An improved PMDI-TDM structure for remotely interrogated optical fiber hydrophone arrays

Abstract

The paper proposed an improved path-matched differential interference (PMDI) structure for noise suppression in remotely interrogated fiber-optics hydrophone (FOH) arrays. By setting a slight arm difference between two parts of the PMDI, the phase generation carrier (PGC) and phase modulation (PM) carriers are loaded into the passive PMDI and the Rayleigh scattering and stimulated Brillouin scattering (SBS) induced phase noises in a 50km transmission system are suppressed below the self-noise level of the short system. On this basis, an adjacent-matched optical structure is applied and the noise caused by the environment disturbance to the long-distance lead fiber is greatly reduced by about 30dB. Using this improved PMDI structure, noises associated with the remote transmission have been effectively suppressed. This structure can be applied in many large-scale remotely interrogated underwater sensing fields with advantages of low noise, simple array structure and low cost.