Abstract
In this paper, an environment-robust polarization-based phase-shift dynamic demodulation method for optical fiber acoustic sensor is proposed. Through optical lever effect of polarization low-coherence interference and amplitude scaling differential cross multiplication (AS-DCM) algorithm, acoustic-source induced interference phase of the acoustic sensor can be demodulated in real-time with high precision. The maximum relative phase demodulation error was only 0.694% when the cavity length had an offset ∼4 μm. The maximum cavity length demodulation error was keeping less than 3.988 nm under the optical power reduced ten times, which demonstrated an ultra-stable demodulation for the largest permitted optical power attenuation range, to our best knowledge. The proposed method has a capability of tolerating large optical power attenuation and large cavity length random offset, providing an environment-robust way for optical fiber acoustic sensor working in extreme environments.
Highlights
OPERATION PRINCIPLEThe proposed amplitude scaling differential cross multiplication (AS-DCM) algorithm adopts three-way lowcoherence interference fringes to calculate
In this paper, an environment-robust polarizationbased phase-shift dynamic demodulation method for optical fiber acoustic sensor is proposed
We proposed orthogonal phase shift as well as four-step phase shift with birefringent crystals [24],[25]
Summary
The proposed AS-DCM algorithm adopts three-way lowcoherence interference fringes to calculate. The Broadband source (BBS) with Boxcarlike spectrum transmits light to EFPI sensor through a circulator. Reflected light is divided into three beams through a 1 × 3 coupler. Each beam passes through a polarizer, a small birefringent crystal block and an analyzer in sequence to form a low-coherent interference fringe, which is received by a detector. Where G k is the BBS spectrum and ID k is the transfer function of demodulator interferometer. The affections caused by the optical power fluctuation and the working cavity length shift because of thermal interference and mechanical vibration can be reduced
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