• Analysis of the carrier suppressed single sideband modulation for long distance optical communication systems

      Paloi, Fadil; Haxha, Shyqyri; University of Bedfordshire; Royal Holloway, University of London (Elsevier GmbH, 2018-02-12)
      In this research paper, we report on a simulation study of the Radio over Fibre (RoF) Carrier Suppressed Single Sideband (CS-SSB) modulation scheme. This scheme is based on a Dual Parallel Dual Drive Mach-Zehnder modulator (DP-DDMZM), for a long-distance transmission. The proposed system consists of the combination of a carrier and a message signal at two parallel modulators, where the laser and link power is varied for the two different dispersion compensation techniques. We found that by suppressing the optical carrier and cancelling one sideband, we can limit the nonlinear effects that are caused by power fading and interference. We demonstrate that by varying the launched laser and link power up to optimised threshold levels, the signal to noise ratio (SNR) increases and the Q-Factor improves significantly. Our proposed RoF optic communication architecture can support an extended reach transmission of up to 200 km without dispersion compensation. Moreover, for the bitrate of 10 Gbit/s and span length of 25 km, we achieved a span ratio of 520, alternatively viewed as the system link signal transmission distance of 13,000 km. Therefore, this method is cost-effective and less complex.
    • Unidirectional light propagation photonic crystal waveguide incorporating modified defects

      Soltani, A.; Ouerghi, F.; AbdelMalek, Fathi; Haxha, Shyqyri; Ademgil, Huseyin; Akowuah, Emmanuel K.; Université de Tunis El Manar; University of Bedfordshire; European University of Lefke; Kwame Nkrumah University of Science and Technology (Elsevier GmbH, 2016-11-29)
      In this paper, we have proposed a design of an Optical Diode-like in two-dimensional (2D) Photonic Crystal (PC) waveguide. The proposed device consists of 2D square-lattice PC structures, and it is based on two PC waveguides with different symmetric guiding modes, where various configurations of defects, including elliptic or/and semi-circular defects have been incorporated. The proposed one-way light propagation Optical Diode has been designed and optimized by employing in-house 2D Finite Difference Time Domain (FDTD) numerical method. We have reported that the unidirectional light propagation depends strongly on the coupling region between the introduced defects and the adjacent waveguides, and it also depends on the matching and mismatching between the defects and waveguide modes. It has been shown also that owing to its tunable features, the proposed Optical Diode can be potentially applied as a building block in future complex optical integrated circuits.