Accuracy limitations on Brillouin lidar measurements of temperature and sound speed in the ocean

Department of Physics, Texas A&M University, College Station, Texas 77843, USA.
Applied Optics (Impact Factor: 1.78). 10/1997; 36(27):6887-94. DOI: 10.1364/AO.36.006887
Source: PubMed


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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    • "From the spectrum, the Brillouin shift and Brillouin line width can be determined by the free spectral range (FSR) of the FPI. Based on the relationship between the ocean parameters and the spectral characteristics the ocean parameters can be obtained, such as, sound speed in the water [4] [5] [9], temperature of the water [2] [10] [11], viscosity of the water [8], attenuation coefficient of light in the water [13], and the salinity of the sea water [3]. So, the Brillouin lidar using FPI technique can measure several ocean parameters. "
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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.
    Full-text · Article · May 2015 · Optics Communications
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    • "The dependence of the refractive index n(S,T,λ) and of the sound velocity vS(S,T) on the salinity S, the temperature T and the wavelength λ are well known [4]. Relying on historical data for the salinity S and measuring the Brillouin shift νB enables us to deduce the temperature T. It should be noted that there is also a dependence on pressure, which has been omitted for clarity in the above equation, but which could be easily taken into account [4]. "
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    ABSTRACT: Temperature profiles of the ocean are of interest for weather forecasts, climate studies and oceanography in general. Currently, mostly in situ techniques such as fixed buoys or bathythermographs deliver oceanic temperature profiles. A LIDAR method based on Brillouin scattering is an attractive alternative for remote sensing of such water temperature profiles. It makes it possible to deliver cost-effective on-line data covering an extended region of the ocean. The temperature measurement is based on spontaneous Brillouin scattering in water. In this contribution, we present the first water temperature measurements using a Yb:doped pulsed fiber amplifier. The fiber amplifier is a custom designed device which can be operated in a vibrational environment while emitting narrow bandwidth laser pulses. The device shows promising performance and demonstrates the feasibility of this approach. Furthermore, the current status of the receiver is briefly discussed; it is based on an excited state Faraday anomalous dispersion optical filter.
    Full-text · Article · Sep 2008 · Sensors

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