Quadrature phase-stabilized three-wavelength interrogation of a 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 laser. Three quadrature wavelengths are chosen to perform high-speed cavity length demodulation by wavelength switching, thereby avoiding imbalances and disturbances between the three optical paths in conventional three-wavelength quadrature phase-demodulation systems. A feedback-stabilization scheme for maintaining the quadrature phase condition is proposed for the first time, to the best of our knowledge, providing potential for long-term monitoring in harsh environments.