1. Physics Department, Technical University of Cluj-Napoca, C. Daicoviciu str. Nr. 15, RO-400 020 Cluj-Napoca, Romania
2. Faculty of Physics, “Babesa-Bolyai” University, Cluj-Napoca, Romania
3. Department of Telecommunications, Technical University of Cluj-Napoca, 15 C. Daicoviciu str, 400 020 Romania