Elimination of drift in a single-mode optical fiber interferometer using a piezoelectrically stretched coiled fiber

Abstract

The feasibility of maintaining a single-mode optical fiber interferometer in quadrature is demonstrated using a servo driven piezoelectrically stretched coiled fiber. The controller has a range of ~10(-5)-1000 rad with a stress voltage coefficient of ~27pi rad/V.

Strain Wave Acquisition by a Fiber Optic Coherent Sensor for Impact Monitoring

“…Differently from conventional interferometric approaches, the key element of the proposed approach is represented by a new polarization and phase diversity coherent demodulation scheme ( Figure 1) where the signal S, back-reflected from the sensing fiber end, and a local oscillator (LO) are combined in a 90° optical hybrid [21][22][23] enabling the extraction of both phase, amplitude and polarization of the optical field S. Indeed, the outputs of the 90° optical hybrid, used in combination with balanced photodetectors, provide the in-phase I and the quadrature Q signals for both polarization σ(t) components (// and ⊥) of S, where I ÷   (( )) and Q ÷   (( )). The four in-phase I and quadrature Q signals are then digitalized and post-processed with demodulation algorithms exploited in coherent optical communications [24,25], allowing the recovery of A(t), θ(t) and σ(t) in a completely passive way without the need of complex active feedbacks for quadrature point stabilization as in conventional fiber optic interferometric and polarimetric schemes [26,27].…”

Digital Demodulation of Interferometric Signals

“…A frequency shift in one of the beams may be accomplished by acousto-optic frequency modulation (Culshaw & Giles, 1982), frequency ramping the optical source (Jackson et al, 1982), or piezoelectric-induced path length changes (Jackson et al, 1980;Cole et al, 1982). These heterodyne modulation approaches have been categorized as true-heterodyne, pseudo-heterodyne, and synthetic-heterodyne techniques.…”

Stabilized Fiber Optic Sensor for Ultrasound Detection

“…Drift in the fiber interferometer results from laser frequency fluctuations along with mechanical and temperature induced strains. An active homodyne technique has been demonstrated by Jackson et al [20] to compensate for drift in a Mach-Zender fiber interferometer. This technique used a piezoelectric fiber stretcher to control the reference fiber length such that quadrature was maintained.…”