22 November 2011 Research on fiber optic gradient hydrophone based on two interferometers scheme
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Proceedings Volume 8199, 2011 International Conference on Optical Instruments and Technology: Optical Sensors and Applications; 81991D (2011) https://doi.org/10.1117/12.907040
Event: International Conference on Optical Instruments and Technology (OIT2011), 2011, Beijing, Beijing, China
Abstract
Fiber optic vector hydrophone gets the acoustic field pressure gradient information by finite difference approximation, smaller as the separation D between the two sensing elements in the same direction is, more accurately the acoustic field information can be obtained. Because the sensitivity of the hydrophone is proportional to the separation D, the reduction of D is limited by the sensing element's geometry and the sensitivity of the hydrophone. For one-dimensional fiber optic gradient hydrophone, D is less than λ/4 as the measurement error of pressure gradient is smaller than 1dB. To achieve more outputs, the hydrophone can be configured by two interferometers scheme, then the pressure in acoustic center of the hydrophone can be acquired by the arithmetic average of the two interferometers' output of pressure, thus λ/7 as the upper limit of D for pressure measurement error 1dB maximum should be obeyed. The sensitivity decreases as the frequence of sound going down when D value is confirmed, so the lower limit of frequency band is mainly determined by optical noise, its minimum detectable signal grows quickly as frequency decrease, hence, good noise cancellation in two interferometers scheme can great improve the low frequency detection.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Fuyin Wang, Shuidong Xiong, Hong Luo, "Research on fiber optic gradient hydrophone based on two interferometers scheme", Proc. SPIE 8199, 2011 International Conference on Optical Instruments and Technology: Optical Sensors and Applications, 81991D (22 November 2011); doi: 10.1117/12.907040; https://doi.org/10.1117/12.907040
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