Efficient and Compact Inline Interferometric Fiber Sensor Array Based on Fiber Bragg Grating and Rectangular-Pulse Binary Phase Modulation

Abstract

In this paper, an efficient and compact inline interferometric fiber sensor array based on Fiber Bragg Grating (FBG) and rectangular-pulse binary phase modulation is proposed. FBGs are made inline on the fiber to act as the reflection mirrors to construct the interferometer working as the sensing area. Polarizer-based polarization diversity receiver method is used to overcome the polarization-induced signal fading. This sensor configuration makes the whole system efficient, compact, and cost-effective while maintaining satisfactory performance. With binary phase modulation imposed on the specific location of the pulsed light source with a rectangular pulse, three phase-shifting steps of ${\pi }/ {2}$ , 0, and − ${\pi } / {2}$ , radians are generated and the phase shifts that carry the vibration signals are demodulated with an orthogonal demodulation algorithm. The method has the advantages of low complexity, low cost, and high real-time capability. The techniques are theoretically analyzed and experimentally demonstrated using a two-channel time-division multiplexing array. The obtained resolution of the sensor system can reach $3\times 10^{-4}\,\,{\mathrm {rad}} /{{\surd \text {Hz}}}$ . The efficiency and compactness of the proposed sensor array further narrow down the gap between the laboratory demonstration and practical use of practical fiber-optic sensors.