.
The maximum acceptable signal at 600 Hz is 140 rad and increases linearly
with decreasing frequency.
This paper describes a form of passive homodyne demodulation for recovering
a signal of interest from a Mach-Zender optical fiber interferometric sensor.
The interferometer uses a 2×2 optical fiber coupler at the input,
a push-pull arrangement to stretch the fibers comprising the two legs of
the interferometer in a differential manner, and a 3×3 optical fiber
coupler at the output, generating three phase-modulated outputs.
The demodulator uses all three outputs in a symmetric manner to reconstruct
the signal of interest. A dynamic range of 115 dB in a 1 Hz bandwidth
has been measured for a circuit implementing this scheme. The minimum
detectable signal at a frequency of 600 Hz is 220 .
The maximum acceptable signal at 600 Hz is 140 rad and increases linearly
with decreasing frequency.
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