1. École Nationale Supérieure de Techniques Avancées de Bretagne, Lab-STICC (UMR CNRS 6285), 2 rue Francois Verny, 29806 Brest Cedex 9, France
2. Institute of Sensors, Signals and Systems, Heriot-Watt University, Edinburgh, Scotland, United Kingdom
3. Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, USA