RSoft Application Gallery Note: Optical Code Division Multiple Access (OCDMA) Link with Encoding/Decoding Based on Pseudo-Orthogonal Code

Tools Used: OptSim

Data access security and ability to support asynchronous, bursty data transmission are two of the main driving forces behind a lot of interest in the OCDMA techniques. On the other hand, the poor spectral efficiency of OCDMA systems demand appropriate choice of coding techniques and multi-access interference (MAI) is often a limiting factor. 

This example illustrates an OCDMA design with a commonly used tree network topology layout as shown below:

OCDMA design

The figure below shows several of the NRZ data bits and corresponding encoder output bits with User 1 signature:

NRZ data bits

One can clearly see both visually and quantitatively the performance degradation in the presence of multiple users due to MAI. As a further exercise, the reader may add more Users at encoding/decoding sides and observe more eye diagrams and their degradation in presence of MAI.

Eye Diagram: One User
Eye Diagram: Two User
Eye Diagram: Three User