Quadrature phase stabilized three-wavelength interrogation of fiber-optic Fabry–Perot acoustic sensor

In this letter, we propose a quadrature phase stabilized three-wavelength demodulation technique for the interrogation of fiber-optic Fabry–Perot acoustic sensors. It is based on accurate and fast tuning of a monolithic modulated grating Y-branch (MG-Y) laser. Three quadrature wavelengths are chosen to perform high-speed cavity length demodulation by wavelength switching, so that avoiding imbalances and disturbances between the three optical paths in the conventional three-wavelength quadrature phase demodulation systems. A feedback stabilization scheme for maintaining the quadrature phase condition has been proposed and demonstrated for the first time, making it potential for long-term monitoring in harsh environments.