Research On Encoding&Decoding Technology For All-Optical Packet Switching Networks

Optical code-division multiple-access(OCDMA) are attracting more attention in optical packet switching networks because of their advantages in asynchrous random access, soft capacity on demand, excellent security, efficent usage of the frequency bandwidth, flexible resource allocation, high-speed all-optical processing and low-complexity. Nowadays, variable-weight and adjustable-power OCDMA system is becoming a new focus as it can provide diversified quality of service (QoS). This thesis focuses on the research of encoding/decoding technologies such as variable-weight code design, system performance analysis, modified en/decoder and detection scheme, and the applications of OCDMA in OPS networks.Firstly, mathematics basic theory and knowledge of address code design for OCDMA systems is introduced. Based on Galios fields, we construct quadratic congruence code (QCC), and then get diversified QCC (DQCC) by using algebraic transformation such as syclic shift, padding and exchange of subsequences, transposition of sequences. Comparing with basic prime code (PC), DQCC have doubled cardinality, multiple codeset, variable code weight, good cross-corelation property and can satisfy the requirement of QoS transmission. Moreover, modified QCC (MQCC) with fixed in-phase cross correlation (IPCC) can be well applied to incoherent spectral-amplitude-coding OCDMA (SAC-OCDMA) systems.To provide diversified QoS transmission, the performance of DQCC in adjustable power and double-weight OCDMA system is analyzed, and the bit error ratio (BER) performance of OCDMA systems are evaluated as the power and code weight change. Based on advanced optical logic AND and XOR gates, we design the double-level and multi-stage composite optical logic gate for the identification of signal of different level powers. The designed composite logic gate can significantly suppress the multiple access interference (MAI) and improve the performance of the system.Based on reconstruction equivalent-chirp technique, we design the balanced FBG decoder for simultaneous dispersion compensation and complete MAI elimination in SAC-OCDMA systems, and analyze, model and evaluate the performance of the system by negative binomial distribution. Comparing with the prediction from Gaussian approximation, the evaluation from NB model is more close to the real value, and can fully reflect the trends of the BER performance as the power changes. Then, to remove the requirements of the codes with fixed IPCC, modified balanced triple-branch signal detection (TBSD) scheme is proposed. The TBSD scheme can achieve the MAI elimination without the limit of the codes with fixed IPCC. Therefore, many common proposed code families can be directly applied to the SAC-OCDMA systems. The code design problem in SAC-OCDMA systems is solved by the modified TBSD scheme.Finally, we introduce the structure and working principle of the core and edge nodes of OPS, and design the architecture of all-optical multi-granularity packet switching node. Based on DQCC, we analyze and evaluate the performance of optical code label in OPS network versus the binomial coefficient, the number of jump and the code weight. Moreover, serial optical code label (SOCL) scheme is proposed and achieved by using parallel encoding structure and fiber delay line module, and the implementation of packet switching is verified by the simulations for the SOCL in OCDMA-OPS networks.