Ome Applications Of Coding Technologies To Security-enhanced Fiber-optical Networks

Network security of high-capacity fiber-optical networks has become an important issue. Various methods from different aspects have to be taken to cope with security threats the fiber-optical network faced. In this thesis, we present some applications of coding technologies to security-enhanced fiber-optical networks. Theoretical analysis together with system simulation and experimentations are carried out.Multi-user optical code-division multiple-access (OCDMA) system transmits multiple optically encoded signals simultaneously. Therefore, the eavesdropper cannot get access to specific user information directly. Part of the thesis focuses on multi-user OCDMA system and subsystem technologies. We propose a novel optical thresholder based on nonlinear polarization rotation (NPR) to mitigate the multiple access interference (MAI). The theoretical analysis of the thresholder is presented. The effectiveness of the NPR thresholder is experimentally investigated in a4-user,2.5Gb/s per user OCDMA system. The NPR thresholder has the advantage of colorless operation over C bands and avoids the spectrum-slicing noise compared with the super-continuum based thresholder.In optical stealth communication, the secure information is hided underneath the host channel signal to avoid the awareness of eavesdropper. We propose optical stealth transmission of temporal phase encoded (TPC) signal in a public WDM network. We systemically study the tolerance of1D TPC system to spectral filtering with simulation and experiments. Based on the above results, spectral notch filtering is proposed to reject the interference on stealth channel from host channel. We experimentally demonstrate a2.5Gb/s stealth transmission of TPC signal with a2.5Gb/s WDM channel.Optical virtual private network (OVPN) technologies can provide low-latency and private communications with public network infrastructures. With some higher-layer encryption methods, a high-security OVPN service can be achieved. We propose to selectively provide OVPN service in a TDM-PON with spectral shaping line coding. In our scheme old service users are not affected. Corresponding protocol is also provided. The feasibility of providing2.5Gb/s OVPN service in155Mb/s upstream TDM-PON is investigated with simulation and experiments.Secure point-to-point (P2P) communication is becoming increasingly important with the prevalent of so-called’cloud’based applications. We propose a long distance P2P secure transmission scheme with CDM and orthogonal frequency division multiplexing (OFDM) based ultra-dense spectral phase coding (UD-SPC) technology. The proposal also employs AES encrypted Gold (AES-Gold) sequences and low-density parity-check (LDPC) coding technology. The principle of UD-SPC system and the correlation property of AES-Gold sequences are presented. The LDPC coding can largely compensate the cross-talk among non-orthogonal AES-Gold sequences as shown by simulation. Therefore, with LDPC coding the number of simultaneously transmitted codes can be increased to increase the transmission rate. We also propose and analyze a dynamic encoding/decoding method with circularly shifted AES-Gold sequences. The performance of5.15Gb/s LDPC-UD-SPC system with160511-length AES-Gold sequences in back to back scenario as well as transmissions over200km and400km standard single mode fiber without fiber dispersion compensation scenarios are investigated by simulation.