Spatial-division-multiplexing addressed fiber laser hydrophone array.

The fiber laser hydrophone is compact, and it is easy to construct an array by using the multiplexing technique. However, the number of hydrophones multiplexed in the array through wavelength-division-multiplexing (WDM) technology is limited. In order to expand the array, a spatial division multiplexing (SDM) method for addressing a fiber laser hydrophone array is researched. An optical switch is used in such array, and four distributed feedback (DFB) fiber laser hydrophones are addressed by switch channels. Experimental results show that the switch channels' crosstalk crucially influences the hydrophone signals' signal-to-noise ratio (SNR). In order to get good SNR, the crosstalk of the switch channels should be lower than -20 dB. Each DFB laser in the SDM-addressed array may be replaced with a WDM-addressed array, so a DFB fiber laser hydrophone array with more than 64 elements can be constructed.