Nonzero-drift differential all-fiber-optic heterodyne Doppler measurement system

Abstract

To eliminate the serious detrimental effects caused by frequency drifts of acousto-optic frequency shifters (AOFSs) in conventional all-fiber-optic heterodyne Doppler measurement systems, a differential allfiber-optic heterodyne configuration is proposed. By delicate arrangement of the fiber-optic path and using only one AOFS, zero drift, which commonly occurs in conventional systems, is eliminated. Based on the proposed configuration, a differential all-fiber-optic heterodyne Doppler measurement system has been built. Using a piezoelectric ceramic oscillator as the moving object, it has been verified that the proposed system is able to eliminate zero drift, and the displacement and velocity measurement accuracies reach 0.775 μm and 0.009 mm∕s, respectively. It has been shown that the differential all-fiber-optic heterodyne Doppler measurement system can achieve good performance in both displacement and velocity measurements, even in a harsh environment with drastic temperature variation.

Drift Error Compensation Algorithm for Heterodyne Optical Seawater Refractive Index Monitoring of Unstable Signals

“…However, the corrected measurement obtained through the corrected optical path needs to guarantee the covariance with the actual measurement optical path and focus on the static reference surface, which is almost impossible in its actual application. X. Zhang et al designed two interferometric optical paths using optical fiber couplers and eliminated the drift error caused by frequency fluctuation through subtraction [11], but did not take the different clock systems of the two systems into account. These methods, through redesigned optical paths, have the same drift-error-removing effect for different types of signals.…”