• 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.
    • Comparative analysis of long-haul system based on SSB modulation utilising dual parallel Mach–Zehnder modulators

      Paloi, Fadil; Haxha, Shyqyri; University of Bedfordshire; Royal Holloway, University of London (Springer New York LLC, 2018-02-08)
      In this paper, we have proposed a long-haul optical transmission system, based on a single sideband (SSB) modulation scheme. Analytical and simulation models have been developed, optimised and demonstrated for the proposed SSB system configurations. The SSB modulation scheme was proposed to overcome dispersion in the fibre. We have shown that the related link losses can be minimized by increasing the quality of the optical signal at the modulation. We have optimised the radio over fibre configuration scheme based on dual parallel dual drive Mach–Zehnder Modulator, thereby increasing transmission length of the fibre. With the proposed SSB, by suppressing some of the harmonics and cancelling one of the sidebands, we have halved the RF power fading and interference. The developed analytical (theoretical/mathematical) model agrees very well with the simulation results using two (both) different commercial simulation tools. The optical signal is boosted while minimizing the number of repeaters. We report a SSB configuration, compensation and amplification with individual spans of 150 km, by extending the length of the link up to 3250 km. The proposed system configuration exhibits high performance with less complexity and lower cost.