Ultra Low Frequency Phase Generated Carrier Demodulation Technique for Fiber Sensors

A Fiber-Optic Interferometric Tri-Component Geophone for Ocean Floor Seismic Monitoring

“…There are two generally adopted methods for demodulation of phase generated carrier (PGC) modulation: differential cross multiplication (DCM) demodulation, and arctangent demodulation [15,22,23], along with several improvements suggested over the years [17,24]. In this paper, we consider the direct modulation phase generated carrier (D-PGC) demodulation by the DCM scheme in each sensing channel, as illustrated in Figure 2.…”

“…In 1987, Gardner et al first reported a mandrel structure fiber-optic interferometer seismometer, which had a detection threshold of 1 $\mathrm{ng}/\sqrt{\mathrm{Hz}}$ within the detection frequency band of 10–1000 Hz [11]; in 1990, Brown et al reported a plate structure seismometer whose application frequency was above 20 Hz [13]; in 2002, Shindo et al reported a seismometer with a plate structured fiber-optic interferometer, which was applied for vibration frequency above 3 Hz; in 2007, Beverini et al reported a low-frequency sensing system whose low frequency limit was 0.05 Hz [14]; in 2011, Lin et al realized a low frequency vibration detection scheme which had the lowest frequency of 0.01 Hz produced by piezoelectric optic fiber stretcher, after comparing two demodulation schemes for phase generated carrier (PGC) [15]. Zeng et al, reported a three-component fiber-optic accelerometer for well logging in 2004 [16] with the frequency range 3–800 Hz, applied to well logging without considering the optical polarization fade in the interferometer.…”