Faraday Michelson Interferometers for Signal Demodulation of Fiber-Optic Sensors

We developed an all-fiber-based optical demodulator for the signal interrogation of low-coherence fiber-optic Fabry-Perot interferometric sensors. The optical demodulator consists of a Michelson interferometer implemented by using a 3 x 3 fiber coupler and two fiber-coupled Faraday reflectors with tunable fiber delay lines. The demodulator's output contains two optical interference signals with a constant phase shift and the output shows no sensitivity to the polarization variation in the light source or fibers. A digital phase recovery algorithm is used to extract the measurand information from the phase-shifted signals at high accuracy, high dynamic range, and high stability. The optical demodulator has been applied to the measurement of high-frequency vibrations and strains using fiber-optic sensors.

Automated summary

The all-fiber optical demodulator developed uses a Michelson interferometer to accurately extract measurand information from phase-shifted signals. It is highly stable and has been successfully applied to measure high-frequency vibrations and strains with fiber-optic sensors.