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.