Multimode fiber-optic hydrophone based on the photoelastic effect

A multimode fiber-optic hydrophone based on the photoelastic effect is described. The device offers the advantages that it is simple, low cost, sensitive, inherently solid state, rugged, and exploits a differential approach for amplitude noise reduction. A minimum detectable pressure of 47 dB re 1 microPa/Hz(1/2) has been demonstrated at 500 Hz, and calculations based on photoelastic material properties indicate that a minimum detectable pressure as low as 15 dB re 1 microPa/Hz(1/2) might be achieved. This device design, therefore, represents an attractive technique for making a practical multimode fiber-optic hydrophone.