A method of transmitting optical signals in a submarine optical network and an optical unit for performing the method, the optical unit is configured for receiving an optical signal comprising a plurality of wavelengths where at least some of the wavelengths comprise traffic data. The optical unit includes a processor unit which is configured for scrambling the shape of at least one wavelength comprising traffic data of the optical signal so as to make said traffic data of said at least one wavelength undetectable for a receiver station.