We demonstrate for the first time a DFB fibre laser used as a hydrophone. The pressure sensitivity of the laser frequency ranges from 1 to 0.5kHz/Pa between 400 and 800kHz. The noise equivalent pressure was ～93dB rel. 1μPa/Hz~(1/2). The angular responsivity at 800kHz had a central lobe with a 3-dB width of 6.4°, corresponding to an effective sensitive length of approximately 6mm, which is much shorter than the laser cavity length of 5cm.
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