Remote Sensing of Temperature and Speed of Sound in the Ocean

Brief History

Currently water temperatures of the ocean are measured by satellite (surface only) or by in-situ techniques such as XBTs (expandable bathythermographs), buoys or gliders.

Therefore, a remote technique would be highly desirable. In particular as the date could provide valuable input in such areas as meteology, ocean-atmosphere interaction and oceanography.

Early on there have been proposals to measure the temperature of the ocean remotely based on either Raman (Leonard) or Brillouin-scattering (J. L. Guagliardo). Practical realizations of such systems, however, failed due to principal problems or due to the absence of laser systems fulfilling the requirements in terms of linewidth and stability. Only recent developments in the area of Opens internal link in current windowinjection seeding of pulsed lasers have changed this situation (Henderson et al.(1986); Fry et al (1991)).

Exact accuracy estimates for our proposal of measuring the temperature profiles based on Brillouin scattering exist (Fry et al., 1996). First laboratory versions of our Brillouin LIDAR have been successfully demonstrated to measure the linewidth of the Brillouin lines as a function of temperature (Fry et al., 2002). Depth resolved measurements without real-time detection has been performed (Schorstein et al., 2009).

In recent developments we have demonstrated a edge filter with high transmission (Rudolf et al., 2012) and have implemnted a full laboratory version of our approach (A. Rudolf et al., 2014).


  • D. A. Leonard et al., Appl. Opt. 18, 1782 (1979)
  • J. L. Guagliardo, Dufilho, Rev. Sci. Instrum. 51, 79 (1980)
  • S. W. Henderson, E.H. Yuen, E.S. Fry, Opt. Lett. 11, 715 (1986)
  • E. S. Fry, Q. Hu, X. Li, Appl. Opt. 30, 1015 (1991)
  • E. S. Fry, Y. Emery, L. Quan, J. Katz, Appl. Opt. 36, 6887 (1996)
  • E. S. Fry, J. Katz, D. Liu, Th. Walther, J. of Mod. Opt. 49, 411 (2002)
  • K. Schorstein, E. S. Fry and Thomas Walther; Applied Physics B 97, 931 (2009)
  • A. Rudolf, Th. Walther; Optics Letter 37, 4477-4479 (2012)
  • A. Rudolf, Th. Walther; Opt. Eng. 53(5), 051407 (2014)


Prof. Dr. Thomas Walther

Laser und Quantenoptik
Institut für Angewandte Physik
Fachbereich 05 - Physik
Technische Universität Darmstadt
Schlossgartenstr. 7
D-64289 Darmstadt

+49 6151 16-20831 (Sekretariat)

+49 6151 16-20834




Optics in our Time

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