Research On Key Techniques Of Optical Code Division Multiplexing (OCDM) And Its Applications

OPTICAL code division multiplexing (OCDM) technique, which combined with the virtues of optical communications and wireless code division multiplexing (CDM) is being considered to have wide applications to some fields, such as optical packets switching (OPS) system, passive optical networks (PON), secret information transmission, and so on. Recently, the research of OCDM technique and its applications has become the hotspot in optical communication fields. However, there are still some technical difficulties in process of heading to practicality of OCDM technique. In this dissertation, some main techniques used in OCDM system and its applications are studied, including optical address codes with good correlations, high security or great capacity, high-powered optical en/decoders, some approaches to improve the performance of OCDM system, applications of OCDM to OPS and secret information transmission.The main works and innovations of this dissertation are as following:(1) In order to improve the security of traditional OCDM-based information transmission, a new construction method for multiple groups optical orthogonal codes (OOC) (MGOOC) is proposed. This MGOOC used in OCDM system is randomly changed to interfere eavesdropping. Therefore, the security of MGOOC-based OCDM networks can be increased. The definition and characteristics of the MGOOC are given and analyzed. In addition, a new OCDM scheme based on MGOOC and traditional optical networks is proposed. This method can transmit secret and open information independently, and has low cost under a certain case (such as secret information transmission in the optical networks), and makes the traditional optical networks upgrade easily. Lastly the MGOOC-based OCDM system is designed and demonstrated by experiment.(2) According to the construction way of the quadratic congruent operator-based OOC, the cubed congruent operator is introduced to construct OOC, and its correlations and performance are discussed. One dimensional cubed congruent-based OOC is extended to two dimensional congruent-based OOC and traditional OOC, or congruent-based OOC and quadratic congruent-based OOC, and the corresponding codes are named as CCC/OOC and QCC/CCC two dimensional codes respectively. The Constructions for these codes are designed, and their correlations and capacities are studied. Some of these codes are used in OCDM, and their performances confirm the validity of the codes.(3) Optical en/decoders are very important for the practicability of OCDM technique. Therefore, they are also studied widely. The coherent and non-coherent optical en/decoders based on photonics crystal (PC) are proposed for the first time. The two methods, togother with their theoretical models are introduced. In order to verify the feasibility of the two schemes, the numerical simulation is carried out and the results confirm the two design schemes. These methods have the advantages of integration and miniaturization.(4) Improvement and evaluation of OCDM system's performance are attracted ones' attention. In order to improve the performance of OCDM system, a novel method using alterable concatenated code to pre-encode is proposed to reduce the impact of system impairment and multiple access interference (MAI) in OCDM system. The comprehensive investigation for different concatenated code type and forward error correcting (FEC) scheme are carried out by simulation. The bit error rate (BER) is derived by taking into account the effect of some noises, dispersion power penalty and the MAI. The theoretical analysis and numerical results show that the proposed system has good performance. This scheme permits implementation of a cost effective OCDM system.(5) The application of OCDM in OPS networks is focused widely. Multiple groups OOC sequences-based optical labels for OPS (MOOCS-OPS) networks are proposed. The MOOCS-OPS scheme is projected and its key parts are performed. With VPI, simulation of this system is performed and the results verify that it is effective. Lastly theoretical analysis of MOOCS-OPS system's performance is presented, and some numerical results are obtained, which show that this scheme is validity in aspect of system performance. (6) To achieve the practicability of the MOOCS-OPS networks, some key technological problems are resolved, such as the processing of MOOCS-based optical labels, the design of the corresponding hardware and their experimental test. According to the characteristics of single pulse for optical label with random and burst, the tunable operation of MOOCS-based optical labels, which has the module with FPGA (field programmable gate array) for single pulse generation and configuring of optical switches, is designed and its validity is demonstrated by experiment. The optical receiver with multiple amplifiers, broaden-net and comparer is designed, fabricated and demonstrated by experiment. Based on the above works, MOOCS-OPS system is established. The experimental results verify that MOOCS-OPS can work properly.