The Optical Grating Hydrophone.
Abstract
An optical hydrophone has been developed, the output of which is a direct intensity modulated representation of an incident acoustic field. The principle of operation involves the relative displacement induced by an acoustic field of two optical gratings which lie between a constant optical source and an optical receiver. The received light intensity is a function of the relative displacement of the two optical gratings. The optical source may be coherent or incoherent light, and a simple pin photodiode detector affords adequate receiver sensitivity. Large, multimode optical fibers can be used to carry the light to and from the hydrophone, and since the device is photon-noise limited, arbitrarily high sensitivities can be obtained by increasing the optical power. The direct intensity modulated output eliminates the need for more sophisticated detection techniques that are often applied to phase modulating optical hydrophones, yet comparable sensitivity can be realized with the optical grating approach. Fabrication of the device is straightforward, without any advanced optical techniques required. Several prototypes have been built and have already demonstrated dynamic ranges as high as 160 dB, with the ability to detect acoustically induced displacements of less than 0.01 Angstroms. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1981
- Accession Number
- ADA096714
Entities
People
- B. W. Tietjen
Organizations
- General Electric