Real Time Phase Unwrapping Implementation Based on Unscented Kalman Filter for Interferometric Fiber Sensor Applications

Phase unwrapping is a vital process in optical interferometric measurement. Phase unwrapping algorithms usually need to face performance and computation complexity compromise. Unscented Kalman filter based phase unwrapping has been proved to be a robust method with high signal-to-noise performance. However, it calls for high computational cost, which increases the operation time and system power consumption. In this paper, we propose an field programmable gate array (FPGA) based solution to use the unscented Kalman filter to fulfill very fast phase unwrapping task. Hardware-friendly algorithm using the unscented Kalman filter is optimized to facilitate the pipeline design. The phase unwrapping engine is fully implemented on an Intel Stratix III FPGA. Both simulation data and actual data collected from phase-sensitive optical time-domain reflectometer (Φ-OTDR) were used to verify the proposed phase unwrapping engine. The realized SNR of the sensor signal is 42.85 dB, and the average phase error is below 0.01 rad compared with its software-version counterpart. The computation speed can be increased by 470 times, which demonstrates its superiority in the high implementation throughput.