Wavelength division multiplexing addressed four-element fiber optical laser hydrophone array

A four-element hydrophone array system using a fiber Bragg grating laser system is described. The demodulation technique for the array combines a 3 × 3 coupler-based interferometer and three wavelength division multiplexers (WDMs). It is believed to be a new passive approach to use a WDM and a unique arithmetic method. The operational frequency limit depends only on the frequency of its electronic portion. The designed system has achieved a minimum of ∼7.2 × 10^-7 pm/√Hz detectable wavelength perturbation for frequencies that are greater than 200 Hz.