High-speed demodulation of a fiber-optic vibration sensor based on cascaded MZIs

A high-speed demodulation scheme of a fiber-optic vibration sensor based on cascaded Mach-Zehnder interferometers (MZIs) is proposed and demonstrated. A two-stage cascaded MZIs structure of four-channel outputs with their center wavelengths precisely aligned is implemented for orthogonally demultiplexing the spectral signal of the interferometric vibration sensor. In the digital domain, an orthogonal demodulation algorithm is developed for phase demodulation of fiber-optic interferometric vibration, and its demodulation speed is only limited by the digital sampling rate. In the experiment, a minimum detectable phase shift of 3.96×10^-5<i>r</i><i>a</i><i>d</i>/<i>H</i><i>z</i> at 100 Hz and 4.3×10^-6<i>r</i><i>a</i><i>d</i>/<i>H</i><i>z</i> at 100 kHz is achieved. Compared to traditional spectral demodulation algorithms, the proposed scheme offers advantages in terms of high demodulation speed, wide bandwidth operation, and ease of implementation, making it highly suitable for industrial and defense applications that demand both high reliability and cost-effectiveness.