Theoretical Studies of Ultrashort Light Pulse Spectrally-Phase-Encoded OCDMA System Using Power-Cubic Optical Nonlinear Preprocessor

In this paper, a spectral-phase-encoded ultrashort light pulse optical code division multiple access (SPE-OCDMA) system employing a novel nonlinear power-cubic optical preprocessor at its receiver´s front end is theoretically investigated. The system´s mathematical model and the statistical distribution of the decision variable Y, prior to the decision module of the receiver, are discussed. The first three moments of the random decision variable Y are obtained in the context of the above OCDMA system and subsequently used in an appropriate Log-Pearson type 3 (LP3) distribution to represent the random decision variable Y. Multiple access interference (MAI) and amplified spontaneous emission (ASE) noises are taken into account to obtain the bit error rate of the system. Furthermore, the effects of shot and thermal noises are also included in the system performance modeling. In this context, performance comparison of the system based on power-cubic preprocessor and systems employing power-quadratic nonlinear optical thresholders, such as second harmonic generation crystals, are discussed. Finally, through numerical calculations under various conditions, we show the superiority of power-cubic systems, especially in high power regime where MAI is the dominant noise.