A construction scheme of variable-weight optical orthogonal codes (VW-OOCs) for asynchronous optical code division multiple access (OCDMA) system is proposed. According to the actual situation, the code family can be obtained by programming in Matlab with the given code weight and corresponding capacity. The formula of bit error rate (BER) is derived by taking account of the effects of shot noise, avalanche photodiode (APD) bulk, thermal noise and surface leakage currents. The OCDMA system with the VW-OOCs is designed and improved. The study shows that the VW-OOCs have excellent performance of BER. Despite of coming from the same code family or not, the codes with larger weight have lower BER compared with the other codes in the same conditions. By taking simulation, the conclusion is consistent with the analysis of BER in theory. And the ideal eye diagrams are obtained by the optical hard limiter.

An electric encoded/optical transmission system of code division multiple access (CDMA) is proposed. It encodes the user signal in electric domain, and transfers the different code slice signals via the different wavelengths of light. This electric domain encoder/decoder is compared with current traditional encoder/decoder. Four-user modulation/ demodulation optical CDMA (OCDMA) system with rate of 2.5 Gbit/s is simulated, which is based on the optical orthogonal code (OCC) designed in our laboratory. The results show that the structure of electric encoding/optical transmission can encode/decode signal correctly, and can achieve the chip rate equal to the user data rate. It can overcome the rate limitation of electronic bottleneck, and bring some potential applications in the electro-optical OCDMA system.

通过分析不同乙烯含量的聚丙烯样品的拉曼光谱, 并结合偏最小二乘法(PLS), 对聚丙烯中的乙烯含量进行了研究。 对比聚乙烯和聚丙烯的拉曼光谱, 分析了50～600, 600～1 600及2 700～3 100 cm-1等三个特征谱段的拉曼光谱谱图; 建立了乙烯含量的PLS回归模型, 发现利用50～3 600 cm-1全谱段拉曼光谱建立的乙烯含量模型的预测效果最佳, 与近红外光谱(NIR)的检测值结果相近, 与真实值间的线性相关系数(r)、 平均相对误差(RAD)和均方根误差(RMSE)分别为0.995, 2.65%和0.319。 对50～3 600 cm-1范围的拉曼光谱进行PLS分析, 发现第一项PLS成分的载荷分布能够反映乙烯含量与聚丙烯分子结构间的关系, 即与CH2的数量成正相关, 而与CH3, C—H和C—C键的数量成负相关。 研究表明, 利用拉曼光谱可实现乙丙共聚聚丙烯中乙烯含量的快速检测。