V. V. Grishachev, D. B. Khalyapin and N. A. Shevchenko, “Method and Device for Actively Protecting Confidential Spoken Information from Leaking over an Acousto-Optic Fibre Channel by Using External Optical Noise Masking,” 2010.
http://www.wipo.int/patentscope/search/en/WO2010126400