A technique for securing data transmission via an optical communication line comprising an optical fiber extending between a first network element and a second network element; the technique comprises conveying a first optical signal carrying data via the optical fiber from the first network element towards the second network element at a predetermined optical wavelength, and conveying a second optical signal at the same predetermined optical wavelength via the same fiber in the opposite direction to create within the optical fiber a combined optical signal such that combination of the first and second optical signals is adapted to hamper an unauthorized non-intrusive extraction of the first optical signal from the combined optical signal.