Muanenda Yonas, Faralli Stefano, Oton Claudio J, Di Pasquale Fabrizio
Opt Express. 2018 Jan 22;26(2):687-701. doi: 10.1364/OE.26.000687.
We propose and experimentally demonstrate a stable homodyne phase demodulation technique in a ϕ-OTDR using a double-pulse probe and a simple direct detection receiver. The technique uses selective phase modulation of one of a pair of pulses to generate a carrier for dynamic phase changes and involves an enhanced phase demodulation scheme suitable for distributed sensing by being robust against light intensity fluctuations, independent of the modulation depth, and convenient for analogue signal processing. The capability of the technique to quantify distributed dynamic phase change due to a generic external impact is experimentally demonstrated by measuring the phase change induced by a nonlinear actuator generating a 2 kHz perturbation at a distance of 1.5 km on a standard singlemode fiber with an SNR of ~24 dB. The demodulated nonlinear response is shown to have a spectrum consistent with one obtained using an FBG sensor and a commercial reading unit.
我们提出并通过实验证明了一种在φ-OTDR中使用双脉冲探头和简单直接检测接收器的稳定零差相位解调技术。该技术利用一对脉冲中一个脉冲的选择性相位调制来生成用于动态相位变化的载波，并且涉及一种增强的相位解调方案，该方案适用于分布式传感，具有抗光强波动能力、与调制深度无关且便于模拟信号处理的特点。通过在标准单模光纤上距离为1.5 km处测量由产生2 kHz扰动的非线性致动器引起的相位变化，信噪比约为24 dB，实验证明了该技术量化由于一般外部冲击引起的分布式动态相位变化的能力。解调后的非线性响应显示出与使用光纤布拉格光栅（FBG）传感器和商业读数单元获得的频谱一致。
