Accuracy limitations on Brillouin lidar measurements of temperature and sound speed in the ocean
ABSTRACT There are five mutually dependent variables relevant to Brillouin lidar measurements of temperature and sound speed in the ocean; they are (1) the Brillouin shift, (2) the sound speed, (3) the index of refraction, (4) the temperature, and (5) the salinity. We use three well-known relations to analyze rigorously the interdependence of these five variables. Clearly, a Brillouin shift measurement does not provide a stand-alone determination of temperature or sound speed; one more variable or one more relation must be known. The use of mean values of salinity that have been obtained by an analysis of a large set of historical in situ data is considered for this additional relation.
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ABSTRACT: Three methods used to achieve Brillouin lidar in actual application are discussed. The scanning F–P interferometer technique cannot make real time measurement although it is high accurate. The edge technique has high sensitivity, but it requires extreme strict stable condition on environment. The technique combining F–P etalon and intensified CCD (ICCD) can stably work with few requirements on environment, and can make real time measurement. Therefore, the technique combining F–P etalon and ICCD will be the good choice for achieving Brillouin lidar practically.Optics Communications 05/2015; 352. DOI:10.1016/j.optcom.2015.04.086 · 1.54 Impact Factor
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ABSTRACT: The knowledge of the temperature profile of the upper-ocean mixed layer is relevant in oceanogra- phy, weather forecasts and climate studies. Currently, only in situ techniques such as fixed buoys or bathythermographs which are deployed by aircrafts or vessels, are accessible to the measure- ment of oceanic temperature profiles. As these techniques are not able to deliver cost-effective on- line data from an extended region of the ocean, a more efficient measurement technique is highly desirable. Guagliardo et al. proposed Brillouin scattering as a possible temperature tracer. The working principle can be understood as an expansion to commonly used airborne lidar bathymetry, exploring the Brillouin scattering for the temperature information. However, only recent progress in laser and receiver technology made an exploitation feasible. In this contribution we present the cur- rent status of our experimental setup, consisting of a light source based on a multi-stage pulsed Yb-doped fiber amplifier and a receiver unit based on an excited state Faraday anomalous disper- sion optical filter.