Optical Encoders and Decoders for OCDMA

The typical network architecture for OCDMA with broadcast star is shown in Fig. 4.1. It can be seen that one of the key issues to implement OCDMA networking and communication is how to encode and decode the user’s data such that the optical channel can be shared, that is, we need to develop the practical encoding and decoding techniques that can be exploited to generate and recognize appropriate code sequences reliably. Therefore, The OCDMA encoders and decoders are the key components to implement OCDMA systems. In order to actualize the data communications among multiple users based on OCDMA communication technology, one unique codeword-waveform is assigned to each subscriber in an OCDMA network, which is chosen from specific OCDMA address codes, and therefore, different users employ different address codeword- waveforms. In an OCDMA network using on-off keying pattern, the user’s data is transmitted by each information bit “1” which is encoded into desired address codeword. However, the transmitter does not produce any optical pulses when the information bit “0” is sent. Figure 4.2 gives the schematic diagrams of waveforms employed to transmit data of three subscribers in an OCDMA network.