for mode coupling.
- Forming an interferometer within the fiber.
- Transferring the optical phase shift to the interference signal at a measurable beat frequency.
- Employing a two-channel lock-in amplifier or time-interval counter for direct phase shift reading.
Main Results:
- Achieved direct phase shift measurement at beat frequencies ranging from kilohertz to hundreds of kilohertz.
- Demonstrated the ability to cascade multiple sensing regions in a single fiber strand.
- Reported crosstalk between cascaded regions below -34 dB.
Conclusions:
- The proposed signal-processing scheme provides an efficient method for interrogating two-mode fiber interferometric sensors.
- The technique allows for direct phase shift measurement and supports multiplexing of multiple sensors.
- Low crosstalk ensures reliable performance in cascaded sensor systems.
