The performance of an all-optical closed-loop chaotic communication system in a transmission link consisting of single mode fibers (SMF) applying two different dispersion management techniques is numerically studied. The first technique is implemented by the usage of dispersion compensating fibers (DCFs), while the second utilizes optical phase conjugators (OPCs). The latter is implemented by means of four wave mixing (FWM) in a dispersion shifted fiber (DSF), where the chaotic carrier corresponds to the signal wave and a high power continuous wave corresponds to the pump wave. Calculation of the recovered message Q-factor values obtained from the corresponding eye diagrams has been carried out applying chaotic modulation (CM) and chaos shift keying (CSK) encryption techniques for two repetition rates (2.4Gbps, 5Gbps). It is shown that the optical phase conjugation is an effective dispersion and non-linear effects compensation technique even if high-bit rate message encoding is applied. The superiority of a transmission system including OPCs to that utilizing (DCFs) is presented. The influence of key system parameters such as optical power, OPC spacing, pump power level, etc. to the transmission performance has been investigated. Acceptable system performance is presented for approximately 600Km at 2.4Gbps and 400Km at 5Gbps.
A detailed investigation of the decoding properties of different receiver configurations in an all-optical chaotic transmission system is presented for two data-encoding techniques and for various dispersion compensation maps. A semiconductor laser subjected to optical feedback generates the chaotic carrier while data is encoded either by Chaotic Modulation (CM) or Chaotic Shift Keying (CSK) methods. The complete transmission module consists of various dispersion management maps, in-line amplifiers and Gaussian optical filters. The receiver, employing a high facet reflectivity laser, is either forming a closed-loop configuration operating at the non-amplification regime or a strongly injected open-loop one. For the latter configuration the possibility of utilizing an anti-reflection (AR) coated laser is also investigated. System's performance is numerically tested by calculating the Q-factor of the eye diagram of the 1 Gb/s received data. The influence of the optical power launched into fibre or the transmission distance to the quality of the decoded message has been investigated. The closed-loop scheme had better performance relative to the open-loop, while CSK method and maps utilizing Dispersion Shifted Fibres are superior to CM and that employing Dispersion Compensating Fibres respectively. When an AR-coated laser is used in the open-loop receiver setup, improved decoding performance occurs.