The Study Of OCDMA Encoders Based On Modulated Polarization

With the development of optical communications in recent years, the demands for communications'capacity and system security are growing immoderately. The emerging technology of Optical Code Division Multiple Access (OCDMA) meets these requirements.Firstly, the paper introduce the principle of OCDMA, theoretical background, development of encoder, existing OCDMA systems and advantages of polarization modulation systems. In this thesis, the OCDMA system based on polarization modulation has strong security and high-fiber bandwidth utility ratio, which is great exploration to optical communications and has future prospects of practical use.Secondly, we experimentally demonstrate the feasibility of polarization-based OCDMA modulator system. We experimentally demonstrate part of a novel optical communication system based on polarization modulation, which includes a semiconductor optical amplifier (SOA) achieving polarization rotation between two orthogonal polarization states. The information of OCDMA user is spread spectrum serial encoded by the bipolar spectrum of m sequences. Two optical power levels of intensity modulated light wave stand for states in bipolar m sequence which injected into the SOA as the pump light. Because of polarization rotation, polarization state of the probe light is rotated between the two orthogonal linear polarization states denoted by p (pass) and s (switch) states. Bipolar user address codes are presented as serials of orthogonal polarization p and s states.In addition, CW laser and SOA hardware are accomplished in order to satisfy the need of certain system. Equipment proposed to achieve the above coding system design specifications, and completed the circuit of welding, debugging. Experimental results show that equipment performance to ensure the realization of this coding system function.Finally, the analysis of system performance and system user interference (MUI) inhibition of the issues are discussed. When the bit "0" transmitted, s state and p state data is not "0" at the same time, so that system will avoid the MUI.