Research and Development of OCDM system using 128 chip orthogonal sequence SSFBG Encoder/decoder

光码分复用(OCDM)对于光路径网络或下一代多媒体接入网络来说是一种有吸引力的技术，因为在发送器和接收器处使用唯一码，并且用户共享相同的传输介质。由于它提供了比OTDM和WDM更简单的光组件和网络控制，因此可以帮助构建复杂而灵活的网络。最近，相移超结构光纤布拉格光栅(SSFBG)被提出用于相干OCDM，因为它具有良好的相关性、高紧凑性、与光纤系统的兼容性以及潜在的低成本。然而，相干OCDM系统除了存在非相干多干扰问题外，还存在严重的相干信号干扰差拍噪声问题。由于差拍噪声增加了信号的功率，因此信噪比不随光接收功率的变化而变化。因此，需要采用超长码片和极短脉冲的编解码器来提高编码增益的信噪比。在本研究中，我们首次成功地在采用SSFBG的OCDM系统中使用128码片的正交序列编解码器实现了实验结果。正交码降低了互相关噪声，降低了相干信号干扰差分噪声。实验实现了超过17个用户的625 Mbps信号多路复用。

Optical code division multiplexing (0CDM) is an attractive technology for photonic path networks or for next generation multimedia access networks, since unique codes are used at the transmitter and receiver, and users share the same transmission media. It can facilitate the construction of a complex and flexible network because it provides simpler optical components and network control than OTDM and WDM. Recently, a super-structured fiber Bragg grating (SSFBG) with phase shift was proposed for coherent OCDM because of its good correlation property, high compactness, compatibility with fiberoptic systems, and potential low cost. However, the coherent OCDM systems have a serious problem of the coherent signal interference beat noise besides the incoherent multiple interferences issues. Because the beat-noise increases the power of signal, SNR is not changed with optical received power. So en/decoder with ultra long chips and extremely short pulses were required to increase SNR by the code gain.In this research, we successfully achieved the first time the experimental results using 128-chip orthogonal sequence En/Decoder in the OCDM system using SSFBG. Orthogonal codes reduce the cross-correlation noise, and the coherent signal interference beat noise. Over 17 users in 625 Mbps signal multiplex possibility is achieved experimentally.