Synchronous Optical Fiber Code-Division Multiple-Access Networks with Bipolar Capacity

A non-coherent synchronous optical fiber code-division multiple-access (CDMA) network is proposed. In this network, sequence-inversion keying (SIK) of intensity modulated unipolar balanced Walsh code sequences is employed, whereby a code sequence is transmitted for each data ‘1 ’ bit while the logical complement of that sequence is transmitted for each data ‘0 ’ bit. At the receiver the received optical signal is correlated with the bipolar form of the reference sequence. Since the code sequences are balanced and the unipolar-bipolar correlation is implemented the same correlation functions as a bipolar system can be obtained. Hence, in the proposed synchronous optical fiber CDMA network, the cross-correlation of the address sequence and the undesired sequences is zero, that is, the interference is completely eliminated. Therefore, a very large number of users can transmit at the same time and very high throughput can be achieved. The novel design of programmable transmitter and receiver for non-coherent synchronous optical fiber CDMA networks using balanced Walsh codes is also presented. The transmitter and receiver are designed based on the use of electro-optical switches and optical delay-lines